Study on the unsteady state oxidative coupling of methane: effects of oxygen species from O 2 , surface lattice oxygen, and CO 2 on the C 2+ selectivity.

This study examined the effects of oxygen species on the unsteady-state oxidative coupling of methane (OCM) using a lengthy catalyst bed of Na 2 WO 4 /Mn/SiO 2 . The reaction conditions, including the methane-to-oxygen ratio, ratio of feed gas dilution by N 2 , quantity of catalyst, and feed flow rate were adjusted for the continuous flow fixed bed reaction system. While the O 2 gas initiated methyl radical formation from methane, the surface lattice oxygen atoms improved the dehydrogenation of paraffins to olefins without significant activation of methane. The addition of CO 2 as a mild oxidizing agent was also tested and slightly improved OCM selectivity with slightly lower methane conversion were observed.