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Classification Characteristics And Applications Of Supercritical Carbon Dioxide Fluid Extraction

Supercritical CO2 Extraction Machine

Supercritical CO₂ fluid extraction process has emerged as a versatile and environmentally friendly substance with a myriad of applications across diverse industries. Its unique properties in the supercritical state, where it exhibits both liquid and gas characteristics, make it an intriguing subject of study.

What is supercritical fluid extraction process

Supercritical fluid refers to a fluid whose temperature and pressure are above its critical temperature (Tc) and critical pressure (pc), between gas and liquid. Stable pure substances can all have a supercritical state (stable means that their chemical properties are stable and will not decompose into pure substances when reaching the critical temperature), and they all have their fixed critical points: critical temperature and critical pressure.

The critical temperature Tc is the temperature at which when the temperature is higher than a certain value, no large pressure can transform the pure substance from the gas phase into the liquid phase;

The critical pressure pc is the lowest pressure at which a gas can be liquefied at the critical temperature. When the temperature of a substance is higher than the critical temperature and the pressure is greater than the critical pressure, the substance is in a supercritical state.

If the fluid is heated or compressed to a state above its critical temperature (Tc) and critical pressure (pc), and the gas in this state is pressurized, the gas will not liquefy, but the density will increase, and it will have liquid-like properties while still retaining Has gas properties.

Characteristics of Supercritical CO₂ extraction process

Common substances that can be used as supercritical fluids include CO₂, alkanes, low-carbon alcohols, water, etc. Among them, CO₂ is a very suitable supercritical fluid because it is non-toxic, non-combustible, non-corrosive, non-polluting, chemically inert, cheap and easy to obtain, and has a low critical point.

Supercritical CO₂ fluid extraction process can be used to separate and extract specific substances from solid media, and can also be used to separate and purify specific components in liquid media.

1. Density and Solvating Power

In the supercritical state, CO₂ exhibits remarkable density and solvating power. This enhanced solubility makes it an excellent medium for extracting various compounds, including essential oils, flavors, and pharmaceuticals. The increased density enables efficient penetration of porous materials, facilitating extraction processes.

2. Tunable Properties

One of the defining characteristics of supercritical CO₂ is its tunable properties. By adjusting temperature and pressure, researchers can tailor the fluid to exhibit specific characteristics, such as varying solubility and selectivity. This flexibility allows for precision in applications like supercritical fluid extraction (SFE) and supercritical fluid chromatography (SFC).

3. Low Environmental Impact

Supercritical CO₂ is gaining traction as an environmentally sustainable alternative. Unlike traditional solvents, it is non-toxic, non-flammable, and readily available from industrial processes. Its low environmental impact has led to increased interest in using it as a green solvent in applications ranging from cleaning processes to pharmaceutical manufacturing.

4. Unique Phase Behavior

The supercritical state offers unique phase behavior, blurring the line between liquid and gas. This property results in enhanced mass transfer rates and diffusivities, making supercritical CO₂ an ideal candidate for various chemical and physical processes, including particle formation and nanoparticle synthesis.

Top 4 Applications of Supercritical CO₂ extraction process

As the characteristics of supercritical CO₂ become apparent, so do its numerous advantages across multiple industries.

  • Applications in Food and Beverage Industry : The food and beverage industry has embraced supercritical CO₂ for its ability to extract flavors and essential oils without leaving residual solvents. This application ensures a purer end product with superior quality, meeting the growing demand for natural and clean-label ingredients.
  • Pharmaceutical Applications : In pharmaceuticals, supercritical CO₂ is utilized for drug particle design and formulation. Its tunable properties allow for precise control over particle size and morphology, enhancing drug delivery systems. Moreover, the environmentally friendly nature of CO₂ aligns with the industry’s push towards sustainable practices.
  • Environmental Remediation : Supercritical CO₂ is making strides in environmental remediation by extracting pollutants and contaminants from soil and water. Its low toxicity and ability to target specific compounds make it a preferred choice for cleaning up contaminated sites.
  • Supercritical CO₂ as a Green Solvent : The fluid’s low environmental impact positions it as a green solvent of choice in various manufacturing processes. From degreasing components to producing pharmaceuticals, supercritical CO₂ offers an eco-friendly alternative to traditional solvents.
Food and BeverageFlavor and essential oil extraction
PharmaceuticalsDrug particle design and formulation
Environmental RemediationExtraction of pollutants from soil and water
ManufacturingGreen solvent for degreasing and production
Supercritical CO2 Extraction Machine

Two major classification characteristics of Supercritical CO₂ fluid extraction process of materials

According to the different forms of materials, the supercritical carbon dioxide (CO₂) fluid extraction process of materials can be divided into two extraction process types: solid phase materials and liquid phase materials.

Supercritical carbon dioxide fluid extraction of solid phase materials

The process flow of supercritical CO₂ fluid extraction is set up according to different extraction objects and to complete different extraction purposes. Theoretically speaking, whether a substance can be extracted and separated depends on whether there is a certain solubility difference between the target component (i.e. solute) in the two different states of the extraction section and the analysis section, that is, the extraction section requires a larger The solubility of the solute is required to be dissolved in the fluid, while in the analysis stage, the solubility of the solute in the fluid is required to be small so that the solute can be resolved from the fluid.

During the extraction process, the extraction efficiency of SFE-CO₂ is determined by the solvent power, the characteristics of the solute (extract), and the solute-matrix combination. Therefore, when selecting extraction conditions, on the one hand, the solubility of the solute in the fluid must be considered, and on the other hand, the ability and speed of the solute to desorb from the active points of the sample matrix and diffuse into the fluid must also be considered.
The SFE-CO₂ process can be described as the following stages:

  • The CO₂ fluid diffuses in the SCF membrane surrounding the solid material particles.
  • The CO₂ fluid penetrates and diffuses in the solid material particles.
  • Solute dissolves in CO₂ fluid.
  • Solute diffuses through solid material particles.
  • Solute diffuses through.

During the separation process, the load solvent enters the separator from one end of the extractor through the pressure reducing valve. Due to changes in temperature and pressure in the separator, soluble substances that can be dissolved in the fluid in the extraction kettle are separated from the supercritical fluid.

Supercritical carbon dioxide fluid extraction of liquid phase materials

Different from the supercritical fluid extraction process of solid phase materials, the extraction kettle needs to continuously repeat operations such as charging and filling, increasing pressure and operating and depressurizing, deflating and unloading, and loading again. Supercritical fluid extraction of liquid phase materials can Using continuous extraction, the process flow has obvious advantages.

The supercritical CO₂ extraction process of liquid phase materials has the following characteristics.

  1. The extraction process is continuous. Since the extraction materials and target products are both liquid, there are no problems such as solid material feeding and slag discharge. The extraction process can be operated continuously, which greatly improves the extraction efficiency of the device and accordingly reduces the energy consumption and gas consumption in the process. consumption, reducing production costs.
  2. The extraction and separation of integrated liquid phase mixtures in the extraction-distillation process can basically be processed by a continuous counter-current supercritical extraction device. Its technical feature is the coupling of CO₂ extraction separation and distillation, which effectively exerts the separation effect of the two to achieve The extraction process and distillation process are integrated, and high-purity products can be obtained continuously.


In conclusion, the advantages and characteristics of supercritical CO₂ fluid position it as a transformative agent across various industries. Its unique properties, tunable nature, and low environmental impact make it an appealing choice for applications ranging from extraction processes to environmental remediation. As research and technology continue to advance, the full potential of supercritical CO₂ is yet to be realized, opening up exciting possibilities for innovation and sustainability.