Prediction of the Vapor-Liquid Interfacial Tension of Nonassociating and Associating Fluids with the SAFT-VR Density Functional Theory

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• 作者：Guy J. Gloor ; George Jackson ; F. J. Blas ; E. Mart&iacute ; n del R&iacute ; o ; E. de Miguel
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：November 1, 2007
• 年：2007
• 卷：111
• 期：43
• 页码：15513 - 15522
• 全文大小：151K
• 年卷期：v.111,no.43(November 1, 2007)
• ISSN：1932-7455

文摘

The SAFT-VR DFT Helmholtz free energy density functional [Gloor, G. J.; Jackson, G.; Blas, F. J.; Martíndel Río, E.; de Miguel, E. J. Chem. Phys. 2004, 121, 12740] is used to describe the vapor-liquid interfaceof nonassociating and associating molecules ranging in size from small molecules to long chains. The functional,which is based on the statistical associating fluid theory for attractive potentials of variable range (SAFT-VR) description of the homogeneous fluid [Gil-Villegas, A.; Galindo, A.; Whitehead, P. J.; Mills, S. J.; Jackson,G.; Burgess, A. N. J. Chem. Phys. 1997, 106, 4168], is constructed by partitioning the free energy densityinto a reference term (which incorporates all of the short-range interactions and is treated locally) and anattractive perturbation (which incorporates the long-range dispersion interactions). This functional accountsexplicitly for the correlations between the segments using a density-averaged correlation function incorporatedinto the perturbative term in a similar way to that proposed by Toxvaerd. The SAFT-VR DFT formalism isused to examine the vapor-liquid interfacial tension of a number of pure components, including: n-alkanes;small associating molecules, such as water; linear alkan-1-ols; and some selected replacement refrigerants. Inthe case of the hydrocarbons and other weakly polar substances, the surface tension can be predicted fromintermolecular parameters derived in the usual way from the bulk fluid phase equilibria (vapor-pressure andsaturated liquid density). By contrast, when one describes the interfacial properties of associating compounds,it is important to include the surface tension data as well as the bulk vapor-liquid phase equilibria in developingthe intermolecular potential model. This provides a means of determining the balance between the dispersiveand associative (hydrogen bonding) contributions to the intermolecular potential. The use of interfacial datain the refinement of the potential model allows one to obtain a reliable set of parameters, which can be usedto predict the bulk and interfacial properties of mixtures for a broad range of thermodynamic conditions.