CN112624086B - Controllable preparation method of lignin-based micro-nano carbon spheres - Google Patents

Abstract

The invention discloses a controllable preparation method of lignin-based micro-nano carbon spheres, which comprises the following steps: mixing a lignin raw material and an organic solvent, and stirring to obtain a lignin solution; adding deionized water into the lignin solution, stirring, and removing the organic solvent to obtain a lignin micro-nanosphere suspension; carrying out hydrothermal reaction on the lignin micro-nano sphere suspension, centrifuging, and freeze-drying to obtain covalently crosslinked lignin micro-nano spheres; carbonizing the covalently crosslinked lignin micro-nano spheres to obtain lignin-based micro-nano carbon spheres. The preparation method can prepare the lignin-based micro-nano carbon spheres with uniform and controllable size, regular appearance and solid structure, realizes the controllable preparation of the lignin-based micro-nano carbon spheres, has the advantages of simple process, mild preparation conditions, low cost and the like, conforms to the green chemical concept, and has higher application value and better application prospect.

Description

A kind of controllable preparation method of lignin-based micro-nano carbon spheres

technical field

The invention relates to a controllable preparation method of lignin-based micro-nano carbon spheres.

Background technique

Carbon nanospheres are widely used in electrode materials, catalysis and adsorption fields because of their controllable size, high specific surface area and high stability. In recent years, the preparation of carbon nanospheres from biomass materials has gradually become a research hotspot. Lignin has the characteristics of high carbon content and is an ideal precursor for the development of carbon nanospheres. However, the existing preparation methods of lignin-based micro-nano carbon spheres still have technical problems such as difficulty in controlling the size and morphology of carbon spheres, unavoidable use of chemical reagents, or harm to the environment. Therefore, it is urgent to develop a simple and green method to realize the efficient and controllable preparation of lignin-based micro-nano carbon spheres, which is of great significance for further expanding the utilization space of lignin.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and to provide a method for the controllable preparation of lignin-based micro-nano carbon spheres with simple process, mild preparation conditions and low cost, and capable of controllably preparing lignin-based micro-nano carbon spheres with uniform and controllable size and regular appearance .

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A controllable preparation method of lignin-based micro-nano carbon spheres, comprising the following steps:

S1, lignin raw material, organic solvent are mixed, stir, obtain lignin solution;

S2, adding deionized water to the lignin solution in step S1, stirring, and removing the organic solvent to obtain a lignin micro-nano sphere suspension;

S3, subjecting the lignin micro-nanosphere suspension obtained in step S2 to hydrothermal reaction, centrifugation, and freeze-drying to obtain covalently cross-linked lignin micro-nanospheres;

S4, carbonizing the covalently cross-linked lignin micro-nano spheres obtained in step S3 to obtain lignin-based micro-nano carbon spheres.

The above-mentioned controllable preparation method of lignin-based micro-nano carbon spheres is further improved. In step S1, the ratio of the lignin raw material to the organic solvent is 5 mg-20 mg: 10 mL.

The above-mentioned controllable preparation method of lignin-based micro-nano carbon spheres is further improved. In step S1, the lignin raw material is at least one of alkali lignin, high-boiling alcohol lignin, and enzymatic hydrolyzed lignin; The organic solvent is at least one of tetrahydrofuran, dioxane and dimethylformamide.

The above controllable preparation method of lignin-based micro-nano carbon spheres is further improved. In step S1, the stirring speed is 100 rpm to 1000 rpm; the stirring time is until the lignin is completely dissolved in the organic solvent.

The above-mentioned controllable preparation method of lignin-based micro-nano carbon spheres is further improved. In step S2, the volume ratio of the lignin solution to deionized water is 1:4.

The above-mentioned controllable preparation method of lignin-based micro-nano carbon spheres is further improved. In step S2, the dropping rate of the deionized water is 2mL/min～20mL/min.

The above-mentioned controllable preparation method of lignin-based micro-nano carbon spheres is further improved. In step S2, the stirring speed is 100rpm-1000rpm; the stirring time is 5h-12h.

The above controllable preparation method of lignin-based micro-nano carbon spheres is further improved. In step S3, the temperature of the hydrothermal reaction is 160°C to 200°C, and the time of the hydrothermal reaction is 12 hours.

The above-mentioned controllable preparation method of lignin-based micro-nano carbon spheres is further improved. In step S4, the carbonization is performed in an inert atmosphere; the heating rate during the carbonization is controlled to be 3°C/min～8°C/min ; The carbonization temperature is 700°C to 900°C; the carbonization time is 2h.

The above-mentioned controllable preparation method of lignin-based micro-nano carbon spheres is further improved, and the inert atmosphere is a nitrogen atmosphere.

Compared with the prior art, the advantages of the present invention are:

(1) The present invention provides a controllable preparation method of lignin-based micro-nano carbon spheres. The lignin micro-nano spheres with uniform size and regular structure are prepared by self-assembly of the solvent-anti-solvent method, and then the micro-nano spheres are prepared by hydrothermal treatment. The lignin molecules in the spheres are cross-linked and polymerized to improve the structural strength and thermal stability of the micro-nano spheres, and finally the micro-nano spheres are cracked by carbonization to obtain micro-nano sphere carbon spheres. In the preparation process, the controllable preparation of micro-nanospheres can be realized by adjusting the initial concentration of lignin in the organic solvent, the acceleration of deionized water droplets and the stirring speed, thereby realizing the regulation of micro-nanocarbon spheres; hydrothermal treatment is mainly to improve the micro-nanospheres. The structural strength of the nanospheres prevents the micro-nanospheres from collapsing during the carbonization process, thus preparing lignin-based micro-nanocarbon spheres with uniform and controllable size, regular morphology and solid structure, realizing the realization of lignin-based micro- and nano-carbon spheres. Controllable preparation of carbon nanospheres. The preparation method of the invention has the advantages of simple process, mild preparation conditions, low cost and the like, conforms to the concept of green chemistry, and has higher application value and better application prospect.

(2) In the present invention, the ratio of lignin raw material to organic solvent is optimized to be 5mg-20mg: 10mL, which can ensure that lignin has good solubility in organic solvents, and is more conducive to obtaining lignin with adjustable particle size and uniformity. At the same time, the volume ratio of lignin raw material and deionized water is optimized to be 1:4, which can ensure that all lignin molecules participate in the formation of micro-nanospheres and the concentration is moderate.

(3) In the present invention, the dropping rate of deionized water is optimized to be 2mL/min～20mL/min, which is convenient for regulating the particle size of lignin micro-nanospheres.

(4) In the present invention, the optimized hydrothermal reaction temperature is 160℃～200℃, and the time is 12h, which can ensure that the lignin molecules in the lignin micro-nanospheres form a cross-linked network, and the structure will not collapse during the carbonization process. .

(5) In the present invention, it is optimized to control the heating rate in the carbonization process to be 3°C/min～8°C/min, the carbonization temperature to be 700°C to 900°C, and the carbonization time to be 2h, which can ensure a higher carbonization rate and is beneficial to the preparation Lignin-based micro-nano carbon spheres with higher carbon content.

Description of drawings

To make the purposes, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention.

FIG. 1 is a SEM image of the lignin-based micro-nano carbon spheres prepared in Example 1 of the present invention.

2 is a TEM image of the lignin-based micro-nano carbon spheres prepared in Example 1 of the present invention.

3 is a particle size distribution diagram of the lignin-based micro-nano carbon spheres prepared in Example 1 of the present invention.

FIG. 4 is a SEM image of the lignin-based carbon material prepared in Comparative Example 1. FIG.

FIG. 5 is a SEM image of the lignin-based carbon material prepared in Comparative Example 2. FIG.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

The materials and instruments used in the following examples are commercially available.

Example 1

A preparation method of lignin-based micro-nano carbon spheres, comprising the following steps:

(1) Take 20 mg of enzymatically hydrolyzed lignin and place it in a 250 mL beaker, add 10 mL of tetrahydrofuran, and stir at 800 rpm until the enzymatically hydrolyzed lignin is dissolved to obtain a lignin solution.

(2) 40 mL of deionized water was added to the lignin solution obtained in step (1) at a dropping rate of 4 mL/min, and continued stirring at 800 rpm for 5 h to completely volatilize the tetrahydrofuran in the solution to obtain a suspension of lignin micro-nano spheres. turbid liquid;

(3) 40 mL of the lignin nanosphere suspension obtained in step (2) was placed in a 100 mL hydrothermal reactor, treated at 160° C. for 12 h, centrifuged, and freeze-dried to obtain covalently cross-linked lignin Pure micro-nano sphere solid powder.

(4) Take a certain amount of the co-crosslinked lignin micro-nanosphere solid powder obtained in step (3) and place it in a corundum ark/tube furnace, and heat it up to 700 °C at a heating rate of 3 °C min ^-1 under a nitrogen atmosphere. Carbonized at ℃ for 2 hours to obtain lignin-based micro-nano carbon spheres.

FIG. 1 is a SEM image of the lignin-based micro-nano carbon spheres prepared in Example 1 of the present invention. 2 is a TEM image of the lignin-based micro-nano carbon spheres prepared in Example 1 of the present invention. 3 is a particle size distribution diagram of the lignin-based micro-nano carbon spheres prepared in Example 1 of the present invention. It can be seen from FIG. 1 and FIG. 2 that the lignin-based micro-nano carbon spheres prepared by the method of the present invention are uniform in size, regular in shape, and have a solid structure. 3, it can be seen that the average particle size of the lignin-based micro-nano carbon spheres prepared by the method of the present invention is 396.98 nm.

Example 2

A controllable preparation method of lignin-based micro-nano carbon spheres is basically the same as the preparation method in Example 1, except that the carbonization temperature in Example 2 is 800°C.

After testing, the lignin-based micro-nano carbon spheres prepared in Example 2 were uniform in size, regular in shape, and had a solid structure with an average particle size of 401.46 nm, which had no significant change compared to Example 1.

Example 3

A controllable preparation method of lignin-based micro-nano carbon spheres is basically the same as the preparation method in Example 1, except that the carbonization temperature in Example 3 is 900°C.

After testing, the lignin-based micro-nano carbon spheres prepared in Example 3 are uniform in size, regular in shape, and have a solid structure with an average particle size of 404.30 nm, which has no obvious change compared to Example 1 and Example 2.

Example 4

A controllable preparation method of lignin-based micro-nano carbon spheres is basically the same as the preparation method in Example 1, except that in Example 4, the amount of enzymatically hydrolyzed lignin is 5 mg, and the carbonization temperature is 800 ° C .

After testing, the lignin-based micro-nano carbon spheres prepared in Example 4 are uniform in size, regular in shape, and have a solid structure with an average particle size of 266.61 nm, which is smaller than that in Example 1 because of the amount of lignin used. When the amount of lignin is reduced, the dissolved lignin molecules in the solution are reduced, resulting in the reduction of lignin molecules participating in the formation of each nanosphere, resulting in the reduction of the particle size of the lignin micro-nanospheres obtained by self-assembly.

Comparative Example 1

A preparation method of lignin-based carbon material, comprising the following steps:

1) Take 20 mg of enzymatically hydrolyzed lignin and place it in a 250 mL beaker, add 10 mL of tetrahydrofuran, stir at 800 rpm until the enzymatically hydrolyzed lignin is dissolved, then titrate 40 mL of deionized water at a speed of 4 mL/min, and continue stirring at 800 rpm for 5 h to make the solution in the solution. The tetrahydrofuran is completely volatilized to obtain a suspension of lignin nano-spheres. Finally, the suspension of lignin nano-spheres is centrifuged and freeze-dried to obtain a solid powder of lignin nano-spheres.

2) Take a certain amount of lignin micro-nanosphere solid powder and place it in a corundum ark/tube furnace, and in a nitrogen atmosphere at a heating rate of 3 ℃ min ^-1 to heat up to 700 ℃ and carbonize for 2 hours to obtain a lignin-based carbon material .

FIG. 4 is a SEM image of the lignin-based carbon material prepared in Comparative Example 1. FIG. It can be seen from Figure 4 that, compared with Example 1, the lignin micro-nanospheres prepared by self-assembly cannot be directly carbonized to form a spherical structure, which shows that the lignin with uniform size and regular morphology cannot be prepared under the condition of omitting hydrothermal treatment. The reason is that the lignin raw material has a random block structure, and its shape cannot be changed during the direct carbonization process, and a spherical structure cannot be formed.

Comparative Example 2

A preparation method of lignin-based carbon material, comprising the following steps:

1) 20 mg of enzymatically hydrolyzed lignin was placed in a 100 mL hydrothermal reactor, treated at 160° C. for 12 hours, and then centrifuged and freeze-dried to obtain solid powder.

2) A certain amount of solid powder was taken and placed in a corundum ark/tube furnace, heated to 700°C for 2 hours at a heating rate of 3°C min ^-1 under nitrogen atmosphere, and carbonized for 2 hours to obtain a lignin-based carbon material.

FIG. 5 is a SEM image of the lignin-based carbon material prepared in Comparative Example 2. FIG. It can be seen from Figure 5 that, compared with Example 1, the hydrothermally treated lignin cannot be directly carbonized to form a spherical structure, which shows that even if the controlled preparation of lignin micro-nanospheres is omitted, uniform size and morphology cannot be prepared. The reason for the regular lignin-based micro-nano carbon spheres is that the hydrothermal treatment process only provides conditions for the condensation reaction of lignin molecules in the lignin nanospheres, and its morphology is difficult to control.

The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All the technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (5)

1. a controllable preparation method of lignin-based micro-nano carbon ball, is characterized in that, comprises the following steps: S1, mixing raw lignin and organic solvent, stirring, to obtain lignin solution; the ratio of described lignin raw material and organic solvent is 20mg: 10mL; S2, adding deionized water to the lignin solution in step S1, stirring, and removing the organic solvent to obtain a suspension of lignin micro-nanospheres; the volume ratio of the lignin solution and deionized water is 1:4; The dropping rate of the deionized water is 2mL/min～20mL/min; the rotating speed of the stirring is 100rpm～1000rpm; the stirring time is 5h～12h; S3. The lignin micro-nanosphere suspension obtained in step S2 is subjected to a hydrothermal reaction, centrifugation, and freeze-drying to obtain covalently cross-linked lignin micro-nanospheres; the temperature of the hydrothermal reaction is 160° C. to 200° C. ℃; the time of the hydrothermal reaction is 12h; S4, carbonizing the covalently cross-linked lignin micro-nano spheres obtained in step S3 to obtain lignin-based micro-nano carbon spheres. 2. The controllable preparation method of lignin-based micro-nano carbon spheres according to claim 1, wherein in step S1, the lignin raw material is alkali lignin, high-boiling alcohol lignin, and enzymatic hydrolysis lignin At least one of; the organic solvent is at least one of tetrahydrofuran, dioxane, and dimethylformamide. 3. The controllable preparation method of lignin-based micro-nano carbon spheres according to claim 1, wherein in step S1, the stirring speed is 100rpm～1000rpm; the stirring time is until the lignin is completely Dissolved in organic solvents. 4. The controllable preparation method of lignin-based micro-nano carbon spheres according to any one of claims 1 to 3, wherein in step S4, the carbonization is performed under an inert atmosphere; The heating rate is controlled to be 3°C/min to 8°C/min; the temperature of the carbonization is 700°C to 900°C; the time of the carbonization is 2h. 5 . The controllable preparation method of lignin-based micro-nano carbon spheres according to claim 4 , wherein the inert atmosphere is a nitrogen atmosphere. 6 .

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