Brønsted-Lewis acidic ionic liquid for the “one-pot” synthesis of biodiesel from waste oil

Abstract

Brønsted–Lewis acidic ionic liquids were employed for the preparation of biodiesel using waste oil as the feedstock. It was found that (3–sulfonic acid)–propyltriethylammonium chloroironinate [HO3S–(CH2)3–NEt3]Cl–FeCl3 (molar fraction of FeCl3 x = 0.67) was an efficient catalyst for the reaction, and a synergetic effect of Brønsted and Lewis acid sites enhanced the catalytic performance of ionic liquid (IL). Using the waste oil with 34.6 mg KOH/g acidic value, the yield of biodiesel was even more than 95% at 120 °C for 4 h. The reusability of IL was good after it was used seven times. Therefore, an efficient and environmentally friendly catalyst is provided for the synthesis of biodiesel from waste oil with high acid value by “one-pot” method.