A new functionalized ionic liquid for efficient glucose conversion to 5-hydroxymethyl furfural and levulinic acid

• Acidic functionalized ionic liquid as catalyst for glucose conversion reaction.
• Brønsted and Lewis acid sites required for glucose conversion to 5-HMF and LA.
• [SMIM][FeCl4] gives highest performance (5-HMF yield: 18%, LA yield: 68%).
• [SMIM][FeCl4] was reused five times without significant loss of activity.

The conversion of glucose to 5-hydroxymethyl furfural (5-HMF) and levulinic acid (LA) using ionic liquid is a promising method for producing liquid fuels from renewable resources. In this study, three types of acidic functionalized ionic liquids (FILs) were prepared and used as catalysts in the conversion of glucose to 5-HMF and LA. The prepared FILs were characterized using CHNS elemental analysis and 1H and 13C NMR. The acidity of the FILs was examined using pyridine-FTIR, Hammett and acid-base titration methods. The FIL with high acidity and with both Brønsted and Lewis acid sites present seemed suitable for 5-HMF and LA production. Among the tested FILs, 1-sulfonic acid-3-methyl imidazolium tetrachloroferrate ([SMIM][FeCl4]) demonstrated the highest catalytic performance. The yields of 5-HMF and LA reached as high as 18% and 68%, respectively after 4 h at 150 °C. The catalyst was reused five times without significant loss of activity. Furthermore, for the kinetic analysis performed for glucose conversion, the activation energy and pre-exponential factor for the reaction were 38 kJ mol−1 and 925 min−1, respectively. The experimental results demonstrated the potential of FIL as a catalyst for biomass transformation to platform chemicals under mild process condition.

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