RU1838421C - Method of pentose sugar preparing - Google Patents

Abstract

Usage: hydrolysis and chemical industry. The essence of the method lies in the fact that the raw material is pre-wetted with 0.4-0.6% sulfuric acid while being treated with a current with an anode density of 0.05-0.09 A / cm2 for 40-60 minutes, extraction and washing of soluble impurities with water, followed by pentose hydrolysis of the purified raw materials, mainly corn cob, with a dilute solution of sulfuric acid in the presence of a current with an anode density of 0.09-0.1 A / cm2, at a hydrolysis temperature of 90-98 ° C, in for 45-100 min and inversion of the resulting hydrolyzate. 2 table.

Description

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FIELD: chemistry. SUBSTANCE: invention relates to hydrolysis, food and chemical industries, namely, to a method for hydrolysis of vegetable raw materials, in particular corn cob, for the production of xylose, xylitol and their derivatives.

The purpose of the invention is the acceleration of the process, improving the quality of the hydrolyzate and the yield of pentose sugars,

This goal is achieved by the fact that in the known method for producing pentose sugars, hydrolysis is carried out in an acidic medium (0.8-1% NAZOl) while being treated with current with an anode density of 0.09-0.1 A / cm2, at a hydrolysis temperature of 90-98 ° C for 45-100 minutes The anode is a titanium – manganese electrode, the cathode is a titanium electrode or any other electrodes insoluble in an acidic medium. The system is irregular. The total hydrolysis time with washing 60-110 minutes

After purification and pentose hydrolysis in the presence of current, the raw material does not swell, does not boil, which provides good filtration / ability of the raw material and quick washing.

The proposed method provides better diffusion of the catalyst into capillaries over the entire volume of the feed (direct diffusion) and the removal of Sugars from the thickness of the feed (reverse diffusion) due to the conductivity of the working solution (transfer of electric charges by N. OH ions from electrode to electrode). Hydrogen discharged from the cathode during the electrolysis of water and acid can be used for hydrogenation in the production of xylitol,

In contrast to the prototype, hydrolysates are characterized by the absence of furfural;

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significantly lower content of impurities - coloring, colloidal and ash substances, maximum content of pentose sugars (more than 98%), mainly xylose, which is the result of better purification of raw materials, milder conditions and acceleration of the hydrolysis process according to the proposed method .

A comparative characteristic of Sugars of pentose hydrolysates and parameters that give an objective to the claimed method are presented in Table. 1 and 2.

The method is illustrated by the following examples.

Etc. and measures 1. CO g of air-dried crushed corn stalk is placed in an electrolytic cell with a capacity of 1 liter, poured with 5 hydraulic modules of 0.4% sulfuric acid and extraction of harmful impurities by electrolysis at constant current with an anode density of 0.05 L / cm2 for 60 minutes The temperature during the process of electrolysis spontaneously increases from 20 to 80 ° C. After 60 minutes, the electrolysis of an aqueous solution of sulfuric acid, inside of which there is gravel, is stopped, the extract is taken away, the raw materials are washed with 5 hydraulic modules of water for 20 minutes.

The purified feed is poured with 3 hydraulic modules of a 1% solution of sulfuric acid; electrolysis is carried out in the same cell for 45 minutes at an anode current density of 0.1 L / cm2. During electrolysis, the temperature rises spontaneously to 98 ° G. After hydrolysis of hemicelluloses, the feed is washed with water for 15 minutes, the remaining cellolignin is sent to hexose hydrolysis or used for other purposes. The anode is a titanium-manganese electrode, the cathode is a titanium electrode. The total hydrolysis time with purification is 120 minutes, and the pentose with washing is GO min.

At the same time, furfural is absent in the pentose hydrolyzate; the yield of hemicelluloses to the feedstock is 27.8% of 33% (84%), i.e. almost all 1-fractions are easily hydrolyzable polysaccharides. The color compared to the prototype is 1.7 times lower, from 70 Stemmer units decreases to 42 Stsmmer units, the ash content remains at the prototype level due to the pre-treatment of raw materials in the presence of current.

Example 2. 60 g of air-dried crushed corn cobs are filled with 3 hydraulic modules of 0.6% sulfuric acid and the impurities are extracted by electrolysis as described in Example 1.

After purification, the feed is poured with 5 hydraulic modules of 0.8% sulfuric acid and electrolysis is carried out for 100 minutes at an anode current density of 0.09 A / cm. During electrolysis, the temperature rises spontaneously to 90-95 ° C.

After hydrolysis, the feed is washed with water for 10 minutes. The electrodes were used the same as in example 1. The time of pentose hydrolysis with washing was 110 min, which is 1.6 times shorter than the known one. Chromaticity is low and is 40 units of Stammer. The yield of hemicelluloses to the feedstock in pentose hydrolysates is

28.1%, no furfural.

Other examples confirming the boundaries of the parameters of the claimed method are presented in table. 1, where a lower yield of sucrose is noted,

Chromatographic analysis of pentose hydrolysates (examples 1 and 2) showed that they contain mainly xylose and arabinose (pentose sugars) with a slight admixture of hexose sugars (glucose, galactose) - 1.6%, which is more than 9 times less compared to the prototype,

Thus, hydrolysates obtained by the claimed method have advantages not only in purity (hydrolysates obtained at present in production, for example, have 170-220 Stammer units in color, 40 Stammer units in the proposed method),

but also in terms of the qualitative composition of the hydrolyzate (see table 1), which will minimize the costs of the final cleaning of hydrolysates after hydrolysis, obtaining xylose, xylitol and their derivatives, in contrast to the known methods, where a lot of time and dp reagents are spent bringing hydrolysates to condition, i.e. reduce the cost of the process.

Acquisition Form

A process for producing pentose sugars,

including wetting the raw material with 0.4-0.6% sulfuric acid while

 anodic density current treatment

0.05-0.09 A / cm2 for 40-GO min, washing with water, extraction of soluble impurities with water, pentose hydrolysis of the purified feed with a dilute sulfuric acid solution and washing of the feed with subsequent inversion of the hydrolyzate, characterized in that the pentose hydrolysis is carried out while current treatment with an anode density of 0.09-0.1 A / cm2 at a hydrolysis temperature of 90-98 ° C for 45-100 minutes

Composition and sugar content of pentose corn stalk hydrolyzate according to the claimed method and prototype

Parameters confirming the purpose of the claimed method

T a & l and ts a 1

table 2

Continuation of Table 2