Abstract:

Crystallization is widely used to separate and purify materials in the pharmaceutical and specialty chemical industries. Successful design of crystallization processes depends upon knowledge of the equilibrium solid-liquid phase behavior of the mixture to be separated. Although the solid-liquid equilibrium properties of a mixture can, in principle, be measured at any condition of interest, it would be useful to develop a theory that predicts phase behavior for mixtures based solely upon knowledge of the components' molecular architecture and intermolecular forces.

The goal of our research is to increase our fundamental understanding of how molecular properties such as size and interactions influence solid-liquid phase equilibria in binary mixtures. Our approach in this work is to calculate phase diagrams via molecular simulation for binary mixtures whose components interact according to the Lennard-Jones intermolecular potential model. The Lennard-Jones model is a simple potential model that accounts for both molecular repulsions (due to their finite size) and molecular attractions. We have chosen to take this approach for three reasons. First, due to the simplicity of the model we can easily isolate the effects of molecular size differences from the effects of intermolecular attractions on the resulting phase diagrams. Second, molecular simulations are exact calculations for a given intermolecular potential model and therefore, our simulation results can be used to test the validity of approximations made in molecular theories based upon the Lennard-Jones model. Finally, it would be helpful to have a thorough understanding of how the essential features of size and interactions influence phase equilibria before we can incorporate more realistic and complex features, such as molecular architecture (the connectivity of atoms) into the potential model.

Publications:

M. H. Lamm and C. K. Hall, "Equilibria between solid, liquid, and vapor phases in binary Lennard-Jones mixtures", Fluid Phase Equilibria (submitted).

M. H. Lamm and C. K. Hall, "Molecular simulation of complete phase diagrams for binary mixtures ", AIChE Journal (in press).

M. H. Lamm and C. K. Hall, ``Monte Carlo simulations of complete phase diagrams for binary Lennard-Jones mixtures'', Fluid Phase Equilibria (in press).

M. R. Hitchcock and C. K. Hall, ``Complete phase diagrams for binary mixtures via Gibbs-Duhem integration'', to appear in Proceedings of the Foundations of Molecular Modeling and Simulation Conference, AIChE Symposium Series.

M. R. Hitchcock and C. K. Hall, ``Solid-liquid phase equilibrium for binary Lennard-Jones mixtures'', J. Chem. Phys., 1999, 110(23), 11433-11444.

Presentations:

``Monte Carlo simulations of complete phase diagrams for binary Lennard-Jones mixtures'', presented at the American Institute of Chemical Engineers Annual Meeting, Los Angeles, CA, November, 2000 (with Carol K. Hall).

``Monte Carlo simulations of complete phase diagrams for binary Lennard-Jones mixtures'', presented at the 16th IUPAC Conference on Chemical Thermodynamics, Halifax, Nova Scotia, Canada, August, 2000 (with Carol K. Hall).

``Complete phase diagrams for binary mixtures via Gibbs-Duhem integration'', poster presented at the Foundations of Molecular Modeling and Simulation Conference, Keystone CO, July, 2000 (presented by Carol K. Hall).

``Monte Carlo simulations of solid-liquid and solid-liquid-liquid phase equilibria for binary Lennard-Jones mixtures'', presented at the American Institute of Chemical Engineers Annual Meeting, Dallas, TX, November, 1999 (with Carol K. Hall).

``Toward a fundamental understanding of chiral drug separations'', poster presented at the American Institute of Chemical Engineers Annual Meeting, Dallas, TX, November, 1999 (with Carol K. Hall).

``Toward a fundamental understanding of chiral drug separations'', presented at the American Chemical Society National Meeting, Anaheim, CA, March, 1999 (with Carol K. Hall).

``Solid-liquid phase equilibrium for binary Lennard-Jones mixtures'', presented at the American Institute of Chemical Engineers Annual Meeting, Miami, FL, November, 1998 (with Carol K. Hall).