CN109012608A - The preparation method and application of lignin nanosphere - Google Patents

Abstract

The invention provides a preparation method and application of lignin nano microspheres. Hydrophobic modification of lignin was carried out by microwave acetylation, and then the acetylated lignin was dissolved in tetrahydrofuran solvent, and finally lignin nanospheres were prepared by solvent exchange and ultrasonic assistance. By adjusting the lignin/tetrahydrofuran solution concentration and ultrasonic intensity, nano-microspheres with uniform appearance, regular shape, good dispersion, single-hole distribution and high yield were prepared. The lignin nano-microspheres have excellent anti-ultraviolet effect. It can be used in fields such as sunscreen. In the process of lignin modification, the traditional modification method using a large amount of solvents and catalysts is avoided. At the same time, the ultrasonic-assisted method is used in the preparation of nanospheres, which avoids time-consuming and difficult separation methods such as dialysis, and effectively reduces the production cost. cost and simplify the preparation process.

Description

Preparation method and application of lignin nanospheres

technical field

The invention relates to a preparation method of nano carbon microspheres, in particular to a preparation method and application of biorefinery lignin nano microspheres.

Background technique

Lignin is mainly an amorphous aromatic polymer composed of guaiacyl (G), syringyl (S) and p-hydroxyphenyl (H) structural units linked by carbon-carbon bonds and ether bonds. Among them, the functional functional groups of lignin mainly include methoxyl groups, phenolic hydroxyl groups, aliphatic hydroxyl groups and carboxyl groups. A total of more than 50 million tons of lignin is produced as waste every year in the pulping and biorefining industries, but only 2-5% of the lignin is utilized, and the rest is mainly used for burning and landfill, which not only causes serious waste of resources and put heavy pressure on the environment. Therefore, how to expand the high value-added utilization of industrial lignin has become a difficult point in current research.

In recent years, the preparation of nano-lignin has attracted the attention of many scholars. Because nano-lignin has a large specific surface area, excellent dispersion and compatibility, and its surface can be modified, it has potential application value in many fields. CN105819426 discloses an alkali lignin carbon nanosphere and its preparation method and application. It first dissolves lignin in N,N-dimethylformamide or glacial acetic acid solution, and obtains lignin microsphere by electrostatic spraying method , and then carry out oxidation treatment at a temperature of 250-280°C, and finally carbonize at a temperature of 400-900°C to obtain alkali lignin microspheres.

CN105293488 discloses a preparation method of lignin-based activated carbon microspheres, which is liquefied under acidic catalyst conditions after mixing wood powder and phenol, and then preparing microspheres by adding stabilizers and surfactants, and then preparing microspheres in Solidify and carbonize at high temperature to prepare activated carbon microspheres.

CN106582549 discloses a preparation method of monodisperse lignin microspheres, by adding a crosslinking agent and a regulator to the lignin solution to prepare a dispersed phase solution, and then adding a certain amount of surfactant to the organic solution to prepare a continuous phase solution , and finally through the shearing of the continuous phase through the capillary to form water-in-oil lignin monodisperse droplets, and then react at a certain temperature for a predetermined time to form lignin microspheres.

The above-mentioned preparation method of lignin microspheres requires curing and carbonization at high temperature or requires a large amount of chemical reagents. Not only the preparation process is cumbersome, the energy consumption is large, but also a large amount of chemical reagents are required, the preparation cost is high and the environment pollution is serious. In addition, the size uniformity of the prepared lignin microspheres is poor, generally between 10nm and 10μm

Contents of the invention

Based on the disadvantages of complex process, high energy consumption, and poor size uniformity and dispersion of lignin microspheres obtained in the above prior art, the purpose of the present invention is to provide a green and simple biorefining lignin microsphere Ball preparation method.

The object proposed by the present invention is achieved through the following technical solutions:

1) Mix lignin and acetic anhydride in a reaction tank evenly, perform acetylation treatment in a microwave system, drop 5-10 times the volume of acid water with pH=2 after the reaction is completed, filter, wash, freeze-dry to obtain acetylation Lignin.

2) Preparation of microspheres: dissolving the acetylated lignin obtained in step 1) in a tetrahydrofuran solution, then uniformly adding water dropwise into the solution, and using ultrasonic assisted treatment to obtain a dispersion of lignin microspheres.

3) The lignin microsphere dispersion prepared in 2) is centrifuged with an ultra-low temperature high-speed centrifuge, and then freeze-dried to obtain lignin microspheres.

4) The lignin microspheres prepared in 3) were mixed with commercial face cream to enhance its anti-ultraviolet ability.

Aforesaid method, step 1) the mass ratio of lignin and acetic anhydride is 1:5.

In the aforementioned method, step 1) when heating up, the microwave power is 400W for 2 minutes, and the heat preservation power is 200W for 10 minutes.

In the aforementioned method, the concentration of the lignin/tetrahydrofuran solution prepared in step 2) is 1-4 mg/mL.

The aforementioned method, step 2) 0-200W of ultrasonic power.

In the aforementioned method, step 3) lignin is added in an amount of 1-5%.

Compared with the prior art, the preparation method of the present invention and the resulting product have the following beneficial effects:

The lignin used in the present invention is biorefinery lignin, but not limited to industrial lignin. The preparation method used is green and environmentally friendly, easy to operate, low in energy consumption, less in the amount of chemicals used, and the prepared lignin microspheres have a higher yield , good dispersion, size uniformity and excellent UV resistance.

Description of drawings

Figure 1 is a scanning electron micrograph of lignin microspheres prepared in Example 1 of the present invention.

Fig. 2 is a transmission electron micrograph of lignin microspheres prepared in Example 1 of the present invention.

Detailed ways:

The present invention will be further described in detail below in conjunction with the embodiments and accompanying drawings, but the protection scope of the present invention is not limited by the specific embodiments.

Example 1

The preparation method of lignin nano microspheres comprises the following steps:

1) Mix 10g of lignin and 50g of acetic anhydride in a reaction tank and put them into a microwave oven, then heat it with 400W power for 2min to 110°C, then keep it warm at 200W power for 10min, after the reaction is over, put the lignin mixture into droplets into 10 times the volume of acidic water with pH=2, and finally filtered, washed, and freeze-dried to obtain acetylated lignin.

2) Dissolve the acetylated lignin obtained in step 1) in tetrahydrofuran solvent to prepare a lignin solution with a concentration of 1 mg/mL, and then add 70 mL of water evenly to the prepared lignin/mL at a rate of 0.2 mL/min. The tetrahydrofuran solution is accompanied by ultrasonic treatment with a power of 200W to obtain a lignin nanosphere dispersion.

3) Centrifuge the lignin microsphere dispersion liquid obtained in step 2) with an ultra-low temperature high-speed centrifuge at a speed of 10,000 r/min for 10 minutes, and finally freeze-dry to obtain lignin nanospheres.

The SEM and TEM images of the lignin nanospheres prepared in this example are shown in Figure 1 (a x 5000, ex 20000) and Figure 2 (a), respectively. It can be seen from the figure that the lignin nano-microsphere material presents a good appearance: solid, small in size, good in uniformity, and has good dispersion performance.

Example 2

The preparation method of lignin nano microspheres comprises the following steps:

1) Mix 10g of lignin and 50g of acetic anhydride in a reaction tank and put them into a microwave oven, then heat it with 400W power for 2min to 110°C, then keep it warm at 200W power for 10min, after the reaction is over, put the lignin mixture into droplets into 10 times the volume of acidic water with pH=2, and finally filtered, washed, and freeze-dried to obtain acetylated lignin.

2) Dissolve the acetylated lignin obtained in step 1) in tetrahydrofuran solvent to prepare a lignin solution with a concentration of 2 mg/mL, and then add 70 mL of water evenly to the prepared lignin/ The tetrahydrofuran solution is accompanied by ultrasonic treatment with a power of 200W to obtain a lignin nanosphere dispersion.

3) Centrifuge the lignin microsphere dispersion liquid obtained in step 2) with an ultra-low temperature high-speed centrifuge at a speed of 10,000 r/min for 10 minutes, and finally freeze-dry to obtain lignin nanospheres.

The SEM and TEM images of the lignin nanospheres prepared in this example are shown in Figure 1(b) x 5000, (f) x 20000 and Figure 2(b), respectively. It can be seen from the figure that the lignin nano-microsphere material presents a good appearance, a single pore structure, larger size than that of Example 1, better uniformity, and good dispersion performance.

Example 3

The preparation method of lignin nano microspheres comprises the following steps:

1) Mix 10g of lignin and 50g of acetic anhydride in a reaction tank and put them into a microwave oven, then heat it with 400W power for 2min to 110°C, then keep it warm at 200W power for 10min, after the reaction is over, put the lignin mixture into droplets into 10 times the volume of acidic water with pH=2, and finally filtered, washed, and freeze-dried to obtain acetylated lignin.

2) Dissolve the acetylated lignin obtained in step 1) in tetrahydrofuran solvent to prepare a lignin solution with a concentration of 3 mg/mL, and then add 70 mL of water evenly to the prepared lignin/ The tetrahydrofuran solution is accompanied by ultrasonic treatment with a power of 200W to obtain a lignin nanosphere dispersion.

3) Centrifuge the lignin microsphere dispersion liquid obtained in step 2) with an ultra-low temperature high-speed centrifuge at a speed of 10,000 r/min for 10 minutes, and finally freeze-dry to obtain lignin nanospheres.

The SEM and TEM images of the lignin nanospheres prepared in this example are shown in Figure 1(c) x 5000, (g) x 20000 and Figure 2(c), respectively. It can be seen from the figure that the lignin nano-microsphere material presents a good appearance, and a single pore structure begins to appear, the size is further increased compared with Example 2, the uniformity is better, and it has good dispersion performance.

Example 4

The preparation method of lignin nano microspheres comprises the following steps:

1) Mix 10g of lignin and 50g of acetic anhydride in a reaction tank and put them into a microwave oven, then heat it with 400W power for 2min to 110°C, keep it warm for 10min at 200W power, and drop the lignin mixture into 10 Double the volume of acid water with pH=2, finally filter, wash and freeze-dry to obtain acetylated lignin.

2) Dissolve the acetylated lignin obtained in step 1) in tetrahydrofuran solvent to prepare a lignin solution with a concentration of 4 mg/mL, and then add 70 mL of water evenly to the prepared lignin/ The tetrahydrofuran solution is accompanied by ultrasonic treatment with a power of 200W to obtain a lignin nanosphere dispersion.

3) Centrifuge the lignin microsphere dispersion liquid obtained in step 2) with an ultra-low temperature high-speed centrifuge at a speed of 10,000 r/min for 10 minutes, and finally freeze-dry to obtain lignin nanospheres.

The scanning electron microscope and transmission electron microscope images of the lignin nanospheres prepared in this example are shown in Figure 1 (d) x 5000, (f) x 20000 and Figure 2 (d), respectively. It can be seen from the figure that the lignin nano-microsphere material presents a good appearance, has a single pore structure, the largest size and good uniformity, and has good dispersion performance.

Example 5

The preparation method of lignin nano microspheres comprises the following steps:

1) The lignin nanospheres prepared in Example 4) were added to the commercial cream at a mass fraction of 5% to prepare a lignin nanosphere-face cream mixture.

2) The lignin nanosphere-face cream mixture prepared in step 1) was stirred overnight with a magnetic stirrer at a speed of 400 r/min in the dark to make it evenly mixed.

3) Apply the mixture prepared in step 2) evenly on the UV test bench to a thickness of about 1 mm, and then test it in the UV spectrum with an integrating sphere.

The lignin nanosphere-face cream mixture prepared in this example has 4 times higher anti-ultraviolet ability than the non-commercial cream.

The above examples are preferred implementations of the present invention, but the implementation of the present invention is not limited by the above examples. Therefore, any other modifications, substitutions and simplifications made without departing from the spirit and principle of the present invention fall within the protection scope of the present invention.

Claims (8)

1. the method for preparing lignin microballoon.It is characterized in that, mainly comprising the steps that

1) lignin is mixed with acetic anhydride, acetylization reaction is carried out in microwave, to which mixture is instilled 5- after the reaction was completed In the sour water (pH=2) of 10 times of volumes, it is filtered, washed, is freeze-dried to obtain acetylation lignin；

2) 1) acetylation lignin obtained in is dissolved in tetrahydrofuran solvent, is dropped evenly until completely dissolved into 7-10 times Water, and with ultrasonic treatment；

3) 2) the microballoon aqueous solution obtained be centrifuged at 8000-10000r/min, filtered, be freeze-dried and obtain lignin Nanosphere；

4) 3) the lignin microballoon obtained is mixed with commercial face cream, is measured for uvioresistant ability.

2. method according to claim 1, which is characterized in that microwave acetylation process used in step 1), wood Quality and acetic anhydride ratio are 1:5-1:10, time 10min.

3. method according to claim 1, which is characterized in that the speed that water is added dropwise in step 2) is 0.2mL/min, wood Quality concentration is 1mg/mL, 2mg/mL, 3mg/mL and 4mg/mL, ultrasound intensity 0,100W and 200W.

4. method according to claim 1, which is characterized in that using centrifuge separation in step 3).

5. method according to claim 1, which is characterized in that lignin additive amount is 1-5% in step 4).

6. according to the lignin nanosphere of the described in any item method preparations of claims 1-3.

7. the lignin nanosphere prepared according to 6 the method for claims, which is characterized in that the lignin nanometer is micro- The yield of ball is high, uniform sphere diameter distribution, and partial size has single pore structure and good dispersion in 100-800nm.

8. the lignin nanosphere according to claims 6 or 7 is preparing the application in anti-ultraviolet material.