The Role of\nCH<sub>4</sub> in Plasma-Assisted CO<sub>2</sub> and CH<sub>4</sub> Conversion in a Rotating Gliding Arc Plasma:\nInsights Revealed by Experiments and Modeling

We investigated the combined conversion of CO<sub>2</sub> and CH<sub>4</sub>, so-called dry reforming of methane (DRM), in\na rotating\ngliding arc (RGA) reactor by experiments and modeling for different\nCO<sub>2</sub>/CH<sub>4</sub> mixing ratios. We obtained the best\nresults at the lowest flow rate (4 L/min) and the lowest amount of\nCH<sub>4</sub> in the feed gas mixture (25%), reaching a conversion\nof 22% and 39% for CO<sub>2</sub> and CH<sub>4</sub>, respectively,\nan energy efficiency of 62% and energy cost of 3.25 eV/molecule. A\nlower energy cost of 2.65 eV/molecule was obtained at 8 L/min. By\nmeans of a 3D computational fluid dynamics model, we show that the\naddition of CH<sub>4</sub> reduces the gas temperature inside the\nplasma, resulting in slower chemical kinetics, explaining why the\nleast amount of CH<sub>4</sub> (i.e., 25/75 CH<sub>4</sub>/CO<sub>2</sub>) yields the highest CO<sub>2</sub> and CH<sub>4</sub> conversion.\nAdditionally, the 25/75 CH<sub>4</sub>/CO<sub>2</sub> mixture also\ndisplays the highest energy efficiency, due to the high conversion,\nas well as due the high CO concentration produced in this gas mixture,\nwhich is the most beneficial product in terms of energy efficiency.\nFinally, by means of a quasi-1D chemical kinetics model, we demonstrate\nthat the addition of CH<sub>4</sub> suppresses the CO recombination\nreactions back into CO<sub>2</sub>, after the plasma, as H-based radicals\nfrom CH<sub>4</sub> quickly react with O radicals that would otherwise\nrecombine with CO.