Co-c-n catalyst, its preparation method and application

Abstract

The application provides a Co-C-N catalyst and a preparation method and application thereof. The preparation method comprises the following steps: (1) uniformly mixing a cobalt source, a zinc source and water, then mixing 2-methyl imidazole twice, and then sequentially performing ultrasonic treatment, stirring treatment and solid-liquid separation to obtain a ZnCo-MOF material; (2) sequentially performing cleaning, drying treatment and calcination treatment on the ZnCo-MOF material obtained in the step (1) to obtain the Co-C-N catalyst. The Co-C-N catalyst prepared through simple mixing, stirring and calcination can completely degrade formaldehyde into water and carbon dioxide at room temperature, and has the advantages of simple preparation process, low cost and long service life.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a Co-based catalyst, specifically a Co-CN catalyst and its preparation method and application. Background Technology

[0002] In recent years, formaldehyde has become a major volatile indoor pollutant in my country, leading to frequent cases of formaldehyde poisoning. Currently, formaldehyde has been identified as a probable carcinogen by the U.S. Environmental Protection Agency and classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC), a branch of the World Health Organization. Formaldehyde is widely released from building materials, decorative items, and furniture materials. To comply with increasingly stringent environmental protection laws and regulations and to meet people's pursuit of a higher quality of life, effectively removing indoor formaldehyde gas has become an urgent problem to be solved.

[0003] Currently, the most commonly used formaldehyde removal technology is activated carbon adsorption and absorption. However, traditional adsorption and absorption control technologies only transfer pollutants from the gas phase to the solid phase, without achieving true removal. Furthermore, the adsorption capacity of adsorption materials is limited, requiring periodic regeneration or replacement, which can easily lead to secondary pollution. Therefore, in practical applications, it is often difficult to meet national indoor air quality standards. Unlike traditional adsorption / absorption formaldehyde removal technologies, formaldehyde room-temperature catalytic oxidation technology utilizes the catalyst's own lattice oxygen or activated adsorbed oxygen to initiate the catalytic reaction, achieving complete decomposition and harmless treatment of formaldehyde at room temperature. It is highly efficient, environmentally friendly, and has broad application prospects.

[0004] CN 103736484A discloses a supported monolithic catalyst for formaldehyde purification and its preparation method. The catalyst consists of a titanium dioxide nanotube array support and a noble metal M, wherein the noble metal M is one or a mixture of at least two of Pt, Ru, Rh, Pd, and Au. The preparation method involves impregnating a precursor solution containing the noble metal onto the titanium dioxide nanotube array support, followed by calcination to obtain a catalyst loaded with the noble metal. This catalyst can then be directly used for the catalytic purification of formaldehyde after reduction with hydrogen or a reducing solution. However, this catalyst has a short lifespan and relatively poor activity.

[0005] CN 106040230A discloses a method for preparing an integrated catalyst for low-temperature catalytic oxidation of formaldehyde. The method includes: anodizing an aluminum plate and then hydrating it in deionized water at 30-95℃ for 5-70 min to obtain a boehm; immersing the boehm in a chloroplatinic acid solution with a concentration of 0.1-0.8 g / L at 25℃ for 1-8 h and drying it at room temperature for 12 h; then reducing it in a sodium borohydride solution with a concentration of 0.05-1 mol / L at 25℃ for 0.5-3 h and drying it at room temperature. When the platinum content is 22.5 wt%, the formaldehyde conversion rate reaches 72% at room temperature. However, the high precious metal content increases the cost and is not conducive to widespread application.

[0006] While supported noble metal (Pt, Au, Pd) catalysts can efficiently degrade formaldehyde at room temperature, their high cost limits their widespread application. Non-noble metal catalysts are inexpensive and readily applicable, but their performance in degrading formaldehyde at room temperature is inferior to that of supported noble metal catalysts. Therefore, it is urgent to develop novel synthetic methods for non-noble metal catalysts to further improve their room temperature performance.

[0007] MOF materials possess a three-dimensional structure, a large specific surface area, and a rich and complex pore structure, providing ample sites for the adsorption and reaction of gas molecules. Two-dimensional materials are a class of materials with special structural properties, where electrons move within a two-dimensional plane, offering a variety of reaction possibilities. MOFs and two-dimensional materials and their derivatives can flexibly modulate the active sites, interface structures, and spatial confinement of catalysts, exhibiting excellent electron transfer capabilities. This facilitates the optimization of the electronic structure of active metals, guiding them towards the optimal structural direction for redox reactivity, thereby improving the intrinsic activity of catalytic reactions while increasing the density and accessibility of active sites.

[0008] In conclusion, it is necessary to provide a low-cost, highly active, and highly stable catalyst that can be widely used for indoor formaldehyde removal. Summary of the Invention

[0009] The purpose of this invention is to provide a Co-CN catalyst, its preparation method, and its application. At room temperature, the Co-CN catalyst exhibits excellent catalytic degradation ability for formaldehyde, even surpassing many noble metal catalysts; moreover, the catalyst raw materials are inexpensive and readily available, the preparation method is simple, and the overall process cost is low.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a Co-CN catalyst, the method comprising the following steps:

[0012] (1) After the cobalt source, zinc source and solvent are mixed evenly, 2-methylimidazole is mixed twice, and then ultrasonic treatment, stirring treatment and solid-liquid separation are performed in sequence to obtain ZnCo-MOF material;

[0013] (2) The ZnCo-MOF material obtained in step (1) is sequentially cleaned, dried and calcined to obtain the Co-CN catalyst.

[0014] This invention can prepare irregular polyhedral ZnCo-MOF materials with a two-dimensional layered structure on the outer surface through a simple mixing and stirring method. Then, through calcination, a Co-CN catalyst with a layered surface distribution is obtained. The Co-CN catalyst has excellent formaldehyde degradation performance at room temperature and a long activity retention time.

[0015] In this invention, when water or ethanol is used as a solvent, the amine N of 2-methylimidazolium (2-MIM) tends to form hydrogen bonds with hydrated protons (because 2-MIM has a lower dissociation constant in water), which in turn leads to Co 2+ The cross-linking between 2-MIM and 2-MIM forms connected building units and an irregular stacked structure.

[0016] As a preferred technical solution of the present invention, the cobalt source in step (1) includes cobalt nitrate.

[0017] Preferably, the zinc source in step (1) includes zinc nitrate and / or zinc acetate.

[0018] As a preferred technical solution of the present invention, the molar ratio of cobalt source, zinc source and 2-methylimidazole in step (1) is 40:480:1~20, for example, it can be 40:480:1, 40:480:4, 40:480:8, 40:480:12, 40:480:16 or 40:480:20, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the solvent in step (1) includes water or ethanol.

[0020] Preferably, the solid-liquid ratio of the total mass of the cobalt source and zinc source to the solvent in step (1) is 0.76g:50~70mL, for example, it can be 0.76g:50mL, 0.76g:54mL, 0.76g:58mL, 0.76g:62mL, 0.76g:66mL or 0.76g:70mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] As a preferred technical solution of the present invention, the mixing temperature in step (1) is 25~35℃, for example, it can be 25℃, 27℃, 29℃, 31℃, 33℃ or 35℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the ultrasonic treatment time in step (1) is 20 to 40 minutes, for example, it can be 20 minutes, 24 minutes, 28 minutes, 32 minutes, 36 minutes or 40 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] In this invention, the ultrasonic treatment ensures that the cobalt and zinc sources in the solvent are fully and uniformly mixed, which is more conducive to the formation of layered structures.

[0024] Preferably, the stirring time in step (1) is 12 to 48 hours, for example, it can be 12 hours, 16 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours or 48 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the stirring speed in step (1) is 8000~10000 r / min, for example, it can be 8000 r / min, 8400 r / min, 8800 r / min, 9200 r / min, 9600 r / min or 10000 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the solid-liquid separation in step (1) includes centrifugation.

[0027] As a preferred technical solution of the present invention, the cleaning solution used in step (2) includes ethanol.

[0028] As a preferred technical solution of the present invention, the drying process in step (2) includes vacuum drying.

[0029] Preferably, the vacuum drying temperature is 60~80℃, for example, 60℃, 64℃, 68℃, 72℃, 76℃ or 80℃, but not limited to the listed values.

[0030] Preferably, the vacuum drying time is 10~12h, for example, it can be 10h, 10.4h, 10.8h, 11.2h, 11.6h or 12h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] As a preferred technical solution of the present invention, the calcination process in step (2) is carried out under an inert gas atmosphere.

[0032] Preferably, the inert gas includes any one or a combination of at least two of nitrogen, argon, or helium. Typical but non-limiting combinations include: a combination of nitrogen and argon, a combination of argon and helium, a combination of nitrogen and helium, or a combination of nitrogen, argon, and helium.

[0033] Preferably, the calcination temperature in step (2) is 900~1050℃, for example, it can be 900℃, 940℃, 980℃, 1020℃ or 1050℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the roasting time in step (2) is 1 to 3 hours, for example, it can be 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] In this invention, the purpose of the calcination treatment is to remove the Zn element from the ZnCo-MOF material. If the calcination temperature is too low, the Zn element will be difficult to remove completely, and a high-performance Co-CN catalyst cannot be formed. If the calcination temperature is too high, it will affect the three-dimensional structure of the catalyst, and pore collapse and / or Co atom aggregation may occur, resulting in a decrease in the activity of the catalyst.

[0036] As a preferred embodiment of the present invention, the method for preparing the Co-CN catalyst provided in the first aspect of the present invention includes the following steps:

[0037] (1) After the cobalt source (cobalt nitrate), zinc source (zinc nitrate) and solvent are mixed evenly at 25~35℃, 2-methylimidazole is mixed twice, and then ultrasonic treatment for 20~40min, stirring treatment at 8000~10000r / min for 12~48h and solid-liquid separation are performed to obtain ZnCo-MOF material.

[0038] The molar ratio of the cobalt source, zinc source, and 2-methylimidazole is 40:480:1~20; the solid-liquid ratio of the total mass of the cobalt source and zinc source to the solvent is 0.76g:50~70mL;

[0039] (2) The ZnCo-MOF material obtained in step (1) is cleaned with ethanol, dried at 60~80℃ for 10~12h, and then calcined at 900~1050℃ for 1~3h in an inert gas atmosphere to obtain the Co-CN catalyst.

[0040] Secondly, the present invention provides a Co-CN catalyst, wherein the Co-CN catalyst is obtained by the preparation method provided in the first aspect.

[0041] Thirdly, the present invention provides an application of the Co-CN catalyst prepared by the method of the first aspect, wherein the Co-CN catalyst is used to degrade formaldehyde.

[0042] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The Co-CN catalyst provided by the present invention has excellent room temperature activity, even better than most precious metal catalysts, and can be widely used in indoor formaldehyde removal catalysts;

[0045] (2) The Co-CN catalyst provided by this invention has excellent selectivity for CO2 and the product has no secondary pollution;

[0046] (3) The raw materials for the preparation of the Co-CN catalyst provided by the present invention are cheap and readily available, the preparation method is simple, and the overall process cost is low. Attached Figure Description

[0047] Figure 1 These are SEM images of the ZnCo-MOF material provided in Embodiment 1 of the present invention at different magnifications;

[0048] Figure 2 These are SEM images of the Co-CN catalyst provided in Example 1 of this invention at different magnifications;

[0049] Figure 3 This is a TEM image of the Co-CN catalyst provided in Example 1 of the present invention;

[0050] Figure 4 This is a graph showing the test results of the Co-CN catalyst catalytic oxidation of formaldehyde provided in Example 1 of the present invention. Detailed Implementation

[0051] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0052] Example 1

[0053] This embodiment provides a Co-CN catalyst, the preparation method of which includes the following steps:

[0054] (1) After mixing cobalt source, zinc source and 60 mL of water at 30℃, 2-methylimidazole was mixed twice, and then ultrasonic treatment for 30 min, stirring treatment at 9000 r / min for 36 h and solid-liquid separation were performed to obtain ZnCo-MOF material.

[0055] The molar ratio of the cobalt source, zinc source, and 2-methylimidazole is 40:480:10; the solid-liquid ratio of the total mass of the cobalt source and zinc source to the solvent is 0.76 g:60 mL.

[0056] (2) The ZnCo-MOF material obtained in step (1) was cleaned with ethanol, dried at 70°C for 11 hours, and then calcined at 1000°C for 2 hours in an inert gas atmosphere to obtain the Co-CN catalyst.

[0057] The SEM images of the ZnCo-MOF material obtained in step (1) of this embodiment at different magnifications are as follows: Figure 1 As shown, the SEM images of the Co-CN catalyst obtained in step (2) at different magnifications are as follows: Figure 2 As shown, the TEM image is as follows Figure 3 As shown.

[0058] according to Figure 1 It can be seen that the microstructure of the ZnCo-MOF material is an irregular polyhedron, and its outer surface has a two-dimensional layered structure; according to Figure 2 and Figure 3 It can be seen that the microstructure of the Co-CN catalyst provided in this embodiment is an irregular polyhedron.

[0059] Example 2

[0060] This embodiment provides a Co-CN catalyst, the preparation method of which includes the following steps:

[0061] (1) After the cobalt source (cobalt nitrate), zinc source (zinc nitrate) and ethanol were mixed evenly at 25℃, 2-methylimidazole was mixed twice, and then ultrasonic treatment for 40 min, stirring treatment at 10000 r / min for 12 h and solid-liquid separation were performed in sequence to obtain ZnCo-MOF material.

[0062] The molar ratio of the cobalt source, zinc source, and 2-methylimidazole is 40:480:1; the solid-liquid ratio of the total mass of the cobalt source and zinc source to the solvent is 0.76 g:50 mL.

[0063] (2) The ZnCo-MOF material obtained in step (1) was cleaned with ethanol, dried at 60°C for 12 hours, and then calcined at 900°C for 3 hours in an inert gas atmosphere to obtain the Co-CN catalyst.

[0064] Example 3

[0065] This embodiment provides a Co-CN catalyst, the preparation method of which includes the following steps:

[0066] (1) After mixing cobalt source (cobalt nitrate), zinc source (zinc acetate) and water at 35℃, 2-methylimidazole was mixed twice, and then ultrasonic treatment for 20 min, stirring treatment at 8000 r / min for 48 h and solid-liquid separation were performed to obtain ZnCo-MOF material.

[0067] The molar ratio of the cobalt source, zinc source, and 2-methylimidazole is 40:480:20; the solid-liquid ratio of the total mass of the cobalt source and zinc source to the solvent is 0.76 g:70 mL.

[0068] (2) The ZnCo-MOF material obtained in step (1) was cleaned with ethanol, dried at 80°C for 12 hours, and then calcined at 1050°C for 1 hour in an inert gas atmosphere to obtain the Co-CN catalyst.

[0069] Example 4

[0070] This embodiment provides a Co-CN catalyst, the preparation method of which differs from that of Example 1 only in that:

[0071] In this embodiment, the molar ratio of cobalt source, zinc source and 2-methylimidazole in step (1) is adjusted to 200:480:20.

[0072] Example 5

[0073] This embodiment provides a Co-CN catalyst, the preparation method of which differs from that of Example 1 only in that:

[0074] In this embodiment, the temperature of the roasting process in step (2) is adjusted to 850℃.

[0075] Example 6

[0076] This embodiment provides a Co-CN catalyst, the preparation method of which differs from that of Example 1 only in that:

[0077] In this embodiment, the temperature of the roasting process in step (2) is adjusted to 1100℃.

[0078] Example 7

[0079] This embodiment provides a Co-CN catalyst, the preparation method of which differs from that of Example 1 only in that:

[0080] In this embodiment, the roasting time in step (2) is adjusted to 0.5h.

[0081] Example 8

[0082] This embodiment provides a Co-CN catalyst, the preparation method of which differs from that of Example 1 only in that:

[0083] In this embodiment, the roasting time in step (2) is adjusted to 3.5 hours.

[0084] Comparative Example 1

[0085] This comparative example provides a Co-CN catalyst, the preparation method of which differs from that of Example 1 only in that:

[0086] This comparative example omits the ultrasonic treatment process described in step (1).

[0087] Comparative Example 2

[0088] This comparative example provides a Co-CN catalyst, the preparation method of which differs from that of Example 1 only in that:

[0089] This comparative example adjusts the mixing process described in step (1) to: (a) mixing cobalt nitrate, water and 2-methylimidazole to obtain a first mixture; (b) mixing zinc nitrate, water and 2-methylimidazole to obtain a second mixture; and (c) mixing the first mixture and the second mixture.

[0090] Comparative Example 3

[0091] This comparative example provides a catalyst, which is the noble metal catalyst for catalytic oxidation of formaldehyde provided in Example 1 of Chinese Patent CN 115301231A.

[0092] The catalysts provided in the above examples and comparative examples were used for the catalytic degradation of formaldehyde, and the test methods are as follows:

[0093] 30 mg of catalyst was placed in a fixed-bed reactor, and the temperature was controlled at 25℃ and the relative humidity at 35%. He was used as the equilibrium gas, and the total flow rate was 100 mL / min. The test was conducted at a space velocity of 200,000 mL / (g∙h). The initial concentration of formaldehyde was 115 ppm. The concentration of formaldehyde in the gas was tested after 150 h of catalysis, and the formaldehyde removal rate was calculated. The results are shown in Table 1.

[0094] In addition, the test results of the Co-CN catalyst for the catalytic oxidation of formaldehyde provided in Example 1 are shown in the figure below. Figure 4 As shown.

[0095] Table 1

[0096]

[0097] The following points can be observed from Table 1:

[0098] (1) Comprehensive analysis of Examples 1-3 shows that the Co-CN catalyst provided by the present invention can completely degrade formaldehyde into water and carbon dioxide at room temperature. The preparation process is simple, does not involve precious metal loading, has low cost and long service life.

[0099] according to Figure 4 It can be seen that the catalyst provided by the present invention can maintain the formaldehyde conversion rate at over 95% within 300 hours;

[0100] (2) Comprehensive analysis of Examples 1 and 4 shows that the molar ratio of Co in Example 4 is too high, which makes it easy to form larger Co particles, which cannot form an effective reaction interface, resulting in a decrease in its formaldehyde catalytic activity.

[0101] (3) Comprehensive analysis of Examples 1 and 5-8 shows that the parameters of the calcination treatment affect the catalytic effect of the obtained catalyst on formaldehyde;

[0102] When the calcination temperature is too high (as in Example 5), the internal structure of the catalyst will collapse; when the calcination temperature is too low (as in Example 6), the zinc element cannot be completely removed.

[0103] When the roasting time is too short (as in Example 7), zinc cannot be completely removed; when the roasting time is too long (as in Example 8), the structure will collapse.

[0104] (4) A comprehensive analysis of Example 1 and Comparative Example 1 shows that the ultrasonic treatment process is very important for the formation of the structure; if the ultrasonic treatment is omitted, a layered structure will be formed on the surface, but a two-dimensional structure cannot be formed.

[0105] (5) Comprehensive analysis of Example 1 and Comparative Example 3 shows that, compared with precious metal catalysts, the catalyst provided by the present invention does not contain precious metals, but its catalytic effect is even better than that of precious metal catalysts.

[0106] In summary, the Co-CN catalyst prepared by the present invention through simple mixing, stirring and calcination can completely degrade formaldehyde into water and carbon dioxide at room temperature. The preparation process is simple, low in cost and has a long service life.

[0107] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a Co-CN catalyst for the catalytic degradation of formaldehyde, characterized in that, The preparation method includes the following steps: (1) After the cobalt source, zinc source and solvent are mixed evenly, 2-methylimidazole is mixed twice, and then ultrasonic treatment for 20~40 min, stirring treatment at 8000~10000 r / min for 12~48 h and solid-liquid separation are performed in sequence to obtain ZnCo-MOF material; the molar ratio of cobalt source, zinc source and 2-methylimidazole in step (1) is 40:480:1~20; the solvent includes water or ethanol; (2) The ZnCo-MOF material obtained in step (1) is sequentially cleaned, dried and calcined to obtain the Co-CN catalyst.

2. The preparation method according to claim 1, characterized in that, The cobalt source in step (1) includes cobalt nitrate.

3. The preparation method according to claim 1, characterized in that, The zinc source in step (1) includes zinc nitrate and / or zinc acetate.

4. The preparation method according to claim 1, characterized in that, In step (1), the liquid-to-solid ratio of the solvent to the total mass of the cobalt and zinc sources is 50-70 mL: 0.76 g.

5. The preparation method according to claim 1, characterized in that, The mixing temperature in step (1) is 25~35℃.

6. The preparation method according to claim 1, characterized in that, The solid-liquid separation in step (1) includes centrifugation.

7. The preparation method according to claim 1, characterized in that, The cleaning solution used in step (2) includes ethanol.

8. The preparation method according to claim 1, characterized in that, The drying process in step (2) includes vacuum drying.

9. The preparation method according to claim 8, characterized in that, The vacuum drying temperature is 60~80℃.

10. The preparation method according to claim 8, characterized in that, The vacuum drying time is 10-12 hours.

11. The preparation method according to claim 1, characterized in that, The calcination process in step (2) is carried out in an inert gas atmosphere.

12. The preparation method according to claim 11, characterized in that, The inert gas includes any one or a combination of at least two of nitrogen, argon, or helium.

13. The preparation method according to claim 1, characterized in that, The roasting temperature in step (2) is 900~1050℃.

14. The preparation method according to claim 1, characterized in that, The roasting process in step (2) takes 1 to 3 hours.

15. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) After the cobalt source, zinc source and solvent are mixed evenly at 25~35℃, 2-methylimidazole is mixed twice, and then ultrasonic treatment for 20~40min, stirring treatment at 8000~10000r / min for 12~48h and solid-liquid separation are performed to obtain ZnCo-MOF material. The molar ratio of the cobalt source, zinc source, and 2-methylimidazole is 40:480:1~20; the solid-liquid ratio of the total mass of the cobalt source and zinc source to the solvent is 0.76g:50~70mL; (2) The ZnCo-MOF material obtained in step (1) is cleaned with ethanol, dried at 60~80℃ for 10~12h, and then calcined at 900~1050℃ for 1~3h in an inert gas atmosphere to obtain the Co-CN catalyst.

16. A Co-CN catalyst, characterized in that, The Co-CN catalyst is obtained by the preparation method according to any one of claims 1-15.

17. An application of the Co-CN catalyst as described in claim 16, characterized in that, The Co-CN catalyst is used for the catalytic degradation of formaldehyde.

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