Preparation of vanadium phosphate catalysts using water as solvent

The synthesis of vanadium phosphorus oxide catalysts for the selective oxidation of n-butane using V2O4 as a starting material with water as solvent is described. In the absence of added water, V2O4 and either H3PO4 or H4P2O7 react at 145 °C to form well crystalline VOHPO4·0.5H2O. The surface area of the precursor is significantly enhanced when water is added as a solvent. On activation in n-butane/air the catalyst surface area is increased from ca. 4 m2/g for the precursor to 10–13 m2/g. The catalytic performance data in terms of n-butane conversion and maleic anhydride selectivity, is comparable to other non-promoted vanadium phosphate catalysts.