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

keywords
abstract
perfluoroalkanes, oxygen, carbon dioxide, density, vapour pressure, solubility,
VLE, LLE, soft-SAFT
The aim of this work is the measurement and modelling of thermodynamic
properties of highly fluorinated compounds. Fluoroalkanes are alkanes where
the hydrogen atoms where total or partially substituted by fluorine atoms. As a
result of their strong intramolecular and weak intermolecular forces they
present peculiar properties that make them able to be used in a variety of areas
including environmental, industrial and biomedical. Their most relevant
applications are actually found in the biomedical field. Based on the large
solubility of respiratory gases in these compounds, perfluorochemicals and
their emulsions can be used in tissue oxygenation fluids, anti-tumural agents,
perfusates for isolated organs, surgical tools for ophthalmology, cell culture
media supplements, drug formulations and delivery, among others.
The choice of the best fluoroalkane to use for each application as well as the
prediction of the behaviour of a given fluoroalkane or mixtures involving
fluoroalkanes is only possible if accurate thermodynamic data for these
compounds is available. Remarkably, experimental data for these systems is
scarce or even inexistent in the open literature and so, limited conclusions can
be taken about the applicability of current thermodynamic models to correctly
describe fluorinated systems.
This work contributes with new experimental data for density, vapour pressure
and solubility of gases and alkanes in liquid fluoroalkanes. New apparatus were
built and validated to measure vapour pressure data and solubility of gases at
atmospheric pressures. Different molecular structures were chosen for the
perfluoroalkanes studied in order to conclude about the influence of the
structure, chain length and the substitution of terminal groups on the
thermodynamic properties of these compounds.
Experimental data measured was modelled using the Statistical Associating
Fluid Theory (SAFT), in this particular case, the soft-SAFT version. According
to the experimental results measured in this work, the equation was improved
by the addition of new terms trying to justify or correctly describe the
experimental evidences observed. For the first time a polar term was included
in the soft-SAFT model to account for the quadrupole moment on the carbon
dioxide and aromatic molecules in order to study its influence on the solubility
of the gas in the liquid perfluorochemicals. Also, to correctly describe the global
phase diagrams of pure perfluoroalkanes, a crossover procedure based on the
renormalization group theory was included to account for the long range
fluctuations that characterize the critical region and that the traditional models
do not account for.