阅读说明：本技术 具有原位Pt固定的氨漏失催化剂 (Ammonia slip catalyst with in situ Pt immobilization ) 是由 陈海英 约瑟夫·费代科 尼尔·格里纳姆 马修·哈里斯 卢静 扬妮克·比达尔 于 2019-03-14 设计创作，主要内容包括：本发明涉及一种催化制品,该催化制品包含：基底,该基底具有入口和出口；第一涂层,该第一涂层包含下列的共混物：(1)载体上的铂和(2)第一SCR催化剂；以及第二涂层,该第二涂层包含第二SCR催化剂；其中该载体包含沸石或SiO2-Al2O3混合氧化物中的至少一种。该铂可以在溶液中固定在该载体上。(The present invention relates to a catalytic article comprising: a substrate having an inlet and an outlet; a first coating comprising a blend of: (1) platinum on a support and (2) a first SCR catalyst; and a second washcoat, the second washcoat comprising a second SCR catalyst; wherein the carrier comprises at least one of zeolite or SiO2-Al2O3 mixed oxide. The platinum may be immobilized on the support in solution.)

1. A catalytic article comprising

A substrate having an inlet and an outlet;

a first coating comprising a blend of: (1) platinum on a support and (2) a first SCR catalyst; and

a second washcoat comprising a second SCR catalyst;

wherein the support comprises a zeolite or SiO₂-Al₂O₃At least one of mixed oxides.

2. The catalytic article of claim 1, wherein the platinum is immobilized on the support in solution.

3. The catalytic article of claim 1, wherein the support comprises SiO₂-Al₂O₃Mixed oxides.

4. The catalytic article of claim 3, wherein SiO₂Is present in an amount of from 1 wt% to about 70 wt% or from about 40 wt% to about 70 wt% of the mixed oxide.

5. The catalytic article of claim 1, wherein the support comprises a zeolite.

6. The catalytic article of claim 5, wherein the zeolite has at least 50m²Per g of external surface area.

7. The catalytic article of claim 5, wherein the zeolite has at least 70m²Per g of external surface area.

8. The catalytic article of claim 5, wherein the zeolite has at least 100m²Per g of external surface area.

9. The catalytic article of claim 5, wherein the zeolite has an average crystal size of less than about 1 μm.

10. The catalytic article of claim 5, wherein the zeolite has an average crystal size of less than about 0.5 μm.

11. The catalytic article of claim 5, wherein the zeolite has an average crystal size of less than about 0.3 μm.

12. The catalytic article of claim 5, wherein the zeolite has a silica to alumina ratio greater than 100.

13. The catalytic article of claim 5, wherein the zeolite has a silica to alumina ratio of greater than 300.

14. The catalytic article of claim 5, wherein the zeolite has a silica to alumina ratio of greater than 1000.

15. The catalytic article of claim 5, wherein the zeolite is selected from the group of framework types 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, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON, BEA, MFI, and FER, and mixtures and/or co-organisms thereof.

16. The catalytic article of claim 5, wherein the zeolite is selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, BEA, MFI, and FER.

17. The catalytic article of claim 1, wherein the second coating completely overlaps the first coating.

18. The catalytic article of claim 1, wherein the second coating partially overlaps the first coating.

19. The catalytic article of claim 1, wherein the second coating extends from the inlet end toward the outlet end covering less than the full length of the substrate.

20. The catalytic article of claim 1, wherein the first coating extends from the outlet end toward the inlet end covering less than the full length of the substrate.

21. The catalytic article of claim 1, wherein the second SCR catalyst is located on an inlet side of the coating comprising the blend of platinum on a support and the first SCR catalyst.

22. The catalytic article of claim 1, wherein the second SCR catalyst is located on an outlet side of the washcoat comprising the blend of platinum on a support and the first SCR catalyst.

23. The catalytic article of claim 1, wherein the platinum is present in an amount of at least one of the following relative to the weight of the support for platinum + the weight of the first SCR catalyst in the blend: (a)0.01 wt% to 0.3 wt%; (b)0.03 wt% to 0.2 wt%; (c)0.05 wt% to 0.17 wt%; and (d)0.07 wt% to 0.15 wt%, inclusive.

24. A catalytic article according to claim 1, wherein the weight ratio of the first SCR catalyst to platinum on the support is in the range of at least one of: (a)0:1 to 300:1, (b)3:1 to 300:1, (c)7:1 to 100: 1; and (d)10:1 to 50:1, inclusive.

25. The catalytic article of claim 1, wherein the blend further comprises at least one of palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), or rhodium (Rh).

26. The catalytic article of claim 1, wherein the second SCR catalyst is a base metal, an oxide of a base metal, a molecular sieve, a metal exchanged molecular sieve, a mixed oxide, or a mixture thereof.

27. The catalytic article of claim 26, wherein the base metal is selected from the group consisting of vanadium (V), molybdenum (Mo), and tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu), and mixtures thereof.

28. The catalytic article of claim 26, further comprising at least one base metal promoter.

29. The catalytic article of claim 26, wherein the molecular sieve or the metal exchanged molecular sieve is small pore, medium pore, large pore, or a mixture thereof.

30. The catalytic article of claim 26, wherein the second SCR catalyst comprises a molecular sieve selected from the group consisting of aluminosilicate molecular sieves, metal-substituted aluminosilicate molecular sieves, aluminophosphate (AlPO) molecular sieves, metal-substituted aluminophosphate (MeAlPO) molecular sieves, silico-aluminophosphate (SAPO) molecular sieves, and metal-substituted silico-aluminophosphate (MeAPSO) molecular sieves, and mixtures thereof.

31. The catalytic article of claim 26, wherein the second SCR catalyst comprises a small pore molecular sieve selected from the group of framework types 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, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, ugi, VNI, yyv, and ZON, and mixtures and/or intergrowths thereof.

32. The catalytic article of claim 26, wherein the second SCR catalyst comprises a small pore molecular sieve selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, and ITE.

33. The catalytic article of claim 26, wherein the second SCR catalyst comprises a molecular sieve selected from the group of framework types consisting of AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, 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, and mixtures and/or co-organisms thereof.

34. The catalytic article of claim 26, wherein the second SCR catalyst comprises a large pore molecular sieve selected from the group of framework types consisting of AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, SSF, SSY, USI, uy, VET, and mixtures and/or intergrowths thereof.

35. The catalytic article of claim 1, wherein the second SCR catalyst comprises promoted Ce-Zr or promoted MnO₂。

36. The catalytic article of claim 1, wherein the first SCR catalyst is a Cu-SCR catalyst or a Fe-SCR catalyst.

37. The catalytic article of claim 1, wherein the substrate is cordierite, high porosity cordierite, a metal substrate, an extruded SCR, a filter, or a SCRF.

38. An exhaust system comprising a catalytic article according to claim 1 and means for introducing a reductant upstream of the catalytic article.

39. The exhaust system of claim 38, further comprising a third SCR catalyst that provides 100% NOx conversion, wherein the third SCR catalyst is a Cu-zeolite SCR catalyst and is disposed in the exhaust stream upstream of the catalytic article of claim 1.

40. An improvement in NH of exhaust gas at a temperature of about 300 ℃ or less₃A method of conversion comprising contacting an exhaust gas comprising ammonia with the catalytic article of claim 1.

41. An improvement in NH of exhaust gas at a temperature of about 300 ℃ or less₃A method of conversion comprising contacting an exhaust gas comprising ammonia with the catalytic article of claim 2.

42. The method of claim 41, wherein the NH is compared to a catalyst comprising a comparative formulation in which platinum is pre-immobilized on a support₃The conversion is about 30% to about 100% higher.

43. A method of treating an exhaust gas comprising ammonia and NOx, the method comprising contacting an exhaust gas comprising ammonia with the catalytic article of claim 1.

44. The method of claim 43, wherein a weight ratio of ammonia to NOx in the exhaust gas is >1.0 for at least a portion of an operating time of the system.

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. Reducing agent adsorptionOn a 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, a catalytic article may comprise: a substrate having an inlet and an outlet; a first coating comprising a blend of: (1) platinum on a support and (2) a first SCR catalyst; and a second washcoat comprising a second SCR catalyst; wherein the support comprises a zeolite or SiO₂-AlO₃At least one of mixed oxides. In some embodiments, the platinum is immobilized on the support in solution. In some embodiments, the first SCR catalyst is a Cu-SCR catalyst or a Fe-SCR catalyst.

In some embodiments, the support comprises SiO₂-AlO₃Mixed oxides. In some embodiments, the SiO₂Is present in an amount of from 1 wt% to about 70 wt% or from about 40 wt% to about 70 wt% of the mixed oxide.

In some embodiments, the support comprises a zeolite.Suitable zeolites may have an external surface area of at least 50m²(ii)/g; at least 70m²(ii)/g; or at least 100m²(ii) in terms of/g. In some embodiments, suitable zeolites have an average crystal size of less than about 1 μm; less than about 0.5 μm; or less than about 0.3 μm. In some embodiments, suitable zeolites have a silica to alumina ratio greater than 100; greater than 300; or greater than 1000. In certain embodiments, the zeolite is selected from the group of framework types 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, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON, BEA, MFI, and FER, and mixtures and/or intergrowths thereof. In some embodiments, the zeolite is selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, BEA, MFI, and FER.

In some embodiments, the second coating completely overlaps the first coating. In some embodiments, the second coating partially overlaps the first coating. In some embodiments, the second coating extends from the inlet end toward the outlet end, covering less than the entire length of the substrate. In some embodiments, the first coating extends from the outlet end toward the inlet end, covering less than the entire length of the substrate. In some embodiments, the second SCR catalyst is located on the inlet side of the washcoat comprising the blend of platinum on a support and the first SCR catalyst. In some embodiments, the second SCR catalyst is located on the outlet side of the washcoat comprising the blend of platinum on a support and the first SCR catalyst.

In some embodiments, the platinum is present in an amount relative to the weight of the support for platinum + the weight of the first SCR catalyst in the blend of at least one of: (a)0.01 wt% to 0.3 wt%; (b)0.03 wt% to 0.2 wt%; (c)0.05 wt% to 0.17 wt%; and (d)0.07 wt% to 0.15 wt%, inclusive. The weight ratio of the first SCR catalyst to the platinum on the carrier may be in the range of at least one of: (a)0:1 to 300:1, (b)3:1 to 300:1, (c)7:1 to 100: 1; and (d)10:1 to 50:1, inclusive.

In some embodiments, the blend further comprises at least one of palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), or rhodium (Rh).

In certain embodiments, the second SCR catalyst is a base metal, an oxide of a base metal, a molecular sieve, a metal exchanged molecular sieve, a mixed oxide, or a mixture thereof. The base metal may be selected from the group consisting of vanadium (V), molybdenum (Mo) and tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu), and mixtures thereof. The second SCR catalyst may also include at least one base metal promoter.

When the second SCR catalyst is a molecular sieve or a metal exchanged molecular sieve, the molecular sieve or the metal exchanged molecular sieve may be small pore, medium pore, large pore or a mixture thereof. In some embodiments, the second SCR catalyst comprises a molecular sieve selected from the group consisting of aluminosilicate molecular sieves, metal-substituted aluminosilicate molecular sieves, aluminophosphate (AlPO) molecular sieves, metal-substituted aluminophosphate (MeAlPO) molecular sieves, silico-aluminophosphate (SAPO) molecular sieves, and metal-substituted silico-aluminophosphate (MeAPSO) molecular sieves, and mixtures thereof. In some embodiments, the second SCR catalyst comprises a small pore molecular sieve selected from the group of framework types 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, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, and mixtures and/or intergrowths thereof. In some embodiments, the second SCR catalyst comprises a small pore molecular sieve selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, and ITE. In some embodiments, the second SCR catalyst comprises a catalyst selected from the group consisting of AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, 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 and mixtures and/or intergrowths thereof. In some embodiments, the second SCR catalyst comprises a large pore molecular sieve selected from the group of framework types consisting of 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, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, and VET, and mixtures and/or intergrowths thereof. In certain embodiments, the second SCR catalyst comprises promoted Ce — Zr or promoted MnO₂。

Suitable substrates may include cordierite, high porosity cordierite, metal substrates, extruded SCR, filters or SCRF.

According to some embodiments of the invention, an exhaust system comprises a catalytic article as described herein and means for introducing a reductant upstream of the catalytic article. The exhaust system may also include a third SCR catalyst that provides 100% NOx conversion, wherein the third SCR catalyst is a Cu-zeolite SCR catalyst and is disposed in the exhaust gas stream upstream of the catalytic article described herein.

According to some embodiments of the invention, the NH of the exhaust gas at a temperature of about 300 ℃ or less is improved₃The method of conversion comprises contacting an exhaust gas comprising ammonia with a catalytic article as described herein.

According to some embodiments of the invention, the NH of the exhaust gas at a temperature of about 300 ℃ or less is improved₃A method of conversion includes contacting an exhaust gas comprising ammonia with a catalytic article having platinum immobilized in solution on the support as described herein. In some embodiments, with a platinum-containing material comprising platinum pre-immobilized thereinCatalyst comparison of comparative formulation on support, NH₃The conversion is about 30% to about 100% higher.

According to some embodiments of the invention, a method of treating an exhaust gas comprising ammonia and NOx comprises contacting an exhaust gas comprising ammonia with a catalytic article as described herein. In some embodiments, the weight ratio of ammonia to NOx in the exhaust gas is >1.0 for at least a portion of the operating time of the system.

Drawings

Fig. 1-8 are schematic illustrations of configurations of catalysts comprising a blend of (1) platinum on a support and (2) a first SCR catalyst. In these figures, the portion of the catalyst comprising a blend of (1) platinum on a support and (2) a first SCR catalyst is labeled "blend".

FIG. 1 depicts a configuration in which a second SCR catalyst is located in the exhaust gas stream above the blend, and the second SCR covers the entire blend.

FIG. 2 depicts a configuration in which a second SCR catalyst is located in the exhaust gas stream before the blend, and the second SCR covers the entire blend.

FIG. 3 depicts a configuration in which a second SCR catalyst is located in the exhaust gas stream before the blend, and the second SCR covers a portion, but not the entire blend.

FIG. 4 depicts a configuration in which a second SCR catalyst is located in the exhaust gas stream before the blend and does not cover the blend.

FIG. 5 depicts a configuration in which a second SCR catalyst covers the entire blend and a portion of the second SCR is located in the exhaust gas stream after the blend.

FIG. 6 depicts a configuration in which a second SCR catalyst covers a portion, but not the entire blend and a portion of the second SCR is located in the exhaust gas stream after the blend.

Fig. 7 depicts a configuration in which the third SCR catalyst is a bottom layer on a substrate, the second layer comprises a blend partially covering the third SCR catalyst, and the third layer comprises the entire second SCR catalyst located over the blend layer and covering the mixture layer.

Fig. 8 depicts a configuration in which the third SCR catalyst is a bottom layer on a substrate, the second layer comprises a blend that partially but not completely covers the third SCR catalyst, and the third layer comprises the second SCR catalyst that is located over the blend layer and partially but not completely covers the mixture layer.

FIG. 9 shows exposure to 1000ppm NH at various ASCs₃One minute pulse of (3) NH₃Loss, N₂O and NOx are formed.

Detailed Description

The catalyst of the present invention relates to ammonia slip catalysts which can provide improved NH at lower temperatures₃Conversion and can be prepared more economically. The catalyst article of embodiments of the invention includes a substrate having a first coating layer having a blend of: (1) platinum on a support, and (2) a first SCR catalyst, wherein the support comprises zeolite and/or SiO₂-Al₂O₃Mixed oxides. The catalyst article further includes a second coating comprising an SCR catalyst. In some embodiments, the platinum is immobilized on the support in solution, i.e., in situ. The catalyst and specific configuration are described in further detail below.

Platinum on carrier/ammoxidation catalyst

Embodiments of the present invention include supported platinum, which may be included as an ammonia oxidation catalyst in a catalyst article as described herein. Preferably, the support comprises zeolite and/or SiO₂-Al₂O₃Mixed oxides. In some embodiments, the platinum may be immobilized on the support in solution, i.e., by in situ Pt immobilization.

The catalytic article of the invention comprises platinum on a support, wherein the support comprises a zeolite and/or SiO₂-Al₂O₃Mixed oxides. In some embodiments, platinum is present on the support in the following amounts: about 0.5 wt% to about 10 wt% of the total weight of platinum and support; about 1 wt% to about 6 wt% of the total weight of platinum and support; about 1.5 wt% to about 4 wt% of the total weight of platinum and support; about 10 wt% of the total weight of platinum and support; of platinum and carrierAbout 0.5 wt% of the total weight; about 1 wt% of the total weight of platinum and support; about 2 wt% of the total weight of platinum and support; about 3 wt% of the total weight of platinum and support; about 4 wt% of the total weight of platinum and support; about 5 wt% of the total weight of platinum and support; about 6 wt% of the total weight of platinum and support; about 7 wt% of the total weight of platinum and support; about 8 wt% of the total weight of platinum and support; about 9 wt% of the total weight of platinum and support; or about 10 wt% of the total weight of the platinum and the support.

In which platinum is supported on SiO₂-Al₂O₃In the embodiment on mixed oxides, SiO₂May be present in the following amounts: about 1 wt% to about 80 wt% of the mixed oxide; about 1 wt% to about 75 wt% of the mixed oxide; about 1 wt% to about 70 wt% of the mixed oxide; about 5 wt% to about 70 wt% of the mixed oxide; about 10 wt% to about 70 wt% of the mixed oxide; about 20 wt% to about 70 wt% of the mixed oxide; about 30 wt% to about 70 wt% of the mixed oxide; about 40 wt% to about 70 wt% of the mixed oxide; about 50 wt% to about 60 wt% of the mixed oxide; about 1 wt% of mixed oxide; about 5 wt% of mixed oxide; about 10 wt% of mixed oxide; about 20 wt% of mixed oxide; about 30 wt% of mixed oxide; about 40 wt% of mixed oxide; about 50 wt% of mixed oxide; about 60 wt% of mixed oxide; about 70 wt% of mixed oxide; about 75 wt% of mixed oxide; or about 80 wt% of the mixed oxide.

In embodiments where platinum is supported on a zeolite, suitable zeolites may have an external surface area of at least about 30m²(ii)/g; at least about 40m²(ii)/g; at least about 50m²(ii)/g; at least about 60m²(ii)/g; at least about 70m²(ii)/g; at least about 80m²(ii)/g; at least about 90m²(ii)/g; or at least about 100m²(ii) in terms of/g. In some embodiments, suitable zeolites may have an average crystal size of about 2 μm or less; about 1.5 μm or less; about 1 μm or less; about 0.5 μm or less; about 0.3 μm or less; less than about 2 μm; less than about 1.5 μm; less than about 1 μm; less than about 0.5 μm; less than about 0.3 μm; about 0.1 μm to about 2 μm; about 0.3 μm to about 1.5 μm; or about 0.5 μm to about 1 μm. Notably, the particle size may be significantly different from the zeolite crystal size, as the particles may be composed of aggregates of many smaller crystals. In some embodiments, suitable zeolites have a silica to alumina ratio of at least 100; at least 200; at least 250; at least 300; at least 400; at least 500; at least 600; at least 750; at least 800; or at least 1000. The zeolite is described in more detail in the SCR catalyst section below. In some embodiments, suitable zeolites for supporting platinum are selected from the group of framework types 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, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON, BEA, MFI, and FER, and mixtures and/or co-organisms thereof. In some embodiments, a suitable zeolite for selecting platinum is selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, BEA, MFI, and FER.

The catalyst article of the present invention may comprise one or more ammonia oxidation catalysts, also known as ammonia slip catalysts ("ASCs"). As noted above, preferred ammonia oxidation catalysts include platinum on a support, however, other or additional ammonia oxidation catalysts may be included in embodiments of the present invention. One or more ammonia oxidation catalysts 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 ammonia oxidation catalyst may be included on the same substrate as the SCR catalyst, or blended with the SCR catalyst. In certain embodiments, the ammonia oxidation catalyst material may be selected and formulated to favor the oxidation of ammonia over NO_xOr N₂And forming O. Generally, preferred catalyst materials include platinum, palladium, or combinations thereof. The ammonia oxidation catalyst may comprise platinum and/or palladium supported on a metal oxide. In some embodiments, the catalyst is disposed on a high surface area support, which comprisesIncluding but not limited to alumina.

In some embodiments, the ammoxidation catalyst comprises a platinum group metal on a siliceous support. The siliceous material may include materials such as: (1) silicon dioxide; (2) a zeolite having a silica to alumina ratio of at least 200; and (3) amorphous silica-doped alumina with SiO2 content of more than or equal to 40%. In some embodiments, the siliceous material may comprise a material such as a zeolite having a silica to alumina ratio of at least 200; at least 250; at least 300; at least 400; at least 500; at least 600; at least 750; at least 800; or at least 1000. In some embodiments, the platinum group metals are 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 1 wt.% to about 6 wt.% of the total weight of the platinum group metal and the support; about 1.5 wt.% to about 4 wt.% of the total weight of the platinum group metal and the support; about 10 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.

In some embodiments, the siliceous support may comprise a molecular sieve having a BEA, CDO, CON, FAU, MEL, MFI, or MWW framework type.

SCR catalyst

The system of the present invention may include one or more SCR catalysts. In some embodiments, the catalyst article can include a first SCR catalyst and a second SCR catalyst. In some embodiments, the first SCR catalyst and the second SCR catalyst may comprise the same formulation as one another. In some embodiments, the first SCR catalyst and the second SCR catalyst may comprise different formulations from each other.

Embodiments of the exhaust system of the present invention may include an SCR catalyst positioned downstream of an injector for introducing ammonia or a compound decomposable to ammonia into the 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).

The SCR catalyst includes 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 base metal-based SCR catalyst formulation, a molecular sieve-based SCR catalyst formulation, a metal-exchanged molecular sieve, or a mixture thereof. Such SCR catalyst formulations are known in the art. Typical compositions are described in U.S. Pat. Nos. 4,010,238 and 4,085,193, both of which are incorporated herein by reference in their entirety.

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.

The metal oxide-based SCR catalyst formulation may comprise or consist essentially of a catalyst supported on a refractory oxideVanadium oxide on (e.g. V)₂O₅) 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, 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 5 to 20 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. These catalysts may comprise other inorganic materials such as SiO2 and ZrO2, which act as binders and promoters.

When the refractory oxide is ceria (e.g., CeO)₂) When so, 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 base metal-based SCR catalyst formulation. Suitable base metals may include vanadium (V), molybdenum (Mo) and tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) and mixtures thereof.

When the SCR catalyst is a base metal or mixed base metal oxide, the catalyst article may further comprise at least one base metal promoter. As used herein, "promoter" is understood to mean a substance that increases the activity of a catalyst when added to the catalyst. Basic priceThe metal promoter may be in the form of a metal, an oxide of a metal, or a mixture thereof. The at least one base metal catalyst promoter may be selected from neodymium (Nd), barium (Ba), cerium (Ce), lanthanum (La), (Pr), magnesium (Mg), calcium (Ca), manganese (Mn), zinc (Zn), niobium (Nb), zirconium (Zr), molybdenum (Mo), tin (Sn), tantalum (Ta), strontium (Sr), and oxides thereof. The at least one base metal catalyst promoter may preferably be MnO₂、Mn₂O₃、Fe₂O₃、SnO₂、CuO、CoO、CeO₂And mixtures thereof. At least one base metal catalyst promoter may be added to the catalyst in the form of an aqueous solution of a salt, such as a nitrate or acetate salt. The at least one base metal catalyst promoter and the at least one base metal catalyst, such as copper, may be impregnated onto the oxide support material from an aqueous solution, may be added to a washcoat comprising the oxide support material, or may be impregnated into a support that has been previously coated with a washcoat.

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., a 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), or mixtures thereof. 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).

Preferably, the molecular sieve-based SCR catalyst formulation comprises or consists essentially of a molecular sieve having an aluminosilicate framework (e.g., a zeolite) or a silicoaluminophosphate framework (e.g., a SAPO). Zeolitic molecular sieves are microporous aluminosilicates having any of the framework structures listed in the zeolite structure databases published by the International Zeolite Association (IZA). Framework structures include, but are not limited to, those of the CHA, FAU, BEA, MFI, MOR types. Non-limiting examples of zeolites having these structures include chabazite, faujasite, zeolite Y, ultrastable zeolite Y, beta, mordenite, silicalite, zeolite X, and ZSM-5.

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; > 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-.

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, LEV, LTA, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SFW, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, or mixtures and/or co-organisms of two or more thereof. Preferably, the small pore molecular sieve has a framework structure represented by FTC selected from the group consisting of: CHA, LEV, AEI, AFX, EM, ERI, LTA, SFW, KFI, DDR, and ITE. More preferably, the small pore molecular sieve has a framework structure represented by FTC selected from the group consisting of: CHA and AEI. The small pore molecular sieve may have a framework structure represented by FTC CHA. The small pore molecular sieve may have a framework structure represented by FTC AEI. When the small pore molecular sieve is a zeolite and has a framework represented by FTC CHA, then the zeolite can be chabazite.

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 the group consisting of: AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, 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 co-organisms of two or more thereof. Preferably, the medium pore molecular sieve has a framework structure represented by FTC selected from the group consisting of: FER, MEL, MFI and STT. More preferably, the medium pore molecular sieve has a framework structure represented by FTC selected from the group consisting of: FER and MFI, in particular MFI. When the intermediate pore size molecular sieve is a zeolite and has a framework represented by FTC FER or MFI, then the zeolite can be ferrierite, silicalite or ZSM-5.

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 the group consisting of: 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, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, -RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, and VET, or a mixture and/or co-organism of two or more thereof. Preferably, the large pore molecular sieve has a framework structure represented by FTC selected from the group consisting of: AFI, BEA, MAZ, MOR and OFF. More preferably, the large pore molecular sieve has a framework structure represented by FTC selected from the group consisting of: BEA, MOR and MFI. When the large pore molecular sieve is a zeolite and has a framework represented by FTC BEA, FAU or MOR, then the zeolite can be beta zeolite, faujasite, zeolite Y, zeolite X or mordenite.

The molecular sieve based SCR catalyst formulation preferably comprises a transition metal exchanged molecular sieve. The metal-exchanged molecular sieve may have at least one metal from one of groups VB, VIB, VIIB, VIIIB, IB, or IIB of the periodic table deposited onto exoskeletal sites on the outer surface or within channels, cavities, or cages of the molecular sieve. The metal may be in one of several forms including, but not limited to, a zero-valent metal atom or cluster, an isolated cation, a mononuclear or polynuclear oxygen-containing cation, or as an extended metal oxide. The transition metal may be selected from cobalt, copper, iron, manganese, nickel, palladium, platinum, ruthenium and rhenium.

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 transition metal exchanged molecules in an amount of 0.10 to 10 wt%, preferably in an amount of 0.2 to 5 wt%.

The metal exchanged molecular sieve may be a copper (Cu) supported small pore molecular sieve having from about 0.1 wt% to about 20.0 wt% copper, based on the total weight of the catalyst. More preferably, the copper is present in an amount of about 0.5 wt% to about 15 wt% based on the total weight of the catalyst. Most preferably, the copper is present in an amount of about 1 wt% to about 9 wt% of the total weight of the catalyst.

Generally, the selective catalytic reduction catalyst comprises a total concentration of 0.5 to 4.0 g-in^-3Preferably 1.0 to 3.04.0 g.in^-3The 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. (a) 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) Group ofAnd (b) the molecular sieve based SCR catalyst formulation 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.

Blends

Embodiments of the invention may include a blend of (1) platinum on a support and (2) an SCR catalyst. In some embodiments, the weight ratio of SCR catalyst to platinum on the support in the blend is from about 3:1 to about 300: 1; about 3:1 to about 250: 1; about 3:1 to about 200: 1; about 4:1 to about 150: 1; about 5:1 to about 100: 1; about 6:1 to about 90: 1; about 7:1 to about 80: 1; about 7:1 to about 100: 1; about 8:1 to about 70: 1; about 9:1 to about 60: 1; about 10:1 to about 50: 1; about 3: 1; about 4: 1; about 5: 1; about 6: 1; about 7: 1; about 8: 1; about 9: 1; about 10: 1; about 15: 1; about 20: 1; about 25: 1; about 30: 1; about 40: 1; about 50: 1; about 75: 1; about 100: 1; about 125: 1; about 150: 1; about 175: 1; about 200: 1; about 225: 1; about 250: 1; about 275: 1; or about 300: 1.

The term "active component loading" refers to the weight of the carrier of platinum + the weight of the first SCR catalyst in the blend. In some embodiments, platinum is present at the following active ingredient loadings: from about 0.01 wt% to about 0.25 wt%, inclusive; from about 0.04 wt% to about 0.2 wt%, inclusive; from about 0.07% to about 0.17% by weight, inclusive; from about 0.05 wt% to about 0.15 wt%, inclusive; about 0.01 wt%; about 0.02 wt%; about 0.03 wt%; about 0.04 wt%; about 0.05 wt%; about 0.06 wt%; about 0.07 wt%; about 0.08 wt%; about 0.1 wt%; about 0.12 wt%; about 0.15 wt%; about 0.17 wt%; about 0.2 wt%; about 0.22 wt%; or about 0.25 wt%.

In some embodiments, the blend comprising platinum on a support and an SCR catalyst further comprises at least one of palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), or rhodium (Rh).

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.

Structure of the device

Embodiments of the invention relate to a catalytic article having a first coating and a second coating, wherein the first coating includes a blend of (1) platinum of a support and (2) a first SCR catalyst, and the second coating includes a second SCR catalyst. The catalytic article may be prepared in various configurations. In some embodiments, the coating is arranged such that the exhaust gas contacts the second coating before contacting the first coating. In some embodiments, the second SCR catalyst is located on the inlet side of the blend. In some embodiments, the SCR catalyst is located on the outlet side of the blend.

In a first configuration, the catalyst can comprise a first washcoat and a second washcoat, the first washcoat comprising a blend of (1) platinum on a support and (2) a first SCR catalyst, and the second washcoat comprising a second SCR catalyst, wherein the second washcoat is located in a layer above the first washcoat and the second washcoat covers all of the first washcoat. Fig. 1 depicts an example of such a configuration, where a second SCR is located in the exhaust gas stream above the blend, and the second SCR covers the entire blend.

In a second configuration, the catalyst can comprise a first washcoat and a second washcoat, the first washcoat comprising (1) a blend of platinum on a support and (2) a first SCR catalyst, and the second washcoat comprising a second SCR catalyst, wherein the first washcoat extends from the outlet end toward the inlet end covering less than the entire length of the substrate and the second washcoat extends the entire length of the substrate completely overlapping the first washcoat. Fig. 2 depicts an example of such a configuration, where the second SCR is located in the exhaust gas stream before the blend, and the second SCR completely overlaps the blend.

In a third configuration, the catalyst can comprise a first washcoat and a second washcoat, the first washcoat comprising (1) a blend of platinum on a support and (2) a first SCR catalyst, and the second washcoat comprising a second SCR catalyst, wherein the first washcoat extends from the outlet end toward the inlet end covering less than the entire length of the substrate and the second washcoat extends from the inlet end toward the outlet end partially overlapping the first washcoat. The amount of overlap of the second SCR catalyst with the first coating can be from about 10% to about 95% (inclusive), preferably from about 50% to about 95% (inclusive). Fig. 3 depicts an example of such a configuration, where the second SCR is located in the exhaust gas stream before the blend, and the second SCR covers a portion, but not all, of the blend. In fig. 3, the second SCR covered about 40% of the blend.

In a fourth configuration, the catalyst can comprise a first washcoat and a second washcoat, the first washcoat comprising (1) a blend of platinum on a support and (2) a first SCR catalyst, and the second washcoat comprising a second SCR catalyst, wherein the first washcoat extends from the outlet end toward the inlet end covering less than the entire length of the substrate and the second washcoat extends from the inlet end toward the outlet end without overlapping the first washcoat. There may be a space between the first coating and the second coating, the first coating and the second coating may meet but not overlap, or there may be a slight and insubstantial overlap of the first coating and the second coating. Fig. 4 depicts an example of such a configuration, where a second SCR is located in the exhaust gas stream before the blend, and the second SCR meets the blend but does not overlap the blend.

In a fifth configuration, the catalyst can comprise a first washcoat and a second washcoat, the first washcoat comprising (1) a blend of platinum on a support and (2) a first SCR catalyst, and the second washcoat comprising a second SCR catalyst, wherein the first washcoat extends from the inlet end toward the outlet end covering less than the entire length of the substrate and the second washcoat extends the entire length of the substrate completely overlapping the first washcoat. FIG. 5 depicts an example of such a configuration, where the second SCR covers the entire blend and a portion of the second SCR is located in the exhaust gas stream after the blend.

In a sixth configuration, the catalyst can comprise a first washcoat and a second washcoat, the first washcoat comprising (1) a blend of platinum on a support and (2) a first SCR catalyst, and the second washcoat comprising a second SCR catalyst, wherein the first washcoat extends from the inlet end toward the outlet end covering less than an entire length of the substrate and the second washcoat extends from the outlet end toward the inlet end covering less than an entire length of the substrate and partially overlapping the first washcoat. The amount of overlap of the second SCR catalyst with the blend can be from about 10% to about 95% (inclusive), preferably from about 50% to about 95% (inclusive). FIG. 6 depicts an example of such a configuration, where the second SCR covers a portion, but not the entire blend and a portion of the second SCR is located in the exhaust gas stream after the blend. In fig. 6, the second SCR covered about 95% of the blend.

In a seventh configuration, the catalyst can comprise a first layer comprising a third SCR catalyst. The first layer may be partially, but not completely, covered by a coating comprising a mixture of (1) platinum on a support and (2) a first SCR catalyst. The amount of blend covering the third SCR catalyst can be from about 10% to about 95% (inclusive), preferably from about 50% to about 95% (inclusive). The blend can be covered by a washcoat comprising a second SCR catalyst, wherein the second SCR catalyst washcoat covers the entire blend washcoat. Fig. 7 depicts an example of such a configuration, where the third SCR catalyst is a bottom layer on the substrate, the second layer comprises a blend partially covering the third SCR catalyst, and the third layer comprises the entire second SCR over the second layer and covering the mixture layer.

In an eighth configuration, the catalyst can comprise a first layer comprising a third SCR catalyst. The first layer may be partially, but not completely, covered by a coating comprising a mixture of (1) platinum on a support and (2) a first SCR catalyst. The amount of blend covering the third SCR catalyst can be from about 10% to about 95% (inclusive), preferably from about 50% to about 95%. The blend can be covered by a washcoat comprising a second SCR catalyst, wherein the second SCR catalyst washcoat partially, but not completely, covers the blend washcoat, and a portion of the second SCR catalyst washcoat is also located downstream of the blend and also covers a portion of a third SCR catalyst downstream of the blend washcoat. The amount of second SCR catalyst coverage of the third SCR catalyst can be from about 10% to about 95% (inclusive), preferably from about 50% to about 95% (inclusive). Fig. 8 depicts an example of such a configuration, where the third SCR catalyst is an underlayer on a substrate, the second layer comprises a blend that partially but not completely covers the third SCR catalyst, and the third layer comprises a second SCR catalyst that is located above the second layer and partially but not completely covers the mixture layer. In fig. 8, the blend layer covers about 60% of the first layer and the layer with the second SCR catalyst covers about 20% of the first layer. The term "overlying" means that portion of a layer that is in direct contact with a different layer.

Reductant/urea injector

The system of some embodiments of the invention may include means for introducing a nitrogenous reductant into the exhaust system upstream of the ammonia slip catalyst. It may be preferred that the means for introducing the nitrogenous reductant into the exhaust system is located directly upstream of the ammonia slip catalyst (e.g., there is no intervening catalyst between the means for introducing the nitrogenous reductant and the ammonia slip 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.

Preparation method

The catalytic articles of some embodiments of the invention may be prepared by any suitable method known in the art. For catalytic articles comprising platinum on a support, such platinum can be immobilized on the support in solution, i.e., in situ, thus eliminating the need for a separate pre-immobilization process. To prepare a coating comprising a blend of (1) platinum on a support and (2) an SCR catalyst, the following steps may be performed:

combining the support material with water into a batch and mixing;

addition of organic acids which act as reducing agents for the platinum and/or create a reducing environment during the subsequent calcination step. Examples of suitable organic acids may include citric acid, succinic acid, oxalic acid, ascorbic acid, acetic acid, formic acid, and combinations thereof;

adding platinum nitrate to the batch in an amount such that the molar ratio of organic acid to platinum is from 20:1 to 1: 1; 10:1 to 1: 1; or 5:1 to 1: 1;

combining platinum batches with SCR batches;

adjusting the rheology and solids% of the combined batch, coating in air and burning at 500-550 ℃.

Application method

Reduction ofMethods of exhaust gas stream emission may comprise contacting an exhaust gas stream with a catalytic article as described herein. In some embodiments, the NH of the exhaust gas at a temperature of about 300 ℃ or less is improved₃The method of conversion may comprise contacting an exhaust gas comprising ammonia with a catalytic article as described herein. In some embodiments, a method of treating an exhaust gas comprising ammonia and NOx may comprise contacting an exhaust gas comprising ammonia with a catalytic article as described herein. In some embodiments, the weight ratio (ANR) of ammonia to nox (ANR) in the exhaust gas is based at least in part on the time of operation of the system>1.0。

Advantageous effects

The catalytic articles of the present invention can improve catalytic activity and selectivity. Ammonia slip catalyst comprising a layer having a blend of (1) a platinum group metal on a support and (2) an SCR catalyst₂Improvements in O formation and NOx re-production are provided, however, some of these catalysts may exhibit disadvantages and/or limitations. In particular, where such catalysts require pre-immobilization of the platinum group metal on a support, such catalysts involve additional costs associated with the pre-immobilization step, and at low temperatures (such as below 300 ℃) and under challenging conditions (such as high NH₃Slip and/or high space velocity) may exhibit lower NH₃And (4) conversion rate.

It has been surprisingly found that the catalytic article of the present invention can minimize or reduce the above-mentioned disadvantages and limitations. For example, by immobilizing the platinum group metals in solution, i.e., in situ, onto the support, the additional cost associated with the pre-immobilization step is eliminated. In addition, such catalytic articles are at low temperatures (such as below 300 ℃) and under challenging conditions (such as high NH)₃Slip and/or high space velocity) exhibit improved NH₃And (4) conversion rate.

In some embodiments, the catalytic article of the present invention having platinum group metal immobilized on a support in solution may provide equivalent or enhanced NH at a temperature of about 300 ℃ or less as compared to a catalytic article that is equivalent except that it has platinum group metal pre-immobilized on a support₃And (4) conversion activity. In some embodiments, with the exception of having the platinum group metal pre-immobilized on a supportCatalytic articles of the invention having a platinum group metal immobilized on a support in solution may have enhanced NH at a temperature of about 300 ℃ or less as compared to otherwise equivalent catalytic articles₃Conversion activity, the catalytic articles of the present invention exhibit at NH at temperatures of about 300 ℃ or less₃An improvement in conversion of about 30% to about 100%; about 35% to about 95%; about 40% to about 90%; about 45% to about 85%; about 50% to about 80%; about 55% to about 75%; about 30% to about 50%; about 35% to about 55%; about 40% to about 60%; about 50% to about 70%; about 60% to about 80%; about 70% to about 90%; about 80% to about 100%; greater than 30%; greater than 40%; greater than 50%; greater than 60%; greater than 70%; greater than 80%; or greater than 90%.

In some embodiments, other than having a fixed, high external surface area zeolite(s) ((s))>50m²/g) or SiO₂-Al₂O₃Compared to equivalent catalytic articles comprising a mixed oxide supported platinum group metal, the inventive catalyst having a high external surface area zeolite>50m²/g) or SiO₂-Al₂O₃A catalytic article of platinum on a mixed oxide support may provide equivalent or enhanced NH3 conversion activity at temperatures of about 300 ℃ or less. In some embodiments, other than having a fixed, high external surface area zeolite(s) ((s))>50m²/g) or SiO₂-Al₂O₃Compared to equivalent catalytic articles comprising a mixed oxide supported platinum group metal, the inventive catalyst having a high external surface area zeolite>50m²/g) or SiO₂-Al₂O₃A catalytic article of platinum on a mixed oxide support may provide equivalent or enhanced NH3 conversion activity at temperatures of about 300 ℃ or less, with the catalytic article of the invention exhibiting NH3 conversion activity at temperatures of about 300 ℃ or less₃An improvement in conversion of about 30% to about 100%; about 35% to about 95%; about 40% to about 90%; about 45% to about 85%; about 50% to about 80%; about 55% to about 75%; about 30% to about 50%; about 35% to about 55%; about 40% to about 60%; about 50% to about 70%; about 60% to about 80%; about 70% to about 90 percent; about 80% to about 100%; greater than 30%; greater than 40%; greater than 50%; greater than 60%; greater than 70%; greater than 80%; or greater than 90%.

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 "calcining" means heating the material in air or oxygen. This definition conforms to the calcined IUPAC definition (IUPAC. Complex of Chemical technology, 2 nd edition ("gold book"), compiled by A.D.McNaught and A.Wilkinson, Blackwell Scientific Publications, Oxford (1997). XML on-line correction version: http:// gold book. IUPAC. org (2006-), created by M.Nic, J.Jerta, B.Kosata; more up-dated by A.Jenkins, ISBN0-9678550-9-8.doi:10.1351/gold book.). Calcination is performed to decompose the metal salt and facilitate the exchange of metal ions within the catalyst, and also to adhere the catalyst to the substrate. The temperature used for calcination depends on the components in the material to be calcined and is typically between about 400 ℃ and about 900 ℃ for about 1 hour to 8 hours. In some cases, the calcination may be performed at a temperature of up to about 1200 ℃. In applications involving the methods described herein, calcination is generally conducted at a temperature of from about 400 ℃ to about 700 ℃ for from about 1 hour to 8 hours, preferably at a temperature of from about 400 ℃ to about 650 ℃ for from about 1 hour to 4 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 "N2 selectivity" 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.

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.