【Frontiers in HaiChuan Chemical Technology】Dalian Institute of Chemical Physics develops a single-atom catalyst for the highly selective oxidation of ethanol to glycolic acid

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Recently, a team led by researchers Ding Yunjie, Yan Li, and Song Xiangen from the Synthesis Gas Conversion and Fine Chemicals Catalysis Research Center (Group DNL0805) in the Department of Fossil Energy and Applied Catalysis at the Dalian Institute of Chemical Physics made new progress in the field of high-value conversion of ethanol. They developed a novel single-atom catalyst that enabled the highly selective and directed conversion of ethanol into glycol under mild conditions, and they also uncovered the water-mediated oxygen shuttle mechanism. As a usable biomass and platform molecule derived from coal chemical industry, ethanol holds potential for being converted into high-value chemicals. Glycolic acid (GA) is an important raw material for producing biodegradable materials; however, a reaction pathway for the direct oxidation of ethanol to produce glycolic acid has not yet been reported. Therefore, it is of great significance to develop efficient catalysts for the production of glycolic acid from ethanol. In this work, the researchers developed a controllable method for synthesizing single-atom catalysts: by adjusting the precursor treatment process, Rh single-atom catalysts coordinated with S/N/I on activated carbon were prepared (Rh1/AC-SNI400). Experimental results show that under the combined stimulation of 160°C, I2, and O2, this catalyst can directly oxidize ethanol to glycolic acid, with a target product selectivity of 93% and a turnover frequency (TOF) of approximately 251 h-1. Studies have found that the synergistic coordination effect of S/N/I enhances the electron delocalization around Rh, thereby reducing the energy barrier for substrate adsorption and the rate-determining step. The activated iodine radical seizes the β-C-H bond of ethanol, thereby preventing the formation of acetaldehyde as a byproduct. Through various in-situ characterizations, the researchers revealed a new water-mediated oxygen shuttle mechanism: •I and •OH radicals sequentially capture and insert into the C–H bonds of ethanol. Highly active •OH radicals can replace the existing OH groups in ethanol to form C=O bonds, thereby ensuring that all oxygen atoms in the glycolic acid products originate from water molecules. Meanwhile, O2 reacts with •I and H species to form HIO, which then decomposes into H2O and O2, completing the catalytic cycle. In recent years, the teams led by Yan Li and Ding Yunjie have been focusing on the research of single-atom catalysts for the selective low-temperature oxidation of low-carbon alkanes and their derivatives (Appl.Catal.B-Environ., 2021 ； Nat. Commun., 2024). Building on previous work, this study expands the research scope to the selective oxidation of low-carbon alcohols into high-value chemicals, providing new insights for the application of efficient single-atom catalysts.