Lipase-catalyzed glycerolysis in ionic liquids directed towards diglyceride synthesis

This work examined the lipase-catalyzed glycerolysis of triglycerides (TG) in a list of commercially available ionic liquids (ILs) with varied cations and anions for the purpose of developing an efficient reaction protocol for diglyceride (DG) production and to understand whether ILs could assist the reaction systems. The reaction performances (reaction rate, TG conversion and DG yield) were found to be greatly dependent on the structure and property of ILs. The reactions in [TOMA·Tf2N] and Ammoeng 120 produced comparable yield of DG to those most efficient conventional systems but with less by-products. Temperature enhancement generally yields positive effect on the conversion of TG, which was much more significant for the ILs with high viscosity. Unusually, increasing substrate concentration in many types of ILs led to enhanced conversion and yield; whereas the increase of glycerol/TG ratio resulted in a dramatic improvement of the reactions in the ILs with strong acidic anions. This work also sorted out some promising IL candidates, namely the ILs with good DG formation selectivity and the ones being able to achieve high TG conversion, which offered possibility to design binary IL systems. Overall, this study presented the first attempt concerning evaluation and characterization of lipase-catalyzed glycerolysis of TG for DG production in IL-based systems.