Oxidation and ammoxidation of propane over Mo–V–Sb mixed oxide catalysts

Abstract

Catalytic oxidation and ammoxidation of propane to acrolein and acrylonitrile, respectively, were carried out over Mo–V–Sb mixed oxide catalysts. V–Sb mixed oxide showed the activity for the oxidative dehydrogenation of propane to propene, and the selectivity to propene remarkably increased with increasing the concentration of cation vacancy in VSbO 4 phase. It is likely that the oxidative dehydrogenation of propane on the VSbO 4 phase is initiated via H-abstraction by acid–base concerted mechanism. The selectivity to acrolein and acrylonitrile increased by the addition of molybdenum species to V–Sb mixed oxide catalyst. Among a series of Mo–V–Sb oxide catalysts, Mo 1V 1Sb 10O x exhibited the highest selectivity to acrolein and acrylonitrile at 430 and 480°C, respectively. The highly dispersed molybdenum suboxide was formed together with the both phases of VSbO 4 and α-Sb 2O 4 in the Mo 1V 1Sb 10O x . The high catalytic activity of Mo 1V 1Sb 10O x can be explained by the bifunctional mechanism of the highly dispersed molybdenum suboxide and the VSbO 4 phases as follows: the oxidative dehydrogenation of propane proceeds on the VSbO 4 phase followed by the oxidation of propene into acrolein or the ammoxidation into acrylonitrile on the molybdenum suboxide phase. When large size of MoO 3 crystallites were formed, cracking reaction, i.e., C–C bond cleavage, occurred leading to non-selective total oxidation, resulting in decreasing the selectivities to acrolein and acrylonitrile.