Platinum oxide-supported metal catalysts

O2 adsorption, 28 38 surface modility, 28 34 surface structure, 28 30, 31 oxidation of CO on, 28 65 oxide-supported metal catalysts, 41 10, 11 -phosphine catalysts achiral, 25 83-85 recovery, 32 354-356, 367-369 selectivity, 30 348 platinum, 30 355 -silica catalysts... 

One of the major reasons why this reaction is not more widely used is that the catalyst is usually deactivated before the oxidation is completed. This deactivation is thought to be caused by either the oxidation of the metal or the blocking of the metal surface by the strong adsorption of reaction by-products. A number of procedures have been employed to minimize this deactivation. Most of the early work in this area used a large amount of platinum, prepared by the hydrogenation of platinum oxide (Adam s catalyst), as the catalyst.52 These larger metal particles are more resistant to oxidation than the smaller particles present on supported platinum catalysts.63 In addition, the large quantity of catalyst ensures that some active species will still be available toward the end of the reaction. 

Galwey AK, Bettany DG, Mortimer M (2006) Kinetic compensation effects observed during oxidation of carbon monoxide on y-alumina supported palladium, platinum, and rhodium metal catalysts toward a mechanistic explanation. Int J Chem Kin 38 689... 

Liquid-phase oxidations of alcohols in the presence of supported metal catalysts are potentially very attractive reactions for the preparation of intermediates and fine chemieals because high selectivities can be obtained with environmentally clean processes. Indeed, they proceed under mild conditions, with molecular oxygen as oxidizing agent and water as solvent. Supported catalysts, based mainly on platinum-group metals, are resistant to leaching, are recyclable, and are readily available from catalyst manufacturers in various compositions and forms. 

T Hattori, R L Burwell, Jr., Role of carbonaceous deposits in the hydrogenation of hydrocarbons on platinum catalysts. Journal ofPhysical Chemistry 83 241-249, 1979. C A. Querini, S C Fung, Temperature programmed oxidation technique kinetics of coke-02 reaction on supported metal catalysts. Applied Catalysts A 117 53-74, 1994. 

Carbon monoxide-metal systems have also been used to demonstrate the effect of carrier material on properties of supported metal catalysts. Eischens and Plisken (1) found that the ratio of concentrations of linear to bridged species was much larger when platinum was supported on silica than when it was supported on alumina. Carbon monoxide on the alumina-supported samples was much more difficult to oxidize than on silica-supported ones. These observations were interpreted as an enhancement of platinum s ability to donate electrons to the metal-CO bond when alumina is the support. However, the mechanism by which... 

Supported platinum and base metal catalysts were evaluated in vehicle tests with converter volumes of 600-4300 cm3. The initial oxidation activity of the catalysts was determined as the vehicle was operated over the 1975 FTP. The ability of the base metal catalysts to control exhaust HC and CO emissions was strongly dependent on the catalyst volume. HC and CO conversion decreased quite rapidly as the converter size was decreased. 

Determination of Coke Location. The TPO technique allows the determination of the coke location on supported metal catalysts, such as naphtha reforming. Since the metal, typically platinum promoted with rhenium, iridium, tin, or germanium, has a catalytic effect for coke burning, the TPO profile displays two main peaks. The low temperature peak is due to the oxidation of the coke directly deposited on the metal particle, or in its vicinity . In this way, it is possible to study the effect of catalyst formulation and operational conditions on the formation of coke on the metal and on the support. 

The equilibrium is more favorable to acetone at higher temperatures. At 325°C 97% conversion is theoretically possible. The kinetics of the reaction has been studied (23). A large number of catalysts have been investigated, including copper, silver, platinum, and palladium metals, as well as sulfides of transition metals of groups 4, 5, and 6 of the periodic table. These catalysts are made with inert supports and are used at 400—600°C (24). Lower temperature reactions (315—482°C) have been successhiUy conducted using 2inc oxide-zirconium oxide combinations (25), and combinations of copper-chromium oxide and of copper and silicon dioxide (26). 

Methanol is a major bulk chemical, and its global annual production exceeds 37 million tons. It is mainly used for the production of formaldehyde and methyl 6butyl ether (MTBE). Especially, formaldehyde is dominantly used for producing resins. At present, methanol and its decomposed derivatives can be oxidized to CO2 and H2O by the proper selection of supported noble metal catalysts such as palladium, platinum, and gold. 

Supported gold catalysts are, in general, less active than platinum group metal catalysts in the complete oxidation of hydrocarbons however, by choosing... 

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