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.