Supercritical fluids, water and CO2 are a specialized topic in the field of thermal processes.
The use of supercritical carbon dioxide (sc-CO2) has numerous advantages compared with other processes, which generally involve solvents. It enables recovery of the extraction medium in a closed-loop process, through fractionated sedimentation of the extract. Supercritical CO2 is also chemically inert with no risk of explosion. Beside its gas-like viscosities, fluid-like densities and very good transportation properties, an advantage of supercritical CO2 is its capacity to dissolve a wide variety of organic components.
The debinding of components, the extraction of plant-based active ingredients and the degreasing of surfaces are just a few examples of applications using supercritical CO2 as a solvent. When highly exothermic reactions, or reactions with oxidizing materials, are carried out, the reaction in supercritical CO2 can be an attractive alternative to conventional syntheses.
Supercritical water (water above 374.12 °C and 221.2 bar) has very different properties to water under familiar conditions. In the supercritical state it can serve, for example, as a solvent for organic compounds, or for the decomposition of electronic waste.