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

gamma-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 gamma-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 Bronsted 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.