Influence of Pulse Repetition Frequency on CH₄ Dry Reforming by Nanosecond Pulsed Dielectric Barrier Discharges

In this paper, the effect of pulse repetition frequency (PRF) on CH4 dry reforming by nanosecond pulsed dielectric barrier discharge (DBD) is evaluated by a zero-dimensional (0D) chemical kinetics model. The calculated conversions and product yields agree well with the reported experimentally measured results. The simulation results indicate that the vibrationally excited CH4 and CO2 molecules have negligible contributions to the CH4 and CO2 conversions with PRF from 3 to 100 kHz. However, their role in the CH4 and CO2 conversions increases due to accumulation with 1 MHz PRF. The relaxation time of CH4(nu(24)) is considered to be around 1 mu s, and the relaxation time of CH4(nu(13)) and CH4(e) is in the range of several hundred ns. The relaxation time of CO2 vibrationally excited states is between 1 mu s and 10 mu s, and the relaxation time of CO2 electronically excited state is within tens of ns. The increase in PRF promotes CO2 and CH4 conversions, with growth rates of CO and H-2 yields much greater than that of C2H6 and C3H8 yields. As the PRF increases from 3 to 10 kHz, the production of CO and H-2 is mainly caused by the electron impact dissociations of CO2 and CH4, respectively. Inversely, the major hydrocarbon products, C2H6 and C3H8, are primarily produced via reactions among neutral species and consumed via electron impact dissociation reactions. This phenomenon suggests that the promotion of PRF on electron impact reactions is much greater than its benefits in reactions between neutral species.