Catalytic Conversion of Glucose into Levulinic Acid Using 2-Phenyl-2-Imidazoline Based Ionic Liquid Catalyst

Levulinic acid (LA) is an industrially important product that can be catalytically valorized into important value-added chemicals. In this study, hydrothermal conversion of glucose into levulinic acid was attempted using Brønsted acidic ionic liquid catalyst synthesized using 2-phenyl-2-imidazoline, and 2-phenyl-2-imidazoline-based ionic liquid catalyst used in this study was synthesized in the laboratory using different anions (NO(3), H(2)PO(4), and Cl) and characterized using (1)H NMR, TGA, and FT-IR spectroscopic techniques. The activity trend of the Brønsted acidic ionic liquid catalysts synthesized in the laboratory was found in the following order: [C(4)SO(3)HPhim][Cl] > [C(4)SO(3)HPhim][NO(3)] > [C(4)SO(3)HPhim][H(2)PO(4)]. A maximum 63% yield of the levulinic acid was obtained with 98% glucose conversion at 180 °C and 3 h reaction time using [C(4)SO(3)HPhim][Cl] ionic liquid catalyst. The effect of different reaction conditions such as reaction time, temperature, ionic liquid catalyst structures, catalyst amount, and solvents on the LA yield were investigated. Reusability of [C(4)SO(3)HPhim][Cl] catalyst up to four cycles was observed. This study demonstrates the potential of the 2-phenyl-2-imidazoline-based ionic liquid for the conversion of glucose into the important platform chemical levulinic acid.