Application of ionic liquids and deep eutectic solvents in biodiesel production: A review

Developing technologies for the production of alternative fuels from biorenewable resources is a field of interest for many researchers. Adequate substitute to diesel fuel is biodiesel that is synthesized through the transesterification of vegetable oils or animal fats and fulfilled the international standards. Ionic liquids (ILs) and deep eutectic solvents (DESs) have gained tremendous attention for their use in biodiesel production because of environmental benefits and process improvements. The present work overviews the use of ILs and DESs in the reaction and purification steps of biodiesel production processes where they are used as catalysts, cosolvents and extracting solvent. In addition, the possibilities of recycling and reusing of ILs and DESs are pointed out. Moreover, optimization and kinetic studies of biodiesel synthesis in the presence of ILs or DESs are discussed. The use of novel technologies combined with ILs or and DESs are also considered. Therefore, the present paper highlights the promising uses of ILs and DESs in biodiesel production in the future.