Showing papers on "Catalyst support published in 1990"

Spontaneous Monolayer Dispersion of Oxides and Salts onto Surfaces of Supports: Applications to Heterogeneous Catalysis

Abstract: Publisher Summary The forms of active components present in heterogeneous catalysts are of importance to catalysis A supported catalyst usually consists of an active component dispersed on a support with a highly specific surface An active component dispersed on a support may end up in one of three forms: (1) it may retain its chemical identity as a separate crystalline or amorphous phase, (2) it may form a new stoichiometric compound with the support or additive, or (3) it may dissolve in the support to give a solid solution This chapter provides a review of various aspects of the phenomenon of spontaneous monolayer dispersion, its nature, effects, and applications Spontaneous monolayer dispersion of compounds on supports is a widespread phenomenon and displays many unique effects The principles involved have applications not only to heterogeneous catalysis, but also to materials science and other related fields

Binder/support effects on the activity and selectivity of iron catalysts in the Fischer-Tropsch synthesis

Abstract: This paper reports on the influence of silica and alumina binders (supports) on the activity and product selectivity of precipitated iron catalyst for Fischer-Tropsch synthesis (FTS) that was studied in a fixed bed reactor at 1.5-3.0 MPa and 220-250{degrees} C, using synthesis gas with H{sub 2}/CO = 1 M feed ratio. Both the FTS and the water gas shift activity decreased with increasing support content. The catalyst deactivation rate decreased with catalysts containing 24 and 100 g of SiO{sub 2} per 100 g of Fe. Secondary reaction (olefin hydrogenation and isomerization) increased with increasing silica content. Hydrocarbon selectivities improved (less gaseous hydrocarbons) with the addition of support, except for the catalyst containing 24 SiO{sub 2}/100Fe. The results were interpreted in terms of interactions between potassium and/or iron with supports.

Addition of aluminium alkyl for improved metallocene catalyst

Abstract: The invention is for a catalyst system for polymerization of olefins using an ionic mettallocene catalyst with aluminum alkyl. The metallocene catalyst is an ion pair formed from a neutral metallocene compound and an ionizing compound. The invention can be used in any method of producing ionic metallocene catalyst. Use of aluminum alkyl with an ionic metallocene catalyst eliminates the need for using methylaluminoxane (MAO). Catalysts produced by the method of this invention have high activity. The invention reduces catalyst poisons which cause low activity, no activity or uncontrolled polymerizations. Polymerizations using this catalyst system are reproducible and controllable.

Catalytic Fuel Combustion—A Way of Reducing Emission of Nitrogen Oxides

Abstract: The present survey has shown that catalytic combustion can be successfully applied to various domestic and industrial fuel-burning devices for improving combustion efficiency and thermal NO x control. The investigation of kinetics of oxidation of nitrogen-containing compounds on solid catalysts has shown that the fuel NO x yield can be decreased by the use of oxide catalysts rather than platinum ones, by low excess air operation, and by decreasing the combustion of fuels in a fluidized catalyst bed in catalytic heat generators makes it possible to conduct technological processes at high fuel loads on a catalyst and at rather low temperatures in the combustion zone (770-1070 K) owing to the combination of heat evolution and heat removal in the same catalyst bed

Catalyst for purification of exhaust gases

Abstract: A catalyst for purification of exhaust gases, comprising a support substrate, a catalyst carrier layer formed on the support substrate and catalyst ingredients loaded on the catalyst carrier layer, wherein the catalyst carrier layer comprises alumina, cerium oxide, zirconium oxide and at least one oxide of rare earth element except cerium and lanthanum, and at least a part of cerium oxide, zirconium oxide and oxide of rare earth element except cerium and lanthanum is present in the form of composite oxide and/or solid solution. The catalyst for purification of exhaust gases is capable of purifying exhaust gases containing carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx).

Effect of cerium addition on the thermal stability of gamma alumina support

Abstract: Transition alumina, such as 7-A1203, 0-A1203 and 6-A1203, has been widely used as a catalyst support. The surface area of the support significantly decreases at high temperature operations, for example in purifying automotive exhaust gas [1]. In this case, it is important to maintain the support with high surface area free of sintering or phase transition, otherwise precious metals (platinum, rhodium etc.) supported on alumina will consequently sinter. Cerium and other rare earth elements have been used as a promoter to improve the catalytic activities for purifying carbon monoxide, nitrogen oxides and hydrocarbons emitted from automotive engines [2-4]. It has been suggested that the addition of cerium plays serveral roles, including the catalysis of the water-gas shift reaction, the oxygen storage in the lattice for oxidation catalysis under rich air-fuel conditions, and the inhibition of the growth of noble metal particles. The present letter describes the influence of the addition of cerium to 7-A1203 catalyst supports on the phase transition of 7-A1203 to ~-A1203 and the sintering of transition alumina below the transition temperature. A series of cerium-added alumina was prepared by the impregnation technique. Powdered 7-A1203 with surface area 170 m 2 g ~ was used as a support, and an aqueous cerium nitrate was used as an impregnation solution. The samples were then dried at 110 ° C for 8 h and calcined at 600°C for 3 h. The starting alumina contained 0.05 wt % impurities, mainly iron and trace silicon, calcium and sodium. The cerium contents of the samples were 0.5, 1, 2, 3, 5 and 10mol% by the CeO2 to the total moles of oxides (CeO2 + A1203). The samples were further calcined in air at a temperature between 1 000 ° C and 1 200 ° C for 5 h in order to examine the thermal stability of the alimina support. The surface area of the samples was derived by application of the BET equation, from nitrogen adsorption data obtained at 77K by a standard volumetric procedure. The phase transition temperature was measured with a DTA apparatus at heating rates of 2.5, 5, 10 and 20Kmin ~ using 0¢-A1203 powder as a reference material. Kissinger's plots [5] were applied to the evaluation of the activation energy of the phase transition from active alumina to c¢-A12 03. Phase analysis was done by the powder X-ray diffraction (XRD) technique. The amount of ~-A1203 in the samples was determined by the XRD intensity of the (1 00) diffraction line of 0~-Al203. The standard data were obtained from the XRD data of the mixtures of u-A1203 powder and 0-A1203 powder which were formed by calcining 7-A1203 at 1 300°C and l 000°C for 10 h. The samples containing 0.01 mol % gadolinium were prepared by the same procedure as above, but using an aqueous solution of gadolinium nitrate. Fig. 1 shows the Surface area of alumina supports containing cerium with different molar concentrations, calcined in air at 1 000 ° C, l 100°C and 1 200°C for 5 h. The thermal stability of alumina was improved by the addition of only 0.5 to 2 mol % cerium, and a gradual decline in surface area was found with increasing cerium content. XRD analysis of the samples calcined in air at 1 200°C indicated that 0.5 mol % Ce-A1203 consisted of 0-, ~and ~-A1203, and that pure A1203 completely transformed to ~-A1203 (Fig. 2). CeO2 phase was found in the samples with more than 2 mol % cerium. These results clearly show that the addition of cerium improves the thermal stability of alumina at 1 200°C by preventing the transformation to ~-A1203. However, the overloading of cerium decreases the surface area of the alumina because of the growth of CeO2 particles. The XRD data of the samples calcined at 1 100°C indicated the formation of 0and ~-A12 03. The decrease in surface area was inhibited by the cerium loading at 1 100 ° C. Kissinger's plots of the data obtained by DTA for both pure AI203 and 0.5 tool % Ce-AI203 and given in Fig. 3 as the relation of ln[(dT/dt)Tn72] with l/Tm. (dT/dt) is the heating rate, and Tm represents the maximum rate temperature of the phase transition. The activation energy of the phase transition was calculated at 581kJmol ~ for pure AI203 and 582 kJ tool ~ for 0.5 mol % Ce-A1203. Although these values are rather high compared with those in the literature [6, 7], it can be found that the alumina in this study has the constant activation energy of the phase transition regardless of the cerium addition. Scanning electron microscopy (SEM) observation of the samples calcined at ! 200 ° C revealed the formation of ~-A1203 particles, 0.1 to 0.3 #m in diameter. The particle size was independent of the content of cerium in the samples. These results can be explained by assuming that the cerium addition decreased the ~-A1203 transformation by influencing the nucleation process of ~-A1203 but not its growth process. Fig. 4 compares the 1 250 ° C isothermal transformation data for pure A1203 with those for 0.5mol % Ce-A1203. The data were analysed using the following empirical kinetic equation

Slurry-phase Fischer-Tropsch synthesis and kinetic studies over supported cobalt carbonyl derived catalysts

Abstract: This paper reports the preparation characterization, and performance of cobalt carbonyl cluster based catalysts for use in slurry-phase Fischer--Tropsch (FT) technology investigated. Using metal carbonyls as active metal precursors allows for the control of metal particle size on the support surface, thus offering the potential for better control of activity and selectivity of the FT reaction. Silica as the support provided the highest catalyst activities. A Co{sub 2}(CO){sub 8}/Zr(OPr){sub 4}/SiO{sub 2} catalyst (3.5% cobalt, 6.6% zirconium) was developed as the most active system in the FT slurry reactor and also gave the best liquid fuel selectivity. Selectivity patterns correlated to the Schulz--Flory prediction. These catalysts exhibited low water/gas shift activity. Diesel fuel product produced by this catalyst was high quality. A kinetic expression that took water inhibition into account was verified, yielding an activation energy of 97 kJ/mol for syngas conversion ranging from 34% to 71% at 240--280{degrees} C.

Partial combustion catalyst of palladium on a zirconia support and a process for using it

Abstract: This invention is a catalyst comprising palladium on a support containing zirconium and a partial combustion process in which the fuel is partially combusted using that catalyst. The choice of catalysts and supports solves a problem dealing with the long term stability of palladium as a partial combustion catalyst. The catalyst structure is stable in operation, has a comparatively low operating temperature, has a low temperature at which oxidation begins, and yet is not susceptible to temperature "runaway". The combustion gas produced by the catalytic process typically is at a temperature below the autocombustive temperature and may be used at that temperature or it may be fed to other combustion stages for further use in a gas turbine, furnace, boiler, or the like.

Multistage process for combusting fuel mixtures using oxide catalysts in the hot stage

Abstract: This invention is a combustion process having a series of stages in which the fuel is combusted stepwise using specific catalysts (desirably palladium-bearing catalysts in the first two zones and metal and oxygen-bearing catalysts in the hot catalytic zone) and catalytic structures and, optionally, a final homogeneous combustion zone. The choice of catalysts and the use of specific structures, including those employing integral heat exchange, results in a catalyst support which is stable due to its comparatively low temperature and yet the product combustion gas is at a temperature suitable for use in a gas turbine, furnace, boiler, or the like, but has low NO x content.

Recovery of double metal cyanide complex catalyst from a polymer

Abstract: A process for recovering double metal cyanide complex catalyst from a polymer such as polypropylene glycol in a form suitable for use as a polymerization catalyst is described. The process comprises the steps of (a) combining the polymer with a non-polar solvent to precipitate the catalyst and (b) filtering the resulting mixture in the presence of a filter aid to separate the polymer from the precipitated catalyst. In contrast to the prior art methods of catalyst removal, the process of the invention yields polymer uniformly low in color as well as recovered catalyst which may be reused in subsequent polymerizations.

Hydrogenolysis reaction and catalyst suitable therefor

Abstract: The invention concerns a method of performing a chemical reaction in which hydrogenation and/or dehydrogenation occurs, in the presence of a supported catalyst comprising a carrier material with copper as active component and iron as a promotor. According to the invention, the proporation of iron, calculated on the amount of copper and iron jointly, on an atomic basis, is no more than 25%. The invention also relates to a catalyst for carrying out the reaction, and to a process for preparing a supported catalyst.

Selective catalysts and their preparation for catalytic hydrocarbon synthesis

Abstract: Supported catalysts for Fischer-Tropsch processes prepared by contacting a suitable support with a catalyst in the form of a metal salt and depositing the catalyst on the support. Where rim type catalyst are preferred, a molten salt starting material is used. For non-rim type catalyst, such as powdered catalyst, solution salt starting materials may be used. The catalyst is prepared without high temperature calcination of the catalyst before reduction by reducing the salt directly on the support to the metal. During the reduction step, the heating rate is a slow single steady heating rate.

Porous metal oxide supported carbon-coated catalysts and method for producing same

Abstract: Supported carbon-coated catalyst material and a method for producing and using same in catalytic reaction processes, preferably in ebullated or fluidized catalyst beds. The catalyst materials are prepared by depositing a porous carbon layer on a support material of a selected metal oxide or compound to produce 5-40 wt. % carbon thereon, then preferentially treating the carbon based layer by partial oxidation, pyrolysis or reduction to enhance and activate the carbon layer on the catalyst. Promoter materials can also be advantageously added either to the support material or to the carbon layer in 0.5-10 wt. % to provide an improved composite carbon-coated catalyst having total pore volume of 0.3-1.0 cc/gm, substantially increased surface area of 80-600 M 2 /gm, low surface acidity, particle strength of 1.8-5 lb/mm with reduced particle attrition losses and improved catalyst performance characteristics.