Catalytic converter for reducing NH3 and NOx emissions from internal combustion engines

Abstract

A catalytic device for removing nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine is disclosed, the catalytic device comprising an upstream SCR catalyst comprising a support substrate and a first washcoat comprising a first SCR catalytically active composition SCR first and optionally at least one first binder, the first washcoat being applied to the support substrate; a downstream ASC catalyst comprising a support substrate and an underlayer comprising an oxidation catalyst and optionally a third washcoat comprising at least one third binder, the underlayer being applied directly onto the support substrate; and a second SCR catalytically active composition SCR second and optionally at least one third binder. and a downstream ASC catalyst comprising an upper layer including a second washcoat, optionally including at least one second binder, the upper layer being applied on the lower layer, the upstream SCR catalyst and the downstream ASC catalyst being on a single support substrate or on two different support substrates, the first and second SCR catalytically active compositions being the same or different from each other, the optional at least one first, second and third binders being the same or different from each other, and the ratio of loadings of the first and second SCR catalytically active compositions in the first and second washcoats given in g / L (AA) being 1.2:1 to 2:1. The first and second SCR catalytically active compositions preferably include molecular sieves, and the oxidation catalyst preferably includes a platinum group metal. The catalytic device can be used to remove nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine.

Description

[Technical Field]

[0001] This invention relates to the emission of NH3 and NO from internal combustion engines, particularly lean-running engines such as diesel engines. x This invention relates to catalytic devices for reducing emissions, methods for manufacturing catalytic devices, and their use in exhaust gas aftertreatment systems. [Background technology]

[0002] Modern internal combustion engines must use catalytic aftertreatment systems to reduce harmful emissions and comply with new legal standards.

[0003] Carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO) x In addition, the raw exhaust gases of diesel engines contain a relatively high oxygen content of up to 15% by volume. They consist mainly of soot residue and possibly organic aggregates, and also contain particulate emissions resulting from the partially incomplete combustion of fuel in the engine cylinders.

[0004] While diesel particulate filters are suitable for removing particulate emissions with or without catalytically active coatings, carbon monoxide and hydrocarbons are rendered harmless by oxidation on suitable oxidation catalysts. Oxidation catalysts are widely described in the literature. They are flow-through substrates on which precious metals such as platinum and palladium are supported as essential catalytically active components on large-area porous, high-melting-point oxides such as aluminum oxide.

[0005] Nitrogen oxides are converted to nitrogen and water on an SCR catalyst by ammonia in the presence of oxygen. SCR catalysts are widely described in the literature. They are generally either so-called mixed oxide catalysts containing vanadium, titanium, and tungsten in particular, or so-called zeolite catalysts containing metal-exchanged materials, particularly porous zeolites. The SCR catalyst active material may be supported on a flow-through substrate or on a wall-flow filter.

[0006] Ammonia used as a reducing agent can be utilized by supplying ammonia precursor compounds to the exhaust gas, which are formed by thermal decomposition and hydrolysis to form ammonia. Examples of such precursors include ammonium carbamate, ammonium formate, and preferably urea. Alternatively, ammonia may be formed by catalytic reactions in the exhaust gas.

[0007] To improve the nitrogen oxide conversion rate in SCR catalysts, it is necessary to supply ammonia at an amount approximately 10-20% higher than required, i.e., exceeding the stoichiometric amount. This, in turn, results in unreacted ammonia in the exhaust gas, which is undesirable from the standpoint of its toxic effects. Ammonia emissions are increasingly restricted under exhaust gas regulations.

[0008] To avoid ammonia emissions, so-called ammonia slip catalysts (ASCs) have been developed. These catalysts typically contain an oxidation catalyst for oxidizing ammonia at the lowest possible temperature. Such oxidation catalysts contain at least one noble metal, preferably a platinum group metal (PGM), such as palladium, and especially platinum. However, oxidation catalysts containing noble metals can oxidize not only nitrogen (N2) but also nitrous oxide (N2O) and nitrogen oxides (NOx). x It also oxidizes ammonia in harmful species such as ) and others. The oxidation of NH3 to nitrogen, N2O, NO, or NO2 is shown in equations (1) to (4), respectively. 4NH3 + 3O2 → 2N2 + 6H2O (1) 6NH3 + 6O2 → 3N2O + 9H2O (2) 4NH3 + 5O2 → 4NO + 6H2O (3) 4NH3 + 7O2 → 4NO2 + 6H2O (4)

[0009] The selectivity of ammonia oxidation to nitrogen can be improved by combining an oxidation catalyst with an SCR catalyst. Such a combination can be carried out in various ways. For example, both components may be mixed, and / or they may be present in separate layers on a carrier substrate. When arranged in layers, usually the SCR layer is the upper layer and is coated on the lower oxidation layer. The ASC catalyst is usually coated on a monolithic carrier substrate such as a flow-through substrate or a wall-flow filter.

[0010] High NO x To achieve a high NO conversion rate, a large amount of active SCR material is required in the ASC. On the other hand, covering the PGM component with a large amount of SCR material significantly reduces its ammonia conversion activity. Therefore, it is necessary to solve this trade-off.

[0011] U.S. Patent Application Publication 2015 / 151288(A1) discloses a catalyst composition comprising a zeolite having a CHA skeleton, a silica-to-alumina molar ratio (SAR) of at least 40, and a copper-to-aluminum atomic ratio of at least 1.25. Copper-CHA zeolite can also be used to promote the oxidation of ammonia. Therefore, copper-CHA zeolite can be formulated to favorably act on the oxidation of ammonia by oxygen, particularly at ammonia concentrations typically encountered downstream of an SCR catalyst (e.g., ammonia slip catalyst (ASC) or other ammonia oxidation (AMOX) catalyst). In this embodiment, the catalyst can be arranged as an upper layer on top of an oxidation underlayer, where the underlayer comprises a platinum group metal (PGM) catalyst or a non-PGM catalyst. The catalyst components in the underlayer are preferably supported on a high-surface-area carrier, such as alumina. In other embodiments, the SCR catalyst, which is copper-CHA as described in U.S. Patent Application Publication 2015 / 181288(A1), can be positioned upstream of the wall-flow filter, with the ammonia slip catalyst positioned at the filter outlet. In yet another embodiment, the SCR catalyst is positioned upstream of the flow-through substrate, with the ASC catalyst positioned downstream thereof. Furthermore, the SCR catalyst and the ASC catalyst can be positioned on separate bricks that are adjacent to and in contact with each other, provided that the SCR catalyst brick is positioned upstream of the ammonia slip catalyst brick.

[0012] International Publication No. WO 2016 / 160953 (A1) discloses a catalytic particulate filter comprising at least three coatings forming at least two zones axially along the porous wall of the filter, where the first coating is a first SCR catalyst coating, the second coating is a second SCR catalyst coating, and the third coating is a platinum group metal coating. The platinum group metal coating can be sandwiched between the first SCR catalyst coating and the second SCR catalyst coating. Alternatively, the filter may comprise at least three zones, where the first SCR catalyst is present in a first upstream zone, the second SCR catalyst is present in an intermediate zone, the PGM group is present in a third downstream zone, and the zones are arranged adjacent to each other. Further, in another embodiment, the first SCR catalyst is present in the upstream zone and the second SCR catalyst and the platinum group metal catalyst are mixed in the downstream zone. The first and second SCR catalysts are independently selected from zeolites, preferably AEI, AFX and CHA. The zeolite is promoted with a transition metal, preferably copper or iron. Appropriate washcoat loadings for the first and second SCR catalysts and the platinum group metal catalyst are given. However, International Publication No. WO 2016 / 160953 (A1) does not mention the ratio of the washcoat loadings.

[0013] International Publication No. WO 2017 / 037006 (A1) discloses an integrated SCR and ammonia oxidation catalyst. The catalyst comprises a first washcoat zone containing copper or iron on a small pore molecular sieve and substantially free of platinum group metals, and a second washcoat zone containing copper or iron on a small pore molecular sieve mixed with platinum on a refractory metal oxide support comprising a mixture and combination of alumina, silica, zirconia, titania and refractory metal oxides. The first washcoat zone is located upstream of the second washcoat zone. In the second zone, platinum or a mixture of platinum and rhodium is present at 3 - 20 g / ft 3It is present in an amount corresponding to 0.106 to 0.706 g / L. The zeolite is promoted with Cu or Fe, preferably with 0.1 to 10% by weight, preferably 0.1 to 5% by weight, of Cu, calculated as CuO. However, International Publication 2017 / 037006(A1) does not mention the appropriate washcoat concentration of zeolite in the two zones, nor does it mention the concentration ratio of zeolite in the first and second zones, respectively.

[0014] International Publication No. 2010 / 062730(A2) states NO x A catalytic system is disclosed comprising an upstream zone effective for catalyzing the conversion of a mixture of NH3 to N2, and a downstream zone effective for the conversion of ammonia to N2. The upstream and downstream zones may be located on a single monolith, or they may be located on two adjacent monoliths. The SCR catalyst is NO x The catalyst for converting a mixture of NH3 to N2 is a silicoaluminate or silicoaluminophosphate zeolite. Preferably, the zeolite is selected from the FAU, MFI, MOR, BEA, and CHA skeleton types. The zeolite is facilitated by a transition metal, preferably copper or iron. An ammonia oxidation catalyst, abbreviated as AMOX, which is effective in converting ammonia to N2, contains a noble metal component selected from ruthenium, rhodium, iridium, palladium, platinum, silver, gold, and mixtures thereof. Optionally, the NH3 oxidation composition may contain components active in ammonia SCR function.

[0015] The AMOX catalyst exists as an undercoat layer, and the SCR catalyst exists as an overcoat layer. When both the SCR and AMOX catalysts are present on a single monolithic substrate, both catalysts cover at least 5–100% of the total length of the monolith, and the overcoat covers at least a portion of the undercoat.

[0016] A wash coat containing the NH3 oxidation composition is first applied to the monolith, thus forming an undercoat layer. Subsequently, the SCR catalyst composition is applied so as to cover at least a portion of the aforementioned undercoat. Therefore, the thickness of the SCR catalyst layer in the upstream zone and the amount of wash coat supported are the same, as are the thickness of the SCR catalyst covering the NH3 oxidation composition and the amount of wash coat supported.

[0017] Optionally, the monolith may be coated with multiple layers of the SCR catalyst composition along its entire length. In embodiments where the SCR function and the NH3 oxidation function are present on the same monolith, the ratio of the length of the forward zone containing the SCR function to the total substrate length is at least 0.4, preferably 0.5 to 0.9, and most preferably 0.6 to 0.8.

[0018] As described above, in another embodiment of International Publication No. 2016 / 062730(A2), the catalyst system is a “bifunctional catalyst” having physically separate compositions for the SCR function and the NH3 oxidation function. Such a modular catalyst system provides greater flexibility and allows for independent adjustment of the reaction rates of the two functions. However, how this adjustment of the reaction rates of the two functions should be carried out is not disclosed.

[0019] International Publication No. 2018 / 183457(A1) discloses a catalyst article for treating exhaust gas streams containing particulate matter, hydrocarbons, carbon monoxide and ammonia, the article comprising (a) a substrate having inlet and outlet ends defining an axial length; (b) a first catalyst coating comprising 1) a platinum group metal distributed on a molecular sieve and 2) a base metal distributed on a molecular sieve; and (c) a second catalyst coating comprising 1) a platinum group metal distributed on a molecular sieve and 2) a base metal distributed on a molecular sieve. The platinum group metal is preferably platinum, palladium, or a combination thereof. The molecular sieve may be a small-pore, medium-pore or large-pore zeolite. Preferably, the molecular sieve is a small-pore zeolite, most preferably selected from CHA, LEV, AEI, AFX, ERI, LTA, SFW, KFI, DDR and ITE. The base metal is preferably copper, iron, or a mixture thereof. Thus, both the first and second catalyst coatings contain an ammonia slip catalyst (ASC or AMOX) and a selective catalytic reduction (SCR) catalyst. The higher the PGM load in one of the layers, the higher the ASC activity in that layer. Conversely, the lower the PGM load in one of the layers, the higher and more selective the ASC reactivity. The higher the selectivity in the ASC layer, the more favorable the formation of N2 is over the formation of N2O, NO, and NO2 (see equations (1) to (4) above). International Publication 2018 / 183457(A1) states that the two catalyst layers can be placed on top of each other, where “on top” means that the upper layer completely covers the lower layer or covers only a portion of the lower layer. In all cases, the lower layer must have higher ASC activity than each of the other layers, and the upper layer must have higher ASC selectivity than each of the other layers. This can be achieved by adjusting the amount of PGM supported, and in various embodiments of International Publication 2018 / 183457(A1), the amount of PGM supported in the upper layer is less than or equal to the amount of PGM supported in the lower layer. Preferred numerical ranges for the PGM supported in the upper and lower layers are shown, respectively. However, International Publication 2018 / 183457(A1) does not mention the amount of SCR catalyst supported. The ASC catalyst can be combined with the upstream SCR function.On the same monolith, the SCR function may be placed upstream and the ASC function downstream, or the SCR function may be placed on a separate monolith.

[0020] International Publication 2018 / 057844(A1) discloses an ammonia slip catalyst (ASC) comprising a first SCR catalyst and an oxidation catalyst comprising ruthenium or a ruthenium mixture such as a platinum-ruthenium mixture, on a support comprising a rutile phase and a substrate. The SCR catalyst may be a small-pore, medium-pore, or large-pore molecular sieve, preferably promoted with copper or iron, or the SCR catalyst may be a base metal or an oxide of a base metal, such as vanadium or vanadium oxide. Ruthenium on a rutile-based support provides superior N2O selectivity compared to platinum-based ammonia slip catalysts. Furthermore, ruthenium on a rutile catalyst provides higher stability and better activity than ruthenium supported on a non-rutile structured support. Lower N2O selectivity in NH3 slip applications can be obtained while maintaining high activity along with improved stability compared to other ruthenium-based catalysts. The ammonia slip catalyst may also include a mixture of the SCR catalyst and the oxidation catalyst. The ammonia slip catalyst may also be placed on a substrate, with at least a portion of the second SCR catalyst placed on at least a portion of the ASC. In another embodiment, the ammonia slip catalyst may be a two-layer structure having an upper layer of the first SCR catalyst and a lower layer containing an oxidation catalyst. In yet another embodiment, as shown in Figure 21 with reference to Figure 16, the ASC catalyst is a two-layer structure having an upper layer containing the first SCR catalyst and a lower layer containing an oxidation catalyst, with the second SCR catalyst placed adjacent to and completely covering the ASC layer. However, International Publication No. 2018 / 057844(A1) does not mention an appropriate loading amount of the SCR catalyst. [Overview of the project] [Problems that the invention aims to solve]

[0021] Not only good activity for converting ammonia, but also converting as much ammonia as possible to nitrogen according to the above formula (1), and not converting to N2O, NO, or NO according to formulas (2), (3), and (4). x There is always a need for an improved ASC catalyst that also exhibits good selectivity, meaning it does not convert to

[0022] Problems to be Solved by the Invention An object of the present invention is to provide a catalyst device for removing nitrogen oxides and ammonia from the exhaust gas of a lean burn engine, which exhibits a high conversion rate of nitrogen oxides to nitrogen, good activity, and good selectivity for the conversion of ammonia to nitrogen. Another object of the present invention is to provide a system for treating the exhaust gas of a lean burn engine including the catalyst device of the present invention. Means for Solving the Problems

[0023] Technical Solution The object of providing a catalyst device for removing nitrogen oxides and ammonia from the exhaust gas of a lean burn engine, which exhibits a high conversion rate of nitrogen oxides to nitrogen, good activity, and good selectivity for the conversion of ammonia to nitrogen, is solved by a catalyst device including the following for removing nitrogen oxides and ammonia from the exhaust gas of a lean burn engine. The catalyst device comprises (a) an upstream SCR catalyst, comprising (i) a carrier substrate, and (ii) a first washcoat comprising a first SCR catalyst active composition SCR 第1 and optionally at least one first binder, the first washcoat being applied to the carrier substrate, the upstream SCR catalyst; (b) a downstream ASC catalyst, comprising (i) a carrier substrate, and (ii) a lower layer comprising an oxidation catalyst and optionally at least one third binder, the lower layer being directly applied onto the carrier substrate, and (iii) a second SCR catalyst active composition SCR 第2The downstream ASC catalyst comprises an upper layer coated on a lower layer and optionally a second wash coat containing at least one second binder, - The upstream SCR catalyst and downstream ASC catalyst are located on a single support substrate or on two different support substrates. -The first and second SCR catalyst active compositions are either the same or different from each other. - At least one of the first, second, and third binders, which may be included, may be the same as or different from each other. - Ratio of the loading amounts of the first and second SCR catalytic active compositions given in g / L in the first and second wash coats

[0024]

number

[0025] The ratio is 1.2:1 to 2:1.

[0026] Remarkably, the combination of a) a high conversion rate of nitrogen oxides to nitrogen, b) good activity for converting ammonia to nitrogen, and c) good selectivity is due to the ratio of the loading amounts of the first and second SCR catalytic active compositions.

[0027]

number

[0028] They found that it was dependent on [something].

[0029] A catalytic converter for removing nitrogen oxides from the exhaust gas of a lean-burn combustion engine, a system for treating the exhaust gas of a lean-burn combustion engine including the catalytic converter, and a method for manufacturing the same are described below, and the present invention encompasses all embodiments shown below, individually and in combination with each other.

[0030] "Upstream" and "downstream" are terms used in relation to the normal flow direction of exhaust gases in the exhaust pipeline. "Zone or catalyst 1 located upstream of zone or catalyst 2" means that zone or catalyst 1 is located closer to the exhaust gas source, i.e., closer to the motor, than zone or catalyst 2. The direction of flow is from the exhaust gas source toward the exhaust pipe. Therefore, in this flow direction, the exhaust gases enter each zone or catalyst at its inlet end and exit each zone or catalyst at its outlet end.

[0031] A "catalyst support substrate," also simply called a "carrier substrate," is a support on which a catalytically active composition is attached to form the final catalyst. Thus, the carrier substrate is a carrier for the catalytically active composition.

[0032] A "catalytically active composition" is a substance or mixture of substances that can convert one or more components of exhaust gas into one or more other components. An example of such a catalytically active composition is, for example, an oxidation catalyst composition that can convert volatile organic compounds and carbon monoxide into carbon dioxide, or ammonia into nitrogen oxides. Another example of such a catalyst is, for example, a selective reduction catalyst (SCR catalyst) composition that can convert nitrogen oxides into nitrogen and water. In the context of the present invention, an SCR catalyst is a catalyst comprising a carrier substrate and a wash coat containing the SCR catalytically active composition. An ammonia slip catalyst (ASC) is a catalyst comprising a carrier substrate, a wash coat containing an oxidation catalyst, and a wash coat containing the SCR catalytically active composition.

[0033] As used in the present invention, "wash coat" refers to an aqueous suspension of a catalytically active composition and optionally at least one binder. Suitable binder materials include, for example, aluminum oxide, titanium dioxide, silicon dioxide, zirconium dioxide, or mixtures thereof, such as a mixture of silica and alumina. In the context of the present invention, each of the first, second, and third wash coats may independently contain or not contain a binder. If at least two or all three of the first, second, and third wash coats contain at least one binder, these wash coats may contain the same binder or different binders.

[0034] In a preferred embodiment, the first, second, and third wash coats all include at least one type of binder.

[0035] A wash coat attached to a catalyst support substrate is called a "coating." It is also possible to attach two or more wash coats to a support substrate. Those skilled in the art know that it is possible to attach two or more wash coats to a single support substrate by "layering" or "zoning," and that layering and zoning can also be combined. In the case of layering, the wash coats are attached to the support substrate one after the other in a continuous manner. The wash coat attached first, and therefore in direct contact with the support substrate, is the "lower layer," and the wash coat attached last is the "upper layer." In the case of zoning, the first wash coat is attached to the support substrate from the first side A toward the other side B, but not along the entire length of the support substrate, but only to the endpoint between sides A and B. Then, the second wash coat is attached to the support, starting from side B and extending to the endpoint between sides B and A. The endpoints of the first and second wash coats do not need to be the same; if they are the same, both wash coat zones are adjacent to each other. However, if the endpoints of the two wash coat zones located between sides A and B of the carrier substrate are not the same, there may be a gap between the first wash coat zone and the second wash coat zone, or they may overlap. As described above, layering and zoning can also be combined, for example, if one wash coat is applied over the entire length of the carrier substrate and the other wash coat is applied only from one side to the endpoint between both sides.

[0036] In the context of the present invention, "wash coat load" refers to the mass of the catalytically active composition per unit volume of the carrier substrate.

[0037] Those skilled in the art know that washcoats are prepared in the form of suspensions and dispersions.

[0038] A suspension or dispersion is a heterogeneous mixture containing solid particles and a solvent. The solid particles do not dissolve but remain suspended throughout the volume of the solvent and free-floating in the medium. If the solid particles have an average particle size of 1 μm or less, the mixture is called a dispersion; if the average particle size is greater than 1 μm, the mixture is called a suspension. A washcoat in the sense of the present invention comprises a solvent, usually water, solvent particles represented by particles of one or more catalytically active compositions, and optionally particles of at least one of the binders described above. This mixture is often called a “washcoat slurry.” The slurry is applied to a carrier substrate and subsequently dried to form the coating described above. In the context of the present invention, the term “washcoat suspension” is used for a mixture of a solvent and particles of one or more catalytically active compositions, regardless of their individual or average particle size, and optionally particles of at least one binder. This means that in the “washcoat suspension” of the present invention, the individual and average particle sizes of the one or more catalytically active solid particles may be less than 1 μm, equal to 1 μm, and / or greater than 1 μm.

[0039] As used in the context of this invention, the term "mixture" refers to a material composed of two or more different substances that are physically combined, in which each component retains its own chemical properties and structure. Despite the fact that there is no chemical change in its components, the physical properties of the mixture, such as its melting point, may differ from those of the individual components.

[0040] The catalyst, also called a "catalyst article" or "brick," consists of a catalyst support substrate and a wash coat, the wash coat comprising a catalytic active composition and optionally at least one binder.

[0041] As used in the context of this invention, “apparatus” refers to a part of equipment designed to serve a particular purpose or perform a particular function. The catalytic apparatus of this invention serves the purpose and function of removing both nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine. As used in this invention, the “apparatus” may consist of one or more catalysts, also called “catalytic articles” or “bricks” as defined above.

[0042] The upstream SCR catalyst and downstream ASC catalyst of the present invention are particularly characterized by the first and second SCR catalyst active compositions among other components. 第1 and SCR 第2 Each of these includes:

[0043] First and second SCR catalytic active compositions 第1 and SCR 第2 Each of these can be selected from molecular sieves independently of the others.

[0044] Molecular sieves are materials having pores of uniform size, i.e., very small holes. The diameter of these pores is similar in size to that of small molecules, and therefore, larger molecules cannot penetrate or adsorb, while smaller molecules can. In the context of this invention, molecular sieves may be zeolites or non-zeolites. Zeolites consist of vertex-shared tetrahedral SiO4 and AlO4 units. They are also called "silicoaluminates" or "aluminosilicates." In the context of this invention, these two terms are used synonymously.

[0045] As used herein, the term “non-zeolite molecular sieve” refers to a vertex-shared tetrahedron skeleton in which at least a portion of the tetrahedron's parts are occupied by elements other than silicon or aluminum. If some, but not all, of the silicon atoms are replaced by phosphorus atoms, it is referred to as a “silicoaluminophosphate” or “SAPOs.” If all of the silicon atoms are replaced by phosphorus, it is referred to as an aluminophosphate or “AlPOs.”

[0046] The "zeolite skeleton type," also called the "skeleton type," represents a vertex-sharing network of atoms coordinated in a tetrahedron. It is common to classify zeolites by their pore size, which is defined by the ring size of the largest pore diameter. Zeolites with large pore diameters have a maximum ring size of 12 tetrahedral atoms, zeolites with medium pore diameters have a maximum pore diameter of 10, and zeolites with small pore diameters have a maximum pore diameter of 8 tetrahedral atoms. Known small-pore zeolites belong particularly to the AEI, CHA (chabazite), ERI (erionite), LEV (levinite), AFX, and KFI skeletons. Examples of large pore diameters include faujasite (FAU) skeleton type zeolites and zeolite beta (BEA).

[0047] A “zeotype” includes any family of materials based on the structure of a particular zeolite. Therefore, a particular “zeotype” includes, for example, silicoaluminates, SAPOs, and AIPOs based on the structure of a particular zeolite skeleton type. Thus, for example, chabazite (CHA), silicoaluminates SSZ-13, Linde R, and ZK-14, silicoaluminophosphate SAPO-34, and aluminophosphate MeAlPO-47 all belong to the chabazite skeleton type. A person skilled in the art will know which silicoaluminates, silicoaluminophosphates, and aluminophosphates belong to the same zeotype. Furthermore, zeolites and non-zeolite molecular sieves belonging to the same zeotype are listed in the International Zeolite Association (IZA) database. A person skilled in the art can use this knowledge and the IZA database without departing from the scope of the claims.

[0048] In a preferred embodiment of the present invention, the molecular sieve is a microporous crystalline aluminosilicate zeolite.

[0049] Suitable crystalline aluminosilicate zeolites are, for example, zeolite skeleton types selected from mixtures and intercrystals containing at least one of the following skeleton types: ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, BEA, BIK, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, ESV, ETL, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON, and other skeleton types. In preferred embodiments of the present invention, first and second SCR catalytic active compositions SCR 第1 and SCR 第2 These molecular sieves are selected independently of each other.

[0050] In a more preferred embodiment of the present invention, the crystalline small-pore aluminosilicate zeolite has a maximum pore diameter of eight tetrahedral atoms and is selected from AEI, AFT, AFX, CHA, DDR, ERI, ESV, ETL, KFI, LEV, UFI and mixtures thereof and intercrystals. In an even more preferred embodiment, the zeolite is selected from AEI, BEA, CHA, AFX and mixtures thereof and intercrystals containing at least one of these skeleton types. In a particularly preferred embodiment, the zeolite is AEI. In another particularly preferred embodiment, the zeolite is CHA.

[0051] The "inter-crystal" structure of zeolite comprises at least two different zeolite skeleton types, or two different zeolite compositions of the same skeleton type.

[0052] In "surface-truncate" zeolites, one skeletal structure grows on top of the other. Therefore, "surface-truncate" refers to a species of "truncate," while "truncate" refers to a genus.

[0053] In the present invention, the zeolite and non-zeolite molecular sieves used as SCR catalysts or as components of SCR catalyst compositions contain transition metals. Preferably, the transition metal is selected from copper, iron, and mixtures thereof.

[0054] The crystalline aluminosilicate zeolite used as the SCR catalytic active composition in the present invention has a silica-to-alumina ratio of 5 to 100, preferably 10 to 50. The silica-to-alumina ratio, SiO2:Al2O3, will hereafter be referred to as the "SAR value" or "SAR".

[0055] Preferably, the crystalline aluminosilicate zeolite used as the SCR catalytic active composition in the present invention is activated with a transition metal selected from copper, iron, or a mixture of copper and iron.

[0056] In one embodiment, the zeolite is promoted with copper. Preferably, the copper-to-aluminum atomic ratio is in the range of 0.005 to 0.555, more preferably 0.115 to 0.445, and even more preferably 0.175 to 0.415. Those skilled in the art know how to adjust the amount of copper introduced during synthesis or by ion exchange to obtain the desired copper-to-aluminum ratio. Those skilled in the art can utilize this knowledge without departing from the claims.

[0057] In another embodiment, the zeolite is promoted with iron. Preferably, the iron-to-aluminum atomic ratio is in the range of 0.005 to 0.555, more preferably 0.115 to 0.445, and even more preferably 0.175 to 0.415. Those skilled in the art know how to adjust the amount of iron introduced during synthesis or by ion exchange to obtain the desired iron-to-aluminum ratio. Those skilled in the art can utilize this knowledge without departing from the claims.

[0058] In yet another embodiment, the zeolite is promoted by both copper and iron. Preferably, the atomic ratio of (Cu+Fe):Al is in the range of 0.005 to 0.555, more preferably 0.115 to 0.445, and even more preferably 0.175 to 0.415.

[0059] The upstream SCR catalyst of the present invention comprises a first SCR catalytic active composition. The first SCR catalytic active composition contains one or more molecular sieves. In embodiments in which the first SCR catalytic active composition comprises two or more molecular sieves, the molecular sieves differ from each other in at least one of the following characteristics: -They have different skeletal structures, and / or - They belong to the same skeletal structure but are different zeotypes, and / or - They belong to the same skeleton type, but the first and second compositions are selected from silicoaluminate and silicoaluminophosphate, or silicoaluminate and aluminophosphate, or silicoaluminophosphate and aluminophosphate, and / or - They are promoted by different transition metals, and / or -The amounts of those transition metal elements are different, and / or -Their SAR values ​​differ.

[0060] For example, because their skeletal structures are different, AEI and CHA can be used as the first and second SCR catalytic active compositions, where both zeolites are silicoaluminates, have the same SAR value, and are promoted with the same amount of copper. Furthermore, two CHA silicoaluminate zeolites or two AEI silicoaluminate zeolites are also considered "different" if they have different SAR values ​​or are promoted with different amounts of copper. Also, two silicoaluminates having the CHA skeleton type, for example, one being SSZ-13 and the other being ZK-14, are considered "different" because they belong to different zeotypes, even if they have the same SAR value and copper content.

[0061] The downstream ASC catalyst of the present invention comprises a second SCR catalytic active composition. The second SCR catalytic active composition contains one or more molecular sieves. In embodiments in which the second SCR catalytic active composition comprises two or more molecular sieves, the molecular sieves differ from each other in at least one of the characteristics given above for the first SCR catalytic active composition.

[0062] In one embodiment of the present invention, the first and second SCR catalytic active compositions are identical in terms of their physicochemical properties. Each of the first and second SCR catalytic active compositions may independently contain one or more of the molecular sieves described above. This means that the SCR catalytic active compositions of the SCR catalyst and the ASC catalyst differ only in their wash coat loading amounts, and the ratio of the loading amounts of the first and second SCR catalytic active compositions given in g / L in the first and second wash coats is...

[0063]

number

[0064] As mentioned above, the ratio is 1.2:1 to 2:1.

[0065] In another embodiment of the present invention, the first and second SCR catalytic active compositions differ in their physicochemical properties. Each of the first and second SCR catalytic active compositions may independently contain one or more of the molecular sieves described above. In this embodiment, the SCR catalytic active compositions of the SCR catalyst and the ASC catalyst differ in at least one of the following characteristics: - At least one type of skeletal structure is present in only one of the SCR catalytic active compositions, and / or - The molecular sieves in both SCR catalytic active compositions belong to the same skeletal structure but are of different zeotypes, and / or - The molecular sieves in both SCR catalytic active compositions belong to the same skeleton type, but the first and second compositions are selected from silicoaluminate and silicoaluminophosphate, or silicoaluminate and aluminophosphate, or silicoaluminophosphate and aluminophosphate, and / or - Molecular sieves in both SCR catalytic active compositions are promoted by different transition metals, and / or -Their transition metal content is different, and / or -Their SAR values ​​differ.

[0066] In this embodiment, the ratio of the loading amounts of the first and second SCR catalytic active compositions given in g / L in the first and second wash coats

[0067]

number

[0068] Furthermore, as mentioned above, the ratio is 1.2:1 to 2:1.

[0069] The oxidation catalyst contained in the third wash coat is a platinum group metal, a platinum group metal oxide, a mixture of two or more platinum group metals, a mixture of two or more platinum group metal oxides, or a mixture of at least one platinum group metal and at least one platinum group metal oxide. The platinum group metals, hereafter abbreviated as PGM, are ruthenium, rhodium, palladium, osmium, iridium, and platinum. In the present invention, PGM is selected from ruthenium, rhodium, palladium, iridium, and platinum. Those skilled in the art will know each of these platinum group metal oxides and can use them in the context of the present invention without departing from the claims. Preferably, the oxidation catalyst is a platinum group metal or a mixture of two or more platinum group metals. More preferably, the oxidation catalyst is selected from platinum, and a mixture of platinum and palladium or platinum and rhodium.

[0070] The amount of wash coat loaded in the third wash coat is 10 to 100 g / L, preferably 20 to 75 g / L. The concentration of PGM in the wash coat is 0.5 to 25 g / ft 3 Preferably 1.5 to 10 g / ft 3 That is the case.

[0071] In preferred embodiments of the present invention, the first, second, and third wash coats all include a binder. The binder can be selected from alumina, silica, non-zeolite silica-alumina, natural clay, TiO2, ZrO2, CeO2, SnO2, and mixtures and combinations thereof. Preferably, the binder is selected from alumina, TiO2, ZrO2, and mixtures and combinations thereof. The binders of the first, second, and third wash coats may be the same or different from each other.

[0072] Surprisingly, the ratio of the loading amounts of the first and second SCR catalyst active compositions given in g / L in the first and second wash coats

[0073]

number

[0074] However, it was found that the ratio must be 1.2:1 to 2:1, preferably 1.3:1 or higher, and more preferably 1.4:1 or higher. The amount of the first and second SCR catalyst active compositions supported

[0075]

number

[0076] The upper limit is preferably 1.6:1 or less. In summary, the ratio of the loading amounts of the first and second SCR catalyst active compositions given in g / L in the first and second wash coats.

[0077]

number

[0078] The ratio is preferably 1.3:1 to 1.6:1, and more preferably 1.4:1 to 1.6:1.

[0079] Preferably, the ratio of the loading amounts of the first and second SCR catalyst active compositions given in g / L in the first and second wash coats.

[0080]

number

[0081] However, under the condition that the preferred lower and upper limits of the range described above are between 1.2:1 and 2:1, the wash coat load of the first SCR catalytic active composition is 100 to 230 g / L, preferably 140 to 200 g / L, and the wash coat load of the second SCR catalytic active composition is 70 to 170 g / L, preferably 90 to 140 g / L.

[0082] The upstream SCR catalyst and the downstream ASC catalyst are present on a single support substrate or on two different support substrates.

[0083] In one embodiment, a single carrier substrate or two different carrier substrates are selected from so-called flow-through substrates or wall-flow filters, respectively.

[0084] Both the flow-through substrate and the wall-flow filter may consist of inert materials such as silicon carbide, aluminum titanate, cordierite, or metal. Such carrier substrates are well known to those skilled in the art and are available on the market.

[0085] Those skilled in the art know that, in the case of wall-flow filters, their average pore size and the average particle size of the first SCR catalytic active composition and / or the oxidation catalyst can be adjusted relative to each other so that the resulting coating is positioned on the porous walls forming the channels of the wall-flow filter (on-wall coating). However, the average pore size and the average particle size of the first SCR catalytic active composition and / or the oxidation catalyst are preferably adjusted relative to each other so that the first SCR catalytic active composition and / or oxidation catalyst are located within the porous walls forming the channels of the wall-flow filter. In this preferred embodiment, the inner surfaces of the pores are coated (in-wall coating). In this case, the average particle size of the first SCR catalytic active composition and / or oxidation catalyst must be small enough to penetrate into the pores of the wall-flow filter. A second washcoat containing a second SCR catalytic active component is coated as an upper layer after coating the oxide layer and is coated on top of the lower layer containing the oxidation catalyst. If the particle size of the catalytic active composition in the second washcoat is small enough, the second washcoat is coated within the walls. If the particle size of the catalytic active composition of the second washcoat is larger than the pores of the porous wall of the wall flow filter, the second washcoat is coated on the wall. If the second washcoat, which contains the oxide layer and the second SCR catalytic active component, is coated on the wall flow filter as an on-wall layer, they are coated on the surface of the outlet channel.

[0086] In another embodiment, the carrier substrate is a corrugated catalytic substrate monolith. The substrate has a wall density of at least 50 g / l but no more than 300 g / l, and a porosity of at least 50%. The substrate monolith is a high silica-content glass paper or E-glass fiber paper. The paper has a diatomaceous earth layer or a titania layer, and the catalyst is the zeolite of the present invention. This corrugated substrate monolith has the advantage that the catalytic zeolite layer does not peel off from the monolith substrate during the starting and stopping of the combustion engine. The SCR catalytic active material is coated onto a monolith substrate having a flat or corrugated shape. The substrate is made from an E-glass fiber sheet or a glass sheet having a high silicon content and a TiO2 or diatomaceous earth layer. High silicon-content glass contains 94-95 wt% SiO2, 4-5 wt% Al2O3, and some Na2O, and these fibers have a fiber diameter of 8-10 μm and a density of 2000-2200 g / l. One example is commercially available SILEX staple fiber. E glass contains 52-56 wt% SiO2, 12-16 wt% Al2O3, 5-10 wt% B2O3, 0-1.5 wt% TiO2, 0-5 wt% MgO, 16-25 wt% CaO, 0-2 wt% K2O / Na2O, and 0-0.8 wt% Fe2O3. The substrate material is selected such that the substrate density is at least 50 g / l but no more than 300 g / l, and the porosity of the substrate wall is at least 50 volume% of the material. The porosity of the monolithic substrate is obtained by pores having a depth of 50 μm to 200 μm and a diameter of 1 μm to 30 μm. The SCR catalytic active material is coated onto the substrate as a layer with a thickness of 10 to 150 μm. The SCR catalytic active material is the zeolite of the present invention. The catalyst is coated by immersing the monolithic substrate in an aqueous slurry of zeolite, binder, and fine particles of defoaming agent. The particle size is 50 μm or less. The binder is preferably a silica sol binder, and the defoaming agent is a silicone defoaming agent. The coated substrate is dried and then calcined at 400 to 650°C, preferably 540 to 560°C, most preferably 550°C. The catalyst element includes a layer of corrugated sheets separated from each other by flat plates. The catalyst element can be in the shape of a box or a cylinder.Corrugated substrate monoliths and their manufacture are disclosed in International Publication No. 2010 / 066345(A1), and the teachings therein can be applied to the present invention without departing from the scope of the claims.

[0087] In one embodiment of the present invention, the upstream SCR catalyst and the downstream ASC catalyst exist as two adjacent zones on a single support substrate. (a) The upstream SCR catalyst extends along the axial length of the support substrate from the upstream end to 40-80% of the total length of the support substrate, (b) The downstream ASC catalyst extends along the axial length of the support substrate from the downstream end to 40-80% of the total length of the support substrate.

[0088] In this embodiment of the zoned catalyst, the upstream SCR catalyst zone and the downstream ASC catalyst zone may be directly adjacent to each other without overlapping, or they may overlap, or there may be a gap between them. If there is a gap between the two zones, the length of the gap accounts for up to 20% of the total axial length of the support. In the case of adjacent zones, there is substantially no overlap or gap between the SCR catalyst zone and the ASC catalyst zone, and the length of both zones accounts for 100% of the total axial length of the support. In the case of overlap, the ASC catalyst zone overlaps the SCR catalyst zone. This means that the layer beneath the ASC catalyst zone is the binder and the first SCR catalytic active composition SCR 第1 The SCR catalyst zone, which includes the ASC catalyst, is superimposed on the SCR catalyst zone, and the lower layer of the ASC catalyst contains the second binder and the second SCR catalyst active composition SCR 第2 This means it is covered with an upper layer that includes a second wash coat.

[0089] In this embodiment, where the upstream SCR catalyst and the downstream ASC catalyst exist as two adjacent zones on a single support substrate, the support substrate is selected from the ceramic, metal, and corrugated support substrates described above. Preferably, the support substrate is a ceramic substrate selected from flow-through substrates and wall-flow filters.

[0090] In another embodiment of the present invention, the upstream SCR catalyst and the downstream ASC catalyst are located on two different carrier substrates that are directly adjacent to each other.

[0091] In this embodiment, where the upstream SCR catalyst and the downstream ASC catalyst are located on two different support substrates, the support substrates are selected from the ceramic, metal, and corrugated support substrates described above. Preferably, the support substrate is a ceramic substrate selected from flow-through substrates and wall-flow filters.

[0092] The objective of providing a system for treating exhaust gases of a lean-burn combustion engine, including a catalytic converter of the present invention, is to be achieved by a system comprising the following for removing nitrogen oxides and ammonia from the exhaust gases of a lean-burn combustion engine, and the system is: (a) Means for injecting ammonia or an ammonia precursor solution into the exhaust stream, (b) The catalyst apparatus of the present invention is located immediately downstream of the means for injecting the ammonia or ammonia precursor solution of (a).

[0093] Those skilled in the art know that the SCR reaction requires the presence of ammonia as a reducing agent. Ammonia can be supplied in a suitable form, such as liquid ammonia or an aqueous solution of an ammonia precursor, and can be added to the exhaust gas stream as needed via means for injecting ammonia or an ammonia precursor. Suitable ammonia precursors are, for example, urea, ammonium carbamate, and ammonium formate. A widely used method is to deliver an aqueous urea solution and, as needed, introduce it into the catalyst of the present invention via an upstream injector and injection unit. Means for injecting ammonia, such as an upstream injector and injection unit, are well known to those skilled in the art and can be used in the present invention without departing from the scope of the claims.

[0094] Accordingly, the present invention also refers to a system for purifying exhaust gases emitted from a lean combustion engine, the system comprising the catalyst according to the present invention, preferably in the form of a coating on a carrier substrate or as a component of the carrier substrate, and comprising an injector for an aqueous urea solution, the injector being positioned upstream of the catalyst of the present invention.

[0095] A system for treating exhaust gases of a lean-burn combustion engine, including the catalytic device of the present invention, may further include an oxidation catalyst for the oxidation of volatile organic compounds, carbon monoxide, and hydrocarbons, the catalyst located immediately upstream of the means for injecting ammonia or an ammonia precursor solution into the exhaust system of a) above.

[0096] In another embodiment, a system for treating exhaust gases of a lean-burn combustion engine, including the catalytic device of the present invention, may further include a filter for removing particulate matter, in addition to an oxidation catalyst for oxidizing volatile organic compounds, carbon monoxide, and hydrocarbons, the filter being positioned immediately downstream of the oxidation catalyst and immediately upstream of means for injecting ammonia or an ammonia precursor solution into the exhaust flow.

[0097] The system for removing nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine disclosed above can be further used for the aftertreatment of exhaust gas from a lean-burn combustion engine.

[0098] The catalyst apparatus of the present invention can be manufactured by processes known in the art. A powder of an SCR catalyst active composition or oxidation catalyst and optionally at least one binder is mixed with water. Optionally, the mixture may be pulverized to adjust the particle size. The concentration of solids in each wash coat is adjusted according to the desired wash coat load. The wash coat is then applied onto the catalyst substrate in a direction perpendicular to the surfaces A and B of the catalyst substrate. This can preferably be done from top to bottom by applying the wash coat under pressure from the top to the bottom. Alternatively, the wash coat can preferably be applied from bottom to top by immersing it under reduced pressure from the bottom to the top. Subsequently, excess wash coat is removed, preferably by suctioning it under reduced pressure or by purging it under pressure. Finally, the washed-coated carrier substrate is dried and baked in an oven. When applying two or more wash coats, the steps of preparing each wash coat slurry, applying it, removing excess wash coat, and drying and baking are repeated. Such processes are known to those skilled in the art and can be applied in the context of the present invention without departing from the claims. [Brief explanation of the drawing]

[0099] [Figure 1] The temperature, volumetric mass flow rate, and amounts of NH3, NO, and NO2 at the inlet of the SCR / ASC catalyst in Example 1 and Comparative Example 1 are shown for the case of an α value of 1.4 in Example 1. [Figure 2a] The NH3 conversion rates for Example 1 and Comparative Example 1, measured in the World Harmonized Transient Cycle (WHTC) of Embodiment 1, are shown relative to the α values. [Figure 2b] The NOx conversion rates for Example 1 and Comparative Example 1, measured in the Worldwide Unified Test Cycle (WHTC) of Embodiment 1, are shown relative to the α values. [Figure 3a]The NH3 conversion rates for Comparative Examples 1 and 2, measured in the Worldwide Unified Test Cycle (WHTC) of Embodiment 1, are shown relative to their α values. [Figure 3b] The NOx conversion rates for Comparative Examples 1 and 2, measured in the Worldwide Unified Test Cycle (WHTC) of Embodiment 1, are shown relative to their α values. [Figure 4] The temperature, volume mass flow rate, and amounts of NH3, NO, and NO2 at the inlet of the SCR / ASC catalysts in Example 1 and Comparative Example 1, as measured in the Federal Test Procedure (FTP) cycle of Embodiment 2, are shown. [Figure 5a] The NH3 conversion rates for Example 1 and Comparative Example 1, measured using the Federal Test Procedure (FTP) cycle of Embodiment 2, are shown. [Figure 5b] The NOx conversion rates for Example 1 and Comparative Example 1, measured using the Federal Test Procedure (FTP) cycle of Embodiment 2, are shown relative to the α values. [Figure 6a] The NH3 slips of Example 1 and Comparative Example 1 in the temperature range of 250 to 500°C in Embodiment 3 are shown. [Figure 6b] The NO slip of Example 1 and Comparative Example 1 in the temperature range of 250 to 500°C in Embodiment 3 is shown. [Figure 6c] Embodiment 3 shows the N2O formation in Example 1 and Comparative Example 1 in the temperature range of 250 to 500°C. [Figure 7a] The NH3 conversion rates for Examples 2 and 3, measured in the Worldwide Unified Test Cycle (WHTC) of Embodiment 3, are shown. [Figure 7b] The NOx conversion rates for Example 2 and the α value of Example 2, measured in the Worldwide Unified Test Cycle (WHTC) of Embodiment 3, are shown. [Figure 8a] The NH3 conversion rates for Examples 2 and 3, measured using the Federal Test Procedure (FTP) cycle of Embodiment 4, are shown. [Figure 8b] The NOx conversion rates for Examples 2 and 3, measured using the Federal Test Procedure (FTP) cycle of Embodiment 4, are shown. [Figure 9a] The NH3 slips from Example 2 (dashed line) and Example 3 (solid line) in the FDT test are shown. [Figure 9b] The NO slip in Example 2 (dashed line) and Example 3 (solid line) in the FDT test is shown. [Modes for carrying out the invention]

[0100] Embodiment Example 1 The catalyst apparatus of the present invention is manufactured on the same carrier substrate, with the SCR zone located upstream and the ASC zone located downstream. The carrier substrate is a cordierite flow-through carrier having a total length of 8 inches (20.32 cm) and a diameter of 10.5 inches (26.67 cm). 400 cpsi (cells per square inch), 4 mil.

[0101] SCR catalyst composition in the SCR section: 194 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of zeolite). SCR zone length: 6 inches (15.24 cm)

[0102] ASC department: Oxidation catalyst: Pt particles supported on TiO2, supported amount 25 g / L, 2 g / ft 3 (0.0707 g / L) of precious metals. SCR catalyst: 135 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of the zeolite). ASC zone length: 2 inches (5.08 cm). ratio SCR 第1 / SCR 第2 It is 1.4. In both the SCR and ASC zones, the binder used for the SCR catalyst is alumina.

[0103] Comparative Example 1 A catalytic device is manufactured on the same carrier substrate with the SCR zone located upstream and the ASC zone located downstream. The carrier substrate is a cordierite flow-through carrier with a total length of 8 inches (20.32 cm) and a diameter of 10.5 inches (26.67 cm). 400 cpsi (cells per square inch), 4 mil. The amount of SCR catalytic active material supported is the same in both the SCR and ASC zones.

[0104] SCR catalyst composition in the SCR section: 180 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of zeolite). SCR zone length: 6 inches (15.24 cm)

[0105] ASC department: Oxidation catalyst: Pt particles supported on TiO2, supported amount 25 g / L, 2 g / ft 3 (0.0707 g / L) of precious metals. SCR catalyst: 180 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of the zeolite). ratio SCR 第1 / SCR 第2 It is 1.0. In both the SCR and ASC zones, the binder used for the SCR catalyst is alumina.

[0106] Comparative Example 2 A catalytic device is manufactured on the same support substrate, with the SCR zone located upstream and the ASC zone located downstream. The support substrate is a cordierite flow-through support with a total length of 8 inches (20.32 cm) and a diameter of 10.5 inches (26.67 cm). 400 cpsi (cells per square inch), 4 mil. The amount of SCR catalytic active material supported in the SCR zone is less than the amount supported in the ASC zone.

[0107] SCR catalyst composition in the SCR section: 171 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of zeolite). SCR zone length: 6 inches (15.24 cm)

[0108] ASC department: Oxidation catalyst: Pt particles supported on TiO2, supported amount 25 g / L, 2 g / ft 3 (0.0707 g / L) of precious metals. SCR catalyst: 207 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of the zeolite). ratio SCR 第1 / SCR 第2 It is 0.83. In both the SCR and ASC zones, the binder used for the SCR catalyst is alumina.

[0109] Embodiment 1: In this embodiment, the performance of Example 1, Comparative Example 1, and Comparative Example 2 is evaluated using the Worldwide Unified Test Cycle (WHTC). Upstream of the SCR / ASC catalyst, a diesel oxidation catalyst (DOC) and a coated diesel particulate filter (cDPF) are used.

[0110] Three consecutive WHTC cycles were performed, and the results of the third test are shown. The amount of NH3 entering the SCR catalyst was adjusted based on the amount of NOx entering the SCR catalyst so that the α value varied from 0.9 to 1.5, where the α value is the NH3 concentration. x It is calculated by dividing by the concentration.

[0111]

number

[0112] Figure 1 shows the temperature, volumetric mass flow rate, and amounts of NH3, NO, and NO2 at the inlet of the SCR / ASC catalyst when the α value is 1.4.

[0113] NH3 and NO in Example 1 and Comparative Example 1 of this embodiment x The conversion rates are shown in Table 1 and Figures 2a and 2b.

[0114] [Table 1]

[0115] Figure 2a shows the NH3 conversion rate against the α value. Compared to the 200 g / L in the SCR layer of the ASC in Comparative Example 1, a higher NH3 conversion rate is obtained with the 150 g / L wash coat loading amount of the second wash coat in Example 1.

[0116] Figure 2b shows NO in relation to α value. x The conversion rate is shown. From the fact that more NH3 is oxidized in WHTC, the NO of Example 1 x The conversion rate is slightly lower than that of Comparative Example 1.

[0117] [Table 2]

[0118] Figure 3a shows the NH3 conversion rate against the α value. Compared to the 200 g / L in the SCR layer of the ASC in Comparative Example 1, the 230 g / L wash coat load in the second wash coat of Comparative Example 2 yields a lower NH3 conversion rate.

[0119] Figure 3b shows NO in relation to α value. x The conversion rate is shown. No difference is observed between Comparative Example 1 and Comparative Example 2.

[0120] Embodiment 2: In this embodiment, both catalyst configurations shown in Example 1 and Comparative Example 1 are evaluated using a Federal Test Procedure (FTP) cycle. Upstream of the SCR / ASC catalyst, a diesel oxidation catalyst (DOC) and a coated diesel particulate filter (cDPF) are used.

[0121] Three consecutive FTP cycles were performed, and the results of the third test are shown. The amount of NH3 entering the SCR catalyst was adjusted so that the α value varied from 0.9 to 1.5 based on the amount of NOx entering the SCR catalyst, where the α value is defined in the same way as in Embodiment 1. For the case where the α value is 1.2, the temperature, volumetric mass flow rate, and amounts of NH3, NO, and NO2 at the inlet of the SCR / ASC catalyst are shown in Figure 4.

[0122] NH3 and NO in Example 1 and Comparative Example 1 of this embodiment x The conversion rates are shown in Table 3 and Figure 5.

[0123] [Table 3]

[0124] Figure 5a shows the NH3 conversion rate against the α value. Compared to the 200 g / L in the SCR layer of the ASC in Comparative Example 1, a higher NH3 conversion rate is obtained with the 150 g / L wash coat loading in the second wash coat of Example 1.

[0125] Figure 5b shows NO in relation to α value. x The conversion rate is shown. From the fact that more NH3 is oxidized at FTP, the NO of Example 1 x The conversion rate is slightly lower than that of Comparative Example 1.

[0126] Embodiment 3: In this embodiment, a supply of 750 ppm NH3, 500 ppm NO, 5% O2, 5% H2O, and N2 as a balance gas is passed through Example 1 and Comparative Example 1 until a steady state is reached. During this time, the temperature is kept constant at 200°C, and the space velocity is 60,000 h. -1 Therefore, after reaching a steady state (i.e., when there are no fluctuations in the concentration and temperature of the measured gas species), the following feed modifications are made simultaneously: remove NH3 from the feed and set the space velocity to 100,000 h -1The supply conditions are rapidly increased, raising the temperature to 500°C at a rate of 250K / min. This sudden change in supply conditions is done to simulate load changes during actual operating conditions, thereby stressing the SCR and ASC catalysts with NH3 slip. Hereafter, this test will be referred to as the Fast Desorption Test (FDT).

[0127] Figures 6a, 6b, and 6c show the NH3 slip, NO slip, and N2O formation in Example 1 (dashed line) and Comparative Example 1 (solid line) during temperature increase, respectively. Here, we can see the advantage of Example 1 in that NH3 and NO slip are reduced compared to Comparative Example 1.

[0128] Example 2 The catalyst apparatus of the present invention is manufactured on the same carrier substrate, with the SCR zone located upstream and the ASC zone located downstream. The carrier substrate is a cordierite flow-through carrier having a total length of 8 inches (20.32 cm) and a diameter of 10.5 inches (26.67 cm). 400 cpsi (cells per square inch), 4 mil.

[0129] SCR catalyst composition in the SCR section: 200 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of zeolite). SCR zone length: 6 inches (15.24 cm)

[0130] ASC department: Oxidation catalyst: Pt particles supported on TiO2, supported amount 25 g / L, 2 g / ft 3 (0.0707 g / L) of precious metals. SCR catalyst: 125 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of the zeolite). ASC zone length: 2 inches (5.08 cm). ratio SCR 第1 / SCR 第2 It is 1.6. In both the SCR and ASC zones, the binder used for the SCR catalyst is alumina.

[0131] Example 3 The catalyst apparatus of the present invention is manufactured on the same carrier substrate, with the SCR zone located upstream and the ASC zone located downstream. The carrier substrate is a cordierite flow-through carrier having a total length of 8 inches (20.32 cm) and a diameter of 10.5 inches (26.67 cm). 400 cpsi (cells per square inch), 4 mil.

[0132] SCR catalyst composition in the SCR section: 200 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of zeolite). SCR zone length: 5 inches (12.7 cm)

[0133] ASC department: Oxidation catalyst: Pt particles supported on TiO2, supported amount 25 g / L, 2 g / ft 3 (0.0707 g / L) of precious metals. SCR catalyst: 150 g / L of catalytically active material (Cu-CHA), SAR = 13; 5.5 wt% Cu (calculated as CuO based on the total weight of the zeolite). ASC zone length: 3 inches (7.62 cm). ratio SCR 第1 / SCR 第2 It is 1.3. In both the SCR and ASC zones, the binder used for the SCR catalyst is alumina.

[0134] Embodiment 4: The performance of Examples 2 and 3 is evaluated using the WHTC cycle in the same manner as described in Example 1.

[0135] [Table 4]

[0136] Figure 7a shows the NH3 conversion rate against the α value. Compared to the 125 g / L in the SCR layer of the ASC in Example 3, a higher NH3 conversion rate is obtained with the 150 g / L wash coat loading in the second wash coat of Example 2.

[0137] Figure 7b shows NO in relation to α value. x The conversion rate is shown. From the fact that more NH3 is oxidized in WHTC, the NO of Example 3 x The conversion rate is slightly lower than that of Example 2.

[0138] NH3 and NO in Examples 2 and 3 x The conversion rates are shown in Table 4 and Figures 7a and 7b.

[0139] Embodiment 5: The performance of Examples 2 and 3 is evaluated using the FTP cycle in the same manner as described in Example 2.

[0140] NH3 and NO in Examples 2 and 3 x The conversion rates are shown in Table 5 and Figures 8a and 8b.

[0141] [Table 5]

[0142] Figure 8a shows the NH3 conversion rate against the α value. Compared to the 125 g / L in the SCR layer of the ASC in Example 2, a higher NH3 conversion rate is obtained with the wash coat loading amount of 150 g / L in the second wash coat of Example 3.

[0143] Figure 8b shows NO in relation to α value. x The conversion rate is shown. From the fact that more NH3 is oxidized at FTP, the NO of Example 3 x The conversion rate is slightly lower than that of Example 2.

[0144] Embodiment 6 For Examples 2 and 3, the FDT test was performed using the same method as described in Example 3.

[0145] Figure 9a shows the NH3 slips of Example 2 (dashed line) and Example 3 (solid line). Compared to the 125 g / L in the SCR layer of ASC in Example 2, a lower ammonia slip is obtained with the 150 g / L wash coat loading of the second wash coat in Example 3.

[0146] Figure 9b shows the NO slip for Example 2 (dashed line) and Example 3 (solid line). Compared to the 125 g / L in the SCR layer of ASC in Example 2, the 150 g / L wash coat load in the second wash coat of Example 3 results in lower NO slip.

Claims

1. A catalytic converter for removing nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine, a. Upstream SCR catalyst, i. Carrier substrate and ii. First SCR catalytic active composition SCR 第１ An upstream SCR catalyst comprising a first wash coat, which optionally includes at least one first binder, and the first wash coat applied to the carrier substrate, b. A downstream ASC catalyst, i. Carrier substrate and ii. A lower layer comprising an oxidation catalyst and an optional third wash coat comprising at least one third binder, wherein the lower layer is directly applied onto the carrier substrate. iii. Second SCR catalytic active composition SCR 第２ The lower layer comprises a downstream ASC catalyst and an upper layer comprising an upper layer coated on the lower layer, and optionally an upper layer comprising a second wash coat comprising at least one second binder. - The upstream SCR catalyst and the downstream ASC catalyst are present on a single carrier substrate, or on two different carrier substrates. - The first and second SCR catalyst active compositions are either the same or different from each other. - At least one of the optional first, second, and third binders is either the same as or different from the others. - Ratio of the amount of the first and second SCR catalyst active compositions supported in g / L in the first and second wash coats [Math 1] However, the ratio is 1.2:1 to 2:1, A catalyst apparatus in which the first SCR catalytic active composition and the second SCR catalytic active composition are Cu-CHA zeolite having an SAR value of 5 to 100 and a copper-to-aluminum atomic ratio in the range of 0.005 to 0.

555.

2. The catalyst apparatus according to claim 1, wherein the crystalline aluminosilicate zeolite has an SAR value of 10 to 50.

3. The catalyst article according to claim 1 or 2, wherein the crystalline aluminosilicate zeolite is promoted with copper, and the atomic ratio of copper to aluminum is in the range of 0.175 to 0.

415.

4. The catalyst apparatus according to any one of claims 1 to 3, wherein the oxidation catalyst comprises a platinum group metal, a platinum group metal oxide, a mixture of two or more platinum group metals, a mixture of two or more platinum group metal oxides, or a mixture of at least one platinum group metal and at least one platinum group metal oxide, and the platinum group metal is selected from ruthenium, rhodium, palladium, iridium, and platinum.

5. The first, second, and third binders are independent of each other and include alumina, silica, non-zeolite silica-alumina, natural clay, and TiO2. ２ , ZrO ２ , CEO ２ , SnO ２ A catalyst apparatus according to any one of claims 1 to 4, further selected from mixtures and combinations thereof.

6. The ratio of the amounts of the first and second SCR catalyst active compositions supported in the first and second wash coats, given in g / L. [Math 2] The catalyst apparatus according to any one of claims 1 to 5, wherein, under the condition that the ratio is 1.2:1 to 2:1, the wash coat load of the first SCR catalyst active composition is 100 to 230 g / L, and the wash coat load of the second SCR catalyst active composition is 70 to 170 g / L.

7. The amount of wash coat supported in the third wash coat is 10 to 100 g / L, and the platinum group metal concentration in the third wash coat is 0.5 to 25 g / ft ３ A catalyst apparatus according to any one of claims 1 to 6, wherein the concentration is (0.018 g / L to 0.88 g / L).

8. The upstream SCR catalyst and the downstream ASC catalyst exist as two adjacent zones on a single carrier substrate. a. The upstream SCR catalyst extends along the axial length of the carrier substrate from the upstream end to 40-80% of the total length of the carrier substrate, b. The downstream ASC catalyst extends along the axial length of the carrier substrate from the downstream end to 40-80% of the total length of the carrier substrate, c. The catalyst apparatus according to any one of claims 1 to 7, wherein there is substantially no overlap or gap between the SCR catalyst zone and the ASC catalyst zone, and the lengths of both zones account for 100% of the total axial length of the carrier.

9. The catalyst apparatus according to claim 8, wherein the carrier substrate is selected from ceramic, metal, and corrugated carrier substrate.

10. The catalyst apparatus according to claim 9, wherein the carrier substrate is a ceramic carrier substrate selected from a flow-through carrier substrate and a wall-flow filter.

11. The catalyst apparatus according to any one of claims 1 to 6, wherein the upstream SCR catalyst and the downstream ASC catalyst are located on two different carrier substrates that are directly adjacent to each other.

12. The catalyst apparatus according to claim 11, wherein the carrier substrates are independently selected from ceramic, metal, and corrugated carrier substrates.

13. The catalyst apparatus according to claim 12, wherein the carrier substrate is a ceramic carrier substrate that is independently selected from a flow-through carrier substrate and a wall-flow filter.

14. A system for removing nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine, a. Means for injecting ammonia or an ammonia precursor solution into the exhaust stream, b. A system comprising a catalyst device according to any one of claims 1 to 13, positioned immediately downstream of means for injecting the ammonia or ammonia precursor solution of a).

15. A system for removing nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine according to claim 14, further comprising an oxidation catalyst for oxidizing volatile organic compounds, carbon monoxide and hydrocarbons, wherein the catalyst is located immediately upstream of means for injecting the ammonia or ammonia precursor solution into the exhaust system.

16. A system for removing nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine according to claim 14 or 15, further comprising a filter for removing particulate matter, wherein the filter is located immediately downstream of the oxidation catalyst and immediately upstream of means for injecting the ammonia or ammonia precursor solution into the exhaust flow.

17. Use of a system for removing nitrogen oxides and ammonia from exhaust gases of a lean-burn combustion engine according to any one of claims 1 to 15, for the aftertreatment of exhaust gases from a lean-burn combustion engine.

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