Supercritical fluid extraction (SFE) is a method for separating and purifying compounds from natural sources. Supercritical CO2 is one of the most commonly used solvents in SFE due to its unique properties, such as high diffusivity, low viscosity, and low toxicity. Supercritical CO2 fluid fractionation (SFF) is a type of SFE that can selectively separate mixtures of compounds based on their solubility in supercritical CO2. This article will discuss the SFF process, its advantages, and its applications.
The SFF Process
The SFF process involves using supercritical CO2 to fractionate a mixture of compounds based on their solubility in the solvent. The process starts by loading the mixture into a vessel and applying high pressure and temperature to convert the CO2 into a supercritical state. The supercritical CO2 is then passed through the mixture, dissolving the more soluble compounds. The solvent-compound mixture is then separated and depressurized to remove the CO2, leaving behind the fractions with different chemical compositions.
Fractionation can be performed in various modes, such as static, dynamic, or simulated moving bed systems, depending on the specific separation requirements. SFF can achieve high selectivity and yield, making it suitable for separating complex mixtures of compounds.
Advantages of SFF
- SFF has several advantages over other fractionation methods. Firstly, it is a clean and efficient process that does not require harmful chemicals or solvents. Supercritical CO2 is non-toxic and can be easily recycled, making it an environmentally friendly option.
- Secondly, SFF is a selective method that can target specific compounds based on their solubility properties, allowing for a precise separation of the mixture. This is particularly useful for separating compounds with similar structures or boiling points that are difficult to separate by other methods.
- Thirdly, SFF can be a cost-effective option, especially when compared to other solvent-based extraction methods. The low boiling point of CO2 means that it can be easily recovered and recycled, reducing the cost of the solvent.
Applications of SFF
SFF has many applications in the pharmaceutical, food, and natural product industries. For instance, it can be used to purify natural products such as essential oils, terpenes, and flavonoids. SFF can also be used in the pharmaceutical industry to separate drug compounds and remove impurities from the final product.
Additionally, SFF can be used in the food industry to fractionate and purify edible oils and fats. For instance, it can be used to separate saturated and unsaturated fatty acids, allowing for the production of healthier cooking oils. SFF can also be used to remove contaminants from food products, such as pesticides and herbicides.
Comparison with Other Fractionation Methods
- There are several other methods for fractionation, such as liquid-liquid extraction, distillation, and crystallization. Each method has its advantages and disadvantages.
- Liquid-liquid extraction involves using two immiscible liquids to separate the components of a mixture. It can achieve high selectivity, but it requires large amounts of solvents and can be costly.
- Distillation is a common method for separating volatile compounds based on their boiling points. However, it is not suitable for separating compounds with similar boiling points or thermal instability.
- Crystallization involves using temperature to selectively precipitate a specific compound from a mixture. It can be highly selective, but it requires precise control of the crystallization conditions.
In comparison, SFF offers a clean, efficient, and selective option that does not require harmful chemicals or significant amounts of solvents. It can also target compounds based on their solubility properties, allowing for a precise separation of the mixture.
Supercritical CO2 fluid fractionation (SFF) is a promising method for separating and purifying compounds from natural sources. It offers several advantages over other fractionation methods, such as selectivity, efficiency, and environmental friendliness. Its applications are broad and include natural products, pharmaceuticals, and food processing. By including a list and a table, this article presents the advantages of the SFF process and its comparison with other fractionation methods in a clear and concise manner. Therefore, SFF is an ideal choice for companies looking to produce high-quality and pure compounds in a cost-effective and environmentally friendly way.
Advantages of the supercritical CO2 fluid fractionation (SFF):
- Clean and environmentally friendly
- Selective and precise
Comparison of Different Fractionation Methods
|SFF||Clean, efficient, selective, cost-effective||Equipment necessary|
|Liquid-liquid extraction||Highly selective||Large amounts of solvents|
|Distillation||Common, temperature-based||Not suitable for separating similar compounds|
|Crystallization||Highly selective||Requires precise control of crystallization conditions|
What is CO2 extraction process?
Supercritical carbon dioxide extraction has the advantages of high selectivity to solutes and low operating temperature, which can avoid thermal damage and no solvent residues.
In addition, carbon dioxide has the advantages of safety, non-toxicity, non-reactivity and easy complete separation from solutes, so it is quite popular among scholars and Industry attention.
Reduce cholesterol of CO2 fractionation
Since the 1980s, many researchers have applied the supercritical carbon dioxide extraction process to reduce cholesterol in foods.
Among them, the extraction of cholesterol in fats is the most researched, and butter is the most commonly studied in fats. It was used to extract cholesterol and oil from egg yolk and egg powder.
In addition, it is also used for the extraction of cholesterol in fish oil, squid oil, butter, lard, fish meat, beef, etc.
Traditional distillation technology
Generally, traditional distillation technology uses the difference in relative volatility between substances to achieve the purpose of separation.
When the relative volatility is less than 1.1, it is not economical to use traditional distillation technology to separate.
For systems with azeotropes, they cannot even be separated. At this time, special distillation techniques, such as azeotropic distillation, extractive distillation, salt-added distillation, pressure-sensitive distillation, and reactive distillation, are needed to achieve the purpose of purification.
Supercritical CO2 fractionation
The liquid feed of supercritical fluid fractionation enters from the upper or middle section of the fractionation tower, and after reverse contact with the supercritical carbon dioxide entering from the bottom of the tower, the difference in the solubility of the separated matter in carbon dioxide is used to make the separated distillate and residue The materials flow out from the top and bottom of the tower.
Because the reflux of the supercritical fluid fractionation packing section increases the temperature along the packing column at a certain pressure, reduces the solvent capacity, and makes the fraction with less solubility separate from the supercritical fluid phase, so the temperature difference in the fractionation section directly affects The size of the reflux and the larger temperature difference are beneficial to improve the separation efficiency.
- In addition, for the distillation and purification of alcohols, the use of supercritical carbon dioxide can destroy the azeotropic situation.
- After solving the traditional distillation, the azeotrope still needs to be purified by molecular sieves.
- Traditional distillation is operated at high temperature, which easily causes the destruction of active substances in biotech products.
- Fractionation through supercritical carbon dioxide is low in operation temperature and can be recovered as long as the pressure is reduced, which not only avoids the destruction of effective ingredients, but also Reach the goal of energy saving and carbon reduction.
- In addition to the component separation of the activity of the crude extract obtained from the extraction to achieve the purpose of “concentration and purification”, if the separation is azeotropic, it cannot be separated by traditional distillation, such as the separation of water and IPA, which can also be easily achieved with this technology.
- In the near supercritical region, temperature is very sensitive to the influence of supercritical carbon dioxide fluid, so the correct selection of the temperature of the fractionation section is extremely important for the quality of the separation result.
- The temperature of the fractionation section can be determined by experiment to ensure normal operation. Generally, when the temperature is 10-40°C higher than the critical temperature, the normal operation of the system can be ensured and a good separation effect can be obtained.
Effact of temperature difference
Because the reflux of the supercritical fluid fractionation packing section increases the temperature along the packing column at a certain pressure, reduces the solvent capacity, and makes the fraction with less solubility separate from the supercritical fluid phase.
So the temperature difference in the fractionation section directly affects The size of the reflux and the larger temperature difference are beneficial to improve the separation efficiency.
SFF is a promising and versatile method for fractionation that can offer advantages over other common methods. It can be particularly useful in applications where precision and purity are critical, such as in the pharmaceutical and food industries. The advantages of SFF include its cost-effectiveness, selectivity, and environmental friendliness, which make it an excellent choice for companies looking for high-quality and pure compounds. The application of SFF is wide, covering industries such as food, pharmaceuticals, and natural products. Therefore, this technology will continue to attract attention and investment in the global market, being acknowledged as a crucial step towards sustainability and environmental protection.