Low temperature NOx adsorbents with improved regeneration efficiency

Abstract

The present disclosure provides a low temperature NOx treatment system for treating exhaust gases. x Adsorbent (LT-NA) catalyst compositions, catalyst articles, and emissions treatment systems are provided, each comprising an LT-NA catalyst composition. The LT-NA catalyst articles are used to treat NO in an exhaust gas stream. x Further provided is a method for reducing the level of NO. Specifically, the LT-NA catalyst composition includes a first zeolite, a first palladium component, and a plurality of platinum nanoparticles. The LT-NA catalyst composition exhibits a high NO level even after hydrothermal aging. x The improved regeneration efficiency is shown in terms of adsorption capacity.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to International Application No. PCT / CN2019 / 112328, filed in its entirety on October 21, 2019.

[0002] The present invention treats the exhaust gas stream of a lean-burn internal combustion engine to reduce nitrogen oxides (NO x The present invention is directed to compositions, articles, systems, and methods suitable for reducing emissions of chlorofluorocarbons (CFCs). [Background technology]

[0003] Environmental regulations regarding emissions from internal combustion engines are becoming increasingly stringent around the world. For example, the operation of lean-burn engines, such as diesel engines, offers users excellent fuel economy by operating at high air-fuel ratios under lean fuel conditions. However, diesel engines also produce high levels of particulate matter (PM), unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO). x) It also emits exhaust gas emissions containing NO x represents various species of nitrogen oxides, including nitric oxide and nitrogen dioxide. x is a harmful component of air pollution. x A variety of treatment methods have been used to treat contained gas mixtures to reduce air pollution.

[0004] NO from the exhaust of a lean-burn engine x An effective method for reducing NO under lean-burn engine operating conditions is with a suitable reducing agent in the presence of a selective catalytic reduction (SCR) catalyst component. x SCR processes typically use ammonia or hydrocarbons in the presence of atmospheric oxygen as the reducing agent, thereby forming primarily nitrogen and steam: 4NO + 4NH3 + O2 → 4N2 + 6H2O (standard SCR reaction) 2NO2 + 4NH3 + O2 → 3N2 + 6H2O (slow SCR reaction) NO + NO2 + 2NH3 → 2N2 + 3H2O (high-speed SCR reaction)

[0005] 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 remove NO at temperatures below 600°C. x It can effectively catalyze the reduction of exhaust components, resulting in reduced NO even under low loading conditions typically associated with low exhaust temperatures. X You can achieve the level.

[0006] 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 cold (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 emissions at temperatures above 200°C. x While catalysts are very effective at converting NO to N2, they do not exhibit sufficient activity at lower temperatures (below 200°C) such as those found during cold starts or long periods of low-speed city driving. Using catalysts that function during low-temperature operation (below 150°C) can help address these increasingly stringent emissions regulations (e.g., Euro-7 regulations). x Since over 80% of the emissions consist of NO, such high NO x It is essential that the adsorbent material has a high efficiency for NO adsorption. x The NOx can be captured and stored, and the downstream catalyst component (i.e., the SCR catalyst component) can be activated to capture and store the NOx. xThere is a great demand for components that can release emissions at higher temperatures (above 200° C.) As a result, considerable efforts are being made to alleviate this problem.

[0007] NO during cold start period x There are several ways to minimize emissions. For example, reducing these exhaust gas emissions (i.e., HC, CO, and NO x Capture systems have been developed that can store NOx (ammonia gas) at low temperatures and then release it at elevated temperatures when the remaining catalytic components of the treatment system have reached sufficient catalytic activity. One such system is the well-known and commercially proven technology known as lean NOx. x The LNT catalyst is a NO trap (LNT) catalyst that traps NO under certain exhaust conditions. x Capture, NO x Contains adsorbent components, e.g., NO x The sorbent components may include, for example, alkaline earth metal oxides and carbonates, including alkaline earth elements, such as oxides of Mg, Ca, Sr, and / or Ba. Other LNT catalysts are suitable for NO x The adsorbent component may contain rare earth metal oxides, such as oxides of Ce, La, Pr, and / or Nd. The LNT catalyst is a catalyst for NO x It further contains a platinum group metal component (PGM), such as platinum, 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. Under lean conditions, the LNT catalyst reduces NO x During the reaction ("capture") of NO x capture and store as inorganic nitrates (e.g., NO x If the adsorbent component is BaO or BaCO3, it is converted to Ba(NO3)2). NO x The adsorbent component absorbs the captured NO x and PGM components release NO under stoichiometric or transiently rich engine operating conditions, or under lean engine operation where external fuel is injected into the exhaust to induce rich conditions. xThe conversion of NO to NO2 is an efficient NO x Although a prerequisite for capture, the reaction rate is very slow when temperatures are below 200°C, which makes conventional LNT catalysts difficult to achieve with cold-start NO capture. x This makes the LNT catalyst inefficient in capturing emissions. Furthermore, a rich purge is required to regenerate the LNT catalyst, which reduces fuel economy, but only minimally. Therefore, the preferred solution is a NOx-free LNT that operates only under lean conditions. x It will have an adsorption / release component.

[0008] NO X Another type of adsorbent is low-temperature NO x adsorbent (LT-NA), which is a NO x The adsorbent mainly uses ion-exchanged Pd in ​​zeolite. Pd / zeolite-based materials have been shown to adsorb nitric oxide (NO) at ambient to low temperatures, and low-temperature NO during the cold start period of an automobile. x However, one major concern with this technology is the adsorption of NO x However, it is released sufficiently during the normal diesel engine temperature cycle to reduce the NO x The inability to adequately regenerate such adsorption capacity results in NOx absorption during the subsequent cold start period. x Therefore, hydrothermal stability, improved adsorption capacity, and NO adsorption optimized to meet the requirements of specific engine applications. x LT-NA with a desorption profile is highly desirable. Summary of the Invention

[0009] The present disclosure generally relates to x Compositions, articles, and exhaust treatment systems including such articles are provided that exhibit improved regeneration efficiency for adsorption. In particular, such compositions, articles, and systems are effective in adsorbing NO at low temperatures. xand NO captured at high temperatures (above 200°C) when downstream catalyst components (i.e., SCR catalysts) become active. x Low temperature NO suitable for releasing x The LT-NA catalyst composition of the present disclosure provides desirable NO adsorption under various engine operating conditions. x Provides adsorption and desorption properties.

[0010] Surprisingly, according to the present disclosure, doping palladium ion-exchanged zeolites with platinum nanoparticles results in NO 3 even after hydrothermal aging. x The regeneration of adsorption capacity is improved and NO is released at a lower temperature range compared to LT-NA catalyst compositions that do not contain such platinum nanoparticles. x When combined with a diesel oxidation catalyst (DOC) composition, such LT-NA catalyst compositions exhibit desirable NO desorption both before and after hydrothermal aging. x The desorption profile was maintained.

[0011] Thus, in one embodiment, a low-temperature NO 3 catalyst is provided that comprises a first zeolite, a first palladium component, and a plurality of platinum nanoparticles. x An adsorbent (LT-NA) catalyst composition is provided, in which at least a portion of the first palladium component is exchanged with a first zeolite.

[0012] In some embodiments, the first palladium component is present in an amount of about 0.01% to about 10% by weight based on the weight of the zeolite, calculated as elemental palladium.

[0013] In some embodiments, at least a portion of the platinum nanoparticles are dispersed on the first zeolite.

[0014] In some embodiments, the platinum nanoparticles have an average particle size of about 1 to about 50 nm. In some embodiments, the platinum nanoparticles have an average particle size of about 1 to about 20 nm. In some embodiments, the platinum nanoparticles have an average particle size of about 1 to about 10 nm. In some embodiments, the platinum nanoparticles have an average particle size of about 1 to about 3 nm.

[0015] In some embodiments, the LT-NA composition further comprises a first refractory metal oxide component, and at least a portion of the platinum nanoparticles are dispersed on the first refractory metal oxide component, hi some embodiments, a portion of the platinum nanoparticles are dispersed on the first zeolite, and a portion of the platinum nanoparticles are dispersed on the first refractory metal oxide component.

[0016] In some embodiments, the first refractory metal oxide component comprises gamma alumina or alumina doped with about 2% to about 10% SiO 2 .

[0017] In some embodiments, the ratio of the first refractory metal oxide component to the first zeolite by weight is from about 10 to about 0.1.

[0018] The platinum nanoparticles are present in an amount of about 0.1% to about 10% by weight, based on the weight of the first zeolite, calculated as elemental platinum.

[0019] In some embodiments, the first zeolite is an aluminosilicate zeolite having a silica-to-alumina ratio (SAR) of from about 5 to about 100. In some embodiments, the aluminosilicate zeolite has a SAR of from about 10 to about 40.

[0020] In some embodiments, the first zeolite has a framework type selected from the group consisting of ABW, ACO, AEI, AEL, AEN, AET, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, APC, APD, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, EZT, FAU, FER, GIS, GME, GON, GOO, HEU, IFR, IFY, IHW, IMF, IRN, ISV, ITE, ITG, ITH, ITW, IWR, IWS, IWV, IWW, JBW, JRY, JSR, JST, KFI, LAU, LEV, LOV, LTA, LTF, LTL, LTN, MAZ, MEI, MEL, MER, MFI, MFS, MON, MOR, MOZ, MRE, MSE, MTF, MTT, MVY, MTW, MWF, MWW, NAB, NAT, NES, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, PAR, PAU, PCR, PHI, PON, PUN, RHO, RON, RRO, RSN, RTE, RTH, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SCO, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGF, SIV, SOF, SOS, SSF, SSY, STF, STI, STO, STT, STW, SVR, SZR, TER, THO, TON, TSC, TUN, UEI, UFI, UOS, USI, UTL, UWY, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, and mixtures or intergrowths thereof.

[0021] In some embodiments, the first zeolite is a medium pore zeolite having a framework 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 first zeolite is a medium pore zeolite having a framework type selected from FER, MEL, MFI, STT, and mixtures or intergrowths thereof. In some embodiments, the first zeolite is FER.

[0022] In some embodiments, the LT-NA composition further comprises a second zeolite, which is a large pore zeolite having a framework 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, 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, SFW, SOF, SOS, STO, SSF, SSY, USI, UWY, VET, and mixtures or intergrowths thereof. In some embodiments, the second zeolite is beta zeolite (BEA).

[0023] In some embodiments, a portion of the first palladium component is ion-exchanged into the second zeolite, hi some embodiments, a portion of the platinum nanoparticles are dispersed on the second zeolite.

[0024] In some embodiments, the LT-NA catalyst composition comprises a 1:1 NO x / Pd molar ratio and the NO present in the exhaust gas stream. x from the exhaust gas stream at a temperature of about 20°C to about 200°C and in an amount of at least 30 to 100% of the theoretical amount, based on the total amount of NO x Absorbs ingredients.

[0025] In some embodiments, the LT-NA catalyst composition is heated to a temperature of about 150° C. to about 300° C., and the NO adsorbed on the LT-NA catalyst composition is heated to a temperature of about 150° C. to about 300° C. x NO in an amount of at least 35 to about 100% by weight based on the total amount of ingredients x The components are released back into the exhaust gas stream.

[0026] In some embodiments, the LT-NA catalyst composition exhibits a high NO content after hydrothermal aging at 750-800°C for a period of about 16 to about 80 hours. x NO adsorption capacity is approximately 0.8 to 2 times x It has an adsorption capacity.

[0027] In another aspect, an LT-NA catalyst article for treating an exhaust stream of an internal combustion engine is provided, the article including a substrate having an inlet end and an outlet end defining an overall length, and a first washcoat disposed on at least a portion of the substrate, the first washcoat including the LT-NA composition disclosed herein.

[0028] In some embodiments, the substrate comprises a honeycomb substrate in the form of a wall-flow filter or a flow-through substrate.

[0029] In some embodiments, the LT-NA catalyst article further includes a second washcoat comprising a diesel oxidation catalyst (DOC) composition disposed on at least a portion of the substrate. In some embodiments, the DOC composition includes a second Pd component and a second refractory metal oxide component, wherein the second Pd component is supported on the second refractory metal oxide component. In some embodiments, the second refractory metal oxide includes gamma alumina or alumina doped with about 2% to about 10% SiO. In some embodiments, the DOC composition further includes a third zeolite. In some embodiments, the third zeolite includes beta zeolite. In some embodiments, the third zeolite further includes beta zeolite substantially free of any platinum group metal (PGM) species.

[0030] In some embodiments, the first and second washcoats are present in a layered configuration, where the first washcoat is disposed directly on the substrate and the second washcoat is disposed over at least a portion of the first washcoat. In some embodiments, the first and second washcoats are present in a layered configuration, where the second washcoat is disposed directly on the substrate and the first washcoat is disposed over at least a portion of the second washcoat. In some embodiments, the first and second washcoats are combined and disposed on the substrate in a single homogenous layer. In some embodiments, the first and second washcoats are present in a zoned configuration, where 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.

[0031] In another aspect, an exhaust gas treatment system is provided that includes the LT-NA catalyst article disclosed herein, wherein the LT-NA catalyst article is downstream of and in fluid communication with an internal combustion engine. In some embodiments, the exhaust gas treatment system is configured to produce a lean NOx-burning engine. xThe fuel cell further comprises one or more of a liquid nitrogen trap (LNT), a selective catalytic reduction (SCR) catalyst, an ammonia or ammonia precursor injection component, a catalyzed soot filter (CSF), or an ammonia oxidation (AMOx) catalyst.

[0032] In another aspect, NO in an exhaust gas stream from an internal combustion engine x Methods for reducing the levels are provided, which include contacting the exhaust gas stream with an LT-NA catalyst article, or an exhaust gas treatment system, as disclosed herein, respectively.

[0033] These and other features, aspects, and advantages of the present disclosure will become apparent from the following detailed description read 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, as well as combinations of any 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 specific embodiment herein. The present disclosure is intended to be read as a whole such that any separable features or elements of the disclosed invention, in any of its various aspects and embodiments, should be considered as intended to be combinable unless the context clearly indicates otherwise. Other aspects and advantages of the present invention will become apparent hereinafter. [Brief explanation of the drawings]

[0034] 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 present invention. The drawings are merely examples and should not be construed as limiting the present invention. The disclosure described herein is illustrated in the accompanying drawings by way of example, and not by way of limitation. For simplicity and clarity of illustration, features shown in the drawings have not necessarily been drawn to scale. For example, the dimensions of some features may be exaggerated relative to other features for clarity. Furthermore, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0035] [Figure 1A] FIG. 1 is a perspective view of a honeycomb-type substrate that may include a catalyst (i.e., low-temperature NOx adsorbent) washcoat according to the present disclosure. [Figure 1B] 1B is a partial cross-sectional view, enlarged compared to FIG. 1A and taken along a plane parallel to the end face of the substrate of FIG. 1A, showing an enlarged view of the multiple gas flow paths shown in FIG. 1 in an embodiment in which the substrate is a flow-through substrate. [Figure 2] 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] 1 is a cross-sectional view of one embodiment of a zoned catalyst article of the present disclosure. [Figure 3B] 1 is a cross-sectional view of one embodiment of a layered catalyst article of the present disclosure. [Figure 3C] FIG. 2 is a cross-sectional view of another embodiment of a layered catalyst article of the present disclosure. [Figure 4] FIG. 1 is a schematic diagram of an embodiment of an exhaust gas treatment system including an LT-NA article of the present disclosure in combination with additional emissions treatment system components. [Figure 5] FIG. 1 is a plot of NOx adsorption / desorption versus time and temperature of an embodiment of the present disclosure. [Figure 6] FIG. 1 is a plot of NOx adsorption / desorption versus time and temperature of an embodiment of the present disclosure. [Figure 7]FIG. 1 is a plot of NOx adsorption / desorption versus time and temperature of an embodiment of the present disclosure. [Figure 8] FIG. 1 is a plot of NOx adsorption / desorption versus time and temperature of an embodiment of the present disclosure. [Figure 9] FIG. 1 is a plot of NOx adsorption / desorption versus time and temperature of an embodiment of the present disclosure. [Figure 10] FIG. 1 is a plot of NOx adsorption / desorption versus time and temperature of an embodiment of the present disclosure. [Figure 11] FIG. 1 is a plot of N2O production versus time and temperature of an embodiment of the present disclosure. [Figure 12] FIG. 2 is a plot of NOx adsorption / desorption versus time and temperature for an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0036] This disclosure generally relates to x The present invention provides compositions, articles, and exhaust gas treatment systems including such articles that are suitable for the adsorption and subsequent thermal release of NO at low temperatures. x (LT-NA) and NO captured at high temperature x Suitable for thermally releasing NO x This is particularly important, for example, when the LT-NA article is placed upstream of a selective catalytic reduction (SCR) catalyst component. The SCR catalyst component absorbs NO at temperatures above 200°C. x Although it is very effective at converting NO to N2, it does not exhibit sufficient activity at lower temperatures (below 200°C), such as during cold starts and before urea can be injected into the exhaust. x Sufficient regeneration of the adsorption capacity ensures sufficient NO production in subsequent cold start cycles. x It is important to maintain the adsorption capacity.

[0037] The present invention will now be described more fully hereinafter. This invention may, however, 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.

[0038] definition The articles "a" and "an" herein refer to one or to more than one (e.g., at least one) of the grammatical object. All ranges cited herein are inclusive. As used throughout, the term "about" is used to express and account for small variations. For example, "about" can mean that a 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, whether explicitly stated or not, are modified by the term "about." Numerical values ​​modified by the term "about" include the specifically identified value. For example, "about 5.0" includes 5.0.

[0039] The term "reduction" means a decrease in quantity caused by any means.

[0040] The term "associated" means, for example, "comprising," "connected to," or "in communication with," e.g., "electrically connected" or "in fluid communication with," or functionally connected. The term "associated" can mean directly associated or indirectly associated, for example, through one or more other items or elements.

[0041] The average particle size is D 50" is synonymous with "particle size," meaning that half the number of particles are larger and half are smaller. Particle size refers to primary particles. Particle size can be measured, for example, by laser light scattering techniques using dispersed or dry powders according to ASTM method D4464. 90 The particle size distribution of indicates that 90% of the particles (by number) have a Feret diameter smaller than a certain size as measured by scanning electron microscope (SEM) or transmission electron microscope (TEM) for submicron-sized particles, or by particle size analyzer for carrier-containing particles (micron-sized).

[0042] 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, a zeolite can be a support for, for example, a platinum group metal (PGM) or base metal active catalytic species. Similarly, refractory metal oxide particles can be a support for a platinum group metal catalytic species. Catalytically active species are also referred to as "promoters" because they promote a chemical reaction. For example, the present PGM-containing zeolites can be referred to as PGM-promoted zeolites. "Promoted zeolites" refer to zeolites to which catalytically active species have been intentionally added.

[0043] The term "catalytic article" or "catalyst article" in this disclosure means an article that includes a substrate having a catalytic coating composition.

[0044] As used herein, "crystal size" refers to the length of one edge of a crystal face, preferably the longest edge, provided that the crystal is not needle-shaped. Direct measurement of crystal size can be performed using microscopy techniques such as SEM and TEM. For example, SEM measurement involves examining the morphology of the material at high magnification (typically 1000x to 10,000x). SEM can be performed by distributing a representative portion of the zeolite powder on a suitable mount, so that individual particles are spread fairly uniformly across the entire field of view at 1000x to 10,000x 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 agglomerates are not included in the measurement. Based on these measurements, the arithmetic mean crystal size of the sample is calculated.

[0045] "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 inserted into the outlet end and the outlet channels inserted into the inlet end. The soot-carrying exhaust gas flow entering the inlet channels is forced through the filter wall before exiting the outlet channels. In addition to soot filtration and regeneration, the CSF may also support an oxidation catalyst to oxidize CO and HC to CO2 and HO or NO to NO2, thereby accelerating downstream SCR catalysts or promoting the oxidation of soot particles at lower temperatures. SCR catalyst compositions can also be coated directly onto wall-flow filters, called SCRoFs.

[0046] As used herein, the phrase "catalytic system" refers to a combination of two or more catalysts or articles, e.g., low temperature NO xRefers to the combination of an adsorbent (LT-NA) and a second catalyst, which can be a DOC, LNT, or SCR catalyst article. Alternatively, the catalyst system can be in the form of a washcoat, where the two catalysts are mixed together or coated in separate layers.

[0047] The term "composed of" as used in the specification and claims is intended to be an open-ended term, similar to the terms "comprise" or "contain." The term "composed of" is not meant to exclude other possible items or elements. The term "composed of" may be equivalent to "adapted."

[0048] "DOC" refers to a diesel oxidation catalyst that converts hydrocarbons and carbon monoxide in the exhaust gas of a diesel engine. Typically, a DOC contains 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.

[0049] Generally, 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 defined catalytic activity or storage / release activity by weight or mole.

[0050] The term "exhaust stream" or "exhaust gas stream" refers to any combination of flowing gases that may contain solid or liquid particulate matter. The stream is, for example, the exhaust of a lean-burn engine, which includes gaseous components and may also contain certain non-gaseous components, such as liquid droplets, solid particulates, etc. The exhaust gas stream of a combustion engine typically contains combustion products (CO and HO), incomplete combustion products (carbon monoxide (CO) and hydrocarbons (HC)), nitrogen oxides (NO x), combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen. As used herein, the terms "upstream" and "downstream" refer to relative directions relative to the flow of engine exhaust gas stream from the engine toward the tailpipe, with the engine being in the upstream position and the tailpipe and any pollution abatement items, such as filters and catalysts, being downstream of the engine. The inlet end of the substrate is synonymous with the "upstream" end or "front" end. The outlet end is synonymous with the "downstream" end or "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.

[0051] The term "high surface area refractory metal oxide support" specifically refers to support particles having pores greater than 20 Å and a broad pore distribution. High surface area refractory metal oxide supports, such as alumina support materials also referred to as "gamma alumina" or "activated alumina," typically have a surface area of ​​60 square meters per gram ("m 2 / g), often up to about 200m 2 / g or greater BET surface area of ​​the fresh material. 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.

[0052] As used herein, "impregnated" or "impregnation" refers to the infiltration of a catalytic material into the porous structure of a support material.

[0053] 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 each other. Articles in fluid communication may be adjacent to each other in the exhaust line. Alternatively, articles in fluid communication may be separated by one or more articles, also referred to as "washcoat monoliths."

[0054] "LNT" stands for Lean NO xThis refers to the trap, which is used to trap NO during lean conditions. x A catalyst containing a platinum group metal, a rare earth metal oxide, and an alkaline earth trapping material (e.g., BaO or MgO) suitable for adsorbing NO under rich conditions. x is released and reduced to nitrogen.

[0055] As used herein, the term "molecular sieve," such as zeolites and other zeolitic framework materials (e.g., isomorphously substituted materials), refers to materials capable of supporting catalytic PGMs or other catalytic metals in particulate form. Molecular sieves are materials based on oxygen ions in an extensive three-dimensional network structure, generally containing tetrahedral sites and having a substantially uniform pore distribution, with an average pore size of 20 angstroms (Å) or less. Molecular sieves can be distinguished primarily according to the shape of the pores formed by the rigid network of (SiO4) / AlO4 tetrahedra. The entrances to the pores are formed from 6, 8, 10, or 12 ring atoms for the atoms forming the entrance opening. Molecular sieves are crystalline materials with fairly uniform pore sizes ranging from about 3 to 10 Å in diameter, depending on the type of molecular sieve and the type and amount of cations contained in the molecular sieve lattice. CHA is an example of an "octa-ring" molecular sieve, having an eight-ring pore opening and a double six-ring secondary structural unit, and a cage-like structure resulting from the connection of the double six-ring structural unit with four ring connections. Molecular sieves include small-pore, medium-pore, and large-pore molecular sieves, or combinations thereof. The pore size is defined by the largest ring diameter.

[0056] As used herein, "nitrogen oxides" or "NO x The term "refers to nitrogen oxides such as NO, NO2, or N2O."

[0057] The terms "on" and "above" in relation to coating layers can be used synonymously. The term "directly on" means in direct contact. Although the disclosed articles, in certain embodiments, are referred to as including one coating layer "on" a second coating layer, such language is intended to encompass embodiments having intervening layers where direct contact between the coating layers is not required (i.e., "on" is not equivalent to "directly on").

[0058] 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).

[0059] "Substantially free" means "little or no" or "not intentionally added," and also means having only trace and / or incidental amounts. For example, in certain embodiments, "substantially free" means less than 2% by weight (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 indicated.

[0060] As used herein, the term "substrate" refers to a monolithic material upon which a catalyst composition, i.e., catalyst coating, is disposed, typically in the form of a washcoat. A washcoat is formed by preparing a slurry containing a particular solids content (e.g., 30% to 90% by weight) of catalyst in a liquid, which is then coated onto the substrate and dried to provide the washcoat layer. Reference to a "monolithic substrate" means a single structure that is homogeneous and continuous from inlet to outlet.

[0061] As used herein, the term "washcoat" has its conventional 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 contain a binder selected from silica, alumina, titania, zirconia, ceria, or combinations thereof. The binder loading is about 0.1 to 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 underlying washcoat layer. The substrate can contain one or more washcoat layers, each of which can differ in some aspect (e.g., the physical properties of the washcoat, such as particle size or crystallite phase, can differ) and / or the chemical catalytic function can differ.

[0062] Unless otherwise indicated, "weight percent (wt %)" is based on the total composition, excluding volatile materials, i.e., dry solids content. Unless otherwise indicated, all parts and percentages are by weight.

[0063] As used herein, the term "zeolite" refers to a specific example of a molecular sieve that further contains silicon and aluminum atoms. Generally, zeolites are defined as aluminosilicates with an open three-dimensional framework structure composed of corner-sharing TO4 tetrahedra, where T is Al or Si, or optionally 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.

[0064] Aluminosilicate zeolite structures do not contain phosphorus or other metals isomorphously substituted in the framework. That is, "aluminosilicate zeolite" excludes aluminophosphate materials such as SAPO, AlPO, and MeAlPO materials, while the broader term "zeolite" includes aluminosilicates and aluminophosphates. For purposes of this disclosure, SAPO, AlPO, and MeAlPO materials are considered non-zeolitic molecular sieves.

[0065] The zeolite may comprise independent SiO / AlO tetrahedra linked by common oxygen atoms to form a three-dimensional network. The silica-to-alumina molar ratio ("SAR") of the zeolite may vary over a wide range, but is generally greater than or equal to 2. For example, the zeolite may have an SAR of from about 5 to about 1000.

[0066] Zeolites are composed of secondary structural units (SBUs) and complex structural units (CBUs) and occur in many different framework structures. Secondary structural units contain up to 16 tetrahedral atoms and are not chiral. Complex structural units are not necessarily achiral and cannot necessarily be used to construct the entire framework. For example, a group of zeolites has single tetrahedral (s4r) complex structural units within their framework structures. In the tetrahedral structure, the "tetra" refers to the position of the silicon and aluminum atoms on the tetrahedron, and the oxygen atoms are located between the tetrahedral atoms. Other complex structural units include, for example, single hexacyclic (s6r) units, double tetrahedral (d4r) units, and double hexacyclic (d6r) units. d4r units are formed by linking two s4r units. d6r units are formed by linking two s6r units. There are 12 tetrahedral atoms in a d6r unit.

[0067] Typically, any framework type zeolite such as ABW, ACO, AEI, AEL, AEN, AET, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, APC, APD, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, EZT, FAU, FER, GIS, GME, GON, GOO, HEU, IFR, IFY, IHW, IMF, IRN, ISV, ITE, ITG, ITH, ITW, IWR, IWS, IWV, IWW, JBW, JRY, JSR, JST, KFI, LAU, LEV, LOV, LTA, LTF, LTL, LTN, MAZ, MEI, MEL, MER, MFI, MFS, MON, MOR, MOZ, MRE, MSE, MTF, MTT, MVY, MTW, MWF, MWW, NAB, NAT, NES, NPO, NPT, NSI, OBW, OFF, OKO, OSO, OWE, PAR, PAU, PCR, PHI, PON, PUN, RHO, RON, RRO, RSN, RTE, RTH, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SCO, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGF, SIV, SOF, SOS, SSF, SSY, STF, STI, STO, STT, STW, SVR, SZR, TER, THO, TON, TSC, TUN, UEI, UFI, UOS, USI, UTL, UWY, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, and their mixtures or skeletal types of twins can be used.

[0068] Zeolites are crystalline materials with fairly uniform pore sizes ranging from about 3 to 10 Å 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 Å, e.g., pore openings on the order of about 3.8 Å.

[0069] Small pore zeolites contain channels defined by up to eight tetrahedral atoms. The phrase "eight-ring" zeolite refers to a zeolite having eight-ring pore openings and double-hexagonal secondary structural units, and having a cage-like structure resulting from the connection of the double-hexagonal structural units by four rings.

[0070] Exemplary small pore zeolites include framework types ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON, and mixtures or intergrowths thereof.

[0071] Medium pore zeolites contain channels defined by 10-membered rings. Exemplary medium pore zeolites include framework types 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.

[0072] 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, SFW, SOF, SOS, STO, SSF, SSY, USI, UWY, VET, and mixtures or intergrowths thereof.

[0073] 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., "such as") 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.

[0074] All US patent applications, pre-grant publications and patents mentioned herein are incorporated by reference in their entirety.

[0075] Low-temperature NO x Adsorbent (LT-NA) catalyst composition The present disclosure provides an LT-NA catalyst composition comprising a first zeolite comprising a first palladium component and a plurality of platinum nanoparticles, these components being further described herein below.

[0076] The first zeolite As mentioned above, the LT-NA catalyst composition of the present invention comprises a first zeolite. As used herein, reference to a "first zeolite" is made to distinguish between additional zeolites (e.g., second and third zeolites) that may be present in some embodiments. The first, and, if present, second and third zeolites described below may be referred to as primary, secondary, and tertiary zeolites, respectively. In some embodiments, the first zeolite is an aluminosilicate zeolite.

[0077] The silica-to-alumina ("SAR") molar ratio of the first zeolite of the present invention can vary over a wide range but is generally greater than or equal to 2. For example, the first zeolite of the present invention may have an SAR of from about 1 to about 1000. In one or more embodiments, the first zeolite has an SAR molar ratio ranging from 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.

[0078] In some embodiments, the first zeolite has a 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.

[0079] In one or more specific embodiments, the first zeolite has an SAR molar ratio in the ranges 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.

[0080] In some embodiments, the first zeolite has an SAR of about 5 to about 100. In some embodiments, the first zeolite has an SAR of about 10 to about 40. In some embodiments, the SAR is about 2 to about 50. In some embodiments, the SAR is about 25.

[0081] According to one or more embodiments, the first zeolite may be based on a framework topology that identifies the structure. For example, the first zeolite of the present invention may be selected from the group consisting of ABW, ACO, AEI, AEL, AEN, AET, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, APC, APD, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, C ZP, DAC, DDR, DFO, DFT, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, EZT, FAU, FER, GIS, GME, GON, GOO, HEU, IFR, IF Y, IHW, IMF, IRN, ISV, ITE, ITG, ITH, ITW, IWR, IWS, IWV, IWW, JBW, JRY, JSR, JST, KFI, LAU, LEV, LOV, LTA, LTF, LTL, LTN, MAZ, MEI, MEL, MER, MFI, MFS, MON, MOR, MOZ, MRE, MSE, MTF, MTT, MVY, MTW, MWF, MWW, NAB, NAT, NES, NPO, NPT, NSI, OBW, OFF, OKO, O SI, OSO, OWE, PAR, PAU, PCR, PHI, PON, PUN, RHO, RON, RRO, RSN, RTE, RTH, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SCO , SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGF, SIV, SOF, SOS, SSF, SSY, STF, STI, STO, STT, STW, SVR, SZR, TER, THO, TON, TSC, TUN, UEI, UFI, UOS, USI, UTL, UWY, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, and mixtures or intergrowths thereof.

[0082] In some embodiments, the first zeolite has a two-dimensional pore system. In some embodiments, the zeolite having a two-dimensional pore system can have a framework type such as, but not limited to, FER, CSV, DAC, HEU, MFS, MWW, NES, RRO, SFG, STI, STT, or TER. Discussions of the synthesis and pore geometry of zeolites having an FER structure are disclosed, for example, in Weitkamp et al., Chem. Eng. Technol. 25, (2002), 3, 273-275; Pinar et al., Proceedings of the 5th Serbian-Croatian-Slovenian Symposium on Zeolites, 32-35; and Parikh et al., Indian Journal of Chemical Technology, 18, September 2011, 335-342, each of which is incorporated herein by reference in its entirety.

[0083] In some embodiments, the first zeolite is a medium pore zeolite having a framework 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 first zeolite is a medium pore zeolite having a framework type selected from FER, MEL, MFI, STT, and mixtures or intergrowths thereof. In some embodiments, the first zeolite has a framework FER. In some embodiments, the first zeolite is ferrierite.

[0084] In some embodiments, the first zeolite has an average crystal size (i.e., of individual crystals, including twins) greater than about 0.1 μm. In some embodiments, the first zeolite has an average crystal size of 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.

[0085] Second Zeolite In some embodiments, the LT-NA composition further comprises a second zeolite, which is a large pore zeolite having a framework 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, 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, SFW, SOF, SOS, STO, SSF, SSY, USI, UWY, VET, and mixtures or intergrowths thereof. In some embodiments, the second zeolite is beta zeolite (BEA).

[0086] First Palladium Component As mentioned above, the disclosed LT-NA catalyst composition includes a first zeolite and a first palladium component, at least a portion of which is ion-exchanged into the first zeolite. As used herein, the term "palladium component" refers to palladium metal, palladium ions, or a palladium compound, e.g., an oxide of palladium. As used herein, reference to "first" with respect to the palladium component is made to distinguish between additional palladium components (e.g., second palladium components) that may be present in some embodiments and may be the same or different. The first and second palladium components are sometimes referred to synonymously as "primary" and "secondary" palladium components, respectively.

[0087] The palladium of the palladium component can be present to varying degrees as palladium ions present at ion-exchange sites. In this disclosure, it should be understood that the first palladium component can be present at the ion-exchange sites of the zeolite, on the surface of the zeolite, or both. In some embodiments, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 99%, or in some cases 100% of the first palladium component in the first zeolite is ion-exchanged.

[0088] In some embodiments, a portion of the first palladium component is ion-exchanged with the second zeolite. In embodiments in which a portion of the first palladium component is ion-exchanged with the second zeolite, the portion of the first palladium component that is ion-exchanged with the second zeolite can range from about 10% to about 90%. For example, about 10% to about 90% of the first palladium component is ion-exchanged with the first zeolite, and about 90% to about 10% of the first palladium component is ion-exchanged with the second zeolite. In some embodiments, about 50% of the first palladium component is ion-exchanged with the first zeolite, and about 50% of the first palladium component is ion-exchanged with the second zeolite.

[0089] The concentration of the first palladium component can vary, but is typically about 0.01 wt. % to about 10 wt. % based on the total weight of the first and second zeolites present. In some embodiments, the concentration of the first palladium component can be about 0.1 to about 6 wt. % based on the total weight of the first and second zeolites. Palladium can be present in the zeolite at, for example, 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. %, about 5.0 wt. %, about 5.5 wt. %, or about 6.0 wt. % based on the total weight of the first and second zeolites. The weight of palladium is measured and reported as elemental Pd.

[0090] Multiple platinum nanoparticles The LT-NA catalyst composition disclosed herein comprises a plurality of platinum nanoparticles. Generally, the platinum in such nanoparticles is in a substantially fully reduced form, meaning that at least about 90% of the platinum content is reduced to the metallic form (Pt(0)). In some embodiments, the amount of platinum in the fully reduced form is even higher, e.g., at least about 92%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% of the platinum is in the fully reduced form. The amount of Pt(0) can be determined using ultrafiltration followed by inductively coupled plasma / optical emission spectroscopy (ICP-OES).

[0091] The average size of the platinum nanoparticles in the LT-NA catalyst composition can vary. In some embodiments, the platinum nanoparticles can have an average particle size (fresh / calcined form) of about 1 nm to about 50 nm, e.g., about 1 nm to about 20 nm, or about 1 to about 10 nm, e.g., about 1 nm, about 3 nm, about 5 nm, about 10 nm, about 15 nm, about 20 nm, about 25 nm, about 30 nm, about 35 nm, about 40 nm, about 45 nm, or about 50 nm. Particular embodiments can have an average particle size (fresh / calcined form) of about 1 to 3 nm.

[0092] In some embodiments, the LT-NA catalyst composition as described herein is fresh. In such embodiments, the average particle size range represents unaged (e.g., untreated) platinum nanoparticles. In other embodiments, the LT-NA catalyst composition has been aged (i.e., "evened"). "Aged" or "evened" means that the composition, or an article containing such a composition, has been exposed to high temperatures for an extended period of time (e.g., temperatures above about 700°C, 800°C, 900°C, or 1000°C), simulating conditions the composition will experience during use in a vehicle exhaust treatment system. Such aging may be referred to as "hydrothermal aging."

[0093] In some embodiments, the platinum nanoparticles in the LT-NA catalyst compositions disclosed herein are substantially monodisperse with respect to particle size, meaning that the nanoparticle population is highly uniform in particle size. Particular monodisperse particle populations useful in the present invention can be characterized by at least 90% of the particles having a particle size within 50 percent, 20 percent, 15 percent, 10 percent, or 5 percent of the average particle size of the particle population (i.e., at least 90% of all particles in the population have a particle size within a given percentage range of about the average particle size). In other embodiments, at least 95%, 96%, 97%, 98%, or 99% of all particles fall within these ranges. In one exemplary embodiment, the average particle size is about 25 nm, and at least 90% (or at least 95%, 96%, 97%, 98%, 99%, or 100%) of all particles in the population have a particle size in the range of about 12.5 nm to about 37.5 nm (i.e., within about 50 percent of the average particle size). In some embodiments, the average particle size is about 25 nm, and at least 90% (or at least 95%, 96%, 97%, 98%, 99%, or 100%) of all particles in the population have a particle size in the range of about 18.75 nm to about 31.25 nm (i.e., within about 25 percent of the average particle size). In some embodiments, the average particle size is about 25 nm, and at least 90% (or at least 95%, 96%, 97%, 98%, 99%, or 100%) of all particles in the population have a particle size in the range of about 22.5 nm to about 27.5 nm (i.e., within about 10 percent of the average particle size). Specific platinum nanoparticle samples for use in the present invention are substantially monodisperse, with an average platinum nanoparticle size of about 20 nm, about 25 nm, about 30 nm, about 35 nm, or about 40 nm.

[0094] The particle size and size distribution of platinum nanoparticles can be determined using transmission electron microscopy (TEM). Such TEM evaluation can be performed, for example, on calcined supported platinum nanoparticles (e.g., as shown in the figure). Such values ​​can be found by visually inspecting a TEM image, measuring the diameter of the particles in the image, and calculating the average particle size of the measured particles based on the magnification of the TEM image. The particle size refers to the smallest diameter sphere that completely surrounds the particle; this measurement relates to an individual particle, as opposed to an agglomeration of two or more particles. The size ranges listed above are average values ​​for particles with a size distribution.

[0095] The particle size distribution and the percentage of particles having a size within a particular range can be determined, for example, by coating the calcined supported platinum nanoparticles onto a substrate and then analyzing them with TEM or scanning electron microscopy (SEM). The calcined supported platinum nanoparticles on the substrate can be analyzed directly by TEM or SEM (viewing the coated substrate) or by scraping or otherwise removing at least a portion of the calcined supported platinum nanoparticles from the substrate and obtaining an image of the scraped / removed supported platinum nanoparticles.

[0096] The amount of platinum particles present in the LT-NA catalyst composition of the present invention can vary. In some embodiments, the platinum nanoparticles are present in an amount of about 0.1 wt. % to about 10 wt. % based on the weight of the first zeolite, calculated as elemental platinum. In some embodiments, the platinum nanoparticles are present in an amount of about 1 to about 6 wt. %. In some embodiments, the platinum nanoparticles are present in an amount of about 2 to about 4 wt. %. In some embodiments, the platinum nanoparticles are present in an amount of about 0.1, about 0.5, about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or about 10 wt. % based on the weight of the first zeolite.

[0097] In some embodiments, at least a portion of the platinum nanoparticles are disposed on the first zeolite. In some embodiments, all of the platinum nanoparticles are disposed on the first zeolite. In some embodiments, a portion of the platinum nanoparticles are disposed on the second zeolite. In some embodiments, the platinum nanoparticles are disposed on the first zeolite and the second zeolite. In some embodiments, a portion of the platinum nanoparticles are disposed on a solid support material, e.g., a refractory metal oxide component. In some embodiments, the platinum nanoparticles are disposed on both the first zeolite and the solid support material, e.g., a refractory metal oxide component. In some embodiments, the platinum nanoparticles are disposed on the first zeolite, the second zeolite, and the solid support material, e.g., a refractory metal oxide component.

[0098] The relative amounts of platinum nanoparticles on the first zeolite, second zeolite, and refractory metal oxide component can vary. For example, in some embodiments, about 10% to about 100%, e.g., about 10%, about 20%, about 30%, about 40%, or about 50% to about 60%, about 70%, about 80%, or about 90%, of the platinum nanoparticles are disposed on the first zeolite. In some embodiments, about 10% to about 90%, e.g., about 10%, about 20%, about 30%, about 40%, or about 50% to about 60%, about 70%, about 80%, or about 90%, of the platinum nanoparticles are disposed on the second zeolite. In some embodiments, about 1% to about 50%, e.g., about 1%, about 5%, about 10%, or about 20% to about 30%, about 40%, or about 50% of the platinum nanoparticles are disposed on the refractory metal oxide component.

[0099] The support material on which the platinum nanoparticles are disposed may comprise a refractory metal oxide that exhibits chemical and physical stability at high temperatures, such as temperatures associated with gasoline or diesel engine exhaust. Exemplary refractory metal oxides include alumina, silica, zirconia, titania, ceria, praseodymium, tin oxide, and the like, as well as physical mixtures or chemical combinations thereof, such as atomically doped combinations, and high surface area or active compounds, such as activated alumina. Metal oxide combinations include 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.

[0100] High surface area metal oxide supports, such as alumina support materials also known as "gamma alumina" or "activated alumina," are typically 60 m 2 / g, often up to about 200m 2 Exemplary refractory metal oxides exhibit a BET surface area of ​​about 50 m / g or greater. 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 for determining surface area by N2 adsorption. Desirably, activated aluminas have a specific surface area of ​​about 60 m 2 / g ~ approx. 350m 2 / g, for example, about 90m 2 / g ~ approx. 250m 2 / g. In some embodiments, the first refractory metal oxide component comprises gamma alumina or alumina doped with about 2% to about 10% SiO.

[0101] The weight ratio of the first refractory metal oxide component to the zeolite (i.e., the first zeolite plus the second zeolite, if present) can vary. In some embodiments, the weight ratio of the first refractory metal oxide component to the zeolite is from about 10 to about 0.1, e.g., from about 10, about 9, about 8, about 7, about 6, about 5, about 4, about 3, about 2, or from about 1 to about 0.9, about 0.8, about 0.7, about 0.6, about 0.5, about 0.4, about 0.3, about 0.2, or about 0.1.

[0102] Diesel Oxidation Catalyst (DOC) Composition In some embodiments, the LT-NA catalyst article disclosed herein further comprises a diesel oxidation catalyst (DOC) composition. Various such DOC compositions are known for use in treating diesel engine exhaust to convert both hydrocarbon (HC) and carbon monoxide (CO) gaseous pollutants into carbon dioxide and water by catalyzing the oxidation of these pollutants. Generally, DOC compositions comprise one or more platinum group metal (PGM) components dispersed on a support, such as a refractory metal support. The term "PGM component" refers to any component containing a PGM (e.g., Ru, Rh, Os, Ir, Pd, Pt, and / or Au). Reference to a "PGM component" takes into account the presence of the PGM in any valence state. For example, the PGM may be in a zero-valence metallic form, or the PGM may be in an oxide form. Terms such as "platinum (Pt) component," "rhodium (Rh) component," "palladium (Pd) component," "iridium (Ir) component," "ruthenium (Ru) component," and the like refer to components that decompose or otherwise convert to a catalytically active form, typically a metal or metal oxide, upon calcination or use of the catalyst (including, for example, but not limited to, platinum or oxide thereof).

[0103] In some embodiments, the DOC compositions disclosed herein include a palladium component (referred to herein as a "second palladium component" to distinguish it from the first palladium component associated with the LT-NA compositions disclosed above). Similar to the "first palladium component," the term "second palladium component" as used herein refers to palladium metal, palladium ions, or a palladium compound, e.g., an oxide of palladium. In certain embodiments, the DOC compositions disclosed herein include a second palladium component and further include a platinum component. In some embodiments, the Pt / Pd ratio of the DOC composition is about 10:1 to about 1:10. In some embodiments, the Pt / Pd weight ratio is about 2:1.

[0104] The Pd component, and, if present, the Pt component, can be present in an amount ranging from about 0.01 to about 20 wt % on a metals basis, based on the total weight of the DOC composition. The DOC composition can include, for example, about 0.1 wt %, 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 % Pd, Pt, or Pd / Pt components, based on the weight of the dry DOC composition.

[0105] Typically, the second palladium component, the Pt component, or both 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 a "non-zeolitic support" or "non-zeolitic support" in the catalyst layer refer to a material that is not a zeolite and that receives a precious metal, stabilizer, promoter, binder, 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. Thus, in some embodiments, the DOC composition includes a refractory metal oxide component (referred to herein as a "second refractory metal oxide component" to distinguish it from the first refractory metal oxide component associated with the LT-NA composition disclosed above), but the second palladium component is supported on the second refractory metal oxide component. Refractory metal oxides generally useful in DOC compositions are typically 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. In certain embodiments, refractory 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). In some embodiments, the second refractory metal oxide comprises gamma alumina or alumina doped with about 2% to about 10% SiO 2 .

[0106] The DOC catalyst composition may contain any of the above-listed second refractory metal oxides in any amount. For example, the second refractory metal oxide of the catalyst composition may comprise 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 DOC catalyst composition. The DOC catalyst composition may contain, for example, about 10 to about 99 wt% Si-doped alumina, about 15 to about 95 wt% Si-doped alumina, or about 20 to about 85 wt% Si-doped alumina.

[0107] In some embodiments, the DOC composition further comprises a zeolite described herein (referred to herein as a "third zeolite" to distinguish it from the first and second zeolites associated with the LT-NA composition described above). In some embodiments, the third zeolite comprises beta zeolite (BEA). In some embodiments, the BEA is substantially free of any platinum group metal (PGM) species.

[0108] 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, also known as capillary impregnation or dry impregnation, is commonly used to synthesize heterogeneous materials, i.e., catalysts. Typically, metal precursors are dissolved in an aqueous or organic solution, and the metal-containing solution is then added to a catalyst support (e.g., a zeolite or refractory metal oxide) containing a pore volume equal to the volume of the added solution. Capillary action draws the solution into the pores of the support. Adding solution beyond the pore volume of the support changes 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 metal 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 within the pores during impregnation and drying. Those skilled in the art will recognize other methods for loading the metal components onto the support of the present compositions, such as adsorption, ion exchange, precipitation, and the like.

[0109] For example, palladium may be impregnated into a zeolite (e.g., a first and / or second zeolite) in preparing a component of the LT-NA catalyst composition. Palladium salts useful for introducing palladium into zeolites include, but are not limited to, nitrates.

[0110] In some embodiments, the palladium component is ion-exchanged in the zeolite (e.g., the first and / or second zeolite). Ion exchange is a commonly used process for exchanging ions present in a porous support with external metal ions of interest. The zeolite framework contains open voids in the form of channels and cages, which are usually occupied by water molecules and replaceable extra-framework cations. Aluminum atoms attract excess negative charges, which are compensated by these cations. The interior of the pore system is represented by the catalytically active surface. The more aluminum and less silicon a zeolite contains, the denser the negative charges in its lattice and the more polar its interior surface becomes.

[0111] Due to the presence of divalent or trivalent cations as tetrahedral centers in the zeolite framework, zeolites receive negative charges in the form of so-called anionic sites, with corresponding cation sites located nearby. The negative charges are compensated for by incorporating cations, e.g., metal cations, into the pores of the zeolite material. The 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 can be removed. These voids and channels are characteristic of each zeolite. The term "exchange site" refers to the cation-available sites that are primarily occupied by ion-exchanged metal cations intentionally added to the zeolite (e.g., palladium).

[0112] While not wishing to be bound by theory, a high zeolite sodium content can adversely affect hydrothermal stability. Therefore, as described herein, low sodium and alkali metal contents in zeolites are generally preferred. In certain embodiments, the zeolite has 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 free of volatiles). In some embodiments, low alkali content zeolites can be provided by ion-exchanging the sodium (Na) form of the zeolite into the ammonium (NH) form. The NH ion-exchange into the zeolite can be carried out at room temperature or at temperatures up to about 80°C for a period of about 1 to 24 hours. In some embodiments, the resulting zeolitic material may be dried, preferably at about 100 to 120°C, to provide an NH-exchanged zeolite. In some embodiments, the NH-exchanged zeolite can be calcined at a temperature of at least about 450°C to obtain an H-exchanged zeolite.

[0113] For example, sodium or NH4 present in the pores +Zeolites prepared with ions can be exchanged with, for example, palladium ions to form palladium ion-exchanged zeolites. This is accomplished by preparing a slurry of the zeolite in a solution containing palladium ions. Optionally, heat may be added during this process. Here, the palladium ions diffuse into the pores of the zeolite and dissolve the ions present, i.e., Na. + and NH4 + to form a palladium ion-exchanged zeolite. "Palladium ion-exchanged" means that at least a portion of the ion-exchange sites are occupied by palladium ions. In particular, it is preferred that more than 50% of the exchangeable sites are exchanged, and preferably more than 70% of the exchangeable sites are exchanged with palladium.

[0114] According to the present disclosure, LT-NA catalyst compositions are generally prepared by associating a colloidal dispersion of platinum (Pt) nanoparticles with any or all of a first zeolite, a second zeolite, and a refractory oxide support material, each as described herein. Such colloidal dispersions, in some embodiments, comprise a plurality of Pt nanoparticles or compositions providing a plurality of Pt nanoparticles, the compositions comprising: a) a platinum metal precursor; b) a dispersing medium; c) a stabilizer; and d) a reducing agent. Advantageously, the Pt in colloidal dispersions useful according to the present disclosure is in a substantially fully reduced form, meaning that at least about 90% of the Pt content (i.e., the majority of the nanoparticles) is reduced to the metallic form (Pt(0)). In some embodiments, the platinum metal precursor may be selected from the group consisting of ammine complex salts, hydroxyl salts, nitrates, carboxylates, ammonium salts, and oxides (e.g., selected from Pt(NH3)4(OH)2, Pt nitrates, Pt citrates, etc.). Once prepared, the Pt colloidal dispersion can have various concentrations of Pt nanoparticles, for example, from about 1 wt. % to about 10 wt. %, e.g., from about 2 wt. % to about 6 wt. %, from about 2 wt. % to about 5 wt. %, or from about 4 wt. % to about 6 wt. % without further processing (e.g., a concentration step). Without wishing to be bound by any particular theory, it is believed that impregnation of the first zeolite with colloidal Pt using preformed Pt nanoparticles can ensure that the Pt enters the zeolite and is not ion-exchanged.

[0115] Methods for impregnating supports with colloidal Pt and PGM materials are described in Xu et al., US2017 / 0304805 and Wei et al., US2019 / 0015781, both of which are incorporated herein by reference in their entireties.

[0116] Similarly, for the preparation of the DOC compositions disclosed herein, an aqueous solution of a soluble compound or complex of a platinum group metal (PGM) is generally used to impregnate a support material (e.g., a refractory metal oxide). Non-limiting examples of suitable compounds include palladium nitrate, tetraamminepalladium nitrate, tetraammineplatinum acetate, and platinum nitrate. During a calcination step, or at least during the initial stages of use of the composite, such compounds are converted to the catalytically active form of the metal or its compound. A suitable method for preparing a DOC catalyst composition is to prepare a mixture of a solution of the desired PGM compound (e.g., a platinum group compound and / or a palladium compound) with at least one support, e.g., a finely divided, high surface area refractory metal oxide support, e.g., silica-doped alumina, where 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 can be lowered 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.

[0117] catalyst article In one or more embodiments, the LT-NA composition is disposed (coated) on a substrate to form a catalytic article (i.e., catalytic component or catalyst article). Such an article is part of an exhaust gas treatment system (e.g., a catalytic article, including, but not limited to, an article comprising the LT-NA composition disclosed herein). As used herein, the terms "catalyst article," "catalytic article," "catalyst component," "catalytic component," "article," and "component" are used interchangeably and without regard to any particular catalytic activity. For example, an LT-NA article may be referred to as a catalytic article, although, without wishing to be bound by any particular theory of operation, it is recognized that such an article possesses an adsorption function rather than a catalytic function. Similarly, "composition" and "catalyst composition" are used interchangeably herein and without regard to any particular catalytic activity.

[0118] In one aspect of the present disclosure, a catalyst article for treating an exhaust stream of an internal combustion engine is provided, the catalyst article including a substrate having an inlet end and an outlet end defining an overall length, and a first washcoat disposed on at least a portion thereof, the first washcoat including the LT-NA composition disclosed herein. In some embodiments, the catalyst article disclosed herein further includes a second washcoat including a diesel oxidation catalyst (DOC) composition disposed on at least a portion of the substrate in a layered or zoned configuration.

[0119] To produce a catalytic article, a substrate is coated with a catalytic composition disclosed herein (i.e., an LT-NA and / or DOC composition). The coating is a "catalytic coating composition" or "catalytic coating." The terms "catalytic composition" and "catalytic coating composition" are synonymous.

[0120] Coating Composition Coating compositions containing the LT-NA and / or DOC compositions disclosed herein can be prepared using a binder, such as a ZrO binder derived from a suitable precursor, such as zirconyl acetate, or any other suitable zirconium precursor, such as zirconyl nitrate. Zirconyl acetate binders provide coatings that remain homogeneous and intact after thermal aging, for example, when the catalyst is exposed to high temperatures of at least about 600°C, e.g., about 800°C, and high water vapor environments of about 5% or more. Other potentially suitable binders include, but are not limited to, alumina and silica. Alumina binders include aluminum oxide, aluminum hydroxide, and aluminum oxyhydroxide. Aluminum salts and colloidal forms of alumina may also be used. Silica binders include various forms of SiO, including silicates and colloidal silica. The binder composition can include any combination of zirconia, alumina, and silica. Other exemplary binders include boehmite, gamma-alumina, or delta / theta alumina, and silica sol. When present, binders are typically used in amounts of about 1-5 wt. % of the total washcoat loading. Alternatively, the binder can be zirconia- or silica-based, e.g., zirconium acetate, zirconia sol, or silica sol. When present, alumina binders are typically used in amounts of about 0.05 g / in. 3 ~Approx. 1g / in 3 is used in amounts of

[0121] Base material Useful substrates are three-dimensional, having a length, diameter, and volume similar to a cylinder. The shape does not necessarily have to conform to a cylinder. The length is the axial length defined by the inlet and outlet ends.

[0122] According to one or more embodiments, the substrate for the disclosed compositions can 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 washcoat composition is applied and adheres, thereby serving as a substrate for the catalyst composition.

[0123] The ceramic substrate may be made from any suitable refractory material, such as cordierite, cordierite-α-alumina, aluminum titanate, silicon titanate, silicon carbide, silicon nitride, zircon-mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, α-alumina, aluminosilicates, and the like.

[0124] The substrate can also be metallic and include one or more metals or metal alloys. Metal substrates can include any metal substrate having openings or "punchouts" in the channel walls. Metal substrates can be used in various shapes, such as pellets, corrugated sheets, or monolith forms. Specific examples of metal substrates include heat-resistant base metal alloys, particularly alloys in which iron is a substantial or major component. Such alloys can contain one or more of nickel, chromium, and aluminum, the total of which metals advantageously comprises at least about 15% by weight (weight percent), in each case based on the weight of the substrate, such as about 10 to about 25% by weight chromium, about 1 to about 8% by weight aluminum, and 0 to about 20% by weight nickel. Examples of metal substrates include those with straight channels, those with protruding blades along the axial channels to disrupt gas flow and open gas flow communication between channels, and those with holes to enhance gas transport between channels, allowing radial gas transport throughout the blades and monolith. In particular, metal substrates are advantageously used in certain embodiments in a close-coupled position, which allows for rapid heating of the substrate and, correspondingly, of the catalyst composition (e.g., the LT-NA catalyst composition) coated therein.

[0125] Any suitable substrate for the catalytic articles disclosed herein may be used, such as a monolith substrate of the type having fine parallel gas passages extending therethrough from an inlet or outlet end face of the substrate so that the passages are open to the fluid flow therethrough ("flow-through substrate"). Another suitable substrate is one having a plurality of fine, substantially parallel gas 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 Publication No. 2016 / 070090, the entire contents of which are incorporated herein by reference.

[0126] 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 discussed further herein below.

[0127] Flow-Through Substrate In some embodiments, the substrate is a flow-through substrate (e.g., a monolith substrate, including a flow-through honeycomb monolith substrate). Flow-through substrates have 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 essentially linear paths from the fluid inlet to the fluid outlet, are defined by walls on which a catalytic coating is disposed so that gas flowing through the passages contacts the catalytic material. The flow passages in flow-through substrates are thin-walled channels and can be of any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, or circular. Flow-through substrates can be ceramic or metallic, as described above.

[0128] The flow-through substrate may be, for example, about 50 in 3 ~About 1200in 3and a cell density (inlet opening) of about 60 cells per square inch (cpsi) to about 500 cpsi or up to 900 cpsi, e.g., about 200 to about 400 cpsi, and a wall thickness of about 50 to about 200 microns or about 400 microns.

[0129] Wall flow filter substrate In some embodiments, the substrate is a wall-flow filter, which generally has a plurality of fine, substantially parallel gas passages extending along the longitudinal axis of the substrate. Typically, each passage is blocked at one end of the substrate body, and every other passage is blocked at the opposite end face. Such monolith 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, oval, triangular, hexagonal, or other polygonal cross sections.

[0130] Figure 2 is a perspective view of an exemplary wall-flow filter. A cross-section of a monolithic wall-flow filter substrate portion is shown in Figure 2, illustrating alternating blocked and open passages (cells). Blocked or blocked ends 100 alternate with open passages 101, with the 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.

[0131] The wall flow filter article substrate may be, for example, about 50 cm 3 , about 100cm 3 , about 200cm 3 , about 300cm 3, about 400cm 3 , about 500cm 3 , about 600cm 3 , about 700cm 3 , about 800cm 3 , about 900cm 3 , or approximately 1000 cm 3 From about 1500cm 3 , about 2000cm 3 , about 2500cm 3 , about 3000cm 3 , about 3500cm 3 , about 4000cm 3 , about 4500cm 3 , or approximately 5000 cm 3 Wall-flow filter substrates typically have 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.

[0132] The walls of a wall-flow filter are porous, typically having a wall porosity of at least about 50% or at least about 60% and an average pore size of at least about 5 microns before the application of a functional coating. For example, in some embodiments, the wall-flow filter article substrate has a porosity of ≥ 50%, ≥ 60%, ≥ 65%, 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 before the application of a catalytic coating. The terms "wall porosity" and "substrate porosity" are interchangeable and mean the same thing. Porosity is the ratio of 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 for high loading of catalyst composition without excessive backpressure during operation.

[0133] Coating layer Substrates are coated with the LT-NA and / or DOC compositions disclosed herein to form articles. The coating can include one or more thin, adherent coating layers disposed on and attached to at least a portion of the substrate. In some embodiments, the articles can include the use of one or more layers and combinations of one or more layers. The coating composition can be present only on the inlet side, only on the outlet side, on both the inlet and outlet sides of the substrate wall, or the wall itself can consist entirely or partially of the coating composition. The coating can be on the substrate wall surface and / or within pores in the substrate wall that are "in" and / or "on" the substrate wall. Thus, the phrase "catalytic coating disposed on a substrate" refers to any surface, e.g., on the wall surface and / or pore surface. The coating layers can include individual functional components, i.e., the LT-NA composition and / or DOC catalyst composition, each described herein.

[0134] The catalyst composition may be applied in the form of a washcoat, typically containing a support material having catalytically active species thereon. The catalyst components may also be combined in a single washcoat in some embodiments. A washcoat is formed by preparing a slurry containing the support at a specific solids content (e.g., about 10 to about 60 wt.%) in a liquid vehicle, then applying the slurry to the substrate, drying, and calcining 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 several desired layers are applied. In one or more embodiments, the catalyst material is applied to the substrate as a washcoat. A binder may also be used, as described above.

[0135] The above catalyst compositions are generally independently mixed with water to form a slurry for the purpose of coating a catalyst substrate, such as a honeycomb-type substrate. In addition to the catalyst particles, the slurry may optionally contain a binder (e.g., alumina, silica), a water-soluble or water-dispersible stabilizer, a promoter, an associative thickener, and / or a surfactant (including 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 thereby adjust the pH. For example, in some embodiments, the pH of the slurry is adjusted by the addition of aqueous ammonium hydroxide or nitric acid.

[0136] The slurry can be milled to improve particle mixing and the formation of a homogeneous 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 to 60% by weight, more specifically, about 20 to 40% by weight. In one embodiment, the slurry after milling has a D of about 10 to about 40 microns, preferably 10 to about 30 microns, and more preferably about 10 to about 15 microns. 90 It is characterized by particle size.

[0137] The slurry is then coated onto a catalyst substrate using any washcoating technique known in the art. In one embodiment, the catalyst 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, typically for about 10 minutes to about 3 hours. After drying and calcination, the final washcoat coating layer can be considered substantially free of solvent.

[0138] After calcination, the catalyst loading achieved by the washcoating technique described above can be determined by calculating the difference between the coated and uncoated weights of the substrate. As will be apparent to those skilled in the art, 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 the coating to a desired loading level or thickness, i.e., two or more washcoats may be applied.

[0139] Washcoats can be applied so that the different coating layers are in direct contact with the substrate. Alternatively, one or more "undercoats" may be present so 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 the undercoat). One or more "overcoats" may be present so 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 the overcoat).

[0140] Different coating layers may be in direct contact with each other without an "intermediate" overlapping zone. Alternatively, different coating layers may not be in direct contact, with a "gap" between the two zones. In the case of an "undercoat" or "overcoat," the gap between 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 contain one or more functional compositions or may be free of functional compositions.

[0141] The catalytic coating may comprise two or more thin, adherent layers, i.e., layers that adhere to each other and to the substrate. The overall coating comprises individual "coating layers." The catalytic coating may advantageously be "zoned" and may comprise zoned catalytic layers. This may also 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. Different coating layers may be adjacent to each other and not overlap each other. Alternatively, different layers may overlap each other to provide a third, "intermediate" zone, which may extend, for example, from about 5% to about 80% of the substrate length, such as about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, or about 70% of the substrate length.

[0142] The different layers may each extend the entire length of the substrate, or each extend a portion of the length of the substrate, and may overlay or underlay one another either partially or completely. Each of the different layers may extend from either the inlet end or the outlet end.

[0143] The different catalyst compositions can each be present in a separate coating layer. For example, one coating layer can include the LT-NA composition disclosed herein, and another coating layer can include the DOC composition disclosed herein. Alternatively, in some embodiments, the LT-NA composition and the DOC composition, each disclosed herein, can be combined and applied to the substrate as a single homogenous layer. In further embodiments, the LT-NA composition can be present in one layer, and the DOC composition components can be divided among one or more additional layers.

[0144] Thus, discussions relating to different layers may apply to any of these layers. The catalytic coating may include one, two, or more than two coating layers. The one or more coating layers together comprise the catalytic composition.

[0145] 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; or four different zones. 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 a certain length from the outlet end 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.

[0146] In some embodiments, the first washcoat is disposed directly on the substrate and the second washcoat is disposed over at least a portion of the first washcoat. In some embodiments, the second washcoat is disposed directly on the substrate and the first washcoat is disposed over at least a portion of the second washcoat. In some embodiments, the first and second washcoat compositions are combined and disposed on the substrate as a single homogeneous layer. In some embodiments, the catalyst article has a zoned configuration, where the first washcoat is disposed on the catalyst substrate from the inlet end for about 10% to about 70% of its total length, and the second washcoat is disposed on the catalyst substrate from the outlet end for about 30% to about 90% of its total length.

[0147] Figures 3A, 3B, and 3C show several 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 illustration; 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 Figure 3A, coating layer 201 extends approximately 50% of the substrate length from the inlet toward the outlet, and coating layer 202 extends approximately 50% of the substrate length from the outlet toward the inlet. The coating layers are adjacent to each other, providing an inlet upstream zone 203 and an outlet downstream zone 204. In Figure 3B, coating layer 202 extends approximately 50% of the substrate length from the outlet, and layer 201 extends more than 50% of the length from the inlet and overlays portions 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, with layer 201 overlaying layer 202. The substrate in Figure 3C does not contain 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. The configuration of such coating layers is not limiting.

[0148] 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. In some embodiments, the LT-NA catalyst composition and the DOC composition are present on the substrate in a single homogenous layer. In some embodiments, the LT-NA catalyst composition and the DOC composition are present in separate, distinct layers. In some embodiments, the LT-NA catalyst composition and the DOC composition are present in a zoned configuration. 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.

[0149] The loading of the present catalyst coating (e.g., LT-NA and / or DOC) on the substrate will depend on substrate characteristics such as porosity and wall thickness. Typically, wall-flow filter catalyst loadings will be lower than catalyst loadings on flow-through substrates. Catalyzed 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 generally have a loading of, for example, about 0.3 to 5.5 g / in based on the substrate. 3 , or about 0.4 g / in 3 , approximately 0.5 g / in 3 , approximately 0.6 g / in 3 , approximately 0.7 g / in 3 , about 0.8g / in 3 , approximately 0.9 g / in 3 , or 1.0 g / in 3 ~approx. 1.5g / in 3 , approximately 2.0 g / in 3 , approximately 2.5 g / in 3 , approximately 3.0 g / in 3 , approximately 3.5 g / in 3 , approximately 4.0 g / in 3 , approximately 4.5g / in 3 , approximately 5.0 g / in 3 , or approximately 5.5 g / in 3The 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.

[0150] In some embodiments, the catalyst article has a viscosity of about 15 g / ft 3 ~about 200g / ft 3 or approximately 60g / ft 3 ~Approx. 120g / ft 3 The first Pd component is included in the loading amount.

[0151] In some embodiments, the LT-NA article has a viscosity of about 1 g / in 3 ~approx. 5g / in 3 or approximately 2 g / in 3 ~About 3g / in 3 zeolite (e.g., first and second zeolites) loading.

[0152] In some embodiments, the catalyst article has a viscosity of about 15 g / ft 3 ~about 200g / ft 3 It contains Pt nanoparticles at a loading of .

[0153] Exhaust Gas Treatment Systems The present disclosure further provides a method for reducing NO in an exhaust gas stream from an internal combustion engine comprising the LT-NA catalyst article as disclosed herein. x In another aspect of the present invention, an exhaust gas treatment system is provided for reducing the level of NO in an exhaust gas stream from an internal combustion engine. xMethods for reducing the level of oxidative stress are provided, the methods comprising contacting an exhaust gas stream with the LT-NA catalytic article disclosed herein or the emissions treatment system disclosed herein. Accordingly, the present invention provides emissions treatment systems incorporating the catalytic articles described herein, e.g., emissions treatment systems generally comprising an engine producing 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 may be, for example, a diesel engine operating under combustion conditions with more air than required for stoichiometric combustion, i.e., lean conditions. In other embodiments, the engine may be an engine associated with a stationary source (e.g., a generator or pumping station). In some embodiments, the emissions treatment system further comprises one or more additional catalytic components. The relative placement of the various catalytic components present in the emissions treatment system may vary.

[0154] 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.

[0155] 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 generating NO at low temperatures. x and NO captured at high temperatures. x The catalyst composition includes an LT-NA catalyst article suitable for releasing NO. x The adsorbent component provides desirable NO under various engine operating conditions. x Provides adsorption and desorption properties.

[0156] 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 exhaust gas emission system reaches a temperature high enough for other catalytic components to activate. Only then can the released NO be efficiently converted to N and exit the exhaust gas treatment system. Therefore, the LT-NA catalyst article is typically positioned upstream of any catalytic components involved in converting the 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 the DOC and / or CSF components.

[0157] In some embodiments, the LT-NA catalyst article is not disposed in a separate component (e.g., on a separate substrate) but may be included in the same component, such as a diesel oxidation catalyst (DOC), a catalyzed soot filter (CSF), or a selective catalytic reduction (SCR) catalyst component, where the catalyst composition for such a component is applied to the substrate in a zoned or layered configuration. In some embodiments, the LT-NA and (DOC) are combined in a single catalyst article.

[0158] The systems of the present disclosure may include, in addition to the LT-NA catalyst article, other catalyst components, such as 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 (CO). Preferably, the DOC can convert at least 50% of the CO or HC components present in the exhaust gas. The DOC may be located downstream of the LT-NA catalyst article, for example. In some embodiments, the DOC is located upstream of the SCR catalyst component and / or the soot filter.

[0159] 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 emissions treatment systems are capable of converting NO 2 to NO 3 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 conditions of low loading typically associated with lower exhaust temperatures. x Preferably, the SCR catalyst component must be 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 that it possesses the ability to catalyze the reaction of O2 with any excess NH3 to form N2, so that NH3 is not emitted to the atmosphere. Useful SCR catalyst components for use in emissions treatment systems should also be thermally resistant to temperatures above 650°C. Such high temperatures may be encountered during the 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.

[0160] In some embodiments, the exhaust gas treatment system further includes one or more of a lean NOx trap (LNT), a selective catalytic reduction (SCR) catalyst, an ammonia or ammonia precursor injection component, a catalyzed soot filter (CSF), or an ammonia oxidation (AMOx) catalyst.

[0161] A particular illustrative exhaust gas treatment system may be more readily understood by reference to FIG. 4 , which illustrates a schematic diagram of a non-limiting exhaust gas treatment system 20 according to an embodiment of the present disclosure. Those skilled in the art will recognize that it may be desirable to arrange the relative positions of each item in a different order than illustrated herein. Such alternative orderings are contemplated by the present disclosure. As shown, the emissions treatment system 20 may include a series of multiple catalyst components downstream of an engine 22, such as a diesel engine. At least one of the catalyst components may be an LT-NA catalyst of the present invention, as described herein. The catalyst composition of the present invention may be combined with multiple additional catalyst materials and may be positioned in various locations relative to the additional catalyst materials. While FIG. 4 illustrates a series of five catalyst components 24, 26, 28, 30, and 32, the total number of catalyst components may vary, and five components is merely an example. Those skilled in the art will recognize that it may be desirable to arrange the relative positions of each item in a different order than illustrated herein. Such alternative orderings are contemplated by the present disclosure.

[0162] Without limitation, Table 1 presents various exhaust gas treatment system configurations of one or more embodiments. Note that each catalyst is connected to the next catalyst via an exhaust conduit such that the engine is upstream of catalyst A, which is upstream of catalyst B, which is upstream of catalyst C, which is upstream of catalyst D, and which is upstream of catalyst E (if present). References to components A-E in the table may be cross-referenced with the same symbols in FIG. 4.

[0163] References to SCR in the tables refer to an SCR catalyst, i.e., any suitable SCR catalyst available in the art.

[0164] References to AMOx in the tables refer to an ammonia oxidation catalyst that can be provided downstream of the catalyst of one or more embodiments of the present invention to remove any fugitive ammonia from the exhaust gas treatment system. In certain embodiments, the AMOx catalyst can include a PGM component. In one or more embodiments, the AMOx catalyst can include a bottom coat having a PGM and a top coat having SCR functionality.

[0165] As will be appreciated by those skilled in the art, in the configurations listed in Table 1, any one or more of components A, B, C, D, or E can be disposed on a particulate filter, such as a wall-flow filter, or on a flow-through honeycomb substrate. In one or more embodiments, the engine exhaust system includes one or more catalyst components mounted in a location near the engine (direct-coupled location, CC), with an additional catalyst component mounted in an underbody location (underfloor location, UF). In one or more embodiments, the exhaust gas treatment system may further include a urea injection component. [Table 1]

[0166] Any of the illustrated exhaust gas treatment systems shown in FIG. 4 may be followed by a selective ammonia oxidation catalyst (AMOx) to remove NH3 released from the SCR catalyst components and selectively oxidize it to N2.

[0167] Method for treating an exhaust gas stream Aspects of the present disclosure are directed to the detection of NO in an exhaust gas stream from an internal combustion engine. x The present invention is directed to a method for reducing the levels of LT-NA in an exhaust gas stream, the method comprising contacting the exhaust gas stream with an LT-NA catalyst article of the present disclosure or an exhaust gas treatment system of the present disclosure.

[0168] In some embodiments, the method includes continuously passing an exhaust gas stream through contact with an LT-NA catalyst article, wherein the exhaust gas stream is at an initial temperature of about 150° C. or less and gradually warms during further engine operation; and removing NO from the exhaust gas stream until the exhaust gas stream reaches a predetermined temperature. x adsorbing and storing NO x The exhaust gas stream exiting the LT-NA article is adsorbed and stored with NO because the NO is released into the exhaust gas stream exiting the LT-NA article, and the exhaust gas stream increases in temperature and heats each downstream catalyst material to an operating temperature of about 200°C to about 450°C. x and continuously passing the mixture into contact with at least one downstream catalytic material for component removal.

[0169] The present articles, systems, and methods are suitable for treating exhaust gas streams from mobile emission sources such as trucks and automobiles. The present articles, systems, and methods are also suitable for treating exhaust streams from stationary sources such as power plants.

[0170] 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. [Example]

[0171] 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 thereof. 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 indicated.

[0172] Preparation of monolithic catalyst articles Various embodiments of the present disclosure were prepared according to the following examples. The composition of each article is summarized in Table 2 below.

[0173] Example 1. (LT-NA, reference article). Ferrierite zeolite material (FER) was incipiently wet impregnated with a diluted Pd(NO3)2 solution, then dried in air at 110°C for 2 hours, followed by calcination in air at 550°C for 1 hour. A diluted Zr acetate solution was prepared, to which the calcined Pd / FER powder was added to form a slurry suspension with a solid content of approximately 50%. The slurry was then mixed to a final particle size of D 90 The catalyst was then crushed to a particle size of 10-12 μm. The slurry was then coated onto a 400 / 4 honeycomb substrate at a solids content of 42-46%. After drying, the catalyst was calcined in air at 590°C for 1 hour. The Pd loading was 80 g / ft 3 and the zeolite washcoat loading was 2.5 g / in 3 and the resulting ZrO2 loading was about 5% of the washcoat composition.

[0174] Example 2. (LT-NA, product of the present invention). Ferrierite zeolite material (FER) was incipiently wet impregnated with a diluted Pd(NO3)2 solution, then dried in air at 110°C for 2 hours, and subsequently calcined in air at 550°C for 1 hour. A diluted Zr acetate solution was prepared, to which the calcined Pd / FER powder was added to form a slurry suspension with a solid content of approximately 50% or more. The slurry was then dried to a final particle size of D 90The catalyst was ground to a particle size of 10-12 μm. A colloidal Pt solution was added dropwise to this slurry. The colloidal Pt solution, containing preformed Pt nanoparticles, was used to prevent the Pt from entering the pores of the zeolite and being ion-exchanged. The slurry was then coated onto a 400 / 4 honeycomb substrate at a solids content of 40-46%. After drying, the catalyst was calcined in air at 590 °C for 1 hour. The Pd loading was 80 g / ft. 3 and the zeolite washcoat loading was 2.5 g / in 3 and the Pt loading is 18g / ft 3 (or about 0.4% Pt on zeolite), resulting in a ZrO2 loading of about 5% of the washcoat composition.

[0175] Example 3. (LT-NA, product of the present invention). Two catalyst compositions with different Pt / Pd ratios were prepared. Zeolite ferrierite material (FER) was impregnated with a diluted Pd(NO3)2 solution by incipient wetness, then dried in air at 110°C for 2 hours, followed by calcination in air at 550°C for 1 hour. A diluted Zr acetate solution was prepared, to which the calcined Pd / FER powder was added to form a slurry suspension with a solid content of approximately 50% or more. The slurry was then mixed to a final particle size D 90 The catalyst was then crushed to a particle size of 10-12 μm. To this slurry, a colloidal Pt solution was added dropwise, followed by the Pd nitrate precursor solution. The slurry was then coated onto a 400 / 4 honeycomb substrate at a solids content of 40-46%. After drying, the catalyst was calcined in air at 590 °C for 1 hour. The Pd loading into the zeolite by impregnation was 80 g / ft. 3 and the zeolite washcoat loading was 2.5 g / in 3 and the total Pt-Pd loading after addition was 18 g / ft 3 (or about 0.4% Pt-Pd on the zeolite) with a Pt-Pd ratio of either 10 / 1 or 2 / 1.

[0176] Example 4. (LT-NA / DOC, reference article). In this example, the Pd / FER slurry (Slurry A) and the PGM / Al2O3 slurry (Slurry B) were prepared separately and then blended into one slurry to form a single homogeneous layer before coating it onto the substrate.

[0177] Slurry A: Ferrierite zeolite material (FER) was incipiently wet impregnated with a diluted Pd(NO3)2 solution, then dried in air at 110°C for 2 hours, followed by calcination in air at 550°C for 1 hour. A diluted Zr acetate solution was prepared, to which the calcined Pd / FER powder was added to form a slurry suspension with a solid content of approximately 50%. The slurry was then refined to a final particle size D 90 The powder was crushed until the particle size reached 10-12 μm. The Pd loading was 80 g / ft 3 and the zeolite loading was 2.5 g / in 3 It was.

[0178] Slurry B: 5% SiO-AlO support material was incipiently impregnated with a diluted Pd nitrate solution and then added to a diluted colloidal Pt solution. The resulting slurry was milled to a 10-15 μm D 90 and then combined with Slurry A to form a single slurry. The substrate was coated as described in the previous example. The total Pt-Pd loading was 27 g / ft 3 The Pt / Pd weight ratio was 2 / 1.

[0179] Example 5. (LT-NA / DOC, reference article). In this example, a two-layer embodiment was prepared. The LT-NA bottom layer was prepared similarly to that described in Example 1. For the DOC top layer, a 5% SiO2-Al2O3 material was incipiently wet impregnated with a dilute Pd nitrate solution to form a slurry suspension. The slurry was coated with 10-15 μm D 90The slurry was then ground to a powder, followed by the addition of H-form beta zeolite (HBEA) and alumina binder material (3.5% of the total washcoat solids). The slurry was then coated onto a Pd / FER / ZrO2 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 , and the beta zeolite loading was 0.35 g / in 3 , and Pd loading of 36g / ft 3 is.

[0180] Example 6. (LT-NA / DOC, product of the present invention). In this example, a two-layer embodiment was prepared: a Pd / FER / ZrO2 / colloidal Pt LT-NA bottom layer was prepared in a manner similar to Example 2, and a DOC top layer was prepared in a manner similar to Example 5.

[0181] Example 7. (LT-NA / DOC, reference article). In this example, two separate two-layer embodiments were prepared, each with a different Pt / Pd ratio in the DOC layer. The Pd / FER / ZrO2 LT-NA bottom layer was prepared similarly to Example 1. For the DOC top layer, a 5% SiO2-Al2O3 material was incipiently wet impregnated with a diluted Pd nitrate solution and then added to a diluted colloidal Pt solution to form a slurry suspension. The pH of the slurry suspension was adjusted to 4-5 with diluted HNO3. The slurry was then filled with 12-15 μm D 90 The slurry was then ground to a powder, and beta zeolite and alumina binder material (3.5% of the 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 hour. The Si-alumina loading was 0.75 g / in 3 , Beta zeolite loading is 0.35g / in 3 , total DOC coated PGM loading is 27g / ft 3 , and the Pt / Pd weight ratio of the DOC layer was 2 / 1 or 1 / 2.

[0182] Example 8 (LT-NA, reference article). Pd / Beta zeolite (BEA) and Pd / FER slurries were prepared using the procedure in Example 1, respectively. The Pd% in each zeolite was maintained at 1.74%. The two slurries were mixed at a 1 / 1 solids ratio, and the resulting slurry was 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 80g / ft 3 and the total zeolite washcoat loading was 2.5 g / in 3 and the resulting ZrO2 loading after firing was about 5% of the washcoat composition.

[0183] Example 9 (LT-NA / DOC, article of the present invention): Pd / BEA and Pd / FER slurries were each prepared using the procedure in Example 1. The Pd% in each zeolite was maintained at 1.74%. The two slurries were mixed at a 1 / 1 solids ratio to give a total of 18 g / ft 3 A colloidal Pt solution of 10 ... 3 and the total zeolite washcoat loading was 2.5 g / in 3 The resulting ZrO2 loading after firing was about 5% of the washcoat composition. The Pt / Pd weight ratio was about 1 / 4. [Table 2]

[0184] Evaluation of monolithic catalyst articles. The monolith catalyst articles prepared in Examples 1-7 above were tested in a diesel vehicle simulator in both steady-state and transient tests. The gas mixture during the steady-state tests consisted of 100 ppm NO, 250 ppm C2H4, 500 ppm CO, 5% H2O, 10% O2, and 5% CO2 with N2 balance. The catalyst dimensions were 1 x 1 x 3 inches, and the space velocity was 30,000 h2. -1 The catalyst was first treated in an O2 / H2O / CO2 / N2 mixture at 500°C for 5 min, and then subjected to adsorption in the complete mixture at 100°C for 10 min. Desorption was carried out in an O2 / H2O / CO2 / N2 mixture from 100°C to 500°C at a ramp rate of 20°C / min. The adsorption-desorption test was carried out three times for each article.

[0185] For the transient FTP test, the feed composition was derived from a diesel engine and contained only NO, inlet NO x Each catalyst was pretreated in situ in 10% O / 5% H O / 5% CO / N for 5 min at 550 °C and then subjected to three consecutive FTP cycles. x The adsorption efficiency was calculated as the NO adsorbed from the start until the inlet temperature first reached 200°C. x was defined as the proportion of

[0186] Example 10. (Comparative results of Examples 1 and 2). The performance of Example 1 (reference) and Example 2 (invention) was compared after hydrothermal aging at 750° C. for 25 hours. Both examples showed similar adsorption profiles and NO x The adsorption capacity of NO was shown in Figure 5. x In the case of desorption, Example 2 shows that both the onset temperature and peak temperature of the first desorption are low. Example 2 also shows that NO x This showed a narrower temperature window for complete desorption (151-397°C in Example 2 vs. 170-476°C in Example 1). This data demonstrates the surprising beneficial effect of adding colloidal Pt to the Pd-impregnated zeolite material in the LT-NA composition.

[0187] Example 11. (Comparative results of Example 2 and Example 4). The performance of inventive Examples 2 and 4 was compared after hydrothermal aging at 750°C for 25 hours, which showed the effect of Pt location (i.e., relative to the zeolite as in Example 2, or relative to the alumina support as in Example 4). Both examples showed similar NO x The desorption profile of NO in Example 4, where Pt was not directly associated with the Pd / zeolite, is shown in Figure 6. x There appeared to be a slight adverse effect on adsorption.

[0188] Example 12. (Comparative results of Examples 1 and 3). The performance of two inventive embodiments (2:1 and 8:1 Pt / Pd ratios) according to Example 1 (reference) and Example 3 was compared after hydrothermal aging at 750° C. for 25 hours. Nearly identical activity was observed for both versions of Example 3 (FIG. 7), both of which showed favorable NO activity compared to Reference Example 1. x The desorption profile was shown.

[0189] Example 13. (Comparative results of Examples 5 and 6). The performance of Example 5 (reference) and Example 6 (invention) was compared after hydrothermal aging at 750° C. for 25 hours. Both examples showed similar NO x Although an adsorption profile was observed, the lack of Pt associated with either the Pd / zeolite washcoat or the DOC layer (Example 5) prevented NO adsorption. x Desorption was shifted to significantly higher temperatures (Figure 8). In comparison, the data from Example 6 demonstrate the surprising beneficial effect of adding colloidal Pt to the LT-NA bottom coat, reducing the NO observed in Example 5. x Without wishing to be bound by theory, the presence of Pt reversed the unfavorable temperature shift of desorption by modulating the oxidation of CO / HC / NO. x It is believed that it may play a role in enhancing desorption.

[0190] Example 14. (Comparison of Example 6 with Examples 5 and 7). The performance of Examples 5 and 7 (reference examples without and with Pt in the DOC layer, respectively) and Example 6 (invention) after 25 hours of hydrothermal aging at 750°C was compared for NOx adsorption from 0 to 400 seconds of the first FTP cycle. All three examples showed nearly complete NOx adsorption by 160 seconds. x Example 5 showed NO adsorption for approximately 300 seconds at relatively high temperatures (200 to 250°C). x However, in Example 6, when colloidal Pt was added to the Pd / zeolite bottom coat, NO was adsorbed at approximately 240°C. x Example 7, which contained both Pt and Pd in ​​the DOC layer, showed a similar desorption profile to Example 6.

[0191] Between 0 and 400 seconds of the second FTP cycle, Example 5 compared the incomplete NO in the first FTP cycle. x By desorption, cold start NO x The results showed that the adsorption was significantly reduced (Fig. 10). Example 6 showed good NO adsorption in 0-180 seconds. x This indicates that the addition of colloidal Pt to the Pd / zeolite layer LT-NA enhances NO adsorption. x This shows desorption. The same effect was observed in Example 7, which included both Pt and Pd in ​​the DOC topcoat. In some cases, manufacturers may desire a Pd-only DOC layer. The results of this experiment demonstrate that the embodiment according to Example 6 can improve the performance of the LT-NA function in such cases.

[0192] The performance of Examples 5, 6, and 7 after 25 hours of hydrothermal aging at 750°C was compared from 0 to 400 seconds of the first FTP cycle in terms of NO production (Figure 11). NO is an undesirable by-product of DOC catalytic oxidation and typically increases with increasing Pt loading in the DOC. Example 5, containing a Pd-only DOC, did not produce any NO until 200 seconds after a cold start. In contrast, Example 7, containing a 2 / 1 DOC layer Pt / Pd ratio, produced more NO starting at a relatively low temperature. Conversely, and surprisingly, Example 6 did not produce significantly higher amounts of NO, demonstrating efficient NO production. x A favorable balance between desorption and minimal N2O production was ensured.

[0193] Example 15 (Comparative results of Examples 8 and 9). The performance of Example 8 (a reference example with Pd / BEA-FER LT-NA) and Example 9 (an inventive example with Pd / BEA-FER / colloidal Pt LT-NA) after 25 hours of hydrothermal aging at 650°C was compared (Figure 12). Example 9 showed a significantly higher NO than Example 8. x Both the onset and peak temperatures of release were shifted by approximately 10°C.

[0194] Furthermore, compared to the results of Example 2 (FIG. 5), the effect of adding colloidal Pt to the mixed Pd / BEA-FER zeolite LT-NA composition of Example 9 was small. Without wishing to be bound by theory, the Pd / BEA LT-NA composition more readily releases NO at low temperatures compared to the Pd / FER. x is thought to emit

Claims

1. Low temperature NO ｘ 1. An adsorbent (LT-NA) catalyst composition comprising: a first zeolite; a first palladium component; and a plurality of platinum nanoparticles; at least a portion of the first palladium component is ion-exchanged in the first zeolite; and At least a portion of the platinum nanoparticles are dispersed on the first zeolite. LT-NA catalyst composition.

2. 10. The LT-NA catalyst composition of claim 1, wherein the platinum nanoparticles have an average particle size of about 1 to about 50 nm.

3. 10. The LT-NA catalyst composition of claim 1, wherein the platinum nanoparticles have an average particle size of about 1 to about 20 nm.

4. 10. The LT-NA catalyst composition of claim 1, wherein the platinum nanoparticles have an average particle size of about 1 to about 10 nm.

5. 10. The LT-NA catalyst composition of claim 1, wherein the platinum nanoparticles have an average particle size of about 1 to about 3 nm.

6. 6. The LT-NA catalyst composition of any one of claims 1 to 5, wherein the first palladium component is present in an amount of from about 0.01 wt % to about 10 wt %, based on the weight of the first zeolite, calculated as elemental palladium.

7. 7. The LT-NA catalyst composition of any one of claims 1 to 6, further comprising a first refractory metal oxide component, wherein at least a portion of said platinum nanoparticles are dispersed on said first refractory metal oxide component.

8. a portion of the platinum nanoparticles dispersed on the first zeolite; 8. The LT-NA catalyst composition of claim 7, wherein a portion of said platinum nanoparticles are dispersed on said first refractory metal oxide component.

9. The first refractory metal oxide component is selected from the group consisting of gamma alumina and about 2% to about 10% SiO ２ 9. The LT-NA catalyst composition of claim 7 or 8, comprising an alumina doped with .

10. 10. The LT-NA catalyst composition of any one of claims 7 to 9, wherein the weight ratio of said first zeolite to said first refractory metal oxide component is from about 10 to about 0.

1.

11. 11. The LT-NA composition of any one of claims 1 to 10, wherein the platinum nanoparticles are present in an amount of about 0.1 wt % to about 10 wt %, based on the weight of the first zeolite, calculated as elemental platinum.

12. 12. The LT-NA catalyst composition of any one of claims 1 to 11, wherein the first zeolite is an aluminosilicate zeolite having a silica-to-alumina ratio (SAR) of about 5 to about 100.

13. 13. The LT-NA catalyst composition of claim 12, wherein the aluminosilicate zeolite has an SAR of about 10 to about 40.

14. The LT-NA catalyst composition according to any one of claims 1 to 13, wherein the first zeolite has a framework type selected from the group consisting of ABW, ACO, AEI, AEL, AEN, AET, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, APC, APD, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, EZT, FAU, FER, GIS, GME, GON, GOO, HEU, IFR, IFY, IHW, IMF, IRN, ISV, ITE, ITG, ITH, ITW, IWR, IWS, IWV, IWW, JBW, JRY, JSR, JST, KFI, LAU, LEV, LOV, LTA, LTF, LTL, LTN, MAZ, MEI, MEL, MER, MFI, MFS, MON, MOR, MOZ, MRE, MSE, MTF, MTT, MVY, MTW, MWF, MWW, NAB, NAT, NES, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, PAR, PAU, PCR, PHI, PON, PUN, RHO, RON, RRO, RSN, RTE, RTH, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SCO, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGF, SIV, SOF, SOS, SSF, SSY, STF, STI, STO, STT, STW, SVR, SZR, TER, THO, TON, TSC, TUN, UEI, UFI, UOS, USI, UTL, UWY, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, and mixtures or twins thereof.

15. 15. The LT-NA catalyst composition of any one of claims 1 to 14, wherein the first zeolite is a medium pore zeolite having a framework 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.

16. 16. The LT-NA catalyst composition of any one of claims 1 to 15, wherein the first zeolite is a medium pore zeolite having a framework type selected from FER, MEL, MFI, STT, and mixtures or intergrowths thereof.

17. 17. The LT-NA catalyst composition of any one of claims 1 to 16, wherein the first zeolite is ferrierite (FER).

18. The method further comprises a second zeolite, wherein the second zeolite is selected from the group consisting of AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, 18. The LT-NA catalyst composition of any one of claims 1 to 17, wherein the second zeolite is a large pore zeolite having a framework type selected from the group consisting of RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFW, SOF, SOS, STO, SSF, SSY, USI, UWY, VET, and mixtures or intergrowths thereof, and a portion of the first palladium component is ion-exchanged into the second zeolite.

19. 19. The LT-NA catalyst composition of claim 18, wherein the second zeolite is beta zeolite (BEA).

20. 20. The LT-NA catalyst composition of claim 18 or 19, wherein a portion of the platinum nanoparticles are dispersed on the second zeolite.

21. The LT-NA composition is mixed with a 1:1 NO mixture at a temperature of about 20° C. to about 200° C. ｘ / Pd molar ratio and NO present in the exhaust gas stream. ｘ and removing NO from the exhaust gas stream in an amount of at least 30 to 100% of the theoretical amount, based on the total amount of ｘ The LT-NA catalyst composition of any one of claims 1 to 20, which absorbs a component.

22. The LT-NA catalyst composition is heated at a temperature of about 150° C. to about 300° C., and the NO adsorbed on the LT-NA catalyst composition is ｘ NO in an amount of at least 35 to about 100% by weight based on the total amount of ingredients. ｘ The LT-NA catalyst composition of any one of claims 1 to 21, wherein the component is released back into the exhaust gas stream.

23. The LT-NA catalyst composition, after hydrothermal aging at 750-800°C for a period of about 16 to about 80 hours, exhibits a NO 3 content before hydrothermal aging. ｘ The NO adsorption capacity is about 0.8 to about 2 times. ｘ 23. The LT-NA catalyst composition of any one of claims 1 to 22, having an adsorption capacity.

24. 24. An LT-NA catalyst article for treating an exhaust stream of an internal combustion engine, the LT-NA catalyst article comprising: a substrate having an inlet end and an outlet end defining an overall length; and a first washcoat disposed on at least a portion of the substrate, the first washcoat comprising the LT-NA catalyst composition of any one of claims 1-23.

25. 25. The LT-NA catalyst article of claim 24, wherein the substrate comprises a honeycomb substrate in the form of a wall-flow filter or a flow-through substrate.

26. 26. The LT-NA catalyst article of claim 24 or 25, further comprising a second washcoat comprising a diesel oxidation catalyst (DOC) composition disposed on at least a portion of the substrate.

27. 27. The LT-NA catalyst article of claim 26, wherein the DOC composition comprises a second Pd component and a second refractory metal oxide component, the second Pd component being supported on the second refractory metal oxide component.

28. The second refractory metal oxide is gamma alumina or about 2% to about 10% SiO ２ 28. The LT-NA catalyst article of claim 27, comprising an alumina doped with

29. The LT-NA catalyst article of any one of claims 26 to 28, wherein the DOC composition further comprises a third zeolite.

30. 30. The LT-NA catalyst article of claim 29, wherein the third zeolite comprises beta zeolite (BEA) substantially free of any platinum group metal (PGM) species.

31. 31. The LT-NA catalyst article of any one of claims 26-30, wherein the first and second washcoats are present in a layered configuration, the first washcoat being disposed directly on the substrate and the second washcoat being disposed on at least a portion of the first washcoat.

32. 31. The LT-NA catalyst article of any one of claims 26-30, wherein the first and second washcoats are present in a layered configuration, the second washcoat being disposed directly on the substrate, and the first washcoat being disposed on at least a portion of the second washcoat.

33. 31. The LT-NA catalyst article of any one of claims 26 to 30, wherein the first washcoat and the second washcoat are combined and disposed on the substrate in a single homogenous layer.

34. 31. The LT-NA catalyst article of any one of claims 26-30, wherein the first and second washcoats are present in a zoned configuration, the first washcoat being disposed on the catalyst substrate from the inlet end for about 10% to about 70% of its total length, and the second washcoat being disposed on the catalyst substrate from the outlet end for about 30% to about 90% of its total length.

35. An exhaust gas treatment system comprising the LT-NA catalyst article of any one of claims 24 to 34, wherein the LT-NA catalyst article is downstream of and in fluid communication with an internal combustion engine.

36. Lean NO ｘ 36. The exhaust gas treatment system of claim 35, further comprising one or more of a trap (LNT), a selective catalytic reduction (SCR) catalyst, an ammonia or ammonia precursor injection component, a catalyzed soot filter (CSF), or an ammonia oxidation (AMOx) catalyst.

37. NO in the exhaust gas stream from an internal combustion engine ｘ 37. A method for reducing the level of cadmium-ion-containing compounds comprising contacting the exhaust gas stream with the LT-NA catalyst article of any one of claims 24 to 34, or the exhaust gas treatment system of claim 35 or 36.

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