Synthesis and purification of glycolic acid from the mixture of methyl levulinate and methyl glycolate via acid-mediated hydrolysis reactions and extraction

Abstract

Biomass-derived methyl glycolate (MG) contains methyl levulinate (MLE). Herein, MLE was separated from MG through acid-mediated hydrolysis reactions and liquid–liquid extraction. H-form β zeolite (Hβ) exhibited higher MLE conversions up to 87.7% compared to other acids. In contrast, MG was much less converted on Hβ. The product levulinic acid could be readily extracted with dimethyl carbonate. The overall content and recovery rate of glycolic acid reached 99.59 wt% and 92.7%, respectively. Control experiments, FTIR, contact angle, and TG-MS results proved that MLE was preferentially adsorbed on slightly hydrophobic Hβ, and DFT calculations verified that the MLE hydrolysis reaction energy barriers were smaller by 2–12 kJ/mol compared to MG. Both effects promoted the transformation of MLE on Hβ. Hβ could be reused at least six times and be regenerated by calcination. Due to dealumination, the number of acid sites on the regenerated Hβ was decreased by 67% while number of strong acid sites was elevated. This paper can shed light on the separation techniques of carboxylic esters via reactive strategies.