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

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 VSbO4 phase. It is likely that the oxidative dehydrogenation of propane on the VSbO4 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, Mo1V1Sb10Ox exhibited the highest selectivity to acrolein and acrylonitrile at 430 and 480 degreesC, respectively. The highly dispersed molybdenum suboxide was formed together with the both phases of VSbO4 and alpha -Sb2O4 in the Mo1V1Sb10Ox. The high catalytic activity of Mo1V1Sb10Ox can be explained by the bifunctional mechanism of the highly dispersed molybdenum suboxide and the VSbO4 phases as follows: the oxidative dehydrogenation of propane proceeds on the VSbO4 phase followed by the oxidation of propene into acrolein or the ammoxidation into acrylonitrile on the molybdenum suboxide phase. When large size Of MoO3 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. (C) 2001 Elsevier Science B.V. All rights reserved.