Monolithic catalysts, methods for their preparation and use, and methods for purifying air

Abstract

The present application relates to the technical field of air pollution control, and discloses a monolithic catalyst, a preparation method and application thereof, and a method for purifying air. The monolithic catalyst comprises a honeycomb carrier, and an alumina matrix, manganese oxide and activated carbon supported on the honeycomb carrier; based on the total weight of the monolithic catalyst, the content of the honeycomb carrier in the monolithic catalyst is 55-85 wt%, the content of the alumina matrix is 5-30 wt%, the content of the manganese oxide is 5-35 wt%, and the content of the activated carbon is 3-20 wt%; wherein the average valence of manganese in the monolithic catalyst is 3.35-3.95. The monolithic catalyst disclosed by the present application can efficiently, stably and for a long period remove formaldehyde in air when applied to air purification.

Description

Technical Field

[0001] This invention relates to the field of air pollution control technology, specifically to an integral catalyst, its preparation method and application, and a method for purifying air. Background Technology

[0002] Formaldehyde is one of the most significant volatile organic compounds (VOCs). Its sources are widespread, including not only wood, flooring, and paint used in renovations, but also often overlooked products such as cosmetics, cleaning agents, incompletely burned tobacco, and textile fibers. Formaldehyde poses significant health risks. Acute poisoning can cause symptoms like burning throat, nausea, fatigue, difficulty breathing, and pulmonary edema. Chronic poisoning can lead to symptoms such as itchy skin, coughing, and chest tightness. Long-term exposure to low doses can result in weakened immune function, neurasthenia leading to memory loss, chronic respiratory diseases, and in severe cases, blood disorders, including leukemia. Therefore, the dangers of formaldehyde cannot be ignored, and its control has become a major concern. How to quickly and effectively reduce the harm of formaldehyde to the human body is an urgent problem that needs to be solved.

[0003] CN105964289A discloses a catalyst for formaldehyde removal at room temperature and its preparation method. Ag-Pt is loaded onto a tetrabutyl titanate modified support to achieve formaldehyde removal at room temperature. However, the catalyst provided by this method is not economically viable due to the use of precious metals, and lacks the basis for large-scale commercial application. CN107983320A discloses a method for preparing and applying a bifunctional thin film for formaldehyde removal. It describes manganese loaded onto a rare earth element nitrate-modified activated carbon support and preparing the film using an electrostatic filament solution. This film simultaneously possesses adsorption and catalytic oxidation functions, achieving the effect of formaldehyde removal. CN110624403A discloses a filter for formaldehyde and odor removal. A manganese catalyst is obtained through hydrothermal synthesis using a solution containing manganese, iron, and oxalate. This catalyst is then dissolved in a silica sol, sprayed onto a filter screen, and dried to achieve the function of formaldehyde removal at room temperature.

[0004] However, the room-temperature formaldehyde removal catalysts provided in the above patent applications are not suitable for large-scale use due to their poor economic efficiency, complex preparation methods, and poor operability. In the field of residential room-temperature formaldehyde removal, the following basic characteristics are required: firstly, strong formaldehyde removal capability; and secondly, national air quality standards require that the formaldehyde content in the home environment not exceed 0.1 mg / m³. 3Firstly, due to the limitations of room temperature formaldehyde removal catalysts, extremely high reactivity is required to meet the requirements. Secondly, high catalyst strength is necessary, as room temperature formaldehyde removal agents need to be used in adsorption and purification devices in large venues such as buildings, office buildings, hospitals, and shopping malls, where space velocities are high, and the catalyst strength must be able to withstand the impact strength requirements under high space velocities. Thirdly, long lifespan is crucial, as formaldehyde removal agents often become less efficient or even completely ineffective as the reaction progresses due to their mechanism. Therefore, there is an urgent need to develop a new type of formaldehyde removal agent to meet the requirements of long-term use. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a monolithic catalyst, its preparation method, its application, and a method for purifying air. The monolithic catalyst described in this invention, when applied to air purification, can efficiently, sustainably, and stably remove formaldehyde from the air.

[0006] To achieve the above objectives, a first aspect of the present invention provides an integral catalyst comprising a honeycomb support and an alumina matrix, manganese oxide, and activated carbon supported on the honeycomb support; based on the total weight of the integral catalyst, the content of the honeycomb support is 55-85% by weight, the content of the alumina matrix is ​​5-30% by weight, the content of the manganese oxide is 5-35% by weight, and the content of the activated carbon is 3-20% by weight.

[0007] The average valence of manganese in the monolithic catalyst is 3.35-3.95.

[0008] A second aspect of the present invention provides a method for preparing a monolithic catalyst, the method comprising the following steps:

[0009] (1) Manganese-based material, alumina matrix and dispersant are mixed to obtain manganese oxide suspension, wherein the average valence of manganese in the manganese-based material is 3.35-3.95;

[0010] (2) The honeycomb carrier is impregnated in manganese oxide suspension and activated carbon suspension by impregnation method, and then dried and optionally calcined.

[0011] The amounts of manganese-based materials, alumina matrix, activated carbon, and honeycomb support used in the prepared monolithic catalyst are such that, based on the total weight of the monolithic catalyst, the content of honeycomb support is 55-85% by weight, the content of alumina matrix is ​​5-30% by weight, the content of manganese oxide is 5-35% by weight, and the content of activated carbon is 3-20% by weight.

[0012] The third aspect of this invention provides the application of the monolithic catalyst described in the first aspect or the monolithic catalyst prepared by the preparation method described in the second aspect in air purification.

[0013] A fourth aspect of the present invention provides a method for purifying air, the method comprising: contacting formaldehyde-containing air with an integral catalyst;

[0014] The monolithic catalyst is either the monolithic catalyst described in the first aspect or the monolithic catalyst prepared by the preparation method described in the second aspect.

[0015] The beneficial effects of the present invention through the above technical solution include:

[0016] The monolithic catalyst provided by this invention is applied to air purification. Utilizing the synergistic effect of a specific content of honeycomb carrier-alumina matrix-manganese oxide-activated carbon, and controlling the average valence of manganese in the monolithic catalyst within the range of 3.35-3.95, it can achieve highly efficient adsorption of formaldehyde in the air. It induces strong chemical adsorption of formaldehyde on the catalyst surface and completes catalytic conversion, thereby purifying pollutants such as formaldehyde. It can reduce formaldehyde levels in the air to 0.08 mg / m³. 3 The following meet national safety standards. Furthermore, the integral catalyst described in this invention can stably remove formaldehyde from the air over a long period.

[0017] The monolithic catalyst preparation method of the present invention is simple, low-cost, highly precise, strong, and has a long service life, which is conducive to industrial promotion. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The first aspect of the present invention provides an integral catalyst, the catalyst comprising a honeycomb support and an alumina matrix, manganese oxide and activated carbon supported on the honeycomb support; based on the total weight of the integral catalyst, the content of the honeycomb support is 55-85% by weight, the content of the alumina matrix is ​​5-30% by weight, the content of the manganese oxide is 5-35% by weight, and the content of the activated carbon is 3-20% by weight.

[0020] The average valence of manganese in the monolithic catalyst is 3.35-3.95.

[0021] In this invention, the average valence of manganese in the monolithic catalyst is 3.35-3.95. Maintaining a high average valence of manganese in the monolithic catalyst is beneficial for improving formaldehyde removal efficiency.

[0022] The average oxidation state (AOS) of manganese described in this invention is calculated using the following formula:

[0023] AOS = 8.956 - 1.126 × ΔE, where ΔE is the difference between the high binding energy and low binding energy of manganese as measured by XPS Mn3S.

[0024] According to the present invention, preferably, based on the total weight of the monolithic catalyst, the content of the honeycomb carrier is 60-80% by weight, the content of the alumina matrix is ​​5-25% by weight, the content of manganese oxide is 10-25% by weight, and the content of activated carbon is 5-15% by weight. This preferred embodiment is beneficial for improving the adsorption and oxidation capacity of the monolithic catalyst for formaldehyde.

[0025] The content of each component in the monolithic catalyst of the present invention is calculated by the amount of feed.

[0026] The total amount of all components in the catalyst described in this invention is 100%.

[0027] The monolithic catalyst of this invention has a special active phase crystal structure, which is beneficial to improving the conversion efficiency of formaldehyde. Preferably, the manganese oxide has an α-MnO2 structure.

[0028] The crystal structure of the manganese oxide described in this invention was determined by XRD.

[0029] The present invention does not particularly limit the type of the honeycomb carrier, and any conventional choice in the art can be used. Preferably, the honeycomb carrier is selected from at least one of cordierite honeycomb carrier, mullite honeycomb carrier, diamond honeycomb carrier, corundum honeycomb carrier, zirconium corundum honeycomb carrier, quartz honeycomb carrier, nepheline honeycomb carrier, feldspar honeycomb carrier, and metal alloy honeycomb carrier, and more preferably cordierite honeycomb carrier.

[0030] A second aspect of the present invention provides a method for preparing a monolithic catalyst, the method comprising the following steps:

[0031] (1) Manganese-based material, alumina matrix and dispersant are mixed to obtain manganese oxide suspension, wherein the average valence of manganese in manganese-based material is 3.35-3.95;

[0032] (2) The honeycomb carrier is impregnated in manganese oxide suspension and activated carbon suspension by impregnation method, and then dried and optionally calcined.

[0033] The amounts of manganese-based materials, alumina matrix, activated carbon, and honeycomb support used in the prepared monolithic catalyst are such that, based on the total weight of the monolithic catalyst, the content of honeycomb support is 55-85% by weight, the content of alumina matrix is ​​5-30% by weight, the content of manganese oxide is 5-35% by weight, and the content of activated carbon is 3-20% by weight.

[0034] According to the present invention, preferably, the amounts of manganese-based material, alumina matrix, activated carbon, and honeycomb carrier are such that, based on the total weight of the monolithic catalyst, the content of honeycomb carrier is 60-80% by weight, the content of alumina matrix is ​​5-25% by weight, the content of manganese oxide is 10-25% by weight, and the content of activated carbon is 5-15% by weight.

[0035] According to the present invention, preferably, the specific surface area of ​​the alumina matrix is ​​greater than 100 m². 2 / g, preferably 120-250m 2 / g.

[0036] According to the present invention, preferably, the pore volume of the alumina matrix is ​​0.3-1.5 mL / g, more preferably 0.5-1 mL / g.

[0037] Using an alumina matrix with the above characteristics is beneficial to improving the utilization rate of manganese oxide.

[0038] The present invention does not have any particular limitation on the source of the alumina matrix. It can be obtained commercially or prepared by conventional methods, as long as the above requirements are met.

[0039] According to the present invention, preferably, the specific surface area of ​​the activated carbon is greater than 500 m². 2 / g, preferably 600-800m 2 / g.

[0040] According to the present invention, preferably, the activated carbon has a pore volume of 0.6-1.5 mL / g, more preferably 0.7-1.4 mL / g.

[0041] Using activated carbon with the above characteristics in combination with manganese oxide is beneficial to improving the formaldehyde decomposition efficiency.

[0042] According to the present invention, preferably, the preparation method of the manganese-based material includes the following steps: precipitating a first aqueous solution of a manganese-containing compound and an aqueous solution of a second aqueous solution of a manganese-containing compound, and then crystallizing them to obtain the manganese-based material.

[0043] According to the present invention, preferably, the precipitation conditions include: a temperature of 30-90°C and a time of 0.3-3 hours.

[0044] According to the present invention, preferably, the crystallization conditions include: a temperature of 100-150°C and a time of 1-20 hours.

[0045] Preferably, the method further includes filtering and washing the crystallized product to obtain a manganese-based material.

[0046] The present invention does not particularly limit the specific methods of filtration and washing, and can refer to conventional methods in the field.

[0047] The present invention does not have a particular limitation on the number of washing cycles, but the pH of the detergent used for washing is 7.

[0048] According to the present invention, preferably, the first manganese-containing compound is potassium permanganate and / or sodium permanganate.

[0049] According to the present invention, preferably, the second manganese-containing compound is at least one selected from manganese sulfate, manganese nitrate and manganese acetate.

[0050] In this invention, a first manganese-containing compound containing high-valence manganese and a second manganese-containing compound containing low-valence manganese are reacted to regulate the average valence of manganese in the manganese-based material.

[0051] According to the present invention, preferably, the concentration of the first aqueous solution containing manganese compound is 2-15 wt%.

[0052] According to the present invention, preferably, the concentration of the second manganese-containing aqueous solution is 30-70 wt%.

[0053] In the preparation of the first and second aqueous solutions containing manganese compounds, ultrasonication or stirring can be used to ensure uniform mixing. The same applies to the preparation of the following solutions.

[0054] The present invention does not particularly limit the amount of the first manganese-containing compound and the second manganese-containing compound, but the average valence of manganese in the manganese-based material is within the above-mentioned range.

[0055] According to the present invention, preferably, in the manganese oxide suspension, the D of the manganese-based material 90 The coating size is no larger than 10 micrometers, preferably 1-5 micrometers. This preferred embodiment makes it easier to form a stable coating layer.

[0056] The present invention does not have any particular limitation on how to obtain the average particle size within the above-mentioned range of the manganese-based material, and it can be achieved by conventional technical means, such as grinding.

[0057] According to the present invention, preferably, the mass ratio of manganese-based material to dispersant is 1:0.05-0.8, more preferably 1:0.1-0.4.

[0058] The present invention allows for a wide range of choices of the dispersant. Preferably, the dispersant is selected from at least one of polyvinyl alcohol, acrylic acid, and methyl acrylate.

[0059] According to the present invention, preferably, the manganese oxide suspension also contains water, with the amount of water being 30-200g relative to 1g of manganese-based material.

[0060] According to the present invention, preferably, the manganese oxide suspension does not contain a surfactant. The surfactant can be a conventional choice in the art, and will not be described in detail here.

[0061] According to a specific embodiment of the present invention, step (1) includes: mixing manganese-based material with dispersant and alumina matrix, and then grinding for 1-3 hours to obtain a uniformly mixed manganese oxide suspension.

[0062] According to the present invention, preferably, in the activated carbon suspension, the D of the activated carbon is... 90 The activated carbon is no larger than 10 micrometers, preferably 1-10 micrometers. Using this preferred embodiment, activated carbon with a similar size range comes into more thorough contact with manganese oxide, resulting in efficient adsorption of formaldehyde by the activated carbon and efficient conversion of manganese oxide during the reaction, thus improving the formaldehyde removal rate.

[0063] The present invention does not have any particular limitation on how to obtain the average particle size of the activated carbon within the above-mentioned range, and it can be achieved by conventional technical means, such as grinding.

[0064] According to the present invention, preferably, the concentration of the activated carbon suspension is 50-200 g / L.

[0065] Preferably, activated carbon is dissolved in water to obtain an activated carbon suspension.

[0066] The present invention does not particularly limit the type of the honeycomb carrier, and any conventional choice in the art can be used. Preferably, the honeycomb carrier is selected from at least one of cordierite honeycomb carrier, mullite honeycomb carrier, diamond honeycomb carrier, corundum honeycomb carrier, zirconium corundum honeycomb carrier, quartz honeycomb carrier, nepheline honeycomb carrier, feldspar honeycomb carrier, and metal alloy honeycomb carrier, and more preferably cordierite honeycomb carrier.

[0067] The present invention does not impose any particular limitation on the size of the cellular carrier, and can make appropriate selections according to different application scenarios.

[0068] According to the present invention, preferably, the impregnation method in step (2) includes: contacting the honeycomb carrier with a manganese oxide suspension, and then drying and calcining it to obtain a solid product; contacting the solid product with an activated carbon suspension, and then drying it.

[0069] The present invention does not particularly limit the contact temperature in step (2), and it can be any temperature that the impregnation liquid can reach. There is also no particular limitation on the contact time, as long as the required amount of metal precursor is loaded onto the carrier. Generally, the higher the contact temperature and the greater the concentration of the impregnation liquid, the shorter the time required to achieve the same impregnation amount (i.e., the weight difference between the carrier after impregnation and before impregnation); conversely, the lower the contact temperature and the greater the concentration of the impregnation liquid, the shorter the time required; and vice versa. Once the required impregnation amount and conditions are determined, it is easy to select a suitable contact time. The specific operation of the impregnation method is well known to those skilled in the art. The impregnation method can be a saturated impregnation method or a supersaturated impregnation method. There is no particular limitation on the environment of the impregnation method. It can be carried out under sealed conditions or in an open environment according to conventional methods in the art. Solvent lost during the contact process can be replenished or not. Various gases, such as air, nitrogen, and water vapor, can be introduced during the contact process, or no new components can be introduced.

[0070] The present invention does not particularly limit the specific conditions for drying, and can refer to conventional methods in the art. Preferably, the drying conditions include: a temperature of 80-120°C and a time of 1-5 hours.

[0071] According to the present invention, preferably, the calcination conditions include a temperature of 300-500°C and a time of 1-5 hours. This preferred embodiment is beneficial for improving the oxidation capacity of the catalyst.

[0072] The third aspect of this invention provides the application of the monolithic catalyst described in the first aspect or the monolithic catalyst prepared by the preparation method described in the second aspect in air purification.

[0073] The integral catalyst described in this invention is suitable for purifying one or more volatile organic compounds such as formaldehyde, ozone, and VOCs in the air, and is especially suitable for purifying formaldehyde in the air.

[0074] A fourth aspect of the present invention provides a method for purifying air, the method comprising: contacting formaldehyde-containing air with an integral catalyst;

[0075] The monolithic catalyst is either the monolithic catalyst described in the first aspect or the monolithic catalyst prepared by the preparation method described in the second aspect.

[0076] The monolithic catalyst of this invention can achieve air purification at low temperature and normal pressure. Preferably, the contact conditions include: a temperature of 20-100°C, more preferably 25-50°C; and a volume hourly space velocity of 1000-200000 h⁻¹. -1 Preferably 2000-20000h -1 .

[0077] The monolithic catalyst described in this invention is applicable to treating formaldehyde of varying concentrations. Preferably, the formaldehyde content in the air is 0.1-100 ppm.

[0078] The integral catalyst described in this invention can be used in various applications, including indoor air and in-vehicle air purification, as well as as a filter element for air purifiers and fresh air systems. It is also suitable for use in environments with high air velocity and low concentration of pollutants.

[0079] The present invention will be described in detail below through embodiments.

[0080] In the following examples, the concentrations of carbon monoxide, sulfur dioxide, and volatile organic compounds in the exhaust gas were measured by gas chromatography.

[0081] Example 1

[0082] Preparation of manganese oxide suspension: 3.97 g of potassium permanganate was dissolved in 32.15 g of deionized water, heated to 60 °C and stirred to form a potassium permanganate solution. This solution was then mixed with 7.26 g of 50% manganese sulfate solution for 3 h, and reacted at 130 °C for 18 h. The resulting brown precipitate was filtered and washed multiple times with deionized water until the pH of the washing solution reached 7. The resulting filter cake was a manganese-based material. The average valence of manganese in the manganese-based material was 3.84. The manganese-based material was ground to D using a ball mill. 90 The surface area is 5 micrometers, then polyvinyl alcohol (Shanghai Petrochemical) and alumina matrix (specific surface area 165 m²) are added. 2 The mixture of polyvinyl alcohol (polyvinyl alcohol), manganese-based material (0.56 mL / g), and water, wherein the mass ratio of polyvinyl alcohol to manganese-based material to water is 1:10:88, was further ground in a ball mill for 2 hours to obtain a manganese oxide suspension.

[0083] Impregnated with manganese oxide suspension: The cordierite honeycomb carrier was impregnated in the manganese oxide suspension for 2 min, then dried at 80 °C for 3 h, and calcined at 500 °C for 2 h to obtain a solid product.

[0084] Impregnated activated carbon suspension: Take activated carbon (specific surface area 650 m²) 2 / g, pore volume 1.1mL / g), placed in water, and ground with a ball mill to D 90 The sample was 10 micrometers in diameter, and an activated carbon suspension with a concentration of 150 g / L was obtained. The solid product was then immersed in the activated carbon suspension for 2 minutes and dried at 120°C for 3 hours to obtain the monolithic catalyst A1. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0085] Example 2

[0086] Preparation of manganese oxide suspension: 3.56 g of potassium permanganate was dissolved in 40.55 g of deionized water, heated to 60 °C and stirred to form a potassium permanganate solution. This solution was then mixed with 6.74 g of 50% manganese sulfate solution for 3 h, and reacted at 130 °C for 18 h. The resulting brown precipitate was filtered and washed multiple times with deionized water until the pH of the washing solution reached 7. The resulting filter cake was a manganese-based material. The average valence of manganese in the manganese-based material was 3.84. The manganese-based material was ground to D using a ball mill. 90 The surface area is 5 micrometers, then an acrylic acid and alumina matrix (specific surface area 178 m²) is added. 2 The mixture of acrylic acid, manganese-based material and water (with a pore volume of 0.76 mL / g) was further ground in a ball mill for 2 hours to obtain a manganese oxide suspension.

[0087] Impregnated with manganese oxide suspension: The cordierite honeycomb carrier was impregnated in the manganese oxide suspension for 2 min, then dried at 80 °C for 3 h, and calcined at 500 °C for 2 h to obtain a solid product.

[0088] Impregnated activated carbon suspension: Take activated carbon (specific surface area 700 m²) 2 / g, pore volume 1.15mL / g), placed in water, and ground with a ball mill to D 90 The sample was 8 micrometers in diameter, and an activated carbon suspension with a concentration of 150 g / L was obtained. The solid product was then immersed in the activated carbon suspension for 2 minutes and dried at 120°C for 3 hours to obtain the monolithic catalyst A2. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0089] Example 3

[0090] Preparation of manganese oxide suspension: 4.02 g of potassium permanganate was dissolved in 40.55 g of deionized water, heated to 60 °C and stirred to form a potassium permanganate solution. This solution was then mixed with 7.26 g of 50% manganese sulfate solution for 3 h, and reacted at 130 °C for 18 h. The resulting brown precipitate was filtered and washed multiple times with deionized water until the pH of the washing solution reached 7. The resulting filter cake was a manganese-based material. The average valence of manganese in the manganese-based material was 3.56. The manganese-based material was ground to D using a ball mill. 90 The surface area is 3 micrometers, then polyvinyl alcohol (Shanghai Petrochemical) and alumina matrix (specific surface area 102 m²) are added. 2 The mixture of polyvinyl alcohol (polyvinyl alcohol), manganese-based material (0.41 mL / g), and water, wherein the mass ratio of polyvinyl alcohol to manganese-based material to water is 1:10:88, was further ground in a ball mill for 2 hours to obtain a manganese oxide suspension.

[0091] Impregnated with manganese oxide suspension: The cordierite honeycomb carrier was impregnated in the manganese oxide suspension for 2 min, then dried at 80 °C for 3 h, and calcined at 500 °C for 2 h to obtain a solid product.

[0092] Impregnated activated carbon suspension: Take activated carbon (specific surface area 650 m²) 2 / g, pore volume 1.1mL / g), placed in water, and ground with a ball mill to D 90 The sample was 6 micrometers in diameter, and an activated carbon suspension with a concentration of 150 g / L was obtained. The solid product was then immersed in the activated carbon suspension for 2 minutes and dried at 120°C for 3 hours to obtain the monolithic catalyst A3. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0093] Example 4

[0094] Preparation of manganese oxide suspension: 6.15 g of potassium permanganate was dissolved in 40.55 g of deionized water, heated to 60 °C and stirred to form a potassium permanganate solution. This solution was then mixed with 6.14 g of a 50% (w / w) manganese sulfate solution for 3 h, and reacted at 130 °C for 18 h. The resulting brown precipitate was filtered and washed multiple times with deionized water until the pH of the washing solution reached 7. The resulting filter cake was a manganese-based material. The average valence of manganese in the manganese-based material was 3.92. The manganese-based material was ground to D using a ball mill. 90 The surface area is 5 micrometers, then polyvinyl alcohol (Shanghai Petrochemical) and alumina matrix (specific surface area 136 m²) are added. 2 The mixture of polyvinyl alcohol (polyvinyl alcohol), manganese-based material (0.66 mL / g), and water, wherein the mass ratio of polyvinyl alcohol to manganese-based material to water is 1:10:88, was further ground in a ball mill for 2 hours to obtain a manganese oxide suspension.

[0095] Impregnated with manganese oxide suspension: The cordierite honeycomb carrier was impregnated in the manganese oxide suspension for 2 min, then dried at 80 °C for 3 h, and calcined at 500 °C for 2 h to obtain a solid product.

[0096] Impregnated activated carbon suspension: Take activated carbon (specific surface area 650 m²) 2 / g, pore volume 1.1mL / g), placed in water, and ground with a ball mill to D 90 The sample was 10 micrometers in diameter, and an activated carbon suspension with a concentration of 150 g / L was obtained. The solid product was then immersed in the activated carbon suspension for 2 minutes and dried at 120°C for 3 hours to obtain the monolithic catalyst A4. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0097] Example 5

[0098] The method of Example 1 was followed, except that the alumina matrix used in the preparation of the manganese oxide suspension had a specific surface area of ​​90 m². 2 / g, pore volume 0.34mL / g.

[0099] The monolithic catalyst A5 was obtained. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0100] Example 6

[0101] The method of Example 1 was followed, except that the manganese-based material was ground to D during the preparation of the manganese oxide suspension. 90 It is 20 micrometers.

[0102] The monolithic catalyst A6 was obtained. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0103] Example 7

[0104] The method described in Example 1 was followed, except that the activated carbon was ground to D during the preparation of the activated carbon suspension. 90 It is 30 micrometers.

[0105] The monolithic catalyst A7 was obtained. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0106] Example 8

[0107] The procedure was carried out according to Example 1, except that the activated carbon used had a specific surface area of ​​550 m². 2 / g, pore volume 0.65mL / g.

[0108] The monolithic catalyst A8 was obtained. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0109] Comparative Example 1

[0110] The method of Example 1 was followed, except that potassium permanganate was not added, but only manganese sulfate was added, so that the manganese oxide content in the prepared monolithic catalyst was still 16% by weight. Specifically, manganese sulfate was mixed with alumina matrix, polyvinyl alcohol and water to obtain a manganese-containing solution.

[0111] The monolithic catalyst D1 was obtained. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0112] Comparative Example 2

[0113] The method was carried out according to Example 1, except that manganese sulfate was not added, only potassium permanganate was added, so that the manganese oxide content in the prepared monolithic catalyst was still 16% by weight. Specifically, potassium permanganate was mixed with alumina matrix, polyvinyl alcohol and water to obtain a manganese-containing solution.

[0114] The monolithic catalyst D2 was obtained. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0115] Comparative Example 3

[0116] The procedure was carried out according to Example 1, except that activated carbon was not added, and the resulting solid product was catalyst D3.

[0117] The monolithic catalyst D3 was obtained. The composition and characteristics of the monolithic catalyst are shown in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] Test Example 1

[0122] This test case includes coating stability testing and formaldehyde removal capability testing. The coating stability test is measured by the weight loss after 30 minutes of ultrasonic testing at 50 Hz.

[0123] Formaldehyde removal test: The monolithic catalysts prepared in the examples and comparative examples were weighed and placed in fixed-bed reactors. Then, air containing formaldehyde (formaldehyde concentration of 10 ppm, O2 of 21% by volume, and the remainder N2) was introduced into the fixed-bed reactors. The reaction was carried out at room temperature and atmospheric pressure, and the volume hourly space velocity of the reaction was 20,000 h⁻¹. -1 Samples were taken for analysis after 5 hours of reaction, and the formaldehyde concentration in the product was recorded. The mixed gas after the reaction was passed into the tail gas absorption tank. After testing and confirming that it met environmental protection requirements, it could be further treated or vented.

[0124] Table 2

[0125]

[0126]

[0127] Test Example 2

[0128] Formaldehyde removal test: Conducted according to the method in Test Example 1, with the following difference:

[0129] Activated carbon particles (30-60 mesh) with a mass ratio of 7:93 and the catalyst prepared in Comparative Example 3 were placed sequentially in a fixed-bed reactor. Formaldehyde-containing air was then passed through the activated carbon first, followed by the catalyst prepared in Comparative Example 3. The results are shown in Table 3.

[0130] Table 3

[0131] Example number <![CDATA[Formaldehyde concentration of the product / (mg / m 3 )]]> Test Example 2 2.11

[0132] As can be seen from the results in Table 2-3, the stability and formaldehyde removal capacity of the integral catalyst coating provided by the present invention are greatly improved, and it has significantly higher purification accuracy in the formaldehyde purification reaction.

[0133] As can be seen from Table 2, the integral catalyst coating described in this invention has good stability, better catalyst performance, and longer lifespan.

[0134] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A monolithic catalyst, said catalyst comprising a honeycomb support and an alumina matrix, manganese oxide, and activated carbon supported on the honeycomb support; based on the total weight of the monolithic catalyst, the content of the honeycomb support is 60-80% by weight, the content of the alumina matrix is ​​5-25% by weight, the content of the manganese oxide is 10-25% by weight, and the content of the activated carbon is 5-15% by weight. in, The average valence of manganese in the monolithic catalyst is 3.41-3.95; The preparation method of the monolithic catalyst includes the following steps: (1) Manganese-based material, alumina matrix and dispersant are mixed to obtain manganese oxide suspension, wherein the average valence of manganese in manganese-based material is 3.41-3.95; (2) The honeycomb carrier is contacted with manganese oxide suspension by impregnation, and then dried and calcined to obtain a solid product; the solid product is contacted with activated carbon suspension and then dried.

2. The catalyst according to claim 1, wherein, The honeycomb carrier is selected from at least one of cordierite honeycomb carrier, mullite honeycomb carrier, diamond honeycomb carrier, corundum honeycomb carrier, zirconium corundum honeycomb carrier, quartz honeycomb carrier, nepheline honeycomb carrier, feldspar honeycomb carrier, alumina honeycomb carrier, and metal alloy honeycomb carrier.

3. The catalyst according to claim 2, wherein, The honeycomb carrier is selected from cordierite honeycomb carrier.

4. A method for preparing the monolithic catalyst according to any one of claims 1-3, the method comprising the following steps: (1) Manganese-based material, alumina matrix and dispersant are mixed to obtain manganese oxide suspension, wherein the average valence of manganese in manganese-based material is 3.41-3.95; (2) The honeycomb carrier is contacted with manganese oxide suspension by impregnation, and then dried and calcined to obtain a solid product; the solid product is contacted with activated carbon suspension and then dried.

5. The method according to claim 4, wherein, The specific surface area of ​​the alumina matrix is ​​greater than 100 m². 2 / g, with a pore volume of 0.3-1.5mL / g.

6. The method according to claim 5, wherein, The specific surface area of ​​the alumina matrix is ​​120-250 m². 2 / g, pore volume is 0.5-1mL / g.

7. The method according to claim 4, wherein, The specific surface area of ​​the activated carbon is greater than 500 m². 2 / g, with a pore volume of 0.6-1.5mL / g.

8. The method according to claim 7, wherein, The specific surface area of ​​the activated carbon is 600-800 m². 2 / g, with a pore volume of 0.7-1.4mL / g.

9. The method according to any one of claims 4-8, wherein, The preparation method of the manganese-based material includes the following steps: precipitating a first aqueous solution of a manganese-containing compound and an aqueous solution of a second aqueous solution of a manganese-containing compound, and then crystallizing them to obtain the manganese-based material.

10. The method according to claim 9, wherein, The precipitation conditions include a temperature of 30-90℃ and a time of 0.3-3h.

11. The method according to claim 9, wherein, The crystallization conditions include a temperature of 100-150℃ and a time of 1-20h.

12. The method according to claim 9, wherein, The first manganese-containing compound is potassium permanganate and / or sodium permanganate.

13. The method according to claim 12, wherein, The concentration of the first aqueous solution containing manganese compound is 2-15 wt%.

14. The method according to claim 9, wherein, The second manganese-containing compound is at least one of manganese sulfate, manganese nitrate, and manganese acetate.

15. The method according to claim 14, wherein, The concentration of the second manganese-containing aqueous solution is 30-70 wt%.

16. The method according to any one of claims 4-8, wherein, In manganese oxide suspension, the D of manganese-based materials 90 No larger than 10 micrometers.

17. The method according to claim 16, wherein, In manganese oxide suspension, the D of manganese-based materials 90 It is 1-5 micrometers.

18. The method according to any one of claims 4-8, wherein, The mass ratio of the manganese-based material to the dispersant is 1:0.05-0.

8.

19. The method according to claim 18, wherein, The mass ratio of the manganese-based material to the dispersant is 1:0.1-0.

4.

20. The method according to any one of claims 4-8, wherein, The dispersant is selected from at least one of polyvinyl alcohol, acrylic acid, and methyl acrylate.

21. The method according to any one of claims 4-8, wherein, The manganese oxide suspension does not contain surfactants.

22. The method according to any one of claims 4-8, wherein, In activated carbon suspension, the D of activated carbon 90 No larger than 10 micrometers.

23. The method according to claim 22, wherein, In activated carbon suspension, the D of activated carbon 90 It ranges from 1 to 10 micrometers.

24. The method according to any one of claims 4-8, wherein, The concentration of the activated carbon suspension is 50-200 g / L.

25. The method according to claim 4, wherein, The roasting conditions include: a temperature of 300-500℃ and a time of 1-5 hours.

26. A method for purifying air, the method comprising: Formaldehyde-containing air is brought into contact with the integral catalyst; The monolithic catalyst is the monolithic catalyst according to any one of claims 1-3 or the monolithic catalyst prepared by the preparation method according to any one of claims 4-25.

27. The method according to claim 26, wherein, The contact conditions include: a temperature of 20-100°C and a volume hourly space velocity of 1000-200000 h⁻¹. -1 .

28. The method according to claim 27, wherein, The contact conditions include: a temperature of 20-50°C and a volume hourly space velocity of 2000-20000 h⁻¹. -1 .

29. The method according to any one of claims 26-28, wherein, The formaldehyde content in the air is 0.1-10 ppm.

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