Plasma-Assisted Dry Reforming of CH4: How Small Amounts of O2 Addition Can Drastically Enhance the Oxygenate Production─Experiments and Insights from Plasma Chemical Kinetics Modeling

Plasma-based dry reforming of methane (DRM) into high-value-added oxygenates is an appealing approach to enable otherwise thermodynamically unfavorable chemical reactions at ambient pressure and near room temperature. However, it suffers from coke deposition due to the deep decomposition of CH4. In this work, we assess the DRM performance upon O2 addition, as well as varying temperature, CO2/CH4 ratio, discharge power, and gas residence time, for optimizing oxygenate production. By adding O2, the main products can be shifted from syngas (CO + H2) toward oxygenates. Chemical kinetics modeling shows that the improved oxygenate production is due to the increased concentration of oxygen-containing radicals, e.g., O, OH, and HO2, formed by electron impact dissociation [e + O2 → e + O + O/O(1D)] and subsequent reactions with H atoms. Our study reveals the crucial role of oxygen-coupling in DRM aimed at oxygenates, providing practical solutions to suppress carbon deposition and at the same time enhance the oxygenates production in plasma-assisted DRM.