(754h) Mixing-Rule Free Description of Dispersive Interactions in Perturbed-Chain Statistical Associating Fluid Theories

Most of the statistical associating fluid theory (SAFT) equations of state are tailored for accurate description of the properties of one-component fluids. But, when it comes to the description of properties of mixtures, empirical mixing rules, such as van der Waals one-fluid mixing rule, are commonly employed in the contribution of the dispersive interactions to thermodynamics. The van der Waals one-fluid mixing rule substitutes the contribution of the dispersive interactions of multi-component fluid by a contribution of effective one-component fluid, with average values of molecular size and interaction parameters. This simplification leads to inaccuracies [1], which tend to increase with the size asymmetry between the mixture components [2].

In order to rigorously formulate the mixing-rule free Barker-Henderson perturbation theory for chain mixtures, an analytical expression for the Laplace transform of the radial distribution function of a mixture of hard-sphere chains of arbitrary segment size and chain length was derived [3] based on the solution of Wertheim integral equation theory in ideal chain approximation [3,4]. Using the formulated approach, a simple variant of the perturbed-chain statistical associating fluid theory is proposed and used to examine properties of several mixtures of chains of different lengths and segment sizes.

References

1. Y. Tang and B. C.-Y. Lu, Fluid Phase Equilib. 165, 183â??196 (1999).

2. S. Hlushak, J. Chem. Phys. 143, 124906 (2015).

3. S. Hlushak and Yu V. Kalyuzhnyi, J. Phys. Stud. 11, 165-177 (2007).

4. J. Chang, S. Sandler, J. Chem. Phys. 103, 124906 (1995).