Supercritical carbon dioxide fluid extraction of solid-phase materials is a method of separating and extracting substances, which uses supercritical carbon dioxide as an extraction agent to extract organic solvents, natural products, and other target compounds in solid samples.
This method works by converting carbon dioxide into a liquid state at supercritical (high temperature, high pressure) conditions and using it as a solvent. When liquid carbon dioxide comes into contact with a solid sample, it absorbs the compounds in the sample and brings them into the solution. After sufficient contact, by controlling conditions such as fluid pressure and temperature, the supercritical carbon dioxide fluid can be restored to a gaseous state, and the compounds are precipitated and collected, and separated.
Compared with traditional organic solvent extraction, supercritical carbon dioxide fluid extraction has many advantages, such as using relatively safe and environmentally friendly renewable solvent carbon dioxide instead of toxic organic solvents; no post-processing steps are required because carbon dioxide is extracted from the extraction process Evaporation; and will not destroy the components of volatile aroma substances and volatile oil samples during the extraction process.
Supercritical CO2 fluid extraction process
The technological process of supercritical CO2 fluid extraction is set according to different extraction objects and for different extraction purposes. Theoretically speaking, whether a certain substance can be extracted and separated depends on whether there is a certain solubility difference between the target component (ie solute) in the extraction section and the analysis section. The solubility of the solute is required to be dissolved in the fluid, while in the analysis section, the solubility of the solute in the fluid is required to be small so that the solute can be resolved from the fluid.
The supercritical CO2 fluid extraction process is mainly composed of two parts: extraction and separation
In the extraction process, the extraction efficiency of supercritical CO2 fluid extraction is determined by the solvent power, the characteristics of the solute (extract), and the combination of the solute and the matrix. Therefore, when selecting extraction conditions, on the one hand, the solubility of the solute in the fluid should be considered, and on the other hand, the ability and speed of the solute to desorb from the active point of the sample matrix and diffuse into the fluid should also be considered.
5 Stages of CO2 Fluid Extraction
The supercritical CO2 fluid extraction process can be described as the following stages:
- CO₂ fluid diffuses in the SCF membrane surrounding solid material particles.
- CO₂ fluid penetrates and diffuses in solid material particles.
- The solute dissolves in the CO₂ fluid.
- The solute diffuses through the solid material particles.
- The solute diffuses through.
Three types of CO2 fluid extraction separation process
The separation and collection of supercritical CO2 fluid extraction usually involve the following steps:
- Separator: A step-down separator that converts fluid from supercritical to gaseous to separate dissolved organics and CO2. Separators are usually operated at reduced temperatures and pressure to separate organics and extraction solvents based on the boiling points of the compounds.
- Collector: Precipitated organic compounds need to be collected and stored in a collector.
- Recycling CO2: The separated CO2 first needs to be recycled to improve the efficiency of the extraction. The CO2 is recycled and injected into the next extractor to reduce CO2 usage and increase the purity of the compound.
The separation and collection method of supercritical CO2 fluid extraction can provide products with high purity, high yield, and high efficiency. This method is widely used in the fields of preparing medicines, essential oils, and cosmetics.
During the separation process, the loaded solvent enters the separator from the extractor end through a pressure-reducing valve. Due to the temperature and pressure changes in the wall, the soluble substances that can be dissolved in the fluid in the extraction tank are separated from the supercritical fluid.
Separation processes can be described in the following types:
- Types 1#: A single pressure change causes the solubility of the solute to drop and precipitate.
- Types 2#: A single temperature change causes the solubility of the solute to decrease and separate.
- Types 3#: Changes in pressure and temperature cause the solubility of the solute to decrease and analyze.