DD222636A1 - METHOD FOR OBTAINING XYL-RELATED HYDROLYSATES WITH INCREASED SUGAR CONCENTRATION FROM HEMICELLULOSE-CONTAINING RAW MATERIALS - Google Patents

Abstract

The invention relates to a process for the hydrolytic degradation of vegetable raw materials (in particular also of bark-containing deciduous wood residues) containing xylan-rich hemicelluloses in strongly dismutated mineral acids. To ensure sufficient hydrolyzate purity, the raw material is pretreated with very dilute ammonia solution and the liquid is squeezed out. The subsequent hydrolysis is carried out with dilute mineral acid (usually sulfuric acid) at 100 C under atmospheric pressure or at 110-130 C and corresponding pressure. The hydrolyzate is pressed off and the residue washed with fresh acid. The hydrolyzate is used after combination with the washing acid several times as a hydrolysis reagent for the pretreated raw material. After the last use, the hydrolyzate is neutralized in the presence of hydrolysis residue and teilentfaerbt. The solids are pressed off and washed with water. From the concentrated solution, xylose can be isolated or obtained after hydrogenation xylitol.

Description

Title of the invention,.

Year go, for the recovery of xylose * calibrate hydrolysates with higher sugar concentration from hemicellulose-containing raw materials

Field of application of the invention

The invention includes a process of hydrolytic degradation pretreated xylanreicher plant raw materials in dilute acids for. Production of sugar-containing solutions _> suitable for obtaining crystalline xylose or crystalline xylitol

Characteristic of the known technical solutions

There are numerous technical solutions involving the hydrolysis of pentosan-containing raw materials with dilute mineral acids, more rarely with dilute organic acids, and seeking to obtain crystalline xylose or crystalline xylitol. The raw materials are annual or bark-free hardwood. A pentosanreiche syrup is also represented by CS Pat · 181485 jaus beech bark.

Hydrolyzing is usually done with freshly added acid. The sugar concentrations achieved in the hydrolysates are usually 2-5%. Since the concentration of xylitol in the hydrogenation by 40%, and the xylose crystallization even by 80 % , the concentration requires considerable amounts of energy. There are internationally different efforts to produce hydrolysates with higher sugar concentrations. In hydrolysis processes, with concentrated hydrochloric acid (US Pat. No. 2,474,669) or with sulfur dioxide solutions (DE-AS 2,338,450), the one-time use of the hydrolysates as hydrolytic reagent has been proposed. It is not recommended to use them more than once, apparently due to the increasing contamination of the hydrolysates and the risk of sugar decomposition. In order to ensure hydrolyzate purity by limiting the decomposition of sugar, the addition of small amounts of a low molecular weight alcohol has been recommended for hydrolysis with prochloric acid (SU Pat No. 755925) * The hydrolyzate is neutralized after removal of prehydrolysis residue. At the foot of the valley, it turns intensely dark. To limit the darkening, it is proposed to neutralize only to pH 5.5-6.5 and to remove the remaining hydrogen ions by ion exchange. About the influence of the present cellolignin on the color intensity of the hydrolysates no publications have become known · · .- '. · ·

After neutralization, the precipitate becomes e.g. separated by screw presses (DE-OS 2553647, DE-OS 2729919) and the hydrolyzate then usually decolorized by activated carbon. The activated carbon is separated off and the solution is then deionized »

The hydrolyzate preparation thus contains 2r 3 Irennoperationen, which are connected after each stage with hydrolyzate losses.

Object of the invention.

The aim of the invention is a hydrolysis process in highly dilute acidic solution, which allows hemicellulose-containing raw materials, including especially bark-containing hardwood waste, for the production of relatively concentrated Zylosehaltiger solutions as a starting point for the recovery of crystalline xylose or crystalline xylitol use »This is a rational and possible conversion of vegetable raw materials into high-quality products as energy-efficiently as possible

Explanation of the essence of the invention

According to the invention, the objective is achieved by first pretreating the hemicellulose-containing raw materials with 0.01 to 0.5% strength ammonia solution at room temperature and then carrying out the hydrolysis with 2-5% strength sulfuric acid with repeated reuse of the hydrolyzate as hydrolysis reagent.

For this purpose, the still moist material from the pretreatment in the reactor with the sulfuric acid in the ratio of dry matter to liquid of 1: 5 to 1: 8 heated between 2 and 5 h at 100 ⁰ C, to avoid loss of liquid s the Brüdendämpfe be condensed. The released energy serves to preheat the fresh acid «

Another embodiment consists in the hydrolysis of the pretreated material under a moderately elevated pressure at Sempera doors of 110-130 ⁰ C and a sulfuric acid concentration of 0.5-2.0 % in 1-3 nv To limit the sugar substitution can be zugese'tzt in a known manner of the fresh acid 0.2% of a - ·· low molecular weight alcohol hydrolyzate and Celloligninrückstand be means of. Screw press so separated that the residue does not contain more than 40% moisture. The hydrolyzate is stored in a thermally insulated container and the residue washed with prewarmed fresh acid (ratio 1: 2) and squeezed. That with; the. Washydric acid "combined hydrolyzate serves optionally as a hydrolysis reagent for the second batch of pretreated chips again after adding ethanol again.

The resulting wash acid is combined with the hydrolyzate and hydrolyzed with this solution, the third batch of pretreated chips. A fourth raw off-off char can be used accordingly. The multiple use of the hydrolysates as hydrolysis reagents is made possible by the pretreatment of the raw materials, whereby components (resins, dyes, etc.) are dissolved out which would impair the 'hydrolyzate quality.' More than three applications of the hydrolyzate as hydrolysis reagent are due to the increasing sugar decomposition not effective "It was found that the dark coloration occurring at the talc point is less intense when neutralized in the presence of the hydrolysis residue and. the neutralization at pH 5j5 - 6.5 is stopped. In the third or fourth batch (1st batch fresh acid use), therefore, the hydrolyzate in the presence of the hydrolysis residue with calcium hydroxide with stirring to about

pH 6 neutralized, for further 'partial decoupling activated charcoal added (1 % relative to the amount of liquid), the pesticide fraction is separated off after thorough mixing with a screw press, the. The residue is washed twice with water (ratio 1: 2) and pressed thoroughly in each case »The 7 / as'chwasser is used for the production of fresh acid. The deionization of the filtrate is carried out with a strongly acidic cation exchanger and a weakly basic anion exchanger. Due to the multiple use of the hydrolyzate, only about one third of the liquid quantity has to be neutralized »discoloring and deionizing ·

The hydrolysates thus obtained have sugar concentrations between 7 and 10%. Where a microbiological further processing is not provided, they are brought to the extraction of xylitol at 40 ⁰ C by means of vacuum to a xylose concentration of at least 40% · These substrates can with a special Uickelkatalysator at 120-135 ⁰ C under a pressure of x 20 IIPA almost be completely hydrolyzed »The purified and decolourised polyol solution is concentrated to at least 70 % and crystallized the Rohsylitol. After crystallization with ethanol, pure xylitol is obtained.

When xylose is desired as the end product, the purified hydrolyzate is concentrated to a sugar content of about 80 %. * From the syrup crystallises crude xylose, which is recrystallized in the usual way,

Embodiment '·

Industrial beech shavings are thoroughly mixed with a 0.05% strength ammonia solution in a ratio of 1: <4 at room temperature for 30 minutes and the pretreatment liquid is squeezed out. Hydrolysis is carried out with addition of 0.2 % ethanol with 3 % sulfuric acid (Klotte 1: 7) 3 h at 100 ^° C. or 2 h with 1% strength sulfuric acid at 120 ^° C. After dex separation of hydrolyzate and residue

with preheated ex fresh acid and uses the combined with the wash acid hydrolyzate after, if necessary, re-ethanol addition as hydrolysis reagent. The processing of a third and fourth batch are carried out analogously. Regardless of whether boiled with fresh acid or with hydrolyzate, the wood degradation is 29 - 30 % and the pentosan 70 τ 80%. The sugar concentration in the hydrolyzate increases, for example, from 2.6 % after fresh acid hydrolysis to 9.4% after three times use of hydrolyzate,

ETach the hydrolysis of the fourth batch is neutralized with calcium hydroxide in the presence of the hydrolysis residue to pH, partially decolorized by activated charcoal, squeezed off the solid and washed twice with water. The wash water is used for fresh acid production. After deionization with the ion exchangers KPS and AD 41 as well

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Concentration, the hydrolyzates are hydrogenated with the catalyst contact 6503 and the resulting polyole again cleaned and further concentrated. The xylitol isolated by crystallization and recrystallization is pure by gas chromatography and has a melting point of 92 - 93 ⁰ C.

Claims (5)

Claims 1.O method for obtaining sylose-containing solutions. Hemicellulose-containing raw materials such as hardwood or bark-containing deciduous wood residues, characterized in that the ammoniacally pretreated raw material is hydrolyzed with a highly diluted mineral acid in the form of fresh acid or hydrolyzate under normal pressure or moderately elevated pressure and the neutralization and partial decolorization of the hydrolyzate used several times in the presence of Hydrolysis residue took place "1: 5 to 1: 8 within a period of 2 - 5 h, usually 3 h, at 100 ° G or with 0.5 - 2.0% sulfuric acid at 110 - 130 ° G in 1 - 3 h performed becomes· 2. Method according to item 1, characterized in that the hydrolysis of the ammoniacally pretreated raw material in 2-5% (preferably 3%) sulfuric acid at a ratio of dry matter to liquid of 3. The method according to item 1 and 2, characterized in that the primary hydrolyzate is used several times as a hydrolysis reagent · 4 · ^{1 The} method according to pkt. 1 'to 3, characterized in that the squeezed after the hydrolysis residue to remove the sugar washed with Prischsäure and the squeezed washing acid is added to the hydrolyzate before reuse. 5. The method according to item 1 to 4, characterized in that the repeatedly used hydrolyzate is neutralized in the presence of Jeststoffanteile still contained Jeststoffanteile of the hydrolysis residue to pH 5.5 to 6.5 and then partially decolorized. Then all the pesticides are squeezed together ».