465589 Mixing-Rule Free Description of Dispersive Interactions in Perturbed-Chain Statistical Associating Fluid Theories

Thursday, November 17, 2016: 5:15 PM
Union Square 22 (Hilton San Francisco Union Square)
Stepan Hlushak, Institute for Condensed Matter Physics, Lviv, Ukraine; Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada

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, 183–196 (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).


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