Entanglement of CH4 and CO2 Chemistries in Plasma-Assisted Dry Reforming of Methane.

Abstract

Plasma-assisted dry reforming of methane converts methane (CH₄) and carbon dioxide (CO₂) into valuable chemicals. To gain further chemical kinetic insights into this process, laboratory-scale experiments is combined using isotopically labeled ¹³CO₂ with detailed chemical modeling. In the experiments, an atmospheric-pressure coaxial dielectric barrier discharge plasma reactor attached to a molecular-beam mass spectrometer is used to detect reaction products from a feed mixture containing equal amounts of CH₄ and CO₂. The experiments confirm that the formation of the observed hydrocarbons is clearly related to the CH₄ chemistry and that the detected double-oxygenated C₂H₄O₂, C₃H₆O₂, and C₄H₈O₂ species can partially be traced back to the CO₂ chemistry. To provide further insights, the chemistry mechanism from the earlier work (Proc. Combust. Inst., 2024, 40, 105404) is expanded to include the formation chemistry of these double-oxygenated products. The updated mechanism predicts the formation of both acids and esters, for example, acetic acid (CH₃COOH) and methyl formate [HC(=O)OCH₃] for the C₂H₄O₂ species. According to the reaction path analysis, the products are formed through the COOH radical that itself stems from the CO+OH reaction, with the CO being partially formed from plasma-initiated CO₂ dissociation.