Abstract: 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.

Key words: sol-gel method, iso-butene, selective oxidation, methacrolein, molybdenum, vanadium, bismuth, aluminum phosphate