In the early stages of this project we are focusing on the accurate modeling of supercritical fluids and simple polymer-solvent systems with the SAFT equation of state. We anticipate this will require the development of a truly global SAFT approach, capable of accurately describing the fluid phase behavior of fluids from the triple point to the critical point, and the incorporation of heterogeneity in the model chain.
SAFT-VR is perhaps the most versatile, fundamentally, based engineering equation of state in use today. However, in common with all analytic equations of state, SAFT-VR exhibits classical behavior in the critical region rather than the non-analytical, singular behavior seen in real fluids. Recently, so-called crossover equations of state have been developed which solve this shortcoming by incorporating the scaling laws valid asymptotically close to the critical point while reducing to the original classical equation of state far from the critical point. We have combined the SAFT-VR equation of state with an analytical crossover technique to obtain the SAFT-VRX equation of state. The SAFT-VRX approach combines the accurate low temperature behavior of SAFT-VR with a precise representation of the critical region. .
View a powerpoint presentation on the application of crossover theory to SAFT-VR equation of state which which illustrate the accuracy of the SAFT-VRX approach over the entire fluid phase region for hydrocarbon systems
|We are also focusing on the study of semifluorinated alkanes or perfluoroalkylalkanes, an important class of diblock polymers, in collaboration with Eduardo Filipe's group. Composed of an alkane chain, H(CH2)n, bonded to a perfluoroalkane chain F(CF2)m, they can be regarded as semi-flexible copolymers of linear alkanes and perfluoroalkanes. These amphiphilic molecules can self-assemble in both hydrocarbon and fluorocarbon solvents (for example, C8F17C16H33 forms micelles in toluene and reverse micelles in perfluoroctane) and have applications from drug delivery to surfactants in supercritical carbon dioxide.
|A short perfluoroalkylalkane|
C. McCabe and S. B. Kiselev, "Molecular Modeling of Fluids Near to and Far from the Critical Region: Application of SAFT-VRX, Fluid Phase Equilibria, accepted for publication (2003).
C. McCabe, S. Kiselev, J. F. Ely, Application of Crossover Theory to the SAFT-VR Equation of State, AIChE Annual Meeting, Indianapolis, Indiana, November 8th 2002.
C. McCabe, Accurate Modeling of Phase Equilibria Including the Critical Region Using a Molecular-Based Equation of State, (Invited) Molecular Thermodynamics and Molecular Simulation 03, Akiu, Sendai, Japan May 28th 2003.
C. McCabe, S. B. Kiselev, and J. F. Ely, Molecular Modeling of Fluids Near to and Far from the Critical Region: Application of SAFT-VRX, 15th Symposium of Thermophysical Properties, Boulder CO, June 25th 2003.
C. McCabe, S. B. Kiselev, and J. F. Ely, SAFT-VRX Modeling of Fluids Near to and Far from the Critical Region, Foundations of Molecular Modeling and Simulation, Keystone Resort, Keystone, CO, July 6th-11th 2003.
F. J. Blas, C. McCabe, P. Morgado, E. J. M. Felipe, "An examination of the vapor-liquid phase behavior of perfluoroalkane-alkane diblock surfactants using the SAFT-VR approach," AIChE Annual Meeting, San Francisco, November 2003.
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This work is supported by NSF
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