CO2 Solubility in Aqueous Solutions of Amine–Ionic Liquid Blends: Experimental Data for Mixtures with AMP and MAPA and Modeling with the Modified Kent–Eisenberg Model

Abstract

Carbon dioxide (CO2) capture using alkanolamines remains the most mature technology, yet faces challenges including solvent loss, high regeneration energy and equipment corrosion. Ionic liquids (ILs) are proposed as alternatives, but their high viscosity and production costs hinder industrial use. Thus, blending ILs with amines offers a promising approach. This work presents new experimental data for aqueous blends of 1-butyl-3-methylimidazolium hydrogen sulfate, (Formula presented.) with 2-amino-2-methyl-1-propanol (AMP) and 3-(methylamino)propylamine (MAPA) and for choline glycine, (Formula presented.), with AMP, modeled using the modified Kent–Eisenberg approach. It was shown that substituting a portion of the amine with (Formula presented.) reduces CO2 uptake per mole of amine due to the lower solution’s basicity, despite the added sites for physical absorption. In contrast, the replacement of an amine portion with (Formula presented.) enhances both physical and chemical interactions, leading to increased CO2 solubility per mole of amine. Finally, replacing a small portion of water with (Formula presented.) does not significantly alter the bulk CO2 solubility (moles of CO2 per kg of solvent) but lowers the solvent’s vapor pressure. Given the non-toxic nature of (Formula presented.), the resulting solvent poses no added environmental risk. Model predictions agree well with experimental data (deviations of 2.0–11.6%) and indicate low unreacted amine content at CO2 partial pressures of 1–10 kPa for carbamate-forming amines, i.e., (Formula presented.), and MAPA. Consequently, at higher CO2 partial pressures, the solubility increases due to carbamate hydrolysis and molecular CO2 dissolution.