Supercritical CO2 (SC-CO2) fluid extraction is a promising method for the extraction of natural products such as essential oils, flavors, and bioactive compounds. The efficiency of the extraction process depends on several factors, including the pressure, temperature, flow rate, extraction time, and the properties of the solute and solvent. This article aims to provide an overview of the key variables affecting SC-CO2 fluid extraction, their interactions, and their optimal values for efficient and sustainable extraction.
Key Variables Affecting SC-CO2 Fluid Extraction
The production and quality of SC-CO2 extracts are influenced by several variables that can be classified as primary (i.e., pressure, temperature, and flow rate) and secondary (i.e., extraction time, solute properties, and solvent properties). These variables interact in complex ways that can affect the extraction efficiency and quality of the final product. Table 1 summarizes the key variables affecting SC-CO2 fluid extraction and their interactions.
Summary of key variables affecting SC-CO2 fluid extraction and their interactions
|Pressure||20-30 MPa||Increases with solubility and density of solute and solvent. Increases with temperature. Decreases with increasing flow rate.|
|Temperature||40-70°C||Increases with the solubility and diffusion rate of solute and solvent. Decreases with increasing pressure. Increases with the viscosity of the solvent.|
|Flow Rate||2-5 mL min-1||Increases with the mass transfer coefficient. Decreases with increasing pressure.|
|Extraction Time||1-2 hours||Increases with the extraction yield and selectivity. Decreases with increasing flow rate and temperature.|
|Solute Properties||Varied||Affects the solubility, selectivity, and stability of the extract. Includes particle size, morphology, polarity, and chemical structure.|
|Solvent Properties||Varied||Affects the solubility, selectivity, and toxicity of the extract. Includes viscosity, density, polarity, and chemical stability.|
Interactions among the key variables can affect extraction efficiency and the quality of the final product. Optimal values depend on the specific solute and solvent being used.
Impacts of Key Variables on SC-CO2 Fluid Extraction
The key variables affecting SC-CO2 fluid extraction can impact the extraction efficiency and product quality in several ways.
- Pressure: Increasing pressure can enhance the solubility and density of the solute and solvent, but also requires higher energy input. This can lead to an increase in SC-CO2 viscosity and a decrease in mass transfer coefficient, reducing extraction efficiency.
- Temperature: Increasing temperature can enhance the solubility and diffusion rate of solute and solvent, but also can lead to thermal degradation, especially in bioactive compounds.
- Flow Rate: Increasing flow rate can enhance the mass transfer coefficient but can also lead to a decrease in extraction yield and a decrease in the quality of final product.
- Extraction Time: An optimal extraction time is necessary to balance the extraction yield and selectivity. Longer extraction time can increase the extraction yield but decrease selectivity.
- Solute Properties: Solute properties such as particle size, polarity can significantly affect solubility, selectivity, and stability of the extract. Different solute properties may require different extraction conditions.
- Solvent Properties: Solvent properties such as viscosity, density, and polarity can also affect solvent penetration, solubility selectivity, and toxicity of the extract. Different solvent properties may require different extraction conditions.
Optimizing Key Variables for Efficient SC-CO2 Fluid Extraction
Optimizing key variables for efficient SC-CO2 fluid extraction requires a comprehensive understanding of the interactions among these variables. Tables 2 and 3 below summarize the optimal values of key variables for the efficient extraction of selected natural products.
Optimal values of key variables for efficient SC-CO2 fluid extraction of essential oils and flavors
|Pressure||15-20 MPa||20-25 MPa|
|Flow Rate||1.5-2 mL min-1||2-3 mL min-1|
|Extraction Time||1-2 hours||1-2 hours|
Optimal values of key variables for efficient SC-CO2 fluid extraction of bioactive compounds
|Flow Rate||2-4 mL min-1|
|Extraction Time||1-2 hours|
These tables serve as a guide for optimizing the key variables for different natural products, but it’s important to note that optimal values may vary depending on the specific solute and solvent being used.
In conclusion, the efficiency of SC-CO2 fluid extraction depends on several key variables that interact in complex ways to affect the extraction efficiency and quality of the final product. Optimizing these variables requires a comprehensive understanding of their interactions and the specific solute and solvent being used. This article provides an overview of the key variables affecting SC-CO2 fluid extraction, their interactions, and optimal values for efficient and sustainable extraction. The use of tables in this article has helped to present the information in a clear and concise manner, making it easier for readers to understand the principles, procedures, and variables involved in this promising extraction method.
List of Key Variables Affecting SC-CO2 Fluid Extraction
The key variables affecting SC-CO2 fluid extraction include:
- Flow rate
- Extraction time
- Solute properties
- Solvent properties
Optimizing these key variables is crucial for efficient and sustainable extraction of natural products using SC-CO2 fluid extraction.
Factors affecting the CO2 Extraction Process
In the actual extraction process, the extracted substances are diverse and their properties are very different. Different substances have different performances in the extraction process, and the state of CO2 in the co2 extraction system also has a great influence on the co2 extraction process.
These effects (such as CO2 temperature, pressure, flow rate, ecosolvent, sample physical form, particle size, viscosity, etc.) are intertwined, making the extraction process more complicated.
Solubility of 6 Materials in the CO2 extraction process
molecular mass and molecular polarity
The relative molecular mass and molecular polarity of organic compounds are the most important factors affecting the solubility of supercritical CO2 fluid, and it is the key to determining whether the substance can be extracted by supercritical CO2 fluid. However, compared with a large number of process studies, the solubility data of different solutes in supercritical CO2 fluids is very lacking.
Dandge measured the solubility data of a series of organic compounds in supercritical CO2 fluid (experimental conditions: 25℃,=0.895g/mL and 32℃,=0.86g/mL, the solubility is expressed as the mass percentage of the supercritical CO2 fluid solute. ), combined with previous work, the empirical law of solute molecular structure and its solubility in supercritical CO2 fluid is as follows:
6 Materials in the CO2 extraction process
The n-alkanes with carbon atoms below 12 can all be mutually soluble in supercritical CO2 fluids. If more than 12 carbon atoms, the solubility will decrease sharply. Compared with normal alkanes, isoalkanes have greater solubility
Normal alcohols with less than 6 carbons can dissolve each other in supercritical CO2 fluid. If the carbon number is further increased, the solubility will decrease significantly. Adding side chains to n-alcohols can appropriately increase solubility just like alkanes.
The solubility of phenol is 3%, and the solubility can be increased when methyl is substituted for phenol. Etherified phenolic hydroxyl will significantly increase solubility4. Carboxylic acidAliphatic carboxylic acids with less than 9 carbons are mutually soluble in supercritical CO2 fluids, while dodecanoic acid (laurel has only 1% solubility. The presence of halogens, hydroxyl groups, and aromatic groups will reduce the solubility of aliphatic carboxylic acids
Esterification will significantly increase the solubility of the compound in supercritical CO2 fluid.
Simple aliphatic aldehydes such as acetaldehyde, valeraldehyde, and heptaldehyde, etc., can dissolve aliphatic aldehydes in supercritical CO2 fluids. The unsaturated structure of aliphatic aldehydes has no obvious effect on its solubility. However, phenyl substitution will reduce unsaturated aldehydes. The solubility of supercritical CO2 fluids.
It occupies an important position in plant mucosal oil and is a key component of various natural fragrances. In the process of supercritical CO2 fluid extraction of natural products such as spices and food, the solubility of terpenoids in supercritical CO2 fluid has a very strong influence. Important practical value.
The relative molecular mass of terpenoids has a certain effect on solubility. From monoterpene pinene to sesquiterpene phyllite and diterpene intetraene, the solubility of terpene compounds in supercritical CO2 fluid gradually decreases, and terpene molecules For every 5 more carbon atoms, the solubility drops about 5 times. The reason for this difference may be that as the relative molecular mass increases, the volatility of the compound decreases.
Compared with the influence of relative molecular mass, the polarity of the compound has a greater influence on its solubility in supercritical CO2 fluids.
Monoterpene compounds such as camphor, citral, citronellol, and 1.8 terpene diol have different Substituents and polarities, although the relative molecular masses are not much different, the solubility is very different.
This fully shows that the molecular structure of the solute is a key factor affecting its solubility in supercritical CO2 fluid. The data shows that as the oxygen-containing substituents in terpenoids increase, the polarity of viscous compounds increases, and their solubility in supercritical CO2 fluids decreases sharply.