Unexpected activity of MgO catalysts in oxidative coupling of methane: Effects of Ca-promoter

Abstract Unexpectedly, we founded very different catalytic activities of MgO in oxidative coupling of methane (OCM) depending on company that supplied the precursors, which was due to the Ca-related impurities. Accordingly, we investigated the effects of Ca-promoter on the catalytic activity of MgO catalysts. Substituting Ca into the MgO catalysts strongly influenced both the formation of oxygen vacancies and the base properties of surface lattice oxygen (Olat), which are key factors in this reaction. The formed oxygen vacancies resulted in high methane conversion through the facile conversion of methane to methyl radical, whereas Olat with medium basicity played an important role in producing ethylene through the facile dehydrogenation of ethane.