CO2 reforming of CH4 by atmospheric pressure ac discharge plasmas

Partial oxidative reactions of methane by carbon dioxide have been studied using atmospheric pressure alternating current plasmas. The reactions were carried out using a Y-type reactor with metal rods as the inner electrodes inside quartz tubes and aluminum foil wrapped around quartz tubes as the ou ter electrodes. The waveforms, input voltages, and currents of the reaction s were monitored with an oscilloscope. Interactions between excited methane and excited carbon dioxide as well as those between one excited species an d the other unexcited species were observed. The products of the reactions include carbon monoxide, hydrogen, ethane, ethylene, propane, and acetylene . The effects of many reaction parameters, including input voltage, total f low rate, mole ratio of methane to carbon dioxide, selective excitation of either reactant, and micro-arc formation, on product distribution and energ y efficiency have been investigated. With an increase in the carbon dioxide -to-methane ratio the selectivity to carbon monoxide increased, and less co ke formed. Micro-arc formation between excited methane and excited carbon d ioxide increased the conversions of both methane and carbon dioxide and fav ored the production of carbon monoxide. The energy efficiency of the reacti on reached a maximum at CH4/CO2 = 1 with micro-are formation, but it was mi nimized at CH4/CO2 = 1 when no micro-arc formed during the reaction. The re action with micro-arc formation had a higher energy efficiency than that wi thout micro-arc formation. (C) 2000 Academic Press.