Non-thermal plasma catalysis of methane: Principles, energy efficiency, and applications

The reaction mechanism and energy efficiency analysis of non-thermal plasma assisted methane conversion are presented. Plasma catalysis is an innovative next-generation green technology that satisfies needs for energy and materials conservation, and environmental protection. Non-thermal plasma uniquely generates reactive species almost independently of reaction temperature. Those species initiate chemical reactions at remarkably lower temperatures than conventional thermochemical reactions. Low-temperature methane conversion is important because it minimizes exergy destruction accompanied by combustion of the initial feed, or production of high-temperature thermal energy, necessary for thermochemical methane reform. Non-thermal plasma has great flexibility to tune the process parameters so that energy and material consumption are minimized. This article explains aspects of plasma-assisted fuel reforming including arc plasma to non-thermal plasma. We specifically examine dielectric barrier discharge (DBD) as viable non-thermal plasma for practical fuel reforming. Second, the energy efficiency of non-oxidative methane conversion using DBD is analyzed. That energy efficiency determined by experimentation was 1%, although theoretical analysis suggested 8%, implying that DBD alone is invariably more inefficient. Finally, DBD-catalysts hybrid reaction is proposed and a synergistic effect between plasma-generated reactive species and catalysts is clarified, suggesting that vibrationally excited species are important for enhancing overall methane conversion efficiency with catalysts.