Experimental and Kinetic Studies on the Conversion of Glucose to Levulinic Acid Catalyzed by Synergistic Cr/HZSM-5 in GVL/H2O Biphasic System

In this paper, modified HZSM-5 catalysts with different ratios of chromium (Cr/HZSM-5) were synthesized and the solvent effect of gamma valerolactone (GVL) on the enhancement of levulinic acid (LA) yield was investigated. Characterization of the Cr/HZSM-5 catalyst revealed that the introduction of Cr did not change the structure of HZSM-5. The LA yield was increased from 42.5% (H2O solvent system) to 51.4% (GVL/H2O solvent system) under optimal conditions. The influence of GVL on the reaction mechanism was investigated through kinetic analysis, revealing that the incorporation of GVL reduces the activation energy barrier for the conversion of glucose to LA, thereby enhancing the glucose dehydration process. The effect of GVL on the product (LA) was studied, based on molecular dynamics. It was found that the addition of GVL squeezes the water in the solvent system into the second solvation shell layer, which causes GVL to distribute around the carbonyl, hydroxyl, and carboxyl groups of LA, and reduces the likelihood of LA side reactions, thus increasing the yield of LA.