Solvent-Mediated Control of Ethanolysis Pathways: Dimethyl Carbonate–Assisted Conversion of Oil Palm Empty Fruit Bunches to Ethyl Levulinate

This study investigates dimethyl carbonate (DMC) as a polar aprotic cosolvent in the direct ethanolysis of oil palm empty fruit bunches (OPEFB) to produce ethyl levulinate. Among several tested cosolvents, DMC significantly improved selectivity and suppressed humin formation, thereby increasing ethyl levulinate yield from 18.69% to 24.49% under relatively mild conditions (140°C, 90 min). Product characterization by GC–MS and FTIR revealed the formation of furan-derived intermediates and humin-type polymers, supporting a reaction network involving hydroxymethylfurfural (HMF) and ethoxymethylfurfural (EMF) intermediates. The results suggest that DMC modifies the reaction microenvironment by regulating solvent polarity and water activity, thereby stabilizing reactive intermediates and redirecting carbon flow toward levulinate esters. This work provides useful insights into solvent-engineering strategies for the selective conversion of lignocellulosic biomass.