KR20130091638A - Fe-bea/fe-mfi mixed zeolite catalyst and process for treating nox in gas streams using the same - Google Patents

Abstract

Preferably a catalyst is provided for use in selective catalytic reduction (SCR). The catalyst comprises at least one zeolite of the MFI structure type and at least one zeolite of the BEA structure type, wherein at least some of the at least one zeolite of the MFI structure type and at least part of the at least one zeolite of the BEA structure type are each iron (Fe) is included. An exhaust gas treatment system comprising the catalyst and also a process for treating a NO _x containing gas stream using the catalyst are provided.

Description

Fe-BEA / FE-MFI MIXED ZEOLITE CATALYST AND PROCESS FOR TREATING NOX IN GAS STREAMS USING THE SAME}

The present invention preferably relates to a catalyst for use in selective catalytic reduction (SCR), an exhaust gas treatment system comprising said catalyst, and a method of treating a NO _x containing gas stream. In particular, the present invention relates to a method for promoting the reduction of nitrogen oxides, in particular the selective reduction of nitrogen oxides with ammonia in the presence of oxygen using metal promoted zeolite catalysts.

Emissions present in the exhaust gases of automobiles can be divided into two groups. Thus, the term "primary emissions" refers to pollutant gases that are formed immediately after the combustion process of fuel in an engine and already present in untreated emissions prior to passing through an exhaust gas treatment system. Secondary emissions are those pollutant gases that can form as byproducts in the exhaust gas treatment system.

The exhaust gas of a lean burn engine comprises a relatively high oxygen content of up to 15 vol%, with the usual primary emissions of carbon monoxide CO, hydrocarbon HC and nitrogen oxides NO _x . For diesel engines, with or without organic agglomerates, there are additional particulate emissions, mainly consisting of soot residues, in addition to gaseous primary emissions resulting from partially incomplete fuel combustion in the cylinders.

In the field of diesel engines, the use of certain diesel particulate filters cannot be avoided in the removal of particulate emissions. In addition, compliance with the emission limits set forth in legislation in Europe and the United States requires the removal of nitrogen oxides (“denitrification”) from exhaust gases. Thus, although carbon monoxide and hydrocarbon contaminant gases from lean exhaust gases can be easily harmed by oxidation over a suitable oxidation catalyst, the reduction of nitrogen oxides to nitrogen is much more difficult due to the high oxygen content of the exhaust gas stream.

Known methods for removing nitrogen oxides from exhaust gases are firstly the use of nitrogen oxide storage catalysts (NSC) and secondly the selective catalytic reduction (SCR) by ammonia over suitable catalysts, simply SCR catalysts.

The cleaning action of the nitrogen oxide storage catalyst is mainly based on the nitrogen oxides stored on the lean operation of the engine by the storage material of the storage catalyst in nitrate form. When the storage capacity of the NSC runs out, the catalyst must be regenerated on subsequent rich operation of the engine. This means that the nitrates formed previously are decomposed and the nitrogen oxides discharged again react with the reducing exhaust gas components on the storage catalyst to produce nitrogen, carbon dioxide and water.

An alternative SCR method is a diesel vehicle exhaust gas, since the implementation of rich operation in diesel engines is not simple and the establishment of rich exhaust gas conditions necessary for the regeneration of the NSC often involves auxiliary means such as post-injection of fuel into the exhaust gas line. It is preferably used for the denitrogenation of. In this method, depending on the engine design and configuration of the exhaust gas system, the "active" SCR method and the "passive" SCR method are distinguished, and the "passive" SCR method is deliberately produced in the exhaust gas system as a reducing agent for denitrification. Entails the use of ammonia secondary emissions.

For example, US Pat. No. 6,345,496 B1 describes a method for cleaning engine exhaust gas, where iteratively establishes alternating lean and rich air / fuel mixtures, and generates the exhaust gas on the inlet side. Passes an exhaust gas system comprising a catalyst that converts NO _x to NH ₃ only under rich exhaust gas conditions, and further catalyst disposed on the outlet side adsorbs or stores NO _x in the lean exhaust gas, It is then discharged, which can react with NH ₃ produced by the inlet catalyst to produce nitrogen. As an alternative, according to US Pat. No. 6,345,496 B1, the NH ₃ adsorption and oxidation catalyst is disposed on the outlet side which stores NH ₃ under rich conditions, desorbs it under lean conditions and oxidizes it with oxygen to produce nitrogen and water. Can be. Further disclosures of this method are known. However, such as the use of nitrogen oxide storage catalysts, this "passive" SCR method has the disadvantage that one of its essential components is to provide rich exhaust gas conditions which are generally required for in situ production of ammonia as the reducing agent.

In comparison to this, in the "active" SCR method, the reducing agent is metered into the exhaust gas line from the addition tank carried in the vehicle by the injection nozzle. Such reducing agents used may be separate from ammonia and may also be compounds which can be readily decomposed into ammonia, for example urea or ammonium carbamate. Ammonia should be supplied to the exhaust gas at least in stoichiometric ratio with respect to nitrogen oxides. Due to the largely changing automotive operating conditions, the accurate metered addition of ammonia is not simple. This in some cases leads to significant ammonia breakthroughs downstream of the SCR catalyst. In order to prevent secondary ammonia emissions, oxidation catalysts are generally disposed downstream of the SCR catalyst, which is intended to oxidize ammonia that breaks through with nitrogen. Such catalysts are referred to as ammonia slip catalysts.

In order to remove particulate emissions from the exhaust gas of diesel vehicles, certain diesel particulate filters can be provided which can be provided with an oxidation catalyst containing coating to improve their properties. This coating acts to lower the activation energy for oxygen-based particulate combustion (soot combustion) and thus lower the soot ignition temperature on the filter, thereby improving passive regeneration performance by oxidation of nitrogen monoxide present in the exhaust gas to nitrogen dioxide. Inhibits hydrocarbon breakthrough and carbon monoxide emissions.

If compliance with legal emission standards requires both denitrification and removal of particulates from the exhaust gas of diesel vehicles, the described means for removing each pollutant gas may be applied in a corresponding conventional exhaust gas system by series connection. Combined. WO 99/39809, for example, describes an oxidation catalyst for the oxidation of NO in NO _x to NO ₂ , a particulate filter, a metering unit for the reducing agent and a post exhaust treatment system followed by an SCR catalyst. In order to prevent ammonia breakthrough, an additional ammonia slip catalyst is generally required downstream of the SCR catalyst and continues a series of catalysts on the outflow side of the SCR catalyst.

In this regard, its use in promoting certain reactions, including both synthetic and natural zeolites and the selective reduction of nitrogen oxides with ammonia in the presence of oxygen, is well known in the art. Zeolites are aluminosilicate crystalline materials with somewhat uniform pore sizes that may range from about 3 to 10 microns in diameter depending on the type of zeolite and the type and amount of cations included in the zeolite lattice.

EP 1 961 933 A1 relates to diesel particulate filters for treating exhaust gases, for example comprising an oxidation catalyst coating, an SCR active coating and a filter body provided with an ammonia storage material. Among the materials that can be used as catalytically active components in the SCR reaction, the document mentions the use of zeolites selected from beta zeolites, Y zeolites, fuserite, mordenite and ZSM-5 which can be exchanged with iron or copper.

EP 1 147 801 A1, on the other hand, is a method of reducing nitrogen oxides present in lean exhaust gas from an internal combustion engine by SCR using ammonia, wherein the reduction catalyst is preferably ZSM- exchanged with copper or iron. 5 relates to a method comprising a zeolite. The document further relates to an SCR catalyst having a honeycomb substrate and having a coating deposited thereon comprising a ZSM-5 zeolite exchanged with iron.

EP 2 123 614 A2 relates to a honeycomb structure comprising, in part, a zeolite and an inorganic binder. In particular, the first zeolite included in the structure further includes a second zeolite ion-exchanged with metals including Cu, Mn, Ag and V, and exchanged with metals including Fe, Ti and Co. With regard to the types of zeolites used in the primary and secondary zeolites, this includes zeolite beta, zeolite Y, ferrilite, ZSM-5 zeolite, mordenite, fuserite, zeolite A and zeolite L.

Finally, US 7,332,148 B2 is a stabilized aluminosilicate zeolite comprising copper or iron, wherein the stabilized zeolite is ZSM-5, ZSM-8, ZSM-11, ZSM-12, zeolite X, zeolite Y, zeolite Zeolites including beta, mordenite and erionite are described.

Accordingly, the prior art relates, in particular, to the recognition of the utility of metal-promoted zeolite catalysts, including iron-promoted and copper-promoted zeolite catalysts, especially for the selective catalytic reduction of nitrogen oxides with ammonia.

Currently, however, increasing stringent legislation with respect to emissions, particularly with regard to automotive exhaust emissions, requires improved catalyst and exhaust treatment systems using such catalysts for their treatment. Thus, the exhaust gas emission legislation in the European Union for the exhaust gas emission stage Euro 6 now requires a reduction of NO _x emissions for most passenger vehicles driven by diesel engines. For this purpose, emissions are tested using the New European Driving Cycle (NEDC), also referred to as the Motor Vehicle Emissions Group (MVEG) cycle, as defined in the European Union Directive 70/220 / EEC. One way to meet this requirement involves the application of SCR catalyst technology to the vehicle's exhaust gas system.

In contrast to the Old European Driving Cycle (ECE-15) driving cycle, a particular feature of the NEDC is that it is integrated with the so-called metropolitan driving cycle, so that the test better represents the typical use of the vehicle in Europe, and thus the conventional Can better represent the emission pattern. More particularly, in NEDC, the Old European Driving Cycle ECE-15 is performed in a time period of 0 to 800 seconds after the metropolitan driving cycle is performed in a time period of 1200 seconds or less.

It is therefore an object of the present invention, in particular, as an improved catalyst for use in selective catalytic reduction, which provides a catalyst that is better suited to the actual emission conditions encountered in automotive use, such as, for example, encountered in NEDC. .

In this regard, it has surprisingly been found that according to the invention as described below, an improved catalyst can be provided. In particular, it has unexpectedly been found that catalysts comprising zeolites of both MFI and BEA structure types, each containing both MFI and BEA type zeolites, respectively, exhibit clearly improved catalytic properties, especially when used in the SCR field.

Accordingly, the present invention preferably comprises a catalyst for use in selective catalytic reduction (SCR), wherein the catalyst comprises at least one zeolite of MFI structure type and at least one zeolite of BEA structure type, and of 1 of MFI structure type At least a portion of the at least one zeolite and at least a portion of the at least one zeolite of the BEA structure type each relates to a catalyst comprising iron (Fe).

Within the meaning of the present invention, the term "selective catalytic reduction", abbreviated as "SCR", means any catalytic process involving the reaction of nitrogen oxides NO _x with a reducing agent. In particular, SCR means a reduction reaction in which NO _x is converted to its reduction product, which is preferably N ₂ . With respect to the term "reducing agent", the term is preferably used for SCR processes in which ammonia and / or any ammonia precursors such as urea and / or ammonium carbamate are preferred, and urea is preferably included in the ammonia precursor. Means any suitable reducing agent. Even more preferably, the term "reducing agent" means ammonia. However, the term "reducing agent" may further include hydrocarbons and / or hydrocarbon derivatives, such as oxidized hydrocarbons, as may be found in automotive fuels and / or automotive exhaust gases, in particular diesel fuels and / or diesel exhaust gases. .

According to the invention, any conceivable zeolite of the MFI or BEA structure type can be used, respectively, as long as it represents the usual structural features of that structure type. With regard to one or more zeolites of MFI structure, this is for example ZSM-5, [As-Si-O] -MFI, [Fe-Si-O] -MFI, [Ga-Si-O] -MFI, AMS -1B, AZ-1, Bor-C, Boralite C, Encilite, FZ-1, LZ-105, Monoclinic H-ZSM-5, Mutinaite, NU-4, NU-5, Silicalite, Selected from the group consisting of TS-1, TSZ, TSZ-III, TZ-01, USC-4, USI-108, ZBH, ZKQ-1B, ZMQ-TB, organic free ZSM-5, and mixtures of two or more thereof It may include one or more zeolites. According to a preferred embodiment of the invention, the at least one zeolite of the MFI structure type comprises ZSM-5.

With respect to one or more zeolites of the BEA structure, it is Beta, [B-Si-O] -BEA, [Ga-Si-O] -BEA, [Ti-Si-O] -BEA, Al enriched beta, CIT- 6, tschernichite, pure silica beta, and one or more zeolites selected from the group consisting of two or more thereof. According to a preferred embodiment of the invention, the at least one zeolite of the BEA structure type comprises zeolite beta.

According to a further preferred embodiment of the invention, the at least one zeolite of the MFI structure type comprises ZSM-5 and the at least one zeolite of the BEA structure type comprises zeolite beta, and according to a particularly preferred embodiment, the MFI structure At least one zeolite of the type comprises ZSM-5 and at least one zeolite of the BEA structure type comprises zeolite beta.

According to the invention, at least some of the at least one MFI type of zeolite and at least some of the at least one BEA type of zeolite each comprise iron. With regard to iron contained in at least a portion of at least one zeolite of at least one MFI type and at least a portion of at least one BEA type of zeolite, the metals may each be contained therein in any conceivable manner and in any conceivable state. have. Thus, according to the present invention, there is no particular limitation as regards the oxidation state of iron contained in the catalyst and also in the manner in which it is included in each type of zeolite. Preferably, however, iron exhibits a positive oxidation state in each zeolite. Iron may also be included on the zeolite surface and / or in the porous structure of each zeolite structure. Alternatively or in addition to being supported on the zeolite surface and / or in its porous structure, iron may be included in the zeolite structure, for example by isotropic substitution. According to a preferred embodiment, iron is supported both on each zeolite surface and / or in its porous structure, even more preferably both on each zeolite surface and in its porous structure. According to a particularly preferred embodiment of the invention, iron is included in at least a portion of one or more zeolites of the MFI and BEA structure types, each in a positive oxidation state, wherein iron is included in its porous structure, Supported on the surface.

The catalyst according to the invention may comprise at least one zeolite of MFI structure type and at least one zeolite of BEA structure type in any conceivable weight ratio, and at least one zeolite of MFI structure type to one kind of BEA structure type The weight ratio of the above zeolite is 1:10 to 10: 1, more preferably 1: 5 to 5, more preferably 1: 2 to 2: 1, more preferably 0.7: 1 to 1: 0.7, more preferably Is preferably in the range from 0.8: 1 to 1: 0.8, even more preferably from 0.9: 1 to 1: 0.9. According to an embodiment of the invention, the weight ratio of zeolite of the MFI type to zeolite of the BEA type is approximately 1: 1.

According to the invention, it is preferred that the at least one zeolite of the MFI structure type and / or the at least one zeolite of the BEA structure type each comprise both Al and Si in its structure, and of the zeolite and BEA structure type of the MFI structure type More preferably, both zeolites comprise both Al and Si in their structure. Thus, according to the invention, it is preferred that at least one, more preferably all of the zeolites comprise both Al and Si in their respective zeolite structures.

With regard to embodiments of the invention wherein at least one zeolite comprises both Al and Si in its respective structure, the zeolite may in principle exhibit any possible ratio of Al to Si. In embodiments of the invention wherein at least one zeolite of MFI structure type comprises both Al and Si in its structure, but the molar ratio (SAR) of silica to alumina in at least one zeolite of MFI structure type is from 5 to 150, It is more preferably in the range from 15 to 100, more preferably from 20 to 50, more preferably from 23 to 30, even more preferably from 25 to 27. Furthermore, in embodiments of the invention wherein at least one zeolite of the BEA structure type comprises both Al and Si in its structure, the SAR in the at least one zeolite of the BEA structure type is 5 to 150, preferably 20 to 100. , More preferably from 30 to 70, more preferably from 35 to 45, even more preferably from 38 to 42. According to an embodiment of the invention wherein at least one zeolite of both MFI and BEA structure types each comprises Al and Si in its structure, the SAR in at least one MFI type zeolite ranges from 5 to 150, and SAR in the above BEA type zeolites ranges from 5 to 150, more preferably SAR in the at least one MFI type zeolite ranges from 15 to 100, and SAR in the at least one BEA type zeolite ranges from 20 to 100. Range, more preferably, SAR in at least one MFI type of zeolite is in the range of 20-50, SAR in at least one BEA type of zeolite is in the range of 30 to 70, and more preferably at least one MFI type SAR in the zeolite of the range of 23 to 30, SAR in the zeolite of one or more BEA type ranges from 35 to 45, even more preferably one or more MFI type SAR is a 25 to 27 range in the zeolite, the SAR at least one of the BEA type zeolite are preferred in addition to the 38 to 42 range.

With regard to the iron contained in the zeolites of the MFI and BEA types respectively, there is no particular limitation according to the invention with respect to their respective amounts. However, according to the invention, it is preferred that the amount of iron (Fe) in the at least one zeolite of the MFI structure type is included in the range of 0.1 to 15% by weight, based on the weight of the at least one zeolite of the MFI structure type, More preferably the amount of Fe is 0.5 to 10% by weight, more preferably 1.0 to 7.0% by weight, more preferably 2.5 to 5.5% by weight, more preferably 3.5 to 4.2% by weight, even more preferably 3.7 To 4.0 wt%. Furthermore, according to the invention, it is preferred that the amount of iron (Fe) in the at least one zeolite of the BEA structure type ranges from 0.05 to 10% by weight, based on the weight of the at least one zeolite of the BEA structure type, more preferably. Preferably the amount of Fe is in the range of 0.1 to 5% by weight, more preferably 0.5 to 2% by weight, even more preferably 1.0 to 1.6% by weight. According to an embodiment of the invention, the amount of iron in the at least one MFI type of zeolite is in the range of 0.1 to 15% by weight, the amount of iron in the at least one BEA type of zeolite is in the range of 0.05 to 10% by weight, more preferably The amount of iron in the zeolite of the at least one MFI type is in the range of 1.0 to 7.0 wt%, the amount of iron in the zeolite of the at least one BEA type is in the range of 0.1 to 5 wt%, more preferably in the zeolite of the at least one MFI type The amount of iron is in the range of 2.5 to 5.5% by weight, the amount of iron in the at least one BEA type zeolite is in the range of 0.5 to 2% by weight, and more preferably the amount of iron in the at least one MFI type of zeolite is 3.5 to 4.2% by weight. Range, the amount of iron in the zeolite of the at least one BEA type is in the range of 0.5 to 2% by weight, and even more preferably, the zeoli of the at least one MFI type An amount of iron in the 3.7 to 4.0% by weight, the amount of 1.0 to 1.6 wt% of the iron in the zeolite of at least one type BEA.

According to the invention, the catalyst may be provided in any conceivable form, such as in the form of a powder, granules or monolith, by way of example. In this connection, it is particularly preferred that the catalyst further comprises a substrate provided with at least one zeolite. In general, the substrate can be made from materials commonly known in the art. For this purpose, the porous material is preferably a base material, in particular ceramic and ceramic like materials such as cordierite, α-alumina, aluminosilicate, cordierite-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconia, Mullite, zircon, zircon mullite, zircon silicate, silimite, magnesium silicate, petalite, spodumene, alumina-silica-magnesia and zirconium silicate, and porous refractory metals and oxides thereof. According to the present invention, "refractory metal" means at least one metal selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Re. The substrate may also be formed from a ceramic fiber composite material. According to the invention, the substrate is preferably formed from cordierite, silicon carbide and / or aluminum titanate, even more preferably cordierite and / or silicon carbide.

Substrates useful in embodiments of the catalyst of the invention may also be metallic in nature and may consist of one or more metals or metal alloys. The metallic substrate can be used in various shapes, such as corrugated sheet or monolithic form. Suitable metallic supports include heat resistant metals and metal alloys, such as titanium and stainless steel, and other alloys in which iron is the real or main component. Such alloys may comprise one or more of nickel, chromium and / or aluminum and the total amount of such metals is advantageously at least 15% by weight of alloys, for example 10-25% by weight of chromium, 3-8% by weight. Aluminum and up to 20% nickel by weight. The alloy may also include small or trace amounts of one or more other metals such as manganese, copper, vanadium, titanium, and the like. The surface or metal substrate can be oxidized at high temperature, for example 1000 ° C. or higher, to form an oxide layer on the surface substrate to improve the corrosion resistance of the alloy.

In addition, the substrate according to the invention may be of any conceivable shape, provided that it should allow fluid contact with at least a portion of each of the one or more zeolites of the MFI and BEA structure types present above. Preferably, the substrate is monolith, more preferably monolith is a flow through monolith. Suitable substrates include any materials commonly used to make catalysts and generally include ceramic or metal honeycomb structures. Thus, the monolith substrate includes a fine, parallel gas flow passage extending from the inlet of the substrate to the outlet face of the substrate, whereby the passage is open to the fluid flow (called a honeycomb flow passage substrate). The passageway, which is an essentially straight path from its fluid inlet to its fluid outlet, is defined by a wall on which one or more zeolites of the MFI and BEA structure types are respectively disposed, so that gas passing through the passage can contact it. The flow passage of the monolith substrate is a thin wall channel that can be any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical or circular. Such a structure may comprise up to 900 gas inlet holes (ie cells) per square inch of cross section, and the structure according to the invention is preferably 50 to 600 per square inch, more preferably 300 to 500 Dogs, even more preferably 350 to 400 holes.

Thus, according to a preferred embodiment of the present invention, the catalyst comprises a monolith substrate, preferably a honeycomb substrate.

According to a further preferred embodiment of the invention, the substrate is a wall flow monolith. For this embodiment, the substrate is preferably a honeycomb wall flow filter, a winding or filled fiber filter, an open cell foam, or a calcined metal filter, with wall flow filters being particularly preferred. For equally preferred flow through monoliths, useful wall flow substrates have a plurality of fine, substantially parallel gas flow passages that extend along the long axis of the substrate. Typically, each passage is blocked at one end of the substrate body and the alternate passages are blocked at opposite end faces. Particularly preferred wall flow substrates for use in the present invention include thin porous wall honeycomb monoliths through which a fluid stream can pass without causing a back pressure or a too large increase in pressure across the catalyst. The ceramic wall flow substrate used in the present invention is preferably formed from a material having a porosity of at least 40%, preferably 40 to 70%, and having an average pore size of at least 5 microns, preferably 5 to 30 microns. . Further preferred are substrates having a porosity of at least 50% and an average pore size of at least 10 microns.

Thus, according to the present invention, the substrates preferably included in the catalyst are preferably a group consisting of a flow through substrate and a wall flow substrate, more preferably a cordierite flow through substrate and a wall flow substrate, and a silicon carbide flow through substrate And wall flow substrates.

In general, according to an embodiment of the invention further comprising a substrate, the zeolite may be provided above in any conceivable manner, and it is preferred that it is provided above in the form of one or more layers, preferably washcoat layers. In a preferred embodiment of the invention, the catalyst comprises a substrate and two or more layers provided thereon, and zeolites may be provided in the two or more layers in any possible manner. Thus, the present invention includes, for example, this preferred embodiment wherein the zeolite is included in only one single layer of two or more layers and the embodiment in which the zeolite is included in one or more of two or more layers. Preferably, however, the zeolite is included in a single layer regardless of the number of layers present on the substrate.

Thus, according to a preferred embodiment of the invention in which the catalyst comprises a substrate, the catalyst comprises at least one layer, preferably a washcoat layer, provided on the substrate, the zeolite in one single layer or at least two independent layers It is further preferred that it is included and preferably the zeolite is included in one single layer.

In a further embodiment of the invention comprising a substrate and at least two layers provided thereon and zeolites included in at least one of the layers, one of the MFI and BEA structure types in the at least one layer comprising the zeolites There is no particular limitation on the distribution of zeolites over species. Thus, in principle, according to the invention, for example, zeolites of the MFI and BEA types may be included in each of the layers comprising zeolites, or alternatively, only some of the layers comprising the zeolites may be of the MFI and BEA types It can include both zeolites. Furthermore, according to this further embodiment of the invention, the single layer does not comprise both MFI and BEA type zeolites, and thus the zeolites are included in an independent layer of the catalyst. However, according to the invention, it is preferred that at least one layer in this embodiment comprises both MFI and BEA type zeolites, and each of the at least two layers of said embodiment comprising zeolite also contain MFI and BEA. Even more preferred is to include both types of zeolites.

In principle, one or more zeolites of the MFI and BEA structure types may each be present in the catalyst in any conceivable amount, provided that an improved catalyst according to the invention can be obtained. Thus, either at least one zeolite of MFI structure type or at least one zeolite of BEA structure type, or at least one zeolite of MFI structure type and at least one zeolite of BEA structure type are each 0.1 to 5.0 g / in. ^It may be present in the catalyst in a loading in the range of ^3, the loading of which is preferably 0.7 to 2.0 g / in ³ , more preferably 1.0 to 1.7 g / in ³ , more preferably 1.15 to 1.55 g / in ³ , more Preferably 1.25 to 1.45 g / in ³ , more preferably 1.32 to 1.38 g / in ³ , even more preferably 1.34 to 1.36 g / in ³ . In particular, each loading of the MFI and BEA type zeolites can be independent of each other in that the preferred loading range can be applied to either of the MFI or to BEA type zeolites, and the loading of one or more zeolites belonging to different structure types Are not particularly limited each, and therefore may be present in any loading or may be limited to different ranges of loading. Thus, the invention also relates to embodiments in which, for example, the loading of zeolites of MFI type ranges from 0.1 to 5.0 g / in ³ , and the loading of zeolites of BEA type ranges from 1.34 to 1.36 g / in ³ , or for example MFI. Embodiments or loadings of zeolites of the MFI type of 1.0 to 1.7 g / in an embodiment wherein the loading of the zeolite of the type ranges from 0.7 to 2.0 g / in ³ and the loading of the zeolite of the BEA type ranges from 1.32 to 1.38 g / in ³ in ³ range is, and the loading of the zeolite of the BEA type 1.25 to 1.45 g / in ³ range of embodiments, or for example the loading is 1.15 to 1.55 g / in ³ range of MFI type zeolite, the loading of the zeolite of the BEA type Embodiments or examples where this ranges from 1.15 to 1.55 g / in ³ , for example, the loading of zeolites of the MFI type ranges from 1.25 to 1.45 g / in ³ , and the loading of the zeolites of the BEA type ranges from 1.0 to 1.7 g / in ^3. Aspect or for example M Embodiments wherein the loading of zeolites of the FI type ranges from 1.32 to 1.38 g / in ³ and the loading of zeolites of the BEA type ranges from 0.7 to 2.0 g / in ³ , for example the loading of zeolites of the MFI type ranges from 1.34 to 1.36 g / in ³ range, wherein the BEA type zeolite has a loading ranging from 0.1 to 5.0 g / in ³ .

In addition to the catalysts mentioned above, the invention also relates to a treatment system for an exhaust gas stream. In particular, the treatment system of the present invention comprises an internal combustion engine, which is preferably a lean burn engine, even more preferably a diesel engine. According to the invention, however, it is also possible to use a lean burn gasoline engine in the treatment system.

The treatment system according to the invention also comprises an exhaust gas conduit in fluid communication with the internal combustion engine. In this regard, any conceivable conduit can be used, provided that it can deliver exhaust gas from an internal combustion engine and be sufficiently resistant to chemical species and temperatures encountered in the exhaust gas of an internal combustion engine, in particular a lean burn engine such as a diesel engine. It should be possible. Within the meaning of the present invention, the fluid communication provided between the exhaust gas conduit and the internal combustion engine means that the processing system allows a constant passage of exhaust gas from the engine to the conduit.

According to the exhaust gas treatment system of the present invention, the catalyst is present in the exhaust gas conduit. In general, the catalyst can be provided in the exhaust gas conduit in any conceivable manner, but it must be present in the exhaust gas conduit in that it can be in contact with the exhaust gas passing through the conduit. Preferably, the catalyst is provided in the exhaust gas conduit on the substrate as described in the background of the present application, particularly on the honeycomb substrate which is preferably a flow through or wall flow honeycomb substrate.

The invention therefore also comprises an exhaust gas treatment system comprising an internal combustion engine and an exhaust gas conduit in fluid communication with the internal combustion engine, wherein the catalyst according to the invention is present in the exhaust gas conduit and the internal combustion engine is preferably a lean burn engine, more Preferably it relates to an exhaust gas treatment system which is a diesel engine.

In this regard and independent of the present invention, the present invention also encompasses an exhaust gas treatment system in which the catalyst of the present invention comprises an internal combustion engine and an exhaust gas conduit in fluid communication with the internal combustion engine, wherein the catalyst is present in the exhaust gas conduit, The internal combustion engine is preferably an embodiment wherein the lean burn engine, more preferably a diesel engine.

According to a preferred embodiment of the invention, the exhaust gas treatment system further comprises means for introducing a reducing agent into the exhaust gas stream, said means being located upstream of the MFI / BEA zeolite catalyst of the invention. In particular, it is preferred to provide means for introducing ammonia and / or urea into the exhaust gas conduit. In this regard, it can be provided that it can be conventionally applied to any means known to those skilled in the art, in particular to an exhaust gas treatment system operated by an active SCR method which requires the direct introduction of said reducing agent. According to a particularly preferred embodiment, a reducing agent, preferably comprising ammonia and / or urea, is introduced by means of an injection nozzle provided in the exhaust gas conduit upstream of the catalyst of the invention.

Within the meaning of the present invention, the exhaust gas treatment system may suitably further comprise any additional component for the effective treatment of the exhaust gas. In particular, the system preferably further comprises an oxidation catalyst or catalyzed soot filter (CSF) or both an oxidation catalyst and CSF. According to this embodiment, the oxidation catalyst and / or CSF is also present in the exhaust gas conduit.

In the present invention, any suitable CSF can be used, provided that it can effectively oxidize soot that may be included in the exhaust gas. To accomplish this, the CSF of the present invention preferably comprises a substrate coated with a washcoat layer comprising at least one catalyst for burning the trapped soot and / or for oxidizing the exhaust gas stream emissions. In general, the soot combustion catalyst may be any known catalyst for the combustion of soot. For example, CSF can be used for the combustion of unburned hydrocarbons and to some extent particulate materials, such as one or more high surface area refractory oxides (eg, alumina, silica, silica alumina, zirconia and zirconia alumina) and / or oxidation catalysts (eg For example, ceria-zirconia or the like). However, preferably the soot combustion catalyst is an oxidation catalyst comprising at least one precious metal catalyst and the at least one precious metal catalyst preferably comprises at least one metal selected from the group consisting of platinum, palladium and rhodium.

Performing any oxidation catalyst suitable for oxidizing non-combusted hydrocarbons, CO and / or NO _x contained in the exhaust gas, in connection with the oxidation catalyst preferably included in the exhaust gas treatment system instead of or in addition to the CSF. Can be used for In particular, oxidation catalysts comprising at least one precious metal catalyst, more preferably at least one precious metal selected from the group consisting of platinum, palladium and rhodium are preferred. According to an embodiment of the invention in which the internal combustion engine of the exhaust gas treatment system is a diesel engine, the oxidation catalyst is preferably a diesel oxidation catalyst. In particular, within the meaning of the present invention, "diesel oxidation catalyst" means any oxidation catalyst which is particularly well suited for the oxidation of diesel exhaust gas, especially with respect to the composition and temperature of the diesel exhaust gas which encounters its treatment.

According to a particularly preferred embodiment, the exhaust gas treatment system further comprises CSF, even more preferably both CSF and oxidation catalyst. Even more preferably, the exhaust gas treatment system further comprises a CSF and a diesel oxidation catalyst.

In principle, in embodiments of the exhaust gas treatment system further comprising an oxidation catalyst and / or CSF, the additional components may be present in any order and at any location within the exhaust gas conduit, provided that Effective treatment should be provided. In particular, however, the presence and / or order and / or location of said additional parts may vary depending on the type, in particular the condition with respect to its temperature and pressure, and the average composition of the treated exhaust gases. Thus, according to the application of the exhaust gas treatment system, the present invention comprises a preferred embodiment in which the oxidation catalyst and / or CSF is located upstream or downstream of the MFI / BEA zeolite catalyst of the invention, and both the oxidation catalyst and the CSF, Preferred embodiments include an oxidation catalyst located upstream thereof and a CSF located downstream thereof, or vice versa, CSF located upstream thereof and an oxidation catalyst located downstream thereof. According to an embodiment of the invention, the oxidation catalyst and / or CSF is located upstream of the MFI / BEA zeolite catalyst of the invention, and even more preferably, the exhaust gas treatment system is upstream of the MFI / BEA zeolite catalyst of the invention. Both oxidation catalysts and CSFs. Within the meaning of the present invention, "upstream" and "downstream" means the flow direction of the exhaust gas through the exhaust gas conduit in fluid communication with the internal combustion engine.

Accordingly, the present invention also provides an exhaust gas treatment system as defined above, wherein the exhaust gas treatment system further comprises an oxidation catalyst and / or a catalyzed soot filter (CSF), wherein the oxidation catalyst and / or CSF are preferably Located upstream of the MFI / BEA zeolite catalyst of the present invention, the oxidation catalyst relates to an exhaust gas treatment system which is a diesel oxidation catalyst (DOC) when the internal combustion engine is a diesel engine.

In addition, as described above, the exhaust gas treatment system preferably further comprises means for introducing a reducing agent into the exhaust gas conduit, said means being located upstream of the MFI / BEA zeolite catalyst of the present invention. In particular, the means allows a reducing agent comprising ammonia and / or urea to be introduced into the exhaust gas conduit. The present invention therefore also further comprises an oxidation catalyst and / or a catalyzed soot filter (CSF), each preferably located upstream of the MFI / BEA zeolite catalyst of the invention, wherein the oxidation catalyst is a diesel engine In addition to or instead of a diesel oxidation catalyst (DOC), the exhaust gas treatment system further comprises means for introducing a reducing agent, preferably comprising ammonia and / or urea, into the exhaust gas conduit, the means of the invention An exhaust gas treatment system located upstream of an MFI / BEA zeolite catalyst.

According to a further preferred embodiment of the invention, the exhaust gas treatment system further comprises an ammonia slip catalyst located downstream of the MFI / BEA zeolite catalyst for oxidizing excess ammonia and / or urea unreacted in the SCR. Include. With regard to the preferred ammonia slip catalyst, the catalyst can be provided in the exhaust gas conduit in any manner commonly known in the art, provided that it can effectively oxidize the excess ammonia and / or urea. In particular, said preferred embodiment comprises an exhaust gas treatment system according to the invention comprising means for introducing a reducing agent into the exhaust gas conduit as defined above.

In addition to the catalyst and the exhaust gas treatment system comprising the catalyst, the present invention relates to a process for treating a NO _x containing gas stream. In general, in the process of the invention, any suitable NO _x containing gas stream may be used, provided that its condition and composition are both suitable for treatment when contacted with the MFI / BEA zeolite catalyst according to the invention, Preferably the treatment involves at least partially selective catalytic reduction of at least a portion of the NO _x contained in the gas. For this purpose, the gas stream used in the process of the invention preferably comprises at least one reducing agent which is preferably ammonia and / or any ammonia precursor such as urea and / or ammonium carbamate, with urea being preferred. Preferably in the ammonia precursor. However, according to a further embodiment of the process of the invention, the gas streams used are also hydrocarbons and / or hydrocarbons such as can be found, for example, in automotive fuels and / or automotive exhaust gases, in particular diesel fuels and / or exhaust gases. Derivatives such as oxidized hydrocarbons. Said further reducing agent may be included in the gas treated in the process of the invention in addition to ammonia, or in accordance with further embodiments, may also be included therein instead of ammonia. However, according to the invention, it is particularly preferred that the gas comprises ammonia and / or urea as a reducing agent, in particular for the treatment of exhaust gas emissions via SCR.

Accordingly, the present invention also relates to a process for treating a NO _x containing gas stream as defined in the present application, wherein the gas stream comprises ammonia and / or urea.

With regard to the content of the reducing agent in the gas stream (the reducing agent preferably comprises ammonia and / or urea), there are no particular limitations in this regard, provided that at least some of the NO _x in the gas is an MFI / BEA of the invention. It should be able to be reduced by SCR when in contact with the zeolite catalyst. However, it is preferable that the above content is not significantly induced from the amount of the reducing agent required for the maximum conversion of NO _x by the catalyst. In this regard, the maximum conversion is included, preferably within, depending on the content of the reducing agent, in particular with respect to the actual state and conditions of both the gas and the catalyst to be treated at any point in time, ie upon contact thereof, in the process of the invention. It reflects the maximum amount of NO _x that can be converted by SCR, depending on the amount of ammonia and / or urea that has been converted. Therefore, the maximum conversion of NO _x is a direct reflection of the maximum amount of reducing agent, preferably ammonia and / or urea to react with the NO _x in the SCR process to a predetermined time.

According to a preferred embodiment of the invention, the gas stream used in the process of the invention is preferably an NO _x containing exhaust gas stream. In this regard, there are no particular limitations on the process of generating such an exhaust gas stream, provided that this may be suitable for treatment with the MFI / BEA zeolite catalyst according to the invention or may be processed into a gas stream suitable for treatment with such catalyst. It should be possible. According to the method of the invention, it is further preferred that the exhaust gas stream is an exhaust gas stream generated from an internal combustion engine, even more preferably a lean burn engine. According to a particularly preferred embodiment, the exhaust gas stream is a diesel engine exhaust gas stream.

In the process according to the invention, the contact is achieved by contacting the gas stream for treatment of the MFI / BEA zeolite catalyst of the invention and by delivering the gas stream over the catalyst or by delivering the gas stream through the catalyst. . However, the contact can also be achieved by delivering a gas stream both over and through the catalyst of the present invention. According to a preferred embodiment, the gas stream is delivered over the catalyst, where the catalyst preferably comprises a flow-through substrate for this purpose, or the gas stream is passed through the catalyst, in which case the catalyst is preferably Wall flow substrates). However, when using wall flow substrates, there are cases where at least a portion of the gas stream may also be delivered over the catalyst, depending on the process conditions and the particular form and dimensions of the catalyst. According to a particularly preferred embodiment of the process of the invention, the catalyst used in the process of the invention comprises either a wall flow honeycomb substrate or a flow through honeycomb substrate.

Accordingly, the present invention also provides a process for treating said gas stream comprising passing the NO _x containing gas stream over and / or through the MFI / BEA zeolite catalyst according to the invention, wherein the gas stream is preferably an exhaust gas stream, More preferably an exhaust gas stream generated from an internal combustion engine, even more preferably a diesel exhaust gas stream.

In the process of the invention, there is no particular limitation on the amount of NO _x present in the gas stream, and preferably, the amount thereof in the gas stream used in the process of the invention is 10% by weight based on the total weight of the exhaust gas. Not exceeding, more preferably 1% by weight, more preferably 0.5% by weight, more preferably 0.1% by weight, more preferably 0.05% by weight, more preferably 0.03% by weight, even more preferably 0.01 It does not exceed the weight percentage.

With regard to the specific composition of the NO _x fraction contained in the treated gas stream in the process of the invention, there is no restriction on the type or content of the particular nitrous oxide gas contained therein. However, in accordance with certain embodiments of the present invention, and the NO ₂ content of the total NO _x content less than 90% by weight, based on 100 wt% of the NO _x, more preferably from 10 to 80% by weight of NO ₂ content, More preferably 30 to 7% by weight, more preferably 35 to 65% by weight, more preferably 40 to 60% by weight, even more preferably 45 to 55% by weight.

In general, the composition of the gas stream used in the process of the invention as defined in the present application means the gas stream before its use in the process of the invention, in particular before its contact with the catalyst. Preferably, however, the composition refers to the composition of the gas stream immediately before contact with the catalyst, ie just prior to its treatment, initiated by its accelerated chemical conversion.

Accordingly, the present invention also provides a process for treating a NO _x containing gas stream as defined herein, wherein prior to contacting the catalyst with the gas stream, its NO ₂ content is no greater than 90 wt%, based on 100 wt% of NO _x . And more preferably, the NO ₂ content is 10 to 80% by weight, more preferably 30 to 70% by weight, more preferably 35 to 65% by weight, more preferably 40 to 60% by weight, even more preferred. Preferably to 45 to 55% by weight.

The catalyst according to the invention can be easily prepared by methods well known in the art. Representative methods are described below. As used herein, "washcoats" are used in the field of thin adhesive coatings of catalysts or other materials applied to substrate carrier materials, such as honeycomb type carrier members, which are preferably sufficiently porous to allow passage therethrough of the gas stream being treated. Has its general meaning.

The various zeolitic components of the catalyst can be applied to the substrate as a mixture of one or more components in sequential steps in a manner readily apparent to those skilled in the art of catalyst preparation. Conventional processes for preparing the catalysts of the present invention each comprise one or more zeolites of the MFI structure type and one or more additional zeolites of the BEA structure type as coating or washcoat layers on the walls of particularly preferred flow through or wall flow honeycomb substrates, respectively. To provide. According to certain preferred embodiments of the invention, the zeolite is provided in a single washcoat on the substrate.

The catalysts according to the invention are however preferably prepared using further one or more binders and can use any conceivable binder used in the field of catalyst production, in particular in the field of automobile SCR catalyst production. In this regard, silica-alumina binders are preferably used, for example, in the preparation of the catalysts of the invention, which binders may be provided with at least one zeolite component, preferably at least one coating on the substrate, more preferably Preferably provided with a zeolite component in at least one washcoat layer.

To prepare the catalyst of the invention, the components of one or possibly more washcoat layers can each be processed into a slurry, preferably an aqueous slurry. The excess slurry is then removed to provide a thin coating of two or more slurries on the walls of the substrate and then the substrates are sequentially immersed with each slurry to apply each washcoat. The coated substrate is then dried and preferably calcined to provide an adhesive coating of each component to the walls of the substrate. Thus, for example, after providing a first washcoat layer over the substrate, preferably after drying and / or calcining the coated substrate, the resulting coated substrate is then immersed in an additional slurry to form the first washcoat layer. It is possible to form a second washer coat layer deposited thereon. Again, the substrate may then be dried and / or calcined and eventually coated with a third washcoat, which in turn may be subsequently dried and / or calcined to provide the final catalyst according to one embodiment of the present invention. With regard to the steps of drying, washing and calcination of the coated catalyst in this way, this is particularly true with respect to the solvents and / or solutions used for washing the coated catalyst, and the temperatures used in the steps of drying and calcination, respectively, Each can be carried out in a manner well known in the art of catalyst preparation in terms of duration and atmosphere. With regard to the calcination step, any possible temperature can be used here, provided that the desired conversion in the catalyst occurs without causing the process to cause any notable or substantial degradation of catalyst stability, particularly with regard to its use in SCR. You have to. Thus, in certain cases, the calcination temperature does not exceed 700 ° C, preferably 650 ° C, more preferably 600 ° C, even more preferably 550 ° C. Thus, at temperatures comprised in the range of 500 ° C. to 650 ° C., preferably 550 ° C. to 600 ° C., more preferably 570 ° C. to 590 ° C., more preferably, even more preferably in the range of 575 ° C. to 585 ° C. Calcination can be carried out at an included temperature, for example.

However, when preparing the catalyst of the present invention in the manner mentioned above, it is preferred not to perform the washing of the washcoat layer after its application and any drying.

Thus, the catalyst of the present invention

(a) providing at least one zeolite of the MFI structure type and at least one additional zeolite selected from zeolites of the BEA structure type, wherein at least some of the at least one zeolite of the MFI structure type and at least one of the BEA structure type At least a portion of the above additional zeolites comprise iron;

(b) providing one or more washcoat compositions, each comprising one or more of zeolites;

(c) applying to the substrate at least one washcoat composition in at least one respective layer, optionally performing a drying step after each application of at least one of each layer;

(d) optionally washing and / or drying the coated substrate, wherein the coated substrate is preferably not washed; And

(e) subjecting the optionally coated substrate to a calcination process

It may be prepared according to a method comprising a.

BRIEF DESCRIPTION OF THE DRAWINGS Fig.

Figure 1 respectively in Example 1 and Comparative Example 2 shows results from the NEDC test of the catalyst composition according to the coordinates of the test period in seconds on the x-axis, and coordinate the NO _x emissions of NO _x in grams on the y-axis The background shows the legally prescribed course of the NEDC test over a period of time in terms of the variation in the speed of the car as defined by the European Union Directive 70/220 / EEC.

[Example]

Example  One

Zeolite of a BEA structure type with a silica to alumina ratio (SAR) of approximately 40 and 1.3% by weight based on the total weight of zeolites of BEA type, 1.35 g / in ³ , a silica to alumina ratio of about 26 and a MFI type of A catalyst composition was prepared comprising 1.35 g / in ³ of zeolite of MFI structure type and 0.3 g / in ³ of silica-alumina binder, comprising 3.8% by weight of iron based on the total weight of zeolite.

Comparative example  2

2.7 g / in ³ of the zeolite of BEA structure type and 0.3 g / in ³ of the silica-alumina binder, having a silica to alumina ratio (SAR) of approximately 40 and containing 1.3 wt% of iron based on the total weight of the BEA type zeolite. A catalyst composition was prepared.

SCR Performance test

The DeNO _x performance of SCR catalysts was evaluated under transient conditions using the New European Driving Cycle, also called the Motor Vehicle Emissions Group (MVEG) cycle. In particular, the test conditions were that the NO _x fraction of the exhaust gas stream comprised approximately 50% by weight of NO ₂ based on the total NO _x content.

For testing, the catalyst compositions according to Example 1 and Comparative Example 2 were respectively prepared with 5.66 "x 5.06" x 6 with a volume of 2.5 L, a cell density of 400 cells per square inch and a wall thickness of approximately 100 μm (4 mil). Coated on a flow-through honeycomb substrate. The catalyst samples prepared in this manner were then tested in an exhaust gas treatment system with a diesel oxidation catalyst (DOC) and a catalyzed soot filter (CSF) positioned upstream of the tested catalyst, respectively. It was.

The results from the NEDC catalyst test are shown in FIG. 1. Thus, as can be taken from the figures, the catalyst of the invention according to Example 1 comprising a combination of BEA and MFI type zeolites is clearly improved compared to the catalyst sample of Comparative Example 2 comprising only BEA type zeolites. Performance was shown. In particular, considering the results shown in FIG. 1 where the level of NO _x emissions is plotted as a function of the NEDC test period, the catalyst of the present invention is compared for a period of 0 to 800 seconds corresponding to the Old European Driving Cycle (ECE-15). Compared to Example 2, the conversion performance was better. However, the advantages of the inventive catalyst of Example 1 are important when considering a test period of 800 to 1200 seconds, which corresponds to the metropolitan part of the run cycle comprising higher space velocity and higher NO _x mass flow.

As a result, the catalyst according to the invention clearly shows better performance in SCR compared to the catalyst according to the prior art represented by Comparative Example 2, especially with regard to the actual driving conditions encountered in the use of automobiles as reflected in the NEDC test. Showed. In particular, this excellent result could be due to the use of certain combinations of zeolite materials as defined by the catalyst of the present invention.

Claims (17)

Preferably for use in selective catalytic reduction (SCR),
At least one zeolite of the MFI structure type, and
One or more zeolites of BEA structure type
A catalyst comprising: at least a portion of at least one zeolite of MFI structure type and at least a portion of at least one zeolite of BEA structure type each comprise iron (Fe). The weight ratio of at least one zeolite of the MFI structure type to at least one zeolite of the BEA structure type is 1:10 to 10: 1, preferably 1: 5 to 5: 1, more preferably 1 Catalyst ranging from 2: 2 to 2: 1, more preferably from 0.7: 1 to 1: 0.7, more preferably from 0.8: 1 to 1: 0.8, even more preferably from 0.9: 1 to 1: 0.9. 3. The catalyst according to claim 1, wherein at least one of the zeolites, preferably all of the zeolites, comprises both Al and Si in their respective zeolite structures. The method according to claim 3, wherein the molar ratio (SAR) of silica to alumina in at least one zeolite of the MFI structure type is 5 to 150, preferably 15 to 100, more preferably 20 to 50, more preferably 23 to 30. Even more preferably in the range from 25 to 27. The molar ratio (SAR) of silica to alumina in at least one zeolite of the BEA structure type is from 5 to 150, preferably from 20 to 100, more preferably from 30 to 70, more preferably. Is in the range 35 to 45, even more preferably 38 to 42. The amount of Fe in at least one zeolite of the MFI structure type is in the range of 0.1 to 15% by weight, preferably Fe, based on the weight of the at least one zeolite. The amount of is in the range of 0.5 to 10% by weight, more preferably 1.0 to 7.0% by weight, more preferably 2.5 to 5.5% by weight, more preferably 3.5 to 4.2% by weight, even more preferably 3.7 to 4.0% by weight. catalyst. The amount of Fe in at least one zeolite of the BEA structure type is in the range of 0.05 to 10% by weight, preferably Fe, based on the weight of the at least one zeolite. The amount of is in the range of 0.1 to 5% by weight, more preferably 0.5 to 2% by weight, more preferably 1.0 to 1.6% by weight. 8. The catalyst according to claim 1, further comprising a substrate, preferably a honeycomb substrate, provided with at least one zeolite. 9. The substrate according to claim 8, wherein the substrate is a group consisting of flow-through substrates and wall-flow substrates, preferably cordierite flow-through substrates and wall flow substrates, and silicon carbide flow-through substrates and And a catalyst selected from the group consisting of wall flow substrates. 10. The catalyst according to claim 8 or 9, wherein the catalyst comprises at least one layer, preferably a washcoat layer, provided on the substrate and the zeolite is contained in one single layer or at least two independent layers, preferably The zeolite is contained in one single layer. The method of claim 1, wherein at least one zeolite of the MFI structure type or at least one zeolite of the BEA structure type, or at least one zeolite of the MFI structure type and one of the BEA structure type. Both species of zeolite are each 0.1 to 5.0 g / in ³ , preferably 0.7 to 2.0 g / in ³ , more preferably 1.0 to 1.7 g / in ³ , more preferably 1.15 to 1.55 g / in ³ , more Preferably in the catalyst with a loading ranging from 1.25 to 1.45 g / in ³ , more preferably 1.32 to 1.38 g / in ³ , even more preferably 1.34 to 1.36 g / in ³ . 12. The catalyst of any one of the preceding claims, wherein the catalyst is included in an exhaust gas treatment system comprising an internal combustion engine and an exhaust gas conduit in fluid communication with the internal combustion engine, wherein the catalyst is present in the exhaust gas conduit and the internal combustion engine Preferably a lean burn engine, more preferably a diesel engine. An exhaust gas treatment system comprising an internal combustion engine and an exhaust gas conduit in fluid communication with the internal combustion engine, wherein the catalyst according to any one of claims 1 to 11 is present in the exhaust gas conduit and the internal combustion engine is preferably lean burn. Exhaust gas treatment system which is an engine, more preferably a diesel engine. The system of claim 13, wherein the exhaust gas treatment system further comprises an oxidation catalyst and / or a catalyzed soot filter (CSF), wherein the oxidation catalyst and / or CSF is preferably any one of claims 1 to 11. Located upstream of the catalyst according to, the oxidation catalyst is a diesel oxidation catalyst (DOC) when the internal combustion engine is a diesel engine. A NO _x treatment method for containing gas stream comprising NO _x contained delivery of a gas stream through any one of claims 1 to 11, wherein in the catalyst to the top and / or a catalyst according to any one of the preceding, the gas stream is preferably an exhaust gas stream, more preferably a method of treating an exhaust gas stream, the nO _x containing gas stream, more preferably a diesel exhaust gas stream produced from an internal combustion engine. The method of claim 15 wherein the gas stream processing method of the NO _x containing gas stream comprises ammonia and / or urea. 17. The method according to claim 15 or 16, wherein prior to contacting the catalyst with the gas stream, the NO ₂ content of the gas stream is at most 90% by weight, based on 100% by weight of NO _x , preferably the NO ₂ content is from 10 to 18. 80 wt%, more preferably 30 to 70 wt%, more preferably 35 to 65 wt%, more preferably 40 to 60 wt%, even more preferably 45 to 55 wt% Process of treating a NO _x containing gas stream.

Images