Reforming of Methane and Carbon Dioxide to C ₂ Hydrocarbons in Microwave Plasma at Atmosphere Pressure

A stable argon plasma at atmospheric pressure can be generated easily with irradiation of a low power of microwave (MW) to promotors like granules of activated carbon, biomass char, electrically conductive media, etc. It is well-known that plasma can contribute to significant activity of reactions. The reforming reaction of methane with carbon dioxide was studied in MW plasma at atmospheric pressure. Low power MW plasma converted methane and carbon dioxide into C2 hydrocarbons like ethylene and acetylene, carbon monoxide, and hydrogen. The effects of power supply, CH4/CO2 ratios, and total flow rate were studied on reforming of CH4 and CO2 in MW plasma at low power conditions. The results showed that increasing power facilitates the decomposition of CH4 and CO2, thereby enlarges the yield of each product. However, high power supply has a negative impact on the selectivity of C2. Higher CH4/CO2 ratio can effectively increase C2 selectivity, although it will reduce CH4 conversion. Longer the reaction time or lower gas flow rate reduces the selectivity of C2, while the high flow rate effectively avoids the re-decomposition of C2 products in the plasma region. Furthermore, it was recognized that an existence of CO2 contributes to activation of methane decomposition in MW plasma as well as the plasma contributes to significantly greater synthesis of C2 hydrocarbons than the yield predicted from the composition in the thermodynamic equilibrium.