Synthesis, characterization, and evaluation of high selectivity mixed molybdenum and vanadium oxide catalysts for oxidative dehydrogenation of propane

Molybdenum and vanadium oxide catalysts with varied compositions (Mo/V = 1/1, 7/3, 8/2, and 9/1) were prepared using a modified citrate-nitrate auto-combustion method for the oxidative dehydrogenation of propane to propylene. These catalysts were characterized by BET-technique, TPR, XRD, SEM, Raman, and UV spectroscopy. The effects of washing and supercritical CO2 drying on catalysts during the preparation steps were investigated. Results show an interaction between the molybdenum and vanadium metal ions in all of these catalysts due to the presence of a peak at 785 cm(-1) from the Raman study, which was assigned to a polymolybdovanadate species V-O-Mo vibration. This interaction could be efficient for alkane activation reaction. The catalysts were evaluated in a fixed bed micro-reactor at temperatures in the range of 350-600 degrees C and at atmospheric pressure. The activity of the catalyst increased by increasing the molybdenum content. All of the catalysts in this study showed 100 % selectivity for propylene in the temperature range of 350-450 degrees C; however, the propylene selectivity was found to decrease with an increase in the temperature. The highest yield of 4.8 % with 100 % propylene selectivity was obtained for a catalyst with Mo/V ratio of 9:1 at 500 degrees C.