Preparation method of manganese oxide-based catalyst modified by nitrogen-containing heterocyclic ring ligand and room-temperature catalytic decomposition of formaldehyde

Abstract

The invention relates to a preparation method of a nitrogen-containing heterocyclic ring ligand modified manganese oxide-based catalyst and room-temperature catalytic decomposition of formaldehyde. The invention relates to a catalyst for catalyzing formaldehyde decomposition and a preparation method thereof, and aims to solve the technical problem of efficient catalytic decomposition of formaldehyde at room temperature. The catalyst for catalyzing formaldehyde decomposition is mainly formed by coupling a nitrogen-containing heterocyclic ring ligand and manganese oxide. Wherein the nitrogen-containing heterocyclic ring ligand refers to one of pyridine, pyrrole, piperidine, indole, DMAP (dimethylaminopyridine), pyrimidine, imidazole, pyrazole, melamine, 1, 2, 4-triazole and the like; and the manganese oxide refers to one or more of MnO2, Mn2O3 and Mn3O4. Through grinding, dipping, centrifugation, ultrasonic treatment, vacuum drying and other methods, the nitrogen-containing heterocyclic ring ligand and manganese oxide are coupled to obtain the high-efficiency catalyst. The nitrogen-containing heterocyclic ligand modified manganese oxide-based catalyst can quickly catalyze formaldehyde to be decomposed into carbon dioxide and water at room temperature, and is environment-friendly, simple in process, easy to control and suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection materials, and particularly relates to a preparation method of a manganese oxide-based catalyst modified with a nitrogen-containing heterocyclic ligand and the catalytic decomposition of formaldehyde at room temperature. Background Art

[0002] Formaldehyde (HCHO) is a major indoor air pollutant released from indoor furniture or building materials (wood-based or floor materials, paints, insulation materials), and poses a great threat to human health. Short-term exposure to HCHO can irritate the respiratory tract, causing symptoms such as tearing, coughing, and nausea; long-term exposure to HCHO may lead to chronic respiratory system diseases, nervous system diseases, leukemia, and cancer. The International Agency for Research on Cancer (IARC) classified HCHO as a Group 1 carcinogen in 2004, and proposed a safety standard for indoor HCHO content of 0.1 mg / m 3 (about 0.08 ppm) [Journal of Environmental Sciences 147 (2025) 642–651]. Therefore, to protect human health, it is urgent to develop technologies for the elimination and treatment of formaldehyde air pollutants. Currently, catalytic oxidation is the most promising technology for removing formaldehyde at room temperature. The active oxygen species on the catalyst surface can completely mineralize formaldehyde into CO2 and H2O, reducing secondary pollution [Chinese Chemical Letters 35 (2024) 109219]. Therefore, designing efficient catalysts is crucial for achieving complete removal of formaldehyde at room temperature.

[0003] Supported noble metal catalysts have the activity of efficiently degrading formaldehyde at room temperature. For example, Wang Ping et al. from South China University of Technology obtained a supported noble metal formaldehyde removal catalyst with high-density cooperative catalytic active sites using noble metal Pt [Patent CN202310019208.7]. Xu Xiaohong et al. from Shandong University invented a monolithic Pd / K2Ti6O 13 -NWs catalyst for room temperature degradation of formaldehyde [Patent CN 201910898908.1]. Chen Binghui et al. from Xiamen University dispersed one of noble metals Ru, Rh, Pt, or Pd on a manganese-based composite oxide support to obtain a catalyst for efficiently removing formaldehyde in air or wastewater at room temperature [Patent CN 201711469575.8]. However, noble metals are expensive and lack stability, which poses a great challenge to the large-scale promotion of catalysts. Reducing the production cost of catalysts and improving the low-temperature stability of catalysts have become key requirements in the field of room temperature purification of formaldehyde.

[0004] Manganese oxide has been widely explored as a catalyst for the degradation of various volatile organic compounds (VOCs) and is considered one of the most promising highly active catalysts. Manganese oxide has a good adsorption effect on formaldehyde molecules and can degrade formaldehyde molecules, completely converting them into carbon dioxide and water [Nanoscale, 2024, 16, 12541]. The crystal phase of manganese oxide has a significant impact on the purification of formaldehyde. It has been found that δ-crystalline manganese oxide shows better performance in degrading formaldehyde [Patent CN110523267 B]. By uniformly mixing a manganese source and a carbon source as raw materials and then calcining them, the manganese source is transformed into manganese dioxide under the activation of the carbon source, and the obtained material can degrade formaldehyde [Patent CN 111889069B]. Using a composite liquid composed of organic solvents or organic waste liquid as a carbon source, mixing it with a manganese source, and using methods such as precipitation, washing, drying, and calcination to obtain a manganese-based composite catalyst for formaldehyde degradation [Patent CN 113976107 A]. Incorporating cobalt elements into the manganese source and obtaining a manganese cobalt oxide catalyst through methods such as calcination to achieve formaldehyde decomposition at room temperature [Patent CN 111013602 A]. By adding an alkaline solution to a manganese solution to adjust the acidity and alkalinity of manganese dioxide, the formaldehyde removal efficiency can be effectively improved [Patent CN 117398992A]. However, a method for modifying manganese oxide with nitrogen-containing heterocyclic ligands to prepare a highly efficient catalyst has not been reported. Summary of the Invention

[0005] The object of the present invention is to provide a highly efficient manganese oxide-based catalyst that can rapidly mineralize formaldehyde molecules into carbon dioxide and water at room temperature, overcoming the deficiencies in the prior art. To achieve the above object, the present invention uses nitrogen-containing heterocyclic ligands to modify manganese oxide, and the specific implementation steps are as follows:

[0006] (1) Prepare manganese oxide using methods such as coprecipitation and hydrothermal treatment, and then fully grind and vacuum-dry the manganese oxide;

[0007] (2) Uniformly disperse nitrogen-containing heterocyclic ligand molecules in deionized water, and then fully stir the vacuum-dried manganese oxide with this solution to obtain a suspension;

[0008] (3) Wash the suspension obtained in step (2) with acetone to obtain a precipitate, and then vacuum-dry and grind the precipitate to obtain a nitrogen-containing heterocyclic ligand-modified manganese oxide-based catalyst;

[0009] The specific surface area of the nitrogen-containing heterocyclic ligand-modified manganese oxide-based catalyst in the present invention is 50-120 m 2 / g, and the pore size is 20-30 nm.

[0010] The beneficial effects of the present invention are as follows:

[0011] The catalyst in the present invention is manganese oxide modified with a nitrogen-containing heterocyclic ligand. Compared with noble metal catalysts, this catalyst is inexpensive;

[0012] The manganese oxide used in the present invention does not require regulation of its crystal form. Compared with the existing δ-crystal form manganese oxide catalyst, the catalyst of the present invention omits the cumbersome steps of adjusting the crystal form of manganese oxide, greatly enhancing the possibility of industrial application;

[0013] The preparation method of the catalyst in the present invention avoids the high-temperature heat treatment process, has low requirements for equipment, reduces energy consumption, and achieves low-carbon environmental protection;

[0014] The preparation method of the catalyst in the present invention is to modify manganese oxide with good stability using nitrogen-containing heterocyclic ligand molecules, which first ensures the stability of the material, and the prepared catalyst has a significant improvement in the performance of catalyzing formaldehyde decomposition at room temperature;

[0015] The catalyst in the present invention, at room temperature, under the conditions that the reaction gas flow rate is 100 - 500 mL / min, 10 - 500 ppm HCHO + 80% Ar + 20% O2, and the humidity is 0 - 70%, keeps formaldehyde completely mineralized into carbon dioxide and water without other intermediate products. Description of the Drawings

[0016] Figure 1 It is the scanning electron microscope (SEM) photograph of the manganese oxide in Examples 1 - 12.

[0017] Figure 2 It is the X-ray diffraction (XRD) of the manganese oxide in Examples 1 - 12. Detailed Description of the Invention

[0018] Example 1:

[0019] (1) Prepare manganese oxide by hydrothermal method

[0020] Disperse potassium permanganate and ammonium oxalate in deionized water respectively. Under the stirring state of the potassium permanganate solution, with the stirring speed of the stirrer being 600 rpm, dropwise add the ammonium oxalate solution into the potassium permanganate solution. The mass ratio of potassium permanganate : ammonium oxalate : deionized water is 2 : 1 : 50. After all the ammonium oxalate solution is completely added dropwise to the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave. Set the temperature of the hydrothermal reaction to 180°C and the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature. Obtain the precipitate by filtration. Keep the above-obtained precipitate in a vacuum drying oven at 60°C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain the hydrothermal method manganese oxide catalyst product. Figure 1-1 and Figure 2-1They are the scanning electron microscope (SEM) photograph and X-ray diffraction (XRD) result of the manganese oxide respectively.

[0021] (2) Pyridine-modified manganese oxide

[0022] First, prepare a pyridine solution according to the mass ratio of pyridine: deionized water being 2:1. Then, disperse the manganese oxide in the prepared pyridine solution with the mass ratio of manganese oxide: pyridine solution being 1:50, and stir for 6 hours to obtain a mixed solution. Ultrasonic, wash and centrifuge the aforementioned mixed solution with acetone, with the mass ratio of mixed solution: acetone being 1:5, ultrasonic frequency being 50 kHz, ultrasonic time being 15 min, ultrasonic times being 2 times, washing times being 2 times, and centrifuging times being 2 times. The centrifuge parameters are set to 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a pyridine-modified manganese oxide catalyst.

[0023] (3) Performance test of pyridine-modified manganese oxide catalyst

[0024] Take 0.1 g of the catalyst, uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tube fixed-bed reactor. The experimental conditions are as follows: 300 ppm HCHO + 80% Ar + 20% O2, reaction gas flow rate is 100 mL / min, humidity is 20%, reaction temperature is 30 °C, the conversion rate of formaldehyde is 72%, and the selectivity of carbon dioxide is 100%.

[0025] Example 2:

[0026] (1) Preparation of manganese oxide by hydrothermal method

[0027] Disperse potassium permanganate and ammonium acetate in deionized water respectively. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the ammonium acetate solution into the potassium permanganate solution. The mass ratio of potassium permanganate: ammonium acetate: deionized water is 2:1:50. After completely dropping all the ammonium acetate solution into the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the temperature of the hydrothermal reaction to 180 °C, and set the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the obtained precipitate in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1-2 and Figure 2-2 They are the scanning electron microscope (SEM) photograph and X-ray diffraction (XRD) result of the manganese oxide respectively.

[0028] (2) Pyridine-modified manganese oxide

[0029] First, prepare a pyridine solution with a mass ratio of pyridine to deionized water of 2:1. Then, disperse manganese oxide in the prepared pyridine solution with a mass ratio of manganese oxide to pyridine solution of 1:50, and stir for 6 hours to obtain a mixture. Ultrasonicate, wash, and centrifuge the aforementioned mixture with acetone. The mass ratio of the mixture to acetone is 1:5, the ultrasonic frequency is 50 kHz, the ultrasonic time is 15 min, the number of ultrasonic treatments is 2 times, the number of washing times is 2 times, the number of centrifugation times is 2 times, and the centrifuge parameters are set to 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a pyridine-modified manganese oxide catalyst.

[0030] (3) Performance test of pyridine-modified manganese oxide catalyst

[0031] Take 0.1 g of the catalyst and uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tubular fixed-bed reactor. The experimental conditions are as follows: 800 ppm HCHO + 80% Ar + 20% O2, the reaction gas flow rate is 100 mL / min, the humidity is 70%, the reaction temperature is 30 °C, the conversion rate of formaldehyde is 35%, and the selectivity of carbon dioxide is 100%.

[0032] Example 3:

[0033] (1) Preparation of manganese oxide by hydrothermal method

[0034] Disperse potassium permanganate and ammonium carbonate in deionized water respectively. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the ammonium carbonate solution into the potassium permanganate solution. The mass ratio of potassium permanganate: ammonium carbonate: deionized water is 2:1:50. After all the ammonium carbonate solution is completely added dropwise to the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the temperature of the hydrothermal reaction to 180 °C, and set the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the above-obtained precipitate in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1 -3 and Figure 2 -3 are the scanning electron microscope (SEM) photos and X-ray diffraction (XRD) results of this manganese oxide respectively.

[0035] (2) Pyridine modification of manganese oxide

[0036] First, prepare a pyridine solution according to the mass ratio of pyridine to deionized water of 2:1. Then, disperse manganese oxide in the prepared pyridine solution with the mass ratio of manganese oxide to pyridine solution of 1:35, and stir for 6 hours to obtain a mixed solution. Ultrasonic, wash and centrifuge the aforementioned mixed solution with acetone, with the mass ratio of mixed solution to acetone of 1:5, ultrasonic frequency of 50 kHz, ultrasonic time of 15 min, ultrasonic times of 2, washing times of 2, and centrifugation times of 2. Set the centrifuge parameters to 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a pyridine-modified manganese oxide catalyst.

[0037] (3) Performance test of pyridine-modified manganese oxide catalyst

[0038] Take 0.1 g of the catalyst, uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tubular fixed-bed reactor. The experimental conditions are as follows: 800 ppm HCHO + 80% Ar + 20% O2, reaction gas flow rate of 100 mL / min, humidity of 40%, reaction temperature of 30 °C, formaldehyde conversion rate of 50%, and carbon dioxide selectivity of 100%.

[0039] Example 4:

[0040] (1) Preparation of manganese oxide by hydrothermal method

[0041] Disperse potassium permanganate and ammonium fluoride in deionized water respectively. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the ammonium fluoride solution into the potassium permanganate solution. The mass ratio of potassium permanganate: ammonium fluoride: deionized water is 2:1:50. After all the ammonium fluoride solution is completely added dropwise to the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the temperature of the hydrothermal reaction to 180 °C, and set the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the precipitate obtained above in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1 -4 and Figure 2 -4 are the scanning electron microscope (SEM) photo and X-ray diffraction (XRD) result of this manganese oxide respectively.

[0042] (2) Pyridine modification of manganese oxide

[0043] First, prepare a pyridine solution with a mass ratio of pyridine to deionized water of 2:1. Then, disperse manganese oxide in the prepared pyridine solution with a mass ratio of manganese oxide to pyridine solution of 1:35, and stir for 6 hours to obtain a mixed solution. Ultrasonic, wash, and centrifuge the aforementioned mixed solution with acetone. The mass ratio of the mixed solution to acetone is 1:5, the ultrasonic frequency is 50 kHz, the ultrasonic time is 15 min, the number of ultrasonic times is 2, the number of washing times is 2, the number of centrifugation times is 2, and the centrifuge parameters are set to 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a pyridine-modified manganese oxide catalyst.

[0044] (3) Performance test of pyridine-modified manganese oxide catalyst

[0045] Take 0.1 g of the catalyst, uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tubular fixed-bed reactor. The experimental conditions are as follows: 800 ppm HCHO + 80% Ar + 20% O2, the reaction gas flow rate is 100 mL / min, the humidity is 70%, the reaction temperature is 30 °C, the conversion rate of formaldehyde is 20%, and the selectivity of carbon dioxide is 100%.

[0046] Example 5:

[0047] (1) Prepare manganese oxide by hydrothermal method

[0048] Disperse potassium permanganate and urea in deionized water respectively. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the urea solution into the potassium permanganate solution. The mass ratio of potassium permanganate:urea:deionized water is 2:1:50. After all the urea solution is completely added dropwise to the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the temperature of the hydrothermal reaction to 180 °C, and set the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the precipitate obtained above in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1 -5 and Figure 2 -5 are the scanning electron microscope (SEM) photo and X-ray diffraction (XRD) result of this manganese oxide respectively.

[0049] (2) Pyrrole-modified manganese oxide

[0050] First, prepare a pyrrole solution with a mass ratio of pyrrole to deionized water of 2:1. Then, disperse manganese oxide in the prepared pyrrole solution with a mass ratio of manganese oxide to pyrrole solution of 1:50, and stir for 6 hours to obtain a mixture. Ultrasonically clean and centrifuge the aforementioned mixture with acetone, with a mass ratio of mixture to acetone of 1:5, an ultrasonic frequency of 50 kHz, an ultrasonic time of 15 min, the number of ultrasonic treatments being 2 times, the number of washing times being 2 times, and the number of centrifugation times being 2 times. Set the centrifuge parameters to 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a pyrrole-modified manganese oxide catalyst.

[0051] (3) Performance test of pyrrole-modified manganese oxide catalyst

[0052] Take 0.1 g of the catalyst, uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tube fixed-bed reactor. The experimental conditions are as follows: 800 ppm HCHO + 80% Ar + 20% O2, the flow rate of the reaction gas is 100 mL / min, the humidity is 30%, the reaction temperature is 30 °C, the conversion rate of formaldehyde is 76%, and the selectivity of carbon dioxide is 100%.

[0053] Example 6:

[0054] (1) Preparation of manganese oxide by hydrothermal method

[0055] Disperse potassium permanganate and ammonium citrate in deionized water respectively. While stirring the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the ammonium citrate solution into the potassium permanganate solution. The mass ratio of potassium permanganate:ammonium citrate:deionized water is 2:1:50. After completely dropping all the ammonium citrate solution into the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave. Set the temperature of the hydrothermal reaction to 180 °C and the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends, naturally cool it to room temperature. Obtain the precipitate by filtration. Keep the above-obtained precipitate in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1 -6 and Figure 2 -6 are the scanning electron microscope (SEM) photo and X-ray diffraction (XRD) result of this manganese oxide respectively.

[0056] (2) Pyrrole modification of manganese oxide

[0057] First, prepare a pyrrole solution with a mass ratio of pyrrole to deionized water of 2:1. Then, disperse manganese oxide in the prepared pyrrole solution with a mass ratio of manganese oxide to pyrrole solution of 1:50, and stir for 6 hours to obtain a mixture. Ultrasonic, wash, and centrifuge the aforementioned mixture with acetone, with a mass ratio of mixture to acetone of 1:5, an ultrasonic frequency of 50 kHz, an ultrasonic time of 15 min, an ultrasonic number of 2 times, a washing number of 2 times, a centrifugation number of 2 times, and the centrifuge parameters set at 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a pyrrole-modified manganese oxide catalyst.

[0058] (3) Performance test of pyrrole-modified manganese oxide catalyst

[0059] Take 0.1 g of the catalyst, uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tube fixed-bed reactor. The experimental conditions are as follows: 500 ppm HCHO + 80% Ar + 20% O2, the reaction gas flow rate is 100 mL / min, the humidity is 50%, the reaction temperature is 30 °C, the conversion rate of formaldehyde is 50%, and the selectivity of carbon dioxide is 100%.

[0060] Example 7:

[0061] (1) Preparation of manganese oxide by hydrothermal method

[0062] Disperse potassium permanganate and ammonium acetate in deionized water respectively. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the ammonium acetate solution into the potassium permanganate solution with a mass ratio of potassium permanganate:ammonium acetate:deionized water of 2:1:50. After all the ammonium acetate solution is completely dropped into the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the temperature of the hydrothermal reaction to 180 °C, and set the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the above-obtained precipitate in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1-2 and Figure 2-2 are the scanning electron microscope (SEM) photograph and X-ray diffraction (XRD) result of the manganese oxide respectively.

[0063] (2) Pyrrole modification of manganese oxide

[0064] First, prepare a pyrrole solution with a mass ratio of pyrrole to deionized water of 2:1. Then, disperse manganese oxide in the prepared pyrrole solution with a mass ratio of manganese oxide to pyrrole solution of 1:35, and stir for 6 hours to obtain a mixture. Ultrasonic, wash, and centrifuge the aforementioned mixture with acetone. The mass ratio of the mixture to acetone is 1:5, the ultrasonic frequency is 50 kHz, the ultrasonic time is 15 min, the number of ultrasonic times is 2, the number of washing times is 2, the number of centrifugation times is 2, and the centrifuge parameters are set to 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a pyrrole-modified manganese oxide catalyst.

[0065] (3) Performance test of pyrrole-modified manganese oxide catalyst

[0066] Take 0.1 g of the catalyst, uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tubular fixed-bed reactor. The experimental conditions are as follows: 400 ppm HCHO + 80% Ar + 20% O2, the reaction gas flow rate is 100 mL / min, the humidity is 10%, the reaction temperature is 30 °C, the conversion rate of formaldehyde is 85%, and the selectivity of carbon dioxide is 100%.

[0067] Example 8:

[0068] (1) Preparation of manganese oxide by hydrothermal method

[0069] Disperse potassium permanganate and ammonium carbonate in deionized water respectively. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the ammonium carbonate solution into the potassium permanganate solution. The mass ratio of potassium permanganate: ammonium carbonate: deionized water is 2:1:50. After all the ammonium carbonate solution is completely dropped into the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the temperature of the hydrothermal reaction to 180 °C, and set the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the precipitate obtained above in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1 -3 and Figure 2 -3 are the scanning electron microscope (SEM) photos and X-ray diffraction (XRD) results of this manganese oxide respectively.

[0070] (2) Pyrrole modification of manganese oxide

[0071] First, prepare a pyrrole solution with a mass ratio of pyrrole to deionized water of 2:1. Then, disperse manganese oxide in the prepared pyrrole solution with a mass ratio of manganese oxide to pyrrole solution of 1:35, and stir for 6 hours to obtain a mixture. Ultrasonic, wash, and centrifuge the aforementioned mixture with acetone. The mass ratio of the mixture to acetone is 1:5, the ultrasonic frequency is 50 kHz, the ultrasonic time is 15 min, the number of ultrasonic times is 2, the number of washing times is 2, and the number of centrifugation times is 2. The centrifuge parameters are set to 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a pyrrole-modified manganese oxide catalyst.

[0072] (3) Performance test of pyrrole-modified manganese oxide catalyst

[0073] Take 0.1 g of the catalyst, uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tube fixed-bed reactor. The experimental conditions are as follows: 600 ppm HCHO + 80% Ar + 20% O2, the reaction gas flow rate is 100 mL / min, the humidity is 70%, the reaction temperature is 30 °C, the conversion rate of formaldehyde is 90%, and the selectivity of carbon dioxide is 100%.

[0074] Example 9:

[0075] (1) Preparation of manganese oxide by hydrothermal method

[0076] Disperse potassium permanganate and ammonium fluoride in deionized water respectively. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the ammonium fluoride solution into the potassium permanganate solution. The mass ratio of potassium permanganate: ammonium fluoride: deionized water is 2:1:50. After all the ammonium fluoride solution is completely added dropwise to the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the temperature of the hydrothermal reaction to 180 °C, and set the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the precipitate obtained above in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain the hydrothermal method manganese oxide catalyst product. Figure 1 -4 and Figure 2 -4 are the scanning electron microscope (SEM) photos and X-ray diffraction (XRD) results of this manganese oxide respectively.

[0077] (2) Imidazole-modified manganese oxide

[0078] First, prepare an imidazole solution with a mass ratio of imidazole to deionized water of 2:1. Then, disperse manganese oxide in the prepared imidazole solution with a mass ratio of manganese oxide to imidazole solution of 1:50, and stir for 6 hours to obtain a mixed solution. Ultrasonic, wash, and centrifuge the aforementioned mixed solution with acetone. The mass ratio of the mixed solution to acetone is 1:5, the ultrasonic frequency is 50 kHz, the ultrasonic time is 15 min, the number of ultrasonic times is 2, the number of washing times is 2, and the number of centrifugation times is 2. The centrifuge parameters are set to 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain an imidazole-modified manganese oxide catalyst.

[0079] (3) Performance test of imidazole-modified manganese oxide catalyst

[0080] Take 0.1 g of the catalyst and uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-tube fixed-bed reactor. The experimental conditions are as follows: 400 ppm HCHO + 80% Ar + 20% O2, the reaction gas flow rate is 100 mL / min, the humidity is 20%, the reaction temperature is 30 °C, and the conversion rate of formaldehyde is 74%.

[0081] Example 10:

[0082] (1) Prepare manganese oxide by hydrothermal method

[0083] Disperse potassium permanganate and urea in deionized water respectively. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, dropwise add the urea solution into the potassium permanganate solution. The mass ratio of potassium permanganate:urea:deionized water is 2:1:50. After all the urea solution is completely added dropwise to the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the temperature of the hydrothermal reaction to 180 °C, and set the time of the hydrothermal reaction to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the above-obtained precipitate in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1 -5 and Figure 2 -5 are the scanning electron microscope (SEM) photo and X-ray diffraction (XRD) result of this manganese oxide respectively.

[0084] (2) Imidazole modification of manganese oxide

[0085] First, an imidazole solution was prepared according to a mass ratio of imidazole to deionized water of 2:1. Then, manganese oxide was dispersed in the prepared imidazole solution with a mass ratio of manganese oxide to imidazole solution of 1:50, and stirred for 6 hours to obtain a mixture. Acetone was used to ultrasonically treat, wash, and centrifuge the aforementioned mixture, with a mass ratio of mixture to acetone of 1:5, an ultrasonic frequency of 50 kHz, an ultrasonic time of 15 min, the number of ultrasonic treatments being 2 times, the number of washing times being 2 times, the number of centrifugation times being 2 times, and the centrifuge parameters being set at 10,000 rpm. The precipitate obtained by centrifugation was kept in a vacuum drying oven at 60 °C for 24 hours, and after taking it out, it was ground to obtain an imidazole-modified manganese oxide catalyst.

[0086] (3) Performance test of imidazole-modified manganese oxide catalyst

[0087] 0.1 g of the catalyst was taken and evenly mixed with 0.1 g of SiO2 powder, and placed in a U-shaped tubular fixed-bed reactor. The experimental conditions were as follows: 500 ppm HCHO + 80% Ar + 20% O2, the flow rate of the reaction gas was 200 mL / min, the humidity was 70%, the reaction temperature was 30 °C, and the conversion rate of formaldehyde was 50%.

[0088] Example 11:

[0089] (1) Preparation of manganese oxide by hydrothermal method

[0090] Potassium permanganate and ammonium oxalate were respectively dispersed in deionized water. Under the stirring state of the potassium permanganate solution with a stirrer speed of 600 rpm, the ammonium oxalate solution was gradually dropped into the potassium permanganate solution, with a mass ratio of potassium permanganate: ammonium oxalate: deionized water of 2:1:50. After all the ammonium oxalate solution was completely dropped into the potassium permanganate solution, it was stirred for 60 minutes, and then transferred to a hydrothermal autoclave. The temperature of the hydrothermal reaction was set at 180 °C, and the time of the hydrothermal reaction was set at 24 hours. After the hydrothermal reaction ended and naturally cooled to room temperature, the precipitate was obtained by suction filtration. The precipitate obtained above was kept in a vacuum drying oven at 60 °C for 24 hours, and after taking out the vacuum-dried precipitate, it was ground to obtain a hydrothermal method manganese oxide catalyst product. Figure 1-1 and Figure 2-1 are respectively the scanning electron microscope (SEM) photograph and X-ray diffraction (XRD) result of this manganese oxide.

[0091] (2) 1,2,4-Triazole modification of manganese oxide

[0092] First, prepare a 1,2,4-triazole solution with a mass ratio of 1,2,4-triazole to deionized water of 2:1. Then, disperse manganese oxide in the prepared 1,2,4-triazole solution with a mass ratio of manganese oxide to 1,2,4-triazole solution of 1:50, and stir for 6 hours to obtain a mixture. Ultrasonically clean and centrifuge the aforementioned mixture with acetone, with a mass ratio of mixture to acetone of 1:5, an ultrasonic frequency of 50 kHz, an ultrasonic time of 15 min, an ultrasonic number of 2 times, a washing number of 2 times, a centrifugation number of 2 times, and a centrifuge parameter setting of 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a 1,2,4-triazole-modified manganese oxide catalyst.

[0093] (3) Performance test of 1,2,4-triazole-modified manganese oxide catalyst

[0094] Take 0.1 g of the catalyst and uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-shaped tubular fixed-bed reactor. The experimental conditions are as follows: 600 ppm HCHO + 80% Ar + 20% O2, the reaction gas flow rate is 300 mL / min, the humidity is 30%, the reaction temperature is 30 °C, the conversion rate of formaldehyde is 100%, and the selectivity of carbon dioxide is 100%.

[0095] Example 12:

[0096] (1) Preparation of manganese oxide by hydrothermal method

[0097] Disperse potassium permanganate and ammonium citrate in deionized water respectively. While stirring the potassium permanganate solution with a stirrer speed of 600 rpm, gradually drop the ammonium citrate solution into the potassium permanganate solution with a mass ratio of potassium permanganate:ammonium citrate:deionized water of 2:1:50. After completely dropping all the ammonium citrate solution into the potassium permanganate solution, stir for 60 minutes, then transfer it to a hydrothermal autoclave, set the hydrothermal reaction temperature to 180 °C, and set the hydrothermal reaction time to 24 hours. After the hydrothermal reaction ends and naturally cools to room temperature, obtain the precipitate by filtration. Keep the above-obtained precipitate in a vacuum drying oven at 60 °C for 24 hours, take out the vacuum-dried precipitate and grind it to obtain a hydrothermal method manganese oxide catalyst product. Figure 1 -6 and Figure 2 -6 are the scanning electron microscope (SEM) photo and X-ray diffraction (XRD) result of this manganese oxide respectively.

[0098] (2) Modification of manganese oxide with 1,2,4-triazole

[0099] First, prepare a 1,2,4-triazole solution with a mass ratio of 1,2,4-triazole to deionized water of 2:1. Then, disperse manganese oxide in the prepared 1,2,4-triazole solution with a mass ratio of manganese oxide to 1,2,4-triazole solution of 1:50, and stir for 6 hours to obtain a mixture. Ultrasonically clean and centrifuge the aforementioned mixture with acetone, with a mass ratio of mixture to acetone of 1:5, an ultrasonic frequency of 50 kHz, an ultrasonic time of 15 min, the number of ultrasonic treatments being 2, the number of washing times being 2, and the number of centrifugation times being 2. The centrifuge parameters are set at 10,000 rpm. Keep the precipitate obtained by centrifugation in a vacuum drying oven at 60 °C for 24 hours, take it out and grind it to obtain a 1,2,4-triazole-modified manganese oxide catalyst.

[0100] (3) Performance test of 1,2,4-triazole-modified manganese oxide catalyst

[0101] Take 0.1 g of the catalyst and uniformly mix it with 0.1 g of SiO2 powder, and place it in a U-tube fixed-bed reactor. The experimental conditions are as follows: 300 ppm HCHO + 80% Ar + 20% O2, the reaction gas flow rate is 300 mL / min, the humidity is 70%, the reaction temperature is 30 °C, and the conversion rate of formaldehyde is 60%.

Claims

1. A catalyst for rapid catalytic decomposition of formaldehyde at room temperature and a preparation method thereof, characterized in that: A highly efficient catalyst was formed by modifying manganese oxide with nitrogen-containing heterocyclic ligands, and then used to catalyze the decomposition of formaldehyde at room temperature, achieving efficient removal of formaldehyde and complete mineralization to produce carbon dioxide and water.

2. The method of forming a highly efficient catalyst by modifying manganese oxide with a nitrogen-containing heterocyclic ligand according to claim 1, characterized in that: The nitrogen-containing heterocyclic ligand is one of pyridine, pyrrole, piperidine, indole, DMAP, pyrimidine, imidazole, pyrazole, melamine, 1,2,4-triazole and the like.

3. The method of forming a highly efficient catalyst using nitrogen-containing heterocyclic ligand-modified manganese oxide according to claim 1, characterized in that: The manganese oxide refers to one or more of MnO2, Mn2O3, and Mn3O4.

4. The method of forming a highly efficient catalyst using nitrogen-containing heterocyclic ligand-modified manganese oxide according to claim 1, characterized in that: The specific surface area of ​​the manganese oxide is 50 to 120 m 2 / g, pore size is 20~30nm.

5. The method of forming a highly efficient catalyst using nitrogen-containing heterocyclic ligand-modified manganese oxide according to claim 1, characterized in that: The catalyst preparation method is as follows: S1, grinding manganese oxide for 30 to 60 minutes, vacuum drying the ground manganese oxide, vacuum drying conditions: temperature of 60 to 100 ° C, time of 12 to 24 hours, to obtain vacuum dried manganese oxide; S2, preparing a nitrogen-containing heterocyclic ligand solution, uniformly dispersing the nitrogen-containing heterocyclic ligand in deionized water, the mass ratio of the nitrogen-containing heterocyclic ligand to deionized water being 2-4:1-4, to obtain a solution 1; S3, dispersing the vacuum-dried manganese oxide into the above solution 1, the mass ratio of solution 1 to manganese oxide is 100-200:1-2, and then fully stirring the mixed system, the stirring speed of the stirrer is 400-600 rpm, and stirring at a temperature of 20-30° C. for 6-24 hours to obtain a mixed suspension 1; S4, mixing the mixed suspension 1 in S3 with acetone, wherein the mass ratio of the mixed suspension 1 to the acetone is 1-2:5-10, to obtain a mixed suspension 2; S5. Ultrasonicate the mixed suspension 2 for 10 to 30 minutes, 1 to 3 times, and then centrifuge with the centrifuge parameters set to a speed of 8000 to 10000 rpm to obtain a precipitate. Wash the precipitate by centrifugation with acetone for 2 to 3 times and then vacuum dry it at a vacuum drying temperature of 60 to 100° C. for 12 to 24 hours to obtain a catalyst.

6. According to claim 1, it is characterized in that: The atmosphere for formaldehyde decomposition is 10-500 ppm HCHO+80% Ar+20% O2, the reaction gas flow rate is 100-500 mL / min, and the humidity is 0-70%.

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