Solubility of CO2 in Methanol, 1-Octyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide, and Their Mixtures

Solubility data of carbon dioxide (CO2) (1) in methanol (2), 1-octyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide ([omim]+[Tf2N]−) (3), and their mixtures (w30.2, 0.5, and 0.8) at temperatures 313.2 and 333.2 K and pressures up to 7.0 MPa were measured by a high-pressure view-cell technique. The solubility of CO2 in methanol (w30), [omim]+[Tf2N]− (w31.0) and their mixtures follows the order of (w30)<(w30.2)< (w30.5)<(w30.8)<(w31.0) at the same temperature and pressure, while the magnitude of Henry's constants follows the reverse order at a given temperature, which is consistent with the COSMO-RS (conductor-like screening for real solvents) calculation. The solubility data of CO2 in methanol and [omim]+[Tf2N]− are correlated with the Peng-Robinson equation of state, and the solubility of CO2 in the mixtures of methanol and [omim]+[Tf2N]− can be well predicted based on the mole fraction average of methanol and [omim]+[Tf2N]− over the solubility of CO2 in pure methanol and [omim]+[Tf2N]−. The mixtures of methanol and [omim]+[Tf2N]− may be used as physical solvents for capturing CO2 with high partial pressures since they combine the advantages of organic solvents and ionic liquids.