WorldWideScience

Sample records for catalyst stability vis-a-vis

  1. Statistical entropy of a nuclear spectrometer vis-a-vis communication channel

    International Nuclear Information System (INIS)

    The aim of this paper is to present an esoteric model of a nuclear spectrometer e.g. a gamma ray spectrometer as a communication channel. The source entropy, receiver entropy, and joint entropy of a gamma ray spectrometer were estimated for an observed 1 K gamma spectrum containing a 662 keV peak from a 137Cs source. The information loss estimated for the observed gamma spectrum was of the order of 94.5%. In a typical communication engineering channel, the information loss is of the order of 30%. The information loss in a gamma spectrometer is far more than that in a communication channel. Hence the information extraction in a nuclear spectrometer is extremely challenging vis-a-vis communication channel. This also explains high redundancy of spectral channels, and justifies that a priori information required is much more than the a posteriori information extracted in nuclear spectrometers. Also the model amply justifies wide ranging results for the IAEA intercomparison of spectral analysis programs in which 212 results from 163 laboratories from 34 countries were compared

  2. 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.

  3. Mechanical properties of high performance fibers vis-a-vis applications in flexible structural composites

    Science.gov (United States)

    Sharma, Varunesh

    Some of the critical properties of high performance organic fibers and fiber assemblies have been addressed vis-a-vis their applications in flexible structural composites. These include: tensile properties; mechanical properties under complex modes of deformation; creep at high tensile loads; changes in physical properties due to thermo-mechanical/chemical treatments used in manufacturing of reinforced rubber goods. The axial elastic modulus of fibers and tautly twisted filament assemblies of high performance organic polymers have been measured along with their crystalline orientation distributions. Based on well established procedures in continuum mechanics of axially symmetric structures, a quantitative relationship has been derived to relate the axial elastic modulus to the second and fourth moment of average crystalline orientation distribution. The latter was determined by X-ray diffraction measurements with yarns. This model, valid for single-phase materials, has been found to provide an excellent fit of data from twisted yams of aromatic polyamide and highly ordered polyethylene fibers, with a wide range of overall crystalline orientation distributions. An important property of concern in engineering applications of polymeric filament assemblies of high performance organic fibers is creep. In this study, creep deformation data of gel-spun Ultra High Molecular Weight Polyethylne (UHMWPE) SpectraRTM 1000 yams have been fitted to a model obtained through an empirical mechanical analog of the viscoelastic process. The non-linear viscoelastic model composed of stress-dependent non-linear mechanical analogs qualitatively predicted the creep response to a series of step-loads applied on the UHMWPE yarns. To understand the mechanical properties of high performance organic fibers under combined bending and extension, a simple pin-test procedure has been employed to characterize fibers and twisted yarns. The results obtained from the test have been interpreted with

  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. PMID:16741810

  5. Measurement of dose rate profile and spectra through a cylindrical duct vis-a-vis Monte Carlo simulation studies for optimisation of reactor shield design

    International Nuclear Information System (INIS)

    In the design of a nuclear reactor, penetrations are provided in the top shield to carry out some essential operations. Radiation streaming is envisaged through such penetrations. To avoid radiation streaming, complementary shielding is provided. Optimisation of complementary shielding is carried out by performing calculations using MCNP code. Uncertainties in the calculations are taken care of by incorporating a safety factor. The assumption of the safety factor, while designing the reactor shielding, has been validated by undertaking experimental measurements on a similar geometry vis-a-vis the computed values obtained using MCNP code. The results of the present work agree with the safety factor of two assumed during the shield design. The details of gamma spectral measurements carried out with high purity germanium detector to understand the pattern of the scattered spectrum are also presented

  6. Insects vis a vis radiations

    International Nuclear Information System (INIS)

    Insects have turned out to be much more radiation resistant. For most insects a dose of about 500-700 Gy is required to kill them within a few weeks of exposure; although cockroaches require 900-1000 Gy. Killing insects in less than a few days requires much higher doses. These doses are for mature insects, the immature stages of some insects can be killed by doses as low as 40 Gy. Some insects can be sterilized at even lower doses, and this has application in insect control. Screw-worms, for example, can be sterilized with doses of 25-50 Gy. By contrast, doses as low as 3 Gy caused death of humans in Hiroshima and Nagasaki and doses of about 6 Gy caused death of fire fighters in the Chernobyl accident. It is not exactly certain what the basis is for the resistance of insects to ionizing radiation. It is not animal size by itself, nor lack of penetration. It is also not because of few dividing cells as these are more radiosensitive than non-dividing ones. The speculation that insects might have lower oxygen tensions, and the lack of oxygen is known to protect cells from radiation also does not work. Insect cells might have an enhanced capacity to repair radiation damage also could not be proven. The number of chromosomes influenced radio-sensitivity, and that insects had fewer chromosomes could be true. The radiation resistance is inherent to the cells, since cells derived from insects are also radiation resistant when grown in cell culture. For example, a dose of 60 Gy is required to produce a 80% kill of insect cells, while doses of 1-2 Gy are sufficient to generate this level of killing in mammalian cells. But, nevertheless, according to recent researches, radiation from Japan's leaking Fukushima nuclear plant has caused mutations in some butterflies. It is therefore clear that insects are resistant to ionizing radiation and that this resistance is an inherent property of their cells. But it is not clear exactly what the basis of this cellular resistance is, although the dominant theory is that it relates to the relatively small amount of DNA in insect cells. One of the difficulties is assessing possible mechanisms is that very little work on insect radiobiology is being carried out?

  7. Miniaturization of environmental chemical assays in flowing systems: The lab-on-a-valve approach vis-a-vis lab-on-a-chip microfluidic devices

    International Nuclear Information System (INIS)

    The analytical capabilities of the microminiaturized lab-on-a-valve (LOV) module integrated into a microsequential injection (μSI) fluidic system in terms of analytical chemical performance, microfluidic handling and on-line sample processing are compared to those of the micro total analysis systems (μTAS), also termed lab-on-a-chip (LOC). This paper illustrates, via selected representative examples, the potentials of the LOV scheme vis-a-vis LOC microdevices for environmental assays. By means of user-friendly programmable flow and the exploitation of the interplay between the thermodynamics and the kinetics of the chemical reactions at will, LOV allows accommodation of reactions which, at least at the present stage, are not feasible by application of microfluidic LOC systems. Thus, in LOV one may take full advantage of kinetic discriminations schemes, where even subtle differences in reactions are utilized for analytical purposes. Furthermore, it is also feasible to handle multi-step sequential reactions of divergent kinetics; to conduct multi-parametric determinations without manifold reconfiguration by utilization of the inherent open-architecture of the micromachined unit for implementation of peripheral modules and automated handling of a variety of reagents; and most importantly, it offers itself as a versatile front end to a plethora of detection schemes. Not the least, LOV is regarded as an emerging downscaled tool to overcome the dilemma of LOC microsystems to admit real-life samples. This is nurtured via its intrinsic flexibility for accommodation of sample pre-treatment schemes aimed at the on-line manipulation of complex samples. Thus, LOV is playing a prominent role in the environmental field, whenever the monitoring of trace level concentration of pollutants is pursued, because both matrix isolation and preconcentration of target analytes is most often imperative, or in fact necessary, prior to sample presentation to the detector

  8. High power pulsed/microwave technologies for electron accelerators vis a vis 10MeV, 10kW electron LINAC for food irradiation at CAT

    International Nuclear Information System (INIS)

    Use of electron accelerators for irradiation of food items is gathering momentum in India. The various technologies for powering the electron LINAC were needed to be developed in the country due to embargo situations as well as reservations of the developers worldwide to share the information related to this development. Centre for Advanced Technology, CAT, Indore, is engaged in the development of particle accelerators for medical industrial and scientific applications. Amongst other electron accelerators developed in CAT, a 10MeV, 10kW LINAC for irradiation of food items has been commissioned and tested for full rated 10kW beam power. The high power pulsed microwave driver for the LINAC was designed, developed and commissioned with full indigenous efforts, and is right now operational at CAT. It consists of a 6MW, 25kW S-band pulsed klystron, 15MW peak power pulse modulator system for the klystron, microwave driver amplifier chain, stabilized generator, protection and control electronics, waveguide system to handle the high peak and average power, gun modulator electronics, grid electronics etc. The present paper highlights various technologies like the pulsed power systems and components, microwave circuits and systems etc. Also the performance results of the high power microwave driver for the 10MeV LINAC at CAT are discussed. Future strategies for developing the state of art technologies are highlighted. (author)

  9. 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...

  10. 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.

  11. 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

    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...

  12. 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

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

    OpenAIRE

    Nor Edi Azhar binti Mohamad; Noriza Mohd Saad

    2012-01-01

    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 inv...

  14. 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.

  15. 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.

  16. 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).

  17. 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.

  18. Stability of bimetallic Pd-Zn catalysts for the steam reforming of methanol

    OpenAIRE

    Conant, T.; Karim, A.; Lebarbier, V.; Wang, Y.; F. Girgsdies; Schlögl, R.; Datye, A.

    2008-01-01

    ZnO-supported palladium-based catalysts have been shown in recent years to be both active and selective towards the steam reforming of methanol, although they are still considered to be less active than traditional copper-based catalysts. The activity of PdZn catalysts can be significantly improved by supporting them on alumina. Here we show that the Pd/ZnO/Al2O3 catalysts have better long-term stability when compared with commercial Cu/ZnO/Al2O3 catalysts, and that they are also stable under...

  19. 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...

  20. Stability analysis of hydrophobic catalysts in presence of tritiated water. Evaluation of polydivynilbenzene support stability

    International Nuclear Information System (INIS)

    The behaviour of hydrophobic catalysts in the isotopic exchange reactions H/D/T was analyzed by quantum chemistry methods. The primary radiolytic effect was analyzed using a two-step radiolytic mechanism: a) the ionization of molecule and spatial redistribution of atoms in order to reach a minimum value of energy, characteristic to the new quantum state; b) the neutralization of molecule by capture of an electron and its rapid dissociation in free radicals. Time period between the capture of electron and molecule dissociation in free radicals is shorter than the time required for geometric reoptimization. Chemical bonds suspected to break are located in the distribution region of LUMO orbital and have minimal bond energy. Evaluation of secondary effects taking place in polymeric structure in the presence of water was carried out through the study of the transition state (activated complex) resulted after the attack of HO· radicals formed in the radiolysis of water. In the case of catalyst on styrene-divinylbenzene copolymer support, the quantum chemistry analysis reveals a good stability of the polymer to the primary radiolytic effect. The secondary effects affect the polymeric structure due to the HO· radicals attack at the benzilic position. These attacks are accompanied by fragmentation of polymeric chain and induction of hydrophobic groups on the chain. Occurrence of these processes is much lower as compared to those taking place in the polytetrafluoroethylene substrate. (authors)

  1. 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. PMID:27506249

  2. 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

  3. 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.

  4. Synthesis and characterization of supported polysugar-stabilized palladium nanoparticle catalysts for enhanced hydrodechlorination of trichloroethylene

    International Nuclear Information System (INIS)

    Palladium (Pd) nanoparticle catalysts were successfully synthesized within an aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping ligand which offers a green alternative to conventional nanoparticle synthesis techniques. The CMC-stabilized Pd nanoparticles were subsequently dispersed within support materials using the incipient wetness impregnation technique for utilization in heterogeneous catalyst systems. The unsupported and supported (both calcined and uncalcined) Pd nanoparticle catalysts were characterized using transmission electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction, and Brunauer–Emmett–Teller surface area measurement and their catalytic activity toward the hydrodechlorination of trichloroethylene (TCE) in aqueous media was examined using homogeneous and heterogeneous catalyst systems, respectively. The unsupported Pd nanoparticles showed considerable activity toward the degradation of TCE, as demonstrated by the reaction kinetics. Although the supported Pd nanoparticle catalysts had a lower catalytic activity than the unsupported particles that were homogeneously dispersed in the aqueous solutions, the supported catalysts retained sufficient activity toward the degradation of TCE. In addition, the use of the hydrophilic Al2O3 support material induced a mass transfer resistance to TCE that affected the initial hydrodechlorination rate. This paper demonstrates that supported Pd catalysts can be applied to the heterogeneous catalytic hydrodechlorination of TCE. (paper)

  5. STABILIZATION AND TESTING OF MERCURY CONTAINING WASTES: BORDEN CATALYST

    Science.gov (United States)

    This report was submitted by the U of Cincinnati in fulfillment of Contract # 68-C7-0057 under the sponsorship of the USEPA. It covers a period from 6/99 - 7/2000; laboratory work was completed as of 7/2000. This report evaluates the chemical stability of spent mercuric chloride ...

  6. Core–shell nanostructure supported Pt catalyst with improved electrocatalytic stability in oxygen reduction reaction

    International Nuclear Information System (INIS)

    Core–shell nanostructure electrode (TiO2@C) for oxygen reduction reaction is prepared with TiO2 nanoparticles at 900 °C in a methane atmosphere. The TiO2@C supported Pt catalyst (Pt/TiO2@C) contains Pt nanoparticles on TiO2@C nanostructure electrodes consisting of TiO2 as a core and carbon as a shell. In the accelerated stability test, the Pt/TiO2@C exhibits a superior ORR stability to conventional carbon supported Pt catalyst. It is likely that the enhanced catalytic properties of the nanostructure supported Pt catalyst may be due to graphite-like carbon and an improved electronic conductivity of the core–shell nanostructure. Highlights: ► We synthesize core–shell nanostructure support (TiO2@C) for oxygen reduction reaction. ► The Pt/TiO2@C shows an excellent ORR activity in comparison with Pt/C. ► The Pt catalyst on TiO2@C exhibits a superior ORR stability to Pt/C.

  7. 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.

  8. 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.

  9. A study on the deactivation and stability of hydrophobic catalyst for hydrogen isotope exchange

    International Nuclear Information System (INIS)

    The hydrophobic catalyst has been prepared by deposition of platinum on porous styrene divinylbenzene copolymers(Pt/SDBC) and at the same time a separated type catalytic reactor has been developed for the Wolsong tritium removal facility(WTRF). Several tests carried out to obtain the experimental performance data of the Pt/SDBC with a recycle reactor system. The long-term stability was also measured with the Pt/SDBC catalyst immersed in water for a long time. The long-term deactivations of the Pt/SDBC catalyst were evaluated quantitatively by mathematical models. The simple mathematical models were presented to evaluate the uniform poisoning and shell progressive poisoning to be occurred simultaneously during the hydrogen isotope exchange between hydrogen gas and liquid water in the Liquid Phase Catalytic Exchange(LPCE) column. The uniform poisoning was well characterized by a time on stream theory and then the deactivation parameters were determined from the experimental performance data. The impurity poisoning was derived by a shell progressive model with two-layer mass transfer. The water vapor condensation was a main cause of the reversible uniform poisoning for the Pt/SDBC catalyst. The values of the decay rate constant (Kd) and order of the decay reaction(m) were of 2 and 4, respectively, based on the experimental data. It indicated that the decay might be attributable to pore mouth poisoning. From the long-term stability of the catalyst immersed in water, there was no intrinsic decay of catalyst activity due to water logging to the catalyst. The activity decreased by only 7% over 18 months, which was equivalent to a catalyst half-life longer than 15 years. On the basis of the above deactivation parameters, the values for kc/kco with Thiele modulus=20 after 3 years and 10 years of operation were expected about 19% and 15% of the initial activity, respectively, while the values for kc/kco with Thiele modulus=100 were of about 22% and 18%, respectively. However

  10. 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.

  11. 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)

  12. The role of rare earth oxides as promoters and stabilizers in combustion catalysts

    International Nuclear Information System (INIS)

    Rare earth oxides (REO) have been increasingly investigated in the last years as potential co-catalysts in several commercial applications. The major role would be that of improved activity and selectivity, and increase in thermal stability of catalytic materials. As a contribution to this area, we have been investigating in the last few years a number of issues concerning the preparation and characterization of ceria, praseodymia and terbia-containing materials with regard to their application as redox and combustion catalysts. Some of these issues will be reviewed here, with special focus on the catalytic properties and structural characterization of catalytic materials obtained by using REO as promoters. Specifically, in this paper the role of REO (CeO2, Tb4O7 and Pr6O11) as stabilizers and promoters in Pd-based catalysts is investigated. Particular attention is paid to their effects on the catalytic combustion of methane and on the dynamics of Pd-PdO transformation. Characterization of supports by in situ XRD, surface area measurements and TPR is also presented

  13. N,N-Dimethylformamide-stabilized gold nanoclusters as a catalyst for the reduction of 4-nitrophenol

    Science.gov (United States)

    Yamamoto, H.; Yano, H.; Kouchi, H.; Obora, Y.; Arakawa, R.; Kawasaki, H.

    2012-06-01

    In this study, we investigated the catalytic properties of N,N-dimethylformamide (DMF)-stabilized gold nanoclusters (AuNCs) in the reduction of 4-nitrophenol (PNP) to 4-aminophenol by NaBH4, a well known model reaction to be catalyzed by metal surfaces. The DMF-stabilized AuNCs were prepared in DMF by a surfactant-free method. The DMF-stabilized AuNCs showed high catalytic activity even when used in small quantities (~10-7 g). The pseudo-first-order rate constant (kapp) and activation energy were estimated to be 3 × 10-3 s-1 and 31 kJ mol-1, respectively, with 1.0 μM of the gold catalyst at 298 K. The catalytic activity of the DMF-stabilized AuNCs was strongly influenced by the layer of adsorbed DMF on the Au NCs. This layer of adsorbed DMF prohibited the reactants from penetrating to the surface of the AuNCs via the diffusion at the beginning of the reaction, resulting in an induction time (t0) before PNP reduction began. Restructuring of the DMF layer (essentially a form of activation) was the key to achieving high catalytic activity. In addition, atomically monodisperse Au25(SG)18NCs (SG: glutathione) showed higher catalytic activity in the PNP reduction (kapp = 8 × 10-3 s-1) even with a low catalyst concentration (1.0 μM), and there was no induction time (t0) in spite of the strongly binding ligand glutathione. This suggested that the catalytically active surface sites of the Au25(SG)18NCs were not sterically hindered, possibly because of the unique core-shell-like structure of the NCs. Retaining these open sites on AuNCs may be the key to making the NCs effective catalysts.In this study, we investigated the catalytic properties of N,N-dimethylformamide (DMF)-stabilized gold nanoclusters (AuNCs) in the reduction of 4-nitrophenol (PNP) to 4-aminophenol by NaBH4, a well known model reaction to be catalyzed by metal surfaces. The DMF-stabilized AuNCs were prepared in DMF by a surfactant-free method. The DMF-stabilized AuNCs showed high catalytic activity even

  14. 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.

  15. 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.

    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... from the low lying valleys and mountains to the glacier snow and ice. These low lying valleys have cultivated lands, vegetation and forests (Marinoni et al. 2001). Figure 2 indicates that the samples with lower ionic strength tend to have almost Fig...

  16. Organic cotton systems improved soil properties vis-a-vis the modern systems

    Science.gov (United States)

    Blaise, D.; Venugopalan, M. V.; Singh, J. V.; Narkhedkar, N. G.; Velmourougane, K.

    2012-04-01

    India is the largest cotton growing country in the world. Traditionally, cotton in India was grown with minimal inputs and resources available on farm were put to efficient use. Advent of hybrids and Bt cotton revolutionized cotton production in the country and lead to heavy reliance on external inputs. However, there is a growing awareness of the detrimental effects of excessive use of pesticides and fertilizers. This is leading to growing interest in organic cultivation of crops. An organic system (OS) was compared with the modern systems (MS) for changes in the soil physical, chemical and biological properties in field experiments conducted both on station and farmers fields in Maharashtra, India on rain dependent cotton grown on Vertisols. Soil samples of the organic plots had significantly greater C content than the MS plots relying on mineral fertilizers and pesticides. Similarly, other nutrients were also greater in the OS than the MS across locations. Most of the increases were noticed in the top 30 cm of the soil profile. Interestingly, enrichment of the soil at lower depths was noticed in the OS which could be due to the surface creep of soils through the cracks in the Vertisols. With regard to the physical properties, water-stable aggregates and mean weight diameter in the MS were significantly lesser than the OS. Differences were restricted to the top 20 cm. Soil biological properties of the two systems were compared through the enzyme assays such as the dehydrogenase, glucosidase, phosphatase, sulfatase periodically during the crop growing season. All the enzyme assays indicated greater activities in the OS than the MS. Further, microfauna (nematodes) monitored indicated less of plant parasitic nematodes in the OS than the MS. Excessive tillage followed in the MS did bring about a reduction in the nematode numbers. But the systems had more parasitic nematodes.

  17. TSO vis-a-vis ISO model : the French experience and way ahead

    International Nuclear Information System (INIS)

    This PowerPoint presentation summarized the operation of the Reseau de Transport d'Electricite (RTE), which is the high and extra high voltage power transmission system in France. It described RTE's mission as an independent system operator, activities, specialities, the general operation of its facilities, its role for the protection of the environment and its contribution to sustainable development. RTE is the largest grid in Europe, providing equal access for all customers to the power system. This presentation described how RTE contribute to the efficiency of the European electricity market by facilitating access to the transmission system and by improving its competitiveness. It also described how RTE ensures the safety of the power system and quality of supply. RTE's effort to ensure minimal environmental impact by transmission facilities were reviewed along with the role of the electricity exchange which was created to ensure better fluidity of the market at the most competitive price possible, while meeting power system safety requirements. tabs., figs

  18. Biomass status vis-a-vis bioenergy prospects and options for India

    International Nuclear Information System (INIS)

    India has a large biomass energy potential if its underutilized resources are used in modernized biofuels and bioenergy conversion systems. India uses about half traditional and half commercial energy sources. However, with a fast-growing population, a relatively slow-growing economy, and few fossil energy resources, the need to use indigenous resources more efficiency is becoming more pressing. Currently, about 400 million tonnes of biomass (fuel wood, crop residues, and cattle dung) is burnt in millions of traditional cooking stoves, especially in the rural sector. The net energy loss could be as much as 5 EJ. Converting only a fraction of this biomass to biogas, a much cleaner and more efficient fuel, could meet the total cooking requirements of the rural sector. The remainder of the biomass could be converted for use as producer of gas and ethanol. Nearly 15 percent of about 0.6 million villages are unelectrified. Modular power generation using biomass-fueled producer gas-fired generators could meet the rural needs at less cost than grid extensions. Ethanol is already proven in Brazil and the U.S. as a gasoline substitute and extender that mitigates air pollution in urban areas. (author)

  19. Remote Sensing Based Methane Emission Inventory Vis-A-Vis Rice Cultural Types Of South Asia

    OpenAIRE

    Manjunath, K. R.; More, R.; P. Chauhan; Vyas, A.; S. Panigrahy; Parihar, J. S.

    2014-01-01

    Rice cultivation has been recognized as one of the major anthropogenic source for methane (CH4) emissions which is a microbial mediated anaerobic activity, mainly favoured by the flooded conditions in the rice fields. Information available on CH4 emission is limited, especially in a spatial domain, mainly because of the complexity involved in generating such data. The current approach demonstrates the use of secondary data sources available on the methane emission scaling factors, co...

  20. Bromination vis-a-vis chlorination as a biocide feasibility study

    International Nuclear Information System (INIS)

    Water is used extensively as a cooling medium in various heat transfer equipment's of a power industry such as condenser, heat exchangers and cooling towers. At elevated temperature, the breeding of microbiological growth can form slimes, underneath of this, accelerated corrosion can take place resulting into sudden and catastrophic failure of equipment's. The microbiological growth unchecked in the various systems especially in low velocity areas can lead to large growth of micro organisms such as algae which can even reduce the flow of the fluid thus affecting the efficiency of plant equipment's. Therefore, chlorination is a mandatory requirement in industrial cooling water to reduce biofouling in heat transfer equipment's. The chlorination in drinking water produces germicidal effect and thus reduces the bacterial counts. At NAPS the water quality is good and mild doses of chlorine (5 ppm) two times a day, as envisaged in design is noticed to be satisfactory. The chlorination of recirculating condenser cooling water presently is being done with the established doses for a fixed time twice a day. Some of the problems noticed with the chlorination process are : Corrosion of constructional material of chlorination plant and equipment's and pipelines causing large input of efforts on maintenance for keeping high availability of the chlorination plant. In addition to this, the leakages in the equipment could be a potential safety hazard. The effectiveness of chlorine is observed to be less in alkaline pH (above 9.0) as encountered at NAPS. This results is large quantities of chlorine injection for extended periods. The cost of chlorine and bleaching powder keeps fluctuating in the market as noticed in past few years. Many a times this results in scarcity of chlorine/bleaching powder causing interruption in biofouling control programme. Hence it was felt prudent to work on the alternative biocides which could be cost effective, non-polluting and nature and user friendly. This paper highlights the brief details on the feasibility studies carried out on bromination. (author)

  1. The justification of homeschooling vis-a-vis the european human rights system

    OpenAIRE

    Warwick Montgomery, John

    2012-01-01

    The very idea of the European Convention on Human Rights is to bring the laws of contracting states into line with fundamental human rights principles. Where the Convention is not explicit, the Court should never rule restrictively so as to reduce the scope of a general right. In the case of homeschooling, the Convention sets forth the general principle that “the state shall respect the right of parents to ensure such education and teaching in conformity with their own religious and philosoph...

  2. Tangency vis-a'-vis differentiability by Peano, Severi and Guareschi

    CERN Document Server

    Dolecki, Szymon

    2010-01-01

    Peano defined 'differentiability' of functions and 'lower tangent cones' in 1887, and 'upper tangent cones' in 1903, but uses the latter concept already in 1887 without giving a formal definition. Both cones were defined for arbitrary sets, as certain limits of appropriate homothetic relations. Around 1930 Severi and Guareschi, in a series of mutually fecundating individual papers, characterized differentiability in terms of 'lower tangent cones' and strict differentiability in terms of 'lower paratangent cones', a notion introduced, independently, by Severi and Bouligand in 1928. Severi and Guareschi graduated about 1900 from the University of Turin, where Peano taught till his demise in 1932.

  3. Antagonisme in vitro de trichoderma spp. vis-a-vis de rhizoctonia solani kuhn

    OpenAIRE

    Camporota, P.

    1985-01-01

    Cet article présente les résultats obtenus lors de la réalisation de la première étape d’un programme de sélection de souches de Trichoderma spp. utilisables pour la lutte biologique contre Rhizoctonia solani dans le sol : 28 souches de Trichoderma ont été confrontées in vitro à 3 souches de R. solani appartenant à des groupes d’anastomose différents. On a mesuré, pour chaque souche de Trichoderma, la capacité à envahir les colonies de l’agent pathogène ainsi que les 3 modes d’action : my...

  4. [Agreement and asymmetry. Population and wages vis vis a vis the globalization of the economy].

    Science.gov (United States)

    Jusidman, C

    1991-01-01

    The free flow of labor and services across national borders will be 1 of the most difficult problems of future negotiations for integration of the markets of the US, Mexico, and Canada. The free flow of products and increasingly of capital have been accepted in general terms, and land and natural resources are entering the globalization process through external investment. In the trilateral free trade treaty between Mexico, the US, and Canada, the US is particularly interested in access to the service markets of Canada and Mexico. Mexico would like freer access to the other markets, and to protect its migrant workers. Canada needs foreign labor for its agricultural production. All 3 countries would potentially benefit from more flexible population movement. Mexico, Canada, and the US have very different structures, population dynamics, and labor markets. Mexico's population growth rate is the highest and its active population is increasing the most rapidly. Mexico must generate 1 million new jobs annually, the US requires 2.1 million, and Canada around 230,000. The 3 countries, with about 360 million inhabitants in 1991, must create 3.4 million new jobs annually. Because of differences in occupational and activity structures, levels of skill, salaries, productivity, and cultures of work in the 3 countries, it is clear that the new jobs correspond to different labor markets, making predictions about average salaries difficult. The 1990 average minimum wage in the US was about 10 times that of Mexico, while the average minimum in the manufacturing sector as about 7 times greater. The degree to which the trilateral treaty can contribute to reducing the differential is an important question. 3 possible scenarios suggest themselves. If current restrictions on mobility of workers are maintained, wage disparities will probably continue unless there is a very great foreign investment in activities throughout Mexico that require significant labor inputs. This would probably have a positive effect on unskilled wages. If Mexico does not open its service market, foreign companies would need to train and advance Mexican workers. A 2nd scenario assumes a general easing of restrictions for high-tech services while restrictions remain for unskilled workers. Unemployment among Mexican professionals and technicians in service industries might increase if they were unable to compete. The final scenario represents the longterm possibility of eliminating all restrictions on labor mobility between the 3 countries, which would result in improving the quality of life and working conditions of a large number of persons. Regardless of the outcome, Mexico faces the task of increasing the productivity of its labor force. PMID:12158110

  5. 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. PMID:27561401

  6. 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.

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

    OpenAIRE

    Pudji Pratitis Wismantara

    2012-01-01

    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...

  8. 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

  9. 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...

  10. Random Motion with Interfacial Contact: Driven Diffusion vis-a-vis Mechanical Activation

    OpenAIRE

    Goohpattader, P. S.; Chaudhury, M. K.

    2012-01-01

    Rolling of a small sphere on a solid support is governed by a non-linear friction that is akin to the Coulombic dry fiction. No motion occurs when the external field is weaker than the frictional resistance. However, with the intervention of an external noise, a viscous friction like property emerges; thus the sphere rolls with an uniform drift velocity that is proportional to the applied field. As the sphere rolls, it rocks forward and backward resulting in substantial fluctuation of displac...

  11. Determination of agarose gel pore size: Absorbance measurements vis a vis other techniques

    International Nuclear Information System (INIS)

    The absorbance measurements in the wavelength range 700 nm to 800 nm were used to probe the agarose gel topology evolution and extract the pore size of the trapped solvent. By following the changes in absorbance and pore size, the gelation process could be clearly divided into three stages - induction stage, gelation stage and pseudo-equilibrium stage. The gelation mechanism is explained as a nucleation and growth process. Following the kinetics of gelation using dynamic light scattering is complicated by multiple scattering (for high concentrations) and large fluctuations in intensity and relaxation time. Comparatively, scanning the absorption spectrum is fast and the method is suitable for a wide range of concentrations and setting temperatures. Pore size determination using absorbance is a fast and non-invasive method when compared to the DNA electrophoresis measurements, which extend over several hours and use probe diffusion

  12. Environmental Economics, Law and Policy: Brazil vis-a-vis India (Part I: Theoretical Modelling)

    OpenAIRE

    Das, Rituparna; Das, Mononita

    2014-01-01

    Amidst the perils of industrialization in the forms of environmental impacts of mining and use of energy and destruction of urban biodiversity, it became imperative for the Latin American countries to design environmental policies in accordance with the respective historicity, demography, and polity of each nation. But in resolving a tussle between eco-environmental maintenance and vigorous industrialization while trying to find a choice between eco-friendly environment or prosperous economic...

  13. Experiences with polyelectrolyte treatment vis-a-vis alum treatment at NAPS

    International Nuclear Information System (INIS)

    Narora Atomic Power Station is a pressurized heavy water having two units of 220 MWe each. The station is situated on the banks of river Ganges in District Bulandhsahar of Uttar Pradesh (U.P.). The cooling water after clarification and polymer treatment is used for cooling purpose in various systems at Narora Atomic Power Station. Raw water clarification at NAPS as envisaged in design was with Alum treatment at dose levels ranging 30 ppm to 80 ppm depending upon the turbidity levels (maximum turbidity levels in input water is observed to be about 2000 NTU). The quantities of Alum added per day was about 6 tons during peak monsoon season. The total quantities of alum consumed per year were about 1400 tones/year costing about Rs.38 lakhs. The paper highlights the various operational and practical aspects of raw water clarification with inorganic electronic electrolyte and organic polymers and their comparative study

  14. 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.

  15. Issues and Prospects from the OTC Industry vis a vis Pharmaceutical Education and OTC Medicines.

    Science.gov (United States)

    Nishizawa, Motohito

    2016-01-01

    In the amendment of the Pharmaceutical Affairs Law in 2013, a new category, Pharmacist Intervention Required Medicines (PIRM), was introduced, and other OTC medicines, which were classified after the 2006 amendment, were allowed to be sold via the Internet. Regarding PIRM, Japan's Ministry for Health, Labour and Welfare designates medicines which require special intervention by a pharmacist who explains their proper use to a patient through a face-to-face consultation, wherein the pharmacist provides guidance based on pharmaceutical knowledge and experience. This encourages consumers to approach their longer term personal healthcare with a rational knowledge of medicines, and dovetails with the direction described in "Japan is Back". Along with the 2006 amendment, an upgraded 6-year curriculum for the study of pharmacy in preparation for becoming a pharmacist was introduced. This allows student pharmacists to have more experience working in community pharmacies, thus supporting and providing pharmacists with the knowledge they need to better help the consumer to rationally use OTC medicines and self-select proper OTC medications. And this is not only restricted to OTC medicines, as there are many items sold in local pharmacies available to be utilized by the consumer with reasonable support by pharmacists. There is an expectation that the pharmacist be prepared to assist the consumer not only with prescriptions, but also with OTC medications, supplements, medical accessories, etc. using their knowledge and experience. PMID:27374957

  16. 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.

  17. 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.

  18. Technical support to an operating PWR vis-a-vis safety analysis

    International Nuclear Information System (INIS)

    Currently a PWR of 300 MWe capacity CHASNUPP-I is in operation since the year 2000. Technical support being provided includes In-core fuel management and corresponding safety analysis for the reshuffled core for the next cycle. Prior to start of cycle six an extension in cycle five based on coast down technique was achieved of almost 30 effective full power days. Cycle 6 was designed to achieve the safe and economical loading pattern. The technique used is designated as out-in mode (modified). In this technique, most of the fresh fuel assemblies are not directly located at the periphery of the core, but near the boundary. This technique has the advantage that no burnable absorbers are used in each cycle and we get less radial neutron leakage and increased discharge burnup and cycle length. Operating experience/feedback shows that this type of loading pattern gives better economy without resorting to the conventional in-out technique. The lifetime of the cycle is predicted as 10371 MWD/MTU or 373 Effective Full Power Days (EFPD at 998.6 MWth). In design calculations, the end of cycle is reached at 10 ppm critical boron concentration in the unroded core. Measured critical boron concentration at HZP, BOL is 1453 ppm compared with the calculated value i.e 1457 ppm, is within the acceptable limits. It is also observed that the calculated reactivity worth of Tl is -1771 pcm as compared to measured value i.e -1802 pcm with difference of only 1.6 % showing the reliability of the design value. The measured Moderator temperature coefficient (MTC) is 2.52 pcm/deg. C at all rods out (ARO) and critical boron concentration (CBC) condition whereas the calculated value is 3.36 pcm/deg. C (at predicted CBC of 1457) having a good agreement with design value. Safety evaluation of cycle 6 was carried out for the reshuffled core. All the probable accident scenarios based on initiating events as given in the FSAR were evaluated with respect to input parameters. For a specific event, the comparison of critical safety related core physics parameters between the reference case and current cycle was undertaken. For instance the scenario related to reduction in feedwater temperature or addition of excessive feedwater flow which can cause an increase in the heat transfer from the primary side to the secondary side in the steam generator and a decrease in RCS temperature was examined with respect to the input parameters. In this event, the most negative moderator temperature coefficient (MTC) and the least negative Doppler coefficient (DC) are the critical parameters. Maximum MTC and Minimum DC were calculated as -52.4 pcm/deg. C and -2.32 pcm/deg. C compared to reference value (FSAR) -59.0 pcm/deg. C and -2.0 pcm/deg. Crespectively. The critical parameters of Cycle 6 are thus bounded by the reference analysis. Similarly, another event was considered of partial or complete loss of forced reactor coolant flow which could result in a rapid increase in the coolant temperature reduction in power because of the negative reactivity insertion. For a conservative analysis, the least negative moderator temperature coefficient and the most negative Doppler coefficient are the critical parameters. Minimum MTC and Maximum DC are calculated as -1.9 pcm/deg. C and -3.04 pcm/deg. Ccompared to reference value 0.0 pcm/deg. C and -3.6 pcm/deg. C respectively. The critical parameters of Cycle 6 are bounded by the reference analysis. Since all initiating events evaluated have relevant parameters within the limits, it is concluded that reactor will operate safely during cycle 6. (author)

  19. 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.

  20. Personal Value Systems and Career Objectives of Men vis-a-vis Women Air Force Officers.

    Science.gov (United States)

    Bartholomew, Charles W.

    Basic objectives of this research were to compare the personal values and career objectives of Air Force women to Air Force men. The research used a personal values questionnaire to establish which values and objectives were most likely to be translated into behavior. Values and objectives of 307 women officers and a control sample of 323 men were…

  1. 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.

  2. MOTHER TONGUE (L1 Vis-A-Vis OTHER TONGUE (L2?

    Directory of Open Access Journals (Sweden)

    Arun Behera

    2012-07-01

    Full Text Available Learning a language is always a difficult thing and more so when it comes to learning a second language (L2 for it reflects the complexity of learning a language which is the other tongue rather than the mother tongue of a person. The present paper proposes to focus on the prospects and benefits of the skill-based learning of the L2. All learners, as such pick up a language by two means: a acquisition of one's own language/mother tongue, and b learning another language. Acquisition is a subconscious and intuitive process, similar to that used by a child to pick up the first language (L1; and the second is conscious learning, in which a learner is aware of his/her own learning process.

  3. The Competitiveness of On-Line vis-a-vis Conventional Retailing: A Preliminary Study

    OpenAIRE

    Png, Ivan

    2000-01-01

    Previous research has directly studied whether on-line retailing is more competitive than conventional retail markets. The evidence from books and music CDs is mixed. Here, I use an indirect approach to compare the competitiveness of on-line with conventional markets. Focusing on the retail market for books, I identify a peculiarity in the pricing of bestsellers relative to other titles. Supposing that competitive barriers are lower in on-line retailing, I analyze how the lower barriers would...

  4. GASB's Proposed Reporting Standards Cause Confusion Vis-a-vis Other Post-Employment Benefits.

    Science.gov (United States)

    Alioto, Nicholas C. A.; Dickson, Roger J.

    2003-01-01

    Discusses proposed Governmental Accounting Standards Board (GASB) accounting standards requiring school districts to report liability associated with other post-employment benefits (OPEBs), such as health care, to future retirees and well as the status of efforts to fund those benefits. (PKP)

  5. Influence of Bhavana on pharmacognostical parameters of Amalaki Rasayana vis-a-vis Amalaki powder

    Directory of Open Access Journals (Sweden)

    Shaizi Layeeq

    2014-01-01

    Full Text Available Background: Rasayana is an ancient concept of Ayurveda, attributed to tissue nourishment and rejuvenation. Bhavana is an important Samskara mentioned in classics by which even a small dose of a drug may be made to produce a very high result. Amalaki Rasayana is a herbal formulation mentioned in classics to treat various disorders. Aims: To screen the differences in pharmocognostical profile of Amalaki Churna before and after Bhavana. Materials and Methods: Amalaki Rasayana was prepared by levigating the Amalaki powder seven times with fresh Amalaki juice (squeezed from mature fruits, procured from local market. Results: After Bhavana significant changes were found in epidermal cells, mesocarp cells and fibres.

  6. New twists to Einstein's two-slit experiment: complementarity vis-a-vis the causal interpretation

    International Nuclear Information System (INIS)

    We consider the new adaptations of Einstein's two-slit experiment in terms of recently performed experiments with neutrons, and analyse them in the light of the complementarity principle. We contrast this with the description in terms of the de Broglie-Bohm causal interpretation. (author)

  7. Understanding and controlling nanoporosity formation for improving the stability of bimetallic fuel cell catalysts.

    Science.gov (United States)

    Gan, Lin; Heggen, Marc; O'Malley, Rachel; Theobald, Brian; Strasser, Peter

    2013-03-13

    Nanoporosity is a frequently reported phenomenon in bimetallic particle ensembles used as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. It is generally considered a favorable characteristic, because it increases the catalytically active surface area. However, the effect of nanoporosity on the intrinsic activity and stability of a nanoparticle electrocatalyst has remained unclear. Here, we present a facile atmosphere-controlled acid leaching technique to control the formation of nanoporosity in Pt-Ni bimetallic nanoparticles. By statistical analysis of particle size, composition, nanoporosity, and atomic-scale core-shell fine structures before and after electrochemical stability test, we uncover that nanoporosity formation in particles larger than ca. 10 nm is intrinsically tied to a drastic dissolution of Ni and, as a result of this, a rapid drop in intrinsic catalytic activity during ORR testing, translating into severe catalyst performance degradation. In contrast, O2-free acid leaching enabled the suppression of nanoporosity resulting in more solid core-shell particle architectures with thin Pt-enriched shells; surprisingly, such particles maintained high intrinsic activity and improved catalytic durability under otherwise identical ORR tests. On the basis of these findings, we suggest that catalytic stability could further improve by controlling the particle size below ca. 10 nm to avoid nanoporosity. Our findings provide an explanation for the degradation of bimetallic particle ensembles and show an easy to implement pathway toward more durable fuel cell cathode catalysts. PMID:23360425

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

    OpenAIRE

    Xu Yu; Gong Cheng; Si-Yang Zheng

    2016-01-01

    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-A...

  9. 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.

  10. 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.

  11. Performance, methanol tolerance and stability of Fe-aminobenzimidazole derived catalyst for direct methanol fuel cells

    Science.gov (United States)

    Sebastián, David; Serov, Alexey; Artyushkova, Kateryna; Atanassov, Plamen; Aricò, Antonino S.; Baglio, Vincenzo

    2016-07-01

    Highly active and durable non-platinum group metals (non-PGM) catalyst based on iron-nitrogen-carbon (Fe-N-C) for the oxygen reduction reaction (ORR) derived from pyrolyzed Fe-aminobenzimidazole (Fe-ABZIM) was synthesized by sacrificial support method (SSM), and characterized by several physical-chemical techniques: scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller method and X-ray photoelectron spectroscopy. In half-cell electrochemical configuration, the Fe-ABZIM catalyst presented a significant improvement of ORR activity with respect to a recently reported non-PGM formulation based on Fe-aminoantipyrine, with an enhancement of half-wave potential of about 85 mV in O2-saturated sulfuric acid solution. To the moment, the gap with respect to a benchmark Pt/C catalyst was about 90 mV. The Fe-ABZIM catalyst showed a remarkably high tolerance to methanol, resulting in superior ORR performance compared to Pt/C at methanol concentrations higher than 0.02 M. In direct methanol fuel cell (DMFC) good performances were also obtained. A durability test (100 h) at 90 °C, feeding 5 M methanol, was carried out. A certain decrease of performance was recorded, amounting to -0.20 mW cm-2 h-1 at the very beginning of test and -0.05 mW cm-2 h-1 at the end. However, the Fe-ABZIM is more adequate than previously reported formulations in terms of both ORR activity and stability.

  12. 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.

  13. 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.

  14. Stabilization and characterization of platinum nano-catalysts formed on highly ordered pyrolytic graphite

    Science.gov (United States)

    Halvorsen, Helga C.

    Platinum catalysts are prepared on highly ordered pyrolytic graphite (HOPG). Two different methods are used to deposit platinum onto HOPG; electrochemical deposition and impregnation followed by thermal decomposition. To increase interactions between the Pt deposits and the carbon support, HOPG is oxidized either electrochemically or with ozone gas. The combination two different deposition techniques and three different substrates (freshly cleaved, electrochemically, and ozone oxidized HOPG) results in six different Pt/carbon electrodes that are studied with respect to their particle morphology, activity towards electrochemically oxidizing adsorbed carbon monoxide (COads), and electrochemical stability. Oxidation of HOPG generated pits on the basal plane; ozone oxidation formed nano-pits, 85 nm in diameter. Regardless of the substrate pre-treatment, electrochemical deposition resulted in clusters of nanoparticles, while impregnation followed by thermal decomposition resulted in individual Pt nano-catalysts. Regardless of the deposition technique, Pt particles are confined to step edges on freshly cleaved HOPG, and dispersed over the basal plane on oxidized HOPG. When comparing all six electrodes it became evident that substrate pre-treatment did not affect the electrochemical activity of the electrodes towards the oxidation of COads, while the method of Pt deposition did significantly affect the measured activity. For example, Pt/HOPG electrodes prepared by electrochemical deposition using short deposition times, polycrystalline Pt foil, while electrodes prepared by impregnation followed by thermal decomposition show faster kinetics compared to polycrystalline Pt foil. For a given substrate, Pt/HOPG electrodes prepared by impregnation followed by thermal decomposition proved to be more electrochemically stable than electrodes prepared by electrochemical deposition. For a given deposition technique, ozone oxidized HOPG has the greatest stabilizing effect. The

  15. 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.

  16. SnO2 nanocluster supported Pt catalyst with high stability for proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Tin oxide nanocluster (SnO2) with parallel nanorods was synthesized via a hard template method and explored as the anode catalyst support for proton exchange membrane fuel cells (PEMFCs). Single cell test demonstrated that SnO2 supported Pt catalyst (Pt/SnO2) exhibited comparable anode performance with conventional Pt/C. Electrochemical measurements showed that Pt/SnO2 exhibited significantly enhanced electrochemical stability than Pt/C under high potential electro-oxidation and potential cycling. The Pt/SnO2 catalyst reserved most of its electrochemically active surface area (ECA) under 10 h potential hold at 1.6 V while its ECA degradation rate was one order of magnitude lower than Pt/C under potential cycling between 0.6 and 1.2 V. Therefore, SnO2 nanocluster can be considered as a promising alternative anode catalyst support for PEMFCs

  17. 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.

  18. 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.

  19. 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. PMID:27240266

  20. 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.

  1. 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.

  2. 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; Arenz, Matthias; Skou, Eivind Morten

    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...

  3. 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

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

    Science.gov (United States)

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-01

    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 × 10(6) and turnover frequencies of ∼1.1 × 10(5) 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(•-))Co(I)(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. PMID:26864496

  5. 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.

  6. 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....

  7. Interplay between pore size and nanoparticle spatial distribution: consequences for the stability of CuZn/SiO2 methanol synthesis catalysts

    OpenAIRE

    Prieto, G; Meeldijk, J.D.; de Jong, K.P.; de Jongh, P.E.

    2013-01-01

    Particle growth is a major deactivation mechanism for supported metal catalysts. This study reveals that the impact of pore size on catalyst stability is very sensitive to the nanoscale metal distribution. A set of ex-nitrate CuZn/SiO2 catalysts was synthesised using SiO2-gel supports (pore size 5-23 nm). The catalyst compositions were adjusted to attain series of catalysts with either constant pore volumetric (1.6 Cu nm-3) or surface (2.0 Cu nm-2) overall metal loading. The procedures of the...

  8. Size and Promoter Effects on Stability of Carbon-Nanofiber-Supported Iron-Based Fischer–Tropsch Catalysts

    Science.gov (United States)

    2016-01-01

    The Fischer–Tropsch Synthesis converts synthesis gas from alternative carbon resources, including natural gas, coal, and biomass, to hydrocarbons used as fuels or chemicals. In particular, iron-based catalysts at elevated temperatures favor the selective production of C2–C4 olefins, which are important building blocks for the chemical industry. Bulk iron catalysts (with promoters) were conventionally used, but these deactivate due to either phase transformation or carbon deposition resulting in disintegration of the catalyst particles. For supported iron catalysts, iron particle growth may result in loss of catalytic activity over time. In this work, the effects of promoters and particle size on the stability of supported iron nanoparticles (initial sizes of 3–9 nm) were investigated at industrially relevant conditions (340 °C, 20 bar, H2/CO = 1). Upon addition of sodium and sulfur promoters to iron nanoparticles supported on carbon nanofibers, initial catalytic activities were high, but substantial deactivation was observed over a period of 100 h. In situ Mössbauer spectroscopy revealed that after 20 h time-on-stream, promoted catalysts attained 100% carbidization, whereas for unpromoted catalysts, this was around 25%. In situ carbon deposition studies were carried out using a tapered element oscillating microbalance (TEOM). No carbon laydown was detected for the unpromoted catalysts, whereas for promoted catalysts, carbon deposition occurred mainly over the first 4 h and thus did not play a pivotal role in deactivation over 100 h. Instead, the loss of catalytic activity coincided with the increase in Fe particle size to 20–50 nm, thereby supporting the proposal that the loss of active Fe surface area was the main cause of deactivation. PMID:27330847

  9. Efficient Methanol Synthesis Catalysts: Long-Term Stability and Deactivation Phenomena

    OpenAIRE

    Fichtl, Matthias

    2014-01-01

    In this thesis the deactivation mechanism on different coprecipitated Cu/ZnO/Al2O3 methanol synthesis catalysts is evaluated. Transmission electron microcopy, X-ray diffraction, chemisorption methods and modeling techniques are applied to correlate the deactivation behavior with structural changes in the active catalyst. Updated models for the catalyst microstructure and deactivation behavior are presented.

  10. Modulating the morphology and electrical properties of GaAs nanowires via catalyst stabilization by oxygen.

    Science.gov (United States)

    Han, Ning; Yang, Zaixing; Wang, Fengyun; Yip, SenPo; Dong, Guofa; Liang, Xiaoguang; Hung, TakFu; Chen, Yunfa; Ho, Johnny C

    2015-03-11

    Nowadays, III-V compound semiconductor nanowires (NWs) have attracted extensive research interest because of their high carrier mobility favorable for next-generation electronics. However, it is still a great challenge for the large-scale synthesis of III-V NWs with well-controlled and uniform morphology as well as reliable electrical properties, especially on the low-cost noncrystalline substrates for practical utilization. In this study, high-density GaAs NWs with lengths >10 μm and uniform diameter distribution (relative standard deviation σ ∼ 20%) have been successfully prepared by annealing the Au catalyst films (4-12 nm) in air right before GaAs NW growth, which is in distinct contrast to the ones of 2-3 μm length and widely distributed of σ ∼ 20-60% of the conventional NWs grown by the H2-annealed film. This air-annealing process is found to stabilize the Au nanoparticle seeds and to minimize Ostwald ripening during NW growth. Importantly, the obtained GaAs NWs exhibit uniform p-type conductivity when fabricated into NW-arrayed thin-film field-effect transistors (FETs). Moreover, they can be integrated with an n-type InP NW FET into effective complementary metal oxide semiconductor inverters, capable of working at low voltages of 0.5-1.5 V. All of these results explicitly demonstrate the promise of these NW morphology and electrical property controls through the catalyst engineering for next-generation electronics. PMID:25700210

  11. 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.

  12. Content of sulfates and their stability – key factors determining the catalytic activity of sulfated zirconia catalysts

    Directory of Open Access Journals (Sweden)

    ALEKSANDRA ZARUBICA

    2007-07-01

    Full Text Available Two series of sulfated zirconia catalysts were synthesized from various precursors using mono- or multi-step sequence preparations under laboratory con­ditions. Their activities/selectivities in the isomerization reaction of n-hexane were correlated to their textural, structural and morphological properties. The slightly higher activity of a commercially sulfated Zr(OH4-based catalyst is in agreement with the differences in the content of SO42-- ions and their thermal stability, textural and structural properties, i.e., crystallite size and possible imperfection of the incor­poration of sulfate groups in the multi-step synthesis of the catalyst having a nitrate origin. The employment of H2 as the carrier gas resulted in no catalytic activity, regardless of the catalyst precursor, preparation method and calcination tempera­ture. When the isomerization reaction was performed under He, the relatively short life-times of all catalyst samples were caused by fast deactivation due to coking in the absence of H2.

  13. 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.

  14. Activity, short-term stability (poisoning tolerance) and durability of carbon supported Pt-Pr catalysts for ethanol oxidation

    Science.gov (United States)

    Corradini, Patricia G.; Antolini, Ermete; Perez, Joelma

    2014-04-01

    Pt-Pr/C electrocatalysts were prepared by a modified formic acid method, and their activity for carbon monoxide and ethanol oxidation, their short term stability and durability were compared to that of commercial Pt/C and Pt-Sn/C (3:1) catalysts. By derivative voltammetry (DV) it was found that ethanol electro-oxidation takes place by two main pathways at different potentials. It was observed that, in the presence of Pr, ethanol electro-oxidation takes place mostly through the pathway at lower potential, which is the most interesting for fuel cell application. The Pt-Pr/C catalysts were less tolerant to poisoning by ethanol oxidation intermediate species than Pt/C. Durability test by a repetitive potential cycling under Ar atmosphere revealed a good structural stability of Pt-Pr/C catalysts. A repetitive potential cycling under CO atmosphere carried out on the Pt-Pr/C (1:1) catalyst, instead, indicated a structural change, likely by formation of a core-shell structure.

  15. 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

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

    International Nuclear Information System (INIS)

    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/MgAl2O4. 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-Al2O3. Then, the metallic phase was also modified by adding a second metal (Ni, Pt or Pd). The Rh-Ni/Y-Al2O3 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/MgAl2O4, which was strongly deactivated after 2h of time-on-stream. (author)

  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, 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)

  18. 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)

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

    International Nuclear Information System (INIS)

    Highlights: • Vanadia supported on titanate nanotube shows enhanced dispersion of vanadia. • Deactivatoin during propane ODH related to the rutile development. • Titanate nanotube transfers to anatase due to calcinations and presence of vanadia. - Abstract: 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kootenaei, A.H. Shahbazi [Department of Chemical Engineering, College of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Towfighi, J., E-mail: towfighi@modares.ac.ir [Department of Chemical Engineering, College of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Khodadadi, A.; Mortazavi, Y. [Catalysis and Nanostructured Materials Laboratory, Oil and Gas Processing Center of Excellence, Department of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran (Iran, Islamic Republic of)

    2014-04-01

    Highlights: • Vanadia supported on titanate nanotube shows enhanced dispersion of vanadia. • Deactivatoin during propane ODH related to the rutile development. • Titanate nanotube transfers to anatase due to calcinations and presence of vanadia. - Abstract: Titanate nanotubes with a high specific surface area were synthesized by the simple hydrothermal method and investigated as support for V{sub 2}O{sub 5} 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.

  1. 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.

  2. Fe phase complexes and their thermal stability in iron phosphate catalysts supported on silica

    International Nuclear Information System (INIS)

    Comparative XRD and Mössbauer spectroscopy studies have been conducted on the effect of temperature on the phase transformations of an iron phosphate catalyst synthesized using the ammonia gel method (CAT1) and a commercial grade FePO 4 catalyst supported on silica using wet impregnation method (CAT2). The XRD patterns of both catalysts showed the presence of iron phosphate and the tridymite phase of aluminum phosphate. Mössbauer spectra of the catalysts show that the phases present in CAT1 are thermally stable up to 500 ∘C, but CAT2 shows significant changes with the tridymite phase of iron phosphate increasing from 6 % to 29 % of the spectral area at a temperature of 500 ∘C

  3. Fe phase complexes and their thermal stability in iron phosphate catalysts supported on silica

    Energy Technology Data Exchange (ETDEWEB)

    Dasireddy, Venkata D. B. C., E-mail: dasireddy@gmail.com; Bharuth-Ram, K.; Harilal, A.; Singh, S.; Friedrich, H. B. [University of KwaZulu-Natal, School of Chemistry and Physics (South Africa)

    2015-04-15

    Comparative XRD and Mössbauer spectroscopy studies have been conducted on the effect of temperature on the phase transformations of an iron phosphate catalyst synthesized using the ammonia gel method (CAT1) and a commercial grade FePO {sub 4} catalyst supported on silica using wet impregnation method (CAT2). The XRD patterns of both catalysts showed the presence of iron phosphate and the tridymite phase of aluminum phosphate. Mössbauer spectra of the catalysts show that the phases present in CAT1 are thermally stable up to 500 {sup ∘}C, but CAT2 shows significant changes with the tridymite phase of iron phosphate increasing from 6 % to 29 % of the spectral area at a temperature of 500 {sup ∘}C.

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

    DEFF Research Database (Denmark)

    Vej-Hansen, Ulrik Grønbjerg

    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......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...... increased activity that has been seen experimentally. We show how the platinum-platinum distance at the surface is decreased for a variety of alloy phases in the core, with greater compression of the overlayer for core phases with lattice parameters which are either much smaller or much larger than pure...

  5. Strategies for improving the performance and stability of Ni-based catalysts for reforming reactions.

    Science.gov (United States)

    Li, Shuirong; Gong, Jinlong

    2014-11-01

    Owing to the considerable publicity that has been given to petroleum related economic, environmental, and political problems, renewed attention has been focused on the development of highly efficient and stable catalytic materials for the production of chemical/fuel from renewable resources. Supported nickel nanoclusters are widely used for catalytic reforming reactions, which are key processes for generating synthetic gas and/or hydrogen. New challenges were brought out by the extension of feedstock from hydrocarbons to oxygenates derivable from biomass, which could minimize the environmental impact of carbonaceous fuels and allow a smooth transition from fossil fuels to a sustainable energy economy. This tutorial review describes the recent efforts made toward the development of nickel-based catalysts for the production of hydrogen from oxygenated hydrocarbons via steam reforming reactions. In general, three challenges facing the design of Ni catalysts should be addressed. Nickel nanoclusters are apt to sinter under catalytic reforming conditions of high temperatures and in the presence of steam. Severe carbon deposition could also be observed on the catalyst if the surface carbon species adsorbed on metal surface are not removed in time. Additionally, the production of hydrogen rich gas with a low concentration of CO is a challenge using nickel catalysts, which are not so active in the water gas shift reaction. Accordingly, three strategies were presented to address these challenges. First, the methodologies for the preparation of highly dispersed nickel catalysts with strong metal-support interaction were discussed. A second approach-the promotion in the mobility of the surface oxygen-is favored for the yield of desired products while promoting the removal of surface carbon deposition. Finally, the process intensification via the in situ absorption of CO2 could produce a hydrogen rich gas with low CO concentration. These approaches could also guide the design

  6. Morphological effects of the nanostructured ceria support on the activity and stability of CuO/CeO2 catalysts for the water-gas shift reaction.

    Science.gov (United States)

    Yao, S Y; Xu, W Q; Johnston-Peck, A C; Zhao, F Z; Liu, Z Y; Luo, S; Senanayake, S D; Martínez-Arias, A; Liu, W J; Rodriguez, J A

    2014-08-28

    Three CuO/CeO2 catalyst with different morphologies of ceria, namely nanospheres, nanorods and nanocubes, were synthesized and used to catalyze the water-gas shift (WGS) reaction. The reactivity tests showed that the Cu supported on the ceria nanospheres exhibited both the highest activity and superior stability when compared with the nanocube and nanorod ceria catalysts. Operando X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) methods were used to characterize these catalysts in their working state. High resolution electron microscopy (HRTEM, STEM) was used to look at the local atomic structure and nano-scale morphology. Our results show that the morphology of the ceria support, which can involve different crystal faces and concentrations of defects and imperfections, has a critical impact on the catalytic properties and influences: (1) the dispersion of CuO in the as-synthesized catalyst; (2) the particle size of metallic Cu upon reduction during the WGS reaction, (3) the stability of the metallic Cu upon variations of temperature, and (4) the dissociation of water on the ceria support. The nanosphere ceria catalyst showed an excellent water dissociation capability, the best dispersion of Cu and a strong Cu-Ce interaction, therefore delivering the best performance among the three WGS catalysts. The metallic Cu, which is the active species during the WGS reaction, was more stabilized on the nanospheres than on the nanorods and nanocubes and thus led to a better stability of the nanosphere catalyst than the other two architectures. Each catalyst exhibited a distinctive line-shape in the 800-1600 cm(-1) region of the DRIFTS spectra, pointing to the existence of different types of carbonate or carboxylate species as surface intermediates for the WGS. PMID:25012908

  7. 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. PMID:27182602

  8. Improving Heterogeneous Catalyst Stability for Liquid-phase Biomass Conversion and Reforming

    OpenAIRE

    Héroguel, Florent Emmanuel; Rozmysłowicz, Bartosz; Luterbacher, Jeremy

    2015-01-01

    Biomass is a possible renewable alternative to fossil carbon sources. Today, many bio-resources can be converted to direct substitutes or suitable alternatives to fossil-based fuels and chemicals. However, catalyst deactivation under the harsh, often liquid-phase reaction conditions required for biomass treatment is a major obstacle to developing processes that can compete with the petrochemical industry. This review presents recently developed strategies to limit reversible and irreversible ...

  9. Electronic spectral studies on Nd3+ in different solvent environment: symmetry of solvato-complex vis a vis solvent nature

    International Nuclear Information System (INIS)

    Electronic spectra of Nd3+ ion in different solvent environments, viz., water, ethanol, acetic acid, ethylacetate, dimethyl sulphoxide and dimethylformamide have been recorded in order to study the effect of solvato-complex formation on the electronic spectral parameters of Nd3+ ion. The variation in the oscillator strengths (P), Judd-Ofelt parameters (Tλ), the inter-electronic repulsion (Racah) parameters (δEk) and the nephelauxetic ratio (β = σE3/σE1) values has been examined in the light of nature of the solvent, the mode of Nd-solvent bonding and the Nd-O solvent donor atom bond distance. The spectral parameters show a dependence on the dielectric constant of the solvent. The Tλ parameters show a marked dependence on Nd-O bond distance. The δE3/δE1 values show a gradual increase with decreasing Nd-O bond distance. Coordination number, follows the order, HOH, Et-OH (CN∼9) > Et-Ac, Ac (CN 8-9) > DMF, DMSO (CN∼8). (author)

  10. 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.

  11. 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…

  12. INAA of trace elements in Indian vegetarian diet and its adequacy vis-a-vis Recommended Dietary Allowances

    International Nuclear Information System (INIS)

    There has been an increasing awareness concerning the adequacy of trace elements in diet as their deficiency or excess may cause abnormal changes in the biochemical processes. Typical Indian vegetarian diet and dietary components such as cereals, grains, pulses, vegetables and spices have been analysed for 19 elements (Br, Cl, Co, Cr, Cu, Fe, Hg, K, Mn, Mo, Na, P, Rb, Sb, Sc, Se, Sr, Th and Zn) by instrumental neutron activation analysis (INAA). Several Standard Reference Materials (SRMs) were analysed for quality assurance. Based on the elemental contents, the daily dietary intake has been calculated and the data compared with those from other countries, Recommended Dietary Allowances (RDAs) and permissible body burden. It has been observed that, although vegetarian, the Indian diet has an adequate content of essential trace elements compared to non-vegetarian oriental (Japan and Taiwan) and western (Germany, Denmark and USA) diets. (author)

  13. A comparative study of the antioxidant potential of various fractions of Podophyllum hexandrum vis-a-vis radiation protection

    International Nuclear Information System (INIS)

    High-altitude Podophyllum hexandrum was fractionated using five different solvents of varying polarity. The biological activities bear direct relevance to radioprotection. REC-2007 had maximum inherent antioxidant potential to combat radiation induced oxidative stress

  14. 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.

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

    Directory of Open Access Journals (Sweden)

    Nazila Isgandarova

    2009-10-01

    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.

  16. Estimate of Equilibrium Real Exchange Rate and Misalignment of Chinese Yuan Vis-a-Vis US Dollar

    Directory of Open Access Journals (Sweden)

    Atabani Adi Agya

    2015-09-01

    Full Text Available The paper examines the misalignment in equilibrium real exchange rate of Chinese Yuan against US dollar. The data covered the period of 1980-2014, it used Vector Autoregressive model, the variables are not stationary at level and became stationary after first differencing and there were three co-integration vectors. The long run coefficients have expected sign except for interest rate differential and are significant at 5 percent significance level. The speed of adjustment of real exchange rate to it equilibrium indicated that the disequilibrium in the last period are corrected by 87 percent each year and highly significant. The Yuan was overvalued by 4 percent, from 1981-1990 and in1990 it was undervalue about 4 percent and move back to equilibrium, the highest overvaluation was in 1993 up to 13 percent from equilibrium value and undervalue in 1994 by 14 percent which was the highest level of undervaluation, between 1996 to 2005 the Yuan was relatively within it equilibrium and slightly over value to 3.8 percent in 2008 back to long time path in 2011 and relatively undervalue by 1-3 percent since 2012, in general the Yuan is not substantially undervalue as claims in some studies both theoretical and empirical estimation and the movement in the exchange rate are consistent with economic fundamental of China.

  17. 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.

  18. Assessing thermochromatography as a separation method for nuclear forensics. Current capability vis-a-vis forensic requirements

    International Nuclear Information System (INIS)

    Nuclear forensic science has become increasingly important for global nuclear security. However, many current laboratory analysis techniques are based on methods developed without the imperative for timely analysis that underlies the post-detonation forensics mission requirements. Current analysis of actinides, fission products, and fuel-specific materials requires time-consuming chemical separation coupled with nuclear counting or mass spectrometry. High-temperature gas-phase separations have been used in the past for the rapid separation of newly created elements/isotopes and as a basis for chemical classification of that element. We are assessing the utility of this method for rapid separation in the gas-phase to accelerate the separations of radioisotopes germane to post-detonation nuclear forensic investigations. The existing state of the art for thermo chromatographic separations, and its applicability to nuclear forensics, will be reviewed. (author)

  19. Effects of gamma irradiation on chickpea seeds vis-a-vis total seed storage proteins, antioxidant activity and protein profiling.

    Science.gov (United States)

    Bhagyawant, S S; Gupta, N; Shrivastava, N

    2015-01-01

    The present work describes radiation—induced effects on seed composition vis—à—vis total seed proteins, antioxidant levels and protein profiling employing two dimensional gel electrophoresis (2D—GE) in kabuli and desi chickpea varities. Seeds were exposed to the radiation doses of 1,2,3,4 and 5 kGy. The total protein concentrations decreased and antioxidant levels were increased with increasing dose compared to control seed samples. Radiation induced effects were dose dependent to these seed parameters while it showed tolerance to 1 kGy dose. Increase in the dose was complimented with increase in antioxidant levels, like 5 kGy enhanced % scavenging activities in all the seed extracts. Precisely, the investigations reflected that the dose range from 2 to 5 kGy was effective for total seed storage proteins, as depicted quantitatively and qualitative 2D—GE means enhance antioxidant activities in vitro. PMID:26516115

  20. Socio-economic status of horse owners vis-a-vis horse feeding and management in Rajasthan

    Directory of Open Access Journals (Sweden)

    P. A. Bala

    2013-05-01

    Full Text Available Aim: To study the socio-economic status, horse feeding and management adopted by horse owners of Rajasthan. Materials and Methods: Primary data was collected through specially structured proforma by personal interview method from the horse owners of Hanumangarh (50, Churu (42, Jhunjhunu (30 and Jalore (40 districts of Rajasthan, India. Results: The district (Churu and Jhunjhunu is mostly rain fed, Hanumangarh is canal-irrigated whereas Jalore is tube well irrigated. Majority of respondents engaged in horse rearing were of other backward class (OBC & general category. Literacy (% among the horse owners was more than 80% in Hanumangarh and Jhunjhunu districts, whereas it was less than 50% in Churu and Jalore districts. Majority of the respondents were maintaining other livestock along with the horses. The average dry roughages provided were 4.82±0.22, 8.143±0.348, 5.267±0.69 and 6.105±0.196kg per horse in Hanumangarh, Churu, Jhunjhunu and Jalore, respectively. The average concentrate offered was 2.81±0.138, 2.452±0.145, 2.933±0.160 and 1.950±0.200kg per horse in Hanumangarh, Churu, Jhunjhunu and Jalore, respectively. It was observed that horse owners were providing green fodder, dry roughages and concentrate depending up on the availability/production of these items in that region. Majority of horse owners were allowing covering of estrus mares between 3rd and 5th day of estrus. Paucity of quality stallions for covering the mares was observed throughout the area surveyed. The respondents had to pay between Rs. 1100/- to 5100/- as covering fee with no guarantee of conception. Most of mares were rebred during foal heat and majority of the respondents were not aware about the symptoms of estrus mare. Vaccination, insurance and use of disinfectants were not adopted in the study indicating the least awareness among the horse owners about the importance of vaccination, insurance and disinfectants. Conclusion: Horses were being maintained for ceremonial purposes and breeding, their feeding in terms of fodder (green & dry and concentrate were observed area specific and were fulfilling the minimum nutrient requirements. There was paucity of true to breed stallions in the areas studied. [Vet World 2013; 6(8.000: 470-475

  1. Stability of Fe-N-C Catalysts in Acidic Medium Studied by Operando Spectroscopy.

    Science.gov (United States)

    Choi, Chang Hyuck; Baldizzone, Claudio; Grote, Jan-Philipp; Schuppert, Anna K; Jaouen, Frédéric; Mayrhofer, Karl J J

    2015-10-19

    Fundamental understanding of non-precious metal catalysts for the oxygen reduction reaction (ORR) is the nub for the successful replacement of noble Pt in fuel cells and, therefore, of central importance for a technological breakthrough. Herein, the degradation mechanisms of a model high-performance Fe-N-C catalyst have been studied with online inductively coupled plasma mass spectrometry (ICP-MS) and differential electrochemical mass spectroscopy (DEMS) coupled to a modified scanning flow cell (SFC) system. We demonstrate that Fe leaching from iron particles occurs at low potential (0.9 V) with a destruction of active sites such as FeNx Cy species. Operando techniques combined with identical location-scanning transmission electron spectroscopy (IL-STEM) identify that the latter mechanism leads to a major ORR activity decay, depending on the upper potential limit and electrolyte temperature. Stable operando potential windows and operational strategies are suggested for avoiding degradation of Fe-N-C catalysts in acidic medium. PMID:26314711

  2. Stability and resistance of nickel catalysts for hydrodeoxygenation:carbon deposition and effects of sulfur, potassium, and chlorine in the feed

    OpenAIRE

    Mortensen, Peter Mølgaard; Gardini, Diego; Hudson W. P. Carvalho; Damsgaard, Christian Danvad; Grunwaldt, Jan-Dierk; Jensen, Peter Arendt; Wagner, Jakob Birkedal; Jensen, Anker Degn

    2014-01-01

    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 mini...

  3. Stabilization of betalains: A review.

    Science.gov (United States)

    Khan, Mohammad Imtiyaj

    2016-04-15

    Betalains are vacuolar pigments composed of a nitrogenous core structure, betalamic acid [4-(2-oxoethylidene)-1,2,3,4-tetrahydropyridine-2,6-dicarboxylic acid]. This compound consists of a chromophore substructure 1,7-diazaheptamethin. Betalamic acid condenses with imino compounds (cyclo-DOPA or its glucosyl derivatives), or amines and/or their derivatives to form a variety of betacyanins (violet) and betaxanthins (yellow), respectively. These pigments exhibit absorption maxima in between 532-550 nm and 457-485 nm, respectively. These colors are currently in use as food additives as they are bioactive and completely safe to consume. However, owing to poor stability, their potential application in pharmaceuticals and cosmetics is severely compromised. There is a lack of scientific reports highlighting their superior tinctorial strength including fluorescence, and their excellent water solubility. For widening the color spectrum and their usage, various betalain-rich extracts have been reviewed here, focusing on their matrix effects on stability vis-a-vis purified pigments of different structural make-up. This review also encompasses work carried out in the past related to stability/stabilization of betalains and future research direction for the same. PMID:26675869

  4. 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.

  5. 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...... showed that Mo2C is transformed to MoO2 in the presence of water at the given conditions, and this was probably the source of deactivation in the experiments. Thus, Mo2C-based catalyst for HDO seems interesting, but requires further stabilization or regeneration of the carbide phase as bio-oil contains...

  6. 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...

  7. Enhancement of Glycerol Steam Reforming Activity and Thermal Stability by Incorporating CeO2 and TiO2 in Ni- and Co-MCM-41 Catalysts

    Science.gov (United States)

    Dade, William N.

    Hydrogen (H2) has many applications in industry with current focus shifted to production of hydrocarbon fuels and valuable oxygenates using the Fischer-Tropsch technology and direct use in proton exchange membrane fuel cell (PEMFC). Hydrogen is generally produced via steam reforming of natural gas or alcohols like methanol and ethanol. Glycerol, a by-product of biodiesel production process, is currently considered to be one of the most attractive sources of sustainable H2 due to its high H/C ratio and bio-based origin. Ni and Co based catalysts have been reported to be active in glycerol steam reforming (GSR); however, deactivation of the catalysts by carbon deposition and sintering under GSR operating conditions is a major challenge. In this study, a series of catalysts containing Ni and Co nanoparticles incorporated in CeO2 and TiO2 modified high surface area MCM-41 have been synthesized using one-pot method. The catalysts are tested for GSR (at H2O/Glycerol mole ratio of 12 and GHSV of 2200 h-1) to study the effect of support modification and reaction temperature (450 - 700 °C) on the product selectivity and long term stability. GSR results revealed that all the catalysts performed significantly well exhibiting over 85% glycerol conversion at 650 °C except Ni catalysts that showed better low temperature activities. Deactivation studies of the catalysts conducted at 650 °C indicated that the Ni-TiO2-MCM-41 and Ni-CeO 2-MCM-41 were resistant to deactivation with ˜100% glycerol conversion for 40 h. In contrast, Co-TiO2-MCM-41 perform poorly as the catalyst rapidly deactivated after 12 h to yield ˜20% glycerol conversion after 40 h. The WAXRD and TGA-DSC analyses of spent catalysts showed a significant amount of coke deposition that might explain catalysts deactivation. The flattening shape of the original BET type IV isotherm with drastic reduction of catalyst surface area can also be responsible for observed drop in catalysts activities.

  8. Attaining control by design over the hydrolytic stability of Fe-TAML oxidation catalysts.

    Science.gov (United States)

    Polshin, Victor; Popescu, Delia-Laura; Fischer, Andreas; Chanda, Arani; Horner, David C; Beach, Evan S; Henry, Jennifer; Qian, Yong-Li; Horwitz, Colin P; Lente, Gabor; Fabian, Istvan; Münck, Eckard; Bominaar, Emile L; Ryabov, Alexander D; Collins, Terrence J

    2008-04-01

    The iron(III) complexes of tetra amidato macrocyclic ligands (TAMLs) ([Fe{1-X1-2-X2C6H2-4,5-(NCOCMe2NCO)2CR2}(OH2)]- , 1: X1 = X2 = H, R2 = Me2 (a), R2 = (CH2)2 (b); X1 = X2 = Cl, R2 = F2 (c), etc.), which the proton is known to demetalate at pH constants for the demetalation (kobs) are linear functions of the acid concentrations, and the effective second-order rate constants k1,eff have a hyperbolic dependence on [H+] (k1,eff = a1[H+]/(b1+[H+]). The rate of demetalation of 1a in H2PO4-/HPO42- buffer is appreciable, but the kobs values for 1b and 1c are immeasurably low, showing that the rates are strongly affected by the CR2 or "tail" fragments, which are known to potently affect the TAML basicity. The reactivities of 1 depend insignificantly on the aromatic ring or "head" group of 1. The proposed mechanism involves precoordination of the acidic buffer species followed by hydrolysis. The demetalating abilities of buffer species depend on their structures and acidities. Thus, although pyridine-2-carboxylic (picolinic) acid catalyzes the demetalation, its 3- and 4-isomers (nicotinic and isonicotininc acids) are inactive. The difference is rationalized to result from the ability that only coordinated picolinic acid has to deliver a proton to an amidato nitrogen in an intramolecular manner. The reaction order in picolinic acid equals one for 1a and two for 1b. For 1b, "inactive" pyridine and nicotinic acid speed up the demetalation in the presence of picolinic acid, suggesting that the second order arises from the axial binding of two pyridine molecules, one of which must be picolinic acid. The binding of pyridine- and imidazole-type ligands was confirmed by UV/vis equilibrium measurements and X-ray crystallography. The implications of these mechanistic findings for designing superior Fe-TAML oxidation catalysts and catalyst formulations are discussed using the results of DFT calculations. PMID:18335938

  9. 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.

  10. High-temperature stability of V2O5/TiO2-WO3-SiO2 SCR catalysts modified with rare-earths

    International Nuclear Information System (INIS)

    The introduction of rare earth elements (RE = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Er and Yb) into a V2O5/TiO2-WO3-SiO2 system leads to a catalyst which shows a significant improvement in thermal stability by hindering transformation of TiO2 (anatase) into TiO2 (rutile). As a consequence, these novel compounds show high removal efficiencies for NO x even after aging at 1023 K, when the state of the art SCR catalysts loose activity and selectivity. This allows potential application of these catalysts in the removal of NO x from diesel or lean-burn automotive engines in addition to stationary applications at high temperatures

  11. Activity and stability enhancement of copper-alumina catalysts using cerium and zinc promoters for the selective production of hydrogen via steam reforming of methanol

    Science.gov (United States)

    Patel, Sanjay; Pant, K. K.

    The catalytic activity and hydrogen selectivity of cerium and zinc promoted copper-alumina catalysts have been investigated for the selective production of hydrogen via steam reforming of methanol (SRM). The SRM was carried out in a fixed bed tubular reactor at atmospheric pressure over a temperature range 200-300 °C. The major reaction products were hydrogen and carbon dioxide with traces of carbon monoxide. Catalysts of varying compositions were prepared by the wet impregnation method and characterized by atomic absorption spectroscopy (AAS), BET surface area, pore volume, pore size, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and thermogravimetry analysis (TGA). Results revealed that the methanol conversion, hydrogen selectivity and carbon monoxide formation varied with the type of promoter and content of copper in the catalyst. Cerium promoted Cu-Zn-Ce-Al-oxide catalysts improved the activity and hydrogen selectivity greatly and also kept the CO formation very low. Using cerium the SRM could be carried out at lower temperature with high methanol conversion, results in suppression of methanol decomposition and reverse water gas shift reactions eventually end-up with the low carbon monoxide and hydrogen rich product stream. Cerium also stabilizes the copper-alumina catalysts effectively that was confirmed by deactivation studies in which cerium promoted Cu-Zn-Ce-Al-oxide catalysts gave the consistent performance for a long run-time compared to catalysts containing only zinc promoter. The optimum operating conditions for SRM have been investigated by detailed study of effects of reaction temperature, contact time and steam to methanol molar ratio on methanol conversion, hydrogen selectivity and CO formation. Reaction pathway has been proposed for the SRM based on results obtained.

  12. Catalytic combustion of diesel soot on Co,K/MgO catalysts. Effect of the potassium loading on activity and stability

    Energy Technology Data Exchange (ETDEWEB)

    Querini, C.A.; Cornaglia, L.M.; Ulla, M.A.; Miro, E.E. [Instituto de Investigaciones en Catalisis y Petroquimica - INCAPE, FIQ, UNL-CONICET, Santiago del Estero 2829, 3000 Santa Fe (Argentina)

    1999-03-08

    Co,K/MgO catalysts with 12wt% of Co and 1.5, 4.5 and 7.5wt% of K, calcined at 400C are active for the combustion of diesel soot. Among them, the one containing 4.5wt% of K is that which burns soot at the lowest temperature (378C). Coincidentally, this is the catalyst presenting the highest K/Mg and K/O surface ratios in XPS measurements. When the calcination temperature is increased at 500C, both the solid containing 4.5% of K and the one containing 1.5% as well as the unpromoted catalyst (Co/MgO) noticeably lose activity due to the formation of a solid solution (Co, Mg). However, the solid with the highest K content (7.5wt%) presents a similar activity at different calcination temperatures (400C, 500C and 700C). It has been found that the activity of these solids is directly related to the reducibility of cobalt, thus indicating that the reaction is carried out by a redox mechanism. Potassium plays different roles in these catalysts: (1) it increases the catalyst-soot contact by increasing surface mobility, (2) it preserves the reducibility and dispersion of cobalt by improving stability against thermal treatments, and (3) it favors the oxidation of soot by consuming the carbon to form carbonate species during soot combustion. It was also found that soot with a higher content of sulfur (1050ppm) is more efficiently burned than that containing low amounts of sulfur (70ppm). However, the severe sulfation of the catalyst leads to a noticeable loss of activity. In experiments of carbon monoxide oxidation, it was found that conversion is practically total between 400C and 500C under the conditions used in this work. The direct impregnation of the soot with either Co or Co and K, showed lower combustion temperatures if compared with the mechanical mixtures of soot and Co/MgO or Co,K/MgO, suggesting that the soot-catalyst contact poses a physical limitation on the oxidation activity. This important result suggests that the soot-catalyst contacting problem is the main

  13. 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.

  14. 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.

  15. On the stability of carbon nanotube and titania nanowire based catalyst materials:from synthesis to applications

    OpenAIRE

    Rautio, A.-R. (Anne-Riikka)

    2016-01-01

    Abstract Degradation of the support and sintering of catalyst nanoparticles inherently leads to a loss of functionality of catalyst materials in converters and sensors. Malfunction in such devices may lead to serious economic and environmental damage. The quest for novel and sustainable catalyst materials with better durability is thus ongoing. In this thesis, one-dimensional nanomaterials such as carbon nanotubes and titanium dioxide nanowires are studied and compared to their convention...

  16. Microstructured fiber@HZSM-5 core-shell catalysts with dramatic selectivity and stability improvement for the methanol-to-propylene process.

    Science.gov (United States)

    Wang, Xiangyu; Wen, Ming; Wang, Chunzheng; Ding, Jia; Sun, Ying; Liu, Ye; Lu, Yong

    2014-06-18

    We report a macroscopic stainless-steel-fiber@HZSM-5 core-shell catalyst by direct growth of 27 wt% HZSM-5 on a 3D microfibrous structure using 20 μm SS fibers, demonstrating dramatic selectivity and stability improvement in the MTP process. The unprecedented performance is due to the promotion of the olefin methylation/cracking cycle in methanol-to-hydrocarbon catalysis. PMID:24798420

  17. Iron porphyrin-based cathode catalysts for polymer electrolyte membrane fuel cells: Effect of NH{sub 3} and Ar mixtures as pyrolysis gases on catalytic activity and stability

    Energy Technology Data Exchange (ETDEWEB)

    Meng Hui; Larouche, Nicholas; Lefevre, Michel; Jaouen, Frederic; Stansfield, Barry [INRS-Energie, Materiaux et Telecommunications, 1650 boulevard Lionel Boulet, Varennes, Quebec, J3X 1S2 (Canada); Dodelet, Jean-Pol, E-mail: dodelet@emt.inrs.c [INRS-Energie, Materiaux et Telecommunications, 1650 boulevard Lionel Boulet, Varennes, Quebec, J3X 1S2 (Canada)

    2010-09-01

    Ten different catalysts were prepared by loading 66 wt% ClFeTMPP on N330, a furnace grade carbon black, and pyrolyzing this catalyst precursor for 10 min at 950 {sup o}C in a NH{sub 3}/Ar gas mixture with various NH{sub 3} volume fractions (from 0% to 100%). The activity and stability of these catalysts were measured in a fuel cell and compared. The only stable catalyst, although the least active, among these was the one pyrolyzed in pure Ar. A notable leap in catalytic activity, but drop in stability, was observed for all catalysts pyrolyzed in gas mixtures containing NH{sub 3}, even with a mere volume fraction of 1.3% NH{sub 3} in the pyrolysis gas mixture. Catalytic activities increased, while stability decreased with increasing volume fraction of NH{sub 3}. The physicochemical properties of these catalysts were correlated with their electrochemical behaviour observed in fuel cell tests. It was found that a volume fraction of only 1.3% NH{sub 3} was enough to double the micropore surface area, the surface nitrogen and iron concentrations in the resulting catalyst. Since the active sites are believed to be of the Fe/N/C type, the sharp increase in catalytic activity with as little as 1.3% NH{sub 3} is attributed to the concurrent increase in microporous surface area, N and Fe surface contents in these catalysts. The only property that apparently correlates with stability is the degree of graphitization of the catalyst, which was estimated either from either X-ray diffraction and Raman spectroscopy measurements. Lastly, it was found that the catalysts' peroxide yield, resulting from the partial reduction of O{sub 2}, does not correlate with their degree of stability.

  18. Improving the stability and ethanol electro-oxidation activity of Pt catalysts by selectively anchoring Pt particles on carbon-nanotubes-supported-SnO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Li, J.J.; Wang, J.S.; Zhao, J.H.; Song, C.Y.; Wang, L.C. [School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou (China); Guo, X. [Department of Chemistry, Tsinghua University, Beijing (China)

    2012-10-15

    To improve the stability and activity of Pt catalysts for ethanol electro-oxidation, Pt nanoparticles were selectively deposited on carbon-nanotubes (CNTs)-supported-SnO{sub 2} to prepare Pt/SnO{sub 2}/CNTs and Pt/CNTs was prepared by impregnation method for reference study. X-ray diffraction (XRD) was used to confirm the crystalline structures of Pt/SnO{sub 2}/CNTs and Pt/CNTs. The stabilities of Pt/SnO{sub 2}/CNTs and Pt/CNTs were compared by analyzing the Pt size increase amplitude using transmission electron microscopy (TEM) images recorded before and after cyclic voltammetry (CV) sweeping. The results showed that the Pt size increase amplitude is evidently smaller for Pt/SnO{sub 2}/CNTs, indicating the higher stability of Pt/SnO{sub 2}/CNTs. Although both catalysts exhibit degradation of electrochemical active surface area (EAS) after CV sweeping, the EAS degradation for the former is lower, further confirming the higher stability of Pt/SnO{sub 2}/CNTs. CV and potentiostatic current-time curves were recorded for ethanol electro-oxidation on both catalysts before and after CV sweeping and the results showed that the mass specific activity of Pt/CNTs increases more than that of Pt/SnO{sub 2}/CNTs, indicating that Pt/CNTs experiences more severe evolution and is less stable. The calculated area specific activity of Pt/SnO{sub 2}/CNTs is larger than that of Pt/CNTs, indicating SnO{sub 2} can co-catalyze Pt due to plenty of interfaces between SnO{sub 2} and Pt. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. 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.

  20. 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.

  1. The stability evaluation of lime mud as transesterification catalyst in resisting CO2 and H2O for biodiesel production

    International Nuclear Information System (INIS)

    Highlights: • Lime mud (LM) is pretreated with calcination, hydration and desiccation. • The alkali solubility is the amount of alkali compounds dissolved in methanol. • The soluble alkali amount in LM700-H is higher than that of CaO–H. • LM700 possesses a stronger capability than CaO in resisting H2O and CO2. - Abstract: The most outstanding property of the heterogeneous transesterification catalysts is recyclable, but their catalytic activity may be depressed for the absorption of moisture (H2O) and carbon dioxide (CO2) in air, especially for the basic ones. Lime mud (LM) is effective in catalyzing transesterification, yet its property in resisting H2O and CO2 is indistinct, which should be emphasized. In this study, the LM based transesterification catalyst is prepared through calcinations. Then, it is hydrated and desiccated to simulate the contamination by H2O and CO2. Further, the fresh and the contaminated catalysts are characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Hammette indicator, Brunauer–Emmett–Teller (BET) surface area and soluble alkali examination, to reveal the mechanism of LM in resisting H2O and CO2. Meanwhile, the analytical grade calcium oxide (CaO) is chosen for comparison. Finally, to comprehensively investigate the influences of H2O and CO2 on LM in catalyzing transesterification, the factors of the catalyst addition percentage, molar ratio of methanol to oil and transesterification temperature are evaluated

  2. 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. PMID:25970204

  3. CdS-sensitized TiO2 in phenazopyridine photo-degradation: Catalyst efficiency, stability and feasibility assessment

    International Nuclear Information System (INIS)

    Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO2, TiO2/CdS, 2, as photo-catalysts. Despite that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd2+ ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO2/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd2+. This indicates limited future applicability of CdS-sensitized TiO2 photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.

  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. CdS-sensitized TiO{sub 2} in phenazopyridine photo-degradation: Catalyst efficiency, stability and feasibility assessment

    Energy Technology Data Exchange (ETDEWEB)

    Zyoud, Ahed H.; Zaatar, Nidal; Saadeddin, Iyad [Department of Chemistry, An-Najah N. University, PO Box 7, Nablus, West Bank, Palestine (Country Unknown); Ali, Cheknane [Laboratoire d' Etude et Developpement des materiaux Dielectriques et Semiconducteurs, Universite Amar Telidji de Laghouat, Laghouat (Algeria); Park, DaeHoon; Campet, Guy [Institut de Chimie de la Matiere Condensee de Bordeaux (ICMCB), 87 Avenue du Dr. A Schweitzer, 33608 Pessac (France); Hilal, Hikmat S., E-mail: hikmathilal@yahoo.com [Department of Chemistry, An-Najah N. University, PO Box 7, Nablus, West Bank, Palestine (Country Unknown)

    2010-01-15

    Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO{sub 2}, TiO{sub 2}/CdS, 2, as photo-catalysts. Despite that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd{sup 2+} ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO{sub 2}/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd{sup 2+}. This indicates limited future applicability of CdS-sensitized TiO{sub 2} photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.

  6. CdS-sensitized TiO2 in phenazopyridine photo-degradation: catalyst efficiency, stability and feasibility assessment.

    Science.gov (United States)

    Zyoud, Ahed H; Zaatar, Nidal; Saadeddin, Iyad; Ali, Cheknane; Park, DaeHoon; Campet, Guy; Hilal, Hikmat S

    2010-01-15

    Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO(2), TiO(2)/CdS, 2, as photo-catalysts. Despite that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd(2+) ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO(2)/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd(2+). This indicates limited future applicability of CdS-sensitized TiO(2) photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented. PMID:19744778

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

    International Nuclear Information System (INIS)

    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 H2 (mol cat)−1 min−1 and maximum hydrogen generation rate of 10,680 L H2 min−1 (mol cat)−1. Poly(N-vinyl-2-pyrrolidone)-protected ruthenium–rhodium nanoparticles also provide activation energy of 47.4 ± 2.1 kJ/mol for the hydrolysis of ammonia borane. - Highlights: • Ru-Rh@PVP NPs provide a TOF of 386 mol H2 (mol cat)−1 min−1 for hydrolysis of AB. • Maximum HG rate is 9680 L H2 min−1 (mol cat)−1 for the hydrolysis of AB. • Activation energy is 47.4 ± 2.1 kJ mol−1 for the hydrolysis of AB

  8. Stability and spinodal decomposition of the solid-solution phase in the ruthenium-cerium-oxide electro-catalyst.

    Science.gov (United States)

    Li, Yanmei; Wang, Xin; Shao, Yanqun; Tang, Dian; Wu, Bo; Tang, Zhongzhi; Lin, Wei

    2015-01-14

    The phase diagram of Ru-Ce-O was calculated by a combination of ab initio density functional theory and thermodynamic calculations. The phase diagram indicates that the solubility between ruthenium oxide and cerium oxide is very low at temperatures below 1100 K. Solid solution phases, if existing under normal experimental conditions, are metastable and subject to a quasi-spinodal decomposition to form a mixture of a Ru-rich rutile oxide phase and a Ce-rich fluorite oxide phase. To study the spinodal decomposition of Ru-Ce-O, Ru0.6Ce0.4O2 samples were prepared at 280 °C and 450 °C. XRD and in situ TEM characterization provide proof of the quasi-spinodal decomposition of Ru0.6Ce0.4O2. The present study provides a fundamental reference for the phase design of the Ru-Ce-O electro-catalyst. PMID:25418197

  9. 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.

  10. Surveillance on quality of turmeric powders vis a vis curcumin content and presence of extraneous color s from city markets of India

    OpenAIRE

    Dixit, Sumita; Purshottam, Shakendra; Khanna, Subhash K; Das, Mukul

    2009-01-01

    Abstract Curcumin, the principal curcuminoid of turmeric is responsible for its yellow colour and serves as a measure of quality of turmeric. The Prevention of Food Adulteration (PFA) Act of India allows only Curcuma longa L. for the production of turmeric powder and prohibits addition of any foreign matter/ artificial colour but does not specify minimum curcumin limit. Therefore, the present surveillance has been undertaken to study the quality of loose versus branded turmeric pow...

  11. CLIMATIC SEVERITY VICTIMS OF UPSTREAM WATER PIRACY STRONGLY EVIDENCING INLAND WATER DEPLETION-CAUSED GLOBAL WARMING VIS-A-VIS COOLING

    Directory of Open Access Journals (Sweden)

    Miah M. Adel

    2014-01-01

    Full Text Available Since the 80’s, the northwestern and the southwestern parts of the tropical Bangladesh located in the downstream Ganges basin have been having summer temperature above 109°F and winter temperature as low as 37°F. Every year people, particularly, the infants die from heat-and cold-related diseases and hospitals become packed-up with the victims of severe climatic condition. The objective of this research is to find the reason for the appearances of the extreme climate in certain parts of the country. Water bodies being reservoirs of heat, the condition of the rivers and other surface water resources has been examined. It is found that the continued water piracy at the upstream from the downstream Bangladesh Ganges discharge, the major source of water for the northwestern and southwestern parts, has depleted surface water resources and sunken the down the groundwater table. About 60% evaporation of the massively extracted groundwater to make up for the surface water shortage goes to merely increase the relative humidity without causing rainfall. Summer time lingering high temperature and high humidity cause the severity of summer weather. In the absence of the virgin surface water bodies, there is little room for storing heat for wintertime warming. The entire Ganges basin loses at least 10 times the heat it used to store in the water-abundant days. Summertime maximum temperature, HDDs and CDDs are negatively and wintertime minimum temperature is positive correlated with the decline of the Ganges’s discharge. Indian Government has to decommission her dams and barrages to mitigate the sufferings of the downstream people in Bangladesh. The greatest implication of this research is the accountability of the anthropogenic actions-caused depleting inland water bodies through storing, distribution via multi-channeling, irrigation, industrial and domestic use, for the occurrences of global heating vis-à-vis cooling and not CO2 and other greenhouse gases accumulation in space. Immediate international actions are needed to end the episode.

  12. CLIMATIC SEVERITY VICTIMS OF UPSTREAM WATER PIRACY STRONGLY EVIDENCING INLAND WATER DEPLETION-CAUSED GLOBAL WARMING VIS-A-VIS COOLING

    OpenAIRE

    Miah M. Adel; Mahmood R. Hossain; Saiyeeda F. Hossain

    2014-01-01

    Since the 80’s, the northwestern and the southwestern parts of the tropical Bangladesh located in the downstream Ganges basin have been having summer temperature above 109°F and winter temperature as low as 37°F. Every year people, particularly, the infants die from heat-and cold-related diseases and hospitals become packed-up with the victims of severe climatic condition. The objective of this research is to find the reason for the appearances of the extreme climate in certain ...

  13. 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...

  14. Estimation of Efficiency, Sustainability and Constraints in SRI (System of Rice Intensification) vis-a-vis Traditional Methods of Paddy Cultivation in North Coastal Zone of Andhra Pradesh

    OpenAIRE

    Rao, I.V.Y. Rama

    2011-01-01

    The study has assessed the economics and sustainability of SRI (system of rice intensification) and traditional methods of paddy cultivation in North Coastal Zone of Andhra Pradesh for the period 2008-09, based on the data of costs and returns of crop. Apart from budgeting techniques, benefit-cost ratio (BCR), yield gap analysis, sustainability index and response priority index have been employed in the study. It has shown that BCR is higher for SRI (1.76) than traditional (1.25) methods. Fur...

  15. 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.

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

    CERN Document Server

    Thaheld, Fred H

    2009-01-01

    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.

  17. Emerging powers vis-a-vis the established power in energy security. Challenge or opportunity for cooperation? The cases of Brazil, India and the U.S.A

    International Nuclear Information System (INIS)

    In recent years emerging powers like Brazil and India have been claiming to play a more active role in economic and political issues. The cooperation/non-cooperation topic among the various states/actors has been extensively studied in the past years. The project examines the way of cooperation between emerging and established powers. The analytical steps of the work include the identification of domestic preferences and security incentives, the presence of variables in governmental positions, the development of specific hypotheses and the discussion the their testing. Special attention is given to the nuclear policy field and the ethanol policy field for Brazil and India.

  18. Effect of supplementation of lysine producing microbes vis-a-vis source and level of dietary protein on performance and egg quality characteristics of post-peak layers

    Directory of Open Access Journals (Sweden)

    G. U. Manju

    2015-04-01

    Full Text Available Aim: The aim was to study the effect of supplementation of lysine producing microbes (LPM as an in vivo source of lysine on performance and egg quality characters of post-peak layers. Materials and Methods: BIS (1992 specified diets (except crude protein [CP] and lysine were prepared using either soybean meal (SBM or groundnut extractions (GNE or sunflower extractions (SFE with 16 and 15% CP resulting in six control diets. Further, each control diet was fortified with either synthetic lysine or LPM to meet BIS (1992 specified lysine requirement resulting in the set of 12 test diets. Each of the eighteen diets was offered to quadruplets groups of 4 post-peak (52 weeks commercial laying hens in each. The trial lasted for 119 days. Result: The results revealed that the feed consumption and body weight changes and Roche yolk color and yolk index were significantly (p ≤ 0.05 different among different treatments. However, egg production, feed efficiency, egg weight, egg shape index, Haugh unit score, albumen index and shell thickness, and net returns remained non-significant (p ≤ 0.05 among different treatments. Among main factors, protein level (16% and 15% CP made a significant (p ≤ 0.05 difference in egg production (79.6 and 75.1% and feed efficiency (2.64 and 2.81 kg feed/kg egg mass, respectively. Among protein source GNE- and SFE-based diet fed groups showed significantly (p < 0.0% higher feed consumption and body weight gain than SBM based diets fed birds. Yolk color (7.0, 7.3 and 7.3, respectively and yolk index (0.40, 0.38 and 0.43, respectively were significantly (p ≤ 0.05 different from the protein sources. CP level and Protein source interaction effects showed significant differences in albumen index and Haugh unit score. Conclusion: Optimum level of protein (16% CP and GNE as a source of protein tended to be superior in increasing the performance and egg characteristics of post-peak layers and supplementation of lysine in either synthetic or LPM form found to be beneficial in optimizing their performance.

  19. An ERP study of good production vis-a-vis poor perception of tones in Cantonese: implications for top-down speech processing.

    Directory of Open Access Journals (Sweden)

    Sam-Po Law

    Full Text Available This study investigated a theoretically challenging dissociation between good production and poor perception of tones among neurologically unimpaired native speakers of Cantonese. The dissociation is referred to as the near-merger phenomenon in sociolinguistic studies of sound change. In a passive oddball paradigm, lexical and nonlexical syllables of the T1/T6 and T4/T6 contrasts were presented to elicit the mismatch negativity (MMN and P3a from two groups of participants, those who could produce and distinguish all tones in the language (Control and those who could produce all tones but specifically failed to distinguish between T4 and T6 in perception (Dissociation. The presence of MMN to T1/T6 and null response to T4/T6 of lexical syllables in the dissociation group confirmed the near-merger phenomenon. The observation that the control participants exhibited a statistically reliable MMN to lexical syllables of T1/T6, weaker responses to nonlexical syllables of T1/T6 and lexical syllables of T4/T6, and finally null response to nonlexical syllables of T4/T6, suggests the involvement of top-down processing in speech perception. Furthermore, the stronger P3a response of the control group, compared with the dissociation group in the same experimental conditions, may be taken to indicate higher cognitive capability in attention switching, auditory attention or memory in the control participants. This cognitive difference, together with our speculation that constant top-down predictions without complete bottom-up analysis of acoustic signals in speech recognition may reduce one's sensitivity to small acoustic contrasts, account for the occurrence of dissociation in some individuals but not others.

  20. 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. PMID:27450758

  1. 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.

  2. Valuation of Strength of Structural Steel Angle Sections, under IS Code: 800-1984--A Case Study with Equal vis-a-vis Unequal Angles

    OpenAIRE

    Manoj Kumar Varshaney

    2015-01-01

    International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computa...

  3. Valuation of Strength of Structural Steel Angle Sections, under IS Code: 800-1984--A Case Study with Equal vis-a-vis Unequal Angles

    Directory of Open Access Journals (Sweden)

    Manoj Kumar Varshaney

    2015-12-01

    Full Text Available International Journal of Engineering Research and Applications (IJERA is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.

  4. 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...

  5. Genotypic variation in grain weight vis-a-vis variation in incorporation of 14C- sucrose in lipid fractions of wheat endosperm

    International Nuclear Information System (INIS)

    Small grain weight in rye as compared to wheat was found to be associated with low incorporation of 14C sucrose in non-starch endosperm lipid fraction (NSELF). It was observed that the synthetic components regulating grain weight showed a positive correlation with NSELF and phospholipid per grain. In the present investigation these aspect have been studied in three wheat genotypes widely differing in grain weight and two of them possess high grain weight. 7 refs., 2 tabs

  6. Efficacy of Seabuckthorn (Hippophae rhamnoides) Oil vis-a-vis Other Standard Drugs for Management of Gastric Ulceration and Erosions in Dogs.

    Science.gov (United States)

    Dogra, Richa; Tyagi, S P; Kumar, Amit

    2013-01-01

    The study was conducted on 20 adult healthy medium-sized mongrel dogs. Injection of dexamethasone @ 1 mg/kg, IV, b.i.d., was administered to create gastric ulcerations and erosions. Thereafter all the animals were randomly divided into 5 equal treatment groups. Animals of groups I, II, III, IV, and V were treated with oral administration of lansoprazole @ 1.5 mg/kg, sucralfate @ 1 g/animal, misoprostol @ 10 µg/kg, famotidine @ 1 mg/kg, and Seabuckthorn seed oil @ 5 mL/animal, twice a day, respectively. Gastroendoscopically, complete healing of GUE lesions was earliest in Seabuckthorn- (SBT-) oil-treated group (7.5 ± 0.87) followed by famotidine (8.25 ± 1.44), lansoprazole (9.00 ± 1.23), misoprostol (10.50 ± 1.50), and sucralfate (13.50 ± 0.87), respectively. A marked improvement in appetite was observed in all animals. Melena was continued till day 3 in SBT group, day 6 in lansoprazole- and famotidine-treated animals, and day 9 in sucralfate and misoprostol group animals. Fecal occult blood test was positive in all animals till there was endoscopic evidence of gastric bleeding. Hematological parameters improved markedly towards the end of the study. Serum biochemical parameters remained within normal physiological limits throughout the study. It is concluded that Seabuckthorn oil was the best therapeutic agent for dexamethasone-induced GUE in dogs followed by famotidine, lansoprazole, misoprostol, and sucralfate. PMID:23853738

  7. Analysis of the determining factors in the attitude of an organ of information vis-a-vis the development of nuclear energy

    International Nuclear Information System (INIS)

    The report is devoted to the study of the role of the media, in France, confronted with the nuclear debate. It has been developed through two distinct and complementary approaches, which are illustrative of the possible attitudes towards the research on media impacts. The first approach deals with a systematic qualitative and quantitative review of the various French newspapers (national and regional). With the help of a sample of events running from January 68 to August 76, this study aims at a classification of the periodicals according to their behaviour towards the nuclear issues. It also tries to make assumptions on the role of the press in the public opinion regarding that matter. The second approach follows an inverse scope. By using the result of a survey on a representative sample of French adult population, regarding the nuclear debate, this study concentrates on the individuals as readers of different newspapers. On an other side, individuals are characterized according to their answers to a series of arguments about nuclear energy. In order to precise the impact of the press, this study puts into emphasis the degree of coherence between the general ideological position and the arguments on nuclear. It is proposed to interpret the discrepancies observed in terms of differential media impacts

  8. The remarkable activity and stability of a highly dispersive beta-brass Cu-Zn catalyst for the production of ethylene glycol

    Science.gov (United States)

    Li, Molly Meng-Jung; Zheng, Jianwei; Qu, Jin; Liao, Fenglin; Raine, Elizabeth; Kuo, Winson C. H.; Su, Shei Sia; Po, Pang; Yuan, Youzhu; Tsang, Shik Chi Edman

    2016-02-01

    Incorporation of Zn atoms into a nanosize Cu lattice is known to alter the electronic properties of Cu, improving catalytic performance in a number of industrially important reactions. However the structural influence of Zn on the Cu phase is not well studied. Here, we show that Cu nano-clusters modified with increasing concentration of Zn, derived from ZnO support doped with Ga3+, can dramatically enhance their stability against metal sintering. As a result, the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol, an important reaction well known for deactivation from copper nanoparticle sintering, can show greatly enhanced activity and stability with the CuZn alloy catalysts due to no noticeable sintering. HRTEM, nano-diffraction and EXAFS characterization reveal the presence of a small beta-brass CuZn alloy phase (body-centred cubic, bcc) which appears to greatly stabilise Cu atoms from aggregation in accelerated deactivation tests. DFT calculations also indicate that the small bcc CuZn phase is more stable against Cu adatom migration than the fcc CuZn phase with the ability to maintain a higher Cu dispersion on its surface.

  9. The remarkable activity and stability of a highly dispersive beta-brass Cu-Zn catalyst for the production of ethylene glycol

    Science.gov (United States)

    Li, Molly Meng-Jung; Zheng, Jianwei; Qu, Jin; Liao, Fenglin; Raine, Elizabeth; Kuo, Winson C. H.; Su, Shei Sia; Po, Pang; Yuan, Youzhu; Tsang, Shik Chi Edman

    2016-01-01

    Incorporation of Zn atoms into a nanosize Cu lattice is known to alter the electronic properties of Cu, improving catalytic performance in a number of industrially important reactions. However the structural influence of Zn on the Cu phase is not well studied. Here, we show that Cu nano-clusters modified with increasing concentration of Zn, derived from ZnO support doped with Ga3+, can dramatically enhance their stability against metal sintering. As a result, the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol, an important reaction well known for deactivation from copper nanoparticle sintering, can show greatly enhanced activity and stability with the CuZn alloy catalysts due to no noticeable sintering. HRTEM, nano-diffraction and EXAFS characterization reveal the presence of a small beta-brass CuZn alloy phase (body-centred cubic, bcc) which appears to greatly stabilise Cu atoms from aggregation in accelerated deactivation tests. DFT calculations also indicate that the small bcc CuZn phase is more stable against Cu adatom migration than the fcc CuZn phase with the ability to maintain a higher Cu dispersion on its surface. PMID:26856760

  10. Radiation stability of a hydrogen getter material (DPPE). [Dimerized phenyl propargyl ether containing Pd on CaCO/sub 3/ catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kazanjian, A.R.

    1976-10-18

    An investigation was made on a hydrogen getter material (DPPE) to determine its radiation stability. Such material has potential for nuclear industry applications. The material is composed of 75 percent of an unsaturated organic compound (1,6-diphenoxy-2,4-hexadiyne) and 25 percent catalyst (5 percent palladium on calcium carbonate). The radiation stability of this material and of the hydrogenated product was determined by exposing them to gamma radiation in air and vacuum and analyzing for radiolysis products and hydrogen capacity. The major products formed were phenol and carbon dioxide. Numerous solid compounds were also formed in much smaller yields. Product yields were much larger in air than in vacuum. Hydrogen uptake curves showed that the hydrogen capacity decreased appreciably after an absorbed dose of about 10/sup 8/ rads, and that irradiation is more detrimental in air than in vacuum. (For SI (metric) use: rads have been replaced by grays (Gy) and 1 gray = 1 joule per kilogram, and 10/sup 8/ rads = 1 megajoule per kilogram.)

  11. 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

  12. Toward Inexpensive Photocatalytic Hydrogen Evolution: A Nickel Sulfide Catalyst Supported on a High-Stability Metal-Organic Framework.

    Science.gov (United States)

    Peters, Aaron W; Li, Zhanyong; Farha, Omar K; Hupp, Joseph T

    2016-08-17

    Few-atom clusters composed of nickel and sulfur have been successfully installed into the Zr(IV)-based metal-organic framework (MOF) NU-1000 via ALD-like chemistry (ALD = atomic layer deposition). X-ray photoelectron spectroscopy and Raman spectroscopy are used to determine that primarily Ni(2+) and S(2-) sites are deposited within the MOF. In a pH 7 buffered aqueous solution, the porous catalyst is able to produce H2 gas at a rate of 3.1 mmol g(-1) h(-1) upon UV irradiation, whereas no H2 is generated by irradiating bare NU-1000. Upon visible light irradiation, little H2 generation was observed; however, with the addition of an organic dye, rose bengal, NiS-AIM can catalyze the production of H2 at an enhanced rate of 4.8 mmol g(-1) h(-1). These results indicate that ALD in MOFs (AIM) can engender reactivity within high surface area supports for applications in the solar fuels field. PMID:27487409

  13. Periodic density functional theory studies of the VOx/TiO2 (anatase) catalysts: Structure and stability of monomeric species

    Science.gov (United States)

    Du, Yu-Jue; Li, Zhen Hua; Fan, Kang-Nian

    2012-06-01

    Periodic density functional theory has been utilized to investigate the structure and stability of monomeric HVOx species on anatase support. The three most stable surfaces of anatase were investigated, namely the (001), (100) and (101) surfaces. Unlike previous theoretical studies it was found that on the (001) surface vanadia species with five-coordinated vanadium atom are more stable than those with tetrahedrally coordinated vanadium atom. On the other hand, on the (100) and (101) surfaces, the vanadium atom in the vanadia species is still tetrahedrally coordinated. The stability of different VOx/TiO2 structures which are not fully dehydrated has been systematically studied and the results show that the vanadia species on the three surfaces follow an order of TiO2 (001) > TiO2 (100) > TiO2 (101). This can be understood from the acidity and basicity of the three anatase surfaces. The results suggest that monomeric VOx species may be better stabilized if the support exposes more (001) surfaces. Our analyses on electronic structure of the most stable VOx/TiO2 structure (D001) suggest that its bridging V-O-Ti oxygen atoms may have higher reactivity than the terminal vanadyl oxygen atoms.

  14. Activity and stability studies of titanates and titanate-carbon nanotubes supported Ag anode catalysts for direct methanol fuel cell

    Science.gov (United States)

    Mohamed, Mohamed Mokhtar; Khairy, M.; Eid, Salah

    2016-02-01

    Titanate-SWCNT; synthesized via exploiting the interaction between TiO2 anatase with oxygen functionalized SWCNT, supported Ag nanoparticles and Ag/titanate are characterized using XRD, TEM-EDX-SAED, N2 adsorption, Photoluminescence, Raman and FTIR spectroscopy. These samples are tested for methanol electrooxidation via using cyclic voltammetry (CV) and impedance measurements. It is shown that Ag/titanate nanotubes exhibited superior electrocatalytic performance for methanol oxidation (4.2 mA cm-2) than titanate-SWCNT, Ag/titanate-SWCNT and titanate. This study reveals the existence of a strong metal-support interaction in Ag/titanate as explored via formation of Ti-O-Ag bond at 896 cm-1 and increasing surface area and pore volume (103 m2 g-1, 0.21 cm3 g-1) compared to Ag/titanate-SWCNT (71 m2 g-1, 0.175 cm3 g-1) that suffers perturbation and defects following incorporation of SWCNT and Ag. Embedding Ag preferably in SWCNT rather than titanate in Ag/titanate-SWCNT disturbs the electron transfer compared to Ag/titanate. Charge transfer resistance depicted from Nyquist impedance plots is found in the order of titanate > Ag/titanate-SWCNT > titanate-SWCNT > Ag/titanate. Accordingly, Ag/titanate indicates a slower current degradation over time compared to rest of catalysts. Conductivity measurements indicate that it follows the order Ag/titanate > Ag/titanate-SWCNT > titanate > titanate-SWCNT declaring that SWCNT affects seriously the conductivity of Ag(titanate) due to perturbations caused in titanate and sinking of electrons committed by Ago through SWCNT.

  15. Stability of cantilevered coaxial shells with internal and annular flow

    International Nuclear Information System (INIS)

    This paper is a theoretical study of the stability of cantilevered coaxial cylindrical shells conveying incompressible fluid in the annular space in- between and within the inner shell. The viscous effects of the mean flow are taken into account, but the perturbations of the equilibrium state on the basis of which stability is assessed is carried out by means of potential flow theory, thus neglecting unsteady viscous effects which are known to become important for narrow annular flows. Shell displacements are described by Flugge's equations of motion. Solution of the coupled fluid-structure equations is carried out by means of the Fourier Transform Method. The main finding of this research is that stability is lost by flutter for internal flow, according to both the inviscid and viscous variants of the theory; for annular flow, however, whereas inviscid theory predicts loss of stability by flutter, viscous theory (with dissipative effects included) predicts that the shell loses stability by divergence and then, at appreciably higher flow, by flutter. Reduction of the annular gap generally destabilizes the system; while increased steady viscous effects slightly stabilize the system for internal flow, they strongly destabilize it for annular flow. Increasing the length of the shell destabilizes the system for both internal and annular flows. The presence of internal flow in addition to annular flow tends to stabilize the system vis-a-vis the case of annular flow, but only at low flow velocities, having the opposite effect at higher flows; the same effects arise when the main flow is internal and an annular flow added to the system

  16. 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. PMID:25370739

  17. Rate-limiting mechanisms in high-temperature growth of catalyst-free InAs nanowires with large thermal stability.

    Science.gov (United States)

    Hertenberger, S; Rudolph, D; Becker, J; Bichler, M; Finley, J J; Abstreiter, G; Koblmüller, G

    2012-06-15

    We identify the entire growth parameter space and rate-limiting mechanisms in non-catalytic InAs nanowires (NWs) grown by molecular beam epitaxy. Surprisingly huge growth temperature ranges are found with maximum temperatures close to ~600°C upon dramatic increase of V/III ratio, exceeding by far the typical growth temperature range for catalyst-assisted InAs NWs. Based on quantitative in situ line-of-sight quadrupole mass spectrometry, we determine the rate-limiting factors in high-temperature InAs NW growth by directly monitoring the critical desorption and thermal decomposition processes of InAs NWs. Both under dynamic (growth) and static (no growth, ultra-high vacuum) conditions the (111)-oriented InAs NWs evidence excellent thermal stability at elevated temperatures even under negligible supersaturation. The rate-limiting factor for InAs NW growth is hence dominated by In desorption from the substrate surface. Closer investigation of the group-III and group-V flux dependences on growth rate reveals two apparent growth regimes, an As-rich and an In-rich regime defined by the effective As/In flux ratio, and maximum achievable growth rates of > 6 µm h(-1). The unique features of high-T growth and excellent thermal stability provide the opportunity for operation of InAs-based NW materials under caustic environment and further allow access to temperature regimes suitable for alloying non-catalytic InAs NWs with GaAs. PMID:22595881

  18. 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.

  19. Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

    OpenAIRE

    Samira Bagheri; Nurhidayatullaili Muhd Julkapli; Sharifah Bee Abd Hamid

    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 nanopa...

  20. 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.

  1. 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.

  2. 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.

  3. First principles study of structural stability and site preference in Co3 (W,X

    Directory of Open Access Journals (Sweden)

    Joshi Sri Raghunath

    2014-01-01

    Full Text Available Since the discovery [1] of γ′ precipitate (L12 – Co3(Al, W in the Co-Al-W ternary system, there has been an increased interest in Co-based superalloys. Since these alloys have two phase microstructures (γ + γ′ similar to Ni-based superalloys [2], they are viable candidates in high temperature applications, particularly in land-based turbines. The role of alloying on stability of the γ′ phase has been an active area of research. In this study, electronic structure calculations were done to probe the effect of alloying in Co3W with L12 structure. Compositions of type Co3(W,X, (where X/Y = Mn, Fe, Ni, Pt, Cr , Al, Si, V, W, Ta, Ti, Nb, Hf, Zr and Mo were studied. Effect of alloying on equilibrium lattice parameters and ground state energies was used to calculate Vegard's coefficients and site preference related data. The effect of alloying on the stability of the L12 structure vis a vis other geometrically close packed ordered structures was also studied for a range of Co3X compounds. Results suggest that the penchant of element for the W sublattice can be predicted by comparing heats of formation of Co3X in different structures.

  4. Improvement of the stability of basic mixed oxides used as catalysts for aldol condensation of bio-derived compounds by palladium addition

    International Nuclear Information System (INIS)

    Aqueous-phase aldol condensation of biomass-derived ketones and aldehydes is a key step in the preparation of fuels and chemicals from renewable resources. Furfural–acetone aldol condensation yielding C8 and C13 adducts was studied at 323 K and 1 MPa in a stirred batch reactor. We propose a new strategy for minimizing catalytic deactivation, consisting of modifying catalysts (MgO–ZrO2 and MgO–Al2O3) by Pd addition (2%). This modification slightly changes the morphology and surface chemistry of the supports, leading to changes on the catalysts performance but not reaction mechanism modifications. If condensation is performed in hydrogen atmosphere, the partial hydrogenation of the condensation adducts increases its water solubility, minimizing catalyst deactivation. In that way, the selectivity for C13 adduct decreases only 25% between two successive reaction cycles using Pd/MgO–ZrO2 catalyst, whereas this decrease is of 90% for the un-doped mixed oxides. These effects are less marked for the MgO–Al2O3 catalyst. Highlights: •Furfural and acetone aldolization on Pd/MgO–ZrO2 and Pd/MgO–Al2O3. •Conversion and selectivity towards C8 and C13 low and unstable catalysts. •Aldolization in H2 decreases coke formation: higher reusability of the catalysts

  5. 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.

  6. Bimetallic Catalysts.

    Science.gov (United States)

    Sinfelt, John H.

    1985-01-01

    Chemical reaction rates can be controlled by varying composition of miniscule clusters of metal atoms. These bimetallic catalysts have had major impact on petroleum refining, where work has involved heterogeneous catalysis (reacting molecules in a phase separate from catalyst.) Experimentation involving hydrocarbon reactions, catalytic…

  7. 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.

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

    Science.gov (United States)

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

    2016-04-01

    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 mA cm-2 at a potential of 0 V versus RHE under 1-sun illumination at pH 13. The calculated turnover number for the catalyst during a 20-h period is 139,000, with an average turnover frequency of 1.9 s-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.

  9. 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.

  10. 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)

  11. 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. PMID:27483762

  12. 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.

  13. The role of carbonaceous deposits in the activity and stability of Ni-based catalysts applied in the dry reforming of methane

    OpenAIRE

    Düdder, H.; Kähler, K.; Krause, B. (Bernd); Mette, K.; S. Kühl; Behrens, M.; Scherer, V.; Muhler, M.

    2014-01-01

    Highly stable Ni catalysts with varying Ni contents up to 50 mol% originating from hydrotalcite-like precursors were applied in the dry reforming of methane at 800 and 900 °C. The integral specific rate of methane conversion determined after 10 h on stream was 3.8 mmol s-1 gcat-1 at 900 °C. Due to the outstanding high activity, a catalyst mass of just 10 mg had to be used to avoid operating the reaction in thermodynamic equilibrium. The resulting WHSV was as high as 1.44 × 106 ml gcat-1 h-1. ...

  14. Preparation and characterization of Pt catalysts supported on TiO2 and ZrO2 stabilized with La2O3 for the elimination of nitric oxide

    International Nuclear Information System (INIS)

    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 (TiO2) and zirconia (ZrO2) which were stabilized with 10 % in mole of lanthanum (La2O3), 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)

  15. 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.

  16. 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.

  17. Highly Selective Ruthenium Metathesis Catalysts for Ethenolysis

    OpenAIRE

    Thomas, Renee M.; Keitz, Benjamin K.; Champagne, Timothy M.; Grubbs, Robert H.

    2011-01-01

    N-aryl, N-alkyl N-heterocyclic carbene (NHC) ruthenium metathesis catalysts are highly selective toward the ethenolysis of methyl oleate, giving selectivity as high as 95% for the kinetic, ethenolysis products over the thermodynamic, self-metathesis products. The examples described herein represent some of the most selective NHC-based ruthenium catalysts for ethenolysis reactions to date. Furthermore, many of these catalysts show unusual preference and stability toward propagating as a methyl...

  18. Thermal and redox stability of PdZn catalysts in vacuum and during methanol adsorption studied by In-situ XPS

    Energy Technology Data Exchange (ETDEWEB)

    Dumbuya, Karifala; Denecke, Reinhard; Steinrueck, H.P. [Lehrstuhl fuer Physikalische Chemie II, Universitaet Erlangen-Nuernberg, Erlangen (Germany)

    2007-07-01

    We have investigated the thermal and redox behaviour of the technically important methanol steam reforming PdZn catalysts between 300-700 K in UHV and during MeOH dosage at 300 K for pressures up to 0.1 mbar. We compare samples from a washcoating process before and after the reduction to PdZn. In both cases, we observed significant structural changes upon heating in the Zn 2p, Pd 3d and O 1s regions, respectively, in agreement with studies on Pd(111). However, annealing both samples to 700 K led to a significant drop in intensity of the Zn 2p signals, indicating alloy destruction in UHV, accompanied by the emergence of large Mg peaks, which are further enhanced by H{sub 2} exposure of the surfaces at this temperature. The resulting surface was exposed to MeOH background pressures (1.2.10{sup -6}-0.1 mbar) at 300 K and C 1s, O 1s, Pd 3d and Zn 2p spectra were collected. A comparison with similar results on fully intact catalysts 3 show slightly different adsorption behaviour of MeOH. This is relevant, because Mg is known to affect the oxidative methanol steam reforming on Pd/ZnO catalysts.

  19. Nanometals and colloids as catalyst precursors

    Energy Technology Data Exchange (ETDEWEB)

    Boennemann, H.H. [Max-Planck-Institut fuer Kohlenforschung (Germany)

    1995-12-01

    Mono- or plurimetallic nanometals and colloids stabilized by surfactant molecules are discussed as pre-prepared precursors for heterogeneous catalysts. This {open_quotes}precursor concept{close_quotes} provides a novel access to supported metal catalysts having active components of controlled particle size, intermetallic ratio and particle structure on surfaces. Possible applications will also be presented.

  20. Catalyst Architecture

    DEFF Research Database (Denmark)

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

    2014-01-01

    How can architecture promote the enriching experiences of the tolerant, the democratic, and the learning city - a city worth living in, worth supporting and worth investing in? Catalyst Architecture comprises architectural projects, which, by virtue of their location, context and their combination...... 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...

  1. 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.

  2. 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

    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......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...

  3. Modified iron-carbon as heterogeneous electro-Fenton catalyst for organic pollutant degradation in near neutral pH condition: Characterization, degradation activity and stability

    International Nuclear Information System (INIS)

    Polytetrafluoroethylene (PTFE) was firstly used to modify the surface characteristics of Fe-C particles and acted as catalyst to degrade 2,4-dichlorophenol (2,4-DCP) by heterogeneous electro-Fenton (EF) in near neutral pH condition. Fe-C particles before and after PTFE modification, and after 15 times consecutive degradations were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectrometry. The modified Fe-C exhibited a good activity for degradation of 120 mg/L 2,4-DCP in near neutral pH condition, achieving over 95% removal efficiency within 120 min under the conditions of Fe-C 6 g/L, current intensity 100 mA and initial pH 6.7. In this heterogeneous EF system, a significant synergetic effect between anodic oxidation and single Fe-C micro-electrolysis was obtained, which attributed to the effective EF oxidation at favorable acidic pH condition that triggered by anodic oxidation. 15 times consecutive runs demonstrated the 2,4-DCP degradation efficiency was stable while the iron leaching ratio was relatively low. Account for the catalytic activity, life span and inexpensive cost, the PTFE modified Fe-C was potential for industrial application as a good electro-Fenton catalyst to abate biorefractory pollutants in neutral pH condition

  4. Synthesis and stability of L-tryptophan adsorbed on Ti/MCM-41 as a catalyst for the regioselective aminolysis of styrene oxide

    Science.gov (United States)

    Aghapoor, Kioumars; Amini, Mostafa M.; Jadidi, Khosrow; Mohsenzadeh, Farshid; Darabi, Hossein Reza; Sayahi, Hani; Jalali, Mohammad Reza

    2015-11-01

    L-tryptophan is adsorbed on the titania surface of Ti/MCM-41 (L-tryp≡Ti/MCM-41) as a novel material via two steps. Ti/MCM-41 was first prepared by grafting TiCl4 on activated MCM-41 mesoporous silica in an anhydrous THF. Subsequent adsorption of L-tryptophan on the surface of grafted Ti sites from an aqueous solution afforded L-tryp≡Ti/MCM-41. Characterization of the material was carried out with thermogravimetric and differential thermogravimetric analyses, powder X-ray diffraction, BET and BJH nitrogen adsorption-desorption methods, Fourier transform infrared, UV-Visible, and energy dispersive X-ray spectroscopes. The results indicate that the adsorption of L-tryptophan on the surface of Ti/MCM-41 occurred. L-tryp≡Ti/MCM-41 was applied successfully as a heterogeneous catalyst for the ring opening of styrene oxide with aniline derivatives and demonstrated high to excellent activity and regioselectivity under microwave irradiation and solvent-free conditions. This thermal-resistant catalyst can be recycled at least five times without appreciable loss of activity, which confirms the strong adsorption of L-tryptophan on Ti/MCM-41.

  5. 固定化细胞磁稳定流化床反应器制备生物柴油%Biodiesel production in magnetically stabilized fluidized bed reactor by whole-cell bio-catalyst

    Institute of Scientific and Technical Information of China (English)

    李丽萍; 陈冠益; 黄业千

    2011-01-01

    为了探索生物酶法制备生物柴油新工艺,克服现有工艺的不足,采用超顺磁性全细胞催化剂在自制的磁稳定流化床中对废油脂连续生产生物柴油进行了试验研究.考察了改变磁场强度、进料醇油摩尔比、催化剂用量及流量等因素对连续酯交换反应的影响,进而得到单级磁流化床酯交换反应的最佳工艺条件:磁稳态操作,醇油摩尔比为1∶1,催化剂用量为原料油质量的12%,进料流量为42.6 mL/min.四级磁流化床连续系统最终转酯化率达到85%以上,连续反应200 h后四级出口的甲酯产率仍在80%以上.这说明全细胞催化剂在磁稳定流化床中活性较高,使用寿命较长,该系统具有良好的操作稳定性.%An experimental study of biodiesel production in a self-made magnetically fluidized bed by superparamagnetic whole-cell catalyst was conducted. By changing the magnetic field strength, methanol to oil molar ratio, catalyst concentration, flow rate and other factors, effects of different factors on the continuous transesterification reaction had been found. The optimized factors of single-stage fluidized bed catalytic transesterification of waste oil were using magnetic steady-state operation, methanol to oil molar ratio of 1:1, quantity of catalyst with 12% of oil and the feed rate of 42.6 mL/min. The final methyl ester production rate of the four-stage continuous magnetically fluidized bed reactor system was over 85%. Even after 200 h continuous operation, the production rate of the forth export was more than 80 %.The results showed that the whole-cell catalyst in the magnetically fluidized bed had high activity and long service life, the system had a good operational stability.

  6. 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)

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

    OpenAIRE

    Berger, R.J.; Doesburg, E.B.M.; Ommen, van, B.; 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 order to find suitable types of nickel catalysts and to obtain more knowledge about the deactivation mechanism(s) occurring during internal reforming, a series of nickel catalysts was prepared and subj...

  8. Novel Reforming Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, Lisa D; Haller, Gary L

    2012-10-16

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

  9. Collaboration between primitive cell membranes and soluble catalysts

    OpenAIRE

    Adamala, Katarzyna P.; Engelhart, Aaron E.; SZOSTAK, JACK W.

    2016-01-01

    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 Mg2+, which is required for ribozyme...

  10. Ruthenium(0) nanoclusters stabilized by a Nanozeolite framework: isolable, reusable, and green catalyst for the hydrogenation of neat aromatics under mild conditions with the unprecedented catalytic activity and lifetime.

    Science.gov (United States)

    Zahmakiran, Mehmet; Tonbul, Yalçin; Ozkar, Saim

    2010-05-12

    The hydrogenation of aromatics is a ubiquitous chemical transformation used in both the petrochemical and specialty industry and is important for the generation of clean diesel fuels. Reported herein is the discovery of a superior heterogeneous catalyst, superior in terms of catalytic activity, selectivity, and lifetime in the hydrogenation of aromatics in the solvent-free system under mild conditions (at 25 degrees C and 42 +/- 1 psig initial H(2) pressure). Ruthenium(0) nanoclusters stabilized by a nanozeolite framework as a new catalytic material is reproducibly prepared from the borohydride reduction of a colloidal solution of ruthenium(III)-exchanged nanozeolites at room temperature and characterized by using ICP-OES, XRD, XPS, DLS, TEM, HRTEM, TEM/EDX, mid-IR, far-IR, and Raman spectroscopy. The resultant ruthenium(0) nanoclusters hydrogenate neat benzene to cyclohexane with 100% conversion under mild conditions (at 25 degrees C and 42 +/- 1 psig initial H(2) pressure) with record catalytic activity (initial TOF = 5430 h(-1)) and lifetime (TTO = 177 200). They provide exceptional catalytic activity not only in the hydrogenation of neat benzene but also in the solvent-free hydrogenation of methyl substituted aromatics such as toluene, o-xylene, and mesitylene under otherwise identical conditions. Moreover, they are an isolable, bottleable, and reusable catalyst in the hydrogenation of neat aromatics. When the isolated ruthenium(0) nanoclusters are reused, they retain 92% of their initial catalytic activity even for the third run in the hydrogenation of neat benzene under the same conditions as those of the first run. The work reported here also includes (i) far-infrared spectroscopic investigation of nanozeolite, ruthenium(III)-exchanged-nanozeolite, and ruthenium(0) nanoclusters stabilized by a nanozeolite framework, indicating that the host framework remains intact after the formation of a nanozeolite framework stabilized ruthenium(0) nanoclusters; (ii) the

  11. 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。

  12. Overproduction of the Escherichia coli Chaperones GroEL-GroES in Rhodococcus ruber Improves the Activity and Stability of Cell Catalysts Harboring a Nitrile Hydratase.

    Science.gov (United States)

    Tian, Yuxuan; Chen, Jie; Yu, Huimin; Shen, Zhongyao

    2016-02-01

    Three combinations of molecular chaperones from Escherichia coli (i.e., DnaK-DnaJ-GrpEGroEL- GroES, GroEL-GroES, and DnaK-DnaJ-GrpE) were overproduced in E. coli BL21, and their in vitro stabilizing effects on a nitrile hydratase (NHase) were assessed. The optimal gene combination, E. coli groEL-groES (ecgroEL-ES), was introduced into Rhodococcus ruber TH3. A novel engineered strain, R. ruber TH3G was constructed with the native NHase gene on its chromosome and the heterologous ecgroEL-ES genes in a shuttle plasmid. In R. ruber TH3G, NHase activity was enhanced 37.3% compared with the control, TH3. The in vivo stabilizing effect of ecGroEL-ES on the NHase was assessed using both acrylamide immersion and heat shock experiments. The inactivation behavior of the in vivo NHase after immersion in a solution of dynamically increased concentrations of acrylamide was particularly evident. When the acrylamide concentration was increased to 500 g/l (50%), the remaining NHase activity in TH3G was 38%, but in TH3, activity was reduced to 10%. Reactivation of the in vivo NHases after varying degrees of inactivation was further assessed. The activity of the reactivated NHase was more than 2-fold greater in TH3G than in TH3. The hydration synthesis of acrylamide catalyzed by the in vivo NHase was performed with continuous acrylonitrile feeding. The final concentration of acrylamide was 640 g/l when catalyzed by TH3G, compared with 490 g/l acrylamide by TH3. This study is the first to show that the chaperones ecGroEL-ES work well in Rhodococcus and simultaneously possess protein-folding assistance functions and the ability to stabilize and reactivate the native NHases. PMID:26562693

  13. Characterization and Dehydrogenation Activity of SBA-15 and HMS Supported Chromia Catalysts

    Institute of Scientific and Technical Information of China (English)

    YUE,Hong-Yong(乐洪咏); ZHENG,Bo(郑波); YUE,Ying-Hong(乐英红); ZHANG,Xue-Zheng(张雪峥); HUA,Wei-Ming(华伟明); GAO,Zi(高滋)

    2002-01-01

    SBA-15 and HMS supported chromia catalysts were prepared and characterized. Chromia is highly dispersed on the mesoporous supports when its loading is ≤7 wt%. The supported catalysts display high activity, selectivity and stability for dehydrogenation of ethyibenzene and propane. ESR measurement of the catalysts before and after reaction shows that the active species for dehydrogenation reaction might be Cr3 + species on the catalyst surface, and the activity of the catalyst is probably correlated with the dispersion of Cr3+ species.

  14. 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

  15. 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.)

  16. ‘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.

  17. El desarrollo de América Latina: vis a vis la estrategia de desarrollo del Japón y la Cuenca del Pacífico

    OpenAIRE

    López Villafañe, Víctor

    1993-01-01

    Partiendo de un análisis comparativo de las economías de la Cuenca del Pacífico y América Latina, el autor, describe los caminos contrapuestos que han tomado estas regiones. Una hacia el desarrollo y el bienestar y la otra hacia la desindustrialización, el endeudamiento y la pobreza. Los interesantes datos estadísticos aportados permiten apreciar con claridad una serie de fenómenos de tipo económico y político que suceden en las regiones estudiadas. El hecho que el 40% de las transacciones co...

  18. The April 25 Incident and Its Implications: A Study of the Buddhist Cult "Falun Gong" vis-a-vis the CCP's Ideological Education Work Among the Youth in a Period of Dramatic Economic Reforms

    OpenAIRE

    Xiao, Hongyan

    2000-01-01

    How did Falun Gong strike such a deep chord in so many Chinese people and find such a fertile ground for recruitment? This paper studies the nature of Falun Gong, and attempts to address issues concerning the Chinese Communist Party’s (CCP) ideological work on the Chinese youth, and crisis of faith among the Chinese people brought forth by economic reforms in recent years. The hypothesis is: the CCP’s reemphasis on ideological education only aggravates the crisis of faith among the youth beca...

  19. 全球化背景下的高等教育领域中的政府角色变迁%The changing role of the state vis-a-vis higher education in a global context

    Institute of Scientific and Technical Information of China (English)

    卢乃桂; 张永平

    2008-01-01

    上个世纪80年代以来,世界各国的高等教育领域都发生了一系列改革,旨在重构政府、高校以及学生之间关系.许多同家的高等教育系统都不同程度地受到了市场力量的影响.与此同时,传统的国家和高等教育的关系也发生了重大变化.将高等教育领域的这一新变化放在更宏观的大时代背景下,即全球化的历史背景下来探讨其成因,并描述在此新背景下政府扮演的新角色是什么,以及政府角色转变背后的实质又是什么.最后,通过选择几个较为典型的国家,分析了在这种类似实质背后各国政府角色变迁的个性化特征.%Since the 1980s, a series of reforms that aimed to reconstruct the relationships among the government, the university, and the student (consumer) have been initiated in the systems of higher education. In varying degrees, these systems of higher education were affected by market forces. Given this, the relationship between the state and higher education has also been changed significantly. The purpose of this paper is to view recent changes in higher education in the historic context of globalization. It attempts to trace the source of these changes and to depict,Against a new backgroud, the new role of the state vis-avis higher education.It also seeks to illuminate the rationale behind the changing role of the state. By using the experiences of selected countries as illustrations, this paper will discuss the salient features of the state's role change in various contexts.

  20. ED-XRF spectrometry-based trace element composition of genetically engineered rhizoclones vis-a-vis natural roots of a multi-medicinal plant, butterfly pea (Clitoria ternatea L.)

    International Nuclear Information System (INIS)

    The energy dispersive X-ray fluorescence set-up incorporating a molybdenum secondary exciter was used for quantitative determination of major and minor elements in genetically transformed root somaclones (rhizoclones) of butterfly pea (Clitoria ternatea L.) which had been established via explant co-cultivation with Agrobacterium rhizogenes. The multi-elemental composition of these transformed rhizoclones was compared with that of the naturally grown in vivo donor plant. Trace elements namely Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Rb, Sr and Pb in addition to two macro-elements K and Ca were identified and quantified in root tissues of both sources. The elemental content of transformed root cultures was found to be at par with that of the natural roots of in vivo grown plants of the same species. These findings are implicated on the context of utilization of such Agrobacterium-mediated genetically transformed root cultures as a viable alternative to natural roots, the former being a fast-proliferating renewable resource of medicinally useful minerals essential for designing of effective drugs, besides providing an ex situ means for plant conservation. (author)

  1. Creative Art and Cinematographic Production Vis-a-Vis the State in Europe. International Colloquy Organised by the European Art and Experimental Cinema Association in Collaboration with the Council of Europe. Cultural Policy Studies Series 3.

    Science.gov (United States)

    Lescure, Jean; Degand, Claude

    Various aspects of the role of the state in fostering creative art and cinematography are discussed in the two reports presented in this volume. In "The Role of the Market in the Relation Between the State and Cinematographic Creation" Jean Lescure emphasizes that this relationship should be viewed as one of complicity rather than assistance or…

  2. Renewable Feedstocks: The Problem of Catalyst Deactivation and its Mitigation.

    Science.gov (United States)

    Lange, Jean-Paul

    2015-11-01

    Much research has been carried out in the last decade to convert bio-based feedstock into fuels and chemicals. Most of the research focuses on developing active and selective catalysts, with much less attention devoted to their long-term stability. This Review considers the main challenges in long-term catalyst stability, discusses some fundamentals, and presents options for their mitigation. Three main challenges are discussed: catalyst fouling, catalyst poisoning, and catalyst destruction. Fouling is generally related to the deposition of insoluble components present in the feed or formed by degradation of the feed or intermediates. Poisoning is related to the deposition of electropositive contaminants (e.g. alkali and alkaline earth metals) on acid sites or of electronegative contaminants (e.g. N and S) at hydrogenation sites. Catalyst destruction results from the thermodynamic instability of most oxidic supports, solid acids/bases, and hydrogenation functions under hydrothermal conditions. PMID:26457585

  3. New improved hydrophobic Pt-catalyst for hydrogen isotope separation

    International Nuclear Information System (INIS)

    This paper presents the studies on preparation methods and applications of the hydrophobic catalysts in deuterium and tritium separation. The objectives of the paper are: (1) to provide a database for selection of the most appropriate catalyst and catalytic packing for above mentioned processes; (2) to evaluate the potentiality of hydrophobic Pt-catalysts in the deuterium and tritium separation; (3) to assess and to find a new procedure for preparation of a new improved hydrophobic catalyst. Unlike the conventional hydrophilic catalysts, the hydrophobic catalysts maintain a high catalytic activity and stability even under the direct contact to liquid water or in the presence of saturated humidity. A large diversity of catalyst types (over 100 catalysts) was prepared and tested for hydrogen isotope separation. The impregnation modes, the type of precursor of active metal, conditions of reduction and waterproofing methods are in detail analysed. As result of this assessment, platinum appears to be the most active catalytic metal and TEFLON is the most hydrophobic agent. A method for preparation of new improved hydrophobic Pt-catalysed has been proposed. The main steps and experimental conditions are largely discussed. The advantages of the hydrophobic catalysts are shown in comparison to hydrophilic catalysts. Some suggestions concerning the deuterium and tritium enrichment by means of hydrophobic catalysts are also discussed.The extension of hydrophobic Pt-catalysts' applications in environmental field is proposed. (author)

  4. High-throughput screening of binary catalysts for oxygen electroreduction

    Science.gov (United States)

    Liu, Jing Hua; Jeon, Min Ku; Woo, Seong Ihl

    2006-01-01

    A series of Pt based and non-Pt catalysts for proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) have been evaluated towards oxygen reduction, by high-throughput optical screening. Fluorescein was first used as pH indicator for detecting pH change of the electrolyte in the vicinity of cathode caused by oxygen reduction. Arrays of catalyst spot comprised of binary catalysts and pure Pt were prepared by using robotic micro-dispenser. The analysis of fluorescence images has showed that some of Pt based catalysts including PtBi, PtCu, PtSe, PtTe and PtIr, as well as RuFe, as a non-Pt catalyst, exhibited higher activities and methanol tolerance than pure Pt. Moreover, acceptable stability of these catalysts at high potential in acid environment suits them to the requirements of cathode catalyst in PEMFC or DMFC.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Graphene-supported platinum catalysts for fuel cells

    DEFF Research Database (Denmark)

    Seselj, Nedjeljko; Engelbrekt, Christian; Zhang, Jingdong

    2015-01-01

    past 15 years. It is focused on polymer electrolyte membrane fuel cells as an environmentally benign and feasible energy source. Graphene is used as a promising support material for Pt catalysts. It ensures high catalyst loading, good electrocatalysis and stability. Attention has been drawn to...

  10. Design strategies for the molecular level synthesis of supported catalysts.

    Science.gov (United States)

    Wegener, Staci L; Marks, Tobin J; Stair, Peter C

    2012-02-21

    Supported catalysts, metal or oxide catalytic centers constructed on an underlying solid phase, are making an increasingly important contribution to heterogeneous catalysis. For example, in industry, supported catalysts are employed in selective oxidation, selective reduction, and polymerization reactions. Supported structures increase the thermal stability, dispersion, and surface area of the catalyst relative to the neat catalytic material. However, structural and mechanistic characterization of these catalysts presents a formidable challenge because traditional preparations typically afford complex mixtures of structures whose individual components cannot be isolated. As a result, the characterization of supported catalysts requires a combination of advanced spectroscopies for their characterization, unlike homogeneous catalysts, which have relatively uniform structures and can often be characterized using standard methods. Moreover, these advanced spectroscopic techniques only provide ensemble averages and therefore do not isolate the catalytic function of individual components within the mixture. New synthetic approaches are required to more controllably tailor supported catalyst structures. In this Account, we review advances in supported catalyst synthesis and characterization developed in our laboratories at Northwestern University. We first present an overview of traditional synthetic methods with a focus on supported vanadium oxide catalysts. We next describe approaches for the design and synthesis of supported polymerization and hydrogenation catalysts, using anchoring techniques which provide molecular catalyst structures with exceptional activity and high percentages of catalytically significant sites. We then highlight similar approaches for preparing supported metal oxide catalysts using atomic layer deposition and organometallic grafting. Throughout this Account, we describe the use of incisive spectroscopic techniques, including high

  11. Design of heterogeneous catalysts

    DEFF Research Database (Denmark)

    Frey, Anne Mette

    was inspired by a computational screening, suggesting that alloys such as Ni-Fe, Co-Ni, and Co-Fe should show superior activity to the industrially used nickel catalyst. Especially the Ni-Fe system was considered to be interesting, since such alloy catalysts should be both more active and cheaper than...... turned out to work well, and the best catalyst prepared had a C5+ yield almost a factor of two higher than a standard air calcined Co catalyst. In the NH3-SCR reaction it is desirable to develop an active and stable catalyst for NOx removal in automotive applications, since the traditionally used...

  12. Studying PW-Amberlite catalyst deactivation in limonene epoxidation by hydrogen peroxide

    OpenAIRE

    Rolando Barrera Zapata; Aída Luz Villa Holguín de P.; Consuelo Montes de Correa

    2010-01-01

    The PW-Amberlite catalyst is active for limonene epoxidation in triphasic conditions; it becomes deactivated in reaction condi- tions. Catalyst stability during the reaction and recovery of catalyst activity when it was treated with several solvents were evalua- ted. It was found that the catalyst recovered 99% of its initial activity when it was washed with toluene and that the recovery was 95% and 97% when ethanol or acetone were used as washing solvents, respectively. Leaching tests ...

  13. CATALYSTS NHI Thermochemical Systems FY 2009 Year-End Report

    International Nuclear Information System (INIS)

    Fiscal Year 2009 work in the Catalysts project focused on advanced catalysts for the decomposition of sulfuric acid, a reaction common to both the Sulfur-Iodine (S-I) cycle and the Hybrid Sulfur cycle. Prior years effort in this project has found that although platinum supported on titanium oxide will be an acceptable catalyst for sulfuric acid decomposition in the integrated laboratory scale (ILS) project, the material has short comings, including significant cost and high deactivation rates due to sintering and platinum evaporation. For pilot and larger scale systems, the catalyst stability needs to be improved significantly. In Fiscal Year 2008 it was found that at atmospheric pressure, deactivation rates of a 1 wt% platinum catalyst could be reduced by 300% by adding either 0.3 wt% iridium (Ir) or 0.3 wt% ruthenium (Ru) to the catalyst. In Fiscal Year 2009, work focused on examining the platinum group metal catalysts activity and stability at elevated pressures. In addition, simple and complex metal oxides are known to catalyze the sulfuric acid decomposition reaction. These metal oxides could offer activities comparable to platinum but at significantly reduced cost. Thus a second focus for Fiscal Year 2009 was to explore metal oxide catalysts for the sulfuric acid decomposition reaction. In Fiscal Year 2007 several commercial activated carbons had been identified for the HI decomposition reaction; a reaction specific to the S-I cycle. Those materials should be acceptable for the pilot scale project. The activated carbon catalysts have some disadvantages including low activity at the lower range of reactor operating temperature (350 to 400 C) and a propensity to generate carbon monoxide in the presence of water that could contaminate the hydrogen product, but due to limited funding, this area had low priority in Fiscal Year 2009. Fiscal Year 2009 catalyst work included five tasks: development, and testing of stabilized platinum based H2SO4 catalysts

  14. 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.

  15. 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.)

  16. Multiphase catalysts for selective reduction of NOx with hydrocarbons

    International Nuclear Information System (INIS)

    Among the existing proposed solutions to reduce emission of NOx there is a promising alternative, the so-called (HC-SCR) selective catalytic reduction of NOx using hydrocarbons as reductant. This thesis is part of a worldwide effort devoted to gain knowledge on the selective catalytic reduction of NOx with hydrocarbons with the final goal to contribute to the development of suitable catalysts for the above mentioned process. Chapter 2 describes the details of the experimental set-up and of the analytical methods employed. Among the catalyst for HC-SCR, Co-based catalyst are known to be active and selective, thus, a study on a series of Co-based catalysts, supported on zeolites, was undertaken and the results are presented in Chapter 3. Correlation between catalytic characteristics and kinetic results are employed to understand the working catalyst and this is used as a basis for catalyst optimization. With the intention to prepare a multi-functional catalyst that will preserve the desired characteristics of the individual components, minimizing their negative aspects, catalysts based on Co-Pt, supported on ZSM-5, were investigated. In Chapter 4 the results of this study are discussed. A bimetallic Co-Pt/ZSM-5 catalysts with low Pt contents (0.1 wt %) showed a synergistic effect by combining high stability and activity of Pt catalysts with the high N2 selectivity of Co catalysts. Furthermore, it was found to be sulfur- and water-tolerant. Its positive qualities brought us to study the mechanism that takes place over this catalyst during HC-SCR. The results of an in-situ i.r mechanistic study over this catalyst is reported in Chapter 5. From the results presented in Chapter 5 a mechanism operating over the Co-Pt/ZSM-5 catalyst is proposed. The modification of Co catalyst with Pt improved the catalysts. However, further improvement was found to be hindered by high selectivity to N2O. Since Rh catalysts are generally less selective to N2O, the modification of Co

  17. An investigation of the activity and stability of Pd and Pd-Zr modified Y-zeolite catalysts for the removal of PAH, CO, CH4 and NOx emissions

    International Nuclear Information System (INIS)

    Pd-Y- and Pd-Zr-Y-zeolite catalysts were prepared by the ion-exchange of parent NH3-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 SO2 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.% H2O, 16h). The de-activation was attributed to the de-alumination as well as to the migration of Pd2+ cations. The catalysts were characterised by XRD, SEM-EDXA, N2-physisorption, O2/SO2/NH3/naphthalene-TPD, XRF and DCP

  18. Coating powdered copper catalyst with yttria sol

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Kuan-Ying [Department of Chemical and Engineering and Materials Science, Yuan Ze University, Chung-Li, Taiwan (China); Fuel Cell Center, Yuan Ze University, Chung-Li, Taiwan (China); Shen, Chia-Chieh, E-mail: ccshen@saturn.yzu.edu.tw [Fuel Cell Center, Yuan Ze University, Chung-Li, Taiwan (China); Department of Mechanical Engineering, Yuan Ze University, Chung-Li, Taiwan (China); Graduate School of Renewable Energy Engineering, Yuan Ze University, Chung-Li, Taiwan (China); Lee, Chi-Yuan; Lee, Shuo-Jen [Fuel Cell Center, Yuan Ze University, Chung-Li, Taiwan (China); Department of Mechanical Engineering, Yuan Ze University, Chung-Li, Taiwan (China); Graduate School of Renewable Energy Engineering, Yuan Ze University, Chung-Li, Taiwan (China); Leu, Chih-Hsing [Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan (China); Wang, Jung-Hui [Fuel Cell Center, Yuan Ze University, Chung-Li, Taiwan (China); Yeh, Chuin-Tih [Department of Chemical and Engineering and Materials Science, Yuan Ze University, Chung-Li, Taiwan (China); Fuel Cell Center, Yuan Ze University, Chung-Li, Taiwan (China)

    2011-07-15

    Research highlights: {yields} The neutral Y{sub 2}O{sub 3} sol is an effective binder for coating powders of CuZnAl catalyst. {yields} A particle size ratio of 15 for catalyst to binder is suggested for stable coating. {yields} Sufficient stirring is an important step in the catalyst slurry preparation. - Abstract: A commercial Y{sub 2}O{sub 3} sol was tested as a binder for coating CuZnAl catalyst powder onto microchannels of a stainless steel plate (SSP). Coated plates were used to fabricate microchannel reactors that generate hydrogen via the steam reforming of methanol (SRM). Washcoating slurries were prepared by suspending catalyst powders into the sol. Slurry parameters, such as solid content, binder content, pH value, and stir time, were optimized to achieve a stable catalyst coating and good SRM performance. The expected stable coating could be obtained from neutral (pH 7) Y{sub 2}O{sub 3} slurry that is required for a negligible dissolution of the copper component of the catalyst. The experimental coating stability generally improved with the slurry stir time. Observed improvements were attributed to a dispersion of catalyst powders in the slurry through a two-step mechanism: the mechanical disassembly of agglomerated CuZnAl powders into primary particles, and the repelling of dissembled particles through adsorption of positively charged Y{sub 2}O{sub 3} binders. A reasonable reaction temperature of 280 deg. C was found for 95% conversion of methanol in SRM from the resulted microchannel reactors. A low CO fraction of 0.3% was also found in the hydrogen-rich gas reformed.

  19. 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].

  20. Development of a stable cobalt-ruthenium Fisher-Tropsch catalyst. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Frame, R.R.; Gala, H.B.

    1995-02-01

    The reverse micelle catalyst preparation method has been used to prepare catalysts on four supports: magnesium oxide, carbon, alumina- titania and steamed Y zeolite. These catalysts were not as active as a reference catalyst prepared during previous contracts to Union Carbide Corp. This catalyst was supported on steamed Y zerolite support and was impregnated by a pore-filling method using a nonaqueous solvent. Additional catalysts were prepared via pore- filling impregnation of steamed Y zeolites. These catalysts had levels of cobalt two to three and a half times as high as the original Union Carbide catalyst. On a catalyst volume basis they were much more active than the previous catalyst; on an atom by atom basis the cobalt was about of the same activity, i.e., the high cobalt catalysts` cobalt atoms were not extensively covered over and deactivated by other cobalt atoms. The new, high activity, Y zerolite catalysts were not as stable as the earlier Union Carbide catalyst. However, stability enhancement of these catalysts should be possible, for instance, through adjustment of the quantity and/or type of trace metals present. A primary objective of this work was determination whether small amounts of ruthenium could enhance the activity of the cobalt F-T catalyst. The reverse micelle catalysts were not activated by ruthenium, indeed scanning transmission electronic microscopy (STEM) analysis provided some evidence that ruthenium was not present in the cobalt crystallites. Ruthenium did not seem to activate the high cobalt Y zeolite catalyst either, but additional experiments with Y zeolite-supported catalysts are required. Should ruthenium prove not to be an effective promoter under the simple catalyst activation procedure used in this work, more complex activation procedures have been reported which are claimed to enhance the cobalt/ruthenium interaction and result in activity promotion by ruthenium.

  1. 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.

  2. 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.

  3. 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

    The synthesis of the components of the dynamic supramolecular hydrogen-bonded catalytic system 2 + 3 is described. The catalytic performance and substrate- and enantioselectivity of Mn(salen) catalyst 2 were investigated in the presence and absence of the Zn(porphyrin) receptor unit 3. The effects...

  4. 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...

  5. 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...

  6. Heterogeneous hydrogenation catalysts

    International Nuclear Information System (INIS)

    The main types of heterogeneous catalysts used for hydrogenation, the methods for their preparation, and the structure and chemistry of their surfaces are considered, as well as the catalytic activity and the mechanism of action in the hydrogenation of unsaturated and aromatic compounds, of CO, and of carbonyl compounds and in the hydrorefining of fuels. Chief attention is paid to supported Ni catalysts, to the methods for their preparation and physicochemical studies, and to the development of novel catalytic systems through modification. A novel type of catalyst for hydrogenation, viz. metal carbides, is described. Some aspects of the mechanochemical treatment of hydrogenation catalysts, including in situ methods, are discussed. Sulfide catalysts for hydrotreating are also discussed in detail. The bibliography includes 340 references.

  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. 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

  9. 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.

  10. Steam Reforming of Glycerol for Hydrogen Production over Ni/SiO2 Catalyst

    OpenAIRE

    Sadanandam, G.; Sreelatha, N.; Phanikrishna Sharma, M. V.; Kishta Reddy, S.; B. Srinivas; Venkateswarlu, K.; Krishnudu, T.; Subrahmanyam, M.; Durga Kumari, V.

    2012-01-01

    The performance of Ni/SiO2 catalyst for glycerol reforming has been investigated in fixed-bed reactor using careful tailoring of the operational conditions. In this paper, a commercial Engelhard catalyst has been sized and compared to gas product distribution versus catalyst size, water-to-carbon ratio, and stability of the catalyst system. Ni/SiO2 catalysts of three sizes (2×2, 2×4, and 3×5 mm) are evaluated using glycerol: water mixture at 600°C to produce 2 L H2 g−1 cat h−1. The results in...

  11. 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. [...

  12. Computational comparison of stepwise oxidation and O-O bond formation in mononuclear ruthenium water oxidation catalysts

    Science.gov (United States)

    Jarvis, Emily A. A.; Lee, Brian; Neddenriep, Bradley; Shoemaker, Wendy

    2013-05-01

    A computational comparison of key steps along proposed water oxidation pathways for eleven distinct mononuclear ruthenium catalysts is presented. Free energies are determined via density functional calculations and analyzed for catalyst structural stability, energetic comparisons to experimentally measured potentials in highly acidic conditions, and other features. A single feature for optimal catalyst design does not emerge; different steps along the oxidation cycle are impacted in subtle and sometimes divergent ways depending on the nature of the ligand modification on the catalyst. The results reinforce the notion observed in previous experimental studies - in such multi-step mechanisms with complex catalysts, a careful balance between energetic optimization and catalyst stability at multiple steps along the cycle may be critical for practical performance considerations. Whereas comparing catalysts at an individual step is likely to provide an incomplete picture, behavior of chemically modified catalysts can be distinguished computationally across multiple mechanistic steps.

  13. 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.

  14. Application of solid ash based catalysts in heterogeneous catalysis.

    Science.gov (United States)

    Wang, Shaobin

    2008-10-01

    Solid wastes, fly ash, and bottom ash are generated from coal and biomass combustion. Fly ash is mainly composed of various metal oxides and possesses higher thermal stability. Utilization of fly ash for other industrial applications provides a cost-effective and environmentally friendly way of recycling this solid waste, significantly reducing its environmental effects. On the one hand, due to the higher stability of its major component, aluminosilicates, fly ash could be employed as catalyst support by impregnation of other active components for various reactions. On the other hand, other chemical compounds in fly ash such as Fe2O3 could also provide an active component making fly ash a catalyst for some reactions. In this paper, physicochemical properties of fly ash and its applications for heterogeneous catalysis as a catalyst support or catalyst in a variety of catalytic reactions were reviewed. Fly-ash-supported catalysts have shown good catalytic activities for H2 production, deSO(x), deNO(x), hydrocarbon oxidation,and hydrocracking, which are comparable to commercially used catalysts. As a catalyst itself, fly ash can also be effective for gas-phase oxidation of volatile organic compounds, aqueous-phase oxidation of organics, solid plastic pyrolysis, and solvent-free organic synthesis. PMID:18939526

  15. Synthesis and properties of catalysts prepared from silicomolybdovanadium heteropoly acid

    International Nuclear Information System (INIS)

    Catalytic properties of samples prepared of silicomolybdovanadium heteropoly acid (HPA) have been investigated. The massive catalyst is shown to be comparatively low effective in the reaction of acrolein oxidation to acrylic acid. Impregnation of coarse-dispersed silica gel by the HPA solution results in the formation of active and selective catalyst, whereas low-active catalyst of deep oxidation is formed on the base of high-dispersed silica gel. The obtained data are explained by the formation and stabilization of different forms of vanadium- and molybdenum-containing compounds on the carrier surface

  16. 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

  17. Study of spent hydrorefining catalysts

    International Nuclear Information System (INIS)

    Aluminonickelmolybdenum catalysts for diesel fuel hydrorefining have been studied by DTA, XSPS, and diffuse reflection spectroscopy. Chemical and phase states of molybdenum compounds in samples of fresh catalyst, regenerated one after one year operation, and clogged with coke catalyst after five year operation, are determined. Chemical reactions and crystal-phase transformations of the molybdenum compounds during catalyst deactivation and regeneration are discussed

  18. SCALEUP OF ALUMINUM PHOSPHATE CATALYST FOR PILOT PLANT LPDMEtm RUN

    Energy Technology Data Exchange (ETDEWEB)

    Andrew W. Wang

    2002-01-01

    The Liquid Phase Dimethyl Ether (LPDME{trademark}) process converts synthesis gas to dimethyl ether in a single slurry bubble column reactor. A mixed slurry of methanol synthesis catalyst and methanol dehydration catalyst in a neutral mineral oil simultaneously synthesizes methanol from syngas and converts some of it to dimethyl ether and water. The reaction scheme is shown below: 2H{sub 2} + CO = CH{sub 3}OH; 2CH{sub 3}OH = CH{sub 3}OCH{sub 3} + H{sub 2}O; H{sub 2}O + CO = CO{sub 2} + H{sub 2}. Most of the water produced in this reaction is converted to hydrogen by reduction with carbon monoxide (water gas shift reaction). This synergy permits higher per pass conversion than methanol synthesis alone. The enhancement in conversion occurs because dehydration of the methanol circumvents the equilibrium constraint of the syngas-to-methanol step. The slurry bubble column reactor provides the necessary heat transfer capacity to handle the greater heat duty associated with high conversion. In order to improve the stability of the catalyst system, non-stoichiometric aluminum phosphate was proposed as the dehydration catalyst for the LPDME{trademark} process. This aluminum phosphate material is a proprietary catalyst. This catalyst system of a standard methanol catalyst and the aluminum phosphate provided stable process performance that met the program targets under our standard test process conditions in the laboratory. These targets are (1) an initial methanol equivalent productivity of 28 gmol/kg/hr, (2) a CO{sub 2}-free, carbon selectivity of 80% to dimethyl ether and (3) stability of both catalysts equivalent to that of the methanol catalyst in the absence of the aluminum phosphate. A pilot plant trial of the LPDME{trademark} process using the aluminum phosphate catalyst was originally planned for March 1998 at the DOE-owned, Air Products (APCI)-operated facility at LaPorte, Texas. Because the aluminum phosphate catalyst is not commercially available, we initiated a

  19. SCALEUP OF ALUMINUM PHOSPHATE CATALYST FOR PILOT PLANT LPDMEtm RUN

    Energy Technology Data Exchange (ETDEWEB)

    Andrew W. Wang

    2002-05-15

    The Liquid Phase Dimethyl Ether (LPDME{trademark}) process converts synthesis gas to dimethyl ether in a single slurry bubble column reactor. A mixed slurry of methanol synthesis catalyst and methanol dehydration catalyst in a neutral mineral oil simultaneously synthesizes methanol from syngas and converts some of it to dimethyl ether and water. The reaction scheme is: 2H{sub 2} + CO = CH{sub 3}OH 2CH{sub 3}OH = CH{sub 3}OCH{sub 3} + H{sub 2}O H{sub 2}O + CO = CO{sub 2} + H{sub 2}. Most of the water produced in this reaction is converted to hydrogen by reduction with carbon monoxide (water gas shift reaction). This synergy permits higher per pass conversion than methanol synthesis alone. The enhancement in conversion occurs because dehydration of the methanol circumvents the equilibrium constraint of the syngas-to-methanol step. The slurry bubble column reactor provides the necessary heat transfer capacity to handle the greater heat duty associated with high conversion. In order to improve the stability of the catalyst system, non-stoichiometric aluminum phosphate was proposed as the dehydration catalyst for the LPDME{trademark} process. This aluminum phosphate material is a proprietary catalyst. This catalyst system of a standard methanol catalyst and the aluminum phosphate provided stable process performance that met the program targets under our standard test process conditions in the laboratory. These targets are (1) an initial methanol equivalent productivity of 28 gmol/kg/hr, (2) a CO{sub 2}-free, carbon selectivity of 80% to dimethyl ether and (3) stability of both catalysts equivalent to that of the methanol catalyst in the absence of the aluminum phosphate. A pilot plant trial of the LPDME{trademark} process using the aluminum phosphate catalyst was originally planned for March 1998 at the DOE-owned, Air Products (APCI)-operated facility at LaPorte, Texas. Because the aluminum phosphate catalyst is not commercially available, we initiated a scaleup project

  20. 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.

  1. 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

  2. Polyaromatic polymers as binders in PEMFC catalyst layers

    Energy Technology Data Exchange (ETDEWEB)

    Peron, J.M.; Edwards, D.; Le Marquand, P.; Shi, Z.; Holdcroft, S. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

    2009-07-01

    The catalyst layers in proton exchange membrane (PEM) fuel cells are typically composed of platinum as the catalyst and carbon as the electron conductor. The binder that ensures the ionic pathway between catalyst particles and the electrolyte membrane is a perfluorinated polymer that brings the electrolyte, gaseous reactants, electrocatalyst and current collector into close contact within a confined spatial region known as the triple-phase-boundary. New non-fluorinated polymers have been developed in an effort to lower the cost and improve the stability of fuel cells. Although polyaromatic polymers have been extensively presented in the literature for membrane preparation, these new materials have been mainly characterized in presence of Nafion as a binder in the catalyst layer. This paper discussed the incorporation of polyaromatic polymers, such as sulfonated-PEEK (sPEEK), and its properties as a binder. sPEEK-based catalyst ink solutions, using different sPEEK/Pt ratios and preparation methods, have been deposited on membranes to form catalyst-coated-membranes (CCM). Initial catalyst ink were characterized using dynamic light scattering to determine agglomerate size. Catalyst layers were examined using SEM and TEM and their porosity was determined by Hg porosimetry. Various electrochemical techniques were used for in-situ characterization of prepared sPEEK CCMs.

  3. TOPICAL REVIEW: Nanostructured catalysts in fuel cells

    Science.gov (United States)

    Zhong, Chuan-Jian; Luo, Jin; Fang, Bin; Wanjala, Bridgid N.; Njoki, Peter N.; Loukrakpam, Rameshwori; Yin, Jun

    2010-02-01

    support materials. The fact that some of the trimetallic nanoparticle catalysts (e.g. PtVFe or PtNiFe) exhibit electrocatalytic activities in fuel cell reactions which are four-five times higher than in pure Pt catalysts constitutes the basis for further exploration of a variety of multimetallic combinations. The fundamental insights into the control of nanoscale alloy, composition, and core-shell structures have important implications in identifying nanostructured fuel cell catalysts with an optimized balance of catalytic activity and stability.

  4. Catalyst for microelectromechanical systems microreactors

    Energy Technology Data Exchange (ETDEWEB)

    Morse, Jeffrey D. (Martinez, CA); Sopchak, David A. (Livermore, CA); Upadhye, Ravindra S. (Pleasanton, CA); Reynolds, John G. (San Ramon, CA); Satcher, Joseph H. (Patterson, CA); Gash, Alex E. (Brentwood, CA)

    2011-11-15

    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.

  5. 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.

  6. Mesoporous molecular sieve catalysts

    DEFF Research Database (Denmark)

    Højholt, Karen Thrane

    the micropores. Furthermore, preliminary work was done using mesoporous ZSM-5 zeolites as support material for anchoring molecular CoMo6 species for the application as potential bi-functional catalyst in simultaneous hydrodesulfurisation (HDS) and hydrocracking. HDS activity tests revealed that the...... of different catalytic applications. Primarily the zeolites were modified regarding the porosity and the introduction of metals to the framework. The obtained materials were used as solid acid catalysts, as an inert matrix for stabilising metal nanoparticles and as an anchoring material for molecular...... only 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...

  7. 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.

  8. Heterogeneous chromium catalysts

    OpenAIRE

    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-containing support, (c) activating the chromium-based silica-containing support, (d) chemically reducing the activated chromium-based silica-containing support to produce a precursor catalyst, (e) r...

  9. Aftermarket catalyst durability evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Bruetsch, R.I.; Cheng, J.P.; Hellman, K.H.

    1986-01-01

    Suppliers have introduced replacement aftermarket catalytic converters which are characterized by design differences from the original equipment converters in the direction of lower costs. The objective of the work reported here was to test a group of nine aftermarket catalysts from three manufacturers for 25,000 miles. Mileage was accumulated on three routes in Maryland and West Virginia characterized by varying degrees of tire wear. All catalysts were dynamometer tested on the same vehicle at the same laboratory.

  10. 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...

  11. Development of industrial hydrogenating catalyst on rhenium base

    International Nuclear Information System (INIS)

    Processes for forming rhenium catalysts on carbon carrier and their catalytic properties in nitrobenzene (NB) reduction were studied. Application of an ammonia preparation to the carbon surface produced impregnated carbon saturated at room temperature with a water solution of the ammonia preparation, taken in a volume equal to the volumetric capacity of the carbon. With one impregnation, 2% rhenium was taken up. Catalysts containing more than 5% rhenium were obtained by impregnating the carbon with heating and use of more concentrated solutions. Catalysts made in this way and dried at 1000C had the composition Re2OH/carbon/. The most active catalysts were those reduced at 200-2500C; higher temperatures, up to 300-5000C, decreased the activity. Study of the catalytic properties of the rhenium catalysts in a liquid phase reduction of NB showed that the specific activity of rhenium depends only slightly on the content of the active component in the catalyst and is close to the specific activity of palladium and considerably exceeds that of nickel. Study of the effect of the NB concentration and hydrogen pressure on the activity and stability of the 5% rhenium catalyst indicated that with NB concentrations from 50 to 10% the process takes place at an essentially constant rate; the order of the reaction was close to zero with an apparent activation energy of about 7000 cal/mole. At pressures of 15-200 atm the yield with the 5% catalyst was proportional to the hydrogen pressure. A big advantage of the rhenium catalysts in the reduction of NB is their high selectivity. With a higher activity than palladium and nickel catalysts, 5% rhenium catalyst produces a high operating capacity in a wide range of contact charges, which has considerable significance for industrial use in contact apparatus of the column type. Comparison of the costs of rhenium catalysts and granular carbon carrier with those of nickel, platinum, and palladium showed that 5% rhenium catalyst can compete

  12. 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.

  13. 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....

  14. Niobia supported on silica as a catalyst for Biodiesel production from waste oil

    OpenAIRE

    Tesser R.; Vitiello R.; Carotenuto G.; Garcia Sancho C.; Vergara A; Maireles Torres P.J.; Li Changzhu; Di Serio M.

    2015-01-01

    The activity and stability of niobia supported on silica catalyst have been tested in continuous micro-pilot reactors, for biodiesel production starting from acid vegetable oils. A catalyst was prepared by the impregnation of silica pellets with a loading of 12% of Nb and was extensively characterized. The activity of this catalyst in both esterification and transesterification was tested in a continuous micro-pilot laboratory plant in which acid oil was fed (FFA 10% w...

  15. Tetranuclear Zn/4f coordination clusters as highly efficient catalysts for Friedel-Crafts alkylation.

    Science.gov (United States)

    Griffiths, Kieran; Kumar, Prashant; Akien, Geoffrey R; Chilton, Nicholas F; Abdul-Sada, Alaa; Tizzard, Graham J; Coles, Simon J; Kostakis, George E

    2016-06-14

    A series of custom-designed, high yield, isoskeletal tetranuclear Zn/4f coordination clusters showing high efficiency as catalysts with low catalytic loadings in Friedel-Crafts alkylation are described for the first time. The possibility of altering the 4f centers in these catalysts without altering the core topology allows us to further confirm their stability via EPR and NMR, as well to gain insights into the plausible reaction mechanism, showcasing the usefulness of these bimetallic systems as catalysts. PMID:27248829

  16. 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...

  17. Magnetic and dendritic catalysts.

    Science.gov (United States)

    Wang, Dong; Deraedt, Christophe; Ruiz, Jaime; Astruc, Didier

    2015-07-21

    The recovery and reuse of catalysts is a major challenge in the development of sustainable chemical processes. Two methods at the frontier between homogeneous and heterogeneous catalysis have recently emerged for addressing this problem: loading the catalyst onto a dendrimer or onto a magnetic nanoparticle. In this Account, we describe representative examples of these two methods, primarily from our research group, and compare them. We then describe new chemistry that combines the benefits of these two methods of catalysis. Classic dendritic catalysis has involved either attaching the catalyst covalently at the branch termini or within the dendrimer core. We have used chelating pyridyltriazole ligands to insolubilize catalysts at the termini of dendrimers, providing an efficient, recyclable heterogeneous catalysts. With the addition of dendritic unimolecular micelles olefin metathesis reactions catalyzed by commercial Grubbs-type ruthenium-benzylidene complexes in water required unusually low amounts of catalyst. When such dendritic micelles include intradendritic ligands, both the micellar effect and ligand acceleration promote faster catalysis in water. With these types of catalysts, we could carry out azide alkyne cycloaddition ("click") chemistry with only ppm amounts of CuSO4·5H2O and sodium ascorbate under ambient conditions. Alternatively we can attach catalysts to the surface of superparamagnetic iron oxide nanoparticles (SPIONs), essentially magnetite (Fe3O4) or maghemite (γ-Fe2O3), offering the opportunity to recover the catalysts using magnets. Taking advantage of the merits of both of these strategies, we and others have developed a new generation of recyclable catalysts: dendritic magnetically recoverable catalysts. In particular, some of our catalysts with a γ-Fe2O3@SiO2 core and 1,2,3-triazole tethers and loaded with Pd nanoparticles generate strong positive dendritic effects with respect to ligand loading, catalyst loading, catalytic activity and

  18. Preparation of Supported Metal Catalysts by Atomic and Molecular Layer Deposition for Improved Catalytic Performance

    Science.gov (United States)

    Gould, Troy D.

    Creating catalysts with enhanced selectivity and activity requires precise control over particle shape, composition, and size. Here we report the use of atomic layer deposition (ALD) to synthesize supported Ni, Pt, and Ni-Pt catalysts in the size regime (number of ALD cycles, Ni weight loadings were varied from 4.7 wt% to 16.7 wt% and the average particle sizes ranged from 2.5 to 3.3 nm, which increased the selectivity for C 3H6 hydrogenolysis by an order of magnitude over a much larger Ni/Al2O3 catalyst. Pt particles were deposited by varying the number of ALD cycles and the reaction chemistry (H2 or O 2) to control the particle size from approximately 1 to 2 nm, which allowed lower-coordinated surface atoms to populate the particle surface. These Pt ALD catalysts demonstrated some of the highest oxidative dehydrogenation of propane selectivities (37%) of a Pt catalyst synthesized by a scalable technique. Dry reforming of methane (DRM) is a reaction of interest due to the recent increased recovery of natural gas, but this reaction is hindered from industrial implementation because the Ni catalysts are plagued by deactivation from sintering and coking. This work utilized Ni ALD and NiPt ALD catalysts for the DRM reaction. These catalysts did not form destructive carbon whiskers and had enhanced reaction rates due to increased bimetallic interaction. To further limit sintering, the Ni and NiPt ALD catalysts were coated with a porous alumina matrix by molecular layer deposition (MLD). The catalysts were evaluated for DRM at 973 K, and the MLD-coated Ni catalysts outperformed the uncoated Ni catalysts in either activity (with 5 MLD cycles) or stability (with 10 MLD cycles). In summary, this thesis developed a new Ni nanoparticle ALD chemistry, explored possibilities for changing Pt ALD particle size, brought the two techniques together to create enhanced bimetallic catalysts, and stabilized the catalysts using MLD.

  19. A New Hydrophobic Catalyst for Tritium Separation from Nuclear Effluents

    International Nuclear Information System (INIS)

    The hydrophobic catalysts were originally conceived in Canada for the deuterium enrichment and tritium separation by hydrogen-liquid water isotopic exchange in nuclear field. Unlike the conventional hydrophilic catalysts, which becomes inefficient to direct contact with liquid water, the hydrophobic catalysts kept a high catalytic activity and stability, even under the direct contact with liquid water or in presence of humid gas. Based on the long experience of the authors, in the preparation, testing and evaluation of the performances of hydrophobic catalysts, and based on the reviewed references, this paper presents up-to-date R and D activities on the preparation methods and applications of the hydrophobic catalysts, in tritium separation. The objectives of the paper are: (1) to provide a database for selection of the most appropriate catalyst and catalytic packing for above mentioned processes, (2) to asses and to find a new procedure for preparation of a new improved hydrophobic catalyst. From reviewed references we consider that platinum remains the most active and efficient catalytic metal and the TEFLON is the best wetproofing agent. A new improved hydrophobic Pt-catalyst has been proposed and is now underway. The main steps and experimental conditions of preparation are largely discussed. A new wet-proofing agent and a new binding agents (titanium oxide, cerium oxide, zirconium oxide) with catalytic role are proposed and tested. The physico-structural parameters of new improved catalyst have been determined and are discussed in details. The new proposal is a promising idea to improve the performances of conventional hydrophobic Pt-catalysts

  20. A New hydrophobic catalyst for tritium separation from nuclear effluents

    International Nuclear Information System (INIS)

    Full text: The hydrophobic catalysts were originally conceived in Canada for the deuterium enrichment and tritium separation by hydrogen-liquid water isotopic exchange in nuclear field. Unlike the conventional hydrophilic catalysts, which becomes inefficient to direct contact with liquid water, the hydrophobic catalysts kept a high catalytic activity and stability, even under the direct contact with liquid water or in presence of humid gas. Based on the long experience of the authors, in the preparation, testing and evaluation of the performances of hydrophobic catalysts, and based on the reviewed references, this paper presents current R and D activities on the preparation methods and applications of the hydrophobic catalysts, in tritium separation. The objectives of the paper are: (1) to provide a database for selection of the most appropriate catalyst and catalytic packing for above mentioned processes; (2) to find and to asses a new procedure for preparation of a new improved hydrophobic catalyst. Based on reviewed references we concluded that platinum appears to be the most active and efficient catalytic metal while the Teflon is the best wet-proofing agent. A new improved hydrophobic Pt-catalyst has been proposed and its study is now underway. The main steps and experimental conditions of preparation are largely discussed. A new wet-proofing agent and new binding agents (titanium oxide, cerium oxide, zirconium oxide) with catalytic role were proposed and now are tested. The physico-structural parameters of newly improved catalyst have been determined and are discussed in details. The new proposal is a promising idea to improve the performances of conventional hydrophobic Pt-catalysts. (authors)

  1. Optimization of catalyst layer composition for PEMFC using graphene-based oxygen reduction reaction catalysts

    Science.gov (United States)

    Park, Jong Cheol; Park, Sung Hyeon; Chung, Min Wook; Choi, Chang Hyuck; Kho, Back Kyun; Woo, Seong Ihl

    2015-07-01

    The focus in recent years is on developing high performance non-precious metal catalysts (NPMCs) to reduce the catalyst cost in fuel cells. However, little attention has been paid to improve the utilization of NPMCs. Thus, this study focuses on the optimization of electrode component, particularly the Nafion content. With the synthesized graphene based oxygen reduction reaction (ORR) catalyst, the catalyst inks were prepared at various Nafion contents with suitable amounts of catalysts sprayed on the gas diffusion media. Twenty different single cells were assembled and measured for polarization, resistance and electrochemical impedance. Electrodes of 66.7 and 50.0% Nafion contents showed the highest performance for hydrogen/oxygen and hydrogen/air operation, respectively. These results were explained using the electrochemical impedance spectra, where the highest performance electrode resulted with the lowest charge transfer resistance. Moreover, negligible change in performance was observed during the 80 h of stability test. The optimization compositions of NPMC-based MEAs were very different to Pt-based MEAs, indicating the importance of optimization studies for the practical use of NPMCs.

  2. 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.

  3. 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. PMID:26745623

  4. Catalyst component interactions in nickel/alumina catalyst

    Directory of Open Access Journals (Sweden)

    Kiš Erne E.

    2007-01-01

    Full Text Available The influence of nickel loading (5; 10; 20 wt% Ni, temperature of heat treatment (400; 700; 1100°C and way of catalyst preparation on the catalyst component interactions (CCI in the impregnated, mechanical powder mixed and co-precipitated catalyst was investigated. For sample characterization, low temperature nitrogen adsorption (LTNA and X-ray diffraction (XRD were applied. Significant differences were revealed, concerning CCI in dependence of nickel loading, temperature of heat treatment and way of catalyst preparation. The obtained results show that the support metal oxide interactions (SMI in impregnated and co-precipitated catalysts are more intensive than in the mechanical powder mixed catalyst. The degree and intensity of CCI is expressed by the ratio of real and theoretical surface area of the catalyst. This ratio can be used for a quantitative estimation of CCI and it is generally applicable to all types of heterogeneous catalysts.

  5. 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.

  6. Computational comparison of stepwise oxidation and O–O bond formation in mononuclear ruthenium water oxidation catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Jarvis, Emily A.A., E-mail: emily.jarvis@lmu.edu [Department of Chemistry and Biochemistry, Loyola Marymount University, 1 LMU Drive, Los Angeles, CA 90045 (United States); Lee, Brian; Neddenriep, Bradley [Department of Chemistry and Biochemistry, Loyola Marymount University, 1 LMU Drive, Los Angeles, CA 90045 (United States); Shoemaker, Wendy [Department of Mechanical Engineering, Loyola Marymount University, 1 LMU Drive, Los Angeles, CA 90045 (United States)

    2013-05-16

    Highlights: • Computational exploration of eleven mononuclear ruthenium catalysts was performed. • Calculations investigate stability, reactivity, and energetic comparison to experimental potentials. • Steps in the water oxidation mechanism are impacted distinctly depending on catalyst modification. • Full picture of catalyst requires comparison across multiple steps of mechanism. - Abstract: A computational comparison of key steps along proposed water oxidation pathways for eleven distinct mononuclear ruthenium catalysts is presented. Free energies are determined via density functional calculations and analyzed for catalyst structural stability, energetic comparisons to experimentally measured potentials in highly acidic conditions, and other features. A single feature for optimal catalyst design does not emerge; different steps along the oxidation cycle are impacted in subtle and sometimes divergent ways depending on the nature of the ligand modification on the catalyst. The results reinforce the notion observed in previous experimental studies – in such multi-step mechanisms with complex catalysts, a careful balance between energetic optimization and catalyst stability at multiple steps along the cycle may be critical for practical performance considerations. Whereas comparing catalysts at an individual step is likely to provide an incomplete picture, behavior of chemically modified catalysts can be distinguished computationally across multiple mechanistic steps.

  7. Deactivation-resistant catalyst for selective catalyst reduction of NOx

    OpenAIRE

    Jensen, Anker Degn; Castellino, Francesco; Rams, Per Donskov; Pedersen, Jannik Blaabjerg; Putluru, Siva Sankar Reddy

    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 treat...

  8. Supported organoiridium catalysts for alkane dehydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Establishing operational stability--developing human infrastructure.

    Science.gov (United States)

    Gomez, Max A; Byers, Ernest J; Stingley, Preston; Sheridan, Robert M; Hirsch, Joshua A

    2010-12-01

    Over the past year, Toyota has come under harsh scrutiny as a result of several recalls. These well publicized mishaps have not only done damage to Toyota's otherwise sterling reputation for quality but have also called into question the assertions from a phalanx of followers that Toyota's production system (generically referred to as TPS or Lean) is the best method by which to structure one's systems of operation. In this article, we discuss how Toyota, faced with the pressure to grow its business, did not appropriately cadence this growth with the continued development and maintenance of the process capabilities (vis a vis the development of human infrastructure) needed to adequately support that growth. We draw parallels between the pressure Toyota faced to grow its business and the pressure neurointerventional practices face to grow theirs, and offer a methodology to support that growth without sacrificing quality. PMID:21990652

  10. 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.

  11. Platinum nanophase electro catalysts and composite electrodes for hydrogen production

    Science.gov (United States)

    Petrik, L. F.; Godongwana, Z. G.; Iwuoha, E. I.

    Nanophase Pt electro catalysts were prepared by impregnating a Pt salt containing solution upon a high surface area hexagonal mesoporous silica (HMS) matrix, which was then carbonized to varying degree by chemical vapour deposition of liquid petroleum gas (LPG). Thereafter the HMS Si matrix could be removed by chemical etching with NaOH to immediately form a Pt containing carbon analogue or ordered mesoporous carbon (OMC) with a porous structure similar to the parent HMS. Nanoparticles of Pt electro catalysts were thus successfully stabilized without agglomeration on both HMS and upon the porous HMS carbon analogue or OMC, which was graphitic in nature. The catalysts were electro active for the hydrogen evolution reaction and their activity compared favourable with an industry standard. Such nanophase Pt electro catalysts could be incorporated successfully in a composite electrode by sequential deposition, upon a suitable substrate and the catalysts in electrodes so formed proved to be stable and active under high-applied potential in high electrolyte environment for hydrogen production by electrolysis of water. This route to preparing a nanophase Pt OMC catalyst may be applicable to prepare active electro catalysts for polymer electrolyte fuel cells and solid polymer electrolyte electrolyzers.

  12. Development of highly active and stable hybrid cathode catalyst for PEMFCs

    Science.gov (United States)

    Jung, Won Suk

    stability under 30,000 potential cycles between 0.6 and 1.0 V. To further increase the stability of the catalyst at high potential cycles (1.0-1.5 V), high temperature treatment is used to obtain graphitized carbon having optimum BET surface area. The novel catalyst synthesis procedure developed in this study was successfully applied for the synthesis of Co-doped Pt catalysts supported on the graphitized carbon which showed high activity and enhanced stability at high potentials.

  13. Synthesis of carbon nanotubes with Ni/CNTs catalyst

    Institute of Scientific and Technical Information of China (English)

    LI; Chunhua; (李春华); YAO; Kefu; (姚可夫); RUAN; Dianbo; (阮殿波); LIANG; Ji; (梁; 吉); XU; Cailu; (徐才录); WU; Dehai; (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.

  14. 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...

  15. Improving Grubbs' II type ruthenium catalysts by appropriately modifying the N-heterocyclic carbene ligand.

    Science.gov (United States)

    Vieille-Petit, Ludovic; Luan, Xinjun; Gatti, Michele; Blumentritt, Sascha; Linden, Anthony; Clavier, Hervé; Nolan, Steven P; Dorta, Reto

    2009-07-01

    The introduction of N-heterocyclic carbene ligands that incorporate correctly substituted naphthyl side chains leads to increased activity and stability in second generation ruthenium metathesis catalysts. PMID:19557281

  16. Electro-oxidation of ethanol on ternary non-alloyed Pt-Sn-Pr/C catalysts

    Science.gov (United States)

    Corradini, Patricia G.; Antolini, Ermete; Perez, Joelma

    2015-02-01

    Ternary Pt-Sn-Pr/C (70:10:20), (70:15:15) and (45:45:10) electro-catalysts were prepared by a modified formic acid method, and their activity for the ethanol oxidation reaction (EOR) was compared with that of Pt-Pr/C catalysts prepared by the same methods and that of commercial Pt-Sn/C (75:25) and Pt/C catalysts. Among all the catalysts, the Pt-Sn-Pr/C (45:45:10) catalyst presented both the highest mass activity and the highest specific activity. The steady state electrochemical stability of ternary Pt-Sn-Pr catalysts increased with the surface Sn/Pt atomic ratio. Following repetitive potential cycling (RPC), the activity for ethanol oxidation of Pt-Sn-Pr/C catalysts with high surface Sn/Pt atomic ratio was considerably higher than that of the corresponding as-prepared catalysts, and increased with increasing the Sn/Pt ratio. The increase of the EOR mass activity following RPC was ascribed to the increase of either the specific activity (for the Pt-Sn-Pr/C (70:15:15) catalyst) or the electrochemically active surface area (for the Pt-Sn-Pr/C (45:45:10) catalyst). Dissolution of Sn and Pr oxides from Pt-Sn-Pr/C catalyst surface was observed following RPC.

  17. 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

  18. Preparation of Pt-SDB hydrophobic catalyst used in H2-H2O isotope exchange reaction

    International Nuclear Information System (INIS)

    The preparation of Pt-SDB hydrophobic catalyst is studied, in which platinum as active metal and polystyrene divinylbenzene (SDB) as the carrier. Hydrogen isotope exchange reaction is carried out with Pt-SDB catalyst in counter-current in the trickle bed. The effect of preparing condition on the activity of catalyst is discussed. The results show that the excellent catalyst is obtained by reduced at the temperature of 200 degree C over 8 hours. Hydrophobic catalyst is high activity and stability as the amount of platinum content is 3%, the platinum can reach the economic use with the content of (1-2)%

  19. 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.

  20. 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 on...

  1. Tight bifunctional hierarchical catalyst.

    Science.gov (United States)

    Højholt, Karen T; Vennestrøm, Peter N R; Tiruvalam, Ramchandra; Beato, Pablo

    2011-12-28

    A new concept to prepare tight bifunctional catalysts has been developed, by anchoring CoMo(6) clusters on hierarchical ZSM-5 zeolites for simultaneous use in HDS and hydrocracking catalysis. The prepared material displays a significant improved activity in HDS catalysis compared to the impregnated counterpart. PMID:22048337

  2. 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.

  3. Heterogeneous CaO–MoO3–SBA-15 catalysts for biodiesel production from soybean oil

    International Nuclear Information System (INIS)

    Highlights: • Solid catalysts were used for biodiesel production in a heterogeneous manner. • The catalyst could give the oil conversion of 83.2%. • The catalyst was characterized by using various techniques. - Abstract: The main aim of this research is to develop efficient and environmentally benign heterogeneous catalysts for biodiesel production. For this purpose, heterogeneous CaO–MoO3–SBA-15 catalysts were prepared by incipient impregnation method, and the prepared catalyst was tested for the transesterification process of soybean oil to produce biodiesel. Various techniques such as X-ray diffraction, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, scanning electron microscopy and thermo gravimetric analysis were employed for the characterization of the solid catalyst. The catalytic activity was dependent on the calcination temperature and loading amount of calcium and molybdenum oxides. The solid catalyst, with the CaO–MoO3 loading of 40% and calcined at 823 K, showed the best catalytic activity. The effect of methanol/oil molar ratio, reaction time, catalyst loading and catalyst stability was investigated. By using a 6 wt.% of catalyst with methanol/oil molar ratio of 50:1 at reflux of methanol, the oil conversion of 83.2% after 50 h of reaction, could be achieved over the solid catalyst. The catalyst can be easily recovered and reused without significant loss of activity

  4. Genetic Algorithm Procreation Operators for Alloy Nanoparticle Catalysts

    DEFF Research Database (Denmark)

    Lysgaard, Steen; Landis, David Dominic; Bligaard, Thomas;

    2014-01-01

    The long-term stability of binary nanoparticles and clusters is one of the main challenges in the development of novel (electro-)catalysts for e.g. CO2 reduction. Here, we present a method for predicting the optimal composition and structure of alloy nanoparticles and clusters, with particular...

  5. 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.

  6. 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.

  7. Studies of potassium-promoted nickel catalysts for methane steam reforming: Effect of surface potassium location

    Science.gov (United States)

    Borowiecki, Tadeusz; Denis, Andrzej; Rawski, Michał; Gołębiowski, Andrzej; Stołecki, Kazimierz; Dmytrzyk, Jaromir; Kotarba, Andrzej

    2014-05-01

    The effect of potassium addition to the Ni/Al2O3 steam reforming catalyst has been investigated on several model systems, including K/Al2O3 with various amounts of alkali promoters (1-4 wt% of K2O), a model catalyst 90%NiO-10%Al2O3 promoted with potassium and a commercial catalyst. The potassium surface state and stability were investigated by means of the Species Resolved Thermal Alkali Desorption method (SR-TAD). The activity of the catalysts in the steam reforming of methane and their coking-resistance were also evaluated. The results reveal that the beneficial effect of potassium addition is strongly related to its location in the catalysts. The catalyst surface should be promoted with potassium in order to obtain high coking-resistant catalysts. Moreover, the catalyst preparation procedure should ensure a direct interaction of potassium with the Al2O3 support surface. Due to the low stability of potassium on θ-Al2O3 this phase is undesirable during the preparation of a stable steam reforming catalyst.

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

    Institute of Scientific and Technical Information of China (English)

    Zhang Daqing; Cui Long; Sun Zuolin

    2002-01-01

    The influence of yttrium and ytterbium on the catalyticperformance 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.

  9. 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.

  10. Structure-activity relationship of surfactant for preparing DMFC anodic catalyst

    International Nuclear Information System (INIS)

    Three kinds of surfactants as stabilizer were applied to the preparation of electrocatalysts for direct methanol fuel cell (DMFC). The catalysts have been characterized by examining their catalytic activities, morphologies and particle sizes by means of cyclic voltammetry, chronoamperometry, X-ray diffraction and transmission electron microscopy (TEM). It is found that the surfactants with different structures have a significantly influence on the catalyst shape and activity. The catalysts prepared with non-ionic surfactants as the stabilizer show higher activity for direct oxidation of methanol. The structure-activity relationship (SAR) analysis has been explored and the effect of hydrophile-lipophile balance (HLB value) has also been discussed

  11. 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.

  12. Dynamical properties of nano-structured catalysts for methane conversion: an in situ scattering study

    DEFF Research Database (Denmark)

    Kehres, Jan

    The reactivity of catalyst particles can be radically enhanced by decreasing their size down to the nanometer range. The nanostructure of a catalyst can have an enormous and positive influence on the reaction rate, for example strong structure sensitivity was observed for methane reforming and...... Ni/NiO particles in a fresh catalyst sample showed a Ni/NiO core shell structure. The Ni lattice parameter decreased during the reduction due to the release of stress between the Ni core and the NiO shell. Ni particles sintered during heating in hydrogen after the reduction of the NiO shell. Dry...... reforming experiments were performed over a Ru/MgAl2O4. The catalyst showed a high sintering stability and no catalyst deactivation was observed. The results presented in this thesis emphasize the advantage of the simultaneous SAXS/W AXS laboratory setup to study nanostructured materials and catalysts in...

  13. 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.

  14. Endurance testing of a WDS catalyst

    International Nuclear Information System (INIS)

    the Pt high efficiency and due to the possibility of hydrophobization. During experiments carried out within this project, the Pt/C/PTFE catalyst used was manufactured from a mixture of Pt/C and Teflon, dyed onto cylindrical shape catalyst of sizes F = 2,5 mm, L = 15 mm and subsequently sintered to improve the mechanical stability. The sintering process was done into a glass equipment at 355-360 deg. C for maximum 10 min. All the experimental parameters will be acquired with a Field-Point acquisition system and the data will be modeled with the LabVIEW software. The results obtained and presented in this paper are part of project more extended. Until now the first objectives were attained, namely, designing and building of the experimental facility and manufacturing of the catalyst that will be used for endurance determinations. (authors)

  15. Production of biodiesel by transesterification of soybean oil using calcium supported tin oxides as heterogeneous catalysts

    International Nuclear Information System (INIS)

    Highlights: • Heterogeneous catalysts were prepared by an impregnation method with different conditions. • The catalysts were efficient in the soybean oil transesterification. • The catalytic activity and stability of the catalyst were investigated. - Abstract: The main objective of this work was to develop an environmentally benign process for the production of biodiesel by using a stable solid base catalyst. To this purpose, different heterogeneous CaO–SnO2 catalysts have been prepared by means of impregnation methods. Various techniques such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were applied for the catalyst characterization. The transesterification of soybean oil with methanol, to produce biodiesel, was carried out under batch conditions at refluxed methanol over the CaO–SnO2 catalysts. The catalytic activity is found to be highly dependent on the Ca/Sn ratio and calcination temperature. The solid catalyst with the Ca/Sn molar ratio of 4:1 and calcined at a temperature of 973 K, performed the best activity, reaching the conversion to methyl esters of 89.3% after 6 h of reaction at methanol reflux temperature (343 K) when a methanol/oil molar ratio of 12:1 and catalyst dosage of 8 wt.% were employed. Further, the solid catalyst is proved to be stable and durable for the transesterification reaction

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

    International Nuclear Information System (INIS)

    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

  17. 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.

  18. Coprecipitated nickel-alumina methanation catalysts

    International Nuclear Information System (INIS)

    In the last few years there has been a renewed interest in the methanation reaction CO+3H2=CH4+H2O. The investigations described in this thesis were performed in relation to the application of this reaction, within the framework of the so-called 'NFE' project, also called 'ADAM' and 'EVA' project. This project, which has been under investigation in West Germany for some years, aims at the investigation of the feasibility of transporting heat from a nuclear high temperature reactor by means of a chemical cycle. A promising possibility to realize such a cycle exists in applying the combination of the endothermic steam reforming of methane and the exothermic methanation reaction. This thesis describes the investigations into a certain type of methanation catalyst, viz. a coprecipitated nickel-alumina catalyst, with the aim to give more insight into the interrelationship between the preparation conditions on the one hand and catalyst properties such as activity and stability on the other hand. (Auth.)

  19. 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.

  20. 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.

  1. 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.

  2. 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)

  3. 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.

  4. 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.

  5. 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.

  6. Study on Performance of Hydrocracking Catalyst CHC-1

    Institute of Scientific and Technical Information of China (English)

    Wang Fucun; Zhang Xuejun; Zhu Jinling; Ge Dongmei

    2003-01-01

    Evaluation of hydrocracking catalyst CHC- l showed superior qualities of catalyst CHC- 1.When it was used for hydrocracking reaction, the yield of middle distillates (jet fuel and diesel fuel)can reach more than 71 m%. When it was used for medium-pressure hydro-upgrading of Daqing FCC diesel fuel, diesel density was decreased by 0.0284-0.0365 g/cm3 (20℃). Cetane number increased by 7.8-10.5 and the contents of sulphur and nitrogen were remarkably reduced. The storage stability of the upgraded diesel was improved.

  7. Chemical and electrochemical promotion of supported rhodium catalyst

    OpenAIRE

    Baranova, Olena; Comninellis, Christos

    2007-01-01

    The chemical and electrochemical promotion of highly dispersed nanofilm Rh catalysts (dispersion: about 10 %, film thickness: 40 nm) has been investigated for the first time. To this end Rh metal was sputter-deposited, either on a purely ionic conductor (8 % Y2O3-stabilized ZrO2) or on a mixed ionic-electronic conductor (TiO2), the latter being a highly dispersed layer of TiO2 (4 µm) deposited on YSZ. These catalysts are designated as Rh/YSZ and Rh/TiO2/YSZ, respectively. It was established a...

  8. Palladium/Zirconium Oxide Nanocomposite as a Highly Recyclable Catalyst for C-C Coupling Reactions in Water

    Directory of Open Access Journals (Sweden)

    Antonio Monopoli

    2010-06-01

    Full Text Available Palladium nanoparticles have been electrochemically supported on zirconium oxide nanostructured powders and all the nanomaterials have been characterized by several analytical techniques. The Pd/ZrO2 nanocatalyst is demonstrated to be a very efficient catalyst in Heck, Ullmann, and Suzuki reactions of aryl halides in water. The catalyst efficiency is attributed to the stabilization of Pd nanophases provided by tetra(alkyl- ammonium hydroxide, which behaves both as base and PTC (phase transfer catalyst agent.

  9. 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.

  10. 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.

  11. 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.

  12. 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 nanost...... catalyst after reaction and after aging tests shows the development of a core-shell type structure after being exposed to reaction conditions....

  13. Oxygen-reducing catalyst layer

    Science.gov (United States)

    O'Brien, Dennis P.; Schmoeckel, Alison K.; Vernstrom, George D.; Atanasoski, Radoslav; Wood, Thomas E.; Yang, Ruizhi; Easton, E. Bradley; Dahn, Jeffrey R.; O'Neill, David G.

    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.

  14. 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.

  15. 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.

  16. Reuse of Hydrotreating Spent Catalyst

    International Nuclear Information System (INIS)

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

  17. Hydrodewaxing with mixed zeolite catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chester, A.W.; McHale, W.D.; Yen, J.H.

    1986-03-11

    A process is described for catalytically dewaxing a hydrocarbon lubricating oil feedstock comprising contacting the feedstock with a dewaxing catalyst, the dewaxing catalyst comprising, in combination: (a) a zeolite catalyst having a Constraint Index not less than 1, (b) an acidic catalytic material selected from the group consisting of Mordenite, TEA Mordenite, Dealuminized Y, Ultrastable Y, Rare Earth Y, amorphous silica-alumina chlorinated alumina, ZSM-4 and ZSM-20, and (c) a hydrogenation component, and recovering a dewaxed product. A process is also described for catalytically dewaxing a hydrocarbon lubricating oil feedstock comprising contacting the feedstock with a dewaxing catalyst, the dewaxing catalyst comprising, in combinations: (a) a first zeolite catalyst selected from the group consisting of ZSM-5, ZMS-11, ZSM-12, ZSM-22, ZSM-23, ZSM-34, ZSM-35, ZSM-38, ZSM-48, TMA Offretite and Erionite, (b) a second catalyst selected from the group consisting of ZSM-12, ZSM-22, ZSM-38 and ZSM-48, the second zeolite catalyst being different from the first zeolite catalyst, and (c) a hydrogenation component, and recovering a dewaxed product.

  18. 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.

  19. Characterization of Al2O3 Supported Nickel Catalysts Derived from RFNon-thermal Plasma Technology

    International Nuclear Information System (INIS)

    Catalysts derived from non-thermal plasma techniques have previously shown unusual and highly advantageous catalytic properties including room temperature reduction, unusual metal particle structure and metal-support interactions, and enhanced selectivity and stability. This study focuses on the characterization of Al2O3 supported Ni catalysts derived from the RF non-thermal plasma technique with in-situ XRD, TPR-MS and STEM and on relating the results to the enhanced activity and stability of benzene hydrogenation. The results suggest that catalysts with plasma treatments before impregnation are relatively easier to be reduced and result in better activities under mild reduction conditions. These plasma treatments stabilize the nickel particle sizes of air(B) and H2(B) catalysts at 600 C by slowing down the sintering process. Plasma treatments after the impregnation of precursors, on the other hand, tend to delay the growth of nickel particles below 600 C, forming smaller Ni particles, but with a sudden increase in particle size near 600 C. It suggests that the structure of Ni nitrate and the metal-support interaction have been altered by the plasma treatments. The reduction patterns of plasma 1 treated catalysts are, therefore, changed. The catalyst with a combination plasma treatment demonstrates that the effect of a combination plasma treatment is larger than either the plasma treatment before or after the impregnation alone. Both plasma treatments before and after the impregnation of metal precursor play important roles in modifying supported metal catalysts.

  20. Covalency-reinforced oxygen evolution reaction catalyst

    Science.gov (United States)

    Yagi, Shunsuke; Yamada, Ikuya; Tsukasaki, Hirofumi; Seno, Akihiro; Murakami, Makoto; Fujii, Hiroshi; Chen, Hungru; Umezawa, Naoto; Abe, Hideki; Nishiyama, Norimasa; Mori, Shigeo

    2015-09-01

    The oxygen evolution reaction that occurs during water oxidation is of considerable importance as an essential energy conversion reaction for rechargeable metal-air batteries and direct solar water splitting. Cost-efficient ABO3 perovskites have been studied extensively because of their high activity for the oxygen evolution reaction; however, they lack stability, and an effective solution to this problem has not yet been demonstrated. Here we report that the Fe4+-based quadruple perovskite CaCu3Fe4O12 has high activity, which is comparable to or exceeding those of state-of-the-art catalysts such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ and the gold standard RuO2. The covalent bonding network incorporating multiple Cu2+ and Fe4+ transition metal ions significantly enhances the structural stability of CaCu3Fe4O12, which is key to achieving highly active long-life catalysts.

  1. 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.

  2. Effect of hierarchical meso–macroporous alumina-supported copper catalyst for methanol synthesis from CO2 hydrogenation

    International Nuclear Information System (INIS)

    Highlights: • CO2 hydrogenation over Cu-loaded unimodal and hierarchical alumina catalysts. • Cu-loaded hierarchical catalyst exhibited higher methanol selectivity and stability. • The presence of macropores reduced the probability of side reaction. - Abstract: Effects of pore structures of alumina on the catalytic performance of copper catalysts for CO2 hydrogenation were investigated. Copper-loaded hierarchical meso–macroporous alumina (Cu/HAl) catalyst exhibited no significant difference in terms of CO2 conversion with copper-loaded unimodal mesoporous alumina (Cu/UAl) catalyst. However, the selectivity to methanol and dimethyl ether of the Cu/HAl catalyst was much higher than that of the Cu/UAl catalyst. This was attributed to the presence of macropores which diminished the occurrence of side reaction by the shortening the mesopores diffusion path length. The Cu/HAl catalyst also exhibited much higher stability than the Cu/UAl catalyst due to the fast diffusion of water out from the catalyst pellets, alleviating the oxidation of metallic copper to CuO

  3. 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.

  4. Neutral nickel(II) phthalocyanine as a stable catalyst for visible-light-driven hydrogen evolution from water.

    Science.gov (United States)

    Yuan, Yong-Jun; Tu, Ji-Ren; Lu, Hong-Wei; Yu, Zhen-Tao; Fan, Xiao-Xing; Zou, Zhi-Gang

    2016-01-28

    Neutral nickel(ii) phthalocyanine was found to be an efficient and stable catalyst for photocatalytic H2 evolution from water when coupled with an iridium complex as the photosensitizer and triethanolamine as the sacrificial electron donor. The result shows that the Ni-N sigma bond can enhance the stability of the catalyst. PMID:26743686

  5. DEHYDROGENATION CATALYST FOR PRODUCTION OF MTBE

    Science.gov (United States)

    The objectives of this project were to better understand the effect of different catalyst preparation parameters, the effect of different catalyst treatment parameters, and the mechanism of deactivation. Accordingly, catalysts were made using various preparation methods and with...

  6. 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...

  7. Graphitised Carbon Nanofibres as Catalyst Support for PEMFC

    DEFF Research Database (Denmark)

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

    2011-01-01

    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......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 for the...... anchorage of Pt catalyst nanoparticles. Modification of the fibre surface is therefore needed. In this study Pt nanoparticles have been deposited onto as-received and surface-modified G-CNFs. The surface modifications of the fibres comprise acid treatment and nitrogen doping by pyrolysis of a polyaniline...

  8. In silico search for novel methane steam reforming catalysts

    Science.gov (United States)

    Xu, Yue; Lausche, Adam C.; Wang, Shengguang; Khan, Tuhin S.; Abild-Pedersen, Frank; Studt, Felix; Nørskov, Jens K.; Bligaard, Thomas

    2013-12-01

    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’) with a microkinetic modeling technique to predict the rates and selectivities of a prospective material. This paper illustrates this screening technique using the steam reforming of methane to carbon monoxide and hydrogen as a test reaction. While catalysts are already commercially available for this process, the method demonstrated in this paper is very general and could be applied to a wide range of catalytic reactions. Following the steps outlined herein, such an analysis could potentially enable researchers to understand reaction mechanisms on a fundamental level and, on this basis, develop leads for new metal alloy catalysts.

  9. In silico search for novel methane steam reforming catalysts

    International Nuclear Information System (INIS)

    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’) with a microkinetic modeling technique to predict the rates and selectivities of a prospective material. This paper illustrates this screening technique using the steam reforming of methane to carbon monoxide and hydrogen as a test reaction. While catalysts are already commercially available for this process, the method demonstrated in this paper is very general and could be applied to a wide range of catalytic reactions. Following the steps outlined herein, such an analysis could potentially enable researchers to understand reaction mechanisms on a fundamental level and, on this basis, develop leads for new metal alloy catalysts. (paper)

  10. Effect of nitrogen post-doping on a commercial platinum-ruthenium/carbon anode catalyst

    Science.gov (United States)

    Corpuz, April R.; Wood, Kevin N.; Pylypenko, Svitlana; Dameron, Arrelaine A.; Joghee, Prabhuram; Olson, Tim S.; Bender, Guido; Dinh, Huyen N.; Gennett, Thomas; Richards, Ryan M.; O'Hayre, Ryan

    2014-02-01

    This work investigates the effects of after-the-fact chemical modification of a state-of-the-art commercial carbon-supported PtRu catalyst for direct methanol fuel cells (DMFCs). A commercial PtRu/C (JM HiSPEC-10000) catalyst is post-doped with nitrogen by ion-implantation, where "post-doped" denotes nitrogen doping after metal is carbon-supported. Composition and performance of the PtRu/C catalyst post-modified with nitrogen at several dosages are evaluated using X-ray photoelectron spectroscopy (XPS), rotating disk electrode (RDE), and membrane electrode assemblies (MEAs) for DMFC. Overall, implantation at high dosage results in 16% higher electrochemical surface area and enhances performance, specifically in the mass transfer region. Rotating disk electrode (RDE) results show that after 5000 cycles of accelerated durability testing to high potential, the modified catalyst retains 34% more electrochemical surface area (ECSA) than the unmodified catalyst. The benefits of nitrogen post-doping are further substantiated by DMFC durability studies (carried out for 425 h), where the MEA with the modified catalyst exhibits higher surface area and performance stability in comparison to the MEA with unmodified catalyst. These results demonstrate that post-doping of nitrogen in a commercial PtRu/C catalyst is an effective approach, capable of improving the performance of available best-in-class commercial catalysts.

  11. Nanofiltration of rhodium tris(triphenylphosphine) catalyst in ethyl acetate solution

    Science.gov (United States)

    Shaharun, Maizatul S.; Mustafa, Ahmad K.; Taha, Mohd F.

    2012-09-01

    Solvent resistant nanofiltration (SRNF) using polymer membranes has recently received enhanced attention due to the search for cleaner and more energy-efficient technologies. The large size of the rhodium tris(triphenylphosphine) [HRh(CO)(PPh3)3] catalyst (>400 Da) - relative to other components of the hydroformylation reaction provides the opportunity for a membrane separation based on retention of the catalyst species while permeating the solvent. The compatibility of the solvent-polyimide membrane (DuraMem{trade mark, serif} 200 and DuraMem{trade mark, serif} 500) combinations was assessed in terms of the membrane stability in solvent plus non-zero solvent flux at 2.0 MPa. Good HRh(CO)(PPh3)3 rejection (>0.95) and solvent fluxes of 9.9 L/m2ṡh1 at 2.0 MPa were obtained in the catalyst-ethyl acetate-DuraMem 500 system. The effect of pressure and catalyst concentration on the solvent flux and catalyst rejection was conducted on the catalyst-ethyl acetate-membrane systems. Increasing pressure substantially improved both solvent flux and catalyst rejection, while increasing catalyst concentration was found to be beneficial in terms of substantial increases in catalyst rejection without significantly affecting solvent flux.

  12. Development and Commercial Application of High-Platinum CCR Catalyst with Low Coke Deposition Rate

    Institute of Scientific and Technical Information of China (English)

    Ma Aizeng; Pan Jincheng; Yang Sennian

    2007-01-01

    By means of selecting proper additives and optimizing catalyst composition and preparation procedures,a high-platinum and low coke deposition catalyst PS-Ⅶ for continuous catalytic reforming (CCR)without reducing its specific surface area has been successfully developed.This catalyst PS-Ⅶ was evaluated in a 100-mL pilot test unit.Study results showed that under the same reaction conditions the newly developed catalyst PS-Ⅶ achieved a 26%reduction in coke deposition as compared to the existing high-platinum CCR catalyst.This catalyst upon its first commercial application in a 1.39Mt/a CCR unit had exhibited good anti-attrition performance and good stability in terms of its specific surface area.Compared to the original CCR catalyst this PS-Ⅶ type catalyst could reduce the coke deposition by 27.32%when operating on feedstock with low potential aromatic content,along with apparent increase in C6+liquid yield,hydrogen yield and aromatics yield,which could grapple with the problem associated with the catalyst regeneration constraints after CCR capacity expansion to ensure the longcycle high-load operation of the CCR unit.

  13. Separation of Hydridocarbonyltris(triphenylphosphine) Rhodium (I) Catalyst Using Solvent Resistant Nano filtration Membrane

    International Nuclear Information System (INIS)

    An investigation was conducted into the nano filtration of rhodium tris(triphenyl-phosphine) [HRh(CO)(PPh3)3] catalyst used in the hydroformylation of olefins. The large size of the catalyst (>400 Da) - relative to other components of the reaction provides the opportunity for a membrane separation based on retention of the catalyst species while permeating the solvent. The compatibility of the solvent-polyimide membrane (STARMEMTM 122 and STARMEMTM 240) combinations was assessed in terms of the membrane stability in solvent plus non-zero solvent flux at 2.0 MPa. The morphology of the membrane was studied by field emission scanning electron microscopy (FESEM). The solvent flux and membrane rejection of HRh(CO)(PPh3)3 was then determined for the catalyst-solvent-membrane combination in a dead-end pressure cell. Good HRh(CO)(PPh3)3 rejection (>0.93) coupled with good solvent fluxes (>72 L/ m2 h1 at 2.0 MPa) were obtained in one of the systems tested. The effect of pressure and catalyst concentration on the solvent flux and catalyst rejection was conducted. Increasing pressure substantially improved both solvent flux and catalyst rejection, while increasing catalyst concentration was found to be beneficial in terms of substantial increases in catalyst rejection without significantly affecting the solvent flux. (author)

  14. 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.

  15. 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

  16. Startup procedure for reforming catalysts

    Energy Technology Data Exchange (ETDEWEB)

    McHale, W.D.; Schoennagel, H.J.

    1984-08-14

    Process for reforming a hydrocarbon charge under reforming conditions in a reforming zone containing a sulfur-sensitive metal containing reforming catalyst wherein over-cracking of the charge stock and excessive temperature rise in the reforming zone is suppressed by pre-conditioning the catalyst, prior to contact with the charge, with a reformate of specified octane number and aromatics content.

  17. Doped palladium containing oxidation catalysts

    Science.gov (United States)

    Mohajeri, Nahid

    2014-02-18

    A supported oxidation catalyst includes a support having a metal oxide or metal salt, and mixed metal particles thereon. The mixed metal particles include first particles including a palladium compound, and second particles including a precious metal group (PMG) metal or PMG metal compound, wherein the PMG metal is not palladium. The oxidation catalyst may also be used as a gas sensor.

  18. Catalysts for low temperature oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Toops, Todd J.; Parks, III, James E.; Bauer, John C.

    2016-03-01

    The invention provides a composite catalyst containing a first component and a second component. The first component contains nanosized gold particles. The second component contains nanosized platinum group metals. The composite catalyst is useful for catalyzing the oxidation of carbon monoxide, hydrocarbons, oxides of nitrogen, and other pollutants at low temperatures.

  19. 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.

  20. An assessment on preparation methods and applications of hydrophobic Pt-catalyst in nuclear and environmental field

    International Nuclear Information System (INIS)

    Based on the long experience of the authors in the preparation, testing and evaluation of the performances of hydrophobic catalysts and based on the reviewed references, this paper presents up-to-date R and D activities on the preparation and application of hydrophobic catalysts for use in nuclear and environmental fields. Unlike the conventional hydrophilic catalysts, the hydrophobic catalysts repel the liquid water and allow the transport of the gaseous reactants and reaction products to and from catalytic active centers. For deuterium and tritium separation, over one hundred hydrophobic catalyst types have been prepared in different experimental conditions and by a large diversity of wet proofing methods. The influence of about twenty parameters on catalytic activity have been also studied. The purpose of this paper is: (1) to provide a database for preparation and selection of he most appropriate method for preparing an active hydrophobic catalyst, (2) to show how to use the hydrophobic catalyst and how to operate efficiently the reactor packed with hydrophobic catalyst, (3) to evaluate the performances and potentiality of hydrophobic catalysts in nuclear and environmental field, (4) evaluation of applications of hydrophobic catalysts in nuclear and environmental fields. As result, the following categories are shown: (1) the hydrophobic catalysts based on platinum and Teflon as wet-proofing proved to have the highest activity and the longest stability, (2) the utilization of hydrophobic catalyst as ordered mixed catalytic packing in the trickle bed or separated bed reactors is more efficient and has been entirely proved on industrial scale for tritium separation process, (3) the extension of the applications of hydrophobic catalysts for other processes which take place in the presence of saturated humidity or liquid water in environmental protection field. The merits of hydrophobic Pt-catalysts for tritium separation are discussed in comparison to other

  1. 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.

  2. 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. PMID:26755755

  3. Some problems of manufacturing and industrial application of CoMo-Al2O3 catalyst

    International Nuclear Information System (INIS)

    The monograph presents results of studies of some selected problems relating to CoMo-Al2O3 catalyst: method of production alumina support and catalyst; application of catalyst in the selected hydro refining processes; physicochemical properties of the used catalyst; reclamation of metal compounds from the spent catalyst. Results of investigations of catalyst preparation illustrate how the physicochemical properties of alumina support and catalyst, mainly porous structure could be controlled by the selection of raw materials and parameters of aluminum hydroxide precipitation, method of forming and calcination temperature of support. Application of the catalyst of modified porous structure has shown its high activity in hydro refining process of light cracking catalytic oil (over 95% hydrodesulphurization) and mild hydro cracking process of vacuum gas oil (sulphur content in product below 0.03% wt.). As an effect of studying of hydro refining process of aromatic hydrocarbon fraction it has been found that H2S concentration in reaction mixture is the main factor influencing process selectivity. Some effect on the selectivity exerts also other process parameters and chemical composition of the catalyst - cobalt molybdenum content ratio and promoters content. Long term exploitation of the domestic CoMo-Al2O3 catalyst in hydrodesulphurization process indicates its satisfied thermal stability although results in deteriorating of mechanical resistance, lowering of specific surface area, increase in mean pore radius and decrease in acidity of catalyst. In the last chapter of the monograph the results of investigations of reclamation of metal compounds (molybdic acid, aluminum hydroxide, cobalt carbonate) from the spent catalyst as well as an original technology of manufacture of the fresh one using these compounds have been presented. (author). 338 refs, 31 figs, 32 tabs

  4. Supported molten-metal catalysts

    Science.gov (United States)

    Datta, Ravindra; Singh, Ajeet; Halasz, Istvan; Serban, Manuela

    2001-01-01

    An entirely new class of catalysts called supported molten-metal catalysts, SMMC, which can replace some of the existing precious metal catalysts used in the production of fuels, commodity chemicals, and fine chemicals, as well as in combating pollution. SMMC are based on supporting ultra-thin films or micro-droplets of the relatively low-melting (<600.degree. C.), inexpensive, and abundant metals and semimetals from groups 1, 12, 13, 14, 15 and 16, of the periodic table, or their alloys and intermetallic compounds, on porous refractory supports, much like supported microcrystallites of the traditional solid metal catalysts. It thus provides orders of magnitude higher surface area than is obtainable in conventional reactors containing molten metals in pool form and also avoids corrosion. These have so far been the chief stumbling blocks in the application of molten metal catalysts.

  5. Catalyst Needs for Thermochemical Hydrogen Production Cycles

    International Nuclear Information System (INIS)

    Thermochemical cycles can be used to split water through a series of chemical reactions where the net result is the production of hydrogen and oxygen at much lower temperatures than direct thermal decomposition. All chemicals within the cycle are fully recycled and the heat to drive the reactions, which tend to be endothermic, must be provided by a primary energy source. When the primary energy driver is nuclear heat, hydrogen can be generated without producing green-house gases, and can provide independence from our dwindling supplies of fossil fuels. A number of thermochemical cycles can be driven by the primary heat of nuclear reactors, especially a very high temperature reactor (VHTR). The sulfur-based family of thermochemical cycles, including the Sulfur- Iodine cycle (S-I), the Hybrid Sulfur cycle, and the Sulfur-Bromine Hybrid cycle, appears promising for producing hydrogen using nuclear heat. These cycles employ a high-temperature sulfuric acid decomposition reaction step. The reaction produces oxygen and generates SO2, which is used in other reaction steps of the cycles. The reaction takes place from 750 to 900 deg. C, or higher, and is facilitated by heterogeneous catalysts. The S-I cycle produces hydrogen by the catalytic decomposition of HI. The calcium-bromine cycle is also being considered as a nuclear powered thermochemical cycle. The various cycles all present requirements of high temperatures and harsh chemical reaction conditions which present significantly challenging environments for catalytic materials. This work will focus on the catalyst needs of thermochemical cycles that are candidates for being powered by nuclear reactors. Specific catalyst activity and stability testing results will be provided for the decomposition of sulfuric acid for the production of oxygen in the sulfur-based family of cycles and for the catalytic decomposition of hydro-iodic acid for the production of hydrogen in the S-I process. Sulfuric acid decomposition results

  6. Proposal for platinum hydrophobic catalyst for hydrogen isotopes separation from nuclear effluents

    International Nuclear Information System (INIS)

    Full text: The hydrophobic catalysts were originally conceived in Canada for deuterium enrichment and tritium separation by hydrogen-liquid water isotopic exchange in nuclear field. Unlike the conventional hydrophilic catalysts, which become inefficient at direct contact with liquid water, the hydrophobic catalysts keep a high catalytic activity and stability, even under direct contact with liquid water or in presence of saturated humidity. A new method for preparation of new improved hydrophobic Pt-catalysts has been proposed and is now underway. The main steps and experimental conditions of preparation are largely discussed. A new wet-proofing agent and some new binding agents (titanium oxide, cerium oxide, zirconium oxide) with catalytic role are proposed and tested. The applications of the new hydrophobic catalyst in nuclear field for tritium separations from tritiated liquid effluents and for the clean-up of the airborne tritium at nuclear facilities are discussed. (authors)

  7. Comprehensive Utilization of Filter Residue from the Preparation Process of Zeolite-Based Catalysts

    Directory of Open Access Journals (Sweden)

    Shu-Qin Zheng

    2016-05-01

    Full Text Available A novel utilization method of filter residue from the preparation process of zeolite-based catalysts was investigated. Y zeolite and a fluid catalytic cracking (FCC catalyst were synthesized from filter residue. Compared to the Y zeolite synthesized by the conventional method, the Y zeolite synthesized from filter residue exhibited better thermal stability. The catalyst possessed wide-pore distribution. In addition, the pore volume, specific surface area, attrition resistance were superior to those of the reference catalyst. The yields of gasoline and light oil increased by 1.93 and 1.48 %, respectively. At the same time, the coke yield decreased by 0.41 %. The catalyst exhibited better gasoline and coke selectivity. The quality of the cracked gasoline had been improved.

  8. 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.

  9. Research on Catalytic Properties of Palladium Catalyst Prepared by Biological Reduction Method

    Institute of Scientific and Technical Information of China (English)

    Zhang Feng; Fu Jiquan

    2013-01-01

    This paper relates to highly dispersed supported Pd/MWCNTs and Pd/α-Al2O3 catalysts prepared by biological reduction method. The physico-chemical properties and the difference in catalytic activity of Pd catalysts prepared by bio-logical reduction method and chemical method, respectively, were investigated using XRD, TEM and speciifc surface char-acterization methods. The catalytic properties of catalysts were studied through activity evaluation means. The test results showed that the catalysts prepared by biological method were characteristic of small Pd nanoparticle size, good dispersion and low agglomeration, while possessing a high activity and stability in styrene hydrogenation reaction in comparison with catalysts prepared via the chemical method.

  10. Hydrocarbon fuel synthesis from sorbitol over bifunctional catalysts: Association of tungstated titania with platinum, palladium or iridium

    OpenAIRE

    Vilcocq, Léa; Cabiac, Amandine; Especel, Catherine; Lacombe, Sylvie; Duprez, Daniel

    2015-01-01

    To selectively transform sorbitol into hydrocarbons in aqueous phase, new bifunctional catalytic systems are designed by associating a hydrogenating metallic catalyst (M/ZrO2, M = Pt, Ir or Pd) and a dehydratingacidic catalyst (TiO2–WOx) in a mechanical mixture. Zirconium oxide was chosen as support because ithas virtually no dehydration activity and gives a good stability to the metal in water. This stability isevaluated through several characterizations before and after contact with the aqu...

  11. 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.

  12. Use of CuNi/YSZ and CuNi/SDC Catalysts for the Reverse Water Gas Shift Reaction

    OpenAIRE

    Maxime Lortie; Isaifan, Rima J.

    2015-01-01

    Cu50Ni50 nanoparticles were synthesized using a modified polyol method and deposited on samarium-doped ceria, SDC, and yttria-stabilized zirconia, YSZ, supports to form reverse water-gas shift, RWGS, catalysts. The best CO yields, obtained with the Cu50Ni50/SDC catalyst, were about 90% of the equilibrium CO yields. In contrast CO yields using Pt/SDC catalysts were equal to equilibrium CO yields at 700°C. Catalyst selectivity to CO was 100% at hydrogen partial pressures equal to CO2 partial...

  13. Development and Commercial Application of a Novel Catalyst DVR-1 for Catalytic Cracking of Daqing Vacuum Residue

    Institute of Scientific and Technical Information of China (English)

    Yang Yinan; Tian Huiping; Chen Yun; Wang Yamin

    2002-01-01

    A newly developed catalyst type DVR- 1 for catalytic cracking of Daqing vacuum resid was put into use in a commercial VRFCC unit. This catalyst features uniquely active matrix and modified ultrastable zeolite. The commercial application results show that the DVR-1 type catalyst has the advantage of high heavy oil conversion, good metal tolerance and good stability for catalyst regeneration. The FCC tests have shown favorable product distribution, acceptable product quality and enormous economic benefits when processing the feedstock containing 75%-100% Daqing VR.

  14. 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.

  15. DEVELOPMENT OF ATTRITION RESISTANT IRON-BASED FISCHER-TROPSCH CATALYSTS

    International Nuclear Information System (INIS)

    The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO+H2) to liquid fuels. Since the reaction is highly exothermic, one of the major problems in control of the reaction is heat removal. Recent work has shown that the use of slurry bubble column reactors (SBCRs) can largely solve this problem. The use of iron-based catalysts is attractive not only due to their low cost and ready availability, but also due to their high water-gas shift activity which makes it possible to use these catalysts with low H2/CO ratios. However, a serious problem with use of Fe catalysts in a SBCR is their tendency to undergo attrition. This can cause fouling/plugging of downstream filters and equipment, makes the separation of catalyst from the oil/wax product very difficult if not impossible, and results in a steady loss of catalyst from the reactor. Recently, fundamental understanding of physical attrition is being addressed by incorporating suitable binders into the catalyst recipe. This has resulted in the preparation of a spray dried Fe-based catalyst having aps of 70 mm with high attrition resistance. This Fe-based attrition resistant, active and selective catalyst gave 95% CO conversion through 125 hours of testing in a fixed-bed at 270 C, 1.48 MPa, H2/CO=0.67 and 2.0 NL/g-cat/h with C5+ selectivity of >78% and methane selectivity of <5%. However, further development of the catalyst is needed to address the chemical attrition due to phase changes that any Fe-catalyst goes through potentially causing internal stresses within the particle and resulting in weakening, spalling or cracking. The objective of this research is to develop robust iron-based Fischer-Tropsch catalysts that have suitable activity, selectivity and stability to be used in the slurry bubble column reactor. Specifically we aim to develop to: (i) improve the performance and preparation procedure of the high activity, high attrition resistant, high alpha iron-based catalysts

  16. Causes of Activation and Deactivation of Modified Nanogold Catalysts during Prolonged Storage and Redox Treatments.

    Science.gov (United States)

    Kolobova, Ekaterina; Kotolevich, Yulia; Pakrieva, Ekaterina; Mamontov, Grigory; Farías, Mario H; Bogdanchikova, Nina; Cortés Corberán, Vicente; Pestryakov, Alexey

    2016-01-01

    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. PMID:27089310

  17. Promotion effect of iron on Mo/Al2O3 catalyst for the CAMERE process

    Directory of Open Access Journals (Sweden)

    Abolfazl Gharibi Kharaji

    2012-08-01

    Full Text Available Reverse Water Gas Shift (RWGS reaction is one of the main reactions that can be used toreduce greenhouse gases emissions. Through this reaction CO2 is converted to CO to produce beneficialchemicals such as methanol. In this paper Mo-Al2O3 catalyst was prepared and then promoted with Feions through co-impregnation method to produce Fe-Mo-Al2O3 catalyst. XRD tests were taken todetermine the structure of the catalysts. Activity, selectivity and stability of both catalysts wereinvestigated in a batch reactor and the results indicate that addition of Fe promoter to Mo-Al2O3 catalystincreased its activity and CO selectivity. Fe-Mo-Al2O3 showed acceptable catalytic stability during RWGSreaction. As a whole, Fe-Mo-Al2O3 can be a suitable candidate for RWGS reaction in CAMERE (carbondioxide hydrogenation to form methanol via a reverse-water-gas-shift reaction process.

  18. 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.

  19. 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.

  20. 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.)

  1. 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 

  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. Site Identification on Heteropolyacid Catalysts using CO & CO2 and Transmission & Diffuse Reflectance IR Spetroscopy

    OpenAIRE

    Kröhnert, Jutta; Jentoft, Friederike C.; Schlögl, Robert

    2003-01-01

    Site Identification on Heteropolyacid Catalysts using CO & CO2 and Transmission & Diffuse Reflectance IR Spectroscopy Jutta Kröhnert, Friederike C. Jentoft, Robert Schlögl Department of Inorganic Chemistry, Fritz-Haber-Institute of the Max Planck Society Faradayweg 4-6, D-14195 Berlin, Germany Introduction Heteropolyacid-based catalysts are used in the industrial production of methacrolic acid from methacrolein [1]. Unfortunately, the (thermal) stability and thus the lifetim...

  4. 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.

  5. 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.

  6. Influence of support material on Ni catalysts for propane dry reforming to synthesis gas

    OpenAIRE

    2008-01-01

    Ni/SiO2 and Ni/Mg(Al)O catalysts with difference metal loadings have been prepared. The activity, selectivity and stability of supported Ni catalysts for propane dry reforming to syngas reaction were investigated by catalytic testing at 600 ºC, C3H8:CO2:H2:N2 (in vol.%) = 10:30:10:50. Ni particle size was investigated by Transmission electron microscopy (TEM). Turn-over frequencies for Ni/SiO2 catalysts were calculated as a guideline to the relationship between catalytic activity and Ni parti...

  7. 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...

  8. Monolithic Catalysts with Low Noble-Metal Content for Exhaust Purification of Small Gasoline Engines

    Institute of Scientific and Technical Information of China (English)

    Zhang Lijuan; Mao Xiaobo; Chen Yaoqiang; Zhong Junbo; Wang Jianli; Zhao Ming; Gong Maochu

    2007-01-01

    A series of low noble-metal content monolithic catalysts for exhaust purification of small gasoline engines was investigated, and it was found that the Pt/Rh-OSM/Al2O3 (where OSM was oxygen storage material) catalyst with Ce0.5Zr0.5-MnOx(3%MnOx) OSM held low light-off temperature for CO, HC, and NO;quite wide three-way window, and outstanding thermal stability. The catalyst could efficiently control exhaust emission of small gasoline engines.

  9. Rhodium (II) carbene C-H insertion in water and catalyst reuse

    International Nuclear Information System (INIS)

    A five-session laboratory experiment is described for the synthesis of a beta-lactam via Rh(II) catalysed intramolecular C-H insertion of a alpha-diazo-alpha-ethoxycarbonyl acetamide. The metallo-carbene, responsible for the C-H bond activation, was generated from the diazo substrate and the catalyst Rh2(OAc)4. The high stability and solubility of the catalyst and the exclusive C-H insertion of the Rh-carbene allows the synthesis of this important heterocycle in water and the catalyst reutilization. (author)

  10. Study of the butyl acetate synthesis - 1. Catalyst selection

    Directory of Open Access Journals (Sweden)

    Álvaro Orjuela Londoño

    2010-04-01

    Full Text Available In this work, a laboratory scale selection study over eight catalytic agents was made, in the acetic acid and butyl alcohol esterification reaction (seven lon exchange resins and a zeolytic solid. Considering some physicochemical characteristics as the activation pre-treating requirements, acidity, thermal stability, reaction performance, etc., it was found that macroporous ion exchange resins are the most efficient catalysts, especially Lewatit K-2431 resin.

  11. In silico search for novel methane steam reforming catalysts

    OpenAIRE

    Xu, Yue; Lausche, Adam C; Wang, Shengguang; Khan, Tuhin Suvra; Abild-Pedersen, Frank; Studt, Felix; Nørskov, Jens K.; Bligaard, Thomas

    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’) with a microkinetic modeling technique to predict the rates and selectivities of a prospective material. This paper illustrates this screening technique using the steam reforming of methane to carbon m...

  12. Magnetically Recoverable Ruthenium Catalysts in Organic Synthesis

    OpenAIRE

    Dong Wang; Didier Astruc

    2014-01-01

    Magnetically recyclable catalysts with magnetic nanoparticles (MNPs) are becoming a major trend towards sustainable catalysts. In this area, recyclable supported ruthenium complexes and ruthenium nanoparticles occupy a key place and present great advantages compared to classic catalysts. In this micro-review, attention is focused on the fabrication of MNP-supported ruthenium catalysts and their catalytic applications in various organic syntheses.

  13. Cable Stability

    CERN Document Server

    Bottura, L

    2014-01-01

    Superconductor stability is at the core of the design of any successful cable and magnet application. This chapter reviews the initial understanding of the stability mechanism, and reviews matters of importance for stability such as the nature and magnitude of the perturbation spectrum and the cooling mechanisms. Various stability strategies are studied, providing criteria that depend on the desired design and operating conditions.

  14. Recycling of waste spent catalyst in road construction and masonry blocks.

    Science.gov (United States)

    Taha, Ramzi; Al-Kamyani, Zahran; Al-Jabri, Khalifa; Baawain, Mahad; Al-Shamsi, Khalid

    2012-08-30

    Waste spent catalyst is generated in Oman as a result of the cracking process of petroleum oil in the Mina Al-Fahl and Sohar Refineries. The disposal of spent catalyst is of a major concern to oil refineries. Stabilized spent catalyst was evaluated for use in road construction as a whole replacement for crushed aggregates in the sub-base and base layers and as a partial replacement for Portland cement in masonry blocks manufacturing. Stabilization is necessary as the waste spent catalyst exists in a powder form and binders are needed to attain the necessary strength required to qualify its use in road construction. Raw spent catalyst was also blended with other virgin aggregates, as a sand or filler replacement, for use in road construction. Compaction, unconfined compressive strength and leaching tests were performed on the stabilized mixtures. For its use in masonry construction, blocks were tested for unconfined compressive strength at various curing periods. Results indicate that the spent catalyst has a promising potential for use in road construction and masonry blocks without causing any negative environmental impacts. PMID:22704771

  15. Electrochemically Stable Titanium Oxy-Nitride Support for Platinum Electro-Catalyst for PEM Fuel Cell Applications

    International Nuclear Information System (INIS)

    Titanium Oxy-Nitride is prepared by an in-situ urea-based sol-gel method as a support for the platinum electro-catalyst for the oxygen reduction reaction (ORR). XRD, BET, SEM and EDX are used to analyze the physicochemical properties of the prepared Pt/TiON catalyst; and its electrochemical properties are evaluated by CV and RDE tests. Electrochemical active surface area is determined and compared to that of the commercial Pt/C electro-catalyst. Pt/TiON electro-catalyst showed a better electrochemical stability than those of the commercial Pt/C electro-catalyst. It is also found that the ORR proceeds via four electron transfer mechanism on both Pt/C and Pt/TiON electro-catalysts

  16. Oxidation catalysts comprising metal exchanged hexaaluminate wherein the metal is Sr, Pd, La, and/or Mn

    Science.gov (United States)

    Wickham, David; Cook, Ronald

    2008-10-28

    The present invention provides metal-exchanged hexaaluminate catalysts that exhibit good catalytic activity and/or stability at high temperatures for extended periods with retention of activity as combustion catalysts, and more generally as oxidation catalysts, that make them eminently suitable for use in methane combustion, particularly for use in natural gas fired gas turbines. The hexaaluminate catalysts of this invention are of particular interest for methane combustion processes for minimization of the generation of undesired levels (less than about 10 ppm) of NOx species. Metal exchanged hexaaluminate oxidation catalysts are also useful for oxidation of volatile organic compounds (VOC), particularly hydrocarbons. Metal exchanged hexaaluminate oxidation catalysts are further useful for partial oxidation, particularly at high temperatures, of reduced species, particularly hydrocarbons (alkanes and alkenes).

  17. SCALEUP OF ALUMINUM PHOSPHATE CATALYST FOR PILOT PLANT LPDMEtm RUN; TOPICAL

    International Nuclear Information System (INIS)

    The Liquid Phase Dimethyl Ether (LPDME(trademark)) process converts synthesis gas to dimethyl ether in a single slurry bubble column reactor. A mixed slurry of methanol synthesis catalyst and methanol dehydration catalyst in a neutral mineral oil simultaneously synthesizes methanol from syngas and converts some of it to dimethyl ether and water. The reaction scheme is shown below: 2H(sub 2)+ CO= CH(sub 3)OH; 2CH(sub 3)OH= CH(sub 3)OCH(sub 3)+ H(sub 2)O; H(sub 2)O+ CO= CO(sub 2)+ H(sub 2). Most of the water produced in this reaction is converted to hydrogen by reduction with carbon monoxide (water gas shift reaction). This synergy permits higher per pass conversion than methanol synthesis alone. The enhancement in conversion occurs because dehydration of the methanol circumvents the equilibrium constraint of the syngas-to-methanol step. The slurry bubble column reactor provides the necessary heat transfer capacity to handle the greater heat duty associated with high conversion. In order to improve the stability of the catalyst system, non-stoichiometric aluminum phosphate was proposed as the dehydration catalyst for the LPDME(trademark) process. This aluminum phosphate material is a proprietary catalyst. This catalyst system of a standard methanol catalyst and the aluminum phosphate provided stable process performance that met the program targets under our standard test process conditions in the laboratory. These targets are (1) an initial methanol equivalent productivity of 28 gmol/kg/hr, (2) a CO(sub 2)-free, carbon selectivity of 80% to dimethyl ether and (3) stability of both catalysts equivalent to that of the methanol catalyst in the absence of the aluminum phosphate. A pilot plant trial of the LPDME(trademark) process using the aluminum phosphate catalyst was originally planned for March 1998 at the DOE-owned, Air Products (APCI)-operated facility at LaPorte, Texas. Because the aluminum phosphate catalyst is not commercially available, we initiated a scaleup

  18. 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.)

  19. Pd-Au/C catalysts with different alloying degrees for ethanol oxidation in alkaline media

    International Nuclear Information System (INIS)

    High alloyed Pd-Au/C catalyst is prepared through a rate-limiting strategy in water/ethylene glycol solution. Pd/C and low alloyed Pd-Au/C catalysts are prepared with trisodium citrate and sodium borohydride as stabilizing and reducing agents, respectively. Transmission electron microscopy (TEM) shows that the synthesized Pd(Au) particles are well dispersed on the catalysts. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) show that the high alloyed Pd-Au/C catalyst presents a relatively homogenous structure while the low alloyed Pd-Au/C catalyst presents a Pd-rich shell/Au-rich core structure. Electrochemical characterization shows that the low alloyed Pd-Au/C catalyst exhibits the best catalytic activity for ethanol oxidation reaction (EOR) in alkaline media, which could be attributed to its relatively large exposed Pd surface area as compared with the high alloyed Pd-Au/C catalyst due to its Pd-rich shell structure and its enhanced adsorption of OHads as compared with Pd/C catalyst due to its core-shell structure

  20. 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.

  1. 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.

  2. Duplex steam reformer: alternate catalyst

    International Nuclear Information System (INIS)

    The manufacturing feasibility of a duplex steam reformer tube for potential use in a high temperature gas cooled reactor has been successfully demonstrated. This technique consists of explosively expanding the inner tube into the outer tube. To successfully achieve the desired 0 to 3 mil radial gap between the tubes it is necessary to perform the expansion in two steps with an intermediate anneal. A catalyst design that would have replaced the conventional Raschig rings with a metal supported catalyst has been evaluated and it has been concluded that further development and testing are needed before fabrication of a full scale prototype is warranted. Consequently, the immediate efforts are directed towards reevaluating the incentives for developing a catalyst and the probability of successfully developing a catalyst that could be used for steam reforming

  3. Alumina supported iridium catalysts - preparation

    International Nuclear Information System (INIS)

    This report describes the method employed in the preparation of alumina supported iridium catalysts, with metal contents between 30 and 40%, that will be used for hydrazine monopropellant decomposition. (author)

  4. Synthesis of highly dispersed and active palladium/carbon nanofiber catalyst for formic acid electrooxidation

    Science.gov (United States)

    Qin, Yuan-Hang; Yue-Jiang; Yang, Hou-Hua; Zhang, Xin-Sheng; Zhou, Xing-Gui; Niu, Li; Yuan, Wei-Kang

    2011-05-01

    Highly dispersed and active palladium/carbon nanofiber (Pd/CNF) catalyst is synthesized by NaBH4 reduction with trisodium citrate as the stabilizing agent. The obtained Pd/CNF catalyst is characterized by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The results show that the Pd nanoparticles with an average particle size of ca. 3.8 nm are highly dispersed on the CNF support even with a small ratio of citrate to Pd precursor, which is believed to be due to the pH adjustment of citrate stabilized colloidal Pd nanoparticles. The cyclic voltammetry and chronoamperometry techniques show that the obtained Pd/CNF catalyst exhibits good catalytic activity and stability for the electrooxidation of formic acid.

  5. Separately supported polymetallic reforming catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kresge, C. T.; Krishnamurthy, S.; McHale, W. D.

    1985-01-15

    There is provided, in accordance with the present invention, a catalyst composition made up of a mixture of two components, one component comprising a minor proportion of platinum and rhenium on a support and the second component comprising a minor proportion of iridium and rhenium on a separate support. A process for reforming a charge stock, such as naphtha, utilizing such catalyst is also provided.

  6. [Study on the spectra of Au/CeO2 catalysts modified by La2O3 additive].

    Science.gov (United States)

    Zhang, Qing; He, Zhen-Liang; Li, Jin-Wei; Zhan, Ying-Ying; Lin, Xing-Yi; Zheng, Qi

    2008-04-01

    For Au-ceria catalysts prepared by deposition-precipitation method, the catalytic performance of water gas shift reaction was studied with different La loadings. In the complete doping range, ceria retains with its cubic fluorite structures. XRD, HRTEM and UV-Vis-DRS, studies showed that La doping can improve the activity of Au-ceria catalyst by stabilizing ceria and modifying its morphology. In addition, the test of catalyst stability evaluation also proved, that a better stability performance of Au-ceria catalyst can be realized by appropriate La doping. The Au/CL5.0 sample with 5 at % La doping showed the best performance in WGS reaction. PMID:18619331

  7. Stability Scores: Measuring Coalitional Stability

    OpenAIRE

    Feldman, Michal; Meir, Reshef; Tennenholtz, Moshe

    2011-01-01

    We introduce a measure for the level of stability against coalitional deviations, called \\emph{stability scores}, which generalizes widely used notions of stability in non-cooperative games. We use the proposed measure to compare various Nash equilibria in congestion games, and to quantify the effect of game parameters on coalitional stability. For our main results, we apply stability scores to analyze and compare the Generalized Second Price (GSP) and Vickrey-Clarke-Groves (VCG) ad auctions....

  8. 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

  9. Glycerol oxidation using gold-containing catalysts.

    Science.gov (United States)

    Villa, Alberto; Dimitratos, Nikolaos; Chan-Thaw, Carine E; Hammond, Ceri; Prati, Laura; Hutchings, Graham J

    2015-05-19

    Glycerol is an important byproduct of biodiesel production, and it is produced in significant amounts by transesterification of triglycerides with methanol. Due to the highly functionalized nature of glycerol, it is an important biochemical that can be utilized as a platform chemical for the production of high-added-value products. At present, research groups in academia and industry are exploring potential direct processes for the synthesis of useful potential chemicals using catalytic processes. Over the last 10 years, there has been huge development of potential catalytic processes using glycerol as the platform chemical. One of the most common processes investigated so far is the catalytic oxidation of glycerol at mild conditions for the formation of valuable oxygenated compounds used in the chemical and pharmaceutical industry. The major challenges associated with the selective oxidation of glycerol are (i) the control of selectivity to the desired products, (ii) high activity and resistance to poisoning, and (iii) minimizing the usage of alkaline conditions. To address these challenges, the most common catalysts used for the oxidation of glycerol are based on supported metal nanoparticles. The first significant breakthrough was the successful utilization of supported gold nanoparticles for improving the selectivity to specific products, and the second was the utilization of supported bimetallic nanoparticles based on gold, palladium, and platinum for improving activity and controlling the selectivity to the desired products. Moreover, the utilization of base-free reaction conditions for the catalytic oxidation of glycerol has unlocked new pathways for the production of free-base products, which facilitates potential industrial application. The advantages of using gold-based catalysts are the improvement of the catalyst lifetime, stability, and reusability, which are key factors for potential commercialization. In this Account, we discuss the advantages of the

  10. 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. PMID:21714388

  11. Nanosized IrOx–Ir Catalyst with Relevant Activity for Anodes of Proton Exchange Membrane Electrolysis Produced by a Cost-Effective Procedure

    OpenAIRE

    Lettenmeier, Philipp; Wang, Li; Golla-Schindler, Ute; Gazdzicki, Pawel; Cañas, Natalia A.; Handl, Michael; Hiesgen, Renate; Hosseiny, S.S.; Gago, Aldo; Friedrich, K. Andreas

    2015-01-01

    We have developed a highly active nanostructured iridium catalyst for anodes of proton exchange membrane (PEM) electrolysis. Clusters of nanosized crystallites are obtained by reducing surfactant-stabilized IrCl3 in water-free conditions. The catalyst shows a five-fold higher activity towards oxygen evolution reaction (OER) than commercial Ir-black. The improved kinetics of the catalyst are reflected in the high performance of the PEM electrolyzer (1 mgIr cm−2), showing an unparalleled low ov...

  12. Hydrophobic catalyst applications in the nuclear field and in environmental studies

    International Nuclear Information System (INIS)

    The paper presents methods of preparation and applications of hydrophobic platinum catalysts in nuclear field and environmental protection. These catalysts allow the transport of gaseous reactants and reaction products to and from catalytic active centers since the pore blocking by water is avoided. Hence the activity and stability of the catalysts increase and isotopic exchange columns with simpler internal structure can be achieved. The aim of the paper is: 1. to give a data base regarding the preparation methods of the optimal catalyst type; 2. to indicate the utilization and operation procedures of hydrophobic catalysts with mixed and simple packings; 3. to evaluate the performances and applications of hydrophobic catalysts. Over one hundred of hydrophobic catalysts of the active metal/support type were prepared in our laboratory. Hydrophobic features were obtained by different methods like these: - coating a hydrophilic conventional catalyst with a hydrophobic agent such as silicone or teflon; - supporting the active metal directly into the pores of a hydrophobic support; - mixing the teflon powder with a hydrophilic conventional catalyst; coating the support with teflon followed by the impregnation with the precursor of the active metal. The most important application of these catalysts is detritiation of the heavy water used as moderator and coolant in CANDU type reactors. Build-up of tritium in heavy water following the neutron capture by deuterium leads to a reduction in the moderating properties and at the same time leads to a contamination hazard for both operation personnel and environment. Tritium recovery leads this way to both improving the moderating qualities of the heavy water and obtaining valuable pure tritium of high importance in fusion research and other laboratory studies. One gram of tritium costs about USD 10,000. The physical chemical process is water-hydrogen catalyzed isotopic exchange. Also discussed in the paper is the separation of

  13. 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.

  14. Benchmarking the Stability of Oxygen Evolution Reaction Catalysts

    DEFF Research Database (Denmark)

    Frydendal, Rasmus; Paoli, Elisa Antares; Knudsen, Brian Peter;

    2014-01-01

    Because of the rising need for energy storage, potentially facilitated by electrolyzers, improvements to the catalysis of the oxygen evolution reaction (OER) become increasingly relevant. Standardized protocols have been developed for determining critical figures of merit, such as the electrochem......Because of the rising need for energy storage, potentially facilitated by electrolyzers, improvements to the catalysis of the oxygen evolution reaction (OER) become increasingly relevant. Standardized protocols have been developed for determining critical figures of merit, such as the...

  15. 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.

  16. 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.

  17. Current advances in precious metal core–shell catalyst design

    International Nuclear Information System (INIS)

    Precious metal nanoparticles are commonly used as the main active components of various catalysts. Given their high cost, limited quantity, and easy loss of catalytic activity under severe conditions, precious metals should be used in catalysts at low volumes and be protected from damaging environments. Accordingly, reducing the amount of precious metals without compromising their catalytic performance is difficult, particularly under challenging conditions. As multifunctional materials, core–shell nanoparticles are highly important owing to their wide range of applications in chemistry, physics, biology, and environmental areas. Compared with their single-component counterparts and other composites, core–shell nanoparticles offer a new active interface and a potential synergistic effect between the core and shell, making these materials highly attractive in catalytic application. On one hand, when a precious metal is used as the shell material, the catalytic activity can be greatly improved because of the increased surface area and the closed interfacial interaction between the core and the shell. On the other hand, when a precious metal is applied as the core material, the catalytic stability can be remarkably improved because of the protection conferred by the shell material. Therefore, a reasonable design of the core–shell catalyst for target applications must be developed. We summarize the latest advances in the fabrications, properties, and applications of core–shell nanoparticles in this paper. The current research trends of these core–shell catalysts are also highlighted. (review)

  18. Ammoxidation of Substituted Toluenes on Silica-Supported VPO Catalysts

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The ammoxidation of substituted toluenes to their corresponding nitriles over silica-supported vanadium phosphorus oxide (VPO/SiO2) catalysts has been studied. The effects of carrier silica, the addition of phosphorus, the substituents and the loadings have been discussed. Compared with unsupported VPO, the VPO/SiO2 catalysts have higher catalytic activity for ammoxidation of substituted toluenes and much lower reaction temperature. XRD shows that vanadium phosphorus oxides exist as amorphous phase and disperse to a high degree on the silica surface in 10 % loading catalyst. When the loadings are over 10 %, the crystalline α-VOPO4 would emerge, which would decrease the yield and selectivity. Additional phosphorus can form composite oxides with vanadia and play concerted catalytic function, which increase the selectivity of nitriles remarkably. Different substituents or same substituents on diffetent positions have different influences because of the variant electronic stability of intermediates, the hindered accessibility of methyl group or the chemisorption state of the substrate molecule on the electrophilic catalyst surface.

  19. 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.

  20. 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.

  1. Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for PEM Fuel Cell

    Science.gov (United States)

    Devrim, Yilser; Albostan, Ayhan

    2016-06-01

    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.

  2. 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)

  3. 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.

  4. 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.

  5. 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.

  6. Hindered rotation in a novel 1,2,4-triazinyl phenanthroline (T-Phen) ligand leading to improved separation of Am3+ and Eu3+ vis-a-vis 1,2,4-triazinyl bipyridine (T-Bipy): synthesis and computational validation of the experimental results

    International Nuclear Information System (INIS)

    A novel nitrogen donor ligand having more pre-organized structure, 1,2,4-triazinyl phenanthroline (T-phen), was synthesized and evaluated for lanthanide - actinide separation. The extraction and selectivity for Am3+ over Eu3+ was found to be improved with T-phen as compared to the analogous 1,2,4-triazinyl bipyridine bipy, which was explained by analyzing their conformational energies and energy differences between the frontier orbitals (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular (LUMO) with the help of ab initio molecular orbital calculations. Higher covalence in Am3+ complexes compared to the Eu3+ complexes were indicated by more shared electrons between Am3+ and bonded 'N' atoms, shorter 'Am-N' bonds and higher overlap between the orbitals of Am3+ and ligands in the frontier orbitals complexes in case of both the ligands. The separation factor values with T-phen and T-bipy are given at varying pH values. The results suggest more efficient separation with T-phen as compared to T-bipy which is attributed to hindered rotation of the former ligand

  7. Catalytic NO reduction with ammonia at low temperatures on V2O5/AC catalysts. Effect of metal oxides addition and SO2

    International Nuclear Information System (INIS)

    The catalytic behavior of the V-M/AC (M=W, Mo, Zr, and Sn) catalysts were studied for the NO reduction with ammonia at low temperatures, especially in the presence of SO2. The presence of the metal oxides does not increase the V2O5/AC activity but decreases it. Except V-Mo/AC, the other catalysts are promoted by SO2 at 250C, especially for V-Sn/AC. However, the promoting effect of SO2 is gradually depressed by catalyst deactivation. Changes in catalyst preparation method can improve the catalyst stability in short-term but cannot completely prevent the catalyst from a long-term deactivation. Mechanisms of the promoting effect and the deactivation of V-Sn/AC catalyst by SO2 were studied using Fourier transform infrared spectroscopy (FT-IR) spectra and measurement of catalyst surface area and pore volume. The results showed that both the SO2 promotion and deactivation are associated with the formation of sulfate species on the catalyst surface. In the initial period of the selective catalytic reduction (SCR) reaction in the presence of SO2, the formed sulfate species provide new acid sites to enhance ammonia adsorption and thus the catalytic activity. However, as the SCR reaction proceeds, excess amount of sulfate species and then ammonium-sulfate salts are formed which is stabilized by the presence of tin oxide, resulting in gradual plugging of the pore structures and the catalyst deactivation

  8. TiO2 and Al2O3 promoted Pt/C nanocomposites as low temperature fuel cell catalysts for electro oxidation of methanol in acidic media

    International Nuclear Information System (INIS)

    Carbon corrosion and platinum dissolution are the two major catalyst layer degradation problems in polymer electrolyte membrane fuel cells (PEMFC). Ceramic addition can reduce the corrosion of carbon and increase the stability of catalysts. Pt/TiO2, Pt/TiO2-C, Pt/Al2O3 and Pt/Al2O3-C catalysts were synthesized and characterized. Electrochemical surface area of Pt/TiO2-C and Pt/Al2O3-C nanocomposite catalysts was much higher than the Pt/TiO2 and Pt/Al2O3 catalysts. Peak current, specific activity and mass activity of the catalysts was also determined by cyclic voltammetry and were much higher for the carbon nanocomposites. Exchange current densities were determined from Tafel plots. Heterogeneous rates of reaction of electro oxidation of methanol were determined for all the catalysts and were substantially higher for titania catalysts as compared to alumina added catalysts. Mass activity of Pt/TiO2-C was much higher than mass activity of Pt/Al2O3-C. Stability studies showed that addition of ceramics have increased the catalytic activity and durability of the catalysts considerably

  9. Towards understanding the improved stability of palladium supported on TS-1 for catalytic combustion.

    Science.gov (United States)

    Setiawan, Adi; Friggieri, Jarrod; Hosseiniamoli, Hadi; Kennedy, Eric M; Dlugogorski, Bogdan Z; Adesina, Adesoji A; Stockenhuber, Michael

    2016-04-21

    A novel Pd supported on TS-1 combustion catalyst was synthesized and tested in methane combustion under very lean and under highly humid conditions (water vapour. We identified water adsorption and in turn the hydrophobicity of the catalyst support as the major factor influencing the long term stability of combustion catalysts. While Pd/Al2O3 catalyst shows a higher turn-over frequency than that of Pd/TS-1 catalyst, the situation reversed after ca. 1900 h on stream. Two linear regions, with different activation energies in the Arrhenius plot for the equilibrium Pd/TS-1 catalyst, were observed. The conclusions were supported by catalyst characterization using H2-chemisorption, TPD, XPS analyses as well as N2-adsorption-desorption, XRD, SEM, TEM. The hydrophobicity and competitive adsorption of water with oxygen is suggested to influence oxygen surface coverage and in turn the apparent activation energy for the oxidation reaction. PMID:27031407

  10. Catalytic hydrolysis of ammonia borane for hydrogen generation using cobalt nanocluster catalyst supported on polydopamine functionalized multiwalled carbon nanotube

    International Nuclear Information System (INIS)

    Hydrogen was generated from ammonia borane complex by hydrolysis using cobalt nanocluster catalyst supported on polydopamine functionalized MWCNTs (multi-walled carbon nanotubes). The impregnation-chemical reduction method was used for the preparation of the supported catalyst. The nanocluster catalyst support was formed by in-situ oxidative polymerization of dopamine on the MWCNTs in alkaline solution at room temperature. The structural and physical–chemical properties of the nanocluster catalyst were characterized by FT-IR (Fourier transform infrared spectroscopy), EDX (energy-dispersive X-ray spectroscopy), SEM (scanning electron microscope), XRD (X-ray diffraction) and TEM (transmission electron microscopy). The nanocluster catalyst showed good catalytic activity for the hydrogen generation from aqueous ammonia borane complex. A reusability test to determine the practical usage of the catalyst was also investigated. The result revealed that the catalyst maintained an appreciable catalytic performance and stability in terms of its reusability after three cycle of reuse for the hydrolysis reaction. Also, the activation energy for the hydrolysis of ammonia borane complex was estimated to be 50.41 kJmol−1, which is lower than the values of some of the reported catalyst. The catalyst can be considered as a promising candidate in developing highly efficient portable hydrogen generation systems such as PEMFC (proton exchange membrane fuel cells). - Highlights: • Co/Pdop-o-MWCNT (Pdop functionalized MWCNT supported cobalt nanocluster) catalyst was synthesized for hydrogen generation. • It is an active catalyst for hydrogen generation via hydrolysis of ammonia borane. • It showed good stability in terms of reusability for the hydrogen generation

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

    Institute of Scientific and Technical Information of China (English)

    ZhangDaqing; CuiLong; 等

    2002-01-01

    The influence of yttrium and ytterbium on the catalytic performance of Pt-Re refoming cata-lysts was studied in a continuous flow pressurized microreactor-chromatograph system and pilot unit.The results of micro-reactor test showed that both yttrium and ytterbium could improve the selectivity of Pt-Re catalysts for the conversion of n-heptane as well as MCP into aromatics,but also suppressed their activity as well.Pilot test results showed that yttrium and ytterbium enhanced both the selectivity and activity of Pt-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 of catalytic stability of yttrium or ytterbium modified Pt-Re catalysts.Yttrium and ytterbium improved the coking resistance of yttrium or ytterbium modified Pt-Re catalysts.TEM determination results indicated that both yttrium and ytterbium had improved the thermal stability of Pt-Re catalysts.

  12. 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.

  13. 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. PMID:21214003

  14. 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.

  15. Deactivation of Hydroprocessing Catalysts: New insights in catalyst structure, activity and stability

    NARCIS (Netherlands)

    Vogelaar, B.M.

    2005-01-01

    In dit proefschrift is de deactivering van hydroprocessing katalysatoren onderzocht. Katalysatoren zijn hulpstoffen die gebruikt worden om chemische reacties te bewerkstelligen, zonder daarbij zelf verbruikt te worden. Een bekend voorbeeld is de uitlaatkatalysator in de auto, die o.a. onverbrande br

  16. 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....../MgAl2O4 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.......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...

  17. Preparation of highly active and hydrothermally stable nickel catalysts.

    Science.gov (United States)

    Li, Shaozhong; Chen, Hui; Shen, Jianyi

    2015-06-01

    The 60%Ni/AlSiO catalysts were prepared by the co-precipitation method, in which AlSiO were the composite supports with different mass ratios of Al2O3 and SiO2. It was found that the catalyst 60%Ni/AlSiO-4 with the Al2O3/SiO2 mass ratio of 4 in the support exhibited the high hydrothermal stability. The addition of proper amount of SiO2 inhibited the hydration of Al2O3 and prevented the growth of supported nickel particles during the hydrothermal treatment. The structure of the composite support in the 60%Ni/AlSiO-4 was stable and the supported nickel particles were highly dispersed. Accordingly, the hydrothermally treated catalyst maintained the high heats and uptakes for the adsorption of H2 and CO, and thus the high activity and stability for the hydrogenation of glucose to sorbitol in aqueous solution. PMID:25700212

  18. 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

  19. 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. PMID:25504857

  20. Sulphur poisoning of palladium catalysts used for methane combustion: Effect of the support

    International Nuclear Information System (INIS)

    Four different supported palladium catalysts (using alumina, silica, zirconia and titania as supports), prepared by incipient wetness impregnation, were tested as catalysts for methane oxidation in presence of sulphur dioxide. The catalyst supported on zirconia showed the best performance, whereas the silica-supported one showed the fastest deactivation. Temperature-programmed desorption experiments of the poisoned catalysts suggest that SO2 adsorption capacity of the support plays a key role in the catalyst poisoning. In order to study the effect of promoters, expected to improve the thermal stability and thioresistance of the catalyst, commercial zirconia modified by yttrium and lantane was tested as supports. It was found that the presence of these promoters does not improve the performance of the zirconia-supported catalyst. A deactivation model - considering two different active sites (fresh and poisoning), pseudo-first order dependence on methane concentration and poisoning rate depending on sulphur concentration and fraction of non-poisoned palladium - was used for modelling the deactivation behaviour

  1. 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.

  2. Thermally-induced microstructural changes in a three-way automotive catalyst

    Energy Technology Data Exchange (ETDEWEB)

    More, K.L.; Kenik, E.A.; Coffey, D.W.; Geer, T.S. [Oak Ridge National Lab., TN (United States); Theis, J.; LaBarge, W.; Beckmeyer, R. [Delphi Automotive Systems, Flint, MI (United States)

    1997-12-01

    The use of advanced electron microscopy techniques to characterize both the bulk and near-atomic level microstructural evolution of catalyst materials during different dynamometer/vehicle aging cycles is an integral part of understanding catalyst deactivation. The study described here was undertaken to evaluate thermally-induced microstructural changes which caused the progressive loss of catalyst performance in a three-way automotive catalyst. Several different catalyst processing variables, for example changing the washcoat ceria content, were also evaluated as a function of aging cycle and thermal history. A number of thermally-induced microstructural changes were identified using high resolution electron microscopy techniques that contributed to the deactivation of the catalyst, including sintering of all washcoat constituents, {gamma}-alumina transforming to {alpha}-, {beta}-, and {delta}-alumina, precious metal redistribution, and constituent encapsulation. The data accumulated in this study have been used to correlate microstructural evolution with thermal history and catalyst performance during various aging cycles and to subsequently evaluate different washcoat formulations for increased thermal stability.

  3. 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%.

  4. 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.

  5. 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)

  6. Hydrogen generation from hydrolysis of sodium borohydride using Ru(0) nanoclusters as catalyst

    International Nuclear Information System (INIS)

    Sodium borohydride is stable in aqueous alkaline solution, however, it hydrolyses in water to hydrogen gas in the presence of suitable catalyst. By this way hydrogen can be generated safely for the fuel cells. Generating H2 catalytically from NaBH4 solutions has many advantages: NaBH4 solutions are nonflammable, reaction products are environmentally benign, rate of H2 generation is easily controlled, the reaction product NaBO2 can be recycled, H2 can be generated even at low temperatures. All of the catalysts that has been used in hydrolysis of sodium borohydride are bulk metals and they act as heterogeneous catalysts. The limited surface area of the heterogeneous catalysts causes lower catalytic activity as the activity of catalyst is directly related to its surface area. Thus, the use of metal nanoparticles with large surface area provides potential route to increase the catalytic activity. Here, we report, for the first time, the use of ruthenium(0) nanoclusters as catalyst in the hydrolysis of sodium borohydride liberating hydrogen gas. The ruthenium nanoparticles are generated from the reduction of ruthenium(III) chloride by sodium borohydride in water and stabilized by specific ligand. The ruthenium(0) nanoclusters are found to be highly active catalyst for the hydrolysis of sodium borohydride

  7. 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.

  8. 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.

  9. Carbon dioxide reforming of methane on monolithic Ni/Al2O3-based catalysts

    Institute of Scientific and Technical Information of China (English)

    S.O.Soloviev; A.Yu.Kapran; S.N.Orlyk; E.V.Gubareni

    2011-01-01

    Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane.Adjusting the surface acid-base properties of catalysts by introduction of alkali metal(Na,K)oxides inhibits the carbonization and as a result,improves the operational stability of these catalysts.An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found.This effect,caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst,is displayed in increase of methane conversion under conditions of an oxidant excess.

  10. Environmental friendly lubricants through selective hydrogenation of rapeseed oil over supported copper catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ravasio, Nicoletta; Zaccheria, Federica; Fusi, Achille; Poli, Nicola; Psaro, Rinaldo [Centro CNR CSSCMTBSO e Dip. Chimica Inorganica Metallorganica e Analitica, Universita degli Studi di Milano, Via Venezian 21, 20133 Milan (Italy); Gargano, Michele [Dipartimento di Chimica, Universita di Bari, Via Orabona 4, 70126 Bari (Italy); Recchia, Sandro [Dipartimento Scienze CCFFMM, Universita dell' Insubria, Via Lucini 3, 22100 Como (Italy)

    2002-07-10

    Different supported copper catalysts are compared in the selective hydrogenation of vegetable oils and their methylesters. The influence of parameters such as the catalysts preparation method, the support used and the activation treatment are critically evaluated in terms of catalytic activity and selectivity. All ex situ reduced catalysts prepared by the chemisorption-hydrolysis (CH) method show better performances than the ones prepared by incipient wetness technique. These data are directly matched up to the different morphology of the supported copper particles obtained with these two methods. By using a 8% Cu/SiO{sub 2} catalyst the trienic component C18:3 can be eliminated and the dienic one lowered from 22 to 3-5% without increasing the stearic C18:0 content and limiting the cis/trans-isomerisation process. These oils, with a C18:1 content up to 88% show remarkable oxidation stability and keep fluid down to -15C.

  11. Interstitial modification of palladium nanoparticles with boron atoms as a green catalyst for selective hydrogenation

    Science.gov (United States)

    Chan, Chun Wong Aaron; Mahadi, Abdul Hanif; Li, Molly Meng-Jung; Corbos, Elena Cristina; Tang, Chiu; Jones, Glenn; Kuo, Winson Chun Hsin; Cookson, James; Brown, Christopher Michael; Bishop, Peter Trenton; Tsang, Shik Chi Edman

    2014-12-01

    Lindlar catalysts comprising of palladium/calcium carbonate modified with lead acetate and quinoline are widely employed industrially for the partial hydrogenation of alkynes. However, their use is restricted, particularly for food, cosmetic and drug manufacture, due to the extremely toxic nature of lead, and the risk of its leaching from catalyst surface. In addition, the catalysts also exhibit poor selectivities in a number of cases. Here we report that a non-surface modification of palladium gives rise to the formation of an ultra-selective nanocatalyst. Boron atoms are found to take residence in palladium interstitial lattice sites with good chemical and thermal stability. This is favoured due to a strong host-guest electronic interaction when supported palladium nanoparticles are treated with a borane tetrahydrofuran solution. The adsorptive properties of palladium are modified by the subsurface boron atoms and display ultra-selectivity in a number of challenging alkyne hydrogenation reactions, which outclass the performance of Lindlar catalysts.

  12. 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.

  13. Chiral Pt/ZrO2 Catalysts. Enantioselective Hydrogenation of 1-phenyl-1,2-propanedione

    Directory of Open Access Journals (Sweden)

    Claudia Urbina

    2010-05-01

    Full Text Available The enantioselective hydrogenation of 1-phenyl-1,2-propanedioneover Pt colloids stabilized with (R,S-4,5-dihydro-4,5-diphenyl-2-(6-cyanopyridinylimidazoline (CI supported on a meso-structured ZrO2 under a pressure of 40 bar of H2 at 298 K has been investigated. The metal loading in all catalysts was 1 wt%. The effect of the amount of chiral modifier on the metal particle size and on the catalytic behavior was analyzed. It was found that as the CI/Pt molar ratio increases from 2.5 to 3.5 the Pt crystal size decreases from 3.0 to 1.8 nm. All catalysts were very active in the studied reaction, with the most active one being the catalyst with smaller Pt particles, whereas the selectivity is higher in those catalysts with larger chiral modified Pt metal particles.

  14. Oxidation Catalysts for Elemental Mercury in Flue Gases—A Review

    Directory of Open Access Journals (Sweden)

    Liliana Lazar

    2012-02-01

    Full Text Available The removal of mercury from flue gases in scrubbers is greatly facilitated if the mercury is present as water-soluble oxidized species. Therefore, increased mercury oxidation upstream of scrubber devices will improve overall mercury removal. For this purpose heterogeneous catalysts have recently attracted a great deal of interest. Selective catalytic reduction (SCR, noble metal and transition metal oxide based catalysts have been investigated at both the laboratory and plant scale with this objective. A review article published in 2006 covers the progress in the elemental mercury (Hgel catalytic oxidation area. This paper brings the review in this area up to date. To this end, 110 papers including several reports and patents are reviewed. For each type of catalyst the possible mechanisms as well as the effect of flue gas components on activity and stability are examined. Advantages and main problems are analyzed. The possible future directions of catalyst development in this environmental research area are outlined.

  15. Behavior of hydrophobic catalysts and NAFION membrane in presence of high activity tritiated water

    International Nuclear Information System (INIS)

    The behavior of hydrophobic catalysts and NAFION membrane was analyzed in presence of high activity tritiated water. Pt/C/PTFE catalysts, NAFION and PTFE samples were immersed in tritiated water.The behavior of catalysts and NAFION membrane has been analyzed by determination of total fluoride emission in HTO and chemical modification in polymeric substrates by FTIR ATR. The catalysts based on PTFE indicate a relative stability in presence of HTO with a radioactive concentration of ∼ 100 Ci/l. The radiolytic processes lead to formation of HF and to minor structural changes of hydrophobic support. The resulted HF from radiolytic processes interacts with metals (stainless steel, Pt) with formation of metallic fluorides. The membranes of NAFION type suffer changes radioinduced by the lost of ionomeric lateral chains (sulphonated polyfloricarbonate). (authors)

  16. 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.

  17. 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 ℃.

  18. Preparation of Meso porous Silica-Supported Palladium Catalysts for Bio fuel Upgrade

    International Nuclear Information System (INIS)

    We report the preparation of two hydrocracking catalysts Pd/CoMoO4/silica and Pd/CNTs/CoMoO4/silica (CNTs, carbon nano tubes). 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 meso porous 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. Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments

    Directory of Open Access Journals (Sweden)

    Khaled Belkacemi

    2011-12-01

    Full Text Available Mesoporous silica materials (MSM with ordered and controllable porous structure, high surface area, pore volume and thermal stability are very suitable catalyst supports, because they provide high dispersion of metal nanoparticles and facilitate the access of the substrates to the active sites. Since the conventional wet-impregnation and deposition-precipitation methods are not appropriate for the incorporation of gold nanoparticles (AuNPs into MSM, considerable efforts have been made to develop suitable methods to synthesize Au/MSM catalysts, because the incorporation of AuNPs into the channel system can prevent their agglomeration and leaching. In this review, we summarize the main methods to synthesize active gold catalysts supported on MSM. Examples and details of the preparative methods, as well as selected applications are provided. We expect this article to be interesting to researchers due to the wide variety of chemical reactions that can be catalyzed by gold supported catalysts.

  20. Catalyst for Decomposition of Nitrogen Oxides

    Science.gov (United States)

    Schryer, David R. (Inventor); Jordan, Jeffrey D. (Inventor); Akyurtlu, Ates (Inventor); Akyurtlu, Jale (Inventor)

    2015-01-01

    This invention relates generally to a platinized tin oxide-based catalyst. It relates particularly to an improved platinized tin oxide-based catalyst able to decompose nitric oxide to nitrogen and oxygen without the necessity of a reducing gas.

  1. Use of lanthanide catalysts in air electrodes

    International Nuclear Information System (INIS)

    A review on the lanthanide catalysts suitable for the reduction catalysis of oxygen in air electrodes is presented. The kinds of lanthanide indicated to be used as catalysts of oxygen reduction are shown. (A.R.H.)

  2. Novel Fischer-Tropsch catalysts. [DOE patent

    Science.gov (United States)

    Vollhardt, K.P.C.; Perkins, P.

    Novel compounds are described which are used as improved Fischer-Tropsch catalysts particularly for the conversion of CO + H/sub 2/ to gaseous and liquid hydrocarbons at milder conditions than with prior catalysts.

  3. Biomass processing over gold catalysts

    CERN Document Server

    Simakova, Olga A; Murzin, Dmitry Yu

    2013-01-01

    The book describes the valorization of biomass-derived compounds over gold catalysts. Since biomass is a rich renewable feedstock for diverse platform molecules, including those currently derived from petroleum, the interest in various transformation routes has become intense. Catalytic conversion of biomass is one of the main approaches to improving the economic viability of biorefineries.  In addition, Gold catalysts were found to have outstanding activity and selectivity in many key reactions. This book collects information about transformations of the most promising and important compounds

  4. 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.

  5. 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

  6. Colloidal nanoparticles as catalysts and catalyst precursors for nitrite hydrogenation

    NARCIS (Netherlands)

    Zhao, Yingnan

    2015-01-01

    The most distinguished advantage to use colloidal methods for catalyst preparation is that the size and the shape of nanoparticles can be manipulated easily under good control, which is normally difficult to achieve by using traditional methods, such as impregnation and precipitation. This facilitat

  7. Catalyst-assisted Probabilistic Entanglement Transformation

    OpenAIRE

    Feng, Yuan; Duan, Runyao; Ying, Mingsheng

    2004-01-01

    We are concerned with catalyst-assisted probabilistic entanglement transformations. A necessary and sufficient condition is presented under which there exist partial catalysts that can increase the maximal transforming probability of a given entanglement transformation. We also design an algorithm which leads to an efficient method for finding the most economical partial catalysts with minimal dimension. The mathematical structure of catalyst-assisted probabilistic transformation is carefully...

  8. Cotter's new plant diets on spent catalysts

    International Nuclear Information System (INIS)

    Cotter Corp.'s new 60-tpd spent-catalyst processing plant that recovers molybdenum, nickel, tungsten and vanadium products from spent catalysts is described. The company entered the business as a sideline to its main activity--the mining and processing of uranium ore. The spent-catalyst plant contains ammonium carbonate and sodium hydroxide leach circuits to provide the versatility required to recover various metals from a variety of spent catalysts

  9. Polymer-bound rhodium hydroformylation catalysts

    OpenAIRE

    Jongsma, Tjeerd

    1992-01-01

    Homogeneous catalysts are superior in activity, selectivity as well as specificity, but heterogeneous catalyst are often preferred in industrial processes, because of their good recoverability and their applicability in continuous flow reactors. It would be of great environmental, commercial and scientific interest to combine the advantages of both catalysts. A route to achieve this goal is to immobilize a potent homogeneous catalyst onto an insoluble resin. In this thesis we have used solubl...

  10. EFFECTS OF CATALYST MORPHOLOGY ON HYDROTREATING REACTIONS

    OpenAIRE

    TYE CHING THIAN

    2008-01-01

    Due to the new environmental regulations for fuel quality, refineries need to process cleaner fuel. This requires an improvement in performance of hydrotreating catalysts. Improvements in catalyst activity require knowledge of the relationships between catalyst morphology and activity. Molybdenum sulfide, the generally agreed catalysts that give the best performance in hydrocracking and hydrotreating was investigated for its morphology effects on hydrotreating reactions. Three types of MoS2 c...

  11. Hydroprocessing full-range of heavy oils and bitumen using ultradispersed catalysts at low severity

    Science.gov (United States)

    Peluso, Enzo

    The progressive exhaustion of light crude oils is forcing the petroleum industry to explore new alternatives for the exploitation of unconventional oils. New approaches are searching for technologies able to produce, transport and refine these feedstocks at lower costs, in which symbiotic processes between the enhanced oil recovery (EOR) and the conventional upgrading technologies are under investigation. The process explored in this thesis is an interesting alternative for in-situ upgrading of these crude oils in the presence of ultradispersed (UD) catalysts, which are included as a disperse phase able to circulate along with the processed feed. The objectives of this work are: (a) study the performance of UD catalysts in the presence of a full range (non fractioned) heavy oil and bitumen and (b) evaluate the recyclability of the UD catalysts. Four different heavy crude oils were evaluated in the presence with UD catalysts at a total pressure of 2.8 MPa, residence time of 8 hours and reaction temperatures from 360 up to 400ºC. Thermal and catalytic hydro-processing were compared in terms of conversion and product stability. A comparison between the different crude oils was additionally derived in terms of SARA, initial micro-carbon content and virgin oil stability among other properties. Advantages of catalytic hydro-processing over thermal hydro-processing were evidenced, with UD catalysts playing an essential hydrogenating role while retarding coke formation; microcarbon and asphaltenes reduction in the presence of UD catalysts was observed. To evaluate the feasibility of recycling the UD catalysts, a micro-slurry recycled unit was developed as part of this research. These main results showed: (a) a successful design of this unit, (b) that temperature, LHSV and fractional recycling ratio have more impact on VGO conversion, while pressure has almost no effect, and (c) an UD catalysts agglomeration process was detected, however this process is slow and reversible.

  12. Attrition resistant catalysts and sorbents based on heavy metal poisoned FCC catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gangwal, S.; Jothimurugesan, K.

    1999-07-27

    A heavy metal poisoned, spent FCC catalyst is treated by chemically impregnating the poisoned catalyst with a new catalytic metal or metal salt to provide an attrition resistant catalyst or sorbent for a different catalytic or absorption process, such as catalysts for Fischer-Tropsh Synthesis, and sorbents for removal of sulfur gases from fuel gases and flue-gases. The heavy metal contaminated FCC catalyst is directly used as a support for preparing catalysts having new catalytic properties and sorbents having new sorbent properties, without removing or passivating the heavy metals on the spent FCC catalyst as an intermediate step.

  13. Attrition resistant catalysts and sorbents based on heavy metal poisoned FCC catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gangwal, Santosh (Cary, NC); Jothimurugesan, Kandaswamy (Hampton, VA)

    1999-01-01

    A heavy metal poisoned, spent FCC catalyst is treated by chemically impregnating the poisoned catalyst with a new catalytic metal or metal salt to provide an attrition resistant catalyst or sorbent for a different catalytic or absorption processes, such as catalysts for Fischer-Tropsh Synthesis, and sorbents for removal of sulfur gasses from fuel gases and flue-gases. The heavy metal contaminated FCC catalyst is directly used as a support for preparing catalysts having new catalytic properties and sorbents having new sorbent properties, without removing or "passivating" the heavy metals on the spent FCC catalyst as an intermediate step.

  14. 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...

  15. deNOx catalysts for biomass combustion

    DEFF Research Database (Denmark)

    Kristensen, Steffen Buus

    , however the alkali in biomass complicate matters. Alkali in biomass severely deactivates the catalyst used for the selective catalytic reduction in matter of weeks, hence a more alkali resistant catalyst is needed. In the thesis a solution to the problem is presented, the nano particle deNOx catalyst...

  16. Silver doped catalysts for treatment of exhaust

    Energy Technology Data Exchange (ETDEWEB)

    Park, Paul Worn (Peoria, IL); Hester, Virgil Raymond (Edelstein, IL); Ragle, Christie Susan (Havana, IL); Boyer, Carrie L. (Shiloh, IL)

    2009-06-02

    A method of making an exhaust treatment element includes washcoating a substrate with a slurry that includes a catalyst support material. At least some of the catalyst support material from the slurry may be transferred to the substrate, and silver metal (Ag) is dispersed within the catalyst support material.

  17. Catalyst for selective oxidation of hydrocarbons

    OpenAIRE

    Álvaro Rodríguez, Mercedes; Amarajothi, Dhakshinamoorthy; García Gómez, Hermenegildo

    2010-01-01

    [EN] The present invention relates to a solid catalyst that includes a metal-organic reticular pattem and an agent promoting the generation of radicals, to a method for obtaining said catalyst and to the use thereof as a catalyst in the selective aerobic oxidation reaction ofhydrocarbons.

  18. Efficient epoxidation of propene using molecular catalysts

    DEFF Research Database (Denmark)

    Markovits, Iulius I. E.; Anthofer, Michael H.; Kolding, Helene; Cokoja, Mirza; Pöthig, Alexander; Raba, Andreas; Herrmann, Wolfgang A.; Fehrmann, Rasmus; Kühn, Fritz E.

    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...

  19. 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....... The effect of two distinct oxidation pre-treatments on the activity and stability have been investigated: (1) thermal oxidation; and (2) oxidation with an oxygen plasma under vacuum. We report that activity and stability can be tuned by using different oxidation pre-treatments. Thermally oxidized...

  20. Highly Efficient, Selective, and Stable CO2 Electroreduction on a Hexagonal Zn Catalyst.

    Science.gov (United States)

    Won, Da Hye; Shin, Hyeyoung; Koh, Jaekang; Chung, Jaehoon; Lee, Hee Sang; Kim, Hyungjun; Woo, Seong Ihl

    2016-08-01

    Electrocatalytic CO2 conversion into fuel is a prospective strategy for the sustainable energy production. However, still many parts of the catalyst such as low catalytic activity, selectivity, and stability are challenging. Herein, a hierarchical hexagonal Zn catalyst showed highly efficient and, more importantly, stable performance as an electrocatalyst for selectively producing CO. Moreover, we found that its high selectivity for CO is attributed to morphology. In electrochemical analysis, Zn (101) facet is favorable to CO formation whereas Zn (002) facet favors the H2 evolution during CO2 electrolysis. Indeed, DFT calculations showed that (101) facet lowers a reduction potential for CO2 to CO by more effectively stabilizing a (.) COOH intermediate than (002) facet. This further suggests that tuning the crystal structure to control (101)/(002) facet ratio of Zn can be considered as a key design principle to achieve a desirable product from Zn catalyst. PMID:27352078

  1. Creating single-atom Pt-ceria catalysts by surface step decoration

    Science.gov (United States)

    Dvořák, Filip; Farnesi Camellone, Matteo; Tovt, Andrii; Tran, Nguyen-Dung; Negreiros, Fabio R.; Vorokhta, Mykhailo; Skála, Tomáš; Matolínová, Iva; Mysliveček, Josef; Matolín, Vladimír; Fabris, Stefano

    2016-02-01

    Single-atom catalysts maximize the utilization of supported precious metals by exposing every single metal atom to reactants. To avoid sintering and deactivation at realistic reaction conditions, single metal atoms are stabilized by specific adsorption sites on catalyst substrates. Here we show by combining photoelectron spectroscopy, scanning tunnelling microscopy and density functional theory calculations that Pt single atoms on ceria are stabilized by the most ubiquitous defects on solid surfaces--monoatomic step edges. Pt segregation at steps leads to stable dispersions of single Pt2+ ions in planar PtO4 moieties incorporating excess O atoms and contributing to oxygen storage capacity of ceria. We experimentally control the step density on our samples, to maximize the coverage of monodispersed Pt2+ and demonstrate that step engineering and step decoration represent effective strategies for understanding and design of new single-atom catalysts.

  2. Self-Assembled Nanocomposite Organic Polymers with Aluminum and Scandium as Heterogeneous Water-Compatible Lewis Acid Catalysts.

    Science.gov (United States)

    Miyamura, Hiroyuki; Sonoyama, Arisa; Hayrapetyan, Davit; Kobayashi, Shū

    2015-09-01

    While water-compatible Lewis acids have great potential as accessible and environmentally benign catalysts for various organic transformations, efficient immobilization of such Lewis acids while keeping high activity and without leaching of metals even under aqueous conditions is a challenging task. Self-assembled nanocomposite catalysts of organic polymers, carbon black, aluminum reductants, and scandium salts as heterogeneous water-compatible Lewis acid catalysts are described. These catalysts could be successfully applied to various C-C bond-forming reactions without leaching of metals. Scanning transmission electron microscopy analyses revealed that the nanocomposite structure of Al and Sc was fabricated in these heterogeneous catalysts. It is noted that Al species, which are usually decomposed rapidly in the presence of water, are stabilized under aqueous conditions. PMID:26228075

  3. Promotion effect of iron on Mo/Al2O3 catalyst for the CAMERE process

    OpenAIRE

    Abolfazl Gharibi Kharaji; Ahmad Shariati

    2012-01-01

    Reverse Water Gas Shift (RWGS) reaction is one of the main reactions that can be used toreduce greenhouse gases emissions. Through this reaction CO2 is converted to CO to produce beneficialchemicals such as methanol. In this paper Mo-Al2O3 catalyst was prepared and then promoted with Feions through co-impregnation method to produce Fe-Mo-Al2O3 catalyst. XRD tests were taken todetermine the structure of the catalysts. Activity, selectivity and stability of both catalysts wereinvestigated in a ...

  4. Supported ZnO catalysts for the conversion of alkanes: About the metamorphosis of a heterogeneous catalyst

    Institute of Scientific and Technical Information of China (English)

    S.Arndt; B.Uysal; A.Berthold; T.Otrebma; Y.Aksu; M.Driess; R.Schom(a)cker

    2012-01-01

    ZnO could be a suitable catalyst for the oxidative conversion of CH4,C2H6 and C3H8.However,the main drawback is its thermal instability.Therefore,ZnO supported on ZrO2,TiO2,γ-Al2O3 and SiO2 was investigated for the oxidative dehydrogenation of propane,and ethane,and the oxidative coupling of methane.The stability of the supported ZnO is partially improved,but ZnO reacts with the support material,forming new compounds (Zn-zirconates,-titanates,-aluminates and-silicates),which already occurs below reaction temperature.This might also be the case for many other heterogeneous catalysts.

  5. 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.

  6. 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.

  7. 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...

  8. Influence of ceria on the thermally durability of Pt/Rh automotive catalyst

    International Nuclear Information System (INIS)

    Full text: The use of cerium oxide as an oxygen storage component in automotive three-way catalysts has been well established. More recently the requirement of the three-way catalysts against the increase of the severity in emission standards has focused attention on the development of more active, durable catalysts. The thermally durability of Pt/Rh catalyst can be achieved by the utilization of thermally stable ceria as well as optimization of washcoat composition and structure in order to control the extent of interaction between PGM and ceria. In the present paper, we describe the influence of newly developed washcoat components and PGM interaction with ceria on catalytic performance. First, to clear that the interaction between PGM and ceria contributes to catalytic performance, several kinds of catalysts which have the varied interactions between PGM and ceria were prepared using engineered washcoat techniques and evaluated in the model gas reactor. It was obvious that the difference in performance among them after aging derived from a diversity of interactions between Pt, Rh, and ceria. Second, for the purpose of determining the thermally durability of the developed Pt/Rh catalyst, the catalysts including the current catalyst were aged under three different temperatures and evaluated on engine dynamometer. Result of engine dynamometer evaluation revealed that significant improvement in the thermal durability can be achieved by optimizing the PGM-ceria interaction. In conclusion, we recognize that a thermal durability of a three-way catalyst can be improved by the stabilization of proper PGM-ceria interaction after aging as well as the utilization of thermally durable ceria material

  9. 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. PMID:26186082

  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

    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.

  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. The Influence of oxide additives on Ni/Al2O3 catalysts in low temperature methane steam reforming

    International Nuclear Information System (INIS)

    Hydrogen is industrially produced by methane steam reforming. The process is catalytic and the usual catalyst is based on Ni as the active element. The main problem of this process is its inefficiency. It requires high temperatures at which Ni also favors the formation of graphite, which deactivates the catalysts. Ni has the advantage of being much cheaper than noble metal catalysts, so many researches are done in order to improve the properties of supported Ni catalysts and to decrease the temperature at which the process is energetically efficient. In order to obtain catalysts with high activity and stability, it is essential to maintain the dispersion of the active phase (Ni particles) and the stability of the support. Both properties can be improved by addition of a second oxide to the support. In this paper we present the results obtained in preparation and characterization of Ni/Al2O3 catalysts modified by addition of CeO2 and La2O3 to alumina support. The following catalysts were prepared by impregnation method: Ni/Al2O3, Ni/CeO2-Al2O3 and Ni/La2O3-Al2O3 (10 wt.% Ni and 6 wt.% additional oxide). The catalytic surface was characterized by N2 adsorption - desorption isotherms. The hydrogen - surface bond was characterized by Thermo-Programmed-Desorption (TPD) method. All catalysts were tested in steam reforming reaction of methane in the range of 600 - 700 deg. C, at atmospheric pressure working with CH4:H2O ratio of 1:3. The modified catalysts showed a better catalytic activity and selectivity for H2 and CO2 formation, at lower temperatures than the simple Ni/Al2O3 catalyst. (authors)

  13. DEACTIVATION OF H2S OF CR2O2 EMISSION CONTROL CATALYST FORCHLORINATED VOC DESTRUCTION

    Science.gov (United States)

    The paper discusses one aspect of catalyst stability (i.e.,deactivation by poisoning) and the concomitant effects on catalystactivity and selectivity in the destruction of chlorinatedhydrocarbons. he study was initiated because nothing isdocumented of the effect of H2S or the oth...

  14. Profiling Physicochemical Changes within Catalyst Bodies during Preparation: New Insights from Invasive and Noninvasive Microspectroscopic Studies

    NARCIS (Netherlands)

    Espinosa-Alonso, L.; Beale, A.M.; Weckhuysen, B.M.

    2013-01-01

    Cylindrical or spherical catalyst bodies with sizes ranging from tens of micrometers to a few millimeters have a wide variety of industrial applications. They are crucial in the oil refining industry and in the manufacture of bulk and fine chemicals. Their stability, activity, and selectivity are la

  15. 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.

  16. 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.

  17. Surface-oxidized carbon black as a catalyst for the water oxidation and alcohol oxidation reactions.

    Science.gov (United States)

    Suryanto, Bryan H R; Zhao, Chuan

    2016-05-11

    Carbon black (CB) is popularly used as a catalyst support for metal/metal oxide nanoparticles due to its large surface area, excellent conductivity and stability. Herein, we show that surface oxidized CB itself, after acidic treatment and electrochemical oxidation, exhibits significant catalytic activity for the electrochemical oxidation of water and alcohols. PMID:27097802

  18. Toward Molecular Catalysts by Computer

    Energy Technology Data Exchange (ETDEWEB)

    Raugei, Simone; DuBois, Daniel L.; Rousseau, Roger J.; Chen, Shentan; Ho, Ming-Hsun; Bullock, R. Morris; Dupuis, Michel

    2015-02-17

    Rational design of molecular catalysts requires a systematic approach to designing ligands with specific functionality and precisely tailored electronic and steric properties. It then becomes possible to devise computer protocols to predict accurately the required properties and ultimately to design catalysts by computer. In this account we first review how thermodynamic properties such as oxidation-reduction potentials (E0), acidities (pKa), and hydride donor abilities (ΔGH-) form the basis for a systematic design of molecular catalysts for reactions that are critical for a secure energy future (hydrogen evolution and oxidation, oxygen and nitrogen reduction, and carbon dioxide reduction). We highlight how density functional theory allows us to determine and predict these properties within “chemical” accuracy (~ 0.06 eV for redox potentials, ~ 1 pKa unit for pKa values, and ~ 1.5 kcal/mol for hydricities). These quantities determine free energy maps and profiles associated with catalytic cycles, i.e. the relative energies of intermediates, and help us distinguish between desirable and high-energy pathways and mechanisms. Good catalysts have flat profiles that avoid high activation barriers due to low and high energy intermediates. We illustrate how the criterion of a flat energy profile lends itself to the prediction of design points by computer for optimum catalysts. This research was carried out in the Center for Molecular Electro-catalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory (PNNL) is operated for the DOE by Battelle.

  19. Direct decomposition of methane over SBA-15 supported Ni, Co and Fe based bimetallic catalysts

    International Nuclear Information System (INIS)

    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 COx 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 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

  20. 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