CO2 solubility in some amino acid-based ionic liquids: Measurement, correlation and DFT studies

The solubility of carbon dioxide (CO2) gas in three amino acidebased ionic liquids (AAILs), 1-butyl-3-methylimidazolium glycinate ([BMIm][Gly]), 1-butyle3-methylimidazolium alaninate ([BMIm][Ala]), and 1-butyle3-methylimidazolium valinate ([BMIm][Val]) has been experimentally investigated by quartz crystal microbalance (QCM). Solubility of CO2 has been evaluated at temperatures from 288.15 to 318.15 K and pressures up to 4 bars. According to the sorption mechanism, CO2 solubility in AAILs was correlated by a reaction equilibrium thermodynamic model. The thermodynamic parameters including Henry's constant, reaction equilibrium constant, enthalpy of physical dissolution, and the chemical reaction were calculated and compared with assess the CO2 absorption performance in AAILs. The obtained results indicate that glycinate anion ([Gly]) has more CO2 sorption capacity compared to alaninate ([Ala]) and valinate ([Val]). The chemical sorption of CO2 via carbamate formation was confirmed using FT-IR spectroscopy. Furthermore, density functional theory (DFT) calculations have been performed to investigate the interactions between the amino acid anion-based ionic liquids and CO2. (C) 2020 Elsevier B.V. All rights reserved.