Bismuth metal-supported

Decen-l-ol is oxidized by air to 9-decenoic acid in aqueous media in the presence of a supported platinum catalyst with bismuth atoms deposited on the surface of the platinum particles [221]. Metal-supported bismuth catalysts have been studied extensively for selective oxidation of hydrocarbons and alcohols for industrial use [222]. 

Mixed bismuth-metal oxychlorides with or without added alkali or alkaline earth cations show low to moderate catalytic performance in the dehydroha-logenation of f rf-butyl halides [93BCJ347]. A Bi-Pd (Bi/Pd = 0.4-0.6) binary system supported on metal oxides is found to be an efficient catalyst for the dehydrohalogenation of 1,1,2-trichlorotrifluoroethane (FC-113) to trifluoroethene, a key intermediate to FC-134a, with 80-90% selectivity at 80-100% conversion [91CL841] (Scheme 5.23). 

Early work on the subject was carried out by Paal and his co-workers (23), who mounted platinum or palladium on various metallic supports and tested the activity of the resulting catalyst for hydrogenation. In some cases, the carrier consisted of the metallic oxide or carbonate. The presence, in the. supported catalyst, of many heavy metals including mercury, lead, bismuth, and tin, also of zinc, cadmium, copper, or iron, was found to inhibit the activity of the platinum or palladium. On the other hand, platinum supported on metallic magnesium was active. Subject to a few modifications, Paal s list of toxic and nontoxic metals has been confirmed and extended by later work by other authors. 

The prototype thermopiles were constructed as thin films of antimony and bismuth metals in regular patterns to form pairs of thermocouple junctions on a thin (38 pm) Mylar support [12]. They were modified to accommodate the living cells by incorporating a small microwell, placed directly over both the active and the reference junctions, to contain the culture medium. The cells were immobilised with fibronectin placed over the active thermopile junctions only (see Figure 45), so that the thermopile electromotive force is proportional only to the temperature difference between the active and reference junctions. A... 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

Wenkin, M., Touillaux, R., Ruiz, P., Delmon, B., and Devillers, M. (1996) Influence of metallic precursors on the properties of carbon-supported bismuth-promoted palladium catalysts for the selective oxidation of glucose to gluconic acid. Appl. Catal., A, 148, 181-199. 

Analytical electron microscopy permits structural and chemical analyses of catalyst areas nearly 1000 times smaller than those studied by conventional bulk analysis techniques. Quantitative x-ray analyses of bismuth molybdates are shown from lOnm diameter regions to better than 5% relative accuracy for the elements 61 and Mo. Digital x-ray images show qualitative 2-dimensional distributions of elements with a lateral spatial resolution of lOnm in supported Pd catalysts and ZSM-5 zeolites. Fine structure in CuLj 2 edges from electron energy loss spectroscopy indicate d>ether the copper is in the form of Cu metal or Cu oxide. These techniques should prove to be of great utility for the analysis of active phases, promoters, and poisons. 

Oxidation in the original Sohio process941,942 was carried out over a bismuth molybdate catalyst, which was later superseded by bismuth phosphomolybdate with various amounts of additional metal ions (Ce, Co, Ni), and multicomponent metal oxides based on Mo, Fe, and Bi supported on silica. 

Strictly speaking, it is difficult to conclude which model is most reasonable. However, summing up the results obtained by the surface analyses, it is sure at least that bismuth molybdates are concentrated on the surface of the catalyst particle. Our investigations for Mo-Bi-Co2+-Fe3+-0 also support the conclusion mentioned above, and the core-shell structure proposed by Wolfs et al. may be essentially reasonable. However, since small amounts of divalent and trivalent metal cations are observed in the surface layers, the shell structure may be incompletely constructed. The epitaxial effect has been assumed on the condensation of bismuth molybdates on the divalent and trivalent metal molybdates on the basis of the fact that the y-phase of bismuth molybdate is mainly formed on NiMo04 but the a-phase is predominant on other divalent and trivalent metal molybdates (46). The... 

A redox mechanism for oxidation catalysis was proposed by Mars and van Krevelen (34) for the oxidation of aromatics over V205. This mechanism introduced the concept that lattice oxygen of a reducible metal oxide could serve as a useful oxidizing agent for hydrocarbons. Moreover, it formed the basis for the early work at SOHIO which led to the development of the bismuth molybdate catalyst. Since that time there have been many reports which support the redox concept. 

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