Supercritical extraction of natural mineral products has become a hot spot in the international industry

Supercritical carbon dioxide extraction (scco2) is a high and new technology developed in the 1980s, which has become a hot topic in the international industry. Supercritical Fluid Extraction (SFE) is a process of Extraction and separation of mixtures by using Supercritical Fluid Extraction (SFE) as the solvent in which the Fluid has high permeability and solubility. The discovery and research on supercritical fluid have been more than a century, and its basic principle is to use the carbon dioxide in the supercritical state to dissolve the active ingredients under high pressure, and release it by lowering the pressure to produce a high-quality supercritical product. The main use of this technology is to extract active ingredients from plants and animals. The supercritical water oxidation process is used to treat the waste water to high purity water and supercritical dyeing. The main feature of this technology is to dissolve, extract and separate substances in supercritical state with carbon dioxide or water as the solvent. It is especially suitable for the separation and purification of biological active substances, and can produce pure natural green products. As the production of supercritical extraction is characterized by high efficiency, low cost, high added value and economic efficiency, and no environmental pollution, it has a very important application value in medicine, food, beverage, cosmetics, chemical energy and environmental protection engineering. Therefore, the supercritical carbon dioxide extraction technology has become a cross - century modern high technology and emerging industry.

Carbon dioxide is a very common gas, but too much carbon dioxide can cause a "greenhouse effect", so it is important to make full use of carbon dioxide. The traditional carbon dioxide utilization technology is mainly used in the production of dry ice (fire extinguishing) or as food additives. At home and abroad are committed to the development of a new type of carbon dioxide utilization technology ─ ─ CO2 supercritical extraction technology. This technology can be used to produce products with high added value. It can extract materials that cannot be extracted by chemical methods in the past, and it is cheap, non-toxic, safe and efficient. Applicable to chemical, pharmaceutical, food and other industries.

Carbon dioxide in Tc = 31.26 ℃ temperature above the critical temperature and pressure is higher than critical pressure (Pc) = 7.2 MPa, the nature of the change, its close to liquid density, viscosity to gas, about 100 times liquid diffusion coefficient, thus has the amazing ability to dissolve. It can dissolve a variety of substances and extract the active ingredients, which has a broad application prospect.

Traditional methods of extracting effective components of substances, such as water steam distillation, decompression distillation, solvent extraction, etc., have complex processes, low product purity, and are easy to remain harmful substances. Supercritical fluid extraction (SCFD) is a new separation technique, which is successfully developed by using the excellent mass transfer characteristics of fluid in supercritical state, such as high density, low viscosity and high diffusion coefficient. It has the advantages of high extraction rate, good product purity, simple process and low energy consumption. The CO2- SFE technology provides the most advanced method for the extraction and separation of volatile components of traditional Chinese medicine. Supercritical CO2 extraction can be used to extract the active ingredients from a number of plants that would not have been available chemically in the past. In addition to chemical and pharmaceutical industries, the technology can also be used in tobacco, spices, food and other aspects. For example, it can be used to remove the caffeine in coffee and tea, and extract the valuable components of allicin, germ oil, sea buckthorn oil, vegetable oil, and opium, atropine, ginseng, ginkgo leaves and yew. It can be seen that this technology has a broad prospect of development in the future.

1.1 basic principles of supercritical fluid extraction

1.1.1 definition of supercritical fluid

There are three phases in any substance - gas, liquid and solid. The point where three phases coexist in equilibrium is called the point of three phases. The point of equilibrium between liquid and gas is called the critical point. The temperature and pressure at the critical point are called critical pressures. Different substances require different pressures and temperatures at their critical points.

In Supercritical fluid (SCF) technology, SCF refers to the fluid whose temperature and pressure are both higher than the critical point, such as carbon dioxide, ammonia, ethylene, propane, propylene, water, etc. A state which is above the critical temperature and pressure and close to the critical point is called a supercritical state. In a supercritical state, the gas-liquid phase is so similar that it cannot be distinguished, so it is called SCF.

At present, carbon dioxide is the most studied supercritical fluid, which is most commonly used because it is non-toxic, non-burning, non-reactive to most materials and cheap. In the supercritical state, the CO2 fluid has the dual characteristics of gas-liquid phase, which not only has the same high diffusion coefficient and low viscosity as the gas, but also has the similar density as the liquid and good solubility of the substance. Its density is very sensitive to temperature and pressure changes and is proportional to solubility within a certain pressure range, so the solubility of a substance can be changed by controlling temperature and pressure.

1.1.2 the basic principle of supercritical fluid extraction

Supercritical fluid extraction and separation process is conducted by using the relation between the solubility of supercritical fluid and its density, that is, the effect of pressure and temperature on the solubility of supercritical fluid. When the gas is in the supercritical state, it becomes a single phase state between the liquid and the gas. It has similar density to the liquid. Although the viscosity is higher than the gas, it is obviously lower than the liquid. Therefore, it has good permeability and strong solubility to materials and can extract some components from materials.

In the supercritical state, the supercritical fluid contacts with the substance to be separated, so that it selectively extracts the components of polarity, boiling point and molecular weight in turn. In addition, the density and permittivity of supercritical fluid increase with the pressure of closed system and the polarity increases. Corresponding to various pressure range, of course, the resulting extracts are not single, but can get the best proportion of mixture composition by controlling conditions, and then with the help of decompression, heating method of supercritical fluid into normal gas, completely or by automatic extraction substance is basic precipitation, so as to achieve the purpose of the separation and purification, and the extraction, separation of the two that is the basic principle of supercritical fluid extraction separation.

1.1.3 solubility of supercritical CO2

Under supercritical state, the solubility of CO2 to different solutes varies greatly, which is closely related to the polarity of solutes, boiling point and molecular weight. Generally speaking, the following laws are followed:

1. Lipophilic, low boiling point components can be extracted at low pressure (104Pa), such as volatile oil, hydrocarbon, ester, etc.

2. The more polar groups a compound has, the harder it is to extract.

3. The higher the molecular weight of the compound, the more difficult to extract.

1.1.4 characteristics of supercritical CO2

Supercritical CO2 has become the most commonly used extractant. It has the following characteristics:

1. The CO2 critical temperature is 31.1 ℃, critical pressure is 7.2 MPa, the critical conditions, easy to achieve.

2. The chemical property of CO2 is inert, colorless, odorless, non-toxic and safe.

3. Cheap, pure and easy to get.

Therefore, CO2 is particularly suitable for extraction of active ingredients of natural products.

2. Characteristics of supercritical fluid extraction

2.1 extraction and separation are combined. When the carbon dioxide supercritical fluid containing dissolved substances flows through the separator, the CO2 and the extract rapidly become two phases (gas-liquid separation) due to pressure drop, and immediately separate. Not only high extraction efficiency, but also less energy consumption, cost saving.

2.2 both pressure and temperature can be used as parameters to regulate the extraction process. A small change in temperature pressure near the critical point will lead to a significant change in CO2 density, which will lead to a change in solubility of the extract. The extraction objective can be achieved by controlling temperature or pressure. The pressure is fixed and the material can be separated by changing the temperature. Conversely, the temperature is fixed, and the pressure is reduced to separate the extract. Therefore, the technological process is short and time-consuming. No pollution to the environment, extraction fluid can be recycled use, truly green production process.

2.3 low extraction temperature, CO2 critical temperature of 31.265 ℃, the critical pressure is 7.18 MPa, can effectively prevent the oxidation of heat sensitive components and dissipation, intact biological activity, but also the high boiling point, low volatile crossing, easy pyrolysis material below its boiling point temperature were extracted.

2.4 under normal conditions, the critical CO2 fluid is gas, non-toxic and completely free of solvent residue after separation from the extraction components, effectively avoiding solvent toxicity residue under traditional extraction conditions. At the same time, it also prevents the extraction process from poisoning the human body and pollution to the environment, 100% natural.

2.5 the polarity of supercritical fluid can be changed. Under certain temperature conditions, materials of different polarity can be extracted as long as the pressure is changed or appropriate entrainer is added.

3. Application of supercritical fluid extraction technology

3.1 application of supercritical fluid technology in natural drug development in China

Using CO2 supercritical fluid extraction technology at home and abroad at present, the available resources are: yew, astragalus root, ginseng leaf, hemp, sweet roe, the plant, ginkgo biloba, fritillary bulb zhang leaves, grass, eucalyptus, rose, jasmine, peppercorns, star anise, osmanthus, ginger, garlic, chili, orange, pomelo, hops, miscanthus, lemongrass, sage, rosemary, clove, cardamom, hippophae rhamnoides, wheat, corn, rice bran, fish, tobacco, tea, coal, oil, etc.

In Supercritical fluid extraction (SFE), Supercritical fluid extraction (SFE) is closely related to the modernization of natural drugs. The extraction of non-polar and medium-polar components by SFE can overcome the loss of samples and environmental pollution caused by solvent recovery in traditional extraction methods, and is especially suitable for the extraction of volatile compounds with temperature and thermal instability. For the compounds with high polarity, the entrainer with added polarity, such as ethanol and methyl alcohol, can be used to change the extraction range and improve the extraction rate.

3.2 advantages of supercritical CO2 extraction in the development of traditional Chinese medicine

Compared with traditional Chinese medicine, the supercritical CO2 extraction technique has many unique advantages:

1, the critical temperature of 31.2 ℃, carbon dioxide can perfectly preserved Chinese medicine effective component does not be destroyed or biochemical, especially suitable for those with strong thermal sensitive, easy oxidation decomposition of the composition of extraction.

2. The solubility of a fluid is related to the size of its density, while small changes in temperature and pressure will cause large changes in the density of the fluid, thus affecting its solubility. Therefore, by adjusting the operating pressure and temperature, the impurities can be reduced to make the effective components of traditional Chinese medicine highly enriched, the product appearance is greatly improved, the extraction efficiency is high, and there is no solvent residue.

3. According to the theory of TCM syndrome differentiation and treatment, the effective components in TCM compounds are mutually restrained and synergistic. Supercritical carbon dioxide extraction is not a simple purification of a component, but the selective separation of effective components, which is more conducive to the development of the advantages of traditional Chinese medicine compound.

4. Supercritical CO2 can also directly extract different parts from single or compound Chinese medicine or extract extracts directly for pharmacological screening and development of new drugs, greatly improving the speed of new drug screening. At the same time, it can extract many substances not mentioned by traditional methods, and it is easier to find new ingredients from traditional Chinese medicine, so as to discover new pharmacological properties and develop new drugs.

5. Carbon dioxide is non-toxic, harmless, non-flammable and explosive, low viscosity, low surface tension and low boiling point, which will not cause environmental pollution easily.

6. Through direct application with GC, IR, MS, LC, etc. to objectively reflect the concentration of active ingredients in the extract, and realize the integration of TCM extraction and quality analysis.

7. Fast extraction time and short production cycle. As soon as the supercritical CO2 extraction (dynamic) cycle begins, the separation begins. Generally, the extraction can be separated and separated within 10 minutes, and the extraction can be completed within 2 to 4 hours. At the same time, it does not require such steps as concentration, even if the entrainer is added, it can be removed by the separation function or simply concentrate.

8. Supercritical CO2 extraction is easy to control operating parameters, so the effective components and product quality are stable.

9. It has been proved by pharmacology and clinical practice that the extraction of traditional Chinese medicine by supercritical CO2 is not only superior in process, stable in quality and easy to control in standard, but also guaranteed in pharmacology and clinical effect.

10. The supercritical CO2 extraction process is simple, easy to operate, labor saving and large amount of organic solvent and reducing waste pollution, which undoubtedly provides a new method of extraction, separation, preparation and concentration for the modernization of traditional Chinese medicine.

In addition, the reiss process and GAS process in supercritical fluid crystallization technology can produce ultra-fine particles with uniform size, which can be used to prepare controlled release pellets and other dosage forms, which can be used to prepare new Chinese medicine dosage forms.

Compared with other traditional technologies, supercritical fluid technology is used to extract and study compound substances of traditional Chinese medicine.

The good extraction ability and high extraction rate. With the continuous progress of SFE technology and the application of entrainer, SFE technology has expanded from the extraction of non-polar and medium-polar substances in the chemical constituents of traditional Chinese medicine to the extraction of the active ingredients or parts in the aqueous solution system.

In SFE, the extraction capacity depends on the fluid density. In other words, as long as the temperature or pressure is changed or one of them is changed at the same time, or supercritical extraction technology is widely used in food, chemical and biological engineering in addition to its obvious advantages in the extraction of the active ingredients of traditional Chinese medicine. The addition of entrainer can change the solubility, and can selectively separate various substances in traditional Chinese medicine. Combined with SFE chromatographic technology and related technologies, it can also completely separate the effective components or effective parts of traditional Chinese medicine.

With low operating temperature, it can well preserve the effective ingredients of Chinese medicine without damage or sub-biochemical. It is especially suitable for extraction of heat-sensitive and easily oxidized decomposition ingredients.

The extraction time is fast, operating parameters are relatively few and easy to control, so the study period is short, active ingredients and product quality is stable, and the influence on the pharmacological experimental results is relatively small.

The technology of hualsfe can directly select different parts from single or compound Chinese medicine or extract extract extract extract to screen pharmacology, develop new drugs and greatly improve screening speed. At the same time, many materials can be extracted by traditional methods, and new ingredients can be found easily, so that new pharmacological properties can be found.

In addition, application of esfe in analysis or GC, IR, MS, LC becomes an efficient analysis method.

Gas directly reflects that extraction products can be obtained by extracting natural products with carbon dioxide in different states, that is, it has good extraction capability and selectivity. In the separation process, the loss of volatile matter caused by evaporation of carbon dioxide is negligible. Application of supercritical fluid technology in other areas

1.1 application in food

At present, supercritical carbon dioxide can be used to extract oil from sunflower seeds, red flower seeds, peanuts, wheat germ and cocoa beans. This method has a higher recovery rate than traditional press method, and there is no solvent separation problem by solvent method.

4.2 application in medicine and health care products

In the production of antibiotic drugs, traditional methods often use organic solvents such as acetone and methanol, but it is very difficult to remove the solvent completely without deterioration.