Mise au point de méthodes de caractérisation de binaires en milieu supercritique et modélisation des propriétés physiques et thermodynamiques mesurées

摘要

This work is focused on the characterization of physical and thermodynamic properties of CO2-cocoa butter (CB) and CO2-PEG400 saturated mixture. Measurements of density, volumetric expansion, viscosity and CO2 solubility were carried out on CB-rich phase at 313 and 353 K and pressures up to 40 MPa. The experimental techniques have previously been compared and validated with DMSO-CO2 mixture. Density measurements were performed using the vibrating tube technology at pressures ranging from 0.1 to 25 MPa. Experimental values were well correlated with the modified Tait equation. CO2 solubility measurements were coupled to the density ones in the same pressures ranges. At 25 MPa, the solubility of CO2 in CB is 31.4 % and 28 .7 % at 313 and 353 K respectively. Phase behaviour was investigated using a view cell in order to follow the expansion of the CB-rich phase with the rise in pressure. Volumetric expansion up to 47 % was measured and correlated to the CO2 solubility. Phase inversion was observed at 313 K and 40 MPa. Lastly, we developed an innovative falling body viscosimeter for high pressure measurements. Viscosity measurements were carried out up to 25 MPa showing a viscosity reduction up to 90 % upon CO2 dissolution. These results were correlated with two empirical models. A new model here presented, was favourably compared with the Grunberg and Nissan model. All the experimental results are consistent with the available literature data. This work opens new perspectives about the determination of the properties of systems such as polymers-CO2 and fats-CO2, which are essential for supercritical process design such as extraction, crystallization, chromatography and synthesis reaction.