Improved catalysts for gasoline engine exhaust gas treatment

Abstract

A three-way catalyst article and its use in an exhaust system for an internal combustion engine is disclosed. The catalyst article for treating exhaust gas comprises a substrate including an inlet end and an outlet end having an axial length L, and a first catalyst region including a first platinum group metal (PGM) component supported on a first PGM support material, the first PGM component including platinum and rhodium, and the first PGM support material including ZrO2-Al2O3.

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 (HC), carbon monoxide (CO), and nitrogen oxides (NO x In gasoline engines, exhaust gases containing various pollutants are produced, including CO2, CO3, and NO3. Emissions control systems that include 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 gasoline engines is the three way catalyst (TWC). The TWC has three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) oxidation of NO2. x A reduction in the amount of

[0003] Improving fuel economy is becoming increasingly important due to market demands as well as stringent emission control regulations. Deceleration fuel shut off (DFSO) has been adopted by all OEMs as the primary fuel saving approach. In a typical DFSO event, fuel injection is either completely stopped or substantially reduced during deceleration or high speed cruising, while intake air is still present. The engine pumps air over a very hot catalyst, oxidizing it and producing NO. x When fuel returns, the engine runs rich, reducing the catalyst surface and disabling its ability to convert NO x However, only a very short rich excursion with a limited number of reductants will come out of the engine, and the outlet of the close coupled ("CC") brick and the entire under floor ("UF") brick will not be fully reducted. During this short rich recovery phase, some NO xIn addition, NH3 is generated during rich recovery after fuel cut. NH3 from the CC catalyst is oxidized on the UF catalyst over the Pd sites to produce NO x The general result is that after each fuel cut event, NO x It's a spike.

[0004] NOx reduction in gasoline vehicles beyond the cold start phase if OEMs use aggressive DFSO strategies and start / stop technologies to meet their fuel economy targets x Emissions reduction is enhanced. A catalyst solution that allows OEMs to meet their fuel economy goals by using DFSO and start / stop and also meets low standard emissions limits is desirable. The present invention addresses this need. Summary of the Invention

[0005] One aspect of the present disclosure is directed to a catalyst article for treating exhaust gases comprising: a substrate including an inlet end and an outlet end having an axial length L; and a first catalyst region including a first platinum group metal (PGM) component supported on a first PGM support material, the first PGM component including platinum and rhodium, and the first PGM support material including ZrO2-Al2O3.

[0006] The present invention also includes an exhaust system for an internal combustion engine which includes a three-way catalyst component of the present invention.

[0007] 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 a three-way catalyst component of the present invention. [Brief description of the drawings]

[0008] [Figure 1] 1 shows one embodiment according to the present invention containing a first catalytic region (single layer) having a length of 100% relative to the axial length L of the substrate. [Figure 2a] 1 shows an embodiment according to the invention in which a first catalyst region extends 100% of the axial length L as a bottom layer and a second catalyst region extends 100% of the axial length L as a top layer. [Figure 2b] 2 illustrates a variation of FIG. 2a. [Figure 3a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends from the inlet end less than 100% of the axial length L, and a second catalyst region extends from the outlet end less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is equal to or less than the axial length L. [Figure 3b] 3 illustrates a variation of FIG. 3a. [Figure 3c] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends from the inlet end less than 100% of the axial length L, and a second catalyst region extends from the outlet end less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is greater than the axial length L. [Figure 3d] 3 illustrates a variation of FIG. 3c. [Figure 4a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region is equal to or less than the axial length L. A third catalyst region extends 100% of the axial length L and is layered as an upper layer onto the first and second catalyst regions. [Figure 4b] 4 illustrates a variation of FIG. 4a. [Figure 4c] 1 illustrates an embodiment according to the present invention in which the third catalyst region is a bottom layer and extends 100% of the axial length L. The first catalyst region extends less than 100% of the axial length L from the inlet end and the second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region is less than or equal to the axial length L. [Figure 4d] 4 illustrates a variation of FIG. 4c. [Figure 5a]1 shows an embodiment according to the invention in which a first catalyst region is a bottom layer extending over 100% of the axial length L, a second catalyst region is a middle layer extending over 100% of the axial length L, and a third catalyst region is a top layer extending over 100% of the axial length L. [Figure 5b] 5 illustrates a variation of FIG. 5a. [Figure 5c] 5 illustrates a variation of FIG. 5a. [Figure 6a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region is greater than the axial length L. A third catalyst region extends 100% of the axial length L and is layered as an upper layer onto the first and second catalyst regions. [Figure 6b] 6 illustrates a variation of FIG. 6a. [Figure 6c] 6 illustrates a variation of FIG. 6a. [Figure 6d] 6 illustrates a variation of FIG. 6a. [Figure 6e] 6 illustrates a variation of FIG. 6a. [Figure 6f] 6 illustrates a variation of FIG. 6a. [Figure 6g] 1 illustrates an embodiment according to the present invention, where a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region can be less than, equal to, or greater than the axial length L. A third catalyst region extends less than 100% of the axial length L from the inlet end and is at least partially stacked to the first catalyst region and / or the second catalyst region. [Figure 6h] 6 illustrates a variation of FIG. 6g. [Figure 6i] 6 illustrates a variation of FIG. 6g. [Figure 6j]1 illustrates an embodiment according to the present invention, where a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region can be less than, equal to, or greater than the axial length L. A third catalyst region extends less than 100% of the axial length L from the outlet end and is at least partially stacked to the second and / or first catalyst regions. [Figure 6k] Illustrates a variation of FIG. 6j. [Figure 6l] Illustrates a variation of FIG. 6j. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DFSO countermeasures have been deployed by OEMs for decades to improve fuel economy, but NO during the rich recovery phase after DFSO x A breakthrough has yet to be successfully addressed, and NO accumulation beyond the cold start period x Current catalytic solutions are focused on reducing diesel NOx. x Trap (NO x The NO trap (NT) concept was borrowed from the NO trap (NT) concept, which uses additional Ba and a support material (such as CeO2). x However, the NO on Ba species / CeO2 x The storage window is much lower than in typical TWC applications, which substantially reduces, if not completely eliminates, the storage capacity of TWC+NT. The inventors have surprisingly demonstrated that Pt and Rh supported on ZrO2-Al2O3 can reduce NO2 after a fuel cut event without adversely affecting ignition function. x It has been found that slip can be effectively reduced.

[0010] One aspect of the present disclosure is directed to a catalyst article for treating exhaust gases comprising: a substrate including an inlet end and an outlet end having an axial length L; and a first catalyst region including a first platinum group metal (PGM) component supported on a first PGM support material, the first PGM component including platinum and rhodium, and the first PGM support material including ZrO2-Al2O3.

[0011] The first catalytic region ZrO2-Al2O3 can be a composite oxide or a mixed oxide. In some embodiments, ZrO2-Al2O3 can contain up to 50 wt% ZrO2. In other embodiments, ZrO2-Al2O3 can contain 1 wt% to 50 wt% ZrO2, 2 wt% to 40 wt% ZrO2, 3 wt% to 30 wt% ZrO2, or 5 wt% to 20 wt% ZrO2. In still other embodiments, ZrO2-Al2O3 can contain 5 wt% to 50 wt% ZrO2, 10 wt% to 45 wt% ZrO2, 10 wt% to 40 wt% ZrO2, 10 wt% to 30 wt% ZrO2, or 10 wt% to 20 wt% ZrO2.

[0012] In certain embodiments, ZrO2-Al2O3 can be doped with a suitable dopant such as La, Mn, Ni, Ti, or Cu, and more preferably, ZrO2-Al2O3 can be doped with La. In further embodiments, ZrO2-Al2O3 can be doped with 1-15 wt. % La, the weight being based on lanthana.

[0013] In some embodiments, the ZrO2-Al2O3 can be substantially free of Ce, and preferably essentially free of Ce.

[0014] The first PGM component may be selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof. In some embodiments, the first PGM component may be Pd, Rh, or mixtures thereof. In other embodiments, the first PGM component may be Pt, Rh, or mixtures thereof. In certain embodiments, the first PGM component may have a Pt / Rh weight ratio of 20:1 to 1:20, 15:1 to 1:15, 10:1 to 1:10, 5:1 to 1:5, or 2:1 to 1:2. In certain embodiments, the first catalyst zone further comprises Pd. In other embodiments, the total PGM loading in the first catalyst zone is up to 50 g / ft 3 , up to 40g / ft 3 , up to 30g / ft 3 , up to 20g / ft 3 , or up to 15g / ft 3 Alternatively, the PGM loading in the first catalyst region may be 1 g / ft 3 ~50g / ft 3 , 2g / ft 3 ~40g / ft 3 , 2g / ft 3 ~30g / ft 3 , 2g / ft 3 ~20g / ft 3 , 2g / ft 3 ~15g / ft 3 , or 2g / ft 3 Or 10g / ft 3 It could be.

[0015] The first PGM component is supported on a first PGM support material, such as ZrO2-Al2O3. The PGM may be supported on the surface and / or within the pores of the ZrO2-Al2O3.

[0016] In certain embodiments, the first catalyst region can further include a first oxygen storage capacity (OSC) material. In some embodiments, the first PGM component is not supported on the first OSC material. Alternatively, the first OSC material is substantially free of the first PGM component, and preferably essentially free of the first PGM component.

[0017] The first OSC material may be cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the first OSC material comprises ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. The ceria-zirconia mixed oxide may further comprise a dopant, such as lanthanum, neodymium, praseodymium, yttrium oxide, etc. In some embodiments, the first OSC material comprises ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0018] In some embodiments, the first catalytic region is substantially free of a first alkali metal or alkaline earth metal, and preferably is essentially free of a first alkali metal or alkaline earth metal (such as Ba).

[0019] As demonstrated in the examples below, the catalyst article in this embodiment can be applied as a TWC catalyst for treating exhaust gases produced by a gasoline engine.

[0020] The first catalyst region can extend over 100 percent of the axial length L (see, e.g., FIGS. 1, 2a, 2b, and 5a-5c). In some embodiments, the first catalyst region can extend over 20-99%, 30-90%, or 40-80% of the axial length L. Alternatively, the first catalyst region can extend over 30-70 percent of the axial length L. Preferably, the first catalyst region can extend over 40-60 percent, more preferably 45-55 percent of the axial length L (see, e.g., FIGS. 3a-5d and 6a-6l).

[0021] The total washcoat loading of the first catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 or 2.5g / in 3Alternatively, the total washcoat loading of the first catalyst region can be between 0.5 and 3.5 g / in 3 and preferably, 0.6 to 3 g / in 3 Or 0.7 to 2.5 g / in 3 It could be.

[0022] Second catalytic region The catalytic article may further include a second catalytic region.

[0023] The second catalyst region may further comprise a second PGM component, a second oxygen storage capacity (OSC) material, a second alkali metal or alkaline earth metal component, and / or a second inorganic oxide.

[0024] The second PGM component may be selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof, hi some embodiments, the second PGM component may be Pd, Rh, or mixtures thereof.

[0025] The second OSC material may be cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the second OSC material includes ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the second OSC material may further include one or more of dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material may function as a support material for the second PGM component. In some embodiments, the second OSC material includes ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0026] The ceria-zirconia mixed oxide may have a weight ratio of zirconia to ceria of at least 50:50, preferably greater than 60:40, more preferably greater than 70:30.Alternatively, the ceria-zirconia mixed oxide may also have a weight ratio of ceria to zirconia less than 50:50, preferably less than 40:60, more preferably less than 30:70.

[0027] 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.

[0028] The loading of the second OSC material in the second catalyst region is 2 g / in 3 In some embodiments, the loading of the second OSC material in the second catalytic region can be less than 1.5 g / in 3 Below, 1.2g / in 3 Below, 1g / in 3 Below, 0.8g / in 3 or less than 0.7g / in 3 The following is the result.

[0029] The second alkali or alkaline earth metal is preferably barium, strontium, a mixed oxide or a composite oxide thereof. Preferably, the barium or strontium, if present, is 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 second catalytic region.

[0030] It is even more preferred that the second alkali or alkaline earth metal is strontium, which, when present, is preferably present in an amount of from 0.1 to 15 wt %, more preferably from 3 to 10 wt %, based on the total weight of the second catalyst region.

[0031] Also, 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% by weight, more preferably 3 to 10% by weight, 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.

[0032] Preferably, the barium or strontium is present as BaCO3 or SrCO3. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

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

[0034] The second OSC material and the second inorganic oxide can 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.

[0035] Alternatively, the second OSC material and the second inorganic oxide can have a weight ratio of 10:1 to 1:10, preferably 8:1 to 1:8 or 5:1 to 1:5, more preferably 4:1 to 1:4 or 3:1 to 1:3, and most preferably 2:1 to 1:2.

[0036] In some embodiments, the second OSC material and the second inorganic oxide can have a weight ratio of 2:1 or greater. In further embodiments, the second OSC material and the second inorganic oxide can have a weight ratio of 10:1 or greater. In other further embodiments, the second OSC material and the second inorganic oxide can have a weight ratio of 20:1 or greater, or 30:1 or greater. In yet other further embodiments, the second OSC material and the second inorganic oxide can have a weight ratio of 40:1 or greater, or 50:1 or greater.

[0037] The total washcoat loading of the second catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 or 2.5g / in 3 Alternatively, the total washcoat loading of the first catalyst region can be between 0.5 and 3.5 g / in 3 and preferably, 0.6 to 3 g / in 3 Or 0.7 to 2.5 g / in 3 It could be.

[0038] The second catalytic region can extend over 100 percent of the axial length L (see, for example, Figures 2a, 2b, and 5a-5c).

[0039] The second catalyst region can extend over 30 to 70 percent of the axial length L. Preferably, it can extend over 40 to 60 percent, more preferably 45 to 55 percent, of the axial length L, and most preferably the total length of the second region and the first region is equal to or greater than the axial length L (see, e.g., Figures 3a-4d and 6a-6l).

[0040] The second catalyst region can overlap the first catalyst region over 0.1 to 99 percent of the axial length L (see, e.g., FIGS. 3c and 3d, where the first catalyst region can be stacked on the second catalyst region, or the second catalyst region can be stacked on the first catalyst region). Alternatively, the total length of the second catalyst region and the first catalyst region can be equal to the axial length L (see, e.g., FIGS. 3a and 3b). In yet another alternative, the total length of the second catalyst region and the first catalyst region can be less than the axial length L, e.g., 95%, 90%, 80%, or 70% or less of the axial length L.

[0041] 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.

[0042] The third catalytic area The catalytic article may further include a third catalytic region.

[0043] The third catalyst region may further comprise a third PGM component, a third oxygen storage capacity (OSC) material, a third alkali metal or alkaline earth metal component, and / or a third inorganic oxide.

[0044] The third PGM component may be selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof, hi some embodiments, the third PGM component may be Pd, Rh, or mixtures thereof.

[0045] The third OSC material may be cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the third OSC material includes ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the third OSC material may further include one or more of dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the third OSC material may function as a support material for the third PGM component. In some embodiments, the third OSC material includes ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0046] The ceria-zirconia mixed oxide may have a weight ratio of zirconia to ceria of at least 50:50, preferably greater than 60:40, more preferably greater than 75:25.Alternatively, the ceria-zirconia mixed oxide may also have a weight ratio of ceria to zirconia less than 50:50, preferably less than 40:60, more preferably less than 25:75.

[0047] The third 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 third catalyst region.

[0048] The loading of the third OSC material in the third catalyst region is 1.5 g / in 3 In some embodiments, the loading of the third OSC material in the second catalytic region can be less than 1.2 g / in 3 Below, 1.0g / in 3 Below, 0.9g / in 3 Below, 0.8g / in 3 or less than 0.7g / in 3 The following is the result.

[0049] The total washcoat loading of the third catalyst region was 3.5 g / in 3 Less than 3.0 g / in3 , 2.5g / in 3 , or 2g / in 3 It could be.

[0050] The third alkali or alkaline earth metal is preferably barium, strontium, a mixed oxide or a composite oxide thereof. Preferably, the barium or strontium, if present, is 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 third catalytic region.

[0051] Even more preferably, the third alkali or alkaline earth metal is strontium, which, when present, is preferably present in an amount of from 0.1 to 15 wt.%, more preferably from 3 to 10 wt.%, based on the total weight of the third catalytic region.

[0052] Also, the third 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% by weight, more preferably 3 to 10% by weight, based on the total weight of the third catalytic region. More preferably, the third alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

[0053] Preferably, the barium or strontium is present as BaCO3 or SrCO3. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0054] The third inorganic oxide is preferably an oxide of an element 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, magnesia, silica, zirconia, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferably, the third inorganic oxide is alumina, lanthanum-alumina, zirconia, or magnesia / alumina composite oxide. One particularly preferred third inorganic oxide is alumina or lanthanum-alumina.

[0055] The third OSC material and the third inorganic oxide can 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.

[0056] 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, more preferably 4:1 to 1:4 or 3:1 to 1:3, and most preferably 2:1 to 1:2.

[0057] In some embodiments, the third OSC material and the third inorganic oxide can have a weight ratio of 2:1 or greater. In further embodiments, the third OSC material and the third inorganic oxide can have a weight ratio of 10:1 or greater. In other further embodiments, the third OSC material and the third inorganic oxide can have a weight ratio of 20:1 or greater, or 30:1 or greater. In yet other further embodiments, the third OSC material and the third inorganic oxide can have a weight ratio of 40:1 or greater, or 50:1 or greater.

[0058] The third catalytic region can extend over 100 percent of the axial length L (see, for example, Figures 4a-4d and 5a-5c).

[0059] The third catalytic region can 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, Figures 6g-6l).

[0060] The second catalyst region can overlap the first catalyst region over 0.1 to 99 percent of the axial length L (see, e.g., Figures 6a-6l), the first catalyst region can be stacked on the second catalyst region, or the second catalyst region can be stacked on the first catalyst region). Alternatively, either the second region or the first region can extend over 30 to 70 percent of the axial length L. Preferably, it can extend over 40 to 60 percent, more preferably 45 to 55 percent, of the axial length L, and most preferably the total length of the second region and the first region is equal to or less than the axial length L (see, e.g., Figures 4a-4d).

[0061] Base material Preferably, the substrate is a flow-through monolith. Alternatively, the substrate can be a wall-flow filter.

[0062] 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., surfaces of walls defining each channel). Each of the plurality of channels has an opening at the first surface and an opening at the second surface. For the avoidance of doubt, the flow-through monolith substrate is not a wall-flow filter.

[0063] The first surface is typically at an inlet end of the substrate and the second surface is at an outlet end of the substrate.

[0064] The channels may be of constant width, and each of the multiple channels may have a uniform channel width.

[0065] 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.

[0066] 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.

[0067] It should be noted that the flow-through monolith substrates described herein are unitary components (i.e., a single brick). Nevertheless, when forming an emission treatment system, the substrates used may be formed by bonding together multiple channels, or by bonding together multiple smaller substrates as described herein. Such techniques, along with suitable casings and configurations of emission treatment systems, are well known in the art.

[0068] In embodiments in which the catalytic article of the present invention includes 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.

[0069] In embodiments in which the catalytic article of the present invention includes 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.

[0070] Another aspect of the present disclosure is a method for producing a NO x The present invention is directed to a method for treating vehicle exhaust gases containing CO, CO, and HC. Catalytic converters equipped with TWCs made according to this method exhibit improved catalytic properties compared to conventional TWCs (having the same PGM loading), and exhibit particularly improved performance under DFSO conditions (see, e.g., the Examples and Table 5).

[0071] Another aspect of the present disclosure is directed to a system for treating vehicle exhaust gases, comprising a catalytic article as described herein along with a conduit for transporting the exhaust gases through the system. In some embodiments, the catalytic article as described herein can be located at the outlet of a close-coupled TWC. In other embodiments, the catalytic article as described herein can be located on an underbody TWC.

[0072] definition The term "region" as used herein refers to an area on a substrate that is typically obtained by drying and / or firing a washcoat. A "region" can be disposed or carried on a substrate as, for example, a "layer" or a "zone." The area or arrangement 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).

[0073] 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 from its average value by more than 10% (e.g., the difference between the maximum and minimum length), preferably a length that does not deviate from its average value by more than 5%, and more preferably a length that does not deviate from its average value by more than 1%.

[0074] Each "region" preferably 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 commonly 1% or less, when comparing one portion of the region to another portion of the region.

[0075] As used herein, the term "zone" refers to a region having a length that is less than the entire length of the substrate, such as a length that is 75% or less of the entire length of the substrate. A "zone" typically has a length that is at least 5% (e.g., 5% or more) of the entire length of the substrate (i.e., a substantially uniform length).

[0076] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0077] Any reference herein to a "zone disposed at the inlet end of a substrate" refers to a zone disposed on or supported by a substrate, which 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, any reference herein to a "zone disposed at the outlet end of a substrate" refers to a zone disposed on or supported by a substrate, which 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.

[0078] 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., an open end) of an inlet channel of the substrate than to the closed end (e.g., a 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.

[0079] 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.

[0080] Similarly, where 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., an open end) of the outlet channel of the substrate than to the closed end (e.g., a 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.

[0081] 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.

[0082] If a washcoat is present on the wall of a wall-flow filter (ie, the zone is within the wall), the zone may satisfy both (a) and (b).

[0083] The term "washcoat" is well known in the art and typically refers to an adherent coating that is applied to a substrate during the production of a catalyst.

[0084] 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. In general, the term "PGM" preferably refers to metals selected from the group consisting of Rh, Pt, and Pd.

[0085] The term "mixed oxide" as used herein generally refers to a mixture of oxides in a single phase, as is 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 is conventionally known in the art.

[0086] 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, e.g., trace impurities, that do not substantially affect the basic properties of the feature. "Consisting essentially of" encompasses the phrase "consisting of."

[0087] The term "substantially free" as used herein with respect to a material typically means that the material is present in a small amount, e.g., 5% by weight or less, preferably 2% by weight or less, more preferably 1% by weight or less, in relation to the contents of a region, layer, or zone. The term "substantially free" encompasses the term "free."

[0088] 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 the context of the contents of a region, layer, or zone. The term "essentially free" encompasses the term "free".

[0089] As used herein, any reference to an amount of dopant expressed as a weight percent, particularly a total amount, refers to the weight of the support material or its refractory metal oxide.

[0090] As used herein, the term "loading" refers to g / ft2 on a metal weight basis. 3 Refers to the measurement in units of .

[0091] 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. EXAMPLES

[0092] Comparative catalyst 1 Comparative catalyst 1 is 4 g / ft 3 Rh, 2g / ft 3 Pt, 1.0g / in 3 La-stabilized alumina and 1.0 g / in 3 The catalyst consisted of OSC materials coated on cordierite substrate. The two PGM nitrate precursors were premixed together and then hydrolyzed on La-stabilized alumina by adjusting the pH to 6-7 with tetraethylammonium hydroxide (TEAOH). 100% Rh and Pt incorporation was confirmed by analyzing the PGM concentration in the supernatant. The OSC slurry was added to the above PGM and alumina slurry followed by concentration. The final WC was then coated on the cordierite substrate, dried and calcined.

[0093] Catalyst 1 of the present invention Catalyst 1 of the present invention has a viscosity of 4 g / ft3 Rh, 2g / ft 3 1.0 g / in 3 ZrO2-Al2O3 composite and 1.0 g / in 3 The catalyst coated on cordierite substrate consisted of OSC materials. Two PGM nitrate precursors were premixed together and then hydrolyzed on ZrO2-Al2O3 composite by adjusting pH to 6-7 with TEAOH. 100% Rh and Pt incorporation was confirmed by analyzing PGM concentration in the supernatant. OSC slurry was added to the above PGM and ZrO2-Al2O3 slurry followed by concentration. The final WC was then coated on cordierite substrate, dried and calcined.

[0094] Catalyst 2 of the present invention Catalyst 1 of the present invention has a viscosity of 4 g / ft 3 Rh, 2g / ft 3 1.0 g / in 3 ZrO2-Al2O3 composite and 1.0 g / in 3 The catalyst consisted of OSC materials coated on cordierite substrate. Two PGM nitrate precursors were premixed together and then hydrolyzed on ZrO2-Al2O3 composite by adjusting pH to 6-7 with TEAOH. 100% Rh and Pt incorporation was confirmed by analyzing PGM concentration in the supernatant. OSC slurry was added to the above PGM and ZrO2-Al2O3 slurry followed by concentration. The final WC was then coated on cordierite substrate, dried and calcined.

[0095] Catalyst 3 of the present invention Catalyst 3 of the present invention has a viscosity of 4 g / ft 3 Rh, 2g / ft 3 1.0 g / in 3 ZrO2-Al2O3 composite and 1.0 g / in 3The catalyst consisted of OSC materials coated on cordierite substrate. Two PGM nitrate precursors were premixed together and then hydrolyzed on ZrO2-Al2O3 composite by adjusting pH to 6-7 with TEAOH. 100% Rh and Pt incorporation was confirmed by analyzing PGM concentration in the supernatant. OSC slurry was added to the above PGM and ZrO2-Al2O3 slurry followed by concentration. The final WC was then coated on cordierite substrate, dried and calcined.

[0096] [Table 1]

[0097] Example 1: Simulated deceleration fuel cut-off test in a reactor Prior to testing, all catalysts were hydrothermally aged at 1000° C. for 40 hours in a laboratory reactor under stoichiometric aging with occasional lean spikes as described below using the gas composition in Table 2. 1. Ramp up to an inlet temperature of 1000°C at 10°C / min using a stoichiometric gas mixture. 2. Five minutes in stoichiometric gas and one minute in lean gas, alternating between stoichiometric and lean modes for 40 hours. 3. Cool to below 400°C with rich gas mixture, then switch to N2 until room temperature.

[0098] [Table 2]

[0099] Decelerated fuel cut-off (DFSO) events in typical transient test cycles such as FTP75, US06, RDEmax, or WLTC have three common characteristics: a) high space velocity, b) high temperature, and c) a lambda swing from lean to rich for the inlet of the near-coupled TWC brick, but lean to stoichiometric for the outlet of the near-coupled TWC and underbody TWC.

[0100] During the simulated DFSO test, the gas flow rate was maintained at a space velocity of about 200,000 / hr. The catalyst inlet temperature was increased from 100°C to 550°C and maintained at the same temperature throughout the test. Once the inlet temperature reached 550°C, gas switching was initiated according to the sequence listed in Table 3. The first half of the test - the "rich recovery" session - was designed to simulate the conditions at the inlet of the proximal coupled TWC brick during a DFSO event. For example, the catalyst was exposed to 12% O2 for 3 minutes to simulate a fuel cut event when the engine's combustion chamber is filled with air during a fuel cut or engine shutdown process. (Step 1) At this time, the Rh and support material in the catalyst were fully oxidized. N2 gas was then flowed through the catalyst to purge the O2 (Step 2), followed by flowing rich gas to recover the Rh catalyst. (Step 3) After further flowing N2 gas, the above sequence (Steps 1-3) was repeated. The second half of the simulated DFSO test - the "stoichiometric recovery" session, in contrast, was designed to simulate the conditions at the outlet of the close-coupled TWC and the underbody TWC. "Stoichiometric recovery" uses the same sequence as "rich recovery", except that "stoichiometric gas" flows past the catalyst surface during the catalyst regeneration step. The exhaust gas composition at each step is listed in Table 4.

[0101] [Table 3]

[0102] [Table 4]

[0103] In the catalyst performance test, at the end of the rich recovery phase and the stoichiometric recovery phase, NO x The NO, CO and THC slips were averaged, respectively. The results are shown in Table 5. x The less CO and THC slip, the more NO xThis indicates that the recovery rate of Rh to the metallic state, which is well known for the reduction of CO and THC, is fast, and therefore indicates good performance as an exhaust gas purification catalyst. All of the catalysts of the present invention using ZrO2-Al2O3 materials produced much less NO than the comparative catalyst 1. x Among the three inventive catalysts, inventive catalyst 2 using 20% ​​ZrO2-Al2O3 is obviously better than the other two, with NO x and THC slip is the smallest. CO slip is the largest among NO x It is noted that the CO slip and THC slip do not seem to follow the same trend. We use high concentrations of CO in both rich (2.28%) and stoichiometric (1.39%) recovery sessions. The mass flow controller (MFC) drifted from run to run, which caused the CO feed gas to be inconsistent. Overall, the CO conversion was about 99.5% or higher for all catalysts, and the difference in CO slip was insignificant.

[0104] [Table 5]

[0105] Another set of catalysts was hydrothermally aged at 1050° C. for 40 hours in a laboratory reactor using the gas composition in Table 6 and the TWC 4-mode redox aging protocol as described below. 1. Ramp up to an inlet temperature of 1050°C at 10°C / min using a stoichiometric gas mixture. 2. Switch gas between stoichiometric mode, lean mode, stoichiometric mode and rich mode for 40 hours with 5 minutes in each mode. 3. Cool to below 400°C with rich gas mixture then switch to N2 until room temperature.

[0106] [Table 6]

[0107] The catalysts aged in TWC4 mode were tested under simulated DFSO conditions to determine NO x The emissions of NO, CO and THC are listed in Table 7. x The advantages of all three inventive catalysts using ZrO2-Al2O3 for controlling NO / THC / CO emissions are very obvious compared to comparative catalyst 1. Among them, inventive catalyst 2 using 20% ​​ZrO2-Al2O3 is significantly better than the other two, and the NO x / THC / CO slip is the smallest.

[0108] [Table 7]

[0109] Example 2: Perturbation ignition test in a reactor Perturbation light-off tests were performed on all aged catalysts using simulated exhaust gas with the composition shown in Table 8. Prior to the perturbation light-off test, the catalysts were pretreated at 700°C in air for 10 minutes and then cooled to 150°C in air. During the perturbation light-off test, the gas flow rate was maintained at a space velocity of about 200,000 / hr. The catalyst inlet temperature was ramped from 150°C to 700°C at a constant rate of 30°C / min and the gas composition was perturbed between lean and rich conditions at 1 Hz.

[0110] [Table 8]

[0111] In the perturbation ignition test, NO x The temperature at which 50% of each of the CO and THC components is converted is called T 50 The lower temperature at which 50% is converted means that the performance of the catalyst as an exhaust gas purification catalyst is better.

[0112] As shown in Table 9 below, the T 50is close to or higher than Comparative Catalyst 1, there is no light-off performance advantage of the catalyst of the present invention using ZrO2-Al2O3 as a replacement for La-alumina.

[0113] [Table 9]

[0114] Deceleration fuel shutoff (DFSO) events and cold start events (light-off) have completely different conditions and therefore different catalyst requirements. A good DFSO catalyst does not guarantee a good cold start emission control function. It is recommended that the PtRh catalyst using ZrO2-Al2O3 as the support material should be located either at the outlet of the close-coupled TWC or the underbody TWC, not at the inlet of the close-coupled TWC, which plays an essential role in cold start emission control.

Claims

1. 1. A catalytic article for treating exhaust gases, comprising: a substrate including an inlet end and an outlet end having an axial length L; a first catalyst region comprising a first platinum group metal (PGM) component supported on a first PGM support material, the first PGM component comprising platinum and rhodium, the first PGM support material being selected from the group consisting of ZrO ２ -Al ２ O ３ and a first catalytic region comprising:

2. The ZrO ２ -Al ２ O ３ 1 to 50 wt. % ZrO ２ The catalytic article of claim 1 comprising:

3. The ZrO ２ -Al ２ O ３ The catalytic article of claim 1 or 2, wherein may further comprise La, Mn, Cu, Ti, or Ni.

4. 3. The catalytic article of claim 1 or 2, wherein the first PGM component is selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof.

5. The catalytic article of claim 4 , wherein the first PGM component comprises Pt and Rh.

6. The ZrO ２ -Al ２ O ３ The catalytic article according to claim 1 or 2, wherein the catalyst is substantially free of Ce.

7. The total PGM loading in the first catalyst region is up to 50 g / ft ３ 3. The catalytic article of claim 1 or 2, wherein:

8. The catalytic article of claim 1 or 2, wherein the first catalytic region further comprises a first oxygen storage capacity (OSC) material.

9. 9. The catalytic article of claim 8, wherein the first OSC material is cerium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof.

10. 3. The catalytic article of claim 1 or 2, wherein the first catalytic region is substantially free of alkaline earth metals.

11. The catalytic article of claim 1 or 2, further comprising a second catalytic region.

12. 12. The catalytic article of claim 11, wherein the second catalytic region comprises a second PGM component, a second OSC material, and / or a second inorganic oxide.

13. 13. The catalytic article of claim 12, wherein the second PGM component is selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof.

14. 13. The catalytic article of claim 12, wherein the second OSC material is cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof.

15. 13. The catalytic article of claim 12, wherein the second inorganic oxide is selected from the group consisting of alumina, magnesia, silica, zirconia, lanthanum, cerium, neodymium, praseodymium, yttrium oxides, and mixed or composite oxides thereof.

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