Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Experimental vapor-liquid equilibrium have been measured for the binary system hexane + 2-methoxy- 2-methylbutane at 50, 75 and 94 kPa, and over the temperature range 321 - 357 K using a vapor-liquid equilibrium still with circulation of both phases. In addition mixing volumes were determined at 298.15 K and atmospheric pressure with a vibrating tube densimeter, while maximum differential bubble pressure tensiometry was used to measure atmospheric interfacial tensions at 303.15 K. According to experimental results, the mixture exhibits slight positive deviation from ideal behavior over the experimental range. The mixing volumes of the system are positive over the whole mole fraction range, and the interfacial tensions exhibit slight negative deviation from the linear behavior. The vapor-liquid equilibrium data of the binary mixture satisfy the Fredenlund's consistency test and were well correlated using the gamma-phi approach with the Wohl, NRTL, Wilson and UNIQUAC equations for all the measured isobars. Mixing volumes and interfacial tensions, in turn, were satisfactorily correlated using the Redlich Kister equation. The experimentally determined phase equilibrium, mixing volume and interfacial tension data were theoretically predicted using the Peng-Robinson Stryjek-Vera equation of state (EoS), which was extended to mixtures using the modified Huron-Vidal mixing rule. In such an approximation, the phi-phi approach was directly linked to the Square Gradient Theory, while the experimental excess Gibbs energy data were directly transferred to the EoS model for calculation purposes. According to the results, accurate predictions of the experimental data were obtained for the vapor-liquid equilibrium and interfacial tensions, while qualitatively correct results were obtained for the mixing volumes.