Oxidation Activity and Acidity of V2O5–P2O5 Catalyst

Abstract

The oxidations of 1-butene, butadiene, and hydrogen in a large excess of air were carried out over various V–P oxide catalysts with different P2O5 contents. The oxidation activities were compared with the dehydration activity for isopropyl alcohol, which was used as a measure of the acidity of the catalysts. The surface area and the acidity per unit of surface area sharply decrease with an increase in the P2O5 content up to about 20 mol% P2O5, while with a further increase in the P2O5 they remain almost unchanged. The activity per unit of surface area for the oxidation of butene and butadiene, as well as that for the isomerization of butene, changes in the same direction as the acidity per unit of surface area. The equilibrium constant for the adsorption of olefin changes analogously. The activity per unit of surface area for the oxidation of hydrogen is not affected by the P2O5 content. The effects of the P2O5 introduced into V2O5 on the activity and selectivity are discussed from the viewpoint of the acidic nature of the catalysts.