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Sample records for catalyst surfaces highly

  1. A structural view of Pd model catalysts : high-pressure surface X-Ray diffraction

    NARCIS (Netherlands)

    Rijn, Richard van

    2012-01-01

    This thesis describes the development of a combined high-pressure/ultrahigh-vacuum flow reactor for the study of model catalysts by means of surface x-ray diffraction and grazing incidence small angle scattering. The system was used to measure a stability diagram for the different oxide phases

  2. Catalyst surface characterized by high magnetic field NMR; Kojiba NMR ni yoru shokubai hyomen no kansatsu

    Energy Technology Data Exchange (ETDEWEB)

    Sato, S. [Chiba University, Chiba (Japan). Faculty of Engineering

    1997-08-01

    This paper introduces studies performed by the authors on observation of surface of solid catalysts by means of solid NMR measurement using the high-speed MAS technology which uses a high magnetic field device. In the studies, a device with 14.1T (resonant frequency of proton at 600 MHz) was used to conduct CP-MAS NMR measurement on {sup 29}Si to identify bonding of silica carrier in a fixed aluminum chloride catalyst. As a result, it was verified that the surface structure of aluminum chloride species deposited on the silica carrier turns to a structure in which AlCl2 species of a monomeric substance is bonded with a surface hydroxyl group and fixed in four- or five-orientation. When adjusted at low temperatures, an Al2Cl5 structure is formed, which is fixed as a dimeric substance with AlCl3 oriented in the AlCl2 species. It is conceived that the Al2Cl5 species has higher electrophilicity than the AlCl2 species as a result of AlCl3 oriented in AlCl2, whereas the hydroxyl group on the silica surface oriented with the Al2Cl5 species dissociates, discharging protons, thus showing strong acidity. 18 refs., 8 figs., 2 tabs.

  3. Bulk-surface relationship of an electronic structure for high-throughput screening of metal oxide catalysts

    International Nuclear Information System (INIS)

    Kweun, Joshua Minwoo; Li, Chenzhe; Zheng, Yongping; Cho, Maenghyo; Kim, Yoon Young; Cho, Kyeongjae

    2016-01-01

    Graphical abstract: - Highlights: • Bulk-surface relationship was predicted by the ligand field nature of metal oxides. • Antibonding and bonding d-bands occupancy clarified the bulk-surface relationship. • Different surface relaxations were explained by the bulk electronic structures. • Transition from the bulk to the surface state was simulated by oxygen adsorption. - Abstract: Designing metal-oxides consisting of earth-abundant elements has been a crucial issue to replace precious metal catalysts. To achieve efficient screening of metal-oxide catalysts via bulk descriptors rather than surface descriptors, we investigated the relationship between the electronic structure of bulk and that of the surface for lanthanum-based perovskite oxides, LaMO_3 (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu). Through density functional theory calculations, we examined the d-band occupancy of the bulk and surface transition-metal atoms (n_B_u_l_k and n_S_u_r_f) and the adsorption energy of an oxygen atom (E_a_d_s) on (001), (110), and (111) surfaces. For the (001) surface, we observed strong correlation between the n_B_u_l_k and n_S_u_r_f with an R-squared value over 94%, and the result was interpreted in terms of ligand field splitting and antibonding/bonding level splitting. Moreover, the E_a_d_s on the surfaces was highly correlated with the n_B_u_l_k with an R-squared value of more than 94%, and different surface relaxations could be explained by the bulk electronic structure (e.g., LaMnO_3 vs. LaTiO_3). These results suggest that a bulk-derived descriptor such as n_B_u_l_k can be used to screen metal-oxide catalysts.

  4. Highly dispersed metal catalyst

    Science.gov (United States)

    Xiao, Xin; West, William L.; Rhodes, William D.

    2016-11-08

    A supported catalyst having an atomic level single atom structure is provided such that substantially all the catalyst is available for catalytic function. A process of forming a single atom catalyst unto a porous catalyst support is also provided.

  5. Pt Single Atoms Embedded in the Surface of Ni Nanocrystals as Highly Active Catalysts for Selective Hydrogenation of Nitro Compounds.

    Science.gov (United States)

    Peng, Yuhan; Geng, Zhigang; Zhao, Songtao; Wang, Liangbing; Li, Hongliang; Wang, Xu; Zheng, Xusheng; Zhu, Junfa; Li, Zhenyu; Si, Rui; Zeng, Jie

    2018-06-13

    Single-atom catalysts exhibit high selectivity in hydrogenation due to their isolated active sites, which ensure uniform adsorption configurations of substrate molecules. Compared with the achievement in catalytic selectivity, there is still a long way to go in exploiting the catalytic activity of single-atom catalysts. Herein, we developed highly active and selective catalysts in selective hydrogenation by embedding Pt single atoms in the surface of Ni nanocrystals (denoted as Pt 1 /Ni nanocrystals). During the hydrogenation of 3-nitrostyrene, the TOF numbers based on surface Pt atoms of Pt 1 /Ni nanocrystals reached ∼1800 h -1 under 3 atm of H 2 at 40 °C, much higher than that of Pt single atoms supported on active carbon, TiO 2 , SiO 2 , and ZSM-5. Mechanistic studies reveal that the remarkable activity of Pt 1 /Ni nanocrystals derived from sufficient hydrogen supply because of spontaneous dissociation of H 2 on both Pt and Ni atoms as well as facile diffusion of H atoms on Pt 1 /Ni nanocrystals. Moreover, the ensemble composed of the Pt single atom and nearby Ni atoms in Pt 1 /Ni nanocrystals leads to the adsorption configuration of 3-nitrostyrene favorable for the activation of nitro groups, accounting for the high selectivity for 3-vinylaniline.

  6. Surface science of single-site heterogeneous olefin polymerization catalysts

    OpenAIRE

    Kim, Seong H.; Somorjai, Gabor A.

    2006-01-01

    This article reviews the surface science of the heterogeneous olefin polymerization catalysts. The specific focus is on how to prepare and characterize stereochemically specific heterogeneous model catalysts for the Ziegler–Natta polymerization. Under clean, ultra-high vacuum conditions, low-energy electron irradiation during the chemical vapor deposition of model Ziegler–Natta catalysts can be used to create a “single-site” catalyst film with a surface structure that produces only isotactic ...

  7. Structure, Mobility, and Composition of Transition Metal Catalyst Surfaces. High-Pressure Scanning Tunneling Microscopy and Ambient-Pressure X-ray Photoelectron Spectroscopy Studies

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zhongwei [Univ. of California, Berkeley, CA (United States)

    2013-12-06

    Surface structure, mobility, and composition of transition metal catalysts were studied by high-pressure scanning tunneling microscopy (HP-STM) and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) at high gas pressures. HP-STM makes it possible to determine the atomic or molecular rearrangement at catalyst surfaces, particularly at the low-coordinated active surface sites. AP-XPS monitors changes in elemental composition and chemical states of catalysts in response to variations in gas environments. Stepped Pt and Cu single crystals, the hexagonally reconstructed Pt(100) single crystal, and Pt-based bimetallic nanoparticles with controlled size, shape and composition, were employed as the model catalysts for experiments in this thesis.

  8. Highly reusability surface loaded metal particles magnetic catalyst microspheres (MCM-MPs) for treatment of dye-contaminated water

    International Nuclear Information System (INIS)

    Liu, Ying; Zhang, Kun; Yin, Xiaoshuang; Yang, Wenzhong; Zhu, Hongjun

    2016-01-01

    The metal-deposited magnetic catalyst microspheres (MCM-MPs) were successfully synthesized by one facile, high yield and controllable approach. Here, the bare magnetic microspheres were firstly synthesized according to the solvothermal method. Then silica shell were coated on the surface of the magnetic microspheres via sol–gel method, and subsequently with surface modifying with amino in the purpose to form SiO_2–NH_2 shell. Thus, metal particles were easily adsorbed into the SiO_2–NH_2 shell and in-situ reduced by NaBH_4 solution. All the obtained products (MCM-Cu, MCM-Ag, MCM-Pd) which were monodisperse and constitutionally stable were exhibited high magnetization and excellent catalytic activity towards dyes solution reduction. The catalytic rate ratio of MCM-Pd: MCM-Cu: MCM-Ag could be 10:3:1. Besides, some special coordination compound Cu_2(OH)_3Br had been generated in the in-situ reduced process of MCM-Cu, which produced superior cyclical stability (>20 times) than that of MCM-Ag and MCM-Pd. In all, those highly reusability and great catalytic efficiency of MCM-MPs show promising and great potential for treatment of dye-contaminated water. - Graphical abstract: Surface loaded metal particles magnetic catalyst microspheres MCM-MPs for rapid decolorizing dye-contaminated water: Synthesis, characterization and possible mechanisms. - Highlights: • A simple and high yield synthetic method for fabricate multi MCM-MPs is proposed with adequately optimize. • The highest reusability of MCM-Cu is attribute to the coordination compounds Cu_2(OH)_3Br. • MCM-MPs show excellent catalytic properties under different situations for various dyes • The catalytic mechanism of MCM-MPs is presented.

  9. Highly reusability surface loaded metal particles magnetic catalyst microspheres (MCM-MPs) for treatment of dye-contaminated water

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ying; Zhang, Kun, E-mail: kun4219@njtech.edu.cn; Yin, Xiaoshuang; Yang, Wenzhong; Zhu, Hongjun

    2016-04-01

    The metal-deposited magnetic catalyst microspheres (MCM-MPs) were successfully synthesized by one facile, high yield and controllable approach. Here, the bare magnetic microspheres were firstly synthesized according to the solvothermal method. Then silica shell were coated on the surface of the magnetic microspheres via sol–gel method, and subsequently with surface modifying with amino in the purpose to form SiO{sub 2}–NH{sub 2} shell. Thus, metal particles were easily adsorbed into the SiO{sub 2}–NH{sub 2} shell and in-situ reduced by NaBH{sub 4} solution. All the obtained products (MCM-Cu, MCM-Ag, MCM-Pd) which were monodisperse and constitutionally stable were exhibited high magnetization and excellent catalytic activity towards dyes solution reduction. The catalytic rate ratio of MCM-Pd: MCM-Cu: MCM-Ag could be 10:3:1. Besides, some special coordination compound Cu{sub 2}(OH){sub 3}Br had been generated in the in-situ reduced process of MCM-Cu, which produced superior cyclical stability (>20 times) than that of MCM-Ag and MCM-Pd. In all, those highly reusability and great catalytic efficiency of MCM-MPs show promising and great potential for treatment of dye-contaminated water. - Graphical abstract: Surface loaded metal particles magnetic catalyst microspheres MCM-MPs for rapid decolorizing dye-contaminated water: Synthesis, characterization and possible mechanisms. - Highlights: • A simple and high yield synthetic method for fabricate multi MCM-MPs is proposed with adequately optimize. • The highest reusability of MCM-Cu is attribute to the coordination compounds Cu{sub 2}(OH){sub 3}Br. • MCM-MPs show excellent catalytic properties under different situations for various dyes • The catalytic mechanism of MCM-MPs is presented.

  10. High surface area niobium oxides as catalysts for improved hydrogen sorption properties of ball milled MgH2

    International Nuclear Information System (INIS)

    Bhat, V.V.; Rougier, A.; Aymard, L.; Nazri, G.A.; Tarascon, J.-M.

    2008-01-01

    We report, high surface area (up to 200 m 2 /g) nanocrystalline niobium oxide (so called p-Nb 2 O 5 ) synthesized by 'chimie douce' route and its importance in enhancing the hydrogen sorption properties of MgH 2 . p-Nb 2 O 5 induces faster kinetics than commonly used commercial Nb 2 O 5 (c-Nb 2 O 5 ) when ball milled with MgH 2 (named (MgH 2 ) catalyst ) by reducing the time of desorption from 35 min in (MgH 2 ) c-Nb 2 O 5 to 12 min in (MgH 2 ) p-Nb 2 O 5 at 300 deg. C. The BET surface area of as-prepared Nb 2 O 5 was tuned by heat treatment and its effect on sorption properties was studied. Among them, both p-Nb 2 O 5 and Nb 2 O 5 :350 (p-Nb 2 O 5 heated to 350 deg. C with a BET specific surface area of 46 m 2 /g) desorb 5 wt.% within 12 min, exhibiting the best catalytic activity. Furthermore, thanks to the addition of high surface area Nb 2 O 5 , the desorption temperature was successfully lowered down to 200 deg. C, with a significant amount of desorbed hydrogen (4.5 wt.%). In contrast, the composite (MgH 2 ) c-Nb 2 O 5 shows no desorption at this 'low' temperature

  11. High-Activity Dealloyed Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Kongkanand, Anusorn [General Motors LLC, Pontiac, MI (United States)

    2014-09-30

    Reduction of costly Pt usage in proton exchange membrane fuel cell electrodes is one of the major challenges towards development and commercialization of fuel cell vehicles. Although few have met the initial-kinetic activity requirements in a realistic fuel cell device, no catalyst material has ever met the demanding fuel cell durability targets set by DOE. In this project, a team of 4 universities and 2 companies came together to investigate a concept that appeared promising in preliminary non-fuel cell tests then to further develop the catalyst to a mature level ready for vehicle implementation. The team consists of academia with technical leadership in their respective areas, a catalyst supplier, and a fuel cell system integrator.The tightly collaborative project enabled development of a highly active and durable catalyst with performance that significantly exceeds that of previous catalysts and meets the DOE targets for the first time (Figure 1A). The catalyst was then further evaluated in full-active-area stack in a realistic vehicle operating condition (Figure 1B). This is the first public demonstration that one can realize the performance benefit and Pt cost reduction over a conventional pure Pt catalyst in a long-term realistic PEMFC system. Furthermore, systematic analyses of a range of catalysts with different performance after fuel cell testing allowed for correlation between catalyst microstructure and its electrocatalytic activity and durability. This will in turn aid future catalyst development.

  12. Gasification of carbon deposits on catalysts and metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Figueiredo, J L

    1986-10-01

    'Coke' deposited on catalysts and reactor surfaces includes a variety of carbons of different structures and origins, their reactivities being conveniently assessed by Temperature Programmed Reaction (TPR). The gasification of carbon deposits obtained in the laboratory under well controlled conditions, and the regeneration of coked catalysts from petroleum refining processes are reviewed and discussed. Filamentary carbon deposits, containing dispersed metal particles, behave as supported metal catalysts during gasification, and show high reactivities. Pyrolytic and acid catalysis carbons are less reactive on their own, as the gasification is not catalysed; however, metal components of the catalyst or metal impurities deposited on the surface may enhance gasification. 26 refs., 8 figs., 2 tabs.

  13. Design of a surface alloy catalyst for steam reforming

    DEFF Research Database (Denmark)

    Besenbacher, F.; Chorkendorff, Ib; Clausen, B.S.

    1998-01-01

    Detailed studies of elementary chemical processes on well-characterized single crystal surfaces have contributed substantially to the understanding of heterogeneous catalysis. insight into the structure of surface alloys combined with an understanding of the relation between the surface compositi...... and reactivity is shown to lead directly to new ideas for catalyst design, The feasibility of such an approach is illustrated by the synthesis, characterization, and tests of a high-surface area gold-nickel catalyst for steam reforming....

  14. A novel catalyst layer structure based surface-patterned Nafion® membrane for high-performance direct methanol fuel cell

    DEFF Research Database (Denmark)

    Chen, Ming; Wang, Meng; Ding, Xianan

    2018-01-01

    .5% respectively, compared with the conventional catalyst layer. Performance improvement is attributed to the fact that the novel catalyst layer structure optimizes the electrolyte membrane/catalyst layer and gas diffusion layer/catalyst layer interfacial structure, which increases the electrochemical reaction......Conventional catalyst layer with a smooth surface exists the larger area of“catalytic dead zone” and reduces the utilization of catalyst. Based on this, a novel catalyst layer structure based surface-patterned Nafion® membrane was designed to achieve more efficient electrochemical reaction...... to prepare the novel catalyst layer, and the effect of pressure on the performance of MEA was investigated. The results suggested that the peak power density of DMFC with optimal novel catalyst layer structure increased by 28.84%, the charge transfer resistances of anode and cathode reduced by 28.8% and 26...

  15. Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts

    International Nuclear Information System (INIS)

    Mayr, Lukas; Klötzer, Bernhard; Penner, Simon; Rameshan, Raffael; Rameshan, Christoph

    2014-01-01

    An ultra-high vacuum (UHV) setup for “real” and “inverse” model catalyst preparation, depth-resolved near-surface spectroscopic characterization, and quantification of catalytic activity and selectivity under technologically relevant conditions is described. Due to the all-quartz reactor attached directly to the UHV-chamber, transfer of the catalyst for in situ testing without intermediate contact to the ambient is possible. The design of the UHV-compatible re-circulating batch reactor setup allows the study of reaction kinetics under close to technically relevant catalytic conditions up to 1273 K without contact to metallic surfaces except those of the catalyst itself. With the attached differentially pumped exchangeable evaporators and the quartz-microbalance thickness monitoring equipment, a reproducible, versatile, and standardised sample preparation is possible. For three-dimensional near-surface sample characterization, the system is equipped with a hemispherical analyser for X-ray photoelectron spectroscopy (XPS), electron-beam or X-ray-excited Auger-electron spectroscopy, and low-energy ion scattering measurements. Due the dedicated geometry of the X-ray gun (54.7°, “magic angle”) and the rotatable sample holder, depth analysis by angle-resolved XPS measurements can be performed. Thus, by the combination of characterisation methods with different information depths, a detailed three-dimensional picture of the electronic and geometric structure of the model catalyst can be obtained. To demonstrate the capability of the described system, comparative results for depth-resolved sample characterization and catalytic testing in methanol steam reforming on PdGa and PdZn near-surface intermetallic phases are shown

  16. Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts

    Science.gov (United States)

    Mayr, Lukas; Rameshan, Raffael; Klötzer, Bernhard; Penner, Simon; Rameshan, Christoph

    2014-05-01

    An ultra-high vacuum (UHV) setup for "real" and "inverse" model catalyst preparation, depth-resolved near-surface spectroscopic characterization, and quantification of catalytic activity and selectivity under technologically relevant conditions is described. Due to the all-quartz reactor attached directly to the UHV-chamber, transfer of the catalyst for in situ testing without intermediate contact to the ambient is possible. The design of the UHV-compatible re-circulating batch reactor setup allows the study of reaction kinetics under close to technically relevant catalytic conditions up to 1273 K without contact to metallic surfaces except those of the catalyst itself. With the attached differentially pumped exchangeable evaporators and the quartz-microbalance thickness monitoring equipment, a reproducible, versatile, and standardised sample preparation is possible. For three-dimensional near-surface sample characterization, the system is equipped with a hemispherical analyser for X-ray photoelectron spectroscopy (XPS), electron-beam or X-ray-excited Auger-electron spectroscopy, and low-energy ion scattering measurements. Due the dedicated geometry of the X-ray gun (54.7°, "magic angle") and the rotatable sample holder, depth analysis by angle-resolved XPS measurements can be performed. Thus, by the combination of characterisation methods with different information depths, a detailed three-dimensional picture of the electronic and geometric structure of the model catalyst can be obtained. To demonstrate the capability of the described system, comparative results for depth-resolved sample characterization and catalytic testing in methanol steam reforming on PdGa and PdZn near-surface intermetallic phases are shown.

  17. Camellia oleifera shell as an alternative feedstock for furfural production using a high surface acidity solid acid catalyst.

    Science.gov (United States)

    Zhang, Luxin; He, Yunfei; Zhu, Yujie; Liu, Yuting; Wang, Xiaochang

    2018-02-01

    This paper focuses on the high-value transformation of camellia oleifera shell, which is an agricultural waste enriched in hemicellulose. An efficient catalytic route employing sulfonated swelling mesoporous polydivinylbenzene (PDVB-SO 3 H) as catalyst in monophasic or biphasic solvents was developed for the conversion of raw camellia oleifera shell into furfural. The reaction parameters were evaluated and optimized for improving the furfural yield. It was found that the solvent greatly influenced the hydrolysis of camellia oleifera shells, and the highest furfural yield of 61.3% was obtained in "γ-butyrolactone + water" system when the feedstock-to-catalyst ratio was 2 for 30 min at 443 K. Camellia oleifera shell exhibited a high potential as feedstock to produce furfural in high yields. The outcome of this study provides an attractive utilization option to camellia oleifera shell, which is currently burned or discarded for producing a bio-based chemical. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Enhancing Pt-Ni/CeO2 performances for ethanol reforming by catalyst supporting on high surface silica

    NARCIS (Netherlands)

    Palma, V.; Ruocco, C; Meloni, E.; Gallucci, F.; Ricca, A.

    2018-01-01

    In this paper, bimetallic Pt-Ni/CeO2 catalysts supported over mesoporous silica were employed for ethanol reforming in the low-temperature range. In particular, catalyst behaviour was investigated under a H2O/C2H5OH/N2 as well as H2O/C2H5OH/AIR mixture between 300 and 600 °C at different space

  19. Alternative route for the synthesis of high surface-area η-Al{sub 2}O{sub 3}/Nb{sub 2}O{sub 5} catalyst from aluminum waste

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, Francisco G.E. [Departamento de Engenharia Química, Universidade Federal de São Carlos, CEP 13565-905, São Carlos, SP (Brazil); Asencios, Yvan J.O. [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Av. Alm. Saldanha da Gama, 89, 11030-400, Santos, SP (Brazil); Rodella, Cristiane B. [Laboratório Nacional de Luz Sincrotron, Rua Giuseppe Máximo Scolfaro, 10.000 Polo II de Alta Tecnologia, 13083-970, Campinas, SP (Brazil); Porto, André L.M. [Departamento de Engenharia Química, Universidade Federal de São Carlos, CEP 13565-905, São Carlos, SP (Brazil); Assaf, Elisabete M., E-mail: eassaf@iqsc.usp.br [Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, 13560-970, São Carlos, SP (Brazil)

    2016-12-01

    This paper describes an alternative route for the production of a high-surface-area η-Al{sub 2}O{sub 3}/Nb{sub 2}O{sub 5} catalyst synthesized from aluminum waste and niobium ammonium oxalate (NH{sub 4}H{sub 2}[NbO−(C{sub 2}O{sub 4}){sub 3}]·3H{sub 2}O). The effects of thermal treatment on the morphology and crystal structure were examined by X-ray powder diffraction (XPD), surface area measurements (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence, dynamic scanning calorimetry (DSC) and thermogravimetry (TG) measurement. The catalysts were evaluated in the glycerol dehydration reaction. Catalytic tests were carried out with reactants in gas-phase with a fixed-bed reactor at 300° and 400 °C. - Highlights: • Alternative route for the production of a high-surface-area Al{sub 2}O{sub 3}/Nb{sub 2}O{sub 5} catalyst. • The catalyst was synthesized from aluminum waste and ammonium oxalato-niobate. • NbAl catalyst obtained showed high specific surface area (330 m{sup 2}/g). • The catalyst produced by this method showed promise in the dehydration of glycerol.

  20. High-throughput heterogeneous catalyst research

    Science.gov (United States)

    Turner, Howard W.; Volpe, Anthony F., Jr.; Weinberg, W. H.

    2009-06-01

    With the discovery of abundant and low cost crude oil in the early 1900's came the need to create efficient conversion processes to produce low cost fuels and basic chemicals. Enormous investment over the last century has led to the development of a set of highly efficient catalytic processes which define the modern oil refinery and which produce most of the raw materials and fuels used in modern society. Process evolution and development has led to a refining infrastructure that is both dominated and enabled by modern heterogeneous catalyst technologies. Refineries and chemical manufacturers are currently under intense pressure to improve efficiency, adapt to increasingly disadvantaged feedstocks including biomass, lower their environmental footprint, and continue to deliver their products at low cost. This pressure creates a demand for new and more robust catalyst systems and processes that can accommodate them. Traditional methods of catalyst synthesis and testing are slow and inefficient, particularly in heterogeneous systems where the structure of the active sites is typically complex and the reaction mechanism is at best ill-defined. While theoretical modeling and a growing understanding of fundamental surface science help guide the chemist in designing and synthesizing targets, even in the most well understood areas of catalysis, the parameter space that one needs to explore experimentally is vast. The result is that the chemist using traditional methods must navigate a complex and unpredictable diversity space with a limited data set to make discoveries or to optimize known systems. We describe here a mature set of synthesis and screening technologies that together form a workflow that breaks this traditional paradigm and allows for rapid and efficient heterogeneous catalyst discovery and optimization. We exemplify the power of these new technologies by describing their use in the development and commercialization of a novel catalyst for the

  1. Molecular metal catalysts on supports: organometallic chemistry meets surface science.

    Science.gov (United States)

    Serna, Pedro; Gates, Bruce C

    2014-08-19

    Recent advances in the synthesis and characterization of small, essentially molecular metal complexes and metal clusters on support surfaces have brought new insights to catalysis and point the way to systematic catalyst design. We summarize recent work unraveling effects of key design variables of site-isolated catalysts: the metal, metal nuclearity, support, and other ligands on the metals, also considering catalysts with separate, complementary functions on supports. The catalysts were synthesized with the goal of structural simplicity and uniformity to facilitate incisive characterization. Thus, they are essentially molecular species bonded to porous supports chosen for their high degree of uniformity; the supports are crystalline aluminosilicates (zeolites) and MgO. The catalytic species are synthesized in reactions of organometallic precursors with the support surfaces; the precursors include M(L)2(acetylacetonate)1-2, with M = Ru, Rh, Ir, or Au and the ligands L = C2H4, CO, or CH3. Os3(CO)12 and Ir4(CO)12 are used as precursors of supported metal clusters, and some such catalysts are made by ship-in-a-bottle syntheses to trap the clusters in zeolite cages. The simplicity and uniformity of the supported catalysts facilitate precise structure determinations, even in reactive atmospheres and during catalysis. The methods of characterizing catalysts in reactive atmospheres include infrared (IR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and nuclear magnetic resonance (NMR) spectroscopies, and complementary methods include density functional theory and atomic-resolution aberration-corrected scanning transmission electron microscopy for imaging of individual metal atoms. IR, NMR, XANES, and microscopy data demonstrate the high degrees of uniformity of well-prepared supported species. The characterizations determine the compositions of surface metal complexes and clusters, including the ligands and the metal

  2. Ozone Decomposition on the Surface of Metal Oxide Catalyst

    Directory of Open Access Journals (Sweden)

    Batakliev Todor Todorov

    2014-12-01

    Full Text Available The catalytic decomposition of ozone to molecular oxygen over catalytic mixture containing manganese, copper and nickel oxides was investigated in the present work. The catalytic activity was evaluated on the basis of the decomposition coefficient which is proportional to ozone decomposition rate, and it has been already used in other studies for catalytic activity estimation. The reaction was studied in the presence of thermally modified catalytic samples operating at different temperatures and ozone flow rates. The catalyst changes were followed by kinetic methods, surface measurements, temperature programmed reduction and IR-spectroscopy. The phase composition of the metal oxide catalyst was determined by X-ray diffraction. The catalyst mixture has shown high activity in ozone decomposition at wet and dry O3/O2 gas mixtures. The mechanism of catalytic ozone degradation was suggested.

  3. Surface-reconstructed graphite nanofibers as a support for cathode catalysts of fuel cells.

    Science.gov (United States)

    Gan, Lin; Du, Hongda; Li, Baohua; Kang, Feiyu

    2011-04-07

    Graphite nanofibers (GNFs), on which surface graphite edges were reconstructed into nano-loops, were explored as a cathode catalyst support for fuel cells. The high degree of graphitization, as well as the surface-reconstructed nano-loops that possess topological defects for uniform metal deposition, resulted in an improved performance of the GNF-supported Pt catalyst.

  4. Catalyst design for enhanced sustainability through fundamental surface chemistry.

    Science.gov (United States)

    Personick, Michelle L; Montemore, Matthew M; Kaxiras, Efthimios; Madix, Robert J; Biener, Juergen; Friend, Cynthia M

    2016-02-28

    Decreasing energy consumption in the production of platform chemicals is necessary to improve the sustainability of the chemical industry, which is the largest consumer of delivered energy. The majority of industrial chemical transformations rely on catalysts, and therefore designing new materials that catalyse the production of important chemicals via more selective and energy-efficient processes is a promising pathway to reducing energy use by the chemical industry. Efficiently designing new catalysts benefits from an integrated approach involving fundamental experimental studies and theoretical modelling in addition to evaluation of materials under working catalytic conditions. In this review, we outline this approach in the context of a particular catalyst-nanoporous gold (npAu)-which is an unsupported, dilute AgAu alloy catalyst that is highly active for the selective oxidative transformation of alcohols. Fundamental surface science studies on Au single crystals and AgAu thin-film alloys in combination with theoretical modelling were used to identify the principles which define the reactivity of npAu and subsequently enabled prediction of new reactive pathways on this material. Specifically, weak van der Waals interactions are key to the selectivity of Au materials, including npAu. We also briefly describe other systems in which this integrated approach was applied. © 2016 The Author(s).

  5. Surface science models of CoMoS hydrodesulfurisation catalysts

    Energy Technology Data Exchange (ETDEWEB)

    De Jong, A.M.; De Beer, V.H.J.; Van Veen, J.A.R.; Niemantsverdriet, J.W. [Schuit Institute of Catalysis, Eindhoven University of Technology, Eindhoven (Netherlands)

    1997-07-01

    Characterization of supported catalysts with surface spectroscopic techniques is often limited due to restraints imposed by the support material. The use of flat conducting substrates as a model support offers a way to apply these techniques to their full potential. Such surface science models of silica and alumina supported CoMoS catalysts have been made by impregnating thin SiO{sub 2} and Al{sub 2}O{sub 3} films with a solution of nitrilotriacetic acid (NTA) complexes of cobalt and molybdenum. X-ray Photoelectron Spectroscopy (XPS) spectra indicate that the order in which cobalt and molybdenum transfer to the sulfided state is reversed with respect to oxidic Co and Mo systems prepared by conventional methods, implying that NTA complexation retards the sulfidation of cobalt to temperatures where MoS{sub 2} is already formed. Catalytic tests show that the CoMoS model catalysts exhibit activities for thiophene desulfurisation and product distributions similar to those of their high surface area counterparts. 25 refs.

  6. Highly sensitive silicon microreactor for catalyst testing

    DEFF Research Database (Denmark)

    Henriksen, Toke Riishøj; Olsen, Jakob Lind; Vesborg, Peter Christian Kjærgaard

    2009-01-01

    by directing the entire gas flow through the catalyst bed to a mass spectrometer, thus ensuring that nearly all reaction products are present in the analyzed gas flow. Although the device can be employed for testing a wide range of catalysts, the primary aim of the design is to allow characterization of model...... catalysts which can only be obtained in small quantities. Such measurements are of significant fundamental interest but are challenging because of the low surface areas involved. The relationship between the reaction zone gas flow and the pressure in the reaction zone is investigated experimentally......, it is found that platinum catalysts with areas as small as 15 mu m(2) are conveniently characterized with the device. (C) 2009 American Institute of Physics. [doi:10.1063/1.3270191]...

  7. Hairy foam" : carbon nanofibers grown on solid foam. A fully accessible, high surface area, graphitic catalyst support

    NARCIS (Netherlands)

    Wenmakers, P.W.A.M.; Schaaf, van der J.; Kuster, B.F.M.; Schouten, J.C.

    2008-01-01

    This paper describes the synthesis of carbon nanofibers (CNFs) on solid carbon foam ("Hairy Foam") by catalytic decompn. of ethylene. The effect of nickel loading on fiber diam. and morphol., CNF coverage, and fiber layer thickness is studied using SEM and N2/Kr-physisorption. The surface area

  8. Highly Stable and Active Catalyst for Sabatier Reactions

    Science.gov (United States)

    Hu, Jianli; Brooks, Kriston P.

    2012-01-01

    Highly active Ru/TiO2 catalysts for Sabatier reaction have been developed. The catalysts have shown to be stable under repeated shutting down/startup conditions. When the Ru/TiO2 catalyst is coated on the engineered substrate Fe-CrAlY felt, activity enhancement is more than doubled when compared with an identically prepared engineered catalyst made from commercial Degussa catalyst. Also, bimetallic Ru-Rh/TiO2 catalysts show high activity at high throughput.

  9. Selective growth of two-dimensional phosphorene on catalyst surface.

    Science.gov (United States)

    Qiu, L; Dong, J C; Ding, F

    2018-02-01

    Although the study of black phosphorene (BP) and its isomers has attracted enormous attention, the method of synthesizing high-quality samples in a large area is still pending. Here we explore the potential of using the chemical vapor deposition method to synthesize large-area two-dimensional (2D) phosphorene films on metal surfaces. Our ab initio calculations show that BP can be synthesized by using tin (Sn) as a catalyst, while one of its isomers, blue phosphorene (BLP), is very possible to be synthesized by using most other metals, such as Ag and Au. Besides, our study also suggests that the large binding energy between the 2D phosphorene and the active metal substrate may prohibit the exfoliation of the 2D phosphorene for real applications and, therefore, tin, silver and gold are predicted to be the most suitable catalysts for the synthesis of BP and BLP.

  10. Report on the evaluation of the development of the catalyst surface high accuracy quantitative analysis technology using electron spectroscopy; Denshi bunkoho ni yoru shokubai hyomen koseido teiryo bunseki gijutsu no kaihatsu hyoka hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    An objective evaluation from a third party was conducted on the purpose, plan, execution method, achievement, etc. of a project 'The devilment of the catalyst surface high accuracy quantitative analysis technology using electron spectroscopy.' The purpose of the project is to make the relationing possible between the analytical results of the catalyst surface and the catalyst performance which has been so far difficult by heightening the accuracy of the catalyst quantitative surface analytical accuracy using the electron spectroscopy. The purpose and significance are judged to be worth a lot. This project is an industry/university/government joint project between the two countries. The project is excellent both in connection among research institutes and leadership of chief researchers, and it is judged that the joint research system fully functioned. The term of the project was shortened from 3 years in the first plan to 2 years, and therefore, the study was finished only on silicon oxide and organic thin films. However, it was determined that the study results are to be run in the magazine 'Surface and Interface Analysis,' which indicates that the achievement was judged to be very worth in the academic viewpoint. (NEDO)

  11. Atomic layer deposition of ruthenium surface-coating on porous platinum catalysts for high-performance direct ethanol solid oxide fuel cells

    Science.gov (United States)

    Jeong, Heon Jae; Kim, Jun Woo; Jang, Dong Young; Shim, Joon Hyung

    2015-09-01

    Pt-Ru bi-metallic catalysts are synthesized by atomic layer deposition (ALD) of Ru surface-coating on sputtered Pt mesh. The catalysts are evaluated in direct ethanol solid oxide fuel cells (DESOFCs) in the temperature range of 300-500 °C. Island-growth of the ALD Ru coating is confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy (XPS) analyses. The performance of the DESOFCs is evaluated based on the current-voltage output and electrochemical impedance spectroscopy. Genuine reduction of the polarization impedance, and enhanced power output with improved surface kinetics are achieved with the optimized ALD Ru surface-coating compared to bare Pt. The chemical composition of the Pt/ALD Ru electrode surface after fuel cell operation is analyzed via XPS. Enhanced cell performance is clearly achieved, attributed to the effective Pt/ALD Ru bi-metallic catalysis, including oxidation of Cdbnd O by Ru, and de-protonation of ethanol and cleavage of C-C bonds by Pt, as supported by surface morphology analysis which confirms formation of a large amount of carbon on bare Pt after the ethanol-fuel-cell test.

  12. High aspect ratio catalytic reactor and catalyst inserts therefor

    Science.gov (United States)

    Lin, Jiefeng; Kelly, Sean M.

    2018-04-10

    The present invention relates to high efficient tubular catalytic steam reforming reactor configured from about 0.2 inch to about 2 inch inside diameter high temperature metal alloy tube or pipe and loaded with a plurality of rolled catalyst inserts comprising metallic monoliths. The catalyst insert substrate is formed from a single metal foil without a central supporting structure in the form of a spiral monolith. The single metal foil is treated to have 3-dimensional surface features that provide mechanical support and establish open gas channels between each of the rolled layers. This unique geometry accelerates gas mixing and heat transfer and provides a high catalytic active surface area. The small diameter, high aspect ratio tubular catalytic steam reforming reactors loaded with rolled catalyst inserts can be arranged in a multi-pass non-vertical parallel configuration thermally coupled with a heat source to carry out steam reforming of hydrocarbon-containing feeds. The rolled catalyst inserts are self-supported on the reactor wall and enable efficient heat transfer from the reactor wall to the reactor interior, and lower pressure drop than known particulate catalysts. The heat source can be oxygen transport membrane reactors.

  13. Fiscal 1998 development report on the high-accuracy quantitative analysis technique of catalyst surfaces by electron spectroscopy; 1998 nendo denshi bunkoho ni yoru shokubai hyomen koseido teiryo bunseki gijutsu no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    This project aims at development of the high-accuracy quantitative analysis technique by electron spectroscopy for surface analysis of catalysts and semiconductors. Since conventional analysis technique using an energy-fixed X-ray excitation source is inadequate to obtain satisfactory surface sensitivity and quantitative accuracy for catalysts, for development of the titled technique, this project makes experiment using energy-variable synchrotron radiation to modify the parameter on motion of low-speed electrons in solids which is obtained by Monte Carlo calculation. For establishment of the high-accuracy quantitative analysis technique of surface compositions of materials such as catalyst of which performance is dominated by utmost surface, the project studies the attenuation length of electrons in solids by electron spectroscopy using soft X-rays from synchrotron radiation. In this fiscal year, the project established the equipment and technique for high-accuracy quantitative analysis of the thickness and electron attenuation length of silicon oxide films on silicon wafers by electron spectroscopy. (NEDO)

  14. Controlling hydrogenation activity and selectivity of bimetallic surfaces and catalysts

    Science.gov (United States)

    Murillo, Luis E.

    Studies of bimetallic systems are of great interest in catalysis due to the novel properties that they often show in comparison with the parent metals. The goals of this dissertation are: (1) to expand the studies of self-hydrogenation and hydrogenation reactions on bimetallic surfaces under ultra high vacuum conditions (UHV) using different hydrocarbon as probe molecules; (2) to attempt to correlate the surface science findings with supported catalyst studies under more realistic conditions; and (3) to investigate the competitive hydrogenation of C=C versus C=O bonds on Pt(111) modified by different 3d transition metals. Hydrogenation studies using temperature programmed desorption (TPD) on Ni/Pt(111) bimetallic surfaces have demonstrated an enhancement in the low temperature hydrogenation activity relative to that of clean Pt(111). This novel hydrogenation pathway can be achieved under UHV conditions by controlling the structures of the bimetallic surfaces. A low temperature hydrogenation activity of 1-hexene and 1-butene has been observed on a Pt-Ni-Pt(111) subsurface structure, where Ni atoms are mainly present on the second layer of the Pt(111) single crystal. These results are in agreement with previous studies of self-hydrogenation and hydrogenation of cyclohexene. However, a much higher dehydrogenation activity is observed in the reaction of cyclohexene to produce benzene, demonstrating that the hydrocarbon structure has an effect on the reaction pathways. On the other hand, self-hydrogenation of 1-butene is not observed on the Pt-Ni-Pt(111) surface, indicating that the chain length (or molecular weight) has a significant effect on the selfhydrogenation activity. The gas phase reaction of cyclohexene on Ni/Pt supported on alumina catalysts has also shown a higher self-hydrogenation activity in comparison with the same reaction performed on supported monometallic catalysts. The effects of metal loading and impregnation sequence of the metal precursors are

  15. Chlorodiethylaluminum supported on silica: A dinuclear aluminum surface species with bridging μ2-Cl-ligand as a highly efficient co-catalyst for the Ni-catalyzed dimerization of ethene

    KAUST Repository

    Kermagoret, Anthony

    2014-05-01

    Silica-supported chloro alkyl aluminum co-catalysts (DEAC@support) were prepared via Surface Organometallic Chemistry by contacting diethylaluminum chloride (DEAC) and high specific surface silica materials, i.e. SBA-15, MCM-41, and Aerosil SiO2. Such systems efficiently activate NiCl 2(PBu3)2 for catalytic ethene dimerization, with turnover frequency (TOF) reaching up to 498,000 molC2H4/ (molNi h) for DEAC@MCM-41. A detailed analysis of the DEAC@SBA-15 co-catalyst structure by solid-state aluminum-27 NMR at high-field (17.6 T and 20.0 T) and ultrafast spinning rates allows to detect six sites, characterized by a distribution of quadrupolar interaction principal values CQ and isotropic chemical shifts δiso. Identification of the corresponding Al-grafted structures was possible by comparison of the experimental NMR signatures with these calculated by DFT on a wide range of models for the aluminum species (mono- versus di-nuclear, mono- versus bis-grafted with bridging Cl or ethyl). Most of the sites were identified as dinuclear species with retention of the structure of DEAC, namely with the presence of μ2-Cl-ligands between two aluminum, and this probably explains the high catalytic performance of this silica-supported co-catalysts. © 2014 Elsevier Inc. All rights reserved.

  16. Surface science models of CoMoS hydrodesulfurisation catalysts

    NARCIS (Netherlands)

    Jong, de A.M.; Beer, de V.H.J.; Veen, van J.A.R.; Niemantsverdriet, J.W.; Froment, G.F.; Delmon, B.; Grange, P.

    1997-01-01

    Characterization of supported catalysts with surface spectroscopic techniques is often limited due to restraints imposed by the support material. The use of flat conducting substrates as a model support offers a way to apply these techniques to their full potential. Such surface science models of

  17. Patched bimetallic surfaces are active catalysts for ammonia decomposition.

    Science.gov (United States)

    Guo, Wei; Vlachos, Dionisios G

    2015-10-07

    Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

  18. High-throughput technology for novel SO2 oxidation catalysts

    International Nuclear Information System (INIS)

    Loskyll, Jonas; Stoewe, Klaus; Maier, Wilhelm F

    2011-01-01

    We review the state of the art and explain the need for better SO 2 oxidation catalysts for the production of sulfuric acid. A high-throughput technology has been developed for the study of potential catalysts in the oxidation of SO 2 to SO 3 . High-throughput methods are reviewed and the problems encountered with their adaptation to the corrosive conditions of SO 2 oxidation are described. We show that while emissivity-corrected infrared thermography (ecIRT) can be used for primary screening, it is prone to errors because of the large variations in the emissivity of the catalyst surface. UV-visible (UV-Vis) spectrometry was selected instead as a reliable analysis method of monitoring the SO 2 conversion. Installing plain sugar absorbents at reactor outlets proved valuable for the detection and quantitative removal of SO 3 from the product gas before the UV-Vis analysis. We also overview some elements used for prescreening and those remaining after the screening of the first catalyst generations. (topical review)

  19. Highly Dispersed Alloy Catalyst for Durability

    Energy Technology Data Exchange (ETDEWEB)

    Murthi, Vivek S.; Izzo, Elise; Bi, Wu; Guerrero, Sandra; Protsailo, Lesia

    2013-01-08

    Achieving DOE's stated 5000-hr durability goal for light-duty vehicles by 2015 will require MEAs with characteristics that are beyond the current state of the art. Significant effort was placed on developing advanced durable cathode catalysts to arrive at the best possible electrode for high performance and durability, as well as developing manufacturing processes that yield significant cost benefit. Accordingly, the overall goal of this project was to develop and construct advanced MEAs that will improve performance and durability while reducing the cost of PEMFC stacks. The project, led by UTC Power, focused on developing new catalysts/supports and integrating them with existing materials (membranes and gas diffusion layers (GDLs)) using state-of-the-art fabrication methods capable of meeting the durability requirements essential for automotive applications. Specifically, the project work aimed to lower platinum group metals (PGM) loading while increasing performance and durability. Appropriate catalysts and MEA configuration were down-selected that protects the membrane, and the layers were tailored to optimize the movements of reactants and product water through the cell to maximize performance while maintaining durability.

  20. Spectroscopic studies of surface-gas interactions and catalyst restructuring at ambient pressure: mind the gap!

    International Nuclear Information System (INIS)

    Rupprechter, Guenther; Weilach, Christian

    2008-01-01

    Recent progress in the application of surface vibrational spectroscopy at ambient pressure allows us to monitor surface-gas interactions and heterogeneous catalytic reactions under conditions approaching those of technical catalysis. The surface specificity of photon-based methods such as polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and sum frequency generation (SFG) spectroscopy is utilized to monitor catalytically active surfaces while they function at high pressure and high temperature. Together with complementary information from high-pressure x-ray photoelectron spectroscopy (HP-XPS) and high-resolution transmission electron microscopy (HRTEM), reaction mechanisms can be deduced on a molecular level. Well defined model catalysts, prepared under ultrahigh vacuum (UHV), are typically employed in such studies, including smooth and stepped single crystals, thin oxide films, and oxide-supported nanoparticles. A number of studies on unsupported and supported noble metal (Pd, Rh) catalysts are presented, focusing on the transformation of the catalysts from the 'as-prepared' to the 'active state'. This often involves pronounced alterations in catalyst structure and composition, for example the creation of surface carbon phases, surface oxides or surface alloys, as well as nanoparticle restructuring. The reactivity studies include CH 3 OH, CH 4 and CO oxidation with gas phase analysis by gas chromatography and mass spectrometry. Differing results between studies under ultrahigh vacuum and ambient pressure, and between studies on single crystals and supported nanoparticles, demonstrate the importance of 'minding the gap' between idealized and realistic conditions

  1. Highly active carbon supported Pd cathode catalysts for direct formic acid fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Mikolajczuk-Zychora, A., E-mail: amikolajczuk@ichf.edu.pl [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Borodzinski, A.; Kedzierzawski, P.; Mierzwa, B. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Mazurkiewicz-Pawlicka, M. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Faculty of Chemical and Process Engineering, Warsaw University of Technology, Warynskiego 1, Warsaw (Poland); Stobinski, L. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Faculty of Chemical and Process Engineering, Warsaw University of Technology, Warynskiego 1, Warsaw (Poland); Ciecierska, E. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Zimoch, A.; Opałło, M. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland)

    2016-12-01

    Highlights: • Palladium catalyst used on the cathode DFAFC is comparable to commercial platinum catalyst. • The treatment of carbon supports in nitric acid(V) increases the electrochemically available metal surface area and the catalytic activity in oxygen reduction reaction of catalysts. - Abstract: One of the drawbacks of low-temperature fuel cells is high price of platinum-based catalysts used for the electroreduction of oxygen at the cathode of the fuel cell. The aim of this work is to develop the palladium catalyst that will replace commonly used platinum cathode catalysts. A series of palladium catalysts for oxygen reduction reaction (ORR) were prepared and tested on the cathode of Direct Formic Acid Fuel Cell (DFAFC). Palladium nanoparticles were deposited on the carbon black (Vulcan) and on multiwall carbon nanotubes (MWCNTs) surface by reduction of palladium(II) acetate dissolved in ethanol. Hydrazine was used as a reducing agent. The effect of functionalization of the carbon supports on the catalysts physicochemical properties and the ORR catalytic activity on the cathode of DFAFC was studied. The supports were functionalized by treatment in nitric acid for 4 h at 80 °C. The structure of the prepared catalysts has been characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry (CV). Hydrophilicity of the catalytic layers was determined by measuring contact angles of water droplets. The performance of the prepared catalysts has been compared with that of the commercial 20 wt.% Pt/C (Premetek) catalyst. The maximum power density obtained for the best palladium catalyst, deposited on the surface of functionalized carbon black, is the same as that for the commercial Pt/C (Premetek). Palladium is cheaper than platinum, therefore the developed cathode catalyst is promising for future applications.

  2. Highly active carbon supported Pd cathode catalysts for direct formic acid fuel cells

    Science.gov (United States)

    Mikolajczuk-Zychora, A.; Borodzinski, A.; Kedzierzawski, P.; Mierzwa, B.; Mazurkiewicz-Pawlicka, M.; Stobinski, L.; Ciecierska, E.; Zimoch, A.; Opałło, M.

    2016-12-01

    One of the drawbacks of low-temperature fuel cells is high price of platinum-based catalysts used for the electroreduction of oxygen at the cathode of the fuel cell. The aim of this work is to develop the palladium catalyst that will replace commonly used platinum cathode catalysts. A series of palladium catalysts for oxygen reduction reaction (ORR) were prepared and tested on the cathode of Direct Formic Acid Fuel Cell (DFAFC). Palladium nanoparticles were deposited on the carbon black (Vulcan) and on multiwall carbon nanotubes (MWCNTs) surface by reduction of palladium(II) acetate dissolved in ethanol. Hydrazine was used as a reducing agent. The effect of functionalization of the carbon supports on the catalysts physicochemical properties and the ORR catalytic activity on the cathode of DFAFC was studied. The supports were functionalized by treatment in nitric acid for 4 h at 80 °C. The structure of the prepared catalysts has been characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry (CV). Hydrophilicity of the catalytic layers was determined by measuring contact angles of water droplets. The performance of the prepared catalysts has been compared with that of the commercial 20 wt.% Pt/C (Premetek) catalyst. The maximum power density obtained for the best palladium catalyst, deposited on the surface of functionalized carbon black, is the same as that for the commercial Pt/C (Premetek). Palladium is cheaper than platinum, therefore the developed cathode catalyst is promising for future applications.

  3. Effects of Activated Carbon Surface Property on Structure and Activity of Ru/AC Catalysts

    Science.gov (United States)

    Xu, S. K.; Li, L. M.; Guo, N. N.

    2018-05-01

    The activated carbon (AC) was modified by supercritical (SC) methanol, HNO3 oxidation, or HNO3 oxidation plus SC methanol, respectively. Then, the original and the modified AC were used as supports for Ru/AC catalysts prepared via the impregnation method. The results showed that the SC methanol modification decreased the content of surface acidic groups of AC. While HNO3 oxidation displayed the opposite behavior. Furthermore, the dispersion of ruthenium and the activity of catalysts were highly dependent on the content of surface acidic groups, and the SC methanol modified sample exhibited the highest activity for hydrogenation of glucose.

  4. Characterization of a surface modified carbon cryogel and a carbon supported Pt catalyst

    Directory of Open Access Journals (Sweden)

    BILJANA M. BABIĆ

    2007-08-01

    Full Text Available A carbon cryogel, synthesized by carbonization of a resorcinol/formaldehyde cryogel and oxidized in nitric acid, was used as catalyst support for Pt nano-particles. The Pt/C catalyst was prepared by a modified polyol synthesis method in an ethylene glycol (EG solution. Characterization by nitrogen adsorption showed that the carbon cryogel support and the Pt/C catalyst were mesoporous materials with high specific surface areas (SBET > 400 m2 g-1 and large mesoporous volumes. X-Ray diffraction of the catalyst demonstrated the successful reduction of the Pt precursor to metallic form. TEM Images of the Pt/C catalyst and Pt particle size distribution showed that the mean Pt particle size was about 3.3 nm. Cyclic voltammetry (CV experiments at various scan rates (from 2 to 200 mV s-1 were performed in 0.5 mol dm-3 HClO4 solution. The large capacitance of the oxidized carbon cryogel electrode, which arises from a combination of the double-layer capacitance and pseudocapacitance, associated with the participation of surface redox-type reactions was demonstrated. For the oxidized carbon cryogel, the total specific capacitance determined by 1/C vs. ν0.5 extrapolation method was found to be 386 F g-1. The hydrogen oxidation reaction at the investigated Pt/C catalyst proceeded as an electrochemically reversible, two-electron direct discharge reaction.

  5. COATING OF POLYMERIC SUBSTRATE CATALYSTS ON METALLIC SURFACES

    Directory of Open Access Journals (Sweden)

    H. HOSSEINI

    2010-12-01

    Full Text Available This article presents results of a study on coating of a polymeric substrate ca-talyst on metallic surface. Stability of coating on metallic surfaces is a proper specification. Sol-gel technology was used to synthesize adhesion promoters of polysilane compounds that act as a mediator. The intermediate layer was coated by synthesized sulfonated polystyrene-divinylbenzene as a catalyst for production of MTBE in catalytic distillation process. Swelling of catalyst and its separation from the metal surface was improved by i increasing the quantity of divinylbenzene in the resin’s production process and ii applying adhesion pro¬moters based on the sol-gel process. The rate of ethyl silicate hydrolysis was intensified by increasing the concentration of utilized acid while the conden¬sation polymerization was enhanced in the presence of OH–. Sol was formed at pH 2, while the pH should be 8 for the formation of gel. By setting the ratio of the initial concentrations of water to ethyl silicate to 8, the gel formation time was minimized.

  6. Flame spray deposition of porous catalysts on surfaces and in microsystems

    DEFF Research Database (Denmark)

    Thybo, Susanne; Jensen, Søren; Johansen, Johnny

    2004-01-01

    Flame spray synthesis is investigated as a method for one step synthesis and deposition of porous catalysts onto surfaces and into microreactors. Using a standard photolithographic lift-off process, catalyst can be deposited on flat surfaces in patterns with sub-millimeter feature sizes....... With shadow masks, porous catalyst layers can be deposited selectively into microchannels. Using Au/TiO$_2$ as test catalyst and CO-oxidation as test reaction, it is found that the apparent activation energy of the deposited catalyst is similar to what is normally seen for supported gold catalysts...

  7. Controlled surface segregation leads to efficient coke-resistant nickel/platinum bimetallic catalysts for the dry reforming of methane

    KAUST Repository

    Li, Lidong; Zhou, Lu; Ould-Chikh, Samy; Anjum, Dalaver; Kanoun, Mohammed; Scaranto, Jessica; Hedhili, Mohamed Nejib; Khalid, Syed; Laveille, Paco; D'Souza, Lawrence; Clo, Alain M.; Basset, Jean-Marie

    2015-01-01

    Surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. The evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core-shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. These catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure. The reform of reforming: A series of alumina-supported Ni/Pt bimetallic nanoparticles (NPs) with controlled surface composition and structure are prepared. Remarkable surface segregation for these bimetallic NPs is observed upon thermal treatment. These bimetallic NPs are active catalysts for CO2 reforming of CH4, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.

  8. Controlled surface segregation leads to efficient coke-resistant nickel/platinum bimetallic catalysts for the dry reforming of methane

    KAUST Repository

    Li, Lidong

    2015-02-03

    Surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. The evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core-shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. These catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure. The reform of reforming: A series of alumina-supported Ni/Pt bimetallic nanoparticles (NPs) with controlled surface composition and structure are prepared. Remarkable surface segregation for these bimetallic NPs is observed upon thermal treatment. These bimetallic NPs are active catalysts for CO2 reforming of CH4, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.

  9. Highly Durable Platinum Single-Atom Alloy Catalyst for Electrochemical Reactions

    DEFF Research Database (Denmark)

    Kim, Jiwhan; Roh, Chi-Woo; Sahoo, Suman Kalyan

    2018-01-01

    Single atomic Pt catalyst can offer efficient utilization of the expensive platinum and provide unique selectivity because it lacks ensemble sites. However, designing such a catalyst with high Pt loading and good durability is very challenging. Here, single atomic Pt catalyst supported on antimony...... functional theory calculations show that replacing Sb sites with Pt atoms in the bulk phase or at the surface of SbSn or ATO is energetically favorable. The Pt1/ATO shows superior activity and durability for formic acid oxidation reaction, compared to a commercial Pt/C catalyst. The single atomic Pt...... structure is retained even after a harsh durability test, which is performed by repeating cyclic voltammetry in the range of 0.05–1.4 V for 1800 cycles. A full cell is fabricated for direct formic acid fuel cell using the Pt1/ATO as an anode catalyst, and an order of magnitude higher cell power is obtained...

  10. Thermal effects in highly dispersed iron catalysts

    International Nuclear Information System (INIS)

    Alvarez, A.M.; Cagnoli, M.V.; Gallegos, N.G.; Marchetti, S.G.; Yeramian, A.A.; Mercader, R.C.

    1994-01-01

    The Moessbauer spectra of three Fe/SiO 2 catalysts with 5 wt% iron content show the presence of several Fe species and display different magnetic behaviours when the precursors are subjected to various thermal treatments. Based on the Moessbauer parameters and CO chemisorption measurements, the average crystal sizes of the catalysts are estimated and discussed in connection with the thermal pretreatment severity and magnetic properties of the samples. (orig.)

  11. Surface spectroscopic characterization of a model methane-activation catalyst

    International Nuclear Information System (INIS)

    Chen, J.G.; Weisel, M.D.; Hoffmann, F.M.; Hall, R.B.

    1992-01-01

    In an effort to understand the details concerning the alkali-promoted selectivity for the oxidative coupling of methane, the authors have carried out a detailed characterization of a model K/NiO/Ni(100) catalyst under well-controlled, ultrahigh vacuum conditions. The authors' systematic approach involved the following procedures: detailed investigation of the formation and structure of NiO on a clean Ni(100) surface; spectroscopic characterization of K-doped NiO by in situ deposition of potassium onto well-characterized NiO/Ni(100) substrate; and determination of the reactivities of NiO/Ni(100) and K/NiO/Ni(100) towards H 2 and CH 4 . In this paper, the authors will use the model K/NiO/Ni(100) system as an example to demonstrate that a detailed, complementary characterization of the model catalyst could best be achieved by using a combination of a variety of surface techniques: The methods of HREELS, LEED, XPS and AES could be applied to obtain properties on and near the surface regions; the technique of FYNES, being a photon-in/photon-out method could be utilized to investigate the bulk properties up to 2000 Angstrom below the surface; the method of FTIR using CO as a probing molecule is, on the other hand, sensitive only to the properties of the top-most surface layer. The result is to be presented in this paper will be mainly those obtained by using the two vibrational spectroscopies (HREELS and FTIR). Results from other surface techniques will also be discussed or presented when they provide additional information to the vibrational data

  12. Facile synthesis of porous graphene-like carbon nitride nanosheets with high surface area and enhanced photocatalytic activity via one-step catalyst-free solution self-polymerization

    Science.gov (United States)

    Wu, Shikai; Wen, Shengwu; Xu, Xinmei; Huang, Guozhi; Cui, Yifan; Li, Jinyu; Qu, Ailan

    2018-04-01

    Porous graphite carbon nitride nanosheets (g-C3N4) are achieved via one-step catalyst-free solution self-polymerization from a single melamine precursor. The resultant porous g-C3N4 nanosheets with the best photodegradation capacity provided the surface area of 669.15 m2/g, which is superior to the surface area of any other porous g-C3N4 reported. Results showed enhanced adsorption and degradation capacity of methyl orange (MO) under UV-visible light irradiation (λ > 350 nm) compared to bulk g-C3N4. The MO oxidation of the porous g-C3N4 nanosheets is driven mostly by the participation of holes, and secondly by rad O2- and rad OH radicals. This approach shed lights on porous g-C3N4 production simply by self-polycondensation of single functional monomer. It also provided a low-cost and eco-friendly method to facilely mass-produce g-C3N4 nanosheets with high surface area for many potential applications.

  13. Development of Highly Nano-Dispersed NiO/GDC Catalysts from Ion Exchange Resin Templates

    Directory of Open Access Journals (Sweden)

    Angel Caravaca

    2017-11-01

    Full Text Available Novel NiO/GDC (Gadolinium-doped Ceria cermet catalysts were developed by the Weak Acid Resin (WAR method using an ion exchange resin template. In addition, the specific surface area of these tunable materials was enhanced by NiO partial dissolution in aqueous acid solution. The whole procedure highly improved the micro-structural properties of these materials compared to previous studies. Catalysts with high metal loadings (≥10%, small Ni nanoparticles (<10 nm, and high specific surface areas (>70 m2/g were achieved. These properties are promising for catalytic applications such as methane steam reforming for H2 production.

  14. Porous bimetallic PdNi catalyst with high electrocatalytic activity for ethanol electrooxidation.

    Science.gov (United States)

    Feng, Yue; Bin, Duan; Yan, Bo; Du, Yukou; Majima, Tetsuro; Zhou, Weiqiang

    2017-05-01

    Porous bimetallic PdNi catalysts were fabricated by a novel method, namely, reduction of Pd and Ni oxides prepared via calcining the complex chelate of PdNi-dimethylglyoxime (PdNi-dmg). The morphology and composition of the as-prepared PdNi were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Furthermore, the electrochemical properties of PdNi catalysts towards ethanol electrooxidation were also studied by electrochemical impedance spectrometry (EIS), cyclic voltammetry (CV) and chronoamperometry (CA) measurement. In comparison with porous Pd and commercial Pd/C catalysts, porous structural PdNi catalysts showed higher electrocatalytic activity and durability for ethanol electrooxidation, which may be ascribed to Pd and Ni property, large electroactive surface area and high electron transfer property. The Ni exist in the catalyst in the form of the nickel hydroxides (Ni(OH) 2 and NiOOH) which have a high electron and proton conductivity enhances the catalytic activity of the catalysts. All results highlight the great potential application of the calcination-reduction method for synthesizing high active porous PdNi catalysts in direct ethanol fuel cells. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Surface science approach to Pt/carbon model catalysts: XPS, STM and microreactor studies

    Science.gov (United States)

    Motin, Abdul Md.; Haunold, Thomas; Bukhtiyarov, Andrey V.; Bera, Abhijit; Rameshan, Christoph; Rupprechter, Günther

    2018-05-01

    Pt nanoparticles supported on carbon are an important technological catalyst. A corresponding model catalyst was prepared by physical vapor deposition (PVD) of Pt on sputtered HOPG (highly oriented pyrolytic graphite). The carbon substrate before and after sputtering as well as the Pt/HOPG system before and after Pt deposition and annealing were examined by XPS and STM. This yielded information on the surface density of defects, which serve as nucleation centres for Pt, and on the size distribution (mean size/height) of the Pt nanoparticles. Two different model catalysts were prepared with mean sizes of 2.0 and 3.6 nm, both turned out to be stable upon UHV-annealing to 300 °C. After transfer into a UHV-compatible flow microreactor and subsequent cleaning in UHV and under mbar pressure, the catalytic activity of the Pt/HOPG model system for ethylene hydrogenation was examined under atmospheric pressure flow conditions. This enabled to determine temperature-dependent conversion rates, turnover frequencies (TOFs) and activation energies. The catalytic results obtained are in line with the characteristics of technological Pt/C, demonstrating the validity of the current surface science based model catalyst approach.

  16. Surface heterogeneity and ionization of Cs promoter in carbon-based ruthenium catalyst for ammonia synthesis

    International Nuclear Information System (INIS)

    Kotarba, Andrzej; Dmytrzyk, Jaromir; Rarog-Pilecka, Wioletta; Kowalczyk, Zbigniew

    2003-01-01

    Second-generation ammonia synthesis cesium-doped ruthenium catalyst supported on turbostratic carbon was investigated by the species resolved thermal alkali desorption method (SR-TAD). Energetic barriers for cesium ions (2.86 eV), ground state (1.96 eV) and electronically excited atoms (5.76 eV) desorbing from the Cs-Ru/C catalyst were determined. In the case of ruthenium-free Cs/C system, cesium desorbs as ground state atoms only, with an energy barrier of 2.87 eV. The work functions determined by the thermionic emission of electrons from Cs/C and Cs-Ru/C were of the same value (2.9 eV). It was concluded that ruthenium induces heterogeneous distribution of cesium on the catalyst surface. The promoter stability is reduced on low work function areas and its surface ionization on high work function areas opens the ionic desorption channel. The Cs desorption from the catalyst is discussed in terms of the literature data for the cesium/graphite system

  17. Spatially Resolved Quantification of the Surface Reactivity of Solid Catalysts.

    Science.gov (United States)

    Huang, Bing; Xiao, Li; Lu, Juntao; Zhuang, Lin

    2016-05-17

    A new property is reported that accurately quantifies and spatially describes the chemical reactivity of solid surfaces. The core idea is to create a reactivity weight function peaking at the Fermi level, thereby determining a weighted summation of the density of states of a solid surface. When such a weight function is defined as the derivative of the Fermi-Dirac distribution function at a certain non-zero temperature, the resulting property is the finite-temperature chemical softness, termed Fermi softness (SF ), which turns out to be an accurate descriptor of the surface reactivity. The spatial image of SF maps the reactive domain of a heterogeneous surface and even portrays morphological details of the reactive sites. SF analyses reveal that the reactive zones on a Pt3 Y(111) surface are the platinum sites rather than the seemingly active yttrium sites, and the reactivity of the S-dimer edge of MoS2 is spatially anisotropic. Our finding is of fundamental and technological significance to heterogeneous catalysis and industrial processes demanding rational design of solid catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Highly active and durable Ca-doped Ce-SBA-15 catalyst for biodiesel production

    International Nuclear Information System (INIS)

    Thitsartarn, Warintorn; Maneerung, Thawatchai; Kawi, Sibudjing

    2015-01-01

    In this work, Ca-doped Ce-incorporated SBA-15 (Ca/CeS) catalyst was successfully synthesized by using direct synthesis of Ce-incorporated SBA-15 followed by impregnation of CaO (calcium oxide). The maximum Si/Ce molar ratio that Ce atoms can be incorporated successfully into the mesoporous framework was found to be 5 (CeS-5). After the impregnation of 30 wt. % Ca, the obtained 30Ca/CeS-5 catalysts showed the superior catalytic performance for transesterification reaction of palm oil with methanol and also the higher catalytic activity as compared to other supported catalysts, i.e. CaO/CeO 2 and CaO–CeO 2 /SBA-15. This can be attributed to the well-dispersion of CaO on the CeS-5 support surface. Furthermore, it was found that the leaching of Si, Ce and Ca from the catalyst into biodiesel produced was negligible (i.e. <1 ppm after 7 cycles), indicating the strong interaction between CaO and CeS-5 support. As a result, the 30Ca/CeS-5 catalyst can be reused at least 15 cycles with insignificant decrease in catalytic activity, offering the efficient CaO-based catalyst for biodiesel production. - Highlights: • Mesoporous Ca-based catalyst was successfully developed for biodiesel production. • Catalyst exhibited high activity towards transesterification (FAME yield > 98%). • Catalyst can be effectively re-used at least 15 cycles. • Extremely low catalyst contaminant (<1 ppm) was presented

  19. High activity PtRu/C catalysts synthesized by a modified impregnation method for methanol electro-oxidation

    International Nuclear Information System (INIS)

    Ma Liang; Liu Changpeng; Liao Jianhui; Lu Tianhong; Xing Wei; Zhang Jiujun

    2009-01-01

    A modified impregnation method was used to prepare highly dispersive carbon-supported PtRu catalyst (PtRu/C). Two modifications to the conventional impregnation method were performed: one was to precipitate the precursors ((NH 4 ) 2 PtCl 6 and Ru(OH) 3 ) on the carbon support before metal reduction; the other was to add a buffer into the synthetic solution to stabilize the pH. The prepared catalyst showed a much higher activity for methanol electro-oxidation than a catalyst prepared by the conventional impregnation method, even higher than that of current commercially available, state-of-the-art catalysts. The morphology of the prepared catalyst was characterized using TEM and XRD measurements to determine particle sizes, alloying degree, and lattice parameters. Electrochemical methods were also used to ascertain the electrochemical active surface area and the specific activity of the catalyst. Based on XPS measurements, the high activity of this catalyst was found to originate from both metallic Ru (Ru 0 ) and hydrous ruthenium oxides (RuO x H y ) species on the catalyst surface. However, RuO x H y was found to be more active than metallic Ru. In addition, the anhydrous ruthenium oxide (RuO 2 ) species on the catalyst surface was found to be less active.

  20. Pt Monolayer Shell on Nitrided Alloy Core—A Path to Highly Stable Oxygen Reduction Catalyst

    Directory of Open Access Journals (Sweden)

    Jue Hu

    2015-07-01

    Full Text Available The inadequate activity and stability of Pt as a cathode catalyst under the severe operation conditions are the critical problems facing the application of the proton exchange membrane fuel cell (PEMFC. Here we report on a novel route to synthesize highly active and stable oxygen reduction catalysts by depositing Pt monolayer on a nitrided alloy core. The prepared PtMLPdNiN/C catalyst retains 89% of the initial electrochemical surface area after 50,000 cycles between potentials 0.6 and 1.0 V. By correlating electron energy-loss spectroscopy and X-ray absorption spectroscopy analyses with electrochemical measurements, we found that the significant improvement of stability of the PtMLPdNiN/C catalyst is caused by nitrogen doping while reducing the total precious metal loading.

  1. Highly Selective TiN-Supported Highly Dispersed Pt Catalyst: Ultra Active toward Hydrogen Oxidation and Inactive toward Oxygen Reduction.

    Science.gov (United States)

    Luo, Junming; Tang, Haibo; Tian, Xinlong; Hou, Sanying; Li, Xiuhua; Du, Li; Liao, Shijun

    2018-01-31

    The severe dissolution of the cathode catalyst, caused by an undesired oxygen reduction reaction at the anode during startup and shutdown, is a fatal challenge to practical applications of polymer electrolyte membrane fuel cells. To address this important issue, according to the distinct structure-sensitivity between the σ-type bond in H 2 and the π-type bond in O 2 , we design a HD-Pt/TiN material by highly dispersing Pt on the TiN surface to inhibit the unwanted oxygen reduction reaction. The highly dispersed Pt/TiN catalyst exhibits excellent selectivity toward hydrogen oxidation and oxygen reduction reactions. With a Pt loading of 0.88 wt %, our catalyst shows excellent hydrogen oxidation reaction activity, close to that of commercial 20 wt % Pt/C catalyst, and much lower oxygen reduction reaction activity than the commercial 20 wt % Pt/C catalyst. The lack of well-ordered Pt facets is responsible for the excellent selectivity of the HD-Pt/TiN materials toward hydrogen oxidation and oxygen reduction reactions. Our work provides a new and cost-effective solution to design selective catalysts toward hydrogen oxidation and oxygen reduction reactions, making the strategy of using oxygen-tolerant anode catalyst to improve the stability of polymer electrolyte membrane fuel cells during startup and shutdown more affordable and practical.

  2. A surface science study of model catalysts : II metal-support interactions in Cu/SiO2 model catalysts

    NARCIS (Netherlands)

    Oetelaar, van den L.C.A.; Partridge, A.; Toussaint, S.L.G.; Flipse, C.F.J.; Brongersma, H.H.

    1998-01-01

    The thermal stability of wet-chemically prepared Cu/SiO2 model catalysts containing nanometer-sized Cu particles on silica model supports was studied upon heating in hydrogen and ultrahigh vacuum. The surface and interface phenomena that occur are determined by the metal-support interactions.

  3. High Performance Fe- and N- Doped Carbon Catalyst with Graphene Structure for Oxygen Reduction

    Science.gov (United States)

    Peng, Hongliang; Mo, Zaiyong; Liao, Shijun; Liang, Huagen; Yang, Lijun; Luo, Fan; Song, Huiyu; Zhong, Yiliang; Zhang, Bingqing

    2013-05-01

    Proton exchange membrane fuel cells are promising candidates for a clean and efficient energy conversion in the future, the development of carbon based inexpensive non-precious metal ORR catalyst has becoming one of the most attractive topics in fuel cell field. Herein we report a Fe- and N- doped carbon catalyst Fe-PANI/C-Mela with graphene structure and the surface area up to 702 m2 g-1. In 0.1 M HClO4 electrolyte, the ORR onset potential for the catalyst is high up to 0.98 V, and the half-wave potential is only 60 mV less than that of the Pt/C catalyst (Loadings: 51 μg Pt cm-2). The catalyst shows high stability after 10,000 cyclic voltammetry cycles. A membrane electrode assembly made with the catalyst as a cathode is tested in a H2-air single cell, the maximum power density reached ~0.33 W cm2 at 0.47 V.

  4. Surface chemistry and catalytic properties of VOX/Ti-MCM-41 catalysts for dibenzothiophene oxidation in a biphasic system

    Science.gov (United States)

    González, J.; Chen, L. F.; Wang, J. A.; Manríquez, Ma.; Limas, R.; Schachat, P.; Navarrete, J.; Contreras, J. L.

    2016-08-01

    A series of vanadium oxide supported on Ti-MCM-41 catalysts was synthesized via the incipient impregnation method by varying the vanadia loading from 5 wt% to 10, 15, 20 and 25 wt%. These catalysts were characterized by a variety of advanced techniques for investigating their crystalline structure, textural properties, and surface chemistry information including surface acidity, reducibility, vanadium oxidation states, and morphological features. The catalytic activities of the catalysts were evaluated in a biphasic reaction system for oxidative desulfurization (ODS) of a model diesel containing 300 ppm of dibenzothiophene (DBT) where acetonitrile was used as extraction solvent and H2O2 as oxidant. ODS activity was found to be proportional to the V5+/(V4+ + V5+) values of the catalysts, indicating that the surface vanadium pentoxide (V2O5) was the active phase. Reaction temperature would influence significantly the ODS efficiency; high temperature, i.e., 80 °C, would lead to low ODS reaction due to the partial decomposition of oxidant. All the catalysts contained both Lewis and Brønsted acid sites but the former was predominant. The catalysts with low vanadia loading (5 or 10 wt%V2O5) had many Lewis acid sites and could strongly adsorb DBT molecule via the electron donation/acceptance action which resulted in an inhibition for the reaction of DBT with the surface peroxometallic species. The catalyst with high vanadia loading (25wt%V2O5/Ti-MCM-41) showed the highest catalytic activity and could remove 99.9% of DBT at 60 °C within 60 min.

  5. Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

    2015-09-14

    Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co3O4 or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

  6. Exposure of metallic copper surface on Cu-Al2O3-carbon catalysts

    NARCIS (Netherlands)

    Menon, P.G.; Prasad, J.

    1970-01-01

    The bifunctional nature of Cu---Al2O3-on-carbon catalysts, used in the direct catalytic conversion of ethanol to ethyl acetate, prompted an examination of the dispersion of Cu on the composite catalyst. For this, the N2O-method of Osinga et al. for estimation of bare metallic copper surface on

  7. Recent progress in synthesis and surface functionalization of mesoporous acidic heterogeneous catalysts for esterification of free fatty acid feedstocks: A review

    International Nuclear Information System (INIS)

    Soltani, Soroush; Rashid, Umer; Al-Resayes, Saud Ibrahim; Nehdi, Imededdine Arbi

    2017-01-01

    Highlights: • Mesoporous catalysts have potential to esterify the wastes feedstocks. • Surface area of mesoporous catalysts depends on materials synthesis methods. • Hydrophobic surface of sulfonated catalyst causes adsorption on FFA particles. • Mesoporous catalysts have large active sites to trap free fatty acids particles. • Recyclability of mesoporous catalyst is a key feature for biodiesel production. - Abstract: Biodiesel is considered as a sulfur free, non-toxic and biodegradable source of energy and its burning provide less pollution than petroleum based fuels. In case of using fried waste oils, animal’s fats and waste cultivated oil which contain high free fatty acid (FFA), esterification is taking place. Through esterification reaction, catalyst is an integral part which accelerates the FFA conversion to the methyl ester (ME) in shorter reaction time. Although, most of the current catalysts have some defect such as poor recyclability, less surface area and poor porosity. Mesoporous materials have been recently attracted remarkable interests because of its desirable properties, such as large and harmonized surface area, tuneable mesoporous channels with flexible pore size, excellent thermal stability, and post-functionalization surface characteristics. The combination of remarkable physico-chemical and textural properties as well as high activity has proposed them as advanced materials. In this review, it has been attempted to present the details of fundamental properties of mesoporous catalysts, various synthetic methods and formation mechanisms, and surface functionalization methodologies. The effects of various factors (such as surface area, porosity, acidity, post-calcination temperature, and reaction parameters) on esterification of different feedstocks are discussed in detail. Furthermore, the kinetic study of esterification reaction in the presence of mesoporous catalysts is also elaborated. At the end, remarkable challenges and outlooks

  8. NO oxidation on Zeolite Supported Cu Catalysts: Formation and Reactivity of Surface Nitrates

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2016-04-18

    The comparative activities of a small-pore Cu-CHA and a large-pore Cu-BEA catalyst for the selective catalytic reduction (SCR) of NOx with NH3, and for the oxidation of NO to NO2 and the subsequent formation of surface nitrates were investigated. Although both catalysts are highly active in SCR reactions, they exhibit very low NO oxidation activity. Furthermore, Cu-CHA is even less active than Cu-BEA in catalyzing NO oxidation but is clearly more active for SCR reactions. Temperature-programed desorption (TPD) experiments following the adsorption of (NO2 + NO + O2) with different NO2:NO ratios reveal that the poor NO oxidation activity of the two catalysts is not due to the formation of stable surface nitrates. On the contrary, NO is found to reduce and decompose the surface nitrates on both catalysts. To monitor the reaction pathways, isotope exchange experiments were conducted by using 15NO to react with 14N-nitrate covered catalyst surfaces. The evolution of FTIR spectra during the isotope exchange process demonstrates that 14N-nitrates are simply displaced with no formation of 15N-nitrates on the Cu-CHA sample, which is clearly different from that observed on the Cu-BEA sample where formation of 15N-nitrates is apparent. The results suggest that the formal oxidation state of N during the NO oxidation on Cu-CHA mainly proceeds from its original +2 to a +3 oxidation state, whereas reaching a higher oxidation state for N, such as +4 or +5, is possible on Cu-BEA. The authors at PNNL gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  9. Final Technical Report: Metal—Organic Surface Catalyst for Low-temperature Methane Oxidation: Bi-functional Union of Metal—Organic Complex and Chemically Complementary Surface

    Energy Technology Data Exchange (ETDEWEB)

    Tait, Steven L. [Indiana Univ., Bloomington, IN (United States)

    2016-10-01

    Stabilization and chemical control of transition metal centers is a critical problem in the advancement of heterogeneous catalysts to next-generation catalysts that exhibit high levels of selectivity, while maintaining strong activity and facile catalyst recycling. Supported metal nanoparticle catalysts typically suffer from having a wide range of metal sites with different coordination numbers and varying chemistry. This project is exploring new possibilities in catalysis by combining features of homogeneous catalysts with those of heterogeneous catalysts to develop new, bi-functional systems. The systems are more complex than traditional heterogeneous catalysts in that they utilize sequential active sites to accomplish the desired overall reaction. The interaction of metal—organic catalysts with surface supports and their interactions with reactants to enable the catalysis of critical reactions at lower temperatures are at the focus of this study. Our work targets key fundamental chemistry problems. How do the metal—organic complexes interact with the surface? Can those metal center sites be tuned for selectivity and activity as they are in the homogeneous system by ligand design? What steps are necessary to enable a cooperative chemistry to occur and open opportunities for bi-functional catalyst systems? Study of these systems will develop the concept of bringing together the advantages of heterogeneous catalysis with those of homogeneous catalysis, and take this a step further by pursuing the objective of a bi-functional system. The use of metal-organic complexes in surface catalysts is therefore of interest to create well-defined and highly regular single-site centers. While these are not likely to be stable in the high temperature environments (> 300 °C) typical of industrial heterogeneous catalysts, they could be applied in moderate temperature reactions (100-300 °C), made feasible by lowering reaction temperatures by better catalyst control. They also

  10. Critical Surface Parameters for the Oxidative Coupling of Methane over the Mn-Na-W/SiO2 Catalyst.

    Science.gov (United States)

    Hayek, Naseem S; Lucas, Nishita S; Warwar Damouny, Christine; Gazit, Oz M

    2017-11-22

    The work here presents a thorough evaluation of the effect of Mn-Na-W/SiO 2 catalyst surface parameters on its performance in the oxidative coupling of methane (OCM). To do so, we used microporous dealuminated β-zeolite (Zeo), or mesoporous SBA-15 (SBA), or macroporous fumed silica (Fum) as precursors for catalyst preparation, together with Mn nitrate, Mn acetate and Na 2 WO 4 . Characterizing the catalysts by inductively coupled plasma-optical emission spectroscopy, N 2 physisorption, X-ray diffraction, high-resolution scanning electron microscopy-energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and catalytic testing enabled us to identify critical surface parameters that govern the activity and C 2 selectivity of the Mn-Na-W/SiO 2 catalyst. Although the current paradigm views the phase transition of silica to α-cristobalite as the critical step in obtaining dispersed and stable metal sites, we show that the choice of precursors is equally or even more important with respect to tailoring the right surface properties. Specifically, the SBA-based catalyst, characterized by relatively closed surface porosity, demonstrated low activity and low C 2 selectivity. By contrast, for the same composition, the Zeo-based catalyst showed an open surface pore structure, which translated up to fourfold higher activity and enhanced selectivity. By varying the overall composition of the Zeo catalysts, we show that reducing the overall W concentration reduces the size of the Na 2 WO 4 species and increases the catalytic activity linearly as much as fivefold higher than the SBA catalyst. This linear dependence correlates well to the number of interfaces between the Na 2 WO 4 and Mn 2 O 3 species. Our results combined with prior studies lead us to single out the interface between Na 2 WO 4 and Mn 2 O 3 as the most probable active site for OCM using this catalyst. Synergistic interactions between the various precursors used and the phase transition are discussed in

  11. Yeast cell surface display for lipase whole cell catalyst and its applications

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yun; Zhang, Rui; Lian, Zhongshuai; Wang, Shihui; Wright, Aaron T.

    2014-08-01

    The cell surface display technique allows for the expression of target proteins or peptides on the microbial cell surface by fusing an appropriate protein as an anchoring motif. Yeast display systems, such as Pichia pastoris, Yarowia lipolytica and Saccharomyces cerevisiae, are ideal, alternative and extensive display systems with the advantage of simple genetic manipulation and post-translational modification of expressed heterologous proteins. Engineered yeasts show high performance characteristics and variant utilizations. Herein, we comprehensively summarize the variant factors affecting lipase whole cell catalyst activity and display efficiency, including the structure and size of target proteins, screening anchor proteins, type and chain length of linkers, and the appropriate matching rules among the above-mentioned display units. Furthermore, we also address novel approaches to enhance stability and activity of recombinant lipases, such as VHb gene co-expression, multi-enzyme co-display technique, and the micro-environmental interference and self-assembly techniques. Finally, we represent the variety of applications of whole cell surface displayed lipases on yeast cells in non-aqueous phases, including synthesis of esters, PUFA enrichment, resolution of chiral drugs, organic synthesis and biofuels. We demonstrate that the lipase surface display technique is a powerful tool for functionalizing yeasts to serve as whole cell catalysts, and increasing interest is providing an impetus for broad application of this technique.

  12. Partial hydrogenation of alkynes on highly selective nano-structured mesoporous silica MCM-41 composite catalyst

    International Nuclear Information System (INIS)

    Kojoori, R.K.

    2016-01-01

    In this research, we have developed a silica MCM-41/Metformin/Pd (II) nano composite catalyst for the selective hydrogenation of alkynes to the corresponding (Z)-alkenes under a mild condition of atmospheric pressure and room temperature. Firstly, functionalized Si-MCM-41 metformin catalyst with the optimum performance was prepared. Then, the synthesized catalyst was elucidated by X-ray powder diffraction, BET surface area, FT-IR spectrophotometer, Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) and applied in partial hydrogenation of different alkynes, with high selectivity and high yield. The products were characterized by 1H-NMR, 13C-NMR, FT-IR, and Mass Spectrometry (MS) that strongly approved the (Z)-double bond configuration of produced alkenes. This prepared catalyst is competitive with the best palladium catalysts known for the selective liquid phase hydrogenation of alkynes and can be easily recovered and regenerated with keeping high activity and selectivity over at least three cycles with a simple regeneration procedure. (author)

  13. Preparation, surface characterization and performance of a Fischer-Tropsch catalyst of cobalt supported on silica nanosprings

    International Nuclear Information System (INIS)

    Kengne, Blaise-Alexis Fouetio; Alayat, Abdulbaset M.; Luo, Guanqun; McDonald, Armando G.; Brown, Justin; Smotherman, Hayden; McIlroy, David N.

    2015-01-01

    Graphical abstract: - Highlights: • Determined that the reduction of Co nanoparticles on silica nanosprings 200 °C higher than the reduction temperature of Co in a solgel support. • The high reduction temperature of Co supported on silica nanosprings is attributed to the heat transfer properties of the nanosprings due to their high surface area. Co-silica nanospring Fischer-Tropsch catalyst can be used to produce drop in fuels such as JP-4. - Abstract: The reduction of cobalt (Co) catalyst supported on silica nanosprings for Fischer-Tropsch synthesis (FTS) has been monitored by X-ray photoelectron spectroscopy (XPS) and compared to FT catalytic activity. The cobalt is present in the starting catalyst as a Co 3 O 4 spinel phase. A two-step reduction of Co 3 O 4 to CoO and then to Co 0 is observed, which is consistent with the results of H 2 -temperature programmed reduction. During the reduction the two steps occur concurrently. The deconvolution of the Co 2p core level state for the catalyst reduced at 385 °C and 1.0 × 10 −6 Torr of H 2 revealed signatures of Co 0 , CoO, and Co 3 O 4 . The reduction saturates at a Co o concentration of approximately 41% after 20 h, which correlates with the activity and lifetime of the catalyst during FTS testing. Conversely, at 680 °C and 10 Torr of H 2 , the catalyst is completely reduced after 10 h. The evolution of the Co d-band at the Fermi level in the valence band XPS spectrum definitively verifies the metallic phase of Co. FTS evaluation of the Co/NS catalyst reduced at 609 °C showed higher production rate (3-fold) of C 6 -C 17 hydrocarbons than the catalyst reduced at 409 °C and is consistent with the XPS analysis.

  14. Oxidation catalyst

    Science.gov (United States)

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

    The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

  15. Nitrogen and Fluorine co-doped carbon catalyst with high oxygen reduction performance, prepared by pyrolyzing a mixture of melamine and PTFE

    International Nuclear Information System (INIS)

    Peng, Hongliang; Liu, Fangfang; Qiao, Xiaochang; Xiong, Ziang; Li, Xiuhua; Shu, Ting; Liao, Shijun

    2015-01-01

    Graphical abstract: A novel N and F co-doped metal-free doped carbon catalyst with three dimensional vesicles structures and ultra thin walls are prepared by pyrolyzing the mixture of melamine and PTFE. The catalyst has high N and F contents (13 and 6 at.%), and exhibits high ORR activity, high stability, and high limitation current density in both alkaline and acid medium. - Highlights: • N and F co-doped carbon catalyst was derived from the mixture of PTFE and melamine. • The N and F contents of the catalyst are up to 13 and 6 at.%, respectively. • The catalyst has three dimensional vesicles structure with ultra thin walls. • ORR activity of the catalyst is superior to that of Pt/C catalyst in alkaline medium. - Abstract: A novel nitrogen and fluorine co-doped carbon catalyst (C-Mela-PTFE) is prepared by pyrolyzing a mixture of melamine and polytetrafluoroethylene (PTFE), the catalyst has a three-dimensional vesicular structure with ultrathin wall, and exhibits excellent ORR performance in both alkaline and acidic mediums. In an alkaline medium, the catalyst exhibits superior ORR activity to that of commercial Pt/C catalyst. Notably, the ORR activity of the catalyst is just slightly lower than that of Pt/C catalyst in acidic medium. It is interesting that the ORR limiting current density of our C-Mela-PTFE catalyst is much higher than that of Pt/C catalyst. The effects of the melamine/PTFE ratio and the pyrolysis temperature on the catalyst's ORR performance are investigated. The optimal melamine/PTFE ratio by weight is 1:1.5, and the optimal pyrolysis temperature is 950 °C. The catalyst samples are characterized by XRD, SEM/TEM, Raman analysis, and XPS, the results reveal the ultra-thin-walled vesicular structure, high surface area and porosity, and high doping amounts of N and F of the catalyst. For the optimal sample, the N and F contents are up to 13 and 6 at.%, respectively, the proportion of pyridinic N is up to 45 at.% according to the

  16. Applications of Neutron Scattering in the Chemical Industry: Proton Dynamics of Highly Dispersed Materials, Characterization of Fuel Cell Catalysts, and Catalysts from Large-Scale Chemical Processes

    Science.gov (United States)

    Albers, Peter W.; Parker, Stewart F.

    The attractiveness of neutron scattering techniques for the detailed characterization of materials of high degrees of dispersity and structural complexity as encountered in the chemical industry is discussed. Neutron scattering picks up where other analytical methods leave off because of the physico-chemical properties of finely divided products and materials whose absorption behavior toward electromagnetic radiation and electrical conductivity causes serious problems. This is demonstrated by presenting typical applications from large-scale production technology and industrial catalysis. These include the determination of the proton-related surface chemistry of advanced materials that are used as reinforcing fillers in the manufacture of tires, where interrelations between surface chemistry, rheological properties, improved safety, and significant reduction of fuel consumption are the focus of recent developments. Neutron scattering allows surface science studies of the dissociative adsorption of hydrogen on nanodispersed, supported precious metal particles of fuel cell catalysts under in situ loading at realistic gas pressures of about 1 bar. Insight into the occupation of catalytically relevant surface sites provides valuable information about the catalyst in the working state and supplies essential scientific input for tailoring better catalysts by technologists. The impact of deactivation phenomena on industrial catalysts by coke deposition, chemical transformation of carbonaceous deposits, and other processes in catalytic hydrogenation processes that result in significant shortening of the time of useful operation in large-scale plants can often be traced back in detail to surface or bulk properties of catalysts or materials of catalytic relevance. A better understanding of avoidable or unavoidable aspects of catalyst deactivation phenomena under certain in-process conditions and the development of effective means for reducing deactivation leads to more energy

  17. New Method to Synthesize Highly Active and Durable Chemically Ordered fct-PtCo Cathode Catalyst for PEMFCs.

    Science.gov (United States)

    Jung, Won Suk; Popov, Branko N

    2017-07-19

    In the bottom-up synthesis strategy performed in this study, the Co-catalyzed pyrolysis of chelate-complex and activated carbon black at high temperatures triggers the graphitization reaction which introduces Co particles in the N-doped graphitic carbon matrix and immobilizes N-modified active sites for the oxygen reduction reaction (ORR) on the carbon surface. In this study, the Co particles encapsulated within the N-doped graphitic carbon shell diffuse up to the Pt surface under the polymer protective layer and forms a chemically ordered face-centered tetragonal (fct) Pt-Co catalyst PtCo/CCCS catalyst as evidenced by structural and compositional studies. The fct-structured PtCo/CCCS at low-Pt loading (0.1 mg Pt cm -2 ) shows 6% higher power density than that of the state-of-the-art commercial Pt/C catalyst. After the MEA durability test of 30 000 potential cycles, the performance loss of the catalyst is negligible. The electrochemical surface area loss is less than 40%, while that of commercial Pt/C is nearly 80%. After the accelerated stress test, the uniform catalyst distribution is retained and the mean particle size increases approximate 1 nm. The results obtained in this study indicated that highly stable compositional and structural properties of chemically ordered PtCo/CCCS catalyst contribute to its exceptional catalyst durability.

  18. Removal of carbonaceous deposits from the surface of cobalt-molybdate catalyst via oxidative regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, Y.; Furimsky, E.

    1986-10-01

    The oxidative regeneration of cobalt-molybdate catalyst used during the hydrodeoxygenation of a phenol solution and for hydrotreatment of Athabasca bitumen was carried out in a fixed-bed reactor. SO/sub 2/, CO and CO/sub 2/ were analysed as the major products. The surface area of the spent catalysts was the main factor influencing the initial rate of regeneration, i.e. the greater the surface area the higher the initial rate. A mechanism proposed includes 12 reactions which may play an important role in the overall burn-off of hydrotreatment catalysts. 10 refs., 4 figs., 3 tabs.

  19. Catalysts prepared by interaction of transition metal organometallic compounds with the surface of supporters

    International Nuclear Information System (INIS)

    Ryndin, Yu.A.; Kuznetsov, B.N.; Moroz, Eh.M.; Tripol'skij, A.A.; Ermakov, Yu.I.

    1977-01-01

    The phase composition and dispersion of the catalyst (W + Pt)/SiO 2 , subjected to oxidation and reduction at an elevated temperature was investigated by roentgenographic methods (radial distribution of atoms and broadening of X-ray lines). The X-ray data are compared with the results of chemisorption measurements of platinum dispersion in the specimens and their activity in reactions of benzene hydration and ethane hydrogenolysis. It has been established that catalysts reduced at 600 deg C and not subjected to oxidation, as well as catalysts oxidized at 200 deg C and then reduced at 600 deg C are characterized by a high platinum dispersion. The dispersion catalysts are noted for their activity in the reaction of benzene hydration and ethane hydrogenolysis. On the other hand, the activity of catalysts oxidized and reduced in rigid conditions (600 deg C, air) is much lower and is close to the activity of the coarsely dispersed PtSiO 2 catalyst

  20. The challenges of treating high strength wastewaters: CWAO using MWNT supported ruthenium catalysts

    International Nuclear Information System (INIS)

    GarcIa, J.; Gomes, H.T.; Figueiredo, J.L.; Faria, J.L.; Garcia, J.; Serp, P.; Kalck, P.

    2005-01-01

    High strength wastewaters containing aromatic compounds are normally not efficiently treated by conventional methods, including the common biological treatment. In these cases a more sophisticated approach is necessary to attain the desired levels of purification. Catalytic wet air oxidation (CWAO) using carbon based catalysts is employed worldwide as effective pre-treatment of effluents with these characteristics. Carbon materials are preferred as active catalysts or support for preparing them due to their morphological and structural characteristics. In the last 10 years, due to a tremendous development in materials production and processing, carbon nano-structures are becoming more accessible and common widening their range of applications [1]. In this context, the scope of the present work is to illustrate a potential use of multi-walled carbon nano-tubes (MWNT) supported ruthenium catalysts for catalytic wet air oxidation of aniline polluted wastewaters. The metal was supported by incipient wetness and excess impregnation, starting from liquid solutions of three different Ru precursors. Impregnation was carried out on modified MWNT, namely on MWNT-COOH (HNO 3 modified) and MWNT-COONa (HNO 3 /Na 2 CO 3 modified). For the 1% weight Ru/MWNT catalysts, the order of activities decreased in the sequence Ru(COD)(COT)≥RuCl 3 ≥Ru(C 5 H 5 ) 2 . The conversion of aniline after 45 min of reaction was 100% for the catalyst prepared with Ru(COD)(COT). The influence of the Ru precursor, preparation method and the support surface modification was studied comparing the conversion of aniline obtained for the different prepared Ru/MWNT catalysts (Figure 1). MWNT as support material, provide a significant metal dispersion with very small Ru nanoparticles (Figure 2) being observed. This will induce an efficient surface contact between the aniline molecule and the active sites [2]. The excellent catalytic performances of Ru/MWNT are explained in terms of the high dispersion of

  1. The challenges of treating high strength wastewaters: CWAO using MWNT supported ruthenium catalysts

    Energy Technology Data Exchange (ETDEWEB)

    GarcIa, J.; Gomes, H.T.; Figueiredo, J.L.; Faria, J.L. [Porto Univ., Lab. de Catalise e Materiais, Dept. de Engenharia Quimica, Faculdade de Engenharia (Portugal); Garcia, J. [Madrid Univ. Complutense, Grupo de Catalisis y Operaciones de Separacion, Dept. de Ingenieria Quimica, Facultad de Ciencias (Spain); Serp, P.; Kalck, P. [Ecole Nationale Superieure des Ingenieurs en Arts Chimiques et Technologiques, Lab. de Catalyse, Chimie Fine et Polymeres, 31 - Toulouse (France)

    2005-07-01

    High strength wastewaters containing aromatic compounds are normally not efficiently treated by conventional methods, including the common biological treatment. In these cases a more sophisticated approach is necessary to attain the desired levels of purification. Catalytic wet air oxidation (CWAO) using carbon based catalysts is employed worldwide as effective pre-treatment of effluents with these characteristics. Carbon materials are preferred as active catalysts or support for preparing them due to their morphological and structural characteristics. In the last 10 years, due to a tremendous development in materials production and processing, carbon nano-structures are becoming more accessible and common widening their range of applications [1]. In this context, the scope of the present work is to illustrate a potential use of multi-walled carbon nano-tubes (MWNT) supported ruthenium catalysts for catalytic wet air oxidation of aniline polluted wastewaters. The metal was supported by incipient wetness and excess impregnation, starting from liquid solutions of three different Ru precursors. Impregnation was carried out on modified MWNT, namely on MWNT-COOH (HNO{sub 3} modified) and MWNT-COONa (HNO{sub 3}/Na{sub 2}CO{sub 3} modified). For the 1% weight Ru/MWNT catalysts, the order of activities decreased in the sequence Ru(COD)(COT){>=}RuCl{sub 3}{>=}Ru(C{sub 5}H{sub 5}){sub 2}. The conversion of aniline after 45 min of reaction was 100% for the catalyst prepared with Ru(COD)(COT). The influence of the Ru precursor, preparation method and the support surface modification was studied comparing the conversion of aniline obtained for the different prepared Ru/MWNT catalysts (Figure 1). MWNT as support material, provide a significant metal dispersion with very small Ru nanoparticles (Figure 2) being observed. This will induce an efficient surface contact between the aniline molecule and the active sites [2]. The excellent catalytic performances of Ru/MWNT are explained

  2. Hydrogen storage of catalyst-containing activated carbon fibers and effect of surface modification

    International Nuclear Information System (INIS)

    Ikpyo Hong; Seong Young Lee; Kyung Hee Lee; Sei Min Park

    2005-01-01

    Introduction: The hydrogen storage capacities of many kind of carbon nano materials have been reported with possibility and improbability. It is reported that specific surface area of carbon nano material has not a close relation to hydrogen storage capacity. This result shows that there is difference between specific surface area measured by isothermal nitrogen adsorption and direct measurement of adsorption with hydrogen and suggests that the carbon material with relatively low specific surface area can have high hydrogen storage capacity when they have effective nano pore. In this study, petroleum based isotropic pitch was hybridized with several kinds of transitional metal base organometallic compound solved with organic solvent and spun by electro-spinning method. The catalyst-dispersed ACFs were prepared and characterized and hydrogen storage capacity was measured. The effect of surface modification of ACFs by physical and chemical treatment was also investigated. Experimental: The isotropic precursor pitch prepared by nitrogen blowing from naphtha cracking bottom oil was hybridized with transitional metal based acetyl acetonates and spun by solvent electro-spinning. Tetrahydrofuran and quinoline were used as solvent with various mixing ratio. High voltage DC power generator which could adjust in the range of 0-60000 V and 2 mA maximum current was used to supply electrostatic force. At the solvent electro-spinning, solvent mixing ratio and pitch concentration, voltage and spinning distance were varied and their influences were investigated. The catalyst-dispersed electro-spun pitch fibers were thermal stabilized, carbonized and activated by conventional heat treatment for activated carbon fiber. Prepared fibers were observed by high resolution SEM and pore properties were characterized by Micromeritics ASAP2020 model physi-sorption analyzer. Hydrogen storage capacities were measured by equipment modified from Thermo Cahn TherMax 500 model high pressure

  3. Coupling molecular catalysts with nanostructured surfaces for efficient solar fuel production

    Science.gov (United States)

    Jin, Tong

    Solar fuel generation via carbon dioxide (CO2) reduction is a promising approach to meet the increasing global demand for energy and to minimize the impact of energy consumption on climate change. However, CO2 is thermodynamically stable; its activation often requires the use of appropriate catalysts. In particular, molecular catalysts with well-defined structures and tunability have shown excellent activity in photochemical CO2 reduction. These homogenous catalysts, however, suffer from poor stability under photochemical conditions and difficulty in recycling from the reaction media. Heterogenized molecular catalysts, particularly those prepared by coupling molecular catalysts with solid-state surfaces, have attracted more attention in recent years as potential solutions to address the issues associated with molecular catalysts. In this work, solar CO2 reduction is investigated using systems coupling molecular catalysts with robust nanostructured surfaces. In Chapter 2, heterogenization of macrocyclic cobalt(III) and nickel (II) complexes on mesoporous silica surface was achieved by different methods. Direct ligand derivatization significantly lowered the catalytic activity of Co(III) complex, while grafting the Co(III) complex onto silica surface through Si-O-Co linkage resulted in hybrid catalysts with excellent activity in CO2 reduction in the presence of p-terphenyl as a molecular photosensitizer. An interesting loading effect was observed, in which the optimal activity was achieved at a medium Co(III) surface density. Heterogenization of the Ni(II) complex on silica surface has also been implemented, the poor photocatalytic activity of the hybrid catalyst can be attributed to the intrinsic nature of the homogeneous analogue. This study highlighted the importance of appropriate linking strategies in preparing functional heterogenized molecular catalysts. Coupling molecular complexes with light-harvesting surfaces could avoid the use of expensive molecular

  4. Surface chemistry and catalytic properties of VOX/Ti-MCM-41 catalysts for dibenzothiophene oxidation in a biphasic system

    International Nuclear Information System (INIS)

    González, J.; Chen, L.F.; Wang, J.A.; Manríquez, Ma.; Limas, R.; Schachat, P.; Navarrete, J.; Contreras, J.L.

    2016-01-01

    Highlights: • Oxidative desulfurization of model diesel was tested in a biphasic system. • ODS activity was proportional to the V 5+ /(V 4+ + V 5+ ) values of the catalysts. • Lewis acidity was related to vanadium content and catalytic activity. • 99.9% DBT was oxidized using 25%V 2 O 5 /Ti-MCM-41 at 60 °C within 60 min. - Abstract: A series of vanadium oxide supported on Ti-MCM-41 catalysts was synthesized via the incipient impregnation method by varying the vanadia loading from 5 wt% to 10, 15, 20 and 25 wt%. These catalysts were characterized by a variety of advanced techniques for investigating their crystalline structure, textural properties, and surface chemistry information including surface acidity, reducibility, vanadium oxidation states, and morphological features. The catalytic activities of the catalysts were evaluated in a biphasic reaction system for oxidative desulfurization (ODS) of a model diesel containing 300 ppm of dibenzothiophene (DBT) where acetonitrile was used as extraction solvent and H 2 O 2 as oxidant. ODS activity was found to be proportional to the V 5+ /(V 4+ + V 5+ ) values of the catalysts, indicating that the surface vanadium pentoxide (V 2 O 5 ) was the active phase. Reaction temperature would influence significantly the ODS efficiency; high temperature, i.e., 80 °C, would lead to low ODS reaction due to the partial decomposition of oxidant. All the catalysts contained both Lewis and Brønsted acid sites but the former was predominant. The catalysts with low vanadia loading (5 or 10 wt%V 2 O 5 ) had many Lewis acid sites and could strongly adsorb DBT molecule via the electron donation/acceptance action which resulted in an inhibition for the reaction of DBT with the surface peroxometallic species. The catalyst with high vanadia loading (25wt%V 2 O 5 /Ti-MCM-41) showed the highest catalytic activity and could remove 99.9% of DBT at 60 °C within 60 min.

  5. Advanced development of catalysts by using the high-brilliance synchrotron radiation in SPring-8

    International Nuclear Information System (INIS)

    2006-10-01

    The advanced development of catalysts by using the high-brilliance synchrotron radiation in SPring-8 is described: (1) the industrial use of SPring-8, (2) the analytical methods of catalyst using SPring-8 (XAFS, powder X-ray diffraction, thin film X-ray scattering, X-ray imaging, infrared analysis, X-ray fluorescence analysis, and photoelectron spectroscopy etc.), (3) the history of synchrotron radiation and catalyst investigations, (4) the new advanced measuring methods of catalyst using synchrotron radiation (various X-ray spectroscopic methods, and application of XAFS to highly-disperse systems of catalyst), and (5) the new advanced development of catalysts using synchrotron radiation and its applications (motor-car catalysts, light catalysts, fuel cells, nanotechnology, and trace amounts of catalyst in wastes). (M.H.)

  6. High performance vanadia-anatase nanoparticle catalysts for the selective catalytic reduction of NO by ammonia

    DEFF Research Database (Denmark)

    Kristensen, Steffen Buus; Kunov-Kruse, Andreas Jonas; Riisager, Anders

    2011-01-01

    Highly active nanoparticle SCR deNO(x) catalysts composed of amorphous vanadia on crystalline anatase have been prepared by a sol-gel, co-precipitation method using decomposable crystallization seeds. The catalysts were characterized by means of XRPD, TEM/SEM, FT-IR, nitrogen physisorption and NH(3......) catalysts reported in the literature in the examined temperature range of 200-400 degrees C. The catalysts showed very high resistivity towards potassium poisoning maintaining a 15-30 times higher activity than the equally poisoned industrial reference catalyst, upon impregnation by 280 mu mole potassium....../g of catalyst. (C) 2011 Elsevier Inc. All rights reserved....

  7. High throughput experimentation for the discovery of new catalysts

    International Nuclear Information System (INIS)

    Thomson, S.; Hoffmann, C.; Johann, T.; Wolf, A.; Schmidt, H.-W.; Farrusseng, D.; Schueth, F.

    2002-01-01

    Full text: The use of combinatorial chemistry to obtain new materials has been developed extensively by the pharmaceutical and biochemical industries, but such approaches have been slow to impact on the field of heterogeneous catalysis. The reasons for this lie in with difficulties associated in the synthesis, characterisation and determination of catalytic properties of such materials. In many synthetic and catalytic reactions, the conditions used are difficult to emulate using High Throughput Experimentation (HTE). Furthermore, the ability to screen these catalysts simultaneously in real time, requires the development and/or modification of characterisation methods. Clearly, there is a need for both high throughput synthesis and screening of new and novel reactions, and we describe several new concepts that help to achieve these goals. Although such problems have impeded the development of combinatorial catalysis, the fact remains that many highly attractive processes still exist for which no suitable catalysts have been developed. The ability to decrease the tiFme needed to evaluate catalyst is therefore essential and this makes the use of high throughput techniques highly desirable. In this presentation we will describe the synthesis, catalytic testing, and novel screening methods developed at the Max Planck Institute. Automated synthesis procedures, performed by the use of a modified Gilson pipette robot, will be described, as will the development of two 16 and 49 sample fixed bed reactors and two 25 and 29 sample three phase reactors for catalytic testing. We will also present new techniques for the characterisation of catalysts and catalytic products using standard IR microscopy and infrared focal plane array detection, respectively

  8. Density functional theory study for the enhanced sulfur tolerance of Ni catalysts by surface alloying

    Science.gov (United States)

    Hwang, Bohyun; Kwon, Hyunguk; Ko, Jeonghyun; Kim, Byung-Kook; Han, Jeong Woo

    2018-01-01

    Sulfur compounds in fuels deactivate the surface of anode materials in solid oxide fuel cells (SOFCs), which adversely affect the long-term durability. To solve this issue, it is important to design new SOFC anode materials with high sulfur tolerance. Unfortunately, it is difficult to completely replace the traditional Ni anode owing to its outstanding reactivity with low cost. As an alternative, alloying Ni with transition metals is a practical strategy to enhance the sulfur resistance while taking advantage of Ni metal. Therefore, in this study, we examined the effects of transition metal (Cu, Rh, Pd, Ag, Pt, and Au) doping into a Ni catalyst on not only the adsorption of H2S, HS, S, and H but also H2S decomposition using density functional theory (DFT) calculations. The dopant metals were selected rationally by considering the stability of the Ni-based binary alloys. The interactions between sulfur atoms produced by H2S dissociation and the surface are weakened by the dopant metals at the topmost layer. In addition, the findings show that H2S dissociation can be suppressed by doping transition metals. It turns out that these effects are maximized in the Au-doped Ni catalyst. Our DFT results will provide useful insights into the design of sulfur-tolerant SOFC anode materials.

  9. Enhanced hydrothermal stability of Cu-ZSM-5 catalyst via surface modification in the selective catalytic reduction of NO with NH_3

    International Nuclear Information System (INIS)

    Zhang, Tao; Shi, Juan; Liu, Jian; Wang, Daxi; Zhao, Zhen; Cheng, Kai; Li, Jianmei

    2016-01-01

    Highlights: • The hydrothermal stability of Cu-ZSM-5 catalyst was enhanced after surface modification. • An inert silica layer was deposited on the surface of Cu-ZSM-5 and formed a protective layer. • The contact between Si and Cu and Al atoms could form Si-O-Al and Si- O−Cu bonds. • The redox and acidity properties of Cu-ZSM-5-CLD-Aged catalyst were largely retained. • The adsorption and activation of NO and NH_3 was almost unchanged over Cu-ZSM-5-CLD catalyst before and after hydrothermal treatment. - Abstract: The surface of Cu-ZSM-5 catalyst was modified by chemical liquid deposition (CLD) of tetraethoxysilane (TEOS) for enhancing its hydrothermal stability in the selective catalytic reduction of NO with NH_3. After hydrothermal aging at 750 °C for 13 h, the catalytic performance of Cu-ZSM-5-Aged catalyst was significantly reduced for NO reduction in the entire temperature range, while that of Cu-ZSM-5-CLD-Aged catalyst was affected very little. The characterization results indicated that an inert silica layer was deposited on the surface of Cu-ZSM-5 and formed a protective layer, which prevents the detachment of Cu"2"+ from ZSM-5 ion-exchange positions and the dealumination of zeolite during the hydrothermal aging process. Based on the data it is hypothesized to be the primary reason for the high hydrothermal stability of Cu-ZSM-5-CLD catalyst.

  10. High Electrocatalytic Hydrogen Evolution Activity of an Anomalous Ruthenium Catalyst

    KAUST Repository

    Zheng, Yao; Jiao, Yan; Zhu, Yihan; Li, Lu Hua; Han, Yu; Chen, Ying; Jaroniec, Mietek; Qiao, Shi Zhang

    2016-01-01

    Hydrogen evolution reaction (HER) is a critical process due to its fundamental role in electrocatalysis. Practically, the development of high-performance electrocatalysts for HER in alkaline media is of great importance for the conversion of renewable energy to hydrogen fuel via photoelectrochemical water splitting. However, both mechanistic exploration and materials development for HER under alkaline conditions are very limited. Precious Pt metal, which still serves as the state-of-the-art catalyst for HER, is unable to guarantee a sustainable hydrogen supply. Here we report an anomalously structured Ru catalyst that shows 2.5 times higher hydrogen generation rate than Pt and is among the most active HER electrocatalysts yet reported in alkaline solutions. The identification of new face-centered cubic crystallographic structure of Ru nanoparticles was investigated by high-resolution transmission electron microscopy imaging, and its formation mechanism was revealed by spectroscopic characterization and theoretical analysis. For the first time, it is found that the Ru nanocatalyst showed a pronounced effect of the crystal structure on the electrocatalytic activity tested under different conditions. The combination of electrochemical reaction rate measurements and density functional theory computation shows that the high activity of anomalous Ru catalyst in alkaline solution originates from its suitable adsorption energies to some key reaction intermediates and reaction kinetics in the HER process.

  11. High Electrocatalytic Hydrogen Evolution Activity of an Anomalous Ruthenium Catalyst.

    Science.gov (United States)

    Zheng, Yao; Jiao, Yan; Zhu, Yihan; Li, Lu Hua; Han, Yu; Chen, Ying; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-12-14

    Hydrogen evolution reaction (HER) is a critical process due to its fundamental role in electrocatalysis. Practically, the development of high-performance electrocatalysts for HER in alkaline media is of great importance for the conversion of renewable energy to hydrogen fuel via photoelectrochemical water splitting. However, both mechanistic exploration and materials development for HER under alkaline conditions are very limited. Precious Pt metal, which still serves as the state-of-the-art catalyst for HER, is unable to guarantee a sustainable hydrogen supply. Here we report an anomalously structured Ru catalyst that shows 2.5 times higher hydrogen generation rate than Pt and is among the most active HER electrocatalysts yet reported in alkaline solutions. The identification of new face-centered cubic crystallographic structure of Ru nanoparticles was investigated by high-resolution transmission electron microscopy imaging, and its formation mechanism was revealed by spectroscopic characterization and theoretical analysis. For the first time, it is found that the Ru nanocatalyst showed a pronounced effect of the crystal structure on the electrocatalytic activity tested under different conditions. The combination of electrochemical reaction rate measurements and density functional theory computation shows that the high activity of anomalous Ru catalyst in alkaline solution originates from its suitable adsorption energies to some key reaction intermediates and reaction kinetics in the HER process.

  12. High Electrocatalytic Hydrogen Evolution Activity of an Anomalous Ruthenium Catalyst

    KAUST Repository

    Zheng, Yao

    2016-11-28

    Hydrogen evolution reaction (HER) is a critical process due to its fundamental role in electrocatalysis. Practically, the development of high-performance electrocatalysts for HER in alkaline media is of great importance for the conversion of renewable energy to hydrogen fuel via photoelectrochemical water splitting. However, both mechanistic exploration and materials development for HER under alkaline conditions are very limited. Precious Pt metal, which still serves as the state-of-the-art catalyst for HER, is unable to guarantee a sustainable hydrogen supply. Here we report an anomalously structured Ru catalyst that shows 2.5 times higher hydrogen generation rate than Pt and is among the most active HER electrocatalysts yet reported in alkaline solutions. The identification of new face-centered cubic crystallographic structure of Ru nanoparticles was investigated by high-resolution transmission electron microscopy imaging, and its formation mechanism was revealed by spectroscopic characterization and theoretical analysis. For the first time, it is found that the Ru nanocatalyst showed a pronounced effect of the crystal structure on the electrocatalytic activity tested under different conditions. The combination of electrochemical reaction rate measurements and density functional theory computation shows that the high activity of anomalous Ru catalyst in alkaline solution originates from its suitable adsorption energies to some key reaction intermediates and reaction kinetics in the HER process.

  13. Chemisorption of oxygen by coke deposited on catalyst surface

    Energy Technology Data Exchange (ETDEWEB)

    Furimsky, E.; Duguay, D.G.; Houle, J.

    1988-02-01

    Chemisorption of oxygen by nickel molybdate catalyst used for hydrotreating heavy oils was shown to increase with increasing temperature and reached a maximum at about 270 degrees C. Yields of CO/sub 2/, CO and SO/sub 2/ formed during isothermal chemisorption were estimated by using a fixed-bed reactor. Experimental observations were interpreted in terms of a hydrocarbon autoxidation mechanism. 11 refs., 7 figs., 1 tab.

  14. Carbon-Supported Fe Catalysts for CO2 Electroreduction to High-Added Value Products: A DEMS Study: Effect of the Functionalization of the Support

    OpenAIRE

    Pérez-Rodríguez, S.; García, G.; Calvillo, L.; Celorrio, V.; Pastor, E.; Lázaro, M. J.

    2011-01-01

    Vulcan XC-72R-supported Fe catalysts have been synthesised for the electroreduction of CO2 to high-added value products. Catalysts were obtained by the polyol method, using ethylene glycol as solvent and reducing agent. Prior to the metal deposition, Vulcan was subjected to different oxidation treatments in order to modify its surface chemistry and study its influence on the physicochemical and electrochemical properties of the catalysts, as well as on the product distribution. The oxidation ...

  15. High Throughput In Situ XAFS Screening of Catalysts

    International Nuclear Information System (INIS)

    Tsapatsaris, Nikolaos; Beesley, Angela M.; Weiher, Norbert; Tatton, Helen; Schroeder, Sven L. M.; Dent, Andy J.; Mosselmans, Frederick J. W.; Tromp, Moniek; Russu, Sergio; Evans, John; Harvey, Ian; Hayama, Shu

    2007-01-01

    We outline and demonstrate the feasibility of high-throughput (HT) in situ XAFS for synchrotron radiation studies. An XAS data acquisition and control system for the analysis of dynamic materials libraries under control of temperature and gaseous environments has been developed. The system is compatible with the 96-well industry standard and coupled to multi-stream quadrupole mass spectrometry (QMS) analysis of reactor effluents. An automated analytical workflow generates data quickly compared to traditional individual spectrum acquisition and analyses them in quasi-real time using an HT data analysis tool based on IFFEFIT. The system was used for the automated characterization of a library of 91 catalyst precursors containing ternary combinations of Cu, Pt, and Au on γ-Al2O3, and for the in situ characterization of Au catalysts supported on Al2O3 and TiO2

  16. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Luan; Tao, Franklin, E-mail: franklin.tao.2011@gmail.com [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, Kansas 66045 (United States)

    2016-06-15

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily.

  17. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis

    International Nuclear Information System (INIS)

    Nguyen, Luan; Tao, Franklin

    2016-01-01

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily.

  18. Mild Hydroprocessing with Dispersed Catalyst of Highly Asphaltenic Pitch

    Science.gov (United States)

    Isquierdo, Fernanda

    Asphaltene are known to have diverse negative impacts on heavy oil extraction and hydroprocessing. This research then, explores the optimal conditions to convert asphaltenes into lighter material using mild conditions of pressure and temperature, and investigates changes in asphaltene structure during hydroprocessing. Feedstock and products were characterized by Simulated Distillation, Microdeasphalting, Sulfur content, X-ray diffraction, X-ray photoelectron spectroscopy, and Nuclear magnetic resonance spectroscopy. Solid catalysts were analyzed by Themogravimetric analysis, X-ray diffraction, and Dynamic light scattering. Based on the results obtained from X-ray diffraction and Nuclear magnetic resonance spectroscopy analysis a mechanism for the asphaltene hydroprocessing at mild conditions is proposed in which the alky peripheric portion from the original asphaltenes is partially removed during the reaction. The consequence of that process being an increase in the stacking of the aromatics sheets in the remaining asphaltenes. Also, this study investigates different for ultradispersed catalyst compositions, where CoWS, CoMoS, NiWS, FeWS, NiMo/NaHFeSi 2O6 and NaHFeSi2O6 showed a high asphaltene conversion as determined by asphaltene microdeasphalting, FeMoS and NaHFeSi 2O6 presented a high Vacuum Residue as determined by distillation (SIMDIST) analysis conversion, and in terms of sulfur removal CoMoS gave the higher conversion. In addition, all the catalyst tested showed a coke production lower than 1%. Finally, a kinetic study for the pitch hydroprocessing using CoMoS as catalysts gave a global activation energy of 97.3 kJ/mol.

  19. Direct observation of surface reconstruction and termination on a complex metal oxide catalyst by electron microscopy

    KAUST Repository

    Zhu, Yihan

    2012-03-19

    On the surface: The surface reconstruction of an MoVTeO complex metal oxide catalyst was observed directly by various electron microscopic techniques and the results explain the puzzling catalytic behavior. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Hierarchical Pd-Sn alloy nanosheet dendrites: an economical and highly active catalyst for ethanol electrooxidation.

    Science.gov (United States)

    Ding, Liang-Xin; Wang, An-Liang; Ou, Yan-Nan; Li, Qi; Guo, Rui; Zhao, Wen-Xia; Tong, Ye-Xiang; Li, Gao-Ren

    2013-01-01

    Hierarchical alloy nanosheet dendrites (ANSDs) are highly favorable for superior catalytic performance and efficient utilization of catalyst because of the special characteristics of alloys, nanosheets, and dendritic nanostructures. In this paper, we demonstrate for the first time a facile and efficient electrodeposition approach for the controllable synthesis of Pd-Sn ANSDs with high surface area. These synthesized Pd-Sn ANSDs exhibit high electrocatalytic activity and superior long-term cycle stability toward ethanol oxidation in alkaline media. The enhanced electrocataytic activity of Pd-Sn ANSDs may be attributed to Pd-Sn alloys, nanosheet dendrite induced promotional effect, large number of active sites on dendrite surface, large surface area, and good electrical contact with the base electrode. Because of the simple implement and high flexibility, the proposed approach can be considered as a general and powerful strategy to synthesize the alloy electrocatalysts with high surface areas and open dendritic nanostructures.

  1. Surface composition of magnetron sputtered Pt-Co thin film catalyst for proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Vorokhta, Mykhailo, E-mail: vorohtam@gmail.com [Charles University in Prague, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague (Czech Republic); Khalakhan, Ivan; Václavů, Michal [Charles University in Prague, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague (Czech Republic); Kovács, Gábor; Kozlov, Sergey M. [Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, c/ Martí i Franquès 1, 08028 Barcelona (Spain); Kúš, Peter; Skála, Tomáš; Tsud, Natalia; Lavková, Jaroslava [Charles University in Prague, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague (Czech Republic); Potin, Valerie [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université Bourgogne, 9 Av. A. Savary, BP 47870, F-21078 Dijon Cedex (France); and others

    2016-03-01

    Graphical abstract: - Highlights: • Nanostructured Pt-Co thin catalyst films were grown on carbon by magnetron sputtering. • The surface composition of the nanostructured Pt-Co films was investigated by surface analysis techniques. • We carried out modeling of Pt-Co nanoalloys by computational methods. • Both experiment and modeling based on density functional theory showed that the surface of Pt-Co nanoparticles is almost exclusively composed of Pt atoms. - Abstract: Recently we have tested a magnetron sputtered Pt-Co catalyst in a hydrogen-fed proton exchange membrane fuel cell and showed its high catalytic activity for the oxygen reduction reaction. Here we present further investigation of the magnetron sputtered Pt-Co thin film catalyst by both experimental and theoretical methods. Scanning electron microscopy and transmission electron microscopy experiments confirmed the nanostructured character of the catalyst. The surface composition of as-deposited and annealed at 773 K Pt-Co films was investigated by surface analysis techniques, such as synchrotron radiation photoelectron spectroscopy and X-ray photoelectron spectroscopy. Modeling based on density functional theory showed that the surface of 6 nm large 1:1 Pt-Co nanoparticles is almost exclusively composed of Pt atoms (>90%) at typical operation conditions and the Co content does not exceed 20% at 773 K, in agreement with the experimental characterization of such films annealed in vacuum. According to experiment, the density of valence states of surface atoms in Pt-Co nanostructures is shifted by 0.3 eV to higher energies, which can be associated with their higher activity in the oxygen reduction reaction. The changes in electronic structure caused by alloying are also reflected in the measured Pt 4f, Co 3p and Co 2p photoelectron peak binding energies.

  2. Surface chemistry and microstructural analysis of CexZr1-xO2-y model catalyst surfaces

    International Nuclear Information System (INIS)

    Nelson, Alan E.; Schulz, Kirk H.

    2003-01-01

    Cerium-zirconium mixed metal oxides are widely used as promoters in automotive emissions control catalyst systems (three-way catalysts). The addition of zirconium in the cubic lattice of ceria improves the redox properties and the thermal stability, thereby increasing the catalyst efficiency and longevity. The surface composition and availability of surface oxygen of model ceria-zirconia catalyst promoters was considered to develop a reference for future catalytic reactivity studies. The microstructure was characterized with X-ray diffraction (XRD) to determine the effect of zirconium substitution on crystalline structure and grain size. Additionally, the Ce/Zr surface atomic ratio and existence of Ce 3+ defect sites were examined with X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) for samples with different zirconium concentrations. The surface composition of the model systems with respect to cerium and zirconium concentration is representative of the bulk, indicating no appreciable surface species segregation during model catalyst preparation or exposure to ultrahigh vacuum conditions and analysis techniques. Additionally, the concentration of Ce 3+ defect sites was constant and independent of composition. The quantity of surface oxygen was unaffected by electron bombardment or prolonged exposure to ultrahigh vacuum conditions. Additionally, XRD analysis did not indicate the presence of additional crystalline phases beyond the cubic structure for compositions from 100 to 25 at.% cerium, although additional phases may be present in undetectable quantities. This analysis is an important initial step for determining surface reactions and pathways for the development of efficient and sulfur-tolerant automotive emissions control catalysts

  3. Fiscal 1999 international cooperation project report. Development of high-precision quantitative analysis technology for catalyst surfaces by electron spectroscopy; 1999 nendo denshi bunkoho ni yoru shokubai hyomen koseido teiryo bunseki bijutsu no kaihatsu seika hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    This project targets to make analysis of surface chemical phenomena of solid catalysts possible, and establish the basis of intelligent design for catalytic materials, through development of an advanced electron spectroscopy for surface analysis. In fiscal 1999, the research was promoted by using the diffraction grating and driving mechanism introduced in fiscal 1998, and by developing the measurement result on silicon oxide films by radiation beam photoelectron spectroscopy. The measurement technique was established by the optimized measurement process which can treat variable parameters as constant. The analysis result of measurement data in fiscal 1999 showed the dependence of an electron damping length in silicon oxide films on radiation photon energy. The energy dependence well agreed with a theoretically obtained inelastic mean free path of electrons qualitatively, while was smaller by nearly 30% than the latter quantitatively. Measurement was made on the damping length in oxidation-active Gd and Nd oxide films. In both cases of Si and Si oxide film substrates, oxidation of substrates or formation of silicate was observed. (NEDO)

  4. Bimetallic Ag-Pt Sub-nanometer Supported Clusters as Highly Efficient and Robust Oxidation Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Negreiros, Fabio R. [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Halder, Avik [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Yin, Chunrong [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Singh, Akansha [Harish-Chandra Research Institute, HBNI, Chhatnag Road Jhunsi Allahabad 211019 India; Barcaro, Giovanni [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Sementa, Luca [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Tyo, Eric C. [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Pellin, Michael J. [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Bartling, Stephan [Institut für Physik, Universität Rostock, Rostock Germany; Meiwes-Broer, Karl-Heinz [Institut für Physik, Universität Rostock, Rostock Germany; Seifert, Sönke [X-ray Science Division, Argonne National Laboratory, Lemont IL USA; Sen, Prasenjit [Harish-Chandra Research Institute, HBNI, Chhatnag Road Jhunsi Allahabad 211019 India; Nigam, Sandeep [Chemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai- 400 085 India; Majumder, Chiranjib [Chemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai- 400 085 India; Fukui, Nobuyuki [East Tokyo Laboratory, Genesis Research Institute, Inc., Ichikawa Chiba 272-0001 Japan; Yasumatsu, Hisato [Cluster Research Laboratory, Toyota Technological Institute: in, East Tokyo Laboratory, Genesis Research Institute, Inc. Ichikawa, Chiba 272-0001 Japan; Vajda, Stefan [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Nanoscience and Technology Division, Argonne National Laboratory, Lemont IL USA; Institute for Molecular Engineering, University of Chicago, Chicago IL USA; Fortunelli, Alessandro [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Materials and Process Simulation Center, California Institute of Technology, Pasadena CA USA

    2017-12-29

    A combined experimental and theoretical investigation of Ag-Pt sub-nanometer clusters as heterogeneous catalysts in the CO -> CO2 reaction (COox) is presented. Ag9Pt2 and Ag9Pt3 clusters are size-selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and by first-principles simulations at realistic coverage. Insitu GISAXS/TPRx demonstrates that the clusters do not sinter or deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano-aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O-2, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species.

  5. Exchange of deuterium with hydrogen of zeolite catalyst surface

    International Nuclear Information System (INIS)

    Minachev, Kh.M.; Dmitriev, R.V.; Penchev, V.; Kanazirev, V.; Minchev, Kh.; Kasimov, Ch.K.; Bylgarska Akademiya na Naukite, Sofia. Inst. za Obshta i Organichna Khimiya; AN Azerbajdzhanskoj SSR, Baku. Inst. Neftekhimicheskikh Protsessov)

    1981-01-01

    Isotope heteromolecular exchange of hydrogen on the reduced nickel-containing zeolites takes places at the temperatures above 100 deg and it is controlled by activated hydrogen transfer from metal particles on the substrate surface. High-temperature redox treatment of nickel-containing zeolites results in the formation of large nickel crystallites on zeolite external faces. The rest part of nickel remains in zeolite pores and conditions a high promoting effect in the exchange reaction. Catalytic activity of reduced zeolites NiCaNaY in toluene disproportionation increases considerably only in the cases when nickel is introduced into zeolite by means of ion exchange. Close spatial location of nickel particles and OH groups promotes the procedure of both isotope exchange and disproportionation of toluene [ru

  6. Synthesis of highly efficient Mn2O3 catalysts for CO oxidation derived from Mn-MIL-100

    Science.gov (United States)

    Zhang, Xiaodong; Li, Hongxin; Hou, Fulin; Yang, Yang; Dong, Han; Liu, Ning; Wang, Yuxin; Cui, Lifeng

    2017-07-01

    In this work, metal-organic frameworks (MOFs) Mn-MIL-100 were first prepared, which were next used as templates to obtain the irregular porous Mn2O3 cubes through calcination with air at different temperature. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), H2-temperature program reduction (H2-TPR) and X-ray photoelectron spectroscopic (XPS). The catalytic activity for CO oxidation over Mn2O3 catalysts was investigated. It was found that calcination temperature had a strong effect on the structure and catalytic activity of Mn2O3 catalyst. Mn2O3 catalyst obtained by calcined at 700 °C (Mn2O3-700) showed a smaller specific surface area, but displayed a high catalytic activity and excellent stability with a complete CO conversion temperature (T98) of 240 °C, which was attributed to the unique structure, a high quantity of surface active oxygen species, smaller particle size, oxygen vacancies and good low temperature reduction behavior. The effect of water vapor on catalytic activity was also examined. The introduction of water vapor to the feedstock induced a positive effect on CO oxidation over Mn2O3-700 catalyst. Furthermore, no obvious drop is observed in activity over catalysts even in the presence of water vapor during 48 h.

  7. Atomic Scale Structure-Chemistry Relationships at Oxide Catalyst Surfaces and Interfaces

    Science.gov (United States)

    McBriarty, Martin E.

    Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. In this work, the tools of surface and interface science and electronic structure theory are applied to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. These studies focus on structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides on the surfaces of alpha-Al2O3 and alpha-Fe2O 3 (0001)-oriented single crystal substrates, two materials with nearly identical crystal structures but drastically different chemical properties. In situ synchrotron X-ray standing wave (XSW) measurements are sensitive to changes in the atomic-scale geometry of single crystal model catalyst surfaces through chemical reaction cycles, while X-ray photoelectron spectroscopy (XPS) reveals corresponding chemical changes. Experimental results agree with theoretical calculations of surface structures, allowing for detailed electronic structure investigations and predictions of surface chemical phenomena. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. Additionally, the structure and chemistry of W deposited on alpha-Fe 2O3 nanopowders is studied using X-ray absorption fine structure (XAFS) measurements in an attempt to bridge single crystal surface studies with real catalysts. These investigations of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

  8. Study on the correlation between the surface active species of Pd/cordierite monolithic catalyst and its catalytic activity

    International Nuclear Information System (INIS)

    Liao, Hengcheng; Zuo, Peiyuan; Liu, Miaomiao

    2016-01-01

    Two Pd-loading routes and three Pd-precursor matters were adopted to prepare Pd/(Ce,Y)O_2/γ-Al_2O_3/cordierite monolithic catalyst. The surface active species on the catalyst were characterized by XPS, and its catalytic activity for methane combustion was tested, and the dynamics of the catalytic combustion reaction was also discussed. Pd-loading route and Pd-precursor mass have a significant influence on the catalytic activity and surface active species. The sol dipping method is more advanced than the aqueous solution impregnating method. PN-sol catalyst, by sol dipping combined with Pd(NO_3)_2-precursor, has the best catalytic activity. The physical reason is the unique active Pd phase coexisting with active PdO phase on the surface, and thus the Pd3d_5_/_2 binding energy of surface species and apparent activation energy of combustion reaction are considerably decreased. The catalytic activity index, Pd3d_5_/_2 binding energy and apparent activation energy are highly tied each other with exponential relations.

  9. Optimization of Reactor Temperature and Catalyst Weight for Plastic Cracking to Fuels Using Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Istadi Istadi

    2011-01-01

    Full Text Available The present study deals with effect of reactor temperature and catalyst weight on performance of plastic waste cracking to fuels over modified catalyst waste as well as their optimization. From optimization study, the most operating parameters affected the performance of the catalytic cracking process is reactor temperature followed by catalyst weight. Increasing the reactor temperature improves significantly the cracking performance due to the increasing catalyst activity. The optimal operating conditions of reactor temperature about 550 oC and catalyst weight about 1.25 gram were produced with respect to maximum liquid fuel product yield of 29.67 %. The liquid fuel product consists of gasoline range hydrocarbons (C4-C13 with favorable heating value (44,768 kJ/kg. ©2010 BCREC UNDIP. All rights reserved(Received: 10th July 2010, Revised: 18th September 2010, Accepted: 19th September 2010[How to Cite: I. Istadi, S. Suherman, L. Buchori. (2010. Optimization of Reactor Temperature and Catalyst Weight for Plastic Cracking to Fuels Using Response Surface Methodology. Bulletin of Chemical Reaction Engineering and Catalysis, 5(2: 103-111. doi:10.9767/bcrec.5.2.797.103-111][DOI: http://dx.doi.org/10.9767/bcrec.5.2.797.103-111 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/797

  10. Catalyst-free site-specific surface modifications of nanocrystalline diamond films via microchannel cantilever spotting

    Czech Academy of Sciences Publication Activity Database

    Davydova, Marina; de los Santos Pereira, Andres; Bruns, M.; Kromka, Alexander; Ukraintsev, Egor; Hirtz, M.; Rodriguez-Emmenegger, Cesar

    2016-01-01

    Roč. 6, č. 63 (2016), s. 57820-57827 ISSN 2046-2069 R&D Projects: GA ČR(CZ) GP14-06054P Institutional support: RVO:68378271 ; RVO:61389013 Keywords : catalysts * nanocrystals * photonic devices * catalyst-free * functionalizations * high reproducibility * micropatterned * multicomponents Subject RIV: BO - Biophysics; CD - Macromolecular Chemistry (UMCH-V) Impact factor: 3.108, year: 2016

  11. Preparation, surface characterization and performance of a Fischer-Tropsch catalyst of cobalt supported on silica nanosprings

    Energy Technology Data Exchange (ETDEWEB)

    Kengne, Blaise-Alexis Fouetio [Department of Physics, University of Idaho, Moscow, ID 83844-0903 (United States); Alayat, Abdulbaset M. [Environmental Science Program, University of Idaho, Moscow, ID 83844-3006 (United States); Luo, Guanqun [Department of Forest, Rangeland & Fire Sciences, University of Idaho, Moscow, ID 83844-1132 (United States); McDonald, Armando G. [Environmental Science Program, University of Idaho, Moscow, ID 83844-3006 (United States); Department of Forest, Rangeland & Fire Sciences, University of Idaho, Moscow, ID 83844-1132 (United States); Brown, Justin; Smotherman, Hayden [Department of Physics, University of Idaho, Moscow, ID 83844-0903 (United States); McIlroy, David N., E-mail: dmcilroy@uidaho.edu [Department of Physics, University of Idaho, Moscow, ID 83844-0903 (United States)

    2015-12-30

    Graphical abstract: - Highlights: • Determined that the reduction of Co nanoparticles on silica nanosprings 200 °C higher than the reduction temperature of Co in a solgel support. • The high reduction temperature of Co supported on silica nanosprings is attributed to the heat transfer properties of the nanosprings due to their high surface area. Co-silica nanospring Fischer-Tropsch catalyst can be used to produce drop in fuels such as JP-4. - Abstract: The reduction of cobalt (Co) catalyst supported on silica nanosprings for Fischer-Tropsch synthesis (FTS) has been monitored by X-ray photoelectron spectroscopy (XPS) and compared to FT catalytic activity. The cobalt is present in the starting catalyst as a Co{sub 3}O{sub 4} spinel phase. A two-step reduction of Co{sub 3}O{sub 4} to CoO and then to Co{sup 0} is observed, which is consistent with the results of H{sub 2}-temperature programmed reduction. During the reduction the two steps occur concurrently. The deconvolution of the Co 2p core level state for the catalyst reduced at 385 °C and 1.0 × 10{sup −6} Torr of H{sub 2} revealed signatures of Co{sup 0}, CoO, and Co{sub 3}O{sub 4}. The reduction saturates at a Co{sup o} concentration of approximately 41% after 20 h, which correlates with the activity and lifetime of the catalyst during FTS testing. Conversely, at 680 °C and 10 Torr of H{sub 2}, the catalyst is completely reduced after 10 h. The evolution of the Co d-band at the Fermi level in the valence band XPS spectrum definitively verifies the metallic phase of Co. FTS evaluation of the Co/NS catalyst reduced at 609 °C showed higher production rate (3-fold) of C{sub 6}-C{sub 17} hydrocarbons than the catalyst reduced at 409 °C and is consistent with the XPS analysis.

  12. Laser-Induced Fluorescence Detection in High-Throughput Screening of Heterogeneous Catalysts and Single Cells Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Su, Hui [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    Laser-induced fluorescence detection is one of the most sensitive detection techniques and it has found enormous applications in various areas. The purpose of this research was to develop detection approaches based on laser-induced fluorescence detection in two different areas, heterogeneous catalysts screening and single cell study. First, we introduced laser-induced imaging (LIFI) as a high-throughput screening technique for heterogeneous catalysts to explore the use of this high-throughput screening technique in discovery and study of various heterogeneous catalyst systems. This scheme is based on the fact that the creation or the destruction of chemical bonds alters the fluorescence properties of suitably designed molecules. By irradiating the region immediately above the catalytic surface with a laser, the fluorescence intensity of a selected product or reactant can be imaged by a charge-coupled device (CCD) camera to follow the catalytic activity as a function of time and space. By screening the catalytic activity of vanadium pentoxide catalysts in oxidation of naphthalene, we demonstrated LIFI has good detection performance and the spatial and temporal resolution needed for high-throughput screening of heterogeneous catalysts. The sample packing density can reach up to 250 x 250 subunits/cm2 for 40-μm wells. This experimental set-up also can screen solid catalysts via near infrared thermography detection.

  13. Laser-Induced Fluorescence Detection in High-Throughput Screening of Heterogeneous Catalysts and Single Cells Analysis

    International Nuclear Information System (INIS)

    Hui Su

    2001-01-01

    Laser-induced fluorescence detection is one of the most sensitive detection techniques and it has found enormous applications in various areas. The purpose of this research was to develop detection approaches based on laser-induced fluorescence detection in two different areas, heterogeneous catalysts screening and single cell study. First, we introduced laser-induced imaging (LIFI) as a high-throughput screening technique for heterogeneous catalysts to explore the use of this high-throughput screening technique in discovery and study of various heterogeneous catalyst systems. This scheme is based on the fact that the creation or the destruction of chemical bonds alters the fluorescence properties of suitably designed molecules. By irradiating the region immediately above the catalytic surface with a laser, the fluorescence intensity of a selected product or reactant can be imaged by a charge-coupled device (CCD) camera to follow the catalytic activity as a function of time and space. By screening the catalytic activity of vanadium pentoxide catalysts in oxidation of naphthalene, we demonstrated LIFI has good detection performance and the spatial and temporal resolution needed for high-throughput screening of heterogeneous catalysts. The sample packing density can reach up to 250 x 250 subunits/cm(sub 2) for 40-(micro)m wells. This experimental set-up also can screen solid catalysts via near infrared thermography detection

  14. N, S co-doped carbon spheres with highly dispersed CoO as non-precious metal catalyst for oxygen reduction reaction

    Science.gov (United States)

    Chen, Linlin; Guo, Xingpeng; Zhang, Guoan

    2017-08-01

    It is still a great challenge in preparing non-precious metal catalysts with high activity and long-term stability to substitute for precious metal catalysts for oxygen reduction reaction (ORR) in fuel cells. Herein, we report a novel and facile catalyst-N, S co-doped carbon spheres with highly dispersed CoO (CoO@NS-CSs), where biomass glucose spheres act as carbon precursor and H2S, NH3 derived from the decomposition of thiourea not only provide N, S sources but also can etch carbon spheres to produce nanoporous structure. CoO@NS-CSs catalyst exhibits excellent ORR activity with a high onset potential of 0.946 V vs. RHE (reversible hydrogen electrode) and a half-wave potential of 0.821 V vs. RHE through a four-electron pathway in alkaline solution, which is comparable to commercial Pt/C catalyst (onset potential: 0.926 V vs. RHE, half-wave potential: 0.827 V vs. RHE). Furthermore, both the long-term stability and methanol-tolerance of CoO@NS-CSs catalyst are superior to those of commercial Pt/C catalyst. The excellent ORR performance of CoO@NS-CSs catalyst can be attributed to its micro-mesopore structure, high specific surface area (667 m2 g-1), and highly dispersed CoO. This work manifests that the obtained CoO@NS-CSs catalyst is promising to be applied to fuel cells.

  15. Bimetallic Catalysts and Platinum Surfaces Studied by X-ray Absorption Spectroscopy and Scanning Tunnelling Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roenning, Magnus

    2000-07-01

    rhenium atoms, leading to weaker metal - support interactions in the bimetallic sample than what is observed for the monometallic sample. Cobalt does not catalyse the reduction of rhenium and more than six hours reduction at 450{sup o}C is required for complete reduction of accessible rhenium. The influence of pretreatment temperature on the metal function of a commercial Pt-Re/Al{sub 2}O{sub 3} reforming catalyst (EUROPT-4) was studied by X-ray absorption spectroscopy. By simultaneously examining the rhenium L{sub III} and platinum L{sub III} EXAFS data, the bimetallic interaction and the metal - support interaction can be distinguished from the overall spectrum. The results show that if the catalyst is dried in air at temperatures {<=} 500{sup o}C before reduction at 480{sup o}C, bimetallic particles of platinum and rhenium are formed. Drying at higher temperatures and in absence of air inhibits the transport of mobile (rhenium) species on the surface causing no intimate contact between the two metals. Platinum L{sub III} EXAFS data show that the average particle size of the bimetallic particles on the alumina surface is less than 10 A. The results from the rhenium L{sub III} EXAFS analysis confirm that rhenium is not completely reduced to metallic rhenium after reduction, with a significant fraction of the rhenium present in low, positive oxidation states and in intimate contact with the support. The EXAFS data are consistent with a structural model of flat rhenium metal particles with smaller platinum particles situated at the boundary of the rhenium particles. Ethene adsorption and subsequent dehydrogenation on the hexagonally reconstructed Pt(100)-hex-R0.7{sup o} surface has been investigated using scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED). The results show that heterogeneous nucleation of the (1x1) domains occur when the hexagonal reconstruction is lifted during ethene adsorption on Pt(100). The (1x1) domains are highly

  16. Characterization of deposits formed on catalyst surfaces during hydrotreatment of coal-derived liquids

    Energy Technology Data Exchange (ETDEWEB)

    Furimsky, E.

    1982-04-01

    Loss of catalyst activity is attributed to the formation of polynuclear aromatic structures on the surface. Heavy species containing N and O heteroatoms were also present in deposits. Phenols, aromatic and heterocyclic compounds are considered to be the precursors for the formation of the deposits. (16 refs.)

  17. Selective formation of diamond-like carbon coating by surface catalyst patterning

    DEFF Research Database (Denmark)

    Palnichenko, A.V.; Mátéfi-Tempfli, M.; Mátéfi-Tempfli, Stefan

    2004-01-01

    The selective formation of diamond-like carbon coating by surface catalyst patterning was studied. DLC films was deposited using plasma enhanced chemical vapor deposition, filtered vacuum arc deposition, laser ablation, magnetron sputtering and ion-beam lithography methods. The DLC coatings were...

  18. Synthesis, Characterizations, and Applications of Metal-Ions Incorporated High Quality MCM-41 Catalysts

    International Nuclear Information System (INIS)

    Lim, Steven S.; Haller, Gary L.

    2013-01-01

    Various metal ions (transition and base metals) incorporated MCM-41 catalysts can be synthesized using colloidal and soluble silica with non-sodium involved process. Transition metal ion-typically V 5+ , Co 2+ , and Ni 2+ -incorporated MCM-41 catalysts were synthesized by isomorphous substitution of Si ions in the framework. Each incorporated metal ion created a single species in the silica framework, single-site solid catalyst, showing a substantial stability in reduction and catalytic activity. Radius of pore curvature effect was investigated with Co-MCM-41 by temperature programmed reduction (TPR). The size of metallic Co clusters, sub-nanometer, could be controlled by a proper reduction treatment of Co-MCM-41 having different pore size and the initial pH adjustment of the Co-MCM-41 synthesis solution. These small metallic clusters showed a high stability under a harsh reaction condition without serious migration, resulting from a direct anchoring of small metallic clusters to the partially or unreduced metal ions on the surface. After a complete reduction, partial occlusion of the metallic cluster surface by amorphous silica stabilized the particles against aggregations. As a probe reaction of particle size sensitivity, carbon single wall nanotubes (SWNT) were synthesized using Co-MCM-41. A metallic cluster stability test was performed by CO methanation using Co- and Ni-MCM-41. Methanol and methane partial oxidations were carried out with V-MCM-41, and the radius of pore curvature effect on the catalytic activity was investigated

  19. Towards Highly Performing and Stable PtNi Catalysts in Polymer Electrolyte Fuel Cells for Automotive Application

    Directory of Open Access Journals (Sweden)

    Sabrina C. Zignani

    2017-03-01

    Full Text Available In order to help the introduction on the automotive market of polymer electrolyte fuel cells (PEFCs, it is mandatory to develop highly performing and stable catalysts. The main objective of this work is to investigate PtNi/C catalysts in a PEFC under low relative humidity and pressure conditions, more representative of automotive applications. Carbon supported PtNi nanoparticles were prepared by reduction of metal precursors with formic acid and successive thermal and leaching treatments. The effect of the chemical composition, structure and surface characteristics of the synthesized samples on their electrochemical behavior was investigated. The catalyst characterized by a larger Pt content (Pt3Ni2/C presented the highest catalytic activity (lower potential losses in the activation region among the synthesized bimetallic PtNi catalysts and the commercial Pt/C, used as the reference material, after testing at high temperature (95 °C and low humidification (50% conditions for automotive applications, showing a cell potential (ohmic drop-free of 0.82 V at 500 mA·cm−2. In order to assess the electro-catalysts stability, accelerated degradation tests were carried out by cycling the cell potential between 0.6 V and 1.2 V. By comparing the electrochemical and physico-chemical parameters at the beginning of life (BoL and end of life (EoL, it was demonstrated that the Pt1Ni1/C catalyst was the most stable among the catalyst series, with only a 2% loss of voltage at 200 mA·cm−2 and 12.5% at 950 mA·cm−2. However, further improvements are needed to produce durable catalysts.

  20. Novel, high-activity hydroprocessing catalysts: Iron group phosphides

    Science.gov (United States)

    Wang, Xianqin

    A series of iron, cobalt and nickel transition metal phosphides was synthesized by means of temperature-programmed reduction (TPR) of the corresponding phosphates. The same materials, Fe2P, CoP and NO, were also prepared on a silica (SiO2) support. The phase purity of these catalysts was established by x-ray diffraction (XRD), and the surface properties were determined by N2 BET specific surface area (Sg) measurements and CO chemisorption. The activities of the silica-supported catalysts were tested in a three-phase trickle bed reactor for the simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene using a model liquid feed at realistic conditions (30 atm, 370°C). The reactivity studies showed that the nickel phosphide (Ni2P/SiO2) was the most active of the catalysts. Compared with a commercial Ni-Mo-S/gamma-Al 2O3 catalyst at the same conditions, Ni2P/silica had a substantially higher HDS activity (100% vs. 76%) and HDN activity (82% vs. 38%). Because of their good hydrotreating activity, an extensive study of the preparation of silica supported nickel phosphides, Ni2P/SiO 2, was carried out. The parameters investigated were the phosphorus content and the weight loading of the active phase. The most active composition was found to have a starting synthesis Ni/P ratio close to 1/2, and the best loading of this sample on silica was observed to be 18 wt.%. Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES) measurements were employed to determine the structures of the supported samples. The main phase before and after reaction was found to be Ni2P, but some sulfur was found to be retained after reaction. A comprehensive scrutiny of the HDN reaction mechanism was also made over the Ni2P/SiO2 sample (Ni/P = 1/2) by comparing the HDN activity of a series of piperidine derivatives of different structure. It was found that piperidine adsorption involved an alpha-H activation

  1. Long term deactivation test of high dust SCR catalysts by straw co-firing

    Energy Technology Data Exchange (ETDEWEB)

    Weigang Lin; Degn Jensen, A.; Bjerkvig, J.

    2009-12-15

    The consequences of carbon dioxide induced global warming cause major concern worldwide. The consumption of energy produced with fossil fuels is the major factor that contributes to the global warming. Biomass is a renewable energy resource and has a nature of CO{sub 2} neutrality. Co-combustion of biomass in existing coal fired power plants can maintain high efficiency and reduce the emission of CO{sub 2} at same time. However, one of the problems faced by co-firing is deactivation of the SCR catalysts. Understanding of the mechanisms of deactivation of the catalyst elements at co-firing conditions is crucial for long term runs of the power plants. Twenty six SCR catalyst elements were exposed at two units (SSV3 and SSV4) in the Studstrup Power Plant for a long period. Both units co-fire coal and straw with a typical fraction of 8-10% straw on an energy basis during co-firing. SSV4 unit operated in co-firing mode most of the time; SSV3 unit co-fired straw half of the operating time. The main objective of this PSO-project is to gain knowledge of a long term influence on catalyst activity when co-firing straw in coal-fired power plants, thus, to improve the basis for operating the SCR-plants for NO{sub x}-reduction. The exposure time of the applied catalyst elements (HTAS and BASF) varied from approximately 5000 to 19000 hours in the power plant by exchanging the element two times. The activity of all elements was measured before and after exposure in a bench scale test rig at the Department of Chemical and Biochemical Engineering, Technical University of Denmark. The results show that the activity, estimated by exclusion of channel clogging of the elements, decreases gradually with the total exposure time. It appears that the exposure time under co-firing condition has little effect on the deactivation of the catalyst elements and no sharp decrease of the activity was observed. The average deactivation rate of the catalyst elements is 1.6 %/1000 hours. SEM

  2. Surface-Bound Ligands Modulate Chemoselectivity and Activity of a Bimetallic Nanoparticle Catalyst

    KAUST Repository

    Vu, Khanh B.

    2015-04-03

    "Naked" metal nanoparticles (NPs) are thermodynamically and kinetically unstable in solution. Ligands, surfactants, or polymers, which adsorb at a particle\\'s surface, can be used to stabilize NPs; however, such a mode of stabilization is undesirable for catalytic applications because the adsorbates block the surface active sites. The catalytic activity and the stability of NPs are usually inversely correlated. Here, we describe an example of a bimetallic (PtFe) NP catalyst stabilized by carboxylate surface ligands that bind preferentially to one of the metals (Fe). NPs stabilized by fluorous ligands were found to be remarkably competent in catalyzing the hydrogenation of cinnamaldehyde; NPs stabilized by hydrocarbon ligands were significantly less active. The chain length of the fluorous ligands played a key role in determining the chemoselectivity of the FePt NP catalysts. (Chemical Presented). © 2015 American Chemical Society.

  3. New insights into proton surface mobility processes in PEMFC catalysts using isotopic exchange methods.

    Science.gov (United States)

    Ferreira-Aparicio, Paloma

    2009-09-01

    The surface chemistry and the adsorption/desorption/exchange behavior of a proton-exchange membrane fuel cell catalyst are analyzed as a case study for the development of tailor-made support materials of enhanced performance and stability. By using H2, D2, and CO as probe molecules, the relevance of some surface functional groups of the catalyst support on several diffusion processes taking place during the adsorption is shown. Sulfonic groups associated with the vulcanized carbon black surface have been detected by means of spectroscopic techniques (X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy) and by analysis of the desorbed products during temperature-programmed desorption tests by mass spectrometry. Such hydrophilic species have been observed to favor proton surface mobility and exchange with Pt-adsorbed deuterium even in the presence of adsorbed CO. This behavior is relevant both for the proper characterization of these kinds of catalysts using adsorption probes and for the design of new surface-modified carbon supports, enabling alternative proton-transfer pathways throughout the catalytic layers toward the membrane.

  4. Influence of surface phenomena in oxidative desulfurization with WOx/ZrO2 catalysts

    Science.gov (United States)

    Torres-García, E.; Canizal, G.; Velumani, S.; Ramírez-Verduzco, L. F.; Murrieta-Guevara, F.; Ascencio, J. A.

    2004-12-01

    Oil refinery related catalysis, particularly hydro desulfurization is viewed as a mature technology, but still we view that more efforts have to be made to boost the efficiency of the existing catalysts. So in this article we report the use of WOx/ZrO2 catalysts for the oxidation of dibenzothiophene (DBT) as a more effective material in nanometer scales. The WOx/ZrO2 samples were prepared by solid impregnation of ZrO2-x(OH)2x with ammonium metatungstate solution maintaining the pH at 10. Detailed structural and surface morphological analyses were carried out using Raman spectroscopy and Atomic force microscopy. In order to understand the catalytic activity which is largely influenced by the surface morphology, an interpretation based on the experimental results is given. The results showed an important correlation between the catalytic efficiency with the morphology of the surface which is identified as arrays of planes with steps of around 10 nm with the structures showing faceting with a preferential angle of 90°. It was established that when the number of W atoms in the surface increase the catalytic efficiency also increases. Thus we conclude that the material efficiency as a catalyst is directly related with the surface structure.

  5. Process and catalysts for hydrocarbon conversion. [high antiknock motor fuel

    Energy Technology Data Exchange (ETDEWEB)

    1940-02-14

    High anti-knock motor fuel is produced from hydrocarbons by subjecting it at an elevated temperature to contact with a calcined mixture of hydrated silica, hydrated alumina, and hydrated zirconia, substantially free from alkali metal compounds. The catalyst may be prepared by precipitating silica gel by the acidification of an aqueous solution of an alkali metal silicate, intimately mixing hydrated alumina and hydrated zirconia therewith, drying, purifying the composite to substantially remove alkali metal compounds, again drying, forming the dried material into particles, and finally calcining. The resultant conversion products may be fractionated to produce gasoline, hydrocarbon oil above gasoling boiling point range, and a gaseous fraction of olefins which are polymerized into gasoline boiling range polymers.

  6. The study on preparation of high dispersion and pure cerium dioxide for producing automotive exhaust catalysts

    International Nuclear Information System (INIS)

    Le Minh Tuan; Nguyen Trong Hung; Nguyen Thanh Chung

    2003-01-01

    The multi-stage counter-current solvent extraction process using TBP as the solvent has been carried out for purifying cerium and the ammonium carbonate precipitation method has been used to produce the cerium oxide of high dispersion and pure. The flow sheet of extraction system includes 3 extraction stages with O/A = 0.7,2 stripping stages and 4 scrubbing stages with O/A = 5. The condition for ammonium carbonate precipitation, drying and calcination have been investigated and a procedure that seem to be practically suitable to prepare cerium dioxide powder with great specific surface area for producing automotive exhaust catalyst has been proposed. (LMT)

  7. High-temperature catalytic reforming of n-hexane over supported and core-shell Pt nanoparticle catalysts: role of oxide-metal interface and thermal stability.

    Science.gov (United States)

    An, Kwangjin; Zhang, Qiao; Alayoglu, Selim; Musselwhite, Nathan; Shin, Jae-Youn; Somorjai, Gabor A

    2014-08-13

    Designing catalysts with high thermal stability and resistance to deactivation while simultaneously maintaining their catalytic activity and selectivity is of key importance in high-temperature reforming reactions. We prepared Pt nanoparticle catalysts supported on either mesoporous SiO2 or TiO2. Sandwich-type Pt core@shell catalysts (SiO2@Pt@SiO2 and SiO2@Pt@TiO2) were also synthesized from Pt nanoparticles deposited on SiO2 spheres, which were encapsulated by either mesoporous SiO2 or TiO2 shells. n-Hexane reforming was carried out over these four catalysts at 240-500 °C with a hexane/H2 ratio of 1:5 to investigate thermal stability and the role of the support. For the production of high-octane gasoline, branched C6 isomers are more highly desired than other cyclic, aromatic, and cracking products. Over Pt/TiO2 catalyst, production of 2-methylpentane and 3-methylpentane via isomerization was increased selectively up to 420 °C by charge transfer at Pt-TiO2 interfaces, as compared to Pt/SiO2. When thermal stability was compared between supported catalysts and sandwich-type core@shell catalysts, the Pt/SiO2 catalyst suffered sintering above 400 °C, whereas the SiO2@Pt@SiO2 catalyst preserved the Pt nanoparticle size and shape up to 500 °C. The SiO2@Pt@TiO2 catalyst led to Pt nanoparticle sintering due to incomplete protection of the TiO2 shells during the reaction at 500 °C. Interestingly, over the Pt/TiO2 catalyst, the average size of Pt nanoparticles was maintained even after 500 °C without sintering. In situ ambient pressure X-ray photoelectron spectroscopy demonstrated that the Pt/TiO2 catalyst did not exhibit TiO2 overgrowth on the Pt surface or deactivation by Pt sintering up to 600 °C. The extraordinarily high stability of the Pt/TiO2 catalyst promoted high reaction rates (2.0 μmol · g(-1) · s(-1)), which was 8 times greater than other catalysts and high isomer selectivity (53.0% of C6 isomers at 440 °C). By the strong metal-support interaction

  8. High-temperature electrochemical characterization of Ru core Pt shell fuel cell catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Bokach, D.; Fuente, J.L.G. de la; Tsypkin, M.; Ochal, P.; Tunold, R.; Sunde, S.; Seland, F. [Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), Sem Saelands veg 12, N-7491 Trondheim (Norway); Endsjoe, I.C. [Washington Mills AS, NO-7300 Orkanger (Norway)

    2011-12-15

    The electrooxidation of methanol was studied at elevated temperature and pressure by cyclic voltammetry and constant potential experiments at real fuel cell electrocatalysts. Ruthenium core and platinum shell nanoparticles were synthesized by a sequential polyol route, and characterized electrochemically by CO stripping at room temperature to quickly confirm the structure of the synthesized core-shell structure as compared to pure commercial Pt/C and Pt-Ru/C alloy catalysts. A significant promotional effect of Pt decorated Ru cores in the methanol oxidation was found at elevated temperatures and rather high-electrode potentials. A negative potential shift of the methanol oxidation peak is observed for the Ru rate at Pt/C core-shell catalyst at moderate temperatures, while a significant shift to positive potentials of the methanol oxidation peak occurs for Pt/C catalysts. The onset potential for methanol oxidation is lowered some 200 mV from room temperature and up to 120 C for all electrocatalysts, indicating that it is the thermal activity of water adsorption that dictates the onset potential. Direct methanol fuel cell experiments showed only small performance differences between Ru rate at Pt/C and Pt/C anode electrocatalysts, suggesting the necessity of render possible the formation of surface oxygen species at lower electrode potentials. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Enhanced hydrothermal stability of Cu-ZSM-5 catalyst via surface modification in the selective catalytic reduction of NO with NH{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tao; Shi, Juan; Liu, Jian, E-mail: liujian@cup.edu.cn; Wang, Daxi; Zhao, Zhen, E-mail: zhenzhao@cup.edu.cn; Cheng, Kai; Li, Jianmei

    2016-07-01

    Highlights: • The hydrothermal stability of Cu-ZSM-5 catalyst was enhanced after surface modification. • An inert silica layer was deposited on the surface of Cu-ZSM-5 and formed a protective layer. • The contact between Si and Cu and Al atoms could form Si-O-Al and Si- O−Cu bonds. • The redox and acidity properties of Cu-ZSM-5-CLD-Aged catalyst were largely retained. • The adsorption and activation of NO and NH{sub 3} was almost unchanged over Cu-ZSM-5-CLD catalyst before and after hydrothermal treatment. - Abstract: The surface of Cu-ZSM-5 catalyst was modified by chemical liquid deposition (CLD) of tetraethoxysilane (TEOS) for enhancing its hydrothermal stability in the selective catalytic reduction of NO with NH{sub 3}. After hydrothermal aging at 750 °C for 13 h, the catalytic performance of Cu-ZSM-5-Aged catalyst was significantly reduced for NO reduction in the entire temperature range, while that of Cu-ZSM-5-CLD-Aged catalyst was affected very little. The characterization results indicated that an inert silica layer was deposited on the surface of Cu-ZSM-5 and formed a protective layer, which prevents the detachment of Cu{sup 2+} from ZSM-5 ion-exchange positions and the dealumination of zeolite during the hydrothermal aging process. Based on the data it is hypothesized to be the primary reason for the high hydrothermal stability of Cu-ZSM-5-CLD catalyst.

  10. Effect of nanoscale flows on the surface structure of nanoporous catalysts.

    Science.gov (United States)

    Montemore, Matthew M; Montessori, Andrea; Succi, Sauro; Barroo, Cédric; Falcucci, Giacomo; Bell, David C; Kaxiras, Efthimios

    2017-06-07

    The surface structure and composition of a multi-component catalyst are critical factors in determining its catalytic performance. The surface composition can depend on the local pressure of the reacting species, leading to the possibility that the flow through a nanoporous catalyst can affect its structure and reactivity. Here, we explore this possibility for oxidation reactions on nanoporous gold, an AgAu bimetallic catalyst. We use microscopy and digital reconstruction to obtain the morphology of a two-dimensional slice of a nanoporous gold sample. Using lattice Boltzmann fluid dynamics simulations along with thermodynamic models based on first-principles total-energy calculations, we show that some sections of this sample have low local O 2 partial pressures when exposed to reaction conditions, which leads to a pure Au surface in these regions, instead of the active bimetallic AgAu phase. We also explore the effect of temperature on the surface structure and find that moderate temperatures (≈300-450 K) should result in the highest intrinsic catalytic performance, in apparent agreement with experimental results.

  11. Non-PGM cell catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Colon-Mercado, H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Elvington, M. [Savannah River Consulting, Aiken, SC (United States); Ganesan, P. [Savannah River Consulting, Aiken, SC (United States)

    2017-09-27

    A unique approach has been developed to probe the non-PGM catalyst active site for the Oxygen Reduction Reaction (ORR) for PEMFCs. Iron based functionalities have been engineered into a variety of catalysts to evaluate their impact on activity for the ORR. A series of high surface area catalysts were synthesized and the impact of the chemical structure on the electrochemical and electrocatalytic properties was investigated. Elemental and surface analyses of the prepared catalysts reveal the incorporation of iron in a targeted and controlled manner. A high surface area framework catalyst was prepared that shows exceptional activity, comparable to state-of-the-art materials. The results of this research project provided critical seed data for the newly awarded ElectroCat project, which focuses on rationally designed framework catalysts for the oxygen reduction reaction.

  12. Promotion of Pt-Ru/C catalysts driven by heat treated induced surface segregation for methanol oxidation reaction

    International Nuclear Information System (INIS)

    Wei Yuchen; Liu Chenwei; Chang Weijung; Wang Kuanwen

    2011-01-01

    Research highlights: → Thermal treatments on the Pt-Ru/C induce different extents of surface segregation. → O 2 treatment results in obvious Ru segregation and formation of RuO 2 . → Catalysts treated in H 2 have the excellent CO de-poisoning ability. → N 2 treatment suppresses the surface Pt depletion and hence promotes the MOR. - Abstract: Carbon supported Pt-Ru/C (1:1) alloy catalysts supplied by E-TEK are widely used for fuel cell research. Heat treatments in various atmospheres are conducted for the promotion of the methanol oxidation reaction (MOR) and the investigation of the structure-activity relationship (SAR) of the catalysts. The alloy structures, surface compositions, surface species, and electro-catalytic activities of the alloy catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV), respectively. The as-received Pt-Ru/C catalysts have a Ru rich in the inner core and Pt rich on the outer shell structure. Thermal treatments on the catalysts induce Ru surface segregation in different extents and thereby lead to their alteration of the alloying degrees. O 2 treatment results in obvious Ru segregation and formation of RuO 2 . Catalysts treated in H 2 have the highest I f /I b value in the CV scans among all samples, indicating the catalysts have the excellent CO de-poisoning ability as evidenced by anodic CO stripping experiments. N 2 treatment may serve as an adjustment process for the surface composition and structure of the catalysts, which can suppress the surface Pt depletion (∼60% Pt on the surface), make the components stable and hence promote the MOR significantly.

  13. Promotion of Pt-Ru/C catalysts driven by heat treated induced surface segregation for methanol oxidation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Wei Yuchen; Liu Chenwei; Chang Weijung [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Wang Kuanwen, E-mail: kuanwen.wang@gmail.com [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China)

    2011-01-12

    Research highlights: > Thermal treatments on the Pt-Ru/C induce different extents of surface segregation. > O{sub 2} treatment results in obvious Ru segregation and formation of RuO{sub 2}. > Catalysts treated in H{sub 2} have the excellent CO de-poisoning ability. > N{sub 2} treatment suppresses the surface Pt depletion and hence promotes the MOR. - Abstract: Carbon supported Pt-Ru/C (1:1) alloy catalysts supplied by E-TEK are widely used for fuel cell research. Heat treatments in various atmospheres are conducted for the promotion of the methanol oxidation reaction (MOR) and the investigation of the structure-activity relationship (SAR) of the catalysts. The alloy structures, surface compositions, surface species, and electro-catalytic activities of the alloy catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV), respectively. The as-received Pt-Ru/C catalysts have a Ru rich in the inner core and Pt rich on the outer shell structure. Thermal treatments on the catalysts induce Ru surface segregation in different extents and thereby lead to their alteration of the alloying degrees. O{sub 2} treatment results in obvious Ru segregation and formation of RuO{sub 2}. Catalysts treated in H{sub 2} have the highest I{sub f}/I{sub b} value in the CV scans among all samples, indicating the catalysts have the excellent CO de-poisoning ability as evidenced by anodic CO stripping experiments. N{sub 2} treatment may serve as an adjustment process for the surface composition and structure of the catalysts, which can suppress the surface Pt depletion ({approx}60% Pt on the surface), make the components stable and hence promote the MOR significantly.

  14. Iron carbide on titania surface modified with group VA oxides as Fischer-Tropsch catalysts

    International Nuclear Information System (INIS)

    Wachs, I.E.; Fiato, R.A.; Chersich, C.C.

    1986-01-01

    A catalyst is described comprising iron carbide supported on a surface modified titania wherein the support comprises an oxide of a metal selected form the group consisting of niobium, vanadium, tantalum or mixture thereof supported on the titania wherein at least a portion of the supported oxide of niobium, vanandium, tantalum or mixture is in a non-crystalline form. The amount of the supported oxide ranges from about 0.5 to 25 weight percent metal oxide on the titania support based on the total support composition and the catalyst contains at least about 2 milligrams of iron, calculated as Fe/sub 2/O/sub 3/, per square meter of support surface

  15. Features of the kinetics of heterogeneous reactions with phase transformations on catalyst surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Berman, A D; Krylov, O V

    1978-01-01

    This paper presents a review of 41 bibliographic references to experiments on the adsorption of various gases (e.g., carbon monoxide, formic acid, ammonia, and oxygen) on metals (e.g., nickel, molybdenum, and platinum) and oxides covers observations of two-dimensional phases during adsorption; the kinetics of adsorption and catalysis associated with two-dimensional phase transitions; and several approximate models for describing the kinetics of heterogeneous catalysis which account for two-dimensional phase transformations on catalyst surfaces.

  16. In-situ observations of catalyst dynamics during surface-bound carbon nanotube nucleation

    DEFF Research Database (Denmark)

    Hofmann, S; Sharma, R; Du, G

    2007-01-01

    nanoparticles on SiOx support show crystalline lattice fringe contrast and high deformability before and during nanotube formation. A single-walled carbon nanotube nucleates by lift-off of a carbon cap. Cap stabilization and nanotube growth involve the dynamic reshaping of the catalyst nanocrystal itself...

  17. Catalysts for synthetic liquid fuels

    Energy Technology Data Exchange (ETDEWEB)

    Bruce, L.A.; Turney, T.W.

    1987-12-01

    Fischer-Tropsch catalysts have been designed, characterized and tested for the selective production of hydrocarbons suitable as synthetic liquid transport fuels from synthesis gas (i.e., by the reduction of carbon monoxide with hydrogen). It was found that hydrocarbons in the middle distillate range, or suitable for conversion to that range, could be produced over several of the new catalyst systems. The various catalysts examined included: (1) synthetic cobalt clays, mainly cobalt chlorites; (2) cobalt hydrotalcites; (3) ruthenium metal supported on rare earth oxides of high surface area; and (4) a novel promoted cobalt catalyst. Active and selective catalysts have been obtained, in each category. With the exception of the clays, reproducibility of catalyst performance has been good. Catalysts in groups 2 and 4 have exhibited very high activity, with long lifetimes and easy regeneration.

  18. Effect of preparation method on the surface characteristics and activity of the Pd/OMS-2 catalysts for the oxidation of carbon monoxide, toluene, and ethyl acetate

    Science.gov (United States)

    Liu, Lisha; Song, Yong; Fu, Zhidan; Ye, Qing; Cheng, Shuiyuan; Kang, Tianfang; Dai, Hongxing

    2017-02-01

    The cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2)-supported Pd (0.5 wt% Pd/OMS-2-DP, 0.5 wt% Pd/OMS-2-PI, and 0.5 wt% Pd/OMS-2-EX) catalysts were prepared by the deposition-precipitation, pre-incorporation, and ion-exchanging strategies, respectively. It is shown that the preparation method exerted an important effect on the physicochemical property of the sample. Among the OMS-2-supported Pd catalysts, 0.5 wt% Pd/OMS-2-DP possessed the highest surface (Mn2+ + Mn3+)/Mn4+ atomic ratio and the highest surface Pd loading and acid sites. The 0.5 wt% Pd/OMS-2 catalysts outperformed the Pd-free counterpart, among which 0.5 wt% Pd/OMS-2-DP presented the best catalytic activity (T50% and T90% were 25 and 55 °C for CO oxidation, 240 and 285 °C for toluene oxidation, and 160 and 200 °C for ethyl acetate oxidation, respectively). We believe that the high Pd surface loading, high surface atomic ratio of (Mn2+ + Mn3+)/Mn4+, and good low-temperature reducibility, good oxygen mobility, and high acidity were responsible for the excellent performance of the 0.5 wt% Pd/OMS-2-DP catalyst.

  19. Highly active Ni/Y-doped ZrO{sub 2} catalysts for CO{sub 2} methanation

    Energy Technology Data Exchange (ETDEWEB)

    Takano, H., E-mail: takano_hi@hitachizosen.co.jp [Hitachi Zosen Corporation, Kashiwa, 277-8515 (Japan); Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, 060-8628 (Japan); Kirihata, Y.; Izumiya, K.; Kumagai, N. [Hitachi Zosen Corporation, Kashiwa, 277-8515 (Japan); Habazaki, H., E-mail: habazaki@eng.hokudai.ac.jp [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, 060-8628 (Japan); Division of Applied Chemistry & Frontier Chemistry Center, Faculty of Engineering, Hokkaido University, Sapporo, 060-8628 (Japan); Hashimoto, K. [Tohoku Institute of Technology, Sendai, 277-8515 (Japan)

    2016-12-01

    Highlights: • The Ni/Y-doped ZrO{sub 2} catalysts show highly catalytic activity for CO{sub 2} methanation. • Bidentate carbonate is a major adsorption spice on the Ni/Y-doped ZrO{sub 2} catalysts. • The oxide support of t-ZrO{sub 2} and/or c-ZrO{sub 2} with oxygen vacancies plays a key role. - Abstract: The catalytic methanation of CO{sub 2} was carried out on Ni catalysts supported on Y-doped ZrO{sub 2} with various Y{sup 3+} concentrations and Ni/(Zr + Y) molar ratio = 1. The catalysts were characterized by X-ray diffraction, scanning transmission electron microscopy, specific surface area, temperature-programmed desorption of CO{sub 2}, and temperature-programmed reaction. In addition, operando diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFT) was used to identify the adsorbed reaction intermediate. Catalysts supported on Y-doped ZrO{sub 2} show higher catalytic activity than the catalyst on Y-free ZrO{sub 2} with a monoclinic ZrO{sub 2} phase. The catalytic activity is also dependent upon the Y{sup 3+} concentration, and the highest activity was obtained for the catalyst with a Y/(Zr + Y) molar ratio of 0.333, which consists mainly of fcc Ni and cubic ZrO{sub 2} phase. Y{sup 3+} doping into ZrO{sub 2} introduces oxygen vacancies, which play an important role in enhancing the catalytic activity. The operando DRIFT study reveals that a CO adsorption intermediate is absent, and bidentate carbonate is an important intermediate for CH{sub 4} formation.

  20. Ammonia synthesis over multi-promoted iron catalysts obtained by high-energy ball-milling

    DEFF Research Database (Denmark)

    Jacobsen, C.J.H.; Jiang, Jianzhong; Mørup, Steen

    1999-01-01

    The feasibility of producing ammonia synthesis catalysts from high-energy ball-milling of a simple mixture of the constituent oxides has been investigated. The effect of ball-milling the fused oxidic precursor of the industrial KM1 ammonia synthesis catalyst has also been studied. The results show...

  1. Catalysts and conditions for the highly efficient, selective and stable heterogeneous oligomerisation of ethylene

    CSIR Research Space (South Africa)

    Heveling, J

    1998-10-11

    Full Text Available The oligomerisation of ethylene into products in the C-4-C-20 range over heterogeneous nickel catalysts in a fixed-bed reactor at low temperature and high pressure (LT-HP) is reported. The catalysts were obtained by Ni (II) exchange or impregnation...

  2. Silica nanoparticles as a highly efficient catalyst for the one-pot ...

    African Journals Online (AJOL)

    Silica nanoparticles as a highly efficient catalyst for the one-pot synthesis of sterically congested ... Bulletin of the Chemical Society of Ethiopia ... 42 nm) as a catalyst under solvent free conditions at room temperature is described. The ease of ...

  3. Highly active self-immobilized FI-Zr catalysts in a PCP framework for ethylene polymerization.

    Science.gov (United States)

    Li, He; Xu, Bo; He, Jianghao; Liu, Xiaoming; Gao, Wei; Mu, Ying

    2015-12-04

    A series of zirconium-based porous coordination polymers (PCPs) containing FI catalysts in the frameworks have been developed and studied as catalysts for ethylene polymerization. These PCPs exhibit good catalytic activities and long life times, producing polyethylenes with high molecular weights and bimodal molecular weight distribution in the form of particles.

  4. Chromium-based metal-organic framework MIL-101 as a highly effective catalyst in plasma for toluene removal

    Science.gov (United States)

    Wu, Junliang; Xia, Qibin; Xiao, Jing; Li, Zhong

    2017-11-01

    Catalytic performance of MIL-101—a type of chromium-based metal-organic frameworks (MOFs)—in a plasma catalysis system for toluene removal was experimentally studied. The MIL-101 was synthesized using a hydrothermal method, and its catalytic performance was compared to two other catalysts, Cr2O3/γ-Al2O3 and γ-Al2O3, in a dielectric barrier discharge (DBD) reactor. Results showed that the presence of a catalyst in plasma changed the voltage and current characteristic substantially, and promoted the performance of the plasma reactor. Among the catalysts, the MIL-101 exhibited a significantly high toluene conversion, which was 20% and 35% higher than Cr2O3/γ-Al2O3 and γ-Al2O3, respectively, under the same testing conditions, as well as higher carbon balance and CO2 selectivity. The analysis of by-products on the surfaces of the catalysts before and after reaction demonstrated that MIL-101 had better resistance towards by-products accumulation compared to Cr2O3/γ-Al2O3 and γ-Al2O3. The loading of MnO x on MIL-101 further promoted its catalytic performance. MIL-101 exhibits attractive catalytic properties as a catalyst in a plasma catalysis system for the decomposition of volatile organic compounds.

  5. Chromium-based metal-organic framework MIL-101 as a highly effective catalyst in plasma for toluene removal

    International Nuclear Information System (INIS)

    Wu, Junliang; Xia, Qibin; Xiao, Jing; Li, Zhong

    2017-01-01

    Catalytic performance of MIL-101—a type of chromium-based metal-organic frameworks (MOFs)—in a plasma catalysis system for toluene removal was experimentally studied. The MIL-101 was synthesized using a hydrothermal method, and its catalytic performance was compared to two other catalysts, Cr 2 O 3 / γ -Al 2 O 3 and γ -Al 2 O 3 , in a dielectric barrier discharge (DBD) reactor. Results showed that the presence of a catalyst in plasma changed the voltage and current characteristic substantially, and promoted the performance of the plasma reactor. Among the catalysts, the MIL-101 exhibited a significantly high toluene conversion, which was 20% and 35% higher than Cr 2 O 3 / γ -Al 2 O 3 and γ -Al 2 O 3 , respectively, under the same testing conditions, as well as higher carbon balance and CO 2 selectivity. The analysis of by-products on the surfaces of the catalysts before and after reaction demonstrated that MIL-101 had better resistance towards by-products accumulation compared to Cr 2 O 3 / γ -Al 2 O 3 and γ -Al 2 O 3 . The loading of MnO x on MIL-101 further promoted its catalytic performance. MIL-101 exhibits attractive catalytic properties as a catalyst in a plasma catalysis system for the decomposition of volatile organic compounds. (paper)

  6. Direct conversion of CO2 into liquid fuels with high selectivity over a bifunctional catalyst

    Science.gov (United States)

    Gao, Peng; Li, Shenggang; Bu, Xianni; Dang, Shanshan; Liu, Ziyu; Wang, Hui; Zhong, Liangshu; Qiu, Minghuang; Yang, Chengguang; Cai, Jun; Wei, Wei; Sun, Yuhan

    2017-10-01

    Although considerable progress has been made in carbon dioxide (CO2) hydrogenation to various C1 chemicals, it is still a great challenge to synthesize value-added products with two or more carbons, such as gasoline, directly from CO2 because of the extreme inertness of CO2 and a high C-C coupling barrier. Here we present a bifunctional catalyst composed of reducible indium oxides (In2O3) and zeolites that yields a high selectivity to gasoline-range hydrocarbons (78.6%) with a very low methane selectivity (1%). The oxygen vacancies on the In2O3 surfaces activate CO2 and hydrogen to form methanol, and C-C coupling subsequently occurs inside zeolite pores to produce gasoline-range hydrocarbons with a high octane number. The proximity of these two components plays a crucial role in suppressing the undesired reverse water gas shift reaction and giving a high selectivity for gasoline-range hydrocarbons. Moreover, the pellet catalyst exhibits a much better performance during an industry-relevant test, which suggests promising prospects for industrial applications.

  7. Catalyst free growth of CNTs by CVD on nanoscale rough surfaces of silicon substrates

    Science.gov (United States)

    Damodar, D.; Sahoo, R. K.; Jacob, C.

    2013-06-01

    Catalyst free growth of carbon nanotubes (CNT) has been achieved using atmospheric pressure chemical vapor deposition (APCVD) on surface modified Si(111) substrates. The effect of the substrate surface has been observed by partially etching with KOH (potassium hydroxide) solution which is an anisotropic etchant. Scanning electron microscopy (SEM) confirmed the formation of CNTs over most of the area of the substrate where substrates were anisotropically etched. Transmission electron microscopy (TEM) was used to observe the internal structure of the CNTs. Raman spectroscopy further confirmed the formation of the carbon nanostructures and also their graphitic crystallinity.

  8. Adsorptive removal of residual catalyst from palm biodiesel: Application of response surface methodology

    Directory of Open Access Journals (Sweden)

    Mjalli Sabri Farouq

    2012-01-01

    Full Text Available In this work, the residual potassium hydroxide catalyst was removed from palm oil-based methyl esters using an adsorption technique. The produced biodiesel was initially purified through a water washing process. To produce a biodiesel with a better quality and also to meet standard specifications (EN 14214 and ASTM D6751, batch adsorption on palm shell activated carbon was used for further catalyst removal. The Central Composite Design (CCD of the Response Surface Methodology (RSM was used to study the influence of adsorbent amount, time and temperature on the adsorption of potassium species. The maximum catalyst removal was achieved at 40°C using 0.9 g activated carbon for 20 h adsorption time. The results from the Response Surface Methodology are in a good agreement with the measured values. The absolute error in prediction at the optimum condition was 3.7%, which is reasonably accurate. This study proves that adsorption post-treatment techniques can be successfully employed to improve the quality of biodiesel fuel for its effective use on diesel engines and to minimize the usage of water.

  9. The Simple, Effective Synthesis of Highly Dispersed Pd/C and CoPd/C Heterogeneous Catalysts via Charge-Enhanced Dry Impregnation

    Directory of Open Access Journals (Sweden)

    Lawrence D’Souza

    2016-05-01

    Full Text Available Pd/C and CoPd/C heterogeneous catalysts have been synthesized by adopting Charge Enhanced Dry Impregnation (CEDI. The particles size distribution, their high metal surface-to-bulk ratios, and synthesis feasibility are unmatchable to any known noble metal bimetallic heterogeneous catalyst preparation techniques. Next generation Fuel Cells and Fischer-Tropsch catalytic processes economy will be benefited from the proposed methodology.

  10. High-throughput selection for cellulase catalysts using chemical complementation.

    Science.gov (United States)

    Peralta-Yahya, Pamela; Carter, Brian T; Lin, Hening; Tao, Haiyan; Cornish, Virginia W

    2008-12-24

    Efficient enzymatic hydrolysis of lignocellulosic material remains one of the major bottlenecks to cost-effective conversion of biomass to ethanol. Improvement of glycosylhydrolases, however, is limited by existing medium-throughput screening technologies. Here, we report the first high-throughput selection for cellulase catalysts. This selection was developed by adapting chemical complementation to provide a growth assay for bond cleavage reactions. First, a URA3 counter selection was adapted to link chemical dimerizer activated gene transcription to cell death. Next, the URA3 counter selection was shown to detect cellulase activity based on cleavage of a tetrasaccharide chemical dimerizer substrate and decrease in expression of the toxic URA3 reporter. Finally, the utility of the cellulase selection was assessed by isolating cellulases with improved activity from a cellulase library created by family DNA shuffling. This application provides further evidence that chemical complementation can be readily adapted to detect different enzymatic activities for important chemical transformations for which no natural selection exists. Because of the large number of enzyme variants that selections can now test as compared to existing medium-throughput screens for cellulases, this assay has the potential to impact the discovery of improved cellulases and other glycosylhydrolases for biomass conversion from libraries of cellulases created by mutagenesis or obtained from natural biodiversity.

  11. Lanthanides-based graphene catalysts for high performance hydrogen evolution and oxygen reduction

    International Nuclear Information System (INIS)

    Shinde, S.S.; Sami, Abdul; Lee, Jung-Ho

    2016-01-01

    Highlights: • Facile, scalable in-situ synthesis of lanthanide (La, Eu, Yb) doped graphene frameworks. • Efficient electrocatalytic performance towards HER and ORR. • Eu-Gr hybrid shows HER performance; onset & overpotential (81 & 160 mV), & Tafel slope (52 mV dec −1 ). • Eu-Gr exhibits superior activity of ORR; onset potential (0.92 V), electron transfer number (4.03). • Excellent long-term stability in HER and ORR, comparable to those of commercial Pt/C catalysts. - Abstract: The design of efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) has received enormous consideration due to their effectiveness in modern renewable energy technologies such as fuel cells, electrolyzers, and metal–air batteries. Herein, we present a facile method to fabricate lanthanides (L = La, Eu, Yb)-doped graphene materials as catalyst for the HER and ORR that show desirable electrocatalytic activities as well as long-term stability. The Eu-graphene hybrid has showed unbeatable HER performance such as small values of onset potential (81 mV), overpotential (160 mV), and Tafel slope (52 mV dec −1 ), along with a high exchange current density (7.55 × 10 −6 A cm −2 ). The L-graphenes also exhibit superior electrocatalytic activity for ORR, including small Tafel slopes (96, 66, and 105 mV dec −1 for La-Gr, Eu-Gr, and Yb-Gr, respectively), positive onset potential (∼0.83–0.92 V), high electron transfer numbers (∼3.84–4.03), and excellent enduring strength, analogous to those of viable Pt/C catalysts. The excellent electrocatalytic performance is attributed to the synergistic effect of abundant edges and doping sites, high electrical conductivity, large active surface areas and fast charge transfer; which renders lanthanide-based graphene hybrids as potentially great candidate for energy conversion systems.

  12. Laser-Induced Fluorescence Detection in High-Throughput Screening of Heterogeneous Catalysts and Single Cells Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Su, Hui [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    Laser-induced fluorescence detection is one of the most sensitive detection techniques and it has found enormous applications in various areas. The purpose of this research was to develop detection approaches based on laser-induced fluorescence detection in two different areas, heterogeneous catalysts screening and single cell study. First, the author introduced laser-induced imaging (LIFI) as a high-throughput screening technique for heterogeneous catalysts to explore the use of this high-throughput screening technique in discovery and study of various heterogeneous catalyst systems. This scheme is based on the fact that the creation or the destruction of chemical bonds alters the fluorescence properties of suitably designed molecules. By irradiating the region immediately above the catalytic surface with a laser, the fluorescence intensity of a selected product or reactant can be imaged by a charge-coupled device (CCD) camera to follow the catalytic activity as a function of time and space. By screening the catalytic activity of vanadium pentoxide catalysts in oxidation of naphthalene, they demonstrated LIFI has good detection performance and the spatial and temporal resolution needed for high-throughput screening of heterogeneous catalysts. The sample packing density can reach up to 250 x 250 subunits/cm2 for 40-μm wells. This experimental set-up also can screen solid catalysts via near infrared thermography detection. In the second part of this dissertation, the author used laser-induced native fluorescence coupled with capillary electrophoresis (LINF-CE) and microscope imaging to study the single cell degranulation. On the basis of good temporal correlation with events observed through an optical microscope, they have identified individual peaks in the fluorescence electropherograms as serotonin released from the granular core on contact with the surrounding fluid.

  13. Design of high-activity single-atom catalysts via n-p codoping

    Science.gov (United States)

    Wang, Xiaonan; Zhou, Haiyan; Zhang, Xiaoyang; Jia, Jianfeng; Wu, Haishun

    2018-03-01

    The large-scale synthesis of stable single-atom catalysts (SACs) in experiments remains a significant challenge due to high surface free energy of metal atom. Here, we propose a concise n-p codoping approach, and find it can not only disperse the relatively inexpensive metal, copper (Cu), onto boron (B)-doped graphene, but also result in high-activity SACs. We use CO oxidation on B/Cu codoped graphene as a prototype example, and demonstrate that: (1) a stable SAC can be formed by stronger electrostatic attraction between the metal atom (n-type Cu) and support (p-type B-doped graphene). (2) the energy barrier of the prototype CO oxidation on B/Cu codoped graphene is 0.536 eV by the Eley-Rideal mechanism. Further analysis shows that the spin selection rule can provide well theoretical insight into high activity of our suggested SAC. The concept of n-p codoping may lead to new strategy in large-scale synthesis of stable single-atom catalysts.

  14. Facile and large-scale synthesis of high quality few-layered graphene nano-platelets via methane decomposition over unsupported iron family catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Awadallah, Ahmed E., E-mail: ahmedelsayed_epri@yahoo.com [Process Development Division, Egyptian Petroleum Research Institute, 11727 Cairo (Egypt); Aboul-Enein, Ateyya A. [Process Development Division, Egyptian Petroleum Research Institute, 11727 Cairo (Egypt); Kandil, Usama F. [Petroleum Application Department, Egyptian Petroleum Research Institute, 11727 Cairo (Egypt); Taha, Mahmoud Reda [Department of Civil Engineering, University of New Mexico, Albuquerque, NM 87131 (United States)

    2017-04-15

    High quality few-layered graphene nano-platelets (GNPs) were successfully prepared via catalytic chemical vapor deposition of methane under ambient pressure using substrate-free unsupported iron, cobalt, and nickel metallic sheets as catalysts. The bulk catalysts were prepared via combustion method using citric acid as a fuel. Various analytical techniques, including high-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), temperature programmed reduction (TPR) and Raman spectroscopy were employed to characterize the fresh and reduced catalysts and to identify the morphological structure of the as-grown GNPs. TEM images of the reduced metal catalysts showed that polycrystalline metallic sheets were easily produced after complete reduction of unsupported metal oxides. The data demonstrated that the formation of zero-valent metallic sheets could effectively promote the growth of GNPs on their surfaces. The unsupported Ni catalyst exhibits higher catalytic growth activity in terms of GNPs yield (254 wt%) compared with all other catalysts. Raman spectra and TEM results established that a few layers of GNPs with high crystallinity and good graphitization were produced. TGA results further demonstrated that the as-grown GNPs exhibit significantly higher thermal stability in air atmosphere compared with other synthesis methods. - Highlights: • Few-layered graphene nanoplatelets were prepared via methane catalytic decomposition. • Metallic sheets of iron group metals were used as novel catalysts. • The surfaces of metallic sheets were found to be very effective for GNPs growth. • The number of layers is dependent on the morphological structure of the catalysts. • The unsupported metallic Ni catalyst exhibited higher catalytic growth activity.

  15. Quantitative Surface Analysis by Xps (X-Ray Photoelectron Spectroscopy: Application to Hydrotreating Catalysts

    Directory of Open Access Journals (Sweden)

    Beccat P.

    1999-07-01

    Full Text Available XPS is an ideal technique to provide the chemical composition of the extreme surface of solid materials, vastly applied to the study of catalysts. In this article, we will show that a quantitative approach, based upon fundamental expression of the XPS signal, has enabled us to obtain a consistent set of response factors for the elements of the periodic table. In-depth spadework has been necessary to know precisely the transmission function of the spectrometer used at IFP. The set of response factors obtained enables to perform, on a routine basis, a quantitative analysis with approximately 20% relative accuracy, which is quite acceptable for an analysis of such a nature. While using this quantitative approach, we have developed an analytical method specific to hydrotreating catalysts that allows obtaining the sulphiding degree of molybdenum quite reliably and reproducibly. The usage of this method is illustrated by two examples for which XPS spectroscopy has provided with information sufficiently accurate and quantitative to help understand the reactivity differences between certain MoS2/Al2O3 or NiMoS/Al2O3-type hydrotreating catalysts.

  16. Surface chemistry and catalytic properties of VO{sub X}/Ti-MCM-41 catalysts for dibenzothiophene oxidation in a biphasic system

    Energy Technology Data Exchange (ETDEWEB)

    González, J. [ESIQIE, Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional s/n, 07738 Col. Zacatenco, Mexico City (Mexico); Chen, L.F., E-mail: lchen@ipn.mx [ESIQIE, Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional s/n, 07738 Col. Zacatenco, Mexico City (Mexico); Wang, J.A.; Manríquez, Ma.; Limas, R. [ESIQIE, Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional s/n, 07738 Col. Zacatenco, Mexico City (Mexico); Schachat, P.; Navarrete, J. [Dirección de Investigación, Instituto Mexicano del Petróleo, Eje Lázaro Cárdenas 152, 07730 México D.F. (Mexico); Contreras, J.L. [Laboratorio de Catálisis y Polímeros, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-A, Av. San Pablo No. 180, 02200 México D.F. (Mexico)

    2016-08-30

    Highlights: • Oxidative desulfurization of model diesel was tested in a biphasic system. • ODS activity was proportional to the V{sup 5+}/(V{sup 4+} + V{sup 5+}) values of the catalysts. • Lewis acidity was related to vanadium content and catalytic activity. • 99.9% DBT was oxidized using 25%V{sub 2}O{sub 5}/Ti-MCM-41 at 60 °C within 60 min. - Abstract: A series of vanadium oxide supported on Ti-MCM-41 catalysts was synthesized via the incipient impregnation method by varying the vanadia loading from 5 wt% to 10, 15, 20 and 25 wt%. These catalysts were characterized by a variety of advanced techniques for investigating their crystalline structure, textural properties, and surface chemistry information including surface acidity, reducibility, vanadium oxidation states, and morphological features. The catalytic activities of the catalysts were evaluated in a biphasic reaction system for oxidative desulfurization (ODS) of a model diesel containing 300 ppm of dibenzothiophene (DBT) where acetonitrile was used as extraction solvent and H{sub 2}O{sub 2} as oxidant. ODS activity was found to be proportional to the V{sup 5+}/(V{sup 4+} + V{sup 5+}) values of the catalysts, indicating that the surface vanadium pentoxide (V{sub 2}O{sub 5}) was the active phase. Reaction temperature would influence significantly the ODS efficiency; high temperature, i.e., 80 °C, would lead to low ODS reaction due to the partial decomposition of oxidant. All the catalysts contained both Lewis and Brønsted acid sites but the former was predominant. The catalysts with low vanadia loading (5 or 10 wt%V{sub 2}O{sub 5}) had many Lewis acid sites and could strongly adsorb DBT molecule via the electron donation/acceptance action which resulted in an inhibition for the reaction of DBT with the surface peroxometallic species. The catalyst with high vanadia loading (25wt%V{sub 2}O{sub 5}/Ti-MCM-41) showed the highest catalytic activity and could remove 99.9% of DBT at 60 °C within 60 min.

  17. Highly efficient and stable catalyst for peroxynitrite decomposition

    Science.gov (United States)

    Yurii V. Geletii; Alan J. Bailey; Jennifer J. Cowan; Ira A. Weinstock; Craig L. Hill

    2001-01-01

    The new cobalt substituted-polyoxometalate K7[CoAlW11O39]•15H2O and the simple CoCl2•6H2O salt are efficient catalysts for peroxynitrite decomposition. These compounds also catalyze the oxidation of ascorbic acid and the nitration of phenol by peroxynitrite.

  18. Studies on recycling and utilization of spent catalysts. Preparation of active hydrodemetallization catalyst compositions from spent residue hydroprocessing catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Marafi, Meena; Stanislaus, Antony [Petroleum Refining Department, Petroleum Research and Studies Center, Kuwait Institute for Scientific Research, P.O. Box 24885, Safat (Kuwait)

    2007-02-15

    Spent catalysts form a major source of solid wastes in the petroleum refining industries. Due to environmental concerns, increasing emphasis has been placed on the development of recycling processes for the waste catalyst materials as much as possible. In the present study the potential reuse of spent catalysts in the preparation of active new catalysts for residual oil hydrotreating was examined. A series of catalysts were prepared by mixing and extruding spent residue hydroprocessing catalysts that contained C, V, Mo, Ni and Al{sub 2}O{sub 3} with boehmite in different proportions. All prepared catalysts were characterized by chemical analysis and by surface area, pore volume, pore size and crushing strength measurements. The hydrodesulfurization (HDS) and hydrodemetallization (HDM) activities of the catalysts were evaluated by testing in a high pressure fixed-bed microreactor unit using Kuwait atmospheric residue as feed. A commercial HDM catalyst was also tested under similar operating conditions and their HDS and HDM activities were compared with that of the prepared catalysts. The results revealed that catalyst prepared with addition of up to 40 wt% spent catalyst to boehmite had fairly high surface area and pore volume together with large pores. The catalyst prepared by mixing and extruding about 40 wt% spent catalyst with boehmite was relatively more active for promoting HDM and HDS reactions than a reference commercial HDM catalyst. The formation of some kind of new active sites from the metals (V, Mo and Ni) present in the spent catalyst is suggested to be responsible for the high HDM activity of the prepared catalyst. (author)

  19. Integrated in situ characterization of molten salt catalyst surface: Evidence of sodium peroxide and OH radical formation

    KAUST Repository

    Takanabe, Kazuhiro; Khan, Abdulaziz M.; Tang, Yu; Nguyen, Luan; Ziani, Ahmed; Jacobs, Benjamin W; Elbaz, Ayman M.; Sarathy, S Mani; Tao, Franklin Feng

    2017-01-01

    Na-based catalysts (i.e., Na2WO4) were proposed to selectively catalyze OH radical formation from H2O and O2 at high temperatures. This reaction may proceed on molten salt state surfaces due to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na2WO4, which can form OH radicals, using in situ techniques including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometer, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). As a result, Na2O2 species, which were hypothesized to be responsible for the formation of OH radicals, has been identified on the outer surfaces at temperatures ≥800°C, and these species are useful for various gas-phase hydrocarbon reactions including the selective transformation of methane to ethane.

  20. Integrated in situ characterization of molten salt catalyst surface: Evidence of sodium peroxide and OH radical formation

    KAUST Repository

    Takanabe, Kazuhiro

    2017-06-26

    Na-based catalysts (i.e., Na2WO4) were proposed to selectively catalyze OH radical formation from H2O and O2 at high temperatures. This reaction may proceed on molten salt state surfaces due to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na2WO4, which can form OH radicals, using in situ techniques including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometer, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). As a result, Na2O2 species, which were hypothesized to be responsible for the formation of OH radicals, has been identified on the outer surfaces at temperatures ≥800°C, and these species are useful for various gas-phase hydrocarbon reactions including the selective transformation of methane to ethane.

  1. Carbon nanocages: a new support material for Pt catalyst with remarkably high durability.

    Science.gov (United States)

    Wang, Xiao Xia; Tan, Zhe Hua; Zeng, Min; Wang, Jian Nong

    2014-03-24

    Low durability is the major challenge hindering the large-scale implementation of proton exchange membrane fuel cell (PEMFC) technology, and corrosion of carbon support materials of current catalysts is the main cause. Here, we describe the finding of remarkably high durability with the use of a novel support material. This material is based on hollow carbon nanocages developed with a high degree of graphitization and concurrent nitrogen doping for oxidation resistance enhancement, uniform deposition of fine Pt particles, and strong Pt-support interaction. Accelerated degradation testing shows that such designed catalyst possesses a superior electrochemical activity and long-term stability for both hydrogen oxidation and oxygen reduction relative to industry benchmarks of current catalysts. Further testing under conditions of practical fuel cell operation reveals almost no degradation over long-term cycling. Such a catalyst of high activity, particularly, high durability, opens the door for the next-generation PEMFC for "real world" application.

  2. Hydroprocessing catalyst development

    Energy Technology Data Exchange (ETDEWEB)

    Boorman, P.M.; Kydd, R.A.; Sorensen, T.S.; Chong, K.; Lewis, J.

    1992-08-01

    Co-Mo and Ni-Mo hydroprocessing catalysts were examined for their activity in removal of sulfur from thiophene in model compounds, and in the cracking and hydrocracking of cumene. Three types of support materials were examined: carbon, modified carbon, and carbon covered alumina. The objective of the study was to examine the correlation between catalyst activity in the hydrodenitrogenation of model compounds, and the resistance of the catalyst to nitrogen poisoning during use in the hydroprocessing of gas oils. The use of model compound testing provided information on the individual catalytic reactions promoted by those materials. Infrared spectroscopy was used to study surface species on the catalysts and to explain many of the trends in activity observed, revealing the role of fluoride and phosphorus as a secondary promoter. Testing of the catalysts in hydrotreating of gas oils allowed comparison of model compound results with those from a real feedstock. The gas oil was also spiked with a model nitrogen compound and the results from catalytic hydrotreating of this material were compared with those from unspiked material. A key finding was that the carbon supported catalysts were the most effective in treating high-nitrogen feeds. The very favorable deactivation properties of carbon and carbon-covered alumina supported catalysts make these promising from an industrial point of view where catalyst deactivation is a limiting factor. 171 refs., 25 figs., 43 tabs.

  3. Determination of surface coverage of catalysts : temperature programmed experiments on platinum and iridium sponge catalysts after low temperature ammonia oxidation

    NARCIS (Netherlands)

    van den Broek, A.C.M.; Grondelle, van J.; Santen, van R.A.

    1999-01-01

    The activity of iridium and platinum sponge catalysts was studied in the low temperature gas phase oxidation of ammonia with oxygen. Under the reaction conditions used, iridium was found to be more active and more selective to nitrogen than platinum. Furthermore it was established from activity

  4. In Situ UV-Visible Assessment of Iron-Based High-Temperature Water-Gas Shift Catalysts Promoted with Lanthana: An Extent of Reduction Study

    Directory of Open Access Journals (Sweden)

    Basseem B. Hallac

    2018-02-01

    Full Text Available The extent of reduction of unsupported iron-based high-temperature water-gas shift catalysts with small (<5 wt % lanthana contents was studied using UV-visible spectroscopy. Temperature- programmed reduction measurements showed that lanthana content higher than 0.5 wt % increased the extent of reduction to metallic Fe, while 0.5 wt % of lanthana facilitated the reduction to Fe3O4. In situ measurements on the iron oxide catalysts using mass and UV-visible spectroscopies permitted the quantification of the extent of reduction under temperature-programmed reduction and high-temperature water-gas shift conditions. The oxidation states were successfully calibrated against normalized absorbance spectra of visible light using the Kubelka-Munk theory. The normalized absorbance relative to the fully oxidized Fe2O3 increased as the extent of reduction increased. XANES suggested that the average bulk iron oxidation state during the water-gas shift reaction was Fe+2.57 for the catalyst with no lanthana and Fe+2.54 for the catalysts with 1 wt % lanthana. However, the UV-vis spectra suggest that the surface oxidation state of iron would be Fe+2.31 for the catalyst with 1 wt % lanthana if the oxidation state of iron in the catalyst with 0 wt % lanthana were Fe+2.57. The findings of this paper emphasize the importance of surface sensitive UV-visible spectroscopy for determining the extent of catalyst reduction during operation. The paper highlights the potential to use bench-scale UV-visible spectroscopy to study the surface chemistry of catalysts instead of less-available synchrotron X-ray radiation facilities.

  5. Effect of preparation method on the surface characteristics and activity of the Pd/OMS-2 catalysts for the oxidation of carbon monoxide, toluene, and ethyl acetate

    International Nuclear Information System (INIS)

    Liu, Lisha; Song, Yong; Fu, Zhidan; Ye, Qing; Cheng, Shuiyuan; Kang, Tianfang; Dai, Hongxing

    2017-01-01

    Highlights: • The framework-structured of cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) has a 2 × 2 square tunnel. • Preparation route has an important impact on physicochemical property of the product. • Pd/OMS-2-DP via the deposition-precipitation route shows excellent catalytic activity. • Pd surface loading, surface atomic ratio of Mn ions, lattice oxygen mobility, oxygen vacancy, reducibility and acidity govern activity. - Abstract: The cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2)-supported Pd (0.5 wt% Pd/OMS-2-DP, 0.5 wt% Pd/OMS-2-PI, and 0.5 wt% Pd/OMS-2-EX) catalysts were prepared by the deposition-precipitation, pre-incorporation, and ion-exchanging strategies, respectively. It is shown that the preparation method exerted an important effect on the physicochemical property of the sample. Among the OMS-2-supported Pd catalysts, 0.5 wt% Pd/OMS-2-DP possessed the highest surface (Mn 2+ + Mn 3+ )/Mn 4+ atomic ratio and the highest surface Pd loading and acid sites. The 0.5 wt% Pd/OMS-2 catalysts outperformed the Pd-free counterpart, among which 0.5 wt% Pd/OMS-2-DP presented the best catalytic activity (T 50% and T 90% were 25 and 55 °C for CO oxidation, 240 and 285 °C for toluene oxidation, and 160 and 200 °C for ethyl acetate oxidation, respectively). We believe that the high Pd surface loading, high surface atomic ratio of (Mn 2+ + Mn 3+ )/Mn 4+ , and good low-temperature reducibility, good oxygen mobility, and high acidity were responsible for the excellent performance of the 0.5 wt% Pd/OMS-2-DP catalyst.

  6. Effect of preparation method on the surface characteristics and activity of the Pd/OMS-2 catalysts for the oxidation of carbon monoxide, toluene, and ethyl acetate

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lisha; Song, Yong; Fu, Zhidan [Key Laboratory of Beijing on Regional Air Pollution Control, Department of Environmental Science, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Ye, Qing, E-mail: yeqing@bjut.edu.cn [Key Laboratory of Beijing on Regional Air Pollution Control, Department of Environmental Science, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Cheng, Shuiyuan; Kang, Tianfang [Key Laboratory of Beijing on Regional Air Pollution Control, Department of Environmental Science, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Dai, Hongxing, E-mail: hxdai@bjut.edu.cn [Beijing Key Laboratory for Green Catalysis and Separation, Key Laboratory of Beijing on Regional Air Pollution Control, Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China)

    2017-02-28

    Highlights: • The framework-structured of cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) has a 2 × 2 square tunnel. • Preparation route has an important impact on physicochemical property of the product. • Pd/OMS-2-DP via the deposition-precipitation route shows excellent catalytic activity. • Pd surface loading, surface atomic ratio of Mn ions, lattice oxygen mobility, oxygen vacancy, reducibility and acidity govern activity. - Abstract: The cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2)-supported Pd (0.5 wt% Pd/OMS-2-DP, 0.5 wt% Pd/OMS-2-PI, and 0.5 wt% Pd/OMS-2-EX) catalysts were prepared by the deposition-precipitation, pre-incorporation, and ion-exchanging strategies, respectively. It is shown that the preparation method exerted an important effect on the physicochemical property of the sample. Among the OMS-2-supported Pd catalysts, 0.5 wt% Pd/OMS-2-DP possessed the highest surface (Mn{sup 2+} + Mn{sup 3+})/Mn{sup 4+} atomic ratio and the highest surface Pd loading and acid sites. The 0.5 wt% Pd/OMS-2 catalysts outperformed the Pd-free counterpart, among which 0.5 wt% Pd/OMS-2-DP presented the best catalytic activity (T{sub 50%} and T{sub 90%} were 25 and 55 °C for CO oxidation, 240 and 285 °C for toluene oxidation, and 160 and 200 °C for ethyl acetate oxidation, respectively). We believe that the high Pd surface loading, high surface atomic ratio of (Mn{sup 2+} + Mn{sup 3+})/Mn{sup 4+}, and good low-temperature reducibility, good oxygen mobility, and high acidity were responsible for the excellent performance of the 0.5 wt% Pd/OMS-2-DP catalyst.

  7. Influence of surface morphology on methanol oxidation at a glassy carbon-supported Pt catalyst

    Directory of Open Access Journals (Sweden)

    S. STEVANOVIC

    2008-08-01

    Full Text Available Platinum supported on glassy carbon (GC was used as a model system for studying the influence of the surface morphology of a Pt catalyst on methanol oxidation in alkaline and acidic solutions. Platinum was deposited by the potential step method on GC samples from H2SO4 + H2PtCl6 solution under the same conditions with loadings from 10 to 80 mg cm-2. AFM and STM images of the GC/Pt electrodes showed that the Pt was deposited in the form of 3D agglomerates composed of spherical particles. Longer deposition times resulted in increased growth of Pt forms and a decrease in the specific area of the Pt. The real surface area of Pt increased with loading but the changes were almost negligible at higher loadings. Nevertheless, both the specific and mass activity of platinum supported on glassy carbon for methanol oxidation in acidic and in alkaline solutions exhibit a volcanic dependence with respect to the platinum loading. The increase in the activity can be explained by the increasing the particle size with the loading and thus an increase in the contiguous Pt sites available for adsorption and decomposition of methanol. However, the decrease in the activity of the catalyst with further increase of loading and particle size after reaching the maximum is related to the decrease of active sites available for methanol adsorption and their accessibility as a result of more close proximity and pronounced coalescence of the Pt particles.

  8. Nano-catalysts: Bridging the gap between homogeneous and heterogeneous catalysis

    Science.gov (United States)

    Functionalized nanoparticles have emerged as sustainable alternatives to conventional materials, as robust, high-surface-area heterogeneous catalyst supports. We envisioned a catalyst system, which can bridge the homogenous and heterogeneous system. Postsynthetic surface modifica...

  9. Highly Stable Bimetallic AuIr/TiO₂ Catalyst: Physical Origins of the Intrinsic High Stability against Sintering.

    Science.gov (United States)

    Han, Chang Wan; Majumdar, Paulami; Marinero, Ernesto E; Aguilar-Tapia, Antonio; Zanella, Rodolfo; Greeley, Jeffrey; Ortalan, Volkan

    2015-12-09

    It has been a long-lived research topic in the field of heterogeneous catalysts to find a way of stabilizing supported gold catalyst against sintering. Herein, we report highly stable AuIr bimetallic nanoparticles on TiO2 synthesized by sequential deposition-precipitation. To reveal the physical origin of the high stability of AuIr/TiO2, we used aberration-corrected scanning transmission electron microscopy (STEM), STEM-tomography, and density functional theory (DFT) calculations. Three-dimensional structures of AuIr/TiO2 obtained by STEM-tomography indicate that AuIr nanoparticles on TiO2 have intrinsically lower free energy and less driving force for sintering than Au nanoparticles. DFT calculations on segregation behavior of AuIr slabs on TiO2 showed that the presence of Ir near the TiO2 surface increases the adhesion energy of the bimetallic slabs to the TiO2 and the attractive interactions between Ir and TiO2 lead to higher stability of AuIr nanoparticles as compared to Au nanoparticles.

  10. Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

    KAUST Repository

    Li, Cheng Chao; Dou, Jian; Chen, Luwei; Lin, Jianyi; Zeng, Hua Chun

    2012-01-01

    We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

    KAUST Repository

    Li, Cheng Chao

    2012-03-20

    We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Surface tailored single walled carbon nanotubes as catalyst support for direct methanol fuel cell

    Science.gov (United States)

    Kireeti, Kota V. M. K.; Jha, Neetu

    2017-10-01

    A strategy for tuning the surface property of Single Walled Carbon Nanotubes (SWNTs) for enhanced methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) along with methanol tolerance is presented. The surface functionality is tailored using controlled acid and base treatment. Acid treatment leads to the attachment of carboxylic carbon (CC) fragments to SWNT making it hydrophilic (P3-SWNT). Base treatment of P3-SWNT with 0.05 M NaOH reduces the CCs and makes it hydrophobic (P33-SWNT). Pt catalyst supported on the P3-SWNT possesses enhanced MOR whereas that supported on P33-SWNT not only enhances ORR kinetics but also possess good tolerance towards methanol oxidation as verified by the electrochemical technique.

  13. High Coke-Resistance Pt/Mg1-xNixO Catalyst for Dry Reforming of Methane.

    Directory of Open Access Journals (Sweden)

    Faris A J Al-Doghachi

    Full Text Available A highly active and stable nano structured Pt/Mg1-xNixO catalysts was developed by a simple co-precipitation method. The obtained Pt/Mg1-xNixO catalyst exhibited cubic structure nanocatalyst with a size of 50-80 nm and realized CH4 and CO2 conversions as high as 98% at 900°C with excellent stability in the dry reforming of methane. The characterization of catalyst was performed using various kinds of analytical techniques including XRD, BET, XRF, TPR-H2, TGA, TEM, FESEM, FT-IR, and XPS analyses. Characterization of spent catalyst further confirms that Pt/Mg1-xNixO catalyst has high coke-resistance for dry reforming. Thus, the catalyst demonstrated in this study, offers a promising catalyst for resolving the dilemma between dispersion and reducibility of supported metal, as well as activity and stability during high temperature reactions.

  14. Surface noble metal modified PdM/C (M = Ru, Pt, Au) as anode catalysts for direct ethanol fuel cells

    International Nuclear Information System (INIS)

    Mao, Han; Huang, Tao; Yu, Aishui

    2016-01-01

    In this article, we studied the surface noble metal modification on Pd nanoparticles, other than the homogeneous or core-shell structure. The surface modification will lead to the uneven constitution within the nanoparticles and thus more obvious optimization effect toward the catalyst brought by the lattice deformation. The surface of the as-prepared Pd nanoparticles was modified with Ru, Pt or Au by a moderate and green approach, respectively. XPS results confirm the interactive electron effects between Pd and the modified noble metal. Electrochemical measurements show that the surface noble metal modified catalysts not only show higher catalytic activity, but also better stability and durability. The PdM/C catalysts all exhibit good dispersion and very little agglomeration after long-term potential cycles toward ethanol oxidation. With only 10% metallic atomic ratio of Au, PdAu/C catalyst shows extraordinary catalytic activity and stability, the peak current reaches 1700 mA mg"−"1 Pd, about 2.5 times that of Pd/C. Moreover, the PdAu/C maintains 40% of the catalytic activity after 4500 potential cycles. - Highlights: • Pd-based catalysts with complicated exposed facets. • Much enhanced electrocatalytic activity and stability with about 10% noble metal M (M = Ru, Pt, Au) on Pd nanoparticles. • The outstanding electrocatalytic performance of PdAu/C towards ethanol oxidation after the Au modification.

  15. Surface noble metal modified PdM/C (M = Ru, Pt, Au) as anode catalysts for direct ethanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Han; Huang, Tao, E-mail: huangt@fudan.edu.cn; Yu, Aishui, E-mail: asyu@fudan.edu.cn

    2016-08-15

    In this article, we studied the surface noble metal modification on Pd nanoparticles, other than the homogeneous or core-shell structure. The surface modification will lead to the uneven constitution within the nanoparticles and thus more obvious optimization effect toward the catalyst brought by the lattice deformation. The surface of the as-prepared Pd nanoparticles was modified with Ru, Pt or Au by a moderate and green approach, respectively. XPS results confirm the interactive electron effects between Pd and the modified noble metal. Electrochemical measurements show that the surface noble metal modified catalysts not only show higher catalytic activity, but also better stability and durability. The PdM/C catalysts all exhibit good dispersion and very little agglomeration after long-term potential cycles toward ethanol oxidation. With only 10% metallic atomic ratio of Au, PdAu/C catalyst shows extraordinary catalytic activity and stability, the peak current reaches 1700 mA mg{sup −1} Pd, about 2.5 times that of Pd/C. Moreover, the PdAu/C maintains 40% of the catalytic activity after 4500 potential cycles. - Highlights: • Pd-based catalysts with complicated exposed facets. • Much enhanced electrocatalytic activity and stability with about 10% noble metal M (M = Ru, Pt, Au) on Pd nanoparticles. • The outstanding electrocatalytic performance of PdAu/C towards ethanol oxidation after the Au modification.

  16. A recyclable Au(I) catalyst for selective homocoupling of arylboronic acids: significant enhancement of nano-surface binding for stability and catalytic activity.

    Science.gov (United States)

    Zhang, Xin; Zhao, Haitao; Wang, Jianhui

    2010-08-01

    Au nanoparticles stabilized by polystyrene-co-polymethacrylic acid microspheres (PS-co-PMAA) were prepared and characterized via X-ray diffraction (XRD), and transmission electron microscope (TEM). The Au nanoparticles supported on the microspheres showed highly selective catalytic activity for homo-coupling reactions of arylboronic acids in a system of aryl-halides and arylboronic acids. X-ray photoelectron spectroscopy (XPS) spectra of the catalyst shows large amounts of Au(I) complexes band to the surface of the Au nanoparticles, which contributes to the selective homocoupling of the arylboronic acids. More importantly, this supported Au complex is a highly recyclable catalyst. The supported Au catalyst can be recycled and reused at least 6 times for a phenylboronic acid reactant, whereas the parent complex shows very low catalytic activity for this compound. The high catalytic activity of this material is attributed to: (1) the high surface to volume ratio which leads to more active sites being exposed to reactants; (2) the strong surface binding of the Au nanoparticle to the Au(I) complexes, which enhances both the stability and the catalytic activity of these complexes.

  17. Epoxidation catalyst and process

    Science.gov (United States)

    Linic, Suljo; Christopher, Phillip

    2010-10-26

    Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

  18. Highly selective oxidative dehydrogenation of ethane with supported molten chloride catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gaertner, C.A.; Veen, A.C. van; Lercher, J.A. [Technische Univ. Muenchen (Germany). Catalysis Research Center

    2011-07-01

    Ethene production is one of the most important transformations in chemical industry, given that C{sub 2}H{sub 4} serves as building block for many mass-market products. Besides conventional thermal processes like steam cracking of ethane, ethane can be produced selectively by catalytic processes. One of the classes of catalysts that have been reported in literature as active and highly selective for the oxidative dehydrogenation of ethane is that of supported molten chloride catalysts, containing an alkali chloride overlayer on a solid support. This work deals with fundamental aspects of the catalytic action in latter class of catalysts. Results from kinetic reaction studies are related to observations in detailed characterization and lead to a comprehensive mechanistic understanding. Of fundamental importance towards mechanistic insights is the oxygen storage capacity of the catalysts that has been determined by transient step experiments. (orig.)

  19. Encapsulated heterogeneous base catalysts onto SBA-15 nanoporous material as highly active catalysts in the transesterification of sunflower oil to biodiesel

    Science.gov (United States)

    Albayati, Talib M.; Doyle, Aidan M.

    2015-02-01

    Alkali metals and their hydroxides, Na, NaOH, Li, and LiOH, were encapsulated onto SBA-15 nanoporous material as highly active catalysts for the production of biodiesel fuel from sunflower oil. The incipient wetness impregnation method was adopted for the prepared catalysts. The characterization properties of the catalysts and unmodified SBA-15 were determined using X-ray diffraction, scanning electron microscopy, EDAX, nitrogen adsorption-desorption porosimetry (Brunauer-Emmett-Teller), Fourier-transform infrared spectroscopy, and transmission electron microscopy. Transesterification was conducted in a batch reactor at atmospheric pressure and 65 °C. The catalysts were highly active with yields of fatty acid methyl ester (FAME) in the range 96-99 %. Na/SBA-15 catalyst was reused for seven consecutive cycles under the same reaction conditions; the yield to FAME on the final cycle was 96 %. This study shows that the alkali metals and their hydroxides supported on SBA-15-based catalyst are excellent catalysts for the biodiesel reaction.

  20. Encapsulated heterogeneous base catalysts onto SBA-15 nanoporous material as highly active catalysts in the transesterification of sunflower oil to biodiesel

    Energy Technology Data Exchange (ETDEWEB)

    Albayati, Talib M., E-mail: talib-albyati@yahoo.com [University of Technology, Department of Chemical Engineering (Iraq); Doyle, Aidan M., E-mail: a.m.doyle@mmu.ac.uk [Manchester Metropolitan University, Division of Chemistry and Environmental Science (United Kingdom)

    2015-02-15

    Alkali metals and their hydroxides, Na, NaOH, Li, and LiOH, were encapsulated onto SBA-15 nanoporous material as highly active catalysts for the production of biodiesel fuel from sunflower oil. The incipient wetness impregnation method was adopted for the prepared catalysts. The characterization properties of the catalysts and unmodified SBA-15 were determined using X-ray diffraction, scanning electron microscopy, EDAX, nitrogen adsorption–desorption porosimetry (Brunauer–Emmett–Teller), Fourier-transform infrared spectroscopy, and transmission electron microscopy. Transesterification was conducted in a batch reactor at atmospheric pressure and 65 °C. The catalysts were highly active with yields of fatty acid methyl ester (FAME) in the range 96–99 %. Na/SBA-15 catalyst was reused for seven consecutive cycles under the same reaction conditions; the yield to FAME on the final cycle was 96 %. This study shows that the alkali metals and their hydroxides supported on SBA-15-based catalyst are excellent catalysts for the biodiesel reaction.

  1. Encapsulated heterogeneous base catalysts onto SBA-15 nanoporous material as highly active catalysts in the transesterification of sunflower oil to biodiesel

    International Nuclear Information System (INIS)

    Albayati, Talib M.; Doyle, Aidan M.

    2015-01-01

    Alkali metals and their hydroxides, Na, NaOH, Li, and LiOH, were encapsulated onto SBA-15 nanoporous material as highly active catalysts for the production of biodiesel fuel from sunflower oil. The incipient wetness impregnation method was adopted for the prepared catalysts. The characterization properties of the catalysts and unmodified SBA-15 were determined using X-ray diffraction, scanning electron microscopy, EDAX, nitrogen adsorption–desorption porosimetry (Brunauer–Emmett–Teller), Fourier-transform infrared spectroscopy, and transmission electron microscopy. Transesterification was conducted in a batch reactor at atmospheric pressure and 65 °C. The catalysts were highly active with yields of fatty acid methyl ester (FAME) in the range 96–99 %. Na/SBA-15 catalyst was reused for seven consecutive cycles under the same reaction conditions; the yield to FAME on the final cycle was 96 %. This study shows that the alkali metals and their hydroxides supported on SBA-15-based catalyst are excellent catalysts for the biodiesel reaction

  2. Cu2+ Montmorillonite K10 Clay Catalyst as a Green Catalyst for Production of Stearic Acid Methyl Ester: Optimization Using Response Surface Methodology (RSM

    Directory of Open Access Journals (Sweden)

    Enas A. Almadani

    2018-01-01

    Full Text Available Clay catalyst has received much attention to replace the homogeneous catalysts in the esterification reaction to produce fatty acid methyl ester as the source of biodiesel as it is low cost, easily available, as well as environmental friendly. However, the use of unmodified clay, in particular montmorillonite K10 (MMT K10, for the esterification of fatty acids showed that the acid conversion was less than 60% and this is not preferable to the production of biodiesel. In this study, synthesis of stearic acid methyl ester using Cu2+-MMT K10 (Cu-MMT K10 was successfully optimized via response surface methodo-logy (RSM based on 3-variable of Box-Behnken design (BB. The parameters were; reaction time (5-180 minutes, reaction temperature (80-120 oC and concentration of Cu2+ in MMT K10 (0.25-1 M. The use of RSM in optimizing the conversion of stearic acid was successfully developed as the actual experimental conversion of stearic acid was found similar to the actual values under the optimum conditions. The model equation predicted that the following conditions would generate the maximum conversion of stearic acid (87.05 %reaction time of 62 minutes, a reaction temperature of 80 oC and catalyst used is 1.0 M Cu-MMT K10. This finding can be considered as green catalytic process as it worked at moderate reaction temperature using low cost clay catalyst with a short reaction time. Copyright © 2018 BCREC Group. All rights reserved Received: 26th July 2017; Revised: 13rd January 2018; Accepted: 13rd January 2018; Available online: 22nd January 2018; Published regularly: 2nd April 2018 How to Cite: Almadani, E.A., Harun, F.W., Radzi, S.M., Muhamad, S.K. (2018. Cu2+ Montmorillonite K10 Clay Catalyst as a Green Catalyst for Production of Stearic Acid Methyl Ester: Optimization Using Response Surface Methodology (RSM. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (1: 187-195 (doi:10.9767/bcrec.13.1.1397.187-195

  3. thesis of high-purity carbon nanotubes over alumina and silica supported bimetallic catalysts

    Directory of Open Access Journals (Sweden)

    Sanja Ratković

    2009-10-01

    Full Text Available Carbon nanotubes (CNTs were synthesized by a catalytic chemical vapor deposition method (CCVD of ethylene over alumina and silica supported bimetallic catalysts based on Fe, Co and Ni. The catalysts were prepared by a precipitation method, calcined at 600 °C and in situ reduced in hydrogen flow at 700 °C. The CNTs growth was carried out by a flow the mixture of C2H4 and nitrogen over the catalyst powder in a horizontal oven. The structure and morphology of as-synthesized CNTs were characterized using SEM. The as-synthesized nanotubes were purified by acid and basic treatments in order to remove impurities such as amorphous carbon, graphite nanoparticles and metal catalysts. XRD and DTA/TG analyses showed that the amounts of by-products in the purified CNTs samples were reduced significantly. According to the observed results, ethylene is an active carbon source for growing high-density CNTs with high yield but more on alumina-supported catalysts than on their silica- supported counterparts. The last might be explained by SMSI formed in the case of alumina-supported catalysts, resulting in higher active phase dispersion.

  4. Response Surface Methodology for Biodiesel Production Using Calcium Methoxide Catalyst Assisted with Tetrahydrofuran as Cosolvent

    Directory of Open Access Journals (Sweden)

    Nichaonn Chumuang

    2017-01-01

    Full Text Available The present study was performed to optimize a heterogeneous calcium methoxide (Ca(OCH32 catalyzed transesterification process assisted with tetrahydrofuran (THF as a cosolvent for biodiesel production from waste cooking oil. Response surface methodology (RSM with a 5-level-4-factor central composite design was applied to investigate the effect of experimental factors on the percentage of fatty acid methyl ester (FAME conversion. A quadratic model with an analysis of variance obtained from the RSM is suggested for the prediction of FAME conversion and reveals that 99.43% of the observed variation is explained by the model. The optimum conditions obtained from the RSM were 2.83 wt% of catalyst concentration, 11.6 : 1 methanol-to-oil molar ratio, 100.14 min of reaction time, and 8.65% v/v of THF in methanol concentration. Under these conditions, the properties of the produced biodiesel satisfied the standard requirement. THF as cosolvent successfully decreased the catalyst concentration, methanol-to-oil molar ratio, and reaction time when compared with biodiesel production without cosolvent. The results are encouraging for the application of Ca(OCH32 assisted with THF as a cosolvent for environmentally friendly and sustainable biodiesel production.

  5. Development of high performance catalyst for off-gas treatment system in BWR

    International Nuclear Information System (INIS)

    Kawasaki, Toru; Kawabe, Kenichi; Maeda, Kiyomitsu; Matsubara, Hirofumi; Aizawa, Motohiro; Iizuka, Hidehiro; Kumagai, Naoki

    2011-01-01

    A high performance catalyst for off-gas treatment system in boiling water reactor (BWR) has been developed. The hydrogen concentration in the outlets of off-gas recombiners increased at several BWR plants in Japan. These phenomena were caused by deactivation of catalysts for the recombiners, and we assumed two types of deactivation mechanisms. The first cause was an increase of the amount of boehmite in the catalyst support due to alternation of the manufacturing process. The other cause was catalysts being poisoned by cyclic siloxanes that were introduced from the silicone sealant used in the upstream of the off-gas recombiners. The catalysts were manufactured by Pt adhering on alumina support. The conventional catalyst (CAT-A) used the aqueous solution of the chloroplatinic acid for adhesion of Pt. A dechlorination process by autoclave was applied to prevent the equipment at the downstream of the recombiners from stress corrosion cracking, but this process caused the support material to transform into boehmite. The boehmite-rich catalysts were deactivated more easily by organic silicon than gamma alumina-rich catalysts. Therefore, the CAT-A was replaced at many Japanese BWR plants by the improved catalyst (CAT-B), and their support was transformed into more stable gamma alumina by heating at 500degC. However, the siloxanes keep being detected in the off-gas though the source of siloxane had been removed and there still remain possibilities to deactivate the catalysts. Therefore, we have been developing high performance catalyst (CAT-C) that has higher activity and durability against poisoning. We investigated the properties of CAT-C by performance tests and instrumental analyses. The dependency of thermal output of nuclear reactor, and durability against siloxane poisoning were investigated. We found that CAT-C showed higher performance and better properties than CAT-B did. Moreover, we have been developing a modeling method to evaluate the hydrogen recombination

  6. Superior mercury-free catalysts for acetylene hydrochlorination to VCM. Achieving high productivities and long catalyst life-time

    Energy Technology Data Exchange (ETDEWEB)

    Liebens, A.T.; Piccinini, M. [Solvay S.A., Bruxelles (Belgium)

    2013-11-01

    New mercury-free catalytic systems based on the use of ionic liquids (IL) and noble metals (e.g. Pd, Au) have been evaluated for the hydrochlorination reaction of acetylene to produce Vinyl Chloride Monomer (VCM). Two different approaches have been investigated: gas-liquid homogeneous catalytic systems in the presence of molten IL/Metal and heterogeneous gas-solid ones using solid materials. For the latter case, very positive results have been obtained using SILP-type catalysts (SILP: Supported Ionic Liquid Phase) where IL/Metal were deposited onto a solid mesoporous support. Remarkably, both systems display very high Space Time Yield (STY) and breakthrough life-time stability. No deactivation is observed even after 500 h on stream indicating the strong advantages of these new materials compared to most investigated Au/C supported systems. The development of heterogeneous catalysts was preferred as the scale-up of gas-liquid technology implies important CAPEX investments to convert current plants from gas-solid to gas-liquid equipment. (orig.)

  7. SU-F-J-20: Commissioning and Acceptance Testing of the C-Rad CatalystHD Surface Imaging System

    International Nuclear Information System (INIS)

    Stanley, D; Rasmussen, K; Kirby, N; Papanikolaou, N; Gutierrez, A

    2016-01-01

    Introduction: With the increasing use of surface-based, nonionizing image-guided radiotherapy (IGRT) systems, a comprehensive set of clinical acceptance and commissioning procedures are needed to ensure correct functionality and proper clinical integration. Although TG-147 provides a specific set of parameters, measurement methodologies have yet to be described. The aim of this study was to provide a comprehensive overview of the commissioning and acceptance analysis performed for the C-Rad CatalystHD imaging system. Methods and Materials: Methodology for the commissioning and acceptance of the C-Rad CatalystHD imaging system was developed using commercially available clinical equipment. Following TG-147 guidelines, the following tests were performed: integration of peripheral equipment, system drift, static spatial reproducibility and localization accuracy, static end-to-end analysis, static rotational accuracy, dynamic spatial accuracy, dynamic temporal accuracy, dynamic radiation delivery and a comprehensive end-to-end analysis. Results: The field of view (FOV) of the CatalystHD was 105×109×83 cm3 in the lateral, longitudinal and vertical directions. For thermal equilibrium and system drift, a thermal drift of 1.0mm was noted. A 45 min warmup time is recommended if the system has been shut off an extended period of time (>24 hours) before the QA procedure to eliminate any thermal drift. Spatial reproducibility was found to be 0.05±0.03 mm using a rigid phantom. For the static localization accuracy, system agreement with couch shifts was within 0.1±0.1 mm and positioning agreement with kV-CBCT was 0.16±0.10 mm. For static rotational accuracy, system agreement with a high precision rotational stage (0.01 deg precision) was within 0.10±0.07 deg. Dynamic spatial and temporal localization accuracy was found to be within 0.2±0.1 mm. Conclusion: A comprehensive commissioning and acceptance study was performed using commercially available phantoms and in

  8. Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment

    Science.gov (United States)

    Li, Chong; Zhang, Guilong; Wang, Min; Chen, Jianfeng; Cai, Dongqing; Wu, Zhengyan

    2014-08-01

    High energy electron beam (HEEB) irradiation and hydrothermal treatment (HT), were applied in order to remove the impurities and enlarge the pore size of diatomite, making diatomite more suitable to be a catalyst support. The results demonstrated that, through thermal, charge, impact and etching effects, HEEB irradiation could make the impurities in the pores of diatomite loose and remove some of them. Then HT could remove rest of them from the pores and contribute significantly to the modification of the pore size distribution of diatomite due to thermal expansion, water swelling and thermolysis effects. Moreover, the pore structure modification improved the properties (BET (Brunauer-Emmett-Teller) specific surface area, bulk density and pore volume) of diatomite and the catalytic efficiency of the catalyst prepared from the treated diatomite.

  9. ZIF-67 incorporated with carbon derived from pomelo peels: A highly efficient bifunctional catalyst for oxygen reduction/evolution reactions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hao; Yin, Feng-Xiang; Chen, Biao-Hua; He, Xiao-Bo; Lv, Peng-Liang; Ye, Cai-Yun; Liu, Di-Jia

    2017-05-01

    Developing carbon catalyst materials using natural, abundant and renewable resources as precursors plays an increasingly important role in clean energy generation and environmental protection. In this work, N-doped pomelo-peel-derived carbon (NPC) materials were prepared using a widely available food waste-pomelo peels and melamine. The synthetic NPC exhibits well-defined porosities and a highly doped-N content (e.g. 6.38 at% for NPC-2), therefore affords excellent oxygen reduction reaction (ORR) catalytic activities in alkaline electrolytes. NPC was further integrated with ZIF-67 to form ZIF-67@NPC hybrids through solvothermal reactions. The hybrid catalysts show substantially enhanced ORR catalytic activities comparable to that of commercial 20 wa Pt/C. Furthermore, the catalysts also exhibit excellent oxygen evolution reaction (OER) catalytic activities. Among all prepared ZIF-67@NPC hybrids, the optimal composition with ZIF-67 to NPC ratio of 2:1 exhibits the best ORR and OER bifunctional catalytic performance and the smallest Delta E (E-OER@10 mA cm(-2)-E-ORR@-1 mA cm(-2)) value of 0.79 V. The catalyst also demonstrated desirable 4-electron transfer pathways and superior catalytic stabilities. The Co-N-4 in ZIF-67, electrochemical active surface area, and the strong interactions between ZIF-67 and NPC are attributed as the main contributors to the bifunctional catalytic activities. These factors act synergistically, resulting in substantially enhanced bifunctional catalytic activities and stabilities; consequently, this hybrid catalyst is among the best of the reported bifunctional electrocatalysts and is promising for use in metal-air batteries and fuel cells. (C) 2016 Elsevier B.V. All rights reserved.

  10. Sn surface-enriched Pt-Sn bimetallic nanoparticles as a selective and stable catalyst for propane dehydrogenation

    KAUST Repository

    Zhu, Haibo

    2014-12-01

    A new one pot, surfactant-free, synthetic route based on the surface organometallic chemistry (SOMC) concept has been developed for the synthesis of Sn surface-enriched Pt-Sn nanoparticles. Bu3SnH selectively reacts with [Pt]-H formed in situ at the surface of Pt nanoparticles, Pt NPs, obtained by reduction of K2PtCl4 by LiB(C2H5)3H. Chemical analysis, 1H MAS and 13C CP/MAS solid-state NMR as well as two-dimensional double-quantum (DQ) and triple-quantum (TQ) experiments show that organo-tin moieties Sn(n-C4H9) are chemically linked to the surface of Pt NPs to produce, in fine, after removal of most of the n-butyl fragment, bimetallic Pt-Sn nanoparticles. The Sn(n-CH2CH2CH2CH3) groups remaining at the surface are believed to stabilize the as-synthesized Pt-Sn NPs, enabling the bimetallic NPs to be well dispersed in THF. Additionally, the Pt-Sn nanoparticles can be supported on MgAl2O4 during the synthesis of the nanoparticles. Some of the Pt-Sn/MgAl2O4 catalyst thus prepared exhibits high activity in PROX of CO and an extremely high selectivity and stability in propane dehydrogenation to propylene. The enhanced activity in propane dehydrogenation is associated with the high concentration of inactive Sn at the surface of Pt nanoparticles which ”isolates” the active Pt atoms. This conclusion is confirmed by XRD, NMR, TEM, and XPS analysis.

  11. Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells.

    Science.gov (United States)

    Kim, Jiyoung; Jang, Jin-Sung; Peck, Dong-Hyun; Lee, Byungrok; Yoon, Seong-Ho; Jung, Doo-Hwan

    2016-08-15

    Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF-supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.

  12. Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells

    Directory of Open Access Journals (Sweden)

    Jiyoung Kim

    2016-08-01

    Full Text Available Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC. The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR activities and the electrochemical double layer compared with common carbon black (CB. To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF–supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.

  13. ZIF-67-derived hollow nanocages with layered double oxides shell as high-Efficiency catalysts for CO oxidation

    Science.gov (United States)

    Kong, Wenpeng; Li, Jing; Chen, Yao; Ren, Yuqing; Guo, Yonghua; Niu, Shengli; Yang, Yanzhao

    2018-04-01

    Constructing non-precious hybrid metal oxides with specific morphology as cost-effective and highly efficient catalysts is a promising way for the automotive exhaust purification. In this work, we report a facile strategy for the fabrication of a unique hollow Co-Ni layered double oxides (HLDO) nanocages by using zeolitic imidazole frameworks (ZIFs) as template. The synthesis of intermediate core-shell and hollow Co-Ni layered double hydroxides (HLDH) nanoflakes as well as the corresponding Co-Ni oxides products were successfully controlled, and the formation process was also explained. Among ZIF-67-derived oxides, HLDO exhibits excellent catalytic activities (complete conversion of CO into CO2 at 118 °C) and long-term stability for CO oxidation. The remarkable catalytic activities of HLDO can be attributed to high surface area (258 m2 g-1) inherited from the HLDH, which could provide more active sites for CO oxidation. In addition, active oxygen species indicated by the O 1 s XPS spectrum and improved synergistic effect between NiO and Co3O4 reflected by H2-TPR, further explain the enhanced performance of the HLDO catalysts. The presented strategy for controlled design and synthesis of hollow multicomponent metal oxides will provide prospects in developing highly effective catalysts.

  14. The role of reaction pathways and support interactions in the development of high activity hydrotreating catalysts

    DEFF Research Database (Denmark)

    Topsøe, Henrik; Hinnemann, Berit; Nørskov, Jens Kehlet

    2005-01-01

    structures may be present as single sulfide sheets. Thus, stacking is not an essential feature of Type II catalysts. The article illustrates how the new scientific insight has aided the introduction of the new high activity BRIM (TM) type catalysts for FCC pre-treatment and production of ultra low sulfur...... exhibiting a metallic character are observed to be involved in adsorption, hydrogenation and C-S bond cleavage. The insight is seen to provide a new framework for understanding the DDS and HYD pathways and the role of steric hindrance and poisons. Density functional theory (DFT) calculations have illustrated...... how support interactions may influence the activity of sulfided catalysts. The brim sites and the tendency to form vacancies are seen to differ in types I and II Co-Mo-S. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) studies show that the high activity Type II...

  15. Transient-response study of CO insertion into CHx surface intermediates on a vanadium-promoted rhodium catalyst

    NARCIS (Netherlands)

    Koerts, T.; Santen, van R.A.

    1992-01-01

    The rate of CO insertion into surface CHx species was investigated on silica-supported rhodium and rhodium-vanadium catalysts. Isotopically labelled 13CO was used in a transient kinetic experiment under steady-state conditions. A main conclusion is that vanadium promotion does not affect the rate of

  16. Effect of support surface treatment on the synthesis, structure, and performance of Co/CNT Fischer-Tropsch catalysts

    NARCIS (Netherlands)

    Eschemann, Thomas O.; Lamme, Wouter S.; Manchester, Rene L.; Parmentier, Tanja E.; Cognigni, Andrea; Ronning, Magnus; de Jong, Krijn P.

    We report the preparation of supported cobalt catalysts (9 wt% Co) on untreated (CNT) and surface-oxidized (CNT-ox) carbon nanotube materials by incipient wetness impregnation with solutions of cobalt nitrate in water, ethanol, or 1-propanol. The results show that by a judicious selection of solvent

  17. Surface Termination of M1 Phase and Rational Design of Propane Ammoxidation Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Guliants, Vadim [Univ. of Cincinnati, OH (United States)

    2015-02-16

    This final report describes major accomplishments in this research project which has demonstrated that the M1 phase is the only crystalline phase required for propane ammoxidation to acrylonitrile and that a surface monolayer terminating the ab planes of the M1 phase is responsible for their activity and selectivity in this reaction. Fundamental studies of the topmost surface chemistry and mechanism of propane ammoxidation over the Mo-V-(Te,Sb)-(Nb,Ta)-O M1 and M2 phases resulted in the development of quantitative understanding of the surface molecular structure – reactivity relationships for this unique catalytic system. These oxides possess unique catalytic properties among mixed metal oxides, because they selectively catalyze three alkane transformation reactions, namely propane ammoxidation to acrylonitrile, propane oxidation to acrylic acid and ethane oxidative dehydrogenation, all of considerable economic significance. Therefore, the larger goal of this research was to expand this catalysis to other alkanes of commercial interest, and more broadly, demonstrate successful approaches to rational design of improved catalysts that can be applied to other selective (amm)oxidation processes.

  18. Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment

    International Nuclear Information System (INIS)

    Li, Chong; Zhang, Guilong; Wang, Min; Chen, Jianfeng; Cai, Dongqing; Wu, Zhengyan

    2014-01-01

    Highlights: • High energy electron beam (HEEB) irradiation and hydrothermal treatment were used. • HEEB irradiation could make the impurities in the pores of diatomite loose. • Hydrothermal treatment (HT) could remove these impurities from the pores. • They could effectively improve pore size distribution and decrease the bulk density. • Catalytic performance of the corresponding catalyst was significantly improved. - Abstract: High energy electron beam (HEEB) irradiation and hydrothermal treatment (HT), were applied in order to remove the impurities and enlarge the pore size of diatomite, making diatomite more suitable to be a catalyst support. The results demonstrated that, through thermal, charge, impact and etching effects, HEEB irradiation could make the impurities in the pores of diatomite loose and remove some of them. Then HT could remove rest of them from the pores and contribute significantly to the modification of the pore size distribution of diatomite due to thermal expansion, water swelling and thermolysis effects. Moreover, the pore structure modification improved the properties (BET (Brunauer–Emmett–Teller) specific surface area, bulk density and pore volume) of diatomite and the catalytic efficiency of the catalyst prepared from the treated diatomite

  19. Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chong [Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029 (China); Zhang, Guilong; Wang, Min [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Chen, Jianfeng [Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029 (China); Cai, Dongqing, E-mail: dqcai@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-08-15

    Highlights: • High energy electron beam (HEEB) irradiation and hydrothermal treatment were used. • HEEB irradiation could make the impurities in the pores of diatomite loose. • Hydrothermal treatment (HT) could remove these impurities from the pores. • They could effectively improve pore size distribution and decrease the bulk density. • Catalytic performance of the corresponding catalyst was significantly improved. - Abstract: High energy electron beam (HEEB) irradiation and hydrothermal treatment (HT), were applied in order to remove the impurities and enlarge the pore size of diatomite, making diatomite more suitable to be a catalyst support. The results demonstrated that, through thermal, charge, impact and etching effects, HEEB irradiation could make the impurities in the pores of diatomite loose and remove some of them. Then HT could remove rest of them from the pores and contribute significantly to the modification of the pore size distribution of diatomite due to thermal expansion, water swelling and thermolysis effects. Moreover, the pore structure modification improved the properties (BET (Brunauer–Emmett–Teller) specific surface area, bulk density and pore volume) of diatomite and the catalytic efficiency of the catalyst prepared from the treated diatomite.

  20. Facile solid-state synthesis of highly dispersed Cu nanospheres anchored on coal-based activated carbons as an efficient heterogeneous catalyst for the reduction of 4-nitrophenol

    Science.gov (United States)

    Wang, Shan; Gao, Shasha; Tang, Yakun; Wang, Lei; Jia, Dianzeng; Liu, Lang

    2018-04-01

    Coal-based activated carbons (AC) were acted as the support, Cu/AC catalysts were synthesized by a facile solid-state reaction combined with subsequent heat treatment. In Cu/AC composites, highly dispersed Cu nanospheres were anchored on AC. The catalytic activity for 4-nitrophenol (4-NP) was investigated, the effects of activation temperature and copper loading on the catalytic performance were studied. The catalysts exhibited very high catalytic activity and moderate chemical stability due to the unique characteristics of the particle-assembled nanostructures, the high surface area and the porous structure of coal-based AC and the good dispersion of metal particles. Design and preparation of non-noble metal composite catalysts provide a new direction for improving the added value of coal.

  1. Copper nitrate redispersion to arrive at highly active silica-supported copper catalysts

    NARCIS (Netherlands)

    Munnik, P.|info:eu-repo/dai/nl/328228524; Wolters, M.|info:eu-repo/dai/nl/304829560; Gabrielsson, A.; Pollington, S.D.; Headdock, G.; Bitter, J.H.|info:eu-repo/dai/nl/160581435; de Jongh, P.E.|info:eu-repo/dai/nl/186125372; de Jong, K.P.|info:eu-repo/dai/nl/06885580X

    2011-01-01

    In order to obtain copper catalysts with high dispersions at high copper loadings, the gas flow rate and gas composition was varied during calcination of silica gel impregnated with copper nitrate to a loading of 18 wt % of copper. Analysis by X-ray diffraction (XRD), N2O chemisorption, and

  2. Diatomite as high performance and environmental friendly catalysts for phenol hydroxylation with H2O2

    Directory of Open Access Journals (Sweden)

    Yuxin Jia et al

    2007-01-01

    Full Text Available A series of diatomite catalysts were treated and characterized. For the first time, the resulting materials were used in catalysis for the hydroxylation of phenol with H2O2 and showed very high hydroxylation activity due to the Fe species in the diatomite. The effect of HCl treatment, contents of catalysts and H2O2 were investigated and the active components of diatomite were discussed. The results show that diatomite is the promising candidate for industrial output due to their high catalytic activity, easy physical separation and very low costs.

  3. Stable amorphous georgeite as a precursor to a high-activity catalyst

    Science.gov (United States)

    Kondrat, Simon A.; Smith, Paul J.; Wells, Peter P.; Chater, Philip A.; Carter, James H.; Morgan, David J.; Fiordaliso, Elisabetta M.; Wagner, Jakob B.; Davies, Thomas E.; Lu, Li; Bartley, Jonathan K.; Taylor, Stuart H.; Spencer, Michael S.; Kiely, Christopher J.; Kelly, Gordon J.; Park, Colin W.; Rosseinsky, Matthew J.; Hutchings, Graham J.

    2016-03-01

    Copper and zinc form an important group of hydroxycarbonate minerals that include zincian malachite, aurichalcite, rosasite and the exceptionally rare and unstable—and hence little known and largely ignored—georgeite. The first three of these minerals are widely used as catalyst precursors for the industrially important methanol-synthesis and low-temperature water-gas shift (LTS) reactions, with the choice of precursor phase strongly influencing the activity of the final catalyst. The preferred phase is usually zincian malachite. This is prepared by a co-precipitation method that involves the transient formation of georgeite; with few exceptions it uses sodium carbonate as the carbonate source, but this also introduces sodium ions—a potential catalyst poison. Here we show that supercritical antisolvent (SAS) precipitation using carbon dioxide (refs 13, 14), a process that exploits the high diffusion rates and solvation power of supercritical carbon dioxide to rapidly expand and supersaturate solutions, can be used to prepare copper/zinc hydroxycarbonate precursors with low sodium content. These include stable georgeite, which we find to be a precursor to highly active methanol-synthesis and superior LTS catalysts. Our findings highlight the value of advanced synthesis methods in accessing unusual mineral phases, and show that there is room for exploring improvements to established industrial catalysts.

  4. Oxygen reduction activities compared in rotating-disk electrode and proton exchange membrane fuel cells for highly active Fe-N-C catalysts

    International Nuclear Information System (INIS)

    Jaouen, F.; Goellner, V.; Lefèvre, M.; Herranz, J.; Proietti, E.; Dodelet, J.P.

    2013-01-01

    In the past three years, two novel synthesis methods for non-precious metal catalysts resulting in a breakthrough of their activity and performance at the cathode of the proton-exchange membrane fuel cell (PEMFC) have been reported by the group of Prof. Dodelet. While the activity of these novel Fe-based catalysts for the oxygen reduction reaction is very high in PEMFC, our preliminary activity measurements with the rotating disk electrode (RDE) technique on one of them showed an activity being a factor 30–100 lower than the one measured in PEMFC at 80 °C. The present work explains to a large extent this huge difference. Two Fe-N-C catalysts synthesized via our novel approaches and one Fe-N-C catalyst synthesized via our classical approach were investigated in RDE and PEMFC. In both systems, the effect of the ink formulation (Nafion-to-catalyst ratio) was investigated. Optimization of the RDE ink formulation explains a factor between 5 and 10 in the two-decade gap mentioned above. Then, the effect of temperature in the RDE system was investigated. An increase from 20 to 80 °C was found to result in a theoretical maximum twofold increase in activity. However, in practice, decreased O 2 solubility with increased temperature cancels this effect. After taking into account these two parameters, a difference in ORR activity between RDE and PEMFC of ca a factor five still remained for one of the two novel Fe-N-C catalysts investigated here. The lower initial activity measured in RDE for this catalyst is shown to be due to the fast adsorption of anions (HSO 4 − ) from the liquid H 2 SO 4 electrolyte on protonated nitrogen atoms (NH + ) found on its surface. The phenomenon of anion adsorption and associated decreased ORR activity also applies to the other novel Fe-N-C catalyst, but is slower and does not immediately occur in RDE.

  5. Synthesis of highly efficient Mn{sub 2}O{sub 3} catalysts for CO oxidation derived from Mn-MIL-100

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaodong, E-mail: fatzhxd@126.com [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Li, Hongxin; Hou, Fulin; Yang, Yang; Dong, Han; Liu, Ning [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Wang, Yuxin [Institute of Applied Biotechnology, Taizhou Vocation & Technical College, Taizhou, Zhejiang 318000 (China); Cui, Lifeng, E-mail: lifeng.cui@gmail.com [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China)

    2017-07-31

    Highlights: • The morphology of porous Mn{sub 2}O{sub 3} cubes was inherited from Mn-MIL-100 template. • Mn{sub 2}O{sub 3} obtained at calcined temperature of 700 °C displayed high activity. • Enhanced activity is attributed to surface active oxygen, and reduction behavior. - Abstract: In this work, metal-organic frameworks (MOFs) Mn-MIL-100 were first prepared, which were next used as templates to obtain the irregular porous Mn{sub 2}O{sub 3} cubes through calcination with air at different temperature. The catalysts were characterized by N{sub 2} adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), H{sub 2}-temperature program reduction (H{sub 2}-TPR) and X-ray photoelectron spectroscopic (XPS). The catalytic activity for CO oxidation over Mn{sub 2}O{sub 3} catalysts was investigated. It was found that calcination temperature had a strong effect on the structure and catalytic activity of Mn{sub 2}O{sub 3} catalyst. Mn{sub 2}O{sub 3} catalyst obtained by calcined at 700 °C (Mn{sub 2}O{sub 3}-700) showed a smaller specific surface area, but displayed a high catalytic activity and excellent stability with a complete CO conversion temperature (T{sub 98}) of 240 °C, which was attributed to the unique structure, a high quantity of surface active oxygen species, smaller particle size, oxygen vacancies and good low temperature reduction behavior. The effect of water vapor on catalytic activity was also examined. The introduction of water vapor to the feedstock induced a positive effect on CO oxidation over Mn{sub 2}O{sub 3}-700 catalyst. Furthermore, no obvious drop is observed in activity over catalysts even in the presence of water vapor during 48 h.

  6. Reuse of Hydrotreating Spent Catalyst

    International Nuclear Information System (INIS)

    Habib, A.M.; Menoufy, M.F.; Amhed, S.H.

    2004-01-01

    All hydro treating catalysts used in petroleum refining processes gradually lose activity through coking, poisoning by metal, sulfur or halides or lose surface area from sintering at high process temperatures. Waste hydrotreating catalyst, which have been used in re-refining of waste lube oil at Alexandria Petroleum Company (after 5 years lifetime) compared with the same fresh catalyst were used in the present work. Studies are conducted on partial extraction of the active metals of spent catalyst (Mo and Ni) using three leaching solvents,4% oxidized oxalic acid, 10% aqueous sodium hydroxide and 10% citric acid. The leaching experiments are conducting on the de coked extrude [un crushed] spent catalyst samples. These steps are carried out in order to rejuvenate the spent catalyst to be reused in other reactions. The results indicated that 4% oxidized oxalic acid leaching solution gave total metal removal 45.6 for de coked catalyst samples while NaOH gave 35% and citric acid gave 31.9 % The oxidized leaching agent was the most efficient leaching solvent to facilitate the metal removal, and the rejuvenated catalyst was characterized by the unchanged crystalline phase The rejuvenated catalyst was applied for hydrodesulfurization (HDS) of vacuum gas oil as a feedstock, under different hydrogen pressure 20-80 bar in order to compare its HDS activity

  7. Selective CO Methanation on Highly Active Ru/TiO2 Catalysts: Identifying the Physical Origin of the Observed Activation/Deactivation and Loss in Selectivity

    DEFF Research Database (Denmark)

    Abdel-Mageed, Ali M.; Widmann, Daniel; Olesen, Sine Ellemann

    2018-01-01

    Ru /TiO2 catalysts are highly active and selective in the selective methanation of CO in the presence of large amounts of CO2, but suffer from a considerable deactivation and loss of selectivity during time on stream. Aiming at a fundamental understanding of these processes, we have systematically...... different effects such as structural effects, adlayer effects such as site blocking effects and changes in the chemical (surface) composition of the catalysts. Operando XANES / EXAFS measurements revealed that an initial activation phase is largely due to the reduction of oxidized Ru species, together...

  8. Natural phosphate-supported palladium: A highly efficient and recyclable catalyst for the suzuki-miyaura coupling under microwave irradiation

    KAUST Repository

    Hassine, Ayoub; Bouhrara, Mohamed; Sebti, Said; Solhy, Abderrahim; Mahfouz, Remi; Luart, Denis; Lene, Christophe; Fihri, Aziz

    2015-01-01

    This report explores Suzuki-Miyaura coupling under microwave irradiation, using a new generation of catalyst that is based on natural phosphate (NP) impregnated by palladium. This catalyst was prepared by the treatment of natural phosphate with bis(benzonitrile)palladium(II) chloride in acetone at room temperature. The catalyst displayed high catalytic activity for the Suzuki-Miyaura coupling of aryl bromides and chlorides with aryl boronic acids in pure water and with the use of microwave irradiation. The low-cost and availability of the solid support, mild reaction conditions, high yields of desired products, recyclability of the catalyst and short reaction times are the notable features of these methods.

  9. Natural phosphate-supported palladium: A highly efficient and recyclable catalyst for the suzuki-miyaura coupling under microwave irradiation

    KAUST Repository

    Hassine, Ayoub

    2015-01-19

    This report explores Suzuki-Miyaura coupling under microwave irradiation, using a new generation of catalyst that is based on natural phosphate (NP) impregnated by palladium. This catalyst was prepared by the treatment of natural phosphate with bis(benzonitrile)palladium(II) chloride in acetone at room temperature. The catalyst displayed high catalytic activity for the Suzuki-Miyaura coupling of aryl bromides and chlorides with aryl boronic acids in pure water and with the use of microwave irradiation. The low-cost and availability of the solid support, mild reaction conditions, high yields of desired products, recyclability of the catalyst and short reaction times are the notable features of these methods.

  10. Phosphorene Co-catalyst Advancing Highly Efficient Visible-Light Photocatalytic Hydrogen Production.

    Science.gov (United States)

    Ran, Jingrun; Zhu, Bicheng; Qiao, Shi-Zhang

    2017-08-21

    Transitional metals are widely used as co-catalysts boosting photocatalytic H 2 production. However, metal-based co-catalysts suffer from high cost, limited abundance and detrimental environment impact. To date, metal-free co-catalyst is rarely reported. Here we for the first time utilized density functional calculations to guide the application of phosphorene as a high-efficiency metal-free co-catalyst for CdS, Zn 0.8 Cd 0.2 S or ZnS. Particularly, phosphorene modified CdS shows a high apparent quantum yield of 34.7 % at 420 nm. This outstanding activity arises from the strong electronic coupling between phosphorene and CdS, as well as the favorable band structure, high charge mobility and massive active sites of phosphorene, supported by computations and advanced characterizations, for example, synchrotron-based X-ray absorption near edge spectroscopy. This work brings new opportunities to prepare highly-active, cheap and green photocatalysts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Catalyst Degradation in High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

    DEFF Research Database (Denmark)

    Cleemann, Lars Nilausen; Buazar, F.; Li, Qingfeng

    2013-01-01

    and multi‐walled carbon nanotubes were used as supports for electrode catalysts and evaluated in accelerated durability tests under potential cycling at 150 °C. Measurements of open circuit voltage, area specific resistance and hydrogen permeation through the membrane were carried out, indicating little...... contribution of the membrane degradation to the performance losses during the potential cycling tests. As the major mechanism of the fuel cell performance degradation, the electrochemical active area of the cathodic catalysts showed a steady decrease in the cyclic voltammetric measurements, which was also......Degradation of carbon supported platinum catalysts is a major failure mode for the long term durability of high temperature proton exchange membrane fuel cells based on phosphoric acid doped polybenzimidazole membranes. With Vulcan carbon black as a reference, thermally treated carbon black...

  12. High power passive μDMFC with low catalyst loading for small power generation

    International Nuclear Information System (INIS)

    Ahmad, M.M.; Kamarudin, S.K.; Daud, W.R.W.; Yaakub, Z.

    2010-01-01

    The main constraint for commercialization of micro direct methanol fuel cell (μDMFC) for small power generation is the performance of the fuel cell. In this study, a high power μDMFC with a power output of 56 mW and an active area of 4 cm 2 was successfully developed. The cell required low catalyst loading of 5 mg cm -2 and 0.5 mg cm -2 at the anode and cathode, respectively. Optimal design parameters for methanol concentration and catalyst loading were examined. Finally, long-term performance testing was performed and OCV curves are reported. The results obtained for this gives the highest power density at low catalyst loading as compare to other researchers in this area.

  13. A Highly Practical Copper(I)/TEMPO Catalyst System for Chemoselective Aerobic Oxidation of Primary Alcohols

    Science.gov (United States)

    Hoover, Jessica M.; Stahl, Shannon S.

    2011-01-01

    Aerobic oxidation reactions have been the focus of considerable attention, but their use in mainstream organic chemistry has been constrained by limitations in their synthetic scope and by practical factors, such as the use of pure O2 as the oxidant or complex catalyst synthesis. Here, we report a new (bpy)CuI/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and the high selectivity for 1° alcohols enables selective oxidation of diols that lack protecting groups. PMID:21861488

  14. Location of adsorbed species in NO-reduction catalysts by high resolution neutron powder diffraction

    International Nuclear Information System (INIS)

    Fowkes, A.J.; Rosseinsky, M.J.

    1999-01-01

    Complete text of publication follows. Catalysts containing copper ion exchanged into zeolites are attracting considerable attention due to their efficiency for both NO decomposition and the selective catalytic reduction of NO x in so-called lean-burn conditions in automotive exhausts. This presentation will describe the application of in-situ high resolution neutron powder diffraction to study active sites in a Cu-zeolite Y catalyst active for NO decomposition. The study under NO pressure reveals the location of two distinct copper sites for sorption. The influence of copper oxidation state on the structure of both the pristine and NO-loaded zeolites will be discussed. (author)

  15. Rambutan-like CNT-Al2O3 scaffolds for high-performance cathode catalyst layers of polymer electrolyte fuel cells

    Science.gov (United States)

    Chang, KwangHyun; Cho, Seonghun; Lim, Eun Ja; Park, Seok-Hee; Yim, Sung-Dae

    2018-03-01

    Rambutan-like CNT-Al2O3 scaffolds are introduced as a potential candidate for CNT-based catalyst supports to overcome the CNT issues, such as the easy bundling in catalyst ink and the poor pore structure of the CNT-based catalyst layers, and to achieve high MEA performance in PEFCs. Non-porous α-phase Al2O3 balls are introduced to enable the growth of multiwalled CNTs, and Pt nanoparticles are loaded onto the CNT surfaces. In a half-cell, the Pt/CNT-Al2O3 catalyst shows much higher durability than those of a commercial Pt/C catalyst even though it shows lower oxygen reduction reaction (ORR) activity than Pt/C. After using the decal process for MEA formation, the Pt/CNT-Al2O3 shows comparable initial performance characteristics to Pt/C, overcoming the lower ORR activity, mainly due to the facile oxygen transport in the cathode catalyst layers fabricated with the CNT-Al2O3 scaffolds. The Pt/CNT-Al2O3 also exhibits much higher durability against carbon corrosion than Pt/C owing to the durable characteristics of CNTs. Systematic analysis of single cell performance for both initial and after degradation is provided to understand the origin of the high initial performance and durable behavior of Pt/CNT-Al2O3-based catalyst layers. This will provide insights into the design of electrocatalysts for high-performance MEAs in PEFCs.

  16. Biodiesel production from Silybum marianum L. seed oil with high FFA content using sulfonated carbon catalyst for esterification and base catalyst for transesterification

    International Nuclear Information System (INIS)

    Fadhil, Abdelrahman B.; Aziz, Akram M.; Al-Tamer, Marwa H.

    2016-01-01

    Highlights: • PET was converted to activated carbon and then sulfonated to prepare carbon acid catalyst. • Carbon acid catalyst was used for esterification of high acid value Silybum marianum L. seed oil. • Biodiesel was obtained with 96.98% efficiency. - Abstract: In this research work, waste of polyethylene terephthalate (PET) was converted into activated carbon and the latter was used in the preparation of a carbon acid catalyst. Waste of PET was converted into activated carbon via carbonization and steam activation, then the activated carbon was sulfonated using fuming sulfuric acid in order to produce the carbon acid catalyst. The prepared carbon acid catalyst was tested for esterification of high acid value non-edible oil, Silybum marianum L. seed oil (SMSO) via optimized protocol. Amount of the carbon acid catalyst, methanol to oil molar ratio, temperature and time were the experimental variables optimized. Esterification of SMSO with methanol using the prepared carbon acid catalyst reduced its parent acid value (20.0 mg KOH/g) to the acceptable limits for base-catalyzed transesterification (<2.0 mg KOH/g) using 6.0% w/w of the catalyst, 15:1 methanol to oil molar ratio, 68 °C reaction temperature and 180 min of reaction. The performance of the catalyst was reduced gradually during its recycling and reached to 60.0% at the 5th cycle. Kinetics of esterification of SMSO using the prepared carbon acid catalyst followed pseudo first order kinetics, and the activation energy was found to be 70.98 kJ/mol. The esterified oil was converted to biodiesel through optimized base-catalyzed transesterification with methanol. Biodiesel with (96.98% yield and purity of 96.69% w/w) yield was obtained using 0.80% KOH w/w, 6:1 methanol to oil molar ratio, 60 °C reaction temperature, 75 min of reaction and 600 rpm rate of stirring. The biodiesel properties were within the recommended biodiesel standards as prescribed by ASTM D 6751 and EN 14214. Transesterification of

  17. High-surface-area active carbon

    International Nuclear Information System (INIS)

    O'Grady, T.M.; Wennerberg, A.N.

    1986-01-01

    This paper describes the preparation and properties of a unique active carbon having exceptionally high surface areas, over 2500 m 2 /gm, and extraordinary adsorptive capacities. The carbon is made by a direct chemical activation route in which petroleum coke or other carbonaceous sources are reacted with excess potassium hydroxide at 400 0 to 500 0 C to an intermediate product that is subsequently pyrolyzed at 800 0 to 900 0 C to active carbon containing potassium salts. These are removed by water washing and the carbon is dried to produce a powdered product. A granular carbon can also be made by further processing the powdered carbon by using specialized granulation techniques. Typical properties of the carbon include Iodine Numbers of 3000 to 3600, methylene blue adsorption of 650 to 750 mg/gm, pore volumes of 2.0 to 2.6 cc/gm and less than 3.0% ash. This carbon's high adsorption capacities make it uniquely suited for numerous demanding applications in the medical area, purifications, removal of toxic substances, as catalyst carriers, etc

  18. Polymer nanocomposite membranes with hierarchically structured catalysts for high throughput dehalogenation

    Science.gov (United States)

    Crock, Christopher A.

    Halogenated organics are categorized as primary pollutants by the Environmental Protection Agency. Trichloroethylene (TCE), which had broad industrial use in the past, shows persistence in the environment because of its chemical stability. The large scale use and poor control of TCE resulted in its prolonged release into the environment before the carcinogenic risk associated with TCE was fully understood. TCE pollution stemmed from industrial effluents and improper disposal of solvent waste. Membrane reactors are promising technology for treating TCE polluted groundwater because of the high throughput, relatively low cost of membrane fabrication and facile retrofitting of existing membrane based water treatment facilities with catalytic membrane reactors. Compared to catalytic fluidized or fixed bed reactors, catalytic membrane reactors feature minimal diffusional limitation. Additionally, embedding catalyst within the membrane avoids the need for catalyst recovery and can prevent aggregation of catalytic nanoparticles. In this work, Pd/xGnP, Pd-Au/xGnP, and commercial Pd/Al2O3 nanoparticles were employed in batch and flow-through membrane reactors to catalyze the dehalogenation of TCE in the presence of dissolved H2. Bimetallic Pd-Au/xGnP catalysts were shown to be more active than monometallic Pd/xGnP or commercial Pd/Al 2O3 catalysts. In addition to synthesizing nanocomposite membranes for high-throughput TCE dehalogenation, the membrane based dehalogenation process was designed to minimize the detrimental impact of common catalyst poisons (S2-, HS-, and H2S -) by concurrent oxidation of sulfide species to gypsum in the presence of Ca2+ and removal of gypsum through membrane filtration. The engineered membrane dehalogenation process demonstrated that bimetallic Pd-Au/xGnP catalysts resisted deactivation by residual sulfide species after oxidation, and showed complete removal of gypsum during membrane filtration.

  19. Highly Selective Liquid-Phase Benzylation of Anisole with Solid-Acid Zeolite Catalysts

    DEFF Research Database (Denmark)

    Poreddy, Raju; Shunmugavel, Saravanamurugan; Riisager, Anders

    2015-01-01

    Zeolites were evaluated as solid acid catalysts for the liquid-phase benzylation of anisole with benzyl alcohol, benzyl bromide, and benzyl chloride at 80 °C. Among the examined zeolites, H-mordenite-10 (H-MOR-10) demonstrated particular high activity (>99 %) and excellent selectivity (>96...

  20. Highly Selective Continuous Gas-Phase Methoxycarbonylation of Ethylene with Supported Ionic Liquid Phase (SILP) Catalysts

    DEFF Research Database (Denmark)

    Khokarale, Santosh Govind; Garcia Suárez, Eduardo José; Fehrmann, Rasmus

    2017-01-01

    Supported ionic liquid phase (SILP) technology was applied for the first time to the Pd-catalyzed continuous, gas-phase methoxycarbonylation of ethylene to selectively produce methyl propanoate (MP) in high yields. The influence of catalyst and reaction parameters such as, for example, ionic liquid...

  1. Silica-supported ionic liquid as highly efficient catalyst for one-pot ...

    Indian Academy of Sciences (India)

    4. Conclusion. A novel multicomponent approach for the synthesis of a series of new acenaphthofuran derivatives utilizing the supported ionic liquid catalyst has been elaborated. The efficient catalysing of used ionic liquid in the synthesis of acenaphtho[1,2-b]furans led to high chemical yields as well as short reaction times.

  2. Calcium Oxide Supported on Monoclinic Zirconia as a Highly Active Solid Base Catalyst

    NARCIS (Netherlands)

    Frey, A.M.; Haasterecht, van T.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    Calcium oxide supported on ZrO2 is a highly active catalyst for base-catalyzed reactions such as aldol-type reactions and transesterification reactions. The role of key parameters during preparation, that is, impregnation versus precipitation, heat treatment, and metal oxide loading on the basicity

  3. Surface properties and catalytic performance of Pt/LaSrCoO4 catalysts in the oxidation of hexane

    Directory of Open Access Journals (Sweden)

    Hua Zhong

    2007-08-01

    Full Text Available Perovskite-type La2 –xSrxCoO4 mixed oxides have been prepared by calcination at various temperatures of precipitates obtained from aqueous solutions in the presence of citric or ethylenediamintetraacetic (EDTA acids, and have been studied by X-ray diffraction (XRD, surface area (BET measurements, temperature programmed desorption (TPD, temperature programmed reduction (TPR and X-ray photoelectron spectroscopy (XPS. These oxides are catalysts for hexane oxidation, with the greatest activity for LaSrCoO4 calcined at 750 C. This has extensive oxygen vacancies and large internal surface area. Pt-modified LaSrCoO4 catalysts are significantly more active than the Pt-free system. Both surface and bulk phases of the preovskitetype oxides contribute to hexane oxidation.

  4. A surface science model for the Phillips ethylene polymerization catalyst : thermal activation and polymerization activity

    NARCIS (Netherlands)

    Kimmenade, van E.M.E.; Kuiper, A.E.T.; Tamminga, Y.; Thuene, P.C.; Niemantsverdriet, J.W.

    2004-01-01

    A series of CrOx/SiO2/Si(100) model catalysts were tested for ethylene polymerization activity, varying chromium loading, and calcination temperature. Chromium coverage of the model catalyst, quantified by Rutherford backscattering spectrometry, decreases with increasing calcination temperature as

  5. Synthesis of a highly dispersed CuO catalyst on CoAl-HT for the epoxidation of styrene.

    Science.gov (United States)

    Hu, Rui; Yang, Pengfei; Pan, Yongning; Li, Yunpeng; He, Yufei; Feng, Junting; Li, Dianqing

    2017-10-10

    A highly dispersed CuO catalyst was prepared by the deposition-precipitation method and evaluated for the catalytic epoxidation of styrene with tert-butyl hydroperoxide (TBHP) as the oxidant under solvent acetonitrile conditions. Compared with MgAl hydrotalcite (MgAl-HT)-, MgO-, TiO 2 -, C-, and MCM-22-supported catalysts, CuO/CoAl-HT exhibited preferable activity and selectivity towards styrene oxide (72% selectivity at 99.5% styrene conversion) due to its high dispersion of CuO and surface area of Cu. The improved dispersion of CuO/CoAl-HT could be ascribed to the nature of HT support, especially the synergistic effect of acidic and basic sites on the surface, which facilitated the formation of highly dispersed CuO species. A structure-performance relationship study indicated that copper(ii) in CuO was the active site for the epoxidation and oxidation of styrene, and that Cu II of rich electronic density favored the improvement of selectivity of styrene oxide. Based on these results, a reaction mechanism was proposed. Moreover, the preferred catalytic performance of CuO/CoAl-HT could be maintained in five reused cycles.

  6. Biopolymer-stabilized Pt nanoparticles colloid: a highly active and recyclable catalyst for biphasic catalysis

    International Nuclear Information System (INIS)

    Wang, Yujia; Shen, Yueyue; Qiu, Yunfei; Zhang, Ting; Liao, Yang; Zhao, Shilin; Ma, Jun; Mao, Hui

    2016-01-01

    Noble metal nanoparticles are promising candidates to replace conventional bulk counterparts owing to their high activity and selectivity. To enable catalyst recovery, noble metal nanoparticles are often supported onto solid matrices to prepare heterogeneous catalyst. Although recycle of noble metal nanoparticles is realized by heterogenization, a loss of activity is usually encountered. In the present investigation, Pt nanoparticles with tunable particle size (1.85–2.80 nm) were facilely prepared by using polyphenols as amphiphilic stabilizers. The as-prepared Pt nanoparticles colloid solution could be used as highly active catalyst in aqueous–organic biphasic catalysis. The phenolic hydroxyls of polyphenols could constrain Pt nanoparticles in aqueous phase, and simultaneously, the aromatic scaffold of polyphenols ensured effective interactions between substrates and Pt nanoparticles. As a consequence, the obtained polyphenols-stabilized Pt nanoparticles exhibited high activity and cycling stability in biphasic hydrogenation of a series of unsaturated compounds. Compared with conventional heterogeneous Pt-C and Pt-Al 2 O 3 catalysts, polyphenols-stabilized Pt nanoparticles showed obvious advantage both in activity and cycling stability.

  7. Biopolymer-stabilized Pt nanoparticles colloid: a highly active and recyclable catalyst for biphasic catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yujia; Shen, Yueyue; Qiu, Yunfei; Zhang, Ting; Liao, Yang; Zhao, Shilin; Ma, Jun, E-mail: 1044208419@qq.com; Mao, Hui, E-mail: rejoice222@163.com [Sichuan Normal University, College of Chemistry and Materials Science (China)

    2016-10-15

    Noble metal nanoparticles are promising candidates to replace conventional bulk counterparts owing to their high activity and selectivity. To enable catalyst recovery, noble metal nanoparticles are often supported onto solid matrices to prepare heterogeneous catalyst. Although recycle of noble metal nanoparticles is realized by heterogenization, a loss of activity is usually encountered. In the present investigation, Pt nanoparticles with tunable particle size (1.85–2.80 nm) were facilely prepared by using polyphenols as amphiphilic stabilizers. The as-prepared Pt nanoparticles colloid solution could be used as highly active catalyst in aqueous–organic biphasic catalysis. The phenolic hydroxyls of polyphenols could constrain Pt nanoparticles in aqueous phase, and simultaneously, the aromatic scaffold of polyphenols ensured effective interactions between substrates and Pt nanoparticles. As a consequence, the obtained polyphenols-stabilized Pt nanoparticles exhibited high activity and cycling stability in biphasic hydrogenation of a series of unsaturated compounds. Compared with conventional heterogeneous Pt-C and Pt-Al{sub 2}O{sub 3} catalysts, polyphenols-stabilized Pt nanoparticles showed obvious advantage both in activity and cycling stability.

  8. Exceptionally High Efficient Co-Co2P@N, P-Codoped Carbon Hybrid Catalyst for Visible Light-Driven CO2-to-CO Conversion.

    Science.gov (United States)

    Fu, Wen Gan

    2018-05-02

    Artificial photosynthesis has attracted wide attention, particularly the development of efficient solar light-driven methods to reduce CO2 to form energy-rich carbon-based products. Because CO2 reduction is an uphill process with a large energy barrier, suitable catalysts are necessary to achieve this transformation. In addition, CO2 adsorption on a catalyst and proton transfer to CO2 are two important factors for the conversion reaction,and catalysts with high surface area and more active sites are required to improve the efficiency of CO2 reduction. Here, we report a visible light-driven system for CO2-to-CO conversion that consists of a heterogeneous hybrid catalyst of Co and Co2P nanoparticles embedded in carbon nanolayers codoped with N and P (Co-Co2P@NPC) and a homogeneous Ru(II)-based complex photosensitizer. The average generation rate of CO of the system was up to 35,000 μmol h-1 g-1 with selectivity of 79.1% in 3 h. Linear CO production at an exceptionally high rate of 63,000 μmol h-1 g-1 was observed in the first hour of reaction. Inspired by this highly active catalyst, we also synthesized Co@NC and Co2P@NPC materials and explored their structure, morphology, and catalytic properties for CO2 photoreduction. The results showed that the nanoparticle size, partially adsorbed H2O molecules on the catalyst surface, and the hybrid nature of the systems influenced their photocatalytic CO2 reduction performance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Activated carbon derived from chitosan as air cathode catalyst for high performance in microbial fuel cells

    Science.gov (United States)

    Liu, Yi; Zhao, Yong; Li, Kexun; Wang, Zhong; Tian, Pei; Liu, Di; Yang, Tingting; Wang, Junjie

    2018-02-01

    Chitosan with rich of nitrogen is used as carbon precursor to synthesis activated carbon through directly heating method in this study. The obtained carbon is activated by different amount of KOH at different temperatures, and then prepared as air cathodes for microbial fuel cells. Carbon sample treated with double amount of KOH at 850 °C exhibits maximum power density (1435 ± 46 mW m-2), 1.01 times improved, which ascribes to the highest total surface area, moderate micropore and mesoporous structure and the introduction of nitrogen. The electrochemical impedance spectroscopy and powder resistivity state that carbon treated with double amount of KOH at 850 °C possesses lower resistance. The other electrochemical measurements demonstrate that the best kinetic activity make the above treated sample to show the best oxygen reduction reaction activity. Besides, the degree of graphitization of samples increases with the activated temperature increasing, which is tested by Raman. According to elemental analysis and X-ray photoelectron spectroscopy, all chitosan samples are nitrogen-doped carbon, and high content nitrogen (pyridinic-N) improves the electrochemical activity of carbon treated with KOH at 850 °C. Thus, carbon materials derived from chitosan would be an optimized catalyst for oxygen reduction reaction in microbial fuel cell.

  10. Electrocatalytic performance of fuel cell reactions at low catalyst loading and high mass transport.

    Science.gov (United States)

    Zalitis, Christopher M; Kramer, Denis; Kucernak, Anthony R

    2013-03-28

    An alternative approach to the rotating disk electrode (RDE) for characterising fuel cell electrocatalysts is presented. The approach combines high mass transport with a flat, uniform, and homogeneous catalyst deposition process, well suited for studying intrinsic catalyst properties at realistic operating conditions of a polymer electrolyte fuel cell (PEFC). Uniform catalyst layers were produced with loadings as low as 0.16 μgPt cm(-2) and thicknesses as low as 200 nm. Such ultra thin catalyst layers are considered advantageous to minimize internal resistances and mass transport limitations. Geometric current densities as high as 5.7 A cm(-2)Geo were experimentally achieved at a loading of 10.15 μgPt cm(-2) for the hydrogen oxidation reaction (HOR) at room temperature, which is three orders of magnitude higher than current densities achievable with the RDE. Modelling of the associated diffusion field suggests that such high performance is enabled by fast lateral diffusion within the electrode. The electrodes operate over a wide potential range with insignificant mass transport losses, allowing the study of the ORR at high overpotentials. Electrodes produced a specific current density of 31 ± 9 mA cm(-2)Spec at a potential of 0.65 V vs. RHE for the oxygen reduction reaction (ORR) and 600 ± 60 mA cm(-2)Spec for the peak potential of the HOR. The mass activity of a commercial 60 wt% Pt/C catalyst towards the ORR was found to exceed a range of literature PEFC mass activities across the entire potential range. The HOR also revealed fine structure in the limiting current range and an asymptotic current decay for potentials above 0.36 V. These characteristics are not visible with techniques limited by mass transport in aqueous media such as the RDE.

  11. Highly active Pd–In/mesoporous alumina catalyst for nitrate reduction

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhenwei; Zhang, Yonggang; Li, Deyi [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Werth, Charles J. [Civil, Architectural and Environmental Engineering, University of Texas at Austin, 301 East Dean Keeton St., Stop C1786, Austin, TX 78712 (United States); Zhang, Yalei, E-mail: zhangyalei2003@163.com [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Zhou, Xuefei, E-mail: zhouxuefei@tongji.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China)

    2015-04-09

    Highlights: • Pd–In nanoparticles (6–7 nm) uniformly form in the mesopores of alumina (4 nm). • Pd–In nanoparticles aggregation is prevented during the synthesis process. • The reduction rate of nitrate is efficient by using the obtained catalyst. • The selectivity toward N{sub 2} is ideal by using the obtained catalyst. - Abstract: The catalytic reduction of nitrate is a promising technology for groundwater purification because it transforms nitrate into nitrogen and water. Recent studies have mainly focused on new catalysts with higher activities for the reduction of nitrate. Consequently, metal nanoparticles supported on mesoporous metal oxides have become a major research direction. However, the complex surface chemistry and porous structures of mesoporous metal oxides lead to a non-uniform distribution of metal nanoparticles, thereby resulting in a low catalytic efficiency. In this paper, a method for synthesizing the sustainable nitrate reduction catalyst Pd–In/Al{sub 2}O{sub 3} with a dimensional structure is introduced. The TEM results indicated that Pd and In nanoparticles could efficiently disperse into the mesopores of the alumina. At room temperature in CO{sub 2}-buffered water and under continuous H{sub 2} as the electron donor, the synthesized material (4.9 wt% Pd) was the most active at a Pd–In ratio of 4, with a first-order rate constant (k{sub obs} = 0.241 L min{sup −1} g{sub cata}{sup −1}) that was 1.3× higher than that of conventional Pd–In/Al{sub 2}O{sub 3} (5 wt% Pd; 0.19 L min{sup −1} g{sub cata}{sup −1}). The Pd–In/mesoporous alumina is a promising catalyst for improving the catalytic reduction of nitrate.

  12. The development of isomerization catalysts for production of high-octane products

    Energy Technology Data Exchange (ETDEWEB)

    Pedrosa, A.M. Garrido; Melo, D.M.A.; Araujo, A.S. [Universidade Federal do Rio Grande do Norte, Natal, RN (Brazil). Dept. de Quimica; Souza, M.J.B.; Silva, A.O.S. [Universidade Federal do Rio Grande do Norte, Natal, RN (Brazil). Dept. de Engenharia Quimica

    2004-07-01

    In current petroleum industry, paraffins larger than C5 are used for catalytic reform. The catalytic reform is one of the most important processes for petroleum refine in reason of all reactions they drive to production of high-octane products. Reformate has high-octane products, but they contain 60% aromatics. Isomerization of C5- C7 can improve the octane number. The octane number of n-heptane is zero and increases after isomerization. For tri branched C7, the octane number reaches 113, which is higher than that of benzene. So, isomerization of C5-C7 is suggested to be a reasonable way to replace or partly replace the catalytic reforming process. It can decrease aromatics content with enhancement of octane number. Liquid acid catalysts were widely used in chemical industry in past decades. However, they face strong environmental challenges. The heavy corrosion of the reactor system is one of the main problems. Thus, solid acid catalysts are investigated for the isomerization reactions. The aim of this work is to develop a catalysts for the production of reformate products. Isomerization is catalyzed by metal-acid bifunctional catalysts. The metal components aid in hydrogenation, while the support, such as, zirconium, clays or zeolites, is the acidic component. (author)

  13. Efficient Hydrogenolysis of Guaiacol over Highly Dispersed Ni/MCM-41 Catalyst Combined with HZSM-5

    Directory of Open Access Journals (Sweden)

    Songbai Qiu

    2016-09-01

    Full Text Available A series of MCM-41 supported Ni catalysts with high metal dispersion was successfully synthesized by simple co-impregnation using proper ethylene glycol (EG. The acquired Ni-based catalysts performed the outstanding hydrogenolysis activity of guaiacol. The effects of the synthesis parameters including drying temperature, calcination temperature, and metal loading on the physical properties of NiO nanoparticles were investigated through the use of X-ray diffraction (XRD. The drying temperature was found to significantly influence the particle sizes of NiO supported on MCM-41, but the calcination temperature and metal loading had less influence. Interestingly, the small particle size (≤3.3 nm and the high dispersion of NiO particles were also obtained for co-impregnation on the mixed support (MCM-41:HZSM-5 = 1:1, similar to that on the single MCM-41 support, leading to excellent hydrogenation activity at low temperature. The guaiacol conversion could reach 97.9% at 150 °C, and the catalytic activity was comparative with that of noble metal catalysts. The hydrodeoxygenation (HDO performance was also promoted by the introduction of acidic HZSM-5 zeolite and an 84.1% yield of cyclohexane at 240 °C was achieved. These findings demonstrate potential applications for the future in promoting and improving industrial catalyst performance.

  14. Alkali resistant Cu/zeolite deNOx catalysts for flue gas cleaning in biomass fired applications

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Riisager, Anders; Fehrmann, Rasmus

    2011-01-01

    to investigate the redox and acidic properties of the catalysts. The poisoning resistivity seems to be due to a combination of high surface area and strong acidity of the Cu/zeolite catalysts. The catalysts might be attractive alternatives to conventional catalysts for deNOx of flue gases from biomass fired...... power plants and other stationary industrial installations....

  15. Hydrothermal performance of catalyst supports

    Energy Technology Data Exchange (ETDEWEB)

    Elam, Jeffrey W.; Marshall, Christopher L.; Libera, Joseph A.; Dumesic, James A.; Pagan-Torres, Yomaira J.

    2018-04-10

    A high surface area catalyst with a mesoporous support structure and a thin conformal coating over the surface of the support structure. The high surface area catalyst support is adapted for carrying out a reaction in a reaction environment where the thin conformal coating protects the support structure within the reaction environment. In various embodiments, the support structure is a mesoporous silica catalytic support and the thin conformal coating comprises a layer of metal oxide resistant to the reaction environment which may be a hydrothermal environment.

  16. Surface-initiated addition polymerization of norbornene by a Pd(II) catalyst bearing acetylacetone ligand on the glass slide

    Science.gov (United States)

    He, Xiaohui; Wang, Kaiti; Chen, Yiwang; Yuan, Bin

    2012-02-01

    A Pd catalyst bearing acetylacetone ligand [(CH3CO)2CHPdCl2] was covalently attracted onto the surface of glass slides, and then these Pd-terminated glass slides were immersed into a toluene solution of norbornene (NB) to produce a vinyl-type addition polynorbornene (PNB) layer on the surface of glass slides. It was found that the contract angles of the PNB-terminated glass slides surface increased with the increasing of polymerization time, and the thickness of the PNB layers were approximately 0-44.0 μm when the polymerization time was 0.5-24 h. The researching on etching also has been operated.

  17. Surface treated carbon catalysts produced from waste tires for fatty acids to biofuel conversion

    Science.gov (United States)

    Hood, Zachary D.; Adhikari, Shiba P.; Wright, Marcus W.; Lachgar, Abdessadek; Li, Yunchao; Naskar, Amit K.; Paranthaman, Mariappan Parans

    2018-02-06

    A method of making solid acid catalysts includes the step of sulfonating waste tire pieces in a first sulfonation step. The sulfonated waste tire pieces are pyrolyzed to produce carbon composite pieces having a pore size less than 10 nm. The carbon composite pieces are then ground to produce carbon composite powders having a size less than 50 .mu.m. The carbon composite particles are sulfonated in a second sulfonation step to produce sulfonated solid acid catalysts. A method of making biofuels and solid acid catalysts are also disclosed.

  18. KF-loaded mesoporous Mg-Fe bi-metal oxides: high performance transesterification catalysts for biodiesel production.

    Science.gov (United States)

    Tao, Guiju; Hua, Zile; Gao, Zhe; Zhu, Yan; Zhu, Yan; Chen, Yu; Shu, Zhu; Zhang, Lingxia; Shi, Jianlin

    2013-09-21

    Using newly developed mesoporous Mg-Fe bi-metal oxides as supports, a novel kind of high performance transesterification catalysts for biodiesel production has been synthesized. More importantly, the impregnation solvent was for the first time found to substantially affect the structures and catalytic performances of the resultant transesterification catalysts.

  19. Microwave-activated Ni/carbon catalysts for highly selective hydrogenation of nitrobenzene to cyclohexylamine.

    Science.gov (United States)

    Lu, Xinhuan; He, Jie; Jing, Run; Tao, Peipei; Nie, Renfeng; Zhou, Dan; Xia, Qinghua

    2017-06-01

    Biocarbon supported Ni catalysts have been prepared by facile impregnation of Ni species by microwave-heating and used for selective hydrogenation of nitrobenzene to cyclohexylamine. These catalysts were characterized by X-ray diffraction, Raman spectra, N2 sorption measurement, X-ray photoelectron spectroscopy, temperature programmed reduction of H2 and H2 temperature-programmed desorption. The morphology and particle size of catalysts were imaged by scanning electron microscope and transmission electron microscope. For the hydrogenation of nitrobenzene to cyclohexylamine, 10%Ni/CSC-II(b) exhibits the best catalytic activity to achieve 100 mol% conversion of nitrobenzene and 96.7% selectivity of cyclohexylamine under reaction conditions of 2.0 MPa H2 and 200 °C, ascribed to high dispersion of Ni species and formation of nanosized Ni particles on the support aided by microwave-heating. Thus-prepared Ni/CSC catalyst is greatly activated, in which the addition of precious metal like Rh is totally avoided.

  20. Thioetherification of chloroheteroarenes: a binuclear catalyst promotes wide scope and high functional-group tolerance.

    Science.gov (United States)

    Platon, Mélanie; Wijaya, Novi; Rampazzi, Vincent; Cui, Luchao; Rousselin, Yoann; Saeys, Mark; Hierso, Jean-Cyrille

    2014-09-22

    A constrained binuclear palladium catalyst system affords selective thioetherification of a wide range of functionalized arenethiols with chloroheteroaromatic partners with the highest turnover numbers (TONs) reported to date and tolerates a large variety of reactive functions. The scope of this system includes the coupling of thiophenols with six- and five-membered 2-chloroheteroarenes (i.e., functionalized pyridine, pyrazine, quinoline, pyrimidine, furane, and thiazole) and 3-bromoheteroarenes (i.e., pyridine and furane). Electron-rich congested thiophenols and fluorinated thiophenols are also suitable partners. The coupling of unprotected amino-2-chloropyridines with thiophenol and the successful employment of synthetically valuable chlorothiophenols are described with the same catalyst system. DFT studies attribute the high performance of this binuclear palladium catalyst to the decreased stability of thiolate-containing resting states. Palladium loading was as low as 0.2 mol %, which is important for industrial application and is a step forward in solving catalyst activation/deactivation problems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. High-BTU gas production from tar-bearing hot coke oven gas over iron catalyst

    Energy Technology Data Exchange (ETDEWEB)

    L.Y. Li; K. Morishita; T. Takarada [Gunma University, Gunma (Japan). Department of Biological and Chemical Engineering

    2005-07-01

    To utilize the tar-bearing hot coke oven gas (the by-product of coke making process) more effectively, a process was developed by converting the hot coke oven gas into a methane rich high-BTU gas over iron-bearing catalysts. The catalytic behaviour of Indonesian limonite ore was mainly discussed. For a reference, a conventional nickel catalyst (Ni/Al{sub 2}O{sub 3}) was employed. Laboratory scale tests were carried out in a two-stage fixed-bed reactor at ambient pressure. A bituminous coal sample was heated at first stage, the volatiles was carried by feed gas and decomposed at second stage. The limonite promoted hydropyrolysis of coal volatiles similar to Ni/Al{sub 2}O{sub 3} catalyst. High yields of total product gas and methane were obtained at 50 vol.% hydrogen atmosphere with a feed gas of 60 ml min{sup -1} hydrogen and 60 ml min{sup -1} nitrogen. After experiments, hydrocarbons heavier than ethane were not observed. Also that, carbon balance was more than 99.8% in coal char, product gases and carbon deposits. It was considered that coal volatiles converted into light gases and carbon almost completely in catalyst bed. Yields of product gas and methane depended upon catalytic temperature. At 923 K, the maximum yield of product gas was achieved at 74.3% for limonite catalyst on carbon balance with methane 83.2 vol.% of the carbonaceous gas products. Comparing with limonite, Fe/Al{sub 2}O{sub 3} and BOF dust samples showed low activities on coal volatiles catalytic decomposition. 21 refs., 5 figs., 3 tabs.

  2. Based on a new support for synthesis of highly efficient palladium/hydroxyapatite catalyst for ethanol electrooxidation

    International Nuclear Information System (INIS)

    Cui, Qian; Chao, Shujun; Bai, Zhengyu; Yan, Huiying; Wang, Kui; Yang, Lin

    2014-01-01

    Based on a new support, hydroxyapatite (HAP), a facile and low–cost preparation of palladium/hydroxyapatite catalyst for ethanol electrooxidation is introduced in this paper through a solvothermal reaction without additives. HAP was employed as the catalyst support for its hydroxyl–rich surface in order to increase the stability and utilization ratio of catalyst. According to transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and X–ray diffraction (XRD) measurements, the as–prepared Pd nanoparticles with face–centered cubic crystal structure were evenly deposited on the surface of HAP. Cyclic voltammetry and chronoamperometry tests demonstrated that the Pd/HAP catalyst possessed a much higher current density (246 mA cm −2 ) than the Pd/C catalyst (109 mA cm −2 ) towards ethanol electrooxidation, and better stability as well. In the direct ethanol fuel cell (DEFC) test, Pd/HAP catalyst gives better performance than that with Pd/C in terms of both open-circuit voltage (OCV) and power density. These results indicate that the HAP is a better support and the catalyst developed in this study may be a better candidate for DEFCs. A possible mechanism consistent with the experimental is also proposed

  3. Arts Integration as a Catalyst for High School Renewal

    Science.gov (United States)

    Dorfman, Dorinne

    2008-01-01

    The director of a small career academy of the arts in a public high school reflects on the conflicting demands to establish a college-preparatory program adhering to state standards and to facilitate the personal growth, artistic discovery, and democratic empowerment of teens. By narrating experiences that go to the heart of philosophical discord,…

  4. Nanographene synthesized in triple-phase plasmas as a highly durable support of catalysts for polymer electrolyte fuel cells

    Science.gov (United States)

    Amano, Tomoki; Kondo, Hiroki; Takeda, Keigo; Ishikawa, Kenji; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

    2018-04-01

    Nanographene was synthesized in triple-phase plasmas comprising a gaseous phase, a gas-liquid boundary layer, and an in-liquid phase using a setup in which one electrode was placed in the gaseous phase while the other was immersed in the liquid phase. The triple-phase plasmas were generated using a pure alcohol, such as ethanol, 1-propanol, or 1-butanol, by applying a high voltage to a pair of electrodes made of copper or graphite. The nanographene synthesized using ethanol had high durability and thus could serve as a catalyst support in polymer electrolyte fuel cells (PEFCs). The PEFCs exhibited low degradation rates in the high-potential cycle test of a half-cell, as a result of which, a loss of only 10% was observed in the effective electrochemical surface area of Pt, even after 10,000 cycles.

  5. High-speed conversion of carbon dioxide into methanol using catalyst. Shokubai ni yoru nisanka tanso no kosoku methanol ka

    Energy Technology Data Exchange (ETDEWEB)

    Inui, T. (Kyoto University, Kyoto (Japan). Faculty of Enineering)

    1993-02-01

    This paper describes high-speed conversion of CO2 into methanol. When a Cu-Zn-Cr-Al oxide-based catalyst (MSCp catalyst) prepared by using a sedimentation process used for synthesizing methanol from CO is applied to converting CO2 into methanol, the methanol yield decreases down to a several fraction of CO to methanol conversion, with a possibility of greater catalytic deactivation. If this catalyst prepared by using a homogeneous gelation process (MSCg catalyst) is used, the yield of methanol from CO2 increases by 240 plus percent over the case of using the MSCp catalyst, and no catalytic deactivation occurs at all during a use for ten and odd hours. Further, when La2O3 is added to the MSCg catalyst at 4% by weight, the methanol yield increases by about two times as much as the case without addition, and the temperature at which the maximum yield is achieved shifts to a lower temperature side by about 20[degree]C. Combining Ag or Pd with the MSCg catalyst provides the same effects. The paper touches on an attempt of high-speed CO2 conversion using this catalyst loaded with ceramic fibers. 15 refs., 5 figs., 2 tabs.

  6. Effect of the prominent catalyst layer surface on reactant gas transport and cell performance at the cathodic side of a PEMFC

    International Nuclear Information System (INIS)

    Perng, Shiang-Wuu; Wu, Horng-Wen

    2010-01-01

    The cell performance enhancement of a proton exchange membrane fuel cell (PEMFC) has been numerically investigated with the prominence-like form catalyst layer surface of the same composition at the cathodic half-cell of a PEMFC. The geometries of the prominence-like form catalyst layer surface are assigned as one prominence, three prominences, and five prominences catalyst layer surfaces with constant distance between two prominences in the same gas diffusion layer (GDL) for the purpose of investigating the cell performance. To confine the current investigation to two-dimensional incompressible flows, we assume that the fluid flow is laminar with a low Reynolds number 15. The results indicate that the prominence-like form catalyst layer surface can effectively enhance the local cell performance of a PEMFC.

  7. Highly efficient bioinspired molecular Ru water oxidation catalysts with negatively charged backbone ligands.

    Science.gov (United States)

    Duan, Lele; Wang, Lei; Li, Fusheng; Li, Fei; Sun, Licheng

    2015-07-21

    The oxygen evolving complex (OEC) of the natural photosynthesis system II (PSII) oxidizes water to produce oxygen and reducing equivalents (protons and electrons). The oxygen released from PSII provides the oxygen source of our atmosphere; the reducing equivalents are used to reduce carbon dioxide to organic products, which support almost all organisms on the Earth planet. The first photosynthetic organisms able to split water were proposed to be cyanobacteria-like ones appearing ca. 2.5 billion years ago. Since then, nature has chosen a sustainable way by using solar energy to develop itself. Inspired by nature, human beings started to mimic the functions of the natural photosynthesis system and proposed the concept of artificial photosynthesis (AP) with the view to creating energy-sustainable societies and reducing the impact on the Earth environments. Water oxidation is a highly energy demanding reaction and essential to produce reducing equivalents for fuel production, and thereby effective water oxidation catalysts (WOCs) are required to catalyze water oxidation and reduce the energy loss. X-ray crystallographic studies on PSII have revealed that the OEC consists of a Mn4CaO5 cluster surrounded by oxygen rich ligands, such as oxyl, oxo, and carboxylate ligands. These negatively charged, oxygen rich ligands strongly stabilize the high valent states of the Mn cluster and play vital roles in effective water oxidation catalysis with low overpotential. This Account describes our endeavors to design effective Ru WOCs with low overpotential, large turnover number, and high turnover frequency by introducing negatively charged ligands, such as carboxylate. Negatively charged ligands stabilized the high valent states of Ru catalysts, as evidenced by the low oxidation potentials. Meanwhile, the oxygen production rates of our Ru catalysts were improved dramatically as well. Thanks to the strong electron donation ability of carboxylate containing ligands, a seven

  8. The structure of a working catalyst : from flat surfaces to nanoparticles

    NARCIS (Netherlands)

    Roobol, Sander Bas

    2014-01-01

    Catalysis is the working horse of the chemical industry. In many cases, it is a poorly understood process taking place at the surfaces of nanoparticles under relatively harsh conditions, such as high pressures and high temperatures. This thesis focuses on new approaches to acquire atomic-scale

  9. Niobium, catalyst repair kit

    International Nuclear Information System (INIS)

    Tanabe, K.

    1991-01-01

    This paper reports that niobium oxides, when small amounts are added to known catalysts, enhance catalytic activity and selectivity and prolong catalyst life. Moreover, niobium oxides exhibit a pronounced effect as supports of metal or metal oxide catalysts. Recently we found that the surface acidity of hydrated niobium pentoxide, niobic acid (Nb 2 O 5 · nH 2 O), corresponds to the acidity of 70% sulfuric acid and exhibits high catalytic activity, selectivity, and stability for acid-catalyzed reactions in which water molecules participate. Although there are few differences in electronegativity and ionic radius between niobium and its neighbors in the periodic table, it is interesting that the promoter effect, support effect, and acidic nature of niobium compounds are quite different from those of compounds of the surrounding elements. Here we review what's known of niobium compounds from the viewpoint of their pronounced catalytic behavior

  10. Unveiling the high-activity origin of single-atom iron catalysts for oxygen reduction reaction.

    Science.gov (United States)

    Yang, Liu; Cheng, Daojian; Xu, Haoxiang; Zeng, Xiaofei; Wan, Xin; Shui, Jianglan; Xiang, Zhonghua; Cao, Dapeng

    2018-06-26

    It is still a grand challenge to develop a highly efficient nonprecious-metal electrocatalyst to replace the Pt-based catalysts for oxygen reduction reaction (ORR). Here, we propose a surfactant-assisted method to synthesize single-atom iron catalysts (SA-Fe/NG). The half-wave potential of SA-Fe/NG is only 30 mV less than 20% Pt/C in acidic medium, while it is 30 mV superior to 20% Pt/C in alkaline medium. Moreover, SA-Fe/NG shows extremely high stability with only 12 mV and 15 mV negative shifts after 5,000 cycles in acidic and alkaline media, respectively. Impressively, the SA-Fe/NG-based acidic proton exchange membrane fuel cell (PEMFC) exhibits a high power density of 823 mW cm -2 Combining experimental results and density-functional theory (DFT) calculations, we further reveal that the origin of high-ORR activity of SA-Fe/NG is from the Fe-pyrrolic-N species, because such molecular incorporation is the key, leading to the active site increase in an order of magnitude which successfully clarifies the bottleneck puzzle of why a small amount of iron in the SA-Fe catalysts can exhibit extremely superior ORR activity.

  11. Highly active Pd-In/mesoporous alumina catalyst for nitrate reduction.

    Science.gov (United States)

    Gao, Zhenwei; Zhang, Yonggang; Li, Deyi; Werth, Charles J; Zhang, Yalei; Zhou, Xuefei

    2015-04-09

    The catalytic reduction of nitrate is a promising technology for groundwater purification because it transforms nitrate into nitrogen and water. Recent studies have mainly focused on new catalysts with higher activities for the reduction of nitrate. Consequently, metal nanoparticles supported on mesoporous metal oxides have become a major research direction. However, the complex surface chemistry and porous structures of mesoporous metal oxides lead to a non-uniform distribution of metal nanoparticles, thereby resulting in a low catalytic efficiency. In this paper, a method for synthesizing the sustainable nitrate reduction catalyst Pd-In/Al2O3 with a dimensional structure is introduced. The TEM results indicated that Pd and In nanoparticles could efficiently disperse into the mesopores of the alumina. At room temperature in CO2-buffered water and under continuous H2 as the electron donor, the synthesized material (4.9 wt% Pd) was the most active at a Pd-In ratio of 4, with a first-order rate constant (k(obs) = 0.241 L min(-1) g(cata)(-1)) that was 1.3× higher than that of conventional Pd-In/Al2O3 (5 wt% Pd; 0.19 L min(-1) g(cata)(-1)). The Pd-In/mesoporous alumina is a promising catalyst for improving the catalytic reduction of nitrate. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Solid state synthesis, characterization, surface and catalytic properties of Pr2CoO4 and Pr2NiO4 catalyst

    International Nuclear Information System (INIS)

    Sinha, K.K.; Indu, N.K.; Sinha, S.K.; Pankaj, A.K.

    2008-01-01

    Full text: The most interesting non-stoichiometric oxides are found in transition metal and rare earth oxides at higher temperatures. The role of Solid State properties in the catalysis using mixed metal oxide as catalyst have wide applications in fertilizer, Petro-chemical, Pharmaceutical, cosmetic, paint detergents, plastics and food-stuff industries and these are also resistive towards acids and alkalies. The use of catalyst has opened up new process routes or revolutioned the existing process in terms of economics and efficiency and has radically changed the industrial scenario. The use of catalyst is so pervasive today that nearly 70 % of modern chemical processes are based on it at some stage or other and 90% new processes developed are catalytic nature. A series of non-stoichiometric spinel type of oxide catalyst of Praseodymium with cobalt and nickel were synthesized by their oxalates through Solid State reaction technique at different activation temperatures i.e. 600, 700, 800 and 900 deg C. The characterization of catalyst was done by XRD, FTIR and ESR methods. X-ray powder diffraction study shows that catalysts are made up of well grown crystallinities mostly in single phase crystal and system is of orthorhombic structure. FTIR is related to inadequate decomposition of oxalate ion from the Catalyst. The kinetic decomposition of Urea was employed as a model reaction to study the catalytic potentiality of different catalysts. Surface and Catalytic Properties of catalysts were measured. A relation between activation temperature and surface properties like excess surface oxygen (E.S.O.), surface acidity and surface area was observed. A linear relationship between the surface area of the catalyst and the amount of ammonia gas evolved per gm of the sample was observed also. Nickel containing catalysts were found a bit more catalytic active in comparison to cobalt oxide catalysts. Transition metal ions (i.e. Ni 2+ and Co 2+ ions) are mainly responsible for

  13. High performance and durability of order-structured cathode catalyst layer based on TiO_2@PANI core-shell nanowire arrays

    International Nuclear Information System (INIS)

    Chen, Ming; Wang, Meng; Yang, Zhaoyi; Wang, Xindong

    2017-01-01

    Highlights: • TiO_2@PANI core-shell nanowire arrays were prepared and applied as catalyst support. • As-prepared Pt-TiO_2@PANI core-shell nanowire arrays were applied as order-structured cathode catalyst layer. • The novel cathode catalyst structure without Nafion"® ionomer enhance the performance and durability of PEMFC. - Abstract: In this paper, an order-structured cathode catalyst layer consisting of Pt-TiO_2@PANI core-shell nanowire arrays that in situ grown on commercial gas diffusion layer (GDL) are prepared and applied to membrane electrode assembly (MEA) of proton exchange membrane fuel cell (PEMFC). In order to prepare the TiO_2@PANI core-shell nanowire arrays with suitable porosity and prominent conductivity, the morphologies of the TiO_2 nanoarray and electrochemical polymerization process of aniline are schematically investigated. The MEA with order-structured cathode catalyst layer is assembled in the single cell to evaluate the electrochemical performance and durability of PEMFC. As a result, the PEMFC with order-structured cathode catalyst layer shows higher peak power density (773.54 mW cm"−"2) than conventional PEMFC (699.30 mW cm"−"2). Electrochemically active surface area (ECSA) and charge transfer impedance (R_c_t) are measured before and after accelerated degradation test (ADT), and the corresponding experimental results indicate the novel cathode structure exhibits a better stability with respect to conventional cathode. The enhanced electrochemical performance and durability toward PEMFC can be ascribed to the order-structured cathode nanoarray structure with high specific surface area increases the utilization of catalyst and reduces the tortuosity of transport pathways, and the synergistic effect between TiO_2@PANI support and Pt nanoparticles promotes the high efficiency of electrochemical reaction and improves the stability of catalyst. This research provides a facile and controllable method to prepare order

  14. High performance and durability of order-structured cathode catalyst layer based on TiO{sub 2}@PANI core-shell nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ming; Wang, Meng; Yang, Zhaoyi [State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China); School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China); Wang, Xindong, E-mail: echem@ustb.edu.cn [State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China); School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China)

    2017-06-01

    Highlights: • TiO{sub 2}@PANI core-shell nanowire arrays were prepared and applied as catalyst support. • As-prepared Pt-TiO{sub 2}@PANI core-shell nanowire arrays were applied as order-structured cathode catalyst layer. • The novel cathode catalyst structure without Nafion{sup ®} ionomer enhance the performance and durability of PEMFC. - Abstract: In this paper, an order-structured cathode catalyst layer consisting of Pt-TiO{sub 2}@PANI core-shell nanowire arrays that in situ grown on commercial gas diffusion layer (GDL) are prepared and applied to membrane electrode assembly (MEA) of proton exchange membrane fuel cell (PEMFC). In order to prepare the TiO{sub 2}@PANI core-shell nanowire arrays with suitable porosity and prominent conductivity, the morphologies of the TiO{sub 2} nanoarray and electrochemical polymerization process of aniline are schematically investigated. The MEA with order-structured cathode catalyst layer is assembled in the single cell to evaluate the electrochemical performance and durability of PEMFC. As a result, the PEMFC with order-structured cathode catalyst layer shows higher peak power density (773.54 mW cm{sup −2}) than conventional PEMFC (699.30 mW cm{sup −2}). Electrochemically active surface area (ECSA) and charge transfer impedance (R{sub ct}) are measured before and after accelerated degradation test (ADT), and the corresponding experimental results indicate the novel cathode structure exhibits a better stability with respect to conventional cathode. The enhanced electrochemical performance and durability toward PEMFC can be ascribed to the order-structured cathode nanoarray structure with high specific surface area increases the utilization of catalyst and reduces the tortuosity of transport pathways, and the synergistic effect between TiO{sub 2}@PANI support and Pt nanoparticles promotes the high efficiency of electrochemical reaction and improves the stability of catalyst. This research provides a facile and

  15. Adsorption of cadmium ions on nickel surface skeleton catalysts and its effect on reaction of cathodic hydrogen evolution

    International Nuclear Information System (INIS)

    Korovin, N.V.; Udris, E.Ya.; Savel'eva, O.N.

    1986-01-01

    Cadmium adsorption from different concentration CdSO 4 solutions on nickel surface skeleton catalysts (Ni ssc ) is studied by recording of polarization and potentiodynamic curves using electron microscopy and X-ray spectrometry. Main regularities of cadmium adsorption on Ni ssc are shown to be similar to those on smooth and skeleton nickel. A conclusion is drawn that increase of catalytic activity in reaction of cathodic hydrogen evolution from alkali solutions of Ni ssc base electrodes after their treatment in solutions containing Cd 2+ ions is due to irreversible desorption of strongly and averagely bound hydrogen from electrode surface at cadmium adsorption on them

  16. High yield growth of patterned vertically aligned carbon nanotubes using inkjet-printed catalyst.

    Science.gov (United States)

    Beard, James D; Stringer, Jonathan; Ghita, Oana R; Smith, Patrick J

    2013-10-09

    This study reports on the fabrication of vertically aligned carbon nanotubes localized at specific sites on a growth substrate by deposition of a nanoparticle suspension using inkjet printing. Carbon nanotubes were grown with high yield as vertically aligned forests to a length of approximately 400 μm. The use of inkjet printing for catalyst fabrication considerably improves the production rate of vertically aligned patterned nanotube forests compared with conventional patterning techniques, for example, electron beam lithography or photolithography.

  17. Immobilization of molecular catalysts in supported ionic liquid phases.

    Science.gov (United States)

    Van Doorslaer, Charlie; Wahlen, Joos; Mertens, Pascal; Binnemans, Koen; De Vos, Dirk

    2010-09-28

    In a supported ionic liquid phase (SILP) catalyst system, an ionic liquid (IL) film is immobilized on a high-surface area porous solid and a homogeneous catalyst is dissolved in this supported IL layer, thereby combining the attractive features of homogeneous catalysts with the benefits of heterogeneous catalysts. In this review reliable strategies for the immobilization of molecular catalysts in SILPs are surveyed. In the first part, general aspects concerning the application of SILP catalysts are presented, focusing on the type of catalyst, support, ionic liquid and reaction conditions. Secondly, organic reactions in which SILP technology is applied to improve the performance of homogeneous transition-metal catalysts are presented: hydroformylation, metathesis reactions, carbonylation, hydrogenation, hydroamination, coupling reactions and asymmetric reactions.

  18. Characterizing interstate vibrational coherent dynamics of surface adsorbed catalysts by fourth-order 3D SFG spectroscopy

    Science.gov (United States)

    Li, Yingmin; Wang, Jiaxi; Clark, Melissa L.; Kubiak, Clifford P.; Xiong, Wei

    2016-04-01

    We report the first fourth-order 3D SFG spectroscopy of a monolayer of the catalyst Re(diCN-bpy)(CO)3Cl on a gold surface. Besides measuring the vibrational coherences of single vibrational modes, the fourth-order 3D SFG spectrum also measures the dynamics of interstate coherences and vibrational coherences states between two vibrational modes. By comparing the 3D SFG to the corresponding 2D and third-order 3D IR spectroscopy of the same molecules in solution, we found that the interstate coherences exist in both liquid and surface systems, suggesting that the interstate coherence is not disrupted by surface interactions. However, by analyzing the 3D spectral lineshape, we found that the interstate coherences also experience non-negligible homogenous dephasing dynamics that originate from surface interactions. This unique ability of determining interstate vibrational coherence dynamics of the molecular monolayer can help in understanding of how energy flows within surface catalysts and other molecular monolayers.

  19. Gram-Scale Synthesis of Highly Active and Durable Octahedral PtNi Nanoparticle Catalysts for Proton Exchange Membrane Fuel Cell

    DEFF Research Database (Denmark)

    Choi, Juhyuk; Jang, Jue-Hyuk; Roh, Chi-Woo

    2018-01-01

    for the commercialization of PEMFCs. In this study, we focus on gram-scale synthesis of octahedral PtNi nanoparticles with Pt overlayers (PtNi@Pt) supported on the carbon, resulting in enhanced catalytic activity and durability. Such PtNi@Pt catalysts show high mass activity (1.24 A mgPt−1) at 0.9 V (vs RHE) for the ORR......Proton exchange membrane fuel cells (PEMFC) are regarded as a promising renewable energy source for a future hydrogen energy society. However, highly active and durable catalysts are required for the PEMFCs because of their intrinsic high overpotential at the cathode and operation under the acidic...... condition for oxygen reduction reaction (ORR). Since the discovery of the exceptionally high surface activity of Pt3Ni(111), the octahedral PtNi nanoparticles have been synthesized and tested. Nonetheless, their milligram-scale synthesis method and poor durability make them unsuitable...

  20. Non-Fermi Liquids as Highly Active Oxygen Evolution Reaction Catalysts.

    Science.gov (United States)

    Hirai, Shigeto; Yagi, Shunsuke; Chen, Wei-Tin; Chou, Fang-Cheng; Okazaki, Noriyasu; Ohno, Tomoya; Suzuki, Hisao; Matsuda, Takeshi

    2017-10-01

    The oxygen evolution reaction (OER) plays a key role in emerging energy conversion technologies such as rechargeable metal-air batteries, and direct solar water splitting. Herein, a remarkably low overpotential of ≈150 mV at 10 mA cm -2 disk in alkaline solutions using one of the non-Fermi liquids, Hg 2 Ru 2 O 7 , is reported. Hg 2 Ru 2 O 7 displays a rapid increase in current density and excellent durability as an OER catalyst. This outstanding catalytic performance is realized through the coexistence of localized d-bands with the metallic state that is unique to non-Fermi liquids. The findings indicate that non-Fermi liquids could greatly improve the design of highly active OER catalysts.

  1. Dry re-forming of methane to synthesis gas over lignite semicokes catalyst at high pressure

    Directory of Open Access Journals (Sweden)

    Fengbo Guo

    2016-11-01

    Full Text Available Dry re-forming of methane has been carried out in a high temperature–pressure reactor at different pressures, using Hongce lignite semicokes catalyst. The results show that CH4 and CO2 conversions are decreased as the reaction pressure increased, but both of them kept basically stable when the reaction pressure is between 0.3 and 1 MPa. The comparison shows that the effects of the temperature and the flow of reactant gas on dry re-forming of methane are consistent with between high pressure and atmospheric pressure. The ratio of CO/H2 decreased as the ratio of CH4/CO2 increased, yet the value of CO/H2 is always more than 1 at different pressures. Hongce lignite semicokes catalyst is characterized by FTIR, XRD, SEM and BET, and the analysis results reveled that the physical specific adsorption peak of CO2 at 2350 cm−1 is strengthened significantly at different pressures, the micropore area and volume of Hongce lignite semicokes reduced form 40.2 m2  g−1 and 0.019 cm3  g−1 to 34.9 m2  g−1 and 0.017 cm3  g−1, respectively. Hongce lignite semicokes catalyst exhibited better activity and stability within 0.3–1 MPa range.

  2. Effect of Chlorine precursor in surface and cataytic properties of Fe/TiO2 Catalysts

    OpenAIRE

    López, Tessi; Pecchi, Gina; Moreno, Abel; García Fierro, José Luis; Gómez, R.; Reyes, P.

    2002-01-01

    Titania-supported iron (1wt%) catalysts were prepared by the sol-gel method using different gelation pH (3 and 9), metal precursors (FeCl2 and FeCl3) and calcination temperatures (873 and 1073K). Characterization data of calcined catalysts revealed that in all samples the dominant iron species is Fe3+ and the crystalline phase of the TiO2 substrate depends on the gelation pH and the metal precursor used. It was found that in the Fe/TiO2 ex-FeCl3 samples an important part of the iron ions beca...

  3. The effects of rare earths on activity and surface properties of Ru/γ-Al2O3 catalyst for water gas shift reaction

    Directory of Open Access Journals (Sweden)

    Laitao Luo

    2007-04-01

    Full Text Available A series of Ru-RE/γ- Al2O3 (RE = Ce, Pr, La, Sm, Tb or Gd and Ru/γ- Al2O3 catalysts were prepared by impregnation method. The influence of rare earths on the catalytic performance of Ru/γ- Al2O3 catalyst for the water gas shift reaction was studied. The catalysts were characterized by X-ray diffraction (XRD, temperature programmed reduction (TPR, temperature programmed desorption (TPD, and CO chemisorption. The results show that the addition of rare earths increases the catalytic activity of Ru based catalyst. Among these cerium is the most remarkably. The addition of cerium increases the active surface area, improves the dispersion of ruthenium, and weakens the interaction between ruthenium and the support. Cerium also affects the adsorption and reduction properties of Ru/γ-Al2O3 catalyst.

  4. Manufacture of highly loaded silica-supported cobalt Fischer–Tropsch catalysts from a metal organic framework

    KAUST Repository

    Sun, Xiaohui; Suarez, Alma I. Olivos; Meijerink, Mark; van Deelen, Tom; Ould-Chikh, Samy; Zečević, Jovana; de Jong, Krijn P.; Kapteijn, Freek; Gascon, Jorge

    2017-01-01

    The development of synthetic protocols for the preparation of highly loaded metal nanoparticle-supported catalysts has received a great deal of attention over the last few decades. Independently controlling metal loading, nanoparticle size

  5. Electrochemical dopamine sensor based on P-doped graphene: Highly active metal-free catalyst and metal catalyst support.

    Science.gov (United States)

    Chu, Ke; Wang, Fan; Zhao, Xiao-Lin; Wang, Xin-Wei; Tian, Ye

    2017-12-01

    Heteroatom doping is an effective strategy to enhance the catalytic activity of graphene and its hybrid materials. Despite a growing interest of P-doped graphene (P-G) in energy storage/generation applications, P-G has rarely been investigated for electrochemical sensing. Herein, we reported the employment of P-G as both metal-free catalyst and metal catalyst support for electrochemical detection of dopamine (DA). As a metal-free catalyst, P-G exhibited prominent DA sensing performances due to the important role of P doping in improving the electrocatalytic activity of graphene toward DA oxidation. Furthermore, P-G could be an efficient supporting material for loading Au nanoparticles, and resulting Au/P-G hybrid showed a dramatically enhanced electrocatalytic activity and extraordinary sensing performances with a wide linear range of 0.1-180μM and a low detection limit of 0.002μM. All these results demonstrated that P-G might be a very promising electrode material for electrochemical sensor applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Synthesis of carbonate esters by carboxymethylation using NaAlO2 as a highly active heterogeneous catalyst

    OpenAIRE

    Ramesh, Sreerangappa; Indukuri, Kiran; Riant, Olivier; Debecker, Damien

    2018-01-01

    Sodium aluminate is presented as a highly active heterogeneous catalyst able to convert a range of alcohols into the corresponding mixed carbonate esters, in high yield and under green conditions. The reaction is carried out using dimethyl carbonate both as a reactant and solvent, at 90°C. Allylic, aliphatic and aromatic alcohols are converted in good yields. The solid catalyst is shown to be truly heterogeneous, resistant to leaching, and recyclable.

  7. Pyrolysis-catalysis of waste plastic using a nickel-stainless-steel mesh catalyst for high-value carbon products.

    Science.gov (United States)

    Zhang, Yeshui; Nahil, Mohamad A; Wu, Chunfei; Williams, Paul T

    2017-11-01

    A stainless-steel mesh loaded with nickel catalyst was produced and used for the pyrolysis-catalysis of waste high-density polyethylene with the aim of producing high-value carbon products, including carbon nanotubes (CNTs). The catalysis temperature and plastic-to-catalyst ratio were investigated to determine the influence on the formation of different types of carbon deposited on the nickel-stainless-steel mesh catalyst. Increasing temperature from 700 to 900°C resulted in an increase in the carbon deposited on the nickel-loaded stainless-steel mesh catalyst from 32.5 to 38.0 wt%. The increase in sample-to-catalyst ratio reduced the amount of carbon deposited on the mesh catalyst in terms of g carbon g -1 plastic. The carbons were found to be largely composed of filamentous carbons, with negligible disordered (amorphous) carbons. Transmission electron microscopy analysis of the filamentous carbons revealed them to be composed of a large proportion (estimated at ∼40%) multi-walled carbon nanotubes (MWCNTs). The optimum process conditions for CNT production, in terms of yield and graphitic nature, determined by Raman spectroscopy, was catalysis temperature of 800°C and plastic-to-catalyst ratio of 1:2, where a mass of 334 mg of filamentous/MWCNTs g -1 plastic was produced.

  8. On the Role of Surface Modifications of Palladium Catalysts in the Selective Hydrogenation of Acetylene

    DEFF Research Database (Denmark)

    Studt, Felix; Abild-Pedersen, Frank; Bligaard, Thomas

    2008-01-01

    Summing Me up: DFT calculations have shown that alloying, subsurface carbon, and hydride formation, all increase the selectivity of Pd catalysts for acetylene hydrogenation by weakening the surface–adsorbate bond. A simple descriptor—the adsorption energy of a methyl group—has been used to quanti...

  9. Optimization of process parameters and catalyst compositions in carbon dioxide oxidative coupling of methane over CaO-MnO/CeO{sub 2} catalyst using response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Istadi,; Amin, Nor Aishah Saidina [Chemical Reaction Engineering Group (CREG), Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, UTM Skudai, Johor Bahru (81310 Malaysia)

    2006-05-15

    The optimization of process parameters and catalyst compositions for the CO{sub 2} oxidative coupling of methane (CO{sub 2}-OCM) reaction over CaO-MnO/CeO{sub 2} catalyst was developed using Response Surface Methodology (RSM). The relationship between the responses, i.e. CH{sub 4} conversion, C{sub 2} hydrocarbons selectivity or yield, with four independent variables, i.e. CO{sub 2}/CH{sub 4} ratio, reactor temperature, wt.% CaO and wt.% MnO in the catalyst, were presented as empirical mathematical models. The maximum C{sub 2} hydrocarbons selectivity and yields of 82.62% and 3.93%, respectively, were achieved by the individual-response optimization at the corresponding optimal process parameters and catalyst compositions. However, the CH{sub 4} conversion was a saddle function and did not show a unique optimum as revealed by the canonical analysis. Moreover pertaining to simultaneous multi-responses optimization, the maximum C{sub 2} selectivity and yield of 76.56% and 3.74%, respectively, were obtained at a unique optimal process parameters and catalyst compositions. It may be deduced that both individual- and multi-responses optimizations are useful for the recommendation of optimal process parameters and catalyst compositions for the CO{sub 2}-OCM process. (author)

  10. High-throughput reactor system with individual temperature control for the investigation of monolith catalysts

    Science.gov (United States)

    Dellamorte, Joseph C.; Vijay, Rohit; Snively, Christopher M.; Barteau, Mark A.; Lauterbach, Jochen

    2007-07-01

    A high-throughput parallel reactor system has been designed and constructed to improve the reliability of results from large diameter catalysts such as monoliths. The system, which is expandable, consists of eight quartz reactors, 23.5mm in diameter. The eight reactors were designed with separate K type thermocouples and radiant heaters, allowing for the independent measurement and control of each reactor temperature. This design gives steady state temperature distributions over the eight reactors within 0.5°C of a common setpoint from 50to700°C. Analysis of the effluent from these reactors is performed using rapid-scan Fourier transform infrared (FTIR) spectroscopic imaging. The integration of this technique to the reactor system allows a chemically specific, truly parallel analysis of the reactor effluents with a time resolution of approximately 8s. The capabilities of this system were demonstrated via investigation of catalyst preparation conditions on the direct epoxidation of ethylene, i.e., on the ethylene conversion and the ethylene oxide selectivity. The ethylene, ethylene oxide, and carbon dioxide concentrations were calibrated based on spectra from FTIR imaging using univariate and multivariate chemometric techniques. The results from this analysis showed that the calcination conditions significantly affect the ethylene conversion, with a threefold increase in the conversion when the catalyst was calcined for 3h versus 12h at 400°C.

  11. Cross-linked lysozyme crystal templated synthesis of Au nanoparticles as high-performance recyclable catalysts

    International Nuclear Information System (INIS)

    Liang Miao; Liu Xia; Qi Wei; Su Rongxin; Huang Renliang; Yu Yanjun; He Zhimin; Wang Libing

    2013-01-01

    Bio-nanomaterials fabricated using a bioinspired templating technique represent a novel class of composite materials with diverse applications in biomedical, electronic devices, drug delivery, and catalysis. In this study, Au nanoparticles (NPs) are synthesized within the solvent channels of cross-linked lysozyme crystals (CLLCs) in situ without the introduction of extra chemical reagents or physical treatments. The as-prepared AuNPs-in-protein crystal hybrid materials are characterized by light microscopy, transmission electron microscopy, x-ray diffraction, and Fourier-transform infrared spectroscopy analyses. Small AuNPs with narrow size distribution reveal the restriction effects of the porous structure in the lysozyme crystals. These composite materials are proven to be active heterogeneous catalysts for the reduction of 4-nitrophenol to 4-aminophenol. These catalysts can be easily recovered and reused at least 20 times because of the physical stability and macro-dimension of CLLCs. This work is the first to use CLLCs as a solid biotemplate for the preparation of recyclable high-performance catalysts. (paper)

  12. Hollow Ag-Pd core–shell nanotubes as highly active catalysts for the electro-oxidation of formic acid

    International Nuclear Information System (INIS)

    Jiang Yuanyuan; Lu Yizhong; Han Dongxue; Zhang Qixian; Niu Li

    2012-01-01

    Ag nanowires are prepared as templates by a polyol reduction process. Then Ag nanotubes coated with a thin layer of Pd are synthesized through sequential reduction accompanied with the galvanic displacement reaction. The products show a hollow core–shell nanotubular structure, as demonstrated by detailed characterizations. The Ag-Pd can significantly improve the electrocatalytic activity towards the electro-oxidation of formic acid and enhance the stability of the Pd component. It is proposed that the enhanced electrochemically active surface area and modulated electron structure of Pd by Ag are responsible for the improvement of electrocatalytic activity and durability. The results obtained in this work are different from those previous reports, in which alloy walls with hollow interiors are usually formed. This work provides a new and simple method for synthesizing novel bimetallic core–shell structure with a hollow interior, which can be applied as high-performance catalysts for the electro-oxidation of formic acid. (paper)

  13. Highly sensitive hydrogen detection of catalyst-free ZnO nanorod networks suspended by lithography-assisted growth

    International Nuclear Information System (INIS)

    Huh, Junghwan; Kim, Gyu Tae; Park, Jonghyurk; Park, Jeong Young

    2011-01-01

    We have successfully demonstrated a ZnO nanorod-based 3D nanostructure to show a high sensitivity and very fast response/recovery to hydrogen gas. ZnO nanorods have been synthesized selectively over the pre-defined area at relatively low temperature using a simple self-catalytic solution process assisted by a lithographic method. The conductance of the ZnO nanorod device varies significantly as the concentration of the hydrogen is changed without any additive metal catalyst, revealing a high sensitivity to hydrogen gas. Its superior performance can be explained by the porous structure of its three-dimensional network and the enhanced surface reaction of the hydrogen molecules with the oxygen defects resulting from a high surface-to-volume ratio. It was found that the change of conductance follows a power law depending on the hydrogen concentration. A Langmuir isotherm following an ideal power law and a cross-over behavior of the activation energy with respect to hydrogen concentration were observed. This is a very novel and intriguing phenomenon on nanostructured materials, which suggests competitive surface reactions in ZnO nanorod gas sensors.

  14. Highly sensitive hydrogen detection of catalyst-free ZnO nanorod networks suspended by lithography-assisted growth.

    Science.gov (United States)

    Huh, Junghwan; Park, Jonghyurk; Kim, Gyu Tae; Park, Jeong Young

    2011-02-25

    We have successfully demonstrated a ZnO nanorod-based 3D nanostructure to show a high sensitivity and very fast response/recovery to hydrogen gas. ZnO nanorods have been synthesized selectively over the pre-defined area at relatively low temperature using a simple self-catalytic solution process assisted by a lithographic method. The conductance of the ZnO nanorod device varies significantly as the concentration of the hydrogen is changed without any additive metal catalyst, revealing a high sensitivity to hydrogen gas. Its superior performance can be explained by the porous structure of its three-dimensional network and the enhanced surface reaction of the hydrogen molecules with the oxygen defects resulting from a high surface-to-volume ratio. It was found that the change of conductance follows a power law depending on the hydrogen concentration. A Langmuir isotherm following an ideal power law and a cross-over behavior of the activation energy with respect to hydrogen concentration were observed. This is a very novel and intriguing phenomenon on nanostructured materials, which suggests competitive surface reactions in ZnO nanorod gas sensors.

  15. Tin-containing zeolites are highly active catalysts for the isomerization of glucose in water

    OpenAIRE

    Moliner, Manuel; Román-Leshkov, Yuriy; Davis, Mark E.

    2010-01-01

    The isomerization of glucose into fructose is a large-scale reaction for the production of high-fructose corn syrup (HFCS; reaction performed by enzyme catalysts) and recently is being considered as an intermediate step in the possible route of biomass to fuels and chemicals. Here, it is shown that a large-pore zeolite that contains tin (Sn-Beta) is able to isomerize glucose to fructose in aqueous media with high activity and selectivity. Specifically, a 10% (wt/wt) glucose solution containin...

  16. Hydrodeoxygenation of water-insoluble bio-oil to alkanes using a highly dispersed Pd-Mo catalyst.

    Science.gov (United States)

    Duan, Haohong; Dong, Juncai; Gu, Xianrui; Peng, Yung-Kang; Chen, Wenxing; Issariyakul, Titipong; Myers, William K; Li, Meng-Jung; Yi, Ni; Kilpatrick, Alexander F R; Wang, Yu; Zheng, Xusheng; Ji, Shufang; Wang, Qian; Feng, Junting; Chen, Dongliang; Li, Yadong; Buffet, Jean-Charles; Liu, Haichao; Tsang, Shik Chi Edman; O'Hare, Dermot

    2017-09-19

    Bio-oil, produced by the destructive distillation of cheap and renewable lignocellulosic biomass, contains high energy density oligomers in the water-insoluble fraction that can be utilized for diesel and valuable fine chemicals productions. Here, we show an efficient hydrodeoxygenation catalyst that combines highly dispersed palladium and ultrafine molybdenum phosphate nanoparticles on silica. Using phenol as a model substrate this catalyst is 100% effective and 97.5% selective for hydrodeoxygenation to cyclohexane under mild conditions in a batch reaction; this catalyst also demonstrates regeneration ability in long-term continuous flow tests. Detailed investigations into the nature of the catalyst show that it combines hydrogenation activity of Pd and high density of both Brønsted and Lewis acid sites; we believe these are key features for efficient catalytic hydrodeoxygenation behavior. Using a wood and bark-derived feedstock, this catalyst performs hydrodeoxygenation of lignin, cellulose, and hemicellulose-derived oligomers into liquid alkanes with high efficiency and yield.Bio-oil is a potential major source of renewable fuels and chemicals. Here, the authors report a palladium-molybdenum mixed catalyst for the selective hydrodeoxygenation of water-insoluble bio-oil to mixtures of alkanes with high carbon yield.

  17. Pd nanoparticles supported on three-dimensional graphene aerogels as highly efficient catalysts for methanol electrooxidation

    International Nuclear Information System (INIS)

    Liu, Mingrui; Peng, Cheng; Yang, Wenke; Guo, Jiaojiao; Zheng, Yixiong; Chen, Peiqin; Huang, Tingting; Xu, Jing

    2015-01-01

    Well-dispersed Pd nanoparticles supported on three-dimensional graphene aerogels (Pd/3DGA) were successfully prepared via a facile and efficient hydrothermal method without surfactant and template. The morphology and structure of the as-prepared Pd/3DGA nanocomposites were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM showed that the Pd nanoparticles with a small average diameter and narrow size distribution were uniformly deposited on the surface of the self-assembled three-dimensional graphene aerogels. Raman spectra revealed the surface properties of 3DGA and its interaction with metallic nanoparticles. Cyclic voltammetric (CV) and chronoamperometric (CA) experiments further exhibited its superior catalytic activity and stability for the electro-oxidation of methanol in alkaline media, making it a promising anodic catalyst for direct alkaline alcohol fuel cells (DAAFCs).

  18. X-Ray photoelectron spectroscopy and diffractometry of MnOx catalysts: surface to bulk composition relationships

    International Nuclear Information System (INIS)

    Zaki, M.I.; Kappenstein, C.

    1992-01-01

    Surface and bulk analyses of variously-composed, synthetic MnO x catalysts were carried out by means of X-ray photoelectron spectroscopy (XPS) and diffractometry (XRD), respectively. The data obtained were processed for a comprehensive assessment of bulk and surface compositions, surface oxidation state, and crystalline size. The XPS data processing revealed that a credible assessment of the surface composition (MnO x (OH) y (OH 2 ) z necessitates: (i) the implementation of experimental sensitivity factors determined on a local reference surface maintaining a close chemical similarity to the test materials, and (ii) the fine evaluation of contributions of various oxygen-containing surface species to the O 1s electron emission. The most prominent result of the present investigation is that the exposure of the bulk composition at the surface is quite proportioned. Such a surface to bulk intimacy is thought to enable genesizing the surface composition appropriate for certain catalytic and selectivity, via a possible control over the bulk formation events. (orig.)

  19. Highly Dispersed Pseudo-Homogeneous and Heterogeneous Catalysts Synthesized via Inverse Micelle Solutions for the Liquefaction of Coal

    Energy Technology Data Exchange (ETDEWEB)

    Hampden-Smith, M.; Kawola, J.S.; Martino, A.; Sault, A.G.; Yamanaka, S.A.

    1999-01-05

    The mission of this project was to use inverse micelle solutions to synthesize nanometer sized metal particles and test the particles as catalysts in the liquefaction of coal and other related reactions. The initial focus of the project was the synthesis of iron based materials in pseudo-homogeneous form. The frost three chapters discuss the synthesis, characterization, and catalyst testing in coal liquefaction and model coal liquefaction reactions of iron based pseudo-homogeneous materials. Later, we became interested in highly dispersed catalysts for coprocessing of coal and plastic waste. Bifunctional catalysts . to hydrogenate the coal and depolymerize the plastic waste are ideal. We began studying, based on our previously devised synthesis strategies, the synthesis of heterogeneous catalysts with a bifunctional nature. In chapter 4, we discuss the fundamental principles in heterogeneous catalysis synthesis with inverse micelle solutions. In chapter 5, we extend the synthesis of chapter 4 to practical systems and use the materials in catalyst testing. Finally in chapter 6, we return to iron and coal liquefaction now studied with the heterogeneous catalysts.

  20. High utilization platinum deposition on single-walled carbon nanotubes as catalysts for direct methanol fuel cell

    International Nuclear Information System (INIS)

    Wang, J.J.; Yin, G.P.; Zhang, J.; Wang, Z.B.; Gao, Y.Z.

    2007-01-01

    This research aims to enhance the activity of Pt catalysts, thus to lower the loading of Pt metal in fuel cell. Highly dispersed platinum supported on single-walled carbon nanotubes (SWNTs) as catalyst was prepared by ion exchange method. The homemade Pt/SWNTs underwent a repetition of ion exchange and reduction process in order to achieve an increase of the metal loading. For comparison, the similar loading of Pt catalyst supported on carbon nanotubes was prepared by borohydride reduction method. The catalysts were characterized by using energy dispersive analysis of X-ray (EDAX), transmission electron micrograph (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrum (XPS). Compared with the Pt/SWNTs catalyst prepared by borohydride method, higher Pt utilization was achieved on the SWNTs by ion exchange method. Furthermore, in comparison to the E-TEK 20 wt.% Pt/C catalyst with the support of carbon black, the results from electrochemical measurement indicated that the Pt/SWNTs prepared by ion exchange method displayed a higher catalytic activity for methanol oxidation and higher Pt utilization, while no significant increasing in the catalytic activity of the Pt/SWNTs catalyst obtained by borohydride method

  1. Selective hydrodechlorination of 1,2-dichloroethane to ethylene over Pd-Ag/Al_2O_3 catalysts prepared by surface reduction

    International Nuclear Information System (INIS)

    Han, Yuxiang; Gu, Guangfeng; Sun, Jingya; Wang, Wenjuan; Wan, Haiqin; Xu, Zhaoyi; Zheng, Shourong

    2015-01-01

    Graphical abstract: - Highlights: • Surface reduction method was used for preparation of Pd-Ag(Cu) bimetallic catalysts. • Hydrodechlorination of 1,2-dichloroethane was investigated for production of ethylene. • Ag(Cu) selectively deposited on Pd surface during surface reduction process. • Ethylene selectivity was enhanced over Pd-Ag(Cu)/Al_2O_3 catalyst prepared by surface reduction. • Isolated Pd site is the key species for ethylene selectivity. - Abstract: Alumina supported Pd-Ag and (Cu) bimetallic catalysts (denoted as sr-Pd-Ag/Al_2O_3 or sr-Pd-Cu/Al_2O_3) with varied Pd/Ag (or Cu) ratios were prepared using the surface reduction method, and the gas-phase catalytic hydrodechlorination of 1,2-dichloroethane over the catalysts were investigated. For comparison, Pd-Ag bimetallic catalysts were prepared by the conventional co-impregnation method (denoted as im-Pd-Ag/Al_2O_3). The catalysts were characterized by N_2 adsorption, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and CO chemisorption. Characterization results indicated that surface reduction led to selective deposition of metallic Ag on the surface of Pd particles, while Pd and Ag just disorderly mixed in the catalyst prepared by impregnation method. Therefore, sr-Pd-Ag/Al_2O_3 exhibited a higher ethylene selectivity than im-Pd-Ag/Al_2O_3 for hydrodechlorination of 1,2-dichloroethane at a similar Ag loading amount. Moreover, among sr-Pd-Ag/Al_2O_3, sr-Pd-Cu/Al_2O_3 and im-Pd-Ag/Al_2O_3 catalysts, the ethylene selectivity decreased over these catalysts following the order: sr-Pd-Ag/Al_2O_3 > sr-Pd-Cu/Al_2O_3 > im-Pd-Ag/Al_2O_3. The present results indicate that surface reduction can be used as a potential method to synthesize catalyst with enhanced ethylene selectivity in hydrodechlorination of 1,2-dichloroethane.

  2. Design of heterogeneous catalysts

    DEFF Research Database (Denmark)

    Frey, Anne Mette

    was inspired by a computational screening, suggesting that alloys such as Ni-Fe, Co-Ni, and Co-Fe should show superior activity to the industrially used nickel catalyst. Especially the Ni-Fe system was considered to be interesting, since such alloy catalysts should be both more active and cheaper than the Ni...... catalyst. The results from the screening were experimentally verified for CO hydrogenation, CO2 hydrogenation, and simultaneous CO and CO2 hydrogenation by bimetallic Ni-Fe catalysts. These catalysts were found to be highly active and selective. The Co-Ni and Co-Fe systems were investigated for CO...... well, and the best catalyst prepared had a C5+ yield almost a factor of two higher than a standard air calcined Co catalyst. In the NH3-SCR reaction it is desirable to develop an active and stable catalyst for NOx removal in automotive applications, since the traditionally used vanadium-based catalyst...

  3. High-Throughput Screening of Heterogeneous Catalysts for the Conversion of Furfural to Bio-Based Fuel Components

    Directory of Open Access Journals (Sweden)

    Roberto Pizzi

    2015-12-01

    Full Text Available The one-pot catalytic reductive etherification of furfural to 2-methoxymethylfuran (furfuryl methyl ether, FME, a valuable bio-based chemical or fuel, is reported. A large number of commercially available hydrogenation heterogeneous catalysts based on nickel, copper, cobalt, iridium, palladium and platinum catalysts on various support were evaluated by a high-throughput screening approach. The reaction was carried out in liquid phase with a 10% w/w furfural in methanol solution at 50 bar of hydrogen. Among all the samples tested, carbon-supported noble metal catalysts were found to be the most promising in terms of productivity and selectivity. In particular, palladium on charcoal catalysts show high selectivity (up to 77% to FME. Significant amounts of furfuryl alcohol (FA and 2-methylfuran (2-MF are observed as the major by-products.

  4. Facile and Low-Cost Preparation of Nb/Al Oxide Catalyst with High Performance for the Conversion of Kiwifruit Waste Residue to Levulinic Acid

    Directory of Open Access Journals (Sweden)

    Rui Wang

    2015-09-01

    Full Text Available The kiwifruit industry is booming worldwide. As a result, a great deal of kiwifruit waste residue (KWR containing monosaccharides is produced and discarded. This material shows great potential for the production of platform chemicals. In this study, a series of Nb/Al oxide catalysts were synthesized via a facile and low-cost coprecipitation method, and their structures were characterized using: thermal gravimetric analysis (TGA, XRD, FESEM, TEM, X-ray photoelectron spectroscopy (XPS, NH3-TPD, N2 adsorption-desorption, and FTIR-Pyridine adsorption. Experimental results of sugar-to-levulinic acid (LA conversion revealed that the 20%Nb/Al oxide catalyst provided the highest catalytic performance and durability in terms of LA yield from fructose (74.2% at 463 K after 10 min and from glucose (47.5% at 473 K after 15 min. Notably, the 20% Nb/Al oxide catalyst with a 10% dosage is capable of converting kiwifruit waste residue to LA at 473 K after 10 min. In conclusion, the enhanced catalytic performance was obtained due to the high acidity, and large surface areaof Nb/Al oxide catalyst.

  5. Highly selective hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C3N4 nanosheets catalysts in water

    Science.gov (United States)

    Chen, Xiufang; Zhang, Ligang; Zhang, Bo; Guo, Xingcui; Mu, Xindong

    2016-06-01

    Graphitic carbon nitride nanosheets were investigated for developing effective Pt catalyst supports for selective hydrogenation of furfural to furfuryl alcohol in water. The nanosheets with an average thickness of about 3 nm were synthesized by a simple and green method through thermal oxidation etching of bulk g-C3N4 in air. Combined with the unique feature of nitrogen richness and locally conjugated structure, the g-C3N4 nanosheets with a high surface area of 142 m2 g-1 were demonstrated to be an excellent supports for loading small-size Pt nanoparticles. Superior furfural hydrogenation activity in water with complete conversion of furfural and high selectivity of furfuryl alcohol (>99%) was observed for g-C3N4 nanosheets supported Pt catalysts. The large specific surface area, uniform dispersion of Pt nanoparticles and the stronger furfural adsorption ability of nanosheets contributed to the considerable catalytic performance. The reusability tests showed that the novel Pt catalyst could maintain high activity and stability in the furfural hydrogenation reaction.

  6. Highly selective hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C3N4 nanosheets catalysts in water.

    Science.gov (United States)

    Chen, Xiufang; Zhang, Ligang; Zhang, Bo; Guo, Xingcui; Mu, Xindong

    2016-06-22

    Graphitic carbon nitride nanosheets were investigated for developing effective Pt catalyst supports for selective hydrogenation of furfural to furfuryl alcohol in water. The nanosheets with an average thickness of about 3 nm were synthesized by a simple and green method through thermal oxidation etching of bulk g-C3N4 in air. Combined with the unique feature of nitrogen richness and locally conjugated structure, the g-C3N4 nanosheets with a high surface area of 142 m(2) g(-1) were demonstrated to be an excellent supports for loading small-size Pt nanoparticles. Superior furfural hydrogenation activity in water with complete conversion of furfural and high selectivity of furfuryl alcohol (>99%) was observed for g-C3N4 nanosheets supported Pt catalysts. The large specific surface area, uniform dispersion of Pt nanoparticles and the stronger furfural adsorption ability of nanosheets contributed to the considerable catalytic performance. The reusability tests showed that the novel Pt catalyst could maintain high activity and stability in the furfural hydrogenation reaction.

  7. Mo-Co catalyst nanoparticles: Comparative study between TiN and Si surfaces for single-walled carbon nanotube growth

    Energy Technology Data Exchange (ETDEWEB)

    Morant, C., E-mail: c.morant@uam.es [Departamento de Fisica Aplicada, C-XII, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Campo, T. [Departamento de Fisica Aplicada, C-XII, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Marquez, F. [School of Science and Technology, University of Turabo, 00778-PR (United States); Domingo, C. [Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid (Spain); Sanz, J.M.; Elizalde, E. [Departamento de Fisica Aplicada, C-XII, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2012-06-01

    Highly pure single-walled carbon nanotubes (SWNT) were synthesized by alcohol catalytic chemical vapor deposition on silicon substrates partially covered by a thin layer of TiN. The TiN coating selectively prevented the growth of carbon nanotubes. Field emission scanning electron microscopy and Raman spectroscopy revealed the formation of high purity vertically aligned SWNT in the Si region. X-ray Photoelectron Spectroscopy and Atomic Force Microscopy indicated that Co nanoparticles are present on the Si regions, and not on the TiN regions. This clearly explains the obtained experimental results: the SWNT only grow where the Co is presented as nanoparticles, i.e. on the Si regions. - Highlights: Black-Right-Pointing-Pointer Single-wall carbon nanotubes (SWNT) ontained by catalytic chemical vapor-deposition. Black-Right-Pointing-Pointer Substrate/Co-Mo catalyst behaviour plays a key role in the SWNT growth. Black-Right-Pointing-Pointer Co nanoparticles (the effective catalyst) have been only observed on the Si region. Black-Right-Pointing-Pointer High purity SWNT were spatially confined in specific locations (Si regions). Black-Right-Pointing-Pointer TiN-coated surfaces, adjacent to a Si oxide region, prevent the growth of SWNT.

  8. Hydrophobic and hydrophilic nanosheet catalysts with high catalytic activity and recycling stability through control of the outermost ligand

    Science.gov (United States)

    Ko, Younji; Kim, Donghee; Kwon, Cheong Hoon; Cho, Jinhan

    2018-04-01

    In this study, we introduce hydrophobic and hydrophilic graphene oxide nanosheet (GON) catalysts prepared by consecutive ligand replacement of hydrophobically stabilized magnetic and catalytic nanoparticles (NPs); it exhibits high catalytic activity, fast magnetic response, and good dispersion in both nonpolar and aqueous media, allowing high loading amount of magnetic and catalytic NPs onto GON sheets. More specifically, these GON catalysts showed a high product yield of 66-99% and notable recyclability (93% of the initial product yield after 10 reaction cycles) in a Suzuki-Miyaura reaction in nonpolar media, outperforming the performance of the conventional hydrophilic GON catalysts. Additional coating of a hydrophilic layer onto GON catalysts also showed the notable performance (product yield ∼99%) in catalytic reactions performed in aqueous media. Given that ligand-controlled catalytic NPs adsorbed onto 2D nanosheets can be used as hydrophobic and hydrophilic stabilizers as well as catalysts, our approach can provide a tool for developing and designing 2D-nanosheet catalysts with high performance in nonpolar and polar media.

  9. Surface analysis of model systems: From a metal-graphite interface to an intermetallic catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kwolek, Emma J. [Iowa State Univ., Ames, IA (United States)

    2016-10-25

    This thesis summarizes research completed on two different model systems. In the first system, we investigate the deposition of the elemental metal dysprosium on highly-oriented pyrolytic graphite (HOPG) and its resulting nucleation and growth. The goal of this research is to better understand the metal-carbon interactions that occur on HOPG and to apply those to an array of other carbon surfaces. This insight may prove beneficial to developing and using new materials for electronic applications, magnetic applications and catalysis.

  10. Using precipitated Cr on the surface of Cu-Cr alloy powders as catalyst synthesizing CNTs/Cu composite powders by water-assisted CVD

    Science.gov (United States)

    Zhou, Honglei; Liu, Ping; Chen, Xiaohong; Bi, Liming; Zhang, Ke; Liu, Xinkuan; Li, Wei; Ma, Fengcang

    2018-02-01

    Given that the conventional catalyst is easily soluble in the matrix to result in the poor performance of the CNTs/Cu composite materials, the Cr nano-particles precipitated on the surface of Cu-Cr particles are first used as catalysts to prepare the CNTs/Cu composite powders by means of water-assisted chemical vapor deposition in situ synthesis. The results show that the morphological difference of the precipitated Cr nano-particle is obvious with the change of solution and aging treatment, and the morphology, length and diameter of the synthetic CNTs are also different. The catalyst of Cr nano-particle has the best morphology and the synthesized CNTs had a good wettability with Cu particles when the Cu-Cr composite powders was solution-treated at 1023 K for 60 min and then was aged at 723 K for 120 min. The length, diameter, yield and purity of the synthesized CNTs can be also affected by the moisture content in the reaction gas. It is the most suitable for the growth of CNTs when the moisture content is 0.4%, and the high purity and defect-free CNTs with the smooth pipe wall, a diameter of 20 ˜ 30 nm and a length of up to 1800 nm can be obtained. The yield of CNTs with the moisture content of 0.4% reached to 138%, which was increased by 119% to compare with that without moisture. In this paper, a feasible technology was offered for the preparation of high performance CNTs/Cu composites.

  11. Graphene sheets/cobalt nanocomposites as low-cost/high-performance catalysts for hydrogen generation

    International Nuclear Information System (INIS)

    Zhang, Fei; Hou, Chengyi; Zhang, Qinghong; Wang, Hongzhi; Li, Yaogang

    2012-01-01

    The production of clean and renewable hydrogen through the hydrolysis of sodium borohydride has received much attention owing to increasing global energy demands. Graphene sheets/cobalt (GRs/Co) nanocomposites, which are highly efficient catalysts, have been prepared using a one-step solvothermal method in ethylene glycol. Co 2+ salts were converted to Co nanoparticles, which were simultaneously inserted into the graphene layers with the reduction of graphite oxide sheets to GRs. The as-synthesized samples were characterized by X-ray diffraction, Fourier transform infrared spectra, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and vibrating sample magnetometer. The maximum saturation magnetization value reached 80.8 emu g −1 , meaning they are more suitable for magnet-controlled generation of H 2 than noble metal catalysts. The catalytic activity of the composite was investigated by the hydrolysis of sodium borohydride in aqueous solution both with and without a GRs support. It was found that the high electronic conductive GRs support increased the hydrogen generation rate (about two times) compared with pure cobalt. The improved hydrogen generation rate, low cost and uncomplicated recycling makes the GRs/Co nanocomposites promising candidates as catalysts for hydrogen generation. Highlights: ► Graphene sheets/cobalt nanocomposites were prepared by a one-step solvothermal method. ► The maximum saturation magnetization value of the composites reached 80.8 emu g −1 . ► The graphene support greatly increased the catalytic activity of cobalt. ► An easily removed, recycled and controlled functional filter was obtained.

  12. Tin-containing zeolites are highly active catalysts for the isomerization of glucose in water.

    Science.gov (United States)

    Moliner, Manuel; Román-Leshkov, Yuriy; Davis, Mark E

    2010-04-06

    The isomerization of glucose into fructose is a large-scale reaction for the production of high-fructose corn syrup (HFCS; reaction performed by enzyme catalysts) and recently is being considered as an intermediate step in the possible route of biomass to fuels and chemicals. Here, it is shown that a large-pore zeolite that contains tin (Sn-Beta) is able to isomerize glucose to fructose in aqueous media with high activity and selectivity. Specifically, a 10% (wt/wt) glucose solution containing a catalytic amount of Sn-Beta (150 Sn:glucose molar ratio) gives product yields of approximately 46% (wt/wt) glucose, 31% (wt/wt) fructose, and 9% (wt/wt) mannose after 30 min and 12 min of reaction at 383 K and 413 K, respectively. This reactivity is achieved also when a 45 wt% glucose solution is used. The properties of the large-pore zeolite greatly influence the reaction behavior because the reaction does not proceed with a medium-pore zeolite, and the isomerization activity is considerably lower when the metal centers are incorporated in ordered mesoporous silica (MCM-41). The Sn-Beta catalyst can be used for multiple cycles, and the reaction stops when the solid is removed, clearly indicating that the catalysis is occurring heterogeneously. Most importantly, the Sn-Beta catalyst is able to perform the isomerization reaction in highly acidic, aqueous environments with equivalent activity and product distribution as in media without added acid. This enables Sn-Beta to couple isomerizations with other acid-catalyzed reactions, including hydrolysis/isomerization or isomerization/dehydration reaction sequences [starch to fructose and glucose to 5-hydroxymethylfurfural (HMF) demonstrated here].

  13. Application of Metal Catalysts for High Selectivity of Glycerol Conversion to Alcohols

    Science.gov (United States)

    2010-11-01

    The objective of this project is to determine the applicability of metal-based catalysts and optimize the process conditions for thermochemically producing primary alcohols. Metal catalysts were evaluated for their selectivities for producing alcohol...

  14. Cobalt-embedded carbon nanofiber derived from a coordination polymer as a highly efficient heterogeneous catalyst for activating oxone in water.

    Science.gov (United States)

    Lin, Kun-Yi Andrew; Tong, Wai-Chi; Du, Yunchen

    2018-03-01

    Carbon fiber (CF) supported cobalt nanoparticles (NPs) are promising catalysts for activating Oxone because carbon is non-metal and earth-abundant, and CF-based catalysts exhibit a high aspect ratio, which affords more accessible and dense catalytic sites. Nevertheless, most of CF-supported catalysts are fabricated by post-synthetic methods, which involve complicated preparations. More importantly, metallic NPs are attached to the outer surface of CF rather than embedded within CF. However, there is still a great demand for developing Co-bearing carbon fibers for Oxone activation via simple and effective methods. Thus, this study proposes to develop a cobalt NP-embedded carbon nanofiber (CCNF) by a simple hydrothermal reaction of Co and nitrilotriacetic acid (NA), followed by one-step carbonization. Owing to the coordinative structure of CoNA, the derivative CCNF exhibits a fibrous carbon matrix embedded with evenly distributed and densely packed Co 3 O 4 and magnetic Co 0 nanoparticles. The fibrous structure, magnetism and embedded Co NPs enable CCNF to be a promising catalyst for Oxone activation. As degradation of Rhodamine B (RhB) is selected as a model reaction, CCNF not only rapidly activates Oxone to fully degrade RhB but also shows a much higher catalytic activity than the most common Oxone activator, Co 3 O 4 . CCNF also exhibits the lowest activation energy than any reported catalysts for Oxone activation to degrade RhB. In addition, CCNF could be re-used to activate Oxone for RhB degradation. These results indicate that CCNF is a conveniently prepared and highly effective fibrous Co/C hybrid material for activating Oxone to oxidize contaminants in water. Copyright © 2017. Published by Elsevier Ltd.

  15. Amide group anchored glucose oxidase based anodic catalysts for high performance enzymatic biofuel cell

    Science.gov (United States)

    Chung, Yongjin; Ahn, Yeonjoo; Kim, Do-Heyoung; Kwon, Yongchai

    2017-01-01

    A new enzyme catalyst is formed by fabricating gold nano particle (GNP)-glucose oxidase (GOx) clusters that are then attached to polyethyleneimine (PEI) and carbon nanotube (CNT) with cross-linkable terephthalaldehyde (TPA) (TPA/[CNT/PEI/GOx-GNP]). Especially, amide bonds belonging to TPA play an anchor role for incorporating rigid bonding among GNP, GOx and CNT/PEI, while middle size GNP is well bonded with thiol group of GOx to form strong GNP-GOx cluster. Those bonds are identified by chemical and electrochemical characterizations like XPS and cyclic voltammogram. The anchording effect of amide bonds induces fast electron transfer and strong chemical bonding, resulting in enhancements in (i) catalytic activity, (ii) amount of immobilized GOx and (ii) performance of enzymatic biofuel cell (EBC) including the catalyst. Regarding the catalytic activity, the TPA/[CNT/PEI/GOx-GNP] produces high electron transfer rate constant (6 s-1), high glucose sensitivity (68 μA mM-1 cm-2), high maximum current density (113 μA cm-2), low charge transfer resistance (17.0 Ω cm2) and long-lasting durability while its chemical structure is characterized by XPS confirming large portion of amide bond. In EBC measurement, it has high maximum power density (0.94 mW cm-2) compatible with catalytic acitivity measurements.

  16. Unraveling the role of support surface hydroxyls and its effect on the selectivity of C{sub 2} species over Rh/γ-Al{sub 2}O{sub 3} catalyst in syngas conversion: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Riguang; Duan, Tian; Wang, Baojun, E-mail: wangbaojun@tyut.edu.cn; Ling, Lixia

    2016-08-30

    Highlights: • The selectivity toward CH{sub x} (x = 1–3) depends on γ-Al{sub 2}O{sub 3} support and its surface properties. • Rh/γ-Al{sub 2}O{sub 3} catalyst exhibits the higher selectivity toward CH{sub x} (x = 1,2) formation from syngas. • C{sub 2} species (C{sub 2}H{sub 2},CHCO,CH{sub 2}CHO) are the main products on Rh/γ-Al{sub 2}O{sub 3} catalyst. • γ-Al{sub 2}O{sub 3} surface hydroxyls affect the selectivity of C{sub 2} species over Rh/γ-Al{sub 2}O{sub 3} catalyst. - Abstract: The supported Rh-based catalysts exhibit the excellent catalytic performances for syngas conversion to C{sub 2} species. In this study, all possible elementary steps leading to C{sub 2} species from syngas have been explored to identify the role of support and its surface hydroxyls over Rh/γ-Al{sub 2}O{sub 3} catalyst; Here, the results are obtained using density functional theory (DFT) method. Two models: Rh4 cluster supported on the dry γ-Al{sub 2}O{sub 3}(110) surface, D(Rh4), and on the hydroxylated γ-Al{sub 2}O{sub 3}(110) surface, H(Rh4), have been used to model Rh/γ-Al{sub 2}O{sub 3} catalyst. Our results show that CO prefers to be hydrogenated to CHO, subsequently, starting from CHO species, CH and CH{sub 2} species are the dominate monomers among CH{sub x}(x = 1–3) species rather than CH{sub 3} and CH{sub 3}OH on D(Rh4) and H(Rh4) surfaces, suggesting that γ-Al{sub 2}O{sub 3}-supported Rh catalyst exhibits the high selectivity towards CH{sub x} formation compared to the pure Rh catalyst. On the other hand, D(Rh4) is more favorable for C{sub 2} hydrocarbon (C{sub 2}H{sub 2}) formation, whereas H(Rh4) surface easily produces C{sub 2} hydrocarbon (C{sub 2}H{sub 2}) and C{sub 2} oxygenates (CHCO,CH{sub 2}CHO), indicating that the surface hydroxyls of support can affect the selectivity of C{sub 2} species over Rh/γ-Al{sub 2}O{sub 3} catalyst in syngas conversion. Moreover, compared to the pure Rh(111) surface, Rh/γ-Al{sub 2}O{sub 3} catalyst can achieve the

  17. CuCr2O4@rGO Nanocomposites as High-Performance Cathode Catalyst for Rechargeable Lithium-Oxygen Batteries

    Science.gov (United States)

    Liu, Jiandi; Zhao, Yanyan; Li, Xin; Wang, Chunge; Zeng, Yaping; Yue, Guanghui; Chen, Qiang

    2018-06-01

    Rechargeable lithium-oxygen batteries have been considered as a promising energy storage technology because of their ultra-high theoretical energy densities which are comparable to gasoline. In order to improve the electrochemical properties of lithium-oxygen batteries (LOBs), especially the cycling performance, a high-efficiency cathode catalyst is the most important component. Hence, we aim to demonstrate that CuCr2O4@rGO (CCO@rGO) nanocomposites, which are synthesized using a facile hydrothermal method and followed by a series of calcination processes, are an effective cathode catalyst. The obtained CCO@rGO nanocomposites which served as the cathode catalyst of the LOBs exhibited an outstanding cycling performance for over 100 cycles with a fixed capacity of 1000 mAh g-1 at a current density of 200 mA g-1. The enhanced properties were attributed to the synergistic effect between the high catalytic efficiency of the spinel-structured CCO nanoparticles, the high specific surface area, and high conductivity of the rGO.[Figure not available: see fulltext.

  18. Highly stable and active Ni-doped ordered mesoporous carbon catalyst on the steam reforming of ethanol application

    Directory of Open Access Journals (Sweden)

    Josh Y.Z. Chiou

    2017-02-01

    Full Text Available A novel one-step direct synthesis of nickel embedded in an ordered mesoporous carbon catalyst (NiOMC is done in a basic medium of nonaqueous solution by a solvent evaporation-induced self-assembly process. The NiOMC sample is characterized by a variety of analytical and spectroscopy techniques, e.g., N2 adsorption/desorption isotherm measurement, X-ray diffraction (XRD, transmission electron microscopy (TEM and temperature-programed reduction (TPR. In this study, the NiOMC catalyst is found to exhibit superior catalytic activity for the steam reforming of ethanol (SRE, showing high hydrogen selectivity and durability. Ethanol can be completely converted at 350 °C over the NiOMC catalyst. Also, the durability of the NiOMC catalyst on the SRE reaction exceeds 100 h at 450 °C, with SH2 approaching 65% and SCO of less than 1%.

  19. Cu2+ Montmorillonite K10 Clay Catalyst as a Green Catalyst for Production of Stearic Acid Methyl Ester: Optimization Using Response Surface Methodology (RSM)

    OpenAIRE

    Enas A. Almadani; Farah W. Harun; Salina M. Radzi; Syamsul K. Muhamad

    2018-01-01

    Clay catalyst has received much attention to replace the homogeneous catalysts in the esterification reaction to produce fatty acid methyl ester as the source of biodiesel as it is low cost, easily available, as well as environmental friendly. However, the use of unmodified clay, in particular montmorillonite K10 (MMT K10), for the esterification of fatty acids showed that the acid conversion was less than 60% and this is not preferable to the production of biodiesel. In this study, synthesis...

  20. Catalyst design for carbon nanotube growth using atomistic modeling

    International Nuclear Information System (INIS)

    Pint, Cary L; Bozzolo, Guillermo; Hauge, Robert

    2008-01-01

    The formation and stability of bimetallic catalyst particles, in the framework of carbon nanotube growth, is studied using the Bozzolo-Ferrante-Smith (BFS) method for alloys. Monte Carlo-Metropolis simulations with the BFS method are utilized in order to predict and study equilibrium configurations for nanoscale catalyst particles which are directly relevant to the catalyst state prior to growth of carbon nanotubes. At the forefront of possible catalyst combinations is the popular Fe-Mo bimetallic catalyst, which we have recently studied experimentally. We explain our experimental results, which indicate that the growth observed is dependent on the order of co-catalyst deposition, in the straightforward interpretation of BFS strain and chemical energy contributions toward the formation of Fe-Mo catalyst prior to growth. We find that the competition between the formation of metastable inner Mo cores and clusters of surface-segregated Mo atoms in Fe-Mo catalyst particles influences catalyst formation, and we investigate the role of Mo concentration and catalyst particle size in this process. Finally, we apply the same modeling approach to other prominent bimetallic catalysts and suggest that this technique can be a powerful tool to understand and manipulate catalyst design for highly efficient carbon nanotube growth

  1. Highly Active N,O Zinc Guanidine Catalysts for the Ring-Opening Polymerization of Lactide.

    Science.gov (United States)

    Schäfer, Pascal M; Fuchs, Martin; Ohligschläger, Andreas; Rittinghaus, Ruth; McKeown, Paul; Akin, Enver; Schmidt, Maximilian; Hoffmann, Alexander; Liauw, Marcel A; Jones, Matthew D; Herres-Pawlis, Sonja

    2017-09-22

    New zinc guanidine complexes with N,O donor functionalities were prepared, characterized by X-Ray crystallography, and examined for their catalytic activity in the solvent-free ring-opening polymerization (ROP) of technical-grade rac-lactide at 150 °C. All complexes showed a high activity. The fastest complex [ZnCl 2 (DMEGasme)] (C1) produced colorless poly(lactide) (PLA) after 90 min with a conversion of 52 % and high molar masses (M w =69 100, polydispersity=1.4). The complexes were tested with different monomer-to-initiator ratios to determine the rate constant k p . Furthermore, a polymerization with the most active complex C1 was monitored by in situ Raman spectroscopy. Overall, conversion of up to 90 % can be obtained. End-group analysis was performed to clarify the mechanism. All four complexes combine robustness against impurities in the lactide with high polymerization rates, and they represent the fastest robust lactide ROP catalysts to date, opening new avenues to a sustainable ROP catalyst family for industrial use. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Graphene Carbon Nanotube Carpets Grown Using Binary Catalysts for High-Performance Lithium-Ion Capacitors.

    Science.gov (United States)

    Salvatierra, Rodrigo Villegas; Zakhidov, Dante; Sha, Junwei; Kim, Nam Dong; Lee, Seoung-Ki; Raji, Abdul-Rahman O; Zhao, Naiqin; Tour, James M

    2017-03-28

    Here we show that a versatile binary catalyst solution of Fe 3 O 4 /AlO x nanoparticles enables homogeneous growth of single to few-walled carbon nanotube (CNT) carpets from three-dimensional carbon-based substrates, moving past existing two-dimensional limited growth methods. The binary catalyst is composed of amorphous AlO x nanoclusters over Fe 3 O 4 crystalline nanoparticles, facilitating the creation of seamless junctions between the CNTs and the underlying carbon platform. The resulting graphene-CNT (GCNT) structure is a high-density CNT carpet ohmically connected to the carbon substrate, an important feature for advanced carbon electronics. As a demonstration of the utility of this approach, we use GCNTs as anodes and cathodes in binder-free lithium-ion capacitors, producing stable devices with high-energy densities (∼120 Wh kg -1 ), high-power density capabilities (∼20,500 W kg -1 at 29 Wh kg -1 ), and a large operating voltage window (4.3 to 0.01 V).

  3. Preparation and characterization of mesoporous TiO{sub 2}-sphere-supported Au-nanoparticle catalysts with high activity for CO oxidation at ambient temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lili; Huang, Shouying; Zhu, Baolin; Zhang, Shoumin; Huang, Weiping, E-mail: hwp914@nankai.edu.cn [Nankai University, College of Chemistry, The Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), and Tianjin Key Lab of Metal and Molecule-based Material Chemistry (China)

    2016-11-15

    Mesoporous TiO{sub 2}-sphere-supported Au-nanoparticles (Au/m-TiO{sub 2}-spheres) catalysts have been synthesized by a simple method using tetrabutyl titanate as TiO{sub 2} precursor and characterized with XRD, BET, ICP, SEM, TEM, UV-Vis DRS, XPS, as well as FT-IR. The samples with the size in the range of 200–400 nm were almost perfectly spherical. The average diameter of pores was about 3.6 nm, and the mesopore size distribution was in the range of 2–6 nm with a narrow distribution. When the catalyst was calcined at 300 °C, the Au NPs with the size ca. 5 nm were highly dispersed on the surfaces of m-TiO{sub 2} spheres and partially embedded in the supports. Remarkably, the specific surface area of the Au/m-TiO{sub 2}-spheres was as high as 117 m{sup 2} g{sup −1}. The CO-adsorbed catalyst showed an apparent IR adsorption peak at 1714 cm{sup −1} that matched with bridging model CO. It means the catalysts should be of high catalytic activity for the CO oxidation due to they could adsorb and activate CO commendably. When Au-content was 0.48 wt.%, the Au/m-TiO{sub 2}-spheres could convert CO completely into CO{sub 2} at ambient temperature.

  4. Rice husk-derived sodium silicate as a highly efficient and low-cost basic heterogeneous catalyst for biodiesel production

    International Nuclear Information System (INIS)

    Roschat, Wuttichai; Siritanon, Theeranun; Yoosuk, Boonyawan; Promarak, Vinich

    2016-01-01

    Graphical abstract: Rice husk-derived sodium silicate exhibits high potential as a low-cost solid catalyst for industrial biodiesel production. - Highlights: • Rice husk-derived sodium silicate was employed as a high performance catalyst for biodiesel production. • 97% yield of FAME was achieved in 30 min at 65 °C. • The room-temperature transesterification gave 94% yield of FAME after only 150 min. - Abstract: In the present work, rice husk-derived sodium silicate was prepared and employed as a solid catalyst for simple conversion of oils to biodiesel via the transesterification reaction. The catalyst was characterized by TG–DTA, XRD, XRF, FT-IR, SEM, BET and Hammett indicator method. Under the optimal reaction conditions of catalyst loading amount of 2.5 wt.%, methanol/oil molar ratio of 12:1, the prepared catalysts gave 97% FAME yield in 30 min at 65 °C, and 94% FAME yield in 150 min at room temperature. The transesterification was proved to be pseudo-first order reaction with the activation energy (Ea) and the frequency factor (A) of 48.30 kJ/mol and 2.775 × 10"6 min"−"1 respectively. Purification with a cation-exchange resin efficiently removed all soluble ions providing high-quality biodiesel product that meets all the ASTM and EN standard specifications. Rice husk-derived sodium silicate showed high potential to be used as a low-cost, easy to prepare and high performance solid catalyst for biodiesel synthesis.

  5. Novel Reforming Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, Lisa D; Haller, Gary L

    2012-10-16

    Aqueous phase reforming is useful for processing oxygenated hydrocarbons to hydrogen and other more useful products. Current processing is hampered by the fact that oxide based catalysts are not stable under high temperature hydrothermal conditions. Silica in the form of structured MCM-41 is thermally a more stable support for Co and Ni than conventional high surface area amorphous silica but hydrothermal stability is not demonstrated. Carbon nanotube supports, in contrast, are highly stable under hydrothermal reaction conditions. In this project we show that carbon nanotubes are stable high activity/selectivity supports for the conversion of ethylene glycol to hydrogen.

  6. Towards an atomic level understanding of niobia based catalysts and catalysis by combining the science of catalysis with surface science

    Directory of Open Access Journals (Sweden)

    Martin Schmal

    2009-06-01

    Full Text Available The science of catalysis and surface science have developed, independently, key information for understanding catalytic processes. One might argue: is there anything fundamental to be discovered through the interplay between catalysis and surface science? Real catalysts of monometallic and bimetallic Co/Nb2O5 and Pd-Co/Nb2O5 catalysts showed interesting selectivity results on the Fischer-Tropsch synthesis (Noronha et al. 1996, Rosenir et al. 1993. The presence of a noble metal increased the C+5 selectivity and decreased the methane formation depending of the reduction temperature. Model catalyst of Co-Pd supported on niobia and alumina were prepared and characterized at the atomic level, thus forming the basis for a comparison with "real" support materials. Growth, morphology and structure of both pure metal and alloy particles were studied. It is possible to support the strong metal support interaction suggested by studies on real catalysts via the investigation of model systems for niobia in comparison to alumina support in which this effect does not occur. Formation of Co2+ penetration into the niobia lattice was suggested on the basis of powder studies and can be fully supported on the basis of model studies. It is shown for both real catalysts and model systems that oxidation state of Co plays a key role in controlling the reactivity in Fischer-Tropsch reactions systems and that the addition of Pd is a determining factor for the stability of the catalyst. It is demonstrated that the interaction with unsaturated hydrocarbons depends strongly on the state of oxidation.As ciências da catálise e da superfície têm desenvolvido independentemente temas básicos para o entendimento de processos catalíticos. Pode-se até questionar se há ainda algo fundamental para ser descoberto através da interface entre catálise eciência da superfície? Catalisadores mono e bimetálicos de Co/Nb2O5 e Pd-Co/ Nb2O5 apresentaram resultados interessantes de

  7. Nano-Structured Bio-Inorganic Hybrid Material for High Performing Oxygen Reduction Catalyst.

    Science.gov (United States)

    Jiang, Rongzhong; Tran, Dat T; McClure, Joshua P; Chu, Deryn

    2015-08-26

    In this study, we demonstrate a non-Pt nanostructured bioinorganic hybrid (BIH) catalyst for catalytic oxygen reduction in alkaline media. This catalyst was synthesized through biomaterial hemin, nanostructured Ag-Co alloy, and graphene nano platelets (GNP) by heat-treatment and ultrasonically processing. This hybrid catalyst has the advantages of the combined features of these bio and inorganic materials. A 10-fold improvement in catalytic activity (at 0.8 V vs RHE) is achieved in comparison of pure Ag nanoparticles (20-40 nm). The hybrid catalyst reaches 80% activity (at 0.8 V vs RHE) of the state-of-the-art catalyst (containing 40% Pt and 60% active carbon). Comparable catalytic stability for the hybrid catalyst with the Pt catalyst is observed by chronoamperometric experiment. The hybrid catalyst catalyzes 4-electron oxygen reduction to produce water with fast kinetic rate. The rate constant obtained from the hybrid catalyst (at 0.6 V vs RHE) is 4 times higher than that of pure Ag/GNP catalyst. A catalytic model is proposed to explain the oxygen reduction reaction at the BIH catalyst.

  8. Advances in catalysts for internal reforming in high temperature fuel cells

    Science.gov (United States)

    Dicks, A. L.

    Catalytic steam reforming of natural gas is an attractive method of producing the hydrogen required by the present generation of fuel cells. The molten carbonate (MCFC) and solid oxide (SOFC) fuel cells operate at high enough temperatures for the endothermic steam reforming reaction to be carried out within the stack. For the MCFC, the conventional anodes have insufficient activity to catalyse the steam reforming of natural gas. For these cells, internal reforming can be achieved only with the addition of a separate catalyst, preferably located in close proximity to the anode. However, in the so-called `Direct Internal Reforming' configuration, attack from alkali in the MCFC may severely limit catalyst lifetime. In the case of the state-of-the-art SOFC, natural gas can be reformed directly on the nickel cermet anode. However, in the SOFC, temperature variations in the cell caused by the reforming reaction may limit the amount of internal reforming that can be allowed in practice. In addition, some external pre-reforming may be desirable to remove high molecular weight hydrocarbons from the fuel gas, which would otherwise crack to produce elemental carbon. Degradation of the SOFC anode may also be a problem when internal reforming is carried out. This has prompted several research groups to investigate the use of alternative anode materials.

  9. Facile synthesis of a platinum-lead oxide nanocomposite catalyst with high activity and durability for ethanol electrooxidation.

    Science.gov (United States)

    Yang, Wei-Hua; Wang, Hong-Hui; Chen, De-Hao; Zhou, Zhi-You; Sun, Shi-Gang

    2012-12-21

    Aimed at searching for highly active and stable nano-scale Pt-based catalysts that can improve significantly the energy conversion efficiency of direct ethanol fuel cells (DEFCs), a novel Pt-PbO(x) nanocomposite (Pt-PbO(x) NC) catalyst with a mean size of 3.23 nm was synthesized through a simple wet chemistry method without using a surfactant, organometallic precursors and high temperature. Electrocatalytic tests demonstrated that the as-prepared Pt-PbO(x) NC catalyst possesses a much higher catalytic activity and a longer durability than Pt nanoparticles (nm-Pt) and commercial Pt black catalysts for ethanol electrooxidation. For instance, Pt-PbO(x) NC showed an onset potential that was 30 mV and 44 mV less positive, together with a peak current density 1.7 and 2.6 times higher than those observed for nm-Pt and Pt black catalysts in the cyclic voltammogram tests. The ratio of current densities per unit Pt mass on Pt-PbO(x) NC, nm-Pt and Pt black catalysts is 27.3 : 3.4 : 1 for the long-term (2 hours) chronoamperometric experiments measured at -0.4 V (vs. SCE). In situ FTIR spectroscopic studies revealed that the activity of breaking C-C bonds of ethanol of the Pt-PbO(x) NC is as high as 5.17 times that of the nm-Pt, which illustrates a high efficiency of ethanol oxidation to CO(2) on the as-prepared Pt-PbO(x) NC catalyst.

  10. Surface/structure functionalization of copper-based catalysts by metal-support and/or metal–metal interactions

    Energy Technology Data Exchange (ETDEWEB)

    Konsolakis, Michalis, E-mail: mkonsol@science.tuc.gr [School of Production Engineering and Management, Technical University of Crete, GR-73100 Chania, Crete (Greece); Ioakeimidis, Zisis [Department of Mechanical Engineering, University of Western Macedonia, Bakola and Sialvera, GR-50100 Kozani (Greece)

    2014-11-30

    Highlights: • The surface chemistry of Cu-based catalysts is adjusted by metal-support or metal–metal interactions. • Three series of catalysts, i.e., Cu/REOs, Cu/Ce{sub 1−x}Sm{sub x}O{sub δ} and Cu–Co/CeO{sub 2} were prepared. • The local structure of Cu sites is remarkably affected by support or active phase modification. • Useful insights toward the fundamental understanding of Cu-catalyzed reactions are provided. - Abstract: Cu-based catalysts have recently attracted great attention both in catalysis and electro-catalysis fields due to their excellent catalytic performance and low cost. Given that their performance is determined, to a great extent, by Cu sites local environment, considerable efforts have been devoted on the strategic modifications of the electronic and structural properties of Cu sites. In this regard, the feasibility of tuning the local structure of Cu entities by means of metal-support or metal–metal interactions is investigated. More specifically, the physicochemical properties of Cu entities are modified by employing: (i) different oxides (CeO{sub 2}, La{sub 2}O{sub 3}, Sm{sub 2}O{sub 3}), or (ii) ceria-based mixed oxides (Ce{sub 1−x}Sm{sub x}O{sub δ}) as supporting carriers, and (iii) a second metal (Cobalt) adjacent to Cu (bimetallic Cu–Co/CeO{sub 2}). A characterization study, involving BET, XRD, TPR, and XPS, reveal that significant modifications on structural, redox and electronic properties of Cu sites can be induced by adopting either different oxide carriers or bimetallic complexes. Fundamental insights into the tuning of Cu local environment by metal-support or metal–metal interactions are provided, paving the way for real-life industrial applications.

  11. The Role of Non-Conventional Supports for Single-Atom Platinum-Based Catalysts in Fuel-Cell Technology: A Theoretical Surface Science Approach

    Science.gov (United States)

    2013-02-05

    could be a promising catalyst for PEM fuel cells. Introduction: Proton exchange membrane fuel cells ( PEMFCs ) have found wide potential...Unfortunately, due to their high cost and low lifespan, wide-scale commercialization of PEMFCs has been greatly impeded and much effort has been made to...lower its cost as well as to improve its durability over time. In an attempt to alleviate the high-cost associated with conventional PEMFC catalysts

  12. Investigation of hybrid plasma-catalytic removal of acetone over CuO/γ-Al2O3 catalysts using response surface method.

    Science.gov (United States)

    Zhu, Xinbo; Tu, Xin; Mei, Danhua; Zheng, Chenghang; Zhou, Jinsong; Gao, Xiang; Luo, Zhongyang; Ni, Mingjiang; Cen, Kefa

    2016-07-01

    In this work, plasma-catalytic removal of low concentrations of acetone over CuO/γ-Al2O3 catalysts was carried out in a cylindrical dielectric barrier discharge (DBD) reactor. The combination of plasma and the CuO/γ-Al2O3 catalysts significantly enhanced the removal efficiency of acetone compared to the plasma process using the pure γ-Al2O3 support, with the 5.0 wt% CuO/γ-Al2O3 catalyst exhibiting the best acetone removal efficiency of 67.9%. Catalyst characterization was carried out to understand the effect the catalyst properties had on the activity of the CuO/γ-Al2O3 catalysts in the plasma-catalytic reaction. The results indicated that the formation of surface oxygen species on the surface of the catalysts was crucial for the oxidation of acetone in the plasma-catalytic reaction. The effects that various operating parameters (discharge power, flow rate and initial concentration of acetone) and the interactions between these parameters had on the performance of the plasma-catalytic removal of acetone over the 5.0 wt% CuO/γ-Al2O3 catalyst were investigated using central composite design (CCD). The significance of the independent variables and their interactions were evaluated by means of the Analysis of Variance (ANOVA). The results showed that the gas flow rate was the most significant factor affecting the removal efficiency of acetone, whilst the initial concentration of acetone played the most important role in determining the energy efficiency of the plasma-catalytic process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Characterization of the impregnated iron based catalyst for direct coal liquefaction by EXAFS

    International Nuclear Information System (INIS)

    Yang Jianli; Zhun Jisheng; Liu Zhenyu; Zhong Bing

    2002-01-01

    Catalyst plays an important role in direct coal liquefaction (DCL). Iron catalysts are regarded as the most attractive catalysts for DCL. To maximize catalytic effect and minimize catalysts usage, ultra-fine size catalysts are preferred. The most effective catalysts are found to be those impregnated onto coal because of their high dispersion on coal surface and intimate contact with coal particles. Besides the physical size, chemical form of a catalyst or a catalyst precursor is also important in determination of DCL activity. The expended X-ray absorption fine structure spectroscopy technique were used in this study. It was shown that the catalysts tested are in nanomater range and have structure mainly in the form of γ-FeOOH and FeS, or possibly of Fe/O/S. The presence of γ-FeOOH can be attributed to the interaction between Fe and the oxygen containing groups of coal or oxygen from moisture

  14. Facile synthesis of highly efficient amorphous Mn-MIL-100 catalysts: The formation mechanism and the structure changes during the application for CO oxidation.

    Science.gov (United States)

    Zhang, Xiaodong; Li, Hongxin; Lv, Xutian; Xu, Jingcheng; Wang, Yuxin; He, Chi; Liu, Ning; Yang, Yiqiong; Wang, Yin

    2018-04-13

    A comprehensive study was carried out on amorphous metal-organic frameworks Mn-MIL-100 as efficient catalysts towards CO oxidation. This study focuses on explaining the crystalline-amorphous-crystalline transformations during thermolysis process of Mn-MIL-100 and studying the structure changes during the reaction process for CO oxidation. A possible formation mechanism of amorphous Mn-MIL-100 was proposed. Amorphous Mn-MIL-100 obtained by calcination at 250°C (a-Mn-250) showed a smaller specific surface area (4 m2/g), but displayed a high catalytic activity. Furthermore, the structure of amorphous Mn-MIL-100 was labile during the reaction process. When used a-Mn-250 were treated with reaction atmosphere at high temperature (named used a-Mn-250-S), the amorphous catalysts transformed to Mn2O3. Meanwhile, BET surface area (164 m2/g) and the catalytic performance both sharply increased. In addition, used a-Mn-250-S catalyst transformed from Mn2O3 to Mn3O4, resulting in the slightly decrease of catalytic activity under the presence of 1 vol% water vapor in the stream. A schematic of the structure changes during the reaction process was proposed. The achievement of our synthesis relies on the increase of BET surface area using CO as retreatment atmosphere, and the enhanced catalytic activity was attributed to the unique structure, a high quantity of surface active oxygen species, oxygen vacancies and good low temperature reduction behavior. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. High-efficiency and conveniently recyclable photo-catalysts for dye degradation based on urchin-like CuO microparticle/polymer hybrid composites

    Science.gov (United States)

    Liu, Xiong; Cheng, Yuming; Li, Xuefeng; Dong, Jinfeng

    2018-05-01

    In this work, we developed a new type of photo-catalysts composed of the urchin-like cupric oxide (CuO) microparticle and polyvinylidene fluoride (PVDF) hybrid composites by the convenient organic-inorganic hybrid strategy, which show high-efficiency and conveniently recyclable for dye degradation including methylene blue (MB), Congo red (CR), and malachite green (MG) by visible light irradiation. The micro-structural characteristics of urchin-like CuO microparticles are crucial and dominant over the photo-degrading efficiency of hybrid catalyst because of their highly exposed {0 0 2} facet and larger specific surface area. Simultaneously, the intrinsic porous framework of PVDF membrane not only remains the excellent photo-catalytic activity of urchin-like CuO microparticles but also facilitates the enrichment of dyes on the membrane, and thereby synergistically contributing to the photo-catalytic efficiency. The microstructures of both urchin-like CuO microparticles and hybrid catalysts are systematically characterized by various techniques including scanning electron microscopy (SEM), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and nitrogen adsorption/desorption isotherms, which evidently support the mentioned mechanism.

  16. Influence of excess sodium ions on the specific surface area formation in a NiO-Al2O3 catalyst prepared by different methods

    Directory of Open Access Journals (Sweden)

    Lazić M.M.

    2008-01-01

    Full Text Available The influence of sodium ions on the specific surface area of a NiO-Al2O3 catalyst in dependence of nickel loading (5, 10, and 20 wt% Ni, temperature of heat treatment (400, 700 and 1100oC and the method of sample preparation was investigated. Low temperature nitrogen adsorption (LTNA, X-ray diffraction (XRD and scanning electron microscopy (SEM were applied for sample characterization. Dramatic differences in the specific surface area were registered between non-rinsed and rinsed Al2O3 and NiO-Al2O3 samples. The lagged sodium ions promote sintering of non-rinsed catalyst samples.

  17. Solution Structures of Highly Active Molecular Ir Water-Oxidation Catalysts from Density Functional Theory Combined with High-Energy X-ray Scattering and EXAFS Spectroscopy.

    Science.gov (United States)

    Yang, Ke R; Matula, Adam J; Kwon, Gihan; Hong, Jiyun; Sheehan, Stafford W; Thomsen, Julianne M; Brudvig, Gary W; Crabtree, Robert H; Tiede, David M; Chen, Lin X; Batista, Victor S

    2016-05-04

    The solution structures of highly active Ir water-oxidation catalysts are elucidated by combining density functional theory, high-energy X-ray scattering (HEXS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. We find that the catalysts are Ir dimers with mono-μ-O cores and terminal anionic ligands, generated in situ through partial oxidation of a common catalyst precursor. The proposed structures are supported by (1)H and (17)O NMR, EPR, resonance Raman and UV-vis spectra, electrophoresis, etc. Our findings are particularly valuable to understand the mechanism of water oxidation by highly reactive Ir catalysts. Importantly, our DFT-EXAFS-HEXS methodology provides a new in situ technique for characterization of active species in catalytic systems.

  18. Biosyngas Fischer. Tropsch conversion by high Fe loaded supported catalysts prepared with ultrasound and microwave

    Energy Technology Data Exchange (ETDEWEB)

    Pirola, C.; Di Fronzo, A.; Boffito, D.C.; Bianchi, C. [Milano Univ. (Italy). Dipt. di Chimica; Di Michele, A. [Perugia Univ. (Italy). Dipt. di Fisica

    2012-07-01

    Catalysts with iron high loading of 30 wt%, promoted with K (2.0 wt%) and Cu (3.75 wt%), have been synthesized according to three different methods: (1) the traditional impregnation method (TR); (2) Ultrasound (US) assisted TR method; (3) Microwave (MW) assisted TR method. All the samples have been fully characterized by BET, ICP/OES, XRPD, TG-DTA, FT-IR, TPR, SEM and TEM and tested in a laboratory pilot plant for Fischer-Tropsch synthesis working at 220 C and 20 bar. The results of the catalysts characterization indicated that the morphology of the samples strongly depends on the method of preparation. The best FTS results in term of C{sub 2+} yield (41%) has been obtained using MW with a good value of the selectivity towards heavy hydrocarbons, while in term of CO conversion (58%), using US. The samples prepared with non-traditional methods show FTS better results, probably due to a more wide and uniform distribution of Fe in the medium during the synthesis phase. (orig.)

  19. Multi-wall carbon nanotubes supported molybdenyl acetylacetonate: Efficient and highly reusable catalysts for epoxidation of alkenes with tert-butyl hydroperoxide

    Energy Technology Data Exchange (ETDEWEB)

    Esnaashari, Fariba [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Moghadam, Majid, E-mail: moghadamm@sci.ui.ac.ir [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Mirkhani, Valiollah, E-mail: mirkhani@sci.ui.ac.ir [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Tangestaninejad, Shahram; Mohammadpoor-Baltork, Iraj; Khosropour, Ahmad Reza; Zakeri, Maryam [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of)

    2012-11-15

    Efficient epoxidation of olefins catalyzed by MoO{sub 2}(acac){sub 2} supported on amines functionalized MWCNTs is reported. The MWCNTs bearing carboxylic acid groups were modified with 2-aminophenol and 2-aminothiophenol. These amine-MWCNTs act as bidentate ligand for attachment of Mo catalyst. These catalysts were characterized by elemental analysis, scanning electron microscopy, FT-IR and diffuse reflectance UV-Vis spectroscopic methods. The prepared catalysts were used for efficient epoxidation of different alkenes such as cyclic and linear ones with tert-butyl hydroperoxide in refluxing 1,2-dichloroethane. These heterogeneous catalysts can be reused several times without significant loss of their catalytic activity. Highlights: Black-Right-Pointing-Pointer Supporting of molybdenyl acetylacetonate on amine-modified MWCNTs. Black-Right-Pointing-Pointer Heterogeneous catalysts were prepared. Black-Right-Pointing-Pointer These catalysts were highly efficient in the epoxidation of alkenes with TBHP. Black-Right-Pointing-Pointer Makes the catalysts reusable.

  20. Multi-wall carbon nanotubes supported molybdenyl acetylacetonate: Efficient and highly reusable catalysts for epoxidation of alkenes with tert-butyl hydroperoxide

    International Nuclear Information System (INIS)

    Esnaashari, Fariba; Moghadam, Majid; Mirkhani, Valiollah; Tangestaninejad, Shahram; Mohammadpoor-Baltork, Iraj; Khosropour, Ahmad Reza; Zakeri, Maryam

    2012-01-01

    Efficient epoxidation of olefins catalyzed by MoO 2 (acac) 2 supported on amines functionalized MWCNTs is reported. The MWCNTs bearing carboxylic acid groups were modified with 2-aminophenol and 2-aminothiophenol. These amine–MWCNTs act as bidentate ligand for attachment of Mo catalyst. These catalysts were characterized by elemental analysis, scanning electron microscopy, FT-IR and diffuse reflectance UV–Vis spectroscopic methods. The prepared catalysts were used for efficient epoxidation of different alkenes such as cyclic and linear ones with tert-butyl hydroperoxide in refluxing 1,2-dichloroethane. These heterogeneous catalysts can be reused several times without significant loss of their catalytic activity. Highlights: ► Supporting of molybdenyl acetylacetonate on amine-modified MWCNTs. ► Heterogeneous catalysts were prepared. ► These catalysts were highly efficient in the epoxidation of alkenes with TBHP. ► Makes the catalysts reusable.

  1. Pathway and Surface Mechanism Studies of 1,3-butadiene Selective Oxidation Over Vanadium-Molybdenum-Oxygen Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, William David [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9-14 m2/g, and compositions were within the solid solution regime, i.e. below 15.0 mol % MoO3/(MoO3 + V2O5). Laser Raman Spectroscopy and XRD data indicated that solid solutions were formed, and pre- and post-reaction XPS data indicated that catalyst surfaces contained some V+4 and were further reduced in 1,3-butadiene oxidation. A reaction pathway for 1,3-butadiene partial oxidation to maleic anhydride was shown to involve intermediates such as 3,4-epoxy-1-butene, crotonaldehyde, furan, and 2-butene-1,4-dial. The addition of water to the reaction stream substantially increased catalyst activity and improved selectivity to crotonaldehyde and furan at specific reaction temperatures. At higher water addition concentrations, furan selectivity increased from 12% to over 25%. The catalytic effects of water addition were related to competitive adsorption with various V2O5-based surface sites, including the vanadyl V=O, corner sharing V-O-V and edge sharing V-O oxygen. Higher levels of water addition were proposed to impose acidic character by dissociative adsorption. In addition, a novel combinatorial synthesis technique for VMoO was used to investigate the phase transitions of V2O5, solid solutions of Mo in V2O5, V9Mo6O40, and other reduced VMoO compounds, characterized by laser Raman spectroscopy. The natural composition gradient imposed by the sputter deposition apparatus was used to create VMoO arrays containing 225 samples ranging from 7.0-42 mol% MoO3/(V2O5 + MoO3), determined by EDS analysis.

  2. Highly efficient nonprecious metal catalyst prepared with metal–organic framework in a continuous carbon nanofibrous network

    Science.gov (United States)

    Shui, Jianglan; Chen, Chen; Grabstanowicz, Lauren; Zhao, Dan; Liu, Di-Jia

    2015-01-01

    Fuel cell vehicles, the only all-electric technology with a demonstrated >300 miles per fill travel range, use Pt as the electrode catalyst. The high price of Pt creates a major cost barrier for large-scale implementation of polymer electrolyte membrane fuel cells. Nonprecious metal catalysts (NPMCs) represent attractive low-cost alternatives. However, a significantly lower turnover frequency at the individual catalytic site renders the traditional carbon-supported NPMCs inadequate in reaching the desired performance afforded by Pt. Unconventional catalyst design aiming at maximizing the active site density at much improved mass and charge transports is essential for the next-generation NPMC. We report here a method of preparing highly efficient, nanofibrous NPMC for cathodic oxygen reduction reaction by electrospinning a polymer solution containing ferrous organometallics and zeolitic imidazolate framework followed by thermal activation. The catalyst offers a carbon nanonetwork architecture made of microporous nanofibers decorated by uniformly distributed high-density active sites. In a single-cell test, the membrane electrode containing such a catalyst delivered unprecedented volumetric activities of 3.3 A⋅cm−3 at 0.9 V or 450 A⋅cm−3 extrapolated at 0.8 V, representing the highest reported value in the literature. Improved fuel cell durability was also observed. PMID:26261338

  3. Reactor for tracking catalyst nanoparticles in liquid at high temperature under a high-pressure gas phase with X-ray absorption spectroscopy.

    Science.gov (United States)

    Nguyen, Luan; Tao, Franklin Feng

    2018-02-01

    Structure of catalyst nanoparticles dispersed in liquid phase at high temperature under gas phase of reactant(s) at higher pressure (≥5 bars) is important for fundamental understanding of catalytic reactions performed on these catalyst nanoparticles. Most structural characterizations of a catalyst performing catalysis in liquid at high temperature under gas phase at high pressure were performed in an ex situ condition in terms of characterizations before or after catalysis since, from technical point of view, access to the catalyst nanoparticles during catalysis in liquid phase at high temperature under high pressure reactant gas is challenging. Here we designed a reactor which allows us to perform structural characterization using X-ray absorption spectroscopy including X-ray absorption near edge structure spectroscopy and extended X-ray absorption fine structure spectroscopy to study catalyst nanoparticles under harsh catalysis conditions in terms of liquid up to 350 °C under gas phase with a pressure up to 50 bars. This reactor remains nanoparticles of a catalyst homogeneously dispersed in liquid during catalysis and X-ray absorption spectroscopy characterization.

  4. Preparation of highly dispersed Ru-Sn bimetallic supported catalysts from the single source precursors Cp(PPh32Ru-SnX3 (X = Cl or Br

    Directory of Open Access Journals (Sweden)

    Ana Cláudia Bernardes Silva

    2003-06-01

    Full Text Available In this work highly dispersed Ru-Sn bimetallic catalysts have been prepared from organobimetallic Cp(PPh32Ru-SnX3 (X = Cl or Br complexes. These single source precursors can be easily impregnated in high surface area supports, such as activated carbon and sol-gel SiO2, and upon controlled thermal treatment the ligands are released as volatile products resulting in the formation of the bimetallic system Ru-Sn. Catalytic reactions, such as hydrodechlorination of CCl4 and chlorobenzene and TPR (Temperature Programmed Reduction experiments carried out with these RuSn catalysts suggested a strong interaction between Ruthenium and Tin. Mössbauer measurements showed that these materials when exposed to air are immediately oxidized to form Sn (IV. It was shown that upon controlled reduction conditions with H2 it is possible to reduce selectively Sn to different oxidation states and different phases. The Sn oxidation state showed significant effect on the catalytic hydrogenation of 1,5-cyclooctadiene. The use of these single source precursors with a controlled decomposition/reduction procedure allows the preparation of unique catalysts with an intimate interaction between the components ruthenium and tin and the possibility of varying the Sn oxidation state around the Ru metal.

  5. Zerodur polishing process for high surface quality and high efficiency

    International Nuclear Information System (INIS)

    Tesar, A.; Fuchs, B.

    1992-08-01

    Zerodur is a glass-ceramic composite importance in applications where temperature instabilities influence optical and mechanical performance, such as in earthbound and spaceborne telescope mirror substrates. Polished Zerodur surfaces of high quality have been required for laser gyro mirrors. Polished surface quality of substrates affects performance of high reflection coatings. Thus, the interest in improving Zerodur polished surface quality has become more general. Beyond eliminating subsurface damage, high quality surfaces are produced by reducing the amount of hydrated material redeposited on the surface during polishing. With the proper control of polishing parameters, such surfaces exhibit roughnesses of < l Angstrom rms. Zerodur polishing was studied to recommend a high surface quality polishing process which could be easily adapted to standard planetary continuous polishing machines and spindles. This summary contains information on a polishing process developed at LLNL which reproducibly provides high quality polished Zerodur surfaces at very high polishing efficiencies

  6. Immobilization of Highly Effective Palladium Catalyst onto Poly(4-Vinylpyridine): Synthesis and Characterization

    International Nuclear Information System (INIS)

    Siti Kamilah Che Soh; Intan Shafinass Kassim; Siti Aminah Jusoh; Mustaffa Samsuddin

    2016-01-01

    A commonly known weakness of homogeneous catalysts is the difficulty to recover the active catalyst from the product. Due to the disadvantage, the designing of supported catalyst has been approached to overcome the separation difficulty of the palladium-based homogeneous catalyst. New polymer supported N 2 O 2 metal complex was successfully immobilized by mixing of poly(4-vinylpyridine) with palladium(II) complex in the presence of ethyl acetate as solvent. Then, the reaction was stirred for 72 hours at room temperature to form corresponding P 4 VP-Pd catalyst. The properties of immobilized catalyst were characterized by various techniques such as fourier transform infrared (FTIR), thermogravimetric (TGA), X-ray diffraction (XRD), scanning electron microscopy/ energy dispersive X-ray (SEM/ EDX) and inductively coupled plasma-optical emission (ICP-OES) spectroscopy. (author)

  7. A possible highly active supported Ni dimer catalyst for O{sub 2} dissociation: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Shan [College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007 (China); Zhang, Yanxing, E-mail: 2016025@htu.edu.cn [College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007 (China); Zhang, Xilin; Mao, Jianjun [College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007 (China); Yang, Zongxian, E-mail: yzx@henannu.edu.cn [College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007 (China); Collaborative Innovation Center of Nano Functional Materials and Applications, Henan Province (China)

    2017-04-30

    Graphical abstract: The minimum energy paths (MEPs) for the dissociation process of O{sub 2} on the surfaces of bare YSZ (111) and Ni{sub n}/YSZ (111) (n = 1, 2 and 3). - Highlights: • The catalytic activity of supported metal catalysts is closely related to the size of metal particles. • The dissociation of O{sub 2} on the YSZ (111) surface is largely enhanced by the supported Ni cluster. • The supported Ni dimer is predicted to be the smallest Ni cluster needed for efficient O{sub 2} dissociation. • The results would provide an important reference to improve the activity and efficiency of the Ni/YSZ(111) nanocomposite catalysts in cost-effective materials. - Abstract: The adsorption and dissociation of O{sub 2} on the supported small nickel clusters with one-, two-, three-Ni atoms on yttria-stabilized zirconia (YSZ) (111) surfaces, as well as those on the bare YSZ(111) and Ni(111) surfaces are comparatively studied using ab initio density functional theory calculations. It is found that the dissociation of O{sub 2} on the YSZ(111) surface is largely enhanced by the supported Ni dimer, which is predicted to be the smallest Ni cluster needed for efficient O{sub 2} dissociation. The results would provide an important reference to improve the activity and efficiency of the Ni/YSZ(111) nanocomposite catalysts in cost-effective materials.

  8. Synthesis of a highly active carbon-supported Ir-V/C catalyst for the hydrogen oxidation reaction in PEMFC

    International Nuclear Information System (INIS)

    Li Bing; Qiao Jinli; Yang Daijun; Zheng Junsheng; Ma Jianxin; Zhang Jiujun; Wang Haijiang

    2009-01-01

    The active, carbon-supported Ir and Ir-V nanoclusters with well-controlled particle size, dispersity, and composition uniformity, have been synthesized via an ethylene glycol method using IrCl 3 and NH 4 VO 3 as the Ir and V precursors. The nanostructured catalysts were characterized by X-ray diffraction and high-resolution transmission electron microscopy. The catalytic activities of these carbon-supported nanoclusters were screened by applying on-line cyclic voltammetry and electrochemical impedance spectroscopy techniques, which were used to characterize the electrochemical properties of fuel cells using several anode Ir/C and Ir-V/C catalysts. It was found that Ir/C and Ir-V/C catalysts affect the performance of electrocatalysts significantly based on the discharge characteristics of the fuel cell. The catalyst Ir-V/C at 40 wt.% displayed the highest catalytic activity to hydrogen oxidation reaction and, therefore, high cell performance is achieved which results in a maximum power density of 563 mW cm -2 at 0.512 V and 70 deg. C in a real H 2 /air fuel cell. This performance is 20% higher as compared to the commercial available Pt/C catalyst. Fuel cell life test at a constant current density of 1000 mA cm -2 in a H 2 /O 2 condition shows good stability of anode Ir-V/C after 100 h of continuous operation.

  9. Sputtered catalysts

    International Nuclear Information System (INIS)

    Tyerman, W.J.R.

    1978-01-01

    A method is described for preparing a supported catalyst by a sputtering process. A material that is catalytic, or which is a component of a catalytic system, is sputtered on to the surface of refractory oxide particles that are compatible with the sputtered material and the sputtered particles are consolidated into aggregate form. The oxide particles before sputtering should have a diameter in the range 1000A to 50μ and a porosity less than 0.4 ml/g, and may comprise MgO, Al 2 O 3 or SiO 2 or mixtures of these oxides, including hydraulic cement. The particles may possess catalytic activity by themselves or in combination with the catalytic material deposited on them. Sputtering may be effected epitaxially and consolidation may be effected by compaction pelleting, extrusion or spray drying of a slurry. Examples of the use of such catalysts are given. (U.K.)

  10. Application of a mixed metal oxide catalyst to a metallic substrate

    Science.gov (United States)

    Sevener, Kathleen M. (Inventor); Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Wisner, Daniel L. (Inventor)

    2009-01-01

    A method for applying a mixed metal oxide catalyst to a metallic substrate for the creation of a robust, high temperature catalyst system for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in propulsion systems. The method begins by forming a prepared substrate material consisting of a metallic inner substrate and a bound layer of a noble metal intermediate. Alternatively, a bound ceramic coating, or frit, may be introduced between the metallic inner substrate and noble metal intermediate when the metallic substrate is oxidation resistant. A high-activity catalyst slurry is applied to the surface of the prepared substrate and dried to remove the organic solvent. The catalyst layer is then heat treated to bind the catalyst layer to the surface. The bound catalyst layer is then activated using an activation treatment and calcinations to form the high-activity catalyst system.

  11. Surface modification of g-C3N4 by hydrazine: Simple way for noble-metal free hydrogen evolution catalysts

    KAUST Repository

    Chen, Yin

    2015-11-02

    The graphitic carbon nitride (g-C3N4) usually is thought to be an inert material and it’s difficult to have the surface terminated NH2 groups functionalized. By modifying the g-C3N4 surface with hydrazine, the diazanyl group was successfully introduced onto the g-C3N4 surface, which allows the introduction with many other function groups. Here we illustrated that by reaction of surface hydrazine group modified g-C3N4 with CS2 under basic condition, a water electrolysis active group C(=S)SNi can be implanted on the g-C3N4 surface, and leads to a noble metal free hydrogen evolution catalyst. This catalyst has 40% hydrogen evolution efficiency compare to the 3 wt% Pt photo precipitated g-C3N4, with only less than 0.2 wt% nickel.

  12. Surface modification of g-C3N4 by hydrazine: Simple way for noble-metal free hydrogen evolution catalysts

    KAUST Repository

    Chen, Yin; Lin, Bin; Wang, Hong; Yang, Yong; Zhu, Haibo; Yu, Weili; Basset, Jean-Marie

    2015-01-01

    The graphitic carbon nitride (g-C3N4) usually is thought to be an inert material and it’s difficult to have the surface terminated NH2 groups functionalized. By modifying the g-C3N4 surface with hydrazine, the diazanyl group was successfully introduced onto the g-C3N4 surface, which allows the introduction with many other function groups. Here we illustrated that by reaction of surface hydrazine group modified g-C3N4 with CS2 under basic condition, a water electrolysis active group C(=S)SNi can be implanted on the g-C3N4 surface, and leads to a noble metal free hydrogen evolution catalyst. This catalyst has 40% hydrogen evolution efficiency compare to the 3 wt% Pt photo precipitated g-C3N4, with only less than 0.2 wt% nickel.

  13. Highly selective hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C3N4 nanosheets catalysts in water

    OpenAIRE

    Chen, Xiufang; Zhang, Ligang; Zhang, Bo; Guo, Xingcui; Mu, Xindong

    2016-01-01

    Graphitic carbon nitride nanosheets were investigated for developing effective Pt catalyst supports for selective hydrogenation of furfural to furfuryl alcohol in water. The nanosheets with an average thickness of about 3 nm were synthesized by a simple and green method through thermal oxidation etching of bulk g-C3N4 in air. Combined with the unique feature of nitrogen richness and locally conjugated structure, the g-C3N4 nanosheets with a high surface area of 142?m2 g?1 were demonstrated to...

  14. Transition Metal Phosphide Nanoparticles Supported on SBA-15 as Highly Selective Hydrodeoxygenation Catalysts for the Production of Advanced Biofuels.

    Science.gov (United States)

    Yang, Yongxing; Ochoa-Hernández, Cristina; de la Peña O'Shea, Víctor A; Pizarro, Patricia; Coronado, Juan M; Serrano, David P

    2015-09-01

    A series of catalysts constituted by nanoparticles of transition metal (M = Fe, Co, Ni and Mo) phosphides (TMP) dispersed on SBA-15 were synthesized by reduction of the corresponding metal phosphate precursors previously impregnated on the mesostructured support. All the samples contained a metal-loading of 20 wt% and with an initial M/P mole ratio of 1, and they were characterized by X-ray diffraction (XRD), N2 sorption, H2-TPR and transmission electron microscopy (TEM). Metal phosphide nanocatalysts were tested in a high pressure continuous flow reactor for the hydrodeoxygenation (HDO) of a methyl ester blend containing methyl oleate (C17H33-COO-CH3) as main component (70%). This mixture constitutes a convenient surrogate of triglycerides present in vegetable oils, and following catalytic hydrotreating yields mainly n-alkanes. The results of the catalytic assays indicate that Ni2P/SBA-15 catalyst presents the highest ester conversion, whereas the transformation rate is about 20% lower for MoP/SBA-15. In contrast, catalysts based on Fe and Co phosphides show a rather limited activity. Hydrocarbon distribution in the liquid product suggests that both hydrodeoxygenation and decarboxylation/decarbonylation reactions occur simultaneously over the different catalysts, although MoP/SBA-15 possess a selectivity towards hydrodeoxygenation exceeding 90%. Accordingly, the catalyst based on MoP affords the highest yield of n-octadecane, which is the preferred product in terms of carbon atom economy. Subsequently, in order to conjugate the advantages of both Ni and Mo phosphides, a series of catalysts containing variable proportions of both metals were prepared. The obtained results reveal that the mixed phosphides catalysts present a catalytic behavior intermediate between those of the monometallic phosphides. Accordingly, only marginal enhancement of the yield of n-octadecane is obtained for the catalysts with a Mo/Ni ratio of 3. Nevertheless, owing to this high selectivity

  15. High Friction Surface Treatments, Transportation Research Synthesis

    Science.gov (United States)

    2018-03-01

    MnDOT and local transportation agencies in Minnesota are considering the use of a high friction surface treatment (HFST) as a safety strategy. HFST is used as a spot pavement surfacing treatment in locations with high friction demand (for example, cr...

  16. Nannochloropsis algae pyrolysis with ceria-based catalysts for production of high-quality bio-oils.

    Science.gov (United States)

    Aysu, Tevfik; Sanna, Aimaro

    2015-10-01

    Pyrolysis of Nannochloropsis was carried out in a fixed-bed reactor with newly prepared ceria based catalysts. The effects of pyrolysis parameters such as temperature and catalysts on product yields were investigated. The amount of bio-char, bio-oil and gas products, as well as the compositions of the resulting bio-oils was determined. The results showed that both temperature and catalyst had significant effects on conversion of Nannochloropsis into solid, liquid and gas products. The highest bio-oil yield (23.28 wt%) and deoxygenation effect was obtained in the presence of Ni-Ce/Al2O3 as catalyst at 500°C. Ni-Ce/Al2O3 was able to retain 59% of the alga starting energy in the bio-oil, compared to only 41% in absence of catalyst. Lower content of acids and oxygen in the bio-oil, higher aliphatics (62%), combined with HHV show promise for production of high-quality bio-oil from Nannochloropsis via Ni-Ce/Al2O3 catalytic pyrolysis. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Electrocatalytic properties of carbon-supported Pt-Ru catalysts with the high alloying degree for formic acid electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu.; Zhou, Yiming; Tang, Yawen; Lu, Tianhong [College of Chemistry and Environmental Science, Nanjing Normal University, Nanjing 210097 (China)

    2010-07-01

    A series of carbon-supported bimetallic Pt-Ru catalysts with high alloying degree and different Pt/Ru atomic ratio have been prepared by a chemical reduction method in the H{sub 2}O/ethanol/tetrahydrofuran (THF) mixture solvent. The structural and electronic properties of catalysts are characterized using X-ray reflection (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). The electrooxidation of formic acid on these Pt-Ru nanoparticles are investigated by using cyclic voltammetry, chronoamperometry and CO-stripping measurements. The results of electrochemical measurements illustrate that the alloying degree and Pt/Ru atomic ratio of Pt-Ru catalyst play an important role in the electrocatalytic activity of the Pt-Ru/C catalyst for formic acid electrooxidation due to the bifunctional mechanism and the electronic effect. Since formic acid is an intermediate in the methanol electrooxidation on Pt electrode in acidic electrolyte, the observation provides an additional fundamental understanding of the structure-activity relationship of Pt-Ru catalyst for methanol electrooxidation. (author)

  18. Highly Efficient Gas-Phase Oxidation of Renewable Furfural to Maleic Anhydride over Plate Vanadium Phosphorus Oxide Catalyst.

    Science.gov (United States)

    Li, Xiukai; Ko, Jogie; Zhang, Yugen

    2018-02-09

    Maleic anhydride (MAnh) and its acids are critical intermediates in chemical industry. The synthesis of maleic anhydride from renewable furfural is one of the most sought after processes in the field of sustainable chemistry. In this study, a plate vanadium phosphorus oxide (VPO) catalyst synthesized by a hydrothermal method with glucose as a green reducing agent catalyzes furfural oxidation to MAnh in the gas phase. The plate catalyst-denoted as VPO HT -has a preferentially exposed (200) crystal plane and exhibited dramatically enhanced activity, selectivity and stability as compared to conventional VPO catalysts and other state-of-the-art catalytic systems. At 360 °C reaction temperature with air as an oxidant, about 90 % yield of MAnh was obtained at 10 vol % of furfural in the feed, a furfural concentration value that is much higher than those (<2 vol %) reported for other catalytic systems. The catalyst showed good long-term stability and there was no decrease in activity or selectivity for MAnh during the time-on-stream of 25 h. The high efficiency and catalyst stability indicate the great potential of this system for the synthesis of maleic anhydride from renewable furfural. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. SUPPORTED LIQUID CATALYSTS FOR REMOVAL OF HIGH TEMPERATURE FUEL CELL CONTAMINANTS

    Energy Technology Data Exchange (ETDEWEB)

    Alan W. Weimer (PI); Peter Czerpak; Patrick Hilbert

    2000-01-01

    A novel catalytic synthesis gas oxidation process using molten carbonate salts supported on compatible fluidized iron oxide particles (supported-liquid-phase-catalyst (SLPC) fluidized bed process) was investigated. This process combines the advantages of large scale fluidized bed processing with molten salt bath oxidation. Molten salt catalysts can be supported within porous fluidized particles in order to improve mass transfer rates between the liquid catalysts and the reactant gases. Synthesis gas can be oxidized at reduced temperatures resulting in low NO{sub x} formation while trace sulfides and halides are captured in-situ. Hence, catalytic oxidation of synthesis gas can be carried out simultaneously with hot gas cleanup. Such SLPC fluidized bed processes are affected by inter-particle liquid capillary forces that may lead to agglomeration and de-fluidization of the bed. An understanding of the origin and strength of these forces is needed so that they can be overcome in practice. Process design is based on thermodynamic free energy minimization calculations that indicate the suitability of eutectic Na{sub 2}CO{sub 3}/K{sub 2}CO{sub 3} mixtures for capturing trace impurities in-situ (< 1 ppm SO{sub x} released) while minimizing the formation of NO{sub x}(< 10 ppm). Iron oxide has been identified as a preferred support material since it is non-reactive with sodium, is inexpensive, has high density (i.e. inertia), and can be obtained in various particle sizes and porosities. Force balance modeling has been used to design a surrogate ambient temperature system that is hydrodynamically similar to the real system, thus allowing complementary investigation of the governing fluidization hydrodynamics. The primary objective of this research was to understand the origin of and to quantify the liquid capillary interparticle forces affecting the molten carbonate SLPC fluidized bed process. Substantial theoretical and experimental exploratory results indicate process

  20. Adsorption of CO on Ru and Pt blacks and catalysts and the possibility of its utilization for the determination of the ruthenium-free surface

    Czech Academy of Sciences Publication Activity Database

    Paseka, Ivo

    2007-01-01

    Roč. 11, č. 1 (2007), s. 52-58 ISSN 1432-8488 R&D Projects: GA ČR(CZ) GA104/03/0409 Institutional research plan: CEZ:AV0Z40320502 Keywords : hydrogen/ carbon monoxide adsorption * platinum/ruthenium catalysts * specific surface Subject RIV: CA - Inorganic Chemistry Impact factor: 1.535, year: 2007

  1. Surface Catalytic Sites Prepared from [HRe(CO)5] and [H3Re3(CO)12]: Mononuclear, Trinuclear, and Metallic Rhenium Catalysts Supported on Magnesia.

    NARCIS (Netherlands)

    Koningsberger, D.C.; Kirlin, P.S.; Zon, F.B.M. van; Gates, B.C.

    1990-01-01

    MgO-supported catalysts were prepared from [HRe(CO)5] and [H,Re3(CO),,] and characterized by extraction of surface organometallics, infrared and ultraviolet/visible spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The EXAFS analysis and other data show that

  2. Enabling Highly Effective Boiling from Superhydrophobic Surfaces

    Science.gov (United States)

    Allred, Taylor P.; Weibel, Justin A.; Garimella, Suresh V.

    2018-04-01

    A variety of industrial applications such as power generation, water distillation, and high-density cooling rely on heat transfer processes involving boiling. Enhancements to the boiling process can improve the energy efficiency and performance across multiple industries. Highly wetting textured surfaces have shown promise in boiling applications since capillary wicking increases the maximum heat flux that can be dissipated. Conversely, highly nonwetting textured (superhydrophobic) surfaces have been largely dismissed for these applications as they have been shown to promote formation of an insulating vapor film that greatly diminishes heat transfer efficiency. The current Letter shows that boiling from a superhydrophobic surface in an initial Wenzel state, in which the surface texture is infiltrated with liquid, results in remarkably low surface superheat with nucleate boiling sustained up to a critical heat flux typical of hydrophilic wetting surfaces, and thus upends this conventional wisdom. Two distinct boiling behaviors are demonstrated on both micro- and nanostructured superhydrophobic surfaces based on the initial wetting state. For an initial surface condition in which vapor occupies the interstices of the surface texture (Cassie-Baxter state), premature film boiling occurs, as has been commonly observed in the literature. However, if the surface texture is infiltrated with liquid (Wenzel state) prior to boiling, drastically improved thermal performance is observed; in this wetting state, the three-phase contact line is pinned during vapor bubble growth, which prevents the development of a vapor film over the surface and maintains efficient nucleate boiling behavior.

  3. Effect of Electric Discharge on Properties of Nano-Particulate Catalyst for Plasma-Catalysis.

    Science.gov (United States)

    Lee, Chung Jun; Kim, Jip; Kim, Taegyu

    2016-02-01

    Heterogeneous catalytic processes have been used to produce hydrogen from hydrocarbons. However, high reforming temperature caused serious catalyst deteriorations and low energy efficiency. Recently, a plasma-catalyst hybrid process was used to reduce the reforming temperature and to improve the stability and durability of reforming catalysts. Effect of electric discharges on properties of nanoparticulate catalysts for plasma-catalysis was investigated in the present study. Catalyst-bed porosity was varied by packing catalyst beads with the different size in a reactor. Discharge power and onset voltage of the plasma were measured as the catalyst-bed porosity was varied. The effect of discharge voltage, frequency and voltage waveforms such as the sine, pulse and square was investigated. We found that the optimal porosity of the catalyst-bed exists to maximize the electric discharge. At a low porosity, the electric discharge was unstable to be sustained because the space between catalysts got narrow nearly close to the sheath region. On the other hand, at a high porosity, the electric discharge became weak because the plasma was not sufficient to interact with the surface of catalysts. The discharge power increased as the discharge voltage and frequency increased. The square waveform was more efficient than the sine and pulse one. At a high porosity, however, the effect of the voltage waveform was not considerable because the space between catalysts was too large for plasma to interact with the surface of catalysts.

  4. Complex catalysts from self-repairing ensembles to highly reactive air-based oxidation systems

    Science.gov (United States)

    Craig L. Hill; Laurent Delannoy; Dean C. Duncan; Ira A. Weinstock; Roman F. Renneke; Richard S. Reiner; Rajai H. Atalla; Jong Woo Han; Daniel A. Hillesheim; Rui Cao; Travis M. Anderson; Nelya M. Okun; Djamaladdin G. Musaev; Yurii V. Geletii

    2007-01-01

    Progress in four interrelated catalysis research efforts in our laboratory are summarized: (1) catalytic photochemical functionalization of unactivated CeH bonds by polyoxometalates (POMs); (2) self-repairing catalysts; (3) catalysts for air-based oxidations under ambient conditions; and (4) terminal oxo complexes of the late-transition metal elements and their...

  5. A NEW TYPE OF HIGHLY-ACTIVE POLYMER-BOUND RHODIUM HYDROFORMYLATION CATALYST

    NARCIS (Netherlands)

    JONGSMA, T; KIMKES, P; CHALLA, G; VANLEEUWEN, PWNM

    1992-01-01

    A new route of attaching phosphites to a (co)polymer chain is described. These copolymers are used for the preparation of a rhodium phosphite hydroformylation catalyst. The catalytic activity of this polymer-bound system is identical to that of the low molecular weight analogue. The catalysts show a

  6. Nanostructured composite TiO{sub 2}/carbon catalysts of high activity for dehydration of n-butanol

    Energy Technology Data Exchange (ETDEWEB)

    Cyganiuk, Aleksandra [Faculty of Chemistry, Nicolaus Copernicus University, 87-100 Torun (Poland); Klimkiewicz, Roman [Institute of Low Temperature and Structure Research PAN, 50-422 Wroclaw (Poland); Bumajdad, Ali [Faculty of Science, Kuwait University, PO Box 5969 Safat, Kuwait 13060 (Kuwait); Ilnicka, Anna [Faculty of Chemistry, Nicolaus Copernicus University, 87-100 Torun (Poland); Lukaszewicz, Jerzy P., E-mail: jerzy_lukaszewicz@o2.pl [Faculty of Chemistry, Nicolaus Copernicus University, 87-100 Torun (Poland)

    2015-08-15

    Highlights: • New biotechnological method for fabrication of composite catalysts. • In situ synthesis of nanosized TiO{sub 2} clusters in the carbon matrix. • High dispersion of TiO{sub 2} in carbon matrix. • High catalytic activity achieved for very low active phase content. • Efficient dehydration of n-butanol to butane-1. - Abstract: A novel method of wood impregnation with titanium ions is presented. Titanium(IV) ions were complexed to peroxo/hydroxo complexes which were obtained by treating a TiCl{sub 4} water solution with H{sub 2}O{sub 2}. The solution of chelated titanium ions was used for the impregnation of living stems of Salix viminalis wood. Saturated stems were carbonized at 600–800 °C, yielding a microporous carbon matrix, in which nanoparticles of TiO{sub 2} were uniformly distributed. A series of composite TiO{sub 2}–carbon catalysts was manufactured and tested in the process of n-butanol conversion to butane-1. The composite catalysts exhibited very high selectivity (ca. 80%) and yield (ca. 30%) despite a low content of titanium (ca. 0.5% atomic). The research proved that the proposed functionalization led to high dispersion of the catalytic phase (TiO{sub 2}), which played a crucial role in the catalyst performance. High dispersion of TiO{sub 2} was achieved due to a natural transport of complexed titanium ions in living plant stems.

  7. Sulfonated reduced graphene oxide as a highly efficient catalyst for direct amidation of carboxylic acids with amines using ultrasonic irradiation.

    Science.gov (United States)

    Mirza-Aghayan, Maryam; Tavana, Mahdieh Molaee; Boukherroub, Rabah

    2016-03-01

    Sulfonated reduced graphene oxide nanosheets (rGO-SO3H) were prepared by grafting sulfonic acid-containing aryl radicals onto chemically reduced graphene oxide (rGO) under sonochemical conditions. rGO-SO3H catalyst was characterized by Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). rGO-SO3H catalyst was successfully applied as a reusable solid acid catalyst for the direct amidation of carboxylic acids with amines into the corresponding amides under ultrasonic irradiation. The direct sonochemical amidation of carboxylic acid takes place under mild conditions affording in good to high yields (56-95%) the corresponding amides in short reaction times. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Efficient Pd@MIL-101(Cr) hetero-catalysts for 2-butyne-1,4-diol hydrogenation exhibiting high selectivity

    KAUST Repository

    Yin, Dongdong

    2017-01-05

    Pd@MIL-101(Cr) hetero-catalysts have been successfully prepared using the metal-organic chemical vapour deposition (MOCVD) approach, by choosing [Pd(η-CH)(η-CH)] as a volatile precursor, and the hydrothermally stable metal-organic framework, MIL-101(Cr) as a support. The prepared Pd@MIL-101(Cr) hetero-catalysts characterized with various analytical techniques, exhibited highly monodispersed immobilized Pd nanoparticles in the MIL-101(Cr) cavities, while retaining the pristine crystallinity and porosity. The intact hybrid Pd@MIL-101(Cr) has been demonstrated to be an efficient catalyst for 2-butyne-1,4-diol hydrogenation with excellent activity, stability and selectivity (2-butene-1,4-diol (>94%)).

  9. Tacticities study of high poly-α-olefins, from poly-1-hexene to poly-1-octadecene, obtained with metallocenes catalysts

    International Nuclear Information System (INIS)

    Silva, Luciano F. da; Galland, Griselda B.

    2003-01-01

    High poly-α-olefins such as poly-1-hexene, poly-1-octene, poly-1-decene, poly-1-dodecene, poly-1-tetradecene, poly-1-hexadecene and poly-1-octadecene were obtained with the homogeneous iso specific catalyst rac-Et[Ind]ZrCl 2 /MAO and with the homogeneous syndiospecific catalyst Me 2 C[Cp(9-Flu)]ZrCl 2 /MAO at the polymerization temperatures of 0 deg C, 30 deg C and 60 deg C. The polymers were analyzed by 13 C NMR to study the influence of the α - olefins sizes, the catalysts type and the polymerization temperatures in their tacticities. The stereospecific control of both catalytic systems decreased with the increase of the reaction temperature and with the α-olefin size. (author)

  10. High-performance bimetallic alloy catalyst using Ni and N co-doped composite carbon for the oxygen electro-reduction.

    Science.gov (United States)

    Jung, Won Suk

    2018-03-15

    In this study, a novel synthesis method for the bimetallic alloy catalyst is reported, which is subsequently used as an oxygen reduction catalyst in polymer electrolyte membrane fuel cells (PEMFCs). The support prepared from the Ni-chelate complex shows a mesoporous structure with a specific surface area of ca. 400 m 2  g -1 indicating the suitable support for PEMFC applications. Ethylenediamine is converted to the nitrogen and carbon layers to protect the Ni particles which will diffuse into the Pt lattice at 800 °C. The PtNi/NCC catalyst with PtNi cores and Pt-rich shells is successfully formed when acid-treated as evidenced by line scan profiles. The catalyst particles thus synthesized are well-dispersed on the N-doped carbon support, while the average particle size is ca. 3 nm. In the PEMFC test, the maximum power density of the PtNi/NCC catalyst shows approximately 25% higher than that of the commercial Pt/C catalyst. The mass activity of the PtNi/NCC catalyst showed approximately 3-fold higher than that of the commercial Pt/C catalyst. The mass activity strongly depends on the ratio of Pt to Ni since the strain effect can be strong for catalysts due to the mismatch of lattice parameters of the Ni and Pt. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Spatially and size selective synthesis of Fe-based nanoparticles on ordered mesoporous supports as highly active and stable catalysts for ammonia decomposition.

    Science.gov (United States)

    Lu, An-Hui; Nitz, Joerg-Joachim; Comotti, Massimiliano; Weidenthaler, Claudia; Schlichte, Klaus; Lehmann, Christian W; Terasaki, Osamu; Schüth, Ferdi

    2010-10-13

    Uniform and highly dispersed γ-Fe(2)O(3) nanoparticles with a diameter of ∼6 nm supported on CMK-5 carbons and C/SBA-15 composites were prepared via simple impregnation and thermal treatment. The nanostructures of these materials were characterized by XRD, Mössbauer spectroscopy, XPS, SEM, TEM, and nitrogen sorption. Due to the confinement effect of the mesoporous ordered matrices, γ-Fe(2)O(3) nanoparticles were fully immobilized within the channels of the supports. Even at high Fe-loadings (up to about 12 wt %) on CMK-5 carbon no iron species were detected on the external surface of the carbon support by XPS analysis and electron microscopy. Fe(2)O(3)/CMK-5 showed the highest ammonia decomposition activity of all previously described Fe-based catalysts in this reaction. Complete ammonia decomposition was achieved at 700 °C and space velocities as high as 60,000 cm(3) g(cat)(-1) h(-1). At a space velocity of 7500 cm(3) g(cat)(-1) h(-1), complete ammonia conversion was maintained at 600 °C for 20 h. After the reaction, the immobilized γ-Fe(2)O(3) nanoparticles were found to be converted to much smaller nanoparticles (γ-Fe(2)O(3) and a small fraction of nitride), which were still embedded within the carbon matrix. The Fe(2)O(3)/CMK-5 catalyst is much more active than the benchmark NiO/Al(2)O(3) catalyst at high space velocity, due to its highly developed mesoporosity. γ-Fe(2)O(3) nanoparticles supported on carbon-silica composites are structurally much more stable over extended periods of time but less active than those supported on carbon. TEM observation reveals that iron-based nanoparticles penetrate through the carbon layer and then are anchored on the silica walls, thus preventing them from moving and sintering. In this way, the stability of the carbon-silica catalyst is improved. Comparison with the silica supported iron oxide catalyst reveals that the presence of a thin layer of carbon is essential for increased catalytic activity.

  12. CuNi NPs supported on MIL-101 as highly active catalysts for the hydrolysis of ammonia borane

    Science.gov (United States)

    Gao, Doudou; Zhang, Yuhong; Zhou, Liqun; Yang, Kunzhou

    2018-01-01

    The catalysts containing Cu, Ni bi-metallic nanoparticles were successfully synthesized by in-situ reduction of Cu2+ and Ni2+ salts into the highly porous and hydrothermally stable metal-organic framework MIL-101 via a simple liquid impregnation method. When the total amount of loading metal is 3 × 10-4 mol, Cu2Ni1@MIL-101 catalyst shows higher catalytic activity comparing to CuxNiy@MIL-101 with different molar ratio of Cu and Ni (x, y = 0, 0.5, 1.5, 2, 2.5, 3). Cu2Ni1@MIL-101 catalyst has the highest catalytic activity comparing to mono-metallic Cu and Ni counterparts and pure bi-metallic CuNi nanoparticles in hydrolytic dehydrogeneration of ammonia borane (AB) at room temperature. Additionally, in the hydrolysis reaction, the Cu2Ni1@MIL- 101 catalyst possesses excellent catalytic performances, which exhibit highly catalytic activity with turn over frequency (TOF) value of 20.9 mol H2 min-1 Cu mol-1 and a very low activation energy value of 32.2 kJ mol-1. The excellent catalytic activity has been successfully achieved thanks to the strong bi-metallic synergistic effects, uniform distribution of nanoparticles and the bi-functional effects between CuNi nanoparticles and the host of MIL-101. Moreover, the catalyst also displays satisfied durable stability after five cycles for the hydrolytically releasing H2 from AB. The non-noble metal catalysts have broad prospects for commercial applications in the field of hydrogen-stored materials due to the low prices and excellent catalytic activity.

  13. Biomass to fuels : Upgrading of flash pyrolysis oil by reactive distillation using a high boiling alcohol and acid catalysts

    NARCIS (Netherlands)

    Mahfud, F.H.; Melian Cabrera, I.V.; Manurung, R.M.; Heeres, H.J.

    We here report our studies on the upgrading of flash pyrolysis oil using an improved alcohol treatment method. The method consists of treating pyrolysis oil with a high boiling alcohol like n-butanol in the presence of a (solid) acid catalyst at 323-353 K under reduced pressure (<10 kPa). Using this

  14. Effect of Surface Modification by Chelating Agents on Fischer- Tropsch Performance of Co/SiO{sub 2} Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Bambal, Ashish S.; Kugler, Edwin L.; Gardner, Todd H.; Dadyburjor, Dady B.

    2013-11-14

    The silica support of a Co-based catalyst for Fischer-Tropsch (FT) synthesis was modified by the chelating agents (CAs) nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA). After the modification, characterization of the fresh and spent catalysts show reduced crystallite sizes, a better-dispersed Co₃O₄ phase on the calcined samples, and increased metal dispersions for the reduced samples. The CA-modified catalysts display higher CO conversions, product yields, reaction rates and rate constants. The improved FT performance of CA-modified catalysts is attributed to the formation of stable complexes with Co. The superior performance of the EDTA-modified catalyst in comparison to the NTA-modified catalyst is due to the higher affinity of the former for complex formation with Co ions.

  15. Direct Observation of Molecular Preorganization for Chirality Transfer on a Catalyst Surface

    DEFF Research Database (Denmark)

    Demers-Carpentier, Vincent; Goubert,, Guillaume; Masini, Federico

    2011-01-01

    The chemisorption of specific optically active compounds on metal surfaces can create catalytically active chirality transfer sites. However, the mechanism through which these sites bias the stereoselectivity of reactions (typically hydrogenations) is generally assumed to be so complex that conti......The chemisorption of specific optically active compounds on metal surfaces can create catalytically active chirality transfer sites. However, the mechanism through which these sites bias the stereoselectivity of reactions (typically hydrogenations) is generally assumed to be so complex...... functional theory calculations reveals the stereodirecting forces governing preorganization into precise chiral modifier-substrate bimolecular surface complexes. The study shows that the chiral modifier induces prochiral switching on the surface and that different prochiral ratios prevail at different...

  16. Surface structure and reaction property of CuCl2-PdCl2 bimetallic catalyst in methanol oxycarbonylation: A DFT approach

    International Nuclear Information System (INIS)

    Meng, Qingsen; Wang, Shengping; Shen, Yongli; Yan, Bing; Wu, Yuanxin; Ma, Xinbin

    2014-01-01

    Surface structure of CuCl 2 -PdCl 2 bimetallic catalyst (Wacker-type catalyst) was built employing density functional theory (DFT) calculations, and the reaction mechanism of methanol oxycarbonylation over the CuCl 2 -PdCl 2 surfaces was also investigated. On the CuCl 2 -PdCl 2 surface, the active site for methanol oxidation was confirmed as Cu-Cl-Cu (Pd). Comparing with pure CuCl 2 surface, the introduction of Pd atom causes the electron repopulation on the surface and lowers the energy barrier for methanol oxidation, but the number of the active site decreases with the increasing of Pd doping volume. Agreed with previous experimental results, the Pd site is most favorable for the CO insertion, indicated by the lowest activation barrier for the formation of COOCH 3 on Pd atom. The lowest energy barrier for the formation of DMC appears when COOCH 3 species adsorbed on Pd atom and methoxyl adsorbed on Cu atoms, which is 0.42 eV. Finally, the reconstruction of the unsaturated surface is a spontaneous and exothermic process. Comparing with other surfaces, the rate-limiting step, methanol oxidation, on CuCl 2 -PdCl 2 surface with Pd/Cu = 1:17 has the lowest energy barrier, which is agreed with the experimental observation that PdCl 2 -CuCl 2 catalyst with Pd/Cu = 1:20 has the favorable activity. The adsorbed methoxyl will further lower the activation barrier of methanol oxidation, which is agreed with experimental observation that the Wacker-type catalysts have an induction period in the methanol oxidative carbonylation system.

  17. Surface structure and reaction property of CuCl{sub 2}-PdCl{sub 2} bimetallic catalyst in methanol oxycarbonylation: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Qingsen [Key Laboratory for Green Chemical Technology of Ministry of Education, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Wang, Shengping, E-mail: spwang@tju.edu.cn [Key Laboratory for Green Chemical Technology of Ministry of Education, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Shen, Yongli; Yan, Bing [Key Laboratory for Green Chemical Technology of Ministry of Education, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Wu, Yuanxin [School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073 (China); Ma, Xinbin [Key Laboratory for Green Chemical Technology of Ministry of Education, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2014-02-15

    Surface structure of CuCl{sub 2}-PdCl{sub 2} bimetallic catalyst (Wacker-type catalyst) was built employing density functional theory (DFT) calculations, and the reaction mechanism of methanol oxycarbonylation over the CuCl{sub 2}-PdCl{sub 2} surfaces was also investigated. On the CuCl{sub 2}-PdCl{sub 2} surface, the active site for methanol oxidation was confirmed as Cu-Cl-Cu (Pd). Comparing with pure CuCl{sub 2} surface, the introduction of Pd atom causes the electron repopulation on the surface and lowers the energy barrier for methanol oxidation, but the number of the active site decreases with the increasing of Pd doping volume. Agreed with previous experimental results, the Pd site is most favorable for the CO insertion, indicated by the lowest activation barrier for the formation of COOCH{sub 3} on Pd atom. The lowest energy barrier for the formation of DMC appears when COOCH{sub 3} species adsorbed on Pd atom and methoxyl adsorbed on Cu atoms, which is 0.42 eV. Finally, the reconstruction of the unsaturated surface is a spontaneous and exothermic process. Comparing with other surfaces, the rate-limiting step, methanol oxidation, on CuCl{sub 2}-PdCl{sub 2} surface with Pd/Cu = 1:17 has the lowest energy barrier, which is agreed with the experimental observation that PdCl{sub 2}-CuCl{sub 2} catalyst with Pd/Cu = 1:20 has the favorable activity. The adsorbed methoxyl will further lower the activation barrier of methanol oxidation, which is agreed with experimental observation that the Wacker-type catalysts have an induction period in the methanol oxidative carbonylation system.

  18. Volume 1, 1st Edition, Multiscale Tailoring of Highly Active and Stable Nanocomposite Catalysts, Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Veser, Goetz

    2009-08-31

    wealth of literature on the formation of mesoporous silica materials motivated investigations of nanocomposite silica catalysts. High surface area silicas are synthesized via sol-gel methods, and the addition of metal-salts lead to the formation of stable nanocomposite Ni- and Fe- silicates. The results of these investigations have increased the fundamental understanding and improved the applicability of nanocatalysts for clean energy applications.

  19. A novel hybrid catalyst for the esterification of high FFA in Jatropha oil for biodiesel production

    International Nuclear Information System (INIS)

    Mushtaq, M.; Tan, I.M.; Sagir, M.; Suleman Tahir, M.; Pervaiz, M.

    2016-01-01

    The synthesis and application of a hybrid catalyst for the esterification of free fatty acids (FFA) in Jatropha oil is reported. Three catalysts, namely silica sulfuric acid, silica supported boron trifluoride and a combination of the two in the weight ratio of 1:1, the hybrid catalyst, were investigated. Jatropha oil samples with a wide range of FFA values i.e. 6.64 to 45.64% were prepared and utilized for the experimental work. This study revealed that silica sulfuric acid and silica supported boron trifluoride were not very effective when used independently. However, a strong synergistic effect was noted in the catalytic activity of the hybrid catalyst which reduced the FFA value from 45.64 to 0.903% with a conversion efficiency of 98%. Reusability of the catalyst was also tested and the results were promising in up to three cycles of use when used with lower amounts of FFA (6.64%) in the oil. Under the influence of the catalyst, the reaction was found to follow first order kinetics. Activation energy was calculated to be 45.42 KJ·mol−1 for 2 wt.% of hybrid catalyst. The products were analyzed by FT-IR and NMR spectroscopic techniques and the results are reported. [es

  20. Atomic layer deposition of highly dispersed Pt nanoparticles on a high surface area electrode backbone for electrochemical promotion of catalysis

    NARCIS (Netherlands)

    Hajar, Y.; di Palma, V.; Kyriakou, V.; Verheijen, M. A.; Baranova, E. A.; Vernoux, P.; Kessels, W. M. M.; Creatore, M.; van de Sanden, M. C. M.; Tsampas, M. N.

    2017-01-01

    A novel catalyst design for electrochemical promotion of catalysis (EPOC) is proposed which overcomes the main bottlenecks that limit EPOC commercialization, i.e., the low dispersion and small surface area of metal catalysts. We have increased the surface area by using a porous composite electrode

  1. Alumina/silica aerogel with zinc chloride as an alkylation catalyst

    Directory of Open Access Journals (Sweden)

    DEJAN U. SKALA

    2001-10-01

    Full Text Available The alumina/silica with zinc chloride aerogel alkylation catalyst was obtained using a one step sol-gel synthesis, and subsequent drying with supercritical carbon dioxide. The aerogel catalyst activity was found to be higher compared to the corresponding xerogel catalyst, as a result of the higher aerogel surface area, total pore volume and favourable pore size distribution. Mixed Al–O–Si bonds were present in both gel catalyst types. Activation by thermal treatment in air was needed prior to catalytic alkylation, due to the presence of residual organic groups on the aerogel surface. The optimal activation temperature was found to be in the range 185–225°C, while higher temperatures resulted in the removal of zinc chloride from the surface of the aerogel catalyst with a consequential decrease in the catalytic activity. On varying the zinc chloride content, the catalytic activity of the aerogel catalyst exhibited a maximum. High zinc chloride contents decreased the catalytic activity of the aerogel catalyst as the result of the pores of the catalyst being plugged with this compound, and the separation of the alumina/silica support into Al-rich and Si-rich phases. The surface area, total pore volume, pore size distribution and zinc chloride content had a similar influence on the activity of the aerogel catalyst as was the case of xerogel catalyst and supported zinc chloride catalysts.

  2. Deactivation-resistant catalyst for selective catalyst reduction of NOx

    DEFF Research Database (Denmark)

    2011-01-01

    The present invention relates to a catalyst for selective catalytic reduction of NOx in alkali metal containing flue gas using ammonia as reductant, the catalyst comprising a surface with catalytically active sites, wherein the surface is at least partly coated with a coating comprising at least...... one metal oxide. In another aspect the present invention relates to the use of said catalyst and to a method of producing said catalyst. In addition, the present invention relates to a method of treating an catalyst for conferring thereon an improved resistance to alkali poisoning....

  3. Application of a Coated Film Catalyst Layer Model to a High Temperature Polymer Electrolyte Membrane Fuel Cell with Low Catalyst Loading Produced by Reactive Spray Deposition Technology

    Directory of Open Access Journals (Sweden)

    Timothy D. Myles

    2015-10-01

    Full Text Available In this study, a semi-empirical model is presented that correlates to previously obtained experimental overpotential data for a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC. The goal is to reinforce the understanding of the performance of the cell from a modeling perspective. The HT-PEMFC membrane electrode assemblies (MEAs were constructed utilizing an 85 wt. % phosphoric acid doped Advent TPS® membranes for the electrolyte and gas diffusion electrodes (GDEs manufactured by Reactive Spray Deposition Technology (RSDT. MEAs with varying ratios of PTFE binder to carbon support material (I/C ratio were manufactured and their performance at various operating temperatures was recorded. The semi-empirical model derivation was based on the coated film catalyst layer approach and was calibrated to the experimental data by a least squares method. The behavior of important physical parameters as a function of I/C ratio and operating temperature were explored.

  4. A smart strategy to fabricate Ru nanoparticle inserted porous carbon nanofibers as highly efficient levulinic acid hydrogenation catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ying; Sun, Cheng-Jun; Brown, Dennis E.; Zhang, Liqiang; Yang, Feng; Zhao, Hairui; Wang, Yue; Ma, Xiaohui; Zhang, Xin; Ren, Yang

    2016-01-01

    Herein, we first put forward a smart strategy to in situ fabricate Ru nanoparticle (NP) inserted porous carbon nanofibers by one-pot conversion of Ru-functionalized metal organic framework fibers. Such fiber precursors are skillfully constructed by cooperative assembly of different proportional RuCl3 and Zn(Ac)2·2H2O along with trimesic acid (H3BTC) in the presence of N,N-dimethylformamide. The following high-temperature pyrolysis affords uniform and evenly dispersed Ru NPs (ca. 12-16 nm), which are firmly inserted into the hierarchically porous carbon nanofibers formed simultaneously. The resulting Ru-carbon nanofiber (Ru-CNF) catalysts prove to be active towards the liquid-phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL), a biomass-derived platform molecule with wide applications in the preparation of renewable chemicals and liquid transportation fuels. The optimal GVL yield of 96.0% is obtained, corresponding to a high activity of 9.23 molLAh–1gRu–1, 17 times of that using the commercial Ru/C catalyst. Moreover, the Ru-CNF catalyst is extremely stable, and can be cycled up to 7 times without significant loss of reactivity. Our strategy demonstrated here reveals new possibilities to make proficient metal catalysts, and provides a general way to fabricate metal-carbon nanofiber composites available for other applications.

  5. A Nitrogen-Doped Carbon Catalyst for Electrochemical CO2 Conversion to CO with High Selectivity and Current Density.

    Science.gov (United States)

    Jhong, Huei-Ru Molly; Tornow, Claire E; Smid, Bretislav; Gewirth, Andrew A; Lyth, Stephen M; Kenis, Paul J A

    2017-03-22

    We report characterization of a non-precious metal-free catalyst for the electrochemical reduction of CO 2 to CO; namely, a pyrolyzed carbon nitride and multiwall carbon nanotube composite. This catalyst exhibits a high selectivity for production of CO over H 2 (approximately 98 % CO and 2 % H 2 ), as well as high activity in an electrochemical flow cell. The CO partial current density at intermediate cathode potentials (V=-1.46 V vs. Ag/AgCl) is up to 3.5× higher than state-of-the-art Ag nanoparticle-based catalysts, and the maximum current density is 90 mA cm -2 . The mass activity and energy efficiency (up to 48 %) were also higher than the Ag nanoparticle reference. Moving away from precious metal catalysts without sacrificing activity or selectivity may significantly enhance the prospects of electrochemical CO 2 reduction as an approach to reduce atmospheric CO 2 emissions or as a method for load-leveling in relation to the use of intermittent renewable energy sources. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Co-Assembled Supported Catalysts: Synthesis of Nano-Structured Supported Catalysts with Hierarchic Pores through Combined Flow and Radiation Induced Co-Assembled Nano-Reactors

    Directory of Open Access Journals (Sweden)

    Galip Akay

    2016-05-01

    -particles dispersed in water which also contains the catalyst precursor nitrate salt. This support-catalyst precursor fluid must have a sufficiently low viscosity but high elastic modulus (high extensional viscosity to form films and bubbles when exposed to processing energy sources such as microwave, thermal, ultra-sound or UV-radiation or their combination. The micro-to-nano structures of the catalyst system are essentially formed at an early stage of energy input. It is shown that the primary particles of silica are transformed to a proto-silica particle state and form lamellar structures with the catalyst precursor. While the nano-structure is forming, water is evaporated leaving a highly porous solid support-catalyst precursor which then undergoes decomposition to form a silica-catalyst oxide system. The final catalyst system is obtained after catalyst oxide reduction. Although the XRD-based catalyst size changes slightly during the subsequent heat treatments, the nano-structure of the catalyst system remains substantially unaltered as evaluated through TEM images. However, if the catalyst preparation is carried out without film formation, the XRD-based catalyst size increases substantially by a factor of 2–8, with no significant alteration in surface area.

  7. Preparation and Characterization of Highly Spherical Silica-titania Aerogel Beads with High Surface Area

    Directory of Open Access Journals (Sweden)

    YU Yu-xi

    2017-02-01

    Full Text Available The silica-titania aerogel beads were synthesized through sol-gel reaction followed by supercritical drying, in which TEOS and TBT as co-precursors, EtOH as solvents, HAC and NH3·H2O as catalysts. The as-prepared aerogel beads were characterized by SEM,TEM,XRD,FT-IR,TG-DTA and nitrogen adsorption-desorption. The results indicate that the diameter distribution of beads are between 1-8mm, the average diameter of beads is 3.5mm. The aerogel beads have nanoporous network structure with high specific surface area of 914.5m2/g, and the TiO2 particles are distributed in the aerogel uniformly, which keep the anatase crystal under high temperature.

  8. A novel [Bmim]PW/HMS catalyst with high catalytic performance for the oxidative desulfurization process

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Ling; Luo, Guangqing; Kang, Lihua; Zhu, Mingyuan; Dai, Bin [Shihezi University, Shihezi (China)

    2013-02-15

    To effectively reduce the sulfur content in model fuel, [Bmim]PW/HMS catalyst was synthesized through impregnating the hexagonal mesoporous silica (HMS) support by phosphotungstic acid (HPW) and ionic liquid [Bmim] HSO{sub 4}. Physical structure characterizations of the catalysts showed that HMS retained mesoporous structure, and [Bmim] PW was well dispersed on the support of HMS. The catalytic activity of the [Bmim]PW/HMS was evaluated in the oxidative desulfurization process, and the optimal reaction conditions including loading of the catalysts, reaction temperature, catalyst amount, O/S (H{sub 2}O{sub 2}/sulfur) molar ratio and agitation speed were investigated. Under the optimal reaction conditions, the conversion of benzothiophene (BT), dibenzothiophene (DBT) and 4, 6-dimethyldibenzothiophene (4, 6-DMDBT) could reach 79%, 98%, 88%, respectively.

  9. A novel [Bmim]PW/HMS catalyst with high catalytic performance for the oxidative desulfurization process

    International Nuclear Information System (INIS)

    Tang, Ling; Luo, Guangqing; Kang, Lihua; Zhu, Mingyuan; Dai, Bin

    2013-01-01

    To effectively reduce the sulfur content in model fuel, [Bmim]PW/HMS catalyst was synthesized through impregnating the hexagonal mesoporous silica (HMS) support by phosphotungstic acid (HPW) and ionic liquid [Bmim] HSO 4 . Physical structure characterizations of the catalysts showed that HMS retained mesoporous structure, and [Bmim] PW was well dispersed on the support of HMS. The catalytic activity of the [Bmim]PW/HMS was evaluated in the oxidative desulfurization process, and the optimal reaction conditions including loading of the catalysts, reaction temperature, catalyst amount, O/S (H 2 O 2 /sulfur) molar ratio and agitation speed were investigated. Under the optimal reaction conditions, the conversion of benzothiophene (BT), dibenzothiophene (DBT) and 4, 6-dimethyldibenzothiophene (4, 6-DMDBT) could reach 79%, 98%, 88%, respectively

  10. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    Science.gov (United States)

    Wang, George T [Albuquerque, NM; Li, Qiming [Albuquerque, NM; Creighton, J Randall [Albuquerque, NM

    2010-06-29

    A method for forming vertically oriented, crystallographically aligned nanowires (nanocolumns) using monolayer or submonolayer quantities of metal atoms to form uniformly sized metal islands that serve as catalysts for MOCVD growth of Group III nitride nanowires.

  11. Catalyst and processing effects on metal-assisted chemical etching for the production of highly porous GaN

    International Nuclear Information System (INIS)

    Geng, Xuewen; Grismer, Dane A; Bohn, Paul W; Duan, Barrett K; Zhao, Liancheng

    2013-01-01

    Metal-assisted chemical etching is a facile method to produce micro-/nanostructures in the near-surface region of gallium nitride (GaN) and other semiconductors. Detailed studies of the production of porous GaN (PGaN) using different metal catalysts and GaN doping conditions have been performed in order to understand the mechanism by which metal-assisted chemical etching is accomplished in GaN. Patterned catalysts show increasing metal-assisted chemical etching activity to n-GaN in the order Ag < Au < Ir < Pt. In addition, the catalytic behavior of continuous films is compared to discontinuous island films. Continuous metal films strongly shield the surface, hindering metal-assisted chemical etching, an effect which can be overcome by using discontinuous films or increasing the irradiance of the light source. With increasing etch time or irradiance, PGaN morphologies change from uniform porous structures to ridge and valley structures. The doping type plays an important role, with metal-assisted chemical etching activity increasing in the order p-GaN < intrinsic GaN < n-GaN. Both the catalyst identity and the doping type effects are explained by the work functions and the related band offsets that affect the metal-assisted chemical etching process through a combination of different barriers to hole injection and the formation of hole accumulation/depletion layers at the metal–semiconductor interface. (paper)

  12. A Highly Efficient Catalyst for Oxime Ligation and Hydrazone-Oxime Exchange Suitable for Bioconjugation

    OpenAIRE

    Rashidian, Mohammad; Mahmoodi, Mohammad M.; Shah, Rachit; Dozier, Jonathan K.; Wagner, Carston R.; Distefano, Mark D.

    2013-01-01

    Imine-based reactions are useful for a wide range of bioconjugation applications. Although aniline is known to catalyze the oxime ligation reaction under physiological conditions, it suffers from slow reaction kinetics, specifically when a ketone is being used or when hydrazone-oxime exchange is performed. Here, we report on the discovery of a new catalyst that is up to 15 times more efficient than aniline. That catalyst, m-phenylenediamine (mPDA), was initially used to analyze the kinetics o...

  13. Computationally Probing the Performance of Hybrid, Heterogeneous, and Homogeneous Iridium-Based Catalysts for Water Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    García-Melchor, Max [SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering, Stanford University, Stanford CA (United States); Vilella, Laia [Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST),Tarragona (Spain); Departament de Quimica, Universitat Autonoma de Barcelona, Barcelona (Spain); López, Núria [Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST), Tarragona (Spain); Vojvodic, Aleksandra [SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park CA (United States)

    2016-04-29

    An attractive strategy to improve the performance of water oxidation catalysts would be to anchor a homogeneous molecular catalyst on a heterogeneous solid surface to create a hybrid catalyst. The idea of this combined system is to take advantage of the individual properties of each of the two catalyst components. We use Density Functional Theory to determine the stability and activity of a model hybrid water oxidation catalyst consisting of a dimeric Ir complex attached on the IrO2(110) surface through two oxygen atoms. We find that homogeneous catalysts can be bound to its matrix oxide without losing significant activity. Hence, designing hybrid systems that benefit from both the high tunability of activity of homogeneous catalysts and the stability of heterogeneous systems seems feasible.

  14. TiO2-Containing Carbon Derived from a Metal-Organic Framework Composite: A Highly Active Catalyst for Oxidative Desulfurization.

    Science.gov (United States)

    Bhadra, Biswa Nath; Song, Ji Yoon; Khan, Nazmul Abedin; Jhung, Sung Hwa

    2017-09-13

    A new metal-organic framework (MOF) composite consisting of Ti- and Zn-based MOFs (ZIF-8(x)@H 2 N-MIL-125; in brief, ZIF(x)@MOF) was designed and synthesized. The pristine MOF [H 2 N-MIL-125 (MOF)]- and an MOF-composite [ZIF(30)@MOF]-derived mesoporous carbons consisting of TiO 2 nanoparticles were prepared by pyrolysis (named MDC-P and MDC-C, respectively). MDC-C showed a higher surface area, larger pore sizes, and larger mesopore volumes than MDC-P. In addition, the TiO 2 nanoparticles on MDC-C have more uniform shapes and sizes and are smaller than those of MDC-P. The obtained MDC-C and MDC-P [together with MOF, ZIF(30)@MOF, pure/nanocrystalline TiO 2 , and activated carbon] were applied in the oxidative desulfurization reaction of dibenzothiophene in a model fuel. The MDC-C, even with a lower TiO 2 content than that of MDC-P, showed an outstanding catalytic performance, especially with a very low catalyst dose (i.e., a very high quantity of dibenzothiophene was converted per unit weight of the catalyst), fast kinetics (∼3 times faster than that for MDC-P), and a low activation energy (lower than that for any reported catalyst) for the oxidation of dibenzothiophene. The large mesopores of MDC-C and the well-dispersed/small TiO 2 might be the dominant factors for the superior catalytic conversions. The oxidative desulfurization of other sulfur-containing organic compounds with various electron densities was also studied with MDC-C to understand the mechanism of catalysis. Moreover, the MDC-C catalyst can be reused many times in the oxidative desulfurization reaction after a simple washing with acetone. Finally, composing MOFs and subsequent pyrolysis is suggested as an effective way to prepare a catalyst with well-dispersed active sites, large pores, and high mesoporosity.

  15. Highly active, recyclable catalyst for the manufacture of viscous, low molecular weight, CO–ethene–propene-based polyketone, base component for a new class of resins

    NARCIS (Netherlands)

    Broekhuis, Antonius A.; Dirkzwager, Hendrik; Mul, Wilhelmus P.; Heeres, Hero J.; Linden, Adrianus J. van der; Orpen, A. Guy

    2002-01-01

    A highly active, recyclable homogeneous palladium(II) catalyst is described for the manufacture of viscous, low molecular weight CO–ethene–propene-based polyketone (Carilite Oligomer), used for the manufacture of a new class of resins (Carilite Resins). The catalyst is composed of palladium acetate,

  16. Highly Durable Direct Methanol Fuel Cell with Double-Layered Catalyst Cathode

    Directory of Open Access Journals (Sweden)

    Jing Liu

    2015-01-01

    Full Text Available Polymer electrolyte membrane (PEM is one of the key components in direct methanol fuel cells. However, the PEM usually gets attacked by reactive oxygen species during the operation period, resulting in the loss of membrane integrity and formation of defects. Herein, a double-layered catalyst cathode electrode consisting of Pt/CeO2-C as inner catalyst and Pt/C as outer catalyst is fabricated to extend the lifetime and minimize the performance loss of DMFC. Although the maximum power density of membrane electrode assembly (MEA with catalyst cathode is slightly lower than that of the traditional one, its durability is significantly improved. No obvious degradation is evident in the MEA with double-layered catalyst cathode within durability testing. These results indicated that Pt/CeO2-C as inner cathode catalyst layer greatly improved the stability of MEA. The significant reason for the improved stability of MEA is the ability of CeO2 to act as free-radical scavengers.

  17. Pt/C Fuel Cell Catalyst Degradation

    DEFF Research Database (Denmark)

    Zana, Alessandro

    This thesis investigates the degradation behavior of Pt/C catalysts under simulated automotive conditions. By using the “tool box” synthesis method the Pt loading has been changed from low to high Pt loadings, therefore permitting to study the role of Pt on the degradation of high surface area (H...

  18. On determination of the dynamics of hydrocarbon molecules on catalyst's surfaces by means of neutron scattering

    International Nuclear Information System (INIS)

    Stockmeyer, R.

    1976-01-01

    The intensity distribution of slow neutrons scattered by adsorbed hydrocarbon molecules contains information on the dynamics of the molecules. In this paper the scattering law for incoherently scattering molecules is derived taking into account the very different mobility perpendicular and parallel to the surface. In contrast to the well known scattering law of threedimensionally diffusing particles the scattering law for twodimensional diffusion diverges logarithmically at zero energy transfer. Conclusions relevant to the interpretation of neutron scattering data are discussed. (orig.) [de

  19. Nitrogen–doped graphitized carbon shell encapsulated NiFe nanoparticles: A highly durable oxygen evolution catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Du, Lei; Luo, Langli; Feng, Zhenxing; Engelhard, Mark; Xie, Xiaohong; Han, Binghong; Sun, Junming; Zhang, Jianghao; Yin, Geping; Wang, Chongmin; Wang, Yong; Shao, Yuyan

    2017-09-01

    Oxygen evolution reaction (OER) plays a crucial role in various energy conversion devices such as water electrolyzers and metal–air batteries. Precious metal catalysts such as Ir, Ru and their oxides are usually used for enhancing reaction kinetics but are limited by their scarce resource. The challenges associated with alternative non–precious metal catalysts such as transition metal oxides and (oxy)hydroxides etc. are their low electronic conductivity and durability. Herein, we report a highly active (360 mV overpotential at 10 mA cm–2GEO) and durable (no degradation after 20000 cycles) OER catalyst derived from bimetallic metal–organic frameworks (MOFs) precursors. This catalyst consists of NiFe nanoparticles encapsulated by nitrogen–doped graphitized carbon shells. The electron-donation/deviation from Fe and tuned electronic structure of metal cores by Ni are revealed to be primary contributors to the enhanced OER activity, whereas N concentration contributes negligibly. We further demonstrated that the structure and morphology of encapsulating carbon shells, which are the key factors influencing the durability, are facilely controlled by the chemical state of precursors.

  20. Low-cost removal of organic pollutants with nickel nanoparticle loaded ordered macroporous hydrogel as high performance catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Mingyi, E-mail: tmyi@tjcu.edu.cn [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Huang, Guanbo, E-mail: gbhuang2007@hotmail.com [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Zhang, Sai [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Liu, Yue [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Li, Xianxian [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Wang, Xingrui [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Pang, Xiaobo [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Qiu, Haixia, E-mail: qhx@tju.edu.cn [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China)

    2014-06-01

    A facile route for the in situ preparation of catalytically active Ni nanoparticles (NPs) in ordered macroporous hydrogel (OMH) has been developed. The hydrogel was fabricated based on polystyrene colloid template. The electronegativity of amide and carboxyl groups on the poly(acrylamide-co-acryl acid) chains of the hydrogel caused strong binding of Ni{sup 2+} ions which made them distribute uniformly inside the hydrogel. When immersed in NaBH{sub 4} aqueous solution, the Ni{sup 2+} ions on the hydrogel were reduced to Ni NPs. The resultant Ni NPs loaded OMH showed good catalytic activity for the reduction of a common organic pollutant, 4-nitrophenol, with NaBH{sub 4}. A kinetic study of the catalytic reaction was carried out. The rate constant per unit weight could reach 0.53 s{sup −1} g{sup −1}, which is much better than many common hydrogel loaded nickel catalysts. Moreover, the current catalyst can be easily separated and recovered with stable catalytic activity. - Highlights: • A new poly(acrylamide-co-acryl acid) hydrogel with ordered macropores. • A simple in situ fabrication of nickel nanoparticles under mild conditions. • High-performance heterogeneous catalyst for removal of nitrophenol from water. • Good recyclability of catalyst without any complicated regeneration process.

  1. Low-cost removal of organic pollutants with nickel nanoparticle loaded ordered macroporous hydrogel as high performance catalyst

    International Nuclear Information System (INIS)

    Tang, Mingyi; Huang, Guanbo; Zhang, Sai; Liu, Yue; Li, Xianxian; Wang, Xingrui; Pang, Xiaobo; Qiu, Haixia

    2014-01-01

    A facile route for the in situ preparation of catalytically active Ni nanoparticles (NPs) in ordered macroporous hydrogel (OMH) has been developed. The hydrogel was fabricated based on polystyrene colloid template. The electronegativity of amide and carboxyl groups on the poly(acrylamide-co-acryl acid) chains of the hydrogel caused strong binding of Ni 2+ ions which made them distribute uniformly inside the hydrogel. When immersed in NaBH 4 aqueous solution, the Ni 2+ ions on the hydrogel were reduced to Ni NPs. The resultant Ni NPs loaded OMH showed good catalytic activity for the reduction of a common organic pollutant, 4-nitrophenol, with NaBH 4 . A kinetic study of the catalytic reaction was carried out. The rate constant per unit weight could reach 0.53 s −1  g −1 , which is much better than many common hydrogel loaded nickel catalysts. Moreover, the current catalyst can be easily separated and recovered with stable catalytic activity. - Highlights: • A new poly(acrylamide-co-acryl acid) hydrogel with ordered macropores. • A simple in situ fabrication of nickel nanoparticles under mild conditions. • High-performance heterogeneous catalyst for removal of nitrophenol from water. • Good recyclability of catalyst without any complicated regeneration process

  2. Palladium-pyridyl catalytic films: a highly active and recyclable catalyst for hydrogenation of styrene under mild conditions.

    Science.gov (United States)

    Gao, Shuiying; Li, Weijin; Cao, Rong

    2015-03-01

    Palladium-pyridyl catalytic films, (PdCl2/bpy)n, were created by alternating immersions of a substrate in PdCl2 and bpy (bpy=4, 4'-bipyridyl) solutions. The as-prepared (PdCl2/bpy)10 catalyst demonstrated a remarkable catalytic activity toward hydrogenation of styrene under mild conditions and the turnover frequency (TOF) is as high as 6944h(-1). Pd(II) ions of (PdCl2/bpy)n films are in situ reduced to Pd nanoparticles (NPs) during the hydrogenation of styrene process, which results in the catalytic activity of the films. The results of X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) further demonstrate that Pd(II) ions of (PdCl2/bpy)n films were gradually converted to Pd(0) states. The catalytic activity is related to bilayer numbers and the activity increases with the number of bilayers below 10 bilayers. The solid substrates coated with (PdCl2/bpy)n multilayer catalysts were easily removed from the reaction mixture without separation filtration. Moreover, (PdCl2/bpy)n catalysts were reused for 10 consecutive reactions without loss of activity. The present (PdCl2/bpy)n heterogeneous catalysts have the advantages of easy separation and good recyclability. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Two 3D structured Co-Ni bimetallic oxides as cathode catalysts for high-performance alkaline direct methanol fuel cells

    Science.gov (United States)

    Liu, Yan; Shu, Chengyong; Fang, Yuan; Chen, Yuanzhen; Liu, Yongning

    2017-09-01

    Two NiCo2O4 bimetallic oxides were synthesized via a facile hydrothermal method. SEM and TEM observations show that these materials have three-dimensional (3D) dandelion-like (DL) and flower-like (FL) morphologies. Their large specific surface areas (90.68 and 19.8 m2·g-1) and porous structures provide many active sites and effective transport pathways for the oxygen reduction reaction (ORR). Electrochemical measurements with a rotating ring-disc electrode (RRDE) indicate that the electron transfer numbers of the NiCo2O4-DL and NiCo2O4-FL catalysts for ORR in an alkaline solution are 3.97 and 3.91, respectively. Fuel cells were assembled with the bimetallic oxides, PtRu/C and a polymer fiber membrane (PFM) as cathode catalysts, anode catalyst and electrolyte film, respectively. For NiCo2O4-DL, the peak power density reaches up to 73.5 mW·cm-2 at 26 °C, which is the highest room-temperature value reported to date. The high catalytic activity of NiCo2O4 is mainly attributed to the presence of many Co3+ cations that directly donate electrons to O2 to reduce it via a more efficient and effective route. Furthermore, the catalytic performance of NiCo2O4-DL is superior to that of NiCo2O4-FL because it has a higher specific surface area and is less crystalline.

  4. Alkali resistant Fe-zeolite catalysts for SCR of NO with NH3 in flue gases

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Jensen, Anker Degn; Riisager, Anders

    2011-01-01

    . The effect of potassium doping on the acidic and redox properties of the Fe-zeolite catalysts were studied. The prepared catalysts showed high surface area and surface acidity. This is essential for increased alkali resistivity in comparison with conventional metal oxide supports like, e.g. TiO2 and ZrO2......, towards e.g. potassium salts in flue gases from biomass fired power plants. These properties allowed both undoped and potassium doped Fe-zeolite catalysts to posses high activity during the selective catalytic reduction (SCR) of NO with NH3. The extent of deactivation of the Fe-zeolite catalysts...

  5. Discovery of fuel cell anode electrocatalysts and dehydrogenation catalysts using combinatorial techniques

    Science.gov (United States)

    Chan, Benny Chun Wai

    A gas diffusion optical screening method was developed for the discovery of catalysts for the electro-oxidation of reformate gas (H2 with 100 ppm CO). The screening cell was designed to accommodate a gas diffusion layer, 715 member catalyst array, and an electrolyte container. Since protons are generated during H2 oxidation, a pH sensitive fluorphore was used to identify active compositions. The cell showed no detectable iR drop across the array and ranked activity of two commercial PtRu and one Pt catalysts. Over 95% of a given catalyst fluoresced at the initial onset potential and a 5 mV difference in onset potential of two different catalysts was statistically different. A gas diffusion half cell was designed similar to the optical screening cell to obtain current-potential curves of bulk catalysts. The screening results correlated with half cell and fuel cell data, internally validating the method. The combinatorial method was then applied to search for catalysts in the PtRuMoIrRh composition space. The catalysts on the array were prepared by hydrogen reduction of the metals salts on carbon. The most active catalysts were from the Pt enriched regions of the PtRuMoRh quaternary. Bulk catalysts were prepared from the active regions and tested in the gas diffusion half cell. The most active catalysts in the optical screening were also the most active catalysts in the half cell. When any homemade catalysts were compared to commercial PtRu, however, the performance was worse. A high surface area, high catalyst activity synthetic method is the most important factor to reliably screen catalysts for "real world" fuel cell application. High surface area catalysts were tested for direct methanol oxidation activity. The optical screening method was compared with disk electrode, high throughput fuel cell testing, and fuel cell testing. Six catalysts examined included two commercial PtRu catalysts, a Pt catalyst, and three homemade PtRu catalysts of varying activity

  6. Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.

    Science.gov (United States)

    Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

    2014-08-01

    We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1catalysts has been proposed by determining the amount of accessible manganese centers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. A High-throughput Selection for Cellulase Catalysts Using Chemical Complementation

    Science.gov (United States)

    Peralta-Yahya, Pamela; Carter, Brian T.; Lin, Hening; Tao, Haiyan; Cornish, Virginia W.

    2010-01-01

    Efficient enzymatic hydrolysis of lignocellulosic material remains one of the major bottlenecks to cost-effective conversion of biomass to ethanol. Improvement of glycosylhydrolases however is limited by existing medium-throughput screening technologies. Here, we report the first high-throughput selection for cellulase catalysts. This selection was developed by adapting chemical complementation to provide a growth assay for bond cleavage reactions. First, a URA3 counter selection was adapted to link chemical dimerizer activated gene transcription to cell death. Next, the URA3 counter selection was shown to detect cellulase activity based on cleavage of a tetrasaccharide chemical dimerizer substrate and decrease in expression of the toxic URA3 reporter. Finally, the utility of the cellulase selection was assessed by isolating cellulases with improved activity from a cellulase library created by family DNA shuffling. This application provides further evidence that chemical complementation can be readily adapted to detect different enzymatic activities for important chemical transformations for which no natural selection exists. Due to the large number of enzyme variants selections can test compared to existing medium-throughput screens for cellulases, this assay has the potential to impact the discovery of improved cellulases and other glycosylhydrolases for biomass conversion from libraries of cellulases created by mutagenesis or obtained from natural biodiversity. PMID:19053460

  8. Single-catalyst high-weight% hydrogen storage in an N-heterocycle synthesized from lignin hydrogenolysis products and ammonia.

    Science.gov (United States)

    Forberg, Daniel; Schwob, Tobias; Zaheer, Muhammad; Friedrich, Martin; Miyajima, Nobuyoshi; Kempe, Rhett

    2016-10-20

    Large-scale energy storage and the utilization of biomass as a sustainable carbon source are global challenges of this century. The reversible storage of hydrogen covalently bound in chemical compounds is a particularly promising energy storage technology. For this, compounds that can be sustainably synthesized and that permit high-weight% hydrogen storage would be highly desirable. Herein, we report that catalytically modified lignin, an indigestible, abundantly available and hitherto barely used biomass, can be harnessed to reversibly store hydrogen. A novel reusable bimetallic catalyst has been developed, which is able to hydrogenate and dehydrogenate N-heterocycles most efficiently. Furthermore, a particular N-heterocycle has been identified that can be synthesized catalytically in one step from the main lignin hydrogenolysis product and ammonia, and in which the new bimetallic catalyst allows multiple cycles of high-weight% hydrogen storage.

  9. Deactivation of molybdate catalysts by nitrogen bases

    Energy Technology Data Exchange (ETDEWEB)

    Furimsky, E.

    1982-10-01

    Nitrogen bases present in petroleum deactivate the surface of molybdate catalysts. The detrimental effect is attributed either to interactions of the bases with Lewis sites via unpaired electrons on nitrogen or to their ability to remove proton from the surface. The later effect results in a decrease of concentration of Bronsted sites known to be active in catalytic reactions. This enhances rate of coke forming reactions. Resistence of molybdate catalysts to coke formation depends on the form and redistribution of active ingredients on the surface. This can be effected by conditions applied during preparation and pretreatment of the catalysts. Processing parameters used during catalytic hydrotreatment are also important; i.e., the coke formation is slow under conditions ensuring high rate of removal of basic nitrogen containing compounds.

  10. Bifunctional composite catalysts using Co3O4 nanofibers immobilized on nonoxidized graphene nanoflakes for high-capacity and long-cycle Li-O2 batteries.

    Science.gov (United States)

    Ryu, Won-Hee; Yoon, Taek-Han; Song, Sung Ho; Jeon, Seokwoo; Park, Yong-Joon; Kim, Il-Doo

    2013-09-11

    Designing a highly efficient catalyst is essential to improve the electrochemical performance of Li-O2 batteries for long-term cycling. Furthermore, these batteries often show significant capacity fading due to the irreversible reaction characteristics of the Li2O2 product. To overcome these limitations, we propose a bifunctional composite catalyst composed of electrospun one-dimensional (1D) Co3O4 nanofibers (NFs) immobilized on both sides of the 2D nonoxidized graphene nanoflakes (GNFs) for an oxygen electrode in Li-O2 batteries. Highly conductive GNFs with noncovalent functionalization can facilitate a homogeneous dispersion in solution, thereby enabling simple and uniform attachment of 1D Co3O4 NFs on GNFs without restacking. High first discharge capacity of 10 500 mAh/g and superior cyclability for 80 cycles with a limited capacity of 1000 mAh/g were achieved by (i) improved catalytic activity of 1D Co3O4 NFs with large surface area, (ii) facile electron transport via interconnected GNFs functionalized by Co3O4 NFs, and (iii) fast O2 diffusion through the ultrathin GNF layer and porous Co3O4 NF networks.

  11. Iridium-catalyst-based autonomous bubble-propelled graphene micromotors with ultralow catalyst loading.

    Science.gov (United States)

    Wang, Hong; Sofer, Zdeněk; Eng, Alex Yong Sheng; Pumera, Martin

    2014-11-10

    A novel concept of an iridium-based bubble-propelled Janus-particle-type graphene micromotor with very high surface area and with very low catalyst loading is described. The low loading of Ir catalyst (0.54 at %) allows for fast motion of graphene microparticles with high surface area of 316.2 m(2)  g(-1). The micromotor was prepared with a simple and scalable method by thermal exfoliation of iridium-doped graphite oxide precursor composite in hydrogen atmosphere. Oxygen bubbles generated from the decomposition of hydrogen peroxide at the iridium catalytic sites provide robust propulsion thrust for the graphene micromotor. The high surface area and low iridium catalyst loading of the bubble-propelled graphene motors offer great possibilities for dramatically enhanced cargo delivery. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Two Catalysts for Selective Oxidation of Contaminant Gases

    Science.gov (United States)

    Wright, John D.

    2011-01-01

    Two catalysts for the selective oxidation of trace amounts of contaminant gases in air have been developed for use aboard the International Space Station. These catalysts might also be useful for reducing concentrations of fumes in terrestrial industrial facilities especially facilities that use halocarbons as solvents, refrigerant liquids, and foaming agents, as well as facilities that generate or utilize ammonia. The first catalyst is of the supported-precious-metal type. This catalyst is highly active for the oxidation of halocarbons, hydrocarbons, and oxygenates at low concentrations in air. This catalyst is more active for the oxidation of hydrocarbons and halocarbons than are competing catalysts developed in recent years. This catalyst completely converts these airborne contaminant gases to carbon dioxide, water, and mineral acids that can be easily removed from the air, and does not make any chlorine gas in the process. The catalyst is thermally stable and is not poisoned by chlorine or fluorine atoms produced on its surface during the destruction of a halocarbon. In addition, the catalyst can selectively oxidize ammonia to nitrogen at a temperature between 200 and 260 C, without making nitrogen oxides, which are toxic. The temperature of 260 C is higher than the operational temperature of any other precious-metal catalyst that can selectively oxidize ammonia. The purpose of the platinum in this catalyst is to oxidize hydrocarbons and to ensure that the oxidation of halocarbons goes to completion. However, the platinum exhibits little or no activity for initiating the destruction of halocarbons. Instead, the attack on the halocarbons is initiated by the support. The support also provides a high surface area for exposure of the platinum. Moreover, the support resists deactivation or destruction by halogens released during the destruction of halocarbons. The second catalyst is of the supported- metal-oxide type. This catalyst can selectively oxidize ammonia to

  13. Preparation of alveolate hydrophobic catalyst for tritium waste gas treatment

    International Nuclear Information System (INIS)

    Yang, Yong; Peng, Shuming; Wang, Heyi; Du, Yang; Li, Jiamao

    2016-01-01

    Highlights: • The catalyst is hydrophobic, it will not be poisoned by steam in room air at room temperature which is better than Pt-Al 2 O 3 . • At room temperature, the conversion of low concentration of H2 and tritium gas in room air over the catalyst is high. • The air resistance of catalyst is much lower than graininess Pt-Al 2 O 3 . • It is inorganic and will not burn. - Abstract: To prepare a catalyst for the detritiation of waste gases at high flow rates, a heat-resistant hydrophobic zeolitic molecular sieve coating was synthesized on the surface of alveolate cordierite by hydrothermal processing. The alveolate hydrophobic catalyst prepared from the support was essentially waterproof and not easily poisoned by moisture. At room temperature, the conversion of low concentrations of H 2 in humid air over the catalyst was higher than 95% at different space velocities (0–16,000 h −1 ) and different relative humidities. The reaction rate constant of the oxidation of tritium over alveolate hydrophobic catalyst is 0.182 s −1 at 293.3 K–293.7 K and 59%–60% RH, it is much higher than the catalyst of reference honeycomb catalyst.

  14. In Situ Studies of Surface Mobility on Noble Metal Model Catalysts Using STM and XPS at Ambient Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Butcher, Derek Robert [Univ. of California, Berkeley, CA (United States)

    2010-06-01

    High Pressure Scanning Tunneling Microscopy (HP-STM) and Ambient Pressure X-ray Photoelectron Spectroscopy were used to study the structural properties and catalytic behavior of noble metal surfaces at high pressure. HP-STM was used to study the structural rearrangement of the top most atomic surface layer of the metal surfaces in response to changes in gas pressure and reactive conditions. AP-XPS was applied to single crystal and nanoparticle systems to monitor changes in the chemical composition of the surface layer in response to changing gas conditions. STM studies on the Pt(100) crystal face showed the lifting of the Pt(100)-hex surface reconstruction in the presence of CO, H2, and Benzene. The gas adsorption and subsequent charge transfer relieves the surface strain caused by the low coordination number of the (100) surface atoms allowing the formation of a (1 x 1) surface structure commensurate with the bulk terminated crystal structure. The surface phase change causes a transformation of the surface layer from hexagonal packing geometry to a four-fold symmetric surface which is rich in atomic defects. Lifting the hex reconstruction at room temperature resulted in a surface structure decorated with 2-3 nm Pt adatom islands with a high density of step edge sites. Annealing the surface at a modest temperature (150 C) in the presence of a high pressure of CO or H2 increased the surface diffusion of the Pt atoms causing the adatom islands to aggregate reducing the surface concentration of low coordination defect sites. Ethylene hydrogenation was studied on the Pt(100) surface using HP-STM. At low pressure, the lifting of the hex reconstruction was observed in the STM images. Increasing the ethylene pressure to 1 Torr, was found to regenerate the hexagonally symmetric reconstructed phase. At room temperature ethylene undergoes a structural rearrangement to form ethylidyne. Ethylidyne preferentially binds at the three-fold hollow sites, which

  15. Preparation and Characterization of NiMo/Al2O3Catalyst for Hydrocracking Processing

    Directory of Open Access Journals (Sweden)

    Widiyadi Aditya

    2018-01-01

    Full Text Available Hydrocracking is a chemical process used in petroleum refineries for converting high boiling hydrocarbons in petroleum crude oils to more valuable lower boiling products such as gasoline, kerosene, and diesel oil that operate at high temperature and pressure. Catalyst was used in hydrocracking to reduce temperature and pressure. Hydrocracking catalyst are composed of active components and support. Alumina is widely used in hydrocracking process as catalyst support due to its high surface area, high thermal stability, and low prices. The objective of this research was preparated NiMo/Al2O3 catalyst that used as hydrocracking catalyst. Catalyst was synthesized by wetness impregnation method and simple heating method with various kind of Al2O3. The physicochemical properties of catalyst were investigated by X-ray diffraction (XRD to determine type of crystal and scanning electron microscopy (SEM to determine morphology of the catalyst. The NiMo/Al2O3 catalyst prepared by aluminium potassium sulfate dodecahydrate exhibited the highest crystallinity of 90.23% and it is clear that MoO3 and NiO crystallites are highly dispersed on the NiMo/Al2O3 catalyst which indicates as the best catalyst. The catalytic activity in hydrocracking process was successfully examined to convert fatty acid into hydrocarbon.

  16. Preparation and Characterization of NiMo/Al2O3Catalyst for Hydrocracking Processing

    Science.gov (United States)

    Widiyadi, Aditya; Guspiani, Gema Adil; Riady, Jeffry; Andreanto, Rikky; Chaiunnisa, Safina Dea; Widayat

    2018-02-01

    Hydrocracking is a chemical process used in petroleum refineries for converting high boiling hydrocarbons in petroleum crude oils to more valuable lower boiling products such as gasoline, kerosene, and diesel oil that operate at high temperature and pressure. Catalyst was used in hydrocracking to reduce temperature and pressure. Hydrocracking catalyst are composed of active components and support. Alumina is widely used in hydrocracking process as catalyst support due to its high surface area, high thermal stability, and low prices. The objective of this research was preparated NiMo/Al2O3 catalyst that used as hydrocracking catalyst. Catalyst was synthesized by wetness impregnation method and simple heating method with various kind of Al2O3. The physicochemical properties of catalyst were investigated by X-ray diffraction (XRD) to determine type of crystal and scanning electron microscopy (SEM) to determine morphology of the catalyst. The NiMo/Al2O3 catalyst prepared by aluminium potassium sulfate dodecahydrate exhibited the highest crystallinity of 90.23% and it is clear that MoO3 and NiO crystallites are highly dispersed on the NiMo/Al2O3 catalyst which indicates as the best catalyst. The catalytic activity in hydrocracking process was successfully examined to convert fatty acid into hydrocarbon.

  17. Self-propagating high-temperature synthesis of Sr-doped LaMnO3 perovskite as oxidation catalyst

    International Nuclear Information System (INIS)

    Hirano, T.; Purwanto, H.; Watanabe, T.; Akiyama, T.

    2007-01-01

    Sr-doped LaMnO 3 perovskite oxide has been focused on as one of the alternative catalysts to precious metals such as platinum that are used for cleaning automotive emission gas. The conventional Solid-state reaction method is a popular productive process for perovskite oxide, however, it is time and energy consuming process because it requires repeated prolonged heat treatment at high temperatures. Therefore, the purposes of this work are to produce Sr-doped LaMnO 3 perovskite by using Self-propagating high-temperature synthesis (SHS) and experimentally examine the oxidation catalytic activity of the product for cleaning automotive emission gas. In the SHS, powders of La 2 O 3 , SrCO 3 , Mn and NaClO 4 were well mixed at the desired ratio and poured in a graphite crucible, where at one end it was ignited by using an electrically heated carbon foil. The wave of exothermic reaction due to oxidation of manganese propagated to the other end in a short time. The obtained products were characterized by means of XRD, FE-SEM, BET and particle size distribution analysis and then evaluated via catalytic oxidation tests by using propane in a fixed bed reactor at several temperatures. From the XRD analysis, the products had the desired composition of La 1-x Sr x MnO 3 (x = 0, 0.1, 0.2 and 0.4) perovskite, in which the replacing ratio x of La and Sr in the products was easily controlled by changing the mixing ratio of raw materials. The catalytic activity test showed that the samples exhibited good catalytic activity for propane oxidation over 200 deg. C , although the products had a relatively small surface area. SHS showed the potential for the production of a relatively inexpensive catalytic converter

  18. Design of Highly Selective Platinum Nanoparticle Catalysts for the Aerobic Oxidation of KA-Oil using Continuous-Flow Chemistry.

    Science.gov (United States)

    Gill, Arran M; Hinde, Christopher S; Leary, Rowan K; Potter, Matthew E; Jouve, Andrea; Wells, Peter P; Midgley, Paul A; Thomas, John M; Raja, Robert

    2016-03-08

    Highly active and selective aerobic oxidation of KA-oil to cyclohexanone (precursor for adipic acid and ɛ-caprolactam) has been achieved in high yields using continuous-flow chemistry by utilizing uncapped noble-metal (Au, Pt & Pd) nanoparticle catalysts. These are prepared using a one-step in situ methodology, within three-dimensional porous molecular architectures, to afford robust heterogeneous catalysts. Detailed spectroscopic characterization of the nature of the active sites at the molecular level, coupled with aberration-corrected scanning transmission electron microscopy, reveals that the synthetic methodology and associated activation procedures play a vital role in regulating the morphology, shape and size of the metal nanoparticles. These active centers have a profound influence on the activation of molecular oxygen for selective catalytic oxidations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. CTAB micelles and the hydroformylation of octene with rhodium/TPPTS catalysts - Evidence for the interaction of TPPTS with micelle surfaces

    DEFF Research Database (Denmark)

    Riisager, Anders; Hanson, Brian E.

    2002-01-01

    The addition of cetyltrimethylammonium bromide (CTAB) to TPPTS/rhodium hydroformylation catalysts has a complicated effect on reaction activity and selectivity. In water alone as the solvent, high CTAB concentration leads to the formation of emulsions and reaction selectivity drops. In aqueous...

  20. Investigation of the Process Conditions for Hydrogen Production by Steam Reforming of Glycerol over Ni/Al₂O₃ Catalyst Using Response Surface Methodology (RSM).

    Science.gov (United States)

    Ebshish, Ali; Yaakob, Zahira; Taufiq-Yap, Yun Hin; Bshish, Ahmed

    2014-03-19

    In this work; a response surface methodology (RSM) was implemented to investigate the process variables in a hydrogen production system. The effects of five independent variables; namely the temperature (X₁); the flow rate (X₂); the catalyst weight (X₃); the catalyst loading (X₄) and the glycerol-water molar ratio (X₅) on the H₂ yield (Y₁) and the conversion of glycerol to gaseous products (Y₂) were explored. Using multiple regression analysis; the experimental results of the H₂ yield and the glycerol conversion to gases were fit to quadratic polynomial models. The proposed mathematical models have correlated the dependent factors well within the limits that were being examined. The best values of the process variables were a temperature of approximately 600 °C; a feed flow rate of 0.05 mL/min; a catalyst weight of 0.2 g; a catalyst loading of 20% and a glycerol-water molar ratio of approximately 12; where the H₂ yield was predicted to be 57.6% and the conversion of glycerol was predicted to be 75%. To validate the proposed models; statistical analysis using a two-sample t -test was performed; and the results showed that the models could predict the responses satisfactorily within the limits of the variables that were studied.

  1. Fluorescence imaging technology (FI) for high-throughput screening of selenide-modified nano-TiO2 catalysts.

    Science.gov (United States)

    Wang, Liping; Lee, Jianchao; Zhang, Meijuan; Duan, Qiannan; Zhang, Jiarui; Qi, Hailang

    2016-02-18

    A high-throughput screening (HTS) method based on fluorescence imaging (FI) was implemented to evaluate the catalytic performance of selenide-modified nano-TiO2. Chemical ink-jet printing (IJP) technology was reformed to fabricate a catalyst library comprising 1405 (Ni(a)Cu(b)Cd(c)Ce(d)In(e)Y(f))Se(x)/TiO2 (M6Se/Ti) composite photocatalysts. Nineteen M6Se/Tis were screened out from the 1405 candidates efficiently.

  2. Polyvinylpolypyrrolidone-Supported Boron Trifluoride; Highly Efficient Catalyst for the Synthesis of N-tert-Butyl Amides

    Directory of Open Access Journals (Sweden)

    Masoud Mokhtary

    2012-01-01

    Full Text Available Highly efficient method for the preparation of N-tert-butyl amides by reaction of nitriles with tert-butyl acetate is described using polyvinylpolypyrrolidone-supported boron trifluoride (PVPP-BF3 at 70°C in good to excellent yields. Selective amidation of benzonitrile in the presence of acetonitrile was also achieved. polyvinylpolypyrrolidone-boron trifluoride complex shows non-corrosive and stable solid catalyst elevated Lewis acid property.

  3. Gold nanoparticles supported on titanium dioxide: an efficient catalyst for highly selective synthesis of benzoxazoles and benzimidazoles.

    Science.gov (United States)

    Tang, Lin; Guo, Xuefeng; Yang, Yu; Zha, Zhenggen; Wang, Zhiyong

    2014-06-11

    A highly efficient and selective reaction for the synthesis of 2-substituted benzoxazoles and benzimidazoles catalyzed by Au/TiO2 has been developed via two hydrogen-transfer processes. This reaction has a good tolerance to air and water, a wide substrate scope, and represents a new avenue for practical C-N and C-O bond formation. More importantly, no additional additives, oxidants and reductants are required for the reaction and the catalyst can be recovered and reused readily.

  4. Quantification of zinc atoms in a surface alloy on copper in an industrial-type methanol synthesis catalyst

    DEFF Research Database (Denmark)

    Kuld, Sebastian; Moses, Poul Georg; Sehested, Jens

    2014-01-01

    Methanol has recently attracted renewed interest because of its potential importance as a solar fuel. Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al2O3 catalyst. The identity of the active site and, in particular, the role of ZnO as a pro......Methanol has recently attracted renewed interest because of its potential importance as a solar fuel. Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al2O3 catalyst. The identity of the active site and, in particular, the role of Zn......O as a promoter for this type of catalyst is still under intense debate. Structural changes that are strongly dependent on the pretreatment method have now been observed for an industrial-type methanol synthesis catalyst. A combination of chemisorption, reaction, and spectroscopic techniques provides a consistent...

  5. The surface chemistry of nanocrystalline MgO catalysts for FAME production: An in situ XPS study of H2O, CH3OH and CH3OAc adsorption

    Science.gov (United States)

    Montero, J. M.; Isaacs, M. A.; Lee, A. F.; Lynam, J. M.; Wilson, K.

    2016-04-01

    An in situ XPS study of water, methanol and methyl acetate adsorption over as-synthesised and calcined MgO nanocatalysts is reported with a view to gaining insight into the surface adsorption of key components relevant to fatty acid methyl esters (biodiesel) production during the transesterification of triglycerides with methanol. High temperature calcined NanoMgO-700 adsorbed all three species more readily than the parent material due to the higher density of electron-rich (111) and (110) facets exposed over the larger crystallites. Water and methanol chemisorb over the NanoMgO-700 through the conversion of surface O2 - sites to OH- and coincident creation of Mg-OH or Mg-OCH3 moieties respectively. A model is proposed in which the dissociative chemisorption of methanol occurs preferentially over defect and edge sites of NanoMgO-700, with higher methanol coverages resulting in physisorption over weakly basic (100) facets. Methyl acetate undergoes more complex surface chemistry over NanoMgO-700, with C-H dissociation and ester cleavage forming surface hydroxyl and acetate species even at extremely low coverages, indicative of preferential adsorption at defects. Comparison of C 1s spectra with spent catalysts from tributyrin transesterification suggest that ester hydrolysis plays a key factor in the deactivation of MgO catalysts for biodiesel production.

  6. Stable amorphous georgeite as a precursor to a high-activity catalyst

    DEFF Research Database (Denmark)

    Kondrat, Simon A.; Smith, Paul J.; Wells, Peter P.

    2016-01-01

    Copper and zinc form an important group of hydroxycarbonate minerals that include zincian malachite, aurichalcite, rosasite and the exceptionally rare and unstable-and hence little known and largely ignored-georgeite. The first three of these minerals are widely used as catalyst precursors...... for the industrially important methanol-synthesis and low-temperature water-gas shift (LTS) reactions, with the choice of precursor phase strongly influencing the activity of the final catalyst. The preferred phase is usually zincian malachite. This is prepared by a co-precipitation method that involves the transient...

  7. Hemoglobin-carbon nanotube derived noble-metal-free Fe5C2-based catalyst for highly efficient oxygen reduction reaction

    Science.gov (United States)

    Vij, Varun; Tiwari, Jitendra N.; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S.

    2016-02-01

    High performance non-precious cathodic catalysts for oxygen reduction reaction (ORR) are vital for the development of energy materials and devices. Here, we report an noble metal free, Fe5C2 nanoparticles-studded sp2 carbon supported mesoporous material (CNTHb-700) as cathodic catalyst for ORR, which was prepared by pyrolizing the hybrid adduct of single walled carbon nanotubes (CNT) and lyophilized hemoglobin (Hb) at 700 °C. The catalyst shows onset potentials of 0.92 V in 0.1 M HClO4 and in 0.1 M KOH which are as good as commercial Pt/C catalyst, giving very high current density of 6.34 and 6.69 mA cm-2 at 0.55 V vs. reversible hydrogen electrode (RHE), respectively. This catalyst has been confirmed to follow 4-electron mechanism for ORR and shows high electrochemical stability in both acidic and basic media. Catalyst CNTHb-700 possesses much higher tolerance towards methanol than the commercial Pt/C catalyst. Highly efficient catalytic properties of CNTHb-700 could lead to fundamental understanding of utilization of biomolecules in ORR and materialization of proton exchange membrane fuel cells for clean energy production.

  8. Alkali resistivity of Cu based selective catalytic reduction catalysts

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Jensen, Anker Degn; Riisager, Anders

    2012-01-01

    The deactivation of V2O5–WO3–TiO2, Cu–HZSM5 and Cu–HMOR plate type monolithic catalysts was investigated when exposed to KCl aerosols in a bench-scale reactor. Fresh and exposed catalysts were characterized by selective catalytic reduction (SCR) activity measurements, scanning electron microscope......–energy dispersive X-ray spectroscopy (SEM–EDX) and NH3-temperature programmed desorption (NH3-TPD). 95% deactivation was observed for the V2O5–WO3–TiO2 catalyst, while the Cu–HZSM5 and Cu–HMOR catalysts deactivated only 58% and 48%, respectively, after 1200 h KCl exposure. SEM analysis of the KCl aerosol exposed...... catalysts revealed that the potassium salt not only deposited on the catalyst surface, but also penetrated into the catalyst wall. Thus, the K/M ratio (M = V or Cu) was high on V2O5–WO3–TiO2 catalyst and comparatively less on Cu–HZSM5 and Cu–HMOR catalysts. NH3-TPD revealed that the KCl exposed Cu–HZSM5...

  9. High Specific and Mass Activity for the Oxygen Reduction Reaction for Thin Film Catalysts of Sputtered Pt3Y

    DEFF Research Database (Denmark)

    Lindahl, Niklas; Zamburlini, Eleonora; Feng, Ligang

    2017-01-01

    Fuel cells have the potential to play an important role in sustainable energy systems, provided that catalysts with higher activity and stability are developed. In this work, it is found that thin alloy films of single-target cosputtered platinum-yttrium exhibit up to seven times higher specific...... additional chemical or thermal treatment. The films show an improvement in stability over the same materials in nanoparticulate form. Physical characterization shows that the thin films form a platinum overlayer supported on an underlying alloy. The high activity is likely related to compressive strain...... in that overlayer. As sputtering can be used to mass-produce fuel cell electrodes, the results open new possibilities for the preparation of platinum-rare earth metal alloy catalysts in commercial devices....

  10. A high-throughput reactor system for optimization of Mo–V–Nb mixed oxide catalyst composition in ethane ODH

    KAUST Repository

    Zhu, Haibo; Laveille, Paco; Rosenfeld, Devon C.; Hedhili, Mohamed N.; Basset, Jean-Marie

    2015-01-01

    75 Mo-V-Nb mixed oxide catalysts with a broad range of compositions were prepared by a simple evaporation method, and were screened for the ethane oxidative dehydrogenation (ODH) reaction. The compositions of these 75 catalysts were systematically changed by varying the Nb loading, and the Mo/V molar ratio. Characterization by XRD, XPS, H2-TPR and SEM revealed that an intimate structure is formed among the 3 components. The strong interaction among different components leads to the formation of a new phase or an "intimate structure". The dependency of conversion and selectivity on the catalyst composition was clearly demonstrated from the results of high-throughput testing. The optimized Mo-V-Nb molar composition was confirmed to be composed of a Nb content of 4-8%, a Mo content of 70-83%, and a V content of 12-25%. The enhanced catalytic performance of the mixed oxides is obviously due to the synergistic effects of the different components. The optimized compositions for ethane ODH revealed in our high-throughput tests and the structural information provided by our characterization studies can serve as the starting point for future efforts to improve the catalytic performance of Mo-V-Nb oxides. This journal is © The Royal Society of Chemistry.

  11. Oxygen reduction on carbon supported platinum catalysts in high temperature polymer electrolytes

    DEFF Research Database (Denmark)

    Qingfeng, Li; Bergqvist, R. S.; Hjuler, H. A.

    1999-01-01

    Oxygen reduction on carbon supported platinum catalysts has been investigated in H3PO4, H3PO4-doped Nafion and PBI polymer electrolytes in a temperature range from 80 to 190°C. Compared with pure H3PO4, using the H3PO4 doped Nafion and PBI polymer electrolytes can significantly improve the oxygen...

  12. Theoretical study of methanol synthesis from CO2 and CO hydrogenation on the surface of ZrO2 supported In2O3 catalyst

    Science.gov (United States)

    Dou, Maobin; Zhang, Minhua; Chen, Yifei; Yu, Yingzhe

    2018-06-01

    The interactions between ZrO2 support and In2O3 catalyst play pivotal role in the catalytic conversion of CO2 to methanol. Herein, a density functional theory study has been conducted to research the mechanism of methanol synthesis from CO2 and CO hydrogenation on the defective ZrO2 supported In2O3(110) surface (D surface). The calculations reveal that methanol is produced mainly via the HCOO reaction pathway from CO2 hydrogenation on D surface, and the hydrogenation of HCOO to form H2COO species with an activation barrier of 1.21 eV plays the rate determining step for the HCOO reaction pathway. The direct dissociation of CO2 to CO on D surface is kinetically and energetically prohibited. Methanol synthesis from CO hydrogenation on D surface is much facile comparing with the elementary steps involved in CO2 hydrogenation. The rate determining step of CO hydrogenation to methanol is the formation of H3CO species on the vacancy site with a barrier of 0.51 eV. ZrO2 support has significant effect on the suppressing of the dissociation of CO2 and stabilization of H2COO species on the surface of In2O3 catalyst.

  13. Flexible, highly graphitized carbon aerogels based on bacterial cellulose/lignin: Catalyst-free synthesis and its application in energy storage devices

    KAUST Repository

    Xu, Xuezhu; Zhou, Jian; Nagaraju, Doddahalli H.; Jiang, Long; Marinov, Val R.; Lubineau, Gilles; Alshareef, Husam N.; Oh, Myungkeun

    2015-01-01

    Currently, most carbon aerogels are based on carbon nanotubes (CNTs) or graphene, which are produced through a catalyst-assisted chemical vapor deposition method. Biomass based organic aerogels and carbon aerogels, featuring low cost, high

  14. Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis

    DEFF Research Database (Denmark)

    Su, Hai-Yan; Gorlin, Yelena; Man, Isabela Costinela

    2012-01-01

    Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen...... reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured α-Mn2O3 and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V...

  15. Study of the oxides nature effect of rare and rare earth elements on the aluminium-chromium catalyst properties

    International Nuclear Information System (INIS)

    Dadashev, B.A.; Abbasov, S.G.; Sarydzhanov, A.A.; AN Azerbajdzhanskoj SSR, Baku. Inst. Neftekhimicheskikh Protsessov)

    1975-01-01

    Adsorption studies have shown that oxides of rare and rare earth elements REE appreciably influence the structure of aluminium-chrome catalyst. Alkaline promotors, unlike REE, contribute to the formation of developed contact surface. Electrophysical investigations show that oxides of rare elements introduced into the catalyst increase its conductivity and activation energy. As for REE oxides, they decrease the conductivity and increase the activation energy. Catalysts with developed surface and high conductivity are also more active in the reaction of isopentane dehydration

  16. High Surface Area Tunnels in Hexagonal WO₃.

    Science.gov (United States)

    Sun, Wanmei; Yeung, Michael T; Lech, Andrew T; Lin, Cheng-Wei; Lee, Chain; Li, Tianqi; Duan, Xiangfeng; Zhou, Jun; Kaner, Richard B

    2015-07-08

    High surface area in h-WO3 has been verified from the intracrystalline tunnels. This bottom-up approach differs from conventional templating-type methods. The 3.67 Å diameter tunnels are characterized by low-pressure CO2 adsorption isotherms with nonlocal density functional theory fitting, transmission electron microscopy, and thermal gravimetric analysis. These open and rigid tunnels absorb H(+) and Li(+), but not Na(+) in aqueous electrolytes without inducing a phase transformation, accessing both internal and external active sites. Moreover, these tunnel structures demonstrate high specific pseudocapacitance and good stability in an H2SO4 aqueous electrolyte. Thus, the high surface area created from 3.67 Å diameter tunnels in h-WO3 shows potential applications in electrochemical energy storage, selective ion transfer, and selective gas adsorption.

  17. Highly-dispersed Ta-oxide catalysts prepared by electrodeposition in a non-aqueous plating bath for polymer electrolyte fuel cell cathodes

    KAUST Repository

    Seo, Jeongsuk; Cha, Dong Kyu; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2012-01-01

    The Ta-oxide cathode catalysts were prepared by electrodeposition in a non-aqueous solution. These catalysts showed excellent catalytic activity and have an onset potential of 0.92 V RHE for the oxygen reduction reaction (ORR). The highly-dispersed Ta species at the nanometer scale on the carbon black was an important contributor to the high activity. © 2012 The Royal Society of Chemistry.

  18. Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

    Science.gov (United States)

    Bagheri, Samira; Muhd Julkapli, Nurhidayatullaili; Bee Abd Hamid, Sharifah

    2014-01-01

    The lack of stability is a challenge for most heterogeneous catalysts. During operations, the agglomeration of particles may block the active sites of the catalyst, which is believed to contribute to its instability. Recently, titanium oxide (TiO2) was introduced as an alternative support material for heterogeneous catalyst due to the effect of its high surface area stabilizing the catalysts in its mesoporous structure. TiO2 supported metal catalysts have attracted interest due to TiO2 nanoparticles high activity for various reduction and oxidation reactions at low pressures and temperatures. Furthermore, TiO2 was found to be a good metal oxide catalyst support due to the strong metal support interaction, chemical stability, and acid-base property. The aforementioned properties make heterogeneous TiO2 supported catalysts show a high potential in photocatalyst-related applications, electrodes for wet solar cells, synthesis of fine chemicals, and others. This review focuses on TiO2 as a support material for heterogeneous catalysts and its potential applications. PMID:25383380

  19. Hydrogen production by steam reforming of liquefied natural gas over a nickel catalyst supported on mesoporous alumina xerogel

    Science.gov (United States)

    Seo, Jeong Gil; Youn, Min Hye; Cho, Kyung Min; Park, Sunyoung; Song, In Kyu

    Mesoporous alumina xerogel (A-SG) is prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/A-SG catalyst is then prepared by an impregnation method, and is applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of the mesoporous alumina xerogel support on the catalytic performance of Ni/A-SG catalyst is investigated. For the purpose of comparison, a nickel catalyst supported on commercial alumina (A-C) is also prepared by an impregnation method (Ni/A-C). Both the hydroxyl-rich surface and the electron-deficient sites of the A-SG support enhance the dispersion of the nickel species on the support during the calcination step. The formation of the surface nickel aluminate phase in the Ni/A-SG catalyst remarkably increases the reducibility and stability of the catalyst. Furthermore, the high-surface area and the well-developed mesoporosity of the Ni/A-SG catalyst enhance the gasification of surface hydrocarbons that are adsorbed in the reaction. In the steam reforming of LNG, the Ni/A-SG catalyst exhibits a better catalytic performance than the Ni/A-C catalyst in terms of LNG conversion and hydrogen production. Moreover, the Ni/A-SG catalyst shows strong resistance toward catalyst deactivation.

  20. Fe(III)-functionalized carbon dots—Highly efficient photoluminescence redox catalyst for hydrogenations of olefins and decomposition of hydrogen peroxide

    KAUST Repository

    Bourlinos, Athanasios B.

    2017-03-21

    We present the first bottom-up approach to synthesize Fe(III)-functionalized carbon dots (CDs) from molecular precursors without the need of conventional thermal or microwave treatment and additional reagents. Specifically, sonication of xylene in the presence of anhydrous FeCl3 results in oxidative coupling of the aromatic substrate towards Fe(III)-functionalized CDs. The as-prepared CDs are spherical in shape with a size of 3–8 nm, highly dispersible in organic solvents and display wavelength-dependent photoluminescence (PL). The iron ions attached to the surface endow the CDs with superior catalytic activity for olefin hydrogenation with excellent conversion and selectivity (up to 100%). The Fe(III)-CDs are more effective in the hydrogenation of a series of electron donating or withdrawing olefin substrates compared to conventional homogeneous or heterogeneous Fe(III)-based catalysts. The as-prepared heterogeneous nanocatalyst can be used repeatedly without any loss of catalytic activity. Importantly, the stability of the new catalysts can be easily monitored by PL intensity or quantum yield measurements, which certainly opens the doors for real time monitoring in a range of applications. Additionally, to the best of our knowledge, for the first time, the oxidative property of Fe-CDs was also explored in decomposition of hydrogen peroxide in water with the first order rate constant of 0.7 × 10−2 min−1, proving the versatile catalytic properties of such hybrid systems.

  1. Fe(III)-functionalized carbon dots—Highly efficient photoluminescence redox catalyst for hydrogenations of olefins and decomposition of hydrogen peroxide

    KAUST Repository

    Bourlinos, Athanasios B.; Rathi, Anuj K.; Gawande, Manoj B.; Hola, Katerina; Goswami, Anandarup; Kalytchuk, Sergii; Karakassides, Michael A.; Kouloumpis, Antonios; Gournis, Dimitrios; Deligiannakis, Yannis; Giannelis, Emmanuel P.; Zboril, Radek

    2017-01-01

    We present the first bottom-up approach to synthesize Fe(III)-functionalized carbon dots (CDs) from molecular precursors without the need of conventional thermal or microwave treatment and additional reagents. Specifically, sonication of xylene in the presence of anhydrous FeCl3 results in oxidative coupling of the aromatic substrate towards Fe(III)-functionalized CDs. The as-prepared CDs are spherical in shape with a size of 3–8 nm, highly dispersible in organic solvents and display wavelength-dependent photoluminescence (PL). The iron ions attached to the surface endow the CDs with superior catalytic activity for olefin hydrogenation with excellent conversion and selectivity (up to 100%). The Fe(III)-CDs are more effective in the hydrogenation of a series of electron donating or withdrawing olefin substrates compared to conventional homogeneous or heterogeneous Fe(III)-based catalysts. The as-prepared heterogeneous nanocatalyst can be used repeatedly without any loss of catalytic activity. Importantly, the stability of the new catalysts can be easily monitored by PL intensity or quantum yield measurements, which certainly opens the doors for real time monitoring in a range of applications. Additionally, to the best of our knowledge, for the first time, the oxidative property of Fe-CDs was also explored in decomposition of hydrogen peroxide in water with the first order rate constant of 0.7 × 10−2 min−1, proving the versatile catalytic properties of such hybrid systems.

  2. Addition of titanium as a potential catalyst for a high-capacity hydrogen storage medium (abstract only)

    International Nuclear Information System (INIS)

    Zuliani, F; Baerends, E J

    2008-01-01

    In recent years there has been increased interest in the characterization of titanium as a catalyst for high-capacity hydrogen storage materials. A first-principles study (Yildirim and Ciraci 2005 Phys. Rev. Lett. 94 175501) demonstrated that a single Ti atom coated on a single-walled nanotube (SWNT) binds up to four hydrogen molecules. The bonding was claimed to be an 'unusual combination of chemisorption and physisorption'. We report an ab initio study by means of the ADF program, which provides a complete insight into the donation/back-donation mechanism characterizing the bond between the Ti atom and the four H 2 molecules, and a full understanding of the catalytic role played by the Ti atom. In addition, we found that the same amount of adsorbed hydrogen can be stored using benzene support for Ti in place of the SWNT, due to the dominant local contribution of the hexagonal carbon ring surrounding the Ti atom. The benzene-Ti-H 2 bonding is discussed on the basis of molecular orbital interaction schemes as provided by ADF. This result advances our insight into the role of titanium as a catalyst and suggests new routes to better storage through different combinations of supports and catalysts

  3. Recent progress in the development of solid catalysts for biomass conversion into high value-added chemicals

    Science.gov (United States)

    Hara, Michikazu; Nakajima, Kiyotaka; Kamata, Keigo

    2015-06-01

    In recent decades, the substitution of non-renewable fossil resources by renewable biomass as a sustainable feedstock has been extensively investigated for the manufacture of high value-added products such as biofuels, commodity chemicals, and new bio-based materials such as bioplastics. Numerous solid catalyst systems for the effective conversion of biomass feedstocks into value-added chemicals and fuels have been developed. Solid catalysts are classified into four main groups with respect to their structures and substrate activation properties: (a) micro- and mesoporous materials, (b) metal oxides, (c) supported metal catalysts, and (d) sulfonated polymers. This review article focuses on the activation of substrates and/or reagents on the basis of groups (a)-(d), and the corresponding reaction mechanisms. In addition, recent progress in chemocatalytic processes for the production of five industrially important products (5-hydroxymethylfurfural, lactic acid, glyceraldehyde, 1,3-dihydroxyacetone, and furan-2,5-dicarboxylic acid) as bio-based plastic monomers and their intermediates is comprehensively summarized.

  4. Recent progress in the development of solid catalysts for biomass conversion into high value-added chemicals

    International Nuclear Information System (INIS)

    Hara, Michikazu; Nakajima, Kiyotaka; Kamata, Keigo

    2015-01-01

    In recent decades, the substitution of non-renewable fossil resources by renewable biomass as a sustainable feedstock has been extensively investigated for the manufacture of high value-added products such as biofuels, commodity chemicals, and new bio-based materials such as bioplastics. Numerous solid catalyst systems for the effective conversion of biomass feedstocks into value-added chemicals and fuels have been developed. Solid catalysts are classified into four main groups with respect to their structures and substrate activation properties: (a) micro- and mesoporous materials, (b) metal oxides, (c) supported metal catalysts, and (d) sulfonated polymers. This review article focuses on the activation of substrates and/or reagents on the basis of groups (a)–(d), and the corresponding reaction mechanisms. In addition, recent progress in chemocatalytic processes for the production of five industrially important products (5-hydroxymethylfurfural, lactic acid, glyceraldehyde, 1,3-dihydroxyacetone, and furan-2,5-dicarboxylic acid) as bio-based plastic monomers and their intermediates is comprehensively summarized. (focus issue review)

  5. Recent progress in the development of solid catalysts for biomass conversion into high value-added chemicals

    Science.gov (United States)

    Hara, Michikazu; Nakajima, Kiyotaka; Kamata, Keigo

    2015-01-01

    In recent decades, the substitution of non-renewable fossil resources by renewable biomass as a sustainable feedstock has been extensively investigated for the manufacture of high value-added products such as biofuels, commodity chemicals, and new bio-based materials such as bioplastics. Numerous solid catalyst systems for the effective conversion of biomass feedstocks into value-added chemicals and fuels have been developed. Solid catalysts are classified into four main groups with respect to their structures and substrate activation properties: (a) micro- and mesoporous materials, (b) metal oxides, (c) supported metal catalysts, and (d) sulfonated polymers. This review article focuses on the activation of substrates and/or reagents on the basis of groups (a)–(d), and the corresponding reaction mechanisms. In addition, recent progress in chemocatalytic processes for the production of five industrially important products (5-hydroxymethylfurfural, lactic acid, glyceraldehyde, 1,3-dihydroxyacetone, and furan-2,5-dicarboxylic acid) as bio-based plastic monomers and their intermediates is comprehensively summarized. PMID:27877800

  6. Surface ionization ion source with high current

    International Nuclear Information System (INIS)

    Fang Jinqing; Lin Zhizhou; Yu Lihua; Zhan Rongan; Huang Guojun; Wu Jianhua

    1986-04-01

    The working principle and structure of a surface ionization ion source with high current is described systematically. Some technological keypoints of the ion source are given in more detail, mainly including: choosing and shaping of the material of the surface ionizer, heating of the ionizer, distributing of working vapour on the ionizer surface, the flow control, the cooling problem at the non-ionization surface and the ion optics, etc. This ion source has been used since 1972 in the electromagnetic isotope separator with 180 deg angle. It is suitable for separating isotopes of alkali metals and rare earth metals. For instance, in the case of separating Rubidium, the maximum ion current of Rbsup(+) extracted from the ion source is about 120 mA, the maximum ion current accepted by the receiver is about 66 mA, the average ion current is more than 25 mA. The results show that our ion source have advantages of high ion current, good characteristics of focusing ion beam, working stability and structure reliability etc. It may be extended to other fields. Finally, some interesting phenomena in the experiment are disccused briefly. Some problems which should be investigated are further pointed out

  7. Full solar spectrum light driven thermocatalysis with extremely high efficiency on nanostructured Ce ion substituted OMS-2 catalyst for VOCs purification

    Science.gov (United States)

    Hou, Jingtao; Li, Yuanzhi; Mao, Mingyang; Yue, Yuanzheng; Greaves, G. Neville; Zhao, Xiujian

    2015-01-01

    The nanostructured Ce ion substituted cryptomelane-type octahedral molecular sieve (OMS-2) catalyst exhibits strong absorption in the entire solar spectrum region. The Ce ion substituted OMS-2 catalyst can efficiently transform the absorbed solar energy to thermal energy, resulting in a considerable increase of temperature. By combining the efficient photothermal conversion and thermocatalytic activity of the Ce ion substituted OMS-2 catalyst, we carried out full solar spectrum, visible-infrared, and infrared light driven catalysis with extremely high efficiency. Under the irradiation of full solar spectrum, visible-infrared, and infrared light, the Ce ion substituted OMS-2 catalyst exhibits extremely high catalytic activity and excellent durability for the oxidation of volatile organic pollutants such as benzene, toluene, and acetone. Based on the experimental evidence, we propose a novel mechanism of solar light driven thermocatalysis for the Ce ion substituted OMS-2 catalyst. The reason why the Ce ion substituted OMS-2 catalyst exhibits much higher catalytic activity than pure OMS-2 and CeO2/OMS-2 nano composite under the full solar spectrum irradiation is discussed.The nanostructured Ce ion substituted cryptomelane-type octahedral molecular sieve (OMS-2) catalyst exhibits strong absorption in the entire solar spectrum region. The Ce ion substituted OMS-2 catalyst can efficiently transform the absorbed solar energy to thermal energy, resulting in a considerable increase of temperature. By combining the efficient photothermal conversion and thermocatalytic activity of the Ce ion substituted OMS-2 catalyst, we carried out full solar spectrum, visible-infrared, and infrared light driven catalysis with extremely high efficiency. Under the irradiation of full solar spectrum, visible-infrared, and infrared light, the Ce ion substituted OMS-2 catalyst exhibits extremely high catalytic activity and excellent durability for the oxidation of volatile organic pollutants

  8. High pressure flow reactor for in situ X-ray absorption spectroscopy of catalysts in gas-liquid mixtures—A case study on gas and liquid phase activation of a Co-Mo/Al2O3 hydrodesulfurization catalyst

    NARCIS (Netherlands)

    van Haandel, L.; Hensen, E.J.M.; Weber, Th.

    2017-01-01

    An in situ characterization of heterogeneous catalysts under industrial operating conditions may involve high pressure and reactants in both the gas and the liquid phase. In this paper, we describe an in situ XAS flow reactor, which is suitable to operate under such conditions (pmax 20 bar, Tmax 350

  9. High surface area fibrous silica nanoparticles

    KAUST Repository

    Polshettiwar, Vivek; Basset, Jean-Marie

    2014-01-01

    Disclosed are high surface area nanoparticles that have a fibrous morphology. The nanoparticles have a plurality of fibers, wherein each fiber is in contact with one other fiber and each fiber has a length of between about 1 nm and about 5000 nm. Also disclosed are applications of the nanoparticles of the present invention, and methods of fabrication of the nanoparticles of the present invention.

  10. High surface area fibrous silica nanoparticles

    KAUST Repository

    Polshettiwar, Vivek

    2014-11-11

    Disclosed are high surface area nanoparticles that have a fibrous morphology. The nanoparticles have a plurality of fibers, wherein each fiber is in contact with one other fiber and each fiber has a length of between about 1 nm and about 5000 nm. Also disclosed are applications of the nanoparticles of the present invention, and methods of fabrication of the nanoparticles of the present invention.

  11. Decommissioning high-level waste surface facilities

    International Nuclear Information System (INIS)

    1978-04-01

    The protective storage, entombment and dismantlement options of decommissioning a High-Level Waste Surface Facility (HLWSF) was investigated. A reference conceptual design for the facility was developed based on the designs of similar facilities. State-of-the-art decommissioning technologies were identified. Program plans and cost estimates for decommissioning the reference conceptual designs were developed. Good engineering design concepts were on the basis of this work identified

  12. Oxygen reduction on carbon supported platinum catalysts in high temperature polymer electrolytes

    DEFF Research Database (Denmark)

    Qingfeng, Li; Hjuler, Hans Aage; Bjerrum, Niels

    2000-01-01

    Oxygen reduction on carbon supported platinum catalysts has been investigated in H3PO4, H3PO4-doped Nafion and polybenzimidazole (PBI) polymer electrolytes in a temperature range up to 190 degrees C. Compared with pure H3PO4, the combination of H3PO4 and polymer electrolytes can significantly...... membrane fuel cell based on H3PO4-doped PBI for operation at temperatures between 150 and 200 degrees C. (C) 2000 Elsevier Science Ltd. All rights reserved....

  13. High sintering resistance of size-selected platinum cluster catalysts by suppressed ostwald ripening

    DEFF Research Database (Denmark)

    Wettergren, Kristina; Schweinberger, Florian F.; Deiana, Davide

    2014-01-01

    on different supports exhibit remarkable intrinsic sintering resistance even under reaction conditions. The observed stability is related to suppression of Ostwald ripening by elimination of its main driving force via size-selection. This study thus constitutes a general blueprint for the rational design...... of sintering resistant catalyst systems and for efficient experimental strategies to determine sintering mechanisms. Moreover, this is the first systematic experimental investigation of sintering processes in nanoparticle systems with an initially perfectly monomodal size distribution under ambient conditions....

  14. Poly (pyrrole-co-aniline) hollow nanosphere supported Pd nanoflowers as high-performance catalyst for methanol electrooxidation in alkaline media

    International Nuclear Information System (INIS)

    Fard, Leyla Abolghasemi; Ojani, Reza; Raoof, Jahan Bakhsh; Zare, Ehsan Nazarzadeh; Lakouraj, Moslem Mansour

    2017-01-01

    In this work, first poly (pyrrole-co-aniline) (PPCA) hollow nanosphere (HN) as a catalyst support material is fabricated through in-situ emulsion polymerization. Then we reported a one-step and template-free approach to fabricate Pd NFs on a PPCA HN coated glassy carbon electrode by a facile electrochemical approach. Several techniques such as FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy) were utilized for the characterization of the synthesized materials. The catalytic performance of Pd NFs/PPCA HN catalyst is evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy toward methanol oxidation as a model reaction in alkaline media. The comparison of specific activities for Pd NFs/PPCA HN (1.79 mA cm"−"2), Pd NFs/PPy (1.28 mA cm"−"2), Pd NFs/PANI (0.93 mA cm"−"2) and Pd NFs (0.78 mA cm"−"2) shows that the PPCA supported Pd NFs with high surface area exhibits the excellent electrocatalytic activity than other electrodes for the electro-oxidation reaction in alkaline media. This might be due to the easier charge transfer at conductive copolymer interfaces, higher electrochemically accessible surface areas and electronic conductivity. This strategy provides a promising platform for direct methanol fuel cells. - Highlights: • Pd nanoflowers supported on poly (pyrrole-co-aniline) hollow nanosphere is prepared by a facile electrochemical approach. • The as-prepared nanocatalyst displays the enhanced electrocatalytic activity and stability for methanol oxidation. • The high performance is attributed to facile electron transfer on poly (pyrrole-co-aniline) hollow nanosphere substrate.

  15. Highly Active Non-PGM Catalysts Prepared from Metal Organic Frameworks

    Directory of Open Access Journals (Sweden)

    Heather M. Barkholtz

    2015-06-01

    Full Text Available Finding inexpensive alternatives to platinum group metals (PGMs is essential for reducing the cost of proton exchange membrane fuel cells (PEMFCs. Numerous materials have been investigated as potential replacements of Pt, of which the transition metal and nitrogen-doped carbon composites (TM/Nx/C prepared from iron doped zeolitic imidazolate frameworks (ZIFs are among the most active ones in catalyzing the oxygen reduction reaction based on recent studies. In this report, we demonstrate that the catalytic activity of ZIF-based TM/Nx/C composites can be substantially improved through optimization of synthesis and post-treatment processing conditions. Ultimately, oxygen reduction reaction (ORR electrocatalytic activity must be demonstrated in membrane-electrode assemblies (MEAs of fuel cells. The process of preparing MEAs using ZIF-based non-PGM electrocatalysts involves many additional factors which may influence the overall catalytic activity at the fuel cell level. Evaluation of parameters such as catalyst loading and perfluorosulfonic acid ionomer to catalyst ratio were optimized. Our overall efforts to optimize both the catalyst and MEA construction process have yielded impressive ORR activity when tested in a fuel cell system.

  16. Full Solar Spectrum Light Driven Thermocatalysis with Extremely High Efficiency on Nanostructured Ce Ion Substituted OMS-2 Catalyst for VOCs Purification

    DEFF Research Database (Denmark)

    Hou, J.T.; Li, Y.Z.; Mao, M.Y.

    2015-01-01

    solar spectrum, visible-infrared, and infrared light, the Ce ion substituted OMS-2 catalyst exhibits extremely high catalytic activity and excellent durability for the oxidation of volatile organic pollutants such as benzene, toluene, and acetone. Based on the experimental evidence, we propose a novel...... in a considerable increase of temperature. By combining the efficient photothermal conversion and thermocatalytic activity of the Ce ion substituted OMS-2 catalyst, we carried out full solar spectrum, visible-infrared, and infrared light driven catalysis with extremely high efficiency. Under the irradiation of full...... mechanism of solar light driven thermocatalysis for the Ce ion substituted OMS-2 catalyst. The reason why the Ce ion substituted OMS-2 catalyst exhibits much higher catalytic activity than pure OMS-2 and CeO2/OMS-2 nano composite under the full solar spectrum irradiation is discussed....

  17. Catalyst-Free Conjugation and In Situ Quantification of Nanoparticle Ligand Surface Density Using Fluorogenic Cu-Free Click Chemistry

    DEFF Research Database (Denmark)

    Jølck, Rasmus Irming; Sun, Honghao; Berg, Rolf Henrik

    2011-01-01

    A highly efficient method for functionalizing nanoparticles and directly quantifying conjugation efficiency and ligand surface density has been developed. Attachment of 3-azido-modifed RGD-peptides to PEGylated liposomes was achieved by using Cu-free click conditions. Upon coupling a fluorophore ...

  18. exchanged Mg-Al hydrotalcite catalyst

    Indian Academy of Sciences (India)

    ) catalysts, ... The catalyst can be easily separated by simple filtration ... surface area by the single-point N2 adsorption method ... concentration of carbonate anions (by treating the cat- .... hydrotalcite phase along with copper hydroxide and.

  19. Study on Endurance and Performance of Impregnated Ruthenium Catalyst for Thruster System.

    Science.gov (United States)

    Kim, Jincheol; Kim, Taegyu

    2018-02-01

    Performance and endurance of the Ru catalyst were studied for nitrous oxide monopropellant thruster system. The thermal decomposition of N2O requires a considerably high temperature, which make it difficult to be utilized as a thruster propellant, while the propellant decomposition temperature can be reduced by using the catalyst through the decomposition reaction with the propellant. However, the catalyst used for the thruster was frequently exposed to high temperature and high-pressure environment. Therefore, the state change of the catalyst according to the thruster operation was analyzed. Characterization of catalyst used in the operation condition of the thruster was performed using FE-SEM and EDS. As a result, performance degradation was occurred due to the volatilization of Ru catalyst and reduction of the specific surface area according to the phase change of Al2O3.

  20. One-pot synthesis of well-defined polyether/polyester block copolymers and terpolymers by a highly efficient catalyst switch approach

    KAUST Repository

    Alamri, Haleema

    2016-04-20

    A highly efficient methodology, based on a novel catalyst switch approach with rapid crossover characteristics, was developed for the one-pot synthesis of block co/terpolymers of cyclic ethers and esters. This new approach, which takes advantage of one of the best catalysts for epoxide (t-BuP4) and cyclic ester (t-BuP2) polymerization, opens new horizons toward the synthesis of cyclic ether/ester complex macromolecular architectures. © The Royal Society of Chemistry 2016.

  1. One-pot synthesis of well-defined polyether/polyester block copolymers and terpolymers by a highly efficient catalyst switch approach

    KAUST Repository

    Alamri, Haleema; Hadjichristidis, Nikolaos

    2016-01-01

    A highly efficient methodology, based on a novel catalyst switch approach with rapid crossover characteristics, was developed for the one-pot synthesis of block co/terpolymers of cyclic ethers and esters. This new approach, which takes advantage of one of the best catalysts for epoxide (t-BuP4) and cyclic ester (t-BuP2) polymerization, opens new horizons toward the synthesis of cyclic ether/ester complex macromolecular architectures. © The Royal Society of Chemistry 2016.

  2. Quantification of zinc atoms in a surface alloy on copper in an industrial-type methanol synthesis catalyst

    DEFF Research Database (Denmark)

    Kuld, Sebastian; Moses, Poul Georg; Sehested, Jens

    2014-01-01

    Methanol has recently attracted renewed interest because of its potential importance as a solar fuel.1 Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al2O3 catalyst. The identity of the active site and, in particular, the role of ZnO as a pr...

  3. A novel hybrid catalyst for the esterification of high FFA in Jatropha oil for biodiesel production

    Directory of Open Access Journals (Sweden)

    Mushtaq, M.

    2016-09-01

    Full Text Available The synthesis and application of a hybrid catalyst for the esterification of free fatty acids (FFA in Jatropha oil is reported. Three catalysts, namely silica sulfuric acid, silica supported boron trifluoride and a combination of the two in the weight ratio of 1:1, the hybrid catalyst, were investigated. Jatropha oil samples with a wide range of FFA values i.e. 6.64 to 45.64% were prepared and utilized for the experimental work. This study revealed that silica sulfuric acid and silica supported boron trifluoride were not very effective when used independently. However, a strong synergistic effect was noted in the catalytic activity of the hybrid catalyst which reduced the FFA value from 45.64 to 0.903% with a conversion efficiency of 98%. Reusability of the catalyst was also tested and the results were promising in up to three cycles of use when used with lower amounts of FFA (6.64% in the oil. Under the influence of the catalyst, the reaction was found to follow first order kinetics. Activation energy was calculated to be 45.42 KJ·mol-1 for 2 wt.% of hybrid catalyst. The products were analyzed by FT-IR and NMR spectroscopic techniques and the results are reported.Se aborda la síntesis mediante el uso de un catalizador híbrido en la esterificación de ácidos grasos libres (AGL de aceites de Jatrofa. Se investigaron tres catalizadores: ácido sulfúrico sobre sílica, trifluoruro de boro sobre sílice y un catalizador híbrido, combinación de los dos anteriores en una relación 1:1en peso. Muestras de aceites de Jatrofa con una amplia gama de valores de FFA: desde 6,64 a 45,64% se prepararon y se utilizaron en la parte experimental de este trabajo. Este estudio mostró que los soportes de ácido sulfúrico sobre sílica y el de trifluoruro de boro sobre sílice no eran muy eficaces cuando se utilizan de forma independiente. Sin embargo, un fuerte efecto sinérgico se observó en la actividad catalítica del catalizador híbrido que reduce el

  4. Influence of surface oxygenated groups on the formation of active Cu species and the catalytic activity of Cu/AC catalyst for the synthesis of dimethyl carbonate

    Science.gov (United States)

    Zhang, Guoqiang; Li, Zhong; Zheng, Huayan; Hao, Zhiqiang; Wang, Xia; Wang, Jiajun

    2016-12-01

    Activated carbon (AC) supported Cu catalysts are employed to study the influence of surface oxygenated groups on the formation of active Cu species and the catalytic activity of Cu/AC catalyst for oxidative carbonylation of methanol to dimethyl carbonate (DMC). The AC supports are thermal treated under different temperatures in order to adjust the levels of surface oxygenated groups. The AC supports are characterized by BET, TPD-MS and XRD, and the Cu/AC catalysts are characterized by BET, XRD, TEM, XPS, AAS, CH3OH-TPD and N2O chemisorption. The results show that as the treatment temperature is below 800 °C, the BET surface area of the corresponding AC supports are nearly unchanged and close to that of the original AC (1529.6 m2/g). But as the thermal treatment temperature is elevated from 1000 to 1600 °C, the BET surface area of AC supports gradually decreases from 1407.6 to 972.2 m2/g. After loading of Cu, the BET surface area of copper catalysts is in the range of 834.4 to 1545.3 m2/g, which is slightly less than that of the respective supports. When AC is thermal treated at 400 and 600 °C, the unstable carboxylic acid and anhydrides groups are selectively removed, which has weakened the mobility and agglomeration of Cu species during the calcination process, and thus improve the Cu species dispersion over AC support. But as the treatment temperature is elevated from 600 °C to 1200 °C, the Cu species dispersion begins to decline suggesting further removal of stable surface oxygenated groups is unfavorable for Cu species dispersion. Moreover, higher thermal treatment temperature (above 1200 °C) promotes the graphitization degree of AC and leds to the decrease of Cu loading on AC support. Meanwhile, the removal of surface oxygenated groups by thermal treatment is conducive to the formation of more π-sites, and thus promote the reduction of Cu2+ to Cu+ and Cu0 as active centers. The specific surface area of (Cu+ + Cu0) is improved by thermal treatment of AC

  5. Synthesis and properties of catalysts prepared from silicomolybdovanadium heteropoly acid

    International Nuclear Information System (INIS)

    Chumachenko, N.N.; Tarasova, D.V.; Nikoro, T.A.; Yaroslavtseva, I.V.

    1984-01-01

    Catalytic properties of samples prepared of silicomolybdovanadium heteropoly acid (HPA) have been investigated. The massive catalyst is shown to be comparatively low effective in the reaction of acrolein oxidation to acrylic acid. Impregnation of coarse-dispersed silica gel by the HPA solution results in the formation of active and selective catalyst, whereas low-active catalyst of deep oxidation is formed on the base of high-dispersed silica gel. The obtained data are explained by the formation and stabilization of different forms of vanadium- and molybdenum-containing compounds on the carrier surface

  6. A microbial-mineralization approach for syntheses of iron oxides with a high specific surface area.

    Science.gov (United States)

    Yagita, Naoki; Oaki, Yuya; Imai, Hiroaki

    2013-04-02

    Of minerals and microbes: A microbial-mineralization-inspired approach was used to facilitate the syntheses of iron oxides with a high specific surface area, such as 253 m(2)g(-1) for maghemite (γ-Fe(2)O(3)) and 148 m(2)g(-1) for hematite (α-Fe(2)O(3)). These iron oxides can be applied to electrode material of lithium-ion batteries, adsorbents, and catalysts. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Final Technical Report for GO15052 Intematix: Combinatorial Synthesis and High Throughput Screening of Effective Catalysts for Chemical Hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Melman, Jonathan [Intematix Corporation, Fremont, CA (United States)

    2017-02-22

    The objectives of this project are: to discover cost-effective catalysts for release of hydrogen from chemical hydrogen storage systems; and to discover cost-effective catalysts for the regeneration of spent chemical hydrogen storage materials.

  8. Nanoparticle-supported and magnetically recoverable palladium (Pd) catalyst: a selective and sustainable oxidation protocol with high turnover number

    Science.gov (United States)

    A magnetic nanoparticle-supported ruthenium hydroxide catalyst was readily prepared from inexpensive starting materials and shown to catalyze hydration of nitriles with excellent yield in benign aqueous medium. Catalyst recovery using an external magnetic field, superior activity...

  9. OSU-6: A Highly Efficient, Metal-Free, Heterogeneous Catalyst for the Click Synthesis of 5-Benzyl and 5-Aryl-1H-tetrazoles

    Directory of Open Access Journals (Sweden)

    Baskar Nammalwar

    2015-12-01

    Full Text Available OSU-6, an MCM-41 type hexagonal mesoporous silica with mild Brönsted acid properties, has been used as an efficient, metal-free, heterogeneous catalyst for the click synthesis of 5-benzyl and 5-aryl-1H-tetrazoles from nitriles in DMF at 90 °C. This catalyst offers advantages including ease of operation, milder conditions, high yields, and reusability. Studies are presented that demonstrate the robust nature of the catalyst under the optimized reaction conditions. OSU-6 promotes the 1,3-dipolar addition of azides to nitriles without significant degradation or clogging of the nanoporous structure. The catalyst can be reused up to five times without a significant reduction in yield, and it does not require treatment with acid between reactions.

  10. Synthesis of partially graphitic ordered mesoporous carbons with high surface areas

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Wenjun; Wan, Ying [Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, Shanghai Normal University, Shanghai 200234 (China); Dou, Yuqian; Zhao, Dongyuan [Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433 (China)

    2011-01-01

    Graphitic carbons with ordered mesostructure and high surface areas (of great interest in applications such as energy storage) have been synthesized by a direct triblock-copolymer-templating method. Pluronic F127 is used as a structure-directing agent, with a low-molecular-weight phenolic resol as a carbon source, ferric oxide as a catalyst, and silica as an additive. Inorganic oxides can be completely eliminated from the carbon. Small-angle XRD and N{sub 2} sorption analysis show that the resultant carbon materials possess an ordered 2D hexagonal mesostructure, uniform bimodal mesopores (about 1.5 and 6 nm), high surface area ({proportional_to}1300 m{sup 2}/g), and large pore volumes ({proportional_to}1.50 cm{sup 3}/g) after low-temperature pyrolysis (900 C). All surface areas come from mesopores. Wide-angle XRD patterns demonstrate that the presence of the ferric oxide catalyst and the silica additive lead to a marked enhancement of graphitic ordering in the framework. Raman spectra provide evidence of the increased content of graphitic sp{sup 2} carbon structures. Transmission electron microscopy images confirm that numerous domains in the ordered mesostructures are composed of characteristic graphitic carbon nanostructures. The evolution of the graphitic structure is dependent on the temperature and the concentrations of the silica additive, and ferric oxide catalyst. Electrochemical measurements performed on this graphitic mesoporous carbon when used as an electrode material for an electrochemical double layer capacitor shows rectangular-shaped cyclic voltammetry curves over a wide range of scan rates, even up to 200 mV/s, with a large capacitance of 155 F/g in KOH electrolyte. This method can be widely applied to the synthesis of graphitized carbon nanostructures. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Exfoliated Pd/HNb{sub 3}O{sub 8} nanosheet as highly efficient bifunctional catalyst for one-pot cascade reaction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Nahaeng; Chung, Young-Min, E-mail: ymchung@kunsan.ac.kr

    2016-05-01

    Graphical abstract: - Highlights: • Ultrathin and highly acidic HNb{sub 3}O{sub 8} nanosheet was prepared by exfoliation of layered niobium oxide. • Pd/HNb{sub 3}O{sub 8} nanosheet showed excellent catalytic performance for one-pot cascade reaction. • The reaction performance of Pd/HNb{sub 3}O{sub 8} nanosheet is 7.1 and 1.2 times higher than that of layered Pd/KNb{sub 3}O{sub 8} or Pd/HNb{sub 3}O{sub 8}, respectively. • Significant promoting effect of support acidity on the reaction performance was observed. - Abstract: Ultrathin two-dimensional metal oxide nanosheets have drawn attention as potential solid acid catalysts owing to their strong acidity, attributed to the bridged OH groups formed on the nanosheets. In this study, a new class of bifunctional acid–metal catalyst was realized by the deposition of Pd on layered niobium oxide (KNb{sub 3}O{sub 8} and HNb{sub 3}O{sub 8}) or its exfoliated nanosheet (Pd/HNb{sub 3}O{sub 8}-NS) and applied to one-pot cascade deacetalization and hydrogenation. It was found that the acid strength of the support exerted a large influence not only on the promotion of the first deacetalization step, but also on the acceleration of the subsequent hydrogenation step. Comparative experiments using a series of Pd/HZSM-5 catalysts with different acidities reconfirmed the crucial role of acid strength on hydrogenation. However, the superior catalytic activity of Pd/HNb{sub 3}O{sub 8}-NS for hydrogenation compared to that of Pd/HZSM-5 of similar acidity suggests a more efficient ensemble effect of the strong acid sites with the nearby metal sites on the nanosheet surface. Among the catalysts used, Pd/HNb{sub 3}O{sub 8}-NS showed the best catalytic performance for one-pot cascade reaction affording the desired product (benzyl alcohol) in approximately 92% yield, which was 7.1 and 1.2 times higher than that of layered Pd/KNb{sub 3}O{sub 8} or Pd/HNb{sub 3}O{sub 8}, respectively. The excellent catalytic performance of Pd/HNb{sub 3

  12. Development of industrial hydrogenating catalyst on rhenium base

    International Nuclear Information System (INIS)

    Chistyakova, G.A.; Bat', I.I.; Rebrova, V.V.

    1975-01-01

    Processes for forming rhenium catalysts on carbon carrier and their catalytic properties in nitrobenzene (NB) reduction were studied. Application of an ammonia preparation to the carbon surface produced impregnated carbon saturated at room temperature with a water solution of the ammonia preparation, taken in a volume equal to the volumetric capacity of the carbon. With one impregnation, 2% rhenium was taken up. Catalysts containing more than 5% rhenium were obtained by impregnating the carbon with heating and use of more concentrated solutions. Catalysts made in this way and dried at 100 0 C had the composition Re 2 OH/carbon/. The most active catalysts were those reduced at 200-250 0 C; higher temperatures, up to 300-500 0 C, decreased the activity. Study of the catalytic properties of the rhenium catalysts in a liquid phase reduction of NB showed that the specific activity of rhenium depends only slightly on the content of the active component in the catalyst and is close to the specific activity of palladium and considerably exceeds that of nickel. Study of the effect of the NB concentration and hydrogen pressure on the activity and stability of the 5% rhenium catalyst indicated that with NB concentrations from 50 to 10% the process takes place at an essentially constant rate; the order of the reaction was close to zero with an apparent activation energy of about 7000 cal/mole. At pressures of 15-200 atm the yield with the 5% catalyst was proportional to the hydrogen pressure. A big advantage of the rhenium catalysts in the reduction of NB is their high selectivity. With a higher activity than palladium and nickel catalysts, 5% rhenium catalyst produces a high operating capacity in a wide range of contact charges, which has considerable significance for industrial use in contact apparatus of the column type. Comparison of the costs of rhenium catalysts and granular carbon carrier with those of nickel, platinum, and palladium showed that 5% rhenium catalyst can

  13. Highly Selective Hydrogenation of Levulinic Acid to γ-Valerolactone Over Ru/ZrO2 Catalysts

    NARCIS (Netherlands)

    Filiz, B.C.; Gnanakumar, E.S.; Martinez-Arias, A.; Gengler, R.; Rudolf, P.; Rothenberg, G.; Shiju, N.R.

    We studied the catalytic hydrogenation of levulinic acid over zirconia supported ruthenium catalysts. Four different Ru/ZrO2 catalysts were prepared by different pre-treatments and using different zirconium supports (ZrOx(OH)4−2x and ZrO2). Although the final compositions of the catalysts are the

  14. Highly Selective Hydrogenation of Levulinic Acid to gamma-Valerolactone Over Ru/ZrO2 Catalysts

    NARCIS (Netherlands)

    Filiz, Bilge Coskuner; Gnanakumar, Edwin S.; Martinez-Arias, Arturo; Gengler, Regis; Rudolf, Petra; Rothenberg, Gadi; Shiju, N. Raveendran

    We studied the catalytic hydrogenation of levulinic acid over zirconia supported ruthenium catalysts. Four different Ru/ZrO2 catalysts were prepared by different pre-treatments and using different zirconium supports (ZrOx(OH)(4-2x) and ZrO2). Although the final compositions of the catalysts are the

  15. Design of Polymer-Coated Multi-Walled Carbon Nanotube/Carbon Black-based Fuel Cell Catalysts with High Durability and Performance Under Non-humidified Condition

    International Nuclear Information System (INIS)

    Yang, Zehui; Berber, Mohamed R.; Nakashima, Naotoshi

    2015-01-01

    To realize a high catalyst utilization, better fuel cell performance and durability as well as low production cost, an efficient design strategy of the catalyst layer that can improve both the oxygen accessibility and structure stability is highly required. Here, we describe the preparation of fuel cell electrocatalysts with an efficient fuel cell performance and better stability based on hybrids of multi-walled carbon nanotubes (MWNTs) and carbon black (CB) which were wrapped by a proton conducting polymer, poly[2,2′-(2,6-pyridine)-5,5′-bibenzimidazole], before deposition of the platinum (Pt) metal catalyst. The catalyst mass activity after feeding only 10%-MWNTs to CB increased by 1.5 and 2 times than those of the MWNTs-based- and CB-based catalysts, respectively. The results also demonstrated that 90 wt% of the MWNTs in the catalyst layer allows it to be replaced by CB without any significant change in its durability and performance under 120 °C and non-humidified condition

  16. Preparation and study of IrO2/SiC–Si supported anode catalyst for high temperature PEM steam electrolysers

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Tomás García, Antonio Luis; Petrushina, Irina

    2011-01-01

    A novel catalyst material for oxygen evolution electrodes was prepared and characterised by different techniques. IrO2 supported on a SiC–Si composite was synthesised by the Adams fusion method. XRD and nitrogen adsorption experiments showed an influence of the support on the surface properties o...

  17. Single-site catalyst promoters accelerate metal-catalyzed nitroarene hydrogenation

    KAUST Repository

    Wang, Liang

    2018-04-04

    Atomically dispersed supported metal catalysts are drawing wide attention because of the opportunities they offer for new catalytic properties combined with efficient use of the metals. We extend this class of materials to catalysts that incorporate atomically dispersed metal atoms as promoters. The catalysts are used for the challenging nitroarene hydrogenation and found to have both high activity and selectivity. The promoters are single-site Sn on TiO2 supports that incorporate metal nanoparticle catalysts. Represented as M/Sn-TiO2 (M = Au, Ru, Pt, Ni), these catalysts decidedly outperform the unpromoted supported metals, even for hydrogenation of nitroarenes substituted with various reducible groups. The high activity and selectivity of these catalysts result from the creation of oxygen vacancies on the TiO2 surface by single-site Sn, which leads to efficient, selective activation of the nitro group coupled with a reaction involving hydrogen atoms activated on metal nanoparticles.

  18. Single-site catalyst promoters accelerate metal-catalyzed nitroarene hydrogenation

    KAUST Repository

    Wang, Liang; Guan, Erjia; Zhang, Jian; Yang, Junhao; Zhu, Yihan; Han, Yu; Yang, Ming; Cen, Cheng; Fu, Gang; Gates, Bruce C.; Xiao, Feng-Shou

    2018-01-01

    Atomically dispersed supported metal catalysts are drawing wide attention because of the opportunities they offer for new catalytic properties combined with efficient use of the metals. We extend this class of materials to catalysts that incorporate atomically dispersed metal atoms as promoters. The catalysts are used for the challenging nitroarene hydrogenation and found to have both high activity and selectivity. The promoters are single-site Sn on TiO2 supports that incorporate metal nanoparticle catalysts. Represented as M/Sn-TiO2 (M = Au, Ru, Pt, Ni), these catalysts decidedly outperform the unpromoted supported metals, even for hydrogenation of nitroarenes substituted with various reducible groups. The high activity and selectivity of these catalysts result from the creation of oxygen vacancies on the TiO2 surface by single-site Sn, which leads to efficient, selective activation of the nitro group coupled with a reaction involving hydrogen atoms activated on metal nanoparticles.

  19. Directly observing catalytic intermediates of methane dry reforming (MDR) on model Ni(111) catalyst via in operando surface techniques

    Science.gov (United States)

    Yuan, Kaidi

    In this work, near ambient pressure x-ray photoelectron spectroscopy was used to trace the in operando catalytic intermediates of methane dry reforming on model Ni(111) catalyst. The following reactive carbon intermediates have been characterized from dissociation of CH4: *CH, *C1 (Ni3C), *Cn (n≥2) and clock-reconstructed Ni2C. They can develop into inert graphene, and the conditions for this transition have been explored. One the other hand, the oxygen intermediates from CO2 dissociation were also studied, which play an important role on restraining graphene growth. Their dynamic coverage decreases with increasing temperature, which is suggested the fundamental mechanism of regional carbon overspill and causes irreversible graphene formation. Therefore, solutions based on Ni-O stabilization were proposed in developing coking resisting catalysts.

  20. Catalyst in Basic Oleochemicals

    Directory of Open Access Journals (Sweden)

    Eva Suyenty

    2007-10-01

    Full Text Available Currently Indonesia is the world largest palm oil producer with production volume reaching 16 million tones per annum. The high crude oil and ethylene prices in the last 3 – 4 years contribute to the healthy demand growth for basic oleochemicals: fatty acids and fatty alcohols. Oleochemicals are starting to replace crude oil derived products in various applications. As widely practiced in petrochemical industry, catalyst plays a very important role in the production of basic oleochemicals. Catalytic reactions are abound in the production of oleochemicals: Nickel based catalysts are used in the hydrogenation of unsaturated fatty acids; sodium methylate catalyst in the transesterification of triglycerides; sulfonic based polystyrene resin catalyst in esterification of fatty acids; and copper chromite/copper zinc catalyst in the high pressure hydrogenation of methyl esters or fatty acids to produce fatty alcohols. To maintain long catalyst life, it is crucial to ensure the absence of catalyst poisons and inhibitors in the feed. The preparation methods of nickel and copper chromite catalysts are as follows: precipitation, filtration, drying, and calcinations. Sodium methylate is derived from direct reaction of sodium metal and methanol under inert gas. The sulfonic based polystyrene resin is derived from sulfonation of polystyrene crosslinked with di-vinyl-benzene. © 2007 BCREC UNDIP. All rights reserved.[Presented at Symposium and Congress of MKICS 2007, 18-19 April 2007, Semarang, Indonesia][How to Cite: E. Suyenty, H. Sentosa, M. Agustine, S. Anwar, A. Lie, E. Sutanto. (2007. Catalyst in Basic Oleochemicals. Bulletin of Chemical Reaction Engineering and Catalysis, 2 (2-3: 22-31.  doi:10.9767/bcrec.2.2-3.6.22-31][How to Link/DOI: http://dx.doi.org/10.9767/bcrec.2.2-3.6.22-31 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/6

  1. Synthesis of MoVTeNb Oxide Catalysts with Tunable Particle Dimensions

    DEFF Research Database (Denmark)

    Kolenko, Yury V.; Zhang, Wei; d'Alnoncourt, Raoul Naumann

    2011-01-01

    Reliable procedures for the controlled synthesis of phase-pure MoVTeNb mixed oxides with M1 structure (ICSD 55097) and tunable crystal dimensions were developed to study the structure sensitivity of the selective oxidation of propane to acrylic acid. A series of powdered M1 catalysts...... catalysts were studied in the selective oxidation of propane to acrylic acid, revealing that active sites appear on the entire M1 surface and illustrating the high sensitivity of catalyst performance on the catalyst synthesis method....

  2. Communicating catalysts

    Science.gov (United States)

    Weckhuysen, Bert M.

    2018-06-01

    The beauty and activity of enzymes inspire chemists to tailor new and better non-biological catalysts. Now, a study reveals that the active sites within heterogeneous catalysts actively cooperate in a fashion phenomenologically similar to, but mechanistically distinct, from enzymes.

  3. Multifunctional magnetic core–shell dendritic mesoporous silica nanospheres decorated with tiny Ag nanoparticles as a highly active heterogeneous catalyst

    International Nuclear Information System (INIS)

    Sun, Zebin; Li, Haizhen; Cui, Guijia; Tian, Yaxi; Yan, Shiqiang

    2016-01-01

    Graphical abstract: - Highlights: • A multifunctional magnetic core–shell dendritic silica nanocatalyst was successfully fabricated by an oil–water biphase stratification coating strategy. • The magnetic core–shell dendritic silica nanomaterials Fe_3O_4@SiO_2@Dendritic-SiO_2 were chosen as the catalyst's support for the first time. • The as-synthesized nanocatalyst exhibited excellent catalytic activity and reusability due to easy accessibility of active sites and superparamagnetism. • The novel catalyst could be conveniently recovered by magnetic separation from the reaction system. - Abstract: In present work, a multifunctional magnetic core–shell dendritic silica nanocatalyst Fe_3O_4@SiO_2@Dendritic-SiO_2-NH_2-Ag with easy accessibility of active sites and convenient recovery was successfully fabricated by an oil–water biphase stratification coating strategy, and characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N_2 adsorption–desorption, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The as-synthesized nanocatalyst Fe_3O_4@SiO_2@Dendritic-SiO_2-NH_2-Ag displayed excellent catalytic activity for the catalytic reduction of 4-nitrophenol and 2-nitroaniline using sodium borohydride in aqueous solution at room temperature due to easy accessibility of active sites. Interestingly, the novel catalyst could be conveniently recovered by magnetic separation from the reaction system and recycled for at least five times without significant loss in activity. These results indicate that the above mentioned approach based on magnetic core–shell dendritic silica Fe_3O_4@SiO_2@Dendritic-SiO_2 provided a useful platform for the preparation of noble metal nanocatalysts with easy accessibility, excellent catalytic activity and convenient recovery.

  4. Effect of Catalyst Pellet-Diameter and Basicity on Transesterification of Soybean Oil into Biodiesel using K2O/CaO-ZnO Catalyst over Hybrid Catalytic-Plasma Reactor

    Directory of Open Access Journals (Sweden)

    Istadi I.

    2018-01-01

    Full Text Available This research is aimed to study the effect of catalyst pellet-diameter and catalyst basicity on the transesterification process of soybean oil into biodiesel over a hybrid catalytic-plasma reactor. Various catalyst diameters (3, 5, and 7 mm were tested in this reaction system. Catalyst basicity was also examined by comparing fresh and used catalyst as well as with and without K2O promoter. All catalysts testing were performed in a hybrid plasma-catalytic reactor (dielectric barrier discharge – DBD type. From the results, the synergistic effects roles of the catalyst and the plasma in the transesterification process are important, in which the energetic electrons within plasma assist the reaction on the catalyst surface by an exciting bonded electron. The catalyst basicity was influenced by the composition of CaO on the catalyst as well as roles of the alkaline K2O promoter. Catalyst basicity is important in producing biodiesel with high performance. Yield of fatty acid alkyl ester (FAAE or biodiesel is slightly influenced by the catalyst diameter within the range of diameter studied.

  5. Catalytic Hydrodeoxygenation of High Carbon Furylmethanes to Renewable Jet-fuel Ranged Alkanes over a Rhenium-Modified Iridium Catalyst.

    Science.gov (United States)

    Liu, Sibao; Dutta, Saikat; Zheng, Weiqing; Gould, Nicholas S; Cheng, Ziwei; Xu, Bingjun; Saha, Basudeb; Vlachos, Dionisios G

    2017-08-24

    Renewable jet-fuel-range alkanes are synthesized by hydrodeoxygenation of lignocellulose-derived high-carbon furylmethanes over ReO x -modified Ir/SiO 2 catalysts under mild reaction conditions. Ir-ReO x /SiO 2 with a Re/Ir molar ratio of 2:1 exhibits the best performance, achieving a combined alkanes yield of 82-99 % from C 12 -C 15 furylmethanes. The catalyst can be regenerated in three consecutive cycles with only about 12 % loss in the combined alkanes yield. Mechanistically, the furan moieties of furylmethanes undergo simultaneous ring saturation and ring opening to form a mixture of complex oxygenates consisting of saturated furan rings, mono-keto groups, and mono-hydroxy groups. Then, these oxygenates undergo a cascade of hydrogenolysis reactions to alkanes. The high activity of Ir-ReO x /SiO 2 arises from a synergy between Ir and ReO x , whereby the acidic sites of partially reduced ReO x activate the C-O bonds of the saturated furans and alcoholic groups while the Ir sites are responsible for hydrogenation with H 2 . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. PVP-stabilized Ru–Rh nanoparticles as highly efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

    International Nuclear Information System (INIS)

    Rakap, Murat

    2015-01-01

    Herein, the utilization of poly(N-vinyl-2-pyrrolidone)-protected ruthenium–rhodium nanoparticles (3.4 ± 1.4 nm) as highly efficient catalysts in the hydrolysis of ammonia borane for hydrogen generation is reported. They are prepared by co-reduction of ruthenium and rhodium metal ions in ethanol/water mixture by an alcohol reduction method and characterized by transmission electron microscopy-energy dispersive X-ray spectroscopy, ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy. They are durable and highly efficient catalysts for hydrogen generation from the hydrolysis of ammonia borane even at very low concentrations and temperature, providing average turnover frequency of 386 mol H 2 (mol cat) −1 min −1 and maximum hydrogen generation rate of 10,680 L H 2 min −1 (mol cat) −1 . Poly(N-vinyl-2-pyrrolidone)-protected ruthenium–rhodium nanoparticles also provide activation energy of 47.4 ± 2.1 kJ/mol for the hydrolysis of ammonia borane. - Highlights: • Ru-Rh@PVP NPs provide a TOF of 386 mol H 2 (mol cat) −1 min −1 for hydrolysis of AB. • Maximum HG rate is 9680 L H 2 min −1 (mol cat) −1 for the hydrolysis of AB. • Activation energy is 47.4 ± 2.1 kJ mol −1 for the hydrolysis of AB

  7. DEVELOPMENT OF ATTRITION RESISTANT IRON-BASED FISCHER-TROPSCH CATALYSTS

    International Nuclear Information System (INIS)

    Adeyinka A. Adeyiga

    2001-01-01

    The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO+H 2 ) to liquid fuels. Since the reaction is highly exothermic, one of the major problems in control of the reaction is heat removal. Recent work has shown that the use of slurry bubble column reactors (SBCRs) can largely solve this problem. The use of iron-based catalysts is attractive not only due to their low cost and ready availability, but also due to their high water-gas shift activity which makes it possible to use these catalysts with low H 2 /CO ratios. However, a serious problem with use of Fe catalysts in a SBCR is their tendency to undergo attrition. This can cause fouling/plugging of downstream filters and equipment, makes the separation of catalyst from the oil/wax product very difficult if not impossible, and results in a steady loss of catalyst from the reactor. Recently, fundamental understanding of physical attrition is being addressed by incorporating suitable binders into the catalyst recipe. This has resulted in the preparation of a spray dried Fe-based catalyst having aps of 70 mm with high attrition resistance. This Fe-based attrition resistant, active and selective catalyst gave 95% CO conversion through 125 hours of testing in a fixed-bed at 270 C, 1.48 MPa, H 2 /CO=0.67 and 2.0 NL/g-cat/h with C 5 + selectivity of >78% and methane selectivity of <5%. However, further development of the catalyst is needed to address the chemical attrition due to phase changes that any Fe-catalyst goes through potentially causing internal stresses within the particle and resulting in weakening, spalling or cracking. The objective of this research is to develop robust iron-based Fischer-Tropsch catalysts that have suitable activity, selectivity and stability to be used in the slurry bubble column reactor. Specifically we aim to develop to: (i) improve the performance and preparation procedure of the high activity, high attrition resistant, high alpha iron

  8. Promising SiC support for Pd catalyst in selective hydrogenation of acetylene to ethylene

    Science.gov (United States)

    Guo, Zhanglong; Liu, Yuefeng; Liu, Yan; Chu, Wei

    2018-06-01

    In this study, SiC supported Pd nanoparticles were found to be an efficient catalyst in acetylene selective hydrogenation reaction. The ethylene selectivity can be about 20% higher than that on Pd/TiO2 catalyst at the same acetylene conversion at 90%. Moreover, Pd/SiC catalyst showed a stable catalytic life at 65 °C with 80% ethylene selectivity. With the detailed characterization using temperature-programmed reduction (H2-TPR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption analysis, CO-chemisorption and thermo-gravimetric analysis (TGA), it was found that SiC owns a lower surface area (22.9 m2/g) and a broad distribution of meso-/macro-porosity (from 5 to 65 nm), which enhanced the mass transfer during the chemical process at high reaction rate and decreased the residence time of ethylene on catalyst surface. Importantly, SiC support has the high thermal conductivity, which favored the rapid temperature homogenization through the catalyst bed and inhabited the over-hydrogenation of acetylene. The surface electronic density of Pd on Pd/SiC catalyst was higher than that on Pd/TiO2, which could promote desorption of ethylene from surface of the catalyst. TGA results confirmed a much less coke deposition on Pd/SiC catalyst.

  9. UV Light-Assisted Synthesis of Highly Efficient Pd-Based Catalyst over NiO for Hydrogenation of o-Chloronitrobenzene.

    Science.gov (United States)

    Jiang, Weidong; Xu, Bin; Fan, Guangyin; Zhang, Kaiming; Xiang, Zhen; Liu, Xiaoqiang

    2018-04-14

    Supported Pd-based catalyst over active nickel oxide (NiO) was repared using the impregnation method companying with UV-light irradiation. Moreover, the catalytic performance of the obtained Pd-based catalysts was evaluated towards the hydrogenation of o -chloronitrobenzene ( o -CNB). Observations indicate that the as-prepared UV-irradiated Pd/NiO catalyst with a mole fraction 0.2% (0.2%Pd/NiO) has higher activity and selectivity in the o -CNB hydrogenation. Especially, UV-light irradiation played a positive role in the improvement of catalytic activity of 0.2%Pd/NiO catalyst, exhibiting an excess 11-fold activity superiority in contrast with non-UV-irradiated 0.2%Pd/NiO catalyst. In addition, it was investigated that effects of varied factors (i.e., reaction time, temperature, o -CNB/Pd ratio, Pd loading, hydrogen pressure) on the selective hydrogenation of ο -CNB catalyzed by UV-irradiated 0.2%Pd/NiO catalyst. Under the reaction conditions of 60 °C, 0.5 h, 1 MPa H₂ pressure, 100% conversion of o -CNB, and 81.1% o -CAN selectivity were obtained, even at high molar ratio (8000:1) of o -CNB to Pd.

  10. CoFe{sub 2}O{sub 4} magnetic nanoparticles as a highly active heterogeneous catalyst of oxone for the degradation of diclofenac in water

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Jing [State Key Laboratory of Pollution Control Reuse, Tongji University, Shanghai 200092 (China); Shao, Yisheng, E-mail: shaoyisheng2011@163.com [State Key Laboratory of Pollution Control Reuse, Tongji University, Shanghai 200092 (China); China Academy of Urban Planning and Design, Beijing 100037 (China); Gao, Naiyun; Tan, Chaoqun; Zhou, Shiqing; Hu, Xuhao [State Key Laboratory of Pollution Control Reuse, Tongji University, Shanghai 200092 (China)

    2013-11-15

    Highlights: • CoFe{sub 2}O{sub 4} MNPs tested as heterogeneous catalyst for the activation of oxone. • The catalytic performance was typically affected by several key operating parameters. • The catalyst exhibited good stability and easily recovered with excellent reusability. • Degradation pathway was proposed according to the results of LC-MS/MS analysis. -- Abstract: A magnetic nanoscaled catalyst cobalt ferrite (CoFe{sub 2}O{sub 4}) was successfully prepared and used for the activation of oxone to generate sulfate radicals for the degradation of diclofenac. The catalyst was characterized by transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The effects of calcination temperature, initial pH, catalyst and oxone dosage on the degradation efficiency were investigated. Results demonstrated that CoFe{sub 2}O{sub 4}-300 exhibited the best catalytic performance and almost complete removal of diclofenac was obtained in 15 min. The degradation efficiency increased with initial pH decreasing in the pH range of 5–9. The increase of catalyst and oxone dosage both had the positive effect on the degradation of diclofenac. Moreover, CoFe{sub 2}O{sub 4} could retain high degradation efficiency even after being reused for five cycles. Finally, the major diclofenac degradation intermediates were identified and the primary degradation pathways were proposed.

  11. CoFe2O4 magnetic nanoparticles as a highly active heterogeneous catalyst of oxone for the degradation of diclofenac in water

    International Nuclear Information System (INIS)

    Deng, Jing; Shao, Yisheng; Gao, Naiyun; Tan, Chaoqun; Zhou, Shiqing; Hu, Xuhao

    2013-01-01

    Highlights: • CoFe 2 O 4 MNPs tested as heterogeneous catalyst for the activation of oxone. • The catalytic performance was typically affected by several key operating parameters. • The catalyst exhibited good stability and easily recovered with excellent reusability. • Degradation pathway was proposed according to the results of LC-MS/MS analysis. -- Abstract: A magnetic nanoscaled catalyst cobalt ferrite (CoFe 2 O 4 ) was successfully prepared and used for the activation of oxone to generate sulfate radicals for the degradation of diclofenac. The catalyst was characterized by transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The effects of calcination temperature, initial pH, catalyst and oxone dosage on the degradation efficiency were investigated. Results demonstrated that CoFe 2 O 4 -300 exhibited the best catalytic performance and almost complete removal of diclofenac was obtained in 15 min. The degradation efficiency increased with initial pH decreasing in the pH range of 5–9. The increase of catalyst and oxone dosage both had the positive effect on the degradation of diclofenac. Moreover, CoFe 2 O 4 could retain high degradation efficiency even after being reused for five cycles. Finally, the major diclofenac degradation intermediates were identified and the primary degradation pathways were proposed

  12. Synthesis of New Silicon-linked Lanthanocene Complexes and Their High Catalytic Activity for Methyl Methacrylate Polymerization with Nanometric Sodium Hydride as Co-catalyst

    Institute of Scientific and Technical Information of China (English)

    谢小敏; 黄吉玲

    2005-01-01

    The synthesis and characterization of four new silicon-linked lanthanocene complexes with pendant phenyl groups on cyclopentadiene were reported. Based on the data of elemental analyses, MS and IR, the complexes were presumed to be unsolvated and dimeric complexes [Me2Si(C5H3CMe2C6H5)2LnC1]2 [Ln=Er (1), Gd (2), Sm (3), Dy (4)]. In conjunction with AlEt3 or sodium hydride as the co-catalyst, these complexes could efficiently catalyze the polymerization of methyl methacrylate (MMA). When the nanometric sodium hydride was used as a co-catalyst, the complexes were highly effective for the polymerization of MMA. At low temperature and in short time, in [MeESi(C5H3CMe2C6H5)2LnC1]2/NaH (nanometric) system, the polymer was obtained in more than 80% yield and the molecular weight was greater than 105. The activity reached that of organolanthanide hydride as a single-component catalyst. In ]MeESi(C5H3CMe2C6H5)2ErC1]2/Nail (nanometric) system, the effects of the molar ratio of MMA/catalyst and catalyst/co-catalyst, and the temperature on polymerization were studied.

  13. Esterification of oily-FFA and transesterification of high FFA waste oils using novel palm trunk and bagasse-derived catalysts

    International Nuclear Information System (INIS)

    Ezebor, Francis; Khairuddean, Melati; Abdullah, Ahmad Zuhairi; Boey, Peng Lim

    2014-01-01

    Highlights: • Novel palm trunk and bagasse derived catalysts have been prepared. • Reduction of FFAs from 42 to <1 wt.% in 15 min under pseudo-infinite methanol. • Transesterification of waste oil results in FAME yield of 80.6–83.2% in 4 h. • Pseudo-infinite methanol affords two-folds FAME yield of conventional methods. - Abstract: Waste cooking oil is increasingly becoming a significant component of biodiesel feedstock and its conversion to FAME requires coupling of esterification and transesterification processes. In this study, new environmentally benign catalysts were prepared from oil palm trunk and sugarcane bagasse, which are sustainable because of the superfluity of oil palm trunk and abundant supply of bagasse. Effect of preparation variable, surface acidity and textural properties, pre-esterification of FFA in oil matrices and transesterification of waste oil under pseudo-infinite methanol and conventional methods were investigated. The preparation variable, H 2 SO 4 impregnation time showed marginal effect on sulfonic acid density after 6 h, and the corresponding values for 6–10 h impregnations were 1.33 ± 0.01–1.41 ± 0.01mmol g −1 for OPT and 1.44 ± 0.01–1.48 ± 0.01mmol g −1 for SCB catalysts. In esterification of palmitic acid, activity of catalysts with different H 2 SO 4 impregnation time correlates with their sulfonic acid density. The catalysts demonstrated rapid esterification of FFA in oil matrices under pseudo infinite methanol, reducing its content from 42 wt.% to <1 wt.% in just 15 min. Similarly, the conversions of waste oil by OPT and SCB derived catalysts were 80.6% and 83.2%, respectively after 4 h under pseudo-infinite methanol, and 43.7% and 45%, respectively after 6 h under conventional method. These catalysts have shown remarkable properties that are suitable for biodiesel production from waste oil

  14. Fuel cell testing of Pt–Ru catalysts supported on differently prepared and pretreated carbon nanotubes

    International Nuclear Information System (INIS)

    Tokarz, Wojciech; Lota, Grzegorz; Frackowiak, Elzbieta; Czerwiński, Andrzej; Piela, Piotr

    2013-01-01

    Proton-exchange membrane fuel cell (PEMFC) testing of Pt–Ru catalysts supported on differently prepared multiwall carbon nanotube (MCNT) supports was performed to elucidate the influence of the different supports on the operating characteristics of the catalysts under real direct methanol fuel cell (DMFC) anode and H 2 -PEMFC anode conditions. The MCNTs were either thin, entangled or thick, disentangled. Pretreatment of the MCNTs was also done and it was either high-temperature KOH etching or annealing (graphitization). The performance of the catalysts was compared against the performance of a commercial Pt–Ru catalyst supported on a high-surface-area carbon black. Among the different MCNT supports, the graphitized, entangled support offered the best performance in all tests, which was equal to the performance of the commercial catalyst, despite the MCNT catalyst layer was ca. 2.2 times thicker than the carbon black catalyst layer. Even for an MCNT catalyst layer, which was almost 7 times thicker than the carbon black catalyst layer, the transport limitations were not prohibitive. This confirmed the expected potential of nanotube supports for providing superior reactant transport properties of the PEMFC catalyst layers

  15. Metals on graphene and carbon nanotube surfaces: From mobile atoms to atomtronics to bulk metals to clusters and catalysts

    KAUST Repository

    Sarkar, Santanu C.

    2014-01-14

    In this Perspective, we present an overview of recent fundamental studies on the nature of the interaction between individual metal atoms and metal clusters and the conjugated surfaces of graphene and carbon nanotube with a particular focus on the electronic structure and chemical bonding at the metal-graphene interface. We discuss the relevance of organometallic complexes of graphitic materials to the development of a fundamental understanding of these interactions and their application in atomtronics as atomic interconnects, high mobility organometallic transistor devices, high-frequency electronic devices, organometallic catalysis (hydrogen fuel generation by photocatalytic water splitting, fuel cells, hydrogenation), spintronics, memory devices, and the next generation energy devices. We touch on chemical vapor deposition (CVD) graphene grown on metals, the reactivity of its surface, and its use as a template for asymmetric graphene functionalization chemistry (ultrathin Janus discs). We highlight some of the latest advances in understanding the nature of interactions between metals and graphene surfaces from the standpoint of metal overlayers deposited on graphene and SWNT thin films. Finally, we comment on the major challenges facing the field and the opportunities for technological applications. © 2013 American Chemical Society.

  16. Catalyst for Carbon Monoxide Oxidation

    Science.gov (United States)

    Davis, Patricia; Brown, Kenneth; VanNorman, John; Brown, David; Upchurch, Billy; Schryer, David; Miller, Irvin

    2010-01-01

    In many applications, it is highly desirable to operate a CO2 laser in a sealed condition, for in an open system the laser requires a continuous flow of laser gas to remove the dissociation products that occur in the discharge zone of the laser, in order to maintain a stable power output. This adds to the operating cost of the laser, and in airborne or space applications, it also adds to the weight penalty of the laser. In a sealed CO2 laser, a small amount of CO2 gas is decomposed in the electrical discharge zone into corresponding quantities of CO and O2. As the laser continues to operate, the concentration of CO2 decreases, while the concentrations of CO and O2 correspondingly increase. The increasing concentration of O2 reduces laser power, because O2 scavenges electrons in the electrical discharge, thereby causing arcing in the electric discharge and a loss of the energetic electrons required to boost CO2 molecules to lasing energy levels. As a result, laser power decreases rapidly. The primary object of this invention is to provide a catalyst that, by composition of matter alone, contains chemisorbed water within and upon its structure. Such bound moisture renders the catalyst highly active and very long-lived, such that only a small quantity of it needs to be used with a CO2 laser under ambient operating conditions. This object is achieved by a catalyst that consists essentially of about 1 to 40 percent by weight of one or more platinum group metals (Pt, Pd, Rh, Ir, Ru, Os, Pt being preferred); about 1 to 90 percent by weight of one or more oxides of reducible metals having multiple valence states (such as Sn, Ti, Mn, Cu, and Ce, with SnO2 being preferred); and about 1 to 90 percent by weight of a compound that can bind water to its structure (such as silica gel, calcium chloride, magnesium sulfate, hydrated alumina, and magnesium perchlorate, with silica gel being preferred). Especially beneficial results are obtained when platinum is present in the

  17. High-performance oxygen reduction catalysts in both alkaline and acidic fuel cells based on pre-treating carbon material and iron precursor

    Energy Technology Data Exchange (ETDEWEB)

    Song, Ping; Barkholtz, Heather M.; Wang, Ying; Xu, Weilin; Liu, Dijia; Zhuang, Lin

    2017-12-01

    We demonstrate a new and simple method for pre-treating the carbon material and iron precursor to prepare oxygen reduction reaction (ORR) catalysts, which can produce super-high performance and stability in alkaline solution, with high performance in acid solution. This strategy using cheap materials is simply controllable. Moreover, it has achieved smaller uniform nanoparticles to exhibit high stability, and the synergetic effect of Fe and N offered much higher performance in ORR than commercial Pt/C, with high maximum power density in alkaline and acid fuel cell test. So it can make this kind of catalysts be the most promising alternatives of Pt-based catalysts with best performance/price.

  18. Manufacture of highly loaded silica-supported cobalt Fischer–Tropsch catalysts from a metal organic framework

    KAUST Repository

    Sun, Xiaohui

    2017-11-16

    The development of synthetic protocols for the preparation of highly loaded metal nanoparticle-supported catalysts has received a great deal of attention over the last few decades. Independently controlling metal loading, nanoparticle size, distribution, and accessibility has proven challenging because of the clear interdependence between these crucial performance parameters. Here we present a stepwise methodology that, making use of a cobalt-containing metal organic framework as hard template (ZIF-67), allows addressing this long-standing challenge. Condensation of silica in the Co-metal organic framework pore space followed by pyrolysis and subsequent calcination of these composites renders highly loaded cobalt nanocomposites (~ 50 wt.% Co), with cobalt oxide reducibility in the order of 80% and a good particle dispersion, that exhibit high activity, C5 + selectivity and stability in Fischer-Tropsch synthesis.

  19. Synergistic effect of carbon nanofiber/nanotube composite catalyst on carbon felt electrode for high-performance all-vanadium redox flow battery.

    Science.gov (United States)

    Park, Minjoon; Jung, Yang-jae; Kim, Jungyun; Lee, Ho il; Cho, Jeaphil

    2013-10-09

    Carbon nanofiber/nanotube (CNF/CNT) composite catalysts grown on carbon felt (CF), prepared from a simple way involving the thermal decomposition of acetylene gas over Ni catalysts, are studied as electrode materials in a vanadium redox flow battery. The electrode with the composite catalyst prepared at 700 °C (denoted as CNF/CNT-700) demonstrates the best electrocatalytic properties toward the V(2+)/V(3+) and VO(2+)/VO2(+) redox couples among the samples prepared at 500, 600, 700, and 800 °C. Moreover, this composite electrode in the full cell exhibits substantially improved discharge capacity and energy efficiency by ~64% and by ~25% at 40 mA·cm(-2) and 100 mA·cm(-2), respectively, compared to untreated CF electrode. This outstanding performance is due to the enhanced surface defect sites of exposed edge plane in CNF and a fast electron transfer rate of in-plane side wall of the CNT.

  20. High activity of novel Pd/TiO2 nanotube catalysts for methanol electro-oxidation

    International Nuclear Information System (INIS)

    Wang Mei; Guo Daojun; Li Hulin

    2005-01-01

    Electro-oxidation of methanol in sulfuric acid solution was studied using palladium well-dispersed on titanium nanotubes, in relation to methanol oxidation processes in the direct oxidation methanol fuel cell. Pd dispersed on titania nanotubes, which leads to high surface area substrates, showed excellent catalytic activities compared to those of pure Pd and Pd-TiO 2 nanoparticles. TEM results show a narrow distribution of TiO 2 nanoparticles whose particle size is about 10nm, and uniform nano-sized TiO 2 nanotubes with 10nm in diameters are seen from HRTEM . A homogeneous structure in the composite nanomaterials is indicated by XRD analysis. The composite electrode activities were measured by cyclic voltammetry (CV) and at 25 deg. C it was found that 3wt% Pd in titania nanotubes had the best activity for methanol oxidation

  1. Extremely high efficient nanoreactor with Au@ZnO catalyst for photocatalysis

    Science.gov (United States)

    Su, Chung-Yi; Yang, Tung-Han; Gurylev, Vitaly; Huang, Sheng-Hsin; Wu, Jenn-Ming; Perng, Tsong-Pyng

    2015-10-01

    We fabricated a photocatalytic Au@ZnO@PC (polycarbonate) nanoreactor composed of monolayered Au nanoparticles chemisorbed on conformal ZnO nanochannel arrays within the PC membrane. A commercial PC membrane was used as the template for deposition of a ZnO shell into the pores by atomic layer deposition (ALD). Thioctic acid (TA) with sufficient steric stabilization was used as a molecular linker for functionalization of Au nanoparticles in a diameter of 10 nm. High coverage of Au nanoparticles anchored on the inner wall of ZnO nanochannels greatly improved the photocatalytic activity for degradation of Rhodamine B. The membrane nanoreactor achieved 63% degradation of Rhodamine B within only 26.88 ms of effective reaction time owing to its superior mass transfer efficiency based on Damköhler number analysis. Mass transfer limitation can be eliminated in the present study due to extremely large surface-to-volume ratio of the membrane nanoreactor.

  2. Water evaporation on highly viscoelastic polymer surfaces.

    Science.gov (United States)

    Pu, Gang; Severtson, Steven J

    2012-07-03

    Results are reported for a study on the evaporation of water droplets from a highly viscoelastic acrylic polymer surface. These are contrasted with those collected for the same measurements carried out on polydimethylsiloxane (PDMS). For PDMS, the evaporation process involves the expected multistep process including constant drop area, constant contact angle, and finally a combination of these steps until the liquid is gone. In contrast, water evaporation from the acrylic polymer shows a constant drop area mode throughout. Furthermore, during the evaporation process, the drop area actually expands on the acrylic polymer. The single mode evaporation process is consistent with formation of wetting structures, which cannot be propagated by the capillary forces. Expansion of the drop area is attributed to the influence of the drop capillary pressure. Furthermore, the rate of drop area expansion is shown to be dependent on the thickness of the polymer film.

  3. Synthesis and Immobilization of Pt Nanoparticles on Amino-Functionalized Halloysite Nanotubes toward Highly Active Catalysts

    Directory of Open Access Journals (Sweden)

    Tingting Yang

    2015-02-01

    Full Text Available A simple and effective method for the preparation of platinum nanoparticles (Pt NPs grown on amino-func‐ tionalized halloysite nanotubes (HNTs was developed. The nanostructures were synthesized through the func‐ tionalization of the HNTs, followed by an in situ approach to generate Pt NPs with diameter of approximately 1.5 nm within the entire HNTs. The synthesis process, composition and morphology of the nanostructures were characterized. The results suggest PtNPs/NH2-HNTs nanostructures with ultrafine PtNPs were successfully synthesized by green chemically-reducing H2PtCl6 without the use of surfactant. The nanostructures exhibit promising catalytic properties for reducing potassium hexacyanoferrate(III to potassium hexacyanoferrate(II. The presented experiment for novel PtNPs/NH2-HNTs nanostructures is quite simple and environmentally benign, permitting it as a potential application in the future field of catalysts.

  4. BiVO4–graphene catalyst and its high photocatalytic performance under visible light irradiation

    International Nuclear Information System (INIS)

    Fu Yongsheng; Sun Xiaoqiang; Wang Xin

    2011-01-01

    Highlights: ► A facile strategy is designed to deposit leaf-like BiVO 4 lamellas on graphene sheet. ► Graphene oxide is reduced to graphene in the hydrothermal reaction process. ► BiVO 4 –graphene system shows high catalytic effects under visible light irradiation. - Abstract: A BiVO 4 –graphene photocatalyst was prepared by a facile one-step hydrothermal method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectra (XPS), and transmission electron microscopy (TEM) techniques. The results show that the graphene sheets in this catalyst are exfoliated and decorated by leaf-like BiVO 4 lamellas. In comparison with the pure BiVO 4 catalyst, the BiVO 4 –graphene system reveals much higher photocatalytic activity for degradation of methyl orange (MO), methylene blue (MB), Rhodamine B (RhB) and active black BL-G in water under visible light irradiation due to the concerted effects of BiVO 4 and graphene sheets or their integrated properties.

  5. Development physicochemical and catalytic characteristics of Mo-containing catalysts for hydrotreatment based on various supports. 1. Adsorption of molybdate anions on the support surface

    International Nuclear Information System (INIS)

    Lur'e, M.A.; Kurest, I.Z.; Krasnopol'skaya, S.M.; Reznikov, S.A.; Babikov, A.F.; Shmidt, F.K.

    1994-01-01

    The amounts of basic OH-groups were determined by means of exchange by F-ions and the adsorption of Mo from acid and alkali ammonium paramolybdate (APM) solutions was investigated on the surface of hydrated titanium dioxide, γ-Al 2 O 3 and palygorskite-montmorillonite clay. The process is adequately described by the exchange equation at pH value of APM solution in excess of the isoelectric point (IEP) of the surface. At opposite correlation between pH of the solution and IEP the Langmuir model is adaptable. They concluded, on experimental data, that in the latter case OH-groups replaced by molybdate-anion stage of synthesis of catalyst. 22 refs., 3 figs

  6. Nitrogen doped RGO-Co3O4 nanograin cookies: highly porous and robust catalyst for removing nitrophenol from waste water

    Science.gov (United States)

    Pervaiz, Erum; Syam Azhar Virk, Muhammad; Bingxue, Zhang; Yin, Conglin; Yang, Minghui

    2017-09-01

    The fabrication of nanograins with a uniform morphology wrapped with reduced graphene oxide (RGO) in a designed manner is critical for obtaining a large surface, high porosity and efficient catalytic ability at mild conditions. Hybrid structures of metal oxides decorated on two-dimensional (2D) RGO lacked an interface and channels between the individual grains and RGO. The present work focuses on the synthesis of RGO-wrapped Co3O4 nanograin architecture in micron-sized polyhedrons and the ability to reduce aromatic nitro compounds. Doping N in the designed microstructure polyhedrons resulted in very large surface area (1085.6 m2 g-1) and pore density (0.47 m3 g-1) microcages. Binding energies from x-ray photoelectron spectroscopy (XPS) and Raman intensities confirmed the presence of doped N and RGO-wrapped around Co3O4 nanograins. However, the morphology and microstructure was supported by FESEM and HRTEM images revealing the fabrication of high integrity RGO-Co3O4 microstructure hybrids composed of a 10 nm grain size with narrower grain size distribution. Ammonia treatment produced interconnected channels and dumbbell pores that facilitated ion exchange between the catalyst surface and the liquid medium at the grain boundary interfaces, and offered less mass transport resistance providing fast adsorption of reactants and desorption of the product causing surface renewal. Prepared N-RGO-Co3O4 shows the largest percentage reduction (96%) of p-nitrophenol (p-NP) at room temperature as compared to pure Co3O4 and RGO-Co3O4 nanograin microstructures over 10 min. Fabricated architectures can be applied effectively for fast and facile treatment of industrial waste streams with complex organic molecules.

  7. Method of Heating a Foam-Based Catalyst Bed

    Science.gov (United States)

    Fortini, Arthur J.; Williams, Brian E.; McNeal, Shawn R.

    2009-01-01

    A method of heating a foam-based catalyst