Preparation method of super-microporous bamboo-based porous carbon

Abstract

The application discloses a preparation method and application of super-microporous bamboo-based porous carbon. The bamboo-based porous carbon material with a super-microporous volume ratio of 80% or above and a pore diameter of less than 1 nm is prepared by adding a nitrogen source and an activating agent through a carbon slurry compression molding process and pyrolysis at high temperature. The material has a large CO2 adsorption capacity under the condition of 273 K / 1 bar and is stable in circulation, and is suitable for industrial carbon capture and new energy fields.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a method for preparing ultramicroporous bamboo-based porous carbon by carbon slurry pressing, and its application in carbon dioxide (CO2) capture and conversion and in the field of new energy. Background Technology

[0002] With the acceleration of industrialization, global greenhouse gas emissions are constantly increasing, especially carbon dioxide emissions, which have become one of the main causes of global warming. To address this challenge, countries are seeking effective carbon reduction and capture technologies. Among these, carbon dioxide adsorption technology, due to its advantages of low energy consumption, ease of operation, and environmental friendliness, has become an important component of the carbon capture, utilization, and storage (CCUS) strategy. Porous carbon materials, due to their excellent specific surface area, pore structure, and chemical stability, have been widely studied for carbon dioxide adsorption.

[0003] Currently, the main methods for preparing porous carbon materials include chemical activation, physical activation, and template methods. Chemical activation typically uses chemical reagents such as KOH and ZnCl2 as activators to form a rich pore structure in the carbon material through chemical reactions. However, these methods have some limitations. For example, the KOH activation process often suffers from insufficient micropore content and uneven pore size distribution, and it is also highly corrosive to equipment, limiting its application in the field of carbon dioxide adsorption.

[0004] Micropores (pore size less than 2 nanometers) play a crucial role in carbon dioxide adsorption. Micropores can adsorb carbon dioxide molecules through van der Waals forces (including induced dipole forces and transient dipole forces), a process particularly pronounced at low temperatures. Therefore, increasing the micropore volume fraction and optimizing the pore size distribution in porous carbon materials are essential for improving their carbon dioxide adsorption performance. However, current technologies lack an efficient preparation method that can effectively increase the micropore volume fraction while simultaneously optimizing the pore size distribution.

[0005] Based on the above considerations, this invention proposes a method for preparing ultramicroporous bamboo-based porous carbon based on carbon slurry pressing. The aim is to solve the above problems through an innovative preparation process and prepare porous carbon materials with ultramicropore content, excellent pore structure stability and efficient carbon dioxide adsorption performance. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low micropore content and unstable structure of porous carbon materials, and to provide a porous carbon material with ultra-high micropore content and its preparation method.

[0007] Another object of the present invention is to provide the above-mentioned ultramicroporous bamboo-based porous carbon suitable for CO2 adsorption.

[0008] The objective of this invention is achieved through the following technical solution: a method for preparing ultramicroporous bamboo-based porous carbon, comprising the following steps:

[0009] (1) Pre-carbonization: Bamboo powder is pyrolyzed under an inert atmosphere to obtain carbon precursor;

[0010] (2) Ball milling: Place the carbon precursor powder from step (1) in a ball milling bottle, add nitrogen source, activator and solvent in a certain proportion, and place it on a ball mill for ball milling to make a slurry;

[0011] (3) Tableting: The slurry obtained in step (2) is compacted into blocks under a certain pressure using a powder tableting machine;

[0012] (4) Carbonization: The compacted solid is placed in a crucible and sent into a tube furnace. The temperature is adjusted to the target temperature and pyrolysis carbonization is carried out under an inert atmosphere to obtain a solid product.

[0013] (5) Acid washing: The solid product was initially washed with hydrochloric acid, then washed with deionized water until the filtrate reached a neutral pH value, and then dried to obtain ultra-microporous bamboo-based porous carbon.

[0014] According to the present invention, the microporous carbon in claim 1 is a porous carbon material in which the volume ratio of micropores is 80% or more and the average pore size is less than 1 nm.

[0015] According to the present invention, the bamboo powder selected in step (1) has a particle size of 20-300 mesh, preferably 80-120 mesh.

[0016] According to the present invention, the inert atmosphere selected in step (1) is nitrogen, helium, neon, argon, krypton and other atmospheres that do not oxidize carbon.

[0017] According to the present invention, the pre-carbonization temperature in step (1) is 200-600℃, the heating rate is 5℃ / min, and the processing time is 3-12h.

[0018] According to the present invention, the nitrogen source selected in step (2) is at least one of urea, chitosan, dicyandiamide, melamine-formaldehyde resin and polyethyleneimine.

[0019] According to the present invention, the activator selected in step (2) is at least one of potassium acetate, potassium propionate and potassium oxalate.

[0020] According to the present invention, in step (2), the ratio of carbon precursor to nitrogen source is 1:1-10.

[0021] According to the present invention, in step (2), the ratio of carbon precursor to activator is 1:1-20.

[0022] According to the present invention, the solvent in step (2) is at least one of methanol, ethanol, propanol, isopropanol, butanol, n-butanol and tert-butanol.

[0023] According to the present invention, in step (3), the powder tablet press is used to compress tablets at a pressure of 1-50 MPa, preferably 10-20 MPa.

[0024] According to the present invention, in step (4), pyrolysis is carried out at a temperature of 600-1000℃ in an inert gas atmosphere for a time of 2-24h, preferably 2-6h. Preferably, the heating rate is 5℃ / min and the inert gas flow rate is 50 mL / min.

[0025] According to the present invention, preferably, the rotation speed of the ball mill in step (2) is 200-1000 rpm and the ball milling time is 2-6 hours.

[0026] According to the present invention, preferably, the hydrochloric acid used in step (5) has a mass fraction of 5-10%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention uses bamboo charcoal made from crushed bamboo as the carbon source. Before carbonization, the charcoal is compressed into tablets to increase the contact area between the precursor and the activator. After compaction, the compacted block forms an interconnected pore network during activation, improving the efficiency of micropore formation. The volume percentage of micropores increases from 55% in traditional processes to over 80%, with a pore size of less than 1 nm. This method has the following advantages: a) Compaction reduces volume, improving furnace production efficiency; b) The microporous bamboo-based porous carbon prepared by this method has a large CO2 adsorption capacity. Attached Figure Description

[0029] Figure 1 This is a TEM image of the ultramicroporous bamboo-based porous carbon prepared in Example 1.

[0030] Figure 2 The nitrogen adsorption-desorption curve is shown for the ultramicroporous bamboo-based porous carbon prepared in Example 1.

[0031] Figure 3 The image shows the pore size distribution of the ultramicroporous bamboo-based porous carbon prepared in Example 1.

[0032] Figure 4 This is a CO2 adsorption diagram of the ultramicroporous bamboo-based porous carbon prepared in Example 1. Detailed Implementation

[0033] The embodiments of the present invention will be described in detail below with reference to the examples. However, the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention.

[0034] Example 1

[0035] Bamboo was washed, dried, pulverized, and sieved to 80-120 mesh. It was then pre-carbonized under a nitrogen atmosphere at a heating rate of 5℃ / min, a pre-carbonization temperature of 600℃, and a pyrolysis time of 6 hours. After natural cooling to room temperature, carbon precursor powder was obtained. 3g of the carbon precursor, 6g of polyethyleneimine, 6g of potassium propionate, and 3ml of ethanol were mixed and ball-milled for 3 hours to form a slurry. The slurry was compacted into blocks at 20MPa and placed in a tube furnace for high-temperature pyrolysis under a nitrogen atmosphere at 800℃ for 5 hours to obtain porous carbon material. This material was then washed with 5% hydrochloric acid and deionized water until the filtrate pH was neutral, and then dried to obtain the final product.

[0036] Figure 1 The image shows a TEM image of the ultramicroporous bamboo-based porous carbon prepared in Example 1. The image reveals a tendency for the pores to interconnect, indicating enhanced pore connectivity, which is beneficial for processes such as gas transport and electrolyte diffusion.

[0037] Figure 2 The figure shows the nitrogen adsorption-desorption curves of the ultramicroporous bamboo-based porous carbon prepared in Example 1. As can be seen from the figure, the sample exhibits typical type I adsorption. The high adsorption capacity within the ultramicroporous absorption range at relative pressures below 0.2 indicates that this porous carbon possesses a large number of ultramicroporous structures.

[0038] Figure 3 The figure shows the pore size distribution of the ultramicroporous bamboo-based porous carbon prepared in Example 1. As can be seen from the figure, the pore size is mainly distributed in the ranges of 0.4-0.7 nm and 0.7-0.9 nm. The sample is predominantly ultramicroporous, with ultramicropores accounting for 84% of the volume, which is beneficial for CO2 adsorption.

[0039] Figure 4 The image shows the CO2 adsorption of the ultramicroporous bamboo-based porous carbon prepared in Example 1. The material has a CO2 adsorption capacity of 300 mg / g at 273 K / 1 bar.

[0040] Examples 2-6

[0041] The difference from Example 1 lies in the nitrogen source and activator used, the carbon precursor and their ratio, and the temperature. The specific volume ratio of the ultramicropores is shown in the table below.

[0042] Example Nitrogen source type Activator Temperature ℃ Carbon precursor / nitrogen source Carbon precursor / activator Ultra-micropore ratio <![CDATA[CO2 adsorption capacity (mg / g)]]> 2 Chitosan Potassium acetate 800 1：1 1：2 83% 295 3 Chitosan Potassium propionate 700 1：2 1：3 81% 290 4 melamine-formaldehyde resin Potassium propionate 900 1：10 1：4 82% 293 5 melamine-formaldehyde resin Potassium acetate 800 1：3 1：10 81% 277 6 Polyethyleneimine Potassium acetate 800 1：5 1：20 83% 292

[0043] Comparative Examples 1-3

[0044] The difference between Comparative Examples 1 and 2 and Examples 2 and 4 is that they were not ball-milled and compacted. The difference between Comparative Example 3 and Example 2 is that the activator used is different. The proportion of porous carbon micropores prepared is shown in the table below.

[0045] Comparative Example Nitrogen source type Activator Temperature ℃ Carbon precursor / nitrogen source Carbon precursor / activator Ultra-micropore ratio <![CDATA[CO2 adsorption capacity (mg / g)]]> 1 Chitosan Potassium acetate 800 1：1 1：2 52% 195 2 melamine-formaldehyde resin Potassium propionate 900 1：10 1：4 58% 210 3 Chitosan potassium hydroxide 800 1：1 1：2 56% 205

Claims

1. A method for preparing ultramicroporous bamboo-based porous carbon, characterized in that, Includes the following steps: (1) Pre-carbonization: Bamboo powder is pyrolyzed under an inert gas atmosphere to obtain carbon precursor; (2) Ball milling: The carbon-containing solid powder from step (1) is placed in a ball milling bottle, and a nitrogen source, activator and solvent are added in a certain proportion. The mixture is then placed in a ball milling machine for ball milling to make a slurry. (3) Tableting: The slurry obtained in step (2) is compacted into blocks under a certain pressure using a tablet press; (4) Carbonization: The compacted solid is placed in a crucible and sent into a tube furnace. The temperature is adjusted to the target temperature and pyrolysis carbonization is carried out under an inert atmosphere to obtain a solid product. (5) Acid washing: The solid product was initially washed with hydrochloric acid, then washed with deionized water until the filtrate reached a neutral pH value, and then dried to obtain ultra-microporous bamboo-based porous carbon.

2. The preparation method according to claim 1, characterized in that, Ultraporous carbon refers to porous carbon materials with an average pore size of less than 1 nm.

3. The preparation method according to claim 1, characterized in that, The bamboo powder used in step (1) has a particle size of 20-300 mesh, preferably 80-120 mesh.

4. The preparation method according to claim 1, characterized in that, The inert atmosphere selected in step (1) is nitrogen, helium, neon, argon, krypton and other atmospheres that do not oxidize carbon.

5. The preparation method according to claim 1, characterized in that, In step (1), the pre-carbonization pyrolysis temperature is 200-600℃ and the processing time is 3-12h.

6. The preparation method according to claim 1, characterized in that, The nitrogen source selected in step (2) is at least one of urea, chitosan, dicyandiamide, melamine-formaldehyde resin and polyethyleneimine.

7. The preparation method according to claim 1, characterized in that, The activator selected in step (2) is at least one of potassium acetate, potassium propionate and potassium oxalate.

8. The method according to claim 1, characterized in that, In step (2), the ratio of carbon precursor to nitrogen source is 1:1-10.

9. The preparation method according to claim 1, characterized in that, In step (2), the ratio of carbon precursor to activator is 1:1-20.

10. The preparation method according to claim 1, characterized in that, The solvent in step (2) is at least one of methanol, ethanol, propanol, isopropanol, butanol, n-butanol and tert-butanol.

11. The preparation method according to claim 1, characterized in that, In step (3), the powder tablet press is used to compress tablets at 1-50 MPa, preferably 10-20 MPa.

12. The preparation method according to claim 1, characterized in that, In step (4), the pyrolysis is carried out at a target temperature of 600-1000℃ under an inert gas atmosphere for 2-24 hours, preferably 2-6 hours.

13. The porous carbon material prepared by any method according to claim 1 has an ultramicropore volume ratio of 80% or more and a pore size of less than 1 nm.

Images