Showing papers on "Catalyst support published in 1995"

Heterogeneous Basic Catalysis

Abstract: Heterogeneous acid catalysis attracted much attention primarily because heterogeneous acidic catalysts act as catalysts in petroleum refinery and are known as a main catalyst in the cracking process which is the largest process among the industrial chemical processes. In contrast to these extensive studies of heterogeneous acidic catalysts, fewer efforts have been given to the study of heterogeneous basic catalysts. The types of heterogeneous basic catalysts are listed in Table 1. Except for non-oxide catalysts, the basic sites are believed to be surface O atoms. The studies of heterogeneous catalysis have been continuous and progressed steadily. They have never been reviewed in the chemical Reviews before. It is more useful and informative to describe the studies of heterogeneous basic catalysis performed for a long period. In the present article, therefore, the cited papers are not restricted to those published recently, but include those published for the last 25 years. The paper first describes the generation of basic sites before describing methods used in the characterization of basic surfaces. These are indicator methods, temperature programmed desorption (TPD) of CO{sub 2}, UV absorption and luminescence spectroscopies, TPD of H{sub 2}, XPS, IR of CO{sub 2}, IR of pyrrole, and oxygen exchange betweenmore » CO{sub 2} and the surface. The paper then discusses studies on the catalysis by heterogeneous basic catalysts. Some of these reactions are dehydration, dehydrogenation, hydrogenation, amination, alkylation, ring transformation, and reactions of organosilanes. Catalysts discussed are single component metal oxides, zeolites, non-oxide types, and superbasic catalysts. 141 refs.« less

Carbon dioxide reforming of methane over nickel alkaline earth metal oxide catalysts

Abstract: The CO2 reforming of CH4 over reduced NiO/alkaline earth metal oxide catalysts was investigated. A CO yield of 95% was obtained from a stoichiometric feed mixture of CH4 and CO2, at high GHSV (60 000 cm3 g−1 h−1), over a reduced NiOMgO with a weight ratio of 0.2. In addition, the catalyst had excellent stability, since the CO yield remained unchanged during 120h. Compared to the reduced NiOMgO catalyst, the reduced NiOCaO,NiO SrO NiO BaO catalysts had low CO yields and very low stabilities. The TPD of CO over the reduced NiOMgO catalyst indicated a lower decomposition of CO to CO2 than over the other catalysts investigated, hence that MgO inhibits the disproportionation reaction 2CO → C + CO2 over Ni. The behavior of the reduced NiOMgO catalyst is probably due to the formation of a NiOMgO solution, as a result of the similar crystalline structures of NiO and MgO.

Polymerization catalyst systems, their production and use

Abstract: This invention is generally directed toward a supported catalyst system useful for polymerizing olefins. The method for supporting the catalyst system of the invention provides for a supported metallocene catalyst and alumoxane activator which when utilized in a polymerization process substantially reduces the reactor fouling and sheeting.

Development of an active Ga2O3 supported palladium catalyst for the synthesis of methanol from carbon dioxide and hydrogen

Abstract: A significant effect of the support on the catalytic activity of palladium-based catalysts for methanol synthesis from carbon dioxide and hydrogen was observed, where Pd/Ga 2 O 3 was more active than Cu/ZnO by a factor of 2 in yield and 20 in turnover frequency

Characterization of cobalt Fischer-Tropsch catalysts I. Unpromoted cobalt-silica gel catalysts

Abstract: The effect of preparation conditions on cobalt-silica gel catalysts has been investigated by temperature-programmed reduction, differential thermal analysis, X-ray photoelectron spectroscopy, and magnetic susceptibility measurements. The results have been correlated with the performance of the catalysts for the conversion of syngas. It has been found that active Fischer-Tropsch (F-T) cobalt catalysts can be partially or totally reduced to the metal phase during activation. However, reducibility of the catalysts is a necessary but not sufficient characteristic in ensuring good activity. The pH of the impregnating solution influences surface charge and solubility of silica gel. Consequently, the physical and chemical properties of the cobalt species on the surface of silica gel are strongly affected by this parameter. At pH

Hydrocarbon reforming catalyst material and configuration of the same

Abstract: A hydrocarbon reforming catalyst material comprising a catalyst support impregnated with catalyst is provided for reforming hydrocarbon fuel gases in an electrochemical generator. Elongated electrochemical cells convert the fuel to electrical power in the presence of an oxidant, after which the spent fuel is recirculated and combined with a fresh hydrocarbon feed fuel forming the reformable gas mixture which is fed to a reforming chamber containing a reforming catalyst material, where the reforming catalyst material includes discrete passageways integrally formed along the length of the catalyst support in the direction of reformable gas flow. The spent fuel and/or combusted exhaust gases discharged from the generator chamber transfer heat to the catalyst support, which in turn transfers heat to the reformable gas and to the catalyst, preferably via a number of discrete passageways disposed adjacent one another in the reforming catalyst support. The passageways can be slots extending inwardly from an outer surface of the support body, which slots are partly defined by an exterior confining wall. According to a preferred embodiment, the catalyst support is non-rigid, porous, fibrous alumina, wherein the fibers are substantially unsintered and compressible, and the reforming catalyst support is impregnated, at least in the discrete passageways with Ni and MgO, and has a number of internal slot passageways for reformable gas, the slot passageways being partly closed by a containing outer wall.

Surface supported cobalt catalysts, process utilizing these catalysts for the preparation of hydrocarbons from synthesis gas and process for the preparation of said catalysts

Abstract: A supported particulate cobalt catalyst is formed by dispersing cobalt, alone or with a metal promoter, particularly rhenium, as a thin catalytically active film upon a particulate support, especially a silica or titania support. This catalyst can be used to convert an admixture of carbon monoxide and hydrogen to a distillate fuel constituted principally of an admixture of linear paraffins and olefins, particularly a C10+ distillate, at high productivity, with low methane selectivity. A process is also disclosed for the preparation of these catalysts.

Ceria-alumina oxidation catalyst

Abstract: Oxidation catalyst compositions include a catalytic material containing ceria and alumina each having a surface area of at least about 10 m2 /g, for example, ceria and activated alumina in a weight ratio of from about 1.5:1 to 1:1.5. Optionally, platinum may be included in the catalytic material in amounts which are sufficient to promote gas phase oxidation of CO and HC but which are limited to preclude excessive oxidation of SO2 to SO3. Alternatively, palladium in any desired amount may be included in the catalytic material. The catalyst compositions have utility as oxidation catalysts for pollution abatement of exhausts contianing unburned fuel or oil. For example, the catalyst compositions may be used in a method to treat diesel engine exhaust by contacting the hot exhaust with the catalyst composition to promote the oxidation of the volatile organic fraction component of particulates in the exhaust.

Heterogeneous catalysis in organic chemistry. Part 10. Effect of the catalyst support on the regiochemistry of the heck arylation reaction

Abstract: Data have been presented which show that dispersed metals can be considered as viable catalysts for synthetically useful organometallic reactions. In addition, the material used as the catalyst support has been shown to influence the regiochemistry of the reaction. In the Heck arylation an acidic support, such as silica, withdraws electrons from the palladium and this leads to predominant β enol ether formation. Palladium supported on a basic support, such as magnesia, which is electron donating, produces primarily the α product. Electron withdrawal also increases the rate of the reaction. As with a number of other synthetically useful reactions the heterogeneously catalyzed Heck arylation takes place on the coordinately unsaturated corner atoms and adatoms on the metal surface. These single atom active sites are the only ones having a sufficient number of orbitals available for interaction with both the aryl species and the enol ether at the same time, a procedure needed for the reaction to take place. A mechanism for the reaction on a tetrahedral corner atom is proposed. This is based on the Frontier Molecular Orbitals of this site and the corresponding mechanism established for the homogenously catalyzed reaction.

Development of composite catalysts made of Cu-Zn-Cr oxide/zeolite for the hydrogenation of carbon dioxide

Abstract: The hydrogenation of carbon dioxide using a Cu-Zn-Cr oxide/zeolite composite catalyst system has been studied. The change in the structure of the oxide catalyst during the reaction was found to be very significant, with the catalytic activity decreasing rapidly at temperatures over 350°C. Measurement of metallic copper surface areas revealed a sharp decrease in exposed metallic copper caused by the sintering of the catalyst. The reaction of methanol over various composite catalyst was also examined. The results indicated that composite catalysts with low metallic copper surface areas promote the methanol to gasoline reaction, while high surface areas caused the decomposition of methanol to carbon monoxide and carbon dioxide. These results suggested that hydrocarbon synthesis and the decomposition of methanol are competitive.

MCM-41 as a support for small platinum particles: a catalyst for low-temperature carbon monoxide oxidation

Abstract: MCM-41 is loaded with platinum via different pathways, resulting in highly active oxidation catalysts.

Method for making supported catalyst systems and catalyst systems therefrom

Abstract: Catalyst systems and methods for supporting catalysts systems and their components, particularly metallocene catalyst components, are provided. The method involves techniques for evenly distributing a small volume of catalyst component over and among a porous support material. Such even distribution is thought to result in reduced fouling.

Operation of diesel engines with reduced particulate emission by utilization of platinum group metal fuel additive and pass-through catalytic oxidizer

Abstract: The invention provides a method employing a fuel additive to improve the operation of a pass-through oxidation catalyst over long periods of time with continued catalytic activity and without the undesirable conversion of SO 2 to SO 3 . A pass-through catalyst support is continuously, selectively catalyzed by the combustion of a fuel containing a platinum group metal composition which burns to release the catalyst metal in active form. The effectiveness of the process is attributed to improved combustion in the engine by the catalyst and the treatment of the catalytic oxidizer with active catalyst metal released during combustion such that, in the exhaust system, the soluble organic fraction of the particulates and the levels of gaseous unburned hydrocarbons and carbon monoxide are significantly reduced. The catalysts conditioned by the present invention cause minimal conversion of SO 2 to SO 3 . The platinum group metal compositions soluble or dispersible in the diesel fuel and are added in amounts effective to provide concentrations of the metal in the fuel of less than 1 part per million (ppm).

Methods and catalysts for the manufacture of carbon fibrils

Abstract: An improved catalyst for producing carbon fibrils is made by incorporating an effective yield-enhancing amount of a carboxylate into a fibril-forming catalyst. Alternatively, such a catalyst is made by coprecipitating a compound of a metal having fibril-forming catalytic properties and an aluminum and/or magnesium compound, optionally in the presence of carbon particles or carbon fibril aggregates. The catalyst may also be made by incorporating a compound of a fibril-forming metal onto magnesia particles in carbon particles or carbon fibril aggregates. The catalysts, methods of using them to form carbon fibrils and those carbon fibrils are also disclosed.

Polystyrene-supported metallocene catalysts for olefin polymerizations

Abstract: Several kinds of polystyrene-supported metallocene catalysts were prepared and used in the polymerizations of propylene and ethylene with methylaluminoxane (MAO) as cocatalyst. It was found that these catalysts are stable even at 70°C. They display fairly high activities when the polymerizations are conducted at high temperatures.

Method of making a high strength catalyst, catalyst support or adsorber

Abstract: A method of making a catalyst, catalyst support or adsorbing structure which involves forming a mixture of raw material which can be ceramic and/or molecular sieve, silicone resin permanent binder, dibasic ester as a solvent for the silicone resin, organic binder of cellulose ether, and/or derivatives thereof, and water, shaping the mixture into a green body which is then dried and heated to develop strength and form the catalyst, catalyst support, or adsorber.

Reductive amination of ethanol with silica-supported cobalt and nickel catalysts

Abstract: The amination of ethanol has been studied using silica-supported cobalt and nickel catalysts prepared by incipient wetness impregnation. Under identical operating conditions, the Co/SiO2 catalyst is considerably more active for ethanol conversion than the Ni/SiO2 catalyst, in spite of the lower measured metal surface area. The higher activity of the Co/SiO2 catalyst combined with its higher selectivity towards the industrially desired lower amines (MEA and DEA) make the metal a promising catalyst. Selectivity to individual ethylamine products (i.e. mono-, di- and triethylamine) is kinetically controlled and a function of the operating parameters as well as of the metal catalyst employed. Temperature programmed reduction (TPR), temperature programmed oxidation (TPO) and hydrogen chemisorption have been used to characterize the physico-chemical differences between the catalysts used in this study.

Close coupled catalyst

Abstract: A stable, close-coupled catalyst, an article comprising the close-coupled catalyst and a related method of operation. The close-coupled catalyst comprises a catalyst support and a palladium catalytic component. Preferably and optionally, there are stabilizers including alkaline metal oxide, and rare earth metal components selected from the neodymium and lanthanum components. The close-coupled catalyst composition includes substantially no additional oxygen storage component such as praseodymium or cerium compounds. There is preferably a catalyst such as a three-way catalyst downstream of the close-coupled catalyst. The downstream catalyst preferably includes an oxygen storage component such as cerium oxide or praseodymium oxide.