A novel approach for 1,2-propylene glycol production from biomass-derived lactic acid

• Efficient hydrothermal conversion of lactic acid to 1,2-propylene glycol over CuO was reported.
• The use of CuO promoted 1,2-propylene glycol production from lactic acid with high selectivity and high yield.
• In situ formed hydrogen by the oxidation of Zn in water is effective for the transformation than added gases hydrogen.

A novel and efficient process for the production of 1,2-propylene glycol with high productivity and high selectivity from biomass-derived lactic acid over CuO was investigated. As a result, CuO exhibited a high catalytic activity while Zn acted as a reductant for the conversion of lactic acid to 1,2-propylene glycol. Among the various reaction parameters, such as catalysts, reductants, temperature, water filling and reaction time we investigated, a 93% yield of 1,2-propylene glycol in the presence of 0.83 mmol lactic acid, 5 mmol CuO and 30 mmol Zn with 35% water filling at 250 °C for 2 h was achieved. In addition, a carbon balance at optimum reaction conditions by TOC indicated that approximately 99% lactic acid was converted into liquid products in the transformation. In situ formed hydrogen by the oxidation of Zn in water is effective for the transformation compared to added gases hydrogen. The proposed mechanism for the conversion of lactic acid to 1,2-propylene glycol over CuO is also discussed.

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