RU2665576C1 - Method of sulphation organosolvent lignin - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to chemical technology and is intended for preparation of water-soluble ammonium or sodium salts of lignin sulphate esters, which can be used as chemical additives to regulate the properties of washing liquids when drilling oil and gas wells, and in the pharmaceutical industry as potential antiviral drugs. Method of sulphation of organosolvent lignins is carried out by the interaction of lignins with the sulfating complex sulfamic acid – urea in the presence of a solvent of N,N-dimethylformamide with stirring and a temperature of 100 °C for 0.5–6.0 hours at a ratio of the amount of lignin to the sulfating complex of 1:3 (pmol). Product is isolated by neutralization and decantation of the solvent, then purified from low molecular weight impurities by dialysis.EFFECT: yield of sulfated lignin is increased, the range of solvents for sulphating lignins in a homogeneous medium is extended.1 cl, 1 tbl, 7 ex

Description

The invention relates to the field of chemical technology and is intended to produce water-soluble ammonium or sodium salts of lignin sulfate esters, which can be used as chemical additives to control the properties of flushing liquids when drilling oil and gas wells, and in the pharmaceutical industry as potential antiviral drugs.

A known method of sulfation of lignin - one of the main components of ligno-carbohydrate materials [B.C. Lisova, V.M. Reznikov. About the nature of sulfur in dioxanlignin sulfonation products by "neutral" pyridine sulfotrioxide. Chemistry of wood, 1980, No. 2, p. 64-67], which consists in processing the original lignin-containing raw materials, for example, hydrolytic lignin, sulfuric anhydride or its complex with pyridine, both in the solid phase and in organic solvents. The reaction is carried out in an ampoule containing dioxanlignin and pyridine sulfotrioxide at a temperature of 136-138 ° C for 3-3.5 hours, resulting in products with a sulfur content of 3.75% (mass).

The method is technologically complex, requires the use of autoclave equipment, as well as highly toxic reagents: pyridine, which has a persistent unpleasant odor and sulfuric anhydride, which has high corrosiveness. Also, the process of obtaining pyridine sulfotrioxide from pyridine and sulfur trioxide is accompanied by the release of a large amount of heat, and therefore, intensive cooling is necessary to maintain the required reaction temperature. In addition, the sulfation reaction is carried out at a high temperature, which can lead to condensed products that are insoluble in water.

Another known method is that the ligno-carbohydrate material composed of cellulose, lignin and hemicelluloses is ground at a vibratory mill without separation into components, and sodium fluorosulfonate in isopropyl alcohol is used as a sulfating agent [RU 2268271, publ. January 20, 2006]. The method consists in the fact that the material is activated with sodium hydroxide for 1 h at a temperature of 70 ° C, then treated with sodium fluorosulfonate in isopropyl alcohol at a temperature of 50-90 ° C for 3-15 hours

The disadvantages of the method include the need for preliminary activation of the raw materials, the use of inaccessible sulfating reagent sodium fluorosulfonate, as well as the treatment of toxic methanol in the process of purification of the product from inorganic impurities. In addition, the resulting sulfated ligno-carbohydrate material has limited solubility in water.

A known method of sulfating a suspension of lignin with complexes of sulfur trioxide with various organic amines (pyridine, trimethylamine, trimethyleneamine) in an aqueous solution at a pH of 11.0-11.8. Sulfation of a lignin suspension is carried out under conditions in which an ionized phenolic hydroxyl group is exposed [US 5013825, publ. 05/07/1991], while in the above methods, alcohol hydroxyl is sulfated due to its greater nucleophilicity. The reaction time is about 60 minutes, and the optimum reaction temperature of the lignin sulfation reaction depends on the type of complex involved in the reaction. So when using the pyridine-sulfur trioxide complex, the optimal result was obtained at 25 ° C, while the use of the trimethylamine-sulfur trioxide complex gave optimal results at 90-100 ° C. The optimum temperature for the reaction of the triethylamine-sulfur trioxide complex is about 60 ° C. It was found that the degree of sulfation increases with increasing concentration of lignin in an aqueous solution. In the described method, the degree of sulfation of the products is described by an acid point, i.e. the number of grams of a 50% aqueous solution of sulfuric acid added to a 0.5% aqueous solution of a sulfated product, taken in an amount of 35 milliliters, before precipitation. The higher the acid point, the greater the degree of sulfation and solubility in water.

One of the main disadvantages of this method, as well as the methods described above, is the use of toxic amines and aggressive sulfur trioxide. In addition, products with a high degree of sulfation can be obtained only by using lignins that are sufficiently soluble in an aqueous solution of alkali, which limits the use of this method of sulfation, and from the description of the patent it is not entirely clear what is the degree of dissolution of sulfated lignins in water. Finally, the absence of free phenolic hydroxyl groups in sulfated products does not allow their use in polycondensation reactions when it is necessary to have preparations with a high molecular weight.

A known method of sulfation of organosolvent lignin by a complex of sulfur trioxide and triethylamine in dimethylacetamide at 65 ° C for 3 hours in the presence of molecular sieves. After sulfation, the reaction mixture was poured into acetone containing triethylamine, and left alone at 4 ° C for 24 hours. The sulfated product released as an oil is washed with cold acetone and suspended for 2 hours in a 30% sodium acetate solution to exchange the triethylammonium cation to sodium cation. The solid sulfated product in the form of sodium salt is isolated by precipitation in ethanol. The sulfated product, according to the authors, is a potential antiviral drug [Discovery of lignin sulfate as potent ingibitor of HSV entry into cells. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University. By Jaj N. Thakkar BS in Pharmacy, University of Bombay. Bombay, India 2003. Director: UMESH].

The main disadvantage of this method is the use for sulfation of the toxic complex SO ₃ -triethylamine, the preparation of which from trimethylamine and sulfur trioxide to maintain the required reaction temperature requires the use of intensive cooling and a long process of isolating the sulfation product. In addition, the authors of the method do not provide data on the sulfur content and solubility in water of the sulfated lignin obtained by them.

The closest in technological essence and the achieved result to the proposed method is a method for sulfating an organosolvent lignin with a sulfamic acid-urea complex, obtained by mixing equimolar amounts of reagents in 1,4-dioxane at a temperature of 80-95 ° C, a hydraulic unit of 1: 5, for 2, 5-3.5 hours, with a ratio of lignin and sulfating complex equal to 1: 6-8 (g: mmol). At the end of the sulfation process, the solvent is decanted, and the remaining solid product is dissolved in a small amount of water and neutralized with aqueous ammonia to pH 8. To remove low molecular weight impurities, the product is dialyzed against water on cellophane for 3-4 hours. After distillation of water in a vacuum, a solid residue is obtained — water and ethanol are a soluble sulfated derivative of lignin in the form of an ammonium salt [RU 2641758, publ. 01/22/2018].

The disadvantage of this method is the low yield of the target product, which is due to the fact that during the reaction the resulting lignin sulfate is insoluble in 1,4-dioxane and precipitates in the form of a thick, resinous mass with a sulfating reagent, which prevents complete sulfation and, therefore, reduces yield of the target product.

The objective of the invention is to improve the method of sulfation of organosolvent lignin, increasing the yield of the target product.

The technical result of the invention:

- increased yield of sulfated organosolvent lignin due to the sulfation process in a homogeneous environment;

- expanded the range of solvents that allow the process of sulfation of ligno-carbohydrate materials in a homogeneous environment.

The technical result is achieved by the fact that in the method of sulfating organosolvent lignins by reacting lignins with a sulfating complex of sulfamic acid-urea in a solvent with stirring and heating, followed by isolation of the target product, according to the invention, the sulfation process is carried out in a homogeneous medium in the presence of a solvent of N, N-dimethylformamide at a temperature of 100 ° C for 0.5-6.0 hours with a ratio of the amount of lignin and sulfating complex equal to 1: 3 (pmol).

A comparative analysis of the invention with the prototype shows that the distinguishing features of the invention:

- carrying out sulfation in a homogeneous medium in the presence of a solvent of N, N-dimethylformamide;

- the ratio of the amount of lignin and sulfating complex is 1: 3 (pmol).

- sulfation conditions: temperature 100 ° C, duration 0.5-6.0 hours.

In the present invention, the initial lignin, sulfating complex and the final product are in the dissolved state during the whole reaction, i.e. in a homogeneous environment.

Due to these distinguishing features, the yield of the sulfated derivative of lignin increased. So, if in the prototype of 2.0 g of lignin received from 1.6-2.0 g of sulfated lignin, in the proposed method from 2.0 g of lignin receive from 2.5-2.8 g

Previously, sulfation of organosolvent lignin with sulfamic acid in N, N-dimethylformamide was not carried out.

F.J., Olivares-Carrillo P. Organosolv extraction of lignin from hydrolyzed almond shells and application of the δ-value theory // Bioresour Technol. 2010. V. 101, N. 21. P. 8252-8260.].For sulfation, ethanolignin isolated from Siberian fir wood (Abies sibirica) was used according to the method described in [Quesada-Medina J.,

FJ, Olivares-Carrillo P. Organosolv extraction of lignin from hydrolyzed almond shells and application of the δ-value theory // Bioresour Technol. 2010. V. 101, N. 21. P. 8252-8260.].

The method is as follows.

To a mixture of sulfamic acid and urea in N, N-dimethylformamide, heated to a temperature of 100 ° C, with vigorous stirring, ethanolignin isolated from fir wood is added. The further sulfation process is carried out at a temperature of 100 ° C for 0.5-6.0 hours. At the end of the sulfation process, the reaction mass is diluted with water and neutralized with aqueous ammonia to pH 8. To remove low molecular weight impurities, the product is dialyzed against water on cellophane for 24 hours. After dialysis, the aqueous lignin sulfate solution is concentrated in vacuo until the water is completely removed and an ammonium salt of lignin sulfate is obtained.

The method is confirmed by specific examples.

Examples 1. In a three-necked flask with a volume of 100 ml, equipped with a stirrer, thermometer and reflux condenser, add 40 ml of N, N-dimethylformamide, load 3.0 g of sulfamic acid, 2.0 g of urea and mix, then at 100 ° C load 2 , 0 g of fir wood ethanolignin. The ratio of the amount of lignin and sulfating complex is 1: 3 (pmol). The mixture is stirred at a temperature of 100 ° C for 0.5 hours. The reaction mass is cooled to a temperature of 15-20 ° C, diluted with 50 ml of water, aqueous ammonia solution is added to pH 8 and filtered. The resulting filtrate was dialyzed against water on cellophane for 24 hours. After dialysis, the ethanol lignin sulfate aqueous solution is concentrated in vacuo until the water is completely removed. The yield of the ammonium salt of ethanol lignin sulfate 2.34 g.

Examples 2-7. Sulfation of ethanolignin is carried out analogously to example 1, with a constant ratio of the amount of lignin and sulfating complex equal to 1: 3 (pmol), differences in the duration of sulfation.

Data on the yield, sulfur content and degree of substitution of samples of ethanol-lignin sulfated in N, N-dimethylformamide depending on the duration of the reaction are given in the table.

* 2.0 g of ethanolignin were sulfated in all experiments

Claims (1)

The method of sulfation of organosolvent lignins by reacting lignins with a sulfating complex sulfamic acid - urea in a solvent with stirring and heating, followed by isolation of the target product, characterized in that the sulfation process is carried out in a homogeneous medium in the presence of a solvent of N, N-dimethylformamide at a temperature of 100 ° C during 0.5-6.0 hours with a ratio of the amount of lignin and sulfating complex equal to 1: 3 (g: mmol).