Solubility of CO₂ in the Ionic Liquids [bmim][CH₃SO₄] and [bmim][PF₆]

A high-pressure view-cell technique based on the synthetic method was used to determine the solubility of carbon dioxide in the ionic liquid 1- n -butyl-3-methylimidazolium methyl sulfate ([bmim][CH 3 SO 4 ]). The temperature ranged from 293.2 K to 413.1 K, the pressure and the carbon dioxide molality reached up to ∼10 MPa and ∼3.3 mol of CO 2 ·(kg of [bmim][CH 3 SO 4 ]) -1, respectively. The (extended) Henry's law was successfully applied to correlate the solubility pressures. The final results for the Henry's constant (at zero pressure) of carbon dioxide in [bmim][CH 3 SO 4 ] (on the molality scale) are correlated within the estimated uncertainty (± 1.3 %) by ln( /MPa) = 7.2738 − 1775/( T /K) − 0.002033( T /K). Furthermore, some small corrections were applied to the experimental results for the solubility of carbon dioxide in the ionic liquid 1- n -butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) reported in previous work. The corrected values for the Henry's constant of carbon dioxide in [bmim][PF 6 ] only slightly and systematically deviate (by about −2 % at given temperature) from the values reported previously.