WorldWideScience

Sample records for catalyst stability vis-a-vis

  1. Power system modeling and optimization methods vis-a-vis integrated resource planning (IRP)

    Science.gov (United States)

    Arsali, Mohammad H.

    1998-12-01

    The state-of-the-art restructuring of power industries is changing the fundamental nature of retail electricity business. As a result, the so-called Integrated Resource Planning (IRP) strategies implemented on electric utilities are also undergoing modifications. Such modifications evolve from the imminent considerations to minimize the revenue requirements and maximize electrical system reliability vis-a-vis capacity-additions (viewed as potential investments). IRP modifications also provide service-design bases to meet the customer needs towards profitability. The purpose of this research as deliberated in this dissertation is to propose procedures for optimal IRP intended to expand generation facilities of a power system over a stretched period of time. Relevant topics addressed in this research towards IRP optimization are as follows: (1) Historical prospective and evolutionary aspects of power system production-costing models and optimization techniques; (2) A survey of major U.S. electric utilities adopting IRP under changing socioeconomic environment; (3) A new technique designated as the Segmentation Method for production-costing via IRP optimization; (4) Construction of a fuzzy relational database of a typical electric power utility system for IRP purposes; (5) A genetic algorithm based approach for IRP optimization using the fuzzy relational database.

  2. Comparative study of ionization chamber detectors vis-a-vis a CCD detector for dispersive XAS measurement in transmission geometry

    Energy Technology Data Exchange (ETDEWEB)

    Poswal, A. K.; Agrawal, A.; Bhattachryya, D.; Jha, S. N.; Sahoo, N. K. [Applied Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai -400 085 (India)

    2013-02-05

    We have designed and fabricated parallel plate ionization chamber detectors and voltage vs. current characteristics (V-I curve) of the detectors were recorded with synchrotron radiation to qualify for use in X-ray Absorption Spectroscopy (XAS) measurements. After qualifying the ionization chambers, the detectors were used in the dispersive EXAFS beamline (BL-08) at INDUS-2 SRS in Turbo-XAS geometry. Using the same setup and under the same setting, XAS spectra were also recorded with a CCD detector and the observation on relative performance of the ionization chamber vis-a-vis the CCD detector is presented in this paper.

  3. Migratory Trends in the Czech Republic: “Divergence or Convergence” vis-a-vis the Developed World?

    Directory of Open Access Journals (Sweden)

    Dušan Drbohlav

    2002-09-01

    Full Text Available The main goal of this paper is to analyse whether the geopolitical and socio-economic integration and “harmonisation” of the Czech Republic with Western Europe is accompanied by a divergence or convergence of the Czech migratory reality vis-a-vis the developed western world. When testing resemblance two kinds of measurements are used: 1 quantitative – (in terms of the numbers of international migrants, and 2 “qualitative” – a in terms of regularities linked with the migration itself and those that tackle mutual relationships among immigration, the socio-economic development of the destination country and subjective attitudes of the majority population towards minority groups: 3 hypotheses are tested in this regard; b in terms of migratory policies and practices. The results clearly show us that convergence rather than divergence is characteristic of the current migratory trends in the Czech Republic as compared to the developed world, mainly Western Europe.

  4. Understanding urban vehicular pollution problem vis-a-vis ambient air quality--case study of a megacity (Delhi, India).

    Science.gov (United States)

    Goyal, S K; Ghatge, S V; Nema, P; M Tamhane, S

    2006-08-01

    Air pollution has become a growing problem in megacities and large urban areas through out the globe, and transportation is recognized as the major source of air pollution in many cities, especially in developing countries. Contribution of automobiles is reported in the range of 40 to 80% of the total air pollution. The challenge facing megacities is how to reduce the adverse environmental impacts and other negative effects of transportation without giving up the benefits of mobility. The dilemma becomes most pressing under conditions of rapid urban growth, which is likely to increase travel demand significantly. The paper is aimed at understanding the problem of vehicular pollution vis-a-vis ambient air quality for a highly traffic affected megacity, Delhi, wherein, the contribution of transport sector was estimated to be as high as 72%. An effort has been made to review and evaluate the benefits (in terms of improved air quality) of the technological interventions/policies adopted for vehicular pollution control in Delhi. It also highlights the outcome of the efforts and suggests further improvements thereon. The importance of public participation and awareness are also discussed. The paper focuses on deriving the benefits of the implementation of management strategies, supported by scientific and technical data/interpretation, so that the people can realize and participate in the government's endeavor for clean city drive in a more effective manner.

  5. Kojic Acid vis-a-vis its Combinations with Hydroquinone and Betamethasone Valerate in Melasma: A Randomized, Single Blind, Comparative Study of Efficacy and Safety

    Science.gov (United States)

    Deo, Kirti S.; Dash, Kedar N.; Sharma, Yugal K.; Virmani, Neha C.; Oberai, Chetan

    2013-01-01

    Background: Melasma is a relatively common, acquired symmetric hypermelanosis characterized by irregular light to gray-brown macules involving sun-exposed areas. Kojic acid, with its depigmenting potential due to tyrosinase inhibition and suppression of melanogenesis, has become a vital component of the dermatologists’ armamentarium against melasma. Aim: To study and compare the efficacy of kojic acid 1% alone, vis-a-vis its separate combinations with 2% hydroquinone or 0.1% betamethasone valerate and a combination of all these three agents with respect to the duration of symptoms and level of pigmentation in the therapy of melasma. Materials and Methods: Eighty patients from a single tertiary care center objectively assessed by calculating the melasma area severity index (MASI) and randomized (simple randomization) into four parallel groups (A, B, C, and D) of 20 each were prescribed once daily local application at night, (participants blinded regarding the difference in identity of interventions), as follows: Group A – kojic acid 1% cream. Group B – kojic acid 1% and hydroquinone 2% cream. Group C – kojic acid 1% and betamethasone valerate 0.1% cream. Group D – kojic acid 1%, hydroquinone 2%, and betamethasone valerate 0.1% cream. Strict photoprotection and use of a SPF 15 sunscreen was advised during the day. Patients were evaluated every 2 weeks and a fall in MASI score was calculated at the end of the study period of 12 weeks by the same investigator. Results: The response was compared according to percentage decrease in MASI score. Efficacy was evaluated among the groups at the end of 3 months using bivariate analysis and calculated by using the paired ‘t’ test. The clinical efficacy of group B was the highest followed closely by group D and group A, that of group C being the lowest. Conclusion: Kojic acid in synergy with hydroquinone is a superior depigmenting agent as compared with other combinations. PMID:23918998

  6. Internet vis-a-vis marine biology

    Digital Repository Service at National Institute of Oceanography (India)

    Chavan, V.S.

    Internet is an amalgum of networks which reaches to more than 100 million people across the globe. The satellite-telecommunication based computer network web hosts information on every aspect of life. Marine biology related information too is being...

  7. Improving Stability of Gasoline by Using Ionic Liquid Catalyst

    Institute of Scientific and Technical Information of China (English)

    Gao Zhirong; Liu Daosheng; Liao Kejian; Jian Heng

    2003-01-01

    The composition, characteristics and preparation of ionic liquids are presented. The factors influencing the stability of gasoline and the significance of improving gasoline stability are discussed. A novel way to improve the stability of gasoline by using ionic liquid catalyst is developed. The contents of olefin, basic nitrogen and sulfur in gasoline are determined and the optimal experimental conditions for improving gasoline stability are established.The ionic liquid catalyst, which is environmentally friendly, can reduce the olefin content in gasoline, and such process is noted for mild reaction conditions, simple operation, short reaction time, easy recycling of the ionic liquid catalyst and ready separation of products and catalyst.

  8. Stability and resistance of nickel catalysts for hydrodeoxygenation

    DEFF Research Database (Denmark)

    Mortensen, Peter Mølgaard; Gardini, Diego; de Carvalho, Hudson W. P.;

    2014-01-01

    of activity. Analysis of the spent catalyst revealed that the adsorption of chlorine on the catalyst was completely reversible, but chlorine had caused sintering of nickel particles. In two experiments, potassium, as either KCl or KNO3, was impregnated on the catalyst prior to testing. In both cases......The long term stability and resistance toward carbon deposition, sulfur, chlorine, and potassium of Ni/ZrO2 as a catalyst for the hydrodeoxygenation (HDO) of guaiacol in 1-octanol (as a model compound system for bio-oil) has been investigated at 250 degrees C and 100 bar in a trickle bed reactor...... setup. Without impurities in the feed good stability of the Ni/ZrO2 catalyst could be achieved over more than 100 h of operation, particularly for a sample prepared with small Ni particles, which minimized carbon deposition. Exposing the catalyst to 0.05 wt% sulfur in the feed resulted in rapid...

  9. Studies of Heterogeneous Catalyst Selectivity and Stability for Biorefining Applications

    Science.gov (United States)

    O'Neill, Brandon J.

    The conversion of raw resources into value-added end products has long underlain the importance of catalysts in economic and scientific development. In particular, the development of selective and stable heterogeneous catalysts is a challenge that continues to grow in importance as environmental, sociological, and economic concerns have motivated an interest in sustainability and the use of renewable raw materials. Within this context, biomass has been identified as the only realistic source of renewable carbon for the foreseeable future. The development of processes to utilize biomass feedstocks will require breakthroughs in fundamental understanding and practical solutions to the challenges related to selectivity and stability of the catalysts employed. Selectivity is addressed on multiple fronts. First, the selectivity for C-O bond scission reactions of a bifunctional, bimetallic RhRe/C catalyst is investigated. Using multiple techniques, the origin of Bronsted acidity in the catalyst and the role of pretreatment on the activity, selectivity, and stability are explored. In addition, reaction kinetics experiments and kinetic modeling are utilized to understand the role of chemical functional group (i.e. carboxylic acid versus formate ester) in determining the decarbonylation versus decarboxylation selectivity over a Pd/C catalyst. Finally, kinetic studies over Pd/C and Cu/gamma-Al2O3 were performed so that that may be paired with density functional theory calculations and microkinetic modeling to elucidate the elementary reaction mechanism, identify the active site, and provide a basis for future rational catalyst design. Next, the issue of catalyst stability, important in the high-temperature, liquid-phase conditions of biomass processing, is examined, and a method for stabilizing the base-metal nanoparticles of a Cu/gamma-Al2O 3 catalyst using atomic layer deposition (ALD) is developed. This advancement may facilitate the development of biorefining by enabling

  10. Thermal Stability of Nanoporous Raney Gold Catalyst

    Directory of Open Access Journals (Sweden)

    Matthew C. Tai

    2015-07-01

    Full Text Available Nanoporous “Raney gold” sponge was prepared by de-alloying an Au-Al precursor alloy. Catalytic tests using a micro-reactor confirmed that Raney gold can serve as an active heterogeneous catalyst for CO oxidation, reduction of NO to N2, and oxidation of NO to NO2. In general, the specific surface area of a heterogeneous catalyst has an influence on its catalytic efficacy. Unfortunately, gold sponges coarsen readily, leading to sintering of their structure and reduction in surface area. This potentially places constraints on their upper operating temperature in catalytic reactors. Here we analyzed the behavior of Raney gold when the temperature was raised. We examined the kinetics and mechanism of coarsening of the sponge using a combination of in situ optical measurements and Metropolis Monte Carlo modeling with a Lennard-Jones interatomic potential. Modeling showed that the sponges started with an isotropic “foamy” morphology with negative average “mean curvature” but that subsequent thermally activated coarsening will drive the morphology through a bi-continuous fibrous state and on, eventually, to a sponge consisting of sintered blobs of predominantly positive “mean curvature”.

  11. Relasi Antagonistik Barat-Timur: Orientalisme vis a vis Oksidentalisme

    Directory of Open Access Journals (Sweden)

    Moh. Fudholi

    2015-10-01

    Full Text Available Encounter of the East and the West due to such various interests as economic, political, scientific, cultural has been a major factor in the study of western scientists (Orientalists about the East that produces a variety of works in the fields of archeology, history, literature, environment, customs, and Islamic studies. Meanwhile, resistance against Orientalism in the form of Occidentalism, as initiated by Hasan Hanafî, seems to be closely related to ‘obsession’ and hopes of someone who frustrated and dissatisfied with the condition of the world he has dealt with as the project of civilization he offered seemed to be too theoretical to be applied into the form of well established science. This is a fact that, unlike Orientalism that has born from strength, power, and has been then smoothly formed, Occidentalism was created by the East that was defeated and suffered from weakness and at the same time merely has an obsession. In spite of the impression, apparently, what has been attempted in Occidentalism is dismantling the text, another interpretation, and building a new, more proportional context.

  12. Independence properties Vis-A-Vis several utility representations

    NARCIS (Netherlands)

    Marley, AAJ; Luce, RD

    2005-01-01

    A detailed theoretical analysis is presented of what five utility representations - subjective expected utility (SEU), rank-dependent (cumulative or Choquet) utility (RDU), gains decomposition utility (GDU), rank weighted utility (RWU), and a configural-weight model (TAX) that we show to be equivale

  13. Syariah REITs Vis-A-Vis Conventional REITs: An Analysis

    Directory of Open Access Journals (Sweden)

    Nor Edi Azhar binti Mohamad

    2012-07-01

    Full Text Available The development of Islamic capital market products has been highly innovative in Malaysia as has pioneered various innovative Syariah compliant products over the past few years. Of importance is the introduction of the first Syariah real estate investment trusts (S-REITs. In November 2005, The Malaysian Government through the Securities Commission (SC of Malaysia has issued the Guidelines for Islamic Real Estate Investment Trusts (S-REITs. Thus it provides new investment opportunity for investors who wish to invest in real estate through Syariah-compliant capital market instruments. Based on this strategic difference, the purpose of this paper is to provide an understanding on the performances of these two natures of REITs in the Malaysian capital market, namely conventional REITs (C-REITs and Syariah REITs by comparing the risk and return of S-REITs and C-REITs from Malaysia perspective. The secondary data for analysis is retrieved from Bloomberg’s Database of 12 listed REITs in the Bursa Malaysia main board for three year period from 2007 to 2009 with quarterly observation. Sharpe Index, Jensen Index and Treynor Index are used as a proxy to the return of REITs, while beta, standard deviation and coefficient of variation are used as a proxy to represent REITs’s risk. Applying correlations and independent sample t-test, the result has provided evidence on the association between return and risk on REITs.

  14. Activity and Stability of Nanoscale Oxygen Reduction Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Shao-Horn, Yang

    2015-07-28

    Design of highly active and stable nanoscale catalysts for electro-oxidation of small organic molecules is of great importance to the development of efficient fuel cells. The amount and instability of Pt-based catalysts in the cathode limits the cost, efficiency and lifetime of proton exchange membrane fuel cells. We developed a microscopic understanding of the factors governing activity and stability in Pt and PtM alloys. Experimental efforts were focused on probing the size and shape dependence of ORR activity of Pt-based nanoparticles supported on carbon nanotubes. A microscopic understanding of the activity was achieved by correlating voltammetry and rotating ring disk electrodes to surface atomic and electronic structures, which were elucidated predominantly by high-resolution transmission electron microscopy (HRTEM), Scanning transmission electron microscopy energy dispersive X-ray Spectroscopy (STEM-EDS) and synchrotron X-ray absorption spectroscopy (XAS).

  15. The Major Asian Powers and the Korean Reunification Process: Catalysts or Deterrents?

    Science.gov (United States)

    1986-06-01

    RD-Ai65 128 THE MAJOR ASIAN POWERS AND THE KOREAN REUNIFICATION 1/2 PROCESS- CATALYSTS OR DETERRENTS?(U) DEFENSE INTELLIGENCE COLL WASHINGTON DC J J...the Korean cultural heritage. This was followed by a review of current economic, political, social, and military systems in North and South Korea ... Korean question. This material supplemented details from current news media on North-South Korean rapprochement and major power actions vis-a-vis Korea

  16. Stabilized tin-oxide-based oxidation/reduction catalysts

    Science.gov (United States)

    Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony Neal (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor)

    2008-01-01

    The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.

  17. Electrochemical Catalyst-Support Effects and Their Stabilizing Role for IrOx Nanoparticle Catalysts during the Oxygen Evolution Reaction.

    Science.gov (United States)

    Oh, Hyung-Suk; Nong, Hong Nhan; Reier, Tobias; Bergmann, Arno; Gliech, Manuel; Ferreira de Araújo, Jorge; Willinger, Elena; Schlögl, Robert; Teschner, Detre; Strasser, Peter

    2016-09-28

    Redox-active support materials can help reduce the noble-metal loading of a solid chemical catalyst while offering electronic catalyst-support interactions beneficial for catalyst durability. This is well known in heterogeneous gas-phase catalysis but much less discussed for electrocatalysis at electrified liquid-solid interfaces. Here, we demonstrate experimental evidence for electronic catalyst-support interactions in electrochemical environments and study their role and contribution to the corrosion stability of catalyst/support couples. Electrochemically oxidized Ir oxide nanoparticles, supported on high surface area carbons and oxides, were selected as model catalyst/support systems for the electrocatalytic oxygen evolution reaction (OER). First, the electronic, chemical, and structural state of the catalyst/support couple was compared using XANES, EXAFS, TEM, and depth-resolved XPS. While carbon-supported oxidized Ir particle showed exclusively the redox state (+4), the Ir/IrOx/ATO system exhibited evidence of metal/metal-oxide support interactions (MMOSI) that stabilized the metal particles on antimony-doped tin oxide (ATO) in sustained lower Ir oxidation states (Ir(3.2+)). At the same time, the growth of higher valent Ir oxide layers that compromise catalyst stability was suppressed. Then the electrochemical stability and the charge-transfer kinetics of the electrocatalysts were evaluated under constant current and constant potential conditions, where the analysis of the metal dissolution confirmed that the ATO support mitigates Ir(z+) dissolution thanks to a stronger MMOSI effect. Our findings raise the possibility that MMOSI effects in electrochemistry-largely neglected in the past-may be more important for a detailed understanding of the durability of oxide-supported nanoparticle OER catalysts than previously thought.

  18. Functionalized Graphitic Supports for Improved Fuel Cell Catalyst Stability Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Physical Sciences Inc. (PSI) together with the University of Connecticut (UCONN) proposes to demonstrate the improved fuel cell catalyst support durability offered...

  19. Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    MuXuhong; ZongBaoning; 等

    2002-01-01

    Amorphous nickel based alloy catalysts(denoted as the SRNA series catalysts)were prepared via rapid quenching method followed by alkali leaching and other activation procedures.The physicochemical characterizations show that nickel,the active component in these catalysts,exists in the amorphous state,and the catalyst particles possess many nanosized voids leading to large surface area(the highest is 145m2/g).The evaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higher activity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups.At present,the SRNA series catalysts have been successfully used in hydrogenation of glucose,hydrogenation of pharmaceutical intermediates and purification of caprolactam.In order to use these catalysts efficiently,a magnetically stabilized bed(MSB) technology has been developed by combining the ferromagnetic property of the catalyst with the good mass transfer characteristics of MSB.The demonstration unit of MSB hydrogenation technology has been set up and has kept running for 2800 hours.The results show that,after running 2800 hours,the catalyst still retained good activity; meanwhile,the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

  20. The development of precipitated iron catalysts with improved stability; Final report, September 1987--September 1992

    Energy Technology Data Exchange (ETDEWEB)

    Abrevaya, H.

    1993-12-27

    Precipitated iron catalysts are expected to be used in next generation slurry reactors for large-scale production of transportation fuels from synthesis gas. These reactors are expected to operate at higher temperatures and lower H{sub 2}:CO ratios relative to the Sasol Arge reactor (Table 1A). The feasibility of using iron catalysts has been demonstrated under relatively mild Arge-type conditions but not under more severe slurry conditions. Possibly, an improvement in catalytic stability will be needed to make iron catalysts suitable for slurry operation. This program was aimed at identifying the chemical principles governing the deactivation of precipitated iron catalysts during Fischer-Tropsch synthesis and use of these chemical principles in the design of more stable catalysts. A new precipitated Fe catalyst was developed in this program for slurry reactor operation. The new Fe catalyst is predicted to perform slightly below the performance targets for slurry bubble column operation. Stability targets appear to be achievable. This catalyst did not noticeably deactivate during 1,740 hours on-stream. Compared to the selectivity target, an excess of 2% C{sub 1} + C{sub 2} was formed at 265{degrees}C. Based on the initial catalyst inventory in the autoclave, the catalyst seems to be short of the activity target by a factor of 1.8 at 265{degrees}C and 1.3 at 275{degrees}C. However, actual specific activities are likely to be closer to target because of catalyst inventory loss across the filter during the run and because catalytic activities were underestimated at low conversions.

  1. Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Amorphous nickel based alloy catalysts (denoted as the SRNA series catalysts) were prepared viarapid quenching method followed by alkali leaching and other activation procedures. The physicochemicalcharacterizations show that nickel, the active component in these catalysts, exists in the amorphous state, andthe catalyst particles possess many nanosized voids leading to large surface area (the highest is 145m2/g). Theevaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higheractivity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups. At present, the SRNA series catalysts have been successfully used in hydrogenation ofglucose, hydrogenation of pharmaceutical intermediates and purification of caprolactam. In order to use thesecatalysts efficiently, a magnetically stabilized bed (MSB) technology has been developed by combining theferromagnetic property of the catalyst with the good mass transfer characteristics of MSB. The demonstrationunit of MSB hydrogenation technology has been set up and has kept running for 2800 hours. The results showthat, after running 2800 hours, the catalyst still retained good activity; meanwhile, the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

  2. Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    Mu Xuhong; Zong Baoning; Meng Xiangkun; Min Enze

    2002-01-01

    Amorphous nickel based alloy catalysts (denoted as the SRNAseries catalysts) were prepared viarapid quenching method followed by alkali leaching and other activation procedures. The physicochemicalcharacterizations show that nickel, the active component in these catalysts, exists in the amorphous state, andthe catalyst particles possess many nanosized voids leading to large surface area (the highest is 145m2/g). Theevaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higheractivity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups. At present, the SRNA series catalysts have been successfully used in hydrogenation ofglucose, hydrogenation of pharmaceutical intermediates and purification of caprolactam. In order to use thesecatalysts efficiently, a magnetically stabilized bed (MSB) technology has been developed by combining theferromagnetic property of the catalyst with the good mass transfer characteristics of MSB. The demonstrationunit of MSB hydrogenation technology has been set up and has kept running for 2800 hours. The results showthat, after running 2800 hours, the catalyst still retained good activity; meanwhile, the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

  3. Stability and Lifetime of K-CoMoSx Mixed Alcohol Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Hensley, J. E.; Ruddy, D.; Schaidle, J.; Ferrell, J.; Thibodeaux, J.

    2013-01-01

    Researchers have studied sulfide-type catalysts for the production of mixed alcohols from synthesis gas for several decades. Despite many advances in the art, these processes are not yet commercial, due in large part to mediocre economics and the added risk associated with uncertainty in catalyst lifetime. This talk will outline some recent studies in the lifetime and stability of K-CoMoSx-type mixed alcohol catalysts. Specifically, studies of long term operation (> 3000h), sulfiding agents, simulated methanol recycle, and morphology (probed via XRD and XPS) will be discussed, with the conclusion that these materials are likely to exhibit acceptable lifetimes in continuous operation.

  4. Towards ALD thin film stabilized single-atom Pd1 catalysts.

    Science.gov (United States)

    Piernavieja-Hermida, Mar; Lu, Zheng; White, Anderson; Low, Ke-Bin; Wu, Tianpin; Elam, Jeffrey W; Wu, Zili; Lei, Yu

    2016-08-18

    Supported precious metal single-atom catalysts have shown interesting activity and selectivity in recent studies. However, agglomeration of these highly mobile mononuclear surface species can eliminate their unique catalytic properties. Here we study a strategy for synthesizing thin film stabilized single-atom Pd1 catalysts using atomic layer deposition (ALD). The thermal stability of the Pd1 catalysts is significantly enhanced by creating a nanocavity thin film structure. In situ infrared spectroscopy and Pd K-edge X-ray absorption spectroscopy (XAS) revealed that the Pd1 was anchored on the surface through chlorine sites. The thin film stabilized Pd1 catalysts were thermally stable under both oxidation and reduction conditions. The catalytic performance in the methanol decomposition reaction is found to depend on the thickness of protecting layers. While Pd1 catalysts showed promising activity at low temperature in a methanol decomposition reaction, 14 cycle TiO2 protected Pd1 was less active at high temperature. Pd L3 edge XAS indicated that the low reactivity compared with Pd nanoparticles is due to the strong adsorption of carbon monoxide even at 250 °C. These results clearly show that the ALD nanocavities provide a basis for future design of single-atom catalysts that are highly efficient and stable.

  5. Skeletal Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    Min Enze

    2004-01-01

    Looking toward 21 century, smaller, cleaner and more energy-efficient technology will be an important trend in the development of chemical industry. In light of the new process requirements,a number of technology breakthroughs have occurred. One of these discoveries, the magnetically stabilized bed (MSB), has been proven a powerful process for intensification. Since its initial research in the late 1980's at Research Institute of Petroleum Processing (RIPP), the MSB technology and related catalytic material have matured rapidly through an intensive research and engineering program, primarily focused on its scaling-up.In this paper, we report the discovery of a novel skeletal amorphous nickel-based alloy and its use in magnetically stabilized bed (MSB). Amorphous alloys are new kinds of catalytic materials with short-range order but long-range disorder structure. In comparison with Raney Ni, the skeletal amorphous nickel-based alloy has an increasingly higher activity in the hydrogenation of reactive groups and compounds including nitro, nitrile, olefin, acetylene, aromatics, etc. Up to now, the amorphous nickel based alloy catalysts, SRNA series catalyst, one with high Ni ratio have been commercially manufactured more than four year. The new SRNA catalyst has been successfully implemented for hydrogenation applications in slurry reactor at Balin Petrochemical, SINOPEC.SRNA catalyst with further improvement in catalytic activity and stability raise its relative stability to 2~4 times of that of conventional catalyst. In the course of the long-cycle operation of SRNA-4 the excellent catalyst activity and stability can bring about such advantage as low reaction temperature, good selectivity and low catalyst resumption.Magnetically stabilized bed (MSB), a fluidized bed of magnetizable particles by applying a spatially uniform and time-invariant magnetic field oriented axially relative to the fluidizing fluid flow, had many advantages such as the low pressure drop and

  6. Biotemplated Palladium Catalysts Can Be Stabilized on Different Support Materials

    KAUST Repository

    Yates, Matthew D.

    2014-07-30

    © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Sustainably biotemplated palladium catalysts generated on different carbon-based support materials are examined for durability under electrochemical (oxidative) and mechanical-stress conditions. Biotemplated catalysts on carbon paper under both stresses retain 95% (at 0.6V) of the initial catalytic activity as opposed to 70% for carbon cloth and 60% for graphite. Graphite electrodes retain 95% of initial catalytic activity under a single stress. Using electrodeposited polyaniline (PANI) and polydimethylsiloxane binder increases the current density after the stress tests by 22%, as opposed to a 30% decrease for Nafion. PANI-coated electrodes retain more activity than carbon-paper electrodes under elevated mechanical (94 versus 70%) or increased oxidative (175 versus 62%) stress. Biotemplated catalytic electrodes may be useful alternatives to synthetically produce catalysts for some electrochemical applications. Sustainable electrode fabrication: The biotemplated synthesis of catalytic porous electrodes is a sustainable process and, according to the results of durability tests under electrochemical and mechanical stress, these electrodes (e.g. the Pd/carbon paper electrode shown in the picture) are durable enough to replace catalytic electrodes based on synthetic materials in certain applications.

  7. Thermal stability of vanadia-tungsta-titania catalysts in the SCR process

    Energy Technology Data Exchange (ETDEWEB)

    Madia, G.; Elsener, M.; Koebel, M.; Raimondi, F.; Wokaun, A. [Paul Scherrer Institute, CH-5232 PSI Villigen (Switzerland)

    2002-11-28

    The thermal behaviour of TiO{sub 2}-WO{sub 3}-V{sub 2}O{sub 5} catalysts with various vanadia contents (1, 2 and 3wt.% V{sub 2}O{sub 5}) was investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and BET surface area determination. The activity and selectivity of the new and thermally treated catalysts were tested in the SCR reaction. Both structural and catalytic investigations have shown that the vanadia content has a strong effect on the thermal behaviour of the SCR catalysts. The structural investigations evidenced anatase sintering, increase of polymeric vanadyl surface species and three-dimensional growth of supported vanadia upon ageing. The catalytic tests have shown that the SCR activity of catalysts containing 1 or 2% V{sub 2}O{sub 5} increased upon ageing, whereas the SCR performance of the catalyst with 3% V{sub 2}O{sub 5} decreased. The observed improvement of the SCR performance is attributed to an increase of the amount of polymeric vanadyl surface species upon ageing. The decrease of the SCR performance of the catalyst with 3% V{sub 2}O{sub 5} is due to the extensive loss of surface area and to the three-dimensional growth of supported vanadia upon ageing. The catalyst containing 2% V{sub 2}O{sub 5} represents the best compromise between high SCR activity and good thermal stability.

  8. Determination of the stability constants for cobalt, nickel and palladium homogeneous catalyst complexes containing triphenylphosphine ligands

    NARCIS (Netherlands)

    Djekic, T.; Zivkovic, Z.; van der Ham, A.G.J.; de Haan, A.B.

    2006-01-01

    Homogeneous catalysts are complex compounds that are always in equilibrium with their free metal, free ligand and other forms of complexes. The ratios between different species are defined by the stability constants, which are influenced by different parameters such as the type of metal, ligand, cou

  9. Bio-oil Stabilization by Hydrogenation over Reduced Metal Catalysts at Low Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huamin; Lee, Suh-Jane; Olarte, Mariefel V.; Zacher, Alan H.

    2016-08-30

    Biomass fast pyrolysis integrated with bio-oil upgrading represents a very attractive approach for converting biomass to hydrocarbon transportation fuels. However, the thermal and chemical instability of bio-oils presents significant problems when they are being upgraded, and development of effective approaches for stabilizing bio-oils is critical to the success of the technology. Catalytic hydrogenation to remove reactive species in bio-oil has been considered as one of the most efficient ways to stabilize bio-oil. This paper provides a fundamental understanding of hydrogenation of actual bio-oils over a Ru/TiO2 catalyst under conditions relevant to practical bio-oil hydrotreating processes. Bio-oil feed stocks, bio-oils hydrogenated to different extents, and catalysts have been characterized to provide insights into the chemical and physical properties of these samples and to understand the correlation of the properties with the composition of the bio-oil and catalysts. The results indicated hydrogenation of various components of the bio-oil, including sugars, aldehydes, ketones, alkenes, aromatics, and carboxylic acids, over the Ru/TiO2 catalyst and 120 to 160oC. Hydrogenation of these species significantly changed the chemical and physical properties of the bio-oil and overall improved its thermal stability, especially by reducing the carbonyl content, which represented the content of the most reactive species (i.e., sugar, aldehydes, and ketones). The change of content of each component in response to increasing hydrogen additions suggests the following bio-oil hydrogenation reaction sequence: sugar conversion to sugar alcohols, followed by ketone and aldehyde conversion to alcohols, followed by alkene and aromatic hydrogenation, and then followed by carboxylic acid hydrogenation to alcohols. Hydrogenation of bio-oil samples with different sulfur contents or inorganic material contents suggested that sulfur poisoning of the reduced Ru metal catalysts was

  10. MAGNETIC POLYMER MICROSPHERE STABILIZED GOLD NANOCOLLOIDS AS A FACILELY RECOVERABLE CATALYST

    Institute of Scientific and Technical Information of China (English)

    Han Zhang; Xin-lin Yang

    2011-01-01

    Magnetically responsive hierarchical magnetite/silica/poly(ethyleneglycol dimethacrylate-co-4-vinylpyridine) (Fe3O4/SiO2/P(EGDMA-co-VPy)) tri-layer microspheres were used as stabilizers for gold metallic nanocolloids as a facilely recoverable catalyst with the reduction of 4-nitrophenol to 4-aminophenol as a model reaction. The magnetic microsphere stabilized gold metallic nanocolloids were prepared by in situ reduction of gold chloride trihydrate with borohydride as reductant via the stabilization effect of the pyridyl groups to gold nanoparticles on the surface of the outer shell-layer of the inorganic/polymer fri-layer microspheres.

  11. Structure, activity, and stability of platinum alloys as catalysts for the oxygen reduction reaction

    DEFF Research Database (Denmark)

    Vej-Hansen, Ulrik Grønbjerg

    In this thesis I present our work on theoretical modelling of platinum alloys as catalysts for the Oxygen Reduction Reaction (ORR). The losses associated with the kinetics of the ORR is the main bottleneck in low-temperature fuel cells for transport applications, and more active catalysts...... are essential for wide-spread use of this technology. platinum alloys have shown great promise as more active catalysts, which are still stable under reaction conditions. We have investigated these systems on multiple scales, using either Density Functional Theory (DFT) or Effective Medium Theory (EMT...... and dealloying due to kinetic barriers, despite the thermodynamic driving force for dissolution. This is followed by our results on trying to decouple the strain and ligand effects for platinum skin structures, and determining whether there is any correlation between adsorption energy and surface stability...

  12. Stability and electrocatalytic activity for oxygen reduction in WC + Ta catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kunchan; Ishihara, Akimitsu; Mitsushima, Shigenori; Kamiya, Nobuyuki; Ota, Ken-ichiro

    2004-09-01

    Tantalum (Ta)-added tungsten carbide (WC) (WC+Ta) was examined in order to obtain surperior characteristics in stability and electrocatalytic activity for the oxygen reduction reaction (ORR) in acid electrolyte. The stability and the electrocatalytic activity of the WC+Ta catalyst were electrochemically investigated and compared to the pure WC. It was proved that the stability of the tungsten carbide was significantly increased by the addition of tantalum compared to the pure WC. The enhanced stability might be due to the formation of the W-Ta alloy in the WC+Ta catalyst. The reduction current of the WC+Ta catalyst for the ORR was observed at a potential of 0.8 V (versus dynamin hydrogen eletrode (DHE)) or less noble potential. This value was about 0.35 V higher than that of the pure WC. The enhanced electrocatalytic activity for the ORR might be caused by the presence of tungsten carbide, which exists on the surface and/or sub-surface.

  13. Stability and activity of molybdenum carbide catalysts for the oxidative reforming of methane

    Science.gov (United States)

    Lamont, David Charles

    Molybdenum carbide catalysts have been studied for oxidative reforming, in particular, the effect on reforming activity of the method by which they were synthesized, their stability under conditions of varying mass transfer, and the measurement of their inherent reaction kinetics. These catalysts show promise as possible alternatives to both conventional supported nickel catalysts, as well as to the rare and expensive noble metal catalysts. Samples of Mo 2C were synthesized in house and compared to a commercial sample of Mo2C for the CO2 (dry) reforming of methane. It was found that high surface areas, previously thought to be important for activity, were not a property of the Mo2C, but instead were attributable to large amounts of excess carbon. This carbon had a detrimental effect on catalyst stability under dry reforming conditions, because it enhanced deposition of refractory carbon via methane cracking. The commercial sample of Mo 2C, while of low surface area and containing no excess carbon, behaved more stably over time. In another investigation, Mo2C was studied for its stability under varying mass transfer conditions, because of evidence showing that the Mo2C can undergo redox chemistry at reforming conditions. Under dry reforming conditions, it was found that some feed mixtures are net oxidizing, but that oxidation in the presence of such feed mixtures could be prevented by operating under mass transfer limited conditions, which resulted in sufficiently high partial pressures of CO and H2 in the catalyst boundary layer. Similar stability was achieved by co-feeding CO to the catalyst bed, which allowed for stable operation under conditions that were not mass transfer limited. Using this approach, measurements of the intrinsic reaction kinetics of Mo2C for dry reforming were successfully achieved. These results pointed to a strong dependence of dry reforming rate on both CH4 and CO2 partial pressures, as well as evidence for a reaction mechanism unique from

  14. Stability of cobalt supported on ZrO{sub 2} catalysts for methane combustion

    Energy Technology Data Exchange (ETDEWEB)

    Milt, V.G.; Lombardo, E.A.; Ulla, M.A. [Instituto de Investigaciones en Catalisis y Petroquimica, INCAPE FIQ, UNL-CONICET, Santiago del Estero 2829, 3000 Santa Fe (Argentina)

    2002-04-08

    Cobalt supported catalysts were prepared by two different techniques: atomic layer epitaxy (ALE) and wet impregnation. Either ZrO{sub 2} or La/ZrO{sub 2} (La-doped ZrO{sub 2}) were used as supports. The solids were characterized by XRD, TPR and XPS before and after hydrothermal and catalytic stability tests (TOS: 150h, 970K). The most active catalysts were those in which cobalt was incorporated using the epitaxial growth technique. Moreover, the initial activity of cobalt supported on ZrO{sub 2} by ALE was significantly higher than that on La/ZrO{sub 2}. But, after maintaining the former catalysts for 150h at 970K on stream (stability test), their initial high activities significantly decreased. On the other hand, when Co was supported on La-doped ZrO{sub 2} the resulting catalysts became much more stable. Combining the catalytic results with the characterization information a simple model is proposed that rationalizes the behavior of these solids.

  15. Electrocatalytic Activity and Stability of M-Fe Catalysts Synthesized by Polymer Complex Method for PEFC Cathode

    KAUST Repository

    Ou, Yiwei

    2011-11-01

    The polymerized complex (PC) method was used to synthesize highly dispersed iron-based catalysts for the oxygen reduction reaction (ORR). The catalysts were prepared with an addition of 1,10-phenanthroline (Phen) and transition metals (M), such as Ta, Ti, and W, in an attempt to enhance the ORR activity and durability of the catalysts. The composition and properties of the catalysts were characterized by thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyst components, after extensive dissolution in a strong acid solution, were characterized by inductively coupled plasma mass spectroscopy and ultraviolet-visible spectroscopy. It was found that the Ti-Fe catalyst showed improved ORR performance, and the Ta-Fe catalyst showed enhanced stability towards ORR in acidic solution. The catalytic activity and stability for ORR was observed by adding Ti or Ta into the catalyst formulation, suggesting that the interaction between added hetero-ions (Ti and Ta) and ionic Fe active sites was beneficial for the ORR. A single-cell test with the synthesized catalyst in the cathode initially generated a high power density, but the low stability remains an issue to be solved.

  16. Stability and kinetic studies of supported ionic liquid phase catalysts for hydroformylation of propene

    DEFF Research Database (Denmark)

    Riisager, Anders; Fehrmann, Rasmus; Haumann, Marco;

    2005-01-01

    Supported ionic liquid phase (SILP) catalysts have been studied with regard to their long-term stability in the continuous gas-phase hydroformylation of propene. Kinetic data have been acquired by variation of temperature, pressure, syngas composition, substrate concentration, and residence time...... exceeded 200 h time on stream with no loss in selectivity. A small decrease in activity could be compensated by a vacuum procedure regaining the initial activity....

  17. Recovery of heavy metals and stabilization of spent hydrotreating catalyst using a glass-ceramic matrix.

    Science.gov (United States)

    Sun, D D; Tay, J H; Cheong, H K; Leung, D L; Qian, G

    2001-10-12

    Chemical analysis of spent Co/Mo/gamma Al(2)O(3) catalyst revealed the presence of carbon, molybdenum, sulfur, vanadium and cobalt at levels of 16.0, 10.9, 7.3, 4.6 and 4.0 wt.%, respectively. It was found that calcination at 500 degrees C provides an effective solution for the removal of carbon and sulfur and this generates the oxide form of the heavy metals. The removal of these heavy metals can be achieved through a two-stage leaching process. During the first stage, in which concentrated ammonia is used and it has been found that this process can be successful in removing as much as 83% (w/v) Mo. In a second stage, it was found that using 10% (v/v) of sulfuric acid, it was possible to account for up to 77% (w/v) Co and 4% (w/v) Mo removal. Leaching test results indicated that the vanadium present in the heated spent catalyst was almost stabilized but the molybdenum and cobalt were not. The combination of two solid wastes, ladle furnace slag (LFS) and treated residue of spent catalyst, could be used for making a high value-added anorthite glass-ceramic materials. Further leaching tests showed that ceramic glass materials provided a very effective method of Co, Mo and V heavy metals stabilization resulting in a product with a possible commercial value.

  18. PVP-Stabilized Palladium Nanoparticles in Silica as Effective Catalysts for Hydrogenation Reactions

    Directory of Open Access Journals (Sweden)

    Caroline Pires Ruas

    2013-01-01

    Full Text Available Palladium nanoparticles stabilized by poly (N-vinyl-2-pyrrolidone (PVP can be synthesized by corresponding Pd(acac2 (acac = acetylacetonate as precursor in methanol at 80°C for 2 h followed by reduction with NaBH4 and immobilized onto SiO2 prepared by sol-gel process under acidic conditions (HF or HCl. The PVP/Pd molar ratio is set to 6. The effect of the sol-gel catalyst on the silica morphology and texture and on Pd(0 content was investigated. The catalysts prepared (ca. 2% Pd(0/SiO2/HF and ca. 0,3% Pd(0/SiO2/HCl were characterized by TEM, FAAS, and SEM-EDS. Palladium nanoparticles supported in silica with a size 6.6 ± 1.4 nm were obtained. The catalytic activity was tested in hydrogenation of alkenes.

  19. Magnetically stabilized bed reactor for selective hydrogenation of olefins in reformate with amorphous nickel alloy catalyst

    Institute of Scientific and Technical Information of China (English)

    Xuhong Mu; Enze Min

    2007-01-01

    A magnetically stabilized bed (MSB) reactor for selective hydrogenation of olefins in reformate was developed by combining the advantages of MSB and amorphous nickel alloy catalyst. The effects of operating conditions, such as temperature, pressure, liquid space velocity, hydrogen-to-oil ratio, and magnetic field intensity on the reaction were studied. A mathematical model of MSB reactor for hydrogenation of olefins in reformate was established. A reforming flow scheme with a post-hydrogenation MSB reactor was proposed. Finally, MSB hydrogenation was compared with clay treatment and conventional post-hydrogenation.

  20. A review of C1 chemistry synthesis using yttrium-stabilized zirconia catalyst

    Institute of Scientific and Technical Information of China (English)

    Antonius Indarto; Jae-Wook Choi; Hwaung Lee; Hyung Keun Song

    2008-01-01

    C1 chemistry based on synthesis gas, methane, and carbon dioxide offers many routes to industrial chemicals. The reactions related to the synthesis of gas can be classified into direct and indirect approach for making such products, such as acetic acid, dimethyl ether, and alcohol. Catalytic syngas processing is currently done at high temperatures and pressures, conditions that could be unfavorable for the life of the catalyst. Another issue of C1 chemistry is related to the methane-initiated process. It has been known that direct methane conversions are still suffering from low yields and selectivity of products resulting in unprofitable ways to produce products, such as higher hydrocarbons, methanol, and so on. However, many experts and researchers are still trying to find the best method to overcome these barriers, for example, by finding the best catalyst to reduce the high-energy barrier of the reactions and conduct only selective catalyst-surface reactions. The application of Yttria-Stabilized Zirconia (YSZ) and its combination with other metals for catalyzing purposes are increasing. The existence of an interesting site that acts as oxygen store could be the main reason for it. Moreover, formation of intermediate species on the surface of YSZ also contributes significantly in increasing the production of some specific products. Understanding the phenomena happening inside could be necessary. In this article, the use of YSZ for some C1 chemistry reactions was discussed and reviewed.

  1. Study of retention properties of fluoro-apatite carbonate relative to Ni(II), Am(III) and Th(IV); Etude des proprietes de retention des carbonate fluoroapatites vis-a-vis de Ni(II), Am(III) et Th(IV)

    Energy Technology Data Exchange (ETDEWEB)

    Perrone, Jane [Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

    1999-07-12

    Apatite minerals and particularly the carbonated species (francolites), are characterized by their chemical and geological stability and also by their capacity to retain durably a large number of elements. Therefore, they should be able to improve the retention properties of the engineered barriers of a deep geological nuclear waste repository. But there is a wide variety of francolites, so we focused our study on a synthetic carbonate fluoro-apatite of formula: Ca{sub 10}(PO{sub 4}){sub 5}(CO{sub 3})(F,OH){sub 3} and on a natural apatite. We first studied their solubility which is an important criterion for the choice of the materials. A particular attention was also paid to the determination of their surface characteristics and to the study of the radionuclide/solution interactions. Sorption experiments have been performed for the three radionuclides and the influence of various parameters has been investigated. The modelling of the sorption isotherms with surface complexation models leads us to estimate the values of the constants associated to the equilibria under consideration. We have also demonstrated that the phosphate ions of the solution participate to the immobilization of americium as the AmPO{sub 4},xH{sub 2}O compound. Both apatites show high retention levels for the actinides: the sorption is quite total over all the pH range studied and the Kd values are close to 10{sup 4} m{sup 3} kg{sup -1}. Consequently, the use of apatites could be considered as a specific solution for the immobilisation of heavy elements, specially actinides. Moreover, the results indicate that high amounts of carbonates and impurities do not alter the retention properties of francolites. This bears out the feasibility of the use of natural apatites as additives for the engineered barrier materials. (author)

  2. The Pd(0) nanoparticles stabilized by collagen fibres as a recyclable heterogeneous catalyst for the Stille reaction under aerobic condition

    Indian Academy of Sciences (India)

    Babak Mohammadi-Aghdam; Siavash Bahari; Rahim Molaei

    2013-07-01

    The stabilized palladium(0) nanoparticles by collagen fibres was a highly active, air-stable and recyclable heterogeneous catalyst that could be used for the Stille coupling reactions between aryl iodides and organostannanes under aerobic conditions. This method offered the several advantages: high yield under facile reaction condition and easy work-up procedure. The catalyst was easily recovered from the reaction mixture by filtration and reused multiple times without significant reduction or decrease in the activity.

  3. Methodology for the effective stabilization of tin-oxide-based oxidation/reduction catalysts

    Science.gov (United States)

    Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony N. (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor)

    2011-01-01

    The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.

  4. Activity and Stability of Rare Earth-Based Hydride Alloys as Catalysts of Hydrogen Absorption-Oxidation Reactions

    Institute of Scientific and Technical Information of China (English)

    Ying Taokai(应桃开); Gao Xueping(高学平); Hu Weikang(胡伟康); Noréus Dag

    2004-01-01

    Rare earth-based AB5-type hydrogen storage alloys as catalysts of hydrogen-diffusion electrodes for hydrogen absorption and oxidation reactions in alkaline fuel cells were investigated. It is demonstrated that the meta-hydride hydrogen-diffusion electrodes could be charged by hydrogen gas and electrochemically discharged at the same time to retain a stable oxidation potential for a long period. The catalytic activities and stability are almost comparable with a Pt catalyst on the active carbon. Further improvement of performances is expected via reduction of catalyst size into nanometers.

  5. Methane dehydro-aromatization over Mo/HZSM-5 catalysts in the absence of oxygen: Effect of steam-treatment on catalyst stability

    Institute of Scientific and Technical Information of China (English)

    Tingting Zhao; Hongxia Wang

    2011-01-01

    The effect of steam-treatment to HZSM-5 zeolite and Mo/HZSM-5 with a steaming time range of 0.5-1 h on the catalytic performance of methane dehydro-aromatization (MDA) over Mo/HZSM-5 catalyst prepared with impregnation has been studied in detail in combination with the characterization of 1H MAS NMR technique.Both the deactivation rate constant (kd) and the Br(o)nsted acid sites per unit cell were calculated to quantitatively evaluate the stability of Mo/HZSM-5 catalysts treated with steam at 813 K before and after impregnation of molybdenum species,and the corresponding variation of their Br(o)nsted acid sites.The results reveal that a V-shape relationship between kd and the number of B 1 acid sites per unit cell is presented on Mo/HZSM-5 catalyst under the tested steam-treatment and reaction conditions.

  6. Dependence on composition of electronic properties and stability of Pt-Fe/C catalysts for oxygen reduction

    Energy Technology Data Exchange (ETDEWEB)

    Malheiro, A.R.; Perez, J.; Villullas, H.M. [Departamento de Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista - UNESP, Caixa Postal 355, R. Francisco Degni, s/n, CEP 14801-970, Araraquara, SP (Brazil)

    2010-11-01

    This work presents studies of electronic characteristics and alloy stability carried out for Pt-Fe/C catalysts of different compositions (10-50% Fe, in atoms) and same particle size. The electronic properties are characterized by in situ dispersive X-ray absorption spectroscopy (DXAS). The results show a steady decrease in Pt d-band occupancy as the amount of Fe in the alloy increases. The alloy stability is evaluated by prolonged potential cycling up to 1.0 V. Catalysts with Fe content up to 30% show good stabilities and keep their activities for oxygen reduction after prolonged cycling. In contrast, catalysts with Fe content above 30% suffer pronounced Fe leaching. (author)

  7. Design of biomimetic catalysts by molecular imprinting in synthetic polymers: the role of transition state stabilization.

    Science.gov (United States)

    Wulff, Günter; Liu, Junqiu

    2012-02-21

    The impressive efficiency and selectivity of biological catalysts has engendered a long-standing effort to understand the details of enzyme action. It is widely accepted that enzymes accelerate reactions through their steric and electronic complementarity to the reactants in the rate-determining transition states. Thus, tight binding to the transition state of a reactant (rather than to the corresponding substrate) lowers the activation energy of the reaction, providing strong catalytic activity. Debates concerning the fundamentals of enzyme catalysis continue, however, and non-natural enzyme mimics offer important additional insight in this area. Molecular structures that mimic enzymes through the design of a predetermined binding site that stabilizes the transition state of a desired reaction are invaluable in this regard. Catalytic antibodies, which can be quite active when raised against stable transition state analogues of the corresponding reaction, represent particularly successful examples. Recently, synthetic chemistry has begun to match nature's ability to produce antibody-like binding sites with high affinities for the transition state. Thus, synthetic, molecularly imprinted polymers have been engineered to provide enzyme-like specificity and activity, and they now represent a powerful tool for creating highly efficient catalysts. In this Account, we review recent efforts to develop enzyme models through the concept of transition state stabilization. In particular, models for carboxypeptidase A were prepared through the molecular imprinting of synthetic polymers. On the basis of successful experiments with phosphonic esters as templates to arrange amidinium groups in the active site, the method was further improved by combining the concept of transition state stabilization with the introduction of special catalytic moieties, such as metal ions in a defined orientation in the active site. In this way, the imprinted polymers were able to provide both an

  8. Chemical characterization of meltwater from East Rathong glacier vis-a-vis Western Himalayan glaciers

    Digital Repository Service at National Institute of Oceanography (India)

    Sharma, B.M.; Tayal, S.; Chakraborty, P.; Bharat, G.K.

    an important role in global hydrological cycle but also for providing significant environmental information of climate change and biogeochemical processes in the surrounding atmosphere. Non-polar regions and mountain glaciers (an elevation greater than 4... and sediment chemistry in high altitude rivers (Wagenbach 1989). Glacier snow and ice have the property to accumulate pollutants, sea salts, acids and other chemical compounds and later release them into atmosphere through air-water gas exchange or during...

  9. Usable Security and E-Banking: ease of use vis-a-vis security

    Directory of Open Access Journals (Sweden)

    Morten Hertzum

    2004-05-01

    Full Text Available Electronic banking must be secure and easy to use. An evaluation of six Danish web-based electronic banking systems indicates that the systems have serious weaknesses with respect to ease of use. Our analysis of the weaknesses suggests that security requirements are among their causes and that the weaknesses may in turn cause decreased security. We view the conflict between ease of use and security in the context of usable security, a concept that is intended to match security principles and demands against user knowledge and motivation. Automation, instruction, and understanding can be identified as different approaches to usable security. Instruction is the main approach of the systems evaluated; automation relieves the user from involvement in security, as far as possible; and understanding goes beyond step-by-step instructions, to enable users to act competently and safely in situations that transcend preconceived instructions. We discuss the pros and cons of automation and understanding as alternative approaches to the design of web-based e-banking systems.

  10. Future challenges for explosive industry vis-a-vis underground coal blasting

    Energy Technology Data Exchange (ETDEWEB)

    Roy, S.K.; Singh, R.R.; Ram, P.; Paul, R.K. [Central Mining Research Institute, Dhanbad (India)

    2002-03-01

    It is apprehended that with contribution of open cast mines in total production of coal going up further, the deterioration trend in coal quality will continue. Production from underground coal mines has to be increased in coming years for sustainable growth of coal industry and to meet the ever increasing power demand. So, to compete with the mechanical cutting of coal, the explosive industry needs a breakthrough in innovativeness, production and uses. The explosive industry and concerned organisations have to accept future challenges in development of safer products, more efficient application technique and strict quality control of products. Change in some of the regulations governing the uses of explosive in underground coal blasting also is called for. 14 refs.

  11. Public-Private Partnerships: an International Development vis a vis Indonesia Experience

    Directory of Open Access Journals (Sweden)

    Rizal Yaya

    2014-08-01

    Full Text Available For more than two decades, Public Private Partnerships (PPP had developed worldwide as an instrument to procure public infrastructure where government funds are limited. This practice supports the covergent theory of the public and private sector. Indonesia experience with PPP follows most of what had been done by countries overseas with some deviations. The main reasons for going for PPP for Indonesia government is to fill the gap in finance and capability in procuring the infrastructure. Unofficial reason such as for off-balance sheet and ideological is not relevant. Up to now, the Government only allow investment in hard economic infrastructure. Instead of using pure private finance, Indonesia Government facilitates public funds either from Central Government or Local Governments to finance PPP projects. In most cases, this involvement is because of marginality of the project. This results in the condition where the Government still has dominant role in the existing PPP projects. Compared to the PPP framework in other countries like in the UK, Indonesia PPP lacks of attention on output specification and risk transfer. This may be because of lacking of experiences as well as due to high degree of Government involvement. Rigorous policy is needed in this area to ensure Government to achieve better value for money.

  12. The Achuar People of the Corrientes Basin: The State vis a vis its own Paradigm

    Directory of Open Access Journals (Sweden)

    Alberto Chirif

    2010-12-01

    Full Text Available The paper analyses the events leading to the 2006 uprising of theAchuar people of the Corrientes basin (Loreto, who have sufferedfour decades of contamination due to oil exploitation. It also examinesthe Peruvian State’s and the oil company´s attitudes throughoutthe protest and after signing an agreement aiming to stop contaminationand remedy environmental and social havoc. Materials usedinclude interviews conducted with different stake holders and a widerange of written records, such as political declarations, reports onlocal people´s health´s and remediation work, agreement documentsand letters exchanged between stake holders, as well as historicaland socio economic background information. Findings highlight thestrength of organized indigenous people´s claiming for their rights;the greater commitment to assuming responsibility shown by the oilcompany´s as compared to the Peruvian State; and the weakness ofa political discourse equating development with the extraction ofnatural resources. The main conclusion is that the Peruvian Statedoes not fulfill the paradigm set in the first article of the Constitution:that the defense of the human person and the respect of its dignityare its supreme aim.

  13. The United States Vis-a-Vis Peru: A Strategy for Defeating Their Communist Insurgency.

    Science.gov (United States)

    1992-02-13

    43.Ev OF "VDNGI5PONSOFNG ft OFF SLczt PROuMAIENT BMSAIDENT M MMI IL ADM $$ KAY . a W C*COW 10SNC OF FUO MMS t1. TITLE P’cA* SocwN Coawfte’t The Uni ted...at the National University of San Cristobal de Huamanga in Ayacucho, Guzman has been the primary force behind the movement’s ideological development

  14. THE DYNAMICS OF THE FORM OF NUSANTARA MOSQUE: ARCHITECTURAL HOMOGENEITY VIS A VIS ARCHITECTURAL HYBRIDITY

    Directory of Open Access Journals (Sweden)

    Pudji Pratitis Wismantara

    2012-09-01

    Full Text Available There are two points of departure in the design of mosque architecture in Nusantara, namely architectural homogeneity and architectural hybridity. Each provides the legitimacy of the architecture of identity formation. This paper seeks to explore the comparative, the concept of homogeneity and hybridity architecture, with a critical theory approach. The  results of this search is, the concept of architectural homogeneity establishing assumption that certain architectural forms are supposed to represent "universal identity and modernity" of Muslim architecture. Meanwhile, the concept of architectural hybridity to show enrichment architecture identity because of the attempt to combine aspects of the universality of Islam with locality of Nusantara. Both these aspects can be positioned as the two subjects of mutual dialogue in a parallel position. As architecture strategy, the concept of hybridity reflects the effort or ijtihad in interpreting local and universal contextuality in the contemporary conditions that are constantly evolving and open.Keywords: Nusantara mosque, hybridity of architecture, homogeneity of architecture, architecture strategy

  15. Russian Energy Policy vis-a-vis Europe: Natural Resources as a Means of Foreign Policy

    Science.gov (United States)

    2012-06-01

    words, states’ behavior is stipulated by the “language of power and interests”39. Another contemporary scholar, Hans Joachim Morgenthau , views...their utility in light both of those preferences and of their perceptions of the nature of reality.” Finally, Morgenthau sees the balance of power... Morgenthau , revised by Kenneth W. Thompson, Politics among Nations: The Struggle for Power and Peace (New York: McGraw-Hill, 1993), 4. 41 Keohane

  16. Personal vis-a-vis social responsibility for disparities in health status: An issue of justice

    Directory of Open Access Journals (Sweden)

    Ayan Jha

    2016-01-01

    Full Text Available Health inequities are disparities which can be avoided through rational actions on the part of policymakers. Such inequalities are unnecessary and unjust and may exist between and within nations, societies, and population groups. Social determinants such as wealth, income, occupation, education, gender, and racial/ethnic groups are the principal drivers of this inequality since they determine the health risks and preventive behaviors, access to, and affordability of health care. Within this framework, there is a debate on assigning a personal responsibility factor over and above societal responsibility to issues of ill health. One school of philosophy argues that when individuals are worse-off than others for no fault of their own, it is unjust, as opposed to health disparities that arise due to avoidable personal choices such as smoking and drug addiction for which there should (can be a personal responsibility. Opposing thoughts have pointed out that the relative socioeconomic position of an individual dictates how his/her life may progress from education to working conditions and aging, susceptibility to diseases and infirmity, and the consequences thereof. The existence of a social gradient in health outcomes across populations throughout the world is a testimony to this truth. It has been emphasized that assuming personal responsibility for health in public policy-making can only have a peripheral place. Instead, the concept of individual responsibility should be promoted as a positive concept of enabling people to gain control over the determinants of health through conscious, informed, and healthy choices.

  17. Results and Perspectives in HEP, vis-a-vis Lattice QCD

    CERN Document Server

    Mangano, Michelangelo L

    2000-01-01

    I review in this presentation some aspects of phenomenology in High Energy Physics which are related to recent and possibly future progress in lattice QCD. In particular, I cover (i) the extraction of CKM matrix elements from B physics, (ii) the determination of epsilon'/epsilon, as well as (iii) some issues emerged in the physics of high energy jets produced in hadronic collisions, where input from non-perturbative calculations would benefit our capability to perform better theoretical predictions.

  18. Personal vis-a-vis social responsibility for disparities in health status: An issue of justice.

    Science.gov (United States)

    Jha, Ayan; Dobe, Madhumita

    2016-01-01

    Health inequities are disparities which can be avoided through rational actions on the part of policymakers. Such inequalities are unnecessary and unjust and may exist between and within nations, societies, and population groups. Social determinants such as wealth, income, occupation, education, gender, and racial/ethnic groups are the principal drivers of this inequality since they determine the health risks and preventive behaviors, access to, and affordability of health care. Within this framework, there is a debate on assigning a personal responsibility factor over and above societal responsibility to issues of ill health. One school of philosophy argues that when individuals are worse-off than others for no fault of their own, it is unjust, as opposed to health disparities that arise due to avoidable personal choices such as smoking and drug addiction for which there should (can) be a personal responsibility. Opposing thoughts have pointed out that the relative socioeconomic position of an individual dictates how his/her life may progress from education to working conditions and aging, susceptibility to diseases and infirmity, and the consequences thereof. The existence of a social gradient in health outcomes across populations throughout the world is a testimony to this truth. It has been emphasized that assuming personal responsibility for health in public policy-making can only have a peripheral place. Instead, the concept of individual responsibility should be promoted as a positive concept of enabling people to gain control over the determinants of health through conscious, informed, and healthy choices.

  19. First evidence of denitrification vis-a-vis monsoon in the Arabian Sea since late Miocene

    Digital Repository Service at National Institute of Oceanography (India)

    Tripathi, S.; Tiwari, M.; Lee, J.; Khim, B.-K.; Pandey, D.K.; Clift, P.D.; Kulhanek, D.K.; Ando, S.; Bendle, J.A; Aharonovich, S.; Griffith, E.M.; Gurumurthy, G.P.; Hahn, A; Iwai, M.; Kumar, A; Kumar, A; Liddy, H.M.; Lu, H.; Lyle, M.W.; Mishra, R.; Radhakrishna, T.; Routledge, C.M.; Saraswat, R.; Saxena, R.; Scardia, G.; Sharma, G.K.; Singh, A; Steinke, S.; Suzuki, K.; Tauxe, L.; Xu, Z.; Yu, Z.

    in contrast to a few previous studies, (ii) on tectonic timescale, both the SAM and the East Asian Monsoon (EAM) varied synchronously, (iii) the first evidence of denitrification and productivity/SAM intensification was at ~3.2–2.8 Ma that coincided with Mid...

  20. ROLE OF STATISTICAL VIS-A-VIS PHYSICS-OFFAILURE METHODS IN RELIABILITY ENGINEERING

    Directory of Open Access Journals (Sweden)

    P.V.Varde

    2009-01-01

    Full Text Available Traditionally the statistical or more specifically probabilistic methods form the basicframework for assessing the reliability characteristics of the components. However the recenttrend for predicting the reliability or life of the component involves application of physics-offailuremethods. This rather new approach is finding wider application as it is based on basicfundamentals of science and thereby provides an improved framework to understand the failuremechanism. Since accelerated testing of component forms part of this approach, the prediction oftime-to-failure of the components is more accurate compared to the existing methods whichdepends only historical data and its evaluation using probabilistic methods. The new approach isall the more relevant when it comes to assessment of reliability of new components as thetraditional probabilistic approach is not adequate to predict reliability of new components as itdepends on historical data for prediction of reliability.In view of the above this paper investigates the role of statistical or probabilisticapproach and physics-of-failure approach for reliability assessment of engineering components ingeneral and electronics components in particular.

  1. The meaning of marriage vis-a-vis childbearing in Europe and the United States

    OpenAIRE

    Holland, Jennifer

    2015-01-01

    This paper extends Holland’s (2013) marriage typology, linking the timing of marriage, childbearing, and cohabitation, and apply it to the Harmonized Histories covering a range of European countries and the United States. The meaning of marriage is organized around six ideal types: Direct Family Forming, Post-Cohabitation Family Forming, Conception-Related Legitimizing, Birth-Related Legitimizing, Reinforcing and Capstone marriage. Although smaller shares of women entered marriage at each age...

  2. Comparing Conventional Bank Credit Vis A Vis Shariah Bank Musharakah: Experimental Economic Approach

    Directory of Open Access Journals (Sweden)

    Muhamad Abduh

    2008-01-01

    Full Text Available Central Bank of Indonesia with dual banking system – i.e Shariah and Conventional Bank – keep on developing system that considered as an answer to generate the national economic growth. One of the banking activities that emphasized by the Central Bank of Indonesia is fund distribution through either conventional bank credit or shariah bank fi nancing. Having the Experimental Economic Approach based on Induced Value Theory and employing ANOVA, this paper found that shariah bank musharakah fi nancing system would come up with higher profi t opportunity compare to conventional credit system. One main reason is that musharakah fi nancing in shariah bank applies profi t and lost sharing (PLS scheme so that will not be a burden to the customer when he fi nd low profi t.Keywords: Credit Loan, Musharakah Financing, Induced Value Theory, Experimental Economic Approach, Analysis of Variance (ANOVA.

  3. Evolution of Zipf's Law for Indian Urban Agglomerations vis-\\`{a}-vis Chinese Urban Agglomerations

    CERN Document Server

    Gangopadhyay, Kausik

    2012-01-01

    We investigate into the rank-size distributions of urban agglomerations for India between 1981 to 2011. The incidence of a power law tail is prominent. A relevant question persists regarding the evolution of the power tail coefficient. We have developed a methodology to meaningfully track the power law coefficient over time, when a country experience population growth. A relevant dynamic law, Gibrat's law, is empirically tested in this connection. We argue that these empirical findings for India goes in contrast with the findings in case of China, another country with population growth but monolithic political system.

  4. Christian Theological Attitudes vis-a-vis Islam: The Effect on West-Muslim Relations

    Science.gov (United States)

    2002-12-01

    which those attitudes were formed, and that understanding how those attitudes were formed explains Christianity’s “ exclusivist ” attitude and refusal to...New York: Vintage Books, 1997). 194 Chapman, 262. 63 Muslims or otherwise, will fall in defeat at the Lord’s coming.195 Such an exclusivist ...followers need to convert to Christianity or face eternal separation from God. This “ exclusivist ” perspective leaves little room for ecumenism. One

  5. Effects of CO2 content on the activity and stability of nickel catalyst supported on mesoporous nanocrystalline zirconia

    Institute of Scientific and Technical Information of China (English)

    M.Rezaei; S.M.Alavi; S.Sahebdelfar; Zi-Feng Yan

    2008-01-01

    The effects of carbon dioxide content on the catalytic performance and coke formation of nickel catalyst supported on mesoporous nanocrystalline zirconia with high surface area and pure tetragonaI crystalline phase were investigated in methane reforming with carbon dioxide.The samples were characterized bV XRD,BET,PR,TPO,TPH,TEM,and SEM techniques.The catalyst prepared showed high surface area and a mesoporous structure with a narrow pore size distribution.The obtained results revealed that the increase in CO2 content increased the methane conversion and stability of the catalyst and significantly reduced the coke deposition.The TPH analysis showed that several species of carbon with different reactivities toward hydrogenation were deposited on the spent catalysts employed under different CO2 contents.

  6. Enhanced stability of multilayer graphene-supported catalysts for polymer electrolyte membrane fuel cell cathodes

    Science.gov (United States)

    Marinkas, A.; Hempelmann, R.; Heinzel, A.; Peinecke, V.; Radev, I.; Natter, H.

    2015-11-01

    One of the biggest challenges in the field of polymer electrolyte membrane fuel cells (PEMFC) is to enhance the lifetime and the long-term stability of PEMFC electrodes, especially of cathodes, furthermore, to reduce their platinum loading, which could lead to a cost reduction for efficient PEMFCs. These demands could be achieved with a new catalyst support architecture consisting of a composite of carbon structures with significant different morphologies. A highly porous cathode catalyst support layer is prepared by addition of various carbon types (carbon black particles, multi-walled carbon nanotubes (MWCNT)) to multilayer graphene (MLG). The reported optimized cathodes shows extremely high durability and similar performance to commercial standard cathodes but with 89% lower Pt loading. The accelerated aging protocol (AAP) on the membrane electrode assemblies (MEA) shows that the presence of MLG increases drastically the durability and the Pt-extended electrochemical surface area (ECSA). In fact, after the AAP slightly enhanced performance can be observed for the MLG-containing cathodes instead of a performance loss, which is typical for the commercial carbon-based cathodes. Furthermore, the presence of MLG drastically decreases the ECSA loss rate. The MLG-containing cathodes show up to 6.8 times higher mass-normalized Pt-extended ECSA compared to the commercial standard systems.

  7. Stabilizing a Platinum1 Single-Atom Catalyst on Supported Phosphomolybdic Acid without Compromising Hydrogenation Activity.

    Science.gov (United States)

    Zhang, Bin; Asakura, Hiroyuki; Zhang, Jia; Zhang, Jiaguang; De, Sudipta; Yan, Ning

    2016-07-11

    In coordination chemistry, catalytically active metal complexes in a zero- or low-valent state often adopt four-coordinate square-planar or tetrahedral geometry. By applying this principle, we have developed a stable Pt1 single-atom catalyst with a high Pt loading (close to 1 wt %) on phosphomolybdic acid(PMA)-modified active carbon. This was achieved by anchoring Pt on the four-fold hollow sites on PMA. Each Pt atom is stabilized by four oxygen atoms in a distorted square-planar geometry, with Pt slightly protruding from the oxygen planar surface. Pt is positively charged, absorbs hydrogen easily, and exhibits excellent performance in the hydrogenation of nitrobenzene and cyclohexanone. It is likely that the system described here can be extended to a number of stable SACs with superior catalytic activities.

  8. Stabilization of supported platinum nanoparticles on gamma-alumina catalysts by addition of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, Jose L., E-mail: jlcl@correo.azc.uam.m [Universidad Autonoma Metropolitana-Azcapotzalco. Energia, CBI, Av. Sn. Pablo 180, Col. Reynosa, 02200, Mexico, D.F. (Mexico); Universidad Autonoma Metropolitana-Iztapalapa Depto. Ingenieria de Procesos e Hidraulica, A.P. 55-534, 09340 Mexico, D.F. (Mexico); Fuentes, Gustavo A. [Universidad Autonoma Metropolitana-Iztapalapa Depto. Ingenieria de Procesos e Hidraulica, A.P. 55-534, 09340 Mexico, D.F. (Mexico); Zeifert, Beatriz; Salmones, Jose [Instituto Politecnico Nacional, ESIQIE, Av. IPN s/n Edif. 8, UPALM, Mexico, D.F. 07738 (Mexico)

    2009-08-26

    The thermal stabilization of Al{sub 2}O{sub 3} using W{sup 6+} ions has been found useful to the synthesis of Pt/Al{sub 2}O{sub 3} catalysts. The simultaneous and sequential methods were used to study the effect of W{sup 6+} upon Pt/gamma-Al{sub 2}O{sub 3} reducibility, Pt dispersion, and benzene hydrogenation. The W/Pt atomic ratios were from 0.49 to 12.4. In the first method we found that the W{sup 6+} ions delayed reduction of a fraction of Pt{sup 4+} atoms beyond 773 K. At the same time, W{sup 6+}inhibited sintering of the metallic crystallites once they were formed on the surface. For the sequential sample with a W/Pt atomic ratio of 3.28 W{sup 6+} did not inhibit the H{sub 2} reduction of Pt oxides even below of 773 K, the Pt oxides were reduced completely. After reduction at 1073 K, sequential samples impregnating Pt on WO{sub x}-gamma-Al{sub 2}O{sub 3} were more active and stable during benzene hydrogenation. TOF of the reaction did not change when the W/Pt atomic ratio, preparation technique and reduction temperature changed and its value was of 1.1 s{sup -1}. W{sup 6+} ions promoted high thermal stability of Pt crystallites when sequential catalysts were reduced at 1073 K and decreased their Lewis acidity.

  9. Analysis of the fluid-bed stability of FCC catalysts at high temperature in terms of bed elasticity

    Institute of Scientific and Technical Information of China (English)

    Paola Lettieri; Luca Mazzer

    2008-01-01

    The effect of temperature on the fluid-bed stability of three FCC catalysts has been analyzed through considerations on fluid-bed elasticity. Experimental findings on the effect of temperature on the elasticity modulus at minimum bubbling conditions, (E)mb, were analyzed using the hydrodynamic fluid-bed stability model developed by Foscolo and Gibilaro (1984) and adopting the interparticle-forces-based stability criterion developed by Mutsers and Rietema (1977). For both models, the parameters which control changes in (E)mb with temperature are discussed, in order to establish the origin of the fluid-bed elasticity and analyze the ability of these models to discriminate between the relative importance of the hydrodynamic and interparticle forces on the stability of the fluidized catalysts.

  10. Effects of supported metallocene catalyst active center multiplicity on antioxidant-stabilized ethylene homo- and copolymers

    KAUST Repository

    Atiqullah, Muhammad

    2014-10-09

    © 2014 Akadémiai Kiadó, Budapest, Hungary. A silica-supported bis(n-butylcyclopentadienyl) zirconium dichloride [( n BuCp)2ZrCl2] catalyst was synthesized. This was used to prepare an ethylene homopolymer and an ethylene-1-hexene copolymer. The active center multiplicity of this catalyst was modeled by deconvoluting the copolymer molecular mass distribution and chemical composition distribution. Five different active site types were predicted, which matched the successive self-nucleation and annealing temperature peaks. The thermo-oxidative melt stability, with and without Irganox 1010 and Irgafos 168, of the above polyethylenes was investigated using nonisothermal differential scanning calorimetric (DSC) experiments at 150 °C. This is a temperature that ensures complete melting of the samples and avoids the diffusivity of oxygen to interfere into polyethylene crystallinity and its thermo-oxidative melt degradation. The oxidation parameters such as onset oxidation temperature, induction period, protection factor, and S-factor were determined by combining theoretical modeling with the DSC experiments. Subsequently, these findings were discussed considering catalyst active center multiplicity and polymer microstructure, particularly average ethylene sequence length. Several insightful results, which have not been reported earlier in the literature, were obtained. The antioxidant effect, for each polymer, varied as (Irganox + Irgafos) ≈ Irganox > Irgafos > Neat polymer. The as-synthesized homopolymer turned out to be almost twice as stable as the corresponding copolymer. The antioxidant(s) in the copolymer showed higher antioxidant effectiveness (AEX) than those in the homopolymer. Irganox exhibited more AEX than Irgafos. To the best of our knowledge, such findings have not been reported earlier in the literature. However, mixed with Irganox or Irgafos, their melt oxidation stability was comparable. The homopolymer, as per the calculated S-factor, showed Irganox

  11. Electrochemical stability and postmortem studies of Pt/SiC catalysts for polymer electrolyte membrane fuel cells

    DEFF Research Database (Denmark)

    Stamatin, Serban Nicolae; Spéder, József; Dhiman, Rajnish

    2015-01-01

    In the presented work, the electrochemical stability of platinized silicon carbide is studied. Postmortem transmission electron microscopy and X-ray photoelectron spectroscopy were used to document the change in the morphology and structure upon potential cycling of Pt/SiC catalysts. Two differen...

  12. Metal–Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin (UC)

    2016-05-06

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal–organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C–H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ~2.5 × 106 and turnover frequencies of ~1.1 × 105 h–1. Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy•–)CoI(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.

  13. Re/HZSM-5: a new catalyst for ethane aromatization with improved stability

    DEFF Research Database (Denmark)

    Krogh, Anne; Hansen, Thomas W.; Christensen, Claus Hviid

    2003-01-01

    Rhenium-impregnated HZSM-5 is found to be a promising catalyst for ethane aromatization. The Re–HZSM-5 catalyst deactivates significantly slower than well-known ethane aromatization Zn–HZSM-5 catalyst. Product selectivities for the two catalysts are similar, indicating that the shape selectivity...... and acid-function of the zeolite are the determining factors, and the metal function is only responsible for the activation of ethane by dehydrogenation to ethylene....

  14. Influence of rhenium speciation on the stability and activity of Re/Pd bimetal catalysts used for perchlorate reduction.

    Science.gov (United States)

    Choe, Jong Kwon; Shapley, John R; Strathmann, Timothy J; Werth, Charles J

    2010-06-15

    Recent work demonstrates reduction of aqueous perchlorate by hydrogen at ambient temperatures and pressures using a novel rhenium-palladium bimetal catalyst immobilized on activated carbon (Re/Pd-AC). This study examines the influence of Re speciation on catalyst activity and stability. Rates of perchlorate reduction are linearly dependent on Re content from 0-6 wt %, but no further increases are observed at higher Re contents. Surface-immobilized Re shows varying stability and speciation both in oxic versus H(2)-reducing environments and as a function of Re content. In oxic solutions, Re immobilization is dictated by sorption of the Re(VII) precursor, perrhenate (ReO(4)(-)), to activated carbon via electrostatic interactions. Under H(2)-reducing conditions, Re immobilization is significantly improved and leaching is minimized by ReO(4)(-) reduction to more reduced species on the catalyst surface. X-ray photoelectron spectroscopy shows two different Re binding energy states under H(2)-reducing conditions that correspond most closely to Re(V)/Re(IV) and Re(I) reference standards, respectively. The distribution of the two redox states varies with Re content, with the latter predominating at lower Re contents where catalyst activity is more strongly dependent on Re content. Results demonstrate that both lower Re contents and the maintenance of H(2)-reducing conditions are key elements in stabilizing the active Re surface species that are needed for sustained catalytic perchlorate treatment.

  15. Synthesis of Self-Assembled Multifunctional Nanocomposite Catalysts with Highly Stabilized Reactivity and Magnetic Recyclability

    Science.gov (United States)

    Yu, Xu; Cheng, Gong; Zheng, Si-Yang

    2016-05-01

    In this paper, a multifunctional Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite catalyst with highly stabilized reactivity and magnetic recyclability was synthesized by a self-assembled method. The magnetic Fe3O4 nanoparticles were coated with a thin layer of the SiO2 to obtain a negatively charged surface. Then positively charged poly(ethyleneimine) polymer (PEI) was self-assembled onto the Fe3O4@SiO2 by electrostatic interaction. Next, negatively charged glutathione capped gold nanoparticles (GSH-AuNPs) were electrostatically self-assembled onto the Fe3O4@SiO2@PEI. After that, silver was grown on the surface of the nanocomposite due to the reduction of the dopamine in the alkaline solution. An about 5 nm thick layer of polydopamine (PDA) was observed to form the Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite was carefully characterized by the SEM, TEM, FT-IR, XRD and so on. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite shows a high saturation magnetization (Ms) of 48.9 emu/g, which allows it to be attracted rapidly to a magnet. The Fe3O4@SiO2@PEI-Au/Ag@PDA nanocomposite was used to catalyze the reduction of p-nitrophenol (4-NP) to p-aminophenol (4-AP) as a model system. The reaction kinetic constant k was measured to be about 0.56 min‑1 (R2 = 0.974). Furthermore, the as-prepared catalyst can be easily recovered and reused for 8 times, which didn’t show much decrease of the catalytic capability.

  16. Study on Coke Formation and Stability of Nickel-Based Catalysts in CO2 Reforming of CH4

    Institute of Scientific and Technical Information of China (English)

    黎先财; 吴敏; 杨沂凤; 何琲

    2004-01-01

    CO2 reforming of CH4 over nickel-based catalysts was investigated by using a fixed-bed reactor. Catalytic activity and amount of carbon deposition effects by nickel loading content, rare earth promoter and promoter contents were evaluated. It is found that nickel loading as well as reaction temperature can influence the activity and carbon deposition amounts,and with the addition of rare earth promoter, it can greatly improve the catalytic activity and exert a strong effect on the anticoking performance of the catalysts. The 5.0%(mass fraction)Ni-0.75%La-BaTiO3 catalyst shows great resistance to coke formation and higher thermal stability as well as the catalytic activity.

  17. Hydrogen production from raw bioethanol steam reforming : optimization of catalyst composition with improved stability against various impurities

    Energy Technology Data Exchange (ETDEWEB)

    Le Valant, A.; Can, F.; Bion, N.; Epron, F.; Duprez, D. [Poitiers Univ., Poitiers (France). Laboratoire de Catalyse en Chimie organique

    2009-07-01

    This study investigated the effects of raw ethanol impurities on catalytic performance during ethanol steam reforming processes. An Rh/MgAI{sub 2}O{sub 4} reference catalyst was used. Steam reforming was conducted in a fixed bed reactor. The study showed that aldehyde, amine, and methanol have no negative impacts on catalytic performance. Deactivation is caused by coke formation as a result of the presence of the impurities in the feed. The composition of the support and metallic phases of the catalyst formulation were then modified in order to improve the stability of the catalyst in the presence of deactivating impurities. Rare earth elements were used to replace magnesium and decrease strong and medium acid sites. Ethanol conversion and hydrogen yield were both increased when the dehydration reaction was disfavoured. The metallic phase was modified by the addition of a second metal. It was concluded that the Rh-NiY-Al{sub 2}O{sub 3} catalyst has the highest hydrogen yield, and is more stable than the reference catalyst. 16 refs., 7 figs.

  18. Comparative study on stability and coke deposition over supported Rh and FePO4 catalysts for oxy-bromination of methane

    Institute of Scientific and Technical Information of China (English)

    Ronghe; Lin; Yunjie; Ding; Runqin; Wang

    2014-01-01

    Rhodium- and iron phosphate-based catalysts are by far the most promising catalysts for oxy-bromination of methane(OBM) reaction. However, most literature reported either Rh- or FePO4-based catalysts, and the results were rarely studied in a uniform environmental condition. In this report, comparative study was conducted on silica- and silicon carbide-supported rhodium and iron phosphate catalysts with the main focuses on stability performance and coke deposition. The catalytic results demonstrated that the stability of both Rh- and FePO4-based catalysts was greatly influenced by the supports used, and silicon carbide-supported catalysts showed much better anti-coking ability as compared with silica-supported ones. Temperature-programmed oxidation over the used catalysts further indicated that the coke formation mechanisms were completely different between silica-supported rhodium and iron phosphate catalysts. While cokes might be caused by condensation of CH2Br2over supported iron phosphate, methane decomposition might be the reason for coke formation over silica-supported rhodium catalyst. These findings might pave the way for designing highly efficient and stable catalysts of the OBM reaction.

  19. Hydrothermal stability of MOx-Ce0.75Zr0.25O2 catalysts for NOx reduction by ammonia

    Institute of Scientific and Technical Information of China (English)

    王敏; 司知蠢; 陈磊; 吴晓东; 於俊

    2013-01-01

    Various acidic components (MOx:phosphate, sulfate, tungstate and niobate) were loaded on Ce0.75Zr0.25O2 powders by an impregnation method. The as-prepared catalysts were hydrothermally treated at 760 ºC for 48 h in air containing 10 vol.%H2O to ob-tain the aged catalysts. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H2 pro-grammed-reduction, NH3 adsorption and deNOx activity measurements. The results showed that, among the catalysts investigated, the phosphated Ce0.75Zr0.25O2 catalyst showed the highest hydrothermal stability. The remained high acidity of the phosphated catalyst with moderate redox property helped to maintain the excellent NH3-SCR activity of hydrothermally aged catalyst. Cerium tungstate led to the poor redox property of the tungstated catalyst although the acidity of catalyst was still high. The decomposition of sulfates at temperatures higher than 600 °C restrained the usage of sulfated catalysts in high temperature conditions. The overall dehydration of niobate to niobium oxides led to the low acidity of hydrothermally aged Nb2O5-Ce0.75Zr0.25O2 catalyst.

  20. Reusability and Stability Tests of Calcium Oxide Based Catalyst (K2O/CaO-ZnO for Transesterification of Soybean Oil to Biodiesel

    Directory of Open Access Journals (Sweden)

    Istadi Istadi

    2016-03-01

    Full Text Available This paper was purposed for testing reusability and stability of calcium oxide-based catalyst (K2O/CaO-ZnO over transesterification reaction of soybean oil with methanol to produce biodiesel. The K2O/CaO-ZnO catalyst was synthesized by co-precipitation method of calcium and zinc nitrates followed by impregnation of potassium nitrate. The fresh and used catalysts were tested after regeneration. The catalysts were characterized by Scanning Electron Microscopy (SEM, X-ray Diffraction (XRD, and BET Surface Area in order to compare the catalyst structure between the fresh and used catalysts. The catalyst testing in transesterification proses was carried out at following operating conditions, i.e. catalyst weight of 6 wt.%, oil to methanol mole ratio of 1:15, and temperature of 60 oC. In addition, metal oxide leaching of K2O/CaO-ZnO catalyst during reaction was also tested. From the results, the catalysts exhibited high catalytic activity (80% fatty acid methyl ester (FAME yield after three-cycles of usage and acceptable reusability after regeneration. The catalyst also showed acceptable stability of catalytic activity, even after three-cycles of usage. Copyright © 2016 BCREC GROUP. All rights reserved Received: 10th November 2015; Revised: 16th January 2016; Accepted: 16th January 2016 How to Cite: Istadi, I., Mabruro, U., Kalimantini, B.A.,  Buchori, L., Anggoro, D.D. (2016. Reusability and Stability Tests of Calcium Oxide Based Catalyst (K2O/CaO-ZnO for Transesterification of Soybean Oil to Biodiesel. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1: 34-39. (doi:10.9767/bcrec.11.1.413.34-39 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.413.34-39

  1. A Highly Efficient and Self-Stabilizing Metallic-Glass Catalyst for Electrochemical Hydrogen Generation.

    Science.gov (United States)

    Hu, Yuan Chao; Wang, Yi Zhi; Su, Rui; Cao, Cheng Rong; Li, Fan; Sun, Chun Wen; Yang, Yong; Guan, Peng Fei; Ding, Da Wei; Wang, Zhong Lin; Wang, Wei Hua

    2016-12-01

    A multicomponent metallic glass (MG) with highly efficient and anomalous durability for catalyzing water splitting is reported. The outstanding performance of the MG catalyst contributed by self-optimized active sites originates from the intrinsic chemical heterogeneity and selective dealloying on the disordered surface; thus, a new mechanism for improving the durability of catalysts is uncovered.

  2. Hydrogen production from raw bioethanol steam reforming: optimization of catalyst composition with improved stability against various impurities

    Energy Technology Data Exchange (ETDEWEB)

    Le Valant, A.; Can, F.; Bion, N.; Epron, F.; Duprez, D. [Laboratoire de Catalyse en Chimie organique, Univ. de Poitiers, Poitiers Cedex (France)], E-mail: florence.epron.cognet@univ-poitiers.fr

    2009-07-01

    Usually, ethanol steam reforming is performed using pure ethanol, whereas the use of raw bioethanol is of major importance for a cost effective industrial application. Raw bioethanol contains higher alcohols as the main impurities and also aldehydes, amines, acids and esters. The effect of these impurities on the catalytic performances for ethanol steam reforming (ESR) has been studied, using a reference catalyst, Rh/MgAl{sub 2}O{sub 4}. It was shown that the aldehyde, the amine and methanol has no negative effect on the catalytic performances, contrary to the ester, acid and higher alcohols. The deactivation is mainly explained by coke formation favored by the presence of these impurities in the feed. In order to improve the stability of the catalyst and its performances in the presence of these deactivating impurities, the catalyst formulation, i.e. the composition of the support and of the metallic phase, was modified. The addition of rare earth elements instead of magnesium to the alumina support leads to a decrease of the strong and medium acid sites and to an increase of the basicity. On these modified supports, the dehydration reaction, leading to olefins, which are coke precursors, is disfavored, the ethanol conversion and the hydrogen yield are increased. The best catalytic performances were obtained with Rh/Y-Al{sub 2}O{sub 3}. Then, the metallic phase was also modified by adding a second metal (Ni, Pt or Pd). The Rh-Ni/Y-Al{sub 2}O{sub 3} catalyst leads to the highest hydrogen yield. This catalyst, tested in the presence of raw bioethanol during 24h was very stable compared to the reference catalyst Rh/MgAl{sub 2}O{sub 4}, which was strongly deactivated after 2h of time-on-stream. (author)

  3. Hydrogen production from raw bioethanol steam reforming: Optimization of catalyst composition with improved stability against various impurities

    Energy Technology Data Exchange (ETDEWEB)

    Le Valant, Anthony; Can, Fabien; Bion, Nicolas; Duprez, Daniel; Epron, Florence [Laboratoire de Catalyse en Chimie organique, UMR6503 CNRS, Universite de Poitiers, 40 avenue du recteur Pineau, 86022 Poitiers Cedex (France)

    2010-05-15

    The use of raw bioethanol is of major importance for a cost effective industrial application. Raw bioethanol contains higher alcohols as the main impurities and also aldehydes, amines, acids and esters. The effect of these impurities on the catalytic performances for ethanol steam reforming (ESR) has been studied, using a reference catalyst, Rh/MgAl{sub 2}O{sub 4}. It was shown that the aldehyde, the amine and methanol have no negative effect on the catalytic performances, contrary to the ester, acid and higher alcohols. The deactivation is mainly explained by coke formation favored by the presence of these impurities in the feed. In order to improve the stability of the catalyst and its performances in the presence of these deactivating impurities, the catalyst formulation, i.e. the composition of the support and of the metallic phase, was modified. The addition of rare earth elements instead of magnesium to the alumina support leads to a decrease of the strong and medium acid sites and to an increase of the basicity. On these modified supports, the dehydration reaction, leading to olefins, which are coke precursors, is disfavored, the ethanol conversion and the hydrogen yield are increased. The best catalytic performances were obtained with Rh/Y-Al{sub 2}O{sub 3}. Then, the metallic phase was also modified by adding a second metal (Ni, Pt or Pd). The Rh-Ni/Y-Al{sub 2}O{sub 3} catalyst leads to the highest hydrogen yield. This catalyst, tested in the presence of raw bioethanol during 24 h was very stable compared to the reference catalyst Rh/MgAl{sub 2}O{sub 4}, which was strongly deactivated after 2 h of time-on -stream. (author)

  4. Study on Chemisorption, Catalytic Behavior, and Stability of Supported Au Catalyst for the Propylene Epoxidation Reaction

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Tin+ site on the surface of the catalyst and that the adsorbing capacity of the catalyst for propylene oxide is larger than that for propylene. Catalytic behavior for propylene epoxidation with H2 and O2 was tested in a micro-reactor. Under typical conditions, the selectivity for propylene oxide is over 87%. The TG curves show that PO successive oxidation cause carbon deposition on the active center and deactivation of the Au catalysts. Because the amounts of Tin+ site decrease significantly, and consequently the separation between Tin+ sites increases, the Au/TiO2-SiO2 catalyst is more stable than Au/TiO2.

  5. Stability and catalytic performance of vanadia supported on nanostructured titania catalyst in oxidative dehydrogenation of propane

    Science.gov (United States)

    Kootenaei, A. H. Shahbazi; Towfighi, J.; Khodadadi, A.; Mortazavi, Y.

    2014-04-01

    Titanate nanotubes with a high specific surface area were synthesized by the simple hydrothermal method and investigated as support for V2O5 catalyst in oxidative dehydrogenation of propane (ODP). The structures of pristine nanotubes as well as the prepared catalysts were investigated by XRD, Raman, FTIR, HRTEM, SEM, EDS, BET, and XPS techniques. The characterization of the as-synthesized nanotubes showed the synthesis of hydrogen titanate nanotube. The incipient wetness impregnation method was utilized to prepare VTNT-x (x = 5, 10, and 15 wt.% vanadia supported on nanotube) together with VTi5 (5 wt.% vanadia supported on Degussa P25). The anatase phase was developed in VTNT-x catalysts upon calcination along with specific surface area loss. Higher vanadia loading resulted in the lowering of support capacity in maintaining vanadia in dispersed state such that eventually crystalline vanadia appeared. The measured catalyst activity demonstrates that in spite of major support surface area loss in VTNT-5 catalyst, the propylene yield is superior in comparison with VTi5 catalyst. The catalyst activity can be correlated with maximum reduction temperature. Deactivation of VTi5 and VTNT-5 as well as VTNT-15 were studied for 3,000 min time-on-stream. It was found that the activity of VTNT-5 catalyst remain unchanged while a decline in catalytic activity observed in VTi5 and VTNT-15 catalysts. The development of rutile was considered as being a major element in the deactivation of the investigated catalysts which is influenced by the presence of vanadium and reaction atmosphere.

  6. 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

  7. Development and Long-Term Stability of a Novel Microbial Fuel Cell BOD Sensor with MnO2 Catalyst

    Science.gov (United States)

    Kharkwal, Shailesh; Tan, Yi Chao; Lu, Min; Ng, How Yong

    2017-01-01

    A novel microbial fuel cell (MFC)-based biosensor was designed for continuous monitoring of biochemical oxygen demand (BOD) in real wastewater. To lower the material cost, manganese dioxide (MnO2) was tested as an innovative cathode catalyst for oxygen reduction in a single chamber air-cathode MFC, and two different crystalline structures obtained during synthesis of MnO2 (namely β- and γ-MnO2) were compared. The BOD sensor was studied in a comprehensive way, using both sodium acetate solution and real domestic wastewater (DWW). The optimal performance of the sensor was obtained with a β-MnO2 catalyst, with R2 values of 0.99 and 0.98 using sodium acetate solution and DWW, respectively. The BOD values predicted by the β-MnO2 biosensor for DWW were in agreement with the BOD5 values, determined according to standard methods, with slight variations in the range from 3% to 12%. Finally, the long-term stability of the BOD biosensor was evaluated over 1.5 years. To the best of our knowledge, this is the first report of an MFC BOD sensor using an MnO2 catalyst at the cathode; the feasibility of using a low-cost catalyst in an MFC for online measurement of BOD in real wastewater broadens the scope of applications for such devices. PMID:28134838

  8. Development and Long-Term Stability of a Novel Microbial Fuel Cell BOD Sensor with MnO₂ Catalyst.

    Science.gov (United States)

    Kharkwal, Shailesh; Tan, Yi Chao; Lu, Min; Ng, How Yong

    2017-01-28

    A novel microbial fuel cell (MFC)-based biosensor was designed for continuous monitoring of biochemical oxygen demand (BOD) in real wastewater. To lower the material cost, manganese dioxide (MnO₂) was tested as an innovative cathode catalyst for oxygen reduction in a single chamber air-cathode MFC, and two different crystalline structures obtained during synthesis of MnO₂ (namely β- and γ-MnO₂) were compared. The BOD sensor was studied in a comprehensive way, using both sodium acetate solution and real domestic wastewater (DWW). The optimal performance of the sensor was obtained with a β-MnO₂ catalyst, with R² values of 0.99 and 0.98 using sodium acetate solution and DWW, respectively. The BOD values predicted by the β-MnO₂ biosensor for DWW were in agreement with the BOD₅ values, determined according to standard methods, with slight variations in the range from 3% to 12%. Finally, the long-term stability of the BOD biosensor was evaluated over 1.5 years. To the best of our knowledge, this is the first report of an MFC BOD sensor using an MnO₂ catalyst at the cathode; the feasibility of using a low-cost catalyst in an MFC for online measurement of BOD in real wastewater broadens the scope of applications for such devices.

  9. Neutron scattering studies of structure, hydrothermal stability and transport in porous silica catalyst supports

    Science.gov (United States)

    Pollock, Rachel A.

    Mesoporous materials are interesting as catalyst supports, because molecules can move efficiently in and out of the pore network, but they must be stable in water if they are to be used for the production of biofuels. Before investigating hydrothermal stability and transport properties, the pore structure of SBA-15 was characterized using small angle neutron scattering (SANS) and non-local density functional theory (NLDFT) analysis of nitrogen sorption isotherms. A new Contrast Matching SANS method, using a range of probe molecules to directly probe the micropore size, gave a pore size distribution onset of 6 ± 0.2 Å, consistent with cylindrical pores formed from polymer template strands that unravel into the silica matrix. Diffraction intensity analysis of SANS measurements, combined with pore size distributions calculated from NLDFT, showed that the secondary pores are distributed relatively uniformly throughout the silica framework. The hydrothermal stability of SBA-15 was evaluated using a post-calcination hydrothermal treatment in both liquid and vapor phase water. The results were consistent with a degradation mechanism in which silica dissolves from regions of small positive curvature, e.g. near the entrance to the secondary pores, and is re-deposited deeper into the framework. Under water treatment at 115 °C, the mesopore diameter increases and the intra-wall void fraction decreases significantly. The behavior is similar for steam treatment, but occurs more slowly, suggesting that transport is faster when condensation occurs in the pores. Quasielastic neutron scattering (QENS) measurements of methane in SBA-15 probed the rotational and translational motion as a function of temperature and loading. A qualitative analysis of the QENS data suggested that for the initial dose of methane at 100 K, the self diffusion constant is similar in magnitude to literature values for methane in ZSM-5 and Y-zeolite, showing that the secondary pores trap methane and limit

  10. New insights into non-precious metal catalyst layer designs for proton exchange membrane fuel cells: Improving performance and stability

    Science.gov (United States)

    Banham, Dustin; Kishimoto, Takeaki; Sato, Tetsutaro; Kobayashi, Yoshikazu; Narizuka, Kumi; Ozaki, Jun-ichi; Zhou, Yingjie; Marquez, Emil; Bai, Kyoung; Ye, Siyu

    2017-03-01

    The activity of non-precious metal catalysts (NPMCs) has now reached a stage at which they can be considered as possible alternatives to Pt for some proton exchange membrane fuel cell (PEMFC) applications. However, despite significant efforts over the past 50 years on catalyst development, only limited studies have been performed on NPMC-based cathode catalyst layer (CCL) designs. In this work, an extensive ionomer study is performed to investigate the impact of ionomer equivalent weight on performance, which has uncovered two crucial findings. Firstly, it is demonstrated that beyond a critical CCL conductance, no further improvement in performance is observed. The procedure used to determine this critical conductance can be used by other researchers in this field to aid in their design of high performing NPMC-based CCLs. Secondly, it is shown that the stability of NPMC-based CCLs can be improved through the use of low equivalent weight ionomers. This represents a completely unexplored pathway for further stability improvements, and also provides new insights into the possible degradation mechanisms occurring in NPMC-based CCLs. These findings have broad implications on all future NPMC-based CCL designs.

  11. Stability improvements of Ni/{alpha}-Al{sub 2}O{sub 3} catalysts to obtain hydrogen from methane reforming

    Energy Technology Data Exchange (ETDEWEB)

    Pompeo, Francisco; Nichio, Nora N. [CINDECA, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET, 47 N 257, 1900 La Plata (Argentina); Facultad de Ingenieria, Universidad Nacional de La Plata, 1 esq. 47, 1900 La Plata (Argentina); Gazzoli, Delia [Dipartimento di Chimica, Universita di Roma ' ' La Sapienza' ' , P.le A. Moro 5, 00185 Rome (Italy)

    2009-03-15

    Ni catalysts supported on commercial {alpha}-Al{sub 2}O{sub 3} modified by addition of CeO{sub 2} and/or ZrO{sub 2} were prepared in the present work. Since the principal objective was to evaluate the behavior of these systems and the support effect on the stability, methane reforming reactions were studied with steam, carbon dioxide, partial oxidation and mixed reforming. Results show that catalysts supported on Ce-Zr-{alpha}-Al{sub 2}O{sub 3} composites present better reforming activity and stability noticeably higher than in the case of the reference support. With respect to composites, the presence of mixed oxides of Ce{sub x}Zr{sub 1-x}O{sub 2} type facilitates the formation of active phases with higher interaction. This fact reduces the deactivation by sintering conferring to the system a higher contribution of adsorbed oxygen species, favoring the deposited carbon elimination. These improvements resulted in being dependent on the Ce:Zr ratio of the composite, thus obtaining more stable catalysts for Ce:Zr = 4:1 ratios. (author)

  12. Nanostructured, mesoporous Au/TiO2 model catalysts – structure, stability and catalytic properties

    Directory of Open Access Journals (Sweden)

    Matthias Roos

    2011-09-01

    Full Text Available Aiming at model systems with close-to-realistic transport properties, we have prepared and studied planar Au/TiO2 thin-film model catalysts consisting of a thin mesoporous TiO2 film of 200–400 nm thickness with Au nanoparticles, with a mean particle size of ~2 nm diameter, homogeneously distributed therein. The systems were prepared by spin-coating of a mesoporous TiO2 film from solutions of ethanolic titanium tetraisopropoxide and Pluronic P123 on planar Si(100 substrates, calcination at 350 °C and subsequent Au loading by a deposition–precipitation procedure, followed by a final calcination step for catalyst activation. The structural and chemical properties of these model systems were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, N2 adsorption, inductively coupled plasma ionization spectroscopy (ICP–OES and X-ray photoelectron spectroscopy (XPS. The catalytic properties were evaluated through the oxidation of CO as a test reaction, and reactivities were measured directly above the film with a scanning mass spectrometer. We can demonstrate that the thin-film model catalysts closely resemble dispersed Au/TiO2 supported catalysts in their characteristic structural and catalytic properties, and hence can be considered as suitable for catalytic model studies. The linear increase of the catalytic activity with film thickness indicates that transport limitations inside the Au/TiO2 film catalyst are negligible, i.e., below the detection limit.

  13. Stabilization of Palladium Catalysts for the Heck Reaction by Support Functionalization and Solvent Selection

    NARCIS (Netherlands)

    De Lima Oliveira, Rafael; Hooijmans, Jasper B. F.; de Jongh, Petra E.; Klein Gebbink, Bert; de Jong, Krijn P.

    2014-01-01

    Pd nanoparticles were synthesized on nonfunctionalized and functionalized SBA-15 grafted with thiol or amine groups. The resulting materials were used as catalysts to study the influence of these functional groups for a similar Pd particle size of approximately 2 nm on the Heck reaction that uses io

  14. Effect of initial nickel particle size on stability of nickel catalysts for aqueous phase reforming

    NARCIS (Netherlands)

    Haasterecht, Van Tomas; Swart, Marten; Jong, De Krijn P.; Bitter, J.H.

    2016-01-01

    The deactivation behavior by crystallite growth of nickel nanoparticles on various supports (carbon nanofibers, zirconia, SiC, α-Al2O3 and γ-Al2O3) was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ∼10 wt% were prepared by impregnation of carbon nanofibers

  15. Stability improvement of the Nieuwland catalyst in the dimerization of acetylene to monovinylacetylene

    Institute of Scientific and Technical Information of China (English)

    Jianguo Liu; Yizan Zuo; Minghan Han; Zhanwen Wang; Dezheng Wang

    2012-01-01

    In the process of dimerization of acetylene to produce monovinylacetylene (MVA),the loss of active component CuCl in the Nieuwland catalyst due to the formation of a dark red precipitate was investigated.The formula of the precipitate was CuCl·2C2H2·1/5NH3,and it was presumed to be formed by the combination of NH3,C2H2 and [Cu]-acetylene π-complex,which was an intermediate in the dimerization reaction.The addition of hydrochloric acid into the catalyst can reduce the formation of precipitate,whereas excessive H+ is unfavorable to the dimerization reaction of acetylene.To balance between high acetylene conversion and low loss rate of CuCl,the optimum mass percentage of HCl in the added hydrochloric acid was determined.The result showed the optimum mass percentage of HCl decreased from 5.0% to 3.2% when the space velocity of acetylene was from 140 h-1 to 360 h-1.The result in this work also indicated the pH of the Nieuwland catalyst should be kept in the range of 5.80-5.97 during the reaction process,which was good for both catalyst life and acetylene conversion.

  16. Influence of dispersity on the activity, selectivity, and stability of Raney-Nickel catalyst during the hydrogenation of 1,4-butynediol into 1,4-butanediol

    Energy Technology Data Exchange (ETDEWEB)

    Rusina, S.V.; Litvin, E.F.; Kheifets, V.I.; Sharf, V.Z.

    1992-07-10

    Raney-nickel catalysts are widely used in the hydrogenation of 1,4-butynediol into 1,4-butanediol, an important intermediate for the preparation of thermostable resins, plasticizers, pharmaceutical preparations, and other compounds. The authors carried out the investigation of the influence of the dispersity of the Raney-nickel catalysts on their activity, selectivity, and stability in the hydrogenation reaction of 1,4-butynediol into 1,4-butanediol.

  17. Polymer versus phosphine stabilized Rh nanoparticles as components of supported catalysts: implication in the hydrogenation of cyclohexene model molecule.

    Science.gov (United States)

    Ibrahim, M; Garcia, M A S; Vono, L L R; Guerrero, M; Lecante, P; Rossi, L M; Philippot, K

    2016-11-28

    The solution synthesis of rhodium nanoparticles (Rh NPs) was achieved from the organometallic complex [Rh(η(3)-C3H5)3] under mild reaction conditions in the presence of a polymer (PVP), a monophosphine (PPh3) and a diphosphine (dppb) as a stabilizer, leading to very small Rh NPs of 2.2, 1.3 and 1.7 nm mean size, with PVP, PPh3 and dppb, respectively. The surface properties of these nanoparticles were compared using a model catalysis reaction namely, hydrogenation of cyclohexene, first under colloidal conditions and then under supported conditions after their immobilization onto an amino functionalized silica-coated magnetite support. PVP-stabilized Rh NPs were the most active catalyst whatever the catalytic conditions as a result of a strong coordination of the phosphine ligands at the metal surface that blocks some surface atoms even after several recycles of the supported nanocatalysts and limit the reactivity of the metallic surface.

  18. A New Bioinspired Perchlorate Reduction Catalyst with Significantly Enhanced Stability via Rational Tuning of Rhenium Coordination Chemistry and Heterogeneous Reaction Pathway.

    Science.gov (United States)

    Liu, Jinyong; Han, Mengwei; Wu, Dimao; Chen, Xi; Choe, Jong Kwon; Werth, Charles J; Strathmann, Timothy J

    2016-06-01

    Rapid reduction of aqueous ClO4(-) to Cl(-) by H2 has been realized by a heterogeneous Re(hoz)2-Pd/C catalyst integrating Re(O)(hoz)2Cl complex (hoz = oxazolinyl-phenolato bidentate ligand) and Pd nanoparticles on carbon support, but ClOx(-) intermediates formed during reactions with concentrated ClO4(-) promote irreversible Re complex decomposition and catalyst deactivation. The original catalyst design mimics the microbial ClO4(-) reductase, which integrates Mo(MGD)2 complex (MGD = molybdopterin guanine dinucleotide) for oxygen atom transfer (OAT). Perchlorate-reducing microorganisms employ a separate enzyme, chlorite dismutase, to prevent accumulation of the destructive ClO2(-) intermediate. The structural intricacy of MGD ligand and the two-enzyme mechanism for microbial ClO4(-) reduction inspired us to improve catalyst stability by rationally tuning Re ligand structure and adding a ClOx(-) scavenger. Two new Re complexes, Re(O)(htz)2Cl and Re(O)(hoz)(htz)Cl (htz = thiazolinyl-phenolato bidentate ligand), significantly mitigate Re complex decomposition by slightly lowering the OAT activity when immobilized in Pd/C. Further stability enhancement is then obtained by switching the nanoparticles from Pd to Rh, which exhibits high reactivity with ClOx(-) intermediates and thus prevents their deactivating reaction with the Re complex. Compared to Re(hoz)2-Pd/C, the new Re(hoz)(htz)-Rh/C catalyst exhibits similar ClO4(-) reduction activity but superior stability, evidenced by a decrease of Re leaching from 37% to 0.25% and stability of surface Re speciation following the treatment of a concentrated "challenge" solution containing 1000 ppm of ClO4(-). This work demonstrates the pivotal roles of coordination chemistry control and tuning of individual catalyst components for achieving both high activity and stability in environmental catalyst applications.

  19. Effects of tungsten oxide on the activity and thermal stability of a sulfate-derived titania supported platinum catalyst for propane oxidation

    Institute of Scientific and Technical Information of China (English)

    Xiaodong Wu; Zhou Zhou; Duan Weng; Bin Wang

    2012-01-01

    A Pt/WO3/TiO2 catalyst for propane oxidation was prepared by a stepwise wet impregnation method,and was aged at 800℃ for 5 hr.Compared to the sulfate-derived titania supported catalyst,the introduction of tungsten oxide as stable Brφnsted acid sites led to the formation of more metallic platinum active sites at the Pt/WO3 interface.The dissociation of surface intermediates for propane oxidation was promoted on the WO3-modified catalyst.This,as well as the inhibition effects of tungsten oxide on the sintering of anatase and the phase transformation to rutile,resulting in a high activity and thermal stability for the Pt/WO3/TiO2 catalyst.

  20. Stabilized rhodium(0) nanoparticles: a reusable hydrogenation catalyst for arene derivatives in a biphasic water-liquid system.

    Science.gov (United States)

    Schulz, J; Roucoux, A; Patin, H

    2000-02-18

    A colloidal system based on an aqueous suspension of rhodium(o) nanoparticles proved to be an efficient catalyst for the hydrogenation of arene derivatives under biphasic conditions. The rhodium nanoparticles (2-2.5 nm) were synthesized by the reduction of RhCl3 x 3H2O with sodium borohydride and were stabilized by highly water-soluble N-alkyl-N-(2-hydroxyethyl)ammonium salts (HEA-Cn). These surfactant molecules were characterized by measurements of the surface tension and the aqueous dispersions with rhodium were observed by transmission electron cryomicroscopy. The catalytic system is efficient under ultramild conditions, namely room temperature and 1 atm H2 pressure. The aqueous phase which contains the protected rhodium(0) colloids can be reused without significant loss of activity. The microheterogeneous behavior of this catalytic system was confirmed on a mercury poisoning experiment.

  1. L-S mass transfer in G-L-S countercurrent magnetically stabilized bed with amorphous alloy SRNA-4 catalyst

    Institute of Scientific and Technical Information of China (English)

    Wei; Li; Baoning; Zong; Xiaofang; Li; Xiangkun; Meng; Jinli; Zhang

    2007-01-01

    Liquid-solid (L-S) mass transfer coefficients (Ks) were characterized in a gas-liquid-solid (G-L-S) three-phase countercurrent magnetically stabilized bed (MSB) using amorphous alloy SRNA-4 as the solid phase. Effects of superficial liquid velocity, superficial gas velocity, magnetic field strength, liquid viscosity and surface tension were investigated. Experimental results indicated that the external magnetic field increased Ks in three-phase MSB, as compared to those in conventional G-L-S fluidized beds; that Ks increased with magnetic field strength, superficial gas and liquid velocities and decreased with liquid viscosity and surface tension; and that Ks showed uniform axial and radial distributions except for small increases close to the wall. Dimensionless correlations were established to estimate Ks of the G-L-S countercurrent MSB using SRNA-4catalyst, with an average error of 3.6%.

  2. Influence of Reduction Promoters on Stability of Cobalt/g-Alumina Fischer-Tropsch Synthesis Catalysts

    Directory of Open Access Journals (Sweden)

    Gary Jacobs

    2014-03-01

    Full Text Available This focused review article underscores how metal reduction promoters can impact deactivation phenomena associated with cobalt Fischer-Tropsch synthesis catalysts. Promoters can exacerbate sintering if the additional cobalt metal clusters, formed as a result of the promoting effect, are in close proximity at the nanoscale to other cobalt particles on the surface. Recent efforts have shown that when promoters are used to facilitate the reduction of small crystallites with the aim of increasing surface Co0 site densities (e.g., in research catalysts, ultra-small crystallites (e.g., <2–4.4 nm formed are more susceptible to oxidation at high conversion relative to larger ones. The choice of promoter is important, as certain metals (e.g., Au that promote cobalt oxide reduction can separate from cobalt during oxidation-reduction (regeneration cycles. Finally, some elements have been identified to promote reduction but either poison the surface of Co0 (e.g., Cu, or produce excessive light gas selectivity (e.g., Cu and Pd, or Au at high loading. Computational studies indicate that certain promoters may inhibit polymeric C formation by hindering C-C coupling.

  3. 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.

  4. Rh nanoparticles stabilized by PEG-substituted triphenyl-phosphine: A highly active and recyclable catalyst for aqueous biphasic hydrogenation of benzene

    Institute of Scientific and Technical Information of China (English)

    Ya Dong Lu; Yan Hua Wang; Zi Lin Jin

    2010-01-01

    Rh nanoparticles stabilized by PEG-substituted triphenyl-phosphine(PETPP,P[C6H4-p-(OCH2CH2)nOH]3)combining double stabilization effects demonstrated high activity and good recyclability in aqueous biphasic hydrogenation of benzene.The value of turnover frequency(TOF)was 3333 h-1.Furthermore,the rhodium nanoparticle catalyst could be easily recycled for five times without loss in activity.

  5. PHENANTHROLINE-STABILIZED PALLADIUM NANOPARTICLES IN POLYETHYLENE GLYCOL—AN ACTIVE AND RECYCLABLE CATALYST SYSTEM FOR THE SELECTIVE HYDROGENATION OF OLEFINS USING MOLECULAR HYDROGEN

    Science.gov (United States)

    1,10-Phenanthroline-stabilized palladium nanoparticles dispersed in a polyethylene glycol (PEG) matrix is synthesized which is found to be a stable and active catalyst for the selective hydrogenation of olefins using molecular hydrogen under mild reaction conditions. A variety of...

  6. Ethanol dehydrogenation on copper catalysts with ytterbium stabilized tetragonal ZrO2 support

    Science.gov (United States)

    Chuklina, S. G.; Pylinina, A. I.; Podzorova, L. I.; Mikhailina, N. A.; Mikhalenko, I. I.

    2016-12-01

    The physicochemical and catalytic properties of Cu-containing crystalline zirconia, obtained via sol-gel synthesis in the presence of Yb3+ ions and polyvinylpyrrolidone, are studied. DTG/DSC, TEM, XRD and BET methods are used to analyze the crystallization, texture, phase uniformity, surface and porosity of ZrO2 nanopowders. It is shown that increasing the copper content (1, 3, and 5 wt % from ZrO2) raises the dehydrogenation activity in the temperature range of 100-400°C and lowers the activation energy of acetaldehyde formation. It is found that the activity of all Cu/ t-ZrO2 catalysts grows under the effects of the reaction medium, due to the migration and redispersion of copper.

  7. Unsupported PVA- and PVP-stabilized Pd nanoparticles as catalyst for nitrite hydrogenation in aqueous phase

    NARCIS (Netherlands)

    Zhao, Y.; Baeza, J.A.; Koteswara Rao, N.; Calvo, L.; Gilarranz, M.A.; Li, Y.D.; Lefferts, L.

    2014-01-01

    Pd colloids stabilized with polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) have been prepared, characterized with TEM, zeta potential measurements, CO chemisorption in aqueous phase, and ATR-IR spectroscopy using CO as a probe molecule, and finally tested for performance in nitrite hydrogena

  8. Mosques as Communities of Memories vis-a-vis Muslim Identity and Integration in the European Union

    Directory of Open Access Journals (Sweden)

    Nazila Isgandarova

    2016-01-01

    Full Text Available Mosques represent an important element of Muslim identity. This identity may be social, political, personal, etc., and depends on language they speak, attitudes they have, place where they live in, and activities they enjoy to do. In this regard, mosques manifest gender, ethnic, social class, religion, and culture dimensions of Muslim identity. As a place of community of memory mosques play the memory-preserving function for Muslim generations and retain Muslim identity. European mosques combine the traditions of the worshippers with those of their new environment. Thus, Muslims' attachment to Europe grows and they start to identify themselves with their places in Europe. During this transaction between the two, not only Muslims change under the current European tendencies, but Europe also changes by Muslims' identities. This becomes more evident in increasing number of mosques in EU and the debate about its place in EU life.

  9. [The elderly and the transition to a market economy in Romania. Discriminating attitudes vis-a-vis the elderly].

    Science.gov (United States)

    Radulescu, S M

    1993-01-01

    Population aging has started late in Romania but has increased rapidly in the last few decades. The share of the population aged 60 and over reached 17% in 1992 and the decline in fertility after 1989 will considerably increase this share in the future. The author provides a detailed analysis of the present economic and social situation of the elderly in Romania. Factors such as the economic crisis, and particularly the deterioration of the standard of living, the very low income (pension) level, the high rate of inflation, and the lack of appropriate medical care have pushed most of the aged population into poverty. According to recent surveys, 1.5 million people out of the 3.8 million aged 60 and over live below the poverty line.

  10. How Can France’s New NATO Policy Be Explained vis-a-vis European Security Cooperation?

    Science.gov (United States)

    2010-05-21

    PERFORMING ORGANIZATION REPORT NUMBER Dr. Charles Pentland, Director, Queen’c Centre for International Relations Queen’s University Robert Sutherland...States Army Dr. Charles Pentland Director, Queen‟s Centre for International Relations Disclaimer The views expressed in the...President George Pompidou initiated this divergence from Gaullism by lifting the French veto, allowing the U.K. into the European Community in 1973

  11. Spirituality vis-a-vis Islam as prerequisite to Arab American well being: the implications of Eurocentrism for mainstream psychology.

    Science.gov (United States)

    Hall, Ronald E; Breland-Noble, Alfiee

    2011-01-01

    Due to the historical preponderance of racial and/or intellectual homogeneity in the field of psychology, Eurocentrism set the "gold standard" for its method of intervention. As such, it might be argued that psychology remains a bastion of Eurocentric thought despite the globalization of knowledge and the influx of racially and ethnically diverse scientists into the research endeavor. At the same time and the significant increase in the immigrant Arab population, Arab Americans remain a less familiar component of society. Among the various Arab populations, spirituality through Islam is fundamental. Thus, psychologists would be remiss to exclude a critical aspect of Arab American life from intervention when it is essential to well-being.

  12. Factors Which Impact the Distribution of Leadership for an ICT Reform: Expertise vis-a-vis Formal Role?

    Science.gov (United States)

    Ho, Jeanne Marie; Ng, David

    2012-01-01

    This study examined the process of Information Communication Technology reform in a Singapore school. The focus was on distributed leadership actions, and the factors which enabled and constrained the distribution of leadership. This study adopted a naturalistic inquiry approach, involving the case study of a school. The study found that…

  13. An Evaluation of Grades 9 and 10 Mathematics Textbooks vis-a-vis Fostering Problem Solving Skills

    Science.gov (United States)

    Buishaw, Alemayehu; Ayalew, Assaye

    2013-01-01

    This study sought to evaluate the adequacy of integration of problematic situations and general problem-solving strategies (heuristics) in grades 9 and 10 mathematics textbooks. Grade 9 and grade 10 mathematics textbooks were used for analysis. Document analysis and interview were used as data gathering instruments. Document analysis was carried…

  14. Evaluation of FFTF fuel pin design procedure vis-a-vis steady state irradiation performance in EBR II

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, R.J.

    1976-11-01

    The FFTF fuel pin design analysis is shown to be conservative through comparison with pin irradiation experience in EBR-II. This comparison shows that the actual lifetimes of EBR-II fuel pins are either greater than 80,000 MWd/MTM or greater than the calculated allowable lifetimes based on thermal creep strain.

  15. A Geo-Environmental Analysis of the Groundwater Resource vis-a-vis Surface Water Scenario in Guwahati City

    Directory of Open Access Journals (Sweden)

    Neelkamal Das

    2013-08-01

    Full Text Available Guwahati city is located on a unique geo-environmental setting with an interface of hills and valleys along with a prominent river front. The existence of various surface water sources, geo-hydrological set up and rainfall intensity play a significant role in the ground water regime of the city. However, rapid urbanisation of the city during the last few decades has altered the landscape of the city and disturbed the water retention capacity as well as the flow dynamics of various surface water sources, thereby affecting the infiltration rate to a great extent. Unprecedented rise in the population of the city has exerted more pressure on the various sources of water, particularly the groundwater resource. It has thus become imperative to utilise the various sources of water in a more systematic and scientific manner, giving due emphasis to the water requirement and the prevailing hydrological conditions of the area. Moreover, it is also observed that the city experiences an average annual rainfall of 162 cm with about 110 rainy days per year. The city thus has enough potential for harvesting the rainwater it receives, instead of allowing it to flow untapped. Rainwater can be tapped and utilised to revive the various surface water sources of the city, thereby facilitating natural groundwater recharge, as surface water bodies like wetlands, lakes and ponds do act as potential groundwater recharge zones.

  16. Clinical and economic outcomes of Acinetobacter vis a vis non-Acinetobacter infections in an Indian teaching hospital

    Directory of Open Access Journals (Sweden)

    Priyendu Asim

    2016-01-01

    Full Text Available Context: Acinetobacter infections are a major nosocomial infection causing epidemics of infection in the Intensive Care Units (ICU. Aims: This study estimates the clinical and economic outcomes of Acinetobacter infections and compares them with those of non-Acinetobacter bacterial infections. Settings and Design: Prospective cross-sectional observational study carried out for 6 months in the medicine ICU of a tertiary care hospital. Materials and Methods: Patients were divided in two groups, one group with Acinetobacter infections and the other with non-Acinetobacter infections. The data was collected for infection, length of stay (LOS, mortality and cost along with patient demographics from the hospital records for analysis. Statistical Analysis Used: The data was analyzed using Statistical Package for the Social Sciences Version 15.0. The LOS and cost of treatment (COT for the two groups were compared using the nonparametric Mann–Whitney U-test. Results: A total of 220 patients were studied out of which 91 had Acinetobacter infections. The median LOS was 20 days in Group-A and 12 days in Group-B (P < 0.0001. The median COT was INR 125,862 in Group-A and INR 68,228 in the Group-B (P < 0.0001. Mortality in Group-A and Group-B was 32.97 and 32.56 (P = 0.949 respectively. Conclusion: The burden of Acinetobacter infections in ICUs is increasing with the increase in LOS and COT for the patients. The infection control team has to play a major role in reducing the rate of nosocomial infections.

  17. Astrophysical limitations to the identification of dark matter: indirect neutrino signals vis-a-vis direct detection recoil rates

    CERN Document Server

    Serpico, Pasquale D

    2010-01-01

    A convincing identification of dark matter (DM) particles can probably be achieved only through a combined analysis of different detections strategies, which provides an effective way of removing degeneracies in the parameter space of DM models. In practice, however, this program is made complicated by the fact that different strategies depend on different physical quantities, or on the same quantities but in a different way, making the treatment of systematic errors rather tricky. We discuss here the uncertainties on the recoil rate in direct detection experiments and on the muon rate induced by neutrinos from dark matter annihilations in the Sun, and we show that, contrarily to the local DM density or overall cross section scale, irreducible astrophysical uncertainties affect the two rates in a different fashion, therefore limiting our ability to reconstruct the parameters of the dark matter particle. By varying within their respective errors astrophysical parameters such as the escape velocity and the velo...

  18. Pd Close Coupled Catalyst

    Institute of Scientific and Technical Information of China (English)

    Zhong Hua SHI; Mao Chu GONG; Yao Qiang CHEN

    2006-01-01

    A catalyst comprised novel high surface area alumina support was prepared to control emission of automobiles. The results showed that prepared catalyst could satisfy the requirements of a high performance close coupled catalyst for its good catalytic activity at low temperature and good stability at high temperature.

  19. PBI-based polymer electrolyte membranes fuel cells. Temperature effects on cell performance and catalyst stability

    Energy Technology Data Exchange (ETDEWEB)

    Lobato, Justo; Canizares, Pablo; Rodrigo, Manuel A.; Linares, Jose J. [Chemical Engineering Department, University of Castilla-La Mancha, Campus Universitario s/n, 13004 Ciudad Real (Spain)

    2007-03-10

    In this work, it has been shown that the temperature (ranging from 100 to 175 C) greatly influences the performance of H{sub 3}PO{sub 4}-doped polybenzimidazole-based high-temperature polymer electrolyte membrane fuel cells by several and complex processes. The temperature, by itself, increases H{sub 3}PO{sub 4}-doped PBI conductivity and enhances the electrodic reactions as it rises. Nevertheless, high temperatures reduce the level of hydration of the membrane, above 130-140 C accelerate the self-dehydration of H{sub 3}PO{sub 4}, and they may boost the process of catalyst particle agglomeration that takes place in strongly acidic H{sub 3}PO{sub 4} medium (as checked by multi-cycling sweep voltammetry), reducing the overall electrochemical active surface. The first process seems to have a rapid response to changes in the temperature and controls the cell performance immediately after them. The second process seems to develop slower, and influences the cell performance in the 'long-term'. The predominant processes, at each moment and temperature, determine the effect of the temperature on the cell performance, as potentiostatic curves display. 'Long-term' polarization curves grow up to 150 C and decrease at 175 C. 'Short-term' ones continuously increase as the temperature does after 'conditioning' the cell at 125 C. On the contrary, when compared the polarization curves at 175 C a continuous decrease is observed with the 'conditioning' temperature. A discussion of the observed trends is proposed in this work. (author)

  20. The Effect of Platinum on Stability of the B2O3/TiO2-ZrO2 Catalyst for Beckmann Rearrangement of Cyclohexanone Oxime

    Institute of Scientific and Technical Information of China (English)

    Dong Sen MAO; Guan Zhong LU

    2006-01-01

    The addition of platinum over the B2O3/TiO2-ZrO2 remarkably enhanced its catalytic stability in the vapor phase Beckmann rearrangement of cyclohexanone oxime under the carrier gas of H2. The content of coke deposited on catalyst surface was decreased from 1.92% over the B2O3/TiO2-ZrO2 to 1.14% over the platinum promoted B2O3/TiO2-ZrO2 after reaction of six hours. This result indicates that the platinum added on the B2O3/TiO2-ZrO2 catalyst plays an important role in reducing the coke formation on the catalyst surface.

  1. Activity and stability of Mo2C/ZrO2 as catalyst for hydrodeoxygenation of mixtures of phenol and 1-octanol

    DEFF Research Database (Denmark)

    Mortensen, Peter Mølgaard; de Carvalho, Hudson W.P.; Grunwaldt, Jan-Dierk

    2015-01-01

    Mo2C/ZrO2 was investigated as catalyst for hydrodeoxygenation (HDO) of phenol in 1-octanol as a simplified bio-oil model system in a fixed-bed setup at 100bar. Mo2C/ZrO2 selectively converted phenol to benzene above 320°C. During long-term testing, limited stability of the catalyst was observed......, with the conversion of 1-octanol and phenol decreasing from 70% to 37% and from 37% to 19%, respectively, over 76h of operation. Repeating the experiment but also co-feeding 30% water, the catalyst deactivated completely within 12h of operation. Thermodynamic calculations and in situ XRD analysis showed that Mo2C...

  2. Bovine lactoperoxidase - a versatile one- and two-electron catalyst of high structural and thermal stability.

    Science.gov (United States)

    Banerjee, Srijib; Furtmüller, Paul G; Obinger, Christian

    2011-02-01

    Lactoperoxidase (LPO), a member of the peroxidase-cyclooxygenase superfamily, is found in multiple human exocrine secretions and acts as a first line of defense against invading microorganisms by production of antimicrobial oxidants. Because of its ability to efficiently catalyze one- and two-electron oxidation reactions of inorganic and organic compounds, the heme peroxidase is widely used in food biotechnology, cosmetic industry, and diagnostic kits. In order to probe its structural integrity, conformational, and thermal stability, we have undertaken a comprehensive investigation by using complementary biophysical techniques including UV-Vis, circular dichroism and fluorescence spectroscopy as well as differential scanning calorimetry (DSC). The oxidoreductase exhibits a high chemical and thermal stability under oxidizing conditions but is significantly destabilized by addition of DTT. Due to its unique ester bonds between the prosthetic group and the protein as well as six intra-chain disulfides, unfolding of the central compact (-helical core occurs concomitantly with denaturation of the heme cavity. The corresponding enthalpic and entropic contributions to the free enthalpy of unfolding are presented. Together with spectroscopic data they will be discussed with respect to the known structure of bovine LPO and homologous myeloperoxidase as well as to its practical application.

  3. Catalysts, methods of making catalysts, and methods of use

    KAUST Repository

    Renard, Laetitia

    2014-03-06

    Embodiments of the present disclosure provide for catalysts, methods of making catalysts, methods of using catalysts, and the like. In an embodiment, the method of making the catalysts can be performed in a single step with a metal nanoparticle precursor and a metal oxide precursor, where a separate stabilizing agent is not needed.

  4. Influence of electrolyte composition on the photovoltaic performance and stability of dye-sensitized solar cells with multiwalled carbon nanotube catalysts.

    Science.gov (United States)

    Seo, Seon Hee; Kim, Su Yeon; Koo, Bo-Kun; Cha, Seung-Il; Lee, Dong Yoon

    2010-06-15

    Efficient dye-sensitized solar cells (DSCs) were realized by using multiwalled carbon nanotubes (CNTs) as the counter-electrode catalyst. The catalytic layers were produced from an aqueous paste of mass-produced raw CNTs with carboxymethylcellulose polymer by low-temperature (70 degrees C) drying. We found that the highly disordered CNTs played the important role of increasing the fill factor of DSCs with electrolytes including large molecules and that the presence of Li(+) as the counter charges for I(3)(-)/I(-) redox couples reduced the chemical stability when using the CNT catalyst. Our experiments showed that by replacing the conventional Pt catalyst and Li(+)-based electrolyte with the proposed CNT catalyst and an electrolyte containing 1-butyl-3-methylimidazolium cations instead of Li(+), the energy conversion efficiency increased from 6.51% to 7.13%. This result suggests that highly defective CNT catalysts prepared by low-temperature drying are viable cost-effective alternatives for DSCs, as long as the electrolytes composition is optimized.

  5. A Platinum Monolayer Core-Shell Catalyst with a Ternary Alloy Nanoparticle Core and Enhanced Stability for the Oxygen Reduction Reaction

    Directory of Open Access Journals (Sweden)

    Haoxiong Nan

    2015-01-01

    Full Text Available We synthesize a platinum monolayer core-shell catalyst with a ternary alloy nanoparticle core of Pd, Ir, and Ni. A Pt monolayer is deposited on carbon-supported PdIrNi nanoparticles using an underpotential deposition method, in which a copper monolayer is applied to the ternary nanoparticles; this is followed by the galvanic displacement of Cu with Pt to generate a Pt monolayer on the surface of the core. The core-shell Pd1Ir1Ni2@Pt/C catalyst exhibits excellent oxygen reduction reaction activity, yielding a mass activity significantly higher than that of Pt monolayer catalysts containing PdIr or PdNi nanoparticles as cores and four times higher than that of a commercial Pt/C electrocatalyst. In 0.1 M HClO4, the half-wave potential reaches 0.91 V, about 30 mV higher than that of Pt/C. We verify the structure and composition of the carbon-supported PdIrNi nanoparticles using X-ray powder diffraction, X-ray photoelectron spectroscopy, thermogravimetry, transmission electron microscopy, and energy dispersive X-ray spectrometry, and we perform a stability test that confirms the excellent stability of our core-shell catalyst. We suggest that the porous structure resulting from the dissolution of Ni in the alloy nanoparticles may be the main reason for the catalyst’s enhanced performance.

  6. Control of thickness and chemical properties of atomic layer deposition overcoats for stabilizing Cu/γ-Al2 O3 catalysts.

    Science.gov (United States)

    O'Neill, Brandon J; Sener, Canan; Jackson, David H K; Kuech, Thomas F; Dumesic, James A

    2014-12-01

    Whereas sintering and leaching of copper nanoparticles during liquid-phase catalytic processing can be prevented by using atomic layer deposition (ALD) to overcoat the nanoparticles with AlOx , this acidic overcoat leads to reversible deactivation of the catalyst by resinification and blocking of the pores within the overcoat during hydrogenation of furfural. We demonstrate that decreasing the overcoat thickness from 45 to 5 ALD cycles is an effective method to increase the rate per gram of catalyst and to decrease the rate of deactivation for catalysts pretreated at 673 K, and a fully regenerable copper catalyst can be produced with only five ALD cycles of AlOx . Moreover, although an overcoat of MgOx does not lead to stabilization of copper nanoparticles against sintering and leaching during liquid-phase hydrogenation reactions, the AlOx overcoat can be chemically modified to decrease acidity and deactivation through the addition of MgOx , while maintaining stability of the copper nanoparticles.

  7. [Catalytic stability in wet air oxidation of carboxylic acids over ZnFe0.25Al1.75 O4 catalyst].

    Science.gov (United States)

    Xu, Ai-hua; Yang, Min; Du, Hong-zhang; Peng, Fu-yong; Sun, Cheng-lin

    2007-07-01

    Oxalic, formic and acetic acid are main intermediate products in catalytic wet air oxidation process (CWAO). The catalytic activity and stability in CWAO of the three short-chain organic acids over ZnFe0.25Al1.75O4 catalyst were studied. Oxalic acid is the only oxidizable intermediate and the largest amount of Fe leaching is 9.5 mg L(-1) at 160 degrees C during CWAO process. Formic and acetic acid have little influence on Fe leaching. Due to the strong reducible ability of oxalic acid, the amount of Fe leaching is larger in nitrogen atmosphere than that in oxygen atmosphere. Salicylic acid can be also degraded by ZnFe0.25Al1.75O4 catalyst with a high catalytic activity and stability.

  8. Hydrothermal Stability of Ru/SiO2–C: A Promising Catalyst for Biomass Processing through Liquid-Phase Reactions

    Directory of Open Access Journals (Sweden)

    Martín N. Gatti

    2016-12-01

    Full Text Available In this work, structural and morphological properties of SiO2–C composite material to be used as support for catalysts in the conversion of biomass-derived oxygenated hydrocarbons, such as glycerol, were investigated in liquid water under various temperatures conditions. The results show that this material does not lose surface area, and the hot liquid water does not generate changes in the structure. Neither change in relative concentrations of oxygen functional groups nor in Si/C ratio due to hydrothermal treatment was revealed by X-ray photoelectron spectroscopy (XPS analysis. Raman analysis showed that the material is made of a disordered graphitic structure in an amorphous silica matrix, which remains stable after hydrothermal treatment. Results of the hydrogenolysis of glycerol using a Ru/SiO2–C catalyst indicate that the support gives more stability to the active phase than a Ru/SiO2 consisting of commercial silica.

  9. Enhancing Stability of PEM Fuel Cell Catalysts via Support Changing%通过载体提高燃料电池催化剂的稳定性

    Institute of Scientific and Technical Information of China (English)

    谢小红; 魏子栋

    2015-01-01

    Pt/C是目前质子交换膜燃料电池使用最广泛的一种催化剂,制约其实际应用的关键技术之一是稳定性,增强燃料电池催化剂稳定性研究一直是该领域的热点.本文结合作者课题组的研究工作,综述了通过改进载体材料来提高Pt基催化剂稳定性的一些方法,指出采用更稳定的载体材料以及发展与金属催化剂纳米颗粒有强相互作用的载体材料,是增强催化剂稳定性的努力方向.%The Pt/C catalyst with highly dispersed Pt nanoparticles supported on carbon has been widely used as the state-of the-art catalyst in proton exchange membrane fuel cells (PEMFCs),while the durability of Pt/C is one of the major barriers for largescale applications of PEMFCs.Thus,enhancing the stability of Pt/C has been a hot issue in this field.In this review,we summarize the recent progress in enhancing the catalyst stability in the view of support material.The future prospects of the PEMFCs catalyst should focus on adopting more stable supports or strengthening the interactions between Pt and supports.

  10. PEG-stabilized palladium nanoparticles: An efficient and recyclable catalyst for the selective hydrogenation of 1,5-cyclooctadiene in thermoregulated PEG biphase system

    Institute of Scientific and Technical Information of China (English)

    Tian Song Huang; Yan Hua Wang; Jing Yang Jiang; Zi Lin Jin

    2008-01-01

    Polyethylene glycol (PEG)-stabilized palladium nanoparticles were prepared and applied to the selective hydrogenation of 1,5-cyclooctadiene (1,5-COD) in thermoregulated PEG biphase system, which allows a reaction in a single-phase at a highertemperature followed by a phase split at a lower temperature. Under the optimized reaction conditions, the conversion of 1,5-CODand the selectivity of cyclooctene (COE) were 100 and 98%, respectively. The catalyst could be easily separated from the product byphase separation and reused for 6 times without evident loss in activity and selectivity.

  11. LaNiO3-based catalyst in gas diffusion electrodes: activity and stability for oxigen reactions

    OpenAIRE

    R.A. Silva; Soares, C. O.; CARVALHO, M. D. de; Jorge, M. E. Melo; Gomes, A.; C. M. Rangel; Pereira, M. I. da Silva

    2013-01-01

    Perovskite-type oxides are potential catalysts for next generation of regenerative fuel cells. In particular, LaNiO3 has been recognised as one of the most promising oxygen electrodes. In this work LaNiO3 perovskite-type oxides, prepared by a self-combustion method [1, 2], have been used for the preparation of porous gas-diffusion electrodes (GDE). Electrodes were prepared on Toray carbon paper (CP) substrates, consisting of a diffusion layer, a catalyst layer and a Nafion® layer. The gas...

  12. Impeded solid state reactions and transformations in ceramic catalysts supports and catalysts

    Directory of Open Access Journals (Sweden)

    Ernő E. Kiss

    2012-12-01

    Full Text Available Impeded chemical reactions and impeded polymorphous transformation in materials are discussed, as desired effects, for stabilization of ceramic catalyst supports and ceramic based catalysts. This paper gives a short overview about the possibilities of slowing down the aging processes in ceramic catalyst supports and catalysts. Special attention is given to alumina and titania based catalysts.

  13. Catalyst-coated cement beads for the degradation and mineralization of fungicide carbendazim using laboratory and pilot-scale reactor: catalyst stability analysis.

    Science.gov (United States)

    Singh, Amanjit; Verma, Anoop; Bansal, Palak; Aggarwal, Kashish; Kaur, Taranjeet; Toor, Amrit Pal; Sangal, Vikas Kumar

    2017-03-18

    The fixed-bed photocatalytic degradation of fungicide carbendazim using catalyst-coated spherical cement beads has been investigated. Thirty beads with optimum size 13 mm along with 0.3 gL(-1) H2O2 with an initial concentration of carbendazim of 10 mgL(-1) were the optimized conditions for better degradation. The reduction in COD and total organic carbon along with the generation of nitrite and nitrate ions under the optimized conditions confirms the complete mineralization of compound. The suggested degradation pathway for carbendazim has also been proposed as intermediates formed during photodegradation were analyzed through gas chromatography-mass spectrometry. The coated cement beads were found to be durable even after 30 cycles as confirmed by scanning electron microscopy and energy dispersive spectroscopy analysis. Scale-up trails have also been carried out in a solar-baffled fixed-bed reactor for the degradation of pollutant to seek the commercial viability of the technique.

  14. Design of colloidal Pt catalysts encapsulated by silica nano membranes for enhanced stability in H2S streams

    NARCIS (Netherlands)

    Calderone, V.R.; Schütz-Widoniak, J.; Bezemer, G.L.; Bakker, G.; Steurs, C.; Philipse, A.P.

    2010-01-01

    Poisoning of platinum catalysts by sulphur compounds is a significant problem that prevents their application in untreated gas streams. We introduce a novel concept to circumvent the poisoning problem by encapsulating individual platinum nano-particles with silica layers that act as selective membra

  15. Oxygen reduction at carbon supported ruthenium-selenium catalysts: Selenium as promoter and stabilizer of catalytic activity

    Science.gov (United States)

    Schulenburg, Hendrik; Hilgendorff, Marcus; Dorbandt, Iris; Radnik, Jörg; Bogdanoff, Peter; Fiechter, Sebastian; Bron, Michael; Tributsch, Helmut

    Carbon supported ruthenium-based catalysts (Ru/C) for the oxygen reduction in acid electrolytes were investigated. A treatment of Ru/C catalysts with selenious acid had a beneficial effect on catalytic activity but no influence on intrinsic kinetic properties, like Tafel slope and hydrogen peroxide generation. Reasons for the increased activity of RuSe x/C catalysts are discussed. Potential step measurements suggest that at potentials around 0.8 V (NHE) a selenium or selenium-oxygen species protects the catalyst from formation of inactive RuO 2-films. This protective effect leads to an enhanced activity of RuSe x/C compared to Ru/C. No evidence was found for a catalytically active stoichiometric selenium compound. The active phase may be described as a ruthenium suboxide RuO x (x RuSe y phase or RuSe yO v (y < 2, v < 2) layer at the particle surface.

  16. Magnetically Recoverable Magnetite/Gold Catalyst Stabilized by Poly(N-vinyl-2-pyrrolidone for Aerobic Oxidation of Alcohols

    Directory of Open Access Journals (Sweden)

    Hidehiro Sakurai

    2010-12-01

    Full Text Available Fe3O4:PVP/Au nanocomposite synthesized via a two-step procedure was tested as a quasi-homogenous alcohol oxidation catalyst. It was found that the nanocomposite was able to carry out aerobic oxidation of alcohols in water at room temperature. Studies show rapid magnetic recoverability and reusability characteristics.

  17. Spatial Distribution of Zeolite ZSM-5 within Catalyst Bodies Affects Selectivity and Stability of Methanol-to-Hydrocarbons Conversion

    NARCIS (Netherlands)

    Castaño, P.; Ruiz-Martinez, J.; Epelde, E.; Gayubo, A.G.; Weckhuysen, B.M.

    2013-01-01

    Solid acids, such as zeolites, are used as catalyst materials in a wide variety of important crude oil refinery, bulk chemical synthesis, and green processes. Examples include fluid catalytic cracking (FCC),[1] methanol-to-hydrocarbons (MTH) conversion,[ 2] plastic waste valorization,[3] and biomass

  18. Platinum and Other Transition Metal Nanoclusters (Pd, Rh) Stabilized by PAMAM Dendrimer as Excellent Heterogeneous Catalysts: Application to the Methylcyclopentane (MCP) Hydrogenative Isomerization.

    Science.gov (United States)

    Deraedt, Christophe; Melaet, Gérôme; Ralston, Walter T; Ye, Rong; Somorjai, Gabor A

    2017-03-08

    Pt, Rh, and Pd nanoclusters stabilized by PAMAM dendrimer are used for the first time in a gas flow reactor at high temperature (150-250 °C). Pt nanoclusters show a very high activity for the hydrogenation of the methylcyclopentane (MCP) at 200-225 °C with turnover freqency (TOF) up to 334 h(-1) and selectivity up to 99.6% for the ring opening isomerization at very high conversion (94%). Rh nanoclusters show different selectivity for the reaction, that is, ring opening isomerization at 175 °C and cracking at higher temperature whereas Pd nanoclusters perform ring enlargement plus dehydrogenation, while maintaining a high activity. The difference in these results as compared to unsupported/uncapped nanoparticles, demonstrates the crucial role of dendrimer. The tunability of the selectivity of the reaction as well as the very high activity of the metal nanoclusters stabilized by dendrimer under heterogeneous conditions open a new application for dendrimer catalysts.

  19. Pt atoms stabilized on hexagonal boron nitride as efficient single-atom catalysts for CO oxidation: A first-principles investigation

    KAUST Repository

    Liu, Xin

    2015-01-01

    Taking CO oxidation as a probe, we investigated the electronic structure and reactivity of Pt atoms stabilized by vacancy defects on hexagonal boron nitride (h-BN) by first-principles-based calculations. As a joint effect of the high reactivity of both a single Pt atom and a boron vacancy defect (PtBV), the Pt-N interaction is -4.40 eV and is already strong enough to prohibit the diffusion and aggregation of the stabilized Pt atom. Facilitated by the upshifted Pt-d states originated from the Pt-N interaction, the barriers for CO oxidation through the Langmuir-Hinshelwood mechanism for formation and dissociation of peroxide-like intermediate and the regeneration are as low as 0.38, 0.10 and 0.04 eV, respectively, suggesting the superiority of PtBV as a catalyst for low temperature CO oxidation.

  20. Thermal stability and hcp-fcc allotropic transformation in supported Co metal catalysts probed near operando by ferromagnetic NMR.

    Science.gov (United States)

    Andreev, Andrey S; d'Espinose de Lacaillerie, Jean-Baptiste; Lapina, Olga B; Gerashenko, Alexander

    2015-06-14

    Despite the fact that cobalt based catalysts are used at the industrial scale for Fischer-Tropsch synthesis, it is not yet clear which cobalt metallic phase is actually at work under operando conditions and what is its state of dispersion. As it turns out, the different phases of metallic cobalt, fcc and hcp, give rise to distinct ferromagnetic nuclear magnetic resonance. Furthermore, within one Co metal particle, the occurrence of several ferromagnetic domains of limited sizes can be evidenced by the specific resonance of Co in multi-domain particles. Consequently, by ferromagnetic NMR, one can follow quantitatively the sintering and phase transitions of dispersed Co metal particles in supported catalysts under near operando conditions. The minimal size probed by ferromagnetic Co NMR is not precisely known but is considered to be in the order of 10 nm for supported Co particles at room temperature and increases to about 35 nm at 850 K. Here, in Co metal Fischer-Tropsch synthesis catalysts supported on β-SiC, the resonances of the fcc multi-domain, fcc single-domain and hcp Co were clearly distinguished. A careful rationalization of their frequency and width dependence on temperature allowed a quantitative analysis of the spectra in the temperature range of interest, thus reflecting the state of the catalysts under near operando conditions that is without the uncertainty associated with prior quenching. The allotropic transition temperature was found to start at 600-650 K, which is about 50 K below the bulk transition temperature. The phase transition was fully reversible and a significant part of the hcp phase was found to be stable up to 850 K. This anomalous behavior that was observed without quenching might prove to be crucial to understand and model active species not only in catalysts but also in battery materials.

  1. Stabilization and regeneration of CeO{sub 2} and CeO{sub 2}/ZrO{sub 2} based Pt catalyst for the water gas shift reaction

    Energy Technology Data Exchange (ETDEWEB)

    Haggblad, R.M.S.; Hulteberg, P.C.; Brandin, J.G.M. [Catator AB, Lund (Sweden)

    2005-07-01

    In this study a water gas shift catalyst consisting of a cerium oxide (CeO{sub 2}) based carrier and a platinum (Pt)-metal active phase was investigated. Issues concerning the stabilization and regeneration of CeO{sub 2} and CeO{sub 2} and zirconium oxide (ZrO{sub 2}) subject to high initial deactivation were presented. The influence of reaction gas species on catalyst deactivation were investigated by hydrogen (H{sub 2}) Temperature Programmed Reduction (TPR). It was noted that the activity measurements enabled different promoters, which will require further investigation. The catalysts were characterized by BET and carbon monoxide-TPR. Deactivated catalyst activity was restored by using various regeneration methods. Of the selected carriers, the CeO{sub 2}-ZrO{sub 2} based Pt catalyst showed the highest resilience to deactivation. Tungsten and rhenium were the best promoters when the catalyst was subject to deactivation. Experiments with H{sub 2}-TPR indicated a rapid initial change in the platinum oxides concentration and composition. The carbon monoxide (CO)-TPR was then used to draw conclusions about the various regeneration effects of water and oxygen on the catalyst. Dominant mechanisms were dependent on the catalyst and the reaction gas composition. It was concluded that it is possible to stabilize the ceria-based water gas shift catalyst by promotion, but primarily by doping. Addition of zirconia to the carrier has an effect on catalyst stability, and future research should be focused in this area. Results of the CO-TPR performed on the regenerated catalysts indicated that steam does not affect the Pt oxides but has a regenerative effect. It was suggested that experiments with regeneration by both steam and oxygen simultaneously may result in more complete regeneration of the catalyst. It was determined that deactivation of the catalyst does not originate from a single mechanism. The results indicated that no other species present has any higher

  2. Progress in magnetically stabilized bed and magnetic catalyst%磁稳定床及磁性催化剂的研究进展

    Institute of Scientific and Technical Information of China (English)

    鲁威; 文庆; 袁华; 吴元欣

    2012-01-01

    The research progress in the application of magnetically stabilized bed ( MSB) in the fields of petrochemical and biology was reviewed. MSB is used in catalytic hydrogenation, dust removal, dry coal separation, biochemical separation, immobilized bioreactors and culture of cells, etc. Compared with the conventional process, this novel reactor combines the advantages of fixed bed reactor and fluidized bed reactor, which can intensify the internal mass and heat transfer and improve the reaction efficiency. The design of magnetic catalyst is the key to the application of the MSB. So far,the magnetic catalysts in MSB are more commonly in coreshell structure with the magnetic core. All these catalysts have excellent magnetic properties and good catalytic performance at lower temperature. The research and development of MSB and magnetic catalyst are promising in catalyst industry.%对磁稳定床及磁性催化剂在石油化工和生物工程等领域的应用进行了归纳总结.磁稳定床已经应用于催化加氢、烟尘净化、干法选煤、生化分离、固定化生物反应器、细胞培养等过程.与传统工艺相比,磁稳定床兼有固定床和流化床的优点,能强化受传质传热限制的反应过程,提高反应效率,在实际应用中显示出独特的优越性.磁性催化剂的设计与开发是磁稳定床应用的关键,目前磁性催化剂以包覆型催化剂为主,其共同特点是具有适宜的磁性和低温反应活性,利于反应操作.磁稳定床及其磁性催化剂的研究开发是催化剂工业发展的一个新方向.

  3. 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.

  4. Hydrogen from bioethanol on Pt/Hydrotalcite catalysts stabilized with WOx; Hidrogeno a partir de bioetanol sobre catalizadores de Pt/hidrotalcita estabilizados con WOx

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, M.A.; Contreras, J.L. [Universidad Autonoma Metropolitana-Azcapotzalco, Mexico, D.F. (Mexico)]. E-mail: jlcl@correo.azc.uam.mx; Fuentes, G.A. [Universidad Autonoma Metropolitana-Iztapalapa, Mexico, D.F. (Mexico); Luna, R. [Universidad Autonoma Metropolitana-Azcapotzalco, Mexico, D.F. (Mexico); Salmones, J.; Zeifert, B. [ESIQIE, Instituto Politecnico Nacional, Mexico, D.F. (Mexico)] Vazquez, A. [Instituto Mexicano del Petroleo, Mexico, D.F. (Mexico)

    2009-09-15

    To produce H{sub 2} from bio-ethanol, the synthesis, characterization and reaction of Pt catalysts exchanged with hydrotalcite were studied. The catalysts obtained were characterized with BET area, x-ray diffraction and Raman, Infrared and UV-vis spectroscopies. The catalytic evaluation was performed with micro-reaction equipment using a water/ethanol ratio of 4 at 45 degrees Celsius. The effect of the W contents was from 0.5 to 3%. X-ray diffraction of the Co and Ni series showed a continuous decrease in crystallinity as W contents increased. Findings from N{sub 2} adsorption show pores in the form of parallel plates and a mesoporous distribution (bimodal) with areas between 151-257 m{sup 2}/g. OH, H{sub 2}O, Al-OH, Mg-OH, W-O and CO32- vibrations and W-O-W surface bonds were observed using infrared and Raman spectroscopy. Tungsten oxide groups were found with UV-vis spectroscopy. The catalyst with the greatest selectivity and stability is between 0.5 and 1% of W, and the highest stability is after 7 h of reaction. In this Pt series, the reaction that most consumed ethanol was that which produces CH{sub 4} and CO{sub 2}. The total conversion increased in function of W contents, between 0.5 and 3%. W stabilized the Pt/hydrotalcite catalyst with 0.5%W being the optimal concentration. The least amount of C{sub 2}H{sub 4} production and no CO was found for this Pt catalyst. [Spanish] Para la produccion de H{sub 2} se estudio la sintesis, caracterizacion y reaccion de catalizadores de Pt intercambiados con hidrotalcita, a partir de bioetanol. Los catalizadores obtenidos se caracterizaron por: area BET, difraccion de rayos X, espectroscopias: Raman, Infrarrojo y UV-vis. La evaluacion catalitica se llevo a cabo en un reactor de lecho fijo usando una relacion agua/etanol de 4 a 450 grados centigrados, se estudio el efecto del contenido de W desde 0.5 hasta 3% en peso. Conforme aumento el contenido de W se encontro por difraccion de rayos X un aumento de la cristalinidad

  5. Toward an Active and Stable Catalyst for Oxygen Evolution in Acidic Media: Ti-Stabilized MnO2

    DEFF Research Database (Denmark)

    Frydendal, Rasmus; Paoli, Elisa Antares; Chorkendorff, Ib;

    2015-01-01

    Catalysts are required for the oxygen evolution reaction, which are abundant, active, and stable in acid. MnO2 is a promising candidate material for this purpose. However, it dissolves at high overpotentials. Using first-principles calculations, a strategy to mitigate this problem by decorating...... undercoordinated surface sites of MnO2 with a stable oxide is developed here. TiO2 stands out as the most promising of the different oxides in the simulations. This prediction is experimentally verified by testing sputter-deposited thin films of MnO2 and Ti-MnO2. A combination of electrochemical measurements...

  6. PVP-stabilized Ru–Rh nanoparticles as highly efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

    Energy Technology Data Exchange (ETDEWEB)

    Rakap, Murat, E-mail: mrtrakap@gmail.com

    2015-11-15

    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{sub 2} (mol cat){sup −1} min{sup −1} and maximum hydrogen generation rate of 10,680 L H{sub 2} min{sup −1} (mol cat){sup −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{sub 2} (mol cat){sup −1} min{sup −1} for hydrolysis of AB. • Maximum HG rate is 9680 L H{sub 2} min{sup −1} (mol cat){sup −1} for the hydrolysis of AB. • Activation energy is 47.4 ± 2.1 kJ mol{sup −1} for the hydrolysis of AB.

  7. Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

    NARCIS (Netherlands)

    van Haasterecht, T.; Ludding, C.C.I.; de Jong, K.P.; Bitter, J.H.

    2013-01-01

    Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 ◦C, autogenous pressure, batch reactor). The initial surface-specific activities

  8. Hexane cracking over steamed phosphated zeolite H-ZSM-5 : Promotional effect on catalyst performance and stability

    NARCIS (Netherlands)

    Van Der Bij, Hendrik E.; Meirer, Florian; Kalirai, Samanbir; Wang, Jian; Weckhuysen, Bert M.

    2014-01-01

    The nature behind the promotional effect of phosphorus on the catalytic performance and hydrothermal stability of zeolite H-ZSM-5 has been studied using a combination of 27Al and 31P MAS NMR spectroscopy, soft X-ray absorption tomography and n-hexane catalytic cracking, complemented with NH3 tempera

  9. Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

    NARCIS (Netherlands)

    Haasterecht, van T.; Ludding, C.C.I.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 ¿, autogenous pressure, batch reactor). The initial surface-specific activities

  10. Hexane cracking over steamed phosphated zeolite H-ZSM-5: promotional effect on catalyst performance and stability.

    Science.gov (United States)

    van der Bij, Hendrik E; Meirer, Florian; Kalirai, Sam; Wang, Jian; Weckhuysen, Bert M

    2014-12-15

    The nature behind the promotional effect of phosphorus on the catalytic performance and hydrothermal stability of zeolite H-ZSM-5 has been studied using a combination of (27) Al and (31) P MAS NMR spectroscopy, soft X-ray absorption tomography and n-hexane catalytic cracking, complemented with NH3 temperature-programmed desorption and N2 physisorption. Phosphated H-ZSM-5 retains more acid sites and catalytic cracking activity after steam treatment than its non-phosphated counterpart, while the selectivity towards propylene is improved. It was established that the stabilization effect is twofold. First, the local framework silico-aluminophosphate (SAPO) interfaces, which form after phosphatation, are not affected by steam and hold aluminum atoms fixed in the zeolite lattice, preserving the pore structure of zeolite H-ZSM-5. Second, the four-coordinate framework aluminum can be forced into a reversible sixfold coordination by phosphate. These species remain stationary in the framework under hydrothermal conditions as well. Removal of physically coordinated phosphate after steam-treatment leads to an increase in the number of strong acid sites and increased catalytic activity. We propose that the improved selectivity towards propylene during catalytic cracking can be attributed to local SAPO interfaces located at channel intersections, where they act as impediments in the formation of bulky carbenium ions and therefore suppress the bimolecular cracking mechanism.

  11. Gold Nanoparticles on Mesoporous SiO2-Coated Magnetic Fe3O4 Spheres: A Magnetically Separatable Catalyst with Good Thermal Stability

    Directory of Open Access Journals (Sweden)

    Huan Liu

    2013-11-01

    Full Text Available Fe3O4 spheres with an average size of 273 nm were prepared in the presence of CTAB by a solvothermal method. The spheres were modified by a thin layer of SiO2, and then coated by mesoporous SiO2 (m-SiO2 films, by using TEOS as a precursor and CTAB as a soft template. The resulting m-SiO2/Fe3O4 spheres, with an average particle size of 320 nm, a high surface area (656 m2/g, and ordered nanopores (average pore size 2.5 nm, were loaded with gold nanoparticles (average size 3.3 nm. The presence of m-SiO2 coating could stabilize gold nanoparticles against sintering at 500 °C. The material showed better performance than a conventional Au/SiO2 catalyst in catalytic reduction of p-nitrophenol with NaBH4. It can be separated from the reaction mixture by a magnet and be recycled without obvious loss of catalytic activity. Relevant characterization by XRD, TEM, N2 adsorption-desorption, and magnetic measurements were conducted.

  12. Oseltamivir prescription and regulatory actions vis-a-vis abnormal behavior risk in Japan: drug utilization study using a nationwide pharmacy database.

    Directory of Open Access Journals (Sweden)

    Hisashi Urushihara

    Full Text Available BACKGROUND: In March 2007, a regulatory advisory was issued in Japan to restrict oseltamivir use in children aged 10-19 years because of safety concerns over abnormal behavior. The effectiveness and validity of regulatory risk minimization actions remain to be reviewed, despite their significant public health implications. To assess the impact of the regulatory actions on prescribing practices and safety reporting. METHODOLOY/PRINICPAL FINDINGS: In this retrospective review of a nationwide pharmacy database, we analyzed 100,344 dispensation records for oseltamivir and zanamivir for the period from November 2006 to March 2009. The time trend in dispensations for these antiviral agents was presented before and after the regulatory actions, contrasted with intensity of media coverage and the numbers of spontaneous adverse reaction reports with regard to antivirals. The 2007 regulatory actions, together with its intense media coverage, reduced oseltamivir dispensation in targeted patients in fiscal year 2008 to 20.4% of that in fiscal year 2006, although influenza activities were comparable between these fiscal years. In contrast, zanamivir dispensation increased approximately nine-fold across all age groups. The number of abnormal behavior reports associated with oseltamivir in children aged 10-19 years decreased from fiscal year 2006 to 2008 (24 to 9 cases; this decline was offset by the increased number of reports of abnormal behavior in children under age 10 (12 to 28 cases. The number of reports associated with zanamivir increased in proportion to increased dispensation of this drug (11 to 114 cases. CONCLUSIONS/SIGNIFICANCE: The 2007 actions effectively reduced oseltamivir prescriptions and the number of reports of abnormal behavior in the targeted group. The observed increase in abnormal behavior reports in oseltamivir patients under age 10 and in zanamivir patients suggests that these patient groups may also be at risk, calling into question the validity of the current discrimination by age and agent (Abstract translation is available in Japanese: Appendix S1.

  13. Can biophysics tell us something about the weak equivalence principle vis a vis the thought experiment of Einstein involving human subjects?

    Science.gov (United States)

    Thaheld, Fred H

    2009-08-01

    Over a period of several decades it has been noticed that most astronauts, either orbiting the earth or on trips to the moon, have observed phosphenes or light flashes (LF) including streaks, spots and clouds of light when their eyes are closed or they are in a darkened cabin. Scientists suspect that two separate components of cosmic rays cause these flashes due to direct interaction with the retina. This phenomenon is not noticed on the ground because of cosmic ray interaction with the atmosphere. The argument is advanced that this effect may provide us with a new method of exploring the weak equivalence principle from the standpoint of Einstein's original thought experiment involving human subjects. This can be done, utilizing the retina only, as an animate quantum mechanical measuring device or, in conjunction with the Anomalous Long Term Effects on Astronauts (ALTEA) facility.

  14. Disciplining of Student's vis-a-vis the Duties/Responsibilities of Vice Principals in Secondary Institutions in Oyo State: Yesterday and Today

    Science.gov (United States)

    Adewusi, Aderogba Oladiran

    2012-01-01

    This paper focused on how Nigeria' teeming youth requires a high level of seriousness from all stakeholders: the student, school administrators, teaching staff, parents, educational agencies and the government. There had been much emphasis on the need for everyone to understand and play specifically assigned roles, and to ensure that the posterity…

  15. Approaches to characterize extended spectrum beta-lactamase/beta-lactamase producing Escherichia coli in healthy organized vis-a-vis backyard farmed pigs in India.

    Science.gov (United States)

    Samanta, Indranil; Joardar, Siddhartha N; Mahanti, Achintya; Bandyopadhyay, Samiran; Sar, Tapas K; Dutta, Tapan K

    2015-12-01

    The study was undertaken to investigate the occurrence and to characterize the ESBL/beta-lactamase producing-Escherichia coli in healthy pigs of organized and backyard farms in West Bengal, India. Total 200 rectal swabs were collected randomly from healthy pigs maintained in four organized farms and 10 backyard farms (n=100 each) and 76 isolates were identified as E. coli from organized (48/100, 48%) and backyard pigs (28/100, 28%). Twelve E. coli isolates (6%) in the present study were detected to possess any of the ESBL/beta-lactamase genes studied. ESBL/beta-lactamase producers were isolated with significantly more frequency from backyard pigs than the organized farm pigs (p=0.026). Six of ESBL/beta-lactamase producing isolates were phenotypically confirmed as CTX-M producers and ten of them were confirmed as TEM/SHV producers. PCR and sequencing of the amplified product from representative isolates revealed the presence of blaCTX-M-9, blaSHV-12 and blaTEM-1. No unique combination of the studied beta lactamase genes for organized and backyard farm pig isolates was noted. The ESBL isolates belonged to O13, O55, O133, O153, O157, O158, O166, rough and OUT serogroups. The association of heat labile toxin (elt) (pIndia.

  16. A Pilot Study to Investigate the Effectiveness of Multimedia CD-ROM vis-a-vis Traditional Print-Based Technology in Teaching Fourth-Grade Children

    Science.gov (United States)

    Shana, Zuhrieh A.

    2009-01-01

    The purpose of this study was to examine the degree of effectiveness of multimedia technology in teaching in comparison to the traditional print-based teaching methods. Multimedia CD was designed to teach the second semester unit of science and Islamic studies for the fourth graders. The unit's content was the same in the print-based teaching…

  17. [Pierre-Joseph Duhem (1758-1807), doctor regicide, and other National Convention physician-deputies vis-a-vis the lawsuit of Louis XVI].

    Science.gov (United States)

    Dupont, Geneviève; Lellouch, Alain; Olry, Régis

    2006-01-01

    On January 16, 1793, seven hundred aud forty nine deputies of the National Convention are called on to express their opinion by word of mouth about this question: "What penalty Louis, former king of the French, brought upon himself ?" Among these deputies, 47 are or were physicians : 22 vote for death without delay, 3 for suspended death sentence, 20 for indulgence (imprisonment till the peace and banishment thereafter), and 2 refuse to vote. This paper aims at summarizing the attitude of the physicians-deputies, and more specifically those of Pierre-Joseph Duhem, at the time of one of the most famous trials of the history of France.

  18. TP53 Mutation vis-a-vis Malignant Progression in Astrocytoma WHO Grade Ⅱ%TP53突变与胶质瘤恶性进展

    Institute of Scientific and Technical Information of China (English)

    岳伟英; 俞苏寰; 李志强; 赵世光; 陈忠平

    2008-01-01

    背景与目的:WHO Ⅱ级的星形细胞瘤手术后在部分患者可能复发,而且,复发时多出现恶性程度增加.本研究探讨TP53蛋白质分子的表达与胶质瘤恶性进展之问的关系.方法:收集第一次手术时为星形细胞瘤(WHO Ⅱ级)的石蜡包埋标本53例份,其中10例复发时第二次手术肿瘤仍然为Ⅱ级(复发无进展组);10例复发时肿瘤级别升高(Ⅲ级或Ⅳ级)(复发进展组);另外13例在5年内没有复发(无复发组).免疫组化检测TP53在肿瘤中的表达,并采用DNA测序法分析TP53蛋白阳性标本TP53外显子5、7、8的突变情况.结果:LTP53阳性率为45.5%(15/33).复发恶性进展组TP53高于无复发组和无进展组(P<0.05);TP53无进展组与无复发组之间差异无统计学意义.基因测序共在6例组织中发现7个(共4类)突变,其中1例同时存在2个突变.所有突变者都是恶性进展组病例.结论:TP53突变/蛋白质分子过表达可能是Ⅱ级星形胶质细胞瘤复发恶性进展的预示指标.

  19. Arsenic accumulation in root and shoot vis-a-vis its effects on growth and level of phytochelatins in seedlings of Cicer arietinum L.

    Science.gov (United States)

    Gupta, D K; Tripathi, R D; Mishra, S; Srivastava, S; Dwivedi, S; Rai, U N; Yang, X E; Huanji, H; Inouhe, M

    2008-05-01

    Arsenic (As) contamination of water and soil has become a subject of prime interest due to its direct effect on human health through drinking water and food. In present study two varieties (CSG-8962 and C-235) of chickpea, Cicer arietinum L., which is a major supplementary food in many parts of India and a valuable source of protein, has been selected to estimate the level of arsenate in root and shoot of five day old seedlings vis-à-vis effect of arsenate on seedling growth and induction of thiols including glutathione (GSH) and phytochelatins (PCs) and their homologues. Both varieties accumulated arsenate to similar levels and most of the metalloid was confined to roots, only about 2.5% was translocated to shoot. Plant growth was also not affected significantly in both the varieties. Arsenate exposure significantly induced the levels of thiols including PCs and homophytochelatins (hPCs). The induction of thiols was much higher in roots than shoots and was greater in var C-235 between the two tested ones. Thus, both varieties tolerated and detoxified arsenic through chelation with GSH, PCs and hPCs, primarily in roots, however var C-235 performed better

  20. Representations et Competencies vis-a-vis de l'Ecrit Chez des Enfants Francais et Allemands d'Age Prescolaire.

    Science.gov (United States)

    Preteur, Yves; Louvet-Schmauss, Eva

    1994-01-01

    Compares German and French preschool children's attitudes about school and literacy. Notes that French preschools aim to prepare children for primary education, whereas German preschools give priority to learning through play. Finds that children developed attitudes in line with their preschool system and that only French children from deprived…

  1. Non-Profit Education Providers vis-a-vis the Private Sector: Comparative Analysis of Non-Governmental Organizations and Traditional Voluntary Organizations in Pakistan

    Science.gov (United States)

    Bano, Masooda

    2008-01-01

    Under the New Policy Agenda, international development institutions have promoted non-profit organizations (NPOs) in developing countries, on a dual logic: firstly, they deliver social services more efficiently than the state; secondly, they mitigate equity concerns around privatization of basic social services by reaching out to the poor. Based…

  2. Premiers resultats experimentaux sur le comportement de Tabebuia heterophylla (DC) Britton et de Hymenaea courbaril L. vis-a vis de la secheresse

    OpenAIRE

    Huc, Roland

    1985-01-01

    Deux espèces de la forêt de basse altitude d’Amérique tropicale (Antilles), Tabebebuia heterophylla (poirier-pays) et Hymenaea courbaril (courbaril), se révèlent intéressantes pour le reboisement des régions les moins arrosées. Le comportement de ces espèces vis-à-vis de la sécheresse est étudié grâce à un traitement sous forme d’arrosage différencié appliqué à des jeunes plants âgés de 1 an, en pépinière. L'évolution de l’état hydrique des plants est suivie au cours de 6 mois d’expéri...

  3. A self-interaction-free local hybrid functional: Accurate binding energies vis-\\`a-vis accurate ionization potentials from Kohn-Sham eigenvalues

    CERN Document Server

    Schmidt, Tobias; Makmal, Adi; Kronik, Leeor; Kümmel, Stephan

    2014-01-01

    We present and test a new approximation for the exchange-correlation (xc) energy of Kohn-Sham density functional theory. It combines exact exchange with a compatible non-local correlation functional. The functional is by construction free of one-electron self-interaction, respects constraints derived from uniform coordinate scaling, and has the correct asymptotic behavior of the xc energy density. It contains one parameter that is not determined ab initio. We investigate whether it is possible to construct a functional that yields accurate binding energies and affords other advantages, specifically Kohn-Sham eigenvalues that reliably reflect ionization potentials. Tests for a set of atoms and small molecules show that within our local-hybrid form accurate binding energies can be achieved by proper optimization of the free parameter in our functional, along with an improvement in dissociation energy curves and in Kohn-Sham eigenvalues. However, the correspondence of the latter to experimental ionization potent...

  4. Development of Some Larval Nematodes in Experimental and Natural Animal Hosts: An Insight into Development of Pathological Lesions vis-a-vis Host-Parasite Interactions

    Directory of Open Access Journals (Sweden)

    N. Chowdhury

    2013-01-01

    Full Text Available Infective third-stage larvae of three spiruroid nematodes, Ascarops strongylina and Physocephalus sexalatus of pigs and Spirocerca lupi of dogs, were recovered from 14 species of coprophagous beetles belonging to 4 different genera. These larvae were fed to rabbits and/or guinea pigs to study their development in these experimental hosts. Larvae of A. strongylina reached the adult stage in all rabbits and one guinea pig. The adult worms recovered in these hosts were 40% and 4%, respectively, and became diminutive in comparison to their natural hosts. The larvae of P. sexalatus became reencysted in the gastric wall of rabbits inducing marked pathological changes. The infective larvae of S. lupi became reencapsulated in the stomach wall of the rabbit and also showed development in the aortic wall. Adults of Toxocara canis of dog, collected from 5 different regions of the Indian subcontinent, varied significantly in size. The mouse passage of infective larvae of one of these types led to the recovery of the adults from the experimental dogs that were smaller in size and caused severe pathology in natural experimental hosts. Developmental effects shown in experimental hosts and host specificity are of value in understanding the evolution of nematode parasitism.

  5. Kojic acid vis-a-vis its combinations with hydroquinone and betamethasone valerate in melasma: A randomized, single blind, comparative study of efficacy and safety

    Directory of Open Access Journals (Sweden)

    Kirti S Deo

    2013-01-01

    Strict photoprotection and use of a SPF 15 sunscreen was advised during the day. Patients were evaluated every 2 weeks and a fall in MASI score was calculated at the end of the study period of 12 weeks by the same investigator. Results: The response was compared according to percentage decrease in MASI score. Efficacy was evaluated among the groups at the end of 3 months using bivariate analysis and calculated by using the paired ′t′ test. The clinical efficacy of group B was the highest followed closely by group D and group A, that of group C being the lowest. Conclusion: Kojic acid in synergy with hydroquinone is a superior depigmenting agent as compared with other combinations.

  6. Mapping Ecology of Literacies in Educational Setting: The Case of Local Mother Tongues Vis-a-Vis Urdu and English Languages in Pakistan

    Science.gov (United States)

    Manan, Syed Abdul; David, Maya Khemlani

    2014-01-01

    This study critically examines the literacy levels of undergraduate students in Pakistan to compare and contrast the proficiency levels, particularly reading and writing of their mother tongues versus Urdu and English, and to study real and perceived vitality of local/regional mother tongues vis-à-vis Urdu and English. The research investigated…

  7. Dissociated reality vis-a-vis integrative planning of AYUSH in Maternal Health Program: A situational analysis in Jaleswar block of Balasore district of Odisha, India.

    Science.gov (United States)

    Dehury, Ranjit Kumar; Chatterjee, Suhita Chopra

    2016-01-01

    Mainstreaming of AYUSH and revitalization of local health traditions is one of the innovative components of the National Rural Health Mission (NRHM) in the state of Odisha, India. In this study, an attempt was made to assess the potential of collocating AYUSH to improve maternal health services in tribal dominated Jaleswar block of the Balasore district. In addition, the study aimed at unearthing the underlying challenges and constraints in mainstreaming AYUSH and linking it with the Maternal Health Program. Review of the policy documents and guidelines, both central and state government, was made to assess the implementation of AYUSH in Odisha. Primary data were collected through interviews with AYUSH doctors, district and block level health administrators, and tribal women. The study revealed the inadequacy of basic amenities, infrastructure, drugs, and consumables in the health centers for integrating AYUSH in the delivery of maternal health services. Analysis of the job chart and work pattern of AYUSH doctors showed underutilization of their specialized knowledge to treat patients. Lack of continued medical education, standard operating procedures for treatment and spatial marginalization made suboptimal utilization of AYUSH services. This is unfortunate given the fact that such regions are economically underdeveloped and already have a distinct orientation toward indigenous health systems. AYUSH, on account of its holistic approach and proven cost-effectiveness, could be a viable option for improving maternal health in the region. The study concluded that although there is huge scope for integrating AYUSH in Maternal Health Program under the ongoing NRHM, the full potential is yet to be exploited.

  8. Globalização vis-a-vis a história do nacionalismo na América Latina: o caso do Brasil

    Directory of Open Access Journals (Sweden)

    Céli Regina Jardim Pinto

    2012-12-01

    Full Text Available The article has as start point a central question: Is it possible to identify a reaction to the globalization of capitalism, in term of a globalized movement that involves an alternative to the system or to the north hegemony in relation to the south countries, many of them in conditions of complete miserably and deep social inequality? To examine this question the article is divided in to four small sections: 1.The Internationalism and nationalism; 2. The Nationalism in Brazil; 3. The global civil society; 4. A conclusion. This article concludes that we are far away from a global civil society able to propose a way of life that problematize the capitalist system and all forms of exploitation and class, gender and race dominations.

  9. A CLINICAL STUDY ON THE EFFICACY OF PATALADI KASHAYA IN THE MANAGEMENT OF ‘VATASHTEELA’ VIS A VIS ‘BPH’ (BENIGN PROSTATIC HYPERTROPHY

    Directory of Open Access Journals (Sweden)

    Pradeep E K

    2013-12-01

    Full Text Available In the present clinical study the cases of disease ‘Vatashteela’, which is a type of Mutraghata in terms of Benign Prostate Hypertrophy (BPH, were considered. The objective of the study was to assess the efficacy of Pataladi kashaya in Vatashteela ‘vis a vis’ BPH. Total 30 patients having signs and symptoms of ‘Vatashteela’ ‘vis a vis’ BPH were included according to criteria of AUA-SI (American Urological Association – Symptom Index, and also after diagnosing BPH by Digital Rectal Examination, and Ultrasonography of Abdomen and pelvis. Patients were assigned into a single group consisting of 30 patients for whom Pataladi kashaya 30 ml thrice a day before food with sukhoshna jala for 30 days was administered. Incomplete emptying, Frequency, Urgency, Intermittency, Straining, Weak stream and Nocturia were the Subjective parameters, data of which were collected before (day 0, during (day 15, after (day 30 and follow up (day 60. The objective parameters were residual urine, volume and size of the prostate. These data were collected before (day 0 and after (day 30 of the clinical trial. The analysis was done statistically by using Repeated Measure ANOVA, student‘t’ test and contingency co-efficient table. The statistical values showed significant results in subjective and objective parameters. In lateral lobe enlargement, symptoms were relieved to a greater extent compared to median lobe enlargement. Residual urine, volume of the prostate, obstructive symptoms showed marked improvement in many of the patients, and there was also significant decrease in size of the prostate. Overall assessment showed marked and moderate improvement in many patients. Pataladi kashaya is useful in reducing the signs and symptoms of ‘Vatashteela’ ‘vis a vis’ ‘BPH’ and even residual urine, volume and size of the prostate. Pataladi kashaya is beneficial due to its properties in improving obstructive symptoms and reducing the size of the prostate.

  10. Visualization and co-occurrence of journals in the area of information science in vis-a-vis the Qualis/Capes system in Brazil

    Directory of Open Access Journals (Sweden)

    Adilson Luiz Pinto

    2016-05-01

    Full Text Available This paper aims at qualifying scientific journals that are part of the listing Qualis/Capes Brazil. The site of Capes only lists a few influential international titles. Included in this list are “Information Processing & Management, Organization Knowledge and Library” but several other important titles in Information Science are not covered. Our study describes 27 scientific worldwide journals, representing the world stage in Information Science, and which for some reason are not well respected in Brazil. The influence of these international journals (which are part of Web of Science is evidenced by measuring the power they have in the scientific field of Information Science as well as the power of major authors (Salton, Spink, Nicholas, Belkin, Saracevic, Dervin, Garfield and others. Citation index comparison with the other journals in the area and index of impact factor are also analyzed. The results highlight the importance of JASIST, Information Processing & Management, College Research Library, Journal of Documentation, ARIST, Journal Information Sciences, Information Retrieval and Library Trends, both in the matter of world representativeness and in the number of citations.

  11. Defect Stabilized Gold Atoms on Graphene as Potential Catalysts for Ethylene Epoxidation: A First-principles Investigation

    KAUST Repository

    Liu, Xin

    2015-11-24

    We performed a first-principles based investigation on the potential role of Au atoms stabilized by defects on graphene in ethylene epoxidation. We showed that the interactions between the Au atoms and vacancies on graphene not only make the Au atomic diffusion a 2.10 eV endothermic process, but also tune the energy level of Au-d states for the activation of O2 and ethylene and promote the formation and dissociation of the peroxametallacycle intermediate. The catalytic cycle of ethylene epoxidation is initiated with the formation of a peroxametallacycle intermediate by the coadsorbed ethylene and O2, through the dissociation of which an ethylene epoxide molecule and an adsorbed O atom are formed. Then, gaseous ethylene reacts with the remnant O atom directly for the formation of another ethylene epoxide molecule. The desorption of ethylene epoxide is facilitated by the subsequent adsorption of O2 or ethylene and a new reaction cycle initiates. The calculated energy barriers for the formation and dissociation of the peroxametallacycle intermediate and the regeneration of Au sites are 0.30, 0.84 and 0.18 eV, respectively, and are significantly lower than those for aldehyde formation. These findings suggest the potential high catalytic performance of these Au atoms for ethylene epoxidation.

  12. Autothermal reforming catalyst having perovskite structure

    Science.gov (United States)

    Krumpel, Michael; Liu, Di-Jia

    2009-03-24

    The invention addressed two critical issues in fuel processing for fuel cell application, i.e. catalyst cost and operating stability. The existing state-of-the-art fuel reforming catalyst uses Rh and platinum supported over refractory oxide which add significant cost to the fuel cell system. Supported metals agglomerate under elevated temperature during reforming and decrease the catalyst activity. The catalyst is a perovskite oxide or a Ruddlesden-Popper type oxide containing rare-earth elements, catalytically active firs row transition metal elements, and stabilizing elements, such that the catalyst is a single phase in high temperature oxidizing conditions and maintains a primarily perovskite or Ruddlesden-Popper structure under high temperature reducing conditions. The catalyst can also contain alkaline earth dopants, which enhance the catalytic activity of the catalyst, but do not compromise the stability of the perovskite structure.

  13. Fischer-Tropsch Synthesis: Influence of CO Conversion on Selectivities H2/CO Usage Ratios and Catalyst Stability for a 0.27 percent Ru 25 percent Co/Al2O3 using a Slurry Phase Reactor

    Energy Technology Data Exchange (ETDEWEB)

    W Ma; G Jacobs; Y Ji; T Bhatelia; D Bukur; S Khalid; B Davis

    2011-12-31

    The effect of CO conversion on hydrocarbon selectivities (i.e., CH{sub 4}, C{sub 5+}, olefin and paraffin), H{sub 2}/CO usage ratios, CO{sub 2} selectivity, and catalyst stability over a wide range of CO conversion (12-94%) on 0.27%Ru-25%Co/Al{sub 2}O{sub 3} catalyst was studied under the conditions of 220 C, 1.5 MPa, H{sub 2}/CO feed ratio of 2.1 and gas space velocities of 0.3-15 NL/g-cat/h in a 1-L continuously stirred tank reactor (CSTR). Catalyst samples were withdrawn from the CSTR at different CO conversion levels, and Co phases (Co, CoO) in the slurry samples were characterized by XANES, and in the case of the fresh catalysts, EXAFS as well. Ru was responsible for increasing the extent of Co reduction, thus boosting the active site density. At 1%Ru loading, EXAFS indicates that coordination of Ru at the atomic level was virtually solely with Co. It was found that the selectivities to CH{sub 4}, C{sub 5+}, and CO{sub 2} on the Co catalyst are functions of CO conversion. At high CO conversions, i.e. above 80%, CH{sub 4} selectivity experienced a change in the trend, and began to increase, and CO{sub 2} selectivity experienced a rapid increase. H{sub 2}/CO usage ratio and olefin content were found to decrease with increasing CO conversion in the range of 12-94%. The observed results are consistent with water reoxidation of Co during FTS at high conversion. XANES spectroscopy of used catalyst samples displayed spectra consistent with the presence of more CoO at higher CO conversion levels.

  14. Stability of catalytic foam diesel-soot filters based on Cs{sub 2}O, MoO{sub 3}, and Cs{sub 2}SO{sub 4} molten-salt catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Van Setten, B.A.A.L.; Spitters, C.G.M.; Bremmer, J.; Mulders, A.M.M.; Makkee, M.; Moulijn, J.A. [Section Reactor and Catalysis Engineering, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, 2628 BL Delft (Netherlands)

    2003-06-10

    The durability of catalytic alumina and zirconia-toughened mullite ceramic foam diesel-soot filters was tested by exposing them to severe, artificial exhaust conditions. The catalytic performance, composition, and mechanical strength were constantly monitored. It was concluded that the mechanical strength of the catalytic filters may be reduced by an interaction of the catalyst with certain compounds of ceramic filters. In practice, it should be possible to minimize the effect by carefully controlling the composition of the ceramic filter. For instance, the presence of phosphorous in alumina-based filters support should be avoided. The stability of the current catalyst phases, based on Cs{sub 2}O, MoO{sub 3}, and Cs{sub 2}SO{sub 4}, is too low for application. Due to partial evaporation, emission of catalyst compounds into the environment is likely and when that happens significant deactivation of the catalytic phase is unavoidable. The catalyst was also found to be soluble in water, which might be disastrous in the case of condensation occurring in the exhaust pipe.

  15. Fuel cell catalyst degradation

    DEFF Research Database (Denmark)

    Arenz, Matthias; Zana, Alessandro

    2016-01-01

    Fuel cells are an important piece in our quest for a sustainable energy supply. Although there are several different types of fuel cells, the by far most popular is the proton exchange membrane fuel cell (PEMFC). Among its many favorable properties are a short start up time and a high power density...... increasing focus. Activity of the catalyst is important, but stability is essential. In the presented perspective paper, we review recent efforts to investigate fuel cell catalysts ex-situ in electrochemical half-cell measurements. Due to the amount of different studies, this review has no intention to give...

  16. Homogeneous catalysts

    CERN Document Server

    Chadwick, John C; Freixa, Zoraida; van Leeuwen, Piet W N M

    2011-01-01

    This first book to illuminate this important aspect of chemical synthesis improves the lifetime of catalysts, thus reducing material and saving energy, costs and waste.The international panel of expert authors describes the studies that have been conducted concerning the way homogeneous catalysts decompose, and the differences between homogeneous and heterogeneous catalysts. The result is a ready reference for organic, catalytic, polymer and complex chemists, as well as those working in industry and with/on organometallics.

  17. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  18. 磁性催化剂与磁稳定床反应器或磁集成强化反应过程%Intensification catalytic reaction by integration of magnetic catalyst and magnetically stabilized bed reactor or magnetic separator

    Institute of Scientific and Technical Information of China (English)

    宗保宁

    2012-01-01

    通过将非晶态镍合金催化剂的磁性和加氢活性与磁稳定床反应器集成,实现了在己内酰胺加氢精制过程的工业应用.磁稳定床加氢精制替代己内酰胺氧化精制过程,显著提高了反应过程的能效和物效,并减少了污染物排放.非晶态镍合金催化剂与磁分离集成,强化了苯甲酸加氢反应过程.磁性Pd/Al2O3和NiSO4/Al2O3催化剂与磁稳定床反应器集成,强化了乙炔选择性加氢反应和烯烃叠合反应,形成了新技术生长点.%Utilizing the excellent hydrogenation activity and magnetism of the amorphous Ni catalyst, a magnetically stabilized bed reactor was developed for the purification of caprolactam, to ensure higher reactor and process efficiency. Integration of amorphous Ni catalyst and magnetic separator has enhanced the benzoic acid hydrogenation reaction to reduce the Pd/C catalyst consumption by 50%, and to increase the plant output by 15%, respectively. Integration of the appropriate magnetic catalyst into the magnetically stabilized bed reactor also allowed improved performances in selective hydrogenation of acetylene and olefin oligomerization, compared with current processes, and thus constitutes a highly effective technique for process intensification.

  19. POLYMER-SUPPORTED LEWIS ACID CATALYSTS. VI. POLYSTYRENE-BONDED STANNIC CHLORIDE CATALYST

    Institute of Scientific and Technical Information of China (English)

    RAN Ruicheng; FU Diankui

    1991-01-01

    A polystyrene-bonded stannic chloride catalyst was synthesized by the method of lithium polystyryl combined with stannic chloride. This catalyst is a polymeric organometallic compound containing 0.25 mmol Sn(IV)/g catalyst. The catalyst showed sufficient stability and catalytic activity in organic reaction such as esterification, acetalation and ketal formation, and it could be reused many times without losing its catalytic activity.

  20. 高水热稳定性加氢脱氧Ni-Mo复合氧化物催化剂的制备%Preparation of Ni-Mo Composite Oxide Catalysts with High Hydrothermal Stability for Hydrodeoxygenation

    Institute of Scientific and Technical Information of China (English)

    任阳阳; 宋运晶; 段艳; 侯凯湖

    2015-01-01

    以动植物油脂为原料加氢脱氧生产生物柴油的关键是开发具有优异加氢脱氧活性和稳定性的新型催化剂.今采用溶胶凝胶法制备了本体型Ni-Mo复合氧化物加氢脱氧催化剂,并对其进行了XRD、BET等表征,以含 20%小桐子油的正辛烷溶液为原料,在连续固定床反应装置上考察了催化剂的活性和水热稳定性.结果表明:溶胶凝胶法可制备出具有优异活性的钼镍复合氧化物催化剂,水热处理后催化剂的比表面积和孔容减小以及形成了部分NiMoO 4新相,前者使催化剂的活性下降,后者使催化剂的活性增加,二者的综合作用使水热处理催化剂的活性下降.提高催化剂的焙烧温度或添加镁铝尖晶石等方法可有效改善催化剂的水热稳定性和调控小桐子油的加氢脱氧反应路径.在330℃、2~5 h?1和310℃、2 h?1条件下,小桐子油在700℃焙烧、水热处理前后的催化剂上的脱氧率均高达99.0%以上.与在水热处理前催化剂上的反应结果相比,小桐子油在水热处理后催化剂上的脱羧基、脱羰基反应产物增加了15%.%Key issue of biodiesel production technique via the hydrodeoxygenation of animal and vegetable fats is to develop novel catalysts with excellent hydrodeoxygenation(HDO) activity and stability. A kind of unsupported Ni-Mo composite oxide catalysts were prepared by the sol-gel method in this paper, The prepared catalysts were characterized by XRD and BET. Using the solution of 20%(vol) jatropha curcas oil + 80%(vol) n-octane as the feed, the HDO performance and hydrothermal stability of the catalysts were investigated in a continuous flow fixed-bed reactor. The results show that Mo-Ni composite oxide catalysts prepared by sol-gel method could possess higher hydrodeoxygenation activity.The surface area and pore volume of the catalysts decreases and the some NiMoO 4 can be formed after the hydrothermal treatment. The surface area and pore volume

  1. Water reduction by a p-GaInP2 photoelectrode stabilized by an amorphous TiO2 coating and a molecular cobalt catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Jing; Yan, Yong; Young, James L.; Steirer, K. Xerxes; Neale, Nathan R.; Turner, John A.

    2015-12-21

    Producing hydrogen through solar water splitting requires the coverage of large land areas. Abundant metal-based molecular catalysts offer scalability, but only if they match noble metal activities. We report on a highly active p-GaInP2 photocathode protected through a 35-nm TiO2 layer functionalized by a cobaloxime molecular catalyst (GaInP2-TiO2-cobaloxime). This photoelectrode mediates H2 production with a current density of ~9"0mA"0cm-2 at a potential of 0"0V versus RHE under 1-sun illumination at pH"013. The calculated turnover number for the catalyst during a 20-h period is 139,000, with an average turnover frequency of 1.9"0s-1. Bare GaInP2 shows a rapid current decay, whereas the GaInP2-TiO2-cobaloxime electrode shows catalyst particle-modified interface. The activity and corrosion resistance of the GaInP2-TiO2-cobaloxime photocathode in basic solution is made possible by an atomic layer-deposited TiO2 and an attached cobaloxime catalyst.

  2. Aspects of stability of K/Al2O3 catalysts for the transesterification of rapeseed oil in batch and fixed-bed reactors

    Institute of Scientific and Technical Information of China (English)

    Petr Kutálek; Libor Čapek; Lucie Smoláková; David Kubička; Martin Hájek

    2014-01-01

    Catalytically active, stable, and mechanically durable solid K/Al2O3 catalysts for the transesterifica-tion of rapeseed oil with methanol was studied. In a batch reactor, high catalytic activity was ac-companied by leaching of K species, caused by glycerol, and mechanical destruction of the solid catalyst as a result of contact with the stirrer. In a fixed-bed reactor, some leaching of K species into the liquid phases was also observed, but approached 0 during 30 h of time-on-stream; the activity of the K/Al2O3 catalyst (~83% ester yield) was stable for 100 h of time-on-stream and no mechanical destruction of the catalyst was observed. The populations of K2O and K-O-Al species for fresh and used K/Al2O3 catalysts were compared using Fourier transform infrared spectroscopy. It was found that some K2O species leached into the liquid phases at the beginning of the reaction.

  3. The effect of methanol on the stability of Pt/C and Pt-RuO{sub x}/C catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Rufino, Elen C.G.; Olivi, Paulo [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, CEP 14040-901, Ribeirao Preto, SP (Brazil)

    2010-12-15

    The behavior of Pt/C and Pt-RuO{sub x}/C electrodes subjected to a larger number of potential scans and constant potential for prolonged time periods was investigated in the absence and presence of methanol. The structural changes were analyzed on the basis of the modifications observed in the X-ray diffraction pattern of the catalysts. Carbon monoxide stripping experiments were performed before and after the potential scans, thus enabling analysis of the behavior of the electrochemically active surface area. The resulting solutions were examined by inductively coupled plasma mass spectrometry (ICP-MS). There was reduction in the electrochemically active surface area, as well as increase in crystallite size and dissolution of catalyst components after the potential scan tests. Catalyst degradation was more pronounced in the presence of methanol, and cyclic potential conditions accelerate the degradation mechanisms. (author)

  4. Stabilization of Hydrogen Production via Methanol Steam Reforming in Microreactor by Al2O3 Nano-Film Enhanced Catalyst Adhesion.

    Science.gov (United States)

    Jeong, Heondo; Na, Jeong-Geol; Jang, Min Su; Ko, Chang Hyun

    2016-05-01

    In hydrogen production by methanol steam reforming reaction with microchannel reactor, Al2O3 thin film formed by atomic layer deposition (ALD) was introduced on the surface of microchannel reactor prior to the coating of catalyst particles. Methanol conversion rate and hydrogen production rate, increased in the presence of Al2O3 thin film. Over-view and cross-sectional scanning electron microscopy study showed that the adhesion between catalyst particles and the surface of microchannel reactor enhanced due to the presence of Al2O3 thin film. The improvement of hydrogen production rate inside the channels of microreactor mainly came from the stable fixation of catalyst particles on the surface of microchannels.

  5. Rational design of gold catalysts with enhanced thermal stability: post modification of Au/TiO2 by amorphous SiO2 matrix

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Haoguo [ORNL; Ma, Zhen [ORNL; Overbury, Steven {Steve} H [ORNL; Dai, Sheng [ORNL

    2007-01-01

    Au/TiO{sub 2} is highly active for CO oxidation, but it often suffers from sintering in high-temperature environments. In this work, we report on a novel design of gold catalysts, in which pre-formed Au/TiO{sub 2} catalysts were post decorated by amorphous SiO{sub 2} to suppress the agglomeration of gold particles. Even after being aged in O{sub 2}-He at 700 C, the SiO{sub 2}-decorated Au/TiO{sub 2} was still active for CO oxidation at ambient temperature.

  6. Factors affecting the long-term stability of mesoporous nickel-based catalysts in combined steam and dry reforming of methane

    OpenAIRE

    Jabbour, K.; El Hassan, N.; Davidson, A.; Casale, S.; Massiani, Pascale

    2016-01-01

    International audience; An ordered mesoporous " one-pot " nickel-alumina catalyst (5 wt% Ni) was synthesized using the evaporation-induced self-assembly method. Compared to an impregnated and to a non-porous catalysts, the ordered "one-pot" Ni-alumina sample displayed, after in-situ reduction, the highest and the most stable catalytic performances along 40h of run at 800°C in combined steam and dry reforming of methane, with conversion and selectivity values close to the thermodynamic expecte...

  7. Highly Active Au/δ-MoC and Cu/δ-MoC Catalysts for the Conversion of CO2: The Metal/C Ratio as a Key Factor Defining Activity, Selectivity, and Stability.

    Science.gov (United States)

    Posada-Pérez, Sergio; Ramírez, Pedro J; Evans, Jaime; Viñes, Francesc; Liu, Ping; Illas, Francesc; Rodriguez, José A

    2016-07-01

    The ever growing increase of CO2 concentration in the atmosphere is one of the main causes of global warming. Thus, CO2 activation and conversion toward valuable added compounds is a major scientific challenge. A new set of Au/δ-MoC and Cu/δ-MoC catalysts exhibits high activity, selectivity, and stability for the reduction of CO2 to CO with some subsequent selective hydrogenation toward methanol. Sophisticated experiments under controlled conditions and calculations based on density functional theory have been used to study the unique behavior of these systems. A detailed comparison of the behavior of Au/β-Mo2C and Au/δ-MoC catalysts provides evidence of the impact of the metal/carbon ratio in the carbide on the performance of the catalysts. The present results show that this ratio governs the chemical behavior of the carbide and the properties of the admetal, up to the point of being able to switch the rate and mechanism of the process for CO2 conversion. A control of the metal/carbon ratio paves the road for an efficient reutilization of this environmental harmful greenhouse gas.

  8. Enhancing the stability of copper chromite catalysts for the selective hydrogenation of furfural with ALD overcoating (II) – Comparison between TiO2 and Al2O3 overcoatings

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongbo; Canlas, Christian; Kropf, A. Jeremy; Elam, Jeffrey W.; Dumesic, James A; Marshall, Christopher L.

    2015-01-01

    TiO2 atomic layer deposition (ALD) overcoatings were applied to copper chromite catalysts to increase the stability for 2-furfuraldehyde (“furfural”) hydrogenation. After overcoating, about 75% activity was preserved compared to neat copper chromite: much higher activity than an alumina ALD overcoated catalyst with a similar number of ALD cycles. The effects of ALD TiO2 on the active Cu nanoparticles were studied extensively using both in-situ TPR/isothermal-oxidation and in-situ furfural hydrogenation via Cu XAFS. The redox properties of Cu were modified only slightly by the TiO2 ALD overcoat. However, a subtle electronic interaction was observed between the TiO2 ALD layers and the Cu nanoparticles. With calcination at 500 °C the interaction between the TiO2 overcoat and the underlying catalyst is strong enough to inhibit migration and site blocking by chromite, but is sufficiently weaker than the interaction between the Al2O3 overcoat and copper chromite that it does not strongly inhibit the catalytic activity of the copper nanoparticles.

  9. Development and Commercial Application of Third Generation Resid Hydrotreating Catalysts

    Institute of Scientific and Technical Information of China (English)

    Hu Dawei; Yang Qinghe; Dai Lishun; Zhao Xinqiang

    2013-01-01

    Based on the mechanism of resid hydrotreating reaction by coordinating the catalyst activity and stability, the diffusion mechanism and catalyst reactivity, the cost and catalyst performance, and the production and application re-quirements, the third-generation series catalysts for residue hydrotreating have been developed by Research Institute of Petroleum Processing, SINOPEC. The new series RHT catalysts possess higher activity for HDS, HDM and HDCCR per-formance as well as longer run length. The commercial results for application of these catalysts have demonstrated that the new catalyst system performs better than the reference ones.

  10. Catalyst mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Masel, Richard I.; Rosen, Brian A.

    2017-02-14

    Catalysts that include at least one catalytically active element and one helper catalyst can be used to increase the rate or lower the overpotential of chemical reactions. The helper catalyst can simultaneously act as a director molecule, suppressing undesired reactions and thus increasing selectivity toward the desired reaction. These catalysts can be useful for a variety of chemical reactions including, in particular, the electrochemical conversion of CO.sub.2 or formic acid. The catalysts can also suppress H.sub.2 evolution, permitting electrochemical cell operation at potentials below RHE. Chemical processes and devices using the catalysts are also disclosed, including processes to produce CO, OH.sup.-, HCO.sup.-, H.sub.2CO, (HCO.sub.2).sup.-, H.sub.2CO.sub.2, CH.sub.3OH, CH.sub.4, C.sub.2H.sub.4, CH.sub.3CH.sub.2OH, CH.sub.3COO.sup.-, CH.sub.3COOH, C.sub.2H.sub.6, O.sub.2, H.sub.2, (COOH).sub.2, or (COO.sup.-).sub.2, and a specific device, namely, a CO.sub.2 sensor.

  11. Effects of Alkali and Alkaline Earth Cocations on the Activity and Hydrothermal Stability of Cu/SSZ-13 NH3-SCR Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Wang, Yilin; Washton, Nancy M.; Kollar, Marton; Szanyi, Janos; Peden, Charles HF

    2015-10-13

    Using a three-step aqueous solution ion-exchange method, cocation modified Cu/SSZ-13 SCR catalysts were synthesized. These catalysts, in both fresh and hydrothermally aged forms, were characterized with several methods including temperature-programmed reduction by H2 (H2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), and 27Al solid-state nuclear magnetic resonance (NMR) and diffuse reflectance Infrared Fourier Transform (DRIFT) spectroscopies. Their catalytic performance was probed using steady-state standard NH3-SCR. Characterization results indicate that cocations weaken interactions between Cu-ions and the CHA framework making them more readily reducible. By removing a portion of Brønsted acid sites, cocations also help to mitigate hydrolysis of the zeolite catalysts during hydrothermal aging as evidenced from 27Al NMR. Reaction tests show that certain cocations, especially Li+ and Na+, promote low-temperature SCR rates while others show much less pronounced effects. In terms of applications, our results indicate that introducing cocations can be a viable strategy to improve both low- and high-temperature performance of Cu/SSZ-13 SCR catalysts.

  12. Photo-oxidation catalysts

    Science.gov (United States)

    Pitts, J. Roland; Liu, Ping; Smith, R. Davis

    2009-07-14

    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  13. Effect of Pd on Cu-Zn catalysts for the hydrogenation of CO2 to methanol : stabilization of Cu metal against CO2 oxidation

    NARCIS (Netherlands)

    López Granados, M.; Melián-Cabrera, I.; Fierro, J.L.G.

    2002-01-01

    A palladium–copper–zinc catalyst (PdO : CuO : ZnO = 2 : 28 : 70), prepared by sequential precipitation of the respective cations, was tested in the hydrogenation of CO2 at high pressure (conditions: 60 bar, CO2 : H2 = 1 : 3 (molar), W/F = 0.0675 kg h/m3, 453–513 K). The methanol yield was improved o

  14. Highly dispersed metal catalyst

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Moessbauer study of function of magnesium in iron oxide catalysts

    Institute of Scientific and Technical Information of China (English)

    YangJie-Xin; MaoLian-Sheng; 等

    1997-01-01

    Moessbauer spectroscopy has been utilized for studying the action of Mg element in iron oxide catalysts used for the dehydrogenation of ethylbenzene to sytrene.The experimental results show that the presence of opportune amount of Mg can enhance the stability and dispersion of catalysts,i.e.Mg is an sueful structure promoter in this kind of catalysts.

  16. Heterogeneous Catalysts

    NARCIS (Netherlands)

    Dakka, J.; Sheldon, R.A.; Sanderson, W.A.

    1997-01-01

    Abstract of GB 2309655 (A) Heterogeneous catalysts comprising one or more metal compounds selected from the group consisting of tin, molybdenum, tungsten, zirconium and selenium compounds deposited on the surface of a silicalite are provided. Preferably Sn(IV) and/or Mo(VI) are employed. The cat

  17. A highly reactive and enhanced thermal stability nanocomposite catalyst based on Au nanoparticles assembled in the inner surface of SiO₂ hollow nanotubes.

    Science.gov (United States)

    Xiang, Sanming; Zhou, Yuming; Zhang, Yiwei; Zhang, Zewu; Sheng, Xiaoli; Zhou, Shijian; Yang, Zunbing

    2014-07-28

    A novel hollow tubular SiO2-Au catalyst with a mesoporous structure (HTMS) was successfully fabricated by a combination of the sol-gel and calcination processes. This method involves the preparation of modified MWCNTs, the sequential deposition of Au and then silica layers through the sol-gel processes, and finally the calcination at the desired temperature to remove the MWCNTs. The obtained samples were characterized by several techniques, such as N2 adsorption-desorption isotherms, transmission electron microscopy, energy-dispersive X-ray spectroscopy analysis, UV-Vis spectra, X-ray diffraction and Thermogravimetric Analysis (TGA). The results established that a different calcination temperature has an obvious influence on the morphology and structure of the final hollow tubular. When the temperature is 550 °C, the obtained materials exhibit the distinctly tubular structure because of the decomposition of MWCNTs and the preservation of hollow tubes. Furthermore, in the catalyst system, the mesoporous silica layer can act as the physical barrier to resist the agglomeration and sintering of Au nanoparticles even after being subjected to harsh treatments up to 650 °C. In our experiments, the catalytic activities of HTMS SiO2-Au were investigated by photometrically monitoring the reduction of p-nitrophenol (p-NPh) by an excess of NaBH4. It was found that the prepared HTMS SiO2-Au catalysts exhibited a high catalytic activity and this sample could be easily recycled without a decrease of the catalytic activities in the reaction.

  18. Latent catalyst; Senzaisei shokubai

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    Epoxy resin, an important function material to support such main industries as electric and electronic devices, automobiles, civil engineering, and building construction, is demanded of development of single liquid type resin having excellent quick hardening performance and storage stability. This requirement comes from environmental problems with an intention of saving energies and reducing resin wastes. The Company, using freely its independent phase separation technology that controls molecular structure of catalysts, developed a latent catalyst having excellent storage stability and high-temperature quick hardening performance. Its major features may be summarized as follows: (1) excellent storage stability at room temperature keeping the product stable for 2.5 months or longer (2 days in conventional products); (2) quick hardening performance hardening the resin in seven seconds at 150 degrees C (equivalent to conventional products); and (3) excellent insulation performance of hardened resin at 140 degrees C of 7 times 10 {sup 13} (ohm) (center dot) cm (2 times 10 {sup 12} (ohm) (center dot) cm in conventional products) (translated by NEDO)

  19. Study on stability of CuO/γ-Al_2O_3 catalyst in catalytic wet hydrogen peroxide oxidation%双氧水催化氧化中Cu/γ-Al_2O_3催化剂的稳定性研究

    Institute of Scientific and Technical Information of China (English)

    罗平; 范益群

    2011-01-01

    CuO/γ-Al2O3 catalysts for the H2O2 wet oxidation of phenol are prepared by impregnating process.The stability and deactivation of heterogeneous Cu/γ-Al2O3 catalysts were studied at room temperature and atmospheric pressure in the catalytic wet hydrogen peroxide oxidation(CWPO).Results showed that both the catalyst preparation conditions and the catalytic oxidation reaction conditions would affect the dissolution of the Cu2+ active component.The catalyst deactivation was related with the loss of active components and the catalyst surface coverage by the oxidation intermediates.The catalyst can be regenerated by calcination at high-temperature.%针对废水湿式双氧水催化氧化,采用浸渍法制备Cu催化剂,研究非均相Cu催化剂在常温常压湿式双氧水催化氧化中的稳定性与失活问题。研究表明,催化剂制备条件及催化氧化反应条件对催化剂中Cu2+溶出均有影响。研究同时表明,催化剂失活与活性组分流失和活性组分被有机中间产物覆盖有关,高温焙烧可对催化剂再生。

  20. Preparation of Hindered Amine Light Stabilizer UV-292 in Presence of Catalyst%催化合成受阻胺光稳定剂UV-292

    Institute of Scientific and Technical Information of China (English)

    王树清; 高崇; 王歆然

    2012-01-01

    The hindered amine light stabilizers(HALS) UV-292 is synthesized in one step through react- ing dimethyl sebacate with 1,2,2,6,6,-pentamethyl-4-piperidinol at 110-120℃ for 2.5h by using petroleum ether as solvent , tetra-tert-butyl titanate supported on granule activated carbon as catalyst. The obtained mixture is washed with water at first, then decolorized with activated carbon and finally with solvent to give HALS UV-292. Contents of 1-methyl-8(1,2,2,6,6- pentamethyl-4-piperidinyl)sebacate(single ester) and bis (1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate (two ester) in products can reach 15-30% (mass fraction)and 65-80% respectively,The yield of HALS UV-292 can reach over 97%,purity of the stearate 2,2,6,6-tetram- ethyl-4-piperidinyl ester (single ester and two ester) is over 96%~The optimal technological conditions were given as follows:reaction time 2.5 h,n (dimethyl sebacate):n (1,2,2,6,6,-pentamethyl-4-piperidinol) equal to 0.1:0.165.the amounts of catalysts is 1.0 g,the amounts of solvent is 40 g(when dimethyl sebacate is 0.1 tool). The catalyst could be used for times without any treatments.%以石油醚为溶剂,颗粒状活性炭负载四丁基钛酸酯为催化剂,-定比例的癸二酸二甲酯和1.2.2.6,6-五甲基-4-羟基哌啶在110~120qC下缩合反应2~5h。然后水洗、活性炭脱色、脱溶齐4等后处理操作。-步合成了产物受阻胺光稳定剂(HALS)UV-292,其中1-甲基-8-(1,2,2,6.6-五甲基-4-哌啶)癸二酸酯(单酯)质量分数为15%~30%和双(1,2,2,6,6-五甲基-4-哌啶基1癸二酸酯(双酯1质量分数为65%~80%),收率超过97%.纯度不低于96%。得到了优化的工艺条件:反应时间为2.5h,在癸二酸二甲酯为0.1IYIOl的情况下,n(癸二酸二甲酯):n(1。2,2,6,6-五甲基-4-羟基哌啶)为0.1:0.165,催化剂用量为1.0g、溶剂的用量为40g。

  1. Catalyst Architecture

    DEFF Research Database (Denmark)

    Kiib, Hans; Marling, Gitte; Hansen, Peter Mandal

    2014-01-01

    of programs, have a role in mediating positive social and/or cultural development. In this sense, we talk about architecture as a catalyst for: sustainable adaptation of the city’s infrastructure appropriate renovation of dilapidated urban districts strengthening of social cohesiveness in the city development...... meaningful for everyone. The exhibited works are designed by SANAA, Diller Scofidio + Renfro, James Corner Field Operation, JBMC Arquitetura e Urbanismo, Atelier Bow-Wow, Ateliers Jean Nouvel, COBE, Transform, BIG, Topotek1, Superflex, and by visual artist Jane Maria Petersen....

  2. 通过Au修饰提高质子交换膜燃料电池PtCo合金催化剂稳定性%Improved Stability of PtCo Alloy Catalysts for Proton Exchange Membrane Fuel Cells by Gold Decoration

    Institute of Scientific and Technical Information of China (English)

    陈磊; 齐意; 木士春

    2015-01-01

    目的:解决质子交换膜燃料电池贵金属催化剂利用率低、电化学稳定性差的问题,从而堆动其产业化进程。方法通过湿化学共沉积法获得低Pt特征的PtCo合金催化剂,采用欠电位沉积方法制备Au修饰的PtCo合金催化剂,应用原子吸收光谱和电化学循环伏安加速测试技术研究Au修饰PtCo合金催化剂的电化学稳定性。结果成功制备了Au修饰的PtCo合金催化剂。 Au修饰后,PtCo合金催化剂的氧还原反应性能几乎没有改变,但Co的溶蚀率得到降低,而且电化学稳定性也得到提高。结论通过采用Au等具有高电化学腐蚀电位的金属修饰Pt合金催化剂,以提高催化剂电化学稳定性的研究思路是可行的。%ABSTRACT:Objective To facilitate the commercialization of proton exchange membrane fuel cells by revolving the key issues in-cluding low utilization and deteriorated stability of noble metal catalysts. Methods After preparation of PtCo alloy catalysts with low Pt loading by a chemical co-deposition method, the gold decorated PtCo alloy catalyst was prepared in terms of an under-potential-deposition method, and then the electrochemical stability of the gold-decorated PtCo alloy catalyst was characterized by atomic ab-sorption spectroscopy and electrochemical accelerated test technique. Results Au-decorated PtCo alloy catalyst was successfully prepared. After decoration of gold, the oxygen reduction reaction activity of PtCo alloy catalysts remained unchanged, and the ero-sion rate of Co element for PtCo alloy catalysts in electrolyte solutions decreased with an improved electrochemical stability. Con-clusion It was feasible to improve the stability of PtCo alloy catalysts by decoration with metals possessing a high corrosion potential such as Au.

  3. Preservation of Fe complexes into layered double hydroxides improves the efficiency and the chemical stability of Fe complexes used as heterogeneous photo-Fenton catalysts

    Science.gov (United States)

    Huang, Zhujian; Wu, Pingxiao; Gong, Beini; Lu, Yonghong; Zhu, Nengwu; Hu, Zhixian

    2013-12-01

    Fe complexes ([Fe(Ox)3]3- and [Fe(Cit)2]3-) have been heterogenized through preservation into MgAl-layered double hydroxides (LDHs). The SEM images and N2 adsorption-desorption isotherm showed that the obtained products were mesoporous materials and the specific surface area of LDHs/Fe-complex composites were obviously greater than pristine LDHs, which is beneficial for the adsorption of organic pollutants. Measurement of adsorptive and heterogeneous photo-Fenton degradation of methylene blue (MB) suggested that the LDHs/Fe-complex composites had an excellent adsorption capacity at different pHs and the adsorption isotherm modeled well with the Langmuir equation. The enhancement of adsorption capacity may be attributed to the external hydroxyl groups of LDHs. MB was enriched on the surface of LDHs/Fe-complex composites, which favors MB degradation in situ. The obtained composites displayed an high photocatalytic activity in a pH range from 4.0 to 6.0 with dissolved Fe cation at a low concentration. Therefore, Fe complexes intercalated into LDHs can be an effective heterogeneous Fenton catalyst for oxidation of organic pollutants in a relatively wide pH range.

  4. Structural, morphological and surface chemical features of Al{sub 2}O{sub 3} catalyst supports stabilized with CeO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Morterra, C.; Magnacca, G.; Bolis, V.; Cerrato, G.; Baricco, M. [Dept. of Inorganic, Physical, and Materials Chemistry. Turin Univ. (Italy); Giachello, A.; Fucale, M. [Fiat Centro Richerche, Orbassano (Italy)

    1995-12-31

    Two families of CeO{sub 2}/Al{sub 2}O{sub 3} (ACE) catalyst supports, containing 3 and 20 % wt CeO{sub 2} respectively, have been examined and compared with the pure oxides CeO{sub 2} and (transition-phase) Al{sub 2}O{sub 3}. Structural data indicate that, also in the presence of CeO{sub 2}, the Al{sub 2}O{sub 3} support undergoes all phase transitions at the usual temperatures. Electron micrographs show that particles morphology and crystals size are mainly imposed by the Al{sub 2}O{sub 3} support. The porosimetric texture indicates a more pronounced meso-porosity in the ACE systems than in pure Al{sub 2}O{sub 3}, especially in the case of low CeO{sub 2} loadings. FTIR spectra and volumetric/calorimetric data of the adsorption of CO at {approx}300 K show that the surface Lewis acidity of aluminas is severely modified by the presence of CeO{sub 2}: the overall CO uptake is increased, there is the formation of one additional family of Lewis acid sites (Ce{sup 4+} ions), and the presence of CeO{sub 2} either leaves unchanged or increases the concentration of the strongest Lewis centres of (transition-phase) aluminas (Al{sup 3+} in tetrahedral coordination). 5 figs., 1 tab., 8 refs.

  5. Towards the Rational Design of Nanoparticle Catalysts

    Science.gov (United States)

    Dash, Priyabrat

    This research is focused on development of routes towards the rational design of nanoparticle catalysts. Primarily, it is focused on two main projects; (1) the use of imidazolium-based ionic liquids (ILs) as greener media for the design of quasi-homogeneous nanoparticle catalysts and (2) the rational design of heterogeneous-supported nanoparticle catalysts from structured nanoparticle precursors. Each project has different studies associated with the main objective of the design of nanoparticle catalysts. In the first project, imidazolium-based ionic liquids have been used for the synthesis of nanoparticle catalysts. In particular, studies on recyclability, reuse, mode-of-stability, and long-term stability of these ionic-liquid supported nanoparticle catalysts have been done; all of which are important factors in determining the overall "greenness" of such synthetic routes. Three papers have been published/submitted for this project. In the first publication, highly stable polymer-stabilized Au, Pd and bimetallic Au-Pd nanoparticle catalysts have been synthesized in imidazolium-based 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) ionic liquid (Journal of Molecular Catalysis A: Chemical, 2008, 286, 114). The resulting nanoparticles were found to be effective and selective quasi-homogeneous catalysts towards a wide-range of hydrogenation reactions and the catalyst solution was reused for further catalytic reactions with minimal loss in activity. The synthesis of very pure and clean ILs has allowed a platform to study the effects of impurities in the imidazolium ILs on nanoparticle stability. In a later study, a new mode of stabilization was postulated where the presence of low amounts of 1-methylimidazole has substantial effects on the resulting stability of Au and Pd-Au nanoparticles in these ILs (Chemical Communications, 2009, 812). In further continuation of this study, a comparative study involving four stabilization protocols for nanoparticle

  6. Electrochemical catalyst recovery method

    Science.gov (United States)

    Silva, Laura J.; Bray, Lane A.

    1995-01-01

    A method of recovering catalyst material from latent catalyst material solids includes: a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications.

  7. Thermal behaviors of deactivation catalysts for synthesizing 2, 3, 5-trimethylhydroquinone

    Institute of Scientific and Technical Information of China (English)

    QIAN Dong; SHI Ai-hua; CHEN Qi-yuan; LIU Zhi-jian

    2005-01-01

    The thermal behaviors of the deposits on supported noble metal catalysts for synthesizing 2, 3, 5-trimethylhydroquinone by DSC were studied. The results show that the supported Pd catalysts have two exothermic peaks at around 312 ℃ and 435 ℃ in the DSC thermograms, respectively, while the supported Pt catalysts have one exothermic peak at approximately 345 ℃. Therefore, it is supposed that the adsorptive states of deposits on supported Pt catalysts and supported Pd catalysts are different, which may be one reason leading to the stability difference between supported Pt catalysts and supported Pd catalysts.

  8. Propene metathesis over silica-supported tungsten oxide catalyst-catalyst induction mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Basrur, A.G.; Patwardhan, S.R.; Vyas, S.N. (Indian Inst. of Tech., Bombay (India))

    1991-01-01

    The propene metathesis reaction was studied from the point of view of elucidating the mechanism of catalyst induction and establishing conditions for maximum activity. Instrumental techniques such as ESR, IR, and TPD were used to study the various aspects. During catalyst induction, trace quantities of acetone and acetaldehyde were detected in the product stream, indicating that lattice oxygen from tungsten oxide might be responsible for these products. Induction appeared to proceed via two steps since pretreatment of the catalyst with nitrogen and hydrogen yielded a decreased amount of acetone in the latter case whereas acetaldehyde remained unaffected. ESR studies indicated some interaction between tungsten oxide and silica at the catalyst preparatory stage as well as stabilization of reduced tungsten species on the catalyst after its use and regeneration. Catalyst activity appeared to depend on conditions of pretreatment. Change in nitrogen pretreatment temperature from 500 to 600{sup o}C resulted in transition from strong to negligible external mass transfer behavior of the catalyst. TPD studies in this context showed possible loss of lattice oxygen from tungsten oxide under the above-mentioned conditions of catalyst pretreatment. ESR studies indicated the reduction of WO{sub 3} to a nonstoichiometric oxidation state. Hence catalytic activity appears to be related to the nonstoichiometric state of tungsten oxide, which may be WO{sub 2.9} (as deduced from the blue-violet color of the used catalyst).

  9. Phosphine-Free EWG-Activated Ruthenium Olefin Metathesis Catalysts

    Science.gov (United States)

    Grela, Karol; Szadkowska, Anna; Michrowska, Anna; Bieniek, Michal; Sashuk, Volodymyr

    Hoveyda-Grubbs catalyst has been successfully fine-tuned by us in order to increase its activity and applicability by the introduction of electron-withdrawing groups (EWGs) to diminish donor properties of the oxygen atom. As a result, the stable and easily accessible nitro-substituted Hoveyda-Grubbs catalyst has found a number of successful applications in various research and industrial laboratories. Some other EWG-activated Hoveyda-type catalysts are commercially available. The results described herewith demonstrate that the activity of ruthenium (Ru) metathesis catalysts can be enhanced by introduction of EWGs without detriment to catalysts stability. Equally noteworthy is the observation that different Ru catalysts turned out to be optimal for different applications. This shows that no single catalyst outperforms all others in all possible applications.

  10. Foundation Flash Catalyst

    CERN Document Server

    Goralski, Greg

    2010-01-01

    This book offers an introduction to Flash Catalyst for designers with intermediate to advanced skills. It discusses where Catalyst sits within the production process and how it communicates with other programs. It covers all of the features of the Flash Catalyst workspace, teaching you how to create designs from scratch, how to build application designs and add functionality, and how to master the Catalyst/Flex workflow. * Introduces Flash Catalyst * Focuses on production process * Covers the interrelation between Flash Catalyst and Photoshop/Illustrator/Flex/Flash What you'll learn Starting f

  11. Catalyst Deactivation and Regeneration in Low Temperature Ethanol Steam Reforming with Rh/CeO2-ZrO2 Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Roh, Hyun-Seog; Platon, Alex; Wang, Yong; King, David L.

    2006-08-01

    Rh/CeO2-ZrO2 catalysts with various CeO2/ZrO2 ratios have been applied to H2 production from ethanol steam reforming at low temperatures. The catalysts all deactivated with time on stream (TOS) at 350 C. The addition of 0.5% K has a beneficial effect on catalyst stability, while 5% K has a negative effect on catalytic activity. The catalyst could be regenerated considerably even at ambient temperature and could recover its initial activity after regeneration above 200 C with 1% O2. The results are most consistent with catalyst deactivation due to carbonaceous deposition on the catalyst.

  12. Study and Pilot Scale Development of Catalyst for Ethylebenzene Synthesis Through Transalkylation of Benzene and Polyethylbenzene

    Institute of Scientific and Technical Information of China (English)

    Wang Jin; Zhang Fengmei; Li Minglin; Hao Xiaoming; Shu Xingtian; He Mingyuan

    2002-01-01

    This paper refers to the results of study and development of benzene and polyethylbenzene transalkylation catalyst (type AEB-1) for synthesis of ethylbenzene. The effect of reaction conditions on the reaction performance of the catalyst was investigated in the pressurized microreactor CDS-900. A transalkylation catalyst with high activity, good selectivity and stability was developed following a 2000-hour test on the activity and stability of the catalyst. The preparation of this catalyst was implemented in pilot scale and this catalyst was tested for activity and stability in a 150 t/a pilot unit for production of ethylbenzene. The test results have shown that this transalkylation catalyst has excellent activity, selectivity and stability. The operation of pilot test unit ran smoothly and the process scheme is viable.

  13. Catalysts for complete oxidation of gaseous fuels

    Energy Technology Data Exchange (ETDEWEB)

    Neyestanaki, A.K.

    1995-12-31

    This thesis presents a study on the complete oxidation of propane, natural gas and the conversion of car exhaust gases over two types of catalysts: (a) knitted silica-fibre supported catalysts and (b) metal-modified ZSM zeolite catalysts. A hybrid textile made up of an organic-inorganic hybrid fibre containing 70 % cellulose and 30 % silicic acid was used as the raw material for preparation of the fibre support for combustion catalysts. The hybrid textile was burnt to obtain a knitted silica-fibre. The changes in the surface area, pore volume and the crystallinity of the obtained support were studied as a function of burning temperature. The stability of the support in steam-rich atmospheres was tested. The knitted silica-fibre obtained by burning the hybrid textile at 1223 K was found to have sufficient strength and high BET specific surface area (140 m{sub 2}/g) to be used as a catalyst support. A series of knitted silica-fibre supported metal oxides (oxides of Co, Ni, Mn, Cr and Cu) and combinations of them, platinum-activated metal oxides (Pt-Co{sub 3}O{sub 4}, Pt-NiO, Pt-MnO{sub 2} and Pt-Cr{sub 2}O{sub 3}) as well as noble metal (Pt, Pd) catalysts were prepared. The location of the metal oxides on the catalyst was studied by SEM equipped with EDXA. The metal oxide was found to be located mostly inside the pores rather than on the exterior surface of the silica-fibre. The catalysts were characterized by XRD, N{sub 2}-physisorption, O{sub 2}-TPD and the chemisorption of propane, carbon monoxide and hydrogen. The activity of the catalysts was tested in the combustion of propane, natural gas and in the conversion of automobile exhaust gases. The effect of residence time and stoichiometry on the conversion behaviour of the catalysts was studied

  14. An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes

    Directory of Open Access Journals (Sweden)

    Zaiku Xie

    2010-05-01

    Full Text Available Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT, etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts.

  15. Pilot plant evaluation of hydrotreating catalysts for heavy gas oil conversion

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Y.; Chen, S.; Chen, J. [CanmetENERGY, Natural Resources Canada (Canada)

    2011-07-01

    As world reserves of oil are depleted, most of the oil remaining is heavy and sour and improvements in the technology are thus required to process it and produce transportation fuels. In terms of catalysts, alumina supported hydrotreating catalysts are commonly used; but activated carbon (AC) could also be a catalyst support option with its high microporosity and surface area combined with its thermal stability and resistance to coke deposition. This paper aims at determining the effect of the catalyst support on heavy crude oil processing. Experiments were conducted using two AC based catalysts, an alumina supported catalyst and two hydrotreating catalysts; results were then analyzed by scanning electron microscopy and transmission electron microscope. Results demonstrated that the AC based catalysts provide a better hydrotreating performance than the other catalysts. This study finds that the use of activated carbon based catalysts can provide better heavy oil conversion than others.

  16. Nickel catalysts for internal reforming in molten carbonate fuel cells

    NARCIS (Netherlands)

    Berger, R.J.; Doesburg, E.B.M.; Ommen, van J.G.; Ross, J.R.H.

    1996-01-01

    Natural gas may be used instead of hydrogen as fuel for the molten carbonate fuel cell (MCFC) by steam reforming the natural gas inside the MCFC, using a nickel catalyst (internal reforming). The severe conditions inside the MCFC, however, require that the catalyst has a very high stability. In orde

  17. Catalyst studies on the hydrotreatment of fast pyrolysis oil

    NARCIS (Netherlands)

    Wildschut, J.; Melian-Cabrera, I.; Heeres, H. J.

    2010-01-01

    Catalytic hydrotreatment is considered an attractive technology for fast pyrolysis oil upgrading to liquid transportation fuels. We here report an experimental study to gain insights in catalyst stability when using Ru/C catalysts for the hydrotreatment of fast pyrolysis oil (350 degrees C and 200 b

  18. The key to the extraordinary thermal stability of P. furiosus holo-rubredoxin: iron binding-guided packing of a core aromatic cluster responsible for high kinetic stability of the native structure.

    Science.gov (United States)

    Prakash, Satya; Sundd, Monica; Guptasarma, Purnananda

    2014-01-01

    Pyrococcus furiosus rubredoxin (PfRd), a small, monomeric, 53 residues-long, iron-containing, electron-transfer protein of known structure is sometimes referred to as being the most structurally-stable protein known to man. Here, using a combination of mutational and spectroscopic (CD, fluorescence, and NMR) studies of differently made holo- and apo-forms of PfRd, we demonstrate that it is not the presence of iron, or even the folding of the PfRd chain into a compact well-folded structure that causes holo-PfRd to display its extraordinary thermal stability, but rather the correct iron binding-guided packing of certain residues (specifically, Trp3, Phe29, Trp36, and also Tyr10) within a tight aromatic cluster of six residues in PfRd's hydrophobic core. Binding of the iron atom appears to play a remarkable role in determining subtle details of residue packing, forcing the chain to form a hyper-thermally stable native structure which is kinetically stable enough to survive (subsequent) removal of iron. On the other hand, failure to bind iron causes the same chain to adopt an equally well-folded native-like structure which, however, has a differently-packed aromatic cluster in its core, causing it to be only as stable as any other ordinary mesophile-derived rubredoxin. Our studies demonstrate, perhaps for the very first time ever that hyperthermal stability in proteins can owe to subtle differences in residue packing vis a vis mesostable proteins, without there being any underlying differences in either amino acid sequence, or bound ligand status.

  19. A New Reaction-controlled Phase-transfer Catalyst System

    Institute of Scientific and Technical Information of China (English)

    Ming Qiang LI; Xi Gao JIAN; Gui Mei WANG; Yan YU

    2004-01-01

    A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxidant. The conversion of H2O2 was 100% and the yield of cyclohexene oxide was 87.1% based on cyclohexene. Infrared spectra showed that both fresh catalyst and the recovered catalyst do have completely same absorption peak, indicating the structure of catalyst is very stability and can be recycled.

  20. First Commercial Application of Upflow Residuum Hydrotreating Catalyst

    Institute of Scientific and Technical Information of China (English)

    Mu Haitao; Sun Zhenguang

    2004-01-01

    This article refers to the first commercial application of upflow residuum hydrotreating serial catalyst, developed by Fushun Research Institute of Petroleum and Petrochemicals (FRIPP), in the residuum hydrotreating unit at Shengli refinery of Qilu Petrochemical Company. This catalyst features large pore volume and large pore diameter. The production practice for more than one year has revealed that the domestic upflow residuum hydrotreating catalyst has shown good performance and stability over the whole period of operation despite its high activity at the start of run, and has basically reached the level of similar imported catalyst.

  1. Effect of La on Partial Oxidation of Ethanol to Hydrogen over Ni/Fe Catalysts

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The partial oxidation of ethanol to hydrogen was investigated over Ni/Fe/La catalysts prepared by the co-precipitation method. The effects of introduction of La promoter and the reaction temperature on the catalytic performance were studied. It was found that the introduction of La into Ni/Fe catalysts is helpful to increase the selectivity to hydrogen and the stability of the catalysts. The results of XRD and XPS characterization show that the structure of the catalyst was changed during the reaction. The existence of LaFeO3 species is possibly the main reason of the increase of the catalyst stability.

  2. ‘Indicator’ carbonaceous phyllite/graphitic schist in the Archean Kundarkocha gold deposit, Singhbhum orogenic belt, eastern India: Implications for gold mineralization vis-a-vis organic matter

    Indian Academy of Sciences (India)

    P R Sahoo; A S Venkatesh

    2014-10-01

    Carbonaceous rocks in the form of graphitic schist and carbonaceous phyllite are the major host rocks of the gold mineralization in Kundarkocha gold deposit of the Precambrian Singhbhum orogenic belt in eastern India. The detection of organic carbon, essentially in the carbonaceous phyllite and graphitized schist within the Precambrian terrain, is noted from this deposit. A very close relationship exists between gold mineralization and ubiquitous carbonaceous rocks containing organic carbon that seems to play a vital role in the deposition of gold in a Precambrian terrain in India and important metallogenetic implications for such type of deposits elsewhere. However, the role played by organic matter in a Precambrian gold deposit is debatable and the mechanism of precipitation of gold and other metals by organic carbon has been reported elsewhere. Fourier transform infrared spectroscopy (FTIR) results and total organic carbon (TOC) values suggest that at least part of the organic material acted as a possible source for the reduction that played a significant role in the precipitation of gold. Lithological, electron probe analysis (EPMA), fluid inclusions associated with gold mineralization, Total Carbon (TC), TOC and FTIR results suggest that the gold mineralization is spatially and genetically associated with graphitic schist, carbonaceous phyllite/shale that are constituted of immature organic carbon or kerogen. Nano-scale gold inclusions along with free milling gold are associated with sulfide mineral phases present within the carbonaceous host rocks as well as in mineralized quartz-carbonate veins. Deposition of gold could have been facilitated due to the organic redox reactions and the graphitic schist and carbonaceous phyllite zone may be considered as the indicator zone.

  3. Reflection on the efficiency criteria for a long duration disposal with respect to temporary abandonment situations; Reflexion sur les criteres de performance d'un entreposage de longue duree (ELD) vis-a-vis des situations de delaissement temporaire

    Energy Technology Data Exchange (ETDEWEB)

    Heriard-Dubreuil, G.; Gadbois, S. [Mutadis, 75 - Paris (France); Chieber, C.; Schneider, Th. [Centre d' Etude sur l' Evaluation de la Protection dans le Domaine Nucleaire, 92 - Fontenay aux Roses (France)

    2002-08-15

    A study carried out by Mutadis and CEPN, on request of the CEA, aimed at supplying some elements allowing to elaborate some performance criteria for a long-term management system in front of situations of temporary abandonment of radioactive waste disposal facilities. The first part of the study has been the identification of case studies illustrating situations of loss of maintenance or temporary abandonment. The second phase has been the selection and analysis of 4 case studies (the ancient underground cavities in Ile-de-France, the regulation relative to new underground quarries, the abandoned mines in Loraine basin, and Unesco's approach for the protection of mankind world patrimony). These cases have been analysed with respect to various aspects: actors involved, construction management and memory preservation, liabilities in time and space, prevention means, scheduling, and resumption strategies. The concepts of abandonment, scheduling and resumption have been precised and analysed in a third part according to the case studies. Three goals - avoiding abandonment, encouraging scheduling and resumption - and eight characteristics are drawn from this analysis, which are indicators of the robustness of the system implemented to fulfill these 3 goals. These characteristics appear as strongly interdependent. (J.S.)

  4. Production of 2-hydroxy-4-methoxybenzaldehyde in roots of tissue culture raised and acclimatized plants of Decalepis hamiltonii Wight & Arn., an endangered shrub endemic to Southern India and evaluation of its performance vis-a-vis plants from natural habitat.

    Science.gov (United States)

    Giridhar, P; Rajasekaran, T; Nagarajan, S; Ravishankar, G A

    2004-01-01

    Axillary buds obtained from field grown plants of D. hamiltonii were used to initiate multiple shoots on Murashige and Skoog's medium (MS) supplemented with 2 mg L(-1) 6-benzyl aminopurine (BA) and 0.5 mg L(-1) indole-3-acetic acid (IAA). Profuse rooting was achieved when the actively growing shoots were cultured on MS medium supplemented with 1.0 mg l(-1) indole-3-butyric acid (IBA). Regenerated plants were grown successfully in the plains, in contrast to wild growth in high altitudes and rocky crevices of hilly regions. Roots of different sizes from one-year-old tissue culture raised field grown plants had the same profile of 2-hydroxy-4-methoxybenzaldehyde as that of wild plants. A maximum of 0.14% and 0.12% 2-hydroxy-4-methoxybenzaldehyde was produced in roots of one year old tissue culture derived plants and greenhouse grown plants respectively.

  5. Lacunary Keggin Polyoxotungstate as Reaction-controlled Phasetransfer Catalyst for Catalytic Epoxidation of Olefins

    Institute of Scientific and Technical Information of China (English)

    LI,Ming-Qiang(李明强); JIAN,Xi-Gao(蹇锡高); YANG,Yong-Qiang(杨永强)

    2004-01-01

    A new reaction-controlled phase-transfer catalyst system, lacunary Keggin polyoxotungstate [C7H7N(CH3)3]9PW9O34 has been synthesized and used for catalytic epoxidation of olefins with H2O2 as the oxidant.Infrared spectra were used to analyze the behavior of the phase transfer of catalyst. In this system, the catalyst not only can act as homogeneous catalyst but also as heterogeneous catalyst to be easily filtered and reused. The epoxidation reaction is clean and exhibits high conversion and selectivity as well as excellent catalyst stability.

  6. Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

    Directory of Open Access Journals (Sweden)

    Samira Bagheri

    2014-01-01

    Full Text Available 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.

  7. 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

  8. Collaboration between primitive cell membranes and soluble catalysts.

    Science.gov (United States)

    Adamala, Katarzyna P; Engelhart, Aaron E; Szostak, Jack W

    2016-03-21

    One widely held model of early life suggests primitive cells consisted of simple RNA-based catalysts within lipid compartments. One possible selective advantage conferred by an encapsulated catalyst is stabilization of the compartment, resulting from catalyst-promoted synthesis of key membrane components. Here we show model protocell vesicles containing an encapsulated enzyme that promotes the synthesis of simple fatty acid derivatives become stabilized to Mg(2+), which is required for ribozyme activity and RNA synthesis. Thus, protocells capable of such catalytic transformations would have enjoyed a selective advantage over other protocells in high Mg(2+) environments. The synthetic transformation requires both the catalyst and vesicles that solubilize the water-insoluble precursor lipid. We suggest that similar modified lipids could have played a key role in early life, and that primitive lipid membranes and encapsulated catalysts, such as ribozymes, may have acted in conjunction with each other, enabling otherwise-impossible chemical transformations within primordial cells.

  9. Study on catalyst for the sodium borohydride hydrolysis

    Institute of Scientific and Technical Information of China (English)

    WANG; Shu-ming; JIANG; Li-jun; LIU; Xiao-peng; WANG; Shu-mao

    2005-01-01

    The effects of preparation methods, supports and active parts on both the activation and stability of catalyst for the sodium borohydride hydrolysis were studied, and the results showed that the activation and stability of the catalysts prepared by impregnation method is better than that prepared by chemical plating. Compared to exchange resin and activated alumina, the diatomite with high BET surface area and porosity is more suitable for as the catalyst's support. Co is much better than Ni when used as catalytic active part.

  10. Surface Chemistry and Properties of Oxides as Catalyst Supports

    Energy Technology Data Exchange (ETDEWEB)

    DeBusk, Melanie Moses [ORNL; Narula, Chaitanya Kumar [ORNL; Contescu, Cristian I [ORNL

    2015-01-01

    Heterogeneous catalysis relies on metal-oxides as supports for the catalysts. Catalyst supports are an indispensable component of most heterogeneous catalysts, but the role of the support is often minimized in light of the one played by the catalytically active species it supports. The active species of supported catalysts are located on the surface of the support where their contact with liquid or gas phase reactants will be greatest. Considering that support plays a major role in distribution and stability of active species, the absorption and retention of reactive species, and in some cases in catalytic reaction, the properties and chemistry that can occur at the surface of an oxide support are important for understanding their impact on the activity of a supported catalyst. This chapter examines this rich surface chemistry and properties of oxides used as catalyst supports, and explores the influence of their interaction with the active species.

  11. New catalysts for exhaust gas cleaning

    Energy Technology Data Exchange (ETDEWEB)

    Haerkoenen, M. [Kemira Metalkat Oy, Oulu (Finland)

    1996-12-31

    Major challenge for future catalyst systems was to develop thermally more stable washcoats for close coupled operating conditions and for engines operating under high speed and load conditions. To design these future emission systems extensive research and development was undertaken to develop methods to disperse and stabilize the key catalytic materials for operation at much higher temperatures. Second priority was to design catalysts that are more effective under low temperature exhaust conditions and have improved oxygen storage properties in the washcoats. Incorporating new materials and modified preparation technology a new generation of metallic catalyst formulations emerged, those being trimetallic K6 (Pt:Pd:Rh and bimetallic K7) (Pd+Pd:Rh). The target was to combine the best property of Pt:Rh (good NO{sub x} reduction) with that of the good HC oxidation activity of Pd and to ensure that precious metal/support interactions were positively maintained. Both K6 and K7 concepts contain special catalyst structures with optimized washcoat performance which can be brick converter configuration. Improvement in light-off, thermal stability and transient performance with these new catalyst formulations have clearly been shown in both laboratory and vehicle testing. (author) (20 refs.)

  12. Ni Catalysts Supported on Modified Alumina for Diesel Steam Reforming

    Directory of Open Access Journals (Sweden)

    Antonios Tribalis

    2016-01-01

    Full Text Available Nickel catalysts are the most popular for steam reforming, however, they have a number of drawbacks, such as high propensity toward coke formation and intolerance to sulfur. In an effort to improve their behavior, a series of Ni-catalysts supported on pure and La-, Ba-, (La+Ba- and Ce-doped γ-alumina has been prepared. The doped supports and the catalysts have been extensively characterized. The catalysts performance was evaluated for steam reforming of n-hexadecane pure or doped with dibenzothiophene as surrogate for sulphur-free or commercial diesel, respectively. The undoped catalyst lost its activity after 1.5 h on stream. Doping of the support with La improved the initial catalyst activity. However, this catalyst was completely deactivated after 2 h on stream. Doping with Ba or La+Ba improved the stability of the catalysts. This improvement is attributed to the increase of the dispersion of the nickel phase, the decrease of the support acidity and the increase of Ni-phase reducibility. The best catalyst of the series doped with La+Ba proved to be sulphur tolerant and stable for more than 160 h on stream. Doping of the support with Ce also improved the catalytic performance of the corresponding catalyst, but more work is needed to explain this behavior.

  13. An investigation of the activity and stability of Pd and Pd-Zr modified Y-zeolite catalysts for the removal of PAH, CO, CH{sup 4} and NO{sup x} emissions

    Energy Technology Data Exchange (ETDEWEB)

    Klingstedt, F.; Kalantar Neyestanaki, A.; Lindfors, L.-E.; Salmi, T. [Process Chemistry Group, Laboratory of Industrial Chemistry, Abo Akademi University, Biskopsg. 8, FIN-20500 Turku (Finland); Heikkila, T.; Laine, E. [Laboratory of Industrial Physics, Department of Physics, University of Turku, Vesilinnant. 5, FIN-20014 Turku (Finland)

    2003-01-30

    Pd-Y- and Pd-Zr-Y-zeolite catalysts were prepared by the ion-exchange of parent NH{sub 3}-Y-zeolite, thermally pre-treated Y-zeolite and hydrothermally pre-treated Y-zeolite. The activity of the catalysts was studied in conversion of gas mixtures simulating the flue gases from the combustion of biofuels and natural gas driven vehicles (NGVs) at temperature ranges of 120-800C. The effect of sulphur-poisoning was examined by the addition of 5ppm SO{sub 2} into the feed gas mixtures. High activity in the removal of the model pollutants was obtained over the fresh catalysts. De-activation was observed as a result of catalyst ageing in the reactants' flow (800C, 6h) or steam treatment (850C, 12vol.% H{sub 2}O, 16h). The de-activation was attributed to the de-alumination as well as to the migration of Pd{sup 2+} cations. The catalysts were characterised by XRD, SEM-EDXA, N{sub 2}-physisorption, O{sub 2}/SO{sub 2}/NH{sub 3}/naphthalene-TPD, XRF and DCP.

  14. Catalyst Alloys Processing

    Science.gov (United States)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  15. Structure-performance relations of molybdenum- and tungsten carbide catalysts for deoxygenation

    NARCIS (Netherlands)

    Stellwagen, D.R.; Bitter, J.H.

    2015-01-01

    This work demonstrates for the first time that carbide particle size is a critical factor for the activity and stability of carbon supported tungsten- and molybdenum carbide catalysts in (hydro-)deoxygenation reactions. The stability of the catalyst was shown to increase for larger particles due to

  16. Resin catalysts and method of preparation

    Science.gov (United States)

    Smith, L.A. Jr.

    1986-12-16

    Heat stabilized catalyst compositions are prepared from nuclear sulfonic acid, for example, macroporous crosslinked polyvinyl aromatic compounds containing sulfonic acid groups are neutralized with a metal of Al, Fe, Zn, Cu, Ni, ions or mixtures and alkali, alkaline earth metals or ammonium ions by contacting the resin containing the sulfonic acid with aqueous solutions of the metals salts and alkali, alkaline earth metal or ammonium salts. The catalysts have at least 50% of the sulfonic acid groups neutralized with metal ions and the balance of the sulfonic acid groups neutralized with alkali, alkaline earth ions or ammonium ions.

  17. Resin Catalyst Hybrids

    Institute of Scientific and Technical Information of China (English)

    S. Asaoka

    2005-01-01

    @@ 1Introduction: What are resin catalyst hybrids? There are typically two types of resin catalyst. One is acidic resin which representative is polystyrene sulfonic acid. The other is basic resin which is availed as metal complex support. The objective items of this study on resin catalyst are consisting of pellet hybrid, equilibrium hybrid and function hybrid of acid and base,as shown in Fig. 1[1-5].

  18. Tungsten Promoted Ni/Al2O3 Catalysts for Carbon Dioxide Reforming of Methane to Synthesis Gas

    Institute of Scientific and Technical Information of China (English)

    XIAO Tian-cun; Thomas Suhartanto; Andrew P. E. York; Malcolm L. H. Green

    2004-01-01

    A series of tungsten promoted alumina supported nickel catalysts has been prepared for the carbon dioxide reforming of methane to synthesis gas. The catalysts have been characterized by means of XRD, TEM,and Laser Raman spectroscopy. It is shown that the addition of tungsten to the nickel catalyst can stabilize the catalyst and increase the resistance to carbon deposition. Adding a suitable amount of tungsten can also increase the catalyst activity to be close to that of supported noble metal catalysts. The carburisation of the tungsten modified nickel catalyst decreases the catalyst activity at lower reaction temperatures(<1123K),but has no effect on the catalyst performance at higher reaction temperatures. The alumina supported nickel catalyst modified by 0. 67 % (mass fraction)WOs has the equivalent equilibrium constant of the dry reforming reaction to that of alumina supported 5% (mass fraction) Ru at 873 K, and also has a lower activation energy for dry reforming than the latter.

  19. 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.

  20. Modulation of the Reactivity, Stability and Substrate- and Enantioselectivity of an Epoxidation Catalyst by Noncovalent Dynamic Attachment of a Receptor Functionality - Aspects on the Mechanism of the Jacobsen-Katsuki Epoxidation Applied to a Supramolecular System

    DEFF Research Database (Denmark)

    Jónsson, Stefán; Odille, Fabrice G. J.; Norrby, Per-Ola;

    2006-01-01

    model of the metal-free system 4 + 5 refutes the earlier assumption that macrocycle 1 is the predominant form of catalyst 2 under the standard epoxidation reaction conditions with 2 + 3. Evidence are provided that receptor-binding substrates and nonbinding substrates, respectively, are epoxidised by two...

  1. Alloy catalyst material

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a novel alloy catalyst material for use in the synthesis of hydrogen peroxide from oxygen and hydrogen, or from oxygen and water. The present invention also relates to a cathode and an electrochemical cell comprising the novel catalyst material, and the process use...

  2. Catalyst for Ammonia Oxidation

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a bimetallic catalyst for ammonia oxidation, a method for producing a bimetallic catalyst for ammonia oxidation and a method for tuning the catalytic activity of a transition metal. By depositing an overlayer of less catalytic active metal onto a more catalytic...

  3. Reducible oxide based catalysts

    Science.gov (United States)

    Thompson, Levi T.; Kim, Chang Hwan; Bej, Shyamal K.

    2010-04-06

    A catalyst is disclosed herein. The catalyst includes a reducible oxide support and at least one noble metal fixed on the reducible oxide support. The noble metal(s) is loaded on the support at a substantially constant temperature and pH.

  4. Magnetic catalyst bodies

    NARCIS (Netherlands)

    Teunissen, Wendy; Bol, A.A.; Geus, John W.

    2001-01-01

    After a discussion about the importance of the size of the catalyst bodies with reactions in the liquid-phase with a suspended catalyst, the possibilities of magnetic separation are dealt with. Deficiencies of the usual ferromagnetic particles are the reactivity and the clustering of the particles.

  5. New Trends in Gold Catalysts

    Directory of Open Access Journals (Sweden)

    Leonarda F. Liotta

    2014-07-01

    Full Text Available Gold is an element that has fascinated mankind for millennia. The catalytic properties of gold have been a source of debate, due to its complete chemical inertness when in a bulk form, while it can oxidize CO at temperatures as low as ~200 K when in a nanocrystalline state, as discovered by Haruta in the late 1980s [1]. Since then, extensive activity in both applied and fundamental research on gold has been initiated. The importance of the catalysis by gold represents one of the fasted growing fields in science and is proven by the promising applications in several fields, such as green chemistry and environmental catalysis, in the synthesis of single-walled carbon nanotubes, as modifiers of Ni catalysts for methane steam and dry reforming reactions and in biological and electrochemistry applications. The range of reactions catalyzed by gold, as well as the suitability of different supports and the influence of the preparation conditions have been widely explored and optimized in applied research [2]. Gold catalysts appeared to be very different from the other noble metal-based catalysts, due to their marked dependence on the preparation method, which is crucial for the genesis of the catalytic activity. Several methods, including deposition-precipitation, chemical vapor deposition and cation adsorption, have been applied for the preparation of gold catalysts over reducible oxides, like TiO2. Among these methods, deposition-precipitation has been the most frequently employed method for Au loading, and it involves the use of tetrachloroauric (III acid as a precursor. On the other hand, the number of articles dealing with Au-loaded acidic supports is smaller than that on basic supports, possibly because the deposition of [AuCl4]− or [AuOHxCl4−x]− species on acidic supports is difficult, due to their very low point of zero charge. Despite this challenge, several groups have reported the use of acidic zeolites as supports for gold. Zeolites

  6. Influence of Pretreatment Conditions on Methane Aromatization Performance of Mo/HZSM-5 and Mo-Cu/HZSM-5 Catalysts

    Institute of Scientific and Technical Information of China (English)

    Yiping Zhang; Dongjie Wang; Jinhua Fei; Xiaoming Zheng

    2003-01-01

    Mo/HZSM-5 is a good catalyst for methane aromatization, and the reaction performance of Mo/HZSM-5 and Cu modified Mo/HZSM-5 catalysts under various pretreatment conditions has been studied. The results indicate that the catalyst presented a distinguished catalytic activity, benzene selectivity and a high stability when the bed temperature was raised in N2 atmosphere.

  7. X-ray characterization of platinum group metal catalysts

    Science.gov (United States)

    Peterson, Eric J.

    Platinum group metals (PGMs) are used extensively as catalysts, employed in several sectors of the world energy economy. Fuel cells employing PGM catalysts show promise as power sources in the proposed hydrogen economy, using alcohols as hydrogen storage media. Currently, the most economically important application for PGMs is for the mitigation of emissions from internal combustion engines via catalytic converters. In all applications, efficient use of these expensive metals to fabricate robust catalysts is of the utmost importance. Understanding the catalyst structure/property relationship is the key to the improvement of existing catalysts and the discovery of new catalysts. For example, catalyst particle size can have profound effects on catalyst activity, as in the case of gold nanoparticles. Catalyst particle size control and stability is also important for the efficient use of PGM metals and catalyst deactivation prevention. The challenge is to identify and characterize structural features and determine if and how these features may relate to catalytic properties. The ultimate goal is to simultaneously measure catalyst structural characteristics and catalytic properties under operando conditions, unambiguously establishing the structure/property link. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are important techniques used for the characterization of PGM catalysts. Microstructural information such as crystallite size, as small as ~ 1 nm, and microstrain can be obtained from Bragg diffraction peak shapes in X-ray diffraction patterns, and long range crystal structure information is found in the intensities and positions of these peaks. In contrast, X-ray absorption spectroscopy provides information about the chemical state and local structure of selected atoms. From the average nearest neighbor coordination numbers, crystallite sizes can also be inferred, with particularly high sensitivity in the sub-nm size range. Electron microscopy

  8. Efficient oxidation of benzyl alcohol with heteropolytungstate as reaction-controlled phase-transfer catalyst

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A series of heteropolytungstates has been synthesized and utilized as catalysts to catalyze oxidation of benzyl alcohol with aqueous hydrogen peroxide. The results indicated that three of these catalysts showed the properties of reaction-controlled phasetransfer catalysis, and they had excellent catalytic ability to the oxidation of benzyl alcohol. No other by-products were detected by gas chromatography. Once the hydrogen peroxide was consumed completely, the catalyst precipitated from solvent, and the results of the catalyst recycle showed that the catalyst had high stability.

  9. Perovskite Catalysts—A Special Issue on Versatile Oxide Catalysts

    Directory of Open Access Journals (Sweden)

    Yu-Chuan Lin

    2014-08-01

    Full Text Available Perovskite-type catalysts have been prominent oxide catalysts for many years due to attributes such as flexibility in choosing cations, significant thermal stability, and the unique nature of lattice oxygen. Nearly 90% metallic elements of the Periodic Table can be stabilized in perovskite’s crystalline framework [1]. Moreover, by following the Goldschmidt rule [2], the A- and/or B-site elements can be partially substituted, making perovskites extremely flexible in catalyst design. One successful example is the commercialization of noble metal-incorporated perovskites (e.g., LaFe0.57Co0.38Pd0.05O3 for automotive emission control used by Daihatsu Motor Co. Ltd. [3]. Thus, growing interest in, and application of perovskites in the fields of material sciences, heterogeneous catalysis, and energy storage have prompted this Special Issue on perovskite catalysts. [...

  10. 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

  11. ALKALI RESISTANT CATALYST

    DEFF Research Database (Denmark)

    2008-01-01

    The present invention concerns the selective removal of nitrogen oxides (NOx) from gasses. In particular, the invention concerns a process, a catalyst and the use of a catalyst for the selective removal of nitrogen oxides in the presence of ammonia from gases containing a significant amount...... of alkali metal and/or alkali-earth compounds which process comprises using a catalyst combined of (i) a formed porous superacidic support, said superacidic support having an Hammett acidity stronger than Ho=-12, and (ii) a metal oxide catalytic component deposited on said superacidic support selected from...

  12. Post-functionalized Hybrid Materials as Multi-site Catalysts

    OpenAIRE

    Rasero Almansa, Antonia María

    2016-01-01

    [EN] Catalysis is one of the fundamental pillars of green chemistry, which was described as the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. The design and application of new catalysts and catalytic systems lead to the dual goals of environmental protection and economic benefit. Heterogeneous catalysts are the most used in industry because they present several advantages such as easy post reaction separation, high stability...

  13. Routes for deactivation of different autothermal reforming catalysts

    Science.gov (United States)

    Pasel, Joachim; Wohlrab, Sebastian; Kreft, Stefanie; Rotov, Mikhail; Löhken, Katrin; Peters, Ralf; Stolten, Detlef

    2016-09-01

    Fuel cell systems with integrated autothermal reforming units require active and robust catalysts for H2 production. In pursuit of this, an experimental screening of catalysts utilized in the autothermal reforming of commercial diesel fuels is performed. The catalysts incorporate a monolithic cordierite substrate, an oxide support (γ-Al2O3, La-Al2O3, CeO2, Gd-CeO2, ZrO2, Y-ZrO2) and Rh as the active phase. Experiments are run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. In most cases, this provokes accelerated catalyst deactivation and permits an informative comparison of the catalysts. Fresh and aged catalysts are characterized by temperature-programmed methods, thermogravimetry and transmission electron microscopy to find correlations with catalytic activity and stability. Using this approach, routes for catalyst deactivation are identified, together with causes of different catalytic activities. Suitable reaction conditions can be derived from our results for the operation of reactors for autothermal reforming at steady-state and under transient reaction conditions, which helps improve the efficiency and the stability of fuel cell systems.

  14. Design criteria for stable Pt/C fuel cell catalysts

    Directory of Open Access Journals (Sweden)

    Josef C. Meier

    2014-01-01

    Full Text Available Platinum and Pt alloy nanoparticles supported on carbon are the state of the art electrocatalysts in proton exchange membrane fuel cells. To develop a better understanding on how material design can influence the degradation processes on the nanoscale, three specific Pt/C catalysts with different structural characteristics were investigated in depth: a conventional Pt/Vulcan catalyst with a particle size of 3–4 nm and two Pt@HGS catalysts with different particle size, 1–2 nm and 3–4 nm. Specifically, Pt@HGS corresponds to platinum nanoparticles incorporated and confined within the pore structure of the nanostructured carbon support, i.e., hollow graphitic spheres (HGS. All three materials are characterized by the same platinum loading, so that the differences in their performance can be correlated to the structural characteristics of each material. The comparison of the activity and stability behavior of the three catalysts, as obtained from thin film rotating disk electrode measurements and identical location electron microscopy, is also extended to commercial materials and used as a basis for a discussion of general fuel cell catalyst design principles. Namely, the effects of particle size, inter-particle distance, certain support characteristics and thermal treatment on the catalyst performance and in particular the catalyst stability are evaluated. Based on our results, a set of design criteria for more stable and active Pt/C and Pt-alloy/C materials is suggested.

  15. Design criteria for stable Pt/C fuel cell catalysts.

    Science.gov (United States)

    Meier, Josef C; Galeano, Carolina; Katsounaros, Ioannis; Witte, Jonathon; Bongard, Hans J; Topalov, Angel A; Baldizzone, Claudio; Mezzavilla, Stefano; Schüth, Ferdi; Mayrhofer, Karl J J

    2014-01-01

    Platinum and Pt alloy nanoparticles supported on carbon are the state of the art electrocatalysts in proton exchange membrane fuel cells. To develop a better understanding on how material design can influence the degradation processes on the nanoscale, three specific Pt/C catalysts with different structural characteristics were investigated in depth: a conventional Pt/Vulcan catalyst with a particle size of 3-4 nm and two Pt@HGS catalysts with different particle size, 1-2 nm and 3-4 nm. Specifically, Pt@HGS corresponds to platinum nanoparticles incorporated and confined within the pore structure of the nanostructured carbon support, i.e., hollow graphitic spheres (HGS). All three materials are characterized by the same platinum loading, so that the differences in their performance can be correlated to the structural characteristics of each material. The comparison of the activity and stability behavior of the three catalysts, as obtained from thin film rotating disk electrode measurements and identical location electron microscopy, is also extended to commercial materials and used as a basis for a discussion of general fuel cell catalyst design principles. Namely, the effects of particle size, inter-particle distance, certain support characteristics and thermal treatment on the catalyst performance and in particular the catalyst stability are evaluated. Based on our results, a set of design criteria for more stable and active Pt/C and Pt-alloy/C materials is suggested.

  16. Selective CO Methanation Catalysts for Fuel Processing Applications

    Energy Technology Data Exchange (ETDEWEB)

    Dagle, Robert A.; Wang, Yong; Xia, Guanguang G.; Strohm, James J.; Holladay, Jamie D.; Palo, Daniel R.

    2007-07-15

    Abstract Selective CO methanation as a strategy for CO removal in micro fuel processing applications was investigated over Ru-based catalysts. Ru loading, pretreatment and reduction conditions, and choice of support were shown to affect catalyst activity, selectivity, and stability. Even operating at a gas-hourly-space-velocity as high as 13,500 hr-1, a 3%Ru/Al2O3 catalyst was able to lower CO in a reformate to less than 100 ppm over a wide temperature range from 240oC to 285 oC, while keeping hydrogen consumption below 10%.

  17. Improved Performance of W/HZSM-5 Catalysts for Dehydroaromatization of Methane

    Institute of Scientific and Technical Information of China (English)

    Nor Aishah Saidina Amin; Kusmiyati

    2004-01-01

    The dehydroaramatization of methane over W-supported ZSM-5 with varying degrees of Li+ ion-exchanged catalysts was studied with and without oxygen at 1073 K and atmospheric pressure.Catalyst activity and stability were found to be influenced by the catalyst acidity related to Bronsted acid sites and by the presence of oxygen in the feed. The NH3-TPD and FTIR-pyridine results demonstrated that partially exchanged of H+ ions by Li+ into the W/HZSM-5 catalysts could be used to control the amount of strong acid sites on the catalyst surface. Without oxygen, the 3WHLi-Z (5:1) catalyst that has strong acid sites equal to nearly 74% of the original strong acid sites in the parent HZSM-5 exhibited the highest methane conversion and selectivity towards aromatics. However, the catalyst deactivated in a five hour period. In the presence of oxygen, the catalyst activity and stability could be improved further.The results of this study revealed that a suitable amount of strong Bronsted acid sites as well as oxygen addition in the feed increased the catalyst activity and stability. The 3WHLi-Z(5:1) catalyst exhibited improved performance in the dehydroaromatization of methane.

  18. Atomistic Processes of Catalyst Degradation

    Energy Technology Data Exchange (ETDEWEB)

    None

    2004-11-27

    The purpose of this cooperative research and development agreement (CRADA) between Sasol North America, Inc., and the oak Ridge National Laboratory (ORNL) was to improve the stability of alumina-based industrial catalysts through the combination of aberration-corrected scanning transmission electron microscopy (STEM) at ORNL and innovative sample preparation techniques at Sasol. Outstanding progress has been made in task 1, 'Atomistic processes of La stabilization'. STEM investigations provided structural information with single-atom precision, showing the lattice location of La dopant atoms, thus enabling first-principles calculations of binding energies, which were performed in collaboration with Vanderbilt University. The stabilization mechanism turns out to be entirely due to a particularly strong binding energy of the La tom to the {gamma}-alumina surface. The large size of the La atom precludes incorporation of La into the bulk alumina and also strains the surface, thus preventing any clustering of La atoms. Thus highly disperse distribution is achieved and confirmed by STEM images. la also affects relative stability of the exposed surfaces of {gamma}-alumina, making the 100 surface more stable for the doped case, unlike the 110 surface for pure {gamma}-alumina. From the first-principles calculations, they can estimate the increase in transition temperature for the 3% loading of La used commercially, and it is in excellent agreement with experiment. This task was further pursued aiming to generate useable recommendations for the optimization of the preparation techniques for La-doped aluminas. The effort was primarily concentrated on the connection between the boehmitre-{gamma}-Al{sub 2}O{sub 3} phase transition (i.e. catalyst preparation) and the resulting dispersion of La on the {gamma}-Al{sub 2}O{sub 3} surface. It was determined that the La distribution on boehmite was non-uniform and different from that on the {gamma}-Al{sub 2}O{sub 3} and thus

  19. Synthesis, characterization and hydrotreating performance of supported tungsten phosphide catalysts

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Supported tungsten phosphide catalysts were prepared by temperature-programmed reduction of their precursors (supported phospho-tungstate catalysts) in H2 and characterized by X-ray diffraction (XRD),BET,temperature-programmed desorption of ammonia (NH3-TPD) and X-ray photoelectron spectroscopy (XPS).The reduction-phosphiding processes of the precursors were investigated by thermogravimetry and differential thermal analysis (TG-DTA) and the suitable phosphiding temperatures were defined.The hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities of the catalysts were tested by using thiophene,pyridine,dibenzothiophene,carbazole and diesel oil as the feed-stock.The TiO2,γ-Al2O3 supports and the Ni,Co promoters could remarkably increase and stabilize active W species on the catalyst surface.A suitable amount of Ni (3%-5%),Co (5%-7%) and V (1%-3%) could increase dispersivity of the W species and the BET surface area of the WP/γ-Al2O3 catalyst.The WP/γ-Al2O3 catalyst possesses much higher thiophene HDS and carbazole HDN activities and the WP/TiO2 catalyst has much higher dibenzothiophene (DBT) HDS and pyridine HDN activities.The Ni,Co and V can obviously promote the HDS activity and inhibit the HDN activity of the WP/γ-Al2O3 catalyst.The G-Ni5 catalyst possesses a much higher diesel oil HDS activity than the sulphided industrial NiW/γ-Al2O3 catalyst.In general,a support or promoter in the WP/γ-Al2O3 catalyst which can increase the amount and dispersivity of the active W species can promote its HDS and HDN activities.

  20. Highly durable and active non-precious air cathode catalyst for zinc air battery

    Science.gov (United States)

    Chen, Zhu; Choi, Ja-Yeon; Wang, Haijiang; Li, Hui; Chen, Zhongwei

    The electrochemical stability of non-precious FeCo-EDA and commercial Pt/C cathode catalysts for zinc air battery have been compared using accelerated degradation test (ADT) in alkaline condition. Outstanding oxygen reduction reaction (ORR) stability of the FeCo-EDA catalyst was observed compared with the commercial Pt/C catalyst. The FeCo-EDA catalyst retained 80% of the initial mass activity for ORR whereas the commercial Pt/C catalyst retained only 32% of the initial mass activity after ADT. Additionally, the FeCo-EDA catalyst exhibited a nearly three times higher mass activity compared to that of the commercial Pt/C catalyst after ADT. Furthermore, single cell test of the FeCo-EDA and Pt/C catalysts was performed where both catalysts exhibited pseudolinear behaviour in the 12-500 mA cm -2 range. In addition, 67% higher peak power density was observed from the FeCo-EDA catalyst compared with commercial Pt/C. Based on the half cell and single cell tests the non-precious FeCo-EDA catalyst is a very promising ORR electrocatalyst for zinc air battery.

  1. Catalyst for microelectromechanical systems microreactors

    Science.gov (United States)

    Morse, Jeffrey D.; Sopchak, David A.; Upadhye, Ravindra S.; Reynolds, John G.; Satcher, Joseph H.; Gash, Alex E.

    2010-06-29

    A microreactor comprising a silicon wafer, a multiplicity of microchannels in the silicon wafer, and a catalyst coating the microchannels. In one embodiment the catalyst coating the microchannels comprises a nanostructured material. In another embodiment the catalyst coating the microchannels comprises an aerogel. In another embodiment the catalyst coating the microchannels comprises a solgel. In another embodiment the catalyst coating the microchannels comprises carbon nanotubes.

  2. 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.

  3. New Catalysts for ROMP

    Institute of Scientific and Technical Information of China (English)

    H. Berke; C. Frech; A. Lhamazares; O. Blacque; H.W. Schmalle; C. Adlhart; P. Chen

    2005-01-01

    @@ 1Introduction Ring Opening Metathesis Polymerization (ROMP) is based on the olefin metathesis reaction, which requires transition metal catalysts. Mainly molybdenum, tungsten and ruthenium based catalysts have up to now been used. The "in-between" metal rhenium was only rarely applied in olefin metathesis reactions, and not at all in ROMP processes.We have found that cationic phosphine substituted dinitrosyl rhenium complexes[1]1a and 1b effectively catalyze ROMP of norbonene, dicyclopentadiene and of cyclooctene. See Fig. 1.

  4. Catalysts, Protection Layers, and Semiconductors

    DEFF Research Database (Denmark)

    Chorkendorff, Ib

    2015-01-01

    Hydrogen is the simplest solar fuel to produce and in this presentation we shall give a short overview of the pros and cons of various tandem devices [1]. The large band gap semiconductor needs to be in front, but apart from that we can chose to have either the anode in front or back using either...... acid or alkaline conditions. Since most relevant semiconductors are very prone to corrosion the advantage of using buried junctions and using protection layers offering shall be discussed [2-4]. Next we shall discuss the availability of various catalysts for being coupled to these protections layers...... and how their stability may be evaluated [5, 6]. Examples of half-cell reaction using protection layers for both cathode and anode will be discussed though some of recent examples under both alkaline and acidic conditions. Si is a very good low band gap semiconductor and by using TiO2 as a protection...

  5. N-doped graphitic layer encased cobalt nanoparticles as efficient oxygen reduction catalysts in alkaline media

    Science.gov (United States)

    Han, Ce; Bo, Xiangjie; Zhang, Yufan; Li, Mian; Nsabimana, Anaclet; Guo, Liping

    2015-03-01

    Nitrogen doped graphitic layer encased cobalt (N-C@Co) nanoparticles, as novel non-precious-metal catalysts for the oxygen reduction reaction (ORR), were fabricated by a facile method using cyanamide and cobalt nitrate as precursors. The N-C@Co catalysts exhibited comparable catalytic performance, better stability and improved methanol tolerance towards the ORR than those of the commercial Pt/C catalyst.Nitrogen doped graphitic layer encased cobalt (N-C@Co) nanoparticles, as novel non-precious-metal catalysts for the oxygen reduction reaction (ORR), were fabricated by a facile method using cyanamide and cobalt nitrate as precursors. The N-C@Co catalysts exhibited comparable catalytic performance, better stability and improved methanol tolerance towards the ORR than those of the commercial Pt/C catalyst. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07571d

  6. 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.

  7. Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

    DEFF Research Database (Denmark)

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei

    2014-01-01

    Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low‐temperature fuel cells. A novel type of catalysts prepared by high‐pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting...... of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR......). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide‐based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts....

  8. Development of New Generation Catalysts for Selective Hydrodesulfurization of FCC Naphtha

    Institute of Scientific and Technical Information of China (English)

    Chu Yang; Li Mingfeng; Li Huifeng; Qu Jinhua; Nie Hong; Li Dadong

    2009-01-01

    The influence of active metal components of catalyst, additives and catalyst preparation method on the reactiv-ity of catalyst for selective hydrodesulfurization (HDS) of FCC naphtha was investigated, and the RSDS-21 catalyst with high HDS performance and the RSDS-22 catalyst with high selectivity were developed by RIPP. The composite loading of a new series of catalysts for selective HDS of FCC gasoline has demonstrated excellent desulfurization activity and selectivity and can under conventional hydrotreating conditions manufacture clean gasoline product meeting the national Ⅳ emission standard and the Euro Ⅴ emission standard with less loss in antiknock index. The finalized new series of FCC catalysts upon being adopted for selective HDS of FCC naphtha have good adaptability to different feedstocks along with good stability.

  9. Decoupling HZSM-5 catalyst activity from deactivation during upgrading of pyrolysis oil vapors.

    Science.gov (United States)

    Wan, Shaolong; Waters, Christopher; Stevens, Adam; Gumidyala, Abhishek; Jentoft, Rolf; Lobban, Lance; Resasco, Daniel; Mallinson, Richard; Crossley, Steven

    2015-02-01

    The independent evaluation of catalyst activity and stability during the catalytic pyrolysis of biomass is challenging because of the nature of the reaction system and rapid catalyst deactivation that force the use of excess catalyst. In this contribution we use a modified pyroprobe system in which pulses of pyrolysis vapors are converted over a series of HZSM-5 catalysts in a separate fixed-bed reactor controlled independently. Both the reactor-bed temperature and the Si/Al ratio of the zeolite are varied to evaluate catalyst activity and deactivation rates independently both on a constant surface area and constant acid site basis. Results show that there is an optimum catalyst-bed temperature for the production of aromatics, above which the production of light gases increases and that of aromatics decrease. Zeolites with lower Si/Al ratios give comparable initial rates for aromatics production, but far more rapid catalyst deactivation rates than those with higher Si/Al ratios.

  10. Polymer Electrolyte Membrane Electrolyzers Utilizing Non-precious Mo-based Hydrogen Evolution Catalysts.

    Science.gov (United States)

    Ng, Jia Wei Desmond; Hellstern, Thomas R; Kibsgaard, Jakob; Hinckley, Allison C; Benck, Jesse D; Jaramillo, Thomas F

    2015-10-26

    The development of low-cost hydrogen evolution reaction (HER) catalysts that can be readily integrated into electrolyzers is critical if H2 from renewable electricity-powered electrolysis is to compete cost effectively with steam reforming. Herein, we report three distinct earth-abundant Mo-based catalysts, namely those based on MoSx , [Mo3 S13 ](2-) nanoclusters, and sulfur-doped Mo phosphide (MoP|S), loaded onto carbon supports. The catalysts were synthesized through facile impregnation-sulfidization routes specifically designed for catalyst-device compatibility. Fundamental electrochemical studies demonstrate the excellent HER activity and stability of the Mo-sulfide based catalysts in an acidic environment, and the resulting polymer electrolyte membrane (PEM) electrolyzers that integrate these catalysts exhibit high efficiency and durability. This work is an important step towards the goal of replacing Pt with earth-abundant catalysts for the HER in commercial PEM electrolyzers.

  11. Preparation of Mesoporous Silica-Supported Palladium Catalysts for Biofuel Upgrade

    OpenAIRE

    Ling Fei; Harvind Kumar Reddy; Joshua Hill; Qianglu Lin; Bin Yuan; Yun Xu; Peter Dailey; Shuguang Deng; Hongmei Luo

    2012-01-01

    We report the preparation of two hydrocracking catalysts Pd/CoMoO4/silica and Pd/CNTs/CoMoO4/silica (CNTs, carbon nanotubes). The structure, morphologies, composition, and thermal stability of catalysts were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and thermogravimetric analysis (TGA). The catalyst activity was measured in a Parr reactor with camelina fatty acid methyl est...

  12. Strontium cobaltite oxygen sponge catalyst and methods of use

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho Nyung; Jeen, Hyoungjeen; Choi, Woo Seok; Biegalski, Michael; Folkman, Chad M.; Tung, I-Cheng; Fong, Dillon D.; Freeland, John W.; Shin, Dongwon; Ohta, Hiromichi; Chisholm, Matthew F.

    2017-01-24

    Rapid, reversible redox activity may be accomplished at significantly reduced temperatures, as low as about 200.degree. C., from epitaxially stabilized, oxygen vacancy ordered SrCoO.sub.2.5 and thermodynamically unfavorable perovskite SrCoO.sub.3-.delta.. The fast, low temperature redox activity in SrCoO.sub.3-.delta. may be attributed to a small Gibbs free energy difference between the two topotactic phases. Epitaxially stabilized thin films of strontium cobaltite provide a catalyst adapted to rapidly transition between oxidation states at substantially low temperatures. Methods of transitioning a strontium cobaltite catalyst from a first oxidation state to a second oxidation state are described.

  13. Highly selective PdCu/amorphous silica-alumina (ASA) catalysts for groundwater denitration.

    Science.gov (United States)

    Xie, Yongbing; Cao, Hongbin; Li, Yuping; Zhang, Yi; Crittenden, John C

    2011-05-01

    Catalytic nitrate reduction is a promising technology in groundwater purification. In this study, PdCu bimetallic catalysts supported on an industrial amorphous silica-alumina (ASA) were synthesized and used to simulate catalytic removal of nitrate in groundwater. The catalysts exhibited very high activity and the highest catalytic selectivity toward N₂O and N₂ was 90.2%. The optimal Pd/Cu weight ratio was four. Relatively low reduction temperature was found benefit the catalytic stability and 300 °C was the appropriate reduction temperature during catalyst preparation. With an average particle size 5.4 nm, the metal particles were very uniformly distributed on the catalyst surface prepared with the codeposition method. This kept the catalyst more stable than the PdCu/Al₂O₂ catalyst with larger metal particles. According to XRD, TEM, and XPS results, the metals maintained zero-valence but aggregated by about 2 nm during the denitration reaction, which caused gradual deactivation of the catalysts. Little leaching of Cu and Pd from the catalyst might also have a slightly negative impact to the stability of the catalysts. A simple treatment was found to redistribute the particles on the deactivated catalysts, and high catalytic activity was recovered after this process.

  14. Supported organoiridium catalysts for alkane dehydrogenation

    Science.gov (United States)

    Baker, R. Thomas; Sattelberger, Alfred P.; Li, Hongbo

    2013-09-03

    Solid supported organoiridium catalysts, a process for preparing such solid supported organoiridium catalysts, and the use of such solid supported organoiridium catalysts in dehydrogenation reactions of alkanes is provided. The catalysts can be easily recovered and recycled.

  15. 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.

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

    Science.gov (United States)

    Al-Doghachi, Faris A J; Islam, Aminul; Zainal, Zulkarnain; Saiman, Mohd Izham; Embong, Zaidi; Taufiq-Yap, Yun Hin

    2016-01-01

    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.

  17. Nafion-Teflon bimembrane-supported palladium catalysts for Suzuki coupling reactions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Nafion-Teflon bimembrane was used as an efficient support for the preparation and application of heterogeneous palladium catalysts. The supported palladium catalysts exhibit high activity and stability in the Suzuki cross-coupling of aryl bromides with arylboronic acids to afford the corresponding biaryls in good to excellent yields, and can be readily recovered and reused several times without significant loss of activity.

  18. Technology development for iron Fischer-Tropsch catalysts

    Energy Technology Data Exchange (ETDEWEB)

    O`Brien, R.J.; Raje, A.; Keogh, R.A. [and others

    1995-12-31

    The objective of this research project is to develop the technology for the production of physically robust iron-based Fischer-Tropsch catalysts that have suitable activity, selectivity and stability to be used in the slurry phase synthesis reactor development. The catalysts that are developed shall be suitable for testing in the Advanced Fuels Development Facility at LaPorte, Texas, to produce either low-or high-alpha product distributions. Previous work by the offeror has produced a catalyst formulation that is 1.5 times as active as the {open_quotes}standard-catalyst{close_quotes} developed by German workers for slurry phase synthesis. In parallel, work will be conducted to design a high-alpha iron catalyst this is suitable for slurry phase synthesis. Studies will be conducted to define the chemical phases present at various stages of the pretreatment and synthesis stages and to define the course of these changes. The oxidation/reduction cycles that are anticipated to occur in large, commercial reactors will be studied at the laboratory scale. Catalyst performance will be determined for catalysts synthesized in this program for activity, selectivity and aging characteristics.

  19. Aerogel derived catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, J. G., LLNL

    1996-12-11

    Aerogels area class of colloidal materials which have high surface areas and abundant mesoporous structure. SiO{sub 2} aerogels show unique physical, optical and structural properties. When catalytic metals are incorporated in the aerogel framework, the potential exists for new and very effective catalysts for industrial processes. Three applications of these metal-containing SiO{sub 2} aerogels as catalysts are briefly reviewed in this paper--NO{sub x} reduction, volatile organic compound destruction, and partial oxidation of methane.

  20. Olefin metathesis catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S.G.; Banks, R.L.

    1986-05-20

    A process is described for preparing a disproportionation catalyst comprising admixing a catalytically effective amount of a calcined and activated catalyst consisting essentially of at least one metal oxide selected from molybdenum oxide and tungsten oxide and a support containing a major proportion of silica or alumina with a promoting amount of a methylating agent selected from the group consisting of dimethyl sulfate, dimethylsulfoxide, trimethyloxonium tetrafluorborate, methyl iodide, and methyl bromide, and subjecting same to inert atmospheric conditions for the methylating agent to promote the activity of the calcined molybdenum and tungsten oxides for the disproportionation of olefins.

  1. Mesoporous molecular sieve catalysts

    DEFF Research Database (Denmark)

    Højholt, Karen Thrane

    be used as solid acid catalysts but can also be used as a size-selective matrix. It was shown that it is possible to encapsulate 1-2 nm sized gold nanoparticles by silicalite-1 or ZSM-5 zeolite crystals thereby forming a sintering-stable and substrate size-selective oxidation catalyst. After carrying out...... calcination experiments, both in situ and ex situ indicated that the gold nanoparticles embedded in the crystals were highly stable towards sintering. The catalytic tests proved that the embedded gold nanoparticles were active in selective aldehyde oxidation and were only accessible through the micropores...

  2. Dynamics of Catalyst Nanoparticles

    DEFF Research Database (Denmark)

    Hansen, Thomas Willum; Cavalca, Filippo; Wagner, Jakob Birkedal

    under gas exposure, dynamic phenomena such as sintering and growth can be observed with sub-Ångstrøm resolution. Metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the production of clean fuels, chemicals...... and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal deactivation, is an important mechanism for the loss of catalyst activity. In order to initiate a systematic study of the dynamics and sintering of nanoparticles, various catalytic systems have been...

  3. Cathodic catalysts in bioelectrochemical systems for energy recovery from wastewater.

    Science.gov (United States)

    Liu, Xian-Wei; Li, Wen-Wei; Yu, Han-Qing

    2014-11-21

    Bioelectrochemical systems (BESs), in which microorganisms are utilized as a self-regenerable catalyst at the anode of an electrochemical cell to directly extract electrical energy from organic matter, have been widely recognized as a promising technology for energy-efficient wastewater treatment or even for net energy generation. However, currently BES performance is constrained by poor cathode reaction kinetics. Thus, there is a strong impetus to improve the cathodic catalysis performance through proper selection and design of catalysts. This review introduces the fundamentals and current development status of various cathodic catalysts (including electrocatalysts, photoelectrocatalysts and bioelectrocatalysts) in BES, identifies their limitations and influential factors, compares their catalytic performances in terms of catalytic efficiency, stability, selectivity, etc., and discusses the possible optimization strategies and future research directions. Special focus is given on the analysis of how the catalytic performance of different catalysts can be improved by fine tuning their physicochemical or physiological properties.

  4. Synthesis of carbon nanotubes with Ni/CNTs catalyst

    Institute of Scientific and Technical Information of China (English)

    李春华; 姚可夫; 阮殿波; 梁吉; 徐才录; 吴德海

    2003-01-01

    Carbon nanotubes (CNTs), owing to their large specific area, good chemical stability and modifiable surface properties after acidic or basic treatment, can be used as catalytic support materials. In this paper, the activities and selectivities of two catalysts, i. e. Ni catalyst supported by carbon nanotubes (Ni/CNTs) and that supported by diatomite (Ni/SiO2), are compared. It is found that the quality of the carbon nanotubes synthesized by the two catalysts is similar, but the yield of the former is 1.5 times higher than that of the latter. The excellent performance of the Ni/CNTs catalyst should be ascribed to the larger specific surface area and proper pore distribution and the structure of the carbon nanotube support.

  5. Synthesis Gas Production from Natural Gas on Supported Pt Catalysts

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900 ℃. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450 ℃. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800 ℃, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800 ℃. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.

  6. Effect of Composition and Mass Ratio on the Catalytic Wet Air Oxidation Catalyst Cu–Fe–La/FSC

    Directory of Open Access Journals (Sweden)

    Wu Chao

    2016-01-01

    Full Text Available The catalytic wet air oxidation (CWAO technology is used for the treatment of the simulated printing and dyeing wastewater and also for investigating the catalyst performance indicators such as catalyst activity and stability. The catalyst activity is mainly reflected from the water decolorization and CODCr removal rates, and the stability of the catalyst is mainly reflected by the quantity of metal dissolution. The experimental results showed that the prepared Cu–Fe–La/FSC catalyst with a 1:1:2 ratio of Cu–Fe–La by the impregnation method exhibited good activity for the treatment of the simulated printing and dyeing wastewater by the CWAO method, and the decolorization and CODCr removal rates using this catalyst were 98.7% and 78.6%, respectively, with a higher catalytic activity, lower concentration of metal dissolution, and good stability.

  7. 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....

  8. Crystal structure of a DNA catalyst.

    Science.gov (United States)

    Ponce-Salvatierra, Almudena; Wawrzyniak-Turek, Katarzyna; Steuerwald, Ulrich; Höbartner, Claudia; Pena, Vladimir

    2016-01-14

    Catalysis in biology is restricted to RNA (ribozymes) and protein enzymes, but synthetic biomolecular catalysts can also be made of DNA (deoxyribozymes) or synthetic genetic polymers. In vitro selection from synthetic random DNA libraries identified DNA catalysts for various chemical reactions beyond RNA backbone cleavage. DNA-catalysed reactions include RNA and DNA ligation in various topologies, hydrolytic cleavage and photorepair of DNA, as well as reactions of peptides and small molecules. In spite of comprehensive biochemical studies of DNA catalysts for two decades, fundamental mechanistic understanding of their function is lacking in the absence of three-dimensional models at atomic resolution. Early attempts to solve the crystal structure of an RNA-cleaving deoxyribozyme resulted in a catalytically irrelevant nucleic acid fold. Here we report the crystal structure of the RNA-ligating deoxyribozyme 9DB1 (ref. 14) at 2.8 Å resolution. The structure captures the ligation reaction in the post-catalytic state, revealing a compact folding unit stabilized by numerous tertiary interactions, and an unanticipated organization of the catalytic centre. Structure-guided mutagenesis provided insights into the basis for regioselectivity of the ligation reaction and allowed remarkable manipulation of substrate recognition and reaction rate. Moreover, the structure highlights how the specific properties of deoxyribose are reflected in the backbone conformation of the DNA catalyst, in support of its intricate three-dimensional organization. The structural principles underlying the catalytic ability of DNA elucidate differences and similarities in DNA versus RNA catalysts, which is relevant for comprehending the privileged position of folded RNA in the prebiotic world and in current organisms.

  9. Formic acid oxidation at platinum-bismuth catalysts

    Directory of Open Access Journals (Sweden)

    Popović Ksenija Đ.

    2015-01-01

    Full Text Available The field of heterogeneous catalysis, specifically catalysis on bimetallic surfaces, has seen many advances over the past few decades. Bimetallic catalysts, which often show electronic and chemical properties that are distinct from those of their parent metals, offer the opportunity to obtain new catalysts with enhanced selectivity, activity, and stability. The oxidation of formic acid is of permanent interest as a model reaction for the mechanistic understanding of the electrooxidation of small organic molecules and because of its technical relevance for fuel cell applications. Platinum is one of the most commonly used catalysts for this reaction, despite the fact that it shows a few significant disadvantages: high cost and extreme susceptibility to poisoning by CO. To solve this problem, several approaches have been used, but generally, they all consist in the modification of platinum with a second element. Especially, bismuth has received significant attention as Pt modifier. According to the results presented in this survey dealing with the effects influencing the formic acid oxidation it was found that two types of Pt-Bi bimetallic catalysts (bulk and low loading deposits on GC showed superior catalytic activity in terms of the lower onset potential and oxidation current density, as well as exceptional stability compared to Pt. The findings in this report are important for the understanding of mechanism of formic acid electrooxidation on a bulk alloy and decorated surface, for the development of advanced anode catalysts for direct formic acid fuel cells, as well as for the synthesis of novel low-loading bimetallic catalysts. The use of bimetallic compounds as the anode catalysts is an effective solution to overcoming the problems of the formic acid oxidation current stability for long term applications. In the future, the tolerance of both CO poisoning and electrochemical leaching should be considered as the key factors in the development

  10. Nanopore and nanoparticle catalysts.

    Science.gov (United States)

    Thomas, J M; Raja, R

    2001-01-01

    The design, atomic characterization, performance, and relevance to clean technology of two distinct categories of new nanocatalysts are described and interpreted. Exceptional molecular selectivity and high activity are exhibited by these catalysts. The first category consists of extended, crystallographically ordered inorganic solids possessing nanopores (apertures, cages, and channels), the diameters of which fall in the range of about 0.4 to about 1.5 nm, and the second of discrete bimetallic nanoparticles of diameter 1 to 2 nm, distributed more or less uniformly along the inner walls of mesoporous (ca. 3 to 10 nm diameter) silica supports. Using the principles and practices of solid-state and organometallic chemistry and advanced physico-chemical techniques for in situ and ex situ characterization, a variety of powerful new catalysts has been evolved. Apart from those that, inter alia, simulate the behavior of enzymes in their specificity, shape selectivity, regio-selectivity, and ability to function under ambient conditions, many of these new nanocatalysts are also viable as agents for effecting commercially significant processes in a clean, benign, solvent-free, single-step fashion. In particular, a bifunctional, molecular sieve nanopore catalyst is described that converts cyclohexanone in air and ammonia to its oxime and caprolactam, and a bimetallic nanoparticle catalyst that selectively converts cyclic polyenes into desirable intermediates. Nanocatalysts in the first category are especially effective in facilitating highly selective oxidations in air, and those in the second are well suited to effecting rapid and selective hydrogenations of a range of organic compounds.

  11. Hydrogen evolution reaction catalyst

    Science.gov (United States)

    Subbaraman, Ram; Stamenkovic, Vojislav; Markovic, Nenad; Tripkovic, Dusan

    2016-02-09

    Systems and methods for a hydrogen evolution reaction catalyst are provided. Electrode material includes a plurality of clusters. The electrode exhibits bifunctionality with respect to the hydrogen evolution reaction. The electrode with clusters exhibits improved performance with respect to the intrinsic material of the electrode absent the clusters.

  12. Heterogeneous chromium catalysts

    NARCIS (Netherlands)

    2005-01-01

    The present invention relates to a heterogeneous chromium catalyst system for the polymerisation of ethylene and/or alpha olefins prepared by the steps of: (a) providing a silica-containing support, (b) treating the silica-containing support with a chromium compound to form a chromium-based silica-c

  13. Deactivation of Oxidation Catalysts

    Science.gov (United States)

    1991-05-01

    Levenspiel (Reference 10) have proposed an equivalent general expression of the form dS _KST (4) dtk to account for deactivation due to catalyst pore...Voorhies, A., IEC, 1954, vol. 37, p. 318. 10. Szepe, S., and 0. Levenspiel , Proc. 4th Europ. Symp. Chem. React. Eng., Pergamon Press, p. 265. 11. U.S

  14. Olefin metathesis and catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S. G.; Banks, R. L.

    1985-05-14

    Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising an inorganic refractory oxide support containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least one methylating agent under conditions suitable for the methylating agent compounds to promote the activity of tungsten and molybdenum oxides for the disproportionation reaction.

  15. Catalysts for Environmental Remediation

    DEFF Research Database (Denmark)

    Abrams, B. L.; Vesborg, Peter Christian Kjærgaard

    2013-01-01

    The properties of catalysts used in environmental remediation are described here through specific examples in heterogeneous catalysis and photocatalysis. In the area of heterogeneous catalysis, selective catalytic reduction (SCR) of NOx was used as an example reaction with vanadia and tungsta...

  16. Microwave-assisted synthesis of high-loading, highly dispersed Pt/carbon aerogel catalyst for direct methanol fuel cell

    Indian Academy of Sciences (India)

    Zhijun Guo; Hong Zhu; Xinwei Zhang; Fanghui Wang; Yubao Guo; Yongsheng Wei

    2011-06-01

    A Pt supported on carbon aerogel catalyst has been synthesized by the microwave-assisted polyol process. The Pt supported on carbon aerogel catalyst was characterized by high resolution transmission electron microscopy and X-ray diffraction. The results show a uniform dispersion of spherical Pt nanoparticles 2.5–3.0 nm in diameter. Cyclic voltammetry and chronoamperometry were used to evaluate the electrocatalytic activity of the Pt/carbon aerogel catalyst for methanol oxidation at room temperature. The Pt/carbon aerogel catalyst shows higher electrochemical catalytic activity and stability for methanol oxidation than a commercial Pt/C catalyst of the same Pt loading.

  17. Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

    DEFF Research Database (Denmark)

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei;

    2014-01-01

    of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR......). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide‐based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts....

  18. Molybdenum sulfide/carbide catalysts

    Science.gov (United States)

    Alonso, Gabriel; Chianelli, Russell R.; Fuentes, Sergio; Torres, Brenda

    2007-05-29

    The present invention provides methods of synthesizing molybdenum disulfide (MoS.sub.2) and carbon-containing molybdenum disulfide (MoS.sub.2-xC.sub.x) catalysts that exhibit improved catalytic activity for hydrotreating reactions involving hydrodesulfurization, hydrodenitrogenation, and hydrogenation. The present invention also concerns the resulting catalysts. Furthermore, the invention concerns the promotion of these catalysts with Co, Ni, Fe, and/or Ru sulfides to create catalysts with greater activity, for hydrotreating reactions, than conventional catalysts such as cobalt molybdate on alumina support.

  19. Oxidation-reduction catalyst and its process of use

    Science.gov (United States)

    Jordan, Jeffrey D. (Inventor); Watkins, Anthony Neal (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor)

    2008-01-01

    This invention relates generally to a ruthenium stabilized oxidation-reduction catalyst useful for oxidizing carbon monoxide, and volatile organic compounds, and reducing nitrogen oxide species in oxidizing environments, substantially without the formation of toxic and volatile ruthenium oxide species upon said oxidizing environment being at high temperatures.

  20. In silico search for novel methane steam reforming catalysts

    DEFF Research Database (Denmark)

    Xu, Yue; Lausche, Adam C; Wang, Shengguang

    2013-01-01

    This paper demonstrates a method for screening transition metal and metal alloy catalysts based on their predicted rates and stabilities for a given catalytic reaction. This method involves combining reaction and activation energies (available to the public via a web-based application ‘CatApp’) w...

  1. CATALYST ACTIVITY MAINTENANCE FOR THE LIQUID PHASE SYNTHESIS GAS-TO-DIMETHYL ETHER PROCESS PART II: DEVELOPMENT OF ALUMINUM PHOSPHATE AS THE DEHYDRATION CATALYST FOR THE SINGLE-STEP LIQUID PHASE SYNGAS-TO-DME PROCESS

    Energy Technology Data Exchange (ETDEWEB)

    Xiang-Dong Peng

    2002-05-01

    At the heart of the single-step liquid phase syngas-to-DME process (LPDME{trademark}) is a catalyst system that can be active as well as stable. In the Alternative Fuels I program, a dual-catalyst system containing a Cu-based commercial methanol synthesis catalyst (BASF S3-86) and a commercial dehydration material ({gamma}-alumina) was demonstrated. It provided the productivity and selectivity expected from the LPDME process. However, the catalyst system deactivated too rapidly to warrant a viable commercial process [1]. The mechanistic investigation in the early part of the DOE's Alternative Fuels II program revealed that the accelerated catalyst deactivation under LPDME conditions is due to detrimental interaction between the methanol synthesis catalyst and methanol dehydration catalyst [2,3]. The interaction was attributed to migration of Cu- and/or Zn-containing species from the synthesis catalyst to the dehydration catalyst. Identification of a dehydration catalyst that did not lead to this detrimental interaction while retaining adequate dehydration activity was elusive. Twenty-nine different dehydration materials were tested, but none showed the desired performance [2]. The search came to a turning point when aluminum phosphate was tested. This amorphous material is prepared by precipitating a solution containing Al(NO{sub 3}){sub 3} and H{sub 3}PO{sub 4} with NH{sub 4}OH, followed by washing, drying and calcination. The aluminum phosphate catalyst has adequate dehydration activity and good stability. It can co-exist with the Cu-based methanol synthesis catalyst without negatively affecting the latter catalyst's stability. This report documents the details of the development of this catalyst. These include initial leads, efforts in improving activity and stability, investigation and development of the best preparation parameters and procedures, mechanistic understanding and resulting preparation guidelines, and the accomplishments of this work.

  2. Solvent effects on Pt-Ru/C catalyst for methanol electro-oxidation

    Institute of Scientific and Technical Information of China (English)

    Jinwei Chen; Chunping Jiang; Hui Lu; Lan Feng; Xin Yang; Liangqiong Li; Ruilin Wang

    2009-01-01

    Alloying degree,particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent(s) used in the preparation process can affect the particle size and alloying degree of the object substance,which lead to a great positive impact on its properties. In this work,three types of solvents and their mixtures were used in preparation of the Pt-Ru/C catalysts by chemical reduction of metal precursors with sodium borohydride at room temperature. The structure of the catalysts was characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The catalytic activity and stability for methanol electro-oxidation were studied by Cyclic Voltammetry (CV) and Chronoamperometry (CA). Pt-Ru/C catalyst prepared in H_2O or binary solvents of H_2O and isopropanol had large particle size and low alloying degree leading to low catalytic activity and less stability in methanol electro-oxidation. When tetrahydrofuran was added to the above solvent systems,Pt-Ru/C catalyst prepared had smaller particle size and higher alloying degree which resulted in better catalytic activity,lower onset and peak potentials,compared with the above catalysts. Moreover,the catalyst prepared in ternary solvents of isopropanol,water and tetrahydrofuran had the smallest particle size,and the high alloying degree and the dispersion kept unchanged. Therefore,this kind of catalyst showed the highest catalytic activity and good stability for methanol electro-oxidation.

  3. Methanol Steam Reforming Reactions on CuZn(Zr)AlO Catalyst

    Institute of Scientific and Technical Information of China (English)

    Yongfeng Li; Xinfa Dong; Weiming Lin

    2004-01-01

    The catalytic performances of methanol steam reforming reactions on CuZn(Zr)AlO catalysts were studied. When the ZrO2 promoter was added to a CuZnAlO catalyst, its methanol conversion,H2 production and H2 selectivity improved greatly. By using the #COPZr-2 catalyst as an example,which exhibited the best catalytic performance, the optimized reaction conditions were established to be:250 ℃, 0.1 MPa, H2O/MeOH=1.3, WHSV=3.56 h-1, and without carrier gas. A 150 h stability test of the #COPZr-2 catalyst showed that the catalyst had good stability, as the methanol conversion and H2 production could be kept at 88% and 83% respectively. Moreover, outlet H2 and CO contents were >63%and 0.20%-0.31%, respectively.

  4. Influence of Yttrium and Ytterbium on Reaction Performance of Platinum-Rhenium Reforming Catalyst

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The influence of yttrium and ytterbium on the catalytic performance of Pt-Re reforming cata-lysts was studied in a continuous flow pressurized microreactor-chromatograph system and pilot unit. Theresults of micro-reactor test showed that both yttrium and ytterbium could improve the selectivity of Pt-Recatalysts for the conversion ofn-heptane as well as MCP into aromatics, but also suppressed their activityas well. Pilot test results showed that yttrium and ytterbium enhanced both the selectivity and activity ofPt-Re catalysts for naphtha reforming. Yttrium showed more improvement than ytterbium. The perfor-mance difference between microreactor test and pilot test might be due to the difference in improvement ofcatalytic stability of yttrium or ytterbium modified Pt-Re catalysts. Yttrium and ytterbium improved thecoking resistance of yttrium or ytterbium modified Pt-Re catalysts. TEM determination results indicatedthat both yttrium and ytterbium had improved the thermal stability of Pt-Re catalysts.

  5. Scale up and stability test for oxidative coupling of methane over Na2WO4-Mn/SiO2 catalyst in a 200 ml fixed-bed reactor

    Institute of Scientific and Technical Information of China (English)

    Haitao Liu; Xiaolai Wang; Dexin Yang; Runxiong Gao; Zhonglai Wang; Jian Yang

    2008-01-01

    The study of scale up for the oxidative coupling of methane (OCM) has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 (W-Mn/SiO2) catalyst. The effects of reaction conditions were investigated in detail. The results showed that, with increasing reaction temperature, the gas-phase reaction was enhanced and a significant amount of methane was converted into COX; with the CH4/O2 molar ratio of 5, the highest C2 (ethylene and ethane) yield of 25% was achieved; the presence of steam (as diluent) had a positive effect on the C2 selectivity and yield. Under lower methane gaseous hourly space velocity (GHSV), higher selectivity and yield of C2 were obtained as the result of the decrease of released heat energy. In 100 h reaction time, the C2 selectivity of 66%-61 % and C2 yield of 24.2%-25.4% were achieved by a single pass without any significant loss in catalytic performance.

  6. Oxidative Dehydrogenation of Ethane to Ethylene over LiCI/MnOx/PC Catalysts

    Institute of Scientific and Technical Information of China (English)

    葛庆杰; 李文钊; 于春英; 徐恒泳

    2001-01-01

    The caalytic stability of LiCl/MnOx/PC catalyst have been investigated, the deactivation mechanism was discussed. Tne experimental results show that ethane conversion decreases and etihylene selectivotu keeps about 90% as reaction time increases. The main deactivation reasons LiCI/MnOx/PCcatalyst for oxidative dehydrogenation of ethane (ODHE) to ethylene are the transiton of active species Mn2O3 TO MnOspecies and the loss of active component Cl in catalyst. Instead of ethane with FCC tailed-gas, the stability of LiCl/MnOx/PC catalyst has been largely improved.

  7. Toluene Oxidation by Non-Thermal Plasma Combined with Palladium Catalysts

    Directory of Open Access Journals (Sweden)

    Monica eMagureanu

    2013-06-01

    Full Text Available The oxidation of toluene in air was investigated using a dielectric barrier discharge (DBD combined with a Pd/Al2O3 catalyst. When using only plasma, rather low selectivity towards CO2 was obtained: 32-35%. By filling the DBD reactor with Pd/Al2O3 catalyst the CO2 selectivity was significantly enhanced (80-90%, however, a large amount of toluene was desorbed from the catalyst when the discharge was operated. By filling a quarter of the discharge gap with catalyst and placing the rest of the catalyst downstream of the plasma reactor, an important increase of CO2 selectivity (~75% and a 15% increase in toluene conversion were achieved as compared to the results with plasma alone. The catalyst exhibited a very good stability in this reaction.

  8. Ti-Si composite oxide-supported cobalt catalysts for CO2 hydrogenation

    Institute of Scientific and Technical Information of China (English)

    Jakrapan Janlamool; Piyasan Praserthdam; Bunjerd Jongsomjit

    2011-01-01

    In the present work,different silica-based supported cobalt (Co) catalysts were synthesized and used for CO2 hydrogenation for methanation.Different supports,such as SSP,MCM-41,TiSSP and TiMCM were used to prepare Co catalysts with 20 wt% Co loading.The supports and catalysts were characterized by means of N2 physisorption,XRD,SEM/EDX,XPS,TPR and CO chemisorption.It is found that after calcination of catalysts,Ti is present in the form of anatase.The introduction of Ti plays important roles in the properties of Co catalysts by.(i) facilitating the reduction of Co oxides species which are strongly interacted with support,(ii) preventing the formation of silicate compounds,and (iii) inhibiting the RWGS reaction.Based on CO2 hydrogenation,the CoTiMCM catalyst exhibites the highest activity and stability.

  9. Ni-CeO2/C Catalysts with Enhanced OSC for the WGS Reaction

    Directory of Open Access Journals (Sweden)

    Laura Pastor-Pérez

    2015-03-01

    Full Text Available In this work, the WGS performance of a conventional Ni/CeO2 bulk catalyst is compared to that of a carbon-supported Ni-CeO2 catalyst. The carbon-supported sample resulted to be much more active than the bulk one. The higher activity of the Ni-CeO2/C catalyst is associated to its oxygen storage capacity, a parameter that strongly influences the WGS behavior. The stability of the carbon-supported catalyst under realistic operation conditions is also a subject of this paper. In summary, our study represents an approach towards a new generation of Ni-ceria based catalyst for the pure hydrogen production via WGS. The dispersion of ceria nanoparticles on an activated carbon support drives to improved catalytic skills with a considerable reduction of the amount of ceria in the catalyst formulation.

  10. Biphasic catalysis using amphiphilic polyphenols-chelated noble metals as highly active and selective catalysts

    Science.gov (United States)

    Mao, Hui; Yu, Hong; Chen, Jing; Liao, Xuepin

    2013-07-01

    In the field of catalysis, it is highly desired to develop novel catalysts that combine the advantages of both homogeneous and heterogeneous catalysts. Here we disclose that the use of plant pholyphenol as amphiphilic large molecule ligand/stabilizer allows for the preparation of noble metal complex and noble metal nanoparticle catalysts. These catalysts are found to be highly selective and active in aqueous-organic biphasic catalysis of cinnamaldehyde and quinoline, and can be reused at least 3 times without significant loss of activity. Moreover, the catalytic activity and reusability of the catalysts can be rationally controlled by simply adjusting the content of polyphenols in the catalysts. Our strategy may be extended to design a wide range of aqueous-organic biphasic catalysis system.

  11. Effect of incorporation manner of Zr promoter on precipitated ironbased catalysts for Fischer-Tropsch synthesis

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hao-jian; MA Hong-fang; ZHANG Hai-tao; YING Wei-yong; FANG Ding-ye

    2012-01-01

    The promotional effects of Zr on the structure,reduction,carburization and catalytic behavior of precipitated iron-based Fischer-Tropsch synthesis (FTS) catalysts were investigated.The catalysts were characterized by N2 physisorption,temperature-programmed reduction (TPR),and M(o)ssbauer effect spectroscopy (MES) techniques.As revealed by N2 physisorption,Zr decreased the BET surface area and pore volume of the catalyst.The results of TPR and MES show that Zr suppresses the reduction and carburization of Fe catalysts because of the interaction between Fe and Zr.The FTS reaction results indicate that Zr decreases the FTS activity of Fe catalysts but improves the catalysts' stability.In addition,Zr promoter restraines the formation of light hydrocarbons (methane and C2~C4) and shifts the production distribution to the heavy hydrocarbons.

  12. Modelling Catalyst Surfaces Using DFT Cluster Calculations

    Directory of Open Access Journals (Sweden)

    Oliver Kröcher

    2009-09-01

    Full Text Available We review our recent theoretical DFT cluster studies of a variety of industrially relevant catalysts such as TiO2, γ-Al2O3, V2O5-WO3-TiO2 and Ni/Al2O3. Aspects of the metal oxide surface structure and the stability and structure of metal clusters on the support are discussed as well as the reactivity of surfaces, including their behaviour upon poisoning. It is exemplarily demonstrated how such theoretical considerations can be combined with DRIFT and XPS results from experimental studies.

  13. Modelling catalyst surfaces using DFT cluster calculations.

    Science.gov (United States)

    Czekaj, Izabela; Wambach, Jörg; Kröcher, Oliver

    2009-11-20

    We review our recent theoretical DFT cluster studies of a variety of industrially relevant catalysts such as TiO(2), gamma-Al(2)O(3), V(2)O(5)-WO(3)-TiO(2) and Ni/Al(2)O(3). Aspects of the metal oxide surface structure and the stability and structure of metal clusters on the support are discussed as well as the reactivity of surfaces, including their behaviour upon poisoning. It is exemplarily demonstrated how such theoretical considerations can be combined with DRIFT and XPS results from experimental studies.

  14. Fluorination process using catalysts

    Science.gov (United States)

    Hochel, R.C.; Saturday, K.A.

    1983-08-25

    A process is given for converting an actinide compound selected from the group consisting of uranium oxides, plutonium oxides, uranium tetrafluorides, plutonium tetrafluorides and mixtures of said oxides and tetrafluorides, to the corresponding volatile actinide hexafluoride by fluorination with a stoichiometric excess of fluorine gas. The improvement involves conducting the fluorination of the plutonium compounds in the presence of a fluoride catalyst selected from the group consisting of CoF/sub 3/, AgF/sub 2/ and NiF/sub 2/, whereby the fluorination is significantly enhanced. The improvement also involves conducting the fluorination of one of the uranium compounds in the presence of a fluoride catalyst selected from the group consisting of CoF/sub 3/ and AgF/sub 2/, whereby the fluorination is significantly enhanced.

  15. Fluorination process using catalyst

    Science.gov (United States)

    Hochel, Robert C.; Saturday, Kathy A.

    1985-01-01

    A process for converting an actinide compound selected from the group consisting of uranium oxides, plutonium oxides, uranium tetrafluorides, plutonium tetrafluorides and mixtures of said oxides and tetrafluorides, to the corresponding volatile actinide hexafluoride by fluorination with a stoichiometric excess of fluorine gas. The improvement involves conducting the fluorination of the plutonium compounds in the presence of a fluoride catalyst selected from the group consisting of CoF.sub.3, AgF.sub.2 and NiF.sub.2, whereby the fluorination is significantly enhanced. The improvement also involves conducting the fluorination of one of the uranium compounds in the presence of a fluoride catalyst selected from the group consisting of CoF.sub.3 and AgF.sub.2, whereby the fluorination is significantly enhanced.

  16. Photo catalyst; Ko shokubai

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-07-01

    While titanium oxide is excited by the light, electrons of titanium oxide are taken away by the light energy to form positive holes. Water will be decomposed into hydrogen ion and hydroxy radical (OH) by these positive holes. This hydroxy radical is a strong reactive substance called active oxygen, it decomposes organisms. Besides this photo- catalyst function, the titanium oxide can also make surface of a substance superhydrophilic. The super hydrophilicity results in not forming water drops on the glass surface but spreading all over the surface to prevent a covering of fog on the glass surface. The published patents concerning the photo catalysts were 593 from Jan. 1998 to Jan. 1999. The applicant order is the first TOTO 143, the second Daikin Industry 19, the third Toshiba Raitech, Nitto Denko, Hitachi 17 respectively. (NEDO)

  17. Novel Hydrophobic Pt/Inorganic Catalyst Used in Hydrogen Isotope Exchange Reaction

    Directory of Open Access Journals (Sweden)

    JIA Qing-qing1;HU Shi-lin1;FENG Xiao-yan2;LIU Ya-ming1

    2016-11-01

    Full Text Available To improve the performance of hydrophobic catalyst and extend its using range, this research adopted the porous columnar inorganic carriers (ø=5 mm to prepare the hydrophobic catalyst used in hydrogen isotopes exchange reaction, the hydrophilic carriers became hydrophobic with the nanostructured CeO2 coating and the catalyst were then fabricated by convenient impregnation method. The samples were characterized by XRD、SEM、EDX、XPS and CO adsorption. The catalytic activity were tested through catalytic exchange reaction between hydrogen and saturated water vapor to investigate the effect of micro structured CeO2 on the catalyst properties. It turned out that the nano-CeO2 coating could build favorable hydrophobic environment for the catalysts and had almost no influence on the pore structure properties of carriers. Although the hydrophobic coating would lead to the decrease of Pt particle dispersion and metallic Pt content, it could make the Pt particles mostly deposit on the surface layer of the catalysts, which would make more Pt particle participate in the reaction at the same time. The catalytic activity of the novel Pt/inorganic catalyst could reach to 80% of the mature Pt/organic catalyst. After being flushed by water for 12 weeks, the catalytic activity of Pt/inorganic catalyst decreased less than 5%. The novel hydrophobic catalyst with good activity and stability was practical and had great application prospects.

  18. 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.

  19. Olefin metathesis and catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S. G.; Banks, R. L.

    1985-03-12

    Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising an inorganic refractory material containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least one treating agent selected from chlorinated silicon compounds, thionyl chloride, and sulfuryl chloride under conditions suitable for the treating agent to promote the activity of tungsten and molybdenum oxides for the disporoportionation reaction.

  20. TECHNOLOGY DEVELOPMENT FOR IRON AND COBALT FISCHER-TROPSCH CATALYSTS

    Energy Technology Data Exchange (ETDEWEB)

    Burtron H. Davis

    1999-04-30

    The impact of activation procedure on the phase composition of precipitated iron Fischer-Tropsch (FT) catalysts has been studied. Catalyst samples taken during activation and FT synthesis have been characterized by Moessbauer spectroscopy. Formation of iron carbide is necessary for high FT activity. Hydrogen activation of precipitated iron catalysts results in reduction to predominantly metallic iron and Fe{sub 3}O{sub 4}. Metallic iron is not stable under FT 3 4 conditions and is rapidly converted to {epsilon}{prime}-Fe{sub 2.2}C. Activation with carbon monoxide or syngas 2.2 with low hydrogen partial pressure reduces catalysts to {chi}-Fe{sub 5}C{sub 2} and a small amount of 5 2 superparamagnetic carbide. Exposure to FT conditions partially oxidizes iron carbide to Fe{sub 3}O{sub 4}; however, catalysts promoted with potassium or potassium and copper maintain a constant carbide content and activity after the initial oxidation. An unpromoted iron catalyst which was activated with carbon monoxide to produce 94% {chi}-Fe{sub 5}C{sub 2}, deactivated rapidly as the carbide was oxidized to Fe{sub 3}O{sub 4}. No difference in activity, stability or deactivation rate was found for {chi}-Fe{sub 5}C{sub 2} and {epsilon}{prime}-Fe{sub 2.2}C.

  1. Preparation and Commercial Application of ZHC-01 Hydrocracking Catalyst

    Institute of Scientific and Technical Information of China (English)

    Xu Xuejun; Liu Dongxiang; Wang Haitao; Feng Xiaoping; Wang Jifeng

    2007-01-01

    The ZHC-01 hydrocracking catalyst,characterized by high hydrogenation activity,good selectivity for middle distillates,strong resistance to nitrogen poisoning,was prepared by co-gelling.The catalyst is not only suited to the single-stage hydrocracking process,but also to the first stage of serial hydrocracking process.In parallel with the fully loaded operation of the 1.4 Mt/a hydrocracking unit at the SINOPEC Qilu Petrochemical Company,a pilot test of the ZHC-01 catalyst was also carried out on the hydrocracking unit.The test results indicated that the activity,the yield of major target products and quality of the ZHC-01 catalyst could comply with the design requirements for the hydrocracking unit,and this catalyst could be applied in the hydrocracking unit.The commercial test results showed that the ZHC-01 catalyst,featuring good activity,stability,and flexibility in production,not only could meet the demand for producing environmentally friendly middle distillates,but could also increase the resource of optimized steam cracking feedstock.

  2. Activity of Catalyst for Liquid Phase Methanol Synthesis

    Institute of Scientific and Technical Information of China (English)

    WANGYuefa; JanezLevec

    2002-01-01

    The effects of reduction procedure, reaction temperature and composition of feed gas on the activity of a CuO-ZnO-Al2O3 catalyst for liquid phase methanol synthesis were studied. An optimized procedure different from conventional ones was developed to obtain higher activity and better stability of the catalyst. Both CO and CO2 in the feed gas were found to be necessary to maintain the activity of catalyst in the synthesis process. Reaction temperature was limited up to 523K, otherwise the catalyst will be deactivated rapidly. Experimental results show that the catalyst deactivation is caused by sintering and fouling, and the effects of CO and CO2 on the catalyst activity are also investigated. The experimental results indicate that the formation of water in the methanol synthesis is negligible when the feed gas contains both CO and CO2. The mechanism for liquid-phase methanol synthesis was discussed and it differed slightly from that for gas-phase synthesis.

  3. Iron Fischer-Tropsch Catalysts Prepared by Solvent-Deficient Precipitation (SDP: Effects of Washing, Promoter Addition Step, and Drying Temperature

    Directory of Open Access Journals (Sweden)

    Kyle M. Brunner

    2015-07-01

    Full Text Available A novel, solvent-deficient precipitation (SDP method for catalyst preparation in general and for preparation of iron FT catalysts in particular is reported. Eight catalysts using a 23 factorial design of experiments to identify the key preparation variables were prepared. The catalysts were characterized by electron microprobe, N2 adsorption, TEM, XRD, and ICP. Results show that the morphology of the catalysts, i.e., surface area, pore volume, pore size distribution, crystallite sizes, and promoter distribution are significantly influenced by (1 whether or not the precursor catalyst is washed, (2 the promoter addition step, and (3 the drying condition (temperature. Consequently, the activity, selectivity, and stability of the catalysts determined from fixed-bed testing are also affected by these three variables. Unwashed catalysts prepared by a one-step method and dried at 100 °C produced the most active catalysts for FT synthesis. The catalysts of this study prepared by SDP compared favorably in activity, productivity, and stability with Fe FT catalysts reported in the literature. It is believed that this facile SDP approach has promise for development of future FT catalysts, and also offers a potential alternate route for the preparation of other catalysts for various other applications.

  4. Carbon Nanotubes Supported Pt-Ru-Ni as Methanol Electro-Oxidation Catalyst for Direct Methanol Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    Fei Ye; Shengzhou Chen; Xinfa Dong; Weiming Lin

    2007-01-01

    Carbon nanotubes (CNTs) supported Pt-Ru and Pt-Ru-Ni catalysts were prepared by chemical reduction of metal precursors with sodium borohydride at room temperature. The crystallographic properties and composition of the catalysts were characterized by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis, and the catalytic activity and stability for methanol electro-oxidation were measured by electrochemical impedance spectroscopy (EIS), linear sweep voltammetries (LSV), and chronoamperometry (CA). The results show that the catalysts exhibit face-centered cubic (fcc) structure.The particle size of Pt-Ru-Ni/CNTs catalyst is about 4.8 nm. The catalytic activity and stability of the Pt-Ru-Ni/CNTs catalyst are higher than those of Pt-Ru/CNTs catalyst.

  5. APPLICATION OF MAGNETIC CATALYSTS TO THE CATALYTIC WET PEROXIDE OXIDATION (CWPO OF INDUSTRIAL WASTEWATER CONTAINING NON BIODEGRADABLE ORGANIC POLLUTANTS

    Directory of Open Access Journals (Sweden)

    Macarena Munoz

    2014-03-01

    Full Text Available A new ferromagnetic -Al2O3-supported iron catalyst has been prepared and its activity and stability have been compared with those of a previous iron-based conventional catalyst and with the traditional homogeneous Fenton process in the oxidation of chlorophenols. The use of solid catalysts improved significantly the efficiency on the use of H2O2, achieving higher mineralization degrees. The magnetic catalyst led to significantly higher oxidation rates than the conventional one due to the presence of both Fe (II and Fe (III. On the other hand, the use of a catalyst with magnetic properties is of interest, since it allows rapid recovery after treatment using a magnetic field. Moreover, it showed a high stability with fairly low iron leaching (<1% upon CWPO runs. An additional clear advantage of this new catalyst is its easy separation and recovery from the reaction medium by applying an external magnetic field.

  6. Iridium-Doped Ruthenium Oxide Catalyst for Oxygen Evolution

    Science.gov (United States)

    Valdez, Thomas I.; Narayan, Sri R.; Billings, Keith J.

    2011-01-01

    NASA requires a durable and efficient catalyst for the electrolysis of water in a polymer-electrolyte-membrane (PEM) cell. Ruthenium oxide in a slightly reduced form is known to be a very efficient catalyst for the anodic oxidation of water to oxygen, but it degrades rapidly, reducing efficiency. To combat this tendency of ruthenium oxide to change oxidation states, it is combined with iridium, which has a tendency to stabilize ruthenium oxide at oxygen evolution potentials. The novel oxygen evolution catalyst was fabricated under flowing argon in order to allow the iridium to preferentially react with oxygen from the ruthenium oxide, and not oxygen from the environment. Nanoparticulate iridium black and anhydrous ruthenium oxide are weighed out and mixed to 5 18 atomic percent. They are then heat treated at 300 C under flowing argon (in order to create an inert environment) for a minimum of 14 hours. This temperature was chosen because it is approximately the creep temperature of ruthenium oxide, and is below the sintering temperature of both materials. In general, the temperature should always be below the sintering temperature of both materials. The iridium- doped ruthenium oxide catalyst is then fabricated into a PEM-based membrane- electrode assembly (MEA), and then mounted into test cells. The result is an electrolyzer system that can sustain electrolysis at twice the current density, and at the same efficiency as commercial catalysts in the range of 100-200 mA/sq cm. At 200 mA/sq cm, this new system operates at an efficiency of 85 percent, which is 2 percent greater than commercially available catalysts. Testing has shown that this material is as stable as commercially available oxygen evolution catalysts. This means that this new catalyst can be used to regenerate fuel cell systems in space, and as a hydrogen generator on Earth.

  7. Selective Oxidation of Isobutane to Methacrylic Acid over Supported V-Mo-P Based Composite Oxide Catalysts

    Institute of Scientific and Technical Information of China (English)

    Feifei Sun; Yunfeng Geng; Shunhe Zhong

    2002-01-01

    Heteropolyacid, the most popular catalyst for the direct oxidation of isobutane, exhibits high catalytic activity, poor thermal stability and a short lifetime. Therefore, the catalyst requires further research to improve its performance. Catalysts composed of mixed oxides (V2O5, P2O5, or MoO3) supported on silica were prepared by the sol-gel method to catalyze the reaction. Results of XRD, IR, and BET corroborated that the mixed oxides were dispersed homogeneously on the surface of support. The activity of lattice oxygen in the catalysts was studied by TPR, and the chemisorption property of isobutane on the surface of the catalysts was investigated by the TPD method. H2-TPR of the catalysts revealed that the lattice oxygen of the vanadium-based catalysts is more active than that of the molybdenum-based catalysts. The rcdox property of V or Mo species is slightly affected by other compositions of the series catalysts. The TPD curves illustrate that there are two kinds of adsorptive species of isobutane on the surface of the V and Mo based catalysts. The adsorbing species on the VMoP/SiO2 catalyst are identical to the main adsorbing species on VP/SiO2 and MoP/SiO2. The catalyst VMoP/SiO2 is more active than others in the selective oxidation of isobutane.

  8. Light Absorbers and Catalysts for Solar to Fuel Conversion

    Science.gov (United States)

    Kornienko, Nikolay I.

    Increasing fossil fuel consumption and the resulting consequences to the environment has propelled research into means of utilizing alternative, clean energy sources. Solar power is among the most promising of renewable energy sources but must be converted into an energy dense medium such as chemical bonds to render it useful for transport and energy storage. Photoelectrochemistry (PEC), the splitting of water into oxygen and hydrogen fuel or reducing CO 2 to hydrocarbon fuels via sunlight is a promising approach towards this goal. Photoelectrochemical systems are comprised of several components, including light absorbers and catalysts. These parts must all synergistically function in a working device. Therefore, the continual development of each component is crucial for the overall goal. For PEC systems to be practical for large scale use, the must be efficient, stable, and composed of cost effective components. To this end, my work focused on the development of light absorbing and catalyst components of PEC solar to fuel converting systems. In the direction of light absorbers, I focused of utilizing Indium Phosphide (InP) nanowires (NWs) as photocathodes. I first developed synthetic techniques for InP NW solution phase and vapor phase growth. Next, I developed light absorbing photocathodes from my InP NWs towards PEC water splitting cells. I studied cobalt sulfide (CoSx) as an earth abundant catalyst for the reductive hydrogen evolution half reaction. Using in situ spectroscopic techniques, I elucidated the active structure of this catalyst and offered clues to its high activity. In addition to hydrogen evolution catalysts, I established a new generation of earth abundant catalysts for CO2 reduction to CO fuel/chemical feedstock. I first worked with molecularly tunable homogeneous catalysts that exhibited high selectivity for CO2 reduction in non-aqueous media. Next, in order to retain molecular tunability while achieving stability and efficiency in aqueous

  9. Preparation and characterization of Pt catalysts supported on TiO{sub 2} and ZrO{sub 2} stabilized with La{sub 2}O{sub 3} for the elimination of nitric oxide; Preparacion y caracterizacion de catalizadores de Pt soportado en TiO{sub 2} y ZrO{sub 2} estabilizados con La{sub 2}O{sub 3} para la eliminacion de oxido nitrico

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar V, A

    2001-07-01

    The objective of this work is the preparation and characterization of catalytic materials with a platinum base, supported in simple and mixed oxides of titanium (TiO{sub 2}) and zirconia (ZrO{sub 2}) which were stabilized with 10 % in mole of lanthanum (La{sub 2}O{sub 3}), the preparation technique of the supports is the one of precipitation, additioning a nominal charge of 1% in weight of active phase (Pt) by means of the impregnation method by conventional wetting. All the solids were calcinated at 500 Centigrade and subsequently reduced to the same temperature in air and hydrogen flow respectively. Their characterization was applying the techniques such as: Thermal gravimetric analysis (TGA), Differential scanning calorimetry (DSC), Surface area (BET), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Decomposition of 2-propanol, Catalytic activity and selectivity. The application of these techniques allow to define and to explain the influence of the preparation method and of the thermal treatments to which were submitted the catalysts, in special the Surface area, X-ray diffraction and Scanning electron microscopy which demonstrated in evidence the morphologic structure and of crystalline phases present in the catalysts under study. The decomposition of 2-propanol, catalytic activity and selectivity show the supports and catalysts skill for the determination of acid or base sites, moreover of the selective reduction of nitric oxide respectively, the results seem to indicate that the preparation technique, precursors and the thermal treatments to what these materials were submitted have an influence on the catalyst and by consequence in the reduction reaction of nitric oxide. (Author)

  10. Commercial Application of the XYA-5 Catalyst in Acrylonitrile Unit

    Institute of Scientific and Technical Information of China (English)

    Li Zhengguang

    2008-01-01

    The XYA-5 catalyst was first applied in commercial scale on an 80-kt/a acrylonitrile unit at the Daqing Refining and Chemical Company.Test results had shown that the once-through yield of acrylonitrile exceeded 80% with the unit consumption of propylene reaching 1032 kg on each ton of acryionitrile.The product quality could be easily put under control and the distribution of reaction products was reasonable with good cleaning performance and stability of the catalyst that was suitable for use on this commercial unit.

  11. Boron nitride: A high potential support for combustion catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Postole, G. [Institut de Recherches sur la Catalyse, CNRS, 69626 Villeurbanne Cedex (France); ' I.G.Murgulescu' Institute of Physical Chemistry of the Romanian Academy Spl. Independentei 202, 060041 Bucharest (Romania); Caldararu, M. [' I.G.Murgulescu' Institute of Physical Chemistry of the Romanian Academy Spl. Independentei 202, 060041 Bucharest (Romania); Ionescu, N.I. [' I.G.Murgulescu' Institute of Physical Chemistry of the Romanian Academy Spl. Independentei 202, 060041 Bucharest (Romania); Bonnetot, B. [Laboratoire des Multimateriaux et Interfaces, UMR CNRS 5615, bat Berthollet, UCB Lyon I, 69622 Villeurbanne Cedex (France); Auroux, A. [Institut de Recherches sur la Catalyse, CNRS, 69626 Villeurbanne Cedex (France)]. E-mail: auroux@catalyse.cnrs.fr; Guimon, C. [LCPM, 2 Av. President Angot, 64053 Pau Cedex 9 (France)

    2005-08-15

    High surface area BN powders have been prepared from different precursors to be used as supports for noble metal catalysts. The more suitable boron nitride powders were obtained using polytrichoroborazine, pTCB, as precursor, leading to a surface area higher than 150 m{sup 2}/g. The BN powders were characterized by XRD, XPS, TG, SEM and adsorption microcalorimetry measurements (aniline and ammonia). The preliminary results showed a remarkable stability of the BN supports, even in the presence of moisture. Palladium impregnation of the BN powders was performed using a classical method and the obtained catalysts exhibited a high dispersion with Pd particles of about 4 nm.

  12. Development of GREET Catalyst Module

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhichao [Argonne National Lab. (ANL), Argonne, IL (United States); Benavides, Pahola T. [Argonne National Lab. (ANL), Argonne, IL (United States); Dunn, Jennifer B. [Argonne National Lab. (ANL), Argonne, IL (United States); Cronauer, Donald C. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-09-01

    In this report, we develop energy and material flows for the production of five different catalysts (tar reforming, alcohol synthesis, Zeolite Socony Mobil-5 [ZSM-5], Mo/Co/ γ-Al2O3, and Pt/ γ-Al2O3) and two chemicals (olivine, dimethyl ether of polyethylene glycol [DEPG]). These compounds and catalysts are now included in the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET™) catalyst module.

  13. Privileged chiral ligands and catalysts

    CERN Document Server

    Zhou, Qi-Lin

    2011-01-01

    This ultimate ""must have"" and long awaited reference for every chemist working in the field of asymmetric catalysis starts with the core structure of the catalysts, explaining why a certain ligand or catalyst is so successful. It describes in detail the history, the basic structural characteristics, and the applications of these ""privileged catalysts"". A novel concept that gives readers a much deeper insight into the topic.

  14. Oxygen-reducing catalyst layer

    Energy Technology Data Exchange (ETDEWEB)

    O' Brien, Dennis P. (Maplewood, MN); Schmoeckel, Alison K. (Stillwater, MN); Vernstrom, George D. (Cottage Grove, MN); Atanasoski, Radoslav (Edina, MN); Wood, Thomas E. (Stillwater, MN); Yang, Ruizhi (Halifax, CA); Easton, E. Bradley (Halifax, CA); Dahn, Jeffrey R. (Hubley, CA); O' Neill, David G. (Lake Elmo, MN)

    2011-03-22

    An oxygen-reducing catalyst layer, and a method of making the oxygen-reducing catalyst layer, where the oxygen-reducing catalyst layer includes a catalytic material film disposed on a substrate with the use of physical vapor deposition and thermal treatment. The catalytic material film includes a transition metal that is substantially free of platinum. At least one of the physical vapor deposition and the thermal treatment is performed in a processing environment comprising a nitrogen-containing gas.

  15. Catalyst systems and uses thereof

    Science.gov (United States)

    Ozkan, Umit S.; Holmgreen, Erik M.; Yung, Matthew M.

    2012-07-24

    A method of carbon monoxide (CO) removal comprises providing an oxidation catalyst comprising cobalt supported on an inorganic oxide. The method further comprises feeding a gaseous stream comprising CO, and oxygen (O.sub.2) to the catalyst system, and removing CO from the gaseous stream by oxidizing the CO to carbon dioxide (CO.sub.2) in the presence of the oxidation catalyst at a temperature between about 20 to about 200.degree. C.

  16. Dehalogenation of Aryl Halides Catalyzed by MontK10 Immobilized PVP-Pd-Sn Catalyst in Aqueous System

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A series of PVP-Pd-Sn/MontK10 catalysts were prepared by immobilization of PVP[poly(N-vinyl-2-pyrrolidone)] supported bimetallic catalyst using MontK10 as carrier. This catalyst has good catalytic activity for hydrogen transfer dehalogenation of aryl halides. The catalytic reaction was carried out in aqueous system in the presence of phase transfer catalyst and sodium formate as hydrogen source. The catalyst with loading Pd 0.19wt% and molar ratio of Pd/Sn 8:1 gives the highest activity and good stability. This catalyst is more reducible with NaBH4. It is also found that the catalyst is easily separated from the reaction system.

  17. Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

    Directory of Open Access Journals (Sweden)

    Andrzej Tracz

    2015-10-01

    Full Text Available Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM and cross metathesis (CM reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities.

  18. Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

    Science.gov (United States)

    Tracz, Andrzej; Matczak, Mateusz; Urbaniak, Katarzyna

    2015-01-01

    Summary Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metathesis (CM) reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities. PMID:26664602

  19. Nitro-Grela-type complexes containing iodides - robust and selective catalysts for olefin metathesis under challenging conditions.

    Science.gov (United States)

    Tracz, Andrzej; Matczak, Mateusz; Urbaniak, Katarzyna; Skowerski, Krzysztof

    2015-01-01

    Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metathesis (CM) reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities.

  20. Synergetic effects leading to coke-resistant NiCo bimetallic catalysts for dry reforming of methane

    KAUST Repository

    Li, Lidong

    2015-01-08

    A new dry reforming of methane catalyst comprised of NiCo bimetallic nanoparticles and a Mgx(Al)O support that exhibits high coke resistance and long-term on-stream stability is reported. The structural characterization by XRD, TEM, temperature-programmed reduction, and BET analysis demonstrates that the excellent performance of this catalyst is ascribed to the synergy of various parameters, including metal-nanoparticle size, metal-support interaction, catalyst structure, ensemble size, and alloy effects.

  1. Reduction of Sulphur-containing Aromatic Nitro Compounds with Hydrazine Hydrate over Iron(Ⅲ) Oxide-MgO Catalyst

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Sulphur-containing aromatic amines were prepared efficiently in good to excellent yields by reduction of the corresponding sulphur-containing aromatic nitro compounds with hydrazine hydrate in the presence of iron(Ⅲ) oxide-MgO catalyst. The catalyst exhibited high activity and stability for the reduction of sulphur-containing aromatic nitro compounds. The yields of sulphur-containing aromatic amines were up to 91-99 % at 355 K after reduction for 1-4 h over this catalyst.

  2. Structure and Stability of Pt-Y Alloy Particles for Oxygen Reduction Studied by Electron Microscopy

    DEFF Research Database (Denmark)

    Deiana, Davide; Wagner, Jakob Birkedal; Hansen, Thomas Willum

    2015-01-01

    Platinum-yttrium alloy nanoparticles show both a high activity and stability for the oxygen reduction reaction. The catalysts were prepared by magnetron sputter aggregation and mass filtration providing a model catalyst system with a narrow size distribution. The structure and stability...... of nanostructured Pt-Y alloy catalysts were studied using transmission electron microscopy techniques. Using elemental X-ray mapping and high-resolution electron microscopy, the specific compositional structure and distribution of the individual nanoparticles was unraveled and the stability assessed. Studying...... the catalyst after reaction and after aging tests shows the development of a core-shell type structure after being exposed to reaction conditions....

  3. Direct decomposition of methane over Pd promoted Ni/SBA-15 catalysts

    Science.gov (United States)

    Pudukudy, Manoj; Yaakob, Zahira; Akmal, Zubair Shamsul

    2015-10-01

    The catalytic performance of Ni/SBA-15 catalysts promoted with different loadings of Pd is investigated for the thermocatalytic decomposition of methane into COx-free hydrogen and nanocarbon. The catalysts are characterized in terms of their structural, textural and redox properties. The results showed that the Pd deposition increased the crystallinity of NiO and allowed the fine dispersion of NiO on the SBA-15 support. The decreased surface area of SBA-15 after Ni loading, due to pore blocking, increased after the Pd deposition. Moreover, it reduced the reduction temperatures of NiO interacting with the SBA-15 due to the spillover effect of hydrogen. Furthermore, the addition of Pd increased the catalytic efficiency of the catalysts. A maximum hydrogen yield of 59% is observed over the 0.4% Pd catalyst within 30 min of time on stream. No deactivation is observed until 420 min of streaming for all of the catalysts, indicating a high catalytic stability of the Ni/SBA-15 catalysts for methane decomposition. A new set of multi-walled carbon nanotubes with open tips were deposited over the catalysts, irrespective of the role of Pd and its loading. Moreover, a high graphitization degree and oxidation stability are observed for the nanotubes deposited over the 0.4% Pd catalyst.

  4. REACTOR FILLED WITH CATALYST MATERIAL, AND CATALYST THEREFOR

    NARCIS (Netherlands)

    Sie, S.T.

    1995-01-01

    Abstract of WO 9521691 (A1) Described is a reactor (1) at least partially filled with catalyst granules (11), which is intended for catalytically reacting at least one gas and at least one liquid with each other. According to the invention the catalyst granules (11) are collected in agglomerates

  5. MCM-41 Bound Ruthenium Complex as Heterogeneous Catalyst for Hydrogenation Ⅰ: Effect of Support, Ligand and Solvent on the Catalyst Performance

    Institute of Scientific and Technical Information of China (English)

    YU, Ying-Min; FEI, Jin-Hua; ZHANG, Yi-Ping; ZHENG, Xiao-Ming

    2006-01-01

    The functionalized MCM-41 mesoporous bound ruthenium complex was synthesized and characterized using elemental analysis, atomic absorption spectrophotometer, BET, XRD and FTIR. Hydrogenation of carbon dioxide to formic acid was investigated over these catalysts under supercritical CO2 condition. The effect of reactant gas partial pressure, supports, solvents and ligands on the synthesis of formic acid was studied. These factors could influence the catalyst activity, stability and reuse performance greatly and no byproduct was detected. These promising catalysts also offered the industrial advantages such as easy separation.

  6. Mechanochemistry, catalysis, and catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Butyagin, P.Yu.

    1987-07-01

    The physical basis of mechanochemistry and the reasons for the initiation and acceleration of chemical reactions upon the mechanical treatment of solids have been considered. The phenomenon of mechanical catalysis has been described in the example case of the oxidation of CO on oxide surfaces, and the nature of the active sites and the laws governing the mechanically activated chemisorption of gases on cleavage and friction surfaces of solids have been examined. The possibilities of the use of the methods of mechanochemistry in processes used to prepare catalysts have been analyzed in examples of decomposition reactions of inorganic compounds and solid-phase synthesis.

  7. Activity of platinum/carbon and palladium/carbon catalysts promoted by Ni2 P in direct ethanol fuel cells.

    Science.gov (United States)

    Li, Guoqiang; Feng, Ligang; Chang, Jinfa; Wickman, Björn; Grönbeck, Henrik; Liu, Changpeng; Xing, Wei

    2014-12-01

    Ethanol is an alternative fuel for direct alcohol fuel cells, in which the electrode materials are commonly based on Pt or Pd. Owing to the excellent promotion effect of Ni2 P that was found in methanol oxidation, we extended the catalyst system of Pt or Pd modified by Ni2 P in direct ethanol fuel cells. The Ni2 P-promoted catalysts were compared to commercial catalysts as well as to reference catalysts promoted with only Ni or only P. Among the studied catalysts, Pt/C and Pd/C modified by Ni2 P (30 wt %) showed both the highest activity and stability. Upon integration into the anode of a homemade direct ethanol fuel cell, the Pt-Ni2 P/C-30 % catalyst showed a maximum power density of 21 mW cm(-2) , which is approximately two times higher than that of a commercial Pt/C catalyst. The Pd-Ni2 P/C-30 % catalyst exhibited a maximum power density of 90 mW cm(-2) . This is approximately 1.5 times higher than that of a commercial Pd/C catalyst. The discharge stability on both two catalysts was also greatly improved over a 12 h discharge operation.

  8. Ni catalysts with different promoters supported on zeolite for dry reforming of methane

    KAUST Repository

    Alotaibi, Raja

    2015-07-08

    Dry reforming of methane (DRM) is considered a high endothermic reaction with operating temperatures between 700 and 1000 °C to achieve high equilibrium conversion of CH4 and CO2 to the syngas (H2 and CO). The conventional catalysts used for DRM are Ni-based catalysts. However, many of these catalysts suffer from the short longevity due to carbon deposition. This study aims to evaluate the effect of La and Ca as promoters for Ni-based catalysts supported on two different zeolite supports, ZL (A) (BET surface area = 925 m2/g, SiO2/Al2O3 mol ratio = 5.1), and ZL (B) (BET surface area = 730 m2/g, SiO2/Al2O3 mol ratio = 12), for DRM. The physicochemical properties of the prepared catalysts were characterized with XRD, BET, TEM and TGA. These catalysts were tested for DRM in a microtubular reactor at reaction conditions of 700 °C. The catalyst activity results show that the catalysts Ni/ZL (B) and Ca-Ni/ZL (B) give the highest methane conversion (60 %) with less time on stream stability compared with promoted Ni on ZL (A). In contrast, La-containing catalysts, La-Ni/ZL (B), show more time on stream stability with minimum carbon content for the spent catalyst indicating the enhancement of the promoters to the Ni/ZL (A) and (B), but with less catalytic activity performance in terms of methane and carbon dioxide conversions due to rapid catalyst deactivation.

  9. 以非晶态合金催化剂SRNA-4为固相的气液固磁稳定床的界面传质研究%Interphase Mass Transfer in G-L-S Magnetically Stabilized Bed with Amorphous Alloy SRNA-4 Catalyst

    Institute of Scientific and Technical Information of China (English)

    李(韦华); 宗保守; 李晓芳; 孟祥坤; 张金利

    2006-01-01

    Gas-liquid (G-L) and liquid-solid (L-S) mass transfer coefficients were characterized in a gas-liquid-solid(G-L-S) three-phase magnetically stabilized bed (MSB) using amorphous alloy SRNA-4 as the solid phase. Effects such as superficial liquid velocity, superficial gas velocity, magnetic strength, liquid viscosity, and particle size were investigated. Experimental results indicated that the G-L volumetric mass transfer coefficients (KLa) increased along with the magnetic strength, superficial gas and liquid velocities. Proper increase of liquid viscosity promoted KLa only in the range of lower liquid viscosity. The external magnetic field made L-S mass transfer coefficients (Ks)in the G-L-S MSB lower than those of conventional fluidized beds. Ks in the MSB almost kept constant as the superficial liquid velocity and superficial gas velocity increased and decreased with the liquid viscosity and surface tension, while increased with the particle size Ks showed uniform axial and radial distributions except of small decreases close to the wall. Dimensionless correlations were established to estimate KLa and Ks of the MSB with SRNA-4 catalysts, which showed the average error of 5.4% and 2.5% respectively.

  10. In-situ characterization of heterogeneous catalysts

    CERN Document Server

    Rodriguez, Jose A; Chupas, Peter J

    2013-01-01

    Helps researchers develop new catalysts for sustainable fuel and chemical production Reviewing the latest developments in the field, this book explores the in-situ characterization of heterogeneous catalysts, enabling readers to take full advantage of the sophisticated techniques used to study heterogeneous catalysts and reaction mechanisms. In using these techniques, readers can learn to improve the selectivity and the performance of catalysts and how to prepare catalysts as efficiently as possible, with minimum waste. In-situ Characterization of Heterogeneous Catalysts feat

  11. Effect of Sr loading on oxydehydrogenation of propane to propylene over Al2O3-supported V-Mo catalysts

    Institute of Scientific and Technical Information of China (English)

    Meilana; Dharma; Putra; Saeed; M.Al-Zahrani; Ahmed; E.Abasaeed

    2013-01-01

    Incorporation of strontium into V-Mo alumina-supported catalyst enhanced its performance (increased conversion and selectivity,decreased reducibility and improved stability) in propane oxydehydrogenation to propylene.12.5% Sr loading was shown to be the optimum content to the V-Mo catalyst.The results were supported by various characterization techniques,namely,BET,XRD,SEM,FTIR and TPD.

  12. Graphitised Carbon Nanofibres as Catalyst Support for PEMFC

    DEFF Research Database (Denmark)

    Yli-Rantala, E.; Pasanen, A.; Kauranen, P.;

    2011-01-01

    Graphitised carbon nanofibres (G-CNFs) show superior thermal stability and corrosion resistance in PEM fuel cell environment over traditional carbon black (CB) and carbon nanotube catalyst supports. However, G-CNFs have an inert surface with only very limited amount of surface defects...... catalyst and the effects of the different surface treatments were discussed. On the basis of these results, new membrane electrode assemblies (MEAs) were manufactured and tested also for carbon corrosion by in situ FTIR analysis of the cathode exhaust gases. It was observed that the G-CNFs showed 5?times...... lower carbon corrosion compared to CB based catalyst when potential reached 1.5?V versus RHE in simulated start/stop cycling....

  13. Highly loaded Ni-based catalysts for low temperature ethanol steam reforming

    Science.gov (United States)

    Wang, Tuo; Ma, Hongyan; Zeng, Liang; Li, Di; Tian, Hao; Xiao, Shengning; Gong, Jinlong

    2016-05-01

    This paper describes the design of high-loading Ni/Al2O3 catalysts (78 wt% Ni) for low temperature ethanol steam reforming. The catalysts were synthesized via both co-precipitation (COP) and impregnation (IMP) methods. All the catalysts were measured by N2 adsorption-desorption, XRD, H2-TPR, and H2 pulse chemisorption. The characterization results demonstrated that the preparation method and the loading significantly affected the nickel particle size, active nickel surface area and catalytic performance. Over COP catalysts, large nickel particles were presented in nickel aluminum mixed oxides. In comparison, IMP catalysts gained more ``free'' NiO particles with weak interaction with the aluminum oxide. Consequently, COP catalysts yielded smaller nickel particles and larger active nickel surface areas than those of IMP catalysts. High loading is beneficial for obtaining sufficient active nickel sites when nickel particles are dispersed via COP, whereas excessive nickel content is not desired for catalysts prepared by IMP. Specifically, the 78 wt% nickel loaded catalyst synthesized by COP possessed small nickel particles (~6.0 nm) and an abundant active nickel area (35.1 m2 gcat-1). Consequently, COP-78 achieved superior stability with 92% ethanol conversion and ~35% H2 selectivity at 673 K for 30 h despite the presence of a considerable amount of coke.

  14. Catalyst design for biorefining.

    Science.gov (United States)

    Wilson, Karen; Lee, Adam F

    2016-02-28

    The quest for sustainable resources to meet the demands of a rapidly rising global population while mitigating the risks of rising CO2 emissions and associated climate change, represents a grand challenge for humanity. Biomass offers the most readily implemented and low-cost solution for sustainable transportation fuels, and the only non-petroleum route to organic molecules for the manufacture of bulk, fine and speciality chemicals and polymers. To be considered truly sustainable, biomass must be derived from resources which do not compete with agricultural land use for food production, or compromise the environment (e.g. via deforestation). Potential feedstocks include waste lignocellulosic or oil-based materials derived from plant or aquatic sources, with the so-called biorefinery concept offering the co-production of biofuels, platform chemicals and energy; analogous to today's petroleum refineries which deliver both high-volume/low-value (e.g. fuels and commodity chemicals) and low-volume/high-value (e.g. fine/speciality chemicals) products, thereby maximizing biomass valorization. This article addresses the challenges to catalytic biomass processing and highlights recent successes in the rational design of heterogeneous catalysts facilitated by advances in nanotechnology and the synthesis of templated porous materials, as well as the use of tailored catalyst surfaces to generate bifunctional solid acid/base materials or tune hydrophobicity.

  15. 反应条件对钌催化剂和铁催化剂的氨合成性能影响%Effects of Reaction Conditions on Performance of Ru Catalyst and Iron Catalyst for Ammonia Synthesis*

    Institute of Scientific and Technical Information of China (English)

    潘崇根; 李瑛; 蒋文; 刘化章

    2011-01-01

    Activated carbon-supported Ru-based catalyst and A301 iron catalyst were prepared, and the influences of reaction temperature, space velocity, pressure, and H2/N2 ratio on performance of iron catalyst coupled with Ru catalyst in series for ammonia synthesis were investigated. The activity tests were also performed on the single Ru and Fe catalysts as comparison. Results showed that the activity of the Ru catalyst for ammonia synthesis was higher than that of the iron catalyst by 33.5%-37.6% under the reaction conditions: 375-400 ℃, 10 MPa, 10000 h-1, H2: N2 = 3, and the Ru catalyst also had better thermal stability when treated at 475 ℃ for 20 h. The outlet ammonia concentration using Fe-Ru catalyst was increased by 45.6%-63.5% than that of the single-iron catalyst at low temperature (375-400 ℃), and the outlet ammonia concentration increased with increasing Ru catalyst loading.

  16. Electroless Nickel-Based Catalyst for Diffusion Limited Hydrogen Generation through Hydrolysis of Borohydride

    Directory of Open Access Journals (Sweden)

    Shannon P. Anderson

    2013-07-01

    Full Text Available Catalysts based on electroless nickel and bi-metallic nickel-molybdenum nanoparticles were synthesized for the hydrolysis of sodium borohydride for hydrogen generation. The catalysts were synthesized by polymer-stabilized Pd nanoparticle-catalyzation and activation of Al2O3 substrate and electroless Ni or Ni-Mo plating of the substrate for selected time lengths. Catalytic activity of the synthesized catalysts was tested for the hydrolyzation of alkaline-stabilized NaBH4 solution for hydrogen generation. The effects of electroless plating time lengths, temperature and NaBH4 concentration on hydrogen generation rates were analyzed and discussed. Compositional analysis and surface morphology were carried out for nano-metallized Al2O3 using Scanning Electron Micrographs (SEM and Energy Dispersive X-Ray Microanalysis (EDAX. The as-plated polymer-stabilized electroless nickel catalyst plated for 10 min and unstirred in the hydrolysis reaction exhibited appreciable catalytic activity for hydrolysis of NaBH4. For a zero-order reaction assumption, activation energy of hydrogen generation using the catalyst was estimated at 104.6 kJ/mol. Suggestions are provided for further work needed prior to using the catalyst for portable hydrogen generation from aqueous alkaline-stabilized NaBH4 solution for fuel cells.

  17. Relating FTS Catalyst Properties to Performance

    Science.gov (United States)

    Ma, Wenping; Ramana Rao Pendyala, Venkat; Gao, Pei; Jermwongratanachai, Thani; Jacobs, Gary; Davis, Burton H.

    2016-01-01

    During the reporting period June 23, 2011 to August 31, 2013, CAER researchers carried out research in two areas of fundamental importance to the topic of cobalt-based Fischer-Tropsch Synthesis (FTS): promoters and stability. The first area was research into possible substitute promoters that might be used to replace the expensive promoters (e.g., Pt, Re, and Ru) that are commonly used. To that end, three separate investigations were carried out. Due to the strong support interaction of ?-Al2O3 with cobalt, metal promoters are commonly added to commercial FTS catalysts to facilitate the reduction of cobalt oxides and thereby boost active surface cobalt metal sites. To date, the metal promoters examined have been those up to and including Group 11. Because two Group 11 promoters (i.e., Ag and Au) were identified to exhibit positive impacts on conversion, selectivity, or both, research was undertaken to explore metals in Groups 12 - 14. The three metals selected for this purpose were Cd, In, and Sn. At a higher loading of 25%Co on alumina, 1% addition of Cd, In, or Sn was found to-on average-facilitate reduction by promoting a heterogeneous distribution of cobalt consisting of larger lesser interacting cobalt clusters and smaller strongly interacting cobalt species. The lesser interacting species were identified in TPR profiles, where a sharp low temperature peak occurred for the reduction of larger, weakly interacting, CoO species. In XANES, the Cd, In, and Sn promoters were found to exist as oxides, whereas typical promoters (e.g., Re, Ru, Pt) were previously determined to exist in an metallic state in atomic coordination with cobalt. The larger cobalt clusters significantly decreased the active site density relative to the unpromoted 25%Co/Al2O3 catalyst. Decreasing the cobalt loading to 15%Co eliminated the large non-interacting species. The TPR peak for reduction of strongly interacting CoO in the Cd promoted catalyst occurred at a measurably lower temperature

  18. Nitrogen and sulfur co-doped carbon with three-dimensional ordered macroporosity: An efficient metal-free oxygen reduction catalyst derived from ionic liquid

    Science.gov (United States)

    Wu, Hui; Shi, Liang; Lei, Jiaheng; Liu, Dan; Qu, Deyu; Xie, Zhizhong; Du, Xiaodi; Yang, Peng; Hu, Xiaosong; Li, Junsheng; Tang, Haolin

    2016-08-01

    The development of efficient and durable catalyst for oxygen reduction reaction (ORR) is critical for the practical application of proton exchange membrane fuel cell (PEMFC). A novel imidazole based ionic liquid is synthesized in this study and used subsequently for the preparation of a N and S co-doped metal-free catalyst with three dimensional ordered microstructure. The catalyst prepared at 1100 °C showed improved ORR catalytic performance and stability compared to commercial Pt/C catalyst. We demonstrate that the high graphitic N content and high degree of graphitization of the synthesized catalyst is responsible for its superb ORR activity. Our results suggest that the N and S co-doped metal-free catalyst reported here is a promising alternative to traditional ORR catalyst based on noble metal. Furthermore, the current study also demonstrate that importance of morphology engineering in the development of high performance ORR catalyst.

  19. Long-Term Testing of Rhodium-Based Catalysts for Mixed Alcohol Synthesis – 2013 Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, Mark A.; Gray, Michel J.; Thompson, Becky L.

    2013-09-23

    The U.S. Department of Energy’s Pacific Northwest National Laboratory has been conducting research since 2005 to develop a catalyst for the conversion of synthesis gas (carbon monoxide and hydrogen) into mixed alcohols for use in liquid transportation fuels. Initially, research involved screening possible catalysts based on a review of the literature, because at that time, there were no commercial catalysts available. The screening effort resulted in a decision to focus on catalysts containing rhodium and manganese. Subsequent research identified iridium as a key promoter for this catalyst system. Since then, research has continued to improve rhodium/manganese/iridium-based catalysts, optimizing the relative and total concentrations of the three metals, examining baseline catalysts on alternative supports, and examining effects of additional promoters. Testing was continued in FY 2013 to evaluate the performance and long-term stability of the best catalysts tested to date. Three tests were conducted. A long-term test of over 2300 hr duration at a single set of operating conditions was conducted with the best carbon-supported catalyst. A second test of about 650 hr duration at a single set of operating conditions was performed for comparison using the same catalyst formulation on an alternative carbon support. A third test of about 680 hr duration at a single set of operating conditions was performed using the best silica-supported catalyst tested to date.

  20. Templating Routes to Supported Oxide Catalysts by Design

    Energy Technology Data Exchange (ETDEWEB)

    Notestein, Justin M. [Northwestern Univ., Evanston, IL (United States)

    2016-09-08

    The rational design and understanding of supported oxide catalysts requires at least three advancements, in order of increasing complexity: the ability to quantify the number and nature of active sites in a catalytic material, the ability to place external controls on the number and structure of these active sites, and the ability to assemble these active sites so as to carry out more complex functions in tandem. As part of an individual investigator research program that is integrated with the Northwestern University Institute for Catalysis in Energy Processes (ICEP) as of 2015, significant advances were achieved in these three areas. First, phosphonic acids were utilized in the quantitative assessment of the number of active and geometrically-available sites in MOx-SiO2 catalysts, including nanocrystalline composites, co-condensed materials, and grafted structures, for M=Ti, Zr, Hf, Nb, and Ta. That work built off progress in understanding supported Fe, Cu, and Co oxide catalysts from chelating and/or multinuclear precursors to maximize surface reactivity. Secondly, significant progress was made in the new area of using thin oxide overcoats containing ‘nanocavities’ from organic templates as a method to control the dispersion and thermal stability of subsequently deposited metal nanoparticles or other catalytic domains. Similar methods were used to control surface reactivity in SiO2-Al2O3 acid catalysts and to control reactant selectivity in Al2O3-TiO2 photocatalysts. Finally, knowledge gained from the first two areas has been combined to synthesize a tandem catalyst for hydrotreating reactions and an orthogonal tandem catalyst system where two subsequent reactions in a reaction network are independently controlled by light and heat. Overall, work carried out under this project significantly advanced the knowledge of synthesis-structure-function relationships in supported

  1. Precious metal-support interaction in automotive exhaust catalysts

    Institute of Scientific and Technical Information of China (English)

    郑婷婷; 何俊俊; 赵云昆; 夏文正; 何洁丽

    2014-01-01

    Precious metal-support interaction plays an important role in thermal stability and catalytic performance of the automotive exhaust catalysts. The support is not only a carrier for active compounds in catalysts but also can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature;meanwhile, noble metals can also enhance the redox per-formance and oxygen storage capacity of support. The mechanism of metal-support interactions mainly includes electronic interaction, formation of alloy and inward diffusion of metal into the support or covered by support. The form and degree of precious metal-sup-port interaction depend on many factors, including the content of precious metal, the species of support and metal, and preparation methods. The research results about strong metal-support interaction (SMSI) gave a theory support for developing a kind of new cata-lyst with excellent performance. This paper reviewed the interaction phenomenon and mechanism of precious metals (Pt, Pd, Rh) and support such as Al2O3, CeO2, and CeO2-based oxides in automotive exhaust catalysts. The factors that affect SMSI and the catalysts developed by SMSI were also discussed.

  2. Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis

    Directory of Open Access Journals (Sweden)

    Masahiko Arai

    2015-05-01

    Full Text Available Heterogeneous metal catalysts rather than homogeneous ones are recommended for industrial applications after considering their performance in activity, separation, and recycling [1]. The recycling of metal catalysts is important from economic and environmental points of view. When supported and bulk metal catalysts are used in liquid-phase organic reactions, there is a possibility that active metal species are leaching away into the liquid phases [2,3]. The metal leaching would make it difficult for the catalysts to maintain their desired initial performance for repeated batch reactions and during continuous ones. The metal leaching would also cause some undesired contamination of products by the metal species dissolved in the reaction mixture, and the separation of the metal contaminants would be required to purify the products. Therefore, various novel methods have been proposed so far to immobilize/stabilize the active metal species and to separate/collect/reuse the dissolved metal species [4]. In addition, knowledge on the heterogeneous and homogeneous natures of organic reactions using heterogeneous catalysts is important to discuss their reaction mechanisms and catalytically working active species. [...

  3. Stereospecific olefin polymerization catalysts

    Science.gov (United States)

    Bercaw, John E.; Herzog, Timothy A.

    1998-01-01

    A metallocene catalyst system for the polymerization of .alpha.-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula ##STR1## wherein: R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.10 alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C.sub.1 to C.sub.10 alkyls as a substituent, C.sub.6 to C.sub.15 aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R.sup.8).sub.3 where R.sup.8 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; R.sup.4 and R.sup.6 are substituents both having van der Waals radii larger than the van der Waals radii of groups R.sup.1 and R.sup.3 ; R.sup.5 is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E.sup.1, E.sup.2 are independently selected from the group consisting of Si(R.sup.9).sub.2, Si(R.sup.9).sub.2 --Si(R.sup.9).sub.2, Ge(R.sup.9).sub.2, Sn(R.sup.9).sub.2, C(R.sup.9).sub.2, C(R.sup.9).sub.2 --C(R.sup.9).sub.2, where R.sup.9 is C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; and the ligand may have C.sub.S or C.sub.1 -symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from .alpha.-olefin monomers.

  4. Metal catalysts for steam reforming of tar derived from the gasification of lignocellulosic biomass.

    Science.gov (United States)

    Li, Dalin; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

    2015-02-01

    Biomass gasification is one of the most important technologies for the conversion of biomass to electricity, fuels, and chemicals. The main obstacle preventing the commercial application of this technology is the presence of tar in the product gas. Catalytic reforming of tar appears a promising approach to remove tar and supported metal catalysts are among the most effective catalysts. Nevertheless, improvement of catalytic performances including activity, stability, resistance to coke deposition and aggregation of metal particles, as well as catalyst regenerability is greatly needed. This review focuses on the design and catalysis of supported metal catalysts for the removal of tar in the gasification of biomass. The recent development of metal catalysts including Rh, Ni, Co, and their alloys for steam reforming of biomass tar and tar model compounds is introduced. The role of metal species, support materials, promoters, and their interfaces is described.

  5. Hydrogen and/or syngas from steam reforming of glycerol. Study of platinum catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Pompeo, Francisco; Santori, Gerardo; Nichio, Nora N. [Facultad de Ingenieria, Universidad Nacional de La Plata, 1 esq 47, 1900 La Plata (Argentina); CINDECA, Facultad de Ciencias Exactas, Universidad Nacional de La Plata-CONICET, 47 N 257, 1900 La Plata (Argentina)

    2010-09-15

    In the present work, Pt catalysts prepared on different supports were evaluated in order to apply them in the steam reforming of glycerol reaction to obtain hydrogen and/or synthesis gas at temperatures lower than 450 C. A strong support effect on the behavior of catalysts was determined. The presence of intermediate products allowed to propose a scheme of reactions that would explain the results obtained at different space times and temperatures studied. Materials with acid properties demonstrated low activity to gaseous products, with formation of lateral products due to dehydration and condensation reactions, which would lead to coke formation and to a fast catalyst deactivation. On the contrary, the catalyst prepared with a support with neutral properties permitted to obtain a catalyst with excellent activity levels to gaseous products, high selectivity to H{sub 2}, and a very well stability in time. (author)

  6. A Selective Octane-Enhancing FCC Catalyst Using ZRP Zeolite as an Active Component

    Institute of Scientific and Technical Information of China (English)

    Huang Dayang; Shu Xingtian; He Mingyuan; Yang Xiaoming; Wang Dianzhong; Zong Baoning

    2001-01-01

    A hetero-crystalline seeding method to prepare a unique MFI type zeolite with mesopores of ca. 4 nm diameter designated as the ZRP zeolite, which possesses high stability and selectivity and is used as component of FCC catalysts to produce high-octane gasoline and light olefins, was developed. With the DOCR and DOCP catalysts containing the ZRP zeolite modified by phosphorus-incorporation as the octaneenhancing catalysts, the commercial trial was carried out in a 0.8Mt/a RFCC unit with a feedstock composed of Daqing atmospheric residue. As compared to the base catalyst, the LPG+gasoline+LCO product yield obtained from this catalyst was increased by 0.53m%. Meanwhile, the RON and MON of gasoline was increased by 1.4 and 2.4 units, respectively. The higher increment of MON is attributable to the higher isoparaffines content in gasoline. This result indicates that the ZRP zeolite possesses higher isomerization selectivity.

  7. An innovative catalyst system for slurry-phase Fischer-Tropsch synthesis: Cobalt plus a water-gas-shift catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Satterfield, C.N.; Yates, I.C.; Chanenchuk, C.

    1991-07-01

    The feasibility of using a mechanical mixture of a Co/MgO/SiO{sub 2} Fischer-Tropsch catalyst and a Cu-ZnO/Al{sub 2}O{sub 3} water-gas-shift (WGS) catalyst for hydrocarbon synthesis in a slurry reactor has been established. Such a mixture can combine the superior product distribution from cobalt with the high activity for the WGS reaction characteristic of iron. Weight ratios of Co/MgO/SiO{sub 2} to Cu-ZnO/Al{sub 2}O{sub 3} of 0.27 and 0.51 for the two catalysts were studied at 240{degrees}C, 0.79 MPa, and in situ H{sub 2}/CO ratios between 0.8 and 3.0. Each catalyst mixture showed stable Fischer-Tropsch activity for about 400 hours-on-stream at a level comparable to the cobalt catalyst operating alone. The Cu-ZnO/Al{sub 2}O{sub 3} catalyst exhibited a very slow loss of activity under these conditions, but when operated alone it was stable in a slurry reactor at 200--220{degrees}C, 0.79--1.48 MPa, and H{sub 2}/CO in situ ratios between 1.0 and 2.0. The presence of the water-gas-shift catalyst did not affect the long-term stability of the primary Fischer-Tropsch selectivity, but did increase the extent of secondary reactions, such as l-alkene hydrogenation and isomerization.

  8. Ni-Cu Hydrotalcite-Derived Mixed Oxides as Highly Selective and Stable Catalysts for the Synthesis of β-Branched Bioalcohols by the Guerbet Reaction.

    Science.gov (United States)

    Hernández, Willinton Y; De Vlieger, Kevin; Van Der Voort, Pascal; Verberckmoes, An

    2016-11-23

    A series of Ni-Cu hydrotalcite-derived mixed oxides have been synthesized and evaluated as heterogeneous catalysts for the dimerization of linear aliphatic alcohols to afford β-branched Guerbet alcohols. The use of the hydrotalcite-structured catalyst precursor highly favors the catalyst stability. This Cu/Ni catalyst has an enhanced reducibility of Ni(2+) species under reaction conditions, favoring the hydrogen transfer and hydrogenation capacity of the catalyst system. Catalytic results are reported for C8 , mixed C8 /C10 , and C18 alcohol feeds, with full conversions and Guerbet product purities of 72.5-96 %.

  9. POLYKETONE FROM ETHYLENE WITH CARBON MONOXIDE CATALYZED BY NOVEL CATALYST SYSTEMS BASED ON COPPER WITH BIDENTATE PHOSPHORUS CHELATING LIGANDS

    Institute of Scientific and Technical Information of China (English)

    Jun Huang; Feng-bo Li; Jin Zou; Guo-qing Yuan; Xiu-li Shi; Ding-sheng Yu

    2003-01-01

    Copolymerization of ethylene with carbon monoxide was performed with Cu catalyst systems. Novel catalyst systems based on Cu (Cu(CH3COO)2/ligand/acid) were firstly reported for the copolymerization of ethylene with carbon monoxide, in which the ligand was a bidentate phosphorus chelating ligand. The experimental results showed that this kind of Cu catalyst system exhibited high activity. When DPPP (1,3-bis(diphenylphosphine)propane) and CH3COOH were used catalyst system had the advantages of high stability and low cost.

  10. Study on Carbon Nanotubes Prepared from Catalytic Decomposition of CH4 over Lanthanum Containing Ni-Base Catalysts

    Institute of Scientific and Technical Information of China (English)

    Wang Minwei; Li Fengyi

    2004-01-01

    A series of lanthanum containing Ni-base catalysts were prepared by citric acid complex method.Carbon nanotubes (CNT) were synthesized bY catalytic decomposing CH4 over these catalysts and characterized by XRD, TEM and TGA.It is found that the addition of lanthanum can not increase the yield of carbon nanotube, but can make the diameter of carbon nanotube thinner and even.The more the lanthanum addsr, the thinner the diameter of CNTs becomes.With the CNTs prepared on Ni-Mg catalyst, the CNTs prepared on Ni-La-Mg catalyst has better crystallinity and thermal stability.

  11. The Electrochemical Performance and Durability of Carbon Supported Pt Catalyst in Contact with Aqueous and Polymeric Proton Conductors

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma; Skou, Eivind Morten

    2014-01-01

    Significant differences in catalyst performance and durability are often observed between the use of a liquid electrolyte (e.g. sulfuric acid), and a solid polymer electrolyte (e.g. Nafion®). To understand this phenomenon, we studied the electrochemical behavior of a commercially available carbon......, an improved proton - catalyst interphase, the restriction of catalyst particle aggregation and the improved stability of the ionomer phase especially after the lamination. Therefore, an innovative electrode HMEA design for ex-situ catalyst characterization is proposed. The electrode structure is identical...

  12. Potential of Ni supported on clinoptilolite catalysts for carbon dioxide reforming of methane

    Energy Technology Data Exchange (ETDEWEB)

    Nimwattanakul, Weetima; Luengnaruemitchai, Apanee; Jitkarnka, Sirirat [The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330 (Thailand)

    2006-01-15

    Carbon dioxide reforming of methane to synthesis gas has been investigated with Ni-supported clinoptilolite catalysts. The catalysts were prepared by using the incipient wetness impregnation method. The catalytic activity of Ni supported on clinoptilolite with varying Ni loadings was determined and the results showed that at 700{sup o}C, 8wt% Ni/clinoptilolite gave the highest activity. It exhibited not only the highest activity and selectivity but also remarkable stability. Moreover, both the activity and stability of this catalyst were observed to vary with the Zr content, exhibiting a maximum at a composition of 2% Zr. The amount of carbonaceous deposits on the spent catalysts was further investigated by temperature-programmed oxidation (TPO) and thermogravimetric analyzer (TGA) studies. (author)

  13. Causes of Activation and Deactivation of Modified Nanogold Catalysts during Prolonged Storage and Redox Treatments

    Directory of Open Access Journals (Sweden)

    Ekaterina Kolobova

    2016-04-01

    Full Text Available The catalytic properties of modified Au/TiO2 catalysts for low-temperature CO oxidation are affected by deactivation and reactivation after long-term storage and by redox treatments. The effect of these phenomena on the catalysts was studied by HRTEM, BET, SEM, FTIR CO, XPS and H2 TPR methods. The main cause for the deactivation and reactivation of catalytic properties is the variation in the electronic state of the supported gold, mainly, the proportion of singly charged ions Au+. The most active samples are those with the highest proportion of singly charged gold ions, while catalysts with a high content of trivalent gold ions are inactive at low-temperatures. Active states of gold, resistant to changes caused by the reaction process and storage conditions, can be stabilized by modification of the titanium oxide support with transition metals oxides. The catalyst modified with lanthanum oxide shows the highest stability and activity.

  14. 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.

  15. Study on Catalysts with Rhodium Loading on Different Cerium-Zirconium Mixed Oxides

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The catalysts with Rh loading on different cerium-zirconium mixed oxides were characterized by BET, H2-TPR and OSC. The effects of different cerium-zirconium mixed oxides on catalytic performance and thermal stability of Rh loaded catalyst were studied. The results show that: (1) Rh can enhance cerium-zirconium mixed oxides OSC and catalytic reaction rates; (2) cerium-zirconium mixed oxides with high Ce contents and low Zr contents are more favorable to the stability of catalysts. Moreover, the contents of CeO2 have important effect on catalysts characteristics, and the addition of some rare earth components, such as La, Pr and Nd also have some influences.

  16. Activity and deactivation behavior of Au/LaMnO3 catalysts for CO oxidation

    Institute of Scientific and Technical Information of China (English)

    JIA Meilin; LI Xu; Zhaorigetu; SHEN Yuenian; LI Yunxia

    2011-01-01

    Perovskite oxide LaMnO3 was prepared by sol-gel method and the nanosize Au/LaMnO3 catalyst was prepared by deposition- precipitation (DP) method in the paper. Characterization of the catalyst sample was made by X-ray diffractometer (XRD), atom absorption spectra (AAS) and X-ray photoelectron spectroscopy (XPS) instrumental methods. The activity, long-term stability and the reasons for deactivation of the gold catalyst in CO oxidation were investigated. The experiment results demonstrated that the Au/LaMnO3 catalyst exhibited high stability in the ambient storage process. However, the gradual decrease in initial activity during 100 h reaction was still observed, which could be ascribed to the aggregation of gold particles and the transfer from gold ion to the metal gold.

  17. Influence of promoters and oxidants on propane dehydrogenation over chromium-oxide catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Lapidus, A.L.; Agafonov, Yu.A.; Shaporeva, N.Yu.; Trushin, D.V.; Gaidai, N.A.; Nekrasov, N.V. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Inst. of Organic Chemistry

    2010-12-30

    Possibilities for increasing the efficiency of supported on SiO{sub 2} chromium-oxide catalysts in propane oxidative dehydrogenation in CO{sub 2} presence are investigated: the introduction of Li, Na, K, Ca in catalysts and the addition of O{sub 2} in the reaction mixture. It was been found that the positive role of K - the increase of the selectivity to propene and stability of catalysts at long-duration tests - appeared at the relation of Cr:K=20. It was shown that the presence of little amount of O{sub 2} (2%) in the reaction mixtures of propane and carbon dioxide resulted in the increase of propene yield and catalyst stability. (orig.)

  18. Ceramic catalyst materials

    Energy Technology Data Exchange (ETDEWEB)

    Sault, A.G.; Gardner, T.J. [Sandia National Laboratories, Albuquerque, NM (United States); Hanprasopwattanna, A.; Reardon, J.; Datye, A.K. [Univ. of New Mexico, Albuquerque, NM (United States)

    1995-08-01

    Hydrous titanium oxide (HTO) ion-exchange materials show great potential as ceramic catalyst supports due to an inherently high ion-exchange capacity which allows facile loading of catalytically active transition metal ions, and an ability to be cast as thin films on virtually any substrate. By coating titania and HTO materials onto inexpensive, high surface area substrates such as silica and alumina, the economics of using these materials is greatly improved, particularly for the HTO materials, which are substantially more expensive in the bulk form than other oxide supports. In addition, the development of thin film forms of these materials allows the catalytic and mechanical properties of the final catalyst formulation to be separately engineered. In order to fully realize the potential of thin film forms of titania and HTO, improved methods for the deposition and characterization of titania and HTO films on high surface area substrates are being developed. By varying deposition procedures, titania film thickness and substrate coverage can be varied from the submonolayer range to multilayer thicknesses on both silica and alumina. HTO films can also be formed, but the quality and reproducibility of these films is not nearly as good as for pure titania films. The films are characterized using a combination of isopropanol dehydration rate measurements, point of zero charge (PZC) measurements, BET surface area, transmission electron microscopy (TEM), and elemental analysis. In order to assess the effects of changes in film morphology on catalytic activity, the films are being loaded with MoO{sub 3} using either incipient wetness impregnation or ion-exchange of heptamolybdate anions followed by calcining. The MoO{sub 3} is then sulfided to form MOS{sub 2}, and tested for catalytic activity using pyrene hydrogenation and dibenzothiophene (DBT) desulfurization, model reactions that simulate reactions occurring during coal liquefaction.

  19. Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts

    Directory of Open Access Journals (Sweden)

    R. Prasad

    2011-05-01

    Full Text Available CuO-CeO2 systems have been proposed as a promising catalyst for low temperature diesel-soot oxidation. CuO-CeO2 catalysts prepared by various methods were examined for air oxidation of the soot in a semi batch tubular flow reactor. The air oxidation of soot was carried out under tight contact with soot/catalyst ratio of 1/10. Air flow rate was 150 ml/min, soot-catalyst mixture was 110 mg, heating rate was 5 0C/min. Prepared catalysts were calcined at 500 0C and their stability was examined by further heating to 800 0C for 4 hours. It was found that the selectivity of all the catalysts was nearly 100% to CO2 production. It was observed that the activity and stability of the catalysts greatly influenced by the preparation methods. The strong interaction between CuO and CeO2 is closely related to the preparation route that plays a crucial role in the soot oxidation over the CuO-CeO2 catalysts. The ranking order of the preparation methods of the catalysts in the soot oxidation performance is as follows: sol-gel > urea nitrate combustion > Urea gelation method > thermal decomposition > co-precipitation. Copyright © 2011 BCREC UNDIP. All rights reserved.(Received: 27th June 2010, Revised: 7th August 2010; Accepted: 13rd October 2010[How to Cite: R. Prasad, V.R. Bella. (2011. Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1: 15-21. doi:10.9767/bcrec.6.1.822.15-21][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.822.15-21 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/822 | View in 

  20. Development of GREET Catalyst Module

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhichao [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division; Dunn, Jennifer B. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division; Cronauer, Donald C. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division

    2014-09-01

    Catalysts are critical inputs for many pathways that convert biomass into biofuels. Energy consumption and greenhouse gas (GHG) emissions during the production of catalysts and chemical inputs influence the life-cycle energy consumption, and GHG emissions of biofuels and need to be considered in biofuel life-cycle analysis (LCA). In this report, we develop energy and material flows for the production of three different catalysts (tar reforming, alcohol synthesis, Zeolite Socony Mobil-5 [ZSM-5]) and two chemicals (olivine, dimethyl ether of polyethylene glycol [DEPG]). These compounds and catalysts are now included in the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET™) catalyst module. They were selected because they are consumed in existing U.S. Department of Energy (DOE) analyses of biofuel processes. For example, a thermochemical ethanol production pathway (indirect gasification and mixed alcohol synthesis) developed by the National Renewable Energy Laboratory (NREL) uses olivine, DEPG, and tar reforming and alcohol synthesis catalysts (Dutta et al., 2011). ZSM-5 can be used in biofuel production pathways such as catalytic upgrading of sugars into hydrocarbons (Biddy and Jones, 2013). Other uses for these compounds and catalysts are certainly possible. In this report, we document the data sources and methodology we used to develop material and energy flows for the catalysts and compounds in the GREET catalyst module. In Section 2 we focus on compounds used in the model Dutta et al. (2011) developed. In Section 3, we report material and energy flows associated with ZSM-5 production. Finally, in Section 4, we report results.

  1. Methane Direct Conversion on Mo/ZSM-5 Catalysts Modified by Pd and Ru

    Institute of Scientific and Technical Information of China (English)

    Priscila Dias Sily; Fabio Bellot Noronha; Fabio Barboza Passos

    2006-01-01

    The effect of addition of Ru and Pd to Mo/HZSM-5 catalysts used in the dehydroaromatization of methane was investigated. Catalytic tests and temperature-programmed oxidation results showed that Pd-based catalysts were more selective to naphthalene and suffered strong deactivation. The presence of Ru improved the activity and stability, with a decrease in the carbonaceous deposit probably because of a mechanism of protection of the Mo2C surface.

  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. Identification of carbon-encapsulated iron nanoparticles as active species in non-precious metal oxygen reduction catalysts

    Science.gov (United States)

    Varnell, Jason A.; Tse, Edmund C. M.; Schulz, Charles E.; Fister, Tim T.; Haasch, Richard T.; Timoshenko, Janis; Frenkel, Anatoly I.; Gewirth, Andrew A.

    2016-08-01

    The widespread use of fuel cells is currently limited by the lack of efficient and cost-effective catalysts for the oxygen reduction reaction. Iron-based non-precious metal catalysts exhibit promising activity and stability, as an alternative to state-of-the-art platinum catalysts. However, the identity of the active species in non-precious metal catalysts remains elusive, impeding the development of new catalysts. Here we demonstrate the reversible deactivation and reactivation of an iron-based non-precious metal oxygen reduction catalyst achieved using high-temperature gas-phase chlorine and hydrogen treatments. In addition, we observe a decrease in catalyst heterogeneity following treatment with chlorine and hydrogen, using Mössbauer and X-ray absorption spectroscopy. Our study reveals that protected sites adjacent to iron nanoparticles are responsible for the observed activity and stability of the catalyst. These findings may allow for the design and synthesis of enhanced non-precious metal oxygen reduction catalysts with a higher density of active sites.

  4. Identification of carbon-encapsulated iron nanoparticles as active species in non-precious metal oxygen reduction catalysts.

    Science.gov (United States)

    Varnell, Jason A; Tse, Edmund C M; Schulz, Charles E; Fister, Tim T; Haasch, Richard T; Timoshenko, Janis; Frenkel, Anatoly I; Gewirth, Andrew A

    2016-08-19

    The widespread use of fuel cells is currently limited by the lack of efficient and cost-effective catalysts for the oxygen reduction reaction. Iron-based non-precious metal catalysts exhibit promising activity and stability, as an alternative to state-of-the-art platinum catalysts. However, the identity of the active species in non-precious metal catalysts remains elusive, impeding the development of new catalysts. Here we demonstrate the reversible deactivation and reactivation of an iron-based non-precious metal oxygen reduction catalyst achieved using high-temperature gas-phase chlorine and hydrogen treatments. In addition, we observe a decrease in catalyst heterogeneity following treatment with chlorine and hydrogen, using Mössbauer and X-ray absorption spectroscopy. Our study reveals that protected sites adjacent to iron nanoparticles are responsible for the observed activity and stability of the catalyst. These findings may allow for the design and synthesis of enhanced non-precious metal oxygen reduction catalysts with a higher density of active sites.

  5. Towards stable catalysts by controlling collective properties of supported metal nanoparticles

    Science.gov (United States)

    Prieto, Gonzalo; Zečević, Jovana; Friedrich, Heiner; de Jong, Krijn P.; de Jongh, Petra E.

    2013-01-01

    Supported metal nanoparticles play a pivotal role in areas such as nanoelectronics, energy storage/conversion and as catalysts for the sustainable production of fuels and chemicals. However, the tendency of nanoparticles to grow into larger crystallites is an impediment for stable performance. Exemplarily, loss of active surface area by metal particle growth is a major cause of deactivation for supported catalysts. In specific cases particle growth might be mitigated by tuning the properties of individual nanoparticles, such as size, composition and interaction with the support. Here we present an alternative strategy based on control over collective properties, revealing the pronounced impact of the three-dimensional nanospatial distribution of metal particles on catalyst stability. We employ silica-supported copper nanoparticles as catalysts for methanol synthesis as a showcase. Achieving near-maximum interparticle spacings, as accessed quantitatively by electron tomography, slows down deactivation up to an order of magnitude compared with a catalyst with a non-uniform nanoparticle distribution, or a reference Cu/ZnO/Al2O3 catalyst. Our approach paves the way towards the rational design of practically relevant catalysts and other nanomaterials with enhanced stability and functionality, for applications such as sensors, gas storage, batteries and solar fuel production.

  6. Nano carbon supported platinum catalyst interaction behavior with perfluorosulfonic acid ionomer and their interface structures

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma

    2016-01-01

    behavior of Nafion ionomer on platinized carbon nano fibers (CNFs), carbon nano tubes (CNTs) and amorphous carbon (Vulcan). The interaction is affected by the catalyst surface oxygen groups as well as porosity. Comparisons between the carbon supports and platinized equivalents are carried out. It reveals......, the ionomer may have an adsorption preference to the platinum nano particle rather than to the overall catalyst. This was verified by a close examination on the decomposition temperature of the carbon support and the ionomer. The electrochemical stability of the catalyst ionomer composite electrode suggests...

  7. A Novel Catalyst for Liquid Phase Hydrogenation of m-Dinitrobenzene to m-Phenylenediamine

    Institute of Scientific and Technical Information of China (English)

    Ying Xin LIU; Zuo Jun WEI; Ji Xiang CHEN; Ji Yan ZHANG; Xin Xue LI; Xiong Hui WEI

    2005-01-01

    A novel lanthana-promoted nickel catalyst supported on silica for the liquid phase hydrogenation of m-dinitrobenzene to m-phenylenediamine was prepared by an incipient wetness sequential impregnation method. It was found that Ni-La/SiO2 catalyst exhibited high activity and stability for m-dinitrobenzene hydrogenation. Over this catalyst, the conversion of m-dinitrobenzene and the yield of m-phenylenediamine were up to 97.1% and 93.5%, respectively,at 373 K and 2.6 MPa hydrogen pressure after reaction for 1 h.

  8. Effect of samarium on methanation resistance of activated carbon supported ruthenium catalyst for ammonia synthesis

    Institute of Scientific and Technical Information of China (English)

    周春晖; 祝一锋; 刘化章

    2010-01-01

    The effects of samarium(Sm) on carbon-methanation and catalytic activity of the Ba-Ru-K/AC (active carbon) catalyst for ammonia synthesis were investigated. The addition of samarium improved significantly the activity and stability of the catalyst. The results of temperature-programmed desorption (H2-TPD) and in-situ-TPSR FTIR indicated that samarium impeded the adsorption of hydrogen on the catalyst surface, thus leading to the high catalytic activity and resistance to carbon-methanation. XRD patterns reve...

  9. Biopolymer-supported ionic-liquid-phase ruthenium catalysts for olefin metathesis.

    Science.gov (United States)

    Clousier, Nathalie; Filippi, Alexandra; Borré, Etienne; Guibal, Eric; Crévisy, Christophe; Caijo, Fréderic; Mauduit, Marc; Dez, Isabelle; Gaumont, Annie-Claude

    2014-04-01

    Original ruthenium supported ionic liquid phase (SILP) catalysts based on alginates as supports were developed for olefin metathesis reactions. The marine biopolymer, which fulfills most of the requisite properties for a support such as widespread abundance, insolubility in the majority of organic solvents, a high affinity for ionic liquids, high chemical stability, biodegradability, low cost, and easy processing, was impregnated by [bmim][PF6 ] containing an ionically tagged ruthenium catalyst. These biosourced catalysts show promising performances in ring-closing metathesis (RCM) and cross-metathesis (CM) reactions, with a high level of recyclability and reusability combined with a good reactivity.

  10. Toluene decomposition by DBD-type plasma combined with metal oxide catalysts supported on ferroelectric materials.

    Science.gov (United States)

    Jeong, Jin Guk; Lee, Hyeong Seok; Kang, Youngjin; Lee, Ki Bong; Yoo, Jung Whan

    2013-06-01

    We investigated toluene decomposition with a single-stage plasma catalytic system operated at atmospheric pressure and working at reduced temperature (T < 75 degrees C), where a synergistic catalyst was integrated on ferroelectric BaTiO3 beads with a high dielectric constant. The catalyst species were characterized by FE-SEM and XPS before and after the experiment. The MnO2/BaTiO3 catalyst showed high stability in igniting plasma during destruction of toluene for 230 hours in a lifetime test.

  11. Relationship between surface microstructure and properties of supported catalyst Rh/Ys

    Institute of Scientific and Technical Information of China (English)

    柳忠阳; 潘平来; 朱长城; 王晓筠; 袁国卿

    1997-01-01

    The inner structure of Rh/Ys,a novel high efficiency supported catalyst,and the spreading of Rh on the Ys surface were analyzed through electron transmission microscopy and scanning tunnel microscopy.The relationship between the distribution of Rh over the support and the preparation temperature of th catalyst was determined.The formation of Rh-C bond was confirmed by XPS and far-IR spectra.The loss of Rh from the surface of the support and the catalytic activity under different preparation conditions have been compared.The internal factors for the high activity and high stability of the novel Rh/Ys catalyst have been discussed.

  12. XAFS characterization of industrial catalysts: in situ study of phase transformation of nickel sulfide

    Science.gov (United States)

    Wang, J.; Jia, Z.; Wang, Q.; Zhao, S.; Xu, Z.; Yang, W.; Frenkel, A. I.

    2016-05-01

    The online sulfiding process for nickel-contained catalyst often ends up with a nickel sulfide mixture in refinery plant. To elucidate the local environment of nickel and its corresponding sulfur species, a model catalyst (nickel sulfide) and model thermal process were employed to explore the possibilities for characterization of real catalysts in industrial conditions. The present investigation shows effectiveness of in situ XANES and EXAFS measurements for studying the phase stability and phase composition in these systems, which could be used to simulate real sulfiding process in industrial reactions, such as hydrodesulfurizations of oil.

  13. Development of Non-Noble Metal Ni-Based Catalysts for Dehydrogenation of Methylcyclohexane

    KAUST Repository

    Al-ShaikhAli, Anaam H.

    2016-11-30

    Liquid organic chemical hydride is a promising candidate for hydrogen storage and transport. Methylcyclohexane (MCH) to toluene (TOL) cycle has been considered as one of the feasible hydrogen carrier systems, but selective dehydrogenation of MCH to TOL has only been achieved using the noble Pt-based catalysts. The aim of this study is to develop non-noble, cost-effective metal catalysts that can show excellent catalytic performance, mainly maintaining high TOL selectivity achievable by Pt based catalysts. Mono-metallic Ni based catalyst is a well-known dehydrogenation catalyst, but the major drawback with Ni is its hydrogenolysis activity to cleave C-C bonds, which leads to inferior selectivity towards dehydrogenation of MCH to TOL. This study elucidate addition of the second metal to Ni based catalyst to improve the TOL selectivity. Herein, ubiquitous bi-metallic nanoparticles catalysts were investigated including (Ni–M, M: Ag, Zn, Sn or In) based catalysts. Among the catalysts investigated, the high TOL selectivity (> 99%) at low conversions was achieved effectively using the supported NiZn catalyst under flow of excess H2. In this work, a combined study of experimental and computational approaches was conducted to determine the main role of Zn over Ni based catalyst in promoting the TOL selectivity. A kinetic study using mono- and bimetallic Ni based catalysts was conducted to elucidate reaction mechanism and site requirement for MCH dehydrogenation reaction. The impact of different reaction conditions (feed compositions, temperature, space velocity and stability) and catalyst properties were evaluated. This study elucidates a distinctive mechanism of MCH dehydrogenation to TOL reaction over the Ni-based catalysts. Distinctive from Pt catalyst, a nearly positive half order with respect to H2 pressure was obtained for mono- and bi-metallic Ni based catalysts. This kinetic data was consistent with rate determining step as (somewhat paradoxically) hydrogenation

  14. ``Greener Shade of Ruthenium'': New Concepts of Activation, Immobilization, and Recovery of Ruthenium Catalysts For Green Olefin Metathesis

    Science.gov (United States)

    Michrowska, Anna; Gulajski, Lukasz; Grela, Karol

    The results described herewith demonstrate that the activity of ruthenium (Ru) metathesis catalysts can be enhanced by introduction of electron-withdrawing groups (EWGs) without detriment to catalysts stability. This principle can be used not only to increase the catalyst activity, but also to alter its physical-chemical properties, such as solubility in given medium or affinity to silica gel. An example of novel immobilisation strategy, based on this concept is presented. The ammonium-tagged Hoveyda-type catalysts can be successfully applied in aqueous media as well as in ionic liquids (IL). Substitution of a benzylidene fragment can be used not only to immobilize the organometallic complex in such media, but also to increase its catalytic activity by electronic activation. The high stability and good application profiles of such modified catalysts in conjunction with their facile removal from organic products can be expected to offer new opportunities in green applications of olefin metathesis.

  15. Hydrogenation of biofuels with formic acid over a palladium-based ternary catalyst with two types of active sites.

    Science.gov (United States)

    Wang, Liang; Zhang, Bingsen; Meng, Xiangju; Su, Dang Sheng; Xiao, Feng-Shou

    2014-06-01

    A composite catalyst including palladium nanoparticles on titania (TiO2) and on nitrogen-modified porous carbon (Pd/TiO2@N-C) is synthesized from palladium salts, tetrabutyl titanate, and chitosan. N2 sorption isotherms show that the catalyst has a high BET surface area (229 m(2)  g(-1)) and large porosity. XPS and TEM characterization of the catalyst shows that palladium species with different chemical states are well dispersed across the TiO2 and nitrogen-modified porous carbon, respectively. The Pd/TiO2@N-C catalyst is very active and shows excellent stability towards hydrogenation of vanillin to 2-methoxy-4-methylphenol using formic acid as hydrogen source. This activity can be attributed to a synergistic effect between the Pd/TiO2 (a catalyst for dehydrogenation of formic acid) and Pd/N-C (a catalyst for hydrogenation of vanillin) sites.

  16. Effects of P content in a P/HZSM-5 catalyst on the conversion of ethanol to hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    Jiangyin Lu; Yancong Liu

    2011-01-01

    A series of P/HZSM-5 catalysts prepared by impregnation method were used for ethanol conversion to lower olefins.The catalysts were characterized by X-ray diffraction(XRD),NH3-temperature-programmed desorption(NH3-TPD)and N2 adsorption-desorption measurements.It was found that the P/HZSM-5 catalysts showed high activity and selectivity toward light olefins.The selectivities of propylene and butylene can be improved with the introduction of phosphorus(P).When the content of P reached 3.0 wt%,more than 18.9% propylene in the gaseous products was obtained over the P/HZSM-5 catalyst at 450 ℃.The introduction of P modified the strong Br()nsted acid sites of the original HZSM-5 catalysts and P/HZSM-5 catalysts could resist coke formation and showed good stability.

  17. Dehydrogenation of propane in the presence of carbon dioxide over chromium and gallium oxides catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Lapidus, A.L.; Agafonov, Yu.A.; Gaidai, N.A.; Nekrasov, N.V.; Menshova, M.V.; Kunusova, R.M. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Inst. of Organic Chemistry

    2011-07-01

    Effective chromium and gallium oxides supported catalysts were prepared and tested in longduration experiments for propane dehydrogenation in the presence of CO{sub 2}. The optimal concentrations of active metals were found. It was shown that the activity, selectivity and stability of chromium oxides catalysts were higher than these parameters for gallium ones. Mechanism of propane oxidative dehydrogenation was studied over both catalysts using unstationary and spectroscopic methods. The employment of these methods allowed to establish the differences in process mechanism. It was shown that surface hydroxides took participation in propene formation over Cr-catalysts and hydrides - over Ga-ones. Propane and carbon dioxide participated in the reaction from the adsorbed state over both catalysts but they were differed by the adsorption capacity of the reaction components: CO2 was tied more firmly than C{sub 3}H{sub 6} over both catalysts, CO{sub 2} and C{sub 3}H{sub 6} were tied more strongly with Cr-catalysts than with Ga-ones. It was shown that CO{sub 2} took active participation in reverse watergas shift reaction and in oxidation of catalyst surface over chromium oxides catalysts. The main role of CO{sub 2} in propane dehydrogenation over gallium catalysts consisted in a decrease of coke formation. Step-schemes of propene and cracking products formation were proposed on the basis of literature and obtained data: via the redox mechanism over Cr-catalysts and through a heterolytic dissociation reaction pathway over Ga-ones. (orig.)

  18. One-step synthesis of nitrogen-iron coordinated carbon nanotube catalysts for oxygen reduction reaction

    Science.gov (United States)

    Choi, Woongchul; Yang, Gang; Kim, Suk Lae; Liu, Peng; Sue, Hung-Jue; Yu, Choongho

    2016-05-01

    Prohibitively expensive precious metal catalysts for oxygen reduction reaction (ORR) have been one of the major hurdles in a wide use of electrochemical cells. Recent significant efforts to develop precious metal free catalysts have resulted in excellent catalytic activities. However, complicated and time-consuming synthesis processes have negated the cost benefit. Moreover, detailed analysis about catalytically active sites and the role of each element in these high-performance catalysts containing nanomaterials for large surface areas are often lacking. Here we report a facile one-step synthesis method of nitrogen-iron coordinated carbon nanotube (CNT) catalysts without precious metals. Our catalysts show excellent long-term stability and onset ORR potential comparable to those of other precious metal free catalysts, and the maximum limiting current density from our catalysts is larger than that of the Pt-based catalysts. We carry out a series of synthesis and characterization experiments with/without iron and nitrogen in CNT, and identify that the coordination of nitrogen and iron in CNT plays a key role in achieving the excellent catalytic performances. We anticipate our one-step process could be used for mass production of precious metal free electrocatalysts for a wide range of electrochemical cells including fuel cells and metal-air batteries.

  19. Electrocatalytic activity of PtAu/C catalysts for glycerol oxidation.

    Science.gov (United States)

    Jin, Changchun; Sun, Chao; Dong, Rulin; Chen, Zhidong

    2012-01-01

    The electrocatalytic oxidation of glycerol on PtAu/C catalysts has been investigated by cyclic voltammetry. PtAu bimetallic nanoparticles are prepared by chemical reduction. Carbon-supported PtAu catalysts are found to exhibit high electrocatalytic activity for the oxidation of glycerol in alkaline solution in terms of oxidation potential and current density as well as stability, and PtAu/C catalysts with different Pt:Au composition ratios show no much difference in catalytic activity. In acidic solution, PtAu/C catalysts exhibit similar to Pt/C catalysts in activity, but the advantage of the PtAu/C catalysts in terms of per unit mass of platinum is still obvious. The PtAu/C catalysts, in a wide Pt:Au ratio range, show a remarkable enhancement in the mass specific activity of platinum with decreasing platinum content in both alkaline and acidic solutions. This is of significance for reducing the usage of platinum and indicates that though platinum acts as main active sites, gold also plays an important role in the function of PtAu/C catalysts.

  20. [Low-temperature catalytic reduction of NO over Fe-MnOx-CeO2/ZrO2 catalyst].

    Science.gov (United States)

    Liu, Rong; Yang, Zhi-Qin

    2012-06-01

    Fe-MnOx-CeO2/ZrO2 catalysts were prepared through impregnation method with nanometer ZrO2 as a carrier and used in selective catalytic reduction of NO with NH3 at low temperature. Effects of active component ratio and loading of promoter on the catalyst activity were investigated. The catalysts were characterized by means of XRD, SEM, EDS and BET. The effects of temperature, SO2 and H2O on NO conversion were studied and the results showed that in the absence of SO2 and H2O, the catalyst of 8% Fe-10% MnOx-CeO2/ZrO2 had good activity and stability as well as the NOx removal efficiency reached 85.23% at 120 degrees C and 92.0% at 180 degrees C. The presence of SO2 and H2O results in the catalyst deactivated. Properties of the catalyst on different reaction stages were characterized by FT-IR to study the inactivation mechanism of the catalyst. The results showed that the catalyst deactivation was due to the deposition of ammonium sulfate on the catalyst and the sulphation of the catalyst.

  1. The innovation catalysts.

    Science.gov (United States)

    Martin, Roger L

    2011-06-01

    A few years ago the software development company Intuit realized that it needed a new approach to galvanizing customers. The company's Net Promoter Score was faltering, and customer recommendations of new products were especially disappointing. Intuit decided to hold a two-day, off-site meeting for the company's top 300 managers with a focus on the role of design in innovation. One of the days was dedicated to a program called Design for Delight. The centerpiece of the day was a PowerPoint presentation by Intuit founder Scott Cook, who realized midway through that he was no Steve Jobs: The managers listened dutifully, but there was little energy in the room. By contrast, a subsequent exercise in which the participants worked through a design challenge by creating prototypes, getting feedback, iterating, and refining, had them mesmerized. The eventual result was the creation of a team of nine design-thinking coaches--"innovation catalysts"--from across Intuit who were made available to help any work group create prototypes, run experiments, and learn from customers. The process includes a "painstorm" (to determine the customer's greatest pain point), a "soljam" (to generate and then winnow possible solutions), and a "code-jam" (to write code "good enough" to take to customers within two weeks). Design for Delight has enabled employees throughout Intuit to move from satisfying customers to delighting them.

  2. Development of Coke-tolerant Transition Metal Catalysts for Dry Reforming of Methane

    KAUST Repository

    Al-Sabban, Bedour E.

    2016-11-07

    Dry reforming of methane (DRM) is an attractive and promising process for the conversion of methane and carbon dioxide which are the most abundant carbon sources into valuable syngas. The produced syngas, which is a mixture of hydrogen and carbon monoxide, can be used as intermediates in the manufacture of numerous chemicals. To achieve high conversion, DRM reaction is operated at high temperatures (700-900 °C) that can cause major drawbacks of catalyst deactivation by carbon deposition, metal sintering or metal oxidation. Therefore, the primary goal is to develop a metal based catalyst for DRM that can completely suppress carbon formation by designing the catalyst composition. The strategy of this work was to synthesize Ni-based catalysts all of which prepared by homogeneous deposition precipitation method (HDP) to produce nanoparticles with narrow size distribution. In addition, control the reactivity of the metal by finely tuning the bimetallic composition and the reaction conditions in terms of reaction temperature and pressure. The highly endothermic dry reforming of methane proceeds via CH4 decomposition to leave surface carbon species, followed by removal of C with CO2-derived species to give CO. Tuning the reactivity of the active metal towards these reactions during DRM allows in principle the catalyst surface to remain active and clean without carbon deposition for a long-term. The initial attempt was to improve the resistance of Ni catalyst towards carbon deposition, therefore, a series of 5 wt.% bimetallic Ni9Pt1 were supported on various metal oxides (Al2O3, CeO2, and ZrO2). The addition of small amount of noble metal improved the stability of the catalyst compared to their monometallic Ni and Pt catalysts, but still high amount of carbon (> 0.1 wt.%) was formed after 24 h of the reaction. The obtained results showed that the catalytic performance, particle size and amount of deposited carbon depends on the nature of support. Among the tested

  3. Steam Reforming of Ethylene Glycol over MgAl₂O₄ Supported Rh, Ni, and Co Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Donghai; Lebarbier, Vanessa M.; Xing, Rong; Albrecht, Karl O.; Dagle, Robert A.

    2015-11-25

    Steam reforming of ethylene glycol (EG) over MgAl₂O₄ supported metal (15 wt.% Ni, 5 wt.% Rh, and 15 wt.% Co) catalysts were investigated using combined experimental and theoretical methods. Compared to highly active Rh and Ni catalysts with 100% conversion, the steam reforming activity of EG over the Co catalyst is comparatively lower with only 42% conversion under the same reaction conditions (500°C, 1 atm, 119,000 h⁻¹, S/C=3.3 mol). However, CH₄ selectivity over the Co catalyst is remarkably lower. For example, by varying the gas hour space velocity (GHSV) such that complete conversion is achieved for all the catalysts, CH₄ selectivity for the Co catalyst is only 8%, which is much lower than the equilibrium CH₄ selectivity of ~ 24% obtained for both the Rh and Ni catalysts. Further studies show that varying H₂O concentration over the Co catalyst has a negligible effect on activity, thus indicating zero-order dependence on H₂O. These experimental results suggest that the supported Co catalyst is a promising EG steam reforming catalyst for high hydrogen production. To gain mechanistic insight for rationalizing the lower CH₃ selectivity observed for the Co catalyst, the initial decomposition reaction steps of ethylene glycol via C-O, O-H, C-H, and C-C bond scissions on the Rh(111), Ni(111) and Co(0001) surfaces were investigated using density functional theory (DFT) calculations. Despite the fact that the bond scission sequence in the EG decomposition on the three metal surfaces varies, which leads to different reaction intermediates, the lower CH₄ selectivity over the Co catalyst, as compared to the Rh and Ni catalysts, is primarily due to the higher barrier for CH₄ formation. The higher S/C ratio enhances the Co catalyst stability, which can be elucidated by the facile water dissociation and an alternative reaction path to remove the CH species as a coking precursor via the HCOH formation. This work was financially supported by the United

  4. Metallic nanoshells on porphyrin-stabilized emulsions

    Science.gov (United States)

    Wang, Haorong; Song, Yujiang; Shelnutt, John A; Medforth, Craig J

    2013-10-29

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  5. Preparation, structural characterization and catalytic properties of Co/CeO2 catalysts for the steam reforming of ethanol and hydrogen production

    Science.gov (United States)

    Lovón, Adriana S. P.; Lovón-Quintana, Juan J.; Almerindo, Gizelle I.; Valença, Gustavo P.; Bernardi, Maria I. B.; Araújo, Vinícius D.; Rodrigues, Thenner S.; Robles-Dutenhefner, Patrícia A.; Fajardo, Humberto V.

    2012-10-01

    In this paper, Co/CeO2 catalysts, with different cobalt contents were prepared by the polymeric precursor method and were evaluated for the steam reforming of ethanol. The catalysts were characterized by N2 physisorption (BET method), X-ray diffraction (XRD), UV-visible diffuse reflectance, temperature programmed reduction analysis (TPR) and field emission scanning electron microscopy (FEG-SEM). It was observed that the catalytic behavior could be influenced by the experimental conditions and the nature of the catalyst employed. Physical-chemical characterizations revealed that the cobalt content of the catalyst influences the metal-support interaction which results in distinct catalyst performances. The catalyst with the highest cobalt content showed the best performance among the catalysts tested, exhibiting complete ethanol conversion, hydrogen selectivity close to 66% and good stability at a reaction temperature of 600 °C.

  6. Amphiphilic phase-transforming catalysts for transesterification of triglycerides

    Science.gov (United States)

    Nawaratna, Gayan Ivantha

    Heterogeneous catalytic reactions that involve immiscible liquid-phase reactants are challenging to conduct due to limitations associated with mass transport. Nevertheless, there are numerous reactions such as esterification, transesterification, etherification, and hydrolysis where two immiscible liquid reactants (such as polar and non-polar liquids) need to be brought into contact with a catalyst. With the intention of alleviating mass transport issues associated with such systems but affording the ability to separate the catalyst once the reaction is complete, the overall goal of this study is geared toward developing a catalyst that has emulsification properties as well as the ability to phase-transfer (from liquid-phase to solid-phase) while the reaction is ongoing and evaluating the effectiveness of such a catalytic process in a practical reaction. To elucidate this concept, the transesterification reaction was selected. Metal-alkoxides that possess acidic and basic properties (to catalyze the reaction), amphiphilic properties (to stabilize the alcohol/oil emulsion) and that can undergo condensation polymerization when heated (to separate as a solid subsequent to the completion of the reaction) were used to test the concept. Studies included elucidating the effect of metal sites and alkoxide sites and their concentration effects on transesterification reaction, effect of various metal alkoxide groups on the phase stability of the reactant system, and kinetic effects of the reaction system. The studies revealed that several transition-metal alkoxides, especially, titanium and yttrium based, responded positively to this reaction system. These alkoxides were able to be added to the reaction medium in liquid phase and were able to stabilize the alcohol/oil system. The alkoxides were selective to the transesterification reaction giving a range of ester yields (depending on the catalyst used). It was also observed that transition-metal alkoxides were able to be

  7. Nickel and cobalt as active phase on supported zirconia catalysts for bio-ethanol reforming: Influence of the reaction mechanism on catalysts performance

    Energy Technology Data Exchange (ETDEWEB)

    Padilla, R.; Rodriguez, L.; Serrano, A.; Munoz, G. [Instituto de Catalisis y Petroleoquimica (CSIC), C/ Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Benito, M.; Daza, L. [Instituto de Catalisis y Petroleoquimica (CSIC), C/ Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Av. Complutense 22, 28040 Madrid (Spain)

    2010-09-15

    Steam reforming of ethanol for hydrogen production was investigated on Co/ZrO{sub 2} and Ni/ZrO{sub 2} catalysts promoted with lanthana. Catalysts were prepared by impregnation method and characterized by XRD and TPR. TPD-R experiments were also carried out to determine the role of active phase on reaction mechanism. The results suggest that adsorbed ethanol is dehydrogenated to acetaldehyde producing hydrogen. Then, the adsorbed acetaldehyde may evolve by different mechanisms, depending on the nature of active phase. On one hand, in cobalt-based catalyst, acetaldehyde could be reformed directly. By acetaldehyde thermal decomposition, methyl and formaldehyde groups are obtained. By coupling of methyl groups, ethane can be obtained. At medium temperature range, WGS reaction contribution is noteworthy. On the other hand, in nickel-based catalyst, acetone was detected in a higher temperature range as the main intermediate reaction product, which indicates that acetaldehyde is transformed into acetone by decarbonylation of acetaldehyde leading to H{sub 2} and CO{sub 2} formation. In addition, acetone can also be reformed to give both H{sub 2} and CO{sub 2}. Contrary to cobalt-based catalyst, ethylene was detected at intermediate range temperature which suggests that it was formed by ethanol dehydration reaction. Ethylene polymerization could easily explain coke formation, which must be avoided. Steam reforming reaction was studied at S/C ratio of 4.84 and 700 C, to verify the activity, selectivity and stability of the catalysts. Ethanol conversion reached 100% and catalysts were very stable for almost 50 h on stream. No significant differences were detected in both catalysts. Nevertheless, TPO experiments performed on used samples demonstrate a higher carbon production on nickel based catalyst that can be correlated to ethanol dehydration contribution on it reaction pathway. (author)

  8. Bimetallic Nanoparticles as Efficient Catalysts: Facile and Green Microwave Synthesis

    Directory of Open Access Journals (Sweden)

    Magda Blosi

    2016-07-01

    Full Text Available This work deals with the development of a green and versatile synthesis of stable mono- and bi-metallic colloids by means of microwave heating and exploiting ecofriendly reagents: water as the solvent, glucose as a mild and non-toxic reducer and polyvinylpirrolidone (PVP as the chelating agent. Particle size-control, total reaction yield and long-term stability of colloids were achieved with this method of preparation. All of the materials were tested as effective catalysts in the reduction of p-nitrophenol in the presence of NaBH4 as the probe reaction. A synergistic positive effect of the bimetallic phase was assessed for Au/Cu and Pd/Au alloy nanoparticles, the latter showing the highest catalytic performance. Moreover, monoand bi-metallic colloids were used to prepare TiO2- and CeO2-supported catalysts for the liquid phase oxidation of 5-hydroxymethylfufural (HMF to 2,5-furandicarboxylic acid (FDCA. The use of Au/Cu and Au/Pd bimetallic catalysts led to an increase in FDCA selectivity. Finally, preformed Pd/Cu nanoparticles were incorporated into the structure of MCM-41-silica. The resulting Pd/Cu MCM-41 catalysts were tested in the hydrodechlorination of CF3OCFClCF2Cl to CF3OCF=CF2. The effect of Cu on the hydrogenating properties of Pd was demonstrated.

  9. Catalytic destruction of dichloromethane using perovskite-type oxide catalysts.

    Science.gov (United States)

    Lou, Jie-Chung; Hung, Chang-Mao; Yang, Bor-Yu

    2004-06-01

    Dichloromethane (DCM, also known as methylene chloride [CH2Cl2]) is often present in industrial waste gas and is a valuable chemical product in the chemical industry. This study addresses the oxidation of airstreams that contain CH2Cl2 by catalytic oxidation in a tubular fixed-bed reactor over perovskite-type oxide catalysts. This work also considers how the concentration of influent CH2Cl2 (Co = 500-1000 ppm), the space velocity (GHSV = 5000-48,000 1/hr), the relative humidity (RH = 10-70%) and the concentration of oxygen (O2 = 5-21%) influence the operational stability and capacity for the removal of CH2Cl2. The surface area of lanthanum (La)-cobalt (Co) composite catalyst was the greatest of the five perovskite-type catalysts prepared in various composites of La, strontium, and Co metal oxides. Approximately 99.5% CH2Cl2 reduction was achieved by the catalytic oxidation over LaCoO3-based perovskite catalyst at 600 degrees C. Furthermore, the effect of the initial concentration and reaction temperature on the removal of CH2Cl2 in the gaseous phase was also monitored. This study also provides information that a higher humidity corresponds to a lower conversion. Carbon dioxide and hydrogen chloride were the two main products of the oxidation process at a relative humidity of 70%.

  10. Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grass, Michael Edward [Univ. of California, Berkeley, CA (United States)

    2008-09-01

    Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H2 and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. Careful control of particle size and shape has been accomplished though solution phase synthesis of Pt and Rh nanoparticles in order to elucidate further structure-reactivity relationships in noble metal catalysis.

  11. Development of industrial catalysts for sustainable chlorine production.

    Science.gov (United States)

    Mondelli, Cecilia; Amrute, Amol P; Moser, Maximilian; Schmidt, Timm; Pérez-Ramírez, Javier

    2012-01-01

    The heterogeneously catalyzed gas-phase oxidation of HCl to Cl(2) offers an energy-efficient and eco- friendly route to recover chlorine from HCl-containing byproduct streams in the chemical industry. This process has attracted renewed interest in the last decade due to an increased chlorine demand and the growing excess of byproduct HCl from chlorination processes. Since its introduction (by Deacon in 1868) and till recent times, the industrialization of this reaction has been hindered by the lack of sufficiently active and durable materials. Recently, RuO(2)-based catalysts with outstanding activity and stability have been designed and they are being implemented for large-scale Cl(2) recycling. Herein, we review the main limiting features of traditional Cu-based catalysts and survey the key steps in the development of the new generation of industrial RuO(2)-based materials. As the expansion of this technology would benefit from cheaper, but comparably robust, alternatives to RuO(2)-based catalysts, a nov el CeO(2)-based catalyst which offers promising perspectives for application in this field has been introduced.

  12. Metal Phosphate-Supported Pt Catalysts for CO Oxidation

    Directory of Open Access Journals (Sweden)

    Xiaoshuang Qian

    2014-12-01

    Full Text Available Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2 have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO46(OH2, denoted as Ca-P-O here also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP atomic emission spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, CO2 temperature-programmed desorption (CO2-TPD, X-ray photoelectron spectroscopy (XPS, and H2 temperature-programmed reduction (H2-TPR. This work furnishes a new catalyst system for CO oxidation and other possible reactions.

  13. Synthesis and characterization of metal oxide promoted alumina catalyst for biofuel production

    Science.gov (United States)

    Anisuzzaman, S. M.; Krishnaiah, D.; Bono, A.; Abang, S.; Sundang, M.; Suali, E.; Lahin, F. A.; Shaik Alawodeen, A.

    2016-06-01

    Alumina has been widely used as a support in catalysis process which owing to its extremely thermal and mechanical stability, high surface area, large pore size and pore volume. The aim of this study was to synthesize calcium oxide-supported basic alumina catalysts (CaO/Al2O3) by impregnation method and to characterize the properties of the catalyst based on its surface area and porosity, functional group, surface morphology and particle size. Impregnation method was chosen for the synthesization of catalyst which involved contacting the support with the impregnating solution for a particular period of time, drying the support to remove the imbibed liquid and calcination process. In the preparation of catalyst, catalytic performance of CaO/Al2O3 catalyst was measured at different calcined temperatures (650°C, 750°C and 800°C). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Mercury intrusion porosimetry (MIP), and particle size analyzer (Zetasizer) was used to characterize the catalyst. The highest total specific area and the total porosity of the catalyst was obtained at 750oC. FTIR analysis basically studied on the functional groups present in each catalyst synthesized, while SEM analysis was observed to have pores on its surface. Moreover, CaO/Al2O3 catalysts at 650°C produced the smallest particle size (396.1 mn), while at 750°C produced the largest particle size (712.4 mn). Thus it can be concluded that CaO/Al2O3 catalysts has great potential coimnercialization since CaO has attracted many attentions compared to other alkali earth metal oxides especially on the transesterification reaction.

  14. Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for PEM Fuel Cell

    Science.gov (United States)

    Devrim, Yilser; Albostan, Ayhan

    2016-08-01

    The aim of this study is the preparation and characterization of a graphene-supported platinum (Pt) catalyst for proton exchange membrane fuel cell (PEMFC) applications. The graphene-supported Pt catalysts were prepared by chemical reduction of graphene and chloroplatinic acid (H2PtCl6) in ethylene glycol. X-ray powder diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy have been used to analyze structure and surface morphology of the graphene-supported catalyst. The TGA results showed that the Pt loading of the graphene-supported catalyst was 31%. The proof of the Pt particles on the support surfaces was also verified by energy-dispersive x-ray spectroscopy analysis. The commercial carbon-supported catalyst and prepared Pt/graphene catalysts were used as both anode and cathode electrodes for PEMFC at ambient pressure and 70°C. The maximum power density was obtained for the Pt/graphene-based membrane electrode assembly (MEA) with H2/O2 reactant gases as 0.925 W cm2. The maximum current density of the Pt/graphene-based MEA can reach 1.267 and 0.43 A/cm2 at 0.6 V with H2/O2 and H2/air, respectively. The MEA prepared by the Pt/graphene catalyst shows good stability in long-term PEMFC durability tests. The PEMFC cell voltage was maintained at 0.6 V without apparent voltage drop when operated at 0.43 A/cm2 constant current density and 70°C for 400 h. As a result, PEMFC performance was found to be superlative for the graphene-supported Pt catalyst compared with the Pt/C commercial catalyst. The results indicate the graphene-supported Pt catalyst could be utilized as the electrocatalyst for PEMFC applications.

  15. Effect of Dimethyl Ether Co-feed on Catalytic Performance of Methane Dehydroaromatization over Mo/HZSM-5 Catalyst

    Institute of Scientific and Technical Information of China (English)

    Huiying Chen; Yonggang Li; Wenjie Shen; Yide Xu; Xinhe Bao

    2004-01-01

    The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehy droaromatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of T=1023 K, p=101 kPa and SV=1500 ml/(g·h). A high benzene yield was obtained and the stability of the catalyst was improved by adding 1.5%DME to the CH4 feed. The C6H6 yield was as high as ca. 10% even after reaction for 6 h. The stability of the catalyst was further improved when DME concentration in the co-feed gas was increased to an appropriate value.TGA and TPO results of the used 6Mo/HZSM-5 catalyst showed that the amount of coke on the used catalyst was reduced and the chemical nature of the coke was changed. When 1.5%DME was added to the CH4 feed, the coke formed on the catalyst could be burned off more easily than that when only CH4 was used as reactant.It is supposed that the oxygen in DME may play a role in preventing the coke burnt off at lower temperature from transforming into the coke burnt off at higher temperature, which results in the improvement of the stability of the catalyst.

  16. Regeneration of Hydrotreating and FCC Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    CM Wai; JG Frye; JL Fulton; LE Bowman; LJ Silva; MA Gerber

    1999-09-30

    Hydrotreating, hydrocracking, and fluid catalytic cracking (FCC) catalysts are important components of petroleum refining processes. Hydrotreating and hydrocracking catalysts are used to improve the yield of high-quality light oil fractions from heavier crude oil and petroleum feedstocks containing high levels of impurities. FCC catalysts improve the yield of higher octane gasoline from crude oil. Residuum hydrotreating and cracking catalysts are susceptible to irreversible deactivation caused by adsorption of sulfur and by metals impurities, such as vanadium and nickel. The gradual buildup of these impurities in a hydrotreating catalyst eventually plugs the pores and deactivates it. Nickel and vanadium adversely affect the behavior of cracking catalysts, reducing product yield and quality. Replacing deactivated catalysts represents a significant cost in petroleum refining. Equally important are the costs and potential liabilities associated with treating and disposing spent catalysts. For example, recent US Environmental Protection Agency rulings have listed spent hydrotreating and hydrorefining catalysts as hazardous wastes. FCC catalysts, though more easily disposed of as road-base or as filler in asphalt and cement, are still an economic concern mainly because of the large volumes of spent catalysts generated. New processes are being considered to increase the useful life of catalysts or for meeting more stringent disposal requirements for spent catalysts containing metals. This report discusses a collaborative effort between Pacific Northwest National Laboratory (PNNL) and Phillips Petroleum, Inc., to identify promising chemical processes for removing metals adhered to spent hydrodesulfurization (HDS, a type of hydrotreating catalyst) and FCC catalysts. This study, conducted by PNNL, was funded by the US Department of Energy's Bartlesville Project Office. Fresh and spent catalysts were provided by Phillips Petroleum. The FCC catalyst was a rare

  17. 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.

  18. Supported noble metal catalysts in the catalytic wet air oxidation of industrial wastewaters and sewage sludges.

    Science.gov (United States)

    Besson, M; Descorme, C; Bernardi, M; Gallezot, P; di Gregorio, F; Grosjean, N; Minh, D Pham; Pintar, A

    2010-12-01

    This paper reviews some catalytic wet air oxidation (CWAO) investigations of industrial wastewaters over platinum and ruthenium catalysts supported on TiO2 and ZrO2 formulated to be active and resistant to leaching, with particular focus on the stability of the catalyst. Catalyst recycling experiments were performed in batch reactors and long-term stability tests were conducted in trickle-bed reactors. The catalyst did not leach upon treatment of Kraft bleaching plant and olive oil mill effluents, and could be either recycled or used for long periods of time in continuous reactors. Conversely, these catalysts were rapidly leached when used to treat effluents from the production of polymeric membranes containing N,N-dimethylformamide. The intermediate formation of amines, such as dimethylamine and methylamine with a high complexing capacity for the metal, was shown to be responsible for the metal leaching. These heterogeneous catalysts also deactivated upon CWAO of sewage sludges due to the adsorption of the solid organic matter. Pre-sonication of the sludge to disintegrate the flocs and improve solubility was inefficient.

  19. Synthesis of biodiesel from vegetable oil with methanol catalyzed by Li-doped magnesium oxide catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Zhenzhong; Yu, Xinhai; Tu, Shan-Tung [School of Mechanical and Power Engineering, East China University of Science and Technology, Meilong Rd. 130, Shanghai 200237 (China); Yan, Jinyue [School of Sustainable Development of Society and Technology, Maelardalen University, SE-721 23 Vaesteraas (Sweden); School of Chemical Science and Engineering, Royal Institute of Technology, Stockholm, SE-100 44 Stockholm (Sweden); Dahlquist, Erik [School of Sustainable Development of Society and Technology, Maelardalen University, SE-721 23 Vaesteraas (Sweden)

    2010-03-15

    The preparation of a Li-doped MgO for biodiesel synthesis has been investigated by optimizing the catalyst composition and calcination temperatures. The results show that the formation of strong base sites is particularly promoted by the addition of Li, thus resulting in an increase of the biodiesel synthesis. The catalyst with the Li/Mg molar ratio of 0.08 and calcination temperature of 823 K exhibits the best performance. The biodiesel conversion decreases with further increasing Li/Mg molar ratio above 0.08, which is most likely attributed to the separated lithium hydroxide formed by excess Li ions and a concomitant decrease of BET values. In addition, the effects of methanol/oil molar ratio, reaction time, catalyst amount, and catalyst stability were also investigated for the optimized Li-doped MgO. The metal leaching from the Li-doped MgO catalysts was detected, indicating more studies are needed to stabilize the catalysts for its application in the large-scale biodiesel production facilities. (author)

  20. Catalyst containing oxygen transport membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Jonathan A.; Wilson, Jamie R.; Christie, Gervase Maxwell; Petigny, Nathalie; Sarantopoulos, Christos

    2017-02-07

    A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a microstructure exhibiting substantially uniform pore size distribution as a result of using PMMA pore forming materials or a bi-modal particle size distribution of the porous support layer materials. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

  1. Catalyst containing oxygen transport membrane

    Science.gov (United States)

    Christie, Gervase Maxwell; Wilson, Jamie Robyn; van Hassel, Bart Antonie

    2012-12-04

    A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a high average pore diameter and the intermediate porous layer has a lower permeability and lower pore diameter than the porous support layer. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

  2. A highly active and reusable copper(I)-tren catalyst for the "click" 1,3-dipolar cycloaddition of azides and alkynes.

    Science.gov (United States)

    Candelon, Nicolas; Lastécouères, Dominique; Diallo, Abdou Khadri; Aranzaes, Jaime Ruiz; Astruc, Didier; Vincent, Jean-Marc

    2008-02-14

    The copper(I) complex [Cu(C18(6)tren)]Br 1 (C18(6)tren = tris(2-dioctadecylaminoethyl)amine) which exhibits a good stability towards aerobic conditions is a versatile, highly reactive and recyclable catalyst for the Huisgen cycloaddition of azides with terminal or internal alkynes and is a useful catalyst for the preparation of "click" dendrimers.

  3. Structured Ni catalysts on porous anodic alumina membranes for methane dry reforming: NiAl 2 O 4 formation and characterization

    KAUST Repository

    Zhou, Lu

    2015-06-29

    This communication presents the successful design of a structured catalyst based on porous anodic alumina membranes for methane dry reforming. The catalyst with a strong Ni-NiAl2O4 interaction shows both excellent activity and stability. This journal is © The Royal Society of Chemistry.

  4. Steam reforming of ethanol over Ni-based catalysts: Effect of feed composition on catalyst stability

    DEFF Research Database (Denmark)

    Trane-Restrup, Rasmus; Dahl, Søren; Jensen, Anker Degn

    2014-01-01

    In this work the effects of steam-to-carbon ratio (S/C), and addition of H2 or O2 to the feed on the product yields and carbon deposition in the steam reforming (SR) of ethanol over Ni/MgAl2O4, Ni/Ce0.6Zr0.4O2, and Ni/CeO2 at 600 °C have been investigated. Increasing the S/C-ratio from 1.6 to 8.......3 over Ni/MgAl2O4 increased conversion of ethanol as well as the yield of H2, while the carbon deposition and yield of hydrocarbons decreased. Oxygen addition at S/C-ratio of 6 over Ni/MgAl2O4, Ni/Ce0.6Zr0.4O2, and Ni/CeO2 increased conversion, decreased the yield of hydrocarbons, and led to a decrease...... showed stable behavior and an average rate of carbon deposition of less than 7 μg C/gCat h. The results indicate that stable operation of ethanol SR is only possible under oxidative conditions....

  5. Ideal Stabilization

    CERN Document Server

    Nesterenko, Mikhail

    2009-01-01

    We define and explore the concept of ideal stabilization. The program is ideally stabilizing if its every state is legitimate. Ideal stabilization allows the specification designer to prescribe with arbitrary degree of precision not only the fault-free program behavior but also its recovery operation. Specifications may or may not mention all possible states. We identify approaches to designing ideal stabilization to both kinds of specifications. For the first kind, we state the necessary condition for an ideally stabilizing solution. On the basis of this condition we prove that there is no ideally stabilizing solution to the leader election problem. We illustrate the utility of the concept by providing examples of well-known programs and proving them ideally stabilizing. Specifically, we prove ideal stabilization of the conflict manager, the alternator, the propagation of information with feedback and the alternating bit protocol.

  6. Application of Ceria and Lanthana in Catalyst for Cleansing Exhaust Gas of Car

    Institute of Scientific and Technical Information of China (English)

    Yang Chunsheng; Chen Jianhua; Dai Shaojun

    2004-01-01

    The importanCe of rare earths being applied in the catalyst for cleansing the exhaust gas out of car was introduced. The acting mechanism of ceria and lanthana in catalyst and its influencing factors were discussed, and its prospect was forecasted. Pt-Rh precious metals three-way catalyst is widely used for decontaminating the exhaust gas of car now. Ceria and lanthana, which can decrease the content of Pt-Rh and increase the content of Pd in the catalyst, are used as additive in the decontaminating catalyst in order to solve the problem of the supply and demand of Pt and Rh.It is reported that increasing the activity of the coat on catalyst, regulating automatically the ratio of air and fuel, acting as catalyst-accelerator, and improving its properties such as thermal stability and strength may primarily amount for the catalyzing, mechanism of ceria and lanthana. The factors, such as their interaction, additive methods, and effects of cocatalyst ZrO2, CuO, AgO, etc. , will remarkably influence the catalyzing function of ceria and lanthana.

  7. Nanocrystalline MgO supported nickel-based bimetallic catalysts for carbon dioxide reforming of methane

    Energy Technology Data Exchange (ETDEWEB)

    Meshkani, Fereshteh [Catalyst and Advanced Materials Research Laboratory, Chemical Engineering Department, Faculty of Engineering, University of Kashan, Kashan (Iran); Rezaei, Mehran [Catalyst and Advanced Materials Research Laboratory, Chemical Engineering Department, Faculty of Engineering, University of Kashan, Kashan (Iran); Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan (Iran)

    2010-10-15

    Nanocrystalline magnesium oxide with high surface area and plate-like shape was employed as catalyst support for preparation of nickel-based bimetallic catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by X-ray diffraction (XRD), N{sub 2} adsorption (BET), Temperature programmed oxidation and desorption (TPO-TPD), Thermal gravimetric and differential thermal gravimetric (TGA-DTG), H{sub 2} chemisorption and Transmission and electron microscopies (TEM and SEM) analyses. CO{sub 2}-TPD data showed the high CO{sub 2} adsorption capacity of catalysts which improves the resistance of catalysts against the carbon formation. The H{sub 2} chemisorption results also indicated that the addition of Pt to nickel catalyst improved the nickel dispersion. The obtained results revealed that the prepared catalysts showed a high activity and stability during the reaction with a low amount of deposited carbon. Addition of Pt to nickel catalyst improved both the activity and resistivity against carbon formation. (author)

  8. Methanation of syngas over coral reef-like Ni/AI2O3 catalysts

    Institute of Scientific and Technical Information of China (English)

    Shengli Ma; Yisheng Tan; Yizhuo Han

    2011-01-01

    Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673>Ni/Al2O3-573>Ni/Al2O3473>Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2 (molar ratio) =1 ∶ 3,593 K,atmospheric pressure and a GHSV of 2500 h- 1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%.

  9. Session 4: A novel catalyst improves hydrogen production in a membrane reactor

    Energy Technology Data Exchange (ETDEWEB)

    Munera, J.; Kihn, M.; Carrara, C.; Irusta, S.; Cornaglia, L.M.; Lombardo, E.A. [Instituto de Investigaciones en Catalisis y Petroquimica (FIQ, UNL-CONICET), Santa Fe-Argentina (Argentina)

    2004-07-01

    The dry reforming of methane as a source of H{sub 2} has been performed using a commercial Ni catalyst and supported Ru, Pd, Ir and Pt catalysts in a hydrogen-permeable membrane reactor. The main problems encountered in this application are the abundant formation of coke, deleterious to the membrane, and catalyst deactivation. Appropriate catalysts preventing carbon deposits formation are needed to avoid membrane damage. In this work, we report the results obtained with a novel catalyst, Rh/La{sub 2}O{sub 3}-SiO{sub 2}, and with Rh/La{sub 2}O{sub 3}. Both the fresh and used catalysts were characterized by DRX, FTIR, BET, Laser Raman spectroscopy and hydrogen chemisorption. The effect of the operation variables upon the performance of the membrane reactor were also studied. The obtained results have shown that the Rh catalysts are very stable under reaction conditions while the presence of tiny amounts of graphite only detectable through LRS does not endanger membrane stability. In all cases, the methane conversions are higher than the thermodynamic values but the best performing formulation (highest Rh dispersion) was obtained using the composite La{sub 2}O{sub 3}-SiO{sub 2} support. (O.M.)

  10. Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

    Energy Technology Data Exchange (ETDEWEB)

    Conrad Ingram; Mark Mitchell

    2006-09-30

    The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of mesoporous aluminosilicate catalyst, Al-SBA-15, containing strong Broensted acid sites and aluminum (Al) stabilized in a totally tetrahedral coordination. The physicochemical characteristics of the catalyst varied as a function of the synthesis conditions. The catalyst possessed surface areas ranging between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm, and pore volumes up 1.03 cm{sup 3}, which were comparable to the parent SBA-15 synthesized under similar conditions. Two wt% Al was present in the catalyst that was obtained from the reaction mixture that contained the highest Al content. The Al remained stable in totally tetrahedral coordination after calcination at 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and the activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. In preparation for the final phase of the project, the catalyst was embedded into psuedoboemite alumina (catapal B) matrix and then formed into pellets. In the final phase of the project, the pelletized catalyst will be evaluated for the conversion of heavy petroleum feedstocks to naphtha and middle distillates.

  11. deNOx catalysts for biomass combustion

    DEFF Research Database (Denmark)

    Kristensen, Steffen Buus

    industrial reference catalyst, after impregnation of 225 mole potassium/g of catalyst. A catalyst plate was synthesised using 20 wt.% sepiolite mixed with nano catalyst, supported by a SiO2-fibre mesh. Realistic potassium poisoning was performed on the catalyst plate, by exposure in a potassium aerosol...... for 632 hours at 350 C. Owing to physical blocking of potassium by sepiolite fibres the composite catalyst showed a further increase in potassium resistance compared with the unsupported catalyst. Finally a refined mechanism was proposed for the nano particle SCR catalyst explaining insitu FTIR...... observation done on the system. Most importantly it indicated that the V=O bond did not break during the SCR reaction, suggesting that another oxygen is responsible for the activity of the active vanadia site....

  12. Rhenium Nanochemistry for Catalyst Preparation

    Directory of Open Access Journals (Sweden)

    Vadim G. Kessler

    2012-08-01

    Full Text Available The review presents synthetic approaches to modern rhenium-based catalysts. Creation of an active center is considered as a process of obtaining a nanoparticle or a molecule, immobilized within a matrix of the substrate. Selective chemical routes to preparation of particles of rhenium alloys, rhenium oxides and the molecules of alkyltrioxorhenium, and their insertion into porous structure of zeolites, ordered mesoporous MCM matrices, anodic mesoporous alumina, and porous transition metal oxides are considered. Structure-property relationships are traced for these catalysts in relation to such processes as alkylation and isomerization, olefin metathesis, selective oxidation of olefins, methanol to formaldehyde conversion, etc.

  13. Quick Guide to Flash Catalyst

    CERN Document Server

    Elmansy, Rafiq

    2011-01-01

    How do you transform user interface designs created in Photoshop or Illustrator into interactive web pages? It's easier than you think. This guide shows you how to use Adobe Flash Catalyst to create interactive UIs and website wireframes for Rich Internet Applications-without writing a single line of code. Ideal for web designers, this book introduces Flash Catalyst basics with detailed step-by-step instructions and screenshots that illustrate every part of the process. You'll learn hands-on how to turn your static design or artwork into working user interfaces that can be implemented in Fla

  14. Study on Deactivation and Cracking Performance of Catalysts Containing Y and MFI Zeolites

    Institute of Scientific and Technical Information of China (English)

    Chen Zhenyu; Li Caiying; Tian Huiping; Huang Zhiqing

    2004-01-01

    This article investigated the deactivation caused by hydrothermal treatment and metal contamination of two cracking catalysts containing the Y and ZRP- 1 zeolites aimed at maximization of light olefin yield.Test results had shown that the hydrothermal stability and resistance to metal contamination of the ZRP-1zeolite were apparently better than those of the Y zeolite. Hydrothermal treatment and metal contamination had not only changed the catalytic cracking performance of respective zeolites, but at the same time had also modified to a definite degree of the relative proportions of effective components in these two zeolites and affected the synergistic effects between them, resulting in a relative enhancement of secondary cracking ability of the catalyst and increased olefin selectivity in the FCC products. In the course of application of catalyst for maximization of light olefins yield appropriate adjustment of the relative proportion of two active components can help to alleviate the products distribution and selectivity changes caused by deactivationof FCC catalysts.

  15. Electro-Deposition Pt Catalysts Supported on Carbon-Nanotubes for Methanol Oxidation

    Institute of Scientific and Technical Information of China (English)

    Hailin Song; Peixia Yang; Xiaoyu Wen; Maozhong An; Jinqiu Zhang

    2015-01-01

    In order to study the properties of supporting Pt catalysts for methanol oxidation, carbon⁃nanotubes are used by electrochemical deposition method. Different deposition turns, different cyclic voltammetry scanning speeds and processing time with ascorbic acid are investigated in this paper. The micrographs of Pt/CNTs catalysts are characterized by scanning electron microscopy, the electro⁃catalytic properties of Pt/CNTs catalysts for methanol oxidation are investigated by cycle voltammetry and chronoamperometry. The results show that the size of platinum will be greater with the faster scanning speed. After dissolution in ascorbic acid, Pt nano⁃particles disperse uniformly. The obtained Pt/CNTs catalysts show a high electro⁃catalytic activity and stability.

  16. A Novel Cu-Mo/ZSM-5 Catalyst for NOx Catalytic Reduction with Ammonia

    Institute of Scientific and Technical Information of China (English)

    Zhe Li; Dang Li; Wei Huang; Kechang Xie

    2005-01-01

    The Cu-Mo/ZSM-5 catalysts with different Cu/Mo ratios were prepared by wet impregnation method, and their catalytic performance for selective catalytic reduction of NOx was studied. The results showed that Cu-Mo/ZSM-5 is a very effective catalyst for NOx catalytic reduction with ammonia, especially when Cu/Mo molar ratio is about 1.5. It not only exhibited the extremely high catalytic activity, but also showed good stability for O2. The bulk phase structure of Cu-Mo/ZSM-5 catalysts was determined by XRD technique, and the results indicated that there is a maximum dispersion for Cu species when Cu/Mo molar ratio is 1.5, and an interaction between Cu and Mo along with HZSM-5 may be present in Cu-Mo/ZSM-5, which may possibly result in a special structure favorable for the catalytic reduction of NOx over Cu-Mo/ZSM-5 catalyst.

  17. 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.

  18. Preparation of Mesoporous Silica-Supported Palladium Catalysts for Biofuel Upgrade

    Directory of Open Access Journals (Sweden)

    Ling Fei

    2012-01-01

    Full Text Available We report the preparation of two hydrocracking catalysts Pd/CoMoO4/silica and Pd/CNTs/CoMoO4/silica (CNTs, carbon nanotubes. The structure, morphologies, composition, and thermal stability of catalysts were studied by X-ray diffraction (XRD, scanning electron microscopy (SEM, Raman spectroscopy, transmission electron microscopy (TEM, energy-dispersive X-ray (EDX, and thermogravimetric analysis (TGA. The catalyst activity was measured in a Parr reactor with camelina fatty acid methyl esters (FAMEs as the feed. The analysis shows that the palladium nanoparticles have been incorporated onto mesoporous silica in Pd/CoMoO4/silica or on the CNTs surface in Pd/CNTs/CoMoO4/silica catalysts. The different combinations of metals and supports have selective control cracking on heavy hydrocarbons.

  19. A catalyst for the carbonylation of methanol to acetic acid in gaseous phase

    Institute of Scientific and Technical Information of China (English)

    潘平来; 柳忠阳; 朱长城; 袁国卿

    1996-01-01

    A novel Rh/Ys catalyst for the carbonylation of methanol to acetic acid in gaseous phase is reported. The porous carbon beads (Ys) prepared from the carbonation of poly(vinylidene chloride) were used as the support. This catalyst has a specific surface area of 1 000 m2/g, high mechanical strength and thermal stability. The average diameter of the pore is in the range of 0.8 - 1.2nm. Experimental evidence showed that this catalyst was of high activity and selectivity, which could compare to those of the homogeneous catalyst from Monsanto. The catalytic rate could get to 900 g AcOH/g Rh·h during the carbonylation of methanol to acetic acid. The fine spreading of Ph over the Ys surface is the key factor for the activity.

  20. R&D and Application of Catalyst for Resid Hydrotreating in Upflow Reactor

    Institute of Scientific and Technical Information of China (English)

    Niu Chuanfeng; Hu Dawei; Dai Lishun; Yang Qinghe

    2008-01-01

    In order to extend the operating cycle of the upflow reactor for resid hydrotreating, the Research Institute of Petroleum Processing taking into account the specifics of resid hydrotreating upflow reactor has developed the high-performance RUF series of catalysts suitable for operation in the upflow reactor. The results of commercial application of catalysts revealed that this RUF series of catalysts loaded after optimized grading could effectively remove metals, sulfur and carbon residue from the residuum to provide improved oil for the following fixed-bed reactor. In the meantime, the RUF series of catalysts have excellent stability to reach an operating cycle of 1.5 years, resulting in minimization of losses caused by refinery downtime.

  1. When magnetic catalyst meets magnetic reactor: etherification of FCC light gasoline as an example.

    Science.gov (United States)

    Cheng, Meng; Xie, Wenhua; Zong, Baoning; Sun, Bo; Qiao, Minghua

    2013-01-01

    The application of elaborately designed magnetic catalysts has long been limited to ease their separation from the products only. In this paper, we for the first time employed a magnetic sulphonated poly(styrene-divinylbenzene) resin catalyst on a magnetically stabilized-bed (MSB) reactor to enhance the etherification of fluidized catalytic cracking (FCC) light gasoline, one of the most important reactions in petroleum refining industry. We demonstrated that the catalytic performance of the magnetic acid resin catalyst on the magnetic reactor is substantially enhanced as compared to its performance on a conventional fixed-bed reactor under otherwise identical operation conditions. The magnetic catalyst has the potential to be loaded and unloaded continuously on the magnetic reactor, which will greatly simplify the current complex industrial etherification processes.

  2. 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.

  3. Ni/Al2O3 catalysts for syngas methanation: Effect of Mn promoter

    Institute of Scientific and Technical Information of China (English)

    Anmin Zhao; Weiyong Ying; Haitao Zhang; Hongfang Ma; Dingye Fang

    2012-01-01

    Ni/Al2O3 catalysts with different amounts of manganese ranging from 1 to 3 wt% as promoter were prepared by co-impregnation method.The catalysts were characterized by N2 physisorption,XRD,TPR,SEM and TEM.Their catalytic activity towards syngas methanation reaction was also investigated using a fixed-bed integral reactor.It was demonstrated that the addition of manganese to Ni/Al2O3 catalysts can increase the catalyst surface area and average pore volume,but decrease NiO crystallite size,leading to higher activity and stability.The effects of reaction temperature,pressure and weight hourly space velocity (WHSV) on carbon oxides conversion and CH4 formation rate were also studied.High carbon oxides conversion,CH4 selectivity and formation rate were achieved at the reaction temperature range of 280-300 ℃.

  4. Chitosan as a Natural Polymer for Heterogeneous Catalysts Support: A Short Review on Its Applications

    Directory of Open Access Journals (Sweden)

    Mengshan Lee

    2015-11-01

    Full Text Available Chitosan, a bio-based polymer which has similar characteristics to those of cellulose, exhibits cationic behavior in acidic solutions and strong affinity for metals ions. Thus, it has received increased attention for the preparation of heterogeneous catalysts. Recent studies demonstrated that chitosan-based catalysts had high sorption capacities, chelating activities, stability and versatility, which could be potentially applied as green reactants in various scientific and engineering applications. This study intends to review the recent development of chitosan-based catalysts, particularly in the aspects of the main mechanisms for preparing the materials and their applications in environmental green chemistry. Studies on the preparation of catalyst nanoparticles/nanospheres supported on chitosan were also reviewed.

  5. On-line regeneration of hydrodesulfurization catalyst

    Science.gov (United States)

    Preston, Jr., John L.

    1980-01-01

    A hydrotreating catalyst is regenerated as it concurrently hydrotreats a hydrocarbon fuel by introducing a low concentration of oxygen into the catalyst bed either continuously or periodically. At low oxygen concentrations the carbon deposits on the catalyst are burned off without harming the catalyst and without significantly affecting the hydrotreating process. In a preferred embodiment the hydrotreating process is hydrodesulfurization, and regenerating is done periodically with oxygen concentrations between 0.1 and 0.5 volume percent.

  6. Development of Ultra-Low Platinum Alloy Cathode Catalysts for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Branko N. [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering; Weidner, John [Univ. of South Carolina, Columbia, SC (United States)

    2016-01-07

    The goal of this project is to synthesize a low cost PEM fuel cell cathode catalyst and support with optimized average mass activity, stability of mass activity, initial high current density performance under H2/air (power density), and catalyst and support stability able to meet 2017 DOE targets for electrocatalysts for transportation applications. Pt*/ACCS-2 catalyst was synthesized according to a novel methodology developed at USC through: (i) surface modification, (ii) metal catalyzed pyrolysis and (iii) chemical leaching to remove excess meal used to dope the support. Pt* stands for suppressed platinum catalyst synthesized with Co doped platinum. The procedure results in increasing carbon graphitization, inclusion of cobalt in the bulk and formation of non-metallic active sites on the carbon surface. Catalytic activity of the support shows an onset potential of 0.86 V for the oxygen reduction reaction (ORR) with well-defined kinetic and mass transfer regions and 2.5% H2O2 production. Pt*/ACCS-2 catalyst durability under 0.6-1.0 V potential cycling and support stability under 1.0-1.5 V potential cycling was evaluated. The results indicated excellent catalyst and support performance under simulated start-up/shut down operating conditions (1.0 – 1.5 V, 5000 cycles) which satisfy DOE 2017 catalyst and support durability and activity. The 30% Pt*/ACCS-2 catalyst showed high initial mass activity of 0.34 A/mgPGM at 0.9 ViR-free and loss of mass activity of 45% after 30,000 cycles (0.6-1.0 V). The catalyst performance under H2-air fuel cell operating conditions showed only 24 mV (iR-free) loss at 0.8 A/cm2 with an ECSA loss of 42% after 30,000 cycles (0.6-1.0 V). The support stability under 1.0-1.5 V potential cycling showed mass activity loss of 50% and potential loss of 8 mV (iR-free) at 1.5 A/cm2. The ECSA loss was 22% after 5,000 cycles. Furthermore, the Pt*/ACCS-2 catalyst showed an

  7. Novel non-platinum metal catalyst material

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a novel non-platinum metal catalyst material for use in low temperature fuel cells and electrolysers and to fuel cells and electrolysers comprising the novel non-platinum metal catalyst material. The present invention also relates to a novel method for synthesizing...... the novel non-platinum metal catalyst material....

  8. Catalysts and methods of using the same

    Energy Technology Data Exchange (ETDEWEB)

    Slowing, Igor Ivan; Kandel, Kapil

    2017-02-14

    The present invention provides a catalyst including a mesoporous silica nanoparticle and a catalytic material comprising iron. In various embodiments, the present invention provides methods of using and making the catalyst. In some examples, the catalyst can be used to hydrotreat fatty acids or to selectively remove fatty acids from feedstocks.

  9. Efficient epoxidation of propene using molecular catalysts

    DEFF Research Database (Denmark)

    Markovits, Iulius I. E.; Anthofer, Michael H.; Kolding, Helene

    2014-01-01

    The epoxidation of propene is performed in homogeneous phase using various molecular catalysts and H2O2 or tert-butyl hydroperoxide as oxidants. A comparison between some molybdenum catalysts and methyltrioxorhenium (MTO) shows that the well known Re catalyst is the best among the examined...

  10. Attrition Resistant Iron-Based Catalysts For F-T SBCRs

    Energy Technology Data Exchange (ETDEWEB)

    Adeyinka A. Adeyiga

    2006-01-31

    of Kentucky. Spray-dried catalysts with compositions 100 Fe/5 Cu/4.2 K/11 (P) SiO{sub 2} and 100 Fe/5 Cu/4.2 K/1.1 (B) SiO{sub 2} have excellent selectivity characteristics (low methane and high C{sub 5+} yields), but their productivity and stability (deactivation rate) need to be improved. Mechanical integrity (attrition strength) of these two catalysts was markedly dependent upon their morphological features. The attrition strength of the catalyst made out of largely spherical particles (1.1 (B) SiO{sub 2}) was considerably higher than that of the catalyst consisting of irregularly shaped particles (11 (P) SiO{sub 2}).

  11. Direct decomposition of methane over SBA-15 supported Ni, Co and Fe based bimetallic catalysts

    Science.gov (United States)

    Pudukudy, Manoj; Yaakob, Zahira; Akmal, Zubair Shamsul

    2015-03-01

    Thermocatalytic decomposition of methane is an alternative route for the production of COx-free hydrogen and carbon nanomaterials. In this work, a set of novel Ni, Co and Fe based bimetallic catalysts supported over mesoporous SBA-15 was synthesized by a facile wet impregnation route, characterized for their structural, textural and reduction properties and were successfully used for the methane decomposition. The fine dispersion of metal oxide particles on the surface of SBA-15, without affecting its mesoporous texture was clearly shown in the low angle X-ray diffraction patterns and the transmission electron microscopy (TEM) images. The nitrogen sorption analysis showed the reduced specific surface area and pore volume of SBA-15, after metal loading due to the partial filling of hexagonal mesopores by metal species. The results of methane decomposition experiments indicated that all of the bimetallic catalysts were highly active and stable for the reaction at 700 °C even after 300 min of time on stream (TOS). However, a maximum hydrogen yield of ∼56% was observed for the NiCo/SBA-15 catalyst within 30 min of TOS. A high catalytic stability was shown by the CoFe/SBA-15 catalyst with 51% of hydrogen yield during the course of reaction. The catalytic stability of the bimetallic catalysts was attributed to the formation of bimetallic alloys. Moreover, the deposited carbons were found to be in the form of a new set of hollow multi-walled nanotubes with open tips, indicating a base growth mechanism, which confirm the selectivity of SBA-15 supported bimetallic catalysts for the formation of open tip carbon nanotubes. The Raman spectroscopic and thermogravimetric analysis of the deposited carbon nanotubes over the bimetallic catalysts indicated their higher graphitization degree and oxidation stability.

  12. 对甲苯磺酸盐作为两相催化剂催化邻苯二酚与羰基化合物的缩合%Ketalization of Catechol with Carbonyl Compounds Catalyzed by Metal p-Toluenesulfonate as Biphasic Acid Catalyst

    Institute of Scientific and Technical Information of China (English)

    梁学正; 高珊; 王雯娟; 程文萍; 杨建国

    2008-01-01

    Ketalization of catechol was studied with various carbonyl compounds using metal p-toluenesulfonate as biphasic catalysts. The results showed that copper p-toluenesulfonate was the most efficient catalysts for the re-action. The advantages of high activity, stability, reusability and low cost for the simple synthetic procedure made the catalyst one of the best choice for the reaction.

  13. Perovskite catalysts for oxidative coupling

    Science.gov (United States)

    Campbell, Kenneth D.

    1991-01-01

    Perovskites of the structure A.sub.2 B.sub.2 C.sub.3 O.sub.10 are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

  14. Biodiesel production using heterogenous catalyst

    Science.gov (United States)

    The current transesterification of triacylglycerides (TAG) to produce biodiesel is based on the homogenous catalyst method using strong base such as hydroxides or methoxides. However, this method results in a number of problems: (1) acid pre-treatment is required of feedstocks high in free fatty ac...

  15. A Novel Carbon Nanotube-Supported NiP Amorphous Alloy Catalyst and Its Hydrogenation Activity

    Institute of Scientific and Technical Information of China (English)

    Yan Ju; Fengyi Li

    2006-01-01

    A carbon nanotube-supported NiP amorphous catalyst (NiP/CNT) was prepared by induced reduction. Benzene hydrogenation was used as a probe reaction for the study of catalytic activity. The effects of the support on the activity and thermal stability of the supported catalyst were discussed based on various characterizations, including XRD, TEM, ICP, XPS, H2-TPD, and DTA. In comparison with the NiP amorphous alloy, the benzene conversion on NiP/CNT catalyst was lower, but the specific activity of NiP/CNT was higher, which is attributed to the dispersion produced by the support, an electron-donating effect, and the hydrogen-storage ability of CNT. The NiP/CNT thermal stability was improved because of the dispersion and electronic effects and the good heat-conduction ability of the CNT support.

  16. Predicting catalyst-support interactions between metal nanoparticles and amorphous silica supports

    Science.gov (United States)

    Ewing, Christopher S.; Veser, Götz; McCarthy, Joseph J.; Lambrecht, Daniel S.; Johnson, J. Karl

    2016-10-01

    Metal-support interactions significantly affect the stability and activity of supported catalytic nanoparticles (NPs), yet there is no simple and reliable method for estimating NP-support interactions, especially for amorphous supports. We present an approach for rapid prediction of catalyst-support interactions between Pt NPs and amorphous silica supports for NPs of various sizes and shapes. We use density functional theory calculations of 13 atom Pt clusters on model amorphous silica supports to determine linear correlations relating catalyst properties to NP-support interactions. We show that these correlations can be combined with fast discrete element method simulations to predict adhesion energy and NP net charge for NPs of larger sizes and different shapes. Furthermore, we demonstrate that this approach can be successfully transferred to Pd, Au, Ni, and Fe NPs. This approach can be used to quickly screen stability and net charge transfer and leads to a better fundamental understanding of catalyst-support interactions.

  17. Nitrogen-doped Carbon Derived from ZIF-8 as a High-performance Metal-free Catalyst for Acetylene Hydrochlorination

    Science.gov (United States)

    Chao, Songlin; Zou, Fang; Wan, Fanfan; Dong, Xiaobin; Wang, Yanlin; Wang, Yuxuan; Guan, Qingxin; Wang, Guichang; Li, Wei

    2017-01-01

    Acetylene hydrochlorination is a major industrial technology for manufacturing vinyl chloride monomer in regions with abundant coal resources; however, it is plagued by the use of mercury(II) chloride catalyst. The development of a nonmercury catalyst has been extensively explored. Herein, we report a N-doped carbon catalyst derived from ZIF-8 with both high activity and quite good stability. The acetylene conversion reached 92% and decreased slightly during a 200 h test at 220 °C and atmospheric pressure. Experimental studies and theoretical calculations indicate that C atoms adjacent to the pyridinic N are the active sites, and coke deposition covering pyridinic N is the main reason for catalyst deactivation. The performance of those N-doped carbons makes it possible for practical applications with further effort. Furthermore, the result also provides guidance for designing metal-free catalysts for similar reactions.

  18. Ni catalysts supported on nanocrystalline magnesium oxide for syngas production by CO2 reforming of CH4

    Institute of Scientific and Technical Information of China (English)

    Fereshteh Meshkani; Mehran Rezaei

    2011-01-01

    CO2 reforming of methane(CDRM)was carried out over MgO supported Ni catalysts with various Ni loadings.The preparation of MgO supported Ni catalysts via surfactant-assisted precipitation method led to the formation of a nanocrystalline carrier for nickel catalysts.The synthesized samples were characterized by XRD,N2 adsorption-desorption,H2 chemisorption,TPR,TPO and SEM techniques.It was found that the high catalytic activity and stability of the prepared catalysts could be attributable to high dispersion of reduced Ni species and basicity of support surface.In addition,the effect of feed ratio,nickel loading and GHSV on the catalytic performance of CDRM over the catalysts were investigated.

  19. Rhenium and manganese bipyridine tricarbonyl catalysts for the electrochemical reduction of carbon dioxide

    Science.gov (United States)

    Sampson, Matthew Dean

    Electrocatalytic reduction of carbon dioxide (CO2) is a profoundly challenging problem that is of interest, not only as a means of counteracting unsustainable emissions of CO2, but also as a method for the development of renewable fuels. Rhenium and manganese bipyridine tricarbonyl complexes are among the most active and robust catalysts for proton-coupled CO 2 reduction to carbon monoxide (CO). X- ray Absorption Spectroscopy studies are reported to reveal the electronic ground state of the Re catalysts, which help explain origins for high selectivity for CO2 reduction over proton reduction. Stopped-flow mixing in tandem with rapid-scan IR spectroscopy is utilized to probe the direct reaction of the Re catalysts with CO 2, observing, for the first time, the binding of CO2 to these catalysts. Manganese bipyridine catalysts are desirable, in comparison with their Re analogs, due to the earth-abundance of Mn and the ability for these catalysts to operate at lower overpotentials. One distinct difference between these Mn catalysts and their Re counterparts is a high tendency for dimerization after one-electron reduction, which contributes to the potential necessary to access their active state and to limiting their catalytic activity. Synthetic modification of the bipyridine ligand (by adding bulky mesityl groups) is used to completely eliminate dimerization for these Mn complexes, allowing the active catalyst to be generated at a 300 mV more positive potential than in typically Mn bipyridine complexes. CO2 reactivities in the presence of weak Bronsted acids, strong Bronsted acids, and Lewis acids have been explored in order to encourage this bulky Mn catalyst to reduce CO2 at low overpotentials. Mechanistic tools, including IR-spectroelectrochemistry, are described to gain insight into these unique catalytic processes. In order to further enhance stability and facilitate product separation, the use of metal-organic frameworks (MOFs) is explored as a means of anchoring

  20. Steam reforming of n-hexane on pellet and monolithic catalyst beds. A comparative study on improvements due to heat transfer

    Science.gov (United States)

    1981-01-01

    Monolithic catalysts with higher available active surface areas and better thermal conductivity than conventional pellets beds, making possible the steam reforming of fuels heavier than naphtha, were examined. Performance comparisons were made between conventional pellet beds and honeycomb monolith catalysts using n-hexane as the fuel. Metal-supported monoliths were examined. These offer higher structural stability and higher thermal conductivity than ceramic supports. Data from two metal monoliths of different nickel catalyst loadings were compared to pellets under the same operating conditions. Improved heat transfer and better conversion efficiencies were obtained with the monolith having higher catalyst loading. Surface-gas interaction was observed throughout the length of the monoliths.

  1. Thermally Stable Forms of Pure Polyaniline Catalyzed by an Acid-Exchanged Montmorillonite Clay Called Maghnite- H + as an Effective Catalyst

    OpenAIRE

    Rahmouni Abdelkader; Harrane Amine; Belbachir Mohammed

    2012-01-01

    Polyaniline salt form (PANI-ES) was synthesized by oxidative polymerization of aniline using potassium persulfate as an oxidant and an acid-exchanged montmorillonite clay called Maghnite-H+ as an effective catalyst. The clay, which was used as a catalyst, was supplied by a local company known as ENOF Maghnia (Western Algeria). The chemical stability of PANI has been investigated by thermogravimetry and differential scanning calorimetry, that a good thermal stability of PANI could be improved ...

  2. Partial Oxidation of Methane with Sol-Gel Fe/Hf/YSZ Catalyst in Dielectric Barrier Discharge: Catalyst Activation by Plasma

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A 1% Fe-30% Hf over yttria-stabilized zirconia catalyst in combination with novel plasma-assisted activation techniques for a direct partial oxidation of methane to methanol was tested using dielectric barrier discharge plasma at ambient temperature and atmospheric pressure. However, instead of methanol, the reaction products were dominated by H2,CO, CO2, C2, and H2O. A catalytically activated plasma process increased the production of methanol compared with a noncatalytic plasma process. The maximum selectivity of methanol production was achieved using a catalyst that was treated at higher applied power.

  3. Effects of Ce on catalytic combustion of methane over Pd-Pt/Al2O3 catalyst

    Institute of Scientific and Technical Information of China (English)

    Xing Fan; Fan Wang; Tianle Zhu; Hong He

    2012-01-01

    Activity and stability of 1%Pd-0.2%Pt/Al2O3 and 1%Pd-0.2%Pt/0.6%Ce/Al2O3 catalysts prepared by impregnation method for catalytic combustion of methane in air were investigated.The catalysts before and after reaction were characterized by BET,CO chemisorption,XRD and XPS techniques.Results showed that the presence of Ce significantly increased the activity and thermal stability of the Pd-Pt/Al2O3 catalyst towards methane combustion,which could be attributed to more highly-dispersed active PdO particles over the Pd-Pt/Ce/Al2O3 catalyst surface as well as the retarded sintering of PdO and the maintained oxidized state of surface Pd during the combustion process in the presence of Ce.

  4. Dehydration of lactic acid to acrylic acid over lanthanum phosphate catalysts: the role of Lewis acid sites.

    Science.gov (United States)

    Guo, Zhen; Theng, De Sheng; Tang, Karen Yuanting; Zhang, Lili; Huang, Lin; Borgna, Armando; Wang, Chuan

    2016-09-14

    Lanthanum phosphate (LaP) nano-rods were synthesized using n-butylamine as a shape-directing agent (SDA). The resulting catalysts were applied in the dehydration of lactic acid to acrylic acid. Aiming to understand the nature of the active sites, the chemical and physical properties of LaP materials were studied using a variety of characterization techniques. This study showed that the SDA not only affected the porosity of the LaP materials but also modified the acid-base properties. Clearly, the modification of the acid-base properties played a more critical role in determining the catalytic performance than porosity. An optimized catalytic performance was obtained on the LaP catalyst with a higher concentration of Lewis acid sites. Basic sites showed negative effects on the stability of the catalysts. Good stability was achieved when the catalyst was prepared using the appropriate SDA/La ratio.

  5. Preparation and influence of performance of anodic catalysts for direct methanol fuel cell

    Institute of Scientific and Technical Information of China (English)

    WANG Zhenbo; YIN Geping; SHI Pengfei

    2007-01-01

    This research aims at increasing the utilization of platinum-ruthenium alloy (Pt-Ru) catalysts and thus lowering the catalyst loading in anodes for methanol electrooxidation.The direct methanol fuel cell's (DMFC) anodic catalysts,Pt-Ru/C,were prepared by chemical reduction with a reducing agent added in two kinds of solutions under different circumstances.The reducing agent was added in hot solution with the protection of inert gases or just air,and in cold solution with inert gases.The catalysts were treated at different temperatures.Their performance was tested by cyclic voltammetry and potentiostatic polarization by utilizing their inherent powder microelectrode in 0.5 mol/L CH3OH and 0.5 mol/L H2SO4 solution.The structures and micro-surface images ofthe catalysts were determined and observed by X-ray diffraction and transmission electron microscopy,respectively.The catalyst prepared in inert gases showed a better catalytic performance for methanol electrooxidation than that prepared in air.It resulted in a more homogeneous distribution of the Pt-Ru alloy in carbon.Its size is small,only about 4.5 nm.The catalytic performance is affected by the order of the reducing agent added.The performance of the catalyst prepared by adding the reductant at constant temperature of the solution is better than that prepared by adding it in the solution at 0℃ and then heating it up to the reducing temperature.The structure of the catalyst was modified,and there was an increase in the conversion of ruthenium into the alloyed state and an increase in particle size with the ascension of heat treatment temperature.In addition,the stability of the catalyst was improved after heat treatment.

  6. Hydrocarbon reforming catalysts and new reactor designs for compact hydrogen generators

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, A.; Schwab, E.; Urtel, H. [BASF SE, Ludwigshafen (Germany); Farrauto, R. [BASF Catalysts LLC, Iselin, NJ (United States)

    2010-12-30

    A hydrogen based future energy scenario will use fuel cells for the conversion of chemically stored energy into electricity. Depending upon the type of fuel cell, different specifications will apply for the feedstock which is converted in the cell, ranging from very clean hydrogen for PEM-FC's to desulfurized methane for SOFC and MCFC technology. For the foreseeable future, hydrogen will be supplied by conventional reforming, however operated in compact and dynamic reformer designs. This requires that known catalyst formulations are offered in specific geometries, giving flexibility for novel reactor design options. These specific geometries can be special tablet shapes as well as monolith structures. Finally, also nonhydrocarbon feedstock might be used in special applications, e.g. bio-based methanol and ethanol. BASF offers catalysts for the full process chain starting from feedstock desulfurization via reforming, high temperature shift, low temperature shift to CO fine polishing either via selective oxidation or selective methanation. Depending upon the customer's design, most stages can be served either with precious metal based monolith solutions or base metal tablet solutions. For the former, we have taken the automobile catalyst monolith support and extended its application to the fuel cell hydrogen generation. Washcoats of precious metal supported catalysts can for example be deposited on ceramic monoliths and/or metal heat exchangers for efficient generation of hydrogen. Major advantages are high through puts due to more efficient heat transfer for catalysts on metal heat exchangers, lower pressure drop with greater catalyst mechanical and thermal stability compared to particulate catalysts. Base metal tablet catalysts on the other hand can have intrinsic cost advantages, larger fractions of the reactor can be filled with active mass, and if produced in unconventional shape, again novel reactor designs are made possible. Finally, if it comes to

  7. Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

    Energy Technology Data Exchange (ETDEWEB)

    Conrad Ingram; Mark Mitchell

    2007-03-31

    The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of a mesoporous aluminosilicate catalyst, AlSBA-15. The Al-SBA-15 mesoporous catalyst contains strong Br{umlt o}nsted acid sites and aluminum (Al) stabilized in a totally tetrahedral coordination. The physicochemical characteristics of the catalyst varied as a function of the synthesis conditions. The catalyst possessed surface areas ranging between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm, and pore volumes up 1.03 cm{sup 3}, which were comparable to the parent SBA-15 synthesized under similar conditions. Two wt % Al was present in the catalyst that was obtained from the reaction mixture that contained the highest Al content. The Al remained stable in totally tetrahedral coordination after calcination at a temperature of 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and the activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. In preparation for the final phase of the project, the catalyst was embedded into a psuedoboemite alumina (catapal B) matrix and then formed into pellets. In the final phase of the project, the pelletized catalyst is being evaluated for the conversion of a heavy petroleum feedstock to naphtha and middle distillates. This phase was significantly delayed during the past six months due to a serious malfunction of the fume hoods in the Clark Atlanta University's Research Center for Science and Technology, where the project is being conducted. The fume hood system was repaired and the catalyst evaluation is now underway.

  8. Regeneration of Commercial SCR Catalysts: Probing the Existing Forms of Arsenic Oxide.

    Science.gov (United States)

    Li, Xiang; Li, Junhua; Peng, Yue; Si, Wenzhe; He, Xu; Hao, Jiming

    2015-08-18

    To investigate the poisoning and regeneration of SCR catalysts, fresh and arsenic-poisoned commercial V2O5-WO3/TiO2 catalysts are researched in the context of deactivation mechanisms and regeneration technology. The results indicate that the forms of arsenic oxide on the poisoned catalyst are related to the proportion of arsenic (As) on the catalyst. When the surface coverage of (V+W+As) is lower than 1, the trivalent arsenic species (As(III)) is the major component, and this species prefers to permeate into the bulk-phase channels. However, at high As concentrations, pentavalent arsenic species (As(IV)) cover the surface of the catalyst. Although both arsenic species lower the NOx conversion, they affect the formation of N2O differently. In particular, N2O production is limited when trivalent arsenic species predominate, which may be related to As2O3 clogging the pores of the catalyst. In contrast, the pentavalent arsenic oxide species (As2O5) possess several As-OH groups. These As-OH groups could not only enhance the ability of the catalyst to become reduced, but also provide several Brønsted acid sites with weak thermal stability that promote the formation of N2O. Finally, although our novel Ca(NO3)2-based regeneration method cannot completely remove As2O3 from the micropores of the catalyst, this approach can effectively wipe off surface arsenic oxides without a significant loss of the catalyst's active components.

  9. MECHANICAL STRENGTH AND RELIABILITY OF SOLID CATALYSTS

    Institute of Scientific and Technical Information of China (English)

    Yongdan Li; Dongfang Wu; Y.S. Lin

    2004-01-01

    The mechanical strength of solid catalysts is one of the key parameters for reliable and efficient performance of a fixed bed reactor. Some recent developments and their basic mechanics within this context are reviewed. The main concepts discussed are brittle fracture which leads to the mechanical failure of the catalyst pellets, measurement and statistical properties of the catalyst strength data, and mechanical reliability of the catalyst pellets and their packed bed. The scientific basis for the issues on the catalyst mechanical properties calls yet for further elucidation and advancement.

  10. An Efficient and Recyclable Nanoparticle-Supported Cobalt Catalyst for Quinoxaline Synthesis.

    Science.gov (United States)

    Rajabi, Fatemeh; Alves, Diego; Luque, Rafael

    2015-11-19

    The syntheses of quinoxalines derived from 1,2-diamine and 1,2-dicarbonyl compounds under mild reaction conditions was carried out using a nanoparticle-supported cobalt catalyst. The supported nanocatalyst exhibited excellent activity and stability and it could be reused for at least ten times without any loss of activity. No cobalt contamination could be detected in the products by AAS measurements, pointing to the excellent activity and stability of the Co nanomaterial.

  11. An Efficient and Recyclable Nanoparticle-Supported Cobalt Catalyst for Quinoxaline Synthesis

    Directory of Open Access Journals (Sweden)

    Fatemeh Rajabi

    2015-11-01

    Full Text Available The syntheses of quinoxalines derived from 1,2-diamine and 1,2-dicarbonyl compounds under mild reaction conditions was carried out using a nanoparticle-supported cobalt catalyst. The supported nanocatalyst exhibited excellent activity and stability and it could be reused for at least ten times without any loss of activity. No cobalt contamination could be detected in the products by AAS measurements, pointing to the excellent activity and stability of the Co nanomaterial.

  12. Carbon nanotubes: A promising catalyst support material for supercritical water gasification of biomass waste

    NARCIS (Netherlands)

    Vlieger, de D.J.M.; Thakur, D.B.; Lefferts, L.; Seshan, K.

    2012-01-01

    Supercritical water (SCW) as a reaction medium is especially promising for the production of renewable chemicals from biomass. Stability issues of catalyst support materials in SCW are a major setback for these reactions and hinder the further development and industrial exploitation of this techniqu

  13. Hydrogenation of Benzene over Mo2C/Al2O3 Catalyst

    Institute of Scientific and Technical Information of China (English)

    Zhang Jing; Wu Weicheng

    2008-01-01

    The process of benzene hydrogenation over Mo2C catalyst has been studied.Mo2C was the active phase in benzene hydrogenation.The major problem with the metal carbides was their poor stability due to deactivation by carbon deposition.

  14. Enhanced High- and Low-Temperature Performance of NOx Reduction Catalyst Materials

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Muntean, George G.; Peden, Charles HF; Howden, Ken; Currier, Neal; Kamasamudram, Krishna; Kumar, Ashok; Li, Junhui; Luo, Jinyong; Stafford, Randy; Yezerets, Aleksey; Castagnola, Mario; Chen, Hai-Ying; Hess, Howard ..

    2014-12-09

    In this annual CRADA program report, we will briefly highlight results from our recent studies of the stability of candidate K-based high temperature NSR materials, and comparative studies of low temperature performance of SSZ-13 and SAPO-34 CHA catalysts; in particular, recent results comparing Fe- and Cu-based CHA materials.

  15. Alkene Isomerization Using a Solid Acid as Activator and Support for a Homogeneous Catalyst

    Science.gov (United States)

    Seen, Andrew J.

    2004-01-01

    An upper-level undergraduate experiment that, in addition to introducing students to catalysis using an air sensitive transition-metal complex, introduces the use of a solid acid as an activator and support for the catalyst is developed. The increased stability acquired in the course of the process affords the opportunity to characterize the…

  16. Automotive Catalyst State Diagnosis Using Microwaves

    Directory of Open Access Journals (Sweden)

    Moos Ralf

    2015-01-01

    Full Text Available The state of catalysts plays a key role in automotive exhaust gas aftertreatment. The soot or ash loading of Diesel particulate filters, the oxygen loading degree in three-way catalysts, the amount of stored ammonia in SCR catalysts, or the NOx loading degree in NOx storage catalysts are important parameters that are today determined indirectly and in a model-based manner with gas sensors installed upstream and/or downstream of the catalysts. This contribution gives an overview on a novel approach to determine the catalyst state directly by a microwave-based technique. The method exploits the fact that the catalyst housing acts as a microwave cavity resonator. As “sensing” elements, one or two simple antennas are mounted inside the catalyst canning. The electrical properties of the catalyst device (ceramic honeycomb plus coating and storage material can be measured. Preferably, the resonance characteristics, e.g., the resonance frequencies, of selected cavity modes are observed. The information on the catalyst interior obtained in such a contactless manner is very well correlated with the catalyst state as will be demonstrated for different exhaust gas aftertreatment systems.

  17. Direct decomposition of methane over SBA-15 supported Ni, Co and Fe based bimetallic catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Pudukudy, Manoj, E-mail: manojpudukudy@gmail.com [Fuel Cell Institute, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor (Malaysia); Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor (Malaysia); Yaakob, Zahira, E-mail: zahirayaakob65@gmail.com [Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor (Malaysia); Akmal, Zubair Shamsul [Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor (Malaysia)

    2015-03-01

    Graphical abstract: - Highlights: • Synthesis and characterization of Ni, Co and Fe based bimetallic catalysts supported over SBA-15. • Thermocatalytic decomposition of methane over the SBA-15 supported bimetallic catalysts. • Enhanced catalytic efficiency of the bimetallic catalysts for the production of CO{sub x} free hydrogen and nanocarbon. • Production of value added open tip hollow multi-walled carbon nanotubes. • Crystalline characterization of carbon nanotubes by XRD, Raman and thermogravimetric analysis. - Abstract: Thermocatalytic decomposition of methane is an alternative route for the production of CO{sub x}-free hydrogen and carbon nanomaterials. In this work, a set of novel Ni, Co and Fe based bimetallic catalysts supported over mesoporous SBA-15 was synthesized by a facile wet impregnation route, characterized for their structural, textural and reduction properties and were successfully used for the methane decomposition. The fine dispersion of metal oxide particles on the surface of SBA-15, without affecting its mesoporous texture was clearly shown in the low angle X-ray diffraction patterns and the transmission electron microscopy (TEM) images. The nitrogen sorption analysis showed the reduced specific surface area and pore volume of SBA-15, after metal loading due to the partial filling of hexagonal mesopores by metal species. The results of methane decomposition experiments indicated that all of the bimetallic catalysts were highly active and stable for the reaction at 700 °C even after 300 min of time on stream (TOS). However, a maximum hydrogen yield of ∼56% was observed for the NiCo/SBA-15 catalyst within 30 min of TOS. A high catalytic stability was shown by the CoFe/SBA-15 catalyst with 51% of hydrogen yield during the course of reaction. The catalytic stability of the bimetallic catalysts was attributed to the formation of bimetallic alloys. Moreover, the deposited carbons were found to be in the form of a new set of hollow

  18. Cationic ruthenium alkylidene catalysts bearing phosphine ligands.

    Science.gov (United States)

    Endo, Koji; Grubbs, Robert H

    2016-02-28

    The discovery of highly active catalysts and the success of ionic liquid immobilized systems have accelerated attention to a new class of cationic metathesis catalysts. We herein report the facile syntheses of cationic ruthenium catalysts bearing bulky phosphine ligands. Simple ligand exchange using silver(i) salts of non-coordinating or weakly coordinating anions provided either PPh3 or chelating Ph2P(CH2)nPPh2 (n = 2 or 3) ligated cationic catalysts. The structures of these newly reported catalysts feature unique geometries caused by ligation of the bulky phosphine ligands. Their activities and selectivities in standard metathesis reactions were also investigated. These cationic ruthenium alkylidene catalysts reported here showed moderate activity and very similar stereoselectivity when compared to the second generation ruthenium dichloride catalyst in ring-closing metathesis, cross metathesis, and ring-opening metathesis polymerization assays.

  19. Enzyme catalysts for a biotechnology-based chemical industry. Quarterly progress report, January 1--April 1, 1998

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, F.H.

    1998-04-20

    The goal of this research is to engineer enzymes to be efficient and economically attractive catalysts for the chemical industry. The author is attempting to demonstrate generally-applicable approaches to enzyme improvement as well as develop specific catalysts for potential industrial application. The research is focused on the following areas: (1) Random mutagenesis of pNB esterase: improved activity and stability; (2) Directed evolution of subtilisin E to enhance thermostability; and (3) Methods for in vitro recombination.

  20. Enzyme catalysts for a biotechnology-based chemical industry. Quarterly progress report, April 1--July 1, 1998

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, F.H.

    1998-07-08

    The goal of this research is to engineer enzymes to be efficient and economically attractive catalysts for the chemical industry. The author is attempting to demonstrate generally-applicable approaches to enzyme improvement as well as develop specific catalysts for potential industrial application. Progress on three tasks are described: Random mutagenesis of pNB esterase--improved activity and stability; Directed evolution of subtilisin E to enhance thermostability; and Methods for invitro recombination.

  1. Enzyme catalysts for a biotechnology-based chemical industry. Quarterly progress report, April 1--June 28, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, F.H.

    1996-07-22

    The goal of this research is to engineer enzymes to be efficient and economically attractive catalysts for the chemical industry. The author is attempted to demonstrate generally-applicable approaches to enzyme improvement as well as develop specific catalysts for potential industrial application. The paper describes the progress in two projects: (a) Random mutagenesis of pNB esterase: Improved activity and stability; and (2) Subtilisin mutants exhibiting improved ligase activity in organic solvents.

  2. Biogas reforming on La-promoted NiMgAl catalysts derived from hydrotalcite-like precursors

    Science.gov (United States)

    Serrano-Lotina, A.; Rodríguez, L.; Muñoz, G.; Daza, L.

    Hydrotalcite-like precursors have been synthesized in order to study the influence of lanthanum on the structure and the properties of the precursors, as well as on the catalytic activity and stability of their derived catalyst on biogas reforming. From XRD, and TPO characterization, we confirmed that hydrotalcite-like precursors where obtained. After calcination at 750 °C, Mg(Ni,Al)O solid solution was detected. High surface areas have been obtained finding the highest surface area on the catalyst without lanthanum. TPR experiments were performed in order to study the reducibility of the catalysts. One reduction peak was found in the catalyst without lanthanum while two peaks were observed in the catalysts with lanthanum. A reduction peak at 900 °C was observed over the sample without Ni and La. Catalytic tests, at 700 °C with a feed of CH 4:CO 2 1:1, were performed after appropriate reduction during 50 h. While a decrease on catalytic activity was observed with the addition and the increase of La content, an enhancement in the stability was observed. No sign of deactivation of the catalyst and no carbon deposition were found on the catalysts doped with lanthanum.

  3. Performance of Co/MgO catalyst for CO2 reforming of toluene as a model compound of tar derived from biomass gasification

    Institute of Scientific and Technical Information of China (English)

    Xiuxiu Bao; Meng Kong; Wen Lu; Jinhua Fei∗; Xiaoming Zheng

    2014-01-01

    Catalytic performances of the CO2 reforming of toluene on Co/MgO catalysts with different cobalt loadings were evaluated in a fluidized-bed reactor. The results showed that the conversion of toluene and the stability of Co/MgO increased, but the apparent reaction rate decreased at the initial stage with increasing the amount of metallic Co formed from the reduction of Co/MgO catalysts at 700◦C. The deactivation of Co/MgO catalysts was mainly resulted from that a part of the metallic Co was oxidized by CO2 and could not be re-reduced by H2 at reaction temperature. Therefore, the excess metallic Co on the higher Co loading catalysts was beneficial to the catalyst stability.

  4. Heteropoly acid promoted V2O5/TiO2 catalysts for NO abatement with ammonia in alkali containing flue gases

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Jensen, Anker Degn; Riisager, Anders;

    2011-01-01

    V2O5/TiO2 and heteropoly acid promoted V2O5/TiO2 catalysts were prepared and characterized by N2 physisorption, XRPD and NH3-TPD. The influence of the calcination temperature from 400 to 700 1C on crystallinity and acidic properties was studied and compared with the activity for the selective...... catalytic reduction (SCR) of NO with ammonia. The SCR activity of heteropoly acid promoted catalysts was found to be much higher than for unpromoted catalysts. The stability of heteropoly acid promoted catalysts is dependent on calcination temperature and there is a gradual decrease in SCR activity...... and acidity with increase in calcination temperatures. Furthermore, the heteropoly acid promoted V2O5/TiO2 catalysts showed excellent alkali deactivation resistance and might therefore be alternative deNOx catalysts in biomass fired power plants....

  5. Assessment of the ethanol oxidation activity and durability of Pt catalysts with or without a carbon support using Electrochemical Impedance Spectroscopy

    Science.gov (United States)

    Saleh, Farhana S.; Easton, E. Bradley

    2014-01-01

    We compared the stability and performance of 3 commercially available Johnson Matthey catalysts with various Pt loadings (20, 40 and 100%) using two different accelerated durability testing (ADT) protocols. The various Pt-loaded catalysts were tested by means of a series of intermittent life tests (1, 200, 400, 1000, 2000, 3000 and 4000 cycles). The electrochemical surface area (ECSA) loss of electrode was investigated by electrochemical technique (CV). The use of EIS as an accelerated-testing protocol distinctly elucidates the extent of degradation of Johnson Matthey catalysts with various Pt loading. Using EIS, it was possible to show that Pt-black catalyst layers suffer from increased electronic resistance over the course of ADT which is not observed when a corrosion stable carbon support is present. The effect of Pt loading was further elucidated by comparing the electrocatalytic activity of the catalyst layers towards ethanol oxidation reaction (EOR). The catalyst layer with the lowest Pt loading showed the enhanced EOR performance.

  6. A percepção das enfermeiras acerca da sua atuação ante os direitos dos clientes La percepción de las enfermeras respecto a su actuación ante los derechos de los clientes Nurses' perception of their work vis-a-vis patients' rights

    Directory of Open Access Journals (Sweden)

    Patrícia Chaves Alves

    2008-06-01

    Full Text Available Com o objetivo de conhecer a percepção das enfermeiras acerca de sua atuação ante os direitos dos clientes e desenvolver um instrumento que possibilitasse mensurar esta percepção, realizou-se uma pesquisa exploratório-descritiva, com uma amostra de 73 enfermeiras de dois hospitais. Mediante um questionário auto-aplicado, foram identificados e validados quatro construtos relacionados à atuação das enfermeiras, quanto aos direitos dos clientes: preservação da individualidade; respeito à autonomia do cliente, identificação pessoal e informação para a tomada de decisão. O construto que apresentou melhor desempenho diz respeito à preservação da individualidade. Já o respeito à autonomia do cliente e a identificação pessoal situaram-se em um nível intermediário, enquanto que o construto informação para a tomada de decisão apresentou-se como o menos realizado pelas enfermeiras. A preservação da individualidade e o respeito à autonomia mostraram-se como os construtos que mais influenciam a percepção das enfermeiras de como, em geral, respeitam os direitos dos clientes.Con el objetivo de conocer la percepción de las enfermeras referentes a su actuación ante los derechos de los clientes y para desarrollar un instrumento para mensurar esta percepción, se realizó una investigación exploratorio-descriptiva, con una muestra de 73 enfermeras de dos hospi-tales. Por medio de un cuestionario auto-aplicado, fueron identificados y validados cuatro constructos relacionados a la actuación de las enfermeras, en cuanto a los derechos de los clientes: preservación de la individualidad, respeto a la autonomía del cliente, identificación personal e información para la toma de decisión. El constructo que presentó un mejor desempeño se refiere a la preservación de la individualidad. Ya el respeto a la autonomía del cliente y la identificación personal se situaron en un nivel intermedio, mientras que el constructo información para la toma de decisión se presentó como el menos realizado por las enfermeras. La preservación de la individualidad y el respecto a la autonomía se mostraron como los constructos que más influencian la percepción de las enfermeras de como, en general, respetan los derechos de los clientes.This exploratory-descriptive survey was carried out with a sample consisting of 73 nurses from two hospitals in order to know the perception they have of their work via-a-vis patients' rights and develop an instrument capable of measuring such perception. Four constructs referring to the nurses' performance via-a-vis patients' rights were identified and validated, based on questions the nurses answered: preservation of individuality; respect for the patient's autonomy; personal identification; and information for decision-taking. Preservation of individuality was the construct with the best performance. Respect for the patient's autonomy and personal identification appear in an intermediate level, whereas the construct information for decision-taking was the least used. In general, preservation of individuality and respect for the patient's autonomy are the constructs that influenced the most nurses' perception on patients' rights.

  7. Contribution to the modeling of elaborate cement barriers behaviour with respect to radioelements migration by the study of ancient analogue materials; Apport de l`etude de materiaux analogues anciens a la modelisation du comportement des barrieres ouvragees en ciment vis-a-vis de la migration des radioelements

    Energy Technology Data Exchange (ETDEWEB)

    Rougeau, P.

    1994-10-13

    The durability of cement matrices and their capacity of radioelements retention are determining factors for their use as elaborate barriers in radioactive waste disposal facilities. This study focusses on the observation of concretes in real situation of alteration or in contact with radioelements for predictive modelling. Two materials have been selected. One is a concrete from a gallery wall of the Margnac uranium mine (Cogema, France) submitted to uranium-rich infiltration waters. The alteration concentrates in two characteristic successive zones: the first is composed of calcium depleted and aluminum enriched calcite and calcium hydro-silicates and the second, between the first zone and the sound matrix, is characterized by a self-filling in process due to massive ettringite precipitation induced by sulfate ions transport. Uranium migration depends closely on the fissures and porosity of the cement matrix. The second series of samples correspond to 2000 years old archaeological cements from Pompei (Italy) made of volcanic ashes and carrying uranium traces. These samples were submitted to burying and alteration is characterized by a carbonation of the cement matrix. The mineralogy is closed to the one defined in the first alteration zone of the uranium mine concrete. Both studies demonstrate that the presence of carbonate ions in the percolation water plays a major role in the alteration process. Sulfate reactions must be considered too and tend to diminish the materials porosity and to increase the delay in radionuclides migration processes. (J.S.). 131 refs., 92 figs., 55 tabs., 51 photos., 15 appends.

  8. Bush v. Bin Laden: Effect of State Emotion on Perceived Threat is Mediated by Emotion Towards the Threat Agent (Bush vs. Ben Laden: l’Effet de l’Emotion etat sur la Menace Percue est Mediatisees par l’Emotion vis-a-vis de l’Agent Menacant)

    Science.gov (United States)

    2009-07-01

    Oshin.Vartanian@drdc-rddc.gc .ca. REVUE INTERNATIONALE DE PSYCHOLOGIE SOCIALE 2010 N° 1 terrorism Mots-ellis Perception de menace, perception de risque... PSYCHOLOGIE SOCIALE 2010 N° 1 • The Present Research We sought to extend the investigation of the effect of emotion on threat-related judgments in...terrorism domain. REVUE INTERNATIONAlE DE PSYCHOlOGIE SOCIAlE 2010 N" 1 Method Participants A sample of 120 (45 male and 75 female) University of

  9. Synthesis and complexation properties towards uranyl cation of carboxylic acid derivatives of p-tert-butyl-calix[6]arene; Synthese et proprietes complexantes vis-a-vis de l'ion uranyle de derives carboxyliques du p-tert-butyl-calix[6]arene

    Energy Technology Data Exchange (ETDEWEB)

    Souane, R

    2005-03-15

    In the fuel reprocessing plants radioactive metals, and more particularly, uranium in UO{sub 2}{sup 2+} form in the various installations, have many varied physico-chemical forms and there is a risk of exposure and internal contamination in the nuclear industry. It is necessary to exert a medical control to ensure the protection of the health of the workers. This medical control is done by dosing uranyl cation in the urine of the exposed people. This work forms part of this context. Indeed, we prepared a ligand able to complex the ion uranyl and which is also to be grafted on a solid support. In the family of calixarenes, the calix[6]arenes functionalized by three or four carboxylic functions were selected like chelating molecules of the ion uranyl. The properties of complexation of these calixarenes were studied by potentiometry in methanol, under these conditions balances of protonation and complexation were determined and the constant partners were obtained using the Hyperquad program. We synthesized tri-carboxylic calix[6]arenes comprising of the groupings nitro (NO{sub 2}) in para position of phenol in order to see the influence of a substitution in para position on the complexation. We also synthesized calix[6]arenes tetra-carboxylic in order to show the role of an additional carboxylic acid grouping. The potentiometric study determined thermodynamic parameters of protonation and complexation of carboxylic calix[6]arenes. The results of the complexation highlighted which complex UO{sub 2}L corresponding to the ligand para-tert-butyl-calix[6]arene tetra-acid is more stable than that corresponding to the ligand mono-nitro calix[6]arene tri-acid ({delta}log{beta}110 = 4.3), and than the effect of the groupings nitro in para position has low influence on the complexation of UO{sub 2}{sup 2+}. This makes it possible to consider as possible the grafting of the calix[6]arenes which one knows the behaviour of trapping. To this end we synthesized the ligand 23. (author)

  10. O desenvolvimento profissional da docência na formação de professores face a utilização das tecnologias/The professional development of teaching in teacher’s formation vis-a-vis the using of technologies

    Directory of Open Access Journals (Sweden)

    Stela Conceição Bertholo Piconez

    2009-06-01

    Full Text Available Neste artigo, descrevemos as contribuições das abordagens de Design Instrucional e do Learning Design para a organização do trabalho pedagógico no STEA – Sistema Transversal Ensino-Aprendizagem que emprega recursos tecnológicos na educação apoiado pelos dados de pesquisa qualitativa e perspectivas teórico-descritivas, em um estudo de caso brasileiro. A abordagem pedagógica na qual o sistema está baseado permeia, em toda sua documentação e práxis: as teorias socioconstrutivistas de Piaget e Vygotsky, os estudos de Ausubel sobre organização dos conceitos prévios da aprendizagem significativa, a concepção de autonomia e liberdade de Paulo Freire, a tipologia conceitual dos conteúdos procedimentais e atitudinais de Zabala bem como a perspectiva andragógica de Knowles que fundamentam a tomada de decisões durante o processo de ensino. Contempla todos os processos de design instrucional - desde planejamento, concepção, implementação, execução e avaliação até a formação e avaliação contínua dos docentes em serviço. Confronta as etapas teórico-práticas do projeto com a abordagem de organização do trabalho pedagógico realizado em um sistema nacional de ensino-aprendizagem, ancorado em bases pedagógicas explícitas, elaborado através de duas décadas de investigação e de práxis. O estudo também inclui material didático produção e ações complementares de investigação acadêmica, contextualizada. Como resultado apresenta as reflexões sobre o projeto de aprendizagem, seus benefícios e desafios e suas contribuições para a inovação no campo da tecnologia educacional. O STEA foi construído de acordo com um modelo pedagógico cuja delimitação conceitual abraça objetivos, organização de conteúdos e metodologias relacionada a diferentes domínios do conhecimento. A elaboração desse modelo atende as necessidades educativas especiais de duas comunidades com características distintas de aprendizagem: a dos jovens e adultos em curso de ensino médio e a formação em ação de estagiários das licenciaturas. In this paper, we describe the contributions of instructional design and Learning Design approaches to pedagogical work organization of STEA – Transversal Teaching-Learning System that employs technological resources in education supported by the use of qualitative research approach and theoretical-descriptive perspectives, we compare theoretical and practical framework of instructional design and Learning Design in a Brazilian case study, which contemplates all of instructional design processes – since planning, design, implementation, execution and evaluation until formation and continuing evaluation of acting teachers. Pedagogical approach, which is the system is based on, is clearly declared and permeates all its documentation and praxis: Piaget and Vygotsky’s socio-constructivists theories, Ausubel’s studies about students’ previous knowing organization, Paulo Freire’s conception of autonomy and freedom, the conceptual typology of Zabala’s procedural and behavioural contents, and Knowles’ andragogic perspective grounds the decisions to been made during teaching process. Describes and analyses the confrontation of theoretician-practical steps of Learning Design approach with pedagogical work organization accomplished in a national teaching-learning system, which is anchored in explicit pedagogical bases, ripened through two decades of research and praxis. The study also encompasses didactical material production and complementary actions of academic research. As results, it represents the reflections about Learning Design benefits and challenges, and its contributions to innovation in educational technology field. STEA was built according to a proper, pedagogical model which its conceptual delineation embraces objectives, organization of contents and methodologies related to different knowledge areas. The elaboration of this model attends particular educational needs of two distinct communities with regard to learning characteristics: young and adult learning during high school course and the formation of educators-trainees to play their roles.

  11. Direct Dehydrogenation of n-Butane Over Pt/Sn/Zn-K/Al2O3 Catalyst: Effect of Hydrogen in the Feed.

    Science.gov (United States)

    Lee, Jong Kwon; Seo, Hyun; Kim, Jeong Kwon; Seo, Hanuk; Cho, Hye-Ran; Lee, Jinsuk; Chang, Hosik; Song, In Kyu

    2016-05-01

    Al2O3 was prepared by a sol-gel method for use as a support. Pt/Sn/Zn-K/Al2O3 catalyst was then prepared by a sequential impregnation method, and it was applied to the direct dehydrogenation of n-butane to n-butenes and 1,3-butadiene. Physicochemical properties of Pt/Sn/Zn-K/Al2O3 catalyst were examined by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm, inductively coupled plasma atomic emission spectroscopy (ICP-AES), temperature-programmed reduction (TPR), CO chemisorption, and temperature-programmed oxidation (TPO) measurements. In order to improve the catalyst stability, the effect of hydrogen in the feed on the catalytic performance in the direct dehydrogenation of n-butane was studied. The catalyst stability and reusability in the direct dehydrogenation of n-butane was also investigated. Experimental results revealed that the addition of hydrogen in the feed decreased conversion of n-butane and yield for total dehydrogenation products but improved the stability of the catalyst. The catalytic activity and stability of regenerated Pt/Sn/Zn-K/Al2O3 catalyst in the presence of hydrogen slightly decreased compared to those of fresh Pt/Sn/Zn-K/Al2O3 catalyst due to the slight sintering of platinum particles.

  12. Fine-tuning the activity of oxygen evolution catalysts

    DEFF Research Database (Denmark)

    Paoli, Elisa Antares; Masini, Federico; Frydendal, Rasmus

    2016-01-01

    Water splitting is hindered by the sluggish kinetics of the oxygen evolution reaction (OER). The choice of materials for this reaction in acid is limited to the platinum group metals; high loading required of these scarce and expensive elements severely limit the scalability of such technology....... Ruthenium oxide is among the best catalysts for OER, however the reported activity and stability can vary tremendously depending on the preparation conditions and pre-treatment. Herein, we investigate the effect of oxidation treatment on mass-selected Ru nanoparticles in the size range between 2 and 10 nm...

  13. Biodiesel production using heterogeneous catalysts.

    Science.gov (United States)

    Semwal, Surbhi; Arora, Ajay K; Badoni, Rajendra P; Tuli, Deepak K

    2011-02-01

    The production and use of biodiesel has seen a quantum jump in the recent past due to benefits associated with its ability to mitigate greenhouse gas (GHG). There are large number of commercial plants producing biodiesel by transesterification of vegetable oils and fats based on base catalyzed (caustic) homogeneous transesterification of oils. However, homogeneous process needs steps of glycerol separation, washings, very stringent and extremely low limits of Na, K, glycerides and moisture limits in biodiesel. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is environmentally benign needs no water washing and product separation is much easier. The present report is review of the progress made in development of heterogeneous catalysts suitable for biodiesel production. This review shall help in selection of suitable catalysts and the optimum conditions for biodiesel production.

  14. Fundamental investigations of catalyst nanoparticles

    DEFF Research Database (Denmark)

    Elkjær, Christian Fink

    area Cu=ZnO=Al2O3 structure that is difficult to study by TEM. We therefore created size-selected CuZn alloy nanoparticles that were transformed by oxidation and reduction into Cu nanoparticles decorated with ZnO. This represents a simplified model system for the high surface area catalyst...... been unknown. We used nanoreactor technology which allows for simultaneous TEM imaging and activity measurement, also referred to as an Operando experiment. With this we revealed that the shape of the Pt nanoparticles changed in phase with changes in global reaction rate. By the use of reactor modeling...... fundamental understanding of catalytic processes and our ability to make use of that understanding. This thesis presents fundamental studies of catalyst nanoparticles with particular focus on dynamic processes. Such studies often require atomic-scale characterization, because the catalytic conversion takes...

  15. Stability Functions

    CERN Document Server

    Burns, Daniel; Wang, Zuoqin

    2008-01-01

    In this article we discuss the role of stability functions in geometric invariant theory and apply stability function techniques to problems in toric geometry. In particular we show how one can use these techniques to recover results of Burns-Guillemin-Uribe and Shiffman-Tate-Zelditch on asymptotic properties of sections of holomorphic line bundles over toric varieties.

  16. UPGRADING OF BIO-OIL MOLECULAR DISTILLATION FRACTION WITH SOLID ACID CATALYST

    Directory of Open Access Journals (Sweden)

    Zuogang Guo

    2011-05-01

    Full Text Available Molecular distillation technology has been adopted to obtain a bio-oil fraction rich in carboxylic acids and ketones. This unique bio-oil fraction was then upgraded with a La-promoted solid acid catalyst. Three washing pretreatments were used to prepare catalysts A, B, and C, with the intention of reducing the amounts of residual sulfuric acid. Model reactions were used to estimate their catalytic activities and the residual amounts of sulfuric acid. Catalyst B, with washing after calcination, displayed higher catalytic activity (80.83% and lower residual amount of sulfuric acid (50 μmol/g. The catalysts were characterized by techniques such as BET, XRD, and SEM to explain the differences in their catalytic activities. The optimum catalyst B was used in the upgrading of the bio-oil molecular distillation fraction. After upgrading, the corrosivity of the bio-oil fraction declined and its storage stability was improved. The carboxylic acid content in the upgraded bio-oil fraction decreased from 18.39% to 2.70%, while the ester content increased from 0.72% to 31.17%. The conversion of corrosive carboxylic acids to neutral esters reduced the corrosivity of the bio-oil fraction. Moreover, the ketones with unsaturated carbon-carbon double bonds (such as 2-cyclopenten-1-one, 3-methyl-2-cyclopenten-1-one, etc. were converted into saturated compounds, which improved the stability of the bio-oil fraction.

  17. The role of surface reactions on the active and selective catalyst design for bioethanol steam reforming

    Energy Technology Data Exchange (ETDEWEB)

    Benito, M. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Ciemat, Av. Complutense 22, 28040 Madrid (Spain); Padilla, R.; Serrano-Lotina, A.; Rodriguez, L.; Daza, L. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Brey, J.J. [Hynergreen Technologies, Av. Buhaira 2, 41018 Sevilla (Spain)

    2009-07-01

    In order to study the role of surface reactions involved in bioethanol steam reforming mechanism, a very active and selective catalyst for hydrogen production was analysed. The highest activity was obtained at 700 C, temperature at which the catalyst achieved an ethanol conversion of 100% and a selectivity to hydrogen close to 70%. It also exhibited a very high hydrogen production efficiency, higher than 4.5 mol H{sub 2} per mol of EtOH fed. The catalyst was operated at a steam to carbon ratio (S/C) of 4.8, at 700 C and atmospheric pressure. No by-products, such as ethylene or acetaldehyde were observed. In order to consider a further application in an ethanol processor, a long-term stability test was performed under the conditions previously reported. After 750 h, the catalyst still exhibited a high stability and selectivity to hydrogen production. Based on the intermediate products detected by temperature programmed desorption and reaction (TPD and TPR) experiments, a reaction pathway was proposed. Firstly, the adsorbed ethanol is dehydrogenated to acetaldehyde producing hydrogen. Secondly, the adsorbed acetaldehyde is transformed into acetone via acetic acid formation. Finally, acetone is reformed to produce hydrogen and carbon dioxide, which were the final reaction products. The promotion of such reaction sequence is the key to develop an active, selective and stable catalyst, which is the technical barrier for hydrogen production by ethanol reforming. (author)

  18. The role of surface reactions on the active and selective catalyst design for bioethanol steam reforming

    Science.gov (United States)

    Benito, M.; Padilla, R.; Serrano-Lotina, A.; Rodríguez, L.; Brey, J. J.; Daza, L.

    In order to study the role of surface reactions involved in bioethanol steam reforming mechanism, a very active and selective catalyst for hydrogen production was analysed. The highest activity was obtained at 700 °C, temperature at which the catalyst achieved an ethanol conversion of 100% and a selectivity to hydrogen close to 70%. It also exhibited a very high hydrogen production efficiency, higher than 4.5 mol H 2 per mol of EtOH fed. The catalyst was operated at a steam to carbon ratio (S/C) of 4.8, at 700 °C and atmospheric pressure. No by-products, such as ethylene or acetaldehyde were observed. In order to consider a further application in an ethanol processor, a long-term stability test was performed under the conditions previously reported. After 750 h, the catalyst still exhibited a high stability and selectivity to hydrogen production. Based on the intermediate products detected by temperature programmed desorption and reaction (TPD and TPR) experiments, a reaction pathway was proposed. Firstly, the adsorbed ethanol is dehydrogenated to acetaldehyde producing hydrogen. Secondly, the adsorbed acetaldehyde is transformed into acetone via acetic acid formation. Finally, acetone is reformed to produce hydrogen and carbon dioxide, which were the final reaction products. The promotion of such reaction sequence is the key to develop an active, selective and stable catalyst, which is the technical barrier for hydrogen production by ethanol reforming.

  19. n-Hexane hydro-isomerization over promoted Pd/HZSM-5 catalysts

    Science.gov (United States)

    Thoa Dao, Thi Kim; Loc Luu, Cam

    2015-09-01

    A series of Pd/HZSM-5 catalysts modified by various metallic species, including Co, Ni, Fe, Re, and Cu, was prepared by sequential impregnation. Contents of Pd and second metals in modified catalysts were 0.8 and 1.0 wt%, respectively. Physico-chemical characteristics of catalysts were investigated by nitrogen physi-sorption (BET), x-ray diffraction (XRD), transmission electron microscopy (TEM), ammonia temperature programmed desorption (NH3-TPD), temperature programmed reduction (TPR) and hydrogen pulse chemisorption (HPC). Coke formation was studied by the method of thermogravimetric analysis (TGA). The activities of catalysts in n-hexane isomerization were studied in a micro-flow reactor under atmospheric pressure at 250 °C, and molar ratio of H2: n-hexane of 5.92. It was found that Co, Ni, Fe, and Re additives exhibited geometric and electronic effects toward Pd/HZSM-5 catalyst, leading to an enhancement of its activity and stability. On the contrary, Cu additive caused Pd/HZSM-5 to become poorer in activity and stability.

  20. Alternative alkali resistant deNOx catalysts

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Kristensen, Steffen Buus; Due-Hansen, Johannes;

    2012-01-01

    Alternative alkali resistant deNOx catalysts were prepared using three different supports ZrO2, TiO2 and Mordenite zeolite. The majority of the catalysts were prepared by incipient wetness impregnation of a commercial support, with vanadium, copper or iron precursor, one catalyst was prepared...... by onepot sol–gel method. All catalysts were characterized by BET, XRPD and NH3-TPD. Initial SCR activities of 8 out of 9 catalysts showed higher NO conversion at least at one temperature in the temperature range 300–500 ◦C compared to the conventional V2O5-WO3/TiO2 catalyst. After potassium poisoning (100......–130 µmol of K/g of catalyst) the relative drop in SCR activity and acidity was lower for all the alternative catalysts compared to the industrial V2O5-WO3/TiO2 catalyst. Furthermore, Cu/MOR and Nano-V2O5/Sul-TiO2 catalysts showed 8–16 times higher SCR activities than the conventional even after high...