Reaction Mechanisms of Aqueous Methane Reforming by Continuous Flow Two-Phase Plasma Discharge

This study explores nonthermal plasma reactions of methane and water in a two-phase system to produce methanol, examining reaction pathways, kinetics, and product distribution over time. The results show that methanol is the dominant liquid phase product among other oxygenates, including ethanol and acetic acid, with hydrogen as the largest fraction among gas-phase products comprising carbon monoxide, carbon dioxide, ethylene, and acetylene. Conductivity and pH trends of reactant water and their influence on reaction products were also analyzed. Methanol was found to be formed principally from the reactive coupling of methyl and hydroxyl radicals, as well as from methoxy and hydrogen radical combinations. Hydrogen was produced from three pathways: stepwise dehydrogenation of methane through electron-mediated hydrogen abstraction, sequential hydrogenation of ethane to acetylene, and water splitting. The methanol-yielding reactions proceeded at different rates in the liquid and gas phases, with gas-phase reactions occurring approximately nine times faster than the liquid-phase reactions. This work provides valuable insights into reaction pathways for direct methane conversion to oxygenates and value-added gas products under mild conditions using water as an environmentally friendly oxidant.