Volumetric, ultrasonic, viscometric and refractive index behavior of binary mixtures of 2,2,4-trimethylpentane with aromatic hydrocarbons: An experimental and theoretical study

Abstract

Measurements of densities, ρ, ultrasonic speeds, u, viscosities, η, and refractive indices, n have been carried out for binary mixtures of 2,2,4-trimethylpentane (TMP) with benzene, toluene, o-xylene, m-xylene, and p-xylene, including those of pure liquids, at 35 °C over the entire composition range. From these experimental data, the values of excess molar volumes, V E, deviations in isentropic compressibilities, Δ k s, and viscosities, Δ η, excess Gibbs free energy of activation of viscous flow, G ⁎ E, deviations in refractive indices, Δ n, and partial molar isentropic compressibility, K¯ 2°, of aromatic hydrocarbons in TMP at infinite dilution were calculated. The variations of these parameters with composition of the mixtures suggest an increasingly better packing of plate-like aromatic molecules into the spaces created by globular-shaped TMP molecules in the sequence: benzene < toluene < m-xylene ≈ p-xylene < o-xylene. Further, for xylenes, the magnitude of these derived parameters is found to depend on the position of –CH 3 groups in the molecule. The excess molar volumes, V E, of the mixtures have also been predicted from Flory's statistical theory and the Prigogine–Flory–Patterson (PFP) theory. Using Flory theory and rigid hard sphere models, the values of isothermal compressibilities, k T, of the present binary mixtures were evaluated and compared with the experimental values. Moreover, theoretical evaluation of viscosity by using one-, two- and three-parameter equations suggests the superiority of the three-parameter equation over one- and two-parameter equations.