Supercritical Carbon Dioxide

Basics

• Carbon Dioxide held above the Critical Point
• Here (and other Supercritical Fluids ) it behaves essentially as both a Liquid and a Gas
• It can be abbreviated as sCO2

Uses

Blowing Agent

• Involves dissolving sCO2 into the material, then rapidly depressurizing it to form a foam
• Need to look into this further for more specific details

Chemical Synthesis

• Need to look into this for specifics, but essentially using CO2 as the solvent for the reaction
• Of interest to the Pharmaceutical Industry, as the Product may be "precipitated" by expanding the mixture out of a nozzle, leaving a fine dry product akin to Spray Drying

Supercritical Fluid Chromatography

• Can be used for Analytic Chemistry, or in Simulated Moving Bed Chromatography at an industrial scale for purification/separation of desirable (or in the case of Decaffeination etc, undesirable) Compounds

Dry Cleaning

• Unlike other solvents, sCO2 has virtually no toxicity (short of it being an Asphyxiant Hazard ) so Disposal/Handling concerns are far less

Extraction

• Supercritical fluid extraction is very common in the Essential Oil Industry (for Fragrances / Food Additives ) ( And also in the Cannabis Industry for High Value High Purity Oils/Resins/Waxes )
• It is effective, and also has little risk of contamination since simply depressurizing the mixture separates out the CO2 (which can then be collected and recycled)
• Main issue is initial cost of equipment
• It is also used for Decaffeination

As a Working Fluid

• It can be used as a Refrigerant , or as a Working Fluid in a Rankine Cycle (Although using Hydrocarbons in the Organic Rankine Cycle may be of more interest, pending a proper Decision Making Matrix or similar investigation as per the relevant OSE Specifications )
• It has the advantage over Butane and other similar proposed hydrocarbons in that it is not flammable
• The Allam-Fetvedt Cycle is a novel Power Generation system utilizing Oxy-Fuel Combustion in an all Supercritical Carbon Dioxide Atmosphere

Desorption of Spent Granulated Activated Carbon

• As per This 2024 Paper in “Chemosphere” Titled “ Regeneration of PFAS-laden granular activated carbon by modified supercritical CO2 extraction” sCO2 can be used to desorb PFAS (also other contaminants, albeit citation needed) from Spent Granulated Activated Carbon
  • Quote:
    • ” With the addition of organic solvents and acid modifiers, the procedure yielded >99% perfluorooctanoic acid (PFOA) desorption after a 60-min treatment in a continuous flow reactor. The mild extraction conditions at T ∼100 °C do not trigger the formation of volatile organic fluorine or changes in GAC sorbent properties. Mechanistically, the high miscibility of co-solvent/scCO2 eliminates diffusion transport limitations, enabling rapid reagent and PFAS transport in a single-phase (gas-like) medium”

Internal Links

• Supercritical Water
  • Supercritical Water Oxidation
  • Supercritical Water Gasification

External Links

• The Wikipedia Page on Supercritical Carbon Dioxide
• A 2012 Paper Titled "Supercritical fluid simulated moving bed chromatography for the separation of ethyl linoleate and ethyl oleate"
• A Video by the YouTube Channel "extraktLAB" Titled "How To Do Supercritical CO2 Extraction" ( ~2 Minute Watch )
• A Video by the YouTube Channel "Applied Science" Titled "A close look at supercritical carbon dioxide CO2" ( ~8 Minute Watch )
• A Video by the YouTube Channel "Applied Science" Titled "Caffeine extraction from green coffee with supercritical CO2" ( ~10 Minute Watch )
• A Video by the YouTube Channel "Applied Science" Titled "Supercritical CO2 extraction of cinnamon, coffee, and vanilla with dry ice " ( ~6 Minute Watch )
• A Video by the YouTube Channel "Applied Science" Titled "Custom supercritical CO2 chamber with easy-to-use lid clamp" ( ~7 Minute Watch )
• A Video by the YouTube Channel "Applied Science" Titled "Effect of long-term high pressure CO2 on acrylic" ( ~2 Minute Watch )
  • Seems the Acrylic is not viable for long term / non-educational demo use
• A Video by the YouTube Channel "Vidya-mitra' Titled "Supercritical fluid extraction: principle and applications (FT)" (A 30 Minute Presentation by Dr. Richa Singh from the Indian Council of Agricultural Research-National Dairy Research Institute (ICAR-NDRI) )