Irregular Ionic Lattice Model for Gas Solubilities in Ionic Liquids

The irregular ionic lattice model (IILM) is applied to predict the vapor pressures and solubilities of carbon dioxide dissolved in 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF₆]) and in 1-n-octyl-3-methylimidazolium tetrafluoroborate ([C8mim][BF₄]) ionic liquids at temperatures ranging from 298.15 to 333.15 K. The model contains only two parameters; they are shown to be independent of an arbitrarily chosen reference state. The parameters show a slight dependence on temperature, but this dependence is ignored in computations to demonstrate the rigor of the IILM in predicting CO₂ solubility at high and low pressures at various temperatures. Model predictions are compared against the experimental data of Anthony et al. (J. Phys. Chem. B 2002, 106, 7315) and of Blanchard et al. (J. Phys. Chem. B 2001, 105, 2437). The usefulness of the model is in predicting CO₂ solubilities at temperatures and pressures where experimental data are unavailable.