Over 90% C2+ Selectivity in Kalium-Doped Manganese Perovskite Oxygen Carriers for Chemical Looping Oxidative Coupling of Methane with Plasma Assistance

Plasma-assisted chemical looping oxidative coupling of methane is a potential route for the conversion of methane into value-added C2+ hydrocarbons under mild conditions. However, the low C2+ selectivity of traditional oxygen carriers limits further development. In this study, we report a series of kalium-doped LaMnO3 oxygen carriers. The optimal doping level of kalium is found to be 1.0%, resulting in a C2+ selectivity of 92.67% at 400 °C, and the performance remained stable after 20 redox cycles. Mechanistic studies show that 1.0% kalium doping inhibits the migration of lattice oxygen (O2 2–) from bulk to the surface and the subsequent evolution of surface oxygen from electrophilic species (O–) to nucleophilic species (O2–). Therefore, the nucleophilic oxygen species (O2–) responsible for the overoxidation of the products was limited and in turn achieved a higher C2+ selectivity.