Method for reducing dosage of noble metal, post-treatment catalyst for natural gas vehicle and preparation method of post-treatment catalyst

Abstract

The invention relates to the technical field of natural gas vehicle tail gas purification catalysts, and particularly discloses a method for reducing the dosage of precious metal, a natural gas vehicle post-treatment catalyst and a preparation method, and the natural gas vehicle post-treatment catalyst comprises an upper catalytic coating and a bottom catalytic coating; the upper catalytic coating comprises precious metal and rare earth composite oxide; the bottom catalytic coating comprises noble metal and modified aluminum oxide, and the modified aluminum oxide is cerium modified aluminum oxide CeAlOx doped with-NH2 groups grafted on the surface of BaSO4; and the total content of noble metals in the upper catalytic coating and the bottom catalytic coating is 20-50g / cfu. The alumina carrier in the bottom catalyst is uniquely modified, so that the freshness and durability of the catalyst can be ensured and improved on the basis that the use amount of noble metal is reduced by more than 50% compared with that of a commercially available catalyst, the durability requirements of laws and regulations are met, and the problem that the cost of the current post-treatment catalyst is high is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas vehicle exhaust purification catalyst, in particular to a method for reducing the amount of noble metal, a natural gas vehicle aftertreatment catalyst and a preparation method. BACKGROUND

[0002] With the increasing demand for heavy natural gas vehicles, the corresponding increase in exhaust pollutants such as hydrocarbons (mainly methane), carbon monoxide and nitrogen oxides. Methane in the exhaust of natural gas vehicles is the most stable alkane, which is more difficult to handle than hydrocarbons in gasoline and diesel vehicles, so the natural gas vehicle aftertreatment catalyst needs to use a high content of noble metal to ensure its catalytic performance on methane. Since the implementation of the national sixth emission standard for heavy natural gas vehicles, although the amount of noble metal in the catalyst has been greatly reduced, the amount of noble metal in each set of the mainstream heavy natural gas vehicle aftertreatment catalyst on the market is still more than 30g, resulting in high cost.

[0003] The engine-aftertreatment system durability test method required by the national sixth emission standard can be carried out on a vehicle or an engine test bench, and the durability test mileage should not be less than the minimum driving distance, among which the minimum driving distance for N3 type 16-ton heavy vehicles is 233000km, and the corresponding bench durability time according to the standard cycle of GB20890-2007 is 1456h (5h bench durability = 800km vehicle mileage). The durability test for such a long time is a great test for the durability of the catalyst, especially after several rounds of cost reduction iteration, the amount of noble metal in the catalyst has been greatly reduced, and if it is further reduced, it will not meet the durability requirements.

[0004] Therefore, how to reduce the amount of noble metal while ensuring the fresh performance of the catalyst and the performance after 1456h standard bench durability, which is equivalent to or better than the mainstream catalyst on the market, is a problem that needs to be solved in the industry. The present application discloses a low-noble-metal catalyst, which reduces the amount of noble metal by more than 50% compared to the mainstream catalyst on the market, which not only solves the problem of high cost of the current aftertreatment catalyst, but also greatly improves the durability of the catalyst, and can meet the durability requirements of the regulations.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] The prior art has the problem that the noble metal content of a natural gas vehicle aftertreatment catalyst is still high, and further reducing the noble metal content will result in the fresh performance and durability of the catalyst failing to meet the requirements, so the application provides a method for reducing the noble metal content, a natural gas vehicle aftertreatment catalyst and a preparation method, which can ensure and improve the freshness and durability of the catalyst on the basis of reducing the noble metal content by more than 50% compared with a commercially available catalyst, meet the durability requirements of regulations, and solve the problem of high cost of the current aftertreatment catalyst.

[0007] The application is implemented by the following technical solutions: In a first aspect, the application provides a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal content, comprising an upper layer of catalytic coating and a bottom layer of catalytic coating. The upper layer of catalytic coating comprises noble metal and rare earth composite oxide. The bottom layer of catalytic coating comprises noble metal and modified alumina, and the modified alumina is cerium-modified alumina CeAlO doped with BaSO4 surface grafted -NH2 groups. x ; The total content of noble metal in the upper layer of catalytic coating and the bottom layer of catalytic coating is 20-50 g / cft.

[0008] Currently, there are many ways to modify alumina carriers, for example, the most common is to use cerium-modified alumina, although cerium-modified alumina can improve the oxygen storage capacity, but the dispersion process is not good, which easily leads to the agglomeration of CeO2, and the cerium-modified alumina is prone to grain coarsening at high temperatures, and no strengthening phase is generated, so its thermal shock resistance is limited. When the addition amount of barium is too much and unevenly dispersed, it will accelerate the collapse of the pore channels of the alumina and the abnormal growth of the crystal grains, resulting in a sharp decrease in the specific surface area and reducing the performance of the catalyst.

[0009] The application further modifies the existing cerium-modified alumina by doping BaSO4 surface grafted -NH2 groups, which can enhance the bonding with alumina, improve the dispersion uniformity of alumina and CeO2, avoid the agglomeration of CeO2, thereby improving the specific surface area retention rate of the alumina material after high-temperature aging, and also increasing the electron density of the noble metal Pd, strengthening the Pd-O bond, optimizing the electronic structure of the Pd / Al2O3 catalyst, inhibiting the high-temperature decomposition of PdO to enhance the stability of PdO, and thus effectively improving the activity of methane combustion.

[0010] Therefore, by adding the special modified alumina material of the application, the fresh performance and the anti-aging ability of the catalyst can be greatly improved, and the performance of the catalyst can be kept equivalent or better than that of the commercially available catalyst even if the amount of noble metal is reduced by half (the total amount of noble metal is 20 g / cft); the amount of noble metal in the catalyst of the application can be selected as 20 g / cft, which is lower than the amount of noble metal in the commercially available catalyst (more than 50 g / cft), and the fresh performance and the anti-aging ability of the catalyst can still be kept equivalent or better than those of the commercially available catalyst.

[0011] In a specific embodiment, the BaSO4 surface is grafted with -NH2 groups by modifying BaSO4 with γ-aminopropyl triethoxysilane (KH-550, A-1100) or γ-(2,3-epoxypropoxy) propyl trimethoxysilane (KH-560, A-187).

[0012] In a specific embodiment, the noble metal in the bottom catalytic coating layer is Pd or Pd and Pt; the content of Pd is 1-50 g / cft, and the content of Pt is 0-50 g / cft; the total content of noble metal in the bottom catalytic coating layer is 1-50 g / cft.

[0013] In a specific embodiment, the noble metal in the upper catalytic coating layer is Pt and Rh; the content of Pt is 1-50 g / cft, and the content of Rh is 0.4-10 g / cft; the total content of noble metal in the upper catalytic coating layer is 1.4-50 g / cft.

[0014] In a specific embodiment, the content of BaSO4 in the modified alumina is 0-5wt% of the content of cerium-modified alumina CeAlO x .

[0015] In a specific embodiment, the rare earth composite oxide is a modified rare earth composite oxide obtained by doping Y, Sm, Pr, and La into a cerium-based oxide.

[0016] The application improves the carrier material in the upper catalytic coating layer, introduces Y, Sm, Pr, and La into CeO2 to form a multi-component composite oxide, which can significantly improve the oxygen storage performance, stability, catalytic performance, and anti-aging performance of the material compared with single doping or the traditional Ce-Zr system; Y 3+ , Sm 3+ , Pr 3+ / Pr 4+ , and La 3+ are low-valence / variable-valence ions, which can produce charge compensation type oxygen vacancies after entering the CeO2 lattice, and at the same time cause multi-level lattice distortion to produce more oxygen vacancies, thereby improving the oxygen storage performance of CeO2, La 3+ , Y 3+It can improve the surface basicity, promote the anchoring of noble metals such as Pt and Pd, reduce the high-temperature sintering tendency, and inhibit the carbon deposition; Sm 3+ It can promote the full dispersion of noble metals in the carrier material and improve the catalytic performance. The carrier of the upper catalytic coating in the application can further improve the catalytic performance and anti-aging performance of the catalyst by using a rare earth composite oxide modified by multi-element doping. The modified alumina can further ensure that the catalyst performance can meet the regulatory requirements after reducing the amount of noble metal.

[0017] In a specific embodiment, the rare earth composite oxide contains the following mass fraction: CeO2 is 50-75 wt%, Y2O3 is 2-5 wt%, Pr2O3 is 2.5-15 wt%, Sm2O3 is 0.5-15 wt%, and La2O3 is 10-15 wt%.

[0018] In a specific embodiment, an intermediate transition layer is arranged between the upper catalytic coating and the bottom catalytic coating, and the intermediate transition layer uses a cerium-zirconium-aluminum-based composite oxide.

[0019] In the application, Ce as the main component ensures the cubic fluorite structure, has a high lattice energy, and can maintain structural stability under high temperature, oxidation or reduction conditions; La can avoid excessive lattice distortion, and appropriate La 3+ Doping can introduce a large number of oxygen vacancies and significantly increase the oxygen vacancy concentration; Pr provides variable valence Pr 3+ / Pr 4+ It can more efficiently adjust the oxygen concentration and inhibit the migration of CeO2 grains at high temperatures to improve the high-temperature stability of the catalyst; and a small amount of Y and Sm doping can promote the anchoring and dispersion of noble metals, reduce their high-temperature sintering tendency, and inhibit carbon deposition.

[0020] Because the material components of the bottom catalytic coating and the upper catalytic coating are quite different, the thermal expansion coefficients of the bottom and the upper layer are quite different. This difference can cause the interface stress of the bottom and the upper layer to be relatively concentrated, leading to the generation of coating cracking, and causing the three-way performance of the catalyst to decrease; at the same time, the layered coating can cause the porosity to increase, causing the effective contact surface of the reaction gas and the catalyst coating to decrease or the pores to be blocked, the diffusion mass transfer resistance to increase, and part of the active sites to be ineffective.

[0021] The present application adds an intermediate transition layer, the thermal expansion coefficient of which is between the bottom layer and the upper layer, and the middle layer coating is not subjected to a separate baking process, but is baked together after the upper layer slurry coating is completed, which can balance the thermal expansion coefficient of the entire catalyst coating, reduce the thermal stress concentration coefficient, enhance the force between the middle layer and the bottom layer and the upper layer, improve the bonding energy of the interface, and ensure the durability of the catalyst; in addition, during preparation, the slurry is ball milled by using zirconium balls with a wider distribution range, so that the middle layer slurry with a larger particle size dispersion can be obtained, which can ensure the high mass transfer capacity of the catalyst and maintain the high capacity of CH4, NO x and CO for a long period of time.

[0022] In a specific embodiment, the mass fraction of each component in the cerium-zirconium-aluminum-based composite oxide is: CeO2 is 30-70 wt%, ZrO2 is 30-60 wt%, Al2O3 is 0-20 wt%, and the additive (La2O3 or Pr2O3) is 0-5 wt%.

[0023] In a specific embodiment, the coating amount of the upper catalytic coating is 50-150 g / L, the coating amount of the bottom catalytic coating is 50-150 g / L, and the coating amount of the intermediate transition layer is 60-100 g / L.

[0024] In a specific embodiment, the bottom catalytic coating further comprises a cerium-zirconium composite oxide, and the ratio of the modified alumina and the cerium-zirconium composite oxide is 1:2-2:1. The present application uses a mixture of modified alumina and cerium-zirconium composite oxide as a noble metal carrier material for the bottom catalytic coating, the alumina material provides a high dispersion platform and a basic structure, and the cerium-zirconium composite oxide provides dynamic oxygen buffering and thermal stability support. They depend on each other and complement each other's functions: the cerium-zirconium composite oxide relies on the large specific surface area of the alumina material to achieve good dispersion of itself and the noble metal, and stabilizes the alumina material structure; the alumina material relies on the oxygen storage function of the cerium-zirconium composite oxide to maintain a wide window and high efficiency, and carries the main oxidation active components, which can further ensure the related performance of the catalyst.

[0025] In a specific embodiment, the cerium-zirconium composite oxide is doped with La and Pr.

[0026] In a second aspect, the present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal dosage, comprising the following steps: S1, bottom catalytic coating preparation: Dissolve BaSO4 powder in a solvent, and then add γ-aminopropyl triethoxysilane to graft -NH2 groups on the surface of BaSO4; Add the -NH2 groups grafted on the surface of BaSO4 to CeAlO xMixing in the slurry, drying, calcining to obtain BaSO4 modified alumina powder carrier; The noble metal is loaded on the BaSO4 modified alumina powder carrier, a bottom layer catalyst slurry is prepared, coated on the surface of the carrier, dried, and calcined to obtain a bottom layer catalyst coating; S2, intermediate transition layer preparation: The cerium zirconium aluminum oxide powder is prepared into a slurry, coated on the bottom layer catalyst coating, and dried; S3, upper layer catalyst coating preparation: The noble metal is loaded on the rare earth composite oxide carrier, an upper layer catalyst slurry is prepared, coated on the dried intermediate transition layer, and after drying and calcining, the intermediate transition layer and the upper layer catalyst coating are co-sintered.

[0027] In a second aspect, the present application provides a method for reducing the amount of noble metal in a three-way catalyst, in which the alumina carrier material in the three-way catalyst is replaced by modified alumina, and the modified alumina is BaSO4 surface grafted with -NH2 group doped cerium modified alumina CeAlO x .

[0028] Compared with the prior art, the present application has the following advantages and beneficial effects: 1. The method for reducing the amount of noble metal, the natural gas vehicle aftertreatment catalyst and the preparation method provided by the embodiments of the present application can ensure and improve the freshness and durability of the catalyst on the basis of reducing the amount of noble metal by more than 50% compared with the commercially available catalyst, meet the durability requirements of regulations, and solve the problem of high cost of the current aftertreatment catalyst; 2. The method for reducing the amount of noble metal, the natural gas vehicle aftertreatment catalyst and the preparation method provided by the embodiments of the present application can further modify the cerium modified alumina by doping BaSO4 surface grafted with -NH2 group, which can enhance the bonding with alumina, improve the dispersion uniformity, avoid CeO2 agglomeration, thereby improve the specific surface area retention rate of the alumina material after high temperature aging, and also can increase the electron density of the noble metal Pd, strengthen the Pd-O bond, optimize the electronic structure of the Pd / Al2O3 catalyst, inhibit the high temperature decomposition of PdO to enhance the stability of PdO, thereby effectively improving the activity of methane combustion; by adding the modified alumina material, the fresh performance and the anti-aging ability of the catalyst can be greatly improved, and the performance of the catalyst can remain the same or be better than that of the commercially available catalyst when the amount of noble metal is reduced by half; 3. The method for reducing the amount of noble metal, the natural gas vehicle aftertreatment catalyst and the preparation method provided by the embodiment of the present application, through improving the carrier material in the upper catalytic coating, introducing Y, Sm, Pr and La four kinds of rare earths to co-dope CeO2 to form a multi-element composite oxide, the oxygen storage performance, stability, catalytic performance and anti-aging performance of the material can be significantly improved, and the modified alumina can synergistically act, so that the catalyst performance can meet the regulatory requirements after the amount of noble metal is reduced; 4. The method for reducing the amount of noble metal, the natural gas vehicle aftertreatment catalyst and the preparation method provided by the embodiment of the present application, by adding an intermediate transition layer between the bottom layer and the upper layer, the thermal expansion coefficient is between the bottom layer and the upper layer, and the middle layer coating does not go through a separate calcination process, but is calcined together after the upper slurry coating is completed, this process can balance the thermal expansion coefficient of the whole catalyst coating, reduce the thermal stress concentration coefficient, enhance the force between the middle layer and the bottom layer and the middle layer and the upper layer, so that the bonding energy of the interface can be improved, the efficient mass transfer capacity and durability of the catalyst can be ensured, so that the ability of efficiently treating CH4, NO x and CO can be maintained for a long time. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor.

[0030] Figure 1 The coating morphology comparison chart of the fresh catalyst provided by the embodiment 1 and the embodiment 3 of the present application; Figure 2 The coating morphology comparison chart of the aged catalyst provided by the embodiment 1 and the embodiment 3 of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present application more clear and obvious, the following will further describe the present application in combination with the embodiments and the drawings, the exemplary embodiments of the present application and the description thereof are only used to explain the present application, and should not be regarded as a limitation on the present application.

[0032] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, it is apparent to those skilled in the art that the present application can be practiced without these specific details. In other embodiments, well-known materials or methods are not specifically described in order to avoid obscuring the present application.

[0033] Throughout this specification, reference can be made to "one embodiment", "an embodiment", "one example", or "an example" meaning that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the application. The appearance of the phrases "in one embodiment", "an embodiment", "in one example" or "an example" in various places in the specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics can be combined in any suitable

[0034] "ranges" disclosed herein are defined by both a lower limit and an upper limit, and the particular range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined by the combination of any lower limit and any upper limit are expressly contemplated and can be either inclusive or exclusive of the stated limits. For example, if a range of 60-120 and a range of 80-110 are listed, it is contemplated that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise specified, a numerical range "a-b" indicates a shorthand way of describing each and every number that is an integer within the given range of a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between 0 and 5 have been listed herein, and "0-5" is merely a shorthand way of describing each and every number that is an integer within the given range of 0 and 5. Additionally, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. Unless otherwise specified, all steps of the application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b) indicates that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method further comprises step (c) indicates that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0035] Example 1 The embodiment of the application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal dosage, comprising the following steps: (1) preparing BaSO4 modified Ce0.2 Ba 0.05 Al 0.75 O x -S material: 1.1 First, BaSO4 powder is mixed with solvent (water / ethanol) at a mass ratio of 1:5, and zirconia milling beads (particle size 0.1-0.5 mm) are added for milling for 4-6 h to obtain a suspension with D50<200 nm. Then 3-5% KH-550 is added, and stirring is carried out at 60°C for 2 h to graft -NH2 groups onto the surface of BaSO4; 1.2 Ce 0.2 Al 0.75 O x material powder is dispersed in water, and the BaSO4 nanosuspension is slowly added dropwise to the Ce 0.2 Al 0.75 O x slurry (wherein the BaSO4 content is 5 wt% of the Ce 0.2 Al 0.75 O x ), and then the slurry is milled for half an hour using a sand mill to obtain a slurry of BaSO4-modified alumina material; 1.3 The above slurry is dried and then calcined at 500°C for 2-4 h to remove the organic dispersant, and finally BaSO4-modified Ce 0.2 Ba 0.05 Al 0.75 O x -S powder is obtained.

[0036] (2) Preparation of bottom catalytic coating Pd is loaded on the modified alumina material supports Ce 0.2 Ba 0.05 Al 0.75 O x -S and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd total loading on the two support materials is 0.4414%) using an equal volume impregnation method, i.e. the content of the bottom noble metal Pd is 15 g / cft, and then Pd / Ce 0.2 Ba 0.05 Al 0.75 O x -S powder and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder are obtained through drying, calcination, etc. The above two catalyst powders Pd / Ce0.2 Ba 0.05 Al 0.75 O x -S 62 wt%, Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x Bottom coating slurry was prepared by ball milling 31 wt%, 7 wt% binder, 200 wt% water, after 30 min ball milling, the bottom coating slurry was obtained; the bottom coating slurry was coated on the surface of cordierite honeycomb ceramic carrier (Φ1*1 in small sample carrier, 400 cpsi, volume 0.01638 L, Φ12*6 in large sample carrier, 400 cpsi, volume 11.12 L), respectively, the coating amount was 129.03 g / L, and then dried, calcined at 500°C in air atmosphere for 2 h to obtain a Pd-containing catalyst bottom layer.

[0037] (3) Preparation of intermediate transition layer The middle layer cerium-zirconium-aluminum composite material CeZrAlO was prepared by coprecipitation x (CeO2 was 30~70 wt%, ZrO2 was 30~60 wt%, Al2O3 was 0~20 wt%, and the auxiliary La2O3 or Pr2O3 was 0~5 wt%), and then washed with deionized water to neutral, dried in a 120°C oven for 4 h, and finally calcined at 400°C in a muffle furnace for 4 h to obtain CeZrAlO x powder; the above CeZrAlO x Ball milling was carried out with 95 wt%, 5 wt% binder, 200 wt% water, and the size distribution of the selected zirconia balls was Φ5~40 mm, the ball milling time was 20 min, and finally a middle layer coating slurry with a wide particle size distribution was obtained; the middle layer coating slurry was coated on the bottom layer, and the coating amount of the middle layer coating slurry was 60 g / L, and after coating, the catalyst semi-finished product was dried to a middle layer coating water loss rate of 95%.

[0038] (4) Preparation of upper catalytic coating 4.1 Material one: preparation of composite oxide with metal ion molar ratio Ce:Y:Sm:Pr:La = 70:5:3:12:10 Ce(NO3)3.6H2O, 2.36 g Y(CH3COO)3.4H2O, 1.60 g Sm(NO3)3.6H2O, 6.2 g Pr (NO3)3.6H2O, 5.15 g La(NO3)3.6H2O were added in proportion, while 41.8 g EDTA acid, 300 ml deionized water, 30 ml 30% H2O2 were added; 80°C water bath stirring to form a solution; dropwise addition of NH3.H2O to pH=8.5, continue to stir to form a homogeneous sol; 120°C drying 12 h and grinding to obtain a powder; the powder was placed in a muffle furnace with a temperature rising rate of 10°C / min at 500°C for 2 h; The prepared material, a powder, was added to a noble metal solution for impregnation for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Pt=13 g / cft; 4.2 Material two: a composite oxide with a metal ion molar ratio of Ce:Zr:Pr:La=20:70:2:8 was prepared by the same method, and then added to a noble metal solution for impregnation for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Rh=2 g / cft; 4.3 The prepared noble metal-loaded powder was added to a ball mill tank according to material one:material two=2:1, acetic acid was added to adjust the pH of the slurry to 2-7, a binder was added to keep the slurry viscous, and then placed in a ball mill for rapid stirring; the prepared slurry was coated on an intermediate transition layer, the coating amount was 80 g / L, and then dried at room temperature for 2-4 h and calcined at 500°C for 2 h to obtain a co-sintered intermediate transition layer and an upper catalytic coating layer.

[0039] Example 2 The embodiment of the present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal consumption, comprising the following steps: (1) Preparation of BaSO4 modified Ce 0.2 Ba 0.05 Al 0.75 O x -S material, same as example 1.

[0040] (2) Preparation of bottom catalytic coating layer Pd and Pt were loaded on the modified alumina material carrier Ce 0.2 Ba 0.05 Al 0.75 O x -S and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x(Pd loading is 0.5886%, Pt loading is 0.2943%), namely the content of the bottom layer noble metal Pd is 10 g / cft, the content of Pt is 5 g / cft, and then Pd / Ce 0.2 Ba 0.05 Al 0.75 O x -S powder and Pt / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder; the two kinds of catalyst powders Pd / Ce 0.2 Ba 0.05 Al 0.75 O x -S are 46.5 wt%, Pt / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x 46.5 wt%, 7 wt% binder, 200 wt% water, after ball milling for 30 min, the bottom coating slurry is obtained; the bottom coating slurry is coated on the surface of the cordierite honeycomb ceramic carrier (Φ1*1 in small sample carrier, 400 cpsi, volume 0.01638 L, Φ12*6 in large sample carrier, 400 cpsi, volume 11.12 L), the coating amount is 129.03 g / L, and then dried and calcined at 500°C in air for 2 h, to obtain a Pd and Pt catalyst bottom layer.

[0041] (3) Preparation of intermediate transition layer The middle layer cerium-zirconium-aluminum composite material CeZrAlO x (CeO2 is 30~70 wt%, ZrO2 is 30~60 wt%, Al2O3 is 0~20 wt%, and the auxiliary La2O3 or Pr2O3 is 0~5 wt%), and then washed with deionized water to neutral, dried in an oven at 120°C for 4 h, and finally calcined in a 400°C muffle furnace for 4 h to obtain CeZrAlO x powder; the above CeZrAlO x is ball milled according to 95 wt%, 5 wt% binder, 200 wt% water, the size distribution of the selected zirconia balls is Ф5~40 mm, the ball milling time is 20 min, and finally the middle layer coating slurry with a wide particle size distribution is obtained; the middle layer coating slurry is coated on the bottom layer, and the coating amount of the middle layer coating slurry is 60 g / L, and after coating, the catalyst semi-finished product is dried to a middle layer coating water loss rate of 95%.

[0042] (4) Preparation of upper catalytic coating 4.1 Material one: Preparation of composite oxide with metal ion molar ratio Ce:Y:Sm:Pr:La = 70:5:3:12:10 Add 36.13 g of Ce(NO3)3·6H2O, 2.36 g of Y(CH3COO)3·4H2O, 1.60 g of Sm(NO3)3·6H2O, 6.2 g of Pr(NO3)3·6H2O, and 5.15 g of La(NO3)3·6H2O in proportion, and add 41.8 g of EDTA acid, 300 ml of deionized water, and 30 ml of 30% H2O2; stir in a water bath at 80°C to form a solution; add NH3·H2O dropwise to pH = 8.5, and continue to stir to form a homogeneous sol; dry at 120°C for 12 h and grind to obtain a powder; place the powder in a muffle furnace and heat at a rate of 10°C / min to 500°C for 2 h; After impregnating the prepared material one powder in a noble metal solution for 4 h, evaporate and dry at 90°C, wherein the content of the noble metal is Pt = 13 g / cft; 4.2 Material two: Prepare a composite oxide with metal ion molar ratio Ce:Zr:Pr:La = 20:70:2:8 by the same method, impregnate in a noble metal solution for 4 h, and evaporate and dry at 90°C, wherein the content of the noble metal is Rh = 2 g / cft; 4.3 Add the prepared noble metal-loaded powder according to material one: material two = 2:1 to a ball mill tank, add acetic acid to adjust the pH of the slurry to 2-7, add a binder to keep the slurry viscous, and place it in a ball mill for rapid stirring; coat the prepared slurry on the intermediate transition layer, with a coating amount of 80 g / L, dry at room temperature for 2-4 h, and then calcine at 500°C for 2 h to obtain a co-sintered intermediate transition layer and upper catalytic coating.

[0043] Example 3 The embodiment of the present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal content, which comprises the following steps: (1) Preparation of BaSO4 modified Ce 0.2 Ba 0.05 Al 0.75 O x -S material: 1.1 First, mix BaSO4 powder with a solvent (water / ethanol) at a mass ratio of 1:5, add zirconia milling beads (particle size 0.1-0.5 mm) and mill for 4-6 h to obtain a suspension with D50<200 nm, then add 3-5% KH-550 and stir at 60°C for 2 h to graft -NH2 groups on the surface of BaSO4; 1.2 Ce 0.2 Al 0.75 O x material powder is dispersed in water, and BaSO4nano-suspension is slowly added dropwise into the Ce 0.2 Al 0.75 O x slurry (wherein the content of BaSO4is 5 wt% of Ce 0.2 Al 0.75 O x ), and then the slurry is ball-milled for half an hour using a sand mill to obtain a slurry of BaSO4modified alumina material; 1.3 The above slurry is dried, then calcined at 500°C for 2-4 h to remove the organic dispersant therein, and finally BaSO4modified Ce 0.2 Ba 0.05 Al 0.75 O x -S powder is obtained.

[0044] (2) Preparation of bottom catalytic coating Pd is loaded on the modified alumina material carriers Ce 0.2 Ba 0.05 Al 0.75 O x -S and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd total loading on the two carrier materials is 0.4414%) respectively by using equal volume impregnation method, i.e. the content of bottom noble metal Pd is 15 g / cft, and then Pd / Ce 0.2 Ba 0.05 Al 0.75 O x -S powder and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder are respectively obtained through drying, calcination and other processes; the above two kinds of catalyst powders Pd / Ce 0.2 Ba 0.05 Al 0.75 O x -S and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O xThe bottom coating slurry was obtained by ball milling for 30 min according to 31 wt%, 7 wt% binder, 200 wt% water; the bottom coating slurry was coated on the surface of the cordierite honeycomb ceramic carrier (Φ1*1 in small sample carrier with a pore number of 400 cpsi and a volume of 0.01638 L, Φ12*6 in large sample carrier with a pore number of 400 cpsi and a volume of 11.12 L), the coating amount was 129.03 g / L, and then dried, calcined at 500°C in an air atmosphere for 2 h to obtain a Pd-containing catalyst bottom layer.

[0045] (3) Preparation of upper catalytic coating 3.1 Material one: preparation of a composite oxide with a metal ion molar ratio of Ce:Y:Sm:Pr:La = 70:5:3:12:10 According to the proportions, 36.13 g of Ce(NO3)3·6H2O, 2.36 g of Y(CH3COO)3·4H2O, 1.60 g of Sm(NO3)3·6H2O, 6.2 g of Pr(NO3)3·6H2O, and 5.15 g of La(NO3)3·6H2O were added, and 41.8 g of EDTA acid, 300 ml of deionized water, and 30 ml of 30% H2O2 were added at the same time; a solution was formed by stirring in a 80°C water bath; NH3·H2O was added dropwise until the pH reached 8.5, and the homogeneous sol was formed by continuous stirring; the powder was obtained by drying at 120°C for 12 h and grinding; the powder was placed in a muffle furnace and calcined at 500°C with a temperature rising rate of 10°C / min for 2 h; The prepared material one powder was immersed in a noble metal solution for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Pt=13 g / cft; 3.2 Material two: a composite oxide with a metal ion molar ratio of Ce:Zr:Pr:La = 20:70:2:8 was prepared by the same method, and then immersed in a noble metal solution for 4 h, and evaporated and dried at 90°C, wherein the content of the noble metal was Rh=2 g / cft; 3.3 The prepared noble metal-loaded powder was added to a ball mill tank according to material one:material two = 2:1, acetic acid was added to adjust the pH of the slurry to 2-7, a binder was added to keep the slurry viscous, and the slurry was quickly stirred in a ball mill; the prepared slurry was coated on the bottom layer, the coating amount was 80 g / L, and then dried at room temperature for 2-4 h and calcined at 500°C for 2 h to obtain an upper catalytic coating.

[0046] The difference between this example and example 1 is that no intermediate transition layer is included.

[0047] Example 4 The present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal dosage, comprising the following steps: (1) Preparation of BaSO4 modified Ce 0.2 Ba 0.05 Al 0.75 O x -S material: 1.1 First, BaSO4 powder is mixed with solvent (water / ethanol) at a mass ratio of 1:5, and zirconia milling beads (particle size 0.1-0.5 mm) are added for ball milling for 4-6 h to obtain a suspension with D50<200 nm. Then 3-5% KH-550 is added, and the mixture is stirred at 60°C for 2 h to graft -NH2 groups onto the surface of BaSO4. 1.2 Ce 0.2 Al 0.75 O x material powder is dispersed in water, and the BaSO4 nanosuspension is slowly added to the Ce 0.2 Al 0.75 O x slurry (with a BaSO4 content of 5 wt% of Ce 0.2 Al 0.75 O x ). Then the slurry is ball milled for half an hour using a sand mill to obtain a slurry of BaSO4 modified alumina material. 1.3 The above slurry is dried and then calcined at 500°C for 2-4 h to remove the organic dispersant, and finally BaSO4 modified Ce 0.2 Ba 0.05 Al 0.75 O x -S powder is obtained.

[0048] (2) Preparation of bottom catalytic coating Pd is loaded on the modified alumina material supports Ce 0.2 Ba 0.05 Al 0.75 O x -S and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd total loading on both support materials is 0.2943%) using an equal volume impregnation method, i.e. the content of bottom noble metal Pd is 10 g / cft, and then Pd / Ce 0.2 Ba 0.05 Al 0.75 O x -S powder and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 Ox Powder; impregnate the prepared material one powder into the noble metal solution for 4 h, and evaporate and dry at 90°C, wherein the content of the noble metal is Pt = 8.5 g / cft; 0.2 Ba 0.05 Al 0.75 O x -S according to 62 wt%, Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x According to 31 wt%, 7 wt% binder, 200 wt% water, after ball milling for 30 min, the bottom coating slurry is obtained; the bottom coating slurry is coated on the surface of the cordierite honeycomb ceramic carrier (small sample carrier Φ1*1 in, 400 cpsi, volume 0.01638 L, large sample carrier Φ12*6 in, 400 cpsi, volume 11.12 L, respectively), the coating amount is 129.03 g / L, and then dried, calcined at 500°C in air atmosphere for 2 h, to obtain a Pd-containing catalyst bottom layer.

[0049] (3) Preparation of the upper catalytic coating 3.1 Material one: preparation of a composite oxide with metal ion molar ratio Ce:Y:Sm:Pr:La = 70:5:3:12:10 Add 36.13 g of Ce(NO3)3·6H2O, 2.36 g of Y(CH3COO)3·4H2O, 1.60 g of Sm(NO3)3·6H2O, 6.2 g of Pr(NO3)3·6H2O, and 5.15 g of La(NO3)3·6H2O in proportion, and simultaneously add 41.8 g of EDTA acid, 300 ml of deionized water, and 30 ml of 30% H2O2; stir to form a solution in a 80°C water bath; add NH3·H2O dropwise until the pH is 8.5, and continue to stir to form a homogeneous sol; dry at 120°C for 12 h and grind to obtain a powder; place the powder in a muffle furnace and calcine at 500°C with a temperature rising rate of 10°C / min for 2 h; Impregnate the prepared material one powder into the noble metal solution for 4 h, and evaporate and dry at 90°C, wherein the content of the noble metal is Pt = 8.5 g / cft; 3.2 Material two: prepare a composite oxide with metal ion molar ratio Ce:Zr:Pr:La = 20:70:2:8 by the same method, impregnate into the noble metal solution for 4 h, and evaporate and dry at 90°C, wherein the content of the noble metal is Rh = 1.5 g / cft; 3.3 The prepared noble metal loaded powder was added to a ball mill tank according to material 1 : material 2 = 2: 1, acetic acid was added to adjust the slurry pH to 2-7, a binder was added to keep the slurry thick, and the slurry was put into a ball mill for rapid stirring; the prepared slurry was coated on the bottom layer, the coating amount was 80 g / L, and after drying at room temperature for 2-4 h, the coating was calcined at 500°C for 2 h to obtain the upper layer catalytic coating.

[0050] The difference between this example and example 3 is that the total amount of noble metal is 20 g / cft.

[0051] Comparative Example 1 The present example provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal usage, comprising the following steps: (1) Preparation of bottom layer catalytic coating The Pd was loaded on commercial Ce 0.2 Al 0.8 O x and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd total loading on two carrier materials is 0.4414%), i.e. the content of Pd in the bottom layer is 15 g / cft, and then Pd / Ce 0.2 Al 0.8 O x powder and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder were obtained through drying, calcination and other processes; the above two catalyst powders Pd / Ce 0.2 Al 0.8 O x 62 wt%, Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x 31 wt%, 7 wt% binder, 200 wt% water, and ball milling for 30 min to obtain a bottom layer coating slurry; the bottom layer coating slurry was coated on the surface of cordierite honeycomb ceramic carrier (small sample carrier Φ1*1 in, 400 cpsi, volume 0.01638 L, and large sample carrier Φ12*6 in, 400 cpsi, volume 11.12 L), the coating amount was 129.03 g / L, and then dried and calcined at 500°C in air for 2 h to obtain a Pd-containing bottom layer.

[0052] (2) Preparation of upper layer catalytic coating 2.1 Material 1: Preparation of composite oxide with metal ion molar ratio Ce:Y:Sm:Pr:La = 70:5:3:12:10 Add 36.13 g of Ce(NO3)3·6H2O, 2.36 g of Y(CH3COO)3·4H2O, 1.60 g of Sm(NO3)3·6H2O, 6.2 g of Pr(NO3)3·6H2O, and 5.15 g of La(NO3)3·6H2O in proportion, and simultaneously add 41.8 g of EDTA acid, 300 ml of deionized water, and 30 ml of 30% H2O2; stir in a water bath at 80°C to form a solution; add NH3·H2O dropwise to pH = 8.5, and continue to stir to form a homogeneous sol; dry at 120°C for 12 h and grind to obtain a powder; place the powder in a muffle furnace and heat at a rate of 10°C / min to 500°C for 2 h; After impregnating the prepared material 1 powder in a noble metal solution for 4 h, evaporate and dry at 90°C, wherein the content of the noble metal is Pt = 13 g / cft; 2.2 Material 2: Prepare a composite oxide with metal ion molar ratio Ce:Zr:Pr:La = 20:70:2:8 by the same method, impregnate in a noble metal solution for 4 h, and evaporate and dry at 90°C, wherein the content of the noble metal is Rh = 2 g / cft; 2.3 Add the prepared noble metal-loaded powder according to material 1:material 2 = 2:1 to a ball mill tank, add acetic acid to adjust the pH of the slurry to 2-7, add a binder to keep the slurry viscous, and place it in a ball mill for rapid stirring; coat the prepared slurry on the bottom layer, and the coating amount is 80 g / L; dry at room temperature for 2-4 h, and then calcine at 500°C for 2 h to obtain an upper layer catalytic coating.

[0053] The difference between this comparative example and example 3 is that a commercial Ce 0.2 Al 0.8 O x is used instead of the modified alumina material carrier Ce 0.2 Ba 0.05 Al 0.75 O x -S.

[0054] Comparative example 2 The present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal content, which comprises the following steps: (1) Preparation of bottom layer catalytic coating Pd is loaded on commercial Ce 0.2 Al 0.8 O x and Ce0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd total loading on two support materials is 0.4414%), i.e. the content of the bottom layer noble metal Pd is 15 g / cft, then through drying, calcination and other processes, Pd / Ce 0.2 Al 0.8 O x powder and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder; the above two catalyst powders Pd / Ce 0.2 Al 0.8 O x According to 62 wt%, Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x According to 31 wt%, 7 wt% binder, 200 wt% water, after ball milling for 30 min, the bottom coating slurry is obtained; the bottom coating slurry is coated on the surface of the cordierite honeycomb ceramic carrier (Φ1*1 in small sample carrier with a pore size of 400 cpsi and a volume of 0.01638 L, Φ12*6 in large sample carrier with a pore size of 400 cpsi and a volume of 11.12 L), the coating amount is 129.03 g / L, and then dried and calcined at 500°C in air for 2 h to obtain a Pd-containing catalyst bottom layer.

[0055] (2) Preparation of the upper catalytic coating 2.1 Material one: preparation of Ce 0.68 Zr 0.32 O2 37.8 g of Ce(NO3)3·6H2O, 16.1 g of Zr(NO3)4·5H2O, 44.9 g of EDTA acid, 300 ml of deionized water, and 30 ml of 30% H2O2 are added together; a homogeneous solution is formed under stirring in a water bath at 80°C; NH3·H2O is added dropwise until the pH is 8.5, and stirring is continued to form a homogeneous sol; the powder is obtained by drying at 120°C for 12 h and grinding; the powder is placed in a muffle furnace and calcined at 500°C with a temperature rising rate of 10°C / min for 2 h; The prepared material one powder is immersed in the noble metal solution for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal is Pt=13 g / cft; 2.2 Material two: composite oxide with metal ion molar ratio Ce:Zr:Pr:La = 20:70:2:8 was prepared by the same method, impregnated with noble metal solution for 4 h, evaporated and dried at 90°C, wherein the noble metal content was Rh = 2 g / cft; 2.3 The prepared noble metal loaded powder was added to the ball mill tank according to material one: material two = 2: 1, acetic acid was added to adjust the slurry pH to 2-7, a binder was added to keep the slurry viscous, and the slurry was quickly stirred in the ball mill; the prepared slurry was coated on the bottom layer, the coating amount was 80 g / L, dried at room temperature for 2-4 h, and then calcined at 500°C for 2 h to obtain the upper layer catalytic coating.

[0056] The difference between this comparative example and example 3 is that commercial Ce 0.2 Al 0.8 O x The modified alumina material carrier Ce 0.2 Ba 0.05 Al 0.75 O x -S, and Ce 0.68 Zr 0.32 O2 of the present application was replaced by composite oxide with metal ion molar ratio Ce:Y:Sm:Pr:La = 70:5:3:12:10. The total amount of catalyst was not changed.

[0057] Comparative example 3 The present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal content, comprising the following steps: (1) Bottom layer catalytic coating preparation Pd was loaded on commercial Ce 0.2 Al 0.8 O x and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd total loading on the two carrier materials was 0.8829%), i.e. the content of bottom layer noble metal Pd was 30 g / cft, and then Pd / Ce 0.2 Al 0.8 O x powder and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder were obtained through drying, calcination and other processes; the above two catalyst powders Pd / Ce 0.2 Al 0.8 O xPd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x Pd / Ce

[0058] (2) Upper layer catalytic coating preparation 2.1 Material one: Preparation of Ce 0.68 Zr 0.32 O2 37.8 g of Ce(NO3)3·6H2O, 16.1 g of Zr(NO3)4·5H2O, 44.9 g of EDTA acid, 300 ml of deionized water, and 30 ml of 30% H2O2 were added together; a homogeneous solution was formed under stirring in a water bath at 80°C; NH3·H2O was added dropwise until the pH was 8.5, and the homogeneous sol was formed by continuous stirring; the powder was obtained by drying at 120°C for 12 h and grinding; the powder was placed in a muffle furnace and calcined at 500°C with a temperature rising rate of 10°C / min for 2 h; The prepared material one powder was added to the noble metal solution for impregnation for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Pt=26 g / cft; 2.2 Material two: A composite oxide with a metal ion molar ratio of Ce:Zr:Pr:La=20:70:2:8 was prepared by the same method, and then impregnated in the noble metal solution for 4 h, and evaporated and dried at 90°C, wherein the content of the noble metal was Rh=4 g / cft; 2.3 The prepared noble metal-loaded powder was added to the ball mill tank according to material one:material two=2:1, acetic acid was added to adjust the pH of the slurry to 2-7, a binder was added to keep the slurry viscous, and then it was quickly stirred in a ball mill; the prepared slurry was coated on the bottom layer, the coating amount was 80 g / L, and then it was dried at room temperature for 2-4 h and calcined at 500°C for 2 h to obtain the upper layer catalytic coating.

[0059] The difference between this comparative example and comparative example 2 is that the total amount of noble metal is 60 g / ft 3 , which is twice the amount used in comparative example 2.

[0060] Comparative example 4 The embodiment of the present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal dosage, comprising the following steps: (1) Preparation of bottom catalytic coating The Pd is loaded on the commercial Ce 0.2 Al 0.8 O x and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd total loading amount on the two carrier materials is 0.2943%), that is, the content of the bottom noble metal Pd is 10 g / cft, and then Pd / Ce 0.2 Al 0.8 O x powder and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder are obtained through drying, calcination and other processes; the two kinds of catalyst powders Pd / Ce 0.2 Al 0.8 O x , Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x are mixed according to 62 wt%, 31 wt% and 7 wt% binder, 200 wt% water, and ball milling for 30 min to obtain a bottom coating slurry; the bottom coating slurry is coated on the surface of cordierite honeycomb ceramic carriers (small sample carriers Φ1*1 in, 400 cpsi, volume 0.01638 L, large sample carriers Φ12*6 in, 400 cpsi, volume 11.12 L), and the coating amount is 129.03 g / L, and then drying and calcination at 500 DEG C in air for 2 h to obtain a bottom layer containing Pd catalyst.

[0061] (2) Preparation of upper catalytic coating 2.1 Material one: preparation of Ce 0.68 Zr 0.32 O2 37.8 g Ce(NO3)3·6H2O, 16.1 g Zr(NO3)4·5H2O, 44.9 g EDTA acid, 300 ml deionized water, 30 ml 30% H2O2 were added together; 80°C water bath stirring to form a homogeneous solution; dropwise addition of NH3·H2O to pH = 8.5, continue to stir to form a homogeneous sol; 120°C drying 12 h and grinding to obtain a powder; the powder was placed in a muffle furnace with a temperature rising rate of 10°C / min at 500°C for 2 h; The prepared material, a powder, was added to a noble metal solution and impregnated for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Pt = 8.5 g / cf; 2.2 Material two: a composite oxide with a metal ion molar ratio of Ce:Zr:Pr:La = 20:70:2:8 was prepared by the same method, added to a noble metal solution and impregnated for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Rh = 1.5 g / cft; 2.3 The prepared noble metal-loaded powder was added to a ball mill tank according to material one:material two = 2:1, acetic acid was added to adjust the pH of the slurry to 2-7, a binder was added to keep the slurry viscous, and the slurry was quickly stirred in a ball mill; the prepared slurry was coated on the bottom layer, the coating amount was 80 g / L, and after drying at room temperature for 2-4 h, it was calcined at 500°C for 2 h to obtain an upper layer catalytic coating.

[0062] The difference between this comparative example and comparative example 2 is that the total amount of noble metal is 20 g / cft, which is 10 g / cft less than that of comparative example 2.

[0063] Comparative example 5 The embodiment of the present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal consumption, which comprises the following steps: (1) Preparation of bottom layer catalytic coating Pd and Pt were loaded on commercial Ce 0.2 Al 0.8 O x and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd loading amount is 1.1772%, Pt loading amount is 0.5886%), i.e. the content of the bottom layer noble metal Pd is 20 g / cft, and the content of Pt is 10 g / cft, and then Pd / Ce 0.2 Al 0.8 O x powder and PtCe 0.4 Zr 0.5 La0.05 Pr 0.05 O x Powder; the two catalyst powders Pd / Ce 0.2 Al 0.8 O x 46.5 wt%, Pt / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x 46.5 wt%, 7 wt% binder, 200 wt% water, after ball milling for 30 min, a bottom coating slurry was obtained; the bottom coating slurry was coated on the surface of cordierite honeycomb ceramic carriers (small sample carriers Φ1*1 in, 400 cpsi, volume 0.01638 L, large sample carriers Φ12*6 in, 400 cpsi, volume 11.12 L, respectively), the coating amount was 129.03 g / L, and then dried, calcined at 500°C in air for 2 h to obtain a Pd and Pt containing catalyst bottom layer.

[0064] (2) Preparation of upper catalytic coating 2.1 Material one: Preparation of Ce 0.68 Zr 0.32 O2 37.8 g Ce(NO3)3·6H2O, 16.1 g Zr(NO3)4·5H2O, 44.9 g EDTA acid, 300 ml deionized water, 30 ml 30% H2O2 were added together; stirred in a water bath at 80°C to form a homogeneous solution; dropwise addition of NH3·H2O to pH=8.5, continue to stir to form a homogeneous sol; dry at 120°C for 12 h and grind to obtain a powder; the powder was placed in a muffle furnace and calcined at 500°C with a temperature rising rate of 10°C / min for 2 h; The prepared material one powder was added to the noble metal solution for impregnation for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Pt=26 g / cft; 2.2 Material two: a composite oxide with a metal ion molar ratio of Ce:Zr:Pr:La=20:70:2:8 was prepared by the same method, impregnated in the noble metal solution for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Rh=4 g / cft; 2.3 The prepared noble metal loaded powder was added to a ball mill tank according to material one: material two=2:1, acetic acid was added to adjust the slurry pH to 2-7, a binder was added to keep the slurry viscous, and then put into a ball mill for rapid stirring; the prepared slurry was coated on the bottom layer, the coating amount was 80 g / L, and then dried at room temperature for 2-4 h and calcined at 500°C for 2 h to obtain an upper catalytic coating.

[0065] The difference between the present comparative example and Comparative Example 3 is that the bottom layer noble metal is: Pd content 20 g / cft, Pt content 10 g / cft.

[0066] Comparative Example 6 The present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal content, comprising the following steps: (1) Preparation of bottom layer catalytic coating Pd and Pt are loaded on the modified alumina material carrier Ce 0.2 Al 0.8 O x and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd loading is 0.5886%, Pt loading is 0.2943%), i.e. Pd content 10 g / cft, Pt content 5 g / cft, and then Pd / Ce 0.2 Al 0.8 O x and Pt / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder are obtained through drying, calcination and other processes; the two catalyst powders Pd / Ce 0.2 Al 0.8 O x and Pt / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x are mixed according to 46.5 wt%, 46.5 wt%, 7 wt% binder, and 200 wt% water, and ball-milled for 30 min to obtain a bottom layer coating slurry; the bottom layer coating slurry is coated on the surface of cordierite honeycomb ceramic carriers (small sample carriers Φ1*1 in, 400 cpsi, volume 0.01638 L, and large sample carriers Φ12*6 in, 400 cpsi, volume 11.12 L), and the coating amount is 129.03 g / L, and then dried and calcined at 500°C in air for 2 h to obtain a bottom layer containing Pd and Pt catalyst.

[0067] (2) Preparation of intermediate transition layer The middle layer cerium-zirconium-aluminum composite material CeZrAlO x(Ce02 is 30-70 wt%, Zr02 is 30-60 wt%, Al203 is 0-20 wt%, and the auxiliary La203 or Pr203 is 0-5 wt%), and then washed with deionized water until neutral, dried in an oven at 120°C for 4 h, and finally calcined in a muffle furnace at 400°C for 4 h to obtain CeZrAlO x powder; the above CeZrAlO x ball-milling was performed at 95 wt%, 5 wt% binder, and 200 wt% water, the size distribution of the selected zirconia balls was Ф5-40 mm, the ball-milling time was 20 min, and finally a middle layer coating slurry with a large particle size range and good dispersion was obtained; the middle layer coating slurry was coated on the bottom layer, the coating amount of the middle layer coating slurry was 60 g / L, and after the coating was completed, the catalyst semi-finished product was dried until the water loss rate of the middle layer coating was 95%.

[0068] (3) Preparation of the upper layer catalytic coating 3.1 Material One: Preparation of a composite oxide with a metal ion molar ratio of Ce:Y:Sm:Pr:La = 70:5:3:12:10 36.13 g of Ce(N03)3-6H20, 2.36 g of Y(CH3COO)3-4H20, 1.60 g of Sm(N03)3-6H20, 6.2 g of Pr(N03)3-6H20, and 5.15 g of La(N03)3-6H20 were added in proportion, 41.8 g of EDTA acid, 300 ml of deionized water, and 30 ml of 30% H202 were added at the same time, and stirring was performed in a water bath at 80°C to form a solution; NH3-H20 was added dropwise until the pH was 8.5, and stirring was continued to form a homogeneous sol; the powder was obtained by drying at 120°C for 12 h and grinding; the powder was placed in a muffle furnace and calcined at 500°C with a temperature rising rate of 10°C / min for 2 h; The prepared material one powder was immersed in a noble metal solution for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Pt = 13 g / cft; 3.2 Material Two: A composite oxide with a metal ion molar ratio of Ce:Zr:Pr:La = 20:70:2:8 was prepared by the same method, immersed in a noble metal solution for 4 h, and then evaporated and dried at 90°C, wherein the content of the noble metal was Rh = 2 g / cft; 3.3 The prepared powder loaded with noble metals was added to a ball mill tank according to material one: material two = 2:1, acetic acid was added to adjust the pH of the slurry to 2-7, a binder was added to keep the slurry viscous, and the slurry was quickly stirred in a ball mill; the prepared slurry was coated on the intermediate transition layer, the coating amount was 80 g / L, and after drying at room temperature for 2-4 h, the intermediate transition layer and the upper layer catalytic coating were co-sintered by calcination at 500°C for 2 h.

[0069] The difference between the present comparative example and Example 2 is that a commercial Ce 0.2 Al 0.8 O x The modified alumina material carrier Ce 0.2 Ba 0.05 Al 0.75 O x -S.

[0070] Comparative Example 7 The present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal dosage, comprising the following steps: (1) Preparation of bottom catalytic coating Pd and Pt are respectively loaded on the modified alumina material carrier Ce 0.2 Ba 0.05 Al 0.75 O x and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd loading is 0.5886%, Pt loading is 0.2943%), i.e. the content of bottom noble metal Pd is 10 g / cft, the content of Pt is 5 g / cft, and then Pd / Ce 0.2 Ba 0.05 Al 0.75 O x and Pt / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder are respectively obtained through drying, calcination and other processes; the above two kinds of catalyst powders Pd / Ce 0.2 Ba 0.05 Al 0.75 O x and Pt / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O xAfter ball milling for 30 min with 46.5 wt%, 7 wt% binder and 200 wt% water, a base coating slurry was obtained; the base coating slurry was coated on the surface of a cordierite honeycomb ceramic support (respectively coated on a small sample support Φ1*1 in, mesh size of 400 cpsi, volume of 0.01638 L, and a large sample support Φ12*6 in, mesh size of 400 cpsi, volume of 11.12 L), with a coating amount of 129.03 g / L. After drying and calcining at 500°C in air atmosphere for 2 h, a base layer containing Pd and Pt catalysts was obtained.

[0071] (2) Preparation of intermediate transition layer Preparation of middle layer cerium-zirconium-aluminum composite CeZrAlO by co-precipitation method x (CeO2 is 30~70 wt%, ZrO2 is 30~60 wt%, Al2O3 is 0~20 wt%, and the additive La2O3 or Pr2O3 is 0~5 wt%), then washed with deionized water to neutrality, dried in a 120℃ oven for 4 h, and finally calcined in a 400℃ muffle furnace for 4 h to obtain CeZrAlO x Powder; the above CeZrAlO x Ball milling was performed according to 95wt%, 5wt% binder and 200wt% water. The size distribution of the zirconia balls selected during ball milling was Ф5~40 mm. The ball milling time was 20 min, and finally a middle layer coating slurry with a large particle size dispersion was obtained; the middle layer coating slurry was coated on the bottom layer, and the coating amount of the middle layer coating slurry was 60 g / L. After the coating was completed, the catalyst semi-finished product was dried until the water loss rate of the middle layer coating was 95%.

[0072] (3) Preparation of upper catalytic coating 3.1 Material 1: Preparation of composite oxide with metal ion molar ratio Ce:Y:Sm:Pr:La=70:5:3:12:10 36.13 g Ce(NO3)3·6H2O, 2.36 g Y(CH3COO)3·4H2O, 1.60 g Sm(NO3)3·6H2O, 6.2 g Pr (NO3)3·6H2O, and 5.15 g La(NO3)3·6H2O were added in proportion, and 41.8 g EDTA acid, 300 ml deionized water, and 30 ml 30% H2O2 were added simultaneously; the mixture was stirred in a water bath at 80°C to form a solution; NH3·H2O was added dropwise until the pH reached 8.5, and stirring was continued to form a homogeneous sol; the mixture was dried at 120°C for 12 h and ground to obtain a powder; the powder was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 10°C / min; The prepared material, powder, is added to the noble metal solution for impregnation for 4 h, and then evaporated and dried at 90°C, with the noble metal content being Pt = 13 g / cft; 3.2 Material two: a composite oxide with a molar ratio of metal ions Ce:Zr:Pr:La = 20:70:2:8 is prepared in the same way, and then added to the noble metal solution for impregnation for 4 h, and then evaporated and dried at 90°C, with the noble metal content being Rh = 2 g / cft; 3.3 The prepared noble metal-loaded powder is added to a ball mill tank according to material one: material two = 2:1, acetic acid is added to adjust the slurry pH to 2-7, a binder is added to keep the slurry thick, and the slurry is quickly stirred in a ball mill; the prepared slurry is coated on the intermediate transition layer, with a coating amount of 80 g / L, and then dried at room temperature for 2-4 h and calcined at 500°C for 2 h to obtain a co-sintered intermediate transition layer and upper layer catalytic coating.

[0073] The difference between this comparative example and Example 2 is that a commercial Ce 0.2 Ba 0.05 Al 0.75 O x The modified alumina material carrier Ce 0.2 Ba 0.05 Al 0.75 O x -S of the application is replaced by

[0074] Comparative Example 8 The present application provides a preparation method of a natural gas vehicle aftertreatment three-way catalyst with reduced noble metal content, comprising the following steps: (1) Preparation of BaSO4 modified Ce 0.2 Ba 0.05 Al 0.75 O x -S material, same as Example 1.

[0075] (2) Preparation of bottom layer catalytic coating Pd is loaded on the modified alumina material carrier Ce 0.2 Ba 0.05 Al 0.75 O x -S and Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x (Pd total loading on the two carrier materials is 0.4414%), i.e. the content of bottom layer noble metal Pd is 15 g / cft, and then Pd / Ce 0.2 Ba 0.05 Al 0.75 Ox - S powder and Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x powder; the two kinds of catalyst powders Pd / Ce 0.2 Ba 0.05 Al 0.75 O x - S 62 wt%, Pd / Ce 0.4 Zr 0.5 La 0.05 Pr 0.05 O x 31 wt%, 7 wt% binder, 200 wt% water, after ball milling for 30 min, the bottom coating slurry was obtained; the bottom coating slurry was coated on the surface of the cordierite honeycomb ceramic carrier (Φ1*1 in small sample carrier, 400 cpsi, volume 0.01638 L, Φ12*6 in large sample carrier, 400 cpsi, volume 11.12 L), respectively, the coating amount was 129.03 g / L, and then dried, calcined at 500°C in air atmosphere for 2 h, to obtain a Pd-containing catalyst bottom layer.

[0076] (3) Preparation of intermediate transition layer The intermediate layer cerium-zirconium-aluminum composite material CeZrAlO was prepared by coprecipitation method x (CeO2 is 30-70 wt%, ZrO2 is 30-60 wt%, Al2O3 is 0-20 wt%, and the auxiliary La2O3 or Pr2O3 is 0-5 wt%), then washed with deionized water to neutral, dried in an oven at 120°C for 4 h, and finally calcined at 400°C in a muffle furnace for 4 h to obtain CeZrAlO x powder; the above CeZrAlO x 95 wt%, 5 wt% binder, 200 wt% water, the size distribution of the selected zirconia balls is Ф5~40 mm, the ball milling time is 20 min, and finally the middle layer coating slurry with a wide particle size distribution is obtained; the middle layer coating slurry is coated on the bottom layer, the coating amount of the middle layer coating slurry is 60 g / L, and after coating, the catalyst semi-finished product is dried to a middle layer coating water loss rate of 95%.

[0077] (4) Preparation of upper catalytic coating 4.1 Material one: preparation of composite oxide with metal ion molar ratio Ce:Y:Sm=70:18:12 36.40 g Ce(NO3)3·6H2O, 7.30 g Y(CH3COO)3·4H2O, and 6.4 g Sm(NO3)3·6H2O were added in proportion, along with 41.9 g EDTA acid, 300 ml deionized water, and 30 ml 30% H2O2; the mixture was stirred in an 80 °C water bath to form a solution; NH3·H2O was added dropwise until the pH reached 8.5, and stirring was continued to form a homogeneous sol; the mixture was dried at 120 °C for 12 h and ground to obtain a powder; the powder was placed in a muffle furnace and calcined at 500 °C for 2 h at a heating rate of 10 °C / min; The prepared material 1 powder was added into the precious metal solution and immersed for 4 hours, and then evaporated and dried at 90℃. The precious metal content was Pt = 13 g / cf. 4.2 Material 2: Prepare a composite oxide with a metal ion molar ratio of Ce:Zr:Pr:La=20:70:2:8 by the same method, add it to the precious metal solution, immerse it for 4 hours, and evaporate it to dryness at 90℃. The precious metal content is Rh=2 g / cft; 4.3 Add the prepared precious metal loaded powder into the ball mill according to the ratio of Material 1: Material 2 = 2:1, add acetic acid to adjust the slurry pH to 2-7, add a binder to keep the slurry viscous, and put it into the ball mill and stir rapidly; apply the prepared slurry on the intermediate transition layer with a coating amount of 80 g / L, dry it at room temperature for 2-4 h, and then calcine it at 500℃ for 2 h to obtain a co-sintered intermediate transition layer and upper catalytic coating. The difference between this comparative example and Example 1 is that the composite oxide with a metal ion molar ratio of Ce:Y:Sm = 70:18:12 is used to replace the composite oxide with a metal ion molar ratio of Ce:Y:Sm:Pr:La = 70:5:3:12:10 of the present invention.

[0078] Performance Testing 1. The 1*1in sample catalysts obtained in the above examples and comparative examples were aged, and the fresh and aged samples were tested for activity. Specifically, the aging conditions and atmosphere are: air, 20 vol% H2O catalyst, 850°C continuous aging for 50h. The test conditions are: the activity evaluation of the catalyst is carried out in a multi-channel fixed continuous flow fixed bed reactor, and the exhaust gas composition of the simulated natural gas vehicle is: CH41500ppm, NOx 1500ppm, H23000ppm, CO 0.3%, CO211%, H2O 20%, N2 balance gas, and the air velocity is 40000h -1, the O2 concentration was adjusted to make λ change at 0.97-0.99-1.01-0.99 at a frequency of 2s / time for dynamic light-off test. The concentrations of CO, NO and CH4 were tested by Fourier infrared gas analyzer, and the results of pollutants of each fresh sample and aged sample were obtained. The results are shown in Tables 1 and 2. 50 , the results of pollutants of each fresh sample and aged sample were obtained. The results are shown in Tables 1 and 2. 90 , the results of pollutants of each fresh sample and aged sample were obtained. The results are shown in Tables 1 and 2.

[0079] 2, the Φ12*6in catalyst samples obtained in the above examples and comparative examples were aged, and the aging conditions and atmosphere were as follows: air, 20 vol% H2O, catalyst 850℃ continuous aging for 50h; and the examples 1-4 and comparative examples 1-5 were subjected to 1456h standard bench durability test according to GB 20890-2007 standard cycle; the above rapid aging catalyst samples and bench durability catalyst samples were subjected to performance evaluation according to WHTC cycle test specified in GB 17691-2018, and the emission results of each scheme were obtained, and the results are shown in Tables 3 and 4.

[0080] 3, the catalyst coating obtained in the above examples 1 and 3 was subjected to coating shedding rate test, and the results are shown in Table 5.

[0081] Table 1 statistical table of T 50 , T 90 of fresh sample

[0082] Table 2 statistical table of T 50 , T 90 of 850℃-50h aged sample

[0083] Table 3 statistical table of bench WHTC cycle test of 850℃-50h aged sample

[0084] Table 4 statistical table of bench WHTC cycle test of 1456h durability sample of GB 20890-2007 standard bench cycle

[0085] Table 5 comparison statistical table of shedding rate of fresh sample and aged sample of example 1 and comparative example 1

[0086] From the results in Table 1 and Table 2, it can be seen that the fresh and aged performance of Example 4 are comparable to those of Comparative Examples 1, 2, and 6-8, indicating that the modified catalyst can still maintain catalytic performance when the amount of precious metal is low; the precious metal content of Example 1 and Example 2 is only 50% of that of Comparative Examples 3 and 5, but the fresh performance of Example 1 and Example 2 is comparable to that of Comparative Examples 3 and 5, and the aged performance of CH4 is T 90 The temperature of the catalyst was reduced by about 15℃, indicating that the addition of the middle layer, the modified bottom layer and the upper layer can improve the aging performance of the catalyst while reducing the cost; compared with the comparative examples 6 and 7, the fresh performance of CH4 and NO x T 90 The temperature dropped by about 25℃, and the aging performance was greatly improved. x T 90 The temperature of the catalyst was reduced by about 60℃, indicating that the addition of Ba element in the upper layer and the modification of the four rare earth elements in the bottom layer can effectively improve the performance and high temperature stability of the catalyst; the lack of La and Pr elements in Comparative Example 8 compared with Example 1 caused the catalyst to have a low temperature of CH4 and NO. x The fresh and aging temperatures T 90 The increase indicates that the synergistic effect of the four elements can effectively improve the catalytic performance. From the results in Table 3 and Table 4, it can be seen that compared with other comparative examples, the gas emissions of Example 1 and Example 2 after the bench durability test are much lower than the National VI emission limit, especially the CO emission, while maintaining the HC and NO x , NH3 high purification performance; Example 4, although the amount of precious metals used is low, the catalytic performance can still meet the national six emission limits, and except for comparative examples 5 and 7, the other comparative examples have CH4, NO x Or the situation where NH3 exceeds the National VI emission limit.

[0087] From Table 5 and Figure 1 、 Figure 2 It can be seen that Example 1 also provides an intermediate transition layer, so its catalyst surface shedding rate is significantly lower than that of Example 3 which does not provide an intermediate transition layer. Especially after aging, the shedding rate of Example 3 is significantly improved. Therefore, the present invention provides an intermediate transition layer between the bottom layer and the upper layer, which can balance the thermal expansion coefficient of the entire catalyst coating, reduce the thermal stress concentration coefficient, and enhance the interaction between the middle layer and the bottom layer, and between the middle layer and the upper layer.

[0088] The above detailed description of the specific embodiments of the present application has been given to understand the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A three-way catalyst for natural gas vehicle aftertreatment that reduces the amount of precious metals used, characterized in that: including an upper catalytic coating and a lower catalytic coating; The upper catalytic coating layer includes precious metals and rare earth composite oxides; The bottom catalytic coating comprises precious metals and modified alumina, wherein the modified alumina is a cerium-modified alumina CeAlO with BaSO4 surface grafted with -NH2 groups. x ; The total content of precious metals in the upper catalytic coating and the lower catalytic coating is 20-50 g / cft.

2. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 1, characterized in that: The precious metal in the bottom catalytic coating is Pd, or Pd and Pt; the Pd content is 1-50 g / cft, and the Pt content is 0-50 g / cft; the total precious metal content in the bottom catalytic coating is 1-50 g / cft.

3. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 1, characterized in that: The precious metals in the upper catalytic coating are Pt and Rh; the Pt content is 1-50 g / cft, and the Rh content is 0.4-10 g / cft; the total precious metal content in the upper catalytic coating is 1.4-50 g / cft.

4. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 1, characterized in that: The content of BaSO4 in modified alumina is cerium modified alumina CeAlO x 0~5 wt% of content.

5. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 1, characterized in that: The rare earth composite oxide is a modified rare earth composite oxide obtained by doping cerium-based oxide with Y, Sm, Pr, and La.

6. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 5, characterized in that: The rare earth composite oxide comprises the following components by mass fraction: CeO2 is 50-75 wt%, Y2O3 is 2-5 wt%, Pr2O3 is 2.5-15 wt%, Sm2O3 is 0.5-15 wt%, and La2O3 is 10-15 wt%.

7. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 1, characterized in that: An intermediate transition layer is provided between the upper catalytic coating and the bottom catalytic coating, and the intermediate transition layer is made of cerium-zirconium-aluminum based composite oxide.

8. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 7, characterized in that: The mass fractions of the components in the cerium-zirconium-aluminum based composite oxide are: CeO2 is 30-70 wt%, ZrO2 is 30-60 wt%, Al2O3 is 0-20 wt%, and the additive (La2O3 or Pr2O3) is 0-5 wt%.

9. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 7, characterized in that: The coating amount of the upper catalytic coating is 50~150 g / L, the coating amount of the bottom catalytic coating is 50~150 g / L, and the coating amount of the middle transition layer is 60~100 g / L.

10. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 1, characterized in that: The -NH2 groups grafted onto the surface of BaSO4 are obtained by modifying BaSO4 with γ-aminopropyltriethoxysilane or γ-(2,3-epoxypropyloxy)propyltrimethoxysilane.

11. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 1, characterized in that: The bottom catalytic coating further comprises a cerium-zirconium composite oxide, and the ratio of the modified alumina to the cerium-zirconium composite oxide is 1:2 to 2:

1.

12. The three-way catalyst for natural gas vehicle aftertreatment with reduced precious metal usage according to claim 11, characterized in that: The cerium-zirconium composite oxide is doped with La and Pr.

13. The method for preparing a natural gas vehicle post-treatment three-way catalyst with reduced precious metal usage according to any one of claims 1 to 12, characterized in that: The steps include: S1, preparation of bottom catalytic coating: BaSO4 powder was dissolved in a solvent, and then γ-aminopropyltriethoxysilane was added to graft -NH2 groups on the surface of BaSO4; Grafting -NH2 groups onto the surface of BaSO4 and adding them to CeAlO x The mixture is mixed in the slurry, dried and calcined to obtain BaSO4 modified alumina powder carrier; The noble metal is loaded on a BaSO4-modified alumina powder carrier to prepare a bottom catalyst slurry, which is then coated on the carrier surface and dried and calcined to obtain a bottom catalyst coating; S2, preparation of intermediate transition layer: The cerium zirconium aluminum oxide powder is prepared into a slurry, coated on the bottom catalyst coating, and dried; S3, preparation of upper catalytic coating: The noble metal is loaded on a rare earth composite oxide carrier to prepare an upper catalyst slurry, which is then coated on the dried intermediate transition layer. After drying and calcining, a co-sintered intermediate transition layer and an upper catalytic coating are obtained.

14. A method for reducing the amount of precious metal used in a three-way catalyst, characterized in that: The alumina carrier in the three-way catalyst is replaced with modified alumina, wherein the modified alumina is a cerium-modified alumina CeAlO with BaSO4 surface grafted with -NH2 groups. x .

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