In order to clarify the relationship between the intrinsic oxidation activity and the basicity of metal oxide, the vapor-phase oxidation of n-hexane, 1-butene, phenol, and methanol was carried out in the presence of an excess of air with two series of Co3O4-based catalysts, the acid-base properties of which had been modified by controlling the amounts of either K2O or P2O5. The main product was CO2, regardless of the reactants used. The catalytic activity for the oxidation of all the reactants was correlated with the basicity of the catalysts, except in the cases were the K2O content was high (K > 2 atom %). No correlation was observed between the activity and the acidity. With the addition of more than 3 atom % K2O, the oxidation activity for n-hexane and 1-butene sharply decreases, an the catalysts containing 10 atom % K2O are almost inactive for these reactants. However, the oxidation activity for phenol and methanol remains active even after the addition of 6 to 10 atom% K2O. It is considered that, in the case of such catalysts, the oxidation activity is no longer governed by the intrinsic oxidation activity, but by the activation of the reactants at the basic sites. The results demonstrate that the intrinsic oxidation activity is associated with the basic property of metal oxide. © 1978.
