Modified alumina material for tail gas treatment, preparation method and three-way catalyst

Abstract

The present application relates to a modified alumina material for exhaust gas treatment, a preparation method, and a three-way catalyst, which comprises: performing a primary growth on alumina to obtain an activated alumina prestructure MgO-BaO-Al2O3; performing a secondary growth on the activated alumina prestructure MgO-BaO-Al2O3 to obtain a modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment, wherein the molar ratio of Si to Mg in the modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment is 3 to 7.5:1. The present application can increase the specific surface area and high-temperature resistance of the alumina material, inhibit the phase transition process of the γ-Al2O3 material at high temperature, thereby improving the high-temperature aging resistance of the alumina material, and at the same time improve the anti-shedding performance of the alumina material when used as a coating material.

Description

Technical Field

[0001] The present application relates to the technical field of tail gas treatment, and in particular to a modified alumina material for tail gas treatment, a preparation method and a three-way catalyst. Background Art

[0002] With the annual increase in the number of vehicles on the road, vehicle exhaust emissions have become a major source of air pollution. Automotive exhaust purification catalysts are the primary strategy for converting pollutants such as carbon monoxide, hydrocarbons, and nitrogen oxides into harmless gases such as carbon dioxide and water vapor. These catalysts typically consist of a honeycomb support and a catalytic coating, primarily composed of catalytic materials such as rare earth oxides and alumina, along with precious metal active components. The alumina serves to disperse the precious metal active components and increase the specific surface area. Alumina materials come in various crystalline forms, including α, β, γ, δ, η, and θ. γ-Al2O3 is the most widely used in automotive exhaust purification catalysts. γ-Al2O3, also known as activated alumina, is a porous, highly dispersed solid material with a high specific surface area, excellent thermal stability, and adsorption properties. It is generally considered to have a defective spinel structure, with oxygen and aluminum atoms occupying octahedral and tetrahedral positions, respectively, and trivalent aluminum ions contributing to the spinel's defects and acidity. γ-Al2O3 is a metastable structure. During vehicle operation, the transient exhaust temperature can sometimes reach over 1000°C. As the temperature rises, γ-Al2O3 (cubic) gradually transforms into δ-Al2O3 (tetragonal) and θ-Al2O3 (monoclinic), and ultimately into α-Al2O3 (hexagonal). This results in a sharp decrease in the specific surface area of ​​the alumina material, causing the dispersed active components to aggregate, resulting in a sharp decrease in catalyst activity. Therefore, increasing the specific surface area and thermal stability of alumina materials is crucial for improving the performance of automotive exhaust purification catalysts.

[0003] Rare earth oxygen storage materials and precious metal active components need to be dispersed onto cordierite, metal and other carriers through alumina coating. Mechanical shocks such as bumps are inevitable during car driving, and high and low temperature thermal shocks will occur during the operation of the exhaust gas processor. This requires the alumina material to have good anti-shedding properties during mechanical and thermal shocks.

[0004] At present, γ-Al2O3 is usually prepared by dehydrating boehmite or pseudo-boehmite precursor (AlOOH) at 500-600°C. Former researchers have conducted a lot of research on improving alumina and its thermal stability, mainly focusing on improving the preparation method and adding different metal elements for modification. Alkaline earth and rare earth elements can change the thermal stability of alumina to a certain extent. CN100484621C discloses a method for preparing a modified alumina with a large specific surface area and high temperature resistance, by adding nitrates of alkali metals, alkaline earth metals, rare earth elements and ethyl orthosilicate to modify the structure of the alumina material. CN109772289A discloses a method for preparing lanthanum-modified alumina, by adding NaBr to regulate the size and pore volume of alumina, by adding lanthanum nitrate as a lanthanum source and polyethylene glycol as a dispersant to modify the alumina material, and the specific surface area of ​​the fresh sample is 200-250m 2 / g, and the specific surface area after calcination at 1000℃ for 12h is 160-200m 2 / g. CN103599768A discloses a method for preparing a modified alumina material, which stabilizes the crystal structure of γ-Al2O3 by adding lanthanum oxide and zirconium oxide. The specific surface area of ​​the material in its fresh state is 237m 2 / g, and the specific surface area after calcination at 1200 for 4 hours is 59m 2 / g. CN 113233484 A discloses a method for preparing high-temperature resistant and high-specific surface active alumina. By introducing cerium nitrate, lanthanum nitrate, and barium hydroxide as structural stabilizers and ammonium bicarbonate as surface modifier, the activated alumina material is prepared by a low-heat solid-phase precursor method combined with a freeze-drying method. The specific surface area of ​​the fresh activated alumina sample is 300m 2 / g, and after aging at 1100℃ for 4 hours, the specific surface area is still 110m 2 For example, CN102962047A discloses an aluminum-cerium-zirconium composite oxide catalytic material and its preparation method, wherein cerium-zirconium doped activated alumina is prepared by precipitation method, and the maximum specific surface area can reach 145m after being kept at 1000℃ for 4 hours. 2 / g. The phosphorus-modified alumina prepared by the equal volume impregnation method in the study on the preparation of modified activated alumina by impregnation has a specific surface area of ​​75.69m after calcination at 1200℃ for 3h. 2 / g.

[0005] Based on the current state of industrialized γ-Al2O3 applications and a systematic analysis of the aforementioned research, the most commonly used γ-Al2O3 material is modified with rare earth elements such as lanthanum. With increasingly stringent emissions regulations and the increasing proportion of hybrid vehicles, the heat resistance and anti-sloughing properties of γ-Al2O3 materials need to be further improved. Non-rare earth element-modified γ-Al2O3 materials, such as those using a silicon source, typically involve multiple organic solvents, complex process flows, and demanding drying conditions, making industrial-scale production difficult. Furthermore, limited research is currently underway on the anti-sloughing properties of alumina materials.

[0006] Therefore, there is an urgent need to develop an alumina material with high temperature resistance, high specific surface area and excellent anti-shedding performance. Summary of the Invention

[0007] The embodiments of the present application provide a modified alumina material, a preparation method, and a three-way catalyst for exhaust gas treatment, which can increase the specific surface area and high-temperature resistance of the alumina material, inhibit the phase transition process of the γ-Al2O3 material at high temperature, thereby improving the high-temperature aging resistance of the alumina material, and at the same time improve the anti-shedding performance of the alumina material when used as a coating material.

[0008] In a first aspect, a method for preparing a modified alumina material for tail gas treatment is provided, which comprises:

[0009] A primary growth is performed on alumina to obtain an active alumina prestructure MgO-BaO-Al2O3;

[0010] Secondary growth is carried out on the activated alumina pre-structure MgO-BaO-Al2O3 to obtain a modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment, wherein the molar ratio of Si to Mg in the modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment is 3 to 7.5:1.

[0011] In some embodiments, in the activated alumina prestructure MgO-BaO-Al2O3, the MgO content is 0.2-4.0 wt%, the BaO content is 0.5-5.0 wt%, and Al2O3 accounts for 5-30% of the total weight of Al2O3 in the modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment.

[0012] In some embodiments, a single growth is performed on alumina to obtain an activated alumina pre-structure MgO-BaO-Al2O3, specifically comprising the following steps:

[0013] Dissolving a soluble aluminum salt, a soluble magnesium salt, a soluble barium salt, and a soluble ammonium salt in a first solvent to prepare a solution A1;

[0014] Alkali solution was added dropwise to solution A1 to adjust the pH of solution A1 to 7-8, and the mixture was stirred evenly and then subjected to a first aging treatment to obtain slurry A2;

[0015] The slurry A2 is subjected to low-temperature calcination and grinding to obtain an activated alumina pre-structure MgO-BaO-Al2O3.

[0016] In some embodiments, the amounts of the soluble aluminum salt, soluble magnesium salt, and soluble barium salt added are as follows:

[0017] Al 3+ Mg 2+ and Ba 2+ The molar ratio of Al 3+ :Mg 2+ :Ba 2+ =90~95:0.2~5:0.1~2.

[0018] In some embodiments, the soluble aluminum salt includes one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride;

[0019] The soluble magnesium salt includes one or more of magnesium nitrate, magnesium sulfate, magnesium acetate and magnesium chloride;

[0020] The soluble barium salt includes one or more of barium nitrate, barium acetate and barium chloride;

[0021] The soluble ammonium salt includes one or more of ammonium sulfate and ammonium nitrate;

[0022] The alkali solution includes one or more of ammonia water and ammonium carbonate.

[0023] In some embodiments, the first aging treatment includes: aging at 20-30° C. for 2-4 hours.

[0024] In some embodiments, the low-temperature calcination treatment includes: calcination at 350-420° C. for 1-3 hours.

[0025] In some embodiments, the slurry A2 is further dried at 60-100°C before being subjected to the low-temperature roasting treatment.

[0026] In some embodiments, the drying is carried out by spraying at 60-100°C.

[0027] In some embodiments, the grinding is performed to a particle size D 90 5-15μm.

[0028] In some embodiments, secondary growth is performed on the activated alumina pre-structure MgO-BaO-Al2O3 to obtain a modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment, specifically comprising the following steps:

[0029] Add the activated alumina pre-structured MgO-BaO-Al2O3 into aqueous ammonia and mix well to obtain solution B1;

[0030] Dissolving pseudo-boehmite powder and polyether-modified siloxane in a second solvent, adding nitric acid, and then adding the second solvent after ball milling to obtain solution B2;

[0031] Heat solution B1 to 70-90°C, add solution B2 while stirring, and add alkali solution to adjust the pH to 8-9. After stirring evenly, perform a second aging treatment to obtain slurry B3;

[0032] The slurry B3 is subjected to a first high-temperature roasting treatment at a preset air flow rate;

[0033] A second high-temperature calcination process is then performed to obtain the modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment.

[0034] In some embodiments, the mass fraction of the ammonia water is 5 to 10 wt %;

[0035] The polyether-modified siloxane is one or more of polyether-modified polydimethylsiloxane, polyether-modified trisiloxane, and polyether-modified heptamethylsiloxane.

[0036] In some embodiments, when the activated alumina pre-structured MgO-BaO-Al2O3 is added to aqueous ammonia, one or more of polyhydroxyethyl acrylate, hydroxypropyl methylcellulose, hydroxypropyl cellulose and polyvinyl alcohol are also added.

[0037] In some embodiments, solution B2 is added while stirring under ultrasonic dispersion conditions.

[0038] In some embodiments, before the slurry B3 is subjected to the first high-temperature roasting treatment, the slurry B3 is further dried at 100-120°C.

[0039] In some embodiments, the second aging treatment comprises: aging at 40-60° C. for 3-5 hours.

[0040] In some embodiments, the first high-temperature calcination treatment includes calcining at 300-500° C. for 1-2 hours.

[0041] In some embodiments, the second high temperature calcination treatment includes calcining at 600-800° C. for 2-5 hours.

[0042] In some embodiments, the preset air flow rate is 50-250 L / min.

[0043] In a second aspect, a modified alumina material for exhaust gas treatment is provided, which is prepared using any of the above methods for preparing a modified alumina material for exhaust gas treatment.

[0044] In a third aspect, a three-way catalyst is provided, which includes the modified alumina material for exhaust gas treatment as described above.

[0045] The beneficial effects of the technical solution provided by this application include:

[0046] The present invention provides a modified alumina material, preparation method, and three-way catalyst for exhaust gas treatment. To improve the high-temperature resistance and specific surface area of ​​the activated alumina material, the current main strategy is to form a porous structure with a high specific surface area in the alumina material during the material preparation and molding process, while simultaneously inhibiting the phase transition process of the alumina material under high-temperature conditions and preventing sintering between alumina particles. Currently, the most commonly used method is to dope the alumina with rare earth oxides (such as La2O3), with some reports also using supplementary doping with alkaline earth metal oxides and silica. These doping techniques typically involve directly modifying the alumina with one or more metal salts or oxides through coprecipitation, sol-gel methods, or other methods. Further improvements in specific surface area and high-temperature resistance are needed. Through extensive research, the present invention has discovered that by first preparing a Mg- and Ba-modified activated alumina prestructure (i.e., MgO-BaO-Al2O3), and then growing a Si-modified activated alumina structure (secondary growth) on this structure, with a Si:Mg molar ratio of 3 to 7.5:1, a modified alumina material with high-temperature resistance and high specific surface area can be obtained without doping with rare earth oxides. At the same time, it was unexpectedly discovered that the modified alumina material prepared by this method can significantly improve the anti-shedding performance of the three-way catalyst coating when it is prepared into a slurry and coated on a ceramic carrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0048] Figure 1 A flow chart of a method for preparing a modified alumina material for tail gas treatment provided in an embodiment of the present application;

[0049] Figure 2 A flow chart for obtaining an activated alumina pre-structure provided in an embodiment of the present application;

[0050] Figure 3A flow chart of performing secondary growth on an activated alumina prestructure to obtain a modified alumina material for exhaust gas treatment is provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0052] See also Figure 1 As shown, the embodiment of the present application provides a method for preparing a modified alumina material for tail gas treatment, which comprises the following steps:

[0053] 101: Perform a primary growth on alumina to obtain an active alumina prestructure MgO-BaO-Al2O3.

[0054] 102: Performing secondary growth on the activated alumina pre-structure MgO-BaO-Al2O3 to obtain a modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment, wherein the molar ratio of Si to Mg in the modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment is 3 to 7.5:1.

[0055] Too high SiO2 will form a dense glass phase, and too low SiO2 will make it difficult to inhibit the high-temperature aging phase transformation of the alumina material. Therefore, after a large number of experimental studies, the molar ratio of Si and Mg was determined to be 3 to 7.5:1. This ratio can improve the adhesion between the alumina material and the ceramic carrier, improve the coating's anti-shedding performance, and also increase the specific surface area.

[0056] To improve the high-temperature resistance and specific surface area of ​​activated alumina materials, the current main strategy is to create a porous structure with a high specific surface area during the material preparation and molding process, while also inhibiting the phase transition process of the alumina material under high-temperature conditions and preventing sintering between alumina particles. Currently, the most commonly used method is to dope the alumina with rare earth oxides (such as La2O3), with reports also using supplementary doping with alkaline earth metal oxides and silica. These doping techniques typically involve directly modifying the alumina with one or more metal salts or oxides through coprecipitation, sol-gel methods, or other methods. Further improvements in specific surface area and high-temperature resistance are needed. Through extensive research, the present applicants have discovered that by first preparing a Mg- and Ba-modified activated alumina prestructure (i.e., MgO-BaO-Al2O3), and then growing a Si-modified activated alumina structure on top of this structure (secondary growth), with a Si:Mg molar ratio of 3 to 7.5:1, a modified alumina material with high-temperature resistance and high specific surface area can be obtained without doping with rare earth oxides. At the same time, it was unexpectedly discovered that the modified alumina material prepared by this method can significantly improve the anti-shedding performance of the three-way catalyst coating when it is prepared into a slurry and coated on a ceramic carrier.

[0057] Among them, the MgO content in the activated alumina prestructure MgO-BaO-Al2O3 is 0.2-4.0wt%, and the BaO content is 0.5-5.0wt%, and the Al2O3 in the activated alumina prestructure accounts for 5-30% of the total weight of Al2O3 in the modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment.

[0058] See also Figure 2 As shown, in order to prepare the required activated alumina prestructure, in the above step 101, a growth is performed on alumina to obtain the activated alumina prestructure MgO-BaO-Al2O3, which specifically includes the following steps:

[0059] 201: Dissolve a soluble aluminum salt, a soluble magnesium salt, a soluble barium salt, and a soluble ammonium salt in a first solvent to prepare solution A1.

[0060] In step 201, the amount of the soluble aluminum salt, soluble magnesium salt, and soluble barium salt added can be adjusted according to the Al content in the corresponding soluble salt. 3+ Mg 2+ and Ba 2+ For example, the addition amount of the soluble aluminum salt, soluble magnesium salt and soluble barium salt is as follows: Al in the soluble aluminum salt is 3+ , Mg in soluble magnesium salts 2+ and Ba in soluble barium salts 2+ The molar ratio of Al 3+:Mg 2+ :Ba 2+ =90~95:0.2~5:0.1~2.

[0061] The role of the soluble ammonium salt is to gradually decompose into gas during the roasting process, which helps to form a porous structure with a high specific surface area. Therefore, the soluble ammonium salt can be added according to actual preparation needs.

[0062] It should be noted that there are multiple options for the soluble aluminum salt, which can be selected according to actual preparation needs. For example, as an example, the soluble aluminum salt includes one or more of aluminum nitrate, aluminum sulfate and aluminum chloride.

[0063] It should be noted that there are multiple options for the soluble magnesium salt, which can be selected according to actual preparation needs. For example, as an example, the soluble magnesium salt includes one or more of magnesium nitrate, magnesium sulfate, magnesium acetate and magnesium chloride.

[0064] It should be noted that there are multiple options for the soluble barium salt, which can be selected according to actual preparation needs. For example, as an example, the soluble barium salt includes one or more of barium nitrate, barium acetate and barium chloride.

[0065] It should be noted that there are multiple options for the soluble ammonium salt, which can be selected according to actual preparation needs. For example, as an example, the soluble ammonium salt includes one or more of ammonium nitrate and ammonium sulfate.

[0066] It should be noted that the function of the first solvent is to dissolve and mix the various soluble salts. There are multiple options for the first solvent, which can be selected according to actual preparation needs. For example, as an example, the first solvent includes one or more of deionized water and distilled water.

[0067] 202: Alkaline solution is added dropwise to solution A1 to adjust the pH of solution A1 to 7-8, and after stirring evenly, a first aging treatment is performed to obtain slurry A2;

[0068] The first aging treatment includes: aging at 20-30° C. for 2-4 hours.

[0069] The alkali solution includes one or more of ammonia water and ammonium carbonate.

[0070] 203: After drying the slurry A2 at 60-100°C, calcining it at low temperature, and grinding it to a particle size of D 90 5-15 μm to obtain the activated alumina pre-structure MgO-BaO-Al2O3.

[0071] The low-temperature calcination treatment includes: calcining at 350-420° C. for 1-3 hours.

[0072] The slurry A2 is preferably dried by spray drying.

[0073] To prepare an activated alumina prestructure with a suitable structure, the alumina is doped and modified by adding appropriate proportions of magnesium salts, barium salts, and soluble ammonium salts. The doped magnesium and barium react with the alumina during a high-temperature solid-phase reaction to form a highly thermally stable aluminate that is dispersed throughout the alumina material, inhibiting bulk diffusion and the γ→δ→α phase transition of the alumina at high temperatures, thereby improving the aging and high-temperature resistance of the activated alumina. The added soluble ammonium salt decomposes near the calcination temperature to release gases such as ammonia (ammonia and ammonium bisulfate if ammonium sulfate is used, and ammonia and nitrogen if ammonium nitrate is used). The diffusion of ammonia gas in the system promotes the formation of a porous structure within the activated alumina prestructure, increasing the material's specific surface area. Due to the need to match the secondary growth process, the control of some process parameters in this preparation process is also different from that of conventional preparation methods. For example, the pH needs to be 7-8, the aging temperature needs to be lower than the conventional aging temperature, and the roasting temperature must reach the formation temperature of γ-Al2O3 on the one hand, and on the other hand, it is necessary to prevent ammonium bisulfate or ammonium nitrate from continuing to decompose violently. Therefore, for ammonium sulfate, the temperature is selected to be 350-420℃, and for ammonium nitrate, it is selected to be roasted at 200-250℃ for 1-2h for pre-decomposition to prevent explosion, and then the temperature is raised to 350-420℃.

[0074] See also Figure 3 As shown, in order to be able to perform secondary growth on the activated alumina pre-structure, in the above step 102, secondary growth is performed on the activated alumina pre-structure MgO-BaO-Al2O3 to obtain the modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment, which specifically includes the following steps:

[0075] 301: Add activated alumina pre-structured MgO-BaO-Al2O3 into aqueous ammonia and mix well to obtain solution B1.

[0076] After stirring, ultrasonication is carried out at 25-35° C. for 30-60 min to obtain a uniformly mixed solution B1.

[0077] The mass fraction of the ammonia water is 5-10 wt %, and the pH value of the solution is adjusted by using the ammonia water.

[0078] When the activated alumina pre-structured MgO-BaO-Al2O3 is added to aqueous ammonia, one or more of polyhydroxyethyl acrylate, hydroxypropyl methylcellulose, hydroxypropyl cellulose and polyvinyl alcohol are also added.

[0079] 302: Pseudo-boehmite powder and polyether-modified siloxane are dissolved in a second solvent, and nitric acid is added. After ball milling for a period of time, such as 0.5 to 1 hour, the second solvent is added to dilute the obtained sol-state viscous material to obtain solution B2.

[0080] The role of nitric acid is to promote the formation of pseudo-boehmite gel network.

[0081] The present application is a method for preparing aluminum oxide using a peptization method: taking advantage of the large peptization index of pseudo-boehmite, an acid is used as a peptizing agent to prepare aluminum oxide. During the peptization process, H+ ions in the peptizing agent are adsorbed on the pseudo-boehmite particles to form new particles. Under the action of stirring / ball milling, the new particles continuously adsorb other pseudo-boehmite particles. The multiple pseudo-boehmite particles are connected together in a network form through the "acidic bridge" of H+ ions, thereby causing the pseudo-boehmite particles to lose fluidity and the pseudo-boehmite solution to become a peptized state. The peptized pseudo-boehmite is then roasted to obtain aluminum oxide.

[0082] There are multiple options for the second solvent, which can be selected according to actual preparation needs. For example, as an example, the second solvent includes one or more of deionized water and distilled water.

[0083] The polyether-modified siloxane is one or more of polyether-modified polydimethylsiloxane, polyether-modified trisiloxane, and polyether-modified heptamethylsiloxane.

[0084] In step 302, the amount of polyether-modified siloxane added can be calculated by reverse calculation based on the Si content in the modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment, which is the final product.

[0085] In addition, it should be noted that the Al2O3 in the activated alumina prestructure MgO-BaO-Al2O3 accounts for a small proportion of the total weight of Al2O3 in the final product, the modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment. In other words, the contribution of Al2O3 in the activated alumina prestructure MgO-BaO-Al2O3 to the Al2O3 in the final product, the modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment is not high. The difference is provided by another source of Al2O3, namely, pseudo-boehmite powder. Therefore, the amount of pseudo-boehmite powder added can be calculated by reverse calculation from the two.

[0086] It should be noted that there is no strict time sequence for steps 301 and 302 , that is, the two steps can be performed simultaneously, or solution B2 can be prepared first and then solution B1 .

[0087] 303: Heat solution B1 to 70-90° C., add solution B2 while stirring, and add alkali solution to adjust the pH to 8-9. After stirring evenly, perform a second aging treatment to obtain slurry B3.

[0088] The second aging treatment includes: aging at 40-60° C. for 3-5 hours.

[0089] During the addition of solution B2, ultrasonic dispersion is preferably added.

[0090] 304: Under a preset air flow rate, the slurry B3 is subjected to a first high-temperature roasting treatment.

[0091] Wherein, before the slurry B3 is subjected to the first high-temperature roasting treatment, the process further includes: drying at 100-120°C.

[0092] The first high-temperature calcination treatment includes: calcining at 300-500° C. for 1-2 hours.

[0093] The preset air flow rate is 50-250 L / min.

[0094] 305: Perform a second high-temperature calcination process to obtain a modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment.

[0095] The second high-temperature calcination treatment includes calcining at 600-800° C. for 2-5 hours.

[0096] Before the secondary growth is carried out, the activated alumina pre-structure is first ground into a powder of suitable particle size to provide a growth substrate of suitable size for the secondary growth, and then the corresponding powder is uniformly dispersed into the ammonia solution by ultrasound. In order to introduce Si doping modification and avoid the introduction of organic solvents in the preparation process, the present application adopts the method of adding polyether modified siloxane to pseudo-boehmite for modification. Avoiding the introduction of organic solvents can, on the one hand, make the material preparation process more green, and on the other hand, facilitate the secondary growth of activated alumina in the aqueous activated alumina pre-structure system to prevent phase separation. In order to enable the silicon-doped modified activated alumina to uniformly grow secondary on the surface of the activated alumina pre-structure particles and prevent the activated alumina pre-structure particles from agglomerating, when the activated alumina pre-structure powder is added to the ammonia solution, it is preferred to add polyhydroxyethyl acrylate, hydroxypropyl methylcellulose, hydroxypropyl cellulose, polyvinyl alcohol and the like to regulate the viscosity of the solution; by adding ultrasonic dispersion in the secondary growth process, the uniform growth and dispersion of the particles are further promoted.

[0097] The calcination process proposed in this application is similar to the conventional calcination process, with the main purpose of completely converting pseudo-boehmite into γ-Al2O3. The difference is that for ammonium sulfate, the incompletely converted ammonium sulfate and the generated ammonium bisulfate will further decompose to generate gases such as ammonia, nitrogen, sulfur dioxide, and water vapor during the process. For ammonium nitrate, the incompletely converted ammonium nitrate will further decompose to generate gases such as ammonia, nitrogen, and water vapor during the process. In order to prevent uneven diffusion and localized accumulation of the gas, it is necessary to control the gas flow rate at 300-500°C. Appropriate gas flow rate control can, on the one hand, allow the diffused gas to form a porous structure in the alumina material, further increasing the specific surface area, and on the other hand, ensure that waste gases such as sulfur dioxide are removed from the system to prevent residual gas from poisoning the precious metal catalyst when preparing the coating slurry.

[0098] The embodiments of the present application also provide a modified alumina material for exhaust gas treatment, which is prepared using any of the above methods for preparing a modified alumina material for exhaust gas treatment.

[0099] The present invention also provides a three-way catalyst comprising the modified alumina material for exhaust gas treatment as described above, and further comprising a cerium-zirconium-based oxygen storage material, an auxiliary material, and at least one precious metal selected from the group consisting of Pt, Pd, and Rh.

[0100] The present application is described in detail below through several examples and comparative examples.

[0101] Characterization methods

[0102] 1. Specific surface area characterization

[0103] The specific surface area of ​​the modified alumina material samples of each embodiment and comparative example was characterized freshly (before aging) and after high-temperature aging at 1100°C (after aging). The test method is as follows: first, the sample was pretreated under vacuum conditions at 300°C for 3 hours, and then an adsorption test was performed at -196°C (liquid nitrogen) using high-purity N2 as the adsorption gas. A desorption test was performed at 25°C. The specific surface area of ​​the sample was calculated using the BET method (AutosorbSI fully automatic specific surface-pore size analyzer, Quantachrome). Specific surface area retention rate = specific surface area after aging / specific surface area before aging × 100%

[0104] 2. Characterization of anti-shedding performance

[0105] First, a three-way catalyst coating slurry was prepared according to this application. To better evaluate the coating material's resistance to shedding under high and low temperature environments and mechanical impact during actual application, this application used ultrasonic vibration and thermal shock methods to measure the coating's durability. Shedding rate = (mass after coating - mass after testing) / (mass after coating - mass before coating) × 100%.

[0106] (1) Ultrasonic vibration

[0107] The sample coated with the three-way catalyst coating material was placed in a sealed container filled with petroleum ether, and then the container was placed in an ultrasonic cleaner for 30 minutes. The sample was then taken out and dried, and the mass of the sample was weighed and the shedding rate was calculated.

[0108] (2) Thermal shock

[0109] Place the sample coated with the three-way catalyst coating material in a muffle furnace at 1000°C for 20 minutes, take out the sample and quickly immerse it in cold water at 0-10°C, then subject the sample to ultrasonic treatment to promote the separation of the detached material (the action time is not longer than 1 minute), repeat this operation several times until the mass no longer decreases, weigh the mass of the sample and calculate the shedding rate.

[0110] Example 1

[0111] A modified alumina material for tail gas treatment:

[0112] Step (1): Weigh 33.48 g of Al(NO3)3·9H2O (including about 10 g of Al2O3) and 3.35 g of (NH4)2SO4, weigh Mg(NO3)2·6H2O and Ba(NO3)2 so that the MgO content in MgO-BaO-Al2O3 is 1% and the BaO content is 2%, and dissolve the corresponding soluble salts in deionized water to prepare solution A1. Ammonia water is added dropwise to the uniformly mixed solution to adjust the pH of the solution to 7. After stirring, the solution is aged at 25°C for 2 hours to obtain slurry A2;

[0113] Step (2): spray-dry the slurry A2 at 80°C, then calcine at 350°C for 3h, and grind the calcined sample into a particle size of D 90 10 μm P powder (MgO-BaO-Al2O3);

[0114] Step (3): adding the P powder prepared in step (2) to a 10 wt% ammonia solution, stirring, and ultrasonicating at 25°C for 60 min to prepare solution B1; weighing pseudo-boehmite powder according to an Al2O3 content of 90 g, and measuring a polyether-modified polydimethylsiloxane solution according to a molar ratio of Si to Mg of 6:1, dissolving them in deionized water, adding nitric acid, and ball milling for 1 h twice, and then adding a certain amount of deionized water to prepare solution B2;

[0115] Step (4): heating solution B1 to 70°C, adding solution B2 to solution B1 at this temperature while stirring, using ultrasonic dispersion during the addition of solution B2, and adjusting the pH of the slurry to 8 by adding ammonia water. After stirring evenly, aging at 40°C for 3 hours;

[0116] Step (5): The slurry obtained by aging in step (4) is dried at 100°C, then calcined at 400°C for 2h, during which the gas flow rate is maintained at 200L / min, and finally calcined at 800°C for 4h to obtain a modified alumina material (SiO2-MgO-BaO-Al2O3) for exhaust gas treatment.

[0117] Example 2

[0118] A modified alumina material for tail gas treatment:

[0119] Step (1): Weigh 33.48 g of Al(NO3)3·9H2O (including about 10 g of Al2O3) and 3.35 g of (NH4)2SO4, weigh Mg(NO3)2·6H2O and Ba(NO3)2 so that the MgO content in MgO-BaO-Al2O3 is 4% and the BaO content is 2%, and dissolve the corresponding soluble salts in deionized water to prepare solution A1. Ammonia water is added dropwise to the uniformly mixed solution to adjust the pH of the solution to 7. After stirring, the solution is aged at 25°C for 2 hours to obtain slurry A2;

[0120] Step (2): spray-dry the slurry A2 at 80°C, then calcine at 350°C for 3h, and grind the calcined sample into a particle size of D 90 10 μm P powder (MgO-BaO-Al2O3);

[0121] Step (3): adding the P powder prepared in step (2) to a 10 wt% ammonia solution, stirring, and ultrasonicating at 25°C for 60 min to prepare solution B1; weighing pseudo-boehmite powder according to an Al2O3 content of 90 g, and measuring a polyether-modified polydimethylsiloxane solution according to a molar ratio of Si to Mg of 3:1, dissolving them in deionized water, adding nitric acid, and ball milling for 1 h twice, and then adding a certain amount of deionized water to prepare solution B2;

[0122] Step (4): heating solution B1 to 70°C, adding solution B2 to solution B1 at this temperature while stirring, using ultrasonic dispersion during the addition of solution B2, and adjusting the pH of the slurry to 8 by adding ammonia water. After stirring evenly, aging at 40°C for 3 hours;

[0123] Step (5): The slurry obtained by aging in step (4) is dried at 100°C, then calcined at 400°C for 2h, during which the gas flow rate is maintained at 200L / min, and finally calcined at 800°C for 4h to obtain a modified alumina material (SiO2-MgO-BaO-Al2O3) for exhaust gas treatment.

[0124] Example 3

[0125] A modified alumina material for tail gas treatment:

[0126] Step (1): Weigh 33.48 g of Al(NO3)3·9H2O (including about 10 g of Al2O3) and 3.35 g of (NH4)2SO4, weigh Mg(NO3)2·6H2O and Ba(NO3)2 so that the MgO content in MgO-BaO-Al2O3 is 1% and the BaO content is 2%, and dissolve the corresponding soluble salts in deionized water to prepare solution A1. Ammonia water is added dropwise to the uniformly mixed solution to adjust the pH of the solution to 7. After stirring, the solution is aged at 25°C for 2 hours to obtain slurry A2;

[0127] Step (2): spray-dry the slurry A2 at 80°C, then calcine at 350°C for 3h, and grind the calcined sample into a particle size of D 90 10 μm P powder (MgO-BaO-Al2O3);

[0128] Step (3): adding the P powder prepared in step (2) to an ammonia solution with a mass fraction of 10 wt%, and adding polyhydroxyethyl acrylate, stirring, and ultrasonicating at 25° C. for 60 min to prepare solution B1; weighing pseudo-boehmite powder according to an Al2O3 content of 90 g, and measuring a polyether-modified polydimethylsiloxane solution according to a molar ratio of Si to Mg of 6:1, dissolving them in deionized water, adding nitric acid, ball milling for 1 h twice, and then adding a certain amount of deionized water to prepare solution B2;

[0129] Step (4): heating solution B1 to 70°C, adding solution B2 to solution B1 at this temperature while stirring, using ultrasonic dispersion during the addition of solution B2, and adjusting the pH of the slurry to 8 by adding ammonia water. After stirring evenly, aging at 40°C for 3 hours;

[0130] Step (5): The slurry obtained by aging in step (4) is dried at 100°C, then calcined at 400°C for 2h, during which the gas flow rate is maintained at 200L / min, and finally calcined at 800°C for 4h to obtain a modified alumina material (SiO2-MgO-BaO-Al2O3) for exhaust gas treatment.

[0131] Example 4

[0132] A modified alumina material for tail gas treatment:

[0133] Step (1): Weigh 33.48 g of Al(NO3)3·9H2O (including about 10 g of Al2O3) and 3.35 g of (NH4)2SO4, weigh Mg(NO3)2·6H2O and Ba(NO3)2 so that the MgO content in MgO-BaO-Al2O3 is 4% and the BaO content is 2%, and dissolve the corresponding soluble salts in deionized water to prepare solution A1. Ammonia water is added dropwise to the uniformly mixed solution to adjust the pH of the solution to 7. After stirring, the solution is aged at 30°C for 4 hours to obtain slurry A2;

[0134] Step (2): spray-dry the slurry A2 at 80°C, then calcine at 420°C for 1 hour, and grind the calcined sample into a particle size of D 90 15 μm P powder (MgO-BaO-Al2O3);

[0135] Step (3): adding the P powder prepared in step (2) to an ammonia solution with a mass fraction of 10 wt%, and adding polyhydroxyethyl acrylate, stirring, and ultrasonicating at 25° C. for 60 min to prepare solution B1; weighing pseudo-boehmite powder according to an Al2O3 content of 50 g, and measuring a polyether-modified polydimethylsiloxane solution according to a molar ratio of Si to Mg of 3:1, dissolving them in deionized water, adding nitric acid, ball milling for 1 h twice, and then adding a certain amount of deionized water to prepare solution B2;

[0136] Step (4): heating solution B1 to 70°C, adding solution B2 to solution B1 at this temperature while stirring, using ultrasonic dispersion during the addition of solution B2, and adjusting the pH of the slurry to 8 by adding ammonia water. After stirring evenly, aging at 60°C for 5 hours;

[0137] Step (5): The slurry obtained by aging in step (4) is dried at 100°C, then calcined at 400°C for 2h, during which the gas flow rate is maintained at 200L / min, and finally calcined at 800°C for 4h to obtain a modified alumina material (SiO2-MgO-BaO-Al2O3) for exhaust gas treatment.

[0138] Comparative Example 1

[0139] A modified alumina material for tail gas treatment:

[0140] Step (1): Weigh 33.48 g of Al(NO3)3·9H2O (including about 10 g of Al2O3) and 3.35 g of (NH4)2SO4, weigh Mg(NO3)2·6H2O and Ba(NO3)2 so that the MgO content in MgO-BaO-Al2O3 is 1% and the BaO content is 2%, and dissolve the corresponding soluble salts in deionized water to prepare solution A1. Ammonia water is added dropwise to the uniformly mixed solution to adjust the pH of the solution to 7. After stirring, the solution is aged at 50°C for 2 hours to obtain slurry A2;

[0141] Step (2): spray-dry the slurry A2 at 80°C, then calcine at 600°C for 3h, and grind the calcined sample into a particle size of D 90 10 μm P powder (MgO-BaO-Al2O3);

[0142] Step (3): adding the P powder prepared in step (2) to a 10 wt% ammonia solution, stirring, and ultrasonicating at 25°C for 60 min to prepare solution B1; weighing pseudo-boehmite powder according to an Al2O3 content of 90 g, and measuring a polyether-modified polydimethylsiloxane solution according to a molar ratio of Si to Mg of 12:1, dissolving them in deionized water, adding nitric acid, and ball milling for 1 h twice, and then adding a certain amount of deionized water to prepare solution B2;

[0143] Step (4): heating solution B1 to 70°C, adding solution B2 to solution B1 at this temperature while stirring, using ultrasonic dispersion during the addition of solution B2, and adjusting the pH of the slurry to 8 by adding ammonia water. After stirring evenly, aging at 40°C for 3 hours;

[0144] Step (5): The slurry obtained by aging in step (4) is dried at 100°C, then calcined at 400°C for 2h, during which the gas flow rate is maintained at 200L / min, and finally calcined at 800°C for 4h to obtain a modified alumina material (SiO2-MgO-BaO-Al2O3) for exhaust gas treatment.

[0145] Comparative Example 2

[0146] A modified alumina material for tail gas treatment:

[0147] Step (1): Weigh 33.48 g of Al(NO3)3·9H2O (including about 10 g of Al2O3), weigh Mg(NO3)2·6H2O and Ba(NO3)2 so that the MgO content in MgO-BaO-Al2O3 is 1% and the BaO content is 2%, and dissolve the corresponding soluble salts in deionized water to prepare solution A1. Ammonia water is added dropwise to the uniformly mixed solution to adjust the pH of the solution to 7. After stirring, the solution is aged at 25°C for 2 hours to obtain slurry A2;

[0148] Step (2): spray-dry the slurry A2 at 80°C, then calcine at 350°C for 3h, and grind the calcined sample into a particle size of D 90 10 μm P powder (MgO-BaO-Al2O3);

[0149] Step (3): adding the P powder prepared in step (2) to a 10 wt% ammonia solution, stirring, and ultrasonicating at 25°C for 60 min to prepare solution B1; weighing pseudo-boehmite powder according to an Al2O3 content of 90 g, and measuring a polyether-modified polydimethylsiloxane solution according to a molar ratio of Si to Mg of 6:1, dissolving them in deionized water, adding nitric acid, and ball milling for 1 h twice, and then adding a certain amount of deionized water to prepare solution B2;

[0150] Step (4): heating solution B1 to 70°C, adding solution B2 to solution B1 at this temperature while stirring, using ultrasonic dispersion during the addition of solution B2, and adjusting the pH of the slurry to 8 by adding ammonia water. After stirring evenly, aging at 40°C for 3 hours;

[0151] Step (5): The slurry obtained by aging in step (4) is dried at 100°C, then calcined at 400°C for 2h, during which the gas flow rate is maintained at 200L / min, and finally calcined at 800°C for 4h to obtain a modified alumina material (SiO2-MgO-BaO-Al2O3) for exhaust gas treatment.

[0152] Comparative Example 3

[0153] A modified alumina material for tail gas treatment:

[0154] Step (1): Weigh 33.48 g of Al(NO3)3·9H2O (including about 10 g of Al2O3) and 3.35 g of (NH4)2SO4, weigh Mg(NO3)2·6H2O so that the MgO content in MgO-Al2O3 is 1%, and dissolve the corresponding soluble salt in deionized water to prepare solution A1. Ammonia water is added dropwise to the uniformly mixed solution to adjust the pH of the solution to 7. After stirring, the solution is aged at 25°C for 2 hours to obtain slurry A2;

[0155] Step (2): spray-dry the slurry A2 at 80°C, then calcine at 350°C for 3h, and grind the calcined sample into a particle size of D 90 10 μm P powder (MgO-Al2O3);

[0156] Step (3): adding the P powder prepared in step (2) to a 10 wt% ammonia solution, stirring, and ultrasonicating at 25°C for 60 min to prepare solution B1; weighing pseudo-boehmite powder according to an Al2O3 content of 90 g, and measuring a polyether-modified polydimethylsiloxane solution according to a molar ratio of Si to Mg of 6:1, dissolving them in deionized water, adding nitric acid, and ball milling for 1 h twice, and then adding a certain amount of deionized water to prepare solution B2;

[0157] Step (4): heating solution B1 to 70°C, adding solution B2 to solution B1 at this temperature while stirring, using ultrasonic dispersion during the addition of solution B2, and adjusting the pH of the slurry to 8 by adding ammonia water. After stirring evenly, aging at 40°C for 3 hours;

[0158] Step (5): The slurry obtained by aging in step (4) is dried at 100°C, then calcined at 400°C for 2h, during which the gas flow rate is maintained at 200L / min, and finally calcined at 800°C for 4h to obtain a modified alumina material (SiO2-MgO-Al2O3) for exhaust gas treatment.

[0159] Comparative Example 4

[0160] A modified alumina material for tail gas treatment:

[0161] Step (1): Weigh 33.48 g of Al(NO3)3·9H2O (including about 10 g of Al2O3) and 3.35 g of (NH4)2SO4, weigh Mg(NO3)2·6H2O and Ba(NO3)2 so that the MgO content in MgO-BaO-Al2O3 is 1% and the BaO content is 2%, and dissolve the corresponding soluble salts in deionized water to prepare solution A1. Ammonia water is added dropwise to the uniformly mixed solution to adjust the pH of the solution to 7. After stirring, the solution is aged at 25°C for 2 hours to obtain slurry A2;

[0162] Step (2): spray-dry the slurry A2 at 80°C, then calcine at 350°C for 3h, and grind the calcined sample into a particle size of D 90 10 μm P powder (MgO-BaO-Al2O3);

[0163] Step (3): adding the P powder prepared in step (2) to an ammonia solution with a mass fraction of 10 wt%, and adding polyhydroxyethyl acrylate, stirring, and ultrasonicating at 25° C. for 60 min to prepare solution B1; weighing pseudo-boehmite powder according to an Al2O3 content of 90 g, and measuring a polyether-modified polydimethylsiloxane solution according to a molar ratio of Si to Mg of 8:1, dissolving them in deionized water, adding nitric acid, ball milling for 1 h twice, and then adding a certain amount of deionized water to prepare solution B2;

[0164] Step (4): heating solution B1 to 70°C, adding solution B2 to solution B1 at this temperature while stirring, using ultrasonic dispersion during the addition of solution B2, and adjusting the pH of the slurry to 8 by adding ammonia water. After stirring evenly, aging at 40°C for 3 hours;

[0165] Step (5): The slurry obtained by aging in step (4) is dried at 100°C, then calcined at 400°C for 2h, during which the gas flow rate is maintained at 200L / min, and finally calcined at 800°C for 4h to obtain a modified alumina material (SiO2-MgO-BaO-Al2O3) for exhaust gas treatment.

[0166] Table 1 Performance indicators of modified alumina materials prepared by Examples and Comparative Examples

[0167]

[0168] From the data in Table 1, it can be seen that the aluminum oxide material prepared in the embodiment has a very high specific surface area and a very low shedding rate, and the attenuation degree after high-temperature aging is also relatively low.

[0169] Compared with Example 1, Example 3 differs in that polyhydroxyethyl acrylate is added. The specific surface area after aging is also higher than that without polyhydroxyethyl acrylate, and the ultrasonic vibration shedding rate is also lower than that without polyhydroxyethyl acrylate. This indicates that when adding activated alumina pre-structured MgO-BaO-Al2O3 to ammonia water, the addition of polyhydroxyethyl acrylate, hydroxypropyl methylcellulose, hydroxypropyl cellulose, polyvinyl alcohol, etc. can adjust the viscosity of the solution, thereby promoting uniform growth and dispersion of particles.

[0170] Compared with Example 2, Example 4 differs in that polyhydroxyethyl acrylate is added. The specific surface area after aging is also higher than that without polyhydroxyethyl acrylate, and the thermal shock shedding rate is also lower than that without polyhydroxyethyl acrylate. This indicates that when adding activated alumina pre-structured MgO-BaO-Al2O3 to ammonia water, the addition of polyhydroxyethyl acrylate, hydroxypropyl methylcellulose, hydroxypropyl cellulose, polyvinyl alcohol, etc. can adjust the viscosity of the solution, thereby promoting uniform growth and dispersion of particles.

[0171] Compared with Example 1, Comparative Example 1 differs in that the molar ratio of Si to Mg is 12:1, and the calcination temperature in step (2) is 600°C. In Comparative Example 1, the molar ratio of Si to Mg exceeds 3 to 7.5:1, and the specific surface area decreases significantly after aging, while the shedding rate increases significantly. This indicates that by controlling the molar ratio of Si to Mg to 3 to 7.5:1, a modified alumina material with high temperature resistance and high specific surface area can be obtained without doping with rare earth oxides. This also significantly improves the anti-shedding performance of the three-way catalyst coating.

[0172] Compared with Example 1, Comparative Example 2 differs in that no ammonium sulfate is added. In this case, the specific surface area decreases significantly after aging, while the shedding rate increases significantly. This indicates that the addition of ammonium sulfate gradually decomposes into gas during the calcination process, which helps form a porous high-specific surface area structure and increases the specific surface area of ​​the alumina material.

[0173] Compared with Example 1, Comparative Example 3 differs in that no barium nitrate is added. In this case, the specific surface area is greatly reduced after aging, while the shedding rate is greatly increased, indicating that a suitable content of BaO can improve the aging resistance of alumina materials.

[0174] Compared with Example 1, Comparative Example 4 differs in that polyhydroxyethyl acrylate is added, and the molar ratio of Si to Mg is 8:1. In this case, the specific surface area decreases significantly after aging, while the shedding rate increases significantly. However, the shedding rate is relatively lower than that of Comparative Example 1. This indicates that when adding polyhydroxyethyl acrylate, hydroxypropyl methylcellulose, hydroxypropyl cellulose, polyvinyl alcohol, etc. to the activated alumina prestructure MgO-BaO-Al2O3 to ammonia water, the viscosity of the solution can be adjusted, thereby promoting uniform growth and dispersion of the particles and reducing the shedding rate.

[0175] In summary, the alumina material for exhaust gas treatment provided in the present application can improve the specific surface area and high temperature resistance of the alumina material, inhibit the phase transformation process of the γ-Al2O3 material at high temperature, thereby improving the high temperature aging resistance of the alumina material, and at the same time improve the anti-shedding performance of the alumina material when used as a coating material. The preparation method has a simple process flow and high production efficiency, and can be introduced into the existing alumina material production line. The gasoline engine exhaust after-treatment module based on the alumina material has very good application prospects in the field of automobile exhaust treatment.

[0176] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0177] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0178] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a modified alumina material for tail gas treatment, characterized in that: It includes: A primary growth is performed on alumina to obtain an active alumina prestructure MgO-BaO-Al2O3; Performing secondary growth on the activated alumina pre-structure MgO-BaO-Al2O3 to obtain a modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment, wherein the molar ratio of Si to Mg in the modified alumina material SiO2-MgO-BaO-Al2O3 for exhaust gas treatment is 3-7.5:1; A growth process is performed on alumina to obtain an activated alumina pre-structure MgO-BaO-Al2O3, specifically comprising the following steps: Dissolving a soluble aluminum salt, a soluble magnesium salt, a soluble barium salt, and a soluble ammonium salt in a first solvent to prepare a solution A1; Alkali solution was added dropwise to solution A1 to adjust the pH of solution A1 to 7-8, and the mixture was stirred evenly and then subjected to a first aging treatment to obtain slurry A2; The slurry A2 is subjected to low temperature calcination and grinding to obtain an activated alumina pre-structure MgO-BaO-Al2O3; The low-temperature calcination treatment includes: calcining at 350-420° C. for 1-3 hours; Secondary growth is performed on the activated alumina pre-structure MgO-BaO-Al2O3 to obtain the modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment, which specifically includes the following steps: Add the activated alumina pre-structured MgO-BaO-Al2O3 into aqueous ammonia and mix well to obtain solution B1; Dissolving pseudo-boehmite powder and polyether-modified siloxane in a second solvent, adding nitric acid, and then adding the second solvent after ball milling to obtain solution B2; Heat solution B1 to 70-90°C, add solution B2 while stirring, and add alkali solution to adjust the pH to 8-9. After stirring evenly, perform a second aging treatment to obtain slurry B3; The slurry B3 was calcined at 300-500°C for 1-2h at a preset air flow rate; A second high-temperature calcination process is then performed to obtain the modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment.

2. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: In the activated alumina prestructure MgO-BaO-Al2O3, the MgO content is 0.2-4.0wt%, the BaO content is 0.5-5.0wt%, and Al2O3 accounts for 5-30% of the total weight of Al2O3 in the modified alumina material SiO2-MgO-BaO-Al2O3 for tail gas treatment.

3. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: The addition amounts of the soluble aluminum salt, soluble magnesium salt, and soluble barium salt are as follows: Al 3+ Mg 2+ and Ba 2+ The molar ratio of Al 3+ :Mg 2+ :Ba 2+ =90~95:0.2~5:0.1~2.

4. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: The soluble aluminum salt includes one or more of aluminum nitrate, aluminum sulfate and aluminum chloride; The soluble magnesium salt includes one or more of magnesium nitrate, magnesium sulfate, magnesium acetate and magnesium chloride; The soluble barium salt includes one or more of barium nitrate, barium acetate and barium chloride; The soluble ammonium salt includes one or more of ammonium sulfate and ammonium nitrate; The alkali solution is aqueous ammonia.

5. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: The first aging treatment includes: aging at 20-30° C. for 2-4 hours.

6. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: Before the slurry A2 is subjected to low-temperature calcination, the process further includes drying at 60-100°C.

7. The method for preparing the modified alumina material for tail gas treatment according to claim 6, wherein: Dry by spraying at 60-100℃.

8. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: Grind to particle size D 90 5-15 μm.

9. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: The mass fraction of the ammonia water is 5-10wt%; The polyether-modified siloxane is one or more of polyether-modified polydimethylsiloxane, polyether-modified trisiloxane, and polyether-modified heptamethylsiloxane.

10. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: When the activated alumina pre-structured MgO-BaO-Al2O3 is added to aqueous ammonia, one or more of polyhydroxyethyl acrylate, hydroxypropyl methylcellulose, hydroxypropyl cellulose and polyvinyl alcohol are also added.

11. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: Under ultrasonic dispersion conditions, solution B2 was added while stirring.

12. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: Before the slurry B3 is subjected to the first high-temperature roasting treatment, the process further includes drying at 100-120°C.

13. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: The second aging treatment includes: aging at 40-60° C. for 3-5 hours.

14. The method for preparing the modified alumina material for tail gas treatment according to claim 1, wherein: The second high-temperature calcination treatment includes calcining at 600-800° C. for 2-5 hours.

15. The method for preparing a modified alumina material for tail gas treatment according to claim 1, wherein: The preset air flow rate is 50-250 L / min.

16. A modified alumina material for tail gas treatment, characterized in that: The modified alumina material is prepared by the method for preparing the modified alumina material for tail gas treatment according to any one of claims 1 to 15.

17. A three-way catalyst, characterized in that: It includes the modified alumina material for tail gas treatment as claimed in claim 16.

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