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Showing papers on "Catalyst support published in 1991"


Journal ArticleDOI
TL;DR: In this article, the molecular structures of the two-dimensional vanadium oxide overlayers on different oxide supports (MgO, Al 2 O 3, ZrO 2, TiO 2 and SiO 2 ) were determined with Raman spectroscopy under ambient conditions.
Abstract: The molecular structures of the two-dimensional vanadium oxide overlayers on different oxide supports (MgO, Al 2 O 3 , ZrO 2 , TiO 2 and SiO 2 ) were determined with Raman spectroscopy under ambient conditions. The surface vanadium oxide molecular structures were found to depend on the net pH at which the surface possesses zero surface charge (point of zero charge, pzc). The net surface pH at pzc is determined by the specific oxide support and the surface coverage of the acidic vanadium oxide overlayer

319 citations


Journal ArticleDOI
B. K. Cho1
TL;DR: In this paper, a commercial ceria powder was chemically modified by doping with gadolinia in order to improve its oxygen storage/transport characteristics, and the catalytic activity of rh impregnated on this modified ceria support was measured and compared with those applied on conventional ceria or alumina support, using a packed-bed reactor and an isotopic reactant (13CO) for the NO + CO reaction under both cycled and steady-feed conditions.

146 citations


Journal ArticleDOI
TL;DR: In this paper, the authors consider the effect of sulfur compounds present in the exhaust on the performance of automotive catalysts and optimize the composition of the three-way catalysts to take into account the effect.

145 citations


Journal ArticleDOI
TL;DR: In this paper, the role of the catalytic material for high-temperature catalytic combustion was discussed and the new concepts of the material design and the preparation technique for combustion catalysts were reviewed.

141 citations


Journal ArticleDOI
TL;DR: The role of Ru in the Ni-based composite catalyst was elucidated as the portholes of hydrogen spillover for the active sites in Ni part in this paper, and the performance of methanol synthesis catalyst was markedly improved by modification with Pd or Ag as anticipated an effect of spillover.

136 citations


Patent
13 Mar 1991
TL;DR: In this paper, an improved method of presulfiding a hydrotreating or hydrocracking catalyst which minimizes sulfur stripping upon start-up of a HPC reactor utilizing such a catalyst is presented.
Abstract: An improved method of presulfiding a hydrotreating or hydrocracking catalyst which minimizes sulfur stripping upon start-up of a hydrotreating or hydrocracking reactor utilizing such a catalyst. The method comprises the steps of contacting a hydrotreating or hydrocracking catalyst with elemental sulfur at a temperature below the melting point of sulfur, thereby forming a sulfur-catalyst mixture, and heating the sulfur-catalyst mixture to a temperature above the melting point of sulfur. Preferably, the sulfur-catalyst mixture is first mixed with at least one member selected from the group consisting of high boiling oils and hydrocarbon solvents to form a prewet mixture prior to heating at a temperature above the melting point of sulfur. Tail gas treating catalysts are also presulfided by these methods.

133 citations


Journal ArticleDOI
TL;DR: 2,6-Diisopropylnaphthalene is selectively produced in the liquid phase alkylation of naphalene with propene or propan-2-ol over H-mordenite catalyst as mentioned in this paper.
Abstract: 2,6-Diisopropylnaphthalene is selectively produced in the liquid phase alkylation of naphthalene with propene or propan-2-ol over H-mordenite catalyst.

90 citations


Journal ArticleDOI
TL;DR: In this paper, carbon molecular sieves (CMS) are shown to be very effective catalysts and catalyst supports for the oxidative dehydrogenation and dehydration of a variety of substrates.
Abstract: Ultrahigh surface area (>2500 m 2 /g) carbon molecular sieves (CMS's) are shown to be very effective catalysts and catalyst supports for the oxidative dehydrogenation and dehydration of a variety of substrates Studies of methanol, ethanol, 1- and 2-propanol, and propanal provide insight concerning the reactivity of these materials The activities are superior to many inorganic oxide based systems As catalysts, CMS systems are shown to have the ability to function via hydride or hydrogen atom abstraction mechanisms, depending on the nature of the substrate As catalyst support, a synergism is demonstrated between the CMS support and metal dopants, which enables the system to have greater activity than that of either of the constituents alone

88 citations


Journal ArticleDOI
TL;DR: In this paper, a tubular-supported ceramic membrane is developed for transport-controlled, volatile-reactant-limited reactions, and the results demonstrate that the main benefit is the more efficient supply of the volatile reactant.
Abstract: A new type of multiphase catalyst is developed for transport-controlled, volatile-reactant-limited reactions: the tubular-supported ceramic membrane. A microporous, catalytically-impregnated γ-Al2O3 film (permeable membrane) coats the inside wall of a hollow, macroporous α-Al2O3 tube. The gas containing the volatile reactant flows through the tube core, and the liquid containing the nonvolatile and dissolved volatile reactants flows on the shell side. Reaction occurs in the film. Results using the hydrogenation of α-methylstyrene to cumene on Pd/Al2O3 reveal that the tubular catalyst compares favorably to conventional catalyst designs. The results demonstrate that the main benefit is the more efficient supply of the volatile reactant. Apparent activation energy analyses reveal that for catalyst temperatures below 40° C, the rate is kinetically-controlled and catalyst utilization nearly complete. A reduction in the activation energy above 45°C indicates the onset of transport limitations or heat effects. A comparison between the tubular catalyst and a fully-wetted pellet reveals rate increases by up to a factor of 20.

74 citations


Patent
Main Chang1
18 Oct 1991
TL;DR: In this paper, the use of silica gel containing from about 10 to about 50% by weight adsorbed water as the catalyst support material was proposed for liquid phase polymerization of olefins.
Abstract: This invention relates to a process for polymerizing olefin using a supported metallocene alumoxane catalyst, which can be used in slurry or liquid phase polymerization of olefins. The invention relates to the use of silica gel containing from about 10 to about 50% by weight adsorbed water as the catalyst support material. It has been found that such silica gel may be safely added to an aluminum trialkyl solution to form by direct reaction with the adsorbed water content of the silica gel catalyst support material the alumoxane component of the catalyst system. An alumoxane coated silica gel was formed to which a metallocene may be added. The resulting material can either be used in this slurry state for slurry polymerization or can be used for liquid phase polymerization.

73 citations


Patent
09 Aug 1991
TL;DR: In this paper, the authors proposed a supported catalysts containing nickel, magnesium oxide and, if desired, further additives, which contain reduced Mg and Ni in a molar ratio of (0.0075 to 0.075):1.
Abstract: Supported catalysts containing nickel, magnesium oxide and, if desired, further additives, which contain reduced Mg and Ni in a molar ratio of (0.0075 to 0.075):1. The catalyst also have an active nickel metal surface area of 110 to 180 m2 /g of Ni, and a BET total surface area of 160 to 450 m2 /g. The invention furthermore relates to a process for the preparation of the catalysts and to their use as catalysts for the hydrogenation of aliphatic and/or aromatic hydrocarbons.

Patent
05 Nov 1991
TL;DR: In this article, a high-silica zeolite having a Si/Al ratio of 40 or more has been subjected to ion exchange with at least one metal selected from Pt, Pd, Rh, Ir and Ru.
Abstract: A catalyst composition for purification of exhaust gas, comprises (a) high-silica zeolite having a Si/Al ratio of 40 or more which has been subjected to ion exchange with at least one metal selected from Pt, Pd, Rh, Ir and Ru, and (b) a heat-resistant oxide containing at least one metal selected from Pt, Pd, Rh, Ir and Ru. The catalyst composition is supported on a monolith carrier as a single layer or with the two components (a) and (b) as separate layers. The catalyst has high activity for exhaust gas purification even when it contains Rh, which is an expensive catalyst component, in a very small amount.

Patent
Joseph C. Dettling1
04 Nov 1991
TL;DR: In this paper, a method of treating internal combustion engine exhaust gases with the catalyst composition is also disclosed, which includes a carrier on which is disposed a catalytic material which may optionally be provided in discrete first and second coats.
Abstract: A catalyst composition includes a carrier on which is disposed a catalytic material which may optionally be provided in discrete first and second coats. The catalyst material contains, e.g., in the first coat, a refractory inorganic oxide first support having a catalytically effective amount of platinum dispersed thereon. The catalyst material also contains, e.g., in the second coat, a stabilized alumina second support having a catalytically effective amount of a second platinum catalyst dispersed thereon, and a third catalyst component which contains a zirconia-stabilized third support, e.g., alumina, having dispersed thereon catalytically effective amounts of rhodium and palladium. A method of treating internal combustion engine exhaust gases with the catalyst composition is also disclosed.

Journal ArticleDOI
TL;DR: In this article, a linear relation between the electronegativity of the metal ion and the stretching vibration of surface hydroxyl groups is proposed for Al, Si, P, and B tetrahedral surface ions.

Patent
11 Oct 1991
TL;DR: In this article, a method for treating engine exhaust gases by contacting the gases under conversion conditions with the catalyst composition is presented, where the catalytic material may be disposed as a catalytic coating directly on the carrier or upon an optional undercoat which is disposed on a carrier and which includes alumina and optionally, ceria and/or, iron oxide.
Abstract: A catalyst composition suitable for three-way conversion of internal combustion engine, e.g., automobile gasoline engine, exhaust gases includes a catalytic material disposed in on a carrier. The catalytic material contains a co-formed (e.g., co-precipitated) rare earth oxide-zirconia support on which a first rhodium catalytic component is dispersed, and an alumina support having a platinum catalytic component dispersed thereon. The catalytic material may also include a second rhodium catalytic component dispersed on the alumina support bearing the platinum or a second alumina support. The catalytic material may be disposed as a catalytic coating directly on the carrier or upon an optional undercoat which is disposed on the carrier and which includes alumina and optionally, ceria and/or, iron oxide. One or more of a metal oxide which is effective for the suppression of hydrogen sulfide emissions (such as bulk nickel oxide), thermal stabilizers such as alkaline earth oxides, rare earth oxides and zirconia may be dispersed throughout the catalytic coat and/or the undercoat. The present invention also provides a method for treating engine exhaust gases by contacting the gases under conversion conditions with the catalyst composition.

Journal ArticleDOI
TL;DR: In this article, an active catalyst for carbon dioxide hydrogenation is obtained by exposing an amorphous Au25Zr75 alloy to CO2 hydrogenation conditions, and the structural and chemical changes are characterized by gas adsorption, X-ray diffraction and thermal analysis.
Abstract: An active catalyst for carbon dioxide hydrogenation is obtained by exposing an amorphous Au25Zr75 alloy to CO2 hydrogenation conditions. During this in situ activation, metallic gold particles of 8.5 nm mean size are formed, and the zirconium component of the catalyst is oxidized to ZrO2. For comparison, a further Au/ZrO2 catalyst was synthesized by coprecipitation, followed by calcination of the amorphous precipitate. The calcination step strongly enhances the activity of the catalyst; gold segregation and zirconia crystallization are found to occur in this process. The structural and chemical changes are characterized by gas adsorption, X-ray diffraction and thermal analysis.The main products of CO2 hydrogenation over these catalysts, as identified by gas chromatography, are methanol and CO. To investigate the reaction mechanism, diffuse reflectance FTIR spectroscopy has been used. Observed surface species are correlated with the formation of gas-phase products. Adsorption of CO2–H2 results in rapid formation of formate as the primary surface intermediate; two types of formate species are clearly detected on the coprecipitated catalyst, and are assigned by means of formic acid adsorption experiments. CO formation from CO2 appears to proceed via surface carbonate, in a surface reaction that corresponds to a ‘basic variant’ of the reverse water-gas-shift reaction. The CO formed in this process is, in turn, the starting point for a series of surface hydrogenation steps that yield π-bonded formaldehyde, surface-bound methylate and finally methanol. This sequence of reactions is confirmed by separate CO–H2 adsorption experiments.

Book ChapterDOI
TL;DR: In this article, the deactivation of noble metal catalyzed liquid phase oxidation of alcohols and related compounds was studied for ten different catalyst systems, using two different substrates, including poly-alumazane, which was prepared by subsequent treatment of silanol rich silica with aluminum trichloride and ammonia.
Abstract: Summary During noble metal catalyzed liquid phase oxidation of alcohols and related compounds, catalyst poisoning by oxygen often occurs. This catalyst deactivation was studied for ten different catalyst systems, using two different substrates. In the oxidation of 5-hydroxy-methylfurfural (HMF) -a versatile intermediate obtainable from carbohydrates- the noble metal catalyst surface was protected by the strongly adsorbing substrate, thus preventing poisoning by oxygen. In the oxidation of methanol, the various noble metal catalysts display four types of oxygen tolerance, depending on the choice of metal and dispersion. Several supports were studied, including so-called poly-alumazane, which is prepared by subsequent treatment of silanol rich silica with aluminum trichloride and ammonia. With the resulting support palladium catalysts with very high dispersion were obtained.

Patent
27 Sep 1991
TL;DR: In this paper, the ozone deodorizing catalyst is used as an ozone decomposing catalyst for catalytically decomposing to eliminate ozone contained in a gas, or as a deodorizer for decomposing offensive odor ingredients.
Abstract: The catalyst according to the present invention can be utilized effectively as an ozone decomposing catalyst for catalytically decomposing to eliminate ozone contained in a gas or as an ozone deodorizing catalyst for decomposing offensive odor ingredients contained in a gas by catalytic oxidation under the presence of ozone, and it comprises a composition containing Mn oxide, metal Pd and/or Pd compound as the essential ingredients formed as a thin film on a support. Further, the performance of the catalyst can be improved by using Mn oxide and Pd as the essential ingredient and using an alumina sol as a binder upon preparation.

Journal ArticleDOI
TL;DR: In this article, a steady-state plug-flow reactor was used to investigate the effect of support material and catalyst loading on the catalytic activity of the catalysts supported over both anatase and rutile phases.

Patent
16 Jan 1991
TL;DR: In this article, the authors describe a process and an apparatus for preparing a heterogeneous catalyst having at least one catalytically active species bound to the surface of a support material.
Abstract: The invention relates to a process and to an apparatus for preparing a heterogeneous catalyst having at least one catalytically active species bound to the surface of a support material. According to the process, the surface of the support (6) is first pretreated. A catalyst reagent containing the catalytically active species or its precursor is vaporised and the vapour is routed into a reaction chamber (6) where it is brought to interact with the support material. The catalyst reagent not bound to the support is withdrawn from the reaction chamber (4) in gaseous form. If necessary, the species bound to the support is post-treatead in order to convert it into a catalytically active form. According to the invention, the amount of catalyst reagent brought into the reaction chamber is at least equal to, preferably in excess of the number of available binding sites on the surface (6). The temperature of the support is kept higher than the condensation temperature of the vapour and at the same time at a sufficiently high level to attain the thermal activation energy needed for forming bonds between the active species and the support. By binding the catalytically active species in this way to the support, it is possible to provide a heterogeneous catalyst having a high activity even at small amounts of the active species.

Journal ArticleDOI
TL;DR: In this article, carbon-supported molybdenum HDS catalysts were investigated using X-ray photoelectron spectroscopy and temperature-programmed desorption, Xray diffraction, titrations and electrophoresis.

Journal ArticleDOI
TL;DR: In this paper, the stability of supported Re2O7 metathesis catalysts was investigated in a micro catalytic flow reactor and it was shown that using a guard bed with tetraethyltin can significantly improve the stability.

Journal ArticleDOI
TL;DR: In this paper, the propene metathesis reaction was studied from the point of view of elucidating the mechanism of catalyst induction and establishing conditions for maximum activity, using ESR, IR, and TPD.

Patent
12 Dec 1991
TL;DR: A catalyst for purifying an exhaust gas to remove nitrogen oxides, carbon monoxide and hydrocarbons from an oxygen-rich exhaust gas is defined in this paper, where a zeolite having an SiO2/Al2O3 mole ratio of at least 15 is used.
Abstract: A catalyst for purifying an exhaust gas to remove nitrogen oxides, carbon monoxide and hydrocarbons from an oxygen-rich exhaust gas containing nitrogen oxides, carbon monoxide and hydrocarbons comprising (i) a zeolite having an SiO2/Al2O3 mole ratio of at least 15 and (ii) (a) cobalt, (b) a rare earth metal and (c) silver, or nickel and/or zinc, or platinum and/or manganese, or copper and/or rhodium, incorporated thereinto.

Journal ArticleDOI
TL;DR: In this article, the authors examined the selective hydrogenation of propyne over copper powder and various supported copper catalysts in a dynamic flow system and found that the exact pattern of activity and selectivity depend upon the particular supported copper system.

Journal ArticleDOI
TL;DR: In this paper, the structure and activity of A1203, TiO2, Al2O3 TiO 2 and Al3+ readsorption supported Pt-Ir bimetal catalysts were studied by two characterization techniques: temperature-programmed reduction/temperatureprogrammed desorption (TPRd/TPD) and ethane hydrogenolysis.

Patent
12 Apr 1991
TL;DR: In this paper, a prepolymerized olefin containing a pre-processed pre-titanium catalyst component was used to obtain a polyolefin with high stereospecificity.
Abstract: This invention provides a solid titanium catalyst component [Ia] containing magnesium, halogen, titanium and a compound having at least two ether linkages with a plurality of intermediately existing bonding atoms; a catalyst and a prepolymerized olefin-containing catalyst prepared by using the solid titanium catalyst component [Ia]; a method for preparing a polyolefin wherein said catalyst or prepolymerized olefin containing catalyst is used. A catalyst and a prepolymerized olefin containing catalyst prepared by using a solid titanium catalyst component [Ib] containing magnesium, halogen, titanium and a specific electron donor (a1), and a compound having at least two ether linkages with a plurality of intermediately existing bonding atoms; a method for preparing a polyolefin wherein said catalyst or prepolymerized olefin containing catalyst is used. By virtue of the use of the catalysts or the prepolymerized olefin-containing catalysts, the polymerization reaction efficiently proceeds with high catalytic activity, giving polymers high in stereospecificity.

Journal ArticleDOI
TL;DR: In this article, the acidity of the catalysts has been determined by the amine titration method and the catalytic activity of these catalysts towards the conversion of ethanol and isopropanol was determined at different temperatures.

Patent
24 Oct 1991
TL;DR: In this paper, a method for water treatment by using the use of a water-soluble catalyst is described. But the method is not suitable for the treatment of large amounts of water.
Abstract: This invention relates to a catalyst for use in water treatment and to a method for the water treatment by the use of the catalyst. The catalyst comprises a first catalyst component e.g. the oxide of titanium, silicon, aluminum and zirconium, and a second catalyst component e.g. manganese, iron, cobalt, nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium, and iridium or a sparingly water-soluble compound of the metal.