Mechanism and Kinetics of CO2 Absorption into an Aqueous Solution of a Triamino-Functionalized Ionic Liquid

A novel ionic liquid (1-aminoethyl-3-methylimidazolium lysinate, [C(2)NH(2)MIm][Lys]) functionalized with three amino groups had been developed for carbon dioxide (CO2) capture in this work. The CO2 absorption loading of [C(2)NH(2)MIm] [Lys] solution was found to be 1.59 mol CO2/mol IL with a concentration of 0.5 mol/L at 313.15 K, which was much higher than that of the most existing dual functionalized Its. Besides, [C(2)NH(2)MIm] [Lys] also owned a good regenerability even after 6 regeneration cycles. According to the results of C-13 nuclear magnetic resonance (C-13 NMR), CO2 absorption into [C(2)NH(2)MIm] [Lys] solution could be divided into two stages, which began with the formation of carbamate, and followed by the hydration of CO2 to form carbonate/bicarbonate. Meanwhile, the desorption of the saturated [C(2)NH(2)MIm] [Lys] was proven to be a reverse process of the adsorption. Based on the Mechanism results, the kinetics of CO2 capture into [C(2)NH(2)MIm] [Lys] solution was investigated by using a double stirred-cell absorber at temperatures ranging from 303 to 333 K. Under the pseudo first-order regime, the overall reaction rate constants (k(ov).) and the forward second-order rate constants (k(2)) under different concentrations and temperature were obtained, which were both increased considerably as temperature increased. Moreover, the values of enhancement factor (E) were linear with C-RNR2 and temperature. The Arrhenius equation of CO2 absorption was also estimated, and the activation energy was calculated to be 25.5 kJ.mol(-1).