RU2702582C1 - Method of sulphating 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 sulphating organosolvent lignins is carried out by reacting lignins with sulfating complex sulfamic acid – urea while stirring in homogeneous medium in presence of diethylene glycol dimethyl ether solvent at temperature of 80–120 °C for 3.0–5.0 hours at a ratio of the amount of lignin to the sulphatation complex equal to 1:3 (g:mmol). Product is isolated by diluting with water, neutralization and purification from low-molecular impurities by dialysis.

EFFECT: high output of sulphated lignin, wider range of solvents for lignin sulphation in a homogeneous medium.

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 in 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 pyridinesulfotrioxide 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 made up 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 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 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 clear what the completeness of dissolution of sulfated lignins in water is. 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.

A known method of sulfation of organosolvent lignin by a complex of sulfamic acid-urea, obtained by mixing equimolar amounts of reagents in 1,4-dioxane at a temperature of 80-95 ° C, a hydraulic module 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 reactions, 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 closest in technological essence and the achieved result to the proposed method is a method for sulfating organosolvent lignins with a complex of sulfamic acid-urea with stirring 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 lignin and sulfating complex equal to 1: 3 (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 24 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 2665576, publ. 08/31/2018].

The objective of the invention is the expansion of the range of solvents for sulfation of organosolvent lignin, increasing the degree of sulfation and yield of the target product.

The technical result of the invention:

- increased yield of sulfated organosolvent lignin by increasing the degree of sulfation;

- expanded the range of solvents that allow the process of sulfation of organosolvent lignins in a homogeneous environment.

The technical result is achieved by the fact that in the method for sulfating organosolvent lignins by reacting lignins with a sulfating complex sulfamic acid-urea when heated and stirring in a homogeneous medium in the presence of a solvent, the ratio of the amount of lignin and sulfating complex is 1: 3 (g: mmol), followed by isolation the target product, according to the invention, the sulfation process is carried out in the presence of a solvent of diethylene glycol dimethyl ether at a temperature of 80-120 ° C in those reading 3.0-5.0 hours.

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

- carrying out sulfation in the presence of a diglyme solvent (diethylene glycol dimethyl ether);

- sulfation conditions: temperature 80-120 ° C, duration 3.0-5.0 hours.

Due to these distinguishing features, the yield and degree of sulfation of lignin increased. So, if in the prototype from 2.0 g of lignin received from 2.5-2.8 g of sulfated lignin, in the proposed method from 2.0 g of lignin receive up to 2.9 g, and the degree of sulfation increases from 53.7 to 64.5%.

Previously, sulfation of organosolvent lignin with sulfamic acid in diglyme 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 diglyme, heated to a temperature of 80-120 ° C, with vigorous stirring, ethanolignin isolated from fir wood is added. The further sulfation process is carried out at a predetermined temperature for 3.0-5.0 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, pour 40 ml of diglyme, load 3.0 g of sulfamic acid, 2.0 g of urea and mix, then at a temperature of 80 ° C, 2.0 g ethanolignin derived from fir wood. The ratio of the amount of lignin and sulfating complex is 1: 3 (g: mmol). The mixture is stirred at a temperature of 80 ° C for 5.0 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 output of the ammonium salt of ethanol lignin sulfate 2.70 g.

Data on the yield, sulfur content and degree of substitution of samples of ethanolignin sulfated in diglyme depending on temperature and duration of reactions are given in the table.

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 (g: mmol), differences in the duration of sulfation and the reaction temperature.

Thus, in the present invention, the range of solvents for sulfation of organosolvent lignin is expanded, the degree of sulfation and the yield of the target product are increased.

Claims (1)

The method of sulfating organosolvent lignins by reacting lignins with a sulfating complex sulfamic acid - urea when heated and stirring in a homogeneous medium in the presence of a solvent with a ratio of the amount of lignin and sulfating complex equal to 1: 3 (g: mmol) with the subsequent isolation of the target product, characterized in that the sulfation process is carried out in the presence of a solvent of diethylene glycol dimethyl ether at a temperature of 80-120 ° C for 3.0-5.0 hours.