A composite amine modified formaldehyde removal air purification material and a preparation method thereof

Abstract

The application discloses a composite amine modified formaldehyde removal air purification material and a preparation method thereof. The air purification material takes coal quality activated carbon, coconut shell activated carbon or zeolite molecular sieve as a porous carrier, is pretreated by a nitric acid solution to introduce oxygen-containing functional groups on the surface of the carrier, is placed in a compounded solvent containing a composite amine modifier to perform constant temperature oscillation impregnation, and is dried to obtain a target material. The composite amine modifier is composed of two or more than two amine components, and the compounded solvent includes two or more than two of deionized water, ethanol, ethylene glycol, n-propanol and isopropanol. The application improves the active site density on the surface of the carrier and the removal effect on formaldehyde through carrier pre-oxidation and composite amine cooperative modification, and is suitable for indoor air purification, automobile interior formaldehyde treatment and industrial waste gas pretreatment and the like.

Description

Technical Field

[0001] This invention relates to the field of air purification materials technology, and in particular to a formaldehyde-removing air purification material modified with a composite amine and its preparation method. Background Technology

[0002] Formaldehyde is one of the most common volatile organic pollutants in indoor air, mainly originating from building decoration materials, furniture, adhesives, and textiles. It has a long release period, is highly toxic, and easily accumulates in enclosed spaces such as homes, offices, and cars. Traditional ventilation and dilution methods have limited effectiveness in treating low concentrations of formaldehyde released over long periods, thus necessitating the development of highly efficient and stable formaldehyde-removing air purification materials.

[0003] Existing physical adsorption materials, such as activated carbon and molecular sieves, mainly rely on specific surface area to adsorb formaldehyde. However, they generally suffer from easy adsorption saturation and desorption rebound. To address these issues, current technologies often employ amine-based chemical modification to improve formaldehyde removal performance. For example, polyhydrazide-grafted modified activated carbon materials have a certain formaldehyde removal capacity, but the synthesis steps are complex, the condensation reagents are expensive, the excipient costs are high, and they are prone to clogging pores. While amine functionalization of MOF materials can improve adsorption performance, its synthesis conditions are harsh and the cost is high, making industrial-scale promotion difficult. Single-amine-modified porous carbon materials introduce a single type of amino functional group onto the carbon matrix surface, resulting in a single type of active site, which typically makes it difficult to simultaneously achieve optimal initial adsorption rate, adsorption capacity, and cycling stability.

[0004] Therefore, how to achieve multi-site amine group synergistic modification with a simple and mild process while maintaining the porous structure of the porous carrier, thereby improving formaldehyde removal performance and taking into account recyclability, remains a technical problem that urgently needs to be solved in this field.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To address the problems of easy saturation of physical adsorption materials, limited modification effect of single amines, and high preparation cost of some existing modification schemes in the prior art, this invention provides a formaldehyde removal air purification material modified with composite amines and its preparation method, so as to improve the formaldehyde removal effect of porous carriers.

[0007] To achieve the above objectives, the first aspect of the present invention provides a formaldehyde-removing air purification material modified with a composite amine, comprising a porous carrier and a composite amine modifier loaded on the surface and / or pores of the porous carrier, wherein the porous carrier is rich in oxygen-containing functional groups on its surface after pretreatment with nitric acid solution; the porous carrier is selected from one of coal-based activated carbon, coconut shell activated carbon, and zeolite molecular sieve; and the composite amine modifier comprises at least two amine modifiers.

[0008] Furthermore, the porous support surface after nitric acid solution pretreatment is rich in oxygen-containing functional groups such as carboxyl groups and / or hydroxyl groups.

[0009] Furthermore, the amine modifier is selected from two or more of methylurea, urea, diethylenetriamine, ethanolamine, polyethyleneimine, ethylenediamine, β-hydroxyethylethylenediamine, propylenediamine, butanediamine, pentanediamine, 2-methylpentanediamine, hexamethylenediamine, and aminosilane.

[0010] Furthermore, the composite amine modifier is selected from any of the following combinations: ethanolamine and polyethyleneimine, ethanolamine and ethylenediamine, ethanolamine and urea, diethylenetriamine and ethanolamine.

[0011] Furthermore, in the solution containing the composite amine modifier, the mass fraction of the amine modifier is 2% to 35%, and the solvent is two or more of deionized water, ethanol, ethylene glycol, n-propanol, and isopropanol.

[0012] Furthermore, the porous carrier is coal-based activated carbon with a particle size of 2 mm.

[0013] Furthermore, the composite amine modifier is a combination of ethanolamine and ethylenediamine.

[0014] Furthermore, the solvent is a compound solvent composed of deionized water, ethanol, and ethylene glycol, with a mass ratio of 5:4:1.

[0015] A second aspect of this invention provides a method for preparing the above-mentioned composite amine-modified formaldehyde-removing air purification material, comprising the following steps: (1) The porous support is immersed in nitric acid solution to oxidize its surface and enrich it with oxygen-containing functional groups; (2) After filtration, rinse repeatedly with deionized water until the filtrate is neutral, and dry to obtain the pretreated carrier; (3) Dissolve two or more amine modifiers in a solvent to prepare a composite amine modifier solution; (4) The pretreated carrier is placed in the composite amine modifier solution and soaked under constant temperature shaking conditions; (5) Remove the soaked carrier, dry it, cool it, and then seal it for storage.

[0016] Furthermore, in step (1), the mass concentration of the nitric acid solution is 5% to 15%, the liquid-solid ratio of the nitric acid solution to the porous carrier is 5 to 20:1 mL / g, and the soaking time is 1 to 4 h.

[0017] Furthermore, in step (2), the drying temperature is 105-120℃ and the drying time is 2-6h.

[0018] Further, in step (3), 2 to 35 parts by weight of amine modifier are added to 100 parts by weight of solvent and stirred or sonicated at room temperature for 2 to 20 minutes to promote dissolution; the solvent includes two or more of deionized water, ethanol, ethylene glycol, n-propanol and isopropanol.

[0019] Furthermore, in step (4), the rotation speed of the constant temperature oscillation is 150-200 rpm, the soaking temperature is 60-80℃, the soaking time is 1-4h, and the liquid-solid ratio of the composite amine modifier solution to the porous carrier is 4-20:1mL / g; in step (5), vacuum drying at 60℃ is carried out for 6-10h.

[0020] A third aspect of the present invention provides the application of the above-mentioned air purification material in removing formaldehyde from the air.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: (1) Pretreatment with nitric acid introduces oxygen-containing functional groups such as carboxyl and hydroxyl groups onto the surface of the porous carrier, which is beneficial for the subsequent loading of the composite amine modifier; (2) By modifying the carrier surface with two or more amine components, more active sites that can act on formaldehyde can be formed, thereby improving the formaldehyde removal effect. (3) Using compound solvents helps to improve the solubility and dispersion of amine modifiers and improve the uniformity of modification; (4) According to the test results of the existing embodiments, the sample modified with compound amine showed better formaldehyde removal performance than the unmodified carrier. Attached Figure Description

[0022] The above and other features and advantages of this disclosure will become more apparent from the detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0023] Figure 1 This is a schematic diagram showing the change of formaldehyde removal rate over time in Examples 1, 4 and Comparative Example 2 of this invention. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention. For those skilled in the art, any equivalent substitutions or improvements made without departing from the concept of the present invention should fall within the scope of protection of the present invention.

[0025] Example 1

[0026] 20g of coal-based activated carbon with a particle size of 2mm was weighed and added to a 5% nitric acid solution (liquid-solid ratio of nitric acid to activated carbon: 5:1 mL / g). The mixture was slowly stirred and soaked for 2 hours. After filtration, it was repeatedly rinsed with deionized water until the pH of the filtrate reached 6.5–7.5. The filtrate was then dried at 120℃ for 2 hours to obtain pretreated activated carbon AC. Separately, 3g of ethanolamine and 1g of polyethyleneimine were weighed and added to 100g of a compound solvent composed of deionized water, ethanol, and ethylene glycol in a mass ratio of 5:4:1. The mixture was stirred for 1 hour to obtain a composite amine modifier solution. The pretreated activated carbon AC was placed in this solution and soaked at 70℃ with constant temperature shaking for 2 hours. After filtration, it was vacuum dried at 60℃ for 6 hours, naturally cooled to room temperature, and then sealed and stored to obtain modified material A.

[0027] Example 2

[0028] Compared with Example 1, the difference is that: a 10% nitric acid solution was used for pretreatment; the pretreated carrier was dried at 105°C for 2 hours; the composite amine modification treatment was carried out by constant temperature shaking and soaking at 80°C for 2 hours; and finally, the modified material B was obtained by vacuum drying at 60°C for 8 hours.

[0029] Example 3

[0030] Compared with Example 1, the difference is that 3g of ethanolamine and 1g of polyethyleneimine were replaced with 2g of ethanolamine and 2g of polyethyleneimine to obtain modified material C.

[0031] Example 4

[0032] Compared with Example 1, the difference is that 3g of ethanolamine and 1g of polyethyleneimine in the composite amine modifier are replaced with 3g of ethanolamine and 1g of ethylenediamine to obtain modified material D.

[0033] Example 5

[0034] Compared with Example 1, the difference is that 3g of ethanolamine and 1g of polyethyleneimine in the composite amine modifier are replaced with 3g of urea and 1g of ethylenediamine to obtain modified material E.

[0035] Example 6

[0036] Compared with Example 1, the difference is that 3g of ethanolamine and 1g of polyethyleneimine in the composite amine modifier are replaced with 5g of diethylenetriamine and 0.5g of ethanolamine to obtain modified material F.

[0037] Example 7

[0038] Compared with Example 1, the difference is that 3g of ethanolamine and 1g of polyethyleneimine in the composite amine modifier are replaced with 3g of ethanolamine, 1g of polyethyleneimine and 1g of urea to obtain modified material G.

[0039] Example 8

[0040] Compared with Example 1, the difference is that the compound solvent was replaced with 100g of deionized water to obtain modified material H.

[0041] Example 9

[0042] Compared with Example 1, the difference is that the coal-based activated carbon with a particle size of 2 mm is replaced with coal-based activated carbon with a particle size of 4 mm to obtain modified material I.

[0043] Example 10

[0044] Compared with Example 1, the difference is that the coal-based activated carbon with a particle size of 2 mm was replaced with zeolite molecular sieve to obtain modified material J.

[0045] Example 11

[0046] Compared with Example 1, the difference is that the coal-based activated carbon with a particle size of 2 mm was replaced with coconut shell activated carbon to obtain modified material K.

[0047] Comparative Example 1 Compared with Example 1, the difference is that the nitric acid pretreatment step is omitted, and the carrier is directly modified with a composite amine solution to obtain modified material L.

[0048] Comparative Example 2 Coal-based activated carbon with a particle size of 2 mm that has not undergone chemical modification is denoted as unmodified coal-based activated carbon O.

[0049] This invention uses formaldehyde removal rate as the main evaluation index, referring to GB / T18801-2022 "Air Purifiers" and QB / T5364-2019 "Technical Requirements and Evaluation Methods for Test Chambers for Air Purifiers," and uses a 1m³ test chamber to test the formaldehyde removal performance of the samples. Solid trioxymethylene was heated to generate gaseous formaldehyde as the pollution source, and the formaldehyde concentration over time was monitored online using a PPM HTV-M portable formaldehyde detector from the UK. The experimental data results are shown in Table 1.

[0050] Table 1. Changes in formaldehyde concentration over time

[0051] Table 1 shows that several substrates exhibit some absorption of formaldehyde pollutants. This is because coal-based activated carbon, coconut shell activated carbon, and zeolite molecular sieves are all porous materials, which can effectively intercept and absorb formaldehyde molecules. Examples 1-11 and Comparative Examples 1-2, totaling 13 samples, were tested in a 1m³ purification chamber using an initial concentration of 0.810–0.820 ppm (formaldehyde concentration at time 0) to ensure a more scientific and effective comparison. The chamber concentration was monitored online every 5 minutes, and recorded until 25 minutes had elapsed.

[0052] Formaldehyde removal rate is calculated using the following formula: Removal rate (%) = [Initial concentration (ppm) - Formaldehyde concentration at different time points (ppm)] / Initial concentration (ppm) × 100%.

[0053] As shown in Table 1, porous carriers such as coal-based activated carbon, coconut shell activated carbon, and zeolite molecular sieves all have a certain adsorption capacity for formaldehyde. However, after modification with composite amine, the formaldehyde removal performance of the samples was significantly improved. Examples 1-11 and Comparative Examples 1-2, totaling 13 samples, were tested under conditions where the initial formaldehyde concentration was 0.810–0.820 ppm. The formaldehyde concentration in the chamber was monitored online every 5 minutes for up to 25 minutes to ensure comparability of the testing conditions between samples.

[0054] The comparison between Examples 1 and 2 and Comparative Example 1 shows that the formaldehyde removal performance of the carrier pretreated with nitric acid is significantly better than that of the carrier without nitric acid pretreatment. This indicates that the nitric acid pretreatment step is beneficial to introducing polar groups such as carboxyl and hydroxyl groups on the surface of the carrier, thereby enhancing the loading effect of the subsequent composite amine modifier and improving the formaldehyde removal performance.

[0055] The comparison between Example 4 and Examples 1, 3, and 5-7 shows that different combinations of amine components have a significant impact on the formaldehyde removal effect. Among them, the combination of ethanolamine and ethylenediamine performed better, indicating that the composite modification of small molecule polyamines with ethanolamines can form a more effective combination of active sites, thereby improving the material's efficiency in removing formaldehyde.

[0056] A comparison of Example 8 and Example 1 shows that using a compound solvent composed of deionized water, ethanol, and ethylene glycol is superior to using deionized water alone. This is presumably because polar organic solvents such as ethanol and ethylene glycol help improve the solubility and dispersion uniformity of amine modifiers, thereby resulting in a more uniform distribution on the carrier surface and within the pores.

[0057] The comparison between Example 9 and Examples 1 and 4 shows that the formaldehyde removal effect of coal-based activated carbon with a particle size of 4 mm is significantly worse than that of coal-based activated carbon with a particle size of 2 mm, indicating that smaller particle size carriers are more conducive to providing a larger effective specific surface area and more available active sites.

[0058] Examples 10 and 11 show that the composite amine modification method of the present invention is not only applicable to coal-based activated carbon, but also to porous carriers such as coconut shell activated carbon and zeolite molecular sieves. Among them, coconut shell activated carbon and 2mm particle size coal-based activated carbon both show good application potential.

[0059] Due to the large amount of data in the embodiments and comparative examples of this invention, they are not all converted into formaldehyde removal rates and presented in a table here. The data processing for Examples 1, 4, and Comparative Example 2 is only shown in Tables 2-4. Figure 1 As shown.

[0060] Table 2 Formaldehyde Removal Rate in Example 1

[0061] Table 3 Formaldehyde Removal Rate in Example 4

[0062] Table 4 Formaldehyde removal rate of Comparative Example 2

[0063] From Table 2, Table 3, Table 4 and Figure 1 It can be seen that Example 4 can reduce the formaldehyde concentration in the purification chamber from 0.818ppm to 0.049ppm in 20 minutes; and further reduce it to 0.033ppm in 25 minutes, corresponding to a formaldehyde removal rate of about 96%, which is significantly better than the formaldehyde removal rate of about 29% of unmodified coal-based activated carbon in 25 minutes, indicating that the composite amine modification can significantly improve the formaldehyde removal capacity of the material.

[0064] Among them, Example 4 showed the best results, using a combination of ethanolamine and ethylenediamine, which was superior to other examples and comparative examples, achieving a formaldehyde removal rate of 96% in 25 minutes.

[0065] The data comparison between Example 9 and Example 4 shows that the formaldehyde removal effect of coal-based activated carbon with a particle size of 4mm is significantly worse than that of coal-based activated carbon with a particle size of 2mm. This is mainly because the larger the particle size of activated carbon of the same mass, the smaller the effective specific surface area and the fewer active sites it can generate. At the same time, the larger the packing gaps between particles during use, the worse the adsorption and filtration effect on formaldehyde.

[0066] The data from Examples 10 and 11 illustrate that the preparation method of the composite amine modified air purification material of the present invention is also applicable to coconut shell activated carbon and zeolite molecular sieve. The calculated formaldehyde removal rates after 25 minutes are approximately 90.7% and 95.0%, respectively, with coconut shell activated carbon showing better performance.

[0067] A comparison of Examples 1 and 8 shows that the compound solvent composed of deionized water, ethanol and ethylene glycol in a mass ratio of 5:4:1 has a better modification effect. Compared with using only deionized water as a solvent, the formaldehyde removal rate is higher. The formaldehyde concentrations of the two solvents at 25 min are 0.064 ppm and 0.089 ppm, respectively, corresponding to formaldehyde removal rates of approximately 92.1% and 89.0%.

[0068] To verify the loading of the composite amine onto the carrier, a bulk density test was conducted, comparing the unmodified coal-based activated carbon with a particle size of 2 mm (Comparative Example 2) with the composite amine-modified activated carbon obtained in Example 4.

[0069] Table 5 Bulk Density Test

[0070] The results showed that the bulk density of the modified sample increased from 458 g / L to 509 g / L, indicating that the mass per unit volume of the material increased after modification. Combined with the BET test results described later, this confirms that the composite amine was loaded onto the surface and / or within the pores of the activated carbon.

[0071] As shown in Table 6, the unmodified activated carbon (Comparative Example 2) has a well-developed microporous structure, with a BET multi-point specific surface area as high as 1171.6 m². 2 / g, with a total pore volume of 0.572cm³ / g, and a micropore volume ratio of over 80%, providing ample space for the loading of the composite amine.

[0072] Table 6 BET Test Results

[0073] After modification with composite amine, the BET specific surface area of ​​the material decreased to 1025.8 m² / g, a decrease of about 12.4%, which is a very reasonable decrease, while still maintaining good adsorption performance; the total pore volume decreased to 0.476 cm³ / g, a decrease of about 16.8%, with the pores being filled by amine groups, and the average pore size slightly decreasing from 1.95 nm to 1.86 nm, indicating that after the micropores were filled, the overall pore size distribution shifted to a smaller direction.

[0074] The above results indicate that the composite amine has been successfully loaded onto the micropores and surface of activated carbon, occupying some adsorption sites and reducing the specific surface area and pore volume that nitrogen can enter. At the same time, the modified material still maintains a specific surface area of ​​over 1000 m² / g and a pore volume of 0.47 cm³ / g, providing sufficient channels for the diffusion and adsorption of formaldehyde molecules and ensuring the formaldehyde removal performance of the material.

[0075] Meanwhile, the modified material still maintains a high specific surface area and pore volume, indicating that the original porous structure of the carrier has not been severely damaged and can still provide channels for the diffusion and adsorption of formaldehyde molecules. Therefore, the increase in bulk density and the changes in BET specific surface area, total pore volume and average pore size together indicate that the composite amine has been successfully loaded onto the surface and / or pores of the carrier. This invention, while introducing chemical interaction sites, still retains the structural characteristics of the porous carrier relatively well.

[0076] To evaluate the long-term effectiveness, a five-cycle test was conducted: specifically, the formaldehyde-removing charcoal prepared in Example 4 was repeatedly used to adsorb formaldehyde in a purification chamber with an initial concentration of 0.810–0.820 ppm. After adsorbing formaldehyde for 25 minutes, formaldehyde was added to the chamber again, and the material was heated to volatilize, raising the formaldehyde concentration in the chamber to 0.810–0.820 ppm. After five cycles, the formaldehyde removal rate remained at 87.1%, demonstrating that the material has good recyclability.

[0077] Table 7 shows the test with 5 cycles.

[0078] As shown in Table 7, the formaldehyde removal rate of the sample in Example 4 was 96.0% in the first cycle, and remained at 87.1% in the fifth cycle. This result indicates that the material of the present invention still has a high formaldehyde removal capacity after multiple reuses and has good recyclability.

[0079] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0080] The above embodiments are merely preferred embodiments of the present invention, used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0081] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A composite amine-modified formaldehyde-removing air purification material, characterized in that, The invention includes a porous carrier and a composite amine modifier loaded on the surface and / or pores of the porous carrier. The porous carrier is pretreated with nitric acid solution and its surface is rich in oxygen-containing functional groups. The porous carrier is selected from one of coal-based activated carbon, coconut shell activated carbon, and zeolite molecular sieve. The composite amine modifier includes at least two amine modifiers.

2. The air purification material according to claim 1, characterized in that, The porous support surface, after being pretreated with nitric acid solution, is rich in oxygen-containing functional groups such as carboxyl groups and / or hydroxyl groups.

3. The air purification material according to claim 1 or 2, characterized in that, The amine modifier is selected from two or more of the following: methylurea, urea, diethylenetriamine, ethanolamine, polyethyleneimine, ethylenediamine, β-hydroxyethylethylenediamine, propylenediamine, butanediamine, pentanediamine, 2-methylpentanediamine, hexamethylenediamine, and aminosilane.

4. The air purification material according to claim 3, characterized in that, The composite amine modifier is selected from any of the following combinations: ethanolamine and polyethyleneimine, ethanolamine and ethylenediamine, ethanolamine and urea, and diethylenetriamine and ethanolamine.

5. The air purification material according to any one of claims 1 to 4, characterized in that, In the solution containing the composite amine modifier, the mass fraction of the amine modifier is 2% to 35%, and the solvent is two or more of deionized water, ethanol, ethylene glycol, n-propanol, and isopropanol.

6. A method for preparing a formaldehyde-removing air purification material modified with a composite amine according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) The porous support is immersed in nitric acid solution to oxidize its surface and enrich it with oxygen-containing functional groups; (2) After filtration, rinse repeatedly with deionized water until the filtrate is neutral, and dry to obtain the pretreated carrier; (3) Dissolve two or more amine modifiers in a solvent to prepare a composite amine modifier solution; (4) The pretreated carrier is placed in the composite amine modifier solution and soaked under constant temperature shaking conditions; (5) Remove the soaked carrier, dry it, cool it, and then seal it for storage.

7. The preparation method according to claim 6, characterized in that, In step (1), the mass concentration of nitric acid solution is 5% to 15%, the liquid-solid ratio of nitric acid solution to porous carrier is 5 to 20:1 mL / g, and the soaking time is 1 to 4 hours.

8. The preparation method according to claim 6 or 7, characterized in that, In step (2), the drying temperature is 105-120℃ and the drying time is 2-6h.

9. The preparation method according to any one of claims 6 to 8, characterized in that, In step (3), 2-35 parts by weight of amine modifier are added to 100 parts by weight of solvent and stirred or sonicated at room temperature for 2-20 minutes to promote dissolution; the solvent includes two or more of deionized water, ethanol, ethylene glycol, n-propanol and isopropanol.

10. The preparation method according to any one of claims 6 to 9, characterized in that, In step (4), the rotation speed of the constant temperature oscillation is 150-200 rpm, the soaking temperature is 60-80℃, the soaking time is 1-4h, and the liquid-solid ratio of the composite amine modifier solution to the porous carrier is 4-20:1mL / g; in step (5), vacuum drying at 60℃ is carried out for 6-10h.

11. The use of the air purification material according to any one of claims 1 to 5 in removing formaldehyde from the air.

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