Prepared Sulfonic-Acid-Based Ionic Liquid for Catalytic Conversion of Furfuryl Alcohol to Ethyl Levulinate

Efficient utilization of Brønsted acids has been advanced through the synthesis of a novel pyridinium propyl sulfonic acid ionic liquid catalyst, [PSna][HSO₄]. Employing niacin and 1,3-propanesulfonic lactone, the synthesis aimed to achieve a catalyst that combines atom-efficiency with stability. Optimal catalytic activity was demonstrated at a temperature of 110 °C over a 2 h reaction time, resulting in a furfuryl alcohol conversion and ethyl levulinate yield of 97.79% and 96.10%, respectively. Notably, the extraction and recovery of [PSna][HSO₄] exhibited commendable repeatability with up to five cycles, maintaining furfuryl alcohol conversion and ethyl levulinate yield at 93.74% and 88.17%, which highlights the catalyst's durability. Density flooding theory (DFT) calculations were employed to determine the most probable reaction pathways and identify all possible transition states and the reaction energy barriers overcome at each step of the reaction.