Propane oxidative dehydrogenation over alumina-supported metal oxides

Alumina-supported oxides of V, Cr, Mn, Zr, and Ba were found to catalyze propane oxidative dehydrogenation to propylene at atmospheric pressure, reaction temperatures of 350-450 degreesC, and a total feed flowrate of 75 cm(3)/min (26.7% propane, 6.6% oxygen, and the rest helium). Maximum propane conversion (26%) and selectivity to olefin (70%) were achieved with vanadium oxide at 450 degreesC. The other metal oxides showed lower conversions (9-17%) and olefins selectivities (36-58%). This observation was explained on the basis of the lattice oxygen reactivity as estimated from the reduction potential of the metal cations. Metals whose cations have high potentials (e.g., vanadium oxide catalyst) were found to favor low COx and high selectivity to propene and ethene. This suggests that the metal-oxide bond strength strongly influences the selectivity to olefins in this reaction. A weak linear correlation between the selectivity to propene and the aqueous reduction potential of the cations was found.