Modelling excited species and their role on kinetic pathways in the non-oxidative coupling of methane by dielectric barrier discharge

A detailed kinetic scheme for non-thermal methane plasma is developed that considers the reactivity and relaxation of electronically and vibrationally excited species. An atmospheric pressure dielectric barrier discharge reactor for methane non-oxidative coupling is modelled. Via 1D fluid modelling short periods of time are investigated, while for longer periods of time, on the order of the reactor residence time, a combined 1D-0D approach is followed. Modelling results are in good qualitative agreement with literature experiments. Around 86% of the energy input is found to channel into the creation of excited species. The vibrationally excited states of methane exhibit very transient responses due to their rapid formation during electron streamers and fast quenching by VV and VT processes. The, higher energy, electronically excited states are rapidly converted, many of which essentially instantly dissociate. Over 70% of methane’s conversion proceeds via electronical excitation, while the contribution of vibrationally excited states is limited.