Gas-Phase Selective Oxidation of Organic Compounds

Because the petrochemical industry is based on hydrocarbons, especially alkenes, the selective oxidation of hydrocarbons to produce organic oxygenates occupies about 20% of total sales of current chemical industries. This is the second largest market after polymerization, which occupies about a 45% share. Selectively oxidized products, such as epoxides, ketones, aldehydes, alcohols and acids, are widely used to produce plastics, detergents, paints, cosmetics, and so on. Since it was found that supported Au catalysts can effectively catalyze gas-phase propylene epoxidation [121], the catalytic performance of Au catalysts in various selective oxidation reactions has been investigated extensively. In this section we focus mainly on the gas-phase selective oxidation of organic compounds. 

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Fig. 13.34. Electrogenerative production of two organic compounds by a fuel cell approach. (Reprinted from K. Otsuka, K. Ishizuka, I. Yamanaka, and M. Hatano, The Selective Oxidation of Toluene to Benzaldehyde Applying a Fuel Cell System in the Gas Phase, J. Elec-trochem. Soc. 138 3178,1991, Fig. 3. Reproduced by permission of The Electrochemical Society, Inc.)...

Usually, in a chamber reactor (see the bottom row in Table 4) the complex chemical systems existing in the atmosphere gas phase are approximated. Especially advantageous for studying gas reactions are the two characteristic features of a chamber reactor a relatively large volume and rather insignificant wall effects. Examples of effectively studied tropospheric reactions in chamber reactors are photo-dissociation and oxidation of a selection of organic compounds, the latter reactions with such oxidants as ozone, OH and NO3. In many... 

The in situ regeneration of Pd(II) from Pd(0) should not be counted as being an easy process, and the appropriate solvents, reaction conditions, and oxidants should be selected to carry out smooth catalytic reactions. In many cases, an efficient catalytic cycle is not easy to achieve, and stoichiometric reactions are tolerable only for the synthesis of rather expensive organic compounds in limited quantities. This is a serious limitation of synthetic applications of oxidation reactions involving Pd(II). However it should be pointed out that some Pd(II)-promoted reactions have been developed as commercial processes, in which supported Pd catalysts are used. For example, vinyl acetate, allyl acetate and 1,4-diacetoxy-2-butene are commercially produced by oxidative acetoxylation of ethylene, propylene and butadiene in gas or liquid phases using Pd supported on silica. It is likely that Pd(OAc)2 is generated on the surface of the catalyst by the oxidation of Pd with AcOH and 02, and reacts with alkenes. 

Finally, a number of gas-phase chemical reactions, such as the oxidation of selected organic compounds, generate nonvolatile condensable products that associate with aerosol particles. A large fraction of the aerosol consists of ammonium sulfate, which derives fi om the oxidation... 

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