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New experimental results are presented for the solubility of carbon dioxide in the ionic liquid 1-N-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) for temperatures from (293 to 393) K and pressures up to about 9.7 MPa. Solubility pressures are correlated by means of the extended Henry's law.

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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(k H,CO 2 (0) /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.

The liquid-liquid phase equilibrium of mixtures of the room temperature ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF 6 ], and three single alkanols (ethanol, 1-propanol, and 1-butanol) was investigated over the entire composition range at ambient pressure. The experiments were conducted from 262 K to the vicinity of the critical solution temperature of the binary mixture (at maximum 362 K) by two different methods, namely, synthetic cloud-point measurements and analytical UV spectroscopy. The cloud-point method was mainly applied for the [bmim][PF 6 ]-rich liquid, whereas UV spectroscopy was used to determine the very small concentrations of [bmim][PF 6 ] in the alkanols, since under these conditions the cloud-point method is no longer applicable. All three systems show an upper critical solution temperature. With increasing chain length of the alcohol, that temperature rises and simultaneously the biphasic region becomes larger. Inspired by recent publications, the liquid-liquid equilibrium of these three binary systems was predicted by applying the COSMO-RS method. Calculations resulted in predictions of a miscibility gap, but the calculated miscibility gap strongly differs from the experimental results. A far better representation of the experimental data was accomplished via a UNIQUAC-based correlation.