Preparation method and application of a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation

Abstract

This invention discloses a method for preparing and applying a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, relating to the field of mineral composite catalytic material preparation technology. The method comprises the following steps: blending montmorillonite with a potassium salt to obtain potassium-based montmorillonite; reacting the potassium-based montmorillonite with potassium permanganate and ammonium oxalate to obtain the MnO2 / montmorillonite composite material. The potassium-based montmorillonite prepared in this application acts as a support and provides a solid potassium source for subsequent reactions; potassium permanganate provides a manganese source; and ammonium oxalate controls and reduces manganese defects in the manganese dioxide crystals, resulting in a manganese-defect-rich MnO2 / montmorillonite composite material. The MnO2 / montmorillonite composite material prepared in this application effectively improves the catalytic activity of the catalyst for formaldehyde oxidation at room temperature and reduces the cost of material preparation and application.

Description

Technical Field

[0001] This invention relates to the field of mineral composite catalytic material preparation technology, specifically to a method for preparing and applying a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation. Background Technology

[0002] Formaldehyde is a major indoor air pollutant, with widespread sources and a long cycle, making it difficult to eradicate at the source. Currently, indoor formaldehyde pollution control strategies can be mainly divided into three types: controlling pollution at the source, daily ventilation, and end-of-pipe treatment. End-of-pipe treatment technologies mainly include physical adsorption, chemical adsorption, thermocatalysis, and photocatalysis. Adsorption methods only transfer pollutants from the gas phase to the solid phase, without achieving true removal, and are subject to adsorption saturation and desorption problems. Currently, most photocatalytic materials on the market, represented by nano-TiO2, can only utilize ultraviolet light. Artificial light sources are costly and have limited lifespans, and photocatalytic oxidation efficiency is usually low, making it difficult to apply on a large scale in the field of indoor air pollution control. Although thermocatalysis technology is highly efficient, the activation of lattice oxygen often requires high temperatures, and the excessively high application temperature makes it difficult to apply on a large scale in indoor environments. In recent years, room temperature catalytic oxidation technology has been considered the most promising indoor formaldehyde purification technology due to its mild reaction conditions and lack of additional energy requirements. However, existing room temperature catalytic materials generally suffer from low efficiency, poor stability, and high cost.

[0003] Transition metal oxides possess significant potential for low-temperature formaldehyde oxidation due to their surface acid-base and redox properties. Among them, manganese oxides (MnO2) exhibit high catalytic activity, good thermal stability, low toxicity, and possess up to 30 different crystal structures, making them the most widely studied transition metal catalysts. Studies have shown that pore size (determining formaldehyde adsorption within the pores), redox properties, and the average valence state of manganese dioxide with different pore structures are key factors determining formaldehyde oxidation performance. The room-temperature oxidation mechanism of formaldehyde by MnO2 is as follows: formaldehyde adsorbed on the MnO2 surface is oxidized to formic acid and carbonate by surface hydroxyl groups. Formic acid is further oxidized by hydroxyl groups to carbon dioxide and water. Carbonate competes with water vapor for adsorption on the surface, thus slowly detaching. The surface hydroxyl groups consumed in this process are regenerated through the reaction of surface active oxygen and water vapor. The process of intermediate products, formate, being converted to carbonate or carbon dioxide is the rate-limiting step in the entire formaldehyde oxidation process, and the rapid regeneration of hydroxyl groups can accelerate this step. Therefore, at room temperature, the more hydroxyl groups on the MnO2 surface, the higher its activity and the faster the formaldehyde adsorption rate. Meanwhile, the abundance of surface reactive oxygen species also determines the regeneration rate of surface hydroxyl groups. Surface reactive oxygen species can be continuously formed through the dissociation of oxygen in the air by surface lattice oxygen under the influence of oxygen vacancies. Therefore, the mobility of oxygen species and the abundance of lattice oxygen play important roles in the purification process.

[0004] Montmorillonite is a natural clay mineral with cation exchange capacity, widely available and inexpensive. Montmorillonite has extremely strong dispersibility in water. Introducing montmorillonite as a carrier in the MnO2 synthesis process allows for uniform loading of MnO2 onto the montmorillonite flakes through cation exchange and the mineral carrier's confinement effect, effectively solving the problems of MnO2's easy agglomeration, difficulty in recovery, and high cost. Furthermore, the introduction of potassium ions can synergistically promote the catalytic degradation of formaldehyde by MnO2, and the presence of potassium ions can also improve O2 content. latt O ads Mn 3+ and Mn 4+ The high content of oxygen vacancies and the generation of a large number of oxygen vacancies enhance the mobility of lattice oxygen and promote the activation of molecular oxygen, resulting in more active oxygen on manganese oxides. Theoretically, this further enhances the ability of MnO2 to catalyze the oxidation of formaldehyde at room temperature. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation. Compared with existing manganese oxides, the MnO2 / montmorillonite composite material prepared by this invention effectively improves the catalytic activity of the catalyst for catalytic oxidation of formaldehyde at room temperature and reduces the cost of material preparation and application.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation includes the following steps:

[0008] S1: After dispersing montmorillonite evenly in water, add potassium salt and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0009] S2: Potassium-based montmorillonite and water are mixed, and potassium permanganate is added and dispersed evenly to obtain a mixed solution;

[0010] S3: Add ammonium oxalate to the mixture obtained in S2, heat to react, filter and wash until neutral, and dry to obtain MnO2 / montmorillonite composite material.

[0011] As a further aspect of the present invention: the montmorillonite is sodium-based montmorillonite with a cation exchange capacity greater than 100 mmol / 100g.

[0012] As a further aspect of the present invention: the potassium salt is obtained by mixing any one or more of potassium chloride, potassium hydroxide, potassium acetate, potassium oxalate, and potassium hydrogen oxalate in any proportion.

[0013] As a further aspect of the present invention: the ratio of montmorillonite to potassium salt in S1 is: 100g of montmorillonite is mixed with 0.02-0.04mol of potassium salt.

[0014] As a further embodiment of the present invention: the mass ratio of potassium-based montmorillonite to potassium permanganate in S2 is 0.5-5g: 3.636g.

[0015] As a further aspect of the present invention: the molar ratio of ammonium oxalate in S3 to permanganate in the mixed solution is 1:1-3.

[0016] As a further aspect of the present invention, the specific steps of the heating reaction in S3 are as follows: heating to 45-95°C and holding the reaction at that temperature for 6-20 hours under stirring.

[0017] As a further aspect of the present invention, the specific steps of the heating reaction in S3 are as follows: heating to 65-95°C and holding the reaction at that temperature for 10-14 hours under stirring.

[0018] The MnO2 / montmorillonite composite material prepared by any of the above methods can be used for the catalytic degradation of formaldehyde.

[0019] The beneficial effects of this invention are:

[0020] This application uses montmorillonite, potassium salt, potassium permanganate, and ammonium oxalate as main raw materials to prepare a MnO2 / montmorillonite composite material that can significantly improve the room temperature catalytic degradation effect of formaldehyde. This application first utilizes the cation exchange function of montmorillonite by mixing and dispersing montmorillonite with potassium salt, and pre-introducing potassium salt into the interlayer or surface of montmorillonite. + Obtain K + The modified potassium-based montmorillonite, namely potassium-based montmorillonite; this application further uses potassium-based montmorillonite as a carrier and provides a solid potassium source for subsequent reactions, and potassium permanganate to provide a manganese source. By adding ammonium oxalate, the manganese defects in the manganese dioxide crystals are controlled and reduced, resulting in a manganese-defect-rich MnO2 / montmorillonite composite material.

[0021] In this application, potassium ions in the potassium-based montmorillonite synergistically modulate the electronic properties of the loaded manganese oxide, inducing lattice distortion in the manganese oxide, thereby enhancing the mobility of lattice oxygen and increasing the abundance of surface active oxygen. This allows manganese dioxide crystals to be uniformly loaded into the montmorillonite lamellar structure, and the potassium ions loaded in the montmorillonite can be effectively adsorbed at manganese defect sites. The MnO2 / montmorillonite composite material prepared in this application exhibits excellent surface hydroxyl content and abundance of active lattice oxygen, as well as rapid migration of active oxygen species.

[0022] The MnO2 / montmorillonite composite material prepared in this invention, when used as a catalytic material for formaldehyde degradation, effectively improves the catalytic activity of formaldehyde oxidation at room temperature compared to existing manganese oxides, while reducing the cost of material preparation and application. It has advantages such as simple production process, low cost, and high catalytic efficiency. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0025] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0026] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0027] Example 2: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0028] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0029] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.426g (0.011mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0030] Example 3: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0031] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0032] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 0.951g (0.008mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0033] Example 4: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0034] S1: Disperse 10g of montmorillonite evenly in water, add 2.24g (0.03mol) of potassium chloride and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0035] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0036] Example 5: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0037] S1: Disperse 10g of montmorillonite evenly in water, add 1.68g (0.03mol) of potassium hydroxide and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0038] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0039] Example 6: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0040] S1: Disperse 10g of montmorillonite evenly in water, add 5.53g (0.03mol) of potassium oxalate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0041] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0042] Example 7: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0043] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0044] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 65℃ and kept at that temperature for 12h. The mixture was filtered and washed until neutral to remove impurities. It was then dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0045] Example 8: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0046] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0047] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 95℃ and kept at that temperature for 12h. The mixture was filtered and washed until neutral to remove impurities. It was then dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0048] Example 9: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0049] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0050] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 10h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0051] Example 10: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0052] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0053] S2: 2g of potassium-based montmorillonite and 100mL of water were mixed, and 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 14h. The mixture was filtered and washed until neutral to remove impurities. It was then dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0054] Example 11: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0055] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0056] S2: 4.667g of potassium-based montmorillonite was mixed with 100mL of water, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0057] Example 12: A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, comprising the following steps:

[0058] S1: Disperse 10g of montmorillonite evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite;

[0059] S2: 0.857g potassium-based montmorillonite was mixed with 100mL of water, then 3.636g (0.023mol) potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain the MnO2 / montmorillonite composite material.

[0060] Comparative Example 1: A method for preparing a MnO2 material for catalytic formaldehyde degradation, comprising the following steps:

[0061] Disperse 100 mL of water and 3.636 g (0.023 mol) of potassium permanganate evenly, add 1.141 g (0.009 mol) of ammonium oxalate and mix, heat to 90 °C, keep the temperature for 12 h, filter and wash until neutral to remove impurities, dry at 70 °C to obtain MnO2 material.

[0062] Comparative Example 2: A method for preparing a MnO2 material for catalytic formaldehyde degradation, comprising the following steps:

[0063] 2g of montmorillonite and 100mL of water were mixed, and then 3.636g (0.023mol) of potassium permanganate was added and dispersed evenly. 1.141g (0.009mol) of ammonium oxalate was added and mixed. The mixture was heated to 90℃ and kept at that temperature for 12h. The mixture was then filtered and washed until neutral to remove impurities. It was dried at 70℃ to obtain MnO2 material.

[0064] Comparative Example 3: A method for preparing a MnO2 / activated carbon composite material for catalytic formaldehyde degradation, comprising the following steps:

[0065] S1: Disperse 10g of activated carbon evenly in water, add 2.94g (0.03mol) of potassium acetate and mix, wash, centrifuge and dry to obtain potassium-based activated carbon;

[0066] S2: Mix 2g of potassium-based activated carbon with 100mL of water, then add 3.636g (0.023mol) of potassium permanganate and disperse evenly. Add 1.141g (0.009mol) of ammonium oxalate and mix. Heat to 90℃ and keep the reaction at this temperature for 12h. Filter and wash until neutral to remove impurities. Dry at 70℃ to obtain MnO2 / activated carbon composite material.

[0067] Comparative Example 4: Commercially available activated carbon.

[0068] Comparative Example 5: Commercially available manganese dioxide formaldehyde removal products.

[0069] Performance testing

[0070] I. Formaldehyde Degradation Performance Test

[0071] 1. Instruments and equipment

[0072] Reaction chamber: Dimensions are 50×50×50cm, with built-in fan, heating plate, stage, and temperature sensor.

[0073] Microsyringe: 25μL capacity, 0.1μL precision.

[0074] Infrared photoacoustic spectrometer: can monitor formaldehyde and carbon dioxide concentrations in real time.

[0075] 2. The detection method follows the national standard GB / T 16129-1995 "Standard Method for Hygienic Examination of Formaldehyde in Residential Atmosphere - Spectrophotometry", and the carbon dioxide concentration in the reactor is monitored in real time using an infrared photoacoustic spectrometer.

[0076] 3. Experimental Procedure

[0077] 3.1 Weigh 0.5g of the catalysts prepared in Examples 1-12 and Comparative Examples 1-3, spread them evenly on glass containers, place them on temperature sensors, and then inject 2.5μL of formaldehyde solution into the heating plate of the sealed box before sealing the box.

[0078] 3.2 Turn on the heating plate, infrared photoacoustic spectrometer, and fan. After the formaldehyde solution has completely evaporated, turn off the heating plate and start the first sampling. The infrared photoacoustic spectrometer continuously monitors the carbon dioxide concentration in the reaction room.

[0079] 3.3 After reacting for 3 hours at a temperature of 26℃ and a relative humidity of 40%Rh, a second sample was taken and the carbon dioxide concentration measured by the infrared photoacoustic spectrometer was recorded.

[0080] 4. Data Processing

[0081] The removal rate is calculated according to formula (1):

[0082] X1=[1-(C2 / C1)]×100% (1)

[0083] In the formula:

[0084] X1 - Removal rate, %;

[0085] C1-Formaldehyde initial concentration, in milligrams per cubic meter (mg / m³) 3 );

[0086] The final concentration of C2-formaldehyde, expressed in milligrams per cubic meter (mg / m³). 3 The test data are shown in Table 1-2.

[0087] The conversion rate is calculated using formula (2):

[0088] X2=[(C4-C3) / C1]×100% (2)

[0089] In the formula:

[0090] X2 - Conversion rate, %;

[0091] C1-Formaldehyde initial concentration, in milligrams per cubic meter (mg / m³) 3 );

[0092] Initial concentration of C3- carbon dioxide, in milligrams per cubic meter (mg / m³) 3 );

[0093] The final concentration of C4 carbon dioxide, expressed in milligrams per cubic meter (mg / m³). 3 The test data are shown in Table 1-2.

[0094] Table 1: Statistical Table of Formaldehyde Degradation Performance Test Data for Examples 1-12 and Comparative Examples 1-3

[0095]

[0096]

[0097] The manganese defect content increases in Comparative Example 2, Example 2, Example 3, and Example 1. Comparative Example 2 is δ-MnO2 / MMT with a theoretical loading of 50% (without potassium ion regulation), while Examples 2, 3, and 1 are all regulated by potassium ions. As can be seen from Table 1, the more manganese defects there are, the higher the formaldehyde removal rate and conversion rate.

[0098] Comparative Examples 2, 1, 4, 5, and 6 respectively used montmorillonite, montmorillonite pretreated with potassium acetate, montmorillonite pretreated with potassium chloride, montmorillonite pretreated with potassium hydroxide, and montmorillonite pretreated with potassium oxalate. Table 1 shows that potassium ion modification of montmorillonite significantly improved formaldehyde removal. Different potassium salts used to modify montmorillonite showed similar effects on improving formaldehyde removal, while the formaldehyde conversion rate increased to varying degrees depending on the potassium salt used. Among these, potassium acetate-modified montmorillonite showed the strongest effect on improving formaldehyde conversion. Studies have shown that K... + The presence of K enhances the redox properties of Mn and maintains the reaction by increasing the mobility of lattice oxygen and preserving the availability of surface active oxygen, thereby promoting catalytic activity. + The presence of K enhances the activity and mobility of lattice oxygen by weakening the Mn-O bonds in manganese oxides, thus promoting the redox performance of the catalyst. Secondly, K... + The increased content leads to more Mn vacancies to achieve charge balance. K + This can increase the average oxidation state (AOS) value of Mn and the proportion of surface-adsorbed oxygen, thereby enhancing the reducing power of oxygen species and promoting the formation of formate and carbonate in the HCHO oxidation reaction. Finally, adding K to MnO2... +It can generate more lattice oxygen, surface adsorbed oxygen, and Mn. 3+ and Mn 4+ This promotes its redox properties and enhances its catalytic ability.

[0099] Comparative Example 3 uses potassium-based activated carbon obtained by treating activated carbon with potassium acetate as a carrier; Example 1 uses potassium-based montmorillonite obtained by treating montmorillonite with potassium acetate as a carrier; this application adds K to the surface of montmorillonite as a base material. + It can promote the formation of more lattice oxygen, surface adsorbed oxygen, and MnO2. 3+ and Mn 4+ This improves the material's ability to catalytically degrade formaldehyde.

[0100] Examples 7, 8, 9, and 10 show that excessively low or high reaction temperatures, as well as excessively short or long reaction times, will affect the formation of manganese dioxide crystals in the montmorillonite carrier and the potassium ion regulation effect, thus hindering the improvement of formaldehyde removal and conversion rates.

[0101] Table 2: Statistical Table of Formaldehyde Degradation Performance Test Data of Example 1, Comparative Examples 1-2, and Comparative Examples 4-5

[0102] Formaldehyde removal rate (%) Formaldehyde conversion rate (%) Example 1 94.34 76.82 Comparative Example 1 83.70 62.50 Comparative Example 2 77.09 55.29 Comparative Example 4 56.32 0 Comparative Example 5 67.24 59.63

[0103] Comparative Examples 1, 2, 4, and 5 represent layered δ-MnO2, MnO2 / MMT with a theoretical loading of 50%, commercially available activated carbon, and commercially available manganese dioxide formaldehyde removal products, respectively. The experiments showed that commercially available activated carbon has no formaldehyde degradation function. Compared with layered MnO2, the catalyst prepared in Example 1 has significantly better performance than pure MnO2 and commercially available manganese dioxide formaldehyde removal products. This indicates that the introduction of montmorillonite support significantly improves the catalytic performance of the catalyst and greatly reduces the catalyst preparation cost.

[0104] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation, characterized in that, Includes the following steps: S1: After dispersing montmorillonite evenly in water, add potassium salt and mix, wash, centrifuge and dry to obtain potassium-based montmorillonite; S2: Potassium-based montmorillonite and water are mixed, and potassium permanganate is added and dispersed evenly to obtain a mixed solution; S3: Add ammonium oxalate to the mixture obtained in S2, heat the reaction, filter and wash until neutral, and dry to obtain MnO2 / montmorillonite composite material; The potassium salt is obtained by mixing any one or more of potassium chloride, potassium hydroxide, potassium acetate, potassium oxalate, and potassium hydrogen oxalate in any proportion; The montmorillonite is sodium-based montmorillonite with a cation exchange capacity greater than 100 mmol / 100g; The ratio of montmorillonite to potassium salt in S1 is: 10g of montmorillonite is mixed with 0.02-0.04mol of potassium salt. The molar ratio of ammonium oxalate in S3 to permanganate in the mixed solution is 1:1-3.

2. The method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation according to claim 1, characterized in that, The mass ratio of potassium-based montmorillonite to potassium permanganate in S2 is 0.5-5g:3.636g.

3. The method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation according to claim 1, characterized in that, The specific steps for the heating reaction in S3 are as follows: heat to 45-95℃ and keep the temperature for 6-20 hours under stirring.

4. The method for preparing a MnO2 / montmorillonite composite material for catalytic formaldehyde degradation according to claim 1, characterized in that, The specific steps for the heating reaction in S3 are as follows: heat to 65-95℃ and keep the temperature for 10-14 hours under stirring.

5. The MnO2 / montmorillonite composite material prepared by any one of claims 1-4 is used for the catalytic degradation of formaldehyde.

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