Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1998-02-23
2000-03-14
Dentz, Bernard
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
252364, 435126, C07D30762
Patent
active
060374802
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the production of ascorbic acid. More particularly, the present invention relates to the recovery of ascorbic acid from aqueous solutions containing the same in dilute concentrations.
As described, e.g., in Kirk-Othmer's Encyclopedia of Chemical Technology, Third Edition, ascorbic acid (L-ascorbic acid, L-xylo-ascorbic acid, L-threo-hex-2-enonic acid .tau.-lactone) is the name recognized by the IUPAC-IUB Commission on Biochemical Nomenclature for vitamin C. The name implies the vitamin's antiscorbutic properties, namely, the prevention and treatment of scurvy. L-ascorbic acid is widely distributed in plants and animals. The pure vitamin (C.sub.6 H.sub.8 O.sub.6, mol. wt. 176.13) is a white crystalline substance derived from L-gulonic acid, a sugar acid, and synthesized both biologically and chemically from D-glucose. ##STR1##
Although natural and synthetic vitamin C are chemically and biologically identical, in recent years a limited amount of commercial isolation from vegetable sources, e.g., rose hips, persimmon, citrus fruit, etc., has been carried out to meet the preference of some persons for vitamin C from natural sources. L-ascorbic acid was the first vitamin to be produced in commercial quantities, and manufacture is based on the well-known Reichstein and Grussner synthesis, which involves the steps of hydrogenation of D-glucose to D-sorbitol; fermentation (oxidation) to L-sorbose; acetonation to bis-isopropylidene-.alpha.-L-sorbofuranose; oxidation to bis-isopropylidene-2-oxo-L-gulonic acid, and hydrolysis, rearrangement and purification to L-ascorbic acid.
A direct fermentation of glucose to ascorbic acid would be very attractive, saving on operations and on expensive reagents, in addition to its being derived from a natural fermentation process, as opposed to a synthesis involving chemical steps. There are indications that such direct fermentation to ascorbic acid is feasible. Yet industrial production of ascorbic acid through direct fermentation seems impractical, in view of the low product concentration in the fermentation liquor, which normally is in the range of less than 0.7 mol/kg. Purifying the ascorbic acid by conventional methods would result in a purified product of concentrations similar to those in the fermentation liquor. Due to its high solubility in water, the cost of ascorbic acid crystallization by water evaporation would be prohibitive.
Several methods were proposed for combining purification of carboxylic acids with their concentration. In the case of citric acid, it is achieved by the addition of lime to crystallize calcium citrate, which has very low solubility in water. This salt is separated, washed and acidulated with sulfuric acid. Purified and concentrated citric acid is obtained. This method is not applicable for ascorbic acid, as its alkali and alkali earth salts are highly soluble.
A process was proposed in which carboxylic acids were extracted and then displaced from the extractant by a solution of concentrated mineral acids. Both liquid (long chain amines) and solid (resins carrying amine groups) anion exchangers could be considered for this purpose. The purity of the displaced carboxylic acid depends on the preference of the extractant to the mineral acid. Such a process might be applicable for ascorbic acid separation and concentration, provided that the extractant is strong enough to reach high extraction yield, that it shows high preference to the displacing acid, and that the ascorbic acid is stable at the high acidity of the displacing solution.
The regeneration of the anion exchanger would require neutralization by a base. Using HCl as the displacing acid and distilling it of the extractant was proposed, but the high temperatures required and the extractant's decomposition at these conditions are prohibitive. If the anion exchanger is represented by B, the ascorbic acid in the fermentation liquor and in the pure form are AA.sub.F and AA.sub.P, respectively, the displacing acid is HCl, and the neutralizing base i
REFERENCES:
patent: 3944606 (1976-03-01), Rieger et al.
patent: 4275234 (1981-06-01), Baniel et al.
Eyal Aharon M.
Hazan Betty
Dentz Bernard
Yissum Research Development Company of The Hebrew University of
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