Isothermal vapor-liquid equilibria for binary mixtures of hexane, heptane, octane, nonane and cyclohexane at 333.15Â K, 343.15Â K and 353.15Â K

Isothermal vapor-liquid equilibria at 333.15 K, 343.15 K and 353.15 K for four binary mixtures of hexane + heptane, heptane + octane, cyclohexane + octane and cyclohexane + nonane have been obtained at pressures ranged from 0 to 101.3 kPa. The NRTL, UNIQUAC and Wilson activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Soave-Redlich-Kwong equation of state in calculating the vapor mole fraction. Liquid and vapor densities were also measured by using two vibrating tube densitometers. Phase behaviors of the P-x-y diagrams indicate that three mixtures of hexane + heptane, heptane + octane, cyclohexane + octane were close to the ideal solution. However, the cyclohexane + nonane mixture presents a large positive deviation from the ideal solution. Only the cyclohexane + octane mixture is negative in the excess Gibbs energy indicates that it is an exothermic system.