Multilayer twc formulations with optimized pgm loading

Abstract

A catalyst article for treating waste gas includes: a substrate having an inlet end and an outlet end, and having an axial length L; a first catalytic region comprising a first palladium component; a second catalytic region comprising a second rhodium component; and a third catalytic region comprising a third palladium component; wherein the first catalytic region is adjacent to the second catalytic region; and wherein, based on elemental composition, the weight ratio of the first palladium component to the second rhodium component is from 3:1 to 19:1.

Description

Technical Field

[0001] This invention relates to catalytic products that can be used to treat exhaust emissions from gasoline engines. Background Technology

[0002] Three-way catalytic converter (TWC) reduces CO, HC and NO from gasoline engine exhaust. x At a stoichiometric air-fuel ratio, approximately 98% of the CO and HC are simultaneously converted into non-toxic compounds. Specifically, the oxidation of CO and HC to CO2 and vapor (H2O) is primarily catalyzed by Pd, while NO... x The reduction to N2 is primarily catalyzed by Rh. Modern TWC utilizes supported platinum group metal (PGM) catalysts (Pd, Rh, Pt, etc.) deposited on monolayer, bilayer, or multilayer supports. The support materials consist of metal oxides with high specific surface areas, primarily stable alumina and cerium dioxide-containing oxygen storage materials. The supported catalyst support is then coated onto a single ceramic substrate. Among the PGMs, Rh is the rarest and most expensive substance on Earth. Therefore, achieving high activation of Rh is the most critical requirement for maintaining excellent TWC performance.

[0003] Rh sintering occurs due to exposure to high temperatures during the lifetime of three-way catalytic converter use, which reduces active Rh catalytic sites, leading to activity degradation. In addition, Rh migration is another important cause of TWC deactivation. Tomida et al. [1] reported dramatic migration of rhodium from one support to another under high-temperature air atmosphere (lean conditions) by EPMA and XPS analysis. It is reasonable to infer that Rh will also migrate from the inlet side of the coated bulk material to the outlet side and / or between multiple support coatings.

[0004] Previously reported methods have included blending some Pd into Rh support coatings as a common approach to stabilizing rhodium by forming Pd-Rh alloys. Goto and others [2] noted that when both Pd and Rh are present in the same support coating, it is advantageous to bring the Pd and Rh nanoparticles close together without forming a core-shell PdRh alloy, which is known for its poor TWC activity. However, Pd and Rh in the same support coating sometimes exhibit detrimental NOx reduction behavior under certain conditions due to the “peroxidation” of reducing agents such as CO / H2 / THC, thus limiting their application to a wider range of TWC communities.

[0005] However, this invention utilizes the Rh migration phenomenon by constructing “Pd nest” layers / regions to capture migrating Rh to form adjacent Pd-Rh nanoparticles. By carefully controlling the Pd loading in the nests to be high enough to capture Rh but not too much to form PdRh alloys with a Pd core-Rh shell structure, a significant improvement in TWC activity has been successfully achieved.

[0006] Non-patent references :

[0007] [1]Tomida et al., "A study of ageing effect: Migration of rhodium underair atmosphere," Catalysis Today, Volume 376, 2021, 81-86

[0008] [2]Goto et al., "Impact of Pd-Rh interaction on the performance of three-way catalysts," No. 2014-01-1503, SAE Technical Paper, 2014. Summary of the Invention

[0009] One aspect of this disclosure relates to a catalyst for treating exhaust gases from a gasoline engine, the catalyst comprising: a substrate including an inlet end and an outlet end, having an axial length L; a first catalytic region comprising a first palladium component; a second catalytic region comprising a second rhodium component; and a third catalytic region comprising a third palladium component; wherein the first catalytic region is adjacent to the second catalytic region; and wherein, based on elemental composition, the weight ratio of the first palladium component to the second rhodium component is from 3:1 to 19:1.

[0010] The present invention also includes an exhaust system for an internal combustion engine, the exhaust system comprising the three-way catalyst component of the present invention.

[0011] The present invention also includes treating exhaust gases from internal combustion engines, specifically exhaust gases from gasoline engines. This method involves contacting the exhaust gases with the components of the three-way catalyst of the present invention. Attached Figure Description

[0012] Figure 1a A configuration is described in which a first catalytic region is a bottom layer directly deposited on a substrate, a second catalytic region is an intermediate layer, and a third catalytic region is a top layer.

[0013] Figure 1b Depicting Figure 1a A variant of .

[0014] Figure 1c Depicting Figure 1a A variant of .

[0015] Figure 1d Depicting Figure 1a A variant of .

[0016] Figure 2a A configuration is described in which a first catalytic region partially covers a third catalytic region as a bottom layer directly deposited on a substrate, and a second catalytic region is a top layer.

[0017] Figure 2b Depicting Figure 2a A variant of .

[0018] Figure 2c A first configuration is depicted, in which a second catalytic region is a bottom layer directly deposited on the substrate, and the first catalytic region partially covers a third catalytic region as a top layer.

[0019] Figure 2d Depicting Figure 2c A variant of .

[0020] Figure 2e Depicting Figure 2a A variant of .

[0021] Figure 2f Depicting Figure 2c A variant of .

[0022] Figure 2g A configuration is described in which a third catalytic region partially covers a first catalytic region as a bottom layer directly deposited on a substrate, and a second catalytic region is a top layer.

[0023] Figure 2h Depicting Figure 2g A variant of .

[0024] Figure 2i A first configuration is depicted, wherein a second catalytic region is a bottom layer directly deposited on the substrate, and a third catalytic region partially covers the first catalytic region as a top layer.

[0025] Figure 2j Depicting Figure 2i A variant of .

[0026] Figure 2k Depicting Figure 2g A variant of .

[0027] Figure 2f Depicting Figure 2i A variant of .

[0028] Figure 3a The NO levels of comparative catalyst A, catalyst 1 of the present invention, and catalyst 2 of the present invention during cold RDE cycling are shown. x Emissions.

[0029] Figure 3b The CO emissions during a cold RDE cycle are shown for comparison of catalyst A and catalysts 1 and 2 of the present invention.

[0030] Figure 3c The THC emissions during a cold RDE cycle are shown for comparative catalyst A and catalysts 1 and 2 of the present invention.

[0031] Figure 3d The NH3 emissions during a cold RDE cycle are shown for comparative catalyst A and catalysts 1 and 2 of the present invention. Detailed Implementation

[0032] This invention relates to the catalytic treatment of combustion exhaust gases (such as exhaust gases produced by gasoline engines and other engines), and specifically to related catalysts and systems. More particularly, this invention relates to the simultaneous treatment of NO in vehicle exhaust systems. x CO and HC. The inventors have discovered the optimal weight ratio of certain catalytically active metals in adjacent layers / regions and their coating method, which unexpectedly produced NO. x It achieves high conversion rates of CO and HC and improves performance during the cold start phase.

[0033] One aspect of this disclosure relates to a catalyst for treating exhaust gases from a gasoline engine, the catalyst comprising: a substrate including an inlet end and an outlet end, having an axial length L; a first catalytic region comprising a first palladium component; a second catalytic region comprising a second rhodium component; and a third catalytic region comprising a third palladium component; wherein the first catalytic region is adjacent to the second catalytic region; and wherein, based on elemental composition, the weight ratio of the first palladium component to the second rhodium component is from 3:1 to 19:1.

[0034] First catalytic region

[0035] The first catalytic region may contain a PGM metal other than the first palladium component, such as platinum.

[0036] The first catalytic region can contain 3g / ft 3 Up to 380g / ft 3 The first palladium component. Preferably, the first catalytic region may contain 5 g / ft. 3 Up to 200g / ft 3 The first palladium component, more preferably 10 g / ft 3 Up to 100g / ft 3 The first palladium component.

[0037] In some embodiments, the weight ratio of the first palladium component to the second rhodium component can be from 3:1 to 18:1. Preferably, the weight ratio of the first palladium component to the second rhodium component can be from 4:1 to 17:1. More preferably, the weight ratio of the first palladium component to the second rhodium component is from 5:1 to 15:1. Most preferably, the weight ratio of the first palladium component to the second rhodium component is from 5:1 to 10:1.

[0038] In some embodiments, the first catalytic region may extend 100% of the axial length L. In other embodiments, the first catalytic region may extend 50% to 99% of the axial length L. Preferably, the first catalytic region may extend 55% to 99% of the axial length L; more preferably 60% to 95%; and even more preferably 70% to 90%.

[0039] The total support coating loading in the first catalytic region can be less than 3.5 g / in. 3 Preferably less than 3.0 g / in 3 2.5g / in 3 Less than 1.5g / in 3 or 1.0g / in 3 .

[0040] The first catalytic region may further include a first oxygen storage capacity (OSC) material, a first alkali metal or alkaline earth metal component, and / or a first inorganic oxide.

[0041] The first OSC material is preferably selected from the group consisting of: cerium oxide, cerium dioxide-zirconia mixed oxide, and alumina-cerium dioxide-zirconia mixed oxide. More preferably, the first OSC material includes cerium dioxide-zirconia mixed oxide. The cerium dioxide-zirconia mixed oxide may also include some dopants, such as lanthanum, neodymium, praseodymium, yttrium oxide, etc. In addition, the first OSC material can be used as a carrier material for the first palladium component.

[0042] The first palladium component may be supported on a first inorganic oxide or a first OSC material, or both.

[0043] The cerium dioxide-zirconia mixed oxide can have the following molar ratio of zirconia to cerium dioxide: at least 50:50, preferably higher than 60:40, and more preferably higher than 75:25.

[0044] Based on the total support coating loading of the first catalytic region, the first OSC material (e.g., cerium dioxide-zirconia mixed oxide) can be 10% to 90% by weight, preferably 25% to 75% by weight, and more preferably 30% to 60% by weight.

[0045] In some embodiments, the first alkali metal or alkaline earth metal may be deposited on the first OSC material. Alternatively or otherwise, the first alkali metal or alkaline earth metal may be deposited on the first inorganic oxide. That is, in some embodiments, the first alkali metal or alkaline earth metal may be deposited on (i.e., present) on both the first OSC material and the first inorganic oxide.

[0046] The first alkali metal or alkaline earth metal is typically in contact with the first inorganic oxide. Preferably, the first alkali metal or alkaline earth metal is supported on the first inorganic oxide. Alternatively, the first alkali metal or alkaline earth metal may be in contact with the first OSC material.

[0047] The first alkali metal or alkaline earth metal is preferably barium or strontium and their mixed oxides or composite oxides. Preferably, the loading of barium or strontium (if present) is 0.1% to 15% by weight, and more preferably 3% to 10% by weight, based on the total weight of the first catalytic region.

[0048] The first inorganic oxide is preferably an oxide of an element from Groups 2, 3, 4, 5, 13, and 14. Preferably, the first inorganic oxide is selected from the group consisting of aluminum oxide, magnesium oxide, silicon dioxide, cerium dioxide, barium oxides, and mixed or composite oxides thereof. Particularly preferably, the first inorganic oxide is aluminum oxide, lanthanum-alumina, cerium dioxide, or a magnesium oxide / alumina composite oxide. A particularly preferred first inorganic oxide is aluminum oxide or a lanthanum-alumina composite oxide.

[0049] The weight ratio of the first OSC material to the first inorganic oxide can be 10:1 to 1:10, preferably 8:1 to 1:8 or 5:1 to 1:5; more preferably 4:1 to 1:4 or 3:1 to 1:3; and most preferably 2:1 to 1:2.

[0050] Second catalytic region

[0051] The second catalytic region may be substantially free of PGM metals other than the second rhodium component.

[0052] In some embodiments, the second catalytic region may extend 100% of the axial length L. In other embodiments, the second catalytic region may extend 50% to 99% of the axial length L; preferably, the second catalytic region may extend 55% to 99% of the axial length L; more preferably 60% to 99% or 60% to 95%; and even more preferably 70% to 90%.

[0053] The second catalytic region may contain PGM metals other than the second rhodium component, such as platinum and / or palladium. The second catalytic region may contain 1 g / ft 3 Up to 20g / ft 3The second rhodium component. Preferably, the second catalytic region may contain 2 g / ft. 3 Up to 14g / ft 3 , preferably 3g / ft 3 Up to 9g / ft 3 The second rhodium component.

[0054] The second catalytic region may further include a second OSC material and / or a second inorganic oxide.

[0055] The second OSC material is preferably selected from the group consisting of cerium oxide, cerium oxide-zirconia mixed oxide, and aluminum oxide-cerium oxide-zirconia mixed oxide. More preferably, the second OSC material includes cerium dioxide-zirconia mixed oxide. Additionally, the second OSC material may also contain one or more dopants, such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material may function as a carrier material for the second rhodium component.

[0056] The second rhodium component can be loaded onto both the second inorganic oxide and the second OSC material.

[0057] The cerium dioxide-zirconia mixed oxide can have the following molar ratio of zirconia to cerium dioxide: at least 50:50, preferably higher than 60:40, and more preferably higher than 75:25.

[0058] Based on the total support coating loading of the second catalytic region, the second OSC material (e.g., cerium dioxide-zirconia mixed oxide) can be 10% to 90% by weight, preferably 25% to 75% by weight, and more preferably 30% to 60% by weight.

[0059] The second catalytic region may be substantially free of alkali metals or alkaline earth metals. The reference to "substantially free" means that the material may be present in trace amounts, intentionally or unintentionally, in the layer. For example, alkali metals or alkaline earth metals may be present in the first catalytic region and / or the third catalytic region, and some alkali metals or alkaline earth metals may unintentionally migrate / infiltrate into the second catalytic region during the coating process.

[0060] The total support coating loading in the second catalytic region can be less than 3.5 g / in. 3 Preferably less than 3.0 g / in 3 2.5g / in 3 Or 1.5g / in 3 .

[0061] The weight ratio of the second OSC material to the second inorganic oxide can be 10:1 to 1:10, preferably 8:1 to 1:8 or 5:1 to 1:5; more preferably 4:1 to 1:4 or 3:1 to 1:3; and most preferably 2:1 to 1:2.

[0062] Third catalytic region

[0063] In some embodiments, the third catalytic region may extend 100% of the axial length L. In other embodiments, the third catalytic region may extend 50% to 99% of the axial length L; preferably, the third catalytic region may extend 55% to 99% of the axial length L; more preferably 60% to 99% or 60% to 95%; and even more preferably 70% to 90%.

[0064] The third catalytic region can be essentially free of PGM metals other than the third palladium component.

[0065] The third catalytic region can contain 3g / ft 3 Up to 380g / ft 3 The third palladium component. In some embodiments, the third catalytic region may contain 5 g / ft. 3 Up to 200g / ft 3 or 10g / ft 3 Up to 100g / ft 3 The third palladium component.

[0066] The total support coating loading in the third catalytic region can be less than 3.5 g / in. 3 Preferably less than 3.0 g / in 3 Or 2.0g / in 3 More preferably less than 1.5 g / in 3 or 1.0g / in 3 .

[0067] The third catalytic region may also include a third OSC material, a third alkali metal or alkaline earth metal component, and / or a third inorganic oxide.

[0068] The third OSC material is preferably selected from the group consisting of: cerium oxide, cerium dioxide-zirconia mixed oxide, and aluminum oxide-cerium dioxide-zirconia mixed oxide. Preferably, the third OSC material comprises cerium dioxide-zirconia mixed oxide with one or more dopants such as lanthanum, neodymium, yttrium, and praseodymium. Additionally, the third OSC material can be used as a carrier material for the third rhodium component.

[0069] Based on the total support coating loading of the third catalytic region, the third OSC material can be 10% to 90% by weight; preferably 25% to 75% by weight; more preferably 35% to 65% by weight.

[0070] The third alkali metal or alkaline earth metal is preferably barium, strontium, or their mixed oxides or composite oxides. Preferably, based on the total weight of the third catalytic region, the amount of barium or strontium (when present) is 0.1% to 15% by weight, and more preferably 3% to 10% by weight of barium or strontium.

[0071] The third inorganic oxide is preferably an oxide of elements from Groups 2, 3, 4, 5, 13, and 14. Preferably, the third inorganic oxide is selected from the group consisting of: aluminum oxide, cerium dioxide, magnesium oxide, silicon dioxide, lanthanum oxide, zirconium oxide, neodymium oxide, praseodymium oxide, and mixed or composite oxides thereof. Particularly preferably, the third inorganic oxide is aluminum oxide, a lanthanum / alumina composite oxide, or a zirconium / alumina composite oxide. A particularly preferred third inorganic oxide is a lanthanum / alumina composite oxide or a zirconium / alumina composite oxide. The third inorganic oxide may be a carrier material for the third palladium component and / or the third OSC material.

[0072] Preferably, the third inorganic oxide has a concentration greater than 80 m. 2 The fresh surface area per g, ranging from 0.1 to 4 mL / g, with a pore volume greater than 100 m² / g. 2 High surface area inorganic oxides with a surface area of ​​ / g are particularly preferred, such as high surface area alumina. Other preferred third inorganic oxides include lanthanum / alumina composite oxides.

[0073] The weight ratio of the third OSC material to the third inorganic oxide can be 10:1 to 1:10, preferably 8:1 to 1:8 or 5:1 to 1:5; more preferably 4:1 to 1:4 or 3:1 to 1:3.

[0074] In some embodiments, the weight ratio of the first palladium component to the third palladium component is 50:1 to 1:50. In another embodiment, the weight ratio of the first palladium component to the third palladium component is 30:1 to 1:30. In yet another embodiment, the weight ratio of the first palladium component to the third palladium component is 10:1 to 1:10. In still another embodiment, the weight ratio of the first palladium component to the second palladium component is 7:1 to 1:7.

[0075] Preferably, the weight ratio of the first palladium component to the third palladium component is greater than 1:1, more preferably at least 3:2, 2:1 or 3:1; and even more preferably at least 4:1, 5:1, 6:1 or 7:1.

[0076] In some embodiments, the weight ratio of the second rhodium component to the third palladium component is 60:1 to 1:60. Preferably, the weight ratio of the second rhodium component to the third palladium component is 40:1 to 1:40. More preferably, the weight ratio of the second rhodium component to the third palladium component is 30:1 to 1:30. Most preferably, the weight ratio of the second rhodium component to the third palladium component is 10:1 to 1:10.

[0077] The catalyst articles of the present invention may contain additional components known to those skilled in the art. For example, the compositions of the present invention may further contain at least one binder and / or at least one surfactant. In the presence of a binder, a dispersible alumina binder is preferred.

[0078] Configuration of the first catalytic region, the second catalytic region and the third catalytic region

[0079] In some implementations, the first catalytic region, the second catalytic region, and the third catalytic region can each independently extend 100% of the axial length L.

[0080] The second catalytic region may overlap the first catalytic region by up to 100% of the axial length L (the first catalytic region may cover the second catalytic region, or the second catalytic region may cover the first catalytic region). Alternatively, the second catalytic region may overlap the first catalytic region by up to 90%, 80%, 70%, 60%, 50%, or even 40% of the axial length L. In some embodiments, the first and second catalytic regions may begin at the same end of the substrate and extend less than 100% of the axial length L, such as each region independently extending up to 90%, 80%, 70%, 60%, 50%, or even 40% of the axial length L. In some embodiments, the first and second catalytic regions may begin at opposite ends of the substrate and extend less than 100% of the axial length L, such as each region independently extending up to 95%, 90%, 80%, 70%, or even 60% of the axial length L.

[0081] In one aspect of the invention, various configurations of a catalytic article including a first catalytic region, a second catalytic region, and a third catalytic region can be prepared as follows.

[0082] Figure 1a A configuration is described in which a first catalytic region is a bottom layer directly deposited on a substrate, a second catalytic region is an intermediate layer, and a third catalytic region is a top layer.

[0083] Figure 1b Depicting Figure 1a A variant of .

[0084] Figure 1c Depicting Figure 1a A variant of .

[0085] Figure 1dDepicting Figure 1a A variant of .

[0086] Figure 2a A configuration is described in which a first catalytic region partially covers a third catalytic region as a bottom layer directly deposited on a substrate, and a second catalytic region is a top layer.

[0087] Figure 2b Depicting Figure 2a A variant of .

[0088] Figure 2c A first configuration is depicted, in which a second catalytic region is a bottom layer directly deposited on the substrate, and the first catalytic region partially covers a third catalytic region as a top layer.

[0089] Figure 2d Depicting Figure 2c A variant of .

[0090] Figure 2e Depicting Figure 2a A variant of .

[0091] Figure 2f Depicting Figure 2c A variant of .

[0092] Figure 2g A configuration is described in which a third catalytic region partially covers a first catalytic region as a bottom layer directly deposited on a substrate, and a second catalytic region is a top layer.

[0093] Figure 2h Depicting Figure 2g A variant of .

[0094] Figure 2i A first configuration is depicted, wherein a second catalytic region is a bottom layer directly deposited on the substrate, and a third catalytic region partially covers the first catalytic region as a top layer.

[0095] Figure 2j Depicting Figure 2i A variant of .

[0096] Figure 2k Depicting Figure 2g A variant of .

[0097] Figure 2f Depicting Figure 2i A variant of .

[0098] The flow-through substrate has a first surface and a second surface defining a longitudinal direction therebetween. The flow-through substrate has a plurality of channels extending between the first and second surfaces. These channels extend in the longitudinal direction and provide a plurality of inner surfaces (e.g., surfaces defining the walls of each channel). Each of the plurality of channels has an opening at the first surface and an opening at the second surface. For the avoidance of confusion, the flow-through substrate is not a wall-flow filter.

[0099] The first surface is typically located at the inlet end of the substrate, and the second surface is located at the outlet end of the substrate.

[0100] The channel can have a constant width, and multiple channels can each have a uniform channel width.

[0101] Preferably, in a plane orthogonal to the longitudinal direction, the monolithic substrate has 300 to 900 channels / square inch, more preferably 400 to 800 channels / square inch. For example, on the first surface, the density of the open first channel and the closed second channel is 600 to 700 channels / square inch. The channel can have a cross-section of: rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal shapes.

[0102] The monolithic substrate acts as a support for holding the catalytic material. Suitable materials for forming the monolithic substrate include ceramic-like materials such as cordierite, silicon carbide, silicon nitride, zirconium oxide, mullite, spodumene, alumina-silica magnesium oxide, or zirconium silicate, or porous refractory metals. Such materials and their uses in the manufacture of porous monolithic substrates are well known in the art.

[0103] It should be noted that the flow-through monolithic substrate described herein is a single component (i.e., a single brick-shaped object). Nevertheless, when forming an emissions treatment system, the substrate used can be formed by adhering multiple channels together or by adhering multiple smaller substrates together, as described herein. Such techniques, as well as suitable housings and configurations for emissions treatment systems, are well known in the art.

[0104] In embodiments where the catalyst article of the present invention comprises a ceramic substrate, the ceramic substrate may be made of any suitable refractory material, such as alumina, silicon dioxide, cerium dioxide, zirconium oxide, magnesium oxide, zeolite, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicates and metallic aluminosilicates (such as cordierite and spodumene), or any mixture or mixed oxide of two or more thereof. Cordierite, magnesium aluminosilicate, and silicon carbide are particularly preferred.

[0105] In embodiments where the catalyst article of the present invention comprises a metal substrate, the metal substrate may be made of any suitable metal, and specifically of heat-resistant metals and metal alloys, such as titanium and stainless steel, and ferritic alloys containing iron, nickel, chromium and / or aluminum in addition to other trace metals.

[0106] Another aspect of this disclosure relates to the treatment of NO-containing products using the catalyst articles described herein. x A method for treating vehicle exhaust gases containing CO and HC. A catalytic converter equipped with TWC prepared according to this method shows improvements compared to conventional TWC (with the same PGM loading), and also shows reductions in NO. x It achieves high conversion rates of CO and HC, and improves performance during the cold start phase.

[0107] Another aspect of this disclosure relates to a system for treating vehicle exhaust gases, the system comprising the catalyst article described herein, together with a conduit for transferring the exhaust gases through the system.

[0108] definition

[0109] As used herein, the term "region" refers to a region on a substrate, typically obtained by drying and / or calcining a carrier coating. For example, a "region" may be set or loaded onto the substrate in the form of a "layer" or "zone". The regions or arrangement on the substrate are generally controlled during the process of applying the carrier coating to the substrate. "Regions" typically have distinct boundaries or edges (i.e., one region can be distinguished from another using conventional analytical techniques).

[0110] Typically, a “region” has a substantially uniform length. In this context, “substantially uniform length” means a length that does not deviate from its average value (e.g., the difference between the maximum and minimum lengths) by more than 10%, preferably more than 5%, and more preferably more than 1%.

[0111] Preferably, each “region” has a substantially uniform composition (i.e., the composition of the carrier coating does not differ significantly when a portion of the region is compared to another portion of the region). In this context, a substantially uniform composition means that the difference in composition between a portion of the region and another portion of the region is 5% or less, typically 2.5% or less, and most typically 1% or less of the material (e.g., region).

[0112] As used herein, the term “zone” refers to a region whose length is less than the total length of the substrate, such as ≤75% of the total length of the substrate. A “zone” typically has a length of at least 5% (e.g., ≥5%) of the total length of the substrate (i.e., a substantially uniform length).

[0113] The total length of the substrate is the distance between its inlet end and its outlet end (e.g., the opposite end of the substrate).

[0114] As used herein, any reference to "a region disposed at the inlet end of the substrate" refers to a region disposed on or loaded on the substrate, wherein the region is closer to the inlet end of the substrate than a region near the outlet end of the substrate. Therefore, the midpoint of this region is closer to the inlet end of the substrate than the midpoint near the outlet end of the substrate (i.e., at half its length). Similarly, as used herein, any reference to "a region disposed at the outlet end of the substrate" refers to a region disposed on or loaded on the substrate, wherein the region is closer to the outlet end of the substrate than a region near the inlet end of the substrate. Therefore, the midpoint of this region is closer to the outlet end of the substrate than the midpoint near the inlet end of the substrate (i.e., at half its length).

[0115] When the substrate is a wall-flow filter, generally speaking, any reference to "the area located at the inlet end of the substrate" refers to the area that is disposed on or loaded on the substrate, which is:

[0116] (a) The area closer to the inlet end (e.g., the open end) of the inlet channel than the area near the closed end (e.g., the sealed end or the blocked end) of the inlet channel, and / or

[0117] (b) The closed end (e.g., the blocked end or the shut end) of the outlet channel closer to the substrate than the area near the outlet end (e.g., the open end) of the outlet channel.

[0118] Therefore, the midpoint of this zone (i.e., at half its length) (a) is closer to the entrance end of the base's entrance channel than the midpoint near the closed end of the entrance channel, and / or (b) is closer to the closed end of the base's exit channel than the midpoint near the exit end of the exit channel.

[0119] Similarly, when the substrate is a wall-flow filter, any reference to "the area located at the outlet end of the substrate" refers to the area disposed on or loaded on the substrate, which is:

[0120] (a) The region closer to the outlet end (e.g., open end) of the outlet channel than the region near the closed end (e.g., closed or blocked end) of the outlet channel, and / or

[0121] (b) The area closer to the closed end (e.g., the sealed end or the blocked end) of the inlet channel than the inlet end (e.g., the open end) of the inlet channel.

[0122] Therefore, the midpoint of this zone (i.e., at half its length) (a) is closer to the exit end of the base's exit channel than the midpoint near the closed end of the exit channel, and / or (b) is closer to the closed end of the base's inlet channel than the midpoint near the inlet end of the inlet channel.

[0123] When the carrier coating is present in the wall of the wall-flow filter (i.e., the zone is in the wall), the zone can satisfy both (a) and (b) at the same time.

[0124] The term "carrier coating" is well known in the art and refers to an adhesive coating that is typically applied to a substrate during catalyst production.

[0125] As used herein, the acronym "PGM" stands for "Platinum Group Metals". The term "Platinum Group Metals" generally refers to metals selected from the group consisting of: Ru, Rh, Pd, Os, Ir, and Pt, and preferably metals selected from the group consisting of: Ru, Rh, Pd, Ir, and Pt. More generally, the term "PGM" preferably refers to metals selected from the group consisting of: Rh, Pt, and Pd.

[0126] As used herein, the term "mixed oxide" generally refers to a mixture of oxides in single-phase form, as is commonly known in the art. As used herein, the term "composite oxide" generally refers to a composition of oxides having more than one phase, as is commonly known in the art.

[0127] As used herein, the expression "consistently composed of..." limits the scope of a feature to include the specified material or step, as well as any other material or step that does not substantially affect the essential properties of that feature, such as, for example, trace impurities. The expression "consistently composed of..." encompasses the expression "composed of...".

[0128] As used herein, the expression "substantially contains no" when referring to a material in the context of its content in a region, layer, or zone usually means a small amount of the material, such as ≤5% by weight, preferably ≤2% by weight, more preferably ≤1% by weight. The expression "substantially contains no" encompasses the expression "does not contain".

[0129] As used herein, the expression “substantially contains” for a material, typically in the context of content in a region, layer, or zone, means that the material is present in trace amounts, such as ≤1% by weight, preferably ≤0.5% by weight, more preferably ≤0.1% by weight. The expression “substantially contains” encompasses the expression “does not contain”.

[0130] As used herein, any reference to the amount of dopant (specifically, the total amount) expressed as a percentage by weight refers to the weight of the carrier material or its refractory metal oxide.

[0131] As used herein, the term "load" refers to a quantity of metal weight in g / ft. 3 Measurement results in units of measurement.

[0132] The following examples are merely illustrative of the invention. Those skilled in the art will recognize the spirit of the invention and many variations within the scope of the claims.

[0133] Example

[0134] Material

[0135] Unless otherwise specified, all materials are commercially available and can be purchased from known suppliers.

[0136] Comparison with catalyst A :

[0137] Comparative catalyst A is a commercially available ternary (Pd-Rh) catalyst with a bilayer structure. The bottom layer consists of Pd supported on a carrier coating consisting of a first CeZr mixed oxide, La-stabilized alumina, and a Ba promoter. The loading of the bottom carrier coating is approximately 2.0 g / in. 3 The Pd loading was 133 g / ft. 3 Using a standard coating procedure, a carrier coating is applied to the inlet and outlet surfaces of the ceramic substrate (750 cpsi, 3.0 mil wall thickness), with a target coating depth of 50% of the substrate length, followed by drying and calcination.

[0138] The top layer consists of Rh loaded onto a carrier coating of a second CeZr mixed oxide and La-stabilized alumina. The carrier coating loading of the top layer is approximately 2.0 g / in. 3 The Rh load is 7 g / ft. 3 Using a standard coating procedure, the carrier coating is applied from above to the inlet and outlet surfaces of the ceramic substrate containing the underlying carrier coating (750 cpsi, 3.0 mil wall thickness), with a target coating depth of 50% of the substrate length, followed by drying and calcination.

[0139] Catalyst 1 of the present invention (according to Figure 1c ) :

[0140] Third catalytic layer (bottom layer) :

[0141] The third catalyst layer consists of Pd supported on a carrier coating of a third CeZr mixed oxide, La-stabilized alumina, and Ba promoter. The carrier coating loading of the third catalyst layer is approximately 1.0 g / in. 3 Among them, Pd is 66.5 g / ft 3 .

[0142] Using a standard coating procedure, a third catalyst layer was coated from the inlet and outlet surfaces of the ceramic substrate (750 cpsi, 3.0 mil wall thickness), with a target coating depth of 50% of the substrate length, followed by drying and calcination.

[0143] First catalytic layer (intermediate layer) :

[0144] The first catalyst layer consists of Pd supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and Ba promoter. The carrier coating loading in the first catalyst region is approximately 1.0 g / in. 3 Among them, Pd is 66.5 g / ft 3 .

[0145] Using a standard coating procedure, the first catalyst layer is coated from above onto the inlet and outlet surfaces of the ceramic substrate containing the third catalyst layer (750 cpsi, 3.0 mil wall thickness), with a target coating depth of 50% of the substrate length, followed by drying and calcination.

[0146] Second catalytic layer (top layer) :

[0147] A second catalyst layer is prepared and coated on top of the first catalyst layer in the same manner as the top Rh layer of the comparative catalyst A.

[0148] Catalyst 2 of the present invention (according to Figure 1c ) :

[0149] Third catalytic layer (bottom layer) :

[0150] The third catalyst layer consists of Pd supported on a carrier coating of a third CeZr mixed oxide, La-stabilized alumina, and Ba promoter. The carrier coating loading of the third catalyst layer is approximately 1.0 g / in. 3 Pd is 98 g / ft 3 .

[0151] Using a standard coating procedure, a third catalyst layer was coated from the inlet and outlet surfaces of the ceramic substrate (750 cpsi, 3.0 mil wall thickness), with a target coating depth of 50% of the substrate length, followed by drying and calcination.

[0152] First catalyst layer (intermediate layer) :

[0153] The first catalyst layer consists of Pd supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and Ba promoter. The carrier coating loading in the first catalyst region is approximately 1.0 g / in. 3 Pd is 35 g / ft 3 .

[0154] Using a standard coating procedure, the first catalyst layer is coated from above onto the inlet and outlet surfaces of the ceramic substrate containing the third catalyst layer (750 cpsi, 3.0 mil wall thickness), with a target coating depth of 50% of the substrate length, followed by drying and calcination.

[0155] Second catalytic layer (top layer) :

[0156] A second catalyst layer is prepared and coated on top of the first catalyst layer in the same manner as the top Rh layer of the comparative catalyst A.

[0157] Table 1 below shows a summary of the PGM loading of comparative catalyst A and catalysts 1 and 2 of the present invention.

[0158] Table 1 Summary of all catalysts

[0159]

[0160] Example 1: Cold RDE test in engine bench testing

[0161] Targeting a peak catalyst bed temperature of 1000°C, all catalysts were bench-aged for 50 hours using a stoichiometric / fuel cut-off aging cycle. The catalysts were tested using a 2.0L engine bench dynamometer that performed a custom-designed OEM Real-World Driving (RDE) cycle, encompassing acceleration and fuel cut-off conditions representing speed stages in cold urban, rural, highway, and hot urban environments. The cycle time from ambient immersion conditions was 2700 seconds, reaching a peak catalyst bed temperature of approximately 700°C and a mass airflow rate of 250 kg / h. NO₂ was measured at the catalyst back location. x The emissions of CO, THC, and NH3 were calculated, and the cumulative mass of each substance over the entire cycle was determined. Three measurements were performed for each catalyst formulation, and the average cumulative emissions over the three measurements were plotted against time and shown in the figure below.

[0162] Figure 3a This is a comparison of NO levels during cold RDE cycles between catalyst A, catalyst 1 of the present invention, and catalyst 2 of the present invention. x Emissions. It is quite clear that the two catalysts of this invention, with optimal Pd loading in the first catalyst layer adjacent to the Rh-containing layer, deliver lower NO emissions throughout the entire cold RDE driving cycle. x Emissions. CO, THC, and NH3 emissions are shown in the figures below. Figure 3b , Figure 3c and Figure 3d In the middle, it showed a similar trend.

Claims

1. A catalyst article for treating waste gas, said catalyst article comprising: A substrate, comprising an inlet end and an outlet end, having an axial length L; A first catalytic region, the first catalytic region comprising a first palladium component; A second catalytic region, wherein the second catalytic region comprises a second rhodium component; A third catalytic region, wherein the third catalytic region comprises a third palladium component; The first catalytic region is adjacent to the second catalytic region; and Based on elemental analysis, the weight ratio of the first palladium component to the second rhodium component is 3:1 to 19:

1.

2. The catalyst article according to claim 1, wherein the first catalytic layer comprises from 3 g / ft 3 to 380 g / ft 3 of the first palladium component.

3. The catalyst article of claim 1 or claim 2, wherein the second catalytic layer comprises 1 g / ft 3 to 20 g / ft 3 of the second rhodium component.

4. The catalyst article according to any one of the preceding claims, wherein the first catalytic region further comprises a first oxygen storage capacity (OSC) material, a first alkali metal or alkaline earth metal component and / or a first inorganic oxide.

5. The catalyst article according to any one of the preceding claims, wherein the first OSC material is selected from the group consisting of: cerium oxide, cerium dioxide-zirconia mixed oxide and alumina-cerium dioxide-zirconia mixed oxide.

6. The catalyst article according to claim 5, wherein the first OSC material comprises the cerium dioxide-zirconia mixed oxide.

7. The catalyst product according to claim 4, wherein the first alkali metal or alkaline earth metal is barium, strontium, or a mixed oxide or composite oxide of barium and strontium.

8. The catalyst article according to claim 7, wherein the first alkali metal or alkaline earth metal is loaded in an amount of 0.1% to 15% by weight based on the total weight of the support coating in the first catalytic region.

9. The catalyst article according to any one of claims 4 to 8, wherein the first inorganic oxide is selected from the group consisting of: alumina, cerium dioxide, magnesium oxide, silicon dioxide, lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide, and mixed oxides or composite oxides thereof.

10. The catalyst product according to claim 9, wherein the first inorganic oxide is alumina, lanthanum oxide / alumina composite oxide, or magnesium oxide / alumina composite oxide.

11. The catalyst article according to any one of the preceding claims, wherein the second catalytic region further comprises a second OSC material and / or a second inorganic oxide.

12. The catalyst article according to claim 11, wherein the second OSC material is selected from the group consisting of: cerium oxide, cerium dioxide-zirconia mixed oxide, and alumina-cerium dioxide-zirconia mixed oxide.

13. The catalyst article of claim 12, wherein the second OSC material comprises the cerium dioxide-zirconia mixed oxide.

14. The catalyst article according to any one of claims 11 to 13, wherein the second inorganic oxide is selected from the group consisting of: alumina, cerium dioxide, magnesium oxide, silicon dioxide, lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide, and mixed oxides or composite oxides thereof.

15. The catalyst product according to claim 14, wherein the second inorganic oxide is alumina, lanthanum oxide / alumina composite oxide, or magnesium oxide / alumina composite oxide.

16. The catalyst article according to any one of the preceding claims, wherein the third catalytic region comprises 3 g / ft 3 Up to 380g / ft 3 The third palladium component.

17. The catalyst article according to any one of the preceding claims, wherein the third catalytic region further comprises a third OSC material, a third alkali metal or alkaline earth metal component and / or a third inorganic oxide.

18. The catalyst article according to claim 17, wherein the third OSC material is selected from the group consisting of: cerium oxide, cerium dioxide-zirconia mixed oxide, and alumina-cerium dioxide-zirconia mixed oxide.

19. The catalyst article of claim 18, wherein the third OSC material comprises the cerium dioxide-zirconia mixed oxide.

20. The catalyst article according to any one of claims 17 to 19, wherein the third inorganic oxide is selected from the group consisting of: alumina, cerium dioxide, magnesium oxide, silicon dioxide, lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide, and mixed oxides or composite oxides thereof.

21. The catalyst product according to claim 20, wherein the third inorganic oxide is alumina, lanthanum oxide / alumina composite oxide, or magnesium oxide / alumina composite oxide.

22. The catalyst article according to any one of claims 17 to 21, wherein the third alkali metal or alkaline earth metal is barium, strontium, or a mixed oxide or composite oxide of barium and strontium.

23. The catalyst article according to claim 22, wherein the third alkali metal or alkaline earth metal is loaded in an amount of 0.1% to 15% by weight based on the total weight of the third catalytic region.

24. The catalyst article according to any one of the preceding claims, wherein the substrate is a flow-through monolithic material.

25. The catalyst article according to any one of the preceding claims, wherein the first catalytic region is directly loaded / deposited on the substrate.

26. The catalyst article according to any one of claims 1 to 24, wherein the second catalytic region is directly supported / deposited on the substrate.

27. The catalyst article according to any one of claims 1 to 24, wherein the third catalytic region is directly supported / deposited on the substrate.

28. An emission treatment system for treating combustion exhaust gas, the emission treatment system comprising a catalyst article according to any one of claims 1 to 27.

29. A method for treating exhaust gas from an internal combustion engine, the method comprising: The exhaust gas is brought into contact with the catalyst article according to any one of claims 1 to 27.

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