Supercritical CO2

The increasing demand for sustainable and environmentally viable technology in the process industry, has caused an increase in the interest in supercritical solvent applications.

The critical point of a substance was discovered in 1822 by the French Baron Cagniard de la Tour. Heating a liquid over a fire in a sealed gun barrel, he concluded from the sound of a moving rock inside the barrel, that at some point the differences between liquid and gas phase fade and even disappear. The temperature and pressure at which this occurred was called the Cagniard de la Tour Point. Later this was defined as the critical point.

Supercritical fluids are hybrid solvents, with features between those of a liquid and a gas. They have a low viscosity, high diffusivity and a very low surface tension. Above that, these features are dependent of pressure and temperature, which makes them ‘tuneable’.

Supercritical CO₂ is the most common fluid used, because supercritical state is reached at relatively low temperature and pressure. CO₂ is also cheap, non-toxic and generally harmless and abundantly available.