Modular Plasma Microreactor for Intensified Hydrogen Peroxide Production

Abstract

Sustainable and decentralized manufacturing of hydrogen peroxide (H 2 O 2 ) 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 H 2 O 2 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., H 2 O 2 concentration, production rate, and energy yield. We found a direct correlation between the H 2 O 2 production rate and the product of the interfacial area and residence time in the plasma region. We investigated the H 2 O 2 formation pathways using DMSO as an •OH radical scavenger and found that H 2 O 2 forms by the dissolution of gaseous H 2 O 2 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 H 2 O 2 . 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.

Microflow chemistry and its electrification for sustainable chemical manufacturing

“…Recirculation and short bubble-liquid contact times; 33% conversion and 94% epoxide selectivity DI water oxidation 310 Helical microreactor in coaxial dielectric barrier discharge (DBD) conguration, liquid ow 0.2 ml min À1 , He ow 320 ml min À1…”

“…17 ). 310 We applied our set-up to the continuous production of highly concentrated hydrogen peroxide (H 2 O 2 ) in a He plasma in contact with de-ionized water. The high gas/liquid flow ratio provided high interfacial area, combined with control of the residence time (by adjusting the gas flow rate and reactor geometry independently) and efficient heating, led to H 2 O 2 concentrations >25 mM without compromising production rate (∼0.1 μmol s −1 ) and energy yield (∼4 g kW −1 h −1 ).…”

Plasma-Induced Selective Propylene Epoxidation Using Water as the Oxygen Source

“…It has been demonstrated recently that H 2 O 2 can be formed with relatively high efficiencies from water at plasma–water interfaces in PLI systems. − Herein, we designed a PLI system that uses this plasma-generated H 2 O 2 to epoxidize C 3 H 6 with very high PO selectivity in excess of 98%. The PLI process employed titanium silicate-1 (TS-1) catalysts dispersed in the water solution designed to contact the in situ produced H 2 O 2 with dissolved C 3 H 6 .…”

“…Reaction pathways of the H 2 O 2 generation at the DC plasma cathode/water anode interface. , H 2 O* refers to the excited water.…”

“…For example, it has been shown that higher energy free electrons formed under an increased applied voltage are expected to result in higher OH· and H 2 O 2 formation rates . Similarly, increasing the flow rates of the plasma-carrying He gas should result in an increase in plasma–liquid interfacial area, enabling more efficient mass transfer of plasma-generated H 2 O 2 . Led by these insights, we analyzed the impact of plasma voltage and He flow rate on the rate of total PO production (detected from both the liquid and gas phases) and its selectivity (Figure ).…”