Showing papers on "Catalyst support published in 1993"

Selectivity Control and Catalyst Design in the Fischer-Tropsch Synthesis: Sites, Pellets, and Reactors

Abstract: Publisher Summary This chapter focuses on selectivity control and catalyst design in the Fischer-Tropsch (FT) synthesis. Chain growth during the FT synthesis is controlled by surface polymerization kinetics that place severe restrictions on our ability to alter the resulting carbon number distribution. Intrinsic chain growth kinetics are not influenced strongly by the identity of the support or by the size of the metal crystallites in supported Co and Ru catalysts. Transport-limited reactant arival and product removal, however, depend on support and metal site density and affect the relative rates of primary and secondary reactions and the FT synthesis selectivity. Diffusion-limited removal of products from catalyst pellets leads to enhanced readsorption and chain initiation by reactive α-olefins. Diffusive and convective transport processes introduce flexibility in the design of catalyst pellets and in the control of FT synthesis selectivity. The model is proposed in the chapter that describes the catalytic behavior of more complex Fe based materials, where several chain termination steps and highly non-uniform and dynamic surfaces introduce additional details into the models required to describe FT synthesis selectivity models.

Support effects in cobalt-based fischer-tropsch catalysis

Abstract: A range of cobalt catalysts supported on kieselguhr, silica, alumina, bentonite, zeolite Y, mordenite and ZSM-5 was examined for catalytic activity and product selectivity in the Fischer-Tropsch reaction. These results were correlated with catalyst reducibility and adsorptive properties, as well as support acidity, surface area and structure. It was found that high surface area supports give high cobalt dispersions and tend to produce highly active Fischer-Tropsch catalysts, as long as the reducibility of the cobalt is not hindered by metal-support interactions or ion exchange, or that pore diffusion or blocking effects are not taking place. All supports produced catalysts with similar methane, carbon dioxide and higher hydrocarbon selectivities, with carbon dioxide selectivity being low in all cases. The nature of the higher hydrocarbons depended strongly upon support acidity, with the non-zeolitic, low acidity supports producing the classic straight chained Fischer-Tropsch product. Of the zeolite supported catalysts, the most strongly acidic ZSM-5 supported catalyst produced the most highly branched product, followed by the zeolite Y supported catalyst. The straight chained character of the product from the mordenite supported catalyst was explained by the inaccessibility of the primary Fischer-Tropsch products to the mordenite acid sites, due to the mordenite channel system and ion exchange properties, thereby preventing secondary reactions such as isomerisation from occurring.

Supported homogeneous catalyst complexes for olefin polymerization

Abstract: A supported catalyst complex having a Group 4 metal cyclopentadienyl derivative and an aluminoxane reacted with silica which show improved resistance to catalyst poisoning. The supported catalyst composition is particularly suitable for producing homogeneous ethylene polymers and copolymers having a narrow molecular weight distribution. The invention further includes the process of preparing the supported catalyst compositions and their use as olefin polymerization catalysts. The catalyst support is prepared by contacting silica with an aluminoxane, preferably either methylaluminoxane or modified methylaluminoxane.

Selective oxidation of glycerol on a platinum-bismuth catalyst by using a fixed bed reactor

Abstract: The selective oxidation of glycerol (GLY) using a fixed bed reactor packed with a Pt-Bi catalyst (weight ratio of Bi to Pt=0.2) supported on granular charcoal was performed. A new catalyst system to perform continuous oxidations was developed. Oxidation of a 50% aqueous solution of GLY at 50° C, oxygen-to-GLY mole ratio of 2 and a GLY aq. soln. based LHSV (h−1) of 0.06 produced dihydroxyace- tone (DHA) with a selectivity of ca. 80% at a GLY conversion of 80%. EPMA (electron probe micro analysis) line analysis of active BiPt catalysts showed the necessity of inner layer impregnation of both elements for selective oxidation of the secondary hydroxy group of GLY. Wood based granular charcoal with a high BET surface area (>1200 m2/g) and a low bulk density (<200 g/l) was the preferred catalyst support.

Supported catalyst for 1-olefin(s) (co)polymerization

Abstract: This invention relates to a supported catalyst composition useful in the polymerization of olefins and to a method for its production. The catalyst is formed by first reacting a trialkylaluminum compound with a transition metal metallocene, and subsequently reacting the resulting material with the undehydrated support material to form a solid product containing at least 20 grams of support material per milimole of transition metal. The resulting supported catalyst has a level of activity comparable to that of conventionally made supported catalysts which are achieved at active metal loadings which are reduced from the loadings used in the previously known metallocene-alumoxane catalysts by at least 20 %, and preferably 50 %. The invention particularly relates to the use of undehydrated silica gel containing from 6 to 20 per cent by weight adsorbed water as the catalyst support material.

Surface properties and porosities of silica and acid-treated montmorillonite catalyst supports: influence on activities of supported ZnCl2 alkylation catalysts

Abstract: A series of progressively acid-treated montmorillonite clays and a range of porous silicas are tested for their effectiveness as supports for ZnCl2 alkylation catalysts. Support materials are characterised in terms of surface areas, pore volumes and pore size distributions, in an attempt to identify surface properties important in conferring catalytic activity to supported ZnCl2. The highest catalytic activities are associated with acid-treated clay and silica supports with significant volumes in pores of diameter 10–12 nm. Supports exhibiting pore diameters below this range produce catalysts of very low activities. The fall in catalytic activity associated with larger pore diameter supports is less dramatic. Suggested mechanisms by which the catalytic activity of ZnCl2 is enhanced in pores within the critical size range are proposed.

Catalyst for exhaust gas purification and process for production thereof

Abstract: A catalyst for exhaust gas purification, comprising a heat-resistant inorganic monolith carrier and a catalyst layer loaded thereon, the catalyst layer including a catalyst composition containing at least one noble metal selected from Pt, Pd and Rh, as an active catalyst component, and active alumina. The catalyst composition has a specific surface area of at least 50 m 2 /g and a porosity of at least 50%. This catalyst for exhaust gas purification contains noble metal(s) in a well dispersed state, has excellent high-temperature durability, and is low in thermal deterioration of catalyst performance. Hence, the catalyst can be suitably used as a converter installed in engine manifolds of gasoline engine automobiles, or as a heater having improved purification ability for the exhaust gases emitted from automobiles during their cold start.

Process of hydrotreating and/or hydrocracking hydrocarbon streams or tail gas treating sulfur-containing gas streams

Abstract: The invention relates to an improved method of presulfurizing a sulfidable metal oxide(s)-containing catalyst which minimizes sulfur stripping upon start-up of a reactor and improves catalyst activity. The method consists of contacting a sulfidable metal oxide(s)-containing catalyst with elemental sulfur at a temperature such that said elemental sulfur is substantially incorporated in the pores of said catalyst by sublimation and/or melting and heating the sulfur-incorporated catalyst in the presence of a liquid olefinic hydrocarbon at a temperature greater than about 150° C.

Method of making a homogeneous-heterogenous catalyst system for olefin polymerization

Abstract: This invention concerns a making a catalyst system comprising at least one homogeneous catalyst and at least one heterogeneous catalyst, specifically, a metallocene catalyst and a conventional Ziegler-Natta catalyst, respectively. This invention is useful for making a catalyst for the polymerization of any polymer in which separate polymerizations with a homogeneous catalyst and with a heterogeneous catalyst are possible, but preferably, polymerization of olefins, more preferably, α-olefins, and, most preferably, propylene. This invention provides a catalyst system which facilitates use of a homogeneous catalyst but eliminates the disadvantages of such a system. This invention produces a polymer with molecular weight distribution (MWD) as broad or broader than the MWD of the heterogeneous catalyst alone. Hydrogen can be used to control molecular weight distribution of a polymer produced with this invention.

Cracking catalyst for the production of light olefins

Abstract: A cracking catalyst for the production of light olefins comprises 0-70% (based on the weight of the catalyst) of clay, 5-99% of inorganic oxides, and 1-50% of zeolite. The zeolite in the catalyst is a mixture of 0-25 wt % of REY or high silica Y zeolite and 75-100 wt % of phosphorus and rare earth containing high silica zeolite having a structure of pentasil. The catalyst exhibits higher hydrothermal activity-stability, conversion level, and C2 -C4 olefin yields in cracking reaction, comparing with the catalyst using HZSM-5 zeolite as active component.

Development of an active and stable ceria-supported palladium catalyst for hydrogenation of carbon dioxide to methanol

Abstract: A Pd/CeO2 catalyst reduced by flowing hydrogen at 500° C for 1 h was found to be an excellent catalyst for the hydrogenation of CO2 to methanol. At 230°C and 30 bar, the C02 conversion was 3% while methanol selectivity reached 90% even if the composition of reactant gas was CO2 : H2 = 1:3. The durability of this catalyst was also extremely high. The effect of the reaction temperature, the contact time of the reactants as well as the CO2/H2 ratio on the reaction performance were investigated. The reaction mechanism is discussed.

Catalyst and catalytic conversion therewith

Abstract: A catalyst composition is provided which comprises a large-pore molecular sieve component and an additive catalyst component, said additive catalyst component having been formulated in a special way to provide an improved catalyst and conversion process. An embodiment of the present invention comprises an improved catalytic cracking process to produce high octane gasoline, and increased lower olefins, especially propylene and butylene.

Hydrodesulfurization of dibenzothiophene in a monolithic catalyst reactor

Abstract: The liquid-phase hydrodesulfurization of dibenzothiophene was studied on a Co-Mo/γ-Al 2 O 3 catalyst. The catalyst support was a monolith with a cell density of 200 cells/in. 2 . The flow pattern was segmented gas-liquid flow. The hydrogen pressures were in the range 6-8 MPa, and the temperatures were in the range 543-573K. A kinetic model consistent with the experimental rate data was developed. The rate expressions are of the Langmuir-Hinshelwood type, assuming two different types of active sites: one active in the hydrodesulfurization reaction and the other active in the hydrogenation reaction. The reaction scheme proposed is a parallel-serial one in which dibenzothiophene desulfurizes to cyclohexylbenzene, either directly or via biphenyl which subsequently undergoes ring hydrogenation. A simple power law model is also presented

Supported polymerization catalysts, their production and use

Abstract: This invention is generally directed toward a supposed catalyst system useful for polymerizing olefins. The method for supposing the catalyst of the invention provides for a supposed metallocene catalyst able to produce polymers having broader molecular weight distribution and a higher molecular weight. Not only are such polymers easily processable as compared with metallocene polymers produced with other support methods but the methods of this invention provides for a supposed catalyst with increased activity.

Activated zeolite beta and its use for hydrocarbon conversion

Abstract: The present invention relates to a zeolite beta catalyst characterized by critical limits of weak and strong acid species and exceptionally high catalytic activity. The catalyst is activated at a temperature effective to substantially reduce the concentration of strong acid species, i.e., hydronium cations, without substantially reducing the concentration of weak acid species, i.e., hydroxoaluminum cations, preferably following a calcining step wherein a synthesized zeolite beta catalyst containing a templating agent is calcined at a temperature in the range of from about 200° to 1000° C. in order to remove a substantial portion of the catalyst templating agent and an ion-exchanging step wherein the calcined catalyst is ion-exchanged with a salt solution containing at least one hydrogen forming cation selected from NH4 + and quaternary ammonium. Conversion processes utilizing the catalyst of the invention, including isomerization of paraffins and alkylaromatics and disproportionation of aromatics, also are disclosed.

Polymeric Aluminoxanes: A Possible Cocatalytic Support Material for Ziegler-Natta-Type Metallocene Catalysts

Abstract: The reaction of methylaluminoxane (MAO) with 1,6-hexanediol or 1,10-decanediol leads to white powdery materials which were studied by 13C and 27Al MAS NMR, scanning electron microscopy (SEM), and whose surface area and porosity was determined according to the BET method. The hydrolysis of trimethylaluminum with hydrogel was carried out and the product was investigated by SEM. © 1993 John Wiley & Sons, Inc.

Process and catalyst for partially hydrogenating aromatics to produce cycloolefins.

Abstract: This is a catalyst and a process for partially hydrogenating polycyclic and monocyclic aromatic hydrocarbons such as benzene, naphthalenes, biphenyls, and alkylbenzenes to produce the corresponding cycloolefins. The catalyst is a hydrogenation catalyst comprising ruthenium on a composite support. It is a process in which the product cycloolefin is produced in high yield and with high selectivity.

Fischer-tropsch synthesis: impact of pretreatment of ultrafine iron oxide upon catalyst structure and selectivity

Abstract: The present study has shown that activation of a high surface area Fe2O3 catalyst in CO in a CSTR using tetralin as solvent results in an activity that is three times that of the material that is activated in H2 or directly in the syngas. Independent of the catalyst activation, similar methane and CO2 selectivities are obtained. This suggests that the active catalytic phase is the same for the three pretreatments. Since the particle size estimated by XRD shows a variation within 30%, the difference among the activities of the differently activated catalysts can be attributed to differences in the concentration of active sites on the catalyst surface rather than the extent of the surface.

Chapter 5 Correlation Between Catalyst Formulation and Catalytic Properties

Abstract: Publisher Summary This chapter discusses the correlation between catalyst formulation and catalytic properties. Modern Fluid Catalytic Cracking (FCC) catalysts consist, in general, of two major components: zeolite and matrix. Some catalysts also contain a third component: one or several additives, designed to boost gasoline octane, increase catalyst metal resistance, reduce SO x emissions, or facilitate CO oxidation. The additive can be incorporated into the catalyst particle or be used as a distinct physical particle. The zeolites used in FCC catalysts are mostly synthetic, faujasite type zeolites: Y and high-silica Y zeolites. Regarding the main applications, commercial FCC catalysts can be broadly classified in three categories: (1) gasoline FCC catalysts, (2) octane FCC catalysts, and (3) resid FCC catalysts. All FCC catalysts, regardless of their specific applications, are designed to have the following catalytic properties: activity, selectivity, and stability. Catalytic activity is because of the presence of acidic sites in the catalyst. It is determined by zeolite content and type, by matrix type, and by the zeolite/matrix activity ratio. Catalytic selectivity is determined by several factors: (1) zeolite type, (2) acid site type (Broensted and/or Lewis), strength, concentration and distribution, (3) pore-size distribution in both matrix and zeolite, (4) matrix surface area and activity, (5) additives present, and (6) contaminants present.

Effect of the support on the fischer-tropsch synthesis with co/nb2o5 catalysts

Abstract: Niobia-supported cobalt catalysts reduced at temperatures between 553 and 773 K have been compared with alumina-supported cobalt catalysts. The hydrogen adsorption capacity and the catalytic properties for the CO–H2 reaction were independent of the temperature of reduction of the alumina-supported catalyst. In contrast, the amount of hydrogen chemisorbed and the activity for CO conversion decreased with increasing reduction temperature for the niobia-supported catalyst. The results are interpreted in terms of the strong metal–support interaction (SMSI) effect, established for Co/Nb2O5 after reduction at 673 and 773 K and not fully destroyed during the catalytic reaction. Higher temperatures of reduction of Co/Nb2O5 catalysts results in a better selectivity towards C5+ compounds and a low selectivity towards C1, in the CO–H2 reaction performed at 533 K.