Absorption of Carbon Dioxide in Aqueous Solution of Protic Ionic Liquid [MEA][Gly]: Experimental Study and Model Fitting

Relatively high viscosity of protic ionic liquids limits their industrial applications in carbon dioxide separation processes. For this purpose, the performance of equilibrium absorption of CO2 in aqueous solution of ionic liquid functionalized with amino acid glycine named monoethanolamine glycinate, [MEA][Gly], was investigated in the temperature range of 303.15-15 323 K and various equilibrium pressures. The results demonstrated that at a constant temperature of 313.15 K, by increasing the presence of water in the solution from 80 to 95 wt%, the CO2 absorption capacity enhances from 1.36 to 2.24 (mol CO2 / mol IL), which is equivalent to 64 % augmentation in CO2 loading. Besides, utilizing a quadratic equation, numerical values of CO2 loading in terms of carbon dioxide partial pressure were developed for all the studied solvent concentrations, so that the calculated results were in good agreement with the values obtained from the experiments. The measurement of the density and viscosity of [MEA][Gly] solution, in the temperature range of 15.303 to 15.323 K, illustrated that as the amount of water in the solution declines, their corresponding values increase dramatically. Applying the empirical correlations, the values of density and viscosity were estimated in terms of temperature and mole fractions. Moreover, Clausius-Clapeyron equation was employed to compute the heat of CO2 absorption into the aqueous solution of [MEA][Gly]. Finally, although [MEA][Gly] is introduced as a novel absorbent in CO2 separation processes, high concentrations of this solvent is not suitable for carbon dioxide capture and separation, mainly due to its high viscosity.