Tetravalent vanadium phosphate compsns. prepn. - for use as oxidation catalysts

摘要

Prodn. of crystalline tetravalent V phosphate compsns. with a specific surface of >=10 (pref. 10-100) m2/g comprises forming a dispersion of a solid particulate V cpd. (0.1-5 g-atoms V/1) in an anhydrous organic medium contg. 1.0-1.5 moles of H3PO4 per g-atom of V. The dispersion is kept at 20-210 degrees C (pref. 80-150 degrees C) for 1-50 hr at a pressure sufficient to maintain the medium in the liq. state. The resulting solid is then sepd. and dried at 50-350 degrees C. The V cpd. contains (a) V and O, (b) V, O and H or (c) V, O, H and C, with 0-20 C atoms, and the V has an average valence of 4.0-4.6. The organic medium comprises one or more inert 1-20C cpds. contg. C, H and O, opt. mixed with an inert diluent. In an example, the V cpd. is prepd. by refluxing V2O5 with isobutanol. Prods. are oxidn. catalysts, esp. useful for converting n-butane to maleic acid. Process gives prods. of practically constant compsn. (P:V atomic ratio 0.9-1.1:1) Corrosion problems due to the use of strong acids are avoided, as is the evapn. of large amts. of solvent.