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Prospect and Prospect of Supercritical Extraction Separation
Release time:
2019/01/30
Substances exist in the form of gas, liquid and solid, and can undergo phase transitions at different pressures and temperatures. When the temperature is higher than a certain value, any large pressure can not make the pure substance from the gas phase to the liquid phase, the temperature at this time is called the critical temperature Tc; and at the critical temperature, the low pressure at which the gas can be liquefied is called the critical pressure Pc.
Substances exist in the form of gas, liquid and solid, and can undergo phase transitions at different pressures and temperatures. When the temperature is higher than a certain value, any large pressure can not make the pure substance from the gas phase to the liquid phase, the temperature at this time is called the critical temperature Tc; and at the critical temperature, the low pressure at which the gas can be liquefied is called the critical pressure Pc. When the temperature of a substance is higher than the critical temperature and the pressure is greater than the critical pressure, the substance is in a supercritical state. In the pressure temperature diagram, the area above the critical temperature and critical pressure is called the supercritical zone. If the fluid is heated or compressed to its critical temperature and critical pressure above, the gas in this state is pressurized, and the gas will not be liquefied. Only the density increases, it has similar liquid properties, while retaining gas properties. The fluid in this state is called supercritical fluid (SCF).
the choice of supercritical fluid:
There are many solvents that can be used as SFE, and different solvents have different critical properties, and different extraction processes require different solvents. The fluids that can be used as supercritical extractants are mainly ethane, ethylene, propylene, carbon dioxide, etc. Using SFE technology to extract natural substances, CO2 is the solvent of choice, because CO2 as a solvent, has the following main advantages:
1) CO2 has good mutual solubility with most organic compounds, and CO2 liquid has greater volatility than the extract, which makes the separation of the extractant and the extract easier;
2) good selectivity, supercritical CO2 on low molecular weight aliphatic hydrocarbons, low polarity lipophilic compounds, such as esters, ethers, lipids, etc. showed excellent solubility;
3) The critical temperature (31.1 ℃) is low, and the enthalpy of vaporization is low, which is more suitable for industrial production;
4) The critical pressure (7.38MPa) is low and easy to reach;
5) Chemical inertness, no danger of combustion and explosion, no toxicity, no corrosion to the equipment, no pollution to the product and the environment; and the price is cheap, high purity CO2 is easy to obtain;
6) In the extraction system, the high concentration of CO2 has the effect of sterilization and oxidation prevention on the product.
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