CO<inf>2</inf> capture by 1-ethyl-3-methylimidazolium acetate: Solubility at low pressure and quantification of chemisorption and physisorption

Abstract

Although chemisorptive ionic liquids (ILs) are widely expected as promising CO2 absorbents, rigorous thermodynamic analyses for such systems remain challenging due to the inevitable co-existence of chemisorption and physisorption. In this work, an experimental approach combining quantitative NMR (qNMR) spectroscopy and mass balance is proposed to straightforwardly quantify the chemisorption and physisorption of CO2 in chemisorptive absorbent, and 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) is selected for an exemplary study. The total CO2 solubility in [Emim][OAc] is measured by the pressure drop method, of which the chemisorption part is quantified by qNMR and the physisorption part is then determined by mass balance. Correspondingly, a large set of CO2 solubilities at four temperatures (298.15 K, 313.15 K, 323.15 K, and 348.15 K) covering the low pressure range below 100 kPa are determined, where the chemisorption and physisorption contribution are distinguished quantitatively. Following that, thermodynamic analyses for the CO2 absorption by [Emim][OAc] are made from chemisorption and physisorption point of view, respectively.