Amino acid-based ionic liquids for CO2 conversion to form cyclic carbonate under solvent-free conditions

Abstract

The amino acid ionic liquids of 1-butyl-3-methylimidazolium aspartic acid [bmim][ASP], 1-butyl-3-methylimidazolium glutamic acid [bmim][Glu], N-octyl-N-methylmorpholinium glutamic acid [mor1,8][Glu] and N-hexylisoquinolinium aspartic acid [HiQuin][ASP] have been synthesized and characterized by 1H NMR, 13C NMR and IR spectroscopy. The catalytic performance of the amino acid ionic liquids for the coupling of various epoxides and CO2 to produce cyclic carbonates was studied. The influence of anion type, catalyst dose, reaction temperature, reaction time and CO2 pressure on the yields of cyclic carbonates was examined. The synthesized ionic liquids were found to be single component bifunctional catalysts in good yields and selectivity, no additional organic solvent required and halogen free. Furthermore, this system provides a reasonably environmentally benign chemical process in terms of potential industrial application.