Catalyst chemistry 426 - oxidation

Promoters. Many industrial catalysts contain promoters, commonly chemical promoters. A chemical promoter is used in a small amount and influences the surface chemistry. Alkali metals are often used as chemical promoters, for example, in ammonia synthesis catalysts, ethylene oxide catalysts, and Fischer-Tropsch catalysts (55). They may be used in as Httie as parts per million quantities. The mechanisms of their action are usually not well understood. In contrast, seldom-used textural promoters, also called stmctural promoters, are used in massive amounts and affect the physical properties of the catalyst. These are used in ammonia synthesis catalysts. 

In this chapter, we have discussed the application of metal oxides as catalysts. Metal oxides display a wide range of properties, from metallic to semiconductor to insulator. Because of the compositional variability and more localized electronic structures than metals, the presence of defects (such as comers, kinks, steps, and coordinatively unsaturated sites) play a very important role in oxide surface chemistry and hence in catalysis. As described, the catalytic reactions also depend on the surface crystallographic structure. The catalytic properties of the oxide surfaces can be explained in terms of Lewis acidity and basicity. The electronegative oxygen atoms accumulate electrons and act as Lewis bases while the metal cations act as Lewis acids. The important applications of metal oxides as catalysts are in processes such as selective oxidation, hydrogenation, oxidative dehydrogenation, and dehydrochlorination and destructive adsorption of chlorocarbons. 

Preparation of Single Site Catalysts on Oxides and Metals Prepared via Surface Organometallic Chemistry... 

The chemistry and function of Rh6(CO)16 and Re2(CO)10 as oxidation catalysts for organic compounds is under continuing investigation. In particular, we are studying the role of Rhe(CO)16 as a labile multisubstrate oxidation catalyst for oxidizing CO and triphenylphosphine (33, 34). 

According to Eq. (25), a cyclic phosphite monomer (MN) 38 is oxidized to a phosphate unit yielding copolymer 40 whereas the a-keto acid monomer (ME) 39 is reduced to the corresponding a-hydroxy acid ester. Thus, the term redox copolymerization has been proposed to designate this type of copolymerization in which one monomer is reduced and the other monomer oxidized. The redox copolymerization clearly differs from the so-called redox polymerization in classical polymer chemistry where the redox reaction between the two catalyst components (oxidant and reductant) is responsible for the production of free radicals. 

Carreon MA, Guliants W. Chapter 6 selective oxidation of n-butane over vanadium-phosphorous oxide. Nanostructured Catalysts Selective Oxidations The Royal Society of Chemistry 2011. p. 141-168. 

Bamoharram, F.F., Heravi, M.M., Roshani, M., and Akharpour, M. 2006h. Catalytic performance of Preyssler heteropolyacid as a green and recyclable catalyst in oxidation of primary aromatic amines. Journal of Molecular Catalysis A Chemistry, 255 193-98. 

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