n - PATh :.: Process and Product Applied Thermodynamics research ...

General Introduction
carbon dioxide is increased if it contains a fluorinated alkyl segment, since CO2 is more
soluble in fluorinated compounds than in their hydrocarbon counterparts (Hoefling et al.,
1991). Non-polar perfluorocarbon species show increased solubility in supercritical CO2
and have been used in the design of CO2-philic surfactants, chelating agents and ligands in
order to improve the solubility of polymers, metals and catalysts (Osswald et al., 2001).
2) As medium in two-phase reaction mixture: in a novel separation and purification
technique that is attracting current interest in organic synthesis and process development,
in the immobilization of expensive metal catalysts called “Fluorous Phase Organic
Synthesis" (FPOS) (Horvath and Rabai, 1994). The hydrophobicity of fluorinated
compounds that makes them immiscible with water and with many common organic
solvents, their ability to form a homogenous solution at elevated temperatures with several
of these solvents, their inertness, their solubility in supercritical CO2 and their ability to
dissolve gases contributes to the increasing popularity of the "Fluorous Phase" in organic
syntheses (Gladysz, 1994; Studer et al., 1997 and Betzemeier and Knochel, 1999). By
introducing perfluorinated ligands, a catalyst is solubilized and simultaneously
immobilized in the "Fluorous Phase". By increasing the temperature, the biphasic system
forms a homogenous solution and the catalytic process can take place. Cooling down the
reaction mixture leads to the reformation of two separate phases. Afterwards, easy product
isolation and the recovery of the perfluoro-tagged metal catalyst can be achieved by simple
phase separation. The isolation and recovery of perfluorinated components can be
accomplished not only by a phase separation of immiscible liquid layers but also by solidliquid
extraction using a perfluorinated non-polar stationary phase (Horvath and Rabai,
1994).
3) As refrigerants: short-chain halocarbons that are used as refrigerants, aerosol
propellants and foam blowing agents. Initially, the chlorofluorocarbons (CFCs) were used
for this purpose, but they were implicated in stratospheric ozone depletion (Molina and
Rowland, 1974) and have subsequently been replaced by the hydrofluorocarbons (HFCs)
(Wallington et al., 1994). The CFCs were typically fully halogenated methanes while the
HFCs are generally partially fluorinated ethanes such as HFC 134a (1,1,1,2tetrafluoroethane),
which is the most commonly used HFC. Other short chain
perfluoroalkanes used as evaporative fluorocarbon cooling for the semiconductor pixel and
- 10 -