Gold catalysts chemical processing

A. Kuperman, R. G. Bowman, H. W. Clark, G. E. Hartwell, B. J. Schoeman, H. E. Tuinstra, G. R. Meima, Process for the hydro-oxidation of olefins to olefin oxides using oxidized gold catalyst, U.S. Patent No. 6,255,499,2001, Assigned to DOW Chemical Company. 

The examples mentioned above require development of new chemical transformation processes. Associated with these processes is the need to develop new catalytic systems. Improved understanding of current catalytic systems would facilitate the scientific discovery of new ones. New experimental and computational techniques are needed. Insufficient understanding of catalysis in general is demonstrated by the system of supported gold catalysts Although these catalysts have a wide variation of reaction selectivity, there is little understanding of the nature of their active sites. 

Gas-soUd catalytic reaction is the most common chemical process in the industry. However, owing to the limitation of this book, only three chapters were devoted to this theme. Chapter 11 describes the preparation of gold clusters and its application on the solid-gas biphasic catalytic reaction. The clarification of catalytic mechanism and reactive sites is very important for designing more efficient catalysts. So the identification of binding and reactive sites in metal cluster catalysis through imaging technique, kinetic study, and other methods are introduced in Chapter 9. To reflect the importance of theoretical calculation on catalysis, the molecular kinetics of the Fischer-Tropsch reaction by computational chemistry is introduced in Chapter 16. 

In the process jointly developed by Bayer and Hoechst,933-935 a palladium-gold-on-silica or alumina catalyst impregnated with KOAc is used. A mixture of ethylene, acetic acid, and oxygen is converted at 150-170°C and about 5-10 atm to produce vinyl acetate with about 91-92% selectivity at about 10% conversion in a highly exothermic reaction. The only major byproduct is C02. KOAc requires continuous replenishment. A similar process was independently developed by U.S.I. Chemicals.932 936... 

The importance of waste reduction through the use of a chemical catalyst can be exemplified by the use of yV-methylimidazole as a catalyst in the leaching step of gold extraction from ores in the mining industry. Cyanide, a toxic substance that poses a major health threat, has traditionally been used for these processes. A sample case is the 1999 leak in a Rumanian facility from a cyanide storage tank into the Rhine River that killed thousands of fish. 

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