Vapor–liquid and liquid–liquid equilibrium calculations in mixtures containing non-ionic glycol ether surfactant using PHSC equation of state

In this study, vapor–liquid and liquid–liquid equilibrium in mixtures containing glycol ether surfactant, non-polar and polar compounds are calculated using Perturbed Hard Sphere Chain (PHSC) equation of state (EoS). Pure liquid density and vapor pressure of surfactants are used for parameter estimation of glycol ether surfactants. The PHSC parameters are calculated for both ethylene glycol ether and propylene glycol ether surfactants. Glycol ether surfactant molecules are modeled as associating components by considering two association sites for each molecule. The results show that the PHSC model is capable of correlating thermodynamic behavior of binary (polar + surfactant) and (non-polar + surfactant) systems. Upper critical solution temperature (UCST) for hydrocarbon + surfactant and lower critical solution temperature (LCST) for water + surfactant systems are accurately calculated. The critical temperatures and the extent of immiscibility are in good agreement with the available experimental data.