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What are the chemical reactions and/or chemical processes that take place during SFE(supercritical fluid extraction)? Namely supercritical $\ce{CO2}$.

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  • $\begingroup$ No ma'am/sir/mammal. I was looking into homemade supercritical decaffeination chamber. AppliedScience (YouTube channel) has an example. $\endgroup$ – Sciiiiience Jul 4 '14 at 22:33
  • $\begingroup$ Any suggestions? I can't yet make tags so, I couldn't figure out what to put. $\endgroup$ – Sciiiiience Jul 4 '14 at 22:48
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Supercritical fluid technology is used primarily to enhance the chemical extraction process. The solubility of a compound in a supercritical solvent increases as the system pressure increases at constant temperature. This is due to the highly pressurized supercritical solvent disrupting the intermolecular attractive forces between the molecules of the compound to be extracted, and replacing those forces with increased attractive forces between the compound and the supercritical solvent. Carbon dioxide is a very common material used for supercritical extraction. It is cheap, not flammable, has low toxicity and, after the extraction is complete you simply return the system to STP, allow the carbon dioxide to evaporate and you are left with only the extracted material. Some examples of commercial uses for supercritical carbon dioxide include caffeine extraction from coffee beans, sterilization of surgical equipment, fracking and dry cleaning.

Chemical reactions involving supercritical carbon dioxide are now being intensely studied. One reaction that has been commercialized involves reaction of supercritical carbon dioxide with hardened, alkaline cements. A harder cement containing carbonate groups throughout the entire volume of cement is formed along with water (environmentally friendly process).

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Ideally no reactions should occur during an SF extraction. In all the extractions a solvent is used to extract different substances from a matrix. In SFE the solvent is a supercritical fluid, in most of the cases is used $CO_{2}$ but not always. The chemicals process related to the extraction is mainly the solubilization of the target substance in the SF depending on the properties of the target substance and the SF (e.g. polar or non polar).

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