EA046217B1 - CATALYTIC COMPOSITION FOR SELECTIVE NOx REDUCTION - Google Patents

Description

Field of technology

The present invention relates to the field of selective catalytic reduction catalysts for nitrogen oxides and to methods for preparing and using such catalysts for selective catalytic reduction. Ammonia and precursors such as ammonia-forming urea are used as reducing agents for such catalysts. In particular, the present invention relates to a catalyst composition for the selective catalytic reduction of _NOx with ammonia or ammonia-releasing compounds under flue gas conditions. The invention further relates to a structural support for use in a flue gas system containing the present catalyst composition, as well as to the use of the catalyst composition. The present invention also relates to a flue gas treatment system containing a catalyst composition according to the present invention. The present invention also relates to a method for the selective catalytic reduction of NO _x with ammonia or ammonia-forming compounds under off-gas conditions.

State of the art

Nitrogen oxide ( _NOx ) emissions have been limited by regulations since the early 1970s, first for power plants in Japan and for passenger cars in California, USA. Passenger cars were based on stoichiometric Otto engines, which easily remove CO, HC and NO _x on three-way catalysts (TCCs) under stoichiometric conditions. Selective catalytic reduction (SCR) for NO _x removal using ammonia as a reducing agent was invented in the 1960s and first used commercially in power plants. These CKB-NH ₃ catalysts were based on vanadium as the active metal located on a porous TiO ₂ -WO ₃ -based support. Vanadium SCR catalysts withstand sulfur oxides (SOX) well, but thermal stability is limited to maximum temperatures of 450-600°C. SCR catalysts are supported on ceramic and metal substrates, or the catalyst material itself forms an extruded SCR catalyst.

Aftertreatment systems (TPS) for the latest emission control for mobile lean burn applications include a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a urea hydrolysis unit, a NO _x removal unit/process, and possibly an ammonia slip catalytic converter (ASC). ). In addition to NH ₃ -CKB, other NO _x removal methods for lean burn applications are hydrocarbon-SCR (HC-SCR), NO decomposition, lean NO _x traps (LNT), and absorption/adsorption methods. Methods vary depending on the intended application and application conditions (lean, lean-rich or stoichiometric). The catalyst compositions are completely different under each method. Heavier vehicles have been fitted with diesel engines where the air/fuel ratio is clearly lean (too much oxygen). In lean flue gases, selective reducing agents are needed to remove _NOx from the flue gases. Ammonia is the main practical and selective NO _x reducer in lean fuel mixtures. Typically, urea ((NH ₂ ) ₂ CO) is used in aqueous solution as a source of ammonia for transport and safety reasons. Urea produces ammonia in thermolysis and hydrolysis reactions when an aqueous solution is injected into heated exhaust gases, possibly using static mixer designs. LNTs operate under conditions that are on average lean, and periodic short rich peaks are necessary to reduce the amount of NO _x adsorbed during lean periods. The disadvantages of LNT are the negative impact on fuel economy, poor durability and _NOx conversion too low for the latest requirements.

Zeolite-based SCR with ammonia as a reducing agent becomes more interesting when after-treatment systems require the use of DSP, in which particle (carbon) oxidation and DSP regeneration lead to high temperatures of up to 700-800°C, which are too high for VSCR catalysts. In addition to vanadium based TiO2 and zeolite, many other SCR catalyst materials have been studied, but they have too poor thermal or chemical durability to be suitable for commercial applications. Zeolites were used for SCR already in the 1980-1990s based on, for example, ZSM-5, USY and Beta zeolites (e.g. US 4,961,917), with a particular focus on high temperature applications, but first generation zeolite-SCR catalysts had lack of low thermal stability and resistance to sulfur.

The structure and composition of copper-chabazite ores were proposed for SCR in the 1970-1990s. For SCR, zeolites of interest are those having an 8-ring pore opening and double 6-ring secondary building blocks having framework structures. The characteristic chabazite (CHA) is a finely porous zeolite (hole size ~3.8 A). Zeolites are natural or synthetic crystalline aluminosilicates with a regular pore structure that varies among different types of zeolites. This property can be exploited to produce shape-specific catalysts, where the molecules that can enter the pores are limited by their shape and size. This reduces the inhibitory effect of HC on SLE reactions. The smallest molecules such as NO, NH ₃ , CO, hydrogen and oxygen are small enough to penetrate the pores of the zeolite. The basic structural unit of zeolites, the alumina tetrahedron, requires a positively charged

- 1 046217 monovalent (+1) cation to be electrically neutral. For this reason, cations usually attach to the aluminum site during ion exchange. Once the zeolite is produced, the cation present in the zeolite is usually sodium, potassium, ammonium or hydrogen. The silicon tetrahedron is electrically neutral. However, using ion exchange methods, they can easily be exchanged for other cations, which give zeolites their catalytic properties (Gates et al., Chemistry of Catalytic Processes, McGraw-Hill 1979). In ion exchange, cations such as copper (Cu ²⁺ ) are typically adsorbed onto zeolites from aqueous solutions, followed by drying and calcination under suitable conditions. The composition of the basic structure of a zeolite is usually described by the Si:Al ₂ molar ratio (SAR), which affects not only the structure of the zeolite, but also hydrophobicity/hydrophilicity, acidity and stability under various circumstances, as well as the amount of the desired cation that can be incorporated into the zeolite by ion exchange. Zeolites used in commercial catalysts are usually synthetic. Pore size and surface properties, which vary depending on the type of zeolite, are important for introducing active components as dissolved compounds by ion exchange or impregnation. The shape, structure and method of channel connections may vary among zeolites. Zeolites may contain large (>0.6 nm, such as Beta and Y) pores and small or medium (<0.6 nm, such as chabazite, ferrierite and ZSM-5) pores.

Chabazite is a naturally occurring mineral that was used in catalysis as early as the 1950s and synthesized as early as the 1980s (US 4,544,538). Natural or synthetic Cu-chabazite (CAS >2) was used for NH ₃ -CKB in the 1970s (US 4,046,888). Copper with chabazite was used together with titanium dioxide as a sulfur-stable NH ₃ -CKB catalyst (US 4,735,927). Cu-chabazite was also included for SCR catalysts in US 5,589,147.

Following the early inventions concerning Cu-SNA for SCR, more recent development has focused on details regarding composition and zeolites. Cu-SNA with CAS >10 for SCR ammonia has been described (US 2003/0069449).

The detailed composition of Cu-SNA with CAS >15 and Cu/Al greater than 0.25 was determined for SCR (WO2008/106519). Cu-CHA and other SCR active zeolites such as AEI and AFX were proposed for SCR in WO2008/118434. Si on various fine-pore zeolites (AGO, AEI, AEN, AFN, AFF, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG and ZON) containing a maximum ring size of eight tetrahedral atoms and transition metals (Cr, Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir and Pt), are described in WO 2008132452. Differences between natural and synthetic SNA as a variable has also been discussed. Due to the description of a broad matrix for zeolite types and active metals, the detailed combination or additives leading to the highest activity and durability in a complete SCR catalyst have often not been identified.

Cu-SNA with lower CAS (5-15) has been proposed for use in SCR (WO 2011/073390, US 2013/0280160, US2012/0269719). SAPO-34, containing aluminum phosphates, has the same structure as chabazite and has also been widely studied as Cu-SCR. AEI (WO2014/141200), AFX and LEV with copper are other microporous zeolites used for SCR.

Off-lattice aluminum (Al) in zeolites has been identified and minimized (<15%) for Cu on CHA and similar zeolites (WO2019049069). Typically, in zeolite-SCR concepts, it has been described that Cu zeolite (CHA, AEI, AFX, etc.) itself forms the basic functionality of SCR with any kind of binders (aluminum oxide, silica, titanium dioxide, cerium oxide, zirconium oxide), whose role is to improve adhesion on structured substrates. However, other materials, in addition to zeolites and conventional binders, can play a critical role in the ultimate SCR functionality and thermal durability.

In summary, the basic composition of the Cu-CHA catalyst for ammonia/urea SCR has been known since the 1970s to 1990s, but since 2000 detailed, slightly varying new compositions have been developed with improved properties. Many conventional, hydrothermally stable Cu-CHA catalysts are based on high CAN (>15-20), which results in low copper loading if the Cu/Al ion exchange ratio (IER) is kept at a reasonable level (<0.5). Copper loading (in grams) is directly related to the total number of active sites and catalyst activity. If the copper concentration is increased on Cu-CNA with high UAN, there is a risk of excessive ammonia oxidation activity at elevated temperatures. This is harmful because it causes additional consumption of the reducing agent (urea), which can be directly understood as an equivalent increase in fuel consumption (high CO ₂ levels). A high Cu/Al ratio with high UAS also poses the risk of copper being partially outside the zeolite structure (non-intercalated Cu compounds), which promotes ammonia oxidation at high temperatures.

Brief description of the invention

The present invention solves many of the problems associated with the prior art, and in particular, a copper ion exchange zeolite catalyst composition containing

- 2 046217 compressing fine-porous Cu zeolite, such as Cu-CHA, and promoters, improving the activity and durability of the catalyst.

The present invention provides an SCR catalyst containing a zeolite (eg, CHA, AEI, AFX, LEV, Beta, or mixtures thereof) with copper as the active metal and a nanocrystalline aluminum compound (Al compound) as fine particles including crystals. The catalyst composition of the present invention is used to reduce NO _x emissions using ammonia, urea and other selective reductants in mobile and stationary lean burn applications. Nanocrystalline Al compound, such as small Al2O3 crystals and particles, improves the hydrothermal (HT) and mechanical stability of the coating layer in SCR catalyst compositions, which are preferably applied to flow substrates, but can also be used for particulate filters.

The addition of small sized Al2O3 crystals near the surface of the zeolite creates surface interaction between the two compounds. Thus, the rate of dealumination from zeolite is hindered. This is an important feature of zeolites with low UAN (UCA below 15), with pure zeolites or zeolites with conventional binders suffering from lower GT durability compared to CNA with UAN in the range of 20-30. SNA with low CAS has the property of achieving higher Cu loads in ion exchange, which allows obtaining more active Cu sites for SCR without excessively high ammonia oxidation activity. The present invention provides a catalyst composition that contains a zeolite with a higher mass load of copper (Cu), lower UAN, but also low ammonia oxidation activity.

Zirconium (Zr) compound is dispersed near Cu-exchanged zeolite particles and nanocrystalline Al compound to improve hydrothermal durability under off-gas conditions. Zirconium compounds (oxides, sulfates, acetates, hydroxides) play a role in maintaining the acidic properties of the SCR catalyst.

To further improve hydrothermal durability, one or more additives selected from the group of La, Y, Hf and Nb are dispersed into fine particles to improve hydrothermal durability. These additives enhance the low-temperature activity of SCR.

The ionic radius of the added compounds (nanocrystalline Al compound, Zr compound, one or more additives) was also selected and determined relative to copper to improve stability without affecting copper as an active site within the zeolite pores.

Coarse particles (CP) are additionally added to improve the hydrothermal stability of zeolite-based SCR catalysts and the mechanical durability of the coating layer. These particles act as large local thermal barriers and heat capacity to protect against high temperature and sintering to pass through the zeolite particles.

To further stabilize the catalytic composition, Si or Ti is added, preferably in the composition of large particles (CP). Si and Ti are present in oxide forms such as SiO ₂ and TiO ₂ or as mixed oxides (SiO _x , TiO _x ) with alumina.

The present SCR catalyst has a microporous structure formed by Cuzeolite particles with CAS <15, a nanocrystalline Al compound that stabilizes Cu-SNA, for example, by suppressing dealumination, dispersed zirconium as a hydrothermal stabilizer, an additive to improve thermal stability and a large particle with a high local heat capacity, acting as a thermal barrier between zeolite particles.

In a broad aspect, the present invention relates to a catalytic composition for the selective catalytic reduction of NOx with ammonia or compounds such as urea that release ammonia under exhaust gas conditions, the composition comprising

a) zeolite particles with ion-exchange copper having a Si/Al ₂ molar ratio (SAR) of 15 or less and a sufficiently high copper content for the catalytic reduction reaction to occur,

b) a nanocrystalline aluminum compound in an amount sufficient to stabilize the zeolite by reducing the rate of dealumination from the zeolite, and

c) a zirconium compound in an amount sufficient to improve the hydrothermal durability of the catalyst composition.

In one embodiment, the zeolite is selected from a framework group consisting of chabazite (CHA), AEI, AFX, LEV, Beta, or mixtures thereof. Preferably SNA.

In yet another embodiment, the zeolite particles with ion-exchange copper have an UAN of 2 to 14.9. Preferably, the CAS is from 5 to 14.9. A CAS greater than 5 is preferred to improve the stability of the base zeolite and to maintain the Cu/Al ratio at a reasonable level.

When the UAN is from 10 to 14.9 and the copper ion content, measured as CuO, in the zeolite is more than 5 wt.%, based on the total weight of the zeolite, it is still possible to have a Cu/Al molar ratio in the zeolite of less than 0.4.

In yet another further embodiment, the copper ion content, measured as CuO, in the zeolite is from 1 to 10 wt%, for example from 2 to 7 wt%, preferably from 4 to 5 wt%, based on the total weight of the zeolite . In yet another embodiment, the copper ion content, measured as CuO, in the zeolite is from 4 to 7 wt.%, based on the total weight of the zeolite.

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In yet another embodiment, the amount of nanocrystalline aluminum compound in the catalyst composition is from 0.5 to 25 wt.%, for example, from 1 to 20 wt.%, for example, 5-15 wt.%, typically 7.8-10 wt.%, based on the total weight of the catalytic composition. Preferably, the aluminum compound is Al ₂ O3 such as gamma Al ₂ O3.

In yet another embodiment, when the catalyst composition has a UAN of 10 to 14.9, the amount of nanocrystalline aluminum compound in the catalyst composition is from 0.5 to 25 wt.%, for example, from 1 to 20 wt.%, for example, 5- 15% by weight, typically 7.8-10% by weight, based on the total weight of the catalyst composition. Preferably, the aluminum compound is Al2O3 such as gamma Al2O3.

In yet another embodiment, the Cu/Al molar ratio of the zeolite is from 0.02 to 0.4, preferably from 0.05 to 0.25.

The Cu/Al molar content of the zeolite is in the range of 0.02 to 0.4, preferably in the range of 0.05 to 0.25, to provide a hydrothermally stable Cu zeolite catalyst with a low ammonia oxidation rate. High NOx performance is achieved at a lower Cu/Al molar ratio than the typical Cu/Al ratio at which Cu-SHA has a high UAN such as >15-20.

In yet another embodiment, the total copper ion content, measured as CuO in the catalyst composition, is from 2 to 6 wt.%, based on the total weight of the catalyst composition.

In yet another embodiment, the ion-exchanged copper zeolite particles have a d ₅₀ size of 1 to 10 μm, for example 2 to 5 μm.

In yet another embodiment, the amount of zirconium compound in the catalyst composition is from 1 to 10 wt.%, in the form of ZrO ₂ based on the total weight of the catalyst composition. Typically, the amount of zirconium compound in the form of ZrO ₂ in the catalyst composition is from 2 to 7% by weight, based on the total weight of the catalyst composition.

This amount of ZrO ₂ is chosen to stabilize other compounds carrying dispersed Zr on other porous catalyst compounds.

In a further embodiment, the nanocrystalline aluminum compound comprises aluminum oxides. Typically, the nanocrystalline Al compound is Al ₂ O ₃ .

In yet another further embodiment, the nanocrystalline Al ₂ O ₃ has a crystal size d ₅₀ of 1 to 8 nm, such as 3-7 nm. In yet another embodiment, the nanocrystalline Al ₂ O ₃ has a crystal size d ₅₀ of 3 to 5 nm.

In yet another embodiment, the nanocrystalline Al2O3 has a dispersed particle size d50 of 5 to 80 nm, such as 10-65 nm. In yet another embodiment, the nanocrystalline Al2O3 has a dispersed particle size d ₅₀ of 10 to 30 nm.

In yet another embodiment, the catalyst composition of the present invention contains coarse particles (CP), such as Al ₂ O ₃ -based coarse particles having a particle size d50 of 3 to 200 μm, preferably 5 to 40 μm.

In particular, the large particle is based on Al ₂ O ₃ . Preferably the coarse particle consists of Al ₂ O ₃ .

In yet another embodiment, the catalyst composition of the present invention further comprises an additive selected from the oxides of La, Y, Hf, Nd and mixtures thereof.

In a further embodiment, the catalyst composition of the present invention contains Si, Ti, or mixtures thereof. Preferably, Si and Ti are attached to and embedded in large particles (CP).

In yet another embodiment, the catalyst composition of the present invention has a total TAC (TAC) of less than 10, where TAC is defined as the Si/Al ₂ molar ratio between the Si in the copper zeolite and the total Al 2 in the copper zeolite and the nanocrystalline aluminum compound. Typically, the OCAC is from 4 to 10. Preferably, the OCAC is from 4 to 8, for example from 5 to 7.

In yet another aspect, the present invention relates to a structural support for use in a flue gas system comprising a catalyst composition according to any of the above aspects and/or any of the above embodiments. Typically, the structure is selected from a ceramic or metal flow substrate and a wall flow substrate, preferably a flow substrate.

In yet another further aspect, the present invention relates to the use of a catalyst composition according to any of the above aspects and/or according to any of the above embodiments for the selective catalytic reduction of NOx with ammonia or ammonia-releasing compounds under flue gas conditions.

In yet another aspect, the present invention relates to a flue gas treatment system comprising a catalyst composition according to any of the above aspects and/or any of the above embodiments for selective catalytic reduction of _NOx with ammonia or compounds, such as urea, that release ammonia under flue gas conditions , applied

- 4 046217 on a structural substrate.

In yet another aspect, the present invention relates to a method for the selective catalytic reduction of NO _x with ammonia or ammonia-releasing compounds under off-gas conditions, comprising applying a catalyst composition according to any of the above aspects and/or any of the above embodiments to a support structure.

In a further aspect, the present invention relates to a catalyst composition for the selective catalytic reduction of NOx _with ammonia or an ammonia-evolving compound under flue gas conditions, a catalyst composition for the selective catalytic reduction of _NOx with ammonia or ammonia-evolving compounds under flue gas conditions, according to any of the above aspects and/or any of the above embodiments, which can be obtained by drying the aqueous catalyst composition and calcining at a temperature of from 400 to 700°C in the presence of oxygen, such as air, containing a) a zeolite particle with ion-exchange copper having a molar ratio of Si/ Al ₂ (CAC) 15 or less, and a copper ion content sufficient to allow the catalytic reduction reaction to occur, b) a nanocrystalline aluminum compound in an amount sufficient to stabilize the zeolite by reducing the rate of dealumination from the zeolite, and c) a zirconium compound in an amount sufficient to improving the hydrothermal durability of the catalytic composition.

In yet another aspect, the present invention relates to an aqueous catalyst composition suitable for use as a catalyst coating on a structural support in the selective catalytic reduction of NO _x with ammonia or ammonia-releasing compounds during the catalytic reduction, the composition comprising

a) a copper ion exchange zeolite particle having a Si/Al2 molar ratio (SAR) of 15 or less and a copper ion content sufficiently high to allow a catalytic reduction reaction to occur in the coating,

b) a nanocrystalline aluminum compound in an amount sufficient to stabilize the zeolite in the coating by reducing the rate of dealumination from the zeolite, and

c) a zirconium compound in an amount sufficient to improve the hydrothermal durability of the catalytic coating.

In yet another embodiment, the zirconium compound is selected from a zirconium compound precursor such as zirconium oxides, zirconium sulfoxides, zirconium sulfates, zirconium nitrates, zirconium acetates, zirconium hydroxides, and mixtures thereof. Preferably, the zirconium compound is selected from zirconium sulfates, zirconium nitrates, zirconium acetates and mixtures thereof.

In yet another embodiment, the nanocrystalline aluminum compound is modified during preparation to provide an acidic surface, wherein the pH under wet (slurry) conditions is typically less than 5, for example, 3. Modification can be carried out during preparation by exposure to HNO ₃ prior to calcination .

Additional objects and advantages of the present invention will be apparent from the following description and claims.

Brief description of drawings

In fig. 1 schematically shows the composition of a supported copper SCR catalyst according to the present invention. The catalyst consists of a support (100), which forms open flow channels (110) for exhaust gases and a catalyst coating is located on the specified walls of the support. The coating is formed by a mixture of Cu zeolite (200, for example, Cu-CHA), Al compound (300), ZrO ₂ (400), additive (Add, 600) and large particles (CN, 500) and Ti and/or Si (700 ).

In fig. 2 is a graph depicting NOx conversion tested on a syngas bench with 40% NO2 and 60% NO (both relative to total _NOx ) in the feed gas at 71,000 h ^-1 OC, for Example 1a, 2 (Compare 1 ), 3 (СрАВН 2) and 4 (СрАВН 3). All samples were subjected to hydrothermal aging at 800°C for 20 hours. The comparison shows the effect of an Al compound with a small crystal size (example 1a) compared to an Al compound with large Al ₂ O ₃ crystal sizes (example 2, CVN 1) and compared with a comparative modern catalyst Cu-CHA (example 3, CPAVN 2) and a second comparative sample obtained in accordance with example 1a, but with a zeolite with CAS 23 (example 4, CPAVN 3).

In fig. 3 shows in two diagrams the improvement in thermal aging stability for Cu-SNA with CAS 11 in combination with Al-1, either with the addition of a zirconium compound or lanthanum oxide as an additive, or with both of these additives. Diagram in Fig. 3a illustrates the conversion of NOx tested on a synthetic gas stand with only NO in the feed gas at OS 50,000 h ^-1 , for example 1b (Cu-SNA with CAS 11 with Al-1), example 5 (Cu-SNA with CAS 11 s Al-1 and 6% ZrO ₂ as a thermal stabilizer), example 6 (Cu-SNA with CAS 11 with Al-1 and 3% La ₂ O ₃ as a thermal stabilizer) and example 7 (Cu-SNA with CAS 11 with Al- 1 and 3% ZrO ₂ plus 3% La ₂ O ₃ as thermal stabilizers). All samples were subjected to hydrothermal aging at 850°C for 20 hours. FIG. 3b shows the NO _x conversion chart for the same set of samples that were tested on a syngas bench with 40% NO ₂ and 60% NO (both relative to total NOx) in the feed gas at 50,000 h ^-1 OC.

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In fig. 4, two diagrams show the improvement in stability to thermal aging for CuSNA with CAS 11 in combination with Al-1 and the addition of large particles (CP).

In the diagram in FIG. Figure 4a shows the NOx conversion tested on a synthetic gas stand with only NO in the feed gas at OS 50,000 h ^-1 , for example 1b (Cu-SNA with CAS 11 with Al-1, total load 140 g/l), example 8a (Cu -SNA with CAS 11 with Al-1 140 g/l and large particles containing Al2O3 as the main oxide and 3% La ₂ O ₃ 40 g/l), example 8b (Cu-SNA with CAS 11 with Al-1 140 g/l and large particles containing Al ₂ O ₃ as the main oxide and 20% SiO ₂ 40 g/l) and example 8c (Cu-SNA with CAS 11 with Al-1 140 g/l and large particles containing Al ₂ O ₃ as the main oxide and 15% ZrO ₂ and 20% SiO ₂ 40 g/l). All samples were subjected to hydrothermal aging at 850°C for 20 hours.

In fig. Figure 4b shows the NOx conversion for the same set of samples that were tested on a syngas bench with 40% NO2 and 60% NO (both relative to total NOx) in the feed gas at 50,000 h ^-1 OC.

In fig. 5 shows in two diagrams the improvement in thermal aging stability for CuCHN with CAS 11 in combination with Al-3 and the addition of a zirconium compound and/or lanthanum oxide as an additive, and with the addition of large particles (CP).

In the diagram in FIG. Figure 5a shows the NOx conversion tested on a synthetic gas stand with only NO in the feed gas at OS 50,000 h ^-1 , for example 1b (Cu-SNA with CAS 11 with Al-1, total load 140 g/l), example 9 (Cu -SNA with CAS 11 with Al-3 and 6% ZrO ₂ as a heat stabilizer 140 g/l and large particles containing Al ₂ O ₃ as the main oxide and 3% La ₂ O ₃ 40 g/l), example 10 ( Cu-SNA with CAS 11 with Al-3 and 6% ZrO ₂ as a thermal stabilizer 140 g/l and large particles containing Al ₂ O ₃ as the main oxide and 20% SiO ₂ and 20% TiO ₂ 40 g/l) , and example 11 (Cu-SNA with CAS 11 with Al-3 and 3% ZrO ₂ plus 3% La ₂ O ₃ as thermal stabilizers 140 g/l and large particles containing Al2O3 as the main oxide and 20% SiO2 and 20 % TiO2 40 g/l). All samples were subjected to hydrothermal aging at 850°C for 20 hours.

In fig. 5b shows the NOx conversion for the same set of samples as the syngas bench test with 40% NO ₂ and 60% NO (both relative to total _NOx ) in the feed gas at 50,000 h ^-1 OC.

In fig. 6 shows the improvement in thermal aging stability for Cu-CHA with CAS 11 in combination with an Al compound using all possible additives according to the present invention. The chart shows a comparison of NO _x conversion tested on a syngas bench with 40% NO2 and 60% NO (both based on total NOx) in the feed gas at 50,000 h ^-1 OC for Example 3, which is a reference modern catalyst Cu-SNA with high CAS and high low-temperature DeNOx activity, and Example 11, which is a fully developed composition of the Cu-zeolite SCR catalyst in accordance with the present invention, consisting of Cu-SNA with CAS 11 with Al compounds Al-3 and 3 % ZrO ₂ plus 3% La ₂ O ₃ as thermal stabilizers 140 g/l and large particles containing Al2O3 as the main oxide and 20% SiO2 and 20% TiO2 40 g/l. Both samples were subjected to hydrothermal aging at 850°C for 20 hours.

Detailed Description of the Invention

The present invention has many advantages in a broad context, as well as additional advantages according to aspects of the embodiments.

The SCR catalyst is composed of certain materials in accordance with the above aspects and/or embodiments of the present invention, wherein the catalyst composition is supported on a structural support, such as a ceramic or metal substrate or particulate filter (media). Total coating amounts range from 20-400 g/l depending on application or media type (cell density, ceramic/metal, continuous/wall flow). In a preferred embodiment, the total amount of coating is in the range from 60 to 200 g/l.

The term copper ion exchange zeolite is used interchangeably with Cu-zeolite and, for example, Cu-CHA means copper ion exchange chabazite.

The SCR catalyst composition according to the present invention is an active microporous zeolite. The copper ion exchange zeolite is preferably in the form of CHA (chabazite) with a UAN in the range of 2 to 14.9, preferably in the range of 5 to 14.9, for example in the range of 10 to 14.9. The copper load is measured as CuO, typically in the range of 2 to 7 wt.%, for example, in the range of 4 to 7 wt.%, typically in the range of 4 to 5 wt.%, in zeolite and about 2 to 6 wt.%, in the catalyst, including all catalyst compounds. The surface area of the zeolite with ion-exchange copper, preferably Cu-CHA, is in the range of 450-700 m ² /g in fresh form (calcined at 550°C/3 hours, before aging). Preferably, the average particle size (d ₅₀ ) of Cu zeolite (such as Cu-CHA) in the catalyst coating is about 2-5 μm.

An important element of the catalyst composition according to the present invention is a nanocrystalline Al compound (Al compound). It is known that UAN is a variable value in zeolite compositions. It has been observed that free Al can exist in zeolites such that not all of the Al is in the lattice (so-called extra-lattice Al). Typically, in the known technology, the goal was to minimize the content of extra-lattice Al in the zeolite to prevent possible

- 6 046217 negative effects such as dealumination. However, when Al is used as a nanocrystalline Al compound in the zeolite catalyst of the present invention, it is done specifically to produce a plurality of Al2O3 crystals/particles that have very close contact with the zeolite structure, preventing dealumination and stabilizing Al in the zeolite lattice. The use of a very small crystalline Al compound (as Al2O3) in the catalyst composition of the present invention has demonstrated improvement in the activity, stability, adhesion and cohesion of the catalyst. For these reasons, various Al2O3 precursors can be used in the porous oxide coating. The Al2O3 source may be a dispersion of Al2O3 itself, a sol of boehmite or other precursor, or even a partially dissolved aluminum salt in the form of Al(NO3)3, corresponding to ranges of certain crystal size and dispersed particle size of the Al compound. Combinations of these sources are also possible.

The examples examined three different types of possible Al compounds. In the experiments, Al-1, Al-2 (САВН 1) and Al-3 were studied as Al compounds. Al-1 has a dispersed particle size in an aqueous medium of 20 nm, a crystalline size of 4.5 nm and an initial BET surface area of 260 m ² /g when calcined at 550°C/3 hours. Al-2 has the corresponding parameters of 90 nm, 9 nm and 200 m ² /g. Al-3 has the corresponding parameters 60 nm, 6 nm and 230 m ² /g. It has been observed that these small crystalline particles and the particle size of the Al compound contribute to the activity. The small size of the dispersed particles is also a key variable to keep the amount of Al compound at a sufficiently low level together with improved adhesion and cohesion to the substrate walls. To achieve the same strength of a coating layer with larger particles of Al compound or Al binder, a higher relative mass amount is required. In addition, a small amount of nitrate may be present in the aqueous coating media (slurry) or on the Al compound precursor, which is important for the formation of a small Al2O3 crystal during chemical and mechanical dispersion. These surface nitrates are decomposed during the final heat treatment, leaving finished nano-sized Al ₂ O ₃ particles in the catalyst structure. The finished Al ₂ O ₃ surface retains acidity on the oxide and hydroxyl groups after calcination under dry conditions.

The particle size of an Al compound (Al ₂ O ₃ ) dispersed in water is in the range of 5 to 80 nm, typically in the range of 10 to 65 nm, for example in the range of 10 to 30 nm, and the crystalline size is in the range of 1 to 8 nm, typically in the range of 3 to 7 nm, for example in the range of 3 to 5 nm. The BET surface area is more than 200 m ² /g when calcined at 550°C/3 hours.

The nanocrystalline aluminum compound forms dispersed particles of 5 to 80 nm, preferably 10 to 65 nm, and crystalline particles of 1 to 8 nm, preferably 3 to 7 nm in water to stabilize the zeolite by reducing the rate of dealumination from the zeolite. The fine particle size and crystalline size are variables that control which locations in the zeolite pores the Al compound has access to. The goal is to have deeper access into the zeolite pores than with conventional Al-containing binders, but not to affect the Cu in the zeolite centers. Negative effects can be caused by the fact that small soluble ions can undergo ion exchange with a copper ion, which, for example, is introduced into the zeolite before preparing the catalyst. The precursors will settle after drying and calcination in the final locations in the dry phase where they settled during production in aqueous media. Thus, the size of the precursor in water or other liquid media plays a key role in where the added promoters are located in the final catalyst composition. In addition to water, wet preparation steps may include organic additives that form a mixture with water and modify, for example, surface tension, viscosity and other surface or liquid/solution/suspension properties. The Al compound is used in the form of a dispersed nanocrystalline form with the above particle sizes, but not in the form of a soluble form when the ionic radius of Al ³⁺ is even smaller than the ionic radius of Cu ²⁺ . The nanocrystalline Al compound has access to the zeolite pores, but not as directly as the Cu ion to the Al centers on the zeolite. Since the ionic radius of (0.50 A) Al ³⁺ is smaller than (0.69 A) Cu ²⁺ , it is introduced not in the form of a soluble ionic form, but in the form of nanocrystalline particles in aqueous media. In contrast, the Zr compound is introduced as an ionic form where the ionic radius of Zr ⁴⁺ is much larger (0.80 A) than that of Cu ²⁺ , resulting in close intercalation in the zeolite but not competing with copper in aqueous environments.

Due to the role of the nanocrystalline Al compound, the standard zeolite UAS is not the only significant variable in these zeolite-based Cu-SCR catalysts. Very small alumina particles affect the stability and dealumination of aluminosilicate-based zeolite catalysts. Nanocrystalline Al2O3 present in close contact with zeolite particles, pores and lattices can change the equilibrium of Al species (Al in zeolite and Al as Al compound), which prevents diffusion of Al from the zeolite structure (dealumination). Even if a small amount of Cu is present in an unencapsulated form (free Cu) after severe hydrothermal aging, the Al compound is a potentially stable scavenger for these free Cu/CuO species, the oxidation state of which (Cu, Cu ⁺ , Cu ²⁺ ) can vary depending depending on the conditions. At high temperatures, Cu on nano-sized Al ₂ O ₃ is more stable

- 7 046217 lysed than Cu on the surface of Si-rich silicate (zeolite). In addition, Cu/A12O3 is also a fairly good SCR catalyst, and thus the overall functionality of the Cu-CHA SCR catalyst does not change too much if Cu/Al2O3 exists and the total amount of free Cu remains low.

Thus, the total CAC (TCAC) was determined, which is calculated as the molar ratio between Si in the zeolite and Al2 in the zeolite + Al2 in the Al compound. Possible larger Al2O3 particles in the binder or CN are excluded in this calculation because they do not have the same positive interaction and contact with the Cu zeolite and other compounds in the composition. OCAC values ranged from 5 to 10 in the studied samples (table below). Preferably, the CAC is in the range of 4 to 8, and is even more strictly defined in the range of 5 to 7. As a combination of these two CAC values, the CAC is defined to have a maximum value of 14.9 and the CAC is specified to have a maximum value of 8, the values of which are achieved by changes in the CAC value of the zeolite and the amount of Al compound in the SCR catalyst.

Based on certain molar values and ranges of UAS and OAS, the amount of Al compound in wt.% Al2O3 is known. The main Cu-SNA in the examples has CAS 11, and then the determination of OKAS 4-10 leads to 1-18 wt.%, Al compounds in the form of Al2O3 from the weight of the zeolite and Al compounds and to 0.9-16.2 wt.%, Al compounds in the form of Al ₂ O3 based on the weight of the zeolite, the Al compound and the maximum amount of the Zr compound (10% ZrO ₂ ). Likewise, the amount of Al compound is known when the additive, CN, Si and Ti are added to the composition, diluting the content of copper zeolite, Al compound and Zr compound. According to OKAS 5-8, the amount of Al compound in the form of Al ₂ O3 is approximately 4-13 wt.% According to the maximum determined CAS value of 14.9, the amount of Al compound is from 4.6 to 21 wt.%, in the form of Al ₂ O ₃ by weight of Cu-zeolite and Al compound and from 4.1 to 18.9 wt.%, with the inclusion of the maximum amount of Zr compound in the form of ZrO2. Thus, the Zr compound only slightly dilutes the amount of Al compound even at maximum concentrations. Thus, the amount of Al compound according to a certain CAS and OKAS ranges from 1 to 21 wt.%, in the form of Al ₂ O ₃ by weight of the copper zeolite and Al compound. Dilution by other added compounds can be calculated directly from their content. In the examples, the amount of Al compound was given in the range of 7.8-10 wt.%, in the form of Al ₂ O ₃ . In embodiments of the invention, the amount of nanocrystalline aluminum compound, such as Al ₂ O ₃ , in the catalyst composition is from 0.5 to 25 wt.%, for example, from 1 to 20 wt.%, for example, 5-15 wt.%, as typically 7.8-10 wt.%, based on the total mass of the catalytic composition. Typically, the aluminum compound is Al ₂ O ₃ such as gamma Al ₂ O ₃ or theta Al ₂ O ₃ .

The binder does not play a completely inert role with respect to the activity and durability of the catalyst, and the activity of SCR does not only depend on certain properties of the zeolite. Pure zeolite may not be tightly bound to the substrate walls, and some types of binders or additives may reduce the catalytic activity of Cu zeolite. Thus, it is important to use Al compounds to replace conventional binders.

Description of zirconia and additives for improved thermal durability.

In addition, the addition of oxides or dispersed Zr compounds and/or additives (La, Y, Hf, Nb) improved thermal stability. These compounds are added as water-soluble or insoluble precursors. The amount of Zr and additive can vary in the range from 0.1 to 30 wt.%, in the form of stable oxides (for example, ZrO ₂ , La ₂ O ₃ ) of the finished calcined coating, preferably in the range from 1 to 10 wt.% Zr together with an additive such as La is also used to create combination activation effects. For example, Zr and La are uniformly distributed on the surface of the zeolite, in the pores of the zeolite, on the surface of the Al compound or on additional binder materials.

The ionic size of elements plays a critical role in interactions. Zeolite pore channel size is limited by size and shape, and small differences in ionic diameter or radius make sense when it comes to metal ion access. It is calculated that the pore opening and ionic sizes of the planned elements are practically in the same range. CNA has 3.8 A holes in the pore structure. The ionic radius of Cu ²⁺ is 0.69 A (Sargent-Welch Scientific Company: Table of periodic properties of the elements, 1968). Thus, the access of Cu cations to Al centers is partially limited by the structure in the tortuous zeolite channels. La ³⁺ has an ionic radius of 1.15 A, Zr ⁴⁺ 0.80 A, Y ³⁺ 0.93 A and Hf4 ⁺ 0.81 A. Thus, a certain additive has a larger ionic radius than the Cu ²⁺ ion. exchanged in zeolite lattices. This is a specific property of the additive according to the present invention. Other basic metals such as Ti ⁴⁺ (0.68 A), Si ⁴⁺ (0.41 A), V, Cr, Mn, Fe, Cr, Co, Ni have smaller ionic radius as their stable states, than Cu ²⁺ , and they were not used as additives because, due to their small size, they can also cause negative effects by competing with Cu in the zeolite centers. Al ³⁺ has an ionic radius of 0.50 A, which is smaller than Cu ²⁺ . Thus, the additive has a larger ionic radius than both Cu ²⁺ and Al ³⁺ in the Al compound. A larger radius slows down or prevents these ions from reaching the same zeolite sites where the Cu (or Al) is located. The goal is to activate and stabilize the zeolite catalyst, but not to disrupt the state and functionality of the Cu sites within the zeolite structured catalyst.

Description of large particles (CP).

- 8 046217

Individual CN particles with promoters act as thermal barriers that prevent the spread of thermal sintering from a zeolite particle to another zeolite particle. These large particles have a high local heat capacity and can act as a heat sink, providing a thermal barrier to protect the zeolite particles active in SCR. Mechanically strong CP particles improve the strength of the coating layer and improve pore diffusion through a thick catalyst layer because large particles leave more open passages between particles than a structure consisting only of small particles.

Preferably, the chemical composition of the CN is alumina with additional promoters, such as Si or Ti, in the form of stable oxides or mixed oxides. The average particle size (d ₅₀ ) of the CN, thermal barrier, particles is determined to be about 3-200 μm, preferably in the range of 5-40 μm, to match them in conventional coating layers. Consequently, their average particle size is larger than that of zeolite and significantly larger than that of Al compound or additives. The particle size (d ₅₀ ) of CN is larger than for zeolite (for example, about 2-5 μm for zeolite and about 5-40 μm for CN). Thus, CN particles will mechanically strengthen the coating layer. The amount of CN can vary in the range from 0.5 to 50 wt.%, of the total amount of coating, preferably in the range from 2 to 25 wt.% Since the amounts of coating are given in g/l, this means: the amount of CN 40 g/l in total coating amount 180 g/l is equivalent to 22.2 wt.%, 20 g/l in 180 g/l is equivalent to 11.1 wt.%, 10 g/l in 140 g/l is equivalent to 7.1 wt.% Examples studied contained a fairly large amount of CN to see better variable effects, but a certain amount may be better applied in the lower range, focusing on thermal and cohesive stabilization with less reduction in the total amount of Cu zeolite. The average pore sizes (d ₅₀ or d ₉₀ ) are larger for CP than for Cu zeolite particles.

In addition, the BET surface area of CP is approximately 100-300 m ² /g, while the BET surface area of Cu zeolite is more than 450 m ² /g in the fresh state (calcined at 550°C/3 hours). There is a risk that pure Cu zeolite with UAN <15 will lose BET surface area below 100 m ² /g at 900-1000°C in air. CPs are capable of maintaining a high BET surface area: >200 m ² /g after aging in air at 900°C and >150 m ² /g after aging in air at 1000°C for 3 hours. Thus, these stable, individual CN particles on the catalyst composition have a stabilizing effect on the zeolite particles. These particles can be added to the finished aqueous (suspension) medium, which is further crushed, or they can be added after grinding, maintaining the original particle size and the large difference in particle size d50 between the zeolite and the CP particles in the final coating. Dilution of the catalyst composition with thermal barrier particles reduces and dilutes the thermal stress on the zeolite particles in the coating layer. It is also possible to add CN only to the bottom or top catalyst layers in two-layer coatings to improve mechanical strength or pore gas diffusion in the coating layers.

CNs can be additionally stabilized by various oxides of Si, Ti, Zr and/or additives, such as SiO ₂ , TiO ₂ , La ₂ O ₃ or ZrO ₂ . Oxides of Si, Ti and Zr increase the acidity of the CN and prevent the effect of catalyst sulfation on alumina-based structures. Metal oxides are typically added during the Al ₂ O ₃ production process itself, but can also be added later in the process. Both procedures can be used for this invention. The added metal oxides can form a mixed oxide or a mixture of oxides with Al ₂ O ₃ , which leads to a very stable CN structure, individual pore size distribution and good stability, for example, of Si and/or Ti oxides in the structure. Metal oxides also play a role in stabilizing the structure of CPs with wide pore sizes, which has a positive effect on pore diffusion and thermal stability.

A zirconium compound is added in a water-soluble form to improve the hydrothermal durability of the catalyst composition. The goal is to have deeper access inside the zeolite pores, but not affect the Cu in the zeolite centers. The Zr compound settles after drying and calcination at the final dry phase locations it reached during production in aqueous media. The Zr compound is introduced as an ionic form where the ionic radius of Zr ⁴⁺ is much larger (0.80 A) than that of Cu ²⁺ , resulting in close activation in the zeolite but not competing with copper in aqueous media. Therefore, the fact that the Zr compound precursor is a soluble form in aqueous media and forms dispersed zirconium oxide upon heat treatment plays a key role in the Zr compound improving the hydrothermal durability of the catalyst composition.

Zr and additives can be introduced during catalyst preparation in the form of nitrates, acetates or other water-soluble compounds, optionally with acidic auxiliaries (nitric or organic acids). The zirconium compound is prepared from precursors such as zirconium oxides, zirconium sulfates, zirconium nitrates, zirconium acetates and zirconium hydroxides such as ZrO ₂ , Zr(OH) ₄ , Zr(OH) ₂ .CO ₃ .ZrO ₂ , Zr(SO ₄ ) ₂ , basic zirconium carbonate Zr(OH) ₂ *CO ₃ *ZrO ₂ , zirconium acetate Zr(acetate) ₂ or zirconium nitrate Zr(NO ₃ )4.

Zr, Ti and Si are inert in the presence of SO _x , which maintains a low tendency to sulfate. Before

- 9 046217 La and Y additives have a higher tendency to form stable sulfates, but they are so stable that they do not decompose or move under normal flue gas conditions.

The catalyst composition of the present invention can be supported on ceramic (eg, cordierite, aluminum titanate or mullite) or oxidation-resistant metal substrates forming a flow structure. The same composition can also be used in particulate filter structures (SiC, cordierite, metal) with modified viscosity and particulate content under suspension conditions.

The SCR catalyst composition according to the present invention can be used as an SCR block in SDO containing DOC, DSF, hydrolysis, SCR and CPA blocks. The SKV block can be located before or after the DOC+DSF blocks. This catalyst composition can also be integrated with a PPA composition that is formed by a catalyst containing a noble metal (eg, Pt) together with the SCR catalyst of the present invention. In CPA, Pt and SCR catalysts are located in the same zone in the axial direction of the exhaust gas flow to achieve high functionality and selectivity of CPA. The catalyst composition of the present invention may also be present in the hydrolysis unit, for example, in the mixer structures upstream of the SCR unit.

All references, including publications, patent applications and patents, referenced herein are incorporated herein by reference to the same extent as if each reference had been individually and specifically indicated for inclusion by reference and set forth herein in its entirety.

All headings and subheadings are used herein for convenience only and are not intended to limit the present invention in any way.

Moreover, any combination of the above-described elements in all possible embodiments is included in the scope of the invention, unless otherwise indicated herein or clearly contrary to the context.

The presentation of ranges of values herein is intended solely for the purpose of facilitating individual reference to each value within the range unless otherwise indicated, and each individual value is included in the description as if it were presented separately. Unless otherwise stated, all exemplary values presented herein are representative of the corresponding approximate values (e.g., all exemplary exact values presented with respect to a particular factor or measurement may also be considered to provide the corresponding approximate measurement, in their respective cases modified by the term approximately).

All methods described herein can be performed in any suitable order unless otherwise indicated or clearly contrary to context.

As used herein, the singular terms refer to both the singular and the plural unless otherwise indicated or clearly inconsistent with the context. Thus, the use of the singular may mean at least one or one or more.

The term and/or as used herein should be considered to cover both alternatives as well as each of the alternatives individually. For example, the expression xxx and/or yyy means xxx and yyy; xxx; or yyy, with all three alternatives corresponding to separate embodiments.

The use of any or all examples or citations (eg, such as) herein are intended solely to better disclose the invention and do not limit the scope of the present invention unless otherwise indicated. Nothing in the specification should be construed as indicating that any element is essential to the practice of the invention unless expressly stated otherwise.

The citation and inclusion of patent documents in this specification are for convenience only and do not reflect any view as to the validity, patentability and/or enforceability of such patent documents.

The description herein of any aspect or embodiment of the invention using terms such as comprising, having or including with reference to an element or elements is intended to support a similar aspect or embodiment of the invention which consists of, consists essentially of or essentially includes the specified specific element or elements unless otherwise indicated or clearly inconsistent with the context (e.g., a description herein of a structure containing a specified element also describes a construction consisting of the specified element unless otherwise indicated or clearly inconsistent with the context).

The present invention covers all modifications and equivalents of the subject matter set forth in the aspects or claims set forth herein to the maximum extent permitted by applicable law.

The features disclosed in the above description may, either individually or in any combination thereof, constitute material for implementing the invention in its various forms.

experimental part

General description of receipt.

- 10 046217

The coating of Cu-SCR catalysts was applied by applying a suspension to cordierite substrates with different geometries. The suspension consists of various materials specified in the present invention. One skilled in the art can select the desired size, porosity, cell density, and other relevant properties of the support using general catalyst design principles. With the exception of comparative studies, synthetic zeolite with ion-exchange copper was used. The zeolite has a SNA framework, which is determined by its Si/Al ₂ molar ratio (SAR). Copper was introduced into the CNA framework (SSZ-13 known as synthetic CNA) by wet ion exchange methods. In the examples, the Cu concentrations were approximately 3-5 wt.% In the examples according to the present invention, the Cu/Al molar ratio was in the range from 0.2 to 0.3. A UAN of approximately 11 and a CuO concentration of 4.1 wt.% resulted in a low Cu/Al molar ratio (based on zeolite Al) of approximately 0.22, which made it possible to obtain a good distribution of copper on Al centers within the zeolite structure (SNA).

The composition of the suspension itself and the corresponding preparation varied depending on the materials studied. Examples 1 to 11 describe corresponding catalyst compositions and preparation details. The substrates were coated on cordierite flow substrates by methods well known in the catalyst art. Coating was carried out in the presence of a fan and suction device to remove excess water and other volatile compounds. The SCR catalysts of the present invention were dried and calcined by standard methods in still air. A gradual increase in temperature was used to calcinate the catalyst to slowly form a final zeolite metal oxide coating layer with good adhesion, cohesion and avoid cracking. Calcination was carried out in the presence of air or oxygen-containing gases at higher temperatures (400 -700°C) to achieve final stable states on the catalyst coating and decomposition of the precursors. Preferably, the calcination temperature was about 550-650° C. in air to form stable states of zeolite, metal oxide and Cu oxide. This high temperature also guarantees stable activity under application conditions.

In the Examples, the first Al compound precursor was added with vigorous stirring to deionized water. In this phase, the Al ₂ O ₃ source was dispersed to form tiny nanoparticles with small crystalline sizes and dispersed particles, with nitrates enhancing the changes. At the second stage, Cu-CHA containing Cu was slowly mixed with the resulting mixture and stirring was continued for 2-4 hours. At the next stage, Zr and an additive (La in the examples) were added. The content of dry substances in the resulting suspension was in the range of 25 -39%. The suspension was further ground using a batch ball mill and a continuous mill for 0.5-4 hours to achieve the target average particle sizes (distribution), which mainly originated from zeolite particles. The CN material was mixed into the slurry after grinding, but it is also possible to add CN during grinding to reduce the original CN particle size and improve interparticle contacts. Coating was added uniformly using dip or metered coating in a controlled manner using 1-3 coating cycles to achieve the target amount of coating. The wet coated substrate was air dried at 60°C and calcined before the next possible coating cycle. The amount of coating was calculated based on the wet slurry (known solids content) and finally on the weight of the calcined dry coating. The final calcination of the samples was carried out at 600°C in air for 4 hours. The uniformity of the coating was confirmed by cutting the substrate into two parts, the quality of which was checked.

Activity Test Conditions: Catalytic activity was tested using syngas benchtop (SGB) experiments. Samples were drilled from a larger substrate (2.5 dm ³ in the examples), with small dimensions for activity testing (diameter 14 mm, length 40 mm), corresponding to the inside of the quartz tube of the reactor. The composition of the SCR feed gas in the SGB experiments was, for NO alone: 1000 ppm NH ₃ , 1000 ppm NO, 8% H ₂ O, 10% O ₂ , 82.8% N ₂ . The gas composition for the rapid SCR measurement contained activating NO2 (simulating the effect of DOC in SCR systems): 1000 ppm NH ₃ , 600 ppm NO, 400 ppm NO2, 8% H ₂ O, 10% O ₂ , 82, 8% N2. In the experiments, the volumetric velocity (SV) was approximately 50,000 or 71,000 h ^-1 .

Hydrothermal (HT) aging was carried out in the presence of air and 10% water at 800 and 850°C with an OS of 4000 h ^-1 above the sample. High temperature aging aims to evaluate the thermal durability of Cu-CHA catalysts in the presence of water.

The invention is described in detail in the following examples, figures and diagrams. The main parameters of the catalyst according to the invention are shown in Fig. 1.

The catalyst in the present invention consists of a support (100), which forms open flow channels (110) for exhaust gases and on the walls of which a catalyst coating is located. The coating is formed by a mixture of Si-zeolite (200, for example, Cu-CNA), Al compound (300), ZrO ₂ (400), additive (Add, 600) and large particles (CN, 500) and Ti and/or Si (700 ).

Catalytic compositions are given in the table.

- 11 046217

Technical characteristics of the catalyst

CN = Coarse Particle Component. CAS = Si/Al2 mol/mol. General CAS (GCA, mol/mol) includes the Al compound, but excludes Al in the CN. Coating on 400 cpsi (cells per square inch) cordierite substrate with 4 mil (101.6 microns) wall thickness.

Example Code CAS Si/A1 ₂ OKAS Si/A1 ₂ ZrO ₂ % wt. AcH/PagOz% wt. C&O g/l CuO% wt. CC g/l Ti, Si Total coverage g/l 1a Si- WITH NA- 11+A1-1 eleven 5.9 0 0 7 3.9 0 No 180 1b Si- WITH NA- 11+A1-1 eleven 5.9 0 0 5 3.9 0 No 140 2 Si- WITH NA- 11+A1-2 eleven 5.9 0 0 7 3.9 0 No 180 3 Si-SNA COMPARED WITH HIGH CAS ~28 But 0 0 ~5 ~3.0 0 No ~180 4 Si- SNA- 23+A1-1 COMPARE 23 8.6 0 0 6 3.3 0 No 180 5 Si- WITH NA- 11+A1- l+6Zr eleven 5.9 6 0 5 3.9 0 No 140

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6 Si- WITH NA- 11+A1l+3La eleven 5.9 0 3 5 3.9 0 No 140 7 Si- WITH NA- 11+A1l+3Zr- 3La eleven 5.9 3 3 5 3.9 0 No 140 8a Si- WITH NA- 11+A1- 1+CC- AlLa AND 5.9* 0 0.6 3% in CN 5 3.0 40 No 180 8b Si- WITH NA- 11+A1- 1+CC- A1S1 eleven 5.9* 0 0 5 3.0 40 20% SiO ₂ vKN 180 8s Si- WITH NA- 11+A1- 1+CC- AlSiZr eleven 5.9* 3.3 15% in CC 0 5 3.0 40 20% SiO ₂ vKN 180 9 Si- WITH NA- 11+A1- 3+6Zr+K Ch-AlLa eleven 5.9* 6 0.6 3% in CN 5 3.0 40 No 180 10 Si- WITH NA- 11+A1- 3+6Zr+K 4-A1S1T1 eleven 5.9* 6 0 5 3.0 40 20% SiO ₂ +20% ΤιΟ ₂ in CN 180 eleven Si- WITH NA- 11+A1- 3+3Zr+3 eleven 5.9* 3 3 5 3.0 40 20% SiO ₂ +20% ΤιΟ ₂ in CN 180 La+KCH- A1S1T1

* excluding large particles, UAS and OKAS based on the Si/Al2 molar ratio. The numbers in the codes indicate the concentration of the compound as an oxide. g/l: grams per volume of catalyst. wt.%, in the catalyst composition/coating, the Al compound, measured as Al2O3, constitutes approximately 10% of the zeolite + Al compound in the resulting compositions. SNA-11/23: SNA with CAS=11 or 23 (3.4 wt.% CuO). Add is short for Additive.

The Cu/Al atomic ratio was approximately 0.22 in the zeolite (4.1 wt.% CuO) on the sample with SNA and CAS = 11 (No. 1a, No. 1b, No. 5-11). The Cu/Al molar ratio of comparative Cu-CHA catalyst No. 3 was estimated to be approximately 0.7 by X-ray fluorescence analysis. The Cu/Al molar ratio of comparative catalyst Cu-CHA No. 4 was estimated to be approximately 0.33 by composition.

Example No. 1. Preparation of a Cu-zeolite catalyst with Al-1.

Chabazite with ion-exchange copper (Cu-CHA, 4.1 wt.%, copper in zeolite, resulting in approximately 7 g/l of catalyst volume, No. 1a) with CAS 11 (zeolite) and OKAS = 5.9 (whole catalyst ) were dispersed together with the nitrate-modified Al compound Al-1 in deionized water. Al-1 had

- 13 046217 crystallite size 4.5 nm and dispersed particle size 20 nm (d ₅₀ ). The amount of Al compound was 10 wt.%, in the form of Al ₂ O3 in the final amount of coating (180 g/l) after calcination. Another sample (#1b) with the same composition but a lower coating amount of 140 g/L was also prepared as a comparison to experiments with additional compounds.

Example No. 2. Preparation of Cu-zeolite catalyst with Al-2.

The same Cu zeolite (CNA with CAS = 11) as in example 1 was also coated with another Al compound under consideration, having a crystal size of 9 nm, a dispersed particle size of 90 nm, which was the comparative compound Al-2 (САВН 1) with larger Al ₂ O3 crystals and dispersed particle sizes in an aqueous solution or suspension. The amount of Al compound was 10 wt.%, in the form of Al ₂ O3 in the final amount of coating after calcination.

Example No. 3. Modern Cu-SHA catalyst as a comparison.

A commercial comparative Cu-SNA with a CAS of approximately 28 was studied as a reference sample (CPAVN 2), representing the state-of-the-art Cu-SNA technology. The cell density was 400 cpsi at 4 mils and the amount of coating was approximately the same as #1a.

Example No. 4. Preparation of a Cu-zeolite catalyst with CAN = 23 as a comparison.

Cu-CNA zeolite with CAS 23 was used as a comparison (CPAVN 3) for samples with Cu-CNA with CAS = 11. This Cu zeolite was coated with Al compound Al-1. The amount of Al-1 was 10 wt.%, in the form of Al ₂ O ₃ in the final amount of coating after calcination.

Example No. 5. Application of zirconium as a thermal stabilizer for the Cu-SNA catalyst.

6% ZrO ₂ (No. 5) (after final calcination) was added as Zr nitrate to the Cu-CHA11 model with Al-1 as the Al compound. The amount of coating after calcination was 140 g/l.

Example No. 6. The use of lanthanum as a thermal stabilizer for the Cu-SNA catalyst.

3% La ₂ O ₃ (No. 6) (after final calcination) was added as water-soluble La nitrate to the Cu-CHA-ΙΙ model with Al-1 as the Al compound. The amount of coating after calcination was 140 g/l.

Example No. 7. Combination of zirconium and lanthanum as thermal stabilizers for Cu-SNA.

3% La ₂ O ₃ and 3% ZrO ₂ (No. 7) (after final calcination) were added as water-soluble Zr and La nitrates to the Cu-SHA model with Al-1 as the Al compound. The amount of coating after calcination was 140 g/l.

Example No. 8a. Application of CN-AlLa in Cu-SHA catalyst.

The same Cu-SNA zeolite as in example 1 was also obtained together with Al-1 and 40 g/l CN, which consisted of aluminum oxide and lanthanum (CN additive). Lanthanum stabilized Al ₂ O ₃ since CN was added to a pre-ground suspension already containing Cu zeolite and Al-1. The particle size ( _d50 ) of these CNs (labeled CN-AlLa) was 30 μm. The calcined catalytic material contained 70.0% Cu-CHA, 7.8% Al-1 in the form of Al ₂ O ₃ and 22.2% CN-Al-La in the form of oxide. The total amount of coating after calcination was 180 g/l.

Example #8b. Application of CN-AlSi particles in Cu-SNA catalyst.

The same Cu-zeolite as in example 1 was also obtained together with Al-1 and 40 g/l CN, stabilized with silicon dioxide Al ₂ O ₃ as CN was added to a pre-ground suspension already containing Cu-zeolite and Al- 1. The particle size ( _d50 ) of these CNs (labeled CN-AlSi) was 35 μm. The calcined catalytic material contained 70.0% Cu-CHA, 7.8% Al-1 in the form of Al ₂ O ₃ and 22.2% CNAlSi in the form of oxide. The total amount of coating after calcination was 180 g/l.

Example No. 8c. Application of CN-AlSiZr particles in Cu-SNA catalyst.

The same Cu zeolite as in example 1 was also prepared together with Al-1 and 40 g/l of CN, which consisted of aluminum oxide, silicon dioxide and zirconium oxide. Silicon dioxide and zirconium oxide stabilized Al2O3, since CP was added to a pre-ground suspension already containing Cu zeolite and Al-1. The particle size ( _d50 ) of these CNs (labeled CN-AlSiZr) was 35 μm. Thus, the initial large particle size of CN was present in the final coating No. 8a-c. The calcined catalytic material contained 70.0% Cu-SNA, 7.8% Al-1 in the form of Al ₂ O ₃ and 22.2% CN-AlSiZr in the form of oxide. The total amount of coating after calcination was 180 g/l.

Example No. 9. Application of Al-3, Zr and CN-AlLa in Cu-SNA catalyst.

The same Cu zeolite as in example 1 was prepared together with the Al compound Al-3, 6% ZrO ₂ and 40 g/l CN consisting of aluminum oxide and lanthanum (CN-AlLa, CN including additive). La stabilized Al ₂ O ₃ since CN was added to a suspension already containing Cu zeolite, Al-3 and 6% ZrO ₂ , based on the calcined coating. Nitric acid-treated nanocrystalline Al-3 was an alternative to Al compound Al-1 and was used in these combination studies of compounds with good properties in the coating process. Water-soluble Zr(NO ₃ ) ₄ is the source of ZrO ₂ in this suspension. The particle size ( _d50 ) of these CNs (CN-AlLa) was 30 μm. The calcined catalytic material contained 67.9% Cu-CHN, 7.6% Al-3 in the form of Al ₂ O ₃ , 3.0% ZrO ₂ and 21.5% CN-AlLa in the form of oxide. The total amount of coating applied to the ceramic substrate after calcination was 180 g/l.

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Example No. 10. Addition of Al-3, Zr and CN-AlSiTi to the Cu-SHA catalyst.

The same Cu zeolite as in example 1 was prepared with the participation of Al-3 together with 6% ZrO ₂ , 40 g/l CN (22.2 wt.%, in the final coating), which consisted of aluminum oxide, dioxide silicon and titanium in the form of stable oxides (CN-AlSiTi). Si-Ti was stabilized by Al ₂ O ₃ , since CN was added to a suspension already containing Cu zeolite, Al-3 and 6% ZrO ₂ , based on the calcined coating. Treated with nitric acid, nanocrystalline Al-3 provided an alternative to the Al compound Al-1 and was used in these combination compound studies. The particle size ( _d50 ) of these CNs (CN-AlSiTi) was 30 μm. The calcined catalytic material contained 67.9% Cu-SNA, 7.6% Al-3 in the form of Al ₂ O ₃ , 3.0% ZrO ₂ and 21.5% CN-AlSiTi in the form of oxide. The total amount of coating applied to the ceramic substrate after calcination was 180 g/l.

Example No. 11. Addition of Al-3, Zr, La and CN-AlSiTi to the Cu-SNA catalyst.

In this example, Cu-SNA with CAS = 11 was prepared with Al-3 (compound A1), 3% ZrO ₂ , 3% La ₂ O ₃ and CNAlSiTi, which consisted of aluminum oxide, silicon dioxide and titanium in the form of stable oxides. Nitric acid-treated, nanocrystalline Al-3 was used in these combination compound studies. The particle size ( _d50 ) of these CNs (CN-AlSiTi) was 30 μm. The mass percentage in the calcined material was 65.8% Cu-CHA, 7.3% Al-3 in the form of Al ₂ O ₃ , 3.0% ZrO ₂ , 3.0% La ₂ O ₃ and 20.9% CN- AlSiTi in the form of oxide. The total amount of coating applied to the ceramic substrate after calcination was 180 g/l.

The functionality of the Al compound and the effect of the various additives used in Examples 1 to 11 are explained below by the NOx conversion test results shown in FIG. 2-6.

Fig. 2. Effect of Al compound with small crystal size and comparison with a comparative modern catalyst Cu-SNA in feed gas NO-NO2 (40% NO2, OS 71,000 h ^-1 ) in SGB experiments with GT aging 800/20 h.

The NOx conversion in fast SCR was clearly higher with the Cu-SNA sample (example 1a) having CAS 11, OKAS 5.9 and A1-1 as compound A1, compared to Cu-SNA with A1-2 (example 2, COMP. 1) with larger crystalline sizes Al ₂ O ₃ . Modern Cu-SNA (example 3, CVN 2) showed good activity at low and medium temperatures, but also a sharp drop when GT800 was aged at high temperatures above 400°C. This is due to excessively high ammonia oxidation, resulting in a low conversion of 52% at 570°C in the NO+NO2 feed gas. The Cu/Al ratio is estimated to be approximately 0.7 for this high CAN Cu-SNA, which is likely responsible for the release of Cu oxides on the zeolite and excessive ammonia oxidation at high temperature. This is a typical property of Cu-CHA zeolites with high CAS in SCR. Using lower Cu/Al on high CAN Cu-SNA will reduce the overall CuO loading, which is detrimental to the important low- and mid-temperature SCR activity. Therefore, the stabilized Cu-SHA with low CAN according to the invention provides a solution for maintaining good SCR functionality at low and high temperatures. Cu-SNA with CAS=11 was also compared with Cu-SNA (example 4, COMPARE 3) with CAS=23, obtained with the addition of Al-1. However, Cu-CHA SCR (CAS=23, Example 4) had higher SCR activity than the activity of the catalyst from Example 2 with larger Al ₂ O ₃ crystals. Thus, it was possible to obtain a thermally stable Cu-SNA catalyst with a low CAN, such as 11, that successfully competes with Cu-CNA with a higher CAN (>20) by activating the nanocrystalline Al compound.

Fig. 3. Increased stability during aging of Cu-SNA with Al-1, zirconium and lanthanum as thermal stabilizers in feed gases only NO (Fig. 3a) and NO+NO2 (Fig. 3b) (50,000 h ^-1 ) in SGB experiments during aging GT850/20h.

In addition, it was possible to improve the activity of SCR on the Cu-SNA catalyst with CAS 11 and Al-1 by adding 6% ZrO2 (example 5) or 3% La2O3 (example 6) in the form of dispersed forms. In these thermal stabilizer experiments, the aging temperature was increased to 850°C to see the stabilizing effects on the zeolites. Reactor conditions were slightly changed from FIG. 2, resulting in an OS of 50,000 h ^-1 in this and subsequent experiments. In addition, only NO and NO+NO2 were used in the feed gases to determine the relative activation and dependence of NO2 in SCR reactions. The improvement due to the added compounds was evident in both NO and NO+NO2 feed gases at low and medium temperatures up to 500°C, a temperature range that covers the main application and engine performance charting conditions in diesel applications.

Nanocrystalline Al-1 can also be used with combinations of 3% ZrO ₂ and 3% La ₂ O ₃ (Example 7), resulting in improvements at low and high temperature. Thus, it is possible to improve the hydrothermal stability of low CAN Cu-CHN such as 11 with Al-1 as the Al compound, together with Zr and La as additives.

Fig. 4. Improved aging stability of Cu-CHN with Al-1 together with large particles (CP) as promoters in feed gases with only NO (Fig. 4a) and NO+NO2 (Fig. 4b) (50,000 h ^-1 ) in experiments SGB with aging GT850/20h.

The SCR activity of Cu-SNA with low CAS 11 and Al-1 was further improved by adding

- 15 046217 CN containing A12O3 as the main oxide, but also containing additives La (in example 8a), Si (in example 8b) or Zr+Si (in example 8c). The addition of CN on Cu-CHA-ΙΙ with Al-1 increased the NO _x conversion throughout the operating window. The CP particles are preferably stabilized with Si or Ti to improve thermal durability and acidity. Si, Ti or Zr on alumina also reduces the adsorption of sulfur on CP. Increased acidity correlates with a lower tendency to adsorb sulfur. In addition, Zr and/or an additive can also be added to the CN particles to improve the stability of the CN against sintering. La is a heat stabilizer, but also reduces acidity and creates basic sites on the CN. The role of La is to reduce the adsorption of ammonia on CP particles under SCR reaction conditions and to direct the adsorption of ammonia onto zeolite centers near the active copper centers. The catalytic composition then contains CNs as thermal barriers, which have minimal ability to adsorb ammonia, which is thus concentrated in the SCR-functional zeolite particles.

Fig. 5. Increased stability during aging of Cu-SNA with Al-3 as a compound of Al, Zr, La as an additive and CN with Si+Ti in the raw gases only NO (Fig. 5a) and NO+NO2 (Fig. 5b) ( 50,000 h ^-1 ) in SGB experiments with aging GT850/20h.

Combinations of Al-3, Zr, La and CN were used to obtain the Cu-SNA catalyst with CAS=11. The stability of the CN was increased using Si+Ti and La (additive). The amount of Cu-CHNA was the same in all these samples. Consequently, the coating layer was also diluted with CN particles, which also have a preventing effect on the spread of sintering under application conditions. Samples with 6% ZrO ₂ (example 9 and example 10) showed high efficiency of SCR in feed gases only NO and NO+NO2 with CN containing La or CN containing Si+Ti. The same applies to a sample with 3% ZrO ₂ and 3% La ₂ O ₃ with CN containing Si+Ti (example 11). Zr, La promoters and stabilized CNs in these catalysts improved the low-temperature activity of SCR. Particular improvement was observed in fast SCR (NO+NO2), since NO2 usually compensates for the poor reaction startup found when feeding NO alone. Consequently, CPs containing Si and Ti improved the performance of CPs in the Cu-SNA catalyst. Ti and Si are capable of stabilizing the alumina surface to reduce the adsorption of sulfur oxides, which is important in lean flue gas applications.

Fig. 6. Comparison of the Cu-SNA catalyst according to the invention with Cu-SNA with high CAS using feed gases NO+NO2 (50,000 h ^-1 ) in SGB experiments with aging GT850/20h.

Finally, the developed Cu-zeolite composition containing an Al compound, 3% ZrO ₂ , 3% La ₂ O ₃ as an additive and alumina-based CN with Si+Ti activation (example 11) was compared with the comparison catalyst Cu-SNA ( example 3, COMPARE 2) with a high CAC of approximately 28. The Cu-CHA composition according to the present invention showed higher _NOx conversion across the entire temperature window and much higher selectivity at higher temperatures above 400°C. The reference catalyst (CRAVN 2) has the property of excessively high ammonia oxidation, which is detrimental to urea consumption and overall _NOx efficiency. A slight drop was also observed after aging the GT850 in Example 11 of the present invention, but NO _x conversion was still about 90% at 500°C and about 80% at 600°C. Accordingly, NO _x conversion was approximately 80% at 500°C and approximately 49% at 600°C for sample SRAVN 2 (example 3) after aging GT850. Under diesel exhaust gas conditions, high SCR activity is required, at least up to 500°C. The low-temperature activity of SCR increased in the presence of NO ₂ due to the activation of Zr, La and CN.

Conclusion and conclusions.

The SCR activity obtained during strong hydrothermal aging of Cu zeolite catalysts at 800 and 850°C proved the stabilization and stimulating effect of the claimed catalytic compositions. The use of low UAN (<15) Cu zeolite (CNA) allows the use of high Cu loads with low Cu/Al molar ratios (<0.4), resulting in low ammonia oxidation at high temperatures and high NOx efficiency with varying NO2 ratios /NOx throughout the entire temperature window under lean exhaust gas conditions. Nanocrystalline Al compound (Al ₂ O ₃ ) improved thermal stability with Cu-CHA zeolite with low CAS=11. Two good examples have been presented as an Al compound; Al-1 with a crystal size of 4.5 nm and Al-3 with a crystal size of 6 nm. Details of the plating method also play a role in which Al compounds are used in the combination compositions. Zirconium in the form of a stable, dispersed form of zirconium oxide showed additional improvements in thermal durability, acidity control and low temperature activity on a Cu zeolite SCR catalyst. The additive (La in the examples) showed additional stabilization and improvements in low temperature functionality on Cu zeolite SCR catalysts. Large particles (CP) with Si and Ti as promoters showed obvious improvement in the stability of Cu zeolite catalyst. CNs also play a key role in the structural and thermal durability of the coating layer. The examples showed several variations in combinations of activating compounds. The total CAC (TCAC) parameter was determined, which changes for Cu-zeolite SCR catalysts depending on the amount of nanocrystalline aluminum oxide. The ionic radius of the added compounds was also determined by the interaction possibilities. Cu ²⁺ inside the zeolite lattice has a key radius, the Al compound with Al ³⁺ has a smaller radius,

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Claims (21)

Zr ⁴⁺ and additive ions have a larger radius and Ti ⁴⁺ /Si ⁴⁺ a smaller radius than Cu ²⁺ . In addition, Si and Ti have almost the same radius as Al ions in their ground stable ionic states. The same promoting effect can also be applied to other zeolite catalysts with low UAN (<20, even lower such as <15). As a microporous zeolite bearing at least copper or iron as an active metal, microporous zeolite structures AEI, AFX, LEV or Beta can be used instead of CHA. CLAIM 1. Catalytic composition for selective catalytic reduction of NO _x with ammonia or compounds that release ammonia under exhaust gas conditions, containing a) zeolite particles with ion-exchange copper having a Si/Al ₂ molar ratio (KAC) of 15 or less and a copper ion content, measured as CuO, in the zeolite from 1 to 10 wt.%, based on the total mass of the zeolite, b) nanocrystalline alumina, wherein the amount of nanocrystalline alumina in the catalyst composition is from 0.5 to 25 wt.%, based on the total weight of the catalyst composition, wherein the nanocrystalline alumina has a crystal size d ₅₀ from 1 to 8 nm, and c ) a zirconium compound, where the content of the zirconium compound in the catalytic composition is from 1 to 10 wt.% ZrO ₂ based on the total weight of the catalytic composition. 2. The catalytic composition according to claim 1, characterized in that the zeolite is selected from the framework group consisting of chabazite (CHA), AEI, AFX, LEV, Beta or mixtures thereof. 3. Catalytic composition according to claim 1 or 2, having a CAS from 2 to 14.9. 4. Catalytic composition according to any one of claims 1 to 3, characterized in that the content of copper ions, measured as CuO, in the zeolite is from 2 to 7 wt.% based on the total weight of the zeolite. 5. Catalytic composition according to any one of claims 1 to 4, characterized in that the amount of nanocrystalline aluminum oxide in the catalytic composition is from 1 to 20 wt.% based on the total weight of the catalytic composition. 6. The catalytic composition according to claim 3, having a CAC from 10 to 14.9, characterized in that the amount of nanocrystalline aluminum oxide in the catalytic composition is from 0.5 to 25 wt.% based on the total weight of the catalytic composition. 7. Catalytic composition according to any one of claims 1 to 6, characterized in that the Cu/Al molar ratio in the zeolite is from 0.02 to 0.4. 8. Catalyst composition according to any one of claims 1 to 7, characterized in that the total content of copper ions, measured as CuO, in the catalyst composition is from 2 to 6 wt.% based on the total weight of the catalytic composition. 9. Catalytic composition according to any one of claims 1-8, characterized in that the zeolite particles with ion-exchange copper have a size d ₅₀ from 1 to 10 μm. 10. Catalytic composition according to any one of claims 1 to 9, characterized in that the content of the zirconium compound in the catalytic composition is from 2 to 7 wt.% ZrO ₂ based on the total weight of the catalytic composition. 11. Catalytic composition according to any one of claims 1 to 10, characterized in that the nanocrystalline aluminum oxide is Al ₂ O ₃ . 12. Catalytic composition according to any one of claims 1-11, characterized in that the nanocrystalline Al ₂ O ₃ has a crystalline size d ₅₀ of 3-7 nm. 13. Catalytic composition according to any one of claims 1-12, characterized in that the nanocrystalline Al ₂ O ₃ contains dispersed particles with a size d ₅₀ from 5 to 80 nm. 14. Catalytic composition according to claim 13, characterized in that the nanocrystalline Al ₂ O ₃ has a dispersed particle size d ₅₀ from 10 to 30 nm. 15. Catalytic composition according to any one of claims 1 to 14, containing particles based on Al ₂ O ₃ having a particle size d ₅₀ from 3 to 200 μm. 16. Catalytic composition according to any one of claims 1 to 15, containing an additive selected from the oxides of La, Y, Hf, Nd and mixtures thereof. 17. Catalytic composition according to any one of claims 1-16, containing Si, Ti and mixtures thereof in the form of stable oxides. 18. Catalytic composition according to claim 17, characterized in that Si and/or Ti is attached to the Al2O3-based particle. 19. The catalytic composition according to any one of claims 1 to 18, having a total TAC (TAC) of less than 10, where TAC is defined as the Si/Al2 molar ratio between Si in the zeolite and total Al2 in the zeolite and nanocrystalline alumina. 20. Catalytic composition according to any one of claims 1-19, having an OKAC from 4 to 10. 21. A support for use in a flue gas system, comprising a catalyst composition according to any one of claims 1 to 20. -