Carbon monoxide adsorbent and method for preparing the same

Abstract

The application relates to the field of adsorbents, and particularly discloses a carbon monoxide adsorbent and a preparation method thereof. The preparation method of the carbon monoxide adsorbent comprises the following steps: S1, pretreating halloysite nanotubes by using HCl vapor to obtain HNTs with activated inner walls; S2, dispersing the HNTs with activated inner walls in a copper-based organic solution to obtain HNTs with HKUST-1 loaded on the inner walls; S3, coating the HNTs with HKUST-1 loaded on the inner walls to obtain HKUST-1@HNTs protected by SiO2; S4, coating the HKUST-1@HNTs protected by SiO2 with Fe-TCPP-MOF to obtain HKUST-1@HNTs with Fe-TCPP-MOF coated on the outer walls; and S5, hydrolyzing the SiO2 coating to obtain the adsorbent. The adsorbent has the advantages of stable performance, large adsorption capacity and fast adsorption rate.

Description

Technical Field

[0001] This application relates to the technical field of adsorbents, and more specifically, to a carbon monoxide adsorbent and a method for preparing the same. Background Technology

[0002] Carbon monoxide (CO) is an important basic chemical raw material, widely used in chemical, petroleum, natural gas, steel plants, power plants, and metal mines. CO can be used not only as a gaseous fuel but also in metal smelting; industrially, CO is commonly used to reduce iron oxide to smelt pig iron. It can also be used as a feedstock for the synthesis of methanol, vinyl acetate, and methyl formate. CO is present in metallurgy, chemistry, graphite electrode manufacturing, coal furnace gas, and steel plant tail gas. In CO gas sources, CO usually coexists with gases such as H2, N2, CH4, and CO2, making CO separation and purification crucial. Currently, the main CO separation methods include cryogenic separation, absorption separation, membrane separation, and adsorption separation. The first three are limited by operating costs and operational stability, making large-scale application difficult. This makes adsorption separation (e.g., PSA - Pressure Swing Adsorption) an important method for carbon monoxide removal. The key to adsorption separation lies in the adsorbent; therefore, the performance of the adsorbent material is crucial to the entire adsorption separation process.

[0003] In related technologies, such as the patent document with publication number CN103418337B, a carbon monoxide adsorbent is disclosed. The raw materials for this adsorbent include 38%-42% cuprous chloride, 18%-23% 13X molecular sieve, 8%-10% aluminum hydroxide, and 28-35% purified attapulgite powder. The preparation of this adsorbent includes the following steps: removing moisture and impurities from various parts of the 13X molecular sieve; then mixing all raw materials in a specific ratio; extruding the mixture into strip-shaped adsorbents; baking the strips at 300-320℃ for 3-3.3 hours; and finally cooling to obtain the finished product. This adsorbent has the advantages of strong adsorption capacity, low cost, and an environmentally friendly preparation process.

[0004] However, in practical applications, the aforementioned adsorbents suffer from poor pore matching due to the 13X molecular sieve. High-temperature baking can cause some micropores to collapse, reducing the effective pore volume and making it difficult for CO molecules to enter and react with the active sites, resulting in a low adsorption capacity. Furthermore, the blockage of collapsed pores increases mass transfer resistance, leading to a slower adsorption reaction rate. On the other hand, at high temperatures, Al2O3 and CuCl readily undergo a solid-phase reaction, consuming the active component and resulting in a low carbon monoxide adsorption capacity in practical applications. Additionally, the acidic sites on the attapulgite surface have high selectivity for CO2, inhibiting the CO adsorption reaction and further slowing the adsorption rate. Therefore, the aforementioned adsorbents suffer from low adsorption capacity and slow adsorption rate. Summary of the Invention

[0005] To improve the adsorption capacity and adsorption reaction rate of CO by the adsorbent, this application provides a carbon monoxide adsorbent and its preparation method.

[0006] The preparation method of a carbon monoxide adsorbent provided in this application adopts the following technical solution:

[0007] A method for preparing a carbon monoxide adsorbent includes the following steps:

[0008] S1. Halloysite nanotubes were pretreated with HCl vapor to obtain HNTs with activated inner walls;

[0009] S2. Disperse the HNTs activated on the inner wall in a copper-based organic solution, sonicate for 1-3 hours, then transfer to a hydrothermal reactor and reflux at 80-90℃ for 10-12 hours. After cooling, centrifuge, wash and dry to obtain HNTs loaded with HKUST-1 on the inner wall.

[0010] S3. Disperse the HNTs with HKUST-1 loaded on the inner wall in anhydrous ethanol, add hexadecyltrimethylammonium bromide and ammonia, stir and react for 10-20 min, then add tetraethyl orthosilicate, stir and react for 3-5 h, centrifuge, wash and dry to obtain SiO2 protected HKUST-1@HNTs;

[0011] S4. Disperse SiO2-protected HKUST-1@HNTs in deionized water, then add tetra-(N-methyl-4-pyridine)-porphyrin-ferric chloride and zinc nitrate hexahydrate for ultrasonic treatment, then transfer to a reaction vessel and react at 110-120℃ for 20-24h. After the reaction is completed, centrifuge, wash and dry to obtain HKUST-1@HNTs with Fe-TCPP-MOF coated on the outer wall.

[0012] S5. Add HKUST-1@HNTs with Fe-TCPP-MOF coating on the outer wall to HF solution, stir and react for 2-3 hours, separate by centrifugation, wash and dry the solid product to obtain the adsorbent.

[0013] This application uses halloysite nanotubes as the adsorbent. Halloysite nanotubes possess a high specific surface area and a unique hollow tubular structure. The tubular channels can guide gas molecules to diffuse rapidly to the active sites within the cavity, shortening the mass transfer distance and increasing the adsorption rate. This application achieves this by loading highly active ferriporphyrin-MOF onto the outer wall of HNTs, and then using Fe... 2+ The strong coordination with CO enables highly selective adsorption, similar to Fe in hemoglobin. 2+The specific binding of CO enables rapid CO capture, shortens the mass transfer distance, and reduces diffusion resistance. Combined with the high specific surface area of ​​MOFs and the selectivity of porphyrins, the adsorption rate and capacity for CO can be effectively improved. This application utilizes HKUST-1 loaded onto the inner wall of HNTs as a capacity-enhancing layer. By leveraging the microporous structure of MOFs and the capillary action of the nanotube pores, CO molecules already inside the tubes undergo physical adsorption or secondary chemical adsorption. The porous structure provides numerous adsorption sites, prolonging the CO residence time and thus enhancing capacity. Simultaneously, the tubular channels of HNTs act as "molecular conduits," reducing diffusion resistance to molecular motion, thereby further expanding the adsorption capacity and rate of the adsorbent.

[0014] The preparation method of this application fully considers the structural characteristics of halloysite nanotubes during the preparation process. Using halloysite nanotubes as a carrier, it utilizes their high specific surface area and unique hollow tubular structure to achieve synergistic adsorption of dual MOFs by loading HKUST-1 on the inner wall and coating Fe-TCPP-MOF on the outer wall. Specifically, S1 uses HCl vapor pretreatment to selectively activate the aluminum hydroxyl groups on the inner wall based on the difference in chemical composition and steric hindrance effect of the inner and outer walls of HNTs, providing more active sites for HKUST-1 loading, thus enabling accurate and stable loading of HKUST-1 on the inner wall of HNTs. S3 forms a silica film on the surface of HNTs loaded with HKUST-1, which acts as a physical barrier to prevent the precursor solution from penetrating into the inner wall and interfering with HKUST-1 during subsequent loading of Fe-TCPP-MOF on the outer wall, ensuring that the outer wall MOF grows only on the outer surface of HNTs. After loading, S5 uses HF solution to hydrolyze and remove the silica film, releasing the adsorption sites of HKUST-1 on the inner wall, allowing both the inner and outer wall MOFs to be exposed and synergistically adsorb CO. The adsorbent prepared by this method has an outer wall Fe-TCPP-MOF that passes through Fe 2+ The strong coordination with CO enables highly selective and rapid adsorption. The inner wall of HKUST-1 utilizes a microporous structure and high specific surface area to enhance adsorption capacity, while the tubular channels of the nanotubes shorten the mass transfer distance, thereby effectively improving adsorption capacity and adsorption reaction rate. At the same time, it ensures the integrity, effectiveness, and stability of the adsorbent structure, which is beneficial to ensuring the adsorbent's lifespan and performance.

[0015] Optionally, the specific method for S1 is as follows:

[0016] Halloysite nanotubes were vacuum dried and then loaded into the reaction chamber of an HCl vapor etching machine. The temperature was raised to 60-70°C, HCl vapor was introduced, and the mixture was kept for 1-2 hours. After the reaction was completed, HNTs with activated inner walls were obtained.

[0017] The reason for using HCl vapor for etching in the above scheme is mainly based on the unique structure and physicochemical properties of halloysite nanotubes (HNTs). Using HCl vapor for etching can efficiently and precisely activate the inner wall. From a molecular perspective, the extremely small size of HCl vapor molecules allows them to easily diffuse into the cavity through the nanotube opening; the tubular structure of the nanotubes forms a natural geometric shield, significantly reducing the probability of contact between the outer wall and HCl vapor, thus creating the prerequisite for selective etching of the inner wall. In terms of chemoselectivity, the adsorption affinity of aluminum hydroxyl groups (Al-OH) on the inner wall for HCl is significantly higher than that of silanol groups (Si-OH) on the outer wall, and the etching rate of aluminum-oxygen bonds (Al-O-Al) is much faster than that of silicon-oxygen bonds (Si-O-Si). This difference ensures that the etching process mainly occurs on the inner wall, achieving directional activation of the aluminum hydroxyl groups on the inner wall and providing abundant active sites for the subsequent loading of HKUST-1. Meanwhile, the water vapor generated during the etching process accumulates inside the tube, forming local pressure that protects the tube wall of the nanotube, inhibits the further diffusion of HCl vapor, and effectively avoids over-etching. This fully activates the inner wall while completely preserving the outer wall structure and the overall morphology of the nanotube, ensuring that the unique tubular structural advantages of HNTs can be continued. This lays a solid foundation for constructing a highly efficient inner and outer wall differentiated load structure. Compared with traditional solution etching, it significantly reduces the risk of damage to the outer wall and significantly improves the controllability and precision of the preparation process.

[0018] Optionally, the partial pressure of the HCl vapor during introduction is controlled at 6-8 Torr.

[0019] By adopting the above technical solution, the temperature and partial pressure conditions can promote the diffusion of HCl vapor into the tube and selectively etch the aluminum hydroxyl groups on the inner wall, while avoiding damage to the silicon hydroxyl layer and overall structure of the HNTs caused by high temperature or excessive partial pressure. This ensures that the activation depth of the inner wall is appropriate and the outer wall structure is intact, laying the foundation for the effective load of HKUST-1 in the future.

[0020] Optionally, in S2, the copper-based organic solution is prepared by mixing copper nitrate, trimesic acid, and N,N-dimethylformamide, and stirring at 50-60℃ for 10-30 min to obtain the copper-based organic solution.

[0021] Optionally, the mass ratio of copper nitrate, trimesic acid, and N,N-dimethylformamide is 1:(1.3-1.5):(6-8).

[0022] The above ratio and temperature conditions allow pyromellitic acid to react fully with copper nitrate, ensuring the Cu content in HKUST-1 crystals. 2+Sufficient exposure of sites enhances the density of chemisorption sites for CO; at the same time, the non-polar environment of DMF inhibits the activation of silanol groups on the outer wall, ensuring that HKUST-1 grows only on the inner wall, thus improving the accuracy and effectiveness of inner wall loading.

[0023] Optionally, in S3, the mass ratio of HNTs loaded with HKUST-1 on the inner wall, anhydrous ethanol, hexadecyltrimethylammonium bromide, ammonia and tetraethyl orthosilicate is 1:(30-50):(0.1-0.3):(1-3):(0.5-0.8).

[0024] By adopting the above technical solution, the HKUST-1 surface loaded with inner wall, especially the copper ion (Cu) content, is improved. 2+ The exposed sites can react with silicate ions (SiO3) generated by the hydrolysis of TEOS. 2- This creates electrostatic attraction, promoting preferential deposition of SiO2 on the inner wall. Hexadecyltrimethylammonium bromide (CTAB), as a cationic surfactant, has its long-chain alkyl portion that can embed into the pores of HKUST-1 through hydrophobic interactions, while the positively charged head (-N(CH3))... 3+ The ions bind to silicate ions, guiding SiO2 nucleation and growth on the HKUST-1 surface and reducing random deposition on the outer wall. This avoids subsequent interference with the coated Fe-TCPP-MOF.

[0025] Optionally, the concentration of the ammonia water is 20-25%.

[0026] Optionally, in S4, the mass ratio of SiO2-protected HKUST-1@HNTs, deionized water, tetra-(N-methyl-4-pyridine)-porphyrin-ferric chloride and zinc nitrate hexahydrate is 1:(50-70):(0.1-0.5):(0.3-0.5).

[0027] Optionally, in S5, the mass concentration of the HF solution is 5%-15%; the mass ratio of the HKUST-1@HNTs with Fe-TCPP-MOF coating on the outer wall to the HF solution is 1:(30-40).

[0028] By adopting the above technical solution, the above concentration and ratio can gently dissolve the SiO2 layer, preserve the crystal integrity of HKUST-1 and Fe-TCPP-MOF to the greatest extent, and fully open the pores of the inner wall HKUST-1, so as to achieve synergistic and efficient adsorption of CO by the inner and outer wall MOFs.

[0029] This application also provides a carbon monoxide adsorbent, which is prepared by the above-described method.

[0030] The adsorbent prepared by the above method can fully leverage the synergistic advantages of the dual MOF structure and halloysite nanotube support, exhibiting high adsorption capacity, rapid adsorption rate, high selectivity, and good structural stability. It demonstrates significant performance advantages and application value in the field of CO adsorption and separation.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. This preparation method uses halloysite nanotubes as a carrier and achieves synergistic adsorption of CO through differential loading on the inner and outer walls, significantly improving the adsorption capacity and rate. The Fe-TCPP-MOF loaded on the outer wall utilizes Fe... 2+ The strong coordination with CO enables a hemoglobin-like specific binding, allowing for rapid CO capture. Combined with the high specific surface area of ​​MOFs and the selectivity of porphyrins, the adsorption rate is effectively enhanced. HKUST-1 loaded on the inner wall serves as a capacity-enhancing layer, utilizing the microporous structure of MOFs and the capillary action of the nanotube pores to provide numerous adsorption sites, prolonging CO residence time and significantly improving adsorption capacity. Simultaneously, the unique hollow tubular structure of halloysite nanotubes acts as a "molecular conduit," guiding gas molecules to rapidly diffuse to the active sites, further reducing mass transfer resistance. This synergistic effect enhances both adsorption capacity and adsorption rate, demonstrating significant performance advantages compared to traditional adsorbents.

[0033] 2. The preparation process of this application fully considers the structural characteristics of halloysite nanotubes, and each step is closely coordinated to achieve precise loading. S1 uses HCl vapor pretreatment to selectively activate the aluminum hydroxyl groups on the inner wall of the HNTs based on the difference in chemical composition and steric hindrance effect of the inner and outer walls, providing active sites for HKUST-1 loading. S3 forms a silica film on the surface of the HNTs loaded with HKUST-1, acting as a physical barrier to prevent the precursor solution from penetrating into the inner wall when loading Fe-TCPP-MOF on the outer wall, ensuring that the MOF on the outer wall grows only on the outer surface of the HNTs. After loading, S5 uses HF solution to hydrolyze and remove the silica film, releasing the adsorption sites of HKUST-1 on the inner wall. The entire process ensures accurate loading of HKUST-1 on the inner wall of the nanotube and coating of Fe-TCPP-MOF on the outer wall, forming a complete and effective double MOF structure, which helps to ensure the structural stability of the adsorbent, thereby guaranteeing its service life and performance.

[0034] 3. The parameter settings in each step of the preparation method in this application effectively enhance the controllability of the preparation process. During HCl vapor etching, a temperature of 60-70℃ and a vapor partial pressure of 6-8 Torr can promote the diffusion of HCl vapor into the tube to selectively etch the inner wall, while avoiding damage to the outer wall and the overall structure; the ratio and temperature conditions for preparing the copper-based organic solution ensure that Cu in the HKUST-1 crystal... 2+The sites are fully exposed and growth occurs only on the inner wall. During the formation of the SiO2 protective layer, the mass ratio of each raw material and the concentration of ammonia promote preferential deposition of SiO2 on the HKUST-1 surface of the inner wall. When removing the SiO2 layer, the concentration and mass ratio of the HF solution can gently dissolve the SiO2 layer while preserving the integrity of the double MOF structure. The precise control of this application ensures high reproducibility of the preparation process, enabling the stable preparation of high-performance carbon monoxide adsorbents and providing a reliable guarantee for industrial production. Detailed Implementation

[0035] Example 1

[0036] A carbon monoxide adsorbent, the preparation method of which is as follows:

[0037] S1. Halloysite nanotubes were vacuum dried at 120°C for 2 hours, then loaded into the reaction chamber of an HCl vapor etching machine, and evacuated to 10°C. -3 Pa, heat to 60℃, introduce HCl vapor, control the partial pressure of HCl vapor at 6 Torr, maintain for 1 h, and after the reaction is completed, HNTs with inner wall activation are obtained;

[0038] S2. Mix 10g copper nitrate, 13g trimesic acid, and 60g N,N-dimethylformamide, and stir at 50℃ for 10min to obtain a copper-based organic solution. Disperse the HNTs activated on the inner wall in the copper-based organic solution with a solid-liquid ratio of 1:5, then sonicate at 50kHz for 1h, and then transfer to a hydrothermal reactor. Reflux at 80℃ for 10h, centrifuge at 10000rpm for 15min, wash the product three times with DMF, and vacuum dry at 60℃ for 12h to obtain HNTs loaded with HKUST-1 on the inner wall.

[0039] S3. Disperse 10g of HNTs with HKUST-1 loaded on the inner wall in 300g of anhydrous ethanol, then add 1g of hexadecyltrimethylammonium bromide and 10g of 20% ammonia water, stir for 10min, then add 5g of tetraethyl orthosilicate, stir for 3h, centrifuge, wash the product three times with deionized water, and vacuum dry at 60℃ for 12h to obtain SiO2 protected HKUST-1@HNTs;

[0040] S4. 10g of SiO2-protected HKUST-1@HNTs were dispersed in 500g of deionized water, and then 1g of tetra-(N-methyl-4-pyridine)-porphyrin-ferric chloride and 3g of zinc nitrate hexahydrate were added. The mixture was sonicated at 50kHz for 1h, and then transferred to a reaction vessel. The reaction was carried out at 110℃ for 20h. After the reaction was completed, the product was centrifuged at 12000rpm for 20min, washed three times with deionized water, and vacuum dried at 100℃ for 12h to obtain HKUST-1@HNTs with Fe-TCPP-MOF coated on the outer wall.

[0041] S5. 10g of HKUST-1@HNTs with Fe-TCPP-MOF coating on the outer wall was added to 300g of HF solution with a mass concentration of 5% and stirred at room temperature for 2h. After centrifugation at 12000rpm for 20min, the solid product was washed 5 times with deionized water and dried under vacuum at 80℃ for 12h to obtain the adsorbent.

[0042] Example 2

[0043] A carbon monoxide adsorbent, the preparation method of which is as follows:

[0044] S1. Halloysite nanotubes were vacuum dried at 120°C for 2 hours, then loaded into the reaction chamber of an HCl vapor etching machine, and evacuated to 10°C. -3 Pa, heat to 65℃, introduce HCl vapor, control the partial pressure of HCl vapor at 7 Torr, maintain for 1.5h, and obtain HNTs with inner wall activation after the reaction is completed;

[0045] S2. Mix 10g copper nitrate, 14g trimesic acid, and 70g N,N-dimethylformamide, and stir at 55℃ for 20min to obtain a copper-based organic solution. Disperse the HNTs activated on the inner wall in the copper-based organic solution with a solid-liquid ratio of 1:5, then sonicate at 50kHz for 2h, and then transfer to a hydrothermal reactor. Reflux at 85℃ for 11h, centrifuge at 10000rpm for 15min, wash the product three times with DMF, and vacuum dry at 60℃ for 12h to obtain HNTs loaded with HKUST-1 on the inner wall.

[0046] S3. Disperse 10g of HNTs with HKUST-1 loaded on the inner wall in 400g of anhydrous ethanol, then add 2g of hexadecyltrimethylammonium bromide and 20g of 22% ammonia water, stir and react for 15min, then add 7g of tetraethyl orthosilicate, stir and react for 4h, centrifuge and wash the product three times with deionized water, and dry under vacuum at 60℃ for 12h to obtain SiO2 protected HKUST-1@HNTs;

[0047] S4. 10g of SiO2-protected HKUST-1@HNTs were dispersed in 600g of deionized water, and then 3g of tetra-(N-methyl-4-pyridine)-porphyrin-ferric chloride and 4g of zinc nitrate hexahydrate were added. The mixture was sonicated at 50kHz for 1h, and then transferred to a reaction vessel. The reaction was carried out at 115℃ for 22h. After the reaction was completed, the product was centrifuged at 12000rpm for 20min, washed three times with deionized water, and vacuum dried at 100℃ for 12h to obtain HKUST-1@HNTs with Fe-TCPP-MOF coated on the outer wall.

[0048] S5. 10g of HKUST-1@HNTs with Fe-TCPP-MOF coating on the outer wall was added to 350g of HF solution with a mass concentration of 10% and stirred at room temperature for 2.5h. After centrifugation at 12000rpm for 20min, the solid product was washed 5 times with deionized water and dried under vacuum at 80℃ for 12h to obtain the adsorbent.

[0049] Example 3

[0050] A carbon monoxide adsorbent, the preparation method of which is as follows:

[0051] S1. Halloysite nanotubes were vacuum dried at 120°C for 2 hours, then loaded into the reaction chamber of an HCl vapor etching machine, and evacuated to 10°C. -3 Pa, heat to 70℃, introduce HCl vapor, control the partial pressure of HCl vapor at 8 Torr, maintain for 2h, and after the reaction is completed, HNTs with inner wall activation are obtained;

[0052] S2. Mix 10g copper nitrate, 15g trimesic acid, and 80g N,N-dimethylformamide, and stir at 60℃ for 30min to obtain a copper-based organic solution. Disperse the HNTs activated on the inner wall in the copper-based organic solution with a solid-liquid ratio of 1:5, then sonicate at 50kHz for 3h, and then transfer to a hydrothermal reactor. Reflux at 90℃ for 12h, centrifuge at 10000rpm for 15min, wash the product three times with DMF, and vacuum dry at 60℃ for 12h to obtain HNTs loaded with HKUST-1 on the inner wall.

[0053] S3. Disperse 10g of HNTs with HKUST-1 loaded on the inner wall in 500g of anhydrous ethanol, then add 3g of cetyltrimethylammonium bromide and 30g of 25% ammonia water, stir and react for 20min, then add 8g of tetraethyl orthosilicate, stir and react for 5h, centrifuge and wash the product three times with deionized water, and dry under vacuum at 60℃ for 12h to obtain SiO2 protected HKUST-1@HNTs;

[0054] S4. 10g of SiO2-protected HKUST-1@HNTs were dispersed in 700g of deionized water, and then 5g of tetra-(N-methyl-4-pyridine)-porphyrin-ferric chloride and 5g of zinc nitrate hexahydrate were added. The mixture was sonicated at 50kHz for 1h, and then transferred to a reaction vessel. The reaction was carried out at 120℃ for 24h. After the reaction was completed, the product was centrifuged at 12000rpm for 20min, washed three times with deionized water, and vacuum dried at 100℃ for 12h to obtain HKUST-1@HNTs with Fe-TCPP-MOF coated on the outer wall.

[0055] S5. 10g of HKUST-1@HNTs with Fe-TCPP-MOF coating on the outer wall was added to 400g of HF solution with a mass concentration of 15% and stirred at room temperature for 3h. After centrifugation at 12000rpm for 20min, the solid product was washed 5 times with deionized water and dried under vacuum at 80℃ for 12h to obtain the adsorbent.

[0056] Example 4

[0057] A carbon monoxide adsorbent, the preparation method of which differs from that of Example 1 is that: in S1, when the halloysite nanotubes are pretreated with HCl vapor, the partial pressure of HCl vapor is controlled at 20 Torr.

[0058] Example 5

[0059] A carbon monoxide adsorbent, the preparation method of which differs from that of Example 1 is as follows: the preparation method of the copper-based organic solution in S2 is as follows: 5g of copper nitrate, 15g of trimesic acid and 80g of N,N-dimethylformamide are mixed and stirred at 60°C for 30min to obtain a copper-based organic solution. The remaining steps and operation methods are the same as those in Example 1.

[0060] Comparative Example

[0061] Comparative Example 1

[0062] A carbon monoxide adsorbent was prepared according to the method in Example 1 of the patent document with announcement number CN103418337B, entitled "A Carbon Monoxide Adsorbent".

[0063] Comparative Example 2

[0064] A carbon monoxide adsorbent is prepared in a manner different from that in Example 1. In this comparative example, the adsorbent is obtained by directly coating HNTs with ferrous porphyrin-MOF. The specific preparation method is as follows:

[0065] 10g halloysite nanotubes were dispersed in 500g deionized water, then 1g tetra-(N-methyl-4-pyridine)-porphyrin-ferric chloride and 3g zinc nitrate hexahydrate were added. The mixture was sonicated at 50kHz for 1h, then transferred to a reaction vessel and reacted at 110℃ for 20h. After the reaction was completed, the product was centrifuged at 12000rpm for 20min, washed three times with deionized water, and dried under vacuum at 100℃ for 12h to obtain the adsorbent.

[0066] Comparative Example 3

[0067] A carbon monoxide adsorbent, the preparation method of which differs from that of Example 1, is that halloysite nanotubes loaded with HKUST-1 are directly used as the adsorbent in this comparative example. The specific preparation method is as follows:

[0068] 10g of copper nitrate, 13g of trimesic acid, and 60g of N,N-dimethylformamide were mixed and stirred at 50℃ for 10min to obtain a copper-based organic solution. Halloysite nanotubes were dispersed in the copper-based organic solution at a solid-liquid ratio of 1:5, and then sonicated at 50kHz for 1h. The mixture was then transferred to a hydrothermal reactor and refluxed at 80℃ for 10h. After centrifugation at 10000rpm for 15min, the product was washed three times with DMF and vacuum dried at 60℃ for 12h to obtain the adsorbent.

[0069] Comparative Example 4

[0070] A carbon monoxide adsorbent is prepared in a manner that differs from that in Example 1 in that the S1 pretreatment step is omitted, and halloysite nanotubes are directly used in the preparation of S2. The remaining steps and operating methods are the same as in Example 1.

[0071] Comparative Example 5

[0072] A carbon monoxide adsorbent, the preparation method of which differs from that of Example 1, is that the step of coating the SiO2 thin film layer in S3 is not performed, and in S4, the HNTs with HKUST-1 loaded on the inner wall obtained in S2 are directly used to participate in the reaction of coating ferriporphyrin-MOF.

[0073] Performance testing

[0074] Test samples: Adsorbents prepared in Examples 1-5 and Comparative Examples 1-5.

[0075] Test items:

[0076] 1. Adsorption capacity test

[0077] Take 10g of adsorbent sample and place it in a vacuum drying oven. Dry it for 1 hour at 40℃ and a vacuum degree ≤0.1MPa to remove physically adsorbed moisture and impurities. Transfer the activated sample to the sample tube of a fully automated gas adsorption instrument. At 25℃, CO gas is sequentially introduced until the pressure reaches 1 bar. Calculate the saturated adsorption capacity based on the data fitted by the Langmuir isotherm model.

[0078] 2. Adsorption rate test

[0079] The adsorbent was uniformly and completely filled into the sample glass column of the fixed-bed adsorption device. Using N2 as the carrier gas at a flow rate of 50 mL / min, the adsorption column was purged for 30 min to remove air. Then, the flow rate was switched to a CO / N2 mixed gas (10% CO by volume, with N2 as the equilibrium gas) at a flow rate of 50 mL / min, and the changes in inlet and outlet CO concentrations over time were recorded. The breakthrough point was defined as when the outlet CO concentration reached 10% of the inlet concentration, and the corresponding time was defined as the breakthrough time. The adsorption rate constant (k) was calculated using the breakthrough curve fitting formula: ln(Ct / C0-Ct)=ln(1 / kT)-kt. Where Ct is the outlet concentration at time t, C0 is the inlet concentration, T is the theoretical saturation time of the adsorbent bed, and t is the breakthrough time. A smaller k value indicates a faster adsorption rate.

[0080] Experimental results: see Table 1.

[0081] Table 1. Experimental Results

[0082]

[0083] As shown in Table 1, the adsorption capacity of the adsorbents in Examples 1-3 remained at 248-256 mL / g, with k values ​​of 0.004-0.006. Compared to Comparative Example 1 (conventional 13X molecular sieve adsorbent, adsorption capacity 34 mL / g, k=0.087), this application employs a halloysite nanotube (HNTs) supported double MOF structure, with Fe-TCPP-MOF on the outer wall. 2+ The adsorbent exhibits strong coordination with CO (similar to the hemoglobin binding mechanism), rapidly capturing CO molecules. The microporous structure of the inner wall HKUST-1 provides numerous physical adsorption sites, prolonging CO residence time and increasing adsorption capacity. The nanotubes reduce diffusion resistance, enhancing adsorption efficiency. Therefore, the adsorbent prepared in this application has the advantages of stable performance, large adsorption capacity, and fast adsorption rate.

[0084] Example 4 showed an adsorption capacity of 103 mL / g and a k value of 0.012, lower than Examples 1-3. The excessively high partial pressure of HCl vapor in S1 (20 Torr) led to excessive etching of the outer wall of the HNTs, damaging the overall structure of the nanotubes. Simultaneously, insufficient activation of the aluminum hydroxyl groups on the inner wall reduced the loading of HKUST-1. This adversely affected the adsorption capacity and adsorption rate of the adsorbent.

[0085] Example 5 showed an adsorption capacity of 178 mL / g and a k value of 0.019, which was lower than that of Examples 1-3. This was due to an imbalance in the copper-based organic solution in S2, resulting in an excess of trimesic acid and insufficient reaction with copper nitrate. The Cu in the HKUST-1 crystals was also lower. 2+ Insufficient site exposure leads to a decrease in the adsorption capacity of the adsorbent and a slight slowdown in the adsorption rate.

[0086] The conventional adsorbents in Comparative Example 1 use 13X molecular sieve and attapulgite. Due to poor pore matching, high temperature causing micropore collapse, and the fact that the acidic sites of attapulgite adsorb CO2 and inhibit the CO reaction, the adsorption capacity and rate are significantly lower than those in this application.

[0087] The adsorbent in Comparative Example 2 only coats the HNTs surface with Fe-TCPP-MOF: lacking the capacity-enhancing layer of HKUST-1, it relies solely on the outer wall monolayer MOF for adsorption, resulting in a limited total number of adsorption sites, and both the adsorption capacity and rate are lower than those of the dual MOF structure.

[0088] In Comparative Example 3, the adsorbent only had HNTs loaded with HKUST-1, lacking the rapid capture capability of the outer wall Fe-TCPP-MOF. CO needed to diffuse into the inner cavity to be adsorbed, resulting in a long mass transfer distance and a slow rate (k=0.071), and it also lacked Fe. 2+ The strong coordination effect, coupled with insufficient selectivity and adsorption capacity, indicates that the synergistic effect of the outer wall Fe-TCPP-MOF and the inner wall HKUST-1 is necessary to jointly improve the adsorption capacity and adsorption rate of the adsorbent.

[0089] The adsorbent in Comparative Example 4 was not pretreated with S1HCl vapor during preparation, and the aluminum hydroxyl groups on the inner wall were not activated. When loaded with HKUST-1, it would be disordered and chaotic, resulting in the adsorption capacity (153 mL / g) and rate (k=0.011) of the adsorbent being only about 60% of that in Example 1.

[0090] In the preparation process of the adsorbent in Comparative Example 5, the SiO2 layer was not coated after loading HKUST-1, resulting in the failure of S3 to form a physical barrier. The Fe-TCPP-MOF precursor on the outer wall penetrated into the inner wall and reacted with HKUST-1, consuming active sites. This led to the disorder of the double MOF structure and a significant decrease in adsorption performance.

[0091] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a carbon monoxide adsorbent, characterized in that, Includes the following steps: S1. Halloysite nanotubes were pretreated with HCl vapor to obtain HNTs with activated inner walls. The specific method is as follows: Halloysite nanotubes were vacuum dried and then loaded into the reaction chamber of an HCl vapor etching machine. The temperature was raised to 60-70°C, HCl vapor was introduced, and the temperature was maintained for 1-2 hours. After the reaction was completed, HNTs with activated inner walls were obtained. The vapor partial pressure of the HCl vapor was controlled at 6-8 Torr. S2. Disperse the HNTs activated on the inner wall in a copper-based organic solution, sonicate for 1-3 hours, then transfer to a hydrothermal reactor and reflux at 80-90°C for 10-12 hours. After cooling, centrifuge, wash, and dry to obtain HNTs loaded with HKUST-1 on the inner wall. The copper-based organic solution is prepared by mixing copper nitrate, trimesic acid, and N,N-dimethylformamide in a mass ratio of 1:(1.3-1.5):(6-8) and stirring at 50-60°C for 10-30 minutes to obtain the copper-based organic solution. S3. Disperse the HNTs with HKUST-1 loaded on the inner wall in anhydrous ethanol, add hexadecyltrimethylammonium bromide and ammonia, stir and react for 10-20 min, then add tetraethyl orthosilicate, stir and react for 3-5 h, centrifuge, wash and dry to obtain SiO2 protected HKUST-1@HNTs; S4. Disperse SiO2-protected HKUST-1@HNTs in deionized water, then add tetra-(N-methyl-4-pyridine)-porphyrin-ferric chloride and zinc nitrate hexahydrate for ultrasonic treatment, then transfer to a reaction vessel and react at 110-120℃ for 20-24h. After the reaction is completed, centrifuge, wash and dry to obtain HKUST-1@HNTs with Fe-TCPP-MOF coated on the outer wall. S5. Add HKUST-1@HNTs with Fe-TCPP-MOF coating on the outer wall to HF solution, stir and react for 2-3 hours, separate by centrifugation, wash and dry the solid product to obtain the adsorbent.

2. The method for preparing a carbon monoxide adsorbent according to claim 1, characterized in that: In S3, the mass ratio of HNTs loaded with HKUST-1 on the inner wall, anhydrous ethanol, hexadecyltrimethylammonium bromide, ammonia and tetraethyl orthosilicate is 1:(30-50):(0.1-0.3):(1-3):(0.5-0.8).

3. The method for preparing a carbon monoxide adsorbent according to claim 2, characterized in that: The ammonia concentration is 20-25%.

4. The method for preparing a carbon monoxide adsorbent according to claim 1, characterized in that: In S4, the mass ratio of SiO2-protected HKUST-1@HNTs, deionized water, tetra-(N-methyl-4-pyridine)-porphyrin-ferric chloride and zinc nitrate hexahydrate is 1:(50-70):(0.1-0.5):(0.3-0.5).

5. The method for preparing a carbon monoxide adsorbent according to claim 1, characterized in that: In S5, the mass concentration of the HF solution is 5%-15%; the mass ratio of the HKUST-1@HNTs with Fe-TCPP-MOF coating on the outer wall to the HF solution is 1:(30-40).

6. A carbon monoxide adsorbent, characterized in that, It is prepared by the preparation method according to any one of claims 1-4.

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