Volumetric Properties of Hexafluoropropylene and Hexafluoropropylene Oxide. Determination of Phase Diagram and Critical Properties

Hydrofluoroalkenes like hexafluoropropylene (HFP) and hexafluoropropylene oxide (HFPO) are being investigated as new fluids for refrigeration systems or interesting fluids for extraction. Considering these different aspects of utilisation, one of the most interesting properties are the densities at and outside saturation. The vibrating tube densitometer technique is used to determine densities for several temperatures between 263.15 and 383.15 K and pressures between 0 and 15 MPa. The Forced Path Mechanical Model (Bouchot and Richon, 2001) is used to correlate, at temperature and pressure, the density to the U-tube vibrating period.

Using the experimental densities values and critical divergence theory concerning density difference between the liquid and vapour phases on the coexistence curve , the critical properties and the phase diagram can be determined.

Bouchot, C., Richon, D., An enhanced method to calibrate vibrating tube densitometer, Fluid Phase Equilib., 2001, 191, 189-208.