Characterization of the ionic liquid bmimPF_6 in supercritical Conditions

摘要

Ionic liquids are organic salts, which, according to their singular characteristics, are the subject of extensive research. They are considered as potential candidates for the replacement of organic solvents. The ionic liquids have a very good solvent capacity for materials organic and inorganic, polar and non-polar. In addition, the ionic liquids are thermally stable, often non flammable and they have a negligible vapor pressure, which reduces environmental pollution and decreases the risks of exposure compared to conventional organic solvents. Ionic liquids and supercritical CO_2 are benign environmental solvents, and each one has its clean and single properties. The combination of the advantages of these two types of green solvent is a new and interesting study. Recently, BRENNECKE and al [1-3] studied the solubility of CO_2 compressed in the ionic liquids. They found that supercritical CO_2 is largely soluble in most ionic liquids, but the solubility of these ionic liquids in the supercritical CO_2 is negligible. Yet, the studies explaining the behaviour of the phases of the ionic liquids in the presence of the supercritical fluids are rare. In the objective to understand the phenomena arising from putting into contact an ionic liquid with a supercritical fluid, we were based in our study on what the other researchers made to set up new measurement techniques of solubility and density of the mixture CO_2/ionic liquid. The processes of generation of divided solids by the use of supercritical fluids (FSC) are industrially promising. Among these processes, the SAS technique (Supercritical AntiSolvent), based here on the use of supercritical CO_2 (CO_2-SC) as anti-solvent and of an ionic liquid as solvent, offers the advantage of being completely clean. However, the phenomena governing this process are badly controlled and many parameters are unknown. Thus, in order to model this process, techniques of characterization of the properties of the binary solvent/antisolvent must be developed.