Selective catalytic reduction articles and systems

Abstract

Selective catalytic reduction (SCR) articles and systems are provided that are suitable for treating exhaust gas streams, for example, from diesel internal combustion engines, that provide high NOx conversion rates with simultaneously low N2O production. [Solution] A selective catalytic reduction article includes a substrate having a front upstream end and a rear downstream end that define the axial length of the substrate, the substrate having a catalytic coating thereon, the catalytic coating including a first coating layer including a first copper-containing molecular sieve and a second, different coating layer including a second copper-containing molecular sieve, the first copper-containing molecular sieve including copper oxide in an amount of 0.1 to 3 wt% relative to its total mass, the second copper-containing molecular sieve including a predetermined amount of copper oxide relative to its total mass, and the amount of copper oxide contained in the first copper-containing molecular sieve being less than the amount of copper oxide contained in the second copper-containing molecular sieve.

Description

[Technical field]

[0001] The present invention is directed to selective catalytic reduction (SCR) articles and systems suitable for use in the exhaust treatment of internal combustion engines. [Background technology]

[0002] Molecular sieves such as zeolites are used in catalysis of certain chemical reactions, for example, selective catalytic reduction (SCR) of nitrogen oxides with reducing agents such as ammonia, urea, or hydrocarbons. Zeolites are crystalline materials with fairly uniform pore sizes ranging from about 3 to about 25 angstroms in diameter, depending on the type of zeolite and the type and amount of cations contained in the zeolite lattice. Zeolites with 8-membered ring pore openings and double 6-membered ring secondary building units, especially zeolites with cage-like structures, are of interest as SCR catalysts. Included in this category are zeolites with the chabazite (CHA) crystal structure, which is a small pore zeolite with 8-membered ring pore openings (about 3.8 angstroms) accessible through its three-dimensional porosity. The cage-like structure results from the linking of double 6-membered ring building units by four rings.

[0003] Catalysts used in SCR processes should ideally be able to retain good catalytic activity under hydrothermal conditions over a wide range of operating temperature conditions, e.g., from about 150° C. to about 600° C. or higher. Hydrothermal conditions are encountered in practice because water is a by-product of fuel combustion, and high temperature hydrothermal conditions occur in diesel exhaust applications, such as during the regeneration of soot filters, a component of exhaust gas treatment systems used to remove carbonaceous particles.

[0004] The SCR process converts nitrogen oxides (NOx) into nitrogen (N 2 ) and water (H 2 O). The undesirable SCR by-product is nitrous oxide (N 2 O). Undesirable N 2 Reduce NOx in the exhaust stream of an internal combustion engine to N while minimizing the formation of O2 Improved articles, systems and processes for selectively converting undesirable N 2 O formation is (NO+NO 2 ) to N 2 The conversion can be observed as a mole percentage to O.

[0005] Nitrogen oxides (NOx) are 2 O, NO, N 2 O 3 , NO 2 , N 2 O 4 , N 2 O 5 OR NO 3 may include: Summary of the Invention [Means for solving the problem]

[0006] In one or more embodiments, the present disclosure provides catalytic articles, systems, and methods for treating exhaust gas streams containing nitrogen oxides. The articles, systems, and methods exhibit high NOx conversion while simultaneously reducing N 2 In certain embodiments, the articles, systems and methods are suitable for treating lean exhaust gas streams of diesel internal combustion engines.

[0007] In one or more embodiments, the present disclosure relates to selective catalytic reduction articles, systems incorporating such articles, and methods of utilizing such articles and systems. The selective catalytic reduction articles utilize at least two different catalytically active molecular sieves, and therefore advantageously provide high NOx conversion with low N 2The method provides a high O production. More specifically, at least a first copper-containing molecular sieve and a second copper-containing molecular sieve are utilized. The copper-containing molecular sieve is coated on at least one substrate. For example, a first coating layer of the first copper-containing molecular sieve and a second coating layer of the second copper-containing molecular sieve are coated on at least one substrate. The first and second coating layers can be coated on the same substrate or on different substrates. For example, the first substrate can have a first coating layer on which the first copper-containing molecular sieve is provided (e.g., in the form of a washcoat), and the second substrate can have a second coating layer on which the second copper-containing molecular sieve is provided (e.g., in the form of a washcoat). Preferably, the first substrate having the first coating layer is provided upstream of the second substrate having the second coating layer with respect to the flow path of the exhaust stream (the second substrate having the second coating layer is provided downstream of the first substrate having the first coating layer). Also, preferably, the first copper-containing molecular sieve in the first coating layer in such a configuration has a lower copper concentration than the copper concentration of the second copper-containing molecular sieve in the second coating layer. Thus, the coating layers are different due to the different copper concentrations. As another example, a substrate can have a first coating layer provided thereon (e.g., in the form of a washcoat) with a first copper-containing molecular sieve, and the same substrate can have a second coating layer provided thereon (e.g., in the form of a washcoat). In such a configuration, the second coating layer is preferably provided downstream of the first coating layer with respect to the flow path of the exhaust stream (therefore, the first coating layer is upstream from the second coating layer). Also, preferably, in such a configuration, the first copper-containing molecular sieve in the first coating layer has a copper concentration lower than the copper concentration of the second copper-containing molecular sieve in the second coating layer, and thus the substrate is divided such that the first zone comprises the first coating layer and the second zone comprises the second coating layer.The zones (and thus the coating layers) may or may not overlap, if desired. Providing a first copper-containing molecular sieve having a first copper concentration and a second copper-containing molecular sieve having a second, higher copper concentration can provide improved NOx conversion and low N, especially when the first copper-containing molecular sieve having a lower copper concentration is located upstream of the second copper-containing molecular sieve having a higher copper concentration. 2 It has been found that the selective catalytic reduction article advantageously achieves the results described herein with respect to O production. The present disclosure, in particular, in some embodiments, provides a selective catalytic reduction article comprising a substrate having a forward upstream end and an aft downstream end defining an axial length, the substrate having a catalytic coating thereon, the catalytic coating comprising a first coating layer comprising a first copper-containing molecular sieve and a second coating layer comprising a second copper-containing molecular sieve.

[0008] Advantageously, the article is compartmentalized to include a first upstream zone including a first coating layer including a first copper-containing molecular sieve, and a second downstream zone including a second coating layer including a second copper-containing molecular sieve.

[0009] The concentration of copper in the upstream zone may be equal to or less than the concentration of copper in the downstream zone, and / or the first molecular sieve may contain less copper than the second molecular sieve, and / or the concentration of the copper-containing molecular sieve in the upstream zone may be equal to or less than the concentration of the copper-containing molecular sieve in the downstream zone.

[0010] Also disclosed is a selective catalytic reduction system comprising a first selective catalytic reduction article comprising a first substrate comprising a first catalytic coating layer comprising a first copper-containing molecular sieve and a second selective catalytic reduction article comprising a second substrate comprising a second catalytic coating layer comprising a second copper-containing molecular sieve, the first and second articles being in fluid communication, e.g., the second article being downstream of the first article.

[0011] A selective catalytic reduction article or system containing a uniform concentration of CuCHA as the sole SCR catalyst achieves a NOx conversion of ≥ 90% (preferably ≥ 99%) and a NOx conversion of ≤ 50% (preferably ≤ 40%) under transient engine test conditions. 2 Also disclosed are selective catalytic reduction articles or systems that can provide ≦40% N O production, respectively. More specifically, the selective catalytic reduction articles, systems, or methods of the present disclosure can provide >90% NOx conversion while providing ≦40% N O production, particularly under transient engine test conditions as described elsewhere herein, as compared to articles, systems, or methods that include or use a uniform concentration of high Cu-containing CuCHA as the sole SCR catalyst. 2 The present disclosure also relates to improved performance through the use of zoning. For example, a selective catalytic reduction article, system, or method according to the present disclosure can include a substrate having a front upstream zone including a catalytic coating and a second downstream zone including a catalytic coating, and can be modified to provide >90% total NOx conversion, with the front upstream zone providing about 30% to about 80% total NOx conversion.

[0012] Also disclosed is an exhaust gas treatment system that includes the aforementioned SCR article or SCR system.

[0013] Also disclosed is a method of treating an exhaust stream containing NOx, comprising passing the exhaust stream through the SCR article, SCR system, or exhaust gas treatment system described above.

[0014] The present articles, systems and methods are particularly suitable for treating exhaust gases produced by diesel engines operating under combustion conditions with more air than is required for stoichiometric combustion, i.e., lean conditions.

[0015] The present invention includes, but is not limited to, the following embodiments.

[0016] Embodiment 1: A selective catalytic reduction article comprising a substrate having a front upstream end and an aft downstream end defining an axial length of the substrate, the substrate having a catalytic coating thereon, the catalytic coating comprising a first coating layer comprising a first copper-containing molecular sieve and a second, different coating layer comprising a second copper-containing molecular sieve.

[0017] Embodiment 2: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the catalytic coating is compartmentalized and includes a first zone adjacent a front upstream end of the substrate and including a first coating layer comprising a first copper-containing molecular sieve, and a second zone adjacent a rear downstream end of the substrate and including a second coating layer comprising a second, different copper-containing molecular sieve.

[0018] Embodiment 3: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first copper-containing molecular sieve in the first zone has a copper concentration that is less than or equal to the copper concentration of the second, different copper-containing molecular sieve in the second zone.

[0019] Embodiment 4: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the substrate is a porous wall-flow filter, or a flow-through monolith.

[0020] Embodiment 5: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first copper-containing molecular sieve comprises copper oxide in an amount of about 0.1 to about 4 wt % and the second copper-containing molecular sieve comprises copper oxide in an amount of about 3 to about 10 wt %, based on the total weight of the molecular sieves.

[0021] Embodiment 6: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first copper-containing molecular sieve comprises copper oxide in an amount of about 1 to about 2.5 wt. % and the second copper-containing molecular sieve comprises copper oxide in an amount of about 3 to about 6 wt. %, based on the total weight of the molecular sieves.

[0022] Embodiment 7: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the Cu / Al atomic ratio of each of the first copper-containing molecular sieve and the second copper-containing molecular sieve is independently from about 0.05 to about 0.55, and the Cu / Al atomic ratio of the first copper-containing molecular sieve is less than the Cu / Al atomic ratio of the second copper-containing molecular sieve.

[0023] Embodiment 8: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first coating layer extends a predetermined distance (length) from the front upstream end of the substrate toward the rear downstream end of the substrate and overlaps a portion of the second coating layer, and the second coating layer extends a predetermined distance from the rear downstream end of the substrate toward the front upstream end of the substrate.

[0024] Embodiment 9: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first coating layer extends from the front upstream end of the substrate to the rear downstream end of the substrate and overlaps the entirety of the second coating layer, and the second coating layer extends from the rear downstream end of the substrate to the front upstream end of the substrate.

[0025] Embodiment 10: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the second coating layer extends a predetermined distance from the front upstream end of the substrate toward the rear downstream end of the substrate and overlaps a portion of the first coating layer, and the first coating layer extends a predetermined distance from the rear downstream end of the substrate toward the front upstream end of the substrate.

[0026] Embodiment 11: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the second coating layer extends from the front upstream end of the substrate to the rear downstream end of the substrate and overlaps the entirety of the first coating layer, and the first coating layer extends from the rear downstream end of the substrate to the front upstream end of the substrate.

[0027] Embodiment 12: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first coating layer and the second coating layer are adjacent and do not overlap one another.

[0028] Embodiment 13: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first coating layer and the second coating layer are in direct contact with one another.

[0029] Embodiment 14: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first copper-containing molecular sieve and the second copper-containing molecular sieve are each eight-ring small pore molecular sieves.

[0030] Embodiment 15: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first copper-containing molecular sieve and the second copper-containing molecular sieve are both independently a zeolite having a structure selected from the group consisting of AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, SAS, SAT, and SAV.

[0031] Embodiment 16: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the first copper-containing molecular sieve and the second copper-containing molecular sieve each have a CHA crystal structure.

[0032] Embodiment 17: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein each of the first copper-containing molecular sieve and the second copper-containing molecular sieve is an aluminosilicate zeolite having a CHA crystal structure and a silica-to-alumina ratio (SAR) of about 5 to about 40.

[0033] Embodiment 18: The selective catalytic reduction article of any preceding or subsequent embodiment, wherein the substrate comprises an undercoat comprising an AMOx catalyst in the second zone.

[0034] Embodiment 19: A selective catalytic reduction system comprising: a first selective catalytic reduction article comprising a first substrate comprising a first catalytic coating layer comprising a first copper-containing molecular sieve having a first amount of copper oxide; and a second selective catalytic reduction article comprising a second substrate comprising a second catalytic coating layer comprising a second copper-containing molecular sieve having a second amount of copper oxide greater than the first amount of copper oxide, wherein the first selective catalytic reduction article and the second selective catalytic reduction article are in fluid communication.

[0035] Embodiment 20: The selective catalytic reduction system of any preceding or subsequent embodiment, wherein the first substrate of the first selective catalytic reduction article is sectioned to include a first catalytic coating layer having a first copper concentration and a second promoter layer having a second copper concentration higher than the first copper concentration.

[0036] Embodiment 21: The selective catalytic reduction system of any preceding or subsequent embodiment, wherein the first substrate and the second substrate are each independently selected from the group consisting of a porous wall-flow filter and a flow-through monolith.

[0037] Embodiment 22: The selective catalytic reduction system of any preceding or subsequent embodiment, wherein the second substrate comprises an undercoat comprising an AMOx catalyst.

[0038] Embodiment 23: An exhaust gas treatment system comprising the selective catalytic reduction article or selective catalytic reduction system of any preceding or subsequent embodiment, and a reductant injector in fluid communication with and upstream of the selective catalytic reduction article or selective catalytic reduction system.

[0039] Embodiment 24: The exhaust gas treatment system of any preceding or subsequent embodiment, further comprising one or more of a diesel oxidation catalyst, a soot filter, and an ammonia oxidation catalyst.

[0040] Embodiment 25: The exhaust gas treatment system of any preceding or subsequent embodiment, further comprising an internal combustion engine in fluid communication with and upstream of the selective catalytic reduction article or selective catalytic reduction system.

[0041] Embodiment 26: A method of treating an exhaust stream containing NOx, comprising passing the exhaust stream through a selective catalytic reduction article, selective catalytic reduction system, or exhaust gas treatment system of any preceding or following embodiment.

[0042] These and other features, aspects and advantages of the present disclosure will become apparent from reading the following detailed description in conjunction with the accompanying drawings, which are briefly described below. The present invention includes any combination of two, three, four or more of the above-mentioned embodiments, as well as any combination of two, three, four or more features or elements described in the present disclosure, whether or not such features or elements are explicitly combined in the description of a particular embodiment herein. The present disclosure, in any of its various aspects and embodiments, is intended to be read as a whole such that any separable features or elements of the disclosed invention are deemed combinable unless the context clearly dictates otherwise. Other aspects and advantages of the present invention will become apparent from the following.

[0043] Reference is made to the accompanying drawings to provide an understanding of embodiments of the present invention, the drawings are not necessarily drawn to scale, and reference numerals in the drawings refer to components of exemplary embodiments of the present invention. The drawings are illustrative only and should not be construed as limiting the present invention. [Brief description of the drawings]

[0044] [Figure 1] 1 is a perspective view of a honeycomb-type substrate support that may include a catalyst article in the form of a washcoat composition according to the present invention. [Diagram 2]2 is an enlarged partial cross-sectional view of FIG. 1 taken along a plane parallel to the end face of the substrate support of FIG. 1 and showing an enlarged view of multiple gas flow paths shown in FIG. 1 in one embodiment in which the substrate support is a monolithic flow-through substrate. [Diagram 3] 2 is a cutaway view of an enlarged portion of FIG. 1, in which the honeycomb-shaped substrate support represents a wall-flow filter substrate monolith. [Figure 4] 4a-4j are partial cross-sectional views illustrating coating layers and / or coating zones on one or more substrates according to exemplary embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Molecular sieves generally refer to materials that have an extensive three-dimensional network of oxygen ions, containing tetrahedral sites and with a relatively uniform pore size distribution. Zeolites are specific examples of molecular sieves, and further include silicon and aluminum. References to "non-zeolite supports" or "non-zeolite supports" in the catalyst layer refer to materials that are not zeolites, but that receive precious metals, stabilizers, promoters, binders, etc. through association, dispersion, impregnation, or other suitable methods. Examples of such non-zeolite supports include, but are not limited to, high surface area refractory metal oxides. High surface area refractory metal oxide supports may include active compounds selected from the group consisting of alumina, zirconia, silica, titania, ceria, lanthana, baria, and combinations thereof.

[0046] The present molecular sieves have, for example, 8-ring pore openings and double 6-ring secondary building units, including, for example, those having the following structure types: AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, SAS, SAT, or SAV. Included are all isotopic framework materials, such as SAPO, AlPO, and MeAPO materials having the same structure types.

[0047] Aluminosilicate zeolite structures do not contain phosphorus or other metals isomorphously substituted within the framework, i.e., "aluminosilicate zeolites" excludes aluminophosphate materials such as SAPO, AlPO, and MeAPO materials, while the broader term "zeolite" includes aluminosilicates and aluminophosphates.

[0048] The 8-ring small pore molecular sieve includes aluminosilicate, borosilicate, gallosilicate, MeAPSO and MeAPO. These include, but are not limited to, SSZ-13, SSZ-62, natural chabazite, zeolite KG, Linde D, Linde R, LZ-218, LZ-235, LZ-236, ZK-14, SAPO-34, SAPO-44, SAPO-47, ZYT-6, CuSAPO-34, CuSAPO-44 and CuSAPO-47. In certain embodiments, the 8-ring small pore molecular sieve has an aluminosilicate composition, such as SSZ-13 and SSZ-62.

[0049] In one or more embodiments, the 8-ring small pore molecular sieve has a CHA crystal structure and is selected from the group consisting of aluminosilicate zeolites having a CHA crystal structure, SAPO, AlPO and MeAPO. In particular, the 8-ring small pore molecular sieve with a CHA crystal structure is an aluminosilicate zeolite having a CHA crystal structure. In certain embodiments, the 8-ring small pore molecular sieve with a CHA crystal structure has an aluminosilicate composition such as SSZ-13 and SSZ-62. Copper-containing chabazite is abbreviated as CuCHA.

[0050] Molecular sieves can be zeolitic (zeolite) or non-zeolitic. Both zeolitic and non-zeolitic molecular sieves can have the chabazite crystal structure, also referred to as the CHA structure by the International Zeolite Association. Zeolitic chabazite has the approximate formula (Ca,Na 2 ,K2 ,Mg)Al 2 S 4 O 12 . 6 H 2 O (i.e., hydrous calcium aluminum silicate), a naturally occurring tectosilicate mineral of the zeolite group. Three synthetic forms of the zeolite chabazite are described in "Zeolite Molecular Sieves" by DW Breck, published by John Wiley & Sons in 1973, which is incorporated herein by reference. The three synthetic forms reported by Breck are Zeolite K-G, described in Barrer et al., J. Chem. Soc., p. 2822 (1956), Zeolite D, described in British Patent No. 868,846 (1961), and Zeolite R, described in U.S. Pat. No. 3,030,181, which are incorporated herein by reference. The synthesis of another synthetic form of the zeolite chabazite, SSZ-13, is described in U.S. Pat. No. 4,544,538. The synthesis of silicoaluminophosphate 34 (SAPO-34), a synthetic form of a non-zeolitic molecular sieve having the chabazite crystal structure, is described in U.S. Patent Nos. 4,440,871 and 7,264,789. A method for the preparation of SAPO-44, yet another synthetic non-zeolitic molecular sieve having the chabazite structure, is described, for example, in U.S. Patent No. 6,162,415.

[0051] Synthetic 8-ring small pore molecular sieves (e.g., having a CHA structure) can be prepared by mixing a silica source, an alumina source, and a structure directing agent under alkaline aqueous conditions. Typical silica sources include various types of fumed, precipitated, and colloidal silica, as well as silicon alkoxides. Typical alumina sources include boehmite, pseudoboehmite, aluminum hydroxide, aluminum salts such as aluminum sulfite or sodium aluminate, and aluminum alkoxides. Typically, sodium hydroxide is added to the reaction mixture. A typical structure directing agent for this synthesis is adamantyltrimethylammonium hydroxide, although other amines and / or quaternary ammonium salts can be substituted or added. The reaction mixture is heated with stirring in a pressure vessel to obtain a crystalline product. Typical reaction temperatures range from about 100°C to about 200°C, for example, from about 135°C to about 170°C. Typical reaction times range from about 1 hour to about 30 days, for example, from 10 hours to 3 days in certain embodiments. At the end of the reaction, the pH is optionally adjusted to about 6 to about 10, for example, about 7 to about 7.5, and the product is filtered and washed with water. An optional acid, for example, nitric acid, can be used for pH adjustment. Optionally, the product may be centrifuged. Organic additives can be used to aid in handling and isolation of the solid product. Spray drying is an optional step in the processing of the product. The solid product is heat treated in air or nitrogen. Alternatively, each gas treatment can be applied in various orders, or a mixture of gases can be applied. Typical calcination temperatures are from about 400°C to about 850°C.

[0052] Molecular sieves having the CHA structure can be prepared, for example, according to the methods disclosed in US Pat. Nos. 4,544,538 and 6,709,644.

[0053] The first and second molecular sieves can have a silica-to-alumina ratio (SAR) of from 1 to about 50, or from about 5 to about 40, respectively.

[0054] The molecular sieve is copper-containing. The copper is present at the ion-exchange sites (pores) of the molecular sieve and is associated with the molecular sieve, but may not be "in" the pores of the molecular sieve. Upon calcination, the unexchanged copper salts decompose to CuO, also referred to herein as "free copper" or "soluble copper." Free copper can be advantageous as disclosed in U.S. Pat. No. 8,404,203. The amount of free copper may be less than, equal to, or greater than the amount of ion-exchanged copper. All copper associated with the molecular sieve is part of any copper-containing molecular sieve.

[0055] Copper-containing molecular sieves are, for example, Na + Molecular sieve containing (Na + It is produced, for example, by ion exchange from Na + The calcined form generally refers to the calcined form without ion exchange. In this form, the molecular sieve generally has Na on the exchange sites. + and H + Contains a mixture of cations: Na + The percentage of sites occupied by the cations will vary depending on the particular zeolite batch and recipe. Optionally, the alkali metal molecular sieve is NH 4 + Replaced, NH 4 + The form is used for ion exchange with copper. Optionally, NH 4 + Exchange molecular sieve H + It is fired into a mold which can also be used for ion exchange with copper.

[0056] For example, as disclosed in U.S. Pat. No. 9,242,238, copper can be oxidized with an alkali metal, NH 3 , using a copper salt such as copper acetate or copper sulfate. 4 + or H + Ion exchange into molecular sieves of the type. For example, Na + , N.H. 4 + or H +The molecular sieves of the type are mixed with the salt water solution and stirred at elevated temperature for a suitable period of time. The slurry is filtered and the filter cake is washed and dried.

[0057] Additionally, at least a portion of the catalytically active metal may be included during the molecular sieve synthesis process such that the conditioning colloid includes a structure directing agent, a source of silica, a source of alumina, and a source of metal ions (eg, copper).

[0058] The amount of copper in the molecular sieves may be from about 0.1 to about 10 wt %. Advantageously, the amount of copper in the first molecular sieve may be less than the amount of copper in the second molecular sieve.

[0059] In some embodiments, the first molecular sieve can be a low copper molecular sieve in that it has a lower copper concentration than the second molecular sieve. Similarly, the second molecular sieve can be a high copper molecular sieve in that it has a higher copper concentration than the first molecular sieve. For example, the low copper molecular sieve or low copper zone or low copper layer can have a copper concentration of about 2.5 wt% or less (e.g., about 0.5 to about 2.5 wt%, about 1 to about 2.5 wt%, or about 2 to about 2.5 wt%). In further embodiments, the low copper molecular sieve or low copper zone or low copper layer can have a copper concentration of about 0.1 to about 4 wt%, or about 0.3 to about 3 wt%. As a further example, the high copper molecular sieve or high copper zone or layer can have a copper concentration of about 3 wt % or more (e.g., about 3 to about 10 wt %, about 3 to about 8 wt %, about 3 to about 6 wt %, or about 3 to about 4 wt %).

[0060] The amount of copper in the molecular sieve is reported as the oxide, CuO.

[0061] The total dry mass of the molecular sieve includes any added / exchanged metals, such as copper.

[0062] The amount of copper in a molecular sieve, such as an aluminosilicate zeolite, can also be defined by the atomic ratio of copper to aluminum. For example, the atomic ratio of Cu / Al of the molecular sieve can be about 0.05 to about 0.55. Advantageously, the atomic ratio of Cu to Al of the first molecular sieve is less than the atomic ratio of Cu to Al of the second copper-containing molecular sieve.

[0063] The molecular sieves of the upstream and downstream zones may be the same or different. For example, they may be the same or different with respect to their SAR. For example, the first molecular sieve may have a SAR lower than, equal to, or higher than that of the second molecular sieve.

[0064] Each copper-containing 8-ring small pore molecular sieve has a sodium content of less than 2 wt. % (Na on a volatile matter free basis) based on the total mass of the calcined molecular sieve. 2 In more specific embodiments, the sodium content is less than 1 wt. % or less than 2500 ppm. The molecular sieves may each have a sodium to aluminum atomic ratio of less than about 0.7, e.g., from about 0.02 to about 0.7. The molecular sieves may each have a copper to sodium atomic ratio of greater than about 0.5, e.g., from about 0.5 to about 50.

[0065] The copper-containing molecular sieve has a molecular sieve resistance of at least about 400m, measured according to DIN 66131. 2 / g, at least about 550m 2 / g or at least about 650m 2 / g, for example, about 400 to about 750 m 2 / g or about 500 to about 750m 2 The molecular sieve may have an average crystal size of about 10 nanometers to about 10 microns, about 50 nanometers to about 5 microns, or about 0.1 microns to about 0.5 microns, as measured by SEM. For example, the molecular sieve crystallites may have an average crystal size of greater than 0.1 microns or 1 micron but less than 5 microns.

[0066] The molecular sieve may be provided in the form of a powder or spray-dried material that is mixed with or coated with a suitable modifier. Modifiers include silica, alumina, titania, zirconia, and refractory metal oxide binders (e.g., zirconium precursors). The powder or spray material, after mixing or coating with a suitable modifier, may optionally be formed into a slurry, for example with water, which is deposited on a suitable substrate, for example as disclosed in U.S. Pat. No. 8,404,203.

[0067] The term "catalyst" refers to a material that promotes a chemical reaction. Catalysts include a "catalytically active species" and a "support" that supports or carries the active species. For example, molecular sieves, including zeolites, are carriers / supports for the present copper active catalytic species. Similarly, refractory metal oxide particles can be supports for platinum group metal catalytic species.

[0068] Catalytically active species are also referred to as "promoters" because they promote a chemical reaction. For example, the present copper-containing molecular sieves may be referred to as copper-promoted molecular sieves. "Promoted molecular sieves" refers to molecular sieves to which catalytically active species have been purposefully added.

[0069] Selective catalytic reduction (SCR) of nitrogen oxides (NOx) is 2 This means selective reduction to

[0070] The term "substrate" generally refers to a monolithic material on which the catalytic coating is disposed, such as a flow-through monolith or a monolithic wall-flow filter. In one or more embodiments, the substrate is ceramic or metal having a honeycomb structure. Any suitable substrate may be used, such as a monolithic substrate of the type having fine, parallel gas flow passages extending from the inlet end to the outlet end of the substrate, the passages being open to the flow of fluid. The passages are substantially linear paths from their fluid inlets to their fluid outlets, and are defined by walls on which the catalytic coating is disposed such that gas flowing through the passages contacts the catalytic material. The flow passages of the monolithic substrate are thin-walled channels and may be of any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, triangular, and the like. Such structures may contain from about 60 to about 900 or more gas inlet openings (i.e., cells) per square inch of cross section.

[0071] The substrate is three-dimensional, similar to a cylinder, having a length, a diameter and a volume. The shape does not necessarily have to conform to a cylinder. The length is the axial length defined by the inlet and outlet ends.

[0072] The flow-through monolith substrate may be, for example, about 50 in 3 ~About 1200in 3 , a cell density of about 200 to about 400 cpsi, and a wall thickness of about 50 to about 200 microns or about 400 microns.

[0073] The substrate may be a "flow-through" monolith as described above. Alternatively, the catalytic coating may be placed on a wall-flow filter soot filter to produce a catalytic soot filter (CSF). When utilizing a wall-flow substrate, the resulting system is capable of removing particulate matter along with gaseous pollutants. Wall-flow filter substrates may be manufactured from materials commonly known in the art, such as cordierite, aluminum titanate, or silicon carbide. The loading of the catalytic coating on the wall-flow substrate depends on substrate properties such as porosity and wall thickness, and is typically lower than the catalyst loading on a flow-through substrate.

[0074] Wall-flow filter substrates useful for carrying SCR catalyst coatings have a plurality of fine, substantially parallel gas flow passages extending along the longitudinal axis of the substrate. Typically, each passage is plugged at one end of the substrate body, with alternating passages plugged at the opposite end face. Such structures may contain about 700 or more passages (or "cells") per square inch of cross section, although much fewer may be used. For example, typical supports usually have about 100 to about 300 cells per square inch ("cpsi"). The cells may have rectangular, square, triangular, hexagonal, or other polygonal cross sections. Wall-flow substrates typically have wall thicknesses of about 50 microns to about 500 microns, e.g., about 150 microns to about 400 microns. Wall-flow filters generally have a wall porosity of at least 40% and an average pore size of at least 10 microns prior to the deposition of the catalyst coating. For example, the wall-flow filter has a wall porosity of about 50 to about 75% and an average pore size of about 10 to about 30 microns prior to disposing the catalytic coating.

[0075] 1 and 2 show an exemplary substrate 2 in the form of a flow-through substrate coated with a washcoat composition as described herein. With reference to FIG. 1, the exemplary substrate 2 has a cylindrical shape, a cylindrical outer surface 4, an upstream end surface 6, and a corresponding downstream end surface 8 identical to end surface 6. The substrate 2 has a plurality of fine, parallel gas flow passages 10 formed therein. As seen in FIG. 2, the flow passages 10 are formed by walls 12 and extend through the substrate 2 from the upstream end surface 6 to the downstream end surface 8, the passages 10 are unobstructed, and a fluid, e.g., a gas stream, can flow through the substrate 2 in the longitudinal direction of the substrate 2 via the gas flow passages 10 of the substrate. As can be more easily seen in FIG. 2, the walls 12 are sized and configured such that the gas flow passages 10 have a substantially regular polygonal shape. As shown, the washcoat composition can be applied in multiple different layers if desired. In the illustrated embodiment, the washcoat consists of both a separate bottom washcoat layer 14 attached to the wall 12 of the carrier member and a second separate top washcoat layer 16 coated over the bottom washcoat layer 14. The invention can be practiced with one or multiple (e.g., two, three or four) washcoat layers and is not limited to the illustrated two-layer embodiment.

[0076] Alternatively, Figures 1 and 3 can show an exemplary substrate 2 in the form of a wall-flow filter substrate coated with a washcoat composition described herein. As seen in Figure 3, the exemplary substrate 2 has a plurality of passages 52. The passages are tubularly surrounded by the inner wall 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. The alternating passages are blocked at the inlet end by inlet plugs 58 and at the outlet end by outlet plugs 60 to form an inverted checkerboard pattern at the inlets 54 and outlets 56. Gas flow 62 enters through the unblocked channel inlets 64, is stopped by the outlet plugs 60, and diffuses through the channel walls 53 (which are porous) to the outlet side 66. The gas cannot return to the inlet side of the wall due to the inlet plugs 58. The porous wall-flow filters used in the present invention are catalyzed since the walls of the elements have or contain one or more catalytic materials thereon. The catalytic material may be present only on the inlet side, only on the outlet side, on both the inlet and outlet sides of the element wall, or the wall itself, in whole or in part, may consist of the catalytic material. The present invention includes the use of one or more layers of catalytic material on the inlet and / or outlet walls of the element.

[0077] Catalytic wall-flow filters are disclosed, for example, in U.S. Patent No. 7,229,597. This reference teaches how to apply a catalytic coating so that the catalytic coating penetrates the porous walls, i.e., is distributed throughout the walls. Flow-through and wall-flow substrates are also taught, for example, in U.S. Patent Application No. 62 / 072,687, published as WO2016 / 070090.

[0078] For example, in the system, the first substrate is a porous wall-flow filter and the second substrate is a flow-through monolith, or the first substrate is a flow-through monolith and the second substrate is a porous wall-flow filter, or both substrates may be the same and may be a flow-through substrate or a wall-flow substrate.

[0079] The catalytic coating may be on the wall surface and / or within the pores of the wall, i.e., "in" and / or "on" the filter wall. Thus, the phrase "having a catalytic coating thereon" means on any surface, for example, on the wall surface and / or on the pore surfaces.

[0080] The term "exhaust stream" or "exhaust gas stream" refers to any combination of flowing gases that may include solid or liquid particulate matter. The stream includes gaseous components, for example, the exhaust of a lean-burn engine, which may contain certain non-gaseous components such as liquid droplets, solid particulates, etc. The exhaust stream of a lean-burn engine typically further includes products of combustion, products of incomplete combustion, oxides of nitrogen, combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and / or nitrogen.

[0081] Certain embodiments relate to the use of articles, systems and methods for removing NOx from the exhaust gas of internal combustion engines, particularly diesel engines, operating under combustion conditions with more air than required for stoichiometric combustion, i.e., lean conditions.

[0082] The inlet end of the substrate is synonymous with the "upstream" or "front" end. The outlet end is synonymous with the "downstream" or "rear" end. The substrate has a length and a width. The upstream zone is upstream of the downstream zone. A zone of the catalytic substrate is defined as a cross-section having some coating structure thereon.

[0083] In the present exhaust gas treatment method, the exhaust gas stream passes through the SCR article, SCR system, or exhaust gas treatment system by entering at the upstream end and exiting at the downstream end.

[0084] The ceramic substrate may be made from any suitable high melting point material, such as, for example, cordierite, cordierite-alpha-alumina, aluminum titanate, silicon carbide, silicon nitride, zircon mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, alpha-alumina, aluminosilicate, and the like.

[0085] Substrates useful in the present invention may also be metallic and include one or more metals or metal alloys. Metal substrates can be used in a variety of shapes, such as pellets, corrugated sheets, or monolithic 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 may include one or more of nickel, chromium, and aluminum, the sum of which advantageously comprises at least about 15 wt. % (mass percent) of the alloy, for example about 10 to about 25 wt. % chromium, about 1 to about 8 wt. % aluminum, and 0 to about 20 wt. % nickel.

[0086] The catalytic coating contains one or more supports containing active catalytic species. The catalytic coating can typically be applied in the form of a washcoat including a support having catalytically active species thereon. The washcoat is formed by making a slurry containing a particular solids content (e.g., 10-60% by weight) of the support in a liquid vehicle, which is then coated onto the substrate, dried, and calcined to provide a coating layer. When multiple coating layers are applied, the substrate is dried and calcined after each layer and / or after the desired number of layers have been applied.

[0087] The coating layer of the molecular sieve is preferably a binder, e.g., ZrO derived from a suitable precursor such as zirconyl acetate or any other suitable zirconium precursor such as zirconyl nitrate. 2The catalyst can be produced using a binder. Zirconyl acetate binders provide catalyst 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, such as about 800°C or higher, and high water vapor environments of about 10% or higher. Other binders that may be suitable 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 are also used. Silica binders include various forms of SiO, including colloidal silica. 2 The binder composition may include any combination of zirconia, alumina, and silica.

[0088] The coating layers are all ZrO 2 Binder and / or Al 2 O 3 may also contain

[0089] The catalytic coating may include two or more thin deposits. The coating is placed on the substrate and adhered to the substrate. The entire coating includes individual "coating layers." The catalytic coating is "sectioned" and includes sectioned catalytic layers. This may also be described as "lateral zones." For example, the first layer may extend from about 5% to about 100%, about 10% to about 90%, or about 20% to about 50% of the length of the substrate from the inlet end to the outlet end. The second layer may extend from about 5% to about 100%, about 10% to about 90%, or about 20% to about 50% of the length of the substrate from the outlet end to the inlet end. The first and second layers may be adjacent to each other and not overlap each other. Alternatively, the first and second layers may overlap a portion of each other to provide a third "middle" zone. The middle zone may extend, for example, from about 5% to about 80% of the length of the substrate. Alternatively, the first layer may extend from the outlet end and the second layer may extend from the inlet end.

[0090] The first and second layers may each extend the entire length of the substrate or a portion of the length of the substrate and may partially or completely overlie or underlie one another. Each of the first and second layers may extend from either the inlet end or the outlet end.

[0091] The first coating layer may extend the entire length of the substrate, and the second coating layer may overlie or underlie part or all of the first layer. For example, the second coating layer may extend from about 10% to about 80% of the length of the substrate from the outlet end toward the inlet end.

[0092] The second coating layer may extend the entire length of the substrate, and the first coating layer may overlie or underlie part or all of the second layer. For example, the first coating layer may extend from about 10% to about 80% of the length of the substrate from the inlet end to the outlet end.

[0093] The zones are defined by the relationship of the first and second coating layers. With respect to the first and second coating layers, there may be only upstream and downstream zones, or there may be upstream, intermediate and downstream zones. If the first and second layers are adjacent and do not overlap, then only upstream and downstream zones exist. If the first and second layers overlap to some extent, then upstream, downstream and intermediate zones exist. For example, if the first coating layer extends the entire length of the substrate and the second coating layer extends a certain length from the exit end to overlap a portion of the first coating layer, then only upstream and downstream zones exist.

[0094] The first and / or second coating layer may be in direct contact with the substrate. Alternatively, one or more layers of "undercoats" may be present, whereby at least a portion of the first and / or second coating layer is not in direct contact with the substrate (rather it is in contact with the undercoat). One or more layers of "overcoats" may also be present, whereby at least a portion of the first and / or second coating layer is not directly exposed to the gas stream or atmosphere (rather it is in contact with the overcoat).

[0095] The first and second coating layers may be in direct contact with each other, with no "middle" overlapping zone. Alternatively, the first and second 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 the first and second SCR layers is called the "middle layer".

[0096] An undercoat is a layer "below" a coating layer, an overcoat is a layer "on" a coating layer, and an interlayer is a layer "between" two coating layers.

[0097] The interlayers, undercoats and overcoats may contain one or more catalysts or may be catalyst-free.

[0098] The catalytic coating may include two or more identical layers, for example, two or more first and / or second layers.

[0099] The simplest article of the invention comprises a flow-through substrate or wall-flow filter having a first coating layer extending from the inlet end toward the outlet end of the monolith or filter and a second coating layer extending from the outlet end toward the inlet end.

[0100] Further disclosed is an SCR article including a substrate having a forward upstream end and an aft downstream end defining an axial length, the substrate being coated over its entire length with a second coating layer including a second copper-containing molecular sieve, the first coating layer including the first copper-containing molecular sieve overlapping a portion of the second coating layer and extending 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80% or the length of the substrate from the inlet end toward the outlet end, in this example, the copper concentration in the first coating layer is advantageously lower than the copper concentration in the second coating layer.

[0101] Also disclosed is a selective catalytic reduction article comprising a substrate having a forward upstream end and an aft downstream end defining an axial length, the substrate being coated over its entire length with a second coating layer comprising a second copper-containing molecular sieve, and a first coating layer comprising the first copper-containing molecular sieve overlying the second coating layer. Again, in this example, the copper concentration in the first coating layer is advantageously lower than the copper concentration in the second coating layer.

[0102] The present catalytic coating, as well as each zone of the catalytic coating or any portion of the coating, may, for example, have a coating weight of about 0.3 g / in based on the substrate. 3 ~ approx. 4.5g / in 3 is present on the substrate at a loading (concentration) of 10 ...

[0103] The term "catalytic article" refers to an element used to promote a desired reaction. The catalytic article includes a substrate having a catalytic coating disposed thereon.

[0104] The system includes two or more items, such as a first SCR item and a second SCR item. The system may also include one or more items including a reductant injector, a diesel oxidation catalyst (DOC), a soot filter, an ammonia oxidation catalyst (AMOx), or a lean NOx trap (LNT).

[0105] An article that includes a reductant injector is a reduction article. The reduction system includes a reductant injector and / or a pump and / or a reservoir, etc.

[0106] The treatment system may further include a diesel oxidation catalyst and / or a soot filter and / or an ammonia oxidation catalyst. The soot filter may be uncatalyzed or catalyzed (CSF). For example, the treatment system may include, from upstream to downstream, a DOC, a CSF, an item including a urea injector, the present zoned SCR item, or a first SCR item and a second SCR item, and an item including AMOx. A lean NOx trap (LNT) may also be included.

[0107] An undercoat layer comprising the AMOx catalyst may be present in a downstream zone of the substrate, for example, the AMOx undercoat layer may extend from the outlet end toward the inlet end for about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, or about 80% of the length of the substrate of the article.

[0108] An AMOx undercoat layer may also be present on the second substrate of the second downstream article, the undercoat layer may extend the entire length of the second substrate, or about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80% or about 90% of the length of the second substrate.

[0109] AMOx catalysts are taught, for example, in U.S. Patent Application Publication No. 2011 / 0271664. The ammonia oxidation (AMOx) catalyst can be a supported precious metal component that is effective for removing ammonia from an exhaust gas stream. The precious metal may include ruthenium, rhodium, iridium, palladium, platinum, silver, or gold. For example, the precious metal component includes a physical mixture or a chemically or atomically doped combination of the precious metals. The precious metal component includes, for example, platinum. The platinum can be present in an amount of about 0.008% to about 2 wt % relative to the AMOx catalyst.

[0110] The precious metal components are typically deposited on a high surface area refractory metal oxide support. Examples of suitable high surface area refractory metal oxides include alumina, silica, titania, ceria and zirconia, as well as physical mixtures, chemical combinations and / or atomically doped combinations thereof. In certain embodiments, the refractory metal oxide may contain mixed oxides such as silica-alumina, amorphous or crystalline aluminosilicates, alumina-zirconia, alumina-lanthana, alumina-barrier, alumina-ceria, and the like. Exemplary refractory metal oxides have a surface area of ​​about 50 to about 300 m. 2 The material contains high surface area γ-alumina having a specific surface area of ​​1.0 μm / g.

[0111] The AMOx catalyst may include a zeolitic or non-zeolitic molecular sieve, for example selected from those of the CHA, FAU, BEA, MFI and MOR types. The molecular sieve may be physically mixed with the oxide-supported platinum component. In an alternative embodiment, the platinum may be distributed on the exterior surface or within the channels, cavities or cages of the molecular sieve.

[0112] This embodiment, including a first selective catalytic reduction article and a second selective catalytic reduction article, may be referred to as a "multi-component" or "multi-brick" system. A "brick" may refer to a single article, such as a monolith or a filter.

[0113] Advantageously, each multi-component article may include a substrate that includes a compartmentalized coating as disclosed herein.

[0114] The catalytic article is effective to catalyze the reduction of nitrogen oxides (NOx) in the presence of a reductant, such as ammonia or urea. During operation, the reductant is metered periodically into the exhaust stream from a location upstream of the SCR article. An injector is in fluid communication with and upstream of the SCR article. The injector is also associated with a reductant reservoir and a pump.

[0115] The present articles, systems and methods are suitable for treating exhaust gas streams from mobile sources such as trucks and automobiles. The articles, systems and methods are also suitable for treating exhaust streams from stationary sources such as power generation equipment.

[0116] Ammonia is the typical reductant for SCR reactions for stationary power plant exhaust gas treatment, while urea is the typical SCR reductant used for mobile source exhaust gas treatment. Urea is decomposed into ammonia and carbon dioxide before or on the SCR catalyst, and ammonia serves as a NOx reductant.

[0117] The articles, systems and methods described herein can, for example, provide high NOx conversion rates. For example, the present catalyst articles can be used for up to 80,000 h -1 The catalyst article may exhibit an aged NOx conversion of at least 50%, at least 55%, or at least 60% at 200° C., measured at a gas hourly space velocity of 100 ppm NO, 500 ppm NH 3 500 ppm, O 2 10% and H 2 5% O, balance N 2 In a gas mixture of -1 The catalyst may exhibit an aging NOx conversion of at least 70%, at least 75%, or at least 80% at 450° C., as measured at a volumetric hourly space velocity of 10% H 2 O, 10% O 2 , remainder N 2The cores are hydrothermally aged at 750° C. for 5 hours in a gas stream containing such SCR activity measurements are given in U.S. Pat. No. 8,404,203.

[0118] Additionally, the articles, systems and methods herein provide > 90% NOx conversion and < 1.5% N under transient HDD FTP conditions. 2 O production.

[0119] For example, some of the present selective catalytic reduction articles or systems have been shown to improve NOx conversion and N conversion under transient engine test conditions for an article or system containing a uniform concentration of CuCHA as the sole SCR catalyst. 2 ≥90% NOx conversion and ≤40% N compared to O production, respectively. 2 The article containing a uniform concentration of CuCHA contains a catalyst coating on a substrate that includes a uniform concentration of CuCHA. CuCHA is the only SCR catalyst present as a reference. Similarly, as a system reference, both substrates contain the same uniform concentration of CuCHA as the only SCR catalyst.

[0120] That is, the present article and system have a smaller N 2 It provides equally good or better NOx conversion while forming O.

[0121] NOx Conversion and N 2 The SCR performance, such as the amount of O generated, is, for example, 200°C to 600°C with a temperature gradient of 0.5°C / min, and NOx is 500 ppm (high-speed SCR condition: NO 2 / NOx=0.5 or standard SCR condition: NO 2 / NOx=0), NH 3 500 ppm, O 2 10% and H 2 5% O, balance N 2 In a gas mixture of 80,000 h under pseudo-steady-state conditions -1 It is measured by the volumetric hourly space velocity of gas.

[0122] The NOx conversion rate is NO and NO 2 It is defined as the mol% conversion rate of the combination of N 2 The amount of O produced is NO and NO 2 Combined with N 2 It is defined as the mol% conversion of NOx to N. A low value is desirable. 2 The percent conversion to N 2 Each molecule of O produces one molecule of NOx and one molecule of NH 3 The calculation is based on the assumption that it is generated from

[0123] The selective catalytic reduction article or system or method can provide >90% total NOx conversion, e.g., the front upstream zone provides about 30% to about 80% total NOx conversion, as measured under transient HDD FTP conditions.

[0124] Exemplary embodiments of the present invention are provided below. The embodiments are provided by way of example and are understood to encompass further combinations of catalytic coatings. Additionally, as illustrated, coating zones and coating layers may be interchangeable, since coating layers may define coating zones.

[0125] In one embodiment, as seen in Figure 4a, a substrate 100 can be coated with a single coating layer 101 that is a combination of multiple catalytically active molecular sieves. For example, the single coating 101 can be a combination of a copper-containing molecular sieve with a low copper concentration (e.g., about 0.1 to about 3 wt% copper) and a copper-containing molecular sieve with a high copper concentration (e.g., about 3 to about 10 wt%).

[0126] In a further embodiment, the substrate 100 can be coated with two non-overlapping zones. As seen in FIG. 4b, a first zone 102 adjacent the front or inlet end 100a of the substrate 100 can include a copper-containing molecular sieve with a low copper concentration (e.g., about 0.1 to about 3 wt. % copper). A second zone 103 adjacent the rear or outlet end 100b of the substrate 100 can include a copper-containing molecular sieve, preferably with a high copper concentration (e.g., about 3 to about 10 wt. %).

[0127] In a further embodiment, as seen in FIG. 4c, the substrate 100 can be coated with a first coating layer 104 extending from the front or inlet end 100a of the substrate 100 to the rear or outlet end 100b of the substrate 100, and a second coating layer 105 coated on the first coating layer 104 adjacent the rear or outlet end 100b of the substrate 100 and extending over only a portion of the length of the substrate 100 (i.e., terminating before reaching the front or inlet end 100a of 100a). The first layer 104 can include a copper-containing molecular sieve with a low copper concentration (e.g., about 0.1 to about 3 wt % copper). The second layer 105 can include a copper-containing molecular sieve, preferably with a high copper concentration (e.g., about 3 to about 10 wt %).

[0128] In yet another embodiment, as seen in FIG. 4d, the substrate 100 can be coated with a first coating layer 106 extending from the front or inlet end 100a of the substrate 100 to the rear or outlet end 100b of the substrate 100, and a second coating layer 107 coated on the first coating layer 106 adjacent the front or inlet end 100a of the substrate 100 and extending over only a portion of the length of the substrate 100 (i.e., terminating before reaching the rear or outlet end 100b of the substrate 100). The first coating layer 106 can include a copper-containing molecular sieve, preferably with a high copper concentration (e.g., about 3 to about 10 wt%). The second coating layer 107 can include a copper-containing molecular sieve with a low copper concentration (e.g., about 0.1 to about 3 wt% copper).

[0129] In another embodiment, as seen in FIG. 4e, the substrate 100 can be coated with a first coating layer 108 extending from the front or inlet end 100a of the substrate 100 to the rear or outlet end 100b of the substrate 100, and a second coating layer 109 coated on the first coating layer 108 and also extending from the front or inlet end 100a of the substrate 100 to the rear or outlet end 100b of the substrate 100. The first coating layer 108 can include a copper-containing molecular sieve, preferably with a high copper concentration (e.g., about 3 to about 10 wt %). The second coating layer 109 can include a copper-containing molecular sieve with a low copper concentration (e.g., about 0.1 to about 3 wt % copper).

[0130] In yet another embodiment, as seen in FIG. 4f, a first substrate 100 can be coated with a first coating layer 110 and a second, separate substrate 100' can be coated with a second coating layer 111. The first coating layer 110 on the first substrate 100 can include a copper-containing molecular sieve with a low copper concentration (e.g., about 0.1 to about 3 wt% copper). The second coating layer 111 on the second, separate substrate 100' can include a copper-containing molecular sieve, preferably with a high copper concentration (e.g., about 3 to about 10 wt%). The first substrate 100 is upstream of the second, separate substrate 100' with respect to the flow path of the exhaust stream. The first coating layer 110 can extend from the front or entrance end 100a to the rear or exit end 100b of the first substrate 100, and the second coating layer 111 can extend from the front or entrance end 100a' to the rear or exit end 100b' of the second substrate 100'.

[0131] In a further embodiment, as seen in Figures 4g and 4i, the substrate 100 may be coated with a first coating layer 112 adjacent the front or entrance end 100a of the substrate 100 and extending only partially along the length of the substrate 100 (i.e., terminating before reaching the rear or exit end 100b of the substrate 100). The substrate 100 may be coated with a second coating layer 113. As seen in Figure 4g, the second coating layer 113 extends from the front or entrance end 100a of the substrate 100 to the rear or exit end 100b of the substrate 100 (thus coating completely over the first coating layer 112). As seen in FIG. 4i, the second coating layer 113 extends a portion of its length from the rear or outlet end 100b of the substrate 100 to a point toward the front or inlet end 100a of the substrate 100, so that the second coating layer 113 coats a portion of the substrate 100 and also coats a portion of the first coating layer 112. The first coating layer 112 on the substrate 100 can include a copper-containing molecular sieve with a low copper concentration (e.g., about 0.1 to about 3 wt% copper). The second coating layer 113 on the substrate 100 can include a copper-containing molecular sieve, preferably with a high copper concentration (e.g., about 3 to about 10 wt%). As mentioned above, the second coating layer 113 can partially cover the first coating layer 112 or can completely cover the first coating layer 112.

[0132] In additional embodiments, as seen in Figures 4h and 4j, the substrate 100 may be coated with a first coating layer 115 adjacent the rear or outlet end 100b of the substrate 100 and extending only partially along the length of the substrate 100 (i.e., terminating before reaching the front or inlet end 100a of the substrate 100). The substrate 100 may be coated with a second coating layer 114. As seen in Figure 4h, the second coating layer 114 extends from the front or inlet end 100a of the substrate 100 to the rear or outlet end 100b of the substrate 100 (thus coating completely over the first coating layer 115). As seen in FIG. 4j, the second coating layer 114 extends a portion of its length from the front or inlet end 100a of the substrate 100 to a point toward the rear or outlet end 100b of the substrate 100, so that the second coating layer 114 coats a portion of the substrate 100 and also coats a portion of the first coating layer 115. The first coating layer 115 on the substrate 100 can include a copper-containing molecular sieve with a low copper concentration (e.g., about 0.1 to about 3 wt% copper). The second coating layer 114 on the substrate 100 can preferably include a copper-containing molecular sieve with a high copper concentration (e.g., about 3 to about 10 wt%). As mentioned above, the second coating layer 114 can partially cover the first coating layer 115 or can completely cover the first coating layer 115.

[0133] "Platinum group metal component" refers to a platinum group metal or one of their oxides. "Rare earth metal component" refers to one or more oxides of the lanthanum series as defined in the Periodic Table of the Elements, which includes lanthanum, cerium, praseodymium, and neodymium.

[0134] "Substantially free" means, for example, "little or no," e.g., "not intentionally added," and having only trace and / or inadvertent amounts. For example, it means less than 2 wt% (by weight), 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 labeled composition.

[0135] "Substantially all" means, for example, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% by mass or number.

[0136] The articles "a" and "an" herein refer to one or more than one (e.g., at least one) of its grammatical object. All ranges cited herein are inclusive. The term "about" used throughout is used to describe 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". Numeric values ​​modified by the term "about" include the specific identified value. For example, "about 5.0" includes 5.0.

[0137] All parts and percentages are by weight unless otherwise indicated. Weight percent (wt%) is based on the total composition not including any volatile materials, i.e., based on the dry solids content, unless otherwise indicated.

[0138] All U.S. patent applications, published patent applications and patents mentioned herein are hereby incorporated by reference. EXAMPLES

[0139] Examples of SCR Articles, Manufacturing and Testing

[0140] A catalytic coating containing CuCHA zeolite is placed by a washcoat process onto a cellular ceramic monolith having a cell density of 400 cpsi and a wall thickness of 6 mils. The coated monolith is dried at 110°C and calcined at about 450°C for 1 hour. The coating process is carried out at a rate of 3 g / in 3 The front and rear zones are zones of equal coating volume. All samples were prepared using 10% H 2 Hydrothermally aged at 750°C for 5 hours in the presence of O / air. The front zone extends from the inlet end of the core to approximately 50% of the core's length and the rear zone extends from the outlet end of the core to approximately 50% of the core's length. The reference sample has a uniform coating.

[0141] The SCR test of the aged sample is performed under the HDD FTP (Heavy Duty Diesel US Federal Test Procedure) cycle conditions. The transient temperature range of the HDD FTP test is 225℃ to 325℃. The cumulative inlet NOx per cycle (1200 seconds) is 5g / L. The transient space velocity is 20K to 120Khr. -1 The FTP NOx conversion rate and N 2 Results are reported for O production. Front and rear zone copper is in wt % based on the total weight of the zeolite. Mass percent Cu is reported as CuO.

[0142] The NOx conversion rate is NO and NO 2 It is defined as the mol% conversion rate of the combination of N 2 The amount of O produced is NO and NO 2 Combined with N 2 It is defined as the mol% conversion of NOx to N. A low value is desirable. 2 The percent conversion to N 2 Each molecule of O produces one molecule of NOx and one molecule of NH 3 The calculation is based on the assumption that it is generated from

[0143] [Table 1]

[0144] [Table 2]

[0145] The samples 1a to 1j of the present invention have the following characteristics compared to the standard sample: 2 It can be seen that the catalyst shows excellent NOx conversion (>91%) while reducing O production, resulting in better overall performance. To achieve 93-95% NOx conversion, a uniform copper loading of 2.5-3.0 N 2 O production, while the fractionated copper substrate produced 1.1% to 1.8% N 2 Samples 1b-1g of the present invention provide at least 92% NOx conversion and a maximum N 2 Achieve O production.

Claims

1. 1. A selective catalytic reduction article comprising a substrate having a forward upstream end and an aft downstream end defining an axial length of the substrate, the substrate having a catalytic coating thereon, the catalytic coating comprising: a first coating layer comprising a first copper-containing molecular sieve; a second different coating layer comprising a second copper-containing molecular sieve; and The first copper-containing molecular sieve comprises copper oxide in an amount of 0.1 to 3 wt %, based on the total weight of the first copper-containing molecular sieve, and the second copper-containing molecular sieve comprises a predetermined amount of copper oxide, based on the total weight of the second copper-containing molecular sieve; and the amount of copper oxide contained in the first copper-containing molecular sieve is less than the amount of copper oxide contained in the second copper-containing molecular sieve; and The selective catalytic reduction article has a NOx conversion of at least 92% and a NOx reduction of 2.3% or less when subjected to Heavy Duty Diesel US Federal Test Procedure cycle conditions. ２ indicates the amount of O produced, and the first copper-containing molecular sieve has a silica-to-alumina ratio equal to the silica-to-alumina ratio of the second copper-containing molecular sieve; and the ratio of the amount of copper oxide in the first copper-containing molecular sieve to the amount of copper oxide in the second copper-containing molecular sieve is in the range of 0.6:3.4 to 2.3:2.7; and the catalytic coating is segmented; a first zone including the first coating layer including the first copper-containing molecular sieve; a second zone comprising said second coating layer comprising said second different copper-containing molecular sieve; and The selective catalytic reduction article, wherein the first zone is upstream of the second zone.

2. 2. The selective catalytic reduction article of claim 1, wherein the first copper-containing molecular sieve has a copper concentration that is less than a copper concentration of the second, different copper-containing molecular sieve in the second zone.

3. The selective catalytic reduction article of claim 1 , wherein the substrate is a porous wall-flow filter or a flow-through monolith.

4. A selective catalytic reduction article as described in claim 1, wherein the second copper-containing molecular sieve contains copper oxide in an amount of 3 to 10 wt. %, based on the total mass of the second copper-containing molecular sieve.

5. 2. The selective catalytic reduction article of claim 1, wherein, based on the total mass of the first copper-containing molecular sieve, the first copper-containing molecular sieve comprises copper oxide in an amount of 1 to 2.5 wt. %, and based on the total mass of the second copper-containing molecular sieve, the second copper-containing molecular sieve comprises copper oxide in an amount of 3 to 6 wt. %.

6. 2. The selective catalytic reduction article of claim 1, wherein the Cu / Al atomic ratio of each of the first copper-containing molecular sieve and the second copper-containing molecular sieve is independently 0.05 to 0.55, and the Cu / Al atomic ratio of the first copper-containing molecular sieve is less than the Cu / Al atomic ratio of the second copper-containing molecular sieve.

7. 2. The selective catalytic reduction article of claim 1, wherein the first coating layer extends a predetermined distance from the forward upstream end of the substrate toward the rear downstream end of the substrate and overlaps a portion of the second coating layer, and the second coating layer extends a predetermined distance from the rear downstream end of the substrate toward the forward upstream end of the substrate.

8. 2. The selective catalytic reduction article of claim 1, wherein the first coating layer extends a predetermined distance from a forward upstream end of the substrate to a rear downstream end of the substrate and overlaps the entire second coating layer, and the second coating layer extends from the rear downstream end of the substrate to the forward upstream end of the substrate.

9. The selective catalytic reduction article of claim 1 , wherein the first coating layer and the second coating layer are adjacent and do not overlap one another.

10. The selective catalytic reduction article of claim 1 , wherein the first coating layer and the second coating layer are in direct contact with each other.

11. 2. The selective catalytic reduction article of claim 1, wherein the first copper-containing molecular sieve and the second copper-containing molecular sieve are each eight-ring small pore molecular sieves.

12. 12. The selective catalytic reduction article of claim 11, wherein the first copper-containing molecular sieve and the second copper-containing molecular sieve are both independently zeolites having a structure selected from the group consisting of AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, SAS, SAT and SAV.

13. 12. The selective catalytic reduction article of claim 11, wherein each of the first copper-containing molecular sieve and the second copper-containing molecular sieve is an aluminosilicate zeolite having a CHA crystal structure and a silica-to-alumina ratio (SAR) of 5-40.

14. 2. The selective catalytic reduction article of claim 1, wherein the substrate comprises an undercoat comprising an ammonia oxidation catalyst (AMOx) in the second zone.

15. A selective catalytic reduction article according to claim 1; a reductant injector in fluid communication with and upstream of the selective catalytic reduction article; and Optionally, an exhaust gas treatment system including one or more of a diesel oxidation catalyst, a soot filter and an ammonia oxidation catalyst, and an internal combustion engine.

16. A method of treating an exhaust stream containing NOx, comprising passing the exhaust stream through the selective catalytic reduction article of claim 1.

17. 20. A method of treating an exhaust stream containing NOx, comprising passing the exhaust stream through an exhaust gas treatment system according to claim 15.

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