Modeling gas solubility in ionic liquids with the SAFT-γ group contribution method

Accurate knowledge of gas solubility is necessary for the development of processes involving ionic liquids (ILs) and gases. In this work, a group contribution approach is used to predict the phase behavior of CO2 + IL systems based on the statistical associating fluid theory (SAFT-γ) as proposed by Lymperiadis et al. The IL molecule is divided into groups of CH3, CH2, cation head, and the anion. The SAFT-γ parameters of CO2 + imidazolium-based ionic liquids with either [PF6], [BF4] or [Tf2N] anions are optimized to experimental data. The ability of the model to describe the phase behavior of these systems is demonstrated within a temperature range of 313.15–353.15 K and pressures up to 100 bars. Moreover, by using the optimized group parameters, the performance of the model is examined by predicting equilibrium data of some CO2 + IL systems not included in the optimization database. The results show good agreement with experimental data.

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► The statistical associating fluid theory (SAFT-γ) model has been modified for binary systems of ionic liquids and CO2.
► New group contributions are obtained to predict the high pressure phase behavior of CO2 in some ionic liquids.
► The new model is capable to both correlate and predict the solubility of CO2 in the investigated ionic liquids.