CN108752485B

CN108752485B - Preparation method of lignin-containing cationized nanocellulose

Info

Publication number: CN108752485B
Application number: CN201810662523.0A
Authority: CN
Inventors: 李滨; 吴美燕; 刘超; 于光; 张跃冬; 冯晓燕; 咸漠
Original assignee: Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
Current assignee: Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
Priority date: 2018-06-25
Filing date: 2018-06-25
Publication date: 2021-04-27
Anticipated expiration: 2038-06-25
Also published as: CN108752485A

Abstract

The invention relates to a preparation method of lignin-containing cationized nano-cellulose, belonging to the technical field of cellulose modification. Crushing agricultural wastes, mixing the crushed agricultural wastes with an alkali solution and a cationic etherifying agent, reacting by using a microwave and ultrasonic combined one-pot method, and nanocrystallizing cellulose, namely preparing the lignin-containing cationic nanocellulose by using the one-pot method. The preparation method has the advantages of simple preparation process, reaction temperature reduction, reaction time saving and high industrialization possibility. Meanwhile, the obtained cationized nano-cellulose containing lignin has the advantages of good stability, high film forming strength and good antibacterial property, and can obtain good effect when being used for adsorbing heavy metal ions in water. Therefore, the cationic nanocellulose prepared by the method has great application value in the fields of antibiosis, adsorption and the like.

Description

Preparation method of lignin-containing cationized nanocellulose

Technical Field

The invention relates to a preparation method of lignin-containing cationized nano-cellulose, belonging to the technical field of cellulose modification.

Background

The nano-cellulose is obtained by treating natural cellulose through a nano technology, and has the advantages of nano-scale, higher specific surface area, excellent stability and the like. Therefore, the nano-cellulose is widely applied in the fields of packaging, biological medicine, photoelectric technology, water treatment and the like (nanoscale.2017,9(39): 14758-.

At present, the preparation method of the nano-cellulose mainly comprises an acid hydrolysis method, a TEMPO catalytic oxidation method, a mechanical method and the like (Progress in chemistry.2017,30(4): 448-. In the preparation of cationized nanocellulose, usually, a cationic etherifying agent is reacted with cellulose for 8 hours or more to quaternize the cellulose to obtain cationized cellulose, the size of the cationized cellulose is reduced by a high-pressure homogenization method, and the cationized nanocellulose is obtained by a two-step treatment. Application No. 201310585231.9 discloses that a cationic nanocellulose is prepared by first subjecting a fiber raw material to a beating treatment, adding a cationic etherifying agent to prepare a cationic cellulose, and then subjecting the cationic cellulose to a nanocrystallization treatment. Application No. 201110058981.1 discloses a method for preparing nanocellulose, and then adding KOH and an etherifying agent to perform cationization modification on the nanocellulose, and the obtained cationic nanocellulose is used for improving the strength and the air permeability of the cigarette paper. Application No. 201710373719.3 discloses a method for obtaining cationized nanocellulose by modifying a nanocellulose sample with a cationic quaternary ammonium salt.

Therefore, the methods disclosed in the above patents and literature documents are both two-step methods, i.e., cationic nanocellulose is prepared first and then cationic nanocellulose is prepared by nanocrystallization, or cationic nanocellulose is prepared first and then cationic nanocellulose is prepared by cationization. Meanwhile, the methods all use needle-leaved wood, broad-leaved wood, gramineous plant fiber and the like as raw materials, and the traditional fiber raw materials have certain limitations and higher cost. In recent years, the energy and material utilization of agricultural waste biomass have been receiving more and more attention from scientists and even the public. Especially, in China, which is a big agricultural country, more than 9 hundred million tons of agricultural waste biomass such as various straws are produced every year, about 30 percent of the waste biomass is returned to the field, 20 percent to 30 percent of the waste biomass is used as rural living fuel, 10 percent to 15 percent of the waste biomass is used as industrial raw materials such as feed or paper making, and the rest waste biomass is wasted in the field. This not only causes a large waste of resources, but also causes problems such as environmental pollution (e.g., straw incineration).

In addition, with the development of microwave-ultrasonic wave coupling technology, the microwave-ultrasonic wave coupling technology is widely applied to the fields of chemical reaction, extraction and the like. However, the application of the modified nano-cellulose in preparation of modified nano-cellulose is only reported.

Disclosure of Invention

The invention aims to provide a preparation method of lignin-containing cationized nanocellulose.

In order to achieve the purpose, the invention adopts the technical scheme that:

a preparation method of lignin-containing cationized nanocellulose comprises the steps of crushing agricultural wastes, mixing the crushed agricultural wastes with an alkali solution and a cationic etherifying agent, reacting by using a microwave and ultrasonic wave combination mode one-pot method, and performing cellulose nanocrystallization, namely the one-pot method is used for preparing the lignin-containing cationized nanocellulose.

Further, the crushed agricultural waste powder, the cationic etherifying agent and the alkali are mixed and added into the organic solvent, then the mixture is reacted and nanocrystallized in the ultrasonic microwave chemical reactor, and the reaction product is filtered and precipitated to obtain the lignin-containing cationic nanocellulose.

And recycling the liquid obtained by filtering.

The crushed agricultural waste powder, the cationic etherifying agent and the alkali are mixed and added into the organic solvent, wherein the using amount of the organic solvent is 10-300 times of the mass of the agricultural waste powder, the using amount of the cationic etherifying agent is 0.5-20 times of the mass of the agricultural waste powder, and the using amount of the alkali is 0.2-5% of the mass of the agricultural waste powder.

Preferably, the dosage of the cationic etherifying agent is 1-10 times of the agricultural waste powder, the dosage of the alkali is preferably 0.5-3% of the agricultural waste powder, and the dosage of the organic solvent is preferably 20-200 times of the agricultural waste powder.

The reaction solution is added into an ultrasonic microwave chemical reactor, the microwave frequency is 500MHz-2450MHz/10W-1000W, the ultrasonic frequency is 10KHz-40KHz/50W, the reaction temperature is 30 ℃ to 70 ℃, and the reaction time is 30min-6 h.

Preferably, the ultrasonic microwave reaction conditions are that the microwave frequency is 2000MHz-2400MHz/1000W, the ultrasonic frequency is 30KHz-40KHz/50W, the reaction temperature is 40 ℃ -70 ℃, and the reaction lasts for 1h-5 h.

The agricultural wastes refer to one or more of corn bracts, corncobs, tobacco stems, Chinese alpine rush, corn straws, wheat straws and bagasse;

the cationic etherifying agent is one or more of 2, 3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyl trimethylammonium bromide, hexadecylpyridinium chloride, tetradecyltrimethylammonium bromide and dodecyl pyridinium chloride; preferably, the cationic etherifying agent is one or more of 2, 3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide;

the organic solvent is DMAC, DMF, DMSO, NMP or NH₄One or more of SCN and NMMO;

preferably, the organic solvent is one or more of DMAC, DMF and DMSO.

The alkali refers to one or two of NaOH and KOH.

The invention has the following advantages:

(1) the raw material used by the method is agricultural waste biomass, so that a new thought is provided for resource utilization of a large amount of agricultural waste, the problems of environmental pollution, land occupation and the like caused by burning or laying aside are effectively avoided, and the method is a treatment method of the agricultural waste biomass which meets the national conditions of China (see the scheme on promoting resource utilization of agricultural waste published by the ministry of agriculture for details).

(2) The invention prepares the cation nano-cellulose by means of the combination of ultrasonic waves and microwaves, and the hydrogen bond combination of the cellulose can be rapidly destroyed by the superposition of two energies, so that the size of the cellulose is reduced. Meanwhile, after the microwave and ultrasonic wave assistance, the reaction system is heated quickly and uniformly, and the quaternization reaction is promoted. Therefore, the invention can obviously reduce the reaction temperature, save the reaction time and realize high-efficiency clean production.

(3) In addition, the preparation method utilizes the microwave and ultrasonic wave to assist the one-pot method to prepare the cation nano-cellulose, and the method directly obtains the cation modified nano-cellulose from simple and easily obtained agricultural wastes without separating an intermediate (cellulose). Compared with the disclosed preparation method (two-step method), the preparation method disclosed by the invention has the advantages that the preparation process is greatly simplified (the method does not have complicated separation and washing processes and delignification processes), the requirement on equipment is low, the economic performance is high, the large-scale production is easy, the method is environment-friendly, and the method is a green preparation method. Meanwhile, the nano-cellulose containing lignin obtained after the reaction has high wet strength and good water resistance, has great application potential in a wet environment after film formation, and effectively realizes high-value application of agricultural waste biomass.

Drawings

Fig. 1 is a TEM image of cationic nanocellulose prepared from tobacco stems according to the present invention.

FIG. 2 is a diagram of a cationic nanocellulose film-forming substance prepared from tobacco stems according to an embodiment of the present invention.

FIG. 3 is a TEM image of cationic nanocellulose prepared from corn bracts as a raw material according to an embodiment of the present invention.

FIG. 4 is a diagram of a cationic nanocellulose membrane formation object using corn bracts as raw materials according to an embodiment of the present invention.

Fig. 5 shows the conductivity change before and after adsorption of magnesium ions by the cationic nanocellulose provided by the example of the present invention.

FIG. 6 shows the change of the solution after the cationic nanocellulose provided by the example of the invention adsorbs magnesium ions for 2min and 4 min.

Detailed Description

The feasibility of the process is further illustrated below by means of specific implementation examples, without the intention that the invention be limited to these examples.

The method comprises the steps of firstly crushing agricultural wastes, mixing the crushed agricultural wastes with an alkali solution and a cationic etherifying agent, promoting the reaction by using a microwave and ultrasonic combined system, and meanwhile, nanocrystallizing cellulose, namely preparing the lignin-containing cationic nanocellulose by a one-pot method. The preparation method has the advantages of simple preparation process, reaction temperature reduction, reaction time saving and high industrialization possibility. Meanwhile, the obtained cationized nano-cellulose containing lignin has the advantages of good stability, high film forming strength and good antibacterial property, and can obtain good effect when being used for adsorbing heavy metal ions in water. Therefore, the cationic nanocellulose prepared by the method has great application value in the fields of antibiosis, adsorption and the like.

Example 1

Preparation of cationized nano-cellulose by taking tobacco stems as raw materials

The tobacco stems were peeled and pulverized, and the raw material analysis is shown in table 1. Mixing tobacco stem powder, 2, 3-epoxypropyl trimethyl ammonium chloride and KOH, and adding the mixture into DMAC (dimethyl acetamide), wherein the dosage of the 2, 3-epoxypropyl trimethyl ammonium chloride is 1 time of the mass of the tobacco stem powder, the dosage of the KOH is 0.5 percent of the mass of the tobacco stem powder, and the dosage of the DMAC is 20 times of the mass of the tobacco stem powder. Adding the reaction solution into an ultrasonic microwave chemical reactor, setting the microwave at 2000MHz/1000W and the ultrasonic frequency at 30KHz/50W, reacting for 5h at 40 ℃, filtering the obtained liquid, recycling the filtrate containing DMAC, and washing the filter residue with deionized water for 5 times to obtain the cationized nano-cellulose.

Verification 1

It can be seen by TEM testing that example 1 has succeeded in obtaining nanocellulose filaments with a diameter of about 50nm (fig. 1). As can be seen from the raw material analysis of the tobacco stalk powder in example 1, the tobacco stalk contains about 24.3% lignin (Table 1). Because the method does not have a delignification process, the prepared nanocellulose contains partial lignin. The cationized nanocellulose is subjected to vacuum filtration to prepare a nanocellulose film, and the mechanical properties of the nanocellulose film are detected according to TAPPI T497 and TAPPIT456 standards, as shown in Table 2. As can be seen from Table 2, the cationized nanocellulose film prepared by the one-pot method using tobacco stems as raw materials has high dry strength (179.7MPa) and wet strength (80.1 MPa). The film was brown in color but had better transparency due to the effect of lignin (fig. 2). In addition, according to GB/T21510-. Therefore, the cationized nano-cellulose can be obtained at a lower temperature (40 ℃), and the prepared cationic nano-cellulose film formed by taking the tobacco stems as the raw materials has higher dry strength and wet strength and better antibacterial property.

Example 2

Preparation of cationized nano-cellulose by taking corn bracts as raw materials

The corn bracts were pulverized, and the raw material analysis thereof is shown in table 3. Mixing the corn bract powder, tetradecyl trimethyl ammonium bromide and KOH, and adding the mixture into DMF (dimethyl formamide), wherein the dosage of the tetradecyl trimethyl ammonium bromide is 10 times of the mass of the corn bract powder, the dosage of the KOH is 3 times of the mass of the corn bract powder, and the dosage of the DMF is 200 times of the mass of the corn bract powder. Adding the reaction liquid into an ultrasonic microwave chemical reactor, setting microwave 2400MHz/800W and ultrasonic frequency 40KHz/50W, reacting for 1h at 40 ℃, filtering the obtained liquid, recycling the DMF-containing filtrate, and washing the filter residue with deionized water for 5 times to obtain the cationized nano-cellulose.

Authentication 2

It can be seen from TEM test that example 2 has succeeded in obtaining nanocellulose filaments with a diameter of less than 40nm (fig. 3), and from raw material analysis of corn bract powder in example 2, it can be seen that the tobacco stalk contains about 11.6% lignin. Because the method does not have a delignification process, the prepared nanocellulose contains partial lignin. The nanocellulose film was prepared by casting the cationized nanocellulose, the mechanical properties of which are shown in table 4. As can be seen from Table 4, the cationized nanocellulose film prepared by the one-pot method using corn bracts as raw materials has high dry strength (152.1MPa) and wet strength (39.8 MPa). Similarly, the film was brown in color due to the action of lignin, but had better transparency (FIG. 4).

The cation nano-cellulose is used as an adsorbent for adsorbing metal ions. The specific method comprises the following steps: 0.1g of absolutely dry cationic nanocellulose is taken and added with 100mL of MgSO 2mg/mL₄Solution, test conductivity. Stirring at room temperature for adsorption for 2min, 4min, 6min, 8min, and 10 min; the sample was centrifuged at 10mL and the supernatant was tested for conductivity. From the test results (fig. 5 and 6), it can be seen that the conductivity rapidly decreases upon adsorption of the cationic nanocellulose, and the equilibrium can be reached after about 4 min. As can also be seen in FIG. 6, cationic nanofibersSignificant flocculation and sedimentation of the pigment occurred. Therefore, the cation nano-cellulose has better magnesium ion adsorption effect.

Example 3

Preparation of cationized nano-cellulose by using Chinese alpine rush as raw material

The Chinese alpine rush was pulverized and the raw material analysis is shown in table 5. Mixing the Chinese alpine rush powder, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and NaOH, and adding the mixture into DMSO, wherein the dosage of the 3-chloro-2-hydroxypropyl trimethyl ammonium chloride is 5 times of the Chinese alpine rush powder, the dosage of the NaOH is 1 time of the Chinese alpine rush powder, and the dosage of the DMSO is 100 times of the Chinese alpine rush powder. Adding the reaction solution into an ultrasonic microwave chemical reactor, setting the microwave at 2300MHz/1000W and the ultrasonic frequency at 35KHz/50W, reacting for 4h at 65 ℃, filtering the obtained liquid, recycling the filtrate containing DMSO, washing the filter residue with deionized water for 5 times, and obtaining the cationized nano-cellulose with the diameter of about 40 nm.

Example 4

Preparation of cationized nano-cellulose by taking bagasse as raw material

Bagasse was pulverized and the raw material analysis is shown in table 6. Mixing bagasse, 2, 3-epoxypropyltrimethylammonium chloride and KOH, and adding the mixture into DMSO, wherein the dosage of the 2, 3-epoxypropyltrimethylammonium chloride is 3 times of the mass of the bagasse powder, the dosage of the KOH is 2% of the mass of the bagasse powder, and the dosage of the DMSO is 50 times of the mass of the bagasse powder. Adding the reaction liquid into an ultrasonic microwave chemical reactor, setting microwave 2400MHz/1000W and ultrasonic frequency 40KHz/50W, reacting for 5 hours at 50 ℃, filtering the obtained liquid, recycling the filtrate containing DMSO for recycling, washing the filter residue for 5 times by using deionized water, and obtaining a cationized nano-cellulose product with the diameter of about 60nm, wherein the content of lignin is about 16 percent and is consistent with that of the bagasse raw material.

Example 5

Preparation of cationized nano-cellulose by using wheat straws as raw materials

Crushing wheat straws, mixing the wheat straws, dodecyl pyridinium chloride and NaOH, and adding the mixture into NMMO, wherein the dosage of the dodecyl pyridinium chloride is 20 times of the mass of the wheat straw powder, the dosage of the NaOH is 5% of the mass of the wheat straw powder, and the dosage of the NMMO is 300 times of the mass of the wheat straw powder. Adding the reaction liquid into an ultrasonic microwave chemical reactor, setting microwave 2450MHz/1000W and ultrasonic frequency 40KHz/50W, reacting for 4h at 60 ℃, filtering the obtained liquid, recovering the NMMO-containing filtrate for recycling, and washing the filter residue with deionized water for 5 times to obtain the cationized nano-cellulose product with the diameter of about 30 nm.

Example 6

Cationic nanocellulose prepared from mixture of corn bracts and wheat straws

The method comprises the steps of crushing and uniformly mixing corn bracts and wheat straws in a mass ratio of 1:1, mixing the mixture of the corn bracts and the wheat straws with 2, 3-epoxypropyltrimethylammonium chloride and NaOH, and adding the mixture into DMF (dimethyl formamide), wherein the dosage of the 2, 3-epoxypropyltrimethylammonium chloride is 10 times of the mass of the mixture of the corn bracts and the wheat straws, the dosage of the NaOH is 3 times of the mass of the mixture of the corn bracts and the wheat straws, and the dosage of the DMF is 200 times of the mass of the mixture of the corn bracts and the wheat straws. Adding the reaction liquid into an ultrasonic microwave chemical reactor, setting the microwave at 2400MHz/900W and the ultrasonic frequency at 40KHz/50W, reacting for 5h at 70 ℃, filtering the obtained liquid, recycling the DMF-containing filtrate, washing the filter residue with deionized water for 5 times, and obtaining the cationized nano-cellulose product with the diameter of 30-70 nm.

Table 1 raw material analysis of tobacco stems in example 1

	Extract (%)	Lignin (%)	Cellulose (%)	Hemicellulose (%)	In total (%)
						Tobacco rod	12.60±1.08	24.30±0.2	40.47±0.6	16.51±0.10	93.87

TABLE 2 mechanical Properties of cationic nanocellulose prepared in example 1 after film formation

TABLE 3 analysis of corn bracts in example 2

	Extract (%)	Lignin (%)	Cellulose (%)	Hemicellulose (%)	In total (%)
						Corn bract	7.07±0.90	11.6±0.80	43.42±0.10	29.93±0.60	92.01

Table 4 mechanical properties of the cationic nanocellulose prepared in example 2 after film formation

Table 5 shows the raw material analysis of Chinese alpine rush in example 3

	Extract (%)	Lignin (%)	Cellulose (%)	Hemicellulose (%)	In total (%)
						Chinese alpine rush	13.27±0.05	16.40±1.10	41.25±0.88	24.71±0.33	95.63

Table 6 shows the raw material analysis of bagasse in example 4.

	Extract (%)	Lignin (%)	Cellulose (%)	Hemicellulose (%)	In total (%)
						Bagasse	5.49±0.34	22.64±0.73	45.26±0.98	24.28±1.21	97.67

By combining the above examples, the preparation method of the cationized nanocellulose based on the agricultural wastes can reduce the reaction temperature and shorten the reaction time, and can directly obtain the cationized nanocellulose from the fiber raw materials by a one-pot method, thereby greatly simplifying the preparation process. Meanwhile, the obtained cationized nano-cellulose containing the lignin has excellent antibacterial effect, higher film forming strength and chelation effect on metal ions in water. Therefore, the cationized nano-cellulose has wide application prospect in the fields of antibiosis, wastewater treatment and the like.

Claims

1. A preparation method of lignin-containing cationized nanocellulose is characterized by comprising the following steps: mixing the crushed agricultural waste powder, a cationic etherifying agent and alkali, adding the mixture into an organic solvent, reacting and nanocrystallizing the mixture in an ultrasonic microwave chemical reactor, and filtering the reaction product after the reaction to obtain a precipitate, namely the lignin-containing cationic nanocellulose;

the lignin-containing cationic nanocellulose is used for adsorbing heavy metal ions in water;

the dosage of the organic solvent is 10-300 times of the mass of the agricultural waste powder, the dosage of the cationic etherifying agent is 0.5-20 times of the mass of the agricultural waste powder, and the dosage of the alkali is 0.2-5% of the mass of the agricultural waste powder;

the microwave frequency is 500MHz-2450MHz, the microwave power is 10W-1000W, the ultrasonic frequency is 10KHz-40KHz, the ultrasonic power is 50W, the reaction temperature is 30 ℃ -70 ℃, and the reaction time is 30min-6 h;

the cationic etherifying agent is one or more of 2, 3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide;

the organic solvent is one or more of DMAC, DMF and DMSO;

the alkali refers to one or two of NaOH and KOH.

2. The method of claim 1, wherein the step of forming the cationic nanocellulose comprises: and recycling the liquid obtained by filtering.

3. The method of claim 1, wherein the step of forming the cationic nanocellulose comprises: the dosage of the cationic etherifying agent is 1-10 times of the agricultural waste powder, the dosage of the alkali is 0.5-3% of the agricultural waste powder, and the dosage of the organic solvent is 20-200 times of the agricultural waste powder.

4. The method of claim 1, wherein the step of forming the cationic nanocellulose comprises: the ultrasonic microwave reaction conditions are that the microwave frequency is 2000MHz-2400MHz, the microwave power is 1000W, the ultrasonic frequency is 30KHz-40KHz, the ultrasonic power is 50W, the reaction temperature is 40 ℃ -70 ℃, and the reaction lasts for 1h-5 h.