Base-Free Oxidative Esterification of 1,2-Propanediol to Methyl Lactate Over Au/CuO

The selective and sustainable production of methyl lactate from biomass-derived polyols remains a significant challenge due to the frequent requirement of homogeneous bases. Herein, an integrated Au/CuO catalyst is reported for the base-free oxidative esterification of 1,2-propanediol to methyl lactate. The Au/CuO catalyst exhibits superior catalytic performance compared with Au supported on other oxides, affording high conversion and selectivity under optimized conditions. Systematic studies reveal that moderate Au loading and reaction conditions are crucial for suppressing over-oxidation and C-C bond cleavage. Mechanistic investigations suggest that the reaction proceeds via parallel oxidation pathways involving both primary and secondary hydroxyl groups, while the Au-CuO interface plays a key role in regulating intermediate oxidation and stabilizing methyl lactate. This work highlights the importance of metal-oxide interfacial effects in base-free oxidative esterification and provides a sustainable route for methyl lactate production from renewable polyols. Graphical