Enhanced Oxidative Coupling of CH 4 to Olefins via CO 2 Assistance over Alkali Metal-Supported Perovskite

Methane oxidative coupling (OCM) based on the chemical-looping (CL) concept represents a promising pathway for the high-value upgrading of methane; however, commercialization is hindered by low olefin yields and deactivation of the oxygen carrier. In this study, we demonstrate that CO 2 assistance significantly improves the performance of Li 2 CO 3 -promoted perovskite oxygen carriers in CL-OCM. The methane conversion increases from 22.7% to 30% and C 2 selectivity increases from 50% to 89.6% when 10% of CO 2 was introduced, while maintaining stable performance over 50 consecutive cycles. The presence of CO 2 stabilizes the crystalline phase of the oxygen carrier. By maintaining the lattice oxygen concentration via a synergistic oxygen replenishment mechanism, the oxygen carrier achieves enhanced and durable catalytic activity. 13 C isotopic labeling experiments elucidate the conversion pathways of CH 4 and CO 2, and 18 O isotope tracing further confirms a surface lattice-oxygen exchange mechanism between CO 2 and the oxygen carrier. These findings provide a viable strategy for advancing the commercialization of OCM and enabling the efficient synergistic utilization of CH 4 and CO 2 .