Liquid Phase Oxidation of Xylenes and Toluic Acids with Oxygen, and Inhibitory Effect of Organic Acids on the Oxidation

Abstract

Reactivities of xylenes in the liquid phase air oxidation at 135°c with cobalt naphthenate catalyst was in order of o->m-≅p-xylene. The velocity of oxidation with cobalt bromide catalyst without solvent in a stationary chainpropagation period was in the order of o-<in-≅p-xylene. The presence of bromine in cobalt catalyst increased the oxidation velocity in the propagation period (with the exception of o-xylene, no solvent system in which the oxidation was decreased). The ratio of the reaction velocity coefficient, k2/k1, in the twostep oxidation of xylenes toluic acids benzenedicaroxylic acids was not much dependent on the kind of xylenes in case of using cobalt naphthenate catalyst. The ratio k2/k1 became smaller with cobalt bromide catalyst than with cobalt naphthenate catalyst. In the liquid phase oxidation of toluic acids at 150°c to benzenedicarboxylic acids, it was found that the reaction was proceeded smoothly in case of m-or p-toluic acids but not in case of o-toluic acid. This may be attributed mainly to inactivation of catalyst by the o-phthalic acid. This kind of inactivation is found commonly in organic acids having a large dissociation constant and was found in case of oxidation of easily oxidizable xylenes too, though the tendency is smoll.