281501 Study of Interfacial Phenomena, Viscosity and Derivative Properties of Common Ionic Liquids with the Soft-SAFT EoS
Ionic Liquids (ILs) are a family of compounds with a very wide variety of properties due to their particular physicochemical characteristics. In particular, their extremely low volatility marks them as environmentally benign alternatives to volatile organic solvents for separation processes. Thermodynamic models tend to focus only on particular properties, such as the density or the solubility. However, it is difficult to find theoretical tools able to reproduce several features of ionic liquids and, in particular, their interfacial, derivative and transport properties.
In this contribution, within the framework of the soft-SAFT EoS  coupled with the Density Gradient Theory (DGT)  and the Free-Volume-Theory, the single-phase equilibrium, surface tensions, viscosities, as well as the critical temperature, pressure and density have been estimated for different ionic liquid families and compared with those reported in the literature from experimental or simulation data. In particular, two different cations (imidazolium and pyridinium) and several anions (BF4, PF6, Tf2N…) have been revised and compared. A correlation for the influence parameter as a function of the molecular weight was obtained, empowering the predictive capabilities of the equation for interfacial tensions of compounds of the family for which experimental data is scarce or unavailable . In addition, surface thermodynamic properties were also derived from the dependence of the surface tension values, and compared with those obtained within the same framework. The viscosity of those compounds is also provided in good agreement with the experimental data. Finally, several second-order thermodynamic properties such as the heat capacities, the isothermal compressibility or the Joule-Thomson coefficient are evaluated. The effect of the molecular parameters on those properties is further discussed.
F. Llovell acknowledges a TALENT grant from AGAUR, Generalitat de Catalunya. M. B. Oliveira acknowledges the financial support from Fundação para a Ciência e a Tecnologia for her Post-Doctoral grant (SFRH/BPD/71200/2010). This work is partially financed by the Spanish Government under project CTQ2008-05370 and CEN2008-01027. Additional support from the Catalan Government is also acknowledged (SGR- 2009SGR-666).
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