Phase behavior of glycol ether surfactant systems in the presence of brine and hydrocarbon: Experiment and modeling

• Liquid–liquid equilibrium measurements were performed for the ternary water/C3P1 or C4E1/decane systems.
• Effect of salinity and surfactant structure on the phase behavior has been studied.
• Phase behavior was predicted by perturbed hard sphere chain (PHSC) equation of state.
• MSA term has been coupled with the PHSC EoS to account the contribution of long range interactions.

In this study, liquid–liquid equilibrium measurements were performed for the ternary (water/non-ionic surfactant/decane) systems at T = 298.15 K and atmospheric pressure. Propylene glycol mono propyl ether and ethylene glycol monobutyl ether were selected as surfactant; the first one is propylene glycol ether, while the second one is ethylene glycol ether. New experimental liquid–liquid equilibrium data were presented for the corresponding systems. Effect of salinity and surfactant structure (EO or PO functional group) on the phase behavior of such systems has been studied by both experimental measurements and thermodynamic modeling. The experimental phase behavior data were predicted by the perturbed hard sphere chain (PHSC) equation of state. In the presence of electrolyte, mean spherical approximation (MSA) term has been coupled with the PHSC EoS to account the contribution of long-range interactions. The calculated results indicate acceptable qualitative agreement of PHSC results with the experimental data.