Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1994-10-31
1996-10-08
Cook, Rebecca
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
562537, C07C 2704
Patent
active
055633030
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/BE93/00013 filed Mar. 17, 1993.
The invention relates to a method of producing xylitol from D-glucose, D-fructose, D-galactose or mixtures thereof.
Amongst the pentitols only xylitol possesses a commercially important value. Today the large scale production of xylitol is based on hydrogenation of D-xylose as described in U.S. Pat. No. 4,008,285. D-xylose is being prepared through hydrolysis of hardwood, straw, corn cobs, oat hulls or other xylan-rich plant material. D-xylose may also be recovered as a side produce from the acidic spent liquors of the sulphite process or other processes that are being used for pulping of hardwoods or other xylan-rich material.
The production costs of xylitol are relatively high because the yield of D-xylose is typically low and complex processes are needed for its purification. In the hope of a more cost-effective production method it has been suggested in several occasions that D-glucose should or could be used as a raw material in the synthesis of xylitol.
In principle the synthesis of xylitol via D-xylose from D-glucose looks very straightforward; the two molecules (D-xylose and D-glycose) are identical except for an additional hydroxymethyl group at C-5 atom of D-glucose. Because of the apparent similarity of the molecules most effort has been put on developing methods of selectively cleaving the bond between C-5 and C-6 atoms of D-glucose. Kiss et al. (Helv. Chim. Acta 58 (1975) 311) converted D-glucose to 1,2-O-isopropylidene-alpha-D-glucofuranose, oxidatively cleaved the bond between the C-5 and C-6 atoms with periodate, removed the protecting isopropylidene group through hydrolysis and finally hydrogenated the resulting xylo-dialdose to xylitol. Later Malmelin (M.Sc. thesis, Helsinki University of Technology, Espoo 1978) evaluated the chemical costs in this method and found them too high for a large-scale production.
At the end of the 1960'ies Onishi ja Suzuki (Appl. Microbiol. 18 (1969) 1031) introduced a fermentation process for making xylitol from D-glucose through D-arabinitol and D-threo-2-pentulose (D-xylulose) as intermediates. The yield of xylitol was, however, low (14%). Later the individual reaction steps of this process were developed by Ohmomo et al. (J. Ferment. Technol. 61 (1983) 373, 63 (1985) 331). They also presented a modification in which D-xylulose was treated with D-xylulose isomerase and the resulting mixture of D-xylulose and D-xylose fermented to xylitol. In another modification D-xylose was separated from the isomerization product mixture and converted to xylitol through hydrogenation as disclosed in EP-A-0,403,392. D-xylulose was returned to the isomerization stage. In one case the mixture of D-xylose and D-xylulose was hydrogenated as such followed by separation of xylitol from the product mixture by chromatography as disclosed in EP-A-0,421,882).
The aim of the invention is to provide for a method of producing xylitol in a way that differs essentially from all the other known methods of producing xylitol from D-glucose, according to which method it is possible not only to use D-glucose but also to use mixtures of D-glucose and D-fructose or D-glucose and D-galactose as the raw material. These mixtures are available as hydrolysates of sucrose and lactose respectively.
This aim is reached by the fact that the method comprises the steps of:
a. oxidation of the starting material to an intermediate that consists mainly of L-xylonic acid, D-arabinonic acid, D-lyxonic acid or a mixture of an least two of said acids, whereby said acids are free or in the form of their salts, lactones or O-formyl derivatives;
b. treatment of said intermediate with a hydrogenation catalyst and hydrogen gas in one or several steps to a product consisting mainly of xylitol or a mixture of xylitol, arabinitol and ribitol;
c. and, if necessary, separation of xylitol from said product and, if said product consist mainly of said mixture of pentitols, feeding of the fractions of arabinitol and ribitol back to the preceding reaction step b.
REFERENCES:
patent: 5096820 (1992-03-01), Leleu et al.
Patent Abstracts of Japan, vol. 83, No. 7, 6, Apr. 1983.
Amylum, n.v.
Cook Rebecca
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