Zeolites photochemical hydrocarbon oxidation

Frei, H. (1997). Highly selective photochemical and dark oxidation of hydrocarbons by 02 in zeolites. In Studies in Surface Science and Catalysis. 3rd World Congress on Oxidation Catalysis, Grasselli, R.K., Oyama, S.T., Gaffney, A.M. and Lyons, J.E. (eds), Vol. 110, pp. 1041-1050. Elsevier Science, New York... 

Highly selective photochemical and dark oxidation of hydrocarbons by O2 in zeolites... 

Selectivity is an especially tough challenge in the case of autoxidation of small olefins in fluid phase because of diversion of the radical chain reaction by termination steps that result in the formation of oxy radicals. These are very reactive species that attack indiscriminately the starting hydrocarbon and primary products. The photochemical reaction in zeolites opens up much better controlled oxidation of low olefins, which are illustrated here briefly for the commercially important case of propylene oxidation. 

Particularly interesting is the finding that small alkanes can be partially oxidized by oxygen using the same photochemical method in alkali and alkaline-earth zeolite Y [21-25], Reactions established thus far are summarized in Scheme 3. Alkyl hydroperoxides and carbonyl compounds are produced with very high selectivity in each case even upon high (>50%) conversion of the hydrocarbon. These partially oxidized alkanes are of commercial importance, and the search for more selective and direct processes is intense [3,4]. 

Photochemical reactions of materials enclosed in zeolites can lead to different proportions of products, or in some cases, to different products than those run in solutions.207 The distribution can vary with the zeolite. The enhanced selectivity in the oxidation of hydrocarbons with oxygen208 was mentioned in Chap. 4. The oxidation of cyclohexane in NaY zeolite with oxygen and visible light to yield cyclohexane hydroperoxide with complete selectivity at more than 40% conversion may have considerable industrial potential. Heating the hydroperoxide yields only cyclohexanone which can be oxidized to adipic acid for use in making nylon 6,6.209... 

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