Diesel Oxidation Catalysts for Ultra-Low NOx Control

Abstract

The present disclosure provides NO over a wide temperature and space velocity range. x Adsorption indicates NO x Shifting desorption to the desired temperature range, low temperature NO x The present invention relates to an absorbent (LT-NA) catalyst composition. In particular, the LT-NA composition comprises a large pore zeolite containing a palladium component and a small or medium pore zeolite containing a palladium component. The present invention also relates to a catalyst article containing the LT-NA catalyst composition, an exhaust gas treatment system for treating exhaust gases containing the catalyst article, and a method for reducing NO in an exhaust gas stream using the catalyst article. x Methods for reducing the levels are provided. [Selected Figure] Figure 1A

Description

[Technical field]

[0001] The present invention treats the exhaust gas stream of an internal combustion engine to reduce nitrogen oxides (NO x The present invention relates to catalyst compositions, articles, systems, and methods suitable for reducing emissions of . [Background technology]

[0002] Environmental regulations regarding internal combustion engine emissions are becoming increasingly stringent around the world. Lean-burn engine operation, such as diesel engines, offers users superior fuel economy by operating at a high air-fuel ratio under fuel-lean conditions. However, diesel engines also produce a large amount of particulate matter (PM), unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x) It also releases exhaust gases containing NO x The terms "soot" and "soot fraction" refer to the various chemical species of nitrogen oxides, including nitric oxide and nitrogen dioxide. The two main components of exhaust particulate matter are the soluble organic fraction (SOF) and the soot fraction. SOF condenses in a layer on top of the soot and generally originates from unburned diesel fuel and lubricating oil. SOF can exist in diesel exhaust as a vapor or an aerosol (i.e., fine droplets of liquid condensate), depending on the temperature of the exhaust gases. Soot is primarily composed of particles of carbon.

[0003] Oxidation catalysts comprising one or more precious metals, such as platinum group metals (PGMs), dispersed on a refractory metal oxide support, such as alumina, are known to be used in treating diesel engine exhaust to convert hydrocarbon and carbon monoxide gas pollutants to carbon dioxide and water by catalyzing the oxidation of these pollutants. Such catalysts are generally contained in units, referred to as diesel oxidation catalysts (DOCs), which are placed in the exhaust flow path from a diesel engine to treat the exhaust before it is released into the atmosphere. Generally, diesel oxidation catalysts are formed on a ceramic or metal substrate, on which one or more catalytic coating compositions are deposited. In addition to converting gaseous HC and CO emissions and particulate matter (SOF fraction), oxidation catalysts comprising one or more PGMs promote the oxidation of NO to NO2. Catalysts are generally characterized by a light-off temperature, i.e., the temperature at which 50% conversion is achieved (T 50 (also called the

[0004] NO x NO is found in exhaust gases from internal combustion engines (e.g., cars and trucks), combustion equipment (e.g., power plants using natural gas, oil, and coal for heating), and nitric acid production plants. x A variety of treatment methods have been used to treat contained gas mixtures to reduce air pollution.

[0005] NO from the exhaust of lean-burn engines, such as gasoline direct injection and partial lean-burn engines x One effective method to reduce NO emissions under lean-burn engine operating conditions is to x and the capture and storage of the captured NO under stoichiometric or rich engine operating conditions, or under lean engine operation with external fuel injected into the exhaust to induce rich conditions. x The lean cycle is usually between 1 and 20 minutes, and the rich cycle is usually short (1 to 10 seconds) to save as much fuel as possible. xTo increase conversion efficiency, short and frequent regenerations are preferred over long but infrequent regenerations. x The capture catalyst is generally x Acquisition and ternary conversion functions must be provided.

[0006] Some dilute NO x The capture (LNT) system contains alkaline earth elements. For example, NO x The sorbent components include alkaline earth metal oxides such as oxides of Mg, Ca, Sr, or Ba. Other dilute LNT systems can include rare earth metal oxides such as oxides of Ce, La, Pr, or Nd. NO x The adsorbent is a catalytic NO x It can be used in combination with a PGM catalyst, such as a platinum component dispersed on a refractory metal oxide (e.g., alumina) support for oxidation and reduction. The LNT catalyst operates under cyclic lean (trap mode) and rich (regeneration mode) exhaust conditions, during which engine-exhaust NO is converted to N2.

[0007] NO from lean-burn engine exhaust x Another effective method for reducing NO under lean-burn engine operating conditions is with a suitable reducing agent, such as ammonia or a hydrocarbon, in the presence of a selective catalytic reduction (SCR) catalyst component. x The SCR process utilizes the catalytic reduction of nitrogen oxides with a reducing agent (e.g., ammonia) in the presence of atmospheric oxygen, resulting in the formation of primarily nitrogen and steam. 4NO+4NH3+O2→4N2+6H2O (standard SCR reaction) 2NO2+4NH3→3N2+6H2O (slow SCR reaction) NO+NO2+NH3→2N2+3H2O (fast SCR reaction)

[0008] Current catalysts used in SCR processes include molecular sieves, such as zeolites, ion-exchanged with catalytic metals, such as iron or copper. Useful SCR catalyst components are those that can reduce NO at temperatures below 600°C. x It can effectively catalyze the reduction of exhaust components, thereby reducing NO2 even under low load conditions, which are typically associated with lower exhaust temperatures. x You can achieve the level.

[0009] A major problem encountered in the treatment of automotive exhaust gas streams is the so-called "cold start" period, which is the period at the beginning of the treatment process when the exhaust gas stream and exhaust gas treatment system are at low temperatures (i.e., below 150°C). At these low temperatures, exhaust gas treatment systems generally produce a high concentration of hydrocarbons (HC), nitrogen oxides (NO x ), and / or carbon monoxide (CO) emissions. Generally, catalyst components, such as SCR catalyst components, do not exhibit sufficient catalytic activity to effectively treat NO x However, they do not perform well at lower temperatures (<200°C) such as during cold starts or long periods of low-speed city driving. x The exhaust can be captured and stored, and when the catalytic component (i.e., the SCR catalytic component) is activated, NO x There is a strong demand for catalytic components that can release emissions at higher temperatures (>200°C). As a result, considerable efforts have been made to mitigate this problem. For example, catalytic components have been developed that store these exhaust gas emissions at low temperatures and then release them (i.e., HC, CO, and NO) when the remaining catalytic components of the treatment system have reached sufficient catalytic activity. x New capture systems have been developed that can release the gas (hydrogen) at higher temperatures.

[0010] For example, zeolites are often used as adsorbent materials in catalytic treatment systems to adsorb and retain gaseous hydrocarbon pollutants during the initial cold start period. As the temperature of the exhaust gas increases, the adsorbed hydrocarbons are driven from the adsorbent material and catalytically oxidized at higher temperatures. However, NO x Adsorbent technology is NO x Its use has been limited to LNT applications where NO (NO and NO2) are adsorbed on base metal oxides (BaO, MgO, CeO2, etc.) under lean conditions and then released and reduced under transient rich conditions. The conversion of NO to NO2 requires efficient NO x Although a prerequisite for capture, the reaction rate is extremely slow when temperatures are below 200°C, which makes conventional LNT catalysts unable to achieve the desired reaction rate for cold start NO x This makes them unsuitable for capturing emissions.

[0011] Due to increasingly strict emission regulations, cold start NO x Improved NO to capture emissions x It is highly desirable to provide a storage component. Cold Start NO x Since >80% of exhaust gas consists of NO, state-of-the-art NO x It is essential that the adsorbent material has good efficiency for NO adsorption. Summary of the Invention

[0012] The present disclosure generally relates to improved NO x The present invention provides a catalyst composition, a catalyst article, and a catalyst system including such a catalyst article, which exhibits NO adsorption at low temperatures. x The adsorption and capture of NO x Suitable for releasing NO at high temperatures x The catalyst composition includes an adsorbent. x The adsorbent component is designed to provide the desired NO under various engine operating conditions. x Provides adsorption and desorption properties.

[0013] Thus, in one embodiment, a low temperature NOx extractor is provided that comprises a first zeolite that is a large pore zeolite and that includes a first palladium component, and a second zeolite that is a small or medium pore zeolite and that includes a second palladium component. x An adsorbent (LT-NA) catalyst composition is provided.

[0014] In some embodiments, the first zeolite and the second zeolite are each an aluminosilicate zeolite. In some embodiments, the silica-to-alumina ratio (SAR) of the first zeolite is from about 10 to about 50. In some embodiments, the SAR of the second zeolite is from about 10 to about 50.

[0015] In some embodiments, the first zeolite has a framework structure type 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, FZU, 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, VET, and mixtures or intergrowths thereof. In some embodiments, the first zeolite is selected from the group consisting of BEA, FAU, and combinations thereof.

[0016] In some embodiments, the second zeolite is a small pore zeolite having a framework structure type selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MFI, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON, and mixtures or intergrowths thereof. In some embodiments, the second zeolite is a small pore zeolite having a framework structure type selected from the group consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, and mixtures or intergrowths thereof. In some embodiments, the second zeolite is a medium pore zeolite having a framework structure type selected from 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, WEN, and mixtures or intergrowths thereof. In some embodiments, the second zeolite has a two-dimensional pore system.

[0017] In some embodiments, the second zeolite is a medium pore zeolite having a framework structure type selected from FER, MEL, MFI, STT, and mixtures or intergrowths thereof. In some embodiments, the second zeolite is selected from the group consisting of FER, MWW, CHA, and combinations thereof. In some embodiments, the first zeolite is BEA and the second zeolite is FER.

[0018] In some embodiments, the catalyst composition further comprises a third zeolite comprising a third palladium component. In some embodiments, the third zeolite is a large pore zeolite, and the first zeolite and the third zeolite have different framework structure types. In some embodiments, the third zeolite is a small pore or medium pore zeolite, and the second zeolite and the third zeolite have different framework structure types.

[0019] In some embodiments, the first palladium component and the second palladium component are present in an amount of about 0.5% to about 6% by weight, or about 1% to about 3% by weight, based on the first zeolite and the second zeolite, respectively. In some embodiments, the weight ratio of the first zeolite to the second zeolite is about 1:9 to about 9:1. In some embodiments, the weight ratio of the first zeolite to the second zeolite is about 1:3 to about 3:1, e.g., the ratio may be about 1:3, about 1:2.5, about 1:2, about 1:1.5, about 1:1, about 3:1, about 2.5:1, about 2:1, about 1.5:1, or about 1:1. In some embodiments, the weight ratio of the first zeolite to the second zeolite is about 0.1:9.9 to about 9:1. In some embodiments, the weight ratio of the first zeolite to the second zeolite is from about 0.1:9.9 to about 0.5:9.5.

[0020] In another aspect, a catalyst article for treating an exhaust stream of an internal combustion engine is provided, the article comprising a catalyst substrate having an inlet end and an outlet end defining an overall length, and a first LT-NA catalyst composition, the first LT-NA catalyst composition being a LT-NA catalyst composition disclosed herein. In some embodiments, the first LT-NA catalyst composition is in the form of a mixture comprising a first zeolite and a second zeolite. In some embodiments, the catalyst article comprises a first washcoat comprising a first zeolite disposed on at least a portion of the length of the catalyst substrate, and a second washcoat comprising a second zeolite disposed on at least a portion of the length of the catalyst substrate. In some embodiments, the second washcoat is directly on the catalyst substrate, and the first washcoat is on at least a portion of the second washcoat. In some embodiments, the first washcoat is directly on the catalyst substrate, and the second washcoat is on at least a portion of the first washcoat. In some embodiments, the catalyst article has a zone configuration such that a first washcoat is disposed on the catalyst substrate from an inlet end for about 10% to about 70% of the total length, and a second washcoat is disposed on the catalyst substrate from an outlet end for about 30% to about 90% of the total length.

[0021] In some embodiments, the catalyst article has a viscosity of about 15 g / ft 3 ~about 100g / ft 3 , or about 60g / ft 3 ~ approx. 90g / ft 3 In some embodiments, the catalyst article comprises a Pd loading of about 1 g / in 3 ~ approx. 5g / in 3 or about 2g / in 3 ~ approx. 4g / in 3In some embodiments, the catalyst article comprises a silica-to-alumina ratio (SAR) of about 5 to about 50 or about 10 to about 35. In some embodiments, the catalyst substrate comprises a honeycomb substrate in the form of a wall-flow filter or a flow-through substrate. In some embodiments, the catalyst article further comprises a first diesel oxidation catalyst (DOC) composition disposed on the substrate. In some embodiments, the first DOC composition comprises a Pt component and a fourth Pd component, wherein the Pt component and the fourth Pd component are supported on a refractory metal oxide support material. In some embodiments, the refractory metal oxide comprises gamma alumina or an alumina doped with about 2% to about 10% SiO2. In some embodiments, the first DOC composition further comprises a beta zeolite substantially free of platinum group metal (PGM) species.

[0022] In some embodiments, the first LT-NA catalyst composition and the first DOC composition are present on the catalyst substrate in a homogenous monolayer. In some embodiments, the first LT-NA catalyst composition comprises a first layer and the DOC composition comprises a second layer. In some embodiments, the first layer is disposed on at least a portion of the length of the catalyst substrate and the second layer is disposed on at least a portion of the length of the catalyst substrate. In some embodiments, the first layer is directly on the catalyst substrate and the second layer is on at least a portion of the first layer. In some embodiments, the second layer is directly on the catalyst substrate and the first layer is on at least a portion of the second layer. In some embodiments, the catalyst article has a zone configuration such that the second layer is disposed on the catalyst substrate from about 10% to about 70% of the total length from the inlet end and the first layer is disposed on the catalyst substrate from about 30% to about 90% of the total length from the outlet end.

[0023] In some embodiments, the catalyst article further comprises a third layer. In some embodiments, the third layer comprises a second DOC composition. In some embodiments, the first layer is disposed between the second layer and the third layer. In some embodiments, the second DOC composition is the same as the first DOC composition.

[0024] In some embodiments, the third layer comprises a second LT-NA catalyst composition. In some embodiments, the second layer is disposed between the first layer and the third layer. In some embodiments, the second LT-NA catalyst composition is the same as the first LT-NA catalyst composition.

[0025] In some embodiments, a catalyst article is provided having a first DOC composition directly on a substrate, a first LT-NA catalyst composition on the first DOC composition, and a second DOC composition on the first LT-NA composition. In some embodiments, a catalyst article is provided having a second DOC composition directly on a substrate, a first LT-NA catalyst composition on the second DOC composition, and a first DOC composition on the first LT-NA composition.

[0026] In some embodiments, catalyst articles are provided having a first LT-NA catalyst composition directly on a substrate, a first DOC catalyst composition on the first LT-NA catalyst composition, and a second LT-NA catalyst composition on the first DOC composition. In some embodiments, catalyst articles are provided having a second LT-NA catalyst composition directly on a substrate, a first DOC composition on the second LT-NA catalyst composition, and a first LT-NA catalyst composition on the first DOC composition.

[0027] In yet another aspect, an exhaust gas treatment system is provided that includes a catalytic article as disclosed herein, the catalytic article downstream of and in fluid communication with an internal combustion engine.

[0028] In yet another embodiment, NO in an exhaust gas stream from an internal combustion engine x Methods for reducing the levels are provided, the methods including passing the exhaust stream through any of the catalyst compositions, catalyst articles, or exhaust gas treatment systems disclosed herein.

[0029] The present disclosure includes, but is not limited to, the following embodiments.

[0030] Embodiment 1: A method for producing a low-temperature NO 3 -catalyst comprising: a first zeolite that is a large pore zeolite and that includes a first palladium component; and a second zeolite that is a small or medium pore zeolite and that includes a second palladium component. x Adsorbent (LT-NA) catalyst composition.

[0031] Embodiment 2: The LT-NA catalyst composition of the previous embodiment, wherein the first zeolite and the second zeolite are each an aluminosilicate zeolite.

[0032] Embodiment 3: The LT-NA catalyst composition of any of the previous embodiments, wherein the first zeolite has a silica-to-alumina ratio (SAR) of about 10 to about 50.

[0033] Embodiment 4: The LT-NA catalyst composition of any of the previous embodiments, wherein the second zeolite has an SAR of about 10 to about 50.

[0034] Embodiment 5: The LT-NA catalyst composition of any of the previous embodiments, wherein the first zeolite has a framework structure type 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, FZU, 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, VET, and mixtures or intergrowths thereof.

[0035] Embodiment 6: The LT-NA catalyst composition of any of the previous embodiments, wherein the first zeolite is selected from the group consisting of BEA, FAU, and combinations thereof.

[0036] Embodiment 7: The LT-NA catalyst composition of any of the preceding or subsequent embodiments, wherein the second zeolite is a small pore zeolite having a framework structure type selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MFI, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON, and mixtures or intergrowths thereof.

[0037] Embodiment 8: The LT-NA catalyst composition of any of the previous embodiments, wherein the second zeolite is a small pore zeolite having a framework structure type selected from the group consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, and mixtures or intergrowths thereof.

[0038] Embodiment 9: The LT-NA catalyst composition of any of the previous embodiments, wherein the second zeolite is a medium pore zeolite having a framework structure type selected from 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, WEN, and mixtures or intergrowths thereof.

[0039] Embodiment 10: The LT-NA catalyst composition of any of the previous embodiments, wherein the second zeolite has a two-dimensional pore system.

[0040] Embodiment 11: The LT-NA catalyst composition of any of the previous embodiments, wherein the second zeolite has a two-dimensional pore system and has a framework structure type selected from FER, CSV, DAC, HEU, MFS, MWW, NES, RRO, SFG, STI, STT and TER.

[0041] Embodiment 12: The LT-NA catalyst composition of any of the previous embodiments, wherein the second zeolite is a medium pore zeolite having a framework structure type selected from FER, MEL, MFI, STT, and mixtures or intergrowths thereof.

[0042] Embodiment 13: The LT-NA catalyst composition of any of the previous embodiments, wherein the second zeolite is selected from the group consisting of FER, MWW, CHA, and combinations thereof.

[0043] Embodiment 14: The LT-NA catalyst composition of any of the previous embodiments, wherein the first zeolite is BEA and the second zeolite is FER.

[0044] Embodiment 15: The LT-NA catalyst composition of any of the previous embodiments, further comprising a third zeolite comprising a third palladium component.

[0045] Embodiment 16: The LT-NA catalyst composition of any of the previous embodiments, wherein the third zeolite is a large pore zeolite, and the first zeolite and the third zeolite have different framework structure types.

[0046] Embodiment 17: The LT-NA catalyst composition of any of the previous embodiments, wherein the third zeolite is a small pore or medium pore zeolite, and the second zeolite and the third zeolite have different framework structure types.

[0047] Embodiment 18: The LT-NA catalyst composition of any of the previous embodiments, wherein the first palladium component and the second palladium component are present in an amount of from about 0.5% to about 64% by weight, or from about 1% to about 2% by weight, based on the first zeolite and the second zeolite, respectively.

[0048] Embodiment 19: The LT-NA catalyst composition of any of the previous embodiments, wherein the weight ratio of the first zeolite to the second zeolite is from about 0.1:9.9 to about 9:1.

[0049] Embodiment 20: The LT-NA catalyst composition of any of the previous embodiments, wherein the weight ratio of the first zeolite to the second zeolite is from about 0.1:9.9 to about 0.5:9.5.

[0050] Embodiment 21: A catalytic article for treating an exhaust stream of an internal combustion engine, comprising a catalytic substrate having an inlet end and an outlet end defining an overall length, and a LT-NA catalytic composition of any of the preceding or subsequent embodiments disposed thereon.

[0051] Embodiment 22: The catalyst article of any of the previous embodiments, wherein the LT-NA catalyst composition is in the form of a mixture comprising a first zeolite and a second zeolite.

[0052] Embodiment 23: The catalytic article of any of the previous embodiments, comprising a first washcoat comprising a first zeolite disposed on at least a portion of the length of the catalytic substrate, and a second washcoat comprising a second zeolite disposed on at least a portion of the length of the catalytic substrate.

[0053] Embodiment 24: The catalytic article of any of the previous embodiments, wherein the second washcoat is directly on the catalytic substrate and the first washcoat is on at least a portion of the second washcoat.

[0054] Embodiment 25: The catalytic article of any of the previous embodiments, wherein the first washcoat is directly on the catalytic substrate and the second washcoat is on at least a portion of the first washcoat.

[0055] Embodiment 26: The catalyst article of any of the previous embodiments, having a zone configuration such that the first washcoat is disposed on the catalyst substrate from the inlet end for about 10% to about 70% of the total length, and the second washcoat is disposed on the catalyst substrate from the outlet end for about 30% to about 90% of the total length.

[0056] Embodiment 27: The catalyst article has a viscosity of about 15 g / ft 3 ~about 200g / ft 3 Or about 60g / ft 3 ~Approx. 120g / ft 3の The catalyst article of any of the preceding embodiments, comprising a Pd loading.

[0057] Embodiment 28: The catalytic article has a coating thickness of about 1 g / in 3 ~ approx. 5g / in 3 or about 2g / in 3 ~ approx. 4g / in 3 The catalyst article of any of the preceding embodiments, comprising a total zeolite loading of

[0058] Embodiment 29: The catalytic article of any of the preceding embodiments, wherein the catalytic article comprises a SAR of from about 5 to about 50, or from about 10 to about 35.

[0059] Embodiment 30: The catalytic article of any of the previous embodiments, wherein the catalytic substrate comprises a honeycomb substrate in the form of a wall-flow filter or a flow-through substrate.

[0060] Embodiment 31: The catalyst article of any of the previous embodiments, further comprising a diesel oxidation catalyst (DOC) composition disposed on the substrate.

[0061] Embodiment 32: The catalyst article of any of the previous embodiments, wherein the DOC composition comprises a Pt component and a fourth Pd component, the Pt component and the fourth Pd component being supported on a refractory metal oxide support material.

[0062] Embodiment 33: The catalytic article of any of the previous embodiments, wherein the refractory metal oxide comprises gamma alumina or alumina doped with about 2% to about 10% SiO2.

[0063] Embodiment 34: The catalyst article of any of the previous embodiments, wherein the DOC composition further comprises a beta zeolite that is substantially free of platinum group metal (PGM) species.

[0064] Embodiment 35: The catalytic article of any of the previous embodiments, wherein the LT-NA catalytic composition and the DOC composition are present on the catalytic substrate in a homogenous monolayer.

[0065] Embodiment 36: The catalyst article of any of the previous embodiments, wherein the LT-NA catalyst composition comprises a first layer and the DOC composition comprises a second layer.

[0066] Embodiment 37: The catalytic article of any of the previous embodiments, wherein the first layer is disposed on at least a portion of the length of the catalytic substrate, and the second zeolite is disposed on at least a portion of the length of the catalytic substrate.

[0067] Embodiment 38: The catalytic article of any of the previous embodiments, wherein the first layer is directly on the catalytic substrate and the second layer is on at least a portion of the first layer.

[0068] Embodiment 39: The catalytic article of any of the previous embodiments, wherein the second layer is directly on the catalytic substrate and the first layer is on at least a portion of the second layer.

[0069] Embodiment 40: The catalyst article of any of the previous embodiments, wherein the catalyst article has a zone configuration such that the second layer is disposed on the catalyst substrate from the inlet end for about 10% to about 70% of the total length, and the first layer is disposed on the catalyst substrate from the outlet end for about 30% to about 90% of the total length.

[0070] Embodiment 41: The catalytic article of any of the preceding embodiments, further comprising a third layer.

[0071] Embodiment 42: The catalytic article of any of the preceding embodiments, wherein the third layer comprises the second DOC composition.

[0072] Embodiment 43: The catalytic article of any of the preceding embodiments, wherein the first layer is disposed between the second layer and the third layer.

[0073] Embodiment 44: The catalytic article of any of the preceding embodiments, wherein the second DOC composition is the same as the first DOC composition.

[0074] Embodiment 45: The catalytic article of any of the preceding embodiments, wherein the third layer comprises the second LT-NA composition.

[0075] Embodiment 46: The catalytic article of any of the preceding embodiments, wherein the second layer is disposed between the first layer and the third layer.

[0076] Embodiment 47: The catalytic article of any of the preceding embodiments, wherein the second LT-NA composition is the same as the first LT-NA composition.

[0077] Embodiment 48: The catalytic article of any of the preceding embodiments, wherein the DOC composition further comprises a third layer, the first layer being disposed between the second layer and the third layer.

[0078] Embodiment 49: The catalytic article of any of the preceding embodiments, wherein the LT-NA composition further comprises a third layer, the second layer being disposed between the first layer and the third layer.

[0079] Embodiment 50: An exhaust gas treatment system including the catalytic article of any of the preceding embodiments, wherein the catalytic article is downstream of and in fluid communication with an internal combustion engine.

[0080] Embodiment 51: NO in the exhaust gas stream from an internal combustion engine x A method for reducing the levels of exhaust gases comprising contacting the exhaust gas stream with the catalytic article of any of the preceding embodiments.

[0081] These and other features, aspects, and advantages of the present disclosure will become apparent upon reading the following detailed description in conjunction with the accompanying drawings, which are briefly described below. The present invention includes any combination of two, three, four, or more of the above-described embodiments, and any combination of two, three, four, or more features or elements described in this disclosure, regardless of whether such features or elements are explicitly combined in the description of a particular embodiment herein. It is intended that this disclosure be read as a whole such that separable features or elements of the disclosed invention should be considered combinable in any of its various aspects and embodiments, unless the context clearly indicates otherwise. Other aspects and advantages of the present invention will become apparent hereinafter. [Brief description of the drawings]

[0082] To provide an understanding of embodiments of the present invention, reference is made to the accompanying drawings, in which reference numerals indicate components of exemplary embodiments of the invention. The drawings are merely examples and should not be construed as limiting the present invention. The disclosure described herein is illustrated by way of example, and not by way of limitation, in the accompanying figures. For simplicity and clarity of illustration, features illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some features may be exaggerated relative to other features for clarity. Moreover, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or similar elements.

[0083] [Figure 1A] FIG. 1 is a perspective view of a honeycomb-type substrate that may include a catalyst (i.e., low temperature NOx adsorber (LT-NA)) washcoat according to the present disclosure. [Figure 1B] 1B is a partial cross-sectional view taken along a plane parallel to the end face of the substrate of FIG. 1A, enlarged relative to FIG. 1A, showing an enlarged view of the multiple gas flows shown in FIG. 1 in an embodiment in which the substrate is a flow-through substrate. [Diagram 2] FIG. 1B is an enlarged cross-sectional cutaway view relative to FIG. 1A, in which the honeycomb-type substrate in FIG. 1A corresponds to a wall-flow filter. [Figure 3A] FIG. 1 is a cross-sectional view of one embodiment of a zoned LT-NA catalyst article of the present disclosure. [Figure 3B] FIG. 1 is a cross-sectional view of an embodiment of a layered LT-NA catalyst article of the present disclosure. [Figure 3C] FIG. 2 is a cross-sectional view of another embodiment of a layered LT-NA catalyst article of the present disclosure. [Figure 4A] FIG. 2 is a cross-sectional view of a homogeneous layer LT-NA catalyst article of the present disclosure. [Figure 4B] 1A-1D are cross-sectional views of two possible configurations of a two-layer LT-NA catalyst article of the present disclosure. [Figure 4C] FIG. 1 is a cross-sectional view of a zoned LT-NA catalyst article of the present disclosure. [Figure 5A] FIG. 2 is a cross-sectional view of a homogeneous layer LT-NA / DOC catalyst article of the present disclosure. [Figure 5B] 1A-1D are cross-sectional views of possible configurations of a two-layer LT-NA / DOC catalyst article of the present disclosure. [Figure 5C] 1A-1D are cross-sectional views of possible configurations of a two-layer LT-NA / DOC catalyst article of the present disclosure. [Figure 5D] FIG. 2 is a cross-sectional view of a zoned LT-NA / DOC catalyst article of the present disclosure. [Figure 5E] FIG. 2 is a cross-sectional view of a possible configuration of a three-layer LT-NA / DOC catalyst article of the present disclosure that includes two DOC layers. [Figure 5F] FIG. 2 is a cross-sectional view of a possible configuration of a three-layer LT-NA / DOC catalyst article of the present disclosure that includes two LT-NA layers. [Figure 6A] FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure, the LT-NA catalyst article being positioned downstream of a diesel oxidation catalyst (DOC) and upstream of a catalyzed soot filter (CSF) and a selective catalytic reduction (SCR) catalyst component. [Figure 6B] FIG. 2 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure, where the LT-NA catalyst article is located upstream of a DOC, a CSF, and an SCR catalyst. [Figure 6C] FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure, the LT-NA catalyst article being located downstream of a DOC and upstream of an SCR catalyst component and a CSF. [Figure 6D] FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure, the LT-NA catalyst article being located upstream of a DOC, an SCR catalyst component, and a CSF. [Figure 7A] FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure in combination with a DOC (LT-NA / DOC), where the LT-NA / DOC is located upstream of the CSF and SCR catalyst components. [Figure 7B] FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure in combination with a DOC (LT-NA / DOC), where the LT-NA / DOC is located upstream of the CSF and SCR catalyst components. [Figure 7C] FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure combined with a DOC (LT-NA / DOC), where the LT-NA / DOC is located upstream of a combined SCR catalyst component-catalyzed soot filter (SCRoF). [Figure 7D] FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure combined with a catalyzed soot filter (LT-NA / CSF), the LT-NA / CSF being located upstream of a DOC and downstream of an SCR catalyst component. [Figure 7E]FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure in combination with an SCR catalyst component (LT-NA / SCR), the LT-NA / SCR being located upstream of the CSF and DOC. [Figure 7F] FIG. 1 is a schematic diagram of one embodiment of an exhaust treatment system including a LT-NA catalyst article of the present disclosure combined with a joint SCR catalyst component-catalyzed soot filter (LT-NA / SCRoF), where the LT-NA / SCROF is located upstream of a DOC. [Figure 8] 1 is a line graph showing NOx concentrations at various times and temperatures for several catalyst compositions of the present disclosure. [Figure 9] 1 is a line graph showing the difference in inlet and outlet cumulative NOx (ie, delta NOx) over time for various catalyst composition samples of the present disclosure. [Figure 10] 1 is a line graph showing catalyst outlet NOx concentration with respect to time for various catalyst composition samples. [Figure 11] 1 is a line graph showing catalyst outlet NOx concentration with respect to time for various catalyst composition samples. [Figure 12] 1 is a graphical comparison of cold start NOx adsorption efficiency over three FTP cycles for a LT-NA only catalyst composition and a LT-NA / DOC catalyst composition. [Figure 13] 1 is a graphical comparison of cold start NOx adsorption efficiency for LT-NA and LT-NA / DOC catalyst compositions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0084] This disclosure generally relates to xの The present invention provides catalysts, catalytic articles, and catalytic systems including such catalytic articles, suitable for adsorption and subsequent thermal release of NO at low temperatures. In particular, such articles and systems are x (LT-NA) and the captured NO x NO suitable for thermal release at higher temperatures xThis is particularly important, for example, when the LT-NA catalyst article is placed upstream of a selective catalytic reduction (SCR) catalyst component. The selective catalytic reduction (SCR) catalyst component is capable of absorbing NO at temperatures above 200° C. X to N2, but does not perform well at lower temperatures (<200°C) such as during cold start and before urea can be injected into the exhaust.

[0085] The present invention will now be described more fully hereinafter. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0086] definition The articles "a" and "an" herein refer to one or more than one (e.g., at least one) of the grammatical object. All ranges cited herein are inclusive. The term "about" used throughout is used to express and account for small variations. For example, "about" means that the numerical value may vary by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1%, or ±0.05%. All numerical values ​​are modified by the term "about", whether or not expressly stated. Numeric values ​​modified by the term "about" include the specific identified value. For example, "about 5.0" includes 5.0.

[0087] The term "reduce" refers to a decrease in amount caused by any means.

[0088] The term "associated" means, for example, "equipped with," "connected," or "in communication," e.g., "electrically connected" or "in fluid communication," or otherwise connected to perform a function. The term "associated" can mean, for example, directly associated or indirectly associated through one or more other items or elements.

[0089] Average particle size is synonymous with D50, meaning that half of the particles by number have a larger size and half have a smaller size. Particle size refers to the primary particle. Particle size may be measured by laser light scattering technique using dispersed or dry powders according to ASTM method D4464. D90 particle size distribution indicates that 90% of the particles (by number) have a Feret diameter smaller than a specified size when measured by scanning electron microscope (SEM) or transmission electron microscope (TEM) for submicron-sized particles and by particle size analyzer for carrier-containing particles (micron-sized).

[0090] The term "catalyst" refers to a material that promotes a chemical reaction. Catalysts include "catalytically active species" and "supports" that carry or support the active species. For example, zeolites are supports for palladium active catalytic species. Similarly, refractory metal oxide particles may be supports for platinum group metal catalytic species. Catalytically active species are also called "promoters" because they promote a chemical reaction. For example, modern palladium-containing zeolites may be called Pd-promoted zeolites. "Promoted zeolites" refer to zeolites to which catalytically active species have been purposely added.

[0091] As used herein, the term "catalytic article" refers to an article that includes a substrate having a catalytic coating composition.

[0092] As used herein, "crystal size" means the length of one edge of a face of the crystal, preferably the longest edge, provided that the crystal is not needle-like. Direct measurement of crystal size can be made using microscopy techniques such as SEM and TEM. For example, SEM measurements examine the morphology of the material at high magnification (usually 1000x to 10,000x). SEM techniques can be performed by distributing a representative portion of the zeolite powder on a suitable mount, so that the individual particles are reasonably uniformly spread across the field of view at 1000x to 10000x magnification. From this population, a statistically significant sample of random individual crystals (e.g., 50-200) is examined and the longest dimension of each individual crystal, parallel to the horizontal line of the straight edge, is measured and recorded. Particles that are clearly large polycrystalline aggregates are not included in the measurement. Based on these measurements, the arithmetic mean of the crystal size of the sample is calculated.

[0093] "CSF" refers to a catalyzed soot filter, which is a wall-flow monolith. Wall-flow filters consist of alternating inlet and outlet channels, with the inlet channels plugged into the outlet end and the outlet channels plugged into the inlet end. The soot-carrying exhaust gas stream entering the inlet channels is forced through the filter walls before exiting the outlet channels. In addition to soot filtration and regeneration, ACSFs may carry oxidation catalysts to oxidize CO and HC to CO2 and H2O, or NO to NO2, thereby accelerating downstream SCR catalysts or facilitating oxidation of soot particles at lower temperatures. SCR catalyst compositions can also be coated directly onto wall-flow filters, called SCRoFs.

[0094] As used herein, the phrase "catalyst system" refers to a combination of two or more catalysts, for example, a first low-temperature NO xRefers to the combination of an adsorbent (LT-NA) catalyst with a second catalyst, which may be a diesel oxidation catalyst (DOC), LNT or SCR catalyst article. Alternatively, the catalyst system may be in the form of a washcoat, where the two catalysts are mixed or coated in separate layers.

[0095] The term "comprised of" as used in the description and claims is intended to be an open-ended term, similar to the terms "comprise" or "contain." The term "comprised of" is not meant to exclude other possible items or elements. The term "comprised of" may be equivalent to "adapted."

[0096] "DOC" refers to a diesel oxidation catalyst that converts hydrocarbons and carbon monoxide in the exhaust gas of a diesel engine. Generally, a DOC includes one or more platinum group metals, such as palladium and / or platinum, a support material, such as alumina, a zeolite for HC storage, and, optionally, a promoter and / or stabilizer.

[0097] In general, the term "effective" means, for example, about 35% to 100% effective, e.g., about 40%, about 45%, about 50% or about 55% to about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90% or about 95% effective in terms of a specified catalytic activity or storage / release activity by weight or mole.

[0098] The term "exhaust stream" or "exhaust gas stream" refers to any combination of flowing gases that may include solid or liquid particulate matter. The stream is, for example, the exhaust of a lean-burn engine that includes gaseous components and may also include non-gaseous components such as liquid droplets, solid particles, etc. The exhaust gas stream of a combustion engine generally contains products of combustion (CO2 and HO), products of incomplete combustion (carbon monoxide (CO) and hydrocarbons (HC)), oxides of nitrogen (NO x), combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen. As used herein, the terms "upstream" and "downstream" refer to the relative directions relative to the flow of the engine exhaust gas stream from the engine toward the tailpipe, with the engine being at the upstream location and the tailpipe and any pollution abatement articles, such as filters and catalysts, being downstream of the engine. The inlet end of the substrate is synonymous with the "upstream" end or the "front" end. The outlet end is synonymous with the "downstream" end or the "rear" end. The upstream zone is upstream of the downstream zone. The upstream zone may be near the engine or manifold, and the downstream zone may be further away from the engine or manifold.

[0099] The term "fluid communication" is used to refer to articles positioned in the same exhaust line, i.e., a common exhaust flow passes through articles that are in fluid communication with one another. Articles in fluid communication may be adjacent to one another in the exhaust line. Alternatively, articles in fluid communication may be separated by one or more articles, also referred to as "washcoat monoliths."

[0100] The term "functional article" in this invention means an article that includes a substrate having a functional coating composition, particularly a catalyst and / or adsorbent coating composition, disposed thereon.

[0101] As used herein, "impregnated" or "impregnation" refers to the infiltration of a catalytic material into the porous structure of a support material.

[0102] "LNT" is a platinum group metal, ceria, and NO under lean conditions. x A catalyst containing an alkaline earth capture material (e.g., BaO or MgO) suitable for adsorbing dilute NO x Under rich conditions, NO x is released and reduced to nitrogen.

[0103] As used herein, the term "molecular sieve", such as zeolites and other zeolitic framework structure materials (e.g., isomorphously substituted materials), refers to materials that may support catalytic PGMs in the form of particles. Molecular sieves are materials based on an extensive three-dimensional network of oxygen ions that generally contain tetrahedral type sites and have a substantially uniform pore distribution with an average pore size of 20 Angstroms (Å) or less.

[0104] The terms "on" and "overlying" in relation to coating layers can be used synonymously. The term "directly on" means in direct contact. Although the disclosed articles are referred to in certain embodiments as including one coating layer "on" a second coating layer, such language is intended to encompass embodiments having intervening layers where direct contact between coating layers is not required (i.e., "on" is not equivalent to "directly on").

[0105] "Platinum group metal component" or "PGM component" refers to one of the platinum group metals or their oxides.

[0106] As used herein, the term "promoted" refers to a component that is intentionally added to the molecular sieve material, typically by ion exchange, as opposed to an inherent impurity in the molecular sieve.

[0107] As used herein, the term "selective catalytic reduction" (SCR) refers to a catalytic process that uses a nitrogenous reductant to reduce nitrogen oxides to dinitrogen (N2).

[0108] As used herein, "nitrogen oxides" or "NO x " refers to oxides of nitrogen such as NO, NO2 or N2O.

[0109] The term "sorbent" refers to a substance of interest, in this invention, NO xand / or CO and / or HC and / or NH3. The adsorbent may advantageously adsorb and / or absorb (store) a substance at a given temperature and desorb (release) the substance at a higher temperature.

[0110] "Substantially free" means "little or no" or "not intentionally added," and also means containing only trace and / or inadvertent amounts. For example, in certain embodiments, "substantially free" means less than 2 wt.%, less than 1.5 wt.%, less than 1.0 wt.%, less than 0.5 wt.%, less than 0.25 wt.%, or less than 0.01 wt.% based on the weight of the total composition given.

[0111] As used herein, the term "substrate" refers to a monolithic material on which a catalytic material, i.e., catalytic coating, is disposed, typically in the form of a washcoat. In one or more embodiments, the substrate is a flow-through monolith and a monolithic wall-flow filter. Flow-through and wall-flow substrates are also disclosed, for example, in International Patent Application No. WO2016 / 070090, which is incorporated herein by reference. A washcoat is formed by preparing a slurry containing a catalyst at a particular solids content (e.g., 30% to 90% by weight) in a liquid, which is then coated onto a substrate and dried to provide a washcoat layer. Reference to a "monolithic substrate" means a single structure that is homogenous and continuous from inlet to outlet. A washcoat is formed by preparing a slurry containing particles at a particular solids content (e.g., 20% to 90% by weight) in a liquid vehicle, which is then coated onto a substrate and dried to provide a washcoat layer.

[0112] As used herein, the term "support" refers to any high surface area material, usually a metal oxide material, onto which a catalytic precious metal is applied.

[0113] As used herein, the term "washcoat" has its ordinary meaning in the art of a thin, adherent coating of catalyst or other material applied to a substrate material, such as a honeycomb-type substrate, that is sufficiently porous to permit the passage of the gas stream to be treated. Washcoats containing the metal-promoted molecular sieves of the present invention may optionally include a binder selected from silica, alumina, titania, zirconia, ceria, or combinations thereof. The binder loading is about 0.1-10 wt. %, based on the weight of the washcoat. As used herein and as described in Heck, Ronald and Farrauto, Robert, Catalytic Air Pollution Control, New York: Wiley-Interscience, 2002, pp. 18-19, a washcoat layer comprises a compositionally distinct layer of material disposed on the surface of a monolithic substrate or an underlying washcoat layer. The substrate may include one or more washcoat layers, and each washcoat layer may differ in some aspect (e.g., the physical properties of the washcoat may differ, such as particle size or crystallite phase) and / or the chemical catalytic functionality may differ.

[0114] Unless otherwise specified, "weight percent (wt%)" is based on the total composition, i.e., dry solids, without any volatile materials. All parts and percentages are by weight unless otherwise stated.

[0115] As used herein, the term "zeolite" refers to a specific example of a molecular sieve that further contains silicon and aluminum atoms. In general, molecular sieves are defined as aluminosilicates with an open three-dimensional framework structure composed of corner-sharing TO4 tetrahedra, where T is Al or Si, or alternatively P. Anionic framework charge-balancing cations are loosely associated with framework oxygens, and the remaining pore volume is filled with water molecules. Non-framework cations are generally exchangeable, and water molecules are removable.

[0116] Aluminosilicate zeolite structures do not contain phosphorus or other metals isomorphously substituted in the framework structure. That is, "aluminosilicate zeolites" excludes aluminophosphate materials such as SAPO, AlPO, and MeA1PO materials, while the broader term "zeolite" includes aluminosilicates and aluminophosphates. For purposes of this disclosure, SAPO, A1PO, and MeA1PO materials are considered to be non-zeolitic molecular sieves.

[0117] The zeolite may comprise independent SiO4 / AlO4 tetrahedra linked by common oxygen atoms to form a three-dimensional network. The silica to alumina ("SAR") molar ratio of the zeolite may vary over a wide range and is generally greater than or equal to 2. For example, the zeolite may have a SAR of from about 5 to about 1000.

[0118] Zeolites can be differentiated according to the shape of the cavities, which are primarily formed by a robust network of SiO4 / AlO4 tetrahedra. The entrances to the cavities are formed from 6, 8, 10 or 12 ring atoms, with the atoms forming the entrance opening.

[0119] Zeolites are composed of secondary structural units (SBUs) and complex structural units (CBUs) and occur in many different framework structures. The secondary structural units contain up to 16 tetrahedral atoms and are not chiral. The complex structural units are not necessarily achiral and are not necessarily usable for the construction of the entire framework. For example, a group of zeolites has single four-ring (s4r) complex structural units in their framework structures. In the four-ring, the "four" indicates the position of the tetrahedral silicon and aluminum atoms, and the oxygen atoms are located between the tetrahedral atoms. Other complex structural units include, for example, single six-ring (s6r) units, double four-ring (d4r) units, and double six-ring (d6r) units. The d4r units result from the combination of two s4r units. The d6r units result from the combination of two s6r units. The d6r units have 12 tetrahedral atoms.

[0120] Generally any framework structure type of zeolite, e.g. ABW, ACO, AEI, AEL, AEN, AET, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AH T, APC, APD, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, SCO , CFI, SGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, FAU, FER, GIS, GME, GON, GOO, HEU, IFR, IFY, IHW, IRN, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, L The following backbone structure types may be used: AU, LEV, LOV, LTA, LTL, LTN, MAZ, MEI, MEL, MER, MFI, MFS, MON, MOR, MOZ, MTF, MTT, MTW, MWF, MWW, NAB, NAT, NES, NPO, NPT, NSI, OBW, OFF, OSI, OSO, OWE, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SFW, SOS, SSY, STF, STI, STT, TER, THO, TON, TSC, UEI, UFI, USI, UTL, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, or combinations thereof.

[0121] For example, the zeolite may comprise a framework structure type selected from the group consisting of AEI, BEA (beta zeolite), CHA (chabazite), FAU (zeolite Y), FER (ferrierite), MFI (ZSM-5) and MOR (mordenite). Non-limiting examples of zeolites having the AEI, BEA, CHA, FAU, FER, MFI and MOR structures include chabazite, faujasite, zeolite Y, ultrastable zeolite Y, beta zeolite, mordenite, silicalite, zeolite X, and ZSM-5.

[0122] For example, modern zeolites can have the chabazite crystal structure, also referred to as the CHA structure by the International Zeolite Association. Zeolite CHA framework structure type molecular sieves have the approximate formula: (Ca,Na2,K2,Mg)Al2Si4O 12 6H2O。Zeolite chabazite is a naturally occurring tectosilicate mineral (e.g., hydrated calcium aluminum silicate) of the zeolite group. Three synthetic forms of zeolite chabazite are described in "Zeolite Molecular Sieves," by DW Breck, published in 1973 by John Wiley & Sons, which is incorporated herein by reference. The three synthetic forms reported by Breck are zeolite KG, described in Barrer et al., J. Chem. Soc., p. 2822 (1956); Al.; zeolite D, described in British Patent No. 868,846 (1961); and zeolite R, described in U.S. Patent No. 3,030,181, which is incorporated herein by reference. The synthesis of another synthetic form of zeolite chabazite SSZ-13 is described in U.S. Patent No. 4,544,538. The synthesis of silicoaluminophosphate 34 (SAPO-34), a synthetic form of a non-zeolitic molecular sieve having the chabazite crystal structure, is described in U.S. Patent No. 4,440,871 and U.S. Patent No. 7,264,789, each of which is incorporated herein by reference in its entirety. A method for making yet another synthetic non-zeolitic molecular sieve having the chabazite structure, SAPO-44, is described, for example, in U.S. Patent No. 6,162,415, which is incorporated herein by reference in its entirety.

[0123] Zeolites are crystalline materials with fairly uniform pore sizes ranging from about 3 to 10 angstroms in diameter, depending on the type of zeolite and the type and amount of cations contained in the zeolite lattice. The pore size is defined by the ring diameter. As used herein, the term "small pore" refers to pore openings smaller than about 5 angstroms, e.g., pore openings on the order of about 3.8 angstroms.

[0124] Small pore zeolites contain channels defined by up to eight tetrahedral atoms. The phrase "eight-ring" zeolites refers to zeolites having eight-ring pore openings and double hexagonal secondary structural units, and having a cage-type structure resulting from the connection of double hexagonal structural units by four rings.

[0125] Exemplary small pore zeolites include framework structure types ACO, AEI, AEN, AFN, AFT, AFX, 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, and mixtures or intergrowths thereof.

[0126] Medium pore zeolites contain channels defined by 10-membered rings. Exemplary medium pore zeolites include 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, WEN framework structure types and mixtures or intergrowths thereof.

[0127] Large pore zeolites contain channels defined by 12-membered rings. Exemplary large pore zeolites include framework types 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, VET, and mixtures or intergrowths thereof.

[0128] All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context. The use of any and all examples or exemplary language (e.g., "etc.") provided herein is intended only to better describe the materials and methods and does not limit the scope unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosed materials and methods.

[0129] All U.S. patent applications, pregrant publications and patents mentioned herein are hereby incorporated by reference in their entirety.

[0130] LT-NA catalyst composition The present disclosure provides a method for producing a low temperature NO 2 catalyst comprising a first zeolite that is a large pore zeolite and includes a first palladium component and a second zeolite that is a small or medium pore zeolite and includes a second palladium component. x Adsorbent (LT-NA) catalyst compositions are provided. In some embodiments, the LT-NA catalyst compositions further comprise a third zeolite comprising a third palladium component. The components of these LT-NA catalyst compositions are discussed herein below.

[0131] Zeolite As referenced above, the LT-NA catalyst composition of the present invention comprises a first zeolite, a second zeolite, and optionally a third zeolite. In some embodiments, the first zeolite is an aluminosilicate zeolite. The first zeolite is advantageously a large pore zeolite, as described herein. In some embodiments, the first zeolite is a large pore zeolite having a framework structure type 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, FZU, 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, VET, and mixtures or intergrowths thereof. In some embodiments, the first zeolite is a large pore zeolite having a framework structure type selected from the group consisting of BEA, FAU, and combinations thereof.

[0132] In some embodiments, the second zeolite is an aluminosilicate.In some embodiments, the second zeolite is a small pore zeolite.For example, in some embodiments, the second zeolite is a small pore zeolite with a framework structure type selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MFI, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON, and mixtures or intergrowths thereof. In some embodiments, the second zeolite is a small pore zeolite having a framework structure type selected from the group consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, and mixtures or intergrowths thereof.

[0133] In some embodiments, the second zeolite is a medium pore zeolite. For example, in some embodiments, the second zeolite is a medium pore zeolite with a framework structure type selected from 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, WEN, and mixtures or intergrowths thereof. In some embodiments, the second zeolite is a medium pore zeolite with a framework structure type selected from FER, MEL, MFI, STT, and mixtures or intergrowths thereof. In some embodiments, the second zeolite is a medium pore zeolite selected from the group consisting of FER, MWW, CHA, and combinations thereof.

[0134] In some embodiments, the second zeolite has a two-dimensional pore system. In some embodiments, the second zeolite having a two-dimensional pore system may have a framework structure type, such as, but not limited to, FER, CSV, DAC, HEU, MFS, MWW, NES, RRO, SFG, STI, STT, or TER. A description of the synthesis and pore geometry of zeolites having an FER structure can be found, for example, in Weitkamp et al., Chem. Eng. Technol. 25, (2002), 3, 273-275, Proceedings of 5th ed. th Serbian-Croatian-Slovenian Symposium on Zeolites, 32-35, and Parikh et al., Indian Journal of Chemical Technology, 18. Sep. 2011, 335-342, each of which is incorporated herein by reference in its entirety.

[0135] In some embodiments, the first zeolite is a large pore zeolite and the second zeolite is a small pore zeolite, hi some embodiments, the first zeolite is a large pore zeolite and the second zeolite is a medium pore zeolite.

[0136] In some embodiments, the first zeolite is a BEA zeolite and the second zeolite is a FER zeolite.

[0137] In some embodiments, the weight ratio of the first zeolite to the second zeolite is about 1:9 to about 9:1. In some embodiments, the weight ratio of the first zeolite to the second zeolite is about 1:3 to about 3:1, for example, the ratio may be about 1:3, about 1:2.5, about 1:2, about 1:1.5, about 1:1, about 3:1, about 2.5:1, about 2:1, about 1.5:1, or about 1:1. In some embodiments, the weight ratio of the first zeolite to the second zeolite is about 0.1:9.9 to about 9:1. In some embodiments, the weight ratio of the first zeolite to the second zeolite is about 0.1:9.9 to about 1:1. In some embodiments, the weight ratio of the first zeolite to the second zeolite is about 0.1:9.9 to about 0.5:9.5, such as about 0.1:9.9, about 0.2:9.8, about 0.3:9.7, about 0.4:9.6, or about 0.5:9.5.

[0138] In some embodiments, the third zeolite is a large pore zeolite. In some embodiments, the first zeolite is a large pore zeolite and the third zeolite is a large pore zeolite. In some embodiments, the first zeolite is a large pore zeolite and the third zeolite is a large pore zeolite, and the first and third zeolites have different framework structure types.

[0139] In some embodiments, the third zeolite is a small pore zeolite. In some embodiments, the third zeolite is a medium pore zeolite. In some embodiments, the first zeolite is a large pore zeolite and the third zeolite is a small pore zeolite. In some embodiments, the first zeolite is a large pore zeolite and the third zeolite is a medium pore zeolite.

[0140] In some embodiments, the first zeolite is a large pore zeolite, the second zeolite is a small pore zeolite, and the third zeolite is a small pore zeolite. In some embodiments, the first zeolite is a large pore zeolite, the second zeolite is a small pore zeolite, and the third zeolite is a small pore zeolite, and the second zeolite and the third zeolite have different framework structure types.

[0141] In some embodiments, the first zeolite is a large pore zeolite, the second zeolite is a small pore zeolite, and the third zeolite is a medium pore zeolite. In some embodiments, the first zeolite is a large pore zeolite, the second zeolite is a medium pore zeolite, and the third zeolite is a medium pore zeolite. In some embodiments, the first zeolite is a large pore zeolite, the second zeolite is a medium pore zeolite, and the third zeolite is a medium pore zeolite, and the second zeolite and the third zeolite have different framework structure types.

[0142] In some embodiments, the first zeolite is a large pore zeolite, the second zeolite is a medium pore zeolite, and the third zeolite is a small pore zeolite.

[0143] In some embodiments, the catalyst composition of the present invention, the first, second, and / or third zeolite comprises an aluminosilicate zeolite crystal having an average crystal size (i.e., the average crystal size of individual crystals, including twins) of greater than about 0.5 μm, preferably from about 0.1 μm to about 15 μm, e.g., from about 0.5 μm to about 5 μm, from about 0.7 μm to about 1.5 μm, from about 1 μm to about 5 μm, or from about 1 μm to about 10 μm. In some embodiments, the first zeolite is a crystalline aluminosilicate zeolite having an average crystal size (i.e., the average crystal size of individual crystals, including twins) of greater than about 0.5 μm, preferably from about 0.1 μm to about 15 μm, e.g., from about 0.5 μm to about 5 μm, from about 0.7 μm to about 1.5 μm, from about 1 μm to about 5 μm, or from about 1 μm to about 10 μm. In some embodiments, the second zeolite is a crystalline aluminosilicate zeolite having an average crystal size (i.e., the average crystal size of individual crystals, including twins) of greater than about 0.5 μm, preferably about 0.1 μm to about 15 μm, e.g., about 0.5 μm to about 5 μm, about 0.7 μm to about 1.5 μm, about 1 μm to about 5 μm, or about 1 μm to about 10 μm. In some embodiments, the third zeolite is a crystalline aluminosilicate zeolite having an average crystal size (i.e., the average crystal size of individual crystals, including twins) of greater than about 0.5 μm, preferably about 0.1 μm to about 15 μm, e.g., about 0.5 μm to about 5 μm, about 0.7 μm to about 1.5 μm, about 1 μm to about 5 μm, or about 1 μm to about 10 μm. In some embodiments, the first and second zeolites, the first and third zeolites, the second and third zeolites, or the first, second and third zeolites are crystalline aluminosilicate zeolites having an average crystal size (i.e., the average crystal size of individual crystals, including twins) greater than about 0.5 μm, preferably from about 0.1 μm to about 15 μm, e.g., from about 0.5 μm to about 5 μm, from about 0.7 μm to about 1.5 μm, from about 1 μm to about 5 μm, or from about 1 μm to about 10 μm.

[0144] In some embodiments, the first, second and / or third zeolite have a silica-to-alumina ratio (SAR) of about 2 to about 300, including about 5 to about 250, about 5 to about 200, about 5 to about 100, and about 5 to about 50. In one or more specific embodiments, the molecular sieve has a SAR molar ratio in the range of about 10 to about 200, about 10 to about 100, about 10 to about 75, about 10 to about 60, and about 10 to about 50, about 15 to about 100, about 15 to about 75, about 15 to about 60, and about 15 to about 50, about 20 to about 100, about 20 to about 75, about 20 to about 60, and about 20 to about 50. In one or more embodiments, the molecular sieve has a SAR molar ratio in the range of about 1, about 2, about 5, about 8, about 10, about 15, about 20 or about 25 to about 30, about 35, about 40, about 45, about 50, about 60, about 70, about 80, about 90, about 100, about 150, about 200, about 260, about 300, about 400, about 500, about 750 or about 1000.

[0145] Without wishing to be bound by theory, high zeolite sodium content may adversely affect hydrothermal stability. Thus, low sodium and alkali metal content in the first, second, and / or third zeolites is generally preferred. In certain embodiments, the first, second, and / or third zeolites have an alkali content of less than 3 wt.%, more preferably less than 1 wt.%, and even more preferably less than 0.1 wt.%, based on the total weight of the calcined zeolite (reported as alkali metal oxides on a volatile-free basis). In some embodiments, low alkali content zeolites can be provided by ion-exchanging the sodium (Na) form of the zeolite into the ammonia (NH4) form. The NH4 ion-exchange into the zeolite may be carried out at room temperature or at a temperature up to about 80° C. for about 1 to 24 hours. In some embodiments, the resulting zeolitic material may be preferably dried at about 100 to 120° C. to provide the NH4-exchanged zeolite. In some embodiments, the NH4 exchanged zeolite may be calcined at a temperature of at least about 450° C. to provide an H exchanged zeolite.

[0146] Palladium Component As referenced above, in the disclosed LT-NA catalyst compositions, the first, second, and third zeolites each generally contain at least one palladium component, where "palladium component" refers to palladium metal or a compound thereof, such as the oxide.

[0147] Typically, as used herein, a "first" palladium component refers to a "first" zeolite, a "second" palladium component refers to a "second" zeolite, and an optional "third" palladium component refers to an optional "third" zeolite. The first and second palladium components (and the third palladium component, if present) can be the same or different. In some embodiments, the first and second palladium components are the same. In some embodiments, the first, second, and third palladium components are the same.

[0148] In some embodiments, the disclosed catalyst compositions are described as comprising a zeolite "comprising" palladium (or comprising palladium "associated with" the zeolite). In such instances, "comprising" (or "associated with") is understood to mean that palladium is present either on the ion-exchange sites of the zeolite, on the surface of the zeolite, or both on the ion-exchange sites and on the surface of the zeolite.

[0149] The concentrations of the first, second, and optional third palladium components may vary, but are typically about 0.01% to about 6% by weight, respectively, based on the total weight of the first, second, and optional third zeolites. In some embodiments, the palladium component concentrations in each of the first, second, and optional third zeolites may vary. For example, the first zeolite may have a higher concentration of palladium component than one or both of the second or third zeolites. Similarly, the second zeolite may include a higher concentration of palladium component compared to the first and / or third zeolites, or the optional third zeolite may include a higher concentration of palladium component compared to the first and / or second zeolites. In some embodiments, the palladium component concentrations in each zeolite are approximately equal.

[0150] Palladium may be present in each of the first and / or second and / or third zeolites, for example, at about 0.1 wt%, about 0.2 wt%, about 0.5 wt%, about 0.7 wt%, about 0.9 wt%, or about 1.0 wt% to about 1.5 wt%, about 2.0 wt%, about 2.5 wt%, about 3.0 wt%, about 3.5 wt%, about 4.0 wt%, about 4.5 wt%, or about 5.0 wt%, based on the total weight of the LT-NA catalyst composition. The weight of palladium is measured and reported as the metal. The total dry weight of the zeolite includes any added / exchanged metal (i.e., palladium).

[0151] The LT-NA catalyst composition, in some embodiments, may include other catalytically active metals, such as copper, iron, manganese, magnesium, cobalt, nickel, platinum, ruthenium, rhodium, or combinations thereof. Such metals may be present in some embodiments such that the zeolite further includes one or more catalytically active metals. In some embodiments, the LT-NA catalyst composition is substantially free of additional active metals.

[0152] While the foregoing description provides some suitable ranges or amounts for the zeolite and palladium components of the LT-NA catalyst composition, it should be noted that the disclosed ranges or amounts of one of these components may be combined with the disclosed ranges or amounts of other components to form new ranges or subranges, and such embodiments are also expressly contemplated by the present invention.

[0153] Diesel Oxidation Catalyst (DOC) Composition Generally, DOC compositions include one or more platinum group metal (PGM) components dispersed on a support, such as a refractory metal support. A variety of such DOC compositions are known for use in treating diesel engine exhaust to catalyze the oxidation of both hydrocarbons (HC) and carbon monoxide (CO) gas pollutants, thereby converting these pollutants to carbon dioxide and water. PGM components useful in the disclosed DOC compositions include any component that includes a PGM, such as platinum, palladium, ruthenium, rhodium, osmium, iridium, and / or gold (Pt, Pd, Ru, Rh, Os, Ir, and / or Au). For example, the PGM may be in a metallic form with a zero valence, or the PGM may be in an oxide form. The PGM component may include PGMs in any valence state. The terms "platinum (Pt) component," "rhodium (Rh) component," "palladium (Pd) component," "iridium (Ir) component," "ruthenium (Ru) component," and the like refer to the respective platinum group metal compounds, complexes, and the like that decompose or are otherwise converted to a catalytically active form, typically a metal or metal oxide, upon calcination or use of the catalyst. In some embodiments, the PGM component is a metal or an oxide thereof (e.g., including, but not limited to, platinum or an oxide thereof).

[0154] In certain embodiments, the DOC compositions disclosed herein include a platinum component and a palladium component (herein referred to as a "fourth palladium component" to distinguish it from the first, second, and optional third palladium components associated with the respective zeolites of the LT-NA compositions disclosed above). The DOC compositions may include, for example, about 0.1 wt. % (weight percent), about 0.5 wt. %, about 1.0 wt. %, about 1.5 wt. %, or about 2.0 wt. % to about 3 wt. %, about 5 wt. %, about 7 wt. %, about 9 wt. %, about 10 wt. %, about 12 wt. %, about 15 wt. %, about 16 wt. %, about 17 wt. %, about 18 wt. %, about 19 wt. %, or about 20 wt. % of the platinum component based on the weight of the dry DOC composition. In some embodiments, the Pt / Pd ratio is about 10:1 to about 1:10. In some embodiments, the Pt / Pd weight ratio is about 2 / 1.

[0155] Typically, both the platinum and palladium components of the disclosed DOC compositions are supported on a support material (the support materials on which the platinum and palladium components are supported can be the same or different). The support material can be zeolitic or non-zeolitic. References to "non-zeolitic supports" or "non-zeolitic supports" in the catalyst layer refer to materials that are not zeolitic and that receive precious metals, stabilizers, promoters, binders, etc. through association, dispersion, impregnation or other suitable methods. Examples of such non-zeolitic supports include, but are not limited to, high surface area refractory metal oxides.

[0156] For example, the support material on which the catalytically active platinum component and the fourth palladium component are deposited includes refractory metal oxides that exhibit chemical and physical stability at high temperatures, such as those associated with gasoline or diesel engine exhaust. Exemplary refractory metal oxides include alumina, silica, zirconia, titania, ceria, praseodymium, tin oxide, and the like, and physical mixtures or chemical combinations thereof, including atomically doped combinations, and also high surface area or active compounds, such as activated alumina. Included are metal oxide combinations such as silica-alumina, ceria-zirconia, praseodymium-ceria, alumina-zirconia, alumina-ceria-zirconia, lanthana-alumina, lanthana-zirconia-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia-alumina, and alumina-ceria. Exemplary aluminas include large pore boehmite, gamma-alumina, and delta / theta alumina. Useful commercially available aluminas used as starting materials in a typical process include activated aluminas, such as high bulk density gamma-alumina, low or medium bulk density large pore gamma-alumina, and low bulk density large pore boehmite.

[0157] High surface area metal oxide supports, such as alumina support materials, also referred to as "gamma alumina" or "activated alumina", are generally 60 m 2 / g, often up to about 200m 2 / g or more. Typical refractory metal oxides have a BET surface area of ​​about 50 m 2 / g~about 300m 2 Activated aluminas include high surface area gamma-aluminas having a specific surface area of ​​about 60 m / g. Such activated aluminas are typically mixtures of gamma and delta phases of alumina, but may also contain significant amounts of eta, kappa, and theta alumina phases. "BET surface area" has its ordinary meaning associated with the Brunauer, Emmett, and Teller method of determining surface area by N2 adsorption. Desirably, the activated alumina has a specific surface area of ​​about 60 m 2 / g ~ approx. 350m 2 / g, for example, about 90m 2 / g ~ approx. 250m2 / g.

[0158] In certain embodiments, metal oxide supports useful in the DOC catalyst compositions disclosed herein are doped alumina materials, such as Si-doped alumina materials (including but not limited to 1-10% SiO2-Al2O3), doped titania materials, such as Si-doped titania materials (including but not limited to 1-10% SiO2-TiO2), or doped zirconia materials, such as Si-doped ZrO2 (including but not limited to 5-30% SiO2-ZrO2).

[0159] Thus, the refractory metal oxide or refractory mixed metal oxide in the DOC catalyst composition is typically selected from the group consisting of alumina, zirconia, silica, titania, ceria, e.g., bulk ceria, manganese oxide, zirconia-alumina, ceria-zirconia, ceria-alumina, lanthana-alumina, baria-alumina, silica, silica-alumina, and combinations thereof.

[0160] The DOC catalyst composition may include any of the refractory metal oxides listed above in any amount. For example, the refractory metal oxide in the catalyst composition may be included in about 15 wt%, about 20 wt%, about 25 wt%, about 30 wt%, or about 35 wt% to about 50 wt%, about 55 wt%, about 60 wt%, about 65 wt%, or about 70 wt%, based on the total dry weight of the catalyst composition. The catalyst composition may include, for example, about 10 to about 99 wt% alumina, about 15 to about 95 wt% alumina, or about 20 to about 85 wt% alumina.

[0161] Preparation of the Catalyst Composition The disclosed LT-NA catalyst and DOC compositions can be prepared in some embodiments by incipient wetness impregnation. Incipient wetness impregnation techniques, also referred to as capillary impregnation or dry impregnation, are commonly used in the synthesis of heterogeneous materials, i.e., catalysts. Typically, metal precursors are dissolved in an aqueous or organic solution, and then the metal-containing solution is added to a catalyst support (e.g., a zeolite or refractory metal oxide) that contains the same pore volume as the volume of the added solution. Capillary action draws the solution into the pores of the support. The solution added beyond the pore volume of the support changes the solution transport from a capillary action process to a much slower diffusion process. The catalyst can then be dried and calcined to remove volatile components in the solution and deposit the metals on the surface of the catalyst support. The maximum loading is limited by the solubility of the precursor in the solution. The concentration profile of the impregnated material depends on the mass transfer conditions in the pores during impregnation and drying. Those skilled in the art will recognize other methods for loading the palladium component onto the support of the present composition, such as adsorption, ion exchange, precipitation, and the like.

[0162] For example, palladium may be impregnated into zeolite in the preparation of the components of the LT-NA catalyst composition. Palladium salts useful for introducing the first, second, and optional third palladium components into the respective zeolites include, but are not limited to, nitrates. In addition, at least a portion of the catalytically active metal may be included in the zeolite synthesis process, whereby a prepared colloid includes a structure directing agent, a silica source, an alumina source, and a metal ion source. In some embodiments, palladium and other metal salts may be mixed and the mixture impregnated into the zeolite. Metals used in the salts may include, but are not limited to, metals selected from the group consisting of copper, iron, manganese, magnesium, cobalt, nickel, platinum, ruthenium, rhodium, and combinations thereof.

[0163] Similarly, for the preparation of DOC compositions, an aqueous solution of a soluble compound or complex of a platinum group metal is generally used to impregnate a support material (e.g., a zeolite or a refractory metal oxide). Non-limiting examples of suitable compounds include palladium nitrate, tetraamminepalladium nitrate, tetraammineplatinum acetate, and platinum nitrate. During the calcination process, or at least during the initial stages of use of the composite material, such compounds are converted to the catalytically active form of the metal or its compounds. A suitable method for preparing a DOC catalyst composition is to prepare a mixture of a solution of the desired platinum group metal compound (e.g., a platinum group compound and / or a palladium compound) with at least one support, such as a finely divided, high surface area, refractory metal oxide support, e.g., gamma alumina. The support is sufficiently dry to absorb substantially all of the solution, thereby forming a moist solid that is later combined with water to form a coatable slurry. In one or more embodiments, the slurry is acidic, e.g., having a pH of about 2 to less than about 7. The pH of the slurry may be reduced by adding an appropriate amount of inorganic or organic acid to the slurry. Considering the compatibility of the acid with the raw materials, a combination of both can be used. Inorganic acids include, but are not limited to, nitric acid. Organic acids include, but are not limited to, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutamic acid, fatty acid, maleic acid, fumaric acid, phthalic acid, tartaric acid, citric acid, etc.

[0164] catalyst article Coating composition To produce a catalytic article, a substrate as disclosed herein is coated with a catalytic composition. The coating is a "catalytic coating composition" or a "catalytic coating." The terms "catalytic composition" and "catalytic coating composition" are synonymous.

[0165] The catalyst and / or sorbent compositions described herein may include one or more supports or "carriers," such as high melting point inorganic solid oxide porous powders that further comprise functionally active species.

[0166] The catalyst and / or sorbent compositions may be prepared using a binder, for example, a ZrO2 binder derived from a suitable precursor such as zirconyl acetate or any other suitable zirconium precursor such as zirconyl nitrate. The zirconyl acetate binder provides a coating that remains homogenous and intact after thermal aging, for example, when the catalyst is exposed to high temperatures of at least about 600°C, for example, about 5% or more, in a steam environment, for example, about 800°C or more. Other potentially suitable binders include, but are not limited to, alumina and silica. Alumina binders include aluminum oxide, aluminum hydroxide, aluminum oxyhydroxide. Aluminum salts and colloidal aspects of alumina may be used. Silica binders include various forms of SiO2, including silicates and colloidal silica. The binder composition may include any combination of zirconia, alumina and silica. Other exemplary binders include bohemite, gamma alumina, or delta / theta alumina, and silica sol. Binders, when present, are generally used in an amount of about 1-5 wt.% of the total washcoat loading. Alternatively, the binder can be zirconia or silica based, such as zirconium acetate, zirconia sol, or silica sol. Alumina binders, when present, are typically used in an amount of about 0.05 g / in. 3 ~Approx. 1g / inch 3 is used in amounts of

[0167] Base material In one or more embodiments, the catalyst composition is disposed on a substrate to form a catalyst article. The catalyst article comprising the substrate is part of an exhaust gas treatment system (e.g., the catalyst article includes, but is not limited to, an article comprising the LT-NA and / or DOC composition disclosed herein). Useful substrates are three-dimensional, with a length, diameter and volume resembling a cylinder. The shape does not necessarily have to conform to a cylinder. The length is the axial length defined by the inlet end and the outlet end.

[0168] According to one or more embodiments, the substrate for the disclosed compositions may be composed of any material typically used to prepare automotive catalysts, and typically includes a metal or ceramic honeycomb structure. The substrate typically provides a plurality of walls onto which the catalytic washcoat composition is applied and adhered, thereby serving as a substrate for the catalytic composition.

[0169] The ceramic substrate may be made from any suitable high melting point material, such as, for example, cordierite, cordierite-alpha-alumina, aluminum titanate, silicon titanate, silicon carbide, silicon nitride, zircon mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, alpha-alumina, aluminosilicates, and the like.

[0170] The substrate may also be metallic, including one or more metals or metal alloys. Metal substrates may include any metal substrate having openings or "punches out" in the channel walls. Metal substrates may be used in various forms such as pellets, corrugated sheets or monolithic forms. Particular examples of metal substrates include heat-resistant base metal alloys, particularly alloys in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium, and aluminum, the sum of which may advantageously comprise at least about 15% by weight of the alloy, for example, about 10-25% by weight chromium, about 1-8% by weight aluminum, and 0-about 20% by weight nickel, in each case based on the weight of the substrate. Examples of metal substrates include those with straight channels, those with blades protruding along the axial channels to disrupt gas flow and open gas flow communication between the channels, and those with blades and also holes to enhance gas transport between the channels, allowing radial gas transport throughout the monolith. In particular, metal substrates are advantageously used in certain embodiments in a closely coupled location, which allows for rapid heating of the substrate and, correspondingly, rapid heating of the catalyst composition (e.g., the LT-NA catalyst composition) coated therein.

[0171] Any suitable substrate for the catalytic article disclosed herein may be used, such as a monolithic substrate of the type having fine parallel gas flow passages extending from an inlet or end face of the substrate through which the passages are open to the flowing fluid stream ("flow-through substrate"). Another suitable substrate is of the type having a plurality of fine substantially parallel gas flow passages extending along the longitudinal axis of the substrate, typically with each passage blocked at one end of the substrate body and every other passage blocked at the opposite end face ("wall-flow filter"). Flow-through and wall-flow substrates are also disclosed, for example, in International Application WO2016 / 070090, the entire contents of which are incorporated herein by reference.

[0172] In some embodiments, the catalytic substrate comprises a honeycomb substrate in the form of a wall-flow filter or a flow-through substrate. In some embodiments, the substrate is a wall-flow filter. Flow-through substrates and wall-flow filters are further described below.

[0173] Flow-Through Substrate In some embodiments, the substrate is a flow-through substrate (e.g., a monolithic substrate, including a flow-through honeycomb monolithic substrate). A flow-through substrate has fine, parallel gas flow passages extending from the inlet end to the outlet end of the substrate such that the passages are open to fluid flow. The passages, which are generally linear paths from the fluid inlet to the fluid outlet, are defined by walls on which a catalytic coating is disposed such that gas flowing through the passages contacts the catalytic material. The flow passages of the flow-through substrate are thin-walled channels and can be of any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. The flow-through substrate can be ceramic or metallic, as described above.

[0174] The flow-through substrate may be, for example, about 50 in 3 ~About 1200in 3 and a cell density (inlet opening) of about 200 to about 400 cpsi, and a wall thickness of about 50 to about 200 microns or about 400 microns.

[0175] A catalytic article can be provided by applying a catalytic coating (e.g., as disclosed herein) to a substrate as a washcoat. Figures 1A and 1B illustrate an exemplary substrate 2 in the form of a flow-through substrate coated with a catalytic composition as described herein. With reference to Figure 1A, the exemplary substrate 2 has a cylindrical shape and a cylindrical outer surface 4, an upstream end face 6, and a corresponding downstream end face 8 that is identical to the end face 6. The substrate 2 has a plurality of fine, parallel gas flow passages 10 formed therein. As seen in Figure 1B, the passages 10 are formed by walls 12 and extend through the carrier 2 from the upstream end face 6 to the downstream end face 8, and the passages 10 are unobstructed to allow a fluid, e.g., a gas stream, to flow longitudinally through the carrier 2 and through the gas flow passages 10 thereof. As can be more easily seen in Figure 1B, the walls 12 are so dimensioned and configured such that the gas flow passages 10 have a substantially regular polygonal shape. As shown, the catalytic composition can be applied in multiple separate layers, if desired. In the illustrated embodiment, the catalyst composition is comprised of both a separate bottom layer 14 adhered to the wall 12 of the support member, and a second separate top layer 16 coated over the bottom layer 14. The invention can be practiced with one or more (e.g., two, three, four or more) catalyst composition layers and is not limited to the two-layer embodiment illustrated in Figure 1B. Additional coating configurations are disclosed herein below.

[0176] Wall Flow Filter Substrate In some embodiments, the substrate is a wall-flow filter, which generally has a plurality of fine, substantially parallel gas flow passages extending along the longitudinal axis of the substrate. Typically, each passage is blocked at one end of the substrate body, and an alternate passage is blocked at the opposite end face. Such monolithic wall-flow filter substrates may contain up to about 900 or more passages (or "cells") per square inch of cross section, although much smaller numbers may be used. For example, the substrate may have about 7 to 600, more typically about 100 to 400 cells per square inch ("cpsi"). The cells may have rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal cross sections.

[0177] FIG. 2 is a perspective view of an exemplary wall-flow filter. A cross-sectional view of a monolithic wall-flow filter substrate section is shown in FIG. 2, which shows alternating blocked and open passages (cells). Blocked or blocked ends 100 and open passages 101 alternate, with opposite ends being open and blocked, respectively. The filter has an inlet end 102 and an outlet end 103. Arrows across the porous cell walls 104 represent exhaust gas flow entering the open cell ends, diffusing through the porous cell walls 104, and exiting the open outlet cell ends. The blocked ends 100 impede gas flow and promote diffusion through the cell walls. Each cell wall has an inlet side 104a and an outlet side 104b. The passages are enclosed by the cell walls. The wall flow filter article substrate is approximately 50 cm 3 , about 100cm 3 , about 200cm 3 , about 300cm 3 , about 400cm 3 , about 500cm 3 , about 600cm 3 , about 700cm 3 So, about 800cm 3 , about 900cm 3 , or about 1000 cm 3 ~Approx. 1500cm 3 , about 2000cm3 , about 2500cm 3 , about 3000cm 3 , about 3500cm 3 , about 4000cm 3 , about 4500cm 3 , or about 5000 cm 3 The wall-flow filter substrate typically has a wall thickness of from about 50 microns to about 2000 microns, for example, from about 50 microns to about 450 microns, or from about 150 microns to about 400 microns.

[0178] The walls of the wall-flow filter are porous and generally have a wall porosity of at least about 50% or at least about 60% and an average pore size of at least about 5 microns prior to the placement of the functional coating. For example, the wall-flow filter article substrate in some embodiments has a porosity of ≧50%, ≧60%, ≧65% or more, or ≧70%. For example, the wall-flow filter article substrate has a wall porosity of about 50%, about 60%, about 65% or about 70% to about 75%, about 80% or about 85% and an average pore size of about 5 microns, about 10, about 20, about 30, about 40 or about 50 microns to about 60 microns, about 70, about 80, about 90 or about 100 microns prior to the placement of the catalytic coating. The terms "wall porosity" and "substrate porosity" are synonymous and interchangeable. Porosity is the ratio of the void volume divided by the total volume of the substrate. Pore ​​size may be determined according to the ISO 15901-2 (static volume) procedure for nitrogen pore size analysis. Nitrogen pore size may be determined on a Micromeritics TRISTAR 3000 series instrument. Nitrogen pore size may be determined using the BJH (Barrett-Joyner-Halenda) calculation and a desorption point of 33. Useful wall-flow filters have high porosity, allowing high loading of catalyst composition without excessive back pressure during operation.

[0179] coating The substrate is coated with the catalyst composition to form a catalyst article. The catalyst coating may include one or more thin, adherent coating layers disposed on and attached to at least a portion of the substrate. In some embodiments, the catalyst article may include the use of one or more catalyst layers, as well as a combination of one or more catalyst layers. The catalyst material may be present only on the inlet side, only on the outlet side, both on the inlet and outlet sides of the substrate wall, or the wall itself may be entirely or partially composed of the catalyst material. The catalyst coating may be on the substrate wall surface and / or within the pores of the substrate wall, i.e., "in" and / or "on" the substrate wall. Thus, the phrase "catalyst coating disposed on the substrate" means on any surface, e.g., on the wall surface and / or on the pore surface. The catalyst coating layer may include individual functional components, i.e., the LT-NA composition and the DOC catalyst composition, respectively, as described herein.

[0180] The catalyst composition may be provided in the form of a washcoat, typically comprising a support material having catalytically active species thereon. The sorbent composition may be provided in the form of a washcoat, typically comprising a sorption-active species. The catalyst and sorbent components may be combined in a single washcoat in some embodiments. The washcoat is formed by preparing a slurry comprising a particular solids content (e.g., about 10 to about 60 wt%) of the support in a liquid vehicle, which is then applied to a substrate and dried and calcined to provide a coating layer. If multiple coating layers are applied, the substrate is dried and calcined after each layer is applied and / or after the desired number of layers are applied. In one or more embodiments, the catalyst material is applied to the substrate as a washcoat. A binder may be used as described above.

[0181] The above catalyst compositions are generally mixed with water independently to form a slurry for coating a catalyst substrate, such as a honeycomb-type substrate. In addition to the catalyst particles, the slurry optionally contains binders (e.g., alumina, silica), water-soluble or water-dispersible stabilizers, promoters, associative thickeners, and / or surfactants (anionic, cationic, nonionic or amphoteric surfactants). The typical pH range of the slurry is from about 3 to about 6. Acidic or basic species may be added to the slurry to adjust the pH accordingly. For example, in some embodiments, the pH of the slurry is adjusted by the addition of aqueous ammonium hydroxide or nitric acid.

[0182] The slurry can be milled to improve particle mixing and formation of a homogenous material. Milling can be accomplished in a ball mill, continuous mill, or other similar equipment, and the solids content of the slurry can be, for example, about 20-60% by weight, more specifically, about 20-40% by weight. In one embodiment, the slurry after milling is characterized by a D90 particle size of about 10 to about 40 microns, preferably 10 to about 30 microns, and more preferably about 10 to about 15 microns.

[0183] The slurry is then coated onto a catalytic substrate using any washcoat technique known in the art. In one embodiment, the catalytic substrate is dipped or otherwise coated with the slurry one or more times. The coated substrate is then dried at an elevated temperature (e.g., 100-150° C.) for a period of time (e.g., 10 minutes to 3 hours) and then calcined, for example, by heating at 400-600° C. for typically about 10 minutes to about 3 hours. After drying and calcination, the final washcoat coating layer can be considered essentially solvent-free.

[0184] After calcination, the catalyst loading obtained by the above washcoat technique can be determined by calculating the difference between the coated and uncoated weights of the substrate. As will be apparent to one skilled in the art, the catalyst loading can be modified by altering the rheology of the slurry. Furthermore, the coating / drying / calcining process to produce a washcoat can be repeated as necessary to build up the coating to a desired loading level or thickness, i.e., more than one washcoat can be applied.

[0185] Washcoats can be applied such that the different coating layers are in direct contact with the substrate. Alternatively, one or more "undercoats" may be present such that the catalyst or adsorbent coating layer or at least a portion of the coating layer is not in direct contact with the substrate (rather, it is in contact with an undercoat). One or more "overcoats" may be present such that at least a portion of the coating layer is not directly exposed to the gas stream or atmosphere (rather, it is in contact with an overcoat).

[0186] The different coating layers may be in direct contact with each other without an "intermediate" overlapping zone. Alternatively, the different coating layers may not be in direct contact, forming a "gap" between the two zones. In the case of an "undercoat" or "overcoat", the gap between the different layers is called an "intermediate layer". An undercoat is a layer "below" a coating layer, an overcoat is a layer "on" a coating layer, and an intermediate layer is a layer "between" two coating layers. Intermediate layers, undercoats, and overcoats may include one or more functional compositions or may not include a functional composition.

[0187] The catalytic coating may include two or more thin attached layers, layers that are attached to each other and to the substrate. The entire coating includes the individual "coating layers". The catalytic coating may advantageously be "zoned" and include zoned catalytic layers. This may be described as "laterally zoned". For example, a layer may extend from the inlet end toward the outlet end and may extend over about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the substrate length. Another layer may extend from the outlet end toward the inlet end and may extend over about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the substrate length. The different coating layers may be adjacent to each other and not overlap each other. Alternatively, different layers may overlay portions of each other to provide a third "intermediate" zone, which may extend, for example, over about 5% to about 80% of the length of the substrate, such as about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60% or about 70% of the length of the substrate.

[0188] The different layers may each extend the entire length of the substrate, or each extend a portion of the substrate's length and partially or totally overlay or underlay one another. Each of the different layers may extend from either the inlet end or the outlet end.

[0189] Different catalyst compositions may be present in each separate coating layer. For example, one coating layer may include an oxidation catalyst composition without any selective sorbent composition, and a second layer may include (or consist entirely of) one or more selective sorbent compositions. Thus, descriptions relating to different layers may correspond to any of these layers. A catalyst coating may include one, two, or more than two coating layers. One or more coating layers together include a catalyst composition.

[0190] The zones of the present disclosure are defined by the relationship of the coating layers. There are several possible zoning configurations for different coating layers. For example, there may be an upstream zone and a downstream zone, an upstream zone, an intermediate zone and a downstream zone, four different zones, etc. If two layers are adjacent and do not overlap, there are upstream and downstream zones. If two layers overlap to some extent, there are upstream, downstream and intermediate zones. For example, if a coating layer extends over the entire length of the substrate and a different coating layer extends from the outlet end to a certain length and overlays a portion of the first coating layer, there are upstream and downstream zones. The present catalytic coating may include two or more identical layers.

[0191] 3A, 3B and 3C show some possible coating layer configurations with two coating layers. A monolithic wall-flow filter substrate wall 200 is shown with coating layers 201 and 202 disposed thereon. This is a simplified view, and in the case of a porous wall-flow substrate, the pores and coatings attached to the pore walls are not shown, and plugged ends are not shown. In FIG. 3A, coating layer 201 extends about 50% of the substrate length from the inlet to the outlet. Coating layer 202 extends about 50% of the substrate length from the outlet to the inlet, the coating layers being adjacent to each other, providing an inlet upstream zone 203 and an outlet downstream zone 204. In FIG. 3B, coating layer 202 extends about 50% of the substrate length from the outlet, and layer 201 extends more than 50% of the length from the inlet and overlays a portion of layer 202, providing an upstream zone 203, an intermediate zone 205 and a downstream zone 204. In Figure 3C, coating layers 201 and 202 each extend the entire length of the substrate such that layer 201 overlays layer 202. The substrate of Figure 3C does not include a zoned coating configuration. Figures 3A, 3B, and 3C may be useful for illustrating coating compositions on wall-through substrates. Figures 3A, 3B, and 3C may also be useful for illustrating coating compositions on flow-through substrates, as described herein below. Such coating layer configurations are not limiting.

[0192] For example, with particular reference to the LT-NA catalyst compositions disclosed herein, the first (Pd-containing) zeolite and the second (Pd-containing) zeolite may each be in separate coating layers. These coating layers may be in a front-to-back zone configuration, a layered configuration, or a combination thereof. Alternatively, the LT-NA catalyst compositions may be present together in one homogenous coating layer, or in some combinations spread across two or three coating layers.

[0193] In some embodiments, the third (Pd-containing) zeolite, if present, may be in a separate coating layer from the first and / or second zeolite. In some embodiments, the third zeolite, if present, may overlap the first zeolite, the second zeolite, or both the first and second zeolites. In some embodiments, the third zeolite, if present, may be in a homogenous mixture with the first zeolite, the second zeolite, or both the first and second zeolites.

[0194] In some embodiments, the LT-NA catalyst article includes a first washcoat including a first zeolite disposed on at least a portion of the length of the catalyst substrate and a second washcoat including a second zeolite disposed on at least a portion of the length of the catalyst substrate. In some embodiments, the second washcoat is directly on the catalyst substrate and the first washcoat is on at least a portion of the second washcoat. In some embodiments, the first washcoat is directly on the catalyst substrate and the second washcoat is on at least a portion of the first washcoat. In some embodiments, the catalyst article has a zone configuration such that the first washcoat is disposed on the catalyst substrate from the inlet end for about 10% to about 70% of the total length and the second washcoat is disposed on the catalyst substrate from the outlet end for about 30% to about 90% of the total length.

[0195] Exemplary non-limiting configurations of LT-NA catalyst compositions comprising a first zeolite and a second zeolite are shown in Figures 4A, 4B, and 4C. Figure 4A is a cross-sectional view of a homogenous LT-NA catalyst composition described herein. Figure 4B is a cross-sectional view of two different bi-layered LT-NA catalyst compositions described herein. Figure 4C is a cross-sectional view of a zoned LT-NA catalyst composition described herein.

[0196] In some embodiments, the LT-NA article further comprises a diesel oxidation catalyst (DOC) composition disposed on the substrate. In some embodiments, the DOC composition comprises a Pt component and a fourth Pd component, where the Pt component and the fourth Pd component are supported on a refractory metal oxide support material. In some embodiments, the refractory metal oxide comprises gamma alumina or alumina doped with about 2% to about 10% SiO2. In some embodiments, the DOC composition further comprises a beta zeolite that is substantially free of platinum group metal (PGM) species. In some embodiments, the DOC composition is in a zoned configuration relative to the LT-NA composition layer. In some embodiments, the DOC composition may overlap one or more layers of the LT-NA composition. Exemplary non-limiting configurations of LT-NA / DOC catalyst composition coatings comprising the inventive LT-NA and DOC compositions disclosed herein are shown in Figures 5A-5F. In some embodiments, the LT-NA catalyst composition and the DOC composition are present on the substrate in a single homogenous layer, as shown in Figure 5A. In some embodiments, the LT-NA catalyst composition and the DOC composition are present in separate, individual layers. Figures 5B and 5C show two possible configurations in which the LT-NA catalyst composition and the DOC composition are present on the substrate in separate layers. A zoned configuration with the DOC composition upstream of the LT-NA catalyst composition is shown in Figure 5D.

[0197] The LT-NA / DOC catalyst article may include more than two layers, for example, there may be three layers. In some embodiments, the catalyst article further includes a third layer. In some embodiments, the third layer includes a second DOC composition. In some embodiments, there may be two DOC composition layers and one LT-NA catalyst composition layer. A possible non-limiting arrangement is shown in FIG. 5E. The two DOC compositions may be the same or different (e.g., with respect to PGM and support components and washcoat loading). In some embodiments, the second DOC composition is the same as the first DOC composition. In some embodiments, the first layer is disposed between the second and third layers. In some embodiments, the first and second DOC compositions both include the same components (e.g., Pt component, fourth Pd component, refractory metal oxide support material as disclosed herein), but the loadings in each washcoat layer may be different.

[0198] Alternatively, in another embodiment of the three-layer configuration, there may be two LT-NA catalyst composition layers and one DOC composition layer. In some embodiments, the third layer comprises a second LT-NA catalyst composition. FIG. 5F shows a three-layer configuration with a DOC composition layer disposed between two separate LT-NA catalyst composition layers. The two LT-NA compositions may be the same or different (e.g., with respect to Pd / zeolite components and washcoat loading). In some embodiments, the second LT-NA catalyst composition is the same as the first LT-NA catalyst composition. In some embodiments, the second layer is disposed between the first and third layers. In some embodiments, the first and second LT-NA compositions both comprise the same components (e.g., first and second Pd components, first and second zeolites as disclosed herein), but the loadings in each washcoat layer may vary.

[0199] In some embodiments, other catalyst compositions may be incorporated above, below, or between any of the LT-NA and DOC catalyst composition layers referenced herein.

[0200] In some embodiments, a catalyst article is provided having a first DOC composition directly on a substrate, a first LT-NA catalyst composition on the first DOC composition, and a second DOC composition on the first LT-NA composition. In some embodiments, a catalyst article is provided having a second DOC composition directly on a substrate, a first LT-NA catalyst composition on the second DOC composition, and a first DOC composition on the first LT-NA composition.

[0201] In some embodiments, a catalyst article is provided having a first LT-NA catalyst composition directly on a substrate, a first DOC catalyst composition on the first LT-NA catalyst composition, and a second LT-NA catalyst composition on the first DOC composition. In some embodiments, a catalyst article is provided having a second LT-NA catalyst composition directly on a substrate, a first DOC composition on the second LT-NA catalyst composition, and a first LT-NA catalyst composition on the first DOC composition.

[0202] The loading of the present catalytic coating on the substrate depends on the substrate properties such as porosity and wall thickness. Typically, wall-flow filter catalyst loadings will be lower than catalyst loadings on flow-through substrates. Catalytic wall-flow filters are disclosed, for example, in U.S. Pat. No. 7,229,597, which is incorporated herein by reference in its entirety. The LT-NA and / or DOC catalyst compositions of the present invention are generally loaded at a concentration of, for example, about 0.3 to 5.5 g / in based on the substrate. 3 , or about 0.4 g / in 3 , about 0.5g / in 3 , about 0.6g / inch 3 , about 0.7g / inch 3 , about 0.8g / inch 3 , about 0.9g / inch 3 or about 1.0g / inch 3 So, about 1.5g / inch 3 , about 2.0g / inch 3 , about 2.5g / in 3 , approx. 3.0g / in 3 , about 3.5g / in 3, approx. 4.0g / in 3 , about 4.5g / in 3 , approx. 5.0g / in 3 , about 5.5g / in 3 The concentration of the catalyst composition or any other component on the substrate refers to the concentration per any one three-dimensional cross-section or zone, for example, either the cross-section of the substrate or the entire substrate.

[0203] In some embodiments, the LT-NA catalyst article has a viscosity of about 15 g / ft 3 ~about 200g / ft 3 , or about 60g / ft 3 ~Approx. 120g / ft 3 In some embodiments, the LT-NA catalyst article comprises a first and second palladium component at a loading of about 1 g / in 3 ~ approx. 5g / in 3 or about 2g / in 3 ~About 3g / in 3 In some embodiments, the catalyst article comprises a silica-to-alumina ratio (SAR) of from about 5 to about 50, or from about 10 to about 35.

[0204] The present LT-NA catalyst articles, which may include a flow-through or wall-flow filter substrate as disclosed herein, provide desirable NO x Provides adsorption and desorption properties, e.g., NO at low temperatures x The adsorption and capture of NO x At higher temperatures, the LT-NA catalyst article releases NO. Preferably, the LT-NA catalyst article is capable of adsorbing a significant portion of the NO present in the exhaust gas stream. In some embodiments, the LT-NA catalyst article adsorbs NO during cold start conditions (e.g., the LT-NA catalyst article is below 200° C.). xを In some embodiments, the LT-NA catalyst article adsorbs NO under high temperature operation (e.g., the LT-NA catalyst article is greater than 300° C.). x Remove and put on.

[0205] Exhaust Gas Treatment Systems The present disclosure further relates to a method for reducing NO in an exhaust gas stream from an internal combustion engine comprising the catalytic article as disclosed herein. x In another aspect of the present invention, an exhaust gas treatment system is provided for reducing the levels of NO in an exhaust gas stream from an internal combustion engine. x A method for reducing the level of oxidative stress is provided, the method comprising contacting an exhaust gas stream with a catalytic article as disclosed herein or an exhaust treatment system as disclosed herein. Thus, the present invention provides an emission treatment system incorporating a catalytic article as disclosed herein, such as an emission treatment system including an engine generating an exhaust gas stream and one or more catalytic articles disposed downstream of the engine in fluid communication with the exhaust gas stream. The engine can be, for example, a diesel engine operating under combustion conditions with more air than is required for stoichiometric combustion, i.e., lean conditions. In other embodiments, the engine can be an engine associated with a stationary source (e.g., a generator or pumping station). In some embodiments, the emission treatment system further comprises one or more additional catalytic components. The relative arrangement of the various catalytic components present in the exhaust treatment system can vary.

[0206] In the present exhaust gas treatment systems and methods, the exhaust gas stream is received into the article or treatment system by entering at an upstream end and exiting at a downstream end. The inlet end of the substrate or article is synonymous with the "upstream" end or "front" end. The outlet end is synonymous with the "downstream" end or "rear" end. The treatment system is generally downstream of and in fluid communication with the internal combustion engine.

[0207] The systems disclosed herein include LT-NA catalyst articles, which may include flow-through or wall-flow filter substrates as disclosed herein. In particular, the systems are capable of producing NO at low temperatures. x The NO adsorbed and captured at high temperatures x The catalyst composition includes an LT-NA catalyst article adapted to release NO. x The adsorbent component is designed to provide the desired NO under various engine operating conditions. xProvides adsorption and desorption properties.

[0208] Preferably, the LT-NA catalyst article is capable of adsorbing a significant portion of the NO present in the exhaust gas stream. However, more importantly, the LT-NA catalyst article does not release NO species until the exhaust gas stream and / or the exhaust gas emission system reaches a temperature high enough for other catalytic components to be activated. Only then can the released NO be efficiently converted to N2 and exit the exhaust gas treatment system. Thus, the LT-NA catalyst article is generally located upstream of any catalytic components involved in the conversion of NO released from the LT-NA. In some embodiments, the LT-NA catalyst article adsorbs NO species present in the exhaust gas stream at low temperatures, which may optionally have been treated with at least DOC and / or CSF components.

[0209] In some embodiments, rather than being disposed in a separate component (e.g., on a separate substrate), the LT-NA catalyst article can be included in the same component, such as a diesel oxidation catalyst (DOC), a catalyzed soot filter (CSF), or a catalytic selective reduction (SCR) catalyst component, where the catalyst composition of such component is applied to the substrate in a zonal or layered configuration.

[0210] In addition to the LT-NA catalyst article, the systems of the present disclosure may also include, for example, a DOC, a reductant injector, an SCR catalyst component, a soot filter (which may be catalyzed or uncatalyzed), and / or an ammonia oxidation catalyst (AMO x ). A DOC suitable for use in an exhaust treatment system can effectively catalyze the oxidation of CO and HC to carbon dioxide (CO2). Preferably, the DOC can convert at least 50% of the CO or HC components present in the exhaust gas. The DOC may be located, for example, downstream of the LT-NA catalyst article. In some embodiments, the DOC is located upstream of the SCR catalyst component and / or the soot filter.

[0211] The exhaust gas treatment system of the present disclosure may further include an SCR catalyst component. The SCR catalyst component may be located upstream or downstream of the DOC and / or soot filter. SCR catalyst components suitable for use in exhaust gas treatment systems are capable of reducing NO 2 at temperatures as high as 650° C. x In addition, the SCR catalyst components can effectively catalyze the reduction of exhaust gas components, even under low load conditions that are typically associated with lower exhaust temperatures. x Preferably, the SCR catalyst component is active for the reduction of NO depending on the amount of reductant added to the system. x At least 50% of the (e.g., NO) components can be converted to N2. Another desirable property of an SCR catalyst component is the ability to catalyze the reaction of O2 with any excess NH3 to form N2, so that NH3 is not released to the atmosphere. A useful SCR catalyst component for use in an exhaust treatment system should also be thermally resistant to temperatures in excess of 650°C. Such high temperatures may occur during regeneration of catalyzed soot filters. Suitable SCR catalyst components are described, for example, in U.S. Pat. Nos. 4,961,917 and 5,516,497, each of which is incorporated herein by reference in its entirety.

[0212] The illustrated exhaust gas treatment system may be more readily understood with reference to Figures 6A-6D and 7A-7F, which show schematic diagrams of exhaust gas treatment systems according to embodiments of the present invention. With reference to Figure 6A, an exhaust gas treatment system 320 is provided in which an exhaust gas stream containing gaseous pollutants (e.g., unburned hydrocarbons, carbon monoxide, and NO) and particulate matter is conveyed from an engine 321 to a DOC 323 via line 322. In the DOC 323, a majority of the unburned gaseous and non-volatile hydrocarbons and carbon monoxide are combusted to form carbon dioxide and water. The exhaust stream is then conveyed via line 324 to a LT-NA catalyst article 325 for adsorption and / or storage of NO. The treated exhaust gas stream 326 is then conveyed to a CSF 327, which captures particulate matter present in the exhaust gas stream. After removal of particulate matter via CSF 327, the exhaust gas stream is conveyed via line 328 to a downstream SCR catalyst component 329 that provides treatment and / or conversion of NO. The exhaust gas is passed through a catalyst component that converts NO in the exhaust gas at any temperature in the exhaust gas before it exits the system. x The SCR catalyst component 329 is passed through the SCR catalyst component 329 at a flow rate capable of reducing (in combination with the reductant) the level of

[0213] Another embodiment of an exhaust gas treatment system of the present invention is shown in Figure 6B, which shows a schematic diagram of an exhaust gas treatment system 330 according to the present disclosure. With reference to Figure 6B, an exhaust gas stream is conveyed from an engine 331 via line 332 to a LT-NA catalyst article 333. The exhaust stream is then conveyed via line 334 to a DOC 335 and further via line 336 to a CSF 337. The treated exhaust gas stream 338 is conveyed to an SCR catalyst component 339 before being discharged into the atmosphere.

[0214] Another embodiment of an exhaust gas treatment system of the present disclosure is shown in Figure 6C, which shows a schematic diagram of an exhaust gas treatment system 340. With reference to Figure 6C, an exhaust gas stream is conveyed from an engine 341 to a DOC 343 via line 342 and further conveyed to a LT-NA 345 via exhaust gas stream 344. The exhaust stream is then conveyed to an SCR catalyst component 347 via line 346 and further conveyed to a CSF 349 via line 348. The treated exhaust gas stream 338 is conveyed to the SCR catalyst component 339 before exiting the system.

[0215] Another embodiment of an exhaust gas treatment system of the present invention is shown in Figure 6D, which shows a schematic diagram of an exhaust gas treatment system 350 according to the present disclosure. With reference to Figure 6D, exhaust gas stream is conveyed from engine 351 via line 352 to LT-NA catalyst article 353 and further via gas exhaust line 354 to DOC 355. Exhaust gas line 356 is conveyed to SCR catalyst component 357 and then exhaust stream 358 is conveyed to CSF ​​359 before exiting the system.

[0216] Another embodiment of an exhaust gas treatment system of the present disclosure is shown in Figure 7A, which shows a schematic diagram of an exhaust gas treatment system 420. With reference to Figure 7A, an exhaust gas stream is conveyed from an engine 421 via line 422 to a combination catalyst 423 having a LT-NA catalyst composition and a DOC on the same substrate. Exhaust gas stream 426 is further conveyed to a CSF 427 and further conveyed via gas exhaust line 428 to an SCR catalyst component 429 before exiting the system.

[0217] Another embodiment of an exhaust gas treatment system of the present disclosure is shown in Figure 7B, which shows a schematic diagram of an exhaust gas treatment system 430. With reference to Figure 7B, an exhaust gas stream is conveyed from an engine 431 via line 432 to a combination catalyst 433 having a LT-NA catalyst composition and a DOC on the same substrate. Exhaust gas stream 436 is further conveyed to an SCR catalyst component 437 and further conveyed via gas exhaust line 438 to a CSF 439 before exiting the system.

[0218] Another embodiment of an exhaust gas treatment system of the present disclosure is shown in Figure 7C, which shows a schematic diagram of an exhaust gas treatment system 440. With reference to Figure 7C, the exhaust gas stream is conveyed from an engine 441 via line 442 to a combination catalyst 443 having a LT-NA catalyst composition and a DOC on the same substrate. The exhaust gas stream 446 is further conveyed to a combination SCR catalyst component and catalyzed soot filter (SCRoF) 447 before exiting the system.

[0219] Another embodiment of an exhaust gas treatment system of the present disclosure is shown in Figure 7D, which shows a schematic diagram of exhaust gas treatment system 450. With reference to Figure 7D, exhaust gas stream is conveyed from engine 451 to DOC 453 via line 452, and exhaust gas stream 456 is further conveyed to combination catalyst 457 having LT-NA catalyst composition and CSF on the same substrate. Exhaust gas stream 458 is further conveyed to SCR catalyst component 459 before exiting the system.

[0220] Another embodiment of an exhaust gas treatment system of the present disclosure is shown in Figure 7E, which shows a schematic diagram of exhaust gas treatment system 461. With reference to Figure 7E, exhaust gas stream is conveyed from engine 461 to DOC 463 via line 462, and exhaust gas stream 466 is further conveyed to CSF ​​467. Resulting exhaust gas stream 468 is further conveyed to combination catalyst 469 having LT-NA catalyst composition and SCR catalyst components on the same substrate before exiting the system.

[0221] Another embodiment of an exhaust gas treatment system of the present disclosure is shown in Figure 7F, which shows a schematic diagram of exhaust gas treatment system 470. Referring to Figure 7F, exhaust gas stream is conveyed from engine 471 via line 472 to DOC 473, and exhaust gas stream 476 is further conveyed to combination catalyst 477 having a LT-NA catalyst composition and SCRoF on the same substrate before exiting the system.

[0222] Any of the exemplary exhaust gas treatment systems shown in FIGS. 6A-6D and 7A-7F may be followed by a selective ammonia oxidation catalyst (AMO) for removing NH3 released from the SCR catalyst components and selectively oxidizing the NH3 to N2. x ) may be provided.

[0223] The articles, systems, and methods of the present invention are suitable for treating exhaust gas streams from mobile exhaust sources such as trucks, automobiles, etc. The articles, systems, and methods of the present invention are also suitable for treating exhaust streams from stationary sources such as power plants.

[0224] It will be readily apparent to those skilled in the relevant art that suitable modifications and adaptations to the compositions, methods, and applications described herein can be made without departing from the scope of any embodiment or aspect thereof. The compositions and methods provided are exemplary and are not intended to limit the scope of the claimed embodiments. All of the various embodiments, aspects, and options disclosed herein can be combined in all variations. The scope of the compositions, formulations, methods, and processes described herein includes all actual or potential combinations of the embodiments, aspects, options, examples, and preferences herein. All patents and publications cited herein are incorporated by reference for their specific teachings, as described, unless other specific statements of incorporation are specifically provided. EXAMPLES

[0225] The present invention is more particularly illustrated by the following examples, which are presented to illustrate the invention and should not be construed as limiting the invention. Unless otherwise specified, all parts and percentages are by weight and all weight percentages are expressed on a dry basis, i.e., water content is excluded unless otherwise specified.

[0226] Preparation of catalyst products Example 1. Pd-large pore zeolite catalyst article The zeolite beta material (BEA) was impregnated with a dilute Pd(NO3)2 solution in the incipient wet state at 110 ° After drying in air for 2 hours at C / 550 ° The calcined Pd / BEA powder was added to a dilute zirconium acetate solution to form a slurry suspension at approximately 50% solids. 90 The slurry was milled until the particle size reached 10-12 μm. The slurry was then coated onto a 400 / 4 honeycomb substrate at 42-46% solids. After drying, the catalyst was calcined in air at 590°C for 1 hour. The Pd loading was 60 g / ft 3 and the zeolite washcoat loading was 2.0 g / in 3 and the ZrO2 loading after calcination was ~5% of the washcoat composition.

[0227] Examples 2A and 2BPd - Medium pore zeolite catalyst articles The zeolite ferrierite material (FER) was impregnated with a dilute Pd(NO3)2 solution in the incipient wet state at 110 ° After drying in air for 2 hours at C / 550 ° The calcined Pd / BEA powder was added to a dilute zirconium acetate solution to form a slurry suspension at approximately 50% solids. 90 The slurry was milled until the particle size reached 10-15 μm. The slurry was then coated onto a 400 / 4 honeycomb substrate at a solid content of 42-46%. After drying, the catalyst was heated at 590° C. in air. ℃ For Example 2A, the Pd loading was 60 g / ft 3 and the zeolite washcoat loading was 2.0 g / in 3 For Example 2B, the Pd loading was 90 g / ft 3 and the zeolite washcoat loading was 3.0 g / in 3 After calcination, the resulting ZrO2 loading in both examples was about 5% of the washcoat composition.

[0228] Example 3. Pd-small pore zeolite catalyst article Zeolite chabazite material (CHA) was impregnated with a dilute Pd(NO3)2 solution in the incipient wet state at 110 ° After drying in air for 2 hours at C / 550 ° The catalyst was calcined in air at 590°C for 1 hour. A diluted zirconium acetate solution was prepared and to it the calcined Pd / BEA powder was added to form a slurry suspension at approximately 50% solids. The slurry was milled until a final particle size D90 of 10-15 μm was reached. The slurry was then coated onto a 400 / 4 honeycomb substrate at 42-46% solids. After drying, the catalyst was calcined in air at 590°C for 1 hour. The Pd loading was 60 g / ft 3 and the zeolite washcoat loading was 2.0 g / in 3 and the ZrO2 loading after calcination was ~5% of the washcoat composition.

[0229] Example 4. Zoned Pd / BEA and Pd / FER LT-NA Catalyst Articles Samples according to Examples 1 and 2 were prepared as described above. Each sample was cut in half and each half was assembled into a zoned sample by placing the Pd / BEA coated substrate at the inlet position and the Pd / FER coated substrate at the outlet position.

[0230] Example 5. LT-NA catalyst article coated with a homogeneous mixture of Pd-large pore zeolite and Pd-medium pore zeolite catalyst compositions Pd / BEA and Pd / FER slurries were prepared as in Example 1 and Example 2, respectively. The Pd% in each zeolite was maintained at 1.74%. The two slurries were mixed at the desired solids / solids ratio and then coated on a 400 / 4 honeycomb substrate at 42-46% solids. After drying, the catalyst was calcined in air at 590°C for 1 hour. The total Pd loading was 60g / ft 3 and the total zeolite washcoat loading was 2.0 g / in 3and the resulting ZrO2 loading after calcination was ~5% of the washcoat composition.

[0231] Example 6. LT-NA Catalyst Article Coated with a Mixture of Pd-Large Pore Zeolite and Pd-Small Pore Zeolite Catalyst Compositions Pd / BEA and Pd / CHA slurries were prepared as in Example 1 and Example 3, respectively. The Pd wt% in each zeolite was maintained at 1.74%. The two slurries were mixed at the desired solids / solids ratio and then coated onto a 400 / 4 honeycomb substrate at 42-46% solids. After drying, the catalyst was calcined in air at 590°C for 1 hour. The total Pd loading was 60g / ft 3 and the total zeolite washcoat loading was 2.0 g / in 3 and the resulting ZrO2 loading after calcination was ~5% of the washcoat composition.

[0232] Example 7. LT-NA / DOC Catalyst Article The LT-NA bottom layer had a Pd loading and washcoat loading of 75% of the original (45 g / ft 3 Pd, 1.5g / in 3 The DOC top layer was prepared similarly to Example 6, except that the 5% SiO2-Al2O3 material was incipiently impregnated with a dilute Pt-ammine complex solution and then added to a dilute Pd nitrate solution to form a slurry suspension. The pH of the slurry suspension was adjusted to 4-5 with dilute HNO3. The slurry was then cooled to 100°C for 24 hours. 90 = 12-15 μm, then beta zeolite and alumina binder material (3.5% of total washcoat solids) were added. The slurry was then coated onto the LT-NA underlayer at 25-30% solids. After drying, the sample was calcined in air at 590 °C for 1 h. The Si-alumina loading was 0.75 g / in 3 , Beta zeolite loading is 0.35g / in 3 , PGM loading is 21g / ft 3 The Pt / Pd weight ratio was 2 / 1.

[0233] Example 8. LT-NA / DOC Catalyst Article The LT-NA bottom layer had a Pd loading and washcoat loading of 80 g / ft 3 and 2.5g / in 3 The DOC layer was prepared as in Example 5, except that the Pd loading was reduced to 0.5 g / m2. The BEA / FER ratio remained at 1:1 and the Pd loading was split evenly between the two zeolites. The DOC layer was prepared as in Example 7.

[0234] Catalytic Article Evaluation The monolithic catalyst article was tested in a diesel vehicle simulator. The feed composition was drawn from a medium-duty diesel engine, with only NO and no inlet NO. x The catalysts were used for the FTP-US06 and FTP-US100 tests. The catalyst dimensions were 1 x 1 x 3 inches. Each catalyst was pretreated in situ with 10% O2 / 5% H2O / 5% CO2 / N2 at 500°C for 15 minutes and then subjected to a continuous sequence of FTP, FTP-US06, and FTP tests. From the start, the inlet temperature was first 200 ℃ NO absorbed until it reaches x The percentage of cold start NO x was defined as the adsorption efficiency.

[0235] Example 9. Exhaust gas treatment results Figure 8 shows the NO vs. time from 0-400 seconds for the first FTP cycle. x The period from 0 to 197 seconds was defined as a cold start where the catalyst inlet temperature remained below 200° C. All three catalyst compositions (Examples 1, 2A, and 3) showed nearly complete NO x The Pd / BEA of Example 1, which has a 12-membered ring structure and a pore size of less than 6 Å, showed NO adsorption just before 200 seconds when the catalyst inlet temperature barely reached 200°C. x Both Pd / FER, with 10-membered rings and <5 Å pore openings, from Example 2A, and Pd / CHA, with 8-membered ring structures and <4 Å pore openings, from Example 3, began to release NO up to higher temperatures.x continued to adsorb.

[0236] FIG. 9 shows that for all three catalysts, Examples 1 to 3, when the maximum temperature was 300° C., complete NO x It is shown that no regeneration was observed at the end of the FTP cycle.

[0237] Figure 10 shows that all three catalysts produce insufficient NO x Desorption resulted in lower NO during the cold start of the subsequent FTP cycle (0–200 s). x The results show that Pd / BEA (Example 1) showed excellent NO adsorption up to 120 seconds. x It continued to show adsorption, but suddenly NO x Desorption occurs immediately, which is consistent with the NO x The adsorption efficiency continued to decrease overall. Example 2A (Pd / FER) appeared to suffer a significant loss of activity at the beginning of the cycle (0-60 seconds), but the adsorption activity quickly recovered. Furthermore, NO x Desorption preferably occurred at ∼260° C. Example 3 (Pd / CHA) was x Not only did it perform worst between 0 and 120 s, when adsorption is most critical, but it also started to show desorption at ∼150 °C.

[0238] Without wishing to be bound by theory, the large differences observed in these three different zeolite structures suggest that Pd in ​​large pore, three-dimensional zeolites such as BEA may be able to inhibit the cold start NO oxidation, especially when regeneration is not efficient. x However, the large pore channels may have less physical interaction with the adsorbed NO molecules, which in turn may reduce the early NO x The Pd / FER (Example 2A), which had a two-dimensional media pore structure, could produce NO emissions at lower temperatures and higher space velocities if not fully regenerated. x However, at intermediate temperatures, NO xIt absorbs NO extremely efficiently and keeps it in the tank until the desired temperature is reached. x was able to be retained.

[0239] The data in Figure 10 show that the mixtures of Pd / BEA and Pd / FER retain the high NO adsorption efficiency of Pd / BEA at low temperatures, while at intermediate temperatures the NO released by Pd / BEA is significantly reduced. x The overall cold start NO x It is suggested that it may be advantageous to improve the adsorption performance.

[0240] Figure 11 provides data confirming the advantages of the dual Pd zeolite components of the present invention. Figure 11 shows the FTP2 NO transients of zoned Pd / BEA and Pd / FER (Example 4) and homogeneous Pd / BEA and Pd / FER mixture catalysts (Example 5). x 1 is a graphical comparison of NO adsorption versus Pd / BEA (Example 1) or Pd / FER only (Example 2A) catalysts. In both cases, the zoned and homogeneous examples show improved NO adsorption in the 20-70 second region compared to Pd / FER, with larger NO adsorption for Pd / BEA. x The emission peak feature was eliminated.

[0241] FIG. 12 shows the cold start (0-197 sec) NO performance of the 1 / 1 Pd / BEA and Pd / CHA mixture catalyst (Example 6) and the LT-NA / DOC combination catalyst (Example 7) that contained a Pd / BEA-Pd / CHA undercoat and a Pt-Pd / Al2O3 and BEA topcoat. x A graphical comparison of the adsorption efficiency is provided. For FTP2, the Pd / BEA-Pd / FER catalyst adsorbed 100% of the released NO at intermediate temperatures. x Due to the better trapping of NO, the Pd / BEA-Pd / CHA catalyst showed higher NO x On the other hand, the Pd / BEA-Pd / CHA catalyst demonstrated a higher FTP3 NO adsorption. x% adsorption, suggesting a more efficient regeneration during the preceding US06 cycle. Furthermore, the addition of a typical DOC layer significantly improved the FTP2 NO adsorption rate despite the lower Pd and zeolite loadings in the LT-NA layer. x % adsorption appeared to improve significantly.

[0242] FIG. 13 shows the cold start (0-197 seconds) NO performance of the LT-NA / DOC catalyst article of the invention (Example 8) versus the LT-NA article of the invention (Example 2B). x 1 shows the graphical results of the adsorption performance. Without wishing to be bound by theory, Example 8 contains lower palladium and zeolite loadings in the LT-NA layer, which may result in a lower initial NO 2 loading in the FTP1 cycle. x The DOC coating on the top side may continue to reduce the NO adsorption efficiency to the LT-NA layer in this configuration. x Nevertheless, the eighth embodiment is a method for preventing access from NO x Example 2B (Pd / BEA+Pd / FER) showed a 13% decrease in adsorption efficiency, while Example 2B (Pd / BEA+Pd / FER) showed a 53% decrease. These results indicate that the addition of the diesel oxidation catalyst (DOC) component significantly improved performance in FTP2.

Claims

1. A catalytic article for treating an exhaust stream of an internal combustion engine, comprising: a catalytic substrate having an inlet end and an outlet end defining an overall length; and a first low temperature NOx gas disposed on said catalytic substrate. ｘ and an adsorbent (LT-NA) catalyst composition; The first LT-NA catalyst composition comprises: a first zeolite which is a large pore zeolite and which comprises a first palladium component; a second zeolite that is a medium pore zeolite and that includes a second palladium component; The catalyst article has a thickness of about 1 to about 5 g / in ３ and A catalytic article for treating an exhaust stream of an internal combustion engine, wherein the first zeolite comprises a BEA framework structure type and the second zeolite comprises a FER framework structure type.

2. 2. The catalytic article of claim 1, wherein said first zeolite is BEA and said second zeolite is FER.

3. 3. The catalytic article of claim 1 or 2, wherein the first zeolite and the second zeolite are each an aluminosilicate zeolite.

4. 3. The catalyst article of claim 1 or 2, wherein the first zeolite has a silica-to-alumina ratio (SAR) of about 10 to about 50.

5. 3. The catalytic article of claim 1 or 2, wherein the second zeolite is a medium pore zeolite.

6. 3. The catalytic article of claim 1 or 2, wherein the second zeolite has a two-dimensional pore system.

7. 3. The catalytic article of claim 1 or 2, further comprising a third zeolite comprising a third palladium component.

8. 8. The catalyst article of claim 7, wherein the third zeolite is a large pore zeolite, and the first zeolite and the third zeolite have different framework structure types.

9. 8. The catalytic article of claim 7, wherein the third zeolite is a small pore or medium pore zeolite, and the second zeolite and the third zeolite have different framework structure types.

10. 3. The catalytic article of claim 1 or 2, wherein the first palladium component and the second palladium component are present in an amount of about 0.5% to about 6% by weight based on the first zeolite and the second zeolite, respectively.

11. 3. The catalyst article of claim 1 or 2, wherein the weight ratio of said first zeolite to said second zeolite is from about 0.1:9.9 to about 9:

1.

12. a first washcoat comprising the first zeolite disposed on at least a portion of the length of the catalytic substrate; a second washcoat comprising said second zeolite disposed on at least a portion of the length of said catalytic substrate.

13. The catalyst article has a viscosity of about 15 to about 200 g / ft ３ 3. The catalytic article of claim 1 or 2, comprising said first and second palladium components at a loading of about 1000 nm to about 1000 nm.

14. The catalyst article of claim 1 or 2, further comprising a first diesel oxidation catalyst (DOC) composition.

15. The catalyst article of claim 14, wherein the first LT-NA catalyst composition comprises a first layer and the first DOC composition comprises a second layer.

16. 3. An exhaust gas treatment system comprising the catalytic article of claim 1 or 2, wherein the catalytic article is downstream of and in fluid communication with an internal combustion engine.

17. NO in the exhaust gas stream from an internal combustion engine ｘ 3. A method for reducing the level of exhaust gases comprising contacting the exhaust gas stream with the catalytic article of claim 1 or 2.

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