Oxidative coupling of methane over Y2O3 and Sr–Y2O3 nanorods

Y2O3 nanorods were prepared via a hydrothermal method. A series of Sr-modified Y2O3 nanorods (Sr–Y2O3–NR) with a Sr/Y molar ratio of 0.02–0.06 were synthesized by an impregnation method, and studied with respect to their performance in the oxidative coupling of methane (OCM). The structural and physicochemical properties of these catalysts were characterized by means of XRD, N2 adsorption, SEM, TEM, XPS, O2-TPD and CO2-TPD. Y2O3 nanorods exhibit higher CH4 conversion and C2–C3 selectivity relative to Y2O3 nanoparticles, which could link with the fact that Y2O3 nanorods predominantly expose (440) and (222) planes. The addition of a small amount of Sr to Y2O3 nanorods enhances the activation of oxygen, the ratio of (O−  + O2−)/O2− and amount of moderate basic sites for the Sr–Y2O3-NR catalysts, thus promoting the OCM performance. The best 0.04Sr–Y2O3-NR catalyst with a Sr/Y molar ratio of 0.04 can give a 23.0% CH4 conversion with 50.2% C2–C3 selectivity at 650 °C. We found that the C2–C3 yield achieved on the Y2O3-based catalysts correlated well with the amount of moderate basic sites present on the catalysts.