Applied Catalysis A: General, Vol.147, No.1, 55-67, 1996
Effect of Compositions of Promoted Vpo Catalysts on the Selective Oxidation of N-Butane to Maleic-Anhydride
A series of vanadium phosphate (VPO) catalysts with different P/V ratios and with or without indium and TEOS additives have been characterized by controlled-environment XRD, ICP, ESCA, TEM, SEM, BET and chemical titration and used for n-butane oxidation to maleic anhydride. The best catalyst contains slightly excess P over V with indium and TEOS promoters. It was found that excess P increases the resistance of catalyst precursors toward oxidation and results in VPO catalysts with a large exposed platelet face of a layer morphology. The promoters reduce the thickness of the platelet and facilitate the oxidation of the precursor which contains disordered VOHPO4 . 0.5H(2)O. The combination of the promoters and excess P results in a VPO catalyst with appropriate oxidizability and morphology and gives high yields of maleic anhydride.
Keywords:PHOSPHORUS OXIDE CATALYSTS;PHYSICOCHEMICAL CHARACTERIZATION;VANADYL PYROPHOSPHATE;P/V RATIO;MECHANISM;PHOSPHATE;PHASES