Isotope Studies in Oxidation of Propane over Vanadium Oxide

The oxidation of propane has been studied over silica-supported vanadium oxide and polycrystalline, bulk MoVTeNb oxide with M1 structure. Temperature-programmed reaction experiments were performed, and the reactivity of propane molecules labeled with deuterium and C-13, respectively, was analyzed under steady-state conditions. The measurement of kinetic isotope effects reveals fundamental differences in the activation of propane over the two catalysts. The reaction network of consecutive and parallel reactions of the formed propylene is comparable. However, oxygen insertion into the CHO group of acrolein under formation of acrylic acid is faster over M1 than oxidation at the CH2 group and decarbonylation to acetaldehyde. In contrast, the latter process is preferred over silica-supported vanadium oxide resulting in lower selectivity to unsaturated oxygenates.