IMPROVED VPO CATALYST WITH LOW VANADIUM OXIDATION STATE FOR MALEIC ANHYDRIDE PRODUCTION

摘要

An oxidation catalyst comprising vanadium, phosphorus, and oxygen having average vanadium valence less than about 4.10, and a method of preparing such catalyst, is provided. The catalyst has side crush strength of at least about 5 lbs. and improved yield of maleic anhydride from n-butane between about 1% and about 6% absolute. The catalyst is formed by exposing a conventional active VPO catalyst having average vanadium valence between about 4.10 and about 4.40 to an organic solvent having a dielectric constant between about 5 and about 55 under conditions that facilitate an oxidation-reduction reaction, reducing the valence of the vanadium below 4.10.