Showing papers on "Catalyst support published in 1999"

Comparative study of Fischer–Tropsch synthesis with H2/CO and H2/CO2 syngas using Fe- and Co-based catalysts

Abstract: Hydrogenation of CO, CO2 and their mixtures has been comparatively studied with a Co–MnO–Aerosil–Pt and a Fe–Al2O3–Cu–K catalyst at the University of Karlsruhe. With iron catalysts as promising for CO2 hydrogenation, their composition was varied: (1) several supports (SiO2, TiO2, Al2O3), (2) alkali promotion (Li, Na, K, Rb), (3) usage of Zeolite Y as catalyst component. The catalysts were characterised by adsorption methods, XRD, TPR and temperature programmed decarburisation after a H2/CO2 treatment (Korea Research Institute of Chemical Technology). Iron and cobalt catalysts behaved differently in CO2 hydrogenation. With the alkalised iron catalyst the same hydrocarbon product composition was obtained from a H2/CO2 and from a H2/CO synthesis gas in spite of the CO partial pressure remaining low, specifically due to water gas shift equilibrium constraints. With the cobalt catalyst at increasing CO2 and respectively decreasing CO content of the syngas, the product composition shifted from a Fischer–Tropsch type (mainly higher hydrocarbons) to almost exclusively methane. These basically different catalyst behaviours are explained by different modes of formation of the kinetic regime of FT synthesis—selective inhibition of methane formation and the selective inhibition of product desorption as a prerequisite for chain growth—in the case of iron through irreversible carbiding and alkali surface coverage and in case of cobalt through strong reversible CO adsorption. Investigation of the various modified iron catalysts showed alumina to be the best support for CO2 hydrogenation and potassium to act as a powerful promotor. With the Fe–Y–zeolite–alkali catalysts, a decrease of methane selectivity was observed in the order Li < Na < K < Rb being applied as promotors.

Preparation of Solid Catalysts

Abstract: Developing Industrial Catalysts. Bulk Catalysts and Supports. Supported Catalysts. Zeolites and Related Molecular Sieves. Solid Superacids. Catalyst Forming. Computer-Aided Catalyst Design.

Direct Epoxidation of Propene Using Gold Dispersed on TS-1 and Other Titanium-Containing Supports

Abstract: Highly dispersed gold catalysts on a titanium-containing support are promising catalysts for the low-temperature direct epoxidation of propene. Gold dispersed on TS-1 and other titanium-based support materials has been used to selectively (>99%) epoxidize propene using a hydrogen−oxygen mixture. The propene conversion, however, remains low (<2%). The mode of operation of these catalysts, which is based on the close cooperation between the gold and the support material, is discussed and some mechanistic models are postulated. An investigation has been made into the cause of the relatively low catalyst activity, the efficiency of the catalyst toward the use of hydrogen, and the deactivation of the catalyst. The most important cause for the low propene oxide yields is explained by a strong adsorption of propene oxide on the catalyst.

Study of the effect of water on alumina supported cobalt Fischer–Tropsch catalysts

Abstract: The effect of water on Co/Al 2 O 3 and CoRe/Al 2 O 3 catalysts has been studied by adding water to the synthesis gas feed and by model studies exposing the catalysts to H 2 O/H 2 feeds using several characterization techniques such as TPR, gravimetry, XPS, TPD and pulse adsorption. It was found that the CoRe/Al 2 O 3 catalyst deactivates when water is added during Fischer–Tropsch synthesis and model-studies showed that this catalyst oxidizes in H 2 O/H 2 mixtures with a ratio much lower than expected for oxidation of bulk cobalt. The reoxidation increases with increasing H 2 O partial pressure and H 2 O/H 2 ratio. TPR and gravimetry showed only small amounts of bulk reoxidation, while pulse adsorption and TPD indicated large decreases in Co-surface metal. It is suggested that oxidation of highly dispersed phases or surface oxidation are the cause for the observed deactivation. Significant differences in behavior of the Co/Al 2 O 3 and the CoRe/Al 2 O 3 catalyst when exposed to H 2 O/H 2 /He were found by gravimetry, TPR, pulse adsorption and XPS. The CoRe/Al 2 O 3 catalyst was reoxidized more easily in H 2 O/H 2 /He mixtures than the Co/Al 2 O 3 catalyst. This is probably a result of the higher dispersion of the CoRe/Al 2 O 3 catalyst, but a direct influence of Re on the reoxidation cannot be excluded. A phase interacting strongly with the alumina support was found in both catalysts after H 2 O/He exposure, but also another oxide phase was formed. This second phase is reduced at lower temperature for the CoRe/Al 2 O 3 catalyst than for the Co/Al 2 O 3 catalyst.

A Comprehensive Study on Carbon Dioxide Reforming of Methane over Ni/γ-Al2O3 Catalysts

Abstract: Carbon dioxide reforming of methane into syngas over Ni/gamma-Al2O3 catalysts was systematically studied. Effects of reaction parameters on catalytic activity and carbon deposition over Ni/gamma-Al2O3 catalysts were investigated. It is found that reduced NiA1204, metal nickel, and active species of carbon deposited were the active sites for this reaction. Carbon deposition on Ni/gamma Al2O3 varied depending on the nickel loading and reaction temperature and is the major cause of catalyst deactivation. Higher nickel loading produced more coke on the catalysts, resulting in rapid deactivation and plugging of the reactor. At 5 wt % Ni/gamma-Al2O3 catalyst exhibited high activity and much lesser magnitude of deactivation in 140 h. Characterization of carbon deposits on the catalyst surface revealed that there are two kinds of carbon species (oxidized and -C-C-) formed during the reaction and they showed different reactivities toward hydrogenation and oxidation. Kinetic studies showed that the activation energy for CO production in this reaction amounted to 80 kJ/mol and the rate of CO production could be described by a Langmuir-Hinshelwood model.

Monolith coating apparatus and method therefor

Abstract: Apparatus for coating a support such as a monolithic catalyst support (5) comprises a dispenser (1) for dispensing a predetermined quantity of coating liquid, a containment (2) for the liquid and a source of vacuum (8, 9) which can be actuated to draw the entire quantity of coating liquid into the support (5). The apparatus and method are particularly useful for coating car catalysts without wastage and with increased design options.

Preparation of Platinum Colloids on Polystyrene Nanospheres and Their Catalytic Properties in Hydrogenation

Abstract: Well-dispersed platinum colloids have been prepared on polystyrene nanospheres with surface-grafted poly(N-isopropylacrylamide) (PNIPAAm) via the reduction of PtCl62- by ethanol. A range of monodisperse nanospheres was obtained by emulsifier-free dispersion copolymerization of styrene with a PNIPAAm macromonomer. The surface compositions of the polystyrene nanospheres before and after immobilization of Pt colloids have been investigated by X-ray photoelectron spectroscopy. Peak fitting of the C 1s core-line spectra provides evidence for the presence of PNIPAAm chains at the surface of polystyrene nanospheres. These immobilized Pt colloids were found to be active and stable heterogeneous catalysts for the hydrogenation of allyl alcohol in water. Both the particle size and activity of platinum colloids showed a marked dependence on the level of surface PNIPAAm. The average diameter of an immobilized Pt colloid is 15.0 A and largely unchanged after seven cycles in hydrogenation, as confirmed by TEM. The immo...

Immobilization of the Copper Catalyst in Atom Transfer Radical Polymerization

Abstract: Immobilization of the catalyst system for atom transfer radical polymerization (ATRP) on various silica and cross-linked polystyrene supports was studied. The catalyst system comprises a copper halide, complexed by various amines. The effect of size of support particles, the amount of immobilized catalyst, and the addition of Cu(II) species as deactivator in the polymerization were investigated. In all cases, polymerization occurred, but generally the reactions were not as well controlled in terms of molecular weight and polydispersities as homogeneous systems. The molecular weights did not match the predicted values, and polydispersities were high (1.5 < Mw/Mn < 10). However, control was improved by either an increase in catalyst concentration or the addition of deactivator still bound to support to the system. Potential reasons for the reduced control could be the low mobility of the supported catalyst and/or the steric hindrance and incompatibilities between the immobilized catalyst and the polymer cha...

Catalyst composition and methods for its preparation and use in a polymerization process

Abstract: The present invention relates to a catalyst composition and a method for making the catalyst composition of a polymerization catalyst and a carboxylate metal salt. The invention is also directed to the use of the catalyst composition in the polymerization of olefin(s). In particular, the polymerization catalyst system is supported on a carrier. More particularly, the polymerization catalyst comprises a bulky ligand metallocene-type catalyst system.

Process for the manufacture of cycloalkyldimethanol

Abstract: A process for making cycloalkyldimethanol, includes hydrogenating at least one cycloalkyldicarboxylic acid and/or an alkyl ester thereof with a catalyst, to produce a cycloalkyldimethanol, where the catalyst contains ruthenium, tin and platinum. Also, a method for regenerating a used catalyst, includes contacting the used catalyst with a base, where the catalyst includes ruthenium, tin and platinum.

Catalyst for purifying exhaust gas

Abstract: PROBLEM TO BE SOLVED: To prevent the deterioration of the durability and exhaust gas purifying capacity of a catalyst for purifying exhaust gas by restraining that an absorbent added to a catalyst layer penetrates into a catalyst support and the absorbent vaporizes and scatters from the catalyst. SOLUTION: A zeolite, silica or titania layer 50 is formed between the catalyst layer 30 to which the absorbent is added and the catalyst support 10. The movement of the absorbent from the layer 30 to the support 10 is restrained by the layer 50 even when the catalyst is used over a long time at high temperature.

Gas-phase nucleation and growth of single-wall carbon nanotubes from high pressure co

Abstract: The present invention discloses the process of supplying high pressure (e.g., 30 atmospheres) CO that has been preheated (e.g., to about 1000 °C) and a catalyst precursor gas (e.g., Fe(CO)5) in CO that is kept below the catalyst precursor decomposition temperature to a mixing zone. In this mixing zone, the catalyst precursor is rapidly heated to a temperature that results in (1) precursor decomposition, (2) formation of active catalyst metal atom clusters of the appropriate size, and (3) favorable growth of SWNTs on the catalyst clusters. Preferably a catalyst cluster nucleation agency is employed to enable rapid reaction of the catalyst precursor gas to form many small, active catalyst particles instead of a few large, inactive ones. Such nucleation agencies can include auxiliary metal precursors that cluster more rapidly than the primary catalyst, or through provision of additional energy inputs (e.g., from a pulsed or CW laser) directed precisely at the region where cluster formation is desired. Under these conditions SWNTs nucleate and grow according to the Boudouard reaction. The SWNTs thus formed may be recovered directly or passed through a growth and annealing zone maintained at an elevated temperature (e.g., 1000 °C) in which tubes may continue to grow and coalesce into ropes.

Characterization of slurry phase iron catalysts for Fischer-Tropsch synthesis

Abstract: The study of Iron Fischer–Tropsch catalysts by conventional powder X-ray diffraction (XRD) is complicated by the number and type of phases present (α-Fe, various iron carbides, Fe x C: 2 3 O 4 ). Peak overlap in the diffraction patterns and differences in the X-ray scattering ability of each phase can make quantitation difficult. This has led to the consensus that activity for Fischer–Tropsch (F–T) synthesis does not correlate with the bulk composition of the iron catalyst, as seen by X-ray diffraction. As we demonstrate in this paper, some of the problems with sample analysis arise from the difficulty in preserving microstructures and composition intact, as the sample is removed from the reactor and prepared for analysis. Our results indicate that Soxhlet extraction, a commonly used procedure to remove the wax from a catalyst, can cause changes in catalyst phase composition. We present a study of a slurry-phase iron F–T synthesis catalyst, where samples have been removed under inert atmosphere and care was taken to preserve the catalyst constituents intact. Quantitative Rietveld structural refinement, combined with step-scanned X-ray diffraction data, allows us to determine changes in composition and morphology in the working catalyst. We conclude that, in its most active form, this Fe catalyst contains the Fe 7 C 3 carbide with small amounts of alpha-iron (α-Fe), while the χ-carbide (hereafter designated as Fe 5 C 2 ), also present in differing amounts during each run, appears to be less active. Major changes in carbide particle size also occur during the course of the F–T synthesis run. The active catalyst contains a significant amount of highly dispersed carbide particles.

A novel carbon-supported vanadium oxide catalyst for NO reduction with NH3 at low temperatures

Abstract: A novel activated carbon-supported vanadium oxide catalyst was studied for SCR of NO with NH 3 at low temperatures (100 – 250°C). The effects of reaction temperature, preparation conditions and SO 2 on SCR activity were evaluated. The results show that this catalyst has a high catalytic activity for NO–NH 3 –O 2 reaction at low temperatures. Preoxidation of the calcined catalyst helps improve catalytic activity. V 2 O 5 loading, other than calcination temperature, gives a significant influence on the activity. SO 2 in the flue gas does not de-activate the catalyst but improves it. A stability test of more than 260 h shows that the catalyst is highly active and stable in the presence of SO 2 .

Molten salts as promising catalysts for oxidation of diesel soot: importance of experimental conditions in testing procedures

Abstract: The catalytic activity for soot oxidation of three eutectic salt mixtures based on oxides or sulphates of molybdenum, vanadium, and cesium, was studied and compared with the activity of catalysts reported in literature. It is shown that some of these mixtures have a high activity above their melting point of about 625 K. The activity of these catalysts can be up to five times higher than the activity of chemically related solid oxide catalysts and this activity is observed throughout the complete conversion trajectory of the soot. The high activity is explained by the better contact between soot and catalyst, which is probably mainly achieved by wetting of the soot by the liquid catalyst, and not via the vapour phase. The eutectic catalysts studied do not evaporate at high temperature. Furthermore, MoO3 and KCl–KVO3 were studied, two catalysts reported in literature to be significantly active. It was found that the high activity of MoO3 is a result of vapour phase mobility. Catalyst selection procedures were evaluated. Thermobalance equipment should be used with caution for the selection of soot oxidation catalysts, because catalytic activities can be overestimated. A low heating rate, preferably 1 K/min or lower, is recommended for temperature programmed oxidation experiments with these types of catalyst. With higher heating rates, promising catalysts can be overlooked.

Influence of the preparation conditions on the synthesis of high surface area SiC for use as a heterogeneous catalyst support

Abstract: The influence of different parameters (temperature, duration and SiO source) on the synthesis of silicon carbide SiC according to the gas-solid reaction between SiO vapors and activated charcoal was investigated. The material obtained retained the general shape of the activated charcoal, which is an advantage because of the difficulty in post shaping SiC, due to the high strength of the material. High temperature (>1250 °C) and long reaction duration led to a high C* → SiC conversion but with a relatively low surface area (20–25 m2 · g−1) due to sintering via the surface diffusion phenomenon. The combination of a lower reaction temperature (1200 °C), longer reaction duration (15 h) and high (Si + SiO2)/C* weight ratio allowed SiC to be obtained with a surface area of around 50 m2 · g−1, which can be used as a support material for heterogeneous catalysis.