阅读说明：本技术 具有对n2的更大选择性的改善的nh3减排 (Has a pair of N2Improved NH of greater selectivity3Emission reduction ) 是由 大卫·米卡莱夫 安德鲁·纽曼 亚历克斯·康内尔·帕森斯 于 2018-12-12 设计创作，主要内容包括：本发明公开了催化剂,该催化剂具有第一催化剂涂层和第二催化剂涂层,所述第一催化剂涂层包含下列的共混物：1)载体上的Pt和2)分子筛,并且所述第二催化剂涂层包含SCR催化剂。(A catalyst having a first catalyst coating and a second catalyst coating, the first catalyst coating comprising a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst.)

1. A catalyst comprising a first catalyst coating and a second catalyst coating,

the first catalyst coating comprises a blend of: 1) pt on a support and 2) a molecular sieve, and

the second catalyst washcoat comprises an SCR catalyst.

2. The catalyst of claim 1, wherein the SCR catalyst comprises a Cu-SCR catalyst comprising copper and a molecular sieve, and/or a Fe-SCR catalyst comprising iron and a molecular sieve.

3. The catalyst of claim 1, wherein the support comprises silica, titania, and/or Me-doped alumina or titania, wherein Me comprises a metal selected from W, Mn, Fe, Bi, Ba, L a, Ce, Zr, or a mixture of two or more thereof.

4. The catalyst of claim 1, wherein the molecular sieve comprises FER, BEA, CHA, AEI, MOR, MFI, and mixtures and intergrowths thereof.

5. The catalyst of claim 1, wherein the Pt is at about 1g/ft relative to the weight of the first catalyst washcoat³To about 10g/ft³Is present in an amount.

6. The catalyst of claim 1, wherein the molecular sieve is at most about 2g/in relative to the weight of the first catalyst coating³Is present in an amount.

7. The catalyst of claim 1, wherein the first catalyst coating and the second catalyst coating are configured such that exhaust gas contacts the second catalyst coating before contacting the first catalyst coating.

8. The catalyst of claim 1, wherein the second catalyst coating completely overlaps the first catalyst coating.

9. The catalyst of claim 1, wherein the second catalyst coating partially overlaps the first catalyst coating.

10. The catalyst of claim 1, wherein the first catalyst coating and the second catalyst coating do not overlap.

11. The catalyst of claim 1, wherein the first catalyst coating comprises a platinum group metal on the molecular sieve.

12. The catalyst of claim 1, wherein the molecular sieve comprises a metal exchanged molecular sieve.

13. The catalyst of claim 11, wherein the metal comprises copper and/or iron.

14. A catalytic article comprising the catalyst of claim 1 and a substrate.

15. The article of claim 14, wherein the substrate is cordierite, high porosity cordierite, a metallic substrate, an extruded SCR, a wall flow filter, a filter, or SCRF.

16. An emission treatment system, comprising:

a. a diesel engine that emits an exhaust stream comprising particulate matter, NOx, and carbon monoxide;

b. the catalyst of any of the preceding claims ("the SCR/ASC").

17. The system of claim 16, further comprising an upstream SCR catalyst upstream of the SCR/ASC.

18. The system of claim 16, wherein the upstream SCR catalyst is closely coupled to the SCR/ASC.

19. The system of claim 16, wherein the upstream SCR catalyst and the SCR/ASC catalyst are located on a single substrate, and the upstream SCR catalyst is located on an inlet side of the substrate, and the SCR/ASC catalyst is located on an outlet side of the substrate.

20. A method of reducing emissions of an exhaust gas stream, the method comprising contacting the exhaust gas stream with the catalyst of claim 1.

21. The method of claim 20, wherein the catalyst provides a lower peak N than an equivalent catalyst except that no molecular sieve is included in the first catalyst coating layer₂And (4) discharging O.

22. The method of claim 20, wherein the catalyst provides a peak N as compared to an equivalent catalyst except that no molecular sieve is included in the first catalyst coating layer₂At least about a 25% reduction in O emissions.

Background

Combustion of hydrocarbons in diesel engines, stationary gas turbines, and other systems produces exhaust gases that must be treated to remove nitrogen oxides (NOx), including NO (nitric oxide) and NO₂(nitrogen dioxide), where NO is the majority of the NOx formed. NOx is known to cause a number of health problems in humans, as well as to cause a number of harmful environmental effects, including the formation of smoke and acid rain. In order to reduce NO in the exhaust gases_xFor human and environmental impact, it is desirable to eliminate these undesirable components, preferably by a process that does not produce other toxic or toxic substances.

Exhaust gases produced in lean burn engines and diesel engines are typically oxidized. In a process known as Selective Catalytic Reduction (SCR), there is a need to selectively reduce NOx with a catalyst and a reductant, which converts NOx to elemental nitrogen (N)₂) And water. In the SCR process, a gaseous reductant (typically anhydrous ammonia, aqueous ammonia or urea) is added to the exhaust gas stream before the exhaust gas contacts the catalyst. The reducing agent is absorbed on the catalyst and NO_xThe gas is reduced as it passes through or over the catalytic substrate. In order to maximize the conversion of NOx, it is often necessary to add an over-stoichiometric amount of ammonia to the gas stream. However, releasing excess ammonia into the atmosphere would be harmful to human health and the environment. In addition, ammonia is caustic, especially in its aqueous form. Condensation of ammonia and water in the exhaust line area downstream of the exhaust catalyst can result in corrosive mixtures that can damage the exhaust system. Therefore, the release of ammonia in the exhaust gas should be eliminated. In many conventional exhaust systems, an ammonia oxidation catalyst (also referred to as an ammonia slip catalyst or "ASC") is installed downstream of the SCR catalyst to remove ammonia from the exhaust gas by converting it to nitrogen. The use of an ammonia slip catalyst may allow greater than 90% NO during a typical diesel drive cycle_xAnd (4) conversion rate.

It may be desirable to have a catalyst that simultaneously provides for NOx removal by SCR and selective conversion of ammonia to nitrogen, where ammonia conversion occurs over a wide range of temperatures in a vehicle drive cycle and forms minimal nitrogen oxide and nitrous oxide byproducts.

Disclosure of Invention

According to some embodiments of the invention, the catalyst comprises a first catalyst coating and a second catalyst coating, wherein the first catalyst coating comprises a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst.

In some embodiments, the SCR catalyst comprises a Cu-SCR catalyst comprising copper and a molecular sieve, and/or a Fe-SCR catalyst comprising iron and a molecular sieve³To about 10g/ft³Is present in an amount. In some embodiments, the molecular sieve is present at up to about 2g/in relative to the weight of the first catalyst coating³Is present in an amount.

In some embodiments, the first catalyst coating and the second catalyst coating are configured such that the exhaust gas contacts the second catalyst coating before contacting the first catalyst coating. In certain embodiments, the second catalyst coating completely overlaps the first catalyst coating. In some embodiments, the second catalyst coating partially overlaps the first catalyst coating. In other embodiments, the first catalyst coating layer does not overlap the second catalyst coating layer.

In some embodiments, the first catalyst coating comprises a platinum group metal on a molecular sieve. The molecular sieve may comprise a metal exchanged molecular sieve; the metal may include, for example, copper and/or iron.

In some embodiments, a catalytic article can include a catalyst as described herein, as well as a substrate. Suitable substrates may include, for example, cordierite, high porosity cordierite, metal substrates, extruded SCR, wall flow filters, or SCRF.

According to some embodiments of the invention, an emission treatment system comprises: a) a diesel engine that emits an exhaust stream comprising particulate matter, NOx, and carbon monoxide; and b) a catalyst as described herein ("SCR/ASC"). In some embodiments, the system may include an upstream SCR catalyst upstream of the SCR/ASC. In some embodiments, the upstream SCR catalyst is closely coupled to the SCR/ASC. In certain embodiments, the upstream SCR catalyst and the SCR/ASC catalyst are located on a single substrate, and the upstream SCR catalyst is located on an inlet side of the substrate, and the SCR/ASC catalyst is located on an outlet side of the substrate.

According to some embodiments of the invention, a method of reducing emissions of an exhaust gas stream comprises contacting the exhaust gas stream with a catalyst described herein. In some embodiments, the catalyst provides a lower peak N O emission compared to an equivalent catalyst except that the molecular sieve is not included in the first catalyst coating. In some embodiments, the catalyst provides at least about a 25% reduction in peak N O emissions compared to an equivalent catalyst except that no molecular sieve is included in the first catalyst coating.

Drawings

Fig. 1 depicts a catalyst configuration having a first catalyst coating layer extending from an outlet end toward an inlet end covering less than an entire axial length of a substrate, and a second catalyst coating layer extending from the inlet end toward the outlet end covering less than the entire axial length of the substrate and overlapping a portion of the first catalyst coating layer.

Fig. 2 depicts a catalyst configuration having a first catalyst coating layer extending from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst coating layer covering the entire axial length of the substrate and overlapping the first catalyst coating layer.

Fig. 3 depicts a catalyst configuration having a first catalyst coating covering the entire axial length of the substrate, and a second catalyst coating extending from the inlet end toward the outlet end, covering less than the entire axial length of the substrate and overlapping a portion of the first catalyst coating.

Fig. 4 depicts a catalyst configuration having a first catalyst coating covering the entire axial length of the substrate, and a second catalyst coating covering the entire axial length of the substrate and overlapping the first catalyst coating.

Fig. 5 depicts a catalyst configuration having a first catalyst coating layer extending from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst coating layer extending from the inlet end toward the outlet end covering less than the entire axial length of the substrate, and wherein the first catalyst coating layer and the second catalyst coating layer do not overlap.

Fig. 6 depicts a catalyst configuration having a first catalyst coating layer extending from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst coating layer extending from the inlet end toward the outlet end covering less than the entire axial length of the substrate, and wherein the first catalyst coating layer and the second catalyst coating layer do not overlap. The catalyst includes another catalyst coating layer covering at least a portion of the first catalyst coating layer.

Fig. 7 depicts a catalyst configuration having a first catalyst coating layer extending from the outlet end toward the inlet end covering less than the entire axial length of the substrate and a second catalyst coating layer extending from the inlet end toward the outlet end covering less than the entire axial length of the substrate, and wherein the first catalyst coating layer and the second catalyst coating layer do not overlap and have a space therebetween.

Fig. 8 depicts a catalyst configuration with an extruded SCR substrate, wherein a first coating and a second coating may be located on the outlet end of the substrate.

Fig. 9 depicts a catalyst configuration having an extruded SCR substrate in which a first catalyst coating extends from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst coating also extends from the outlet end toward the inlet end, completely covering the first catalyst coating and extending some distance beyond, but not covering, the entire axial length of the substrate.

FIG. 10 shows the N3/4 conversion and N₂And (4) O selectivity test results.

Detailed Description

The catalyst of the present invention relates to a catalyst article having Selective Catalytic Reduction (SCR) and Ammonia Slip Catalyst (ASC) functionality. The catalyst article can have a layer comprising an SCR catalyst (which can be referred to herein as a second catalyst washcoat), and a layer comprising a blend of: 1) platinum on a support and 2) molecular sieves. Traditionally, such catalyst articles include SCR functionality in the top or front layer and ASC functionality in the bottom or back layer. In the catalyst of the present invention, the catalyst coating layer may be arranged such that the exhaust gas contacts the second catalyst coating layer before contacting the first catalyst coating layer. It has been surprisingly found that including a molecular sieve of N in both the first and second layers₃The conversion provides various benefits and advantages, as well as a zoned ASC configuration with desirable selectivity and catalyst activity. In particular, incorporation of molecular sieves, such as zeolites and metal zeolites, into the oxygenated component of an ASC can improve N₃Reduction of emission and for N₂Selectivity of (2).

The catalytic article of the invention can have a variety of configurations on a substrate having an axial length. In some embodiments, the catalytic article has a first catalyst coating layer extending from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst coating layer extending from the inlet end toward the outlet end covering less than the entire axial length of the substrate and overlapping a portion of the first catalyst coating layer.

In some embodiments, the catalytic article has a first catalyst coating layer extending from the outlet end toward the inlet end, covering less than the entire axial length of the substrate, and a second catalyst coating layer covering the entire axial length of the substrate and overlapping the first catalyst coating layer.

In some embodiments, the catalytic article has a first catalyst coating layer covering the entire axial length of the substrate, and a second catalyst coating layer extending from the inlet end toward the outlet end, covering less than the entire axial length of the substrate and overlapping a portion of the first catalyst coating layer.

In some embodiments, the catalytic article has a first catalyst coating layer covering the entire axial length of the substrate, and a second catalyst coating layer covering the entire axial length of the substrate and overlapping the first catalyst coating layer.

In some embodiments, the catalytic article has a first catalyst coating layer extending from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst coating layer extending from the inlet end toward the outlet end covering less than the entire axial length of the substrate, and wherein the first catalyst coating layer and the second catalyst coating layer do not overlap.

In some embodiments, the catalytic article has a first catalyst coating layer extending from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst coating layer extending from the inlet end toward the outlet end covering less than the entire axial length of the substrate, wherein the first catalyst coating layer and the second catalyst coating layer are non-overlapping, and another catalyst coating layer extending from the outlet end and covering at least a portion of the first catalyst coating layer.

In some embodiments, the catalytic article has a first catalyst coating layer extending from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst coating layer extending from the inlet end toward the outlet end covering less than the entire axial length of the substrate, and wherein the first catalyst coating layer and the second catalyst coating layer do not overlap and have a space therebetween.

In some embodiments, the substrate is an extruded SCR. In some embodiments having an extruded substrate, at least a portion of the extruded substrate remains uncoated. In some embodiments, the first coating and the second coating may be located on the outlet end of the extruded substrate. In some embodiments, the second coating extends further toward the inlet end of the substrate than the first coating.

Ammonia oxidation catalyst

The catalyst article of the present invention may comprise one or more ammonia oxidation catalysts, also known as ammonia slip catalysts ("ASCs"). One or more ASCs may be included in or downstream of the SCR catalyst to oxidize excess ammonia and prevent its release into the atmosphere.

In some embodiments, the ASC may be included on the same substrate as the SCR catalyst, or blended with the SCR catalyst. In certain embodiments, the ASC material may be selected to favor ammonia oxidation to nitrogen, rather than NO_xOr N₂In some embodiments, the support may comprise silica, titania, and/or Me-doped alumina or titania, where Me may be a metal selected from the list of W, Mn, Fe, Bi, Ba, L a, Ce, Zr, or a mixture of two or more thereof.

In some embodiments, the ASC may comprise a blend of: 1) platinum group metal on a support, and 2) molecular sieves. The ASC may comprise, consist essentially of, or consist of a blend of: 1) platinum group metal on a support, and 2) molecular sieves. In some embodiments, the molecular sieve comprises a zeolite. In some embodiments, the molecular sieve comprises a metal exchanged molecular sieve; the metal may include, for example, copper and/or iron. In some embodiments, suitable molecular sieves include, for example, FER, BEA, CHA, AEI, MOR, MFI, and mixtures and intergrowths thereof. The molecular sieve may comprise any of the molecular sieves described in detail below.

In some embodiments, the ASC may comprise an amount of about 1g/ft relative to the total volume of the ASC³To about 10g/ft³(ii) a About lg/ft³To about 5g/ft³(ii) a About 1g/ft³To about 3g/ft³(ii) a About 1g/ft³(ii) a About 2g/ft³(ii) a About 3g/ft³(ii) a About 4g/ft³(ii) a About 5g/ft³(ii) a About 6g/ft³(ii) a About 7g/ft³(ii) a About 8g/ft³(ii) a About 9g/ft³(ii) a Or about 10g/ft³Of a platinum group metal of (a).

In some embodiments, the ASC may comprise an amount of up to about 2g/in relative to the total volume of the ASC³(ii) a About 0.1g/in³To about 2g/in³(ii) a About 0.1g/in³To about 1g/in³(ii) a About 0.1g/in³To about 0.5g/in³(ii) a About 0.2g/in³To about 0.5g/in³(ii) a About 0.1g/in³(ii) a About 0.2g/in³(ii) a About 0.3g/in³(ii) a About 0.4g/in³(ii) a About 0.5g/in³(ii) a About 1g/in³(ii) a About 1.5g/in³(ii) a Or about 2g/in³The molecular sieve of (1).

In some embodiments, the ASC comprises a platinum group metal distributed on a molecular sieve. The ASC may comprise, consist of, or consist essentially of a molecular sieve based ASC formulation.

Generally, the molecular sieve included in the ASC may include molecular sieves having an aluminosilicate framework (e.g., zeolite), an aluminophosphate framework (e.g., A1PO), a silicoaluminophosphate framework (e.g., SAPO), a heteroatom-containing aluminosilicate framework, a heteroatom-containing aluminophosphate framework (e.g., MeAlPO, where Me is a metal), or a heteroatom-containing silicoaluminophosphate framework (e.g., mespo, where Me is a metal). The heteroatoms (i.e., in the heteroatom-containing backbone) may be selected from: boron (B), gallium (Ga), titanium (Ti), zirconium (Zr), zinc (Zn), iron (Fe), vanadium (V) copper (Cu) and combinations of any two or more thereof. Preferably, the heteroatom is a metal (e.g., each of the heteroatom-containing backbones described above can be a metal-containing backbone).

The description herein of molecular sieves describes molecular sieves that may be suitable as a support for a platinum-based metal and/or as a component blended with a platinum-based metal on a support. In some embodiments, the molecular sieve present in the ASC comprises or consists essentially of a molecular sieve having an aluminosilicate framework (e.g., a zeolite) or a silicoaluminophosphate framework (e.g., a SAPO).

When the molecular sieve has an aluminosilicate framework (e.g., the molecular sieve is a zeolite), then the molecular sieve typically has a silica to alumina molar ratio (SAR) of from 5 to 200 (e.g., from 10 to 200), from 10 to 100 (e.g., from 10 to 30 or from 20 to 80), such as from 12 to 40, or from 15 to 30. In some embodiments, suitable molecular sieves have a SAR > 200; is more than 600; or > 1200. In some embodiments, the molecular sieve has a SAR of about 1500 to about 2100.

Typically, the molecular sieve is microporous. Microporous molecular sieves have pores with diameters less than 2nm (e.g., according to the IUPAC definition of "micropores" [ see Pure & appl. chem., 66(8), (1994), 1739-.

The molecular sieves contained in the ASC may include a small pore molecular sieve (e.g., a molecular sieve having a maximum ring size of eight tetrahedral atoms), a medium pore molecular sieve (e.g., a molecular sieve having a maximum ring size of ten tetrahedral atoms), or a large pore molecular sieve (e.g., a molecular sieve having a maximum ring size of twelve tetrahedral atoms), or a combination of two or more thereof.

When the molecular sieve is a small pore molecular sieve, then the small pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, L EV, L TA, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SFW, SIV, THO, TSC, UFI, VNI, YUG and ZON, or a mixture and/or intergrowth of two or more thereof.

When the molecular sieve is a medium pore molecular sieve, then the medium pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from AE L, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, L AU, L OV, ME L, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, -PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, -SVR, SZR, TER, TON, TUN, UOS, VSV, WEI and WEN, or mixtures and/or intergrowths of two or more thereof, preferably, the medium pore molecular sieve has a framework structure represented by a molecular sieve selected from the group consisting of medium pore molecular sieves, STM L, MFE, MFI, MFE.

When the molecular sieve is a large pore molecular sieve, then the large pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, L TF, L T L, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, MOR, -OSI, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STOP, SSF, SSY, VEUSI, WUY and BEY, or a mixture of two or more of these, preferably a large pore molecular sieve, a zeolite having a framework structure represented by FTC, FTX, FTC, a zeolite having a framework structure, preferably a zeolite, a zeolite having a framework structure represented by FAX, FTY, a zeolite, a.

In some embodiments, the platinum group metals are present on the support in the following amounts: about 0.1 wt.% to about 10 wt.% of the total weight of the platinum group metal and the support; about 0.1 wt.% to about 6 wt.% of the total weight of the platinum group metal and the support; about 0.1 wt.% to about 5 wt.% of the total weight of the platinum group metal and the support; about 0.1 wt.% to about 4 wt.% of the total weight of the platinum group metal and the support; about 0.1 wt.% of the total weight of the platinum group metal and the support; about 0.3 wt.% of the total weight of the platinum group metal and the support; about 0.5 wt.% of the total weight of the platinum group metal and the support; about 1 wt.% of the total weight of the platinum group metal and the support; about 2 wt.% of the total weight of the platinum group metal and the support; about 3 wt.% of the total weight of the platinum group metal and the support; about 4 wt.% of the total weight of the platinum group metal and the support; about 5 wt.% of the total weight of the platinum group metal and the support; about 6 wt.% of the total weight of the platinum group metal and the support; about 7 wt.% of the total weight of the platinum group metal and the support; about 8 wt.% of the total weight of the platinum group metal and the support; about 9 wt.% of the total weight of the platinum group metal and the support; or about 10 wt.% of the total weight of the platinum group metal and the support. When the support comprises a non-zeolitic support, the platinum group metals may be present on the support in the following amounts: about 0.05 wt.% to about 1 wt.% of the total weight of the platinum group metal and the support; about 0.1 wt.% to about 1 wt.% of the total weight of the platinum group metal and the support; about 0.1 wt.% to about 0.7 wt.% of the total weight of the platinum group metal and the support; about 0.1 wt.% to about 0.5 wt.% of the total weight of the platinum group metal and the support; about 0.2 wt.% to about 0.4 wt.% of the total weight of the platinum group metal and the support; or about 0.3 wt% of the total weight of the platinum group metal and the support. When the support comprises a zeolite support, the platinum group metals may be present on the support in the following amounts: about 0.5 wt.% to about 10 wt.% of the total weight of the platinum group metal and the support; about 0.5 wt.% to about 7 wt.% of the total weight of the platinum group metal and the support; about 1 wt.% to about 5 wt.% of the total weight of the platinum group metal and the support; about 2 wt.% to about 4 wt.% of the total weight of the platinum group metal and the support; or about 0.3 wt% of the total weight of the platinum group metal and the support.

In some embodiments, the catalyst article may comprise an ASC composition in the first catalyst coating and an ASC composition in the second catalyst coating. In some embodiments, the ASC compositions in the first catalyst coating and the second catalyst coating may comprise the same formulation as each other. In some embodiments, the ASC compositions in the first catalyst coating and the second catalyst coating may comprise different formulations from each other.

SCR catalyst

The system of the present invention may comprise one or more SCR catalysts.

The exhaust system of the present invention may include an SCR catalyst positioned downstream of an injector for introducing ammonia or a compound decomposable thereto into exhaust gas. The SCR catalyst may be positioned directly downstream of the injector for injecting ammonia or compounds that may decompose to ammonia (e.g., there is no intervening catalyst between the injector and the SCR catalyst).

In some embodiments, an SCR catalyst comprises a substrate and a catalyst composition. The substrate may be a flow-through substrate or a filter substrate. When the SCR catalyst has a flow-through substrate, then the substrate may comprise the SCR catalyst composition (i.e., the SCR catalyst is obtained by extrusion), or the SCR catalyst composition may be disposed or supported on the substrate (i.e., the SCR catalyst composition is applied to the substrate by a washcoat process).

When the SCR catalyst has a filtering substrate, then it is a selective catalytic reduction filter catalyst, which is abbreviated herein as "SCRF". SCRFs include a filter substrate and a Selective Catalytic Reduction (SCR) composition. Reference throughout this application to the use of an SCR catalyst should be understood to also include the use of an SCRF catalyst where applicable.

The selective catalytic reduction composition may comprise or consist essentially of a metal oxide-based SCR catalyst formulation, a molecular sieve-based SCR catalyst formulation, or a mixture thereof. Such SCR catalyst formulations are known in the art.

The selective catalytic reduction composition may comprise or consist essentially of a metal oxide-based SCR catalyst formulation. The metal oxide based SCR catalyst formulation comprises vanadium or tungsten or a mixture thereof supported on a refractory oxide. The refractory oxide may be selected from the group consisting of alumina, silica, titania, zirconia, ceria, and combinations thereof.

SCR catalyst based on metal oxidesThe formulation may comprise or consist essentially of a vanadium oxide (e.g., V) supported on a refractory oxide₂O₅) And/or tungsten oxide (e.g., WO)₃) Composition, the refractory oxide being selected from titanium dioxide (e.g., TiO)₂) Cerium oxide (e.g., CeO)₂) And mixed or composite oxides of cerium and zirconium (e.g., Ce)_xZr_(1-x)O₂Where x is 0.1 to 0.9, preferably x is 0.2 to 0.5).

When the refractory oxide is titanium dioxide (e.g., TiO)₂) When so desired, the concentration of vanadium oxide is preferably 0.5 to 6 wt.% (e.g., in a metal oxide-based SCR formulation), and/or tungsten oxide (e.g., WO)₃) Is in a concentration of 3 to 15 wt.%. More preferably, vanadium oxide (e.g., V)₂O₅) And tungsten oxide (e.g., WO)₃) Supported on titanium dioxide (e.g. TiO)₂) The above.

When the refractory oxide is ceria (e.g., CeO)₂) When so desired, the concentration of vanadium oxide is preferably 0.1 to 9 wt.% (e.g., in a metal oxide-based SCR formulation), and/or tungsten oxide (e.g., WO)₃) Is 0.1 to 9% by weight.

The metal oxide-based SCR catalyst formulation may comprise or consist essentially of a catalyst supported on titanium dioxide (e.g., TiO)₂) Vanadium oxide (e.g., V) of (C)₂O₅) And optionally tungsten oxide (e.g., WO)₃) And (4) forming.

The selective catalytic reduction composition may comprise or consist essentially of a molecular sieve based SCR catalyst formulation. The molecular sieve-based SCR catalyst formulation comprises a molecular sieve, which is optionally a transition metal exchanged molecular sieve. Preferably, the SCR catalyst formulation comprises a transition metal exchanged molecular sieve.

Generally, a molecular sieve-based SCR catalyst formulation can include a molecular sieve having an aluminosilicate framework (e.g., zeolite), an aluminophosphate framework (e.g., AlPO), a silicoaluminophosphate framework (e.g., SAPO), a heteroatom-containing aluminosilicate framework, a heteroatom-containing aluminophosphate framework (e.g., MeAlPO, where Me is a metal), or a heteroatom-containing silicoaluminophosphate framework (e.g., MeAPSO, where Me is a metal). The heteroatoms (i.e., in the heteroatom-containing backbone) may be selected from: boron (B), gallium (Ga), titanium (Ti), zirconium (Zr), zinc (Zn), iron (Fe), vanadium (V), and combinations of any two or more thereof. Preferably, the heteroatom is a metal (e.g., each of the heteroatom-containing backbones described above can be a metal-containing backbone).

A molecular sieve-based SCR catalyst formulation can comprise or consist essentially of a molecular sieve having an aluminosilicate framework (e.g., a zeolite) or a silicoaluminophosphate framework (e.g., a SAPO).

When the molecular sieve has an aluminosilicate framework (e.g., the molecular sieve is a zeolite), then the molecular sieve typically has a silica to alumina molar ratio (SAR) of from 5 to 200 (e.g., from 10 to 200), preferably from 10 to 100 (e.g., from 10 to 30 or from 20 to 80), such as from 12 to 40, more preferably from 15 to 30.

Typically, the molecular sieve is microporous. Microporous molecular sieves have pores with diameters less than 2nm (e.g., according to the IUPAC definition of "micropores" [ see Pure & appl. chem., 66(8), (1994), 1739-.

A molecular sieve-based SCR catalyst formulation can include a small pore molecular sieve (e.g., a molecular sieve having a maximum ring size of eight tetrahedral atoms), a medium pore molecular sieve (e.g., a molecular sieve having a maximum ring size of ten tetrahedral atoms), or a large pore molecular sieve (e.g., a molecular sieve having a maximum ring size of twelve tetrahedral atoms), or a combination of two or more thereof.

When the molecular sieve is a small pore molecular sieve, then the small pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, L EV, L TA, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SFW, SIV, THO, TSC, UFI, VNI, YUG and ZON, or a mixture and/or intergrowth of two or more thereof.

When the molecular sieve is a medium pore molecular sieve, then the medium pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from AE L, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, L AU, L OV, ME L, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, -PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, -SVR, SZR, TER, TON, TUN, UOS, VSV, WEI and WEN, or mixtures and/or intergrowths of two or more thereof, preferably, the medium pore molecular sieve has a framework structure represented by a molecular sieve selected from the group consisting of medium pore molecular sieves, STM L, MFE, MFI, MFE.

When the molecular sieve is a large pore molecular sieve, then the large pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, L TF, L T L, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, MOR, -OSI, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STOP, SSF, SSY, VEUSI, WUY and BEY, or a mixture of two or more of these, preferably a large pore molecular sieve, a zeolite having a framework structure represented by FTC, FTX, FTC, a zeolite having a framework structure, preferably a zeolite, a zeolite having a framework structure represented by FAX, FTY, a zeolite, a.

The molecular sieve based SCR catalyst formulation preferably comprises a transition metal exchanged molecular sieve. The transition metal may be selected from cobalt, copper, iron, manganese, nickel, palladium, platinum, ruthenium and rhenium.

The transition metal may be copper. An advantage of SCR catalyst formulations comprising copper exchanged molecular sieves is that such formulations have excellent low temperature NO_xReduction activity (e.g., low temperature NO which may be superior to iron exchanged molecular sieves_xReduction activity). The Cu-SCR catalyst formulation can comprise, for example, a Cu-exchanged SAPO-34, a Cu-exchanged CHA zeolite, a Cu-exchanged AEI zeolite, a Cu-exchanged FER zeolite, or a combination thereof.

The transition metal may be present at extra-framework sites on the outer surface of the molecular sieve, or within channels, cavities, or cages of the molecular sieve.

Typically, the transition metal exchanged molecular sieve comprises a transition metal in an amount of from 0.10 to 10 wt% of the transition metal exchanged molecular sieve, preferably in an amount of from 0.2 to 5 wt% of the transition metal exchanged molecular sieve.

Generally, the selective catalytic reduction catalyst comprises a total loading of 0.5g in³To 4.0g in³Preferably 1.0gin³To 3.0g in³The selective catalytic reduction composition of (1).

The SCR catalyst composition can comprise a mixture of a metal oxide-based SCR catalyst formulation and a molecular sieve-based SCR catalyst formulation. Suitable metal oxide-based SCR catalyst formulations can comprise, consist of, or consist essentially of a catalyst supported on titanium dioxide (e.g., TiO)₂) Vanadium oxide (e.g., V) of (C)₂O₅) And optionally tungsten oxide (e.g., WO)₃) And (4) forming. Suitable molecular sieve based SCR catalyst formulations may comprise a transition metal exchanged molecular sieve.

When the SCR catalyst is SCRF, then the filter substrate may preferably be a wall-flow filter substrate monolith. Wall-flow filter substrate monoliths (e.g., those of SCR-DPF) typically have a cell density of 60 to 400 cells per square inch (cpsi). It is preferred that the wall-flow filter substrate monolith has a cell density of from 100cpsi to 350cpsi, more preferably from 200cpsi to 300 cpsi.

The wall-flow filter substrate monolith may have a wall thickness (e.g., average inner wall thickness) of 0.20mm to 0.50mm, preferably 0.25mm to 0.35mm (e.g., about 0.30 mm).

Generally, the uncoated wall-flow filter substrate monolith has a porosity of from 50% to 80%, preferably from 55% to 75%, and more preferably from 60% to 70%.

The uncoated wall-flow filter substrate monolith typically has an average pore size of at least 5 μm. Preferably, the average pore size is from 10 μm to 40 μm, such as from 15 μm to 35 μm, more preferably from 20 μm to 30 μm.

The wall-flow filter substrate may have a symmetric pore design or an asymmetric pore design.

Generally, for SCRF, the selective catalytic reduction composition is disposed within the walls of a wall flow filter substrate monolith. Additionally, the selective catalytic reduction composition may be disposed on the walls of the inlet channels and/or on the walls of the outlet channels.

Coating and configuration

Embodiments of the invention may include a coating comprising an SCR catalyst and a coating comprising an ASC. In some embodiments, the SCR catalyst is contained in the second catalyst washcoat and the ASC is contained in the first catalyst washcoat. The second catalyst coating can comprise, consist essentially of, or consist of an SCR catalyst. The first catalyst coating may comprise, consist essentially of, or consist of a blend of: 1) platinum group metal on a support, and 2) molecular sieves. In some embodiments, the use of molecular sieves and metal exchanged molecular sieves in ASC technology may improve N3/4 removal and N₂And (4) selectivity. Such a concept can work because it introduces a mechanism for NH₃An alternative mechanism to challenge the oxidation reaction, specifically below about 400 c, is removed. At these temperatures, N₂O is NH₃The main product of the oxidation. It has surprisingly been found that inclusion of an ammonia storage component in the oxide layer can be provided withBeneficial effect due to NH₃Can be oxidized or stored; at higher temperatures, NH₃Is released and will then be used to remove NOx.

In some embodiments, the first catalyst coating and the second catalyst coating overlap to form three zones: first zone for removing mainly NOx, oxidizing mainly ammonia to N₂And a third zone that primarily oxidizes carbon monoxide and hydrocarbons. In some embodiments, the first catalyst coating and the second catalyst coating are configured to form two zones: a first zone for removing mainly NOx, and oxidizing mainly ammonia to N₂The second region of (1).

In some embodiments, the SCR catalyst comprises a Cu-SCR catalyst comprising copper and a molecular sieve, and/or an Fe-SCR catalyst comprising iron and a molecular sieve. Typically, the transition metal exchanged molecular sieve comprises a transition metal in an amount of from 0.10 to 10 wt% of the transition metal exchanged molecular sieve, from 0.10 to 8 wt% of the transition metal exchanged molecular sieve, from 0.20 to 7 wt% of the transition metal exchanged molecular sieve, preferably from 0.2 to 5 wt% of the transition metal exchanged molecular sieve. Generally, the selective catalytic reduction catalyst comprises a total loading of 0.5g in³To 4.0g in³Preferably 1.0g in³To 3.0g in³The selective catalytic reduction composition of (1).

As described herein, the first catalyst coating comprises a blend of: 1) platinum group metals on a support and 2) molecular sieves. In some embodiments, the first catalyst coating comprises platinum on a support, wherein the support comprises a metal oxide, gamma alumina, silica titania such as silica (12%) titania (88%), silica, titania, and/or Me doped alumina or titania, wherein Me may be a metal selected from the following list: w, Mn, Fe, Bi, Ba, Fa, Ce, Zr, or a mixture of two or more thereof. In some embodiments, the first catalyst coating may comprise platinum supported on a molecular sieve, such as a zeolite. Molecular sieves suitable for use in such supports may include, for example, FER, BEA, CHA, AEI, MOR, MFI, and mixtures and intergrowths thereof.

In some embodiments, the molecular sieve in the first catalyst coating is a zeolite. In some embodiments, the molecular sieve comprises a metal exchanged molecular sieve; the metal may include, for example, copper and/or iron. In some embodiments, suitable molecular sieves include, for example, FER, BEA, CHA, AEI, MOR, MFI, and mixtures and intergrowths thereof.

The first catalyst coating may comprise a content of about 1g/ft relative to the total volume of the first catalyst coating³To about 10g/ft³(ii) a About 1g/ft³To about 5g/ft³(ii) a About 1g/ft³To about 3g/ft³(ii) a About 1g/ft³(ii) a About 2g/ft³(ii) a About 3g/ft³(ii) a About 4g/ft³(ii) a About 5g/ft³(ii) a About 6g/ft³(ii) a About Vg/ft³(ii) a About 8g/ft³(ii) a About 9g/ft³(ii) a Or about 10g/ft³Of (2) platinum. The first catalyst coating may comprise an amount of about 0.1g/in relative to the total volume of the first catalyst coating³To about 5g/in³(ii) a About 0.2g/in³To about 4g/in³(ii) a About 0.2g/in³To about 0.5g/in³(ii) a About 1g/in³To about 5g/in³(ii) a About 2g/in³To about 4g/in³(ii) a About 0.1g/in³(ii) a About 0.2g/in³(ii) a About 0.3g/in³(ii) a About 0.4g/in³(ii) a About 0.5g/in³(ii) a About 1g/in³(ii) a About 1.5g/in³(ii) a About 2g/in³(ii) a About 3g/in³(ii) a About 4g/in³(ii) a Or about 5g/in³The molecular sieve of (1). When the support does not comprise molecular sieve, the first catalyst coating may comprise an amount of about 0.1g/in relative to the total volume of the first catalyst coating³To about 2g/in³(ii) a About 0.1g/in³To about 1g/in³(ii) a About 0.1g/in³To about 0.5g/in³(ii) a About 0.2g/in³To about 0.5g/in³(ii) a About 0.1g/in³(ii) a About 0.2g/in³(ii) a About 0.3g/in³(ii) a About 0.4g/in³(ii) a About 0.5g/in³(ii) a About 1g/in³(ii) a About 1.5g/in³(ii) a Or about 2g/in³The molecular sieve of (1). When the support comprises a molecular sieve, the first catalyst coating may comprise a catalyst relative to the first catalystThe total volume of the agent coating is about 0.1g/in³To about 5g/in³(ii) a About 1g/in³To about 5g/in³(ii) a About 1.5g/in³To about 4.5g/in³(ii) a About 2g/in³To about 4g/in³(ii) a About 0.1g/in³(ii) a About 0.5g/in³(ii) a About 1g/in³(ii) a About 2g/in³(ii) a About 3g/in³(ii) a About 4g/in³(ii) a Or about 5g/in³The molecular sieve of (1).

Referring to fig. 1, a catalytic article according to embodiments of the invention may include a first catalyst coating and a second catalyst coating, the first catalyst coating comprising a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst. The catalytic article can be configured such that the first catalyst coating extends from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and the second catalyst coating extends from the inlet end toward the outlet end covering less than the entire axial length of the substrate and overlaps a portion of the first catalyst coating.

Referring to fig. 2, a catalytic article according to embodiments of the invention may include a first catalyst coating and a second catalyst coating, the first catalyst coating comprising a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst. The catalytic article can be configured such that the first catalyst coating extends from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and the second catalyst coating covers the entire axial length of the substrate and overlaps the first catalyst coating.

Referring to fig. 3, a catalytic article according to embodiments of the invention may include a first catalyst coating and a second catalyst coating, the first catalyst coating comprising a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst. The catalytic article can be configured such that the first catalyst coating covers the entire axial length of the substrate and the second catalyst coating extends from the inlet end toward the outlet end, covering less than the entire axial length of the substrate and overlapping a portion of the first catalyst coating.

Referring to fig. 4, a catalytic article according to embodiments of the invention may include a first catalyst coating and a second catalyst coating, the first catalyst coating comprising a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst. The catalytic article can be configured such that the first catalyst coating covers the entire axial length of the substrate and the second catalyst coating covers the entire axial length of the substrate and overlaps the first catalyst coating.

Referring to fig. 5, a catalytic article according to embodiments of the invention may include a first catalyst coating and a second catalyst coating, the first catalyst coating comprising a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst. The catalytic article can be configured such that the first catalyst coating extends from the outlet end toward the inlet end covering less than the entire axial length of the substrate and the second catalyst coating extends from the inlet end toward the outlet end covering less than the entire axial length of the substrate, and wherein the first catalyst coating and the second catalyst coating do not overlap.

Referring to fig. 6, a catalytic article according to embodiments of the invention may include a first catalyst coating and a second catalyst coating, the first catalyst coating comprising a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst. The catalytic article can be configured such that the first catalyst coating extends from the outlet end toward the inlet end covering less than the entire axial length of the substrate and the second catalyst coating extends from the inlet end toward the outlet end covering less than the entire axial length of the substrate, wherein the first catalyst coating and the second catalyst coating do not overlap, and wherein the catalyst comprises another catalyst coating that covers at least a portion of the first catalyst coating.

Referring to fig. 7, a catalytic article according to embodiments of the invention may include a first catalyst coating and a second catalyst coating, the first catalyst coating comprising a blend of: 1) pt on a support and 2) a molecular sieve, and the second catalyst washcoat comprises an SCR catalyst. The catalytic article can be configured such that the first catalyst coating extends from the outlet end toward the inlet end over less than the entire axial length of the substrate and the second catalyst coating covers less than the entire axial length of the substrate, wherein the first catalyst coating and the second catalyst coating do not overlap and wherein a gap exists between the first catalyst coating and the second catalyst coating.

Referring to fig. 8, a catalytic article according to embodiments of the invention may include a coating on an extruded SCR catalyst. A first catalyst washcoat having a blend of 1) Pt on a support and 2) a molecular sieve may extend from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst washcoat having an SCR catalyst may extend from the outlet end toward the inlet end covering less than the entire axial length of the substrate, wherein the second catalyst washcoat covers all or a portion of the first catalyst washcoat.

Referring to fig. 9, a catalytic article according to embodiments of the invention may be coated on an extruded SCR catalyst. A first catalyst washcoat having a blend of 1) Pt on a support and 2) a molecular sieve may extend from the outlet end toward the inlet end covering less than the entire axial length of the substrate, and a second catalyst washcoat having an SCR catalyst may extend from the outlet end toward the inlet end covering less than the entire axial length of the substrate, wherein the second catalyst washcoat covers the first catalyst washcoat and extends some distance beyond the first catalyst washcoat but does not cover the entire axial length of the substrate.

DOC

The catalyst articles and systems of the present invention may include one or more diesel oxidation catalysts. Oxidation catalysts, and in particular Diesel Oxidation Catalysts (DOCs), are well known in the art. The oxidation catalyst is designed to oxidize CO to CO₂And oxidizing the gas phase Hydrocarbons (HC) and the organic fraction of the diesel particles (soluble organic fraction) to CO₂And H₂And O. Typical oxidation catalysts include high surface area inorganic oxide supports such as alumina, silica-alumina and platinum on zeolites, and optionally also palladium.

Substrate

The catalysts of the invention may also each comprise a flow-through substrate or a filter substrate. In one embodiment, the catalyst may be coated onto a flow-through substrate or filter substrate, and preferably deposited on the flow-through substrate or filter substrate using a wash-coating procedure.

The combination of the SCR catalyst and the filter is referred to as a selective catalytic reduction filter (SCRF catalyst). SCRF catalysts are single substrate devices that combine the functions of an SCR and a particulate filter and are suitable for use in embodiments of the invention as desired. The description and reference throughout this application to an SCR catalyst should be understood to also include SCRF catalysts where applicable.

A flow-through substrate or filter substrate is a substrate capable of containing a catalyst/sorbent component. The substrate is preferably a ceramic substrate or a metal substrate. The ceramic substrate may be made of any suitable refractory material, for example alumina, silica, titania, ceria, zirconia, magnesia, zeolite, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicates, metal 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.

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, among other trace metals.

The flow-through substrate is preferably a flow-through monolith having a honeycomb structure with a plurality of small parallel thin-walled channels extending axially through the substrate and extending from an inlet or outlet of the substrate. The channel cross-section of the substrate can be any shape, but is preferably square, sinusoidal, triangular, rectangular, hexagonal, trapezoidal, circular, or elliptical. The flow-through substrate may also be of high porosity such that the catalyst penetrates into the substrate wall.

The filter substrate is preferably a wall-flow monolith filter. The channels of a wall-flow filter are alternately blocked, which allows the exhaust gas stream to enter the channels from the inlet, then flow through the channel walls, and exit the filter from different channels leading to the outlet. Thus, particulates in the exhaust gas stream are trapped in the filter.

The catalyst/sorbent can be added to the flow-through substrate or filter substrate by any known means, such as a washcoat procedure.

Reductant/urea injector

The system may include means for introducing a nitrogenous reductant into the exhaust system upstream of the SCR and/or SCRF catalyst. It may be preferred that the means for introducing nitrogenous reductant into the exhaust system is located directly upstream of the SCR or SCRF catalyst (e.g., there is no intervening catalyst between the means for introducing nitrogenous reductant and the SCR or SCRF catalyst).

The reducing agent is added to the flowing exhaust gas by any suitable means for introducing the reducing agent into the exhaust gas. Suitable devices include sprayers, or feeders. Such devices are well known in the art.

The nitrogenous reductant used in the system can be ammonia itself, hydrazine, or an ammonia precursor selected from the group consisting of urea, ammonium carbonate, ammonium carbamate, ammonium bicarbonate, and ammonium formate. Urea is particularly preferred.

The exhaust system may further comprise means for controlling the introduction of a reductant into the exhaust gas in order to reduce NOx therein. The preferred control means may comprise an electronic control unit, optionally an engine control unit, and may additionally comprise a NOx sensor located downstream of the NO reduction catalyst.

System and method

The emission treatment systems of the present invention may include a diesel engine that emits an exhaust stream comprising particulate matter, NOx, and carbon monoxide, and a catalytic article as described herein. The system may include an SCR catalyst upstream of the catalytic article. In some embodiments, the SCR catalyst is tightly coupled to the catalytic article. In some embodiments, the SCR catalyst and the catalytic article are located on a single substrate, with the SCR catalyst located on the inlet side of the substrate and the catalytic article located on the outlet side of the substrate.

The methods of the present invention may comprise contacting the exhaust gas stream with a catalytic article as described herein.

Advantageous effects

It has been surprisingly found that the inclusion of molecular sieves in both the first and second layers provides various benefits and advantages for N3/4 conversion, as well as a zoned ASC configuration with desirable selectivity and catalyst activity₂Selectivity of (2).

In some embodiments, the inclusion of molecular sieves in the first catalyst coating may be used for N by incorporation₃ ³/₄Removal provides a beneficial effect with an alternative mechanism that challenges the oxidation reaction. In some embodiments, such beneficial effects are at N₂O is N₃Temperatures at which the main product of the oxidation is present, such as temperatures below about 400 c, are particularly advantageous. It has been surprisingly found that inclusion of an ammonia storage component in the oxide layer can provide beneficial effects, as N₃Can be oxidized or stored; at higher temperatures, N3/4 is released and will then be used to remove NOx.

As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a catalyst" includes mixtures of two or more catalysts, and the like.

The term "ammonia slip" means the amount of unreacted ammonia that passes through the SCR catalyst.

The term "support" means a material to which the catalyst is immobilized.

The term "calcination" means heating the material in air or oxygen, which definition conforms to the IUPAC definition of calcination (IUPAC. complex of Chemical Terminology, 2 nd edition ("gold book"), compiled by a.d.mcnaught and a.wilkinson, Blackwell Scientific Publications, Oxford (1997) XM L online corrected version: http:// goldbook. iupac.org (2006-), created by m.nic, j.jirit, b.kosata; updated by a.jenkins, ISBN 0-9678550-9-8. doi: 10.1351/goldbook.). calcination is performed to decompose the metal salt and facilitate the exchange of metal ions within the catalyst, and the catalyst is also adhered to the substrate. the temperature for calcination depends on the components in the material to be calcined and is typically performed between about 400 ℃ and about 900 ℃ for about 1 hour, and preferably in the case that the calcination is performed at a temperature of about 650 ℃ to about 1200 ℃ for some hours, and the method is preferably performed at a temperature of about 400 ℃ to about 1200 ℃ to about 8 ℃ for some hours.

When one or more ranges are provided for various numerical elements, the one or more ranges may include the stated value, unless otherwise specified.

The term "N₂Selectivity "refers to the percentage of ammonia converted to nitrogen.

The terms "diesel oxidation catalyst" (DOC), "diesel exothermic catalyst" (DEC), "NOx absorber", "SCR/PNA" (selective catalytic reduction/passive NOx adsorber), "cold start catalyst" (CSC) and "three way catalyst" (TWC) are terms well known in the art which are used to describe various types of catalysts used to treat exhaust gas from a combustion process.

The term "platinum group metal" or "PGM" refers to platinum, palladium, ruthenium, rhodium, osmium, and iridium. The platinum group metal is preferably platinum, palladium, ruthenium or rhodium.

The terms "downstream" and "upstream" describe the orientation of the catalyst or substrate in which the flow of exhaust gases is from the inlet end to the outlet end of the substrate or article.