ABSTRACT
For more than 100 years, scientists and engineers have been aware that supercritical fluid (SCF) solvents offer the potential of novel processing protocols. However, it is only in the past three decades that SCF solvents have been investigated or applied as solvents for processing foods, nutraceuticals, and polymeric materials; as reaction media for polymerization processes; as environmentally preferable solvents for solution coatings, powder formation, impregnation, encapsulation, cleaning, crystal growth, and antisolvent precipitation; and as mixing/blending aids for crystalline or viscous materials. This broad range of applications could be extended even further if a better understanding of the underlying physics and chemistry of SCF-solute behavior can be established. At present, efficient development of SCF-based processing technology suffers from the limitation that equations of state utilized for process simulation and modeling of SCF-solute mixture behavior are still not facile enough to describe the large changes in solution properties exhibited for an SCF-based process when realistic intermolecular potential functions are used. As a consequence, the approach taken in this chapter is to describe a molecular thermodynamic basis for interpreting SCF-solute phase behavior that relies on a physicochemical interpretation of experimental data. With this approach, the types and the strengths of energetic interactions are related to the chemical nature of the SCF solvent and to the chemical features of the solute.
