Concurrent production and purification of glycolic acid from mixed esters via selective hydrolysis reactions catalyzed and thermodynamically promoted by MgO

Methyl glycolate (MG) in the presence of methyl levulinate (MLE) was selectively converted into magnesium glycolate via MgO-mediated hydrolysis reactions under mild conditions. The conversion of MG reached 95.2% while that of MLE was 15.1%, with reaction selectivity of 100%. After facile isolation procedures, the magnesium glycolate was readily transformed into glycolic acid, monomer of biodegradable plastic, with recovery rate of 90.2%. The basic sites with medium strength on MgO dominated the catalytic activity. The precipitation of magnesium glycolate led to the shift of chemical equilibrium for MG hydrolysis. DFT calculation results showed that the energy barriers for MG hydrolysis were smaller than those for MLE hydrolysis by 46-47 kJ/mol. Both the shift of chemical equilibrium and lower energy barriers contributed to the much higher reactivity of MG compared to MLE. This paper sheds light on the selective hydrolysis of esters and complete hydrolysis of an ester.

Automated summary

Methyl glycolate (MG) can be selectively converted into magnesium glycolate through MgO-mediated hydrolysis reactions in the presence of methyl levulinate (MLE), with a conversion rate of 95.2% for MG and 15.1% for MLE. The catalysts on MgO played a crucial role in the catalytic activity, and the precipitation of magnesium glycolate affected the chemical equilibrium of MG hydrolysis. Energy barrier calculations demonstrated that the hydrolysis of MG had lower energy barriers compared to MLE. This study provides insights into the selective hydrolysis of esters and complete hydrolysis of an ester.