Liquid–Liquid Equilibria in Binary Solutions Formed by [Pyridinium-Derived][F₄B] Ionic Liquids and Alkanols: New Experimental Data and Validation of a Multiparametric Model for Correlating LLE Data

Experimental solubility data are presented for a set of binary systems composed of ionic liquids (IL) derived from pyridium, with the tetrafluoroborate anion, and normal alcohols ranging from ethanol to decanol, in the temperature interval of 275–420 K, at atmospheric pressure. For each case, the miscibility curve and the upper critical solubility temperature (UCST) values are presented. The effects of the ILs on the behavior of solutions with alkanols are analyzed, paying special attention to the pyridine derivatives, and considering a series of structural characteristics of the compounds involved. Miscibility curves are modeled using, for the first time in a LLE study, an adimensional form of a semiempirical model proposed for the Gibbs excess function, G^E = G^E(p,T,x) [Ind. Eng. Chem. Res. 2010, 49, 406], whose particular form in this work isgE(T,x)=z(x)[1−z(x)]∑i=0rgi(T)zi(x)The results are compared with those of an extended form of the Non-Random Two-Liquids (NRTL) equation, using temperature-dependent parameters. In both cases, a rigorous procedure is carried out to calculate the LLE data, considering the isoactivity criteria, and a global test to check the phase stability for the solutions studied. The final evaluation of the application with the new equation gave satisfactory results.