Plasma-Assisted Partial Oxidation of Methane to Methanol Using Water

Methanol (CH₃OH) is an important precursor for chemicals and fuels that is industrially synthesized from methane (CH₄) in a multi-step, highly energy-intensive process. There is interest in improving the conversion process, ultimately towards direct partial oxidation. Non-thermal plasma catalysis offers an electrified, single-step conversion route for CH₃OH synthesis. This work explores the conversion of CH₄ to CH₃OH in atmospheric pressure plasma catalytic systems with a water vapor (H₂O) oxidant source. Non-thermal plasma can activate CH₄ and H₂O molecules to generate radical species such as CH₃• and •OH, which are key intermediates for CH₃OH synthesis. However, the plasma also facilitates a complex network of side reactions, leading to the formation of undesired hydrocarbons (e.g., C₂H₆) and oxygenates (e.g., HCHO), reducing CH₃OH selectivity. To enhance CH₃OH yield, we hypothesize that bifunctional catalysts (such as metal-acid systems) can promote selective C–H bond activation of CH₄ to favor CH₃• formation and thus CH₃OH. Metal sites (e.g., Pt) can lower activation barriers for C–H cleavage, while acid sites (TiO₂) stabilize surface intermediates and suppress deep oxidation or C–C coupling pathways.