Autoxidation of Aromatic Hydrocarbons Catalyzed with Cobaltic Acetate in Acetic Acid Solution. II. Oxidation of Ethylbenzene and Cumene

Abstract

Abstract The oxidation of ethylbenzene and cumene catalyzed with cobaltic acetate in acetic acid was studied kinetically in order to elucidate the reaction mechanism and the roles of cobaltic salt. The maximum absorption rate of oxygen as well as the maximum reduction rate of Co(III) in the oxidation of ethylbenzene or cumene were of first order with respect to the initial concentration of hydrocarbon, of inverse first order with respect to the initial concentration of Co(II), and of second order with respect to the initial concentration of Co(III). The kinetic equations are therefore just the same as in the case of toluene, but d[Co(III)]/d[O2] gave a quite different average value of 3.8, showing that almost no regeneration of Co(III) from Co(II) due to oxidation with peroxidic compounds occurred. Both rates were remarkably accelerated by the addition of sodium acetate and also influenced by a small amount of water. The order of oxygen absorption rate in oxidation was toluene>ethylbenzene>cumene in contrast to the order of hydrogen abstraction rate by peroxy radicals. The apparent activation energy for these hydrocarbons was found to be 10.1 kcal mol−1.