a method for manufacturing a catalyst comprising Copper cha zeolite catalysts

TECHNICAL FIELD [0002] Embodiments of the invention relate to methods for preparing copper-zeolite CHA catalysts.

BACKGROUND OF THE INVENTION [0003] Zeolites are aluminosilicate crystalline materials with fairly uniform pore sizes, which, depending on the type of zeolite and the type and amount of cations contained in the zeolite crystal lattice, generally have a diameter ranging from about 3 to 10 Angstroms. Both synthetic and natural zeolites and their use to support certain reactions, including the selective reduction of nitrogen oxides with ammonia in the presence of oxygen, are well known in the art. US 4297328 discloses a method for the catalytic combustion of carbon monoxide and hydrocarbons and the catalytic reduction of nitrogen oxides contained in a gas stream. The method includes thoroughly contacting a gaseous stream with a catalyst bed comprising copper metal or copper ions and a high silica zeolite.

[0004] Metal promoted zeolite catalysts are known, including, inter alia, iron-promoted zeolite catalysts and copper-promoted, for the selective catalytic reduction of nitrogen oxides with ammonia. The iron-beta zeolite was an efficient catalyst for the selective reduction of nitrogen oxides with ammonia. Unfortunately, it has been found that under severe hydrothermal conditions, such as the reduction of NOx from flue gas at temperatures exceeding 500 ° C, the activity of many metal-promoted zeolites begins to decrease. It is believed that this decrease in activity occurs due to the destabilization of the zeolite, such as by the de-gelling, and thus the reduction in the number of metal-containing catalytic centers in the zeolite. In order to maintain total NOx reduction activity, increased concentrations of iron-promoted zeolite catalyst should be provided. Since the zeolite catalyst concentrations are increased to ensure adequate NOx removal, it is obvious that the cost-effectiveness of the NOx removal process decreases as the catalyst costs increase.

[0005] There is a need for materials that provide SCR (low temperature selective catalytic) activity at low temperature and / or increased hydrothermal strength compared to existing zeolites, for example catalytic materials that are stable at temperatures up to at least about 650 ° C and higher. .

SUMMARY [0006] Aspects of the invention relate to zeolites that have a CHA crystal structure (which is determined by the International Zeolite Association), to catalysts containing such zeolites, and to flue gas cleaning processes using such catalysts. The catalyst can be part of the exhaust gas cleaning system used to purify the exhaust gas streams, especially those emitted from gasoline or diesel engines.

[0007] One embodiment of the present invention relates to copper-CHA catalysts and their use in exhaust gas systems, such as those intended for the reduction of nitrogen oxides. In certain embodiments, new copper-chabasite catalysts are provided that exhibit enhanced SCR NOx using NH3. The copper-chasmase catalysts produced according to one or more aspects of the present invention provide a catalytic material that exhibits excellent hydrothermal stability and high catalytic activity over a wide temperature range. Compared with other zeolite catalysts that find use in the field, such as Fe Beta zeolites, copper-CHA catalytic materials in accordance with embodiments of the present invention provide enhanced low-temperature activity and hydrothermal stability.

One embodiment of the invention relates to a catalyst comprising a zeolite having a crystalline structure of CHA and a molar ratio of silica to alumina of 15 to 256, and the atomic ratio of copper to aluminum is from 0.25 to 0.50. In a more specific embodiment, the molar ratio of silica to alumina is from 25 to 40. In an even more specific embodiment, the molar ratio of silica to alumina is about 30. In a particular embodiment, the copper to aluminum has a copper atomic ratio of 0.30 to 0.50. In a particular embodiment, the atomic ratio of copper to aluminum is about 0.40. In a particular embodiment, the molar ratio of silica to alumina is from 25 to 40 and the atomic ratio of copper to aluminum is from 0.30 to 0.50. In another particular embodiment, the silica to alumina ratio is about 30, and the atomic ratio of copper to alumina is about 0.40.

[0009] In a particular embodiment, the catalyst comprises ion exchanged copper and a certain amount of non-exchangeable copper, sufficient to maintain the efficiency of the catalyst in the conversion of NOx in the exhaust gas stream containing oxides of nitrogen after the hydrothermal aging of the catalyst. In one embodiment, the catalyst efficiency in NOx conversion at about 200 ° C, after aging, accounts for at least 90% of catalyst efficiency in NOx conversion, at about 200 ° C, prior to aging. In a particular embodiment, the catalyst contains at least about 2.00 percent by weight copper oxide.

[0010] In at least one of the embodiments, the catalyst is deposited on a honeycomb base. In one or more embodiments, the honeycomb structure comprises a flow-through-wall substrate. In other embodiments, the honeycomb structure comprises a flow substrate. In some embodiments, at least a portion of the flow substrate is CuCHA coated adapted to reduce the nitrogen oxides contained in the gas stream flowing through the substrate. In a particular embodiment, at least a portion of the flow substrate is coated with Pt and CuCHA adapted to oxidize ammonia in the exhaust gas stream.

[0011] In embodiments that utilize a flow-through-wall substrate, at least a portion of the flow-through-wall substrate is coated with CuCHA adapted to reduce the nitrogen oxides contained in the gas stream flowing through the substrate. In other embodiments, at least a portion of the flow-through substrate is coated with Pt and CuCHA adapted to oxidize ammonia in the exhaust gas stream.

In a particular embodiment, the catalyst product comprises a honeycomb structure comprising a zeolite with a crystalline structure of CHA deposited on a support in which the zeolite molar ratio of silica to alumina is greater than about 15 and the atomic ratio of copper to aluminum exceeds about 0.25, and which contains free copper in an amount greater than copper subjected to ion exchange. In one embodiment, the free copper is present in an amount sufficient to prevent the hydrothermal decomposition of the catalyst for the conversion of nitric oxide. In one or more embodiments, the free copper prevents the hydrothermal decomposition of the catalyst for the conversion of nitric oxide after hydrothermal aging. The catalyst may further comprise a binder. In particular embodiments, copper subjected to ion exchange is replaced using copper acetate.

BRIEF DESCRIPTION OF THE DRAWINGS [0013]

Fig. 1 is a graph showing the nitrogen oxides removal efficiency (%), ammonia consumption (%) and N2O produced (ppm) using a CuCHA catalyst, as a function of the reaction temperature, for CuCHA produced according to the methods of Example 1;

Fig. 1A is a graph showing the nitrogen oxides removal efficiency (%), ammonia consumption (%) and N2O produced (ppm) using a CuCHA catalyst as a function of the reaction temperature for CuCHA produced according to the methods of Examples 1 and 1A;

Fig. 2 is a graph showing the nitrogen oxides removal efficiency (%), ammonia consumption (%) and N2O produced (ppm) using a CuCHA catalyst, as a function of the reaction temperature, for CuCHA produced according to the methods of Example 2;

Fig. 3 is a graph showing the nitrogen oxides removal efficiency (%), ammonia consumption (%) and N2O produced (ppm) using a CuCHA catalyst, as a function of the reaction temperature, for CuCHA produced according to the methods of Example 3;

Fig. 4 is a graph showing the nitrogen oxides removal efficiency (%), ammonia consumption (%) and N2O produced (ppm) using a CuCHA catalyst as a function of the reaction temperature for CuCHA produced according to the methods of Example 4;

Fig. 5 is a graph showing the effect of CO, propene, n-octane and water on CuCHA SCR activity at different temperatures;

Fig. 5A is a graph showing HC amounts that are stored, released, deposited as coke and coke fired for a test sample according to Example 12A; Fig. 5B is a bar graph showing the efficiency of CuCHA against a hydrocarbon compared to the CuY and Fe beta zeolites of Example 12A;

Fig. 6 is a graph showing NH3, NOx (= NO + NO2), N2O and N2 emissions from an AMOX catalyst outlet, given as ppm relative to the nitrogen atom, produced and aged according to the method of Examples 13 and 14;

Fig. 7 is a graph showing the nitrogen oxides removal efficiency (%), ammonia consumption (%) and N2O produced (ppm) using a CuCHA catalyst, as a function of the reaction temperature, for CuCHA produced according to the methods of Example 16;

Fig. 8 is a graph showing the nitrogen oxides removal efficiency (%), ammonia consumption (%) and N2O produced (ppm) using a CuCHA catalyst, as a function of the reaction temperature, for CuCHA produced according to the methods of Example 17;

Fig. 9 is a graph showing the nitrogen oxides removal efficiency (%), ammonia consumption (%) and N2O produced (ppm) using a CuCHA catalyst, as a function of the reaction temperature, for CuCHA produced according to the methods of Example 18;

Figs. 10A, 10B and 10C are schematic representations of three exemplary embodiments of the system according to the invention for emission purification;

Fig. 11 shows the UV / VIS spectrum from Examples 22 and 22A; and

Fig. 12 shows the spectrum ²⁷Al MAS NMR from Examples 22 and 22A, compared to

CHA and for aged CHA samples.

DETAILED DESCRIPTION [0014] Before describing several exemplary embodiments of the invention, it will be appreciated that the invention is not limited to the construction details or to the process steps outlined herein. The invention allows other forms and different ways of carrying out or carrying out.

[0015] In one embodiment of the invention, zeolites having a CHA structure, such as chabasite, are provided. In one or more embodiments, a zeolite having a crystal structure of CHA is provided and a molar ratio of silica to alumina greater than about 15 and an atomic ratio of copper to aluminum greater than about 0.25. In certain embodiments, the molar ratio of silica to alumina is about 30, and the atomic ratio of copper to aluminum is about 0.40. Other zeolites with a CHA structure include, but are not limited to, SSZ13, LZ-218, Linde D, Linde R, Phi, ZK-14 and ZYT-6.

[0016] The synthesis of zeolites with a CHA structure can be carried out according to various techniques known in the art. For example, in a typical SSZ-13 synthesis, a silica source, an alumina source and an organic targeting agent are mixed together under aqueous alkaline conditions. Typical sources of silica include various types of fumed silica, precipitated silica and colloidal silica, as well as silicon alkoxides. Typical sources of alumina include bemitics, pseudobemites, aluminum hydroxides, aluminum salts such as aluminum sulphate and aluminum alkoxides. Sodium hydroxide is usually added to the reaction mixture, but this is not required. A typical targeting agent for this synthesis is adamantyltrimethylammonium hydroxide, although other amines and / or quaternary ammonium salts may be substitutes or be added to the latter targeting agent. The reaction mixture is heated in a stirred tank under pressure to produce the crystalline product SSZ-13. A typical reaction temperature is in the range of 150 to 180 ° C. The typical reaction time is from 1 to 5 days.

[0017] After completion of the reaction, the product is filtered off and washed with water. Alternatively, the product can be centrifuged. Organic additives may be used to assist in the handling of the solid product and its separation. Spray drying is an optional step in the treatment of the product. The solid product is subjected to heat treatment in an air or nitrogen atmosphere. Alternatively, any gas treatment can be carried out in a different order or gas mixtures can be used. A typical calcination temperature is in the range of 400 ° C to 700 ° C.

[0018] CuCHA zeolite catalysts according to one or more embodiments of the invention can be used in catalytic processes that include oxidation and / or hydrothermal conditions, for example at temperatures in excess of about 600 ° C, for example higher than about 800 ° C and in the presence of about 10% water vapor. In particular, it has been found that the CuCHA zeolite catalysts that have been produced in accordance with embodiments of the invention have increased hydrothermal stability compared to CuY and CuBeta zeolites. The CuCHA zeolite catalysts prepared according to the embodiments of the invention show increased activity in the selective catalytic reduction of NOx with ammonia, especially when operating at high temperatures of at least about 600 ° C, e.g. about 800 ° C and above, and in an environment with a high water vapor content of about 10% or more. CuCHA has a high specific activity, which allows the use of smaller amounts of catalytic material, which in turn should reduce the back pressure of honeycomb substrates coated with intermediate layers of CuCHA catalysts. In one or more embodiments, hydrothermal aging refers to subjecting the catalyst to a temperature of about 800 ° C in an environment with a high water vapor content of about 10% or more, for at least about 5 to about 25 hours, and in certain specific embodiments to about 50 hours. which in turn should reduce the back pressure of honeycomb substrates coated with intermediate layers of CuCHA catalysts. In one or more embodiments, hydrothermal aging refers to subjecting the catalyst to a temperature of about 800 ° C in an environment with a high water vapor content of about 10% or more, for at least about 5 to about 25 hours, and in certain specific embodiments to about 50 hours. which in turn should reduce the back pressure of honeycomb substrates coated with intermediate layers of CuCHA catalysts. In one or more embodiments, hydrothermal aging refers to subjecting the catalyst to a temperature of about 800 ° C in an environment with a high water vapor content of about 10% or more, for at least about 5 to about 25 hours, and in certain specific embodiments to about 50 hours.

[0019] Embodiments of the present invention also relate to a method for reducing NOx in a flue gas stream produced by an internal combustion engine using CuCHA zeolite catalysts with a silica to alumina molar ratio greater than about 15 and an atomic copper to aluminum ratio exceeding about 0.25. Other embodiments relate to SCR catalysts containing a CuCHA zeolite catalyst with a silica to alumina molar ratio greater than about 15 and a copper to aluminum atomic ratio greater than about 0.25 and exhaust gas treatment systems containing CuCHA zeolite catalysts. Still other forms concern catalysts (AMOX) for ammonia oxidation and exhaust gas cleaning systems, containing an AMOX catalyst containing a CuCHA zeolite catalyst with a silica to alumina molar ratio greater than about 15 and a copper to aluminum atomic ratio greater than about 0.25. According to one or more embodiments, the catalysts and systems use CuCHA catalysts containing ion exchanged copper and sufficient excess free copper to prevent thermal decomposition of the catalysts when operating at high temperatures of at least about 600 ° C, e.g. about 800 ° C and higher, and in an environment with a high water vapor content of about 10% or more.

[0020] Experiments have shown that the increased efficiency of the catalysts according to the embodiments of the invention is related to the Cu load. Although Cu may be mentioned, it has been found that in order to increase the Cu level associated with the exchange sites in the zeolite structure, it is preferred to leave the Cu which is not mentioned in the salt form, for example as CuSO4 in the zeolite catalyst. As a result of calcination, the copper salt decomposes on CuO, which can be referred to herein as "free copper" or "soluble copper." According to one or more embodiments, this free Cu is both active and selective, which results in the formation of copper. small amounts of N2O when used to purify the gas stream containing nitrogen oxides. It was unexpectedly found

[0021] Although it is intended that the embodiments of the invention are not bound by a particular base, it is believed that the relatively small CHA channel openings do not allow high molecular weight (HC) hydrocarbons typical of diesel fuel to enter and adsorb in the CuCHA structure. . In contrast to other zeolites, such as Beta or ZSM5, the CHA catalysts produced according to the embodiments of the invention have a relatively low affinity to adsorb these high molecular weight HC components. This is a preferred property for use in selective catalytic reduction catalysts (SCR).

[0022] In systems that use SCR after the diesel fuel oxidation catalyst (DOC), the properties of CuCHA catalysts provide one or more favorable numbers, in accordance with embodiments of the invention. During start-up and long-term operation at low temperatures, only SCR or diesel oxidation catalyst (DOC) or DOC and catalyzed soot filter (CSF) before the CuCHA SCR catalyst are not fully activated for the oxidation of HC. According to one or more embodiments, due to the fact that low temperature HC does not affect the CuCHA SCR catalyst, it remains active over a wide range of low operating chamber temperatures. According to one or more embodiments, low temperatures refer to temperatures of about 250 ° C and below.

[0023] According to one or more embodiments, CuCHA catalysts operate in the low temperature range. Over time, an exhaust gas treatment system comprising a DOC precocatalor after the engine, followed by a SCR and CSF catalyst or DOC pre-catalyst before CSF and SCR, DOC tends to both activate the low temperature thermal catalyst and HC fuel combustion. It is advantageous if in such systems the SCR catalyst can maintain its ability to operate at low temperatures. Since the oxidation catalysts lose their ability to oxidize NO to NO2, it is useful to provide an SCR catalyst that can process NO as effectively as NO2. The CuCHA catalysts prepared according to embodiments of the invention have the ability to reduce NO by using NH3 at low temperatures.

[0024] According to embodiments of the invention, the SCR catalyst may be in the form of self-supporting catalytic particles or as a honeycomb monolith made from the SCR catalyst composition. However, in one or more embodiments of the invention, the SCR catalyst composition is embedded as an intermediate layer or as a combination of intermediate layers on a ceramic or metal substrate, for example on a honeycomb flow substrate.

[0025] In a specific embodiment of the emission purification system, the SCR catalyst is produced from a zeolite CHA material with said Cu, containing in addition to the copper ion-exchange free copper.

[0026] When deposited onto monolithic honeycomb bases, such SCR catalyst compositions are deposited at a concentration of at least about 0.5 g / in³ (0.0305 g / cm³), for example about 1.3 g / inch³ (0.0793 g / cm³), about 2.4 g / inch³ (0.1464 g / cm³) or more, to ensure that the desired NOx reduction is achieved and to ensure adequate catalyst life during prolonged use.

[0027] The term "SCR" catalyst is used herein in a broader sense and means a selective catalytic reduction in which a catalyzed reaction of nitrogen oxides with a reducing agent takes place to reduce nitrogen oxides. The terms "reducing agent" or "reducing agent" are also used in a wide range herein and mean any chemical agent or compound that tends to reduce NOx at elevated temperatures. In certain embodiments, the reducing agent is ammonia, in particular an ammonia precursor, i.e. urea, and SCR is a nitrogen-reducing SCR. However, according to a broader scope of the invention, the reducing agent can comprise fuel, in particular diesel fuel and its fractions, as well as any hydrocarbon and oxidized hydrocarbons, collectively referred to as HC reducer.

SUBSTRATES [0028] The catalyst compositions are deposited on a substrate. The substrate may be any of these materials typically used in the preparation of catalysts and typically comprises a ceramic or metal honeycomb structure. Any suitable support may be used, such as a monolithic support of a type comprising small, parallel gas channels extending through them extending from the inlet or outlet front section of the substrate so that the channels are open to the fluid passing through them (referred to as flow media with honeycomb). The channels, which are essentially straight paths from their fluid inlet to their fluid outlet, are defined by the walls on which the catalytic material is deposited as an intermediate layer, so that the gases flowing through the channels contact the catalytic material. The flow channels in the monolithic substrate are thin-walled channels, which can have any suitable shape and size of the cross-section, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular etc. Such structures can contain from about 60 to about 400 or more gas inlet openings (i.e. cells) per square inch (from about 9.3 to about 62.0 or more numbers of gas inlet openings (i.e., cells) per square centimeter) of cross-section.

[0029] The substrate may also be a wall flow filter medium in which the channels are blocked alternately, allowing the gas stream to enter the channels from one direction (inlet direction), flow through the channel walls and exits from the channels from another direction (direction outlet). The AMOX and / or SCR catalyst composition can be applied to a flow filter or flow through the wall. If a flow-through-wall substrate is used, the resulting system will be able to remove solid particles together with gaseous impurities. The wall flow filter medium can be manufactured from materials known in the art, such as cordierite, aluminum titanate or silicon carbide. It should be understood

The ceramic substrate can be made from any refractory material, for example from cordierite, cordierite-aluminum oxide, silicon nitride, zirconium mullite, spodumene, alumina-silica-magnesium oxide, zirconium silicate, silymannite, magnesium silicate, zirconium, petalite, alpha. aluminum oxide, aluminosilicate and the like.

[0031] Substrates useful for catalysts according to embodiments of the present invention may also be metallic and consist of one or more metals or metal alloys. Metallic substrates with different shapes, such as corrugated sheet or monolithic form, may be used. Suitable metal substrates include heat-resistant metals and metal alloys, such as titanium and stainless steel, as well as other alloys in which iron is a significant or major component. Such alloys may contain one or more nickel, chromium and / or aluminum components, and the total amount of these metals may preferably be at least 15% by weight. alloy, for example 10-25 wt.% chromium, 3-8 wt% aluminum and up to 20% by weight nickel. The alloys may also contain small or trace amounts of one or more other metals, such as manganese, copper, vanadium, titanium and the like. The surface of metal substrates can be oxidized at high temperatures, for example at 1000 ° C and higher, in order to increase the resistance of the alloy to corrosion by forming an oxide layer on the surfaces of the substrates. Such high temperature oxidation may increase the adhesion to the substrate of the components in the form of a refractory metal oxide carrier and catalytically promoting metal components.

[0032] In alternative embodiments, one or both of the CuCHA catalyst compositions can be deposited on an open cell foam substrate. Such substrates are well known in the art and are usually made of refractory ceramic or metal materials.

Preparation of the intermediate layer [0033] According to one or more embodiments, the intermediate layers of CuCHA can be produced using a binder. According to one or more embodiments, a ZrO2 binder is used, derived from a suitable precursor, such as a zirconium acetate or any other suitable zirconium precursor, such as zirconyl nitrate. In one embodiment, the zirconyl acetate as a binder provides a catalytic coating that remains homogeneous and intact after thermal aging, for example when the catalyst is subjected to high temperatures, at least about 600 ° C, e.g. about 800 ° C and above, and in a high-temperature environment. a water vapor content of around 10% or more. Keeping the intact intermediate layer is beneficial, because a loose or loose coating could clog the posterior CSF causing an increase in backpressure. [0034] According to one or more embodiments, the CuCHA catalysts can be used as a catalyst for ammonia oxidation. Such AMOX catalysts are useful for exhaust gas cleaning systems, including SCR catalysts. As disclosed in US Pat. No. 5,516,477 to the same applicant, a gaseous stream containing oxygen, nitrogen oxides and ammonia may pass successively through first and second catalysts, a first catalyst promoting reduction of nitrogen oxides, and a second catalyst favoring oxidation or other decomposition of excess ammonia. As described in US Patent No. 5,511,497, the first catalyst may be an SCR catalyst containing zeolite,

[0035] As is known in the field, in order to reduce the emission of nitrogen oxides from exhaust and exhaust gases, ammonia is added to the gaseous stream containing nitrogen oxides, and then the gaseous stream is contacted with the appropriate catalyst at elevated temperature to catalyze the reduction of nitrogen oxides ammonia. Such gas streams, for example combustion products of an internal combustion engine or a gas turbine engine or a diesel engine, often also contain inherently significant amounts of oxygen. Typical exhaust gases from a turbine engine contain from about 2 to 15 percent by volume oxygen and from about 20 to 500 parts by volume per million nitrogen oxides, the latter usually comprising a mixture of NO and NO2. Typically, there is enough oxygen in the gas stream to oxidize the residual ammonia, even if excess is used over the stoichiometric amount of ammonia required to reduce all the nitrogen oxides present. However, in cases where a very large excess of ammonia is used over the stoichiometric amount or when the gaseous stream to be purified does not contain or has a low oxygen content, the oxygen-containing gas, usually air, may be introduced between the first catalyst zone and the second catalyst zone , to ensure that an appropriate amount of oxygen is in the zone of the second catalyst to oxidize residuals or excess ammonia. even if excess is used above the stoichiometric amount of ammonia required to reduce all nitric oxides present. However, in cases where a very large excess of ammonia is used over the stoichiometric amount or when the gaseous stream to be purified does not contain or has a low oxygen content, the oxygen-containing gas, usually air, may be introduced between the first catalyst zone and the second catalyst zone , to ensure that an appropriate amount of oxygen is in the zone of the second catalyst to oxidize residuals or excess ammonia. even if excess is used above the stoichiometric amount of ammonia required to reduce all nitric oxides present. However, in cases where a very large excess of ammonia is used over the stoichiometric amount or when the gaseous stream to be purified does not contain or has a low oxygen content, the oxygen-containing gas, usually air, may be introduced between the first catalyst zone and the second catalyst zone , to ensure that an appropriate amount of oxygen is in the zone of the second catalyst to oxidize residuals or excess ammonia.

[0036] Metal promoted zeolites are used to promote the reaction of ammonia with nitrogen oxides to form nitrogen and H2O, selectively against competing oxygen and ammonia reactions. Therefore, sometimes the catalyzed reaction of ammonia and nitrogen oxides is referred to as selective catalytic reduction ("SCR") of nitrogen oxides or sometimes in the present description simply as an "SCR process". Theoretically, it would be desirable for the SCR process to provide ammonia in excess of the stoichiometric amount required to be completely reacted with the nitrogen oxides present therein, both to promote completion of the reaction and to overcome the inappropriate mixing of ammonia in the gas stream. However, in reality, there is usually no substantial excess of ammonia above the stoichiometric amount, because the discharge of unreacted ammonia from the catalyst into the atmosphere would cause a problem with air pollution. Such discharge of unreacted ammonia can occur even in cases where ammonia is present only in a stoichiometric or substoichiometric amount, as a result of the unreacted reaction and / or poor mixing of ammonia in the gas stream, which leads to the formation of channels of high ammonia concentration therein. Such channel formation is of particular relevance when using catalysts comprising honeycomb monolithic supports comprising refractory materials having a plurality of fine, parallel gas flow paths extending therethrough, as unlike in the case of a particulate catalyst,

According to embodiments of the present invention, the CuCHA catalysts may be formulated to promote either (1) an SCR process, i.e. a reduction of nitrogen oxides with ammonia to form nitrogen and H 2 O, or (2) oxidation of ammonia to produce nitrogen and H 2 O, with selectivity The catalyst is adjusted by controlling the Cu content in the zeolite. U.S. Patent No. 5,511,497 discloses levels of iron and copper loading on zeolites other than copper-CHA to obtain selectivity in the SCR reaction and selectivity of the catalyst for ammonia oxidation at the expense of the SCR process, thereby increasing the ammonia removal. According to the embodiments of the invention,

The above principles are utilized by providing a stepwise or dual zone catalyst in which, after the first zone of the copper catalyst loaded zeolite, which promotes SCR, there is a second catalyst zone containing copper-loaded zeolite and / or a noble metal component that promotes oxidation of ammonia. Thus, the resulting catalyst composition contains a first zone (in the front portion) that promotes the reduction of nitrogen oxides with ammonia and a second zone (in the rear part) that promotes oxidation of ammonia. In this way, when ammonia is present in excess in relation to the stoichiometric amount, regardless of whether in the entire cross-section of the flow of the gaseous stream which is being treated or in localized channels with a high concentration of ammonia, Oxidation of residual ammonia by oxygen is promoted by the back part or the second catalyst zone. The amount of ammonia in the gas stream discharged from the catalyst is thus reduced or removed. The first zone and the second zone may be on a single catalyst support or be separate substrates.

[0039] It has been shown that an intermediate layer of CuCHA catalyst containing a noble metal, for example Pt, provides an AMOX catalyst. It is expected that not only ammonia is decomposed in the gas flowing through the catalyst, but that NOx is continuously removed as a result of conversion to N2. In a particular embodiment, the SiO2 / Al2O3 ratio in the zeolite is from about 15 to about 256, and the Al / M ratio is between 2 and 10, wherein M is the total Cu and noble metal content. In one embodiment, the noble metal is platinum and the platinum content is between 0.02% and 1.0% by weight of the catalyst, and the element load is from about 0.5 to about 5 g / in.³ (from about 0.0305 to about 0.3050 g / cm³).

[0040] According to one or more aspects of the invention, the CuCHA SCR catalysts can be deposited on a filter with a flow through the wall or on a catalyzed soot filter. The intermediate layers of the CuCHA catalyst can be coated on a porous filter to provide soot combustion and to perform SCR and AMOX functions.

[0041] In one or more embodiments of the present invention, the catalyst comprises a noble metal component, i.e. a metal component from the platinum group. For example, as mentioned above, AMOX catalysts typically contain a platinum component. Suitable noble metal components include platinum, palladium, rhodium and mixtures thereof. The individual components (e.g. CuCHA and noble metal component) of the catalyst material can be applied to the refractory support element, i.e. to the substrate, as a mixture of two or more components or as separate components in subsequent steps in a manner that will be readily understood by specialists in the field of catalyst production. As described above and in the examples, a typical method of preparing catalysts in accordance with an embodiment of the present invention includes providing a catalytic material as a coating or intermediate layer on the gas channel walls of a respective carrier element. This can be achieved by soaking the substrate material from a refractory metal oxide in the form of fine particles, e.g. gamma alumina, with one or more catalyst metal components, such as a noble metal, i.e. a platinum group, a chemical compound or other precious metals or metals baseless, drying and roasting the soaked substrate particles and creating an aqueous suspension of these particles. The copper-Chabasite catalyst particles present in bulk may be contained in the slurry.tabulating and then drying (e.g. at 110 ° C for one hour) and calcination (for example at 550 ° C for one hour) of soaked, activated alumina to form a stabilizing metal oxide dispersed on alumina. The non-noble metal catalysts may optionally also be impregnated with activated alumina, for example by impregnating with a non-noble metal nitrate solution on alumina particles and calcining, to provide a non-noble metal oxide dispersed in alumina particles.

[0042] The carrier can then be immersed in a suspension of impregnated activated alumina, and the excess of the slurry removed to provide a thin coating of the slurry on the tubular walls to flow gas in the carrier. The coated carrier is then dried and calcined in order to obtain an adhering coating of the catalytic component and optionally from the copper-CHA material to the walls of its channels. One or more additional layers can be placed on the carrier. After applying each layer or after applying a plurality of desired layers, the carrier is then dried and calcined to obtain a finished catalyst element in accordance with an embodiment of the present invention.

[0043] Alternatively, alumina or particles of another substrate impregnated with a noble metal or non-noble metal component may be mixed with loose or deposited copper-chabasite material particles in an aqueous slurry and this mixed slurry of catalytic component particles and copper-chabasite material particles may be applied as a coating for channel walls for gas flow in the carrier.

[0044] The used flue gas stream may be contacted with a catalyst made in accordance with embodiments of the present invention. For example, CuCHA catalysts prepared in accordance with embodiments of the present invention are well suited for the purification of engine exhausts, including diesel engines.

[0045] Without intending to limit the invention in any way, the embodiments of the present invention will be described in more detail in the following examples.

EXAMPLE 1 [0046] A CuCHA powder catalyst was prepared by mixing 100 g CHA in NH4 form⁺, with a silica / alumina molar ratio of 30, with 400 ml of a 1.0 M copper (II) sulphate solution. The pH was adjusted to 3.5 with nitric acid. The reaction of ion exchange between CHA in the form of NH4⁺ and copper ions were performed by stirring the suspension at 80 ° C for 1 hour. The resulting mixture was then filtered, washed with 800 ml of deionized water in three portions until the filtrate became clear and colorless, indicating that substantially no soluble or free copper remained in the sample and the washed sample was dried at 90 ° C. The above process, including ion exchange, filtration, washing and drying, was repeated once.

[0047] The resulting CuCHA product was then calcined at 640 ° C in air for 6 hours. The CuCHA catalyst obtained contained 2.41% by weight CuO, as determined by ICP analysis. A suspension of CuCHA was prepared by mixing 90 g CuCHA described above from 215 ml of deionized water. The mixture was ground in a ball mill. 15.8 g of zirconium acetate in dilute acetic acid (containing 30% ZrO2) was added to the suspension while stirring.

[0048] The suspension was applied to cellular ceramic cores 1 "Dx3" L with a cell density of 400 cpsi (cells per square inch) (62 cells per square centimeter) and a wall thickness of 6.5 mils. The coated cores were dried at 110 ° C for 3 hours and calcined at 400 ° C for 1 hour. The coating process was repeated once to obtain a target intermediate layer load of 2.4 g / in³ (0.1464 g / cm³).

[0049] The efficiency of selective catalytic reduction (SCR) of nitrogen oxides and selectivity of the fresh catalyst core was measured by feeding a mixture of 500 ppm NO, 500 ppm NH3, 10% O2, 5% H2O, and N2 as a supplement to the reactor at steady state containing the catalyst core 1 "D x 3" L. The reaction was carried out at a space speed of 80,000 hours^-1 in the temperature range of 150 ° C to 460 ° C.

The hydrothermal stability of the catalyst was measured by hydrothermal aging of the catalyst core in the presence of 10% H 2 O at 800 ° C for 50 hours and then measuring the SCR yields of nitrogen oxides and selectivity in the same process as described above for the SCR assessment on the fresh catalyst core.

[0051] Figure 1 is a graph showing the conversion of NOx and the generation or formation of N2O depending on the temperature of this sample. These results are summarized in Table 1. This sample, which did not contain soluble copper prior to calcination, as shown by the color of the filtrate described above, showed no increased resistance to thermal aging.

EXAMPLE 1A Copper sulfate pentahydrate was added to the coating suspension from Example 1 to increase the total CuO content to 3.2%. The suspension was applied to a monolith and aged and tested for the presence of SCR NOx as described above in Example 1, except that the monolith was calcined at 640 ° C. The catalytic efficiency was compared with Example 1 in Figure 1A. The addition of copper sulfate to the coating suspension improved significantly hydrothermal stability and low temperature activity.

EXAMPLE 2 [0053] A CuCHA powder catalyst was prepared by mixing 17 kg CHA in NH4 form⁺, with a silica / alumina molar ratio of 30, with 68 L of a 1.0 M copper (II) sulphate solution. The pH was adjusted to 3.5 with nitric acid. The reaction of ion exchange between CHA in the form of NH4⁺ and copper ions were performed by stirring the suspension at 80 ° C for 1 hour. The resulting mixture was then filtered and air-dried. The above process, including ion exchange and filtration, was repeated once. The wet cake was then resuspended in 40 L of deionized water, followed by filtration and drying at 90 ° C. The resulting CuCHA product was then calcined at 640 ° C in an air atmosphere for 6 hours. The CuCHA catalyst obtained contained 2.75% by weight of CuO.

[0054] Preparation of the slurry, coating and evaluation of SCR NOx was done in the same way as described above in Example 1. The product of this example contained free copper and showed increased hydrothermal stability compared to Example 1.

EXAMPLE 3 A CuCHA catalyst containing 3.36 wt% CuO was prepared using the same process as in Example 2 followed by first humidity impregnation. [0056] Using the procedure of Example 2, 134 grams of CuCHA were prepared with a CuO content of 3.11% by weight. A copper sulfate solution containing 1.64 g of copper sulfate pentahydrate and 105 ml of deionized water was added to this material. The impregnated sample was dried at 90 ° C and calcined at 640 ° C for 6 hours.

[0057] Preparation of the slurry, coating and evaluation of the SCR of NOx was done in the same way as described above in Example 1. As shown in Figure 3, the sample containing more unspecified copper showed, in addition to hydrothermal stability, higher activity at low temperature.

EXAMPLE 4 [0058] The CuCHA catalyst containing 3.85% by weight of CuO was made exclusively as a result of the first humidity impregnation process. A solution of copper sulphate containing 18.3 g of copper sulphate pentahydrate and 168 ml of deionized water was impregnated with 140 g of CHA in the form of NH4⁺, with a silica / aluminum oxide molar ratio of 30. The impregnated sample was then dried at 90 ° C and calcined at 640 ° C for 6 hours.

[0059] Preparation of the slurry, coating and evaluation of SCR NOx was performed in the same manner as described above in Example 1. As shown in Figure 4, the product of Example 4 showed a decrease in efficiency at temperatures between 350 ° C and 450 ° C after hydrothermal aging.

EXAMPLE 5 A CuCHA catalyst containing 1.94% by weight of CuO was prepared using the same process as in Example 1, except that this sample was made by single ion exchange.

[0061] Preparation of the slurry, coating and evaluation of the SCR of NOx was done in the same way as described above in Example 1, except that the hydrothermal stability was not measured. EXAMPLE 6 [0062] A CuCHA powder catalyst was prepared by mixing 0.2 g of CHA in a mold

NH4⁺, with a silica / alumina molar ratio of 15, with 16 ml of a 25 mM solution of copper (II) sulfate. The reaction of ion exchange between CHA in the form of NH4⁺ and copper ions were performed by stirring the suspension at 80 ° C for 1 hour. The resulting mixture was then filtered, washed with deionized water and dried at 90 ° C. The above process, including ion exchange, filtration, washing and drying, was repeated once. The resulting CuCHA product was then calcined at 540 ° C in air for 16 hours. The CuCHA catalyst obtained contained 4.57% by weight CuO.

[0063] The powder catalyst was subjected to hydrothermal aging in the presence of 10% H2O at 800 ° C for 50 hours, and then the SCR efficiency of the nitrogen oxides was measured.

[0064] The catalyst efficiency was evaluated using a microchannel catalytic reactor containing a bed of about 12.6 mm³ catalyst. The flow rate (under standard temperature and pressure conditions) was 500 ml / min for reagents of 500 ppm NOx, 500 ppm NH3, 10% O2, 5% H2O, supplemented with He, and 25 ml / min of water vapor passed through the bed in various temperatures (200, 250, 300, 350, 400, 450 and 500 ° C) to determine the reactivity of the catalyst. The NOx conversion was determined as 100 * (NOx on the feed - NOx on the outlet) / (NOx on the feed) using a mass spectrum analyzer. EXAMPLE 7 [0065] A CuCHA powder catalyst was prepared containing 2.94 wt% CuO using the same process as that in Example 6, including ion exchange, filtration, washing, drying, calcination and hydrothermal aging, except that molar ratio the silica / aluminum oxide was 30, and that the ion exchange process was repeated 4 times.

[0066] The assessment of the SCR of NOx is the same as described above for Example 6.

EXAMPLE 8 [0067] A CuCHA powder catalyst was prepared containing 0.45% by weight CuO using the same process as that in Example 6, including ion exchange, filtration, washing, drying, calcination and hydrothermal aging, except that the silica molar ratio / aluminum oxide was 50.

[0068] The assessment of the NOx SCR is the same as described above for Example 6

EXAMPLE 9 [0069] A CuCHA powder catalyst was prepared by mixing 15.0 g CHA in NH4 form⁺, with a silica / aluminum oxide molar ratio of 256, with 61 ml of a 0.64 M copper (II) sulfate solution. The reaction of ion exchange between CHA in the form of NH4⁺ and copper ions were performed by stirring the suspension at 80 ° C for 1 hour. The resulting mixture was then filtered, washed with deionized water and dried at 90 ° C. The above process, including ion exchange, filtration, washing and drying, was repeated 4 times. The resulting CuCHA product was then calcined at 540 ° C in air for 16 hours. The CuCHA catalyst obtained contained 2.63% by weight of CuO.

[0070] Hydrothermal aging and assessment of SCR NOx was the same as described above for Example 6.

COMPARATIVE EXAMPLE [0071] A powder catalyst of Cu / Y zeolite having a silica / alumina molar ratio of 5 was prepared as described in more detail below.

[0072] A Cu / Y powder catalyst was prepared by mixing 500 g of Zeolite Y in NH4 form⁺, with a silica / alumina molar ratio of ~ 5, with 2,500 ml of 0.1 M copper (II) sulphate solution. The pH was between 2.9 and 3.3. The reaction of ion exchange between the Y-zeolite in the NH4 form⁺ and copper ions were performed by stirring the suspension at 80 ° C for 1 hour. The resulting mixture was then filtered, washed with deionized water and dried at 90 ° C. The above process, including ion exchange, filtration, washing and drying, was repeated for a total of 5 exchanges, the pH value being similar to the above. The resulting product in the form of a Cu / Y zeolite was then calcined at 640 ° C in an atmosphere of air for 16 hours. The resulting Cu / Y zeolite catalyst contained 4.60% by weight CuO.

[0073] A Cu / Y suspension was prepared by mixing 200 g Cu / Y, which was described above, with 400 ml deionized water. The mixture was milled by passing it twice through an Eigermill device to obtain a slurry that contained 90% of particles smaller than 8 μm. 8.7 g of zirconium acetate in dilute acetic acid (containing 30% ZrO2) was added to this suspension under stirring.

[0074] The suspension was applied to cellular ceramic cores 1 "Dx3" L, with a cell density of 400 cpsi (cells per square inch) (62 cells per square centimeter) and a wall thickness of 6.5 mils (0.1651 mm). Two coatings were required to obtain the target intermediate load of 1.6 g / in³ (0.0976 g / cm³). The coated cores were dried at 90 ° C for 3 hours and the cores were calcinated at 450 ° C for 1 hour after the second drying step.

[0075] Hydrothermal aging and SCR evaluation were the same as described in Example 1, except that they were carried out at 750 ° C for 25 hours.

COMPARATIVE EXAMPLE 11.

[0076] A Cu / Beta powder catalyst with a silica / alumina molar ratio of 35 was prepared using a procedure similar to the sample prepared in EXAMPLE 10. Hydrothermal aging and SCR evaluation are the same as described in Example 1.

[0077] A summary of data for Examples 1-5 and Comparative Examples 10-11 is given in the following Table 1.

Table 1

<td rowspan="2">Example</td><td rowspan="2">Atomic ratio Cu / Al</td><td rowspan="2">CuO %</td><td colspan="4">NOx conversion (%)</td><td colspan="2">Generated N2O, ppm</td>

<td>210 ° C fresh</td><td>210 ° C after aging</td><td>460 ° C fresh</td><td>460 ° C after aging</td><td>460 ° C fresh</td><td>460 ° C after aging</td>

<td>1</td><td>0.30</td><td>2.41</td><td>75</td><td>43</td><td>95</td><td>82</td><td>0.8</td><td>5.3</td>

<td>2</td><td>0.33</td><td>2.75</td><td>62</td><td>59</td><td>90</td><td>83</td><td>3.1</td><td>9.3</td>

<td>3</td><td>0.38</td><td>3.36</td><td>74</td><td>70</td><td>91</td><td>81</td><td>2.7</td><td>10.5</td>

<td>4</td><td>0.44</td><td>3.85</td><td>76</td><td>60</td><td>88</td><td>72</td><td>3.5</td><td>14.2</td>

<td>5</td><td>0.24</td><td>1.94</td><td>50</td><td>thirty</td><td>95</td><td>75</td><td>0.2</td><td>5.0</td>

<td>10</td><td>0.23</td><td>4.6</td><td>43</td><td>42</td><td>99</td><td>96</td><td>26</td><td>51</td>

<td>11</td><td>0.36</td><td>2.5</td><td>92</td><td>23</td><td>84</td><td>53</td><td>10</td><td>9.4</td>

<td>12</td><td>0.46</td><td>3.7</td><td>75</td><td>78</td><td>89</td><td>80</td><td>5.4</td><td>11.7</td>

<td>1A</td><td>0.40</td><td>3.2</td><td></td><td>61</td><td></td><td>82</td><td></td><td>11.3</td>

[0078] Table 1 indicates that in Example 3 the best combination of low temperature activity, high temperature activity and slight deterioration due to hydrothermal aging was obtained.

[0079] Table 2 shows the normalized NOx conversion for Examples 6-9, with different molar ratios of SiO2 / Al2O3 and Cu / Al atomic ratios. In Example 7, the best efficiency was achieved. Although the efficiencies of Examples 6, 8 and 9 were not optimal, it should be noted that in each of these Examples, aging was carried out at a relatively high temperature of 800 ° C. Not all catalysts will be exposed to such high temperatures and it is believed that samples aged at lower temperatures should show acceptable performance with a wider range of acceptable silica / alumina ratio. For example, in an exhaust gas cleaning system comprising an SCR catalyst downstream of a catalyzed soot filter, the SCR is typically exposed to high temperatures, exceeding, for example, about 700 ° C. If the SCR is deposited on CSF, the SCR may be exposed to a temperature of even about 800 ° C or higher. According to embodiments of the present invention, greater flexibility in the placement of a catalyst, such as an SCR catalyst, in an exhaust gas purification system is provided due to CuCHA catalysts that exhibit enhanced hydrothermal stability compared to other types of zeolite materials. It would be expected that samples with a silica to alumina ratio in the range between about 15 and 256, which are exposed to operating temperatures below about 800 ° C, provide an acceptable NOx conversion at low temperature. Thus, according to embodiments of the invention, the silica to alumina ratios of about 15 to about 256 are within the scope of the invention,

Table 2

<td rowspan="2">Example</td><td rowspan="2">Ratio molar SiO2 / Al2O3</td><td rowspan="2">CuO %</td><td rowspan="2">Ratio atomic Cu / Al</td><td colspan="3">NOx conversion, aged, normalized</td>

<td>200 ° C</td><td>250 ° C</td><td>300 ° C</td>

<td>6</td><td>15</td><td>4.57</td><td>0.30</td><td>0.34</td><td>0.61</td><td>0.81</td>

<td>7</td><td>thirty</td><td>2.94</td><td>0.36</td><td>1.00</td><td>1.00</td><td>0.98</td>

<td>8</td><td>50</td><td>0.45</td><td>0.089</td><td>0.39</td><td>0.54</td><td>1.00</td>

<td>9</td><td>256</td><td>2.63</td><td>2.6</td><td>0.10</td><td>0.70</td><td>0.88</td>

EXAMPLE 12. CUCHA INHIBITION TEST:

[0080] Samples tested in this Example were prepared in the following manner. A CuCHA powder catalyst was prepared by mixing 250 g CHA in NH4 form⁺, with a silica / alumina molar ratio of 30, with 2.0 L of a 0.1 M copper (II) sulphate solution. The pH was adjusted to 3.0 - 3.4 with nitric acid. The reaction of ion exchange between CHA in the form of NH4⁺ and copper ions were performed by stirring the suspension at 80 ° C for 1 hour. The resulting mixture was then filtered, washed with deionized water and dried at 90 ° C. The above process, including ion exchange, filtration, washing and drying, was repeated a total of 5 times. The resulting CuCHA product was then calcined at 640 ° C in air for 16 hours. The CuCHA catalyst obtained contained 3.68% by weight of CuO.

[0081] The effect of CO, propene, n-octane and water on the activity of CuCHA SCR at temperatures 170, 200, 250, 300 and 350 ° C was investigated. The catalyst cores were tested in a simulated exhaust mixture from a diesel engine. The main gas concentrations were: 500 ppm NO, 500 ppm NH3, 10% CO2, 10% O2. The following ingredients were added sequentially to test their effect on NOx conversion: 5% H2O, 300 ppm C3H6 as C1, 600 ppm C3H6 as C1, 100 ppm octane as C1 and 500 ppm CO. The volumetric speed in the experiments was set at 142,000 hours^-1. The reaction was allowed to reach equilibrium at the following temperature points: 170 ° C, 200 ° C, 250 ° C, 300 ° C and 350 ° C, and then the conversion and interaction of components was recorded. Gas analysis of NO, NO2, N2O, NH3, CO2, CO, C3H6 and H2O was carried out using the MKS 2030 MultiGas FTIR device operating at 0.5 cm resolution^-1.

[0082] The results are summarized in Figure 5. At low temperatures 170 ° C and 200 ° C water was the main inhibitor, high propene 200 ppm (600 ppm C1) exerted a slight inhibitory effect at 200 ° C, 100 ppm propene (300 ppm C1 ), CO and n-octane had no effect. At temperatures higher than 250 ° C, the action of water as a promoter is clearly visible. None of the tested components inhibited NOx conversion at 250 ° C, on the contrary, all were promoters. At 300 ° C CO and n-octane supported SCR NOx, while 600 ppm of propene as C1 inhibited the reaction. At 350 ° C only 600 ppm of propene as C1 had a slight inhibitory effect, and all other components had a beneficial effect. It is believed that this efficiency is better than the performance of other SCR catalysts promoted Cu, in which medium and large pores are used, for example beta zeolites. SCR catalysts are known to be susceptible to short-term poisoning by long-chain hydrocarbons that can fill the pores with coke. These studies show that the small-pored CuCHA zeolite does not show this problem.

EXAMPLE 12A

HOW TO COLLECT / RELEASE HC:

GASES AND OFFICE:

[0083] A CuCHA catalyst core coated on a ceramic monolith (400 cpsi (62 cells per square centimeter) / 6 mils (0.1524 mm)) having a cross-section of 144 open cells and 1 inch in length, was first aged for 50 hours at 800 ° C, in 10% H2O, 10% O2, supplemented with nitrogen. The catalyst was then placed in a laboratory reactor. The catalyst was treated with a gas mixture containing 4% H 2 O, 14% O 2, 100 ppm NO, supplemented with N 2, and heated to 100 ° C. After the temperature has stabilized at 100 ° C, a mixture of toluene and octane is fed through the mass flow regulator to obtain a target concentration of 100 ppm C1 as octane and 100 ppm C1 as toluene, with a total volume velocity of 104 kh^-1. The waste gas was led through an afterburner that contained a Pt / alumina based oxidation catalyst and was kept at a constant temperature of 600 ° C. Any hydrocarbon emissions, including partial oxidation products and CO that may have been produced above the CuCHA catalyst, will be oxidized to CO 2 while passing through the afterburner. The exhaust CO2 from the afterburner is monitored by an IR analyzer for CO2. At the same time, a part of the waste stream from the CuCHA catalyst passing next to the afterburner is analyzed by the FID-HC analyzer.

PROTOCOL FROM THE TESTS:

After stabilizing the CuCHA catalyst at 100 ° C in a mixture of 4% H 2 O, 14% O 2, 100 ppm NO, supplemented with N 2, a hydrocarbon mixture of octane and toluene was introduced. The catalyst temperature was maintained at 100 ° C for 10 minutes. At this time, HC is collected above the catalyst, which leads to a CO2 signal at the exit of the afterburner below the inlet HC concentration. After the storage period, the temperature rises linearly from 100 ° C to 600 ° C at a rate of 20 ° C / min. The CO2 signal from the afterburner increases sharply, which is caused by the release of accumulated HC from the catalyst. At the end of the desorption, the CO2 signal returns to the initial value (which = the concentration in the feed gas). As the temperature rises, a small decrease in the CO2 signal at the afterburner output below the level in the feed gas indicates the second HC removal due to the deposition of carbon deposits, produced from toluene and octane on the catalyst. As the temperature rises further, all the generated carbon deposits burn out and cause an increased CO2 signal at the exit of the afterburner. After firing the carbon deposits, the CO2 signal from the afterburner eventually returns to its initial value.

DATA ANALYSIS:

[0085] The CO2 signal from the afterburner was quantified in order to determine the amount of HC that is collected, released, deposited as coke and fired coke. Corresponding points of the intersection of the CO2 signal at the afterburner output shown in Fig. 5A, with the HC concentration in the feed gas, were used as integration limits. For CuCHA, for example, these integration limits were approximately appropriately between 0 and 800 s for collection, between 800 s and 1000 s for release, between 1000 s and 1,400 s for coking. The amounts of HC that were collected, released, deposited as coke and then fired, are expressed in mg of HC, based on the average ratio of C: H in the HC feed stream.

RESULTS:

[0086] This study was carried out with SCR, Cu-Y catalysts (after aging for 25 h at 750 ° C, 10% H2O, 10% O2, supplemented with N2) and Fe-Beta (after aging for 50 h at 800 ° C, in 10% H2O, 10% O2, supplemented with N2) of the same volume under the same conditions. It turned out that in the case of CuCHA very low coking occurs and therefore there is no visible firing signal. The results are shown in Fig. 5B. It is obvious that the CuCHA catalyst accumulates the smallest amount of HC, most of which is released as HC, and little deposited as coke. In contrast, the Cu-Y catalyst does not produce a significant amount of carbon deposits in the temperature range of about 200 ° C to 450 ° C. Part of the accumulated coke is then fired at higher temperatures.

EXAMPLE 13. MANUFACTURE OF AMOX CATALYST.

[0087] An ammonia oxidation catalyst containing CuCHA was prepared as in Example 12, with a copper content of 3.68%, measured as CuO and with a SiO2 / Al2O3 ratio of 30. This material was applied to a standard cordierite monolithic substrate with square cell geometry with 400 cells /inch³, to ensure a total load of 2.40 g / inch³ (0.1464 g / cm³) based on the volume of the monolith. This pre-coated monolith was then immersed in the platinum containing precursor solution (platinum complex with hydroxyamine) to distribute the platinum precursor completely and evenly over this element. The element was dried at 110 ° C and then calcined at 450 ° C for one hour. This resulted in a platinum load on this element of 4.3 g / foot³ (0.1158 g / l), based on the volume of the monolith. Thus, the catalyst had the following composition: 3.68% CuO + 0.10% Pt embedded on a CuCHA support, applied to a 400/6 standard cordierite substrate at a total load of approximately 2.4 g / inch³ (0.1464 g / cm³). The atomic ratio Al: Cu: Pt in the present catalyst is about 190: 90: 1. The ratio Al / M (M = Cu + Pt) is about 2.1.

EXAMPLE 14-SAMPLE TESTING OF EXAMPLE 13

[0088] The ammonia removal efficiency and product oxidation selectivity for the aged hydrothermal AMOX catalyst produced as described in Example 13 were measured by feeding a mixture of a feed gas composed of 500 ppm NH3, 10% O2, 5% H2O, supplemented with N2 (as air ), to a stationary reactor containing a square cylindrical catalyst core of 3.0 inches (7.62 cm) long with a frontal cross-section containing 144 open cells. The reaction was carried out at a space velocity of 100,000 h^-1 in the temperature range of 150 ° C to 460 ° C. The hydrothermal aging conditions were: 10 hours at 700 ° C with 10% H 2 O in an atmosphere of air. Figure 6 is a graph showing emissions compared to those of a hydrothermal aged CuCHA specimen. The data show 1) the very selective conversion of NH3 to N2, catalyzed by the CuCHA catalyst without Pt impregnation and 2) that the conversion of NH3 can be strongly increased by including the platinum containing component, without deteriorating the high selectivity of N2. The latter is important because the prior art shows that platinum in the form of a metallic mesh or deposited on other oxides or zeolite supports is essentially selective for the production of N2O or NOx.

EXAMPLE 15 [0089] Comparison of the CuCHA composition on a flow substrate and a flow-through filter at comparable loads. The flow through wall filter was coated with the same catalyst as the catalyst flow carrier of Example 3 and was measured on two samples to compare their catalytic activity.

[0090] A CuCHA suspension was prepared by mixing 90 g of CuCHA, which was described above, with 215 ml of deionized water. The mixture was ground in a ball mill for 11 hours to obtain a slurry that contained 90% of particles smaller than 10 μm. 15.8 g of zirconium acetate in dilute acetic acid (containing 30% ZrO 2) was added to the suspension while stirring.

The suspension was applied to cellular ceramic filter cores with a flow through the 1 "D x 6" L wall with a cell density of 300 cpsi (cells per square inch) (46.5 cells per square centimeter) and a 12 mil (0.3048 mm) wall thickness. . Coated cores were dried at 120 ° C for 3 hours and calcinated at 540 ° C for 1 hour. The coating process was repeated once to obtain a target intermediate load of 2.0 g / in³ (0.1220 g / cm³).

[0092] The efficiency of the selective catalytic reduction (SCR) of nitrogen oxides and selectivity of the fresh catalyst core was measured by supplying a feed gas mixture of 500 ppm NO, 500 ppm NH3, 10% O2, 5% H2O, supplemented with N2, to the stationary reactor containing the core Catalyst 1 "D x 6" L The reaction was carried out at a space velocity of 40,000 h^-1 in the temperature range of 150 ° C to 400 ° C.

The hydrothermal stability of the catalyst was measured by hydrothermal aging of the catalyst core in the presence of 10% H 2 O at 750 ° C for 25 hours and then measuring the SCR efficiency of nitrogen oxides and selectivity by the same method as described above for the SCR assessment on the fresh catalyst core.

[0094] Table 3 below shows a comparison of SCR efficiency for heat-treated aged CuCHA applied to a filter with respect to CuCHA applied to the flow catalyst support.

Table 3: Comparison of SCR efficiency (% conversion) for the filtration and flow medium.

<td>WELL</td><td>NO2</td><td>NOx</td><td>NH3</td><td>Preparation of N2O (ppm)</td><td>Sample temperature (C degrees)</td>

<td colspan="6">CuCHA on a flow medium aged for 50 h at 800 ° C w / 10% water</td>

<td>74.6</td><td>83.5</td><td>75.0</td><td>76.9</td><td>8.4</td><td>211</td>

<td>96.3</td><td>95.6</td><td>96.2</td><td>93.9</td><td>9.2</td><td>255</td>

<td>97.6</td><td>97.5</td><td>97.6</td><td>97.3</td><td>7.6</td><td>309</td>

<td>82.7</td><td>36.5</td><td>81.0</td><td>98.1</td><td>12.3</td><td>441</td>

<td colspan="6">CuCHA on the filter, aged for 25 h at 750 ° C w / 10% water</td>

<td>74.7</td><td>81.5</td><td>75.1</td><td>76.0</td><td>8.8</td><td>207</td>

<td>96.4</td><td>96.1</td><td>96.4</td><td>96.5</td><td>9.9</td><td>255</td>

<td>98.6</td><td>97.7</td><td>98.5</td><td>96.8</td><td>8.7</td><td>304</td>

<td>96.2</td><td>90.7</td><td>95.9</td><td>98.7</td><td>8.2</td><td>352</td>

<td>91.1</td><td>62.4</td><td>89.8</td><td>99.4</td><td>11.7</td><td>400</td>

Despite some differences in the precise details of the experiment, the comparison clearly confirms the equivalence of the CuCHA catalytic efficiency on the filter core and on the monolithic flow catalyst.

EXAMPLE 16 [0096] A NH4 slurry was prepared⁺-CHA by mixing 608 g NH4⁺-CHA with a silica / aluminum oxide molar ratio of 30 with 796 ml of deionized water. The mixture was ground using a Netzsch Mill mill to obtain a suspension that contained

90% of particles smaller than 8.4 μm. 106 g of zirconium acetate in dilute acetic acid (containing 30% ZrO 2) were added to the suspension while stirring.

The slurry was applied to cellular ceramic cores 1 "Dx3" L with a cell density of 400 cpsi (62 cells per square centimeter) and a wall thickness of 6.5 mils (0.1651 mm). The coated cores were dried at 110 ° C for 3 hours. The coating process was repeated once to obtain a target intermediate layer load of 2.4 g / in³ (0.1464 g / cm³).

[0098] This pre-coated monolith was then immersed in a 0.25 M copper acetate solution for 5 minutes at room temperature. The core was purged gently with an air pistol and dried at 110 ° C for 3 hours and then calcined at 400 ° C for 1 hour. This provided a CuO loading on CHA of 2.72 wt%, based on the weight of the CHA on the monolith.

[0101] The SCR NOx evaluation of fresh catalyst was the same as described for Example 1. Hydrothermal stability of the catalyst was measured by hydrothermal aging of the catalyst core, in the presence of 10% water vapor at 850 ° C for 6 h, and then by measuring SCR NOx yield, which is described for fresh catalyst.

Figure 7 is a graph showing the NOx conversion and the formation of N2O depending on the temperature of this sample.

EXAMPLE 17 [0101] 12.1 g copper acetate monohydrate was dissolved in 420 g deionized water, then 141 g NH4 was added.⁺-CHA with a silica / aluminum oxide molar ratio of 30. The mixture was ground in a Netzsch Mill mill to obtain a slurry that contained 90% of particles smaller than 3.5 μm.

[0102] The suspension was applied to cellular ceramic cores 1 "Dx3" L with a cell density of 400 cpsi (62 cells per square centimeter) and a wall thickness of 6.5 mils (0.1651 mm). The coated cores were dried at 110 ° C for 3 hours. The coating process was repeated twice to obtain the target intermediate layer load of 2.4 g / in³(0.1464 g / cm³). The coated cores were then calcined at 400 ° C for 1 hour. This ensured a loading of CuO on CHA of 3.3 wt%.

[0103] The SCR NOx evaluation of fresh catalyst was the same as described for Example 1. The hydrothermal stability of the catalyst was measured by hydrothermal aging of the catalyst core, in the presence of 10% water vapor at 850 ° C for 6 hours, followed by measuring the SCR performance of NOx, which described for fresh catalyst.

[0104] Figure 8 is a graph showing the NOx conversion and the formation of N2O depending on the temperature of this sample.

EXAMPLE 18 [0105] A CuCHA powder catalyst was prepared by ion exchange with copper acetate. A 0.40 M copper (II) acetate monohydrate solution was prepared by dissolving 89.8 g of the copper salt in 1.125 L of deionized water at 70 ° C. Then 300 g of CHA in the form of NH4 were added to this solution⁺. The reaction of ion exchange between CHA in the form of NH4⁺ and copper ions were performed by stirring the suspension at 70 ° C for 1 hour. During the reaction, the pH was between 4.8 and 4.5. The resulting mixture was then filtered, washed until the filtrate had a conductivity of &lt;200 μScm^-1, which indicated that essentially no soluble or free copper was left in the sample and the washed sample was dried at 90 ° C. The CuCHA catalyst obtained contained 3.06% by weight of CuO and 140 ppm of Na2O.

[0106] The preparation of the slurry, coating and evaluation of the NOx SCR was the same as described above for Example 1. As shown in Fig. 7, Example 18 exhibited the same SCR efficiency as Example 3, which was produced by exchanging ions with copper sulphate twice impregnation using the initial moisture method.

EXAMPLE 19 [0107] A CuCHA catalyst containing 2.99 wt% CuO was prepared using the same process as that in Example 18, except that the sample was made in a 0.30 M Cu solution.

EXAMPLE 20 [0108] A CuCHA catalyst containing 2.69% by weight CuO was prepared using the same process as that in Example 18, except that the ion exchange process was carried out at 45 ° C.

EXAMPLE 21 [0109] A CuCHA catalyst containing 2.51% by weight CuO was prepared using the same process as that in Example 19, except that the ion exchange process was carried out at 45 ° C.

[0110] In Table 4, the Cu loads of Examples 18-21 were compared with that of Example 1. It can be seen that copper acetate is more effective than copper sulfate in providing the desired Cu load using a low copper concentration solution at a lower reaction temperature.

Table 4

<td>Example</td><td>Salt Cu</td><td>Concentration of Cu²+, M</td><td>Reaction temperature, ° C</td><td>CuO, wt%</td>

<td>1</td><td>Cu sulphate</td><td>1.0</td><td>80</td><td>2.41</td>

<td>18</td><td>Cu acetate</td><td>0.40</td><td>70</td><td>3.06</td>

<td>19</td><td>Cu acetate</td><td>0.30</td><td>70</td><td>2.99</td>

<td>20</td><td>Cu acetate</td><td>0.40</td><td>45</td><td>2.69</td>

<td>21</td><td>Cu acetate</td><td>0.30</td><td>45</td><td>2.51</td>

EXAMPLE 22- Hydrothermal Aging and Chemical Analysis of Example 2 [0111] The Cu / CHA powder prepared in Example 2 was subjected to hydrothermal aging in the presence of 10% H 2 O in an air atmosphere at 800 ° C for 48 hours. The analyzed material from Example 2 was designated as Example 22 in Figures 11 and 12 and in Tables 5 and 6. The hydrothermal aged sample is designated as Example 22A in Tables 5 and 6 and in Figures 11 and 12.

[0112] Powder X-ray diffractograms were made using standard techniques. The generator was set to 45 kV and 40 mA. The diffractometer optics consist of a variable divergence gap, Soller's slit incident beam, a receiving slot, a graphite monochromator, and a scintillation counter using Bragg-Brentano para-focus geometry. Distances d were calculated from lattice parameters, a = 13.58 and c = 14.76 A for Example 22, and a = 13.56 and c = 14.75 A for Example 22A.

Parameters of the crystal lattice were determined by scanning the sample with the LaB6 instrument, mixed in as an internal standard. The data range was 15 - 38.5 degrees two theta, they used step size 0.01 and pulses for 5 seconds. The obtained diffractogram was processed by cleaning the profile in the JADE computer program. The parameters of the LaB6 network were kept constant at 5.169 A in order to compensate for errors resulting from sample shifts. Table 5 shows the powder X-ray diffraction lines for Example 22 and Example 22A. The crystalline structure of CHA was retained after aging with steam for 48 hours at 800 ° C.

Table 5

<td colspan="3">Example 22</td><td colspan="3">Example 22A</td>

<td>2-Theta</td><td>d (A)</td><td>AND(%)</td><td>2-Theta</td><td>d (A)</td><td>AND(%)</td>

<td>9.63</td><td>9.201</td><td>100%</td><td>9.62</td><td>9.189</td><td>100%</td>

<td>13.02</td><td>6.793</td><td>37%</td><td>13.04</td><td>6,782</td><td>36%</td>

<td>14,15</td><td>6.252</td><td>8%</td><td>14.17</td><td>6.247</td><td>7%</td>

<td>16.21</td><td>5,465</td><td>28%</td><td>16.23</td><td>5.457</td><td>26%</td>

<td>18.01</td><td>4.921</td><td>32%</td><td>18,03</td><td>4.917</td><td>thirty%</td>

<td>19,28</td><td>4,600</td><td>3%</td><td>19.30</td><td>4.595</td><td>3%</td>

<td>20.85</td><td>4,258</td><td>89%</td><td>20.88</td><td>4.251</td><td>82%</td>

<td>22.29</td><td>3,985</td><td>4%</td><td>22.31</td><td>3,981</td><td>4%</td>

<td>22.65</td><td>3.922</td><td>5%</td><td>22.69</td><td>3,916</td><td>4%</td>

<td>23.33</td><td>3,809</td><td>8%</td><td>23.37</td><td>3,804</td><td>7%</td>

<td>25,27</td><td>3,521</td><td>41%</td><td>25.29</td><td>3,519</td><td>38%</td>

<td>26.22</td><td>3.397</td><td>24%</td><td>26.26</td><td>3,391</td><td>23%</td>

<td>27.98</td><td>3.186</td><td>5%</td><td>28.03</td><td>3,181</td><td>5%</td>

<td>28.53</td><td>3,126</td><td>6%</td><td>28.56</td><td>3,123</td><td>5%</td>

<td>29.91</td><td>2,985</td><td>3%</td><td>29.96</td><td>2,980</td><td>3%</td>

<td>30.98</td><td>2,885</td><td>57%</td><td>31.03</td><td>2,880</td><td>53%</td>

<td>31.21</td><td>2,864</td><td>17%</td><td>31,23</td><td>2,862</td><td>17%</td>

<td>31.48</td><td>2,840</td><td>28%</td><td>31.51</td><td>2,837</td><td>26%</td>

<td>31.99</td><td>2,795</td><td>4%</td><td>32.04</td><td>2.792</td><td>4%</td>

<td>32.75</td><td>2.733</td><td>3%</td><td>32.80</td><td>2.728</td><td>3%</td>

<td>33.73</td><td>2,655</td><td>2%</td><td>33.78</td><td>2,651</td><td>2%</td>

<td>33.95</td><td>2,639</td><td>4%</td><td>33.98</td><td>2,637</td><td>4%</td>

<td>34.92</td><td>2,568</td><td>13%</td><td>34.98</td><td>2,563</td><td>12%</td>

<td>35.38</td><td>2,535</td><td>3%</td><td>35.43</td><td>2,531</td><td>2%</td>

<td colspan="3">Example 22</td><td colspan="3">Example 22A</td>

<td>36.50</td><td>2,460</td><td>9%</td><td>36.54</td><td>2,457</td><td>8%</td>

<td>38.72</td><td>2,324</td><td>2%</td><td>38.78</td><td>2,320</td><td>1%</td>

<td>38.90</td><td>2,313</td><td>1%</td><td>38.93</td><td>2,312</td><td>1%</td>

<td>39.13</td><td>2,300</td><td>2%</td><td>39.18</td><td>2,297</td><td>2%</td>

<td>39.56</td><td>2,276</td><td>1%</td><td>39,62</td><td>2,273</td><td>1%</td>

<td>39,78</td><td>2,264</td><td>2%</td><td>39.84</td><td>2,261</td><td>2%</td>

[0113] The UV / VIS dispersed reflection spectra expressed with F (R) were collected using a reflection adapter scattered with BaSO4-coated integration sphere and BaSO4 within a Cary 300 UV-Vis spectrometer. UV / VIS from Examples 22 and 22A are shown in Figure 11.

[0114] Table 6 summarizes the data ²⁹Si MAS NMR and the calculated range of the Si / Al atomic ratio of Examples 22 and 22A. For comparison, data on CHA and CHA aged from 10% water vapor for 48 hours at 800 ° C are also included. These data indicate that some degree of reflexivity occurs after aging both the CHA and Cu / CHA samples. However, the Cu / CHA sample becomes significantly less deglacted after aging. It was also observed that the Cu exchange process itself slightly changes the range of the Si / Al atomic ratio from 15 to 17.

[0115] Figure 12 shows the spectra ²⁷Al (Nuclear Magnetic Resonance with magical rotation) from Examples 22 and 22A, as well as samples of CHA and CHA subjected to aging. These spectra indicate that some tetrahedral forms of Al are transformed into penta- and octa-coordinated forms as a result of Cu exchange. The spectra clearly show that after aging, the Cu / CHA sample is significantly less dephasized than the CHA sample.

Table 6

<td rowspan="2">A sample</td><td colspan="4">% Intensity</td><td rowspan="2">Si / Al</td>

<td>Si (0Al) - 114 PP^m</td><td>Si (0Al) - 111 PP^m</td><td>Si (1Al) - 105 PP^m</td><td>Si (1Al) - 101 PP^m</td>

<td>CHA</td><td>2</td><td>71</td><td>16</td><td>11</td><td>15</td>

<td>CHA subjected to aging</td><td>0</td><td>95</td><td>1</td><td>4</td><td>82</td>

<td>Example 22</td><td>2</td><td>75</td><td>19</td><td>5</td><td>17</td>

<td>Example 22A</td><td>4</td><td>85</td><td>11</td><td>&lt;1</td><td>34</td>

[0116] Exemplary forms of emission purification systems are shown in Figs. 10A, 10B and 10C. One form of the emission purification system according to the invention is designated as

11A is schematically illustrated in FIG. 10A. The exhaust fumes containing gaseous pollutants (including unburnt hydrocarbons, carbon monoxide and NOx) and particulate matter are transferred from the engine 19 to the rear part of the exhaust system, in which a reducing agent, i.e. ammonia or ammonia precursor, is added to the exhaust stream. The reducer is injected as a mist through a nozzle (not shown) into the exhaust stream. The aqueous urea solution shown on line 25 can serve as an ammonia precursor that can be mixed with air in another line 26 in the mixing station 24. The valve 23 can be used to accurately dispense the amount of aqueous urea solution that is converted into ammonia in the exhaust stream.

[0117] The exhaust stream with added ammonia is sent to the SCR catalyst substrate 12 (also referred to herein, including the claims as a "first substrate") containing CuCHA according to one or more forms. By passing through the first substrate 12, the NOx component in the exhaust gas is converted by selective catalytic reduction of NOx using NH3 to N2 and H2O. Furthermore, the excess NH3 that exits the inlet zone can be converted by oxidation at the rear by an ammonia oxidation catalyst (not shown) also containing CuCHA for converting ammonia to N2 and H2O. The first substrate is usually a monolithic flow medium.

[0118] An alternative embodiment of the emission purification system, designated 11B is shown in FIG. 10B, which comprises a second substrate 27 disposed between the NH3 injector and the first substrate 12. In this embodiment, the second substrate is coated with an SCR catalyst composition that may be the same as the composition used to coat the first substrate 12 or other composition. A preferred feature of this embodiment is that the SCR catalyst compositions that are used to coat the substrate can be selected in such a way as to optimize the conversion of NOx to operating conditions characteristic at a given location along the exhaust system. For example, the second substrate may be coated with an SCR catalyst composition that is better suited for operation at higher temperatures that are present in the front segments of the exhaust system,

[0119] In the embodiment shown in FIG. 10B, the second substrate 27 may be a honeycomb flow substrate, a foam substrate with open cells, or a honeycomb structure with a flow through the wall. In embodiments of this embodiment in which the second substrate is a wall flow medium or a high efficiency foam filter with open cells, the system can remove more than 80% solids, including soot and SOF fractions. The flow-through substrate coated with SCR and its suitability for reducing NOx and particulate matter are described, for example, in copending U.S. Patent Application Serial No. 10 / 634,659, filed August 5, 2003.

[0120] In some applications, it may be advantageous to add an oxidation catalyst upstream of the ammonia / ammonia precursor injection site. For example, in the embodiment shown in FIG. 10C the oxidation catalyst is deposited on the catalyst support 34. The emission cleaning system 11C includes a first substrate 12 and optionally includes a second substrate 27. In this embodiment, the exhaust stream is first directed to the catalyst substrate 34, where at least some of the gaseous hydrocarbons, CO and solid particles are burned to harmless components. In addition, a significant proportion of NO from the exhaust gas NOx component is converted to NO2. The higher NO2 content in the NOx component facilitates the reduction of NOx to N2 and H2O on the SCR catalyst (s) placed (s) on. It should be noted that in the embodiment shown in Fig. 10C, the first substrate 12 can be catalyzed soot filter, and the SCR catalyst can be deposited on a catalyzed soot filter. In an alternative embodiment, the second substrate 27 containing the SCR catalyst may be placed upstream of the catalyst substrate 34.

[0121] Methods of making and using zeolite catalysts with a crystalline CHA structure are disclosed. The catalysts can be used to remove nitrogen oxides from the gaseous medium over a wide temperature range and exhibit hydrothermal stability at high reaction temperatures. The zeolite catalysts contain a zeolite support with a silica to alumina ratio of 15: 1 to 256: 1 and a copper to alumina ratio of 0.25: 1 to 0.5: 1.