Simultaneous Vapor−Liquid−Liquid Equilibria and Phase Molar Densities of a Quaternary System of Propane + Pentane + Octane + Water

This paper presents a new procedure to measure simultaneously equilibrium phase compositions and phase densities of multicomponent fluid mixtures. This is accomplished using a uniquely designed pressure/volume/temperature-vapor/liquid/liquid equilibrium apparatus ( PVT -VLLE) connected to a modified sampling system for gas chromatographic analysis (GC) at high pressures and temperatures. The data reported in this paper include (1) three-phase equilibrium compositions and pressures of hexane + water and (2) three-phase equilibrium compositions and phase molar densities for a quaternary system of propane + pentane + octane + water. The equilibrium compositions and three-phase equilibrium pressures for hexane and water compare well with the published data of Tsonopolous and Wilson, which are considered as a calibration test to validate our procedure. Thus we conclude that this methodology is suitable for determining volumetric and phase equilibria properties of multiphase systems.