Selective catalytic reduction catalyst containing copper carbonate

Abstract

The present disclosure relates to the detection of nitrogen oxides (NO x The present invention provides a catalyst composition capable of reducing NOx emissions, a catalyst article coated with such a composition, and a process for preparing such a catalyst composition and article. x The present invention also relates to a metal ion-exchanged zeolite useful for selective catalytic reduction (SCR) of NO in an exhaust gas stream. x A method for reducing

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of priority in its entirety to U.S. Provisional Application No. 62 / 845,366, filed May 9, 2019.

[0002] This disclosure generally relates to the field of exhaust gas treatment catalysts, and more particularly to catalyst compositions capable of selectively reducing nitrogen oxides in engine exhaust, catalyst articles coated with such compositions, and processes for preparing such catalyst compositions. More specifically, improved metal - promoted zeolites that may be useful as selective catalytic reduction (SCR) catalysts, and processes for preparing them, are provided.

Background Art

[0003] Over the years, the harmful components of nitrogen oxides (NO x ) have caused air pollution. NO x is contained in the exhaust gases from internal combustion engines (e.g., automobiles and trucks), combustion facilities (e.g., power plants heated by natural gas, oil, or coal), and nitric acid production plants, etc.

[0004] NO x To treat NO - containing gas mixtures to reduce air pollution, various treatment methods have been used. One type of treatment involves the catalytic reduction of nitrogen oxides. There are two processes: (1) a non - selective reduction process in which carbon monoxide, hydrogen, or low - molecular - weight hydrocarbons are used as reducing agents, and (2) a selective reduction process in which ammonia or an ammonia precursor is used as a reducing agent. In the selective reduction process, a stoichiometric amount of the reducing agent can be used to achieve a high level of nitrogen oxide removal.

[0005] The selective reduction process is referred to as the SCR (Selective Catalytic Reduction) process. The SCR process utilizes the catalytic reduction of nitrogen oxides using a reducing agent (e.g., ammonia) in the presence of oxygen in the atmosphere, resulting in the formation of mainly nitrogen and steam: 4NO + 4NH3 + O2 → 4N2 + 6H2O (standard SCR reaction) 2NO2 + 4NH3 + O2 → 3N2 + 6H2O (slow SCR reaction) NO + NO2 + 2NH3 → 2N2 + 3H2O (fast SCR reaction)

[0006] The catalyst used in the SCR process should ideally be able to maintain good catalytic activity under hydrothermal conditions over a wide range of operating temperature conditions, e.g., 200 °C to 600 °C or higher. SCR catalysts are generally used under hydrothermal conditions, such as during the regeneration of a soot filter, which is a component of an exhaust gas treatment system used for particle removal.

[0007] Current catalysts used in the SCR process include metal-promoted zeolites that are used for the SCR of nitrogen oxides with reducing agents such as ammonia, urea, or hydrocarbons in the presence of oxygen. Among them, metal-promoted zeolite SCR catalysts including iron-promoted and copper-promoted zeolite catalysts are known. For example, iron-promoted zeolite beta was an effective commercial catalyst for the selective reduction of nitrogen oxides by ammonia. Unfortunately, under harsh hydrothermal conditions (such as those shown during the regeneration of a soot filter at temperatures locally exceeding 700 °C), it has been found that the activity of many metal-promoted zeolites begins to decline. This decline is due to dealumination of the zeolite and the resulting loss of metal-containing active centers in the zeolite.

[0008] Metal-promoted, specifically copper-promoted aluminosilicate zeolites having the CHA structure type have attracted great interest as catalysts for SCR of nitrogen oxides in lean burn engines using nitrogenous reducing agents. These materials exhibit activity within a wide temperature window and excellent hydrothermal durability, as described in U.S. Patent No. 7,601,662.

[0009] The catalyst described in U.S. Patent No. 7,601,662 exhibits excellent properties and is thus useful, for example, in the context of SCR catalysis. However, there is still a continuing need for SCR catalysts with improved performance over an extended and / or different temperature window. One of the challenges in meeting current government NO x regulations is to provide improved low-temperature performance for metal-promoted zeolite-based SCR catalysts. Accordingly, there is still a need for an even improved process for preparing metal-promoted zeolite SCR and selective catalytic reduction on filter (SCRoF) catalysts having improved low- and high-temperature performance compared to currently available metal-promoted zeolite SCR and SCRoF catalysts. SUMMARY OF THE INVENTION

[0010] The present disclosure generally relates to a process for preparing advanced selective catalytic reduction (SCR) catalysts and selective catalytic reduction on filter (SCRoF) catalysts, and to articles comprising SCR or SCRoF catalysts prepared by the disclosed process. Surprisingly, the process of the present disclosure provides SCR and SCRoF catalysts that achieve high catalytic activity such as significantly increased NO x conversion rates at any temperature, particularly low temperatures, compared to standard Cu-chabazite reference SCR catalysts.

[0011] Accordingly, in one aspect, a process for preparing an SCR catalyst or an SCRoF catalyst is provided, wherein the SCR or SCRoF catalyst comprises a metal ion-exchanged zeolite, and the process comprises (i) mixing the zeolite with an aqueous mixture comprising water and a metal ion source comprising a carbonate of copper, iron, or a mixture thereof to form a slurry comprising the treated zeolite.

[0012] In some embodiments, the process further comprises adding a binder during the mixing step.

[0013] In some embodiments, the process further includes grinding the aqueous mixture before performing the mixing step. In some embodiments, the aqueous mixture includes particles of a metal ion source having a D90 value of from about 0.5 to about 20 micrometers. In some embodiments, the aqueous mixture includes particles of a metal ion source having a D50 value of from about 1 to about 3 micrometers and a D90 value of from about 4 to about 10 micrometers. In some embodiments, the aqueous mixture further includes one or more additives selected from one or more of sugar, a dispersant, a surface tension reducing agent, a rheology modifier, or combinations thereof.

[0014] In some embodiments, the zeolite has a framework type selected from the group consisting of ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFV, AFX, AFY, AHT, ANA, APC, APD, AST, 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, CSV, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, EWT, EZT, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFO, IFR, IFU, IFW, IFY, IHW, IMF, IRN, IRR, IRY, ISV, ITE, ITG, ITH, ITN, ITR, ITT, ITV, ITW, IWR, IWS, IWV, IWW, JBW, JNT, JOZ, JRY, JSN, JSR, JST, JSW, KFI, LAU, LEV, LIO, LIT, LOS, LOV, LTA, LTF, LTJ, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, MRE, MSE, MSO, MTF, MTN, MTT, MTW, MVY, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSO, OWE, PAR, PAU, PCR, PHI, PON, POS, PSI, PUN, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBN, SBS, SBT, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFV, SFW, SGT, SIV, SOD, SOF, SOS, SSF, SSO, SSY, STF, STI, STO, STT, STW, SVR, SVV, SZR, TER, THO, TOL, TON, TSC, TUN, UEI, UFI, UOS, UOV, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WEI, WEN, YUG, ZON, and mixtures or intergrowths thereof.In some embodiments, the zeolite has a framework type selected from the group consisting of CHA and AEI. In some embodiments, the zeolite has a CHA framework type.

[0015] In some embodiments, the zeolite has a framework composed of Si, Al, and O, and the molar ratio of Si to Al in the framework, calculated as the molar ratio of SiO2:Al2O3, is from about 2:1 to 50:1. In some embodiments, the molar ratio of SiO2:Al2O3 is about 25:1.

[0016] In some embodiments, the zeolite contains, calculated as CuO, from about 0 wt% to about 1.25 wt% copper based on the weight of the zeolite prior to mixing with the aqueous mixture. In some embodiments, the zeolite is in the NH4 + form prior to mixing with the first aqueous mixture.

[0017] In some embodiments, the zeolite contains particles having a D50 value of about 1 to about 5 micrometers and a D90 value of about 4 to about 10 micrometers. In some embodiments, the zeolite has a BET specific surface area of about 200 to about 1500 m 2 / g.

[0018] In some embodiments, the binder contains oxides of Al, Si, Ti, Zr, Ce, or a mixture of two or more thereof. In some embodiments, the binder contains alumina, silica, zirconia, a mixture thereof, or a mixed oxide containing Al, Si and optionally Zr. In some embodiments, the binder has a BET specific surface area of about 200 to about 1500 m 2 / g. In some embodiments, the binder has a D90 of about 0.5 to about 20 micrometers. In some embodiments, the binder has a D90 of about 4 to about 8 micrometers.

[0019] In some embodiments, the processed zeolite particles have a D90 value of about 0.5 to about 20 micrometers. In some embodiments, the slurry has a solids content of about 15 to about 45 wt% based on the weight of the mixture.

[0020] In some embodiments, the amount of metal contained in the processed zeolite is in the range of about 2 to about 10 wt%, about 2.5 to about 5.5 wt%, about 3 to about 5 wt%, or about 3.5 to about 4 wt% based on the weight of the metal ion-exchanged zeolite, calculated as metal oxide.

[0021] In some embodiments, the metal ion source is basic copper carbonate. In some embodiments, the metal ion source is iron carbonate. In some embodiments, the metal ion source further comprises one or more of copper oxide, copper hydroxide, copper nitrate, copper chloride, copper acetate, copper acetylacetonate, copper oxalate, or copper sulfate.

[0022] In some embodiments, this process comprises (ii) optionally, grinding the slurry comprising the processed zeolite; (iii) contacting a substrate with the slurry comprising the processed zeolite to form a coating on a substrate comprising an inlet end, an outlet end, an axial length extending from the inlet end to the outlet end, and a plurality of passages defined by an inner wall of the substrate extending therethrough; (iv) drying the substrate comprising the slurry disposed thereon; (v) firing the substrate obtained in (iv); (vi) optionally, repeating (iii) to (v) one or more times.

[0023] In some embodiments, the drying is carried out at a temperature of about 100 to about 150 °C. In some embodiments, the firing is carried out at a temperature of about 400 to about 600 °C.

[0024] In some embodiments, the substrate is a flow-through filter or a wall-flow filter.

[0025] In another aspect, a processed zeolite is provided, wherein the processed zeolite is obtained by or is obtainable by the processes disclosed herein.

[0026] In some embodiments, the efficiency of metal ion exchange onto the zeolite, as defined by the ratio of exchanged metal ions to all metal ions, is determined by a combination of ammonia back-exchange and inductively coupled plasma optical emission spectrometry (ICP-OES) and is greater than 80%.

[0027] In some embodiments, a powder sample of the processed zeolite exhibits higher H2 consumption below 300 °C and a lower onset temperature of the first H2-TPR peak compared to a processed zeolite prepared by a process in which the metal ion source is an acetate of copper, iron, or a mixture thereof, after aging at 450 °C for 2 hours.

[0028] In some embodiments, a powder sample of the processed zeolite is characterized by a higher proportion of exchanged copper ions as determined by the peak area of the metal ion signal from the T-O-T bond in the diffuse reflectance infrared Fourier transform spectrogram compared to a processed zeolite prepared by a process in which the metal ion source is copper acetate.

[0029] In a further aspect, an SCR or SCRoF catalyst article is provided that includes a substrate and a processed zeolite disposed on at least a portion thereof, wherein the substrate includes an inlet end, an outlet end, an axial length extending from the inlet end to the outlet end, and a plurality of passages defined by an inner wall of the substrate extending therethrough, and the SCR or SCRoF catalyst article is obtained by or is obtainable by a process as disclosed herein.

[0030] In some embodiments, the NO to nitrogen conversion at 250 °C of the SCR or SCRoF catalyst article is enhanced compared to the SCR or SCRoF catalyst article prepared by a process in which the treated zeolite has a metal ion source that is a copper acetate. x is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To provide an understanding of embodiments of the present invention, the accompanying drawings are referred to, in which reference numerals indicate components of exemplary embodiments of the present invention. The drawings are merely examples and are not to be construed as limiting the present invention. The disclosure described herein is shown in the accompanying figures by way of example, and not as a limitation. For the sake of brevity and clarity, the features shown in the figures are not necessarily drawn to scale. For example, the dimensions of some features may be exaggerated relative to other features for clarity. Further, reference numerals may be repeated in multiple drawings to indicate corresponding or similar elements where appropriate.

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[0032] The present disclosure generally relates to processes for preparing advanced selective catalytic reduction (SCR) catalysts and selective catalytic reduction on filter (SCRoF) catalysts, and articles comprising SCR or SCRoF catalysts prepared by the disclosed processes. Surprisingly, the in-situ ion exchange process disclosed herein provides higher efficiency of metal ion exchange into zeolites and has been found to provide SCR and SCRoF catalysts with higher metal ion incorporation compared to prior ion exchange processes. The metal ion-exchanged zeolite SCR and SCRoF catalysts so prepared achieve significantly increased NO x conversion rates, such as high catalytic activity, at any temperature, particularly low temperatures, compared to a standard Cu-chabazite reference SCR catalyst.

[0033] Definitions As used herein, the articles “a” and “an” refer to one or more than one (e.g., at least one) grammatical object. All ranges recited herein are inclusive. The term “about” is used throughout to represent small variations and is used to explain such. For example, “about” can mean that a numerical value can vary by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1%, or ±0.05%. All numerical values are modified by the term “about” whether explicitly indicated or not. A numerical value modified by the term “about” includes the particular identified value. For example, “about 5.0” includes 5.0. The recitation of a range of values herein is intended merely as a shorthand method of referring individually to each separate value within the range, unless otherwise indicated herein, and each separate value is incorporated herein as if it were individually recited herein.

[0034] The term "reduction" means a decrease in amount caused by some means.

[0035] "AMOx" refers to a selective ammonia oxidation catalyst, which is a catalyst containing one or more metals (typically Pt, but not limited thereto) and an SCR catalyst suitable for converting ammonia to nitrogen.

[0036] The term "associated" means, for example, "provided with", "connected to", or "communicating with", for example, "electrically connected" or "in fluid communication", or connected in some other way to perform a certain function. The term "associated" can mean, for example, being directly related or indirectly related through one or more other articles or elements.

[0037] "Average particle size" is synonymous with D50, that is, it means that half of the number of particles have a size larger than this and half have a size smaller than this. The particle size refers to primary particles. The particle size can be measured, for example, by laser light scattering technology using a dispersed or dry powder according to ASTM method D4464. The particle size distribution of D90 indicates that 90% (by number) of the particles have a Feret diameter smaller than a certain specific size when measured by a scanning electron microscope (SEM) or a transmission electron microscope (TEM) for sub-micron sized particles and by a particle size analyzer for carrier-containing particles (micron size).

[0038] As used herein, "BET surface area" has its ordinary meaning related to the Brunauer, Emmett, Teller method for determining surface area by N2 adsorption. Pore diameter and pore volume can also be determined using BET-type N2 adsorption or desorption experiments.

[0039] The term "catalyst" refers to a material that promotes a chemical reaction. Since the catalytic active species promotes a chemical reaction, it is also called an "accelerator".

[0040] The term "catalytic article" or "catalyst article" refers to a component used to promote a desired reaction. This catalytic article includes a "substrate" having at least one catalytic coating disposed thereon.

[0041] As used herein, "crystal size" means the length of one edge of a face of a crystal, preferably the longest edge, provided that the crystal is not acicular. Direct measurement of crystal size can be performed using microscopy methods such as SEM and TEM. For example, measurement by SEM involves examining the morphology of the material at high magnification (typically 1000× to 10,000×). The SEM method can be carried out by dispensing a representative portion of the zeolite powder onto a suitable mount, whereby the individual particles are spread moderately uniformly across the entire field of view at a magnification of 1000× to 10,000×. From this population, a statistically significant sample (e.g., 50 to 200) of random individual crystals is examined, and the longest dimension of the individual crystals, parallel to the horizontal line of the linear edge, is measured and recorded. Particles that are clearly large polycrystalline aggregates are not included in the measurement. Based on these measurements, the arithmetic mean of the crystal size of the sample is calculated.

[0042] "CSF" refers to a catalyzed soot filter that is a wall-flow monolith. A wall-flow filter consists of alternately positioned inlet channels and outlet channels, where the inlet channels are inserted into the outlet ends and the outlet channels are inserted into the inlet ends. The exhaust gas flow carrying soot that enters the inlet channels is passed through the filter walls before exiting through the outlet channels. In addition to soot filtration and regeneration, the CSF can carry an oxidation catalyst to oxidize CO and HC to CO2 and H2O, or to oxidize NO to NO2, to accelerate the downstream SCR catalyst or to promote the oxidation of soot particles at lower temperatures. When located behind the LNT catalyst, the CSF has an H2S oxidation function and can suppress H2S emissions during the LNT desulfurization process. The SCR catalyst composition can also be directly coated onto a wall-flow filter called SCRoF.

[0043] "DOC" refers to a diesel oxidation catalyst that converts hydrocarbons and carbon monoxide in the exhaust gas of a diesel engine. Typically, the DOC contains one or more platinum group metals, such as palladium and / or platinum; a carrier material, such as alumina; zeolite for HC storage; and optionally, promoters and / or stabilizers.

[0044] Generally, the term "effective" means having an effect, in weight or moles, with respect to a defined catalytic activity or storage / release activity, for example, about 35% to 100%, for example, 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%.

[0045] The term "exhaust stream" or "exhaust gas stream" refers to any combination of flowing gases that may contain solid or liquid particulate matter. This stream contains gaseous components and may contain certain non-gaseous components such as droplets, solid particles, etc., for example, the exhaust of a lean burn engine. The exhaust gas stream of a combustion engine typically contains combustion products (CO2 and H2O), incomplete combustion products (carbon monoxide (CO) and hydrocarbons (HC)), nitrogen oxides (NO x ), combustible and / or carbonaceous particulate matter (soot), and further contains unreacted oxygen and nitrogen.

[0046] "GDI" refers to a gasoline direct injection gasoline engine operating under lean burn conditions.

[0047] 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 exhibit a BET surface area of greater than 60 square meters per gram ("m 2 / g"), and in many cases, up to about 200 m 2 / g or more for fresh materials. Such activated alumina is usually a mixture of the gamma and delta phases of alumina, but may also contain significant amounts of the eta, kappa, and theta alumina phases.

[0048] As used herein, "impregnated" or "impregnation" refers to permeating a catalyst material into the pore structure of a support material.

[0049] The term "in fluid communication" is used to refer to articles located on the same exhaust line, i.e., a common exhaust stream 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 a "washcoat monolith".

[0050] As used herein, the term "intrapore site" refers to a site available to cations within the pore structure of a zeolite. A zeolite is a porous solid that includes pores and channels of various dimensions. A wide variety of cations can occupy these pores and move through these channels. The intrapore site refers to all internal spaces within the pore structure of a zeolite that can be occupied by cations, such as, for example, exchange sites and / or defect sites. An "exchange site" refers to a site available to cations that is primarily occupied by ion-exchanged metal cations that are often referred to as active metals and that are intentionally added to a zeolite to facilitate a chemical reaction. A "defect site" refers to an intrapore site where a portion of the Si-O-Al framework of a zeolite is damaged, thereby breaking an Al-O bond and replacing it with silanol functional groups (e.g., at least one but no more than four silanol groups (Si-OH)), creating an empty space or cavity. These sites are often occupied by copper oxide molecules with much weaker interactions, and when heated, these ions can easily leave to form metal oxide clusters.

[0051] As used herein, "LNT" refers to a lean NO x catalyst that contains a platinum group metal, ceria, and an alkaline earth metal trap material (e.g., BaO or MgO) suitable for adsorbing NO x during lean conditions. Under rich conditions, NO x is released and reduced to nitrogen.

[0052] As used herein, the expression "molecular sieve" refers to framework materials such as zeolites and other framework materials (e.g., isomorphous substitution materials), which in particulate form can be used as catalysts in combination with one or more promoter metals. A molecular sieve is generally a material based on oxygen ions with a tetrahedral site, a substantially uniform pore distribution, and an average pore diameter of 20 Å or less, having an extensive three-dimensional network structure.

[0053] Molecular sieves can be distinguished mainly according to the shape of the voids formed by the robust network structure of (SiO4) / AlO4 tetrahedra. The entrances to the voids are formed from 6, 8, 10, or 12 ring atoms for the atoms forming the entrance openings. A molecular sieve is a crystalline material having a fairly uniform pore diameter in the range of about 3 to 10 Å, 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 "eight-ring" molecular sieve that has eight-ring pore openings and a double six-ring secondary structural unit and has a cage-like structure resulting from the connection of double six-ring structural units by four-ring connections. Molecular sieves include small-pore, medium-pore, and large-pore molecular sieves or combinations thereof. The pore diameter is defined by the maximum ring diameter.

[0054] "NO x " The term refers to nitrogen oxide compounds such as NO, NO2, or N2O.

[0055] The terms "above" and "upper" related to the coating layer can be used synonymously. The term "directly above" means in direct contact. The disclosed article, in certain embodiments, is referred to as including one coating layer "above" a second coating layer, but such terminology is intended to encompass embodiments having intervening layers where direct contact between the coating layers is not required (i.e., "above" is not equivalent to "directly above").

[0056] As used herein, the term "promoted" refers to a component that is typically added intentionally to a zeolite material, for example, by ion exchange, as contrasted with the inherent impurities in the zeolite. A zeolite can be promoted, for example, with copper (Cu) and / or iron (Fe), but other catalytic metals such as manganese, cobalt, nickel, cerium, platinum, palladium, rhodium, or combinations thereof can be used.

[0057] In the context of zeolite SCR catalysts, the term "promoter metal" refers to one or more metals added to an ion-exchanged zeolite to produce a modified "metal-promoted" molecular sieve. By adding a promoter metal to an ion-exchanged zeolite, the catalytic activity of the active metal present at the exchange sites in the zeolite is enhanced compared to an ion-exchanged zeolite that does not contain a promoter metal. For example, by adding aluminum or an aluminum oxide as a "promoter metal" to a copper ion-exchanged zeolite, the catalytic activity of copper is enhanced by preventing and / or reducing the formation of catalytically inactive copper oxide clusters.

[0058] As used herein, the term "selective catalytic reduction" (SCR) refers to a catalytic process that uses a nitrogenous reducing agent to reduce nitrogen oxides to dinitrogen (N2).

[0059] "SCRoF" refers to an SCR catalyst composition directly coated on a wall flow filter.

[0060] "Substantially free of" 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 of" means less than 2 weight percent (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 shown.

[0061] As used herein, the term "substrate" refers to a monolithic material on which a catalyst composition, i.e., a catalyst coating, is typically disposed in the form of a washcoat. In one or more embodiments, the substrate is a flow-through monolith and a monolithic wall flow filter. Reference to a "monolithic substrate" means a homogeneous and continuous single structure from an inlet to an outlet.

[0062] As used herein, the terms "carrier" or "carrier material" refer to any material, typically a high surface area material, usually a refractory metal oxide material, to which a metal (e.g., PGM, stabilizer, promoter, binder, etc.) is applied by precipitation, association, dispersion, impregnation or other suitable means. Exemplary carriers include porous refractory metal oxide carriers as described hereinbelow. The term "supported" means "dispersed on", "incorporated in", "impregnated in", "impregnated on", "impregnated with", "deposited on", or otherwise bonded.

[0063] As used herein, the terms "upstream" and "downstream" refer to the relative directions in accordance with the flow of engine exhaust gas from the engine towards the tailpipe, with the engine in the upstream position and the tailpipe and any pollutant reduction articles such as filters and catalysts downstream of the engine. 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 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.

[0064] "Washcoat" has its ordinary meaning in the art of a thin, adherent coating of a material (e.g., a catalyst) applied to a "substrate", e.g., a honeycomb flow-through monolith substrate or a filter substrate that is porous enough to allow passage of the gas stream being treated. As used herein, and as described in Heck, Ronald, and Farrauto, Robert, Catalytic Air Pollution Control, New York: Wiley-Interscience, 2002, pp. 18-19, the washcoat layer comprises a compositionally distinct layer of material disposed on the surface of the monolith substrate or underlying washcoat layer. A washcoat is formed by preparing a slurry containing a catalyst having a specific solids content (e.g., 10 wt% to 50 wt%) in a liquid, then coating this onto the substrate and drying to provide the washcoat layer. The substrate can contain one or more washcoat layers, and each washcoat layer can differ in some way (e.g., the physical properties of the washcoat, such as particle size or crystallite phase, can be different), and / or the chemical catalytic function can be different.

[0065] As used herein, the term "zeolite" refers to a particular example of a molecular sieve that further contains silicon and aluminum atoms. Generally, zeolites are defined as aluminosilicates having an open three-dimensional framework structure composed of corner-sharing TO4 tetrahedra (where T is Al or Si, or optionally P). Zeolites can include SiO4 / AlO4 tetrahedra linked by common oxygen atoms so as to form a three-dimensional network structure. Cations that balance the charge of the anionic framework are loosely bound to the framework oxygen, and the remaining pore volume is filled with water molecules. Non-framework cations are generally exchangeable, and water molecules are removable. The aluminosilicate zeolite structure does not contain phosphorus or other metals that are 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 the purposes of this disclosure, SAPO, AlPO, and MeAlPO materials are considered non-zeolite molecular sieves.

[0066] A zeolite is a porous solid that contains pores and channels of various dimensions. Cations that balance the charge of the anionic framework are loosely bound to the framework oxygen, and the remaining pore volume is filled with water molecules. Non-framework cations are generally exchangeable, and water molecules are removable. A wide variety of cations can occupy these pores and move through these channels. As used herein, the term "intrapore site" refers to sites available to cations within the pore structure of a zeolite. Intrapore sites refer to all internal spaces within the pore structure of a zeolite that can be occupied by cations, such as, for example, exchange sites and / or defect sites. "Exchange site" refers to a site available to cations that is primarily occupied by ion-exchanged metal cations (e.g., Cu or Fe) intentionally added to the zeolite to adsorb and promote chemical reactions.

[0067] Unless otherwise specified, all parts and percentages are by weight. Unless otherwise indicated, "percent by weight (wt%)" is based on the entire composition excluding volatile substances, i.e., the dry solids content.

[0068] All methods described herein can be performed in any suitable order, unless otherwise indicated herein or unless clearly inconsistent with the context. The use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better explain the materials and methods and is not limiting of the scope unless otherwise claimed. No language in this specification should be construed as indicating any non-claimed element as essential to the practice of the disclosed materials and methods.

[0069] All U.S. patent applications, published patent applications, and patents referred to herein are hereby incorporated by reference.

[0070] I. A process for preparing an SCR or SCRoF catalyst, and an SCR or SCRoF catalyst prepared by the disclosed process In one aspect of the present disclosure, a process for preparing a selective catalytic reduction (SCR) catalyst or selective catalytic reduction on filter (SCRoF) catalyst, wherein the SCR or SCRoF catalyst comprises a metal ion-exchanged zeolite, is provided. This process includes the following: (i) Mixing a zeolite with an aqueous mixture comprising water and a metal ion source comprising a carbonate of copper, iron, or a mixture thereof to form a slurry comprising the treated zeolite.

[0071] Aqueous mixture In some embodiments, the aqueous mixture comprises water and a metal ion source comprising a carbonate of copper, iron, or a mixture thereof. The components of the first aqueous mixture are described in detail herein below.

[0072] Metal ion source As disclosed herein, the process for preparing an SCR catalyst or an SCRoF catalyst requires a metal ion source comprising a carbonate of copper, iron, or a mixture thereof. In some embodiments, the metal ion source is copper carbonate. In some embodiments, the metal ion source is copper carbonate. In some embodiments, the metal ion source is basic copper carbonate (Cu(OH)2Cu(CO3)). In some embodiments, the metal ion source is iron carbonate (Fe(CO3) or Fe2(CO3)3). In some embodiments, the metal ion source further comprises one or more of copper oxide, copper hydroxide, copper nitrate, copper chloride, copper acetate, copper acetylacetonate, copper oxalate, or copper sulfate.

[0073] In some embodiments, the method further comprises grinding the aqueous mixture prior to performing the mixing step. In some embodiments, the aqueous mixture comprises particles of the metal ion source having a D90 value of about 0.5 to about 20 micrometers. D90 is defined as the particle size at which 90% of the particles have a finer particle size. In some embodiments, the aqueous mixture comprises particles of the metal ion source having a D90 value of about 4 to about 10 micrometers. In some embodiments, the aqueous mixture comprises particles of the metal ion source having a D50 value of about 1 to about 3 micrometers. D50 is defined as the particle size at which 50% of the particles have a finer particle size.

[0074] The solids content of the aqueous mixture can vary and can be, for example, in the range of about 4 to about 30 wt%.

[0075] In some embodiments, the aqueous mixture further comprises one or more additives selected from one or more of sugar, dispersant, surface tension reducing agent, rheology modifier, or combinations thereof.

[0076] Zeolite As described previously herein, the term "zeolite" refers to a particular example of a molecular sieve that further contains silicon and aluminum atoms. According to one or more embodiments, the zeolite may be based on a framework topology that identifies the structure. Typically, any structural type of zeolite, e.g., ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, SCO, CFI, SGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EON, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, IHW, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LIT, LOS, LOV, LTA, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, MSO, MTF, MTN, MTT, MTW, MWW, NAB, NAT, NES, NON, NPO, NSI, OBW, OFF, OSI, OSO, OWE, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SGT, SOD, SOS, SSY, STF, STI, STT, TER, THO, TON, TSC, UEI, UFI, UOZ, USI, UTL, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, or a combination thereof can be used.

[0077] This zeolite can be a small-pore, medium-pore, or large-pore zeolite.

[0078] Small pore zeolites contain channels defined by up to eight tetrahedral atoms. As used herein, the term "small pore" refers to pore openings smaller than about 5 angstroms, e.g., on the order of about 3.8 angstroms. Exemplary small pore molecular sieves 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.

[0079] Intermediate pore zeolites contain channels defined by 10-membered rings. Exemplary intermediate 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.

[0080] The large pore zeolite contains channels defined by 12-membered rings. Exemplary large pore zeolites include framework types AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, VET, and mixtures or intergrowths thereof.

[0081] In some embodiments, the zeolite has a framework structure type selected from the group consisting of CHA, AEI, RTH, AFX, mixtures of two or more thereof, and mixed types of two or more thereof. In some embodiments, the zeolite has a framework structure type selected from the group consisting of CHA and AEI. In some embodiments, the zeolite has a framework type CHA. In some embodiments, the zeolite is SSZ-13.

[0082] The silica to alumina molar ratio (“SAR”) of the present zeolite can vary over a wide range, but is generally 2 or more. For example, the present zeolite can have an SAR of about 5 to about 1000. In one or more embodiments, the zeolite has a silica to alumina molar ratio (SAR) in the range of 2 to 300, including 5 to 250, 5 to 200, 5 to 100, and 5 to 50. In some embodiments, the zeolite has an SAR in the ranges of 10 to 200, 10 to 100, 10 to 75, 10 to 60, and 10 to 50, 15 to 100, 15 to 75, 15 to 60, and 15 to 50, 20 to 100, 20 to 75, 20 to 60, and 20 to 50. In some embodiments, the silica to alumina molar ratio (SiO2:Al2O3) is about 2 to about 50. In some embodiments, the molar ratio of SiO2 to Al2O3 is about 25.

[0083] In some embodiments, the zeolite is in the H form prior to mixing with the aqueous mixture. In some embodiments, the zeolite is in the NH4 + form prior to mixing with the aqueous mixture. In some embodiments, the zeolite contains an amount of copper, calculated as CuO, based on the weight of the zeolite, for example from about 0 wt% to about 1.25 wt% copper. In other words, the zeolite may have been pre-ion exchanged with a low level of copper prior to the mixing step.

[0084] The particle size of the zeolite can vary. Generally, the zeolite may be characterized in that the D90 particle size is from about 1 to about 40 micrometers, from about 1 to about 20 micrometers, or from about 1 to about 10 micrometers. In some embodiments, the zeolite of the second aqueous mixture comprises particles having a D50 value of from about 1 to about 5 micrometers and a D90 value of from about 4 to about 10 micrometers.

[0085] The present zeolite has a high surface area, for example, determined according to DIN66131, of at least about 200 m 2 / g, at least about 400 m 2 / g, at least about 500 m 2 / g, or at least about 750, or at least about 1000 m 2 / g, for example, from about 200 to about 1000 m 2 / g, or from about 500 to about 750 m 2 / g BET surface area. "BET surface area" has its normal meaning in relation to the Brunauer, Emmett, Teller method of determining surface area by N2 adsorption. In one or more embodiments, the BET surface area is from about 550 to about 700 m 2 / g.

[0086] Binder In some embodiments, the mixing step further includes adding a binder during the mixing step. The binder, for example, provides a homogeneous and intact catalyst after thermal aging when the catalyst is exposed to high temperatures of at least about 600 °C, such as about 800 °C or higher, and high steam environments of about 5% or higher. In some embodiments, the binder comprises oxides of Al, Si, Ti, Zr, Ce, or mixtures of two or more thereof. In some embodiments, the binder comprises alumina, silica, mixtures thereof, or mixed oxides containing Al and Si. In some embodiments, the binder is a mixture of alumina and silica. Examples of alumina binders include aluminum oxide, aluminum hydroxide, and aluminum oxyhydroxide. Aluminum salts and colloidal forms of alumina can also be used. Silica binders include various forms of SiO2, including silicates and colloidal silica.

[0087] The particle size of the binder can vary. Generally, the particle size of the binder can be characterized in that the D90 particle size is from about 0.1 to about 40 micrometers, from about 0.1 to about 30 micrometers, or from about 0.1 to about 25 micrometers. In some embodiments, the binder comprises particles having a D90 value of from about 0.5 to about 20 micrometers.

[0088] The binder has a high surface area, for example, determined according to DIN66131, of at least about 200 m 2 / g, at least about 400 m 2 / g, at least about 500 m 2 / g, at least about 750, or at least about 1000 m 2 / g, for example, from about 200 to about 1000 m 2 / g, or from about 500 to about 750 m 2 / g of BET surface area. In one or more embodiments, the BET surface area of the binder is from about 550 to about 700 m 2 / g.

[0089] Mixing A process as disclosed herein involves mixing a zeolite with an aqueous mixture comprising water and a metal ion source containing a carbonate of copper, iron, or a mixture thereof to form a slurry containing the treated zeolite.

[0090] The mixing step promotes an ion exchange reaction between the metal ion source and the zeolite. Without wishing to be bound by theory, it is believed that the use of the carbonate of the metal ion source can promote the ion exchange reaction with the zeolite by releasing carbon dioxide (CO2). The proposed ion exchange mechanism (“in-situ ion exchange”) is shown in Equation 1: H-zeolite + M x (CO3) y → M-zeolite + H2O + CO2 (1) Wherein, H-zeolite represents the hydrogen ion form of the zeolite, M represents a metal ion (e.g., copper, iron, or both), and x and y represent the stoichiometry of the metal ion source determined by the valence of the metal ion. Without wishing to be bound by theory, the ion exchange process begins at least during the mixing step, and the resulting slurry is believed to contain an amount of metal ion-exchanged zeolite referred to herein as “treated zeolite”. However, the ion exchange process initiated in the mixing step may proceed further, for example, during calcination or subsequent processing steps.

[0091] In some embodiments, the zeolite can be ion-exchanged with copper. In some embodiments, the zeolite can be ion-exchanged with iron. In some embodiments, the zeolite can be ion-exchanged with both copper and iron. If both metals are to be included in the metal ion-exchanged zeolite, multiple metal precursors (e.g., copper and iron precursors) can be ion-exchanged simultaneously or separately. In certain embodiments, iron can be exchanged into a zeolite material first promoted with copper (e.g., iron can be exchanged into a copper-promoted zeolite material). In certain embodiments, copper can be exchanged into a zeolite material first promoted with iron (e.g., copper can be exchanged into an iron-promoted zeolite material). In some embodiments, copper and iron are exchanged simultaneously into the zeolite (i.e., the metal ion source is a mixture of basic copper carbonate and iron carbonate).

[0092] The mixing step can be carried out at various temperatures, such as high temperatures, to promote the ion-exchange reaction. In some embodiments, the mixing is carried out at a temperature higher than about 10°C and lower than the decomposition temperature of the metal carbonate being used. More specifically, the mixing can be carried out at a temperature of about 10°C to about 150°C, about 20°C to about 120°C, or about 30°C to about 100°C. In certain embodiments, the temperature can be about 10°C to about 35°C, for example, about 20°C.

[0093] Preferably, the mixing is carried out over a time period of about 5 minutes or more, about 10 minutes or more, about 15 minutes or more, about 30 minutes or more, or about 45 minutes or more, such as about 5 minutes to about 240 minutes, about 10 minutes to about 180 minutes, about 15 minutes to about 180 minutes, about 20 minutes to about 120 minutes, or about 30 minutes to about 90 minutes, within the above temperature range.

[0094] In some embodiments, the process may include additional steps. For example, following the mixing step, prior to or after an optional grinding step, a slurry containing particles of the treated (i.e., metal ion-exchanged) zeolite can be subjected to one or more filtration steps, either alone or in combination with washing. For example, the metal ion-exchanged zeolite can be filtered from the aqueous medium to provide the final product. In some embodiments, washing and filtration can be performed using a filter press. In such a method, the metal ion-exchanged zeolite slurry is pumped into the filter press unit and the metal ion-exchanged zeolite solids collect on the filter web. The increasing pressure on the filter web as the solids are collected is beneficial for forcing the non-solids through the web into the filtrate. Optionally, air can be forced through the filter cake to further remove non-solids. In one or more embodiments, filtration can be performed using a funnel filter (e.g., a Buchner filter) and a suitable filter paper, and the filtration can be enhanced by applying a vacuum.

[0095] The filter cake having the metal ion-exchanged zeolite can be washed by pumping an aqueous solvent through the filter cake on the web. The aqueous solvent can be, in some embodiments, deionized water. In some embodiments, the washing can be carried out until the filtrate has a desired conductivity. Any recognized method for measuring the conductivity of the filtrate, such as the Standard Test Methods for Electrical Conductivity and Resistivity of Water of ASTM D1125-14, can be utilized according to the present disclosure. A standard conductivity measurement device such as a VWR® Symphony™ handheld meter having a conductivity probe can be used, and preferably, this device is calibrated with a conductivity standard. The washing is preferably carried out until the filtrate has a conductivity measurement value of about 400 micromhos or less, about 300 micromhos or less, about 250 micromhos or less, or about 200 micromhos or less, more specifically, about 10 micromhos to about 400 micromhos, about 25 micromhos to about 300 micromhos, or about 50 micromhos to about 200 micromhos. In some embodiments, washing can be used in particular to remove various ions such as sodium, iron, copper, ammonium, etc. from the solution.

[0096] In some embodiments, the slurry containing the treated zeolite particles thus obtained is milled to provide a specific particle size range, to enhance the mixing of the particles, or to form a homogeneous material. The milling can be achieved with a ball mill, a continuous mill, or other similar devices. In some embodiments, the treated zeolite particles have a D90 value of about 0.5 to about 20 micrometers.

[0097] The slurry may optionally contain various additional components. Typical additional components include, but are not limited to, binders as described herein, for example, additives for controlling the pH and viscosity of the slurry. Additional components can include hydrocarbon (HC) storage components (e.g., zeolites), associative thickeners, and / or surfactants (including anionic, cationic, nonionic, or amphoteric surfactants). A typical pH range for the slurry is from about 3 to about 6. Acidic or basic species may be added to the slurry to adjust the pH. For example, in some embodiments, the pH of the slurry is adjusted by the addition of an aqueous acetic acid solution.

[0098] The solids content of the slurry containing the particles of the treated zeolite can vary depending on the intended use. In some embodiments, the slurry has a solids content of from about 15 to about 45 weight percent, based on the weight of the mixture.

[0099] treated zeolite In another aspect, there is provided an SCR or SCRoF catalyst comprising a treated zeolite, wherein the treated zeolite is prepared by the process disclosed herein. The metal ion-exchanged zeolite prepared by this process can be characterized according to certain characteristics. Many of these functions are advantageous for providing an SCR or SCRoF catalyst having high efficiency with respect to NO x conversion rate, especially at low temperatures.

[0100] Various base metal-promoted zeolites and methods for preparing them are well known. Generally, base metals (e.g., copper, iron, etc.) are ion-exchanged into the zeolite. Such base metals generally replace alkali metals or NH4 +exchanged into the zeolite (this can be prepared, for example, by NH4 ion exchange into an alkali metal zeolite by methods known in the art, as disclosed in Bleken, F. et al., Topics in Catalysis 2009, 52, 218 - 228, which is incorporated herein by reference). + Although not wishing to be bound by theory, the methods disclosed herein provide metal ion - exchanged zeolites having a higher metal ion concentration and / or a higher percentage of ion - exchanged metal (i.e., metal ions present at the ion - exchange sites in the zeolite) compared to metal ion - exchanged zeolites produced by equivalent processes that do not utilize carbonates and that use conventional metal ion sources such as metal acetates.

[0101] The amount of metal ions exchanged in the metal ion - exchanged zeolite can vary. In some embodiments, the amount of metal contained in the metal ion - exchanged zeolite, calculated as the metal oxide, is in the range of about 1 to about 15 wt%, about 2 to about 10 wt%, about 2.5 to about 5.5 wt%, about 3 to about 5 wt%, or about 3.5 to about 4 wt% based on the weight of the metal ion - exchanged zeolite. In one or more specific embodiments, the ion - exchanged metal contains Cu, and the Cu content of the metal ion - exchanged zeolite calculated as CuO is in the range of up to about 10 wt%, including about 9, about 8, about 7, about 6, about 5, about 4, about 3, about 2, about 1, about 0.5, and about 0.1 wt%, in each case based on the weight of the final ion - exchanged zeolite and reported on a volatile - free basis.

[0102] In certain embodiments as disclosed herein, the copper present in the metal ion-exchanged zeolite can exist as different species and can be differently distributed as described herein. In addition to the copper that is exchanged to increase the level of copper associated with the exchange sites within the zeolite structure, non-exchanged copper in salt form can be present in the zeolite as so-called free copper. In some embodiments, free copper is not present in the zeolite. Surprisingly, according to the present disclosure, the efficiency of metal ion exchange into the zeolite, defined as the ratio of exchanged metal ions to all metal ions, is found in some embodiments to be greater than the efficiency of metal ion exchange when conventional metal ion sources (e.g., acetates, nitrates, oxides, hydroxides) are utilized. In some embodiments, the efficiency is greater than 80%. The efficiency of metal ion exchange can be determined, for example, by a combination of ammonia back-exchange and inductively coupled plasma optical emission spectroscopy (ICP-OES). In ammonia back-exchange, the ion-exchanged metal in the zeolite material is removed and the remaining non-exchanged metal remains in the form of a metal oxide. The amount of the remaining metal is determined by ICP-OES, and the difference in metal concentration before and after ammonia back-exchange is the amount of ion-exchanged metal. In some embodiments, the metal ion-exchanged zeolite as disclosed herein exhibits a weight ratio of ion-exchanged metal to metal oxide of at least about 1 when measured after calcining the zeolite at 450 °C in air for 1 hour. In some embodiments, this ratio is at least about 1.5. In some embodiments, this ratio is at least about 2. In some embodiments, the metal is copper and the ratio of ion-exchanged Cu to CuO is at least about 2.

[0103] Copper species that can be present in zeolite materials (e.g., copper oxide, metal, and ion-exchanged copper) can be identified by monitoring perturbed T-O-T bond (Si-O-Al and Si-O-Si) vibrations by diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy. The use of this FTIR technique has been demonstrated in the literature, e.g., Giamello et al., J. Catal. 136, 510-520 (1992). The structural vibrations of the T-O-T bonds in zeolites have absorption peaks at 1300-1000 cm -1 and 850-750 cm -1 for the asymmetric and symmetric vibration modes, respectively. Since the frequency of the asymmetric T-O-T vibration of the oxygen-containing ring is sensitive to the interaction with the cation, when interacting with the cation, the IR band shifts from the normal 1000-1300 cm -1 (characteristic position of the unperturbed ring) to about 850-1000 cm -1 . The shifted band appears in the transmission window between the two strong bands of the T-O-T asymmetric and symmetric vibrations. The position of such a shifted band depends on the characteristics of the cation. Such perturbed T-O-T bond vibrations are observed when copper ions are exchanged at the cation exchange positions of the zeolite framework structure, based on the strong interaction between the copper ions and adjacent oxygen atoms in the framework structure. The peak position depends on the state of the compensating cation and the structure of the zeolite framework. The peak intensity depends on the amount of compensating cation at the exchange site. In some embodiments, a powder sample of a metal ion-exchanged zeolite as disclosed herein, when measured by DRIFT spectroscopy, exhibits a higher peak area of the metal ion signal from the T-O-T bond compared to a metal ion-exchanged zeolite prepared by a process in which the metal ion source is, for example, copper acetate.

[0104] Surprisingly, according to the present disclosure, in some embodiments, the processed (i.e., metal ion-exchanged) zeolite prepared by the process disclosed herein exhibits improved SCR catalyst properties compared to metal ion-exchanged zeolites prepared by conventional processes. Without wishing to be bound by theory, it is believed that an increase in the concentration of metal ions within the ion exchange sites of the zeolite contributes to this increase in activity.

[0105] Temperature-programmed reduction (TPR) is a method for quantitatively characterizing the reducibility of metal species-containing compounds by hydrogen consumption. Metal species that undergo reduction include both metal ions and metal oxides (e.g., Cu +2 、Cu +1 、and CuO). Generally, a reducing gas mixture (typically 3% - 17% hydrogen diluted in argon or nitrogen) flows over the sample. A thermal conductivity detector (TCD) is used to measure changes in the thermal conductivity of the gas stream to provide hydrogen consumption data as a function of time and temperature. The use of this technique to evaluate metal-containing zeolites has been demonstrated in the literature, e.g., Yan et al., Journal of Catalysis, 161, 43 - 54 (1996). Higher total hydrogen consumption and lower temperatures for the onset of hydrogen uptake generally correlate with increased overall and low-temperature catalytic activity. In some embodiments, the powder sample of the metal ion-exchanged zeolite of the present disclosure, after aging at 450 °C for 2 hours, exhibits higher H2 consumption below 300 °C and a lower onset temperature of the first H2-TPR peak compared to a metal ion-exchanged zeolite prepared by a process in which the metal ion source is copper acetate.

[0106] II. Process for Preparing an SCR or SCRoF Catalytic Article, and SCR or SCRoF Articles Prepared by the Disclosed Process In some embodiments, a process as disclosed herein for preparing a selective catalytic reduction (SCR) catalyst or a selective catalytic reduction on filter (SCRoF) catalyst further includes steps directed to the preparation of an SCR or SCRoF catalyst article that includes a substrate and a treated zeolite prepared as disclosed herein. In some embodiments, an SCR or SCRoF catalyst article prepared by the process disclosed herein is provided.

[0107] In some embodiments, a process for preparing an SCR catalyst or an SCRoF catalyst as disclosed herein comprises (ii) optionally, grinding a slurry comprising the treated zeolite; (iii) contacting the substrate with a slurry comprising the treated zeolite to form a coating on the substrate that includes an inlet end, an outlet end, an axial length extending from the inlet end to the outlet end, and a plurality of passages defined by an inner wall of the substrate extending therethrough; (iv) drying the coated substrate; (v) firing the coated substrate obtained in (iv); (vi) optionally, repeating (iii) to (v) one or more times.

[0108] The processes and components of the SCR catalyst or SCRoF catalyst so obtained are described in detail hereinbelow.

[0109] Substrate In one or more embodiments, the present SCR catalyst or SCRoF catalyst is disposed on a substrate to form an SCR catalyst or SCRoF catalytic article. The catalytic article including the substrate is generally used as part of an exhaust gas treatment system (e.g., examples of the catalytic article include, but are not limited to, articles including the SCR catalyst or SCRoF catalyst disclosed herein). Useful substrates are three-dimensional and have a length, diameter, and volume similar to a cylinder. The shape does not necessarily have to conform exactly to a cylinder. The length is the axial length defined by an inlet end and an outlet end.

[0110] According to one or more embodiments, the substrate for the disclosed catalyst may be composed of any suitable material typically used to prepare automotive catalysts, and typically includes a metal or ceramic honeycomb structure. The substrate typically provides a plurality of walls to which a catalyst washcoat is applied and adhered, thereby functioning as a substrate for the catalyst.

[0111] The ceramic substrate can be made from any suitable refractory material, such as cordierite, cordierite-α-alumina, aluminum titanate, silicon titanate, silicon carbide, silicon nitride, zircon mullite, lischite, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, α-alumina, aluminosilicate, and the like.

[0112] The substrate can also be a metal and includes one or more metals or metal alloys. The metal substrate can include any metal substrate having openings or "punch-outs" in the channel walls. The metallic substrate can be used in various shapes such as pellets, compressed metallic fibers, corrugated sheets, or monolithic forms. Specific examples of metal substrates include base metal alloys with heat resistance, particularly alloys in which iron is a substantial or major component. Such alloys can contain one or more of nickel, chromium, and aluminum, and the total of these metals is advantageously in each case at least about 15 wt% (weight percent) of the alloy, based on the weight of the substrate, for example, about 10 to about 25 wt% chromium, about 1 to about 8 wt% aluminum, and 0 to about 20 wt% nickel. Examples of metal substrates include those having straight channels, those having blades protruding along the axial channels to obstruct the gas flow and open the communication of the gas flow between the channels, and those having holes for improving the gas transport between the channels to enable radial gas transport across the blades and the monolith.

[0113] Any suitable substrate for the catalytic articles disclosed herein can be used, such as a monolithic substrate ("flow-through substrate") of the type having fine parallel gas flow paths extending through from the inlet or outlet end face of the substrate so as to be open to the flowing fluid stream. Another suitable substrate is of the type having a plurality of fine substantially parallel gas flow paths 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 No. WO2016 / 070090, which is incorporated herein by reference in its entirety.

[0114] In some embodiments, the catalyst substrate includes 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. In some embodiments, the substrate is a flow-through substrate. The flow-through substrate and the wall flow filter are further described below.

[0115] Flow-through substrate In some embodiments, the substrate is a flow-through substrate (e.g., a monolithic substrate including a flow-through honeycomb monolithic substrate). The flow-through substrate has fine and parallel gas flow channels extending from an inlet end of the substrate to an outlet end such that the channels are open to the fluid flow. The channels, which are essentially straight paths from the fluid inlet to the fluid outlet, are defined by walls, and on or in the walls, the catalytic coating is arranged such that the gas flowing through the channels contacts the catalytic material. The flow channels of the flow-through substrate are thin-walled channels and can have any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. The flow-through substrate can be ceramic or metal as described above.

[0116] The flow-through substrate has, for example, a volume of about 50 in 3 ~ about 1200 in 3 and a cell density (inlet opening) of about 60 cells per square inch (cpsi) to about 500 cpsi or up to 900 cpsi, for example, about 200 to about 400 cpsi, and a wall thickness of about 50 to about 200 microns or about 400 microns.

[0117] Wall flow filter substrate In some embodiments, the substrate is a wall flow filter, which generally has a plurality of fine and substantially parallel gas flow paths 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 a monolithic wall flow filter substrate may contain up to about 900 or more flow paths (or "cells") per square inch of cross-section, although far fewer numbers may be used. For example, the substrate may have from about 7 to 600, more typically from about 100 to 400 cells per square inch ("cpsi"). The cells can have a rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal cross-section. The wall flow filter substrate may be ceramic or metallic as described above.

[0118] Referring to FIG. 1a, an exemplary wall flow filter substrate is cylindrical and has a cylindrical outer surface with a diameter D and an axial length L. FIG. 1b is a perspective view of an exemplary wall flow filter. A cross-sectional view of a monolithic wall flow filter substrate section is illustrated in FIG. 1b, showing alternating blocked and open passages (cells). The blocked or closed ends 100 and the open passages 101 are alternately positioned, with the opposite ends of each being open and blocked, respectively. The filter has an inlet end 102 and an outlet end 103. The arrows across the porous cell walls 104 represent that the exhaust gas flow enters the open cell ends, diffuses through the porous cell walls 104, and exits from the open outlet cell ends. The blocked ends 100 impede the 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 surrounded by the cell walls.

[0119] The wall flow filter article substrate is, for example, about 50 cm 3 , about 100 in 3 , about 200 in 3 , about 300 in 3 , about 400 in 3 , about 500 in 3 , about 600 in 3, about 700 in 3 , about 800 in 3 , about 900 in 3 , or about 1000 in 3 to about 1500 in 3 , about 2000 in 3 , about 2500 in 3 , about 3000 in 3 , about 3500 in 3 , about 4000 in 3 , about 4500 in 3 , or about 5000 in 3 It may have a volume up to. The wall flow filter substrate typically has a wall thickness of about 50 microns to about 2000 microns, for example, about 50 microns to about 450 microns, or about 150 microns to about 400 microns.

[0120] The walls of the wall flow filter are porous and generally have a wall porosity of at least about 40% or at least about 50% before applying the functional coating, and the average pore diameter is at least about 10 microns. For example, the wall flow filter article substrate in some embodiments has a porosity of ≧40%, ≧50%, ≧60%, ≧65%, or ≧70%. For example, the wall flow filter article substrate will have a wall porosity from about 50%, about 60%, about 65%, or about 70% to about 75% and an average pore diameter from about 10 microns or about 20 microns to about 30 microns or about 40 microns before applying the catalytic coating. The terms "wall porosity" and "substrate porosity" have the same meaning and are interchangeable. Porosity is the ratio of the void volume (or pore volume) to the total volume of the substrate material. The pore diameter and pore diameter distribution are typically determined by Hg porosimetry measurements.

[0121] Coating process of the substrate To manufacture the SCR or SCRoF catalytic article of the present disclosure, a substrate as described herein is contacted with an SCR or SCRoF catalyst as disclosed herein to provide a coating (i.e., a slurry containing particles of the treated zeolite is disposed on the substrate). The coating is a "catalytic coating composition" or a "catalytic coating". "Catalyst composition" and "catalytic coating composition" are synonymous.

[0122] The present SCR or SCRoF catalyst can typically be applied in the form of one or more washcoats containing an SCR or SCRoF catalyst as disclosed herein. A washcoat is formed by preparing a slurry containing a specific solids content of the catalyst in a liquid vehicle (e.g., about 10% to about 60% by weight), which is then applied to the substrate using any washcoat technique known in the art and dried and calcined to provide a coating layer. When multiple coatings are applied, the substrate is dried and / or calcined after each washcoat is applied and / or after the desired number of multiple washcoats are applied. In one or more embodiments, the catalytic material is applied to the substrate as a washcoat.

[0123] In some embodiments, drying is carried out at a temperature of about 100°C to about 150°C. In some embodiments, drying is carried out in a gas atmosphere. In some embodiments, the gas atmosphere contains oxygen. In some embodiments, drying is carried out over a period ranging from 10 minutes to 4 hours, more preferably from 20 minutes to 3 hours, and even more preferably from 50 minutes to 2.5 hours.

[0124] In some embodiments, the firing is carried out at a temperature of about 300 - 900 °C, about 400 - about 650 °C, or about 450 - about 600 °C. In some embodiments, the firing is carried out in a gas atmosphere. In some embodiments, the gas atmosphere contains oxygen. In some embodiments, the firing is carried out over a period ranging from 10 minutes to about 8 hours, about 20 minutes to about 3 hours, or about 30 minutes to about 2.5 hours.

[0125] After firing, the catalyst loading obtained by the above washcoat technique can be determined by calculating the difference between the coated weight and the uncoated weight of the substrate. As will be apparent to those skilled in the art, the catalyst loading can be adjusted by changing the rheology of the slurry. Further, the coating / drying / firing process for generating the washcoat layer (coating layer) can be repeated as needed to build up the coating to the desired loading level or thickness, i.e., it is possible to apply more than one washcoat. In some embodiments, the catalyst washcoat loading is about 0.8 - 2.6 g / in 3 , about 1.2 - 2.2 g / in 3 , or about 1.5 - about 2.2 g / in 3 is in the range.

[0126] This SCR or SCRoF catalyst coating may include one or more coating layers, and at least one layer includes this SCR or SCRoF catalyst. The catalyst coating may include one or more thin adherent coating layers disposed on and adhering to at least a portion of the substrate. The entire coating includes individual "coating layers".

[0127] Composition of the Coating In some embodiments, the present SCR or SCRoF catalytic article may include the use of one or more catalyst layers and combinations of one or more catalyst layers. The catalyst material may be present only on the inlet side of the substrate wall, only on the outlet side, both on the inlet side and the outlet side, or the wall itself may be entirely or partially composed of the catalyst material. The catalyst coating may be on the surface of the substrate wall and / or within the pores of the substrate wall, i.e., "in" and / or "on" the substrate wall. Thus, the expression "washcoat disposed on a substrate" means on any surface, e.g., on the wall surface and / or on the pore surface.

[0128] The washcoat may be applied such that different coating layers are in direct contact with the substrate. Alternatively, one or more "undercoats" may be present, whereby at least a portion of the catalytic coating layer or coating layers do not directly contact the substrate (rather, they contact the undercoat). One or more "overcoats" may be present such that at least a portion of the coating layer is not directly exposed to the gas flow or atmosphere (rather, it contacts the overcoat).

[0129] Alternatively, the catalyst composition may be present in a top coating layer that covers the bottom coating layer. The catalyst composition may be present in both the top layer and the bottom layer. Any one layer may extend over the entire axial length of the substrate. For example, the bottom layer may extend over the entire axial length of the substrate, and the top layer may also extend over the entire axial length of the substrate above the bottom layer. The top layer and the bottom layer may each extend from either the inlet end or the outlet end.

[0130] For example, both the bottom coating layer and the top coating layer can extend from the same substrate end, the top layer partially or completely overlays the bottom layer, the bottom layer extends over a partial length or the entire length of the substrate, and the top layer extends over a partial length or the entire length of the substrate. Alternatively, the top layer may overlay a part of the bottom layer. For example, the bottom layer can extend over the entire length of the substrate, and the top layer can extend from either the inlet end or the outlet end to about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the length of the substrate.

[0131] Alternatively, the bottom layer can extend from either the inlet end or the outlet end to about 10%, about 15%, about 25%, about 30%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, or about 95% of the length of the substrate, the top layer can extend from either the inlet end or the outlet end to about 10%, about 15%, about 25%, about 30%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, or about 95% of the length of the substrate, and at least a part of the top layer overlays the bottom layer. This "overlay" zone can extend, for example, from about 5% to about 80%, for example, about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60, or about 70% of the length of the substrate.

[0132] In some embodiments, an SCR or SCRoF catalyst as disclosed herein disposed on a substrate as disclosed herein includes a first washcoat disposed on at least a part of the length of the catalyst substrate.

[0133] In some embodiments, the first washcoat is disposed directly on the catalyst substrate, and the second washcoat (which may be the same or contain different catalysts or catalyst components) is disposed on at least a portion of the first washcoat. In some embodiments, the second washcoat is disposed directly on the catalyst substrate, and the first washcoat is disposed on at least a portion of the second washcoat. In some embodiments, the first washcoat is disposed directly on the catalyst substrate from the inlet end to a length of about 10% to about 50% of the total length, and the second washcoat is disposed on at least a portion of the first washcoat. In some embodiments, the second washcoat is disposed directly on the catalyst substrate from the inlet end to a length of about 50% to about 100% of the total length, and the first washcoat is disposed on at least a portion of the second washcoat. In some embodiments, the first washcoat is disposed directly on the catalyst substrate from the inlet end to a length of about 20% to about 40% of the total length, and the second washcoat extends from the inlet end to the outlet end. In some embodiments, the first washcoat is disposed directly on the catalyst substrate from the outlet end to a length of about 10% to about 50% of the total length, and the second washcoat is disposed on at least a portion of the first washcoat. In some embodiments, the first washcoat is disposed directly on the catalyst substrate covering 100% of the total length, and the second washcoat covers 100% of the total length and is disposed on the first washcoat.In some embodiments, the second washcoat covers 100% of the total length and is disposed directly on the catalyst substrate, and the first washcoat covers 100% of the total length and is disposed on the second washcoat.

[0134] The catalytic coating can advantageously be "zoned" and includes zoned catalytic layers, i.e., the catalytic coating contains different compositions over the axial length of the substrate. This can also be described as "laterally zoned". For example, the layer may extend from the inlet end to 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 to the inlet end and may extend over about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the substrate length. The different coating layers may be adjacent to each other and may not overlay each other. Alternatively, different layers may overlay a portion of each other to provide a third "intermediate" zone. The intermediate zone may extend, for example, over 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.

[0135] The zones of the present disclosure are defined by the relationship of the coating layers. For different coating layers, there are several possible zoning configurations. For example, there may be an upstream zone and a downstream zone, there may be an upstream zone, an intermediate zone, and a downstream zone, or there may be four different zones. When two layers are adjacent and do not overlap, there are an upstream zone and a downstream zone. When two layers overlap to some extent, there are upstream, downstream, and intermediate zones. For example, when the coating layer extends over the entire length of the substrate and different coating layers extend from the outlet end to a certain length and overlay a portion of the first coating layer, there are upstream and downstream zones.

[0136] For example, an SCR or SCRoF article may include an upstream zone including a first washcoat layer and a downstream zone including a second washcoat layer including a different catalyst material or component. Alternatively, the upstream zone may include the second washcoat layer and the downstream zone may include the first washcoat layer.

[0137] In some embodiments, the first washcoat is disposed on the catalyst substrate from the inlet end to a length of about 10% to about 50% of the total length, and the second washcoat is disposed on the catalyst substrate from the outlet end to a length of about 50% to about 90% of the total length. In some embodiments, the first washcoat is disposed on the catalyst substrate from the outlet end to a length of about 10% to about 50% of the total length, and the second washcoat is disposed on the catalyst substrate from the inlet end to a length of about 50% to about 90% of the total length.

[0138] Figures 3a, 3b, and 3c show some possible coating layer configurations having two coating layers. A substrate wall 200 is shown with a coating layer 201 (top coat) and a coating layer 202 (bottom coat) disposed thereon. This is a simplified drawing and, in the case of a porous wall flow-through substrate, pores and coatings adhering to the pore walls are not shown, and closed ends are not shown. In Figure 3a, the bottom coating layer 202 extends from the outlet for about 50% of the substrate length, and the top coating layer 201 extends from the inlet for more than 50% of the substrate length, overlaying a portion of layer 202, providing an upstream zone 203, an intermediate overlay zone 205, and a downstream zone 204. In Figure 3b, the coating layers 201 and 202 each extend over the entire length of the substrate, and the top layer 201 overlays the bottom layer 202. The substrate of Figure 3b does not include a zoned coating configuration. Figure 3c illustrates a zoned configuration having a coating layer 202 that extends from the outlet for about 50% of the substrate length to form a downstream zone 204 and a coating layer 201 that extends from the inlet for about 50% of the substrate length to provide an upstream zone 203. Figures 3a, 3b, and 3c may be useful for exemplifying SCR or SCRoF coatings on a wall-through substrate or a flow-through substrate.

[0139] In some embodiments, an SCR or SCRoF catalyst article is provided that includes a substrate as disclosed herein and a treated zeolite as disclosed herein disposed on at least a portion of the substrate. The substrate includes an inlet end, an outlet end, an axial length extending from the inlet end to the outlet end, and a plurality of passages defined by an inner wall of the substrate extending therethrough. Such an SCR or SCRoF catalyst article can be obtained or is obtainable by a process as disclosed herein. In some embodiments, an SCR or SCRoF catalyst article as disclosed herein exhibits an improved NO x conversion rate. In some embodiments, the NO to nitrogen at low temperature (<300 °C) xThe conversion rate is improved compared to SCR or SCRoF catalyst articles in which metal ion-exchanged zeolites are prepared by conventional processes where the metal ion source is, for example, a copper acetate.

[0140] III. Exhaust Gas Treatment System In a further aspect, an exhaust gas treatment system is provided that includes a lean burn engine that generates an exhaust gas stream and an SCR or SCRoF article as disclosed herein. The engine can be, for example, a diesel engine that operates under combustion conditions with air in excess of that required for stoichiometric combustion, i.e., lean conditions. In other embodiments, the engine can be an engine associated with a stationary source (e.g., a generator or a pump yard). In some embodiments, the emissions treatment system further includes one or more additional catalytic components. The relative arrangement of the various catalytic components present within the emissions treatment system can vary.

[0141] In the present exhaust gas treatment system and method, the exhaust gas stream enters at an upstream end and exits from a downstream end and is received by the article or treatment system. 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 an internal combustion engine.

[0142] The systems disclosed herein include a catalytic article as disclosed herein and may further include one or more additional components. In some embodiments, the one or more additional components are a diesel oxidation catalyst (DOC), a soot filter (which may or may not be catalyzed), a selective catalytic reduction (SCR) catalyst, a urea injection component, an ammonia oxidation catalyst (AMOx), a low temperature NO x absorbent (LT-NA), a lean NO xselected from the group consisting of traps (LNTs) and combinations thereof. The system can include, for example, a selective catalytic reduction catalyst (SCR) as disclosed herein, a diesel oxidation catalyst (DOC), a reductant injector, a soot filter, an ammonia oxidation catalyst (AMOx), or a lean NO x one or more articles including a trap (LNT). The article including the reductant injector is a reducing article. The reducing system includes a reductant injector and / or a pump and / or a reservoir, etc. The treatment system can further include a soot filter and / or an ammonia oxidation catalyst. The soot filter may or may not be catalyzed, or may be catalyzed (CSF). For example, the treatment system can include an article including a DOC, a CSF, a urea injector, an SCR article, and an article including an AMOx, from upstream to downstream. Lean NO x traps (LNTs) may also be included.

[0143] The relative arrangements of the various catalytic components present within the exhaust treatment system can vary. In the present exhaust gas treatment system and method, the exhaust gas stream enters at an upstream end and exits at a downstream end to be received by an article or treatment system. The inlet end of a 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 an internal combustion engine.

[0144] One exemplary emissions treatment system is illustrated in FIG. 4, which shows a schematic of emissions treatment system 20. As shown, the emissions treatment system can include a plurality of catalyst components in series downstream of an engine 22, such as a lean burn gasoline engine. At least one of the catalyst components will be an SCR catalyst of the present invention as described herein. The catalyst composition of the present invention can be combined with a number of additional catalyst materials and placed at various positions relative to the additional catalyst materials. FIG. 4 illustrates five catalyst components 24, 26, 28, 30, 32 in series, although the total number of catalyst components can vary and the five components are merely an example. One of ordinary skill in the art will recognize that there may be instances where it is desirable to arrange the relative positions of the various articles in an order different from that illustrated herein. Such alternative orderings are contemplated by this disclosure.

[0145] Without limitation, Table 1 presents various exhaust gas treatment system configurations of one or more embodiments. Note that for each catalyst, 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, which is upstream of catalyst E (if present), and is connected to the next catalyst via an exhaust duct. References to components A - E in the table can be cross - referenced with the same symbols in FIG. 4.

[0146] The LNT catalyst described in Table 1 can be any catalyst that has been conventionally used as a NO x trap and typically includes base metal oxides (such as BaO, MgO, CeO2, etc.) and platinum group metals (e.g., Pt and Rh) for the oxidation and reduction of NO by the catalyst, and a NO x adsorbent composition.

[0147] The LT - NA catalyst described in Table 1 can be any catalyst that can adsorb NO x (e.g., NO or NO2) at low temperatures (<250°C) and release it into the gas stream at high temperatures (>250°C). The released NO Xis generally converted to N2 and H2O on a downstream SCR or SCRoF catalyst as disclosed herein. Typically, the LT-NA catalyst comprises a Pd-promoted zeolite or a Pd-promoted refractory metal oxide.

[0148] References to SCR in the table refer to SCR catalysts that may include the SCR catalyst compositions of the present invention. References to SCRoF (i.e., SCR on a filter) refer to particulate or soot filters (e.g., wall-flow filters) that may include the SCR catalyst compositions of the present invention. When both SCR and SCRoF are present, one or both may include the SCR catalyst of the present disclosure, or one of the catalysts may include a conventional SCR catalyst (e.g., the SCR catalyst is prepared by a conventional ion exchange process).

[0149] References to AMOx in the table refer to ammonia oxidation catalysts that are provided downstream of the catalysts of one or more embodiments of the present invention and can remove any leaked ammonia from the exhaust gas treatment system. In certain embodiments, the AMOx catalyst may include a PGM component. In one or more embodiments, the AMOx catalyst may include a bottom coat having PGM and a top coat having an SCR function.

[0150] As will be recognized 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 comprises one or more catalyst components attached at a location near the engine (a close-coupled location, CC), and additional catalyst components are at a location below the vehicle body (an underfloor location, UF). In one or more embodiments, the exhaust gas treatment system may further comprise a urea injection component.

Table 1

[0151] IV. Method for Treating Engine Exhaust Gas Flow Another aspect of the present invention is directed to a method of treating an exhaust gas stream of a lean burn engine, particularly a lean burn gasoline engine or a diesel engine. Generally, the method includes contacting the exhaust gas stream with the catalytic article of the present disclosure or the exhaust treatment system of the present disclosure. The method may include placing an SCR or SCRoF catalytic article according to one or more embodiments of the present invention downstream of the engine and flowing the engine exhaust gas stream over the catalyst. In one or more embodiments, the method further includes placing additional catalyst components downstream of the engine, as described above. In some embodiments, the method includes one or more NOs that may be present in the exhaust gas stream x contacting the exhaust gas stream with the catalytic article of the present disclosure or the exhaust gas treatment system at a time and temperature sufficient to reduce the level of the component.

[0152] The present catalyst composition, article, system, and method are suitable for treating exhaust gas streams of internal combustion engines, such as gasoline, small diesel, and large diesel engines. The catalyst composition is also suitable for treating emissions from stationary industrial processes, removing harmful or toxic substances from indoor air, or catalyzing in chemical reaction processes.

[0153] It will be readily apparent to those skilled in the relevant art that suitable modifications and adaptations to the compositions, methods, and uses described herein can be made without departing from the scope of any embodiment or aspects 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 all of the embodiments, aspects, options, examples, and preferences herein. All patents and publications cited herein are incorporated herein by reference for their specific teachings as described, unless a specific other incorporation description is provided.

Example

[0154] Aspects of the present invention are more fully illustrated by the following examples, which are presented to illustrate certain aspects of the invention and should not be construed as limiting the invention. Before describing some exemplary embodiments, it is to be understood that the invention is not limited to the details of the configurations or process steps described in the following description, that other embodiments are possible, and that the invention can be practiced or carried out in various ways. Unless otherwise specified, all parts and percentages are by weight, and all weight percentages are expressed on a dry basis, i.e., the water content is excluded unless otherwise indicated.

[0155] Preparation of Copper Ion-Exchanged Zeolite In-situ ion exchange (ISIE) was performed using CHA zeolite pre-exchanged with 1.25 wt% copper (measured on a CuO basis). CHA had a silica-to-alumina ratio (SiO2:Al2O3) of 25, a primary particle size of less than about 0.5 micrometers, and a BET specific surface area of about 600 m 2 / g. Various copper salts were used as the copper ion source, including copper oxide, copper oxide and acetic acid, copper oxide and zirconium acetate, copper acetate, copper nitrate, copper oxide and nitric acid, copper hydroxide, and basic copper carbonate.

[0156] In each case, the copper salt was dissolved or suspended in water in an amount to achieve a target loading of 3.31 wt% copper (as CuO). The resulting mixture was milled so that the D50 value of the particles was about 2.5 micrometers and the D90 value of the particles was about 5 micrometers. After this step, the CHA zeolite was added to the copper-containing slurry and the resulting slurry was thoroughly mixed. The resulting slurry was milled until the D90 value of the particles was about 4.5 micrometers. After completion of the ISIE process, the sample was calcined at 450 °C for 2 hours.

[0157] Copper Exchange Efficiency The copper exchange efficiency of the ISIE process was evaluated for samples prepared using various copper salts. The exchange efficiency was defined as the ratio of the exchanged copper to all copper and determined by ammonia back-exchange and inductively coupled plasma optical emission spectrometry (ICP-OES). The analysis was performed after drying the slurry at 130 °C for 1 hour and firing the dried powder at 450 °C for 2 hours.

[0158] As shown in Table 1, all of the copper ion-exchanged zeolites prepared by ISIE using either CuO with or without acetic acid or nitric acid, copper acetate, copper nitrate, or basic copper carbonate exhibited high levels of exchange efficiency (84.6 - 89.9%). Surprisingly, the copper ion-exchanged zeolite prepared from basic copper carbonate exhibited a significantly higher proportion of Cu 2+ as ion-exchanged copper as measured by DRIFT.

[0159] Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were performed on a THERMO NICOLET instrument equipped with an MCT (HgCdTe) detector and in a Harrick environmental chamber equipped with a ZnSe window. The copper ion-exchanged zeolite material was ground into fine powder using a mortar and pestle and placed in a sample cup. The powder was dehydrated in flowing Ar at 40 mL / min at 400 °C for 1 hour, cooled to 30 °C, and spectra were recorded using KBr as a reference.

[0160] The copper species in the zeolite material can be identified by monitoring the perturbed T-O-T bond (Si-O-Al and Si-O-Si) vibrations by infrared (IR) spectroscopy. The structural vibrations of the T-O-T bonds in zeolites have absorption peaks at 1300-1000 cm-1 and 850-750 cm-1 for the asymmetric and symmetric vibration modes, respectively. The frequency of the asymmetric T-O-T vibration of the oxygen ring is sensitive to the interaction with the cation. When interacting with the cation, the IR band shifts from the normal 1000-1300 cm-1 (the position characteristic of the unperturbed ring) to about 850-1000 cm-1. The shifted band appears in the transmission window between the two strong bands of the T-O-T asymmetric and symmetric vibrations. The position of such a shifted band depends on the characteristics of the cation. Such perturbed T-O-T bond vibrations are observed when copper ions are exchanged into the cation positions of the zeolite framework structure, based on the strong interaction between the copper ions and the adjacent oxygen atoms in the framework structure. The peak position depends on the state of the compensating cation and the structure of the zeolite framework. The peak intensity depends on the amount of the compensating cation at the exchange site.

[0161] Peak fitting was performed using Origin 9.1 software. In peak fitting, the peaks were modeled as Gaussian peaks, and peak fitting was carried out until a chi-squared tolerance value of 1E-6 was reached. The IR signal in the wavelength range of 900-955 cm-1 due to the perturbed T-O-T bond vibration absorption was attributed to the exchanged copper ions within the zeolite material. The absorption peak with a maximum value at a wavelength of 900 cm-1 was due to the perturbed T-O-T bond vibration by Cu 2+ and the absorption peak with a maximum value at a wavelength of 955 cm-1 was due to the perturbed T-O-T bond vibration by Cu(OH)+. To enable peak deconvolution by the software, the peak position at a wavelength of 935 cm-1 was included. The sum of the peak areas from 955-900 cm-1 indicates the total of the exchanged copper ions at the exchange site, including CuOH + and Cu 2+ .

Table 2

[0162] Catalytic activity measured by TPR Examples of copper ion-exchanged zeolites prepared from various copper sources were evaluated by hydrogen TPR to determine the reactivity of the catalyst. The experimental conditions were as follows: Pretreatment: He, 50 cc / min, 1 hour at 110 °C. H2-TPR: 5% H2 / N2, 50 cc / min, 80 °C to 900 °C, 10 °C / min.

[0163] The same amount of catalyst powder was used in the TPR experiment. The first step was to pretreat with He at 50 cc / min for 1 hour at 110 °C to remove weakly bound adsorbents and clean the catalyst surface. The second step was to supply a mixed gas of H2 in N2 at 50 cc / min at 80 °C to 900 °C with a temperature ramp rate of 10 °C / min. The resulting spectra were recorded and used to determine the temperature and amount of H2 consumption.

[0164] Results from samples prepared according to embodiments of the methods disclosed herein (using basic copper carbonate), as well as comparative examples generated from various copper sources, are described in Table 3 and Figure 5. Examples prepared by the methods disclosed herein (using basic copper carbonate) exhibited a lower onset temperature (low temperature peak, "LT") for the first H2-TPR peak and higher H2 consumption compared to the comparative examples. These results demonstrate that the copper ion-exchanged zeolites prepared by the methods disclosed herein are more reducible and, thus, more reactive catalysts.

Table 3

[0165] Preparation of Catalytic Articles The previously prepared copper ion-exchanged zeolite prepared from CuO-zirconium acetate (comparison) and basic copper carbonate (the present invention) was mixed with an Al-based promoter (94 wt% Al2O3, 6 wt% SiO2, having a BET specific surface area of 173 m 2 / g and a Dv90 of about 5 micrometers) to form a mixture having a solids content of 38 wt% based on the weight of the mixture. The amount of copper ion-exchanged zeolite was calculated such that the filled amount of the zeolite after firing was 87.8% of the filled amount of the coating in the catalyst after firing. The resulting slurry was milled until the particles reached a Dv90 value of about 4.5 micrometers.

[0166] A porous uncoated wall flow filter substrate (silicon carbide) was coated twice with the final slurry over 100% of the axial length of the substrate from the inlet end to the outlet end. To do so, the substrate was immersed in the final slurry from the inlet end until the slurry reached the top of the substrate. Further, a pressure pulse was applied to the inlet end to distribute the slurry uniformly in the substrate. The coated substrate was dried at 130 °C for 2 hours and fired at 450 °C for 2 hours. This process was repeated once. The final coating fill amount after firing was 1.97 g / in 3 , which, calculated as CuO, is about 1.79 g / in based on the weight of the copper ion-exchanged zeolite, 0.18 g / in 3 of alumina + silica, and contains 3.63 wt% Cu. 3

[0167] Evaluation of Catalytic Articles - Engine Tests Comparative articles and articles of the present invention prepared according to embodiments of the present disclosure were evaluated in engine tests. The maximum NO achieved for the articles prepared by the disclosed method x conversion rate is significantly higher by about 300 °C or less compared to articles prepared using CuO-zirconium acetate as the copper ion source. xThe conversion rate was presented (Table 4). The performance evaluation was carried out in an engine test cell under the following steady-state conditions: (1) 192 °C, 120 m 3 / h, and 140 ppm of NO x , NO2 / NOx SCRoF inlet 4%, (2) 221 °C, 130 m 3 / h, and 190 ppm of NO x , NO2 / NOx SCRoF inlet 4%, (3) 283 °C, 140 m 3 / h, and 420 ppm of NO x , NO2 / NOx SCRoF inlet 11%, (4) 595 °C, 60 m 3 / h, and 180 ppm of NO x , NO2 / NOx SCRoF inlet 13%, and (5) 642 °C, 110 m 3 / h, and 350 ppm of NO x , NO2 / NOx SCRoF inlet 15%.

[0168] The values of temperature [°C], volumetric flow rate [m 3 / h], NO x emission [ppm], and NO2 / NO x ratio SCRoF inlet [%] were averaged over the dosing time.

Table 4

[0169] The maximum NO x conversion rate achieved for the articles prepared by the disclosed method was significantly higher at 192 °C and 221 °C compared to the articles prepared using CuO-zirconium acetate as the copper ion source when limited to 20 ppm of ammonia slip. The NO x conversion rate was presented (Table 5).

Table 5

[0170] The ammonia storage capacity of the articles prepared by the disclosed method was significantly higher at 221 °C compared to articles prepared using CuO - zirconium acetate (which forms copper acetate in situ) as the copper ion source (Table 6).

Table 6

[0171] In summary, the data presented in Tables 1 - 6 show that the process disclosed herein provides copper ion - exchanged zeolites with higher copper loadings and increased ion - exchanged copper, and that articles containing such copper ion - exchanged zeolites exhibit enhanced low - temperature conversion rates of NO x and ammonia storage compared to the comparative examples.

Claims

1. A process for preparing a selective catalytic reduction (SCR) catalyst or a selective catalytic reduction on filter (SCRoF) catalyst, wherein the SCR or SCRoF catalyst comprises a metal ion-exchanged zeolite, and the process comprises: (i) mixing a zeolite with an aqueous mixture comprising water and a metal ion source comprising a carbonate of copper, iron or a mixture thereof to form a slurry comprising the treated zeolite; (ii) performing an ion exchange of copper and / or iron with the treated zeolite; and the zeolite contains more than 0 wt% and at most 1.25 wt% copper, calculated as CuO, based on the weight of the zeolite, prior to mixing with the aqueous mixture, and the slurry contains particles of the metal ion source having a D90 value of from about 0.5 to about 20 micrometers.

2. The process according to claim 1, wherein the mixing step further comprises adding a binder during the mixing step.

3. The process according to claim 1 or 2, further comprising grinding the aqueous mixture before performing the mixing step.

4. The process according to claim 1, wherein the slurry contains particles of the metal ion source having a D50 value of from about 1 to about 3 micrometers and a D90 value of from about 4 to about 10 micrometers.

5. The process according to any one of claims 1 to 4, wherein the aqueous mixture further comprises one or more additives selected from one or more of sugar, a dispersant, a surface tension reducing agent, a rheology modifier, or a combination thereof.

6. The process according to any one of claims 1 to 5, wherein the zeolite has a framework type selected from the group consisting of ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, 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, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, EZT, FAU, FER, FRA, GIS, GIU, 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, LIO, LIT, LOS, LOV, LTA, LTF, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, MRE, MSE, MSO, MTF, MTN, MTT, MVY, MTW, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, PAR, PAU, PCR, PHI, PON, PUN, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SCO, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGF, SGT, SIV, SOD, SOF, SOS, SSF, SSY, STF, STI, STO, STT, STW, SVR, SZR, TER, THO, TON, TSC, TUN, UEI, UFI, UOS, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, and mixtures or twins thereof.

7. The process according to any one of claims 1 to 6, wherein the zeolite has a framework type selected from the group consisting of CHA and AEI.

8. The process according to any one of claims 1 to 7, wherein the zeolite has a CHA framework type.

9. The zeolite has a framework composed of Si, Al, and O, and the molar ratio of SiO ２ :Al ２ O ３ in the framework is from about 1 to about 100, or from about 2 to about 50, the process according to any one of claims 1 to 8.

10. The process according to any one of claims 1 to 9, wherein the zeolite comprises particles having a D50 value of about 1 to about 5 micrometers and a D90 value of about 4 to about 10 micrometers before mixing with the aqueous mixture.

11. The zeolite has a BET specific surface area of about 200 to about 1500 m ２ / g, and the process according to any one of claims 1 to 10.

12. The process according to any one of claims 2 to 11, wherein the binder comprises an oxide of Al, Si, Ti, Zr, Ce, or a mixture of two or more thereof.

13. The process according to any one of claims 2 to 12, wherein the binder comprises alumina, silica, zirconia, a mixture thereof, or a mixed oxide comprising Al, Si and optionally Zr.

14. The binder has a BET specific surface area of about 200 to about 1000 m ２ / g, and the process according to any one of claims 2 to 13.

15. The process according to any one of claims 2 to 14, wherein the binder has a D90 of about 0.5 to about 20 micrometers.

16. The process according to any one of claims 2 to 15, wherein the binder has a D90 of about 4 to about 8 micrometers.

17. The process according to any one of claims 1 to 16, wherein the treated zeolite comprises particles having a D90 value of about 0.5 to about 20 micrometers.

18. The process according to any one of claims 1 to 17, wherein the slurry has a solids content of about 15 to about 45 wt% based on the weight of the mixture.

19. The amount of metal contained in the treated zeolite, calculated as the metal oxide, is in the range of about 2 to about 10 wt%, about 2.5 to about 5.5 wt%, about 3 to about 5 wt%, or about 3.5 to about 4 wt% based on the weight of the metal ion-exchanged zeolite, according to any one of claims 1 to 18.

20. The process according to any one of claims 1 to 19, wherein the metal ion source is basic copper carbonate.

21. The process according to any one of claims 1 to 19, wherein the metal ion source is iron carbonate.

22. The process according to claim 20 or 21, wherein the metal ion source further comprises one or more of copper oxide, copper hydroxide, copper nitrate, copper chloride, copper acetate, copper acetylacetonate, copper oxalate, or copper sulfate.

23. (iii) Optionally, grinding the slurry comprising the treated zeolite; (iv) contacting the substrate with the slurry comprising the treated zeolite to form a coating on the substrate comprising an inlet end, an outlet end, an axial length extending from the inlet end to the outlet end, and a plurality of passages defined by an inner wall of the substrate extending therethrough; (v) drying the coated substrate; (vi) firing the coated substrate obtained in (v); (vii) optionally, repeating (iv) to (vi) one or more times, the process according to any one of claims 1 to 22. (Claim 24) (23) The process according to claim 23, wherein the drying is carried out at a temperature of about 100 to about 150 °C. (Claim 25) (23) The process according to claim 23 or 24, wherein the firing is carried out at a temperature of about 400 to about 600 °C. (Claim 26) (23) The process according to any one of claims 23 to 25, wherein the substrate is a flow-through monolith or a wall-flow substrate. (Claim 27) A treated zeolite, wherein the treated zeolite is obtained by the process according to any one of claims 1 to 22. (Claim 28) (27) The treated zeolite according to claim 27, wherein the efficiency of metal ion exchange into the zeolite is determined by a combination of ammonia back-exchange and inductively coupled plasma optical emission spectrometry (ICP-OES) when defined as the ratio of exchanged metal ions to all metal ions and is more than 80%. (Claim 29) An SCR or SCRoF catalyst article comprising a substrate and a treated zeolite disposed on at least a portion thereof, the substrate comprising an inlet end, an outlet end, an axial length extending from the inlet end to the outlet end, and a plurality of passages defined by an inner wall of the substrate extending therethrough, the SCR or SCRoF catalyst article being obtained by the process according to any one of claims 23 to 26.

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