Ionic liquids as a reaction medium for lipase-catalyzed methanolysis of sunflower oil

Ionic liquids, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIm][PF6]) and 1-ethyl-3-methyl imidazolium hexafluorophosphate ([EMIm][PF6]), were used for the methanolysis of sunflower oil using Candida antarctica lipase (Novozyme 435) and gave yields of fatty acid methyl esters at 98–99% within 10 h. The optimum conditions of methanolysis in hydrophobic ionic liquids are 2% (w/w) lipase, 1:1 (w/w) oil/ionic liquid and 1:8 (mol/mol) oil/methanol at 58–60°C. Methanolysis using hydrophilic ionic liquids, 3-methyl imidazolium tetrafluoroborate ([HMIm][BF4]) and 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIm][BF4]), gave very poor yields. A hydrophobic ionic liquid thus protects the lipase from methanol. Recovered ionic liquids and lipase were used for four successive reaction cycles without any significant loss of activity.