The effect of glycols in the organic preparation of V/P mixed oxide, catalyst for the oxidation of n-butane to maleic anhydride

V/P/O catalysts have been prepared using the organic procedure, by reduction of V2O5 with isobutanol in the presence of phosphoric acid and of a glycol, chosen amongst 1,2-ethandiol, 1,3-propandiol, 1,3-butandiol and 1,4-butandiol. The addition of the glycol considerably affected the morphological features of the vanadyl orthophosphate hemihydrate, the V/P/O catalyst precursor, the organic compounds being retained in the precursor. The thermal treatment of the precursor, aimed at the development of the vanadyl pyrophosphate, led to the removal of the organic fraction. When the treatment was carried out in the absence of molecular oxygen, bulk oxygen was involved in the combustion of organic residues. Consequently a fraction of the V4+ ions was reduced to V3+ species, and the compound which finally developed was in part amorphous. In some cases it was possible to transfer the morphological features of the precursor up to the vanadyl pyrophosphate, and thus to finally affect the catalytic performance.