Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Process involving micro-organisms of different genera in the...
Reexamination Certificate
2001-03-07
2002-04-09
Lilling, Herbert J. (Department: 1651)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Process involving micro-organisms of different genera in the...
C435S140000, C435S170000, C435S252700
Reexamination Certificate
active
06368819
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to improved methods for the microbial production of acetic acid. More particularly, the invention relates to extraction of acetic acid from aqueous streams, and from the microbial fermentation of desirable chemical products from gaseous streams, such as waste gas streams, industrial gas streams, or from gas streams produced from the gasification of carbonaceous materials.
BACKGROUND OF THE INVENTION
Methods for the anaerobic fermentation of carbon monoxide, and/or hydrogen and carbon dioxide to produce acetic acid, acetate salts or other products of commercial interest, such as ethanol, have been performed at laboratory bench scale. See, e.g., Vega et al, (1989)
Biotech. Bioeng.,
34:785-793; Klasson et al (1990)
Appl. Biochem. Biotech.,
24/25: 1; Vega et al (1989)
Appl. Biochem. Biotech.,
20/21: 781-797; and Klasson et al (1992)
Enz. Microbio. Tech.,
19: 602-608, among others. More recently, the present inventors have discussed large-scale methods for the fermentation of industrial gas streams, particularly waste gas streams, into products of commercial use by using methods employing fermentation of the gas stream, an aqueous nutrient medium and an anaerobic bacteria or mixtures thereof in a bioreactor. See, e.g., U.S. Pat. Nos. 5,173,429; 5,593,886 and International Patent Publication No. WO98/00558, incorporated herein by reference.
According to the above-cited prior art of the inventors, one such large scale process involves the following summarized steps. Nutrients are continuously fed to a bioreactor or fermenter in which resides a culture, either single or mixed species, of anaerobic bacteria. A gas stream is continuously introduced into the bioreactor and retained in the bioreactor for sufficient time to maximize efficiency of the process. Exhaust gas containing inert and unreacted substrate gases, are then released. The liquid effluent is passed to a centrifuge, hollow fiber membrane, or other solid-liquid separation device to separate out microorganisms that are entrained. These microorganisms are returned to the bioreactor to maintain a high cell concentration which yields a faster reaction rate. Separation of the desired biologically produced product(s) from the permeate or centrifugate occurs by passing the permeate or centrifugate to an extractor where it is contacted with a solvent, such as a di-alkyl and tri-alkyl amine in a suitable cosolvent, or tributyl phosphate, ethyl acetate, tri-octyl phosphine oxide and related compounds in a co-solvent. Suitable cosolvents include long chain alcohols, hexane, cyclohexane, chloroform, and tetrachloroethylene.
The nutrients and materials in the aqueous phase pass back to the bioreactor and the solvent/acid/water solution passes to a distillation column, where this solution is heated to a sufficient temperature to separate the acid and water from the solvent. The solvent passes from the distillation column through a cooling chamber to lower the temperature to the optimum temperature for extraction, then back to the extractor for reuse. The acid and water solution passes to a final distillation column where the desired end product is separated from the water and removed. The water is recirculated for nutrient preparation.
Further, a variety of acetogenic bacteria are well known to produce acetic acid and other commercially interesting products when subjected to such fermentation processes, including novel strains of
Clostridium ljungdahlii
[See, e.g., U.S. Pat. Nos. 5,173,429 and 5,593,886 and International Patent Publication No. WO98/00558].
Despite such knowledge and advances in the art of microbial fermentation of a variety of gas streams, acetic acid production is limited by the acetic acid loading potential of the solvent used, and by the degradation of the solvent as it travels through the production process, among other issues. In view of the ever-increasing need to produce acetic acid, as well as to convert industrial waste gases into useful non-polluting products, there remains a need in the art for processes which are more efficient in producing the desired commercial product and compositions which can enhance performance of such methods.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a modified water-immiscible solvent useful in the extraction of acetic acid from aqueous streams comprising a substantially pure mixture of isomers of highly branched di-alkyl (or secondary) amines. This solvent can extract the acid in the absence of a co-solvent. In a preferred embodiment, this solvent is a modified form of Adogen283® solvent [Witco Corp.] which is substantially reduced in its content of alcohols and monoalkyl (or primary) amines. In another preferred embodiment, the solvent is further reduced in content (i.e. substantially purified) of tri-alkyl (or tertiary) amines.
In another aspect, the invention provides a method for treating a solvent comprising alcohols, monoalkyl amines, a mixture of isomers of highly branched di-alkyl amines and tri-alkyl amines to improve its acetic acid extractive capacity comprising distilling from the solvent substantially all the alcohols and monoalkyl amines. In another embodiment, the method involves subjecting the distilled solvent to a second distillation to remove substantially all tri-alkyl amines.
In yet a further aspect, the invention provides a novel water-immiscible solvent/co-solvent mixture useful for the extraction of acetic acid, preferably at concentrations less than 10%, from an aqueous stream comprising an above-described modified water-immiscible solvent useful in the extraction of acetic acid from aqueous streams comprising a substantially pure mixture of isomers of highly branched di-alkyl amines and a selected cosolvent. In a preferred embodiment, the cosolvent is a low boiling hydrocarbon having from 9 to 11 carbon atoms, which hydrocarbon forms an azeotrope with water and acetic acid.
In still another aspect, the invention provides a non-fermenting process for obtaining acetic acid from an aqueous stream comprising contacting the stream with a modified solvent/cosolvent mixture as described above; extracting the acetic acid from the aqueous phase into the solvent phase; and distilling the acetic acid from its admixture with the solvent under a temperature not exceeding 160° C.
In yet a further aspect, the invention provides a non-fermenting process for obtaining acetic acid from an aqueous stream comprising contacting the stream with a solvent/cosolvent mixture as described above; extracting the acetic acid from the aqueous phase into the solvent/cosolvent phase; and distilling the acetic acid from its admixture with the solvent/cosolvent under a temperature not exceeding 160° C. under a vacuum.
In a further aspect, the present invention provides an anaerobic microbial fermentation process for the production of acetic acid, the process comprising the steps of (a) fermenting in a bioreactor an aqueous stream comprising a gas selected from the group consisting of carbon monoxide, carbon monoxide and hydrogen, hydrogen and carbon dioxide, and carbon monoxide, carbon dioxide and hydrogen, in a nutrient mixture with an anaerobic acetogenic bacterium, thereby producing a broth comprising acetic acid; (b) continuously extracting acetic acid from the broth with a modified solvent/cosolvent mixture as described above; (c) continuously distilling from the product of (b) the acetic acid separately from the solvent at a temperature not exceeding 160° C., and (d) optionally recycling the solvent and the broth through the bioreactor. The extracting and distilling steps occur without substantially degrading the amine to an amide, thus enhancing the efficiency of acetic acid recovery from the broth.
In still another aspect, the present invention provides a method for enhancing the recovery of acetic acid from a fermentation broth comprising an aqueous stream containing one or more of carbon monoxide, carbon dioxide and hydrogen, and an anaerobic acetogenic bacter
Clausen Edgar C.
Gaddy James L.
Ko Ching-Whan
Wade Leslie E.
Wikstrom Carl V.
Bioengineering Resources, Inc.
Howson and Howson
Lilling Herbert J.
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