Advanced Physical Extraction Technology-Supercritical fluid extraction
Supercritical fluid extraction (SFE) is the most advanced physical extraction technology in the world. At lower temperatures, when the pressure of the gas increases continuously, the gas will be converted into liquid. When the temperature increases, the volume of the liquid will increase. There is always a critical temperature (Tc) and a critical pressure (Pc) for a particular substance. When the temperature and the critical pressure are higher than the critical temperature and the critical pressure, the substance will not become liquid or gas. It's the critical point. In the range above the re-critical point, the material state is between gas and liquid, and the fluid in this range becomes supercritical fluid (SF).
Supercritical fluids have strong penetration capacity similar to gases and high density and solubility similar to liquids. They have good solvent properties and can be used as solvents for extraction and separation of monomers. Supercritical fluid extraction (SFE) is a new and high technology in modern chemical separation. SFE combines traditional distillation with organic solvent extraction and effectively separates, extracts and purifies the matrix and extract by using supercritical CO2 as a solvent.
SFE uses supercritical CO2 to extract materials.
CO2 is a safe, non-toxic, cheap liquid. Supercritical CO2 has similar gas diffusion coefficient, liquid dissolving force, zero surface tension, can quickly penetrate into solid substances, extract its essence, and has the characteristics of high efficiency, no oxidation, pure nature, no chemical pollution and so on. Supercritical fluid extraction separation technology uses the solubility of supercritical fluid to be closely related to its density. By changing pressure or temperature, the density of supercritical fluid can be greatly changed. In the supercritical state, the supercritical fluid is contacted with the substance to be separated, so that the components with different polarity, boiling point and relative molecular mass can be extracted selectively.
When extracting natural products by supercritical fluid extraction, CO2 is usually used as extractant. This is because:a)
The critical temperature and critical pressure are low (Tc=31.1 C, Pc=7.38MPa), the operating conditions are mild, and less damage to the effective components, so it is especially suitable for the treatment of high boiling point heat sensitive substances, such as essence, spices, oils, vitamins, etc.
(b) CO2 can b e regarded as a non-toxic and cheap organic solvent similar to water;
c) CO2 is stable, non-toxic, non-combustible, safe and non-polluting in use, and can avoid oxidation of products; d) the extract of CO2 contains no nitrate and harmful heavy metal, and there is no residual harmful solvent;
e) CO2 is extracted in supercritical CO2 extraction. The extracted material can be precipitated by lowering pressure or raising temperature without repeated extraction operation, so the supercritical CO2 extraction process is simple. Therefore, supercritical CO2 extraction is especially suitable for the extraction and purification of biology, food, cosmetics and drugs.