Trace transition metal-containing 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 are disclosed. The catalyst article for treating exhaust gases includes 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 and a first transition metal component, wherein the first PGM component includes platinum (Pt), the first transition metal component is Fe or Cu, and the molar ratio of Pt to the first transition metal is between 0.2 and 10.0.

Description

[Technical Field]

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

[0002] In an internal combustion engine, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x The exhaust gas produced by the engine contains various pollutants, including CO, CO₂, CO₂, and CO₂. Emissions control systems 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 a gasoline engine is the TWC (three way catalyst). The TWC performs three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) oxidation of NO₂. x The reduction is carried out.

[0003] Despite advances in TWC technology, there remains a need for improved catalytic converters for specific engine platforms that simultaneously improve performance during the cold start phase, provide better light-off performance, and provide a better window of performance for air-to-fuel ratios (A / F) during the hot transient phase. Flexible use of Pd and / or Pt in TWCs is necessary to mitigate potential risks of PGM price fluctuations and to conserve and efficiently use natural PGM resources. In particular, Pt has disadvantages in TWC performance compared to Pd. The present invention addresses these issues, among others. Summary of the Invention

[0004] One aspect of the present disclosure relates to a catalyst composition comprising a platinum group metal (PGM) component and a transition metal component, wherein the PGM component comprises platinum (Pt), the transition metal component is Fe or Cu, and the molar ratio of Pt to the transition metal is 0.2 to 10.0.

[0005] Another aspect of the present disclosure relates to a catalyst article for treating exhaust gases, the catalyst article comprising: a substrate including an inlet end and an outlet end having an axial length L; and a first catalyst region comprising a first platinum group metal (PGM) component and a first transition metal component, wherein the first PGM component comprises platinum (Pt), the first transition metal component is Fe or Cu, and the molar ratio of Pt to the first transition metal is between 0.2 and 10.0.

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

[0007] The present invention also encompasses treating 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 explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows an embodiment according to the present invention containing a first catalyst region (single layer) having a length of 100% of the axial length L of the substrate. [Figure 2a] FIG. 1 shows an embodiment according to the invention in which a first catalyst region is a bottom layer and extends over 100% of the axial length L, and a second catalyst region is a top layer and extends over 100% of the axial length L. [Figure 2b] FIG. 2b is a diagram of 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] FIG. 3b is a diagram of 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] FIG. 3c is a diagram of a variation of FIG. [Figure 4a] 1 is a graph showing the state of Pt for Comparative Catalyst A and Catalyst C as evaluated by X-ray diffraction (XRD). [Figure 4b] 1 is a graph showing the state of Pt for Comparative Catalyst A and Catalyst F as assessed by XRD. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention is directed to the catalytic treatment of combustion exhaust gases, such as those produced by gasoline and other engines, and related catalyst compositions, catalyst articles, and systems. More specifically, the present invention relates to the treatment of NO in vehicle exhaust systems. xThe present invention relates to the simultaneous treatment of CO, CO, and HC. While most technological developments in TWCs have focused on Pd-based catalysts, the heavy reliance on Pd has caused serious economic and environmental problems, such as a dramatic increase in PGM prices and the depletion of natural PGM resources. While the use of Pt is a promising approach to achieving flexible utilization of Pd and / or Pt, the potentially lower catalytic activity of Pt in TWCs has been identified as a significant technical problem. The present inventors surprisingly discovered the functionalization of Pt-based catalysts by doping with transition metal components, Fe or Cu. The present inventors discovered that the potential performance of TWCs under light-off and air-fuel window performance tests can be improved by this invention. The process of the present invention also conserves natural PGM resources, contributing to economic benefits and environmental sustainability.

[0010] One aspect of the present disclosure relates to a catalyst composition comprising a platinum group metal (PGM) component and a transition metal component, wherein the PGM component comprises platinum (Pt), the transition metal component is Fe or Cu, and the molar ratio of Pt to the transition metal is 0.2 to 10.0.

[0011] Through intensive research, the inventors have found that by incorporating small amounts of transition metals (such as Fe or Cu) (“TM”) into Pt-containing TWC catalyst compositions, these novel compositions demonstrated superior catalytic properties (e.g., THC / NMHC, CO, and NO). x All catalytic conversions of can be improved by doping TM into Pt-based catalysts as described in this invention).

[0012] The molar ratio of Pt to transition metal is based on the elemental metal. In some embodiments, the molar ratio of Pt to transition metal in the catalyst composition can be 0.2 to 5.0, 0.5 to 5.0, 0.2 to 3.0, or 0.2 to 2.0.

[0013] In some embodiments, the PGM component may further comprise palladium, rhodium, or a combination thereof, hi other embodiments, the catalyst composition is essentially free of other PGM components other than platinum.

[0014] The catalyst composition may further comprise an oxygen storage capacity (OSC) material and / or an inorganic oxide.

[0015] The OSC material may be cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the 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 oxide, neodymium oxide, praseodymium oxide, or yttrium oxide. Additionally, the OSC material may function as a support material for the PGM components. In some embodiments, the OSC material comprises ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0016] The inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, or 14. The inorganic oxide is preferably selected from the group consisting of alumina, magnesia, silica, zirconia, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferred inorganic oxides are alumina, lanthanum-alumina, zirconia, or magnesia / alumina composite oxides. One particularly preferred inorganic oxide is alumina or lanthanum-alumina.

[0017] The OSC material and 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.

[0018] Alternatively, the OSC material and 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.

[0019] In some embodiments, the OSC material and inorganic oxide may have a weight ratio of 2:1 or greater. In further embodiments, the OSC material and inorganic oxide may have a weight ratio of 10:1 or greater. In other further embodiments, the OSC material and inorganic oxide may have a weight ratio of 20:1 or greater, or 30:1 or greater. In yet other further embodiments, the OSC material and inorganic oxide may have a weight ratio of 40:1 or greater, or 50:1 or greater.

[0020] The catalyst composition may further comprise an alkali metal or alkaline earth metal. In some embodiments, the catalyst composition may be substantially free of alkali metals or alkaline earth metals.

[0021] The alkali metal or alkaline earth metal is preferably barium or strontium, and mixed oxides or composite oxides thereof. Preferably, barium or strontium, if present, is supported in an amount of 0.1 to 15 wt. %, more preferably 3 to 10 wt. %, of barium or strontium, based on the total weight of the catalyst composition.

[0022] Preferably, the barium or strontium is present as BaCO or SrCO. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0023] In some embodiments, the Pt loading in the catalyst composition can be 0.2-10 wt %, 0.5-5 wt %, or 1-5 wt %.

[0024] The TM may be incorporated into the catalyst composition in a variety of ways. In some embodiments, the TM may be incorporated into the OSC material as a dopant. In other embodiments, the TM may be incorporated into the inorganic oxide as a dopant. In still other embodiments, the TM may be incorporated into the catalyst composition as a simple physical mixture (e.g., a physical blend). For example, the TM may be incorporated as an oxide that is physically blended with the OSC material and / or the inorganic oxide. In other embodiments, the TM may be incorporated into the framework of the OSC material (e.g., the TM doped into the crystal lattice of the OSC solid solution material as formed). In certain embodiments, the TM may be incorporated into the catalyst composition in any combination of the embodiments described above; for example, in some embodiments, at least a portion of the TM component may be supported on an inorganic oxide.

[0025] In some embodiments, the catalyst composition may comprise no more than 10 wt. %, no more than 5 wt. %, or no more than 2 wt. % of the TM component (on an elemental basis) based on the total weight of the catalyst composition.

[0026] Throughout this application, "wt% of TM" is calculated on an elemental basis.

[0027] As demonstrated in the examples below, the catalyst composition in this embodiment can be applied as a TWC catalyst for treating exhaust gases produced by gasoline engines.

[0028] Another aspect of the present disclosure relates to a catalyst article for treating exhaust gases, the catalyst article comprising: a substrate including an inlet end and an outlet end having an axial length L; and a first catalyst region comprising a first platinum group metal (PGM) component and a first transition metal component, wherein the first PGM component comprises platinum (Pt), the first transition metal component is Fe or Cu, and the molar ratio of Pt to the first transition metal is between 0.2 and 10.0.

[0029] First catalytic region The molar ratio of Pt to the first transition metal is based on the elemental metal. In some embodiments, the molar ratio of Pt to the first transition metal in the catalyst composition can be 0.2 to 5.0, 0.5 to 5.0, 0.2 to 3.0, or 0.2 to 2.0.

[0030] In some embodiments, the first PGM component may further comprise palladium, rhodium, or a combination thereof, hi other embodiments, the first catalytic region is essentially free of other PGM components other than platinum.

[0031] The first catalytic region may further include a first oxygen storage capacity (OSC) material and / or a first inorganic oxide.

[0032] The first OSC material can 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 oxide, neodymium oxide, praseodymium oxide, or yttrium oxide. The first OSC material may also function as a support material for the first PGM component (e.g., as the first PGM support material). In some embodiments, the first OSC material comprises ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

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

[0034] The first OSC material and the first 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 first OSC material and the first inorganic oxide can have a weight ratio of 10:1 to 1:10, preferably 8:1 to 1:8 or 5:1 to 1:5, more preferably 4:1 to 1:4 or 3:1 to 1:3, and most preferably 2:1 to 1:2.

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

[0037] The first catalyst region may further comprise a first alkali metal or alkaline earth metal. In some embodiments, the first catalyst region may be substantially free of the first alkali metal or alkaline earth metal. The first alkali metal or alkaline earth metal is preferably barium or strontium, and mixed oxides or composite oxides thereof. Preferably, barium or strontium, if present, is supported in an amount of 0.1 to 15 wt. %, more preferably 3 to 10 wt. %, based on the total weight of the first catalyst region.

[0038] Preferably, the barium or strontium is present as BaCO or SrCO. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0039] In some embodiments, the Pt loading in the first catalyst region is between 5 and 300 g / ft 3 , 10~200g / ft 3 , or 50 to 150 g / ft 3 It could be.

[0040] The TM may be incorporated into the first catalyst region in a variety of ways. In some embodiments, the TM may be incorporated into the first OSC material as a dopant. In other embodiments, the TM may be incorporated into the first inorganic oxide as a dopant. In still other embodiments, the TM may be incorporated into the first catalyst region as a simple physical mixture (e.g., a physical blend). For example, the TM may be incorporated as an oxide that is physically blended with the first OSC material and / or the first inorganic oxide. In other embodiments, the TM may be incorporated into the framework of the first OSC material (e.g., the TM doped into the crystal lattice of the OSC solid solution material as it is formed). In certain embodiments, the TM may be incorporated into the first catalyst region in any combination of the embodiments described above; for example, in some embodiments, at least a portion of the TM component may be supported on the first inorganic oxide.

[0041] In some embodiments, the first catalytic region may be no more than 10 wt. %, no more than 5 wt. %, or no more than 2 wt. % of the first TM component (on an elemental basis).

[0042] 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 gasoline engines.

[0043] The first catalyst region can extend over 100 percent of the axial length L (see, e.g., Figures 1, 2a, and 2b). In some embodiments, the first catalyst region can extend over 20 to 99 percent, 30 to 90 percent, or 40 to 80 percent of the axial length L. Alternatively, the first catalyst region can extend over 30 to 70 percent of the axial length L. Preferably, the first catalyst region extends over 40 to 60 percent, and more preferably, over 45 to 55 percent of the axial length L (see, e.g., Figures 3a-3d).

[0044] The total washcoat loading of the first catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 or 2.5 g / in 3 Alternatively, the total washcoat loading of the first catalyst region can be between 0.5 and 3.5 g / in 3 Preferably, it is 0.6 to 3 g / in 3 or 0.7 to 2.5 g / in 3 It could be.

[0045] Second catalytic region The catalytic article may further include a second catalytic region.

[0046] 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.

[0047] 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.

[0048] The second OSC material can 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 can further include one or more dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material can 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.

[0049] The ceria-zirconia mixed oxide may have a weight ratio of ceria to zirconia 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.

[0050] The second OSC material (e.g., 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.

[0051] 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 catalyst 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.

[0052] The second alkali metal or alkaline earth metal is preferably barium, strontium, or a mixed oxide or composite oxide thereof. Preferably, the barium or strontium, if present, is in an amount of 0.1 to 15 wt. % barium or strontium, more preferably 3 to 10 wt. % barium or strontium, based on the total weight of the second catalyst region.

[0053] Even more preferably, the second alkali metal or alkaline earth metal is strontium, which, when present, is preferably present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the second catalyst region.

[0054] The second alkali metal or alkaline earth metal is preferably a mixed oxide or composite oxide of barium and strontium. Preferably, the mixed oxide or composite oxide of barium and strontium is present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the second catalyst region. More preferably, the second alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

[0055] Preferably, the barium or strontium is present as BaCO or SrCO. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0056] The second inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, and 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 preferred is alumina, lanthanum-alumina, zirconia, or a magnesia / alumina composite oxide. One particularly preferred second inorganic oxide is alumina or lanthanum-alumina.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] The total washcoat loading of the second catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 or 2.5 g / in 3 Alternatively, the total washcoat loading of the first catalyst region can be between 0.5 and 3.5 g / in 3 Preferably, it is 0.6 to 3 g / in 3 or 0.7 to 2.5 g / in 3 It could be.

[0061] The second catalytic region can extend over 100 percent of the axial length L (see, eg, Figures 2a and 2b).

[0062] The second catalyst region can extend over 30 to 70 percent of the axial length L. Preferably, it extends 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 and first regions is equal to or greater than the axial length L (see, e.g., Figures 3a-3d).

[0063] 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 3c and 3d; 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., Figures 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.

[0064] 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.

[0065] The catalyst article of the present invention may contain additional components known to those skilled in the art. For example, the composition of the present invention may further comprise at least one binder and / or at least one surfactant. When a binder is present, a dispersible alumina binder is preferred.

[0066] Base material Preferably, the substrate is a flow-through monolith. Alternatively, the substrate can be a wall-flow filter.

[0067] The flow-through monolith substrate has a first surface and a second surface defining a longitudinal direction therebetween. The flow-through monolith substrate has a plurality of channels extending between the first surface and the second surface. The plurality of channels extend longitudinally and provide a plurality of interior surfaces (e.g., wall surfaces defining each channel). Each of the plurality of channels has an opening in the first surface and an opening in the second surface. For the avoidance of doubt, the flow-through monolith substrate is not a wall-flow filter.

[0068] The first surface is typically at the inlet end of the substrate and the second surface is at the outlet end of the substrate.

[0069] The channels may be of constant width, and each of the plurality of channels may have a uniform channel width.

[0070] 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 the open first channels and closed second channels is 600 to 700 channels per square inch. These channels can have cross sections that are rectangular, square, circular, oval, triangular, hexagonal, or other polygonal shapes.

[0071] 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.

[0072] It should be noted that the flow-through monolith substrates described herein are single components (i.e., a single brick). Nevertheless, when forming waste treatment systems, the substrates used may be formed by bonding multiple channels together, or by bonding multiple smaller substrates together as described herein. Such techniques, along with suitable casings and configurations of waste treatment systems, are well known in the art.

[0073] In embodiments in which the catalyst article of the present invention comprises a ceramic substrate, the ceramic substrate can 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.

[0074] In embodiments in which the catalytic article of the present invention comprises a metal substrate, the metal substrate may be made of any suitable metal, particularly heat-resistant metals and metal alloys such as titanium and stainless steel, and ferritic alloys containing iron, nickel, chromium, and / or aluminum in addition to other trace metals.

[0075] Another aspect of the present disclosure is a method for producing NOx using the catalytic articles described herein. x The present invention is directed to a method for treating vehicle exhaust gases containing PGMs, CO, and HC. Catalytic converters equipped with TWCs produced according to this method exhibit improved catalytic properties compared to conventional TWCs (having the same PGM loading), and also exhibit improved performance, particularly during cold start phases, and better THC light-off performance (see, e.g., Examples 1-2 and Tables 2-4).

[0076] Another aspect of the present disclosure is directed to a system for treating vehicle exhaust gases that includes a catalytic article as described herein along with a conduit for transporting the exhaust gases through the system.

[0077] definition The term "region," as used herein, refers to an area on a substrate that is typically obtained by drying and / or baking a washcoat. A "region" may be disposed or carried on the 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).

[0078] 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 (e.g., the difference between the maximum and minimum length) by more than 10%, 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%.

[0079] Preferably, each "region" has a substantially uniform composition (i.e., there is no substantial difference in the composition of the washcoat when comparing one portion of the region to another portion of the region). Substantially uniform composition in this context refers to a material (e.g., region) that has a composition difference of 5% or less, usually 2.5% or less, and most commonly 1% or less when comparing one portion of the region to another portion of the region.

[0080] The term "zone," as used herein, refers to a region having a length less than the entire length of the substrate, such as a length of 75% or less of the entire length of the substrate. A "zone" typically has a length of at least 5% (e.g., 5% or more) of the entire length of the substrate (i.e., a substantially uniform length).

[0081] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0082] As used herein, any reference to a "zone disposed at the inlet end of the substrate" refers to a zone disposed on or carried by a substrate that is closer to the inlet end of the substrate than to the outlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the inlet end of the substrate than to the outlet end of the substrate. Similarly, as used herein, any reference to a "zone disposed at the outlet end of the substrate" refers to a zone disposed on or carried by a substrate that is closer to the outlet end of the substrate than to the inlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the outlet end of the substrate than to the inlet end of the substrate.

[0083] 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 carried by the substrate, (a) a zone that is closer to the inlet end (e.g., open end) of an inlet channel of a substrate than to the closed end (e.g., blocked or plugged end) of the inlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an outlet channel of a substrate than to the outlet end (e.g., open end) of the outlet channel.

[0084] 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.

[0085] Similarly, when the substrate is a wall-flow filter, any reference to "a zone disposed at the outlet end of the substrate" includes a zone disposed on or carried by the substrate, (a) a zone that is closer to the outlet end (e.g., open end) of the outlet channel of the substrate than to the closed end (e.g., blocked or plugged end) of the outlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an inlet channel of a substrate than to the inlet end (e.g., open end) of the inlet channel.

[0086] 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.

[0087] When the 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).

[0088] The term "washcoat" is well known in the art and typically refers to an adherent coating applied to a substrate during the production of a catalyst.

[0089] 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.

[0090] The term "mixed oxide," as used herein, generally refers to a mixture of oxides in a single phase, as conventionally known in the art. The term "complex oxide," as used herein, generally refers to a composition of oxides having two or more phases, as conventionally known in the art.

[0091] The phrase "consisting essentially of," as used herein, 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. The phrase "consisting essentially of" encompasses the phrase "consisting of."

[0092] The term "substantially free," as used herein with respect to a material, typically means a small amount of material relative to the contents of a region, layer, or zone, such as 5% by weight or less, preferably 2% by weight or less, and more preferably 1% by weight or less. The term "substantially free" encompasses the term "free."

[0093] The term "essentially free," when used herein with respect to a material, typically means that the material is present in trace amounts relative to the contents of a region, layer, or zone, such as 1% by weight or less, preferably 0.5% by weight or less, and more preferably 0.1% by weight or less. The term "essentially free" encompasses the term "free."

[0094] As used herein, any reference to an amount, particularly a total amount, of dopant expressed as a weight percent refers to the weight of the support material or refractory metal oxide thereof.

[0095] The term "loading" as used herein refers to g / ft on a metal weight basis. 3 Refers to a measurement in units of .

[0096] The following examples are merely illustrative of the present invention, and those skilled in the art will recognize many variations that are within the spirit and scope of the claims. [Example]

[0097] Example 1: Improvement of light-off and A / F window performance by Fe doping Comparison catalyst A: Comparative Catalyst A is a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalytic region consists of Pt supported on a washcoat of CeZr mixed oxide and La-stabilized alumina using a Pt nitrate precursor. The washcoat loading of the catalytic region is approximately 2 g / in. 3 and the Pt loading is 100 g / ft 3 It was.

[0098] Catalyst B: Catalyst B is a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalytic region consists of Pt supported on a washcoat of CeZr mixed oxide and La-stabilized alumina using a Pt nitrate precursor. The washcoat loading in the catalytic region is approximately 2 g / in. 3 and the Pt loading is 100 g / ft 3 The Fe content was 0.1 wt % (calculated as Fe), and the molar ratio of Pt to Fe was 10:1.

[0099] Catalyst C: Catalyst C is a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalytic region consists of Pt supported on a washcoat of CeZr mixed oxide and La-stabilized alumina using a Pt nitrate precursor. The washcoat loading of the catalytic region is approximately 2 g / in. 3 and the Pt loading is 100 g / ft 3 The Fe content was 1.0 wt % (calculated as Fe), and the molar ratio of Pt to Fe was 0.8:1.

[0100] Catalyst D: Catalyst D is a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalytic region consists of Pt supported on a washcoat of CeZr mixed oxide and La-stabilized alumina using a Pt nitrate precursor. The washcoat loading in the catalytic region is approximately 2 g / in. 3 and the Pt loading is 100 g / ft3 The Fe content was 5.0 wt % (calculated as Fe), and the molar ratio of Pt to Fe was about 0.2:1.

[0101] Comparative Catalyst A and Comparative Catalysts B-D were tested separately in a Synthetic Catalyst Activity Test (SCAT) apparatus. Light-off performance was tested with a gas flow of 5% by volume HO + 15% by volume CO + 0.2% by volume H + 1260 ppm C CH + 0.6% by volume CO + 0.6% by volume O + 1000 ppm NO, with the balance being N. The temperature gradient was 20°C / min. HC, CO, and NO x The conversion rate was calculated by comparing the concentration of the feed gas with the concentration of the gas at the catalyst outlet. Comparative catalyst A and catalysts B to D were hydrothermally aged at 1050°C for 4 hours under the redox conditions in Table 1.

[0102] [Table 1]

[0103] HC, CO, and T of aged catalysts A and B to D 80 Light-off temperature and NO x The light-off conversions at η=320° C. are shown in Table 2. Catalyst C of the present invention provides significantly improved light-off performance compared to Comparative Catalyst A, with T values ​​about 15° C. and about 8° C. lower for HC and CO, respectively. 80 (T 80 is the temperature at which the conversion rate reaches 80%), NO x is about 3% higher at η=320°C (η=320°C is the conversion when the temperature reaches 320°C).

[0104] [Table 2]

[0105] The A / F window performance of Comparative Catalyst A and Catalyst C by SCAT was tested at gas flows of A / F = 15.4 (10 vol% H2O + 14 vol% CO2 + 0.17 vol% H2 + 1200 ppm C3H6 + 0.5 vol% CO + 1.54 vol% O2 + 500 ppm NO, balance N2) to A / F = 14.0 (10 vol% H2O + 14 vol% CO2 + 0.7 vol% H2 + 1200 ppm C3H6 + 2.11 vol% CO + 0.5 vol% O2 + 500 ppm NO, balance N2). The temperature was 300°C / min. Rich CO and rich NO x The conversion of CO and NO was calculated by comparing the concentration of the feed gas with the concentration of the gas at the catalyst outlet. x The conversions of CO and NO are shown in Table 2. Catalyst C of the present invention showed significantly improved rich CO and rich NO conversions when compared to Comparative Catalyst A. x gave the performance of

[0106] [Table 3]

[0107] The state of Pt in Comparative Catalyst A and Catalyst C was evaluated by X-ray diffraction (XRD). As shown in Figure 4a, a peak attributed to Pt particles was obtained around 39.7° for Comparative Catalyst A, while Pt-Fe alloy formation was observed for Catalyst C, with a diffraction peak around 40.3°.

[0108] Example 2: Improving light-off performance by Cu doping Catalyst E: Catalyst E is a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalytic region consists of Pt supported on a washcoat of CeZr mixed oxide and La-stabilized alumina using a Pt nitrate precursor. The washcoat loading in the catalytic region is approximately 2 g / in. 3 and the Pt loading is 100 g / ft 3The Cu content was 0.2 wt % (calculated as Cu), and the molar ratio of Pt to Cu was 5:1.

[0109] Catalyst F: Catalyst F is a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalytic region consists of Pt supported on a washcoat of CeZr mixed oxide and La-stabilized alumina using a Pt nitrate precursor. The washcoat loading of the catalytic region is approximately 2 g / in. 3 and the Pt loading is 100 g / ft 3 The Cu content was 0.5 wt % (calculated as Cu), and the molar ratio of Pt to Cu was 2:1.

[0110] Catalyst G: Catalyst G is a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalytic region consists of Pt supported on a washcoat of CeZr mixed oxide and La-stabilized alumina using a Pt nitrate precursor. The washcoat loading in the catalytic region is approximately 2 g / in. 3 and the Pt loading is 100 g / ft 3 The Cu content was 1.0 wt % (calculated as Cu), and the molar ratio of Pt to Cu was 1:1.

[0111] Comparative Catalyst A and Comparative Catalysts E-G were tested separately in a Synthetic Catalytic Activity Test (SCAT) apparatus. Light-off performance was tested with a gas flow of 10% by volume H2O + 15% by volume CO2 + 0.2% by volume H2 + 1260 ppm C3H6 + 0.6% by volume CO + 0.6% by volume O2 + 1000 ppm NO, with the balance being N2. The temperature gradient was 20°C / min. HC, CO, and NO x The conversion rate was calculated by comparing the concentration of the feed gas with the concentration of the gas at the catalyst outlet. Comparative catalyst A and catalysts G to I were hydrothermally aged at 1050°C for 4 hours under the redox conditions in Table 1.

[0112] HC, CO T of aged catalyst A and catalysts F to G50 Light-off temperature and NO x The light-off conversions at η=300° C. are shown in Table 4. Surprisingly, inventive catalyst F provided significantly improved light-off performance compared to comparative catalyst A, with T values ​​about 92° C. and about 85° C. lower for HC and CO, respectively. 50 (T 50 is the temperature at which the conversion rate reaches 50%. x The conversion performance observed was between Comparative Catalyst A and Catalyst F.

[0113] [Table 4]

[0114] The state of Pt in Comparative Catalyst A and Catalyst F was evaluated by XRD. As shown in Figure 4b, a peak at around 39.8° attributed to Pt particles was obtained for Comparative Catalyst A, while for Catalyst F, the formation of a Pt-Cu alloy was observed, with a diffraction peak at around 40.3°.

Claims

1. A catalyst composition comprising a platinum group metal (PGM) component and a transition metal component, wherein the PGM component comprises platinum (Pt), the transition metal component is Fe or Cu, and the molar ratio of Pt to the transition metal is 0.2 to 10.

0.

2. 10. The catalyst composition of claim 1, further comprising an oxygen storage capacity (OSC) material, an inorganic oxide, and / or an alkali metal or alkaline earth metal.

3. 3. The catalyst composition of claim 2, wherein the OSC material is selected from the group consisting of cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.

4. 4. The catalyst composition according to claim 2 or 3, wherein the inorganic oxide is selected from the group consisting of alumina, magnesia, silica, ceria, barium oxide, and mixed or composite oxides thereof.

5. 5. The catalyst composition according to claim 2, wherein the alkali metal or alkaline earth metal is barium or strontium, or a mixed oxide or composite oxide thereof.

6. The catalyst composition of any one of claims 2 to 4, wherein the catalyst composition is substantially free of barium.

7. The catalyst composition of any one of claims 1 to 6, wherein the PGM component further comprises palladium, rhodium, or a mixture thereof.

8. The catalyst composition according to any one of claims 2 to 7, wherein the amount of Pt supported is 0.2 to 10 wt%.

9. 9. The catalyst composition according to claim 1, wherein the molar ratio of Pt to the transition metal is from 0.2 to 5.

0.

10. The catalyst composition according to any one of claims 1 to 9, which is a three-way catalyst (TWC).

11. 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 catalytic region comprising a first platinum group metal (PGM) component and a first transition metal component, wherein the first PGM component comprises platinum (Pt), the first transition metal component is Fe or Cu, and the molar ratio of Pt to the first transition metal is 0.2 to 10.

0.

12. 12. The catalytic article of claim 11, wherein the first catalytic region further comprises a first oxygen storage capacity (OSC) material and / or a first inorganic oxide.

13. The catalytic article of claim 12, wherein the first OSC material is selected from the group consisting of cerium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.

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

15. The catalytic article of any one of claims 11 to 14, wherein the molar ratio of Pt to the first transition metal in the first catalytic region is from 0.2 to 5.

0.

16. The catalytic article of any one of claims 11 to 15, wherein the first catalytic region contains 0.1 to 10 wt% of the first transition metal component on an elemental basis.

17. The amount of Pt loaded in the first catalyst region is 5 to 300 g / ft ３ The catalyst article according to any one of claims 11 to 16, wherein

18. The catalyst article of any one of claims 11 to 17, wherein the first PGM component further comprises Pd, Rh, or a combination thereof.

19. The catalytic article of any one of claims 11 to 18, further comprising a second catalytic region.

20. 20. The catalytic article of claim 19, wherein the second catalytic region comprises a second PGM component.

21. 21. The catalytic article of claim 20, wherein the second PGM component is selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof.

22. The catalytic article of any one of claims 19 to 21, wherein the second catalytic region further comprises a second OSC material and / or a second inorganic oxide.

23. 23. The catalytic article of claim 22, wherein the second OSC material is selected from the group consisting of cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.

24. 24. The catalytic article of claim 22 or claim 23, wherein the second inorganic oxide is selected from the group consisting of alumina, magnesia, silica, zirconia, lanthanum oxide, cerium oxide, neodymium oxide, praseodymium oxide, yttrium oxide, and mixed or composite oxides thereof.

25. The catalyst article of any one of claims 11 to 24, wherein the first catalyst region extends over the axial length L.

26. The catalytic article of any one of claims 19 to 25, wherein the second catalytic region extends over the axial length L.

27. 27. The catalytic article of claim 25 or 26, wherein the first catalytic region is supported / deposited directly on the substrate.

28. 27. The catalytic article of claim 25 or 26, wherein the second catalytic region is supported / deposited directly on the substrate.

29. The catalyst article of any one of claims 11 to 24, wherein the first catalyst region extends over less than the axial length L.

30. The catalyst article of any one of claims 19 to 25, wherein the second catalyst region extends over less than the axial length L.

31. 31. The catalytic article of claim 29 or 30, wherein the first catalytic region is supported / deposited directly on the substrate.

32. 31. The catalytic article of claim 29 or 30, wherein the second catalytic region is supported / deposited directly on the substrate.

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