EP4017629A1 - Catalyseur pour réduire les émissions d'ammoniac - Google Patents

Catalyseur pour réduire les émissions d'ammoniac

Info

Publication number
EP4017629A1
EP4017629A1 EP20754284.6A EP20754284A EP4017629A1 EP 4017629 A1 EP4017629 A1 EP 4017629A1 EP 20754284 A EP20754284 A EP 20754284A EP 4017629 A1 EP4017629 A1 EP 4017629A1
Authority
EP
European Patent Office
Prior art keywords
composition
catalyst
metal oxide
platinum
substrate
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.)
Pending
Application number
EP20754284.6A
Other languages
German (de)
English (en)
Inventor
Birgit FRIEDRICH
Gordon KEITL
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 EP4017629A1 publication Critical patent/EP4017629A1/fr
Pending 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
    • 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
    • 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
    • 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
    • B01D53/9436—Ammonia
    • 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
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • B01D53/9477—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on separate bricks, e.g. exhaust systems
    • 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
    • B01J35/19—Catalysts containing parts with different compositions
    • 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
    • B01J35/20—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state
    • B01J35/23—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state in a colloidal state
    • 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
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • B01J37/0225—Coating of metal substrates
    • 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
    • B01J37/08—Heat treatment
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation catalysts
    • 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]
    • 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
    • F01N3/24—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 constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2807—Metal other than sintered metal
    • F01N3/281—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates
    • 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
    • B01D2255/10—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
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20707—Titanium
    • 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
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/063—Titanium; Oxides or hydroxides thereof
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/08—Silica
    • 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
    • F01N2370/00—Selection of materials for exhaust purification
    • F01N2370/02—Selection of materials for exhaust purification used in catalytic reactors
    • 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
    • F01N2510/00—Surface coverings
    • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
    • 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
    • F01N2510/00—Surface coverings
    • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
    • F01N2510/068—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings
    • F01N2510/0682—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/14—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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/18—Ammonia
    • 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
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • Flow-through substrates are known to the person skilled in the art and are available on the market. They consist, for example, of cordierite, aluminum titanate or metal foil.
  • corrugated substrates can also be used as flow substrates. These are known to those skilled in the art as substrates made of corrugated sheets made of inert materials. Suitable inert materials are, for example, fibrous materials with an average fiber diameter of 50 to 250 ⁇ m and an average fiber length of 2 to 30 mm. Fibrous heat-resistant materials made of silicon dioxide, in particular made of glass fibers, are preferred.
  • sheets made of the fiber materials mentioned are corrugated in a known manner and the individual corrugated sheets are shaped into a cylindrical monolithically structured body with channels running through the body.
  • a monolithically structured body with a cross corrugation structure is formed.
  • smooth sheets can be arranged between the corrugated sheets.
  • Metal carrier substrates usually consist of structures made of corrugated sheet metal into which smooth sheet metal layers can also be incorporated. As a rule, these sheets are wound so that channel structures are formed whose channels run parallel and extend from one end of the substrate to the other end. The sheets can be continuous or with holes be provided to enable gas exchange between the channels. In addition, these sheet-metal structures can be shaped in such a way that potential particle emissions are captured by the structure (so-called "open" filter substrates).
  • a wall flow filter is a support body which comprises channels of length L which extend parallel between a first and a second end of the wall flow filter, which are closed alternately at either the first or the second end and which are separated by porous walls.
  • They consist, for example, of silicon carbide, aluminum titanate or cordierite.
  • wall flow filters In the uncoated state, wall flow filters have porosities of, for example, 30 to 80%, in particular 50 to 75%. Their average pore size in the uncoated state is, for example, 5 to 30 micrometers.
  • the pores of the wall flow filter are so-called open pores, i.e. they have a connection to the channels. Furthermore, the pores are usually connected to one another. This enables on the one hand the light coating of the inner pore surfaces and on the other hand an easy passage of the exhaust gas through the porous walls of the wall flow filter.
  • noble metals are used as catalytically active solids in exhaust gas catalysis. Due to the high precious metal prices, the best possible utilization of these precious metals is an important point in catalyst development. A large surface area is achieved using small precious metal particles, whereby the ideal particle size can vary depending on the application, carrier and precious metal.
  • EP1547682A1 discloses platinum catalysts supported on S1O2-Al2O3, two of these catalysts being arranged sequentially and the front having smaller platinum particles than the rear.
  • the optimal platinum particle size is 20 nm.
  • Rymes et al (“Pt combustion catalysts prepared from w / o microemulsions"; Studies in Surface Science and Catalysts 143, Elsevier Science BB 2002 p. 121-129) have the influence of the platinum particle size on aluminum oxide pellets investigated supported platinum catalysts for the Tso temperature for the oxidation of certain hydrocarbons.
  • the ideal particle size is 55 nm.
  • JPH09103651A describes an exhaust system for NOx reduction.
  • the optimal platinum particle size is 37 nm.
  • US2009 / 0011177A1 discloses platinum colloids with a particle size of up to 271 nm on g-aluminum oxide for NO oxidation.
  • US2003 / 0185736A1 describes new carrier oxides, their production as carriers for platinum, palladium and / or rhodium with a particle size of up to 45 nm for exhaust gas aftertreatment, in particular the conversion of nitrogen oxides.
  • ASC ammonia slip catalyst
  • JP2010149097A platinum catalysts with platinum particle sizes of 150-500 nm are described.
  • the ammonia formed serves as a reducing agent for the reduction of nitrogen oxides over the SCR catalyst into nitrogen: x NH 3 + y NOx (+ 0 2) - »1/2 (x + y) N 2 + 3x / 2 H 2 0
  • the reaction runs particularly quickly at a ratio of NO / NO2 ⁇ 1:
  • ammonia slip catalysts which convert unconverted ammonia over the SCR catalyst.
  • the ammonia is oxidized to nitrogen:
  • the catalyst components active for the ammonia oxidation are called AMOX in the following.
  • platinum catalysts show the highest ammonia oxidation activity (Hansen T.K. (2017). Kgs. Lyngby: Technical Univ. Of Denmark (DTU)).
  • Aluminum oxide (Al2O3) is generally used as the carrier material for the precious metal for the AMOX component, as this has excellent thermal stability.
  • conventional AMOX catalysts supported by AI2O3 show insufficient selectivity for the oxidation to nitrogen (N2). Oxidation of ammonia to NOx and N2O occurs as undesirable side reactions. This is of course counterproductive for reducing nitrogen oxides.
  • N2O is also problematic due to its effect as a greenhouse gas.
  • the above AMOX catalyst is also combined with SCR-active catalyst compositions (W02016 / 205506A1, US2008 / 292519A1, US2014 / 212350A1, US2014 / 0157763A1,
  • the object of this invention is therefore to provide a platinum catalyst which has both a high activity for ammonia oxidation but also good selectivity for the oxidation to nitrogen and which minimizes the harmful by-products.
  • the invention relates to a composition which has both a surprisingly low light-off temperature for the ammonia oxidation and a high selectivity for the oxidation to N2.
  • the invention relates to a composition with platinum supported on metal oxide A in the form of platinum particles, the platinum particles having an average particle diameter of 50-200 nm, preferably 80-120 nm, metal oxide A being titanium oxide.
  • the average particle diameter in the context of this invention is the average diameter of the Pt crystallites, which is calculated from X-ray diffraction recordings using the [III] main reflex at about 39.8 ° 2Theta over the peak width (full width at half maximum; FWHM).
  • the standard used here is silicon with a peak at 28.4 ° 2Theta and an FWHM of 0.06 ° 2Theta.
  • the composition does not contain any noble metal other than platinum.
  • Noble metals that are not included in this variant are in particular palladium, rhodium, ruthenium, iridium, gold and silver.
  • the titanium oxide which is predominantly present as titanium dioxide, contains the crystalline phases anatase and Rutile.
  • the anatase and rutile phases are preferably present in a ratio greater than 9: 1.
  • the platinum loading of the metal oxide A is in particular in the range from 0.5 to 20% by weight, preferably 3 to 8% by weight, based on the metal oxide A.
  • the temperature stability of the metal oxide A can be increased by doping with silicon oxide, a silicon oxide content of 1-10% by weight in the metal oxide A preferably being used.
  • the platinum-supported metal oxide A is mixed with a further metal oxide, metal oxide B.
  • metal oxide B aluminum oxide, titanium oxide, silicon oxide, cerium oxide or zirconium oxide can be used. Mixtures of these oxides or their mixed oxides can also be used.
  • Metal oxide B can be different from metal oxide A here. However, metal oxide A and metal oxide B are preferably the same metal oxide, with metal oxide B carrying noble metal in one embodiment, for example platinum, palladium and / or rhodium, and in another embodiment carrying no noble metal.
  • the invention includes a method for producing the composition according to the invention with platinum particles supported on metal oxide A, the platinum being deposited from a solution on the metal oxide A and then, after drying, subjected to a thermal treatment at 700 ° C to 900 ° C and thus the platinum is fixed to the metal oxide.
  • the invention also includes a catalyst, the composition according to the invention being applied to a ceramic carrier substrate of length L in the form of a coating.
  • the composition is applied over at least 80% of the total length of the carrier substrate.
  • a coating that is as complete as possible results in the longest possible contact time between the exhaust gas and the catalytic converter and thus the highest possible ammonia conversion.
  • the composition is applied over 10% to 80% of the total length of the carrier substrate and thus enables the construction of a zoned catalyst.
  • the composition according to the invention can be applied together with another catalytically active composition, in particular with a composition active for the SCR reaction, in a layer on a carrier substrate.
  • the invention comprises a catalyst in which the composition according to the invention and another catalytically active composition are arranged in different zones and / or layers.
  • the carrier substrate used for the above-mentioned catalysts can be made of ceramic or metal. This can be a flow-through substrate. A so-called “corrugated substrate” can also be used as a carrier substrate. Filter substrates can also be used.
  • the invention also includes a catalyst system using the catalyst of the invention.
  • the invention also includes a method for reducing nitrogen oxides in exhaust gases from lean-burn internal combustion engines, the exhaust gas being passed through an exhaust system which has a catalytic converter for the selective reduction of nitrogen oxides (SCR) and an ammonia slip catalytic converter (ASCR) that follows the exhaust gas flow ), the ASC being the catalyst according to the invention
  • the SCR catalyst can be a vanadium oxide-based catalyst or a zeolite-based catalyst of the Fe-zeolite or Cu-zeolite type.
  • Zeolites are two- or three-dimensional structures, the smallest substructures of which can be viewed as S1O4 and AI04 tetrahedra. These tetrahedra form larger structures, two of which are connected to one another via an oxygen atom. In this way, ring structures of different sizes can be formed, such as ring structures made of 4, 6, or even nine tetrahedrally coordinated Si or Al atoms.
  • the different zeolite types are often defined by the largest ring size, since this size determines which guest molecules can penetrate the zeolite structure.
  • the zeolites are classified by the Structural Commission of the International Zeolite Association into structural types which are indicated by three-letter codes.
  • Both large and medium or small pore zeolites can be used for the composition according to the invention.
  • suitable zeolites belong to the structure types ABW, AEI, AFX, BEA, CHA, DDR, ERI, ESV, FAU, FER, KFI, LEV, LTA, MER MFI, MWW, SOD or STT.
  • a small-pore zeolite of the structure type AEI, AFX, CHA or LEV is preferred.
  • a zeolite of the structure type CHA is particularly preferred.
  • An Si: Al ratio of 2 to 100, particularly preferably 5:50, and furthermore preferably 10:40 is used.
  • zeolite also includes molecular sieves, which are sometimes referred to as “zeolite-like structures”. Molecular sieves of the structural types mentioned above are preferably used. Examples include silicon-aluminum-phosphate zeolites, which are also known as SAPO, and aluminum-phosphate zeolites, which are known as AIPO.
  • the carrier substrates can be coated using methods familiar to the person skilled in the art, for example using the customary dip coating processes or pump and suction coating processes with subsequent thermal aftertreatment (calcination).
  • the person skilled in the art is aware that in the case of wall flow filters, their average pore size and the average particle size of the materials to be coated can be coordinated so that they lie on the porous walls that form the channels of the wall flow filter (on-wall coating).
  • the mean particle size of the to be coated However, materials can also be selected so that they are located in the porous walls that form the channels of the wall flow filter, so that the inner pore surfaces are coated (in-wall coating). In this case, the mean particle size of the materials to be coated must be small enough to penetrate into the pores of the wall flow filter.
  • Zoned catalysts can be designed differently.
  • the zones can overlap, touch, or have a gap.
  • the composition according to the invention can be applied over the length L a, while an SCR coating is applied over Lb.
  • the zone of length Lb can extend over zone L a and thus take over the subsequent reduction of NOx to N2, as described above.
  • L b can also be chosen to be identical to the length of the substrate.
  • the inlet channels can also be coated with an SCR-active coating and the outlet channels can be coated with an ASC coating, the composition according to the invention being excellently suited as the AMOX-active component of the ASC coating. Zoning over the length of the substrate can also be used.
  • composition according to the invention is outstandingly suitable for use as an ammonia oxidation catalyst in a system for reducing nitrogen oxides in exhaust gases from lean-burn internal combustion engines.
  • a system including a catalytic converter for the selective reduction of nitrogen oxides (SCR) and an ammonia slip catalytic converter (ASC) following the exhaust gas flow, the ASC containing the powder or powder mixture according to the invention with AMOX catalytic converter function.
  • SCR catalytic converter for this can in principle be selected from all catalytic converters which are active for the SCR reaction of nitrogen oxides with ammonia, in particular from those which are known to the person skilled in the art of automobile exhaust gas catalysis as customary.
  • This also includes catalysts of the mixed oxide type as well as catalysts based on zeolites, in particular on transition metal-exchanged zeolites.
  • An AMOX catalyst according to the invention is described below in comparison with one that corresponds to the prior art.
  • Example C1 The platinum is precipitated from an aqueous solution of tetraethylammonium hexahydoxoplatinate (EP 3 210 989 B1) by adding dilute nitric acid to the titanium oxide powder, which is stabilized with 5% by weight of silicon oxide, in order to produce a material with a concentration of 3% by weight % Pt (based on the titanium oxide powder).
  • the powder produced in this way is then filtered off, dried and subjected to at 800 ° C. for 2 hours
  • the powder is suspended in water and the desired loading of 0.14% by weight Pt (based on the total titanium oxide powder) is set by adding uncoated titanium oxide.
  • This washcoat is used to coat a commercially available ceramic flow-through substrate with a cell structure of 400 cpsi and 110 ⁇ m wall thickness in the usual way.
  • the coated substrate is then dried at 110 ° C. and calcined at 600 ° C. for 6 hours.
  • the washcoat loading of the catalyst is 25 g / l, the platinum loading of the catalyst is 0.0353 g / l.
  • a catalyst with the same platinum content with ⁇ -aluminum oxide as the carrier powder is used as a comparative reference.
  • the platinum is precipitated from an aqueous solution of tetraethylammonium hexahydoxoplatinate by adding dilute nitric acid onto the carrier powder.
  • ⁇ -aluminum oxide is used as the carrier powder.
  • the washcoat produced in this way is then coated in the usual way on a commercially available flow-through substrate. The coated substrate is then dried at 110 ° C. and calcined at 600 ° C. for 6 hours.
  • the washcoat loading of the catalyst is 25 g / l.
  • drill cores with a diameter of 25.4 mm and a length of 76.2 mm were taken from the finished catalysts. These drill cores were measured on a model gas system, the gas composition and space velocity being selected as indicated in Table 1.
  • FIG. 1 shows the conversion curve as a function of temperature for Kl (dotted line) and the comparative example VK1 (solid line).
  • the catalyst according to the invention has a significantly earlier light-off. While Kl achieves a conversion of 50% at 197 ° C, this only succeeds at 237 ° C using VK1. In addition, a conversion of 10% is already achieved with Kl at 150 ° C., while no conversion can be observed with VK1 at this temperature.
  • FIG. 2 shows the selectivity to N2O for the two catalysts.
  • the result for Kl is dotted and shown for VK1 with a solid line.
  • the AMOX catalyst according to the invention has a lower selectivity for N2O than the reference catalyst.
  • the maximum measured I O concentration in the exhaust gas according to ASC was 47 ppm for Kl, which is one Selectivity of 34% corresponded, and for VK1 60 ppm, which corresponded to a selectivity of 44%.
  • FIG. 3 shows the ammonia conversion over the catalyst according to the invention Kl fresh (a), and after aging of the catalyst under a reducing atmosphere (10% O2, 10% H2O, remainder nitrogen) at 650 ° C (b), 700 ° C (c ), 800 ° C (d), 900 ° C (e) and 1000 ° C (f).
  • the aging time was 16 hours with the exception of aging at 650 ° C., for which it was 12 hours.
  • a higher aging temperature, and thus a larger platinum particle diameter leads to lower selectivity to N2O and to a lowering of the light-off temperature for the ammonia conversion, up to 900 ° C the maximum ammonia conversion sinks and falls 1000 ° C the catalytic activity is severely impaired.
  • the range around 800 ° C can therefore be regarded as the preferred temperature range for thermal pretreatment.
  • the platinum is precipitated from an aqueous solution of tetraethylammonium hexahydoxoplatinate (EP 3 210 989 B1) by adding dilute nitric acid to the titanium oxide powder, which is stabilized with 5% by weight of silicon oxide, in order to produce a material with a concentration of 3% by weight of Pt based on the titanium oxide powder.
  • the powder produced in this way is then filtered off, dried and fixed at 800 ° C. for 2 hours under an air atmosphere.
  • the powder is slurried in water and the desired loading of 0.4% by weight Pt (based on the total titanium oxide powder) is set by adding uncoated titanium oxide.
  • This washcoat is used to coat a commercially available ceramic flow-through substrate with a cell structure of 400 cpsi, 110 ⁇ m wall thickness in the usual way.
  • the coated substrate is then dried at 110 ° C. and calcined at 600 ° C. for 6 hours.
  • the washcoat loading of the catalyst is 25 g / l
  • the platinum loading of the catalyst is 0.1059 g / l-
  • the catalyst is produced identically to C2, but with the precipitation of the platinum from the aqueous solution onto the titanium oxide powder, a material with a concentration of 4% by weight Pt, based on the titanium oxide powder, is produced.
  • the catalyst is produced identically to C2, but with the precipitation of the platinum from the aqueous solution onto the titanium oxide powder, a material with a concentration of 8% by weight Pt, based on the titanium oxide powder, is produced.
  • the catalysts K2, K3 and K4 are aged for 16 hours at 800 ° C under reducing conditions (10% O2, 10% H2O, remainder nitrogen), the ammonia conversion and the N2O and NO concentration after the catalyst are measured.
  • FIG. 4 the results of Examples K2 (circle), K3 (triangle) and K4 (star) are shown comparatively.
  • the catalytic properties are almost identical, with a higher Pt loading of the titanium oxide powder reducing the amount of powder to be processed and thus also the production costs.
  • a powder mixture, produced by mixing Pt-containing powder with Pt-free powder, is therefore a preferred variant of the substance according to the invention.

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Abstract

La présente invention concerne une composition comprenant du platine supporté sur de l'oxyde de titane, les particules de platine ayant un diamètre moyen de particule de 50 à 200 nm. La composition présente une température de dégagement de lumière étonnamment basse pour l'oxydation de l'ammoniac et une sélectivité élevée pour l'oxydation à N2.
EP20754284.6A 2019-08-20 2020-08-18 Catalyseur pour réduire les émissions d'ammoniac Pending EP4017629A1 (fr)

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EP19192428.1A EP3782727A1 (fr) 2019-08-20 2019-08-20 Catalyseur permettant de réduire les émissions d'ammoniaque
PCT/EP2020/073040 WO2021032702A1 (fr) 2019-08-20 2020-08-18 Catalyseur pour réduire les émissions d'ammoniac

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WO2021032702A1 (fr) 2021-02-25
BR112022003110A2 (pt) 2022-05-17
JP2022545056A (ja) 2022-10-25
EP3782727A1 (fr) 2021-02-24
CN114206490A (zh) 2022-03-18
US20220297093A1 (en) 2022-09-22
CN114206490B (zh) 2023-12-05

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