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 is disclosed. The catalyst article for treating exhaust gas comprises: a substrate having an axial length L, the substrate comprising an inlet end and an outlet end; and a first catalyst region on the substrate, the first catalyst region comprising a first PGM component and a first alumina, the first alumina being doped with at least 5 wt. % of a first dopant, the first dopant being selected from the group consisting of Zr, Ta, Mo, W, Ti, Nb, and combinations thereof.

Description

[Technical field]

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

[0002] In internal combustion engines, the main components of the exhaust gas are hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxide (NO x ), which produces exhaust gases containing a variety of pollutants, including CO, HC, and NO. 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 of gasoline engines is the three way catalyst (TWC). TWCs perform three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) oxidation of NO. x A reduction in the amount of

[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 better OSC performance during the hot transient phase in a wide range of Pt, Pd, and / or Rh applications. The present invention solves 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, the catalytic article comprising: a substrate having an axial length L, including an inlet end and an outlet end; and a first catalytic region on the substrate, the first catalytic region comprising a first PGM component and a first alumina, the first alumina being doped with at least 5 wt. % of a first dopant, the first dopant being selected from the group consisting of Zr, Ta, Mo, W, Ti, Nb, and combinations thereof.

[0005] The present invention also includes an exhaust system for an internal combustion engine which includes a three-way catalyst component of the present invention.

[0006] The present invention also encompasses the treatment of exhaust gases from internal combustion engines, particularly gasoline engines, which method comprises contacting the exhaust gases with a three-way catalyst component of the present invention. [Brief description of the drawings]

[0007] [Figure 1] 1 shows one embodiment according to the present invention containing a first catalytic region (single layer) having a length of 100% relative to the axial length L of the substrate. [Diagram 2] 1 shows an embodiment according to the invention in which a first catalyst region is a lower layer and extends over 100% of the axial length L, and a second catalyst region is an upper layer and extends over 100% of the axial length L. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 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 is directed to the catalytic treatment of NO in vehicle exhaust systems. x , CO, and HC simultaneous processing. While most of the technology development to improve TWC performance has focused on increasing the thermal stability of the support alumina material by doping with lanthanum or other rare earth elements, the inventors have surprisingly discovered that modification of the alumina material with transition metals such as titanium and niobium further impacts the improved light-off performance and resulting emission control performance of the TWC. The inventors have discovered that the potential performance of the TWC under light-off tests and the actual performance under emission control tests are improved by the present invention. The method of the present invention also significantly reduces the PGM loading in the TWC, saving valuable natural resources and reducing the cost of the catalyst product.

[0009] One aspect of the present disclosure is directed to a catalytic article for treating exhaust gases, the catalytic article comprising: a substrate having an axial length L, including an inlet end and an outlet end; and a first catalytic region on the substrate, the first catalytic region comprising a first PGM component and a first alumina, the first alumina being doped with at least 5 wt. % of a first dopant, the first dopant being selected from the group consisting of Zr, Ta, Mo, W, Ti, Nb, and combinations thereof.

[0010] Through intensive research, the inventors have found that by doping primary dopants such as Ti and Nb into the TWC catalyst compositions, these novel compositions exhibited superior catalytic properties (e.g., by using Ti or Nb containing catalysts as described in the present invention, all emissions, THC / NMHC, CO and NO x (Emissions from diesel engines were significantly reduced during vehicle testing.)

[0011] Throughout this application, "weight percent" for dopants is calculated on a metal oxide basis.

[0012] The first catalytic region The first PGM component may be selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof. In some embodiments, the first PGM component may be Pd, Rh, or mixtures thereof. In other embodiments, the first PGM component may be rhodium. In further embodiments, the first catalyst region is substantially free of PGMs other than Rh. In yet other embodiments, the first PGM component may be platinum and rhodium; palladium and rhodium; or platinum, palladium, and rhodium. In further embodiments, the first PGM component may be platinum and rhodium; or platinum, palladium, and rhodium.

[0013] The first alumina can be alumina, lanthania / alumina, or silica / alumina composite oxide. In some embodiments, the first alumina is lanthania-alumina (e.g., lanthanum stabilized alumina), with the lanthania being up to 10% by weight of the first alumina, preferably 2-8, 3-7, or 4-6% by weight. In certain embodiments, the first alumina can be gamma alumina. In other embodiments, the first alumina can be theta alumina.

[0014] In some embodiments, the first dopant can be selected from the group consisting of Zr, Ta, Ti, Nb, and combinations thereof. In further embodiments, the first dopant can be Ti, Nb, or combinations thereof. In yet another further embodiment, the first dopant can be Ti or Nb. In certain embodiments, the first dopant can be Ti. In other embodiments, the first dopant can be Nb. In certain embodiments, the content of the first dopant in the first alumina can be 5% to 90% by weight. In some further embodiments, the content of the first dopant in the first alumina can be 5% to 20% by weight.

[0015] In other further embodiments, the content of the first dopant in the first alumina can be 20% to 80% by weight. In yet other further embodiments, the content of the first dopant in the first alumina can be 30% to 70% by weight or 40% to 60% by weight. In certain embodiments, the specific surface area (SSA) of the doped first alumina is 80 to 180 m as measured by the Brunauer-Emmett-Teller (BET) method. 2 / g, 100-165m 2 / g, or 130-150m 2 / g. In some embodiments, the doped first alumina can have a crystallite size of 5-30 nm, 10-25 nm, or 15-20 nm. 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 can be 1-60 mS / g as measured by BET. 2 / g, 2-30m 2 / g, or 4 to 10m 2 / g. In some embodiments, the aged doped first alumina can have a crystallite size of 50-300 nm, 80-200 nm, or 100-150 nm. When the first dopant is Ti, the crystalline phase of TiO2 in the fresh Ti-doped alumina can be anatase, and the crystalline phase of TiO2 in the aged Ti-doped alumina can be rutile.

[0016] The first catalytic region may further include a first oxygen storage capacity (OSC) material, and / or a first alkali metal or alkaline earth metal component.

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

[0018] The first catalytic region may further comprise a first alkali metal or alkaline earth metal.

[0019] The first alkali or alkaline earth metal is preferably barium or strontium and mixed 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.

[0020] Preferably, the barium or strontium is present as BaCO3 or SrCO3. Such materials can be made by any method known in the art, such as incipient wetness impregnation or spray drying.

[0021] In some embodiments, the first PGM component can be supported on a first alumina.

[0022] A first dopant, such as titanium (Ti) or niobium (Nb), can be incorporated into the first catalytic region in a variety of ways. In some embodiments, Ti can be incorporated into the first alumina material as a dopant, and the first alumina material can include up to 80 wt% Ti, preferably up to 60 wt% Ti, based on the total weight of the first alumina material. Alternatively, the first alumina material can include 5-80 wt% Ti, preferably 10-70 wt% Ti, more preferably 20-65 wt% Ti, and even more preferably 40-60 wt% Ti, based on the total weight of the first alumina material.

[0023] In other embodiments, Nb can be incorporated as a dopant into the first alumina material, which can include up to 80 wt% Nb, preferably up to 50 wt% Nb, and more preferably up to 25 wt% Nb, based on the total weight of the first alumina material. Alternatively, the first alumina material can include 5-80 wt% Nb, preferably 10-50 wt% Nb, more preferably 10-30 wt% Nb, and even more preferably 15-25 wt% Nb, based on the total weight of the first alumina material.

[0024] As demonstrated in the examples below, the catalyst article in this embodiment can be applied as a TWC catalyst for treating exhaust gases produced by a gasoline engine.

[0025] The first catalytic region can extend over 100 percent of the axial length L (see, eg, FIGS. 1 and 2).

[0026] The total washcoat loading of the first catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 or 2.5g / in 3 Alternatively, the total washcoat loading of the first catalyst region can be between 0.5 and 3.5 g / in 3 and preferably 0.6 to 3 g / in 3 Or 0.7 to 2.5 g / in 3 It could be.

[0027] The second catalytic region The catalytic article may further include a second catalytic region.

[0028] 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.

[0029] 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, Pt, or mixtures thereof.

[0030] The second OSC material may be cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the second OSC material includes ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the second OSC material may further include one or more of dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material may function as a support material for the second PGM component. In some embodiments, the second OSC material includes ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0031] The ceria-zirconia mixed oxide may have a weight ratio of zirconia to ceria of at least 50:50, preferably greater than 60:40, more preferably greater than 70:30.Alternatively, the ceria-zirconia mixed oxide may also have a weight ratio of ceria to zirconia less than 50:50, preferably less than 40:60, more preferably less than 30:70.

[0032] The second OSC material (eg, ceria-zirconia mixed oxide) can be 10-90 wt %, preferably 25-75 wt %, more preferably 30-60 wt %, based on the total washcoat loading of the second catalyst region.

[0033] The loading of the second OSC material in the second catalyst region is 2 g / in 3 In some embodiments, the loading of the second OSC material in the second catalytic region can be less than 1.5 g / in 3 , 1.2g / in 3 , 1g / in 3 , 0.8g / in 3 , or 0.7 g / in 3 The following is the result.

[0034] The second alkali or alkaline earth metal is preferably barium, strontium, a mixed oxide or a composite oxide thereof. Preferably, the barium or strontium, if present, is in an amount of 0.1 to 15 wt. %, more preferably 3 to 10 wt. %, barium or strontium, based on the total weight of the second catalytic region.

[0035] It is even more preferred that the second alkali or alkaline earth metal is strontium, which, when present, is preferably present in an amount of from 0.1 to 15 wt %, more preferably from 3 to 10 wt %, based on the total weight of the second catalyst region.

[0036] Also, the second alkali metal or alkaline earth metal is preferably a mixed oxide or composite oxide of barium and strontium. Preferably, the mixed oxide or composite oxide of barium and strontium is present in an amount of 0.1 to 15% by weight, more preferably 3 to 10% by weight, based on the total weight of the second catalyst region. More preferably, the second alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

[0037] Preferably, the barium or strontium is present as BaCO3 or SrCO3. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0038] The second inorganic oxide is preferably an oxide of an element of group 2, group 3, group 4, group 5, group 13, and group 14. The second inorganic oxide is preferably selected from the group consisting of alumina, magnesia, silica, zirconia, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferably, the second inorganic oxide is alumina, lanthania-alumina, zirconia, or silica / alumina composite oxide. More preferably, the second inorganic oxide is alumina, lanthania-alumina, or 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 up to 10% by weight of the second inorganic oxide, preferably 2-8, 3-7, or 4-6% by weight.

[0039] In some embodiments, the second inorganic oxide is doped with at least 5 wt.% of the second dopant, the second dopant being 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 still 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 (such as 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.%.

[0040] The total washcoat loading of the second catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3or 2.5g / in 3 Alternatively, the total washcoat loading of the first catalyst region can be between 0.5 and 3.5 g / in 3 and preferably 0.6 to 3 g / in 3 Or 0.7 to 2.5 g / in 3 It could be.

[0041] The second catalytic region can extend over 100 percent of the axial length L (see, eg, FIG. 2).

[0042] 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.

[0043] The catalyst article of the present invention may include additional components that are well known to those skilled in the art. For example, the composition of the present invention may further include at least one binder and / or at least one surfactant. When a binder is present, a dispersible alumina binder is preferred.

[0044] Base material Preferably, the substrate is a flow-through monolith. Alternatively, the substrate can be a wall-flow filter.

[0045] The flow-through monolith substrate has a first surface and a second surface defining a longitudinal direction therebetween. The flow-through monolith substrate has a plurality of channels extending between the first surface and the second surface. The plurality of channels extend longitudinally and provide a plurality of interior surfaces (e.g., surfaces of walls defining each channel). Each of the plurality of channels has an opening at the first surface and an opening at the second surface. For the avoidance of doubt, a flow-through monolith substrate is not a wall-flow filter.

[0046] The first surface is typically at an inlet end of the substrate and the second surface is at an outlet end of the substrate.

[0047] The channels may be of constant width, and each of the multiple channels may have a uniform channel width.

[0048] Preferably, in a plane perpendicular to the longitudinal direction, the monolith substrate has 300 to 900 channels per square inch, preferably 400 to 800 channels per square inch. For example, on the first face, the density of open first channels and closed second channels is 600 to 700 channels per square inch. The channels can have cross-sections that are rectangular, square, circular, oval, triangular, hexagonal, or other polygonal shapes.

[0049] 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.

[0050] It should be noted that the flow-through monolith substrates described herein are unitary components (i.e., a single brick). Nevertheless, when forming an emission treatment system, the substrates used may be formed by bonding together multiple channels, or by bonding together multiple smaller substrates as described herein. Such techniques, along with suitable casings and configurations of emission treatment systems, are well known in the art.

[0051] In embodiments in which the catalytic article of the present invention includes a ceramic substrate, the ceramic substrate may be made of any suitable refractory material, such as alumina, silica, ceria, zirconia, magnesia, zeolites, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicates and metalloaluminosilicates (such as cordierite and spodumene), or mixtures or mixed oxides of any two or more thereof. Cordierite, magnesium aluminosilicate, and silicon carbide are particularly preferred.

[0052] In embodiments in which the catalytic article of the present invention includes a metal substrate, the metal substrate may be made of any suitable metal, particularly heat-resistant metals and metal alloys such as titanium and stainless steel, and ferritic alloys containing iron, nickel, chromium, and / or aluminum in addition to other trace metals.

[0053] Another aspect of the present disclosure is a method for producing a NO x The present invention is directed to a method for treating vehicle exhaust gases containing THC, CO, and NO. Catalytic converters equipped with TWCs made according to this method exhibit improved catalytic properties compared to conventional TWCs (having the same or lower PGM loadings), and exhibit particularly good light-off performance and improved catalytic properties for THC, CO, and NO. x The results show the emission control performance of the above-mentioned compounds (see, for example, Examples 1 to 4 and Tables 1 to 5).

[0054] Another aspect of the present disclosure is directed to a system for treating vehicle exhaust gases that includes a catalytic article as described herein along with a conduit for transporting exhaust gases through the system.

[0055] definition The term "region" as used herein refers to an area on a substrate that is typically obtained by drying and / or calcining a washcoat. A "region" can be disposed or carried on a substrate as, for example, a "layer" or a "zone." The area or arrangement on the substrate is generally controlled during the process of applying the washcoat to the substrate. A "region" typically has a distinct boundary or edge (i.e., it is possible to distinguish one region from another using conventional analytical techniques).

[0056] Typically, a "region" has a substantially uniform length. Reference to a "substantially uniform length" in this context refers to a length that does not deviate from its average value by more than 10% (e.g., the difference between the maximum and minimum length), preferably a length that does not deviate from its average value by more than 5%, and more preferably a length that does not deviate from its average value by more than 1%.

[0057] Each "region" preferably has a substantially uniform composition (i.e., there is no substantial difference in the composition of the washcoat when comparing one portion of the region to another portion of the region). Substantially uniform composition in this context refers to a material (e.g., region) that has a composition difference of 5% or less, usually 2.5% or less, and most commonly 1% or less, when comparing one portion of the region to another portion of the region.

[0058] As used herein, the term "zone" refers to a region having a length that is less than the entire length of the substrate, such as a length that is 75% or less of the entire length of the substrate. A "zone" typically has a length that is at least 5% (e.g., 5% or more) of the entire length of the substrate (i.e., a substantially uniform length).

[0059] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0060] Any reference herein to a "zone disposed at the inlet end of a substrate" refers to a zone disposed on or supported by a substrate, which is closer to the inlet end of the substrate than to the outlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the inlet end of the substrate than to the outlet end of the substrate. Similarly, any reference herein to a "zone disposed at the outlet end of a substrate" refers to a zone disposed on or supported by a substrate, which is closer to the outlet end of the substrate than to the inlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the outlet end of the substrate than to the inlet end of the substrate.

[0061] When the substrate is a wall-flow filter, generally any reference to "a zone disposed at the inlet end of the substrate" refers to a zone disposed on or supported by the substrate, (a) a zone that is closer to the inlet end (e.g., an open end) of an inlet channel of the substrate than to the closed end (e.g., a blocked or plugged end) of the inlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an outlet channel of a substrate than to the outlet end (e.g., open end) of the outlet channel.

[0062] 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.

[0063] Similarly, where the substrate is a wall-flow filter, any reference to a "zone disposed at the outlet end of the substrate" refers to a zone disposed on or carried by the substrate, (a) a zone that is closer to the outlet end (e.g., an open end) of the outlet channel of the substrate than to the closed end (e.g., a blocked or plugged end) of the outlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an inlet channel of a substrate than to the inlet end (e.g., open end) of the inlet channel.

[0064] 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.

[0065] If the washcoat is present on the wall of a wall-flow filter (ie, the zone is intramural), the zone may satisfy both (a) and (b).

[0066] The term "washcoat" is well known in the art and typically refers to an adherent coating that is applied to a substrate during the production of a catalyst.

[0067] The acronym "PGM" as used herein refers to "platinum group metals." The term "platinum group metals" generally refers to metals selected from the group consisting of Ru, Rh, Pd, Os, Ir, and Pt, preferably metals selected from the group consisting of Ru, Rh, Pd, Ir, and Pt. In general, the term "PGM" preferably refers to metals selected from the group consisting of Rh, Pt, and Pd.

[0068] The term "mixed oxide" as used herein generally refers to a mixture of oxides in a single phase, as is conventionally known in the art. The term "complex oxide" as used herein generally refers to a composition of oxides having two or more phases, as is conventionally known in the art.

[0069] As used herein, the phrase "consisting essentially of" limits the scope of a feature to include the specified materials or steps and any other materials or steps, e.g., trace impurities, that do not substantially affect the basic properties of the feature. "Consisting essentially of" encompasses the phrase "consisting of."

[0070] As used herein with respect to a material, the term "substantially free" typically means that the material is present in a small amount, e.g., 5% by weight or less, preferably 2% by weight or less, more preferably 1% by weight or less, in relation to the contents of a region, layer, or zone. The term "substantially free" encompasses the term "free."

[0071] As used herein with respect to a material, the term "essentially free" typically means that the material is present in trace amounts, e.g., 1% by weight or less, preferably 0.5% by weight or less, more preferably 0.1% by weight or less, in the context of the contents of a region, layer, or zone. The term "essentially free" encompasses the term "free."

[0072] As used herein, any reference to an amount of dopant expressed as weight percent, particularly a total amount, refers to the weight of the support material or refractory metal oxide thereof.

[0073] As used herein, the term "loading" refers to g / ft2 on a metal weight basis. 3 Refers to the measurement in units of .

[0074] The following examples are merely illustrative of the present invention, and those skilled in the art will recognize many variations that are within the spirit and scope of the claims. EXAMPLES

[0075] material All materials are commercially available and were obtained from known sources unless otherwise stated.

[0076] Basic procedure for synthesizing doped inorganic oxides Approximately 180m 2 Commercially available La-stabilized γ-Al2O3 with a surface area of ​​about 60 m 2 Nd-stabilized zirconia with a surface area of ​​0.1 μg / g was used as the Al2O3 and ZrO2 support materials, respectively. The addition of dopants such as Nb or Ti to the support was carried out as follows.

[0077] An aqueous solution containing ammonium niobium (V) oxalate hydrate as dopant Nb was impregnated into Al2O3 or ZrO2 support materials at the target loading of Nb, followed by drying at 150°C for 3 hours and calcination at 500°C for 2 hours in air to obtain Nb-doped support materials.

[0078] Dopant as Ti: Titanium isopropoxide liquid was added to the slurry of Al2O3 support material with the target loading of Ti, followed by filtration, drying at 150 °C for 3 h, and calcination at 500 °C for 2 h in air to obtain Ti-doped Al2O3 material.

[0079] Example 1: Synthesis of NB-doped support materials Light-off performance in catalytic activity tests Comparative catalyst A Comparative Catalyst A 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 The Rh loading is 15 g / ft 3 It was.

[0080] 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 consisted of Rh supported on a washcoat of La-stabilized alumina and Nd-stabilized zirconia, where the Rh was pre-immobilized on the zirconia support. The washcoat loading was approximately 2.0 g / in 3The Rh loading is 15 g / ft 3 It was.

[0081] Comparative catalyst C Comparative Catalyst C 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 5 wt. % Nb-doped zirconia, where the Rh was pre-immobilized on the zirconia support. The washcoat loading was approximately 2.0 g / in 3 The Rh loading is 15 g / ft 3 It was.

[0082] 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 20 wt. % Nb-doped zirconia, where the Rh was pre-immobilized on the zirconia support. The washcoat loading was approximately 2.0 g / in 3 The Rh loading is 15 g / ft 3 It was.

[0083] Catalyst E Catalyst E 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 5 wt.% Nb-doped alumina and Nd-doped zirconia, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 2.0 g / in. 3 The Rh loading is 15 g / ft 3 It was.

[0084] Catalyst F Catalyst F 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 20 wt.% Nb-doped alumina and Nd-doped zirconia, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 2.0 g / in. 3The Rh loading is 15 g / ft 3 It was.

[0085] Comparative catalysts A to D, as well as catalysts E and F, were tested separately in a Synthetic Catalyst Activity Test (SCAT) apparatus. The light-off performance was evaluated 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 60000 h -1 ) gas flow with a temperature gradient of 30°C / min. THC, CO, and NO 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-D and catalysts E and F were hydrothermally aged at 1000°C for 4 hours under 10% steam in air.

[0086] HC, CO, and NO for aged comparative catalysts A-D and catalysts E and F x T 50 The light-off temperatures are shown in Table 1. The data surprisingly show that the Nb-doped alumina-containing catalysts E and F of the present invention provided significantly improved light-off performance when compared to comparative catalysts A and B (alumina and zirconia without Nb) and comparative catalysts C and D (Nb-doped zirconia). The impact of the improved light-off performance was seen in the reduction of CO, HC and NO, respectively, for Catalyst E of 5 wt% Nb-doped alumina compared to Comparative Catalyst C of 5 wt% Nb-doped zirconia. x About 20℃, 45℃ and 35℃ lower T 50 (T 50 (where is the temperature at which the conversion reaches 50%). The effect is also evident for the 20 wt% Nb-doped alumina catalyst F versus the 20 wt% Nb-doped zirconia comparison catalyst D, with the CO, HC and NO x 19℃, 30℃ and 20℃ lower T 50Nb doping can improve both the zirconia and alumina supports of Rh, but the effect is much larger on the alumina support.

[0087] [Table 1]

[0088] Example 2: Light-off performance in the synthesis catalytic activity test of TI and NB doped alumina Comparative catalyst G Comparative Catalyst G 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 CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 2.0 g / in 3 The Rh loading is 8.6 g / ft 3 It was.

[0089] Catalyst H Catalyst H 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 5% Nb-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 2.0 g / in. 3 The Rh loading is 8.6 g / ft 3 It was.

[0090] Catalyst I Catalyst I 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 5% Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 2.0 g / in. 3 The Rh loading is 8.6 g / ft 3 It was.

[0091] Catalyst J Catalyst J 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 5% Ti-doped La-free gamma-phase alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 8.6 g / ft 3 It was.

[0092] Catalyst K Catalyst K 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 5% Ti-doped La-stabilized theta-phase alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 8.6 g / ft 3 It was.

[0093] Comparative Catalyst G and Catalysts H and I were separately tested in a Synthetic Catalyst Activity Test (SCAT) apparatus after hydrothermal aging at 1000° C. for 4 hours under 10% steam in air.

[0094] HC, CO, and NO for aged Comparative Catalyst G and Catalysts H and I x T 50 The light-off temperatures are shown in Table 2. The data surprisingly show that the inventive Nb-doped alumina-containing Catalysts E and F provided significantly improved light-off performance when compared to Comparative Catalyst G. Catalyst I with Ti-doped alumina further improves light-off performance relative to Catalyst H (TWC containing Nb-doped alumina).

[0095] [Table 2]

[0096] Catalysts I, J, and K were tested separately in a Synthetic Catalyst Activity Test (SCAT) apparatus after hydrothermal aging at 1050° C. for 4 hours under air containing 10% steam.

[0097] HC, CO and NO for aged catalysts I, J and K x T 50 The light-off temperatures are shown in Table 3. The data surprisingly show that Ti doping on the La stabilized alumina of theta phase catalyst K provided significantly improved light-off performance when compared to Ti doped La stabilized gamma phase alumina catalyst I and Ti doped La free gamma alumina catalyst J. Theta phase of alumina can further improve Rh catalytic performance on Ti doped alumina support.

[0098] [Table 3]

[0099] Example 3: Synthesis of TI-doped alumina with various TI contents and light-off performance in catalytic activity test Comparison catalyst L Comparative Catalyst L 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 CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was about 1.6 g / in 3 The Rh loading is 2.0 g / ft 3 It was.

[0100] Catalyst M Catalyst M 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 5 wt% Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 2.0 g / ft 3 It was.

[0101] Catalyst N Catalyst N 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 10 wt% Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in 3 The Rh loading is 2.0 g / ft 3 It was.

[0102] Catalyst O Catalyst O 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 20 wt% Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in 3 The Rh loading is 2.0 g / ft 3 It was.

[0103] Catalyst P Catalyst P 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 50 wt. % Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 2.0 g / ft 3 It was.

[0104] Catalyst Q Catalyst Q 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 80 wt. % Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 2.0 g / ft3 It was.

[0105] Comparative catalysts G and L and catalysts MQ were separately tested in a Synthetic Catalyst Activity Test (SCAT) apparatus after hydrothermal aging at 1000° C. for 4 hours under air containing 10% steam.

[0106] HC, CO, and NO of aged comparative catalysts G and L and catalysts MQ x T 50 The light-off temperatures are shown in Table 4. The data surprisingly show that all Ti-doped alumina TWCs of inventive catalysts MQ through Q were significantly higher than comparative catalyst L (2.0 g / ft 3 The results show that the Ti-containing alumina with the same Rh loading of 8.6 g / ft 2 provided significantly improved light-off performance compared to the Ti-free alumina with the same Rh loading of 8.6 g / ft 2. 3 Furthermore, compared to the comparative catalyst G, which has a higher Rh loading of 2.0 g / ft 3 Catalyst P, a 50 wt. % Ti-doped alumina TWC with a Rh loading of 1.0, was found to be effective in reducing CO, HC and NO. x 32°C, 79°C, and 107°C lower, respectively. 50 The light-off performance was significantly improved at 1000 nm. Thus, the use of a high Ti-containing alumina support can dramatically reduce the Rh loading by more than 75% while improving the light-off performance of the TWC. The present invention can conserve the precious natural resource of Rh used in the automotive industry, and can provide a cleaner air environment through the significant performance improvement of the TWC, thereby reducing air pollution caused by automobiles.

[0107] [Table 4]

[0108] Example 4: Emissions Control Performance in Gasoline Passenger Vehicles Comparative catalyst R Comparative Catalyst R is a two-layer TWC containing a first catalyst region in an upper layer and a second catalyst region in a lower layer coated on a ceramic substrate (600 cpsi, 4.3 mil wall thickness) (see, e.g., FIG. 2).

[0109] First catalytic region: The first catalytic region is made of Rh and La stabilized alumina supported on a washcoat of CeZr mixed oxide. The washcoat loading of the second catalytic region is about 2.0 g / in 3 The Rh loading is 15 g / ft 3 It was.

[0110] Second catalytic region: The second catalytic region is made of Pd supported on a washcoat of CeZr mixed oxide, La stabilized alumina, and Ba promoter. The washcoat loading of the first catalytic region is about 2.0 g / in 3 The Pd loading is 100g / ft 3 It was.

[0111] Catalyst S Catalyst S is a dual-layer TWC containing a first catalyst region in an upper layer and a second catalyst region in a lower layer coated on a ceramic substrate (600 cpsi, 4.3 mil wall thickness) (see, e.g., FIG. 2).

[0112] First catalytic region: The first catalytic region is made of Rh and 5% Nb stabilized alumina supported on a washcoat of CeZr mixed oxide. The washcoat loading of the second catalytic region is about 2.0 g / in 3 The Rh loading is 15 g / ft 3 It was.

[0113] Second catalytic region: The second catalytic region is made of Pd supported on a washcoat of CeZr mixed oxide, La stabilized alumina, and Ba promoter. The washcoat loading of the first catalytic region is about 2.0 g / in 3 The Pd loading is 100g / ft 3 It was.

[0114] Comparative Catalyst R and Catalyst S were bench aged for 100 hours in a fuel cut aging cycle at a peak temperature of 1000° C. Vehicle emissions were performed in a commercial vehicle with a 2.5 liter engine. Emissions were measured before and after the catalyst.

[0115] [Table 5]

[0116] As shown in Table 5, Catalyst S had a significantly lower emission rate of HC, CO, and NO compared to Comparative Catalyst R. x showed a significant decrease in emissions from the two groups (36%, 37%, and 51%, respectively).

[0117] Example 5: Effective range of SSA and crystal size Catalyst T Catalyst T 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 50 wt. % Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 2.0 g / ft 3 The specific surface area (SSA) of 50 wt% Ti-doped La-stabilized alumina was 205 m 2 / g, and the anatase crystallite size after drying at 150 °C for 3 h and calcining at 500 °C for 2 h in air is 7 nm. The SSA of 50 wt % Ti-doped La-stabilized alumina is 18 nm. 2 / g and the rutile crystallite size after hydrothermal aging at 1000° C. for 4 hours under 10% steam in air is 91 nm.

[0118] Catalyst U Catalyst U 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 50 wt.% Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 2.0 g / ft 3 The SSA of 50 wt% Ti-doped La-stabilized alumina was 200m 2 / g, and the anatase crystallite size after drying at 150 °C for 3 h and calcining at 500 °C for 2 h in air is 9 nm. The SSA of 50 wt % Ti-doped La-stabilized alumina is 13 m 2 / g and the rutile crystallite size after hydrothermal aging at 1000° C. for 4 hours under 10% steam in air is 117 nm.

[0119] Catalyst V Catalyst V 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 50 wt. % Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 2.0 g / ft 3 The SSA of 50 wt% Ti-doped La-stabilized alumina was 168m 2 / g, and the anatase crystallite size after drying at 150 °C for 3 h and calcining at 500 °C for 2 h in air is 12 nm. The SSA of 50 wt % Ti-doped La-stabilized alumina is 15 m 2 / g and the rutile crystallite size after hydrothermal aging at 1000° C. for 4 hours under 10% steam in air is about 132 nm.

[0120] Catalyst W Catalyst W 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 50 wt.% Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 2.0 g / ft 3 The SSA of 50 wt% Ti-doped La-stabilized alumina was 152m 2 / g, and the anatase crystallite size after drying at 150 °C for 3 h and calcining at 500 °C for 2 h in air is 14 nm. The SSA of 50 wt % Ti-doped La-stabilized alumina is 10 m 2 / g and the rutile crystallite size after hydrothermal aging at 1000° C. for 4 hours under 10% steam in air is 152 nm.

[0121] Catalyst X Catalyst X 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 50 wt.% Ti-doped La-stabilized alumina and CeZr mixed oxide, where the Rh was pre-immobilized on the alumina support. The washcoat loading was approximately 1.6 g / in. 3 The Rh loading is 2.0 g / ft 3 The SSA of 50 wt% Ti-doped La-stabilized alumina was 137m 2 / g, and the anatase crystallite size after drying at 150 °C for 3 h and calcining at 500 °C for 2 h in air is 19 nm. The SSA of 50 wt % Ti-doped La-stabilized alumina is 7 m 2 / g and the rutile crystallite size after hydrothermal aging at 1000° C. for 4 hours under 10% steam in air is 121 nm.

[0122] Catalysts T–X were tested separately in a synthetic catalyst activity test (SCAT) apparatus after hydrothermal aging at 1000°C for 4 h under air containing 10% steam.

[0123] HC, CO and NO of catalysts T~X x T 50 The light-off temperatures are shown in Table 6. The data surprisingly show that 137 nm of 100% 100% 100% 137% 10 ... 2 Catalyst X, with a surface area of ​​152 to 205 m / g, was doped with 50 wt% Ti on La-stabilized alumina. 2 It is shown that the larger surface area of ​​TWC at 1000 nm / g and smaller crystallite size of 7–14 nm gave significantly improved light-off performance when compared to catalysts T–W. The physical properties such as SSA and crystallite size of the titania phase of Ti-doped alumina greatly affect the catalytic performance of TWC.

[0124] [Table 6]

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; the first alumina is doped with at least 5 wt. % of a first dopant; The catalytic article, wherein the first dopant is selected from the group consisting of Zr, Ta, Mo, W, Ti, Nb, and combinations thereof.

2. 2. The catalytic article of claim 1, wherein the content of the dopant in the first alumina is 5% to 90% by weight.

3. 3. The catalytic article according to claim 1, wherein the content of the first dopant in the first alumina is 5% by weight to 20% by weight.

4. 3. The catalytic article according to claim 1, wherein the content of the first dopant in the first alumina is 20% by weight to 80% by weight.

5. 3. The catalytic article of claim 1 or 2, wherein the dopant is Ti or Nb.

6. The catalyst article of claim 1 or 2, wherein the first alumina is further stabilized with La.

7. 3. The catalyst article of claim 1 or 2, wherein the first PGM component is Rh.

8. 8. The catalytic article of claim 7, wherein the first catalytic region is substantially free of PGMs other than Rh.

9. 3. The catalytic article of claim 1 or 2, further comprising a first oxygen storage capacity (OSC) material and / or a first alkali metal or alkaline earth metal component.

10. 3. The catalyst article of claim 1 or 2, wherein the first PGM component is supported on the first alumina.

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

12. The catalytic article of claim 11 , wherein the second catalytic region comprises a second PGM component.

13. 13. The catalytic article of claim 12, wherein the second PGM component is selected from the group consisting of Pd, Pt, Rh, and mixtures thereof.

14. 12. The catalytic article of claim 11, wherein the second catalytic region further comprises a second oxygen storage capacity (OSC) material, a second alkali metal or alkaline earth metal component, and / or a second inorganic oxide.

15. The catalytic article of claim 11 , wherein the second catalytic region is supported / deposited directly on the substrate.

16. The catalytic article of claim 11 , wherein the first catalytic region is supported / deposited on the second catalytic region.

17. 3. An emissions treatment system for treating a combustion exhaust gas stream comprising the catalytic article of claim 1 or 2.

18. A method for treating exhaust gas from an internal combustion engine, comprising contacting said exhaust gas with the catalytic article of claim 1 or 2.

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