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The solubility (vapor−liquid equilibria) of carbon dioxide (CO2) has been measured in ionic liquids, 1-ethyl-3-methylimidazolium acetate (emimAc), 1-ethyl-3-methylimidazolium trifluoroacetate (emimTFA), and a mixture containing a fixed mole ratio of 49.98 (emimAc)/50.02 (emimTFA) using a gravimetric microbalance at three temperatures (298.1, 323.1, and 348.1) K and pressures up to about 2 MPa. The emimAc strongly (chemically) absorbed CO2 with hardly any vapor pressure above the mixture up to about 20 % mole fraction of CO2 at 298.1 K. The emimTFA did not show the same behavior and physically absorbed CO2. The ionic liquid mixture containing equimolar amounts of emimAc and emimTFA showed a combination of both chemical and physical effects, and the CO2 solubility was well predicted at a fixed pressure using either a molar average of the pure component solubilities or a model based on linear isobaric lines in the ternary phase diagram. The binary pressure−temperature (PTx) data at 298.1 K have also been analyzed by use of an equation-of-state (EOS) model, and predictions at higher temperatures and of the ternary system are reasonable.
Shiflett et al. (Wed,) studied this question.