Recently, plasma catalysis has garnered significant interest as, through its use, the activation of thermodynamically stable reactants can be accomplished under milder conditions than with thermal catalysis. One of the areas where plasma catalysis bears the potential to bring significant improvements is the conversion of methane. The combination of plasma-enhanced C-H bond activation of light alkanes with recent advantages in natural gas production presents an attractive avenue for the valorization of an ubiquitous and affordable commodity. In this work, we computationally investigate the partial oxidation of methane (POM) and dry reforming of methane (DRM) reactions under thermal and selected plasma conditions. To this end, we have adapted an existing microkinetic model and linear scaling relationships for metallic catalysts to obtain reactivity and selectivity trends across a 2D descriptor space. The model was augmented with plasma-specific reaction events, for instance, the adsorption for radical species formed in the plasma phase. The required energy parameters were estimated from density functional theory. (DFT) We identified a number of favorable plasma conditions for which the product formation rate can be enhanced by several orders of magnitude for a wide range of descriptor pairs. These favorable conditions have in common that they pre-activate the strong C-H bond in methane and eliminate methane activation as rate limiting step and/or involve CHx radicals creating highly reactive intermediates. In contrast, the pre-activation of O2 or the formation of O radicals in the plasma tends to decrease the production rate and/or selectivity towards the desired products. Most interestingly, the volcano peaks for the desired products generated in the POM and DRM reactions are predicted to shift perpendicular to the trendline that connects pure metals in the descriptor space. This suggests that by simultaneously tuning plasma properties and catalyst composition it may be possible to design an efficient plasma-catalytic process for the economical upgrade of abundant natural gas.

Potential benefits of plasma-assisted catalysis on the partial oxidation and dry reforming of methane

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.