MOLECULAR CHARISMA IN SUPERCRITICAL FLUIDS

The unique properties of supercritical fluids (SCF) solutions near the critical region are often a manifestation of local properties which a re significantly different than bulk properties. A variety of spectros copic measurements, as well as thermodynamic and theoretical treatment s, support the existence of local density and local composition augmen tations in the vicinity of large solute molecules in SCF solutions. Op portunities to exploit this concept of molecular charisma exist for a variety of engineering application including separations using cosolve nt/SCF systems and chemical reactions in SCF solvents. The component o f cosolvent effect on solubilities in SCF systems resulting from molec ular charisma is discussed and related to specific solute/cosolvent in teractions and cosolvent concentration. As a consequence of two effect s of molecular charisma, the potential to adjust reaction rates and re action selectivities in SCF solvents is also enhanced. Reaction rates may be altered through the concentration of reactants at the reaction site. Additionally, modification of local solvent strength in SCF solu tions, a property of the local reactant environment, can alter reactio n rates and selectivities.