Acetic acid stability in the presence of oxygen over vanadium phosphate catalysts: comments on the design of catalysts for the selective oxidation of ethane

The stability of acetic acid in the presence of excess oxygen is evaluated for a range of vanadium phosphate and oxide catalysts. In the temperature range 300–400 °C most oxides catalyse the total oxidation of acetic acid to carbon dioxide and water. However, over molybdenum oxide acetic acid oxidation is not significant. This is consistent with Mo being a major component of oxide catalysts that have, to date, been identified for the selective oxidation of ethane to acetic acid at this temperature. Interestingly, VO(H2PO4)2, a phase that is very non-selective for the partial oxidation of n-butane, exhibits the highest stability for acetic acid under oxidising conditions. It is proposed that catalysts based on VO(H2PO4)2 may provide the basis of improved ethane partial oxidation catalysts.