Processes for producing aromatic dicarboxylic acids are disclosed, the processes including a step of combining in a reaction medium a dialkyl aromatic, a solvent comprising water and a saturated organic acid having from 2-4 carbon atoms, and an oxygen-containing gas, at a temperature from about 125.degree. C. to about 155.degree. C., in the presence of a catalyst composition comprising cobalt, manganese, zirconium, and bromine, wherein the weight ratio of cobalt to manganese in the reaction mixture is from about 10 to about 400. The processes provide improved conversion, while reducing the formation of carbon oxides and other by-products.