Modeling Vapor–Liquid Equilibria and Surface Tension of Carboxylic Acids + Water Mixtures Using Peng–Robinson Equation of State and Gradient Theory

This work has been dedicated to modeling the vapor–liquid equilibria and surface tension of carboxylic acids + water mixtures at different temperatures. The Peng–Robinson equation of state with modified Huron–Vidal + Wilson mixing rule correctly models the vapor pressure and vapor mole fraction of these mixtures. The modified Huron–Vidal mixing rule was better than quadratic mixing rule to model the phase equilibria properties for the mixtures studied in this work. The parachor method and linear gradient theory were used to model the surface tension of these mixtures. Finally, a new symmetric parameter dependent on the liquid molar fraction and temperature was necessary to correctly adjust the surface tension of the carboxylic acids + water mixtures using linear gradient theory. The surface tension results obtained in this work are better than those published so far.