Supercritical fluid extraction

Kristiina Kreek

POKE

2013 Tallinn

Supercritical fluid

Density of carbon dioxide

Properties of supercritical fluids

Properties

High solvating power (ability of a solvent to dissolve a solute): is a good solvent due to it`s near liquid density

High diffusivity – due to it`s gas like properties

Because of lower density then liquids, they have more space for particles to move

High temperatures – particles move faster

Viscosity: 10-100 times smaller then for liquids, particles are far apart

No surface tension (no liquid/gas phase boundary)

Polarity: most supercritical fluids behave like non-polar solvents.

Possible to tune their properties by adding a polar co-solvent

Advantages of SCF-s

Combination of useful propertis of liquids and gases

Good solvents

Penetrate materials easily

Properties can be altered by varying pressure and temperature

Easy solvent removal

Recyclability

Critical parameters of solvents

CO2 as an extrahent

Adventages

Non toxic

Not Flammable

Cheap

Obtained as a byproduct of industriaal processes

Critical point can be „easily“ achieved

Disadvantages

Can`t be used for extracting polar molecules

Expesive equipment

High pressures

The system used for extraction

Advantages of SFE

Low temperature extraction results in minimal degradation of volatile compounds

Faster

High product yields

Spent material is left undamaged

Solvent is easily removed

Somewhat selective

Using CO2 for extraction is cheap and safe

Disadvantages – expensive equipment, not suitable for extracting wet materials.

Applications of SCF-s

Extraction

Decaffinated coffee and tea, hop extract, extraction of lipids, vitamins, preparation of essential oils, pesticide removal, laboratory test methods

Cleaning

Impregnation

Solvent in chemical reactions

Materials synthesis

Formation of nanoparticles

Drying

Supercritical drying

Surface tensions do not exist in supercritical state.

Can be used for making aerogels

Conclusion

Supercritical fluids are the link between liquid and gas, giving the possibility to fine-tune the properties of the solvent.

SCF-s can be used for many diferent applications, from extraction to synthesis.