The Chemistry of Plasma-Assisted Dry Reforming of Methane

Dry reforming of methane is a chemical process that converts two greenhouse gases, methane (CH₄) and carbon dioxide (CO₂), into a syngas mixture of carbon monoxide (CO) and hydrogen (H₂). Because low-temperature plasmas can initiate chemical conversion through the generation of charged species, radicals, and excited-state species, plasma-assisted reforming is considered a promising alternative to the conventional thermal catalytic reforming. In the present work, we studied the chemistry of plasma-assisted dry reforming of methane in a dielectric barrier discharge plasma flow reactor activated by a nanosecond repetitively pulsed discharge. Using molecular-beam mass spectrometry, which has a unique role in analyzing reactive gas mixtures, we measured the species pool formed in CH₄/CO₂ plasmas, including positive ions, radicals, and molecules. To trace the individual contributions of CH₄ and CO₂ to the observed products, we conducted experiments using isotopically labeled ¹³CO₂.  We found that CO₂ contributes to the formation of organic acids (formic acid, acetic acid, etc.). We combined our experimental work with the development of a kinetic model and, based on our experimental data and model analysis, we provide new kinetic insights into plasma-assisted dry reforming of methane.