RU2618892C1 - Method for complex processing of birch bark - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of birch bark processing includes milling the cortex and its division into the phloem and bark; processing bark alcohol-aqueous alkaline solution; separation of the solid residue; distilled off from the filtrate ethanol; betulin fallen branch; suberin deposition of hydrochloric acid in the cold; separating precipitated suberin, followed by drying under vacuum; processing bast alcohol-aqueous alkaline solution; separation of the solid residue; distilled water-alcohol solution from the filtrate until a dry residue - polyphenols; polyphenols dissolve in water; addition of formaldehyde solution to form a gel; gel space into ethanol to replace the water in the alcohol phase; drying at room temperature and pressure to form a finished product - an organic airgel; combining the solid remains of bast and birch bark; neutralization and washing with subsequent drying of the finished product - enterosorbent.

EFFECT: process is environmentally friendly, cost-effective to produce a valuable chemical products - betulin, suberin, organic aerogels enterosorbents.

1 dwg, 1 ex

Description

The invention relates to the chemical processing of wood waste, in particular to the integrated processing of birch bark into valuable chemical products for the pharmaceutical, medical and wood chemical industries, as well as for woodworking enterprises.

Birch bark is a large-tonnage waste of plywood and pulp and paper enterprises, consisting of two components: the outer layer - birch bark and the inner layer - bast. The main valuable chemical components of birch bark are triterpene dihydric alcohol - betulin, suberin - a polyester of irregular structure, as well as polyphenols and lignin. The bast in its composition contains easily and hardly hydrolyzable polysaccharides, lignin, polyphenols, tannins and a number of other compounds. Therefore, the integrated processing of birch bark with the allocation of valuable chemical products and the receipt on their basis of value-added products is relevant.

A known method of producing betulin from birch bark [RU 2340624 from 10.12.2008], including alkaline hydrolysis with an aqueous solution of sodium hydroxide with a concentration of 15-25% wt. at a temperature of 100 ° C, a hydromodule 5-6 for 1-2 hours, followed by extraction of betulin with ethyl alcohol. Next, the solution is filtered, the solid residue is separated, the alcohol is distilled off from the solution, and the remaining solution is diluted with water, and betulin precipitates, which is filtered off, washed on the filter with hot water and dried.

The disadvantage of this method is the use of highly concentrated alkali, as well as the inability to isolate other valuable chemical products.

A known method of producing betulin and suberin from birch bark, described in the patent [RU 2119503 from 09/27/1998]. The bark freed from the bast, after activation under conditions of explosive hydrolysis at a pressure of 3-5 MPa, a temperature of 180-260 ° C and a duration of 60-360 s, is subjected to hydrolysis in an aqueous alkaline medium at boiling for 20 minutes. Then the mixture was cooled to 70 ° C, ethanol was added to the reaction mixture and boiled for another 5 minutes. The hot solution is filtered, the alcohol is distilled off, the residue is diluted with water and betulin is separated by filtration. The remaining aqueous solution is acidified with sulfuric acid to pH 4-5, suberin is filtered off and washed with cold water.

The disadvantage of this method lies in the complex activation process, requiring expensive equipment, as well as in the low quality of the resulting betulin, which is contaminated with derivatives of alcohols, polyphenols, acids, including suberinic. This disadvantage is caused by activation under conditions of explosive hydrolysis, as a result of which a difficultly separable homogeneous mixture is formed.

A known method, including the extraction of betulin from birch bark with carbon dioxide under supercritical conditions, followed by hydrolysis with water-alcohol solutions of inorganic bases and extraction of suberinic acids, acidification of the filtrate to pH 4.7 with a solution containing 6% wt. hydrochloric acid [US 6392070, publ. 08/14/2003].

The disadvantages of the method are the complexity of the equipment for supercritical CO ₂ extraction at high pressure, the low content of betulin in concentrates of CO ₂ extracts, as well as the large loss of alcohol solutions at the stage of extraction of suberin substances.

A known method of obtaining enterosorbent from the bast of birch bark [RU 2311954 from 12/10/2007], including grinding the bast, sequential extraction with a number of solvents: hexane, ethyl acetate, isopropanol and water, processing of 0.5-2.0% wt. a solution of sodium hydroxide at a temperature of 60-100 ° C, hydromodule 7 for 0.5-1 hours, the neutralization of 10% wt. acetic acid solution, washing with water, thickening and drying.

A similar method of obtaining enterosorbent from birch bark [RU 2389498 from 05.20.2010] includes crushing the bark, processing it 0.5-2.0% wt. sodium hydroxide solution under the same conditions, but without prior extraction with toxic solvents.

However, the method is intended to obtain only one product from the birch bark - enterosorbent, as a result, many valuable substances are found in the waste.

A known method of processing wood bark [US 2009/0077871 dated 03/26/2009], including crushing the bark, extraction with low molecular weight aliphatic alcohols, distilling off alcohol, separating solid and liquid phases, washing and drying both phases, using a liquid phase containing polyphenols of various molecular weights, for the preparation of thermosetting resins (organic aerogels) using aldehydes and / or isocyanates as crosslinking agents.

The disadvantages of this method is the low yield of the polyphenolic fraction and the low range of products.

A known method of processing birch bark [RU 2352350 from 04/20/2009], including grinding the birch bark without separation into bark and bast, extraction with a non-polar solvent, processing the obtained extract 20-25% wt. aqueous alkali with the release of betulin. Subsequent hydrolysis of the extracted bark is carried out with a water-alcohol-alkaline solution to obtain a tannic extract. The remainder of the bark after receiving the tannic extract is subjected to carbonization with the release of a carbon sorbent.

The disadvantages of this method include extraction with a non-polar solvent, which reduces the environmental safety of the method, since the solvent is toxic and requires additional costs for regeneration and disposal.

Closest to the technological essence of the present invention is a method of processing birch bark [RU 2305550 from 09/10/2007], including sequential grinding of the bark, its separation into birch bark and bast, solvent extraction of birch bark in the form of an azeotropic mixture of tetrachlorethylene-water for 0.5- 1.4 hours at a temperature of 89-115 ° C, pressure 0.1-1.0 MPa, separation of the solution from the meal at a temperature of 80-100 ° C, keeping the filtrate in the mold for 1-5 hours at a temperature of -5 ° C to + 25 ° C, separation of precipitated crystals from the mother liquor ora by filtration, washing the crystals with distilled water or a 20% aqueous solution of ethyl alcohol, followed by drying the resulting product - a mixture of three-five-triterpenic compounds, evaporating the mother liquor to obtain a dry residue, washing it with distilled water, followed by drying of the obtained product - a mixture of five-seventeen-triterpene compounds; removing solvent from the meal by evaporation, mixing the meal with dry sodium hydroxide and isopropyl alcohol, boiling the resulting mixture for 0.5-5.0 hours, separating the solid precipitate from the solution at a temperature of 40-80 ° C, washing the precipitate with distilled water, followed by drying the obtained product - lignin (amorphous powder, tan or brown); acidification of the filtrate with acetic, carbonic or hydrochloric acid to a pH of 4.5-5.5, holding it at a temperature of -5 - (+ 25) ° C for 0.5-15 hours, separating the precipitated precipitate from the solution, washing the precipitate with distilled water and drying the finished product - birch wax; additional grinding of the bast to particles with a size of 0.1-5.0 mm, mixing 1 kg of bast with water in an amount of 7-10 liters, keeping the mixture at a temperature of 15-40 ° C for 1-10 days, separating the precipitate from the obtained product - birch kvass; drying the sediment, which is a feed additive for farm animals and birds.

The disadvantages of the method include the complexity and duration of the separation processes and the insufficient assortment of valuable chemical products. So, during the processing of birch bark a mixture of triterpene compounds, the main of which is betulin, is obtained in two stages and with a low yield.

The present invention is the creation of a new environmentally friendly and economical method of processing birch bark with an expanded assortment of valuable chemical products.

The technical result of the invention is an environmentally friendly and economical method for the integrated processing of birch bark to produce valuable chemical products - betulin, suberin, polyphenols and value-added products based on them - enterosorbents, organic aerogels and binders.

The technical result of the invention is achieved by the fact that in the method of complex processing of birch bark, including crushing the bark, separating it into bark and bast, hydrolysis of the raw material with alkali and alcohol by heating and stirring, separating the solution from the solid residue by filtration, sedimentation of suberin from the filtrate by acidification with hydrochloric acid solution to pH 4.5-5.0 with exposure at a temperature of 0 - (+ 2) ° C for 12 hours, separation of the mixture into a solution and a solid residue, separation of the precipitated precipitate by filtration, washing with water, followed by by drying the finished product — suberin, treating the bast with a solution, separating the solution from the solid residue by filtration, washing the solid residue with water, followed by drying the target product, according to the invention, hydrolysis of birch bark is carried out together with extraction in an aqueous solution containing 3% wt. alkali and 80% wt. ethyl alcohol at a temperature of 95 ° C for 80 min, precipitated betulin is filtered off, washed and dried at 105 ° C to constant weight; precipitation of suberin from the filtrate is carried out at a temperature of 0 - (+ 2) ° C by acidification with a 1M hydrochloric acid solution and the resulting suberin is dried under vacuum; the forehead is treated with an aqueous alkaline solution containing 0.2% wt. alkali and 20% wt. ethyl alcohol, at a temperature of 90-95 ° C for 90 minutes, the hot mixture is separated by filtration, the water-alcohol mixture is distilled off with the precipitation of polyphenols, then the polyphenols are dissolved in water with hydromodule 4, 40% wt. an aqueous solution of formaldehyde and kept at a temperature of 85 ° C for 5 days, the resulting gel is placed in ethyl alcohol and kept for 3 days to replace water with the alcohol phase; dried for 7 days at room temperature to obtain an organic airgel; enterosorbents are obtained by combining solid residues of bast and birch bark with subsequent neutralization of 2% wt. acetic acid solution, washing with distilled water and drying until air-dry.

A comparative analysis of the features of the prototype and the claimed invention shows that the common features are:

- raw materials - birch bark;

- separation of bark into bark and forehead;

- alkaline hydrolysis of raw materials;

- acidification of the filtrate with hydrochloric acid to a pH of 4.5-5.0 with an exposure of 12 hours at a temperature of 0 - (+ 2) ° C;

- separation of the mixture into a solution and a solid residue, which is washed with water and dried to obtain suberin - (in the prototype birch wax);

- processing of bast to obtain a solid residue.

Distinctive features of the claimed invention from the prototype:

- in the claimed invention, birch bark is hydrolyzed with an aqueous solution containing 3% wt. alkali and 80% wt. ethyl alcohol, the mixture is separated into a solid residue and the solution from which betulin is precipitated, in the prototype, birch bark is pre-extracted with a solvent - an azeotropic mixture of tetrachlorethylene-water containing chlorine, then it is separated into a solid residue (meal) and the solution from which a mixture of triterpene compounds is isolated , the main of which is betulin;

- in the claimed invention, after separation of betulin, a 1M hydrochloric acid solution is poured into the filtrate at a temperature of 0 - (+ 2) ° C, then it is placed in a refrigerator and kept for 12 hours to enlarge the particles of precipitated suberin, which, after separation and washing, are dried under vacuum. In the prototype, suberin is isolated from the solid residue of birch bark (meal) obtained by separation of the mixture after extraction of betulin, which is mixed with water before hydrolysis and the water is evaporated with a solvent, then hydrolyzed by mixing meal with dry sodium hydroxide and isopropyl alcohol, while boiling for 0, 5-5.0 hours, the solid precipitate is separated from the solution at a temperature of 40-80 ° C, and then the solution is acidified with hydrochloric acid to a pH of 4.5-5.5, kept at a temperature of -5 - (+ 25) ° C in within 0.5-15 hours, the precipitate formed is separated from the solution, the dis tilled water and dried - birch wax (in the claimed invention - suberin);

- in the claimed invention, in contrast to the prototype, polyphenols are isolated by treating the bast with an aqueous solution containing 0.2% wt. alkali and 20% wt. ethyl alcohol, the resulting polyphenols are dissolved in water, add 40% wt. an aqueous solution of formaldehyde is kept at a temperature of 85 ° C for 5 days, the resulting gel is placed in ethyl alcohol and kept for 3 days to replace water with the alcohol phase, dried for 7 days at room temperature to obtain porous products - organic airgels;

- in the claimed invention, in contrast to the prototype, the solid residues of bast and birch bark are combined to obtain enterosorbents, processing them with 2% wt. acetic acid solution to neutralize the alkali, then they are washed with distilled water and dried at room temperature until air-dry.

The invention is illustrated in the drawing, which shows a diagram of the process of complex processing of birch bark.

The invention allows complex processing of birch bark to produce betulin, suberin, organic airgels and enterosorbents.

The method of complex processing of birch bark into chemical products is confirmed by a specific example.

Example. In a glass flask with a volume of 1000 ml, 20 g of air-dried birch birch, fractional composition of 0.5-2.5 mm, are loaded, 300 ml of a solution containing 3% wt. alkali and 80% wt. ethyl alcohol. The birch bark hydrolysis is carried out by continuously mixing the reaction mixture at a temperature of 95 ° C for 80 minutes. The solid residue of birch bark is filtered off, and alcohol is distilled off from the filtrate (up to 95% by weight). The precipitated powder is white or light beige - Betulin is filtered off, washed and dried at 105 ° C to constant weight. Betulin yield - 4.5 g.

A 1 M hydrochloric acid solution is poured into the filtrate at a temperature of 0 - (+2) ° C to a pH of 4.5-5.0, then placed in a refrigerator and incubated for 12 hours to enlarge the particles of precipitated suberin. The precipitate is separated from the solution by filtration, washed on the filter with distilled water until the washings are neutral (pH 6-7). Suberin is dried under vacuum to constant weight. The yield of suberin is 6.2 g.

The binding properties of suberin are evaluated by determining the strength characteristics of the fuel briquettes obtained by pressing. Fuel briquettes obtained using suberin as a binder had a compressive strength of 37-38 MPa and water absorption of 12-13% wt.

In a glass three-necked flask with a volume of 500 ml, equipped with a stirrer, thermometer and reflux condenser, load 25 g of air-dry bast, fractional composition 1.0-1.5 mm, pour 200 ml of 0.2% wt. a solution of sodium hydroxide and 63 ml of ethyl alcohol (20% wt. in solution). The reaction flask is placed in a thermostat, maintaining a constant temperature of 90-95 ° C. The extraction is carried out for 90 minutes The hot reaction mixture is then filtered to separate unreacted bast. From the aqueous-alcohol-alkaline extract obtained after hot filtration, the solvent is removed by distilling off the aqueous-alcohol mixture on a rotary evaporator until polyphenols precipitate in the form of a brown powder.

2.5 g of bast polyphenol powder is dissolved in 100 g of water with constant stirring. To the resulting solution was added 5 g of a 40% aqueous formaldehyde solution. The resulting solution has a pH of ~ 11. Hermetically sealed solutions are kept at a temperature of 85 ° C for 5 days. The resulting gels are removed from the tubes, cut and placed in ethyl alcohol to replace water with the alcohol phase and remove possible by-products from the pores of the hydrogels. Ethyl alcohol is replaced daily for 3 days. Then the gels are dried at room temperature and pressure for 7 days with the formation of organic airgels. The yield of aerogels is 2.3 g with a total porosity of 70-80% and a pore volume of up to 2 cm ³ / g.

The solid residues of birch bark and bast, after treatment with water-alcohol-alkaline solutions, are combined, neutralize 2% wt. a solution of acetic acid with a hydromodule 5 for 30 min and a temperature of 20 ° C to obtain enterosorbent. The enterosorbent is dried to an air-dry state at 50 ° C and ground to a particle size of less than 250 microns. The obtained enterosorbent, a powder of light brown color, has a sorption activity for methylene blue of 58.9 mg / g and gelatin of 36.4 mg / g. The residual content of water-soluble substances in the enterosorbent is 3.8% of the mass. Enterosorbent yield - 29 g.

Thus, the claimed method provides an environmentally friendly and economical method for complex processing of birch bark to produce valuable chemical products - betulin, suberin, polyphenols and value-added products based on them - enterosorbents, organic airgels and binders. When processing 1 ton of birch bark (20% of the mass. - birch bark, 80% of the mass. - bast) by the proposed method receive: betulin 45-48 kg; suberin binder 62-65 kg; organic airgels 120-125 kg; enterosorbent 520-530 kg.

Claims (1)

The method of complex processing of birch bark, including crushing the bark, separating it into bark and bast, hydrolysis of the raw material with alkali and alcohol with heating and stirring, separating the solution from the solid residue by filtration, sedimentation of suberin from the filtrate by acidification with hydrochloric acid to pH 4.5-5, 0 with exposure at a temperature of 0 - (+ 2) ° C for 12 hours, separating the precipitate by filtration, washing it with water, followed by drying, treating the bast with a solution, separating the solution from the solid residue by filtration, washing with TV a residue with water, followed by drying of the target product, characterized in that the birch bark hydrolysis is carried out together with extraction in an aqueous solution containing 3 wt.% alkali and 80 wt.% ethyl alcohol, at a temperature of 95 ° C for 80 min, precipitated betulin is filtered off, washed and dried at 105 ° C to constant weight; precipitation of suberin from the filtrate is carried out at a temperature of 0 - (+ 2) ° C by acidification with a 1M hydrochloric acid solution and drying the resulting suberin under vacuum; the forehead is treated with an alcohol-water-alkaline solution containing 0.2 wt.% alkali and 20 wt.% ethyl alcohol, at a temperature of 90-95 ° C for 90 minutes, the hot mixture is filtered, the water-alcohol mixture is distilled off from the filtrate with precipitation polyphenols, which are dissolved in water with a hydromodule 4, add 40% wt. an aqueous solution of formaldehyde and kept at a temperature of 85 ° C for 5 days, the resulting gel was placed in ethyl alcohol and kept for 3 days to replace water with the alcohol phase, dried for 7 days at room temperature to obtain organic airgels; enterosorbents are obtained by combining solid residues of bast and birch bark, followed by neutralization with a 2 wt.% acetic acid solution, washing with distilled water and drying to an air-dry state.

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