Effects of feed compositions on oxidative dehydrogenation of propane over Mn-P-O catalyst

Catalytic oxidative dehydrogenation of natural gas components such as propane to propene and other more useful products is technologically relevant, but catalysts proposed so far exhibit moderate performances. A manganese phosphate catalyst was prepared, characterized (BET, FTIR and XPS), and tested for the reaction at atmospheric pressure and a temperature range of 450-550 degreesC. In the temperature range, the propane conversion changed from 4.1 to 40.7%, and the selectivity to propene showed an insignificant change at 41 +/- 3%. In addition to other products, oxygen-containing compounds of about 5% were obtained at high temperatures. Variation of propane/oxygen partial pressures at 450-490 degreesC elucidated the relevance of gas-phase oxygen on the selectivity to propene. At high propane ratios (C3H8/O-2 = 4.0), the catalyst exhibited a propane conversion of 7.0% and selectivity to propene of 78.0% with the balance COx (CO + CO2). At low ratios (C3H8/O-2 = 0.5) and low conversion, only CO was produced. Thus, selectivity to propene could be improved by employing low or moderate oxygen partial pressure.