Modeling the density of ionic liquids with ePC-SAFT

ePC-SAFT was used to model the densities of ionic liquids (ILs) up to high pressures and temperatures. The ILs under consideration contained one of the IL-cations [Cnmim]+, [Cnpy]+, [Cnmpy]+, [Cnmpyr]+ or [THTDP]+, and one of the IL-anions [Tf2N]−, [PF6]−, [BF4]−, [tfo]−, [DCA]−, [SCN]−, [C1SO4]−, [C2SO4]−, [eFAP]−, Cl−, [Ac]− or Br−, respectively. Within the ePC-SAFT framework, IL-ion specific parameters were applied that are valid independent of the IL they are part of. Each IL-ion was modeled as a non-spherical species exerting repulsive, dispersive and Coulomb forces. The ePC-SAFT parameters for [Cnmim]+ (n = 2, 4, 6 and 8), [Tf2N]−, [PF6]−, and [BF4]- were taken from our previous work (Fluid Phase Equilibria 2012 (335) 64–73). Based on these parameters, all parameters of the other IL-ions were fitted to experimental density of pure ILs up to high pressures in a broad temperature range. Being provided with ion-specific and linearly molecular-weight-dependent parameters, ePC-SAFT allows reliably representing/predicting pure-IL and mixed-IL density up to high pressures.