The solubility of the major constituents of natural gas in ionic liquids (ILs) can be used to identify their potential for acid gas removal from a producing gas stream. We have developed models for the solubility of H 2 S, CH 4 , and C 2 H 6 in ILs at typical conditions encountered in natural gas treatment. In this work, a conductor-like screening model for realistic solvation was used to predict the activity coefficients for solutes in ILs and a cubic EOS was used for vapor-phase corrections from ideality. Empirical correlations were developed to extrapolate solubilities where experimental data are not available at desired conditions; targeted in this study at 298.15 K and 2000 kPa. Over 400 possible ILs were ranked based on the higher selectivity of absorption of CO 2 and H 2 S over CH 4 and C 2 H 6 . The best 15% (58) of promising ILs for sour gas treatment predominantly contain the anions BF 4 , NO 3 , and CH 3 SO 4 and the cations N 4111 , pmg, and tmg.

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Solubility information for CO2 in different ionic liquids, ILs, in part can potentially be used to select a specific IL for the separation of CO2 from hydrocarbon fluids. Unfortunately, not all CO2–IL systems have been experimentally described at similar temperatures and pressures; therefore, a direct comparison of performance by process simulation is not always possible. In the extreme cases, the design of a CO2 separation process may require predicting the CO2–IL equilibria for which there are no available solubility data. To address the need for this information, a semi‐empirical correlation was developed to estimate the dissolution of CO2 in CO2–IL solvent systems. The theoretical COSMO–RS calculation method was used to calculate the chemical potential of CO2 in a wide variety of ILs and the Soave–Redlich–Kwong equation was used to calculate the fugacity coefficient of the CO2 vapour phase. The model was correlated with available literature data, yielding an average error of AAR = 23% and small bias. © 2012 Canadian Society for Chemical Engineering