RU2740098C1 - Method for hydrolysis of hemicelluloses of plant materials for producing xylose solutions - Google Patents

Abstract

FIELD: chemistry; food industry.

SUBSTANCE: invention relates to chemical and food industries, specifically to production of xylitol solutions for xylitol production. Method of hydrolyzed birchwood hemicelluloses for producing xylose solutions for xylitol production involves hydrolysis with sulfuric acid with concentration of 0.15-0.5% at ratio of raw material - ground birch wood : brewing solution 1:(2-5), temperature 160-180°C for 20-60 minutes with subsequent extraction of water-soluble mono- and oligosaccharides and acid with water, evaporation of the extract to concentration of sugars - 25-30% and acid - 0.5-1.5% with simultaneous inversion of oligosaccharides during evaporation. After that, the obtained concentrate is neutralized with lime, filtration and deionization of the solution. Preferably, the extract is evaporated on three or more stepped evaporator plants, where at the last steps, for complete inversion of the oligosaccharides, evaporation is carried out for 2-4 hours at temperature of 100-120°C depending on concentration of acid in the extract.

EFFECT: invention simplifies the process of xylose hydrolyzates purification and reduces consumption of reagents and energy resources for its implementation.

1 cl, 4 ex

Description

The invention relates to the chemical and food industries, namely to the production of xylose solutions suitable for hydrogenation into xylitol.

A known method of processing plant raw materials to obtain pentose hydrolysates containing mainly xylose to obtain xylitol (RF patent 2109059) where as xylose-containing raw materials used brewer's grains, which is a waste of brewing production. According to this method, high-temperature washing of spent grains is carried out, in which the solid phase is mixed with water in a ratio of 1: 3-5, kept with periodic stirring for 10-30 minutes at 140-160 ° C, followed by separation of the solid phase. The washed mass is then subjected to hemicellulose hydrolysis of 0.5-2.5% sulfuric acid for 2-4 hours at 100-120 ° C.

The total sugar content in the hydrolyzate is 4.8%, while of the total sugar concentration, the amount of xylose is 71.0%, arabinose 17.0%, galactose 10.0% and glucose 2.0%. The good quality of the hydrolyzate is 80.0%.

The closest method for the hydrolysis of hemicelluloses of plant raw materials to obtain xylose solutions for the subsequent production of xylitol is described in the monograph by Yu.I. Kholkina "Technology of hydrolysis production" M, "Timber industry" 1988. Methods for producing xylitol include: refining of crushed plant raw materials with a dilute solution of sulfuric acid at a temperature of 100-120 ° C with a collection of 3-4 GM acid extract; hydrolysis of raw materials using 0.5-2.5% sulfuric acid at 120-140 ° C for 2-4 hours or acid-free hydrolysis at 180 ° C for 6 hours; inversion of the hydrolyzate at 100 ° C for 4-6 hours; acid neutralization with lime to pH4-6; filtration of the neutralizer using coagulants; discoloration of the neutralizer with activated carbon; evaporation of the purified neutralizer to a concentration of 65% sugars.

The developed processes for the production of xylose solutions have a number of significant disadvantages, in particular:

- to carry out acid and acid-free hydrolysis requires a large consumption of thermal energy and capital-intensive equipment in an acid-resistant design;

- in parallel with the hydrolysis of polysaccharides, partial dissolution of lignin and decomposition of sugars occur, which reduces the yield of xylose and contributes to the production of hydrolysates with low quality (about 70%).

- hemicellulose xylose hydrolysates have a low concentration of sugars (less than 5%), high color, which requires significant costs for evaporation and purification of xylose from impurities;

- in the process of hydrolysis, a large amount of solid and liquid waste containing toxic impurities of the decomposition of sugars (furfural, oxymethylfurfural) is formed, the disposal of which requires additional costs.

To eliminate these disadvantages, a new method of hydrolysis of hemicelluloses of plant raw materials to obtain hydrolysates containing xylose for xylitol production is proposed.

The technical result consists in carrying out the hydrolysis of hemicelluloses of plant raw materials with ultra-low concentrations of sulfuric acid in continuous conditions; extraction of the obtained mono- and oligosaccharides with water; subsequent evaporation of the acidic hydrolyzate with simultaneous inversion of the oligosaccharides; simplifying the process of purification of xylose hydrolysates and reducing the consumption of reagents and energy resources for its implementation.

The problem is solved, and the technical result is achieved by the fact that for hydrolysis, birch wood is treated in a reactor with sulfuric acid with a concentration of 0.15-0.5% at a ratio of raw materials: cooking solution 1: (2-5), temperature 160-180 ° C, pressure 6-9 bar for 20-60 minutes Obtained during the hydrolysis of hemicelluloses, mono- and oligosaccharides are extracted with water from the hydrolyzate mass. The extract is evaporated to a sugar concentration of 20-25% and an acid concentration of 0.5-1.5%, carrying out the inversion of oligosaccharides simultaneously with evaporation.

Preferably, the evaporation of the extract is carried out in three or more staged evaporation plants, where in the last stages of evaporation, for complete inversion of oligosaccharides, evaporation is carried out for 2-4 hours at a temperature of 100-120 ° C, depending on the concentration of acid in the extract.

Further processing of the concentrate is carried out according to known methods and includes the neutralization of sulfuric acid with lime, decolorization with activated carbon, filtration and deionization of the solution. [Kholkin Yu.I. Modern technology of xylitol ONTITVI Microbioprom, M., 1988, - 56 p.]

This method provides a high yield of sugars with a xylose content of up to 80%. The method allows to reduce the cost of material and energy resources, can be carried out on compact high-performance equipment with low labor costs. The consumption of sulfuric acid by the proposed method is reduced from 300 to 106 kg / t, and lime from 250 to 75 kg / t of xylose.

The use of ultra-low concentrations of sulfuric acid for the hydrolysis of hemicelluloses of plant raw materials is unknown. Thus, the invention meets the “inventive step” condition of protection.

The invention is illustrated by examples.

Example 1. Birch chips and sawdust are continuously fed into a hydrolysis apparatus with a simultaneous supply of sulfuric acid with a concentration of 0.15%, a temperature of 180 ° C and a pressure of more than 9 atm, with a wood: cooking solution ratio of 1: 5. The feed rate of the raw material and the cooking solution is selected from the condition of the residence time of the mass in the apparatus of 60 minutes. Under these conditions, birch hemicelluloses are completely hydrolyzed. The hydrolyzate mass is cooled and continuously discharged from the apparatus, the mass is fed into a countercurrent extractor to isolate the formed mono- and oligosaccharides and acid. The extract with a sugar concentration of 5-8% is evaporated to a solids concentration of 30% and an acid of 1.0%. The extract is evaporated at the last stages of evaporation at a temperature of 120 ° C for 2 hours. In the process of evaporation, the oligosaccharides are inverted to monosaccharides. The inverted concentrate is neutralized with lime to pH 3.5-4.5, filtered and purified from salts on ion-exchange filters. Acid consumption is 33 kg / t of xylitol, xylose yield is 23% of d.w.

Example 2. Birch chips and sawdust are continuously fed into a hydrolysis apparatus with a simultaneous supply of sulfuric acid with a concentration of 0.5%, a temperature of 160 ° C and a pressure of more than 6 atm, with a wood: cooking solution ratio of 1: 2. The feed rate of the raw material and the cooking solution is selected from the condition of the residence time of the mass in the apparatus of 60 minutes. Under these conditions, birch hemicellulose is completely hydrolyzed. The hydrolyzate mass is cooled, continuously unloaded from the apparatus and fed into a countercurrent extractor to isolate the formed mono- and oligosaccharides and acid. The extract with a sugar concentration of 5-8% is evaporated to a solids concentration of 25% and an acid of 1.0%. Evaporation of the extract in the last stages of evaporation is carried out at a temperature of 100 ° C for 4 hours. In the process of evaporation, the oligosaccharides are inverted to monosaccharides. The inverted concentrate is neutralized with lime to pH 3.5-4.5, filtered and purified from salts on ion-exchange filters. Acid consumption is 25 kg / t of xylitol, xylose yield is 23.5% of d.w.

Example 3. Birch chips and sawdust are continuously fed into a hydrolysis apparatus with a simultaneous supply of sulfuric acid with a concentration of 0.5%, a temperature of 180 ° C and a pressure of more than 9 atm, with a wood: cooking solution ratio of 1: 5. The feed rate of the raw material and the cooking solution is selected on the basis of the residence time of the mass in the apparatus of 20 minutes. Under these conditions, birch hemicellulose is completely hydrolyzed. The hydrolyzate mass is cooled, continuously unloaded from the apparatus, and fed into a countercurrent extractor to isolate the formed mono- and oligosaccharides and acid. The extract with a sugar concentration of 5-8%) is evaporated to a dry matter concentration of 25% and an acid of 1.5%. Evaporation of the extract at the last stages of evaporation is carried out at a temperature of 100 ° C for 2 hours. In the process of evaporation, the oligosaccharides are inverted to monosaccharides. The inverted concentrate is neutralized with lime to pH 3.5-4.5, filtered and purified from salts on ion-exchange filters. Acid consumption is 40 kg / t of xylitol, xylose yield is 24.5% of d.w.

Example 4. Birch chips and sawdust are continuously fed into a hydrolysis apparatus with a simultaneous supply of sulfuric acid with a concentration of 0.15%, a temperature of 180 ° C and a pressure of more than 9 atm, with a wood: cooking solution ratio of 1: 2. The feed rate of the raw material and the cooking solution is selected from the condition of the residence time of the mass in the apparatus of 60 minutes. Under these conditions, birch hemicellulose is completely hydrolyzed. The hydrolyzate mass is cooled, continuously unloaded from the apparatus, and fed into a countercurrent extractor to isolate the formed mono- and oligosaccharides and acid. The extract with a sugar concentration of 5-8% is evaporated to a dry matter concentration of 25% and an acid concentration of 0.5%. Evaporation of the extract at the last stages of evaporation is carried out at a temperature of 120 ° C for 4 hours. In the process of evaporation, the oligosaccharides are inverted to monosaccharides. The inverted concentrate is neutralized with lime to pH 3.5, filtered and purified from salts on ion-exchange filters. Acid consumption is 15 kg / t of xylitol, xylose yield is 22.5% of d.w.

Claims (2)

1. A method of hydrolysis of hemicelluloses of birch wood to obtain xylose solutions for the production of xylitol, characterized in that the hydrolysis is carried out with sulfuric acid with a concentration of 0.15-0.5% at a ratio of raw material - crushed birch wood: cooking solution 1: (2-5) , a temperature of 160-180 ° C for 20-60 minutes, followed by the extraction of water-soluble mono- and oligosaccharides and acid with water, evaporation of the extract to a sugar concentration of 25-30% and an acid of 0.5-1.5% with simultaneous inversion of oligosaccharides into the process of evaporation, subsequent neutralization of the resulting concentrate with lime, filtration and deionization of the solution. 2. The method according to claim 1, characterized in that the evaporation of the extract is carried out in three or more staged evaporation plants, where in the last stages of evaporation, for complete inversion of oligosaccharides, evaporation is carried out for 2-4 hours at a temperature of 100-120 ° C in depending on the concentration of acid in the extract.