Catalytic transfer hydrogenation of biomass-derived levulinic acid and its esters to γ-valerolactone over ZrO2 catalyst supported on SBA-15 silica

A series of ZrO2 catalysts supported on mesoporous SBA-15 silica were synthesized and examined as catalysts in the production of gamma-valerolactone (GVL) from biomass-derived levulinic acid and its esters via a catalytic transfer hydrogenation (CTH) using several alcohols as hydrogen donors. Among the catalysts examined, ZrO2 supported on high-surface-area SBA-15 silica bearing highly-dispersed zirconium species exhibited the highest catalytic activity, of which reaction rate was 1.7 times higher than that of the conventional bulk ZrO2 catalyst. Zr K-edge XAFS analysis revealed that Zr4+-oxide species with a low-coordination state anchored on silica surface is the dominant active species. Such a Zr species efficiently converted levulinic acid and its esters to GVL (similar to 95% yields) under mild reaction conditions (150 degrees C, 1.0 MPa Ar), and was reusable over multiple catalytic cycles without significant loss of catalytic performances. Comparative experiments, combined with detailed characterizations using NH3/CO2-TPD and in-situ FTIR, proposed a plausible reaction mechanism where basic Zr OH site triggers the CTH reaction involving a six-member ring transition state. (C) 2016 Elsevier B.V. All rights reserved.