Monoethanolamine + Ethylene Glycol + Choline Chloride: An Effect of the Mixture Composition on the CO2 Absorption Capacity, Density, and Viscosity

In the present paper, a systematic investigation of the influence of amine and salt concentration on the CO2 absorption capacity (mCO2, moles of CO2 absorbed by 1 kg of a solution) and amine efficiency (cCO2, moles of CO2 absorbed by 1 mole of amine) of the ternary mixtures composed of monoethanolamine (MEA), ethylene glycol (EG), and choline chloride (ChCl) was carried out. We demonstrate that, in general, the presence of a fixed amount of ChCl in a mixed {MEA + EG} solvent cannot improve mCO2 over an entire range of solvent composition and weakly decreases cCO2 with the effect more pronounced for the mixtures containing greater amount of MEA. The influence of ChCl concentration on the above properties was analyzed for the mixtures with a fixed MEA/EG mole ratio but various ChCl concentrations. It was shown that a decrease in mCO2 observed with an increase in ChCl, again, is rather caused by an overall decrease in MEA content in a mixture as its efficiency cCO2 does not change when ChCl concentration increases. In addition, properties such as density (ρ) and viscosity (η) of the binary {MEA + EG} and ternary {MEA + EG + ChCl} mixtures were obtained within a wide range of temperatures for both neat and CO2-loaded samples. We show that regardless of the {MEA + EG} mixed solvent composition, the presence of ChCl increases both ρ and η. For CO2-loaded samples, both properties increase significantly with a greater contribution for the mixtures containing greater amount of MEA.