Nonthermal plasmas (NTP) offer a potential opportunity to electrify ethane dehydrogenation (EDH) to ethylene. In this work, we explore the boundaries of ethylene selectivity and energy efficiency in NTP-driven EDH, considering known ethane plasma chemistry and potential plasma reactor operating modes. To conduct this exploration, we used ZDPlasKin, a zero-dimensional plasma-kinetic modeling software, and reaction mechanisms from literature; we validated the chemistry in the model by comparing to plasma-only experimental measurements of ethane conversion and product selectivity. Rate analysis, calculated at typical conditions in a batch reactor model, revealed that higher ethylene selectivity arises from a balance between promoting ethane conversion and limiting ethylene destruction. This balance captures the interplay of electronic and thermal reactions and the role of highly-active radicals produced by the plasma. We also analyzed energy information and found that peak energy efficiency occurs at low radical density, due to lower rates of exothermic recombination reactions. The use of nanosecond-pulsed plasma has been suggested in literature to promote ethylene production and improve energy efficiency. Thus, we developed a specialized, pulsed-plasma reactor model to explore the underlying mechanisms that capitalize on high efficiency regimes. This model can simulate more realistic operating conditions and degrees of freedom, including pulsing frequency, discharge duration, and plasma volume fraction. By testing a variety of conditions, we found that higher ethylene selectivity is achieved at low-frequency regimes, where short durations of high reduced-electric-field promote ethylene formation while minimizing subsequent reactions. Interestingly, energy efficiency is not diminished in high-frequency regimes, as a result of the plasma accessing high efficiency during each pulse. The model results highlight that pulsed operation, with pulsing frequencies matched to high-efficiency segments of the plasma chemistry, enables control over time in plasma and therefore improved selectivity control, offering a pathway to improved reactor design.
