What is supercritical carbon dioxide?

What is supercritical carbon dioxide?

Supercritical carbon dioxide (scCO₂) is carbon dioxide (CO₂) that has been heated and pressurized beyond its critical point, where it no longer behaves purely as a gas or a liquid but as a supercritical fluid — a state with unique properties of both.

Here are the key facts:

• Critical temperature: 31.1 °C (87.9 °F)
• Critical pressure: 73.8 bar (1070 psi)

Properties of scCO₂

• Density like a liquid, allowing it to dissolve substances effectively (useful as a solvent).
• Viscosity and diffusivity like a gas, enabling it to penetrate porous materials easily.
• Easily tunable — small changes in pressure or temperature can change its solvent power.
• Non-toxic, non-flammable, inexpensive, and environmentally friendly.

Common Applications

• Extraction: Used to extract caffeine from coffee (decaffeination), essential oils, flavors, and bioactive compounds.
• Cleaning: Precision cleaning of electronics or medical instruments.
• Polymer processing: Used to create foams or modify polymer structures.
• Reaction medium: Acts as a solvent for certain chemical or biochemical reactions.