High pressure speed of sound and density of (decalin + n-decane), (decalin + n-hexadecane) and (n-decane + n-hexadecane) systems and thermodynamic modeling with PHCT equation of state

Abstract

Decalin, n-decane and n-hexadecane are chemicals asymmetrical in shape, length and chemical nature that can be found in diesel and kerosene fractions. To evaluate the influence of these differences on the physical properties of mixtures involving these components, speed of sound for n-decane, n-hexadecane and decalin, as well as for binary mixtures composed of these hydrocarbons, were determined at pressures (0.1, 5, 10, 15, 20 and 25)MPa and temperatures (313.15, 323.15 and 333.15)K at different compositions. Additional density data at atmospheric pressure for the same systems were measured experimentally at temperatures of (313.15, 323.15 and 333.15)K. From these results and thermodynamic definitions, density at high pressures and excess molar volume were calculated. The experimental data were correlated with the Perturbed-Hard-Chain Theory (PHCT) equation of state. The PHCT model correlated well experimental densities for pure components and mixtures but did not correlate so well the speed of sound dependency with temperature and pressure. The model calculated well excess molar volumes, with correct signs, magnitudes, and the qualitative effect of pressure and temperature on this property.