Chemical looping oxidative coupling of methane (CLOCM) is a promising method for the direct conversion of methane to produce C₂₊ hydrocarbons. However, high reaction temperatures (800^oC-900^oC) are required to ensure high redox activity, leading to the server sintering of oxygen carriers. Here, we report plasma-assisted chemical looping oxidative coupling of methane and investigate its performance under mild conditions (100^oC-400^oC). The results demonstrate that the plasma-assisted CLOCM reaction can be initiated at temperatures as low as 100^oC. Particularly, LaMnO₃ shows high CH₄ conversion of 35.33% and C₂₊ yield of 12.26% at 400^oC. The performance merely decreased after 20 redox cycles. Mechanism study implies that the high-performance results from plasma generate high-energy electrons (1-20 eV) to activate methane (4.3 eV) at low temperatures, and to increase the electron vacancies on the surface of the oxygen carrier for the binding oxygen species, inhibiting methane overoxidation. We hope the promotion effect of plasma can be extended to enable more fuel conversion processes under mild conditions.
 

Plasma; Chemical looping oxidative coupling of methane; Oxygen carrier; Oxygen vacancy.