MX2014000499A - Method for coating a catalysed particulate filter and a particulate filter. - Google Patents

Method for coating a catalysed particulate filter and a particulate filter.

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Publication number
MX2014000499A
MX2014000499A MX2014000499A MX2014000499A MX2014000499A MX 2014000499 A MX2014000499 A MX 2014000499A MX 2014000499 A MX2014000499 A MX 2014000499A MX 2014000499 A MX2014000499 A MX 2014000499A MX 2014000499 A MX2014000499 A MX 2014000499A
Authority
MX
Mexico
Prior art keywords
catalyst
ammonia
filter
active
coating
Prior art date
Application number
MX2014000499A
Other languages
Spanish (es)
Inventor
Pär L Gabrielsson
Keld Johansen
Original Assignee
Haldor Topsøe As
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 Haldor Topsøe As filed Critical Haldor Topsøe As
Publication of MX2014000499A publication Critical patent/MX2014000499A/en

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    • 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
    • B01D53/9463—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 one brick
    • B01D53/9468—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 one brick in different layers
    • 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
    • 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
    • B01J37/02—Impregnation, coating or precipitation
    • 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
    • B01J37/0244—Coatings comprising several layers
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • 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
    • F01N3/2832—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support granular, e.g. pellets
    • 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
    • B01D2255/1023—Palladium
    • 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
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20761—Copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • 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
    • B01D2255/915—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
    • 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
    • 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
    • B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
    • 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
    • B01J23/56—Platinum group metals
    • B01J23/63—Platinum group metals with rare earths or actinides
    • 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
    • B01J29/82—Phosphates
    • B01J29/84—Aluminophosphates containing other elements, e.g. metals, boron
    • B01J29/85—Silicoaluminophosphates [SAPO compounds]
    • 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
    • B01J37/0036—Grinding
    • 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
    • B01J37/0219—Coating the coating containing organic compounds
    • 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
    • F01N2510/0684—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings having more than one coating layer, e.g. multi-layered coatings
    • 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]
    • F01N3/2073—Selective catalytic reduction [SCR] with means for generating a reducing substance from the exhaust gases
    • 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

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  • Chemical & Material Sciences (AREA)
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  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Combustion & Propulsion (AREA)
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  • Environmental & Geological Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
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  • Analytical Chemistry (AREA)
  • Biomedical Technology (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Toxicology (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Filtering Materials (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

Method for the preparation of a wall flow particulate filter catalysed at its inlet side with a first catalyst having activity in the removal of residual hydrocarbons and carbon monoxide and catalysing at rich burn engine operation conditions the reaction of nitrogen oxides with hydrogen and/or carbon monoxide to ammonia and catalysed at its outlet side with a second catalyst having activity in the selective reduction of NOx by reaction with ammonia being formed in the inlet side. The method involves the provision of a first catalyst having a particle size smaller than the filter wall mean pore size, and a second catalyst having a particle size larger than the filter wall mean pore size, and mixing the first and second catalyst into one suspension, which is used for washcoating from the outlet end. The first catalyst thereby diffuses into the partition wall.

Description

METHOD FOR COVERING A CATALYZED PARTICULATE FILTER AND A PARTICULATE FILTER Field of the Invention The present invention relates to a particulate filter for exhaust gas of multi-functional catalysed engine. In particular, the invention is a method for the preparation of a multifunctional catalysed particulate filter that is catalysed with a three-way catalyst (TWC) and a catalyst that is active in the removal of nitrogen oxides by means of of the known process of selective NH3 catalytic reduction (SCR) and optionally with a catalyst having activity in the oxidation of excess ammonia to nitrogen.
The multi-functional catalytic filter is useful in particular for cleaning the exhaust gas of lean-mix gasoline engines, such as the direct fuel injection (GDI) engine.
Background of the Invention GDI engines generate more carbonaceous soot than pre-mixed gasoline injection engines. In Europe, the Euro 5+ Diesel legislation is expected to be used for GDI in the future with a mass limit of particulate material at 4.5 mg / km, which requires filtering the engine exhaust gas in order to reach the previous limit.
Typically, filters for use in automotive applications are the flow-through-the-wall filter consisting of a body with a honeycomb structure, wherein the particulate material is captured on or in the partition walls of the honeycomb structure. These filters have a plurality of longitudinal flow channels that are separated by gas permeable partition walls. The gas inlet channels open at their gas inlet side and lock at the opposite outlet end and the gas outlet channels open at the outlet end and lock at the inlet end, so that A stream of gas entering the filter with flow through the walls is forced through the partition walls before entering the outlet channels.
In addition to the soot particles, the exhaust gas from gasoline engines contains oxides of nitrogen (Ox), carbon monoxide and unburned hydrocarbons, which are chemical compounds that represent an environmental and health risk and should be reduced or removed from the exhaust gas.
The catalysts that are active in the removal or reduction of NOx, carbon monoxide and hydrocarbons to Harmless compounds are known per se in the field.
The patent literature discloses numerous cleaning systems comprising separate catalyst units for the removal of dangerous compounds from the engine exhaust gas.
Also known in the field are particulate exhaust gas filters coated with catalysts that accelerate the oxidation of hydrocarbons and particulate together with the catalytic, selective (SCR) reduction of NOx by means of a reaction with ammonia which is added as such or as a precursor of it in the exhaust gas.
Multifunctional diesel particulate filters that are coated with different catalysts that accelerate the aforementioned reactions are also known in the field.
In the known multifunctional filters, the different catalysts are coated in a segmental manner or by zones in different areas of the filter.
The segmental or zone coating of different catalysts on the filter is a costly and difficult preparation process.
Summary of the Invention In comparison with the known technique, the present invention suggests an easier method for the preparation of particulate filters that are catalyzed with different catalysts for the selective reduction of nitrogen oxides with ammonia and the removal of excess hydrocarbons, carbon monoxide and ammonia.
Detailed description of the invention In this way, the invention provides a method for the preparation of a filter catalyzed with flow through the walls, comprising the steps consisting of a) providing a filter body with flow through the walls with a plurality of inlet flow channels and longitudinal outlet flow channels that are separated by porous gas permeable partition walls; b) provide a catalyst support coating comprising a first catalyst composition that is active in the reaction of nitrogen oxides with carbon monoxide and hydrogen to ammonia together with a second catalyst composition that is active in the selective reduction of oxides of nitrogen by means of the reaction with ammonia to nitrogen, the first catalyst composition has a particle size that is smaller than the average pore diameter of the porous partition walls and the second catalyst composition has a particle size that is larger than the average pore diameter of the porous partition walls, c) coating the filter body with the catalyst support coating by introduction of the support coating at the outlet end of the outlet channels; Y d) drying and heat treating the coated filter body to obtain the catalyzed particulate filter.
The advantage is that either the first catalyst has a smaller particle size than the average pore diameter of the partition walls and the second catalyst particles have a particle size larger than the average pore diameter of the walls for allowing the first catalyst particles to diffuse effectively within the partition walls and prevent the second catalyst from diffusing into channels where the specific catalytic activity is not desired.
It is then possible to coat the filter body with different catalysts, the inlet and outlet flow channels with an individual support coating.
The catalysts useful for the reaction of NOx to ammonia are prepared by means of the following reaction: NOx + H2 / CO = NH3 + C02 + H20 are palladium, platinum, a mixture of palladium and rhodium and a mixture of palladium, platinum and rhodium.
These catalysts accelerate the formation of ammonia under operating conditions with rich mixture of gasoline engine, ie? < 1. Palladium is the preferred catalyst with the highest ammonia formation.
The ammonia that is formed in this way within the inlet channels by means of the above reaction permeates through the partition walls of the filter within the outlet channels and during the rich operating conditions is adsorbed on the SCR catalyst. in the outflow channels.
Both the ammonia forming catalyst and the SCR catalyst are preferably deposited on the partition walls on the sides facing the inlet channel and the outlet channel, respectively.
In a subsequent poor mixing cycle of the engine, the NOx that is present in the exhaust gas reacts with the ammonia stored in the SCR catalyst by means of the following reaction: NOx + NH3 = N2 + H20 As already mentioned above, the SCR catalysts are known per se in the field. For use in the invention, the preferred catalyst that is active in the selective reduction of nitrogen oxides comprises at least one of a zeolite, a silica-aluminum phosphate, a zeolite with exchanged ions, silica-aluminum phosphate promoted with iron and / or copper, one or more common metal oxides.
A preferred SCR catalyst, additional for use in the invention is a silica-aluminum phosphate with chabazite structure, such as SAPO 34, promoted with copper and / or iron.
For the purpose of removing excess ammonia that has not reacted with NOx, the filter with flow through the walls additionally comprises in one embodiment of the invention an ammonia oxidation catalyst disposed in each outlet flow channel at least in the region of the output end of the filter.
A preferred ammonia oxidation catalyst comprises palladium, platinum or a mixture thereof.
Through contact with the ammonia oxidation catalyst, the ammonia is oxidized to nitrogen and water.
The ammonia oxidation catalyst can be deposited directly on the partition wall in the filter outlet channels in the outlet region or may be provided as a surface layer on the surface of the SCR catalyst layer.
The invention further provides a method for the preparation of a filter catalyzed with flow through the walls.
In its broad embodiment, the invention provides a method for the preparation of a catalyzed filter with flow through the walls, comprising the steps consisting of a) providing a filter body with flow through the walls with a plurality of inlet flow channels and longitudinal outlet flow channels that are separated by porous gas permeable partition walls; b) provide a catalyst support coating comprising a first catalyst composition that is active in the reaction of nitrogen oxides with carbon monoxide and hydrogen to ammonia and a second catalyst composition that is active in the selective reduction of oxides of nitrogen by means of the reaction with ammonia to nitrogen, the first catalyst composition has a fashion particle size that is smaller than the average pore diameter of the porous partition walls and the second composition of catalyst has a fashion particle size that is larger than the average pore diameter of the porous partition walls; c) coating the filter body with the catalyst support coating by introducing the support coating at the outlet end of the outlet channels; Y d) drying and heat treating the coated filter body to obtain the catalyzed particulate filter.
Specific catalyst compositions for use in the invention are mentioned hereinabove and are further disclosed in claims 2 to.
In a further embodiment of the invention, the filter is additionally coated with a commonly called ammonia synthesis catalyst, which is a catalyst that is active in the oxidation of excess ammonia to nitrogen and water.
Thus, in this embodiment, the inventive method comprises the steps consisting of providing a second support coating containing a catalyst composition that is active in the selective oxidation of ammonia; Y coating at least a part of the outlet channels with the support coating after the coating with the catalyst support coating.
When preparing the support coatings for use in the invention, the catalysts which are usually in the form of particles are milled or agglomerated to the required particle size and suspended in water or organic solvents, optionally with the addition of binding substances, viscosity improvers, foaming agents or other processing aids.
The filter is then applied with a support coating in accordance with common practice, which includes vacuum application in the filter, pressurization of the support coating or by dip coating.
The amount of the first catalyst coated on the filter is typically 10 to 140 g / 1 and the amount of the second catalyst on the filter is typically 10 to 100 g / 1. The total catalyst load on the filter is typically in the range of 40 to 200 g / 1.
Examples of suitable filter materials for use in the invention are silicon carbide, aluminum titanate, cordierite, alumina, mullite or combinations thereof.
Example A suspension of the first catalyst composition is prepared in a first step from a powder mixture of palladium and rhodium deposited on particles of cerium oxide and alumina of a particle size smaller than the average pore size of the wall of the filter.
A suspension of the first catalyst of the mixture is prepared by mixing 20 g of these powders in 40 ml of demineralized water per liter of filter. A dispersion agent Zephrym ?? - ???? ^ and an antifoaming agent are added. The suspension is milled in a ball mill. The particle sizes of the final suspension should be smaller than the average pore diameter of the pores in the filter wall with flow through the walls.
A suspension of a second catalyst is made by mixing and dispersing 100 g of silica-aluminum phosphate SAPO-34MR promoted with 2% copper in 200 ml of demineralized water per liter of filter. A dispersion agent Zephrym ?? - ???? ^ and an antifoaming agent are added. The particle sizes must be larger than the average pore diameter of the pores in the filter wall with flow through the walls.
The suspensions of the first catalyst and the second catalyst are then mixed to a suspension.
A filter with conventionally high porosity plugged flow through the SiC walls (approximately 60% and a mean pore size of the wall of approximately 18 μ) is used.
The mixed suspensions of the first catalyst and the second catalyst are applied as a support coating from the outlet end of the filters on the permeate side of the filters by means of standard methods of applying the support coating on the permeate side, and they are dried and they burn at 750 ° C.

Claims (6)

1. A method for the preparation of a catalyzed filter with flow through the walls, characterized in that it comprises the steps consisting of: a) providing a filter body with flow through the walls with a plurality of inflow channels and longitudinal outlet flow channels that are separated by porous gas permeable partition walls; b) provide a catalyst support coating comprising a first catalyst composition that is active in the reaction of nitrogen oxides with carbon monoxide and hydrogen to ammonia and a second catalyst composition that is active in the selective reduction of oxides of nitrogen by means of the reaction with ammonia to nitrogen, the first catalyst composition has a fashion particle size smaller than the average pore diameter of the porous partition walls and the second catalyst composition has a particle size of fashion larger than the average pore diameter of the porous partition walls; c) coating the filter body with the catalyst support coating by introducing the support coating at the outlet end of the outlet channels; and d) drying and heat treating the coated filter body to obtain the catalyzed particulate filter.
2. The method according to claim 1, characterized in that the catalyst which is active in the conversion of nitrogen oxides to ammonia includes palladium, platinum, a mixture of palladium and rhodium and a mixture of palladium, platinum and rhodium.
3. The method according to claim 1, characterized in that the catalyst that is active in the conversion of nitrogen oxides to ammonia consists of palladium.
4. The method according to any of claims 1 to 3, characterized in that the catalyst that is active in the selective reduction of nitrogen oxides comprises at least one of a zeolite, a silica-aluminum phosphate, an ion exchange zeolite. , silica-aluminum phosphate promoted with iron and / or copper and one or more common metal oxides.
5. The method according to any of the preceding claims, characterized in that it further comprises the steps consisting in providing a second support coating containing a catalyst composition that is active in the oxidation of ammonia; and coating a part of the outlet channels in the region at the outlet end with the second support coating.
6. A catalyzed filter with flow through the walls, characterized in that it is prepared according to any of the preceding claims.
MX2014000499A 2011-07-13 2012-06-14 Method for coating a catalysed particulate filter and a particulate filter. MX2014000499A (en)

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