Showing papers on "Catalyst support published in 1996"

Carbon Dioxide Reforming of Methane To Produce Synthesis Gas over Metal-Supported Catalysts: State of the Art

Abstract: Carbon dioxide reforming of methane produces synthesis gas with a low hydrogen to carbon monoxide ratio, which is desirable for many industrial synthesis processes. This reaction also has very important environmental implications since both methane and carbon dioxide contribute to the greenhouse effect. Converting these gases into a valuable feedstock may significantly reduce the atmospheric emissions of CO2 and CH4. In this paper, we present a comprehensive review on the thermodynamics, catalyst selection and activity, reaction mechanism, and kinetics of this important reaction. Recently, research has centered on the development of catalysts and the feasible applications of this reaction in industry. Group VIII metals supported on oxides are found to be effective for this reason. However, carbon deposition causing catalyst deactivation is the major problem inhibiting the industrial application of the CO2/CH4 reaction. Ni-based catalysts impregnated on certain supports show carbon-free operation and thus attract much attention. To develop an effective catalyst for CO2 reforming of CH4 and accelerate the commercial application of the reaction, the following are identified to be the most important areas for future work: (1) selection of metal and support and studying the effect of their interaction on catalyst activity; (2) the effect of different promoter on catalyst activity; (3) the reaction mechanism and kinetics; and (4) pilot reactor performance and scale-up operation.

Effects of Microstructure of Carbon Support in the Catalyst Layer on the Performance of Polymer‐Electrolyte Fuel Cells

Abstract: In the case of the Polymer-electrolyte fuel cells (PEFCs), the reaction sites exist on the platinum (Pt) surface covered with PFSI Though PFSI membrane is used as an electrolyte of the PEFC, the membrane does not soak deeply into the electrodes as a liquid electrolyte does Therefore, PFSI solution was impregnated into the catalyst layers to increase the contact areas between Pt and PFSI In our previous work we proposed a new preparation method of the M&E assembly which emphasized the colloid formation of the PFSI to optimize the network of PFSIs in the catalyst layer and also to simplify the fabrication process of the M&E assembly Following this work, we focused on the microstructure of the catalyst layer The importance of the morphological properties of the gas-diffusion electrodes on performance has been reported in several papers The catalyst layer was claimed to have had two distinctive pore distributions with a boundary of ca 01 {mu}m The smaller pore (primary pore) was identified with the space in and between the primary particles in the agglomerate of the carbon support and the larger one (secondary pore) was that between the agglomerates In our recent work, we reported that the PFSI wasmore » distributed only in the secondary pores, and the reaction sites were therefore limited to that location The results indicated that the PEFC system required a particular design rather than a conventional one for the fuel cells with liquid electrolytes We proposed that novel structure and/or preparation methods of the catalyst layer were keys to higher utilization of Pt« less

Comparative Study of Carbon Dioxide Reforming of Methane to Synthesis Gas over Ni/La2O3 and Conventional Nickel-Based Catalysts

Abstract: Carbon dioxide reforming of methane to synthesis gas was studied by employing a Ni/La2O3 catalyst as well as conventional nickel-based catalysts, i.e., Ni/γ-Al2O3, Ni/CaO/γ-Al2O3, and Ni/CaO. It is observed that, in contrast to conventional nickel-based catalysts, which exhibit continuous deactivation with time on stream, the rate of reaction over the Ni/La2O3 catalyst increases during the initial 2−5 h and then tends to be essentially invariable with time on stream. X-ray photoelectron spectroscopy (XPS) studies show that the surface carbon on spent Ni/Al2O3 catalyst is dominated by −C−C− species that eventually block the entire Ni surface, leading to total loss of activity. The surface carbon on the working Ni/La2O3 catalyst is found to consist of −C−C− species and a large amount of oxidized carbon. Both XPS and secondary ion mass spectrometry results reveal that a large fraction of surface Ni on the working Ni/La2O3 catalyst is not shielded by carbon deposition. FTIR studies reveal that the enhancement...

Synthesis and Characterization of Hexagonally Packed Mesoporous Tantalum Oxide Molecular Sieves

Abstract: The synthesis and characterization of Ta-TMS1, a new member of a growing family of hexagonally packed transition-metal oxide mesoporous molecular sieves (termed TMS1) is described. Ta-TMS1 exhibits a hexagonal array of pores which can be varied in size from 20 to 40 A and surface areas of over 500 m2/g. The thermal and hydrothermal stabilities of Ta-TMS1 are 500 and 450 °C, respectively, making this system the most stable transition-metal oxide molecular sieve yet isolated. The high hydrocarbon adsorption capacities of this material make it a promising candidate as a catalyst support for hydrocarbon re-forming processes. The synthesis of this material was achieved by a novel approach involving the careful hydrolysis of long-chain primary amine complexes of Ta(OEt)5. This ligand-assisted templating mechanism represents a new approach to the synthesis of porous materials in that the inorganic precursor is covalently bonded to the template throughout synthesis. The high thermal stability, ease of synthesis a...

Thermal stabilization of catalyst supports and their application to high-temperature catalytic combustion

Abstract: Recent studies concerning thermal stabilization of catalyst supports and their application to a catalytic gas turbine combustor were reviewed. Development of heat-resistant catalysts has received considerable attention for the development of high-tempearture combustion catalysts. The use of additives such as La, Si, Ba, etc., is a promising way to improve the thermal stability of alumina-based support materials. Preparation routes also influence the surface area and the pore structure at operation temperatures. The effects were discussed from the solid state sintering mechanism of transition alumina. The authors have developed a noble alumina-based catalyst, hexaaluminate, as a thermally stable combustion catalyst, which can be used above 1200°C. In the second half of this review, we discussed fundamental catalytic properties of hexaaluminates and the results of practical applications to a gas turbine combustor.

Characterization and composition of commercial V2O5zWO3zTiO2 SCR catalysts

Abstract: The surface and bulk structure and composition of a commercial VzWzTi oxide catalyst used for denitrification of waste gases from power plants has been investigated by XRD, XRF, ICP, TG-DTA, FT-IR and SEM-EDS analyses and by comparison with ‘model’ catalysts. The catalyst powder consists of a full ‘monolayer’ of surface complexes, mainly constituted by wolframyl species with the addition of small amounts of vanadyl and sulphate species over high-area TiO2-anatase. The characteristics of the surface vanadyl, wolframyl and sulphate species fully consist with those previously reported for model VzTi, WzTi, VzWzTi and sulphated titania catalysts. The catalyst powder is mixed with glass-like particles, playing the role of mechanical promoters. The possibility of contamination of the catalyst particles by Mg or other alkali or alkali earth cations possibly arising from the glass particles during monolith preparation and during reactor start-up and shut-off procedures as well as during catalyst operation is suggested.

Carbon materials in catalysis

Abstract: The Pennsylvania State University, University Park, PennsylvaniaI. Fundamental Issues A. Introduction B. Cradle-to-Grave Approach c. A More Fundamental ApproachII. Applications A. Carbon as a Support for Fine Chemicals Catalysts B. Carbon as a Support for Petroleum Refining Catalysts C. Carbon as a Support for Environmental ControlCatalysts D. Carbon Use as a CatalystIII. ConclusionsReferences243 243 246 252312 313 323325 326 334Carbon materials have been used for decades in heterogeneous catalytic reactions. They help to increase the rate and control the selectivity ofmany chemical reactions. They can satisfy most of the desirable requirements for a suitable support: chemical inertness, stability (especially in the absence of molecular oxygen), mechanical resistance, high surface area and optimum porosity. As early as 1963 [1], Hassler reviewed the uses of activated carbon as a catalyst primarily, but also as a catalyst support. Today activated carbon is a well-established, commercially available catalyst support [2]. It is used predominantly for precious metal catalysts (see, for example, Refs. [3,4]), which are widely used in the synthesis of high-value-added chemical products [5]. For example, the Catalytic Reaction Guide published by Johnson Matthey, one of world's leading suppliers of catalysts, has a list of 69 organic reactions catalyzed by precious metals, nine of which (e.g., hydrogenation of benzene, hydrogenation of aliphatic and aromatic nitro compounds) use carbon as the only support material. However, very few large-volume catalytic processes currently use carbon-supported catalysts, despite the steady research in some promising areas such as hydrodesulfurization (HDS) of petroleum fractions or hydrogenation of carbon monoxide. Consequently, a very small fraction of carbon production is destined for catalyst manufacturing. It has been estimated [6], for example, that catalytic applications represent less than 5% of the market value of activated carbons. Yet much research has been done and continues to be conducted in this field, as evidenced by the information summarized in Fig. 1 and from the voluminous literature cited in this review. This situation is a reflection of the fact thatcarbon materials enjoy a mixed reputation in both industry and academia, especially as catalyst supports.

A review of the use of plasma techniques in catalyst preparation and catalytic reactions

Abstract: The application of plasma techniques in the preparation of catalysts and in catalytic reactions published during the last fifteen years is briefly reviewed. Two different types of plasma are used in this field: low temperature plasma (low pressure plasma) and high temperature plasma. The first type of plasma technique is widely used for the modification of surface oxides, and for the preparation and regeneration of catalysts as well as for catalytic synthesis and decomposition. The second type is applied for the preparation of ceramic-based supports, recovery of precious metals from used catalysts, and catalytic reactions. Both oxides and supported metal catalysts have been prepared by this method. The catalytic reactions involving the plasma technique essentially involve NO, methane or ammonia as reactants. An interesting potential for this technique is its application in the recovery of the precious metals from car exhaust catalysts.

Hydrogenation of carbon dioxide over alumina supported Fe-K catalysts

Abstract: The hydrogenation of CO2 has been studied over Fe/alumina and Fe-K/alumina catalysts. The addition of potassium increases the chemisorption ability of CO2 but decreases that of H2. The catalytic activity test at high pressure (20 atm) reveals that remarkably high activity and selectivity toward light olefins and C2+ hydrocarbons can be achieved with Fe-K/alumina catalysts containing high concentration of K (K/Fe molar ratio = 0.5, 1.0). In the reaction at atmospheric pressure, the highly K-promoted catalysts give much higher CO formation rate than the unpromoted catalyst. It is deduced that the remarkable catalytic properties in the presence of K are attributable to the increase in the ability of CO2 chemisorption and the enhanced activity for CO formation, which is the preceding step of C2+ hydrocarbon formation.

Monomodal and polymodal catalyst supports and catalysts having narrow pore size distributions and their production

Abstract: Monomodal or polymodal catalyst supports or catalysts having a BET specific surface area of from 0.01 to 250 m 2 /g and a monomodal or polymodal pore size distribution having a mean pore diameter of from 50 to 300,000 nm measured by the mercury pressure porosimetry method, wherein a) from 10 to 95% of the pore volume is at from 0.2 to 100 times the mean pore diameter and/or b) from 10 to 80% of the pore volume is at from 0.8 to 100 times the mean pore diameter and/or c) from 50 to 95% of the pore volume is at from 0.2 to 1 times the mean pore diameter and/or d) from 50 to 80% of the pore volume is at from 0.8 to 1 times the mean pore diameter and e) the width at half height of the pore size distribution is less than 0.6 times the mean pore diameter, which are useful for the preparation of chlorine from hydrogen chloride in a non-steady-state Deacon process, for the reaction of ethylbenzene to give styrene in a non-steady-state oxydehydrogenation, for preparing aziridine from ethanolamine, in reductions, hydrogenations, oxidations, dehydrogenations, acid- or base-catalyzed reactions or reactions in a fluidized bed, for removing combustion residues from diesel exhaust gases and for removing NO x from waste gases, in bioreactors together with bacteria and as biocatalyst supports with immobilized enzymes or microbes, and a process for producing said monomodal or polymodal catalyst support or catalyst.

Burned gas purifying catalyst

Abstract: An exhaust gas emission control catalyst includes an under catalyst layer containing at least one of barium and lanthanum and an over catalyst layer containing an agent for absorbing water in a gas, at least one of the under catalyst layer and over catalyst layer containing catalytic metal

Supported catalyst and process for catalytic oxidation of volatile organic compounds

Abstract: A catalyst for effective oxidation of volatile organic compounds (VOCs) includes 0.010-2 wt. % of a noble metal such as platinum in combination with 0.5-15 wt. % of a transition metal oxide such as chromium oxide (Cr2 O3), with at least the noble metal being deposited as a thin outer layer or shell not exceeding 0.10 mm thickness on a porous inert support such as alumina or silica having surface area of 10-400 m2 /g. The catalyst is made by adding the transition metal oxide such as chromium oxide (Cr2 O3) to the support material particles, and then subsequently mixing a solution of ammonium platinum nitrate with a suitable carrier liquid so as to form a "cluster" structure on the support material and which limits penetration of the active noble metal into the porous support, then drying, reducing, and calcining the metals-loaded support material. This catalyst composition and structure is highly effective for the oxidative destruction of VOCs in vapor form at concentrations of 1 ppm--5 vol. % and at reaction temperatures of 50°-500° C., 0-600 psig pressure, and space velocity of 1000-200,000 hr-1 to produce essentially only carbon dioxide and water products.

Platinum-aluminum alloy catalyst for fuel cells and method of its production and use

Abstract: A catalyst for use in a fuel cell containing a platinum-aluminum alloy on a conductive carbon carrier, wherein the atomic ratio of platinum to aluminum is from 80:20 to 60:40 and the alloy is present on the carbon carrier in carbidized form with the structure of platinum-aluminum carbide Pt 3 AlC 0 .5. Also disclosed are multimetallic alloy catalysts for use as electrode catalysts in fuel cells. Catalysts with high activity and stability are obtained on the basis of carbidized platinum-aluminum alloy catalysts by adding alloying elements of the groups VIB, VIIB, VIII and IB of the Periodic Table of Elements.

Promotional effect of Pt on non-oxidative methane transformation over Mo-HZSM-5 catalyst

Abstract: The influence of modification of Mo-HZSM-5 catalyst by Pt on methane non-oxidative transformation to ethylene and aromatics is investigated. Carbon accumulation on the catalyst is studied by means of DTA and TG methods. It is demonstrated that the addition of Pt to Mo-HZSM-5 considerably enhances the catalyst stability and reduces the carbon deposition on the catalyst. In the meanwhile, Mo-HZSM-5 is shown not to be a good catalyst for methane non-oxidative conversion because the total efficiency for methane conversion to useful products is even lower than it is in the oxidative coupling process.

Titanium-containing catalyst and process for the production of polyester

Abstract: A catalyst comprises (a) a finely dispersed hydrated TiO2, obtd. by hydrolysis, of formula y TiO2.zH2O, or (b) a finely dispersed titanate of compsn. (MenO)x.(TiO2)y.(H2O)z, where (a) and (b) have a high surface, i.e. have crystallite size not above 100 nm and specific surface above 10 m /g, and have a particle/aggregate size below 10 mu m. Me = Li, Na, K, Rb, Cs, Mg, Ca, Sr or Ba; n = 1 when Me is an alkaline earth, or n = 2 when Me is an alkali; x = 0.0001-6; y = 1; z = 0.01-2.

Polymer supported catalyst for olefin polymerization

Abstract: The present invention is directed to a novel supported Ziegler-Natta catalyst useful for the polymerization of α-olefins. More specifically, the supported Ziegler-Natta catalyst of the present invention comprises a particulate functionalized copolymeric support, an organometallic compound and a transition metal compound. A novel method of preparing the particulate functionalized copolymeric supports of the instant invention is also provided.

Conversion of Athabasca Bitumen with Dispersed and Supported Mo-Based Catalysts as a Function of Dispersed Catalyst Concentration

Abstract: A hydrocracking study of Athabasca bitumen using a batch reactor with varying concentrations of a microdispersed metal sulfide catalyst (MoS2) in the presence and absence of a common commercial supported catalyst is reported. The work compares the effects of a wide range of MoS2 dispersed catalyst concentrations (0−6000 ppm) on the conversion of residuum and the effects of using that dispersed catalyst with a commercial extruded hydrogenation catalyst. Hydrocracking runs using only the MoS2 microdispersed catalyst showed reduced coke formation only at low Mo concentrations. In the presence of the supported catalyst, solids formation increased significantly and overall catalyst performance was lowered as a function of increased MoS2 microdispersed catalyst concentration.

Preparation of oxide catalysts and catalyst supports - A review of recent advances

Abstract: Recent progress in the understanding of the effect of preparation variables on the properties of oxide materials, either to be used as catalysts or catalyst supports, are summarized. The methods include sol-gel technique, use of surfactant to prepare mesoporous and related materials, equilibrium adsorption technique, preparation of hydrotalcite materials, and use of preformed multicomponent complexes. The control of the properties of the oxide material, such as pore size, surface area, and homogeneity by controlling the preparation variables in different methods, and the chemical processes involved in these methods are discussed.

Solid catalyst component and catalyst for polymerization of olefins

Abstract: A solid catalyst component for polymerization of olefins prepared by reacting a titanium halide, a diester of aromatic dicarboxylic acid and a dialkoxymagnesium having a bulk density of at least 025 g/ml and an average particle size of 1 to 100 μm The average rate of temperature rise from the temperature at which the titanium halide is allowed to come in contact with the dialkoxymagnesium to the temperature at which the reaction is initiated is in a range of from 05 to 20° C/min Such catalyst can further comprise an organic aluminum compound and an organic silicon compound The use of said catalyst makes it possible to efficiently obtain a polyolefin having a high stereoregularity, a high bulk density and excellent particle properties

Virtually no environmental impact : the biphasic oxo process

Abstract: Water-soluble catalysts offer significant advances in homogeneous catalysis: the “heterogenization” of the catalyst in a second, immiscible liquid phase immobilises the catalyst phase, thus combining the advantages of heterogeneous catalysis, e.g. long lifetime, easy separation of product from catalyst, with those of the homogeneous type, namely, defined species of catalyst, gentle reaction conditions, high activity and selectivity. The first successful large-scale application of aqueous catalysts is the oxo process of Ruhrchemie/Rhone-Poulenc, using a HRh(CO)[P-(3-sulfophenyl-Na)3]3 catalyst, dissolved in water. This survey reviews 10 years' experience of this process against the background of biphasic catalyses, especially the way in which this environmental benign technique, which is highly economic and thus very environmentally sound, reduces pollution.

Promoting Effects of Carbon Dioxide on Dehydrogenation of Propane over a SiO2-supported Cr2O3 Catalyst.

Abstract: The effects of carbon dioxide in the dehydrogenation of C3H8 to produce C3H6 were investigated over several Cr2O3 catalysts supported on Al2O3, active carbon and SiO2. Carbon dioxide exerted promoting effects only on SiO2-supported Cr2O3 catalyst. The promoting effects of carbon dioxide over a Cr2O3/SiO2 catalyst were to enhance the yield of C3H6 and to suppress the catalyst deactivation.