SYNTHESIS AND CHARACTERIZATION OF NEW VPO CATALYSTS FOR PARTIAL NORMAL-BUTANE OXIDATION TO MALEIC-ANHYDRIDE

In order to try to control the V4+/V5+ ratio of VPO catalysts for butane oxidation to maleic anhydride, a new method of preparation of these catalysts has been developed: it consists of the reaction of VCl3(V3+) with V2O5(V5+) for the preparation of the precursor. Two series of catalysts have been prepared in aqueous and organic media. The V3+/V5+ ratio has been varied and its influence on the physicochemical features and on the catalytic properties of the catalysts has been studied. The best catalysts in both preparation media correspond to V3+/V5+ = 1 in the starting material. Catalysts have been characterized using X-ray diffraction, infrared spectroscopy, UV diffuse reflectance, Raman spectroscopy, 3'p MAS NMR, and XPS techniques. The combination of all these techniques led us to conclude that the best catalyst consisted of an oxidized surface (γ-VOPO4) (V5+) in interaction with reduced matrix ((VO)2P207) (V4+). © 1991.