Converting ethane with CO2 to produce value-added oxygenated hydrocarbons is an attractive opportunity to upgrade underutilized ethane while simultaneously reducing atmospheric CO2 concentrations. Currently, the production of alcohols, aldehydes, and acids from ethane involves either multistep, high-pressure heterogeneous catalysis processes or homogeneous catalytic reactions that entail significant product separation challenges. One-step conversion of ethane and CO2 to oxygenates is not thermodynamically feasible under mild conditions and has not been previously achieved as a one-step process. To circumvent thermodynamic limitations, nonequilibrium plasma may be employed to overcome the activation barriers of the reaction while maintaining the reactant gases near room temperature. Furthermore, modular plasma-activated reactions are more easily adaptable to renewable electricity and small-scale CO2 capture than are large-scale thermally activated processes. Nonthermal plasma was used to demonstrate one-step production of alcohols, aldehydes, and acids as well as C1–C5+ hydrocarbons under ambient pressure, with a maximum total oxygenate selectivity of 12%. The effects of plasma power, feed gas ratio, and catalyst addition on activity and selectivity were investigated in an atmospheric pressure flow reactor based on time-on-stream results. Isotope-labeling experiments were combined with a plasma chemical kinetic model to reveal the reaction pathways. The reaction proceeded primarily via oxidation of activated ethane derivatives by CO2-derived oxygen-containing species, demonstrating a mechanism that is fundamentally different from thermocatalytic alcohol synthesis. Results from this study illustrate the potential to use plasma for the direct synthesis of value-added alcohols, acids, and aldehydes from the greenhouse gas CO2 and underutilized ethane under ambient pressure.

Oxygenate production from plasma-activated reaction of CO2 and ethane

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