Supercritical Fluid Extraction (SFE)
1. Introduction
Supercritical Fluid Extraction (SFE) is an advanced separation and
purification technique that uses a substance maintained above its
critical temperature and critical pressure, where it exists as a
supercritical fluid.
A supercritical fluid is a substance that is kept above its critical
temperature and critical pressure, so it is neither a distinct liquid
nor a gas.
It has liquid-like density (good solvent power) and gas-like
viscosity and diffusivity (flows easily and penetrates solids).
SFE is valued for high selectivity, solvent-free products, and
environmentally benign operation, making it an important “green
technology” in food processing, pharmaceuticals, natural product
isolation, and environmental analysis.
2. Principle of Operation
Critical Point Concept: A supercritical fluid forms when a
substance is subjected to temperature (T) and pressure (P) above
its critical point (Tc and Pc). Beyond this, the boundary between
liquid and gas disappears.
Density Control: The density of a supercritical fluid—and hence
its solvating strength—can be finely tuned by small adjustments in
P and T.
Selective Extraction: Target compounds dissolve in the
supercritical phase and are separated by depressurization or
temperature reduction, which decreases the fluid’s solvating power
and causes the solute to precipitate.
3. Key Critical Parameters
, Substance Critical Temperature Critical Pressure
(°C) (bar)
Carbon dioxide (CO₂) 31.1 73.8
Water 374 221
Ethane 32 48
Carbon dioxide is the most widely used because of its mild
critical conditions, non-toxicity, and cost-effectiveness.
4. Properties of Supercritical Fluids
Liquid-like Density: Provides strong solvating ability similar to
organic solvents.
Gas-like Viscosity & Diffusion: Facilitates fast penetration into
pores of solids and high mass transfer rates.
Variable Solvent Power: Density and polarity can be altered by
minute changes in pressure or temperature.
Environmentally Safe: Inert, non-flammable (for CO₂), and easily
removed from the product.
5. Process Flow of SFE
5.1
Feed Preparation
Raw material is dried and ground to increase surface area and
avoid water condensation or ice formation.
5.2
Pressurization and Heating
A high-pressure pump delivers the fluid (commonly CO₂) and the
heater raises it above Tc.
1. Introduction
Supercritical Fluid Extraction (SFE) is an advanced separation and
purification technique that uses a substance maintained above its
critical temperature and critical pressure, where it exists as a
supercritical fluid.
A supercritical fluid is a substance that is kept above its critical
temperature and critical pressure, so it is neither a distinct liquid
nor a gas.
It has liquid-like density (good solvent power) and gas-like
viscosity and diffusivity (flows easily and penetrates solids).
SFE is valued for high selectivity, solvent-free products, and
environmentally benign operation, making it an important “green
technology” in food processing, pharmaceuticals, natural product
isolation, and environmental analysis.
2. Principle of Operation
Critical Point Concept: A supercritical fluid forms when a
substance is subjected to temperature (T) and pressure (P) above
its critical point (Tc and Pc). Beyond this, the boundary between
liquid and gas disappears.
Density Control: The density of a supercritical fluid—and hence
its solvating strength—can be finely tuned by small adjustments in
P and T.
Selective Extraction: Target compounds dissolve in the
supercritical phase and are separated by depressurization or
temperature reduction, which decreases the fluid’s solvating power
and causes the solute to precipitate.
3. Key Critical Parameters
, Substance Critical Temperature Critical Pressure
(°C) (bar)
Carbon dioxide (CO₂) 31.1 73.8
Water 374 221
Ethane 32 48
Carbon dioxide is the most widely used because of its mild
critical conditions, non-toxicity, and cost-effectiveness.
4. Properties of Supercritical Fluids
Liquid-like Density: Provides strong solvating ability similar to
organic solvents.
Gas-like Viscosity & Diffusion: Facilitates fast penetration into
pores of solids and high mass transfer rates.
Variable Solvent Power: Density and polarity can be altered by
minute changes in pressure or temperature.
Environmentally Safe: Inert, non-flammable (for CO₂), and easily
removed from the product.
5. Process Flow of SFE
5.1
Feed Preparation
Raw material is dried and ground to increase surface area and
avoid water condensation or ice formation.
5.2
Pressurization and Heating
A high-pressure pump delivers the fluid (commonly CO₂) and the
heater raises it above Tc.
