阅读说明：本技术 利用溶解浆预蒸煮废液制备木质素磺酸盐的方法和应用 (Method for preparing lignosulfonate by using dissolving pulp precooking waste liquid and application ) 是由 施晓旦 赵吉 金霞朝 于 2020-07-02 设计创作，主要内容包括：本发明公开了一种利用溶解浆预蒸煮废液制备木质素磺酸盐的方法和应用。该方法包括如下步骤：(1)在pH值为9～11的条件下,溶解浆预蒸煮废液经过滤,收集滤液为物料A；物料A的固含量为5％～7％；(2)物料A经超滤膜处理,得浓缩液和滤液,收集浓缩液为物料B,物料B的固含量为10％～15％,超滤膜处理的温度为至少50℃；(3)物料B经氧化反应,制得物料C；(4)物料C与甲醛进行缩聚反应,制得物料D；(5)物料D经磺化反应,制得木质素磺酸盐。采用膜法直接提取溶解浆预蒸煮废液中的木质素,并进行磺化,大幅减少了木质素提取过程中废水、废气的产生,提高了溶解浆预蒸煮废液的利用率。(The invention discloses a method for preparing lignosulfonate by using dissolving pulp precooking waste liquid and application. The method comprises the following steps: (1) filtering the pre-cooking waste liquid of the dissolving pulp under the condition that the pH value is 9-11, and collecting filtrate as a material A; the solid content of the material A is 5-7 percent; (2) treating the material A with an ultrafiltration membrane to obtain a concentrated solution and a filtrate, collecting the concentrated solution as a material B, wherein the solid content of the material B is 10-15%, and the temperature of ultrafiltration membrane treatment is at least 50 ℃; (3) carrying out oxidation reaction on the material B to obtain a material C; (4) performing polycondensation reaction on the material C and formaldehyde to obtain a material D; (5) and (3) carrying out sulfonation reaction on the material D to obtain lignosulfonate. The method adopts a membrane method to directly extract the lignin in the dissolving pulp pre-cooking waste liquid and carries out sulfonation, thereby greatly reducing the generation of waste water and waste gas in the lignin extraction process and improving the utilization rate of the dissolving pulp pre-cooking waste liquid.)

1. A method for preparing lignosulfonate by using dissolving pulp precooking waste liquid is characterized by comprising the following steps of:

(1) Filtering the pre-cooking waste liquid of the dissolving pulp under the condition that the pH value is 9-11, and collecting filtrate as a material A; the solid content of the material A is 5-7%;

(2) treating the material A with an ultrafiltration membrane to obtain a concentrated solution and a filtrate, collecting the concentrated solution as a material B, wherein the solid content of the material B is 10-15%, and the temperature of ultrafiltration membrane treatment is at least 50 ℃;

(3) carrying out oxidation reaction on the material B to obtain a material C;

(4) performing polycondensation reaction on the material C and formaldehyde to obtain a material D;

(5) and carrying out sulfonation reaction on the material D to prepare the lignosulfonate.

2. The method for preparing lignosulfonate using dissolving pulp precooking waste liquor in accordance with claim 1, wherein in the step (1), the method for preparing dissolving pulp precooking waste liquor comprises the following steps: cooking the wood in water at the temperature of 160-170 ℃, wherein the cooking time is 0.5-1.5 h; the wood is preferably one or more of eucalyptus, poplar and pine, more preferably eucalyptus;

and/or in the step (1), adjusting the pH value of the system to 9-11 by adopting an alkaline substance; wherein, the alkaline substance is preferably 30 to 35 percent by mass of sodium hydroxide aqueous solution, more preferably 32 percent by mass of sodium hydroxide aqueous solution;

And/or in the step (1), the pH value is 10-11;

and/or, in the step (1), the solid content of the dissolving pulp pre-cooking waste liquid is 5-7%, preferably 6-7%;

and/or in the step (1), the density of the dissolving pulp pre-cooking waste liquid is 1.01-1.04 g/mL, preferably 1.02-1.04 g/mL;

and/or in the step (1), the pH value of the dissolving pulp pre-cooking waste liquid is 3.5-5.5, preferably 4.5-5.5;

and/or, in the step (1), the dissolving pulp pre-cooking waste liquor comprises lignin and hemicellulose; wherein, the mass percentage of the lignin in the solid matters in the dissolving pulp pre-cooking waste liquid is preferably 20-28%, more preferably 24-28%; the mass percentage of the hemicellulose to the solid matters in the dissolving pulp pre-cooking waste liquid is preferably 35-45%, and more preferably 40-45%.

3. The method for preparing lignosulfonate from dissolving pulp precooking waste liquor according to claim 1, wherein in the step (1), the aperture of the filtering membrane for filtration is 5-20 μm, preferably 10-20 μm;

and/or, in step (1), the filtration is carried out in a filter, preferably a 325 mesh stainless steel mesh filter;

And/or, in the step (1), the temperature of the filtration is at least 60 ℃, preferably 60-70 ℃, and more preferably 65-70 ℃.

4. The method for preparing lignosulfonate from dissolving pulp precooking waste liquid according to claim 1, wherein in the step (2), an ultrafiltration membrane used for ultrafiltration membrane treatment has a molecular weight cutoff of 1000-3000, preferably 2000-3000;

and/or in the step (2), the temperature of ultrafiltration membrane treatment is 50-70 ℃, preferably 60-70 ℃;

and/or in the step (2), the membrane inlet pressure of the ultrafiltration membrane treatment is 10-50 bar, preferably 15-45 bar, and more preferably 25-45 bar;

and/or in the step (2), the solid content of the material B is 13-15%;

and/or in the step (2), the density of the material B is 1.03-1.08 g/mL, preferably 1.05-1.08 g/mL;

and/or in the step (2), the mass percentage of the lignin in the material B in the solid matter of the material B is 50-65%, preferably 58-64%.

5. The method for preparing lignosulfonate using dissolving pulp precooking waste liquor according to claim 1, wherein in the step (3), the oxidizing agent in the oxidation reaction is aqueous hydrogen peroxide; the concentration of the aqueous hydrogen peroxide solution is preferably 30 wt%; the mass percentage of the oxidant in the lignin in the material B is preferably 10-30%, more preferably 20-30%;

And/or, in the step (3), the temperature of the oxidation reaction is 50-75 ℃, preferably 65-75 ℃;

and/or, in the step (3), the time of the oxidation reaction is 30 to 100min, preferably 45 to 100min, and more preferably 70 to 100 min.

6. The method for preparing lignosulfonate using dissolving pulp precooking waste liquor according to claim 1, wherein in the step (3), the oxidation reaction further comprises a concentration treatment; the mass percentage of lignin in the concentrated material in the solid content of the concentrated material is preferably 25-30%.

7. The method for preparing lignosulfonate from dissolving pulp precooking waste liquor according to claim 1, wherein in the step (4), the formaldehyde accounts for 10-50% of the lignin in the material C, preferably 15-45%, and more preferably 25-45%;

and/or, in the step (4), the formaldehyde is added in the form of a formaldehyde aqueous solution, wherein the mass percentage of the formaldehyde in the formaldehyde aqueous solution is 37%;

and/or, in the step (4), the temperature of the polycondensation reaction is 50-75 ℃, preferably 55-75 ℃, and more preferably 65-75 ℃;

And/or, in the step (4), the time of the polycondensation reaction is 30 to 100min, preferably 45 to 100min, and more preferably 70 to 100 min.

8. The method for preparing lignosulfonate using dissolving pulp precooking waste liquor according to claim 1, wherein in the step (5), the sulfonating agent for sulfonation is one or more of sulfur dioxide, sodium sulfite and sodium bisulfite, preferably sulfur dioxide; the mass percentage of the sulfonation reagent in the lignin in the material D is preferably 10% to 50%, more preferably 15% to 45%, and still more preferably 25% to 45%;

and/or, in the step (5), the temperature of the sulfonation reaction is 80-100 ℃, preferably 85-100 ℃, and more preferably 95 ℃;

and/or, in the step (5), the sulfonation reaction time is 60-150 min, preferably 90-150 min.

9. The method for preparing lignosulfonate by using the pre-cooking waste liquid of dissolving pulp according to any one of claims 1 to 8, wherein in the step (5), the sulfonation reaction further comprises a drying treatment to prepare lignosulfonate powder;

preferably, the particle size of the lignosulfonate powder is 50-80 meshes;

Preferably, the drying process is carried out in a centrifugal spray dryer;

when a centrifugal spray dryer is adopted for drying treatment, the temperature of a steam inlet is 200-240 ℃, preferably 220-235 ℃;

when a centrifugal spray dryer is used for the drying treatment, the outlet temperature is 90 to 120 ℃, preferably 105 to 115 ℃.

10. Use of lignosulfonate as a dispersant in the field of dyes, characterized in that it is prepared according to the method for the preparation of lignosulfonate as claimed in any one of claims 1 to 9.

Technical Field

The invention relates to a method for preparing lignosulfonate by using dissolving pulp precooking waste liquid and application.

Background

Dissolving pulp pulping is one of the newly emerging pulping methods in recent years, and is characterized in that a front-stage pre-cooking process is added on the basis of the original sulfate pulping process, hemicellulose and lignin in raw materials are further removed, cellulose with higher purity is obtained, the cellulose is used for producing viscose fibers, a large amount of hemicellulose sugar and more lignin are removed in the pre-cooking process under the high-temperature action of steam or water, the solid content of feed liquid is low, the heat value is low, a large amount of steam is consumed for concentration during combustion, the heat value of the feed liquid is low, the feed liquid is not easy to combust, the load of an alkali furnace is increased, the COD of the feed liquid is over ten thousand, a waste water system is difficult to bear, and the existing method is only combustion treatment. Lignin and hemicellulose sugar in the waste liquid are not utilized better.

The lignin is the main component of the waste liquid generated in the pre-cooking process in the dissolving pulp pulping process and accounts for about 20-30% of the solid content. Lignin is a substance produced by polymerization of aromatic alcohol, is present in woody tissues and mainly functions to harden cell walls, which are the main component of secondary walls, by forming a network of cross-links. The lignin is mainly located between cellulose fibers and plays a role in supporting and resisting pressure. In woody plants, lignin accounts for about 20% to 25%, the second most abundant natural macromolecule in nature. The lignin is non-toxic, has excellent universality in performance and has wide application in industry. In addition, the lignin structure contains various groups, is easy to generate chemical reaction for modification, and can be used for producing various chemical materials, such as a dispersing agent, a cement water reducing agent and the like. The lignin as a degradable environment-friendly material can well replace some non-degradable materials, and has important significance for environmental protection.

At present, a plurality of pulping and papermaking enterprises in China adopt a dissolving pulp pulping process, a large amount of pre-cooking waste liquid generated every year is not well utilized, hundreds of thousands of tons of dissolving pulp exist in the solar paper industry, the Juntai paper industry and the Qingshan paper industry, nearly millions of tons of dissolving pulp pre-cooking waste liquid exist, at present, the dissolving pulp pre-cooking waste liquid is rarely utilized in the pulping and papermaking industry, and most of the dissolving pulp pre-cooking waste liquid is not utilized and can only be used for combustion. Chinese patent application 201711336163.7 provides a method for preparing lignosulfonate from pre-cooked waste liquor of dissolving pulp, which can also prepare lignosulfonate with better performance, but the preparation method has higher cost and lower yield.

Therefore, there is a need in the art to develop a utilization approach of the pre-digestion waste liquid of dissolving pulp, so as to realize efficient utilization of the pre-digestion waste liquid of dissolving pulp and realize high-value utilization of resources.

Disclosure of Invention

The invention aims to overcome the defects that the prior art adopts a combustion mode to treat the dissolving pulp pre-cooking waste liquid, not only pollutes the environment, but also reduces the utilization rate of the dissolving pulp pre-cooking waste liquid and the like, and provides a method for preparing lignosulfonate by using the dissolving pulp pre-cooking waste liquid and application thereof. The method directly extracts the lignin in the dissolving pulp pre-cooking waste liquid by adopting a membrane method, carries out sulfonation, does not need to extract the lignin by black liquor acidification, greatly reduces the generation of waste water and waste gas in the lignin extraction process, and improves the utilization rate of the dissolving pulp pre-cooking waste liquid.

The raw materials dissolving pulp precooking waste liquid that this application used is for adopting the waste liquid that the pulping process of dissolving pulp precooking produced, because of its self poor stability, the content of lignin is less relatively in the dissolving pulp precooking waste liquid, and the content of carbohydrate is higher, and the separation degree of difficulty that leads to carbohydrate and lignin is big, has increased the degree of difficulty of its development. Therefore, the waste is generally treated by combustion in the field, and is rarely reused. The two substances can be effectively separated through creative labor, and the cost is reduced; the prepared lignosulfonate has high yield, good heat resistance and good dispersibility.

In order to achieve the purpose, the invention provides the following technical scheme:

the invention provides a method for preparing lignosulfonate by using dissolving pulp precooking waste liquid, which comprises the following steps of:

(1) filtering the pre-cooking waste liquid of the dissolving pulp under the condition that the pH value is 9-11, and collecting filtrate as a material A; the solid content of the material A is 5-7%;

(2) treating the material A with an ultrafiltration membrane to obtain a concentrated solution and a filtrate, collecting the concentrated solution as a material B, wherein the solid content of the material B is 10-15%, and the temperature of ultrafiltration membrane treatment is at least 50 ℃;

(3) Carrying out oxidation reaction on the material B to obtain a material C;

(4) performing polycondensation reaction on the material C and formaldehyde to obtain a material D;

(5) and carrying out sulfonation reaction on the material D to prepare the lignosulfonate.

In the step (1), the preparation method of the dissolving pulp pre-cooking waste liquid can be that wood is cooked in water with the temperature of 160-170 ℃, and the cooking time is 0.5-1.5 h.

Wherein the wood may be hardwood, preferably one or more of eucalyptus, poplar and pine, conventionally used in the preparation of precooking liquor in the art.

In the step (1), the aperture of the filter membrane for filtration may be 5-20 μm, preferably 10-20 μm.

In the step (1), the condition and the method for adjusting the pH value of the system to 9-11 can be conventional in the field, and an alkaline substance is generally adopted for adjustment.

The alkaline substance can be an alkaline substance conventionally used in the operation in the field, and is preferably a 30-35% by weight aqueous solution of sodium hydroxide, for example, a 32% by weight aqueous solution of sodium hydroxide. The mass percent is the mass percent of sodium hydroxide in the aqueous sodium hydroxide solution that is conventionally considered in the art to be sodium hydroxide in the aqueous sodium hydroxide solution.

In the step (1), the pH value is preferably 10 to 11.

In the step (1), the solid content of the dissolving pulp pre-cooking waste liquid can be the solid content of the substances in the field, generally 5-7%, preferably 6-7%.

In the step (1), the density of the pre-cooking waste liquid of the dissolving pulp can be the conventional density of the substances in the field, and generally can be 1.01-1.04 g/mL, and preferably 1.02-1.04 g/mL.

In the step (1), the pH of the pre-digestion waste liquid of the dissolving pulp can be the conventional pH of the substances in the field, and generally can be 3.5 to 5.5, and preferably 4.5 to 5.5.

In step (1), the dissolving pulp pre-cooking waste liquor can be waste liquor generated in the pre-cooking process of the dissolving pulp pulping method in the field, and generally comprises lignin and hemicellulose.

The mass percentage of the lignin in the solid content of the dissolving pulp pre-cooking waste liquid can be conventional in the art, and is preferably 20-28%, and more preferably 24-28%. The solids in the art are the remaining material of the dissolving pulp pre-cooked waste liquor after drying.

The mass percentage of the hemicellulose to the solid matters in the dissolving pulp pre-cooking waste liquid can be conventional in the field, and is preferably 35-45%, and more preferably 40-45%.

In step (1), the filtration is generally carried out in a filter, preferably a 325 mesh stainless steel mesh filter. The purpose of the filtration is to remove wood chips and particulate impurities from the dissolving pulp precooking waste liquor.

In the step (1), the temperature of the filtration may be at least 60 ℃, preferably 60 to 70 ℃, and more preferably 65 to 70 ℃.

In the step (2), the ultrafiltration membrane used for the ultrafiltration membrane treatment has a cut-off molecular weight of 1000 to 3000, preferably 2000 to 3000.

In the step (2), the temperature of the ultrafiltration membrane treatment is preferably 50 to 70 ℃, more preferably 60 to 70 ℃.

In the step (2), the membrane feeding pressure of the ultrafiltration membrane treatment may be the membrane feeding pressure conventional in the operation in the field, preferably 10 to 50bar, more preferably 15 to 45bar, and further more preferably 25 to 45 bar.

In the step (2), the solid content of the material B is preferably 13-15%. In the art, the solid content is the mass percentage of the solid content of the material B in the material B.

In the step (2), the density of the material B can be conventional in the art, and is preferably 1.03-1.08 g/mL, more preferably 1.05-1.08 g/mL.

In the step (2), the mass percentage of the lignin in the material B in the solid matter of the material B may be 50% to 65%, and preferably 58% to 64%.

In step (3), the oxidizing agent in the oxidation reaction may be an oxidizing agent conventional in the art, and is preferably an aqueous hydrogen peroxide solution.

The concentration of the aqueous hydrogen peroxide solution may be, among others, the concentration conventionally used in such operations in the art, and is preferably 30% by weight.

The mass percentage of the oxidant in the lignin in the material B may be conventional in the art, and is preferably 10% to 30%, and more preferably 20% to 30%.

In the step (3), the temperature of the oxidation reaction may be a temperature conventionally used in the operation in the field, preferably 50 to 75 ℃, and more preferably 65 to 75 ℃.

In the step (3), the time of the oxidation reaction may be a time conventionally used in the operation in the field, and is preferably 30 to 100min, more preferably 45 to 100min, and further more preferably 70 to 100 min.

In the step (3), the oxidation reaction may further include a concentration treatment.

The conditions and methods of the concentration treatment may be those conventional in such operations in the art. The mass percentage of lignin in the concentrated material in the solid matter of the concentrated material is 25-30%.

The concentration process is typically carried out in a triple effect evaporator.

In the step (4), the mass percentage of the formaldehyde in the lignin in the material C may be conventional in the field, preferably 10% to 50%, more preferably 15% to 45%, and still more preferably 25% to 45%. The purpose of the polycondensation reaction is to increase the molecular weight of the lignin.

In the step (4), the formaldehyde is generally added in the form of an aqueous formaldehyde solution, and the mass percentage of the formaldehyde in the aqueous formaldehyde solution can be 37%.

In step (4), the temperature of the polycondensation reaction may be a temperature conventionally used in the art, preferably 50 to 75 ℃, more preferably 55 to 75 ℃, and still more preferably 65 to 75 ℃.

In the step (4), the time of the polycondensation reaction may be a time conventionally used in the art, and is preferably 30 to 100min, more preferably 45 to 100min, and further more preferably 70 to 100 min.

In step (5), the sulfonation reagent of the sulfonation reaction may be a sulfonation reagent conventionally used in such operations in the art, preferably one or more of sulfur dioxide, sodium sulfite and sodium bisulfite, and more preferably sulfur dioxide.

The mass percentage of the sulfonation reagent in the lignin in the material D may be the same as the operation routine in the field, and is preferably 10% to 50%, more preferably 15% to 45%, and further more preferably 25% to 45%.

In the step (5), the temperature of the sulfonation reaction may be a temperature that is conventional in the art, preferably 80 to 100 ℃, more preferably 85 to 100 ℃, for example 95 ℃.

In the step (5), the sulfonation reaction time may be a time conventionally used in the art, and is preferably 60 to 150min, and more preferably 90 to 150 min.

In the step (5), drying treatment can be further performed after the sulfonation reaction, so as to obtain lignosulfonate powder.

The conditions and methods of the drying treatment may be those conventional in the art, and are typically carried out in a centrifugal spray dryer.

When a centrifugal spray dryer is used for the drying process, the steam inlet temperature may be as conventional in such operations in the art, preferably 200 to 240 ℃, more preferably 220 to 235 ℃.

When a centrifugal spray dryer is used for the drying process, the outlet temperature is the temperature conventionally used in such operations in the art, preferably 90 to 120 ℃, more preferably 105 to 115 ℃.

The particle size of the lignosulfonate powder can be 50-80 meshes.

The invention also provides application of lignosulfonate as a dispersant in the field of dyes, wherein the lignosulfonate is prepared by the preparation method of the lignosulfonate.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows: directly extracting lignin in the pre-cooking waste liquor of the dissolving pulp by adopting an ultrafiltration membrane treatment method, and sulfonating; the lignin is extracted without performing black liquor acidification, so that the generation of waste water and waste gas in the lignin extraction process is greatly reduced; the treatment process greatly reduces the wastewater discharge, produces lignosulfonate with high added value, reduces the discharge of the pre-cooking waste liquid of dissolving pulp, and realizes the classified high-value utilization of resources.

Drawings

FIG. 1 is an infrared absorption spectrum of sodium lignosulfonate made in example.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

In the following examples, the content of lignin in the material B was measured by the Clarsen method. The Clarsen method is that a sample to be detected is treated by a sulfuric acid aqueous solution with the mass percent of 50%, water is added, the pH value of the system is reduced to 1-3, boiling is carried out, solid-liquid separation is carried out by adopting a vacuum filtration method, and solids are collected and dried. The mass percentage of the lignin is equal to the mass of the dried insoluble substances/the mass of the oven-dried sample of the product to be detected multiplied by 100 percent.

In the following examples and comparative examples, the method for preparing the spent dissolving pulp precooking liquor used specifically comprises the following steps: pre-cooking the eucalyptus wood by adopting high-temperature water with the temperature of 160 ℃, wherein the cooking time is 1.5h, and the pre-cooking waste liquid of the dissolving pulp is obtained.