Novel ultrahigh-specific-surface-area efficient ozone decomposition catalyst and coating process thereof

Abstract

The invention discloses a novel ultrahigh-specific-surface-area efficient ozonolysis catalyst and a coating process thereof, relates to the technical field of ozonolysis, and aims to solve the problem of low ozonolysis efficiency in the prior art. The catalyst is a catalyst in a suspension form, and is prepared by the following steps; the preparation method comprises the following steps: A1, synthesizing nano manganese dioxide with a nanowire, nanosheet or ultrathin nanoflower structure by adopting a hydrothermal method or a coprecipitation method; a2, freeze-drying the synthesized nano-manganese dioxide to obtain black nano-manganese dioxide powder; and A3, mixing the nano manganese dioxide powder with deionized water, a binder, a thickening agent and a dispersing agent, and then grinding for 12-24 hours by adopting a ball mill or a sand mill to form a stable and uniform catalyst in a suspension form. The device has the advantage of realizing efficient ozonolysis.

Description

Technical Field

[0001] This invention relates to the field of ozone decomposition technology, and more specifically, to a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst and its coating process. Background Technology

[0002] Ozone, as a strong oxidizing gas, is widely used in disinfection, water treatment, air purification and other fields. However, excessive ozone can harm the human respiratory tract and nervous system and accelerate the aging of materials. Therefore, ozone decomposition and purification technology has become one of the key needs in the field of environmental protection.

[0003] Currently, the most commonly used ozone decomposition method in industry is catalytic decomposition, and the key lies in the compatibility between the performance of the ozone decomposition catalyst and the coating process.

[0004] Existing ozone decomposition catalysts mostly use manganese dioxide as the active component. However, traditional manganese dioxide is often in the form of bulk or low specific surface area particles, and is frequently prepared as fixed-bed particle catalysts or coated catalysts. The limited specific surface area of ​​the active component leads to insufficient contact between ozone and the catalyst's active sites, resulting in low decomposition efficiency. Therefore, we propose a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst and its coating process. Summary of the Invention

[0005] The purpose of this invention is to provide a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst and its coating process, aiming to solve the problem of low ozone decomposition efficiency in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst, which is a suspension catalyst, and is prepared by the following steps; A1. Nano-manganese dioxide with nanowire, nanosheet, or ultrathin nanoflower structures is synthesized by hydrothermal method or co-precipitation method; A2. The synthesized nano-manganese dioxide was freeze-dried to obtain black nano-manganese dioxide powder; A3. Mix nano-manganese dioxide powder with deionized water, binder, thickener and dispersant, and then grind it in a ball mill or sand mill for 12-24 hours to form a stable and uniform suspension of the catalyst.

[0007] Preferably, in A3 above, the binder is one of boehmite or silica sol, the thickener is sodium carboxymethyl cellulose, and the dispersant is polyethylene glycol.

[0008] Preferably, in A3 above, the nano-manganese dioxide powder is mixed with deionized water, binder, thickener and dispersant in the following order of mass percentages: 15%-30%: 40%-60%: 10%-20%: 0.5%-2%: 1%-5%.

[0009] The present invention also discloses a coating process for a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst, the coating process comprising the following steps; B1. Select cordierite to make cordierite honeycomb carrier, then completely immerse the cordierite honeycomb carrier in the above-mentioned suspension catalyst, and remove it after waiting for 8-15 minutes; B2. High-speed airflow is used to blow through each channel of the cordierite honeycomb carrier, thereby removing excess catalyst from the channels of the cordierite honeycomb carrier, ensuring that the channel walls are covered with only a thin and uniform layer of catalyst, and keeping all channels unobstructed. B3. Repeat B1 and B2 above until the catalyst loading on the inner wall of each channel of the cordierite honeycomb carrier reaches 8-13 mg / cm². B4. Air-dry the catalyst on the cordierite honeycomb support at room temperature, then dry the catalyst on the cordierite honeycomb support at 80-100℃, and finally calcine for 2-4 hours.

[0010] Preferably, in step B1 above, the prepared cordierite honeycomb carrier is further cleaned to remove surface impurities, and the cleaning of the cordierite honeycomb carrier is performed by either acid washing or ultrasonic cleaning.

[0011] Preferably, the process also includes roughening the cleaned cordierite honeycomb carrier to increase its surface roughness and provide more anchoring points for subsequent coating.

[0012] Preferably, the cordierite honeycomb carrier is either rectangular or cylindrical with a honeycomb structure.

[0013] Preferably, the roughening treatment involves pre-coating a layer of γ-Al2O3 on the surface of the cordierite honeycomb carrier and inside each pore.

[0014] Preferably, in the above B4, the calcination is carried out by segmented heating with inert gas protection. First, the temperature is raised from room temperature to 150°C at a rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 300-450°C at a rate of 10°C / min and calcined for 2-4 hours, while nitrogen is introduced as a protective gas.

[0015] Preferably, in B1 above, when the cordierite honeycomb carrier is completely immersed in the catalyst, the temperature of the catalyst is maintained at 25-30°C.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention synthesizes nano-manganese dioxide with nanowire, nanosheet, or ultrathin nanoflower structures via hydrothermal or co-precipitation methods. These nano-manganese dioxide structures possess extremely high specific surface areas. Freeze-drying further preserves the porous characteristics and surface active sites of the nano-manganese dioxide. The resulting suspension catalyst, formed by mixing and grinding with deionized water, binders, and other materials, forms a thin and uniform coating on the pore walls of a cordierite honeycomb carrier. The ultra-high specific surface area provides a wider reaction interface when the catalyst comes into contact with ozone, significantly improving the adsorption and decomposition efficiency of ozone molecules.

[0017] This invention, through repeated immersion of the catalyst and high-speed airflow purging, can precisely control the catalyst loading on the inner wall of the cordierite honeycomb carrier pores. This avoids insufficient catalytic efficiency due to underloading and prevents overloading from clogging the carrier pores and affecting gas flow. At the same time, the cleaning and roughening treatment of the cordierite honeycomb carrier not only removes surface impurities to prevent them from interfering with the catalytic reaction, but also increases the surface roughness of the carrier, providing more anchoring points for the catalyst coating. This significantly improves the bonding strength between the catalyst and the cordierite honeycomb carrier, effectively reducing catalyst loss during use and extending the catalyst's service life. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the catalyst preparation process in this invention. Figure 2 This is a schematic diagram of the coating process in this invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Example 1 In this embodiment, the catalyst is formed by mixing nano-manganese dioxide powder with deionized water, binder, thickener and dispersant, and then grinding it with a ball mill or sand mill for 12-24 hours to form a stable and uniform suspension. in: The mass percentages of nano-manganese dioxide powder, deionized water, binder, thickener, and dispersant are 15%-30% : 40%-60% : 10%-20% : 0.5%-2% : 1%-5%; The binder is one of boehmite or silica sol, the thickener is sodium carboxymethyl cellulose, and the dispersant is polyethylene glycol; Furthermore, the nano-manganese dioxide powder is a black powder obtained by freeze-drying nano-manganese dioxide with nanowire, nanosheet, or ultrathin nanoflower structures synthesized by hydrothermal method. The specific steps are as follows: Step 1: Prepare the precursor solution: Dissolve the manganese salt and oxidant in deionized water at a molar ratio of 3:2 and stir vigorously to obtain a mixed solution; Step 2: Transfer to the reactor: Transfer the mixed solution to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, with a filling degree of 70-80%; Step 3, hydrothermal reaction: Place the reactor in an oven and carry out the reaction at a temperature of 120-180°C for 6-24 hours; Step 4, Cooling and Washing: After the reaction is complete, allow the product to cool naturally to room temperature, remove the product, and wash it repeatedly by centrifugation with deionized water and ethanol to remove impurity ions; Step 5: Drying: The above product is then freeze-dried to obtain a black powder, avoiding high-temperature calcination (calcination will cause nanoparticles to agglomerate and sinter, drastically reducing the specific surface area).

[0021] The catalyst coating process in this embodiment includes: Cordierite was selected to make a cordierite honeycomb carrier. The prepared cordierite honeycomb carrier was cleaned to remove surface impurities. During the cleaning process, one of acid washing or ultrasonic cleaning was used. After cleaning, the cordierite honeycomb carrier was roughened (a layer of γ-Al2O3 was pre-coated on the surface and inside each channel of the cordierite honeycomb carrier) to increase its surface roughness and provide more anchoring points for subsequent coating. Then, the cordierite honeycomb carrier was completely immersed in the above-mentioned catalyst in suspension form (keeping the catalyst temperature at 25-30℃) and removed after waiting for 8-15 minutes. Then, high-speed airflow is used to blow through each channel of the cordierite honeycomb carrier, thereby removing excess catalyst from the channels of the cordierite honeycomb carrier, ensuring that the channel walls are covered with only a thin and uniform layer of catalyst, and keeping all channels unobstructed. Repeat the above steps until the catalyst loading on the inner wall of each channel of the cordierite honeycomb carrier reaches 8-13 mg / cm². The catalyst on the cordierite honeycomb support was then air-dried at room temperature, and then dried at 80-100℃. Finally, the catalyst was calcined using a staged heating method with inert gas protection. First, the temperature was raised from room temperature to 150℃ at a rate of 5℃ / min and held for 1 hour. Then, the temperature was raised to 300-450℃ at a rate of 10℃ / min and calcined for 2-4 hours, while nitrogen was introduced as a protective gas.

[0022] It should be noted that in this embodiment, the cordierite honeycomb carrier is a rectangular structure with a honeycomb structure.

[0023] It should also be noted that in this embodiment, the cordierite honeycomb carrier coated with the catalyst is used in air purifiers, aircraft cabins, offices, and ozone generators for ozone decomposition.

[0024] In this embodiment, nano-manganese dioxide powder with nanowire, nanosheet, or ultrathin nanoflower structures is synthesized via a hydrothermal method. The resulting black powder, after freeze-drying, possesses an ultra-high specific surface area, providing abundant active sites for ozone decomposition. This powder is then mixed and ground with deionized water, a specific binder, thickener, and dispersant to form a stable and uniform suspension. The cordierite honeycomb carrier is then cleaned and roughened to enhance the bonding force between the carrier and the catalyst. Subsequently, the dip-coating conditions are controlled, and high-speed airflow is used to remove excess catalyst, followed by repeated coating to the target loading. This ensures that the catalyst forms a thin and uniform coating on the carrier pore walls, with unobstructed pores, fully exposing the ultra-high specific surface area of ​​the nano-manganese dioxide. Finally, staged heating and inert gas-protected calcination further enhance the catalyst's stability and activity. The resulting catalyst-coated cordierite honeycomb carrier can be efficiently applied in air purifiers, aircraft cabins, offices, and ozone generators, achieving efficient ozone decomposition and effectively improving the corresponding ambient air quality due to the ultra-high specific surface area of ​​the nano-manganese dioxide.

[0025] Example 2 This embodiment is basically the same as Embodiment 1, except that the nano-manganese dioxide powder is a black powder obtained by freeze-drying nano-manganese dioxide with nanowire, nanosheet, or ultrathin nanoflower structure synthesized by co-precipitation method. The specific steps are as follows: The first step is to dissolve the manganese salt and the oxidizing agent separately.

[0026] The second step is to rapidly add the manganese salt solution to the oxidant solution while stirring vigorously.

[0027] Third step: Continue stirring until the reaction is complete.

[0028] Step 4: Filter or centrifuge and wash until neutral.

[0029] Step 5: Freeze-drying (same as freeze-drying by hydrothermal method).

[0030] The precipitation method used in this embodiment does not require the high temperature and high pressure reaction conditions and special reaction equipment required by the hydrothermal method. The operation process is simpler and easier to scale up, which can reduce the difficulty of preparing nano-manganese dioxide powder and the energy consumption of production, thereby reducing the overall catalyst preparation cost. At the same time, the precipitation method has a relatively short reaction cycle, which can shorten the synthesis time of nano-manganese dioxide powder and improve the overall production efficiency of the catalyst from raw material preparation to final coating. However, the control of morphology is not as precise as that of the hydrothermal method, the uniformity of the product is slightly worse, and the specific surface area is usually lower than that of the hydrothermal method.

[0031] Example 3 This embodiment is basically the same as Embodiment 1, except that the cordierite honeycomb carrier in this embodiment is a cylindrical structure with a honeycomb structure.

[0032] In this embodiment, the cylindrical structure with a honeycomb structure can better withstand airflow impact and slight external vibrations, reducing the probability of cordierite honeycomb carrier breakage due to structural stress. At the same time, it also facilitates more uniform catalyst coating during the production process, further ensuring the stability of overall catalytic performance.

[0033] The embodiments disclosed in this invention are preferred embodiments, but are not limited thereto. Those skilled in the art can easily understand the spirit of this invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of this invention, they are all within the protection scope of this invention.

Claims

1. A novel ultra-high specific surface area high-efficiency ozone decomposition catalyst, characterized in that, The catalyst is a suspension catalyst, which is prepared by the following steps; A1. Nano-manganese dioxide with nanowire, nanosheet, or ultrathin nanoflower structures is synthesized by hydrothermal method or co-precipitation method; A2. The synthesized nano-manganese dioxide was freeze-dried to obtain black nano-manganese dioxide powder; A3. Mix nano-manganese dioxide powder with deionized water, binder, thickener and dispersant, and then grind it in a ball mill or sand mill for 12-24 hours to form a stable and uniform suspension of the catalyst.

2. The novel ultra-high specific surface area high-efficiency ozone decomposition catalyst according to claim 1, characterized in that, In A3 above, the binder is either boehmite or silica sol, the thickener is sodium carboxymethyl cellulose, and the dispersant is polyethylene glycol.

3. The novel ultra-high specific surface area high-efficiency ozone decomposition catalyst according to claim 1, characterized in that, In A3 above, the nano-manganese dioxide powder is mixed with deionized water, binder, thickener and dispersant in the following order of mass percentages: 15%-30%: 40%-60%: 10%-20%: 0.5%-2%: 1%-5%.

4. A coating process for a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst, wherein the coating process is applicable to the novel ultra-high specific surface area high-efficiency ozone decomposition catalyst described in any one of claims 1-3, characterized in that, The coating process includes the following steps; B1. Select cordierite to make cordierite honeycomb carrier, then completely immerse the cordierite honeycomb carrier in the above-mentioned suspension form of catalyst, and remove it after waiting for 8-15 minutes; B2. High-speed airflow is used to blow through each channel of the cordierite honeycomb carrier, thereby removing excess catalyst from the channels of the cordierite honeycomb carrier, ensuring that the channel walls are covered with only a thin and uniform layer of catalyst, and keeping all channels unobstructed. B3. Repeat B1 and B2 above until the catalyst loading on the inner wall of each pore of the cordierite honeycomb carrier reaches 8-13 mg / cm². B4. Air-dry the catalyst on the cordierite honeycomb support at room temperature, then dry the catalyst on the cordierite honeycomb support at 80-100℃, and finally calcine for 2-4 hours.

5. The coating process for a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst according to claim 4, characterized in that, In B1 above, the process also includes cleaning the prepared cordierite honeycomb carrier to remove surface impurities, and the cleaning of the cordierite honeycomb carrier is carried out by either acid washing or ultrasonic cleaning.

6. The coating process for a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst according to claim 5, characterized in that, It also includes roughening the cleaned cordierite honeycomb carrier to increase its surface roughness and provide more anchoring points for subsequent coating.

7. The coating process for a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst according to claim 4, characterized in that, The cordierite honeycomb carrier is either rectangular or cylindrical with a honeycomb structure.

8. The coating process for a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst according to claim 6, characterized in that, The roughening treatment involves pre-coating a layer of γ-Al2O3 on the surface of the cordierite honeycomb carrier and inside each channel.

9. The coating process for a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst according to claim 4, characterized in that, In the above B4, calcination is carried out by segmented heating with inert gas protection. First, the temperature is raised from room temperature to 150°C at a rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 300-450°C at a rate of 10°C / min and calcined for 2-4 hours, while nitrogen is introduced as a protective gas.

10. The coating process for a novel ultra-high specific surface area high-efficiency ozone decomposition catalyst according to claim 4, characterized in that, In B1 above, the temperature of the catalyst is maintained at 25-30°C when the cordierite honeycomb carrier is completely immersed in the catalyst.

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