CN117957058A

CN117957058A - Catalyst for gasoline exhaust gas treatment with improved ammonia emission control

Info

Publication number: CN117957058A
Application number: CN202280060192.8A
Authority: CN
Inventors: 盖伊·理查德·钱德勒; S·康特; V·费兰德; M·霍华德; 长冈修平; A·鲍威尔; 张晓瑞
Original assignee: Johnson Matthey PLC
Current assignee: Johnson Matthey PLC
Priority date: 2021-11-02
Filing date: 2022-10-27
Publication date: 2024-04-30

Abstract

A three-way catalyst article with improved ammonia emission control and its use in an emission system for a gasoline engine are disclosed. A catalyst article for treating exhaust gas from a gasoline engine comprising: a base including an inlet end, an outlet end, having an axial length L; a first catalytic zone beginning at the inlet end, wherein the first catalytic zone comprises a first zeolite; and a second catalytic region beginning at the outlet end, wherein the second catalytic region comprises a second Platinum Group Metal (PGM) component, a second Oxygen Storage Capacity (OSC) material, and a second inorganic oxide; wherein the second PGM component is selected from the group consisting of: palladium, platinum, rhodium, and combinations thereof.

Description

Catalyst for gasoline exhaust gas treatment with improved ammonia emission control

Technical Field

The present invention relates to catalytic articles useful for treating exhaust emissions from gasoline engines.

Background

Internal combustion engines produce exhaust gas that contains a variety of pollutants including Hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides ("NO _x"). Emission control systems incorporating exhaust gas catalytic conversion catalysts are widely used to reduce the amount of these pollutants emitted into the atmosphere. A common catalyst for gasoline engine exhaust gas treatment is TWC (three-way catalyst). TWCs perform three main functions: (1) oxidation of CO; (2) oxidation of unburned HC; and (3) reduction of NO _x. However, ammonia (NH ₃) has been considered as a byproduct when using TWCs to reduce NO _x. Thus, NH ₃ presents new pollutant emission problems, such as secondary inorganic aerosol formations, which can lead to degradation of air quality. Future emission control regulations are expected to limit the emission of NH ₃ from gasoline engines.

In order to meet future regulations and enable NH ₃ emissions to be controlled, others have attempted to use an Ammonia Slip Catalyst (ASC), which is a typical emission control method in Heavy Duty Diesel (HDD) aftertreatment systems. However, due to the different composition (diesel versus gasoline) and different operating conditions (lean versus stoichiometric) in the fuel source, typical ASC designs are not very effective for NH ₃ emission control over stoichiometric gasoline engines. Thus, there remains a need for improved NH ₃ emission control catalysts specifically designed for treating exhaust emissions from stoichiometric gasoline engines.

Disclosure of Invention

One aspect of the present disclosure relates to a catalyst article for treating exhaust gas from a gasoline engine, the catalyst article comprising: a base including an inlet end, an outlet end, having an axial length L; a first catalytic zone beginning at the inlet end, wherein the first catalytic zone comprises a first zeolite; and a second catalytic region beginning at the outlet end, wherein the second catalytic region comprises a second Platinum Group Metal (PGM) component, a second Oxygen Storage Capacity (OSC) material, and a second inorganic oxide; wherein the second PGM component is selected from the group consisting of: palladium, platinum, rhodium, and combinations thereof.

The present invention also encompasses an exhaust system for a gasoline engine comprising the catalyst article of the present invention.

The invention also contemplates treating exhaust gas from a gasoline engine. The method comprises contacting the exhaust gas with the catalyst article of the present invention.

Drawings

Fig. 1 shows an embodiment according to the invention in which the first catalytic zone extends as top layer by 100% of the axial length L; the second catalytic zone extends as a bottom layer 100% of the axial length L.

FIG. 2a shows that the first catalytic zone extends from the inlet end less than 100% of the axial length L, according to one embodiment of the invention; the second catalytic zone extends from the outlet end less than 100% of the axial length L. The total length of the second catalytic zone and the first catalytic zone is equal to the axial length L.

FIG. 2b shows that the first catalytic zone extends from the inlet end less than 100% of the axial length L, according to one embodiment of the invention; the second catalytic zone extends 100% of the axial length L from the outlet end. The total length of the second catalytic zone and the first catalytic zone is greater than the axial length L.

FIG. 2c shows that the first catalytic zone extends from the inlet end less than 100% of the axial length L, according to one embodiment of the invention; the second catalytic zone extends 100% of the axial length L from the outlet end. The total length of the second catalytic zone and the first catalytic zone is greater than the axial length L.

FIG. 2d shows that the first catalytic zone extends from the inlet end less than 100% of the axial length L, according to one embodiment of the invention; the second catalytic zone extends from the outlet end less than 100% of the axial length L. The total length of the second catalytic zone and the first catalytic zone is less than the axial length L.

FIG. 3a shows that the first catalytic zone extends from the inlet end less than 100% of the axial length L, according to one embodiment of the invention; the second catalytic zone extends from the outlet end less than 100% of the axial length L. The total length of the second catalytic zone and the first catalytic zone is equal to the axial length L. The third catalytic zone extends from the outlet end less than 100% of the axial length L.

Fig. 3b shows an embodiment according to the invention, wherein the first catalytic zone extends as top layer by 100% of the axial length L; the second catalytic zone extends as a bottom layer by 100% of the axial length L; and the third catalytic zone extends 100% of the axial length L as an intermediate layer.

Detailed Description

The present invention relates to catalytic treatment of exhaust gas, such as exhaust gas produced by a stoichiometric gasoline engine, and to related catalytic articles and systems. More particularly, the present invention relates to inhibiting ammonia emissions while simultaneously treating NO _x, CO, and HC in the vehicle exhaust system.

First catalytic zone

The first zeolite may be a silica-containing zeolite such as a siliceous zeolite, and it may also be an aluminosilicate zeolite, a metal-substituted aluminosilicate zeolite, an aluminophosphate (AlPO) zeolite, a metal-substituted (MeAIPO) zeolite, a Silicoaluminophosphate (SAPO) or a metal-substituted silicoaluminophosphate (MeAPSO) or a Zr, P-modified zeolite. Preferably, the zeolite is an aluminosilicate or Silicoaluminophosphate (SAPO) zeolite. More preferably, the zeolite is an aluminosilicate.

The zeolite may be microporous or microporous zeolite, and it is preferred that the zeolite has a framework type ：ACO、AEI、AEN、AFN、AFT、AFX、ANA、APC、APD、AST、ASV、ATT、BCT、BEA、BEC、BOF、BOG、BRE、CAN、CDO、CFI、CGS、CHA、CHI、CON、DAC、DDR、DFT、EAB、EDI、EPI、ERI、FER、GIS、GOD、IHW、ITE、ITW、LEV、KFI、MER、MFI、MON、NSI、OWE、PAU、PHI、RHO、RTH、SAT、SAV、SIV、THO、TSC、UEI、UFI、VNI、YUG、ZON. selected from the group consisting of each of the three letter codes described above represent framework types according to the IUPAC zeolite naming commission and/or the international zeolite association structural commission. More preferably, the first zeolite has a framework type selected from AEI, BEA, CHA, FER, FAU, MFA or LEV. In some embodiments, the first zeolite may be AEI, BEA, FER, LEV or CHA. In another embodiment, the first zeolite can be LEV, FER, CHA or AEI. In yet another embodiment, the first zeolite may be FER, AEI or CHA. In yet another embodiment, the first zeolite may be FER. In yet another embodiment, the first zeolite can be AEI. In yet another embodiment, the first zeolite may be CHA. Generally, the first zeolite can have a silica to alumina ratio (SAR) of from 2 to 500, preferably from 4 to 250, and more preferably from 8 to 150. In some embodiments, the first zeolite is FER or CHA or AEI having a SAR ranging from 8 to 40. In another embodiment, the first zeolite is FER or CHA or AEI with SAR ranging from 10 to 30.

In certain embodiments, the first catalytic region may further comprise a first transition metal, which may be selected from the group consisting of: fe. Cu, co, mn, ni, zn, ce, mo, ag, and combinations of any two or more. In another embodiment, the first transition metal may be selected from Ce, mn, cu, co, ni or Fe, and combinations of any two or more. In yet other embodiments, the first transition metal may be Cu and/or Fe. In certain embodiments, the first transition metal is 0.01 wt% to 20 wt%; preferably from 0.1 to 15 wt%; more preferably, from 0.5 to 10 wt% based on the weight of the first zeolite; even more preferably, 1 to 9 wt% or 2 to 8 wt% based on the weight of the first zeolite.

In certain embodiments, the first catalytic zone may extend 100% of the axial length L. In other embodiments, the first catalytic zone may extend from 30% to 90%, from 40% to 80%, or from 40% to 60% of the axial length L. Alternatively, the first catalytic zone may extend 30% to 80% or 30% to 70% of the axial length L.

The total washcoat loading of the first catalytic zone may be less than 3.5g/in ³, preferably less than 3.0g/in ³ or 2.5g/in ³. Alternatively, the total washcoat loading of the first catalytic zone may be from 0.5g/in ³ to 3.5g/in ³; preferably, it may be from 0.6g/in ³ to 3g/in ³ or 0.7g/in ³ to 2.8g/in ³.

Second catalytic zone

In some embodiments, the second PGM component can be Pd and Rh. In other embodiments, the second PGM component may be Pt and Rh. In yet another embodiment, the second PGM component may be Pt.

The second OSC material may be ceria, zirconia, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the second OSC material comprises ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the second OSC material may also comprise one or more dopants, such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material may have a function as a carrier material for the second PGM component. In some embodiments, the second OSC material comprises a ceria-zirconia mixed oxide and an alumina-ceria-zirconia mixed oxide.

The ceria-zirconia mixed oxide may have the following weight ratio of zirconia oxide to ceria oxide: at least 50:50, preferably above 60:40, more preferably above 65:35. Alternatively, the ceria-zirconia mixed oxide may also have the following ceria oxide to zirconia oxide weight ratio: less than 50:50, preferably less than 40:60, more preferably less than 35:65.

The second OSC material (e.g., ceria-zirconia mixed oxide) may be from 10 wt% to 90 wt%, preferably from 20 wt% to 90 wt%, more preferably from 30 wt% to 90 wt%, based on the total support coating load of the second catalytic region.

The second OSC material loading in the second catalytic region may be less than 2g/in ³. In some embodiments, the second OSC material loading in the second catalytic zone is no greater than 2g/in ³、1.5g/in³、1.2g/in³、1.0g/in³ or 0.8g/in ³.

The second inorganic oxide is preferably an oxide of a group 2, 3,4, 5, 13 and 14 element. The second inorganic oxide is preferably selected from the group consisting of: alumina, zirconia, magnesia, silica, lanthanum, yttrium, neodymium, praseodymium oxides, and mixed or composite oxides thereof. Particularly preferably, the second inorganic oxide is alumina, lanthanum-alumina, zirconia, or magnesia/alumina composite oxide. A particularly preferred second inorganic oxide is alumina or lanthanum-alumina.

The second OSC material and the second inorganic oxide may have the following weight ratios: not greater than 10:1, preferably not greater than 8:1, more preferably not greater than 5:1, most preferably not greater than 4:1.

Alternatively, the second OSC material and the second inorganic oxide may have the following weight ratios: 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.

In some embodiments, the second catalytic zone may further comprise a second alkali metal or alkaline earth metal.

The second alkali metal or alkaline earth metal is preferably barium, strontium, their mixed oxides or composite oxides. Preferably, the amount of barium or strontium (when present) is from 0.1 wt% to 15 wt%, and more preferably from 3 wt% to 10 wt% barium or strontium, based on the total weight of the second catalytic region.

Preferably, the barium or strontium is in the form of BaCO ₃ or SrCO ₃. Such materials may be preformed by any method known in the art, such as incipient wetness impregnation or spray drying.

In some embodiments, the second catalytic zone is substantially free of a second alkali metal or alkaline earth metal. In another embodiment, the second catalytic zone is substantially free or free of a second alkali metal or alkaline earth metal.

In certain embodiments, the first catalytic zone may extend 100% of the axial length L. In other embodiments, the second catalytic zone may extend from 30% to 90%, from 40% to 80%, or from 40% to 70% of the axial length L. Alternatively, the second catalytic zone may extend 40% to 90% of the axial length L; preferably, the axial length L is 45% to 60%. Alternatively, the second catalytic region may be no greater than 90%, 85%, 80% or 75% of the axial length L.

In some embodiments, the second catalytic region may overlap with the first catalytic region. In another embodiment, the second catalytic region may overlap the first catalytic region by 5% to 40% of the axial length L. Preferably, the total length of the second region and the first region is equal to or greater than the axial length L. In certain embodiments, the total length of the first catalytic region and the second catalytic region is equal to 100% l. In other embodiments, the total length of the first catalytic region and the second catalytic region is less than 100% L, such as no greater than 99%, 95%, 85%, or 80% of the axial length L.

In certain embodiments, the second catalytic region may be directly supported/deposited on the substrate.

The total washcoat loading of the second catalytic zone may be less than 3.5g/in ³, preferably less than 3.0g/in ³ or 2.5g/in ³. Alternatively, the total washcoat loading of the second catalytic zone may be from 0.5g/in ³ to 3.5g/in ³; preferably, it may be from 0.6g/in ³ to 3.5g/in ³ or 0.7g/in ³ to 3.0g/in ³.

Third catalytic zone

The catalytic article may further comprise a third catalytic zone. In some embodiments, the third catalytic zone may begin at the outlet end. In another embodiment, the third catalytic zone may extend an axial length L. In other embodiments, the third catalytic zone may extend less than 100% of the axial length L.

The third catalytic region may further comprise a third PGM component, a third Oxygen Storage Capacity (OSC) material, a third alkali metal or alkaline earth metal component, and/or a third inorganic oxide.

The third PGM component can be selected from the group consisting of: platinum, palladium, rhodium, and mixtures thereof. In some embodiments, the third PGM component may be palladium, rhodium, or mixtures thereof. In another embodiment, the third PGM component may be palladium, rhodium, or mixtures thereof.

The third OSC material may be ceria, zirconia, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the third OSC material comprises ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the third OSC material may further comprise one or more dopants, such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the third OSC material may have a function as a carrier material for the third PGM component. In some embodiments, the third OSC material comprises a ceria-zirconia mixed oxide and an alumina-ceria-zirconia mixed oxide.

The third OSC material (e.g., ceria-zirconia mixed oxide) may be from 10 wt% to 90 wt%, preferably 25 wt% to 75 wt%, more preferably 30 wt% to 60 wt%, based on the total support coating load of the third catalytic region.

The third OSC material loading in the third catalytic region may be less than 2g/in ³. In some embodiments, the third OSC material loading in the second catalytic zone is no greater than 2.0g/in ³、1.5g/in³、1.2g/in³、1.0g/in³ or 0.8g/in ³.

The total washcoat loading of the third catalytic zone may be less than 3.5g/in ³, preferably no greater than 3.0g/in ³、2.5g/in³ or 2g/in ³.

The third alkali metal or alkaline earth metal is preferably barium, strontium, their mixed oxides or composite oxides. Preferably, the amount of barium or strontium (when present) is from 0.1 wt% to 15 wt%, and more preferably from 3 wt% to 10 wt% barium or strontium, based on the total weight of the third catalytic zone.

Even more preferably, the third alkali or alkaline earth metal is barium. Barium (when present) is preferably present in an amount of 0.1 wt% to 15 wt%, and more preferably 3 wt% to 10 wt%, based on the total weight of the third catalytic region.

It is also preferred that the third alkali or alkaline earth metal is a mixed or composite oxide of barium and strontium. Preferably, the mixed oxide or composite oxide of barium or strontium is present in an amount of 0.1 to 15 wt%, and more preferably 3 to 10wt%, based on the total weight of the third catalytic zone. More preferably, the third alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

In some embodiments, the third catalytic zone is substantially free of a third alkali metal or alkaline earth metal. In another embodiment, the third catalytic zone is substantially free or free of a third alkali metal or alkaline earth metal.

The third inorganic oxide is preferably an oxide of a group 2, 3,4, 5, 13 and 14 element. The third inorganic oxide is preferably selected from the group consisting of: alumina, zirconia, magnesia, silica, lanthanum, neodymium, praseodymium, yttrium oxide, and mixed or composite oxides thereof. Particularly preferably, the third inorganic oxide is alumina, lanthanum-alumina, zirconia, or magnesia/alumina composite oxide. A particularly preferred third inorganic oxide is alumina or lanthanum-alumina.

The third OSC material and the third inorganic oxide may have the following weight ratios: no greater than 10:1, preferably no greater than 8:1 or 5:1, more preferably no greater than or 5:1, most preferably no greater than 4:1.

Alternatively, the third OSC material and the third inorganic oxide may have the following weight ratios: 10:1 to 1:10, preferably 8:1 to 1:8, or more preferably 5:1 to 1:5 or, and most preferably 4:1 to 1:4.

The third catalytic zone may extend 100% of the axial length L (see, e.g., fig. 3 b). Alternatively, the third catalytic zone may be less than the axial length L, for example not more than 95%, 90%, 80% or 70% of the axial length L (see, for example, fig. 3 a).

Substrate

Preferably, the substrate is a flow-through monolith.

The length of the substrate may be less than 8 inches, preferably from 2 inches to 6 inches.

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

The first face is generally at an inlet end of the substrate and the second face is at an outlet end of the substrate.

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

Preferably, the monolith substrate has 300 channels per square inch to 900 channels per square inch, preferably 400 channels per square inch to 800 channels per square inch, in a plane orthogonal to the longitudinal direction. For example, the density of the open first channels and the closed second channels on the first face is 600 channels per square inch to 700 channels per square inch. The channel may have the following cross-section: rectangular, square, circular, oval, triangular, hexagonal, or other polygonal shape.

The monolith substrate acts as a support for holding the catalytic material. Suitable materials for forming the monolith substrate include ceramic-like materials such as cordierite, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica magnesia or zirconium silicate, or porous refractory metals. Such materials and their use in the manufacture of porous monolithic substrates are well known in the art.

It should be noted that the flow-through monolith substrates described herein are individual components (i.e., individual bricks). Nevertheless, when forming an emission treatment system, the substrate used may be formed by adhering multiple channels together or by adhering multiple smaller substrates together, as described herein. Suitable housings and configurations for such techniques and emission treatment systems are well known in the art.

In embodiments where the catalyst article of the present invention comprises a ceramic substrate, the ceramic substrate may be made of any suitable refractory material, such as alumina, silica, ceria, zirconia, magnesia, zeolite, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicate and metalloid aluminosilicates (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.

In embodiments in which the catalyst article of the present invention comprises a metal substrate, the metal substrate may be made of any suitable metal, and in particular, 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.

In some embodiments, the first catalytic region may be located on a different substrate than the second (or optionally third) catalytic region.

Another aspect of the present disclosure relates to a method of treating vehicle exhaust from a gasoline engine, the vehicle exhaust containing NO _x, CO, HC, and ammonia, using the catalyst article described herein. The test catalysts prepared according to the present invention showed significantly improved NH ₃ control performance compared to conventional TWCs (see, e.g., example 4; and tables 9 and 10).

Another aspect of the present disclosure relates to a system for treating vehicle exhaust gas comprising a catalyst article as described herein, along with a conduit for transferring the exhaust gas through the system.

In some embodiments, the system may further comprise a TWC article. In another embodiment, the TWC article is upstream of the catalyst article of the first aspect. In certain embodiments, the upstream TWC article and the catalyst article of the first aspect may be located on different substrates. In other embodiments, the upstream TWC article and the catalyst article of the first aspect may be located on the same substrate.

Definition of the definition

As used herein, the term "area" refers to an area on a substrate that is typically obtained by drying and/or calcining a washcoat. For example, the "regions" may be provided or carried on the substrate in the form of "layers" or "zones". The area or arrangement on the substrate is typically controlled during the application of the washcoat to the substrate. "regions" typically have different boundaries or edges (i.e., one region can be distinguished from another using conventional analysis techniques).

Typically, the "regions" have a substantially uniform length. In this context, reference to a "substantially uniform length" means a length that does not deviate by more than 10%, preferably by more than 5%, more preferably by more than 1% from its average value (e.g., the difference between the maximum and minimum lengths).

Preferably, each "region" has a substantially uniform composition (i.e., there is no significant difference in the composition of the washcoat when comparing one portion of the region to another portion of the region). In this context, a substantially uniform composition refers to a material (e.g., region) in which the difference in composition is 5% or less, typically 2.5% or less, and most typically 1% or less when comparing one portion of the region to another portion of the region.

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

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

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

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 or carried on the substrate that:

(a) Closer to the inlet end (e.g., open end) of the inlet channel of the substrate than to the region of the inlet channel close to the closed end (e.g., blocked end or plugged end), and/or

(B) The closed end (e.g., the blocked or plugged end) of the outlet channel of the substrate is closer than the region near the outlet end (e.g., the open end) of the outlet channel.

Thus, the midpoint of the zone (i.e., at half its length) is (a) closer to the inlet end of the inlet channel of the substrate than to the midpoint of 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 midpoint of the outlet end of the outlet channel.

Similarly, when 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 or carried on the substrate that:

(a) Closer to the outlet end (e.g., open end) of the outlet channel of the substrate than to the region of the outlet channel that is close to the closed end (e.g., closed end or blocked end), and/or

(B) The closed end (e.g., the blocked end or plugged end) of the inlet channel of the substrate is closer than the region near the inlet end (e.g., the open end) of the inlet channel.

Thus, the midpoint of the zone (i.e., at half its length) is (a) closer to the outlet end of the outlet channel of the substrate than to the midpoint of 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 midpoint of the inlet end of the inlet channel.

When the washcoat is present in the walls of the wall-flow filter (i.e., the zone is in the walls), the zone may satisfy both (a) and (b) simultaneously.

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

As used herein, the acronym "PGM" refers to "platinum group metal". The term "platinum group metal" generally refers to a metal selected from Ru, rh, pd, os, ir and Pt, preferably a metal selected from Ru, rh, pd, ir and Pt. Generally, the term "PGM" preferably refers to a metal selected from Rh, pt and Pd.

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

As used herein, the expression "consisting essentially of … …" limits the scope of the feature to include a specified material or step, as well as any other material or step that does not materially affect the basic characteristics of the feature, such as trace impurities. The expression "consisting essentially of … …" encompasses the expression "consisting of … …".

As used herein, the expression "substantially free" as used with respect to a material, generally in the context of the content of a region, layer or zone, refers to a small amount of material, such as less than or equal to 5 wt%, preferably less than or equal to 2 wt%, more preferably less than or equal to 1wt%. The expression "substantially free of" encompasses the expression "not comprised of".

As used herein, the expression "substantially free" as used with respect to a material, generally in the context of the content of a region, layer or zone, means that the material is in trace amounts, such as less than or equal to 1 wt%, preferably less than or equal to 0.5 wt%, more preferably less than or equal to 0.1 wt%. The expression "substantially free of" encompasses the expression "not comprised of".

As used herein, any reference to the amount of dopant, specifically the total amount, in wt% refers to the weight of the support material or refractory metal oxide thereof.

As used herein, the term "loading" refers to the measurement in g/ft ³ based on the weight of the metal.

The following examples merely illustrate the invention. Those skilled in the art will recognize many variations that are within the spirit of the invention and scope of the claims.

Examples

Material

All materials are commercially available and available from known suppliers unless otherwise indicated.

Catalyst A

A catalyst having a single layer was prepared. The layer consisted of Fe and a binder supported on a FER type zeolite ranging from SAR to 17, the total support coating loading of the monolayer being about 1.6g/in ³, wherein the Fe loading is about 3 wt% (based on the weight of FER).

The washcoat was coated on a ceramic substrate (400 cpsi,4 mil wall thickness) using standard coating procedures.

Catalyst B

A catalyst having a single layer was prepared. The layer consisted of an AEI type zeolite with SAR ranging from 20 and a binder, with a total carrier coat load of about 1.6g/in ³ for a monolayer.

Catalyst C

A catalyst having a single layer was prepared. The layer consisted of Cu and binder supported on an AEI-type zeolite having a SAR range of-20, the total support coating loading of the monolayer was about 1.6g/in ³, with a Cu loading of about 2 wt% (based on the weight of the AEI).

Catalyst D

A catalyst having a single layer was prepared. The layer consisted of Cu and binder supported on an AEI-type zeolite having a SAR range of-17, the total support coating loading of the monolayer was about 1.6g/in ³, with a Cu loading of about 4 wt% (based on the weight of the AEI).

Example 1 NH ₃ storage test

Catalysts a to D were aged at 850 ℃ for 4 hours under Hydrocarbon (HC) redox conditions as shown in table 1.

TABLE 1 HC Redox aging conditions

The in-process protocol for testing NH ₃ storage performance of catalyst a through catalyst D after HC redox aging is shown in table 2.

Table 2 NH ₃ stores test protocols

Preconditions of preconditions	Increasing the temperature to 500 ℃ at 25 ℃/min under N ₂ gas
		Pre-storage	Cooling to 150deg.C and maintaining under N ₂ gas for 3min
Storage of	Allowing the gas with the remaining 1000ppm NH ₃、10％H₂O、N₂ to flow for 10min

As shown in table 3 below, catalyst a, catalyst C, and catalyst D showed excellent/improved NH ₃ storage capacity when compared to catalyst B, although catalyst B showed its NH ₃ storage capacity.

TABLE 3 NH ₃ storage test for aged catalyst A to catalyst D

Example 2-thermal NH ₃ conversion with stoichiometric NH ₃ feed

The in-process protocol for testing the thermal NH ₃ conversion performance of catalyst a to catalyst D after HC redox aging is shown in table 4.

Table 4 Hot NH ₃ test protocol with stoichiometric NH ₃ feed

Catalyst a, catalyst C and catalyst D show good NH ₃ and NO conversions at stoichiometric feed conditions, as shown in table 5 below.

Table 5 thermal NH ₃ conversion test for aged catalyst a to catalyst D

	NH ₃ conversion (%)	Conversion of NO (%)
			Catalyst A	23	27
Catalyst B	0	5
			Catalyst C	74	69
Catalyst D	95	74

Example 3 thermal NH ₃ conversion with NH ₃ -rich feed

Catalyst a and catalyst D were aged at 850 ℃ for 4 hours under different conditions as shown in table 6.

Example 6: aging conditions

Period of disturbance	5Min [ stoichiometry ], 1min [ lean ]
		Stoichiometric gas conditions	10% H ₂O、N₂ remainder
Lean gas conditions	20% Of O ₂、10％H₂O、N₂ balance
		Flow rate	3L/min

After aging, the in-process protocol for the hot NH ₃ conversion performance test of catalysts a and D was tested as shown in table 7.

TABLE 7 thermal NH ₃ test protocol with NH ₃ -rich feed

As shown in table 8 below, catalyst a and catalyst D showed good NH ₃ and NO conversions at rich feed conditions.

Table 8 thermal NH ₃ conversion test for aged catalyst A and catalyst D

	NH ₃ conversion (%)	Conversion of NO (%)
			Catalyst A	18	13
Catalyst D	96	39

TWC-1

TWC-1 is a typical three-way (Pd-Rh) catalyst with a double layer structure in two catalytic regions as shown in FIG. 1. The bottom layer consists of Pd, la stabilized alumina, ba promoters supported on a washcoat of the first CeZr mixed oxide. The washcoat loading of the bottom layer was about 2.0g/in ³ with a Pd loading of 16g/ft ³. The washcoat was applied using standard coating procedures from each end face of the ceramic substrate (400 cpsi,4.3 mils wall thickness) with a coating depth target of 50% of the substrate length, dried at 100 ℃ and calcined at 500 ℃ for 45min.

The top layer consisted of Rh, la stabilized alumina supported on a washcoat of a second CeZr mixed oxide. The washcoat loading of the second layer was about 1.5g/in ³ with an Rh loading of 4g/ft ³. The second washcoat was then applied from above from each end face of the ceramic substrate containing the primer layer using standard coating procedures, with a coating depth target of 50% of the substrate length, dried at 100 ℃ and calcined at 500 ℃ for 45min.

TWC-2

TWC-2 is a typical three-way (Pd-Rh) catalyst having a single layer structure. The catalyst layer is composed of Pd and Rh, la stabilized alumina and Ba promoter supported on a washcoat of a first CeZr mixed oxide. The washcoat loading of this layer was about 3.0g/in ³ with a Pd loading of 2g/ft ³ and a Rh loading of 8g/ft ³. The washcoat was applied using standard coating procedures from each end face of the ceramic substrate (400 cpsi,4.3 mils wall thickness) with a coating depth target of 50% of the substrate length, dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst article 1

A catalyst having two catalytic zones is prepared. (see, e.g., fig. 2 a).

First catalytic zone

The first catalytic zone consisted of Fe and binder supported on a FER type zeolite having a SAR range of-16-20, the total support coating loading of this catalytic zone being about 1.5g/in ³, wherein the Fe loading is about 3 wt% (based on the weight of FER).

The washcoat of the first catalytic zone was coated from the inlet end face of the ceramic substrate (400 cpsi,4.3 mils wall thickness) using standard coating procedures, with a coating depth target of 50% of the substrate length.

Second catalytic zone

The washcoat of the second catalytic zone consisted of La-alumina, ceria-zirconia mixed oxide, platinum, rhodium (about 3.0g/in ³ with Pt loading of 6.7g/ft ³ and Rh loading of 3.3g/ft ³). The washcoat was applied from above from the outlet end face of the ceramic substrate containing the first catalytic zone using standard coating procedures, wherein the coating depth target was 50% of the substrate length.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst article 2

A catalyst having two catalytic zones is prepared. (see, e.g., fig. 2 a).

First catalytic zone

Second catalytic zone

The washcoat of the second catalytic zone consisted of La-alumina, ceria-zirconia mixed oxide, platinum (about 3.0g/in ³ with a Pt loading of 10g/ft ³). The washcoat was applied from above from the outlet end face of the ceramic substrate containing the first catalytic zone using standard coating procedures, wherein the coating depth target was 50% of the substrate length.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst article 3

A catalyst having two catalytic zones is prepared. (see, e.g., fig. 2 a).

First catalytic zone

Second catalytic zone

The washcoat of the second catalytic zone consisted of La-alumina, ceria, platinum, rhodium (about 3.0g/in ³ with Pt loading of 6.7g/ft ³ and Rh loading of 3.3g/ft ³). The washcoat was applied from above from the outlet end face of the ceramic substrate containing the first catalytic zone using standard coating procedures, wherein the coating depth target was 50% of the substrate length.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst article 4

A catalyst having two catalytic zones is prepared. (see, e.g., FIG. 1).

First catalytic zone

The washcoat of the first catalytic zone was coated from both the inlet end face and the outlet end face of the ceramic substrate (400 cpsi,4.3 mil wall thickness) using standard coating procedures, with the coating depth target being 50% of the substrate length to obtain complete coverage of the ceramic substrate.

Second catalytic zone

The washcoat of the second catalytic zone consisted of La-alumina, ceria-zirconia mixed oxide, platinum, rhodium (about 3.0g/in ³ with Pt loading of 6.7g/ft ³ and Rh loading of 3.3g/ft ³). The washcoat of the second catalytic zone was coated from both the inlet end face and the outlet end face of the ceramic substrate (400 cpsi,4.3 mil wall thickness) using standard coating procedures, with the coating depth target being 50% of the substrate length to obtain complete coverage of the ceramic substrate.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst performance testing was performed with synthetic exhaust gas and catalyst samples were aged in 10% water, 5% o ₂, balance N ₂ at 800 ℃ for 10 hours.

Catalyst article 5

A catalyst having two catalytic zones is prepared. (see, e.g., fig. 2 a).

First catalytic zone

The first catalytic zone consisted of Cu and a binder supported on a CHA-type zeolite having a SAR range of-16, the total support coating loading of this catalytic zone being about 1.5g/in ³, wherein the Cu loading is about 3.3 wt% (based on the weight of CHA).

Second catalytic zone

As described in catalyst article 2.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst article 6

A catalyst having two catalytic zones is prepared. (see, e.g., fig. 2 a).

First catalytic zone

The first catalytic zone consisted of Cu and binder supported on an AEI-type zeolite having a SAR range of-20, the total support coating loading of this catalytic zone being about 1.2g/in ³, wherein the Cu loading is about 3.8 wt% (based on the weight of the AEI).

Second catalytic zone

As described in catalyst article 2.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst article 7

A catalyst having two catalytic zones is prepared. (see, e.g., fig. 2 a).

First catalytic zone

The first catalytic zone consisted of Cu and binder supported on an AEI-type zeolite having a SAR range of-20, the total support coating loading of this catalytic zone being about 1.5g/in ³, wherein the Cu loading is about 3.8 wt% (based on the weight of the AEI).

Second catalytic zone

As described in catalyst article 2.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst article 8

A catalyst having two catalytic zones is prepared. (see, e.g., fig. 2 a).

First catalytic zone

The first catalytic zone consisted of Cu and binder supported on an AEI-type zeolite having a SAR range of-20, the total support coating loading of this catalytic zone being about 2.2g/in ³, wherein the Cu loading is about 3.8 wt% (based on the weight of the AEI).

Second catalytic zone

As described in catalyst article 2.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

Catalyst article 9

A catalyst having two catalytic zones is prepared. (see, e.g., fig. 2 a).

First catalytic zone

The first catalytic zone consisted of Cu and binder supported on an AEI-type zeolite having a SAR range of-20, the total support coating loading of this catalytic zone being about 2.8g/in ³, wherein the Cu loading is about 3.8 wt% (based on the weight of the AEI).

Second catalytic zone

As described in catalyst article 2.

The catalyst article was dried at 100 ℃ and calcined at 500 ℃ for 45min.

NH ₃ storage test:

The catalyst sample was heated to 150 ℃ and 400ppm NH ₃, 10% water, the balance N ₂ gas feed was added. The space velocity was 110k h ^-1. The total amount of NH ₃ stored when the catalyst was saturated with NH ₃ was recorded.

NH ₃ oxidation test:

A sample of the catalyst saturated with NH ₃ was heated from 100 ℃ to 500 ℃ at 50 ℃/min with a gas mixture of 300ppm NH ₃、0.5％O₂, 300ppm NO, the balance N ₂. The temperature at which the NH ₃ conversion reached 50% was recorded.

The catalyst performance results from TWC-2 catalyst articles 1 to 9 are shown in table 9. The ammonia storage capacity of the catalyst articles 1 to 4 is comparable to and significantly higher than the TWC-2 technology. Catalyst articles 6 through 9 show increased Cu zeolite loading increased the amount of ammonia storage. The NH ₃ oxidation light-off for catalyst articles 1-9 was significantly lower than TWC-2. These results show that conventional TWC technology is not as effective as catalyst articles 1-9 and controls NH ₃ emissions.

TABLE 9 NH ₃ storage and Oxidation from synthetic emission test

Example 4 improved catalyst Performance

The layout of the upstream TWC-1 and downstream TWC-2 was used to test the catalytic performance of the following system:

comparative system 1: TWC-1 only

Comparison System 2: TWC-1+TWC-2

System 3: TWC-1+TWC-2+catalyst article 2

Catalyst performance testing was performed on a gasoline vehicle at an actual run emission (RDE) representative run period. RDE testing is considered a reliable way for emissions assessment of engine operation. The final RDE emission value is the sum of emissions divided by the distance travelled. The vehicle used was a Euro 6d full-certified vehicle with a 1.5L turbocharged direct injection engine. The catalyst system was aged for 60 hours using a fuel cut aging period at a target inlet temperature of TWC-1 of 950 ℃ to represent the end of service life. The catalyst temperature downstream of TWC-1 during aging was 830 ℃.

The emissions results for comparison system 1 and comparison system 2 for a gasoline vehicle during the RDE period are shown in table 10. The results show that the NH ₃ emissions of both comparative catalyst system 1 and comparative catalyst system 2 failed to meet the expected European light NH ₃ requirement of 10 mg/km. Thus, comparison systems 1 and 2 using typical catalysts in gasoline applications do not meet NH ₃ emission requirements. Adding the catalyst article 2 of the present invention to the system 3 (as shown in table 10) effectively controls NH ₃ emissions below the expected european light vehicle requirements.

Table 10 results regarding emissions from a gasoline vehicle during RDE cycle

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Claims

1. A catalyst article for treating exhaust gas from a gasoline engine, the catalyst article comprising:

a base including an inlet end, an outlet end, having an axial length L;

A first catalytic zone beginning at the inlet end, wherein the first catalytic zone comprises a first zeolite; and

A second catalytic region beginning at the outlet end, wherein the second catalytic region comprises a second Platinum Group Metal (PGM) component, a second Oxygen Storage Capacity (OSC) material, and a second inorganic oxide;

wherein the second PGM component is selected from the group consisting of: palladium, platinum, rhodium, and combinations thereof.

2. The catalyst article of claim 1, wherein the first catalytic region extends less than the axial length L.

3. The catalyst article of claim 1 or claim 2, wherein the first catalytic region extends from 30% to 90% of the axial length L.

4. The catalyst article of any one of the preceding claims, where the second catalytic region extends from 30% to 90% of the axial length L.

5. The catalyst article of any one of the preceding claims, where the second catalytic region overlaps the first catalytic region.

6. The catalyst article of claim 6, wherein the second catalytic region overlaps the first catalytic region by 5% to 40% of the axial length L.

7. The catalyst article of any one of claims 1 to 4, wherein the second catalytic region does not overlap with the first catalytic region.

8. The catalyst article of claim 7, wherein the total length of the first catalytic region and the second catalytic region is equal to 100% l.

9. The catalyst article of claim 7, wherein the total length of the first catalytic region and the second catalytic region is less than 100% l.

10. The catalyst article of any one of the preceding claims, where the first catalytic region further comprises a first transition metal selected from the group consisting of: fe. Cu, mn, co, ni, zn, and combinations thereof.

11. The catalyst of claim 10, wherein the first transition metal is Cu and/or Fe.

12. The catalyst article of claim 11, wherein Fe is 0.01 wt% to 20 wt%, based on the weight of the first zeolite.

13. The catalyst article of claim 11, where Cu is 0.01 wt% to 20 wt%, based on the weight of the first zeolite.

14. The catalyst article of any one of the preceding claims, where the first zeolite has a framework type selected from the group consisting of ：ACO、AEI、AEN、AFN、AFT、AFX、ANA、APC、APD、AST、ASV、ATT、BCT、BEA、BEC、BOF、BOG、BRE、CAN、CDO、CFI、CGS、CHA、CHI、CON、DAC、DDR、DFT、EAB、EDI、EPI、ERI、FER、GIS、GOD、IHW、ITE、ITW、LEV、KFI、MER、MFI、MON、NSI、OWE、PAU、PHI、RHO、RTH、SAT、SAV、SIV、THO、TSC、UEI、UFI、VNI、YUG、ZON.

15. The catalyst article of claim 14, wherein the first zeolite has a framework type selected from AEI, BEA, CHA, FER, FAU, MFA or LEV.

16. The catalyst article of any one of the preceding claims, where the first catalytic region has a washcoat loading of 0.5g/in ³ to 3.5g/in ³.

17. The catalyst article according to any of the preceding claims, where the second OSC material is selected from the group consisting of: ceria, zirconia, ceria-zirconia mixed oxide, and alumina-ceria-zirconia mixed oxide.

18. The catalyst article of claim 17, where the second OSC material comprises the ceria-zirconia mixed oxide.

19. The catalyst article of any one of the preceding claims, where the second inorganic oxide is selected from the group consisting of: alumina, zirconia, magnesia, silica, lanthanum, yttrium, neodymium, praseodymium oxides, and mixed or composite oxides thereof.

20. The catalyst article of claim 19, wherein the second inorganic oxide is alumina, a lanthanum oxide/alumina composite oxide, or a magnesium oxide/alumina composite oxide.

21. The catalyst article of any one of the preceding claims, where the second catalytic zone further comprises a second alkali metal or alkaline earth metal.

22. The catalyst article of any one of the preceding claims, where the second alkali metal or the alkaline earth metal is barium or strontium.

23. The catalyst article of any one of the preceding claims, further comprising a third catalytic zone.

24. The catalyst article of claim 23, where the third catalytic region begins at the outlet end and extends less than the axial length L.

25. The catalyst article according to claim 23 or 24, the third catalytic region comprising 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.

26. The catalyst article of any one of the preceding claims, where the substrate is a flow-through monolith or a wall-flow filter.

27. The catalyst article of any one of the preceding claims, where the second catalytic region is directly supported/deposited on the substrate.

28. An emission treatment system for treating a gasoline engine exhaust gas stream, the emission treatment system comprising the catalyst article of any one of claims 1 to 27.

29. The emission treatment system of claim 28, further comprising a TWC article located upstream of the catalyst article.

30. A method of treating exhaust gas from a gasoline engine, the method comprising contacting the exhaust gas with the catalyst article of any one of claims 1 to 27.