Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Liquid-liquid equilibrium (LLE) temperatures have been determined for benzaldehyde + CH3(CH2)nCH3 (n = 8, 10,12,14) mixtures by means of the opalescence method using a laser scattering technique. All the solutions show an upper critical solution temperature (UCST), which increases almost linearly with n. Benzaldehyde + benzene, or + alkyl-benzene, or + alkane mixtures have been treated in terms of the group contribution model DISQUAC. The corresponding interaction parameters for the contacts formyl/aromatic; formyl/aliphatic; formyl/c-CH2 are reported. The former are entirely dispersive; the remainder contacts are characterized by both dispersive and quasichemical interaction parameters. The model correctly describes excess molar enthalpies and the phase equilibrium diagrams, liquid-liquid, vapour-liquid (VLE) and solid-liquid (SLE) of the investigated solutions, over a wide range of temperature using the same set of interaction parameters. Complex phase diagrams including simultaneous LLE and SLE are also well represented by DISQUAC. It is shown that interactions between benzaldehyde and an aromatic hydrocarbon are mainly dispersive, and that those between benzaldehyde molecules in alkane solutions are of dipolar type.