Thermodynamic modeling of CO2 solubility in ionic liquid with heterosegmented statistical associating fluid theory

Abstract

a b s t r a c tHeterosegmented statistical associating fluid theory is used to represent the CO 2 solubility in ionic liquids. As in our previous work, ionic liquid molecule is divided into several groups representing the alkyls, cation head, and anion. The cation of ionic liquid is modeled as a chain molecule that consists of one spherical segment representing the cation head and groups of segments of different types representing different substituents (alkyls). The anion of ionic liquid is modeled as a spherical segment of different type. To account for the electrostatic/polar interaction between the cation and anion, the spherical segments representing cation head and anion each have one association site, which can only cross associate. Carbon dioxide is modeled as a molecule with three association sites, two sites of type O and one site of type C, where sites of the same type do not associate with each other. The parameters of CO 2 are obtained from the fitting of the density and the saturation vapor pressure of CO 2 . For the CO 2 -ionic liquid systems, cross association between site of type C in CO 2 and another association site in anion is allowed to occur to account for the Lewis acid-base interaction. The parameters for cross association interactions and the binary interaction parameters used to adjust the dispersive interactions between unlike segments are obtained from the fitting of the available CO 2 solubility in ionic liquids. The model is found to well represent the CO 2 solubility in the imidazolium ionic liquids from 283 to 415 K and up to 200 bar.

Modeling imidazolium-based ionic liquids with ePC-SAFT

“…Cross-interaction parameters were used to adjust the dispersion energy between IL and CO 2 ; cross association between IL and CO 2 molecules was not taken into account. Using heterosegmented SAFT, the density of BF 4 -, PF 6 -, and Tf 2 N-imidazolium-based ILs, the corresponding CO 2 solubility, and the molar volumes of CO 2 -IL systems were represented [15][16][17]. The IL was considered to consist of a chain-like cation and a spherical anion with each one having association sites to account for the electrostatic/polar interactions.…”

Prediction of molar volume and partial molar volume for CO2/ionic liquid systems with heterosegmented statistical associating fluid theory

“…Each group has five parameters, i.e., segment number m, segment volume v oo , segment energy u/k, the reduced range of the potential well , and group bond number n B , which is the effective number of bonds contributed by the group and used to calculate the bond fraction in the chain term. We note that our description of the cation head in our previous publications [41,42] was not accurate. In fact, the cation head is a short chain with an effective number of segments of one.…”

“…The detailed description of the molecular model and theory are given in our previous work [41,42], and only a brief summary is given.…”

“…Two additional parameters, i.e., the well depth of the association sitesite potential ε and the parameter related to the volume available for bonding Ä are used to describe this cross association [41]. CO 2 is modelled as a molecule with one type of segment having three association sites, two sites of type O and one site of type C, where sites of the same type do not associate with each other [42].…”

A SAFT equation of state for the quaternary H2S–CO2–H2O–NaCl system

“…In our previous work, the properties for H 2 S (Ji and Zhu, 2010), CO 2 (Ji and Adidharma, 2010), H 2 O , NaCl-H 2 O (Ji and Adidharma, 2007), and H 2 S-H 2 O (Ji and Zhu, 2010) were investigated with SAFT2. For completeness, the model results are summarized in the Appendix B.…”