Oxidative coupling of methane over SrCO3 and SrO
Abstract
The oxidative coupling of methane has been studied with an SrCO3–SrO mixed catalyst. Two surface states (an SrO-rich surface and an SrCO3-rich surface) were prepared and examined by various methods including XPS. SrO-rich surfaces, prepared by H2 treatment of SrCO3, had a high C2 yield, and evolved CO2 was absorbed by the catalyst at 1023 K. The bulk diffusion of CO2 was considered to be rapid enough to absorb most of the evolved CO2 and to keep SrO partly on the surface (SrCO3-rich surface) at 1023 K. SrCO3-rich surfaces gave low C2 yields, and the surface was composed of both oxides and carbonates. The active sites were considered to be oxides. The SrO surface was more active than MgO in this reaction. However, it was less active under the steady state because of carbonate formation.