Control of methane plasma oxidative pathways by altering the contribution of oxygen species

Abstract

The methane oxidation process has attracted great research attention in recent years because of its vital role in chemical synthesis and hydrocarbon fuels combustion. Here we demonstrate three kinds of methane plasma oxidative pathways including selective oxidation to H2O2 and organic oxygenates, oxidative coupling of methane to C2 hydrocarbons, partial oxidation of methane to synthesis gas, respectively, can be strengthened by altering the contribution of oxygen species. Based on the diagnosis results of optical emission spectra and the kinetic data of combustion modeling, it can be deduced that the reaction of O(1D) + CH4 → OH + CH3 plays a key role for plasma promoted methane conversion, on the other hand, the ground state of O leads to synthesis gas production through the reaction of O with CH3 and CH2. We believe our discovery may be of a general nature for methane plasma oxidation and can enlighten for understanding the plasma oxidation and combustion chemistry.