Liquid phase catalytic transfer hydrogenation of ethyl levulinate to γ-valerolactone over ZrO2/SBA-15

Abstract

γ-Valerolactone (GVL) is an important bio-derived platform molecule whose atom- and energy efficient, and scalable, catalytic synthesis is highly desirable. Catalytic transfer hydrogenation (CTH) of ethyl levulinate (EL) to γ-valerolactone (GVL) has been selectively performed in batch and continuous flow over ZrO₂/SBA-15 solid acid catalysts. Tuning the zirconia adlayer delivered maximum CTH activity for 11.6 wt% Zr, ascribed to the optimal ratio of Lewis and Brønsted acid sites for the two-step cascade reaction. EL conversion almost doubled under flow versus batch operation, accompanied by a small rise in selectivity to GVL, tripling average GVL productivity in continuous flow (5.2 vs. 1.37 mmol g⁻¹ h⁻¹). Turnover frequency (TOF) is significantly improved under flow conditions (14.5 h⁻¹) relative to batch (3.6 h⁻¹), demonstrating the utility of flow chemistry for accelerating the manufacture of valuable bio-derived molecules.