Study on the unsteady state oxidative coupling of methane: effects of oxygen species from O2, surface lattice oxygen, and CO2 on the C2+ selectivity.

ABSTRACT

This study examined the effects of oxygen species on the unsteady-state oxidative coupling of methane (OCM) using a lengthy catalyst bed of Na2WO4/Mn/SiO2. The reaction conditions, including the methane-to-oxygen ratio, ratio of feed gas dilution by N2, quantity of catalyst, and feed flow rate were adjusted for the continuous flow fixed bed reaction system. While the O2 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 CO2 as a mild oxidizing agent was also tested and slightly improved OCM selectivity with slightly lower methane conversion were observed.