WO2015059904A1 - 排気ガス浄化触媒装置及び排気ガス浄化方法 - Google Patents
排気ガス浄化触媒装置及び排気ガス浄化方法 Download PDFInfo
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- WO2015059904A1 WO2015059904A1 PCT/JP2014/005229 JP2014005229W WO2015059904A1 WO 2015059904 A1 WO2015059904 A1 WO 2015059904A1 JP 2014005229 W JP2014005229 W JP 2014005229W WO 2015059904 A1 WO2015059904 A1 WO 2015059904A1
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- 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
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/08—Other arrangements or adaptations of exhaust conduits
- F01N13/10—Other arrangements or adaptations of exhaust conduits of exhaust manifolds
- F01N13/102—Other arrangements or adaptations of exhaust conduits of exhaust manifolds having thermal insulation
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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
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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
- B01D53/9481—Catalyst preceded by an adsorption device without catalytic function for temporary storage of contaminants, e.g. during cold start
- B01D53/9486—Catalyst preceded by an adsorption device without catalytic function for temporary storage of contaminants, e.g. during cold start for storing hydrocarbons
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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
- B01J37/0248—Coatings comprising impregnated particles
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
- F01N3/0835—Hydrocarbons
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D2255/10—Noble metals or compounds thereof
- B01D2255/102—Platinum group metals
- B01D2255/1023—Palladium
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D2255/00—Catalysts
- B01D2255/10—Noble metals or compounds thereof
- B01D2255/102—Platinum group metals
- B01D2255/1025—Rhodium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
- B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
- B01J29/74—Noble metals
- B01J29/7415—Zeolite Beta
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- 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
- F01N2340/00—Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the apparatus; Spatial arrangements of exhaust apparatuses
- F01N2340/02—Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the apparatus; Spatial arrangements of exhaust apparatuses characterised by the distance of the apparatus to the engine, or the distance between two exhaust treating apparatuses
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- 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
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- 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
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- 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
- the present invention relates to an exhaust gas purification catalyst device and an exhaust gas purification method.
- trimetallic catalysts mainly containing platinum (Pt), palladium (Pd), and rhodium (Rh) as catalytic metals have been used for purification of exhaust gas discharged from gasoline engines.
- Pt platinum
- Pd palladium
- Rh rhodium
- a two-layer type catalyst containing Pt in at least one layer has been proposed.
- a catalyst in which the catalytic metal is separated and supported on the upstream side and the downstream side in the exhaust gas flow direction, and a catalyst in which different catalytic metal species are supported in the central portion and the peripheral portion of the honeycomb carrier Various types of catalysts have been proposed, such as catalysts prepared with different supporting metal concentrations at the central part and the peripheral part of the honeycomb carrier.
- HCCI combustion is a combustion method in which gasoline in a combustion chamber is combusted by compression self-ignition in a lean atmosphere in accordance with the operating state of the engine.
- HCCI combustion is limited by the maximum in-cylinder pressure (Pmax) and the in-cylinder pressure increase rate (dP / d ⁇ ), so its operating range is limited at present, so the low load side of the engine is driven by HCCI combustion.
- Pmax maximum in-cylinder pressure
- dP / d ⁇ in-cylinder pressure increase rate
- SI spark ignition
- the present inventors investigated the exhaust gas composition of HCCI combustion, it was found that the exhaust gas contained a relatively large amount of saturated hydrocarbons having 5 carbon atoms (n-pentane, i-pentane) and CO. did. This is considered to be due to the fact that the fuel is gasoline and this is burnt at a low temperature.
- Such saturated hydrocarbons are also contained in the exhaust gas of the engine burned in the vicinity of the normal stoichiometric, though not as much as the exhaust gas of the HCCI combustion engine. For this reason, in an ordinary gasoline engine, when the exhaust gas temperature is low, such as when the engine is started, the catalyst metal has not yet been activated, and thus the saturated hydrocarbon is not sufficiently oxidized and discharged. Will be.
- Patent Document 1 discloses a hydrocarbon combustion catalyst in which a platinum group metal is supported on silica-alumina having an aluminum (Al) / silicon (Si) atomic ratio of 5 to 60.
- Pd when Pd is supported as a platinum group metal in the above catalyst, it is excellent in combustion of propane (C 3 H 8 ), which is a saturated hydrocarbon, and can be used for boilers, aircraft jet engines, and automobiles. It is said that it is suitable as a catalyst used in a high-temperature combustor using a catalytic combustion system such as a gas turbine or a power generation gas turbine.
- Patent Document 1 Although the catalyst of Patent Document 1 is excellent in propane combustion as described above, it is not clear whether pentane (C 5 H 12 ), which has a higher carbon number than propane and is difficult to burn, can be burned efficiently. In addition, when the air-fuel ratio changes greatly depending on operating conditions as in the case of an automobile engine and the catalyst temperature is relatively low immediately after starting, there is also a problem that it is difficult to purify hydrocarbons because the catalyst performance cannot be fully exhibited. . In particular, since lean combustion is performed during the HCCI combustion, when Pd is used as the catalyst metal, Pd is maintained in an oxidized state, and hydrocarbons cannot be burned sufficiently. In addition to the saturated hydrocarbons, the exhaust gas components include aromatic hydrocarbons and unsaturated hydrocarbons. In addition to the hydrocarbons, exhaust gas components include CO and NO x (nitrogen oxides). It is also important to be able to purify these efficiently.
- the present invention has been made in view of the above problems, and an object of the present invention is to efficiently purify saturated hydrocarbons even in a gasoline engine having a low exhaust gas temperature, and to perform aromatic carbonization other than saturated hydrocarbons. Another object is to efficiently purify other exhaust gas components such as hydrogen and unsaturated hydrocarbons.
- Pt as a catalyst metal is supported on silica-alumina, and this is contained in the catalyst layer that the exhaust gas emitted from the engine first contacts. I let you.
- An exhaust gas purification catalyst device is an exhaust gas purification catalyst device that is disposed in an exhaust gas passage of an engine and has a plurality of catalyst layers, and purifies exhaust gas exhausted from the engine.
- the supported silica-alumina is contained in the catalyst layer that the exhaust gas of the plurality of catalyst layers contacts first.
- silica-alumina is used as a support material for supporting Pt, and silica-alumina has a large specific surface area and can improve the dispersibility of the supported Pt. Furthermore, since silica-alumina has a small pore diameter, Pt can be supported in a large amount on the surface, not in the pores. As a result, the contact property between Pt and exhaust gas containing saturated hydrocarbons can be improved. Pt is excellent in the oxidation purification performance of saturated hydrocarbons, and it is possible to oxidize and purify saturated hydrocarbons with high efficiency by improving the contact between such Pt and exhaust gas containing saturated hydrocarbons. It becomes. In addition, Pt-supported silica-alumina is particularly excellent in the oxidation purification ability of saturated hydrocarbons having 5 or more carbon atoms.
- Rh and Pd are contained as catalytic metals in addition to Pt.
- Rh contributes to the steam reforming reaction, and H 2 is generated by this reaction. Therefore, the reduction purification of NO x can be promoted, and HC such as saturated hydrocarbons and other aromatic hydrocarbons and unsaturated hydrocarbons can be promoted. It also contributes to partial oxidation of CO.
- Pd is excellent in low-temperature oxidation ability and can oxidize the HC and CO partially oxidized by Rh with high efficiency. Therefore, exhaust gas can be purified with high efficiency.
- the plurality of catalyst layers are laminated, and the Pt-supported silica-alumina is the uppermost layer of the laminated catalyst layers that the exhaust gas first contacts with. It is preferable that it is contained.
- the uppermost layer is Pt-supported silica-alumina, which has excellent oxidation purification performance for saturated hydrocarbons, so that the contact between Pt-supported silica-alumina and saturated hydrocarbons is improved, making saturated hydrocarbons highly efficient.
- by oxidizing and purifying saturated hydrocarbons from a low temperature in the uppermost layer it is possible to prevent unpurified saturated hydrocarbons from interfering with purification of other exhaust gas components by Rh or Pd contained in the lower layer.
- Rh or Pd contained in the lower layer As described above, when saturated hydrocarbons having a large number of carbon atoms such as C 5 H 12 among the saturated hydrocarbons are oxidized and purified, the reaction heat generated at that time is large. The catalyst temperature can be raised and the catalyst performance can be sufficiently exerted.
- the uppermost layer further includes Rh, and the lower layer than the uppermost layer includes Pd.
- Pd has slightly lower heat resistance than Rh, and when exposed to high temperature exhaust gas for a long time, it is easy to form an alloy with other catalytic metals. Therefore, Pd is contained in the lower layer and Rh is contained in the upper layer. By separating each, good catalyst performance can be obtained.
- the plurality of catalyst layers include three stacked layers, and the lowest layer among the three stacked layers includes the Pd, Preferably, the intermediate layer of the three layers includes the Rh, and the uppermost layer of the stacked three layers includes the Pt-supported silica-alumina.
- the layer containing Pt-supported silica-alumina is in the uppermost layer, as described above, it is possible to prevent unpurified saturated hydrocarbons from interfering with purification of other exhaust gas components of Rh and Pd. Further, since the intermediate layer containing Rh and the lowermost layer containing Pd are separately provided in the lower layer, as described above, Pd can be prevented from being exposed to high temperature for a long time, and alloying of Pd and Rh can be achieved. Can be prevented.
- the Pt-supported silica-alumina is also contained in a catalyst layer other than the uppermost layer among the plurality of stacked catalyst layers, and the Pt-supported silica in the uppermost layer.
- the content of silica-alumina is preferably larger than the content of the Pt-supported silica-alumina in the catalyst layer other than the uppermost layer.
- the exhaust gas purifying catalyst device comprises a first catalyst and a second catalyst disposed downstream of the first catalyst in the exhaust gas flow direction, wherein the first catalyst is the exhaust gas first. It is preferable that the catalyst layer is in contact with the Pt-supported silica-alumina.
- the first catalyst which is provided upstream of the exhaust gas passage closer to the engine and includes Pt-supported silica-alumina, is heated relatively faster than the second catalyst disposed downstream thereof,
- the catalytic activity can be increased.
- saturated hydrocarbons having a large number of carbon atoms such as C 5 H 12 can be efficiently oxidized and purified from a low temperature.
- the reaction heat generated at that time is large.
- the saturated hydrocarbon can be improved purification performance of aromatic hydrocarbons and unsaturated hydrocarbons such as HC, CO and NO x.
- the first catalyst further includes the Pd.
- the catalytic performance of the first catalyst can be improved particularly immediately after the engine is started.
- the first catalyst and the second catalyst are separated from each other.
- the thermal energy of the exhaust gas can be concentrated and input to the first catalyst, so that the temperature of the first catalyst is raised earlier and the oxidation reaction is started.
- the temperature rise of the downstream second catalyst due to the heat of reaction generated in the first catalyst is also accelerated, and the catalyst performance can be efficiently exhibited.
- the exhaust gas purifying catalyst device includes an HC trap portion including an HC trap material disposed downstream of the first catalyst in the exhaust gas flow direction, and the second catalyst is more than the HC trap portion.
- the second catalyst is disposed downstream of the exhaust gas flow direction, and the second catalyst includes a catalyst layer containing Pd and Rh as catalytic metals as one of the plurality of catalyst layers, and the first catalyst includes Pd and Rh. It is preferably not included.
- HC trap section traps HC and reduces the amount of HC flowing into the second catalyst. be able to. Thereafter, the temperature of the exhaust gas flowing into the HC trap part and the second catalyst rises, so that HC is desorbed from the HC trap part and the second catalyst is activated, so that it is desorbed by the activated second catalyst.
- the released HC can be oxidized and purified efficiently.
- the second catalyst contains Rh and Pd, and Rh contributes to the steam reforming reaction, and H 2 is generated by this reaction. Therefore, reduction purification of NO x can be promoted, and saturated hydrocarbons It also contributes to partial oxidation of HC and CO such as and other aromatic hydrocarbons and unsaturated hydrocarbons.
- Pd is excellent in low-temperature oxidation ability and can oxidize the HC and CO partially oxidized by Rh with high efficiency. That is, exhaust gas can be purified with high efficiency.
- the second catalyst includes an HC trap layer containing an HC trap material, and a Pd / Rh containing layer containing Pd and Rh as the catalyst metal on the HC trap layer. Is preferably provided as one of the plurality of catalyst layers.
- HC when the exhaust gas temperature is low, HC can be trapped not only in the HC trap part but also in the HC trap layer of the second catalyst, and the HC is desorbed and activated after the exhaust gas temperature rises.
- HC can be oxidized and purified efficiently.
- a heat insulating layer is provided on the inner wall of at least one of the first catalyst and the second catalyst on the upstream side in the exhaust gas flow direction from the first catalyst. It is preferable to be provided.
- the heat insulating means it is possible to adopt at least one of the exhaust gas passage having a double pipe structure and the provision of a heat insulating layer made of a low thermal conductive material on the wall of the exhaust gas passage. .
- the first catalyst is disposed in an exhaust port of the engine, and the catalyst layer containing the Pt-supported silica-alumina and first contacting with the exhaust gas is a metal. It is preferably formed on a carrier.
- the Pt-supported silica-alumina is contained in the first catalyst provided in the exhaust port closer to the combustion chamber of the engine, the catalyst activity can be increased by raising the temperature relatively quickly. For this reason, the saturated hydrocarbon can be efficiently oxidized and purified.
- a heat insulating means is provided upstream of the first catalyst in the exhaust port in the exhaust gas flow direction.
- the heat insulating means in this case, at least one of a double pipe structure for the exhaust gas passage and a heat insulating layer made of a low thermal conductive material on the wall of the exhaust gas passage can be employed. .
- the first catalyst using the metal carrier further includes Pd as a catalyst metal.
- the second catalyst preferably contains Pd and Rh as catalyst metals.
- Rh contributes to the steam reforming reaction, and H 2 is generated by this reaction. Therefore, the reduction purification of NO x can be promoted, and HC such as saturated hydrocarbons and other aromatic hydrocarbons and unsaturated hydrocarbons can be promoted. It also contributes to partial oxidation of CO.
- Pd is excellent in low-temperature oxidation ability and can oxidize the HC and CO partially oxidized by Rh with high efficiency.
- the exhaust gas purifying method according to the present invention is an exhaust gas purifying method for purifying exhaust gas discharged from an engine, and is a Pt-supported silica-alumina in which Pt is supported on silica-alumina modified with silicon by alumina.
- the first catalyst layer containing the first catalyst layer is disposed so that the exhaust gas contacts first
- the second catalyst layer including Pd or Rh is disposed so that the exhaust gas contacts after the first catalyst layer
- the first catalyst layer Is used to oxidize and purify saturated hydrocarbons having 5 or more carbon atoms in the exhaust gas from a lower temperature, increase the temperature of the exhaust gas flowing into the second catalyst layer by the reaction heat generated along with the oxidation purification, It is characterized by improving oxidation purification of hydrocarbons other than saturated hydrocarbons having 5 or more carbon atoms in exhaust gas.
- the reaction heat generated at that time is large.
- the catalyst temperature of the second catalyst layer arranged to increase the temperature can be increased, and the catalyst performance can be sufficiently exhibited. Thereby, exhaust gas components can be purified efficiently.
- an HC trap portion including an HC trap material is disposed between the first catalyst layer and the second catalyst layer, and hydrocarbons in the exhaust gas discharged immediately after the engine is started.
- the HC trap is trapped by the HC trap unit, and the first catalyst layer is used to oxidize and purify saturated hydrocarbons having 5 or more carbon atoms in the exhaust gas after the engine is started, and the HC trap is generated by reaction heat generated by the oxidative purification.
- the exhaust gas flowing into the second catalyst layer is increased by increasing the temperature of the exhaust gas flowing into the first and second catalyst layers, desorbing the trapped hydrocarbons by increasing the temperature of the exhaust gas flowing into the HC trap portion. It is preferable that the second catalyst layer is activated by increasing the gas temperature and the hydrocarbons desorbed from the HC trap part are oxidized and purified by the second catalyst.
- the HC trap traps HC in the exhaust gas immediately after the engine is started. Therefore, when the exhaust gas temperature has not yet risen and the catalytic activity is not sufficiently exerted, the HC is not purified and is discharged to the outside. It can prevent discharge. When the exhaust gas temperature rises, HC can be desorbed and oxidized and purified by the downstream second catalyst.
- the engine is preferably an engine capable of HCCI combustion.
- the exhaust gas of HCCI combustion contains a large amount of saturated hydrocarbons having 5 carbon atoms (n-pentane, i-pentane), and the present invention has a high purifying ability for such saturated hydrocarbons.
- the exhaust gas purification catalyst device By applying the exhaust gas purification catalyst device to an engine capable of HCCI combustion, exhaust gas purification can be performed with high efficiency.
- the contact property between Pt and exhaust gas containing saturated hydrocarbons can be improved. It is possible to oxidize and purify saturated hydrocarbons with high efficiency. Further, since the Pt-supported silica-alumina is contained in the catalyst layer first contacted with the exhaust gas, the catalytic activity of the catalyst layer subsequently brought into contact with the exhaust gas is increased by the reaction heat generated by the oxidation purification of the saturated hydrocarbon. Can be improved.
- FIG. 1 is a schematic diagram illustrating a configuration of an exhaust gas purification catalyst device according to a first embodiment of the present invention. It is the perspective view and partial enlarged view of the catalyst in the same exhaust gas purification catalyst apparatus. It is sectional drawing which shows the catalyst layer structure of the two-layer structure in the same exhaust gas purification catalyst apparatus. It is sectional drawing which shows the catalyst layer structure of the three-layer structure in the same exhaust gas purification catalyst apparatus.
- FIG. 6 is a graph showing the results of X-ray diffraction (XRD) performed on Pt-supported silica-alumina and Pt-supported ⁇ -alumina.
- XRD X-ray diffraction
- (A) and (b) are graphs showing the pore distribution of Pt-supported silica-alumina and Pt-supported ⁇ -alumina, (a) shows the case where no aging treatment is performed, and (b) shows the aging treatment. This shows the case where It is a graph showing the C 5 H 12 purification performance of Pt-supported silica-alumina and Pt-supported ⁇ -alumina.
- It is a schematic diagram which shows the structure of the exhaust gas purification catalyst apparatus which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the catalyst layer structure of the 1st catalyst in the same exhaust gas purification catalyst apparatus. It is sectional drawing which shows the catalyst layer structure of the 2nd catalyst in the same exhaust gas purification catalyst apparatus.
- (A) is a perspective view of the 1st catalyst in the exhaust-gas purification catalyst apparatus
- (b) is an enlarged view which shows a part of cross section of the 1st catalyst. It is sectional drawing which shows the catalyst layer structure of the 1st catalyst in the same exhaust gas purification catalyst apparatus. It is sectional drawing which shows the catalyst layer structure of the 2nd catalyst in the same exhaust gas purification catalyst apparatus. It is a graph which shows the HC purification rate of Examples 7 and 8 and Comparative Examples 8 and 9.
- the engine in the present invention is not limited to one that performs only spark ignition (SI) combustion in which fuel is combusted with the assistance of a normal spark plug.
- SI spark ignition
- the low load side of the engine is set as an operation region by premixed compression self-ignition (Homogeneous ⁇ Charge Compression Ignition: HCCI) combustion
- the high load side is spark ignition (Spark Ignition: SI) that burns fuel with the assistance of the spark plug.
- An engine that switches a combustion mode as an operation region by combustion may be used, or an engine that performs HCCI combustion in the entire region from a low load to a high load.
- FIG. 1 shows a configuration of an exhaust gas purification catalyst apparatus 1 according to a first embodiment of the present invention, in which 2 is a cylinder head of a 4-cylinder gasoline engine, 3 is an exhaust manifold connected to an exhaust port of the engine, Reference numeral 4 denotes an exhaust pipe connected to the downstream end of the exhaust manifold in the exhaust gas flow direction, and reference numeral 10 denotes a catalyst provided in the exhaust pipe.
- the catalyst 10 is provided in the exhaust pipe 4.
- the present invention is not limited to this.
- the catalyst 10 may be provided in the exhaust manifold 3.
- FIG. 2 shows the configuration of the catalyst 10.
- the catalyst 10 is configured by arranging a laminated catalyst 30 on an exhaust gas passage wall of a honeycomb carrier 20 made of cordierite.
- the laminated catalyst 30 is configured by laminating a plurality of catalyst layers.
- the catalyst layer structure according to the present embodiment will be described with reference to FIG.
- the laminated catalyst 30 in the present embodiment includes a Pd-containing catalyst layer (lower layer) 31 formed on the exhaust gas passage wall (base material) of the honeycomb carrier 20, and the Pd-containing catalyst layer 31.
- the Pt / Rh-containing catalyst layer (upper layer) 32 is formed on the exhaust gas passage side so that the exhaust gas discharged from the engine comes into contact first.
- the Pd-containing catalyst layer 31 contains Pd as a catalyst metal supported on the support material.
- the Pd-containing catalyst layer 31 includes a Pd-supported alumina in which Pd is supported on activated alumina ( ⁇ alumina), and a Pd-supported ZrCe-based composite oxide in which Pd is supported on a ZrCe-based composite oxide containing Zr and Ce. including.
- the Pd-containing catalyst layer 31 may include an OSC material such as ceria having oxygen storage / release capacity (OSC).
- OSC oxygen storage / release capacity
- the Pd-containing catalyst layer 31 contains a binder, and for example, zirconyl nitrate can be used as the binder raw material.
- the Pt / Rh-containing catalyst layer 32 includes Pt-supported silica-alumina in which Pt is supported on silica-alumina. Further, the Pt / Rh-containing catalyst layer 32 contains Rh as the catalyst metal supported on the support material.
- the Pt / Rh-containing catalyst layer 32 includes, for example, Rh-supported alumina in which Rh is supported on activated alumina ( ⁇ alumina), and Rh-supported ZrCe-based composite in which Rh is supported on a ZrCe-based composite oxide containing Zr and Ce. Contains oxides.
- the Pt / Rh-containing catalyst layer 32 also contains a binder, and for example, zirconyl nitrate can be used as the binder raw material.
- FIG. 3 shows the laminated catalyst 30 having a two-layer structure
- the present invention is not limited to this, and the laminated catalyst may have, for example, a three-layer structure.
- the laminated catalyst 35 having a three-layer structure will be described with reference to FIG.
- the laminated catalyst 35 having a three-layer structure includes a Pd-containing catalyst layer (lower layer) 31 formed on the exhaust gas passage wall (base material) of the honeycomb carrier 20, and the Pd-containing catalyst layer 31.
- the Rh-containing catalyst layer (intermediate layer) 36 formed on the Rh-containing catalyst layer 36 and the Pt-containing catalyst layer (uppermost layer) 37 formed on the Rh-containing catalyst layer 36 are included. That is, in the laminated catalyst 35 having a three-layer structure, the Pt / Rh-containing catalyst layer 32 is divided into an Rh-containing catalyst layer 36 as an intermediate layer and a Pt-containing catalyst layer 37 as an uppermost layer in FIG. It differs from the laminated catalyst 30 shown.
- the Rh-containing catalyst layer 36 contains Rh supported on a support material such as the Rh-supported alumina and the Rh-supported ZrCe-based composite oxide.
- the Pt-containing catalyst layer 37 contains the Pt-supported silica-alumina.
- Pt-supported silica-alumina may also be included in the lower layer and the intermediate layer other than the uppermost layer. However, in this case, it is preferable that the uppermost layer contains the most Pt-supported silica-alumina.
- the ZrCeNd composite oxide can be prepared using a coprecipitation method. Specifically, an 8-fold diluted solution of 28 mass% ammonia water was mixed with a nitrate solution obtained by mixing cerium nitrate hexahydrate, zirconium oxynitrate solution, neodymium nitrate hexahydrate, and ion-exchanged water. A coprecipitate is obtained by neutralization.
- the operation of removing the supernatant from the solution containing the coprecipitate (dehydration), adding ion-exchanged water thereto and stirring (washing with water) is repeated as many times as necessary. Thereafter, the coprecipitate is dried in the atmosphere at about 150 ° C. for a whole day and night, pulverized, and then baked in the atmosphere at about 500 ° C. for 2 hours. Thereby, the CeZrNd composite oxide powder can be obtained.
- Pd can be supported on the ZrCeNd composite oxide by subjecting the obtained ZrCeNd composite oxide powder to an evaporation-drying method using an aqueous palladium nitrate solution.
- the evaporation to dryness method can be performed as follows. First, ion-exchanged water is added to the ZrNdPr composite oxide particle material to form a slurry, which is sufficiently stirred with a stirrer or the like. Subsequently, a predetermined amount of dinitrodiamine Pd nitric acid solution is dropped into the slurry while stirring, and sufficiently stirred. Thereafter, stirring is continued while heating to completely evaporate water. After evaporation, the Pd-supported ZrCeNd composite oxide is obtained by firing in the atmosphere at about 500 ° C. for 2 hours.
- This ZrCe-based composite oxide may be one in which a rare earth metal such as La or Y is added in addition to Nd.
- La-containing alumina containing, for example, 4% by mass of La 2 O 3 can be used as alumina.
- a Pd-supported alumina can be obtained by subjecting this La-containing alumina to an evaporation to dryness method using a dinitrodiamine Pd nitric acid solution in the same manner as described above.
- a Pd-supported ZrCeNd composite oxide and Pd-supported alumina obtained as described above and an OSC material such as ceria and ZrCeNd composite oxide are mixed with a binder such as zirconyl nitrate and ion-exchanged water, and mixed to form a slurry.
- a binder such as zirconyl nitrate and ion-exchanged water
- the slurry is coated on a support, dried at about 150 ° C., and then calcined at about 500 ° C. for 2 hours, whereby a Pd-containing catalyst layer can be formed on the support.
- Rh-supported ZrCeNd composite oxide can be obtained by evaporating and drying the ZrCeNd composite oxide prepared as described above using an aqueous rhodium nitrate solution as described above.
- Rh-supported alumina can also be obtained by evaporating and drying the alumina using an aqueous rhodium nitrate solution.
- alumina La-containing alumina may be used in the same manner as described above, or Zr—La-containing alumina, which is La-containing alumina carrying a Zr-based composite oxide containing Zr, is used. Also good.
- a method for preparing a Pt / Rh-containing catalyst layer or a catalyst component containing Pt contained in the Pt-containing catalyst layer will be described.
- a method for preparing silica-alumina for supporting Pt will be described.
- a predetermined amount of aluminum alkoxide and silicon alkoxide are suspended in glycol, and the suspension is heat-treated at about 200 ° C. to 400 ° C. for about 2 hours in an inert gas atmosphere such as nitrogen. Thereafter, the obtained reaction product is washed with methanol or the like, dried and then calcined at about 500 ° C. to 1500 ° C. for 2 hours. Thereby, silica-alumina can be obtained.
- Pt-supported silica-alumina can be obtained by subjecting the obtained silica-alumina to the above evaporation-drying method using a dinitrodiamine Pt nitric acid solution.
- silica-alumina may be obtained by a sol-gel method, and Pt may be supported on the silica-alumina by the evaporation to dryness method.
- a binder raw material such as zirconyl nitrate and ion-exchanged water are added to and mixed with a component supporting Rh and Pt-supported silica-alumina obtained as described above to form a slurry.
- the slurry is coated on the Pd-containing catalyst layer, dried at about 150 ° C., and then fired at about 500 ° C. for 2 hours to form a Pt / Rh-containing catalyst layer on the Pd-containing catalyst layer. it can.
- a binder raw material such as zirconyl nitrate and ion-exchanged water are added to the component supporting Rh obtained as described above, and the resulting slurry is obtained in the same manner as described above. Is coated, dried and fired to form a Rh-containing catalyst layer on the Pd-containing catalyst layer. Thereafter, a binder raw material such as zirconyl nitrate and ion-exchanged water are added to Pt-supported silica-alumina, and the resulting slurry is coated on the Rh-containing catalyst layer, dried and fired in the same manner as described above, and then the Rh-containing catalyst layer. A Pt-containing catalyst layer is formed thereon.
- silica-alumina is used as the support material supporting Pt as described above, instead of ordinary activated alumina ( ⁇ alumina).
- the silica-alumina used in the present embodiment is not a mixture of SiO 2 and Al 2 O 3 or a zeolite having a specific pore diameter of about 10 mm represented by ZSM-5, but Al 2 This is a complex oxide state in which O 3 is modified by Si and Si atoms and Al atoms are bonded through O atoms.
- Pt-supported silica-alumina (20) contains 20% by weight of SiO 2 in silica-alumina.
- Pt-supported silica-alumina (14) is silica-alumina. it is those that contain SiO 2 is 14% by weight in, Pt-supported silica - alumina (7), silica - those that contain SiO 2 is 7 wt% in the alumina.
- silica-alumina contains O atoms shared by Si atoms and Al atoms.
- Pt-supported silica-alumina (20) includes O atoms shared with Al atoms. It is assumed that SiO 2 contains 20% by weight.
- the amount of SiO 2 to be contained in silica-alumina is not particularly limited, but if it is about 30% by weight, the SiO 2 crystal phase may be isolated, leading to a decrease in specific surface area. It is preferably less than 30% by weight, more preferably 20% by weight or less.
- FIG. 6A shows the result when the aging process is not performed
- FIG. 6B shows the result when the aging process is performed.
- Table 1 shows the measurement results of the specific surface area.
- the Pt-supported silica-alumina has the largest peak at 10 nm or less both in the case where the aging treatment is performed and in the case where the aging treatment is not performed.
- Pt-supported ⁇ -alumina has the largest peak at about 20 nm to 30 nm. That is, Pt-supported silica-alumina has a smaller pore diameter than Pt-supported ⁇ -alumina.
- Pt is supported on the support material by the evaporation to dryness method using the above-mentioned dinitrodiamine Pt nitric acid solution. In this case, the particle size of the supported Pt is about 10 nm.
- Pt-supported ⁇ -alumina supports more Pt particles in the pores
- Pt-supported silica-alumina allows more Pt particles to be supported on the surface rather than in the silica-alumina pores.
- Pt-supported silica-alumina is used, Pt is present on the surface of the silica-alumina, so that the contact between Pt and the exhaust gas can be improved, and saturated hydrocarbons in the exhaust gas can be improved. It is suggested that combustion can be performed with high efficiency.
- the specific surface area of Pt-supported silica-alumina is higher than that of Pt-supported ⁇ -alumina in both cases where the aging treatment is performed and not performed. Recognize. For this reason, the dispersibility of Pt can be improved by supporting Pt on silica-alumina. That is, when Pt-supported silica-alumina is used, the contact property between Pt and exhaust gas can be improved, and it is suggested that combustion of saturated hydrocarbons in the exhaust gas can be performed with high efficiency.
- a cordierite hexagonal cell honeycomb carrier (diameter 25.4 mm, length 50 mm) having a cell wall thickness of 3.5 mil and a carrier capacity of 25 ml having a cell number of 600 per square inch is used.
- the Pt-supported silica-alumina and the Pt-supported ⁇ -alumina were provided. Specifically, by adding ion exchange water and a binder to each of Pt-supported silica-alumina and Pt-supported ⁇ -alumina as described above, the resulting slurry is coated on the carrier, dried and fired, They were provided on a carrier.
- silica-alumina and ⁇ -alumina which are support materials, were respectively provided on a carrier at 100 g / L (supported amount per 1 L of carrier, the same applies hereinafter), and Pt was supported at 0.5 g / L.
- the honeycomb catalyst thus obtained was subjected to an aging treatment at 900 ° C. for 50 hours in a gas atmosphere similar to the measurement of the pore distribution, and then the C 5 H 12 purification rate was measured.
- each prepared honeycomb catalyst was attached to a model gas flow reactor, and a model gas containing pentane (isopentane) was introduced.
- the composition of the model gas is 3000 ppmC for isopentane (i-C 5 H 12 ), 1700 ppm for CO, 10.5% for O 2 , 13.9% for CO 2 , 10% for H 2 O, and the balance for N 2 is there.
- the temperature of the model exhaust gas flowing into the catalyst is gradually increased from normal temperature, the change in the C 5 H 12 concentration of the gas flowing out from the catalyst is detected, and each honeycomb catalyst is determined based on the amount of C 5 H 12 flowing out.
- the C 5 H 12 purification rate of was measured. The measurement results are shown in FIG.
- the weight ratio of silica (SiO 2 ) and alumina (Al 2 O 3 ) in the silica-alumina supporting Pt and the catalyst performance was changed and C the purification rate of 5 H 12 were measured.
- the light-off temperature (T50) was measured as the C 5 H 12 purification performance.
- the light-off temperature (T50) is the catalyst inlet gas temperature when the temperature of the model gas flowing into the catalyst is gradually increased from room temperature and the C 5 H 12 purification rate reaches 50%.
- the composition of the model gas is the same as in the above test.
- the weight ratio of SiO 2 in the silica-alumina supporting Pt was 20 wt%, 10 wt%, or 5 wt%.
- the purification rate (T50) of C 5 H 12 was measured not only for silica-alumina but also for Pt-supported silica in which Pt was supported on silica. The measurement results are shown in Table 2.
- the H 2 C 12 purification performance was highest when the content of SiO 2 in silica-alumina was 20 wt%, and the purification performance was reduced as the SiO 2 content was decreased. . Further, when Pt was supported on silica instead of silica-alumina, the purification performance of H 5 C 12 was clearly reduced as compared with the case where Pt was supported on silica-alumina. This shows that H 5 C 12 can be purified with high efficiency by using silica-alumina as a support material supporting Pt.
- the Pt / Rh-containing catalyst layer 32 or the Pt-containing catalyst layer 37 is provided on the upper layer of the stacked catalysts 30 and 35.
- Silica-alumina contained in them has a large specific surface area, can improve the dispersibility of the supported Pt, and has a small pore diameter, so that a large amount of Pt can be supported not on the pore but on the surface. it can.
- the Pt / Rh-containing catalyst layer 32 and the Pt-containing catalyst layer 37 are disposed in the uppermost layer, the contact property between Pt and exhaust gas containing saturated hydrocarbons can be improved.
- Pt is excellent in the oxidation purification performance of saturated hydrocarbons, and it is possible to oxidize and purify saturated hydrocarbons with high efficiency by improving the contact between such Pt and exhaust gas containing saturated hydrocarbons. It becomes.
- the Pt / Rh-containing catalyst layer 32 and the Pt-containing catalyst layer 37 are arranged in the uppermost layer, that is, the exhaust gas is arranged so as to be in contact with the first, so that it is generated by oxidation of H 5 C 12 or the like. When the reaction heat flows to the lower catalyst layer, the catalytic activity of the lower catalyst layer can be improved.
- a first catalyst 50 is provided at a collecting portion located downstream of the exhaust manifold 3 in the exhaust gas flow direction.
- Two catalysts 60 are provided. That is, the first catalyst 50 is provided upstream in the exhaust gas flow direction, and the second catalyst 60 is provided downstream from the first catalyst 50.
- the first catalyst 50 and the second catalyst 60 are configured by disposing a catalyst layer on the exhaust gas passage wall of the honeycomb carrier 20 made of cordierite. ing.
- the heat insulation layer 70 is provided on the inner wall of the exhaust manifold 3.
- the exhaust gas from the engine can flow to the first catalyst 50 while maintaining its temperature.
- the catalytic activity of the first catalyst 50 can be improved.
- a heat insulating layer 70 as a heat insulating means may be formed on the inner wall of the exhaust gas passage between the first catalyst 50 and the second catalyst 60. In this way, even when the exhaust gas flows from the first catalyst 50 to the second catalyst 60, the temperature can be maintained, which is advantageous for improving the activity of the second catalyst 60.
- the heat insulating layer 70 is not particularly limited as long as it is made of a material having a lower thermal conductivity than the material of the exhaust gas passage wall.
- a silicone resin mainly composed of Si or a silica is used. Acid glass or the like can be used.
- the heat insulating means is not limited to the heat insulating layer 70, and the exhaust manifold 3 may have a double pipe structure, for example.
- the engine is not limited to performing only spark ignition (Spark ⁇ ⁇ Ignition: SI) combustion in which fuel is burned with the assistance of a normal spark plug.
- the low load side of the engine is set as an operation region by premixed compression self-ignition (Homogeneous ⁇ Charge Compression Ignition: HCCI) combustion
- the high load side is spark ignition (Spark Ignition: SI) that burns fuel with the assistance of the spark plug.
- An engine that switches a combustion mode as an operation region by combustion may be used, or an engine that performs HCCI combustion in the entire region from a low load to a high load.
- FIG. 9 is a cross-sectional view showing a catalyst layer configuration of the first catalyst 50
- FIG. 10 is a cross-sectional view showing a catalyst layer configuration of the second catalyst 60.
- the Pt-containing catalyst layer 51 is a catalyst layer to which exhaust gas discharged from the engine first contacts, and this catalyst layer contains Pt-supported silica-alumina in which Pt is supported on silica-alumina. .
- the Pt-containing catalyst layer 51 contains a binder, and for example, zirconyl nitrate can be used as the binder raw material.
- the first catalyst 50 may contain Pd as a catalyst metal in addition to Pt. In this case, the Pt-containing catalyst layer 51 may contain Pd, or a Pd-containing catalyst layer 61 described below is provided between the Pt-containing catalyst layer 51 and the exhaust gas passage wall of the honeycomb carrier 20. A layer structure may be used.
- a Pd-containing catalyst layer (lower layer) 61 is formed on the exhaust gas passage wall (base material) of the honeycomb carrier 20, and on the Pd-containing catalyst layer 61, That is, an Rh-containing catalyst layer (upper layer) 62 is formed on the exhaust gas passage side.
- the Pd-containing catalyst layer 61 contains Pd as a catalyst metal supported on the support material.
- the Pd-containing catalyst layer 61 includes a Pd-supported alumina in which Pd is supported on activated alumina ( ⁇ alumina), and a Pd-supported ZrCe-based composite oxide in which Pd is supported on a ZrCe-based composite oxide containing Zr and Ce. including.
- the Pd-containing catalyst layer 61 may include an OSC material such as ceria having oxygen storage / release capability (OSC).
- OSC oxygen storage / release capability
- the Pd-containing catalyst layer 61 contains a binder, and for example, zirconyl nitrate can be used as the binder raw material.
- the Rh-containing catalyst layer 62 contains Rh as a catalyst metal supported on the support material.
- the Rh-containing catalyst layer 62 includes, for example, Rh-supported alumina in which Rh is supported on activated alumina ( ⁇ -alumina), and Rh-supported ZrCe-based composite in which Rh is supported on a ZrCe-based composite oxide containing Zr and Ce. Contains oxides.
- the Rh-containing catalyst layer 62 also contains a binder, and for example, zirconyl nitrate can be used as the binder raw material.
- each catalyst material included in the first catalyst 50 and the second catalyst 60 is the same as that in the first embodiment, and the description thereof is omitted here.
- the reaction heat generated at that time is large and is provided upstream in the exhaust gas flow direction.
- the reaction heat generated in the first catalyst containing the Pt-supported silica-alumina can raise the catalyst temperature of the second catalyst provided on the downstream side, so that the catalyst performance can be sufficiently exhibited. Thereby, exhaust gas can be purified with high efficiency.
- T50 The light-off temperature relating to the purification of the isopentane (C 5 H 12 ) of the example containing the Pt-supported silica-alumina in the uppermost layer shown in the first embodiment was measured, and the Pt-supported silica-alumina in the uppermost layer. It was compared with T50 of a comparative example not containing.
- Example 1 to 4 a honeycomb carrier similar to the honeycomb carrier used in the C 5 H 12 purification rate measurement test in FIG. 7 was used. In Examples 1 and 2, a laminated catalyst having a two-layer structure was provided on the carrier. In Examples 3 and 4, a laminated catalyst having a three-layer structure was provided on a support.
- the components of the catalyst layer common to Examples 1 to 4 are shown in Table 3. In Table 3, the amount of each component is shown as an amount per 1 L of carrier (g / L).
- the composition of ZrO 2 : CeO 2 : Nd 2 O 3 67: 23: 10 (mass ratio)
- Example 1 30 g / L of Pt-supported silica-alumina was further contained in the Rh-containing layer of Table 3.
- Example 2 18 g / L of Pt-supported silica-alumina was further contained in the Rh-containing layer of Table 3, and 12 g / L was contained in the Pd-containing layer.
- Example 3 a Pt-containing layer was further provided on the Rh-containing layer in Table 3 to form a three-layer structure, and the Pt-containing layer contained 30 g / L of Pt-supported silica-alumina and a predetermined amount of zirconyl nitrate as a binder. And coated.
- Example 4 a Pt-containing layer was provided on the Rh-containing layer in Table 3 to form a three-layer structure.
- the Pt-containing layer contained 18 g / L of Pt-supported silica-alumina and a predetermined amount of zirconyl nitrate as a binder.
- the Pd-containing layer and the Rh-containing layer were each coated with 6 g / L of Pt-supported silica-alumina.
- Comparative Example 1 was a catalyst containing only the catalyst components shown in Table 3.
- the light-off temperature (T50) was measured as the C 5 H 12 purification performance after aging treatment at 930 ° C. for 50 hours.
- the light-off temperature (T50) is the catalyst inlet gas temperature when the temperature of the model gas flowing into the catalyst is gradually increased from room temperature and the C 5 H 12 purification rate reaches 50%.
- the composition of the model gas is as follows: isopentane (C 5 H 12 ) is 3000 ppmC, CO is 1700 ppm, O 2 is 10.5%, CO 2 is 13.9%, H 2 O is 10%, and the balance is N 2 .
- Table 4 shows the measurement results of T50 according to C 5 H 12 of each catalyst.
- Examples 1 to 4 and Comparative Examples 1 to 5 have a lower light-off temperature (T50) and higher C 5 H 12 purification performance. I understand that.
- T50 light-off temperature
- Example 1 (two-layer structure) and Example 3 (three-layer structure) are compared, there is no significant difference in T50. That is, it is suggested that the purification performance of C 5 H 12 is almost equal between the two-layer catalyst and the three-layer catalyst.
- saturated hydrocarbons can be purified with high efficiency by using Pt-supported silica-alumina as a catalyst component, and the purification performance is further improved by containing more Pt-supported silica-alumina in the uppermost layer of the laminated catalyst. It was suggested that you can.
- Example 5 The HC purification performance of Example 5 provided was measured, and the HC purification of Comparative Example 6 in which the first catalyst contained a mixed catalyst material of Pt-supported silica and Pt-supported alumina instead of Pt-supported silica-alumina. The performance was measured and compared.
- Example 5 a first catalyst obtained by forming a Pt-containing catalyst layer containing Pt-supported silica-alumina on the same honeycomb carrier as used in Examples 1 to 4, the Pd-containing catalyst layer, and Rh A second catalyst including a laminated catalyst having a two-layer structure obtained by sequentially forming the containing catalyst layer on the same honeycomb carrier as used in Examples 1 to 4 was produced.
- the Pt-containing catalyst layer of the first catalyst was produced according to the method for preparing the Pt-containing catalyst layer.
- Pt was supported on the silica-alumina powder by evaporation to dryness using a 5% by weight dinitrodiamine Pt nitric acid solution.
- Pt-containing catalyst is prepared by adding ion-exchanged water and a binder to the prepared Pt-supported silica-alumina, and coating the resulting slurry on the honeycomb carrier, followed by drying at 150 ° C. and firing at 500 ° C. for 2 hours.
- a layer was provided on the support.
- the support was provided with a Pt-containing catalyst layer so that 100 g / L (supported amount per 1 L of support) of Pt-supported silica-alumina was included.
- the Pd-containing catalyst layer and the Rh-containing catalyst layer of the second catalyst were produced according to the method for preparing the Pd-containing catalyst layer and the Rh-containing catalyst layer.
- Table 5 shows the components of these catalyst layers. In Table 5, the amount of each component is shown as an amount (g / L) per 1 L of carrier.
- Pd and Rh supported by evaporation to dryness were dried and fired at 450 ° C.
- drying and baking after coating the slurry prepared by mixing the above catalyst material and ion-exchanged water on the support takes 1.5 hours at a constant heating rate until the support is brought from room temperature to 450 ° C. The temperature was raised and the temperature was maintained for 2 hours.
- the support provided with the Pd-containing catalyst layer and the Rh-containing catalyst layer was impregnated with an aqueous barium acetate solution. After impregnation, the support was heated from room temperature to 200 ° C. at a substantially constant heating rate over 1.5 hours, and held at that temperature (dried) for 2 hours. Thereafter, the temperature was raised from 200 ° C. to 500 ° C. at a substantially constant heating rate over 4 hours, and kept at that temperature for 2 hours (baking).
- the second catalyst is the same as in Example 5, and only the configuration of the first catalyst is different.
- the Pt-containing catalyst layer of the first catalyst contains Pt-supported silica and Pt-supported alumina in a ratio of 20:80 (mass ratio) instead of Pt-supported silica-alumina.
- Pt-supported silica was obtained by supporting Pt by evaporation to dryness using a dinitrodiamine Pt nitric acid solution on silica powder.
- Pt-supported alumina was obtained by supporting Pt by evaporation to dryness using a 5% by weight dinitrodiamine Pt nitric acid solution with respect to the alumina powder.
- the prepared Pt-supported silica and Pt-supported alumina were mixed at a mass ratio of 20:80, ion-exchanged water and a binder were added, and the resulting slurry was coated on the honeycomb carrier, then dried at 150 ° C. and 500 ° C.
- the Pt-containing catalyst layer was provided on the support by calcining for 2 hours.
- the support was provided with a Pt-containing catalyst layer so that 100 g / L (supported amount per liter of support) of Pt-supported silica and Pt-supported alumina were included.
- the first catalyst and the second catalyst of each of Example 5 and Comparative Example 6 were attached to the model gas flow reactor, and the model gas containing the HC component was flowed to measure the HC purification performance. These catalysts were attached to the model gas flow reactor so that the first catalyst and the second catalyst were separated from each other and the first catalyst was positioned upstream of the second catalyst in the gas flow direction.
- the catalysts were previously subjected to aging treatment at 800 ° C. for 24 hours in an atmosphere of 2% O 2 and 10% H 2 O. Thereafter, the temperature of the catalyst is maintained at 100 ° C. in an N 2 atmosphere, and after 5 minutes from introduction of the model gas into the catalyst, the model gas temperature is increased from 100 ° C. at 30 ° C./min.
- the composition of the model gas is 1000 ppmC for n-pentane, 1000 ppmC for i-pentane, 2000 ppmC for toluene, 1500 ppm for CO, 30 ppm for NO, 10% for O 2 , 10% for H 2 O, and the balance for N 2 .
- FIG. 11 shows the measurement results of the HC purification rate at 250 ° C. and 300 ° C. in Example 5 and Comparative Example 6.
- Example 5 has a higher HC purification rate. This is considered to be because, in Example 5, Pt-supported silica-alumina was included in the first catalyst, and in particular, the oxidation purification ability of n-pentane, i-pentane, etc. was higher than that of the catalyst of Comparative Example 6. It is done. Furthermore, it is considered that the heat of reaction due to oxidation of n-pentane, i-pentane or the like flows to the second catalyst on the downstream side to improve the activity of the second catalyst. Thus, it was suggested that the exhaust gas purification performance of HC or the like can be improved by providing the first catalyst containing Pt-supported silica-alumina on the upstream side of the second catalyst.
- the HC trap unit 40 is provided on the upstream side of the exhaust pipe 4 in the exhaust gas flow direction, and the second catalyst 60 is provided on the downstream side of the exhaust gas flow direction. Is provided. That is, in the exhaust gas passage, the first catalyst 50, the HC trap unit 40, and the second catalyst 60 are sequentially arranged from the upstream side to the downstream side in the exhaust gas flow direction.
- a heat insulating layer 70 as a heat insulating means is provided on the inner wall of the exhaust manifold 3 as in the second embodiment.
- the heat insulating means is not limited to the heat insulating layer 70.
- the exhaust manifold 3 may have a double pipe structure.
- the configuration of the first catalyst 50 and the second catalyst 60 is the same as that of the second embodiment. That is, the first catalyst 50 includes a Pt-containing catalyst layer 51 that first contacts exhaust gas discharged from the engine (see FIG. 9), and this Pt-containing catalyst layer 51 contains Pt-supported silica-alumina.
- the second catalyst 60 includes a Pd-containing catalyst layer 61 and an Rh-containing catalyst layer 62 (FIG. 10).
- the HC trap unit 40 differs from the first catalyst 50 only in that an HC trap layer containing an HC trap material is formed on the exhaust gas passage wall of the honeycomb carrier 20 instead of the catalyst layer.
- an HC trap layer containing an HC trap material is formed on the exhaust gas passage wall of the honeycomb carrier 20 instead of the catalyst layer.
- the second catalyst 60 in the second embodiment, the configuration including the two-layer structure of the Pd-containing catalyst layer 31 and the Rh-containing catalyst layer 32 has been described, but one catalyst layer containing Pd and Rh is an exhaust gas of the honeycomb carrier 20. The structure formed on the gas passage wall may be sufficient.
- an HC trap layer 39 containing an HC trap material is provided between the Pd / Rh-containing catalyst layer 38 containing Pd and Rh and the exhaust gas passage wall of the honeycomb carrier 20. It may be a configuration. Further, the HC trap layer 39 may be provided between the Pd-containing catalyst layer 31 and the Rh-containing catalyst layer 32 and the exhaust gas passage wall of the honeycomb carrier 20.
- HC trap layer By providing the HC trap layer in this manner, HC can be trapped not only in the HC trap section 40 but also in the HC trap layer 39 in the second catalyst 30 when the exhaust gas temperature is low.
- the HC can be efficiently oxidized and purified by the desorbed and activated second catalyst 30.
- HC trap material used for the HC trap unit 40 a commonly used HC trap material can be used, for example, ⁇ zeolite.
- the ⁇ zeolite is mixed with a predetermined solvent, coated on the exhaust gas passage wall of the honeycomb carrier, dried at about 150 ° C., and fired at about 500 ° C. for 2 hours to obtain an HC trap portion.
- the HC and the lap portion 40 can trap the HC in the exhaust gas until the activity of the second catalyst 60 is improved, the HC and the lap portion 40 are discharged to the outside when the catalyst is not activated, such as immediately after the engine is started. HC amount can be reduced.
- Example 6 and Comparative Example 7 of the present embodiment will be described.
- Exhaust gas according to Example 6 in which a first catalyst containing Pt-supported silica-alumina, an HC trap part containing an HC trap material, and a second catalyst containing Pd and Rh were sequentially provided from the upstream side to the downstream side in the exhaust gas flow direction.
- the HC purification rate of the gas purification catalyst device was measured.
- a catalyst device of Comparative Example 7 was produced using a mixture of Pt-supported silica and Pt-supported alumina instead of Pt-supported silica-alumina in the first catalyst, and the HC purification rate was measured.
- the honeycomb carrier used in the C 5 H 12 purification rate measurement test of FIG. 7 was used.
- the structure of the 1st catalyst of Example 6 is the same as the 1st catalyst of Example 5 (2nd Embodiment).
- the second catalyst of Example 6 is obtained by forming the Pd-containing layer and the Rh-containing layer shown in Table 3 on the cell wall of the honeycomb carrier.
- the HC trap part was obtained by coating the honeycomb carrier with ⁇ zeolite so as to be 100 g / L, drying at 150 ° C. and firing at 500 ° C. for 2 hours.
- Comparative Example 7 the configurations of the second catalyst and the HC trap unit are the same as in Example 6 described above, and only the configuration of the first catalyst is different.
- the first catalyst of Comparative Example 7 has the same configuration as the first catalyst of Comparative Example 6.
- the first catalyst, the HC trap part, and the second catalyst of Example 6 and Comparative Example 7 were attached to a model gas flow reactor, and a model gas containing an HC component was flowed to measure HC purification performance.
- the first catalyst, the HC trap part, and the second catalyst have the HC trap part located downstream of the first catalyst in the exhaust gas flow direction and the second catalyst located downstream of the HC trap part in the exhaust gas flow direction.
- the same aging treatment as in Example 5 and Comparative Example 6 was performed on these catalysts in advance. Thereafter, the HC purification rate until the model gas temperature rose to 250 ° C. and the HC purification rate until the model gas temperature rose to 300 ° C. were measured under the same conditions and methods as in Example 5 and Comparative Example 6.
- Example 6 has an HC purification rate of up to 250 ° C. and up to 300 ° C. of the model gas temperature. It can be seen that both the HC purification rates during the period are high. This is presumably because in Example 6, the first catalyst contained Pt-supported silica-alumina, and in particular, the oxidation purification ability of n-pentane, i-pentane, etc. was higher than that in Comparative Example 7. Furthermore, it is considered that the heat of reaction due to oxidation of n-pentane, i-pentane or the like flows to the second catalyst on the downstream side to improve the activity of the second catalyst. Thus, it was suggested that the exhaust gas purification performance of HC or the like can be improved by providing the first catalyst containing Pt-supported silica-alumina on the upstream side of the second catalyst.
- 1 is an exhaust gas purification catalyst device according to the present embodiment
- 2 is a cylinder head of the engine
- 2a is an exhaust port of the engine
- 3a is a flange of the exhaust manifold 3 connected to the exhaust port 2a.
- a flange 3 a is coupled to the cylinder head 2.
- a first catalyst 50 is provided in each exhaust port 2 a of the cylinder head 2
- a second catalyst 60 is provided at a collecting portion located downstream of the exhaust manifold 3 in the exhaust gas flow direction.
- a first catalyst 50 and a second catalyst 60 are sequentially arranged in the exhaust gas passage from the upstream side to the downstream side in the exhaust gas flow direction.
- a heat insulating means 70 is provided on the inner wall of the exhaust port 2 a and the inner wall of the exhaust manifold 3.
- FIG. 16 is a cross-sectional view showing an exhaust port 2a portion of the engine.
- the exhaust valve is not shown for simplification of the drawing.
- the first catalyst 50 is provided at the downstream end of the exhaust port 2a in the exhaust gas flow direction.
- the first catalyst 50 is attached to a cylindrical attachment member 80 inserted into the exhaust port 2a from the downstream side in the exhaust gas flow direction.
- the attachment member 80 has a flange portion 80a at one end portion in the longitudinal direction (downstream side in the exhaust gas flow direction).
- the flange portion 80a has a portion protruding outward in the radial direction of the mounting member 80 and a portion protruding outward in the radial direction.
- the flange portion 80a is connected to the flange portion 3a on the upstream side of the exhaust manifold 3 in the exhaust gas flow direction.
- the first catalyst 50 is inserted into the mounting member 80, and the outer peripheral surface of the first catalyst 50 is joined to the inner peripheral surface of the flange portion 80a of the mounting member 80 by welding. Since the flange portion 80a protrudes not only in the radial direction outside the attachment member 80 but also inside, the gap between the inner peripheral surface of the main body portion of the attachment member 80 excluding the flange portion 80a and the outer peripheral surface of the first catalyst 50 is provided. A gap is formed.
- the joint portion of the first catalyst 50 with the flange portion 80a may not be an end portion on the downstream side in the exhaust gas flow direction. That is, the downstream end of the first catalyst 50 may be inserted into the exhaust manifold 3.
- the heat insulating means 70 a heat insulating double pipe made of stainless steel is provided on the inner peripheral surface of the exhaust port 2a in a state where it is cast into the cylinder head.
- the downstream end of the heat insulating means 70 made of this heat insulating double tube is in contact with the upstream end of the mounting member 80.
- the attachment member 80 and the exhaust manifold 3 are also comprised by the heat insulation double tube.
- a heat insulating double pipe is used as the heat insulating means 70, but is not limited thereto, and as described above, a heat insulating layer made of a material having a lower thermal conductivity than the material of the exhaust gas passage wall is provided. May be.
- FIG. 17 shows the configuration of the first catalyst 50.
- FIG. 17A is a perspective view of the first catalyst 50
- FIG. 17B is an enlarged view showing a part of the cross section of the first catalyst 50.
- the first catalyst 50 is configured by disposing the catalyst layer 12 on the exhaust gas passage wall of the metal carrier 11 made of metal.
- the metal carrier 11 is formed by inserting a stainless steel plate 11a and a corrugated plate 11b, which are formed in a spiral shape, into a cylindrical member 11c made of stainless steel. Thereby, many cell passages (exhaust gas passages) are formed between the flat plate 11a and the corrugated plate 11b.
- the metal carrier 11 is provided with a catalyst layer 12 after the surface thereof is oxidized.
- the second catalyst 60 is different from the first catalyst 50 only in the components and size of the catalyst layer 12, and the other configurations are the same.
- a Pt-containing catalyst layer 13 is provided as the catalyst layer 12 on the exhaust gas passage wall (base material) of the metal carrier 11.
- the Pt-containing catalyst layer 13 is a catalyst layer that the exhaust gas discharged from the engine first contacts, and is configured in the same manner as the Pt-containing catalyst layer 51 of the first catalyst 50 of the second embodiment shown in FIG. Yes. That is, the Pt-containing catalyst layer 13 contains Pt-supported silica-alumina.
- a Pd-containing catalyst layer (lower layer) 21 is formed on the exhaust gas passage wall (base material) of the metal carrier 11, and the Pd-containing catalyst layer 21 is exhausted.
- An Rh-containing catalyst layer (upper layer) 22 is formed on the gas passage side.
- the Pd-containing catalyst layer 21 and the Rh-containing catalyst layer 22 are configured in the same manner as the Pd-containing catalyst layer 61 and the Rh-containing catalyst layer 62 of the second catalyst 60 of the second embodiment shown in FIG.
- the configuration including the two-layer structure of the Pd-containing catalyst layer 21 and the Rh-containing catalyst layer 22 as the second catalyst 60 has been described.
- one catalyst layer containing Pd and Rh is the exhaust gas passage wall of the metal carrier 11. The structure formed above may be used.
- Examples 7 and 8 and Comparative Examples 8 and 9 of the present embodiment will be described.
- the engine bench was used, the first catalyst containing Pt-supported silica-alumina was provided in the exhaust port, the second catalyst containing Pd and Rh was provided at the downstream end of the exhaust manifold, and the HC purification rate was increased. It was measured.
- catalyst devices of Comparative Examples 8 and 9 were prepared using a mixture of Pt-supported silica and Pt-supported alumina instead of Pt-supported silica-alumina in the first catalyst, and the HC purification rate was measured.
- Example 7 a Pt-containing catalyst layer containing Pt-supported silica-alumina was formed on a metal carrier (diameter 60 mm, length 100 mm) to obtain a first catalyst.
- the structure of the Pt-containing catalyst layer is the same as the Pt-containing catalyst layer of the first catalyst of Example 5.
- the second catalyst of Example 7 was obtained by forming a Pd-containing catalyst layer and an Rh-containing catalyst layer on the same metal support.
- the configurations of the Pd-containing catalyst layer and the Rh-containing catalyst layer are the same as those of the second catalyst of Example 6 (Table 3).
- Example 8 differs from Example 7 in that a Pd-containing catalyst layer is provided between the exhaust gas passage wall of the carrier and the Pt-containing catalyst layer in the first catalyst.
- the catalyst powder of the Pd-containing catalyst layer carries Pd by evaporation to dryness using a 2.5 wt% dinitrodiamine Pd nitric acid solution with respect to the alumina powder, and the obtained powder is dried at 150 ° C. It was obtained by baking at 500 ° C. for 2 hours.
- This catalyst powder is mixed with a predetermined amount of binder, coated on a support so that the amount of catalyst powder is 40 g / L, dried at 150 ° C., and calcined at 500 ° C. for 2 hours to form a Pd-containing catalyst layer. Obtained.
- a catalyst layer having a two-layer structure was obtained by forming the Pt-containing catalyst layer on the Pd-containing catalyst layer.
- Comparative Example 8 the configuration of the second catalyst is the same as in Example 7, and only the configuration of the first catalyst is different.
- Comparative Example 9 the configuration of the second catalyst is the same as in Example 8, and only the configuration of the first catalyst is different.
- the Pt-containing catalyst layer of the first catalyst had 20:80 (mass ratio) of Pt-supported silica and Pt-supported alumina instead of Pt-supported silica-alumina. It is contained in proportions.
- the configuration of the Pt-containing catalyst layer of the first catalyst of Comparative Examples 8 and 9 is the same as that of the Pt-containing catalyst layer of the first catalyst of Comparative Example 6.
- the first catalyst of each of Examples 7 and 8 and Comparative Examples 8 and 9 is attached to the exhaust port of the engine bench, and the second catalyst is attached to the collection part of the exhaust manifold to operate the engine. And the HC purification rate at 250 ° C. was measured. These catalysts were previously subjected to an aging treatment at 800 ° C. for 24 hours in an atmosphere of 2% O 2 and 10% H 2 O. Further, the gas temperature was measured at a position 5 mm upstream of the first catalyst in the exhaust port.
- the engine operating conditions at 200 ° C. were a net average effective pressure (Pe) of 100 kPa and an engine speed of 1000 rpm, and the engine operating conditions at 250 ° C. were Pe of 200 kPa and an engine speed of 1000 rpm.
- Examples 7 and 8 are the cases where the exhaust gas temperatures are both 200 ° C. and 250 ° C. HC purification rate is high.
- the first catalyst contains Pt-supported silica-alumina, and in particular, the oxidation purification ability of n-pentane, i-pentane and the like is higher than those in Comparative Examples 8 and 9. it is conceivable that.
- the reaction heat generated with the oxidation of n-pentane, i-pentane or the like flows to the second catalyst on the downstream side to improve the activity of the second catalyst.
- Example 8 has a higher HC purification rate. This is considered to be due to the fact that in Example 8, the first catalyst contains Pd and its low-temperature activity is high.
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Abstract
Description
図1は、本発明の第1の実施形態に係る排気ガス浄化触媒装置1の構成を示しており、2は4気筒ガソリンエンジンのシリンダヘッド、3はエンジンの排気ポートに接続された排気マニホールド、4は排気マニホールドの排気ガス流れ方向下流端に接続された排気管、10は排気管に設けられた触媒をそれぞれ示している。なお、本実施形態では、触媒10を排気管4に設けているが、これに限られず、例えば排気マニホールド3に設けられていても構わない。
本実施形態において、積層触媒30は複数の触媒層が積層されて構成されている。本実施形態に係る触媒層構成について図3を参照しながら説明する。
次に、上記の触媒層に含まれる触媒材の調製方法について説明する。
本実施形態では、上記のようにPtを担持するサポート材として、通常の活性アルミナ(γアルミナ)ではなく、シリカ-アルミナを用いている。本実施形態で用いられるシリカ-アルミナは、SiO2とAl2O3とが単に混合されたもの、或いはZSM-5に代表される10Å前後の特定の細孔径を有したゼオライトではなく、Al2O3がSiにより修飾されたものであり、Si原子とAl原子とがO原子を介して結合している複合酸化物の状態である。ここで、本実施形態で用いられるPt担持シリカ-アルミナと、通常のγアルミナにPtが担持されたPt担持γアルミナに対してX線回折(XRD)を行って、それらの結晶構造を解析した結果を図5に示す。
次に、本発明の第2の実施形態に係る排気ガス浄化触媒装置について説明する。なお、本実施形態では、第1の実施形態と同一部材については同一の符号を付けてその説明を省略し、異なる部分について説明する。
次に、本実施形態の第1触媒50及び第2触媒60の触媒層構成について説明する。図9は第1触媒50の触媒層構成を示す断面図であり、図10は第2触媒60の触媒層構成を示す断面図である。
次に、本発明の第3実施形態に係る排気ガス浄化触媒装置について説明する。なお、本実施形態では、先の各実施形態と同一部材については同一の符号を付けてその説明を省略し、異なる部分について説明する。
HCトラップ部40に用いるHCトラップ材としては、通常用いられるHCトラップ材を用いることができ、例えばβゼオライトを用いることができる。βゼオライトを所定の溶媒と混合し、ハニカム担体の排気ガス通路壁にコーティングした後、150℃程度で乾燥し、500℃程度で2時間焼成することでHCトラップ部を得ることができる。
次に、上記排気ガス浄化触媒装置1を用いて、排気ガスを浄化する方法について説明する。本方法では、まず、エンジン始動直後において排出される排気ガス中の炭素数5以上の飽和炭化水素以外の炭化水素を優先的にHCトラップ部40でトラップする。また、第1触媒50によりエンジン始動以降の排気ガス中の特に炭素数5以上の飽和炭化水素を酸化浄化し、その酸化浄化に伴って発生する反応熱によってHCトラップ部40及び第2触媒60に流入する排気ガス温度を高める。そうすると、HCトラップ部40に流入する排気ガス温度の上昇によって、トラップされた炭素数5以上の飽和炭化水素以外の炭化水素が脱離し、また、第2触媒60に流入する排気ガス温度の上昇により第2触媒60の活性が向上する。これによりHCトラップ部40から脱離された炭素数5以上の飽和炭化水素以外の炭化水素を活性化した第2触媒60が酸化浄化する。
次に、本発明の第4の実施形態に係る排気ガス浄化触媒装置について説明する。なお、本実施形態では、先の各実施形態と同一部材については同一の符号を付けてその説明を省略し、異なる部分について説明する。
次に、本実施形態の第1触媒50及び第2触媒60の触媒層構成について説明する。
2 シリンダヘッド
3 排気マニホールド
4 排気管
10 触媒
11 メタル担体
20 ハニカム担体
30,35 触媒層
31 Pd含有触媒層(下層,最下層)
32 Pt/Rh含有触媒層(上層)
36 Rh含有触媒層(中間層)
37 Pt含有触媒層(最上層)
38 Pd/Rh含有触媒層(上層)
39 HCトラップ層
40 HCトラップ部
50 第1触媒
51 Pt含有触媒層
60 第2触媒
61 Pd含有触媒層
62 Rh含有触媒層
70 断熱層
Claims (19)
- エンジンの排気ガス通路に配置され且つ複数の触媒層を有し、前記エンジンから排出される排気ガスを浄化する排気ガス浄化触媒装置であって、
Ptを触媒金属として含み、
前記触媒金属としてのPtは、サポート材としての、アルミナがケイ素によつって修飾されたシリカ-アルミナに担持されており、
前記シリカ-アルミナに前記Ptが担持されてなるPt担持シリカ-アルミナは、前記複数の触媒層のうちの前記排気ガスが最初に接触する触媒層に含まれていることを特徴とする。 - 請求項1の排気ガス浄化触媒装置において、
前記複数の触媒層は、積層されており、
前記Pt担持シリカ-アルミナは、前記積層された触媒層のうちの前記排気ガスが最初に接触する最上層に含まれていることを特徴とする。 - 請求項2の排気ガス浄化触媒装置において、
前記積層された複数の触媒層のうちの最上層には、さらに前記Rhが含まれており、
前記積層された複数の触媒層のうちの最上層よりも下層には、前記Pdが含まれていることを特徴とする。 - 請求項2の排気ガス浄化触媒装置において、
前記複数の触媒層として、積層された三層を備え、
前記積層された三層のうちの最下層には、前記Pdが含まれており、
前記積層された三層のうちの中間層には、前記Rhが含まれており、
前記積層された三層のうちの最上層には、前記Pt担持シリカ-アルミナが含まれていることを特徴とする。 - 請求項2の排気ガス浄化触媒装置において、
前記Pt担持シリカ-アルミナは、前記積層された複数の触媒層のうちの最上層以外の触媒層にも含まれており、
前記最上層における前記Pt担持シリカ-アルミナの含有量は、最上層以外の触媒層における前記Pt担持シリカ-アルミナの含有量よりも大きいことを特徴とする。 - 請求項1の排気ガス浄化触媒装置において、
第1触媒と、該第1触媒よりも排気ガス流れ方向下流側に配設された第2触媒とを備え、
前記第1触媒が前記排気ガスが最初に接触する触媒層を備え、該触媒層が前記Pt担持シリカ-アルミナを含むことを特徴とする。 - 請求項6の排気ガス浄化触媒装置において、
前記第1触媒と前記第2触媒とは離間していることを特徴とする。 - 請求項6の排気ガス浄化触媒装置において、
前記第1触媒よりも排気ガス流れ方向下流側に配置され、HCトラップ材を含むHCトラップ部を備え、
前記第2触媒は、前記HCトラップ部よりも排気ガス流れ方向下流側に配置されており、
前記第2触媒が、触媒金属としてのPd及びRhを含む触媒層を上記複数の触媒層の一つとして備え、前記第1触媒はPd及びRhを含まないことを特徴とする。 - 請求項8の排気ガス浄化触媒装置において、
前記第2触媒は、HCトラップ材を含むHCトラップ層を備え、該HCトラップ層の上に前記触媒金属としてのPd及びRhを含むPd/Rh含有層を上記複数の触媒層の一つとして備えていることを特徴とする。 - 請求項6の排気ガス浄化触媒装置において、
前記第1触媒よりも排気ガス流れ方向上流側、及び前記第1触媒と前記第2触媒との間のうちの少なくとも一方の排気ガス通路に断熱手段が設けられていることを特徴とする。 - 請求項10の排気ガス浄化触媒装置において、
前記断熱手段として、前記排気ガス通路を二重管構造とすること、及び前記排気ガス通路の壁に低熱伝導材からなる断熱層を設けることのうちの少なくとも一方が採用されていることを特徴とする。 - 請求項6の排気ガス浄化触媒装置において、
前記第1触媒は、前記エンジンの排気ポート内に配置されていて、前記Pt担持シリカ-アルミナを含有し前記排気ガスが最初に接触する触媒層がメタル担体上に形成されていることを特徴とする。 - 請求項12の排気ガス浄化触媒装置において、
前記排気ポートにおける前記第1触媒よりも排気ガス流れ方向上流側に断熱手段が設けられていることを特徴とする。 - 請求項13の排気ガス浄化触媒装置において、
前記断熱手段として、前記排気ポートを二重管構造とすること、及び前記排気ポートの壁に低熱伝導材からなる断熱層を設けることのうちの少なくとも一方が採用されていることを特徴とする。 - 請求項12の排気ガス浄化触媒装置において、
前記第1触媒は、触媒金属としてPdをさらに含むことを特徴とする。 - 請求項12の排気ガス浄化触媒装置において、
前記第2触媒は、触媒金属としてPd及びRhを含むことを特徴とする。 - 請求項1の排気ガス浄化触媒装置において、
前記エンジンは、HCCI燃焼が可能なエンジンであることを特徴とする。 - エンジンから排出される排気ガスを浄化する排気ガス浄化方法であって、
アルミナがケイ素によって修飾されたシリカ-アルミナにPtが担持されてなるPt担持シリカ-アルミナを含む第1触媒層を排気ガスが最初に接触するように配置し、Pd又はRhを含む第2触媒層を前記第1触媒層よりも後に排気ガスが接触するように配置し、
前記第1触媒層により前記排気ガス中の炭素数5以上の飽和炭化水素を酸化浄化し、その酸化浄化に伴って発生する反応熱によって前記第2触媒層に流入する排気ガス温度を高め、
前記排気ガス温度の上昇により活性化された前記第2触媒層によって前記排気ガス中の前記炭素数5以上の飽和炭化水素以外の炭化水素を酸化浄化することを特徴とする。 - 請求項18の排気ガス浄化方法において、
前記第1触媒層と前記第2触媒層の間にHCトラップ材を含むHCトラップ部を配置し、
エンジン始動直後に排出される排気ガス中の炭化水素を前記HCトラップ部でトラップし、
前記第1触媒層によりエンジン始動以降の前記排気ガス中の炭素数5以上の飽和炭化水素を酸化浄化し、その酸化浄化に伴って発生する反応熱によって前記HCトラップ部及び第2触媒層に流入する排気ガス温度を高め、
前記HCトラップ部に流入する排気ガス温度の上昇によって、前記トラップされた前記炭化水素を脱離させ、
前記第2触媒層に流入する排気ガス温度の上昇によって、前記第2触媒層を活性化させ、前記HCトラップ部から脱離する炭化水素を前記第2触媒によって酸化浄化することを特徴とする。
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EP3617465A4 (en) * | 2017-06-05 | 2020-04-08 | Mazda Motor Corporation | DEVICE FOR TREATING EXHAUST GAS FROM AN ENGINE AND METHOD FOR PRODUCING THE DEVICE |
US11377995B2 (en) * | 2019-11-19 | 2022-07-05 | Kawasaki Jukogyo Kabushiki Kaisha | Catalyst unit and exhaust structure of engine including same |
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