RU-2861352-C1 - METHOD FOR ACTIVATING CELLULOSE

RU2861352C1RU 2861352 C1RU2861352 C1RU 2861352C1RU-2861352-C1

Abstract

FIELD: chemical industry. SUBSTANCE: invention relates to the field of modification of macromolecular compounds. A method for activating cellulose includes treating defibrated cellulose with supercritical carbon dioxide in a sealed reactor at a temperature of 40-70°C and a pressure of 15-35 MPa for 15-120 minutes, followed by a sharp pressure release to atmospheric pressure. The activated cellulose is then degassed to remove residual carbon dioxide. EFFECT: increasing the environmental safety and technological efficiency of the cellulose activation process, which has increased reactivity and is suitable for chemical processing into highly substituted cellulose esters both at specialised enterprises and at enterprises producing wood pulp. 3 cl, 2 dwg, 1 tbl

Inventors

Garaeva Miliausha Radikovna
Khalikov Artur Tagirovich
Baranova Natalia Viktorovna
Nikitina Natalia Nikolaevna
Aiupova Rozaliia Alfretovna
Shakirov Timur Rustamovich

Dates

Publication Date: 20260505
Application Date: 20251017

Claims (3)

1. A method for activating cellulose, which includes treating de-fibered cellulose with supercritical carbon dioxide in a sealed reactor at a temperature of 40-70°C and a pressure of 15-35 MPa for 15-120 minutes, followed by a sharp release of pressure to atmospheric pressure and degassing of the activated cellulose to remove residual carbon dioxide.
2. The method according to paragraph 1, characterized in that the fiberization of cellulose is carried out using a hammer mill.
3. The method according to paragraph 1, characterized in that the processing is carried out with continuous supply of supercritical carbon dioxide into the reactor.

Description

The invention relates to the field of modification of high-molecular compounds and is intended for obtaining cellulose with increased reactivity. In the context of import substitution of strategically important raw materials and the production of high-quality cellulose suitable for chemical processing, scientific research into improving the physicochemical properties of cellulose obtained from domestic wood raw materials is becoming increasingly relevant. One of the industry's key challenges is developing an effective method for activating cellulose obtained from domestic wood raw materials, which will enable the synthesis of high-quality cellulose ethers for various industries. A prior art method for activating cellulose, which can be used as a raw material for the chemical, pharmaceutical, food, and other industries, is known. Cellulose activation is accomplished as follows. Ground cellulose is treated with an aqueous solution of sodium pyrosulfate at a concentration of 1.0-9.0% by weight, and the cellulose is dried at a temperature of 100-105°C for 60 minutes. This maximizes the cellulose's fragility, and milling for 6-8 minutes disrupts the macromolecular and fibrous structure by breaking hydrogen bonds. This produces a free-flowing, highly reactive cellulose powder, containing 98.87% by weight of the cellulose fraction with particle sizes of 10-320 μm. Activated cellulose powder can be used in the process of copolymerization with unsaturated monomers, as well as a thickener and raw material for the paint and varnish and textile industries (patent EA 020359 B1, C08B 1/00, published 10/30/2014). However, the described method has drawbacks: the use of potassium persulfate and sodium pyrosulfate solutions during activation requires an additional wastewater treatment step. Furthermore, the method requires the use of a large amount of inorganic salts per unit mass of processed cellulose, making the process less efficient. A method is known for improving the quality and reactivity of cellulose, which includes the following stages of action on cellulose: impregnation and hydrolysis of cellulose in a hydrolysis solution medium, filtration of cellulose from the hydrolysis solution, its washing, squeezing and drying, wherein the stages of impregnation and hydrolysis of cellulose in a hydrolysis solution medium, the stage of filtration from the hydrolysis solution, the stages of washing, squeezing and drying are carried out with simultaneous thermal vacuum-pulse action in cycles, each of which includes heating of cellulose to a temperature of no more than 115°C, high-speed pulse action of vacuum within a pressure of no more than 100 mm Hg. in less than 10 seconds, followed by holding the cellulose under vacuum and releasing the vacuum (patent RU 2609803 C1, C08B 1/00, C08B 1/02, published 06.02.2017). The disadvantage of this method is the use of hydrolysis solutions, including, for example, metal hydroxides, ammonia, amines, dimethylformamides, dimethyl sulfoxides, acetic acid, which requires the inclusion of neutralization and/or solution recovery stages in the technological process. A known method for activating cellulose is steam explosion in an alkaline medium. This involves the following steps: mixing the cellulose-containing raw material in an alkaline solution, flushing with nitrogen, heating to the required temperature of 140-150°C for 20-30 minutes, maintaining it under excess pressure, completely releasing the pressure over 10 seconds, rinsing with water, and drying. During the processing of the cellulose raw material, by abruptly opening the drain valve, the pressure in the thermal device is sharply reduced, causing instantaneous boiling of the liquid phase throughout the entire volume, including within the plant fibers, generating steam. The hydrolysis liquid in the form of steam is discharged through the drain cock, and the cellulose fibers remain in the device that carries out the thermal action under pressure, thanks to the existing safety mesh. Due to the sharp boiling, an additional physical effect occurs in the form of rupture of the cellulose fibers by steam bubbles, which leads to loosening of their supramolecular structure, which subsequently facilitates the access of reagents and the removal of reaction products both during preparatory operations and during the further production of cellulose ethers (patent RU 2684020, C08B 11/06, D21C 9/08, published 03.04.2019). A disadvantage of this method is the use of alkali during the activation stage, which makes the process less environmentally friendly. Furthermore, during the activation process, the cellulose is exposed to elevated temperatures, which causes partial hydrolysis and, consequently, a decrease in its reactivity. A method for activating cellulose by treating it with ammonia is known and accepted as a prototype, in which, in order to reduce the consumption of the activating agent and increase the reactivity of cellulose, the treatment i