Modeling Interfacial Tension of Heptane + Alcohol Mixtures Using Cubic Plus Association Equation of State Plus Simplified Gradient Theory

This work has been dedicated to modeling the interfacial tension of the heptane + alcohol mixtures in the temperature range of 288.15 K to 333.15 K. The cubic plus association equation of state is applied to the liquid–vapor phase equilibrium calculations. The binary interaction parameters are obtained according to the experimental isothermal and isobaric phase equilibrium data. For the binary interaction parameters, correlations have been obtained as a function of temperature for isothermal phase equilibrium, and a constant value for isobaric phase equilibrium. The linear gradient theory is used as a predictive and adjustment approach to describe the interfacial tension of the heptane + alcohol mixtures. The influence parameters of the pure components were constant and the symmetric parameters of the binary mixtures were correlated with the temperature. The results of this work show that the cubic plus association equation of state is capable of simultaneously representing the phase equilibrium and interfacial tension of the mixtures studied. The results obtained in the interfacial tension are in agreement with those published in the literature.