Modulating Lattice Oxygen through an Alkaline Earth Metal Promoter for Chemical Looping Oxidative Dehydrogenation of Propane

Rational design of metal oxide-type redox catalysts for selective propylene production is of paramount importance, yet remains challenging. This paper describes the structural and electronic effect of an alkaline earth metal promoter on lattice oxygen reactivity for chemical looping oxidative dehydrogenation (CL-ODH) of propane through the configuration of core-shell-type redox catalysts, which consist of a redox-active FeVO4 core and a selective mixed alkaline earth metal oxide shell. A systematic study demonstrates that Mg is the optimal promoter among all alkali and alkaline earth metals investigated, and the formed Mg2V2O7 outer shell provides a catalytic surface for C-H activation while blocking the nonselective sites for FeVO4, typically as an oxygen carrier. The core-shell redox catalyst with a higher coverage of the Mg2V2O7 layer achieves an enhanced propylene selectivity of 80.8% at an operation temperature of 550 degrees C. The design strategy highlights the exploration of alkaline earth metals in redox catalysts for chemical looping processes.