Modeling the [NTf2] Pyridinium Ionic Liquids Family and Their Mixtures with the Soft Statistical Associating Fluid Theory Equation of State
authors Oliveira, MB; Llovell, F; Coutinho, JAP; Vega, LF
nationality International
journal JOURNAL OF PHYSICAL CHEMISTRY B
keywords LENNARD-JONES CHAINS; DIRECTIONAL ATTRACTIVE FORCES; CARBON-DIOXIDE SOLUBILITY; BINARY-SYSTEMS; PHASE-BEHAVIOR; VAPOR-LIQUID; PHYSICOCHEMICAL PROPERTIES; THERMOPHYSICAL PROPERTIES; SAFT EQUATION; N-ALKANES
abstract In this work, the soft statistical associating fluid theory (soft-SAFT) equation of state (EoS) has been used to provide an accurate thermodynamic characterization of the pyridinium-based family of ionic liquids (ILs) with the bis(trifluoromethylsulfonyl)imide anion [NTf2](-). On the basis of recent molecular simulation studies for this family, a simple molecular model was proposed within the soft-SAFT EoS framework. The chain length value was transferred from the equivalent imidazolium-based ILs family, while the dispersive energy and the molecular parameters describing the cation anion interactions were set to constant values for all of the compounds. With these assumptions, an appropriate set of molecular parameters was found for each compound fitting to experimental temperature density data at atmospheric pressure. Correlations for the nonconstant parameters (describing the volume of the IL) with the molecular weight were established, allowing the prediction of the parameters for other pyridiniums not included in the fitting. Then, the suitability of the proposed model and its optimized parameters were tested by predicting high-pressure densities and second-order thermodynamic derivative properties such as isothermal compressibilities of selected [NTf2] pyridinium ILs, in a large range of thermodynamic conditions. The surface tension was also provided using the density gradient theory coupled to the soft-SAFT equation. Finally, the soft-SAFT EoS was applied to describe the phase behavior of several binary mixtures of [NTf2] pyridinium ILs with carbon dioxide, sulfur dioxide, and water. In all cases, a temperature-independent binary parameter was enough to reach quantitative agreement with the experimental data. The description of the solubility of CO2 in these ILs also allowed identification of a relation between the binary parameter and the molecular weight of the ionic liquid, allowing the prediction of the CO2 + C(12)py[NTf2] mixture. The good agreement with the experimental data shows the excellent ability of the soft-SAFT EoS to describe the thermophysical properties of ILs as well as their phase behavior. Results prove that this equation of state can be a valuable tool to assist the design of ILs (in what concerns cation and anion selection) in order to obtain ILs with the desired properties and, consequently, enhancing their potential industrial applications.
publisher AMER CHEMICAL SOC
issn 1520-6106
year published 2012
volume 116
issue 30
beginning page 9089
ending page 9100
digital object identifier (doi) 10.1021/jp303166f
web of science category Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000306989800039
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journal impact factor 3.146
5 year journal impact factor 3.101
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