Co- scr denitration catalyst, preparation method and application thereof

Abstract

The application belongs to the technical field of denitration catalysts, and discloses a CO-SCR denitration catalyst, a preparation method and application thereof. The preparation method comprises the following steps: (1) placing a honeycomb cordierite in a muffle furnace for preliminary calcination to obtain a carrier; (2) immersing the carrier in a mixed solution containing an aluminum source and an alkaline nitrogen source for hydrothermal treatment, taking out the carrier after the hydrothermal treatment for washing and drying to obtain a surface modified carrier; (3) preparing a bottom coating liquid containing catalyst powder and a first pore-forming agent; preparing a surface coating liquid containing catalyst powder and a second pore-forming agent; wherein the average particle size of the first pore-forming agent is greater than that of the second pore-forming agent; (4) immersing the surface modified carrier in the bottom coating liquid for coating, after preliminary drying, immersing the surface modified carrier in the surface coating liquid for coating, and after drying treatment, obtaining a catalyst precursor; (5) performing calcination treatment on the catalyst precursor to obtain a CO-SCR denitration catalyst.

Description

Technical Field

[0001] This invention relates to the technical field of denitrification catalysts, and more specifically, to CO-SCR denitrification catalysts, their preparation methods, and applications. Background Technology

[0002] With the rapid development of the global economy and the accelerating pace of industrialization, environmental pollution problems are becoming increasingly serious. Nitrogen oxides (NOx) x NO and carbon monoxide (CO) are major air pollutants that have attracted widespread attention. x Not only is NO a key component of acid rain and photochemical smog, but it also poses a serious threat to human health. Carbon monoxide is a toxic gas, and long-term exposure can lead to respiratory and cardiovascular diseases. Therefore, developing efficient purification technologies to reduce NO is crucial. x CO emissions have become an important research direction in the field of environmental protection.

[0003] Currently, selective catalytic reduction (SCR) technology is the main method for removing NO. x The mainstream technology is SCR. Traditional SCR catalysts are usually based on vanadium-titanium or zeolite-based materials, using ammonia as a reducing agent. However, this traditional NH3-SCR technology has obvious limitations: first, under high temperature and complex flue gas conditions, the catalyst has a narrow activity window and poor tolerance to SO2 and H2O; second, ammonia itself is corrosive and toxic, and "ammonia escape" is prone to occur during use, causing secondary pollution. In contrast, CO-SCR technology uses CO, a pollutant already present in the flue gas, as a reducing agent to reduce NO. x This not only avoids the problem of ammonia escape, but also removes two pollutants at the same time, achieving "waste treatment with waste", and has great application potential.

[0004] Based on the manufacturing process, monolithic honeycomb catalysts are mainly divided into two categories: extrusion and coating. Extrusion catalysts are formed by directly extruding a mixture of active components and slurry. While the active components are evenly distributed, the mechanical strength is relatively low, and the expensive active components are embedded within the framework, resulting in low utilization. In contrast, coating catalysts involve attaching a slurry containing active components to the surface of a high-strength inert support (such as cordierite). This offers advantages such as high mechanical strength, good thermal shock resistance, low back pressure, and concentrated active components on the surface, making it particularly suitable for treating flue gas from mobile sources or stationary sources with complex operating conditions.

[0005] However, existing coated CO-SCR catalysts still face severe technical bottlenecks in their preparation and application, mainly in the following two aspects: Firstly, the coatings prepared by traditional coating processes are often structurally simple and relatively dense, resulting in greater diffusion resistance of gases within the coating and hindering the reaction of gases (CO and NO). xThe inert support has difficulty reaching the active sites in the substrate, resulting in low utilization of the active components. On the other hand, due to the smooth surface and high chemical inertness of the inert support, the active components are difficult to adhere firmly when directly coated. In practical applications, the coating is easily cracked or peeled off due to the combined effects of high-speed airflow and thermal expansion and contraction, leading to a significant reduction in catalyst life. Although adhesion can be improved by adding excessive binder, this not only physically covers the active sites on the catalyst surface but also easily blocks the micro-reaction channels, resulting in a significant decrease in the denitrification performance of the catalyst. It is difficult to achieve a balance between "high adhesion strength" and "high catalytic activity". Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a CO-SCR denitrification catalyst with high mechanical stability and denitrification efficiency, its preparation method and application, and the technical solution is as follows:

[0007] The preparation method of CO-SCR denitration catalyst includes the following steps:

[0008] (1) The honeycomb cordierite was placed in a muffle furnace for preliminary calcination to obtain a carrier;

[0009] (2) The carrier is immersed in a mixed solution containing aluminum source and alkaline nitrogen source for hydrothermal treatment. After hydrothermal treatment, it is taken out, washed and dried to obtain surface modified carrier.

[0010] (3) Prepare a bottom coating liquid containing catalyst powder and a first pore-forming agent; prepare a top coating liquid containing catalyst powder and a second pore-forming agent; wherein the average particle size of the first pore-forming agent is greater than the average particle size of the second pore-forming agent.

[0011] (4) The surface-modified carrier is immersed in the bottom coating liquid for coating. After preliminary drying, it is immersed in the top coating liquid for coating. After drying, the catalyst precursor is obtained.

[0012] (5) The catalyst precursor is calcined to obtain CO-SCR denitrification catalyst.

[0013] As a further improvement to the above preparation method: in step (1), the initial calcination is carried out at 300-500℃ for 2-4 hours.

[0014] As a further improvement to the above preparation method: in step (2), the hydrothermal treatment is carried out in a high-pressure reactor and kept at 120-150°C for 4-6 hours; the aluminum sol in the mixed solution is an aluminum source with a mass fraction of 5-15%, and the alkaline nitrogen source is urea with a mass fraction of 10-20%.

[0015] As a further improvement to the above preparation method: In step (3), the particle size of the catalyst powder is 0.5-3 micrometers. The preparation method is as follows: at least one of copper nitrate, cobalt nitrate, cerium nitrate, and iron nitrate is dissolved in deionized water to prepare a mixed precursor solution; a precipitant is added dropwise to the mixed precursor solution under stirring conditions; after the reaction is completed, the precipitate is collected and washed, dried, pulverized and calcined in sequence to obtain the catalyst powder; the precipitant is at least one of sodium carbonate solution, sodium bicarbonate solution or ammonia water.

[0016] As a further improvement to the above preparation method: the total metal ion concentration of the mixed precursor solution is 0.5-1.2 mol / L; the precipitant is a sodium carbonate solution with a concentration of 1.0-2.0 mol / L, and the pH at the reaction endpoint is 8.5-9.5; calcination is carried out in an air atmosphere and kept at 500-600℃ for 3-5 hours.

[0017] As a further improvement to the above preparation method: In step (3): the bottom coating liquid and the top coating liquid also contain additives, the additives including Tween-20 and glass fiber; the bottom coating liquid and the top coating liquid are both prepared by deionized water and binder, and the amount of deionized water and binder added is controlled according to making the viscosity of the bottom coating liquid 480-600 mPa·s and the viscosity of the top coating liquid 200-350 mPa·s; the first pore-forming agent is polystyrene microspheres or camphor powder with a particle size of 1-5 micrometers; in the bottom coating liquid, the mass ratio of catalyst powder, additive and first pore-forming agent is (70-80):(15-20):(5-10); the second pore-forming agent is carbon nanospheres with a particle size of 10-50 nanometers; in the top coating liquid, the mass ratio of catalyst powder, additive and second pore-forming agent is (80-85):(10-15):(3-5).

[0018] As a further improvement to the above preparation method: in step (4), microwave drying is used, with a microwave frequency of 2450MHz, a power of 500-800 watts, and a processing time of 1-5 minutes.

[0019] As a further improvement to the above preparation method: in step (5), the calcination treatment is to keep warm at 500-600℃ for 3-5 hours.

[0020] The CO-SCR denitrification catalyst was prepared by the method described above.

[0021] The flue gas purification method uses the aforementioned CO-SCR denitrification catalyst to remove NO from the flue gas. x CO is converted into N2 and CO2, respectively.

[0022] The CO-SCR denitration catalyst, its preparation method, and its application of the present invention have the following advantages:

[0023] (1) This invention first removes organic residues from the surface and pores of the carrier through preliminary calcination, clears the micropores, and restores the specific surface area, providing a clean, hydrophilic, and structurally open carrier for subsequent steps. Then, an aluminum source is used to grow an aluminum-based transition layer (such as boehmite or a thin layer of alumina) rich in hydroxyl groups in situ on the smooth surface of cordierite under high temperature and high pressure. This not only greatly increases the specific surface area and roughness of the carrier, providing more physical anchor points, but also allows the active hydroxyl groups on the surface to form strong chemical bonds with the components in the subsequent coating solution. The addition of an alkaline nitrogen source plays a role in adjusting the pH value and inducing crystal growth, optimizing the microstructure of the transition layer. Thus, by using preliminary calcination and hydrothermal treatment of the carrier with aluminum and nitrogen sources, the interfacial bonding force between the carrier and the active coating is significantly enhanced, effectively solving the problem of easy peeling of traditional coatings and greatly improving the coating's resistance to airflow erosion and thermal shock stability.

[0024] (2) This invention adds a first pore-forming agent with a larger average particle size to the bottom coating liquid and a second pore-forming agent with a smaller average particle size to the top coating liquid. After calcination, a through-pore structure is formed in the bottom layer and a rich mesoporous structure is formed in the top layer. The through-pore structure in the bottom layer acts as a "highway" for rapid gas transport, which can significantly reduce the diffusion resistance of gas deep in the coating and prevent reactants or products from accumulating in the bottom layer. The rich mesoporous structure in the top layer provides a huge specific surface area and sufficient reactive sites, ensuring that the gas can react rapidly when it comes into contact with the catalyst surface. In particular, due to the reduction of NO by CO x The reaction rate is limited by the diffusion of CO within the micropores. The macroporous structure at the bottom layer specifically solves the mass transfer hysteresis problem of CO molecules in the thick coating, significantly improving the low-temperature ignition activity. Thus, a double-layer gradient pore structure is formed inside the coating, significantly improving the overall utilization rate of the active components and the denitrification efficiency of the catalyst.

[0025] (3) This invention first provides a stable substrate for the construction of a double-layer gradient coating through preliminary calcination and surface modification. Then, through stepwise coating and calcination, a tight interlayer interaction is formed between the upper and lower coatings and between the coating and the carrier, avoiding interlayer delamination. At the same time, the gradient distribution of the pore-forming agent also alleviates the thermal stress concentration of the coating during high-temperature calcination and reaction, further suppressing the generation of microcracks. It can be seen that the preparation process of this invention achieves deep synergy between each step and each component, improving catalytic performance while ensuring mechanical strength.

[0026] In summary, this invention organically combines the preliminary calcination and surface modification of the carrier with the double-layer gradient pore-forming technology, successfully constructing a CO-SCR denitrification catalyst with high mechanical stability, excellent diffusion performance, and high catalytic activity. It effectively solves the core problems in the prior art, such as poor coating adhesion, simple pore structure, and low utilization rate of active sites. It is particularly suitable for flue gas denitrification treatment under high space velocity and complex working conditions, and has strong practicality in the field of industrial waste gas treatment and environmental protection.

[0027] The embodiments of the invention provided in this specification will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the embodiments of the invention provided in this specification will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the invention provided in this specification. Attached Figure Description

[0028] The accompanying drawings, which form part of the embodiments of the invention provided in this specification, are used to aid in understanding the embodiments of the invention provided in this specification. The content provided in the drawings and the related descriptions in the embodiments of the invention provided in this specification can be used to explain the embodiments of the invention provided in this specification, but do not constitute an undue limitation on the embodiments of the invention provided in this specification. In the drawings:

[0029] Figure 1 The nitrogen adsorption-desorption isotherm of the CO-SCR denitrification catalyst in Example 1 is shown.

[0030] Figure 2 This is a diagram of the catalytic performance testing device of the present invention. Detailed Implementation

[0031] The embodiments of the invention provided in this specification will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. Before describing the embodiments of the invention provided in this specification in conjunction with the accompanying drawings, it should be particularly noted that:

[0032] The technical solutions and features provided in the embodiments of the invention provided in this specification, including the following description, can be combined with each other without conflict.

[0033] Furthermore, the embodiments of the inventions provided in this specification mentioned below are generally only a portion of the embodiments of the inventions provided in this specification, and not all of them. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the inventions provided in this specification without creative effort should fall within the scope of protection of the embodiments of the inventions provided in this specification.

[0034] Regarding the terminology and units in the embodiments of the invention provided in this specification: The terms "comprising," "including," "having," and any variations thereof in the description, claims, and related parts of the embodiments of the invention provided in this specification are intended to cover non-exclusive inclusion. Furthermore, other relevant terms and units in the embodiments of the invention provided in this specification can be reasonably interpreted based on the relevant content of the embodiments of the invention provided in this specification.

[0035] Example 1

[0036] The preparation method of the CO-SCR denitration catalyst in this embodiment includes the following steps:

[0037] (1) Place the honeycomb cordierite into a muffle furnace, heat it from room temperature to 400°C at a heating rate of 5°C / min and keep it at that temperature for 3 hours. The carrier is obtained by cooling it with the furnace.

[0038] (2) The carrier is immersed in a mixed solution of 5% aluminum sol and 10% urea and placed in a high-pressure reactor for hydrothermal treatment. The solution is kept at 150°C for 4 hours. After the reaction is completed, the carrier is taken out, washed and dried to obtain the surface-modified carrier.

[0039] (3) Dissolve cobalt nitrate and cerium nitrate in deionized water at a molar ratio of 1:1.5 to prepare a mixed precursor solution with a total metal ion concentration of 1 mol / L; under stirring conditions, add sodium carbonate solution with a concentration of 1.5 mol / L as a precipitant to the solution until the pH value at the reaction endpoint reaches 9; collect the precipitate and wash, dry and pulverize it in sequence; in an air atmosphere, heat from room temperature to 550℃ at a heating rate of 5℃ / min and keep it at that temperature for 4 hours to obtain catalyst powder with a particle size of 0.5-3 micrometers.

[0040] Preparation of the undercoating solution: Weigh and mix the catalyst powder, additives, and first pore-forming agent in a mass ratio of 75:18:8, then add and adjust the amount of deionized water and binder to make the slurry viscosity 489 mPa·s, thus obtaining the undercoating solution; wherein, the first pore-forming agent is selected as polystyrene microspheres with a particle size of 1-5 micrometers.

[0041] Preparation of surface coating solution: Weigh and mix the catalyst powder, additives, and second pore-forming agent in a mass ratio of 82:13:4, then add and adjust the amount of deionized water and binder to make the slurry viscosity 205 mPa·s, thus obtaining the surface coating solution; wherein, the second pore-forming agent is selected as carbon nanospheres with a particle size of 10-50 nanometers.

[0042] The additives are Tween-20 and glass fiber in a mass ratio of 1.2:1, with the glass fiber having a diameter of 10-15 micrometers and a length of 20-50 micrometers.

[0043] (4) First, the surface-modified carrier is immersed in the bottom coating solution for coating, and then removed and pre-dried (dried at 50°C for 5 minutes); then immersed in the top coating solution for secondary coating; after coating, microwave dried for 3 minutes at 2450MHz and 600W to obtain the catalyst precursor.

[0044] (5) The catalyst precursor is placed in a muffle furnace and heated from room temperature to 550°C at a heating rate of 5°C / min and held for 4 hours to obtain the CO-SCR denitrification catalyst.

[0045] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 62.2% at 250°C, 94.4% at 280°C, and 96.2% at 350°C.

[0046] The coating loading of the CO-SCR denitrification catalyst is 25.01 g / 100 g, and the coating strength is 98.6%.

[0047] Example 2

[0048] Compared with Example 1, the preparation method of the CO-SCR denitrification catalyst in this example is different in that: the mass fraction of aluminum sol is 15%, the mass fraction of urea is 20%, and the temperature is maintained at 120°C for 6 hours.

[0049] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 60.2% at 250°C, 93.5% at 280°C, and 95.5% at 350°C.

[0050] The coating loading of the CO-SCR denitrification catalyst is 24.65 g / 100 g, and the coating strength is 95.4%.

[0051] Example 3

[0052] Compared with Example 1, the preparation method of the CO-SCR denitrification catalyst in this example is different in that the mass ratio of catalyst powder, additives and first pore-forming agent is 70:15:5; and the mass ratio of catalyst powder, additives and second pore-forming agent is 80:10:3.

[0053] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 56.9% at 250°C, 92.7% at 280°C, and 93.8% at 350°C.

[0054] The coating loading of the CO-SCR denitrification catalyst is 24.34 g / 100 g, and the coating strength is 94.8%.

[0055] Example 4

[0056] Compared with Example 1, the preparation method of the CO-SCR denitrification catalyst in this example is different in that: the mass ratio of catalyst powder, additive, and first pore-forming agent is 80:20:10; and the mass ratio of catalyst powder, additive, and second pore-forming agent is 85:15:5.

[0057] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 54.3% at 250°C, 90.7% at 280°C, and 91.8% at 350°C.

[0058] The coating loading of the CO-SCR denitrification catalyst is 25.81 g / 100 g, and the coating strength is 93.7%.

[0059] Example 5

[0060] Compared with Example 1, the difference in the preparation method of the CO-SCR denitrification catalyst in this example is that the viscosity of the bottom coating liquid is 497 mPa·s and the viscosity of the surface coating liquid is 215 mPa·s.

[0061] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 61.5% at 250°C, 94.0% at 280°C, and 95.9% at 350°C.

[0062] The coating loading of the CO-SCR denitrification catalyst is 25.32 g / 100 g, and the coating strength is 98.1%.

[0063] Example 6

[0064] Compared with Example 1, the difference in the preparation method of the CO-SCR denitrification catalyst in this example is that the viscosity of the bottom coating liquid is 524 mPa·s and the viscosity of the surface coating liquid is 268 mPa·s.

[0065] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 60.4% at 250°C, 93.2% at 280°C, and 95.1% at 350°C.

[0066] The coating loading of the CO-SCR denitrification catalyst is 25.88 g / 100 g, and the coating strength is 97.4%.

[0067] Example 7

[0068] Compared with Example 1, the difference in the preparation method of the CO-SCR denitrification catalyst in this example is that the viscosity of the bottom coating liquid is 550 mPa·s and the viscosity of the surface coating liquid is 298 mPa·s.

[0069] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 58.7% at 250°C, 92.1% at 280°C, and 94.3% at 350°C.

[0070] The coating loading of the CO-SCR denitrification catalyst is 26.45 g / 100 g, and the coating strength is 96.5%.

[0071] Example 8

[0072] Compared with Example 1, the difference in the preparation method of the CO-SCR denitrification catalyst in this example is that the viscosity of the bottom coating liquid is 598 mPa·s and the viscosity of the surface coating liquid is 347 mPa·s.

[0073] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 58.1% at 250°C, 91.2% at 280°C, and 93.5% at 350°C.

[0074] The coating loading of the CO-SCR denitrification catalyst is 27.12 g / 100 g, and the coating strength is 95.2%.

[0075] Compare with Example 1

[0076] Compared with Example 1, the difference in the preparation method of the CO-SCR denitration catalyst in this comparative example is that step (1) was not performed.

[0077] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 48.5% at 250°C, 85.6% at 280°C, and 88.2% at 350°C.

[0078] The coating loading of the CO-SCR denitrification catalyst is 24.8 g / 100 g, and the coating strength is 88.5%.

[0079] Compare with Example 2

[0080] Compared with Example 1, the difference in the preparation method of the CO-SCR denitrification catalyst in this comparative example is that steps (1) and (2) were not performed.

[0081] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 42.3% at 250°C, 78.4% at 280°C, and 81.5% at 350°C.

[0082] The coating loading of the CO-SCR denitrification catalyst is 18.56 g / 100 g, and the coating strength is 72.3%.

[0083] Compare with Example 3

[0084] Compared with Example 1, the difference in the preparation method of the CO-SCR denitrification catalyst in this comparative example is that the bottom coating liquid is coated twice, and the surface coating liquid is not coated.

[0085] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 51.2% at 250°C, 87.5% at 280°C, and 89.8% at 350°C.

[0086] The coating loading of the CO-SCR denitrification catalyst is 26.5 g / 100 g, and the coating strength is 96.8%.

[0087] Compare with Example 4

[0088] Compared with Example 1, the difference in the preparation method of the CO-SCR denitration catalyst in this comparative example is that neither the bottom coating liquid nor the top coating liquid contains a pore-forming agent.

[0089] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 35.6% at 250°C, 68.2% at 280°C, and 72.4% at 350°C.

[0090] The coating loading of the CO-SCR denitrification catalyst is 26.12 g / 100 g, and the coating strength is 98.8%.

[0091] Compare with Example 5

[0092] Compared with Example 1, the difference in the preparation method of the CO-SCR denitration catalyst in this comparative example is that the viscosity of the bottom coating liquid is 612 mPa·s.

[0093] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 52.8% at 250°C, 85.5% at 280°C, and 89.1% at 350°C.

[0094] The coating loading of the CO-SCR denitrification catalyst is 27.45 g / 100 g, and the coating strength is 93.4%.

[0095] Compare with Example 6

[0096] Compared with Example 1, the difference in the preparation method of the CO-SCR denitration catalyst in this comparative example is that the viscosity of the surface coating liquid is 358 mPa·s.

[0097] Tests showed that for a mixed gas containing NO, CO and O2, the CO-SCR denitrification catalyst of this embodiment had a denitrification efficiency of 49.5% at 250°C, 86.2% at 280°C, and 88.7% at 350°C.

[0098] The coating loading of the CO-SCR denitrification catalyst is 26.80 g / 100 g, and the coating strength is 92.1%.

[0099] Figure 1 The nitrogen adsorption-desorption isotherm is shown for the CO-SCR denitrification catalyst in Example 1. Figure 1 As shown, the curve exhibits the characteristics of a type IV isotherm, accompanied by a type H3 hysteresis loop, indicating that the material has a rich mesoporous structure; the adsorption amount in the low-pressure region and the unsaturated adsorption in the high-pressure region indicate the simultaneous existence of microporous and macroporous structures.

[0100] Figure 2 This is a diagram of the catalytic performance testing apparatus of the present invention. Figure 2 As shown, N2, NO, O2, and CO are mixed in a mixing bottle to form a mixed gas. The concentration of NO in the mixed gas is 500 ppm, the concentration of O2 is 15 vol%, the concentration of CO is 2500 ppm, and the space velocity is 5000 h⁻¹. -1The mixed gas passed through a reaction bed filled with CO-SCR denitrification catalyst at a flow rate of 2.5 L / min, with the reaction temperature at 250-350℃. The NO concentration in the exhaust gas passing through the reaction bed was measured using an infrared flue gas analyzer and recorded as C. NO Then, the formula "NO removal rate = (1-C)" is used. NO The NO removal rate is calculated as (500) × 100%.

[0101] Viscosity testing was performed using a digital color screen viscometer (Shanghai Shuju Instrument Technology Co., Ltd., NDJ-5S), with rotor number 2 selected and speed set to 60 rpm.

[0102] The coating strength test was conducted using the ultrasonic method, specifically as follows: First, the material was dried to constant weight, denoted as G1; then, the material was immersed in water and ultrasonically treated at 40 kHz for 2 minutes, removed, dried at 80℃ for 12 hours, and weighed, denoted as G2; the mass of the blank carrier was denoted as G3; finally, the coating strength was tested using the formula... Calculate the coating strength D1.

[0103] Coating loading = (G1-G3) / G3, G3 = 100g.

[0104] The CO-SCR denitrification catalyst of the present invention was prepared by any of the preparation methods described in the above embodiments.

[0105] An embodiment of the flue gas purification method of the present invention is a CO-SCR denitrification catalyst prepared by any of the preparation methods described in the above embodiments, which removes NO from the flue gas. x CO is converted into N2 and CO2, respectively.

[0106] The embodiments of the invention provided in this specification have been described above. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. All other preferred embodiments and implementations obtained by those skilled in the art based on the above description of the embodiments of the invention provided in this specification without inventive effort should fall within the protection scope of the embodiments of the invention provided in this specification.

Claims

1. A method for preparing a CO-SCR denitration catalyst, characterized in that, Includes the following steps: (1) The honeycomb cordierite was placed in a muffle furnace for preliminary calcination to obtain a carrier; (2) The carrier is immersed in a mixed solution containing aluminum source and alkaline nitrogen source for hydrothermal treatment. After hydrothermal treatment, it is taken out, washed and dried to obtain surface modified carrier. Hydrothermal treatment involves holding the temperature at 120-150℃ for 4-6 hours. (3) Prepare a bottom coating liquid containing catalyst powder and a first pore-forming agent; prepare a top coating liquid containing catalyst powder and a second pore-forming agent; wherein the average particle size of the first pore-forming agent is greater than the average particle size of the second pore-forming agent; the particle size of the first pore-forming agent is 1-5 micrometers; the particle size of the second pore-forming agent is 10-50 nanometers. (4) The surface-modified carrier is immersed in the bottom coating liquid for coating. After preliminary drying, it is immersed in the top coating liquid for coating. After drying, the catalyst precursor is obtained. (5) The catalyst precursor is calcined to obtain CO-SCR denitrification catalyst.

2. The preparation method according to claim 1, characterized in that: In step (1), the initial calcination is carried out at 300-500℃ for 2-4 hours.

3. The preparation method according to claim 1, characterized in that: In step (2), the hydrothermal treatment is carried out in a high-pressure reactor; the aluminum sol in the mixed solution is an aluminum source with a mass fraction of 5-15%, and the alkaline nitrogen source is urea with a mass fraction of 10-20%.

4. The preparation method according to claim 1, characterized in that: In step (3), the particle size of the catalyst powder is 0.5-3 micrometers. The preparation method is as follows: at least one of copper nitrate, cobalt nitrate, cerium nitrate, and iron nitrate is dissolved in deionized water to prepare a mixed precursor solution; a precipitant is added dropwise to the mixed precursor solution under stirring conditions; after the reaction is completed, the precipitate is collected and washed, dried, pulverized and calcined in sequence to obtain the catalyst powder. The precipitant is at least one of sodium carbonate solution, sodium bicarbonate solution, or ammonia water.

5. The preparation method according to claim 4, characterized in that: The total metal ion concentration of the mixed precursor solution is 0.5-1.2 mol / L; the precipitant is a sodium carbonate solution with a concentration of 1.0-2.0 mol / L, and the pH at the reaction endpoint is 8.5-9.5; calcination is carried out in air atmosphere and kept at 500-600℃ for 3-5 hours.

6. The preparation method according to claim 1, characterized in that: In step (3): The base coat and top coat also contain additives, including Tween-20 and glass fiber; Both the base coat and the top coat are formulated with deionized water and an adhesive. The amount of deionized water and adhesive added is controlled to make the viscosity of the base coat 480-600 mPa·s and the viscosity of the top coat 200-350 mPa·s. The first pore-forming agent is polystyrene microspheres or camphor powder; in the bottom coating liquid, the mass ratio of catalyst powder, additives and the first pore-forming agent is (70-80):(15-20):(5-10); The second pore-forming agent is carbon nanospheres; in the surface coating liquid, the mass ratio of catalyst powder, additives and the second pore-forming agent is (80-85):(10-15):(3-5).

7. The preparation method according to claim 1, characterized in that: In step (4), microwave drying is used with a microwave frequency of 2450MHz, a power of 500-800 watts, and a processing time of 1-5 minutes.

8. The preparation method according to claim 1, characterized in that: In step (5), the calcination treatment is to keep warm at 500-600℃ for 3-5 hours.

9. A CO-SCR denitrification catalyst, characterized in that: It is prepared by the preparation method according to any one of claims 1-8.

10. A method for purifying flue gas, characterized in that: The CO-SCR denitrification catalyst described in claim 9 is used to convert NOx and CO in flue gas into N2 and CO2, respectively.

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