Prediction of CO₂ solubility in ionic liquids using the PSRK model

The predictive Soave-Redlich-Kwong (PSRK) model was applied to predict CO₂ solubility in imidazolium-based ionic liquids containing bis(trifluoromethylsulfonyl)imide [Tf₂N], tetrafluoroborate [BF₄], and hexafluorophosphate [PF₆] anions. The UNIFAC PSRK matrix was extended to include these new groups. Binary interaction parameters were obtained by regressing experimental vapor-liquid equilibrium data available in the literature. Experimental data were subjected to a consistency test, and only consistent data were considered during the regression. The model predictions showed satisfactory agreement with the experimental data at pressures up to 5 MPa, with an overall root mean square deviation (RMSD) of 0.31. The prediction ability of the model was tested for ionic liquids containing long alkyl chains, exhibiting an overall RMSD of 0.40. The results indicated that the PSRK model provides a reasonable prediction of CO₂ solubility in ionic liquids at pressures not in the vicinity of the critical pressures of CO₂ and ionic liquids.