Enable mild and efficient biodiesel esterification via a reusable sulfonic acid-functionalized ionic liquid catalyst

Ionic liquids serve as environmentally friendly alternatives to traditional catalysts for biodiesel production. In this work, the sulfonic acid-functionalized ionic liquid [TMG-PS][HSO₄] was synthesized via two steps and demonstrated high catalytic efficiency for esterification. The reaction process of myristic acid and methanol was optimized using single-factor experiments and response surface methodology. Specifically, [TMG-PS][HSO₄] achieved a high conversion rate of 97.53 % under the reaction conditions: temperature of only 42 °C, time of 5 h, catalyst dosage of 6.0 wt%, and molar ratio of methanol to myristic acid of 12:1. Remarkably, the catalyst displayed excellent stability for ten cycles. Moreover, [TMG-PS][HSO₄] also displayed generality and high catalytic activity in catalyzing the reactions of other free fatty acids (FFAs) with methanol to produce biodiesel. Therefore, these results demonstrate that [TMG-PS][HSO₄] has significant potential for biodiesel applications.