Stable kilohertz spark discharges for high-efficiency conversion of methane to hydrogen and acetylene

Stable kilohertz spark discharges with a unique waveform of discharge current were studied for high-efficiency conversion of methane to hydrogen and acetylene at atmospheric pressure for the first time. Discharge stability was confirmed by the concentration variation in the product streams with 220 min discharge time using pure methane as the feed gas. Utilizing the stable kilohertz spark discharges, the hydrogen concentration in the product stream could be as high as 72.1 vol% at an energy cost of 6.7 eV per H-2 molecule produced and 81.5% of methane conversion. The acetylene concentration could reach 18.4 vol% at an energy cost of 21.2 eV per C2H2 molecule produced and 70.3% of methane conversion. For methane conversion ranging from 51.9% to 81.5%, the energy costs were 6.6-10.7 eV per CH4 molecule converted, 4.4-6.7 eV per H-2 molecule produced and 16.9-27.6 eV per C2H2 molecule produced. This study showed the high-concentration production of COx-free hydrogen and acetylene from methane at a low energy cost by stable kilohertz spark discharges.