Catalyst supported activated carbon adsorbent material and method of preparation

Abstract

The application relates to the technical field of pollutant adsorption, and discloses a catalyst-loaded activated carbon adsorption material and a preparation method. Water, a precursor and zinc nitrate are added into a flask, stirred and mixed, dried after filtration, ground and mixed with potassium hydroxide, placed in a tube furnace, calcined, and the catalyst-loaded activated carbon adsorption material is obtained. The activated carbon has a high specific surface area and a high pore volume, can promote the adsorption of formaldehyde, the nano zinc oxide is uniformly distributed in the activated carbon matrix and is not prone to agglomeration, has higher photocatalytic degradation performance on formaldehyde, and significantly improves the removal rate of the catalyst-loaded activated carbon adsorption material on formaldehyde.

Description

Technical Field

[0001] This invention relates to the field of pollutant adsorption technology, specifically to a catalyst-supported activated carbon adsorption material and its preparation method. Background Technology

[0002] The combustion of chemical fuels, chemical industrial production, and building decoration processes release large amounts of gaseous pollutants such as sulfur dioxide, carbon monoxide, and formaldehyde, causing serious air pollution and endangering human health and safety. Therefore, the effective treatment of gaseous pollutants is of great significance. Common methods include adsorption and photocatalytic degradation. Activated carbon has diverse preparation methods, adjustable specific surface area and pore structure, and is widely used in gas adsorption and catalyst support. Precursors for activated carbon mainly include natural biomass, polymer resins, and microporous polymers.

[0003] Polyvinyl alcohol (PVA) is inexpensive, readily available, environmentally friendly, and possesses some char-forming properties, making it an ideal precursor for activated carbon. Zinc oxide exhibits excellent photocatalytic activity, capable of photocatalytically degrading pollutants such as formaldehyde, nitrite, and organic dyes, and has wide applications in pollutant treatment. Loading zinc oxide onto carriers such as activated carbon can disperse and reduce agglomeration, increase photocatalytic sites, and simultaneously adsorb pollutants. Summary of the Invention

[0004] This invention solves the problem that activated carbon has a low specific surface area and low adsorption and degradation performance for gases such as formaldehyde.

[0005] The technical solution of this invention is: a method for preparing catalyst-supported activated carbon adsorbent material.

[0006] (1) Add glacial acetic acid, 1,3,5-tris(4-aminophenyl)benzene and trimellitic anhydride to a flask equipped with a reflux condenser, react, cool and filter, wash the precipitate with water and ethanol, and dry to obtain a carboxyl crosslinking agent.

[0007] (2) Add dimethyl sulfoxide and polyvinyl alcohol to the flask, heat and stir to dissolve, cool to the reaction temperature, add carboxyl crosslinking agent, dicyclohexylcarbodiimide and 4-dimethylaminopyridine, stir to react, add ice water to dilute the solution, filter and wash the product with ice water and ethanol in turn, dry to obtain the precursor.

[0008] (3) Add water and precursor to the flask, heat and stir, cool and add zinc nitrate, stir and mix, filter and dry the mixture, grind and mix with potassium hydroxide, place in a tube furnace for calcination, cool and wash with water, dry to obtain catalyst-supported activated carbon adsorbent material.

[0009] Furthermore, in (1), the ratio of 1,3,5-tris(4-aminophenyl)benzene to trimellitic anhydride is 1 mol: (3-3.3) mol.

[0010] Furthermore, the reaction temperature in (1) is 115-120℃ and the reaction time is 18-24h.

[0011] Furthermore, in (2), the reaction temperature is 20-30℃ and the reaction time is 24-36h.

[0012] Furthermore, in (2), the ratio of polyvinyl alcohol, carboxyl crosslinking agent, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 100g:(80-140)mmol:(160-280)mmol:(24-40)mmol. By adjusting the ratio of dicyclohexylcarbodiimide and carboxyl crosslinking agent, some carboxyl groups of the carboxyl crosslinking agent are activated and undergo esterification with the hydroxyl groups of polyvinyl alcohol.

[0013] Furthermore, in (3), the ratio of precursor, zinc nitrate and potassium hydroxide is 100g: (5-20)g: (240-320)g.

[0014] Furthermore, in (3), the temperature during stirring and mixing is 20-40℃, and the stirring time is 2-3h.

[0015] Furthermore, in (3), the calcination is first carried out in a nitrogen atmosphere, heated to 650-750℃ and held for 2-3 hours, and then held in an air atmosphere at 450-500℃ for 2-3 hours.

[0016] The beneficial technical effects of this invention are as follows: The carboxyl crosslinking agent of this invention contains multiple carboxyl groups. Some of the carboxyl groups undergo esterification with the hydroxyl groups of polyvinyl alcohol, crosslinking the linear polyvinyl alcohol into a three-dimensional network structure. This promotes the formation of a porous activated carbon structure with a high specific surface area during high-temperature carbonization. At the same time, the carboxyl crosslinking agent contains a large number of rigid benzene rings and imide nitrogen-acid fused ring structures, which can serve as a carbon skeleton, improving the char-forming properties of the polyvinyl alcohol precursor and the structural stability of the activated carbon, reducing carbon layer collapse, further increasing the specific surface area and total pore volume of the activated carbon, and promoting the adsorption of formaldehyde.

[0017] This invention introduces nitrogen heterocycles and carboxyl groups into a polyvinyl alcohol precursor using a carboxyl crosslinking agent. High-temperature carbonization forms a nitrogen-doped active structure, increasing the electron cloud density of activated carbon and enhancing its formaldehyde adsorption capacity. The carboxyl groups and the hydroxyl groups of polyvinyl alcohol form coordination complexes with zinc ions, adsorbing a large number of zinc ions into the precursor. During high-temperature carbonization in a nitrogen atmosphere, zinc ions form zinc precursors. During high-temperature carbonization in an air atmosphere, the zinc precursors pyrolyze to generate a large amount of nano-zinc oxide, which is uniformly distributed within the activated carbon matrix. The nano-zinc oxide is less prone to agglomeration, and the higher zinc oxide loading in the activated carbon results in superior photocatalytic degradation performance for formaldehyde, significantly improving the formaldehyde removal rate of the catalyst-supported activated carbon adsorbent material. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0019] Example 1 (1) 400 mL of glacial acetic acid, 50 mmol of 1,3,5-tris(4-aminophenyl)benzene, and 150 mmol of trimellitic anhydride were added to a flask equipped with a reflux condenser. The mixture was heated to 115 °C and stirred for 24 h. After cooling, the mixture was filtered, and the precipitate was washed with water and ethanol and dried to obtain a carboxyl crosslinking agent. The reaction formula is as follows:

[0020] .

[0021] (2) Add 1.2 L of dimethyl sulfoxide and 40 g of polyvinyl alcohol (model PVA1788, the same below) to the flask, heat and stir to dissolve, cool to 25 °C, add 32 mmol of carboxyl crosslinking agent, 64 mmol of dicyclohexylcarbodiimide and 9.6 mmol of 4-dimethylaminopyridine, stir to react for 24 h, add ice water to dilute the solution, filter and wash the product with ice water and ethanol in turn, dry to obtain the precursor.

[0022] (3) Add 1.2L of water and 50g of precursor to the flask, heat to 90℃, stir for 30min, cool to 20℃, add 2.5g of zinc nitrate, stir and mix for 3h, filter and dry the mixture, grind and mix with 130g of potassium hydroxide, place in a tube furnace, first heat to 700℃ in a nitrogen atmosphere and keep warm for 2h; then keep warm at 450℃ in an air atmosphere for 3h, cool, wash with water and dry to obtain catalyst-supported activated carbon adsorbent material.

[0023] Example 2 (1) Add 500 mL of glacial acetic acid, 60 mmol of 1,3,5-tris(4-aminophenyl)benzene and 198 mmol of trimellitic anhydride to a flask equipped with a reflux condenser. Heat to 120 °C and stir for 18 h. After cooling, filter, wash the precipitate with water and ethanol, and dry to obtain a carboxyl crosslinking agent.

[0024] (2) Add 1.3 L of dimethyl sulfoxide and 40 g of polyvinyl alcohol to the flask, heat and stir to dissolve, cool to 20 °C, add 40 mmol of carboxyl crosslinking agent, 80 mmol of dicyclohexylcarbodiimide and 12 mmol of 4-dimethylaminopyridine, stir to react for 36 h, add ice water to dilute the solution, filter and wash the product with ice water and ethanol in turn, dry to obtain the precursor.

[0025] (3) Add 1.4L of water and 50g of precursor to the flask, heat to 95℃, stir for 20min, cool to 30℃, add 5g of zinc nitrate, stir and mix for 2h, filter and dry the mixture, grind and mix with 160g of potassium hydroxide, place in a tube furnace, first heat to 650℃ in a nitrogen atmosphere and keep warm for 3h; then keep warm at 500℃ in an air atmosphere for 2h, cool and wash with water, dry to obtain catalyst-supported activated carbon adsorbent material.

[0026] Example 3 (1) Add 480 mL of glacial acetic acid, 60 mmol of 1,3,5-tris(4-aminophenyl)benzene and 180 mmol of trimellitic anhydride to a flask equipped with a reflux condenser. Heat to 120 °C and stir for 18 h. After cooling, filter, wash the precipitate with water and ethanol, and dry to obtain a carboxyl crosslinking agent.

[0027] (2) Add 1.2 L of dimethyl sulfoxide and 35 g of polyvinyl alcohol to the flask, heat and stir to dissolve, cool to 20 °C, add 42 mmol of carboxyl crosslinking agent, 84 mmol of dicyclohexylcarbodiimide and 11.9 mmol of 4-dimethylaminopyridine, stir to react for 36 h, add ice water to dilute the solution, filter and wash the product with ice water and ethanol in sequence, dry to obtain the precursor.

[0028] (3) Add 1.5L of water and 50g of precursor to the flask, heat to 95℃, stir for 20min, cool to 40℃, add 7.5g of zinc nitrate, stir and mix for 2h, filter and dry the mixture, grind and mix with 120g of potassium hydroxide, place in a tube furnace, first heat to 750℃ in a nitrogen atmosphere and keep warm for 2h; then keep warm at 450℃ in an air atmosphere for 3h, cool and wash with water, dry to obtain catalyst-supported activated carbon adsorbent material.

[0029] Example 4 (1) 600 mL of glacial acetic acid, 70 mmol of 1,3,5-tris(4-aminophenyl)benzene and 210 mmol of trimellitic anhydride were added to a flask equipped with a reflux condenser. The mixture was heated to 115 °C and stirred for 24 h. After cooling, the mixture was filtered, and the precipitate was washed with water and ethanol and dried to obtain a carboxyl crosslinking agent.

[0030] (2) Add 1.2 L of dimethyl sulfoxide and 35 g of polyvinyl alcohol to the flask, heat and stir to dissolve, cool to 30 °C, add 49 mmol of carboxyl crosslinking agent, 98 mmol of dicyclohexylcarbodiimide and 14 mmol of 4-dimethylaminopyridine, stir to react for 36 h, add ice water to dilute the solution, filter and wash the product with ice water and ethanol in turn, dry to obtain the precursor.

[0031] (3) Add 1.5L of water and 50g of precursor to the flask, heat to 90℃, stir for 30min, cool to 20℃, add 10g of zinc nitrate, stir and mix for 3h, filter and dry the mixture, grind and mix with 145g of potassium hydroxide, place in a tube furnace, first heat to 700℃ in a nitrogen atmosphere and keep warm for 2h; then keep warm at 450℃ in an air atmosphere for 3h, cool and wash with water, dry to obtain catalyst-supported activated carbon adsorbent material.

[0032] Comparative Example 1 differs from Example 1 in that 1,3,5-tris(4-carboxyphenyl)benzene is used instead of the carboxyl crosslinking agent.

[0033] (1) Add 1.2 L of dimethyl sulfoxide and 40 g of polyvinyl alcohol to a flask, heat and stir to dissolve, cool to 25 °C, add 32 mmol of 1,3,5-tris(4-carboxyphenyl)benzene (CAS No. 50446-44-1), 64 mmol of dicyclohexylcarbodiimide and 9.6 mmol of 4-dimethylaminopyridine, stir and react for 24 h, add ice water to dilute the solution, filter and wash the product with ice water and ethanol in turn, dry to obtain the precursor.

[0034] (2) Add 1.2L of water and 50g of precursor to the flask, heat to 90℃, stir for 30min, cool to 20℃, add 2.5g of zinc nitrate, stir and mix for 3h, filter and dry the mixture, grind and mix with 130g of potassium hydroxide, place in a tube furnace, first heat to 700℃ in a nitrogen atmosphere and keep warm for 2h; then keep warm at 450℃ in an air atmosphere for 3h, cool and wash with water, dry to obtain catalyst-supported activated carbon adsorbent material.

[0035] The main difference between Comparative Example 2 and Example 1 is that 1,3,5-tris(4-aminophenyl)benzene is replaced with 4,4'-diaminodiphenylmethane.

[0036] (1) Add 400 mL of glacial acetic acid, 50 mmol of 4,4'-diaminodiphenylmethane, and 100 mmol of trimellitic anhydride to a flask equipped with a reflux condenser. Heat to 115 °C and stir for 24 h. After cooling, filter, wash the precipitate with water and ethanol, and dry to obtain a carboxyl crosslinking agent with the following structural formula: .

[0037] (2) Add 1.2 L of dimethyl sulfoxide and 40 g of polyvinyl alcohol to the flask, heat and stir to dissolve, cool to 25 °C, add 32 mmol of carboxyl crosslinking agent, 64 mmol of dicyclohexylcarbodiimide and 9.6 mmol of 4-dimethylaminopyridine, stir to react for 24 h, add ice water to dilute the solution, filter and wash the product with ice water and ethanol in sequence, dry to obtain the precursor.

[0038] (3) Add 1.2L of water and 50g of precursor to the flask, heat to 90℃, stir for 30min, cool to 20℃, add 2.5g of zinc nitrate, stir and mix for 3h, filter and dry the mixture, grind and mix with 130g of potassium hydroxide, place in a tube furnace, first heat to 700℃ in a nitrogen atmosphere and keep warm for 2h; then keep warm at 450℃ in an air atmosphere for 3h, cool, wash with water and dry to obtain catalyst-supported activated carbon adsorbent material.

[0039] The specific surface area and pore size distribution of activated carbon adsorbent materials were determined by measuring the N2 adsorption-desorption isotherm curves and the BET equation using a specific surface area analyzer.

[0040] The formaldehyde removal rate of activated carbon adsorbent materials was tested according to GB / T 46580-2025 standard.

[0041] Table 1

[0042] Example 1 534.8 0.686 77.9 Example 2 1124.5 1.323 91.0 Example 3 415.0 0.579 72.3 Example 4 857.4 0.912 95.4 Comparative Example 1 456.8 0.562 61.7 Comparative Example 2 417.1 0.509 48.5

[0043] The activated carbon adsorbents in each embodiment have higher specific surface area and total pore volume, resulting in higher formaldehyde removal rates. This is mainly because the carboxyl crosslinking agent contains multiple carboxyl groups, which undergo esterification with the hydroxyl groups of polyvinyl alcohol, crosslinking linear polyvinyl alcohol into a three-dimensional network structure. High-temperature carbonization forms a porous activated carbon structure with a high specific surface area. At the same time, the carboxyl crosslinking agent contains a large number of rigid benzene rings and imide nitrogen-containing heterocyclic ring structures, which can serve as a carbon skeleton, improving the char formation of the polyvinyl alcohol precursor and the structural stability of the activated carbon, reducing carbon layer collapse, and further increasing the specific surface area and total pore volume of the activated carbon. Furthermore, the polyvinyl alcohol precursor contains nitrogen heterocycles, which, through high-temperature carbonization, form a nitrogen-doped active structure, increasing the electron cloud density of the activated carbon and enhancing its adsorption capacity for formaldehyde. Furthermore, some of the carboxyl groups of the carboxyl crosslinking agent undergo esterification with polyvinyl alcohol. The unreacted carboxyl groups and the hydroxyl groups of polyvinyl alcohol form coordination complexes with zinc ions, adsorbing a large number of zinc ions into the precursor. During the high-temperature carbonization process in the air atmosphere, the zinc precursor pyrolyzes to generate a large amount of nano-zinc oxide, which is uniformly distributed in the activated carbon matrix. The nano-zinc oxide is not easy to agglomerate, and the zinc oxide loading in the activated carbon is higher, resulting in higher photocatalytic degradation performance for formaldehyde and significantly improving the formaldehyde removal rate of the catalyst-supported activated carbon adsorbent material.

[0044] The 1,3,5-tris(4-carboxyphenyl)benzene in Comparative Example 1 does not contain an imide nitrogen-containing fused ring structure. The structural stability of the carbon skeleton generated by carbonization is lower than that in Example 1, and the carbon layer is prone to collapse, resulting in a lower specific surface area and pore volume than in Example 1. The formaldehyde removal rate is also lower than that in Example 1.

[0045] The carboxyl crosslinking agent in Comparative Example 2 has a lower content of aromatic rings and carboxyl groups. The structural stability of the carbon skeleton generated by carbonization is lower than that in Example 1. The carbon layer is prone to collapse, resulting in a lower specific surface area and pore volume than in Example 1. Furthermore, the precursor generated has a lower content of carboxyl groups, resulting in a weaker adsorption capacity for zinc ions. Most of the zinc ions are washed away, leading to a lower content of zinc oxide in the activated carbon. Consequently, the adsorption and photocatalytic degradation capacity for formaldehyde is lower, and the removal rate is lower than that in Example 1.

[0046] The above-described embodiments are intended to provide a detailed description of the present invention and are illustrative rather than limiting. It will be apparent to those skilled in the art that various modifications and variations can be made to the method of the present invention without departing from its scope and overall concept, and such modifications and variations should fall within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst-supported activated carbon adsorbent material, characterized in that, The preparation method includes the following steps: S1. Add dimethyl sulfoxide and polyvinyl alcohol to a flask, heat and stir to dissolve, cool to the reaction temperature, add carboxyl crosslinking agent, dicyclohexylcarbodiimide and 4-dimethylaminopyridine, stir to react, add ice water to dilute the solution, filter and wash the product, dry to obtain the precursor. S2. Add water and precursor to the flask, heat and stir, cool and add zinc nitrate, stir and mix, filter and dry the mixture, grind and mix with potassium hydroxide, place in a tube furnace for calcination, cool and wash with water, dry to obtain catalyst-supported activated carbon adsorbent material.

2. The method for preparing catalyst-supported activated carbon adsorbent material according to claim 1, characterized in that, The reaction temperature in S1 is 20-30℃, and the reaction time is 24-36h.

3. The method for preparing catalyst-supported activated carbon adsorbent material according to claim 1, characterized in that, The ratio of polyvinyl alcohol, carboxyl crosslinking agent, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine in S1 is 100g:(80-140)mmol:(160-280)mmol:(24-40)mmol.

4. The method for preparing catalyst-supported activated carbon adsorbent material according to claim 3, characterized in that, The preparation method of the carboxyl crosslinking agent is as follows: glacial acetic acid, 1,3,5-tris(4-aminophenyl)benzene and trimellitic anhydride in a ratio of 1 mol: (3-3.3) mol are added to a flask equipped with a reflux condenser. The mixture is heated to 115-120℃ and stirred for 18-24 hours. After cooling, the mixture is filtered, the precipitate is washed, and the mixture is dried to obtain the carboxyl crosslinking agent.

5. The method for preparing catalyst-supported activated carbon adsorbent material according to claim 1, characterized in that, The temperature during stirring and mixing in S2 is 20-40℃, and the stirring time is 2-3 hours.

6. The method for preparing catalyst-supported activated carbon adsorbent material according to claim 1, characterized in that, The ratio of precursor, zinc nitrate and potassium hydroxide in S2 is 100g:(5-20)g:(240-320)g.

7. The method for preparing catalyst-supported activated carbon adsorbent material according to claim 1, characterized in that, The calcination in S2 is first carried out in a nitrogen atmosphere, heated to 650-750℃ and held for 2-3 hours, and then in an air atmosphere, held at 450-500℃ for 2-3 hours.

8. A catalyst-supported activated carbon adsorbent material obtained by the preparation method according to any one of claims 1-7.