Microwave-assisted esterification of oleic acid using pyrrolidonium-based bronsted-acidic ionic liquids catalyst

Biodiesel is a liquid fuel obtained by the transesterification reaction of triglycerides and the esterification reaction of free fatty acids. In this study, pyrrolidonium-based Br & Oslash;nsted-acidic ionic liquids (ILs) were applied as catalysts for the production of biodiesel by microwave-assisted esterification of oleic acid with methanol. The effects of reaction temperature, catalyst amount, methanol/oleic acid molar ratio, and reaction time on the oleic acid conversion were investigated. Under optimal conditions, the results demonstrated that N-methyl-2-pyrrolidonium hydrogen sulfate (IL1) and 2-pyrrolidonium hydrogen sulfate (IL2) can achieve conversion rates exceeding 98 %. A comparative analysis with other IL catalysts showed the superior performance of pyrrolidonium-based ILs, especially in terms of Turn Over Frequency (TOF) values. To investigate the effects of different heating methods on the esterification of oleic acid, the esterification reaction was carried out using both conventional and microwave methods. The microwave method is more effective than the conventional method. The reusability of the IL catalyst was investigated, and the recovered catalyst showed excellent stability when it was reused for five consecutive runs without significant loss of activity.