Simultaneous conversion of carbon dioxide and methane using thermal plasma

This study presents the thermal plasma-based process for the simultaneous conversion of carbon dioxide (CO₂) and methane (CH₄), targeting the production of hydrogen (H 2 ) and value-added solid carbon without catalysts. The triple thermal plasma torch system was employed, enabling direct injection of process gases into the high-temperature plasma zone. Three different gas injection configurations were tested: simultaneous CO₂ and CH₄ injection through the co-flow injection nozzle, and separate injections through the co-flow and counter-flow injection nozzles. Simultaneous co-flow injection achieved CO 2 and CH 4 conversion rates of approximately 96.5% and 98.8%, respectively, with H 2 and CO selectivities of 87.2% and 77.3%, respectively. The corresponding specific energy requirement for H 2 production was 159.74 kWh/kg-H 2 . The recovered-carbon yields were 1.55% and 4.66% under conditions 2 and 3, respectively, relative to the total carbon supplied in CH 4 and CO 2 . Carbon flakes with a layered structure were obtained when CH₄ was injected via the co-flow nozzle and CO₂ via the counter-flow nozzle, as characterized by Raman spectroscopy and TEM analysis. Conversely, carbon black-like material was obtained when CO₂ was injected through the co-flow nozzle and CH₄ through the counter-flow nozzle. These results highlight the influence of process gas injection configuration on gaseous product performance, solid carbon recovery, and recovered carbon structure.