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 (w₃ 0.2, 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 (w₃=0), omim]⁺Tf₂N]^- (w₃=1.0) and their mixtures follows the order of (w₃=0)<(w₃=0.2)< (w₃=0.5)<(w₃=0.8)<(w₃=1.0) 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.