Screening of ionic liquids to capture CO2 by COSMO-RS and experiments

A screening method is proposed for the molecular design of ionic liquids (ILs) to capture carbon dioxide (CO2), which can reduce efficiently the necessary experimental efforts. The COSMO-RS method is implemented to predict the Henry's law constants of CO2 in 408 ILs with various combinations of cations and anions. It is found by the screening that the ILs with the anion tris(pentafluoroethyl)trifluorophosphate ([FEP]) show improved capability to capture CO2, compared with other ILs reported in literature. Then, three [FEP]-based ILs are chosen to perform the solubility measurements by the intelligent gravimetric analyzer (IGA 003, Hiden Analytical), with cations of 1-hexyl-3-methylimidazolium ([hmim]), 1-butyl-1-methylpyrrolidinium ([bmpyrr]), and S-ethyl-N,N,N',N'-tetramethylthiouronium ([ETT]) at 283.2, 298.2, and 323.2 K, up to the pressure of 1.8 MPa. The experimental data show that the solubility of CO2 in [hmim][FEP] is about 15% higher than that in 1-hexyl-3-methylimidazolium bis(tri-fluoromethylsulfonyl)imide ([hmim][Tf2N]), which is in fair agreement with the screening results, indicating the method proposed in this work is reliable. (C) 2008 American Institute of Chemical Engineers.