CN110357096B - Nitrogen-doped activated carbon based on alkali/urea dissolving system and preparation method thereof - Google Patents
Nitrogen-doped activated carbon based on alkali/urea dissolving system and preparation method thereof Download PDFInfo
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- CN110357096B CN110357096B CN201910674408.XA CN201910674408A CN110357096B CN 110357096 B CN110357096 B CN 110357096B CN 201910674408 A CN201910674408 A CN 201910674408A CN 110357096 B CN110357096 B CN 110357096B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
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- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/318—Preparation characterised by the starting materials
- C01B32/324—Preparation characterised by the starting materials from waste materials, e.g. tyres or spent sulfite pulp liquor
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/342—Preparation characterised by non-gaseous activating agents
Abstract
The invention discloses nitrogen-doped activated carbon based on an alkali/urea dissolving system and a preparation method thereof. Meanwhile, under the activation action of alkali, the plant raw materials and the three-dimensional polymer form a skeleton structure of the activated carbon in the heat treatment process, and the specific surface area of the activated carbon product is favorably improved. Therefore, the invention can prepare the activated carbon product with high specific surface area and high nitrogen content, and the process has the advantages of environmental protection, simple operation and reproducible product.
Description
Technical Field
The invention belongs to the technical field of activated carbon preparation, and particularly relates to nitrogen-doped activated carbon based on an alkali/urea dissolving system and a preparation method thereof.
Background
With the increasing increase of air pollution, the demand of green high-efficiency adsorbents is larger and larger, and active carbon as a porous carbon-containing substance has huge specific surface area, developed pore structure and abundant surface oxygen-containing functional groups, so that the active carbon is more and more valued and applied in the fields of adsorption, catalysis, catalyst carriers and the like. With social development and technological progress, the application field of the activated carbon is continuously expanded, and the requirements on the activated carbon are higher and higher. Therefore, a novel multifunctional carbon material with high adsorption and wide application has become a hot spot of research and attack at present.
Nitrogen-doped activated carbon has been gaining attention as a new functional material. The preparation of nitrogen-doped activated carbon materials is mainly divided into two categories: an active carbon post-treatment surface modification method and a nitrogen-rich precursor in-situ synthesis method. However, both methods have difficulty in producing an activated carbon product having both a "high specific surface area" and a "high nitrogen content". Therefore, the research and development of the activated carbon product with high specific surface area and high nitrogen doping amount are significant.
Disclosure of Invention
The invention aims to provide nitrogen-doped activated carbon based on an alkali/urea dissolving system and a preparation method thereof, and the prepared activated carbon product has the advantages of high specific surface area and high nitrogen doping amount, green and environment-friendly process, simple operation, renewable product and contribution to industrial popularization.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for preparing nitrogen-doped activated carbon based on an alkali/urea dissolving system comprises the following preparation steps:
(1) selecting plant material with particle size of 0.18-0.25 mm, and drying;
(2) preparing an alkali/urea solution, and freezing;
(3) mixing the plant raw material in the step (1) with the alkali/urea solution unfrozen in the step (2), adding a nitrogen-rich organic compound, freezing at low temperature, and then activating;
(4) and (4) after the sample in the step (3) is cooled to room temperature, carrying out acid washing and water washing until the pH value is neutral, and then drying to obtain the nitrogen-doped activated carbon.
The plant raw materials comprise sawdust, bamboo scraps, fruit shells, grass scraps and the like.
The alkali is one or the mixture of sodium hydroxide and potassium hydroxide, the alkali/urea solution is the mixture of alkali, urea and water, the nitrogen-rich compound is melamine, polyaniline, acetonitrile and chitosan, the mass ratio of the alkali to the urea in the alkali/urea solution is 1:1-3:1, the mass ratio of the plant raw material to the alkali/urea solution is 1:1-1:4, the mass ratio of the nitrogen-rich organic compound to the plant raw material is 1:2-1:20, the low-temperature freezing time is 1-4h, the activation temperature is 600-900 ℃, and the activation time is 1-4 h.
The invention has the beneficial effects that: plant raw materials are added into a low-temperature alkali/urea dissolving system, alkali and water can form new hydrogen bonds with hydroxyl groups in cellulose between molecules and in molecules, so that the cellulose is dissolved, and meanwhile, a nitrogen-rich compound is added, so that a crosslinking reaction can be generated between the nitrogen-rich compound and aromatic hydrocarbon groups, aliphatic hydrocarbon groups, hydroxymethyl groups and other groups in the plant raw materials, a three-dimensional polymer is formed, stable structural nitrogen can be formed on the surface of an active carbon material in situ, and the nitrogen doping amount of the active carbon is increased. Meanwhile, under the activation action of alkali, the plant raw materials and the three-dimensional polymer form a skeleton structure of the activated carbon in the heat treatment process, and the specific surface area of the activated carbon product is favorably improved. The invention is a new technology which is green and environment-friendly, simple to operate and reproducible in product.
Detailed Description
In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.
Example 1
The alkali/urea solution (20 g of sodium hydroxide, 20g of potassium hydroxide, 40g of urea, 160g of water) was frozen. And then, mixing 80g of sawdust with the granularity of 0.18-0.25 mm with the unfrozen alkali/urea solution, adding 20g of melamine, freezing at low temperature for 4 hours, then activating at 850 ℃ for 1 hour, cooling to room temperature, carrying out acid washing and water washing until the pH value is neutral, and drying to obtain the nitrogen-doped activated carbon.
The obtained nitrogen-doped active carbon in this example has an iodine adsorption value of 1142 mg/g and a specific surface area of 1270 m 2 In terms of a/g, the nitrogen content was 9.64%.
Example 2
The base/urea solution (20 g of sodium hydroxide, 20g of urea, 40g of water) was frozen. And then, mixing 80g of bamboo sawdust with the granularity of 0.18-0.25 mm with the unfrozen alkali/urea solution, adding 40g of acetonitrile, freezing at low temperature for 1h, then activating at 600 ℃ for 3h, cooling to room temperature, carrying out acid washing and water washing until the pH value is neutral, and drying to obtain the nitrogen-doped activated carbon.
The obtained nitrogen-doped active carbon in the example has an iodine adsorption value of 546 mg/g and a specific surface area of 612 m 2 The nitrogen content was 8.26% per gram.
Example 3
The base/urea solution (60 g potassium hydroxide, 20g urea, 120g water) was frozen. And then, mixing 80g of grass clippings with the granularity of 0.18-0.25 mm with the unfrozen alkali/urea solution, adding 40g of polyaniline, freezing for 3 hours at a low temperature, then activating for 2 hours at 900 ℃, cooling to room temperature, carrying out acid washing and water washing until the pH value is neutral, and drying to obtain the nitrogen-doped activated carbon.
The obtained nitrogen-doped active carbon in the example has an iodine adsorption value of 1314 mg/g and a specific surface area of 1460 m 2 In terms of a/g, the nitrogen content was 4.41%.
Example 4
The base/urea solution (40 g of sodium hydroxide, 30g of urea, 100g of water) was frozen. And then, mixing 80g of grass clippings with the granularity of 0.18-0.25 mm with the unfrozen alkali/urea solution, adding 30g of chitosan, freezing at low temperature for 2h, then activating at 800 ℃ for 1h, cooling to room temperature, carrying out acid washing and water washing until the pH value is neutral, and drying to obtain the nitrogen-doped activated carbon.
The iodine adsorption value of the nitrogen-doped active carbon obtained in the example is 1126 mg/g, and the specific surface area is 1242 m 2 In terms of a/g, the nitrogen content was 5.26%.
Example 5
The alkali/urea solution (60 g of sodium hydroxide, 40g of potassium hydroxide, 60g of urea, 160g of water) was frozen. And then, mixing 80g of fruit shells with the granularity of 0.18-0.25 mm with the unfrozen alkali/urea solution, adding 30g of melamine, freezing at low temperature for 2.5h, then activating at 700 ℃ for 4h, cooling to room temperature, carrying out acid washing and water washing until the pH value is neutral, and drying to obtain the nitrogen-doped activated carbon.
The obtained nitrogen-doped active carbon in the example has an iodine adsorption value of 984 mg/g and a specific surface area of 1066 m 2 The nitrogen content was 12.46% per gram.
Example 6
The alkali/urea solution (30 g of sodium hydroxide, 10g of potassium hydroxide, 20g of urea, 40g of water) was frozen. And then, mixing 80g of bamboo sawdust with the granularity of 0.18-0.25 mm with the unfrozen alkali/urea solution, adding 4g of chitosan, freezing at low temperature for 3h, then activating at 850 ℃ for 2h, cooling to room temperature, carrying out acid washing and water washing until the pH value is neutral, and drying to obtain the nitrogen-doped activated carbon.
The obtained nitrogen-doped active carbon in this example has an iodine adsorption value of 1096 mg/g and a specific surface area of 1204 m 2 In terms of a/g, the nitrogen content was 2.12%.
TABLE 1 Performance of nitrogen-doped activated carbon under different Process conditions
Note: in the table, the alkali is mixed alkali of potassium hydroxide of sodium hydroxide, the mass ratio is 1:1, the mass ratio of the alkali to the urea in the alkali/urea solution is 1:1, the mass ratio of the wood chips to the alkali/urea solution is 1:3, the ratio of melamine to the wood chips is 1:4, the activation temperature is 850 ℃, and the activation time is 1 h.
As can be seen from the table, the specific surface area and the nitrogen content of the nitrogen-doped activated carbon (sample 1) prepared by the low-temperature alkali/urea system are higher than those of the activated carbon (sample 2) prepared by the normal-temperature alkali/urea system; compared with the activated carbon (sample 3) prepared by taking a wood material as a raw material, the nitrogen-rich organic compound is introduced into a low-temperature alkali/urea system, so that the specific surface area and the nitrogen content of the activated carbon (sample 1) are favorably improved. Therefore, the nitrogen-rich compound is added into the low-temperature alkali/urea dissolving system, alkali and water can form new hydrogen bonds with hydroxyl groups in cellulose between molecules and in molecules, so that the cellulose is dissolved, and the nitrogen-rich compound enters the interior of wood to generate a crosslinking reaction with aromatic hydrocarbon groups, aliphatic hydrocarbon groups, hydroxymethyl groups and other groups in the wood material to form a three-dimensional polymer, thereby being beneficial to forming stable structural nitrogen on the surface of the activated carbon material in situ, improving the nitrogen doping amount of the activated carbon, and simultaneously, crosslinking and enlarging a pore structure under the action of alkali, so that the specific surface area is increased. Therefore, the invention can prepare the activated carbon product with high specific surface area and high nitrogen doping amount.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (7)
1. A method for preparing nitrogen-doped activated carbon based on an alkali/urea dissolving system is characterized by comprising the following steps: the method comprises the following steps:
(1) selecting plant material with particle size of 0.18-0.25 mm, and oven drying;
(2) preparing an alkali/urea solution and freezing;
(3) mixing the plant raw material in the step (1) with the alkali/urea solution unfrozen in the step (2), adding a nitrogen-rich organic compound, freezing at low temperature, and activating at 900 ℃ for 2 hours;
(4) and cooling to room temperature, carrying out acid washing and water washing until the pH value is neutral, and drying to obtain the nitrogen-doped active carbon.
2. The method of claim 1, wherein: the plant material is one or more of sawdust, bamboo sawdust, fruit shell, and grass sawdust.
3. The method of claim 1, wherein: the alkali is one or a mixture of sodium hydroxide and potassium hydroxide.
4. The method of claim 1, wherein: the mass ratio of the alkali to the urea in the alkali/urea solution is 1:1-3:1, the solvent is water, and the mass ratio of the plant raw material to the alkali/urea solution is 1:1-1: 4.
5. The method of claim 1, wherein: the nitrogen-rich organic compound is one of melamine, polyaniline, acetonitrile and chitosan, and the mass ratio of the nitrogen-rich organic compound to the plant raw material is 1:2-1: 20.
6. The method of claim 1, wherein: the low-temperature freezing time is 1-4 h.
7. An right as rightThe nitrogen-doped activated carbon based on the alkali/urea dissolving system prepared by the method of claim 1 is characterized in that: the iodine adsorption value of the nitrogen-doped active carbon is 546-1314 mg/g, and the specific surface area is 612-1460 m 2 The nitrogen content is 2.12-12.46 percent per gram.
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| CN103950929A (en) * | 2014-05-23 | 2014-07-30 | 福建农林大学 | Method for preparing granular active carbon by adopting chemical method |
| CN107416820A (en) * | 2017-07-18 | 2017-12-01 | 广西大学 | A kind of N, O, the preparation method of the netted graphitized carbon nano material of S doping |
| CN108190885A (en) * | 2018-02-14 | 2018-06-22 | 福建农林大学 | A kind of preparation method of the activated carbon of Uniform Doped metal |
| KR101966229B1 (en) * | 2017-11-06 | 2019-04-05 | 한국에너지기술연구원 | Method for preparation of hierarchically porous nitrogen-doped carbon derived from biomass |
| CN109775692A (en) * | 2017-11-15 | 2019-05-21 | 南京理工大学 | The preparation method of heteroatom doped graphene |
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| CN103950929A (en) * | 2014-05-23 | 2014-07-30 | 福建农林大学 | Method for preparing granular active carbon by adopting chemical method |
| CN107416820A (en) * | 2017-07-18 | 2017-12-01 | 广西大学 | A kind of N, O, the preparation method of the netted graphitized carbon nano material of S doping |
| KR101966229B1 (en) * | 2017-11-06 | 2019-04-05 | 한국에너지기술연구원 | Method for preparation of hierarchically porous nitrogen-doped carbon derived from biomass |
| CN109775692A (en) * | 2017-11-15 | 2019-05-21 | 南京理工大学 | The preparation method of heteroatom doped graphene |
| CN108190885A (en) * | 2018-02-14 | 2018-06-22 | 福建农林大学 | A kind of preparation method of the activated carbon of Uniform Doped metal |
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