DE1929268C3 - Process for obtaining D-xylose from material containing xylan - Google Patents

Description

The invention relates to a method for obtaining D-xylose from a hydrolyzate by acidic, partial hydrolysis of plant material containing xylan, which does not decompose the cellulose present, Removal of the cellulosic material, neutralization and concentration to dry or partially dry.

D-xylose is widespread in the plant sector, in the form of complex polysaccharides, xylan, which mainly consists of xylose units, combined with a small amount of arabinose and Uronic acids, is applied.

The largest deposits of xylan are found in deciduous trees and stalk plants where the xylan content, determined as xylose, is generally in the range from 10 to 25 ⁰ O. For example, "White Birch" and "Yellow Birch" have a xylan content of 24 to 20 "", while the European birch has a xylan content of 17 ° 0.

Culms like wheat, oats, esparto, etc. contain about 17 °. «Xylan, while the xylan content in bagasse, from which sucrose has been removed, to 30 per cent is increased. The relative proportion of xylan increases if one of the main components not containing xylan is used removed.

From the xylan-containing substances, all of which have a relatively high cellulose and lignin content, by means of suitable hydrolysis methods, relatively small amounts of hydrolysis products can be produced from cellulose and lignin containing xylose solutions, and thus 268

achieve a xylose content in the hydrolyzate that is geeenüber the original in the plant material is doubled or even greater, and hydrolysis can be carried out in such a way that a hydrolyzate is obtained which not only contains a lot of D-xylose, but also allows a simple production of pure D-xylose with good yield.

The invention relates to a method for obtaining D-xylose from a hydrolyzate by acidic, partial, non-decomposing cellulose Hydrolysis of xylan-containing plant material, removal of cellulose material, neutralization and concentration to dry or partially dry state has been obtained, that is characterized in that the hydrolyzate of a liquid-liquid extraction at a Temperature between 30 and 110 ° C with a water-miscible, polar organic solvent or solvent mixture that has a dielectric constant between 10 and 27 at 20 C, subject, the water content of the system being between 4 and 28 percent by weight of the total weight of the extraction system is whereupon the xylose after driving off the solvent from the Brings extract to crystallization.

The crystalline D-xylose obtained in this way has a high degree of purity and is good Yield achieved.

The xylose-containing extract obtained during the extraction can enrich the xylose after the solvent z. B. driven off with steam is subjected to fermentation with Saccharomyces to remove hexoses, after which the D-xylose is made to crystallize.

This operation is only recommended if a starting product with a high content of hexoses is used Is used so that fermentation alcohol is noticeable in usable quantities.

The fermented aqueous xylose extract can be used with advantage treat with a cation exchanger in the Η form in order to remove existing cations and to convert the salts into the acid and then can the extract with chips of treat chrome-tanned leather that has been extracted with ammonia and washed with water, to remove lignonsulfonic acids and sulfocarboxylic acids by absorbing them into the collagen and are bound to it, after which the D-Xy-Iose is brought to crystallization.

According to the invention, isopropanol is preferably used as the polar organic solvent, while the xylose is preferably crystallized from methanol.

In the methods used to date to obtain D-xylose from material containing xylan the lignin remains undissolved during hydrolysis, while a significant part of the cellulose is glucose is resolved. To produce pure D-xylose from this hydrolyzate, a difficult and costly process has to be carried out Fractionation process to separate the D-xylose from the glucose can be carried out. According to the present invention, a partial hydrolysis with a weakly acidic buffer solution, in particular bisulfite solution, carried out in such a way that the cellulose content in the xylan-containing plant material remains unaffected while the xylan with some or all of the lignin in dissolution goes. After blunting or neutralizing

of the hydrolyzate with basic or truncating salts, in particular CaCO ₃ and / or Ca (OH) ₀ , the hydrolyzate is concentrated to a concentration suitable for the subsequent extraction.

The extraction runs as a liquid-liquid extraction, including a polar solvent or solvent mixture, especially with dielectric constant in the pure solvent or solvent mixture between 10 and 27 at 20 ° C is used, preferably in countercurrent is led to the xylose-containing, concentrated hydrolyzate. Extraction temperature and water content of the system depend on the chosen solvent, so that one with an organic High polarity solvents with low water content and low temperature must work, while a solvent with a lower polarity has a higher water content and a higher temperature have to work.

According to the method according to the invention, an extract, for. B. preferably in Isupropanol obtained containing 50 to 70% xylose and 30 to 50% impurities, in which also other sugars are included. That the subsequent, simple, one-time crystallization from one low alcohol, preferably from methanol, considering this large amount of impurities without further additional cleaning operations, such as. B. treatment with ion exchanger or with absorbent, crystalline xylose results, which has a degree of purity that can be used for pharmaceutical Purposes allowed, was not expected and is for those who deal with the crystallization of sugars Extremely surprising to the person skilled in the art.

The table shows the relationship between the type (polarity) of the solvent used and the water content of the extraction system for seven polar solvents:

No. Solvent used Epsilon 20 ° C in
pure
solvent Water content, weight
percent of the total
Minimum maximum 21.8
16.1
12.2 1
2
3 Isopropanol
N-propanol
Isobutanol 20th
21
18th 6.9
5.2
6.0 0.2 4th
5 Ethyl acetate
Butanediol (1.4) 6th
31 0.0 20.4
16.3 6th
7th N-butanol
acetone 18th
21 7.2
4.7

It is clear that the most selective release of D-xylose from concentrates of xylan hydrolyzate, in particular bisulfite waste liquor from hardwood, depending on the organic Solvent has a polarity lower than that for methanol. It is known, for example from NO-PS 91 670 that methanol is used to fractionate lignosulfonates when triggered of low molecular weight lignosulphonate from sulphite waste liquor can be used. However, it can processes described therein for obtaining D-xylose cannot be used.

Ethanol, which has a dielectric constant of 25 at 20 ° C, is likely to be close to the limit of feasibility of the present process are, albeit ethanol, as in the example below shown can be used in an extraction in which the water content is about 5% and the Temperature is 65 ° C. The concentration in this case is quite viscous, making it a borderline case for liquid-liquid extraction is to be considered. In case of further addition of water and further temperature increase attempts to reduce the viscosity of the concentrate phase result in dark extracts, which result in a low yield of xylose and poor quality.

The condition for the usability of a polar, organic solvent for the extraction of D-xylose, according to the method of the invention, can thus be expressed as the dielectric constant of the pure solvent or solvent mixture lower than 27 at 20 ° C have to be. One can also use a condition of the lower polarity limit in the pure. solvent because you cannot use any solvents with a dielectric constant lower than 10 has found. This is evident from Example 6, where ethyl acetate with a dielectric constant of 6 is used 20 ° C was attempted. At this low polarity is the solubility of xylose in the pure solvent practically zero, and the solubility of water in the solvent is also minimal.

The water content of the extraction system plays an essential role in the selectivity of extractions of D-xylose, and very precise limits can be drawn for each individual solvent, the water content being between 4 and 28 percent by weight of the total weight of the system.

So you can do a liquid-liquid extraction on the one hand perform and on the other hand prevent too much impurities in the form of low molecular weight Lignosulfonates, aldonic acid salts or sulfocarboxylic acid salts go into dissolution.

The water content and the extraction temperature of the system as a function of the dielectric constant in the pure, polar and organic solvent or mixture of pure, polar and organic solvents Solvents which are used according to the invention for the extraction of D-xylose are im Triangle diagram, Fig. 1, shown graphically.

In Examples 1 and 2 below, the procedure for carrying out the process is illustrated and it is

5 6

onto the flow diagram, FIG. 2 referenced. The current situation: 14.2 g of D-xylose with some examples 3 to 9 explain the dependence on the taste of water.

water content of the extraction system. After stirring in cold methanol (50 ml),

Filter off, wash with methanol and dry:

Example 1 ⁵ 12.8 g D-xylose = 12.8 percent by weight on dry

based on fuel, with a purity of more than 97 ° / o, calculated

100 g sulphite liquor powder from birch wood with a water content according to thin layer chromatography and ash of 6.6% (93.4 g dry matter) analysis.

3g Ca (OH) ₂ and 300ml 96% ethanol Example 3a

added. The whole thing was in a container with io ^v

The reflux condenser was stirred with heating to 70 ° C. 100 ml of a 100% isopropanol were un-

The powder had a slight tendency to form lumps, but stirring and heating 28 g of sulphite liquor dry

the system that now contains 16.2 g of water = 4.76 weight of birchwood-based material in the form of 30 g

percent contained, was still as a solid powder with a water content of 6.6%, which 1 g Ca (OH) ,,

View liquid extraction. Water was added 15 were added. The temperature was on

added dropwise until the powder ^{adjusted to a 7O 0} C and kept constant while

viscous concentrate phase with a good phase difference, water was added drop by drop from a burette

sintered together to form the ethanol phase. Total water was. After adding 6 ml, the powder clumped

Amount: 18.3 g = 5.14% . together into a viscous mass, and the isopropane

After stirring for 15 minutes, the mixture gave a phase which was completely clear with a pale yellow color. the

at 65 ⁰ C and 20 minutes standing 216 ml of a high amount of water that the system at this point in time

th, yellow-brown extract. contains the minimum amount of water below

The concentrate that has now been extracted was given as = 8 ml = 6.9 percent by weight. 200 ml of 96% ethanol were added to the water. It was added without further heating, heated with stirring and added to fresh water until the sulfite phase was slightly liquid and the phases were added because the concentrate was much more viscous than when it was separated a little diffuse with a somewhat unclear iso-first extraction. 1.2 ml were added and the propane phase became. The amount of water attached. which should mean a water content of about 5% in the system 28.2 ml, together with the original water. After stirring for 15 minutes, the maximum water content below corresponds to -65 ° C. and standing for 20 minutes, 198 ml of the specified amount of water = 30.2 ml = 21.8 tracts were decanted. Weight percent of the total weight of the system.

The concentrate was added 2 more times according to this. After stirring at 55 ° C for 10 minutes, this became the

same procedure as in the first two Extrak systems for sedimentation and cooling for 20 minutes

ions, extracted and the entire extracts of the put. Decantation resulted in a brown colored Dc-

4 extractions with a dry matter content of 35 kantat, 57.2 g, which was still unclear. The Dckan-

of 33.8 g after vacuum evaporation on a water bath. tat was zn on a boiling water bath in vacuo

After dissolving the dry matter in 50 ml of a practically dry, bubbly sugar melt

ßem ethanol evaporated to a relatively thick liquid weighing 4.2 g. The sugar melt c

xylose crystallized during the night and was dissolved in 10 ml of methanol and allowed to cool

Fridge. 40 and crystallize. After 24 hours of standing

Yield: 10.8 g of D-xylose = 10.8% by weight, the crystallized material was filtered off, with 3 · 10 m!

cent, based on the weight of the powder, washed with a pure methanol and dried after 3 hours

degrees over 95 ° / o, calculated according to thin-layer chromatography, weighed at 80 ° C and 2 hours in a CaCl _{2 desiccator}

matography and ash analysis. Yield: 1.5 g of poor quality xylose unc

45 color.

^Bei P ^{iel 2} Example 3b

138 g of a sulphite liquor concentrate with 72.5% in the same way as in Example 3a

Dry matter content 3 g Ca (OH) _{2 were} added, 100 ml isopropanol and 28 g sulphite liquor dry

which the latter quickly in the heated up to 50 ° C 50 fabric of birch wood 6 ml of water to achieve the dei

Concentrate were stirred in. Thereupon a minimum amount of water, 6.9 percent by weight, at

250 ml of 90% isopropanol with stirring and given. The chewy sulphite liquor was at 70 ° C

Heating to 70 ° C added. The water content digested for 10 minutes, followed by 20 minutes

57.6 g of a total amount of standing was now in the system, resulting in a very light decantate of 61.5 g

of 337.5 g = 17.1 percent by weight. The mixture 55 This was evaporated as before, to 2.8 g dry

gave after 15 minutes of stirring at 70 ⁰ C and kenstoff, which after the above-described Kri-

20 minutes standing 148 ml of a light, yellow expansion treatment 1.1g xylose very good quality

tracts. The extracted concentrate was added on and gave color, new 15OmI 90% strength isopropanol added, and

the mixture was again stirred at 70 ° C. for 15 minutes. 60 Example 4a The same thing was repeated twice more, and the

Total extracts of the four extractions were found to be. In the same manner as above, dei

a dry matter content of 31.8 g according to vacuum - minimum water content for 28 g sulphite liquor dry

evaporate on water bath. After dissolving the substance of birch wood in 100 nuN propanol at 87 ⁰ C Tn ^ V ^ stoft «,« 50 ml of warm H ^ -mol, cheese * = · !!: - 's to δ-ml · -5 , 2 percent by weight. Maximali

Sized D-xylose during the night in the refrigerator, amount of water 21.0 ml = 16.1 percent by weight, he

whereupon it was filtered off, washed with methanol and gave a decantate brownish yellow color of 59.4 g unc

was dried. 3.2 g of dry sugar after evaporation. Nacl

Crystallization was a yield of 1.0 g of xylose with a light, almost white color, but with a bitter taste.

Example 4b

A minimum amount of water was 100 ml N-propanol and 28 g of sulphite liquor dry matter from birch wood were added at 87 ° C., as in Example 4 a. This time, however, the powder did not quite want to clump together. More water was used to sinter together added, and a total of 9.5 ml of water + 2 ml = 11.5 ml = 9.55 percent by weight added. After stirring for 10 minutes at 87 ° C, standing and decanting 62.4 g of decantate, which was significantly darker than the decantate from Example 3b was evaporated to 2.8 g of dry matter and crystallized in methanol. Yield: 1.2 g of good quality xylose.

20th

Example 5a

For 100 ml isobutanol and 28 g sulphite liquor dry matter as before, the minimum water content at 86 ° C. was determined to be 7 ml = 6.0 percent by weight. With a maximum water content of 15.2 ml = 12.2 percent by weight, 63.3 g of decantate were obtained, which is something was darker than in Example 4b. After evaporation to 2.9 g of dry matter and crystallization was the Yield 0.8 g of poor quality xylose.

Example 5b

100 ml isobutanol and 28 g sulphite liquor dryer, substance made of birch wood with a minimal amount of water gave 6.0 percent by weight after stirring for 10 minutes at 86 ° C, standing and decanting 64.2 g of decantate, a sugar solids of 1.7 g and a yield of 0.6 g of good quality xylose.

Example 6

100 ml of ethyl acetate and 28 g of sulphite liquor dry matter made of birch wood resulted in different amounts of water and temperatures - as expected - No release of D-xylose due to poor miscibility with water and too low dielectric constant (6).

Example 7

100 ml butanediol (1,4) and 28 g sulphite liquor dry matter made of birch wood gave a real solution even with minimal amounts of water and low levels Temperature, as expected, for butanediol- (1,4) which is hygroscopic and a dielectric constant of 3C at 25 ° C.

Example 8a

For 100 ml n-butanol and 28 g sulphite liquor dry matter, as before, the minimum water content of the system at 95 ° C became 8.5 ml = 7.2 percent by weight definitely. At a maximum water content of 28 ml ^ 20.4 percent by weight, you got 53.7 § Decantate of dark color. After evaporation to 3.1 lbs dry matter and crystallization the yield was 0.5 g D-xylose light color but with a bitter taste.

Example 8b

100 ml n-butanol and 28 g sulphite liquor dry matter from birch wood with a minimum amount of water 7.2 percent by weight resulted after 10 minutes of stirring at 95 ° C and standing a decantate before 64.0 g. After evaporation to 2.8 g and crystallization the yield was 0.5 g of good quality D-xylose.

Example 9a

For 100 ml of acetone and 28 g of sulphite dry matter from birch wood, as before, the mini paints amount of water at 50 ⁰ C to 5.3 ml = 4.68 weight percent was determined. At a maximum water content of 21 ml = 16.3 percent by weight, 63.6 g of decantate resulted in a dry sugar substance of 3.8 g, which gave a yield of 0.6 g of poor quality xylose.

Example 9b

100 ml acetone and 28 g sulphite liquor dry matter made of birch wood with a minimal amount of water, 4.68 percent by weight, resulted in scrambled eggs after 10 minutes at 50 ° C a very weakly colored decantate 62.3 g, which after evaporation to 0.8 g dry substance and crystallization resulted in a yield of 0.1 g of good quality Xy loose.

For this purpose 2 sheets of drawings

Claims (3)

Claims: 19 1. A method for obtaining D-xylose from a hydrolyzate which has been obtained by acidic, partial hydrolysis of xylan-containing plant material, which does not decompose the cellulose present, removal of the cellulose material, neutralization and concentration to dry or partially dry state, there- »o characterized in that the hydrolyzate is subjected to a liquid-liquid extraction at a temperature between 30 and 110 ⁰ C with a water-miscible, polar organic solvent or solvent mixture which has a dielectric constant between 10 and 27 at 20 ° C, wherein the water content of the system is between 4 and 28 percent by weight of the total weight of the extraction system, whereupon the xylose ao crystallizes after the solvent has been driven off from the extract. 2. The method according to claim 1, characterized in that the extract is aborted subjecting the solvent to fermentation with Saccharomyces with steam. 3. The method according to claim 2, characterized in that the fermented aqueous Xylose extract with a cation exchanger in Η form and then with chips of chrome-tanned Leather extracted with ammonia and washed with water treated.