Screening ionic liquids as candidates for separation of acid gases: Solubility of hydrogen sulfide, methane, and ethane

Abstract

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. © 2013 American Institute of Chemical Engineers AIChE J , 59: 2993–3005, 2013