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• • 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
• • 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
  • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
• • 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
  • B01J23/48—Silver or gold
  • B01J23/52—Gold
• • 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
  • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/66—Silver or gold
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • 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
  • B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
• • 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
  • B01J29/18—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the mordenite type
• • 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
  • B01J29/7007—Zeolite Beta
• • 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
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
  • B01J35/391—Physical properties of the active metal ingredient
  • B01J35/393—Metal or metal oxide crystallite size
• • 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
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
  • B01J35/396—Distribution of the active metal ingredient
  • B01J35/397—Egg shell like
• • 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
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
  • B01J35/396—Distribution of the active metal ingredient
  • B01J35/398—Egg yolk like
• • 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
  • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
  • B01J35/51—Spheres
• • 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
  • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
  • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
• • 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
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
  • B01J37/0027—Powdering
  • B01J37/0045—Drying a slurry, e.g. spray drying
• • 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
  • B01J37/0201—Impregnation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/102—Platinum group metals
  • B01D2255/1021—Platinum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/102—Platinum group metals
  • B01D2255/1023—Palladium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
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  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/106—Gold
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/206—Rare earth metals
  • B01D2255/2065—Cerium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2255/209—Other metals
  • B01D2255/2092—Aluminium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
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  • B01D2255/40—Mixed oxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
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  • B01D2255/50—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
  • B01D2255/902—Multilayered catalyst
  • B01D2255/9022—Two layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/912—HC-storage component incorporated in the catalyst
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/92—Dimensions
  • B01D2255/9202—Linear dimensions
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49345—Catalytic device making

Definitions

• the invention relates to a catalytically active material containing platinum, palladium and gold as catalytically active components, and to a diesel oxidation catalyst containing this catalytically active material.
• the exhaust gas from diesel engines typically contains carbon monoxide CO, hydrocarbons HC and nitrogen oxides NO x , and a relatively high oxygen content of up to 15% by volume.
• particulate emissions are contained, which consist predominantly of solid carbon black residues and optionally organic agglomerates (so-called "Volatile Organic Fraction” VOF or "Soluble Organic Fraction” SOF) and result from a partially incomplete fuel combustion in the cylinder.
• the harmful gases carbon monoxide and hydrocarbons can be rendered harmless by oxidation to a suitable oxidation catalyst.
• Diesel particulate filters with and without catalytically active coating are suitable aggregates for removing particulates.
• Nitrogen oxides are today preferably removed by selective catalytic reduction (SCR) to nitrogen with ammonia liberated from urea solution as a reducing agent ("denitrification" of the exhaust gas), wherein urea solution must be added as an excipient from a source independent of the engine to the exhaust gas.
• SCR selective catalytic reduction
• urea solution must be added as an excipient from a source independent of the engine to the exhaust gas.
• Diesel oxidation catalysts for the oxidative removal of carbon monoxide (CO), gaseous hydrocarbons (HC) and optionally VOF have long been known in the art and described in various embodiments.
• CO carbon monoxide
• HC gaseous hydrocarbons
• VOF optionally VOF
• platinum and / or palladium are used as oxidation-catalytically active components in these catalysts. Whether one of the precious metals is used alone or in combination with others and in what proportion of the precious metals may be present depends not infrequently on the design of the exhaust system in which the catalyst is to be used, since the precious metals, the various, in the system catalyze possible oxidation reactions with different effectiveness.
• platinum is suitable particularly good for the oxidation of nitrogen monoxide contained in the raw exhaust NO to nitrogen dioxide N0 2
• palladium has the highest oxidation activity of all precious metals over short-chain hydrocarbons (HC).
• Another oxidation-active noble metal is gold, which is known in the prior art, for example, as being excellent in catalyzing the oxidation of carbon monoxide CO to CO 2 even at very low temperatures ( ⁇ 100 ° C.).
• Gold-containing catalysts for the oxidative aftertreatment of diesel exhaust have also been described.
• WO 2009/074308 and EP 2 070 581 A1 disclose a diesel oxidation catalyst which has a coating on a catalytically inert carrier body (for example honeycomb body) which contains platinum, palladium and a promoter applied to a carrier oxide and zeolite.
• a catalytically inert carrier body for example honeycomb body
• platinum palladium
• a promoter applied to a carrier oxide and zeolite.
• gold can be used as the promoter.
• EP 1 925 362, US 2008/0124514, US Pat. No. 7,517,826 and US 7,534,738 disclose diesel oxidation catalysts in which a mixture of a first and a second catalytically active material is present.
• a first and a second catalytically active material are present.
• palladium is supported, besides gold, on a lanthana stabilized alumina.
• platinum is optionally applied together with palladium or bismuth onto lanthanum oxide-stabilized aluminum oxide.
• the two catalytically active materials may be applied to an inert honeycomb body as a homogeneous powder mixture in a catalytically active layer or in the form of several different coatings (e.g., as a zone catalyst or layered catalyst).
• zeolite-containing interlayers and / or layers comprising palladium supported on cerium oxide can furthermore be present.
• WO 2009/106849 discloses diesel oxidation catalysts which are distinguished inter alia by high conversion rates for methane and preferably contain palladium and gold as active components in alloyed form.
• palladium ex palladium nitrate and gold ex tetrachloroauric acid are applied by precipitation and calcination on alumina as support material. From the powder component thus obtained, a suspension for coating conventional natural monocyteßwaben redesign can be prepared as a catalyst substrate.
• WO 2008/117941 discloses diesel oxidation catalysts characterized by improved HC oxidation activity and containing gold alloyed palladium on alumina as the first catalytically active material besides palladium alloyed platinum on alumina as the second catalytically active material.
• alumina it is also possible to use other inorganic carrier oxides, such as, for example, silicon dioxide, aluminum silicate, silicates, titanium oxide, zirconium oxide, SiC and carbon black.
• a diesel oxidation catalyst prepared from the mixture of the catalytically active materials may further contain oxygen-storing rare earth metal oxides.
• US 2008 / 125308A1 describes catalytic converters which comprise a platinum-containing catalyst and a palladium-and-gold-containing catalyst and which may additionally contain zeolite as an absorbent for hydrocarbons.
• the two catalysts are arranged in different catalytically active zones of the catalytic converter in such a way that the exhaust gas first meets the platinum-containing catalyst. This is achieved by means of conventional layer or zone arrangement of the two catalysts or by the fact that both catalysts are supported on different monoliths.
• a catalytically active material consisting of an inner core (1) and an outer shell (2) surrounding this core, wherein the core is formed of palladium and gold, which are fixed together on a first carrier oxide, and wherein the Shell contains platinum, which is fixed on a second carrier oxide.
• FIG. 1 shows the structure of the catalytically active material according to the invention of inner core (1) and outer shell (2).
• the special structure of the catalytically active material ensures an intensive interaction between palladium and gold, which contributes significantly to the improvement in the CO conversion performance of the resulting catalyst.
• This microscopic separation of the palladium-gold-containing phase from the platinum-containing phase avoids a direct interaction between platinum and gold, which, in the case of prior art catalysts having comparable compositions, not infrequently leads to irreversible deactivation phenomena after an extended period of use the platinum-containing component leads.
• the noble metals palladium and gold present in the core of the catalytically active material according to the invention are preferably in the form of alloyed metal clusters.
• the weight ratio of palladium to gold in the core of the catalytically active material is preferably 0.9-1: 1: 1, more preferably 1: 1.
• the outer shell (2) of the catalytically active material according to the invention is formed in one embodiment of platinum fixed on the second carrier oxide. In preferred embodiments, however, contains the outer shell (2) as another noble metal palladium. This can be present in mixed form and / or in alloyed form with the platinum also present therein. Particularly preferably, at least part of the palladium present in the shell is present in platinum-alloyed form. If both noble metals are used in the outer shell, the weight ratio of platinum to palladium is preferably between 12: 1 and 1: 1, more preferably in the range 6: 1 to 2: 1 and most preferably 4: 1.
• the outer shell (2) preferably envelops the inner core (1) almost completely and particularly preferably completely.
• the weight ratio of the precious metals contained in outer shell (2) and inner core (1) is platinum: palladium: gold in the particularly preferred embodiments 1: 1: 1.
• the outer shell (2) in addition to platinum or next to platinum and Palladium also a zeolite compound with HC-storing properties.
• the catalytically active material according to the invention is thus equipped with a hydrocarbon storage and retention function, which requires that hydrocarbons which can not be fully reacted at operating temperatures below the ignition temperature for the hydrocarbon oxidation, not "break through” the resulting diesel oxidation catalyst, but in the inventive catalytically active material are retained until the HC conversion sufficient temperatures are reached.
• the zeolite compounds are preferably selected from the group consisting of FAU, MOR, zeolite beta, MFI and mixtures thereof. They are in the outer shell (2) preferably at 10 to 60 wt .-%, more preferably from 20 to 50 wt .-% and most preferably from 25 to 35 wt .-% before, in each case based on the total weight of the outer Shell (2).
• the first and / or second carrier oxide used is preferably one from the group consisting of cerium oxide, zirconium oxide, aluminum oxide, silicon oxide and mixed oxides and / or mixtures thereof. Particularly preferred are aluminum oxide, aluminum silicates and aluminum-silicon mixed oxides.
• the particles of the catalytically active material according to the invention which, as described above, of inner core (1) and outer shell (2) are each of different composition are approximately spherical and preferably have an average diameter of 1 to 12 ⁇ , more preferably from 3 to 8 ⁇ on.
• the volume fraction of the core on a spherical particle in the preferred embodiments of the catalytically active material according to the invention is preferably 50 to 80%, particularly preferably about 60%.
• the catalytically active material according to the invention is prepared by processes known to those skilled in the art.
• the optionally graded co-precipitation and / or co-impregnation of the noble metals from water-soluble precursors to carrier oxides and the systematic grinding of pulverulent precursors to form defined conglomerates can be used.
• pH values in the strongly acidic range ie pH ⁇ 4
• pH values in the strongly basic range ie pH> 8
• acetic acid to lower the pH and organic bases such as tetraethylammonium hydroxide (TEAH) to raise the pH.
• TEAH tetraethylammonium hydroxide
• the present invention also provides a diesel oxidation catalyst comprising a catalytically inert support body and at least one catalytically active coating applied thereto, characterized in that the coating contains a catalytically active material as described above.
• a coating suspension of the above-described catalytically active material is prepared by processes known to those skilled in the art, which can be applied to an inert support body with likewise known coating methods (immersion, suction and / or pumping).
• the resulting catalyst then consists of a catalytically inert carrier body and at least one catalytically active coating applied thereto, which contains the catalytically active material according to the invention.
• the catalytically inert carrier body is preferably selected from the group of ceramic and metallic fürflußwaben redesign or from the group of ceramic Wandflußfiltersubstrate. If the catalytically active material according to the invention contains no or insufficient zeolite in the outer shell (2), it is also possible to add to the coating a zeolite compound having HC-storing properties selected from the group consisting of FAU, MOR, zeolite beta, MFI and mixtures thereof. The proportion of zeolite compound in the coating is then preferably 15 to 45 wt .-%, particularly preferably 20 to 30 wt .-%, based on the total weight of this coating.
• the entire zeolitic material is present in the outer shell (2) of the catalytically active material, in particular in a proportion of 15 to 45 wt .-%, based on the total weight of the catalytically active material.
• the diesel oxidation catalyst according to the invention is suitable for the oxidative reduction of carbon monoxide and / or hydrocarbons in the exhaust gas of diesel engines.
• the exhaust gas is passed over the diesel oxidation catalyst.
• the diesel oxidation catalyst is preferably used as part of an exhaust gas purification system, which is also the subject of the present invention.
• the diesel oxidation catalyst according to the invention is preferably arranged close to the engine.
• a diesel particle filter is preferably connected downstream in the flow direction of the exhaust gas to be cleaned.
• the diesel particulate filter can be followed by a denitration stage, so that the effective reduction of all legally contained pollutants contained in the diesel exhaust gas is ensured.
• Suitable diesel particulate filters and denitration stages such as NO x storage and SCR catalysts are described in the literature and known to the person skilled in the art.
• the diesel oxidation catalyst according to the invention is characterized in particular by very high CO conversion rates and by an extraordinarily high thermal aging stability and thus has important properties that are suitable for application in modern emission control systems for fulfilling, for example, the legal emission specifications known under "Euro 5" and "Euro 6" are inevitable. Furthermore, the catalyst of the invention shows cost advantages over the otherwise customary catalysts, which generally contain a significantly higher proportion of the most expensive noble metal platinum. Exemplary embodiment:
• alumina is suspended in water. With stirring, tetrachloroauric acid and palladium nitrate solution are added to the suspension. After an adsorption time of about one hour, the solid contained in the suspension is separated by filtration from the liquid phase and washed with demineralized water until no significant amounts of Chloridlonen are more detectable in the wash water. To remove optionally adsorbed chloride ions, the solid is then washed once more with dilute, aqueous ammonia solution. Then the solid is dried at about 120 ° C over the course of 4 hours followed by calcination at 400 ° C for a period of 3 Hours. The powder thus obtained forms the "core material" for the catalytically active material according to the invention to be produced in the last stage.
• Step 2 Making the "shell material”.
• the "core material" prepared in step 1 is suspended in water and optionally ground until an average particle size of 4-8 ⁇ m is achieved with the narrowest possible particle size distribution prepared "shell material” also suspended in water and optionally milled until an average particle size of 1 - 2 ⁇ is achieved with the narrowest possible particle size distribution.
• the suspension thus obtained is admixed with a suitable zeolite compound for storing the hydrocarbons present in the exhaust gas, which likewise has the finest possible particle size distribution and has, if appropriate, been correspondingly ground in a separate preparation step.
• the two suspensions obtained above are combined and subjected to a controlled spray drying.
• the finely divided particles of the "shell material” form a shell around the coarser particles of the "core material”.
• Step 4 Preparation of the catalyst according to the invention:
• the catalytically active material obtained in step 3 is resuspended in water and applied to a conventional ceramic or metallic fürflußwaben redesign with a known in the art, usual dipping, suction or pumping.
• the amount of Coating suspension and the number of coating steps according to the method should be selected so that the honeycomb body after drying at 120 ° C and a calcination at 400 ° C over the period of 3 hours, a coating amount of 130 to 150 grams of solid per liter of component volume.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
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• Exhaust Gas After Treatment (AREA)

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• 2011
  • 2011-10-19 WO PCT/EP2011/068229 patent/WO2012055730A1/de active Application Filing
  • 2011-10-19 CN CN201180048825.5A patent/CN103153458B/zh not_active Expired - Fee Related
  • 2011-10-19 EP EP11774020.9A patent/EP2632587A1/de not_active Withdrawn
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