Isobaric vapor-liquid equilibria of the system toluene + n-butanol at 94.0, 70.5, and 56.4 kPa

Isobaric vapor-liquid equilibrium (VLE) data were measured for the binary toluene + n-butanol system at 94.0, 70.5, and 56.4 kPa using a modified Malanowski equilibrium still. The experimental VLE data showed significant positive deviation from ideality. Upon reducing the pressure from 94.0 to 56.4 kPa, the azeotrope had shifted from an azeotropic mole fraction (of toluene) of 0.67 to 0.82. The thermodynamic consistency of the VLE data was verified by correlating the excess Gibbs energy with composition using the UNIQUAC model. The experimental data of this work, in addition to some literature VLE data for the same binary system, have been analyzed using three activity coefficient models; UNIQUAC, ASOG, and UNIFAC.