Methods and catalytic articles

Abstract

This disclosure relates to: (a) H + or NH4 + The present disclosure further relates to a method for forming a catalyst article, the method comprising: (a) mixing together a crystalline small pore molecular sieve in the form of a ferrous sulfate, an inorganic matrix component, an organic coagent, an aqueous solvent, and optionally inorganic fibers to form a plastic mixture having a solids content of greater than 50% by weight; (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 catalyst articles, exhaust systems, and methods for treating exhaust gases.

Description

[Technical field]

[0001] The present disclosure relates to a method for forming a catalyst article comprising an iron-loaded small pore molecular sieve. In particular, the present invention relates to a method for reducing nitrogen oxide (NO) in exhaust gases. x The present disclosure further relates to catalyst articles, exhaust systems, and methods for treating exhaust gases. [Background technology]

[0002] Millions of catalytic converters are manufactured each year for use in treating emissions from mobile and stationary sources. Catalytic converters for use in automobiles typically comprise an extruded ceramic honeycomb monolith that is provided with channels for the flow of exhaust gases therethrough. The channels of the monolith may be coated with a catalytically active material (known as a "washcoat"). Alternatively, the extruded monolith itself is formed of the catalytically active material (referred to as a "fully active extrudate" or "extruded catalyst").

[0003] To produce a fully active extrudate, the catalytically active components are included in an extrusion composition whose rheological properties are set to be suitable for the extrusion process. The extrusion composition is a plastic (i.e., easily shaped or moldable), highly viscous composition. To impart the desired rheological properties to the extrusion composition and to impart the mechanical properties to the extrudate, typically binders or additives are added to the extrusion composition. The plastic composition is then subjected to an extrusion process, for example to prepare a honeycomb body. The so-called "green" body thus obtained is then subjected to a high-temperature calcination treatment to form the final extruded catalyst body.

[0004] The fully active extrudate generally comprises a monolithic structure in the form of a honeycomb with uniformly sized and parallel channels extending from a first end to a second end of the extrusion. Typically, the channels are open at both the first and second ends, a so-called "flow-through" structure. Alternatively, the channels at the first upstream end can be plugged with a suitable ceramic cement, and the channels that are not plugged at the first upstream end can also be plugged at the second downstream end to form a so-called wall-flow filter.

[0005] Nitrogen oxides (NO x Selective catalytic reduction of NO (NH3-SCR) is a process for the reduction of NO from exhaust gases emitted by stationary and mobile engines, primarily diesel engines, for vehicles such as automobiles, trucks, locomotives, and marine vehicles. x This is considered to be the most practical and efficient technique for mitigating

[0006] Known SCR (selective catalytic reduction) catalysts include vanadium-based catalysts and molecular sieves. Useful molecular sieves include crystalline or paracrystalline materials that can be, for example, aluminosilicates (zeolites) or silicoaluminophosphates (SAPOs). Such molecular sieves are built, for example, of repeating SiO4, AlO4, and optionally PO4 tetrahedral units linked in rings to form a framework with regular intracrystalline cavities and channels of molecular dimensions. A particular arrangement of the tetrahedral units (ring members) gives rise to the framework of the molecular sieve, 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 frameworks that are known SCR catalysts include the framework type codes CHA (chabazite), BEA (beta), MOR (mordenite), AEI, MFI, and LTA.

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

[0008] The molecular sieve catalyst may be metal promoted. Examples of metal promoted molecular sieve catalysts include iron, copper and palladium promoted molecular sieves, where the metal may be supported within the molecular sieve. In metal supported molecular sieves, the supported metal is of the "extra-framework metal" variety, i.e., a metal present within and / or at least a portion of the molecular sieve surface, and does not include atoms that make up the molecular sieve framework.

[0009] Certain iron- and copper-loaded small- and medium-pore zeolites are known to demonstrate high catalytic activity in selective catalytic reduction of nitric oxide and / or nitrogen dioxide with ammonia (NH3-SCR) and are being actively investigated. It is known that relatively good low-temperature (200-450°C) NH3-SCR catalytic activity can be obtained from Cu-SSZ-13 (CHA) zeolites (see, for example, WO 2008 / 132452(A2)). However, Fe-loaded zeolites generally exhibit better high-temperature catalytic activity than Cu-containing zeolites, and therefore Fe-loaded zeolites are of particular interest for NH3-SCR applications. Furthermore, the use of Cu-containing zeolites may result in the formation of NO at higher reaction temperatures.

[0010] Several methods for preparing Fe-loaded zeolites are mentioned in the literature. The direct synthesis of iron-loaded 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 subsequently add iron by post-synthesis treatment of the zeolite, either by wet impregnation, wet ion exchange, or solid-state ion exchange.

[0011] Known wet ion exchange methods for loading molecular sieves with iron typically use an iron salt, such as iron acetate, as the active metal precursor, which reacts with the molecular sieve in an aqueous solution. To accelerate the ion exchange, such processes typically require a heating step, where 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., filtering, evaporation, spray drying, calcination, etc.) may be required before the resulting metal-loaded molecular sieve can be used in an extrusion paste to form a fully activated extrudate.

[0012] Furthermore, a problem associated with the preparation of Fe-loaded zeolites by post-synthesis treatment is the aggregation of iron species, which leads to a non-uniform distribution of iron species in the zeolite (see, for example, L. Kustov et al., Topics in Catalysis, 238 (2006) pp. 250-259).

[0013] WO 2020 / 148186 describes a method for forming iron-loaded zeolite which requires (i) treating zeolite crystallites to introduce mesoporosity, (ii) introducing a metal to the product of (i) via wet impregnation or wet ion exchange, and (iii) performing hydrothermal crystallization on the product of (ii).

[0014] The present invention provides an improved process for the preparation of extruded catalyst articles using iron-loaded small pore molecular sieves as the catalytically active material.

[0015] According to a first aspect of the present disclosure, there is provided a method for forming a catalytic article, the method comprising: (a) containing at least the following components: (i)H + or NH4 + a crystalline small pore molecular sieve of the form (ii) iron sulfate; (iii) an inorganic matrix component; and (iv) an organic auxiliary; (v) an aqueous solvent, by mixing together to form a plastic mixture, The mixture has a solids content of greater than 50% by weight (based on the total weight of the mixture); and (b) molding the plastic mixture into a shaped article; (c) calcining the shaped article to form a solid catalyst body; Step (a) is carried out at a temperature in the range of 10 to 35°C.

[0016] Advantageously, it has been found that the heat used to calcinate the shaped article can be used to promote iron loading on the molecular sieve. This can avoid the requirement for any heating step during the wet ion exchange or impregnation process, and for expensive high temperature resistant equipment. Furthermore, the long reaction periods and / or energy and labor intensive processes such as spray drying that are typical in wet ion exchange or impregnation processes can be avoided. This can make the method according to the first aspect more efficient and economical.

[0017] It has further been found that the mixture prepared in step (a) of the method according to the first aspect can be directly used as an extrusion paste without the need for any further processing steps. In particular, the method of the first aspect can reduce the total amount of water consumed in producing an extruded catalyst comprising an iron-supported small pore molecular sieve, since conventionally, a powder form of the pre-supported small pore molecular sieve was used, which was prepared via a wet process followed by drying and / or calcination.

[0018] Advantageously, it has been found that catalysts prepared according to the first aspect can provide comparable NOx conversion to catalysts prepared in a similar manner using copper salts, can provide improved NOx conversion compared to vanadium-based SCR catalysts, and in both cases can provide significantly improved NO selectivity at high temperatures. Additionally, it has surprisingly been found that catalysts prepared according to the first aspect can have improved thermal expansion properties.

[0019] According to a second aspect of the present disclosure, there is provided a catalyst article obtained or obtainable by the method of the first aspect.

[0020] According to a third aspect of the present disclosure, there is provided a catalyst article comprising an extruded solid catalyst body, the solid catalyst body comprising an iron-loaded small pore molecular sieve and having a coefficient of thermal expansion (CTE) of 0 or greater at temperatures ranging from 100° C. to 700° C. Preferably, the catalyst article has a coefficient of thermal expansion (CTE) of 0 to 5×10 at temperatures ranging from 100° C. to 700° C. -6 / K, e.g. 0.5×10 -6 / K~4×10 -6 / K range.

[0021] According to a fourth aspect of the present disclosure, there is provided an exhaust system comprising a nitrogen-based reductant source and an injector for injecting the nitrogen-based reductant into a flowing exhaust gas, the injector being disposed upstream from a catalyst article according to the second or third aspect.

[0022] According to a fifth aspect of the present disclosure, there is provided a method for treating exhaust gas, the method comprising contacting the exhaust gas with a catalyst according to the second or third aspect. Preferably, the exhaust gas has a temperature in the range of 300 to 600° C., more preferably 350 to 550° C., for example 400 to 500° C. The exhaust gas may be from a stationary source.

[0023] According to a sixth aspect, there is provided the use of a catalytic article according to the second or third aspect for selectively reducing nitrogen oxides in an exhaust gas to dinitrogen using a nitrogen-based reductant. [Brief description of the drawings]

[0024] [Figure 1]FIG. 1 is a graph showing NOx conversion achieved by a catalyst prepared according to a first aspect of the present disclosure compared to (i) a catalyst prepared using a copper salt instead of iron sulfate, (ii) a catalyst prepared using an alternative iron salt, (iii) a catalyst prepared using a pre-exchanged iron-loaded zeolite, and (iv) a vanadium-based SCR catalyst. [Diagram 2] FIG. 1 is a graph showing the NO selectivity achieved by a catalyst prepared according to a first aspect of the present disclosure compared to (i) a catalyst prepared using a copper salt instead of iron sulfate, (ii) a catalyst prepared using an alternative iron salt, (iii) a catalyst prepared using a pre-exchanged iron-loaded zeolite, and (iv) a vanadium-based SCR catalyst. [Diagram 3] 1 is a graph showing the CTE of a catalyst article according to the present disclosure. [Figure 4] 1 is a graph showing NOx conversion achieved by a catalyst prepared according to a first embodiment of the present disclosure. [Diagram 5] 1 is a graph showing the N2O selectivity achieved by a catalyst prepared according to the first embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present disclosure will now be further described. In the following passages, 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 aspect / embodiment, unless expressly indicated otherwise. 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.

[0026] Additionally, as used herein, the term "comprising" can be interchanged with the definitions "consisting essentially of" or "consisting of." The term "comprising" is intended to mean that the specified elements are essential, although other elements may be added and still form a structure within the scope of the claim. The term "consisting essentially of" limits the scope of the claim to the specified materials or steps, as well as those that do not materially 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 recited, except for impurities ordinarily associated therewith.

[0027] Crystalline molecular sieves are typically composed of aluminum, silicon, and / or phosphorus. Crystalline molecular sieves generally have a three-dimensional arrangement (e.g., framework) of repeating SiO4, AlO4, and optionally PO4 tetrahedral units bonded by shared oxygen atoms. Small pore molecular sieves have a ring size of up to 8 tetrahedral atoms.

[0028] In relation to molecular sieves, "H + The term "morphology" refers to the structure in which the backbone charge is a proton (i.e., H + This refers to a molecular sieve that has an anionic framework balanced by cations.

[0029] In relation to molecular sieves, the term "NH4 + The "morphology" is that the charge on the backbone is an ammonium cation (NH4 + This refers to a molecular sieve that has an anionic framework balanced by cations.

[0030] When the crystalline small pore molecular sieve has an aluminosilicate framework, the molecular sieve is preferably a zeolite.

[0031] The small pore molecular sieve may have a framework type selected from the group of framework 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, and mixtures thereof and / or intergrowth. Preferably, the small pore molecular sieve has a framework type selected from the group of framework 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 framework type which is AEI, AFX, CHA, LTA, ERI, or an AEI-CHA intergrowth. Most preferably, the small pore molecular sieve has a CHA framework type.

[0032] When the crystalline molecular sieve is a zeolite, the silica-to-alumina ratio (SAR) of the zeolite may be from 5 to 200, preferably from 5 to 100, and more preferably from 10 to 80. For example, the zeolite may have a silica-to-alumina ratio (SAR) of from 5 to 30 or from 10 to 30.

[0033] The crystalline small pore molecular sieve is preferably a powdered crystalline molecular sieve (i.e., in particulate form), the particles comprising individual crystals, agglomerates of crystals, or a combination of both. The crystalline molecular sieve may have an average crystal size of 0.5 or more, preferably about 0.5 to about 15 μm, e.g., 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, as measured by scanning electron microscopy (SEM).

[0034] The powdered crystalline molecular sieve preferably has a D90 particle size of less than about 30 μm. The powdered crystalline molecular sieve preferably has a D99 particle size of less than about 50 μm. As used herein, the terms "D90 particle size" and "D99 particle size" refer to particle size distribution. The value of the D90 particle size corresponds to the particle size value below which 90% by volume of the total particles in a particular sample state are present. The value of the D99 particle size corresponds to the particle size value below which 99% by volume of the total particles in a particular sample state are present. The D90 particle size and the D99 particle size can be determined using laser diffraction methods (e.g., using a Malvern Mastersizer 2000).

[0035] If desired, prior to forming the plastic mixture in step a) of the process of the first embodiment, the molecular sieve may be subjected to a particle size reduction treatment such as jet milling, wet milling, or steam assisted jet milling.

[0036] The components mixed together in step (a) of the first embodiment are + or NH4 + The resulting solid catalyst body formed in step (c) may comprise two or more different types of iron-loaded molecular sieves.

[0037] The ferrous sulfate can be ferrous sulfate (II) or ferrous sulfate (III).

[0038] The ferrous sulfate may be combined with other ingredients to form a plastic mixture in crystalline form.

[0039] The relative amounts of molecular sieve and ferrous sulfate used in step (a) will depend on the target iron loading of the molecular sieve. The iron-loaded molecular sieve present in the solid produced in step (c) may have an iron loading of from 0.1 to 10.0 wt.%, preferably from 0.1 to 7.0 wt.%, more preferably from 0.5 to 5.0 wt.% (based on the total weight of the iron-loaded molecular sieve).

[0040] In particular, the crystalline small pore molecular sieve is a zeolite and the relative amounts of molecular sieve and iron sulfate used in step (a) may be selected to provide a solid catalyst body comprising iron-loaded zeolite having an iron to aluminium ratio in the range of 0.03 to 0.6, preferably in the range of 0.05 to 0.5, for example 0.1 to 0.4, more preferably in the range 0.1 to 0.2.

[0041] As used herein, the term "aqueous solvent" refers to a solvent that contains water. 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 demineralized water.

[0042] The plastic mixture formed in step (a) has a solids content of at least 50% by weight, preferably at least 60% by weight. "Solids content" refers to the percentage of solid material present in the plastic mixture based on the total weight of the mixture. In particular, the plastic mixture may be in the form of a paste. The solids content of the mixture is preferably in the range of 60-80% by weight, more preferably in the range of 70-80% by weight. For example, the solids content of the mixture may be about 75% by weight.

[0043] The inorganic matrix component may include an inert filler (also referred to as a permanent binder) that provides structural integrity and / or porosity to the final solid catalyst body. During firing, the inorganic matrix component may form sintered bridges to provide rigidity and mechanical strength to the solid catalyst body. Some inorganic matrix components may contribute desirable properties to aid in manufacturing. For example, clays are inherently plastic and may be included in the mixture formed in step (a) to achieve or promote a desired level of plasticity.

[0044] Preferably, the inorganic matrix component comprises an alumina precursor, such as boehmite or bayerite, which forms alumina upon firing. The inorganic matrix component preferably comprises boehmite.

[0045] Alternatively or additionally, the inorganic matrix component may include silica or a silica precursor, such as, for example, colloidal silica, a silane, or a polysiloxane.

[0046] Alternatively or additionally, the inorganic matrix component may comprise a clay. Suitable clays include bentonite, fireclay, attapulgite, fullers earth, sepiolite, hectorite, smectite, kaolin, diatomaceous earth, and mixtures of any two or more thereof.

[0047] Optionally, the components mixed together in step (a) may further comprise 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 may improve the mechanical robustness of the fired product.

[0048] Organic aids are used to improve processing or to introduce desired properties into the final solid catalyst body, but are burned off during the calcination step. Such materials can improve plastic processing and / or introduce porosity into the solid catalyst body. Organic aids suitable for use in step (a) of the first embodiment may include at least one of acrylic fibers (extrusion aids and pore formers), 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.

[0049] In some embodiments, for example where it is desired that the catalytic article be multifunctional (i.e., perform more than one catalytic function), additional catalytically active material may be included in the plastic mixture formed in step (a).

[0050] The relative quantitative proportions of the components used in step (a) can be selected so that the plastic mixture has the required solid content and so that the solid catalyst body after the organic auxiliaries are burned off contains 55-85 wt. %, preferably 60-85 wt. % of the iron-loaded molecular sieve and 20-40 wt. % of the inorganic matrix component (based on the total weight of the solid catalyst body). The selection of the appropriate amounts of starting materials is well within the capabilities of the skilled artisan. Preferably, the relative quantitative proportions of the components used in step (a) are selected so that the solid catalyst body produced in step (c) contains 60-85 wt. % of the iron-loaded molecular sieve, 20-40 wt. % of the inorganic matrix component and 0-10 wt. % of the inorganic fiber (based on the total weight of the solid catalyst body).

[0051] The plastic mixture formed in step (a) may, for example, contain 25 to 70 weight percent (based on the total weight of the plastic mixture) of H + or NH 4+ % of an inorganic matrix component; 0-8 wt. % of inorganic fibers; and up to 15 wt. % of an organic auxiliary.

[0052] In step (a), the plastic mixture is formed by mixing the components together. The components may be mixed together in any order. Preferably, the mixture is substantially homogenous, i.e., the distribution of the components in the mixture is substantially uniform. The components may be mixed by any suitable method. Preferably, the components are mixed by kneading.

[0053] The pH of the plastic mixture may optionally be adjusted by the addition of acid or base.

[0054] 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. For example, step (a) may be carried out at a temperature in the range of 18 to 28° C.

[0055] A particular advantage of the present invention is that the plastic mixture formed in step (a) can be used directly as an extrusion paste, so that the mixture formed in step a) can be used directly in step b) without any additional processing steps.

[0056] In step (b), the mixture may be molded by extrusion techniques well known in the art, for example, the mixture may be molded using an extrusion press or an extruder equipped with an extrusion die.

[0057] 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 in the range of 10 to 30° C. For example, step (b) may be carried out at a temperature in the range of 18 to 28° C.

[0058] Most preferably, both steps (a) and (b) are carried out at a temperature in the range of 10-35°C, preferably 10-30°C, more preferably 18-28°C.

[0059] Preferably, the temperature of the plastic mixture prior to the firing in step (c) does not exceed 35° C. For example, the temperature of the plastic mixture prior to the firing in step (c) may be maintained at or below 30° C. or below 28° C.

[0060] Preferably, the shaped article is in the form of a honeycomb monolith. The honeycomb body may have any convenient size and shape. Alternatively, the shaped article may be in other shapes, such as a plate or pellet.

[0061] Prior to the firing of step (c), the shaped article may be subjected to a drying process. Thus, the method of the first aspect may further comprise drying the shaped article formed in step (b) prior to carrying out step (c). Drying of the shaped article may be carried out by standard techniques, including freeze-drying and microwave drying (see, for example, WO 2009 / 080155).

[0062] In step (c) of the first embodiment, the (optionally dried) shaped article formed in step (b) is calcined to form a solid catalyst body. The terms "calcining" or "calcination" refer to a heat treatment step. Calcination removes any residual solvent, as well as organic auxiliary agents (e.g., by burning off), thereby solidifying the shaped article.

[0063] Firing of the shaped articles can be carried out by techniques well known in the art. In particular, firing can be carried out statically (for example, using a belt furnace) or dynamically.

[0064] When the shaped article has the shape of a honeycomb monolith, a flow-through firing technique can be used in which heated gas is flowed through the channels of the honeycomb.

[0065] Preferably, the calcination step (c) is carried out at a temperature in the range of 500 to 900°C, preferably 600 to 800°C.

[0066] Preferably the shaped article is baked for up to 5 hours, preferably from 1 to 3 hours.

[0067] The calcination carried out in step (c) may comprise multiple heat treatment steps, for example the shaped article may be subjected to a first heat treatment at a first temperature and then a second heat treatment at a second temperature.

[0068] For example, calcination can be carried out under a reducing or oxidizing atmosphere. When multiple heat treatment steps are used, different steps can be carried out under different atmospheres.

[0069] In the catalyst article according to the third embodiment, the solid catalyst body may comprise 60-85 wt % of the Fe-loaded small pore molecular sieve, 20-40 wt % of the matrix component, and 0-10 wt % of the inorganic fiber.

[0070] Advantageously, the extruded solid catalyst body of the catalyst article according to the third aspect has a CTE that is zero or positive at temperatures in the range of 100 to 700°C. If the CTE is positive, it is preferably close to zero. The coefficient of thermal expansion (CTE) is a measure of how much an object expands or contracts when heated. A catalyst article with a negative CTE may be susceptible to contraction.

[0071] Preferably, the solid catalyst body has a melting point of 0 to 5×10 at a temperature in the range of 100° C. to 700° C. -6 / K. For example, the solid catalyst body has a CTE of 0.5×10 -6 / K~5×10 -6 / K range or 0.5×10 -6 / K~4×10 -6 / K range.

[0072] The catalytic article according to the second or third aspect of the present disclosure may be used for treating a combustion exhaust gas stream. That is, the catalytic article may be used to treat exhaust gases originating from a combustion process, such as an internal combustion engine (either mobile or stationary), a gas turbine, or a power plant (e.g., a coal or oil-fired power plant). In particular, the catalytic article may be used to treat exhaust gases having a temperature in the range of 300-600°C, more preferably 350-550°C, for example 400-500°C. A preferred application of the catalytic article of the present disclosure is in exhaust systems for treating exhaust gases from a stationary source, such as a stationary internal combustion engine, a gas turbine, or a power plant. In particular, the catalytic article may be used as an SCR catalyst.

[0073] In some embodiments, for example where it is desired that the catalyst article be multifunctional (i.e. perform two or more catalytic functions simultaneously), the method may include the further step of applying a catalytic washcoat to the catalyst article. Thus, the method of the first aspect may further include step (d) of 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 slip catalyst (ASC). Such a washcoating step may be carried out by processes well known in the art. Thus, the catalyst article according to the second or third aspect may further comprise a catalytic washcoat applied to the solid catalyst body.

[0074] The solid catalyst body may be configured as a flow-through honeycomb monolith, with each channel open at both ends and extending over the entire axial length of the substrate. Alternatively, the solid catalyst body may be configured as a filter substrate, with some channels plugged at one end of the article and others plugged at the opposite end. Such an arrangement has become known in the art as a wall-flow filter. The formation of a wall-flow filter may be influenced by suitable configuration of the porosity of the solid catalyst body. The porosity of the final solid catalyst body may be controlled, for example, by incorporating organic pore-forming components into the organic coagent used in step (a) of the first embodiment.

[0075] The catalyst article can be part of an exhaust gas treatment system, with the catalyst article disposed downstream of a nitrogenous reductant source. EXAMPLES

[0076] The present disclosure will be further described with reference to the following examples, which are intended to be illustrative and not limiting of the invention.

[0077] ·Comparative example A Powdered H+ form SSZ-13 (CHA) zeolite was mixed with copper carbonate (CuCO3.Cu(OH)2), clay minerals, powdered synthetic boehmite alumina (Pural® SB), and glass fibers (CP160, available from MUHLMEIER), and then mixed with carboxymethylcellulose, plasticizer / extrusion aid (Zusoplast, a mixture of oleic acid, glycol, acid, and alcohol, a trade name of Zschimmer & Schwarz GmbH & Co KG), and polyethylene oxide (Alkox® PEO) in an aqueous solution having a pH value of 4 at room temperature to form a moldable paste. The moldable paste had a solids content of 64% by weight. The quantitative proportions of the starting materials were selected so that the final solid catalyst body contained 65 wt. % copper and zeolite (with a Cu / Al ratio of 0.16, based on the total amount of Cu and zeolite), 25 wt. % γ-Al2O3 and clay minerals, and 10 wt. % glass fibers.

[0078] The moldable paste was extruded at 20° C. into flow-through honeycombs with a circular cross-section of 1 inch diameter and a cell density of 500 cpsi (cells per square inch). The extruded honeycombs were freeze-dried at 2 mbar for several hours and then calcined at a temperature of 600° C. in a laboratory-scale muffle furnace to form solid catalyst bodies, according to the methods described in WO 2009 / 080155.

[0079] Example 1 A moldable paste was prepared according to the method used in Comparative Example A, except that crystalline iron (II) sulfate was used instead of copper carbonate. All other ingredients used in the paste preparation were the same. The quantitative proportions of the starting materials were selected to provide a final solid catalyst body containing 65 wt. % iron and zeolite (containing an Fe / Al ratio of 0.16 based on the total amount of Fe and zeolite), 25 wt. % γ-Al2O3 and clay minerals, and 10 wt. % glass fibers. The moldable paste was then extruded into a flow-through honeycomb having the same shape and dimensions as Comparative Example A, and then dried and fired in the same manner to form a solid catalyst body.

[0080] Example 2 A moldable paste was prepared according to the method used in Example 1. The quantitative proportions of the starting materials were selected to provide a final solid catalyst body containing 65 wt.% iron and zeolite (based on the total amount of Fe and zeolite, with an Fe / Al ratio of 0.08), 25 wt.% γ-Al2O3 and clay minerals, and 10 wt.% glass fibers. The moldable paste was then extruded into a flow-through honeycomb having the same shape and dimensions as Comparative Example A, and then dried and fired in the same manner to form a solid catalyst body.

[0081] Example 3 A moldable paste was prepared according to the method used in Example 1. The quantitative proportions of the starting materials were selected to provide a final solid catalyst body containing 65 wt.% iron and zeolite (based on the total amount of Fe and zeolite, with an Fe / Al ratio of 0.24), 25 wt.% γ-Al2O3 and clay minerals, and 10 wt.% glass fibers. The moldable paste was then extruded into a flow-through honeycomb having the same shape and dimensions as Comparative Example A, and then dried and fired in the same manner to form a solid catalyst body.

[0082] ·Comparative example B A moldable paste was prepared according to the method used in Example 1, except that iron citrate (ammonium iron(III) citrate) was used in crystalline form instead of iron sulfate. All other ingredients used in the paste preparation were the same. The quantitative proportions of the starting materials were selected to provide a final solid catalyst body containing 65 wt. % iron and zeolite (containing an Fe / Al ratio of 0.16 based on the total amount of Fe and zeolite), 25 wt. % γ-Al2O3 and clay minerals, and 10 wt. % glass fibers. The moldable paste was then extruded into a flow-through honeycomb having the same shape and dimensions as in Example 1, and then dried and fired in the same manner to form a solid catalyst body.

[0083] ·Comparative example C A commercially available extruded vanadium-based SCR having the same shape and dimensions as in Example 1 was obtained.

[0084] ·Comparative example D H + A moldable paste was prepared according to the method used in Example 1, except that pre-exchanged iron-loaded SSZ-13 (CHA) zeolite (previously prepared via a wet impregnation process) having an Fe / Al ratio of 0.16 was used instead of zeolite in the form of ferric sulfate. The quantitative proportions of the starting materials were selected to provide a final solid catalyst body containing 65 wt. % iron-loaded zeolite, 25 wt. % γ-Al2O3 and clay minerals, and 10 wt. % glass fibers. The moldable paste was then extruded into a flow-through honeycomb having the same shape and dimensions as in Example 1, and then dried and fired in the same manner to form a solid catalyst body.

[0085] Comparative Example E Without adding metal salts, H + A moldable paste was prepared according to the method used in Example 1, except that only SSZ-13 (CHA) zeolite in the form of zeolite was used. The quantitative proportions of the starting materials were 65% by weight of H +The mixture was selected to provide a final solid catalyst body containing type zeolite, 25% by weight of γ-Al2O3 and clay minerals, and 10% by weight of glass fibers. The moldable paste was then extruded into a flow-through type honeycomb having the same shape and dimensions as in Example 1, and then dried and fired in the same manner to form a solid catalyst body.

[0086] Catalyst testing Identical volumes of samples of Comparative Examples A, B, C, D, and Example 1 were run for 120,000 hours in a synthetic catalytic activity test (SCAT) apparatus at 500° C. using the following inlet gas mixture: 300 ppm NO (0% NO2), 300 ppm NH3 (Ammonia to NOx ratio (ANR)=1.0), 9.3% O2, 7% H2O, balance N2. -1 The test was performed at a space velocity (SV) of 1000 s.

[0087] The results are shown in Figures 1 and 2.

[0088] Figure 1 shows the NO2 emission in situ at 500 °C. x Conversion is shown and FIG. 2 shows the N2O selectivity measured for each sample at 500° C.

[0089] As demonstrated by the data shown in Figures 1 and 2, Example 1 exhibited similar NO xConversion and improved N2O selectivity are achieved, as well as improved NOx conversion and improved N2O selectivity compared to Comparative Example B. Indeed, for the catalyst article prepared according to Example 1, no N2O was detected, while both Comparative Examples A and B showed N2O formation. Furthermore, the performance of Example 1 was comparable to that of Comparative Example D, indicating that the iron loading achieved in Example 1 is similar to that of the pre-exchanged iron-loaded zeolite. Advantageously, the preparation of Example 1 required fewer process steps and reduced energy consumption compared to the overall preparation of Comparative Example D. Furthermore, the catalyst article of Example 1 showed significantly improved NOx conversion and improved N2O selectivity compared to the conventional vanadium-based catalyst (Comparative Example C). x and achieve N2O performance.

[0090] Samples of the catalyst articles prepared in Example 1 and Comparative Example E were subjected to CTE measurements over a range of temperatures using a dilatometer (Linseis L75 VS 1750°C). The results are shown in Figure 3. As can be seen from Figure 3, Example 1 has a positive CTE over the entire temperature range tested. Advantageously, the CTE of Example 1 is closer to zero than the CTE of Comparative Example E.

[0091] Identical volume samples of the catalyst articles prepared in Examples 1, 2, and 3 were run for 120,000 hours in a Synthetic Catalytic Activity Test (SCAT) apparatus at 500° C. using the following inlet gas mixture: 300 ppm NO (0% NO2), 300 ppm NH3 (ammonia to NOx ratio (ANR)=1.0), 9.3% O2, 7% H2O, balance N2. -1 The results are shown in Figures 4 and 5.

[0092] Figure 4 shows the NO2 emission in situ at 500 °C. x The conversion is shown and FIG. 5 shows the N2O selectivity measured for each sample at 500° C.

[0093] As demonstrated by the data shown in Figures 4 and 5, all of the catalyst articles prepared in Examples 1, 2, and 3 achieve high NOx conversion and excellent NO selectivity. In fact, no NO was detected for any of the catalyst articles prepared according to Examples 1, 2, or 3. Furthermore, the data shown in Figure 4 shows that the Fe / Al ratio of the iron-loaded zeolite can affect NOx conversion.

[0094] Further aspects and embodiments of the present disclosure are described in the following numbered clauses. Clause 1. A method for forming a catalyst article, comprising: (a) containing at least the following components: (i)H + or NH4 + a crystalline small pore molecular sieve of the form (ii) iron sulfate; (iii) an inorganic matrix component; and (iv) an organic auxiliary; (v) an aqueous solvent, by mixing together to form a plastic mixture, The mixture has a solids content of greater than 50% by weight; and (b) molding the plastic mixture into a shaped article; (c) calcining the shaped article to form a solid catalyst body.

[0095] Clause 2. The method as defined in clause 1, wherein the ingredients mixed together in step (a) further comprise (vi) inorganic fibers.

[0096] Clause 3. A method for forming a catalyst article, comprising: (a) containing: (i)H + or NH4 + a crystalline small pore molecular sieve of the form (ii) iron sulfate; (iii) an inorganic matrix component; and (iv) an organic auxiliary; (v) an aqueous solvent; (vi) optionally inorganic fibers, by mixing together to form a plastic mixture, The mixture has a solids content of greater than 50% by weight; and (b) molding the plastic mixture into a shaped article; (c) calcining the shaped article to form a solid catalyst body.

[0097] Clause 4. A method for forming a catalyst article, comprising: (a) containing: (i)H + or NH4 + a crystalline small pore molecular sieve of the form (ii) iron sulfate; (iii) an inorganic matrix component; and (iv) an organic auxiliary; (v) an aqueous solvent; (vi) optionally inorganic fibers, by mixing together to form a plastic mixture, The plastic mixture has a solids content of greater than 50% by weight; and (b) molding the plastic mixture into a shaped article; (c) calcining the shaped article to form a solid catalyst body; The method, wherein after step (b) and before step (c), the shaped article is optionally dried.

[0098] Clause 5. The method of any one of clauses 1 to 4, 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 wt. % iron-loaded molecular sieve, 20 to 40 wt. % inorganic matrix component, and 0 to 10 wt. % inorganic fibers.

[0099] Clause 6. The method of any one of clauses 1 to 5, 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 wt. % iron-loaded molecular sieve, 20 to 40 wt. % inorganic matrix component, and 0 to 10 wt. % inorganic fibers.

[0100] Clause 7. The plastic mixture formed in step (a) comprises 25 to 70 weight percent (based on the total weight of the plastic mixture) of H + or NH 4+ % by weight of an inorganic matrix component; 0-8% by weight of inorganic fibers; and up to 15% by weight of an organic auxiliary agent.

[0101] Clause 8. The process as defined in any one of clauses 1 to 7, wherein the crystalline small pore molecular sieve is a small pore zeolite.

[0102] Clause 9. The method of clause 8, wherein the zeolite has a framework type selected from AEI, AFT, AFX, CHA, DDR, ERI, KFI, LEV, LTA, SFW, and RHO.

[0103] Clause 10. The process as defined in any one of clauses 1 to 9, wherein the crystalline small pore molecular sieve is a small pore zeolite having a framework type selected from CHA, AEI or AFX, LTA, or ERI, preferably CHA or AEI.

[0104] Clause 11. The process of any one of clauses 1 to 10, wherein the crystalline molecular sieve is a zeolite having a silica-alumina ratio (SAR) of 5 to 200, 5 to 100, 10 to 80, or 5 to 30.

[0105] Clause 12. The process as defined in any one of clauses 1 to 11, wherein the crystalline small pore molecular sieve is in particulate form and has a D90 particle size of less than 30 μm.

[0106] Clause 13. The process as defined in any one of clauses 1 to 12, wherein the crystalline small pore molecular sieve is in particulate form and has a D99 particle size of less than 50 μm.

[0107] Clause 14. Component (i) is H + or NH4 + 14. The process of any one of clauses 1 to 13, comprising two or more small pore crystalline molecular sieves of the form.

[0108] Clause 15. The method of any one of clauses 1 to 14, wherein the iron sulfate is in crystalline form.

[0109] Clause 16. The method according to any one of clauses 1 to 15, wherein the ferrous sulfate is ferrous sulfate (II).

[0110] Clause 17. The method according to any one of clauses 1 to 15, wherein the ferrous sulfate is ferrous sulfate (III).

[0111] Clause 18. The process according to any one of clauses 1 to 17, wherein the aqueous solvent consists essentially of water.

[0112] Clause 19. The method according to any one of clauses 1 to 18, wherein the aqueous solvent is water.

[0113] Clause 20. The process of any one of clauses 1 to 19, wherein the plastic mixture formed in step (a) has a solids content of at least 60% by weight.

[0114] Clause 21. The process as defined in any one of clauses 1 to 20, wherein the plastic mixture formed in step (a) has a solids content in the range of 60 to 80% by weight, more preferably in the range of 70 to 80% by weight.

[0115] Clause 22. The method as defined in any one of clauses 1 to 21, wherein the inorganic matrix component comprises boehmite and / or bayerite, preferably boehmite.

[0116] Clause 23. The method of any one of clauses 1 to 22, wherein the inorganic matrix component comprises a clay.

[0117] Clause 24. The method as defined in clause 23, wherein the clay is selected from bentonite, fireclay, attapulgite, fuller's earth, sepiolite, hectorite, smectite, kaolin, diatomaceous earth, and mixtures of any two or more of these.

[0118] Clause 25. The method of any one of clauses 1 to 24, wherein in step (a), the components mixed together further comprise (vi) inorganic fibers, the inorganic fibers comprising 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.

[0119] Clause 26. The method of any one of clauses 1 to 25, wherein the organic auxiliary comprises at least one of an acrylic fiber, a cellulose derivative, an organic plasticizer, a lubricant, and a water-soluble resin.

[0120] Clause 27. The method according to any one of clauses 1 to 26, wherein in step (a) the components are mixed together by kneading.

[0121] Clause 28. The method according to any one of clauses 1 to 27, wherein step (a) is carried out at ambient temperature.

[0122] Clause 29. The process according to any one of clauses 1 to 28, wherein step (a) is carried out at a temperature in the range of 10 to 35°C, in the range of 10 to 30°C, or in the range of 18 to 28°C.

[0123] Clause 30. The method according to any one of clauses 1 to 29, wherein the plastic mixture formed in step a) is used directly in step b) without any additional processing steps.

[0124] Clause 31. The method according to any one of clauses 1 to 30, wherein step (b) is carried out by extrusion.

[0125] Clause 32. The method according to any one of clauses 1 to 31, wherein step (b) is carried out at ambient temperature.

[0126] Clause 33. The process according to any one of clauses 1 to 32, wherein step (b) is carried out at a temperature in the range of 10 to 35°C, in the range of 10 to 30°C, or in the range of 18 to 28°C.

[0127] Clause 34. The process as defined in any one of clauses 1 to 33, wherein prior to the firing in step (c), the temperature of the plastic mixture does not exceed 35°C, preferably does not exceed 30°C, more preferably does not exceed 28°C.

[0128] Clause 35. A method as defined in any one of clauses 1 to 34, wherein the shaped article is a honeycomb monolith.

[0129] Clause 36. The method defined in any one of clauses 1 to 35, wherein the method further comprises drying the shaped article formed in step (b) prior to step (c).

[0130] Clause 37. The process as defined in any one of clauses 1 to 36, wherein step (c) is carried out at a temperature in the range of 500 to 900°C, preferably in the range of 600 to 800°C.

[0131] Clause 38. The process as defined in any one of clauses 1 to 37, wherein in step (c), the calcination is carried out for a period of up to 5 hours, preferably from 1 to 3 hours.

[0132] Clause 39. The process of any one of clauses 1 to 38, wherein the solid catalyst body formed in step (c) comprises an iron-loaded small pore molecular sieve.

[0133] Clause 40. The process of any one of clauses 1 to 39, wherein the solid catalyst body formed in step (c) comprises an iron-loaded small pore molecular sieve that is catalytically active for SCR.

[0134] Clause 41. A catalytic article obtained or obtainable by a process as defined in any one of clauses 1 to 40.

[0135] Clause 42. A catalyst article comprising a solid catalyst body, the solid catalyst body comprising an iron-loaded small pore molecular sieve and having a coefficient of thermal expansion (CTE) that is zero or positive at temperatures in the range of 100 to 700°C.

[0136] Clause 43. The solid catalyst body has a temperature of 100°C to 700°C and a melting point of 0 to 5×10 -6 Catalyst articles as defined in Clause 42 having a CTE in the range of 0.15 to 0.25 μm / K.

[0137] Clause 44. The solid catalyst body has a melting point of 0.5×10 at a temperature in the range of 100°C to 700°C. -6 / K~4×10 -6 Catalyst articles as defined in Clause 43 having a CTE in the range of 0.15 to 0.25 μm / K.

[0138] Clause 45. A catalyst article as defined in any one of clauses 41 to 44, wherein the solid catalyst body comprises 60 to 85 wt. % of an Fe-loaded small pore molecular sieve, 20 to 40 wt. % of a matrix component, and 0 to 10 wt. % of inorganic fibers.

[0139] Clause 46. A catalytic article as defined in any one of clauses 41 to 45 configured as a flow-through honeycomb monolith or a wall-flow filter.

[0140] Clause 47. A catalytic article as defined in any one of clauses 41 to 46 which is catalytically active for SCR.

[0141] Clause 48. An exhaust system comprising a source of nitrogen-based reductant and an injector for injecting the nitrogen-based reductant into a flowing exhaust gas, the injector being disposed upstream from a catalytic article defined in any one of clauses 41 to 47.

[0142] Clause 49. A method for treating an exhaust gas, comprising contacting the exhaust gas with a catalytic article according to any one of clauses 41 to 47.

[0143] Clause 50. The method defined in clause 49, wherein the exhaust gas has a temperature in the range of 300 to 600°C, more preferably 350 to 550°C, for example 400 to 500°C.

[0144] Clause 51. A method as specified in clause 49 or 50 in which the exhaust gas originates from a stationary source.

Claims

1. 1. A method for forming a catalyst article, comprising: (a) at least the following components: (i) H ＋ or NH ４ ＋ a crystalline small pore molecular sieve in the form of (ii) iron sulfate; (iii) an inorganic matrix component; and (iv) an organic auxiliary; and (v) an aqueous solvent, and forming a plastic mixture by mixing together the mixture has a solids content of greater than 50% by weight; and (b) molding the plastic mixture into a shaped article; (c) calcining the shaped article to form a solid catalyst body; The method wherein step (a) is carried out at a temperature in the range of 10 to 35°C.

2. The method of claim 1 , wherein the ingredients mixed together in step (a) further comprise (vi) inorganic fibers.

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

4. 10. The method of claim 1, wherein the crystalline small pore molecular sieve is a zeolite, and the relative amounts of the molecular sieve and iron sulfate used in step (a) can be selected to provide a solid catalyst body comprising iron-loaded zeolite having an iron to aluminum ratio in the range of 0.03 to 0.6, 0.05 to 0.5, 0.1 to 0.4, or 0.1 to 0.

2.

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

6. The method of claim 1 , wherein the aqueous solvent is water.

7. 2. The method of claim 1, wherein the plastic mixture formed in step (a) has a solids content of at least 60% by weight, preferably in the range of 60 to 80% by weight, more preferably in the range of 70 to 80% by weight.

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

9. 10. The method of claim 1, wherein the iron sulfate is crystalline.

10. 10. The method of claim 1, wherein step (a) is carried out at a temperature in the range of 10 to 30°C, or in the range of 18 to 28°C.

11. 10. The method of claim 1, wherein step (b) is carried out at a temperature in the range of 10 to 35°C, in the range of 10 to 30°C, or in the range of 18 to 28°C.

12. 10. The method of claim 1, wherein the plastic mixture formed in step a) is used directly in step b) without any additional processing steps.

13. 2. The method of claim 1, wherein the temperature of the plastic mixture before the firing of step (c) does not exceed 35°C, preferably does not exceed 30°C, more preferably does not exceed 28°C.

14. A catalytic article obtained or obtainable by the method defined in any one of claims 1 to 13.

15. A catalyst article comprising a solid catalyst body, the solid catalyst body comprising an iron-loaded small pore molecular sieve and having a coefficient of thermal expansion (CTE) that is zero or positive at temperatures in the range of 100 to 700°C.

16. The solid catalyst body has a viscosity of 0 to 5×10 at a temperature in the range of 100° C. to 700° C. －６ 16. The catalytic article of claim 15, having a CTE in the range of 1 / K.

17. The solid catalyst body is a. 60-85 wt. % iron-loaded small pore molecular sieve; b. 20-40 wt. % of a matrix component; and c. 0 to 10 wt % of inorganic fibers.

18. 15. An exhaust system comprising: a nitrogen-based reductant source; and an injector for injecting the nitrogen-based reductant into a flowing exhaust gas, the injector being disposed upstream from the catalytic article of claim 14.

19. An exhaust system comprising a nitrogen-based reducing agent source and an injector for injecting the nitrogen-based reducing agent into flowing exhaust gas, the injector being disposed upstream from the catalytic article described in claim 15.

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