Modeling the phase behavior of ternary systems ionic liquid + organic + CO₂ with a Group Contribution Equation of State

This work presents the results of the use of a Group Contribution Equation of State (GC-EOS) to model experimental data obtained for ternary systems of the type bmim[BF₄] + organic solute + CO₂ with four different organic compounds, namely acetophenone, 1-phenylethanol, 4-isobutylacetophenone, and 1-(4-isobutylphenyl)-ethanol. Our results show that the GC-EOS is able to qualitatively predict not only L+V[rightward arrow]L but also L₁+L₂[rightward arrow]L phase transitions. As the two two-phase boundaries L+V and L₁+L₂ of the experimentally found three-phase region L₁+L₂+V almost coincide with the saturated vapor pressure curve of pure CO₂, the phase transitions L+V[rightward arrow]L₁+L₂+V and L₁+L₂+V[rightward arrow]L₁+L₂ have been represented as this vapor-pressure curve by the model. The average absolute deviations between experimental and predicted values for all phase transitions have been found to be very satisfactory. © 2009 American Institute of Chemical Engineers AIChE J, 2009