Synergistic Effect between Cobalt(II) and Manganese(II) Acetates Catalysts in the Liquid Phase Autoxidation of p-Xylene

The synergistic effect between cobalt(II) acetate (Go(II)) and manganese(II) acetate(Mn (II)) in the liquid phase autoxidation of p-xylene in the presence or absence o f hydrog bromide (HBr) in acetic acid has been studied at 65∼95°C. The remarkable synergistic effect of Mn(II) was obserbed both in the presence and abser of HBr by replacing about only 1 mol% of Co(II) by Mn(II). Thus the induction period creased, and the oxygen-absorption rate in the chain-propagation step and the total amou of absorbed oxygen increased remarkably. In addition, the concentration of hydroperoxide creased, and the yields of oxidation products such as p-tolualdehyde and p-toluic acid creased. The mechanism of synergistic effect was also discussed.