Chemical looping oxidative coupling of methane (CLOCM) is a promising process for direct methane conversion to C 2 products. Under the chemical looping approach, the oxygen carrier that provides lattice oxygen, in place of molecular oxygen, is used for methane oxidation. This study performs redox experiments that probe the C 2 selectivity enhancement properties of a Mg−Mn composite oxygen carrier through the use of a low concentration of Li dopant. It was found that the C 2 selectivity of the Li-doped oxygen carrier in CLOCM is universally higher than that of the undoped Mg 6 MnO 8 oxygen carrier with a maximum improvement in selectivity of ∼50% . Density functional theory simulation reveals that the Li dopant has a short-range effect on the formation of oxygen vacancies. The Li-doping-induced oxygen vacancy reduces the adsorption energy of methyl radicals and increases the C−H activation barrier. These findings provide a catalytic dopant screening strategy for CLOCM, which will substantially enhance the C 2 selectivity with desired oxygen carrier recyclability.

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Directly upgrading natural gas is limited by the stability of its primary component, methane, and process economics. Since the 1980s, oxidative coupling of methane (OCM) has shown potential to produce ethylene and ethane (C2s). The typical OCM approach catalytically converts methane to C2 products using molecular oxygen, reducing process efficiency. To overcome this, chemical looping OCM converts methane to hydrocarbons via intermediate oxygen carriers rather than gaseous cofed oxidants. The chemical looping approach for OCM has been studied mechanistically for the first time with a Mn–Mg-based catalytic oxygen carrier (COC). The COC delivered stable performance in a fixed bed for 100 cycles for more than 50 h with a 63.2% C2 selectivity and 23.2% yield. These experimental results and original process simulations of an OCM chemical looping system for C2 or liquid fuel production with electricity cogeneration present a direct method for methane utilization.

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