Hydrogen and Solid Carbon Production via Methane Pyrolysis in a Rotating Gliding Arc Plasma Reactor.

Plasma-induced methane pyrolysis is a promising hydrogen production method. However, few studies have focused the decomposition of pure methane as a discharge gas. Herein, a rotating gliding arc reactor was used for the conversion of methane (discharge gas and feedstock) into hydrogen and solid carbon. Methane conversion, gaseous product selectivity, and energy usage efficiency(specific energy requirement for hydrogen production(SER)) were investigated as functions of operating parameters, e.g., specific energy input(SEI), residence time, and reactor design. SEI was positively(almost linearly) correlated with methane conversion and hydrogen yield and negatively correlated with SER. Conversion and efficiency of energy usage increased when reactor designs providing higher thermal densities were used. With the increasing flow rate of methane at constant SEI, the reaction volume and, hence, the residence time of the gas inside the reaction zone increased, which resulted in methane conversion and hydrogen selectivity enhancement. The solid carbon featured four distinct domains, namely graphitic carbon, turbostratic carbon, few-layer graphene, and amorphous carbon, which indicated a nonuniform temperature distribution in the reaction zone. But it seems that graphitic carbon dominates amorhphous one. This study highlights the potential of rotating gliding arc plasma systems for efficient methane conversion into hydrogen and valuable solid carbon products.