Method for forming a catalyst article

Abstract

This provides an improved process for forming wash-coated catalyst articles. [Solution] (a) At least the following components: (i) H + or NH4 + A method comprising: (ii) forming a slurry by mixing together a crystalline molecular sieve, wherein the crystalline molecular sieve is a microporous molecular sieve, (ii) an insoluble active metal precursor containing copper(II) carbonate, and (iii) an aqueous solvent, wherein the slurry has a solid content of up to 50% by weight, and step (a) is carried out at a temperature in the range of 10 to 35°C; (b) coating a substrate with the slurry formed in step (a); and (c) firing the coated substrate formed in step (b) to form a catalyst layer on the substrate. Further providing catalyst articles and exhaust systems suitable for use in the selective catalytic reduction of nitrogen oxides.

Description

[Technical Field]

[0001] The present invention relates to a method for forming a catalyst article. In particular, the present invention relates to a method for forming a catalyst article suitable for use in the selective catalytic reduction of nitrogen oxides (NOx) in exhaust gas. [Background technology]

[0002] Numerous catalytic converters are manufactured each year for use in treating emissions from mobile and stationary power sources. Catalytic converters for use in automobiles typically comprise an extruded ceramic monolith with channels provided for exhaust gas through-flow. The channels in the monolith may be coated with a catalytic activator. Alternatively, the extruded monolith itself is formed of the catalytic activator (referred to as a "fully activated extruded product" or "extruded catalyst").

[0003] In the production of coated catalysts, compositions known as “washcoats” are applied to a substrate (e.g., a ceramic monolith). Washcoats typically comprise a liquid and a catalytic activator. Washcoats can take the form of a solution, slurry, or suspension of the catalytic material in a solvent. Once coated onto the substrate, the washcoat typically undergoes a calcination process to remove the solvent and fix the catalytic activator to the substrate.

[0004] Substrates for use in catalytic converters generally include a honeycomb-shaped integral structure having parallel channels of uniform size extending from a first end to a second end of the molded product. Typically, the channels are open at both ends of the first and second ends, forming a so-called "flow-through" structure. Alternatively, the channels at the first upstream end can be sealed with suitable ceramic cement, and the channels that are not sealed at the first upstream end can also be sealed at the second downstream end to form a so-called wall-flow filter.

[0005] Nitrogen oxides (NOx) produced by ammonia (NH3-SCR) x Selective catalytic reduction of NOx is used for vehicles such as automobiles, trucks, locomotives, and ships, and for stationary and mobile engines, primarily diesel engines, to remove exhaust gases. x This is considered the most practical and efficient technique for mitigating [the problem].

[0006] Known SCR (selective catalytic reduction) catalysts include molecular sieves. Useful molecular sieves include crystalline or quasicrystalline materials that may be aluminosilicates (zeolites) or silicoaluminophosphates (SAPO). Such molecular sieves are constructed of, for example, ring-linked repeating SiO4, AlO4, and optionally PO4 tetrahedral units to form a framework with regular intracrystalline cavities and channels of molecular size. The specific arrangement of the tetrahedral units (ring members) gives rise to the molecular sieve framework, and by convention, each unique framework is assigned a unique three-letter code (e.g., "CHA") by the International Zeolite Association (IZA). Examples of molecular sieve skeletons that are known SCR catalysts include the skeleton codes CHA (chabazite), BEA (beta), MOR (mordenite), AEI, MFI, and LTA.

[0007] Molecular sieves (e.g., zeolites) can also be classified by pore size, for example, the maximum number of tetrahedral atoms present in the molecular sieve's framework. As defined herein, “small-pore” molecular sieves, such as CHA, have a maximum ring size of 8 tetrahedral atoms, while “medium-pore” molecular sieves, such as MFI, have a maximum ring size of 10 tetrahedral atoms, and “large-pore” molecular sieves, such as BEA, have a maximum ring size of 12 tetrahedral atoms. Small-pore and medium-pore molecular sieves, in particular small-pore molecular sieves, are preferred for use in SCR catalysts because they can provide, for example, improved SCR performance and / or improved hydrocarbon resistance.

[0008] Molecular sieve catalysts can be metal-promoting. Examples of metal-promoting molecular sieve catalysts include iron, copper, and palladium-promoting molecular sieves, in which the metal can be supported within the molecular sieve. In metal-supported molecular sieves, the supported metal is of the "extra-skeleton metal" type, i.e., a metal present within and / or on at least a portion of the molecular sieve surface, and does not contain atoms that constitute the molecular sieve skeleton. For example, iron and copper-supported zeolites are known to promote SCR reactions.

[0009] Several methods for preparing metal-supported molecular sieves, particularly metal-supported zeolites, have been described in the literature. Direct synthesis of metal-supported zeolites is a complex process and depends on the synthesis conditions (see M. Moliner, ISRN Materials Science, 2012, Article ID 789525). An alternative is to use commercially available zeolite supports and then add the metal by post-synthesis treatment of the zeolite, such as wet impregnation, wet ion exchange, or solid ion exchange.

[0010] In known wet ion exchange methods for adding metals to molecular sieves (e.g., zeolites), soluble metal salts such as metal acetates, metal sulfates, or metal chlorides are typically used as active metal precursors, which react with the molecular sieves in aqueous solution. To accelerate ion exchange, such processes typically require a heating step, in which the mixture may be heated to a temperature in the range of 70-80°C for up to several hours. Furthermore, additional processing steps (e.g., filtration, evaporation, spray drying, etc.) may be required before the resulting metal-supported molecular sieves can be used in washcoat compositions for forming catalyst articles. Moreover, when certain metal acetates (e.g., copper acetate) are used in the preparation of metal-supported molecular sieves (e.g., metal-supported zeolites) used as SCR catalysts, it has been found that any residual metal acetates remaining after calcination may have a poisoning effect on ammonia slip catalysts (ASCs) used downstream of or near the SCR catalyst.

[0011] The present invention provides an improved process for preparing wash-coated catalyst articles using metal-supported crystalline molecular sieves as catalyst activators.

[0012] According to a first aspect of this disclosure, a method for forming a catalyst article is provided, the method is (a) At least the following components: (i)H + or NH4 + Morphological crystalline molecular sieves, (ii) an insoluble active metal precursor, (iii) Forming a slurry by mixing an aqueous solvent together with the following: The slurry has a solid content of up to 50% by weight, and step (a) is carried out at a temperature in the range of 10 to 35°C to form the slurry. (b) Coating the substrate with the slurry formed in step (a), (c) The coated substrate formed in step (b) is fired to form a catalyst layer on the substrate.

[0013] Advantageously, it has been found that the heat used to calcine the coated substrate can be used to promote metal loading onto the molecular sieve. This avoids the requirements for any heating steps and expensive high-temperature equipment in wet ion exchange or impregnation processes. Furthermore, it avoids the long reaction periods and / or energy-intensive processes such as spray drying that are typical in wet ion exchange or impregnation processes. Thus, the method according to the first embodiment may be more efficient and economical.

[0014] Furthermore, it was found that the slurry prepared in step (a) of the first embodiment of this method can be used directly as a wash coat composition without requiring any further processing steps.

[0015] Furthermore, the use of insoluble metal species such as metal carbonates as active metal precursors may result in the generation of fewer hazardous species during calcination compared to the use of metal acetates as active metal precursors. Therefore, the use of insoluble active metal precursors may offer health and safety benefits.

[0016] Furthermore, it was found that catalysts prepared by the process according to the first embodiment can provide at least equivalent SCR activity to catalysts containing metal-supported molecular sieves (e.g., metal-supported zeolites) prepared by wet ion exchange or impregnation. Moreover, it was found that poisoning of the associated ammonia slip catalyst can be reduced compared to catalysts containing metal-supported molecular sieves prepared using metal acetate salts as the active metal precursor.

[0017] According to a second aspect of this disclosure, a catalyst article is provided which is obtained or can be obtained by the method of the first aspect.

[0018] According to a third aspect of the present disclosure, an exhaust system is provided, the exhaust system comprising a nitrogen-based reducing agent source and an injector for injecting the nitrogen-based reducing agent into the flowing exhaust gas, the injector being disposed upstream of the catalyst article according to the second aspect.

Brief Description of the Drawings

[0019] [Figure 1] A graph showing the NOx conversion rate and N2O selectivity achieved by a catalyst article prepared according to a first aspect of the present disclosure, compared with a catalyst article prepared via prior art methods. [Figure 2] A graph showing the NOx conversion rate and N2O selectivity achieved by a catalyst according to a first aspect of the present disclosure.

Mode for Carrying Out the Invention

[0020] Hereinafter, the present disclosure will be further described. In the following sections, different aspects / embodiments of the present disclosure are defined in more detail. Each aspect / embodiment so defined can be combined with any other aspect / embodiment or aspects / embodiments unless otherwise clearly indicated. In particular, any feature indicated as being preferred or advantageous can be combined with any other feature or features indicated as being preferred or advantageous.

[0021] Furthermore, as used herein, the term “comprising” may be interchanged with the definitions “consisting essentially of” or “consisting of.” The term “comprising” is intended to mean that the specified elements are essential, but other elements may be added and still form a configuration within the scope of the claim. The term “consisting essentially of” limits the scope of the claim to the specified materials or processes, and to those that do not substantially affect the basic and novel characteristics of the claimed invention. The term “consisting of” closes the claim to the inclusion of materials other than those enumerated, except for impurities that are usually associated with them.

[0022] Crystalline molecular sieves are typically composed of aluminum, silicon, and / or phosphorus. Crystalline molecular sieves generally have a three-dimensional arrangement (e.g., a skeleton) of repeating SiO4, AlO4, and optionally PO4 tetrahedral units bonded by the covalent sharing of oxygen atoms.

[0023] In relation to molecular sieves, "H + The term "morphology" refers to the fact that the charge of the skeleton is a proton (i.e., H + This refers to molecular sieves with an anionic skeleton that maintain equilibrium through cations.

[0024] In relation to molecular sieves, term NH4 + Morphologically, the charge of the skeleton is an ammonium cation (NH4 + This refers to molecular sieves with an anionic skeleton that maintain equilibrium through cations.

[0025] When the crystalline molecular sieve has an aluminosilicate skeleton, the molecular sieve is preferably a zeolite.

[0026] Molecular sieves can be small-pore molecular sieves (i.e., having a maximum ring size of 8 tetrahedral atoms) or medium-pore molecular sieves (i.e., having a maximum ring size of 10 tetrahedral atoms).

[0027] When the crystalline molecular sieve is a microporous molecular sieve, the microporous molecular sieve may be selected from the group of skeleton types consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, KFI, LEV, LTA, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SFW, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, as well as mixtures thereof and / or intercrystals. Preferably, the microporous molecular sieve has a skeleton type selected from the group of skeleton types consisting of AEI, AFT, AFX, CHA, DDR, ERI, KFI, LEV, LTA, SFW, and RHO. More preferably, the small-pore crystalline molecular sieve has a skeletal structure that is AEI, AFX, CHA, LTA, ERI, or AEI-CHA intercrystal.

[0028] When the crystalline molecular sieve is a medium-pore molecular sieve, the medium-pore molecular sieve may be selected from the group of skeletal types consisting of AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, -SVR, SZR, TER, TON, TUN, UOS, VSV, WEI, and WEN, as well as mixtures and / or intercrystals thereof. Preferably, the medium-pore crystalline molecular sieve is selected from the group of skeletal types consisting of FER, MEL, MFI, STI, and STT.

[0029] Preferably, the crystalline molecular sieve is a small-pore molecular sieve having a skeletal structure of CHA, AEI, AFX, LTA, or ERI.

[0030] When the crystalline molecular sieve is a zeolite, the zeolite may have a silica-to-alumina ratio (SAR) of 5 to 200, preferably 5 to 100, and more preferably 10 to 80. For example, the silica-to-alumina ratio (SAR) of the zeolite may be 5 to 30.

[0031] If the crystalline molecular sieve is SAPO, the SAPO may have a silicon content in the range of 5 to 30% by weight, preferably 8 to 16% by weight (based on the total weight of the molecular sieve).

[0032] Crystalline molecular sieves are preferably powdery crystalline molecular sieves (i.e., in particulate form), where the particles include individual crystals, aggregates of crystals, or combinations thereof. When measured by scanning electron microscopy (SEM), crystalline molecular sieves may have an average crystal size of 0.5 μm or more, preferably about 0.5 to about 15 μm, for example, about 0.5 to 10 μm, about 0.5 to about 5 μm, about 1 to about 5 μm, or about 2 to about 5 μm.

[0033] Powdered crystalline molecular sieves preferably have a D90 particle size of less than 10 μm. For example, powdered crystalline molecular sieves may have a D90 particle size in the range of 2 to 9 μm, preferably 3 to 8 μm. As used herein, the term "D90 particle size" refers to the particle size distribution. The D90 particle size value corresponds to the following particle size values ​​in which 90% by volume of the total particles in a particular sample are present. The D90 particle size can be determined using laser diffraction (for example, using a Malvern Mastersizer 2000).

[0034] If desired, before forming the slurry in step (a) of the method of the first aspect, the molecular sieve can be subjected to a particle size reduction treatment such as jet milling, wet milling, or steam-assisted jet milling.

[0035] The components mixed together in step (a) of the first aspect can include two or more crystalline molecular sieves in the form of H + or NH4 + Thus, the catalyst layer formed and obtained in step (c) can include two or more different types of metal-supported molecular sieves.

[0036] As used herein, "active metal precursor" refers to a metal species that can supply an extra-framework metal to the crystalline molecular sieve. As used herein, the term "extra-framework metal" is present within the molecular sieve (i.e., within the micropores at either an ion-exchanged position or a non-ion-exchanged position) and / or on at least a part of the surface of the molecular sieve (e.g., in the form of ions or oxides), and refers to a metal that does not include the metal atoms of the tetrahedral units forming the framework of the molecular sieve. It will be understood that additional metal species can be present in the slurry formed in step (a) that are not themselves involved in metal loading.

[0037] By "insoluble active metal precursor" is meant a water-insoluble active metal precursor. In particular, the insoluble active metal precursor can have a water solubility of less than 1 g / 100 ml, for example, less than 0.1 g / 100 ml, or less than 0.01 g / 100 ml. The property of water solubility is a measure of the amount of material that dissolves in a specific volume of water at a determined temperature and pressure to form a saturated solution. As used herein, in relation to the insoluble active metal precursor, the term "water solubility" refers to the amount (in grams) of the insoluble active metal precursor that dissolves in 100 milliliters of water (g / 100 ml) at a temperature of 20 °C and 1 atmosphere of pressure.

[0038] Suitable insoluble active metal precursors include certain metal salts. In particular, the insoluble active metal precursor can be a metal carbonate, a metal hydroxide, or a metal oxalate.

[0039] The insoluble active metal precursor preferably includes a metal salt that is thermally decomposed by thermal decomposition at a temperature of less than 500°C.

[0040] Insoluble active metal precursors may include salts of transition metals, noble metals, or rare earth metals. For example, insoluble active metal precursors may include one or more salts of copper, manganese, nickel, cobalt, iron, palladium, platinum, cerium, yttrium, niobium, lanthanum, zinc, calcium, and magnesium, or any mixture of two or more of them.

[0041] In particular, the insoluble active metal precursor may be selected from the group consisting of copper carbonate, manganese carbonate, nickel carbonate, cobalt carbonate, iron carbonate, palladium carbonate, platinum carbonate, cerium carbonate, yttrium carbonate, niobium carbonate, lanthanum carbonate, zinc carbonate, zirconium carbonate, calcium carbonate, magnesium carbonate, copper hydroxide, manganese hydroxide, nickel hydroxide, cobalt hydroxide, iron hydroxide, palladium hydroxide, platinum hydroxide, cerium hydroxide, yttrium hydroxide, niobium hydroxide, lanthanum hydroxide, zinc hydroxide, zirconium hydroxide, calcium hydroxide, magnesium hydroxide, copper oxalate, calcium oxalate, iron oxalate, manganese oxalate, cobalt oxalate, cerium oxalate, yttrium oxalate, zinc oxalate, and any mixture of two or more of these.

[0042] Preferably, the insoluble active metal precursor may include one or more of copper(II) carbonate, copper(II) hydroxide, and copper oxalate. More preferably, the insoluble active metal precursor includes copper(II) carbonate. In one example, the insoluble active metal precursor may include a mixture of copper(II) carbonate and cerium carbonate.

[0043] In addition to the insoluble active metal precursor, the components mixed in step (a) may further include a soluble (i.e., water-soluble) active metal precursor. Preferred soluble active metal precursors may include soluble metal salts, such as metal acetates or metal nitrates, or any mixture of two or more thereof. In one example, the insoluble active metal precursor may include copper carbonate, and the soluble active metal precursor may include cerium acetate.

[0044] The relative amounts of molecular sieves and insoluble activated metal precursors used in step (a) depend on the target metal load of the molecular sieves and the amount of any soluble activated metal precursor used. The metal-supported molecular sieves present in the catalyst layer produced in step (c) may have a metal load of 0.1% to 10% by weight, preferably 0.1% to 7% by weight, and more preferably 0.1% to 5% by weight.

[0045] In particular, when the crystalline molecular sieve is a zeolite, the relative amounts of the molecular sieve, insoluble active metal precursor, and optional soluble active metal precursor used in step (a) can be selected to provide a metal-alumina ratio in the metal-supported zeolite in the range of 0.2 to 0.5, preferably 0.3 to 0.5.

[0046] As used herein, the term “aqueous solvent” refers to an aqueous liquid medium (i.e., a water-containing liquid medium) and does not necessarily indicate that any component will dissolve in it. For example, the aqueous solvent may be a water-containing liquid medium in which components (i) and (ii) are dispersed during step (a). However, those skilled in the art will understand that partial or complete dissolution of some components in an aqueous solvent may occur. For example, a rheological modifier that may be optionally used in step (a) may dissolve in the aqueous solvent itself. Preferably, the aqueous solvent consists essentially of water; that is, the aqueous solvent contains water but may also contain trace amounts of non-aqueous (e.g., organic or inorganic) impurities. The water may be deionized water or desalinated water.

[0047] The slurry formed in step (a) has a solid content of up to 50% by weight. "Solid content" refers to the proportion of solid material present in the slurry based on the total weight of the slurry. The solid content of the slurry is preferably in the range of 30 to 50% by weight, more preferably in the range of 30 to 48% by weight.

[0048] The components mixed together in step (a) may further include binder components, rheological modifiers, and / or other additives.

[0049] In particular, the components mixed together in step (a) may further include a binder component selected from alumina, alumina precursors (such as boehmite and / or bayerite), aluminum hydroxide, TiO2, SiO2, ZrO2, CeZrO2, SnO2, aluminophosphates, non-zeolite aluminosilicates, silica-alumina, clay, or mixtures thereof.

[0050] The binder may be present in the slurry in an amount ranging from 5 to 15% by weight, preferably 8 to 12.5% ​​by weight, for example, 10 to 12.5% ​​by weight, based on the total weight of the slurry.

[0051] The components mixed together in step (a) may further include a rheological modifier. The rheological modifier may be selected from polysaccharides, starch, cellulose, alginates, or mixtures thereof. The rheological modifier may be present in the slurry in an amount of up to 0.4% by weight, preferably 0.2% by weight or less.

[0052] Optionally, the components mixed together in step (a) may further include organic additives, such as pore-forming agents, surfactants, and / or dispersants as processing aids.

[0053] In some embodiments, the components mixed together in step (a) may further include additional catalytic activators (such as materials active in catalytic action of ammonia slip) where it is desired that the catalyst article be multifunctional (i.e., perform functions beyond catalytic function).

[0054] The relative amounts of each component used in step (a) can be selected such that the slurry has the required solid content, and the catalyst layer formed in step (c) after removal of the solvent and any organic matter contains a desired proportion of metal-supported molecular sieves. This is within the capabilities of those skilled in the art. Preferably, the relative amounts of each component used in step (a) are selected such that the catalyst layer formed in step (c) contains 85-92% by weight of metal-supported molecular sieves and 8-15% by weight of binder.

[0055] In step (a), the slurry is formed by mixing the components together. Preferably, the slurry is substantially uniform (e.g., homogeneous), meaning that the distribution of the components in the slurry is substantially uniform. These components can be mixed by any preferred method. Preferably, the components are mixed by stirring.

[0056] Optionally, the pH of the slurry can be adjusted by adding an acid or a base. Advantageously, it has been found that variability in the pH of the slurry has little effect on the performance of the SCR catalyst prepared according to the method of the first embodiment. This is in contrast to some prior art methods in which the pH of the washcoat composition is known to affect the performance of the final catalyst.

[0057] Step (a) may be carried out at ambient temperature. Preferably, step (a) is carried out at a temperature in the range of 10 to 30°C, preferably 18 to 28°C.

[0058] A notable advantage of the present invention is that the slurry formed in step (a) can be used directly as a wash coat composition. Therefore, the slurry formed in step (a) can be used directly in step (b) without any additional process steps.

[0059] In step (b), the slurry formed in step (a) can be coated onto a substrate by a wash coating technique well known in the art. One such method involves positioning the monolithic substrate such that the channels are substantially vertically oriented, applying the wash coat to a first surface (e.g., the top surface) of the substrate, and subjecting the second surface (e.g., the bottom surface) on the opposite side of the substrate to at least partial vacuum to achieve the movement of the wash coat through the channels. The monolithic substrate can be coated in a single dose, and the wash coat can be applied to the substrate in a single step while the substrate remains in a single orientation. Alternatively, the substrate can be coated in two injections. For example, in the first dose, the monolithic substrate is in a first orientation with the first surface at the top and the second surface at the bottom. The coating is applied to the first surface, coating a length portion of the substrate. The substrate is then inverted so that the second surface is at the top. Next, the coating is applied to the second surface to coat the portion of the substrate that was not coated in the first injection. International Publication No. 99 / 47260 describes a general method for coating monolithic substrates.

[0060] The coating should be applied to the substrate in an amount sufficient to provide the desired wash coat filler. Preferably, the coating is 0.5 to 5 g / in. 3 range, preferably 1.5 to 3.5 g / in 3 It is applied in an amount sufficient to provide a wash coat filling amount within the range.

[0061] The substrate is preferably a honeycomb monolith substrate. Honeycomb monoliths are well known in the art. The “honeycomb monolith substrate” as defined herein includes a metal and ceramic flow-through monolith having a plurality of channels or cells extending longitudinally along the length of the substrate structure, the channels being open at both ends thereof, and the metal and ceramic filters include a ceramic wall-flow type filter having a plurality of channels or cells extending longitudinally along the length of the substrate structure, the channels at the first open end of the substrate being closed at the opposite end, the channels that are open at the opposite end being closed at the first end, and all other adjacent cells having an open end (or closed end) at the first end of the wall-flow type filter and a closed end (or open end) at the opposite end thereof, so that when the end of the wall-flow type filter is visible, it is arranged to resemble a chessboard of open and closed channels. Fluid communication between the open channel at the first end of the wall-flow type filter and the open channel at the opposite end is through the porous wall structure of the wall-flow type filter.

[0062] Alternatively, the substrate may be a plate-type substrate.

[0063] The substrate may be an asymmetric substrate. The substrate may be composed of a ceramic material or a metallic material. For example, the substrate may be made of or composed of cordierite (SiO2-Al2O3-MgO), silicon carbide (SiC), Fe-Cr-Al alloy, Ni-Cr-Al alloy, aluminum titanate, or stainless steel alloy.

[0064] If it is desirable for the catalyst article to be multifunctional (i.e., to perform functions beyond catalytic activity simultaneously), the substrate may already possess catalytic activity before being coated with the slurry formed in step (a) of the first embodiment. For example, the substrate may be all active extrudeds. Alternatively, the substrate may already have a first wash coat layer. In this example, the slurry formed in step (a) may be coated as a second wash coat layer on top of the first wash coat layer, and / or as an adjacent or overlapping wash coat layer if the first wash coat layer does not cover the entire length of the substrate. For example, if the present invention provides an SCR catalyst, the slurry may be coated in a position that will be on or upstream of the ASC catalyst during use.

[0065] In principle, the substrate can be of any shape or size. However, the shape and size of the substrate are usually selected to optimize the exposure of the catalytic activator in the catalyst article to exhaust gas during use.

[0066] Step (b) may be carried out at ambient temperature. Preferably, step (b) is carried out at a temperature in the range of 10 to 35°C, preferably 10 to 30°C, and more preferably 18 to 28°C.

[0067] Most preferably, both steps (a) and (b) are carried out at a temperature in the range of 10 to 35°C, for example, 10 to 30°C or 18 to 28°C.

[0068] The coated substrate formed in step (b) may undergo a drying process before firing in step (c). Thus, the method of the first embodiment may further include drying the coated substrate formed in step (b) before carrying out step (c).

[0069] Drying of coated substrates can be carried out at temperatures below 120°C. For example, drying of coated substrates can be carried out at a temperature of about 100°C. Drying can be carried out statically (e.g., using a batch oven) or continuously (e.g., using a belt oven).

[0070] In step (c) of the first embodiment, the coated substrate formed in step (b) (optionally dried) is subjected to calcination to form a catalyst layer on the substrate containing the metal-supported molecular sieve. The terms “calcination” or “fired” refer to a heat treatment process. Calcination fixes the catalyst activator to the substrate and causes the removal of any remaining solvent and any residual organic components, such as the decomposition of the active metal precursor or organic matter derived from organic additives contained in the slurry formed in step (a).

[0071] While we do not wish to be bound by any particular theory, it is conceivable that metal support occurs on at least some of the molecular sieves during the firing of the coated substrate. For example, solid-state ion exchange may occur during firing.

[0072] The firing of the coated substrate can be carried out by techniques well known in the art. In particular, the firing can be carried out statically (e.g., using a batch oven) or continuously (e.g., using a belt furnace).

[0073] Preferably, the firing step (c) is carried out at a temperature of up to 550°C, preferably in the range of 450 to 550°C.

[0074] Preferably, the coated substrate is baked for a maximum of 3 hours, preferably 30 minutes to 2 hours.

[0075] The firing carried out in step (c) may include multiple heat treatment steps, for example, the coated substrate may be subjected to a first heat treatment at a first temperature and then to a second heat treatment at a second temperature.

[0076] Drying and firing may be optionally combined in a continuous process, and the coated substrate is transported on a belt furnace through multiple heating zones, each zone set to a different temperature.

[0077] A catalyst article according to a second aspect of this disclosure may be used for treating combustion exhaust gas flows. That is, the catalyst article can be used to treat exhaust gases from combustion processes such as internal combustion engines (either mobile or stationary), gas turbines, or power plants (e.g., coal or oil-fueled power plants). A preferred application of the catalyst article of this disclosure is in exhaust systems for automobile vehicles. In particular, the catalyst article may be used as an SCR catalyst.

[0078] In some embodiments, for example, if it is desired that the catalyst article be multifunctional (i.e., to perform functions beyond catalytic function at the same time), the method of the first embodiment may include, after step (b), a step of coating the substrate with an additional wash coat composition. The additional wash coat composition may be applied directly on top of or adjacent to the coating applied in step (b). Such a step may be carried out either before or after step (c).

[0079] The catalytic article may be part of an exhaust gas treatment system, and it is located downstream of the nitrogen-based reducing agent source. [Examples]

[0080] The present invention will be further described with reference to the following examples, which are illustrative and not intended to limit the present invention.

[0081] • Comparative Example Particle SSZ-13(CHA) zeolite was combined with water to form a slurry with a solid content of 37% by weight, and then the particle size of the zeolite was reduced to 7 μm D90 using bead grinding.

[0082] Copper acetate was added to the slurry, and the resulting mixture was heated at 70°C for 4 hours. After cooling to room temperature, a sample of the slurry was taken for ICP analysis, which confirmed that more than 84% of the copper was incorporated.

[0083] Additional water was added to the slurry to replace the water lost by evaporation during heating, adjusting the solid content back to 37% by weight. Tetraethylammonium hydroxide (TEAOH) was then added to combine any remaining free copper ions in the supernatant.

[0084] Next, a binder component (Dispersal, available from water-soluble boehmite-Sasol) was added to the slurry, and the mixture was then stirred under continuous high shear conditions until homogenization occurred.

[0085] The rheology of the slurry was adjusted by adding a cellulose rheology modifier to make it suitable for wash coating. The pH of the slurry was adjusted to 3.8 by adding a base.

[0086] Next, the final slurry was wash-coated onto a square-cell ceramic flow-through substrate using a vacuum deposition wash-coating technique (as described in International Publication No. 99 / 47260). The coated substrate was then dried, completing the drying process using a dynamic line dryer. The dried coated substrate was then calcined in a dynamic line calcinerator at 500°C for at least 30 minutes to form a catalyst layer on the substrate.

[0087] The quantitative proportions of the starting materials were selected so that the catalyst layer contained 87.5% by weight of copper-supported zeolite and 12.5% ​​by weight of alumina.

[0088] • Example 1 Particle SSZ-13(CHA) zeolite was combined with water to form a slurry with a solid content of 37% by weight, and the zeolite particle size was reduced to 7 μm D90 using bead grinding.

[0089] Copper carbonate was added to the slurry, and the resulting mixture was stirred under high shear conditions for at least 20 minutes. The amount of copper carbonate was selected to obtain an equivalent weight percentage of copper in the final slurry, as provided in the comparative example.

[0090] Next, a binder component (Dispersal, available from water-soluble boehmite-Sasol) was added to the slurry, and the mixture was then stirred under continuous high shear conditions until homogenization occurred.

[0091] The rheology of the slurry was adjusted by adding a cellulose rheology modifier to make it suitable for wash coating. The pH of the slurry was adjusted to approximately 3.8 by adding a base.

[0092] Next, the final slurry was wash-coated onto a substrate having the same shape and dimensions as that used in the comparative example, in the same manner as described in relation to the comparative example. Then, the coated substrate was dried and fired in the same manner as described in relation to the comparative example.

[0093] The quantitative proportions of the starting materials were selected so that the final catalyst layer contained 87.5% by weight of copper and zeolite, and 12.5% ​​by weight of alumina.

[0094] • Example 2 Example 1 was repeated, except that the pH of the slurry was adjusted to 4.

[0095] • Example 3 Example 1 was repeated, except that the pH of the slurry was adjusted to 7.

[0096] • Catalyst testing Identical volume core samples were taken from the catalyst articles prepared in each of the Comparative Example and Examples 1-3 and tested in a synthetic catalytic activity test (SCAT) apparatus at a flow rate of 31.6 L / min and a selected inlet temperature using the following inlet gas mixture: 500 ppm NO, 750 ppm NH3, 10% H2O, 5% O2, 350 ppm CO, and the remainder N2. Catalyst samples were tested both in their fresh state and after hydrothermal aging (16 hours in 10% water at 800°C).

[0097] The results are shown in Figures 1 and 2.

[0098] Figure 1 compares the NOx conversion rate and N2O selectivity achieved by the catalyst articles of Example 1 and the Comparative Example at the selected inlet temperature.

[0099] Figure 2 compares the NOx conversion rate and N2O selectivity achieved by the catalyst articles of Examples 1-3 at selected inlet temperatures.

[0100] As demonstrated by the data shown in Figure 1, the catalyst article of Example 1 achieves comparable NOx conversion rates and similar or slightly improved N2O selectivity compared to the comparative example.

[0101] Advantageously, compared to the overall preparation of the comparative examples, the preparation of Example 1 required fewer process steps, as well as reduced water and energy consumption.

[0102] As demonstrated by the data shown in Figure 2, changes in the pH of the slurry for wash coating have little effect on the performance of the final catalyst article.

[0103] Further aspects and embodiments of this disclosure are described in the following numbered clauses.

[0104] Clause 1. A method for forming a catalyst article, (a) At least the following components: (i)H +or NH4 + Morphological crystalline molecular sieves, (ii) an insoluble active metal precursor, (iii) Forming a slurry by mixing an aqueous solvent together with the following: The slurry has a solid content of up to 50% by weight, and step (a) is carried out at a temperature in the range of 10 to 35°C to form the slurry. (b) Coating the substrate with the slurry formed in step (a), (c) A method comprising firing the coated substrate formed in step (b) to form a catalyst layer on the substrate.

[0105] Clause 2. The method specified in Clause 1, wherein in step (a), the components to be mixed together further include (iv) a binder component and / or (v) a rheological modifier.

[0106] Article 3. A method for forming a catalyst article, (a) The following ingredients: (i)H + or NH4 + Morphological crystalline molecular sieves, (ii) an insoluble active metal precursor, (iii) an aqueous solvent, (iv) A binder component, (v) Forming a slurry by mixing an optional rheological modifier together with the following: The slurry has a solid content of up to 50% by weight, and step (a) is carried out at a temperature in the range of 10 to 35°C to form the slurry. (b) Coating the substrate with the slurry formed in step (a), (c) A method comprising firing the coated substrate formed in step (b) to form a catalyst layer on the substrate.

[0107] Article 4. A method for forming a catalyst article, (a) The following ingredients: (i)H +or NH4 + Morphological crystalline molecular sieves, (ii) an insoluble active metal precursor, (iii) an aqueous solvent, (iv) A binder component, (v) Forming a slurry by mixing an optional rheological modifier together with the following: The slurry has a solid content of up to 50% by weight, and step (a) is carried out at a temperature in the range of 10 to 35°C to form the slurry. (b) Coating the substrate with the slurry formed in step (a), (b i )Optionally, drying the coated substrate formed in step (b), (c) process (b) or (b i A method comprising firing a coated substrate formed with ) to form a catalyst layer on the substrate.

[0108] Clause 5. The method specified in Clauses 2, 3, or 4, wherein the binder component is selected from alumina, alumina precursors, aluminum hydroxide, TiO2, SiO2, ZrO2, CeZrO2, SnO2, aluminophosphates, non-zeolite aluminosilicates, silica-alumina, clay, or mixtures thereof.

[0109] Clause 6. The method specified in Clause 5, wherein the binder component is an alumina precursor selected from boehmite and bayerite.

[0110] Clause 7. The method specified in any one of Clauses 2 to 6, wherein the rheological modifier is selected from polysaccharides, starches, cellulose, alginates, or mixtures thereof.

[0111] The method specified in any one of the clauses 1 to 7, wherein the relative quantitative proportions of the components used in step (a) are selected such that the catalyst layer formed in step (c) contains 85 to 92% by weight of metal-supported molecular sieves and 8 to 15% by weight of a binder.

[0112] Clause 9. A method specified in any one of Clauses 1 to 8, wherein the crystalline molecular sieve is a small-pore or medium-pore molecular sieve.

[0113] Clause 10. The crystalline molecular sieve is a small-pore molecular sieve, as specified in any one of Clauses 1 to 9.

[0114] Clause 11. The method specified in Clause 10, wherein the small-pore molecular sieve has a skeletal structure selected from AEI, AFT, AFX, CHA, DDR, ERI, KFI, LEV, LTA, SFW, and RHO.

[0115] Clause 12. The method specified in any one of Clauses 1 to 11, wherein the crystalline molecular sieve is a small-pore zeolite having a skeletal structure selected from CHA, AEI, AFX, LTA, or ERI.

[0116] Clause 13. The method specified in Clause 9, wherein the crystalline molecular sieve is a medium-pore molecular sieve.

[0117] Clause 14. The method specified in Clause 13, wherein the medium-pore molecular sieve has a skeletal structure selected from FER, MEL, MFI, STI, and STT.

[0118] Clause 15. The crystalline molecular sieve is a zeolite, as specified in any one of Clauses 1 to 14.

[0119] Clause 16. The method specified in Clause 15, wherein the zeolite has a silica-alumina ratio (SAR) of 5-200, 5-100, 10-80, or 5-30.

[0120] Clause 17. The crystalline molecular sieve is in particulate form and has a D90 particle size of less than 10 μm, as specified in any one of Clauses 1 to 16.

[0121] Clause 18. The method specified in Clause 17, wherein the crystalline molecular sieve has a D90 particle size in the range of 2 to 9 μm, or in the range of 2 to 8 μm.

[0122] Clause 19. Component (i) is H + or NH4 + A method as defined in any one of Clauses 1 to 18, comprising two or more forms of crystalline molecular sieves.

[0123] Clause 20. A method specified in any one of Clauses 1 to 19, wherein the insoluble active metal precursor has water solubility of less than 1 g / 100 ml, less than 0.1 g / 100 ml, or less than 0.01 g / 100 ml.

[0124] Clause 21. The method specified in any one of Clauses 1 to 20, wherein the insoluble active metal precursor is selected from metal carbonates, metal hydroxides, metal oxalates, or any mixture of two or more thereof.

[0125] Clause 22. The method prescribed in any one of Clauses 1 to 21, wherein the insoluble active metal precursor comprises salts of copper, manganese, nickel, cobalt, iron, palladium, platinum, cerium, yttrium, niobium, lanthanum, zinc, calcium, magnesium, or any mixture of two or more of these.

[0126] Clause 23. The method prescribed in any one of Clauses 1 to 22, wherein the insoluble active metal precursor is selected from the group consisting of copper carbonate, manganese carbonate, nickel carbonate, cobalt carbonate, iron carbonate, palladium carbonate, platinum carbonate, cerium carbonate, yttrium carbonate, niobium carbonate, lanthanum carbonate, zinc carbonate, zirconium carbonate, calcium carbonate, magnesium carbonate, copper hydroxide, manganese hydroxide, nickel hydroxide, cobalt hydroxide, iron hydroxide, palladium hydroxide, platinum hydroxide, cerium hydroxide, yttrium hydroxide, niobium hydroxide, lanthanum hydroxide, zinc hydroxide, zirconium hydroxide, calcium hydroxide, magnesium hydroxide, copper oxalate, calcium oxalate, iron oxalate, manganese oxalate, cobalt oxalate, cerium oxalate, yttrium oxalate, zinc oxalate, and any mixture of two or more of these.

[0127] Clause 24. A method specified in any one of Clauses 1 to 23, wherein the insoluble active metal precursor comprises one or more of copper(II) carbonate, copper(II) hydroxide, and copper oxalate.

[0128] Clause 25. A method specified in any one of Clauses 1 to 24, wherein the insoluble active metal precursor comprises copper(II) carbonate.

[0129] Clause 26. A method as prescribed in any one of Clauses 1 to 25, wherein the insoluble active metal precursor comprises a mixture of copper(II) carbonate and cerium carbonate.

[0130] Clause 27. Insoluble active metal precursor, 500 ℃ A method specified in any one of clauses 1 to 26, comprising one or more metal salts that have been thermally decomposed by thermal decomposition at a temperature below a certain temperature.

[0131] Clause 28. The method specified in any one of Clauses 1 to 27, wherein the components mixed together in step (a) further comprises (vi) a soluble active metal precursor.

[0132] Clause 29. The aqueous solvent is essentially made from water, as specified in any one of Clauses 1 to 28.

[0133] Clause 30. The aqueous solvent is water, as specified in any one of Clauses 1 to 29.

[0134] Clause 31. The method specified in any one of Clauses 1 to 30, wherein the slurry formed in step (a) has a solid content in the range of 30 to 50% by weight or 30 to 48% by weight.

[0135] Clause 32. In step (a), the components are mixed together by stirring, as specified in any one of Clauses 1 to 31.

[0136] Clause 33. Step (a) is carried out at ambient temperature using the method specified in any one of Clauses 1 to 32.

[0137] Clause 34. The method specified in any one of Clauses 1 to 33, wherein step (a) is carried out at a temperature in the range of 10 to 30°C, preferably in the range of 18 to 28°C.

[0138] Clause 35. A method specified in any one of Clauses 1 to 34, wherein the substrate is a honeycomb monolith substrate.

[0139] Clause 36. The honeycomb monolith substrate is a flow-through monolith, as specified in Clause 35.

[0140] Clause 37. The method specified in Clause 35, wherein the honeycomb monolith substrate is a wall-flow type filter.

[0141] Clause 38. Step (b) is carried out at ambient temperature using any one of Clauses 1 to 37.

[0142] Clause 39. Step (b) is carried out in any one of Clauses 1 to 38 by a method specified in any one of Clauses 1 to 38, at a temperature in the range of 10 to 35°C, or 10 to 30°C, or 18 to 28°C.

[0143] Clause 40. Step (b) is carried out in any one of Clauses 1 to 39 by a method specified in any one of Clauses 1 to 39, at a temperature in the range of 10 to 35°C, or 10 to 30°C, or 18 to 28°C.

[0144] Clause 41. A method specified in any one of Clauses 1 to 40, further comprising drying the coated substrate formed in step (b) before step (c).

[0145] Clause 42. The method specified in any one of Clauses 1 to 41, wherein step (c) is carried out at a maximum temperature of 550°C, preferably in the range of 450 to 550°C.

[0146] Clause 43. In step (c), the firing is carried out for a period of up to 3 hours, preferably 30 minutes to 2 hours, as specified in any one of Clauses 1 to 42.

[0147] Clause 44. The method specified in any one of Clauses 1 to 43, wherein the catalyst layer formed in step (c) includes a metal-supported molecular sieve.

[0148] Clause 45. A method as defined in any one of Clauses 1 to 44, wherein the catalyst layer formed in step (c) comprises a metal-supported molecular sieve that is catalytically active for SCR.

[0149] Clause 46. During process (c), metal loading of at least a portion of the molecular sieve occurs in a manner specified in any one of Clauses 1 to 45.

[0150] Clause 47. Catalyst articles obtained or obtainable by any one of Clauses 1 to 46.

[0151] Clause 48. A catalyst article as defined in Clause 47, configured as a flow-through honeycomb monolith or wall-flow type filter.

[0152] Clause 49. A catalyst article as defined in Clause 47 or 48, which is catalytically active for SCR.

[0153] Clause 50. An exhaust system comprising a nitrogen-based reducing agent source and an injector for injecting the nitrogen-based reducing agent into flowing exhaust gas, wherein the injector is located upstream of the catalyst article specified in Clause 49.

Claims

1. A method for forming a catalyst article, (a) at least the following components: (i) H ＋ or NH ４ ＋ Morphological crystalline molecular sieves, (ii) Insoluble active metal precursors, (iii) Forming a slurry by mixing an aqueous solvent together, The slurry has a solid content of up to 50% by weight, and step (a) is carried out at a temperature in the range of 10 to 35°C to form the slurry. (b) Coating the substrate with the slurry formed in step (a), (c) A method comprising firing the coated substrate formed in step (b) to form a catalyst layer on the substrate.

2. The method according to claim 1, wherein in step (a), the components mixed together further comprises (iv) a binder component and / or (v) a rheological modifier.

3. The aforementioned binder component is alumina, alumina precursor, aluminum hydroxide, TiO ２ SiO ２ , ZrO ２ CeZrO ２ , SnO ２ The method according to claim 2, selected from aluminophosphates, non-zeolite aluminosilicates, silica-alumina, clay, or mixtures thereof.

4. The method according to claim 2 or 3, wherein the rheological modifier is selected from polysaccharides, starch, cellulose, alginate, or a mixture thereof.

5. The method according to any one of claims 1 to 4, wherein the relative quantitative proportion of the components used in step (a) is selected such that the catalyst layer formed in step (c) comprises 85 to 92% by weight of a metal-supported molecular sieve and 8 to 15% by weight of a binder.

6. The method according to any one of claims 1 to 5, wherein the crystalline molecular sieve is a small-pore zeolite having a skeletal structure selected from CHA, AEI, or AFX, LTA, or ERI.

7. The method according to any one of claims 1 to 6, wherein the insoluble active metal precursor is selected from the group consisting of copper carbonate, manganese carbonate, nickel carbonate, cobalt carbonate, iron carbonate, palladium carbonate, platinum carbonate, cerium carbonate, yttrium carbonate, niobium carbonate, lanthanum carbonate, zinc carbonate, zirconium carbonate, calcium carbonate, magnesium carbonate, copper hydroxide, manganese hydroxide, nickel hydroxide, cobalt hydroxide, iron hydroxide, palladium hydroxide, platinum hydroxide, cerium hydroxide, yttrium hydroxide, niobium hydroxide, lanthanum hydroxide, zinc hydroxide, zirconium hydroxide, calcium hydroxide, magnesium hydroxide, copper oxalate, calcium oxalate, iron oxalate, manganese oxalate, cobalt oxalate, cerium oxalate, yttrium oxalate, zinc oxalate, and any mixture of two or more of these.

8. The method according to any one of claims 1 to 7, wherein the insoluble active metal precursor comprises one or more of copper(II) carbonate, copper(II) hydroxide, and copper oxalate.

9. The method according to any one of claims 1 to 8, wherein the aqueous solvent is water.

10. The method according to any one of claims 1 to 9, wherein the slurry formed in step (a) has a solid content in the range of 30 to 50% by weight or 30 to 48% by weight.

11. The method according to any one of claims 1 to 10, wherein step (a) is carried out at a temperature in the range of 10 to 30°C, preferably in the range of 18 to 28°C.

12. The method according to any one of claims 1 to 11, wherein step (b) is carried out at a temperature in the range of 10 to 35°C, preferably in the range of 10 to 30°C, more preferably in the range of 18 to 28°C.

13. A catalyst article obtained or obtainable by the method specified in any one of claims 1 to 12.

14. The catalyst article according to claim 13, which is catalytically active for SCR.

15. An exhaust system comprising a nitrogen-based reducing agent source and an injector for injecting the nitrogen-based reducing agent into flowing exhaust gas, wherein the injector is disposed upstream of the catalyst article defined in claim 14.

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