Often, the entrainer and extractant are not substances in the same state, so the quantity of entrainer is generally expressed by a convenient mass fraction instead of the quantity ratio and volume ratio of substances.
The following are some introductions and a paper on supercritical fluid extraction and entrainer for reference only.
Supercritical fluid extraction (SFE) is a new practical technology with rapid development and wide application. Traditional methods for extracting effective components from substances, such as steam distillation, vacuum distillation, solvent extraction, etc. The process is complex, the product purity is low, and harmful substances are easy to remain. Supercritical fluid extraction is successfully developed by using the excellent mass transfer characteristics of fluid in supercritical state, such as high density, low viscosity and large diffusion coefficient. It has the advantages of high extraction rate, good product purity, simple process and low energy consumption.
What is supercritical? Any substance exists in three states-gas, liquid and solid. The point where three phases are in equilibrium is called the three-phase point. The point at which liquid and gas are in equilibrium is called the critical point. The critical temperature and pressure are called critical temperature and critical pressure. The critical points of different substances require different pressures and temperatures. Supercritical fluid (SCF) refers to the fluid that exceeds the critical temperature (Tc) and critical pressure (Pv). Above the critical temperature and pressure, the state close to the critical point is called supercritical state.
Supercritical extraction principle: The principle of supercritical fluid extraction separation process is based on the relationship between the solubility of supercritical fluid and its density, that is, the influence of pressure and temperature on the solubility of supercritical fluid. In supercritical state, supercritical fluid has good fluidity and permeability. The supercritical fluid is contacted with the substance to be separated, so that it can selectively extract components with polarity, boiling point and molecular weight in turn. Of course, it is impossible to obtain a single extract corresponding to each pressure range, but the optimum proportion of mixed components can be obtained by controlling the conditions, and then the supercritical fluid can be converted into ordinary gas by heating under reduced pressure, so that the extracted substance can be completely or basically precipitated, thus achieving the purpose of separation and purification. Therefore, the supercritical fluid extraction process consists of extraction and separation.
Selection of Supercritical Fluid (SCF): The solubility of solute in solvent is positively correlated with the density of solvent, and SCF is similar to this. Therefore, by changing the pressure and temperature and changing the density of SCF, many different types of substances can be dissolved and various types of compounds can be selectively extracted. Many substances can be used as SCF, such as carbon dioxide, nitrous oxide, sulfur hexafluoride, ethane, methanol, ammonia and water. Carbon dioxide is close to room temperature because of its low critical temperature (TC = 3 1.3℃). The critical pressure is small (PV = 7. 15 MPa), and the diffusion coefficient is 0/00 times that of liquid, so it has amazing solubility. And colorless, odorless, non-toxic, non-flammable, chemically inert, low expansion, low price, easy to prepare high-purity gas and other characteristics, is now the most widely used. ?
Solubility of supercritical carbon dioxide extraction: In supercritical state, the solubility of CO2 to different solutes is very different, which is closely related to the polarity, boiling point and molecular weight of solutes. Generally speaking, there are the following rules: lipophilic and low-boiling components, such as volatile oil, hydrocarbons, esters, lactones, ethers and epoxy compounds, such as aromatic components in natural plants and fruits, such as eucalyptus, can be extracted below 104KPa. The more polar groups (such as -OH, -COOH, etc.). ) Yes, the more difficult it is to extract. The extraction pressure of strongly polar substances such as sugar and amino acids should be above 4× 104KPa; The larger the molecular weight of the compound, the more difficult it is to extract. Components with molecular weight in the range of 200 ~ 400 are easy to extract, and some low molecular weight and volatile components can even be directly extracted with CO2 liquid. High molecular weight substances (such as protein, gum and wax) are difficult to extract. Characteristics of supercritical CO2 extraction;
1, which can be extracted near room temperature (35-40℃) and covered with CO2 gas, effectively preventing the oxidation and escape of heat-sensitive substances, completely retaining biological activity, and extracting substances with high boiling point, low volatility and easy pyrolysis below its boiling point temperature. 2. Because no organic solvent is used in the whole process, there is no residual solvent in the extract, and at the same time, the toxicity to human body and environmental pollution in the extraction process are avoided. 100% pure natural, in line with the current high-end pursuit of "green environmental protection" and "returning to nature". 3. Different products can be separated by controlling process parameters, which can be used to extract a variety of products, and heavy metals, inorganic substances and dust in raw materials will not be dissolved by CO2.
4. Distillation and extraction are combined into one, which can complete the two processes at the same time, especially suitable for the separation of difficult-to-separate substances, such as the separation and refining of organic mixtures and homologues.
5. Less energy consumption; Hot water and cold water are fully closed, and there is no waste water and waste residue discharge. CO2 is also a closed cycle, and only a little is brought out when it is discharged, which will not pollute the environment. Because of less energy consumption, fewer people and less material consumption, the operating cost is very low.
Therefore, CO2 is especially suitable for the extraction of effective components from natural products. For the extraction of natural materials, its products can really be called 100% pure natural "green products".
Main factors affecting supercritical extraction;
1. density: the strength of solvent is related to the density of SCF. When the temperature is constant, the density (pressure) increases, which can increase the strength of solvent and the solubility of solute.
2. Entrainer: Most solvents suitable for SFE are low polar solvents, which is beneficial to selective extraction, but limits its application to more polar solutes. Therefore, a small amount of entrainer (such as ethanol, etc. ) can be added to these SCFs to change the polarity of the solvent. SFE-CO2 with certain entrainer can create extraction conditions that ordinary solvents can't achieve, and greatly improve the yield.
3. Particle size: The diffusion of solute in sample particles can be described by Fick's second law. Particle size will affect the extraction rate. Generally speaking, small particle size is beneficial to SFE-CO2 extraction.
4. Liquid volume: The molecular structure of the extract is related to the required SCF volume. Increasing liquid volume can improve oil recovery.
Research and application progress of supercritical fluid extraction technology
, Liu Guimin, Wu
(School of Chemical Engineering, Hebei University of Technology, Tianjin 300 130)
The basic principle of supercritical fluid extraction and the methods to improve the efficiency of supercritical fluid extraction, including the addition and use of entrainers, are reviewed.
High-voltage electric field and ultrasonic wave, etc. The latest application of supercritical fluid extraction technology in biochemical, food, medicine and environmental protection industries is introduced.
Introduction.
Key words: supercritical fluid extraction; Extraction efficiency; Entrainment agent; App application
China Library Classification Number: TQ028.8 Document Identification Number: A Document Number:1008-1267 (2007) 03-0010-03.
Supercritical fluid extraction (SFE) is the use of supercritical fluid.
As an extractant, specific components are extracted from liquids or solids to
A new product separation technology. Supercritical flow
Integral extraction has incomparable advantages over other separation methods: easy combination.
Product separation, safety, non-toxicity, no environmental pollution and mild operating conditions.
And effective components which are not easy to be destroyed. Therefore, supercritical fluid extraction technology
Surgery in biochemistry, medicine, daily chemical, environmental protection, petrochemical and other fields.
The application prospect is broad.
1 supercritical fluid extraction
1. 1 supercritical fluid
Supercritical fluid refers to critical temperature and critical temperature.
Non-condensable high-density fluid with critical pressure (PC) [1]. supercutical fluid
It has the characteristics of both gas and liquid, and its density is close to that of liquid, while
The viscosity and diffusion coefficient are close to those of gas, so it not only has the same properties as liquid.
Bulk solvents have considerable solubility and excellent mass transfer performance.
Yes
The solubility of supercritical fluid is different from supercritical fluid and supercritical fluid.
The similarity of solute properties to be separated is not only related to the operating temperature.
The operating temperature is related to the critical state of supercritical fluid.
The closer the temperature is, the stronger its solubility is. No matter how high the working pressure is,
Supercritical fluid cannot be liquefied, but the density of fluid increases with the increase of pressure.
The bigger it is, the more soluble it is.
1.2 supercritical fluid extraction principle
Supercritical fluid extraction technology uses the above supercritical flow.
The special properties of the body are separated under the high pressure of the extraction tower.
Solid or liquid mixture contact, adjust the operating temperature and pressure of the system.
Force, extract the required components; After entering the separation tower, it rises at constant pressure.
Reduce the density of supercritical fluid by temperature, isothermal decompression or adsorption.
Degree, so that the solubility of this component in supercritical fluid is reduced, and thus
Separate.
1.3 methods to improve extraction efficiency
The method to improve the extraction efficiency is not only to appropriately increase the extraction pressure,
In addition to selecting suitable extraction temperature and increasing supercritical fluid flow, it also
Adding an appropriate amount of entrainer, high voltage electric field and ultrasonic wave can be used.
Wave and other measures.
1.3. 1 Add entrainer.
Adding proper amount of entrainer can obviously improve the supercritical flow.
Selectivity and solubility of solids to extraction components. Zhang Kun and others [2]
Dissolution and extraction of supercritical fluid by adding solvent methanol
The selectivity was studied, and the results showed that the addition of methanol might be important.
The solubility of the fluid increases, and the degree of increase increases with the addition of methanol.
It increases with the increase of dose, which is beneficial to polar substances to some extent.
Mass extraction, but adding methanol will reduce the selectivity of the fluid.
Low. Therefore, when adding the entrainer, the best dosage should be selected.
Surfactants can also be used as entrainers to enhance supercritical flow.
The improvement of volume extraction efficiency is related to its molecular structure. molecule
The higher the fat-soluble fraction of supercritical fluid, the higher the extraction efficiency of supercritical fluid.
The higher, the more [3]. Regarding the action principle of entrainer, 8 zlemcü >: lü-
Stündag et al [4] think that the addition of entrainer changes the solvent.
Density or interaction between internal molecules.
The following points should be paid attention to when selecting extractant: (1) When extracting,
At this stage, the interaction between entrainer and solute is dominant, that is, entrainment.
The addition of reagent can greatly improve the solubility of solute; (2) in
In the stage of solute regeneration (separation), the entrainer should be easy to separate from solute;
(3) When separating products related to human health, such as medicines, food and
Date of receipt: 2006- 10- 10
Issue 3, Volume 2 1
May 2007
Volume 265438 +0 No.3
May 2007
Tianjin chemical industry
Tianjin chemical industry
Cosmetics and so on. Also pay attention to the toxicity of the entrainer.
1.3.2 using high voltage electric field
High voltage pulsed electric field can significantly improve the extraction rate of solute and membrane lipid.
The mutual solubility of components and the mass transfer ability of substances through cell walls vary from
And the extraction efficiency is improved. Ning Zhengxiang et al. [5] used high voltage pulsed electric field to strengthen.
Supercritical CO2 extraction of litchi seed essential oil, pressure 300MPa,
High pressure pulse treatment can obviously improve the efficiency of supercritical extraction; special
When the extraction rate is lower than 80%, the effect of high voltage pulsed electric field is significant.
1.3.3 Use ultrasonic waves.
Effective extraction of natural biological resources by supercritical fluid
In the separation process, strengthening measures are taken to reduce the external diffusion resistance of extraction.
Very good extraction results can usually be obtained. Chen Jun et al [6] developed a new method.
Ultrasonic transducer extractor uses ultrasonic to enhance supercritical extraction.
Fang Ruibin et al [7] enhanced supercritical CO2 with ultrasonic wave.
Extraction of paclitaxel. Studies have shown that if paclitaxel is to be completely extracted, it is not strong.
The extraction time of chemical ultrasonic supercritical CO2 is enhanced ultrasonic supercritical CO2.
In the extraction experiment of 1. 1% paclitaxel extract,
Supercritical CO2 extraction with enhanced ultrasound quickly reached 100%, but it did not.
Supercritical extraction using enhanced ultrasound takes three times as long as the same dose.
The extraction rate is only 4 1%, which fully shows the supercritical extraction.
Combine the advantages of ultrasonic technology. Ai-Hu Jun et al [8] on ultrasound.
Enhanced supercritical fluid extraction of coix seed oil and coix seed.
The study of nonyl ester also shows that ultrasonic strengthening technology can greatly
And the extraction efficiency is improved.
In addition, there are some strengthening measures including stirring and increasing flow.
Or a moving bed, etc. All these measures are aimed at reducing exploitation.
The purpose of diffusion resistance at home and abroad.
Application of supercritical fluid extraction technology in industry
App application
2. Application of1in biochemistry
According to the characteristics of supercritical fluid, it is especially suitable for heating.
Separation and extraction of sensitive biological substances. Supercritical fluid extraction currently
Technology has been applied to the extraction and refining of mixed oils and fats, such as using EPA (II).
The total content of docosahexaenoic acid and DHA is
EPA and EPA with purity as high as 90% can be obtained from 60% fish oil.
DHA[9]. Marionétisse et al. [10] concentrated by supercritical fluid extraction.
The operation conditions of EPA and DHA in sardines were optimized.
Yuan Chengling et al [1 1] Supercritical fluid extraction of microbial fermentation.
The oil production by fungi was studied, and the results showed that supercritical fluid was used.
Method for enriching polyunsaturated fatty acids in microbial mycelium by CO2
The process is feasible, but the enrichment effect needs to be further improved.
Supercritical fluid extraction of bile solids from bovine brain by noun (abbreviation of Noun) Vedaraman et al. [12]
Studied alcohol.
2.2 Application in food industry
Supercritical fluid extraction technology has been applied to food industry.
It has a long history. Removal of coffee beans by supercritical fluid extraction.
And caffeine in tea has long been industrialized. Germany SKW
The company produces decaffeinated tea, which is produced by supercritical fluid extraction technology.
The production capacity reaches 6000 tons/year. In addition, SKW will also carry out supercritical flow.
Volume extraction technology is applied to beer production, the company's supercritical fluid.
The production capacity of hops extraction and processing equipment is 104t/a[ 13].
SeiedMahdiPourmortazavi et al. [14] studied the use of supercritical fluids.
The experiment of extracting plant essential oil by boundary fluid shows that,
Compared with this method, it has obvious advantages such as short extraction time, low cost and good product quality.
Pure. P.Ambrosino et al. [15] on supercritical fluid extraction of corn protein.
The botulinum toxin was studied.
The application of supercritical fluid technology in food field can make food.
The appearance, flavor and taste are good, so supercritical fluid extraction technology
Technology has a broad application prospect in food industry.
2.3 Application in pharmaceutical industry
Supercritical fluid extraction is widely used in pharmaceutical industry.
Widely used, especially in the extraction of effective components of traditional Chinese medicine.
At present, supercritical fluid extraction of traditional Chinese medicine.
Effective ingredients have been industrialized, and Zhejiang Kanglaite Company will
Yunnan Senju Company has two sets 1000L of anticancer Chinese medicines.
Supercritical fluid extraction device for extracting pyrethrum components [16].
Du Yuzhi et al. [17] research shows that supercritical carbon dioxide extraction is more effective than petroleum.
Ether extraction method is superior, with high yield, short extraction time and no solvent residue.
Is suitable for preparing anshen pills. Liu Ben et al [18]
The extraction technology of Rhizoma Coptidis from Rhizoma Coptidis by supercritical fluid was studied.
Many scholars have extracted the effective components of traditional Chinese medicine by supercritical fluid.
Grinding, such as Rhizoma Chuanxiong, Radix Angelicae Dahuricae, Radix Angelicae Sinensis, and Rhizoma Coptidis.
2.4 Application in Environmental Protection
Supercritical fluid extraction technology is applied to the field of environmental protection, especially
The treatment of polluted solid substances and water bodies has broad prospects.
Application prospect.
Yu Enping [19] used supercritical fluid extraction to treat PCBs.
The study of benzene pollutants shows that supercritical fluid extraction technology can
Removal of organic toxic substances from solid materials. High consistency and equivalent [20] refining
SFE studied the soil in coking workshop of iron and steel plant, and compared the temperature with the temperature.
Pressure of supercritical fluid extraction of polycyclic aromatic hydrocarbons
The effects of compounds were analyzed by GC-MS (gas-mass spectrometry).
Compared with Soxhlet extraction method, the recovery rate is far from Soxhlet extraction method.
Zhao Dongsheng et al., Vol.21,No.3: Research and application progress of supercritical fluid extraction technology 1 1
The recovery rate is higher than that of Soxhlet extraction. Jing You et al [2 1] studied the use of solid phase.
Enrichment of organic pollutants in water by adsorption and supercritical fluid extraction
The results show that supercritical fluid extraction has strong polarity in water.
The treatment of organic compounds is feasible. V.Librando et al. [22] on Super
Extraction of Polycyclic Aromatic Hydrocarbons from Marine Sediments and Soil Samples by Critical Fluid
The hydrocarbon pollutants were studied, and the recovery rate of polycyclic aromatic hydrocarbons reached 90%
Kong-HwaChiu et al. [23] also used supercritical fluid extraction technology.
It is used to treat organic pollutants in the environment.
In addition to the applications mentioned above, supercritical fluids
Extraction technology has also been paid attention to in the fields of daily chemical, ceramics and instrumental analysis.
Important applications.
3 outlook
Compared with gas and liquid, supercritical fluid has both advantages and disadvantages.
Both advantages and disadvantages are overcome. Supercritical flow
The operating conditions of batch extraction are mild, so supercritical fluid extraction technology phase
Compared with other separation methods, it has obvious advantages. At present, supercritical fluid
There are still many problems in the application of extraction technology in various fields.
Solution, I believe that through the joint efforts of experts at home and abroad, the technology is
Its application in various fields will be deepened and broadened.
The role of industrial production will also become increasingly prominent.