Sulphonic Acid-Functionalized Benzimidazolium Based Poly Ionic Liquid Catalyzed Esterification of Levulinic Acid
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Esters of levulinic acid (LA) are bio-based compounds having widespread applications and have the remarkable potential to be blended with commercial diesel or gasoline. In this study, a sulphonic acid-functionalized benzimidazolium based poly ionic liquid (SAFBPIL) catalyst was prepared and characterized by NMR, FT-IR, elemental analysis (C, H, N, S), TGA and BET surface area. Brønsted acidity was determined by anion-exchange/neutralization titration method and was found to be 5.55 mmol/g. The heterogeneous ionic liquid catalyst showed an excellent thermal stability up to 270 °C. Experiments were carried at different temperatures, LA to ethanol molar ratios, catalyst loadings and duration of the reaction in a batch reactor. The highest conversion was obtained at 70 °C using an initial LA:ethanol molar ratio of 1:10 and a catalyst loading of 15 wt% in 9 h. It was observed that ethyl levulinate (EL) could be effectively obtained over SAFBPIL with a selectivity higher than 99.5%. This is due to more acidic sites exhibited on SAFBPIL catalyst under optimized conditions. Herein, we are reporting for the first time an esterification of LA to EL using a new SAFBPIL as a catalyst. The catalyst was recycled for five runs without significant loss of catalytic activity.
KeywordsSulphonic acid-functionalized Levulinic acid Benzimidazolium Poly ionic liquid Esterification Brønsted acid
We gratefully acknowledge SIF DST-VIT-FIST, VIT-Vellore for providing NMR, GC–MS, FT-IR. The authors also acknowledge the financial help provided by DST-SERB (ECR/2016/001866) and ‘VIT SEED GRANT’, VIT-Vellore for carrying out this research work. The authors express gratitude to “Smart Materials Laboratory for Bio-sensing and Catalysis” for providing basic facilities.
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