Catalytic synthesis of hydrogen peroxide in microreactors

The direct synthesis of hydrogen peroxide from hydrogen and oxygen was investigated using capillary and stacked microreactors in which the silicone wall of a microchannel had been coated with Pd/C catalyst. To make the H2O2 production system compact, a flow-through solid polymer electrolyte (SPE) electrolyzer, which was used for the H2- and O2-feeds instead of gas cylinders, was connected to the microreactor. The influence of the gas and liquid flow rates and of the reaction temperature on H2O2 production was investigated to identify the optimal operating conditions for the stacked microreactor. In the previous study [Kusakabe, K., Kawaguchi, K., Maehara, S. and Taneda, M., 2007, Direct formation of hydrogen peroxide over palladium catalyst based on water electrolysis, J Chem Eng Jpn, 40: 523–528], direct synthesis of H2O2 over Pd/C catalyst was performed using a slurry batch reactor with two sheets of electrode for H2 and O2 evolution. The maximum H2O2 concentration of 3.4 × 10−3 mol/L was attained after a 3-h reaction. In this study, a H2O2 concentration of 8.3 × 10−3 mol/L was obtained at 10 °C in a 0.1 mol/L solution of HCl at the residence time of 93 s in the stacked microreactor. In addition, H2O2 was successfully produced when pure water was used as the reaction liquid with H2 and O2 in the stacked microreactor.