Amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method

Abstract

The application belongs to the technical field of CO2 adsorption materials, and discloses an amine modified mesoporous activated carbon for CO2 adsorption with high adsorption capacity and excellent cycle stability and a preparation method thereof. The preparation method of the amine modified mesoporous activated carbon for CO2 adsorption comprises the following steps: (1) kneading and forming bamboo charcoal powder, a binder and a dispersing agent to obtain a green body; (2) performing carbonization treatment on the green body to obtain carbonized material; (3) performing one-stage activation treatment on the carbonized material to obtain a precursor; (4) performing two-stage activation treatment on the precursor to obtain mesoporous activated carbon; (5) performing amine modification treatment on the mesoporous activated carbon by using a polyene polyamine compound and a crosslinking agent to obtain the amine modified mesoporous activated carbon; wherein the one-stage activation treatment and the two-stage activation treatment are continuous water vapor heat activation treatments, the one-stage activation treatment temperature is higher than the two-stage activation treatment temperature, and the water vapor consumption of the one-stage activation treatment is less than that of the two-stage activation treatment.

Description

Technical Field

[0001] This invention relates to the technical field of CO2 adsorption materials, and more specifically, to amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method. Background Technology

[0002] Direct air capture (DAC) carbon dioxide technology has attracted widespread attention. Current carbon capture technologies are mainly divided into two categories: liquid absorption and solid adsorption. While liquid absorption technologies (such as alkaline hydroxide solutions and amine solutions) can achieve efficient capture through chemical reactions, their regeneration process typically requires high-temperature desorption at 120–150°C, resulting in extremely high capture energy consumption and poor economic efficiency. In contrast, solid adsorption technology has become a research hotspot due to its lower regeneration energy consumption. Among many solid adsorbent materials, metal-organic frameworks (MOFs) possess high specific surface area and tunable pore structure, but their raw materials often contain precious metals, leading to high preparation costs. Furthermore, in practical applications, environmental humidity can easily cause a decrease in their CO2 adsorption capacity of more than 40%.

[0003] To reduce costs and improve stability, researchers have developed solid amine adsorbents supported on porous materials, specifically loading amine groups such as polyethyleneimine (PEI) and tetraethylenepentamine (TEPA) onto silica or activated carbon. Activated carbon, with its wide availability, high specific surface area, well-developed pores, and good physicochemical stability, is considered one of the most promising low-cost supports. However, existing activated carbon-based solid amine adsorbents still face significant performance bottlenecks in practical applications.

[0004] Existing activated carbon preparation processes typically employ a conventional two-stage carbonization followed by a single-stage activation process. Activated carbon produced by this traditional method often exhibits a predominantly microporous structure, lacking well-developed mesopores. When amine modification is performed, large polyene-polyamine compounds readily clog these narrow micropores, leading to a sharp reduction in the specific surface area of ​​the modified adsorbent. This severely hinders the diffusion of CO2 molecules within the pores, making it difficult to improve the actual adsorption capacity of the material. Simultaneously, the density of oxygen-containing and other active functional groups on the surface of activated carbon prepared by traditional methods is insufficient, significantly limiting its amine loading capacity. Furthermore, existing technologies often employ simple physical impregnation methods for amine modification, where the amine groups are bound to the carbon support only by weak physical adsorption forces. During subsequent temperature-dependent adsorption-desorption cycles, amine volatilization and loss are highly likely, resulting in extremely poor cycle stability of the adsorbent. Therefore, existing activated carbon-based solid amine adsorbents struggle to simultaneously achieve high adsorption capacity and excellent cycle stability. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide an amine-modified mesoporous activated carbon for CO2 adsorption that combines high adsorption capacity and excellent cycling stability, and a method for its preparation. The technical solution is as follows: The preparation method of amine-modified mesoporous activated carbon for CO2 adsorption includes the following steps: (1) Mix bamboo charcoal powder, binder and dispersant together to form a blank; (2) Carbonize the billet to obtain carbonized material; (3) The carbonized material is subjected to a first-stage activation treatment to obtain the precursor; the temperature of the first-stage activation treatment is 900-950℃ and the steam hourly space velocity is 0.45-0.55 g / (g·h); (4) The precursor is subjected to a two-stage activation treatment to obtain mesoporous activated carbon; the temperature of the two-stage activation treatment is 800-900℃, and the temperature of the first-stage activation treatment is at least 50℃ higher than that of the second-stage activation treatment, and the water vapor mass hourly velocity is 1.4-1.6 g / (g·h). (5) The mesoporous activated carbon is modified with polyene polyamine compounds and crosslinking agents to obtain amine-modified mesoporous activated carbon; the polyene polyamine compounds are tetraethylenepentamine or polyethyleneimine, and the crosslinking agents are polyethylene glycol diglycidyl ether. The first-stage activation treatment and the second-stage activation treatment are continuous steam thermal activation treatments.

[0006] The method for preparing amine-modified mesoporous activated carbon for CO2 adsorption of the present invention has the following advantages: (1) This invention breaks through the technical bottleneck of conventional single activation leading to excessive micropores and easy blockage by macromolecular amines. It innovatively adopts a "two-stage continuous steam thermal activation" process with reverse control of temperature and steam usage. In the first stage of activation, a higher temperature and a lower steam usage are used to quickly open the initial pores and form a basic microporous framework inside the carbonized material. In the second stage of activation, the temperature is appropriately reduced to avoid excessive burning of the carbon framework, while the steam usage is significantly increased. The strong pore-expanding effect of a large amount of steam is used to directionally expand the micropores generated in the first stage of activation into mesopores, thereby constructing an activated carbon carrier with a well-developed mesoporous structure. This rich mesoporous structure effectively solves the problem of macromolecular organic amines easily blocking the pores and causing a sharp reduction in specific surface area, providing a spacious accommodation space and a fast CO2 mass transfer channel for subsequent high-loading amine modification.

[0007] (2) In the amine modification stage, this invention introduces a combination of polyene-polyamine compounds and crosslinking agents. The crosslinking agents can react with polyene-polyamine molecules to construct a stable three-dimensional crosslinked network structure within the mesoporous channels of activated carbon. This crosslinked network not only significantly increases the density of active sites for effective CO2 capture, but more importantly, it produces a significant synergistic physical confinement and chemical anchoring effect with the well-developed mesoporous structure of the support. The mesopores provide ample space for the crosslinking reaction, while the macromolecular network formed after crosslinking is firmly locked inside the mesopores, effectively overcoming the defects of weak amine binding force and easy volatilization and loss in the traditional physical impregnation method. Among them, tetraethylenepentamine or polyethyleneimine has extremely high amino density, ensuring high adsorption capacity; polyethylene glycol diglycidyl ether, as a flexible crosslinking agent, can effectively crosslink polyamine molecules without destroying their active spatial conformation for CO2 capture.

[0008] In summary, this invention successfully prepared a solid amine adsorbent with low cost, high CO2 adsorption capacity, and excellent cycling stability through the deep synergy of two-stage activated directional mesoporosis and cross-linked amine modification, effectively solving the technical problem that existing activated carbon-based adsorbents cannot achieve both high loading and high stability.

[0009] As a further improvement to the above preparation method: in step (1), the bamboo charcoal powder is obtained by heating fresh bamboo powder to 500-600°C at a heating rate of 5-10°C / min under inert gas protection and holding it at that temperature for 2-4 hours, followed by grinding and sieving; the binder is coal tar; the dispersant is water; the mass ratio of bamboo charcoal powder, binder and dispersant is 10:(4.5-5.5):(3.3-3.7).

[0010] As a further improvement to the above preparation method, step (1) further includes the addition of a nitrogen-sulfur dopant, wherein the nitrogen-sulfur dopant is at least one of thiourea, melamine, or tetramethylthiuram disulfide, and the mass ratio of bamboo charcoal powder to nitrogen-sulfur dopant is 10:(0.5-0.8). Thus, the nitrogen-sulfur dopant is in situ incorporated into the carbon framework during heat treatment, which increases the alkaline sites and polarity on the carrier surface, further enhancing the affinity for acidic CO2 molecules and the chemisorption capacity for amine groups.

[0011] As a further improvement to the above preparation method: step (1) further includes adding a pore-forming template agent, wherein the pore-forming template agent is calcium acetate or magnesium acetate, and the mass ratio of bamboo charcoal powder to the pore-forming template agent is 10:(0.2~0.5); after the two-stage activation treatment, the metal oxides generated by the pore-forming template agent are removed by acid washing, and the mixture is washed until neutral and dried, and then subjected to amine modification treatment. Thus, the pore-forming template agent decomposes at high temperature to generate metal oxide nanoparticles, which play a role in creating pores in situ with a hard template. After acid washing, the mesopore abundance is further increased, and the pore-expansion efficiency is improved in synergy with water vapor activation.

[0012] As a further improvement to the above preparation method: in step (2), the carbonization conditions are as follows: under the protection of inert gas, the temperature is raised to 500-600°C at a heating rate of 5-10°C / min and held for 90-120 minutes.

[0013] As a further improvement to the above preparation method: in steps (3) and (4): The activation time for the first stage of activation treatment is 110–130 minutes; The activation time for the two-stage activation process is 80–100 minutes.

[0014] This ensures precise control of the first stage of activation to create micropores and the second stage of activation to expand mesopores, maximizing mesopore yield and preventing carbon skeleton collapse.

[0015] As a further improvement to the above preparation method: in step (5), the conditions for amine modification are as follows: First, mesoporous activated carbon is added to a polyene-polyamine compound solution at room temperature and impregnated for 1-2 hours. Then, a crosslinking agent is added and the temperature is raised to 45-55°C and impregnated for 3-5 hours. The mass ratio of the polyene-polyamine compound to the crosslinking agent is 100:(3-5), and the mass ratio of mesoporous activated carbon to the polyene-polyamine compound is 1:(0.25-0.35). The solvent was then removed by rotary evaporation, and the product was dried for 10–14 hours under a vacuum of no more than 5 kPa and a temperature of 55–65 °C.

[0016] Therefore, room temperature impregnation allows polyene and polyamine compounds to fully penetrate deep into the pores before crosslinking is performed, avoiding premature pore blockage caused by excessively rapid crosslinking; vacuum low-temperature drying effectively prevents the amine groups from being oxidized and deactivated at high temperatures during the drying process.

[0017] As a further improvement to the above preparation method: In step (5), before the amine modification treatment, the mesoporous activated carbon is further immersed in a 10-15% hydrogen peroxide solution, oxidized at 60-70°C for 2-4 hours, washed and dried, and then added to the polyene-polyamine compound solution. Thus, the hydrogen peroxide pre-oxidation treatment significantly increases the density of oxygen-containing functional groups (such as hydroxyl and carboxyl groups) on the surface of the activated carbon, providing more chemical anchoring sites for subsequent amine modification, further enhancing the amine loading and anti-leakage ability.

[0018] The amine-modified mesoporous activated carbon for CO2 adsorption was prepared by the method described above.

[0019] The embodiments of the invention provided in this specification will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the embodiments of the invention provided in this specification will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the invention provided in this specification. Attached Figure Description

[0020] The accompanying drawings, which form part of the embodiments of the invention provided in this specification, are used to aid in understanding the embodiments of the invention provided in this specification. The content provided in the drawings and the related descriptions in the embodiments of the invention provided in this specification can be used to explain the embodiments of the invention provided in this specification, but do not constitute an undue limitation on the embodiments of the invention provided in this specification. In the drawings: Figure 1 This is a SEM image of the mesoporous activated carbon from Example 1.

[0021] Figure 2 This is a SEM image of the mesoporous activated carbon from Example 7. Detailed Implementation

[0022] The embodiments of the invention provided in this specification will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. Before describing the embodiments of the invention provided in this specification in conjunction with the accompanying drawings, it should be particularly noted that: The technical solutions and features provided in the embodiments of the invention provided in this specification, including the following description, can be combined with each other without conflict.

[0023] Furthermore, the embodiments of the inventions provided in this specification mentioned below are generally only a part of the embodiments of the inventions provided in this specification, and not all of them. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the inventions provided in this specification without creative effort should fall within the scope of protection of the embodiments of the inventions provided in this specification.

[0024] Regarding the terminology and units in the embodiments of the invention provided in this specification: The terms "comprising," "including," "having," and any variations thereof in the description, claims, and related parts of the embodiments of the invention provided in this specification are intended to cover non-exclusive inclusion. Furthermore, other relevant terms and units in the embodiments of the invention provided in this specification can be reasonably interpreted based on the relevant content of the embodiments of the invention provided in this specification.

[0025] Example 1

[0026] The amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this embodiment are as follows: (1) Under inert gas protection, fresh bamboo powder was heated to 550°C at 8°C / min and kept at that temperature for 3 hours. After that, it was ground and sieved (200-300 mesh) to obtain bamboo charcoal powder. Bamboo charcoal powder, coal tar as a binder, and water as a dispersant were kneaded for 30 minutes at a mass ratio of 10:5:3.5. The kneaded material was loaded into a mold and extruded into columnar materials with a diameter of 3 mm through a hydraulic extruder under a pressure of 25 MPa. After the columnar materials were dried at 40°C for 24 hours, they were cut into particles of 5.0 (±0.3) mm, which were the green body.

[0027] (2) Carbonization treatment: The billet is placed in a carbonization furnace under the protection of inert gas, heated from room temperature to 600°C at a heating rate of 8°C / min, and held for 90 minutes to carry out carbonization treatment to obtain carbonized material.

[0028] (3) First-stage activation treatment: The carbonized material is transferred into a split-type drum activation furnace and heated from room temperature to 900°C at a heating rate of 10°C / min. Water vapor with a mass hourly space velocity of 0.55 g / (g·h) is introduced (i.e., 0.55 g of water vapor is introduced per hour and per gram of carbonized material) to perform a first-stage activation treatment on the carbonized material for 130 minutes to obtain the precursor.

[0029] (4) Two-stage activation treatment: The temperature was lowered to 800℃ at a cooling rate of 5℃ / min, and the mass hourly space velocity of water vapor was increased to 1.6 g / (g·h). The precursor was then subjected to a two-stage activation treatment for 100 minutes to obtain mesoporous activated carbon.

[0030] (5) Amine modification treatment: According to the mass ratio of mesoporous activated carbon to tetraethylenepentamine of 1:0.35, the mesoporous activated carbon was first added to tetraethylenepentamine solution (solvent is anhydrous ethanol, concentration is 40 wt%) at room temperature and fully impregnated for 2 hours; then, according to the mass ratio of tetraethylenepentamine to polyethylene glycol diglycidyl ether of 100:5, polyethylene glycol diglycidyl ether was added to the system, and the temperature was raised to 50°C and impregnated for 4 hours; after the impregnation reaction was completed, the solvent was removed by rotary evaporation, and finally the product was dried under a vacuum degree not higher than 5 kPa and a temperature of 60°C for 12 hours to obtain amine-modified mesoporous activated carbon for CO2 adsorption.

[0031] The specific surface area of ​​the mesoporous activated carbon in this embodiment was tested to be 1415.3 m². 2 / g, total pore volume is 0.70cm³ 3 / g, with a mesoporous ratio of 73.3%; the CO2 adsorption capacity of amine-modified mesoporous activated carbon is 2.73 mmol / g, and the adsorption capacity retention rate after 10 cycles is 90.2%.

[0032] Example 2

[0033] Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this example is: (3) First-stage activation treatment: The carbonized material is transferred into a split-type drum activation furnace and heated from room temperature to 950°C at a heating rate of 10°C / min. Water vapor with a mass hourly space velocity of 0.45 g / (g·h) is introduced to perform a first-stage activation treatment on the carbonized material for 110 minutes to obtain the precursor.

[0034] (4) Two-stage activation treatment: The temperature was lowered to 900℃ at a cooling rate of 5℃ / min, and the mass hourly space velocity of water vapor was increased to 1.4 g / (g·h). The precursor was then subjected to a two-stage activation treatment for 80 minutes to obtain mesoporous activated carbon.

[0035] The specific surface area of ​​the mesoporous activated carbon in this embodiment was tested to be 1324.9 m². 2 / g, total pore volume is 0.64cm³ 3 / g, with a mesoporous ratio of 84.1%; the CO2 adsorption capacity of amine-modified mesoporous activated carbon is 2.65 mmol / g, and the adsorption capacity retention rate after 10 cycles is 90.8%.

[0036] Example 3

[0037] Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this example is: (3) First-stage activation treatment: The carbonized material is transferred into a split-type drum activation furnace and heated from room temperature to 930°C at a heating rate of 10°C / min. Water vapor with a mass hourly space velocity of 0.5 g / (g·h) is introduced to perform a first-stage activation treatment on the carbonized material for 120 minutes to obtain the precursor.

[0038] (4) Two-stage activation treatment: The temperature was lowered to 850°C at a cooling rate of 5°C / min, and the mass hourly space velocity of water vapor was increased to 1.5 g / (g·h). The precursor was then subjected to a two-stage activation treatment for 90 minutes to obtain mesoporous activated carbon.

[0039] The specific surface area of ​​the mesoporous activated carbon in this embodiment was tested to be 1382.5 m². 2 / g, total pore volume is 0.68cm³ 3 / g, with a mesoporous ratio of 78.5%; the CO2 adsorption capacity of amine-modified mesoporous activated carbon is 2.70 mmol / g, and the adsorption capacity retention rate after 10 cycles is 90.5%.

[0040] Example 4

[0041] Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this example is: (5) Amine modification treatment: the mass ratio of mesoporous activated carbon to tetraethylenepentamine is 1:0.25, and the mass ratio of tetraethylenepentamine to polyethylene glycol diglycidyl ether is 100:3.

[0042] The CO2 adsorption capacity of the amine-modified mesoporous activated carbon in this embodiment was tested to be 2.48 mmol / g, and the adsorption capacity retention rate was 88.6% after 10 cycles of use.

[0043] Example 5

[0044] Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this example is: (5) Amine modification treatment: the polyene polyamine compound is polyethyleneimine, the mass ratio of mesoporous activated carbon to polyethyleneimine is 1:0.3, and the mass ratio of polyethyleneimine to polyethylene glycol diglycidyl ether is 100:4.

[0045] The CO2 adsorption capacity of the amine-modified mesoporous activated carbon in this embodiment was tested to be 2.82 mmol / g, and the adsorption capacity retention rate was 91.7% after 10 cycles of use.

[0046] Example 6

[0047] Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this example is that: in step (1), a nitrogen-sulfur dopant is added, wherein the nitrogen-sulfur dopant is thiourea, and the mass ratio of bamboo charcoal powder to thiourea is 10:0.8.

[0048] The specific surface area of ​​the mesoporous activated carbon in this embodiment was tested to be 1418.2 m². 2 / g, total pore volume is 0.72cm³ 3 / g, with a mesoporous ratio of 74.5%; the CO2 adsorption capacity of amine-modified mesoporous activated carbon is 2.95 mmol / g, and the adsorption capacity retention rate after 10 cycles is 91.4%.

[0049] Example 7

[0050] Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this example is that: in step (1), a pore-forming template agent is added, wherein the pore-forming template agent is calcium acetate, and the mass ratio of bamboo charcoal powder to calcium acetate is 10:0.5; after the two-stage activation treatment, the metal oxides generated by calcium acetate are removed by acid washing, and the carbon is washed until neutral and dried, and then amine modification treatment is performed.

[0051] The specific surface area of ​​the mesoporous activated carbon in this embodiment was tested to be 1452.8 m². 2 / g, total pore volume is 0.82cm³ 3 / g, with a mesoporous ratio of 82.4%; the CO2 adsorption capacity of amine-modified mesoporous activated carbon is 3.25 mmol / g, and the adsorption capacity retention rate after 10 cycles is 92.1%.

[0052] Figure 1 This is a SEM image of the mesoporous activated carbon from Example 1. Figure 2 This is a SEM image of the mesoporous activated carbon from Example 7. The comparison shows that the mesoporous activated carbon of Example 7 has a greater number of pores.

[0053] Example 8

[0054] Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this example is that: in step (1), nitrogen and sulfur dopants and pore-forming template agents are added, wherein the nitrogen and sulfur dopants are thiourea, the pore-forming template agents are calcium acetate, and the mass ratio of bamboo charcoal powder, thiourea and calcium acetate is 10:0.5:0.2; after the two-stage activation treatment, the metal oxides generated by the pore-forming template agent are removed by acid washing, and the carbon is washed until neutral and dried, and then amine modification treatment is performed.

[0055] The specific surface area of ​​the mesoporous activated carbon in this embodiment was tested to be 1465.5 m². 2 / g, total pore volume is 0.85cm³ 3 / g, with a mesoporous ratio of 83.6%; the CO2 adsorption capacity of amine-modified mesoporous activated carbon is 3.58 mmol / g, and the adsorption capacity retention rate after 10 cycles is 92.5%.

[0056] Example 9

[0057] Compared with Example 8, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this example is that: in step (5), before the amine modification treatment, the mesoporous activated carbon is soaked in a 12% hydrogen peroxide solution, oxidized at 60°C for 3 hours, washed and dried, and then added to a polyene polyamine compound solution.

[0058] The CO2 adsorption capacity of the amine-modified mesoporous activated carbon in this embodiment was tested to be 3.82 mmol / g, and the adsorption capacity retention rate was 93.1% after 10 cycles of use.

[0059] Compare with Example 1 Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this comparative example is that the water vapor mass hourly space velocity (WHSV) of the two-stage activation treatment is increased. Specifically, the temperature is lowered to 800°C at a cooling rate of 5°C / min, increasing the WHSV to 1.8 g / (g·h), and the precursor is further subjected to a two-stage activation treatment for 100 minutes to obtain activated carbon.

[0060] The specific surface area of ​​the activated carbon in this control example was tested to be 1125.4 m². 2 / g, total pore volume is 0.61cm³ 3 / g, with a mesoporous ratio of 64.2%; the CO2 adsorption capacity of the amine-modified activated carbon is 2.15 mmol / g, and the adsorption capacity retention rate after 10 cycles is 85.5%.

[0061] Compare with Example 2 Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this comparative example is that only a conventional single-stage activation treatment is performed. Specifically, the carbonized material is transferred into a split-type drum activation furnace and heated from room temperature to 900°C at a heating rate of 10°C / min. Water vapor with a mass hourly space velocity of 0.45 g / (g·h) is introduced to activate the carbonized material for 210 minutes to obtain activated carbon.

[0062] The specific surface area of ​​the activated carbon in this control example was tested to be 1117.0 m². 2 / g, total pore volume is 0.51cm³ 3 / g, with a mesoporous ratio of 22.8%; the CO2 adsorption capacity of the amine-modified activated carbon was 2.02 mmol / g, and the adsorption capacity retention rate after 10 cycles was 84.6%.

[0063] Compare with Example 3 Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this comparative example is that it is first activated at low temperature and high steam hourly space velocity (SHOBV), and then activated at high temperature and low SHOBV. Specifically: (3) First-stage activation treatment: The carbonized material is transferred into a split-type drum activation furnace and heated from room temperature to 800°C at a heating rate of 10°C / min. Water vapor with a mass hourly space velocity of 1.6 g / (g·h) is introduced to perform a first-stage activation treatment on the carbonized material for 100 minutes to obtain the precursor.

[0064] (4) Two-stage activation treatment: The precursor is heated to 900°C at a heating rate of 5°C / min, and the mass hourly space velocity of water vapor is reduced to 0.55 g / (g·h). The precursor is then subjected to a two-stage activation treatment for 130 minutes to obtain activated carbon.

[0065] The specific surface area of ​​the activated carbon in this control example was tested to be 1226.4 m². 2 / g, total pore volume is 0.56cm³ 3 / g, with a mesoporous ratio of 52.8%; the CO2 adsorption capacity of the amine-modified activated carbon was 2.13 mmol / g, and the adsorption capacity retention rate after 10 cycles was 83.4%.

[0066] Compare with Example 4 Compared with Example 1, the difference between the amine-modified mesoporous activated carbon for CO2 adsorption and its preparation method in this comparative example is that no crosslinking agent was used in the amine modification treatment. Specifically, the mesoporous activated carbon was added to a tetraethylenepentamine solution (solvent is anhydrous ethanol, concentration is 40wt%) at a mass ratio of 1:0.35, and fully impregnated at 50°C for 6 hours. After the impregnation reaction was completed, the solvent was removed by rotary evaporation, and finally the product was dried under a vacuum of no more than 5 kPa and a temperature of 60°C for 12 hours to obtain the amine-modified mesoporous activated carbon for CO2 adsorption.

[0067] The CO2 adsorption capacity of the amine-modified mesoporous activated carbon in this control example was tested to be 2.28 mmol / g, and the adsorption capacity retention rate was 68.3% after 10 cycles of use.

[0068] In the above examples and comparative examples, the test method for CO2 adsorption capacity is as follows: Take 20 mL of sample, weigh it, and place it in a reaction tube with an inner diameter of 29 mm. Perform adsorption testing at 25 °C. Before the adsorption test, purge the reaction tube with high-purity N2 until the outlet CO2 concentration is 0. Then, introduce 2000 ppm CO2 at a gas flow rate of 1 L / min and a reaction space velocity of 3000 h⁻¹. -1 .

[0069] ; In the formula, 2000 represents the CO2 concentration in the cylinder gas; t The time required to reach the adsorption saturation point; Integral for the penetration curve; m This refers to the mass of a 20 mL sample.

[0070] Before each cycle of the cyclic performance test, the following steps are performed: cut off the CO2 gas source, switch back to high-purity N2 for purging, then raise the temperature to 100°C and maintain it for 1 hour to complete the desorption. Continue to purge with N2 and cool down to the adsorption temperature (25°C) before starting the next adsorption test.

[0071] The embodiments of the invention provided in this specification have been described above. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. All other preferred embodiments and implementations obtained by those skilled in the art based on the above description of the embodiments of the invention provided in this specification without inventive effort should fall within the protection scope of the embodiments of the invention provided in this specification.

Claims

1. A method for preparing amine-modified mesoporous activated carbon for CO2 adsorption, characterized in that: Includes the following steps: (1) Mix bamboo charcoal powder, binder and dispersant together to form a blank; (2) Carbonize the billet to obtain carbonized material; (3) The carbonized material is subjected to a first-stage activation treatment to obtain the precursor; the temperature of the first-stage activation treatment is 900-950℃ and the steam hourly space velocity is 0.45-0.55 g / (g·h); (4) The precursor is subjected to a two-stage activation treatment to obtain mesoporous activated carbon; the temperature of the two-stage activation treatment is 800-900℃, and the temperature of the first-stage activation treatment is at least 50℃ higher than that of the second-stage activation treatment, and the water vapor mass hourly velocity is 1.4-1.6 g / (g·h). (5) The mesoporous activated carbon is modified with polyene polyamine compounds and crosslinking agents to obtain amine-modified mesoporous activated carbon; the polyene polyamine compounds are tetraethylenepentamine or polyethyleneimine, and the crosslinking agents are polyethylene glycol diglycidyl ether. The first-stage activation treatment and the second-stage activation treatment are continuous steam thermal activation treatments. In step (5), the conditions for amine modification treatment are as follows: First, mesoporous activated carbon is added to a polyene-polyamine compound solution at room temperature and impregnated for 1-2 hours. Then, a crosslinking agent is added and the temperature is raised to 45-55°C and impregnated for 3-5 hours. The mass ratio of the polyene-polyamine compound to the crosslinking agent is 100:(3-5), and the mass ratio of mesoporous activated carbon to the polyene-polyamine compound is 1:(0.25-0.35). The solvent was then removed by rotary evaporation, and the product was dried for 10–14 hours under a vacuum of no more than 5 kPa and a temperature of 55–65 °C.

2. The preparation method according to claim 1, characterized in that: In step (1), the bamboo charcoal powder is obtained by heating fresh bamboo powder to 500-600°C at a heating rate of 5-10°C / min under inert gas protection and holding it at that temperature for 2-4 hours, followed by grinding and sieving; the binder is coal tar; the dispersant is water; and the mass ratio of bamboo charcoal powder, binder, and dispersant is 10:(4.5-5.5):(3.3-3.7).

3. The preparation method according to claim 2, characterized in that: Step (1) also includes adding a nitrogen-sulfur dopant, wherein the nitrogen-sulfur dopant is at least one of thiourea, melamine or tetramethylthiuram disulfide, and the mass ratio of bamboo charcoal powder to nitrogen-sulfur dopant is 10:(0.5-0.8).

4. The preparation method according to claim 2, characterized in that: Step (1) also includes adding a pore-forming template agent, which is calcium acetate or magnesium acetate, and the mass ratio of bamboo charcoal powder to pore-forming template agent is 10:(0.2~0.5). After the two-stage activation treatment, the metal oxides generated by the pore-forming template agent are removed by acid washing, and the mixture is washed until neutral and dried before amine modification treatment.

5. The preparation method according to claim 1, characterized in that: In step (2), the carbonization conditions are as follows: under inert gas protection, heat to 500-600°C at a heating rate of 5-10°C / min and hold for 90-120 minutes.

6. The preparation method according to claim 1, characterized in that: In steps (3) and (4): The activation time for the first stage of activation treatment is 110–130 minutes; The activation time for the two-stage activation process is 80–100 minutes.

7. The preparation method according to claim 1, characterized in that: In step (5), before the amine modification treatment, the mesoporous activated carbon is soaked in a hydrogen peroxide solution with a mass fraction of 10-15%, oxidized at 60-70°C for 2-4 hours, washed and dried, and then added to the polyene polyamine compound solution.

8. Amine-modified mesoporous activated carbon for CO2 adsorption, characterized in that: It is prepared by the preparation method according to any one of claims 1-7.

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