The effect of oxygen vacancy of alkaline-earth metal Sr doped Sm2Zr2O7 catalysts in the oxidative coupling of methane

Highlights: • The Sr/Sm₂Zr₂O₇ catalysts were prepared by the coprecipitation method. • The basicity and oxygen vacancy played an important role in the Sr/Sm₂Zr₂O₇ catalyst. • The Sr doped into Sm₂Zr₂O₇ catalyst significantly increased catalytic activity for OCM. • The 7.6%Sr/Sm₂Zr₂O₇ catalyst exhibited the best catalytic activity and high stability. A series of the Sr/Sm₂Zr₂O₇ catalysts with different Sr contents prepared by the coprecipitation method were used for OCM. The results revealed that the basicity and oxygen vacancies concentration on the surface of the Sm₂Zr₂O₇ catalyst were notably increased because of the addition of Sr. Activation of O₂ by the oxygen vacancies was responsible for the formation of C₂. Specifically, the 7.6% Sr/Sm₂Zr₂O₇ catalyst possessed 18.4% C₂ yield at 750 °C due to the presence of moderate basicity and the highest ratio of the oxygen species O₂^– to lattice oxygen O^2–. More importantly, the 7.6%Sr/Sm₂Zr₂O₇ catalyst possessed high stability.