Common in supercritical fluid, because C02 is chemically stable, non-toxic and non corrosive, easy to fly and not explosive, the critical state is easy to realize, and the critical temperature (31. IC) close to room temperature, in food and medicine aroma components, physiological active substances, enzymes and proteins such as heat sensitive material without damage thus, C02 is commonly used as the extractant for supercritical extraction.
The critical pressure of pure C02 is 7. 3MPai critical temperature is 31 working seven. When the pressure of C02 and temperature were more than 7.3MPa and 3 cover engineering degrees, this state is called a C02 supercritical C02. in the supercritical state, C02 fluid is a kind of high density compressible fluid, become the nature between liquid and gas phase single, double: it has the characteristic of gas-liquid two-phase flow the density is close to the liquid viscosity, liquid 1%, self diffusion coefficient is 100 times liquid, so it has high diffusion coefficient and gas equivalent and low viscosity, and is similar to the liquid density and strong solubility of certain substances, can be said that the supercritical C02 has special permeability and solubility for some materials.
Supercritical C02 extraction process
Supercritical C02. The density is very sensitive to changes in temperature and pressure, so the adjustment check using the C02 official pressure and temperature, can by adjusting the density of C02 to adjust the C02 to extract Z9 from the corresponding solution; the pressure range of extract is not single, mixed components to control conditions get the best proportion, then the supercritical fluid into ordinary gas by means of decompression and heating, and is extracted completely or basically separately, so as to achieve the aims of separation and purification, which is a supercritical C02 extraction process.
Dissolution selectivity of supercritical C02
Supercritical state C02 has selective dissolution of low molecular weight, weak polar, fat soluble and low boiling point components such as hydrocarbons, volatile oil, cool, cool, ether, epoxy compounds exhibit excellent solubility, and the polar group (-OH, -COON) compounds. The more polar group, more difficult to extract, so polyol, and the base of the polybasic aromatic substances insoluble compounds in supercritical Cos. with high molecular weight, molecular weight is higher, more difficult extraction, polymer molecular weight more than 500 is almost insoluble, so for this kind of material extraction we need to increase the extraction pressure, or join the third group has changed the solute solubility to active ingredients and supercritical C02 consisting of two yuan in the system (i.e., entrainer) to change the original effective component content; degree of hydrolysis. Generally speaking, it has good solubility, and the volume agent is often a good entrainer, such as methanol, ethanol, acetone, acetic acid vinegar and so on.
The characteristics and advantages of supercritical fluid extraction:
Compared with the traditional separation technology, the supercritical C02 extraction technology has the following unique advantages:
The extraction temperature is low.
At close to room temperature (30-50C and C02 gas shadow extraction, can effectively prevent the oxidation and diffusion, heat sensitive material to retain the integrity of biological activity, and the high boiling point, low volatility, easy to pyrolysis material at its boiling temperature following extraction;
The extraction rate is high (795%).
It is easy to change the solubility of C02 in the system by adjusting the pressure and temperature, so as to increase the yield of products, and is suitable for the extraction of valuable and high added value substances.
The whole process is not organic. It can effectively avoid the residual toxicity of traditional Chinese medicine under the traditional extraction conditions, meanwhile, it also prevents the toxicity and environmental pollution caused by the extraction process, without waste gas and wastewater. Even the waste residue can be comprehensively utilized.
The production cycle is short.
When the extraction (dynamic) cycle begins, the separation begins to proceed. Generally, the extraction is separated for about 10 minutes or so, and it can be extracted completely for about 2-4 hours. At the same time, it does not need to concentrate step, even if adding entrainer, it can be removed or simply concentrated by separation function.
Low energy consumption.
The extraction and separation. When the dissolved matter be made one, full of C02 through the separator, the pressure drop between CO2 and extract was separated immediately and become two-phase, no phase transition process of materials, saves a large amount of heat, greatly reduce the production cost, and simplify the process; CO2 recycling, without recovery of solvent. Not only the high extraction efficiency and less energy consumption, cost savings;
No flammable and explosive danger.
The whole system is mainly based on CO2; the volume agent, and C02 itself is an inert gas, so it can truly realize the green production process.
A set of devices for a variety of uses.
. solubility of supercritical C02 can be adjusted. Under certain temperature conditions, as long as the change in pressure or adding entrainer can be suitable to extract different polar substances. The solubility changes every time C02, is in the use of a new solvent, which enables the extraction of a supercritical C02 extraction device applicable to dozens and dozens of substances, greatly improving the use range of the device;
The operating parameters are easy to control.
Supercritical C02 extraction of various natural products (such as Chinese herbal medicine) is not only technically superior, but also easy to control operation parameters and make product quality stable. Supercritical 002 also has antioxidant and sterilization effect, which is conducive to ensuring and improving product quality.
The main factors affecting the supercritical 002 fluid extraction
The main factors affecting the supercritical 002 fluid extraction include the extraction pressure, the extraction temperature, the extraction time, the carbon dioxide flow and the properties of the material.
1 the effect of pressure on extraction:
During the extraction process, the change of SC-C02 density directly affects the extraction effect. The extraction pressure is an important parameter affecting the density of SC-C02. When the temperature is fixed, the pressure increases with the extraction pressure.