Effects of Bi on the Catalytic Performance of MoVO/AlPO_4 Catalyst for Selective Oxidation of Isobutene

MoVO/AlPO4 and MoVBiO/AlPO4 catalysts have been prepared by the sol-gel method.The effects of Bi on surface acidity,distribution of active species,V5+/V4+ ratio,crystalline phase,and catalytic performance for selective oxidation of isobutene to methacrolein were investigated.The catalysts were characterized by X-ray diffraction,FT-Raman spectroscopy,temperature programmed reduction and X-ray photoelectron spectroscopy.The results showed that the addition of Bi at a proper amount obviously improves the catalytic performance of catalyst for selective oxidation of isobutene.Methacrolein selectivity is elevated from 29.1% to 75.2% with the increase of Bi/V ratio from 0 to 0.5.The surface acidity,crystalline phase,and dispersion of molybdenum and vanadium oxides species are responsible for the catalytic properties of the MoVBiO/AlPO4 catalyst,which are especially related to the V5+/V4+ ratio on the surface.