Biphasic gas–liquid millifluidic system for carbon dioxide plasma chemistry: Application to controlled selective epoxidation

Abstract

The integration of nonthermal CO2 plasma for olefin epoxidation within a biphasic gas–liquid millifluidic system is presented. In this innovative approach, CO2 is efficiently reduced to CO and O atoms, facilitating the epoxidation of olefins. Analysis of the system’s effluent shows that epoxide production efficiency and yields, optimized to 90 %, significantly surpass those of traditional plasma methods, attributed to the enhanced gas–liquid mass transfer within the millifluidic environment. Moreover, O atoms generated from CO2 decomposition was observed to travel up to 30 mm in the post-plasma discharge area, enhancing the gas–liquid flow system’s efficiency. By capturing O atoms in the epoxidation reaction with olefins, the reverse reaction with CO is minimized, which in turn, markedly increases CO yield under the same conditions without olefins. These findings demonstrate that olefin epoxidation can be activated through CO2 plasma discharge in a controlled, selective, and catalyst-free manner under gentle conditions. This synergy between nonthermal plasma and millifluidic technologies paves the way for overcoming current limitations in plasma chemistry with industrial relevance.