Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing oxygen-containing organic compound
Patent
1996-11-25
1998-07-14
Lilling, Herbert J.
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing oxygen-containing organic compound
435139, 435141, 435142, 435144, 562580, 562584, 562589, 562593, C12P 740, C07C 5148, B01D 1104
Patent
active
057802769
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns quite generally the recovery of a carboxylic acid from an amine-based, water-immiscible organic extractant solution thereof obtained by liquid-liquid contact extraction of carboxylic acid from an aqueous starting solution. The term "carboxylic acid" as used herein is to be understood as meaning any aliphatic, cycloaliphatic, aromatic and heterocyclic mono- and polycarboxylic acid and also includes amino acids. The amine-based extractant used for the extraction of the starting solution contains (i) a primary, secondary or tertiary long-chain alkyl amine in which the aggregate number of carbon atoms is at least 20; (ii) a liquid hydrocarbon; and (iii) a polar, non-carboxylic organic compound which during the extraction of the carboxylic acid from the aqueous starting solution serves as extraction enhancer. One typical, but not exclusive field of application of the invention is the recovery of a carboxylic acid from an aqueous fermentation broth, comprising in a first stage a liquid-liquid contact extraction of the fermentation broth with an extractant of the kind specified and in a second stage back-extraction of the carboxylic acid from the organic extractant solution into an aqueous phase.
BACKGROUND OF THE INVENTION
The extraction of carboxylic acid from aqueous solutions by amine-based, water-insoluble organic extractants was described for the first time by Smith and Page, J. Soc. Chem. Ind, 67, 48 (1948). Since then, numerous studies were published and a number of industrial processes established. Typical of the latter is the recovery of citric acid from fermentation broths described in U.S. Pat. No. 4,275,234 (Baniel, et al.), according to which the acid is extracted at low temperature with an amine-containing, water-immiscible organic extractant and subsequently recovered as an aqueous solution by back-extraction with water at a higher temperature. As described in U.S. Pat. No. 4,275,234 and as indeed has become common practice, the extraction power of an amine-containing organic extractant is enhanced by the incorporation of a non-carboxylic, neutral, essentially water insoluble polar organic compound, e.g. an alkanol such as n-octanol, a ketone such as butanone, an ester such as butylacetate, an ether such as dibutylether, a bifunctional compound such as CH.sub.3.CH.sub.2.CH.sub.2.CH.sub.2 OCH2.CH.sub.2 OH etc. Such compounds, generally referred to as enhancers, modifiers or active diluents, increase the base strength of the amine in the extractant and thereby facilitate the transfer of carboxylic acid from the starting aqueous solution such as a fermentation broth, into the organic extractant phase. Put in other words, the presence of an enhancer shifts the carboxylic acid equilibrium in an aqueous phase/organic extractant phase system in favor of the organic phase. This very shifting of equilibrium, however, creates a problem for the back-extraction in that the transfer of the carboxylic acid from the organic to the aqueous phase is inhibited, and this inhibition may occasionally be so pronounced as to render back-extraction of the organic acid with water impractical even at temperatures close to 100.degree. C.
The fact that in accordance with the prior art only essentially water insoluble enhancers are used is due to the apparent drawbacks that attach to the use of water soluble ones and notably the need to use excess amounts of enhancer and recover it both from the extract and the aqueous extraction residue. Typically, industrial processes use enhancers such as octanol that remain in the organic extractant phase both during extraction and back-extraction by virtue of their water immiscibility.
Several approaches have been proposed to overcome this difficulty, inherent in carboxylic acid recovery processes of this kind. According to one extreme approach, back extraction is foregone altogether and carboxylic acid is recovered from the organic extract by distillation. Obviously, this procedure can be considered only for stable, relatively vo
REFERENCES:
patent: 4275234 (1981-06-01), Baniel et al.
patent: 5104492 (1992-04-01), King et al.
patent: 5132456 (1992-07-01), King et al.
patent: 5412126 (1995-05-01), King et al.
patent: 5426219 (1995-06-01), Lehnhardt et al.
patent: 5510526 (1996-04-01), Baniel et al.
Innova S.A.
Lilling Herbert J.
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