Oxidative Coupling of Methane: Examining the Inactivity of the MnO -Na WO /SiO Catalyst at Low Temperature.

Oxidative coupling of methane (OCM) catalyzed by MnO -Na WO /SiO has great industrial promise to convert methane directly to C products, but its high light-off temperature is the most challenging obstacle to commercialization and its working mechanism is still a mystery. We report the discovery of a low-temperature active and selective MnO -Na WO /SiO catalyst enriched with Q units in the SiO carrier, being capable of converting 23 % CH with 72 % C selectivity at 660 °C. From experiments and theoretical calculations, a large number of Q units in the MnO -Na WO /SiO catalyst is a trigger for markedly lowering the light-off temperature of the Mn ↔Mn redox cycle involved in the OCM reaction because of the easy formation of MnSiO . Notably, the MnSiO formation proceeds merely through the SiO -involved reaction in the presence of Na WO : Mn SiO +6 SiO ↔7 MnSiO +1.5 O . The Na WO not only drives the light-off of this cycle but also gets it working with substantial selectivity toward C products. Our findings shine a light on the rational design of more advanced MnO -Na WO based OCM catalysts through establishing new Mn ↔Mn redox cycles with lowered light-off temperature.