Ionic liquid and microwave irradiation synergism for efficient biodiesel synthesis from waste cooking oil

Abstract

Ionic liquid (IL) and microwave irradiation synergism was successfully employed in the catalytic conversion of waste cooking oil (WCO) into biodiesel: 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO4) was used as an IL catalyst, and tested parameters influencing the biodiesel conversion were reaction time and reaction temperature, catalyst amount, and the methanol:oil molar ratio. A biodiesel conversion of 93.4% was achieved in a reaction time of 4 h, at a reaction temperature of 150°C, using a methanol:oil molar ratio of 28:1, and 10 wt% of [Bmim]HSO4. A comparison was made between conventional and microwave methods. While high conversion was achieved after 4 h with the microwave method, high conversion was achieved after 6 h with the conventional method. A kinetic study was also carried out for biodiesel conversion, and the activation energy and pre-exponential factor were found to be 73.30 kJ/mol and 1.36 × 107min−1, respectively. Finally, the properties of the produced biodiesel were assessed, and it was found to be compatible with fuel specifications based on the American Society for Testing and Materials (ASTM) D6751 standard.