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Validation and prediction of solubility parameters of ionic liquids for CO 2 capture
, L. Jain, A. Khanna
Published in
Volume: 97
Pages: 51 - 64
The present study attempts to screen a number of ionic liquids (ILs) for CO 2 capture and its separation from flue gas mixture based on Hildebrand solubility parameter (δ). Solubility parameters of various ILs have been computed through molecular dynamic simulations in Material Studio. Initially the density and solubility parameters of seven ILs have been validated with experimental values available in the literature and are found to be in close correspondence. A group contribution correlation for δ of IL is developed and expressed as the weighted sum of attractions and repulsions of cation and anion as: δIL2=0.6 δcaδan-0. 2δca2-0.2δan2. This correlation was used to find out the δ values of cation and anion. The solubility parameters of 21 cations and 10 anions have successfully been determined by using δ values of 31 ILs and the correlation. Furthermore, using δ values of 21 cations and 10 anions and the group contribution correlation, the δ values of 210 ILs have been predicted. The δ values obtained by correlation match well with the δ values obtained by direct molecular simulations for twenty seven ILs, suggesting that correlation equation is reliable to predict the δ values of several ILs. Furthermore, comparison of the literature solubility data of different gases in ILs with that of solubility parameters in the present study reveals that the δ values are able to successfully explain the experimental solubility trends. Of all ILs studied, δ values of phosphonium cation based ILs (δ = 20.7-18.3 MPa 0.5) and ILs containing tris(nonafluorobutyl)trifluorophosphate ([bFAP] -) anion (δ = 20.5-18.3 MPa 0.5) are observed to be closer to that of CO 2 (δ = 17.85 MPa 0.5) and are significantly far from that of other flue gases like CH 4, N 2, H 2 and H 2O. Thus, by using the fluorinated anion and phosphonium cation based ILs, CO 2 can be more selectively separated from the major flue gases. © 2012 Elsevier B.V. All rights reserved.
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