Abstract
The density gradient theory (GT) combined with a SAFT-type (Statistical Associating Fluid Theory) equation of state has been used for modeling the surface tension of associating fluids represented by a series of six alkanols ranging from methanol to 1-pentanol. The effect of nonzero dipole moment of the selected alkanols on the predicted surface tension was investigated in this study. Results of the GT + non-polar Perturbed Chain (PC) SAFT equation of state were compared to predictions of GT combined with the PC-polar-SAFT, i.e. PCP-SAFT, equation. Both GT + PC-SAFT and GT + PCP-SAFT give reasonable prediction of the surface tension for pure alkanols. Results of both models are comparable as no significant difference in the modeled saturation properties and in the predicted surface tension using GT was found. Consideration of dipolar molecules of selected alkanols using PCP-SAFT had only minor effect on the predicted properties compared to the non-polar PC-SAFT model.
Highlights
The surface tension of associating fluids, e.g., water, alkanols, amines, plays an important role in many environmental processes and engineering applications such as nucleation, flow through porous media, and distillation
The results for gradient theory (GT) combined with the original Perturbed Chain (PC)-SAFT equation of state (EoS) with neglected polarity of alcohol molecules are compared to the GT + Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) model extended by the polar interactions
Gross and Vrabec call PC-SAFT extended by the polar interactions as PC-Polar-SAFT, i.e. PCP-SAFT
Summary
The surface tension of associating fluids, e.g., water, alkanols, amines, plays an important role in many environmental processes and engineering applications such as nucleation, flow through porous media, and distillation. The Cahn-Hilliard density gradient theory (GT) [1] combined with the physically based equation of state (EoS) are used to model the surface tension for several associating systems. The original Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) [2] has been extended by the association and the polar interactions between molecules. A set of six various light alkanols, ranging from methanol to 1-pentanol, has been chosen to examine the predictive ability of the GT + PC-SAFT EoS to model surface tension of associating polar fluids. The results for GT combined with the original PC-SAFT EoS with neglected polarity of alcohol molecules are compared to the GT + PC-SAFT model extended by the polar interactions
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