Zone-Type TWC Catalyst for Exhaust Gas Treatment of Gasoline Engines

Abstract

A catalyst article for treating exhaust gas, comprising a substrate having an axial length L and including an inlet end and an outlet end, a first catalyst region starting at the inlet end and extending over a length less than the axial length L, the first catalyst region comprising a first platinum group metal (PGM) component, a first inorganic oxide, and an optional first oxygen storage capacity (OSC) material, a second catalyst region starting at the outlet end and extending over a length less than the axial length L, the second catalyst region comprising a second PGM component, an optional second inorganic oxide, and a second OSC material, and a third catalyst region, wherein the weight ratio of the optional first OSC material to the first inorganic oxide is greater than 1:1.

Description

Technical Field

[0001] The present invention relates to a catalytic article useful for treating exhaust gas emissions from gasoline engines.

Background Art

[0002] In internal combustion engines, exhaust gases containing various pollutants, including hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (nitrogen oxide, "NO x "), are generated. Emission control systems including exhaust gas catalytic conversion catalysts are widely used to reduce the amounts of these pollutants emitted into the atmosphere. The catalyst commonly used for treating the exhaust of gasoline engines is a TWC (three way catalyst). With the TWC, the following three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) reduction of NO x are carried out.

[0003] Typically, the three-way catalyst contains a precious metal (PGM) such as palladium, rhodium, or platinum, or a combination thereof, an oxygen storage material (oxygen storage component, OSC) such as cerium-zirconium mixed oxide, and alumina. In some TWC catalysts, both the OSC and alumina are used as carrier materials for the precious metal(s) to improve dispersion, prevent PGM sintering, and / or prevent alloying when two or more precious metals are used in the same washcoat. However, in other TWC catalysts, the PGM targets one of either the alumina or OSC carrier materials in order to have some unique catalytic action in certain situations such as sudden changes in the exhaust gas air-fuel ratio (lambda disturbance), light-off function during the cold start period, etc. Therefore, there is a continuing need to develop catalysts with different PGM distributions on different carrier materials to meet more stringent exhaust gas regulations, including both normal engine operating conditions and special situations.

[0004] It is well known that the performance of a TWC catalyst is affected by the oxidation state of the PGM. For example, metallic Rh is much more active than rhodium oxide (Rh 2 O 3 ). There is also much discussion in the published literature about the preferred Pd oxidation state. Almost certainly, depending on the reaction conditions, either metallic Pd or palladium oxide is preferred.

[0005] A typical method of "fixing" PGM on a target carrier material is the incipient wetness impregnation method. That is, after diluting a water-soluble salt of PGM and impregnating the pores of the carrier material, it is dried and calcined to prepare a PGM-containing powder. This powder is then slurried, blended with another carrier slurry, wash-coated onto a honeycomb substrate, and used as a catalyst through another calcination step. If there are multiple layers of wash-coat on the same substrate and calcination is performed after each layer coating, two rounds or more of calcination are carried out, resulting in initial sintering of the PGM nanoparticles.

[0006] Alternatively, the hydrolysis method is used to precipitate PGM on the target carrier material by changing the pH of the wash-coat to convert soluble PGM salts into insoluble species. For example, rhodium nitrate can be converted to rhodium hydroxide through ammonia addition and precipitated onto either alumina or a CeZr oxide carrier. However, this hydrolysis method is insufficient to control the affinity of Pd, which can occur due to the high Pd loading in a typical TWC formulation.

[0007] The present invention solves the problem of the affinity of Pd in a TWC wash-coat having both alumina and CeZr oxide without using the conventional incipient wetness impregnation method, which is not cost-effective. SUMMARY OF THE INVENTION

[0008] One aspect of the present disclosure is a catalyst article for treating exhaust gas, comprising a substrate having an axial length L, including an inlet end and an outlet end, a first catalyst region starting at the inlet end and extending over a length less than the axial length L, the first catalyst region comprising a first platinum group metal (PGM) component, a first inorganic oxide, and an optional first oxygen storage capacity (OSC) material, a second catalyst region starting at the outlet end and extending over a length less than the axial length L, the second catalyst region comprising a second PGM component, a second inorganic oxide, and an optional second OSC material, and a third catalyst region, wherein the weight ratio of the optional first OSC material to the first inorganic oxide in the first catalyst region is greater than 1:1.

[0009] The present invention also encompasses an exhaust system for an internal combustion engine comprising the three-way catalyst component of the present invention.

[0010] The present invention also encompasses treating exhaust gas from an internal combustion engine, particularly treating exhaust gas from a gasoline engine. The method includes contacting the exhaust gas with the three-way catalyst component of the present invention.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention is directed to the catalytic treatment of combustion exhaust gases, such as those produced by gasoline engines and other engines, and related catalysts and systems. More specifically, the present invention relates to the simultaneous treatment of NO x , CO, and HC in a vehicle exhaust system. The inventors have developed a zone-type Pd layer configuration TWC catalyst in which most of the Pd species are forced to land on either alumina or CeZr oxide by controlling the weight ratio of two carriers in the inlet washcoat or the outlet washcoat.

[0013] One aspect of the present disclosure is a catalyst article for treating exhaust gas, comprising a substrate having an axial length L, an inlet end, and an outlet end, a first catalyst region starting at the inlet end and extending over a length less than the axial length L, the first catalyst region comprising a first platinum group metal (PGM) component, a first inorganic oxide, and an optional first oxygen storage capacity (OSC) material, a second catalyst region starting at the outlet end and extending over a length less than the axial length L, the second catalyst region comprising a second PGM component, an optional second inorganic oxide, and a second OSC material, and a third catalyst region, wherein the weight ratio of the first inorganic oxide to the optional first OSC material is greater than 1:1.

[0014] The inventors have found that these catalysts thus coated exhibit better catalytic performance that cannot be achieved with conventional uniform Pd layer configurations. The unexpected advantages of the present invention include, in particular, an improvement in TWC performance in transient operating cycles beyond the cold start phase, a significant reduction in the emissions of exhaust pollutants, and thus easier achievement of emission targets, compared to conventional TWC catalysts with similar concentrations (e.g., washcoat loading).

[0015] The first catalyst region The first catalyst region can extend over 20 to 90 percent of the axial length L. Preferably, the first catalyst region can extend over 25 to 80 percent, more preferably 30 to 70 percent of the axial length L.

[0016] The first PGM component can be Pd, Pt, Rh, or a combination thereof. Preferably, the first PGM component can be Pd, Pt, or a combination thereof. More preferably, the first PGM component can be Pd. Alternatively, the first PGM component can be Rh.

[0017] The first inorganic oxide is preferably an oxide of an element of Group 2, Group 3, Group 4, Group 5, Group 13, and Group 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 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.

[0018] When present, the optional 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 contains a ceria-zirconia mixed oxide. The ceria-zirconia mixed oxide can further contain some dopants such as lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide, etc.

[0019] The weight ratio of the first inorganic oxide to the optional first OSC material can be at least 3:2, preferably at least 2:1, or at least 5:2.

[0020] Alternatively, the weight ratio of the first inorganic oxide to the first OSC material can be from 10:1 to 3:2, preferably from 8:1 to 3:2 or from 5:1 to 3:2, more preferably from 10:1 to 2:1 or from 8:1 to 2:1, and most preferably from 5:1 to 2:1.

[0021] The ceria-zirconia mixed oxide can have a weight ratio of zirconia to ceria of at least 50:50, preferably higher than 55:45, and more preferably at least 60:40, 70:30, or 80:20.

[0022] The first PGM component can be supported on both the first inorganic oxide and the first OSC material.

[0023] The first catalyst region can contain from 0.1 to 300 g / ft 3 of the first PGM component. Preferably, the first catalyst region can contain from 50 to 250 g / ft 3 of the first PGM component, more preferably from 100 to 220 g / ft 3 of the first PGM component. Alternatively, the first catalyst region can contain from 0.1 to 20 g / ft 3 of the first PGM component. In some embodiments, the first catalyst region can contain from 1 to 20 g / ft 3 or from 2 to 15 g / ft 3 of the first PGM component.

[0024] The optional loading amount of the first OSC material in the first catalyst region can be less than 2 g / in 3 . In some embodiments, the optional loading amount of the first OSC material in the first catalyst region is 1.5 g / in 3 or less, 1.2 g / in 3 or less, 1.0 g / in 3 or less, 0.9 g / in 3 or less, 0.8 g / in 3 or less, or 0.7 g / in 3 or less.

[0025] The total washcoat loading of the first catalyst region is less than 4 g / in 3 less, preferably less than 3.5 g / in 3 less, less than 3.0 g / in 3 less, less than 2.5 g / in 3 less, or less than 1.5 g / in 3 and may be less. Alternatively, the total washcoat loading of the first catalyst region is 0.5 - 4 g / in 3 0.5 - 3.5 g / in 3 preferably 0.5 - 3.0 g / in 3 1.0 - 3.0 g / in 3 1.0 - 2.5 g / in 3 or 1.5 - 2.5 g / in 3 and may be.

[0026] The first catalyst region can further contain a first alkali metal component or an alkaline earth metal component.

[0027] In some embodiments, the first alkali metal or alkaline earth metal may be deposited on the first OSC material. Alternatively, or in addition thereto, 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 both the first OSC material and the first inorganic oxide, i.e., may be present thereon.

[0028] The first alkali metal or alkaline earth metal is generally in contact with the first inorganic oxide. Preferably, the first alkali metal or alkaline earth metal is supported on the first inorganic oxide. Alternatively, the first alkali metal or alkaline earth metal may be in contact with the first OSC material.

[0029] The first alkali metal or alkaline earth metal is preferably barium or strontium, and their mixed oxides or composite oxides. Preferably, when barium or strontium is present, it is supported in an amount of 0.1 to 15% by weight, more preferably 3 to 10% by weight of barium or strontium, based on the total weight of the first catalyst region.

[0030] Preferably, barium is present as BaCO 3 and.

[0031] The second catalyst region The second catalyst region can extend over 20 to 90 percent of the axial length L. Preferably, the second catalyst region can extend over 25 to 80 percent, more preferably 30 to 70 percent of the axial length L.

[0032] The second PGM component can be Pd, Pt, Rh, or a combination thereof. Preferably, the second PGM component can be Pd, Pt, or a combination thereof. More preferably, the second PGM component can be Pd. Alternatively, the second PGM component can be Rh.

[0033] The optional second inorganic oxide, when present, is preferably an oxide of an element of Group 2, Group 3, Group 4, Group 5, Group 13, and Group 14. The optional second inorganic oxide is preferably selected from the group consisting of alumina, magnesia, silica, ceria, barium oxide, and their mixed oxides or composite oxides. Particularly preferably, the optional second inorganic oxide is alumina, lanthanum-alumina, ceria, or magnesia / alumina composite oxide. One of the particularly preferred second inorganic oxides is alumina or lanthanum-alumina composite oxide.

[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 contains a ceria-zirconia mixed oxide. The ceria-zirconia mixed oxide can further contain some dopants such as lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide.

[0035] The optional second inorganic oxide and the second OSC material can have a weight ratio of less than 1:1, preferably 2:3 or less, and more preferably 1:2 or 2:5 or less.

[0036] Alternatively, the second inorganic oxide and the second OSC material can have a weight ratio of 2:3 to 1:10, preferably 2:3 to 1:8 or 2:3 to 1:5, more preferably 1:2 to 1:10 or 1:2 to 1:8, and most preferably 1:2 to 1:5.

[0037] The ceria-zirconia mixed oxide can have a weight ratio of zirconia to ceria of at least 20:80, preferably higher than 50:50, and more preferably at least 55:45, 60:40, 70:30, or 80:20.

[0038] The second PGM component can be supported on both the second inorganic oxide and the second OSC material.

[0039] The second catalyst region can contain 0.1 to 300 g / ft 3 of the second PGM component. Preferably, the second catalyst region can contain 50 to 250 g / ft 3 of the second PGM component, and more preferably 100 to 220 g / ft 3 of the second PGM component. Alternatively, the second catalyst region can contain 0.1 to 20 g / ft 3 of the second PGM component. In some embodiments, the second catalyst region can contain 1 to 20 g / ft 3 or 2 to 15 g / ft 3 of the second PGM component.

[0040] The supported amount of the second OSC material in the second catalyst region can be at least 0.5 g / in 3 In some embodiments, the supported amount of the second OSC material in the second catalyst region can be at least 0.7 g / in 3 , 0.8 g / in 3 , 0.9 g / in 3 , 1.0 g / in 3 , 1.5 g / in 3 , 2.0 g / in 3 , or 2.5 g / in 3 .

[0041] The total washcoat supported amount of the second catalyst region is less than 4 g / in 3 , preferably less than 3.5 g / in 3 , less than 3.0 g / in 3 , less than 2.5 g / in 3 , or less than 1.5 g / in 3 . Alternatively, the total washcoat supported amount of the second catalyst region can be 0.5 to 4.0 g / in 3 , 0.5 to 3.5 g / in 3 , preferably 0.5 to 3.0 g / in 3 , 1.0 to 3.0 g / in 3 , 1.0 to 2.5 g / in 3 , or 1.5 to 2.5 g / in 3 .

[0042] The second catalyst region can further include a second alkali metal component or an alkaline earth metal component.

[0043] In some embodiments, the second alkali metal or alkaline earth metal may be deposited on the second OSC material. Alternatively, or in addition thereto, 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 both the second OSC material and the second inorganic oxide, that is, may be present thereon.

[0044] The second alkali metal or alkaline earth metal is generally in contact with the second inorganic oxide. Preferably, the second alkali metal or alkaline earth metal is supported on the second inorganic oxide. Alternatively, the second alkali metal or alkaline earth metal may be in contact with the second OSC material.

[0045] The second alkali metal or alkaline earth metal is preferably barium or strontium, and their mixed oxides or composite oxides. Preferably, when barium or strontium is present, it 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 second catalyst region.

[0046] Preferably, barium is present as BaCO 3 and.

[0047] The third catalyst region In some embodiments, the third catalyst region can extend over 100 percent of the axial length L. In other embodiments, the third catalyst region can extend over less than 100 percent, such as less than 95%, less than 90%, or less than 85% of the axial length L. Alternatively, the third catalyst region can extend over 50 to 95 percent or 60 to 95 percent of the axial length L.

[0048] The third catalyst region can include a third PGM component, a third OSC material, a third alkali metal component or alkaline earth metal component, and / or a third inorganic oxide.

[0049] The third PGM component can include Rh. In some embodiments, the third PGM component can further include Pd and / or Pt. In other embodiments, the third catalyst region may essentially not contain PGM metals other than the rhodium component. Alternatively, the third PGM component can include Pt and / or Pd.

[0050] The third catalyst region can include a third PGM component of 0.1 to 20 g / ft 3 In some embodiments, the third catalyst region can include a third PGM component of 1 to 20 g / ft 3 or 2 to 15 g / ft 3 In some embodiments, the third catalyst region can include a third PGM component of 0.1 to 300 g / ft 3 Preferably, the third catalyst region can include a third PGM component of 50 to 250 g / ft 3 More preferably, the third catalyst region can include a third PGM component of 100 to 220 g / ft 3

[0051] The total washcoat loading of the third catalyst region is less than 4.0 g / in 3 Preferably less than 3.5 g / in 3 Less than 3.0 g / in 3 Less than or 2 g / in 3 Preferably less than 1.5 g / in 3 Less than or 1.0 g / in 3 It can be less than

[0052] The third OSC material is preferably selected from the group consisting of cerium oxide, ceria-zirconia mixed oxides, and alumina-ceria-zirconia mixed oxides. Preferably, the third OSC material includes a ceria-zirconia mixed oxide and one or more of dopants such as lanthanum, neodymium, yttrium, praseodymium, etc. In addition, the third OSC material can function as a carrier material for the third rhodium component.

[0053] The third catalyst region can further include a third alkali metal component or alkaline earth metal component, and / or a third inorganic oxide.

[0054] For the ceria-zirconia mixed oxide, the molar ratio of zirconia to ceria can be at least 50:50, preferably higher than 60:40, and more preferably higher than 80:20.

[0055] ​ The third OSC material can be 10 to 90% by weight, preferably 25 to 75% by weight, more preferably 35 to 65% by weight, based on the total washcoat loading of the third catalyst region.

[0056] The loading of the third OSC material in the third catalyst region can be less than 2 g / in 3 In some embodiments, the loading of the third OSC material in the third catalyst region is 1.5 g / in or less 3 Hereinafter, 1.2 g / in or less 3 Hereinafter, 1.0 g / in or less 3 Hereinafter, or 0.5 g / in or less 3 Hereinafter.

[0057] The third catalyst region may be substantially free of the third alkali metal or alkaline earth metal. Reference to "substantially free of" means that the listed material may be present in small amounts, either intentionally or unintentionally, within the listed layer. For example, an alkali metal or alkaline earth metal may be present in the first catalyst region and / or the second catalyst region, and some of the alkali metal or alkaline earth metal may migrate / leach into the third catalyst region unintentionally during the coating process.

[0058] The third inorganic oxide is preferably an oxide of elements of Group 2, Group 3, Group 4, Group 5, Group 13, and Group 14. The third inorganic oxide is preferably selected from the group consisting of alumina, ceria, magnesia, silica, lanthanum oxide, zirconium oxide, neodymium oxide, praseodymium oxide, and mixed oxides or composite oxides thereof. Particularly preferably, the third inorganic oxide is alumina, a lanthanum / alumina composite oxide, or a zirconium / alumina composite oxide. One particularly preferred third inorganic oxide is a lanthanum / alumina composite oxide or a zirconium / alumina composite oxide. The third inorganic oxide may be a carrier material for the third rhodium component and / or a carrier material for the third OSC material.

[0059] The fourth catalyst region In some embodiments, the catalyst article may further include a fourth catalyst region. In certain embodiments, the fourth catalyst region can extend over less than 100%, such as less than 95%, less than 90%, or less than 85% of the axial length L. Alternatively, the fourth catalyst region can extend over 50 to 95 percent or 60 to 95 percent of the axial length L.

[0060] The fourth catalyst region can include a fourth PGM component, a fourth OSC material, a fourth alkali metal component or alkaline earth metal component, and / or a fourth inorganic oxide.

[0061] The fourth PGM component can include Rh. In some embodiments, the fourth PGM component can further include Pd and / or Pt. In other embodiments, the fourth catalyst region may essentially not contain PGM metals other than the rhodium component. Alternatively, the fourth PGM component can include Pt and / or Pd.

[0062] The fourth catalyst region can include a fourth PGM component of 0.1 to 20 g / ft 3 . In some embodiments, the fourth catalyst region can include a fourth PGM component of 1 to 20 g / ft 3 or 2 to 15 g / ft 3 . Alternatively, the fourth catalyst region can include a fourth PGM component of 0.1 to 300 g / ft 3 . Preferably, the fourth catalyst region can include a fourth PGM component of 50 to 250 g / ft 3 , more preferably, 100 to 220 g / ft 3 of the fourth PGM component.

[0063] The total washcoat loading of the fourth catalyst region is less than 4.0 g / in 3 , preferably less than 3.5 g / in 3 , less than 3.0 g / in 3 , or less than 2 g / in 3 , more preferably less than 1.5 g / in 3 , or less than 1.0 g / in3 may be less than.

[0064] The fourth OSC material is preferably selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide. Preferably, the fourth OSC material includes a ceria-zirconia mixed oxide and one or more of dopants such as lanthanum, neodymium, yttrium, praseodymium. In addition, the fourth OSC material can function as a carrier material for the fourth rhodium component.

[0065] The fourth catalyst region can further include a fourth alkali metal component or alkaline earth metal component, and / or a fourth inorganic oxide.

[0066] For the ceria-zirconia mixed oxide, the molar ratio of zirconia to ceria can be at least 50:50, preferably higher than 60:40, more preferably higher than 80:20.

[0067] Based on the total washcoat loading of the fourth catalyst region, the fourth OSC material can be 10 - 90 wt%, preferably 25 - 75 wt%, more preferably 35 - 65 wt%.

[0068] The loading of the fourth OSC material in the fourth catalyst region can be less than 2 g / in 3 In some embodiments, the loading of the fourth OSC material in the fourth catalyst region can be less than 1.5 g / in 3 or less, 1.2 g / in 3 or less, 1.0 g / in 3 or less, or 0.5 g / in 3 or less.

[0069] The fourth catalyst region may be substantially free of a fourth alkali metal or alkaline earth metal. The reference to "substantially free of" means that the listed material may be present in small amounts, either intentionally or unintentionally, within the listed layer. For example, an alkali metal or alkaline earth metal may be present in the first catalyst region and / or the second catalyst region, and some of the alkali metal or alkaline earth metal may migrate / leach into the fourth catalyst region unintentionally during the coating process.

[0070] The fourth inorganic oxide is preferably an oxide of an element of Group 2, Group 3, Group 4, Group 5, Group 13, and Group 14. The fourth inorganic oxide is preferably selected from the group consisting of alumina, ceria, magnesia, silica, lanthanum oxide, zirconium oxide, neodymium oxide, praseodymium oxide, and mixed oxides or composite oxides thereof. Particularly preferably, the fourth inorganic oxide is alumina, a lanthanum / alumina composite oxide, or a zirconium / alumina composite oxide. One particularly preferred fourth inorganic oxide is a lanthanum / alumina composite oxide or a zirconium / alumina composite oxide. The fourth inorganic oxide may be a carrier material for the fourth rhodium component and / or a carrier material for the fourth OSC material.

[0071] The catalyst article of the present invention may include additional components known to those skilled in the art. For example, the composition of the present invention may further include at least one binder and / or at least one surfactant. When a binder is present, a dispersible alumina binder is preferred.

[0072] Configuration of the first catalyst region, the second catalyst region, the third catalyst region, and the fourth catalyst region The second catalyst region may overlap with the first catalyst region over 1 to 70 percent of the axial length L, preferably the overlap is 2 to 60 percent, 2 to 50 percent, 2 to 40 percent, 2 to 30 percent, 2 to 20 percent, 3 to 20 percent, or 3 to 10 percent of the axial length L (see, for example, FIGS. 1b and 1c, where the first catalyst region can cover the second catalyst region, or the second catalyst region can cover the first catalyst region). Alternatively, the total lengths of the second catalyst region and the first catalyst region may be equal to the axial length L (see, for example, FIGS. 1a, 2a, 2b, 3a, and 3b). In yet another alternative, the total lengths of the second catalyst region and the first catalyst region may be less than the axial length L, for example, 95% or less, 90% or less, 80% or less, or 70% or less of the axial length L (see, for example, FIGS. 2a and 2b).

[0073] In one aspect of the present invention, the various configurations of the catalyst article including the first catalyst region, the second catalyst region, the third catalyst region, and the fourth catalyst region can be prepared as follows.

[0074] FIG. 1a shows an embodiment according to the present invention in which the first catalyst region extends from the inlet end by less than 100% of the axial length L and the second catalyst region extends from the outlet end over less than 100% of the axial length L. The total lengths of the second catalyst region and the first catalyst region are equal to the axial length L. The third catalyst region extends to 100% of the axial length L and covers the first catalyst region and the second catalyst region as an upper layer.

[0075] FIG. 1b shows an embodiment according to the present invention in which the first catalyst region extends from the inlet end by less than 100% of the axial length L and the second catalyst region extends from the outlet end over less than 100% of the axial length L. The total lengths of the second catalyst region and the first catalyst region are greater than the axial length L. The third catalyst region extends to 100% of the axial length L and covers the first catalyst region and the second catalyst region as an upper layer.

[0076] FIG. 1c shows a modified example of FIG. 1b.

[0077] FIG. 1d shows an embodiment according to the present invention, in which the first catalyst region extends from the inlet end by less than 100% of the axial length L, and the second catalyst region extends from the outlet end over less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is smaller than the axial length L. The third catalyst region extends to 100% of the axial length L and covers the first catalyst region and the second catalyst region as an upper layer.

[0078] FIG. 1e shows an embodiment according to the present invention, in which the third catalyst region extends to 100% of the axial length L as a bottom layer, the first catalyst region extends from the inlet end by less than 100% of the axial length L, and the second catalyst region extends from the outlet end over less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is equal to (it may also be larger or smaller than) the axial length L.

[0079] FIG. 2a shows an embodiment according to the present invention, in which the first catalyst region extends from the inlet end by less than 100% of the axial length L, and the second catalyst region extends from the outlet end over less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is equal to (it may also be larger or smaller than) the axial length L. The third catalyst region extends from the outlet end by less than 100% of the axial length L.

[0080] FIG. 2b shows an embodiment according to the present invention, in which the first catalyst region extends from the inlet end by less than 100% of the axial length L, and the second catalyst region extends from the outlet end over less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is equal to (it may also be larger or smaller than) the axial length L. The third catalyst region extends from the inlet end by less than 100% of the axial length L.

[0081] Figure 3a shows an embodiment according to the present invention in which the first catalyst region extends from the inlet end by less than 100% of the axial length L, and the second catalyst region extends from the outlet end over less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is equal to (and may be greater or less than) the axial length L and constitutes the bottom layer. The third catalyst region extends from the inlet end by less than 100% of the axial length L, and the fourth catalyst region extends from the outlet end over less than 100% of the axial length L. The total length of the third catalyst region and the fourth catalyst region is equal to (and may be greater or less than) the axial length L and constitutes the upper layer.

[0082] Figure 3b shows an embodiment according to the present invention in which the third catalyst region extends from the inlet end by less than 100% of the axial length L, and the fourth catalyst region extends from the outlet end over less than 100% of the axial length L. The total length of the third catalyst region and the fourth catalyst region is equal to (and may be greater or less than) the axial length L and constitutes the bottom layer. The first catalyst region extends from the inlet end by less than 100% of the axial length L, and the second catalyst region extends from the outlet end over less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is equal to (and may be greater or less than) the axial length L and constitutes the upper layer.

[0083] The flow-through monolith substrate has a first face and a second face, defining a longitudinal direction therebetween. The flow-through monolith substrate has a plurality of channels extending between the first face and the second face. The plurality of channels extend in the longitudinal direction and provide a plurality of inner surfaces (e.g., the surfaces of the walls defining each channel). Each of the plurality of channels has an opening at the first face and an opening at the second face. To avoid doubt, the flow-through monolith substrate is not a wall-flow filter.

[0084] The first face is typically at the inlet end of the substrate, and the second face is at the outlet end of the substrate.

[0085] The channels can be of a constant width, and each of the plurality of channels can have a uniform channel width.

[0086] Preferably, in a plane orthogonal to the longitudinal direction, the monolithic substrate has 300 to 900 channels, preferably 400 to 800 channels per square inch. For example, on the first surface, the density of the open first channels and the closed second channels is 600 to 700 channels per square inch. These channels can have a cross-section that is rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal shape.

[0087] The monolithic substrate acts as a carrier for holding the catalyst material. Suitable materials for forming the monolithic 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 monolithic substrates are well known in the art.

[0088] It should be noted that the flow-through monolithic substrate described herein is a single component (i.e., a single brick-like mass). Nevertheless, when forming an exhaust treatment system, the substrate used can be formed by bonding a plurality of channels together, or by bonding a plurality of smaller substrates together as described herein. Such techniques are well known in the art, together with suitable casings and configurations for the exhaust treatment system.

[0089] In embodiments where the catalyst article of the present invention includes a ceramic substrate, the ceramic substrate can be made of any suitable refractory material, such as alumina, silica, ceria, zirconia, magnesia, zeolite, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicates and metalloaluminosilicates (such as cordierite and spodumene), or a mixture or mixed oxide of any two or more of these. Cordierite, magnesium aluminosilicate, and silicon carbide are particularly preferred.

[0090] In embodiments where the catalyst article of the present invention includes a metal substrate, the metal substrate can be made of any suitable metal, particularly heat-resistant metals and metal alloys such as titanium and stainless steel, and ferrite alloys containing iron, nickel, chromium, and / or aluminum in addition to other trace metals.

[0091] In some embodiments, the first catalyst region can be supported / deposited directly on the substrate (see, for example, FIGS. 1a-1d). In certain embodiments, the second catalyst region can be supported / deposited directly on the substrate (see, for example, FIGS. 1a-1d). In other embodiments, the third catalyst region is supported / deposited directly on the substrate (see, for example, FIGS. 1e, 3b).

[0092] In certain embodiments, at least 50% of the first catalyst region is not covered by the second catalyst region and / or the third catalyst region. In preferred embodiments, at least 60%, 70%, or 80% of the first catalyst region is not covered by the second catalyst region and / or the third catalyst region. In more preferred embodiments, at least 90% or 95% of the first catalyst region is not covered by the second catalyst region and / or the third catalyst region. In the most preferred embodiment, 100% of the first catalyst region is not covered by the second catalyst region and / or the third catalyst region.

[0093] Another aspect of the present disclosure is the use of the catalyst article described herein for NO x、CO, and HC in the vehicle exhaust gas to process the method for the object. According to this method was produced by the TWC catalyst converter, the conventional TWC (having the same PGM loading) compared to show improved, cold start / light-off phase beyond the transient state also shows improved performance in particular.

[0094] Another aspect of the present disclosure, together with a conduit for transferring the exhaust gas through the system, the catalyst article described herein, a system for processing vehicle exhaust gas for the object.

[0095] Definition The term "region", as used herein, typically refers to an area on a substrate obtained by drying and / or firing the washcoat. "Region" may be disposed or supported on the substrate, for example, as a "layer" or "zone". Area or arrangement on the substrate is generally controlled during the process of applying the washcoat to the substrate. "Region" typically has a distinct boundary or edge (i.e., using conventional analytical techniques, it is possible to distinguish one region from another region).

[0096] Typically, the "region" has a substantially uniform length. Reference to "substantially uniform length" in this context means a length that does not deviate by more than 10% from its average value (e.g., the difference between the maximum length and the minimum length), preferably does not deviate by more than 5% from its average value, more preferably does not deviate by more than 1% from its average value.

[0097] Each "region" preferably has a substantially uniform composition (i.e., when comparing a portion of the region with another portion of the region, there is no substantial difference in the composition of the washcoat). Substantially uniform composition in this context refers to a material (e.g., region) in which the difference in composition is 5% or less, usually 2.5% or less, and most commonly 1% or less when comparing a portion of the region with another portion of the region.

[0098] As used herein, the term "zone" refers to an area having a length less than the full length of the substrate, such as a length of 75% or less of the full length of the substrate. A "zone" typically has a length of at least 5% (e.g., 5% or more) of the full length of the substrate (i.e., a substantially uniform length).

[0099] The full length of the substrate is the distance between its inlet end and its outlet end (e.g., both ends of the substrate).

[0100] Any reference herein to a "zone disposed at the inlet end of the substrate" refers to a zone disposed or carried on the 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., the point at half its length) is closer to the inlet end of the substrate than to the outlet end of the substrate. Similarly, any reference herein to a "zone disposed at the outlet end of the substrate" refers to a zone disposed or carried on the 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., the point at half its length) is closer to the outlet end of the substrate than to the inlet end of the substrate.

[0101] 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 or carried on the substrate that (a) is closer to the inlet end (e.g., the open end) of the inlet channel of the substrate than to the closed end (e.g., the blocked or plugged end) of the inlet channel, and / or (b) is closer to the closed end (e.g., the blocked or plugged end) of the outlet channel of the substrate than to the outlet end (e.g., the open end) of the outlet channel. Accordingly, the midpoint of the zone (i.e., the point at half its length) is closer to (a) the inlet end of the inlet channel of the substrate than to the closed end of the inlet channel and / or (b) the closed end of the outlet channel of the substrate than to the outlet end of the outlet channel.

[0102] Similarly, when the substrate is a wall flow filter, any reference to "the zone disposed at the outlet end of the substrate" refers to a zone disposed or carried on the substrate, (a) a zone where the outlet end (e.g., the open end) of the outlet channel of the substrate is closer to the outlet end of the substrate than to the closed end (e.g., the blocked or sealed end) of the outlet channel, and / or (b) a zone where the closed end (e.g., the blocked or sealed end) of the inlet channel of the substrate is closer to the outlet end of the substrate than to the inlet end (e.g., the open end) of the inlet channel. Accordingly, the midpoint of the zone (i.e., the point at half its length) is closer to (a) the outlet end of the outlet channel of the substrate than to the closed end of the outlet channel and / or (b) the closed end of the inlet channel of the substrate than to the inlet end of the inlet channel.

[0103] When the washcoat is present on the wall of the wall flow filter (i.e., the zone is within the wall), the zone can satisfy both (a) and (b).

[0104] The term "washcoat" is well known in the art and generally refers to an adhesive coating applied to a substrate during the production of a catalyst.

[0105] The acronym "PGM", as used herein, 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.

[0106] 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 "composite oxide", as used herein, generally refers to a composition of oxides having two or more phases, as conventionally known in the art.

[0107] The expression "consisting essentially of", as used herein, limits the scope of a feature to include a particular material or process and any other materials or processes that do not substantially affect the basic characteristics of that feature, such as trace impurities. The expression "consisting essentially of" encompasses the expression "consisting of".

[0108] The expression "substantially free of", as used herein with respect to a material, typically means that the material is present in a small amount, such as 5 wt% or less, preferably 2 wt% or less, more preferably 1 wt% or less, in relation to the contents of a region, layer, or zone. The expression "substantially free of" encompasses the expression "free of".

[0109] The expression "essentially free of", as used herein with respect to a material, typically means that the material is present in a trace amount, such as 1 wt% or less, preferably 0.5 wt% or less, more preferably 0.1 wt% or less, in relation to the contents of a region, layer, or zone. The expression "essentially free of" encompasses the expression "free of".

[0110] As used herein, any reference to the amount of dopant expressed as weight %, particularly to the total amount, refers to the weight of the carrier material or its refractory metal oxide.

[0111] The term "loading" as used herein, when measured in units of g / ft on a metal weight basis, 3 refers to the measured value.

[0112] The following examples are merely illustrative of the present invention. Those skilled in the art will recognize many variations within the spirit and scope of the present invention and the claims.

Examples

[0113] Materials All materials are commercially available and were obtained from known suppliers unless otherwise noted.

[0114] Comparative Catalyst A: Comparative Catalyst A is a commercially available three-way (Pd-Rh) catalyst having a bilayer structure. The bottom layer consists of Pd supported on a washcoat of a first CeZr mixed oxide, La-stabilized alumina, and a Ba promoter. The washcoat loading of the bottom layer is about 2.4 g / in 3 and the Pd loading is 131 g / ft 3 Of these, either the La-stabilized alumina loading or the first CeZr mixed oxide loading is 1.0 g / in 3 and the weight ratio of the two Pd carrier materials is 1:1. The first CeZr mixed oxide contains about 40% ceria. Using standard coating procedures, the washcoat was coated from the inlet and outlet faces of a ceramic substrate (750 cpsi, wall thickness 3.0 mil) with a target coating depth of 50% of the substrate length, then dried and fired.

[0115] The top layer consists of Rh supported on a washcoat of a second CeZr mixed oxide and La-stabilized alumina. The washcoat loading of the top layer is about 1.5 g / in 3 and the Rh loading is 9 g / ft3 It was. Using a standard coating procedure, with 50% of the length of the substrate as the target coating depth, the wash coat was coated from the inlet and outlet surfaces of the ceramic substrate (750 cpsi, wall thickness 3.0 mil) containing the above-mentioned bottom layer wash coat, and then dried and fired.

[0116] Catalyst 1 of the present invention: First catalyst region: The first catalyst region consists of Pd supported on a wash coat of La-stabilized alumina and a Ba promoter. The wash coat loading of the first catalyst region is about 2.8 g / in 3 and the Pd loading is 131 g / ft 3 Among these, the La-stabilized alumina loading is 2.0 g / in 3 and it substantially does not contain a CeZr mixed oxide.

[0117] Using a standard coating procedure, with 50% of the length of the substrate as the target coating depth, the first wash coat was coated from the inlet surface of the ceramic substrate (750 cpsi, wall thickness 3.0 mil) containing the above-mentioned first catalyst region, and then dried.

[0118] Second catalyst region: The second catalyst region consists of Pd supported on a wash coat of a first CeZr mixed oxide and an alumina binder. The wash coat loading of the second catalyst region is about 2.3 g / in 3 and the Pd loading is 131 g / ft 3 Among these, the first CeZr mixed oxide loading is 2.0 g / in 3 and it substantially does not contain La-stabilized alumina. The first CeZr mixed oxide contains about 40% ceria.

[0119] Using standard coating procedures, a second wash coat was coated from the exit surface of a ceramic substrate (750 cpsi, wall thickness 3.0 mil) with 50% of the substrate length as the target coating depth, and then dried and fired.

[0120] Third catalyst region: The third catalyst region was prepared and coated in the same manner as the upper layer of Comparative Catalyst A.

[0121] Comparative Catalyst B: Comparative Catalyst B was prepared and coated in the same manner as Catalyst 1 of the present invention, except that the second wash coat was coated from the inlet surface of a ceramic substrate (750 cpsi, wall thickness 3.0 mil), and the first wash coat was coated from the exit surface of the ceramic substrate with 50% of the substrate length as the target coating depth using standard coating procedures.

[0122] Catalyst 2 of the present invention: First catalyst region: The first catalyst region consists of Pd supported on a wash coat of a first CeZr mixed oxide, La-stabilized alumina, and a Ba promoter. The wash coat loading of the first catalyst region is about 2.6 g / in 3 and the Pd loading is 131 g / ft 3 Among these, the La-stabilized alumina loading is 1.5 g / in 3 and the first CeZr mixed oxide loading is 0.5 g / in 3 and the weight ratio of La-stabilized alumina to the first CeZr mixed oxide is 3:1. The first CeZr mixed oxide contains about 40% ceria.

[0123] Using standard coating procedures, with 50% of the substrate length as the target coating depth, a first wash coat was coated from the inlet surface of a ceramic substrate (750 cpsi, wall thickness 3.0 mil) containing the above first catalyst region, and then dried.

[0124] Second catalyst region: The second catalyst region consists of Pd supported on a washcoat of a first CeZr mixed oxide, La-stabilized alumina, and a Ba promoter. The washcoat loading amount of the second catalyst region is about 2.3 g / in 3 and the Pd loading amount is 131 g / ft 3 Among these, the La-stabilized alumina loading amount is 0.5 g / in 3 and the first CeZr mixed oxide loading amount is 1.5 g / in 3 and the weight ratio of La-stabilized alumina to the first CeZr mixed oxide is 1:3. The first CeZr mixed oxide contains about 40% ceria.

[0125] Using standard coating procedures, with 50% of the substrate length as the target coating depth, a second washcoat was coated from the outlet face of a ceramic substrate (750 cpsi, wall thickness 3.0 mil), then dried and fired.

[0126] Third catalyst region: The third catalyst region was prepared and coated in the same manner as the upper layer of Comparative Catalyst A.

[0127] Comparative Catalyst C: Comparative Catalyst C was prepared and coated in the same manner as Catalyst 2 of the present invention, except that the second washcoat was coated from the inlet face of a ceramic substrate (750 cpsi, wall thickness 3.0 mil), and the first washcoat was coated from the outlet face of the ceramic substrate with 50% of the substrate length as the target coating depth using standard coating procedures.

[0128] Catalyst 3 of the present invention: Catalyst 3 of the present invention was prepared according to the same procedure as Catalyst 1 of the present invention, except that the coating depths of the first and second catalyst regions are at least 75% but less than 100% of the substrate length.

[0129] Comparative Catalyst D: Comparative catalyst D was prepared according to the same procedure as Comparative catalyst B, except that the coating depths of the first catalyst region and the second catalyst region were at least 75% but less than 100% of the length of the substrate.

[0130] Catalyst 4 of the present invention: Catalyst 4 of the present invention was prepared according to the same procedure as Catalyst 2 of the present invention, except that the coating depths of the first catalyst region and the second catalyst region were at least 75% but less than 100% of the length of the substrate.

[0131] Comparative catalyst E: Comparative catalyst E was prepared according to the same procedure as Comparative catalyst C, except that the coating depths of the first catalyst region and the second catalyst region were at least 75% but less than 100% of the length of the substrate.

[0132] Comparative catalyst F: Comparative catalyst F is a commercially available three-way (Pd-Rh) catalyst having a double-layer structure. The bottom layer consists of Pd supported on a washcoat of a first CeZr mixed oxide, La-stabilized alumina, and a Ba promoter. The washcoat loading of the bottom layer is about 2.4 g / in 3 and the Pd loading is 112 g / ft 3 Of these, either the La-stabilized alumina loading or the first CeZr mixed oxide loading is 1.0 g / in 3 and the weight ratio of the two Pd support materials is 1:1. The first CeZr mixed oxide contains about 20% ceria. Using a standard coating procedure, with a target coating depth of 50% of the length of the substrate, this washcoat was coated from the inlet and outlet surfaces of a ceramic substrate (750 cpsi, wall thickness 3.0 mil), then dried and fired.

[0133] The top layer consists of Rh supported on a washcoat of a second CeZr mixed oxide and La-stabilized alumina. The washcoat loading of the top layer is about 2.0 g / in 3 and the Rh loading is 8 g / ft 3It was. Using standard coating procedures, with 50% of the substrate length as the target coating depth, the washcoat was coated from the inlet and outlet surfaces of the ceramic substrate (750 cpsi, wall thickness 3.0 mil) containing the above-mentioned bottom layer washcoat, then dried and fired.

[0134] Catalyst 5 of the present invention: First catalyst region: The first catalyst region consists of Pd supported on a washcoat of a first CeZr mixed oxide, La-stabilized alumina, and a Ba promoter. The washcoat loading of the first catalyst region is about 2.4 g / in 3 and the Pd loading is 112 g / ft 3 Among these, the La-stabilized alumina loading is 1.5 g / in 3 and the first CeZr mixed oxide loading is 0.5 g / in 3 and the weight ratio of La-stabilized alumina to the first CeZr mixed oxide is 3:1. The first CeZr mixed oxide contains about 20% ceria.

[0135] Using standard coating procedures, with 50% of the substrate length as the target coating depth, the first washcoat was coated from the inlet surface of the ceramic substrate (750 cpsi, wall thickness 3.0 mil) containing the above-mentioned first catalyst region, then dried.

[0136] Second catalyst region: The second catalyst region consists of Pd supported on a washcoat of a first CeZr mixed oxide, La-stabilized alumina, and a Ba promoter. The washcoat loading of the second catalyst region is about 2.3 g / in 3 and the Pd loading is 131 g / ft 3 Among these, the La-stabilized alumina loading is 0.5 g / in 3 and the first CeZr mixed oxide loading is 1.5 g / in 3and the weight ratio of La-stabilized alumina to the first CeZr mixed oxide is 1:3. The first CeZr mixed oxide contains about 20% ceria.

[0137] Using standard coating procedures, a second washcoat was coated from the exit face of a ceramic substrate (750 cpsi, wall thickness 3.0 mil) with a target coating depth of 50% of the substrate length, then dried and fired.

[0138] Third catalyst region: The third catalyst region was prepared and coated in the same manner as the upper layer of Comparative Catalyst F.

[0139] Comparative Catalyst G: Comparative Catalyst G is a commercially available three-way (Pd-Rh) catalyst having a double-layer structure. The bottom layer consists of Pd supported on a washcoat of the second CeZr mixed oxide, La-stabilized alumina, and a Ba promoter. The washcoat loading of the bottom layer is about 2.4 g / in 3 and the Pd loading is 133 g / ft 3 Of these, either the La-stabilized alumina loading or the second CeZr mixed oxide loading is 1.0 g / in 3 and the weight ratio of the two Pd support materials is 1:1. The second CeZr mixed oxide contains about 20% ceria. Using standard coating procedures, this washcoat was coated from the inlet and exit faces of a ceramic substrate (750 cpsi, wall thickness 3.0 mil) with a target coating depth of 50% of the substrate length, then dried and fired.

[0140] The upper layer consists of Rh supported on a washcoat of the first CeZr mixed oxide, La-stabilized alumina. The washcoat loading of the upper layer is about 2.0 g / in 3 and the Rh loading is 7 g / ft 3It was. Using standard coating procedures, with 50% of the substrate length as the target coating depth, the wash coat was coated from the inlet and outlet surfaces of the ceramic substrate (750 cpsi, wall thickness 3.0 mil) containing the above-mentioned bottom layer wash coat, then dried and fired.

[0141] Catalyst 6 of the present invention: First catalyst region: The first catalyst region consists of Rh supported on a wash coat of La-stabilized alumina. The wash coat loading of the first catalyst region is about 2.0 g / in 3 and the Rh loading is 7 g / ft 3 It was. Among these, the La-stabilized alumina loading is 2.0 g / in 3 and it substantially does not contain CeZr mixed oxide.

[0142] Using standard coating procedures, with 50% of the substrate length as the target coating depth, the first wash coat was coated from the inlet surface of the ceramic substrate (750 cpsi, wall thickness 3.0 mil) containing the above-mentioned first catalyst region, then dried.

[0143] Second catalyst region: The second catalyst region consists of Rh supported on a wash coat of the first CeZr mixed oxide and an alumina binder. The wash coat loading of the second catalyst region is about 2.2 g / in 3 and the Rh loading is 7 g / ft 3 It was. Among these, the first CeZr mixed oxide loading is 2.0 g / in 3 and it substantially does not contain La-stabilized alumina. The first CeZr mixed oxide contains about 20% ceria.

[0144] Using standard coating procedures, with 50% of the substrate length as the target coating depth, the second wash coat was coated from the outlet surface of the ceramic substrate (750 cpsi, wall thickness 3.0 mil), then dried and fired.

[0145] The third catalyst region: The third catalyst region was prepared and coated in the same manner as the Pd underlayer of Comparative Catalyst G.

[0146] The configuration of Catalyst 6 of the present invention is shown in Fig. 1e). The third catalyst region was first coated on a ceramic substrate, then dried and fired. Subsequently, the first catalyst region and the second catalyst region were coated from the inlet and the outlet, and a drying step was provided therebetween. Finally, the completed catalyst was subjected to a second firing.

[0147] Catalyst 7 of the present invention: The first catalyst region: The first catalyst region consists of Rh supported on a washcoat of a first CeZr mixed oxide and La-stabilized alumina. The washcoat loading of the first catalyst region was about 2.0 g / in 3 and the Rh loading was 7 g / ft 3 Among these, the La-stabilized alumina loading was 1.5 g / in 3 and the first CeZr mixed oxide loading was 0.5 g / in 3 The weight ratio of La-stabilized alumina to the first CeZr mixed oxide was 3:1. The first CeZr mixed oxide contains about 20% ceria.

[0148] Using a standard coating procedure, with 50% of the substrate length as the target coating depth, the first washcoat was coated from the inlet face of a ceramic substrate (750 cpsi, wall thickness 3.0 mil) containing the above first catalyst region and then dried.

[0149] The second catalyst region: The second catalyst region consists of Rh supported on a washcoat of a first CeZr mixed oxide and La-stabilized alumina. The washcoat loading of the second catalyst region was about 2.0 g / in 3 and the Rh loading was 7 g / ft 3 Among these, the La-stabilized alumina loading was 0.5 g / in3 and the first CeZr mixed oxide loading is 1.5 g / in 3 and the weight ratio of the first CeZr mixed oxide to the La-stabilized alumina is 1:3. The first CeZr mixed oxide contains about 20% ceria.

[0150] Using standard coating procedures, a second washcoat was coated from the exit face of a ceramic substrate (750 cpsi, wall thickness 3.0 mil) with a target coating depth of 50% of the substrate length, then dried and fired.

[0151] Third catalyst region: The third catalyst region was prepared and coated in the same manner as the Pd underlayer of Comparative Catalyst G.

[0152] The configuration of Catalyst 7 of the present invention is shown in FIG. 1e). The third catalyst region was first coated onto the ceramic substrate, then dried and fired. Next, the first and second catalyst regions were coated from the inlet and outlet, with a drying step provided in between. Finally, the completed catalyst was subjected to a second firing.

[0153]

Table 1

[0154] Example 1: Engine bench test procedures and results Catalysts A - E and Catalysts 1 - 4 of the present invention were subjected to 100 - hour engine bench aging in a stoichiometric / fuel - cut - aging cycle targeting a peak catalyst bed temperature of 1000°C. The catalysts were tested using a 2.0L engine bench dynamometer, and a custom - designed real - world driving (RDE) cycle containing acceleration and fuel - cutoff conditions representing speed profiles in cold cities, rural areas, highways, and hot cities was implemented. The cycle length was 2700 seconds from ambient soak conditions, reaching a peak catalyst bed temperature of approximately 700°C and a mass air flow rate of 250 kg / h. A low - temperature RDE test was used as a pre - condition cycle. Then, with a 5 - minute soak time in between, three high - temperature RDE cycles were repeated. While the engine is at operating temperature, the catalyst bed temperature remains high. The advantage of using low - temperature RDE as a pre - condition for high - temperature RDE experiments is that the reproducibility of engine - out emissions is very good because there is no consistency in temperature during the cold - start period. To further improve data accuracy, NO x , CO, and THC cumulative conversion rates were used to compare different catalysts as shown in Table 2. The emissions of NO x , CO, and THC at the engine - out position and after the catalyst were measured, and the cumulative mass of each species was calculated over the entire cycle. The cumulative conversion rate was calculated based on the cumulative post - catalyst emissions and the cumulative engine - out emissions. The results were presented as the average of three high - temperature RDE experiments and shown in Table 2.

[0155] The data in Table 2 clearly show that all the catalysts of the present invention provide some NO x and CO performance advantages compared to Comparative Catalyst A, while the THC conversion rate remains equivalent to that of the reference. When the alumina - rich catalyst region is on the inlet side, there are distinct NO x advantages in their configurations compared to their counterparts with a CeZr - oxide - rich region on the inlet side. For example, Catalyst 1 of the present invention has a higher NOx conversion rate than Comparative Catalyst B, Catalyst 2 of the present invention has a higher NO x conversion rate than Comparative Catalyst C, and Catalysts 3 of the present invention and Comparative Catalyst D have the same trend. Catalyst 4 of the present invention and Comparative Catalyst E have equivalent NOx The conversion rate was shown. This could be because of the long addition length and having both alumina and CeZr oxide in the first catalyst region and the second catalyst region, being almost the same as Comparative Catalyst A. Among the total four formulations of the present invention, the best catalyst is Catalyst 2 of the present invention which has an alumina-rich addition on the inlet side and a weight ratio of La-stabilized alumina to CeZr oxide of 3:1.

[0156] The average cumulative CO conversion rates of all the catalysts are compared in Table 2. CO conversion is more sensitive to the addition length. The normal addition length (50%) with an alumina-rich addition at the inlet is more beneficial for CO conversion compared to their counterparts with CeZr oxide on the inlet side. For example, Catalyst 1 of the present invention has a higher CO conversion rate than Comparative Catalyst B, and Catalyst 2 of the present invention has a higher CO conversion rate than Comparative Catalyst C.

[0157] The catalyst bed temperature is above 450 °C during the entire high-temperature RDE cycle, and thus, the THC conversion rates of all the catalysts are equally high due to the high bed temperature.

[0158]

Table 2

[0159] Example 2: Low-temperature RDE test in an engine test Comparative Catalyst F and Catalyst 5 of the present invention were engine bench-aged for 150 hours in a stoichiometric / fuel cut-off aging cycle targeting a peak catalyst bed temperature of 1000 °C. The catalysts were tested using a 2.0L bi-turbo, 4-cylinder Eu(VI)b calibrated engine bench dynamometer, and an RDE cycle designed by a custom OEM was implemented, including acceleration and fuel cut-off conditions representing cold start urban, highway, and hot urban speed profiles. The cycle length was 2700 seconds from ambient soak conditions, reaching a peak catalyst temperature of approximately 700 °C at a vehicle speed of about 140 km / h and a mass air flow rate of 400 kg / h. NO at the post-catalyst position xEmissions of , CO, and THC were measured and the cumulative mass of each species was calculated over the cycle. Three experiments were performed for each catalyst formulation and the cumulative emissions for the three experiments against time were plotted and are shown in the figures below.

[0160] FIG. 4a shows the NO2-induced degradation of comparative catalyst F and inventive catalyst 5 during a low-temperature RDE cycle. x The catalyst 5 of the present invention, which has a zoned configuration with an alumina-rich addition on the inlet side and a CeZr mixed oxide-rich addition on the outlet side, exhibits lower NO emissions over the entire low-temperature RDE operating cycle. x It is very clear that the CO and THC emissions are shown in Figures 4b and 4c, respectively. The two catalysts show comparable CO and THC emissions.

[0161] Example 3: Engine bench test procedures and results Comparative catalyst G and inventive catalysts 6 and 7 were engine bench aged for 50 hours in a stoichiometric / fuel cut aging cycle targeting a peak catalyst bed temperature of 1000°C. A 2.0L engine bench dynamometer was used to test the catalysts and a custom OEM designed real road driving (RDE) cycle was performed including acceleration and fuel cut conditions representing cold city, rural, highway, and hot city speed phases. The cycle length was 2700 seconds from ambient soak conditions, reaching a peak catalyst bed temperature of approximately 700°C and a mass air flow rate of 250 kg / hr. A low temperature RDE test was used as the precondition cycle. Three high temperature RDE cycles were then repeated with a 5 minute soak time in between. The catalyst bed temperature is still high while the engine is at operating temperature. The advantage of running the high temperature RDE with the low temperature RDE as the precondition is that the repeatability of engine out emissions is very good due to the inconsistency in temperature during the cold start period. To further improve the data accuracy, NO x The cumulative conversions of NO, CO, and THC were used to compare the different catalysts, as shown in Table 3. xThe emissions of CO, and THC were measured, and the cumulative mass of each species was calculated over the entire cycle. The cumulative conversion rate was calculated based on the cumulative post-catalyst emissions and the cumulative engine-out emissions. The results were presented as the average of three high-temperature RDE experiments and shown in Table 3. Additionally, the cumulative mass of ammonia generation over the entire three high-temperature RDE cycles was averaged for each sample and listed in Table 3.

[0162] Catalyst 6 of the present invention showed performance comparable to that of Comparative Catalyst G, while Catalyst 7 of the present invention showed a slight advantage compared to Comparative Catalyst G, and Catalyst 7 of the present invention also produced less NH 3 .

[0163] [Table 3]

Claims

1. A catalytic article for treating exhaust gases, A base material having an axial length L, including an inlet end and an outlet end, A first catalyst region beginning at the inlet end and extending over an axial length less than L, the first catalyst region comprising a first platinum group metal (PGM) component, a first inorganic oxide, and an optional first oxygen storage capacity (OSC) material, A second catalyst region beginning at the outlet end and extending over an axial length less than L, the second catalyst region comprising a second PGM component, an optional second inorganic oxide, and a second OSC material, A third catalytic region is provided, A catalyst article wherein the weight ratio of the first inorganic oxide to the optional first OSC material is greater than 1:

1.

2. The catalyst article according to claim 1, wherein the first catalyst region extends over 20 to 90 percent of the axial length L.

3. The catalyst article according to claim 1, wherein the second catalyst region extends over 20 to 90 percent of the axial length L.

4. The catalyst article according to claim 1, wherein the weight ratio of the first inorganic oxide to the optional first OSC material is at least 2:

1.

5. The catalyst article according to claim 1, wherein the weight ratio of the optional second inorganic oxide to the second OSC material is less than 1:

1.

6. The catalyst article according to claim 1, wherein the weight ratio of the optional second inorganic oxide to the second OSC material is 1:2 or less.

7. The catalyst article according to claim 1, wherein the first PGM component is Pd, Pt, Rh, or a combination thereof.

8. The catalyst article according to claim 1, wherein the optional first OSC material is selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.

9. The catalyst article according to claim 1, wherein the first inorganic oxide is selected from the group consisting of alumina, ceria, magnesia, silica, lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide, and mixed oxides or composite oxides thereof.

10. The catalyst article according to claim 1, wherein the second PGM component is Pd, Pt, Rh, or a combination thereof.

11. The catalyst article according to claim 1, wherein the second OSC material is selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.

12. The catalyst article according to claim 1, wherein the optional second inorganic oxide is selected from the group consisting of alumina, ceria, magnesia, silica, lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide, and mixed oxides or composite oxides thereof.

13. The catalyst article according to claim 1, wherein the first catalyst region is directly supported / deposited on the substrate.

14. The catalyst article according to claim 1, wherein the third catalyst region is directly supported / deposited on the substrate.

15. An exhaust treatment system for treating a flow of combustion exhaust gas, comprising a catalytic article according to any one of claims 1 to 14.

16. A method for treating exhaust gas from an internal combustion engine, comprising contacting the exhaust gas with a catalyst article according to any one of claims 1 to 14.

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