A tightly coupled multifunctional exhaust gas treatment catalyst and its application

Abstract

This invention belongs to the field of diesel vehicle exhaust aftertreatment technology, specifically relating to a tightly coupled multifunctional exhaust treatment catalyst and its application. The catalyst includes: a substrate; a first coating extending from the outlet end of the substrate to the inlet end and applied to the substrate, the length of the first coating being less than the length of the substrate; the first coating includes platinum group metal components and a first metal oxide support; a second coating applied to the first coating and the substrate not covered by the first coating; the second coating includes zeolite containing Fe and / or Cu; and a third coating extending from the inlet end of the substrate to the outlet end and applied to the second coating, the length of the third coating being less than the length of the substrate; the third coating includes platinum group metal components and a second metal oxide support. This catalyst integrates multiple functions such as anti-HC poisoning, efficient NOx reduction, active regeneration heating for DOCF, and inhibition of greenhouse gas N2O generation.

Description

Technical Field

[0001] This invention belongs to the field of diesel vehicle exhaust aftertreatment technology, specifically relating to a tightly coupled multifunctional exhaust treatment catalyst and its application. Background Technology

[0002] With increasingly stringent emission regulations for diesel engine exhaust aftertreatment, the integration and efficiency of aftertreatment systems have become inevitable trends. Placing a selective catalytic reduction (SCR) catalyst pre-coupled (closely coupled) during the low-temperature cold start phase can improve NOx conversion efficiency, but it also introduces problems such as catalyst susceptibility to HC poisoning and limited functionality. CN112675901A proposes a bilayer SCR catalyst, where a Fe / Cu-containing zeolite is fully coated on a support as the bottom SCR catalyst, and then a surface layer containing precious metals (PGMs) is partially coated on top of the bottom layer, starting from the inlet end. This design utilizes the PGM layer at the inlet end to oxidize unburned hydrocarbons (HC) in the exhaust gas, effectively protecting the lower SCR catalyst and preventing its deactivation due to HC coking. However, with the introduction of MFC+DOCF+SCR / ASC aftertreatment system layouts, and the increasing demands on the active regeneration efficiency of the new DOCF and greenhouse gas emissions... The higher requirements for emission control of (high greenhouse gases) have revealed significant shortcomings in the above design: First, the structure only solves the HC poisoning problem of the lower-layer SCR, failing to utilize the PGM layer to oxidize HC and provide an efficient and controllable active regenerative heat source for the downstream diesel particulate filter (DOCF); Second, during the HC oxidation process, HC-SCR occurs in the PGM layer, generating byproducts. Existing coating structures lack effective control methods against HC poisoning. Therefore, it is necessary to develop a coating that can effectively resist HC poisoning, provide sufficient heat source for active DOCF regeneration, achieve efficient NOx reduction, and effectively suppress NOx. The development of tightly coupled multifunctional exhaust gas treatment catalysts has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a tightly coupled multifunctional exhaust gas treatment catalyst and its application. This tightly coupled multifunctional exhaust gas treatment catalyst integrates resistance to HC poisoning, efficient NOx reduction, active regeneration heating for DOCF, and suppression of greenhouse gases. It has multiple functions such as generation.

[0004] The technical solution adopted in this invention is as follows: On one hand, the present invention provides a tightly coupled multifunctional exhaust gas treatment catalyst, comprising: A substrate, the substrate including an air inlet end and an air outlet end, having an axial length L; The first coating, which extends from the outlet end to the inlet end of the substrate and is applied onto the substrate, with the length L1 of the first coating < L; the first coating comprises a platinum group metal component and a first metal oxide support; The second coating, which is applied onto the first coating and the substrate not covered by the first coating; the second coating comprises a zeolite containing Fe and / or Cu; The third coating, which extends from the inlet end to the outlet end of the substrate and is applied onto the second coating, with the length L3 of the third coating < L; the third coating comprises a platinum group metal component and a second metal oxide support.

[0005] In the above technical solution of the present invention, the first coating and the third coating are PGM layers, and the second coating is an SCR coating. The main function of the third coating is to oxidize the unburned HC directly emitted by the engine to form a "barrier", effectively inhibiting the entry of HC into the second coating, fundamentally protecting the second coating from HC coking deactivation, and reducing the risk of HC poisoning of the second coating. The main function of the second coating is to efficiently catalyze the reduction of NOx. The main function of the first coating is to oxidize the high-concentration HC generated by the post-injection of the engine and release heat efficiently when DOCF active regeneration is required. Since the first coating is located downstream of the carrier, the generated heat energy is directly transferred to the downstream DOCF, with high thermal efficiency and rapid temperature rise, effectively reducing the fuel consumption and frequency of DOCF active regeneration, and ensuring that the DOCF unit efficiently burns particulate matter.

[0006] In addition, on the one hand, the third coating oxidizes most of the HC upstream, avoiding the direct contact of high-concentration HC with the second coating, and reducing the opportunity of the coupling of incomplete oxidation of HC and HC-SCR reaction on the second coating to generate On the other hand, the second coating isolates the first coating from NOx in the mainstream of the exhaust gas, avoiding the non-selective reduction of NOx on the first coating to generate . Therefore, overall, the generation of is significantly reduced, and the greenhouse gas emission is reduced; that is, through the synergistic effect of the first coating, the second coating, and the third coating, the catalyst of the present invention can effectively inhibit the oxidation of to generate , and reduce the selectivity.

[0007] The close-coupled multi-functional exhaust gas treatment catalyst of the present invention can be precisely matched and optimized for different exhaust gas conditions (HC concentration, sulfur content, regeneration strategy) of the engine by independently adjusting the types, contents, ratios, and coating lengths of the platinum group metal components of the first coating and the third coating, as well as the zeolite and active site types and loadings of the second coating.

[0008] Furthermore, the platinum group metal component is at least one of platinum, palladium, and rhodium.

[0009] Preferably, the platinum group metal component is Pd or a Pt / Pd combination to balance activity and thermal stability.

[0010] Further, the first metal oxide support is at least one of aluminum oxide, silicon dioxide, zirconium oxide, titanium dioxide, cerium oxide, and lanthanum oxide; the second metal oxide support is at least one of aluminum oxide, silicon dioxide, zirconium oxide, titanium dioxide, cerium oxide, and lanthanum oxide.

[0011] Furthermore, the length L1 of the first coating is 10%-60%L, and / or the length L3 of the third coating is 10%-60%L.

[0012] The lengths L1 of the first coating and L3 of the third coating can be adjusted according to the exhaust gas conditions of different engines. Their values ​​can be 10%L, 20%L, 30%L, 40%L, 50%L, 60%L, or any other value within the above range.

[0013] Furthermore, the zeolite is at least one of the following structures: CHA, AEI, AFT, FAU, MFI, LTA, BEA, and AFX.

[0014] Furthermore, the coating amount of the first coating is 60-200 g / L, and the coating amount of the platinum group metal component in the first coating is 2-60 g / L. The coating amount of the third coating is 60-200 g / L, and the coating amount of the platinum group metal component in the third coating is 2-60 g / L. .

[0015] Furthermore, the application amount of the second coating is 60-200 g / L.

[0016] It should be noted that the coating amount and the coating amount of the platinum group metal components mentioned above are calculated based on the substrate volume.

[0017] Furthermore, the substrate is a flow-through honeycomb ceramic carrier.

[0018] Specifically, the substrate can be selected from ceramic honeycomb carriers or metal honeycomb carriers.

[0019] On the other hand, the present invention also provides a system for treating diesel vehicle exhaust gases, the system comprising the above-described tightly coupled multifunctional exhaust gas treatment catalyst.

[0020] Furthermore, the present invention also provides an application of the above-mentioned tightly coupled multifunctional exhaust gas treatment catalyst in diesel vehicle exhaust gas treatment.

[0021] The present invention has the following beneficial effects: The tightly coupled multifunctional exhaust gas treatment catalyst of the present invention, through the setting of the catalyst coating structure, has a first coating that actively regenerates and heats DOCF, a second coating that efficiently catalyzes NOx reduction, and a third coating that oxidizes HC to reduce the risk of HC poisoning from the second coating. The three layers work synergistically to effectively inhibit NOx poisoning. Oxidation generation ,reduce This invention achieves, for the first time, resistance to HC poisoning, efficient NOx reduction, active heating for DOCF regeneration, and suppression of greenhouse gases on a single tightly coupled catalyst. The generated collaborative integration.

[0022] The tightly coupled multifunctional exhaust gas treatment catalyst of the present invention can be precisely matched and optimized for different engine exhaust gas conditions (HC concentration, sulfur content, regeneration strategy) by independently adjusting the type, content, ratio, and coating length of platinum group metal components in the first and third coatings, as well as the zeolite and active site type and loading of the second coating. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the tightly coupled multifunctional exhaust gas treatment catalyst of the present invention; Figure 2 This is a schematic diagram of the system for treating diesel vehicle exhaust according to the present invention; The components are: 1. substrate, 2. first coating, 3. second coating, and 4. third coating. Detailed Implementation

[0024] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to specific examples. However, the scope of protection of this invention is not limited to the following specific embodiments. The described embodiments are merely some, not all, of the embodiments of this invention, and are not intended to limit the invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0026] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention are commercially available or can be prepared using existing methods. Unless otherwise specified, the parts mentioned in this invention are parts by weight.

[0027] Examples 1-4 were designed for the tightly coupled multifunctional exhaust gas treatment catalyst of the present invention, and comparative examples 1-3 were set up. The key parameters of the catalysts of examples 1-4 and comparative examples 1-3 are shown in Table 1.

[0028] Table 1 Key Parameters of Examples and Comparative Examples

[0029] Figure 1 This is a schematic diagram of the structure of a tightly coupled multifunctional exhaust gas treatment catalyst according to an embodiment of the present invention, wherein 1 is the substrate, 2 is the first coating, 3 is the second coating, and 4 is the third coating.

[0030] In addition, the substrates used in the examples and comparative examples are all ceramic honeycomb carriers manufactured by NGK, with a diameter of 7.5 inches, a length L of 4 inches, a mesh count of 400, and a wall thickness of 4 mil. Example 1.

[0031] The preparation method of the tightly coupled multifunctional tail gas treatment catalyst of Example 1 of the present invention includes the following steps: S1. Grind the alumina powder and mix it with water to prepare an alumina suspension. Add platinum nitrate and palladium nitrate solutions, ensuring that the mass ratio of metallic platinum to palladium is 1:1. After coating, the total concentration of platinum group metals is 10. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the first coating slurry. The first coating slurry is applied to the substrate with a coating length (from the air outlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is then dried at 120°C to form the first coating. S2. Mix Cu-CHA zeolite with water until homogeneous, then add 15 g / L of water-based alumina. Adjust the slurry solid content to 32% with water, and add cellulose hydroxyethyl ether as a thickener to adjust the slurry viscosity to 3000 cps, thus obtaining the second coating slurry. Apply the second coating slurry to the first coating and the substrate not covered by the first coating, with a coating amount (dry weight) of 115 g / L; dry at 120°C to form the second coating. S3. The ground alumina was mixed with water to prepare an alumina suspension. Palladium nitrate solution was added, and the total concentration of platinum group metals after coating was 20%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the third coating slurry. The third coating slurry is applied to the second coating, with a coating length (from the air inlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is dried at 120°C to form the third coating, and then calcined at 550°C. Example 2.

[0032] The preparation method of the tightly coupled multifunctional tail gas treatment catalyst of Example 2 of the present invention includes the following steps: S1. Grind the alumina powder and mix it with water to prepare an alumina suspension. Add platinum nitrate and palladium nitrate solutions, ensuring that the mass ratio of metallic platinum to palladium is 1:2. After coating, the total concentration of platinum group metals is 15%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the first coating slurry. The first coating slurry is applied to the substrate with a coating length (from the air outlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is then dried at 120°C to form the first coating. S2. Mix Cu-AEI zeolite with water until homogeneous, then add 15 g / L of water-based alumina. Adjust the slurry solid content to 32% with water, and add cellulose hydroxyethyl ether as a thickener to adjust the slurry viscosity to 3000 cps, thus obtaining the second coating slurry. Apply the second coating slurry to the first coating and the substrate not covered by the first coating, with a coating amount (dry weight) of 115 g / L; dry at 120°C to form the second coating. S3. Grind cerium oxide and mix with water to prepare a cerium oxide suspension. Add palladium nitrate solution, and the total concentration of platinum group metals after coating is 15%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the third coating slurry. The third coating slurry is applied to the second coating, with a coating length (from the air inlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is dried at 120°C to form the third coating, and then calcined at 550°C. Example 3.

[0033] The preparation method of the tightly coupled multifunctional tail gas treatment catalyst in Example 3 of this invention includes the following steps: S1. Grind the alumina powder and mix it with water to prepare an alumina suspension. Add platinum nitrate and palladium nitrate solutions, ensuring that the mass ratio of metallic platinum to palladium is 2:1. After coating, the total concentration of platinum group metals is 15%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the first coating slurry. The first coating slurry is applied to the substrate with a coating length (from the air outlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is then dried at 120°C to form the first coating. S2. Mix Cu-CHA zeolite with water until homogeneous, then add 15 g / L of water-based alumina. Adjust the slurry solid content to 32% with water, and add cellulose hydroxyethyl ether as a thickener to adjust the slurry viscosity to 3000 cps, thus obtaining the second coating slurry. Apply the second coating slurry to the first coating and the substrate not covered by the first coating, with a coating amount (dry weight) of 115 g / L; dry at 120°C to form the second coating. S3. Mix the ground silica with water to prepare a silica suspension. Add platinum nitrate and palladium nitrate solutions, ensuring that the mass ratio of metallic platinum to palladium is 1:1. After coating, the total concentration of platinum group metals is 15%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the third coating slurry. The third coating slurry is applied to the second coating, with a coating length (from the air inlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is dried at 120°C to form the third coating, and then calcined at 550°C. Example 4.

[0034] The preparation method of the tightly coupled multifunctional tail gas treatment catalyst in Example 4 of this invention includes the following steps: S1. Grind the titanium dioxide powder and mix it with water to prepare a titanium dioxide suspension. Add platinum nitrate and palladium nitrate solutions to ensure that the mass ratio of metallic platinum to palladium is 1:2. After coating, the total concentration of platinum group metals is 15%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the first coating slurry. The first coating slurry is applied to the substrate with a coating length (from the air outlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is then dried at 120°C to form the first coating. S2. Mix Cu-CHA zeolite with water until homogeneous, then add 15 g / L of water-based alumina. Adjust the slurry solid content to 32% with water, and add cellulose hydroxyethyl ether as a thickener to adjust the slurry viscosity to 3000 cps, thus obtaining the second coating slurry. Apply the second coating slurry to the first coating and the substrate not covered by the first coating, with a coating amount (dry weight) of 115 g / L; dry at 120°C to form the second coating. S3. Mix the ground alumina with water to obtain an alumina suspension. Add platinum nitrate and palladium nitrate solutions, ensuring that the mass ratio of metallic platinum to palladium is 1:1. After coating, the total concentration of platinum group metals is 15%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the third coating slurry. The third coating slurry is applied to the second coating, with a coating length (from the air inlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is dried at 120°C to form the third coating, and then calcined at 550°C. Comparative Example 1.

[0035] The preparation method of the catalyst in Comparative Example 1 includes the following steps: Mix Cu-CHA zeolite with water until homogeneous, then add 15 g / L of water-based alumina. Adjust the slurry solid content to 32% with water, and add cellulose hydroxyethyl ether as a thickener to adjust the slurry viscosity to 3000 cps to obtain the SCR slurry. Apply the SCR slurry to the substrate with a coating amount (dry weight) of 115 g / L. Dry at 120°C to form an SCR layer, and then calcine at 550°C. Comparative Example 2.

[0036] The preparation method of the catalyst in Comparative Example 2 includes the following steps: S1. Mix Cu-CHA zeolite with water until homogeneous, then add 15 g / L of water-based alumina. Adjust the slurry solid content to 32% with water, and add cellulose hydroxyethyl ether as a thickener to adjust the slurry viscosity to 3000 cps to obtain the SCR slurry. Apply the SCR slurry to the substrate with a coating amount (dry weight) of 115 g / L; dry at 120°C to form an SCR layer. S2. Grind the alumina and mix it with water to prepare an alumina suspension. Add platinum nitrate and palladium nitrate solutions, ensuring that the mass ratio of metallic platinum to palladium is 2:1. After coating, the total concentration of platinum group metals is 30%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the upper slurry. The upper slurry is applied to the SCR layer with a coating length (from the air inlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is dried at 120°C to form the upper coating layer, and then calcined at 550°C. Comparative Example 3.

[0037] The preparation method of the catalyst in Comparative Example 3 includes the following steps: S1. Grind the alumina powder and mix it with water to prepare an alumina suspension. Add platinum nitrate and palladium nitrate solutions, ensuring that the mass ratio of metallic platinum to palladium is 2:1. After coating, the total concentration of platinum group metals is 30%. The slurry has a solid content of 22%, and the viscosity is adjusted to 2000 cps by adding cellulose hydroxyethyl ether as a thickener, thus obtaining the base slurry. The base slurry is applied to the substrate with a coating length (from the air outlet end) of 2 inches and a coating amount (dry weight) of 80 g / L; it is then dried at 120°C to form the base coating. S2. Mix Cu-CHA zeolite with water until homogeneous, then add 15 g / L of water-based alumina. Adjust the slurry solid content to 32% with water, and add cellulose hydroxyethyl ether as a thickener to adjust the slurry viscosity to 3000 cps to obtain the SCR slurry. Apply the SCR slurry to the undercoat and the substrate not covered by the undercoat, with a coating amount (dry weight) of 115 g / L. Dry at 120°C to form the SCR layer, and then calcine at 550°C.

[0038] Samples with a diameter of 1 inch and a length of 4 inches were drilled from the catalysts prepared in the embodiments and comparative examples of this invention, and their performance was tested on a laboratory sample testing instrument.

[0039] 1. Experimental conditions (the concentration of gases not specified is in ppm) Table 2-1 Experimental conditions for HC poisoning

[0040] Table 2-2 Experimental Conditions 1

[0041] Table 2-3 Experimental Conditions 2

[0042] 2. Performance Testing (1) The NOx conversion efficiency of the samples from Examples 1-2 and Comparative Example 1 at 200℃ and 250℃ was tested using the simulated gas under experimental condition 1. After the test, the samples were treated with the simulated gas under HC poisoning experimental conditions at 300℃ for 50h to carry out hydrocarbon accelerated poisoning aging. After the poisoning aging was completed, the NOx conversion efficiency of the samples at 200℃ and 250℃ was tested again using the simulated gas under experimental condition 1. The test results are shown in Table 3.

[0043] Table 3. NOx conversion efficiency before and after HC poisoning in the examples and comparative examples.

[0044] The results showed that the NOx conversion efficiencies of the samples in Examples 1-2 and Comparative Example 1 were similar before HC poisoning. The NOx conversion efficiency of the sample in Comparative Example 1 (without the PGM layer) decreased significantly after HC poisoning, while the NOx conversion efficiency of the samples in Examples 1 and 2 (with double-layer PGM) decreased only slightly after HC poisoning, especially at a low temperature of 200°C, where their NOx conversion efficiency was approximately 40 percentage points higher than that of Comparative Example 1. This indicates that the upper PGM layer effectively protected the middle SCR coating, improving its resistance to HC poisoning.

[0045] (2) Using the simulated gas under experimental condition 2, the transient heating and ignition performance of HC and CO samples from Examples 3-4 and Comparative Example 3 were tested. During the test, the sample temperature was increased from 100℃ to 300℃ at a heating rate of 10℃ / min to evaluate the ignition heating capacity of the samples. The test results are shown in Table 4.

[0046] Table 4 HC Ignition Temperature Rise Capacity

[0047] The results showed that the CO T90 of Example 3 and Example 4 (double-layer PGM) were significantly lower than those of Example 4 (double-layer PGM). T90 was significantly lower than that of CO in Comparative Example 3. T90 indicates that the samples of Examples 3 and 4 of the present invention have excellent low-temperature oxidation activity and can achieve efficient conversion of CO and HC at lower temperatures, indicating that the double-layer PGM can significantly reduce the ignition temperature of HC and improve the ability to oxidize HC and CO.

[0048] (3) Steady-state performance tests were conducted on the samples of Example 1, Example 3, and Comparative Examples 2-3 under experimental conditions 1, and the outlet temperature was measured at 250°C. Concentration. Test results are shown in Table 5.

[0049] Table 5 Emission concentration

[0050] The results showed that, compared with comparative examples 2-3, the samples of Examples 1 and 3 of the present invention could effectively inhibit... This is because, in Comparative Example 2, due to the oxidation of the upper PGM layer... Producing more Comparative Example 3 also produces a certain amount of NOx due to its reduction at the underlying PGM. In Examples 1 and 3, the upper PGM layer oxidizes most of the HC, and the middle SCR layer isolates NOx from the bottom PGM layer, resulting in an overall... The amount generated was significantly lower than that of Comparative Example 2 and Comparative Example 3.

[0051] Figure 2 A specific embodiment of the system for treating diesel vehicle exhaust gas according to the present invention is shown. The system includes: the tightly coupled multifunctional exhaust gas treatment catalyst (MFC in the figure), DOCF unit, SCR unit, and SCR2 / ASC unit of the present invention, which are sequentially connected to the engine turbocharger outlet. Urea solution injection units are provided between the engine turbocharger outlet and the MFC, and between the DOCF unit and the SCR unit. The ASC unit is integrated on the SCR2 unit.

[0052] Because this system includes the tightly coupled multifunctional exhaust gas treatment catalyst of the present invention, it possesses resistance to HC poisoning, high NOx reduction efficiency, and greenhouse gas suppression capabilities. It has the characteristics of high generation and high thermal efficiency.

[0053] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0054] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0055] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A tightly coupled multifunctional exhaust gas treatment catalyst, characterized in that, Comprising: A substrate, the substrate including an air inlet end and an air outlet end, having an axial length L; A first coating, the first coating extending from the air outlet end of the substrate towards the air inlet end, coated on the substrate, the length L1 of the first coating < L; the first coating includes a platinum group metal component and a first metal oxide support; A second coating, the second coating coated on the first coating and the substrate not covered by the first coating; the second coating includes a zeolite containing Fe and / or Cu; A third coating, the third coating extending from the air inlet end of the substrate towards the air outlet end, coated on the second coating, the length L3 of the third coating < L; the third coating includes a platinum group metal component and a second metal oxide support.

2. The tightly coupled multifunctional exhaust gas treatment catalyst according to claim 1, characterized in that, The platinum group metal component is at least one of platinum, palladium, and rhodium.

3. The tightly coupled multifunctional exhaust gas treatment catalyst according to claim 1, characterized in that, The first metal oxide support is at least one of alumina, silica, zirconia, titania, ceria, and lanthanum oxide; the second metal oxide support is at least one of alumina, silica, zirconia, titania, ceria, and lanthanum oxide.

4. The tightly coupled multifunctional exhaust gas treatment catalyst according to claim 1, characterized in that, The length L1 of the first coating is 10% - 60% of L, and / or, the length L3 of the third coating is 10% - 60% of L.

5. The tightly coupled multifunctional exhaust gas treatment catalyst according to claim 1, characterized in that, The zeolite is at least one of CHA, AEI, AFT, FAU, MFI, LTA, BEA, and AFX structures.

6. The tightly coupled multifunctional exhaust gas treatment catalyst according to claim 1, characterized in that, The coating amount of the first coating is 60-200 g / L, and the coating amount of the platinum group metal component in the first coating is 2-60 g / L. ; The coating amount of the third coating is 60-200 g / L, and the coating amount of the platinum group metal component in the third coating is 2-60 g / L. .

7. The tightly coupled multifunctional exhaust gas treatment catalyst according to claim 1, characterized in that, The coating amount of the second coating is 60 - 200 g / L.

8. The tightly coupled multifunctional exhaust gas treatment catalyst according to claim 1, characterized in that, The substrate is a flow-through honeycomb ceramic carrier.

9. A system for treating diesel vehicle exhaust gas, the system including the close-coupled multifunctional exhaust gas treatment catalyst according to any one of claims 1 - 8.

10. An application of the close-coupled multifunctional exhaust gas treatment catalyst according to any one of claims 1 - 8 in the treatment of diesel vehicle exhaust gas.

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