Active and selective catalysts for the synthesis of C2H4 and C2H6 via oxidative coupling of methane

Active and selective catalysts for oxidative coupling of methane were tested over many metal oxides (30 oxides) under the experimental conditions chosen (T = 973 K, PO2 = 0.4 kPa, PCH4 = 18.2 kPa, PHe = 82.7 kPa). In general, the oxides of rare earth elements showed higher C2-selectivity (C2H6 + C2H4) than 80%. Among the various metal oxides tested, Sm2O3 was the most active and selective catalyst in the formation of C2-hydrocarbons (selectivity 93%). No appreciable decrease in activity and selectivity was observed after the experiments for 180 h at 973 K. The kinetic studies on the reaction over Sm2O3 were carried out under different experimental conditions. Relative rates of reactions of CH4, C2H6, and C2H4 suggest that the overall reaction of CH4 proceeds as follows: