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

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.