Efficient CO2 absorption in aqueous dual functionalized cyclic ionic liquids

Abstract Novel dual functionalized ionic liquids were synthesized using four different cyclic anions, azolide/ piperazine, in combination with triethylenetetramine cation. These ionic liquids were used to absorb CO2 in aqueous form at 300 K and ambient pressure and [TETAH][Pz], [TETAH][Im], [TETAH][Py] and [TETAH][Tz], showed 2.05, 1.81, 1.73 and 1.50, CO2loading in mol of CO2 / mol ionic liquids, respectively, higher than industrial amine absorbents like monoethanolamine, which have 0.65−0.68 mol of CO2 /mol . Based on kinetics of CO2 absorption, Hatta number was calculated for comparative a study, and it showed that high interfacial area is favorable for higher absorption rate. Aqueous [TETAH][Im] and [TETAH][Py] showed high basicity and good yields of carbamate in these two DFILs. 13C NMR results suggest that steric hindrance effect decreased in aqueous medium, and the reaction of piperazine anion with CO2 and [TETAH][Pz] resulted in higher CO2 loading. Bond length and angle of CO2 -amines system was calculated by geometry optimization simulation and shows attraction of CO2 is higher in [Pz] anion. Regeneration cyclic efficiency was found to be around 90–95 % for multiple absorption desorption cycles with negligible absorbent loss.