New precursors to vanadium phosphorus oxide catalysts

Abstract

New precursors to vanadium phosphorus oxide catalysts have been synthesized based on alteration of the layered structure found in the active VPO catalysts. n-Alkyl amine intercalation compounds of vanadyl hydrogen phosphate hemihydrate have been prepared that are transformed into active vanadyl pyrophosphate catalysts. Catalytic performance for selective oxidation of n-butane to maleic anhydride improves with length of alkyl chain. Vanadyl phosphonates and vanadyl phosphite have been prepared containing vanadyl dimer structures that are thermally transformed into vanadyl pyrophosphate below 650 K for the phosphonates and 550 K for the phosphite. The VPO catalyst from the vanadyl phosphite precursor had a high surface area of 35 m 2/g, and displayed better selectivity for maleic anhydride from n-butane oxidation than the conventional unpromoted catalyst. Mixed vanadyl phosphite-phosphate materials, which were found to be very reactive for intercalation of amines, were intercalated with 3-aminopropyltriethoxysilane and calcined to produce the first thermally stable pillared VPO catalyst.