Binary Liquid–Liquid Equilibria for Systems of Mono- or Disubstituted Haloalkanes (Cl, Br) and Pyridinium-Based Ionic Liquids. Advances in the Experimentation and Interpretation of Results

This work presents the measurements made to define the temperature–composition curves for a set of binary systems composed of several pyridinium-based ionic liquids (ILs) [bpy]­[BF₄] and [b<i>Y</i>mpy]­[BF₄] (<i>Y</i> = 2,3,4) with mono- and dihaloalkanes (Cl and Br) in the temperature interval [280–473] K and at atmospheric pressure. With the exception of the short chain dichloroalkanes (1,1- and 1,2-), all the compounds present some degree of immiscibility with the ionic liquids selected. Solubility points (<i>x</i>_IL,<i>T</i>) are determined by an image identification experimental procedure, which is described in detail and permits a more accurate definition of the liquid–liquid equilibria coexistence curves. A semiempirical model is proposed to correlate the experimental results of liquid–liquid equilibria (LLE) and the fits are compared with those obtained with the NRTL model. In both cases, a rigorous procedure is proposed to estimate LLE data considering the isoactivity criteria and a global test to guarantee the stability of the phases of the systems studied. H¹–NMR spectra are determined for some of the systems chosen to study the molecular interactions and their influence on the experimental results