RU2143437C1 - Method of preparing highly pure arabinogalactane - Google Patents

Abstract

FIELD: pulp and paper and wood-working industries. SUBSTANCE: described is method of preparing highly pure arabinogalactane by aqueous extraction of larch wood, concentration of extract and product is precipitated with aliphates alcohol, Lurch wood is treated with ethyl acetate, extracted with water at 80-90 C. Extract is concentrated, coagulant and flocculant are added, separated from precipitate, product is precipitated with ethyl alcohol from filtrate. EFFECT: highly pure arabinogalactane and use of hydroqiercitin production waste as stock. 2 cl

Description

 The invention relates to the pulp and paper and wood processing industries and for the production of larch (DL) from wood high purity arabinogalactan (AG). Arabinogalactan can also be used in the food and pharmaceutical industries (V. A. Babkin et al. Waste-free complex processing of biomass of Siberian and Daurian larch. Chemistry for sustainable development. 1997. N5. P. 105-115).

A known method of producing arabinogalactan from larch wood (Pat. RF N2002756 C 08 B 37/00, bull N 41-42, 1993) by extraction with water for 1 hour at a temperature of 95 ^o C, filtration and centrifugation from fine solids, turbulent treatment polyamide sorbent with subsequent filtration, concentration of the filtrate by ultrafiltration, isolation of the target product by spray drying.

The disadvantages of this method are
multi-stage process;
the use of a polyamide sorbent that does not have industrial production in the Russian Federation, the need for its regeneration;
the use of expensive equipment (ultracentrifuges).

Closest to the claimed is a method (US Pat. US N3509126 C1 260-209 5 C 08 B 1967), in which arabinogalactan is extracted from wood larch water extraction (module 1: 4) for 24 hours at 24 ^o C. Phenolic colored substances in the extract is oxidized for 1 hour with stirring with 0.5% chlorine dioxide, the excess of which is then removed by purging with nitrogen. The extract was partially evaporated at 60-70 ^° C and AG was reprecipitated in a five-fold volume of methyl alcohol at 60 ^° C. The precipitate was washed with a triple amount of methanol and dried at 65-70 ^° C.

This known method has several disadvantages:
the use and formation in the process of strong oxidizing agents (chlorine dioxide and hypochlorous acid), which requires the use of special acid-resistant equipment;
the use of methyl alcohol - a dangerous poison that requires special safety of the process, special storage conditions and a special mode of operation with it;
high consumption of methyl alcohol;
the duration of the process.

 Arabinogalactan is still not a product of industrial production. In connection with the development and implementation of the technology for the production of dihydroquercetin (DHQ), AG became a waste product and practically either goes into waste water or is thrown out with wood chips. The technology for producing AG developed by us can be combined with the technology for producing DHQ.

 The purpose of the invention is the production of high-purity arabinogalactan when using dihydroquercetin production waste as a raw material.

This goal is achieved by the fact that the DL extraction in the form of crushed technological chips is carried out with water (1: 3 module to the mass of absolutely dry raw materials) at a temperature of 80-90 ^o C in continuous circulation for 2 hours after removing the DCB with an organic solvent and drying the chips in sparing mode; the aqueous extract of AG is concentrated under reduced pressure, treated with stirring with aqueous solutions of the coagulant and flocculant, filtered and precipitated with stirring in a four-fold volume of ethyl alcohol, the supernatant is decanted, the precipitate of AG is washed with alcohol and dried. Aluminum sulfate was used as a coagulant, and “Sunfloc”, a high molecular weight polyacrylamide, as a flocculant.

The proposed method retains the advantages of the prototype and is characterized by the following advantages:
the extraction of crushed larch wood with water is carried out in an apparatus that provides continuous circulation of the extractant, which reduces its consumption (1: 3 instead of 1: 4 in the prototype);
AG extraction is carried out from already oil-free wood freed from the main extractive water-soluble phenolic component of dihydroquercetin, the content of which in the extract is only 0.01%;
water extraction of AG at elevated temperature allows to increase the degree of its extraction to 98-99%;
the use of methyl alcohol, a dangerous toxic substance that requires special storage conditions and operating rules, is excluded;
the use of strong oxidizing agents and, accordingly, the need for special equipment are excluded;
ecologically safe coagulants and flocculants used in wastewater treatment are used to remove colored substances;
precipitation with ethyl alcohol does not require an increase in the temperature of the precipitant;
ethyl alcohol can be regenerated from aqueous solutions in 80% yield.

 A quantitative analysis of the component composition of the AH extract obtained by the claimed method showed that it contains 14.3% AH (the solids content in the extract was 16.5%).

 To obtain the commercial preparation AH, the method of planting it in ethanol was chosen. However, the precipitate obtained from the crude extract is cream colored. It is known that the composition of aqueous extracts of AG includes concomitant colored substances, including phenolic in nature.

 To remove impurities, the extract was treated with our proposed coagulant and flocculant solutions used in industry. The purity of the drug was monitored by HPLC and spectroscopy for the absence of phenols and coloring substances, recording the absorption in the 280 and 450 nm regions.

 The following examples illustrate the invention.

Example 1. 200 g of crushed larch wood (humidity 31.2%), previously extracted with ethyl acetate and dried from solvent residues in vacuo, was filled with 350 ml of water and extracted in an apparatus with continuous circulation at a temperature of 90 ^o C for 2 hours.

 The hot aqueous solution was drained, filtered from solids and concentrated in vacuo on a rotary evaporator to reduce the volume by 3 times. Received 100 ml of an extract with a solids concentration of 16.5%. The extract was gradually poured into 400 ml of ethyl alcohol with stirring. The supernatant was drained from the precipitate formed, the precipitate was washed on the filter with ethyl alcohol, and dried under reduced pressure. The output of AG is 13.5 g (81.8% of dry matter). The content of phenolic impurities is 0.009%, the ash content is 2.3%. The resulting product has a cream color (has an absorption in the region of 450 nm).

Example 2. 200 g of crushed larch wood (humidity 31.2%), previously extracted with ethyl acetate and dried from solvent residues in vacuo, was filled with 350 ml of water and extracted in an apparatus with continuous circulation at a temperature of 90 ^o C for 2 hours.

 The hot aqueous solution was drained, filtered from solids and concentrated in vacuo on a rotary evaporator to reduce the volume by 3 times. Received 100 ml of an extract with a solids concentration of 16.5%.

 To 100 ml of the concentrated extract, 1 ml of a 10% aqueous solution of a coagulant and 1 ml of a 1% aqueous solution of a flocculant were added with stirring for 2 hours. The precipitate formed was filtered off, the filtrate was gradually poured into 400 ml of ethyl alcohol with stirring. The supernatant was drained from the precipitate formed, the precipitate was washed on the filter with ethyl alcohol, and dried under reduced pressure. The yield of AG was 13.6 g (82.4% of dry matter). Phenolic impurities and no ash. The product is white (no absorption at 450 nm).

 Example 3. The extraction was carried out in a pilot plant for the production of DHQ. 200 kg of larch wood crushed to wood chips (moisture content 39.3%), previously extracted with ethyl acetate in order to extract dihydroquercetin from it without unloading from the extractor, was dried from the remaining ethyl acetate.

Then 350 l of hot demineralized water, continuously circulating at a temperature of 80 ^° C, were fed into the extractor. Extraction was carried out for 2 hours. The hot aqueous extract was drained (300 L), filtered and evaporated to reduce the volume by 3 times. Received 100 l of concentrated extract with a solids content of 16.2%.

 To 1 l of extract was added 5 ml of a 10% aqueous solution of a coagulant and 10 ml of a 1% aqueous solution of a flocculant, kept for 2 hours. The precipitate formed was filtered off, the filtrate was gradually poured into 4 l of ethyl alcohol with stirring. The supernatant was drained from the precipitate formed, the precipitate was washed on the filter with ethyl alcohol, and dried under reduced pressure. The AG yield was 80.5% of dry matter, there were no phenolic impurities, and no ash content.

Example 4. In the conditions of example 3, the chips were extracted with 350 l of hot demineralized water, continuously circulating at a temperature of 80 ^o C. The extraction was carried out for 2 hours. The hot aqueous extract was drained (300 L), filtered and evaporated to reduce the volume by 3 times. Received 100 l of condensed extract with a solids concentration of 16.3%.

 To 10 l of AG extract was added 100 ml of a 10% aqueous coagulant solution and 130 ml of a 1% aqueous flocculant solution, kept for 2 hours. The precipitate formed was filtered off, the filtrate was gradually poured into 40 l of ethanol with stirring. The supernatant was drained from the precipitate formed, the precipitate was washed on the filter with ethyl alcohol, and dried under reduced pressure. The output of hypertension was 81.2% of dry matter. There are no phenolic impurities, no ash content, no absorption at 450 nm.

 The method of producing AH is combined with the method of producing DHQ and does not require additional equipment; the claimed method is tested on a pilot semi-industrial installation with a capacity of AG 160 kg per month; The claimed method allows to obtain high purity AG.

Claims (2)

1. The method of obtaining high-purity arabinogalactan by water extraction of larch wood, concentrating the extract and planting the product with aliphatic alcohol, characterized in that the larch wood is treated with ethyl acetate, dried, extracted with water at a temperature of 80 - 90 ^o C, the extract is concentrated, coagulant and flocculant are added, separated from the precipitate, the product is precipitated from the filtrate with ethyl alcohol.  2. The method according to claim 1, characterized in that as a coagulant use aluminum sulfate, and as a flocculant "Sunfloc", which is a high molecular weight polyacrylamide.