Modular Plasma Microreactor for Intensified Hydrogen Peroxide Production

Sustainable and decentralized manufacturing of hydrogen peroxide (H2O2) has been extensively sought to replace the energy- and waste-intensive anthraquinone process. We introduce a helical biphasic microreactor in a coaxial dielectric barrier discharge (DBD) configuration as a modular, adaptable, and scalable intensified unit for H2O2 production. Geometric and operating parameters such as electrode length, applied voltage, and gas and liquid flow rates can be tuned to regulate the residence time, delivered power, and gas–liquid interfacial area. In turn, these affect the key output parameters, i.e., H2O2 concentration, production rate, and energy yield. We found a direct correlation between the H2O2 production rate and the product of the interfacial area and residence time in the plasma region. We investigated the H2O2 formation pathways using DMSO as an ·OH radical scavenger and found that H2O2 forms by the dissolution of gaseous H2O2 at low interfacial areas and is enhanced probably due to the interfacial recombination of ·OH radicals at a large gas–liquid interfacial area. The reactor temperature can also be externally controlled to intensify the production rate and energy yield of H2O2. Concentrations of up to 33 mM can be attained with a small footprint reactor that features a maximum energy yield of 4 g kWh–1. The plasma microreactor could epitomize a powerful process intensification tool for sustainable and distributed chemical manufacturing.