Liquid CO.sub.2 /cosolvent extraction
AssigneeCF Systems Corporation
InventorJohn M. Moses
Life of this patent
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Abstract
Disclosed are a fluid extractant, and a process and apparatus for using the extractant to separate an organic liquid from an aqueous mixture. The extractant comprises a first fluid solvent which is a gas in its near-critical or supercritical state and a cosolvent. A preferred first fluid solvent is near-critical liquid carbon dioxide. Preferred cosolvents are 2-ethyl hexanol for ethanol extraction, and hexanoic acid for acetic acid extraction. Organic compounds such as monohydric alcohols, monoacids, ketones, ethers, aldehydes and esters can be recovered from dilute aqueous solutions more economically than possible by prior art processes of distillation.
Claims5
A quaternary fluid extraction system comprising:
- water as a first component of said system;
- an organic solute as a second component of said system;
- a fluid extractant formed of the third and fourth components of said system, said fluid extractant comprising a mixture of liquid carbon dioxide as said third component and a monofunctional hydrocarbon cosolvent said fourth component, which cosolvent is a liquid at about 60.degree. C. and standard pressure;
- is a substantially better solvent for the liquid solute than for the water;
- has a solubility in liquid carbon dioxide greater than 1 weight percent than under the conditions of extraction and separation, the carbon dioxide/cosolvent mixture forms a single phase;
- in the absence of solute, has a distribution coefficient (carbon dioxide/water) of greater than 3 on a weight basis;
- has a boiling point substantially above or below that of the liquid solute at atmospheric pressure;
- and is substantially chemically unreactive under process conditions with the first solvent fluid, the liquid solute and water.
Dependencies are inferred from the claim text.