CO2 absorption properties of imidazolium based ionic liquids using a magnetic suspension balance

We have investigated the CO2 absorption properties in 1-ethyl-3-methylimidazolium (Emim) ionic liquids with the anions (TFSA, bis(trifluoromethanesulfonyl)amide; BETA, bis(pentafluoroethanesulfonyl)amide; NFBS, nonafluorobutanesulfonate; BF4, tetrafluoroborate) using a magnetic suspension balance at 313.15 K and pressures up to 6 MPa. To obtain accurate CO2 solubility, the buoyancy correction was made by taking account of the volume expansion of ionic liquids caused by CO2 dissolution. In the present work, Sanchez–Lacombe equation of state was used for such volume corrections at high pressures. As a result, the solubilities of carbon dioxide in [Emim][TFSA] are consistent with the literature data. The solubilities of carbon dioxide in the ionic liquids studied showed typical pressure dependence as physical absorption, and increased in the following order of the anion: BF4 < NFBS < TFSA < BETA.