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 °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 °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 °C.