Sustainable and Continuous Flow Preparation of High-Concentration H<sub>2</sub>O<sub>2</sub> by Visible-Light-Activated Molecular Oxygen Oxidation of Lower Alcohols
Zongyi Yu, Jingnan Zhao, Yufeng Wu, Lixiang Guo, Cunfei Ma, Hongfei Zhu, Jianing Li, Liyuan Duan, Zunchao Liu, Huinan Sun, Guofeng Zhao, Qingwei Meng
Abstract
H 2 O 2 is a multifunctional green oxidant, and the preparation of H 2 O 2 by photocatalysis is a kind of green and efficient method; however, the production of terminal H 2 O 2 with a high concentration of up to 10 mmol·g –1 ·h –1 under visible light irradiation is a challenge. With this objective, herein, we report a strategy for the homogeneous visible light photocatalytic preparation of H 2 O 2 via the HAT (hydrogen atom transfer) process using commercially available 2-ethylanthraquinone (EAQ) as the photocatalyst. Even under intermittent conditions, the H 2 O 2 generation rate could reach up to 323.32 mM/h (526.6 mmol·g –1 ·h –1 ), which represents the fastest photochemical H 2 O 2 production reaction reported. The continuous flow strategy could significantly improve the yield of H 2 O 2 by 91 times to ∼29460 mM/h. A liquid–liquid extraction device that connects with the flow reactor could realize the continuous separation of H 2 O 2 in aqueous solution of up to 11.1 wt % in 1 h with a lower EAQ loading of 0.2–0.3 mol % (∼6.2–9.3 g/L). Compared with the AO method, EAQ efficiency is significantly elevated by 10–20 times in this continuous flow photocatalysis strategy.