RU2413045C1 - Method of producing cellulose intermediate product - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: water suspension of crushed aspen wood is put into a flow reactor and ozonised. Ozonation is carried out with concentration of ozone in the ozone-oxygen mixture equal to 90 mg/l, gas flow rate equal to 2-4 l/h and temperature of 20C and hydromodulus between 0.1:1.0 and 1.6:1.0. ^ EFFECT: high quality of the cellulose intermediate product, low consumption of reagents, high ecological cleanness of the process. ^ 5 ex, 2 tbl

Description

The invention relates to the field of chemical processing of wood and can be used in the pulp and paper industry to obtain a pulp prefabricated. The semi-finished product thus obtained can be used as an adsorbent for the absorption of water vapor and other compounds, and also as a basis for the synthesis of chemically modified carbohydrate and ligno-carbohydrate materials.

The essence of the claimed invention lies in the fact that the crushed hardwood is ozonized at a temperature of 20 ° C. The method allows to obtain cellulose prefabricated with a high content of cellulose and a low content of lignin.

To obtain cellulose prefabricated from hardwood, cooking processes are traditionally used. A known method of producing cellulose prefabricated by cooking wood chips with a mixture of 90% acetic acid and 30% hydrogen peroxide in the presence of a sulfuric acid catalyst [SU 821614, 04.15.81]. The disadvantage of this method is the low yield of the target product, its two-stage, significant consumption of hydrogen peroxide and sulfuric acid catalyst.

Closest to the claimed invention is a one-stage method for producing a cellulose prefabricated by cooking chopped aspen wood in a mixture of 37% hydrogen peroxide and 30% acetic acid, taken in a molar ratio of 0.3-0.5 at a hydraulic unit of 10: 1 and a temperature of 120-140 ° C for 2-5 hours in the presence of sulfuric acid in an amount of 1.5-2.5% by weight of absolutely dry wood [RU 2150538, 10.06.2000]. The disadvantage of this method is the use of sulfuric acid catalyst, since it contributes to the destruction of wood carbohydrates, which reduces the cellulose content in the cellulose prefabricated. The disadvantage of this method is the significant consumption of reagents (hydrogen peroxide and acetic acid) and sulfuric acid catalyst, which leads to pollution of wastewater.

Patents are known regarding the use of ozone as an environmentally friendly reagent in the process of bleaching lignocellulosic materials [US Patent 5164043, 11/17/1992]. In a number of countries, ozone is used in the manufacture of paper as one of the delignifying agents in the pulp bleaching stage [J. Rounsaville, R. G. Rice. Ozone Science & Engineering 18, 549 (1997)].

The problem solved by the claimed invention is to create an environmentally friendly technology that allows to obtain in high yield cellulose semi-finished product, characterized by a high content of cellulose, a low content of lignin, and also allows to reduce the specific consumption of reagents when it is received.

The problem is solved by ozonation of aspen wood, located in an aqueous suspension. Ozonation of an aqueous suspension of chopped aspen wood is carried out in a flow reactor at an ozone concentration of 90 mg / l in an ozone-oxygen mixture, a gas flow rate of 2-4 l / h and a temperature of 20 ° C with a hydraulic module from 0.1: 1.0 to 1, 6: 1.0.

An essential distinguishing feature of the claimed technical solution is the use of ozone as a reagent. Ozone is a strong oxidizing agent, the only conversion product of which is oxygen; ozone is characterized by high reactivity with respect to aromatic compounds, which contributes to the selective oxidation of wood lignin. Carrying out the process with a different hydraulic module allows it to be optimized in terms of the quality of the cellulosic semi-finished product and the specific consumption of the reagent - ozone and solvent - water. The use of a catalytic ozone decomposition cartridge at the outlet of the reactor [RU 2077946, 04/27/97] avoids the release of unreacted ozone into the atmosphere and improves the environmental safety of the process.

The essence of the proposed method for producing cellulose prefabricated is illustrated by the following examples.

Example 1 (table 1). 0.1 g of water is added to 1 g of absolutely dry chopped aspen wood (particle size 0.315-0.63 mm), this suspension is placed in a flow reactor and an ozone-oxygen mixture with an ozone concentration of 90 mg / l is passed. Gas flow rate 4 l / h, temperature 20 ° C. Ozonation is carried out until the absorption of ozone has stopped. The yield of cellulose prefabricated is 82%, the cellulose content is 60%, the residual lignin content is 21.3%.

Example 2. Ozonation is carried out under the same conditions as in example 1, but with a hydraulic module of 0.3: 1.0. The yield of cellulose prefabricated is 62%. The cellulose content in it is 67%, the residual lignin content is 4.8%.

Example 3. Ozonation is carried out under the same conditions as in examples 1-2, but with a hydraulic module of 0.6: 1.0. The yield of cellulose prefabricated is 55%. The cellulose content in it is 75%, the residual lignin content is 3.5%.

Example 4. Ozonation is carried out under the same conditions as in examples 1-3, but with a hydraulic module of 1.0: 1.0. The yield of cellulose prefabricated is 55%. The cellulose content in it is 75%, the residual lignin content is 3.1%.

Example 5. Ozonation is carried out under the same conditions as in examples 1-3, but with a water ratio of 1.6: 1.0. The yield of cellulose prefabricated is 50%. The cellulose content in it is 78%, the residual lignin content is 1.7%.

Examples 6, 7 of table 2 show that at a flow rate of 2 l / h with increasing hydromodule, ozone consumption increases; while the degree of delignification increases from 15.8% to 81%.

Examples 8, 9 of table 2. With a hydraulic module of 0.6: 1.0-1.0: 1.0, the consumption of ozone is 1.1-1.3 g of ozone per gram of absolutely dry wood with a delignification degree of 86.2-87.7 %

Example 10 of table 2. With a hydraulic module of 1.6: 1.0 - the degree of delignification of 93.3%, ozone consumption of 3.0 g of ozone per gram of wood.

Thus, with a water module of 0.1: 1.0 - the highest yield of cellulose prefabricated, however, it has a high lignin content (21.3% o) and a low cellulose content. An increase in the hydromodule above 1.0: 1.0 results in a decrease in the yield of the cellulose prefabricated product due to partial destruction of carbohydrates in the wood, which is accompanied by a significant increase in ozone consumption.

To obtain a cellulose prefabricated product with a yield of 55% with a high content of cellulose in it (75%) and a moderate consumption of ozone, it is advisable to ozonize the aspen wood with a hydraulic module of 0.6: 1.0-1.0: 1.0. The degree of delignification in this case is 86.2-87.7%.

Table 1 Influence of the hydraulic module on the output of the cellulose prefabricated The ozone concentration in the ozone-oxygen mixture is 90 mg / l, the gas flow rate is 4 l / h, temperature is 20 ° C. Example Hydraulic module The output of the semi-finished product,% ** The lignin content in the semi-finished product,% * The cellulose content in the semi-finished product,% one 0.1: 1.0 82 21.3 60 2 0.3: 1.0 62 4.8 67 3 0.6: 1.0 55 3,5 75 four 1.0: 1.0 55 3,1 75 5 1.6: 1.0 fifty 1.7 78 * by weight of absolutely dry semi-finished product ** by weight of wood ash

Table 2. The influence of the hydraulic module on the ozone consumption and the degree of delignification of the cellulose prefabricated Example Hydraulic module Ozone consumption g ozone / g asd The degree of delignification,% 6 0.1: 1.0 0.1 15.8 7 0.3: 1.0 0.9 81.0 8 0.6: 1.0 1.1 86.2 9 1.0: 1.0 1.3 87.7 10 1.6: 1.0 3.0 93.3 The ozone concentration in the ozone-oxygen mixture is 90 mg / l, the gas flow rate is 2 l / h, temperature is 20 ° C.

Claims (1)

A method of producing a cellulosic semifinished product by ozonation of chopped aspen wood in the form of an aqueous suspension, characterized in that the cellulosic semifinished product is obtained by ozonizing wood in a flow reactor at a gas flow rate of 2-4 l / h, the concentration of ozone in the ozone-oxygen mixture 90 mg / l, hydromodule from 0.1: 1.0 to 1.6: 1.0 and a temperature of 20 ° C.