Absorption of CO{sub 2} in the Ionic Liquid 1-n-Hexyl-3-methylimidazolium Tris(pentafluoroethyl)trifluorophosphate ((hmim)(FEP)): A Molecular View by Computer Simulations
- Beijing Institute of Chemical Technology, Beijing (China)
Using a computational screening methodology, we predicted (AlChE J. 2008, 54, 2717) that the anion tris(pentafluoroethyl)trifluorophosphate ((FEP)) should increase the solubility of CO{sub 2} in ionic liquids (ILs) relative to a wide range of conventional anions. This prediction was confirmed experimentally. In this work, we develop a united-atom force field for the (FEP) anion and use the continuous fractional component Monte Carlo (CFC MC) method to predict CO{sub 2} absorption isotherms in 1-n-hexyl-3-methylimidazolium ((hmim)) (FEP) at 298.2 and 323.2 K and pressures up to 20.0 bar. The simulated isotherms overestimate the solubility of CO{sub 2} by about 20% but capture the experimental trends quite well. Additional Monte Carlo (MC) and molecular dynamics (MD) simulations are performed to study the mechanisms of CO{sub 2} absorption in (hmim)(FEP) and (hmim)(PF6). The site-site radial distribution functions (RDFs) show that CO{sub 2} is highly organized around the (PF6) anion due to its symmetry and smaller size, while less ordered distributions were found around (FEP) and (hmim). However, more CO{sub 2} can be found in the first coordination shell of (FEP) compared with (PF6). The Structures of ILs, illustrated by P-P radial distribution functions, change very little upon the addition of as much as 50 mol % CO{sub 2}. An energetic analysis shows that the van der Waals interactions between CO{sub 2} and ILs are generally larger than electrostatic interactions.
- OSTI ID:
- 21197967
- Journal Information:
- Journal of Physical Chemistry B, Vol. 113, Issue 2; ISSN 1520-6106
- Country of Publication:
- United States
- Language:
- English
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