EP3694643A1 - Active scr catalyst - Google Patents

Active scr catalyst

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Publication number
EP3694643A1
EP3694643A1 EP18773183.1A EP18773183A EP3694643A1 EP 3694643 A1 EP3694643 A1 EP 3694643A1 EP 18773183 A EP18773183 A EP 18773183A EP 3694643 A1 EP3694643 A1 EP 3694643A1
Authority
EP
European Patent Office
Prior art keywords
catalyst according
iron
catalyst
sodium
zeolite
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP18773183.1A
Other languages
German (de)
French (fr)
Inventor
Fei WEN
Nicola Soeger
Yvonne Demel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Umicore AG and Co KG
Original Assignee
Umicore AG and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Umicore AG and Co KG filed Critical Umicore AG and Co KG
Publication of EP3694643A1 publication Critical patent/EP3694643A1/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
    • B01J29/76—Iron group metals or copper
    • B01J29/7615—Zeolite Beta
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/42—Platinum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/613—10-100 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/615—100-500 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0246—Coatings comprising a zeolite
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/202—Alkali metals
    • B01D2255/2027—Sodium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20738—Iron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/50—Zeolites
    • B01D2255/502—Beta zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/915—Catalyst supported on particulate filters
    • B01D2255/9155—Wall flow filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/40—Nitrogen compounds
    • B01D2257/404—Nitrogen oxides other than dinitrogen oxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea

Definitions

  • the present invention relates to an SCR-active catalyst for
  • Exhaust gases from motor vehicles with a predominantly lean-burn internal combustion engine contain, in addition to particulate emissions, in particular the primary emissions carbon monoxide CO, hydrocarbons HC and
  • Nitrogen oxides NOx Due to the relatively high oxygen content of up to 15% by volume, carbon monoxide and hydrocarbons can be rendered relatively harmless by oxidation. The reduction of nitrogen oxides to nitrogen, however, is much more difficult.
  • One known method of removing nitrogen oxides from exhaust gases in the presence of oxygen is selective catalytic reduction (SCR) using ammonia on a suitable catalyst.
  • SCR selective catalytic reduction
  • the nitrogen oxides to be removed from the exhaust gas are reacted with ammonia to nitrogen and water.
  • the ammonia used as the reducing agent can be prepared by metering in an ammonia precursor compound, such as urea, ammonium carbamate or
  • Ammonium formate are made available in the exhaust system and subsequent hydrolysis.
  • zeolites As SCR catalysts, for example, certain metal-exchanged zeolites can be used. Zeolites are often divided into large, medium and small pore zeolites by the ring size of their largest pore openings. Large pore zeolites have a maximum ring size of 12 tetrahedrally coordinated atoms and medium pore zeolites one of 10. Small pore zeolites have a maximum ring size of 8.
  • SCR catalysts based on iron-exchanged ⁇ -zeolites ie one large pore zeolites of the structural type BEA, used.
  • WO02 / 41991 A2 discloses a heat treatment in the presence of water vapor. It should form alumina chains that are not part of the three-dimensional zeolite structure, but are still associated with this or even bound to them.
  • WO03 / 022430 A2 teaches to improve the hydrothermal stability of an Fe-.beta.-zeolite by increasing the Fe (OH) content in the catalyst.
  • the increase in the Fe (OH) content is to be achieved, inter alia, that the sodium content of the zeolite is brought to less than 500 ppm before the iron exchange.
  • Fe-.beta.-zeolites are hydrothermally stable if, contrary to the teaching of WO03 / 022430 A2, they contain a certain amount of sodium which is 500 ppm or higher.
  • the present invention relates to an iron-containing zeolite of the structural type BEA, which is characterized in that it contains sodium in an amount of 0.05 to 1 wt .-%, based on the iron-exchanged zeolites and calculated as sodium metal.
  • the catalyst of the invention may contain iron in various forms. In particular, it is present in ion-exchanged form. This means that by formal replacement of Si 4+ - by Al 3+ ions in the Zeolite skeleton negative charge is neutralized by means of a corresponding amount of iron cations.
  • the iron may also be partially present as iron metal and / or as iron oxide in the zeolite structure and / or on the surface of the zeolite structure.
  • Zeolites of structural type BEA are known in the art and can be purchased on the market.
  • the products known by the name "Beta” or " ⁇ ” find many uses, i.a. also for the production of catalysts for the selective reduction of nitrogen oxides from the exhaust gas of internal combustion engines with ammonia.
  • iron or containing iron zeolites of the structural type BEA can be purchased. Alternatively, however, they can also be obtained by aqueous ion exchange or solid-state ion exchange according to methods known per se.
  • the iron-containing zeolite of the structural type BEA according to the invention has an iron content of 1 to 10% by weight, preferably 3 to 6% by weight, based on the iron-containing zeolite and calculated as
  • the zeolite of the structure type BEA has, in particular, a SAR (silica-to-alumina molar ratio) of from 1 to 50, preferably from 5 to 35. Particularly preferred SAR values are 5 to 15, most preferred SAR values are 7 to 12
  • the content of sodium is according to the invention at 0.05 to 1 wt .-%, based on the iron-containing zeolites and calculated as
  • the sodium metal is especially in
  • ion-exchanged form may also be present in part as sodium oxide in the zeolite structure and / or on the surface of the zeolite structure.
  • the iron-containing structure-type zeolites BEA according to the invention can be prepared, for example, in a simple manner and in a manner known per se, that the zeolite in a first step with an iron compound, for example a water-soluble iron compound and in a second step with a sodium compound, for example a water-soluble sodium compound , is offset.
  • an iron compound for example a water-soluble iron compound
  • a sodium compound for example a water-soluble sodium compound
  • iron (III) nitrate has proved to be suitable as the iron compound, while, for example, sodium nitrate, sodium sulfate, sodium chloride, sodium acetate or sodium formate are suitable as the sodium compound.
  • the zeolite may also in the first step with a water-soluble sodium compound and in the second step with a water-soluble
  • Carrier substrates may be so-called flow-through substrates or wall-flow filters. Both can be made of inert materials, for example of silicon carbide,
  • Aluminum titanate or cordierite Such carrier substrates are known to the person skilled in the art and are available on the market.
  • the application of the catalyst according to the invention to the carrier substrate can be carried out by methods familiar to the person skilled in the art, for example by the customary dip coating methods or pumping and suction coating methods followed by thermal aftertreatment (calcination).
  • Inventive catalyst can be coordinated so that the resulting coating on the porous walls, the forming the channels of the wall flow filter lie (on-wall coating). But are preferred average pore size and medium
  • Particle size of the catalyst according to the invention be small enough to penetrate into the pores of the wall flow filter.
  • it is itself present as part of a carrier substrate, that is, for example, a flow-through substrate or also a wall-flow filter.
  • these carrier substrates contain a matrix component. As matrix components, all else to
  • catalyst substrates used in inert materials used so for example, silicates, oxides, nitrides or carbides.
  • catalytically active carrier substrates for example, a mixture of, for example, 10 to 95% by weight of inert matrix component and 5 to 90% by weight of catalytically active material is extruded by methods known per se.
  • support substrates constructed of corrugated sheets of inert materials may also be used.
  • Suitable inert materials are for example fibrous materials with a
  • fibrous materials are heat-resistant and consist of silicon dioxide, in particular of glass fibers.
  • sheets of said fiber materials are corrugated in a known manner, and the individual corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the individual corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the individual corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the individual corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the individual corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the individual corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body.
  • the corrugated sheets are formed
  • Substrates of corrugated sheets can be coated directly with the catalyst according to the invention, but preferably they are first coated with an inert material, for example titanium dioxide, and only then with the catalytic material.
  • an inert material for example titanium dioxide
  • the catalyst according to the invention can advantageously be used for purifying exhaust gas from lean-burn internal combustion engines, in particular diesel engines. It converts nitrogen oxides contained in the exhaust gas into the harmless compounds nitrogen and water.
  • the present invention accordingly also relates to a method for
  • the reducing agent used in the process according to the invention is preferably ammonia.
  • the required ammonia can be formed for example in the exhaust system upstream of the particle filter according to the invention, for example by means of an upstream nitrogen oxide storage catalyst (Jean NOx trap - LNT). This process is known as "passive SCR.”
  • ammonia can also be carried in suitable form, such as urea, ammonium carbamate, or ammonium formate, and added to the exhaust gas stream as needed metered into the catalyst according to the invention via an injector on the inflow side.
  • the present invention thus also relates to a system for purifying exhaust gas from lean-burn internal combustion engines, which is characterized in that it comprises a catalyst according to the invention, preferably in the form of a coating on a carrier substrate or as part of a carrier substrate, and an injector for aqueous
  • the present invention thus also relates to a system for purifying exhaust gas of lean-burn internal combustion engines, which is characterized in that it comprises an oxidation catalyst, an injector for aqueous urea solution and a catalyst according to the invention, preferably in the form of a coating on a carrier substrate or as part of a carrier substrate , having.
  • the oxidation catalyst used is platinum on a support material.
  • Suitable carrier material for the platinum are all those skilled in the art for this purpose materials into consideration. They have a BET surface area of from 30 to 250 m 2 / g, preferably from 100 to 200 m 2 / g (determined to DIN 66132) and are in particular aluminum oxide, silicon oxide,
  • the system according to the invention is used such that an oxidation catalyst, then an aqueous urea solution injector and finally a catalyst according to the invention are arranged in the flow direction of the exhaust gas.
  • the oxidation catalyst is typically as
  • Carrier substrates can be any suitable carrier substrate before.
  • Flow-through substrates or wall flow filter Flow-through substrates or wall flow filter.
  • the catalyst according to the invention surprisingly has advantages compared to iron-containing zeolites of the structural type BEA, which contain a lower or a higher amount of sodium.
  • FIG. 1 shows the SCR activity from K1 to K4 and also VK1 and VK2 in a hydrothermally aged state (100 hours at 550 ° C.)
  • a commercially available zeolite of the structural type BEA with a SAR of 10 is mixed in water with an amount of Fe (NÜ3) 3, the one
  • Iron content of 4.5 wt .-% (based on the iron-containing zeolite and calculated as Fe 2 03) corresponds, and stirred overnight. Then, sodium nitrate is added in an amount corresponding to 0.5% by weight (based on the iron-containing zeolite and calculated as Na metal) and stirred for 30 minutes.
  • the suspension thus obtained is used directly as a coating suspension (washcoat) for coating a commercially available flow-through substrate made of cordierite.
  • the resulting catalyst (hereinafter referred to as Kl) is dried at 90 ° C, then calcined stepwise at 350 ° C and at 550 ° C in air.
  • Example 1 is repeated with the difference that the amount of sodium nitrate is such that a loading with sodium of 1 wt .-% results.
  • the catalyst thus obtained is hereinafter referred to as K2.
  • Example 1 is repeated with the difference that the amount of sodium nitrate is such that a loading with sodium of 0.1 wt .-% results.
  • the catalyst thus obtained is hereinafter referred to as K3.
  • Example 1 is repeated with the difference that the amount of sodium nitrate is such that a loading with sodium of 0.2 wt .-% results.
  • the catalyst thus obtained is hereinafter referred to as K4.
  • Example 1 is repeated with the difference that the amount of
  • Example 1 is repeated with the difference that the addition of sodium nitrate is dispensed with.
  • the loading of sodium is thus 0 wt .-%.
  • the catalyst thus obtained is hereinafter referred to as VK2.
  • VKl shows the worst overall NOx conversion over the entire temperature range.
  • VK2 is almost equivalent to the catalysts Kl to K4 at higher temperatures, it shows an equally low NOx conversion at lower temperatures than VKl.
  • the catalysts of the invention Kl to K4 significantly better results, especially at low temperatures. This is especially true for Kl and K2 (sodium contents of 0.5 and 1 wt .-%, respectively).

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Catalysts (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

The invention relates to a catalyst containing a BEA-type zeolite which contains iron as well as 0.05 to 1 percent by weight of sodium, the weight percentage being relative to the iron-exchanged zeolite and being calculated as metallic sodium.

Description

SCR-aktiver Katalysator  SCR active catalyst
Die vorliegende Erfindung betrifft einen SCR-aktiven Katalysator zur The present invention relates to an SCR-active catalyst for
Verminderung von Stickoxiden im Abgas von Verbrennungsmotoren. Reduction of nitrogen oxides in the exhaust gas of internal combustion engines.
Abgase von Kraftfahrzeugen mit einem überwiegend mager betriebenen Verbrennungsmotor enthalten neben Partikelemissionen insbesondere die Primäremissionen Kohlenmonoxid CO, Kohlenwasserstoffe HC und Exhaust gases from motor vehicles with a predominantly lean-burn internal combustion engine contain, in addition to particulate emissions, in particular the primary emissions carbon monoxide CO, hydrocarbons HC and
Stickoxide NOx. Aufgrund des relativ hohen Sauerstoffgehaltes von bis zu 15 Vol.-% können Kohlenmonoxid und Kohlenwasserstoffe durch Oxidation relativ leicht unschädlich gemacht werden. Die Reduktion der Stickoxide zu Stickstoff gestaltet sich jedoch wesentlich schwieriger. Nitrogen oxides NOx. Due to the relatively high oxygen content of up to 15% by volume, carbon monoxide and hydrocarbons can be rendered relatively harmless by oxidation. The reduction of nitrogen oxides to nitrogen, however, is much more difficult.
Ein bekanntes Verfahren zur Entfernung von Stickoxiden aus Abgasen in Gegenwart von Sauerstoff ist die selektive katalytische Reduktion (SCR-Ver- fahren) mittels Ammoniak an einem geeigneten Katalysator. Bei diesem Verfahren werden die aus dem Abgas zu entfernenden Stickoxide mit Ammoniak zu Stickstoff und Wasser umgesetzt. Der als Reduktionsmittel verwendete Ammoniak kann durch Eindosieren einer Ammoniakvorläufer- Verbindung, wie beispielsweise Harnstoff, Ammoniumcarbamat oder One known method of removing nitrogen oxides from exhaust gases in the presence of oxygen is selective catalytic reduction (SCR) using ammonia on a suitable catalyst. In this method, the nitrogen oxides to be removed from the exhaust gas are reacted with ammonia to nitrogen and water. The ammonia used as the reducing agent can be prepared by metering in an ammonia precursor compound, such as urea, ammonium carbamate or
Ammoniumformiat, in den Abgasstrang und anschließende Hydrolyse verfügbar gemacht werden . Ammonium formate, are made available in the exhaust system and subsequent hydrolysis.
Als SCR-Katalysatoren können beispielsweise bestimmte Metall-ausge- tauschte Zeolithe verwendet werden. Zeolithe werden oftmals nach der Ringgröße ihrer größten Porenöffnungen in groß-, mittel- und kleinporige Zeolithe unterteilt. Großporige Zeolithe weisen eine maximale Ringgröße von 12 tetraedrisch koordinierten Atomen und mittelporige Zeolithe eine solche von 10 auf. Kleinporige Zeolithe weisen eine maximale Ringgröße von 8 auf. As SCR catalysts, for example, certain metal-exchanged zeolites can be used. Zeolites are often divided into large, medium and small pore zeolites by the ring size of their largest pore openings. Large pore zeolites have a maximum ring size of 12 tetrahedrally coordinated atoms and medium pore zeolites one of 10. Small pore zeolites have a maximum ring size of 8.
Im Bereich Schwerlastkraftwagen werden in großem Umfang SCR- Katalysatoren auf Basis von Eisen-ausgetauschten ß-Zeolithen, also eines großporigen Zeolithen des Strukturtyps BEA, verwendet. Bei diesen In the area of heavy goods vehicles, SCR catalysts based on iron-exchanged β-zeolites, ie one large pore zeolites of the structural type BEA, used. In these
Produkten wird allerdings mit zunehmender Einsatzdauer eine relativ stark ausgeprägte Agglomerierung von Eisenteilchen, sowie eine Dealuminierung der Zeolith-Struktur beobachtet. Eine schnelle Schädigung eines Fe- ß- Systems erfolgt schon bei relativ milden Bedingungen von < 650°, die zum Beispiel im Schwerlastbereich bei der passiven Ruß-Regeneration auftreten. Products, however, a relatively pronounced agglomeration of iron particles, as well as a dealumination of the zeolite structure is observed with increasing duration of use. Rapid damage to an Fe-ß system takes place even at relatively mild conditions of <650 °, which occur, for example, in the heavy-duty range in passive soot regeneration.
Es hat deshalb nicht an Versuchen gefehlt Fe-ß-Produkte zu stabilisieren. So offenbart die WO02/41991 A2 eine Hitzebehandlung in Gegenwart von Wasserdampf. Dabei sollen sich Aluminiumoxid-Ketten bilden, die nicht Teil der dreidimensionalen Zeolithstruktur sind, aber dennoch mit dieser assoziiert oder sogar an diese gebunden sind. There has therefore been no lack of attempts to stabilize Fe-ß products. Thus, WO02 / 41991 A2 discloses a heat treatment in the presence of water vapor. It should form alumina chains that are not part of the three-dimensional zeolite structure, but are still associated with this or even bound to them.
Die WO03/022430 A2 lehrt, die hydrothermale Stabilität eines Fe- ß- Zeolithen durch Erhöhung des Fe(OH)-Gehaltes im Katalysator zu ver- bessern. Die Erhöhung des Fe(OH)-Gehaltes soll unter anderem dadurch gelingen, dass der Natrium-Gehalt des Zeolithen vor dem Eisen-Austausch auf weniger als 500 ppm gebracht wird .  WO03 / 022430 A2 teaches to improve the hydrothermal stability of an Fe-.beta.-zeolite by increasing the Fe (OH) content in the catalyst. The increase in the Fe (OH) content is to be achieved, inter alia, that the sodium content of the zeolite is brought to less than 500 ppm before the iron exchange.
Trotz all dieser Versuche besteht weiterhin Bedarf nach hydrothermal stabilen Fe-ß-Zeolithen. Despite all these attempts, there is still a need for hydrothermally stable Fe-.beta.-zeolites.
Es wurde nun überraschend gefunden, dass Fe-ß-Zeolithe hydrothermal stabil sind, wenn sie entgegen der Lehre der WO03/022430 A2 eine bestimmte Menge an Natrium enthalten, die 500ppm oder höher ist. It has now surprisingly been found that Fe-.beta.-zeolites are hydrothermally stable if, contrary to the teaching of WO03 / 022430 A2, they contain a certain amount of sodium which is 500 ppm or higher.
Die vorliegende Erfindung betrifft demnach einen Eisen enthaltenden Zeolithen vom Strukturtyp BEA, der dadurch gekennzeichnet ist, dass er Natrium in einer Menge von 0,05 bis 1 Gew.-%, bezogen auf den mit Eisen ausgetauschten Zeolithen und berechnet als Natriummetall enthält. Accordingly, the present invention relates to an iron-containing zeolite of the structural type BEA, which is characterized in that it contains sodium in an amount of 0.05 to 1 wt .-%, based on the iron-exchanged zeolites and calculated as sodium metal.
Der erfindungsgemäße Katalysator kann Eisen in verschiedener Form enthalten. Insbesondere liegt es in ionenausgetauschter Form vor. Dies bedeutet, dass die durch formalen Ersatz von Si4+- durch AI3+-Ionen im Zeolith-Gerüst entstandene negative Ladung mittels einer entsprechenden Menge an Eisen-Kationen neutralisiert wird . Daneben kann das Eisen aber auch teilweise als Eisenmetall und/oder als Eisenoxid in der Zeolith-Struktur und/oder auf der Oberfläche der Zeolith-Struktur vorliegen. The catalyst of the invention may contain iron in various forms. In particular, it is present in ion-exchanged form. This means that by formal replacement of Si 4+ - by Al 3+ ions in the Zeolite skeleton negative charge is neutralized by means of a corresponding amount of iron cations. In addition, however, the iron may also be partially present as iron metal and / or as iron oxide in the zeolite structure and / or on the surface of the zeolite structure.
Zeolithe vom Strukturtyp BEA sind dem Fachmann bekannt und können am Markt erworben werden. Insbesondere finden die unter der Bezeichnung „Beta" oder„ß" bekannten Produkte vielfache Verwendung, u.a. auch für die Herstellung von Katalysatoren zur selektiven Reduktion von Stickoxiden aus dem Abgas von Verbrennungsmotoren mit Ammoniak. Zeolites of structural type BEA are known in the art and can be purchased on the market. In particular, the products known by the name "Beta" or "β" find many uses, i.a. also for the production of catalysts for the selective reduction of nitrogen oxides from the exhaust gas of internal combustion engines with ammonia.
Auch bereits mit Eisen ausgetauschte bzw. Eisen enthaltende Zeolithe vom Strukturtyp BEA können käuflich erworben werden. Alternativ können sie aber auch etwa durch wässrigen Ionenaustausch oder Festkörperionenaustausch nach an sich bekannten Methoden erhalten werden.  Also already exchanged with iron or containing iron zeolites of the structural type BEA can be purchased. Alternatively, however, they can also be obtained by aqueous ion exchange or solid-state ion exchange according to methods known per se.
Der erfindungsgemäße, Eisen enthaltende Zeolith vom Strukturtyp BEA weist insbesondere einen Eisengehalt von 1 bis 10 Gew.-%, bevorzugt 3 bis 6 Gew.-%, bezogen auf den Eisen enthaltenden Zeolithen und berechnet als In particular, the iron-containing zeolite of the structural type BEA according to the invention has an iron content of 1 to 10% by weight, preferably 3 to 6% by weight, based on the iron-containing zeolite and calculated as
Der Zeolith vom Strukturtyp BEA weist erfindungsgemäß insbesondere einen SAR (silica-to-alumina molar ratio) von 1 bis 50, bevorzugt 5 bis 35 auf. Besonders bevorzugte SAR-Werte sind 5 bis 15, ganz besonders bevorzugte SAR-Werte sind 7 bis 12 According to the invention, the zeolite of the structure type BEA has, in particular, a SAR (silica-to-alumina molar ratio) of from 1 to 50, preferably from 5 to 35. Particularly preferred SAR values are 5 to 15, most preferred SAR values are 7 to 12
Der Gehalt an Natrium liegt erfindungsgemäß bei 0,05 bis 1 Gew.-%, bezogen auf den Eisen enthaltenden Zeolithen und berechnet als The content of sodium is according to the invention at 0.05 to 1 wt .-%, based on the iron-containing zeolites and calculated as
Natriummetall. Es hat sich herausgestellt, dass ein Gehalt von mehr als 1 Gew.-% die Agglomerierung von Eisen im Zeolithen extrem fördert und somit vermieden werden sollte. Bevorzugt liegt der Natriumgehalt bei 0,1 bis 1 Gew.-%, besonders bevorzugt bei 0,5 bis 1 Gew.-%. Wie für Eisen oben beschrieben liegt das Natrium insbesondere in Sodium metal. It has been found that a content of more than 1 wt .-% extremely promotes the agglomeration of iron in the zeolite and should therefore be avoided. The sodium content is preferably from 0.1 to 1% by weight, more preferably from 0.5 to 1% by weight. As described for iron above, the sodium is especially in
ionenausgetauschter Form vor. Es kann aber auch teilweise als Natriumoxid in der Zeolith-Struktur und/oder auf der Oberfläche der Zeolith-Struktur vorliegen. ion-exchanged form. However, it may also be present in part as sodium oxide in the zeolite structure and / or on the surface of the zeolite structure.
Die erfindungsgemäßen Eisen enthaltende Zeolithe vom Strukturtyp BEA können beispielsweise in einfacher und in an sich bekannter Weise dadurch hergestellt werden, dass der Zeolith in einem ersten Schritt mit einer Eisenverbindung, beispielsweise einer wasserlöslichen Eisenverbindung und in einem zweiten Schritt mit einer Natriumverbindung, beispielsweise einer wasserlöslichen Natriumverbindung, versetzt wird. The iron-containing structure-type zeolites BEA according to the invention can be prepared, for example, in a simple manner and in a manner known per se, that the zeolite in a first step with an iron compound, for example a water-soluble iron compound and in a second step with a sodium compound, for example a water-soluble sodium compound , is offset.
Als Eisenverbindung hat sich insbesondere Eisen(III)nitrat bewährt, während als Natriumverbindung beispielsweise Natriumnitrat, Natriumsulfat, Natriumchlorid, Natriumacetat oder Natriumformiat in Betracht kommen. Alternativ kann der Zeolith auch im ersten Schritt mit einer wasserlöslichen Natrium-Verbindung und im zweiten Schritt mit einer wasserlöslichen In particular iron (III) nitrate has proved to be suitable as the iron compound, while, for example, sodium nitrate, sodium sulfate, sodium chloride, sodium acetate or sodium formate are suitable as the sodium compound. Alternatively, the zeolite may also in the first step with a water-soluble sodium compound and in the second step with a water-soluble
Eisenverbindung versetzt werden. Iron compound are added.
In Ausführungsformen des erfindungsgemäßen Katalysators liegt er in Form einer Beschichtung auf einem Trägersubstrat vor. Trägersubstrate können sogenannte Durchflusssubstrate oder auch Wandflussfilter sein. Beide können aus inerten Materialien, beispielsweise aus Silicium-Carbid, In embodiments of the catalyst according to the invention, it is in the form of a coating on a carrier substrate. Carrier substrates may be so-called flow-through substrates or wall-flow filters. Both can be made of inert materials, for example of silicon carbide,
Aluminium-Titanat oder Cordierit, bestehen. Solche Trägersubstrate sind dem Fachmann bekannt und am Markt erhältlich. Aluminum titanate or cordierite. Such carrier substrates are known to the person skilled in the art and are available on the market.
Das Aufbringen des erfindungsgemäßen Katalysators auf das Trägersubstrat kann nach dem Fachmann geläufigen Methoden erfolgen, so etwa nach den üblichen Tauchbeschichtungsverfahren bzw. Pump- und Saug- Beschichtungs-verfahren mit sich anschließender thermischer Nachbehandlung (Kalzination). The application of the catalyst according to the invention to the carrier substrate can be carried out by methods familiar to the person skilled in the art, for example by the customary dip coating methods or pumping and suction coating methods followed by thermal aftertreatment (calcination).
Dem Fachmann ist bekannt, dass im Falle von Wandflussfiltern dessen durchschnittliche Porengröße und die mittlere Teilchengröße des The expert is known that in the case of wall flow filters whose average pore size and the average particle size of
erfindungsgemäßen Katalysators so aufeinander abgestimmt werden können, dass die resultierende Beschichtung auf den porösen Wänden, die die Kanäle des Wandflussfilters bilden, liegen (auf-Wand-Beschichtung). Bevorzugt werden aber durchschnittliche Porengröße und mittlere Inventive catalyst can be coordinated so that the resulting coating on the porous walls, the forming the channels of the wall flow filter lie (on-wall coating). But are preferred average pore size and medium
Teilchengröße so aufeinander abgestimmt, dass sich der erfindungsgemäße Katalysator in den porösen Wänden, die die Kanäle des Wandflussfilters bilden, befinden, dass also eine Beschichtung der inneren Porenoberflächen erfolgt (in-Wand-Beschichtung). In diesem Fall muss die mittlere Particle size coordinated so that the catalyst according to the invention are in the porous walls that form the channels of the wall flow filter, so that a coating of the inner pore surfaces takes place (in-wall coating). In this case, the middle one must
Teilchengröße des erfindungsgemäßen Katalysators klein genug sein, um in die Poren des Wandflussfilters einzudringen. In anderen Ausführungsformen des erfindungsgemäßen Katalysators liegt er selbst als Bestandteil eines Trägersubstrates vor, also zum Beispiel eines Durchflusssubstrates oder auch Wandflussfilters. Neben dem erfindungsgemäßen Katalysator enthalten diese Trägersubstrate eine Matrixkomponente. Als Matrixkomponenten können alle auch sonst zur Particle size of the catalyst according to the invention be small enough to penetrate into the pores of the wall flow filter. In other embodiments of the catalyst according to the invention, it is itself present as part of a carrier substrate, that is, for example, a flow-through substrate or also a wall-flow filter. In addition to the catalyst according to the invention, these carrier substrates contain a matrix component. As matrix components, all else to
Herstellung von Katalysatorsubstraten verwendeten inerten Materialien verwendet werden, also beispielsweise Silikate, Oxide, Nitride oder Carbide. Manufacture of catalyst substrates used in inert materials used, so for example, silicates, oxides, nitrides or carbides.
Zur Herstellung katalytisch aktiver Trägersubstrate wird zum Beispiel eine Mischung aus beispielsweise 10 bis 95 Gew.-% inerter Matrixkomponente und 5 bis 90 Gew.-% katalytisch aktiven Materials nach an sich bekannten Verfahren extrudiert. For the preparation of catalytically active carrier substrates, for example, a mixture of, for example, 10 to 95% by weight of inert matrix component and 5 to 90% by weight of catalytically active material is extruded by methods known per se.
Alternativ können auch Trägersubstrate verwendet werden, die aus gewellten Blättern aus inerten Materialien aufgebaut sind . Geeignete inerte Materialien sind zum Beispiel faserförmige Materialien mit einem Alternatively, support substrates constructed of corrugated sheets of inert materials may also be used. Suitable inert materials are for example fibrous materials with a
durchschnittlichen Faserdurchmesser von 50 bis 250 pm und einer durchschnittlichen Faserlänge von 2 bis 30 mm. Bevorzugt sind average fiber diameter of 50 to 250 pm and an average fiber length of 2 to 30 mm. Preferred are
faserförmige Materialien hitzebeständig und bestehen aus Siliziumdioxid, insbesondere aus Glasfasern. fibrous materials are heat-resistant and consist of silicon dioxide, in particular of glass fibers.
Zur Herstellung solcher Trägersubstrate werden zum Bespiel Blätter aus den genannten Fasermaterialien in bekannter weise gewellt und die einzelnen gewellten Blätter zu einem zylindrischen monolithisch strukturierten Körper mit den Körper durchziehenden Kanälen geformt. Vorzugsweise wird durch Aufschichten einer Anzahl der gewellten Blätter zu parallelen Schichten mit unterschiedlicher Orientierung der Wellung zwischen den Schichten ein monolithisch strukturierter Körper mit einer kreuzweisen Wellungsstruktur geformt. In einer Ausführungsform können zwischen den gewellten Blättern ungewellte, d .h. flache Blätter angeordnet sein. To produce such carrier substrates, for example, sheets of said fiber materials are corrugated in a known manner, and the individual corrugated sheets are formed into a cylindrical monolithically structured body with channels passing through the body. Preferably is through Laying a number of the corrugated sheets into parallel layers with different orientation of the corrugation between the layers formed a monolithic structured body having a criss-cross corrugation structure. In one embodiment, undulating, i.e. be arranged flat leaves.
Substrate aus gewellten Blättern können direkt mit dem erfindungsgemäßen Katalysator beschichtet werden, vorzugsweise werden sie aber zunächst mit einem inerten Material, zum Beispiel Titandioxid, und erst dann mit dem katalytischen Material beschichtet.  Substrates of corrugated sheets can be coated directly with the catalyst according to the invention, but preferably they are first coated with an inert material, for example titanium dioxide, and only then with the catalytic material.
Der erfindungsgemäße Katalysator kann mit Vorteil zur Reinigung von Abgas von mager betriebenen Verbrennungsmotoren, insbesondere von Dieselmotoren, verwendet werden. Er setzt im Abgas enthaltene Stickoxide in die unschädlichen Verbindungen Stickstoff und Wasser um. The catalyst according to the invention can advantageously be used for purifying exhaust gas from lean-burn internal combustion engines, in particular diesel engines. It converts nitrogen oxides contained in the exhaust gas into the harmless compounds nitrogen and water.
Die vorliegende Erfindung betrifft demnach auch ein Verfahren zur The present invention accordingly also relates to a method for
Reinigung von Abgas von mager betriebenen Verbrennungsmotoren, das dadurch gekennzeichnet ist, dass das Abgas über einen erfindungsgemäßen Katalysator geleitet wird . Purification of exhaust gas from lean-burn internal combustion engines, which is characterized in that the exhaust gas is passed over a catalyst according to the invention.
Als Reduktionsmittel wird bei dem erfindungsgemäßen Verfahren bevorzugt Ammoniak verwendet. Der benötigte Ammoniak kann beispielsweise im Abgassystem anströmseitig zum erfindungsgemäßen Partikelfilter etwa mittels eines anströmseitigen Stickoxidspeicherkatalysators (Jean NOx trap - LNT) gebildet werden. Dieses Verfahren ist als„passive SCR" bekannt. Ammoniak kann aber auch in geeigneter Form, wie zum Beispiel in Form von Harnstoff, Ammoniumcarbamat oder Ammoniumformiat, mitgeführt und bei Bedarf dem Abgasstrom zugegeben werden. Es ist weit verbreitet, wässrige Harnstofflösung mitzuführen und diese bedarfsgerecht über einen Injektor anströmseitig in den erfindungsgemäßen Katalysator einzu- dosieren. Die vorliegende Erfindung betrifft somit auch ein System zur Reinigung von Abgas von mager betriebenen Verbrennungsmotoren, das dadurch gekennzeichnet ist, dass es einen erfindungsgemäßen Katalysator, bevorzugt in Form einer Beschichtung auf einem Trägersubstrat oder als Bestandteil eines Trägersubstrats, sowie einen Injektor für wässrige The reducing agent used in the process according to the invention is preferably ammonia. The required ammonia can be formed for example in the exhaust system upstream of the particle filter according to the invention, for example by means of an upstream nitrogen oxide storage catalyst (Jean NOx trap - LNT). This process is known as "passive SCR." However, ammonia can also be carried in suitable form, such as urea, ammonium carbamate, or ammonium formate, and added to the exhaust gas stream as needed metered into the catalyst according to the invention via an injector on the inflow side. The present invention thus also relates to a system for purifying exhaust gas from lean-burn internal combustion engines, which is characterized in that it comprises a catalyst according to the invention, preferably in the form of a coating on a carrier substrate or as part of a carrier substrate, and an injector for aqueous
Harnstofflösung umfasst, wobei sich der Injektor vor dem erfindungsgemäßen Katalysator befindet. Contains urea solution, wherein the injector is in front of the catalyst of the invention.
Beispielsweise aus SAE-2001-01-3625 ist bekannt, dass die SCR-Reaktion mit Ammoniak schneller verläuft, wenn die Stickoxide in einer 1 : 1 Mischung aus Stickstoffmonoxid und Stickstoffdioxid vorliegen oder jedenfalls diesem Verhältnis nahekommen. Da das Abgas von mager betriebenen For example, from SAE-2001-01-3625 it is known that the SCR reaction with ammonia is faster if the nitrogen oxides are present in a 1: 1 mixture of nitrogen monoxide and nitrogen dioxide or at least approximate this ratio. Because the exhaust gas is operated by lean
Verbrennungsmotoren in der Regel einen Überschuss von Stickstoffmonoxid gegenüber Stickstoffdioxid aufweist, schlägt das Dokument vor, den Anteil an Stickstoffdioxid mit Hilfe eines Oxidationskatalysators zu erhöhen. Internal combustion engines usually has an excess of nitrogen monoxide over nitrogen dioxide, the document proposes to increase the proportion of nitrogen dioxide with the aid of an oxidation catalyst.
Die vorliegende Erfindung betrifft somit auch ein System zur Reinigung von Abgas von mager betriebenen Verbrennungsmotoren, das dadurch gekennzeichnet ist, dass es einen Oxidationskatalysator, einen Injektor für wässrige Harnstofflösung und einen erfindungsgemäßen Katalysator, bevorzugt in Form einer Beschichtung auf einem Trägersubstrat oder als Bestandteil eines Trägersubstrats, aufweist. The present invention thus also relates to a system for purifying exhaust gas of lean-burn internal combustion engines, which is characterized in that it comprises an oxidation catalyst, an injector for aqueous urea solution and a catalyst according to the invention, preferably in the form of a coating on a carrier substrate or as part of a carrier substrate , having.
In Ausführungsformen der vorliegenden Erfindung wird als Oxidations- katalysator Platin auf einem Trägermaterial verwendet. In embodiments of the present invention, the oxidation catalyst used is platinum on a support material.
Als Trägermaterial für das Platin kommen alle dem Fachmann für diesen Zweck geläufigen Materialien in Betracht. Sie weisen eine BET-Oberfläche von 30 bis 250 m2/g, bevorzugt von 100 bis 200 m2/g auf (bestimmt nach DIN 66132) und sind insbesondere Aluminiumoxid, Siliziumoxid, Suitable carrier material for the platinum are all those skilled in the art for this purpose materials into consideration. They have a BET surface area of from 30 to 250 m 2 / g, preferably from 100 to 200 m 2 / g (determined to DIN 66132) and are in particular aluminum oxide, silicon oxide,
Magnesiumoxid, Titanoxid, Zirkonoxid, Ceroxid sowie Mischungen oder Mischoxide aus mindestens zwei dieser Oxide. Bevorzugt sind Aluminiumoxid und Aluminium/Silizium- Mischoxide. Sofern Aluminiumoxid verwendet wird, so ist es besonders bevorzugt stabilisiert, beispielsweise mit Lanthanoxid. Das erfindungsgemäße System wird so verwendet, dass in Strömungsrichtung des Abgases ein Oxidationskatalysator, dann ein Injektor für wässrige Harnstofflösung und schließlich ein erfindungsgemäßer Katalysator angeordnet sind . Der Oxidationskatalystor liegt typischerweise als Magnesium oxide, titanium oxide, zirconium oxide, cerium oxide and mixtures or mixed oxides of at least two of these oxides. Preference is given to aluminum oxide and aluminum / silicon mixed oxides. If alumina is used, it is particularly preferably stabilized, for example with lanthanum oxide. The system according to the invention is used such that an oxidation catalyst, then an aqueous urea solution injector and finally a catalyst according to the invention are arranged in the flow direction of the exhaust gas. The oxidation catalyst is typically as
Beschichtung auf einem Trägersubstrat vor. Trägersubstrate können Coating on a carrier substrate before. Carrier substrates can
Durchflusssubstrate oder auch Wandflussfilter sein. Flow-through substrates or wall flow filter.
Der erfindungsgemäße Katalysator weist in überraschender Weise Vorteile im Vergleich zu Eisen enthaltenden Zeolithen vom Strukturtyp BEA auf, die eine geringere oder eine höhere Menge an Natrium enthalten. The catalyst according to the invention surprisingly has advantages compared to iron-containing zeolites of the structural type BEA, which contain a lower or a higher amount of sodium.
Die Erfindung wird in den nachstehenden Beispielen und Figuren näher erläutert. The invention is explained in more detail in the following examples and figures.
Figur 1 zeigt die SCR-Aktivität von Kl bis K4, sowie VK1 und VK2 in hydrothermal gealtertem Zustand (100 Stunden bei 550°C) FIG. 1 shows the SCR activity from K1 to K4 and also VK1 and VK2 in a hydrothermally aged state (100 hours at 550 ° C.)
Beispiel 1 example 1
Ein handelsüblicher Zeolith des Strukturtyps BEA mit einem SAR von 10 wird in Wasser mit einer Menge an Fe( NÜ3)3 gemischt, die einem  A commercially available zeolite of the structural type BEA with a SAR of 10 is mixed in water with an amount of Fe (NÜ3) 3, the one
Eisengehalt von 4,5 Gew.-% (bezogen auf den Eisen enthaltenden Zeolithen und berechnet als Fe203) entspricht, und über Nacht gerührt. Anschließend wird mit Natriumnitrat in einer Menge, die 0,5 Gew.-% (bezogen auf den Eisen enthaltenden Zeolithen und berechnet als Na-Metall) entspricht, versetzt und für 30 Minuten gerührt. Die so erhaltene Suspension wird direkt als Beschichtungssuspension (Washcoat) zur Beschichtung eines handelsüblichen Durchflusssubstrates aus Cordierit verwendet. Der erhaltene Katalystor (nachstehend als Kl bezeichnet) wird bei 90°C getrocknet, danach schrittweise bei 350°C und bei 550°C in Luft kalziniert. Beispiel 2 Iron content of 4.5 wt .-% (based on the iron-containing zeolite and calculated as Fe 2 03) corresponds, and stirred overnight. Then, sodium nitrate is added in an amount corresponding to 0.5% by weight (based on the iron-containing zeolite and calculated as Na metal) and stirred for 30 minutes. The suspension thus obtained is used directly as a coating suspension (washcoat) for coating a commercially available flow-through substrate made of cordierite. The resulting catalyst (hereinafter referred to as Kl) is dried at 90 ° C, then calcined stepwise at 350 ° C and at 550 ° C in air. Example 2
Beispiel 1 wird wiederholt mit dem Unterschied, dass die Menge an Natriumnitrat so bemessen wird, dass eine Beladung mit Natrium von 1 Gew.-% resultiert. Der so erhaltene Katalysator wird nachstehend als K2 bezeichnet.  Example 1 is repeated with the difference that the amount of sodium nitrate is such that a loading with sodium of 1 wt .-% results. The catalyst thus obtained is hereinafter referred to as K2.
Beispiel 3 Example 3
Beispiel 1 wird wiederholt mit dem Unterschied, dass die Menge an Natriumnitrat so bemessen wird, dass eine Beladung mit Natrium von 0,1 Gew.-% resultiert. Der so erhaltene Katalysator wird nachstehend als K3 bezeichnet.  Example 1 is repeated with the difference that the amount of sodium nitrate is such that a loading with sodium of 0.1 wt .-% results. The catalyst thus obtained is hereinafter referred to as K3.
Beispiel 4 Example 4
Beispiel 1 wird wiederholt mit dem Unterschied, dass die Menge an Natriumnitrat so bemessen wird, dass eine Beladung mit Natrium von 0,2 Gew.-% resultiert. Der so erhaltene Katalysator wird nachstehend als K4 bezeichnet.  Example 1 is repeated with the difference that the amount of sodium nitrate is such that a loading with sodium of 0.2 wt .-% results. The catalyst thus obtained is hereinafter referred to as K4.
Vergleichsbeispiel 1 Comparative Example 1
Beispiel 1 wird wiederholt mit dem Unterschied, dass die Menge anExample 1 is repeated with the difference that the amount of
Natriumnitrat so bemessen wird, dass eine Beladung mit Natrium von 2 Gew.-% resultiert. Der so erhaltene Katalysator wird nachstehend als VKl bezeichnet. Vergleichsbeispiel 2 Sodium nitrate is such that a loading with sodium of 2 wt .-% results. The catalyst thus obtained is hereinafter referred to as VKl. Comparative Example 2
Beispiel 1 wird wiederholt mit dem Unterschied, dass auf die Zugabe von Natriumnitrat verzichtet wird . Die Beladung mit Natrium beträgt also 0 Gew.-%. Der so erhaltene Katalysator wird nachstehend als VK2 bezeichnet.  Example 1 is repeated with the difference that the addition of sodium nitrate is dispensed with. The loading of sodium is thus 0 wt .-%. The catalyst thus obtained is hereinafter referred to as VK2.
Vergleichsversuche a) Die Katalysatoren Kl bis K4, sowie VKl und VK2 wurden gealtert und dann verglichen. Die Alterung wurde bei 550°C in 10% H20 und 10% O2 in N2 für 100 Stunden durchgeführt. b) Die SCR-Aktivität der gealterten Katalysatoren Kl bis K4, sowie VKl und VK2 wurde in einer Labormodellgasanlage unter den in nachstehender Tabelle angegebenen Bedingungen getestet. Comparative tests a) The catalysts Kl to K4, as well as VKl and VK2 were aged and then compared. The aging was carried out at 550 ° C in 10% H 2 O and 10% O 2 in N 2 for 100 hours. b) The SCR activity of the aged catalysts Kl to K4, as well as VKl and VK2 was tested in a laboratory model gas plant under the conditions given in the table below.
Die Ergebnisse sind in Figur 1 gezeigt. The results are shown in FIG.
Demnach zeigt VKl insgesamt den schlechtesten NOx-Umsatz über den gesamten Temperaturbereich. VK2 ist zwar bei höheren Temperaturen nahezu gleichwertig mit den Katalysatoren Kl bis K4, zeigt aber bei niedrigeren Temperaturen einen ebenso schlechten NOx-Umsatz wie VKl . Dagegen weisen die erfindungsgemäßen Katalysatoren Kl bis K4 deutlich bessere Ergebnisse, insbesondere bei niedrigen Temperaturen auf. Dies gilt insbesondere für Kl und K2 (Natriumgehalte von 0,5 bzw. 1 Gew.-%).  Accordingly, VKl shows the worst overall NOx conversion over the entire temperature range. Although VK2 is almost equivalent to the catalysts Kl to K4 at higher temperatures, it shows an equally low NOx conversion at lower temperatures than VKl. In contrast, the catalysts of the invention Kl to K4 significantly better results, especially at low temperatures. This is especially true for Kl and K2 (sodium contents of 0.5 and 1 wt .-%, respectively).

Claims

Patentansprüche claims
1. Eisen enthaltender Zeolith vom Strukturtyp BEA, dadurch 1. zeolite containing zeolite of the structural type BEA, characterized
gekennzeichnet, dass er Natrium in einer Menge von 0,05 bis 1 Gew.-%, bezogen auf den mit Eisen ausgetauschten Zeolithen und berechnet als Natriummetall enthält. characterized in that it contains sodium in an amount of 0.05 to 1 wt .-%, based on the iron-exchanged zeolites and calculated as sodium metal.
2. Katalysator gemäß Anspruch 1, dadurch gekennzeichnet, dass der Eisengehalt 1 bis 10 Gew.-%, bezogen auf den Eisen enthaltenden 2. A catalyst according to claim 1, characterized in that the iron content of 1 to 10 wt .-%, based on the iron-containing
Zeolithen und berechnet als Fe203, beträgt. Zeolites and calculated as Fe 2 03, is.
3. Katalysator gemäß Anspruch 1 und/oder 2, dadurch gekennzeichnet, dass der Eisengehalt 3 bis 6 Gew.-%, bezogen auf den Eisen enthaltenden Zeolithen und berechnet als Fe2Ü3, beträgt. 3. A catalyst according to claim 1 and / or 2, characterized in that the iron content of 3 to 6 wt .-%, based on the iron-containing zeolites and calculated as Fe 2 Ü3, is.
4. Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass der Zeolithen vom Strukturtyp BEA einen SAR-Wert (silica-to-alumina molar ratio) von 1 bis 50 aufweist. 4. Catalyst according to one or more of claims 1 to 3, characterized in that the zeolite of the structure type BEA has a SAR value (silica-to-alumina molar ratio) of 1 to 50.
5. Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass der Zeolithen vom Strukturtyp BEA eine SAR-Wert (silica-to-alumina ratio) von 5 bis 35 aufweist. 5. Catalyst according to one or more of claims 1 to 4, characterized in that the zeolite of the structure type BEA has a SAR value (silica-to-alumina ratio) of 5 to 35.
6. Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass er einen Natriumgehalt von 0,1 bis 1 Gew.-%, aufweist. 6. Catalyst according to one or more of claims 1 to 5, characterized in that it has a sodium content of 0.1 to 1 wt .-%, comprising.
7. Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass er einen Natriumgehalt von 0,5 bis 1 Gew.-%, aufweist. 7. Catalyst according to one or more of claims 1 to 6, characterized in that it has a sodium content of 0.5 to 1 wt .-%, comprising.
8. Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass er in Form einer Beschichtung auf einem Trägersubstrat vorliegt. 8. Catalyst according to one or more of claims 1 to 7, characterized in that it is in the form of a coating on a carrier substrate.
9. Katalysator gemäß Anspruch 8, dadurch gekennzeichnet, dass das Trägersubstrat ein Durchflusssubstrat oder ein Wandflussfilter ist. 9. Catalyst according to claim 8, characterized in that the carrier substrate is a flow-through substrate or a wall-flow filter.
10. Katalysator gemäß Anspruch 8 und/oder 9, dadurch gekennzeichnet, dass das Trägersubstrat inert ist und aus Silicium-Carbid, Aluminium- Titanat oder Cordierit besteht. 10. A catalyst according to claim 8 and / or 9, characterized in that the carrier substrate is inert and consists of silicon carbide, aluminum titanate or cordierite.
11. Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass er als Bestandteil eines Trägersubstrats vorliegt. 11. A catalyst according to one or more of claims 1 to 7, characterized in that it is present as part of a carrier substrate.
12. Verfahren zur Reinigung von Abgas von mager betriebenen 12. A process for purifying exhaust gas from lean operated
Verbrennungsmotoren, dadurch gekennzeichnet, dass das Abgas über einen Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 11 geleitet wird . Internal combustion engines, characterized in that the exhaust gas is passed over a catalyst according to one or more of claims 1 to 11.
13. System zur Reinigung von Abgas von mager betriebenen Verbrennungsmotoren, dadurch gekennzeichnet, dass es einen Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 11, sowie einen Injektor für wässrige Harnstofflösung umfasst, wobei sich der Injektor vor dem Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 11 befindet. 13. A system for purifying exhaust gas from lean-burn internal combustion engines, characterized in that it comprises a catalyst according to one or more of claims 1 to 11, and an injector for aqueous urea solution, wherein the injector before the catalyst according to one or more of claims 1 to 11 is located.
14. System gemäß Anspruch 13, dadurch gekennzeichnet, dass es einen Oxidationskatalysator, einen Injektor für wässrige Harnstofflösung und einen Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 11 aufweist, wobei sich der Injektor vor dem Katalysator gemäß einem oder mehreren der Ansprüche 1 bis 11 befindet. 14. The system according to claim 13, characterized in that it comprises an oxidation catalyst, an aqueous urea solution injector and a catalyst according to one or more of claims 1 to 11, wherein the injector before the catalyst according to one or more of claims 1 to 11 located.
15. System gemäß Anspruch 14, dadurch gekennzeichnet, dass als Oxidationskatalysator Platin auf einem Trägermaterial verwendet wird. 15. System according to claim 14, characterized in that is used as the oxidation catalyst platinum on a support material.
EP18773183.1A 2017-10-09 2018-09-21 Active scr catalyst Withdrawn EP3694643A1 (en)

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FR2789911B1 (en) * 1999-02-18 2001-05-04 Grande Paroisse Sa PROCESS FOR SIMULTANEOUSLY KILLING NITRIC OXIDES AND NITROGEN PROTOXIDE IN THE GASES CONTAINING THE SAME
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CN100425534C (en) * 2005-05-31 2008-10-15 中国石油化工股份有限公司 Modified beta zeolite
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WO2011024847A1 (en) * 2009-08-27 2011-03-03 東ソー株式会社 Highly heat-resistant aqueous scr catalyst and manufacturing method therefor
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