WO2012140775A1 - 内燃機関の排気浄化装置 - Google Patents
内燃機関の排気浄化装置 Download PDFInfo
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- WO2012140775A1 WO2012140775A1 PCT/JP2011/059407 JP2011059407W WO2012140775A1 WO 2012140775 A1 WO2012140775 A1 WO 2012140775A1 JP 2011059407 W JP2011059407 W JP 2011059407W WO 2012140775 A1 WO2012140775 A1 WO 2012140775A1
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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
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
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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
- B01D53/9404—Removing only nitrogen compounds
- B01D53/9409—Nitrogen oxides
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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
- B01D53/9477—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on separate bricks, e.g. exhaust systems
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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
- F01N13/009—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 having two or more separate purifying devices arranged in series
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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
- F01N13/009—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 having two or more separate purifying devices arranged in series
- F01N13/0093—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 having two or more separate purifying devices arranged in series the purifying devices are of the same type
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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
- F01N13/009—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 having two or more separate purifying devices arranged in series
- F01N13/0097—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 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
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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
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
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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
- F01N3/0842—Nitrogen oxides
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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
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/10—Noble metals or compounds thereof
- B01D2255/102—Platinum group metals
- B01D2255/1023—Palladium
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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
- B01D2255/1025—Rhodium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/20—Metals or compounds thereof
- B01D2255/209—Other metals
- B01D2255/2092—Aluminium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/90—Physical characteristics of catalysts
- B01D2255/91—NOx-storage component incorporated in the catalyst
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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
- F01N2330/00—Structure of catalyst support or particle filter
- F01N2330/60—Discontinuous, uneven properties of filter material, e.g. different material thickness along the longitudinal direction; Higher filter capacity upstream than downstream in same housing
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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
- F01N2510/0682—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
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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 apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine that includes a NOx storage reduction catalyst and a NOx selective reduction catalyst.
- Patent Document 1 discloses a catalyst device for NOx reduction removal.
- the catalyst device of Patent Document 1 is for reducing and removing NOx using HC in a fuel as a reducing agent.
- This catalyst device has two catalysts having different cell dimensions inside. The two catalysts are arranged adjacent to each other in series so that the catalyst having a large cell size is on the upstream side.
- an exhaust purification system in which a three-way catalyst (TWC), a NOx storage reduction catalyst (NSR catalyst), and a NOx selective reduction catalyst (SCR catalyst) are arranged in this order from the upstream side of the exhaust passage of the internal combustion engine.
- TWC three-way catalyst
- NSR catalyst NOx storage reduction catalyst
- SCR catalyst NOx selective reduction catalyst
- Japanese Unexamined Patent Publication No. 10-205325 Japanese Patent Laid-Open No. 2001-079405 Japanese Unexamined Patent Publication No. 2010-265802 Japanese Unexamined Patent Publication No. 2003-245523
- the NSR catalyst tends to cause so-called sulfur poisoning in which its catalytic performance is lowered by the sulfur content contained in the fuel.
- the NOx purification performance of the NSR catalyst decreases, a state may occur in which NOx discharged downstream can not be completely purified by the SCR catalyst. Therefore, even in a purification system using an NSR catalyst and an SCR catalyst, it is desired to suppress sulfur poisoning of the NSR catalyst.
- the above-described prior art catalytic device is intended to improve the purification performance by ensuring the flow of exhaust gas to the entire HC-SCR catalyst by increasing the upstream cell size. Therefore, the above prior art does not contribute at all to sulfur poisoning suppression of the NSR catalyst.
- the present invention has been made to solve the above-described problems, and an object of the present invention is to provide an exhaust purification apparatus improved so as to maintain a high NOx purification rate while suppressing sulfur poisoning of the NSR catalyst. To do.
- the present invention is an exhaust purification device for an internal combustion engine, and includes an NOx occlusion reduction catalyst that is disposed in an exhaust path of the internal combustion engine and occludes or reduces NOx in the exhaust gas.
- the NOx occlusion reduction catalyst is formed on the inner wall surface of a cell through which exhaust gas flows, and includes a coat layer having a function as a catalyst. The thickness of the coat layer on the upstream side of the exhaust gas flow is thinner than the thickness of the coat layer on the downstream side.
- the exhaust purification device may include at least two NOx occlusion reduction catalysts, and these NOx occlusion reduction catalysts may be connected in series to the exhaust gas flow.
- the thickness of the coat layer of the NOx storage reduction catalyst arranged on the upstream side is made thinner than the thickness of the coat layer of the downstream NOx storage reduction catalyst.
- the NOx occlusion reduction catalyst may have at least two adjacent regions divided into an upstream side and a downstream side.
- the thickness of the coat layer in each of the regions is made uniform, and the thickness of the coat layer in the upstream region among these regions is thinner than the thickness of the coat layer in the downstream region.
- the NOx occlusion reduction catalyst may be formed inside the NOx occlusion reduction catalyst so that the thickness of the coat layer becomes thinner as it goes downstream.
- the coat layer may contain Rh or Pd, or may contain Al 2 O 3 .
- the coating layer on the inner wall surface of the cell of the NOx storage reduction catalyst is such that the thickness of the upstream coating layer is thinner than the thickness of the downstream coating layer.
- the NOx occlusion catalyst tends to take in the sulfur component as the coat layer becomes thicker and tends to cause sulfur poisoning.
- the coat layer becomes thinner the purification performance of the catalyst becomes lower. There is a tendency.
- the sulfur poisoning is suppressed by arranging the thin part of the coat layer on the upstream side where the sulfur component is easily taken up, while the thick part of the coat layer is arranged on the downstream side where the sulfur component is difficult to be taken up. This ensures high purification performance. That is, according to the exhaust emission control device of the present invention, it is possible to suppress a decrease in purification performance due to sulfur poisoning and to ensure high purification performance.
- Embodiments of the present invention will be described below with reference to the drawings.
- symbol is attached
- the present invention is not limited to the following embodiments.
- Embodiment 1 FIG.
- FIG. 1 is a diagram for explaining the overall configuration of a system according to an embodiment of the present invention.
- the system according to the present embodiment includes an internal combustion engine 10.
- An exhaust passage 12 communicates with each cylinder of the internal combustion engine 10.
- a start catalyst (hereinafter referred to as “SC”) 14 that is a three-way catalyst is disposed in the exhaust passage 12.
- a NOx occlusion reduction catalyst (hereinafter also referred to as “NSR catalyst”) 16 is disposed downstream of the exhaust passage 12 in the SC 14.
- the NSR catalyst 16 includes two NSR catalysts 161 and 162, and both the NSR catalysts 161 and 162 are connected in series.
- a NOx selective reduction catalyst (hereinafter also referred to as “SCR catalyst”) 18 is disposed downstream of the NSR catalyst 16.
- each NSR catalyst 161, 162 is composed of a Pt layer containing platinum (Pt), an Rh-Pd layer containing rhodium (Rh) and palladium (Pd), and an underlying alumina (Al 2 O 3 ).
- the Al 2 O 3 layer is formed by laminating in order from the surface.
- Each layer constituting both NSR catalysts 161 and 162 contains the bases Ba, Li, and K, and these function as occlusion materials.
- the thickness of the coat layer of the upstream NSR catalyst 161 is 240 g / L.
- the thickness of the coat layer of the downstream NSR catalyst 162 is 270 g / L. That is, the coating layer of the upstream NSR catalyst 161 is thinner than the coating layer of the NSR catalyst 162.
- the internal combustion engine 10 easily discharges HC and CO when the air-fuel ratio is rich. Further, it is easy to exhaust NOx when the air-fuel ratio is lean.
- the SC 14 reduces NOx (purifies to N 2 ) while adsorbing oxygen (O 2 ) in a lean atmosphere.
- NOx purifies to N 2
- O 2 oxygen
- HC and CO are oxidized (purified to H 2 O, CO 2 ) while releasing oxygen.
- ammonia (NH 3 ) is generated by the reaction of nitrogen and hydrogen or HC and NOx contained in the exhaust gas.
- the NSR catalyst 16 occludes NOx contained in the exhaust gas under a lean atmosphere. Further, the NSR catalyst 16 releases NOx stored in a rich atmosphere. NOx released in a rich atmosphere is reduced by HC and CO. At this time, NH 3 is also generated in the NSR catalyst 16 as in the case of SC14.
- the SCR catalyst 18 is configured as a Cu-based zeolite catalyst, and the SC 14 and the NSR catalyst 16 occlude NH 3 produced in a rich atmosphere.
- NH 3 is used as a reducing agent, and NOx in exhaust gas is absorbed. It has the function of selectively reducing.
- the SCR catalyst 18 can effectively prevent a situation in which NH 3 and NOx blown downstream of the NSR catalyst 16 are released into the atmosphere.
- FIG. 2 is a schematic diagram for explaining the storage mechanism of the NSR catalyst under a lean atmosphere when the NSR catalyst is functioning normally.
- FIG. 3 is a diagram for explaining a purification rate when a purification system having an NSR catalyst and an SCR catalyst is functioning normally.
- the horizontal axis represents the load, and the vertical axis represents the NOx purification rate (%).
- the (a) line represents the purification rate of the exhaust gas discharged from the NSR catalyst
- the (b) line represents the NOx purification rate of the exhaust gas that subsequently flows into the SCR catalyst and discharged from the SCR catalyst. ing.
- FIG. 4 is a schematic diagram for explaining the storage mechanism of the NSR catalyst in a lean atmosphere when the NSR catalyst causes sulfur poisoning.
- FIG. 5 is a diagram for explaining the purification rate of the purification system having the NSR catalyst and the SCR catalyst when the NSR catalyst is poisoned with sulfur.
- the horizontal axis represents the load, and the vertical axis represents the NOx purification rate (%).
- line (c) represents the purification rate of exhaust gas discharged from the NSR catalyst
- line (d) represents the purification rate of exhaust gas that subsequently flows into the SCR catalyst and is discharged from the SCR catalyst. Yes.
- the NSR catalyst 16 is configured to suppress sulfur poisoning of the NSR catalyst as described above.
- the NSR catalyst 16 includes the upstream NSR catalyst 161 and the downstream NSR catalyst 162, and the thickness of the coat layer on the cell surface is different between the upstream NSR catalyst 161 and the downstream NSR catalyst 162. It is configured as follows.
- the sulfur component tends to adhere when the coating layer of the catalyst is thick, and tends to become difficult to adhere when it becomes thin.
- the attached sulfur component also tends to be difficult to desorb when the coat layer is thick, but tends to be easily desorbed when the coat layer is thin. That is, it is considered that the NSR catalyst is likely to cause sulfur poisoning when the coat layer is thick, and the NSR catalyst is less likely to cause sulfur poisoning when the coat layer is thin.
- the NOx purification performance of the NSR catalyst may be reduced. That is, in order to maintain the purification performance of the NSR catalyst high, a certain amount of coat layer thickness is required. Further, the sulfur component tends to adhere from the upstream side and hardly reach the downstream side.
- the coating layer of the upstream NSR catalyst 161 is thin, and the coating layer of the downstream NSR catalyst 162 is thick.
- the NSR catalyst 161 having a thin coat layer is disposed on the upstream side where sulfur poisoning is likely to occur. .
- an NSR catalyst 162 having a thick catalyst layer with high catalyst purification performance is disposed. Thereby, the fall of the purification performance by sulfur poisoning as the whole NSR catalyst 16 can be suppressed, and the purification performance of the whole purification system can be maintained high.
- the coat layer is configured by sequentially stacking the Pt layer, the Rh—Pd layer, and the Al 2 O 3 layer as the lower precoat layer.
- the coat layer is not limited to this configuration.
- the coating layer may not include the Al 2 O 3 layer but may be formed only from the Pt layer and the Rh—Pd layer, or may be a layer using Ti. Regardless of which coat layer is used, the upstream NSR catalyst coat layer is made thin, and the downstream NSR catalyst coat layer is made thick so that the influence of sulfur poisoning is suppressed and high. Purification performance can be ensured.
- the upstream NSR catalyst 161 coat layer is 240 g / L and the downstream NSR catalyst 162 coat layer is 270 g / L has been described.
- the thickness of the coat layer is not limited to this, and is appropriately set according to the required purification rate.
- the NSR catalyst is not limited to this in the present invention.
- three or more NSR catalysts having different coat layer thicknesses may be arranged. Even if the number of NSR catalysts increases, it is possible to ensure high purification performance while suppressing sulfur poisoning by installing an NSR catalyst having a thinner coat layer on the upstream side.
- FIG. 6 is a schematic diagram showing an example of another NSR catalyst used as the purification system according to the embodiment of the present invention.
- the NSR catalyst 26 in FIG. 6 is a catalyst that is used alone instead of the two NSR catalysts 161 and 162 in the purification system in FIG.
- the NSR catalyst 26 is divided into two regions 261 and 262 having different coating layer thicknesses.
- the coating layer on the cell surface of the NSR catalyst 26 is thin in the upstream region 261 and thick in the downstream region 262.
- the coat layer is formed with a substantially uniform thickness.
- FIG. 6 illustrates the case where the area is divided into two areas 261 and 262.
- the NSR catalyst may have three or more regions.
- the thickness of the coat layer may be increased stepwise from the upstream region to the downstream region.
- the NSR catalyst is not limited to one in which the inside is divided into a plurality of regions and the thickness of the coat layer is increased stepwise.
- the NSR catalyst of the present invention may be configured such that the thickness of the coat layer gradually increases from the upstream side to the downstream side.
- a plurality of NSR catalysts having different coating layer thicknesses inside one NSR catalyst as described above may be arranged in series.
- the sulfur poisoning can be achieved by making the coat layer thicker stepwise or gradually from the upstream side of the upstream NSR catalyst toward the downstream side of the downstream NSR catalyst. Purifying performance can be ensured while suppressing the above.
- SCR catalyst NOx selective reduction catalyst
Abstract
Description
実施の形態1.
図1は、本発明の実施の形態のシステムの全体構成を説明するための図である。図1に示すように、本実施の形態のシステムは内燃機関10を備えている。内燃機関10の各気筒には排気通路12が連通している。排気通路12には三元触媒であるスタート触媒(以下、「SC」と称する)14が配置されている。
このシステムにおいて、内燃機関10は、空燃比がリッチである場合に、HCおよびCOを排出し易い。また、空燃比がリーンである場合にNOxを排出しやすい。SC14は、リーン雰囲気では酸素(O2)を吸着しながらNOxを還元(N2に浄化)する。他方、リッチ雰囲気では、酸素を放出しながらHCおよびCOを酸化(H2O、CO2に浄化)する。また、リッチ雰囲気下では、排気ガス中に含まれる窒素と水素、或いはHCとNOxが反応することにより、アンモニア(NH3)が生成される。
ところで、従来のNSR触媒は、燃料中に含まれる硫黄成分により被毒しやすく(以下、「硫黄被毒」)、その結果、浄化性能の低下を起こしやすい傾向にある。図2は、NSR触媒が正常に機能している場合の、リーン雰囲気下でのNSR触媒の吸蔵メカニズムについて説明するための模式図である。図3は、NSR触媒とSCR触媒とを有する浄化システムが正常に機能している場合の浄化率を説明するための図である。図3において横軸は負荷を表し、縦軸はNOx浄化率(%)を表している。また、図3において(a)線はNSR触媒から排出された排気ガスの浄化率を表し、(b)線は、その後SCR触媒に流入しSCR触媒から排出された排気ガスのNOx浄化率を表している。
本実施の形態の浄化システムにおいてNSR触媒16は、上記のようなNSR触媒の硫黄被毒を抑制するよう構成されている。上述したように、NSR触媒16は、上流のNSR触媒161と下流のNSR触媒162とで構成され、上流のNSR触媒161と下流のNSR触媒162とで、セル表面のコート層の厚さが異なるように構成されている。
12 排気通路
14 スタート触媒(SC)
16、26、161、162 NOx吸蔵還元触媒(NSR触媒)
18 NOx選択還元触媒(SCR触媒)
Claims (6)
- 内燃機関の排気経路に配置され排気ガス中のNOxを吸蔵又は還元するNOx吸蔵還元触媒を備え、
前記NOx吸蔵還元触媒は、排気ガスが流通するセルの内壁面に形成され、触媒としての機能を有するコート層を備え、
排気ガスの流れの上流側の前記コート層の厚さは、下流側の前記コート層の厚さよりも薄いことを特徴とする内燃機関の排気浄化装置。 - 少なくとも2つの前記NOx吸蔵還元触媒を備え、
前記NOx吸蔵還元触媒は、排気ガスの流れに対して直列に接続され、
前記NOx吸蔵還元触媒のうち、上流側に配置されるNOx吸蔵還元触媒のコート層は、下流側に配置されるNOx吸蔵還元触媒のコート層よりも薄いことを特徴とする請求項1に記載の内燃機関の排気浄化装置。 - 前記NOx吸蔵還元触媒は、上流側と下流側とに分けられた隣接する少なくとも2つ領域を有し、
前記領域のそれぞれにおける前記コート層の厚さは均一であり、かつ、前記領域のうち、上流側の領域の前記コート層の厚さは、下流側の領域の前記コート層の厚さよりも薄いことを特徴とする請求項1又は2に記載の内燃機関の排気浄化装置。 - 前記NOx吸蔵還元触媒の前記コート層の厚さは、下流側になるにつれて薄くなるように形成されていることを特徴とする請求項1又は2に記載の内燃機関の排気浄化装置。
- 前記コート層は、Rh又はPdを含むことを特徴とする請求項1から4のいずれか1項に記載の内燃機関の排気浄化装置。
- 前記コート層は、Al2O3を含むことを特徴とする請求項1から5のいずれか1項に記載の内燃機関の排気浄化装置。
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EP11863459.1A EP2698515A4 (en) | 2011-04-15 | 2011-04-15 | EXHAUST GAS CLEANER FOR A COMBUSTION ENGINE |
JP2013509720A JP5626457B2 (ja) | 2011-04-15 | 2011-04-15 | 内燃機関の排気浄化装置 |
CN201180070137.9A CN103477045B (zh) | 2011-04-15 | 2011-04-15 | 内燃机的排气净化装置 |
PCT/JP2011/059407 WO2012140775A1 (ja) | 2011-04-15 | 2011-04-15 | 内燃機関の排気浄化装置 |
US14/002,268 US9255509B2 (en) | 2011-04-15 | 2011-04-15 | Exhaust cleaner for internal combustion engine |
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EP (1) | EP2698515A4 (ja) |
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Cited By (3)
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JP2016093760A (ja) * | 2014-11-12 | 2016-05-26 | 株式会社キャタラー | 排ガス浄化用触媒 |
JP2016123890A (ja) * | 2014-12-26 | 2016-07-11 | 日産自動車株式会社 | ハニカム型モノリス触媒およびその製造方法 |
JP2017031960A (ja) * | 2015-08-06 | 2017-02-09 | トヨタ自動車株式会社 | 内燃機関の排気浄化装置 |
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JP6545962B2 (ja) * | 2015-01-22 | 2019-07-17 | 株式会社キャタラー | 排ガス浄化用触媒 |
JP6569637B2 (ja) * | 2016-10-14 | 2019-09-04 | トヨタ自動車株式会社 | 内燃機関の排気浄化装置 |
WO2020183496A1 (en) * | 2019-03-11 | 2020-09-17 | Hero MotoCorp Limited | Catalyst system for treatment of exhaust gas of automobile and process for making the same |
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- 2011-04-15 US US14/002,268 patent/US9255509B2/en not_active Expired - Fee Related
- 2011-04-15 JP JP2013509720A patent/JP5626457B2/ja not_active Expired - Fee Related
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CN103477045B (zh) | 2016-09-07 |
EP2698515A4 (en) | 2014-09-03 |
US20140023561A1 (en) | 2014-01-23 |
CN103477045A (zh) | 2013-12-25 |
JPWO2012140775A1 (ja) | 2014-07-28 |
EP2698515A1 (en) | 2014-02-19 |
US9255509B2 (en) | 2016-02-09 |
JP5626457B2 (ja) | 2014-11-19 |
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