Method of forming a catalyst article

Abstract

The present disclosure relates to a process for forming a catalyst article comprising: (a) forming a plastic mixture having a solids content greater than 50 wt.% by mixing together a crystalline small or medium pore molecular sieve in the H + or NH4 + form, an insoluble active metal precursor, an inorganic matrix component, an organic adjuvant, an aqueous solvent, and optionally an inorganic fiber; (b) molding the plastic mixture into a shaped article; and (c) calcining the shaped article to form a solid catalyst body. The present disclosure further relates to a catalyst article, in particular a catalyst article suitable for selective catalytic reduction of nitrogen oxides, and to an exhaust system.

Description

Technical Field

[0001] This invention relates to a method for forming catalyst articles. Specifically, this invention relates to a method for forming catalyst articles suitable for the selective catalytic reduction of nitrogen oxides (NOx) in exhaust gases. Background Technology

[0002] Every year, a large number of catalytic converters are manufactured to treat emissions from both mobile and stationary sources. Catalytic converters for motor vehicles typically consist of an extruded ceramic honeycomb monolith with channels through which exhaust gases flow. The channels of the monolith may be coated with a catalytically active material (called a "carrier coating"). Alternatively, the extruded monolith itself may be formed from a catalytically active material (called a "fully active extrudate" or "extrusion catalyst").

[0003] To produce a fully active extrudate, a catalytically active component is incorporated into an extrusion composition whose rheological properties have been tailored to suit the extrusion process. This extrusion composition is a plastic (i.e., easily formable or moldable) viscous composition. To set the desired rheological properties of the extrusion composition and the mechanical properties of the extrudate, binders or additives are typically added. This plastic composition is then subjected to an extrusion process for the preparation of, for example, honeycomb structures. The resulting so-called "green" body is then subjected to high-temperature calcination to form the finished extruded catalyst body.

[0004] Fully active extruders typically comprise a monolithic structure in the form of a honeycomb, having uniformly sized and parallel channels extending from a first end to a second end. Typically, the channels are open at both the first and second ends—a so-called "flow through" configuration. Alternatively, the channels at the first upstream end may be blocked, for example, with suitable ceramic cement, and the unblocked channels at the first upstream end may be blocked at the second downstream end to form a so-called wall-flow filter.

[0005] Nitrogen oxides (NOx) are selectively reduced by ammonia (NH3-SCR). x NO is considered to be used to remove NO from exhaust gases emitted from stationary sources as well as from mobile engines (primarily diesel engines) in vehicles such as cars, trucks, locomotives, and ships. x The most practical and efficient technology.

[0006] Known SCR (Selective Catalytic Reduction) catalysts include molecular sieves. Available molecular sieves include crystalline or quasi-crystalline materials, such as aluminosilicates (zeolites) or aluminosilicate phosphates (SAPO). These molecular sieves consist of repeating SiO4, AlO4, and optionally PO4 tetrahedral units, which are linked together, for example, in rings to form a framework with regular intracrystalline cavities and molecular-sized channels. The specific arrangement of the tetrahedral units (ring members) produces the framework of the molecular sieve, and by convention, the International Zeolite Association (IZA) assigns a unique three-letter code (e.g., "CHA") to each unique framework. Examples of molecular sieve frameworks for known SCR catalysts include framework type codes CHA (chamferrocene), BEA (β), MOR (mordenite), AEI, MFI, and LTA.

[0007] Molecular sieves (e.g., zeolites) can also be classified according to pore size, such as the maximum number of tetrahedral atoms present in the sieve framework. As defined herein, "small-pore" molecular sieves such as CHA have a maximum ring size of eight tetrahedral atoms, while "mesopore" molecular sieves such as MFI have a maximum ring size of ten tetrahedral atoms; and "macropore" molecular sieves such as BEA have a maximum ring size of twelve tetrahedral atoms. Small-pore and mesopore molecular sieves, especially small-pore molecular sieves, are preferred for SCR catalysts because they can, for example, provide improved SCR performance and / or improved hydrocarbon tolerance.

[0008] Molecular sieve catalysts can be metal-driven. Examples of metal-driven molecular sieve catalysts include iron-driven, copper-driven, and palladium-driven molecular sieves, in which a metal can be loaded into the molecular sieve. In metal-supported molecular sieves, the supported metal is a type of "ex-framework metal," that is, a metal residing within the molecular sieve and / or on at least a portion of the molecular sieve surface, and not including atoms that constitute the molecular sieve framework. For example, iron-supported and copper-supported microporous and mesoporous zeolites are known to be used as SCR catalysts.

[0009] Several methods for preparing metal-supported molecular sieves, particularly metal-supported zeolites, have been mentioned in the literature. The direct synthesis of metal-supported zeolites is a complex process and depends heavily on the synthetic conditions (see M. Moliner, ISRN Materials Science, 2012, article number 789525). An alternative approach is to use a commercially available zeolite support and subsequently add the metal through post-synthetic treatments such as wet impregnation, wet ion exchange, or solid-state ion exchange.

[0010] Known wet ion exchange methods for incorporating metals into molecular sieves (e.g., zeolites) typically employ soluble metal salts, such as metal acetates, metal sulfates, or metal chlorides, as active metal precursors, which react with the molecular sieve in an aqueous solution. To accelerate ion exchange, such methods often require a heating step, where the mixture can be heated to temperatures in the range of 70°C to 80°C for several hours. Furthermore, additional processing steps (e.g., filtration, evaporation, spray drying, calcination, etc.) may be required before the resulting metal-supported molecular sieve can be used to extrude a paste to form a fully active extrudate. Moreover, it has been found that in the case of using certain metal acetates (e.g., copper acetate) to prepare metal-supported molecular sieves (e.g., metal-supported zeolites) for use as SCR catalysts, any residual metal acetate remaining after calcination can be poisonous to ammonia escaping catalysts (ASCs) used downstream of or near the SCR catalyst.

[0011] This invention provides an improved method for preparing extrusion catalyst products, wherein the method uses metal-supported small-pore or mesopore crystalline molecular sieves as catalytically active materials.

[0012] According to a first aspect of this disclosure, a method for forming a catalyst article is provided, the method comprising:

[0013] (a) A plastic mixture is formed by mixing at least the following components together:

[0014] (i) H + or NH4 + Crystalline microporous or mesoporous molecular sieves;

[0015] (ii) Insoluble active metal precursors;

[0016] (iii) Inorganic matrix components;

[0017] (iv) Organic auxiliaries;

[0018] (v) Aqueous solvents;

[0019] The solids content of the mixture is greater than 50% by weight (based on the total weight of the mixture);

[0020] (b) molding the plastic mixture into a molded article; and

[0021] (c) Calcine the molded product to produce a solid catalyst body.

[0022] Advantageously, it has been found that the heat used for calcining the molded articles can be used to promote the loading of metal onto the molecular sieve. Therefore, the need for any heating steps during wet ion exchange or wet impregnation processes, as well as the need for expensive, high-temperature equipment, can be avoided. Furthermore, the long reaction times typical of wet ion exchange or wet impregnation processes and / or energy- and labor-intensive processes such as spray drying can be avoided. Therefore, the method according to the first aspect is more energy-efficient and economical.

[0023] Furthermore, it has been found that the mixture prepared in step (a) of the method according to the first aspect can be used directly as an extrusion paste without any further processing steps. Specifically, the method of the first aspect can reduce the overall water consumption in the manufacture of extrusion catalysts containing metal-supported small-pore or mesoporous molecular sieves, since conventionally pre-supported small / mesoporous molecular sieves in powder form are prepared by a wet process followed by drying and / or calcination.

[0024] Furthermore, it has been found that catalysts prepared according to the method of the first aspect can provide SCR activity at least comparable to catalysts containing metal-supported small / mesoporous molecular sieves (e.g., metal-supported zeolites) (prepared via wet ion exchange or wet impregnation). Additionally, it has been found that the poisoning of related ammonia escape catalysts can be mitigated compared to SCR catalysts containing metal-supported crystalline molecular sieves prepared using metal acetates as active metal precursors.

[0025] According to a second aspect of this disclosure, a catalyst article is provided that is obtained according to or can be obtained according to the method of the first aspect.

[0026] According to a third aspect of this disclosure, an exhaust system is provided, comprising: a nitrogen-containing reducing agent source and an injector for injecting the nitrogen-containing reducing agent into a flowing exhaust gas, wherein the injector is disposed upstream of a catalyst article according to a second aspect. Attached Figure Description

[0027] Figure 1 This illustrates the NO production achieved by a catalyst prepared according to the first aspect of this disclosure. x Conversion rate and NO achieved by catalysts prepared using existing techniques x A chart comparing conversion rates.

[0028] Figure 2 This is a graph showing the N2O selectivity achieved by the catalyst prepared according to the first aspect of this disclosure compared with the N2O selectivity achieved by the catalyst prepared by prior art methods.

[0029] Figure 3 This illustrates the NO production achieved by a catalyst prepared according to the first aspect of this disclosure. xConversion rate and NO achieved using catalysts prepared with soluble active metal precursors x A chart comparing conversion rates.

[0030] Figure 4 This is a graph showing the N2O selectivity achieved by a catalyst prepared according to the first aspect of this disclosure compared to the N2O selectivity achieved by a catalyst prepared using a soluble active metal precursor. Detailed Implementation

[0031] This disclosure will now be described further. In the following paragraphs, different aspects / implementations of this disclosure are defined in more detail. Unless expressly stated to the contrary, each aspect / implementation so defined may be combined with any other aspect / implementation or multiple aspects / implementations. Specifically, any feature indicated as preferred or advantageous may be combined with one or more other features indicated as preferred or advantageous.

[0032] Additionally, as used herein, the term "comprising" can be replaced by the definitions of "substantially consisting of" or "consisting of". The term "comprising" is intended to indicate that the stated element is necessary, but other elements may be added and still form a construction within the scope of the claims. The term "substantially consisting of" limits the scope of the claims to the specified materials or steps and those that do not materially affect the essential and novel features of the invention protected by the claims. The term "consisting of" defines the claims as excluding materials other than those listed, except for impurities typically associated with them.

[0033] Crystalline molecular sieves are typically composed of aluminum, silicon, and / or phosphorus. They generally have a three-dimensional arrangement (e.g., framework) of repeating SiO4, AlO4, and optionally PO4 tetrahedral units linked by shared oxygen atoms. The maximum ring size for small-pore molecular sieves is eight tetrahedral atoms. The maximum ring size for mesoporous molecular sieves is ten tetrahedral atoms.

[0034] The term "H" for molecular sieves + "Form" refers to a molecular sieve with an anionic framework, wherein the charge of the framework is generated by protons (i.e., H+). + (Cation) balance.

[0035] The term "NH4" is related to molecular sieves. + "Form" refers to a molecular sieve with an anionic framework, wherein the charge of the framework is determined by ammonium cations (i.e., NH4+). + (Cation) balance.

[0036] When the crystalline molecular sieve has an aluminosilicate framework, the molecular sieve is preferably a zeolite.

[0037] When the crystalline molecular sieve is a small-pore molecular sieve, the small-pore molecular sieve may have a framework type selected from the group 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 and / or commensal organisms thereof. Preferably, the small-pore molecular sieve has a framework type selected from the group consisting of AEI, AFT, AFX, CHA, DDR, ERI, KFI, LEV, LTA, SFW, and RHO. More preferably, the small-pore crystalline molecular sieve has a framework type that is AEI, AFX, CHA, LTA, ERI or AEI-CHA symbiotic.

[0038] When the crystalline molecular sieve is a mesoporous molecular sieve, the mesoporous molecular sieve can be selected from the group 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 commensal organisms thereof. Preferably, the mesoporous crystalline molecular sieve is selected from the group consisting of the framework types of FER, MEL, MFI, STI, and STT.

[0039] Preferably, the crystalline molecular sieve is a small-pore zeolite with a framework type of CHA, AEI, AFX, LTA, or ERI.

[0040] When the crystalline molecular sieve is zeolite, the silica to alumina ratio (SAR) of the zeolite can be from 5 to 200, preferably from 5 to 100, and more preferably from 10 to 80. For example, the silica to alumina ratio (SAR) of the zeolite can be from 5 to 30.

[0041] When the crystalline molecular sieve is SAPO, the silicon content of SAPO can be in the range of 5% to 30% by weight, preferably 8% to 16% by weight (based on the total weight of the molecular sieve).

[0042] The crystalline microporous molecular sieve or mesoporous molecular sieve is preferably a powdered crystalline molecular sieve (i.e., in granular form), wherein these particles comprise individual crystals, aggregates of crystals, or a combination of both. As measured by scanning electron microscopy (SEM), the average crystal size of the crystalline molecular sieve can be ≥0.5 μm, preferably between about 0.5 μm and about 15 μm, such as about 0.5 μm to 10 μm, about 0.5 μm to about 5 μm, about 1 μm to about 5 μm, or about 2 μm to about 5 μm.

[0043] The D90 particle size of the powdered crystalline molecular sieve is preferably less than about 30 μm. The D99 particle size of the powdered crystalline molecular sieve is preferably less than about 50 μm. As used herein, the terms "D90 particle size" and "D99 particle size" refer to particle size distribution. The D90 particle size value corresponds to the particle size value of 90% (by volume) of the total particles in a particular sample. The D99 particle size value corresponds to the particle size value of 99% (by volume) of the total particles in a particular sample. The D90 and D99 particle sizes can be determined using laser diffraction methods (e.g., using a Malvern Mastersizer 2000).

[0044] If necessary, the molecular sieve may undergo a particle size reduction process, such as jet milling, wet milling, or steam-assisted jet milling, before forming the plastic mixture in step a) of the method in the first aspect.

[0045] The components mixed together in step (a) of the first aspect may contain two or more H + or NH4 + The resulting solid catalyst body formed in step (c) can be a crystalline microporous molecular sieve or a mesoporous molecular sieve. Therefore, the resulting solid catalyst body may contain two or more different types of metal-supported molecular sieves.

[0046] As used herein, “active metal precursor” refers to a metal component capable of supplying an extra-framework metal to crystalline microporous or mesoporous molecular sieves. As used herein, “extra-framework metal” refers to a metal residing within the molecular sieve (i.e., within the microporous structure, at ion-exchange or non-ion-exchange sites) and / or on at least a portion of the molecular sieve surface (e.g., in ionic or oxide form) and not comprising the metal atoms of the tetrahedral units constituting the molecular sieve framework. It should be understood that additional metal components may be present in the mixture formed in step (a), and these metal components themselves will not participate in metal loading.

[0047] "Insoluble active metal precursor" refers to an active metal precursor that is insoluble in water. Specifically, the water solubility of an insoluble active metal precursor can be less than 1 g / 100 ml, for example, less than 0.1 g / 100 ml or less than 0.01 g / 100 ml. Water solubility is a measure of the amount of material that will dissolve in a given volume of water to form a saturated solution at a specified temperature and pressure. As used herein, the term "water solubility" with respect to insoluble active metal precursors means the amount (in grams) (g / 100 ml) of insoluble active metal precursor that will dissolve in 100 ml of water at a temperature of 20°C and a pressure of 1 atmosphere.

[0048] Suitable insoluble active metal precursors include certain metal salts. Specifically, insoluble active metal precursors can be metal carbonates, metal hydroxides, or metal oxalates.

[0049] The insoluble active metal precursor preferably comprises a metal salt that has undergone thermal decomposition through pyrolysis at a temperature below 500°C.

[0050] Insoluble active metal precursors may comprise salts of transition metals, noble metals, or rare earth metals. For example, insoluble active metal precursors may comprise one or more copper salts, manganese salts, nickel salts, cobalt salts, iron salts, palladium salts, platinum salts, cerium salts, yttrium salts, niobium salts, lanthanum salts, zinc salts, calcium salts, magnesium salts, or any mixture of two or more of these.

[0051] Specifically, 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 them.

[0052] Preferably, the insoluble active metal precursor may comprise one or more of the following: copper(II) carbonate, copper(II) hydroxide, and copper oxalate. More preferably, the insoluble active metal precursor comprises copper(II) carbonate. In one example, the insoluble active metal precursor may comprise a mixture of copper(II) carbonate and cerium carbonate.

[0053] In addition to the insoluble active metal precursor, the components mixed together in step (a) may further include one or more soluble (i.e., water-soluble) active metal precursors. Suitable soluble active metal precursors may include metal acetates or metal nitrates or any two or more of them. In one example, the insoluble active metal precursor may contain copper carbonate, and the soluble active metal precursor may contain cerium acetate.

[0054] The relative amounts of the molecular sieve and the insoluble active metal precursor used in step (a) will depend on the targeted metal loading of the molecular sieve and the amount of any soluble active metal precursor used. The metal loading of the molecular sieve present in the solid produced in step (c) can be ≥0.1 wt% to ≤10 wt%, preferably ≥0.1 wt% and ≤7 wt%, more preferably ≥0.1 wt% and ≤5 wt%.

[0055] Specifically, when the crystalline microporous molecular sieve or mesoporous molecular sieve is a zeolite, the relative amounts of the molecular sieve, insoluble active metal precursor, and any soluble active metal precursor used in step (a) can be selected to provide a solid catalyst body comprising metal-loaded zeolite in which the metal to alumina ratio is in the range of 0.2 to 0.5, preferably in the range of 0.3 to 0.5.

[0056] As used herein, the term "aqueous solvent" refers to a solvent containing water. Preferably, an aqueous solvent consists essentially of water. That is, an 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 demineralized water.

[0057] The solid content of the plastic mixture formed in step (a) is at least 50% by weight, preferably at least 60% by weight. "Solid content" means the proportion of solid material present in the plastic mixture based on the total weight of the mixture. Specifically, the plastic mixture may be in the form of a paste. The solid content of the mixture is preferably in the range of 60% to 80% by weight, more preferably in the range of 70% to 80% by weight. For example, the solid content of the mixture may be about 75% by weight.

[0058] The inorganic matrix component may contain inert fillers (also known as permanent binders) that provide structural integrity and / or porosity to the final solid catalyst body. During calcination, the inorganic matrix component may form sintered bridges to provide stiffness and mechanical strength within the solid catalyst body. Some inorganic matrix components may also contribute desired properties that aid in the manufacture. For example, clay is inherently plastic, and therefore its inclusion in the mixture formed in step (a) can achieve or promote a desired level of plasticity.

[0059] Preferably, the inorganic matrix component comprises an alumina precursor, such as boehmite or calcite, that forms alumina during calcination. The inorganic matrix component preferably comprises boehmite.

[0060] Alternatively, the inorganic matrix component may contain silica or silica precursors, such as colloidal silica, silanes, or polysiloxanes.

[0061] Alternatively, the inorganic matrix component may contain clay. Suitable clays include bentonite, refractory clay, palygorskite, bleaching clay, sepiolite, lithium montmorillonite, green clay, kaolin, diatomite, and mixtures of any two or more thereof.

[0062] Optionally, the components mixed together in step (a) may further include inorganic fibers. Suitable inorganic fibers may be selected from the group consisting of: carbon fibers, glass fibers, metal fibers, boron fibers, alumina fibers, silica fibers, silica-alumina fibers, silicon carbide fibers, potassium titanate fibers, aluminum borate fibers, and ceramic fibers. Advantageously, inorganic fibers can improve the mechanical robustness of the calcined product.

[0063] Organic additives are used to improve processing or introduce desired properties into the final solid catalyst body, but are calcined during the calcination step. Such materials can improve processing plasticity and / or introduce porosity in the solid catalyst body. The organic additives suitable for step (a) of the first aspect may comprise at least one of the following: acrylic fibers (extrusion aids and pore-forming agents), cellulose derivatives (plasticizers and / or drying aids), other organic plasticizers (e.g., polyvinyl alcohol (PVA) or polyethylene oxide (PEO)), lubricants (extrusion aids), and water-soluble resins.

[0064] In some embodiments, additional catalytically active materials may be incorporated into the plastic mixture formed in step (a), for example, when it is desired that the catalyst article is multifunctional (i.e., performs more than one catalytic function).

[0065] The relative quantitative proportions of the components used in step (a) can be selected such that the plastic mixture has the desired solids content, and that after calcination of the organic auxiliaries, the solid catalyst body contains 55% to 85% by weight, preferably 60% to 85% by weight, of metal-supported molecular sieves and 20% to 40% by weight of inorganic matrix components (based on the total weight of the solid catalyst body). The selection of appropriate amounts of starting materials is entirely within the capabilities of those skilled in the art. Preferably, the relative quantitative proportions of the components used in step (a) are selected such that the solid catalyst body produced in step (c) contains 60% to 85% by weight of metal-supported molecular sieves, 20% to 40% by weight of inorganic matrix components, and 0% to 10% by weight of inorganic fibers (based on the total weight of the solid catalyst body).

[0066] The plastic mixture formed in step (a) may, for example, contain 25% to 70% by weight of H + or NH 4+ The crystalline microporous or mesoporous molecular sieve is in the form of 0.06 wt% to 8 wt% insoluble active metal precursor; 12 wt% to 33 wt% inorganic matrix component; 0 wt% to 8 wt% inorganic fiber; and up to 15 wt% organic auxiliaries (based on the total weight of the plastic mixture).

[0067] In step (a), a plastic mixture is formed by mixing the components together. Preferably, the mixture is substantially homogeneous, meaning that the distribution of the components throughout the mixture is substantially uniform. The components can be mixed by any suitable method. Preferably, the components are mixed by kneading.

[0068] Optionally, the pH of the plastic mixture can be adjusted by adding an acid or a base.

[0069] Step (a) can be performed at ambient temperature. Preferably, step (a) is performed at a temperature in the range of 10°C to 35°C, and more preferably in the range of 10°C to 30°C. For example, step (a) can be performed at a temperature in the range of 18°C ​​to 28°C.

[0070] A specific advantage of this invention is that the plastic mixture formed in step a) can be used directly as an extrusion paste. Therefore, the mixture formed in step a) can be used directly in step b) without any additional processing steps.

[0071] In step (b), the mixture can be molded using extrusion techniques well known in the art. For example, the mixture can be molded using extrusion pressing or an extruder including an extrusion die.

[0072] Step (b) can be performed at ambient temperature. Preferably, step (b) is performed at a temperature in the range of 10°C to 35°C, and more preferably in the range of 10°C to 30°C. For example, step (b) can be performed at a temperature in the range of 18°C ​​to 28°C.

[0073] Most preferably, both steps (a) and (b) are carried out at a temperature in the range of 10°C to 35°C, preferably 10°C to 30°C, and more preferably 18°C ​​to 28°C.

[0074] Preferably, the temperature of the plastic mixture does not exceed 35°C before calcination in step (c). For example, the temperature of the plastic mixture may be maintained at ≤30°C or ≤28°C before calcination in step (c).

[0075] Preferably, the molded article is in the form of a single piece of honeycomb structure. The honeycomb structure can have any convenient size and shape. Alternatively, the molded article can take other forms, such as plates or granules.

[0076] Prior to calcination in step (c), the molded article may undergo a drying process. Therefore, the method of the first aspect may further include drying the molded article formed in step (b) prior to step (c). Drying of the molded article can be performed using standard techniques, including freeze-drying and microwave drying (e.g., see WO2009 / 080155).

[0077] In step (c) of the first aspect, the (optionally dried) molded article formed in step (b) undergoes calcination to form a solid catalyst body. The term "calcination" refers to a heat treatment step. Calcination causes the molded article to solidify by removing any remaining solvent and removing (e.g., by firing) organic additives.

[0078] Unwilling to be bound by theory, it is believed, surprisingly, that at least some metal loading of small-pore or mesopore molecular sieves occurs during the calcination of the molded article. For example, solid-state ion exchange can occur during calcination.

[0079] The calcination of the molded articles can be carried out using techniques well known in the art. Specifically, calcination can be performed statically or dynamically (e.g., using a belt furnace).

[0080] When the molded product is made of a single material with a honeycomb structure, a flow-through calcination technique can be used, in which heated gas is guided through the channels of the honeycomb structure.

[0081] Preferably, the calcination step (c) is carried out at a temperature in the range of 500°C to 900°C, preferably 600°C to 800°C.

[0082] Preferably, the molded product is calcined for up to 5 hours, and more preferably for 1 to 3 hours.

[0083] The calcination performed in step (c) may include multiple heat treatment steps, for example, the molded article may be subjected to a first heat treatment at a first temperature and then to a second heat treatment at a second temperature.

[0084] Calcination can be carried out, for example, in a reducing or oxidizing atmosphere. In cases involving multiple heat treatment steps, different steps can be performed under different atmospheres.

[0085] The catalyst article according to the second aspect of this disclosure can be used to treat combustion exhaust gases. That is, the catalyst article can be used to treat exhaust gases originating from combustion processes, such as exhaust gases from internal combustion engines (whether mobile or stationary), gas turbines, or power plants (such as coal-fired or oil-fired power plants). A preferred application of the catalyst article of this disclosure is in motor vehicle exhaust systems. Specifically, the catalyst article can be used as an SCR catalyst.

[0086] In some embodiments, for example, where it is desired that the catalyst article is multifunctional (i.e., the catalyst article performs more than one catalytic function simultaneously), the method may include an additional step of applying a catalyst support coating to the catalyst article. Therefore, the method of the first aspect may further include step (d): coating the solid catalyst body produced in step (c) with a composition comprising a catalytically active material. For example, the composition may comprise an SCR catalyst and / or an ammonia escape catalyst (ASC). This support coating step may be performed according to methods well known in the art.

[0087] The catalyst article can be configured as a flow-through honeycomb structure monolith, wherein each channel is open at both ends and extends through the entire axial length of the substrate. Alternatively, the catalyst article can be configured as a filter substrate, wherein some channels are blocked at one end of the article and other channels are blocked at the opposite ends. Such an arrangement is known in the art as a wall-flow filter. The formation of a wall-flow filter can be achieved by appropriately setting the porosity of the catalyst article. The final porosity of the catalyst article can be controlled, for example, by incorporating an organic pore-forming agent component into the organic auxiliaries used in step (a) of the first aspect.

[0088] The catalyst product can be part of an exhaust gas treatment system, wherein the catalyst product is located downstream of a nitrogen-containing reducing agent source.

[0089] Example

[0090] The present disclosure will now be further described with reference to the following embodiments, which are illustrative but not limiting of the invention.

[0091] · Comparative Example A

[0092] Powdered copper-exchanged SSZ-39(AEI) zeolite (prepared beforehand via wet ion exchange, followed by spray drying and calcination) was combined with clay minerals and powdered synthetic boehmite alumina. SB) and glass fiber (CP160, available from The mixture was then prepared in an aqueous solution at pH 4 with carboxymethyl cellulose, a plasticizer / extrusion aid (Zusoplast (a mixture of oleic acid, glycol, acid and alcohol) – a brand name of Zschimmer & Schwarz GmbH & Co KG), and polyethylene oxide (…). PEO is mixed to form a moldable paste. The moldable paste has a solids content of 64% by weight. The quantitative proportions of the starting materials are selected such that the final solid catalyst body contains 65% by weight copper-exchanged zeolite, 25% by weight γ-Al2O3 and clay minerals, and 10% by weight glass fiber.

[0093] A moldable paste was extruded at 20°C into a flow-through honeycomb structure with a circular cross-section of 1 inch in diameter and a cell density of 600 cpsi (cells per square inch). The extruded honeycomb structure was freeze-dried at 2 mbar for several hours according to the method described in WO 2009 / 080155, and then calcined in a laboratory-scale muffle furnace at 600°C to form a solid catalyst body.

[0094] · Example 1

[0095] The moldable paste was prepared according to the method used in Comparative Example A, except that instead of pre-exchanged copper zeolite, the corresponding H was used. + The zeolite and copper carbonate (CuCO3.Cu(OH)2) were used in the same form. All other components used in the paste formulation were identical. The amount of copper carbonate was selected to provide an equivalent weight percent of copper as provided by the Cu-exchanged zeolite used in Comparative Example A. The quantitative proportions of the starting materials were selected to provide a final solid catalyst body containing 65 weight percent of copper and zeolite, 25 weight percent of γ-Al2O3 and clay minerals, and 10 weight percent of glass fiber. The moldable paste was then extruded into a flow-through honeycomb structure having the same shape and size as that of the Comparative Example, and then dried and calcined in the same manner to form a solid catalyst body.

[0096] · Example 2

[0097] The solid catalyst body was prepared according to the method described in Example 1, except that copper hydroxide (Cu(OH)2) was used instead of copper carbonate.

[0098] · Comparative Example B

[0099] The solid catalyst body was prepared according to the method described in Example 1, except that copper nitrate (Cu(NO3)2) (i.e., a soluble active metal precursor) was used instead of copper carbonate.

[0100] · Example 3

[0101] The solid catalyst body was prepared according to the method described in Example 1, except that H- + The form SSZ-13(CHA) is used as a zeolite.

[0102] · Catalyst testing

[0103] The same volume samples of Comparative Example A and Example 1 were tested in a Synthetic Catalytic Activity Test (SCAT) apparatus using the following inlet gas mixture at the selected inlet gas temperature: 300 ppm NO (0% NO2), 300 ppm NH3 (ammonia to NOx ratio (ANR) = 1.0), 9.3% O2, 7% H2O, balance N2, for 120,000 h. -1 The space velocity (SV) was measured. Catalyst samples were tested under fresh conditions and after hydrothermal aging (10 vol% H2O at 650°C for 50 h).

[0104] The results are shown in Figure 1 and Figure 2 middle.

[0105] Figure 1 The NO levels achieved by each sample at the selected inlet temperature are shown. x Conversion rate, and Figure 2 The N2O selectivity activity achieved by each sample at the selected inlet temperature is shown.

[0106] like Figure 1 and Figure 2 As demonstrated by the data shown, Example 1 achieved similar or slightly better NOx conversion and similar N2O selectivity compared to Comparative Example A. The comparable catalytic performance indicates that the catalyst body prepared in Example 1 comprises Cu-supported zeolite, and that the achieved copper support is similar to the copper support of the powdered pre-exchanged zeolite used in Comparative Example A.

[0107] Advantageously, compared with the overall preparation of Comparative Example A, the preparation of Example 1 requires fewer processing steps and reduces water and energy consumption.

[0108] Under the same conditions described above, samples of the same volume from Examples 2 and 3 and Comparative Example B under fresh conditions were tested in a Synthetic Catalytic Activity Test (SCAT) apparatus.

[0109] The results are shown in Figure 3 and Figure 4 In the meantime. For comparative purposes, the results of Example 1 under fresh conditions are also included. Figure 3 and Figure 4 It reappears in the middle.

[0110] Other aspects and implementations of this disclosure are set forth in the following numbered clauses:

[0111] Clause 1: A method for forming a catalyst article, the method comprising:

[0112] (a) A plastic mixture is formed by mixing at least the following components together:

[0113] (i) H + or NH4 + Crystalline microporous or mesoporous molecular sieves;

[0114] (ii) Insoluble active metal precursors;

[0115] (iii) Inorganic matrix components;

[0116] (iv) Organic auxiliaries;

[0117] (v) Aqueous solvents;

[0118] The solid content of the mixture is greater than 50% by weight;

[0119] (b) molding the plastic mixture into a molded article; and

[0120] (c) Calcine the molded product to form a solid catalyst body.

[0121] Clause 2: The method according to Clause 1, wherein in step (a), the components to be mixed together further include: (vi) inorganic fibers.

[0122] Clause 3: A method for forming a catalyst article, the method comprising:

[0123] (a) A plastic mixture is formed by mixing the following components together:

[0124] (i) H + or NH4 + Crystalline microporous or mesoporous molecular sieves;

[0125] (ii) Insoluble active metal precursors;

[0126] (iii) Inorganic matrix components;

[0127] (iv) Organic auxiliaries;

[0128] (v) Aqueous solvents;

[0129] (vi) Optional inorganic fibers;

[0130] The solid content of the mixture is greater than 50% by weight;

[0131] (b) molding the plastic mixture into a molded article; and

[0132] (c) Calcine the molded product to form a solid catalyst body.

[0133] Clause 4: A method for forming a catalyst article, the method comprising:

[0134] (a) A plastic mixture is formed by mixing the following components together:

[0135] (i) Insoluble active metal precursors;

[0136] (ii) Inorganic matrix components;

[0137] (iii) Organic auxiliaries;

[0138] (iv) Aqueous solvents;

[0139] (v) Optional inorganic fibers;

[0140] The solid content of the plastic mixture is greater than 50% by weight;

[0141] (b) molding the plastic mixture into a molded article; and

[0142] (c) Calcining the molded product to form a solid catalyst body;

[0143] Optionally, the molded article is dried after step (b) and before step (c).

[0144] Clause 5: The method according to any of the preceding clauses, wherein the relative quantitative proportions of the components used in step (a) are selected such that the solid catalyst body formed in step (c) contains 55% to 85% by weight of metal-supported molecular sieves, 20% to 40% by weight of inorganic matrix components, and 0% to 10% by weight of inorganic fibers.

[0145] Clause 6: The method according to any of the preceding clauses, wherein the relative quantitative proportions of the components used in step (a) are selected such that the solid catalyst body formed in step (c) contains 60% to 85% by weight of metal-supported molecular sieves, 20% to 40% by weight of inorganic matrix components, and 0% to 10% by weight of inorganic fibers.

[0146] Clause 7: The method according to any of the preceding clauses, wherein the plastic mixture formed in step (a) comprises 25% to 70% by weight of H + or NH 4+The crystalline microporous or mesoporous molecular sieve is in the form of 0.06 wt% to 8 wt% insoluble active metal precursor; 12 wt% to 33 wt% inorganic matrix component; 0 wt% to 8 wt% inorganic fiber; and up to 15 wt% organic auxiliaries (based on the total weight of the plastic mixture).

[0147] Clause 8: The method described in any of the preceding clauses, wherein the crystalline molecular sieve is a small-pore molecular sieve.

[0148] Clause 9: The method according to Clause 8, wherein the small-pore molecular sieve has a framework type selected from AEI, AFT, AFX, CHA, DDR, ERI, KFI, LEV, LTA, SFW and RHO.

[0149] Clause 10: The method according to any of the preceding clauses, wherein the crystalline molecular sieve is a small-pore zeolite having a framework type selected from CHA, AEI or AFX, LTA or ERI, preferably selected from CHA or AEI.

[0150] Clause 11: The method according to any of the preceding clauses, wherein the crystalline molecular sieve is a zeolite having a silica to alumina ratio (SAR) of 5 to 200, 5 to 100, 10 to 80, or 5 to 30.

[0151] Clause 12: The method according to any of the preceding clauses, wherein the crystalline molecular sieve is in particulate form and has a D90 particle size of less than 30 μm.

[0152] Clause 13: The method according to any of the preceding clauses, wherein the crystalline molecular sieve is in particulate form and has a D99 particle size of less than 50 μm.

[0153] Clause 14: The method according to any of the preceding clauses, wherein component (i) comprises two or more H + or NH4 + Small-pore or medium-pore crystalline molecular sieves.

[0154] Clause 15: The method according to any of the preceding clauses, wherein the water solubility of the insoluble active metal precursor is less than 1 g / 100 ml, less than 0.1 g / 100 ml, or less than 0.01 g / 100 ml.

[0155] Clause 16: The method according to any of the preceding clauses, wherein the insoluble active metal precursor is selected from metal carbonates, metal hydroxides, metal oxalates, or any two or more mixtures thereof.

[0156] Clause 17: The method according to any of the preceding clauses, wherein the insoluble active metal precursor comprises copper salt, manganese salt, nickel salt, cobalt salt, iron salt, palladium salt, platinum salt, cerium salt, yttrium salt, niobium salt, lanthanum salt, zinc salt, calcium salt, magnesium salt, or any mixture of two or more of the above.

[0157] Clause 18: The method according to any of the preceding clauses, 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 them.

[0158] Clause 19: The method according to any of the preceding clauses, wherein the insoluble active metal precursor comprises one or more of copper(II) carbonate, copper(II) hydroxide, and copper oxalate.

[0159] Clause 20: The method according to any of the preceding clauses, wherein the insoluble active metal precursor comprises copper(II) carbonate.

[0160] Clause 21: The method according to any of the preceding clauses, wherein the insoluble active metal precursor comprises a mixture of copper(II) carbonate and cerium carbonate.

[0161] Clause 22: The method according to any of the preceding clauses, wherein the insoluble active metal precursor comprises one or more metal salts, the metal salts undergoing thermal decomposition by pyrolysis at a temperature below 500°C.

[0162] Clause 23: The method according to any of the preceding clauses, wherein in step (a), the component to be mixed further comprises: (vii) a soluble active metal precursor.

[0163] Clause 24: The method described in any of the preceding clauses, wherein the aqueous solvent is substantially composed of water.

[0164] Clause 25: The method according to any of the preceding clauses, wherein the aqueous solvent is water.

[0165] Clause 26: The method according to any of the preceding clauses, wherein the solid content of the plastic mixture formed in step (a) is at least 60% by weight.

[0166] Clause 27: The method according to any of the preceding clauses, wherein the solid content of the plastic mixture formed in step (a) is in the range of 60% to 80% by weight, more preferably in the range of 70% to 80% by weight.

[0167] Clause 28: The method according to any of the preceding clauses, wherein the inorganic matrix component comprises boehmite and / or calcite, preferably boehmite.

[0168] Clause 29: The method according to any of the preceding clauses, wherein the inorganic matrix component comprises clay.

[0169] Clause 30: The method according to Clause 29, wherein the clay is selected from bentonite, refractory clay, palygorskite, bleaching clay, sepiolite, lithium montmorillonite, chlorite, kaolinite, diatomite, and any two or more mixtures thereof.

[0170] Clause 31: The method according to any of the preceding clauses, wherein in step (a), the components to be mixed together further include: (vi) inorganic fibers, and wherein the inorganic fibers comprise one or more of carbon fibers, glass fibers, metal fibers, boron fibers, alumina fibers, silica fibers, silica-alumina fibers, silicon carbide fibers, potassium titanate fibers, aluminum borate fibers, and ceramic fibers.

[0171] Clause 32: The method according to any of the preceding clauses, wherein the organic auxiliaries comprise at least one of acrylic fibers, cellulose derivatives, organic plasticizers, lubricants, and water-soluble resins.

[0172] Clause 33: The method according to any of the preceding clauses, wherein in step (a), the components are mixed together by kneading.

[0173] Clause 34: The method according to any of the preceding clauses, wherein step (a) is performed at ambient temperature.

[0174] Clause 35: The method according to any one of Clauses 1 to 33, wherein step (a) is carried out at a temperature in the range of 10°C to 35°C, in the range of 10°C to 30°C, or in the range of 18°C ​​to 28°C.

[0175] Clause 36: The method according to any of the preceding clauses, wherein the plastic mixture formed in step a) is used directly in step b) without any additional processing steps.

[0176] Clause 37: The method according to any of the preceding clauses, wherein step (b) is performed by extrusion.

[0177] Clause 38: The method described in any of the preceding clauses, wherein step (b) is performed at ambient temperature.

[0178] Clause 39: The method according to any one of Clauses 1 to 37, wherein step (b) is carried out at a temperature in the range of 10°C to 35°C, in the range of 10°C to 30°C, or in the range of 18°C ​​to 28°C.

[0179] Clause 40: The method according to any of the preceding clauses, wherein the temperature of the plastic mixture does not exceed 35°C, preferably not more than 30°C, and more preferably not more than 28°C before calcination in step (c).

[0180] Clause 41: The method described in any of the preceding clauses, wherein the molded article is a single piece of honeycomb structure.

[0181] Clause 42: The method according to any of the preceding clauses further includes drying the molded article formed in step (b) prior to step (c).

[0182] Clause 43: The method according to any of the preceding clauses, wherein step (c) is performed at a temperature in the range of 500°C to 900°C, preferably in the range of 600°C to 800°C.

[0183] Clause 44: The method according to any of the preceding clauses, wherein in step (c), calcination is carried out for a period of up to 5 hours, preferably 1 to 3 hours.

[0184] Clause 45: The method according to any of the preceding clauses, wherein the solid catalyst body formed in step (c) comprises a metal-supported molecular sieve.

[0185] Clause 46: The method according to any of the preceding clauses, wherein the solid catalyst body formed in step (c) comprises a metal-supported molecular sieve having catalytic activity for SCR.

[0186] Clause 47: The method according to any of the preceding clauses, wherein at least some of the metal loading of the molecular sieve occurs during step (c).

[0187] Clause 48: A catalyst article which is obtained by or can be obtained by the method described in accordance with any of the preceding clauses.

[0188] Clause 49: The catalyst article as described in Clause 48 is configured as a flow-through honeycomb structure bulk filter or a wall-flow filter.

[0189] Clause 50: The catalyst article described in Clause 48 or 49 has catalytic activity for SCR.

[0190] Clause 51: An exhaust system comprising: a nitrogen-containing reducing agent source and an injector for injecting the nitrogen-containing reducing agent into a flowing exhaust gas, wherein the injector is disposed upstream of the catalyst article as described in Clause 50.

[0191] To avoid any doubt, the entire contents of any and all references cited herein are incorporated herein by reference.

Claims

1. A process for forming a catalyst article, the process comprising: (a) forming a plastic mixture by mixing together at least: (i) in the form of a crystalline small or medium pore molecular sieve having the H + or NH4 + form; (ii) an insoluble active metal precursor; (iii) an inorganic matrix component; (iv) an organic adjuvant; (v) an aqueous solvent; wherein the solids content of the mixture is greater than 50 wt%; 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, 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 thereof; and wherein step (a) is conducted at a temperature in the range of 10°C to 35°C; (b) molding the plastic mixture into a shaped article; and (c) calcining the shaped article to form a solid catalyst body; wherein the plastic mixture formed in step (a) is used directly in step (b) without any additional processing steps.

2. The method of claim 1, wherein in step (a), the components to be mixed together further comprise: (vi) an inorganic fiber.

3. The process of claim 2, wherein the crystalline molecular sieve is a small pore zeolite having a framework type selected from CHA, AEI or AFX, LTA or ERI.

4. The process of claim 2, wherein the insoluble active metal precursor comprises one or more of copper (II) carbonate and copper oxalate.

5. The process of claim 2, wherein the solids content of the plastic mixture formed in step (a) is at least 60 wt%.

6. The process of claim 1, wherein the relative quantitative proportions of the components used in step (a) are selected such that the solid catalyst body formed in step (c) contains 60 wt% to 85 wt% of metal-loaded molecular sieve, 20 wt% to 40 wt% of matrix component, and 0 wt% to 10 wt% of inorganic fiber.

7. The process of claim 1, wherein the crystalline molecular sieve is a small pore zeolite having a framework type selected from CHA, AEI or AFX, LTA or ERI.

8. The process of claim 1, wherein the insoluble active metal precursor comprises one or more of copper (II) carbonate and copper oxalate.

9. The process of claim 1, wherein the aqueous solvent is water.

10. The process of claim 1, wherein the solids content of the plastic mixture formed in step (a) is at least 60 wt%.

11. The process of claim 1, wherein the inorganic matrix component comprises an alumina precursor and / or a clay.

12. The process of claim 1, wherein the organic adjuvant comprises at least one of an acrylic fiber, a cellulose derivative, an organic plasticizer, a lubricant, and a water-soluble resin.

13. The process of claim 1, wherein step (b) is conducted at a temperature in the range of 10 °C to 35 °C.

14. The process of claim 1, wherein the insoluble active metal precursor comprises copper (II) carbonate.

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