Supported catalysts preparation

P. H. Cuong, B. Christophe, D. Thierry, E. Babrielle, E. Claude, and J. L. Marc, High surface area silicon carbide doped with zirconium for use as catalyst support preparation, characterization and catalytic application, Appl. Catal. A 180, 385—397 (1999). 

Despite the efforts of many research groups due to the high level applicability of this field, many questions remain unanswered, for example, the reaction mechanism, the nature of the active site and so on. One of the main problems to finding answers is the correlation of the results obtained after using such a variety of parameters different catalysts, supports, preparation methods and so on. Therefore, a great deal of research is still required. 

Dry impregnation catalyst support preparation [CATALYSTS - SUPPORTED] (Vol 5)... 

Fig. 1 shows the XRD patterns for the catalyst supports prepared by the citric acid... 

Zhang Y, Y oneyama Y, T subaki N Simultaneous introduction of chemical and spatial effects via a new bimodal catalyst support preparation method, Chem Commun 11 1216—1217, 2002. 

Spatial Effects via a New Bimodal Catalyst Support Preparation Method Chem. Commun. 2002,1216-1217. 

Sodium alumiaate is widely used in the preparation of alumina-based catalysts. Aluminosilicate [1327-36-2] can be prepared by impregnating siHca gel with alumiaa obtained from sodium alumiaate and aluminum sulfate (41,42). Reaction of sodium alumiaate with siHca or siHcates has produced porous crystalline alumiaosiHcates which are useful as adsorbents and catalyst support materials, ie, molecular sieves (qv) (43,44). 

Gibbsite is aii important technical product and world production, predominantly by the Bayer process, is more than 50 million metric tons aimuaHy. Alost (90%) is calcined to alumina [1344-28-1 j, Al202, to be used for aluminum production. Tlie remainder is used by the chemical industry as filler for paper, plastics, rubber, and as the starting material for the preparation of various aluminum compounds, alumina ceramics, refractories, polishing products, catalysts, and catalyst supports. 

Gelatinous boehmite, called alumina gel in commeicial use, is used in the piepaiation of adsorbents, desiccants (qv), catalysts, and catalyst supports (see Catalysts, SUPPORTBd). A significant amount is used in pharmaceutical preparations. 

Nicotinonitrile is produced by ammoxidation of alkylpyridines (11—24). A wide variety of different catalysts have been developed for this appHcation. For example, a recent patent describes a process ia which 3-methylpyridine is reacted over a molybdenum catalyst supported on siHca gel. The catalyst (PV Mo 20 ) was prepared from NH VO, H PO, and (NH Moy024. Reaction at 380°C at a residence time of 2.5 seconds gave 95% of nicotinonitrile at a 99% conversion (16). 

High Density Polyethylene. High density polyethylene (HDPE), 0.94—0.97 g/cm, is a thermoplastic prepared commercially by two catalytic methods. In one, coordination catalysts are prepared from an aluminum alkyl and titanium tetrachloride in heptane. The other method uses metal oxide catalysts supported on a carrier (see Catalysis). 

Transition aluminas are good catalyst supports because they are inexpensive and have good physical properties. They are mechanically stable, stable at relatively high temperatures even under hydrothermal conditions, ie, in the presence of steam, and easily formed in processes such as extmsion into shapes that have good physical strength such as cylinders. Transition aluminas can be prepared with a wide range of surface areas, pore volumes, and pore size distributions. 

The catalysts are prepared by impregnating the support with aqueous salts of molybdenum and the promoter. In acidic solutions, molybdate ions are present largely in the form of heptamers, [Mo2024] , and the resulting surface species are beHeved to be present in islands, perhaps containing only seven Mo ions (100). Before use, the catalyst is treated with H2 and some sulfur-containing compounds, and the surface oxides are converted into the sulfides that are the catalyticaHy active species. 

The performance of a catalyst often depends as much on the care and method of preparation as on the identity of the active components. This fact has been learned by many who have failed to obtain reproducibiUty among catalyst preparations ia the laboratory or have been responsible for quaUty assurance ia catalyst manufacture. Also, there are many examples of strong effects of trace impurities ia raw material or catalyst support on catalyst performance. 

Rapoport s findings have been confirmed in the authors laboratory where the actions of carbon-supported catalysts (5% metal) derived from ruthenium, rhodium, palladium, osmium, iridium, and platinum, on pyridine, have been examined. At atmospheric pressure, at the boiling point of pyridine, and at a pyridine-to-catalyst ratio of 8 1, only palladium was active in bringing about the formation of 2,2 -bipyridine. It w as also found that different preparations of palladium-on-carbon varied widely in efficiency (yield 0.05-0.39 gm of 2,2 -bipyridine per gram of catalyst), but the factors responsible for this variation are not knowm. Palladium-on-alumina was found to be inferior to the carbon-supported preparations and gave only traces of bipyridine,... 

The polymer-supported chiral oxazaborolidinone catalyst 5 prepared from valine was found by Ituno and coworkers to be a practical catalyst of the asymmetric Diels-Alder reaction [7] (Scheme 1.12). Of the several cross-linked polymers with a... 

Materials, such as activated carbons, that are derived from natural products differ greatly in their effectiveness when used as catalyst supports, but it is difficult to delimit the factors present in the carbon that influence performance, Certain broad statements, such as that carbons with excessive sulfur or ash content tend to make inferior catalysts, only begin to touch on the problem. One of the advantages of buying commercial catalysts, instead of using laboratory preparations, is that commercial suppliers have solved this problem already by empirical testing of many carbons. They provide catalysts that are best by test. 

Recently some information became available on a new type of highly active one-component ethylene polymerization catalyst. This catalyst is prepared by supporting organometallic compounds of transition metals containing different types of organic ligands [e.g. benzyl compounds of titanium and zirconium 9a, 132), 7r-allyl compounds of various transition metals 8, 9a, 133), 7r-arene 134, 185) and 71-cyclopentadienyl 9, 136) complexes of chromium]. 

Oxazoborolidinone 8 is an example of catalyst supported on silica gel. It is prepared by immobilizing the N-tosyl-0-allyl-(S)-tyrosine with mercaptopropyl silica and treatment with BF3 and has been used to catalyze the Diels-Alder reaction of methacrolein with cyclopentadiene [17] (Equation 4.2). The cycloaddition occurs with good diastereoselectivity but with low enantioselec-tivity. 

The preparation of novel triazole-containing 20-22 membered macrocyclic azacrown ether-thioethers was reported <96JCR(S)182> and the first selective synthetic method fra the synthesis of dicyanotriazolehemiporhyrazines was published <96JOC6446>. 1,2,4-Triazole-containing polyimide beads were prepared and employed as Mo(VI) epoxidation catalyst supports, liie 1,2,4-nitronyl nitroxide 29 was also synthesized and found to have remarkable magnetic properties <96AM60>. 

A silica-supported catalyst was prepared by anaerobic impregnation of Mo2Rh(/a-CO)(CO)4((7 -C,H,s),i (Fig. 70) from CHiCF solution, followed by evacuation at room temperature. Decomposition processes were observed at the... 

A catalyst supported on y-AFO was prepared from Re2Pt(CO)i2l (Fig. 70) and characterized by IR. X-ray photoelectron spectroscopy (XPS), and TPR. The chemi.sorbed cluster was treated with H2 at about 150 C resulting in fragmentation and formation of rhenium subcarbonyls at 400 C the sample was completely decarbonylated. A catalyst prepared from a mixture of Re3(//-H)3(CO)i2l and PtMe2(// -cod)] and treated under equivalent conditions showed the rhenium to... 

The preparation method of titania support was described in the previous paper [6]. Titanium tetraisopropoxide (TTIP 97%, Aldrich) was used as a precursor of titania. Supported V0x/Ti02 catalysts were prepared by two different methods. The precipitation-deposition catalysts (P-V0x/Ti02) were prepared following the method described by Van Dillen et al. [7], in which the thermal decomposition of urea was used to raise homogeneously the pH of a... 

Preparation, characterization, and catalytic activity of H3PW12O40 heteropolyacid catalyst supported on mesoporous Y-AI2O3... 

A 5 wt.% CoOx/Ti02 catalyst was prepared via an incipient wetness technique in which an aqueous solution of Co(N03)2 6H20 (Aldrich, 99.999%) was impregnated onto a shaped Ti02 (Milleimium Chemicals, commercially designated as DT51D, 30/40 mesh), as described in detail elsewhere [6]. Other supported metal oxide catalysts, such as FeOx, CuO, and NiOx, were obtained in a fashion similar to that used for preparing the CoO, catalyst. 

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