Epoxidation of trans-stilbene in a microfluidic plasma reactor

•Epoxidation reaction at the gas-liquid interface of microbubbles using gas plasma.•Microfluidic plasma reactor for the generation of highly reactive oxygen species.•Operating strategy to improve overall epoxide yield and selectivity. Novel organic synthesis routes that circumvent the need for a catalyst and reduce unwanted by-products are highly sought by industry. A novel microfluidic plasma reactor that generates a dielectric barrier discharge (DBD) plasma in the vicinity of the gas-liquid interface and facilitate a chemical reaction at the interface of microbubbles has been used for trans-stilbene epoxidation. Three different operating strategies were implemented to optimise the transfer of species selectivity: single pass, multi-pass and continuous recirculation. The effect of initial trans-stilbene concentration, oxygen content in the feed gas mixture and reaction time on the epoxide formation was studied to optimise the chemical reaction. The optimum operating conditions were found to be short bubble-liquid contact times (~2 s) with frequent exposure to freshly generated microbubbles containing reactive species by continuous liquid recirculation, and under these conditions the overall epoxide yield was ~94% with an overall epoxide selectivity of 10:1.