Honeycomb monolithic catalyst as well as preparation method and application thereof

Abstract

The invention provides a honeycomb monolithic catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing and reacting a silicon-aluminum molecular sieve with an acidic solution to obtain an acidic dispersion liquid of a dealumination modified molecular sieve; mixing the acid dispersion liquid of the dealumination modified molecular sieve, a cobalt source, a manganese source and an alkaline solution to obtain a precursor solution, and crystallizing, filtering, washing and drying the precursor solution to obtain a CoMnAl-LDH / dealumination molecular sieve composite material; and mixing the CoMnAl-LDH / dealumination molecular sieve composite material with an auxiliary agent and an organic binder to form slurry, dipping a cordierite honeycomb matrix in the slurry, vacuumizing, drying, and calcining to obtain the honeycomb monolithic catalyst. According to the preparation method, the interface bonding strength between the non-noble metal active component and the matrix and the wear resistance of the monolithic catalyst can be improved, the agglomeration of the non-noble metal active component in calcination is reduced, and the catalytic oxidation activity of the catalyst is improved.

Description

Technical Field

[0001] This invention relates to the field of new environmental catalytic materials technology, and in particular to a honeycomb monolithic catalyst, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) are a class of pollutants that are ubiquitous in the air and have a complex composition. They can promote the formation of photochemical smog and haze, seriously affecting the quality of the atmospheric environment and endangering human health. In recent years, with the increasingly serious air pollution problem and increasingly stringent environmental regulations, VOCs waste gas treatment has become a top priority in air pollution prevention and control. At present, VOCs end-of-pipe treatment technologies mainly include adsorption, absorption, condensation, membrane separation, photocatalytic degradation, plasma degradation, direct combustion, and catalytic oxidation technologies. Among them, catalytic oxidation technology is widely used as the most economical and effective means of VOCs treatment, especially suitable for the treatment of large-volume, low-concentration VOCs gases [He Chi, Cheng Jie, Zhang Xin, et al. Recent advances in the catalytic oxidation of volatile organic compounds: A review based on pollutant sorts and sources. Chem. Rev., 2019, 119, 4471-4568.]. The core of catalytic oxidation technology is the catalyst, which mainly uses cordierite honeycomb as the matrix and noble or non-noble metals as the active components. Among them, noble metal catalysts have disadvantages such as high price, scarcity of resources, easy poisoning, and easy sintering and deactivation at high temperature [Liotta LFCatalytic oxidation of volatile organic compounds on supported noble metals. Appl. Catal B: Environ., 2010, 100(3-4), 403-412.]. Compared with noble metal catalysts, non-noble metal catalysts are mainly transition metal oxides (such as Co, Mn, Ce, Zr and La, etc.), which have advantages such as abundant resources, low price, multiple valence states and good heat resistance, and have become a research hotspot for catalytic oxidation of VOCs [Xu Feng, Xu Zechen, Liu Pei, Zhu Lihua. Experimental study on the catalytic performance of Co-Mn composite oxide catalyst for low concentration gas combustion. Journal of Heilongjiang University of Science and Technology, 2023, 33(4): 487-496.]. However, non-precious metal-based catalysts typically suffer from drawbacks such as low catalytic activity, high ignition temperature, and high operating energy consumption. Improving the robustness and dispersibility of the non-precious metal active components on the surface of a cordierite honeycomb rigid matrix is ​​generally an effective means of enhancing the catalytic activity of non-precious metal-based catalysts.

[0003] CN116139917A (application number 202211356319.9) proposes a method to improve the dispersibility and adhesion strength of active components by utilizing the large specific surface area and well-developed pore structure of molecular sieves. The technical solution involves first loading the active component onto a molecular sieve powder carrier via impregnation, then combining the resulting active component / molecular sieve powder with additives and vacuum coating it onto the surface of a cordierite or honeycomb ceramic matrix, followed by high-temperature calcination to obtain an integral catalyst. While this technology alleviates the agglomeration of the active component and improves its dispersibility to some extent, the interfacial bonding between the active component and the matrix is ​​weak. Molecular sieves also suffer from drawbacks such as difficulty in molding and susceptibility to cracking during high-temperature calcination. Essentially, it does not improve the interfacial bonding strength between the active component and the cordierite honeycomb matrix, and technical problems such as easy wear and detachment still exist. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a monolithic honeycomb catalyst, its preparation method, and its application. This preparation method can improve the interfacial bonding strength between the non-precious metal active components and the cordierite honeycomb matrix, enhance the wear resistance of the monolithic catalyst, and further mitigate the agglomeration problem of the non-precious metal active components during the calcination process on the cordierite honeycomb matrix surface, thereby comprehensively improving the catalytic oxidation activity of the catalyst.

[0005] To achieve the above objectives, the present invention provides a method for preparing a honeycomb monolithic catalyst, the method comprising:

[0006] S1. Mix the silica-alumina molecular sieve with an acidic solution and react to obtain an acidic dispersion of dealuminized molecular sieve.

[0007] S2. The acidic dispersion of the dealuminized molecular sieve, cobalt source, manganese source and alkaline solution are mixed to obtain a precursor solution. The precursor solution is crystallized, filtered, washed and dried to obtain CoMnAl-LDH / deaminated molecular sieve composite material.

[0008] S3. The CoMnAl-LDH / dealuminized molecular sieve composite material is mixed with additives and organic binders to form a slurry. The cordierite honeycomb matrix is ​​impregnated in the slurry, vacuumed, dried, and calcined to obtain the honeycomb monolithic catalyst.

[0009] In the above preparation method, in S1, an acidic solution is used to pre-treat the silica-alumina molecular sieve by removing aluminum. The aluminum element in the molecular sieve dissolves into the acidic molecular sieve to form aluminum ions. The dissolved aluminum can be used as an aluminum source for synthesizing CoMnAl-LDH without the need to add an additional aluminum source. Furthermore, the molecular sieve after the removal treatment has a high silicon content, which makes it less prone to cracking during high-temperature sintering and is beneficial for the formation of the cordierite honeycomb matrix surface.

[0010] In the above preparation method, in step S1, the mass content of alumina in the silica-alumina molecular sieve is generally above 20%. Further, the mass content of alumina in the silica-alumina molecular sieve can be 20%-30%. The alumina content in the silica-alumina molecular sieve used in this invention ensures sufficient aluminum source for the synthesis of CoMnAl-LDH and guarantees the original properties of the molecular sieve after dealumination treatment.

[0011] In the above preparation method, in S1, the molar concentration of the acidic solution can be 0.5-2.0 mol / L, for example, specific values ​​such as 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, etc., and a range with any two of the above specific values ​​as endpoints; the mass ratio of the silica-alumina molecular sieve to the acidic solution can be 0.05-0.25:1, for example, specific values ​​such as 0.05:1, 0.10:1, 0.15:1, 0.20:1, 0.25:1, etc., and a range with any two of the above specific values ​​as endpoints.

[0012] In the above preparation method, in S1, the acidic solution includes, but is not limited to, one or more combinations of hydrochloric acid solution, sulfuric acid solution, nitric acid solution, citric acid solution, and oxalic acid solution.

[0013] In the above preparation method, in step S1, the reaction time is 2-10 hours.

[0014] In the above preparation method, in S2, the molar ratio of the cobalt source and the manganese source can be 0.4-0.6:1, for example, specific values ​​such as 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, and a range with any two of the above specific values ​​as endpoints.

[0015] In the above preparation method, the cobalt source can be a soluble cobalt salt, specifically including one or more of cobalt chloride, cobalt sulfate, cobalt nitrate, and cobalt acetate.

[0016] In the above preparation method, in step S2, the manganese source can be a soluble manganese salt, specifically including one or more of manganese chloride, manganese sulfate, manganese nitrate, or manganese acetate.

[0017] According to a specific embodiment of the present invention, in S2, the manganese source and the cobalt source may contain the same or different anions; preferably, the manganese source and the cobalt source contain the same anions to reduce the introduction of impurities.

[0018] In the above preparation method, in S2, the ratio of the sum of the masses of the cobalt source and the manganese source to the mass of the silica-alumina molecular sieve can be 0.6-1.9:1, for example, specific values ​​such as 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, etc., and a range with any two of the above specific values ​​as endpoints.

[0019] In the above preparation method, in step S2, the pH value of the precursor solution can be 9-11, for example, specific values ​​such as 9, 9.5, 10, 10.5, 11, etc., or a range with any two of the above specific values ​​as endpoints. The amount of alkaline solution can be adjusted accordingly based on the pH value of the precursor solution.

[0020] In the above preparation method, in step S2, the concentration of the alkaline solution is 0.5-1.5 mol / L.

[0021] In the above preparation method, in S2, the alkaline solution includes, but is not limited to, one or a combination of two or more of potassium hydroxide, sodium hydroxide, or ammonia water.

[0022] In the above preparation method, in step S2, the crystallization temperature is 75-85℃ and the crystallization time is 3-6h.

[0023] In the above preparation method, in step S2, the washing process may include washing the filtered filtrate until the pH value is 7-7.5.

[0024] In the above preparation method, in step S2, the drying temperature can be 60-80℃.

[0025] In the above preparation method, in step S3, the auxiliary agent includes glycerin and / or soybean oil.

[0026] In the above preparation method, in step S3, the organic binder includes one or more of hydroxypropyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, or acrylic resin.

[0027] In the above preparation method, in S3, the mass ratio of the additive to the CoMnAl-LDH / dealuminized molecular sieve composite material can be 0.15-0.45:1, for example, specific values ​​such as 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, and a range with any two of the above specific values ​​as endpoints.

[0028] In the above preparation method, in S3, the mass ratio of the organic binder to the CoMnAl-LDH / dealuminized molecular sieve composite material is 0.05-0.2:1, for example, specific values ​​such as 0.05:1, 0.1:1, 0.15:1, 0.2:1, etc., and a range with any two of the above specific values ​​as endpoints.

[0029] In the above preparation method, in S3, the cordierite honeycomb matrix can be cordierite that is commonly sold on the market. The present invention does not have any special limitations on the cordierite honeycomb matrix.

[0030] In the above preparation method, in step S3, the mixing temperature of the CoMnAl-LDH / dealuminized molecular sieve composite material, additives, and organic binder can be 40-60℃.

[0031] In the above preparation method, in step S3, the slurry is generally a colloidal slurry.

[0032] In the above preparation method, in step S3, vacuum filtration can be used to promote the full impregnation of the cordierite honeycomb matrix by the slurry. The impregnation method may include: completely impregnating the cordierite honeycomb matrix with the slurry under sealed conditions, using a vacuum pump to create a vacuum, impregnating for 20-40 minutes, blowing away any residual slurry in the honeycomb matrix channels after impregnation to retain the interconnected channels in the cordierite honeycomb matrix, and then allowing it to air dry naturally.

[0033] In the above preparation method, in step S3, the drying can be performed using microwave drying. Compared to conventional drying methods that involve heat transfer from the surface to the interior, microwave drying allows for simultaneous heating of the object inside and out, resulting in more uniform heating. In some specific embodiments, the microwave drying temperature can be 90-120℃, and the microwave drying time can be 20-40 minutes.

[0034] In the above preparation method, in step S3, the calcination temperature can be 550-700℃, and the calcination time can be 3-5h.

[0035] In the above preparation method, in S3, CoMnAl-LDH in the cordierite honeycomb matrix loses its water of crystallization and rapidly decomposes into non-precious metal oxide particles loaded on the surface of the honeycomb matrix during high-temperature calcination, reducing the agglomeration of non-precious metal active components and improving dispersion performance. Furthermore, CoMnAl-LDH generates active alumina during high-temperature calcination, which is uniformly mixed with non-precious metal oxide active components such as manganese and cobalt and sintered on the surface of the cordierite honeycomb matrix. This greatly improves the interfacial bonding strength between non-precious metal active components such as manganese and cobalt and the cordierite honeycomb matrix, reduces its wear rate, and extends the service life of the catalyst.

[0036] According to a specific embodiment of the present invention, the above preparation method may specifically include:

[0037] S1. Mix the silica-alumina molecular sieve (alumina content of more than 20%) with an acidic solution (molar concentration of 0.5-2.0 mol / L) at a mass ratio of 0.05-0.25:1, and stir at room temperature for 2-10 hours to obtain an acidic dispersion of dealuminized molecular sieve.

[0038] S2. Mix the acidic dispersion of dealuminized molecular sieve, soluble cobalt salt, soluble manganese salt, and alkaline solution with a molar concentration of 0.5-1.5 mol / L to obtain a precursor solution with a pH of 9-11. The molar ratio of soluble cobalt salt to soluble manganese salt is 0.4-0.6:1, and the ratio of the sum of the masses of soluble cobalt salt and soluble manganese salt to the mass of silica-alumina molecular sieve is 0.6-1.9:1, for example, 0.61-1.89:1.

[0039] The precursor solution was heated to 75-85℃ and stirred for 3-6 hours for crystallization. The solution was then filtered and washed until the pH of the filtrate was neutral (7-7.5). The solution was dried at 60-80℃ and pulverized to obtain the CoMnAl-LDH / dealuminized molecular sieve composite material.

[0040] S3. The CoMnAl-LDH / dealuminized molecular sieve composite material is mixed with additives and organic binders at 40-60℃ to form a colloidal slurry, wherein the mass ratio of additives to CoMnAl-LDH / dealuminized molecular sieve composite material is 0.15-0.45:1, and the mass ratio of organic binders to CoMnAl-LDH / dealuminized molecular sieve composite material is 0.05-0.2:1; under sealed conditions, the cordierite honeycomb matrix is ​​immersed in the above slurry, a vacuum pump is used to evacuate the vacuum, the immersion time is 20-40 min, after the immersion is completed, the matrix is ​​purged to remove the slurry, air-dried naturally, microwave-dried at 90-120℃ for 20-40 min, and then calcined at 550-700℃ for 3-5 h to obtain the honeycomb monolithic catalyst.

[0041] The present invention also provides a honeycomb monolithic catalyst, which is obtained by the above preparation method. The above-mentioned honeycomb monolithic catalyst is a Co-Mn non-noble metal honeycomb monolithic catalyst.

[0042] This invention also provides the application of the above-mentioned honeycomb monolithic catalyst in the catalytic oxidation of VOCs. The VOCs can be benzene-based gases, such as xylene, benzene, and toluene. The above-mentioned honeycomb monolithic catalyst can be applied to the catalytic oxidation of VOCs gases, promoting gas conversion. The active components in the honeycomb monolithic catalyst are uniformly dispersed, exhibiting high catalytic activity in the catalytic oxidation reaction; the interfacial bonding strength between the active components and the matrix of this catalyst is high, exhibiting high wear resistance and a long service life in the catalytic oxidation reaction.

[0043] The beneficial effects of this invention include:

[0044] 1. This invention employs an acidic solution to pre-treat the molecular sieve for dealumination. The aluminum element in the molecular sieve is dissolved in the acidic solution to form aluminum ions, which can be used as an aluminum source for the synthesis of CoMnAl-LDH without the need for additional aluminum salt raw materials. The dealumination-modified molecular sieve has a high silicon content, making it less prone to cracking during high-temperature sintering, which is beneficial for its formation on the cordierite honeycomb surface.

[0045] 2. The active alumina generated during the high-temperature calcination of the CoMnAl-LDH coated on the cordierite surface and the additional Al(OH)3 (the Al removed from the silica-alumina molecular sieve in this invention is excessive relative to the Al content required for CoMnAl-LDH) will be uniformly mixed with the active components of non-precious metal oxides such as manganese and cobalt and sintered on the surface of the cordierite honeycomb matrix. This greatly improves the interfacial bonding strength between the active components of non-precious metals such as manganese and cobalt and the cordierite honeycomb matrix, reduces its wear rate, and extends the catalyst's service life. Furthermore, there is no need to additionally coat the cordierite honeycomb matrix with an active alumina coating, shortening the production process and cycle, and reducing manufacturing costs.

[0046] 3. In this invention, CoMnAl-LDH is first grown in situ on the surface of aluminized molecular sieve as a precursor, and then non-precious metal oxides such as manganese and cobalt are generated by high-temperature calcination. Its advantage is that CoMnAl-LDH loses its water of crystallization during high-temperature calcination, rapidly decomposes into non-precious metal oxide particles, and is uniformly loaded on the surface of the honeycomb carrier, thereby further reducing the agglomeration of non-precious metal active components such as manganese and cobalt, greatly improving their dispersion performance, and thus improving catalytic activity. Attached Figure Description

[0047] Figure 1 The X-ray diffraction (XRD) spectra of the silica-alumina molecular sieve, CoMnAl-LDH / dealuminized molecular sieve, and Mn-Co non-precious metal honeycomb monolithic catalyst surface coating of Example 4 are shown.

[0048] Figure 2 This is a scanning electron microscope image of the CoMnAl-LDH / dealuminized molecular sieve in Example 4.

[0049] Figure 3 This is an SEM image of the surface coating of the cordierite honeycomb substrate in Example 4.

[0050] Figure 4 This is a SEM image of the surface coating of the cordierite honeycomb substrate in Comparative Example 2.

[0051] Figure 5 This is a photograph of the honeycomb catalyst sample prepared in Example 4. Detailed Implementation

[0052] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0053] The present invention will be further described below through specific embodiments and comparative examples. The present invention is not limited to the following embodiments. Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional reagents, which can be purchased commercially or synthesized according to conventional methods in the art; the experimental methods, unless otherwise specified, are all conventional methods.

[0054] The scanning electron microscope (SEM) is from Zeiss GmbH, Germany, model SUPRA55.

[0055] Example 1

[0056] This embodiment provides a honeycomb monolithic catalyst, the preparation method of which includes:

[0057] 1. While stirring, add 1.0 kg of silica-alumina molecular sieve powder (aluminum mass is calculated as aluminum oxide, aluminum mass content ≥20%) to 4.0 kg of hydrochloric acid solution with a molar concentration of 0.5 mol / L, and stir the reaction at room temperature for 10 hours to obtain an acidic dispersion of dealuminized molecular sieve.

[0058] 2. While stirring, add 0.20 kg of cobalt chloride (CoCl2·6H2O) and 0.41 kg of manganese chloride (MnCl2·4H2O) to the entire acidic dispersion obtained in step 1. Then, add potassium hydroxide solution with a molar concentration of 0.5 mol / L dropwise until the pH of the system is 9. Raise the temperature to 85°C and continue stirring to carry out the crystallization reaction for 3 hours. Filter and wash until the pH of the filtrate is 7. Dry and pulverize at a temperature of 60°C to obtain a CoMnAl-LDH / dealuminized molecular sieve composite material.

[0059] 3. Take 1.0 kg of the CoMnAl-LDH / dealuminized molecular sieve composite powder obtained in step 2, 0.15 kg of glycerol and 0.05 kg of hydroxypropyl cellulose, mix and stir evenly, and disperse into a colloidal slurry at 40℃. Then, under sealed conditions, completely immerse the cordierite honeycomb matrix (diameter 28 mm, height 14 mm, internal square channel side length 1 mm, Jiangsu Chuangpin New Material Co., Ltd., the same below) into the colloidal slurry, use a vacuum pump to evacuate, and coat for 40 minutes. After removal, blow away the residual slurry in the honeycomb matrix channels, air dry naturally, and microwave dry at 90℃ for 40 minutes. Finally, calcine the dried honeycomb at 550℃ for 5 hours to obtain a Co-Mn non-precious metal honeycomb monolithic catalyst.

[0060] Example 2

[0061] This embodiment provides a honeycomb monolithic catalyst, the preparation method of which includes:

[0062] 1. While stirring, add 1.0 kg of silica-alumina molecular sieve powder (aluminum mass is calculated as aluminum oxide, aluminum mass content ≥20%) to 20 kg of sulfuric acid solution with a molar concentration of 2.0 mol / L. Stir and react at room temperature for 2 hours to obtain an acidic dispersion of dealuminized molecular sieve.

[0063] 2. While stirring, add 0.94 kg of cobalt sulfate (CoSO4·7H2O) and 0.95 kg of manganese sulfate (MnSO4·H2O) to the entire acidic dispersion obtained in step 1. Then, add an ammonia solution with a molar concentration of 1.5 mol / L dropwise until the pH of the system is 11. Raise the temperature to 75°C and continue stirring for 6 hours to carry out the crystallization reaction. Filter and wash until the pH of the filtrate is 7.5. Dry and pulverize at 80°C to obtain a CoMnAl-LDH / dealuminized molecular sieve composite material.

[0064] 3. Take 1.0 kg of the CoMnAl-LDH / dealuminized molecular sieve composite powder obtained in step 2, 0.45 kg of glycerol and 0.2 kg of acrylic resin, mix and stir evenly, and disperse into a colloidal slurry at 60℃. Then, under sealed conditions, completely immerse the cordierite honeycomb matrix in the colloidal slurry, use a vacuum pump to evacuate, and coat for 20 minutes. After removal, blow away the residual slurry in the honeycomb matrix channels, let it air dry naturally, and microwave dry at 120℃ for 20 minutes. Finally, calcine the dried honeycomb at 700℃ for 3 hours to obtain a Co-Mn non-precious metal honeycomb monolithic catalyst.

[0065] Example 3

[0066] This embodiment provides a honeycomb monolithic catalyst, the preparation method of which includes:

[0067] 1. While stirring, add 1.0 kg of silica-alumina molecular sieve powder (aluminum mass is calculated as aluminum oxide, aluminum mass content ≥20%) to 6.7 kg of nitric acid solution with a molar concentration of 1.5 mol / L. Stir and react at room temperature for 6 hours to obtain an acidic dispersion of dealuminized molecular sieve.

[0068] 2. While stirring, add 0.53 kg of cobalt nitrate (Co(NO3)2·6H2O) and 0.65 kg of manganese nitrate (Mn(NO3)2) to the entire acidic dispersion obtained in step 1. Then, add sodium hydroxide solution with a molar concentration of 1.2 mol / L dropwise until the pH of the system is 10. Raise the temperature to 80°C and continue stirring to carry out the crystallization reaction for 4 hours. Filter and wash until the pH of the filtrate is 7.3. Dry and pulverize at 70°C to obtain a CoMnAl-LDH / dealuminized molecular sieve composite material.

[0069] 3. Take 1.0 kg of the CoMnAl-LDH / dealuminized molecular sieve composite powder obtained in step 2, 0.3 kg of glycerol and 0.125 kg of hydroxyethyl cellulose, mix and stir evenly, and disperse into a colloidal slurry at 50℃. Then, under sealed conditions, completely immerse the cordierite honeycomb matrix in the colloidal slurry, use a vacuum pump to evacuate, and coat for 30 minutes. After removal, blow off the residual slurry in the honeycomb matrix channels, let it air dry, and microwave dry at 105℃ for 30 minutes. Finally, calcine the dried honeycomb at 625℃ for 4 hours to obtain a Co-Mn non-precious metal honeycomb monolithic catalyst.

[0070] Example 4

[0071] This embodiment provides a honeycomb monolithic catalyst, the preparation method of which includes:

[0072] 1. While stirring, add 1.0 kg of silica-alumina molecular sieve powder (aluminum mass is calculated as aluminum oxide, aluminum mass content ≥20%) to 10.0 kg of oxalic acid solution with a molar concentration of 1.0 mol / L, and stir the reaction at room temperature for 5 hours to obtain an acidic dispersion of dealuminized molecular sieve.

[0073] 2. While stirring, add 0.35 kg of cobalt acetate (C4H6CoO4·4H2O) and 0.48 kg of manganese acetate (C4H6MnO4) to the entire acidic dispersion obtained in step 1. Then, add sodium hydroxide solution with a molar concentration of 1.0 mol / L dropwise until the pH of the system is 10. Raise the temperature to 80°C and continue stirring to carry out the crystallization reaction for 5 hours. Filter and wash until the pH of the filtrate is 7.5. Dry and pulverize at a temperature of 75°C to obtain a CoMnAl-LDH / dealuminized molecular sieve composite material.

[0074] 3. Take 1.0 kg of the CoMnAl-LDH / dealuminized molecular sieve composite powder obtained in step 2, 0.2 kg of glycerol and 0.15 kg of polyvinyl alcohol, mix and stir evenly, and disperse into a colloidal slurry at 55℃. Then, under sealed conditions, completely immerse the cordierite honeycomb matrix in the colloidal slurry, use a vacuum pump to evacuate, and coat for 35 minutes. After removal, blow away the residual slurry in the honeycomb matrix channels, let it air dry, and microwave dry at 100℃ for 25 minutes. Finally, calcine the dried honeycomb at 650℃ for 4 hours to obtain a Co-Mn non-precious metal honeycomb monolithic catalyst.

[0075] Comparative Example 1

[0076] This comparative example provides a honeycomb monolithic catalyst. Compared with Example 4, in Comparative Example 1, the "dealuminization and modification of molecular sieve" step in Example 4 is deleted, but in step 2, the same equivalent of soluble aluminum salt is added as the aluminum source for CoMnAl-LDH. Other processes remain unchanged, and the specific steps are as follows:

[0077] 1. While stirring, add 1.0 kg of silicon-aluminum molecular sieve powder (aluminum mass is calculated as aluminum oxide, aluminum mass content ≥20%) to 10.0 kg of deionized water. After uniform dispersion, add 0.35 kg of cobalt acetate (C4H6CoO4·4H2O), 0.48 kg of manganese acetate (C4H6MnO4), and 1.07 kg of aluminum chloride (AlCl3·6H2O) in sequence. Then, add sodium hydroxide solution with a molar concentration of 1.0 mol / L dropwise until the pH of the system is 10. Raise the temperature to 80℃ and continue stirring for 5 hours. Filter and wash until the pH of the filtrate is 7.5. Dry and pulverize at 75℃ to obtain a CoMnAl-LDH / molecular sieve composite material.

[0078] 2. Take 1.0 kg of the CoMnAl-LDH / molecular sieve composite powder obtained in step 2, 0.2 kg of glycerol and 0.15 kg of polyvinyl alcohol, mix and stir evenly, and disperse into a colloidal slurry at 55℃. Then, under sealed conditions, completely immerse the cordierite honeycomb matrix in the colloidal slurry, use a vacuum pump to evacuate, and coat for 35 minutes. After removal, blow away the residual slurry in the honeycomb matrix channels, let it air dry, and microwave dry at 100℃ for 25 minutes. Finally, calcine the dried honeycomb at 650℃ for 4 hours to obtain a Co-Mn non-precious metal honeycomb monolithic catalyst.

[0079] Comparative Example 2

[0080] This comparative example provides a honeycomb monolithic catalyst. Compared with Example 4, in Comparative Example 2, the "CoMnAl-LDH in-situ synthesis process" in step 2 of Example 4 is replaced with "Co and Mn ion equal-volume impregnation process", while other processes remain unchanged. The specific steps are as follows:

[0081] 1. While stirring, add 1.0 kg of silica-alumina molecular sieve powder (aluminum mass is calculated as aluminum oxide, aluminum mass content ≥20%) to 10.0 kg of oxalic acid solution with a molar concentration of 1.0 mol / L, and stir the reaction at room temperature for 5 hours to obtain an acidic dispersion of dealuminized molecular sieve.

[0082] 2. While stirring, add 0.35 kg of cobalt acetate (C4H6CoO4·4H2O) and 0.48 kg of manganese acetate (C4H6MnO4) to the acidic dispersion obtained in step 1. Heat to 80°C, continue stirring to evaporate and remove moisture, then dry and pulverize to obtain a Co... 2+ Mn 2+ Supported dealuminolite molecular sieve composite;

[0083] 3. Take 1.0 kg of the Co obtained in step 2. 2+ Mn 2+ A loaded dealuminol molecular sieve composite, 0.2 kg of glycerol, and 0.15 kg of polyvinyl alcohol were mixed and stirred evenly to form a colloidal slurry at 55°C. Then, a cordierite honeycomb matrix was completely immersed in the colloidal slurry under sealed conditions, and a vacuum pump was used to evacuate the substrate for 35 minutes. After removal, the residual slurry in the honeycomb matrix pores was blown away, and the substrate was allowed to air dry naturally. Finally, the substrate was microwave-dried at 100°C for 25 minutes. The dried honeycomb was then calcined at 650°C for 4 hours to obtain a Co-Mn non-precious metal honeycomb monolithic catalyst.

[0084] Structural characterization

[0085] Figure 1The images show the XRD patterns of the silica-alumina molecular sieve, CoMnAl-LDH / dealuminized molecular sieve composite material, and honeycomb monolithic catalyst surface coating used in Example 4. Figure 1 It can be seen that for the CoMnAl-LDH / dealuminized molecular sieve composite material, the diffraction characteristic peaks of CoMnAl-LDH are at 2θ = 10.8° and 2θ = 21.6°. After high-temperature calcination treatment ( Figure 1 In the CoMn / dealuminized molecular sieve, the diffraction peaks of CoMnAl-LDH disappeared, and new characteristic peaks appeared at 2θ = 36.1° and 2θ = 36.7°, corresponding to Mn3O4 and Co3O4, respectively. This indicates that CoMnAl-LDH decomposes after high-temperature calcination to form Mn3O4 and Co3O4 non-noble metal oxide active components.

[0086] Figure 2 This is a SEM image of the CoMnAl-LDH / dealuminized molecular sieve composite material from Example 4. Figure 2 As can be seen, a large number of sheet-like CoMnAl-LDH particles are aggregated on the surface of the micron-sized molecular sieve support.

[0087] Figure 3 This is a SEM image of the surface coating on the cordierite honeycomb substrate in Example 4. Figure 3 As can be seen, a large number of metal oxide particles are uniformly loaded on the surface of the honeycomb carrier, and the non-precious metal active components have good dispersion on the substrate surface.

[0088] Figure 4 This is a SEM image of the surface coating on the cordierite honeycomb substrate in Comparative Example 2. (Source: [Original Text]) Figure 4 As can be seen, the coating shows some cracking, and the non-precious metal active components are mixed randomly with the molecular sieve, with poor particle dispersion.

[0089] Overall performance evaluation

[0090] Catalytic oxidation performance testing procedures: The catalytic oxidation performance of the honeycomb catalyst samples in this invention was evaluated using p-xylene as a simulated gas. The catalyst activity evaluation was conducted on a VOC adsorption-desorption catalytic reactor (VDRT-3000 model, Wode Instrument Co., Ltd., Quzhou City, Zhejiang Province). The honeycomb catalyst samples prepared in this invention (e.g.,...) were then... Figure 5 The image shows the actual honeycomb sample prepared in Example 4, with a diameter of 28 mm, a height of 14 mm, and an internal square channel with a side length of 1 mm. (Jiangsu Chuangpin New Materials Co., Ltd.) It was placed in a quartz tube with an inner diameter of 30 mm. The p-xylene simulation gas was generated by bubbling p-xylene solvent from nitrogen at room temperature. High-purity air was used as the carrier gas. The p-xylene concentration was controlled by adjusting the flow rates of the bubbling gas and the carrier gas; specifically, the air flow rate was 450 mL / min and the nitrogen flow rate was 30 mL / min, resulting in a p-xylene concentration of 2000 mg / m³.3 The concentration of p-xylene was analyzed online using a GC-2014 gas chromatograph. The temperature (T) corresponding to a p-xylene conversion rate of 99% was determined by testing. 99 To evaluate the performance of the catalyst. 99 The lower the temperature, the higher the catalyst activity and the better the catalytic oxidation performance. In this experiment, the conversion temperature (T) corresponding to a 99% conversion rate of p-xylene was measured at 1 h and 10 h, respectively. 99 ).

[0091] Wear resistance evaluation: Before the experiment, the mass of the sample and the fine powder collector containing it was weighed. Then, following the aeration process described in the above test steps, a catalytic oxidation reaction was carried out for 10 hours. Afterward, the fine powder collector was removed and weighed. The cumulative wear rate was calculated using the following formula:

[0092]

[0093] Where: m f Let m be the mass of fine powder collected at a certain moment, in g; m be the initial mass of the added particles, in g; A e The cumulative wear rate is expressed as a percentage.

[0094] The catalysts prepared in the above examples and comparative examples were evaluated using the above method, and the test results are shown in Table 1.

[0095] Table 1

[0096] name <![CDATA[T 99 / ℃(1h)]]> Cumulative wear rate / % <![CDATA[T 99 / ℃(10h)]]> Example 1 292 0.11 295 Example 2 293 0.09 297 Example 3 291 0.10 294 Example 4 288 0.08 290 Comparative Example 1 328 0.32 351 Comparative Example 2 315 0.14 332

[0097] As shown in Table 1, comparing the conversion temperatures corresponding to a 99% p-xylene conversion rate at 1 h and 10 h, it can be clearly found that T in the embodiments of the present invention... 99 The temperature change value is lower than that of the comparative example, which indicates that the catalyst prepared by the present invention has excellent wear resistance and less loss of active components on the cordierite matrix surface, so the catalyst has good catalytic activity and extends its service life.

[0098] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a honeycomb monolithic catalyst, the method comprising: S1. Mix the silica-alumina molecular sieve with an acidic solution and react to obtain an acidic dispersion of dealuminized molecular sieve. S2. The acidic dispersion of the dealuminized molecular sieve, cobalt source, manganese source and alkaline solution are mixed to obtain a precursor solution. The precursor solution is crystallized, filtered, washed and dried to obtain CoMnAl-LDH / deaminated molecular sieve composite material. S3. The CoMnAl-LDH / dealuminized molecular sieve composite material is mixed with additives and organic binders to form a slurry. The cordierite honeycomb matrix is ​​impregnated in the slurry, vacuumed, dried, and calcined to obtain the honeycomb monolithic catalyst.

2. The preparation method according to claim 1, wherein, The alumina content in the silica-alumina molecular sieve is 20% or more by mass.

3. The preparation method according to claim 1, wherein, The molar concentration of the acidic solution is 0.5-2.0 mol / L, and the mass ratio of the silica-alumina molecular sieve to the acidic solution is 0.05-0.25:

1.

4. The preparation method according to claim 1, wherein, In S1, the reaction time is 2-10 hours.

5. The preparation method according to claim 1, wherein, The molar ratio of the cobalt source to the manganese source is 0.4-0.6:1; And / or, the ratio of the sum of the masses of the cobalt source and the manganese source to the mass of the silica-alumina molecular sieve is 0.6-1.9:1; And / or, the pH of the precursor solution is 9-11.

6. The preparation method according to claim 1, wherein, The cobalt source includes one or more of cobalt chloride, cobalt sulfate, cobalt nitrate, and cobalt acetate; And / or, the manganese source includes one or more of manganese chloride, manganese sulfate, manganese nitrate, and manganese acetate.

7. The preparation method according to claim 1, wherein, In S2, the crystallization temperature is 75-85℃, and the crystallization time is 3-6h.

8. The preparation method according to claim 1, wherein, The mass ratio of the additive to the CoMnAl-LDH / dealuminized molecular sieve composite material is 0.15-0.45:1; The mass ratio of the organic binder to the CoMnAl-LDH / dealuminized molecular sieve composite material is 0.05-0.2:

1.

9. The preparation method according to claim 1, wherein, The adjuvants include glycerin and / or soybean oil; And / or, the organic binder includes one or more of hydroxypropyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, or acrylic resin.

10. The preparation method according to claim 1, wherein, In S3, the drying is microwave drying, the temperature of the microwave drying is 90-120℃, and the time of the microwave drying is 20-40 minutes. And / or, the calcination temperature is 550-700℃, and the calcination time is 3-5h.

11. A honeycomb monolithic catalyst, obtained by the preparation method according to any one of claims 1-10.

12. The application of the honeycomb monolithic catalyst according to claim 11 in the catalytic oxidation of VOCs.

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