Flower-like Sr-La2O3 Microspheres with Hierarchically Porous Structures for Oxidative Coupling of Methane

Catalysis for oxidative coupling of methane (OCM) is a promising and challengeable technology. In this work, we demonstrate that OCM over Sr-doped flower-like La2O3 microspheres with hierarchically porous structures (Sr0.1LaOx-H) happened at a temperature as low as 440 °C along with the formation of C2 hydrocarbon and reached to the optimum C2 yield (∼19%) at 550 °C. Although we introduced Sr into La2O3 in a simple impregnation method, there was a strong interaction between Sr and La for Sr0.1LaOx-H, which led to an effective doping of Sr into La2O3. This, in turn, enhanced the activation toward oxygen and then conversion of methane in OCM. Also, Sr isolated the active sites of the catalyst and introduced strong basic sites, which correlated with an improvement on C2 selectivity. In addition, Sr0.1LaOx-H deactivated during OCM in ∼30 h, but a small amount of Zr added made it display good stability in OCM.