Oxidative coupling of methane and oxidative dehydrogenation of ethane over strontium-promoted rare earth oxide catalysts

Sr-promoted rare earth (viz. La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb) oxide catalysts (Sr/rare earth ratio = 0.1) are compared for their performance in the oxidative coupling of methane (OCM) to C 2 hydrocarbons and oxidative dehydrogenation of ethane (ODE) to ethylene at different temperatures (700 and 800°C) and CH 4 (or C 2 H 6 )/O 2 ratios (4-8), at low contact time (space velocity = 102000 cm 3 g -1 h -1 ). For the OCM process, the Sr-La 2 O 3 catalyst shows the best performance. The Sr-promoted Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 and Er 2 O 3 catalysts also show good methane conversion and selectivity for C 2 hydrocarbons but the Sr-CeO 2 and Sr-Dy 2 O 3 catalysts show very poor performance. However, for the ODE process, the best performance is shown by the Sr-Nd 2 O 3 catalyst. The other catalysts also show good ethane conversion and selectivity for ethylene; their performance is comparable at higher temperatures (≥800°C), but at lower temperature (700°C) the Sr-CeO 2 and Sr-Pr 6 O 11 catalysts show poor selectivity.