A novel multi-zone TWC for the treatment of exhaust gases from gasoline engines

Abstract

To provide: an improved catalyst article for certain engine platforms that simultaneously improve the performance in a cold start stage and / or give better light-off performance; and an emission treatment system for treating a flow of a combustion exhaust gas comprising the catalyst article.SOLUTION: A catalyst article for treating exhaust gas comprises: a substrate comprising an inlet end and an outlet end and having an axial length L; a first catalytic region beginning at the inlet end and extending for less than the axial length L, where the first catalytic region comprises a first palladium component; a second catalytic region beginning at the outlet end and extending for less than the axial length L, where the second catalytic region comprises a second palladium component; a third catalytic region beginning at the outlet end and extending for less than the axial length L, where the third catalytic region comprises a third rhodium component; and where the third catalytic region overlies the second catalytic region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to catalytic articles useful for treating exhaust gas emissions from gasoline engines. [Background technology]

[0002] In internal combustion engines, hydrocarbons (HCs), carbon monoxide (CO), and nitrogen oxides (NO x The exhaust gas produced by the engine contains various pollutants, including CO, HC, and NO. 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 NO. x The following will be reduced:

[0003] In most catalytic converters, TWCs are coated on high-surface-area substrates that can withstand high temperatures, such as flow-through honeycomb substrates. The large surface area of ​​these substrates promotes efficient heterogeneous reactions, 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, such as those described in U.S. Pat. Nos. 6,022,825, 9,352,279, 9,040,003, and U.S. Patent Application Publication No. 2016 / 0228818, there remains a need for improved catalytic converters for certain engine platforms that simultaneously improve performance during cold start phases 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 directed to a catalyst for treating exhaust gases from a gasoline engine, the catalyst comprising: a substrate including an inlet end, an outlet end, and having an axial length L; a first catalyst region beginning at the inlet end and extending over an axial length L that is less than the axial length L, the first catalyst region including a first palladium component; a second catalyst region beginning at the outlet end and extending over an axial length L that is less than the axial length L, the second catalyst region including a second palladium component; and a third catalyst region beginning at the outlet end and extending over an axial length L that is less than the axial length L, the third catalyst region including a third rhodium component; wherein the third catalyst region coats the second catalyst 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 1] 1 shows an embodiment according to the present invention in which the total length of the second catalyst region and the first catalyst region is equal to the axial length L of the substrate. [Figure 2a] 1 shows two embodiments according to the present invention in which the second catalytic region overlaps with the first catalytic region. [Figure 2b] 1 shows two embodiments according to the present invention in which the second catalytic region overlaps with the first catalytic region. [Figure 3] 1 illustrates an embodiment according to the present invention, in which the total length of the second catalyst region and the first catalyst region is less than the axial length L of the substrate. [Figure 4a] 1 shows cumulative dilute bag emissions of THC, CO, and NOx in vehicle tests for Catalyst A, Comparative Catalyst B, and Comparative Catalyst C, respectively. [Figure 4b]1 shows cumulative dilute bag emissions of THC, CO, and NOx in vehicle tests for Catalyst A, Comparative Catalyst B, and Comparative Catalyst C, respectively. [Figure 4c] 1 shows cumulative dilute bag emissions of THC, CO, and NOx in vehicle tests for Catalyst A, Comparative Catalyst B, and Comparative Catalyst C, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention is directed to the catalytic treatment of combustion exhaust gases produced, for example, 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 conversions of CO, HC, and CO, improves performance during the cold start phase, and provides better light-off performance. The process of the present invention also reduces catalyst costs.

[0009] One aspect of the present disclosure is directed to a catalytic article for treating exhaust gases, the catalytic article comprising: a substrate including an inlet end, an outlet end and having an axial length L; a first catalytic region beginning at the inlet end and extending over an axial length L less than the axial length L, the first catalytic region comprising a first palladium component; a second catalytic region beginning at the outlet end and extending over an axial length L less than the axial length L, the second catalytic region comprising a second palladium component; and a third catalytic region beginning at the outlet end and extending over an axial length less than the axial length L, the third catalytic region comprising a third rhodium component; wherein the third catalytic region coats the second catalytic 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 lower costs used in the catalyst.

[0011] The first catalyst region may extend over 30 to 70% of the axial length L. Preferably, the first catalyst region may extend over 40 to 60% of the axial length L, more preferably 45 to 55%.

[0012] The second catalyst region may extend over 30 to 70% of the axial length L. Preferably, the second catalyst region may extend over 40 to 60% of the axial length L, more preferably 45 to 55%.

[0013] The second catalyst region may overlap the first catalyst region over 0.1 to 15% of the axial length L (see, e.g., Figures 2a and 2b; the first catalyst region may cover the second catalyst region, or the second catalyst region may cover the first catalyst region). Alternatively, the total length of the second catalyst region and the first catalyst region may be equal to the axial length L (see, e.g., Figure 1). In yet another alternative, the total length of the second catalyst region and the first catalyst region may be less than the axial length L, e.g., 95%, 90%, 80%, or 70% or less of the axial length L (see, e.g., Figure 3).

[0014] The third catalyst region may extend over 50 to 99% of the axial length L. Preferably, the third catalyst region may extend over 50 to 95% of the axial length L, more preferably over 60 to 95%.

[0015] The first catalytic region may be essentially free of PGM metals other than the first palladium component.

[0016] The first catalyst layer may comprise PGM metals other than the first palladium component, such as platinum and / or rhodium. The first catalyst region may have a concentration of 0.1 to 300 g / ft 3 Preferably, the first catalyst region has a first palladium or platinum-palladium component of 50 to 250 g / ft 3 the first palladium or platinum-palladium component, more preferably 100 to 220 g / ft 3 The weight ratio of platinum to palladium may be 60:1 to 1:60, preferably 30:1 to 1:30, and more preferably 10:1 to 1:10.

[0017] 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.

[0018] The first catalytic region can further include a first oxygen storage capacity (OSC) material, a first alkali metal or alkaline earth metal component, and / or a first inorganic oxide.

[0019] The first OSC material is preferably selected from the group consisting of cerium oxide, zirconium 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 oxides of lanthanum, neodymium, praseodymium, and yttrium. Additionally, the first OSC material may function as a support material for the first palladium component.

[0020] The first palladium component can be supported on both the first inorganic oxide and the first OSC material.

[0021] 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.

[0022] 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.

[0023] 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 / 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.

[0024] In some embodiments, the first alkali metal or alkaline earth metal may be deposited on the first OSC material. Alternatively, or in addition, 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, or present on, both the first OSC material and the first inorganic oxide.

[0025] The first alkali or alkaline earth metal is generally in contact with a first inorganic oxide. Preferably, the first alkali or alkaline earth metal is supported on the first inorganic oxide. Alternatively, the first alkali or alkaline earth metal may be in contact with the first OSC material.

[0026] The first alkali metal or 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 %, barium or strontium, based on the total weight of the first catalyst region.

[0027] Even more preferably, the first alkali metal or 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.

[0028] The first alkali metal or 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 alkaline earth metal is a composite oxide of barium and strontium.

[0029] 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.

[0030] The first inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, or 14. The first 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 first inorganic oxide is alumina or lanthanum-alumina composite oxide.

[0031] 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.

[0032] Alternatively, the first OSC material and the first inorganic oxide may 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.

[0033] The second catalytic region may be essentially free of PGM metals other than the second palladium component.

[0034] The second catalyst layer may comprise a PGM metal other than the second palladium component, such as platinum and / or rhodium. The second catalyst region may have a concentration of 0.1 to 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.

[0035] The second catalytic region can further include a second oxygen storage capacity (OSC) material, a second alkali metal or alkaline earth metal component, and / or a second inorganic oxide.

[0036] The second OSC material is preferably selected from the group consisting of cerium oxide, zirconium 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, and yttrium. Furthermore, the second OSC material may function as a support material for the second palladium component.

[0037] The second palladium or platinum-palladium component can be supported on both the second inorganic oxide and the second OSC material.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] In some embodiments, the second alkali metal or alkaline earth metal may be deposited on the second OSC material. Alternatively, or in addition, the second alkali metal or alkaline earth metal may be deposited on the second inorganic oxide. That is, in some embodiments, the second alkali metal or alkaline earth metal may be deposited on, or present on, both the second OSC material and the second inorganic oxide.

[0043] The second alkali metal or alkaline earth metal is generally in contact with a second inorganic oxide. Preferably, the second alkali metal or 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 alkaline earth metal may be in contact with a second OSC material.

[0044] The second alkali metal or alkaline earth metal is preferably barium, strontium, or a mixed oxide or composite oxide thereof. Preferably, the barium or strontium, if present, is in an amount of 0.1 to 15 wt. % barium or strontium, more preferably 3 to 10 wt. % barium or strontium, based on the total weight of the second catalyst region.

[0045] Even more preferably, the second alkali metal or 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.

[0046] The second alkali metal or 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 alkaline earth metal is a composite oxide of barium and strontium.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Alternatively, the second OSC material and the second inorganic oxide may 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.

[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 Preferably, the third catalyst region comprises 3 to 15 g / ft of a third rhodium or platinum-rhodium component. 3 , more preferably 5 to 13 g / ft 3 The weight ratio of platinum to rhodium may be 20:1 to 1:20, preferably 15:1 to 1:15, more preferably 10:1 to 1:10.

[0053] The total washcoat loading in the second catalyst zone was 3.5 g / in 3 Preferably less than 3.0 g / in 3 or 2 g / in 3 less than 1.5 g / in 3 or 1.0 g / in3 It may be less than.

[0054] The third catalytic region can further include a third oxygen storage capacity (OSC) material, a third alkali metal or alkaline earth metal component, and / or a third inorganic oxide.

[0055] The third OSC material is preferably selected from the group consisting of cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide. Preferably, the third OSC material comprises 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.

[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, more preferably greater than 80:20.

[0057] The third OSC material can be 10 to 90 wt %, preferably 25 to 75 wt %, and 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] Preferably, the third catalyst region is substantially free of a third alkali metal or alkaline earth metal, more preferably essentially free of a third alkali metal or alkaline earth metal.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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 5:1 to 1:5.

[0065] It is preferred that the first palladium component and the second palladium component have a weight ratio of greater than 1:1, more preferably at least 3:1 or 4:1, and even more preferably at least 5:1.

[0066] 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.

[0067] 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 comprise at least one binder and / or at least one surfactant. When a binder is present, a dispersible alumina binder is preferred.

[0068] Preferably, the substrate is a flow-through monolith.

[0069] The substrate may be greater than 90 mm in length.

[0070] 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.

[0071] The first surface is typically at the inlet end of the substrate and the second surface is at the outlet end of the substrate.

[0072] The channels may be of constant width, and each of the plurality of channels may have a uniform channel width.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] In some embodiments, the first catalytic region may be supported / deposited directly on the substrate. In certain embodiments, the second catalytic region may be supported / deposited directly on the substrate.

[0079] Another aspect of the present disclosure is a method for producing NOx using the catalytic articles described herein. xCatalytic converters with TWCs made according to this method are improved compared to conventional TWCs (with the same PGM loading), and also exhibit improved performance, particularly during cold start phases, and better THC light-off performance (see, e.g., Examples 1 and 2 and Tables 1 and 2).

[0080] Another aspect of the present disclosure is directed 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.

[0081] 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).

[0082] 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.

[0083] 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.

[0084] 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).

[0085] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0086] As used herein, any reference to a "zone disposed at the inlet end of a substrate" refers to a zone disposed on or carried on 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 a substrate" refers to a zone disposed on or carried on 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.

[0087] When the substrate is a wall-flow filter, generally any reference to a "zone disposed at the inlet end of the substrate" refers to a zone disposed on or supported 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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).

[0092] The term "washcoat" is known in the art and refers to an adherent coating that is typically applied to a substrate during the manufacture of a catalyst.

[0093] 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.

[0094] 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.

[0095] 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."

[0096] 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."

[0097] 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."

[0098] 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.

[0099] As used herein, the term "loading" refers to g / ft on a metal weight basis. 3 Refers to a measurement in units of .

[0100] 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]

[0101] material All materials were commercially available and obtained from known sources unless otherwise stated.

[0102] Catalyst A: First catalytic region: The first catalytic region consisted of Pd supported on a first CeZr mixed oxide, La-stabilized alumina, and a Ba-promoter washcoat. The washcoat loading of the first catalytic region was about 1.7 g / in. 3 The Pd loading is 200 g / ft 3 It was.

[0103] This washcoat was then coated onto a ceramic substrate (750 cpsi, 2.5 mil wall thickness) from the inlet face using standard coating procedures with a target coating depth of 50% of the substrate length and dried at 90°C.

[0104] Second catalytic region: The second catalytic region consisted of Pd supported on a second CeZr mixed oxide, La-stabilized alumina, and a Ba-promoter washcoat. The washcoat loading for the second catalytic region was approximately 1.7 g / in. 3 The Pd loading was 34 g / ft 3 It was.

[0105] This second washcoat was then coated onto the outlet face of the ceramic substrate containing the first catalyst region using standard coating procedures, with a target coating depth of 50% of the substrate's length, dried at 90°C, and calcined at 500°C for 45 minutes.

[0106] 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 1.3 g / in. 3 The Rh loading is 8g / ft 3 It was.

[0107] 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 length, dried at 90°C, and calcined at 500°C for 45 minutes.

[0108] Comparative catalyst B: Comparative Catalyst B is prepared following the same procedure as Catalyst A, except that in Comparative Catalyst B the third catalytic zone is coated over the entire length (i.e., 100%) of the substrate. The total Pd loading is 117 g / ft 3 The total Rh loading is 8 g / ft 3 It was.

[0109] Comparison catalyst C: Comparative Catalyst C is a commercially available ternary (Pd-Rh) catalyst with a double-layer 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 1.7 g / in. 3 The Pd loading was 117 g / ft 3 The upper layer consisted of Rh supported on a second CeZr mixed oxide and La-stabilized alumina washcoat. The washcoat loading of the upper layer was approximately 1.3 g / in. 3 The Rh loading is 8g / ft 3The total washcoat loading of catalyst C was approximately 3.0 g / in 3 It was.

[0110] Catalyst D Catalyst D was prepared following the same procedure as catalyst A, except that 50% of the Ba promoter was replaced with Sr in the first catalytic region.

[0111] Catalyst E Catalyst E was prepared following the same procedure as catalyst A, except that 100% of the Ba promoter was replaced with Sr in the first catalytic region.

[0112] Example 1: Vehicle Test Procedures and Results The fresh performance of Catalyst A and Comparative Catalysts B and C was tested on a 1.5 liter engine vehicle in the New European Driving Cycle (NEDC). Tailpipe bag data is shown in Table 1. Catalyst A of the present invention reduced THC, CO, and NO compared to Comparative Catalysts B and C. x (See, for example, the following related improved performance: Catalyst A compared to Comparative Catalyst B shows significantly lower emissions of THC, CO, and NO.) x emissions are improved by approximately 20%, 10% and 24%, respectively).

[0113] [Table 1]

[0114] In addition, as shown in Figures 4a, 4b, and 4c, Inventive Catalyst A exhibits significantly improved emission control performance during the cold start phase compared to Comparative Catalysts B and C. A summary of the cumulative emission data for the first 30, 50, and 100 seconds from the drive cycle is shown in Table 2.

[0115] [Table 2]

[0116] Example 2: Light-off performance test in engine test Catalyst A and Comparative Catalyst B were tested separately in a gasoline engine. Light-off performance was measured under typical conditions of an exhaust flow rate of 80 kg / hr, a temperature gradient of 30°C / min, and an air-fuel ratio (AFR) lambda of 14.55. THC, CO, and NO x The conversion was calculated by comparing the concentration of the feed gas and the gas concentration at the catalyst outlet. Prior to engine light-off testing, Catalyst A and Comparative Catalyst B were bench aged under the same 6.1 L engine for 100 hours of operation with a peak catalyst bed temperature of 980°C and a four-mode aging cycle.

[0117] HC, CO, and NO for Catalyst A and Comparative Catalyst B x T 50 The light-off temperatures are shown in Table 3. The data surprisingly show that the multi-zone catalyst A of the present invention has a T that is about 20°C lower than the comparative catalyst B of the two-layer example. 50 (T 50 is the temperature at which 50% conversion is reached), resulting in significantly improved light-off performance.

[0118] [Table 3]

[0119] Example 3: Vehicle Test Procedures and Results Bench-aged samples of Catalyst A, Catalyst D, and Catalyst E were tested in a 1.5-liter vehicle on the New European Driving Cycle (NEDC). Bench aging was performed in the same 6.1-liter engine with a 4-mode aging cycle at a peak catalyst bed temperature of approximately 980°C and the same 150-hour run. Vehicle exhaust dilution bag data results are shown in Table 4. Catalysts D and E of the present invention significantly reduced THC, CO, and NO compared to Catalyst A. x (See, for example, the related improved performance below. When catalyst E is compared to catalyst A, the results show lower emissions of THC, CO, and NO. xemissions are improved by approximately 26%, 18%, and 14%, respectively).

[0120] [Table 4]

Claims

1. A catalytic article for treating exhaust gases, comprising: a substrate including an inlet end and an outlet end and having an axial length L; a first catalytic region beginning at the inlet end and extending over 40-60% of the axial length L, the first catalytic region including a first palladium component; a second catalytic region beginning at the outlet end and extending over 40-60% of the axial length L, the second catalytic region including a second palladium component; a third catalytic region beginning at the outlet end and extending over 50 to 95% of the axial length L, the third catalytic region including a third rhodium component; wherein the third catalytic region coats the second catalytic region and the first catalytic region, and the first palladium component and the second palladium component have a weight ratio of greater than 1:

1.

2. 2. The catalyst article of claim 1, wherein the second catalyst region overlaps with the first catalyst region over 1 to 15% of the axial length L.

3. The catalyst article of claim 1 , wherein the total length of the second catalyst region and the first catalyst region is equal to the axial length L.

4. The catalyst article of claim 1 , wherein the total length of the second catalyst region and the first catalyst region is less than the axial length L.

5. The catalytic article of any one of claims 1 to 4, wherein the first catalytic region is free of PGM metals other than the first palladium component.

6. The catalytic article of any one of claims 1 to 5, wherein the first catalytic region comprises 3.53 g / m 3 to 1.06×10 4 g / m 3 of the first palladium component.

7. 7. The catalytic article of claim 1, 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.

8. The catalytic article of any one of claims 1 to 7, wherein the second catalytic region is free of PGM metals other than the second palladium component.

9. The catalytic article of any one of claims 1 to 8, wherein the second catalytic region comprises 3.53 g / m 3 to 1.77×10 3 g / m 3 of the second palladium component.

10. 10. The catalytic article of any one of claims 1 to 9, wherein the second catalytic region further comprises a second oxygen storage capacity (OSC) material, a second alkali metal or alkaline earth metal component, and / or a second inorganic oxide.

11. The catalytic article of any one of claims 1 to 10, wherein the third catalytic region comprises 3.53 g / m 3 to 7.06×10 2 g / m 3 of the third rhodium component.

12. 12. The catalytic article of any one of claims 1 to 11, wherein the third catalytic region further comprises a third oxygen storage capacity (OSC) material, a third alkali metal or alkaline earth metal component, and / or a third inorganic oxide.

Images