Catalytic Upgrading of Renewable Levulinic Acid to Levulinate Esters Using Perchloric Acid Decorated Nanoporous Silica Gels

Catalytic upgrading of renewable biomass resource toward useful chemicals is interesting but challenged, in this paper, several inorganic acids were examined for the catalytic esterification of levulinic acid with alcohol, and then ulteriorly loaded on the applicable supports to obtain the heterogeneous catalysts. Among them, HClO4/SiO2 nanoporous solid-acid catalyst exhibits the highest catalytic activity for the synthesis of ethyl levulinate. The resulting HClO4/SiO2 catalyst was characterized by FT-IR, Energy Dispersive X-ray (EDX)-mapping, X-ray Diffraction (XRD), NH3-Temperature-Programmed-Desorption (TPD), and N-2 desorption. Various reaction factors including loading of HClO4, catalyst dosage, reaction time and temperature were checked and optimized. As expected, the targeted catalyst affords 99% yield of ethyl levulinate and a durable activity even with five runs. Finally, esterification of levulinic acid with various alcohols over the HClO4/SiO2 was further expanded based on the optimal reaction condition.