Particle Formation Techniques Using Supercritical Fluids

In the last decade, the supercritical fluid (SCF)-assisted technology generation of micro- or nano- particles of organic, inorganic, or their composite compounds has attracted a growing interest for increasingly sophisticated applications among scientists in various fields. The purpose of this review is to summarize the recent patent literature concerning particle formation techniques using SCFs. Three distinct classes were grouped and surveyed: physical approach, chemical approach, and physico-chemical processes. For the first class, patents are reviewed related to rapid expansion of supercritical solution (RESS), supercritical anti-solvent (SAS), atomization with assistance of SCFs (e.g., particle generation from gas-saturated solutions, carbon dioxide nebulization with a bubble-dryer, and supercriticalassisted atomization), emulsion/suspension-drying process, and impregnation with assistance of SCF. For the second class, patent literature relevant to processes that use SCF as a reactant, i.e. supercritical hydrothermal/solvothermal synthesis, processes that use a SCF as solvent (e.g., thermal decomposition with a supercritical solvent, polymerization in SCFs, and reaction in SCF microemulsion) is summarized. For the third class, patent information concerning reaction- SCF drying and reaction-RESS/SAS is introduced.