RU2776126C1 - Method for delignification of cellulose materials - Google Patents

Abstract

FIELD: pulp and paper industry.

SUBSTANCE: invention relates to the pulp and paper industry, namely to the methods for delignification of cellulose in the processing of mainly wood. This method can also be used for processing other types of cellulose materials: cake, cotton, flax, hemp, jute, straw, rice husks and others. Delignification of cellulose materials is carried out by sequential treatment with lipase and an oxidizing agent, and the treatment of cellulose materials is carried out with a mixture of one percent solutions of lipase and oxyethylated fatty acid or its derivative at a mass ratio of 1:1÷4 for 0.5-1.5 hours at a temperature of 20-40°C. Penta-oxyethylated tridecanoic acid monoethanolamide ester with the formula C₁₂H₂₅CONHCH₂CH₂O(C₂H₄O)₅H is mainly used as a derivative of oxyethylated higher fatty acid. Lipase is selected from Candida, Aspergillus, Pseudomonas, Humicola, Chromobacter. A delignification cellulose material is obtained at a lower temperature and time of suspension processing and a target product with a reduced lignin content. An increase in the reactivity of cellulose to viscose formation after delignification is also achieved.

EFFECT: method allows for the delignification of cellulose materials, while simultaneously achieving a low degree of environmental impact.

3 cl, 1 tbl, 29 ex

Description

The invention relates to the pulp and paper industry, and in particular to methods of pulp delignification in the processing of mainly wood. This method can also be used to process other types of cellulosic materials: cake, cotton, flax, hemp, jute, straw, rice husks and others. After delignification, cellulosic materials contain a reduced amount of lignin.

Cellulose raw material is a complex material that consists of cellulose, hemicellulose, lignin, and other minor components. Lignin is associated with cellulose and hemicelluloses, and is probably covalently associated with both cellulose and hemicellulose. Lignin is usually removed from raw materials because it imparts a brownish color, reduces strength, and imparts other undesirable characteristics to the finished product. Most of the lignin is removed from the cellulosic feedstock by chemical pulping (eg, the kraft process). During the post-bleaching process, the pulp reacts with hydrogen peroxide, chlorine and other oxidizing chemicals to further remove lignin, providing stable, bleached pulp. However, the treatment of cellulosic materials with chemicals is undesirable from an environmental point of view, since the resulting wastewater contains a large amount of toxic compounds (for example, chlorinated phenols). Concerns about the environmental impact of chemical bleaching of pulp have prompted the industry to look for delignification techniques to reduce bleaching chemicals.

A known method of bleaching pulp by bleaching it with ozone in the presence of the addition of ethoxylated alkylolamides of synthetic fatty acids [Ed. certificate USSR 518544, D21C 9/10, 07/22/1976]. According to this method, bleaching is carried out for 5 hours in an acidic environment, and the addition of ethoxylated alkylolamides of synthetic fatty acids is carried out to maintain the required pH. The disadvantages of this method are the low quality of the fiber, the long duration and the low degree of delignification of the final pulp.

Enzymes derived from fungal and bacterial sources are used to delignify cellulosic materials prior to bleaching. Regardless of the mechanism, enzyme treatment reduces the consumption of chemicals during subsequent bleaching, including hydrogen peroxide, chlorine dioxide, etc. This, in turn, reduces the amount of effluent generated during such processes.

A known method of pulp delignification, including enzymatic treatment of kraft pulp with xylanase before peroxide bleaching [US Pat. 5683911, D21C 9/10, 11/04/1997]. The xylanases are active at high temperatures and alkaline pH and act on the hemicellulose-cellulose matrix of the suspension to which the lignin is bound, so that after treatment with the enzyme the lignin is released and/or made available for isolation with an appropriate extractant.

The disadvantage of this method is the insufficient degree of delignification. When using xylanases as an enzyme, there is also low selectivity with a slight decrease in the amount of sugar released in the filtrate, which indicates the impossibility of xylanase to degrade hexenuronic acids.

There is also known a method for bleaching kraft pulp from pulp by treatment with lipase from the fungus Aspergillus niger, followed by a sequence of stages of chemical bleaching, including peroxide bleaching [Rashedi H., Amoabediny Gh., Eskandari S. et al. Application of a commercial lipase enzyme on biobleaching of kraft bagasse pulp // Cellulose Chemistry and Technology, 2008.V. 42. No. 7. pp. 397-402].

The disadvantages of this method is a slight decrease in residual lignin after the stage of peroxide treatment (by 0.2-0.28%) with a sufficiently high consumption of reagents for both enzymatic treatment and oxidative degradation.

The prototype of the present invention is a method for delignification of cellulose, including enzymatic treatment of kraft pulp with lipase obtained from Aspergillus [Nguyen D., Zhang X., Jiang Z.H., Tsang A. Bleaching of kraft pulp by a commercial lipase: Accessor enzymes degrade hexenuronic acids // Enzyme and Microbial Technology 2008. V. 43. N. 2. pp. 130-136]. According to this method, kraft pulp is subjected to an enzymatic treatment with lipase prior to peroxide bleaching. The treatment is carried out at a temperature of 50-80°C for 2 hours. As a result of a decrease in the Kappa number (lignin content), depending on the type of pulp - sulfate hardwood and sulfate softwood - occurs by 1.7 units (11.8%) and 0 .6 units (1.9%), respectively, while decreasing the content of hexenuronic acids in cellulose, respectively, by 15.9% and 13.0% (description of the prototype is attached).

The disadvantages of the prototype are the insufficient degree of delignification, the long duration, the high temperature of the enzyme treatment, the low reactivity of cellulose to viscose after delignification.

The objective of the present invention is to eliminate these shortcomings, namely, obtaining a delignified cellulose material at a lower temperature and suspension processing time and obtaining a target product with a reduced lignin content.

The problem is solved by the fact that the method of delignification of cellulose materials includes the sequence of processing cellulose materials with lipase and an oxidizing agent, and the processing of cellulose materials is carried out with a mixture of 1% solutions of lipase and ethoxylated fatty acid or its derivative at a mass ratio of 1:1÷4 for 0.5 -1.5 hours at a temperature of 20-40°C.

Preferably, tridecanoic acid monoethanolamide pentaoxyethylated ester of the formula C ₁₂ H ₂₅ CONHCH ₂ CH ₂ O(C ₂ H ₄ O) ₅ H is used as the ethoxylated higher fatty acid or its derivative.

The lipase is selected from the group Candida, Aspergillus, Pseudomonas, Humicola, Chromobacter. For other types of lipase, the numerical values of the whiteness of delignified cellulose are somewhat lower.

The essential features of the proposed method is an inseparable set of features specified in the claims. In the claimed solution, the use of lipase and ethoxylated higher fatty acid or its derivative in the claimed combination of substances in combination with the other features mentioned above makes it possible to achieve the above result. Based on this, we can conclude that the differences in the claimed solution are significant.

As cellulosic materials, for example, sulfate pulp or sulfite pulp of various types of wood is used.

Pentaoxyethylated ester of tridecanoic acid monoethanolamide is mainly used as the oxyethylated higher fatty acid or its derivative (HFA), since in this case the highest whiteness of cellulose is achieved.

According to the claimed method, a mixture of lipase and OFA is added to a suspension of unbleached pulp, for example, sulfate hardwood or sulfite softwood, at a concentration of 10% with stirring at a speed of, for example, 150 rpm, a mixture of lipase and OFA is added at their mass ratio of 1:1÷4 (for example, at pH 7, temperature 20-40°C, mixture flow rate 500 mg/kg cellulose) and incubated, for example, 0.5-1.5 hours in a water bath. After treatment, the cellulose suspension is filtered on a Buchner funnel and washed with water. Then the suspension of the same concentration is subjected to chemical delignification by treatment with an oxidizing agent, for example sodium hydroxide in the presence of hydrogen peroxide, for example, for 1 hour at a temperature of 75°C. Pulp is obtained, which is analyzed for lignin content (Kappa number) determined according to GOST 11960-79, whiteness - according to GOST 30437-96 (ISO 3688-77), reactivity to viscose formation - according to GOST 9003-75.

As a result of using the claimed method due to the complex action of substances, leading to the formation of a developed surface of fibers of cellulose materials with simultaneous hydrolysis of the bonds of the ligno-carbohydrate complex of cellulose, a product with a reduced lignin content is obtained, at temperatures and duration lower than in the prototype. At the same time, the delignification product has a higher reactivity to viscose formation.

Example 1 - prototype

To a suspension of unbleached sulphate hardwood pulp with a Kappa number of 20 units. (weighing 10 g of absolutely dry cellulose), consistency 10% with stirring at a speed of 150 rpm was added lipase (0.15 ml of 1% solution of Aspergillus lipase) at a temperature of 50°C and kept for 2 hours. After treatment with the enzyme, the cellulose suspension was filtered on a Buchner funnel and washed with water. Then the suspension was treated with sodium hydroxide in the presence of hydrogen peroxide for 1 hour at a temperature of 85°C. As a result, pulp was obtained with a Kappa number of 12 units, a whiteness of 71%, with a reactivity of 100/14%.

Example 2

Compared with the prototype, in this example the temperature is reduced to 20°C, the duration is up to 0.5 hours. To a suspension of unbleached sulphate hardwood pulp with a Kappa number of 20 units. (weighing 10 g of absolutely dry cellulose), at a concentration of 10% with stirring at a speed of 150 rpm, lipase (0.15 ml of 1% Aspergillus lipase solution) was introduced at a temperature of 20°C and kept for 0.5 hour. After treatment with the enzyme, the cellulose suspension was filtered on a Buchner funnel and washed with water. Then the suspension was treated with sodium hydroxide in the presence of hydrogen peroxide for 1 hour at a temperature of 75°C. As a result, pulp was obtained with a Kappa number of 19 units, a whiteness of 75%, with a reactivity of 125/15%. As can be seen from this example, a decrease in temperature and duration leads to a significant increase in the Kappa number in the delignification product and a decrease in the reactivity of this product.

Examples 3-11 (Table 1).

To a suspension of unbleached sulphate hardwood pulp with a Kappa number of 20 units. (weighing 10 g of absolutely dry cellulose), at a concentration of 10% with stirring at a speed of 150 rpm, a mixture of lipase:OFA was added at their mass ratio of 1:2.3 (0.15 ml of 1% Aspergillus lipase solution) and 0.35 ml of a 1% solution of tridecanoic acid monoethanolamide pentaoxyethylated ester with the formula C ₁₂ H ₂₅ CONHCH ₂ CH ₂ O (C ₂ H ₄ O) ₅ H at a temperature of 20-40 ° C and kept under stirring for 0.5-1.5 hours. After treatment with the enzyme, the cellulose suspension was filtered on a Buchner funnel and washed with water. Then the suspension was treated with sodium hydroxide in the presence of hydrogen peroxide for 1 hour at a temperature of 75°C. The numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Examples 12-14 (Table 1).

The method was carried out similarly to examples 3-11, but unbleached sulfite softwood pulp with a Kappa number of 30.1 units was used as a raw material. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 15 (Table 1).

The method was carried out analogously to example 7, but used lipase from Pseudomonas. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 16 (Table 1).

The method was carried out analogously to example 7, but used lipase from Candida. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 17 (Table 1).

The method was carried out analogously to example 7, but used lipase from Humicola. The numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 18 (Table 1).

The method was carried out analogously to example 7, but used lipase from Chromobacter. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 19 (Table 1).

The method was carried out analogously to example 7, but decaethylene glycol ester of stearic acid C ₁₇ H ₃₅ COO (C ₂ H ₄ O) ₁₀ H was used as the OLC. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in Table one.

Example 20 (Table 1).

The method was carried out analogously to example 7, but decaethylene glycol ether of nonadecanoic acid C ₁₈ H ₃₇ COO (C ₂ H ₄ O) ₁₀ H was used as the OFA. The numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 21 (Table 1).

The method was carried out analogously to example 16, but decaethylene glycol ester of stearic acid C ₁₇ H ₃₅ COO (C ₂ H ₄ O) ₁₀ N was used as the OLC. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in Table one.

Example 22 (Table 1).

The method was carried out analogously to example 7, but the ratio of lipase:OZHK equal to 1:4. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 23 (Table 1).

The method was carried out analogously to example 7, but the ratio of lipase:OZHK equal to 1:1. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 24 (Table 1).

The method was carried out analogously to example 7, but the ratio of lipase:OZHK equal to 1:3. The numerical values of the Kappa number, whiteness, reactivity in the deligcification product are presented in table. one.

Example 25 (Table 1).

The method was carried out analogously to example 16, but the ratio of lipase:OZHK equal to 1:4. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 26 (Table 1).

The method was carried out analogously to example 7, but decaoxyethylated ester of tridecanoic acid monoethanolamide C ₁₂ H ₂₅ CONHCH ₂ CH ₂ O (C ₂ H ₄ O) ₁₀ H was used as the OLC. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table . one.

Example 27 (Table 1).

The method was carried out analogously to example 7, but used lipase from Alcaligenes. Numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 28 (Table 1).

Chlorine dioxide was used as the oxidizing agent, followed by treatment with sodium hydroxide. To a suspension of unbleached sulphate hardwood pulp with a Kappa number of 20 units. (weighing 10 g of absolutely dry cellulose), at a concentration of 10% with stirring at a speed of 150 rpm, a mixture of lipase:OFA was added at their mass ratio of 1:2.3 (0.15 ml of 1% Aspergillus lipase solution) and 0.35 ml of a 1% solution of tridecanoic acid monoethanolamide pentaoxyethylated ester with the formula C ₁₂ H ₂₅ CONHCH ₂ CH ₂ O(C ₂ H ₄ O) ₅ H at a temperature of 30°C and kept for 1 hour. The suspension was then treated with an aqueous solution of chlorine dioxide (ClO ₂ ) at a concentration of 5 g/l with a volume of 18 ml, corresponding to a consumption of 0.9% to cellulose at 45°C for 50 minutes with the addition of sulfuric acid to maintain a pH of 2.5. After treatment, the suspension was filtered through a Buchner funnel and washed with water, and the suspension of cellulose was kept at a concentration of 10% for 1 hour at a temperature of 75°C with a sodium hydroxide content of 1.3% in solution. The numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

Example 29 (Table 1)

Sodium hypochlorite was used as the oxidizing agent, followed by treatment with sodium hydroxide. To a suspension of unbleached sulphate hardwood pulp with a Kappa number of 20 units. (weighing 10 g of absolutely dry cellulose), at a concentration of 10% with stirring at a speed of 150 rpm, a mixture of lipase:OFA was added at their mass ratio of 1:2.3 (0.15 ml of 1% Aspergillus lipase solution) and 0.35 ml of a 1% solution of tridecanoic acid monoethanolamide pentaoxyethylene ester with the formula C ₁₂ H ₂₅ CONHCH ₂ CH ₂ O(C ₂ H ₄ O) ₅ H at a temperature of 30°C and kept for 1 hour. After treatment with the enzyme, the cellulose suspension was filtered on a Buchner funnel and washed with water. Then the pulp was poured with a solution of sodium hypochlorite (73 ml of a solution with a concentration of 10 g/l bleaching reagent consumption corresponded to 7.3% by weight of the pulp) and water, resulting in a suspension of pulp, corresponded to a concentration of 10%. The suspension was kept at a temperature of 40°C for 1 hour. After treatment, the suspension was filtered through a Buchner funnel and washed with water, and the suspension of cellulose was kept at a concentration of 10% for 1 hour at a temperature of 75°C with a sodium hydroxide content of 1.3% in solution. The numerical values of the Kappa number, whiteness, reactivity in the delignification product are presented in table. one.

The table shows that the claimed method in the claimed implementation parameters provides a solution to the problems described above. The cellulose material obtained after delignification has a high reactivity and can be used to produce chemical fibers.

The use of the invention also makes it possible to increase the reactivity of cellulose to viscose formation after delignification.

The use of tridecanoic acid monoethanolamide pentaoxyethylated ester with the formula C ₁₂ H ₂₅ CONHCH ₂ CH ₂ O(C ₂ H ₄ O) ₅ H as a derivative of an ethoxylated higher fatty acid makes it possible to achieve the best whiteness of the delignification product.

The delignification product can be used on its own, but also subjected to further bleaching, the consumption of chemical reagents is significantly reduced. This method can be used to process other types of cellulose materials: cake, cotton, flax, hemp, jute, straw, rice husks and others. The claimed method, in addition to reducing the consumption of bleaching reagents, helps to reduce the negative impact on the environment and increase the safety of human life.

Claims (3)

1. The method of delignification of cellulose materials, including sequential treatment with lipase and an oxidizing agent, characterized in that the treatment of cellulose materials is carried out with a mixture of one percent solutions of lipase and ethoxylated fatty acid or its derivative at a mass ratio of 1:1÷4 for 0.5-1, 5 hours at a temperature of 20-40°C; 2. The method according to p. 1, characterized in that the pentaoxyethylated ester of tridecanoic acid monoethanolamide with the formula C ₁₂ H ₂₅ CONHCH ₂ CH ₂ O (C ₂ H ₄ O) ₅ H is used as a derivative of an ethoxylated higher fatty acid. 3. The method according to p. 1, characterized in that the lipase is selected from Candida, Aspergillus, Pseudomonas, Humicola, Chromobacter.