WO2012160355A1 - Système et procédé de génération de no2 - Google Patents

Système et procédé de génération de no2 Download PDF

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Publication number
WO2012160355A1
WO2012160355A1 PCT/GB2012/051121 GB2012051121W WO2012160355A1 WO 2012160355 A1 WO2012160355 A1 WO 2012160355A1 GB 2012051121 W GB2012051121 W GB 2012051121W WO 2012160355 A1 WO2012160355 A1 WO 2012160355A1
Authority
WO
WIPO (PCT)
Prior art keywords
catalyst
hydrogen
silver
silver catalyst
soot
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.)
Ceased
Application number
PCT/GB2012/051121
Other languages
English (en)
Inventor
Paul James Millington
Edward James Richard Moss
Raj Rao Rajaram
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.)
Johnson Matthey PLC
Original Assignee
Johnson Matthey PLC
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 Johnson Matthey PLC filed Critical Johnson Matthey PLC
Publication of WO2012160355A1 publication Critical patent/WO2012160355A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • B01J23/50—Silver
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
    • C01B21/36—Nitrogen dioxide (NO2, N2O4)
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/956—Silicon carbide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/202—Hydrogen
    • 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
    • B01D2255/104—Silver
    • 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
    • F01N3/023—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 using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/0231—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 using means for regenerating the filters, e.g. by burning trapped particles using special exhaust apparatus upstream of the filter for producing nitrogen dioxide, e.g. for continuous filter regeneration systems [CRT]
    • 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
    • F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
    • F01N3/2066—Selective catalytic reduction [SCR]

Definitions

  • the present invention concerns improvements in catalytic processes, and more particularly concerns improvements in the oxidation of nitric oxide (also known as nitrogen monoxide or "NO").
  • nitric oxide also known as nitrogen monoxide or "NO"
  • CRT ® system comprises a platinum-based oxidation catalyst coated on a flow-through monolith substrate and downstream thereof a soot filter, preferably a wall-flow filter.
  • the filter can be catalysed with a catalyst for reducing the combustion temperature of trapped soot, in which case the catalysed filter is often referred to as a Catalysed Soot Filter (CSF).
  • CSF Catalysed Soot Filter
  • the CRT ® reaction i.e. N0 2 + C (i.e. soot) ⁇ NO + CO
  • the CRT ® reaction has been adapted and utilised extensively in recent years to provide a variety of approaches and systems for exhaust gas aftertreatment.
  • CSF Catalysed Soot Filter
  • a catalytic Pt coating is applied to a wall-flow filter which is disposed in the exhaust gas line.
  • the filter surface generally has further catalysts to promote the soot oxidation reaction.
  • the CSF tends to operate by accumulating soot when the vehicle is operated at low speeds, such as in an urban environment.
  • the exhaust gas temperatures under low loads/low speeds are too low effectively to generate N0 2 or to cause the oxidation of soot by the CRT reaction.
  • the CSF may be regenerated to remove the accumulation of soot by running the engine at higher speeds and/or under higher load or by engine management to create higher temperatures within the CSF. Whilst the CSF is effective, essentially it requires coatings containing expensive Pt for the purpose of generating N0 2 .
  • SCR Selective Catalytic Reduction
  • HC- SCR HydroCarbon Selective Catalytic Reduction
  • hydrocarbon which is already present on-board in the form of fuel, has been found to have the ability to chemically reduce NOx.
  • the necessary hydrocarbon may be supplied to the gas stream entering the SCR catalyst in a number of ways, including by post-combustion injection into the cylinders, and by injection of fuel into the exhaust gas stream.
  • N0 2 :NO mixture in gas entering a SCR catalyst beneficially improves the rate of NO x reduction, compared to the same process practised on an exhaust gas wherein NO x is present entirely as NO or particularly wherein NO x is present entirely as N0 2 .
  • EP 1054722 discloses the oxidation of NO to N0 2 thereby to provide a mixture of NO and N0 2 at the SCR catalyst inlet.
  • the present invention provides a process for the generation of N0 2 by oxidation of NO in the presence of a catalyst, comprising the step of passing NO in the presence of a gaseous oxidising agent over a silver catalyst, in the presence of a quantity of hydrogen, wherein:
  • the silver catalyst is deposited on a soot filter or as a component of a Catalytic Soot Filter;
  • the silver catalyst is disposed upstream of a soot filter
  • the silver catalyst is disposed upstream of a selective catalytic reduction catalyst.
  • the invention also provides an exhaust system for an internal combustion engine, which system comprising a catalyst chamber, a silver catalyst positioned within the catalyst chamber and means to supply a quantity of hydrogen to the catalyst chamber, wherein the silver catalyst is disposed in one of the following arrangements:
  • the silver catalyst is deposited on a soot filter or as a component of a Catalytic Soot Filter;
  • the silver catalyst is disposed upstream of a soot filter
  • the silver catalyst is disposed upstream of a selective catalytic reduction catalyst
  • N0 2 is generated by contacting the silver catalyst with hydrogen.
  • the system of feature (iii) comprises means for injecting a nitrogenous reductant between the silver catalyst and the SCR catalyst and a source of nitrogenous reductant.
  • the silver catalyst is silver on an alumina support.
  • the silver is desirably present as dispersed silver particles or Ag 2 0 clusters, but in the preferred catalysts, the particles are too small to be seen by Transmission Electron Microscopy. Larger silver particles are not particularly active.
  • the alumina is in the form of boehmite or gamma alumina.
  • the silver is present in an amount below 10% by weight of the alumina, more preferably below 5wt%, and most preferably an amount of approximately 2wt%.
  • Suitable silver catalysts may be prepared in known manner.
  • Suitable alumina supports are commercially available, such as “Disperal ® (Sasol) and "SCF140” (Condea).
  • the mixture of NO and gaseous oxidising agent is conveniently an exhaust stream from an internal combustion engine. If the quantity of oxidising agent is too low for the desired quantity of reaction, for example the exhaust stream is from a stoichiometric engine, supplementary air may be added. Conveniently, the gas mixture is from a lean burn engine such as a diesel engine.
  • the quantity of hydrogen suitable for the present invention is in the region of 200-5000ppm of the total gas present in the catalyst chamber, such as 500-3000ppm or 750-2000ppm, but is conveniently around lOOOppm.
  • the hydrogen may conveniently be supplied to the gas stream before it enters the catalyst chamber, although other ways of injecting or admixing the hydrogen may be considered. It will be noted that such quantities of hydrogen are relatively small and even where present the exhaust gas remains lean overall.
  • N0 2 in the present invention is, as with every catalytic reaction, temperature sensitive, although the method may be used over a usefully broad temperature range of approximately 150°C to 450°C. Desirably, the method operates at 200°C to 400°C, especially in the range 220°C to 300°C.
  • the present invention offers a useful control over the generation of N0 2 , because N0 2 is produced in the present invention mainly or exclusively when hydrogen is supplied to the catalyst chamber.
  • Existing Pt catalysts can generate relatively high tailpipe N0 2 levels, which may present the engine/vehicle designer with difficulties in meeting required levels of regulated emissions. So, for example, the California Air Resources Board (CARB) has proposed that a maximum of 20% of tailpipe NO x of the relevant drive cycle is emitted as N0 2 .
  • N0 2 is toxic and can cause headaches, dizziness and nausea in low doses. It also has an objectionable
  • the means for supplying the hydrogen in the present invention may therefore provide for continuous hydrogen supply, but in at least some applications, the means may desirably provide for intermittent supply, e.g. by a pre-programmed control means, desirably in response to engine operating conditions which are known to be associated with increased soot formation, or in response to sensed accumulation of soot on a filter by feedback control, e.g. again controlled by pre-programmed means. This may be achieved using known technology.
  • the silver catalyst may be incorporated in a CSF, to replace all or a proportion of the Pt catalyst normally present.
  • the CSF is generally of single "brick" design, that is to say, a single filter substrate which is coated with all necessary catalytic coatings, including zoned or homogeneous arrangements.
  • Alternative designs such as the conventional CRT ® system, or a SCRT ® system, in which a filter (which may itself be catalysed to reduce the soot oxidation temperature) is separate from the N0 2 generating catalyst, may also benefit from the present invention, i.e. in order from upstream to downstream, the exhaust system comprises an oxidation catalyst, a filter e.g. a wall-flow filter, an injector for ammonia or a precursor thereof, such as urea and a SCR catalyst (see EP 1054722, the entire contents of which is incorporated herein by reference).
  • the invention is expected to be applied initially to so-called LDD (light duty diesel) engines, which are used widely in personal automobiles and light commercial applications. It is expected to be subsequently applied to heavy duty diesel (HDD) applications, such as trucks, buses and stationary sources.
  • LDD light duty diesel
  • HDD heavy duty diesel
  • the invention should not be considered as limited to diesel applications, however, and gasoline engine or other applications may be developed in the future.
  • the required hydrogen may be supplied from a variety of sources. It may be convenient, for example, to produce hydrogen by fuel reforming or by exhaust gas reforming.
  • the on-board reforming of fuel or exhaust gas is currently under active development by commercial and academic teams.
  • the reformate gas may, in certain cases, be used directly without purification or separation, in the present invention.
  • an emission control catalyst it is conventional to deposit an emission control catalyst on a flow-through substrate or on a filter.
  • Conventional catalyst substrates and filters may be used to support the silver catalyst in the present invention, and conventional deposition techniques may be used.
  • the catalyst may include other components which assist or do not significantly degrade the performance of the silver catalyst.
  • a model, (i.e. synthetic) LDD exhaust gas containing 12% 0 2 , lOOOppm CO, 300ppm NO, 300ppm C 3 H 6 , 4.5% H 2 0, 4.5% C0 2 , balance nitrogen is passed over the catalyst bed at various catalyst temperatures, and the quantity of N0 2 in the outlet gas is measured.
  • the results are shown in Figure 1 , for the same catalyst of 2wt% Ag deposited on Disperal alumina, both with the standard gas and for the standard gas with lOOOppm H 2 added. It can be seen from Figure 1 that without H 2 , negligible N0 2 is produced until at about 450°C, approximately 20ppm is produced. However, the addition of H 2 has an immediate and dramatic effect, peaking at approximately 160ppm at a temperature of approximately 250°C.

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

Abstract

L'invention concerne un système d'échappement pour un moteur à combustion interne comprenant une chambre de catalyseur, un catalyseur à l'argent placé à l'intérieur de la chambre de catalyseur et des moyens pour fournir une quantité d'hydrogène à la chambre de catalyseur. Le catalyseur à l'argent est disposé dans un des arrangements suivants : (i) le catalyseur à l'argent est déposé sur un filtre à particules ou en tant que composant d'un filtre à particules catalytique ; (ii) le catalyseur à l'argent est disposé en amont d'un filtre à particules ; et/ou (iii) le catalyseur à l'argent est disposé en amont d'un catalyseur de réduction catalytique sélectif et le N02 est généré par mise en contact du catalyseur à l'argent avec de l'hydrogène.
PCT/GB2012/051121 2011-05-20 2012-05-18 Système et procédé de génération de no2 Ceased WO2012160355A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US201161488480P 2011-05-20 2011-05-20
US61/488,480 2011-05-20
GB201111180A GB201111180D0 (en) 2011-05-20 2011-06-30 System and method for generating NO2
GB1111180.4 2011-06-30

Publications (1)

Publication Number Publication Date
WO2012160355A1 true WO2012160355A1 (fr) 2012-11-29

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DE (1) DE102012208399B4 (fr)
GB (2) GB201111180D0 (fr)
WO (1) WO2012160355A1 (fr)

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0341832A2 (fr) 1988-05-13 1989-11-15 Johnson Matthey Inc. Traitement de gaz d'échappement de moteur diesel
JPH11319563A (ja) * 1998-05-11 1999-11-24 Mazda Motor Corp 排気ガス浄化用触媒
EP1054722A1 (fr) 1998-02-06 2000-11-29 Johnson Matthey Public Limited Company Systeme de reduction de nox dans des gaz d'echappement
DE10261817A1 (de) * 2002-12-19 2004-07-01 INSTITUT FüR ANGEWANDTE CHEMIE BERLIN-ADLERSHOF E.V. Verfahren zur katalytischen Umwandlung von Stickoxiden in Stickstoff
EP1504722A2 (fr) 2003-08-08 2005-02-09 Genefast S.r.l. Dispositif pour prélever des échantillons biologiques et/ou chimiques
US20070031310A1 (en) * 2005-08-05 2007-02-08 Lee Jong-Hwan Reduction of NOx emissions using a staged silver/alumina catalyst system
US20080069741A1 (en) * 2006-09-20 2008-03-20 Gerald Stephen Koermer Catalysts to Reduce NOx in an Exhaust Gas Stream and Methods of Preparation
US20100000202A1 (en) * 2008-07-07 2010-01-07 Fisher Galen B Dual catalyst NOx reduction system for exhaust from lean burn internal combustion engines
EP2223735A1 (fr) * 2007-11-08 2010-09-01 Honda Motor Co., Ltd. Épurateur de gaz d'échappement pour moteur à combustion interne et procédé de purification de gaz d'échappement
US20100284875A1 (en) * 2009-05-11 2010-11-11 Basf Corporation Treatment of power utilities exhaust
EP2301650A1 (fr) * 2009-09-24 2011-03-30 Haldor Topsøe A/S Procédé et système de catalyseur pour SCR de NOx

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0341832A2 (fr) 1988-05-13 1989-11-15 Johnson Matthey Inc. Traitement de gaz d'échappement de moteur diesel
EP1054722A1 (fr) 1998-02-06 2000-11-29 Johnson Matthey Public Limited Company Systeme de reduction de nox dans des gaz d'echappement
JPH11319563A (ja) * 1998-05-11 1999-11-24 Mazda Motor Corp 排気ガス浄化用触媒
DE10261817A1 (de) * 2002-12-19 2004-07-01 INSTITUT FüR ANGEWANDTE CHEMIE BERLIN-ADLERSHOF E.V. Verfahren zur katalytischen Umwandlung von Stickoxiden in Stickstoff
EP1504722A2 (fr) 2003-08-08 2005-02-09 Genefast S.r.l. Dispositif pour prélever des échantillons biologiques et/ou chimiques
US20070031310A1 (en) * 2005-08-05 2007-02-08 Lee Jong-Hwan Reduction of NOx emissions using a staged silver/alumina catalyst system
US20080069741A1 (en) * 2006-09-20 2008-03-20 Gerald Stephen Koermer Catalysts to Reduce NOx in an Exhaust Gas Stream and Methods of Preparation
EP2223735A1 (fr) * 2007-11-08 2010-09-01 Honda Motor Co., Ltd. Épurateur de gaz d'échappement pour moteur à combustion interne et procédé de purification de gaz d'échappement
US20100000202A1 (en) * 2008-07-07 2010-01-07 Fisher Galen B Dual catalyst NOx reduction system for exhaust from lean burn internal combustion engines
US20100284875A1 (en) * 2009-05-11 2010-11-11 Basf Corporation Treatment of power utilities exhaust
EP2301650A1 (fr) * 2009-09-24 2011-03-30 Haldor Topsøe A/S Procédé et système de catalyseur pour SCR de NOx

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
N BOGDANCHIKOVA: "On the nature of the silver phases of Ag/Al2O3 catalysts for reactions involving nitric oxide", APPLIED CATALYSIS. B, ENVIRONMENTAL, vol. 36, no. 4, 28 March 2002 (2002-03-28), pages 287 - 297, XP055033355, ISSN: 0926-3373, DOI: 10.1016/S0926-3373(01)00286-7 *
SAZAMA P ET AL: "Enhancement of decane-SCR-NOx over Ag/alumina by hydrogen. Reaction kinetics and in situ FTIR and UV-vis study", JOURNAL OF CATALYSIS, ACADEMIC PRESS, DULUTH, MN, US, vol. 232, no. 2, 10 June 2005 (2005-06-10), pages 302 - 317, XP004905893, ISSN: 0021-9517, DOI: 10.1016/J.JCAT.2005.03.013 *
VILLANI ET AL: "Catalytic carbon oxidation over Ag/Al2O3", JOURNAL OF CATALYSIS, ACADEMIC PRESS, DULUTH, MN, US, vol. 236, no. 1, 15 November 2005 (2005-11-15), pages 172 - 175, XP005126884, ISSN: 0021-9517, DOI: 10.1016/J.JCAT.2005.09.018 *

Also Published As

Publication number Publication date
GB2491244A (en) 2012-11-28
DE102012208399B4 (de) 2015-06-11
GB201208763D0 (en) 2012-07-04
DE102012208399A1 (de) 2012-11-22
GB2491244B (en) 2014-05-07
GB201111180D0 (en) 2011-08-17

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