Transition metal incorporated alumina for improved three-way catalysts.

Abstract

A three-way catalyst article and its use in an exhaust system for an internal combustion engine are disclosed. Specifically, the catalyst article for treating exhaust gases includes a substrate having an axial length L and including an inlet end and an outlet end, and a first catalyst region on the substrate, wherein the first catalyst region includes a first PGM component and a first alumina, the first alumina being doped with 0.01 to less than 5.0 wt. % Ta, based on the total weight of the doped alumina.

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 a three-way catalyst (TWC). The TWC performs three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) oxidation of NO₂. x is reduced.

[0003] Despite advances in TWC technology, there remains a need for improved catalytic converters for specific engine platforms that simultaneously improve performance during cold start phases, provide better light-off performance, and provide better OSC performance during hot transient phases with a wide range of Pt, Pd, and / or Rh applications. The present invention addresses these problems, among others. Summary of the Invention

[0004] One aspect of the present disclosure is directed to a catalytic article for treating exhaust gases, comprising: a substrate having an axial length L and including an inlet end and an outlet end; and a first catalytic region on the substrate, wherein the first catalytic region comprises a first PGM component and a first alumina, the first alumina being doped with from 0.01 to less than 5.0 wt. % Ta, based on the total weight of the doped alumina.

[0005] The present invention also includes an exhaust gas treatment system for treating a combustion exhaust gas stream, the exhaust gas treatment system comprising a catalytic article of the present invention.

[0006] The present invention also includes a fuel combustion and exhaust gas treatment system comprising an engine and an exhaust gas treatment system of the present invention.

[0007] The present invention also includes a method for treating exhaust gases from an internal combustion engine, comprising contacting the exhaust gases with a catalytic article of the present invention. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows an embodiment according to the present invention, including a first catalyst region (single layer) having a length of 100% of the axial length L of the substrate. [Figure 2] 1 shows an embodiment according to the invention in which the first catalyst region is a lower layer and extends over 100% of the axial length L, and the second catalyst region is an upper layer and extends over 100% of the axial length L. 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 to improve TWC performance have focused on increasing the thermal stability of alumina support materials by doping with lanthanum or other rare earth elements, the present inventors have surprisingly discovered that modifying alumina materials with tantalum can further impact the improved light-off performance and resulting emissions control performance of TWCs. The present inventors have discovered that the potential performance of TWCs under light-off tests and their actual performance under emissions control tests are improved by the present invention. The process of the present invention can also significantly reduce the PGM loading requirements in TWCs, thereby conserving valuable natural resources and reducing the cost of catalyst products.

[0010] One aspect of the present disclosure is directed to a catalytic article for treating exhaust gases, comprising: a substrate having an axial length L and including an inlet end and an outlet end; and a first catalytic region on the substrate, wherein the first catalytic region comprises a first PGM component and a first alumina, the first alumina being doped with from 0.01 to less than 5.0 wt. % Ta, based on the total weight of the doped alumina.

[0011] Through intensive research, the inventors have surprisingly found that by doping the first alumina with Ta, particularly with 0.01 to less than 5.0 wt. % Ta, based on the total weight of the doped alumina, these novel compositions can exhibit excellent catalytic properties (e.g., by using the catalysts described herein, emissions, THC / NMHC, CO, and NOx were reduced during vehicle testing). x (One or more of the following emissions can be significantly reduced.) More specifically, doping alumina with Ta surprisingly reduces NO xThe light-off temperature for NOx and THC conversion was found to improve even more significantly after lean orientation aging (e.g., 1000°C for 4 hours). This improvement was noted relative to a reference catalyst containing La-doped alumina, Ta2O5 as the sole support material, and a mixture of 87 wt% La-doped alumina and 13 wt% Ta2O5, each with Rh supported thereon. The Ta-doped sample of the present invention exhibited excellent results at all temperatures, but specifically at NOx. x and THC at lower temperatures (i.e., lower light-off temperatures). Catalysts containing Ta2O5 as the sole support material provide significantly lower THC and NO2, especially at higher temperatures. x Conversion rate, especially NO x It has a conversion rate.

[0012] A slight improvement may also be seen for the catalyst of the present invention after redox aging.

[0013] Moreover, surprisingly, the above effects that can be imparted by doping alumina with Ta can be greater than the effects imparted by doping alumina with other transition metals such as Zr, Mo, W, Ti, and / or Nb.

[0014] Without wishing to be bound by theory, doping Ta into alumina can increase the hydrothermal stability of alumina, and then the lean orientation and oxidation-reduction, aging, etc., can prevent NO from being generated even after high temperatures. x and may maintain its interaction with the supported Rh, which is beneficial for THC conversion.

[0015] As is conventional in the art, the term "light-off temperature," as used herein, may refer to the temperature at which 50% conversion of a particular pollutant is reached.

[0016] Throughout this application, "wt %" for dopants is calculated based on the metal oxide, i.e., the wt % of Ta in the first alumina is calculated based on Ta oxide (Ta2O5).

[0017] Preferably, the catalyst article is for treating exhaust gases from a gasoline engine. Preferably, the catalyst article is a TWC article.

[0018] The term "doped alumina," as used herein, may encompass all materials including the first alumina, the Ta doped into the first alumina, and any other additional dopants that may be doped into the first alumina.

[0019] Preferably, the doped alumina is in the form of a mixed oxide. Alternatively, the doped alumina may be present in the form of a composite oxide.

[0020] First catalytic region The first catalyst region is on a substrate. Unless otherwise specified, the first catalyst region may be disposed directly on the substrate, i.e., without an intervening material, and / or may be disposed indirectly on the substrate, i.e., using an intervening material. If the substrate is porous, the catalyst composition may be disposed therein, for example, within the pores of the substrate, i.e., the catalyst composition is disposed thereon and / or therein. The catalyst composition is typically disposed on the substrate in the form of a washcoat. As used herein, the term "washcoat" is well known in the art and typically refers to an adherent coating applied to a substrate during catalyst production.

[0021] Preferably, the first alumina is doped with 0.1 to less than 5.0 wt.% Ta, more preferably 0.1 to 4.9 wt.% Ta, even more preferably 0.1 to 4.5 wt.% Ta, even more preferably 0.1 to less than 4.5 wt.% Ta, even more preferably 0.1 to 4.4 wt.% Ta, even more preferably 0.2 to 4.0 wt.% Ta, even more preferably 0.2 to 3.5 wt.% Ta, even more preferably 0.2 to 3.0 wt.% Ta, and even more preferably 0.2 to 2.5 wt.% Ta, based on the total weight of the doped alumina. In some preferred embodiments, the first alumina is doped with 0.2 to 2.0 wt.% Ta, based on the total weight of the doped alumina. In some preferred embodiments, the first alumina is doped with 0.2 to 1.5 wt.% Ta, based on the total weight of the doped alumina. In some preferred embodiments, the first alumina is doped with 0.2 to 1.0 wt % Ta, based on the total weight of the doped alumina.

[0022] Preferably, the first alumina comprises a further dopant comprising one or more of lanthanum, neodymium, yttrium, niobium, praseodymium, hafnium, molybdenum, titanium, vanadium, zinc, cadmium, copper, silicon, calcium, barium, strontium, cesium, magnesium, potassium, and sodium, more preferably one or more of lanthanum, neodymium, praseodymium, hafnium, and yttrium, even more preferably lanthanum. Preferably, the further dopant is present in the first alumina in an amount of 0.01 to 10.0 wt.%, more preferably 0.1 to 8.0 wt.%, even more preferably 1.0 to 7.0 wt.%, even more preferably 2.0 to 6.0 wt.%, and even more preferably 3.0 to 6.0 wt.%, based on the total weight of the doped alumina.

[0023] Preferably, the first PGM component comprises one or more of platinum, palladium, rhodium, and mixtures or alloys thereof, more preferably the first PGM component comprises Pd and / or Rh, even more preferably the first PGM component comprises Rh, and even more preferably the first PGM component consists of Rh. In some embodiments, the first catalyst region is preferably substantially free of PGMs other than Rh.

[0024] In certain embodiments, the first alumina preferably comprises gamma alumina. In other embodiments, the first alumina preferably comprises theta alumina.

[0025] In certain embodiments, the doped first alumina preferably has a specific surface area (SSA) of 100 to 220 m as measured by the Brunauer-Emmett-Teller (BET) method. 2 / g, more preferably 120 to 200m 2 / g, and even more preferably 150 to 180 m 2 After hydrothermal aging at 1000° C. for 4 hours under 10% steam in air, in certain embodiments, the SSA of the aged doped first alumina is preferably 30 to 120 mS / g, as measured by BET. 2 / g, more preferably 50 to 110m 2 / g, and even more preferably 60 to 100m 2 / g.

[0026] Preferably, the first catalyst region further comprises a first oxygen storage capacity (OSC) material and / or a first alkali metal and / or alkaline earth metal component.

[0027] Preferably, the first OSC material comprises 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. Preferably, the ceria-zirconia mixed oxide further comprises a dopant, such as lanthanum, neodymium, praseodymium, or yttrium oxide. In some embodiments, the first OSC material preferably functions as a support material for the first PGM component (e.g., as the first PGM support material). In some embodiments, the first OSC material preferably comprises ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0028] Preferably, the first catalytic region further comprises a first alkali metal and / or alkaline earth metal.

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

[0030] 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.

[0031] Preferably, the first PGM component is supported on the first alumina, in other words, the first PGM component is preferably supported directly on the first alumina.

[0032] The catalyst article in this embodiment may be applied as a TWC catalyst for treating exhaust gases produced by gasoline engines.

[0033] The first catalytic region can extend over 100 percent of the axial length L (see, eg, FIGS. 1 and 2).

[0034] The total washcoat loading of the first catalyst region is preferably 3.5 g / in 3 less than 3.0 g / in 3 less than, and even more preferably 2.5 g / in 3 Alternatively, the total washcoat loading of the first catalyst region is preferably 0.5 to 3.5 g / in 3 , more preferably 0.6 to 3 g / in 3 , and even more preferably 0.7 to 2.5 g / in 3 is.

[0035] Second catalytic region Preferably, the catalytic article further comprises a second catalytic region.

[0036] Preferably, the second catalyst region further comprises a second PGM component, a second oxygen storage capacity (OSC) material, a second alkali metal and / or alkaline earth metal component, and / or a second inorganic oxide.

[0037] The second PGM component preferably comprises one or more of platinum, palladium, rhodium, and mixtures or alloys thereof, hi some embodiments, the second PGM component preferably comprises Pd, Pt, or mixtures or alloys thereof.

[0038] Preferably, the second OSC material comprises cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the second OSC material comprises ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the second OSC material preferably further comprises one or more dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material preferably functions as a support material for the second PGM component. In some embodiments, the second OSC material preferably comprises ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0039] The ceria-zirconia mixed oxide preferably has 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 can also have a weight ratio of ceria to zirconia less than 50:50, preferably less than 40:60, more preferably less than 30:70.

[0040] The second catalyst region preferably comprises a second OSC material (e.g., a ceria-zirconia mixed oxide) in an amount of 10-90 wt %, preferably 25-75 wt %, more preferably 30-60 wt %, based on the total washcoat loading of the second catalyst region.

[0041] The second OSC material loading in the second catalyst region is preferably 2 g / in 3 In some embodiments, the loading of the second OSC material in the second catalyst region is preferably less than 1.5 g / in 3 Less than or equal to 1.2 g / in, preferably 1.2 g / in 3 or less, and even more preferably 1 g / in 3 or less, and even more preferably 0.8 g / in 3 or less, and even more preferably 0.7 g / in 3 The following is the result.

[0042] 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.

[0043] 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.

[0044] The second alkali metal or alkaline earth metal preferably comprises 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.

[0045] 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.

[0046] The second inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, or 14. The second inorganic oxide is preferably selected from the group consisting of alumina, magnesia, silica, zirconia, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferred is alumina, lanthania-alumina, zirconia, or a silica / alumina composite oxide. More preferably, the second inorganic oxide is alumina, lanthania-alumina, or a silica / alumina composite oxide. One particularly preferred second inorganic oxide is alumina or lanthania-alumina. In some embodiments, the second inorganic oxide is lanthania-alumina (e.g., lanthanum-stabilized alumina), and lanthania is present in an amount of up to 10% by weight of the second inorganic oxide, preferably 2-8, 3-7, or 4-6% by weight.

[0047] In some embodiments, the second inorganic oxide is doped with at least 5 wt. % of a second dopant, and the second dopant is selected from the group consisting of Zr, Ta, Mo, W, Ti, Nb, and combinations thereof. In further embodiments, the second dopant can be selected from the group consisting of Zr, Ta, Ti, Nb, and combinations thereof. In even further embodiments, the second dopant can be Ti, Nb, or combinations thereof. In yet other further embodiments, the second dopant can be Ti or Nb. In certain embodiments, the second dopant can be Ti. In other embodiments, the second dopant can be Nb. In certain embodiments, the content of the second dopant in the second inorganic oxide (e.g., alumina) can be 5 wt. % to 90 wt. In some further embodiments, the content of the second dopant in the second inorganic oxide can be 5 wt. % to 20 wt. In other further embodiments, the content of the second dopant in the second inorganic oxide can be 20 wt. % to 80 wt.

[0048] Preferably, the total washcoat loading of the second catalyst region is 3.5 g / in 3 less than 3.0 g / in 3less than, and even more preferably 2.5 g / in 3 Alternatively, the total washcoat loading of the first catalyst region is preferably 0.5 to 3.5 g / in 3 , more preferably 0.6 to 3 g / in 3 , and even more preferably 0.7 to 2.5 g / in 3 is.

[0049] The second catalytic region can extend over 100 percent of the axial length L (see, eg, FIG. 2).

[0050] In some embodiments, the first catalytic region is preferably supported / deposited directly on the substrate, and then the second catalytic region is preferably supported / deposited directly on the first catalytic region. In certain embodiments, the second catalytic region is preferably supported / deposited directly on the substrate, and then the first catalytic region is preferably supported / deposited directly on the second catalytic region.

[0051] 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 optionally further comprise at least one binder and / or at least one surfactant. When a binder is present, a dispersible alumina binder is preferred.

[0052] Base material Preferably, the substrate is a flow-through monolith. Alternatively, the substrate may be a wall-flow filter.

[0053] The flow-through monolith substrate may comprise a first surface and a second surface, defining a longitudinal direction therebetween. The flow-through monolith substrate may have a plurality of channels extending between the first surface and the second surface. The plurality of channels may extend longitudinally and may provide a plurality of interior surfaces (e.g., wall surfaces defining each channel). Each of the plurality of channels may have an opening in the first surface and an opening in the second surface. For the avoidance of doubt, a flow-through monolith substrate is not a wall-flow filter.

[0054] The first surface may typically be at the inlet end of the substrate, and the second surface may be at the outlet end of the substrate.

[0055] The channels may be of constant width, and each of the plurality of channels may have a uniform channel width.

[0056] 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 preferably 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.

[0057] The monolith substrate can act as a support for holding 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.

[0058] 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.

[0059] In embodiments in which the catalyst article of the present invention comprises a ceramic substrate, the ceramic substrate may be made of any suitable refractory material, such as alumina, silica, ceria, zirconia, magnesia, zeolites, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicates and metalloaluminosilicates (such as cordierite and spodumene), or mixtures or mixed oxides of any two or more thereof. Cordierite, magnesium aluminosilicate, and silicon carbide are particularly preferred.

[0060] 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.

[0061] Another aspect of the present disclosure is directed to an exhaust gas treatment system for treating a stream of combustion exhaust gas, the exhaust gas treatment system comprising the catalytic article of the first aspect. All preferred embodiments and features described herein with respect to the first aspect apply equally to this aspect.

[0062] Another aspect of the invention is directed to a fuel combustion and exhaust gas treatment system comprising an engine and an exhaust gas treatment system of the above aspect. Preferably, the engine is a gasoline engine. All preferred embodiments and features described herein in relation to the first aspect apply equally to this aspect.

[0063] Another aspect of the present disclosure is directed to a method of treating exhaust gas from an internal combustion engine, comprising contacting the exhaust gas with the catalytic article of the first aspect.

[0064] definition As used herein, the terms "article" or "catalyst article" may include an article on or within which a catalyst is supported. The article may take the form of, for example, a honeycomb monolith, or a filter, such as a wall-flow or flow-through filter.

[0065] As used herein, the term "inlet end" may encompass an end of a substrate intended to be disposed in an upstream direction. In contrast, as used herein, the term "outlet end" may encompass an end of a substrate intended to be disposed in a downstream direction. As used herein, the term "upstream" refers to a direction in a system toward an exhaust gas source. In contrast, as used herein, the term "downstream" refers to a direction in a system away from an exhaust gas source.

[0066] 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" can 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).

[0067] 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%.

[0068] 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.

[0069] 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).

[0070] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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).

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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."

[0081] The term "substantially free," when 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, more preferably 1% by weight or less, even more preferably 0.5% by weight or less, still more preferably 0.1% by weight or less, and even more preferably 0.01% by weight or less. The term "substantially free" encompasses the term "free."

[0082] The term "loading" as used herein refers to g / ft on a metal weight basis. 3 Refers to a measurement in units of .

[0083] Unless otherwise specified or implied, the use of terms such as "first," "second," etc. are intended as labels only and are not intended to indicate the relative position or location of particular features.

[0084] 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]

[0085] material All materials were commercially available and obtained from known sources unless otherwise stated.

[0086] Generally, about 170-200m 2 Commercially available La-stabilized γ-Al2O3 or Ta-doped La-stabilized γ-Al2O3 with a surface area of ​​1 / g and approximately 80 m 2 Nd-stabilized zirconia with a surface area of ​​1 / g was used as the Al2O3 and ZrO2 support material, respectively.

[0087] Approximately 5m 2 Tantalum pentoxide with a surface area of ​​0.05 wt. / g was used in place of La-stabilized γ-Al 2 O 3 in one of the comparative catalysts.

[0088] Example 1: Synthesis of support material using TA Light-off performance in catalytic activity test Comparative catalyst A Comparative Catalyst A was a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of La-stabilized alumina and Nd-stabilized zirconia, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 2.0 g / in. 3 and the Rh loading is 2 g / ft 3 It was.

[0089] Comparative catalyst B Comparative Catalyst B is a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consists of Rh supported on a washcoat of tantalum pentoxide and Nd-stabilized zirconia, where the Rh was pre-immobilized on the tantalum pentoxide support. The washcoat loading was approximately 2.0 g / in. 3 and the Rh loading is 2 g / ft 3 It was.

[0090] Catalyst C Catalyst C was a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of 5 wt.% Ta-doped, La-stabilized alumina and Nd-stabilized zirconia, where the Rh was pre-immobilized on the 5 wt.% Ta-doped, La-stabilized alumina support. The washcoat loading was approximately 2.0 g / in. 3 and the Rh loading is 2 g / ft 3 It was.

[0091] Comparative Catalysts A and B, and Catalyst C were tested separately in a Synthetic Catalyst Activity Test (SCAT) device. Light-off performance was measured using a mixture of 10% by volume H2O + 15% by volume CO2 + 1260 ppm C3H6 + 0.2% by volume H2 + 0.6% by volume CO + 0.53% by volume O2 + 1000 ppm NO, balance N2 (space velocity 60,000 h2). -1 ) gas flow with a temperature gradient of 30°C / min. x The conversion of was calculated by comparing the concentration of the feed gas with that of the gas at the catalyst outlet. A series of comparative catalysts A and B, as well as catalyst C, were hydrothermally aged at 1000 °C for 4 hours under agitated gas flows of 10 vol% H2O + 0.125 vol% C3H6 and 10 vol% H2O + 20 vol% O2 with the remainder being N2. The space velocity was 4 L min -1 , the perturbation cycle was 60 seconds for each type of gas flow, and the shutdown was less than 100% N2.

[0092] HC and NO of aged comparative catalysts A and B, and catalyst C x T 50 The light-off temperatures are shown in Table 1. The data surprisingly show that inventive catalyst C (having 5 wt. % Ta-doped La-stabilized alumina and a Nd-stabilized zirconia support) provided significantly improved light-off performance when compared to comparative catalysts A (having La-stabilized alumina and a Nd-stabilized zirconia support) and B (having tantalum pentoxide and a Nd-stabilized zirconia support). The impact on light-off performance improvement was observed for HC and NO, respectively, using catalyst C with 5 wt. % Ta-doped La-stabilized alumina compared to comparative catalyst A. x About 65°C and 44°C lower T 50 (T 50 (T is the temperature at which 50% conversion is reached). Comparative Catalyst B has a much lower T of 58°C for HC. 50 However, CO and NO x The conversion rate was higher than that of Comparative Catalyst A. 50 It was demonstrated that Ta doping into La-stabilized alumina can significantly benefit the Rh TWC catalyst performance.

[0093] [Table 1]

[0094] Example 2: Synthesis of TA-doped alumina with different TA doping amounts and light-off performance in catalytic activity test Comparative catalyst D Comparative Catalyst D is a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of La-stabilized alumina and Nd-stabilized zirconia, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 2.0 g / in. 3 and the Rh loading is 2 g / ft 3 It was.

[0095] Catalyst E Catalyst E was a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of 0.2 wt% Ta-doped, La-stabilized alumina and Nd-stabilized zirconia, where the Rh was pre-immobilized on a 0.2 wt% Ta-doped, La-stabilized alumina support. The washcoat loading was approximately 2.0 g / in. 3 and the Rh loading is 2 g / ft 3 It was.

[0096] Catalyst F Catalyst F was a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of 1 wt. % Ta-doped, La-stabilized alumina and Nd-stabilized zirconia, where the Rh was pre-immobilized on the 1 wt. % Ta-doped, La-stabilized alumina support. The washcoat loading was approximately 2.0 g / in. 3 and the Rh loading is 2 g / ft 3 It was.

[0097] Catalyst G Catalyst G was a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of 5 wt.% Ta-doped, La-stabilized alumina and Nd-stabilized zirconia, where the Rh was pre-immobilized on the 5 wt.% Ta-doped, La-stabilized alumina support. The washcoat loading was approximately 5.0 g / in. 3 and the Rh loading is 2 g / ft 3 It was.

[0098] Catalyst H Catalyst H was a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of 10 wt.% Ta-doped, La-stabilized alumina and Nd-stabilized zirconia, where the Rh was pre-immobilized on the 10 wt.% Ta-doped, La-stabilized alumina support. The washcoat loading was approximately 5.0 g / in. 3 and the Rh loading is 2 g / ft3 It was.

[0099] Comparative Catalyst D and Catalysts E-H were tested separately in a Synthetic Catalyst Activity Test (SCAT) device after hydrothermal aging for 4 hours at 1000 °C under perturbing gas flows of 10 vol% H2O + 0.125 vol% C3H6 and 10 vol% H2O + 20 vol% O2 with the remainder being N2. The space velocity was 4 L min -1 , the perturbation cycle was 60 seconds for each type of gas flow, and the shutdown was less than 100% N2.

[0100] HC and NO of aged comparative catalyst D and catalysts E to H x T 50 The light-off temperatures are shown in Table 2. The data surprisingly demonstrate that the Ta-doped La-stabilized alumina TWC catalysts E-G of the present invention (with Ta doping levels of 0.2, 1, and 5 wt. %, respectively) significantly reduced the HC and NO emissions when compared to comparative catalyst D (which had a La-stabilized alumina support without Ta). x Catalyst H (having 10 wt. % Ta-doped La-stabilized alumina support) gave significantly improved light-off performance in terms of conversion. x Among catalysts E to G, catalysts E (having 0.2 wt% Ta-doped La-stabilized alumina) and F (having 1 wt% Ta-doped La-stabilized alumina) showed high T50 for conversion. x The light-off performance of catalyst E was similar to that of catalyst G (having 5 wt.% Ta-doped La-stabilized alumina), and the conversion of HC and NO was better than that of catalyst G. x The T50 values ​​for Catalyst D were 25°C and 35°C lower than those for Comparative Catalyst D. This indicates that, compared with the commonly used Ta-free La-stabilized alumina support, a small amount of Ta doping of 0.2-1 wt% is better than a high amount of Ta doping for improving Rh TWC performance. This invention can conserve the precious natural resource of Rh used in the automotive industry, and can provide a cleaner air environment through the significant improvement in TWC performance, thereby reducing air pollution caused by automobiles.

[0101] Table 2

Claims

1. 1. A catalytic article for treating exhaust gases, comprising: a substrate having an axial length L and including an inlet end and an outlet end; a first catalytic region on the substrate; the first catalytic region comprises a first PGM component and a first alumina; A catalytic article wherein the first alumina is doped with 0.01 to less than 5.0 wt. % Ta, based on the total weight of the doped alumina.

2. 10. The catalyst article of claim 1, wherein the first alumina is doped with 0.1 to less than 5.0 wt. % Ta, based on the total weight of the doped alumina.

3. 3. The catalyst article of claim 1, wherein the first alumina is doped with 0.1 to 4.9 wt. % Ta, based on the total weight of the doped alumina.

4. 3. The catalyst article of claim 1, wherein the first alumina is doped with 0.1 to 4.5 wt. % Ta, based on the total weight of the doped alumina.

5. 5. The catalyst article of any one of claims 1 to 4, wherein the first alumina is doped with 0.1 to 4.4 wt. % Ta, based on the total weight of the doped alumina.

6. 6. A catalytic article according to any one of claims 1 to 5, wherein the first alumina comprises a further dopant comprising one or more of lanthanum, neodymium, yttrium, niobium, praseodymium, hafnium, molybdenum, titanium, vanadium, zinc, cadmium, copper, silicon, calcium, barium, strontium, cesium, magnesium, potassium, and sodium, preferably one or more of lanthanum, neodymium, praseodymium, hafnium, and yttrium.

7. The catalytic article of claim 6 , wherein the additional dopant comprises lanthanum.

8. 8. A catalytic article according to claim 6 or 7, wherein the further dopant is present in the first alumina in an amount of 0.01 to 10.0 wt. %, preferably 0.1 to 8.0 wt. %, based on the total weight of the doped alumina.

9. 9. The catalytic article of any one of claims 1 to 8, wherein the first PGM component comprises Rh, preferably the first PGM component consists of Rh.

10. 10. The catalytic article of claim 9, wherein the first catalytic region is substantially free of PGMs other than Rh.

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

12. The catalyst article of any one of claims 1 to 11, wherein the first PGM component is supported on the first alumina.

13. The catalytic article of any one of claims 1 to 12, further comprising a second catalytic region.

14. The catalytic article of claim 13 , wherein the second catalytic region comprises a second PGM component.

15. 15. The catalytic article of claim 14, wherein the second PGM component comprises one or more of Pt, Pd, Rh, and mixtures or alloys thereof.

16. 16. The catalytic article of any one of claims 13 to 15, wherein the second catalytic region further comprises a second oxygen storage capacity (OSC) material, a second alkali metal and / or alkaline earth metal component, and / or a second inorganic oxide.

17. The catalytic article of any one of claims 13 to 16, wherein the second catalytic region is supported / deposited directly on the substrate.

18. 20. The catalytic article of claim 17, wherein the first catalytic region is supported / deposited directly on the second catalytic region.

19. The catalytic article of any one of claims 13 to 16, wherein the first catalytic region is supported / deposited directly on the substrate.

20. 20. The catalytic article of claim 19, wherein the second catalytic region is supported / deposited directly on the first catalytic region.

21. An exhaust gas treatment system for treating a flow of combustion exhaust gases, the exhaust gas treatment system comprising a catalytic article according to any one of claims 1 to 20.

22. 22. A fuel combustion and exhaust gas treatment system comprising: an engine; and the exhaust gas treatment system of claim 21.

23. 23. The fuel combustion and exhaust gas treatment system of claim 22, wherein the engine is a gasoline engine.

24. A method for treating exhaust gases from an internal combustion engine, comprising contacting said exhaust gases with a catalytic article according to any one of claims 1 to 20.

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