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

Abstract

Abstract A screening method is proposed for the molecular design of ionic liquids (ILs) to capture carbon dioxide (CO 2 ), which can reduce efficiently the necessary experimental efforts. The COSMO‐RS method is implemented to predict the Henry's law constants of CO 2 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 CO 2 , 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 CO 2 in [hmim][FEP] is about 15% higher than that in 1‐hexyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf 2 N]), which is in fair agreement with the screening results, indicating the method proposed in this work is reliable. © 2008 American Institute of Chemical Engineers AIChE J, 2008