Methane conversion and reforming by nonthermal plasma on pins

Nonthermal plasma on pins means nonthermal or nonequilibrium plasmas produced between two pin electrodes, pin-to-plane, or multipin configurations working at atmospheric pressure. In this paper, it is shown that nonthermal plasma on pins can produce not only the corona discharges but also the homogeneous glow discharge and pseudo glow discharge by using a 1-2 kHz ac power supply. The electrode configurations and input power control the amplitude and duration of the discharge current pulses. It is found that the discharge conditions determined the product selectivity in direct nonoxidative methane conversion, The glow discharge produces acetylene, ethylene, and ethane in approximately equal quantities, while the corona discharge is mainly selective to acetylene. In the pseudo glow discharge, the product distribution can be controlled by the specific energy input. With lower specific energy input, the product distribution is almost the same as that in glow discharge, while with higher specific energy input, it is mainly selective to acetylene. Pseudo glow discharges have been studied for the CO2 reforming of methane to synthesis gas. With one pair of pins and 60-70 kJ/L specific energy input, CH4 and CO2 conversions were higher than 70% and 60%, respectively. The H-2/CO ratio could be controlled and depended on the concentration of CO2 in the feed gas. No carbon or soot formation was detected in the Co-2-rich feed (CO2 content > 50%).