Nanosecond pulsed plasma assisted dry reforming of CH4: The effect of plasma operating parameters

Dry reforming is a promising approach to converting CH4 and CO2 (i.e., two common greenhouse gases) into clean fuels and valuable chemicals. Non-thermal plasma, acting as an alternative to the traditional reforming processes, achieves considerable gas conversion with low energy consumption under mild operating conditions. In this study, CH4 and CO2 were converted to syngas (i.e., H2 and CO) in a nanosecond pulsed dielectric barrier discharge plasma at a total gas flow rate of 50 sccm. Through evaluating the effects of electrical parameters on reforming performance, the experimental results showed that CH4 and CO2 conversions increased with the increase of pulse repetition frequency owing to the increased energy injection. Shorter rise and fall times resulted in better CH4 and CO2 conversions and higher energy conversion efficiencies, due to the rapid acceleration of electrons in a shorter discharge time. In the case where the optimal pulse peak width was 150 ns, the secondary discharge was improved because of the charge accumulation in the primary discharge, thereby increasing the CH4 and CO2 conversions. Among all experiments, when the pulse repetition frequency was 10 kHz and the discharge power was 55.7 W, the maximum conversions of CH4 and CO2 were 39.6% and 22.9%, respectively, while the total energy conversion efficiencies of the syngas and all detected products were 5.0% and 7.1%, respectively. Furthermore, an optical emission spectroscopy was used to characterize the active species formed during the reforming process.