KR20150052335A - Transition metal/zeolite scr catalysts - Google Patents

Abstract

The present invention relates to a method for converting nitrogen oxides in a gas to nitrogen by contacting the nitrogen oxides with a nitrogen reducing agent in the presence of a zeolite catalyst containing at least one transition metal wherein the zeolite has eight tetrahedral Wherein the at least one transition metal is selected from the group consisting of Cr, Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir And Pt.

Description

Transition metal / zeolite SCR catalysts {TRANSITION METAL / ZEOLITE SCR CATALYSTS}

The present invention is directed to a method of converting nitrogen oxides in a gas to nitrogen, such as the exhaust gas of a lean-burn internal combustion engine for transportation, by contacting the nitrogen oxides with a nitrogen reducing agent in the presence of a transition metal-containing zeolite catalyst.

Selective catalytic reduction (SCR) of NO _x by nitrogen compounds such as ammonia or urea was originally developed for the processing of stationary applications in industrial applications. SCR technology was first used in Japanese thermal power plants in the late 1970s and has been used in a wide range of applications in Europe since the mid-1980s. In the United States, SCR systems were introduced for gas turbines in the 1990s, and more recently have been used in coal-fired power plants. In addition to coal-fired cogeneration facilities and gas turbines, SCR applications include equipment in the chemical processing industry, refining heaters and boilers, furnaces, coke ovens, municipal waste treatment plants and incinerators. More recently, NO _x reduction systems based on SCR technology for diesel exhaust gas processing have been developed in a number of transportation (stationary) applications in Europe, Japan and the United States.

In the NH ₃ SCR system, several chemical reactions take place, all of which show a favorable reaction to reduce NO _x to nitrogen. The main reaction is represented by the following reaction formula (1).

<Reaction Scheme 1>

4NO + 4NH ₃ + O ₂ ? 4N ₂ + 6H ₂ O

Competitive and non-selective reactions with oxygen can produce secondary emissions, or they can consume ammonia unproductive. One such non-selective reaction is the complete oxidation of ammonia, represented by reaction (2) below.

<Reaction Scheme 2>

4NH ₃ + 5O ₂ ? 4NO + 6H ₂ O

The side reactions can also lead to undesired products such as N ₂ O, as indicated by the following reaction scheme (3).

<Reaction Scheme 3>

_{4NH 3 + 5NO + 3O 2 →} 4N 2 O + 6H 2 O

Aluminosilicate zeolites are used as catalysts for the SCR of NO _x with NH ₃ . One application is to control the NO _x emissions of diesel engines for transportation, where reducing agents are obtainable from ammonia precursors such as urea or by ammonia originally injected. In order to enhance the catalyst promoting activity, the transition metal is incorporated into the aluminosilicate zeolite. The most commonly studied transition metal zeolites are Cu / ZSM-5, Cu / Beta, Fe / ZSM-5 and Fe / Beta because they have relatively wide temperature active regions. Generally, Cu-based zeolite catalysts exhibit better low temperature NO _x reduction activity than Fe-based zeolite catalysts.

However, in use ZSM-5 and beta zeolite have a number of drawbacks. They are sensitive to dealumination during high temperature hydrothermal aging, resulting in loss of acidity, especially in Cu / beta and Cu / ZSM-5 catalysts. Both beta-and ZSM-5-based catalysts are also affected by hydrocarbons, which adsorb on the catalyst at relatively low temperatures and oxidize as the temperature of the catalyst system rises, producing a severe exotherm, . This problem is particularly acute in the field of diesel applications for vehicles in which a considerable amount of hydrocarbons can be adsorbed onto the catalyst at low temperature-onset; In addition, beta and ZSM-5 zeolites tend to be coked by hydrocarbons.

In general, Cu- based zeolite catalysts are less thermally durable, and compared to the Fe- based zeolite catalyst, to produce an N ₂ O of higher concentrations. However, this has the advantage that it slips less ammonia in use compared to the corresponding Fe-zeolite catalyst.

It has been reported that aluminophosphate zeolites containing transition metals exhibit improved catalyst promoting activity and excellent thermal stability in the SCR of NO _x using hydrocarbons compared to aluminosilicate zeolite catalysts (lean NO _x catalyst or " NO _x catalyst "(e.g., Ishihara et al. , Journal of Catalysis, 169 (1997) 93)). In a similar vein, WO 2006/064805 discloses an electrical treatment technique for treating diesel exhaust gases using corona discharge. A combination of a device for adding a NO _x reducing agent (hydrocarbon or fuel) and a Cu-SAPO-34 NO _x reduction catalyst may be disposed downstream of the electrical treatment apparatus. However, as far as we know, no literature has reported any investigation of transition metal-containing aluminophosphate zeolites for NO _x SCR using NH ₃ (or urea).

WO 00/72965 discloses iron (Fe) exchanged zeolites for the selective catalytic reduction of nitrogen monoxide by ammonia for NO _x emission control from fossil-fuel power plants and engines. The proposed Fe-exchange, and optionally Fe-rare earth-exchanged, such as Fe-Ce-exchanged zeolites, include: ZSM-5, mordenite, SAPO, clinoptilolite, Chabazite, ZK-4 and ZK-5. No specific SAPO zeolite was named, nor was an experiment using SAPO zeolite. WO '965 also discloses zeolites having a series of pore sizes, such as large (mordenite), medium (ZSM-5, clinoptilolite) and small (chaiseite, ZK-4, ZK- 5) pore zeolite, and Fe-ZSM-5 is preferred. There is no teaching or suggestion of any advantage in using small pore zeolites compared to medium and large pore zeolites. In addition, ZK-4 zeolites are potentially hydrothermal instabilities.

US Pat. No. 4,735,927 discloses an extrusion-type NH ₃ -SCR catalyst having stability to sulfur toxicity, including representative area titania in the form of a mullite and natural or synthetic zeolite. The zeolite must be acidic or thermally convertible in acidic form in the catalyzed product. Examples of suitable zeolites include zeolite Y, which is mordenite, natural clinoptilolite, erionite, heulandite, ferrierite, natural faujasite or its synthetic counterparts, Chabazite, and gmelinite. The preferred zeolite is natural clinoptilolite, which can be mixed with another acid-stable zeolite such as chaebolite. The catalyst may optionally contain a small amount (0.1% or more based on the element weight) of vanadium oxide, copper oxide, molybdenum oxide or a combination thereof precursor form promoter (0.2 wt% Cu and up to 1.6 wt% has exist). Extrusion-type catalysts are generally less durable than catalyst coatings applied to inert monolithic substrates, have lower chemical strength, require more catalyst material to achieve the same activity, and are more complex to manufacture Do.

US Pat. No. 5,417,949 also discloses an extrusion-type NH ₃ -SCR catalyst comprising a zeolite with a constraint index of 12 or less and a titania binder. ("Constraint Index" is a test for measuring shape-selective catalytic behavior in zeolites.) This is a test for the thermal decomposition of n -hexane and its isomer, 3-methylpentane, under competitive conditions (See VJ Frillette et al. , J Catal. 67 (1991) 218).

US Patent No. 5,589,147 discloses an ammonia SCR catalyst comprising a molecular sieve and a metal, and the catalyst can be coated on a substrate monolith. Molecular sieves useful in the invention are not limited to any particular molecular sieve material and generally include all metal silicates, metal phosphates, silicoaluminophosphates, and materials on layered and columnar beds. The metal is typically selected from one or more metals of the group IIIA, IB, IIB, VA, VIA, VIIA, VIIIA of the periodic table and combinations thereof. Examples of such metals include at least one of copper, zinc, vanadium, chromium, manganese, cobalt, iron, nickel, rhodium, palladium, platinum, molybdenum, tungsten, cerium and mixtures thereof.

The disclosure of US 5,589,147 is not clear if a small pore zeolite (as defined herein) has certain applicability to the process of the invention. For example, on the one hand, certain small pore zeolites, e. G., Erionite and chaebolite, are mentioned as possible zeolites for use in the invention, among which the molecular entity SAPO-34 is "considered ". On the other hand, there is a table listing the values of the constraint index (CI) for some typical zeolites, including those suitable as catalysts in the process of the present invention. Nearly all of the CI values in the table are well below 10, with the exception of erionite (38 at 316 ° C) and ZSM-34 (50 at 371 ° C). However, it is evident that mesoporous zeolites, such as those having pore sizes of from about 5 to less than 7 angstroms, are preferred for the process of the invention. In particular, the above disclosure describes the desirability of mesoporous zeolites, since it provides for confinement to access and escape from free space within the crystal: "mesoporous zeolites are ... &lt; RTI ID = 0.0 &gt; Having an effective pore size to adsorb freely ... If the only pore region in the crystal is formed by an 8-membered ring of oxygen atoms, the access to larger cross-sectional molecules is eliminated compared to n-hexane, It is not a substance of medium pore size ". Only extruded Fe-ZSM-5 is illustrated.

WO 2004/002611 discloses an NH ₃ -SCR catalyst comprising a ceria-doped aluminosilicate zeolite.

US 6,514,470 discloses a process for reducing the NO _x in the exhaust gas stream containing catalyst to promote the NOx reducing agent and the substance. The catalyst comprises an aluminum silicate material and a metal in an amount of about 0.1 weight percent or less based on the total weight of the catalyst. All of the examples use ferrierite.

Long et al. Journal of Catalysis 207 (2002) 274-285 reports on the study of Fe ^{3 +} -exchanged zeolites for the selective catalytic reduction of NO using ammonia. The investigated zeolites were mordenite, clinoptilolite, beta, ferrierite and chaebazite. It has been found that under the conditions studied, SCR activity decreases in the following order: Fe-mordenite>Fe-clinoptilolite>Fe-ferrierite>Fe-beta> Fe-chaebateite. Chabazite used in the preparation of Fe-chabazite was a naturally occurring mineral.

US Patent No. 4,961,917 discloses a zeolite having a pore structure interconnected at all three crystallographic dimensions by pores having a silica-to-alumina ratio of at least about 10 and an average kinetic pore diameter of at least about 7 angstroms, and a Cu or Fe promoter It discloses the NH ₃ -SCR catalyst comprising a. The catalyst is said to have high activity, reduced NH ₃ oxidation and reduced sulfur toxicity. Zeolite beta and zeolite Y are two kinds of zeolites satisfying the required requirements.

US Pat. No. 3,895,094 discloses an NH ₃ -SCR process using a zeolite catalyst with a crystalline pore size of greater than 6 angstroms. There is no mention of exchanging zeolites using transition metals.

US Pat. No. 4,220,632 also discloses an NH ₃ -SCR process, this time using Na or H-type zeolites with pore sizes of 3-10 angstroms.

WO 02/41991 discloses a metal promoted zeolite beta for NH ₃ -SCR in which the zeolite is pre-treated to provide improved hydrothermal stability therein.

Has a relatively good low temperature SCR activity, with selectivity relatively to the high N ₂ - in particular was N ₂ O formed is less, relative to have excellent heat durability, a need for a relatively resistant SCR catalyst with respect to the hydrocarbon inhibition It exists in the industry. Finally, a group of transition metal-containing zeolites has been found that meet or meet this need.

In one aspect, the present invention provides a method of converting nitrogen oxides in a gas to nitrogen by contacting the nitrogen oxides with a nitrogen reducing agent in the presence of a zeolite catalyst containing at least one transition metal, wherein the zeolite has a maximum ring size Wherein the at least one transition metal is selected from the group consisting of Cr, Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir, and Pt.

The term "zeolite catalyst containing at least one transition metal" as used herein means a zeolite structure having at least one metal added by ion exchange, impregnation or isomorphous substitution. The terms "transition metal-containing zeolite catalyst" and "zeolite catalyst containing at least one transition metal" and similar terms are used interchangeably herein.

It will be appreciated that by defining the zeolite with its Framework Type Code it is intended to include "Type Material" and any and all isoform backbone materials (the "orthopedic material" The first to be used to do so). Reference is made to Table 1 which lists a set of exemplary zeolite zeotype framework materials for use in the present invention. For the sake of clarity, unless stated otherwise, reference to a zeolite by the name "chaebasite" herein refers to the zeolite material itself (in this case, chaebasiite, a naturally occurring type of material) Quot; is not meant to refer to any other material designated by the backbone type code, such as any other isomeric backbone material. Thus, for example, when the appended claims deny the zeolite catalyst, such a disclaimer should be narrowly interpreted so that " when the transition metal-containing micropore zeolite is not Cu / chaiseite " -13. &Lt; / RTI &gt; Likewise, the use of FTC herein is intended to refer to the orthopedic materials and all isoform skeletal materials defined by the FTC. For further information, please direct your readers to the International Zeolite Association website at www.iza-online.org.

The distinction between a zeolite orthopedic material, such as a naturally occurring (i.e., mineral) chaebolite, and an isoform belonging to its skeletal type code is not merely arbitrary, but instead, Lt; / RTI &gt; See, for example, Long et al. In addition to the description to be mentioned below with reference to the Journal of Catalysis 207 (2002) 274-285, naturally occurring carbazites have a lower silica-to-alumina ratio than aluminosilicate isomers such as SSZ-13, The generated Cha barzite has a lower acidity than the aluminosilicate isoforms such as SSZ-13, and the activity of the material in the method of the present invention is relatively low (Cu / naturally occurring carbazate Cu / Comparison with SAPO-34).

The zeolite catalyst for use in the present invention may be coated on a suitable integral substrate or may be formed as an extrusion-type catalyst, but is preferably used as a catalyst coating.

Although prior art (for example, those discussed in the Background section above) refers to a small number of small pore zeolites containing at least one transition metal to convert nitrogen oxides in the gas to nitrogen using a nitrogen reducing agent, It is not recognized in the prior art that the specific advantages of using small pore zeolites containing one or more transition metals for the same purpose can be found. Thus, the prior art suggests the use of large, medium and small pore zeolites containing at least one transition metal indiscriminately. Thus, for this reason only, it is intended to exclude any particular small pore zeolite containing one or more transition metals mentioned.

In this regard, in one embodiment, the zeolite catalyst is not one of Co, Ga, Mn, In or Zn, or any combination of two or more thereof / epistilbite (see US Pat. No. 6,514,470). In yet another embodiment, the transition metal-containing micropore zeolite is selected from the group consisting of Cu / cha-baryte, Mo / cha-baryte, Cu-Mo / chaebazite, Cu / erionite, Mo / It is not an erionite (see US Pat. No. 4,735,927). In another embodiment, the transition metal-containing micropore zeolite is not Ce / erionite (see WO 2004/002611). In another embodiment, the transition metal-containing micropore zeolite is selected from the group consisting of Fe / chaebastite, Fe / ZK-5, Fe / ZK-4, Fe-rare earth / chaiseite, Fe-rare earth / ZK- / ZK-4 (see WO 00/72965). On the other hand, although WO 00/72965 discloses the use of Ce / SAPO zeolites and Ce-rare earths / SAPO zeolites in general, it is also possible to use SAPO-17, SAPO-18, SAPO-34, SAPO- , SAPO-43 and SAPO-56, which are applicable to the present invention. In another embodiment, the transition metal-containing micropore zeolite is not Fe / chaebolite (see Long et al. Journal of Catalysis 207 (2002) 274-285). For reasons presented above, it is not believed that US Pat. No. 5,589,147 discloses the use of small pore zeolites containing one or more transition metals according to the process of the present invention, but for safety reasons, in another embodiment, The zeolite catalyst may be any one of copper, zinc, chromium, manganese, cobalt, iron, nickel, rhodium, palladium, platinum, molybdenum, cerium or mixtures thereof / aluminosilicate chaebaiite, aluminosilicate erionite, Aluminosilicate ZSM-34 and SAPO-34. In another embodiment, the transition metal-containing zeolite catalyst is not LTA or Fe / CHA.

Chabazite is a small pore zeolite according to the regulations adopted herein, and the above-mentioned Long et al. Report that Fe / chabazite has the lowest activity among all catalysts tested You will know. Without wishing to be bound by any theory, it is believed that the poor performance of Fe / ChaBaZit in the above studies is due to two main causes. First, the natural tea bajaite can contain basic metal cations including potassium, sodium, strontium and calcium. Since the basic metal is a known toxic substance in the zeolite acid site, in order to obtain an active substance, it is necessary that the basic metal cation be exchanged with, for example, iron cations. In the reported work, natural minerals are first treated with NH ₄ Cl solution in an attempt to "wash away" the existing cations. However, one explanation for the poorly reported activity is believed to be that the acidic site of the research carbazate remains toxicized by basic metal cations.

Secondly, iron ions can form metal complexes (coordination compounds) with suitable ligands in ion exchange media. In this connection, Long notes that FeCl ₂ aqueous solution is used for ion exchange. Since the zeolite pores are relatively small, it is possible that a large coordination compound may not be accessible to the active sites located in the pores.

For example, in the following Table 1, it will be understood that "MeAPSO" and "MeAlPO" mean a zeotype substituted with one or more metals. Suitable substituent metals include, but are not limited to, at least one of As, B, Be, Co, Fe, Ga, Ge, Li, Mg, Mn, Zn and Zr.

In certain embodiments, the micropore zeolites for use in the present invention may be selected from the group consisting of aluminosilicate zeolites, metal-substituted aluminosilicate zeolites, and aluminophosphate zeolites.

Aluminophosphate zeolites to which the present invention is applied include aluminophosphate (AlPO) zeolite, metal substituted zeolite (MeAlPO) zeolite, silica-aluminophosphate (SAPO) zeolite and metal substituted silico-aluminophosphate .

The present invention also relates to transition metal-containing micropore zeolites according to the invention, and mesoporous-meso-pore zeolites (transition metal (e. G. It will be understood that the present invention extends to an integrated substrate of the catalyst coating and extrusion type which includes both non-small pore zeolites (whether or not metallized) It should also be understood that the integrated catalyst-coating and extrusion-type substrate for use in the present invention may comprise a combination of two or more transition metal-containing micropore zeolites. In addition, each of the small pore zeolites in such combinations may contain one or more transition metals selected from the group defined above. For example, the first small pore zeolite may contain both Cu and Fe , The second small pore zeolite combined with the first small pore zeolite may contain Ce.

In the present invention, it has been found that the transition metal-containing micropore zeolite is a catalyst favorable for the SCR of NO _x using NH ₃ . Compared to transition metal-containing medium, large or mesoporous zeolite catalysts, transition metal-containing micropore zeolite catalysts exhibit significantly improved NO _x reduction activity, especially at low temperatures. It also exhibits a high selectivity for N ₂ (such as low N ₂ O formation) and good hydrothermal stability. Small pore zeolites containing one or more transition metals can also be prepared from larger pore zeolites, such as zeolites with a medium pore size such as ZSM-5 (zeolite having a maximum ring size of 10) or large pore zeolites such as beta Ring size zeolite). &Lt; / RTI &gt; Small pore aluminophosphate zeolites for use in the present invention include SAPO-17, SAPO-18, SAPO-34, SAPO-35, SAPO-39, SAPO-43 and SAPO-56.

In one embodiment, the micropore zeolite is selected from the group of skeleton type codes consisting of: ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EIB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, UFI, VNI, YUG and ZON.

The zeolite used in the present invention may include those treated to improve hydrothermal stability. Exemplary hydrothermal stability enhancing methods include the following:

(i) dealumination with: acidification using an acid or complexing agent (e.g., EDTA-ethylenediamine tetraacetic acid) and acid extraction; Treatment with an acid and / or a complexing agent; Treatment with a gaseous stream of SiCl ₄ (replacing Al in the zeolite framework with Si);

(ii) cation exchange - the use of polyvalent cations such as La; And

(iii) the use of phosphorus containing compounds (see, e.g., US Pat. No. 5,958,818).

Small pore zeolites can minimize the harmful effects of hydrocarbons due to the molecular sieve effect so that small pore zeolites allow NO and NH ₃ to diffuse into the active sites inside the pores while the diffusion of the hydrocarbon molecules is limited &Lt; / RTI &gt; In this regard, the kinematic diameter of both NO (3.16 A) and NH ₃ (2.6 A) is, for example, that of conventional hydrocarbons present in diesel engine exhaust (C ₃ H ₆ to 4.5 A, nC ₈ H ₁₈ to 4.30 A And C ₇ H ₈ ~ 6.0 A). Thus, in one embodiment, the micropore zeolite catalyst for use in the present invention has a pore size of less than 4.3 A in one or more dimensions. Illustrative examples of suitable small pore zeolites are shown in Table 1.

Lean-presented the exhaust gas, for example a small pore zeolite has a particular applicability to process the NO _x from the exhaust gas of a vehicle internal combustion engine the combustion in Table 2 below.

Small pore aluminosilicate zeolites for use in the present invention may have a silica-to-alumina ratio (SAR) of 2 to 300, optionally 4 to 200, preferably 8 to 150. A larger SAR ratio is desirable to improve thermal stability, but you may know that this can have a negative impact on the transition metal exchange. Thus, in selecting a preferred material, the SAR can be considered so that the balance between these two properties can be balanced.

The gas containing nitrogen oxides can contact the zeolite catalyst at a gas hourly space velocity of from 5,000 hr ^-1 to 500,000 hr ^-1 , optionally from 10,000 hr ^-1 to 200,000 hr ^-1 .

In one embodiment, the small pore zeolite for use in the present invention does not comprise an aluminophosphate zeolite as defined herein. In other embodiments, small pore zeolites (as defined herein) for use in the present invention are limited to aluminophosphate zeolites (as defined herein). In another embodiment, the small pore zeolites for use in the present invention are aluminosilicate zeolites and metal substituted aluminosilicate zeolites (and not aluminophosphate zeolites as defined herein).

Small pore zeolites for use in the present invention can have a three dimensional dimensionality, i.e., a pore structure interconnected at all three crystallographic dimensions, or a two dimensional dimensionality. In one embodiment, the micropore zeolite for use in the present invention consists of a zeolite having a three dimensional dimensionality. In another embodiment, the small pore zeolite for use in the present invention consists of a zeolite having a two-dimensional dimensionality.

In one embodiment, the at least one transition metal is selected from the group consisting of Cr, Ce, Mn, Fe, Co, Ni, and Cu. In a preferred embodiment, the at least one transition metal is selected from the group consisting of Cu, Fe and Ce. In certain embodiments, the at least one transition metal is comprised of Cu. In another specific embodiment, the at least one transition metal is comprised of Fe. In another particular embodiment, the at least one transition metal is Cu and / or Fe.

The total amount of the at least one transition metal that can be included in the at least one transition metal-containing zeolite may be 0.01 to 20 wt% based on the total weight of the zeolite catalyst containing at least one transition metal. In one embodiment, the total of one or more transition metals that may be included may be from 0.1 to 10 wt%. In certain embodiments, the total amount of one or more transition metals that can be included is from 0.5 to 5 wt%.

Preferred transition metal-containing two-dimensional miniature pore zeolites for use in the present invention are composed of Cu / LEV such as Cu / Nu-3, while preferred transition metal-containing three-dimensional small pore zeolite / The naphosphate zeolite is composed of Cu / CHA such as Cu / SAPO-34 or Cu / SSZ-13. In another embodiment, especially when the ratio of NO / NO ₂ is adjusted to about 1: 1 by using a suitable oxidation catalyst (see below), Fe-CHA such as Fe / SAPO-34 or An Fe-containing zeolite catalyst such as Fe / SSZ-13 is preferred. According to preliminary analysis, Cu / SSZ-13 and Cu / Nu-3 were subjected to long-term severe lean hydrothermal aging (4.5% H ₂ O / air mixture at 900 ° C. for 3 hours compared to equivalent Cu / SAPO-34 See Example 4).

One or more transition metals may be included in the zeolite in any possible way. For example, it can be added after the zeolite has been synthesized, for example by incipient wetness or an exchange process; Or one or more metals may be added during zeolite synthesis.

A zeolite catalyst for use in the present invention may be, for example, a metal or ceramic flow-through integrated substrate or filter substrate, such as a washcoat component, such as a wall-flow filter or a sintered metal or partial filter / 80978 or EP 1057519, the latter document describing a substrate comprising a swirling flow path that slows down the passage of soot through at least one of them) . Alternatively, the zeolite for use in the present invention may be directly synthesized on a substrate. Alternatively, the zeolite catalyst according to the present invention can be formed with an extrusion-type flow-through catalyst.

Small pore zeolite catalysts containing one or more transition metals for use in the present invention are coated onto a suitable integral substrate. Extrusion type as for the coating of on the integrated substrate for producing one-piece substrate a washcoat composition containing a zeolite for use in the present invention are alumina, silica, (non zeolite) silica-alumina, naturally-occurring clay, TiO _2, ZrO _2, And SnO &lt; ₂ &gt;.

In one embodiment, the nitrogen oxides are reduced by a reducing agent at a temperature above 100 캜. In another embodiment, the nitrogen oxides are reduced by a reducing agent at a temperature of about 150 &lt; 0 &gt; C to 750 &lt; 0 &gt; C. The latter embodiment provides an exhaust gas from an engine including an exhaust system comprising heavy and light duty diesel engines, and in particular a diesel particulate filter which is activated and regenerated (optionally catalyzed) by injecting hydrocarbons into the exhaust system upstream of the filter Especially where the zeolite catalyst for use in the present invention is located downstream of the filter.

In certain embodiments, the temperature range is 175 to 550 占 폚. In yet another embodiment, the temperature range is 175 to 400 占 폚.

In another embodiment, the nitrogen oxide reduction is carried out in the presence of oxygen. In another embodiment, the nitrogen oxide reduction is performed in the absence of oxygen.

Zeolites for use in the present invention include natural and synthetic zeolites, and synthetic zeolites are preferred, since the zeolites are more uniform: silica-to-alumina ratio (SAR), crystallite size, crystalline form, and impurities Soil metal).

The source of the nitrogen reducing agent may be ammonia itself, hydrazine or any suitable ammonia precursor such as urea ((NH ₂ ) ₂ CO), ammonium carbonate, ammonium carbamate, ammonium hydrogen carbonate or ammonium formate.

The method may be carried out in a gas derived from a combustion process such as an internal combustion engine (whether movable or stationary), a gas turbine, and a coal or petroleum combustion plant. The process may also be used to treat gases from industrial processes such as refining, refining heaters and boilers, furnaces, chemical processing industries, coke ovens, municipal waste treatment plants and incinerators, coffee roasting facilities, and the like.

In certain embodiments, the method is used to treat exhaust gas from a lean-burn internal combustion engine for a vehicle such as a diesel engine, a lean-burn gasoline engine, or an engine driven by liquid petroleum gas or natural gas.

In another aspect, the present invention provides a process for the production of a zeolite catalyst, comprising: a conduit for conveying flowing exhaust gas, a source of nitrogen reductant, a zeolite catalyst disposed in the flow path of the exhaust gas and containing at least one transition metal, Wherein the zeolite catalyst is a small pore zeolite containing eight tetrahedral atoms of maximum ring size, wherein the at least one transition metal is selected from the group consisting of Cr, Mn, Fe, Co The exhaust system for the lean burn internal combustion engine for transportation is selected from the group consisting of Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, .

In order to avoid doubt, the small pore transition metal-containing zeolites for use in the exhaust system embodiments of the present invention include everything used in the process according to the invention as described above.

In one embodiment, the zeolite catalyst may be a flow-through integrated substrate (i.e., a honeycomb monolithic catalyst support structure having many small parallel channels passing axially through the entire component), or a wall flow filter, Coated on the same filter-integrated substrate. In another embodiment, the zeolite catalyst is formed from an extrusion-type catalyst.

The system can be metered into the exhaust gas flowing with the nitrogen reducing agent only when it is ascertained that the zeolite catalyst can catalyze NO _x reduction at a desired efficiency or above, such as above 100 ° C, above 150 ° C, or above 175 ° C in use. And means for controlling the metering and inputting means to be charged. Confirmation by the control means may be assisted by one or more suitable sensor information indicative of the engine condition selected from the group consisting of: exhaust gas temperature, catalytic temperature, accelerator position, mass flow rate of the exhaust gas in the system, The manifold vacuum, ignition timing, engine speed, the lambda valve of the exhaust gas, the amount of fuel injected from the engine, the position of the exhaust gas recirculation (EGR) valve and hence the amount of EGR, and the boost pressure.

In certain embodiments, metering inputs may be performed directly (using a suitable NO _x sensor) or by correlating any one or more of the above-mentioned information indicative of, for example, the engine condition with the NO _x content in the expected exhaust gas, Controlled in response to the amount of nitrogen oxide in the exhaust gas indirectly measured using a pre-correlation look-up table or map stored in the control means.

The adjusting means may comprise a pre-programming processor, such as an electronic control unit (ECU).

The metering addition of the nitrogen reducing agent can be adjusted so that 60% to 200% of the theoretical ammonia is present in the exhaust gas entering the SCR catalyst, calculated from 1: 1 NH ₃ / NO and 4: 3 NH ₃ / NO ₂ .

In other embodiments, an oxidation catalyst for oxidizing nitrogen monoxide in the exhaust gas to nitrogen dioxide may be located upstream of the point where the nitrogen reducing agent is metered into the exhaust gas. In one embodiment, the oxidation catalyst is an SCR zeolite catalyst inlet gas stream having a NO to NO ₂ ratio of about 4: 1 to about 1: 3 by volume at an exhaust gas temperature of 250 ° C to 450 ° C, for example at the oxidation catalyst inlet . Such a concept can be found in S. [S. Kasaoka et al. "Effect of Inlet NO / NO ₂ Molar Ratio and Contribution of Oxygen in the Catalytic Reduction of Nitrogen Oxides with Ammonia", Nippon Kagaku Kaishi, 1978; 6, pp. 874-881 and WO 99/39809.

The oxidation catalyst may comprise one or more platinum-based metals (or any combination thereof) coated on a flow-through integrated substrate, such as platinum, palladium or rhodium. In one embodiment, the at least one platinum-based metal is platinum, palladium, or a combination of both platinum and palladium. The platinum-group metal may be supported on a representative area washcoat component such as alumina, zeolite such as aluminosilicate zeolite, silica, non-zeolite silica alumina, ceria, zirconia, titania, or mixed or composite oxides containing both ceria and zirconia. .

In another embodiment, a suitable filter substrate is positioned between the oxidation catalyst and the zeolite catalyst. The filter substrate may be selected from any of those mentioned above, such as a wall flow filter. Where the filter is catalyzed, for example, by an oxidation catalyst of the type discussed above, preferably the point at which the nitrogen reducing agent is metered in is located between the filter and the zeolite catalyst. Alternatively, if the filter is not catalyzed, the means for metering the nitrogen reducing agent may be located between the oxidation catalyst and the filter. It will be appreciated that such an arrangement is disclosed in WO 99/39809.

In another embodiment, the zeolite catalyst for use in the present invention is coated on a filter located downstream of the oxidation catalyst. Where the filter comprises a zeolite catalyst for use in the present invention, the point at which the nitrogen reducing agent is metered in is preferably located between the oxidation catalyst and the filter.

In one embodiment, the control means metering the nitrogen reducing agent into the flowing exhaust gas only when the outlet gas temperature is above 100 ° C, for example only when the outlet gas temperature is between 150 ° C and 750 ° C.

In another aspect, a lean-burn engine for a vehicle comprising an exhaust system in accordance with the present invention is provided.

The lean-burn internal combustion engine for the vehicle may be a diesel engine, a lean-burn gasoline engine, or an engine driven by liquid petroleum gas or natural gas.

In order that the invention may be more fully understood, reference is made to the following examples as pure examples, with reference to the accompanying drawings, in which:
Figure 1 shows that after a relatively mild lean hydrothermal aging performed in a laboratory reactor, the transition metal-containing aluminosilicate catalyst is compared to a transition metal-containing aluminophosphate / small pore zeolite catalyst and a NO _x conversion rate of 30,000 hr ^-1 At a space velocity per hour);
Figure 2 is a graph showing N ₂ O formation in the test shown in Figure 1;
Figure 3 is an after relatively moderate lean hydrothermal aging, Cu / Beta zeolite and Cu / SAPO-34 catalyst a transition metal carried out in a laboratory reactor-containing aluminophosphate / as compared with the small pore zeolite catalysts, NO _x conversion (100,000 hr ^{- 1} at a space velocity per gaseous hour);
4 after relatively severe lean hydrothermal aging performed on a laboratory reactor, the transition metal-containing aluminosilicate catalyst the transition metal-containing aluminophosphate / small pore zeolite as compared to the catalyst, NO _x conversion (of 30,000 hr ^-1 gas At a space velocity per hour);
5 is a graph showing the NO _x conversion in a new Cu / zeolite catalyst;
6 is a graph showing the NO _x conversion in an aged Cu / zeolite catalyst;
Figure 7 is a graph showing N ₂ O formation in the new Cu / zeolite catalyst of Figure 5;
8 is a graph showing N ₂ O formation in the aged Cu / zeolite catalyst of FIG. 6;
9 is a graph showing the effect of addition of HC species to Cu / zeolite catalysts during NH ₃ SCR at 300 ° C;
10 is a graph showing the hydrocarbon breakdown following hydrocarbon species addition to a Cu / zeolite catalyst at NH ₃ SCR at 300 ° C;
11 is a graph showing the adsorption profile of n-octane flowing through a Cu zeolite catalyst at 150 &lt; 0 &gt;C;
12 is a graph of temperature programming desorption (TPD) of HC species for Cu / zeolite catalyst after HC adsorption at 150 &lt; 0 &gt;C;
FIG. 13 is a graph similar to FIG. 6, comparing the NO _x conversion activity in aged Cu / Sigma-1, Cu-SAPO-34, Cu / SSZ-13 and Cu / Beta;
FIG. 14 is a graph similar to FIG. 8, comparing N ₂ O formation in the aged Cu / zeolite catalyst of FIG. 13;
FIG. 15 is a graph similar to FIG. 13 comparing the NO _x conversion activity in aged Cu / ZSM-34, Cu / SAPO-34, Cu / SSZ-13 and Cu / Beta catalysts;
16 is a graph comparing the NO _x conversion activities of the new and the aged Cu-SAPO-34 and Cu / SSZ-13 catalysts;
Figure 17 is a graph comparing the NO _x conversion activity of a new sample of Cu / SAPO-34 with a Cu / naturally occurring chaotropic crystal material;
18 is a bar chart comparing the NO _x conversion activity of the new Cu / SAPO-34 with that of the two new Cu / naturally occurring chalcometric formulations at two temperature data points;
Figure 19 is a bar chart comparing the NO _x conversion activity of aged Cu / beta, Cu / SAPO-34, Fe / SAPO-34 and Fe / SSZ-13 catalysts at two temperature data points;
Figure 20 is a bar chart comparing the hydrocarbon inhibiting effect of n-octane incorporation on the feed gas for the new Fe / beta and Fe / SSZ-13 catalysts;
Figure 21 is a graph showing hydrocarbon breakdown following n-octane incorporation in the Figure 20 experiment;
22 is a bar chart comparing the effect of using 100% NO as the feed gas component and the effect of NO _x conversion activity using 1: 1 NO: NO ₂ on the new Fe / SSZ-13 catalyst;
23 is a schematic diagram of an embodiment of an exhaust system according to the present invention.
Figure 23 is a schematic diagram of an exhaust system embodiment in accordance with the present invention wherein the diesel engine 12 includes an exhaust line 14 for delivering exhaust gas from the engine to the atmosphere through an exhaust line 15, System 10 shown in FIG. In the flow path of the exhaust gas, a platinum or platinum / palladium NO oxidation catalyst 16 coated on a ceramic flow-through integrated substrate is disposed. Located downstream of the oxidation catalyst 16 of the exhaust system is the ceramic wallflow filter 18.
The iron / small pore zeolite SCR catalyst 20 coated on the ceramic flow-through integrated substrate is also disposed downstream of the wall flow filter 18. NH ₃ oxidized clean-up or slip catalyst 21 is coated on the downstream end of the SCR catalyst integrated substrate. Alternatively, the NH ₃ slip catalyst may be coated on a separate substrate located downstream of the SCR catalyst. (Injector 22) for introducing a nitrogen reducing agent fluid (element 26) into the exhaust gas carried from the reservoir 24 in the exhaust line 14 is provided. The injector 22 is controlled using a valve 28, which is again controlled by the electronic control device 30 (valve control indicated by the dashed line). The electronic control device 30 receives the closed loop feedback control information from the NO _x sensor 32 located downstream of the SCR catalyst.
In use, the oxidation catalyst 16 only slightly oxidizes the NO to NO ₂ , and the particulate material is captured in the filter 18 and burned in the NO ₂ . The NO _x released from the filter is reduced on the SCR catalyst 20 in the presence of ammonia from the injected element through the injector 22. It is also desirable that a mixture of NO and NO ₂ (about 1: 1) in the total NO _x content of the exhaust gas entering the SCR catalyst is preferred because NO _x reduction on the SCR catalyst is more easily reduced to N ₂ Know. The NH ₃ slip catalyst 21 oxidizes NH ₃ to be discharged into the atmosphere if not. A similar arrangement is described in WO 99/39809.

<Examples>

Example 1 - New 5 wt% Fe / beta beta or SAPO- 34, or 3 wt% Process for preparing SSZ- 13 zeolite catalyst

Commercially available beta zeolite, SAPO-34 or SSZ-13 was NH ₄ ⁺ ion-exchanged in NH ₄ NO ₃ solution and then filtered. While stirring the material produced was added to the Fe (NO _{3) 3} aqueous solution. The slurry was filtered, washed and dried. To achieve the desired metal loading, this procedure can be repeated. The final product was calcined.

Example 2 - Preparation of new 3 wt% Cu / zeolite

Commercially available SAPO-34, SSZ-13, Sigma-1, ZSM-34, Nu-3, ZSM-5 and beta zeolite were NH ₄ ⁺ ion exchanged in NH ₄ NO ₃ solution and then filtered. While stirring the material to be produced is added to the Cu (NO _{3) 2} aqueous solution. The slurry was filtered, washed and dried. To achieve the desired metal loading, this procedure can be repeated. The final product was calcined.

Example 3 - Lean hydrothermal aging

Example 1 and was lean hydrothermal aging in 750 ℃ for 24 hours in a 4.5% H ₂ O / air mixture of the catalyst obtained by the second.

Example 4 - Severe lean hydrothermal aging

Examples 1 and for 1 hour in a 4.5% H ₂ O / air mixture of the catalyst obtained by the two hard to 900 ℃ was lean hydrothermal aging.

Example 5 - Long-term Severe Lean Hydrothermal Aging

Example 1 and from a 4.5% H ₂ O / air mixture of the catalyst obtained by the second for a 3 hour period to 900 ℃ were severely lean hydrothermal aging.

Example 6 - Test conditions

Beta / beta beta, Cu / ZSM-5 and Cu / SAPO-34 prepared according to Example 2 were aged according to Examples 3 and 4, 350 ppm NO, 350 ppm NH ₃ , 14% O ₂ , 4.5% H ₂ O, 4.5% CO ₂ , N ₂ qs. The results are shown in Figs.

Example 2 is prepared according to the aging according to Example 3 Cu / Beta Beta, Cu / ZSM-5, Cu / SAPO-34 and Cu / Nu-3 were carried out to even on the test, 12% O ₂ would be that the use Except that the same gas mixtures as above were used in the laboratory apparatus. The results are shown in Figs.

Example 7 - Conditions for n-octane adsorption test

NH ₃ SCR (350 ppm NO, 350 ppm NH ₃ , 12% O ₂ , 4.5% H ₂ O, 4.5% CO ₂ , adequate N ₂ ) at a temperature of 300 ° C (As C1 equivalent) of propene, n-octane or toluene. The hydrocarbon desorption was measured by tilting the temperature to 10 ° C / min at 12% O ₂ , 4.5% H ₂ O, 4.5% CO ₂ , N ₂ at the appropriate volume.

Example 8 - Experimental results shown in Figs. 1 to 4

Figure 1 compares the NO _x reduction efficiencies of the Cu / SAPO-34 catalyst versus a series of aluminosilicate zeolite supported transition metal catalysts (Cu / ZSM-5, Cu / Beta and Fe / have. The results clearly show that Cu / SAPO-34 has improved low-temperature activity in the SCR of NO _x with NH ₃ .

Figure 2 compares N ₂ O formation on the catalyst. It is clear that the Cu / SAPO-34 catalyst produced a lower concentration of N ₂ O than the other two Cu-containing catalysts. The Fe-containing catalyst also exhibits low N ₂ O formation, but as shown in FIG. 1, the Fe catalyst is less active at low temperatures.

3 is a further tested at a higher gas hourly space velocity compared to the NO _x reduction efficiency of a Cu / SAPO-34 catalyst compared to a Cu / Beta catalyst. Cu / SAPO-34 catalysts are significantly more active than Cu-Beta catalysts at low reaction temperatures.

Figure 4 shows the NO _x reduction efficiency of a Cu / SAPO-34 catalyst and a series of aluminosilicate zeolite supported transition metal catalysts (Cu / ZSM-5, Cu / Beta and Fe / Beta) after severe lean hydrothermal aging. The results clearly show that the Cu / SAPO-34 catalyst has excellent hydrothermal stability.

Example 9 - Experimental results shown in Figs. 5 to 12

In Figure 5, the NH ₃ SCR activity of the new pore zeolite SAPO-34 and the new (i.e., un-aged) Cu supported on Nu-3 was compared to that of the supported Cu on the zeolite of the larger pore . The corresponding activity in the same catalyst aged under severe lean hydrothermal conditions is shown in FIG. A comparison of the active profile of the new and aged shows that hydrothermal stability is achieved for the aluminosilicate zeolite only if Cu is supported on the micropore zeolite.

The measured N ₂ O formation for the new and aged catalysts is shown in Figures 7 and 8, respectively. The results clearly show that N ₂ O formation is significantly reduced by supporting Cu on zeolites that do not have large pores.

Figure 9 compares the effect of HC on Cu / zeolite catalysts when SAPO-34 and Nu-3 are used as examples of small pore zeolitic materials. For comparison, ZSM-5 and beta zeolite were used as examples of medium and large pore zeolites, respectively. The samples were exposed to different HC species (propene, n-octane and toluene) during the NH ₃ SCR reaction at 300 ° C. Figure 10 shows the corresponding HC breakthrough following HC addition.

Figure 11 shows the adsorption profile of n-octane flowing through a different Cu / zeolite catalyst at &lt; RTI ID = 0.0 &gt; 150 C. &lt; / RTI &gt; HC breakdown was observed almost immediately in the pellets supported on the small pore zeolite SAPO-34 and Nu-3, while significant HC inhalation was observed in Cu on the beta zeolite and ZSM-5. Figure 12 shows the HC desorption profile as a function of the subsequent increased temperature, where large amounts of HC are stored when Cu is supported on the zeolite of larger pores, whereas very small HCs are used when small pore zeolites are used To be stored.

Example 10 - Experimental results shown in Figs. 13 and 14

The Cu / SSZ-13, Cu / SAPO-34, Cu / Sigma-1 and Cu / beta prepared according to Example 2 were aged in the manner described in Example 4 and tested according to Example 6. The results are shown in Fig. 13, in which the NO _x conversion activity of each of the heavily lean aged Cu / SSZ-13, Cu / SAPO-34 and Cu / Sigma-1 samples is comparable to that of the corresponding large-pore zeolite Cu / &Lt; / RTI &gt; In addition, in FIG 14, Cu / Beta Cu / small - it can be seen that sikindaneun generate significantly more than the N ₂ O pore zeolite catalyst.

Example 11 - Experimental results shown in Fig. 15

The Cu / ZSM-34, Cu / SAPO-34, Cu / SSZ-13 and Cu / Beta prepared according to Example 2 were aged in the manner described in Example 3 and tested according to Example 6. The results are shown in FIG. 15, where the NO _x conversion activity of each of the lean hydrothermally aged Cu / SSZ-13, Cu / SAPO-34 and Cu / ZSM-34 samples is comparable to that of the corresponding Cu / beta zeolite Which is significantly better.

Example 12 - Experimental results shown in Fig. 16

A new sample of Cu / SSZ-13 and Cu / SAPO-34 was prepared according to Example 2 and the sample was aged in the manner described in Example 5. New (i.e., not aged) samples and aged samples were tested according to Example 6 and the results are shown in Figure 16, indicating that the NO _x conversion activity of Cu / SSZ-13 is retained even after prolonged severe lean aging .

Example 13 - Experimental results shown in Figs. 17 and 18

Cu / SAPO-34 and Cu / naturally occurring carbazate stabilizers (with an SAR of about 4) were prepared according to Example 2 and the new materials were tested according to Example 6. The results are shown in FIG. 17, which shows that the NO _x conversion activity of naturally occurring Cu / chaiseite is considerably lower than that of Cu / SAPO-34. 18 is a bar chart comparing the NO _x conversion activity of two new Cu / naturally occurring carbazite shaped materials prepared according to Example 2 at two temperature data points (200 ° C and 300 ° C) The chaebasite material has a SAR of about 4, and the secondary bazaar material has a SAR of about 7. It can be seen that the activity of the SAR 7 tertiary bazazite is also significantly lower than that of the new Cu / SAPO-34, although the NO _x conversion activity of the SAR 7 tertiary bisureite is better than that of the SAR quaternary bisureite material .

* Example 14 - Experimental results shown in Fig. 19

Cu / SAPO-34 and Cu / Beta were prepared according to Example 2. Fe / SAPO-34 and Fe / SSZ-13 were prepared according to Example 1. The samples were aged according to Example 4 and the aged samples were tested according to Example 6. The NO _x activity at 350 ° C and 450 ° C data points is shown in Figure 19 where Cu / SAPO-34, Fe / SAPO-34 and Fe / SSZ-13 samples have similar or better performance than Cu / .

Example 15 - Experimental results shown in Figs. 20 and 21

The Fe / SSZ-13 and Fe / beta prepared according to Example 1 were tested in their new state as described in Example 7, where n-octane (mimicking the effect of unburned diesel fuel in the exhaust gas) Was introduced into the test on the 8th minute. The results shown in Figure 20 show the NO _x conversion activity at the 8th minute of the test but after 8 minutes (HC +) when n-octane was introduced into the feed gas (HC-) and n-octane was introduced into the feed gas . Fe / beta activity is drastically decreased after introduction of n-octane compared to Fe / SSZ-13. This effect is believed to be due to the coking of the catalyst.

The hypothesis that the coking of the Fe / Beta catalyst is responsible for the abrupt decrease in the NO _x conversion activity is due to the fact that the C1 hydrocarbon is detected almost immediately downstream of the Fe / SSZ-13 catalyst after n-octane is introduced into the feed gas in the eighth minute 21 &lt; / RTI &gt; By comparison, significantly lower amounts of C1 hydrocarbons are observed in the Fe / Beta sample effluent. This result implies that it contributes to the loss of NO _x conversion activity by coking on the Fe / Beta catalyst, since there are significantly fewer C1 hydrocarbons in the effluent of the Fe / beta sample and n-octane would have gone somewhere do.

Example 16 - Experimental results shown in Fig. 22

The Fe / SSZ-13 prepared according to Example 1 was tested in the new state, i.e. in the manner described in Example 6, without aging. Next, the test was repeated using the same conditions except that 350 ppm NO was replaced with a mixture of 175 ppm NO and 175 ppm NO ₂ , i.e., 350 ppm total NO _x . The results of the positive test are shown in FIG. 22, which shows a significant improvement obtained by increasing the NO ₂ content in the NO _x of the feed gas by 1: 1. , NO at run time: NO ₂ ratio can be adjusted by oxidizing NO in the exhaust gas of a diesel engine for example, using a suitable oxidation catalyst located upstream of the NH ₃ -SCR catalyst.

To avoid any doubt, the entire contents of any and all prior art documents referred to herein are incorporated herein by reference.

Claims (50)

Comprising contacting a nitrogen oxide with a nitrogen reducing agent in the presence of a zeolite catalyst containing at least one transition metal wherein the zeolite is a small pore zeolite containing eight tetrahedral atoms of maximum ring size and at least one transition metal Is selected from the group consisting of Cr, Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir and Pt. And converting the oxide to nitrogen. The process according to claim 1, wherein the zeolite is an isoform containing at least one substituent skeleton metal. The method of claim 2, wherein the or each substituent skeleton metal is selected from the group consisting of As, B, Be, Co, Fe, Ga, Ge, Li, Mg, Mn, Zn and Zr. The process according to any one of claims 1 to 3, wherein the small pore zeolite is not a skeletal orthopedic material having a skeletal type code LTA or any isomeric zeolite thereof. The process according to any one of claims 1 to 4, wherein the transition metal-containing micropore zeolite is not Ce / erionite. The method of any one of claims 1 to 5, wherein the transition metal-containing micropore zeolite is selected from the group consisting of Cu / chaebastite, Mo / chaiseite, Cu-Mo / chaebazite, Cu / erionite, Mo / Lt; RTI ID = 0.0 &gt; Cu-Mo / erionite. &Lt; / RTI &gt; 7. The method of any one of claims 1 to 6, wherein the transition metal-containing micropore zeolite is selected from the group consisting of Fe / chaebast, Fe / ZK-5, Fe / ZK-4, Fe-rare earth / Rare earth / ZK-5 or Fe-rare earth / ZK-4. 8. A process according to any one of claims 1 to 7, wherein the transition metal-containing micropore zeolite is not Fe / chaebolite. 9. The process according to any one of claims 1 to 8, wherein the small pore zeolite is selected from the group consisting of aluminosilicate zeolites, metal-substituted aluminosilicate zeolites and aluminophosphate zeolites. The process of claim 9, wherein the or each aluminophosphate zeolite is selected from the group consisting of AlPO zeolite, MeAlPO zeolite, SAPO zeolite, and MeAPSO zeolite. 11. A process according to any one of claims 1 to 10 wherein the small pore zeolite is selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, Lt; RTI ID = 0.0 &gt; YUG &lt; / RTI &gt; and ZON. 12. The method of claim 11 wherein the small pore zeolite containing the largest ring size of eight tetrahedral atoms is selected from the group of backbone type codes consisting of CHA, LEV, ERI and DDR. 13. The process of claim 12, wherein the CHA skeletal type cord zeolite is SAPO-34 or SSZ-13. 13. The method of claim 12 wherein the LEV framework type zeolite is Nu-3. 13. The method of claim 12, wherein the ERI skeletal type code zeolite is ZSM-34. 13. The method of claim 12, wherein the DDR skeletal type code zeolite is Sigma-1. 17. The process according to any one of claims 1 to 16, wherein the zeolite is treated to improve hydrothermal stability. 18. The process according to any one of claims 1 to 17, wherein the pore size of the zeolite in the at least one dimension is less than 4.3 ANGSTROM. 19. The process according to any one of claims 1 to 18, wherein the zeolite has a three-dimensional dimensionality. 19. The process according to any one of claims 1 to 18, wherein the zeolite has a two-dimensional dimensionality. 21. The method according to any one of claims 1 to 20, wherein the at least one transition metal is selected from the group consisting of Cr, Ce, Mn, Fe, Co, Ni and Cu. 22. The process according to any one of claims 1 to 21, wherein the at least one transition metal is selected from the group consisting of Fe, Ce and Cu. 23. The process according to any one of claims 1 to 22, wherein the at least one transition metal is Fe and / or Cu. 24. The process according to any one of claims 1 to 23, wherein the total of at least one transition metal present in the catalyst is from 0.01 to 20% by weight, based on the total weight of the zeolite catalyst. 25. The process according to any one of claims 1 to 24, wherein the total of at least one transition metal present in the catalyst is from 0.1 to 10% by weight, based on the total weight of the zeolite catalyst. 26. The process according to claim 25, wherein the total of at least one transition metal present in the catalyst is from 0.5 to 5% by weight based on the total weight of the zeolite catalyst. 27. The process according to any one of claims 1 to 26, wherein the zeolite catalyst is composed of Fe / CHA, especially Fe / SAPO-34 or Fe / SSZ-13. 27. The process according to any one of claims 1 to 26, wherein the zeolite catalyst consists of Cu / CHA, especially Cu / SAPO-34 or Cu / SSZ-13. 29. The method according to any one of claims 1 to 28, wherein the nitrogen oxide is reduced by a reducing agent at a temperature of 100 DEG C or higher. 30. The method of claim 29, wherein the temperature is from about 150 DEG C to 750 DEG C. 31. The method according to any one of claims 1 to 30, wherein the nitrogen oxide reduction is carried out in the presence of oxygen. Any one of claims 1 to 31. A method according to any one of claims, wherein the NH ₃ in the zeolite catalyst inlet 1: 1 NH ₃ / NO and 4: 60% to 200% of theoretical ammonia calculated at ₃ NH 3 / NO ₂ is And controlling the addition of the nitrogen reducing agent so as to be controlled so that the nitrogen reducing agent is controlled to be controlled. 33. The process according to any one of claims 1 to 32, wherein the nitrogen monoxide in the gas is oxidized to nitrogen dioxide using an oxidation catalyst located upstream of the zeolite catalyst, the resulting gas is mixed with a nitrogen reducing agent, Wherein the oxidation catalyst is adjusted to yield a zeolite catalyst input gas stream having a NO to NO ₂ ratio of from about 4: 1 to about 1: 3 by volume. 34. The process according to any one of claims 1 to 33, wherein the zeolite is a synthetic zeolite. Any one of claims 1 to 34. A method according to any one of claims, wherein the nitrogen-reducing agent is ammonia itself, hydrazine or elements _{((NH 2) 2 CO)} , ammonium carbonate, ammonium carbamate, ammonium hydrogen carbonate and ammonium Formate &lt; / RTI &gt; 37. The process according to any one of claims 1 to 35, wherein the gas containing nitrogen oxides is derived from a combustion process. 37. The method of claim 36, wherein the combustion process is combustion of fuel in a lean-burn internal combustion engine for a vehicle. A conduit for transporting the flowing exhaust gas, a source of nitrogen reducing agent, a zeolite catalyst disposed in the flow path of the exhaust gas and containing at least one transition metal, and a nitrogen reducing agent metered into the exhaust gas flowing upstream of the zeolite catalyst Wherein the zeolite catalyst is a small pore zeolite containing eight tetrahedral atoms of maximum ring size and the at least one transition metal is selected from the group consisting of Cr, Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga , Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir and Pt. 39. The exhaust system of claim 38, wherein the zeolite catalyst is coated on the flow-through substrate. Claim 38 or 39, wherein controlling method, measuring input means so that the zeolite catalyst is introduced metered into the desired efficiency or higher to discharge gas to flow only in a nitrogen reducing agent, if the NO _x reduction is whether determined whether to promote the catalyst when used in Wherein said means for determining comprises: 41. A method as claimed in claim 40, wherein the control means is adapted to control the flow rate of the exhaust gas, the catalytic phase temperature, the accelerator position, the mass flow rate of the exhaust gas in the system, the vacuum manifold, the ignition timing, the engine speed, The amount of fuel, and the position of the exhaust gas recirculation (EGR) valve and hence the amount of EGR and the boost pressure. 42. An exhaust system according to claim 41, wherein the control means controls the metering input of the nitrogen reducing agent in response to the amount of nitrogen oxides in the exhaust gas measured during use. Of claim 40 to claim 42 according to any one of, wherein the control means is, when using the 1: 1 NH ₃ / NO and 4: ₃ NH 3 / NO ₂ theoretically 60% to 200% of ammonia, a zeolite catalyst calculated at Wherein the nitrogen reducing agent is present in the exhaust gas entering the exhaust gas. 44. A discharge system according to any one of claims 40 to 43, wherein the control means comprises a pre-programming processor. 44. An exhaust system according to any one of claims 38 to 44, wherein an oxidation catalyst for oxidizing nitrogen monoxide to nitrogen dioxide is located upstream of the means for metering into the exhaust gas flowing through the nitrogen reducing agent. 46. The exhaust system of claim 45, wherein the oxidation catalyst comprises at least one platinum-based metal, and preferably comprises platinum. Claim 45 or according to 46 wherein the catalyst is by volume in the exhaust gas temperature 150 ℃ to 750 ℃ in the oxidation catalyst inlet, in use, about 4: 1 to about 1: 3, adapted to calculate the NO for NO ₂ ratio exhaust system. 50. The exhaust system according to any one of claims 38 to 47, wherein the filter substrate is positioned between the oxidation catalyst and the zeolite catalyst. An apparatus comprising a lean-burn engine for a vehicle and an exhaust system according to any one of claims 38 to 48. 50. The apparatus of claim 49, wherein the engine is a diesel engine, a lean-burn gasoline engine, or an engine driven by liquid petroleum gas or natural gas.

Images