Microwave‐Assisted Esterification of Oleic Acid Using an Ionic Liquid Catalyst

The combination of 1‐butyl‐3‐methylimidazolium hydrogen sulfate ([Bmim]HSO 4 ) ionic liquid (IL) and microwave heating was used to esterify oleic acid as a green approach in biodiesel synthesis. To compare the heating systems, conventional heating and the ultrasonic method were employed but the microwave method was found to be more effective. H 2 SO 4 and 1‐methyl imidazole hydrogen sulfate ([Hmim]HSO 4 ) were also used in the esterification of oleic acid and their catalytic activities were compared to that of [Bmim]HSO 4 . ILs provided some advantages such as reusability, easy recyclability, and very stable activity. There was only a small decrease in the catalytic activity of [Bmim]HSO 4 after four successive applications, which means that ILs can be reused, contrary to homogeneous catalysts. The combination of IL catalysts and microwave irradiation proved to be a potential alternative method for biodiesel production.