CN113563604B - Method for regulating and controlling industrial alkali lignin molecules - Google Patents

Abstract

The invention belongs to the field of alkali lignin utilization in pulping and papermaking industries, and relates to a method for regulating and controlling industrial alkali lignin molecules, which comprises the following steps: alkali lignin in pulping and papermaking industry is used as a raw material, and the alkali lignin is purified by an organic solvent and an acid precipitation method. The purified alkali lignin reacts in a 1, 6-dibromohexane/dimethylformamide/potassium carbonate system to obtain the alkali lignin regulated and controlled by molecules. The novel technology developed by the application improves the molecular weight of the alkali lignin, reduces the polydispersity of partial fractions, regulates the content of phenolic hydroxyl groups, changes the color depth of the alkali lignin and lays a foundation for subsequent modification and application of the alkali lignin. By controlling the adding amount, the reaction time and the temperature of the 1, 6-dibromohexane, the molecular weight of the alkali lignin can be improved by 353-1643 percent, the polydispersity of partial fractions is reduced, the content of the phenolic hydroxyl group is regulated and controlled to be reduced by 2-80 percent, and the color of the alkali lignin can be changed.

Description

A method for regulating industrial alkali lignin molecules

technical field

The invention belongs to the field of alkali lignin utilization in the pulp and paper industry, and in particular relates to a method for regulating the molecular weight and main functional groups of alkali lignin.

Background technique

Lignin is a general term for a class of substances with common properties existing in woody plants, herbaceous plants and all vascular plants. It is the second largest biomass resource in the plant kingdom after cellulose. At the same time, lignin is the only renewable aromatic polymer compound, which can be used to prepare resin materials and functional polymer materials. areas play an important role. Currently only about 2% of lignin is used to produce high value-added products, and most of it is only used as cheap fuel. Lignin is mainly derived from the pulp and paper industry. As a by-product of pulping, the annual output of the world is about 50 million tons, of which about 15 million tons are in my country. 95% of the lignin is not separated or utilized, but is discharged directly or The way of burning will cause serious environmental problems. Today, most pulp and paper mills in the world use alkaline pulping, and the lignin produced is mainly alkali lignin. Therefore, it is of more economic, social and ecological significance to make full use of alkali lignin resources to produce high value-added alkali lignin-based products. The small molecular weight, high polydispersity and low reactivity of alkali lignin severely limit its application.

Contents of the invention

In order to overcome the above-mentioned problems, the present invention uses alkali lignin in the pulp and paper industry as a raw material, and adopts a novel alkylation system of 1,6-dibromohexane/dimethylformamide/potassium carbonate to efficiently increase the molecular weight of alkali lignin, regulate Polydispersity, regulation of functional groups such as phenolic hydroxyl groups. By controlling the addition of 1,6-dibromohexane, reaction time and temperature, the molecular weight of alkali lignin can be increased by 353%-1643%, the polydispersity of some fractions can be reduced, and the content of phenolic hydroxyl groups can be adjusted to reduce by 2%-80%. , and can change the color of alkali lignin.

In order to realize the above-mentioned technical purpose, the present invention adopts following technical scheme:

The first aspect of the present invention provides a method for regulating industrial alkali lignin molecules, including:

Purify industrial alkali lignin to obtain purified alkali lignin;

The purified alkali lignin is subjected to an alkylation reaction in a 1,6-dibromohexane/dimethylformamide/potassium carbonate system to obtain molecularly regulated alkali lignin.

The new technology developed by this application increases the molecular weight of alkali lignin, reduces the polydispersity of some fractions, regulates the content of phenolic hydroxyl groups, changes the color depth of alkali lignin, and lays the foundation for the subsequent modification and application of alkali lignin. foundation.

The second aspect of the present invention provides molecularly regulated alkali lignin prepared by any one of the above-mentioned methods.

The third aspect of the present invention provides that the above-mentioned molecularly regulated alkali lignin can be used in the preparation of resin materials, functional polymer materials, and oil extraction, construction concrete water reduction, printing and dyeing dye dispersion, pesticide slow-release dispersion, fertilizer slow-release applications in the field.

The beneficial effects of the present invention are:

(1) The entire alkali lignin molecular regulation process uses organic solvents and acid precipitation to purify alkali lignin, and a new alkylation system of 1,6-dibromohexane/dimethylformamide/potassium carbonate can be used according to different Different application requirements of alkali lignin, adjusting its molecular weight, reducing the polydispersity of some fractions, regulating the content of phenolic hydroxyl groups, and changing the color depth of alkali lignin are of great significance to the subsequent modification and application of alkali lignin.

(2) The operation method of the present application is simple, low in cost, high in efficiency, universal in applicability, and easy for large-scale production.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

Figure 1 shows the color change of alkali lignin before and after regulation in Example 1 of the present invention.

Fig. 2 shows the color change of alkali lignin before and after regulation in Example 2 of the present invention.

Fig. 3 shows the color change of alkali lignin before and after regulation in Example 3 of the present invention.

Figure 4 shows the color change of alkali lignin before and after regulation in Example 4 of the present invention.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

A method for regulating industrial alkali lignin molecules, using the pulp and paper industry alkali lignin as a raw material, comprising the following steps:

The dried crude alkali lignin was added to an acidic dioxane aqueous solution (dioxane/water=9:1, v:v, pH=2). The mixture was stirred at 87-90°C for 2-2.5 hours, and then centrifuged to remove the precipitate. The supernatant to which sodium bicarbonate was added was kept stirring for 3-4 hours to neutralize the acid in the solution. After centrifuging again to remove the precipitate, the supernatant was rotovapped under vacuum at 55 °C to remove and recover dioxane. The supernatant after vacuum rotary evaporation was added to a hydrochloric acid solution with pH=2, and then centrifuged to obtain a precipitate. The precipitate was freeze-dried to obtain purified alkali lignin (PAL) as a solid powder. Dissolve PAL in dimethylformamide at a ratio of 1:20-25. Add _K2CO3 equivalent to 0.6-08 times the mass of purified alkali lignin to the above mixed solution as an acid binder to absorb the acid generated in the _reaction , and add a trace amount of KI as 1,6-dibromohexane the activator. Under nitrogen protection, heat the above mixture to the specified temperature (60-90°C), add 1,6-dibromohexane, keep the temperature for 1-4 hours, and then add 2mol/L hydrochloric acid aqueous solution to end the reaction. The reacted alkali lignin was precipitated with aqueous hydrochloric acid (pH=2). The precipitate was obtained by centrifugation, washed with hydrochloric acid aqueous solution (pH=2), and freeze-dried to obtain a solid powdery substance, which is molecularly regulated alkali lignin (CAL).

In some embodiments, the alkali lignin is crude alkali lignin separated and extracted from alkaline pulping black liquor, in the form of powder or block.

The grades of chemical reagents used in the patent of the present invention are all chemically pure.

The invention uses alkali lignin in the pulp and paper industry as raw material, utilizes organic solvents and acid precipitation to purify alkali lignin, and adopts a novel alkylation system 1,6-dibromohexane/dimethylformamide/potassium carbonate Lignin molecules are regulated, and the detailed steps are as follows:

(1) Organic solvent purification of crude alkali lignin: add dry crude alkali lignin into acidic dioxane aqueous solution (dioxane/water=9:1, v:v, pH=2). The mixture was stirred at 87-90°C for 2-2.5 hours, and then centrifuged to remove the precipitate. The supernatant to which sodium bicarbonate was added was kept stirring for 3-4 hours to neutralize the acid in the solution. After centrifuging again to remove the precipitate, the supernatant was rotovapped under vacuum at 55 °C to remove and recover dioxane.

(2) Separation and purification of alkali lignin by acid precipitation: adding the supernatant after vacuum rotary evaporation to a hydrochloric acid solution with pH=2, and then centrifuging to obtain a precipitate. The precipitate was freeze-dried to obtain purified alkali lignin (PAL) as a solid powder.

(3) Alkylation of PAL: Dissolve PAL in dimethylformamide at a ratio of 1:20-25. Add _K2CO3 equivalent to 0.6-08 times the mass of purified alkali lignin to the above mixed solution as an acid binder to absorb the acid generated in the _reaction , and add a trace amount of KI as 1,6-dibromohexane the activator. Under nitrogen protection, heat the above mixture to the specified temperature (60-90°C), add 1,6-dibromohexane, keep the temperature for 1-4 hours, and then add 2mol/L hydrochloric acid aqueous solution to end the reaction.

(4) Acid analysis of CAL: Precipitate the reacted alkali lignin with aqueous hydrochloric acid (pH=2). The precipitate was obtained by centrifugation, washed with aqueous hydrochloric acid (pH=2), and freeze-dried to obtain a solid powder, which was molecularly regulated alkali lignin (CAL).

Specifically include the following steps:

(1) Add dry crude alkali lignin into acidic dioxane aqueous solution (dioxane/water=9:1, v:v, pH=2). The mixture was stirred at 87-90°C for 2-2.5 hours, and then centrifuged to remove the precipitate. The supernatant to which sodium bicarbonate was added was kept stirring for 3-4 hours to neutralize the acid in the solution. After centrifuging again to remove the precipitate, the supernatant was rotovapped under vacuum at 55 °C to remove and recover dioxane.

(2) Add the supernatant after the vacuum rotary evaporation in the step (1) to the hydrochloric acid solution with pH=2, and then centrifuge to obtain the precipitate. The precipitate was freeze-dried to obtain purified alkali lignin (PAL) as a solid powder.

(3) Dissolve PAL in step (2) in dimethylformamide at a ratio of 1:20. Add _K2CO3 equivalent to 0.6-08 times the mass of purified alkali lignin to the above mixed solution as an acid binder to absorb the acid generated in the _reaction , and add a trace amount of KI as 1,6-dibromohexane the activator. Under nitrogen protection, heat the above mixture to the specified temperature (60-90°C), add 1,6-dibromohexane, keep the temperature for reaction for 1-4 hours, then add 2mol/L hydrochloric acid aqueous solution to end the reaction.

(4) Precipitating the reacted alkali lignin from the mixture in step (3) with aqueous hydrochloric acid (pH=2). The precipitate was obtained by centrifugation, washed with aqueous hydrochloric acid (pH=2), and freeze-dried to obtain a solid powder, which was molecularly regulated alkali lignin (CAL).

The present invention will be described in further detail below in conjunction with specific examples. It should be pointed out that the specific examples are to explain rather than limit the present invention.

Example 1: Molecular regulation of alkali lignin in the pulp and paper industry, prepared through the following steps.

(1) Organic solvent purification of crude alkali lignin: add acidic dioxane aqueous solution (dioxane/water=9:1, v:v, pH=2). The mixture was stirred at 87°C for 2 hours, then centrifuged to remove the precipitate. The supernatant to which sodium bicarbonate was added was kept stirring for 3 hours to neutralize the acid in the solution. After centrifuging again to remove the precipitate, the supernatant was rotovapped under vacuum at 55 °C to remove and recover dioxane.

(2) Separation and purification of alkali lignin by acid precipitation: the supernatant after vacuum rotary evaporation was added to 2000 mL of hydrochloric acid solution (pH=2), and then centrifuged to obtain a precipitate. The precipitate was freeze-dried to obtain purified alkali lignin (PAL) as a solid powder.

(3) Alkylation of PAL: Dissolve PAL in dimethylformamide at a ratio of 1:20. Add _K2CO3 equivalent to 0.6 times the mass of purified alkali lignin to the above mixture as an acid binder to absorb the acid produced in the _reaction , and add a trace amount of KI as an activation of 1,6-dibromohexane agent. Under the protection of nitrogen, after heating the above mixture to 70°C, add 1,6-dibromohexane according to 0.05g/g _lignin , keep the temperature for 4 hours, and then add 2mol/L hydrochloric acid aqueous solution to end the reaction.

(4) Acid analysis of CAL: Precipitate the reacted alkali lignin with aqueous hydrochloric acid (pH=2). The precipitate was obtained by centrifugation, washed with aqueous hydrochloric acid (pH=2), and freeze-dried to obtain a solid powdery substance, which is molecularly regulated alkali lignin (CAL). The changes in the molecular weight and phenolic hydroxyl content of the obtained CAL are shown in Table 1, and the color changes are shown in Figure 1.

Table 1 Changes of alkali lignin molecular weight and phenolic hydroxyl content before and after regulation

Example 2: Molecular regulation of alkali lignin in the pulp and paper industry, prepared through the following steps.

(1) Organic solvent purification of crude alkali lignin: add acidic dioxane aqueous solution (dioxane/water=9:1, v:v, pH=2). The mixture was stirred at 87°C for 2 hours, then centrifuged to remove the precipitate. The supernatant to which sodium bicarbonate was added was kept stirring for 3 hours to neutralize the acid in the solution. After centrifuging again to remove the precipitate, the supernatant was rotovapped under vacuum at 55 °C to remove and recover dioxane.

(2) Separation and purification of alkali lignin by acid precipitation: the supernatant after vacuum rotary evaporation was added to 2000 mL of hydrochloric acid solution (pH=2), and then centrifuged to obtain a precipitate. The precipitate was freeze-dried to obtain purified alkali lignin (PAL) as a solid powder.

(3) Alkylation of PAL: Dissolve PAL in dimethylformamide at a ratio of 1:20. Add _K2CO3 equivalent to 0.6 times the mass of purified alkali lignin to the above mixture as an acid binder to absorb the acid produced in the _reaction , and add a trace amount of KI as an activation of 1,6-dibromohexane agent. Under the protection of nitrogen, after heating the above mixture to 70°C, add 1,6-dibromohexane according to 0.60 g/g _lignin , keep the temperature for 4 hours, and then add 2 mol/L hydrochloric acid aqueous solution to end the reaction.

(4) Acid analysis of CAL: Precipitate the reacted alkali lignin with aqueous hydrochloric acid (pH=2). The precipitate was obtained by centrifugation, washed with aqueous hydrochloric acid (pH=2), and freeze-dried to obtain a solid powdery substance, which is molecularly regulated alkali lignin (CAL). The changes in the molecular weight and phenolic hydroxyl content of the obtained CAL are shown in Table 2, and the color changes are shown in Figure 2.

Table 2 Changes of alkali lignin molecular weight and phenolic hydroxyl content before and after regulation

Example 3: Molecular regulation of alkali lignin in the pulp and paper industry, prepared through the following steps.

(1) Organic solvent purification of crude alkali lignin: add acidic dioxane aqueous solution (dioxane/water=9:1, v:v, pH=2). The mixture was stirred at 87°C for 2 hours, then centrifuged to remove the precipitate. The supernatant to which sodium bicarbonate was added was kept stirring for 3 hours to neutralize the acid in the solution. After centrifuging again to remove the precipitate, the supernatant was rotovapped under vacuum at 55 °C to remove and recover dioxane.

(2) Separation and purification of alkali lignin by acid precipitation: the supernatant after vacuum rotary evaporation was added to 2000 mL of hydrochloric acid solution (pH=2), and then centrifuged to obtain a precipitate. The precipitate was freeze-dried to obtain purified alkali lignin (PAL) as a solid powder.

(3) Alkylation of PAL: Dissolve PAL in dimethylformamide at a ratio of 1:20. Add _K2CO3 equivalent to 0.6 times the mass of purified alkali lignin to the above mixture as an acid binder to absorb the acid produced in the _reaction , and add a trace amount of KI as an activation of 1,6-dibromohexane agent. Under the protection of nitrogen, after heating the above mixture to 70°C, add 1,6-dibromohexane according to 0.60 g/g _lignin , keep the temperature for 1 hour, and then add 2 mol/L hydrochloric acid aqueous solution to end the reaction.

(4) Acid analysis of CAL: Precipitate the reacted alkali lignin with aqueous hydrochloric acid (pH=2). The precipitate was obtained by centrifugation, washed with aqueous hydrochloric acid (pH=2), and freeze-dried to obtain a solid powdery substance, which is molecularly regulated alkali lignin (CAL). The changes in the molecular weight and phenolic hydroxyl content of the obtained CAL are shown in Table 3, and the color changes are shown in Figure 3.

Table 3 Changes in molecular weight and phenolic hydroxyl content of alkali lignin before and after regulation

Example 4: Molecular regulation of alkali lignin in the pulp and paper industry, prepared through the following steps.

(1) Organic solvent purification of crude alkali lignin: add acidic dioxane aqueous solution (dioxane/water=9:1, v:v, pH=2). The mixture was stirred at 87°C for 2 hours, then centrifuged to remove the precipitate. The supernatant to which sodium bicarbonate was added was kept stirring for 3 hours to neutralize the acid in the solution. After centrifuging again to remove the precipitate, the supernatant was rotovapped under vacuum at 55 °C to remove and recover dioxane.

(2) Separation and purification of alkali lignin by acid precipitation: the supernatant after vacuum rotary evaporation was added to 2000 mL of hydrochloric acid solution (pH=2), and then centrifuged to obtain a precipitate. The precipitate was freeze-dried to obtain purified alkali lignin (PAL) as a solid powder.

(3) Alkylation of PAL: Dissolve PAL in dimethylformamide at a ratio of 1:20. Add _K2CO3 equivalent to 0.6 times the mass of purified alkali lignin to the above mixture as an acid binder to absorb the acid produced in the _reaction , and add a trace amount of KI as an activation of 1,6-dibromohexane agent. Under the protection of nitrogen, after heating the above mixture to 90°C, add 1,6-dibromohexane according to 0.30 g/g _lignin , keep the temperature for 4 hours, and then add 2 mol/L hydrochloric acid aqueous solution to end the reaction.

(4) Acid analysis of CAL: Precipitate the reacted alkali lignin with aqueous hydrochloric acid (pH=2). The precipitate was obtained by centrifugation, washed with aqueous hydrochloric acid (pH=2), and freeze-dried to obtain a solid powdery substance, which is molecularly regulated alkali lignin (CAL). The molecular weight and phenolic hydroxyl content changes of the obtained CAL are shown in Table 4, and the color changes are shown in Figure 4.

Table 4 Changes in molecular weight and phenolic hydroxyl content of alkali lignin before and after regulation

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or part of them may be equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. A regulation and control method of industrial alkali lignin molecule, is characterized in that, comprises: Purify industrial alkali lignin to obtain purified alkali lignin; Alkylation reaction of purified alkali lignin in 1,6-dibromohexane/dimethylformamide/potassium carbonate system to obtain molecularly regulated alkali lignin; The purification includes: organic solvent purification and acid precipitation purification; Add a trace amount of KI as an activator for 1,6-dibromohexane; The specific steps of the alkylation reaction are: dissolving the purified alkali lignin in dimethylformamide to obtain a mixed solution; adding K ₂ CO ₃ to the mixed solution as an acid binder, and adding a trace amount of KI as Activator of 1,6-dibromohexane; under the protection of nitrogen, after heating the above mixture to 60-90°C, add 1,6-dibromohexane, keep the temperature for 1-4 hours, then add hydrochloric acid aqueous solution to end reaction; precipitation with hydrochloric acid aqueous solution; the precipitate is washed with hydrochloric acid aqueous solution, and freeze-dried to obtain a solid powdery substance, which is the molecularly regulated alkali lignin. 2. the regulation and control method of industrial alkali lignin molecule as claimed in claim 1, is characterized in that, the concrete step of organic solvent purification is: the concrete step of described organic solvent purification process is: add dry alkali lignin into acidic dihydrogen In the oxane aqueous solution, stir the mixture at 87-90°C for 2-2.5 hours, then centrifuge to remove the precipitate; add sodium bicarbonate to the supernatant and keep stirring for 3-4 hours to neutralize the acid in the solution; centrifuge again to remove the precipitate Afterwards, the supernatant was rotovapped in vacuo to remove and recover dioxane. 3. The regulation method of industrial alkali lignin molecule as claimed in claim 1, is characterized in that, the concrete step of described acid precipitation is: the supernatant that obtains after organic solvent purification is added in the hydrochloric acid solution of pH=2 , and then centrifuged to obtain a precipitate; the precipitate was freeze-dried to obtain solid powder purified alkali lignin. 4. The regulation method of industrial alkali lignin molecules as claimed in claim 1, characterized in that the volume ratio of purified alkali lignin to dimethylformamide is 1:20-25. 5. The method for regulating industrial alkali lignin molecules according to claim 1, characterized in that the mass ratio of purified alkali lignin to K ₂ CO ₃ is 1:0.6-0.8. 6. The molecularly regulated alkali lignin prepared by the method according to any one of claims 1-5. 7. the described alkali lignin of claim 6 is prepared resin material, functional macromolecule material through molecular control, and oil exploitation, building concrete water reduction, printing and dyeing dye dispersion, pesticide slow-release dispersion, fertilizer slow-release field application.

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