US20050172614A1 - Exhaust emission control device for an internal combustion engine - Google Patents

Exhaust emission control device for an internal combustion engine Download PDF

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US20050172614A1
US20050172614A1 US11/029,694 US2969405A US2005172614A1 US 20050172614 A1 US20050172614 A1 US 20050172614A1 US 2969405 A US2969405 A US 2969405A US 2005172614 A1 US2005172614 A1 US 2005172614A1
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United States
Prior art keywords
catalyst element
exhaust emission
catalyst
microporous
exhaust
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US11/029,694
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English (en)
Inventor
Yasuki Tamura
Keisuke Tashiro
Akihisa Okumura
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INTERNATIONAL CATALYSYT TECHNOLOGY Inc
ICT Co Ltd
Mitsubishi Motors Corp
International Catalyst Technology Inc
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ICT Co Ltd
Mitsubishi Motors Corp
International Catalyst Technology Inc
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Assigned to ICT CO., LTD., MITSUBISHI JIDOSHA KOGYO KABUSHIKI KAISHA, INTERNATIONAL CATALYSYT TECHNOLOGY, INC. reassignment ICT CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: OKUMURA, AKIHISA, TAMURA, YASUKI, TASHIRO, KEISUKE
Publication of US20050172614A1 publication Critical patent/US20050172614A1/en
Assigned to MITSUBISHI JIDOSHA KOGYO K.K. (A.K.A. MITSUBISHI MOTORS CORPORATION) reassignment MITSUBISHI JIDOSHA KOGYO K.K. (A.K.A. MITSUBISHI MOTORS CORPORATION) ADDRESS CHANGE Assignors: MITSUBISHI JIDOSHA KOGYO K.K. (A.K.A. MITSUBISHI MOTORS CORPORATION)
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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
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • 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
    • 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
    • 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
    • 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
    • F01N3/0857—Carbon oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
    • F01N2430/06—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by varying fuel-air ratio, e.g. by enriching fuel-air mixture
    • 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
    • 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 emission control device for an internal combustion engine,. and more specifically to a technology for raising purification efficiency of a three-way catalyst.
  • a three-way catalyst is commonly used as an exhaust gas purifying catalyst for an internal combustion engine for a vehicle.
  • the three-way catalyst is designed to bring an exhaust air-fuel ratio close to a theoretical air-fuel ratio (Stoichio) for optimization of the oxidation of HC (hydrocarbons) and CO (carbon monoxide) and the reduction of NOx to promote the purification of exhaust gases.
  • An exhaust emission control device that has been lately developed has a construction in which the catalyst is for example a porous structure to trap NOx, Oxygen (O 2 ), HC and CO in pores, to thereby trap HC and CO in the pores and oxidize them using the trapped NOx and O 2 in a reducing atmosphere, and on the other hand to thereby trap NOx and O 2 in the pores and reduce NOx using the trapped HC and CO in an oxidizing atmosphere.
  • the catalyst is for example a porous structure to trap NOx, Oxygen (O 2 ), HC and CO in pores, to thereby trap HC and CO in the pores and oxidize them using the trapped NOx and O 2 in a reducing atmosphere, and on the other hand to thereby trap NOx and O 2 in the pores and reduce NOx using the trapped HC and CO in an oxidizing atmosphere.
  • the oxidation-reduction reaction of CO and NOx is faster than that of HC and NOx in reaction speed. This means that if it is possible to separate HC and CO from each other and to preferentially cause the oxidation-reduction reaction of CO and NOx, NOx can be improved in its purifying performance.
  • the present invention has been made to solve the above problems, and an object thereof is to provide an exhaust emission control device for an internal combustion engine designed to actively separate HC and CO and preferentially produce oxidation-reduction reaction of CO and NOx on a catalyst, to thereby upgrade an exhaust gas purifying performance.
  • a three-way catalyst in an exhaust channel of an internal combustion engine comprises one or more catalyst elements and has two or more pore groups different in average pore opening size in a washcoat.
  • FIG. 1 is a schematic view of a construction of an exhaust emission control device for an internal combustion engine according to an embodiment 1 of the present invention, which is installed in a vehicle;
  • FIG. 2 shows a view (a) of a quarter portion of a unit cell of a microporous catalyst element, an enlarged view (b) of catalysts coating the quarter portion, and an enlarged view (c) of one particle of a washcoat (W/C);
  • FIG. 3 shows a view (a) of a quarter portion of a unit cell of a macroporous catalyst element; an enlarged view (b) of catalysts coating the quarter portion; and an enlarged view (c) of one particle of a washcoat (W/C);
  • FIG. 4 is a graph showing frequency distribution of pore opening size in the microporous catalyst element (solid line) and in the macroporous catalyst element (broken line), and average pore opening size X and average pore opening size Y of the microporous and macroporous catalyst elements, respectively;
  • FIG. 5 is a flowchart showing a control routine of O 2 F/B control according to the first embodiment
  • FIG. 6 is a view showing a three-way catalyst according to another embodiment of the first embodiment
  • FIG. 7 is a view showing a three-way catalyst according to a second embodiment
  • FIG. 8 is a view showing a three-way catalyst according to another embodiment of the second embodiment.
  • FIG. 9 is a view showing a quarter portion of a unit cell of a three-way catalyst according to a third embodiment
  • FIG. 10 is a view showing a quarter portion of a unit cell of a three-way catalyst according to a fourth embodiment.
  • FIG. 11 is a flowchart showing a control routine of A/F modulation control according to a fifth embodiment.
  • FIG. 1 is a schematic view of a construction of an exhaust emission control for an internal combustion engine according to the present invention, which is installed in a vehicle.
  • the exhaust emission control device will be provided.
  • a cylinder head 2 of an engine body (such as a gasoline engine, and hereinafter simply referred to as engine) 1 that is an internal combustion engine there is disposed an ignition plug 4 in each cylinder.
  • an ignition plug 4 Connected to the ignition plug 4 is an ignition coil 8 for outputting high voltage.
  • an intake port is formed for each cylinder, and one end of an intake manifold 10 is connected to the cylinder 2 so as to communicate with each intake port.
  • An electromagnetic fuel injection valve 6 is attached to the intake manifold 10 , and a fuel supply device, not shown, having a fuel tank is connected to the fuel injection valve 6 through a fuel pipe 7 .
  • An electromagnetic throttle valve 14 for adjusting an intake air amount is disposed upstream from the fuel injection valve 6 of the intake manifold 10 together with a throttle position sensor (TPS) 16 for detecting the opening of the throttle valve 14 .
  • TPS throttle position sensor
  • an air flow sensor 18 for measuring the intake air amount.
  • an exhaust port is formed for each cylinder, and one end of an exhaust manifold 12 is connected to the cylinder head 2 so as to communicate with the exhaust port.
  • An exhaust pipe (exhaust channel) 20 is connected to the other end of the exhaust manifold 12 .
  • a monolith-type three-way catalyst 30 having a catalyst support honeycombed in section is interposed as an exhaust gas purifying catalyst device.
  • the three-way catalyst 30 includes any one of copper (Cu), cobalt (Co), silver (Ag), platinum (Pt), rhodium (Rh) and palladium (Pd) as active metal for a washcoat of a support surface.
  • the three-way catalyst 30 not only has the active metal but includes a great number of pores formed in a washcoat.
  • the three-way catalyst 30 comprises a microporous catalyst element 30 a having a micropore group whose average pore opening size is smaller than molecular size (prescribed size) of HC and a macroporous catalyst element 30 b having a macropore group whose average pore opening size is larger than the molecular size of HC, in which the microporous catalyst element 30 a is disposed on the upstream side of the exhaust flow, and the macroporous catalyst element 30 b is disposed on the downstream side of the exhaust flow in series with the microporous catalyst element 30 a.
  • FIG. 2 shows a view (a) of a quarter portion of a unit cell of a microporous catalyst element 30 a together with an enlarged view (b) of catalysts coating the quarter portion and an enlarged view (c) of one particle of a washcoat (W/C).
  • W/C washcoat
  • FIG. 3 shows a view (a) of a quarter portion of a unit cell of a macroporous catalyst element 30 b together with an enlarged view (b) of catalysts coating the quarter portion and an enlarged view (c) of one particle of a washcoat (W/C).
  • W/C washcoat
  • FIG. 4 shows frequency distribution of pore opening size in the microporous catalyst element 30 a (solid line) and in the macroporous catalyst element 30 b (broken line), and average pore opening size X and average pore opening size Y of the microporous and macroporous catalyst elements, respectively.
  • the microporous catalyst element 30 a and the macroporous catalyst element 30 b are differentiated in the average pore opening size.
  • the three-way catalyst 30 is capable of trapping CO, O 2 , NOx and H 2 having smaller molecular size than HC in the micropores S in the microporous catalyst element 30 a located on the upstream side of the exhaust flow and is also capable of trapping HC having large molecular size in the macropores L in the macroporous catalyst element 30 b located on the downstream side of the exhaust flow.
  • the pore opening size is controlled by an impregnation method, a CVD (Chemical Vapor Deposition) method, or the like.
  • the microporous catalyst element 30 a is for example zeolite 3A, Ca-mordenite, or the like, and about 3 to about 3.8 angstroms in diameter.
  • the macroporous catalyst element 30 b is for example zeolite 5A, ZSM-5, ⁇ , or the like, and about 5 to about 6 angstroms in diameter.
  • the macroporous catalyst element 30 b may be an ordinary catalyst (such as one composed mainly of Al 2 O 3 and the like), instead of being the above-described one.
  • Substances, on which control of effective pore diameters is introduced include zeolite, SAPO (silicoaluminophosphate), and ALPO (aluminophosphate), but are not limited to these. Any other substances may be utilized as long as the substances are different in pore diameter. Moreover, the substances may be of any other size and shapes on condition that the substances can sieve HC, CO, NOx, H 2 , etc.
  • an air-fuel ratio sensor 22 for detecting an exhaust air-fuel ratio (exhaust A/F), based on the concentration of oxygen in the exhaust emission.
  • an air-fuel ratio sensor 22 Utilized as the air-fuel ratio sensor 22 is an O 2 sensor, but a linear A/F sensor (LAFS) or the like may be employed instead.
  • LAFS linear A/F sensor
  • An ECU (electrical control unit) 40 comprises an input/output device, memories (ROM, RAM, nonvolatile RAM, etc.), a central processing unit (CPU), a time counter, and the like.
  • the ECU 40 performs comprehensive control of the exhaust emission control device including the engine 1 .
  • a crank angle sensor 42 for detecting a crank angle of the engine 1 , in addition to the TPS 16 , the air flow sensor 18 and the air-fuel ratio sensor 22 . Detection information from these sensors is inputted to the ECU 40 . Based on the crank angle information from the crank angle sensor 42 , engine revolution speed Ne is detected.
  • various output devices including the fuel injection valve 6 , the ignition coil 8 , the throttle valve 14 and the like.
  • the air-fuel ratio is set to a proper target air-fuel ratio (target A/F), based on the detection information from the various sensors, and fuel of an amount adjusted according to the target A/F is injected from the fuel injection valve 6 with the right timing. Furthermore, the throttle valve 14 is adjusted to have proper opening, and spark ignition is carried out by the ignition plug 4 with the right timing.
  • target A/F target air-fuel ratio
  • O 2 feedback (O 2 F/B) control is performed so that the exhaust A/F becomes the target A/F (for example, Stoichio), based on the information from the air-fuel ratio sensor 22 .
  • the fuel injection amount fluctuates, and practically, the exhaust A/F periodically fluctuates between a rich air-fuel ratio (rich A/F) side and a lean air-fuel ratio (lean A/F) side with the target A/F therebetween (air-fuel ratio modulating means).
  • FIG. 5 shows a control routine of the O 2 F/B control in a flowchart, and explanations will be provided with reference to the flowchart.
  • Step S 10 judges whether the exhaust A/F is the lean A/F or the rich A/F at present, based on the information from the O 2 sensor that is the air-fuel ratio sensor 22 . If it is judged that the exhaust A/F is the lean A/F, rich operation is carried out in Step S 12 . To be concrete, the fuel injection amount is compensated to increase.
  • the exhaust A/F turns to the rich A/F, and a good deal of CO, in addition to HC, is contained in the exhaust emission.
  • the reducing atmosphere is produced in the three-way catalyst 30 .
  • Step S 10 judges that the exhaust A/F is the rich A/F
  • the lean operation is then provided in Step S 14 .
  • the fuel injection amount is compensated to decrease.
  • the exhaust A/F turns to the lean A/F, and a great deal of NOx is contained in the exhaust emission together with O 2 .
  • the oxidizing atmosphere is therefore produced in the three-way catalyst 30 .
  • the released CO is preferentially and reliably reacted with NOx contained in the exhaust emission in the microporous catalyst element 30 a located on the upstream side of the exhaust flow due in part to the fact that the oxidation-reduction reaction of CO and NOx is faster than that of HC and NOx in reaction speed.
  • the released HC is fully reacted with O 2 contained in the exhaust emission in the macroporous catalyst element 30 b located on the downstream side of the exhaust flow.
  • the exhaust A/F is modulated between the lean A/F and the rich A/F due to the O 2 F/B control, to thereby satisfactorily create the oxidizing atmosphere and the reducing atmosphere. Therefore, CO and HC are repeatedly trapped well in the three-way catalyst 30 so as to be separated from each other in the reducing atmosphere.
  • the released CO and H 2 are preferentially and surely reacted with NOx contained in the exhaust emission without being hampered by the released HC. As a result, the purifying performance of NOx is upgraded.
  • the released HC is well reacted with O 2 contained in the exhaust emission, which enhances the purifying performance of HC. Consequently, the exhaust gas purifying performance of the three-way catalyst 30 is improved as a whole and is maintained in a high level.
  • the above explanation has been provided taking as an example the three-way catalyst 30 in which the microporous catalyst element 30 a and the macroporous catalyst element 30 b are completely coupled and integrated with each other in a direction of the exhaust flow as illustrated in FIG. 1 .
  • the microporous catalyst element 30 a and the macroporous catalyst element 30 b do not have to be coupled to each other but may be located away from each other in the direction of the exhaust flow as another embodiment, as illustrated in FIG. 6 .
  • the second embodiment is different from the first only in that a three-way catalyst 301 is employed in place of the three-way catalyst 30 .
  • the three-way catalyst 301 comprises a macroporous catalyst element 301 a having pores whose average pore opening size is larger than the molecular size of HC and a microporous catalyst element 301 b having pores whose average pore opening size is smaller than the molecular size of HC.
  • the macroporous catalyst element 301 a is disposed on the upstream side of the exhaust flow, and the microporous catalyst element 301 b on the downstream side. In other words, in the three-way catalyst 301 , the microporous and macroporous catalyst elements are reversely positioned, compared to the three-way catalyst 30 .
  • the trapped NOx and O 2 are released to produce the oxidation-reduction reaction with CO and HC contained in the exhaust emission as seen in the above embodiment. Since the oxidation-reduction reaction of CO and NOx is faster than that of HC and NOx in reaction speed, the released NOx is reacted with CO by priority, whereas the released O 2 is well reacted with HC.
  • HC of large molecular size is satisfactorily trapped in macropores L of the macroporous catalyst element 301 a located on the upstream side of the exhaust flow, while CO and H 2 having smaller molecular size than HC are satisfactorily trapped in micropores S of the microporous catalyst element 301 b located on the downstream side of the exhaust flow.
  • HC and CO are actively separated from each other and trapped in the macroporous catalyst element 301 a and the microporous catalyst element 301 b, respectively.
  • the trapped HC, CO and H 2 are released to cause the oxidation-reduction reaction with O 2 and NOx contained in the exhaust emission.
  • HC and CO are separately trapped in the macroporous catalyst element 301 a and the microporous catalyst element 301 b, respectively. Therefore, in the macroporous catalyst element 301 a located on the upstream side of the exhaust flow, the released HC is well reacted with O 2 contained in the exhaust emission.
  • the microporous catalyst element 301 b located on the downstream side of the exhaust flow the released CO and H 2 are well reacted with NOx contained in the exhaust emission without being hindered by the released HC.
  • the macroporous catalyst element 301 a and the microporous catalyst element 301 b do not have to be coupled and integrated with each other.
  • the macroporous catalyst element 301 a and the microporous catalyst element 301 b may be located away from each other in the direction of the exhaust flow as another embodiment, as illustrated in FIG. 8 .
  • the third embodiment differs from the first simply in that a three-way catalyst 302 is employed in place of the three-way catalyst 30 .
  • FIG. 9 shows a quarter portion of a unit cell of the three-way catalyst 302 .
  • the three-way catalyst 302 is formed in layers of a microporous catalyst element 302 a having pores whose average pore opening size is smaller than the molecular size of HC and a macroporous catalyst element 302 b having pores whose average pore opening size is larger than the molecular size of HC.
  • the microporous catalyst element 302 a is disposed on a surface layer side, whereas the macroporous catalyst element 302 b on an internal layer side.
  • the trapped NOx and O 2 are released to cause the oxidation-reduction reaction with CO and HC contained in the exhaust emission as seen in the above embodiments.
  • the released NOx is preferentially reacted with CO, while the released O 2 is well reacted with HC.
  • the released CO and H 2 are preferentially and surely reacted with NOx contained in the exhaust emission in the microporous catalyst element 302 a located on the surface layer side, due in part to the fact that the oxidation-reduction reaction of CO and NOx is faster than that of HC and NOx in reaction speed.
  • the released HC is fully reacted with O 2 contained in the exhaust emission in the macroporous catalyst element 302 b located on the internal layer side.
  • This upgrades not only the purifying performance of NOx but that of HC, thereby enhancing the exhaust gas purifying performance of the three-way catalyst 302 as a whole.
  • microporous catalyst element 302 a and the macroporous catalyst element 302 b are formed in layers, at the time of cold start of the engine 1 , the microporous catalyst element 302 a and the macroporous catalyst element 302 b are raised in temperature substantially at the same time and are successfully activated.
  • the fourth embodiment differs from the third only in that a three-way catalyst 303 is employed in place of the three-way catalyst 302 .
  • FIG. 10 shows a quarter portion of a unit cell of the three-way catalyst 303 .
  • the three-way catalyst 303 is formed in layers of a macroporous catalyst element 303 a having pores whose average pore opening size is larger than the molecular size of HC and a microporous catalyst element 303 b having pores whose average pore opening size is smaller than the molecular size of HC.
  • the macroporous catalyst element 303 a is disposed on the surface layer side, and the microporous catalyst element 303 b on the internal layer side. In other words, in the three-way catalyst 303 , the microporous and macroporous catalyst elements are reversely positioned, compared to the three-way catalyst 302 .
  • the trapped NOx and O 2 are released to cause the oxidation-reduction reaction with CO and HC contained in the exhaust emission as seen in the above embodiments. Since the oxidation-reduction reaction of CO and NOx is faster than that of HC and NOx in reaction speed, the released NOx is reacted with CO by priority, whereas the released O 2 is well reacted with HC.
  • HC of large molecular size is satisfactorily trapped in macropores L of the macroporous catalyst element 303 a located on the surface layer side.
  • CO having smaller molecular size than HC is successfully trapped in micropores S of the microporous catalyst element 303 b located on the internal layer side.
  • HC and CO are actively separated from each other and trapped in the macroporous catalyst element 303 a and the microporous catalyst element 303 b, respectively.
  • the trapped HC and CO are released to produce the oxidation-reduction reaction with O 2 and NOx contained in the exhaust emission.
  • HC and CO are trapped separately in the macroporous catalyst element 303 a and the microporous catalyst element 303 b, respectively. Therefore, the released HC is well reacted with O 2 contained in the exhaust emission in the macroporous catalyst element 303 a located on the surface layer side, and the released CO is relatively well reacted with NOx contained in the exhaust emission without being severely hindered by the released HC in the microporous catalyst element 303 b located on the internal layer side.
  • the macroporous catalyst element 303 a and the microporous catalyst element 303 b are formed in layers, so that at the time of cold start of the engine 1 , the macroporous catalyst element 303 a and the microporous catalyst element 303 b are raised in temperature substantially at the same time and are successfully activated.
  • the fifth embodiment is different from the first simply in that A/F modulation (air-fuel ratio modulating means) is forcibly implemented instead of performing the O 2 F/B control.
  • FIG. 11 shows a control routine of A/F modulation control in a flowchart. Explanations will be provided with reference to the flowchart.
  • Step S 20 judges whether a time counter has counted predetermined time t 1 .
  • the predetermined time t 1 is set equal to or less than the amount of time that is expected to be taken before a trapping amount of CO in the microporous catalyst element 30 a of the three-way catalyst 30 reaches a saturated state, or a breakthrough point, based on for example a preliminary experiment or the like. That is to say, Step S 20 judges whether the trapping amount of CO is at a stage immediately before reaching the breakthrough point.
  • Step S 20 If a result of the judgement in Step S 20 is “NO”, which means that the prescribed time t 1 has not yet elapsed, the trapping of CO is considered to be quite possible. The procedure then advances to Step S 22 , and the rich operation is carried out or continued. On the contrary, if the result of the judgement is “YES”, which means that the prescribed time t 1 has elapsed, the procedure proceeds to Step S 24 .
  • Step S 24 it is judged whether the time counter has counted prescribed time t 2 .
  • Prescribed time t 2 -t 1 is set equal to or less than time that is expected to be taken before a trapping amount of NOx in the microporous catalyst element 30 a of the tree-way catalyst 30 reaches a saturated state, or a breakthrough point, based on for example a preliminary experiment or the like.
  • Step S 24 judges whether the trapping amount of NOx is at a stage immediately before reaching the breakthrough point.
  • Step S 24 If a result of the judgement of Step S 24 is “NO”, which means that the prescribed time t 2 has not yet elapsed, NOx is considered to be quite trappable. Subsequently the procedure advances to Step S 26 , and the lean operation is implemented or continued. On the contrary, the result of the judgement of Step S 24 is “YES”, which means that the prescribed time t 2 has elapsed, the procedure proceeds to Step S 28 , and the time counter is reset to zero. Thereafter the rich operation and the lean operation are repeatedly implemented.
  • the exhaust A/F is efficiently modulated between the rich A/F and the lean A/F within a range in which the trapping amounts of CO and NOx in the three-way catalyst 30 do not reach the respective breakthrough points.
  • the exhaust A/F is efficiently modulated between the lean A/F and the rich A/F due to the A/F modulation control, to thereby satisfactorily create the oxidizing and reducing atmospheres. Therefore, CO and HC repeatedly and satisfactorily continues to be trapped in the three-way catalyst 30 while being separated from each other in the reducing atmosphere.
  • the released CO is surely reacted with NOx contained in the exhaust emission by priority without being hampered by the released HC. Accordingly, the purifying performance of NOx is improved.
  • the released HC is fully reacted with O 2 contained in the exhaust emission, resulting in the enhancement of the purifying performance of HC. Consequently, the exhaust gas purifying performance of the three-way catalyst 30 is upgraded as a whole and is constantly maintained in a high level.
  • the three-way catalyst 30 of the first embodiment used in the above explanation, the three-way catalyst is not limited to this, and the fifth embodiment is applicable if using any one of the three-way catalysts 301 , 302 and 303 of the second, third and fourth embodiments.
  • the three-way catalyst is provided with the microporous and macroporous catalyst elements that are different in average pore opening size, to thereby separate CO and HC, that is, two components contained in the exhaust emission. It is also possible, however, to further vary the average pore opening size according to components to be trapped and dispose three or more catalyst elements (pore group), to thereby separate three or more components contained in the exhaust emission. Furthermore, components to be separated, which are contained in the exhaust emission, are not limited to CO and HC. On the contrary, the components to be separated may be selected as needed.
  • the gasoline engine is employed as the engine 1
  • the engine 1 may be a diesel engine.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Health & Medical Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Catalysts (AREA)
US11/029,694 2004-01-08 2005-01-06 Exhaust emission control device for an internal combustion engine Abandoned US20050172614A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2004-002999 2004-01-08
JP2004002999A JP2005193171A (ja) 2004-01-08 2004-01-08 内燃機関の排気浄化装置

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US20050172614A1 true US20050172614A1 (en) 2005-08-11

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US11/029,694 Abandoned US20050172614A1 (en) 2004-01-08 2005-01-06 Exhaust emission control device for an internal combustion engine

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US (1) US20050172614A1 (ja)
JP (1) JP2005193171A (ja)
CN (1) CN100410503C (ja)
DE (1) DE102005000827B4 (ja)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100024396A1 (en) * 2008-07-30 2010-02-04 Ford Global Technologies, Llc Hydrocarbon retaining and purging system
US20100326273A1 (en) * 2006-09-29 2010-12-30 Uop Llc Plasticization resistant membranes

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6219871B2 (ja) * 2015-03-27 2017-10-25 トヨタ自動車株式会社 排ガス浄化用触媒
WO2022085753A1 (ja) * 2020-10-23 2022-04-28 株式会社キャタラー 炭化水素吸着装置

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US4388171A (en) * 1981-10-30 1983-06-14 Beggs James M Administrator Of Supercritical multicomponent solvent coal extraction
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US20020057997A1 (en) * 1996-12-20 2002-05-16 Hiroshige Mizuno Catalyst for exhaust gas purification and system for exhaust gas purification
US6059560A (en) * 1997-03-04 2000-05-09 The United States Of America As Represented By The United States Department Of Energy Periodic equivalence ratio modulation method and apparatus for controlling combustion instability
US20010053745A1 (en) * 1999-02-16 2001-12-20 Karl C. Kharas Catalytic converter having catalyst witth noble metal on alumina and molecular sieve crystal surface and methods of making same
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US20040001782A1 (en) * 2002-06-27 2004-01-01 Engelhard Corporation Multi-zoned catalyst and trap

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100326273A1 (en) * 2006-09-29 2010-12-30 Uop Llc Plasticization resistant membranes
US20100024396A1 (en) * 2008-07-30 2010-02-04 Ford Global Technologies, Llc Hydrocarbon retaining and purging system
US8375701B2 (en) 2008-07-30 2013-02-19 Ford Global Technologies, Llc Hydrocarbon retaining and purging system

Also Published As

Publication number Publication date
CN1648424A (zh) 2005-08-03
CN100410503C (zh) 2008-08-13
JP2005193171A (ja) 2005-07-21
DE102005000827A1 (de) 2005-08-18
DE102005000827B4 (de) 2006-11-23

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