A gasoline engine exhaust gas purification three-way catalyst and a preparation method thereof

Abstract

The application provides a gasoline engine exhaust purification three-way catalyst and a preparation method thereof. The gasoline engine exhaust purification three-way catalyst comprises a catalyst carrier and a coating layer coated on the carrier. The coating layer comprises a first coating layer and a second coating layer. The first coating layer comprises active components Pt, Pd and Ba modified Al2O3 material. The second coating layer comprises active components Ru, Co-Ni-Mg-Ce-Zr composite oxide and Al2O3. The gasoline engine exhaust purification three-way catalyst is low in price and can directly decompose by-products NH3, thereby reducing the emission of NH3 in exhaust gas.

Description

Technical Field

[0001] This invention relates to the field of three-way catalyst preparation, specifically, to a three-way catalyst for purifying gasoline engine exhaust and its preparation method. Background Technology

[0002] Exhaust gas treatment for natural gas engines is a significant environmental issue, especially given the stringent China VI emission standards. Natural gas engine exhaust gas treatment primarily relies on three-way catalytic converters (TWCs), which mainly utilize Pt-Pd-Rh noble metals as the active components.

[0003] Rh catalytically reduces NO in a ternary catalyst x The performance of Rh has always played a crucial role. The price of the precious metal Rh has remained high for many years, and researchers have been searching for alternatives, even using the previously relatively low-cost Pd, but so far, no true replacement for Rh has been achieved in terms of performance and practical application. Hybrid electric vehicles (HEVs) represent a relatively ideal technological route for the transition from pure electric to fully electric internal combustion engines, and are of great significance for energy conservation and emission reduction. In the current stage of China VI emission standards, mild hybrid vehicles have relatively good torque control and thermal management, and their engine operating conditions change more gently than those of traditional gasoline vehicles. The engine operates mostly in a high-efficiency range with low emissions, and during cold start-up, the engine's torque output can be controlled to be smaller, reducing emissions during cold starts and lowering the requirements for the ignition performance and durability of the three-way catalytic converter. Therefore, using low-cost active materials to replace Rh to reduce NO in the three-way catalytic converter is a viable option. x The reduction efficiency of [the substance] has become one of the research hotspots in the field of motor vehicle exhaust aftertreatment, and has very important technical and economic significance.

[0004] Recent studies have found that gasoline vehicles produce a certain amount of NH3 during operation. NH3 emissions seriously impact the environment and human health. NH3 emissions from light-duty gasoline vehicles are byproducts of the catalytic reaction of three-way catalytic converters. Primarily, CO and H2O in the exhaust gas react in the three-way catalytic converter to produce H2. Under the catalysis of Rh, H2 further catalyzes the reduction of some NO to NH3. Motor vehicle exhaust emissions are mainly concentrated in densely populated areas, potentially making them a significant source of NH3 emissions in urban areas. Statistics show that in 2014, the total NH3 emissions from motor vehicles in Shanghai were approximately 1300 tons, accounting for 12% of the city's total NH3 emissions. Therefore, it is necessary to control NH3 emissions from light-duty gasoline vehicles, and the currently being drafted China VII emission standards for light-duty gasoline vehicles may include NH3 in the emission control indicators.

[0005] Therefore, achieving complete replacement of Rh and enhancing the treatment effect of three-way catalysts on NH3 are currently research hotspots in the field of catalytic purification aftertreatment of gasoline engine exhaust. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to propose a novel three-way catalyst that is low in cost and reduces NH3 emissions in exhaust gas. According to embodiments of the invention, the preparation method is simple and the steps are easy to operate. This invention uses Pt and Pd as active components to form the first coating, and Ru as the active component to form the second coating. The first and second coatings respectively employ novel Ba-modified Al2O3 material and Co-Ni-Mg-Ce-Zr composite oxide material, improving the catalytic effect of the active components. The second coating, by introducing the lower-priced Ru to completely replace the expensive Rh, achieves a significant reduction in coating cost, while the formulation and process design of the first and second coatings ensures the catalytic effect of the three-way catalyst. Furthermore, the introduction of Ru and the Co-Ni-Mg-Ce-Zr composite oxide can also achieve the direct decomposition of the byproduct NH3, thereby reducing NH3 emissions in exhaust gas.

[0007] In one aspect, this invention provides a three-way catalytic converter for purifying gasoline engine exhaust gases. According to an embodiment of the invention, the three-way catalytic converter includes a catalyst support and a coating applied to the support. The coating includes a first coating and a second coating. The first coating includes active components Pt, Pd, and Ba-modified Al2O3 material, and the second coating includes active components Ru, Co-Ni-Mg-Ce-Zr composite oxide, and Al2O3. This three-way catalytic converter for purifying gasoline engine exhaust gases is inexpensive and can directly decompose the byproduct NH3, thereby reducing NH3 emissions in the exhaust gas.

[0008] According to embodiments of the present invention, the above-mentioned three-way catalytic converter for gasoline engine exhaust purification may further include at least one of the following additional technical features:

[0009] According to embodiments of the present invention, the mass ratio of BaO to Al2O3 in the Ba-modified Al2O3 material is 0.1–0.2. The inventors have found that this ratio range improves the thermal stability of Pt and Pd, while a ratio below this range provides limited improvement in thermal stability, and a ratio above this range has a certain impact on the stability of Al2O3 itself.

[0010] According to an embodiment of the present invention, the mass ratio of Co-Ni-Mg-Ce-Zr composite oxide to Al2O3 in the second coating is 0.5 to 0.8. The inventors have found that within this ratio range, the oxygen storage performance of the composite oxide and the ignition performance of Al2O3 can be balanced; below this range, the oxygen storage performance decreases, and above this range, the ignition performance is affected to some extent.

[0011] According to an embodiment of the present invention, the mass ratio of Co, Ni, Mg, Ce, and Zr in the Co-Ni-Mg-Ce-Zr composite oxide is (0.1–0.2):(0.1–0.2):(0.2–0.3):(1–2):(1–2). The inventors have found that within this ratio range, both oxygen storage performance and Ru activity are significantly improved; deviations from this range result in a certain degree of performance impact.

[0012] According to an embodiment of the present invention, the coating amount of the first coating is 60–80 g / L. The inventors have found that this range achieves an optimal balance between the fresh and aged properties of the catalyst.

[0013] According to an embodiment of the present invention, the coating amount of the second coating is 80–100 g / L. The inventors have found that this range achieves an optimal balance between the fresh and aged properties of the catalyst.

[0014] According to an embodiment of the present invention, the first coating covers the catalyst support, and the second coating covers the first coating.

[0015] According to an embodiment of the present invention, the catalyst support is a cordierite honeycomb ceramic support.

[0016] In another aspect, the present invention also provides a method for preparing a three-way catalytic converter for gasoline engine exhaust purification. According to an embodiment of the present invention, the method includes:

[0017] 1) Ba-modified Al2O3 material is mixed with water to obtain a first mixture. The first mixture is then mixed with a modified precursor solution of Pt and Pd to obtain a second mixture. The second mixture is then aged and then aluminum sol is added to obtain a first coating slurry.

[0018] 2) The first coating slurry is coated onto the catalyst support, and a first drying treatment and a first calcination treatment are performed to obtain a catalyst support coated with the first coating.

[0019] 3) The Co-Ni-Mg-Ce-Zr composite oxide, Al2O3 and water are subjected to a third mixing treatment to obtain a third mixture. The third mixture is then subjected to a fourth mixing treatment with a Ru-modified precursor solution to obtain a second coating slurry.

[0020] 4) The second coating slurry is coated onto the catalyst support coated with the first coating, followed by a second drying treatment and a second calcination treatment to obtain the gasoline engine exhaust gas purification three-way catalyst. This method is simple to operate, inexpensive, and suitable for large-scale industrial production. Furthermore, the gasoline engine exhaust gas purification three-way catalyst obtained by this method can directly decompose the byproduct NH3, thereby reducing the emission of NH3 in the exhaust gas.

[0021] According to embodiments of the present invention, the above method may further include at least one of the following additional technical features:

[0022] According to an embodiment of the present invention, the mass ratio of BaO to Al2O3 in the Ba-modified Al2O3 material is 0.1 to 0.2.

[0023] According to an embodiment of the present invention, the Ba-modified Al2O3 material is prepared by the following method:

[0024] Barium acetate is dissolved in water to obtain a barium acetate solution. Aluminum sol with a solid content of 30-40% is then mixed with the barium acetate solution in a fourth mixing process, a drying process, and a third calcination process to obtain the Ba-modified Al2O3 material. The mass ratio of BaO to Al2O3 is 0.1-0.2.

[0025] According to an embodiment of the present invention, the drying process is carried out by microwave drying.

[0026] According to an embodiment of the present invention, the drying rate after the drying treatment is >90%.

[0027] According to an embodiment of the present invention, the temperature of the third calcination treatment is 500-600°C.

[0028] According to an embodiment of the present invention, the third calcination treatment takes 2 to 4 hours.

[0029] According to an embodiment of the present invention, the solid content of the first mixture is 30-40%.

[0030] According to an embodiment of the present invention, the D90 of the first mixture is 8 to 15 μm.

[0031] According to an embodiment of the present invention, the second mixing treatment is carried out by adding a modified precursor solution of Pt and Pd dropwise to the first mixture under stirring conditions, wherein the dropwise acceleration rate is controlled to be 5-6 mL / min.

[0032] According to an embodiment of the present invention, the aging treatment temperature is 60–80°C.

[0033] According to an embodiment of the present invention, the aging process takes 1 to 2 hours.

[0034] According to an embodiment of the present invention, the mass of the aluminum sol relative to the cured product of the second mixture after aging treatment is 1 to 3%.

[0035] According to an embodiment of the present invention, the catalyst support is a cordierite honeycomb ceramic support.

[0036] According to an embodiment of the present invention, the coating amount of the first coating in the catalyst support coated with the first coating is 60-80 g / L.

[0037] According to an embodiment of the present invention, the temperature of the first drying process is 150-200°C.

[0038] According to an embodiment of the present invention, the drying rate of the first drying process is above 90%.

[0039] According to an embodiment of the present invention, the temperature of the first calcination treatment is 500-600°C.

[0040] According to an embodiment of the present invention, the first calcination treatment time is 2 to 4 hours.

[0041] According to an embodiment of the present invention, the coating amount of the second coating is 80-100 g / L.

[0042] According to an embodiment of the present invention, the temperature of the second drying process is 150-200°C.

[0043] According to an embodiment of the present invention, the drying rate of the second drying process is above 90%.

[0044] According to an embodiment of the present invention, the temperature of the second calcination treatment is 500-600°C.

[0045] According to an embodiment of the present invention, the second calcination treatment time is 2 to 4 hours.

[0046] According to an embodiment of the present invention, the mass ratio of the Co-Ni-Mg-Ce-Zr composite oxide to Al2O3 is 0.5 to 0.8.

[0047] According to an embodiment of the present invention, the mass ratio of Co, Ni, Mg, Ce and Zr in the Co-Ni-Mg-Ce-Zr composite oxide is (0.1~0.2):(0.1~0.2):(0.2~0.3):(1~2):(1~2).

[0048] According to an embodiment of the present invention, the Co-Ni-Mg-Ce-Zr composite oxide is prepared by the following method:

[0049] Cobalt nitrate, nickel nitrate, magnesium nitrate, and cerium nitrate were dissolved in water, and then zirconium sol with a solid content of 30-40% was added to obtain a mixed solution. The solution was then dried and subjected to a fifth calcination treatment to obtain the Co-Ni-Mg-Ce-Zr composite oxide.

[0050] According to an embodiment of the present invention, the drying process is carried out by microwave drying.

[0051] According to an embodiment of the present invention, the drying rate of the drying process is >90%.

[0052] According to an embodiment of the present invention, the temperature of the fifth calcination treatment is 500–600°C.

[0053] According to an embodiment of the present invention, the fifth calcination treatment takes 2 to 4 hours.

[0054] In another aspect, the present invention also provides a three-way catalyst for purifying gasoline engine exhaust gases. According to an embodiment of the present invention, the three-way catalyst for purifying gasoline engine exhaust gases comprises a cordierite honeycomb ceramic carrier, a first coating coated on the cordierite honeycomb carrier, and a second coating coated on the first coating; the first coating comprises Pt and Pd noble metal active components and Ba-modified Al2O3 material; the second coating comprises Ru noble metal active component, Co-Ni-Mg-Ce-Zr composite oxide, and Al2O3.

[0055] According to embodiments of the present invention, the above-mentioned three-way catalytic converter for gasoline engine exhaust purification may further include at least one of the following additional technical features:

[0056] According to an embodiment of the present invention, the first coating contains a Ba-modified Al2O3 material, wherein the mass ratio of BaO to Al2O3 is 0.1 to 0.2.

[0057] According to an embodiment of the present invention, the mass ratio of Co-Ni-Mg-Ce-Zr composite oxide to Al2O3 in the second coating is 0.5 to 0.8.

[0058] According to an embodiment of the present invention, the Co-Ni-Mg-Ce-Zr composite oxide in the second coating has a mass ratio of Co:Ni:Mg:Ce:Zr of 0.1~0.2:0.1~0.2:0.2~0.3:1~2:1~2.

[0059] According to an embodiment of the present invention, the coating amount of the first coating is 60-80 g / L; the coating amount of the second coating is 80-100 g / L.

[0060] In another aspect, the present invention also provides a method for preparing a three-way catalytic converter for purifying gasoline engine exhaust gases. According to an embodiment of the present invention, the method includes the following steps:

[0061] (1) Preparation of Ba-modified Al2O3 material: Barium acetate was added to sufficient deionized water and stirred to dissolve. According to the mass ratio of BaO to Al2O3 of 0.1 to 0.2, aluminum sol with a solid content of 30 to 40% was added to the above barium acetate solution and stirred thoroughly to mix evenly. Then the above mixture was microwave dried. The drying was completed when the drying rate was >90%. After that, the powder was calcined at 500 to 600°C for 2 to 4 hours to obtain Ba-modified Al2O3 material.

[0062] (2) Preparation of the first coating slurry: The slurry prepared in step (1) is mixed with deionized water to prepare a slurry. The amount of deionized water added is controlled so that the solid content of the slurry is 30-40%. Then the slurry is ball-milled so that the slurry D90 is 8-15μm. Pt and Pd modified precursor solutions are added dropwise while the slurry is stirred. The drop rate is controlled at 5-6mL / min. After the drop is completed, the slurry is aged at 60-80℃ for 1-2h. 1-3% aluminum sol relative to the mass of the solidified slurry is added to obtain the first coating slurry.

[0063] (3) Preparation of the first coating: The first coating slurry obtained in step (2) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier. After the coating is completed, the cordierite honeycomb ceramic carrier is dried rapidly at 150-200℃ to ensure that the drying rate is above 90%. Then the cordierite honeycomb ceramic carrier is calcined at 500-600℃ for 2-4 hours to complete the preparation of the first coating.

[0064] (4) Preparation of Co-Ni-Mg-Ce-Zr composite oxide: Cobalt nitrate, nickel nitrate, magnesium nitrate, and cerium nitrate were dissolved in sufficient deionized water and stirred evenly. Then, zirconium sol with a solid content of 30-40% was added and the mixture was stirred evenly. The mass ratio of Co:Ni:Mg:Ce:Zr in the above mixture was controlled at 0.1-0.2:0.1-0.2:0.2-0.3:1-2:1-2. Subsequently, the above mixture was microwave dried. Drying was completed when the drying rate was >90%. Then, the powder was calcined at 500-600℃ for 2-4 hours to obtain Co-Ni-Mg-Ce-Zr composite oxide.

[0065] (5) Preparation of the second coating slurry: The Co-Ni-Mg-Ce-Zr composite oxide and Al2O3 prepared in step (4) are mixed at a mass ratio of 0.5 to 0.8, and deionized water is added to prepare a slurry. The amount of deionized water added is controlled so that the solid content of the slurry is 20 to 30%. Then the slurry is ball-milled so that the slurry D90 is 10 to 20 μm. The Ru modified precursor solution is added dropwise while the slurry is stirred. The drop rate is controlled at 0.5 to 1 mL / min. After the drop is completed, the slurry is aged at room temperature for 8 to 12 h. 1 to 3% of aluminum sol relative to the mass of the solidified slurry is added to obtain the second coating slurry.

[0066] (6) Preparation of the second coating: The second coating slurry obtained in step (5) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier coated with the first coating obtained in step (3). After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 150-200℃ to ensure that the drying rate is above 90%. Then, the cordierite honeycomb ceramic carrier is calcined at 500-600℃ for 2-4 hours to complete the preparation of the second coating.

[0067] According to embodiments of the present invention, the above method may further include at least one of the following additional technical features:

[0068] According to an embodiment of the present invention, the Al sol in steps (2) and (5) has a solid content of 20-30%.

[0069] According to an embodiment of the present invention, the Pt and Pd modified precursor solution in step (2) is a solution of platinum nitrate and palladium nitrate with added acetic acid, wherein the amount of acetic acid added is 5 to 10% of the mass of Pt and Pd.

[0070] According to an embodiment of the present invention, the Ru-modified precursor solution in step (5) is a ruthenium nitrate solution with added oxalic acid, wherein the amount of oxalic acid added is 5-15% of the mass of Ru.

[0071] According to an embodiment of the present invention, the Al2O3 in step (5) has a γ-phase crystal form and a specific surface area of ​​100-200 m². 2 / g.

[0072] According to embodiments of the present invention, the preparation method of the present invention is simple and the steps are easy to operate.

[0073] According to embodiments of the present invention, Pt and Pd are used as active components to form the first coating, and Ru is used as the active component to form the second coating. The first and second coatings respectively employ novel Ba-modified Al2O3 material and Co-Ni-Mg-Ce-Zr composite oxide material, thereby enhancing the catalytic effect of the active components. The second coating significantly reduces coating costs by introducing the lower-priced Ru to completely replace the expensive Rh, while the formulation and process design of the first and second coatings ensures the catalytic effect of the three-way catalyst. Furthermore, the introduction of Ru and the Co-Ni-Mg-Ce-Zr composite oxide also enables the direct decomposition of the byproduct NH3, thereby reducing NH3 emissions in the exhaust gas. Detailed Implementation

[0074] The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0075] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0076] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0077] Example 1:

[0078] A three-way catalytic converter for gasoline engine exhaust purification includes a cordierite honeycomb ceramic support with dimensions of Ф118.4mm × 152.4mm, a pore density of 750cpsi, a pore wall thickness of 2mil, and a volume of 1.678L. The support is coated with a first coating and a second coating. The first coating has a coating amount of 60g / L, and the second coating has a coating amount of 80g / L. The first coating includes Pt and Pd noble metal active components, with a Pt content of 30g / ft. 3 Pd: 30g / ft 3 The second coating includes a Ru noble metal active component, with a Ru content of 20 g / ft. 3 .

[0079] The preparation method of a three-way catalytic converter for gasoline engine exhaust purification includes the following steps:

[0080] (1) Preparation of Ba modified Al2O3 material: Barium acetate was added to sufficient deionized water and stirred to dissolve. According to the mass ratio of BaO to Al2O3 of 0.1, aluminum sol with a solid content of 30% was added to the above barium acetate solution and stirred thoroughly to mix evenly. Then the above mixture was microwave dried. The drying was completed when the drying rate was 95%. After that, the powder was calcined at 500℃ for 4h to obtain Ba modified Al2O3 material.

[0081] (2) Preparation of the first coating slurry: The Ba modified Al2O3 material prepared in step (1) is mixed with deionized water to prepare a slurry. The amount of deionized water added is controlled so that the solid content of the slurry is 30%. Then the slurry is ball-milled so that the slurry D90 is 8μm. Under the stirring state of the slurry, a solution of platinum nitrate and palladium nitrate mixed with acetic acid is added dropwise. The amount of acetic acid added is 5% of the mass of Pt and Pd elements. The dropping rate is controlled at 5mL / min. After the dropping is completed, the slurry is aged at 60℃ for 2h. 1% of aluminum sol (aluminum sol solid content is 20%) relative to the mass of the solidified slurry is added to obtain the first coating slurry.

[0082] (3) Preparation of the first coating: The first coating slurry obtained in step (2) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier. After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 150°C with a drying rate of 93%. Then, the cordierite honeycomb ceramic carrier is calcined at 500°C for 4 hours to complete the preparation of the first coating.

[0083] (4) Preparation of Co-Ni-Mg-Ce-Zr composite oxide: Cobalt nitrate, nickel nitrate, magnesium nitrate, and cerium nitrate were dissolved in sufficient deionized water and stirred evenly. Then, zirconium sol with a solid content of 30% was added and the mixture was stirred evenly again. The mass ratio of Co:Ni:Mg:Ce:Zr in the above mixture was controlled at 0.1:0.1:0.2:1:1. Subsequently, the above mixture was microwave dried until the drying rate reached 92%. The powder was then calcined at 500℃ for 4 hours to obtain the Co-Ni-Mg-Ce-Zr composite oxide.

[0084] (5) Preparation of the second coating slurry: The Co-Ni-Mg-Ce-Zr composite oxide prepared in step (4) and γ-phase Al2O3 are mixed at a mass ratio of 0.5. The specific surface area of ​​the Al2O3 is 100 m². 2 / g, then deionized water was added to prepare a slurry. The amount of deionized water added was controlled so that the solid content of the slurry was 20%. The slurry was then ball-milled to make the slurry D90 10μm. Ruthenium nitrate solution containing oxalic acid was added dropwise while the slurry was stirred. The amount of oxalic acid added was 5% of the mass of Ru elemental. The dropping rate was controlled at 0.5mL / min. After the dropping was completed, the slurry was aged at room temperature for 8h. 1% aluminum sol (aluminum sol solid content of 20%) relative to the mass of the solidified slurry was added to obtain the second coating slurry.

[0085] (6) Preparation of the second coating: The second coating slurry obtained in step (5) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier coated with the first coating obtained in step (3). After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 150°C with a drying rate of 93%. Then, the cordierite honeycomb ceramic carrier is calcined at 500°C for 4 hours to complete the preparation of the second coating.

[0086] Example 2:

[0087] A three-way catalyst for gasoline engine exhaust purification includes a cordierite honeycomb ceramic carrier with dimensions of Ф118.4mm × 152.4mm, a pore density of 750cpsi, a pore wall thickness of 2mil, and a volume of 1.678L. The carrier is coated with a first coating and a second coating. The first coating has a coating amount of 80g / L, and the second coating has a coating amount of 100g / L. The first coating includes Pt and Pd noble metal active components, with a Pt content of 30g / ft. 3 Pd: 30g / ft 3 The second coating includes a Ru noble metal active component, with a Ru content of 20 g / ft. 3 .

[0088] The preparation method of a three-way catalytic converter for gasoline engine exhaust purification includes the following steps:

[0089] (1) Preparation of Ba modified Al2O3 material: Barium acetate was added to sufficient deionized water and stirred to dissolve. According to the mass ratio of BaO to Al2O3 of 0.2, aluminum sol with a solid content of 40% was added to the above barium acetate solution and stirred thoroughly to mix evenly. Then the above mixture was microwave dried. The drying was completed when the drying rate was 94%. After that, the powder was calcined at 600℃ for 2h to obtain Ba modified Al2O3 material.

[0090] (2) Preparation of the first coating slurry: The Ba modified Al2O3 material prepared in step (1) is mixed with deionized water to prepare a slurry. The amount of deionized water added is controlled so that the solid content of the slurry is 40%. Then the slurry is ball-milled so that the slurry D90 is 15μm. Under the stirring state of the slurry, a solution of platinum nitrate and palladium nitrate mixed with acetic acid is added dropwise. The amount of acetic acid added is 10% of the mass of Pt and Pd elements. The dropping rate is controlled at 6mL / min. After the dropping is completed, the slurry is aged at 80℃ for 1h. 3% of aluminum sol (aluminum sol solid content is 30%) relative to the mass of the solidified slurry is added to obtain the first coating slurry.

[0091] (3) Preparation of the first coating: The first coating slurry obtained in step (2) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier. After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 200°C with a drying rate of 92%. Then, the cordierite honeycomb ceramic carrier is calcined at 600°C for 2 hours to complete the preparation of the first coating.

[0092] (4) Preparation of Co-Ni-Mg-Ce-Zr composite oxide: Cobalt nitrate, nickel nitrate, magnesium nitrate, and cerium nitrate were dissolved in sufficient deionized water and stirred evenly. Then, zirconium sol with a solid content of 40% was added and the mixture was stirred evenly again. The mass ratio of Co:Ni:Mg:Ce:Zr in the above mixture was controlled at 0.2:0.2:0.3:2:2. Subsequently, the above mixture was microwave dried until the drying rate reached 95%. The powder was then calcined at 600℃ for 2 hours to obtain the Co-Ni-Mg-Ce-Zr composite oxide.

[0093] (5) Preparation of the second coating slurry: The Co-Ni-Mg-Ce-Zr composite oxide prepared in step (4) and γ-phase Al2O3 are mixed at a mass ratio of 0.8. The specific surface area of ​​the Al2O3 is 200 m². 2 / g, then add deionized water to prepare a slurry, control the amount of deionized water added to make the slurry solid content 30%, then ball mill the slurry to make the slurry D90 20μm, and add ruthenium nitrate solution containing oxalic acid dropwise while stirring the slurry, wherein the amount of oxalic acid added is 15% of the mass of Ru elemental, and the dropping rate is controlled at 1mL / min. After the dropping is completed, the slurry is aged at room temperature for 12h, and 3% of aluminum sol (aluminum sol solid content is 30%) relative to the mass of the slurry solids are added to obtain the second coating slurry;

[0094] (6) Preparation of the second coating: The second coating slurry obtained in step (5) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier coated with the first coating obtained in step (3). After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 200°C with a drying rate of 92%. Then, the cordierite honeycomb ceramic carrier is calcined at 600°C for 2 hours to complete the preparation of the second coating.

[0095] Example 3:

[0096] A three-way catalyst for gasoline engine exhaust purification includes a cordierite honeycomb ceramic carrier with dimensions of Ф118.4mm × 152.4mm, a pore density of 750cpsi, a pore wall thickness of 2mil, and a volume of 1.678L. The carrier is coated with a first coating and a second coating. The first coating has a coating amount of 60g / L, and the second coating has a coating amount of 100g / L. The first coating includes Pt and Pd noble metal active components, with a Pt content of 30g / ft. 3 Pd: 30g / ft 3 The second coating includes a Ru noble metal active component, with a Ru content of 20 g / ft. 3 .

[0097] The preparation method of a three-way catalytic converter for gasoline engine exhaust purification includes the following steps:

[0098] (1) Preparation of Ba modified Al2O3 material: Barium acetate was added to sufficient deionized water and stirred to dissolve. According to the mass ratio of BaO to Al2O3 of 0.15, aluminum sol with a solid content of 35% was added to the above barium acetate solution and stirred thoroughly to mix evenly. Then the above mixture was microwave dried. The drying was completed when the drying rate was 95%. After that, the powder was calcined at 550℃ for 3h to obtain Ba modified Al2O3 material.

[0099] (2) Preparation of the first coating slurry: The Ba modified Al2O3 material prepared in step (1) is mixed with deionized water to prepare a slurry. The amount of deionized water added is controlled so that the solid content of the slurry is 35%. Then the slurry is ball-milled so that the slurry D90 is 12μm. Under the stirring state of the slurry, a solution of platinum nitrate and palladium nitrate mixed with acetic acid is added dropwise. The amount of acetic acid added is 8% of the mass of Pt and Pd elements. The dropping rate is controlled at 6mL / min. After the dropping is completed, the slurry is aged at 70℃ for 1h. 2% of aluminum sol (aluminum sol solid content is 25%) relative to the mass of the solidified slurry is added to obtain the first coating slurry.

[0100] (3) Preparation of the first coating: The first coating slurry obtained in step (2) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier. After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 180°C with a drying rate of 93%. Then, the cordierite honeycomb ceramic carrier is calcined at 550°C for 3 hours to complete the preparation of the first coating.

[0101] (4) Preparation of Co-Ni-Mg-Ce-Zr composite oxide: Cobalt nitrate, nickel nitrate, magnesium nitrate, and cerium nitrate were dissolved in sufficient deionized water and stirred evenly. Then, zirconium sol with a solid content of 35% was added and the mixture was stirred evenly again. The mass ratio of Co:Ni:Mg:Ce:Zr in the above mixture was controlled at 0.15:0.15:0.25:1.5:1.5. Subsequently, the above mixture was microwave dried until the drying rate reached 96%. The powder was then calcined at 550℃ for 3 hours to obtain the Co-Ni-Mg-Ce-Zr composite oxide.

[0102] (5) Preparation of the second coating slurry: The Co-Ni-Mg-Ce-Zr composite oxide prepared in step (4) and γ-phase Al2O3 are mixed at a mass ratio of 0.6. The specific surface area of ​​the Al2O3 is 150 m². 2 / g, then deionized water was added to prepare a slurry. The amount of deionized water added was controlled so that the solid content of the slurry was 25%. The slurry was then ball-milled to make the slurry D90 15μm. Ruthenium nitrate solution containing oxalic acid was added dropwise while the slurry was stirred. The amount of oxalic acid added was 10% of the mass of Ru elemental. The dropping rate was controlled at 1mL / min. After the dropping was completed, the slurry was aged at room temperature for 10h. 2% aluminum sol (aluminum sol solid content of 25%) relative to the mass of the solidified slurry was added to obtain the second coating slurry.

[0103] (6) Preparation of the second coating: The second coating slurry obtained in step (5) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier coated with the first coating obtained in step (3). After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 180°C with a drying rate of 94%. Then, the cordierite honeycomb ceramic carrier is calcined at 550°C for 3 hours to complete the preparation of the second coating.

[0104] Example 4:

[0105] A three-way catalyst for gasoline engine exhaust purification includes a cordierite honeycomb ceramic carrier with dimensions of Ф118.4mm × 152.4mm, a pore density of 750cpsi, a pore wall thickness of 2mil, and a volume of 1.678L. The carrier is coated with a first coating and a second coating, with the first coating having a coating weight of 80g / L and the second coating having a coating weight of 80g / L. The first coating includes Pt and Pd noble metal active components, with a Pt content of 30g / ft.3 Pd: 30g / ft 3 The second coating includes a Ru noble metal active component, with a Ru content of 20 g / ft. 3 .

[0106] The preparation method of a three-way catalytic converter for gasoline engine exhaust purification includes the following steps:

[0107] (1) Preparation of Ba modified Al2O3 material: Barium acetate was added to sufficient deionized water and stirred to dissolve. According to the mass ratio of BaO to Al2O3 of 0.16, aluminum sol with a solid content of 37% was added to the above barium acetate solution and stirred thoroughly to mix evenly. Then the above mixture was microwave dried. The drying was completed when the drying rate was 95%. After that, the powder was calcined at 550℃ for 3h to obtain Ba modified Al2O3 material.

[0108] (2) Preparation of the first coating slurry: The Ba modified Al2O3 material prepared in step (1) is mixed with deionized water to prepare a slurry. The amount of deionized water added is controlled so that the solid content of the slurry is 30%. Then the slurry is ball-milled so that the slurry D90 is 13μm. Under the stirring state of the slurry, a solution of platinum nitrate and palladium nitrate mixed with acetic acid is added dropwise. The amount of acetic acid added is 7% of the mass of Pt and Pd elements. The dropping rate is controlled at 6mL / min. After the dropping is completed, the slurry is aged at 70℃ for 2h. 2% of aluminum sol (aluminum sol solid content is 25%) relative to the mass of the solidified slurry is added to obtain the first coating slurry.

[0109] (3) Preparation of the first coating: The first coating slurry obtained in step (2) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier. After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 160°C with a drying rate of 92%. Then, the cordierite honeycomb ceramic carrier is calcined at 550°C for 4 hours to complete the preparation of the first coating.

[0110] (4) Preparation of Co-Ni-Mg-Ce-Zr composite oxide: Cobalt nitrate, nickel nitrate, magnesium nitrate, and cerium nitrate were dissolved in sufficient deionized water and stirred evenly. Then, zirconium sol with a solid content of 30% was added and the mixture was stirred evenly again. The mass ratio of Co:Ni:Mg:Ce:Zr in the above mixture was controlled at 0.15:0.15:0.2:2:1.5. Subsequently, the above mixture was microwave dried until the drying rate reached 96%. The powder was then calcined at 550℃ for 3 hours to obtain the Co-Ni-Mg-Ce-Zr composite oxide.

[0111] (5) Preparation of the second coating slurry: The Co-Ni-Mg-Ce-Zr composite oxide prepared in step (4) and γ-phase Al2O3 are mixed at a mass ratio of 0.7. The specific surface area of ​​the Al2O3 is 180 m². 2 / g, then deionized water was added to prepare a slurry. The amount of deionized water added was controlled so that the solid content of the slurry was 24%. The slurry was then ball-milled to make the slurry D90 16μm. Ruthenium nitrate solution containing oxalic acid was added dropwise while the slurry was stirred. The amount of oxalic acid added was 12% of the mass of Ru elemental. The dropping rate was controlled at 1mL / min. After the dropping was completed, the slurry was aged at room temperature for 9h. 2% of aluminum sol (aluminum sol solid content was 30%) relative to the mass of the solidified slurry was added to obtain the second coating slurry.

[0112] (6) Preparation of the second coating: The second coating slurry obtained in step (5) is coated onto the inner wall pores of the cordierite honeycomb ceramic carrier coated with the first coating obtained in step (3). After the coating is completed, the cordierite honeycomb ceramic carrier is rapidly dried at 160°C with a drying rate of 93%. Then, the cordierite honeycomb ceramic carrier is calcined at 550°C for 4 hours to complete the preparation of the second coating.

[0113] Comparative Example 1:

[0114] Comparative Example 1 is a commercial three-way catalyst used in the "China VI b" emission standard stage, with the same support size and specifications as Examples 1-4. The Pt and Pd noble metal contents of Comparative Example 1 are the same as in Examples 1-4, and the Rh content is 4 g / ft. 3 It does not contain Ru components.

[0115] Performance comparison test:

[0116] The three-way catalysts corresponding to Examples 1-4 and Comparative Example 1 were respectively encapsulated into exhaust purifiers and installed in the exhaust system of a 1.5T displacement China VI light-duty gasoline vehicle (Category I vehicle), with a tight coupling installation position. Subsequently, a Type I test as specified in GB18352.6-2016 was conducted on a vehicle swivel, comparing the fresh CO, THC, and NO levels of each scheme. x And NH3 gaseous pollutant emissions. The catalysts from the above-mentioned schemes were then installed on a gasoline engine test bench and aged using the Standard Bench Cycle (SBC) according to GB18352.6-2016 requirements for 200 hours. After aging, the catalysts from each scheme were installed in the exhaust system of a 1.5T displacement China VI light-duty gasoline vehicle, and the Type I test specified in GB18352.6-2016 was conducted on a vehicle swivel. The emission comparison test results are shown in Table 1.

[0117] Table 1 Comparison of gaseous pollutant emissions from each Scheme in Type I trials

[0118]

[0119] Table 1 shows that the catalysts prepared using the methods in Examples 1-4 of this invention have varying levels of CO, THC, and NO in both their fresh and aged states. x The pollutant emission values ​​are basically equivalent to those of Comparative Example 1, and all meet the China VI (b) emission limits. Furthermore, the NH3 emissions of Examples 1-4 are significantly lower than those of Comparative Example 1. Because this invention uses Ru and Co-Ni-Mg-Ce-Zr composite oxides as the active components of the second coating, it effectively ensures that the coating effectively controls NO emissions without using expensive Rh metals. x The conversion efficiency is high, especially since the active components mentioned above can effectively decompose NH3, thereby reducing the emission of NH3 in the exhaust gas. Since the price of Ru is only about one-tenth of that of Rh, in Examples 1-4 and Comparative Example 1, with the same Pt ​​and Pd noble metal content, the total price of Ru in the former is only about half the total price of Rh in the latter, thus significantly reducing the coating cost.

[0120] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A three-way catalytic converter for purifying gasoline engine exhaust gases, characterized in that, The catalyst includes a catalyst support and a coating applied to the support. The coating includes a first coating and a second coating. The first coating includes active components Pt, Pd, and Ba-modified Al2O3 material, and the second coating includes active components Ru, Co-Ni-Mg-Ce-Zr composite oxide, and Al2O3. The mass ratio of Co-Ni-Mg-Ce-Zr composite oxide to Al2O3 in the second coating is 0.5~0.8; The mass ratio of Co, Ni, Mg, Ce and Zr in the Co-Ni-Mg-Ce-Zr composite oxide is (0.1~0.2): (0.1~0.2): (0.2~0.3): (1~2): (1~2).

2. The three-way catalytic converter for gasoline engine exhaust purification according to claim 1, characterized in that, The mass ratio of BaO to Al2O3 in the Ba-modified Al2O3 material is 0.1~0.

2.

3. The three-way catalytic converter for gasoline engine exhaust purification according to claim 1, characterized in that, The coating amount of the first coating is 60~80 g / L; Optionally, the coating amount of the second coating is 80~100 g / L; Optionally, the first coating covers the catalyst support, and the second coating covers the first coating; Optionally, the catalyst support is a cordierite honeycomb ceramic support.

4. A method for preparing a three-way catalytic converter for gasoline engine exhaust purification as described in any one of claims 1 to 3, characterized in that, include: 1) Ba-modified Al2O3 material is mixed with water to obtain a first mixture. The first mixture is then mixed with a modified precursor solution of Pt and Pd to obtain a second mixture. The second mixture is then aged and then aluminum sol is added to obtain a first coating slurry. 2) The first coating slurry is coated onto the catalyst support, and then subjected to a first drying treatment and a first calcination treatment to obtain a catalyst support coated with the first coating. 3) The Co-Ni-Mg-Ce-Zr composite oxide, Al2O3 and water are subjected to a third mixing treatment to obtain a third mixture. The third mixture is then subjected to a fourth mixing treatment with a Ru-modified precursor solution to obtain a second coating slurry. 4) The second coating slurry is coated onto the catalyst carrier coated with the first coating, and then subjected to a second drying treatment and a second calcination treatment to obtain the three-way catalyst for purifying gasoline engine exhaust gas.

5. The method according to claim 4, characterized in that, The mass ratio of BaO to Al2O3 in the Ba-modified Al2O3 material is 0.1~0.2; Optionally, the Ba-modified Al2O3 material is prepared by the following method: Barium acetate is dissolved in water to obtain a barium acetate solution. Aluminum sol with a solid content of 30-40% is then mixed with the barium acetate solution in a fourth mixing process, a drying process, and a third calcination process to obtain the Ba-modified Al2O3 material. The mass ratio of BaO to Al2O3 is 0.1-0.

2. Optionally, the drying process is carried out by microwave drying; Optionally, the drying rate after the drying treatment is >90%; Optionally, the temperature of the third calcination treatment is 500~600 ℃; Optionally, the third roasting treatment takes 2 to 4 hours.

6. The method according to claim 4, characterized in that, The solid content of the first mixture is 30-40%; Optionally, the D90 of the first mixture is 8~15 μm; Optionally, the second mixing process is carried out by adding a modified precursor solution of Pt and Pd dropwise to the first mixture under stirring conditions, wherein the dropwise acceleration rate is controlled at 5~6 mL / min; Optionally, the aging treatment temperature is 60~80 ℃; Optionally, the aging process takes 1 to 2 hours; Optionally, the mass of the aluminum sol relative to the cured product of the second mixture after aging is 1 to 3%.

7. The method according to claim 4, characterized in that, The catalyst support is a cordierite honeycomb ceramic support; Optionally, the coating amount of the first coating in the catalyst support is 60~80 g / L; Optionally, the temperature of the first drying treatment is 150~200℃; Optionally, the drying rate of the first drying treatment is above 90%; Optionally, the temperature of the first calcination treatment is 500~600 ℃; Optionally, the first calcination treatment time is 2 to 4 hours; Optionally, the coating amount of the second coating is 80~100 g / L; Optionally, the temperature of the second drying process is 150~200℃; Optionally, the drying rate of the second drying treatment is above 90%; Optionally, the temperature of the second calcination treatment is 500~600 ℃; Optionally, the second roasting treatment time is 2 to 4 hours.

8. The method according to claim 4, characterized in that, The mass ratio of the Co-Ni-Mg-Ce-Zr composite oxide to Al2O3 is 0.5~0.8; Optionally, the mass ratio of Co, Ni, Mg, Ce, and Zr in the Co-Ni-Mg-Ce-Zr composite oxide is (0.1~0.2):(0.1~0.2):(0.2~0.3):(1~2):(1~2); Optionally, the Co-Ni-Mg-Ce-Zr composite oxide is prepared by the following method: Cobalt nitrate, nickel nitrate, magnesium nitrate, and cerium nitrate were dissolved in water, and then zirconium sol with a solid content of 30-40% was added to obtain a mixed solution. The solution was then dried and subjected to a fifth calcination treatment to obtain the Co-Ni-Mg-Ce-Zr composite oxide. Optionally, the drying process is carried out by microwave drying; Optionally, the drying rate of the drying process is >90%; Optionally, the temperature of the fifth calcination treatment is 500~600 ℃; Optionally, the fifth calcination treatment takes 2 to 4 hours.

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