Mechanisms of molybdenum substitution in vanadium antimonate

Abstract The formation of a solid solution containing the three elements V, Sb and Mo, which are key-elements in the design of light alkane oxidation catalysts, has been studied by incorporating molybdenum into the pure VSbO 4 compound as obtained in air at 700°C (V 3+ 0.28 V 4+ 0.64 □ 0.16 Sb 5+ 0.92 O 4 ). Monophasic compounds with a rutile-type structure have been obtained and characterized by X-ray diffraction, electron microscopy, Infrared Fourier transform, X-ray absorption and electron spin resonance spectroscopies. At low molybdenum content, Mo 6+ substitute V 4+ in the cationic-deficient structure. The charge balance is maintained by an increase of the cationic vacancy number. This leads to the formation of a solid solution corresponding to the formula V 3+ 0.28 V 4+ 0.64−3 x Mo 6+ 2 x □ 0.16+ x Sb 5+ 0.92 O 4 with 0 x 5+ are stabilized and substitute Sb 5+ in the rutile structure: V 3+ 0.28 V 4+ 0.37 Mo 6+ 0.18 □ 0.25 Mo 5+ y Sb 5+ 0.9− y O 4 with 0 y 2 O 4 and a new mixed vanadium molybdenum antimonate.