Supercritical Crystallization of Organic Materials: The Gas Antisolvent (GAS) Process
Nonconventional processing methods can lead to the development of materials with unique chemical, physical or mechanical characteristics that make them suitable for specialized applications. One such method is crystallization with supercritical fluids (SCFs), where the unique fluid characteristics and solvent properties of supercritical fluids are utilized. Crystallization using SCFs have several advantages over conventional liquid solvents/antisolvents crystallization as their physical properties such as density and solubility can be âtunedâ within a wide range of processing conditions by varying both temperature and pressure. As most organic materials have poor solubility in SCFs, antisolvent techniques are more attractive. Among these is the gas antisolvent (GAS) process. In the GAS process, high pressure SCF is injected into the liquid phase solution, which causes a sharp reduction of the solute solubility in the expanded liquid phase. As a result, precipitation of the dissolved compound occurs. The potential advantages of the GAS crystallization process lies in the possibility of obtaining solvent free, micron and submicron particles with a narrow size distribution.