Enhanced transfer hydrogenation of bio-derived Ethyl levulinate to γ-valerolactone over Zr-based catalysts through a formic acid modification strategy

Abstract

Conversion of biomass platform compounds to γ-Valerolactone (GVL) is of significant for biomass high-value utilization. In this study, a range of innovative zirconium-based catalysts (Zr-5ASA-X) were synthesized utilizing 5-aminosalicylic acid (5-ASA) as the ligand through a formic acid (FA) modification strategy. Zr-5ASA (2:1)-300 exhibited excellent catalytic activity for transfer hydrogenation of bio-derived ethyl levulinate (EL) to GVL with a high EL conversion of 98.8 % and GVL selectivity of 98.6 % in isopropanol under moderate reaction conditions (170 ℃ and 5 h). The characterization results revealed that H+ dissociated from FA combined with the electron donating group -NH2 to generate electron-withdrawing effects, further boosting the intensity of Zr4+ Lewis acid active sites. More importantly, the catalyst can repetitively use at least five runs without an obvious loss of activity. Finally, a kinetic model describing this reaction was established and the possible reaction mechanism was proposed.