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 degrees C) and CH4 (or C2H6)/O-2 ratios (4-8), at low contact time (space velocity = 102000 cm(3) g(-1) h(-1)). For the OCM process, the Sr-La2O3 catalyst shows the best performance. The Sr-promoted Nd2O3, Sm2O3, Eu2O3 and Er2O3 catalysts also show good methane conversion and selectivity for C-2 hydrocarbons but the Sr-CeO2 and Sr-Dy2O3 catalysts show very poor performance. However, for the ODE process, the best performance is shown by the Sr-Nd2O3 catalyst. The other catalysts also show good ethane conversion and selectivity for ethylene; their performance is comparable at higher temperatures (greater than or equal to 800 degrees C), but at lower temperature (700 degrees C) the Sr-CeO2 and Sr-Pr6O11 catalysts show poor selectivity.