Anomalous Effect of the Concentration of Metal-salt Catalysts in the Liquid-phase Oxidation of p-Xylene and Toluene

Abstract

Abstract By studying the relation between the concentration and the oxidation activity of various metal catalysts, mostly naphthenates, oleates, linoleates, and caprates of manganese, cobalt, and nickel salts, as well as mixed catalysts of two kinds, it has been established that, in general, there is an anomalous effect of the catalyst concentration-namely, the catalytic activity disappears above a certain point in the concentration of the catalyst. The anomalous concentration effect of a catalyst is observed in the oxidation of toluene and p-xylene with all the catalysts, but chromium naphthenate is a lone exception in the oxidation of p-xylene. It has been shown that the anomalous effect is due to the association of the catalyst in the hydrocarbon solvent to be oxidised, and that the associated catalyst does not act to promote oxidation. The association is reversible, being dependent on the concentration of the catalyst, so the anomalous concentration effect of a catalyst disappears on dilution.