Design of Ordered Mesoporous Sulfonic Acid Functionalized ZrO2/organosilica Bifunctional Catalysts for Direct Catalytic Conversion of Glucose to Ethyl Levulinate

Ordered mesoporous sulfonic acid functionalized ZrO2/organosilica catalysts (SO42-/ZrO2-PMO-SO3H) bearing tunable Bronsted, and Lewis acid site distributions were prepared by a P123-directed sol-gel co-condensation route followed by ClSO3H functionalization. As-prepared catalysts were applied in the conversion of glucose to ethyl levulinate in ethanol medium. The SO42-/ZrO2-PMO-SO3H-catalyzed target reaction followed a glucose-ethyl glucoside-ethyl fructoside-5-ethoxymethylfurfural-ethyl levulinate pathway dominated by the synergistic effect of the super strong Bronsted acidity, and moderate Lewis acidity of the catalysts. Additionally, by combining the advantages of the considerably high Bronsted (696 mu eq g(-1)), Lewis acid site density (703 mu eq g(-1)), optimal Bronsted/Lewis molar ratio (0.99), and excellent porosity properties, the SO42-/ZrO2-PMO-SO(3)H1.0 obtained at an initial Si/Zr molar ratio of 1.0 exhibited the highest ethyl levulinate yield (42.3 %) among the various tested catalysts. Moreover, the SO42-/ZrO2-PMO-SO3H can be reused three times without obvious changes in activity, morphology, and chemical structure.