Overcoming Thermodynamic Constraints on Product Yield in Plasma-Chemical Processes Using Selective Trapping of Volatile Intermediates

The yield of target molecules is limited by thermodynamic constraints in many plasma-chemical processes. This means that valuable products can be converted into undesired byproducts. Take direct methane to methanol (DMtM) conversion as one example. While producing methanol is favorable, the process ultimately yields CO and CO₂ due to their higher stability. This is a common challenge in many single-step plasma-chemical processes. In this work, we present a two-pronged approach to produce target products with high selectivity at high conversion, something that is constrained by unwanted target product conversion in many plasma-chemical processes. This work employs pulsed diffused discharges to vibrationally excite methane molecules, selectively steering the oxidation reaction pathways toward the formation of desired products. A product extraction strategy is then implemented to isolate these target molecules before they undergo further conversion. This approach bypasses thermodynamic limitations that typically restrict product yield by incorporating a different phase to extract products over timescales faster than they can be converted. We develop a zero-order pseudo-kinetic model to generalize this idea using production generation and product extraction timescales, while also demonstrating the scalability of product yield. Using this approach, we show a pathway to scalable total liquid oxygenate (i.e., methanol, ethanol, and acetic acid) yields at near room temperature and atmospheric pressure without catalysts for both partial oxidation of methane (CH₄ + O₂) and dry reforming of methane (CH₄ + CO₂).