阅读说明：本技术 高氮掺杂木质素基多孔碳及其制备方法 (High-nitrogen-doped lignin-based porous carbon and preparation method thereof ) 是由 熊福全 谭雨姣 王鑫 丁佳蓉 许瀚 吴义强 于 2021-01-27 设计创作，主要内容包括：本发明公开了一种高氮掺杂木质素基多孔碳及其制备方法,该高氮掺杂木质素基多孔碳是以木质素、尿素、氯化锌和碱式碳酸镁为原料经煅烧后制备得到。本发明中,以木质素为碳源,使得氮元素更容易掺杂进入到木质素基多孔碳中,从而有利于提高木质素基多孔碳中的氮含量。相比其他碳源制成的氮掺杂多孔碳,本发明中以木质素为原料时能够制备得到氮含量高的木质素基多孔碳,具有原料来源广、成本低廉、氮含量高、比表面积大等优点,有着较高的应用价值和较好的应用前景。本发明制备方法,具有工艺简单、操作方便、制备条件温和可控、成本低廉等优点,能实现高氮掺杂木质素基多孔碳的一步法制备,且能实现木质素基多孔碳氮含量和比表面积的可调制备。(The invention discloses a high-nitrogen-doped lignin-based porous carbon and a preparation method thereof. According to the invention, lignin is used as a carbon source, so that nitrogen elements can be more easily doped into lignin-based porous carbon, and the nitrogen content in the lignin-based porous carbon can be increased. Compared with nitrogen-doped porous carbon prepared from other carbon sources, the lignin-based porous carbon with high nitrogen content can be prepared by taking lignin as a raw material, has the advantages of wide raw material source, low cost, high nitrogen content, large specific surface area and the like, and has high application value and good application prospect. The preparation method has the advantages of simple process, convenient operation, mild and controllable preparation conditions, low cost and the like, can realize one-step preparation of the high-nitrogen-doped lignin-based porous carbon, and can realize adjustable preparation of the nitrogen content and the specific surface area of the lignin-based porous carbon.)

1. The high-nitrogen-doped lignin-based porous carbon is characterized by being prepared by calcining lignin, urea, zinc chloride and basic magnesium carbonate serving as raw materials.

2. The high-nitrogen-doped lignin-based porous carbon according to claim 1, wherein the mass ratio of urea to lignin is 0.5-2: 1; the mass ratio of the zinc chloride to the basic magnesium carbonate to the lignin is 1: 1-5: 1.

3. The high nitrogen-doped lignin-based porous carbon according to claim 1 or 2, wherein the mass content of nitrogen element in the high nitrogen-doped lignin-based porous carbon is 5.78-7.46%; the specific surface area of the high-nitrogen doped lignin-based porous carbon is 1094.5m²/g～1342.5m²/g。

4. A preparation method of high-nitrogen-doped lignin-based porous carbon is characterized by comprising the following steps:

s1, mixing lignin, urea, zinc chloride and basic magnesium carbonate, and grinding to obtain a mixed raw material;

s2, calcining the mixed raw material obtained in the step S1 to obtain carbonized powder;

and S3, soaking the carbonized powder obtained in the step S2 in an acid solution, washing to be neutral, and drying to obtain the high-nitrogen-doped lignin-based porous carbon.

5. The preparation method according to claim 4, wherein in the step S1, the mass ratio of the urea to the lignin is 0.5-2: 1; the mass ratio of the zinc chloride to the basic magnesium carbonate to the lignin is 1: 1-5: 1.

6. The method according to claim 4 or 5, wherein in the step S1, the grinding time is 5 to 10 min.

7. The method according to claim 4 or 5, wherein in the step S2, the calcination is performed under an inert gas atmosphere; the heating rate in the calcining process is 1-20 ℃/min; the calcining temperature is 600-1000 ℃; the calcining time is 0.5-5 h.

8. The method of claim 7, wherein the inert gas is nitrogen.

9. The production method according to claim 4 or 5, wherein in the step S3, the acid solution is a hydrochloric acid solution; the mass concentration of the acid solution is 10-15%; the soaking time is 12-24 h; the drying is carried out under vacuum conditions; the drying time is 24-48 h.

10. The preparation method according to claim 4 or 5, wherein the mass content of nitrogen element in the high-nitrogen doped lignin-based porous carbon is 5.78-7.46%; the specific surface area of the high-nitrogen doped lignin-based porous carbon is 1094.5m²/g～1342.5m²/g。

Technical Field

The invention belongs to the field of biomass carbon materials, and relates to a high-nitrogen-doped lignin-based porous carbon and a preparation method thereof.

Background

The carbon material has the characteristics of low price, developed pores, good conductivity, stable performance, easy surface modification, adjustable pore size, various forms and the like, and can be widely applied to the fields of electrode materials, catalytic materials, adsorption materials and the like. At present, most raw materials for preparing carbon materials are derived from petrochemical raw materials, and generally need to be carbonized firstly and then activated, so that the problems of complex preparation process and high cost exist.

With the rapid development of global economy, the use of renewable biomass as a carbon source to replace increasingly depleted fossil resources has become a new important direction of development. The lignin is used as a renewable natural resource with the content second to that of cellulose, and the global annual lignin yield is up to 7000 ten thousand tons; meanwhile, the lignin has the carbon content of up to 60 percent and can be used as a porous carbon precursor, which has very important significance for preparing the porous carbon material with low cost and high specific surface area. The doped porous carbon material can improve the utilization performance of the doped porous carbon material in the aspects of electrode materials and catalytic materials, for example, the nitrogen-doped porous carbon shows high capacitance and high catalytic activity, and the nitrogen doping can also improve the physical and chemical characteristics of the porous carbon material, so that the adsorption performance of the porous carbon material on heavy metal ions is improved. However, the existing nitrogen-doped porous carbon still has the defect of low nitrogen content, and the nitrogen-doped lignin-based porous carbon with high nitrogen doping amount is difficult to prepare in the existing preparation method, so that the wide application of the nitrogen-doped porous carbon is greatly limited. In addition, the existing preparation method of the lignin-based porous carbon has the problems of complex process, high cost, difficulty in realizing adjustability of specific surface area and the like. Therefore, the obtained high-nitrogen-doped lignin-based porous carbon has the advantages of wide raw material source, low cost, high nitrogen content and large specific surface area, and the matched method for preparing the high-nitrogen-doped lignin-based porous carbon has the advantages of simple process, convenience in operation, mild and controllable preparation conditions and low cost, and has very important significance for improving the use value and the application range of the high-nitrogen-doped lignin-based porous carbon.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides the high-nitrogen-doped lignin-based porous carbon with wide raw material source, low cost, high nitrogen content and large specific surface area, and also provides a method for preparing the high-nitrogen-doped lignin-based porous carbon with simple process, convenient operation, mild and controllable preparation conditions and low cost.

In order to solve the technical problems, the invention adopts the technical scheme that:

the high-nitrogen-doped lignin-based porous carbon is prepared by calcining lignin, urea, zinc chloride and basic magnesium carbonate serving as raw materials.

The high-nitrogen-doped lignin-based porous carbon is further improved, wherein the mass ratio of urea to lignin is 0.5-2: 1; the mass ratio of the zinc chloride to the basic magnesium carbonate to the lignin is 1: 1-5: 1.

In the highly nitrogen-doped lignin-based porous carbon, the content of nitrogen in the highly nitrogen-doped lignin-based porous carbon is further improved to be 5.78-7.46% by mass; the specific surface area of the high-nitrogen doped lignin-based porous carbon is 1094.5m²/g～1342.5m²/g。

As a general technical concept, the present invention also provides a method for preparing a high nitrogen-doped lignin-based porous carbon, comprising the steps of:

s1, mixing lignin, urea, zinc chloride and basic magnesium carbonate, and grinding to obtain a mixed raw material;

s2, calcining the mixed raw material obtained in the step S1 to obtain carbonized powder;

and S3, soaking the carbonized powder obtained in the step S2 in an acid solution, washing to be neutral, and drying to obtain the high-nitrogen-doped lignin-based porous carbon.

In the above preparation method, the mass ratio of the urea to the lignin in the step S1 is further improved to be 0.5-2: 1; the mass ratio of the zinc chloride to the basic magnesium carbonate to the lignin is 1: 1-5: 1.

In the above preparation method, further improvement is provided, in the step S1, the grinding time is 5min to 10 min.

In a further improvement of the above preparation method, in step S2, the calcination is performed under the protection of an inert gas; the heating rate in the calcining process is 1-20 ℃/min; the calcining temperature is 600-1000 ℃; the calcining time is 0.5-5 h.

In the preparation method, the inert gas is nitrogen.

In a further improvement of the above preparation method, in step S3, the acid solution is a hydrochloric acid solution; the mass concentration of the acid solution is 10-15%; the soaking time is 12-24 h; the drying is carried out under vacuum conditions; the drying time is 24-48 h.

The preparation method is further improved, and the mass content of nitrogen element in the high-nitrogen-doped lignin-based porous carbon is 5.78-7.46%; the specific surface area of the high-nitrogen doped lignin-based porous carbon is 1094.5m²/g～1342.5m²/g。

Compared with the prior art, the invention has the advantages that:

(1) the invention provides a high-nitrogen-doped lignin-based porous carbon which is prepared by calcining lignin, urea, zinc chloride and basic magnesium carbonate serving as raw materials, wherein the lignin serving as a carbon source and the urea serving as a nitrogen source are calcined under the action of the zinc chloride and the basic magnesium carbonate, so that nitrogen elements are more easily doped into the lignin-based porous carbon, and the nitrogen content in the lignin-based porous carbon is favorably improved, and the high-nitrogen-doped lignin-based porous carbon is prepared. Compared with nitrogen-doped porous carbon prepared from other carbon sources, the lignin-based porous carbon with high nitrogen content can be prepared by taking lignin as a raw material, has the advantages of wide raw material source, low cost, high nitrogen content, large specific surface area and the like, and has high application value and good application prospect.

(2) The invention provides a preparation method of high-nitrogen-doped lignin-based porous carbon, which is prepared by mixing lignin, urea, zinc chloride and basic magnesium carbonate and then calcining the mixture in one step. According to the invention, lignin is used as a carbon source, urea is used as a nitrogen source, and calcination is carried out under the action of zinc chloride and basic magnesium carbonate, so that nitrogen elements can be more easily doped into lignin-based porous carbon, and the nitrogen content in the lignin-based porous carbon can be improved, and the high-nitrogen-doped lignin-based porous carbon with high nitrogen content can be prepared; meanwhile, in the calcining process, urea is gradually decomposed along with the increase of the carbonization temperature, so that nitrogen elements are introduced into the carbonized matrix; zinc chloride is converted into zinc oxide along with the temperature rise, the zinc oxide is converted into a zinc simple substance by further raising the temperature, and the porous carbon can generate macropores and mesopores by sublimating the zinc simple substance; the basic magnesium carbonate is converted into magnesium oxide along with the temperature rise, and then dissolved into a hydrochloric acid solution to generate mesopores and micropores in the porous carbon, so that the specific surface area of the lignin-based porous carbon can be remarkably increased. The preparation method of the high-nitrogen-doped lignin-based porous carbon has the advantages of simple process, convenient operation, mild and controllable preparation conditions and low cost, and simultaneously can realize one-step preparation of the high-nitrogen-doped lignin-based porous carbon, and the content of lignin-based porous carbon and nitrogen and the adjustable specific surface area can be realized by changing the preparation conditions.

(3) In the preparation method of the high-nitrogen-doped lignin-based porous carbon, the mass ratio of urea to lignin is optimized to be 0.5-2: 1, so that sufficient nitrogen sources can be ensured, nitrogen elements can be effectively doped into the lignin-based porous carbon, the nitrogen content of the lignin-based porous carbon can be improved, and the high-nitrogen-doped lignin-based porous carbon with higher nitrogen content can be obtained finally; by optimizing the mass ratio of the zinc chloride to the basic magnesium carbonate to the lignin to be 1: 1-5: 1, the pore structure of the lignin-based porous carbon can be optimized to have a hierarchical porous structure, and the specific surface area of the lignin-based porous carbon can be further increased to have a higher specific surface area.

(4) In the preparation method of the high-nitrogen-doped lignin-based porous carbon, the calcination condition is optimized, and the calcination is carried out at the temperature of 600-1000 ℃, so that the preparation method is more favorable for preparing the high-nitrogen-doped lignin-based porous carbon with high nitrogen content and large specific surface area.

Drawings

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.

Fig. 1 is a scanning electron microscope image of the highly nitrogen-doped lignin-based porous carbon prepared in example 1 of the present invention.

Fig. 2 is an adsorption and desorption graph of the high nitrogen-doped lignin-based porous carbon prepared in example 1 of the present invention.

Fig. 3 is a pore size distribution diagram of the highly nitrogen-doped lignin-based porous carbon prepared in example 1 of the present invention.

Detailed Description

The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.

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

Example 1

A high-nitrogen doped lignin-based porous carbon is prepared by calcining lignin, urea, zinc chloride and basic magnesium carbonate serving as raw materials, and comprises the following steps:

mixing 0.5g of lignin, 0.25g of urea, 1.5g of zinc chloride and 0.5g of basic magnesium carbonate, and grinding for 10min to obtain a mixed raw material; then, under the protection of nitrogen, the ground sample (mixed raw material) is heated from room temperature to 900 ℃ at the heating rate of 3 ℃/min, the temperature is kept for 2h, and the temperature is naturally reduced to obtain carbonized powder; and then, putting the carbonized sample (carbonized powder) into a hydrochloric acid solution with the mass concentration of 10% to be soaked for 24h, washing the sample to be neutral by using deionized water, and drying the sample in vacuum for 24h to obtain the high-nitrogen doped lignin-based porous carbon.

Fig. 1 is a scanning electron microscope image of the highly nitrogen-doped lignin-based porous carbon prepared in example 1 of the present invention. As can be seen from fig. 1, the high-nitrogen-doped lignin-based porous carbon prepared by the method has a porous structure, and the mass content of nitrogen in the high-nitrogen-doped lignin-based porous carbon measured by an element analyzer is 5.78%.

Fig. 2 is an adsorption and desorption graph of the high nitrogen-doped lignin-based porous carbon prepared in example 1 of the present invention. As can be seen from FIG. 2, the surface area of the highly nitrogen-doped lignin-based porous carbon prepared by the method is 1283.6m²/g。

Fig. 3 is a pore size distribution diagram of the highly nitrogen-doped lignin-based porous carbon prepared in example 1 of the present invention. As can be seen from fig. 3, the highly nitrogen-doped lignin-based porous carbon prepared by the present invention has a microporous structure and a mesoporous structure, and the results are the same as those in fig. 1.

Example 2

A high-nitrogen doped lignin-based porous carbon is prepared by calcining lignin, urea, zinc chloride and basic magnesium carbonate serving as raw materials, and comprises the following steps:

mixing 0.5g of lignin, 0.5g of urea, 1.5g of zinc chloride and 0.5g of basic magnesium carbonate, and grinding for 10min to obtain a mixed raw material; then, under the protection of nitrogen, the ground sample (mixed raw material) is heated from room temperature to 900 ℃ at the heating rate of 3 ℃/min, the temperature is kept for 2h, and the temperature is naturally reduced to obtain carbonized powder; and then, putting the carbonized sample (carbonized powder) into a hydrochloric acid solution with the mass concentration of 10% to be soaked for 24h, washing the sample to be neutral by using deionized water, and drying the sample in vacuum for 24h to obtain the high-nitrogen doped lignin-based porous carbon.

Through testing, the high-nitrogen-doped lignin-based porous carbon prepared in example 2 has a porous structure; the mass content of nitrogen element in the high-nitrogen-doped lignin-based porous carbon measured by an element analyzer is 6.77%, which is increased compared with the nitrogen content in example 1; the surface area of the sample was 1094.5m as measured by a specific surface analyzer²The specific surface area is reduced compared with that of example 1.

Example 3

A high-nitrogen doped lignin-based porous carbon is prepared by calcining lignin, urea, zinc chloride and basic magnesium carbonate serving as raw materials, and comprises the following steps:

mixing 0.5g of lignin, 0.25g of urea, 2g of zinc chloride and 0.5g of basic magnesium carbonate, and grinding for 10min to obtain a mixed raw material; then, under the protection of nitrogen, the ground sample (mixed raw material) is heated from room temperature to 900 ℃ at the heating rate of 3 ℃/min, the temperature is kept for 2h, and the temperature is naturally reduced to obtain carbonized powder; and then, putting the carbonized sample (carbonized powder) into a hydrochloric acid solution with the mass concentration of 10% to be soaked for 24h, washing the sample to be neutral by using deionized water, and drying the sample in vacuum for 24h to obtain the high-nitrogen doped lignin-based porous carbon.

Through testing, the high-nitrogen-doped lignin-based porous carbon prepared in example 3 has a porous structure; the mass content of nitrogen element in the high-nitrogen-doped lignin-based porous carbon measured by an element analyzer is 7.29%, and compared with the nitrogen content in the embodiment 1, the nitrogen content is increased; the surface area of the sample was 1299.8m as measured by a specific surface analyzer²The specific surface area was moderately increased as compared with example 1.

Example 4

A high-nitrogen doped lignin-based porous carbon is prepared by calcining lignin, urea, zinc chloride and basic magnesium carbonate serving as raw materials, and comprises the following steps:

mixing 0.5g of lignin, 0.25g of urea, 1.5g of zinc chloride and 1g of basic magnesium carbonate, and grinding for 10min to obtain a mixed raw material; then, under the protection of nitrogen, the ground sample (mixed raw material) is heated from room temperature to 900 ℃ at the heating rate of 3 ℃/min, the temperature is kept for 2h, and the temperature is naturally reduced to obtain carbonized powder; and then, putting the carbonized sample (carbonized powder) into a hydrochloric acid solution with the mass concentration of 10% to be soaked for 24h, washing the sample to be neutral by using deionized water, and drying the sample in vacuum for 24h to obtain the high-nitrogen doped lignin-based porous carbon.

Through testing, the high-nitrogen-doped lignin-based porous carbon prepared in example 4 has a porous structure; the mass content of nitrogen element in the high-nitrogen-doped lignin-based porous carbon measured by an element analyzer is 7.46%, and compared with the nitrogen content in the embodiment 1, the nitrogen content is increased; the surface area of the sample was 1342.5m as measured by a specific surface analyzer²The specific surface area was moderately increased as compared with example 1.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-described embodiments. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.