Copper cha zeolite catalysts

(54) Title: CATALYST, SYSTEM OF (57) Summary:

TREATMENT OF EXHAUST GAS, PROCESS FOR THE REDUCTION OF NITROGEN OXIDES, AND,

CATALYST ARTICLE.

(30) Unionist priority: 27/02/2007 US6O / 891835 (73) Holder (s): Basf Catalysts LLC (72) Inventor (s): Ahmad Moini, Gerald Stephen Koermer, Ivor Bull, Joseph A. Patchett, Joseph Charles Dettling, Matthew Tyler Caudle, Patrick Burk, R. Samuel Boorse, Wen-Mei Xue, William M. Jaglowski (74) Attorney (s): Momsen, Leonardos & Cia.

(86) International Order: pct US2008055140 of 27/02/2008 (87) International Publication: wo 2oos / io65i9de 04/09/2008

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reaction temperature C "CATALYST, EXHAUST GAS TREATMENT SYSTEM, NITROGEN OXIDE REDUCTION PROCESS, AND, CATALYST ARTICLE"

CROSS REFERENCE TO RELATED ORDER

This application claims priority benefit under 35 USC § 119 (e) to US Patent Application N² 60 / 891,835, filed on February 27, 2007, and US Patent Application No.² 12 / 038,423, filed on February 27, 2008, which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

Embodiments of the invention relate to zeolites that have the structure of the CHA crystal, methods for their manufacture, and catalysts comprising such zeolites. More particularly, embodiments of the invention relate to copper CHA zeolite catalysts and methods for their manufacture and use in exhaust gas treatment systems.

TECHNICAL FUNDAMENTALS

Zeolites are crystalline aluminosilicate materials preferably having uniform pore sizes which, depending on the type of zeolite and the type and quantity of cations included in the zeolite lattice, typically range from about 3 to 10 Angstroms in diameter. Both synthetic zeolites as natural and their use in promoting certain reactions, including the selective reduction of nitrogen oxides with ammonia in the presence of oxygen, are well known in Computer Technician ca.

Metal-promoted zeolite catalysts including, but not limited to, iron-promoted and copper-promoted zeolite catalysts for the selective catalytic reduction of nitrogen oxides with ammonia are known. Iron-promoted beta zeolite was an effective catalyst for the selective reduction of nitrogen oxides with ammonia. Unfortunately, it was found2 that under severe hydrothermal conditions, such as reduction of NOx from gas discharge at temperatures exceeding 500 ° C, the activity of many metal-promoted zeolites began to decline. This decline in activity was believed to be due to the destabilization of the zeolite as well as by dealumination and the consequent reduction of catalytic sites containing metal within the zeolite. To maintain the global NOx reduction activity, increased levels of the iron-promoted zeolite catalyst must be provided. As the levels of the zeolite catalyst are increased to provide adequate NOx removal, there is an obvious reduction in the cost efficiency of the process for removing NOx as the catalyst costs rise.

There is a desire to prepare materials that offer low temperature SCR activity and / or improved hydrothermal durability in existing zeolites, for example, catalyst materials that are stable at temperatures up to at least about 650 ° C and above. SUMMARY

Aspects of the invention are directed to zeolites that have the CELA crystal structure (as defined by the International Zeolite Association), catalysts comprising such zeolites, and exhaust gas treatments that incorporate such catalysts. The catalyst can be part of a flue gas treatment system used to treat flue gas streams, especially those emanating from gasoline or diesel engines.

One embodiment of the present invention concerns copper CHA catalysts and their application in exhaust gas systems such as those designed to reduce nitrogen oxides. In specific embodiments, new copper chabazite catalysts are provided that exhibit NH SCR₃ improved NOx. Copper chabazite catalysts manufactured according to one or more embodiments of the present invention provide a catalyst material that exhibits excellent hydrothermal stability and high catalytic activity over a wide temperature range. When compared with other zeolitic catalysts that find application in this field, such as Beta Fe zeolites, copper CHA catalyst materials according to embodiments of the present invention offer improved low temperature activity and hydrothermal stability.

An embodiment of the invention relates to a catalyst comprising a zeolite having a CHA crystal structure and a molar ratio of silica to alumina greater than about 15 and an atomic ratio of copper to aluminum exceeding about 0.25. In a specific embodiment, the molar ratio of silica to alumina is about 15 to about 256 and the atomic ratio of copper to aluminum is about 0.25 to about 0.50. In a more specific embodiment, the molar ratio of silica to alumina is about 25 to about 40. Still in a more specific embodiment, the molar ratio of silica to alumina is about 30. In a particular embodiment, the atomic ratio of copper to aluminum is about 0.30 to about 0.50. In a specific embodiment, the atomic ratio of copper to aluminum is about 0.40. In a specific embodiment, the molar ratio of silica to alumina is about 25 to about 40 and the atomic ratio of copper to aluminum is about 0.30 to about 0.50. In another specific embodiment, the silica to alumina is about 30 and the atomic ratio of copper to alumina is about 0.40.

In a particular embodiment, the catalyst contains ion exchange copper and an amount of unchanged copper sufficient to maintain NOx conversion performance of the catalyst in a discharge gas stream containing nitrogen oxides after the hydrothermal aging of the catalyst. In one embodiment, the NOx conversion performance of the catalyst at about 200 ° C after aging is at least 90% of the NOx conversion performance of the catalyst at about 200 ° C before aging. In a particular embodiment, the catalyst contains at least about 2.00 weight percent copper oxide.

In at least one embodiment, the catalyst is deposited on a substrate in an alveolar form. In one or more embodiments, the honeycomb substrate comprises a wall flow substrate. In other embodiments, the honeycomb substrate comprises a through-flow substrate. In certain embodiments, at least a portion of the through-flow substrate is coated with CuCHA adapted to reduce nitrogen oxides contained in a gas stream flowing through the substrate. In a specific embodiment, at least a portion of the through-flow substrate is coated with Pt and CuCHA adapted to oxidize ammonia in the exhaust gas stream.

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

In a specific embodiment, a catalyst article comprises an alveolar substrate having a zeolite having the CHA crystal structure deposited on the substrate, the zeolite having a molar ratio of silica to alumina greater than about 15 and a ratio atomic copper to aluminum exceeding about 0.25 and containing an amount of free copper exceeding ion exchange copper. In one embodiment, free copper is present in an amount sufficient to prevent hydrothermal degradation from the conversion of nitrogen oxide to the catalyst. In one or more embodiments, free copper prevents hydrothermal degradation from the conversion of nitrogen oxide from the catalyst to hydrothermal aging. The catalyst can further comprise a binder. In particular embodiments, the ion exchange copper is exchanged using copper acetate.

Other aspects of the invention concern exhaust gas treatment systems that incorporate catalysts of the type described above. Still other aspects concern a process for the reduction of nitrogen oxides contained in a gas stream in the presence of oxygen wherein said process comprises contacting the gas stream with the catalyst described above.

Another aspect concerns an exhaust gas treatment system comprising a discharge gas stream containing NOx, and a catalyst described above effective for the selective catalytic reduction of at least one NOx component in the exhaust gas stream. Yet another aspect concerns an exhaust gas treatment system comprising a discharge gas stream containing ammonia and a catalyst as described above effective to destroy at least a portion of the ammonia in the discharge gas stream.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.l is a graph that describes the efficiency of nitrogen oxide removal in (%), ammonia consumption in (%) and N₂The generated in (ppm) of CuCHA catalyst as a function of reaction temperatures for CuCHA prepared according to the methods of Example 1;

Fig. IA is a graph that describes the efficiency of nitrogen oxide removal in (%), ammonia consumption in (%) and N₂The generated in (ppm) of CuCHA catalyst as a function of reaction temperatures for CuCHA prepared according to the methods of Examples 1 and

ΙΑ;

Fig. 2 is a graph that describes the efficiency of nitrogen oxide removal in (%), ammonia consumption in (%) and N₂The generated in (ppm) of CuCHA catalyst as a function of reaction temperatures, for CuCHA prepared according to the methods of Example 2;

Fig. 3 is a graph that describes the efficiency of nitrogen oxide removal in (%), ammonia consumption in (%) and N₂The generated in (ppm) of CuCHA catalyst as a function of reaction temperatures for CuCHA prepared according to the methods of Example 3;

Fig. 4 is a graph that describes the efficiency of nitrogen oxide removal in (%), ammonia consumption in (%) and N₂The generated in (ppm) of CuCHA catalyst as a function of reaction temperatures for CuCHA prepared according to the methods of Example 4;

Fig. 5 is a graph depicting the effects of CO, propene, n-octane and water on the SCC activity of CuCHA at various temperatures;

Fig. 5A is a graph showing the amounts of HC that are stored, released, deposited as coke and burnt coke for a sample tested according to Example 12A;

Fig. 5B is a bar graph showing the performance of CuCHA hydrocarbon compared to beta zeolites of CuY and Fe according to Example 12A;

Fig. 6 is a graph that describes NH emissions₃, NOx (= NO + NO₂), N₂O, and N₂ from the output of the AMOX catalyst, supplied as ppm on a nitrogen atom base prepared and aged according to the method of Examples 13 and 14;

Fig. 7 is a graph that describes the efficiency of nitrogen oxide removal in (%), ammonia consumption in (%) and N₂The generated in (ppm) of CuCHA catalyst as a function of reaction temperatures, for CuCHA prepared according to the methods of Example 16;

Fig. 8 is a graph describing the efficiency of nitrogen oxide removal in (%), ammonia consumption in (%) and N₂The generated in (ppm) of CuCHA catalyst as a function of reaction temperatures, for CuCHA prepared according to the methods of Example 17;

Fig. 9 is a graph that describes the efficiency of nitrogen oxide removal in (%), ammonia consumption in (%) and N₂The generated in (ppm) of CuCHA catalyst. as a function of reaction temperatures for CuCHA prepared according to the methods of Example 18;

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

Fig. 11 is UV / VIS of Example 22 and 22A; and

Fig. 12 is ²⁷In the MAS NMR spectrum of Example 22 and 22A, compared to CHA and aged CHA samples.

DETAILED DESCRIPTION

Before describing various exemplary embodiments of the invention, it should be understood that the invention is not limited to the details of the construction or process steps presented in the following description. The invention is capable of other embodiments and of being practiced or carried out in various ways.

In an embodiment of the invention, zeolites having the CHA structure such as chabazite are provided. In one or more embodiments, a zeolite having the CHA crystal structure and a silica to alumina molar ratio greater than about 15 and an atomic copper to aluminum ratio exceeding about 0.25 is provided. In specific 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 having the CHA structure include, are not limited to SSZ-13, LZ218, Linde D, Linde R, Phi, ZK-14, and ZYT-6.

Synthesis of zeolites having the CHA structure can be performed according to several techniques known in the art. For example, in a typical SSZ-13 synthesis, a silica source, an alumina source, and an organic conducting agent are mixed under aqueous alkaline conditions. Typical silica sources include various types of fumed silica, precipitated silica, and colloidal silica, as well as silicon alkoxides. Typical alumina sources include boehmites, pseudo-boehmites, aluminum hydroxides, aluminum salts such as aluminum sulfate, and aluminum alkoxides. Sodium hydroxide is typically added to the reaction mixture, but it is not necessary. A typical driving agent for this synthesis is adamantyl trimethylammonium hydroxide, although other amines and / or quaternary ammonium salts can be substituted or added to the last driving agent. The reaction mixture is heated in a pressurized vessel with stirring to produce the crystalline SSZ-13 product. Typical reaction temperatures are in the range of 150 and 180 ° C. Typical reaction times are between 1 and 5 days.

Upon completion of the reaction, the product is filtered and washed with water. Alternatively, the product can be centrifuged. Organic additives can be used to assist with the handling and isolation of the solid product. Spray drying is an optional step in product processing. The solid product is heat treated in air or nitrogen. Alternatively, each gaseous treatment can be applied in several sequences, or mixtures of gases can be applied. Typical calcination temperatures are in the range of 400 ° C to 700 ° C.

CuCHA zeolite catalysts according to one or more embodiments of the invention can be used in catalytic processes involving oxidation and / or hydrothermal conditions, for example at temperatures in excess of about 600 ° C, for example, above about 800 ° C and in the presence of about 10% water vapor. More specifically, it has been found that CuCHA zeolite catalysts that have been prepared according to embodiments of the invention have increased hydrothermal stability compared to CuY and CuBeta zeolites. CuCHA zeolite catalysts prepared according to embodiments of the invention produce improved activity in selective catalytic reduction of NOx with ammonia, especially when operated under high temperatures of at least about 600 ° C, for example, about 800 ° C and more high, and environments with a high water vapor content of about 10% or more. CuCHA has high intrinsic activity that allows the use of lower amounts of catalyst material, which in turn should reduce the back pressure of substrates in alveolar form coated with reactive coating compositions of CuCHA catalysts. In one or more embodiments, hydrothermal aging refers to the exposure of 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 specific embodiments, up to about 50 hours.

Embodiments of this invention also relate to a process for reducing NO_X in a discharge gas stream generated by an internal combustion engine using CuCHA zeolite catalysts having a molar ratio of silica to alumina greater than about 15 and an atomic ratio of copper to aluminum exceeding about 0.25. Other embodiments concern SCR catalysts comprising a CuCHA zeolite catalyst having a molar ratio of silica to alumina greater than about 15 and an atomic ratio of copper to aluminum exceeding about 0.25, and treatment systems of discharge gas incorporating CuCHA zeolite catalysts. Still other embodiments concern ammonia oxidation catalysts (AMOX) and exhaust gas treatment systems incorporating

AMOX comprising a CuCHA zeolite catalyst having a molar ratio of silica to alumina greater than about 15 and an atomic ratio of copper to aluminum exceeding about 0.25. According to one or more embodiments, catalysts and systems use CuCHA catalysts having ion exchange copper and sufficient excess free copper to prevent thermal degradation of the catalysts when operated under high temperatures of at least about 600 ° C, for example, about 800 ° C and higher, and environments with a high water vapor content of about 10% or more.

The experimentation indicated that improved performance of catalysts according to embodiments of the invention is associated with Cu loading. Although Cu can be exchanged to increase the level of Cu associated with the exchange sites in the zeolite structure, it has been found to be beneficial to leave Cu not exchanged in the form of salt, for example, as CuSO₄inside the zeolite catalyst. In calcination, copper salt breaks down CuO, which can be referred to here as "free copper" or "soluble copper." According to one or more embodiments, this free Cu is both active and selective, resulting in low N formation₂O when used to treat a gas stream containing nitrogen oxides. Unexpectedly, it was found that this "free" Cu communicates greater stability in catalysts subjected to thermal aging at temperatures up to about 800 ° C.

Although embodiments of the invention are not intended to be linked by a particular principle, it is believed that the relatively small CHA channel openings do not allow large molecular weight hydrocarbons (HCs) typical of diesel fuel to enter and adsorb within the structure of CuCHA. Unlike other zeolites like Beta or ZSM5, CHA catalysts prepared according to embodiments of the invention have a relatively low affinity for adsorbing these large molecular weight HC species. This is a beneficial property for use in selective catalytic reduction (SCR) catalysts.

In systems using an SCR downstream of a diesel oxidation catalyst (DOC), the properties of the CuCHA catalysts provide one or more beneficial results according to embodiments of the invention. During extended low temperature startup and operation, SCR alone or a diesel oxidation catalyst (DOC) or DOC and catalytic soot filter (CSF) upstream of the CuCHA SCR are not fully activated to oxidize HCs. According to one or more embodiments, because the CuCHA SCR catalyst is not influenced by low temperature HCs, it remains active over a wider range of the low temperature operating window. According to one or more embodiments, low temperature refers to temperatures of about 250 ° C and lower.

According to one or more embodiments, CuCHA catalysts operate within a low temperature window. Over time in an exhaust gas treatment system having a DOC pre-catalyst downstream of the engine followed by an SCR catalyst and a CSF, or a DOC pre-catalyst upstream of a CSF and SCR, DOC will tend to activate both for low temperature start-up and for burning HC fuel. In such systems, it is beneficial if the SCR catalyst can maintain its ability to operate at low temperatures. Since oxidation catalysts will lose their ability to oxidize NO to NO₂, it is useful to provide an SCR catalyst that can treat NO as effectively as NO₂. CuCHA catalysts produced according to embodiments of the invention have the ability to reduce NO with NH₃ at low temperatures. This attribute can be enhanced by the addition of unchanged Cu to the zeolite catalyst.

According to embodiments of the invention, the SCR catalyst can be in the form of self-supporting catalyst particles or as an alveolar shaped monolith formed from the SCR catalyst composition. In one or more embodiments of the invention, however, the SCR catalyst composition is arranged as a reactive coating composition or as a combination of reactive coating compositions on a ceramic or metal substrate, for example a cross-flow shaped substrate alveolar.

In a specific embodiment of an emission treatment system the SCR catalyst is formed from a CHA zeolite material exchanged in Cu having free copper in addition to ion exchange copper.

When deposited on the monolith substrates in an alveolar form, such SCR catalyst compositions are deposited in a □ -5 concentration of at least about 0.5 g / in (30.5 kg / m), for example, about 1 , 3 g / in (79.3 kg / m) about 2.4 g / in (146.4 kg / m) or higher to ensure that the desired NOx reduction is achieved and to ensure adequate catalyst durability about prolonged use.

The term "SCR" catalyst is used here in a broader sense to mean a selective catalytic reduction in which a catalyzed reaction of nitrogen oxides with a reducer occurs to reduce nitrogen oxides. "Reducer" or "reducing agent" is also widely used here to mean any chemical or compound that tends to reduce NOx at elevated temperatures. In specific embodiments, the reducing agent is ammonia, specifically an ammonia precursor, that is, urea and the SCR is a nitrogen reducing SCR. However, according to a broader scope of the invention, the reducer can include fuel, particularly diesel fuel and fractions thereof as well as any collectively oxygenated hydrocarbons and hydrocarbons referred to as an HC reducer.

SUBSTRATES

The catalyst compositions are arranged on a substrate. The substrate can be any of those materials typically used to prepare catalysts, and will usually comprise a ceramic or metallic honeycomb structure. Any suitable substrate can be used, such as a monolithic substrate of the type having thin, parallel gas flow passages extending through it from an inlet or an outlet face of the substrate, such that the passages are opened for the fluid to flow through them (referred to as alveolar through-flow substrates). The passages, which are essentially straight paths from their fluid inlet to their fluid outlet, are bounded by walls on which the catalytic material is arranged as a reactive coating composition so that gases flowing through the passages contact the material catalytic. The flow passages of the monolithic substrate are thin-walled channels, which can be of any shape in suitable cross section and size such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular, etc. Such structures can contain from about 60 to about 400 or more of gas inlet openings (i.e., cells) per square inch of cross section.

The substrate can also be a wall flow filter substrate, where the channels are alternately blocked, allowing a gas stream that enters the channels from one direction (inlet direction) to flow through the channel walls and out of the channels. channels from the other direction (exit direction). The AMOX and / or SCR catalyst composition can be coated on the through-flow or wall-flow filter. If a wall flow substrate is used, the resulting system will be able to remove particulate matter together with gaseous pollutants. The wall flow filter substrate can be manufactured from materials commonly known in the art, such as cordierite, aluminum titanate or silicon carbide. It will be understood that loading of the catalytic composition onto a wall flow substrate will depend on substrate properties such as porosity and wall thickness, and will typically be lower than loading on a through-flow substrate.

The ceramic substrate can be made of any suitable refractory material, for example, cordierite, cordierite-alumina, silicon nitride, zirconium mullite, spodumene, magnesia silica alumina, zirconium silicate, silimanite, magnesium silicate, zirconium, petalite , alpha-alumina, an aluminosilicate and the like.

The substrates useful for the catalysts of embodiments of the present invention can also be metallic in nature and be composed of one or more metals or metal alloys. Metal substrates can be used in various forms such as corrugated sheet or monolithic form. Suitable metal supports include heat-resistant metals and metal alloys such as titanium and stainless steel as well as other alloys in which iron is a substantial or major component. Such alloys can contain one or more of nickel, chromium and / or aluminum, and the total amount of these metals can advantageously comprise at least 15% by weight of the alloy, for example, 10 to 25% by weight of chromium, 3 to 8% by weight of aluminum and up to 20% by weight of nickel. The alloys may also contain small amounts or trace amounts of one or more other metals such as manganese, copper, vanadium, titanium and the like. The metal surface or substrates can be oxidized at high temperatures, for example, 1000 ° C and higher, to improve the corrosion resistance of the alloys by forming an oxide layer on the substrate surfaces. Such oxidation induced by high temperature can increase the adhesion of the refractory metal oxide support and catalytically promote the metallic components to the substrate.

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 typically formed of ceramic or metallic reffective materials.

Reactive Coating Composition Preparation

According to one or more embodiments, CuCHA reactive coating compositions can be prepared using a binder. According to one or more embodiments the use of a ZrO binder₂ derived from a suitable precursor such as zirconyl acetate or any other suitable zirconium precursor such as zirconyl nitrate. In one embodiment, zirconyl acetate binder provides a catalytic coating that remains homogeneous and intact after thermal aging, for example, when the catalyst is exposed to high temperatures of at least about 600 ° C, for example, about 800 ° C and higher, and environments with a high water vapor content of about 10% or more. Keeping the reactive coating composition intact is beneficial because the loose or free coating can buffer the CSF downstream causing the back pressure to increase.

According to one or more embodiments, CuCHA catalysts can be used as an ammonia oxidation catalyst. Such AMOX catalysts are useful in exhaust gas treatment systems including an SCR catalyst. As discussed in United States Patent commonly designated No. 5,516,497, the entire content of which is incorporated herein by reference, a gas stream containing oxygen, nitrogen oxides and ammonia can be sequentially passed through the first and second catalysts, the first catalyst favoring the reduction of nitrogen oxides and the second catalyst favoring oxidation or other decomposition of excess ammonia. As described in United States Patent N^The 5,516,497, the first catalysts can be an SCR catalyst comprising a zeolite and the second catalyst can be an AMOX catalyst comprising a zeolite.

As is known in the art, to reduce emissions of nitrogen oxides from combustible and discharge gases, ammonia is added to the gas stream containing the nitrogen oxides and the gas stream is then contacted with a suitable catalyst at elevated temperatures in order to catalyze the reduction of nitrogen oxides with ammonia. Such gaseous streams, for example, the combustion products of an internal combustion engine or a fuel gas or fuel oil turbine engine, often and inherently also contain substantial amounts of oxygen. A typical exhaust gas from a turbine engine contains about 2 to 15 percent by volume of oxygen and about 20 to 500 parts per million by volume of nitrogen oxides, the latter usually comprising a mixture of NO and NO₂. Usually, there is sufficient oxygen present in the gas stream to oxidize residual ammonia, even when an excess of the stoichiometric amount of ammonia needed to reduce all nitrogen oxides present is used. However, in cases where a very large excess over the stoichiometric amount of ammonia is used, or where the gas stream to be treated is absent or low in oxygen content, a gas containing oxygen, usually air, can be introduced between the first catalyst zone and the second catalyst zone, to ensure that adequate oxygen is present in the second catalyst zone for the oxidation of residual or excess ammonia.

Metal-promoted zeolites were used to promote the reaction of ammonia with nitrogen oxides to form nitrogen and H₂The selectively in the competition reaction of oxygen and ammonia. The catalyzed reaction of ammonia and nitrogen oxides is therefore sometimes referred to as the selective catalytic reduction ("SCR") of nitrogen oxides or, as sometimes here, simply as the "SCR process". Theoretically, it would be desirable in the SCR process to supply ammonia in excess of the stoichiometric amount needed to react completely with the nitrogen oxides present, both to favor the conduct of the reaction at completion and to help overcome the inadequate mixture of ammonia in the gas stream. However, in practice, significant excess ammonia in such a stoichiometric amount is not normally provided because the unreacted ammonia discharge from the catalyst into the atmosphere alone would cause an air pollution problem. Such unreacted ammonia discharge can occur even in cases where ammonia is present only in a stoichiometric or sub-stoichiometric amount, as a result of incomplete reaction and / or deficient ammonia mixing in the gas stream, resulting in the formation of high ammonia concentration. Such channel formation is of particular interest when using catalysts comprising carriers of the monolithic alveolar shape type comprising refractory bodies having a plurality of thin, parallel gas flow paths extending through these because, unlike the case of catalyst beds particulate matter, there is no opportunity for gas mixing between channels.

According to embodiments of the present invention, CuCHA catalysts can be formulated to favor (1) the SCR process, that is, the reduction of nitrogen oxides with ammonia to form nitrogen and H₂O, or (2) oxidation of ammonia with oxygen to form nitrogen and H₂O, the selectivity of the catalyst being adapted by controlling the Cu content of the zeolite. United States Patent No. 5,516,497 shows loading levels of iron and copper in zeolites except CELA, of copper to obtain selectivity for an SCR reaction and selectivity of the catalyst for oxidation of ammonia by oxygen at the expense of the SCR process, improving thereby removing the ammonia. According to embodiments of the invention, CuCHA copper loading can be adapted to obtain selectivity for SCR reactions and ammonia oxidation by oxygen and to provide exhaust gas treatment systems using both types of catalyst.

The above principles are used by providing a staged or two-zone catalyst in which a first zone of copper-loaded catalyst in a zeolite, which promotes SCR followed by a second catalyst zone comprising a zeolite having over this copper loading and / or a precious metal component that promotes oxidation of ammonia. The resulting catalyst composition thus has a first zone (upstream) that favors the reduction of nitrogen oxides with ammonia, and a second zone (downstream) that favors ammonia oxidation. In this way, when ammonia is present in excess of the stoichiometric amount, if throughout the cross section of the flow of the gaseous stream being treated or in localized channels of high ammonia concentration, oxidation of residual ammonia by oxygen is favored by the downstream or secondary catalyst. The amount of ammonia in the gas stream discharged from the catalyst is thereby reduced or eliminated. The first zone and the second zone can be on a single catalyst substrate or as separate substrates.

A CuCHA reactive coating composition containing a precious metal, for example, Pt, has been shown to provide an AMOX catalyst. It is expected that not only ammonia was in the gas flow through the destroyed catalyst, but there was continuous removal of NOx by conversion to N₂. In a specific embodiment, the zeolite has an S1O2 / AI2O3 ratio of about 15 to about 256, and an Al / M ratio of between 2 and 10, where M represents total Cu and precious metal. In one embodiment, the precious metal comprises platinum and the platinum content is between

0.02% and 1.0% by weight of the catalyst, and the loading in part is about 0.5 to about 5 g / in (30.5 to about 305.1 kg / m).

According to one or more embodiments of the invention, SCC CuCHA catalysts can be arranged in a wall flow filter or catalyzed soot filter. Reactive coating compositions of CuCHA can be coated on a porous filter to take into account soot combustion, SCR and AMOX functions.

In one or more embodiments of the present invention, the catalyst comprises a precious metal component, that is, a platinum group metal component. For example, as noted above, AMOX catalysts typically include a platinum component. Suitable precious metal components include platinum, palladium, rhodium and mixtures thereof. The various components (eg CuCHA and precious metal component) of the catalyst material can be applied to the refractory catalyst member, that is, the substrate, as a mixture of two or more components or as individual components in sequential steps in one way that will be readily evident to those skilled in the art of catalyst manufacturing. As described above and in the examples, a typical method of making a catalyst according to an embodiment of the present invention is to provide the catalyst material as a coating or layer of reactive coating composition on the walls of the gas flow passages. a suitable carrier member. This can be accomplished by impregnating a fine particulate refractory metal oxide support material, for example, gamma alumina, with one or more catalytic metal components such as a precious metal, that is, platinum group, compound or other noble metals or base metals, drying and calcining the impregnated support particles and forming an aqueous slurry of these particles. Particles of the bulk copper chabazite can be included in the slurry. Activated alumina can be thermally stabilized before the catalytic components are dispersed in it, as is well known in the art, by impregnating it with, for example, a solution of a soluble salt of barium, lanthanum, zirconium, rare earth metal or other precursor suitable stabilizer, and then drying (for example, at 110 ° C for one hour) and calcining (for example, at 550 ° C for one hour) the activated alumina impregnated to form a stabilizing metal oxide dispersed over the alumina. Base metal catalysts optionally may also have been impregnated in the activated alumina, for example, by impregnating a solution of a base metal nitrate into the alumina particles and calcining to provide a base metal oxide dispersed in the alumina particles.

The carrier can then be immersed in the impregnated activated alumina slurry and removed excess slurry to provide a thin coating of the slurry on the walls of the carrier gas flow passages. The coated carrier is then dried and calcined to provide an adherent coating of the catalytic component and, optionally, the copper CHA material, to the walls of its passages. One or more additional layers can be provided to the carrier. After each layer is applied, or after several desired layers are applied, the carrier is then dried and calcined to provide a finished catalyst member according to an embodiment of the present invention.

Alternatively, alumina or other support particles impregnated with the precious metal or base metal component can be mixed with bulk or sustained particles of copper chabazite material in an aqueous slurry, and this mixed slurry of component particles catalytic and copper chabazite material particles can be applied as a coating to the walls of the carrier gas flow passages.

In use, the discharge gas stream can be contacted with a catalyst prepared according to embodiments of the present invention. For example, CuCHA catalysts manufactured according to embodiments of the present invention are well suited for treating the discharge of engines, including diesel engines.

Without intending to limit the invention in any way, embodiments of the present invention will be more fully described by the following examples.

EXAMPLE 1

A CuCHA powder catalyst was prepared by mixing 100 g of CHA in the form of NH /, having a silica / alumina molar ratio of 30, with 400 mL of a 1.0 Μ copper (II) sulfate solution . The pH was adjusted to 3.5 with nitric acid. An ion exchange reaction between CHA in the form of NH₄ and the copper ions were carried out by stirring the slurry 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 was clear and colorless, which indicated 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, filtering, washing and drying was repeated once.

The resulting CuCHA product was then calcined at 640 ° C in air for 6 hours. The CuCHA catalyst obtained comprised 2.41% by weight CuO, as determined by ICP analysis. A CuCHA slurry was prepared by mixing 90 g of CuCHA, as described above, with 215 ml of deionized water. The mixture was ground by beads. 15.8 g of zirconium acetate in dilute acetic acid (containing 30% ZrO₂) was added to the stirred slurry.

The slurry was coated in 1 ”Dx3” L cell ceramic cores, having a cell density of 400 cpsi (cells per square inch) (62cpcm) and a wall thickness of 6.5 mil (0.16 mm). 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 reactive coating composition charge of 2.4 g / in³ (146.4 kg / m³).

Efficiency and selectivity of the selective catalytic reduction (SCR) of nitrogen oxides from a fresh catalyst core was measured by adding a feed gas mixture of 500 ppm NO, 500 ppm NH3, 10% O2, 5% H₂O, balanced with N₂ to a steady state reactor containing a l ”Dx3” L catalyst core. The reaction was carried out at a space speed of 80,000 h '¹ across a 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% H₂O at 800 ° C for 50 hours, followed by measurement of SCR efficiency and selectivity of nitrogen oxides by the same process as outlined above for the assessment of SCR in a fresh catalyst core.

Figure 1 is a graph showing the conversion of NO_X and manufacturing or forming N₂The versus temperature for this sample. These results are summarized in Table 1. This sample, which does not contain soluble copper before calcination as indicated by the color of the filtrate described above, does not show enhanced resistance to thermal aging.

EXAMPLE IA

The coating slurry of Example 1 was added copper sulfate pentahydrate to raise the level of total CuO to 3.2%. The slurry was coated on the monolith and aged and tested for NO_X of SCR as outlined above for Example 1, except that the monolith was calcined at 640 ° C. The catalytic performance was compared to Example 1 in Figure IA. The addition of copper sulphate in the coating slurry significantly improved hydrothermal stability and low temperature activity. EXAMPLE 2

A CuCHA powder catalyst was prepared by mixing 17 kg of CELA as NH₄', having a silica / alumina molar ratio of

30, with 68 L of a 1.0 Μ copper (II) sulfate solution. The pH was adjusted to 3.5 with nitric acid. An ion exchange reaction between CHA in the form of NH4⁺ and the copper ions were carried out by stirring the slurry at 80 ° C for 1 hour. The resulting mixture was then filtered and dried in air. The above process including ion exchange and filtration was repeated once.

Then, the moist filter cake was pasted again 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 air for 6 hours. The CuCHA catalyst obtained comprised 2.75% by weight CuO.

Preparation of the slurry, coating and NO evaluation_X SCR values ​​were the same as outlined above for Example 1. This example contained free copper, and improved displayed hydrothermal stability compared to Example 1.

EXAMPLE 3

The CuCHA catalyst comprising 3.36% CuO by weight was prepared by the same process as in Example 2 followed by an incipient moisture impregnation.

Using the procedure in Example 2, 134 grams of CuCHA at 3.11% CuO by weight was prepared. To this material, a copper sulphate solution comprising 1.64 g of copper sulphate pentahydrate and 105 ml of deionized water was added. The impregnated sample was dried at 90 ° C and calcined at 640 ° C for 6 hours.

Preparation of the slurry, coating and NO evaluation_Xof SCR is the same as outlined above for Example 1. As shown in Figure 3, the sample containing more unchanged copper exhibited activity at a higher low temperature in addition to hydrothermal stability.

EXAMPLE 4

The CuCHA catalyst comprising 3.85% CuO by weight was prepared by an incipient moisture impregnation process only. A copper sulphate solution comprising 18.3 g of copper sulphate pentahydrate and 168 ml of deionized water was impregnated in 140 g of CHA in the form of NHZ, having a silica / alumina molar ratio of 30. The impregnated sample was then dried at 90 ° C and calcined at 640 ° C for 6 hours.

Preparation of the slurry, coating and NO evaluation_XSCR values ​​are the same as outlined above for Example 1. As shown in Fig. 4, Example 4 exhibited a decline in performance between 350 ° C and 450 ° C after hydrothermal aging.

EXAMPLE 5

The CuCHA catalyst comprising 1.94% CuO by weight was prepared by the same process as in Example 1, except that this sample was prepared by a single ion exchange.

Preparation of the slurry, coating and NO evaluation_XSCR values ​​are the same as outlined above for Example 1, except that hydrothermal stability has not been measured.

EXAMPLE 6

A CuCHA powder catalyst was prepared by mixing 0.2 g of CHA in the form of ΝΕΕνζ having a silica / alumina molar ratio of 15, with 16 ml of a 25 mM copper (II) sulfate solution. An ion exchange reaction between CHA in the form of NH₄⁺ and the copper ions were carried out by stirring the slurry 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, filtering, 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 comprised 4.57 wt% CuO.

The catalyst powder was hydrothermally aged in the presence of 10% H₂O at 800 ° C for 50 hours, followed by measurement of the SCR efficiency of nitrogen oxides.

The performance of the catalyst was assessed using a microchannel catalytic reactor containing a bed of approximately 12.6 mm of catalyst. The flow rate (standard temperature and pressure) of 500 cm / min of reagents, which consists of 500 ppm NO_X, 500 ppm NH₃, 10% of 02, 5% of H₂O, balanced with He, plus 25 cm / min of the steam passed over the bed at various temperatures (200, 250, 300, 350, 400, 450 and 500 ° C) to determine the reactivity of the catalyst. NO conversion_X was determined by 100 * (NO_X powered - NO_X deleted) / (NO_x powered) using a mass spectral analyzer.

EXAMPLE 7

The CuCHA powder catalyst comprising 2.94% CuO by weight was prepared by the same process as in Example 6, including ion exchange, filtration, washing, drying, calcination and hydrothermal aging, except that the molar ratio of silica / alumina was 30 and that the ion exchange process was repeated 4 times.

NO assessment_X SCR is the same as outlined above for example 6.

EXAMPLE 8

The CuCHA powder catalyst comprising 0.45% CuO by weight was prepared by the same process as in Example 6, including ion exchange, filtration, washing, drying, calcination and hydrothermal aging, except that the molar ratio of silica / alumina was 50.

NO assessment_X SCR is the same as outlined above for example 6.

EXAMPLE 9

A CuCHA powder catalyst was prepared by mixing 15.0 g of CHA in the form of ΝΗΛ, having a silica / alumina molar ratio of 256, with 61 mL of a 0.64 copper (II) sulfate solution. M. An ion exchange reaction between the CHA in the form of NR / and the copper ions was carried out by stirring the slurry 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, filtering, 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 comprised 2.63% by weight CuO.

Hydrothermal aging and NO assessment_X SCR was the same as outlined above for example 6.

COMPARATIVE EXAMPLE 10

A Cu / Y zeolite powder catalyst was prepared having a silica / alumina molar ratio of 5 as described below.

A Cu / Y powder catalyst was prepared by mixing

500 g of Zeolite Y in the form of NT1₄⁺, having a silica / alumina molar ratio of ~ 5, with 2500 mL of a solution of copper (II) sulfate of 0.1 Μ. The pH was between 2.9 and 3.3. An ion exchange reaction between zeolite Y in the form of NH, / and copper ions was carried out by stirring the slurry 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, filtering, washing and drying was repeated for a total of 5 changes where the pH was similar to the above. The resulting Cu zeolite product Y was then calcined at 640 ° C in air for 16 hours. The Cu Zeolite Y catalyst obtained comprised CuO at 4.60% by weight.

The Cu / Y slurry was prepared by mixing 200 g of

Cu / Y, as described above, with 400 mL of deionized water. The mixture was ground by passing twice through an Eigermill to obtain a slurry that comprised 90% of particles smaller than 8 pm. 8.7 g of zirconium acetate in dilute acetic acid (containing 30% ZrO₂) were added to the stirred slurry.

The slurry was coated in 1 ”Dx3” L cell ceramic cores, having a cell density of 400 cpsi (cells per square inch) (62cpcm) and a wall thickness of 6.5 mil (0.16 mm). Two coatings were required to obtain a composition charge of

-3 -3 target reactive coating of 1.6 g / in (97.6 kg / cm). The coated cores were dried at 90 ° C for 3 hours, and the cores were calcined at 450 ° C for 1 hour after the second drying step.

Hydrothermal aging and SCR assessment are the same as outlined in Example 1, except that aging in was carried out at 750 ° C for 25 hours.

COMPARATIVE EXAMPLE 11

A Cu / Beta powder catalyst was prepared having a silica / alumina molar ratio of 35 using a procedure similar to the sample prepared in EXAMPLE 10. The hydrothermal aging and SCR evaluation are the same as outlined in Example 1.

A summary of the data for Examples 1 to 5 and Comparative Examples 10 to 11 is contained in Table 1 below. Table 1

<td rowspan="2">Example</td><td rowspan="2">Atomic ratio of Cu / Al</td><td rowspan="2">% CuO</td><td colspan="3">NO conversion_X (%)</td><td colspan="3">Preparation of N₂O, ppm</td>

<td>210 ° C, fresh</td><td>210 ° C, aged</td><td>460 ° C, fresh</td><td>460 ° C, aged</td><td>460 ° C, fresh</td><td>460 ° C, aged</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> 3,8</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> 30</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>IA</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>

Table 1 indicates that Example 3 exhibited the best combination of activity at low temperature, activity at high temperature and showed little degradation due to hydrothermal aging.

Table 2 shows the conversion of NO_X normalized for examples 6 to 9, which contained varying molar ratios of SiO₂/ Al₂O₃ and Cu / Al atomic ratios. Example 7 exhibited the best performance. Although the performance of Examples 6, 8 and 9 was not ideal, it should be noted that each of the Examples was aged at a preferably elevated temperature of 800 ° C. Not all catalysts will experience such high temperatures, and samples aged at lower temperatures are believed to exhibit acceptable performance at a wider acceptable silica / alumina ratio. For example, in an exhaust gas treatment system having an SCR catalyst downstream of a catalyzed soot filter, the SCR would typically be exposed to elevated temperatures, for example, exceeding about 700 ° C. If the SCR is arranged in the CSF, the SCR can experience temperatures as high as about 800 ° C, or higher. According to embodiments of the present invention, greater flexibility in locating a catalyst such as an SCR catalyst in an exhaust gas treatment system is provided due to CuCHA catalysts that exhibit improved hydrothermal stability compared to other types of zeolite. Samples having a range of silica to alumina ratio between about 15 and 256 that experience operating temperatures below about 800 ° C would be expected to exhibit NO conversion_X at an acceptable low temperature. Thus, according to embodiments of the invention, silica to alumina ratios of about 15 to about 256 are within the scope of the invention, however, narrower ranges having a lower end point of about 10, 20 , about 25 and about 30 and a higher end point of 150, 100, 75, 50 and 40 are within the scope of the invention.

Table 2

<td rowspan="2">Example</td><td rowspan="2">Molar ratio of SiO₂/ Al₂O₃</td><td rowspan="2">% CuO</td><td rowspan="2">Atomic ratio of Cu / Al</td><td colspan="3">NO conversion_X, 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> 30</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

STUDY OF CUCHA INHIBITION:

The samples tested in this example were prepared as follows. A CuCHA powder catalyst was prepared by mixing 250 g of CHA in the form of NELÇ, having a silica / alumina molar ratio of 30, with 2.0 L of a copper (II) sulfate solution of 0.1 Μ. The pH was adjusted to 3.0 to 3.4 with nitric acid. An ion exchange reaction between CHA in the form of NHf and copper ions was carried out by stirring the slurry 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, filtering, washing and drying was repeated for a total of 5 times. The resulting CuCHA product was then calcined at 640 ° C in air for 16 hours. The obtained CuCHA catalyst comprised 3.68% by weight CuO.

The impact of CO, propene, n-octane and water on CuCHA's SCR activity at temperatures 170, 200, 250, 300 and 350 ° C was investigated. The catalyst cores were tested in a simulated diesel exhaust mixture. The main gas concentrations were as follows: 500 ppm NO, 500 ppm NH₃, 10% CO₂, 10% O₂. The following components were added sequentially to investigate the effect on NO conversion_X: 5% H₂O, 300 ppm C₃H₆ as Cl, 600 ppm of C₃H₆ as Cl, 100 ppm Octane as Cl and 500 ppm CO. The spatial speed of the experiments was adjusted to 142,000 h¹. The reaction was allowed to reach steady state at temperature points of 170 ° C, 200 ° C, 250 ° C, 300 ° C and 350 ° C and subsequent conversions and component interactions were recorded. NO, NO gas analysis₂, N₂O, NH₃, CO₂, CO, C₃H₆ and H₂The was performed using an MKS 2030 MultiGas FTIR driving at a resolution of, 5 cm '¹.

The results are summarized in Figure 5. At low temperatures of 170 ° C and 200 ° C, water was the main inhibitor, high level of propylene at 200 ppm (600 ppm Cl) was slightly inhibiting at 200 ° C, 100 ppm propylene (300 ppm Cl), CO, and n-octane had no impact. At temperatures higher than 250 ° C, water was observed to be a promoter. None of the tested components was inhibiting the conversion of NO_X The

250 ° C, on the contrary they were all promoters. At 300 ° C, CO and n-octane promoted NO_X of SCR, while 600 ppm of Cl propene inhibited the reaction. At 350 ° C, only 600 ppm of Cl propene had less inhibition, and the other components all had a positive effect. This performance was believed to be better than the performance of other catalysts for

Cu promoted SCR using medium and large pore zeolites, for example, beta zeolites. SCR catalysts are known to be susceptible to transient poisoning by long-chain hydrocarbons, which can fill pores with coke. These tests show that the small pore CuCElA zeolite does not show this problem.

EXAMPLE 12A

HC STORAGE / RELEASE TEST:

GASES AND APPLIANCE:

A CuCHA catalyst core coated in a ceramic monolith (400 cpsi (cells per square inch) (62cpcm) / 6 mil (0.15 mm)) with a cross section of 144 open cells and a length of 1 ”was first aged during 50 h at 800 ° C in 10% H₂O, 10% O₂, nitrogen balance. Subsequently, the catalyst was placed in a laboratory reactor. The catalyst was exposed to a gas mixture comprising 4% H₂O, 14% O₂, 100 ppm NO, N balance₂ and heated to 100 ° C. After the temperature stabilized at 100 ° C, a combination of toluene and octane was added via a mass flow controller to obtain a target concentration of 100 ppm Cl as octane and 100 ppm Cl as toluene at a rate total space of 104 kh '¹. The effluent gas was conducted in an afterburner which was comprising an oxidation catalyst based on Pt / alumina and maintained at a constant temperature of 600 ° C. Any hydrocarbon emissions including partial oxidation and CO products that can be formed in the

CuCHA will be oxidized to CO₂ when passed in the afterburner. The CO effluent₂ afterburner is monitored by a CO analyzer₂in Go. In parallel, a sliding current of the CuCHA catalyst effluent that deflects the afterburner was analyzed by an FID-HC analyzer.

TEST PROTOCOL:

After stabilizing the CuCHA catalyst at 100 ° C in a mixture of 4% H₂O, 14% O₂, 100 ppm NO, N balance₂, the combination of octane hydrocarbon and toluene was introduced. For 10 min the temperature of the catalyst was maintained at 100 ° C. During this period, HCs are stored in the catalyst that leads to a CO₂ out of signal below HC input concentration. After the storage period, the temperature is raised linearly from 100 ° C to 600 ° C at an increase of 20 ° C / min. The CO afterburner signal₂ increases severely which is due to a release of stored from

Catalyst HCs. Upon completion of desorption, the CO signal₂ returns to the reference value (= gas concentration). As the temperature rises, a small decrease in afterburner without CO₂below the feed gas level it indicates a second type of HC removal which is due to the deposition of carbonaceous deposits formed of toluene and octane on the catalyst. As the temperature increases further, any carbonaceous deposits formed will burn and cause a signal outside of high CO2 combustion. After the burning of the carbonaceous deposits is completed, the CO afterburner signal₂ eventually it will return to its reference value.

DATA ANALYSIS:

The CO afterburner signal₂ was quantitatively evaluated in order to determine the amounts of HC that are stored, released, deposited as coke and burnt coke. The corresponding intersections of the CO trace₂ outside the afterburner shown in Fig. 5 A with the HC feed gas concentration were used as integration limits. For the CuCHA example, these integration limits were approximately between 0 and 800s for storage, between 800s and 10000s for release, between 10000s and 1400s for coking, respectively. The amounts of HC that have been stored, released, deposited as coke and subsequently burned are expressed as mg HC based on the average C: H ratio of the HCs in the feed stream.

RESULTS:

This experiment was carried out with Cu-Y SCR catalysts (after aging for 25 h @ 750 ° C in 10% H₂O, 10% O₂, N balance₂) and Fe-Beta (after aging for 50 h at 800 ° C in 10% H₂O, 10% O₂, N balance₂) of the same volume under the same conditions. In the case of CuCHA, there appears to be very little coking and consequently there is no noticeable sign of burning. The results are plotted in Fig. 5B. It is evident that the CuCHA catalyst stores the minimum amount of HCs of which most are released as HCs and little is deposited as coke. The Cu-Y catalyst in contrast did not form a substantial amount of carbonaceous deposits in the temperature range of about 200 ° C to 450 ° C. Part of the constructed coke is subsequently burned at higher temperatures.

EXAMPLE 13

PREPARATION OF THE AMOX CATALYST

An ammonia oxidation catalyst comprising an

CuCELA was prepared as in Example 12 and having a copper content of 3.68% measured as CuO, and S1O2 / AI2O3 ratio of 30. This material was coated on a standard monolithic cordierite support, having a

-3 400 square cell geometry of 400 cells / in (62cpcm), to provide a

The □ total load of 2.4 g / in (146.4 kg / m) based on the weight of monolith volume. This pre-coated monolith was then immersed in a solution of a precursor containing platinum (a platinum hydroxy amine complex) to completely and evenly distribute the platinum precursor to the part. The part was dried at 110 ° C and then calcined at 450 ° C for one hour. This provided

-3 -3 a platinum charge in the 4.3 g / ft (0.15 kg / m) portion based on the mass volume of monolith. Thus the catalyst had the following composition: 3.68% CuO + 0.10% Pt sustained in CuCELA, coated on a standard 400/6 cordierite support at a total partial load of about 2.4 g / in (146, 4 kg / m). The atomic ratio of Al: Cu: Pt in the present catalyst is about 190: 90: 1. The ratio of Al / M (M = Cu + Pt) is equal to about 2.1.

EXAMPLE 14 - SAMPLE TESTING OF EXAMPLE 13

The ammonia removal efficiency and selectivity of the hydrothermally aged AMOx catalyst core oxidation product prepared as described in Example 13 were measured by adding a feed gas mixture of 500 ppm NH₃, 10% O2, 5% H₂O, balanced with N₂ (as air) to a steady state reactor containing a 3.0 inch long cylindrical-square catalyst core with a facial cross section containing 144 open cells. The reaction was carried out at a space speed of 100,000 h '¹ across a temperature range of 150 ° C to 460 ° C. Hydrothermal aging conditions are 10 hours at 700 ° C with 10% H₂The in air. Figure 6 is a graph showing emissions compared to those from a hydrothermally aged sample of CuCHA. The data show

1) conversion of NH₃ highly selective to N₂ catalyzed by the CuCHA catalyst in the absence of Pt impregnation, and 2) that the NH conversion₃ can be dramatically enhanced by including the platinum component without compromising the high selectivity of N₂. The latter is significant in that the prior art shows that platinum as a metallic gauze or supported on other zeolitic oxides or supports is generally selective for the production of N₂O or NO_X.

EXAMPLE 15

Comparison of the CuCELA formulation on a through-flow substrate and a wall-flow filter at comparable loads. A wall flow filter was coated with the same catalyst as the cross-flow catalyst carrier of Example 3 and the two samples measure to compare their catalytic activity.

A CuCHA slurry was prepared by mixing 90 g of CuCHA, as described above, with 215 ml of deionized water. The mixture was ground by spheres for 11 hours to obtain a slurry that comprised 90% particles smaller than 10 μιη. 15.8 g of zirconium acetate in dilute acetic acid (containing 30% ZrO₂) were added to the stirred slurry.

The slurry was coated in 1 ”Dx6” L cell ceramic wall flow filter cores, having a cell density of 300 cpsi (cells per square inch) (46.5 cm) and a wall thickness of 12 mil ( 0.3 mm). The coated cores were dried at 120 ° C for 3 hours and calcined at 540 ° C for 1 hour. The coating process was repeated once to obtain a target reactive coating composition charge of 2.0 g / in³ (122 kg / m³).

Efficiency and selectivity of selective catalytic reduction (SCR) of nitrogen oxides from a fresh catalyst core were measured by adding a feed gas mixture of 500 ppm NO, 500 ppm NH₃, 10% O₂, 5% H₂O, balanced with N₂ to a steady state reactor containing a 1 ”Dx6” L catalyst core. The reaction was carried out at a space speed of 40,000 h '¹ across a 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% H₂O at 750 ° C for 25 hours, followed by measurement of SCR efficiency and selectivity of nitrogen oxides by the same process as outlined above for the assessment of SCR in a fresh catalyst core.

Table 3 below shows the comparison of the performance of

Hydrothermally aged SCR of CuCHA coated on a filter versus CuCHA coated on a through-flow catalyst carrier.

Table 3: Comparison of SCR (% conversion) performance of filter and through-flow substrates

<td>AT THE</td><td>at the₂</td><td>AT THE_X</td><td>nh₃</td><td>Preparation of N₂O (ppm)</td><td>Sample Temp (degrees C)</td>

<td colspan="6">CuCHA in through flow, aged 50 H @ 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 in filter, aged 25 H @ 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 exact experimental detail, the comparison clearly supports the equivalence of the catalytic performance of CuCHA on the filter core and the through-flow monolith catalyst.

EXAMPLE 16

An NH4-CIIA slurry was prepared by mixing 608 g of NH4⁺-CHA, having a silica / alumina molar ratio of 30, with 796 mL of deionized water. The mixture was ground using a Netzsch Mill to obtain a slurry that comprised 90% of particles smaller than 8.4 pm. 106 g of zirconium acetate in dilute acetic acid (containing 30% ZrO2) was added to the slurry with stirring.

The slurry was coated in 1 ”Dx3” L cell ceramic cores, having a cell density of 400 cpsi (cells per square inch) (62cpcm) and a wall thickness of 6.5 mil (0.16 mm). The coated cores were dried at 110 ° C for 3 hours. The coating process was repeated once to obtain a target reactive coating composition charge of 2.4 g / in (146.4 kg / m).

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

NO assessment_X of SCR from the fresh catalyst was the same as outlined for Example 1. Hydrothermal stability of the catalyst was measured by hydrothermal aging of the catalyst core in the presence of 10% steam at 850 ° C for 6 h, followed by measuring the efficiency of NO_X of SCR as outlined for the fresh catalyst.

Figure 7 is the graph showing the conversion of NO_X and N formation₂The versus temperature for this sample.

EXAMPLE 17

12.1 g of copper acetate monohydrate was dissolved in 420 g of deionized water, then 141 g of NH₄-CHA, having a silica / alumina molar ratio of 30, was added in. The mixture was ground using a Netzsch Mill to obtain a slurry that comprised 90% of particles smaller than 3.5 μτη.

The slurry was coated in 1 ”Dx3” L cell ceramic cores, having a cell density of 400 cpsi (cells per square inch) (62cpcm) and a wall thickness of 6.5 mil (0.16 mm). The coated cores were dried at 110 ° C for 3 hours. The coating process was repeated twice to obtain a 2.4 g / in (146.4 kg / m) target reactive coating composition charge. The coated cores were then calcined at 400 ° C for 1 hour. This provided a load of CuO in the CHA of 3.3% by weight.

NO assessment_X of SCR of the fresh catalyst was the same as outlined for Example 1. Hydrothermal stability of the catalyst was measured by hydrothermal aging of the catalyst core in the presence of 10% steam at 850 ° C for 6 h, followed by measurement of NO efficiency_X of SCR as outlined for the fresh catalyst.

Figure 8 is a graph showing the conversion of NO_X and N formation₂The versus temperature for this sample.

EXAMPLE 18

A CuCHA powder catalyst was prepared by ion exchange with copper acetate. 0.40 M copper (II) acetate solution monohydrate was prepared by dissolving 89.8 g of copper salt in 1.125 L deionized water at 70 ° C. 300 g of CHA in the form of NH₄⁺ then it was added to this solution. An ion exchange reaction between CHA in the form of NH₄⁺ and the copper ions were carried out by stirring the slurry at 70 ° C for 1 hour. The pH was between 4.8 and 4.5 during the reaction. The resulting mixture was then filtered, washed until the filtrate had a conductivity of &lt;200 pScm '¹, which indicated that substantially no soluble or free copper remained in the sample, and the washed sample was dried at 90 ° C. The CuCHA catalyst obtained comprised 3.06 wt% CuO and Na₂O at 140 ppm.

Preparation of the slurry, coating and NO evaluation_XSCR values ​​were the same as outlined above for Example 1. As shown in Fig. 7, Example 18 exhibited the same SCR performance as Example 3 which was prepared by ion exchange twice with copper sulfate plus an impregnation incipient moisture.

EXAMPLE 19

The CuCHA catalyst comprising 2.99% CuO by weight was prepared by the same process as in Example 18, except that this sample was prepared in 0.30 M Cu solution.

EXAMPLE 20

The CuCHA catalyst comprising 2.69% CuO by weight was prepared by the same process as in Example 18, except that the ion exchange was processed at 45 ° C.

EXAMPLE 21

The CuCHA catalyst comprising 2.51% CuO by weight was prepared by the same process as in Example 19, except that the ion exchange was processed at 45 ° C.

The Cu charges of Examples 18 to 21 are compared to those of Example 1 in Table 4. We found that copper acetate is more efficient than copper sulfate to provide the desired Cu charge with a low concentration of copper solution at lower reaction temperature.

Table 4

<td>Example</td><td>Cu Salt</td><td>Cone, from Cu^{2 +}, M</td><td>Reaction T, ° C</td><td>% by weight of CuO</td>

<td> 1</td><td>Cu Sulfate</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

The Cu / CHA powder prepared in Example 2 was hydrothermally aged in the presence of 10% H₂O in air at 800 ° C for 48 hours. The material analyzed from Example 2 is labeled in Example 22 in Figures 11 and 12 and Tables 5 and 6. The hydrothermally aged sample is labeled in Example 22A in Tables 5 and 6 and Figures 11 and 12.

X-ray powder diffraction patterns were determined by standard techniques. Generator settings are 45 kV and 40 mA. The optical diffractometer consists of a slit of variable divergence, incident beam slots, a receiving slit, a graphite monochromator, and a scintillation counter using Bragg-Brentano screwing geometry. Spacing d was calculated from the structural parameters of a - 13.58 and c = 14.76 Â for example 22 and a = 13.56 and c - 14.75 Â for example 22A. Structural parameters were determined by scanning the sample with LaB6 mixed as an internal standard. The data range was 15 to 38.5 degrees two theta using a step size of 0.01 and counting for 5 seconds. The resulting example was conducted through profile refinement in the JADE software. The structural parameters of LaB6 were kept constant at 5.169 A to compensate for sample displacement errors. Table 5 shows the X-ray powder diffraction lines for Example 22 and Example 22A. The crystalline structure of CHA retained after aging by steam at 800 ° C 48 hours.

Table 5

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

<td>2-Theta</td><td>gives)</td><td>I (%)</td><td>2-Theta</td><td>gives)</td><td>I (%)</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> 30%</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> 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>

The UV / VIS diffuse reflectance spectrum expressed by F (R) was collected using a diffuse reflectance connection with an integration and reference sphere coated with BaSC> 4 inside a spectrometer of

UV-Vis Cary 300. The UV / VIS of Example 22 and 22A are shown in Figure 11.

Table 6 lists the NMR data for ²⁹Si MAS and the Si / Al atomic ratio of structure calculated from Example 22 and 22A. Data for CHA and CHA aged with 10% steam at 800 ° C, 48 hours, are also included for comparison. The data indicate that a degree of de-alumination occurs in the aging of both CHA and Cu / CHA samples. However, the Cu / CHA sample undergoes much less dealumination as it ages. It is also observed that the Cu exchange process alone slightly changes the Si / Al atomic ratio of structure from 15 to 17.

Figure 12 shows the spectra of ²⁷A1 (Magic Angle Spinning Nuclear Magnetic Resonance) from Example 22 and 22A, as well as the aged CELA and CHA samples. The spectra indicate that some of the tetrahedral Al species are converted to penta- and octacoordinate species in Cu exchange. The spectra strongly maintain that the Cu / CHA sample undergoes much less dealumination on aging than the CHA sample.

Table 6

<td rowspan="2">Sample</td><td colspan="4">% intensity</td><td rowspan="2">Si / Al</td>

<td>Si (OAl) -114 ppm</td><td>Si (OAl) -111 ppm</td><td>Si (lAl) -105 ppm</td><td>Si (lAl) -101 ppm</td>

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

<td>Aged CHA</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>

Exemplary embodiments of emission treatment systems are shown in Figs. 10A, 10B and 10C. An embodiment of the inventive emission treatment system denoted 11A is schematically represented in FIG. 10A. The discharge, containing gaseous pollutants (including unburned hydrocarbons, carbon monoxide and NO_X) and particulate matter, is transported from the engine 19 to a downstream position in the discharge system where a reducer, that is, ammonia or an ammonia precursor, is added to the discharge stream. The reducer is injected as a spray through a nozzle (not shown) into the discharge stream. The aqueous urea shown in one line 25 can serve as the precursor to ammonia that can be mixed with air in another line 26 in a mixing station 24. Valve 23 can be used to measure exact amounts of aqueous urea which are converted into the ammonia discharge stream.

The discharge stream with the added ammonia is transported to the SCR 12 catalyst substrate (also referred to herein including the claims as "the first substrate") containing CuCHA according to one or more embodiments. Upon passing through the first substrate 12, the NO component_X discharge current is converted through selective catalytic reduction of NO_X with NH₃ to N₂ and H₂O. In addition, NH₃ excess that emerges from the inlet zone can be converted through oxidation by a downstream ammonia oxidation catalyst (not shown) also containing CuCHA to convert ammonia to N₂ and H₂O. The first substrate is typically a through-flow monolith substrate.

An alternative embodiment of the emission treatment system, denoted as 11B, is shown in FIG. 10B containing a second substrate 27 interposed between the NH injector₃ and the first substrate 12. In this embodiment, the second substrate is coated with an SCR catalyst composition that can be the same composition as is used to cover the first substrate 12 or a different composition. An advantageous feature of this embodiment is that the SCR catalyst compositions that are used to cover the substrate can be selected to optimize the NO conversion_X regarding the operational conditions characteristic of that site along the discharge system. For example, the second substrate can be coated with an SCR catalyst composition that is more suitable for the higher operating temperatures experienced in segments upstream of the discharge system, while another SCR composition can be used to cover the first substrate. (that is, the entrance zone of the first substrate) which is most suitable for cooling the discharge temperature that is experienced in segments downstream of the discharge system.

In the embodiment shown in FIG. 10B, the second substrate 27 can be a through-flow substrate in an alveolar shape, an open cell foam substrate or a wall-flow substrate in an alveolar shape. In configurations of this embodiment where the second substrate is a wall flow substrate or a high efficiency open cell foam filter, the system can remove more than 80% of the particulate matter including the soot fraction and the SOF. A SCR coated wall flow substrate and its usefulness in reducing NO_X and particulate matter have been described, for example, in the co-pending US patent application Ser. N^The 10 / 634,659, deposited on August 5, 2003, the disclosure of which is hereby incorporated by reference.

In some applications it may be advantageous to include an oxidation catalyst upstream of the ammonia injection site / ammonia precursor. For example, in the embodiment shown in FIG. 10C an oxidation catalyst is arranged on a catalyst substrate 34. The emission treatment system 11C is provided with the first substrate 12 and optionally includes a second substrate 27. In this embodiment, the discharge stream is first transported to the catalyst substrate 34 where at least some of the gaseous hydrocarbons, CO and particulate matter are burned to innocuous components. In addition, a significant fraction of the NO of the NO component_X of the discharge is converted to NO₂. Higher proportions of NO₂ in the NO component_X facilitate NO reduction_X to N₂ and H₂The SCR catalyst (s) located downstream. It will be appreciated that in the embodiment shown in Fig. 10C, the first substrate 12 can be a catalyzed soot filter, and the SCR catalyst can be arranged on the catalyzed soot filter. In an alternative embodiment, the second substrate 27 comprising an SCR catalyst can be located upstream of the catalyst substrate 34.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention encompasses modifications and variations of this invention as long as they fall within the scope of the appended claims and their equivalents.