Avoiding solid carbon deposition in plasma-based dry reforming of methane

Abstract

Solid carbon deposition is a persistent challenge in dry reforming of methane (DRM), affecting both classical and plasma-based processes. In this work, we use a microwave plasma in reverse vortex flow configuration to overcome this issue in CO₂/CH₄ plasmas. Indeed, this configuration efficiently mitigates carbon deposition, enabling operation even with pure CH₄ feed gas, in contrast to other configurations. At the same time, high reactor performance is achieved, with CO₂ and CH₄ conversions reaching 33% and 44% respectively, at an energy cost of 14 kJ L⁻¹ for a CO₂ : CH₄ ratio of 1 : 1. Laser scattering and optical emission imaging demonstrate that the shorter residence time in reverse vortex flow lowers the gas temperature in the discharge, facilitating a shift from full to partial CH₄ pyrolysis. This underscores the pivotal role of flow configuration in directing process selectivity, a crucial factor in complex chemistries like CO₂/CH₄ mixtures and very important for industrial applications.