A solvent-free method of preparation of a vanadium(V) phosphate is described and discussed. Reaction of V2O5 with H3PO4 in the absence of water at 150 degreesC leads to the formation of a new catalytic material that is designated as "anhydrous" VOPO4. The material readily hydrates to form VOPO4. 2H(2)O and has been characterised using powder X-ray diffraction, in situ Raman spectroscopy and P-31 MAS NMR spectrometry. On activation in dry N-2 followed by reaction with butane/air another novel material is formed that has an intrinsic activity for maleic anhydride that is similar to catalysts derived from VOHPO4.0.5H(2)O under comparable conditions. Activation of VOPO4. 2H(2)O under comparable conditions leads to the formation of alpha (I)-VOPO4 which exhibits no partial oxidation activity. Reaction of "anhydrous" VOPO4 with alcohols leads to the exclusive formation of VO(H2PO4)(2) in further contrast to VOPO4. 2H(2)O which under similar conditions leads to the synthesis of VOHPO4.0.5H(2)O.