Abstract: A process is disclosed for the oxidation of di- or trimethyl benzenes with molecular oxygen under liquid-phase conditions in the presence of a recovered cobalt and manganese catalyst, which has been recovered by heating oxidation incinerator ash in the presence of acetic acid and a reducing agent wherein the weight ratio of acetic acid to said oxidation incinerator ash is from about 1:1 to about 50:1, and the ratio of electrons which the reducing agent can deliver to atoms of the cobalt plus manganese in the oxidation incinerator ash is from about 0.1:1 to about 4:1 at about the boiling point of the acetic acid at atmospheric pressure and recovering the cobalt and manganese in liquid solution as the metal acetic acid salt, wherein the oxidation is carried out at a temperature of from about 100.degree. C. to about 250.degree. C.