Optimization of Nonthermal Plasma (NTP) Catalytic CO2 Methanation: The effect of excitation waveform, pellet size and residence time

Abstract

Nonthermal plasma (NTP) catalysis is a promising electrified catalytic technology for many sustainable applications, such as energy storage and decarbonization reactions, in the scenarios powered by renewable energy (via green electricity). Dielectric barrier discharge (DBD) plasmas, commonly driven by sinusoidal waveform, are widely employed by NTP catalytic research. However, the energy efficiency of such DBDs is relatively low due to various reasons such as excessive capacitive currents and poor selectivity. Here this study investigates the impact of plasma excitation waveforms, catalyst pellet sizes and residence time on the performance of NTP catalytic CO2 methanation over a Ni/MgAlOx catalyst. Especially, the critical role of discharge waveform in optimizing the DBD NTP catalytic system was systematically explored. The findings demonstrate the advantages of multi-pulse waveform of minimizing capacitive losses, delivering higher energy per discharge event and sustaining energy interactions over extended durations, which mitigate the affect incurred by changing the other process parameters of pellet size and residence time (across the conditions investigated here). As a result, our DBD system (by multi-pulse wave excitation, with 710–900 μm catalyst pellets and ~25 mm bed length) achieved a very high CH4 yield (~72.3%) at significantly lower volumetric power densities (~7 W/cm3).