Methane conversion to C2 hydrocarbons and hydrogen in atmospheric non-thermal plasmas generated by different electric discharge techniques

Methane conversion to C2 hydrocarbons and hydrogen has been investigated in a needle-to-plate reactor by pulsed streamer and pulsed spark discharges and in a wire-to-cylinder dielectric barrier discharge (DBD) reactor by pulsed DC DBD and AC DBD at atmospheric pressure and ambient temperature. In the former two electric discharge processes, acetylene is the dominating C2 products. Pulsed spark discharges gives the highest acetylene yield (54%) and H2 yield (51%) with 69% of methane conversion in a pure methane system and at 10 SCCM of flow rate and 12 W of discharge power. In the two DBD processes, ethane is the major C2 products and pulsed DC DBD provides the highest ethane yield. Of the four electric discharge techniques, ethylene yield is less than 2%. Energy costs for methane conversion, acetylene or ethane (for DBD processes) formation, and H2 formation increase with methane conversion percentage, and were found to be: in pulsed spark discharges (methane conversion 18‐69%), 14‐25, 35‐65 and 10‐17 eV/molecule; in pulsed streamer discharges (methane conversion 19‐41%), 17‐21, 38‐59, and 12‐19 eV/molecule; in pulsed DBD (methane conversion 6‐13%), 38‐57, 137‐227 and 47‐75 eV/ molecule; in AC DBD (methane conversion 5‐8%), 116‐175, 446‐637, and 151‐205 eV/molecule, respectively. The immersion of the gAl2O3 pellets in the pulsed streamer discharges, or in the pulsed DC DBD, or in the AC DBD has a positive effect on increasing methane conversion and C2 yield. # 2004 Elsevier B.V. All rights reserved.