Numerical study on the reaction mechanism of CO2 hydrogenation in atmospheric-pressure dielectric barrier discharge.

Recently, the catalytic conversion of greenhouse gases by plasma technology has attracted more and more attention. In this paper, a two-dimensional fluid model is developed to study the reaction mechanism of plasma CO₂ hydrogenation in atmospheric-pressure dielectric barrier discharge (DBD). The effect of varying volume ratio of CO₂/H₂ on reaction mechanism of CO₂ hydrogenation is studied carefully, such as temporal and spatial density distributions of main radicals and ions, dynamics of streamer propagation, and generation and loss pathways of H, CO, and CH₃OH. It is found that H, O, and CO are the three most abundant species, and lower hydrogen content in gas mixture promotes streamer propagation and the formation of conduction current in plasma column. Besides, H is mainly produced by electron-impact dissociation of H₂ (e + H₂ ⇒ e + 2H); O and CO are dominantly produced by electron-impact dissociation of CO₂ (e + CO₂ ⇒ e + CO + O). Interestingly, H addition reaction to the intermediate species CH₃O (CH₃O + H<subscript />⇒ CH₃OH) is found to be the main reaction pathway for methanol formation. Finally, a schematic overview of dominant reaction pathways for plasma CO₂ hydrogenation in atmospheric DBD is presented, which ultimately leads to a better understanding of the intrinsic reaction mechanism. [ABSTRACT FROM AUTHOR]