WO2025002948A1

WO2025002948A1 - SCR CATALYSTS FOR IMPROVED NOx REDUCTION

Info

Publication number: WO2025002948A1
Application number: PCT/EP2024/067120
Authority: WO
Inventors: Fei WEN; Ruediger Hoyer; Mattia SIST; Leen VAN TENDELOO
Original assignee: Umicore Ag & Co. Kg
Priority date: 2023-06-30
Filing date: 2024-06-19
Publication date: 2025-01-02

Abstract

The present invention discloses catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines, comprising a carrier substrate of length L, a bottom layer comprising a zone D extending from a second side over a length L_Z and comprising a first SCR composition consisting of one or more manganese-containing mixed oxides, or a mixture of one or more manganese-containing mixed oxides and one or more metal-promoted small-pore zeolites; and a zone C' extending from a first side over a length L_Y = L - L_Zand comprising a third SCR composition consisting of a V/TiO₂SCR catalyst composition which comprises at least one oxide of vanadium, and a top layer comprising a material zone C extending over the carrier substrate and comprising a second SCR composition consisting of a V/TiO₂SCR catalyst composition which comprises at least one oxide of vanadium.

Description

SCR catalysts for improved NO_X reduction

Description

The present invention relates to catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines. The catalytic devices comprise a carrier substrate, a bottom layer and a top layer. The bottom layer comprises a material zone comprising an SCR catalytically active composition consisting of one or more manganese-containing mixed oxides or a mixture of one or more manganese-con- taining mixed oxides and one or more metal-promoted small-pore zeolites. The material zone in the bottom layer, which comprises said SCR catalytically active composition, extends from the downstream end over 20 to 100% of the length of the carrier substrate. Optionally, the bottom layer additionally comprises a material zone which extends from the upstream end over 80 to 0% of the carrier substrate; said additional material zone comprising a vanadia-titania based SCR catalyst composition. The bottom layer is directly affixed to the carrier substrate. The top layer is affixed to the bottom layer and extends over the total length of the carrier substrate. It comprises a vanadia-titania based SCR catalyst composition. Methods for making the catalytic devices as well as uses thereof are also envisaged.

Modern internal combustion engines require the use of catalytic aftertreatment systems to reduce harmful emissions and respect the new legislation standards. The exhaust gas of combustion processes, in particular that of diesel engines, but also that of direct-injection lean-mixture-operated gasoline engines, contains carbon monoxide (CO) and hydrocarbons (HC) resulting from incomplete combustion of the fuel. In addition, the exhaust gas also contains particulate matter (PM) and nitrogen oxides (NO_X). Furthermore, the exhaust gas of diesel engines contains, for example, up to 15 vol.-% oxygen. It is known that the oxidizable harmful gases CO and HC can be converted to harmless carbon dioxide (CO2) and water (H2O) by passing them over suitable oxidation catalytic converters and that particulates can be removed by passing the exhaust gas through a suitable particulate filter. Nitrogen oxides may be converted on an SCR catalyst in the presence of oxygen to nitrogen and water by means of ammonia. “SCR” stands for “selective catalytic reduction”. A major driver for the recent and future development of catalysts are the increasingly stringent world-wide legislative emission levels for road (e.g. passenger cars, trucks) and non-road (e.g. ships, trains) applications. In the specific case of removing nitrogen oxides from the exhaust gas of lean burn engines, there is a global need for more active, more selective and more stable catalysts, due to tightened legislative emission levels and the increased need of catalysts which show a good denitration performance even at low exhaust gas temperatures. One effective method to remove nitrogen oxides (NO_X) from the exhaust gas of these lean burn engines is selective catalytic reduction (SCR) with ammonia (NH₃). In NH₃-SCR, the NO_X molecules are catalytically reduced to N₂ using NH₃ as reducing agent. The ammonia used as reducing agent may be made available by feeding an ammonia precursor compound into the exhaust gas which is thermolyzed and hydrolyzed to form ammonia. Alternatively, the ammonia may be formed from an ammonia precursor compound by catalytic reactions within the exhaust gas. Examples of such precursor compounds are ammonium carbamate, ammonium formate and preferably urea. In most cases, ammonia is fed as a less hazardous urea solution, which is decomposed to ammonia in the catalytic unit, and can be filled and stored in the vehicle in a dedicated reservoir.

The catalytic reduction of NO_X with NH₃ can be represented by different reaction equations. Nitric oxide (NO) is the main NO_X compound produced in an engine. The reduction of NO is referred to as the “standard” NH₃-SCR reaction:

NO₂ is more reactive than NO. In presence of mixtures of NO and NO₂, the NH₃-SCR reaction is easier, and the so-called “fast” NH₃-SCR reaction can occur:

To take profit of the fast NH₃-SCR reaction, an additional catalyst is needed to oxidize part of the NO into NO₂.

Also, side reactions may occur and result in unwanted products or the unproductive consumption of ammonia:

4NH₃ + 3O₂ N₂ + 6 H₂0 (3)

In official driving cycles, exhaust gas temperatures of latest generation engines and hybrid vehicles with reduced fuel consumption and low CO2 emission are significantly lower than with previous engine generations. Therefore, it is necessary to obtain a NH₃-SCR catalyst which shows a high low-temperature NO_X conversion. Furthermore, NH₃-SCR catalyst should release as little N2O as possible.

SCR catalysts are described extensively in literature as well. They are generally either so-called mixed oxide catalysts, or so-called zeolite catalysts. Mixed oxide catalysts either comprise oxides of vanadium and titanium and optionally oxides of other metals like tungsten, molybdenum, antimony and cerium, or they are based on manganese-contain- ing mixed oxides or manganese of manganese oxide supported on metal oxides. Zeolite catalysts comprise metal-promoted zeolites.

The SCR systems known in the prior art comprise SCR catalysts which effectively reduce nitrogen oxides NO_X from exhaust gas flows of internal combustion engines during operation in normal to high temperature ranges, for example in temperature ranges between approximately 250°C and 450°C. However, during the cold start of an engine but also in low-load operation, the exhaust gas temperatures may fall to low temperature ranges between approximately 60°C and approximately 250°C. In such temperature ranges, conventional SCR catalysts, which are either based on oxides of vanadium and titanium or on metal-promoted zeolites, do not succeed in effectively reducing NO_X from exhaust gas flows. The reason for this is that engines generally generate only little NO2 and oxidation catalysts do not convert enough NO into NO2 at the temperatures during the cold start and the warm-up phase (< 150°C) for the NO_X reduction to become effective. Moreover, it is difficult to sufficiently provide ammonia from urea in such temperature ranges for effective NO_X reduction, since thermolysis and hydrolysis of the urea sometimes proceed incompletely. In order to convert more NO to NO2 in low exhaust gas temperature operating ranges, an oxidation catalyst with large amounts of platinum can be used. Oxidation catalysts of this type are costly and can entail additional disadvantages. The person skilled in the art is also aware of so-called low- temperature SCR catalysts, which can effectively reduce nitrogen oxides at low temperatures below a temperature threshold value of 100°C to 250°C, sometimes even at temperatures below 100°C. In particular, SCR catalysts which contain manganese-containing mixed oxides or manganese or manganese oxide supported on metal oxides exhibit very high NO conversions even at low temperatures, sometimes even below 100°C. However, a disadvantage of such manganese-containing SCR catalysts is that activity and selectivity are very poor at high temperatures, so that, for example, large amounts of N2O are formed. They also have a low stability to high aging temperatures and tend to be contaminated by SO_X, wherein the possibilities for desulfurization are limited due to low aging stability. The above-mentioned metal-promoted zeolites are also sensitive to SO_X contamination. By contrast, SCR catalyst which are based on based on oxides of vanadium and titanium are resistant to SO_X contamination, but their low-temperature performance is rather low.

WO 2017/168327 A1 addresses the problem of sulfur poisoning of metal-promoted zeolites. The invention provides methods for low temperature desulfating sulfur-poisoned SCR catalysts, and emission control systems adapted to apply such desulfating methods, in order to regenerate catalytic NO_X conversion activity. The methods are adapted for treating an SCR catalyst to desorb sulfur from the surface of the SCR catalyst and increase NOx conversion activity of the SCR catalyst, the treating step including treating the SCR catalyst with a gaseous stream comprising a reductant for a first treatment time period and at a first treatment temperature, wherein the first treatment temperature is about 350°C or less, followed by a second treatment time period and a second treatment temperature higher than the first treatment temperature, wherein the molar ratio of reductant to NO_X during the treating step is about 1.05:1 or higher. The reductant can be ammonia or any precursor thereof. Under harsh hydrothermal conditions, for example as exhibited during the desulfation of an SCR catalyst or the regeneration of a soot filter with temperatures locally exceeding well over 600 °C, the catalytic activity of many metal- promoted zeolites begins to decline. This decline has been attributed to dealumination of the zeolite and the consequent loss of metal-containing active centers within the zeolite. Introduction of an ammonia based reductant at low temperature to a poisoned SCR catalyst composition promotes ion exchange of the metal sulfate species within the molecular sieve with the ammonia or precursor thereof to from an ammonium sulfate species, which can at temperature lower than 600 °C dissociate from the catalyst and free the metal in the molecular sieve to regain its catalytic activity for NO_X conversion. WO 2019/115187 A1 discloses an exhaust-gas aftertreatment system for selective catalytic reduction with a plurality of SCR catalytic converters, which exhaust-gas aftertreatment system is able to reduce NO_X in a large temperature range and can store SO_X. The invention further relates to a method for treating an exhaust gas flow, in which method the exhaustgas aftertreatment system according to the invention is used. The system comprises a high- temperature SCR catalyst for temperature ranges between 250°C and 750°C and a low- temperature SCR catalyst arranged downstream thereof for temperature ranges between 60°C and less than 250°C. There is a reductant supply system directly upstream of the high- temperature SCR catalyst. The high-temperature SCR catalyst is designed to reduce NO_X in exhaust gas that has a temperature above a temperature threshold value and to store SOx in the temperature range below the threshold value. The low-temperature SCR catalyst reduces NO_X in the temperature range below the threshold value. In each case, the exhaust gas flows through the high-temperature SCR catalyst. An exhaust-gas bypass valve or flow control valve is arranged directly upstream of the low-temperature SCR catalyst. If the temperature of the exhaust gas is greater than or equal to the temperature threshold value, the exhaust gas is completely conducted past the low-temperature SCR catalyst. The high-tem- perature SCR catalyst advantageously contains a molecular sieve as a catalytically active layer, and the catalytically active layer of the low-temperature SCR catalyst is preferably a manganese-containing mixed oxide.

WO 2022/174814 A1 relates to a SCR catalytic article, wherein the sulfurization and desulfurization are carried out in accordance with the processes as described in the specification, and to an exhaust treatment system comprising the same. The invention also relates to a method for determining whether a metal-promoted small pore zeolite is resistant to irreversible sulfur poisoning and a method for evaluating whether a metal- promoted small pore zeolite is qualified for resistance to irreversible sulfur poisoning. The background of this invention is that, in addition to the hydrothermal aging deactivation, another significant factor impacting the performance of the SCR catalytic articles is chemical poisoning such as sulfur poisoning. Sulfur poisoning originates from the cumulative exposure of the catalyst to sulfur species in the fuel and fuel-derived sulfur-containing contaminants. Sulfur content in diesel fuel has been significantly reduced in recent years, which may be even less than 15 ppm sulfur with the introduction of Ultra-Low Sulfur Diesel (ULSD) in North America for example. However, cumulative exposure of catalysts over their lifetime in heavy duty diesel engine exhaust treatment system may amount to kilograms of sulfur. The situation could be even worse for some off-road applications or in certain regions where high sulfur diesels (>350 ppm sulfur) are not uncommon.

SCR catalytic articles may be regenerated at high temperatures, which is commonly accomplished during the regeneration of the soot filter. The NO_X reduction activity of the SCR catalytic articles degraded by sulfur poisoning will be recovered significantly by the regeneration. However, a proportion of NO_X reduction activity loss cannot be remedied by the regeneration, resulting in permanent sulfur poisoning damage to the SCR catalyst activity, which is also known as irreversible sulfur poisoning.

Therefore, WO 2022/174814 A1 provides a SCR catalytic article, comprising a substrate and thereon a copper-containing small pore zeolite, having a crystal structure characterized by a decrease of unit cell volume upon sulfurization and desulfurization of less than 10 A³ as determined by an X-ray powder diffraction, wherein the sulfurization is carried out by passing a gas stream containing 35 ppmv SO2, 350 ppmv NO, 10 vol% O2, 10 vol% H2O and balanced N2 through a Pt-containing diesel oxidation catalyst (DOC) under an inlet temperature of 650 °C for partially oxidizing SO2 to provide a SO2 to SO3 ratio of 30 : 70 and then through the SCR catalytic article under an outlet temperature of 400°C, at a space velocity of 10,000 hr¹ based on the volume of the SCR catalytic article, for a period to provide 40 g/L of sulfur exposure based on the volume of the SCR catalytic article, wherein the SCR catalytic article has been hydrothermally aged prior to the sulfurization; and the desulfurization is carried out by passing a gas stream containing 10 vol% O2, 8 vol% H2O, 7 vol% CO2 and balanced N2 through the SCR catalytic article having been subjected to the sulfurization at a space velocity of 60,000 IT¹ at 550 °C for 30 minutes.

US 2016/001228 A1 discloses an ammonia slip control catalyst having a layer containing perovskite and a separate layer containing an SCR catalyst. The ammonia slip catalyst can have two stacked layers, with the top overlayer containing an SCR catalyst, and the bottom layer containing a perovskite. The ammonia slip catalyst can alternatively be arranged in sequential layers, with the SCR catalyst being upstream in the flow of exhaust gas relative to the perovskite. A system comprising the ammonia slip catalyst upstream of a PGM-containing ammonia oxidation catalyst and methods of using the system are also described. The system allows for high ammonia oxidation with good nitrogen selectivity. Furthermore, methods of making and using the ammonia slip catalyst to reduce ammonia slip and selectively convert ammonia to N2 are described. The SCR catalyst comprises an oxide of a base metal, a molecular sieve, a metal-exchanged molecular sieve or a mixture thereof. If the SCR catalyst is an oxide of base metal, e.g. a vanadium- based SCR catalyst, it can be supported on a refractory metal oxide such as alumina, silica, zirconia, titania, ceria and combinations thereof. The base metal is selected from the group consisting of cerium, chromium, cobalt, copper, iron, manganese, molybdenum, nickel, tungsten, vanadium and mixtures thereof. The perovskite preferably has the formula ABO3, wherein A comprises at least one of calcium, barium, bismuth, cadmium, cerium, copper, lanthanum, lead, neodymium, nickel, strontium and yttrium; and B comprises at least one of aluminum, cerium, chromium, cobalt, iron, manganese, niobium, tin, titanium and zirconium. Preferably, the metal A in the perovskite is lanthanum.

US 2018/229224 A1 describes catalysts effective to abate NOx, hydrocarbons, and carbon monoxide from a gasoline engine exhaust gas. Such catalysts include a substrate having a first and second material disposed thereon, the first material effective to catalyze selective catalytic reduction of nitrogen oxides in the presence of ammonia and the second material effective to abate hydrocarbons and carbon monoxide. The first material comprises comprising a molecular sieve promoted with copper and/or iron in a low loading. The second material comprises at least one base metal oxide on a support. The base metal oxide is selected from vanadium, tungsten, titanium, copper, iron, cobalt, nickel, chromium, manganese, neodymium, barium, cerium, lanthanum, praseodymium, magnesium, calcium, zinc, niobium, zirconium, molybdenum, tin, tantalum, cerium, and strontium, or combinations thereof. Preferably, the metal oxide is an oxide of nickel, iron, manganese, cobalt, or copper. The refractory metal oxide support is selected from activated alumina, bulk ceria, zirconia, alpha alumina, silica and titania. The first and the second material are applied onto the catalyst substrate in the form of a first and a second layer. The first and the second layer can be arranged in zones, wherein the first layer is disposed on the upstream end of the substrate, and the second layer is disposed on the downstream end, or vice versa. Alternatively, either the first or the second layer can be disposed on the substrate, and the respective other layer at least partially overlies it.

CN 102 039 120 A discloses a cerium-containing nano MnTi composite oxide catalyst. The catalyst is prepared from titanic acid butyl acetate, n-butyl alcohol, deionized water, glacial acetic acid, soluble salt of manganese and soluble salt of cerium which serve as raw materials by a sol-gel method, wherein the volume ratio of the titanic acid butyl acetate to the n-butyl alcohol to the deionized water to the glacial acetic acid is 1 :(2.0- 3.0):(0.2-0.4):(0.2-0.4); and the molar ratio of titanium contained in the titanic acid butyl acetate to cerium contained in the soluble salt of the cerium to manganese contained in the soluble salt of the manganese is 1 :(0.01-0.1):(0.1 -1). The catalyst disclosed by the invention has high thermal stability, high activity and nanoscale particle size and can be applied to a low-temperature selective catalytic reduction (SCR) denitration reaction. When the NO concentration is 800 ppm and the spatial space velocity is 100,000 h’¹, the transformation rate of NO by using the catalyst is up to 100 percent. The Examples shown in ON 102 039 120 A show MnCeTi ternary oxides with various molar ratios Mn:Ce:Ti. The molar ratios of cerium in these Examples range between 0.019 and 0.4.

ON 102 600 832 A discloses a combined catalyst for improving denitration performance and an application thereof. In the catalyst, industrial anatase crystal form TiC>2 is taken as a carrier. X^Os-WOs/TiCh is applied onto the front section of the carrier substrate, and MnO_x-CeO2/TiO2 is applied onto the back section of the carrier substrate. “Front section” refers to a section where an air current main body is contacted firstly; the back section refers to a section where the air current main body is contacted secondly. The mass ratio of the front section to the back section is 1 : 1-1 :3. V2O5 accounts for 2-4 percent of the mass of the carrier TiO2; WO3 accounts for 8-10 percent of the mass of the carrier TiCh; Mn accounts for 10-20 percent of the mass of the carrier TiCh; CeC>2 accounts for 8-10 percent of the mass of the carrier TiO2; and MnO_x is taken as the general name of MnC>2 and Mn2C>3. V2O5 is 2%~ 4%, WO3 is 8% to 10% of the mass of the carrier TiC>2, Mn is 10% to 20% of the mass of the carrier TiC>2, and CeC>2 is 8% to 10% of the mass of the carrier TiC>2. It is expressly stated that TiC>2 serves as the carrier material, and therefore, it deals with a binary oxide MnO_x-CeC>2 and not with a ternary oxide MnCeTiO_x. The amount of oxygen in the oxides is given as “x” because it can vary, depending on the oxidation state of manganese. The combined catalyst can be applied to an integral catalyst for industrial application. The combined catalyst has a wider active temperature window; particularly, the removing efficiency of NO_X by NH3-SCR is greatly increased under the exhaust low-temperature wording condition of a diesel engine; and moreover, the same NO_X removing efficiency as the conventional catalyst can be obtained at a medium-high temperature section.

T Shang, S Hui, Y Niu, L Liang, C Liu and D Wang: “Effect of the addition of Ce to MnO_x/Ti catalyst on reduction of N2O in low-temperature SCR”, Asia-Pac J Chem Eng 2014, 9, 810-817, studied the effect of MnO_x/Ti catalyst doped with Ce prepared by sol- gel method at a low temperature on N2O formation during the selective catalytic reduction of NO with NH3. Results showed that the production of N2O was primarily controlled by two paths: (1) direct reaction of NO and NH3 and (2) oxidation of NH3 with O2. The overoxidation of NH3 was the dominant step in N2O reduction. Addition of Ce to MnO_x/Ti catalyst increased the proportion of lattice oxygen on the catalyst surface. Meanwhile, the stability of lattice oxygen, which contributed to the decrease in N2O formation by inhibiting the overoxidation of NH3, on the catalyst surface was the best when the Ce/Ti mole ratio reached 0.1.

In A Kumar, MA Smith, K Kamasamudram, NW Currier and H An, “Impact of different forms of feed sulfur on small-pore Cu-zeolite SCR catalyst”, Catal Today 2014, 231 , 75- 82, the effect of SO2 and SO3 in the presence of water vapor on the catalyst performance of copper zeolites at 200 and 400°C was investigated. At 200°C, the effect of sulfur poisoning was modest an independent of whether it dealt with SO2 or SO3. However, at 400°C, the presence of SO3 resulted in a substantially more significant impact on the catalyst performance, which was also more difficult to reverse. It was assumed that sulfur poisoning of Cu-zeolite catalysts can occur via different mechanisms, from indiscriminate adsorption of SO_X species on Cu sites at lower temperatures to a reversible chemical reaction of SO3 or H2SO4 produced in the wet feed, with the catalyst material at elevated temperatures.

EP 4 039 365 A1 relates to an SCR catalyst for removing nitrogen oxides (NO_X) from exhaust gas, comprising: 0.01-70 wt% of zeolite having an average pore size of 5 A or more; 25-90 wt% of titanium dioxide (TiCh); and 4-10 wt% of vanadium pentoxide (V2O5). Furthermore, the catalyst may comprise 0.01 to 15 wt.-% WO3. The zeolite is preferably selected from zeolite-Y, ZSM-5 zeolite, AEL zeolite, AFI zeolite, AFO zeolite, AFR zeolite, BEA zeolite, HEU zeolite, MFI zeolite, MOR zeolite, MEL zeolite, and MTW zeolite. Preferably, the zeolite is not promoted with a metal component, for instance with a metal selected from iron, cobalt, nickel, copper, chromium, zinc or manganese, because said metals promote the reaction of SO2 to a sulfate, for instance ammonium sulfate (AS), ammonium bisulfate (ABS). The sulfur tolerance was tested by deactivating the catalyst with 30 ppm SO2 over 24 hours. According to the inventors, the SCR catalyst exhibits denitrification performance in a low-temperature area that is superior to that of a conventional SCR catalyst, has improved tolerance for a sulfur compound, and also has an excellent regeneration rate. WO 2014/160289 A1 discloses SCR catalyst systems comprising a first SCR catalyst composition and a second SCR catalyst composition arranged in the system, the first SCR catalyst composition promoting higher N2 formation and lower N2O formation than the second SCR catalyst composition, and the second SCR catalyst composition having a different composition than the first SCR catalyst composition, the second SCR catalyst composition promoting lower N2 formation and higher N2O formation than the first SCR catalyst composition. The first SCR catalyst composition preferably comprises a mixed oxide, which can be selected from Fe/titania (e.g. FeTiOa), Fe/alumina (e.g. FeAhCh), Mg/titania (e.g. MgTiCh), Mg/alumina (e.g. MgAhCh), Mn/alumina (e.g. MnAhCh), Mn/ti- tania (MnOx/TiCh), Cu/titania (e.g. CuTiOa), Ce/Zr (CeZrC>2), Ti/Zr (e.g. TiZrCh), vana- dia/titania (e.g. X^Os/TiCh) and mixtures thereof. Preferably, the mixed oxide comprises vanadia/titania, which may optionally be stabilized with tungsten. Vanadia concentrations of 1 to 10 wt.-% and tungsten concentrations of 0.1 to 10 wt.-% are preferred. The second SCR catalyst composition preferably is a small-pore zeolite, more preferably CHA or AEI, and it is preferably promoted with a metal selected from Cu, Fe, Co, Ce and Ni. More preferably, the zeolite is promoted with 2 to 8 wt.-% of Cu. In one embodiment, the first and the second SCR catalyst compositions are arranged in zones on the substrate, with the mixed oxide SCR catalysts composition being arranged on the upstream end, and the zeolite SCR catalyst composition being arranged on the downstream end, of the carrier substrate. The first zone covers 20 to 80% of the length L of the substrate, with the second zone covering the remainder of the length L of the substrate. In another embodiment, the first and the second SCR catalyst are arranged in layers, wherein the mixed oxide SCR catalyst, i.e. the first SCR catalyst, is present in the top layer, and the second SCR catalyst is present in the bottom layer. In both arrangements, the sulfur- tolerant vanadia/titania SCR catalyst composition shall protect the downstream sulfursensitive metal-promoted small-pore zeolite from sulfur poisoning.

There remains a constant need for new SCR catalysts having an improved low temperature performance and, concomitantly, a good sulfur resistance.

Problem to be solved by the invention

It is an object of the present invention to provide SCR catalytic devices with an improved low temperature performance and, concomitantly, a good sulfur resistance. The novel SCR catalytic devices show a good NO_X removal over a wide temperature range, and also a low formation of N2O. Methods for making the novel SCR catalytic devices and uses thereof are also envisaged.

Solution of the problem

The object to provide SCR catalytic devices with an improved low temperature performance and, concomitantly, a good sulfur resistance is solved by catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines, comprising a) a carrier substrate of length L, said length L extending from a face side A to a face side B, and b) a bottom layer comprising

- a material zone D affixed to the carrier substrate; said material zone D comprising a first SCR catalytically active composition and extending from face side B over a length L_z which is 20 to 100% of the length L of the carrier substrate; wherein the first SCR catalytically active composition in said material zone D consist of one or more manganese-containing mixed oxides, or a mixture of one or more manganese-containing mixed oxides and one or more metal- promoted small-pore zeolites

- a material zone C’ affixed to the carrier substrate; said material zone C’ comprising a third SCR catalytically active composition and extending from face side A over a length L_y = L - L_z which is 80 to 0% of the total length of the carrier substrate; wherein the third SCR catalytically active composition in said material zone C’ consists of a V/TiC>2 SCR catalyst composition which comprises at least one oxide of vanadium supported on titanium dioxide;

- wherein L_y + L_z = L, and c) a top layer affixed to the bottom layer, said top layer comprising a material zone C comprising a second SCR catalytically active composition and extending from face side A to face side B of the carrier substrate; wherein the second SCR catalytically active composition in said material zone C consists of a V/TiC>2 SCR catalyst composition which comprises at least one oxide of vanadium supported on titanium dioxide, and wherein the second and the third SCR catalytically active composition are identical or different from one another.

The SCR catalysts with an improved low temperature performance and a good sulfur resistance, the method for making said SCR catalysts and uses thereof are explained below, with the invention encompassing all the embodiments indicated below, both individually and in combination with one another.

The selective catalytic reduction of nitrogen oxides is hereinafter referred to as “SCR” or “SCR reaction”.

A “catalytically active composition” is a substance or a mixture of substances which is capable to convert one or more components of an exhaust gas into one or more other components. An example of such a catalytically active composition is, for instance, an oxidation catalyst composition which is capable of converting volatile organic compounds and carbon monoxide to carbon dioxide or ammonia to nitrogen oxides. Another example of such a catalyst is, for example, a selective catalytic reduction catalyst (SCR) composition which is capable of converting nitrogen oxides to nitrogen and water. In the context of the present invention, an SCR catalyst is a catalyst comprising a carrier substrate and a washcoat comprising an SCR catalytically active composition. An ammonia slip catalyst (ASC) is a catalyst comprising a carrier substrate, a washcoat comprising an oxidation catalyst, and a washcoat comprising an SCR catalytically active composition.

A molecular sieve is a material with pores, i.e. with very small holes, of uniform size. These pore diameters are similar in size to small molecules, and thus large molecules cannot enter or be adsorbed, while smaller molecules can. In the context of the present invention, a molecular sieve is zeolitic. Zeolites are made of corner-sharing tetrahedral SiC>4 and AIO4 units. They are also called “silicoaluminates” or “aluminosilicates”. In the context of the present invention, these two terms are used synonymously. As used herein, the terminology “non-zeolitic molecular sieve” refers to corner-sharing tetrahedral frameworks wherein at least a portion of the tetrahedral sites are occupied by an element other than silicon or aluminum. If a portion, but not all silicon atoms are replaced by phosphorous atoms, it deals with so-called “silico aluminophosphates” or “SAPOs”. If all silicon atoms are replaced by phosphorous, it deals with aluminophosphates or “AlPOs”.

A “zeolite framework type”, also referred to as “framework type”, represents the cornersharing network of tetrahedrally coordinated atoms. It is common to classify zeolites according to their pore size which is defined by the ring size of the biggest pore aperture. Zeolites with a large pore size have a maximum ring size of 12 tetrahedral atoms, zeolites with a medium pore size have a maximum pore size of 10 and zeolites with a small pore size have a maximum pore size of 8 tetrahedral atoms. Well-known small-pore zeolites belong in particular to the AEI, CHA (chabazite), ERI (erionite), LEV (levyne), AFX and KFI framework. Examples having a large pore size are zeolites of the faujasite (FAU) framework type and zeolite Beta (BEA).

A ’’zeotype” comprises any of a family of materials based on the structure of a specific zeolite. Thus, a specific “zeotype” comprises, for instance, silicoaluminates, SAPOs and AlPOs that are based on the structure of a specific zeolite framework type. Thus, for example, chabazite (CHA), the silicoaluminates SSZ-13, Linde R and ZK-14, the sili- coaluminophosphate SAPO-34 and the aluminophosphate MeAIPO-47 all belong to the chabazite framework type. The skilled person knows which silicoaluminates, silico aluminophosphates and aluminophosphates belong to the same zeotype. Furthermore, ze- olitic and non-zeolitic molecular sieves belonging to the same zeotype are listed in the database of the International Zeolite Association (IZA). The skilled person can use this knowledge and the IZA database without departing from the scope of the claims.

The silica to alumina molar ratio (SiC^AhCh) of the zeolites is hereinafter referred to as the “SAR value”.

A “catalyst carrier substrate”, also just called a “carrier substrate” is a support to which the catalytically active composition is affixed and shapes the final catalyst. The carrier substrate is thus a carrier for the catalytically active composition. A “washcoat” as used in the present invention is an aqueous suspension of a catalytically active composition and optionally at least one binder and/or optionally at least one stabilizer. Materials which are suitable binders and stabilizers are, for example, aluminum oxide, titanium dioxide, silicon dioxide, zirconium dioxide, cerium dioxide, lanthanum oxide or mixtures thereof, for example mixtures of silica and alumina.

A washcoat that has been affixed to a catalyst carrier substrate is called a “coating”. It is also possible to affix two or more washcoats to the carrier substrate. The skilled person knows that affixing two or more washcoats onto one single carrier substrate is possible by “layering” or by “zoning”, and it is also possible to combine layering and zoning. In case of layering, the washcoats are affixed successively onto the carrier substrate, one above the other. The washcoat that is affixed first and thus in direct contact with the carrier substrate represents the “bottom layer”, and the washcoat that is affixed last is the “top layer”. In case of zoning, a first washcoat is affixed onto the carrier substrate from a first face side A of the carrier substrate towards the other face side B, but not over the entire length of the carrier substrate, but only to an endpoint which is between face sides A and B. Afterwards, a second washcoat is affixed onto the carrier, starting from face side B until an endpoint between face sides B and A. The endpoints of the first and the second washcoat need not be identical: if they are identical, then both washcoat zones are adjacent to one another. If, however, the endpoints of the two washcoat zones, which are both located between face sides A and B of the carrier substrate, are not identical, there can be a gap between the first and the second washcoat zone, or they can overlap. As mentioned above, layering and zoning can also be combined, if, for instance, one washcoat is applied over the entire length of the carrier substrate, and the other washcoat is only applied from one face side to an endpoint between both face sides.

In the context of the present invention, the “washcoat loading” is the sum of a) the mass of the catalytically active composition per volume of the carrier substrate and b) the masses of the at least one binder and/or at least one stabilizer, if binders and/or stabilizers are present in the washcoat.

The skilled person knows that washcoats are prepared in the form of suspensions and dispersions.

Suspensions and dispersions are heterogeneous mixtures comprising solid particles and a solvent. The solid particles do not dissolve, but get suspended throughout the bulk of the solvent, left floating around freely in the medium. If the solid particles have an average particle diameter of less than or equal to 1 pm, the mixture is called a dispersion; if the average particle diameter is larger than 1 pm, the mixture is called a suspension. Washcoats in the sense of the present invention comprise a solvent, usually water, and suspended or dispersed particles represented by particles of one or more the catalytically active compositions, and optionally particles of at least one binder as described above. This mixture is often referred to as the “washcoat slurry”. The slurry is applied to the carrier substrate and subsequently dried to form the coating as described above. In the context of the present invention, the term “washcoat suspension” is used for mixtures of solvents, particles of one or more catalytically active compositions, and optionally particles of at least one binder, irrespective of the individual or average particle sizes. This means that in “washcoat suspensions” according to the present invention, the size of individual particles as well as the average particle size of the one or more catalytically active solid particles can be less than 1 pm, equal to 1 pm and/or larger than 1 pm.

The term “mixture” as used in the context of the present invention is a material made up of two of more different substances which are physically combined and in which each ingredient retains its own chemical properties and makeup. Despite the fact that there are no chemical changes to its constituents, the physical properties of a mixture, such as its melting point, may differ from those of the components.

The term “mixed oxide”, as used in the present invention, refers to a substance that is composed of several oxides, i.e. whose crystal lattice consists of oxygen ions and the cations of more than one chemical element or cations of a single element in several states of oxidation. More specifically, the term refers to solid ionic compounds that contain the oxide anion O²' and two or more metal cations. A “manganese-containing mixed oxide” is a mixed oxide according to this definition wherein one of the metal cations is a manganese cation. The manganese-containing mixed oxides used in the present invention are mixed oxides in the sense of this definition, because they contain cations of two or more different chemical elements.

By contrast, a “mixture of oxides” is a physical mixture of two or more oxides, wherein each oxide has its own crystal lattice. A physical mixture of MnC>2, CeC>2 and TiC>2, for example, is a mixture of three different oxides with three different crystal lattices, namely those of MnC>2, CeC>2 and TiC>2. On the other hand, one group of the manganese-containing mixed oxides which can be used in the context of the present invention has the general formula Mn_aCebTi_cO_x. In this formula, a, b and c represent the molar fractions of manganese, cerium and titanium, based on the total molar amount of manganese, cerium and titanium in the ternary oxide; and wherein a, b and c are, independently from one another, larger than zero and smaller than 1 ; and wherein a, b and c add up to 1 ; and wherein x is the molar amount of oxygen. In these manganese-containing mixed oxides, cations of manganese, cerium and titanium and anions of oxygen are present in one crystal lattice. The same applies, mutatis mutandis, for the other manganese-containing mixed oxides, which we be explained in more detail below. These manganese- containing mixed oxides are also mixed oxides in the sense of the above definition, by contrast to a mixture of the oxides of the corresponding metals.

A “catalysed substrate monolith” is a carrier substrate comprising a catalytically active composition. The carrier may be coated with a washcoat comprising the catalytically active composition, wherein the washcoat comprises a catalytically active composition and optionally at least one binder. Alternatively, the catalytically active composition can be a component of the carrier substrate itself.

A “device” as used in the context of the present invention is a piece of equipment designed to serve a special purpose or perform a special function. The catalytic devices according to the present invention serve the purpose and have the function to remove nitrogen oxides from the exhaust gas of combustion engines. A “device” as used in the present invention may consist of one or more catalyst, also called “catalytic articles” or “bricks” as defined above.

“Upstream” and “downstream” are terms relative to the normal flow direction of the exhaust gas in the exhaust pipeline. A “zone or catalyst 1 which is located upstream of a zone or catalyst 2” means that the zone or catalyst 1 is positioned closer to the source of the exhaust gas, i.e. closer to the motor, than the zone or catalyst 2. The flow direction is from the source of the exhaust gas to the exhaust pipe. Accordingly, in this flow direction the exhaust gas enters each zone or catalyst at its inlet end, and it leaves each zone or catalyst at its outlet end.

The term “nitrogen oxides”, as used in the context of the present invention, encompasses nitrogen monoxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O). By contrast, the term “NO_X”, however, only encompasses NO and NO2, but not N2O, although nitrous oxide is also an oxide of nitrogen. This distinction between “nitrogen oxides” and “NOx” is, however, widely used by skilled persons. The term “NO_X conversion”, as used in the context of the present invention, means the percent conversion of NO_X without taking N2O in the gas phase after the catalyst into account. “N2O selectivity” means the percent conversion of NO_X and NH3 in the gas feed into N2O.

The N2O selectivity can be calculated according to the equation

Wherein

IX^Oin = amount of N2O at the inlet end of a catalytic device IXhOout = amount of N2O at the outlet end of a catalytic device

NH₃,in = amount of NH3 at the inlet end of a catalytic device

N Hs.out = amount of NH3 at the outlet end of a catalytic device

NO_x,in = amount of NO_X at the inlet end of a catalytic device

NO_x,out = amount of NO_X at the outlet end of a catalytic device

The “catalytic activity” or just “activity” is the increase in rate of a chemical reaction caused by the presence of a catalytically active composition.

The skilled person knows that the SCR reaction requires a reductant to reduce nitrogen oxides to nitrogen and water. A suitable reductant is ammonia, and the SCR reaction in presence of ammonia is known as “NH3-SCR”. The ammonia used as reducing agent may be made available by feeding liquid or gaseous ammonia or an ammonia precursor compound into the exhaust gas. If an ammonia precursor is used, it is thermolyzed and hydrolyzed to form ammonia. Examples of such ammonia precursors are ammonium carbamate, ammonium formate and preferably urea. Alternatively, the ammonia may be formed by catalytic reactions of the ammonia precursor within the exhaust gas.

The skilled person knows that the NO_X conversion of an exhaust gas comprising NO_X depends on several factors, for example on the chemical nature of the SCR catalytically active composition, the amount of the SCR catalytically active composition that is present in the catalytic device, the NO2 to NO_X ratio of the exhaust gas, the temperature of the exhaust gas, and the presence and quantity of catalyst poisons. There is a constant need for SCR catalysts that show a good NOx conversion over a large temperature range, in particular at low temperatures, and that are, at the same time, sulfur-tolerant, i.e. which are not easily intoxicated or deactivated by sulfur components in the exhaust gas. Well- known SCR catalytically active compositions are a) mixed oxides comprising oxides of vanadium and titanium, b) transition metal-promoted zeolites and c) ternary mixed oxides comprising manganese, cerium and titanium.

Mixed oxides comprising oxides of titanium and vanadium show a good NO_X conversion at low temperatures, but their NO_X conversion at high temperatures is not as good as that of transition metal-promoted zeolites. However, mixed oxides comprising oxides of titanium and vanadium are largely sulfur-tolerant. Transition-metal promoted zeolites show a good NO_X conversion over a wide temperature range. They show the best NO_X conversion at high temperatures of all three groups of SCR catalytically active compositions mentioned above. Transition metal-promoted zeolites are prone to sulfur intoxication and sulfur deactivation; but the intoxication and deactivation is partly reversible. Ternary mixed oxides comprising manganese, cerium and titanium show the best low temperature NO_X conversion, but they are very sensitive to sulfur intoxication and deactivation, and in their case, the intoxication and deactivation is not reversible.

The object of the present invention to provide SCR catalytic devices with an improved low temperature performance and, concomitantly, a good sulfur resistance is solved by combining mixed oxides comprising oxides of vanadium and titanium with ternary oxides comprising manganese, cerium and titanium, and optionally also with transition metal- promoted zeolites in such a way that good NO_X conversion over the a broad temperature range, in particular at low temperatures, and at the same time high sulfur tolerance result.

The carrier substrates of the catalytic devices according to the present invention can be so-called honeycomb flow-through substrates and wall-flow filters as well as corrugated substrates, extruded substrates, wound or packed fiber filters, open cell foams and sintered metal filters. In a preferred embodiment, the carrier substrate is a honeycomb flow- through substrate, a wall-flow filter or a corrugated substrate.

Flow-through substrates and wall-flow filters may consist of inert materials, such as silicon carbide, aluminum titanate and cordierite. Such carrier substrates are well-known to the skilled person and available on the market. Corrugated substrates are made of ceramic E-glass fiber paper or of metal or metal alloys. They are also well known to the skilled person and available on the market.

A bottom layer comprising a material zone D is affixed to the carrier substrate. Said material zone D extends from face side B over a length L_z which is 20 to 100% of the length L of the carrier substrate. Preferably, L_z is 30 to 100%, more preferably 35 to 95% of the length L.

The first SCR catalytically active composition in said material zone D consists of one or more manganese-containing mixed oxides, or a mixture of one or more manganese- containing mixed oxides and one or more metal-promoted small-pore zeolites.

In one embodiment, the first SCR catalytically active composition in said material zone D consists of one or more manganese-containing mixed oxides.

The manganese-containing mixed oxides can be selected from manganese cerium titanium oxides Mn_aCebTi_cO_x. In this formula, a, b and c represent the molar fractions of manganese, cerium and titanium, based on the total molar amount of manganese, cerium and titanium in the ternary oxide; and wherein a, b and c are, independently from one another, larger than zero and smaller than 1 ; and wherein a, b and c add up to 1 ; and wherein x is the molar amount of oxygen.

In one embodiment, a ranges from 0.05 to 0.50, preferably from 0.10 to 0.40, more preferably 0.12 to 0.35; b ranges from 0.05 to 0.50, preferably from 0.10 to 0.40, more preferably 0.12 to 0.3; and c ranges from 0.30 to 0.90, preferably from 0.35 to 0.80, more preferably 0.40 to 0.75, provided that a + b + c add up to 1 as described above; and x ranges from 1.5 to 2. The molar ratios of manganese, cerium and titanium may vary, as will be explained in more detail below. Therefore, the molar ratios of Mn, Ce and Ti are indicated with a, b and c in the general formula. The molar ratio of oxygen is likewise indicated with x. The skilled person knows that the molar ratio of oxygen must be selected so that electrical neutrality of the ternary mixed oxide Mn_aCebTi_cO_x is given.

The manganese-containing mixed oxides can furthermore be selected from compounds having the general formula MndMei-dO_w, wherein d, 1-d and w represent the molar fractions of manganese, a metal Me and oxygen. The metal Me is selected from the group consisting of Fe, Co, Ni, Cu, Zr, Nb, Mo, W, Ag, Sn, Ce, Pr, La, Nd, Ti, Al, Si and Y. Me is particularly advantageously selected from Fe, Cu, Nb, Mo, W, Sn, Al, Si and Ti. More preferably, Me is selected from Fe, Cu, Nb, W, Al and Si. In this embodiment, d ranges from 0.02 to 0.98 and w ranges from 1.0 to 2.5. As above, the skilled person knows that the molar ratio of oxygen must be selected so that electrical neutrality of the binary mixed oxide MndMei-dOw is given. The manganese-containing mixed oxides can furthermore be selected from compounds having the general formula Mn_eCefMei-_e.fO_v, wherein e, f, 1-e-f- and v represent the molar fractions of manganese, cerium, the metal Me and oxygen. The metal Me is selected from the group consisting of Fe, Co, Ni, Cu, Zr, Nb, Mo, W, Ag, Sn, Ce, Pr, La, Nd, Ti, Al, Si and Y. Me is particularly advantageously selected from Fe, Cu, Nb, Mo, W, Sn, Al, Si and Ti. More preferably, Me is selected from Fe, Cu, Nb, W, Al and Si. In this embodiment, e ranges from 0.02 to 0.98, f ranges from 0.02 to 0.98 and v ranges from 1.0 to 2.5. As above, the skilled person knows that the molar ratio of oxygen must be selected so that electrical neutrality of the ternary mixed oxide Mn_eCefMei-_e.fO_v is given.

The manganese-containing mixed oxides can furthermore be selected from spinels having the general formula MnS2C>4 or SM^CL, wherein S is selected from Fe, Al, Cr, Co and Cu.

If the first SCR catalytically active composition in material zone D consists of one manganese-containing mixed oxide, said manganese-containing mixed oxide can be selected from any of the compounds having the general formula Mn_aCebTi_cO_x, MndMei-dO_w, Mn_eCefMei-_e.fO_v, MnS2C>4 or SM^CL as defined above.

If the first SCR catalytically active composition in material zone D consists of two or more manganese-containing mixed oxides, said manganese-containing mixed oxides can be selected from any of the compounds having the general formula Mn_aCebTi_cO_x, MndMei. dO_w, Mn_eCefMei-_e.fO_v, MnS2C>4 or SM^CL as defined above. This means that, if it deals with two manganese-containing mixed oxides, it can deal with a) two manganese-containing mixed oxides having the same general formula, but different molar ratios of the elements; or it can deal b) with two manganese-containing mixed oxides having different general formulas. If it deals with at least three manganese-containing mixed oxides, said mixed oxides can be c) all selected from manganese-containing mixed oxides having the same general formula, but different molar ratios of the elements; or d) they can be selected from manganese-containing mixed oxides having all different structural formulas, or e) it can deal with a mixture of manganese-containing mixed oxides having the same general formula, but different molar ratios of the elements and manganese-containing mixed oxides having different structural formulas.

In another embodiment, the first SCR catalytically active composition in said material zone D consists of a mixture of one or more manganese-containing mixed oxides and one or more metal-promoted small-pore zeolites. In this embodiment, the manganese- containing mixed oxides are selected from compounds having the general formula Mn_aCebTi_cO_x, MndMei-dO_w, Mn_eCefMei-_e.fO_v, MnS2C>4 or SMn2O4 as defined above.

Suitable small-pore zeolites, which have a maximum pore size of eight tetrahedral atoms as explained above, are, for instance, AGO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, 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 mixtures and intergrowths thereof.

In a preferred embodiment of the present invention, the small-pore zeolites are chosen from AEI, AFT, AFX, CHA, DDR, ERI, ESV, ETL, KFI, LEV, UFI and mixtures and intergrowths thereof. In a more preferred embodiment, the zeolites are selected from AEI, CHA, AFX, LEV, ERI and mixtures and intergrowths that contain at least one of these framework types. Even more preferred, the zeolites are chosen from AEI and CHA and mixtures and intergrowths that contain at least one of these framework types. In a particularly preferred embodiment, the zeolite is AEI. In another particularly preferred embodiment, the zeolite is CHA.

An “intergrowth” of a zeolite comprises at least two different zeolite framework types or two different zeolite compositions of the same framework type.

In an “overgrowth” zeolite, one framework structure grows on top of the other one. Thus, “overgrowth” represents a species of “intergrowth”, and “intergrowth” is the genus.

If the small-pore zeolite has the CHA framework type, this comprises all zeotypes having the CHA framework type, provided that they are crystalline aluminosilicates. Such zeotypes are, for example, SSZ-13, LZ-218, Linde D, Linde R, Phi, ZK-14, with SSZ-13 being preferred.

If the small-pore zeolite has the AEI framework type, this comprises all zeotypes having the AEI framework type, provided that they are crystalline aluminosilicates. Such zeotypes are, for instance, SSZ-39 and SIZ-8.

If the small-pore zeolite has the AFX framework type, this comprises all zeotypes having the AFX framework type, provided that they are crystalline aluminosilicates. Such a ze- otype is, for instance, SSZ-16.

If the small-pore zeolite has the LEV framework type, this comprises all zeotypes having the LEV framework type, provided that they are crystalline aluminosilicates. Such zeotypes are, for instance, ZK-20, LZ-132 and Nu-3. If the small-pore zeolite has the ERI framework type, this comprises all zeotypes having the ERI framework type, provided that they are crystalline aluminosilicates. Such zeotypes are, for instance, LZ-220, UZM-12 and SSZ-98.

The small-pore zeolite has a molar ratio of silica-to-alumina (SAR) value of 5 to 50, preferably 6 to 40, more preferably 7 to 30.

The at least one small-pore zeolite is metal-promoted. In embodiments of the present invention, the small-pore zeolite is promoted with copper and optionally with one or two additional metals M1 and M2. The copper to aluminum atomic ratio in these zeolites is between 0.12 and 0.55, and the copper content is between 2.0 and 6.5wt.-%, calculated as CuO and based on the total weight of the zeolite. If promoter metals M1 and M2 are present, they are, independently from one another, selected from magnesium, calcium, barium, strontium, yttrium, titanium, zirconium, niobium, manganese, iron, zinc, silver, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, provided that, if both M1 and M2 are present, they are different from one another.

In one embodiment, copper is the only promoter metal, and the Cu:AI atomic ratio is between 0.12 and 0.55.

In embodiments wherein only one promoter metal M1 is present in addition to copper, the M1 :Cu atomic ratio is in the range of 0.05 to 0.95, and the (Cu + M1) : Al atomic ratio is in the range of 0.11 to 0.96.

In embodiments wherein two promoter metals M1 and M2 are present in addition to copper, the M1 :Cu ratio and the M2:Cu atomic ratio are both in the range of 0.05 to 0.95, and the (Cu + M1 + M2) : Al atomic ratio is in the range of 0.2 to 0.80, under the proviso that M1 and M2 are different from one another.

As mentioned above, the copper content in all these embodiments is between 2.0 to 6.5 wt.-% calculated as CuO and based on the total weight of the zeolite.

In one embodiment, the at least one small-pore zeolite is promoted with copper and a metal M1 which is manganese, but not with a metal M2. In this embodiment, the smallpore zeolite comprises 2.0 to 6.5 wt.-% copper, calculated as CuO and based on the total weight of the zeolite, and the Cu : Al molar ratio is between 0.12 to 0.40. The (Cu + Mn) : Al molar ratio ranges between 0.11 and 0.96. In this embodiment, the preferred SAR value is between 7 and 30. The small-pore zeolite preferably has a CHA framework type. More preferably, the zeolite has a CHA framework type and a SAR value of between 7 and 30.

In another embodiment, the at least one small-pore zeolite is promoted with copper and two additional metals. In this embodiment, the small-pore zeolite comprises at least 2.0 wt.-% copper, calculated as CuO and based on the total weight of the zeolite, and the Cu : Al molar ratio is between 0.12 and 0.55. The first additional metal M1 is manganese, and the Mn : Cu atomic ratio is between 0.05 and 0.95. The second additional metal M2 is selected from magnesium, calcium, barium, strontium, yttrium, titanium, zirconium, niobium, iron, zinc, silver, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and mixtures thereof, and the M2:Cu atomic ratio is between 0.05 and 0.80. The sum of the atomic ratios of the metals Cu, Mn and M2 to aluminum; (Cu + Mn + M2) : Al is between 0.20 and 0.80. The at least one small-pore zeolite preferably has as framework type selected from AEI, CHA, AFX and LEV and a SAR value of 5 to 50, preferably 6 to 30, more preferably 7 to 25. Most preferably, the small-pore zeolite has a CHA or AEI framework and is promoted with copper, manganese, and a metal M2 selected from Fe, and Sm.

In yet another embodiment, the at least one small-pore zeolite is promoted with copper and two additional metals. In this embodiment, the small-pore zeolite comprises at least 2.0 wt.-% copper, calculated as CuO and based on the total weight of the zeolite, and the Cu : Al molar ratio is between 0.12 and 0.55. The first additional metal M1 is selected from calcium, magnesium or strontium, wherein the M1 : Cu atomic ratio is between 0.10 and 0.92. The second additional metal M2 is selected from magnesium, calcium, barium, strontium, yttrium, titanium, zirconium, niobium, iron, zinc, silver, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and mixtures thereof. The M2 : Cu atomic ratio is between 0.05 and 0.80; and M1 and M2 are different from one another. In this embodiment, the small-pore zeolite does not comprise manganese. The sum of the atomic ratios of copper, metal M1 and metal M2 to aluminum, (Cu + M1 + M2) : Al, is between 0.20 and 0.80. The small-pore zeolite preferably has as framework type selected from AEI, CHA, AFX and LEV and a SAR value of 5 to 50, preferably 6 to 30, more preferably 7 to 25. Most preferably, the small-pore zeolite has a CHA or AEI framework and is promoted with copper, a metal M1 which is calcium, and a metal M2 selected from Fe, and Sm.

It is possible to use only one metal-promoted small-pore zeolite or mixtures or at least two metal-promoted small-pore zeolites. In the latter case, the at least two metal-promoted small-pore zeolites can be selected from all embodiments described above.

Furthermore, if at least two metal-promoted small-pore zeolites containing copper are used, they are different from one another.

This means that they differ from one another in at least one of the following features:

- they have different framework structures and/or

- they belong to the same framework structure, but represent different ze- otypes, and/or

- they have different SAR values, and/or

- their Cu:AI atomic ratios are different, and/or

- they contain different metals M1 and M2, in case M2 is present, and/or,

- they all contain only a metal M1 , but not a metal M2, and the metal M1 is the same in all zeolites, but the ratios (Cu+M1):AI are different, and/or

- they contain the same metals M1 and M2, but the atomic ratios of the individual metals copper, M1 and M2, (Cu+M_totai):AI, are different.

In a preferred embodiment, only one metal promoted small pore zeolite, selected form the zeolites promoted with copper only or with copper and a metal M1 , or with copper and metals M1 and M2, as described above, is used.

In embodiments wherein the SCR catalytically active composition in material zone D consists of a mixture of at least one manganese-containing mixed oxide and at least one metal-promoted small-pore zeolite, the weight ratio of at least one manganese-containing mixed oxide to the at least one metal-promoted small-pore zeolite is in the range of 0.1 to 99 wt.%, preferably 1 to 90 wt%.

The catalytic device according to the present invention comprises a bottom layer comprising a material zone C’ affixed to the carrier substrate said material zone C’ comprising a third SCR catalytically active composition and extending from face side A over a length L_y = L - L_z which is 80 to 0% of the total length of the carrier substrate, and a top layer affixed to the bottom layer, said top layer comprising a material zone C comprising a second SCR catalytically active composition and extending from face side A to face side B of the carrier substrate. Both the second and the third SCR catalytically active composition consist of a V/TiCh SCR catalyst composition which comprises at least one oxide of vanadium supported on titanium dioxide. The second and the third SCR catalytically active composition are identical or different from one another.

In embodiments wherein the length L_z of material zone D is less than 100%, said material zone C’ is also present, said material zone C’ extending from face side A of the carrier substrate over a length L_y = L - L_z. Material zone C’ is also affixed to the carrier substrate. In embodiments wherein the length L_z of material zone D is 100%, a material zone C’ is not present, because material zone D extends over the entire length of the carrier substrate from face side A to face side B.

The second and third SCR catalytically active composition in said material zones C and C’ consist of at least one oxide of vanadium supported on titanium dioxide. Such SCR catalyst compositions are known to the skilled person. They are based on titanium dioxide and oxides of vanadium, in particular vanadium pentoxide and vanadium dioxide. The titanium dioxide can be selected from anatase, rutile, brookite, and mixtures thereof. Suitable titanium dioxides comprise at least 95 wt.-% of anatase, preferably at least 98 wt.-%, and even more preferably at least 99.5 wt.-%. The remainder for adding up to 100 wt.-% is preferably represented by rutile and/or brookite, more preferably by rutile. SCR catalyst compositions comprising at least one oxide of vanadium supported on titanium dioxide are hereinafter referred to as “V/TiC>2 catalyst compositions”.

The V/TiC>2 catalyst compositions may additionally contain other oxides, such as those of silicon, molybdenum, tungsten, antimony, niobium, tantalum, hafnium, zirconium, cerium and mixtures thereof.

In embodiments of the present invention, the second and third V/TiC>2 SCR catalyst compositions comprise, independently from one another

- at least one oxide of vanadium in an amount of 1 to 10 wt.-%, and

- at least one oxide of tungsten in an amount of 0 to 15 wt.-%, and,

- at least one oxide of silicon in an amount of 0 to 18 wt.-%, and

- at least one oxide of molybdenum, antimony, niobium, zirconium, tantalum, hafnium, cerium in a total amount of these oxides of 0 to 20 wt.-%, and

- at least one oxide of titanium in an amount that is measured so as to result in a total of 100 wt.-%, in each case based on the total weight of the V/TiC>2 catalyst and calculated as V2O5, WO3, SiC>2, MO2O3, Sb20s, Nb20s, ZrC>2, Ta20s, HfC>2, CeC>2 or TiC>2.

As will be understood by the skilled person, the above composition mandatorily contains oxides of vanadium and titanium, and optionally oxides of tungsten, silicon, molybdenum, antimony, niobium, zirconium, tantalum, hafnium, cerium or mixtures thereof in the amounts as given above.

In one embodiment, the second and third V/TiCh SCR catalyst compositions contain, independently from one another,

- at least one oxide of vanadium in an amount of 1 to 6.5 wt.-%, preferably 2 to 5 wt.-%, and

- at least one oxide of tungsten in an amount of 0 to 15 wt.-%, preferably 1 to 9 wt- %, and

- at least one oxide of antimony in an amount of 0 to 5 wt.-%, preferably 0 to 5 wt.- %, and

- at least one oxide of zirconium in an amount of 0 to 1 .0 wt.-%, preferably 0 wt.- %, and

- at least one oxide of cerium in an amount of 0 to 5 wt.-%, preferably 0 to 2 wt.- %, and

- at least one oxide of titanium in an amount that is measured so as to result in a total of 100 wt.-%, in each case based on the total weight of the V/TiCh catalyst and calculated as V2O5, WO3, Sb20s, ZrC>2, CeC>2 or TiC>2.

More preferably, the V/TiC>2 catalyst of this embodiment does not contain any oxide of zirconium, based on the total weight of the V/TiCh catalyst composition and calculated as ZrC>2.

In yet another embodiment, the second and third V/TiCh SCR catalyst compositions contain, independently from one another,

- at least one oxide of vanadium in an amount of 2.0 to 6.0 wt.-%, and

- at least one oxide of tungsten in an amount of 0.5 to 2.0 wt.-%, and

- at least one oxide of antimony in an amount of 1 .0 to 7.0 %, and

- at least one oxide of cerium in and amount of 2.0 to 4.0 wt.-%, and

- optionally at least one oxide of silicon in an amount of 2.0 to 7.0 wt.-%, and

- optionally at least one oxide of molybdenum, niobium, zirconium, tantalum and/or hafnium in a total amount of these oxides of 0.5 to 20.0 wt.-%, and - at least one oxide of titanium in an amount that is measured so as to result in a total of 100 wt.-%, in each case based on the total weight of the V/TiCh catalyst and calculated as V2O5, WO3, Sb2Os, CeC>2, SiC>2, MoOa, Nb2Os, ZrC>2, Ta2Os, HfC>2 or TiC>2.

More preferably, the V/TiCh catalyst of this embodiment contains at least one oxide each of vanadium, tungsten, antimony, cerium, silicon and titanium as listed above, but no oxides of molybdenum, niobium, zirconium, tantalum and/or hafnium.

In yet another embodiment, the second and third V/TiCh catalyst compositions contain, independently from one another,

- at least one oxide of vanadium in an amount of 2.0 to 6.0 wt.-%, and

- at least one oxide of cerium in and amount of 2.0 to 4.0 wt.-%, and

- at least one oxide of niobium in an amount of 1.0 to 7.0 %, and

- optionally at least one oxide of tungsten in an amount of 0.001 to 2.0 wt.-%, and

- optionally at least one oxide of molybdenum, antimony, zirconium, tantalum and/or hafnium in a total amount of these oxides of 0.5 to 20.0 wt.-%, and

- at least one oxide of titanium in an amount that is measured so as to result in a total of 100 wt.-%, in each case based on the total weight of the V/TiCh catalyst and calculated as V2O5, CeC>2, Nb20s, WO3, SiC>2, MoOs, Sb20s, ZrC>2, Ta2Os, HfC>2 or TiC>2.

More preferably, the V/TiCh catalyst of this embodiment contains at least one oxide each cerium, niobium and titanium and at least one oxide of silicon and/or tungsten as listed above, but no oxides of molybdenum, antimony, zirconium, tantalum and/or hafnium.

- at least one oxide of vanadium in an amount of 4.0 to 6.0 wt.-%, and

- at least one oxide of tungsten in an amount of 0.5 to 2.0 wt.-%, and

- at least one oxide of antimony in an amount of 4.0 to 6.0 %, and

- at least one oxide of cerium in and amount of 2.0 to 4.0 wt.-%, and

- at least one oxide of titanium in an amount that is measured so as to result in a total of 100 wt.-%, in each case based on the total weight of the V/TiCh catalyst and calculated as V2O5, WO3, Sb20s, CeC>2, or TiC>2. In embodiments of the V/TiC>2 catalyst composition wherein at least one oxide of silicon is present, said oxide can be present in the form of silica-doped titanium dioxide, or as a separate oxide of silicon, or a mixture of both. The skilled person knows how to calculate the total amount of silica present in the V/TiC>2 catalyst composition.

In embodiments of the present invention, the V/TiO2 catalyst compositions in the material zone C and C’ can be identical or different from one another. If they are different from one another, they differ from one another in that they either comprise oxides of different metals, and/or they comprise oxides of the same metal, but in different amounts. For example, one of these two catalyst compositions can comprise Sb20s, but no Nb20s, whereas the other one comprises Nb20s, but no Sb20s. Alternatively, they can both comprise Sb₂O₅, but in different amounts.

If the catalyst compositions in material zones C and C’ are identical, this means that both compositions comprise the same oxides in identical amounts. In a preferred embodiment, the catalyst compositions in material zones C and C’ are identical.

The skilled person knows that the amount of the at least one oxide of vanadium in the V/TiC>2 SCR catalyst composition can be adjusted according to the intended NO_X conversion at different temperatures: if a high NO_X conversion at low temperatures, e.g. below 250°C, is needed, the amount of vanadium oxides should be rather high. A high amount of oxides of vanadium will, however, decrease the NO_X conversion of the V/TiCh SCR catalyst compositions at high temperature, e.g. above 400 °C. By contrast, a rather low amount of oxides of vanadium will increase the NO_X conversion at high temperatures, e.g. above 400°C, and at the same decrease the NO_X conversion at low temperatures. “High” and “low” amounts of oxides of vanadium refer to the lower and upper limits for these oxides as given above. In other words: the closer the amount of vanadium oxides is to the upper limits of the amounts given above, the better the NO_X conversion at low temperatures, and vice versa.

The amounts of copper, manganese, titanium, vanadium, aluminum, silicon, magnesium, calcium, barium, strontium, molybdenum, antimony, niobium, zirconium, tantalum, hafnium, iron, zinc, silver, platinum, palladium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium can be measured by ICP-AES (inductively coupled plasma atomic emission spectroscopy), ICP-OES (inductively coupled plasma optical emission spectroscopy) or XRF (X-ray fluorescence spectroscopy). Energy-dispersive X-ray spectroscopy, known as EDS, EDX, or EDXS) allows to analyze elements having an atomic number of 8 or larger, thus enable the measurement of the above- mentioned mentals and oxygen alike. The skilled person knows how to perform such analyses and can apply this knowledge to the zeolites according to the present invention without departing from the scope of the claims. It is furthermore common knowledge that many of the metals mentioned above occur in more than one oxidation state. For example, vanadium, antimony and niobium can occur in the oxidation states III and V, and therefore, they can form the oxides V2O3, VO2, V2O5, Sb20a, Sb20s, Nb20a and Nb20s. With the methods indicated above, in particular with EDX, the skilled person can easily detect these oxides and convert the result for the oxide of a specific metal in one oxidation state to the corresponding value for the oxide of the same metal in a different oxidation state.

SAR values of zeolites can be determined by FTIR. Metal to metal molar ratios, for example copper to aluminum molar ratios or copper to manganese molar ratios in zeolites can be measured by ICP-OES. These methods are known to the skilled person and can be applied in the context of the present invention without departing from the scope of the claims.

The material zones C, D, and optionally C’ are affixed to the carrier substrate or to the bottom layer, respectively, in the form of washcoat suspensions using known wash-coating techniques.

In embodiments of the present invention, the washcoat loading in the material zones C and, if present, C’, is, independently from one another, in the range of from 25 to 400 g/L, preferably 50 to 300 g/L. If material zone C’ is present, its washcoat loading is preferably identical to that of material zone C.

In embodiments of the present invention, the washcoat loading in material zone D is in the range of from 50 to 300 g/L, preferably 70 to 250 g/L. This applies for embodiments wherein the first SCR catalytically active composition in material zone D consists of one or more manganese-containing mixed oxides as well as for embodiments wherein the first SCR catalytically active composition in material zone D consists of a mixture of one or more manganese-containing mixed oxides and one or more metal-promoted smallpore zeolites. In other embodiments of the present invention, the total washcoat loading of the material zones C, D and optionally C’ is in the range of from 75 to 450 g/L.

In a preferred embodiment, the washcoat loadings of material zones C and optionally C’ are identical and in the range of from 25 to 250 g/L each, the washcoat loading of material zone D is in the range of from 50 to 250 g/L, and the total washcoat loading of material zones C, D and optionally C’ is in the range of from 75 to 400 g/L.

In this approach the solid catalyst composition, which is usually present in the form of a powder, is suspended in a liquid medium, preferably water, optionally together with binder(s) and/or stabilizer(s). The washcoat suspension can then be affixed to the carrier substrate or onto the bottom layer. Independently from one another, the washcoat suspensions optionally also contain binders selected from TiC>2, SiC>2, AI2O3, ZrC>2, CeC>2, La2C>3 and combinations thereof. Preferably, the binder is present in an amount of 0 to 20 wt.-%, preferably in an amount of 0.1 to 20 wt.-%, more preferably 0.2 to 15 wt.-%, based on the total weight of the SCR catalytically active composition and the binder.

The washcoat suspension may furthermore optionally comprise an additive. The additive may be present together with a binder, as mentioned above, or the washcoat suspension may comprise only a binder or only an additive. Suitable additives are polysaccharides, linear or branched primary or secondary polyhydric alcohols, polyvinylalcohols, aminoalcohols, dialkyl sulfosuccinate salts, glycerol; linear or branched-chain poly-functionalized organic molecules having two or more carbon atoms in the chain, with up to about 12 carbon atoms (C_n; wherein 2 < n < 12); salts of basic quaternary amines, wherein one or more quaternary amine groups are attached to four carbon chains having length of C_n, where 1 < n < 5 and wherein the cation is balanced as a salt using, but not limited to, one of the following anions: hydroxide, fluoride, chloride, bromide, iodide, carbonate, sulfate, sulfite, oxalate, maleate, phosphate, aluminate, silicate, borate, or other suitable organic or inorganic counter ions; inorganic bases taken from, but not limited to the following list: lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide; and, simple salts of transition or rare earth elements, including, but not limited to the following: nitrates, carbonates, sulfates, phosphates, borates of rare earth elements from atomic number 57 (La) to 71 (Lu) and including Sc, Y, Ti, Zr, and Hf, as mentioned above.

In one embodiment, the additive is a polysaccharide selected from the group consisting of a galactomannan gum, xanthan gum, guar gum curdlan, Schizophyllan, Scleroglucan, Diutan gum, Welan gum, a starch, a cellulose or an alginate or is derived from a starch, a cellulose (i.e. cellulosic) or an alginate, and mixtures of thereof. Cellulosic additives may be selected from the group consisting of carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose and ethyl hydroxyethyl cellulose. Preferably, the polysaccharide is selected from xanthan gum, guar gum or a mixture thereof. Even more preferably the additive is xanthan gum.

In another embodiment, the additive is a dialkyl sulfosuccinate salt. The dialkyl sulfosuccinate can optionally be admixed with a linear or branched primary or secondary polyhydric alcohol.

The washcoat suspension may furthermore additionally comprise pH modifiers, surfactants and/or antifoaming agents. The skilled persons knows suitable pH modifiers, surfactants, antifoaming agents and can apply them without departing from the scope of the claims.

In case the first, second and/or the third washcoat suspension comprises an additive, said additive is present in an amount of up to 20 wt.-%, preferably 3 to 15 wt.-%, more preferably 6 to 10 wt.-%, based on the total weight of the oxides, wherein the “total weight of the oxides” is the sum of weights of the metal oxides, zeolite (if present) and the binder. It will be understood that, if the washcoat suspension does not comprise a binder, the “total weight of the oxides” corresponds to the weight of metal oxides and the zeolite (if present). The first, second and third washcoat suspensions contain the first, second and third SCR catalytically active compositions, respectively.

The washcoat suspensions for the material zones C, D and optionally C’, may, independently from one another, only contain the respective SCR catalyst composition, or the SCR catalyst composition and at least one binder, or the SCR catalyst composition and at least one additive, or the SCR catalyst composition and at least one binder and at least one additive, each together with at least one solvent, which is preferably water. In one embodiment, the washcoat suspension for material zone D comprises the at least one SCR catalytically active composition, at least one binder, and at least one additive, together with the at least one solvent. Preferably, the washcoat suspension for material zone D comprises the SCR catalytically active composition, at least one binder, and at least one solvent, but no additive.

In another embodiment, the washcoat suspensions for material zones C and optionally C’ comprise the at least one V/TiC>2 SCR catalyst composition, at least one binder, and at least one additive, together with the at least one solvent. Preferably, the washcoat suspensions for material zones C and C’ comprise the at least one metal-promoted zeolite, at least one additive, and at least one solvent, but no binder.

Preferably, the washcoat suspension for material zone D contains the respective SCR catalytically active composition, water and at least one binder, and the washcoat suspensions for material zones C and optionally C’ comprise the V/TiCh SCR catalyst composition, water and at least one additive.

In all embodiments, the at least one binder and/or at least one additive in the washcoat suspensions for material zones C, D and optionally C’ can be identical or different from one another.

In one embodiment, the compositions of the washcoat suspensions for material zones C and C’ are identical. This means that the second washcoat suspension is used for affixing both material zones C and C’.

When preparing the first, second and/or third washcoat suspension, the one or more manganese-containing mixed oxide and, if present, the one or more metal-promoted small-pore zeolites, as well as the components of the V/TiC>2 SCR catalyst composition can optionally be milled. The same applies for the binder, if it shall be present in the washcoat. Milling can take place before suspending the one or more manganese-containing mixed oxide and the one or more metal-promoted small-pore zeolite and/or the binder and/or the additive and/or pH modifiers and/or surfactants and/or antifoaming agents, or afterwards. Milling can, for example, be carried by circular milling in a bead mill, an agitator mill or an agitator bead mill.

Coating a carrier substrate is well known to the skilled person. First, the carrier substrate is oriented such that the channels thereof are substantially vertical. Then, the washcoat suspension is brought into contact with the carrier substrate, either by a bottom-up or a top-down process. In case of a bottom-up process, the carrier substrate is dipped into the washcoat suspension, or the washcoat suspension is pumped into the carrier substrate from the lower end face of the substrate to the upper end face. In case of a top- down process, the washcoat suspension is poured or pumped onto the upper end face of the carrier substrate. In both cases, the application of the washcoat suspension can optionally be performed under vacuum or over-pressure. Furthermore, in both cases, excess washcoat suspension can optionally be removed by applying vacuum or overpressure. After the application of the washcoat suspension and, optionally, removal of excess washcoat suspension, the washcoated carrier substrate is dried and calcined.

The procedure described above is repeated to apply a second or further washcoats. Optionally, the carrier substrate which has been coated with the first washcoat can be turned 180 degrees so that the former lower end face becomes the new upper end face and vice versa prior to the application of the second or further washcoat.

Methods for making the novel SCR catalytic devices and uses thereof are also envisaged.

In a first embodiment, the method for making the SCR catalytic devices according to the present invention comprises the following steps: a) orienting the carrier substrate such that the channels thereof are substantially vertical, b) pumping the first washcoat suspension into the carrier substrate from the lower end face over a length L_z, c) sucking out excess first washcoat suspension from the lower end face, d) drying and calcining the washcoated carrier substrate obtained after step d), e) orienting the washcoated carrier substrate obtained after step d) such that the channels thereof are substantially vertical, f) pouring the second washcoat suspension onto the upper end face of the carrier substrate obtained after step e), g) applying vacuum at the lower end face of the carrier substrate and soaking the second washcoat suspension applied in step f) through the monolith, h) drying and calcining the washcoated carrier substrate obtained after step g).

Drying the monolith in steps d) and h) is preferably carried out at a temperature of between 100 and 150°C, preferably 110 to 130 °C.

Calcining the monolith in steps d) and h) is preferably carried out at a temperature of between 300 and 700°C.

In step e), the washcoat carrier substrate is oriented such that the channels thereof are substantially vertical. This can mean that the end face which has been the lower end face in step b) also becomes the lower end face in step e). Alternatively, the end face which has been the lower end face in step b) can become the upper end face in step e). This latter option is preferred in case the carrier substrate is a wall-flow filter.

Alternatively, the first washcoat can be poured onto the upper end face of the carrier substrate in step b), followed by sucking out excess washcoat in step c), if material zone D shall extend over the entire length L of the carrier substrate; and/or the second washcoat can be pumped into the carrier substrate from the lower end face in step f), followed by step g), which is applying vacuum at lower end face of the carrier substrate and soaking the second washcoat suspension applied in step f) through the monolith.

In a second embodiment, the method for making the SCR catalytic devices according to the present invention comprises the following steps: a) orienting the carrier substrate such that the channels thereof are substantially vertical, b) pumping the first washcoat suspension into the carrier substrate from the lower end face over a length L_z, c) sucking out excess first washcoat suspension from the lower end face, d) drying and calcining the washcoated carrier substrate obtained after step d), e) orienting the carrier substrate such that the channels thereof are substantially vertical and so that the end face which has been the lower end face in step b) now represents the upper end face, f) pumping the third washcoat suspension into the carrier substrate from the lower end face over a length L_y, g) sucking out excess third washcoat from the lower end face, h) drying and calcining the washcoated carrier substrate obtained after step g), i) orienting the washcoated carrier substrate obtained after step d) such that the channels thereof are substantially vertical, j) pouring the second washcoat suspension onto the upper end face of the carrier substrate obtained after step e), k) applying vacuum at the lower end face of the carrier substrate and soaking the second washcoat suspension applied in step f) through the monolith, l) drying and calcining the washcoated carrier substrate obtained after step g).

Drying and calcining the monolith in steps d), h) and I) is carried out as described above. It will be understood by the skilled person that this embodiment is particularly suitable if a material zone C’ shall be present which is different from material zone C. Alternatively, the first washcoat can be poured onto the upper end face of the carrier substrate in step b), followed by sucking out excess washcoat in step c), if material zone D shall extend over the entire length L of the carrier substrate; and/or the second washcoat can be pumped into the carrier substrate from the lower end face in step i), followed by step, k), which is applying vacuum at lower end face of the carrier substrate and soaking the second washcoat suspension applied in step i) through the monolith.

Optionally, the washcoat suspension of the V/TiO2 SCR catalytically active does not comprise all the oxides of vanadium and, if desired, additionally tungsten, silicon, molybdenum, antimony, niobium, cerium, tantalum and/or hafnium as mentioned above. In these cases, oxides which have not been applied as components of the washcoat suspension can be applied in a subsequent step, for instance by impregnating the second washcoat with these oxides and/or with precursors thereof. Impregnation can be carried out, for example, by dipping the carrier substrates, which are washcoated with the second washcoat suspension, into an aqueous solution of the precursors of these oxides. Calcination as described above for the first and the second embodiment the method for making the SCR catalytic devices and all alternatives thereof converts precursors of these oxides into the corresponding oxides. Method of applying V/TiC>2 SCR catalytically compositions, including applying a part of the oxides in the form of impregnation, are well known to the skilled person. They are, for instance, disclosed in WO 2022/058404 A1 , and can be applied in the present invention without departing from the scope of the claims.

In other embodiments, the carrier substrates may be catalytically active on their own, and they may further comprise catalytically active compositions, i.e. the first SCR catalytically active compositions as described above. In addition to the catalytically active compositions, these carrier substrates comprise a matrix component. All inert materials which are otherwise used for the manufacturing of catalyst substrates may be used as matrix components in this context. It deals, for instance, with silicates, oxides, nitrides or carbides, with magnesium aluminum silicates being particularly preferred.

In other embodiments of the catalytic devices according to the present invention, the first SCR catalytically active compositions themselves form part of the carrier substrate, for example as part of a flow-through substrate. Such carrier substrates additionally comprise the matrix components described above. Catalysed substrate monoliths comprising the SCR catalytically active compositions according to the present invention may be used as such in exhaust purification. Alternatively, they may be coated with catalytically active compositions. Insofar as these materials shall exhibit an SCR catalytic activity, the second SCR catalytically active compositions mentioned above are suitable materials for said coatings.

In one embodiment, catalytically active carrier materials are manufactured by mixing 10 to 95 wt.-% of at least one inert matrix component and 5 to 90 wt.-% of a catalytically active composition, followed by extruding the mixture according to well-known protocols. As already described above, inert materials that are usually used for the manufacture of catalyst substrates may be used as the matrix components in this embodiment. Suitable inert matrix materials are, for example, silicates, oxides, nitrides and carbides, with magnesium aluminum silicates being particularly preferred. Catalytically active carrier materials obtainable by such processes are known as “extruded catalysed substrate monoliths”. In the context of the present invention, an “extruded catalysed substrate monolith” is an extruded monolith wherein the catalytically active composition is a crystalline aluminosilicate zeolite having a maximum ring size of eight tetrahedral atoms, said zeolite comprising copper, manganese and a metal M as described above.

The application of the catalytically active components onto either the inert carrier substrate or onto a carrier substrate which is catalytically active on its own as well as the application of a catalytically active coating onto a carrier substrate, said carrier substrate comprising a catalyst according to the present invention, can be carried out following manufacturing processes well known to the person skilled in the art, for instance by widely used dip coating, pump coating and suction coating, followed by subsequent thermal post-treatment (calcination).

The skilled person knows that in the case of wall-flow filters, their average pore sizes and the mean particle size of the catalytically active components according to the present invention may be adjusted to one another in a manner that the coating thus obtained is located onto the porous walls which form the channels of the wall-flow filter (on-wall coating). However, the average pore sizes and the mean particle sizes are preferably adjusted to one another in a manner that the catalyst according to the present invention is located within the porous walls which form the channels of the wall-flow filter. In this preferable embodiment, the inner surfaces of the pores are coated (in-wall coating). In this case, the mean particle size of the catalysts according to the present invention has to be sufficiently small to be able to penetrate the pores of the wall-flow filter. Wall-flow filters which are coated with an SCR catalytically active compositions are also known as “SDPF” (SCR on DPF, i.e. an SCR catalytically active composition coated onto a diesel particulate filter) or as “SCRF” (SCR on filter). Thus, the present invention encompasses catalysed substrate monoliths wherein the monolith is a wall-flow filter, and the SCR catalytically compositions comprises SCR catalytically active compositions as described above.

The catalytic devices according to the present invention can be used in systems and methods for the removal of NO_X from combustion exhaust gases. The catalytic devices are applicable in exhaust purification systems of mobile and stationary combustion engines. Mobile combustion engines are, for example, gasoline and diesel engines and also hydrogen internal combustion engines (H2 ICE). The skilled person knows that combustion processes usually take place under oxidizing conditions, and that either fuels comprises nitrogen or nitrogen compounds, which can be oxidized to NO_X, and/or that the combustion takes place in the presence of air, wherein the oxygen which is present in the air acts as the oxidant, and at least a part of the nitrogen which is present in can be oxidized to NO_X.

Mobile combustion engines can be engines for on-road and off-road applications, for example, gasoline and diesel engines and also hydrogen internal combustion engines for passenger cars, agricultural machinery like agricultural and forestry tractors and harvesting machines, construction wheel loaders, bulldozers, highway excavators, forklift trucks, road maintenance equipment, snow plows, ground support equipment in airports, aerial lifts and mobile cranes.

Stationary combustion engines are, for example, power stations, industrial heaters, cogeneration plants including wood-fired boilers, stationary diesel and gasoline engines, industrial and municipal waste incinerators, industrial drilling rigs, compressors, manufacturing plants for glass, steel and cement, manufacturing plants for nitrogen-containing fertilizers, nitric acid production plants (for example plants applying the Ostwald process) and ammonia burners for fueling gas turbines of nitric acid production. In a preferred embodiment, the catalytic devices according to the present invention can be used in a process for the removal of NO_X from automotive combustion exhaust gases, said exhaust gases deriving from diesel or gasoline engines.

Furthermore, the present invention encompasses ammonia slip catalysts (ASC). It is well known to the skilled person that in exhaust gas purification systems, an ASC is preferably located downstream of the SCR, because recognizable amounts of NH3 leave the SCR due to the dynamic driving conditions. Therefore, the conversion of excess ammonia which leaves the SCR is mandatory, since ammonia is also an emission regulated gas. Oxidation of ammonia leads to the formation of NO as main product, which would consequently contribute negatively to the total conversion of NO_X of the whole exhaust system. An ASC may thus be located downstream the SCR to mitigate the emission of additional NO. The ASC catalyst combines the key NH3 oxidation function with an SCR function. Ammonia entering the ASC is partially oxidized to NO. The freshly oxidized NO and NH3 inside the ASC, not yet oxidized, can consequently react to N2 following the usual SCR reaction schemes. In doing so, the ASC is capable of eliminating the traces of ammonia by converting them in a parallel mechanism to N2.

It will be understood by the skilled person that the SCR catalyst and the ASC catalyst may be present as two consecutive catalytic articles, or the SCR functionality and the ASC functionality may be present on one single catalytic article. In case of two consecutive catalytic articles, the upstream catalytic article is the SCR catalyst, i.e. a catalytic device for the selective catalytic reduction of nitrogen oxides according to the present invention, and the downstream catalytic article is the ASC catalyst comprising a carrier substrate, a washcoat comprising an oxidation catalyst, and a washcoat comprising an SCR catalytically active composition.

In case the SCR catalyst and the ASC catalyst are present on one single substrate, the catalytic device for the selective catalytic reduction of nitrogen oxides according to the present invention represents the upstream zone of the carrier substrate, and the downstream zone of said carrier substrate contains a bottom layer with a washcoat comprising an oxidation catalyst and a top layer with a washcoat comprising an SCR catalytically active composition.

The SCR catalytically active composition of the ASC can be selected from manganese- containing mixed oxides, metal-promoted small-pore zeolites and V/TiC>2 SCR catalyst compositions according to the present invention, and mixtures thereof. Platinum group metals are used as oxidation catalysts in an ASC. The precious metal is a platinum group metal selected from ruthenium, rhodium, palladium, osmium, iridium, platinum and mixtures thereof. Preferably, the precious metal is chosen from palladium, platinum, rhodium and mixtures thereof, more preferably, the precious metal is platinum. In a preferred embodiment, the platinum group metal is added in the form of a precursor salt to a washcoat slurry and applied to the carrier monolith. The platinum group metal is present in a concentration of 0.01 to 10 wt.-%, preferably 0.05 to 5 wt.-%, even more preferably 0.1 to 3 wt.-%, calculated as the respective platinum group metal and based on the total weight of the washcoat loading. In a preferred embodiment, the platinum group metal is platinum, and it is present in a concentration of 0.1 to 1 wt.-%, calculated as Pt and based on the total weight of washcoat loading.

In one embodiment, the ASC catalyst is a catalysed substrate monolith, wherein the monolith is a flow-through monolith coated with a bottom layer comprising an oxidation catalyst and a top layer comprising manganese-containing mixed oxides, metal-promoted small-pore zeolites and V/TiC>2 SCR catalyst compositions according to the present invention, and mixtures thereof.

The present invention furthermore provides an emissions treatment system for the removal of NOx emissions from exhaust gases of internal combustion engines, and optionally also for the removal of particulate matter, the system comprising, in the following order, from upstream to downstream: a) means for injecting ammonia or an ammonia precursor solution into the exhaust gas stream, b) a catalytic device for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to the present invention, wherein the carrier substrate is selected from honeycomb flow-through substrates, honeycomb wall-flow filters, corrugated substrates, wound or packed fiber filters, open cell foams, sintered metal filters and extruded catalysed substrate monoliths.

It will be understood by the skilled person that in case the carrier substrate is a flow- through monolith or a corrugated substrate, the corresponding catalysed substrate monolith will remove NO_X emissions only. If, however, the carrier substrate is a wall-flow filter, the corresponding catalysed carrier substrate will also remove particulate matter. The skilled person knows that the SCR reaction requires the presence of ammonia as a reductant. Ammonia may be supplied in an appropriate form, for instance in the form of liquid ammonia or in the form of an aqueous solution of an ammonia precursor, and added to the exhaust gas stream as needed via means for injecting ammonia or an ammonia precursor. Suitable ammonia precursors are, for instance urea, ammonium carbamate or ammonium formate. Alternatively, the ammonia may be formed by catalytic reactions within the exhaust gas.

A widespread method is to carry along an aqueous urea solution and to and to dose it into the catalyst according to the present invention via an upstream injector and a dosing unit as required. Means for injecting ammonia, for example an upstream injector and a dosing unit, are well known to the skilled person and can be used in the present invention without departing from the scope of the claims.

It will furthermore be understood that an emissions treatment system for the removal of NOx emissions from exhaust gases of internal combustion engines, and optionally also for the removal of particulate matter, the system comprising a catalytic device according to the present, may comprise additional catalytic articles, for instance a diesel oxidation catalyst (DOC), an ammonia slip catalyst (ASC), a catalysed or uncatalysed particulate filter, a passive NO_X adsorber (PNA), and/or a lean NO_X trap (LNT). A catalysed particulate filter may be coated with a diesel oxidation catalyst, thus forming a “catalysed diesel particulate filter (CDPF), or it may be coated with an SCR catalytically active composition, thus forming an SDPF.

In one embodiment of the present invention, the emissions treatment system comprising a catalytic device according to the present invention is arranged in a close-coupled position. The term “close-coupled” refers to a position of a catalytic device in an engine’s exhaust gas treatment system which is less than 1 meter downstream of the engine’s exhaust gas manifold or turbocharger. In a preferred embodiment, the emissions treatment system comprising a catalytic device according to the present invention furthermore comprises one or more particulate filters. In this embodiment, the “first” filter is the filter that is arranged closest to the engine. The “second” filter, if present, is located downstream of the first filter, either directly following the first filter, or in a position further downstream. In this embodiment, the catalytic device according to the present invention, which is arranged in a close-coupled position, is arranged upstream of the first filter. As mentioned above, the catalytic device according to the present invention can be a honeycomb flow-through substrate, a honeycomb wall-flow filter, a corrugated substrate, a wound or packed fiber filter, an open cell foam or a sintered metal filter. Preferably, it is a honeycomb flow-through substrate, a wall-flow filter or a corrugated substrate. If the catalytic device according to the present invention is a honeycomb wall-flow filter, it deals with an SDPF.

In yet another embodiment of the present invention, the emissions treatment system is arranged in an underfloor position. Underfloor catalyst members are also known in the prior art and are located downstream of any close-coupled and/or medium- coupled catalysts under the floor of the vehicle adjacent to or in combination with the vehicle's muffler. In this embodiment, the catalytic device according to the present invention is arranged downstream the first filter. The substrates catalytic device according to the present invention are the same as those mentioned above for the close-coupled arrangement.

In yet another embodiment of the present invention, the emissions treatment system comprising a catalytic device according to the present invention is arranged upstream of the first particulate filter, but 1 meter or more downstream of the engine’s exhaust gas manifold or turbocharger. In this embodiment, the catalytic device according to the present invention preferably is the first brick downstream of the engine’s exhaust gas manifold or turbocharger.

In yet another embodiment of the present invention, the emissions treatment system comprising a catalytic device according to the present invention is arranged downstream of the first particulate filter.

In these embodiments wherein the catalytic device according to the present invention is located either upstream or downstream of the first particulate filter, the catalytic devices according to the present invention are the same as those mentioned above for the close- coupled arrangement and the underfloor arrangement.

In all emissions treatment systems described above, face side A of the catalytic device according to the present invention is positioned upstream, and face side B is positioned downstream. The present invention furthermore provides a method for the removal of NO_X emissions from exhaust gases of internal combustion engines, and optionally also for the removal of particulate matter, the method comprising, in the following order, from upstream to downstream: a) injecting ammonia or an ammonia precursor solution into the exhaust gas stream, b) introducing the exhaust gas from step a) into a catalytic device for the removal of nitrogen oxides from the exhaust gas of combustion engines according to the present invention, and wherein the carrier substrate is selected from honeycomb flow-through substrates, honeycomb wall-flow filters, corrugated substrates, wound or packed fiber filters, open cell foams, sintered metal filters and extruded substrate monoliths.

Preferably, the substrate monolith is selected from honeycomb flow-through substrates, wall-flow filters, and corrugated substrates. More preferably, the carrier substrate is a flow-through substrate or a corrugated substrate.

As mentioned above for the emissions treatment system, it will be understood by the skilled person that in case the carrier substrate used in step b) of the method above is a flow-through monolith or a corrugated substrate, the corresponding catalytic device will remove NO_X emissions only. If, however, the carrier substrate used in step b) of the method above is a wall-flow filter, the corresponding catalysed carrier substrate will also remove particulate matter.

Brief description of the Drawings

A face side A of the substrate monolith, perpendicular to the flow direction of the exhaust gas

B face side B of the substrate monolith, perpendicular to the flow direction of the exhaust gas

L total length of the substrate monolith; L = L_y + L_z

L_y 80 to 0% of L, starting from face side A

L_z 20 to 80% of L, starting from face side B Fig. 1 shows an embodiment of the present invention wherein S is the carrier substrate, C represents the top layer wherein the SCR catalytically active composition consists of a V/TiC>2 catalyst composition, and D represents the bottom layer wherein the SCR catalytically active composition consists of one or more manganese-containing mixed oxides, or a mixture of one or more manganese-containing mixed oxides and one or more metal-promoted small-pore zeolites. Both layers extend over the entire length of the substrate monolith from face side A to face side B.

Here: L = Lz

Fig. 2 shows an embodiment of the present invention wherein S is the carrier substrate, C represents the top layer having a length L, wherein the SCR catalytically active composition consists of a V/TiCh catalyst composition; C’ represents the upstream bottom layer having a length L_y, wherein the SCR catalytically active composition consists of a V/TiC>2 catalyst composition; and D represents the downstream bottom layer having a length L_z and wherein the SCR catalytically active composition consists of one or more manganese-containing mixed oxides, or a mixture of one or more manganese-containing mixed oxides and one or more metal-promoted small-pore zeolites.

Fig. 3 shows the NO_X conversion after sulfur deactivation of Comparative Example 1.

Fig. 4 shows the NO_X conversion after sulfur deactivation of Comparative Example 2.

Fig. 5 shows the NO_X conversion after sulfur deactivation of Comparative Example 3.

Fig. 6 shows the NO_X conversion after sulfur deactivation of Comparative Example 4.

Fig. 7 shows the NO_X conversion after sulfur deactivation of Comparative Example 5.

Fig. 8 shows the NO_X conversion after sulfur deactivation of Example 1.

Fig. 9 shows the NO_X conversion for Comparative Example 1 (“Cu-SCR”), Comparative Example 2 (“Mn-SCR”), Comparative Example 3 (“V-SCR”) and Example 1 (“Example”): White columns: NO_X conversion without sulfur; black columns: NO_X conversion after exposure to 2g S/L; hatched columns: NO_X conversion after exposure to 2g S/L and subsequent desulfation at 400°C.

Fig. 10 shows the NO_X conversion loss ((NO_x%_Without sulfur - NO_x%_With suifur)/NO_x%_Without sulfur) at 225°C after exposure to 2g S/L for Comparative Example 1 (“Cu-SCR”), Comparative Example 2 (“Mn-SCR”), Comparative Example 4 (“V-SCR as top layer for Cu-SCR”) and Examples 1, 2, 3 and 4. All examples showed less NO_X conversion loss than the comparative examples after the same sulfur exposure.

Embodiments

Comparative Example 1 (CE1): Cu-zeolite based SCR catalyst

Preparation of powders for Comparative Example 1

A commercially available zeolite powder with the CHA framework structure, in H⁺-form, and with an SAR of 15.8 was used as base zeolite material. 1.06 kg of the base zeolite was impregnated with an aqueous solution of Cu(NO₃)2, which was dosed over 30 min while constantly mixing the powder in a closed stainless steel container. The aqueous CU(NO₃)₂ solution was prepared from a mixture of 550 g water and 151.8 g CU(NO3)2' 3H2O, where the Cu-salt was fully dissolved before addition to the zeolite powder. After impregnation, the Cu-loaded zeolite was dried for 8 h at 120°C and calcined at 600°C for 2 h.

Preparation of coated catalyst:

A slurry consisting of H2O, AI2O3 as binder, and the Cu-loaded zeolite prepared from Comparative Example 1 was mixed and left for stirring overnight. The commercial monolith carrier was submerged into the slurry, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The results of the sulfur deactivation of Comparative Example 1 are shown in Fig. 3.

Comparative Example 2 (CE 2): manganese-containing mixed oxide SCR catalyst:

Preparation of powders for Comparative Example 2:

497.1 g of Mn(NO₃)₂-4H₂O, 795.5 g Ce(NO₃)₃-6H₂O and 894.5 g TiOSO4 were dissolved separately in water and the aqueous solution was then mixed under stirring. Ammonium carbonate was added slowly into the mixed solution and the pH was set to above 6. After stirring for at least 1 h, the slurry was filtered and washed with water.

The filter cake was dried at 60°C for 24 h and further calcined at 500°C for 2 h. Preparation of coated catalyst:

A slurry consisting of H2O and the Mn-based powder prepared from Comparative Example 2 was mixed and left for stirring overnight. The commercial monolith carrier was submerged into the slurry, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The results of the sulfur deactivation of Comparative Example 2 are shown in Fig. 4.

Comparative Example 3 (CE3): V/TiO2-based SCR catalyst

Preparation of powders for Comparative Example 3

A commercially available titanium dioxide in the anatase form was dispersed in water and then vanadium dioxide (VO2), tungsten trioxide (WO3), cerium dioxide (CeCh) and antimony pentoxide (Sb20s) were added in amounts so as to result in a catalyst of the composition 87 wt% TiC>2, 5.0 % V2O5, 1 wt% WO3, 2 wt% CeC>2 and 5.0 wt% Sb20s. The slurry was vigorously stirred and then milled in a commercially available agitator bead mill.

Preparation of coated catalyst:

The commercial monolith carrier was submerged into the slurry, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The catalyst was calcined at 580 °C for 2 hours

The results of the sulfur deactivation of Comparative Example 3 are shown in Fig. 5.

Comparative Example 4 (CE 4):

The catalyst from Comparative Example 1 was submerged into the slurry prepared in comparative example 3, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 65 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The catalyst was calcined at 580 °C for 2 hours.

The results of the sulfur deactivation of Comparative Example 4 are shown in Fig. 6.

Comparative Example 5 (CE 5):

The catalyst from Comparative Example 1 was submerged into the slurry prepared in comparative example 3, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 100 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The catalyst was calcined at 580 °C for 2 hours.

The results of the sulfur deactivation of Comparative Example 5 are shown in Fig. 7.

Example 1 (Ex 1):

The catalyst from Comparative Example 2 was submerged into the slurry prepared in comparative example 3, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The catalyst was calcined at 580 °C for 2 hours.

The results of the sulfur deactivation of Example 1 are shown in Fig. 8.

Example 2 (Ex 2):

Preparation of powders for Example 2:

497.1 g of Mn(NO3)2‘4H2O, 800.1 g Fe(NC>3)3-9H2O and 894.5 g TiOSO4 were dissolved separately in water and the aqueous solution was then mixed under stirring. Ammonium carbonate was added slowly into the mixed solution and the pH was set to above 6. After stirring for at least 1 h, the slurry was filtered and washed with water.

A slurry consisting of H2O, the Mn-based powder prepared from Example 2, and Cu/CHA from Comparative Example 1 were mixed and left for stirring overnight. The weight ratio of Mn-based powder to Cu/CHA is 1 :1. The commercial monolith carrier was submerged into the slurry, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The results of the sulfur deactivation of Example 2 are shown in Fig. 10.

Example 3 (Ex 3):

A slurry consisting of H2O, the Mn-based powder prepared from Comparative Example

2, and Cu/CHA from Comparative Example 1 were mixed and left for stirring overnight. The weight ratio of Mn-based powder to Cu/CHA is 3:7. The commercial monolith carrier was submerged into the slurry, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The prepared catalyst was submerged into the slurry prepared in comparative example

3, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L.

The catalyst was calcined at 580 °C for 2 hours.

The results of the sulfur deactivation of Example 3 are shown in Fig. 10.

Example 4 (Ex 4):

A slurry consisting of H2O, the Mn-based powder prepared from Comparative Example 2, and Cu/CHA from Comparative Example 1 were mixed and left for stirring overnight. The weight ratio of Mn-based powder to Cu/CHA is 3:7. The commercial monolith carrier was submerged into the slurry and coated only 70% of the channel length from face B, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L. The substrate applied was commercially available with the dimensions 5.66” diameter and 3.0” length, and with channel dimensions 400 cpsi and wall thickness of 4 mil.

The prepared catalyst was submerged into the slurry prepared in comparative example 3, and subsequently dried by a flow of hot air. The process was repeated until reaching a loading of the dry coating of 150 g/L.

The catalyst was calcined at 580 °C for 2 hours.

The results of the sulfur deactivation of Example 4 are shown in Fig. 10.

Sulfur deactivation

The coated catalysts were measured after preparation in a model gas reactor for NOx for sulfur deactivation. The NO_X conversion of the catalysts was tested during sulfur exposure.

Test procedure:

1. Preconditioning at 400 °C in 10% O2 for 10 min.

2. NOx conversion test at 225°C under 500 ppm NO, 600 ppm NH3, 10% O2, 5% H2O.

3. NOx conversion test at 225°C during sulfur exposure under 0.8 ppm SO2, 500 ppm NO, 600 ppm NH3, 10% O2, 5% H2O. The holding time is 24 hrs for 2 g S/L exposure.

4. Desulfation at 400°C under same gas condition as 3 for 30 mins.

5. NOx conversion test at 225°C under 500 ppm NO, 600 ppm NH3, 10% 02, 5% H2O.

Nitrogen was applied as balanced gas. The gas hourly space velocity (GHSV) for the measurements of the catalysts was at 80,000 IT¹ at all measurement temperatures.

As illustrated in Figure 8, the Example 1 , according to the present invention, showed almost no deactivation during sulfation and a much better sulfur resistance than Comparative Example 1 , 2, 4, and 5. Furthermore, the NO_X conversion at 225°C of the current invention is higher than Comparative Example 3. After desulfation at 400°C, Comparative Example 1 could be recovered to certain extent, as shown in Figure 9, but it showed a still lower NO_X conversion than the Example 1.

Claims

1. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines, comprising a) a carrier substrate of length L, said length L extending from a face side A to a face side B, and b) a bottom layer comprising

- a material zone D affixed to the carrier substrate; said material zone D comprising a first SCR catalytically active composition and extending from face side B over a length L_z which is 20 to 100% of the length L of the carrier substrate; wherein

- the first SCR catalytically active composition in said material zone D consist of one or more manganese-containing mixed oxides, or a mixture of one or more manganese-containing mixed oxides and one or more metal-promoted small-pore zeolites

2. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 1 , wherein the carrier substrate is a honeycomb flow-through substrate, a wall-flow filter or a corrugated substrate.

3. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 1 or 2, wherein Lz is 30 to 100% of length L.

4. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 3, wherein the first SCR catalytically active composition consists of one or more manganese- containing mixed oxides, wherein the one or more manganese-containing mixed oxides are selected from a) Mn_aCebTi_cOx, wherein a, b and c are, independently from one another, larger than zero and smaller than 1 , and wherein a , b and c add up to 1 , and wherein x is the molar amount of oxygen, a ranges from 0.05 to 0.50; b ranges from 0.05 to 0.50; c ranges from 0.30 to 0.90 and x ranges from 1.5 to 2.0; and b) MndMei-dOw, wherein d, 1-d and w represent the molar fractions of manganese, a metal Me and oxygen, and wherein Me is selected from the group consisting of Fe, Co, Ni, Cu, Zr, Nb, Mo, W, Ag, Sn, Ce, Pr, La, Nd, Ti, Al, Si and Y, and wherein d ranges from 0.02 to 0.98 and w ranges from 1.0 to 2.5; and c) Mn_eCefMei-_e.fO_v, wherein e, f, 1-e-f and v represent the molar fractions of manganese, cerium, a metal Me and oxygen, and wherein Me is selected from the group consisting of Fe, Co, Ni, Cu, Zr, Nb, Mo, W, Ag, Sn, Ce, Pr, La, Nd, Ti, Al, Si and Y, and wherein e ranges from 0.02 to 0.98, f ranges from 0.02 to 0.98, and v ranges from 1.0 to 2.5; and d) spinels having the general formula MnS2C>4 or SM^CL, wherein S is selected from Fe, Al, Cr, Co and Cu.

5. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 3, wherein the first SCR catalytically active composition in material zone D consists of a mixture of one or more manganese-containing mixed oxides according to claim 4 and one or more metal-promoted small-pore zeolites.

6. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 5, wherein the one or more small-pore zeolites are selected from ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, 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 mixtures and intergrowths thereof.

7. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 5 or 6, wherein the at least one small-pore zeolite has a molar ratio of silica-to-alumina (SAR) value of 5 to 50.

8. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claim 5 to claim 7, wherein the small-pore zeolite is promoted with copper and optionally with one or two additional metals M1 and M2, and wherein the copper to aluminum atomic ratio is between 0.12 and 0.55, and the copper content is between 2.0 and 6.5wt.- %, calculated as CuO and based on the total weight of the zeolite, and wherein the promoter metals M1 and M2 are, independently from one another, selected from magnesium, calcium, barium, strontium, yttrium, titanium, zirconium, niobium, manganese, iron, zinc, silver, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, provided that, if both M1 and M2 are present, they are different from one another.

9. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 8, wherein copper is the only promoter metal, and the Cu:AI atomic ratio is between 0.12 and 0.55.

10. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 8, wherein only one promoter metal M1 is present in addition to copper, the M1 :Cu atomic ratio is in the range of 0.05 to 0.95, and the (Cu + M1) : Al atomic ratio is in the range of 0.11 to 0.96.

11. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 8, wherein two promoter metals M1 and M2 are present in addition to copper, the M1 :Cu ratio and the M2:Cu atomic ratio are both in the range of 0.05 to 0.95, and the (Cu + M1 + M2) : Al atomic ratio is in the range of 0.2 to 0.80, under the proviso that M1 and M2 are different from one another.

12. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 5, wherein the weight ratio of at least one manganese-containing mixed oxide to the at least one metal-promoted small-pore zeolite is in the range of 0.1 to 99 wt.%.

13. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 10, wherein the V/TiCh catalyst compositions in material zones C and C’ comprise, independently from one another,

- at least one oxide of vanadium in an amount of 1 to 10 wt.-%, and

- at least one oxide of tungsten in an amount of 0 to 15 wt.-%, and,

- at least one oxide of silicon in an amount of 0 to 18 wt.-%, and

- at least one oxide of titanium in an amount that is measured so as to result in a total of 100 wt.-%, in each case based on the total weight of the V/TiCh catalyst and calculated as V2O5, WO3, SiC>2, MO2O3, Sb2Os, Nb2Os, ZrC>2, Ta₂C>5, HfC>2, CeC>2 or TiC>2.

14. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 7, wherein material zone C is affixed to the bottom layer and, if present, material zone C’ is affixed to the carrier in the form of washcoats, wherein the washcoat loadings are, independently from one another, in the range of from 25 to 400 g/L.

15. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 8, wherein material zone D is affixed to the bottom layer in the form of a washcoat, wherein the washcoat loading is in the range of from 50 to 300 g/L.

16. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 9, wherein the total washcoat loading of material zones C, D and optionally C’ is in the range of from 75 to 450 g/L.

17. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 8 to 10, wherein the washcoats, independently from one another, contain binders selected from TiC>2, SiC>2, AI2O3, ZrC>2, CeC>2 and combinations thereof in an amount of 0 to 20 wt.-%, based on the total weight of the SCR catalytically active composition and the binder.

18. An emissions treatment system for the removal of NO_X emissions from exhaust gases of internal combustion engines, and optionally also for the removal of particulate matter, the system comprising, in the following order, from upstream to downstream: a) means for injecting ammonia or an ammonia precursor solution into the exhaust gas stream, b) a catalytic device for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to anyone of claims 1 to 17 the present invention, wherein the carrier substrate is selected from honeycomb flow-through substrates, honeycomb wall-flow filters, corrugated substrates, wound or packed fiber filters, open cell foams, sintered metal filters and extruded catalysed carrier substrates.

19. The emissions treatment system according to claim 18, wherein said emissions treatment system is arranged in a close-coupled position.

20. The emissions treatment system according to claim 18, wherein said emissions treatment system is arranged in an underfloor position.

21. A method for the removal of NO_X emissions from exhaust gases of internal combustion engines, and optionally also for the removal of particulate matter, the method comprising, in the following order, from upstream to downstream: a) injecting ammonia or an ammonia precursor solution into the exhaust gas stream, b) introducing the exhaust gas from step a) into a catalytic device for the removal of nitrogen oxides from the exhaust gas of combustion engines according to anyone of claim 1 to 17, and wherein the carrier substrate is selected from honeycomb flow-through substrates, honeycomb wall-flow filters, corrugated substrates, wound or packed fiber filters, open cell foams, sintered metal filters and extruded substrate monoliths.

22. A method according to claim 21 , wherein the internal combustion engine is selected from gasoline, diesel and hydrogen internal combustion engines (H2 ICE).