19.1 Introduction

Supercritical fluids (SCF) are widely used for a broad field of industrial applications. The interest in using this technology is due to the special properties that are inherent to this class of fluids: the viscosity and the diffusivity of a SCF which are found in between that of a gas and liquid and the ability to vary the solvent density and the solvent properties easily and over a large extent by changing either the pressure or the temperature.

The applications often involve solutes that are in solid state at conditions where the solvent is in a supercritical condition. Among these applications, the SCF-assisted particle generation is a new and promising route to produce fine powders in mild operating conditions. It has attracted a lot of interest particularly in the pharmaceutical industry.1 By using pressure as an operating parameter, these processes lead to the production of fine and mono-disperse powders. There exist three families of processes (RESS, SAS, and PGSS) according to the way in which the FSC generally CO ₂ is used.

To develop them, the knowledge of the solid compound solubility in the corresponding involved medium is essential for evaluating the feasibility. Indeed, solubility is a good measurement of interactions between species. Moreover, the accurate determination of the influence of pressure and temperature on the solubility level provides insight into optimum operating conditions.

The most...