WO2021190110A1

WO2021190110A1 - Method for preparing microcrystalline cellulose by treating poplar wood powder with deep eutectic solvent combined with acid

Info

Publication number: WO2021190110A1
Application number: PCT/CN2021/072455
Authority: WO
Inventors: 杨桂花; 颜家强; 张凯; 陈嘉川
Original assignee: 齐鲁工业大学
Priority date: 2020-03-25
Filing date: 2021-01-18
Publication date: 2021-09-30
Also published as: CN111187356A

Abstract

Provided is a method for preparing a microcrystalline cellulose by treating a poplar wood powder with a deep eutectic solvent combined with an acid, the method involving: mixing the poplar wood powder, the deep eutectic solvent and the acid, then heating same to 150-200°C for a reaction, and filtering the reacted material to obtain the microcrystalline cellulose, wherein the deep eutectic solvent is prepared from choline chloride, polyethylene glycol and 1,4-butanediol as raw materials; and the addition amount of the acid is 20-35% of the mass of the poplar wood powder. In the present invention, by means of the treatment of the poplar wood powder with the deep eutectic solvent system containing a small amount of the acid, processes such as bleaching and acidolysis of crude cellulose can be omitted, thereby resulting in simple operation steps, and further leading to less corrosion of the equipment and a safe working environment.

Description

Method for preparing microcrystalline cellulose by treating poplar wood powder with eutectic solvent and acid

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on March 25, 2020, the application number is 202010217765.6, and the invention title is "Method for preparing microcrystalline cellulose by treating poplar wood powder with eutectic solvent synergistic acid" , Its entire content is incorporated into this application by reference.

Technical field

The invention belongs to the technical field of preparation and application of microcrystalline cellulose, and relates to a method for preparing microcrystalline cellulose by using a eutectic solvent to synergize acid processing poplar wood powder.

Background technique

Disclosure of the background information is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an acknowledgement or any form of suggestion that the information constitutes the prior art known to those of ordinary skill in the art.

Microcrystalline cellulose is a white powdery substance that is hydrolyzed to a limit degree of polymerization from natural cellulose after chemical or biological treatment. It has a high degree of crystallinity. The particle size range is usually 20～80μm, and the limit degree of polymerization is 15～ 375, is another form of multifunctional polymer material of cellulose. Microcrystalline cellulose is mainly composed of cellulose-based organic matter (about 99.95%) and microcrystalline inorganic matter (about 0.05%). Its raw materials are mainly wood with high cellulose content and some non-wood plants. Fiber raw materials, such as cotton and crop stalks. Microcrystalline cellulose not only has the characteristics of good thermal stability, low degree of polymerization, high modulus and strong fluidity, but also has the advantages of good hydrophilicity, green pollution-free and good biocompatibility. It is used in the polyurethane industry and light chemical industry. It is widely used in industry, cosmetics industry, food industry and pharmaceutical industry.

According to the research and understanding of the inventor of the present invention, the current preparation methods of microcrystalline cellulose are mainly acid hydrolysis and enzymatic hydrolysis, among which the most commonly used is acid hydrolysis. The acids used are hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid and phosphotungsten. Sour etc. However, in the process of preparing microcrystalline cellulose by acid hydrolysis, there will be concentrated acid corrosion equipment, waste liquid is difficult to handle, a large amount of residual acid and impurities in the reaction system, the resulting product needs to be washed many times, the water consumption is huge, and the preparation process is cumbersome. And other shortcomings. Enzymatic hydrolysis is a new method for preparing microcrystalline cellulose. At present, microcrystalline cellulose is mainly prepared by cellulase. The endoglucose enzyme in cellulase can randomly hydrolyze and cut the cellulose molecular chain in the amorphous region. A large number of crystalline cellulose molecules are formed, and the cellulose is hydrolyzed to the limit of polymerization to form microcrystalline cellulose. Compared with the acid hydrolysis method for preparing microcrystalline cellulose, the biological enzymatic method has the advantages of mild process conditions, less chemical dosage, green and non-toxic. However, the preparation of microcrystalline cellulose by biological enzymatic method also has some disadvantages: for example, the cellulose crystallinity is low, the preparation cost is high, the reaction conditions are relatively harsh, and the enzymolysis temperature, enzymolysis substrate, enzymolysis time and solution pH are all set. Requirements. If the reaction conditions are too weak and the biological enzyme activity is too low, it may not be able to completely hydrolyze the amorphous area; if the reaction conditions are too strong, it may cause the biological enzymes to lose activity or excessive enzymatic hydrolysis, which may damage the cellulose structure. In addition, whether it is acid hydrolysis or enzymatic hydrolysis, the raw materials need to be subjected to multiple acid-base treatments and bleaching in the pretreatment stage to remove lignin, hemicellulose, extracts and other substances, and the treatment process is very cumbersome. Moreover, the use of elemental chlorine bleach in the pretreatment stage will cause a certain pollution load on the environment.

Summary of the invention

In order to solve the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing microcrystalline cellulose by using a eutectic solvent and acid treatment of poplar wood powder without acid-base treatment, bleaching, etc., simplifying the preparation process, and In the preparation process, element-free chlorine bleaching agent is used to reduce the amount of acid (especially to reduce the amount of sulfuric acid), so as to solve part of the problems in the preparation of microcrystalline cellulose by acid hydrolysis.

In order to achieve the above objective, the technical solution of the present invention is:

On the one hand, a method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid. The material is filtered to obtain microcrystalline cellulose; the eutectic solvent is prepared from choline chloride, polyethylene glycol, and 1,4-butanediol as raw materials, and the added amount of the acid is the mass of poplar wood powder Of 25 to 35%.

The invention uses the hydrogen bonds formed between the components in the eutectic solvent system to reduce the activation energy required for the breaking of the ether bonds in the lignin, remove the lignin and hemicellulose components in the wood flour, and retain the wood The cellulose component in the powder, at the same time, in a eutectic system containing a small amount of acid, the non-crystalline area of cellulose is easily degraded, thereby obtaining microcrystalline cellulose. The present invention uses eutectic solvent and acid treatment to prepare microcrystalline cellulose, not only omits the steps of removing lignin, hemicellulose, etc., such as acid-base treatment and bleaching, but also uses element-free chlorine bleaching agent to reduce pollution load and reduce The amount of acid used (for example, the existing sulfuric acid hydrolysis method requires a lot more sulfuric acid than 35% of the wood flour mass).

After experiments, it was found that the eutectic solvent was prepared by using choline chloride, polyethylene glycol and 1,4-butanediol, and the eutectic solvent and a small amount of acid were used as the reaction solvent system to process poplar wood powder without acid-base treatment and Pretreatment steps such as bleaching remove lignin, hemicellulose and other substances, and only need to filter the product. The lignin and hemicellulose in the finally obtained microcrystalline cellulose are basically completely removed, and the yield of microcrystalline cellulose is relatively high.

On the other hand, a microcrystalline cellulose is obtained by the above-mentioned method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid.

The microcrystalline cellulose prepared by the invention has the characteristics of low polymerization degree, high purity, good thermal stability, excellent performance and the like.

The beneficial effects of the present invention are:

1. The present invention uses a eutectic solvent and a small amount of acid as the reaction solvent system, which not only omits processes such as bleaching and acidolysis of crude cellulose, but also reduces the amount of acid used (especially the amount of sulfuric acid), and simplifies the process flow. , The preparation process is green and environmentally friendly, and at the same time, the corrosion of the equipment to the acid is reduced.

2. The microcrystalline cellulose prepared by the invention has low polymerization degree, high purity, good thermal stability, excellent performance, and high yield of microcrystalline cellulose.

3. The eutectic solvent prepared by the present invention can be recycled and reused, so the method provided by the present invention is a green microcrystalline cellulose preparation method.

Detailed ways

It should be pointed out that the following detailed descriptions are all exemplary and are intended to provide further description of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

It should be noted that the terms used here are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and/or "including" are used in this specification, they indicate There are features, steps, operations, devices, components, and/or combinations thereof.

The eutectic solvent of the present invention is a kind of ionic liquid, a low-temperature eutectic mixture composed of hydrogen bond acceptors (such as quaternary ammonium salts) and hydrogen bond donors (such as carboxylic acids, polyols) in a certain molar ratio.

The wood powder of the present invention is obtained by pulverizing wood.

In view of the disadvantages of the existing methods for preparing microcrystalline cellulose, the process is complicated, the use of elemental chlorine-containing bleaching agent in the raw material pretreatment process causes pollution load, and the amount of acid added in the acid hydrolysis process is relatively high. Method for preparing microcrystalline cellulose by processing poplar wood powder.

A typical embodiment of the present invention provides a method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent in conjunction with an acid. After mixing poplar wood powder, a eutectic solvent and an acid, it is heated to 150～150. The reaction was carried out at 200°C, and the reacted materials were filtered to obtain microcrystalline cellulose; the eutectic solvent was prepared from choline chloride, polyethylene glycol, and 1,4-butanediol as raw materials. The added amount is 25-35% of the mass of poplar wood powder.

The invention uses the hydrogen bonds formed between the components in the eutectic solvent system to reduce the activation energy required for the breaking of the ether bonds in the lignin, remove the lignin and hemicellulose components in the wood flour, and retain the wood The cellulose component in the powder, at the same time, in a eutectic system containing a small amount of acid, the non-crystalline area of cellulose is easily degraded, thereby obtaining microcrystalline cellulose. The present invention utilizes eutectic solvent and acid treatment to prepare microcrystalline cellulose, which not only omits the steps of removing lignin, hemicellulose, etc., such as acid-base treatment and bleaching, but is also environmentally friendly and reduces the amount of acid (for example, The existing sulfuric acid hydrolysis method requires much more sulfuric acid than 35% of the wood flour mass).

Through experiments, it was found that choline chloride, polyethylene glycol and 1,4-butanediol are used as raw materials to prepare eutectic solvents. When eutectic solvents are used in synergistic acid treatment, there is no need for acid-base treatment and bleaching to remove lignin, The steps of hemicellulose and other substances only need to filter the product, and the lignin and hemicellulose in the finally obtained microcrystalline cellulose are basically completely removed, and the yield of microcrystalline cellulose is relatively high. The invention can obtain poplar wood microcrystalline cellulose with a degree of polymerization of 220-375, a purity of 97%-99%, and a particle size of less than or equal to 75 μm.

In one or more examples of this embodiment, the temperature of the reaction between poplar wood powder, eutectic solvent and acid is 155-165°C.

In one or more examples of this embodiment, the time for the reaction of poplar wood powder, eutectic solvent and acid is 4 to 8 hours. It is found through experiments that the yield of microcrystalline cellulose and the removal rate of lignin are related to the reaction time. When the reaction time is 4 to 8 hours, it can ensure that the removal rate of lignin and the yield of microcrystalline cellulose are higher.

In one or more examples of this embodiment, the acid is a sulfuric acid solution with a mass fraction of 96-99%.

In one or more examples of this embodiment, the mass ratio of poplar wood powder, eutectic solvent and acid is 1:15-25:0.25-0.35.

In one or more examples of this embodiment, the polyethylene glycol is polyethylene glycol-200.

In one or more examples of this embodiment, the mass ratio of choline chloride, polyethylene glycol, and 1,4-butanediol is 4.5 to 5.5: 15.5 to 16.5: 3.5 to 4.5.

In one or more examples of this embodiment, the preparation method of the eutectic solvent is: heating choline chloride, polyethylene glycol, and 1,4-butanediol to 65-75°C for reaction.

In one or more examples of this embodiment, the poplar wood powder has a particle size of 60-80 mesh.

In one or more examples of this embodiment, after the poplar wood powder is subjected to benzene alcohol extraction, the extracted poplar wood powder eutectic solvent is mixed and reacted with an acid.

In this series of embodiments, the volume ratio of benzene to ethanol in the benzene-alcohol extraction is 2:0.9-1.1.

The benzene alcohol extraction process described in the present invention is carried out in accordance with GB/T2677.6.

In one or more examples of this embodiment, the method of filtration is vacuum filtration.

In one or more examples of this embodiment, the filtered solid is washed.

In this series of embodiments, the washing liquid is 1,4-dioxane.

In this series of embodiments, the filtered solid is washed with 1,4-dioxane until it is colorless, and then washed with water.

In one or more examples of this embodiment, the filtered and washed solid is freeze-dried. The freeze-drying time is 22～26h, and the temperature is -55～-45℃.

Another embodiment of the present invention provides a microcrystalline cellulose obtained by the above-mentioned method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid.

In order to enable those skilled in the art to understand the technical solutions of the present invention more clearly, the technical solutions of the present invention will be described in detail below in conjunction with specific embodiments.

The analysis method used in the embodiment of the present invention is as follows:

Determination of the degree of cellulose polymerization: refer to the copper ethylenediamine-capillary viscometer method in GB/T 1548-2004 "Determination of Pulp Viscosity".

Determination of the particle size of microcrystalline cellulose: Use a particle size analyzer MASTERSIZER 3000 (Malvern PANalytical, UK) to measure the particle size of microcrystalline cellulose.

Determination of the purity of microcrystalline cellulose: The cellulose content in the product was determined by the National Renewable Energy Laboratory (NREL) method.

Yield of microcrystalline cellulose:

X ₁ —The yield of microcrystalline cellulose;

m ₁ -is the quality of microcrystalline cellulose obtained by treatment with eutectic solvent;

m ₂ -is the quality of the cellulose contained in the raw wood flour;

The remaining experimental methods that are not described in detail are conventional experimental methods in the field.

Example 1

The preparation method of microcrystalline cellulose is obtained by the following steps:

(1) Pretreatment: Take relatively uniform poplar wood chips, air-dry, crush, and then sieving to obtain wood flour of 60-80 mesh.

(2) Phenyl alcohol extraction: prepare a benzene-ethanol mixed solution with a volume ratio of 2:1, and extract the wood flour for 6-8 hours in accordance with GB/T2677.6 for step (1) wood flour, dry and constant weight.

(3) Preparation of eutectic solvent: mix choline chloride, polyethylene glycol-200 and 1,4-butanediol at a mass ratio of 5:16:4, reaction temperature is 70°C, heating and stirring time For 2h, eutectic solvent A is obtained.

(4) Treatment with eutectic solvent: Mix the absolutely dry poplar wood powder, eutectic solvent A, and 98% sulfuric acid in a mass ratio of 1:20:0.3 after benzene alcohol extraction in step (2). The reaction temperature is 160°C, and the heating and stirring time is 4h.

(5) Terminating the reaction: After the reaction, the reaction flask containing the eutectic solvent A and poplar wood powder is placed in water at room temperature for 5 minutes.

(6) Suction filtration and washing: Pour the reaction product in the cooled reaction flask into the Buchner funnel on the suction flask, and perform vacuum filtration. After all the eutectic solvent A enters the reaction flask, collect the low eutectic solvent A. Solvent A, and then wash the solid residue in the Buchner funnel with 1,4-dioxane, and then wash with deionized water after the 1,4-dioxane washing solution becomes colorless.

(7) Freeze drying: The cellulose on the Buchner funnel washed with deionized water is washed into a petri dish with deionized water, and finally the petri dish is placed in a freeze dryer. The freeze drying time is 24h and the temperature is -50°C to obtain microcrystalline cellulose.

Results: Through testing, the lignin removal rate was 98.52%. The degree of polymerization of the microcrystalline cellulose prepared in this example was 293.22, the yield was 74.16%, the purity was 98.45%, and the particle size was 51.65 μm.

Example 2

(4) Treatment with eutectic solvent: Mix the absolutely dry poplar wood powder, eutectic solvent A, and 98% sulfuric acid in a mass ratio of 1:20:0.3 after benzene alcohol extraction in step (2). The reaction temperature was 160°C, and the heating and stirring time was 8 hours.

Results: Through testing, the lignin removal rate was 98.70%. The degree of polymerization of the microcrystalline cellulose prepared in this example was 213.22, the yield was 71.16%, the purity was 98.96%, and the particle size was 52.90 μm.

The above descriptions are only preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

A method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent in conjunction with an acid. The latter material is filtered to obtain microcrystalline cellulose; the eutectic solvent is prepared from choline chloride, polyethylene glycol, and 1,4-butanediol as raw materials, and the added amount of the acid is poplar wood powder 20 to 35% of the quality.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1, wherein the temperature of the reaction between the poplar wood powder, the eutectic solvent and the acid is 155-165°C .
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1 or 2, characterized in that the reaction time of the poplar wood powder, the eutectic solvent and the acid is 4~ 8h.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1, wherein the acid is a sulfuric acid solution with a mass fraction of 96-99%.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1 or 4, wherein the mass ratio of the poplar wood powder, the eutectic solvent and the acid is 1: 15～25: 0.25～0.35.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1, characterized in that the preparation method of the eutectic solvent is: combining choline chloride, polyethylene dichloride Alcohol and 1,4-butanediol are heated to 65～75℃ to react.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid as claimed in claim 1 or 6, characterized in that the choline chloride, polyethylene glycol, 1,4-butanedi The mass ratio of alcohol is 4.5 to 5.5: 15.5 to 16.5: 3.5 to 4.5.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1 or 6, characterized in that the polyethylene glycol is polyethylene glycol-200.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1, characterized in that after the poplar wood powder is subjected to benzene alcohol extraction, the extracted poplar wood powder , Mix and react with eutectic solvent and acid.
The method for preparing microcrystalline cellulose by treating poplar wood powder with eutectic solvent and acid treatment according to claim 9, characterized in that the volume ratio of benzene to ethanol in the benzene alcohol extraction is 2:0.9-1.1.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1, wherein the method of filtration is vacuum filtration.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 1, characterized in that, after the filtering, the method further comprises: washing the filtered solid.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 12, wherein the washing liquid for washing is 1,4-dioxane.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 12 or 13, characterized in that the filtered solid is washed with 1,4-dioxane to be colorless After that, wash with water again.
The method for preparing microcrystalline cellulose by using a eutectic solvent and acid-treated poplar wood powder to prepare microcrystalline cellulose according to claim 12, characterized in that, after the washing, the method further comprises: freeze-drying the filtered and washed solid.
The method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to claim 15, characterized in that the freeze-drying time is 22 to 26 hours, and the temperature is -55 to -45°C.
A microcrystalline cellulose, characterized in that it is obtained by the method for preparing microcrystalline cellulose by treating poplar wood powder with a eutectic solvent and acid treatment according to any one of claims 1-16.