Novel multi-region twc catalysts for gasoline engine exhaust gas treatments
Patent Information
- Application Number
- JP2025160222
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2020-01-07
- Filing Date
- 2025-09-26
- Publication Date
- 2025-12-23
Smart Images
Figure 2025186496000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to catalytic articles useful for treating exhaust gas emissions from gasoline engines. [Background technology]
[0002] In an internal combustion engine, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x The exhaust gas produced by the engine contains various pollutants, including CO, CO₂, CO₂, and CO₂. Emissions control systems containing exhaust gas catalytic conversion catalysts are widely used to reduce the amount of these pollutants emitted into the atmosphere. The catalyst typically used to treat the exhaust gas of a gasoline engine is the TWC (three-way catalyst). The TWC performs three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) oxidation of NO₂. x The following will be reduced:
[0003] In most catalytic converters, TWCs are coated onto high-surface-area substrates that can withstand high temperatures, such as flow-through honeycomb substrates. The large surface area of these substrates promotes increased efficiency of the heterogeneous reaction, but can also contribute to increased exhaust backpressure, i.e., restricting the flow of exhaust gas from the engine to the transition pipe. Despite advances in TWC technology, there remains a need for improved catalytic converters for specific engine platforms that simultaneously improve cold-start performance and / or provide better light-off performance. The present invention addresses these problems, among others. Summary of the Invention
[0004] One aspect of the present disclosure is a catalyst for treating gasoline engine exhaust gas, comprising: a first catalyst region beginning at an inlet end and extending over an axial length L, the first catalyst region comprising a first palladium component and a first oxygen storage capacity (OSC) material comprising ceria; a second catalyst region beginning at an outlet end and extending over an axial length L, the second catalyst region comprising a second palladium component and a second OSC material comprising ceria; and a third catalyst region beginning at the outlet end and extending over an axial length L, the third catalyst region comprising a third rhodium component and a third OSC material comprising ceria. and a third catalytic region, wherein at least a portion of the first catalytic region is not covered by the second catalytic region and / or the third catalytic region, and (a) the amount of ceria in the first catalytic region is less than 50% of the total amount of ceria in the first catalytic region, the second catalytic region, and the third catalytic region, or (b) the amount of ceria loaded in the first catalytic region is less than 50% of the sum of the amount of ceria loaded in the first catalytic region, the second catalytic region, and the third catalytic region.
[0005] The present invention also includes an exhaust system for an internal combustion engine that includes the three-way catalyst component of the present invention.
[0006] The present invention also encompasses the treatment of exhaust gases from internal combustion engines, particularly gasoline engines, which method comprises contacting the exhaust gases with the three-way catalyst component of the present invention. [Brief explanation of the drawings]
[0007] [Figure 1a] A first configuration is shown in which a first catalyst region extends from the inlet end, a second catalyst region extends from the outlet end and partially covers the first catalyst region, and a third catalyst region extends from the outlet end and partially covers the first catalyst region. [Figure 1b] A variation of FIG. 1a is shown. [Figure 2a]A second configuration is shown in which a second catalyst region extends from the outlet end, a first catalyst region extends from the inlet end, and a third catalyst region extends from the outlet end and covers the first catalyst region. [Figure 2b] A variation of FIG. 2a is shown. [Figure 3a] A third configuration is shown in which the second catalyst region extends from the outlet end, the third catalyst region extends from the outlet end, and the first catalyst region extends from the inlet end and partially covers the third catalyst region. [Figure 3b] A variation of FIG. 3a is shown. [Figure 4a] A fourth configuration is shown in which the second catalyst region extends from the outlet end, the third catalyst region extends from the outlet end and partially covers the second catalyst region, and the first catalyst region extends from the inlet end and partially covers the third catalyst region. [Figure 4b] A variation of FIG. 4a is shown. [Figure 5a] A fifth configuration is shown in which the second catalyst region extends from the outlet end, the third catalyst region extends from the outlet end and covers the second catalyst region, and the first catalyst region extends from the inlet end and partially covers the third catalyst region. [Figure 5b] A variation of FIG. 5a is shown. [Figure 6a] A sixth configuration is shown in which a second catalyst region extends from the outlet end, a third catalyst region extends from the outlet end and partially covers the second catalyst region, and the first catalyst region extends from the inlet end. [Figure 6b] A variation of FIG. 6a is shown. [Figure 7a]
[0023] Figure 7 shows a seventh configuration, in which the second catalyst region extends from the outlet end, the third catalyst region extends from the outlet end and covers the second catalyst region, and the first catalyst region extends from the inlet end. Preferably, the substrate is a flow-through monolith. [Figure 7b] A variation of FIG. 7a is shown. DETAILED DESCRIPTION OF THE INVENTION
[0008] The present invention is directed to the catalytic treatment of combustion exhaust gases, for example, produced by gasoline and other engines, and related catalysts and systems. More specifically, the present invention relates to the treatment of NOx in vehicle exhaust systems. x The present inventors have investigated the simultaneous treatment of NO, CO, and HC. x We have discovered a synergistic relationship between certain catalytically active metals and their coating methods that results in unexpectedly high conversion of CO, CO, and HC, improves performance during the cold start phase, provides better light-off performance, and provides low backpressure. The process of the present invention also reduces catalyst costs.
[0009] One aspect of the present disclosure is a catalyst for treating gasoline engine exhaust gas, comprising: a first catalyst region beginning at an inlet end and extending over an axial length L, the first catalyst region including a first palladium component and a first oxygen storage capacity (OSC) material including ceria; a second catalyst region beginning at an outlet end and extending over an axial length L, the second catalyst region including a second palladium component and a second OSC material including ceria; and a second catalyst region beginning at the outlet end and extending over an axial length L, the second catalyst region including a second palladium component and a second OSC material including ceria. and a third catalyst region, the third catalyst region comprising a third rhodium component and a third OSC material including ceria, wherein at least a portion of the first catalyst region is not covered by the second catalyst region and / or the third catalyst region, and (a) the amount of ceria in the first catalyst region is less than 50% of the total amount of ceria in the first catalyst region, the second catalyst region, and the third catalyst region, or (b) the amount of ceria loading in the first catalyst region is less than 50% of the combined amount of ceria loading in the first catalyst region, the second catalyst region, and the third catalyst region.
[0010] The inventors have found that coating these catalysts in this manner results in better catalytic performance than would be achieved by using the catalysts separately or with conventional coating methods. Unexpected benefits of the present invention include improved light-off performance during the cold start phase of a vehicle compared to conventional TWC catalysts of similar concentration (e.g., washcoat loading), and significantly reduced emissions of exhaust pollutants, thereby facilitating the achievement of emission targets. Achieving these benefits translates into lower precious metal amounts and costs used in the catalyst.
[0011] First catalytic region The first catalyst region may extend over 1 to 50 percent of the axial length L. Preferably, the first catalyst region may extend over 10 to 40 percent of the axial length L, more preferably 25 to 35 percent.
[0012] The first catalyst layer may comprise a PGM metal other than the first palladium component, such as platinum and / or rhodium. The first catalyst region may further comprise a first rhodium component.
[0013] The first catalyst region is 0.1 to 300 g / ft 3 Preferably, the first catalyst region comprises a first palladium or rhodium-palladium component of 50 to 250 g / ft 3 the first palladium or rhodium palladium component, more preferably 100 to 220 g / ft 3 The weight ratio of rhodium to palladium may be 60:1 to 1:60, preferably 30:1 to 1:30, more preferably 10:1 to 1:10.
[0014] The total washcoat loading of the first catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 Less than 2.5g / in 3 , or 1.5g / in 3 It could be.
[0015] The amount of ceria in the first catalyst region can be no more than 40%, 30%, 20%, or even 15% of the total amount of ceria in the first, second, and third catalyst regions. Alternatively, or in addition, the amount of ceria loading in the first catalyst region can be no more than 40%, 30%, or even 25% of the combined amount of ceria loading in the first, second, and third catalyst regions.
[0016] The first OSC material is preferably selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide. More preferably, the first OSC material comprises ceria-zirconia mixed oxide. The ceria-zirconia mixed oxide may further comprise some dopants, such as lanthanum, neodymium, praseodymium, and yttrium oxide. In addition, the first OSC material may function as a support material for the first palladium component.
[0017] The first catalytic region can further comprise a first alkali metal component or a first alkaline earth metal component, and / or a first inorganic oxide.
[0018] The first palladium component can be supported on both the first inorganic oxide and the first OSC material.
[0019] The ceria-zirconia mixed oxide may have a molar ratio of zirconia to ceria of at least 50:50, preferably greater than 60:40, more preferably greater than 75:25.
[0020] The first OSC material (eg, ceria-zirconia mixed oxide) can be 10-90 wt %, preferably 25-75 wt %, more preferably 30-60 wt %, based on the total washcoat loading of the first catalyst region.
[0021] The loading of the first OSC material in the first catalyst region is 1.5 g / in 3 In some embodiments, the loading of the first OSC material in the first catalyst region can be less than 1.2 g / in3 , 1.0g / in 3 , 0.9g / in 3 , 0.8g / in 3 , or 0.7 g / in 3 The following is the result.
[0022] In some embodiments, the first alkali metal or first alkaline earth metal may be deposited on the first OSC material. Alternatively, or in addition, the first alkali metal or first alkaline earth metal may be deposited on the first inorganic oxide. That is, in some embodiments, the first alkali metal or first alkaline earth metal may be deposited on, or present on, both the first OSC material and the first inorganic oxide.
[0023] The first alkali metal or first alkaline earth metal is generally in contact with a first inorganic oxide. Preferably, the first alkali metal or first alkaline earth metal is supported on the first inorganic oxide. Alternatively, the first alkali metal or first alkaline earth metal may be in contact with the first OSC material.
[0024] The first alkali metal or first alkaline earth metal is preferably barium or strontium, and mixed oxides or composite oxides thereof. Preferably, the barium or strontium, if present, is supported in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, of barium or strontium, based on the total weight of the first catalyst region.
[0025] Even more preferably, the first alkali metal or first alkaline earth metal is strontium, and when present, strontium is preferably supported in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the first catalyst region.
[0026] The first alkali metal or first alkaline earth metal is preferably a mixed oxide or composite oxide of barium and strontium. Preferably, the mixed oxide or composite oxide of barium and strontium is present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the first catalyst region. More preferably, the first alkali metal or first alkaline earth metal is a composite oxide of barium and strontium.
[0027] Preferably, the barium or strontium is present as BaCO or SrCO. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.
[0028] The first inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, and 14. Preferably, the first inorganic oxide is selected from the group consisting of alumina, magnesia, silica, ceria, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferably, the first inorganic oxide is alumina, lanthanum-alumina, ceria, or magnesia / alumina composite oxide. One particularly preferred first inorganic oxide is alumina or lanthanum-alumina composite oxide.
[0029] The first OSC material and the first inorganic oxide may have a weight ratio of 10:1 or less, preferably 8:1 or 5:1 or less, more preferably 4:1 or 3:1 or less, and most preferably 2:1 or less.
[0030] Alternatively, the first OSC material and the first inorganic oxide can have a weight ratio of 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.
[0031] Second catalytic region The second catalytic region may be essentially free of PGM metals other than the second palladium component.
[0032] The second catalyst region may extend over 50 to 90 percent of the axial length L. Preferably, the second catalyst region may extend over 55 to 85 percent of the axial length L, and more preferably over 60 to 80 percent.
[0033] The second catalyst zone may comprise a PGM metal other than the second palladium component, such as platinum and / or rhodium. The second catalyst zone may comprise a PGM metal of between 0.1 and 100 g / ft 3 Preferably, the second catalyst region has a second palladium or platinum-palladium component of 5 to 60 g / ft 3 , more preferably 10 to 50 g / ft 3 The weight ratio of platinum to palladium may be 60:1 to 1:60, preferably 30:1 to 1:30, more preferably 10:1 to 1:10.
[0034] The second OSC material is preferably selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide. More preferably, the second OSC material includes ceria-zirconia mixed oxide. In addition, the second OSC material may further include one or more dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material may function as a support material for the second palladium component.
[0035] The second catalytic region may further comprise a second alkali metal component or a second alkaline earth metal component, and / or a second inorganic oxide.
[0036] The second palladium or platinum-palladium component can be supported on both the second inorganic oxide and the second OSC material.
[0037] The ceria-zirconia mixed oxide may have a molar ratio of zirconia to ceria of at least 50:50, preferably greater than 60:40, more preferably greater than 75:25.
[0038] The second OSC material (eg, ceria-zirconia mixed oxide) can be 10-90 wt %, preferably 25-75 wt %, more preferably 30-60 wt %, based on the total washcoat loading of the second catalyst region.
[0039] The loading of the second OSC material in the second catalyst region is 1.5 g / in 3 In some embodiments, the loading of the second OSC material in the second catalyst region can be less than 1.2 g / in 3 , 1.0g / in 3 , 0.9g / in 3 , 0.8g / in 3 , or 0.7 g / in 3 The following is the result.
[0040] The total washcoat loading of the second catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 Less than 2.5g / in 3 , or 1.5g / in 3 It could be.
[0041] In some embodiments, the second alkali metal or second alkaline earth metal may be deposited on the second OSC material. Alternatively, or in addition, the second alkali metal or second alkaline earth metal may be deposited on the second inorganic oxide. That is, in some embodiments, the second alkali metal or second alkaline earth metal may be deposited on, or present on, both the second OSC material and the second inorganic oxide.
[0042] The second alkali metal or second alkaline earth metal is generally in contact with a second inorganic oxide. Preferably, the second alkali metal or second alkaline earth metal is supported on the second inorganic oxide. In addition to or instead of being in contact with the second inorganic oxide, the second alkali metal or second alkaline earth metal may be in contact with a second OSC material.
[0043] The second alkali metal or second alkaline earth metal is preferably barium, strontium, a mixed oxide or composite oxide thereof, and preferably, when present, the barium or strontium is present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the second catalyst region.
[0044] Even more preferably, the second alkali metal or second alkaline earth metal is strontium, which, when present, is preferably present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the second catalyst region.
[0045] The second alkali metal or second alkaline earth metal is preferably a mixed oxide or composite oxide of barium and strontium. Preferably, the mixed oxide or composite oxide of barium and strontium is present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the second catalyst region. More preferably, the second alkali metal or second alkaline earth metal is a composite oxide of barium and strontium.
[0046] Preferably, the barium or strontium is present as BaCO or SrCO. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.
[0047] The second inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, or 14. The second inorganic oxide is preferably selected from the group consisting of alumina, magnesia, silica, ceria, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferred is alumina, lanthanum-alumina, ceria, or magnesia / alumina composite oxide. One particularly preferred second inorganic oxide is alumina or lanthanum-alumina composite oxide.
[0048] The second OSC material and the second inorganic oxide may have a weight ratio of 10:1 or less, preferably 8:1 or 5:1 or less, more preferably 4:1 or 3:1 or less, and most preferably 2:1 or less.
[0049] Alternatively, the second OSC material and the second inorganic oxide can have a weight ratio of 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] The third catalytic region The third catalyst region can extend over 50 to 99 percent of the axial length L. Preferably, the third catalyst region can extend over 50 to 95 percent, more preferably 60 to 95 percent, of the axial length L.
[0051] The third catalytic region may be essentially free of PGM metals other than the third rhodium component.
[0052] The third catalyst zone is 0.1 to 20 g / ft 3 In some embodiments, the third catalytic region may comprise a third rhodium or platinum-rhodium component of between 3 and 15 g / ft 3 or 5 to 13 g / ft 3 The weight ratio of platinum to rhodium may be 20:1 to 1:20, 15:1 to 1:15, or 10:1 to 1:10.
[0053] The total washcoat loading of the second catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 or 2 g / in 3 less than 1.5 g / in 3 or 1.0 g / in 3 It may be less than.
[0054] The third OSC material is preferably selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide. Preferably, the third OSC material comprises a ceria-zirconium mixed oxide and one or more dopants such as lanthanum, neodymium, yttrium, praseodymium, etc. Additionally, the third OSC material may function as a support material for the third rhodium component.
[0055] The third catalytic region may further comprise a third alkali metal or alkaline earth metal component and / or a third inorganic oxide.
[0056] The ceria-zirconia mixed oxide may have a molar ratio of zirconia to ceria of at least 50:50, preferably greater than 60:40, and more preferably greater than 80:20.
[0057] The third OSC material can be 10 to 90 wt %, preferably 25 to 75 wt %, more preferably 35 to 65 wt % (based on the total washcoat loading of the third catalyst region).
[0058] The loading of the third OSC material in the third catalyst region is 2 g / in 3 In some embodiments, the loading of the third OSC material in the third catalyst region can be less than 1.5 g / in 3 Below, 1.2g / in 3 Below, 1.0g / in 3 or less, or 0.5g / in 3 The following is the result.
[0059] In some embodiments, the ceria loading in the second catalytic region is greater than the ceria loading in the third catalytic region, and in further embodiments, the ratio of the ceria loading in the second catalytic region to the ceria loading in the third catalytic region can be at least 3:2 or 2:1.
[0060] The third catalyst region can be substantially free of a third alkali metal or a third alkaline earth metal. Reference to "substantially free" means that the recited material may be intentionally or unintentionally present in the recited layer in small amounts. For example, an alkali metal or alkaline earth metal may be present in the first and / or second catalyst region, and some of the alkali metal or alkaline earth metal may unintentionally migrate / leach into the third catalyst region during the coating process.
[0061] The third inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, or 14. The third inorganic oxide is preferably selected from the group consisting of alumina, ceria, magnesia, silica, lanthanum, zirconium, neodymium, praseodymium oxide, and mixed oxides or composite oxides thereof. Particularly preferred is alumina, lanthanum / alumina composite oxide, or zirconium / alumina composite oxide. One particularly preferred third inorganic oxide is lanthanum / alumina composite oxide or zirconium / alumina composite oxide. The third inorganic oxide may be a support material for the third rhodium component and / or a support material for the third OSC material.
[0062] The preferred third inorganic oxide is preferably virgin and 80 ml 2 / g and a pore volume in the range of 0.1 to 4 mL / g. 2 Particularly preferred are high-surface-area inorganic oxides, such as high-surface-area alumina, having a specific surface area of more than 1 / g. Another preferred third inorganic oxide is a lanthanum / alumina composite oxide, which optionally further contains a zirconium-containing component, such as zirconia. In such cases, zirconium may be present on the surface of the lanthanum / alumina composite oxide, for example, as a coating.
[0063] The third OSC material and the third inorganic oxide may have a weight ratio of at least 1:1, preferably at least 2:1, and more preferably at least 3:1.
[0064] Alternatively, the third OSC material and the third inorganic oxide can have a weight ratio of 10:1 to 1:10, preferably 8:1 to 1:8 or 5:1 to 1:5, and more preferably 4:1 to 1:4 or 3:1 to 1:3.
[0065] In some embodiments, the first palladium component and the second palladium component have a weight ratio of 50:1 to 1:50. In further embodiments, the first palladium component and the second palladium component have a weight ratio of 30:1 to 1:30. In other further embodiments, the first palladium component and the second palladium component have a weight ratio of 10:1 to 1:10. In yet other further embodiments, the first palladium component and the second palladium component have a weight ratio of 7:1 to 1:7.
[0066] The first palladium component and the second palladium component have a weight ratio of 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.
[0067] In some embodiments, the third rhodium component and the first palladium component have a weight ratio of 60:1 to 1:60. Preferably, the third rhodium component and the first palladium component have a weight ratio of 40:1 to 1:40. More preferably, the third rhodium component and the first palladium component have a weight ratio of 30:1 to 1:30. Most preferably, the third rhodium component and the first palladium component have a weight ratio of 10:1 to 1:10.
[0068] In certain embodiments, the total washcoat loading in the first catalyst region may be less than 50% of the sum of the total washcoat loadings in the first, second, and third catalyst regions. In further embodiments, the total washcoat loading in the first catalyst region may be no more than 40% or 30% of the sum of the total washcoat loadings in the first, second, and third catalyst regions. In yet other further embodiments, the total washcoat loading in the first catalyst region may be no more than 25% of the sum of the total washcoat loadings in the first, second, and third catalyst regions.
[0069] The catalyst article of the present invention may contain additional components known to those skilled in the art. For example, the composition of the present invention may further contain at least one binder and / or at least one surfactant. When a binder is present, a dispersible alumina binder is preferred.
[0070] Configuration of the first catalyst region, the second catalyst region, and the third catalyst region The second catalyst region can overlap the first catalyst region over 1 to 15 percent of the axial length L (see, e.g., Figures 1a, 2a, 3b, 4b, and 5b; the first catalyst region can overlie the second catalyst region, or the second catalyst region can overlie the first catalyst region). Alternatively, the total length of the second catalyst region and the first catalyst region can be equal to the axial length L. In yet another alternative, the total length of the second catalyst region and the first catalyst region can be less than the axial length L, e.g., 95%, 90%, 80%, or 70% or less of the axial length L (see, e.g., Figures 6a, 6b, 7a, and 7b).
[0071] In one aspect of the invention, various configurations of catalyst articles including a first catalyst region, a second catalyst region, and a third catalyst region can be prepared as follows.
[0072] FIG. 1a shows a first configuration in which a first catalyst region extends from the inlet end, a second catalyst region extends from the outlet end and partially covers the first catalyst region, and a third catalyst region extends from the outlet end and partially covers the first catalyst region.
[0073] In the first configuration, preferably, the first catalyst region can extend over 5 to 50 percent or 10 to 50 percent of the axial length L, more preferably 20 to 50 percent of the axial length L, and even more preferably 25 to 40 percent of the axial length L.
[0074] The second catalyst region and the third catalyst region can each independently extend over 30 to 95 percent or 40 to 90 percent of the axial length L, more preferably 50 to 85 percent of the axial length L, and even more preferably 65 to 80 percent of the axial length L. In some embodiments, the overlap between the first catalyst region and the second catalyst region can be at least 5%, 10%, or 15% of the axial length L. In particular embodiments, the overlap between the second catalyst region and the third catalyst region can be at least 5%, 10%, or 15% of the axial length L.
[0075] FIG. 1b shows a variation of the first configuration, in which the second catalyst region is above the third catalyst region.
[0076] FIG. 2a shows a second configuration in which a second catalyst region extends from the outlet end, a first catalyst region extends from the inlet end, and a third catalyst region extends from the outlet end and covers the first catalyst region.
[0077] FIG. 2b shows a variation of the second configuration, in which the second catalyst region is above the third catalyst region.
[0078] FIG. 3a shows a third configuration in which the second catalyst region extends from the outlet end, the third catalyst region extends from the outlet end, and the first catalyst region extends from the inlet end and partially covers the third catalyst region.
[0079] FIG. 3b shows a third configuration variation, in which the second catalyst region is above the third catalyst region.
[0080] FIG. 4a shows a fourth configuration in which the second catalyst region extends from the outlet end, the third catalyst region extends from the outlet end and partially covers the second catalyst region, and the first catalyst region extends from the inlet end and partially covers the third catalyst region.
[0081] FIG. 4b shows a fourth configuration variation in which the second catalyst region is above the third catalyst region.
[0082] FIG. 5a shows a fifth configuration in which the second catalyst region extends from the outlet end, the third catalyst region extends from the outlet end and covers the second catalyst region, and the first catalyst region extends from the inlet end and partially covers the third catalyst region.
[0083] FIG. 5b shows a fifth configuration variation, in which the second catalyst region is above the third catalyst region.
[0084] FIG. 6a shows a sixth configuration in which a second catalyst region extends from the outlet end, a third catalyst region extends from the outlet end and partially covers the second catalyst region, and the first catalyst region extends from the inlet end.
[0085] FIG. 6b shows a sixth configuration variation, in which the second catalyst region is above the third catalyst region.
[0086] 7a shows a seventh configuration in which the second catalyst region extends from the outlet end, the third catalyst region extends from the outlet end and covers the second catalyst region, and the first catalyst region extends from the inlet end. Preferably, the substrate is a flow-through monolith.
[0087] FIG. 7b shows a seventh configuration variation in which the second catalyst region is above the third catalyst region.
[0088] The flow-through monolith substrate has a first surface and a second surface defining a longitudinal direction therebetween. The flow-through monolith substrate has a plurality of channels extending between the first surface and the second surface. The plurality of channels extend longitudinally and provide a plurality of interior surfaces (e.g., wall surfaces defining each channel). Each of the plurality of channels has an opening in the first surface and an opening in the second surface. For the avoidance of doubt, a flow-through monolith substrate is not a wall-flow filter.
[0089] The first surface is typically at the inlet end of the substrate and the second surface is at the outlet end of the substrate.
[0090] The channels may be of constant width, and each of the plurality of channels may have a uniform channel width.
[0091] Preferably, in a plane perpendicular to the longitudinal direction, the monolith substrate has 300 to 900 channels per square inch, preferably 400 to 800 channels per square inch. For example, on the first face, the density of open first channels and closed second channels is 600 to 700 channels per square inch. The channels may have cross sections that are rectangular, square, circular, oval, triangular, hexagonal, or other polygonal shapes.
[0092] The monolith substrate acts as a support to hold the catalytic material. Suitable materials for forming the monolith substrate include ceramic-like materials such as cordierite, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica magnesia, or zirconium silicate, or porous refractory metals. Such materials and their use in the manufacture of porous monolith substrates are well known in the art.
[0093] It should be noted that the flow-through monolith substrates described herein are unitary components (i.e., a single brick). Nevertheless, when forming an effluent treatment system, the substrates used may be formed by bonding together multiple channels, or may be formed by bonding together multiple smaller substrates as described herein. Such techniques, along with suitable casings and configurations of effluent treatment systems, are known in the art.
[0094] In embodiments in which 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, silica, ceria, zirconia, magnesia, zeolites, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicates and metalloaluminosilicates (such as cordierite and spodumene), or mixtures or mixed oxides of any two or more thereof. Cordierite, magnesium aluminosilicate, and silicon carbide are particularly preferred.
[0095] In embodiments in which the catalytic article of the present invention comprises a metal substrate, the metal substrate may be made of any suitable metal, particularly 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.
[0096] In some embodiments, the first catalyst region can be supported / deposited directly on the substrate (see, e.g., Figures 1a-7b). In certain embodiments, the second catalyst region can be supported / deposited directly on the substrate (see, e.g., Figures 1a, 2a, 3a, 4a, 5a, 6a, and 7a). In other embodiments, the third catalyst region is supported / deposited directly on the substrate (see, e.g., Figures 1b, 2b, 3b, 4b, 5b, 6b, and 7b).
[0097] In certain embodiments, at least 50% of the first catalyst region is not covered by the second and / or third catalyst region. In preferred embodiments, at least 60%, 70%, or 80% of the first catalyst region is not covered by the second and / or third catalyst region. In more preferred embodiments, at least 90% or 95% of the first catalyst region is not covered by the second and / or third catalyst region. In the most preferred embodiment, 100% of the first catalyst region is not covered by the second and / or third catalyst region.
[0098] Another aspect of the present disclosure is a method for producing NOx using the catalytic articles described herein. x The present invention relates to a method for treating vehicle exhaust gases containing THC, CO, and HC. Catalytic converters equipped with TWCs made according to this method are improved compared to conventional TWCs (with the same PGM loading), showing improved performance, especially during cold start phases, and better THC and NO emissions. x Light-off performance is also shown.
[0099] Another aspect of the present disclosure relates to a system for treating vehicle exhaust gases that includes a catalytic article as described herein along with a conduit for transporting exhaust gases through the system.
[0100] definition As used herein, the term "region" refers to a location on a substrate that is typically obtained by drying and / or firing a washcoat. A "region" may be disposed or carried on the substrate as, for example, a "layer" or a "zone." The location or placement on the substrate is generally controlled during the process of applying the washcoat to the substrate. A "region" typically has a distinct boundary or edge (i.e., it is possible to distinguish one region from another using conventional analytical techniques).
[0101] Typically, a "region" has a substantially uniform length. Reference to a "substantially uniform length" in this context refers to a length that does not deviate more than 10% from its average value (e.g., the difference between the maximum and minimum length), preferably a length that does not deviate more than 5% from its average value, and more preferably a length that does not deviate more than 1% from its average value.
[0102] Preferably, each "region" has a substantially uniform composition (i.e., there is no substantial difference in the composition of the washcoat when comparing one portion of the region to another portion of the region). Substantially uniform composition in this context refers to a material (e.g., region) that has a composition difference of 5% or less, usually 2.5% or less, and most usually 1% or less when comparing one portion of the region to another portion of the region.
[0103] As used herein, the term "zone" refers to a region having a length less than the entire length of the substrate, such as a length of 75% or less of the entire length of the substrate. A "zone" typically has a length of at least 5% (e.g., 5% or more) of the entire length of the substrate (i.e., a substantially uniform length).
[0104] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).
[0105] As used herein, any reference to a "zone disposed at the inlet end of the substrate" refers to a zone disposed on or carried by a substrate that is closer to the inlet end of the substrate than to the outlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the inlet end of the substrate than to the outlet end of the substrate. Similarly, as used herein, any reference to a "zone disposed at the outlet end of the substrate" refers to a zone disposed on or carried by a substrate that is closer to the outlet end of the substrate than to the inlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the outlet end of the substrate than to the inlet end of the substrate.
[0106] In general, when the substrate is a wall-flow filter, any reference to "a zone disposed at the inlet end of the substrate" refers to a zone disposed on or carried by the substrate, (a) a zone that is closer to the inlet end (e.g., open end) of an inlet channel of the substrate than to the closed end (e.g., blocked or plugged end) of the inlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an outlet channel of a substrate than to the outlet end (e.g., open end) of the outlet channel.
[0107] Thus, the midpoint of the zone (i.e., the point at half its length) is (a) closer to the inlet end of the inlet channel of the substrate than to the closed end of the inlet channel, and / or (b) closer to the closed end of the outlet channel of the substrate than to the outlet end of the outlet channel.
[0108] Similarly, if the substrate is a wall-flow filter, any reference to "a zone disposed at the outlet end of the substrate" refers to a zone disposed on or carried by the substrate, (a) a zone that is closer to the outlet end (e.g., open end) of the outlet channel of the substrate than to the closed end (e.g., blocked or plugged end) of the outlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an inlet channel of a substrate than to the inlet end (e.g., open end) of the inlet channel.
[0109] Thus, the midpoint of the zone (i.e., the point at half its length) is (a) closer to the outlet end of the outlet channel of the substrate than to the closed end of the outlet channel, and / or (b) closer to the closed end of the inlet channel of the substrate than to the inlet end of the inlet channel.
[0110] If the washcoat is present on the wall of a wall-flow filter (ie, the zone is intra-wall), the zone may satisfy both (a) and (b).
[0111] The term "washcoat" is known in the art and typically refers to an adherent coating applied to a substrate during the preparation of a catalyst.
[0112] As used herein, the acronym "PGM" refers to "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, preferably metals selected from the group consisting of Ru, Rh, Pd, Ir, and Pt. Generally, the term "PGM" preferably refers to metals selected from the group consisting of Rh, Pt, and Pd.
[0113] The term "mixed oxide" as used herein generally refers to a mixture of oxides in a single phase, as conventionally known in the art. The term "complex oxide" as used herein generally refers to a composition of oxides having two or more phases, as conventionally known in the art.
[0114] As used herein, the phrase "consisting essentially of" limits the scope of a feature to include the specified materials or steps and any other materials or steps, including, for example, trace impurities, and that do not substantially affect the basic properties of the feature. The phrase "consisting essentially of" encompasses the phrase "consisting of."
[0115] The term "substantially free" as used herein with respect to a material typically means that the material is present in small amounts, e.g., 5% by weight or less, preferably 2% by weight or less, more preferably 1% by weight or less, relative to the contents of a region, layer, or zone. The term "substantially free" encompasses the term "free."
[0116] The term "essentially free" as used herein with respect to a material typically means that the material is present in trace amounts, e.g., 1% by weight or less, preferably 0.5% by weight or less, more preferably 0.1% by weight or less, in relation to the contents of a region, layer, or zone. The term "essentially free" encompasses the term "free."
[0117] As used herein, any reference to an amount, particularly a total amount, of dopant expressed as a weight percent refers to the weight of the support material or refractory metal oxide thereof.
[0118] As used herein, the term "loading" refers to g / ft on a metal weight basis. 3 Refers to a measurement in units of .
[0119] The following examples are merely illustrative of the present invention, and those skilled in the art will recognize many variations that are within the spirit and scope of the claims. [Example]
[0120] material All materials were commercially available and obtained from known sources unless otherwise stated.
[0121] Comparison catalyst A: Comparative Catalyst A is a commercially available ternary (Pd-Rh) catalyst with a dual-layer zone structure. The bottom layer consists of Pd supported on a first CeZr mixed oxide, La-stabilized alumina, and a Ba-promoter washcoat. The washcoat loading of the bottom layer is approximately 1.9 g / in. 3 The Pd loading was 81 g / ft 3 and 34g / ft 3 The washcoat was applied to the inlet and outlet faces of a ceramic substrate (600 cpsi, 2.5 mil wall thickness) using standard coating procedures with a target coating depth of 50% of the substrate length, dried at 90°C, and fired at 500°C for 45 minutes.
[0122] The top layer consisted of a second CeZr mixed oxide, La-stabilized alumina, and Rh supported on a Ba-promoter washcoat. The washcoat loading of the top layer was approximately 1.6 g / in. 3 The Rh loading was 4.5 g / ft 3 This washcoat was applied to the inlet and outlet faces of a ceramic substrate (600 cpsi, 2.5 mil wall thickness) using standard coating procedures with a target coating depth of 50% of the substrate length, dried at 90°C, and fired at 500°C for 45 minutes.
[0123] The total washcoat loading of Comparative Catalyst A was approximately 3.5 g / in 3 The amount of ceria in the bottom layer was about 23.5 g, and the amount of ceria supported was 0.36 g / in 3 The amount of ceria in the upper layer was about 15.5 g, and the amount of ceria supported was 0.24 g / in 3 It was.
[0124] Catalyst B: First catalytic region: The first catalytic region consisted of a first CeZr mixed oxide, Pd, La-stabilized alumina, and Rh supported on a Ba-promoter washcoat. The washcoat loading of the first catalytic region was about 1.5 g / in. 3 The Pd loading was 133 g / ft 3 The Rh loading was 3.6 g / ft 3 It was.
[0125] The washcoat was applied to the inlet face of the ceramic substrate containing the first catalyst region using standard coating procedures with a target coating depth of 35% of the substrate length and dried at 90°C.
[0126] Second catalytic region: The second catalytic region consisted of Pd supported on a first CeZr mixed oxide, La-stabilized alumina, and a Ba-promoter washcoat. The washcoat loading for the second catalytic region was approximately 1.8 g / in. 3The Pd loading was 18 g / ft 3 It was.
[0127] The washcoat was applied to a ceramic substrate (600 cpsi, 2.5 mil wall thickness) from the exit face using standard coating procedures with a target coating depth of 65% of the substrate length, dried at 90°C, and fired at 500°C for 45 minutes.
[0128] Third catalytic region: The third catalytic region consisted of a third CeZr mixed oxide and Rh supported on a washcoat of La-stabilized alumina. The washcoat loading of the third catalytic region was about 1.7 g / in. 3 The Rh loading was 4.5 g / ft 3 It was.
[0129] A third washcoat was then coated from the outlet face of the ceramic substrate containing the first and second catalyst regions using standard coating procedures, with a target coating depth of 90% of the substrate's length, dried at 90°C, and calcined at 500°C for 45 minutes.
[0130] The coating order was second region, first region, and third region (see, for example, Figure 2a).
[0131] Catalyst C: Catalyst C was prepared following the same procedure as Catalyst B, except that the coating order was changed to the second region, the third region, and then the first region (see, for example, Figure 3a).
[0132] Catalyst D: Catalyst D was prepared following the same procedure as Catalyst C, except that the lengths of the first and second catalyst regions were changed from 35% and 65% to 30% and 70%, respectively.
[0133] Catalyst E: Pd / Rh loading in the first catalyst zone was 133 / 4.1 g / ft 3Catalyst E was prepared following the same procedure as catalyst C, except that
[0134] Catalyst F: Pd / Rh loading in the first catalyst zone was 133 / 8.5 g / ft 3 Catalyst F was prepared following the same procedure as catalyst C, except that
[0135] Table A below summarizes the ceria amount and ceria loading in each catalyst zone of Catalysts B to F.
[0136] [Table 1]
[0137] Example 1: Backpressure reduction The back pressure (BP) performance of Comparative Catalyst A and Catalysts B to D was tested across a gas flow system. As shown, Catalysts B to D of the present invention in Table 1 exhibit significantly lower BP compared to Comparative Catalyst A.
[0138] [Table 2]
[0139] Example 2: Vehicle Test Procedures and Results The fresh performance of Comparative Catalyst A and Catalysts B-D was tested on a 1.0 liter engine vehicle with WLTC (Worldwide harmonized Light vehicles Test Cycle). The tailpipe bag data is shown in Table 2. Catalysts B, C, and D of the present invention reduced THC and NO compared to Comparative Catalyst A. x (See, for example, the related improved performance below.) When Catalyst D is compared to Comparative Catalyst A, the emissions of THC and NO are significantly lower. x emissions are improved by approximately 22% and 52%, respectively).
[0140] [Table 3]
[0141] Example 3: Vehicle Test Procedures and Results Bench-aged samples of Comparative Catalyst A and Catalysts B-D were separately tested in a 1.0-liter engine vehicle with a WLTC. Comparative Catalyst A and Catalysts B-D were bench-aged under the same 4.3-liter engine with a peak catalyst bed temperature of 980°C and a four-mode aging cycle for 50 hours.
[0142] The bag data from the transition piece is shown in Table 3. Inventive catalysts B, C, and D reduced THC, CO, and NO compared to comparative catalyst A. x shows significantly lower emissions.
[0143] [Table 4]
[0144] Example 4: Vehicle Test Procedures and Results Bench-aged samples of Comparative Catalyst A, Catalyst C, E, and Catalyst F were tested across a 1.0-liter engine vehicle with a WLTC. Bench aging was performed in the same 4.3-liter engine with a 50-hour run, four-mode aging cycle, with a catalyst peak bed temperature of approximately 980°C. Vehicle exhaust dilution bag data results are shown in Table 4. Inventive Catalysts C, E, and F reduced THC, CO, and NO compared to Comparative Catalyst A. x (See, for example, the related improved performance below.) When Catalyst F is compared to Comparative Catalyst A, it exhibits lower emissions of THC, CO, and NO. x emissions are improved by approximately 45%, 47%, and 50%, respectively).
[0145] [Table 5]
Claims
1. 1. A catalytic article for treating exhaust gases, comprising: a substrate having an axial length L and including an inlet end and an outlet end; a first catalyst region beginning at the inlet end and extending over less than the axial length L, the first catalyst region including a first palladium component and a first oxygen storage capacity (OSC) material including ceria; a second catalyst region beginning at the outlet end and extending over less than the axial length L, the second catalyst region comprising a second palladium component and a second OSC material comprising ceria; a third catalyst region beginning at the outlet end and extending over less than the axial length L, the third catalyst region comprising a third rhodium component and a third OSC material comprising ceria; At least a portion of the first catalyst region is not covered by the second catalyst region and / or the third catalyst region; (a) the amount of ceria in the first catalyst region is less than 50% of the total amount of ceria in the first catalyst region, the second catalyst region, and the third catalyst region; or (b) the amount of ceria loaded in the first catalyst region is less than 50% of the sum of the amount of ceria loaded in the first catalyst region, the second catalyst region, and the third catalyst region.
2. The catalyst article of claim 1 , wherein the first catalyst region extends over 1 to 50 percent of the axial length L.
3. 3. The catalytic article of claim 1, wherein the second catalytic region extends over 50 to 90 percent of the axial length L.
4. The catalyst article of any one of claims 1 to 3, wherein the second catalyst region overlaps the first catalyst region over 1 to 15 percent of the axial length L.
5. The catalyst article according to any one of claims 1 to 3, wherein the total length of the second catalyst region and the first catalyst region is equal to the axial length L.
6. The catalyst article according to any one of claims 1 to 3, wherein the total length of the second catalyst region and the first catalyst region is less than the axial length L.
7. The catalyst article of any one of claims 1 to 6, wherein the third catalyst region extends over 50 to 95 percent of the axial length L.
8. The catalytic article of any one of claims 1 to 7, wherein the first catalytic region further comprises a first rhodium component.
9. The first catalyst region has a viscosity of 0.1 to 300 g / ft ３ 9. The catalytic article of claim 1, comprising said first palladium component of
10. 10. The catalyst article of claim 1, wherein the amount of ceria in the first catalyst region is 40% or less of the total amount of ceria in the first catalyst region, the second catalyst region, and the third catalyst region.
11. 11. The catalyst article according to claim 1, wherein the amount of ceria loaded in the first catalyst region is 40% or less of the total amount of ceria loaded in the first catalyst region, the second catalyst region, and the third catalyst region.
12. 12. The catalytic article of any one of claims 1 to 11, wherein the first OSC material is selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.
13. The catalytic article of claim 12, wherein said first OSC material comprises said ceria-zirconia mixed oxide.
14. The catalytic article of any one of claims 1 to 13, wherein the first catalytic region further comprises a first alkali metal component or a first alkaline earth metal component, and / or a first inorganic oxide.
15. 15. The catalytic article of claim 14, wherein the first alkali metal or the first alkaline earth metal is barium, strontium, or a mixed oxide or composite oxide of barium and strontium.
16. 16. The catalyst article of claim 15, wherein the first alkali metal or the first alkaline earth metal is supported in an amount of 0.1 to 15 wt %, based on the total washcoat weight of the first catalyst region.
17. 17. The catalytic article according to any one of claims 14 to 16, wherein the first inorganic oxide is selected from the group consisting of alumina, ceria, magnesia, silica, lanthanum, neodymium, praseodymium, yttrium oxides, and mixed or composite oxides thereof.
18. 18. The catalytic article of claim 17, wherein the first inorganic oxide is alumina, a lanthana / alumina composite oxide, or a magnesia / alumina composite oxide.
19. The catalytic article of any one of claims 1 to 18, wherein the second catalytic region is essentially free of PGM metals other than the second palladium component.
20. The second catalyst region has a carbon content of 0.1 to 50 g / ft ３ The catalytic article of any one of claims 1 to 19, comprising said second palladium component of
21. 21. The catalytic article of any one of claims 1 to 20, wherein the second OSC material is selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.
22. The catalytic article of claim 21, wherein said second OSC material comprises said ceria-zirconia mixed oxide.
23. 23. The catalytic article of any one of claims 1 to 22, wherein the second catalytic region further comprises a second alkali metal component or a second alkaline earth metal component, and / or a second inorganic oxide.
24. 24. The catalytic article of claim 23, wherein the second alkali metal or the second alkaline earth metal is barium, strontium, or a mixed oxide or composite oxide of barium and strontium.
25. 25. The catalyst article of claim 24, wherein the second alkali metal or second alkaline earth metal is supported in an amount of 0.1 to 15 wt %, based on the total weight of the second catalyst region.
26. 26. The catalytic article of any one of claims 23 to 25, wherein the second inorganic oxide is selected from the group consisting of oxides of alumina, ceria, magnesia, silica, lanthanum, neodymium, praseodymium, yttrium, and mixed or composite oxides thereof.
27. 27. The catalytic article of claim 26, wherein the second inorganic oxide is alumina, a lanthana / alumina composite oxide, or a magnesia / alumina composite oxide.
28. the third catalyst region has a viscosity of 0.1 to 20 g / ft ３ The catalytic article of any one of claims 1 to 27, comprising said third rhodium component of
29. 29. The catalytic article of any one of claims 1 to 28, wherein the third OSC material is selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.
30. 30. The catalytic article of claim 29, wherein said third OSC material comprises said ceria-zirconia mixed oxide.
31. 31. The catalytic article of any one of claims 1 to 30, wherein the third catalytic region further comprises a third alkali metal component or a third alkaline earth metal component, and / or a third inorganic oxide.
32. 32. The catalytic article of claim 31, wherein the third inorganic oxide is selected from the group consisting of oxides of alumina, ceria, magnesia, silica, lanthanum, neodymium, praseodymium, yttrium, and mixed or composite oxides thereof.
33. 32. The catalytic article of claim 31, wherein the third inorganic oxide is alumina, a lanthana / alumina composite oxide, or a magnesia / alumina composite oxide.
34. 34. The catalytic article of any one of claims 31 to 33, wherein the third catalytic region is substantially free of the third alkali metal or the third alkaline earth metal.
35. The catalytic article of any one of claims 1 to 34, wherein the substrate is a flow-through monolith.
36. The catalytic article of any one of claims 1 to 35, wherein the first catalytic region is supported / deposited directly on the substrate.
37. The catalytic article of any one of claims 1 to 36, wherein the second catalytic region is supported / deposited directly on the substrate.
38. The catalytic article of any one of claims 1 to 36, wherein the third catalytic region is supported / deposited directly on the substrate.
39. 39. The catalytic article of any one of claims 1 to 38, wherein 100% of the first catalytic region is not covered by the second catalytic region and / or the third catalytic region.
40. 40. The catalyst article of any one of claims 1 to 39, wherein the Pd loading in the first catalyst region is greater than the Pd loading in the second catalyst region.
41. 41. The catalyst article of any one of claims 1 to 40, wherein the ratio of the Pd loading in the first catalyst region to the Pd loading in the second catalyst region is at least 3:
2.
42. 42. The catalyst article of any one of claims 1 to 41, wherein a total washcoat loading in the first catalyst region is less than 50% of a sum of total washcoat loadings in the first catalyst region, the second catalyst region, and the third catalyst region.
43. The catalytic article of any one of claims 1 to 42, wherein the third catalytic region overlies the second catalytic region.
44. 44. The catalytic article of claim 43, wherein the ceria loading in the second catalytic region is greater than the ceria loading in the third catalytic region.
45. An emissions treatment system for treating a combustion exhaust gas stream comprising the catalytic article of any one of claims 1 to 44.
46. A method for treating exhaust gases from an internal combustion engine, comprising contacting the exhaust gases with a catalytic article according to any one of claims 1 to 44.