Platinum-rich multi-zone catalyst for cng engine exhaust treatment

Abstract

A three-way catalyst article, and its use in exhaust systems for compressed natural gas engines, are disclosed. A catalyst article for treating exhaust gas of a compressed natural gas (CNG) engine comprises: a substrate comprising an inlet end and an outlet end, and having an axial length L; a first catalytic zone starting at the inlet end and extending less than the axial length L, wherein the first catalytic zone comprises a first platinum component; and a second catalytic zone starting at the outlet end and extending less than the axial length L, wherein the second catalytic zone comprises a second palladium component; and a third catalytic zone, wherein the third catalytic zone comprises a third rhodium component.

Description

Technical Field

[0001] This invention relates to catalytic articles that can be used to treat exhaust emissions from compressed natural gas (CNG) engines. Background Technology

[0002] Compressed natural gas (CNG) contains simple hydrocarbons (primarily methane), which results in significantly lower CO2 production per unit of energy, and CNG has been used as a clean energy alternative to conventional gasoline and diesel fuels. Furthermore, CNG is favored by the market due to its abundant supply and relatively low price, leading to increasing attention on CNG engines in the automotive market in recent years, especially for heavy-duty vehicles operating under stoichiometric calibration. Even when operating with CNG, vehicle exhaust emissions are unavoidable, typically containing pollutants such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). x Furthermore, CNG engine exhaust emission control typically employs conventional gasoline emission catalysts, specifically the three-way catalytic converter (TWC).

[0003] Palladium (Pd) and rhodium (Rh) have been widely used in catalyst formulations to reduce harmful emissions from gasoline vehicles. Similar Pd-Rh TWCs are commonly used in stoichiometric CNG engine applications, typically containing relatively high Pd loadings. However, in recent years, the prices of these precious metals have risen due to increasing market demand, making them more expensive. On the other hand, stricter environmental regulations worldwide have forced the automotive industry to use even more expensive metals in their catalytic converters. Meanwhile, platinum (Pt) has become a more attractive option for gasoline applications due to its relatively lower price; currently, Pd is still almost twice the price of Pt. Therefore, there is a significant financial incentive to incorporate Pt into catalyst formulations, or at least partially replace Pd, while maintaining comparable catalytic performance. Historically, for existing Pd-Rh TWC formulations, simply replacing Pd with Pt has generally resulted in poorer performance, especially as the replacement ratio increases.

[0004] To meet increasingly stringent regulations and achieve cost savings, the use of Pt in CNG applications has gained widespread market attention. This work introduces new approaches to catalyst design; this novel Pt-rich TWC design not only exhibits improved emission control performance but also provides significant cost reductions by optimizing the Pt and Pd positions in multiple catalytic regions, as described in this invention. Summary of the Invention

[0005] One aspect of the present invention relates to a catalyst article for treating exhaust gas from a compressed natural gas (CNG) engine, comprising: a substrate having an inlet end and an outlet end and having an axial length L; a first catalytic region starting at the inlet end and extending less than the axial length L, wherein the first catalytic region comprises a first platinum component; a second catalytic region starting at the outlet end and extending less than the axial length L, wherein the second catalytic region comprises a second palladium component; and a third catalytic region comprising a third rhodium component.

[0006] The present invention also includes an exhaust system for a CNG engine, which contains the catalyst article of the present invention.

[0007] The present invention also includes a method for treating exhaust gases from CNG engines, particularly exhaust gases from stoichiometric CNG engines. This method includes contacting the exhaust gases with the catalyst article of the present invention. Attached Figure Description

[0008] Figure 1a The illustration shows an embodiment of the invention in which a first catalytic region extends from the inlet end by less than 100% of the axial length L; a second catalytic region extends from the outlet end by less than 100% of the axial length L. The total length of the second and first catalytic regions is equal to the axial length L. A third catalytic region extends 100% of the axial length L and serves as a top layer covering the first and second catalytic regions.

[0009] Figure 1b The illustration shows an embodiment of the invention in which a first catalytic region extends from the inlet end by less than 100% of the axial length L; a second catalytic region extends from the outlet end by less than 100% of the axial length L. The total length of the second and first catalytic regions is greater than the axial length L. A third catalytic region extends 100% of the axial length L and serves as a top layer covering the first and second catalytic regions.

[0010] Figure 1c Showing Figure 1b A variant of .

[0011] Figure 1d The illustration shows an embodiment of the invention in which a first catalytic region extends from the inlet end for less than 100% of the axial length L; a second catalytic region extends from the outlet end for less than 100% of the axial length L. The total length of the second and first catalytic regions is less than the axial length L. A third catalytic region extends for 100% of the axial length L and serves as a top layer covering the first and second catalytic regions.

[0012] Figure 1eThis illustration shows an embodiment of the invention, in which a third catalytic region extends as the bottom layer for 100% of the axial length L, a first catalytic region extends from the inlet end for less than 100% of the axial length L, and a second catalytic region extends from the outlet end for less than 100% of the axial length L. The total length of the second and first catalytic regions is equal to (or may be greater than or less than) the axial length L.

[0013] Figure 2a This illustration shows an embodiment of the invention where a first catalytic region extends from the inlet end for less than 100% of the axial length L; a second catalytic region extends from the outlet end for less than 100% of the axial length L. The total length of the second and first catalytic regions is equal to (or may be greater than or less than) the axial length L. A third catalytic region extends from the inlet end for less than 100% of the axial length L.

[0014] Figure 2b This illustration shows an embodiment of the invention where a first catalytic region extends from the inlet end for less than 100% of the axial length L; a second catalytic region extends from the outlet end for less than 100% of the axial length L. The total length of the second and first catalytic regions is equal to (or may be greater than or less than) the axial length L. A third catalytic region extends from the outlet end for less than 100% of the axial length L. Detailed Implementation

[0015] This invention relates to the catalytic treatment of combustion exhaust gases, such as those produced by stoichiometric CNG engines, and to related catalytic products and systems. More specifically, this invention relates to Pt-containing TWCs that improve the treatment of CH4 and NO in vehicle exhaust systems. x The present invention improves emission control performance and also reduces catalyst cost by replacing Pd with Pt.

[0016] One aspect of the present invention relates to a catalyst article for treating exhaust gas from a compressed natural gas (CNG) engine, comprising: a substrate having an inlet end and an outlet end and having an axial length L; a first catalytic region starting at the inlet end and extending less than the axial length L, wherein the first catalytic region comprises a first platinum component; a second catalytic region starting at the outlet end and extending less than the axial length L, wherein the second catalytic region comprises a second palladium component; and a third catalytic region comprising a third rhodium component.

[0017] First catalytic region

[0018] The first catalytic region can contain 0.1 to 300 g / ft 3 The first Pt component. Preferably, the first catalytic region may contain 10 to 200 g / ft. 3 The first Pt component, more preferably 15 to 150 g / ft 3The first Pt component. In some embodiments, the first catalytic region may further comprise a first Pd component, wherein the weight ratio of Pd to Pt in the first catalytic region may be less than 1:1; preferably less than 1:2; more preferably not greater than 1:3, 1:5, 1:8, 1:10, or 1:20.

[0019] Optionally, the first catalytic region may be substantially free of other PGM components besides the first Pt component.

[0020] The first catalytic region may further include a first oxygen storage capacity (OSC) material, a first alkali metal or alkaline earth metal component, and / or a first inorganic oxide.

[0021] The first OSC material can be cerium dioxide, zirconium oxide, a cerium dioxide-zirconia mixed oxide, an aluminum oxide-cerium dioxide-zirconia mixed oxide, or a combination thereof. More preferably, the first OSC material comprises a cerium dioxide-zirconia mixed oxide, an aluminum oxide-cerium dioxide-zirconia mixed oxide, or a combination thereof. The cerium dioxide-zirconia mixed oxide may further comprise one or more dopants such as oxides of lanthanum, neodymium, praseodymium, yttrium, etc. The first OSC material can serve as a carrier material for the first Pt component. In some embodiments, the first OSC material comprises a cerium dioxide-zirconia mixed oxide and an aluminum oxide-cerium dioxide-zirconia mixed oxide.

[0022] The first inorganic oxide is preferably an oxide of elements from Groups 2, 3, 4, 5, 13, and 14. The first inorganic oxide is preferably an oxide selected from aluminum oxide, zirconium oxide, magnesium oxide, silicon dioxide, lanthanum, neodymium, praseodymium, yttrium, and their mixed oxides or composite oxides. Particularly preferred is aluminum oxide, lanthanum-alumina, zirconium oxide, or a magnesium oxide / alumina composite oxide. Even more preferred is aluminum oxide, lanthanum / alumina composite oxide, or a magnesium oxide / alumina composite oxide. A particularly preferred first inorganic oxide is aluminum oxide or lanthanum-alumina.

[0023] The weight ratio of the first OSC material to the first inorganic oxide can be no greater than 10:1, preferably no greater than 8:1 or 5:1, more preferably no greater than 4:1, and most preferably no greater than 3:1.

[0024] Optionally, the weight ratio of the first OSC material to the first inorganic oxide can be 10:1 to 1:10, preferably 8:1 to 1:8; more preferably 5:1 to 1:5; and most preferably 4:1 to 1:4.

[0025] The loading of the first OSC material in the second catalytic region can be less than 2 g / in. 3In some implementations, the loading of the first OSC material in the first catalytic region is no greater than 1.5 g / in. 3 1.2g / in 3 1g / in 3 0.8g / in 3 or 0.7g / in 3 .

[0026] The first alkali metal or alkaline earth metal is preferably barium or strontium, and their mixed oxides or complex oxides. Preferably, the amount of barium or strontium present is 0.1 to 15 wt% based on the total weight of the first catalytic region, more preferably 1.5 to 10 wt% of barium or strontium.

[0027] Preferably, barium or strontium is present as BaCO3 or SrCO3. This material can be prepared by any method known in the art, such as initial wetting, wet impregnation, or spray drying.

[0028] In some embodiments, the first catalytic region is substantially free of the first alkali metal or alkaline earth metal. In another embodiment, the first catalytic region is substantially free of or contains no first alkali metal or alkaline earth metal.

[0029] In some embodiments, the first catalytic region may extend from 10% to 90%, 20% to 80%, or 30% to 70% of the axial length L. Optionally, the first catalytic region may extend from 35% to 65% of the axial length L. Preferably, it extends from 40% to 65% of the axial length L, more preferably from 45% to 65%.

[0030] Optionally, the first catalytic region may not exceed 99%, 95%, 90%, or 85% of the axial length L. Optionally, in some embodiments, the first catalytic region may not exceed 50%, 40%, 30%, or 20% of the axial length L.

[0031] The first catalytic region may further comprise a first rare earth metal component, such as lanthanum, neodymium, praseodymium, yttrium, gadolinium, scandium, etc., or mixtures thereof. These rare earth metal components may be introduced as dopants or mixed in as physical mixtures / blends, such as in the form of oxides.

[0032] The total support coating loading in the first catalytic region can be less than 3.5 g / in. 3 Preferably less than 3.0 g / in 3 or 2.5g / in 3 Optionally, the total support coating loading in the first catalytic region can be from 0.5 to 3.5 g / in. 3 The preferred dosage is 0.6 to 3 g / in. 3 or 0.7 to 2.5 g / in 3 .

[0033] Second catalytic region

[0034] The second catalytic region can contain 0.1 to 150 g / ft 3 The second Pd component. Preferably, the second catalytic region may contain 5 to 120 g / ft. 3 The second Pd component, more preferably 10 to 90 g / ft 3 The second Pd component. In some embodiments, the second catalytic region may further include a second Pt component, wherein the weight ratio of Pt to Pd in ​​the second catalytic region may be less than 1:1; preferably less than 1:2; more preferably not greater than 1:3, 1:5, 1:8, 1:10, or 1:20.

[0035] Optionally, in some embodiments, the weight ratio of Pd to Pt in the second catalytic region may be less than 1:1; preferably less than 1:2; more preferably at least 1:3, 1:5, 1:8, 1:10, or 1:20.

[0036] Alternatively, the second catalytic region may be substantially free of other PGM components besides the second Pd component.

[0037] The second catalytic region may further include a second oxygen storage capacity (OSC) material, a second alkali metal or alkaline earth metal component, and / or a second inorganic oxide.

[0038] The second OSC material can be cerium dioxide, zirconium oxide, a cerium dioxide-zirconia mixed oxide, an aluminum oxide-cerium dioxide-zirconia mixed oxide, or a combination thereof. More preferably, the second OSC material comprises a cerium dioxide-zirconia mixed oxide, an aluminum oxide-cerium dioxide-zirconia mixed oxide, or a combination thereof. Additionally, the second OSC material may further comprise one or more dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material may function as a support material for the second Pd and / or Pt component. In some embodiments, the second OSC material comprises a cerium dioxide-zirconia mixed oxide and an aluminum oxide-cerium dioxide-zirconia mixed oxide.

[0039] The weight ratio of zirconium dioxide to cerium dioxide in the cerium dioxide-zirconia mixed oxide is at least 50:50, preferably higher than 60:40, and more preferably higher than 65:35. Optionally, the weight ratio of cerium dioxide to zirconium dioxide in the cerium dioxide-zirconia mixed oxide may also be less than 50:50, preferably less than 40:60, and more preferably less than 35:65.

[0040] The second OSC material (e.g., cerium dioxide-zirconia mixed oxide) can be 10 to 90 wt%, preferably 20 to 90 wt%, more preferably 30 to 90 wt%, based on the total carrier coating loading of the second catalytic region.

[0041] The loading of the second OSC material in the second catalytic region can be less than 2 g / in. 3 In some implementations, the loading of the second OSC material in the second catalytic region is no greater than 1.5 g / in. 3 1.2g / in 3 1g / in 3 0.8g / in 3 or 0.7g / in 3 .

[0042] The second alkali metal or alkaline earth metal is preferably barium, strontium, or their mixed oxides or complex oxides. Preferably, the amount of barium or strontium present is 0.1 to 15 wt% based on the total weight of the second catalytic region, more preferably 1.5 to 10 wt% of barium or strontium.

[0043] Even more preferably, the second alkali metal or alkaline earth metal is strontium. The preferred amount of strontium present is 0.1 to 15 wt%, more preferably 1.5 to 10 wt%, based on the total weight of the second catalytic region.

[0044] Preferably, the second alkali metal or alkaline earth metal is a mixed oxide or composite oxide of barium and strontium. Preferably, the amount of the mixed oxide or composite oxide of barium and strontium is 0.1 to 15 wt% based on the total weight of the second catalytic region, more preferably 1.5 to 10 wt%. More preferably, the second alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

[0045] Preferably, barium or strontium is present as BaCO3 or SrCO3. This material can be prepared by any method known in the art, such as initial wetting, wet impregnation, or spray drying.

[0046] In some embodiments, the second catalytic region is substantially free of a second alkali metal or alkaline earth metal. In another embodiment, the second catalytic region is substantially free of or contains no second alkali metal or alkaline earth metal.

[0047] The second inorganic oxide is preferably an oxide of elements from Groups 2, 3, 4, 5, 13, and 14. The second inorganic oxide is preferably an oxide selected from aluminum oxide, zirconium oxide, magnesium oxide, silicon dioxide, lanthanum, yttrium, neodymium, praseodymium, and their mixed or composite oxides. Particularly preferred is aluminum oxide, lanthanum-alumina, zirconium oxide, or a magnesium oxide / alumina composite oxide. A particularly preferred second inorganic oxide is aluminum oxide or lanthanum-alumina.

[0048] The weight ratio of the second OSC material to the second inorganic oxide can be no greater than 10:1, preferably no greater than 8:1, more preferably no greater than 5:1, and most preferably no greater than 4:1.

[0049] Optionally, the weight ratio of the second OSC material to the second inorganic oxide can be 10:1 to 1:10, preferably 8:1 to 1:8; more preferably 5:1 to 1:5; and most preferably 4:1 to 1:4.

[0050] In some embodiments, the second catalytic region may extend 10% to 90%, 20% to 80%, or 30% to 70% of the axial length L. Optionally, the second catalytic region may extend 35% to 65% of the axial length L. Preferably, it extends 40% to 65% of the axial length L, more preferably 45% to 65%.

[0051] Optionally, the second catalytic region may be no greater than 99%, 95%, 90%, or 85% of the axial length L.

[0052] Preferably, the total length of the second region and the first region is equal to or greater than the axis length L.

[0053] The second catalytic region may overlap the first catalytic region by 1 to 80% of its axial length L; preferably 1 to 60%; more preferably 1 to 50%, 1 to 30%, 1 to 20%, or even 1 to 15%. Optionally, the total length of the second and first catalytic regions may be equal to the axial length L. Still alternatively, the total length of the second and first catalytic regions may be less than the axial length L, for example, not greater than 95%, 90%, 80%, or 70% of the axial length L.

[0054] In some embodiments, the first catalytic region can be directly loaded / deposited on the substrate. In some embodiments, the second catalytic region can be directly loaded / deposited on the substrate.

[0055] The second catalytic region may further contain a second rare earth metal component, such as lanthanum, neodymium, praseodymium, yttrium, gadolinium, scandium, or combinations thereof. These rare earth metal components may be introduced as dopants or mixed in as physical mixtures / blends, such as in the form of oxides.

[0056] The total support coating loading in the second catalytic region can be less than 3.5 g / in. 3 Preferably less than 3.0 g / in 3 or 2.5g / in 3 Optionally, the total support coating loading in the first catalytic region can be from 0.5 to 3.5 g / in. 3 The preferred dosage is 0.6 to 3 g / in. 3 or 0.7 to 2.5 g / in 3 .

[0057] Third catalytic region

[0058] The third catalytic region can contain 0.1 to 30 g / ft 3 The third Rh component. Preferably, the third catalytic region may contain 0.5 to 15 g / ft. 3 The third Rh component, more preferably 1 to 10 g / ft 3 The third Rh component.

[0059] The third catalytic region may further include a third PGM component, a third oxygen storage capacity (OSC) material, a third alkali metal or alkaline earth metal component, and / or a third inorganic oxide.

[0060] The third PGM component can be platinum, palladium, or a mixture thereof.

[0061] Alternatively, the third catalytic region may be substantially free of other PGM components besides the third Rh component.

[0062] The third OSC material can be cerium dioxide, zirconium oxide, a cerium dioxide-zirconia mixed oxide, an aluminum oxide-cerium dioxide-zirconia mixed oxide, or a combination thereof. More preferably, the third OSC material comprises a cerium dioxide-zirconia mixed oxide, an aluminum oxide-cerium dioxide-zirconia mixed oxide, or a combination thereof. Additionally, the third OSC material may further comprise one or more dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the third OSC material may function as a carrier material for the third Rh and / or PGM components. In some embodiments, the third OSC material comprises a cerium dioxide-zirconia mixed oxide and an aluminum oxide-cerium dioxide-zirconia mixed oxide.

[0063] The weight ratio of zirconium oxide to cerium dioxide in the cerium dioxide-zirconia mixed oxide can be at least 50:50, preferably higher than 60:40, and more preferably higher than 65:35. Optionally, the cerium dioxide-zirconia mixed oxide can also have a weight ratio of cerium dioxide to zirconium oxide of less than 50:50, preferably less than 40:60, and more preferably less than 35:65.

[0064] The third OSC material (e.g., cerium dioxide-zirconia mixed oxide) can be 10 to 90 wt%, preferably 25 to 75 wt%, more preferably 30 to 60 wt%, based on the total carrier coating loading of the third catalytic region.

[0065] The loading of the third OSC material in the third catalytic region can be less than 2 g / in. 3 In some implementations, the loading of the third OSC material in the second catalytic region is no greater than 1.5 g / in. 3 1.2g / in 3 0.9g / in3 0.8g / in 3 or 0.7g / in 3 .

[0066] The total support coating loading in the third catalytic region can be less than 3.5 g / in. 3 Preferably, the concentration is no greater than 3.0 g / in. 3 2.5g / in 3 or 2g / in 3 .

[0067] The third alkali metal or alkaline earth metal is preferably barium, strontium, or their mixed oxides or complex oxides. Preferably, the amount of barium or strontium present is 0.1 to 15 wt% based on the total weight of the third catalytic region, more preferably 3 to 10 wt% of barium or strontium.

[0068] Even more preferred is the third alkali metal or alkaline earth metal, strontium. The preferred amount of strontium present is 0.1 to 15 wt%, more preferably 1.5 to 10 wt%, based on the total weight of the third catalytic region.

[0069] Preferably, the third alkali metal or alkaline earth metal is a mixed oxide or composite oxide of barium and strontium. Preferably, the amount of the mixed oxide or composite oxide of barium and strontium is 0.1 to 15 wt% based on the total weight of the third catalytic region, more preferably 1.5 to 10 wt%. More preferably, the third alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

[0070] Preferably, barium or strontium is present as BaCO3 or SrCO3. This material can be prepared by any method known in the art, such as initial wetting, wet impregnation, or spray drying.

[0071] In some embodiments, the third catalytic region is substantially free of a third alkali metal or alkaline earth metal. In another embodiment, the third catalytic region is substantially free of or contains no third alkali metal or alkaline earth metal.

[0072] The third inorganic oxide is preferably an oxide of elements from Groups 2, 3, 4, 5, 13, and 14. The third inorganic oxide is preferably an oxide selected from aluminum oxide, zirconium oxide, magnesium oxide, silicon dioxide, lanthanum, neodymium, praseodymium, yttrium, and their mixed or composite oxides. Particularly preferred is aluminum oxide, lanthanum-alumina, zirconium oxide, or a magnesium oxide / alumina composite oxide. A particularly preferred third inorganic oxide is aluminum oxide or lanthanum-alumina.

[0073] The weight ratio of the third OSC material to the third inorganic oxide can be no greater than 10:1, preferably no greater than 8:1 or 5:1, more preferably no greater than 5:1, and most preferably no greater than 4:1.

[0074] Optionally, the weight ratio of the third OSC material to the third inorganic oxide can be 10:1 to 1:10, preferably 8:1 to 1:8; or more preferably 5:1 to 1:5; or most preferably 4:1 to 1:4.

[0075] The third catalytic region can extend to 100% of the axial length L. Alternatively, the third catalytic region can be smaller than the axial length L, for example, not greater than 95%, 90%, 80%, or 70% of the axial length L. In some embodiments, the third catalytic region can extend from the inlet end. In other embodiments, the third catalytic region can extend from the outlet end. In some embodiments, the third catalytic region can be directly loaded / deposited on the substrate.

[0076] In some embodiments, the first Pt component in the first catalytic region may be at least 50%, 60%, 70%, or even 80% of the total Pt loading in the catalyst article.

[0077] In some implementations, the ratio (by weight) of the total Pt load to the total Pd load is at least 1:5, at least 1:4, at least 1:3, at least 2:5, or 1:2.

[0078] Construction of the first, second and third catalytic regions

[0079] The second catalytic region may overlap the first catalytic region by 1 to 80% of its axial length L; preferably 1 to 60%; more preferably 1 to 50%, 1 to 30%, 1 to 20%, or even 1 to 15% (see, for example, [link to relevant documentation]). Figure 1b , Figure 1c The first catalyst region may cover the second catalyst region, or the second catalyst region may cover the first catalyst region. Optionally, the total length of the second catalyst region and the first catalyst region may be equal to the axial length L (see, for example, [link to relevant documentation]). Figure 1a , Figure 2a Alternatively, the total length of the second catalytic region and the first catalytic region may be less than the axial length L, for example, not greater than 95%, 90%, 80%, or 70% of the axial length L (see, for example, see...). Figure 1d ).

[0080] In one aspect of the invention, catalyst articles comprising different structures of first, second and third catalytic regions can be prepared as follows.

[0081] Figure 1a The illustration shows an embodiment of the invention in which a first catalytic region extends from the inlet end by less than 100% of the axial length L; a second catalytic region extends from the outlet end by less than 100% of the axial length L. The total length of the second and first catalytic regions is equal to the axial length L. A third catalytic region extends 100% of the axial length L and serves as a top layer covering the first and second catalytic regions.

[0082] Figure 1b The illustration shows an embodiment of the invention in which a first catalytic region extends from the inlet end by less than 100% of the axial length L; a second catalytic region extends from the outlet end by less than 100% of the axial length L. The total length of the second and first catalytic regions is greater than the axial length L. A third catalytic region extends 100% of the axial length L and serves as a top layer covering the first and second catalytic regions.

[0083] Figure 1c Showing Figure 1b A variant of .

[0084] Figure 1d The illustration shows an embodiment of the invention in which a first catalytic region extends from the inlet end for less than 100% of the axial length L; a second catalytic region extends from the outlet end for less than 100% of the axial length L. The total length of the second and first catalytic regions is less than the axial length L. A third catalytic region extends for 100% of the axial length L and serves as a top layer covering the first and second catalytic regions.

[0085] Figure 1e This illustration shows an embodiment of the invention, in which a third catalytic region extends as the bottom layer for 100% of the axial length L, a first catalytic region extends from the inlet end for less than 100% of the axial length L, and a second catalytic region extends from the outlet end for less than 100% of the axial length L. The total length of the second and first catalytic regions is equal to (or may be greater than or less than) the axial length L.

[0086] Figure 2a This illustration shows an embodiment of the invention where a first catalytic region extends from the inlet end for less than 100% of the axial length L; a second catalytic region extends from the outlet end for less than 100% of the axial length L. The total length of the second and first catalytic regions is equal to (or may be greater than or less than) the axial length L. A third catalytic region extends from the inlet end for less than 100% of the axial length L.

[0087] Figure 2b This illustration shows an embodiment of the invention where a first catalytic region extends from the inlet end for less than 100% of the axial length L; a second catalytic region extends from the outlet end for less than 100% of the axial length L. The total length of the second and first catalytic regions is equal to (or may be greater than or less than) the axial length L. A third catalytic region extends from the outlet end for less than 100% of the axial length L.

[0088] substrate

[0089] Preferably, the substrate is a flow-through monolithic material.

[0090] The length of the substrate can be less than 200mm, preferably 60 to 160mm.

[0091] The flow-through monolithic substrate has a first surface and a second surface defining a longitudinal length therebetween. The flow-through monolithic substrate has a plurality of channels extending between the first and second surfaces. These channels extend longitudinally and provide a plurality of inner surfaces (e.g., surfaces defining the walls of 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 ambiguity, the flow-through monolithic substrate is not a wall-flow filter.

[0092] The first side is typically located at the inlet end of the substrate, and the second side is located at the outlet end of the substrate.

[0093] Channels can have a constant width, and multiple channels can each have a uniform channel width.

[0094] Preferably, in a plane perpendicular to the longitudinal direction, the monolithic substrate has 300 to 900 channels per square inch, more preferably 400 to 800. For example, on the first surface, the density of open first channels and closed second channels is 600 to 700 channels per square inch. The cross-section of the channels can be rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal.

[0095] The monolithic substrate serves as a carrier for the catalytic material. Suitable materials for forming the monolithic substrate include ceramic materials such as cordierite, silicon carbide, silicon nitride, zirconium oxide, mullite, spodumene, alumina-silica magnesium oxide or zirconium silicate, or porous, refractory metal materials. Such materials and their uses in the manufacture of porous monolithic substrates are well known in the art.

[0096] It should be noted that the flow-through monolithic substrate described herein is a single element (i.e., a single block). However, when forming an emission treatment system, the substrate used can be formed by adhering multiple channels together, or by adhering multiple smaller substrates described herein together. This technique is well known in the art, as are suitable housings and constructions for emission treatment systems.

[0097] In embodiments of the catalyst article of the present invention comprising a ceramic substrate, the ceramic substrate may be made of any suitable refractory material, such as alumina, silicon dioxide, cerium dioxide, zirconium oxide, magnesium oxide, zeolite, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicates and quasi-metallic aluminosilicates (e.g., cordierite and spodumene), or any mixture or mixed oxide of two or more thereof. Cordierite (a type of magnesium aluminosilicate) and silicon carbide are particularly preferred.

[0098] In embodiments of the catalyst article of the present invention comprising 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, as well as ferritic alloys containing iron, nickel, chromium and / or aluminum and other trace metals.

[0099] Another aspect of the present invention relates to a method for treating NO-containing products using the catalyst described herein. x A method for processing CNG engine exhaust gases containing CO and HC (methane). Test catalysts prepared according to this method exhibit improved catalytic performance compared to conventional TWCs (with the same or similar PGM loading) (see, for example, Examples 1-3; and Tables 2-4).

[0100] Another aspect of the invention relates to a system for treating exhaust gases from CNG engine vehicles, comprising the catalyst article described herein and a connected conduit for conveying the exhaust gases through the system.

[0101] definition

[0102] As used herein, the term "region" refers to an area on a substrate, typically derived from the drying and / or calcination of a carrier coating. A "region" may be located or loaded on the substrate, for example, as a "layer" or "interval." The extent or arrangement on the substrate is typically controlled during the method of applying the carrier coating to the substrate. A "region" typically has a distinct boundary or edge (i.e., one region can be distinguished from another using conventional analytical techniques).

[0103] Typically, a “region” has a generally uniform length. In this context, “generally uniform length” means a length whose deviation from its average (e.g., the difference between the maximum and minimum lengths) is no more than 10%, preferably no more than 5%, and more preferably no more than 1%.

[0104] Preferably, each “region” has a substantially uniform composition (i.e., there is no significant difference in the composition of the carrier coating when one part of the region is compared to another part of the region). In this context, a substantially uniform composition refers to a material (e.g., a region) in which the composition differs by 5% or less, typically 2.5% or less, and most typically 1% or less when one part of the region is compared to another part of the region.

[0105] As used herein, the term “interval” refers to a region whose length is less than the total length of the substrate, for example, ≤75% of the total length of the substrate. The typical length of an “interval” (i.e., a substantially uniform length) is at least 5% (e.g., ≥5%) of the total length of the substrate.

[0106] The total length of the substrate is the distance between its inlet end and its outlet end (e.g., the opposite end of the substrate).

[0107] As used herein, any reference to "an area located at the inlet end of the substrate" means an area located on or loaded onto the substrate, wherein the area is closer to the inlet end of the substrate than the area to the outlet end of the substrate. Therefore, the midpoint of the area (i.e., at half its length) is closer to the inlet end of the substrate than the midpoint of the area to the outlet end of the substrate. Similarly, as used herein, any reference to "an area located at the outlet end of the substrate" means an area located on or loaded onto the substrate, wherein the area is closer to the outlet end of the substrate than the area to the inlet end of the substrate. Therefore, the midpoint of the area (i.e., at half its length) is closer to the outlet end of the substrate than the midpoint of the area to the inlet end of the substrate.

[0108] When the substrate is a wall-flow filter, any reference to "the section located at the inlet end of the substrate" generally refers to the section located on or loaded onto the substrate, which:

[0109] (a) Closer to the inlet end (e.g., open end) of the inlet channel than the closed end (e.g., blocked or shut-off end) of the inlet channel from the interval to the substrate, and / or

[0110] (b) Closer to the closed end (e.g., blocked or shut-off end) of the outlet channel than the outlet end (e.g., open end) of the outlet channel from the interval to the substrate.

[0111] Therefore, the midpoint of the interval (i.e., at half its length) is (a) closer to the entrance end of the inlet channel than the closed end of the inlet channel to the substrate, and / or (b) closer to the closed end of the outlet channel than the outlet end of the outlet channel to the substrate.

[0112] Similarly, when the substrate is a wall-flow filter, any reference to "the section located at the outlet end of the substrate" refers to the section located on or loaded onto the substrate, which:

[0113] (a) Closer to the outlet end (e.g., open end) of the outlet channel than the closed end (e.g., blocked or shut-off end) of the outlet channel from the interval to the substrate, and / or

[0114] (b) It is closer to the closed end (e.g., the closed or blocked end) of the inlet channel than to the inlet end (e.g., the open end) of the inlet channel to the substrate.

[0115] Therefore, the midpoint of the interval (i.e., at half its length) (a) is closer to the exit end of the outlet channel than the closed end of the outlet channel to the substrate, and / or (b) is closer to the closed end of the inlet channel than the inlet end of the inlet channel to the substrate.

[0116] When the carrier coating is present in the wall of the wall-flow filter (i.e., the interval is inside the wall), the interval can satisfy both (a) and (b).

[0117] The term "carrier coating" is well known in the art and refers to an adhesive coating that is typically applied to a substrate during catalyst production.

[0118] As used herein, the acronym “PGM” refers to “platinum group metals”. The term “platinum group metals” generally refers to metals selected from Ru, Rh, Pd, Os, Ir, and Pt, preferably metals selected from Ru, Rh, Pd, Ir, and Pt. Typically, the term “PGM” preferably refers to metals selected from Rh, Pt, and Pd.

[0119] As used herein, the term "mixed oxide" generally refers to a mixture of single-phase oxides, as is known in the art. As used herein, the term "composite oxide" generally refers to an oxide composition having more than one phase, as is known in the art.

[0120] As used herein, the phrase "consistently composed of..." limits the scope of a feature to include the specified material or step, and any other material or step that does not substantially affect the essential properties of the feature, such as trace amounts of impurities. The phrase "consistently composed of..." encompasses the phrase "composed of...".

[0121] As used herein, the expression “substantially contains” refers to a small amount of material, typically in the context of a region, layer, or interval, such as ≤5% by weight, preferably ≤2% by weight, more preferably ≤1% by weight. The expression “substantially contains” encompasses the expression “contains”.

[0122] As used herein, the expression “substantially contains” refers to trace amounts of material, typically in the context of a region, layer, or interval, such as ≤1% by weight, preferably ≤0.5% by weight, more preferably ≤0.1% by weight. The expression “substantially contains” encompasses the expression “contains”.

[0123] As used herein, any reference to the amount of dopant, especially the total amount, expressed as % by weight, refers to the weight of the carrier material or its refractory oxide.

[0124] As used herein, the term "load capacity" refers to a quantity expressed in g / ft. 3 The measured values ​​are based on a metal weight gauge.

[0125] The following examples are merely illustrative of the invention. Those skilled in the art will recognize many variations that fall within the spirit and scope of the claims.

[0126] Example

[0127] Material

[0128] All materials are commercially available and, unless otherwise stated, are obtained from known suppliers.

[0129] Catalyst 1 (Comparison)

[0130] Catalyst 1 is a typical Pt-Pd-Rh ternary catalyst with three catalytic regions in a bilayer structure, such as... Figure 1a As shown.

[0131] First catalytic region:

[0132] The first catalytic region begins at the inlet end and consists of Pt and Pd supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkaline metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pt loading is 11 g / ft 3 The Pd loading capacity is 23g / ft 3 .

[0133] This carrier coating is then applied from the inlet face of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, and dried at 100°C.

[0134] Second catalytic region:

[0135] The second catalytic region begins at the outlet end and consists of Pt and Pd supported on a carrier coating, which is the same as that used in the first catalytic region.

[0136] This carrier coating is then applied from the exit side of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, followed by drying at 100°C and calcination at 500°C for 45 min.

[0137] Third catalytic region:

[0138] The third catalytic region consists of Rh supported on a La-stabilized alumina carrier coating of the second CeZr mixed oxide. The carrier coating loading in the third region is approximately 1.3 g / in. 3 And the Rh load is 4g / ft 3 .

[0139] This carrier coating is then applied from each end face of the ceramic substrate containing the first and second catalytic regions above using a standard coating procedure, with a target coating depth of 50% of the substrate length per dose, followed by drying at 100°C and calcination at 500°C for 45 min.

[0140] Catalyst 2 (Comparison)

[0141] Catalyst 2 is a Pt-Pd-Rh ternary catalyst with three catalytic regions in a bilayer structure.

[0142] First catalytic region:

[0143] The first catalytic region begins at the inlet end and consists of Pd supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkali metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pd loading capacity is 34g / ft 3 .

[0144] This carrier coating is then applied from the inlet face of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 67% of the substrate length, and dried at 100°C.

[0145] Second catalytic region:

[0146] The second catalytic region begins at the outlet and consists of Pt supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkaline metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pt loading is 34 g / ft 3 .

[0147] This carrier coating is then applied from the exit side of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 33% of the substrate length, followed by drying at 100°C and calcination at 500°C for 45 min.

[0148] Third catalytic region:

[0149] The third catalytic region consists of Rh supported on a La-stabilized alumina carrier coating of the second CeZr mixed oxide. The carrier coating loading in the third region is approximately 1.3 g / in. 3 And the Rh load is 4g / ft 3 .

[0150] This carrier coating is then applied from each end face of the ceramic substrate containing the first and second catalytic regions above using a standard coating procedure, with a target coating depth of 50% of the substrate length per dose, followed by drying at 100°C and calcination at 500°C for 45 min.

[0151] Catalyst 3

[0152] Catalyst 3 is a Pt-Pd-Rh ternary catalyst with three catalytic regions in a bilayer structure.

[0153] First catalytic region:

[0154] The first catalytic region begins at the inlet end and consists of Pt supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkali metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pt loading is 34 g / ft 3 .

[0155] This carrier coating is then applied from the inlet face of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 33% of the substrate length, and dried at 100°C.

[0156] Second catalytic region:

[0157] The second catalytic region begins at the outlet and consists of Pd supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkaline metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pd loading capacity is 34g / ft 3 .

[0158] This carrier coating is then applied from the exit side of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 67% of the substrate length, followed by drying at 100°C and calcination at 500°C for 45 min.

[0159] Third catalytic region:

[0160] The third catalytic region consists of Rh supported on a La-stabilized alumina carrier coating of the second CeZr mixed oxide. The carrier coating loading in the third region is approximately 1.3 g / in. 3 And the Rh load is 4g / ft 3 .

[0161] This carrier coating is then applied from each end face of the ceramic substrate containing the first and second catalytic regions above using a standard coating procedure, with a target coating depth of 50% of the substrate length per dose, followed by drying at 100°C and calcination at 500°C for 45 min.

[0162] Catalyst 4 (Comparison)

[0163] Catalyst 4 is a Pd-Rh ternary catalyst with three catalytic regions in a bilayer structure.

[0164] First catalytic region:

[0165] The first catalytic region begins at the inlet end and consists of Pd supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkali metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pd loading capacity is 34g / ft 3 .

[0166] This carrier coating is then applied from the inlet face of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, and dried at 100°C.

[0167] Second catalytic region:

[0168] The second catalytic region begins at the outlet end and consists of Pd supported on a carrier coating, which is the same as that used in the first catalytic region.

[0169] This carrier coating is then applied from the exit side of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, followed by drying at 100°C and calcination at 500°C for 45 min.

[0170] Third catalytic region:

[0171] The third catalytic region consists of Rh supported on a La-stabilized alumina carrier coating of the second CeZr mixed oxide. The carrier coating loading in the third region is approximately 1.3 g / in. 3 And the Rh load is 4g / ft 3 .

[0172] This carrier coating is then applied from each end face of the ceramic substrate containing the first and second catalytic regions above using a standard coating procedure, with a target coating depth of 50% of the substrate length per dose, followed by drying at 100°C and calcination at 500°C for 45 min.

[0173] Catalyst 5 (Comparison)

[0174] Catalyst 5 is a Pt-Rh ternary catalyst with three catalytic regions in a bilayer structure.

[0175] First catalytic region:

[0176] The first catalytic region begins at the inlet end and consists of Pt supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkali metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pt loading is 34 g / ft 3 .

[0177] This carrier coating is then applied from the inlet face of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, and dried at 100°C.

[0178] Second catalytic region:

[0179] The second catalytic region begins at the outlet end and consists of Pt loaded on a support coating, which is the same as that used in the first catalytic region.

[0180] This carrier coating is then applied from the exit side of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, followed by drying at 100°C and calcination at 500°C for 45 min.

[0181] Third catalytic region:

[0182] The third catalytic region consists of Rh supported on a La-stabilized alumina carrier coating of the second CeZr mixed oxide. The carrier coating loading in the third region is approximately 1.3 g / in. 3 And the Rh load is 4g / ft 3 .

[0183] This carrier coating is then applied from each end face of the ceramic substrate containing the first and second catalytic regions above using a standard coating procedure, with a target coating depth of 50% of the substrate length per dose, followed by drying at 100°C and calcination at 500°C for 45 min.

[0184] Catalyst 6 (Comparison)

[0185] Catalyst 6 is a Pt-Pd-Rh ternary catalyst with three catalytic regions in a bilayer structure.

[0186] First catalytic region:

[0187] The first catalytic region begins at the inlet end and consists of Pd supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkali metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pd loading capacity is 34g / ft 3.

[0188] This carrier coating is then applied from the inlet face of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, and dried at 100°C.

[0189] Second catalytic region:

[0190] The second catalytic region begins at the outlet and consists of Pt supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkaline metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pd loading capacity is 34g / ft 3 .

[0191] This carrier coating is then applied from the exit side of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, followed by drying at 100°C and calcination at 500°C for 45 min.

[0192] Third catalytic region:

[0193] The third catalytic region consists of Rh supported on a La-stabilized alumina carrier coating of the second CeZr mixed oxide. The carrier coating loading in the third region is approximately 1.3 g / in. 3 And the Rh load is 4g / ft 3 .

[0194] This carrier coating is then applied from each end face of the ceramic substrate containing the first and second catalytic regions above using a standard coating procedure, with a target coating depth of 50% of the substrate length per dose, followed by drying at 100°C and calcination at 500°C for 45 min.

[0195] Catalyst 7

[0196] Catalyst 7 is a Pt-Pd-Rh ternary catalyst with three catalytic regions in a bilayer structure.

[0197] First catalytic region:

[0198] The first catalytic region begins at the inlet end and consists of Pt supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkali metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pt loading is 34 g / ft 3 .

[0199] This carrier coating is then applied from the inlet face of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, and dried at 100°C.

[0200] Second catalytic region:

[0201] The second catalytic region begins at the outlet and consists of Pd supported on a carrier coating of a first CeZr mixed oxide, La-stabilized alumina, and an alkaline metal promoter. The carrier coating loading in the first region is approximately 2.4 g / in. 3 And the Pd loading capacity is 34g / ft 3 .

[0202] This carrier coating is then applied from the exit side of the ceramic substrate (400 cpsi, 4.3 mil wall thickness) using a standard coating procedure, with a target coating depth of 50% of the substrate length, followed by drying at 100°C and calcination at 500°C for 45 min.

[0203] Third catalytic region:

[0204] The third catalytic region consists of Rh supported on a La-stabilized alumina carrier coating of the second CeZr mixed oxide. The carrier coating loading in the third region is approximately 1.3 g / in. 3 And the Rh load is 4g / ft 3 .

[0205] This carrier coating is then applied from each end face of the ceramic substrate containing the first and second catalytic regions above using a standard coating procedure, with a target coating depth of 50% of the substrate length per dose, followed by drying at 100°C and calcination at 500°C for 45 min.

[0206] Catalyst 8

[0207] Catalyst 8 is a Pt-Pd-Rh ternary catalyst with three catalytic regions in a bilayer structure, identical to comparative catalyst 1, except that the first and second catalytic regions have the same Pt ​​loading of 4 g / ft. 3 And the same Pd loading capacity 8g / ft 3 Furthermore, the Rh load in the third region is 1 g / ft. 3 .

[0208] Example 1: Ignition performance test in the activity test of synthesis catalyst

[0209] Catalyst performance tests were conducted on comparative catalyst 1, comparative catalyst 2, and catalyst 3 using simulated exhaust gas under the following conditions, exhibiting fluctuations in composition as shown in Table 1.

[0210] Table 1. Simulated gas composition used for performance testing

[0211]

[0212] In the catalyst performance test, the gas flow rate was set at 40,000 m / h, the temperature was increased from 100°C to 550°C at a heating rate of 10°C / min, and the gas composition was analyzed after passing through the catalyst. Lower T 50 (Temperature at 50% conversion) indicates better catalytic performance. Comparative catalysts 1, 2, and 3 were oven aged for 36 hours at 850°C in air with 10% H2O.

[0213] As shown in Table 2, catalyst 3 is used for CH4 and NO compared to comparative catalysts 1 and 2. x The temperature at which 50% conversion is achieved is significantly lower.

[0214] Table 2 SCAT CH4 and NO x Ignition test results

[0215]

[0216] Example 2: CNG Vehicle Test Procedures and Results

[0217] Comparative catalysts 1, 2, and 3 were also tested under the World Light Vehicles Test Cycle (WLTC) in a light-duty CNG vehicle equipped with a 1.6L engine to evaluate emission control capabilities. The catalysts were aged for 73 hours on a gasoline engine bench under SBC 860 conditions.

[0218] As shown in Table 3, the CNG vehicle emission results indicate that catalyst 3 exhibits comparable CH4 emissions to the comparative catalyst 2, and significantly lower NO emissions compared to comparative catalysts 1 and 2. x emission.

[0219] Table 3 Emissions results from CNG vehicle dilution bag data

[0220]

[0221] Example 3: CNG station test procedure and results

[0222] Catalyst performance was tested using a natural gas engine under the Universally Harmonized Transient Cycle (WHTC). WHTC testing is considered a reliable method for evaluating engine emissions. Cold and hot WHTC tests were performed on each catalyst, and emissions after catalytic conversion were measured. The final WHTC emission value is the sum of the cold and hot WHTC values, representing 14% and 86%, respectively.

[0223] In WHTC testing, the aftertreatment system consisted of two parts, arranged with either catalyst 4, 5, or 6 or catalyst 7 upstream, and catalyst 8 downstream. The catalytic performance of the following systems was tested:

[0224] System 1 Comparison of catalyst 4 and catalyst 8

[0225] System 2 Comparison of catalyst 5 and catalyst 8

[0226] System 3 Comparison of catalyst 6 and catalyst 8

[0227] System 4 Catalyst 7 + Catalyst 8

[0228] The above-mentioned parts were aged in an oven at 850°C for 36 hours using air containing 10% H2O. Table 4 shows the emission results of systems 1 to 3 on a natural gas engine. The results show that system 4 exhibits the lowest NO emission at 275 mg / kWh. x Emissions, when catalyst 7 is replaced by any of the comparative catalysts 4 to 6, NO x Emissions have increased significantly. The CO and CH4 emissions from all systems (1-3) remain largely within the limits set by Chinese VI laws.

[0229] Table 4 Emissions results of natural gas engines under WHTC cycle

[0230]

Claims

1. A catalyst article for treating exhaust gas from a compressed natural gas (CNG) engine, comprising: The substrate includes an inlet end and an outlet end, and has an axial length L; A first catalytic region, which begins at the inlet end and extends less than the axial length L, wherein the first catalytic region contains a first platinum component; A second catalytic region, which begins at the outlet end and extends less than the axial length L, wherein the second catalytic region contains a second palladium component; and The third catalytic region, which contains a third rhodium component. The first Pt component in the first catalytic region is at least 50% of the total Pt loading in the catalyst product.

2. The catalyst article according to claim 1, wherein the first catalytic region extends 10 to 90% of the axial length L.

3. The catalyst article according to claim 1 or 2, wherein the second catalytic region extends 10 to 90% of the axial length L.

4. The catalyst article according to claim 1 or 2, wherein the second catalytic region overlaps the first catalytic region by 1 to 80% of the axial length L.

5. The catalyst article according to claim 1 or 2, wherein the total length of the second catalytic region and the first catalytic region is equal to the axial length L.

6. The catalyst article according to claim 1 or 2, wherein the total length of the second catalytic region and the first catalytic region is less than the axial length L.

7. The catalyst article according to claim 1 or 2, wherein the third catalytic region extends 100% of the axial length L.

8. The catalyst article according to claim 1 or 2, wherein the third catalytic region extends less than 100% of the axial length L.

9. The catalyst article according to claim 1 or 2, wherein the first catalytic region further comprises a first OSC material, a first alkali metal or alkaline earth metal component, a first inorganic oxide and / or a first rare earth component.

10. The catalyst article according to claim 1 or 2, wherein the second catalytic region further comprises a second platinum component, a second OSC material, a second alkali metal or alkaline earth metal component, a second inorganic oxide and / or a second rare earth component.

11. The catalyst article according to claim 1 or 2, wherein the third catalytic region further comprises a third platinum group metal (PGM) component, a third OSC material, a third alkali metal or alkaline earth metal component and / or a third inorganic oxide.

12. The catalyst article according to claim 11, wherein the third PGM component is Pd, Pt, or a combination thereof.

13. The catalyst article according to claim 1 or 2, wherein the substrate is a flow-through monolithic material.

14. The catalyst article according to claim 1 or 2, wherein the first catalytic region is directly supported / deposited on the substrate.

15. The catalyst article according to claim 1 or 2, wherein the second catalytic region is directly supported / deposited on the substrate.

16. The catalyst article according to claim 1 or 2, wherein the third catalytic region is directly supported / deposited on the substrate.

17. An emission treatment system for treating CNG exhaust gas, comprising a catalyst article according to any one of claims 1-16.

18. A method for treating CNG engine exhaust gas, comprising contacting the exhaust gas with a catalyst article according to any one of claims 1-16.

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