Partition Coefficients of Organics between Water and Carbon Dioxide Revisited: Correlation with Solute Molecular Descriptors and Solvent Cohesive Properties

High-pressure phase behavior of systems
containing water, carbon
dioxide and organics has been important in several environment- and
energy-related fields including carbon capture and storage, CO2 sequestration and CO2-assisted enhanced oil recovery.
Here, partition coefficients (K-factors) of organic
solutes between water and supercritical carbon dioxide have been correlated
with extended linear solvation energy relationships (LSERs). In addition
to the Abraham molecular descriptors of the solutes, the explanatory
variables also include the logarithm of solute vapor pressure, the
solubility parameters of carbon dioxide and water, and the internal
pressure of water. This is the first attempt to include also the properties
of water as explanatory variables in LSER correlations of K-factor data in CO2–water–organic
systems. Increasing values of the solute hydrogen bond acidity, the
solute hydrogen bond basicity, the solute dipolarity/polarizability,
the internal pressure of water and the solubility parameter of water
all tend to reduce the K-factor, that is, to favor
the solute partitioning to the water-rich phase. On the contrary,
increasing values of the solute characteristic volume, the solute
vapor pressure and the solubility parameter of CO2 tend
to raise the K-factor, that is, to favor the solute
partitioning to the CO2-rich phase.