Methane coupling in nanosecond pulsed plasmas: Correlation between temperature and pressure and effects on product selectivity

We present a zero-dimensional kinetic model to characterise specifically the gas-phase dynamics of methane conversion in a nanosecond pulsed discharge (NPD) plasma reactor. The model includes a systematic approach to capture the nanoscale power discharges and the rapid ensuing changes in electric field, gas and electron temperature, as well as species densities. The effects of gas temperature and reactor pressure on gas conversion and product selectivity are extensively investigated and validated against experimental work. We discuss the important reaction pathways and provide an analysis of the dynamics of the heating and cooling mechanisms. H radicals are found to be the most populous plasma species and they participate in hydrogenation and dehydrogenation reactions, which are the dominant recombination reactions leading to C2H4 and C2H2 as main products (depending on the pressure).

Automated summary

We propose a zero-dimensional kinetic model to study the gas-phase dynamics of methane conversion in a nanosecond pulsed discharge plasma reactor. The model accurately captures the rapid changes in electric field, gas and electron temperature, and species densities. By validating against experimental data, we investigate the effects of gas temperature and reactor pressure on gas conversion and product selectivity. Furthermore, we analyze the important reaction pathways and the dynamics of the heating and cooling mechanisms. H radicals are identified as the most abundant plasma species, participating in hydrogenation and dehydrogenation reactions that mainly lead to the formation of C2H4 and C2H2 as products (depending on the pressure).