Comparison of vanadium phosphate catalysts derived from VOPO4·2H2O prepared from H3PO4 and H4P2O7

Abstract

Vanadium phosphate catalysts prepared from VOPO₄ ·2H₂O are described and discussed. The use of H₄P₂O₇ as a phosphorus source, as compared with H₃PO₄, is shown to give an improved synthesis of VOPO₄·2H₂O. Reduction of VOPO₄·2H₂O with alcohols from both the materials leads to the formation of VOHPO₄·0.5H₂O. However, the material derived from H₄P₂O₇ has a higher intrinsic activity (mol maleic anhydride formed per unit surface area) than that derived from H₃PO₄. The final catalysts are shown to comprise (VO)₂P₂O₇ together with a range of V(V) VOPO₄ phases and the origin of the enhanced activity is discussed in terms of the catalyst structure.