WO2005039759A1 - 排気ガス浄化用触媒 - Google Patents
排気ガス浄化用触媒 Download PDFInfo
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- WO2005039759A1 WO2005039759A1 PCT/JP2004/015575 JP2004015575W WO2005039759A1 WO 2005039759 A1 WO2005039759 A1 WO 2005039759A1 JP 2004015575 W JP2004015575 W JP 2004015575W WO 2005039759 A1 WO2005039759 A1 WO 2005039759A1
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- exhaust gas
- purifying catalyst
- gas purifying
- temperature
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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
-
- 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
- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
-
- 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
- B01J23/58—Platinum group metals with alkali- or alkaline earth metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/56—Platinum group metals
- B01J23/63—Platinum group metals with rare earths or actinides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
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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 purifying catalyst for purifying exhaust gas from an internal combustion engine of an automobile or the like.
- exhaust gas emitted from internal combustion engines such as automobile engines contains substances such as hydrocarbon compounds (hereinafter referred to as “HC”), carbon monoxide (CO), and nitrogen oxides (NOx). Is included.
- HC hydrocarbon compounds
- CO carbon monoxide
- NOx nitrogen oxides
- a method of removing substances contained in the exhaust gas using an exhaust gas purification catalyst is generally used.
- a so-called three-way catalyst in which a noble metal such as platinum (Pt), rhodium (Rh), and palladium (Pd) is supported on a porous metal oxide carrier such as alumina.
- a noble metal such as platinum (Pt), rhodium (Rh), and palladium (Pd) is supported on a porous metal oxide carrier such as alumina.
- the three-way catalysts are both the oxidation of CO and HC, are known to have an ability to reduce NOx to N 2.
- a system was developed in which combustion was performed constantly under lean conditions with excess oxygen, and the exhaust gas was used as a reducing atmosphere to temporarily reduce the NOx to a stoichiometric to rich condition. .
- a NOx storage-reduction type exhaust gas purification catalyst that uses a NOx storage material that stores NOx in a lean atmosphere and releases NOx stored in a stoichiometric atmosphere, which is optimal for this system.
- This NOx storage-reduction type exhaust gas purifying catalyst is composed of a porous layer of a porous metal oxide such as alumina, and a layer of an N 2 Ox storage material composed of an alkali metal, an alkaline earth metal, or a rare earth element.
- a noble metal catalyst such as platinum is supported on the surface of the carrier.
- NOx contained in the exhaust gas is oxidized by the noble metal catalyst and stored in the NOx storage material in the form of nitrate.
- the NOX stored in the NOX storage material is released during this time, and is purified by reacting with the reducing components of HC and CO.
- the air-fuel ratio of the exhaust gas is returned to lean again, the storage of NOx in the NOx storage material is started, and NOx can be efficiently purified even with the exhaust gas from the lean burn engine.
- this NOx storage-reduction type exhaust gas purifying catalyst has a problem that the NOx purifying ability is considerably reduced particularly at an exhaust gas temperature of 500 ° C or higher. Therefore, an exhaust gas purification catalyst composed of perovskite-type composite oxides that has high NOx purification performance even at high temperatures Has been proposed (see, for example, Japanese Patent Application Laid-Open No. 2002-142648).
- This exhaust gas purification catalyst is said to have high NOx purification performance over a wider temperature range than before because it has a promoted NOX direct decomposition action of the belovskite-type composite oxide. At about 700 ° C, NO x storage reached a plateau, and NO x could not be retained at higher temperatures. Also, under practical conditions, a sufficient NO X purification rate was not achieved.
- the present invention achieves NOx purification up to a high temperature of 100 ° C by using a zirconium composite oxide having a specific element in the crystal structure as a catalyst support.
- the purpose of the present invention is to provide an exhaust gas purifying catalyst capable of reducing exhaust gas. Disclosure of the invention
- an exhaust gas purifying catalyst comprising a crystalline zirconium composite oxide carrying an alkali metal and a noble metal, wherein the zirconium composite oxide is , Alkaline earth metal, rare earth metal, and at least one element selected from the group consisting of group III elements, zirconium is partially replaced by at least one element. It is a value.
- At least one element selected from the group consisting of the alkaline earth metal, the rare earth metal, and the group III element is a zirconium composite oxide. 5 to 50 mol% based on the total number of moles of all metal elements in the metal.
- a part of zirconium is replaced by lanthanum.
- the alkali metal supported on the zirconium composite oxide is cesium.
- the noble metal supported on the zirconium composite oxide is platinum.
- FIG. 1 is a diagram for explaining the appearance of an ultra-basic basic point in the catalyst of the present invention.
- FIG. 1 (A) shows the crystal structure of zirconium oxide
- FIG. 1 (B) shows the crystal structure of zirconium oxide.
- FIG. 1C shows a crystal structure in which a part of zirconium is substituted by lanthanum
- FIG. 1C shows a crystal structure of the zirconium composite oxide of the present invention.
- FIG. 2 is a diagram for explaining a production process of the catalyst of the present invention.
- FIG. 3 is an overall view of a spark ignition type internal combustion engine.
- Fig. 4 is a diagram for explaining the state of adsorption and dissociation of nitric oxide.
- Fig. 4 (A) and Fig. 4 (B) show that nitric oxide was adsorbed on a carrier having an ultra-basic basic point.
- FIG. 4 (C) shows a state in which nitrogen is dissociated
- FIG. 4 (D) shows a state in which oxygen is desorbed.
- FIG. 5 is a diagram showing the relationship between the amount of energy to be applied and the temperature of the exhaust gas purifying catalyst.
- FIG. 6 is a diagram showing a map of the amount of nitric oxide in exhaust gas.
- FIG. 7 is a diagram showing the amount of energy applied.
- FIG. 8 is a flowchart for controlling the application of energy.
- FIG. 9 is a diagram showing the air-fuel ratio rich control.
- FIG. 10 is a time chart showing changes in the oxygen concentration and the NOx concentration.
- Figure 11 shows the relationship between the amount of reducing agent to be supplied and the temperature of the exhaust gas purifying catalyst. It is a figure showing a relation.
- FIG. 12 is a diagram showing the rich control of the air-fuel ratio.
- FIG. 13 is a flowchart for controlling the supply of the reducing agent.
- FIG. 14 is a flowchart for performing a reduction treatment of ion nitrate and nitric oxide.
- FIG. 15 is a diagram showing elapsed time.
- FIG. 16 is a flowchart for controlling the supply of the reducing agent.
- FIG. 17 is an overall view showing another embodiment of the spark ignition type internal combustion engine.
- FIG. 18 is a diagram for controlling the supply of the reducing agent.
- FIG. 19 is an overall view showing still another embodiment of the spark ignition type internal combustion engine.
- FIG. 20 is an overall view showing still another embodiment of the spark ignition type internal combustion engine.
- FIG. 21 is an overall view showing a compression ignition type internal combustion engine.
- FIG. 22 is a diagram showing a particulate filter
- FIG. 22 (A) is a front view
- FIG. 22 (B) is a side sectional view.
- FIG. 23 is a diagram showing the amount of smoke generated.
- Fig. 24 (A) is a graph showing the relationship between the average gas temperature in the combustion chamber and the crank angle
- Fig. 24 (B) is a graph showing the relationship between the fuel and the surrounding gas temperature and the crank angle. is there.
- Fig. 25 is a diagram showing the operating regions I and II.
- FIG. 26 is a diagram showing the air-fuel ratio A / F.
- FIG. 27 is a diagram showing a change in the throttle valve opening and the like.
- Figure 28 is a graph showing the lattice spacing of lanthanum zirconia.
- Figure 29 is a graph showing the high-temperature NOx storage performance of the catalyst.
- the exhaust gas purifying catalyst of the present invention is obtained by supporting an alkali metal and a noble metal on a crystalline zirconium compound oxide carrier.
- Lithium, sodium, potassium, rubidium, cesium, and francium can be used as the alkali metal, and platinum, palladium, rhodium, and the like can be used as the noble metal.
- the supported amount of the alkali metal is preferably 0.05 to 0.3 mol L, and the supported amount of the noble metal is preferably 1 to 5 gZL.
- the carrier in the exhaust gas purifying catalyst of the present invention basically has a crystal structure of zirconium oxide, as shown in FIG. 1 (A), and a part of the zirconium in this crystal structure is converted to aluminum.
- the alkaline earth metal beryllium, magnesium, calcium, strontium, and barium can be used.
- rare earth metals are scandium, yttrium, lanthanum, neodymium, promethium, samarium, euium pium, gadolinium, dysprosium, honolemium, enolebium, turium, itenorebium, norenium. Tetium can be used.
- group III element boron, aluminum, gallium, indium, and thallium can be used.
- the content of at least one element selected from the group consisting of alkaline earth metals, rare earth metals, and group II elements is based on the total moles of all metal elements in the zirconium composite oxide. 5 to 50 mol%.
- zirconium constituting crystalline zirconium oxide is tetravalent, when it is replaced with a divalent alkaline earth metal, a trivalent rare earth metal, or a group IIIB element such as lanthanum, the result is shown in Fig. 1 (B). Thus, oxygen vacancies without oxygen are formed in the crystal lattice.
- the composite oxide supports an alkali metal, for example, cesium, and the cesium provides electrons e to oxygen vacancies as shown in FIG. 1 (C).
- the oxygen vacancies donated with electrons show extremely strong basicity, and thus the oxygen vacancies donated with electrons are hereinafter referred to as super strong base points.
- the zirconium composite oxide as a carrier has a crystal structure as shown in FIG. 1 (C) over its entirety, and is innumerable over its entirety. Are distributed uniformly.
- a conventional catalyst using a carrier in which a part of zirconium in zirconium oxide is replaced by lanthanum or the like is manufactured by a conventional composite oxide manufacturing method such as a coprecipitation method or an alkoxide method.
- the lanthanum could not be sufficiently substituted with zirconium, the amount of super strong base points was not sufficient, and the super strong base points could not be uniformly distributed.
- a sufficient amount of lanthanum or the like can be replaced with zirconium by using the predetermined method, and a sufficient amount of the super strong base point can be uniformly formed. Can be distributed. This substitution of a sufficient amount of lanthanum and the like is reflected by the fact that the crystal lattice elongation of the zirconium oxide due to element substitution is approximately the theoretical value.
- zirconium is partially replaced by at least one element selected from the group consisting of alkaline earth metals, rare earth metals, and Group II elements, and the crystal lattice is changed by this element replacement.
- Zirconium composite oxide whose elongation is approximately the theoretical value, is obtained by the following method. Can be manufactured.
- the hydrolysis of zirconium organic compounds at their interface leads to hydroxylation of zirconium.
- the second element is incorporated into the product, and the obtained composite hydroxide (precursor) is calcined to obtain a composite oxide of zirconium and the second element.
- an organic compound which hydrolyzes to produce a hydroxide of zirconium is known, and any of them can be used in the present invention.
- zirconium alkoxide and acetylaceton zirconium complex can be mentioned.
- Zirconyl two ⁇ beam Z r (OR) 4 of the hydrolysis reaction are also known, in the format specifically, Z r (OR) 4 + 4 H 2 O ⁇ Z r (OH) 4 + 4 ROH, then represented by Z r (OH) 4 ⁇ Z r O 2 + 2 H 2 O.
- Organometallic compounds such as zirconium alkoxide acetyl aceton zirconium complex can be relatively easily dissolved by selecting an appropriate solvent from polar organic solvents and non-polar organic solvents.
- organic solvents include hydrocarbons such as cyclohexane and benzene, straight-chain alcohols such as hexanol, and ketones such as acetone.
- As criteria for selecting an organic solvent in addition to the solubility of the surfactant, the size of a region in which a microemulsion is formed (molar ratio of water Z surfactant is large) Etc.
- a water-in-oil emulsion and a micro-mouth emulsion in which an aqueous phase is finely dispersed with a surfactant in an organic phase (oil phase) are formed, and the organic phase (oil phase) is formed in the organic phase (oil phase).
- fine metal hydroxides or oxides are formed by adding a metal compound (a solution of an organic metal compound in an organic solvent) and stirring.
- a metal compound a solution of an organic metal compound in an organic solvent
- a large number of micelle surfaces composed of an aqueous phase surrounded by a surfactant can serve as reaction nuclei or stabilize hydroxide particles generated by the surfactant. It is believed that fine product particles are obtained.
- one of the hydrolyzable organometallic compounds (compound containing zirconia) is made to exist in the organic phase, and when the organic phase and the aqueous phase come into contact with each other, an alkaline earth metal or a rare earth metal is used.
- the second metal element selected from the group consisting of,, and Group III elements, and the third and subsequent metal elements are present as ions in the aqueous phase, not in the organic phase as in the past. It is characterized by
- ions in the aqueous phase as water-soluble metal salts, especially inorganic salts such as nitrates and chlorides, as well as acetates, lactates and oxalic acids
- Organic salts such as salts can be used.
- the ion of the second element present in the aqueous phase may be a simple ion of a metal or a complex ion containing the second element. The same applies to ions of the third and subsequent elements.
- the second metal ion in the aqueous phase When hydrolyzed, the second metal ion in the aqueous phase induces an alkoxide and the hydrolysis proceeds, or a small hydroxide of alkoxide hydrolyzes a predetermined amount of metal ion in the aqueous phase. It is thought that they are captured and aggregated.
- the ion of the second metal element present in the aqueous phase is contained in the hydroxide obtained by hydrolyzing the organic zirconium compound of zirconium in the organic phase.
- a hydroxide in which zirconium and the second metal element in the obtained hydroxide are very uniformly dispersed can be obtained, and the uniformity can be obtained by the conventional alkoxide method, that is, in the organic phase. It has been found that it can be remarkably superior to the case where a plurality of metal alkoxides are present.
- the relative ratio between zirconium and the second metal element in the composite oxide used in the present invention can be adjusted by the ratio between the amount of zirconium in the organic phase and the amount of the second metal element in the aqueous phase.
- the reaction system is preferably a water-in-oil emulsion system or a microemulsion system.
- the microemulsion diameter is several ⁇ !
- the diameter of the aqueous phase of the microphone mouth emulsion is preferably 2 to 40 nm, more preferably 2 to 15 nm, and even more preferably 2 to 10 nm.
- a method of forming a water-in-oil type emollination system or a microphone mouth emollination system is known.
- the organic phase medium those similar to the above organic solvents such as hydrocarbons such as cyclohexane and benzene, linear alcohols such as hexanol, and ketones such as acetone can be used.
- Surfactants that can be used in the present invention include a variety of surfactants such as nonionic surfactants, anionic surfactants, and cationic surfactants, and can be used in combination with an organic phase (oil phase) component according to the intended use. Can be used.
- Polyoxyethylene alkyl ether-based surfactants represented by, for example, polyoxyethylene sorbitan-based surfactants represented by, for example, polyoxyethylene sorbitan oleate can be used.
- Examples of the zwitterion-based surfactant include sodium di-ethylenehexylsulfosulfonate, and examples of the cationic surfactant include cetyl trimethylammonium chloride. Docetyl trimethylammonium bromide can be used. A water-in-oil emulsion system or a micro-mouth emulsion system is preferred, but an oil-in-water emulsion system can also be used.
- the third and subsequent elements are present in the aqueous phase.
- a heterogeneous product is formed in the organic phase due to a difference in stability between the hydrolyzable organometallic compounds.
- the zirconium and the second metal element be uniform, but if uniformity is not important between the zirconium and the third metal element, the organometallic compound of the third element should be used in the organic phase. It may be present inside.
- a hydroxide precursor
- the product is dried and then calcined to produce a composite oxide.
- the method of separating and drying the product may be the same as before.
- the firing conditions may be the same as in the past, and the firing temperature, firing atmosphere, and the like may be selected according to the type of the specific composite oxide. However, in general, it can be fired at a lower temperature than before. It is considered that the energy required to diffuse the metal element in the solid is small because the metal element is uniformly dispersed in advance.
- Figure 2 shows the method for producing the zirconium composite oxide described above. This is shown schematically using an example of synthesis using Luconia's microphone mouth microphone mouth emulsion.
- lanthanum zirconia is synthesized by dissolving lanthanum nitrate or the like in the aqueous phase of micromicroemulsion ME, and adding and mixing zirconium alkoxide. That is, only one type of metal alkoxide, namely zirconium alkoxide, is added to the organic phase of the micro-microemulsion.
- the second element ions in the aqueous phase are electrically attracted to the hydrophilic groups of the surfactant, and are incorporated at the same time as the organic zirconium and the compound are hydrolyzed, thereby containing the second element. It becomes a composite oxide.
- zirconium contained in the organic zirconium compound and the second element in the aqueous phase may be uniformly dispersed and mixed in the hydrolysis reaction product and further in the composite oxide.
- the zirconium composite oxide obtained in this manner was used as a carrier, and an alkali metal and a noble metal were supported on the carrier in the same manner as in the conventional method.
- the exhaust gas purifying catalyst of the present invention is obtained.
- FIG. 3 shows a case where the exhaust gas purifying catalyst of the present invention is applied to a spark ignition type internal combustion engine.
- the present invention can also be applied to a compression ignition type internal combustion engine.
- 1 is the engine body
- 2 is the cylinder block
- 3 is the cylinder head
- 4 is the piston
- 5 is the combustion chamber
- 6 is the electrically controlled fuel injection valve
- 7 is the spark plug
- 8 Denotes an intake valve
- 9 denotes an intake port
- 10 denotes an exhaust valve
- 11 denotes an exhaust port.
- the intake port 9 is connected to the surge tank 13 via the corresponding intake branch pipe 12, and the surge tank 13 is connected to the air cleaner 15 via the intake duct 14.
- a throttle valve 17 driven by a step motor 16 is disposed in the intake duct 14, and an intake air for detecting a mass flow rate of the intake air is further included in the intake duct 14.
- a quantity sensor 18 is arranged.
- the exhaust port 11 is connected via an exhaust manifold 19 to a catalytic converter 21 having an exhaust gas purifying catalyst 20 of the present invention.
- the exhaust manifold 19 and the surge tank 13 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 22, and an electrically controlled EGR control valve 23 is disposed in the EGR passage 22. Is done.
- a cooling device 24 for cooling the EGR gas flowing in the EGR passage 22 is disposed around the EGR passage 22. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 24, and the engine cooling water cools the EGR gas.
- each fuel injection valve 6 is connected to a fuel reservoir, a so-called common rail 26, via a fuel supply pipe 25.
- the common rail 26 is supplied with fuel from an electrically controlled variable discharge fuel pump 27, and the fuel supplied into the common rail 26 is supplied to the fuel injection valve 6 via each fuel supply pipe 25. Supplied to Common rail 2 6
- the fuel pressure sensor 28 for detecting the fuel pressure in the common rail 26 is attached to the fuel cell, and the fuel pressure in the common rail 26 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 28. Thus, the discharge amount of the fuel pump 27 is controlled.
- the electronic control unit 30 is composed of a digital computer and is connected to each other by a bidirectional path 31 1.
- ROM read only memory
- RAM random access memory
- CPU micro processor
- the output signals of the intake air amount sensor 18 and the fuel pressure sensor 28 are input to the input port 35 via the corresponding AD converter 37.
- a load sensor 41 that generates an output voltage proportional to the amount of depression L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is supplied via the corresponding AD converter 37.
- the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crank shaft rotates, for example, 30 °.
- the output port 36 is connected to the fuel injection valve 6, spark plug 7, throttle valve driving step motor 16, £ 01 control valve 23, and fuel pump 27 via the corresponding drive circuit 38. Connected.
- a cavity 43 is formed on the top surface of the piston 4, and fuel F is injected from the fuel injection valve 6 into the cavity 43 when the engine is under a low load operation.
- This fuel F is guided by the bottom wall surface of the cavity 43 toward the ignition port 7, whereby an air-fuel mixture is formed around the ignition plug 7.
- this air-fuel mixture is ignited by the spark plug 7, and stratified combustion is performed.
- the average air-fuel ratio in the combustion chamber 5 is lean, and accordingly, the air-fuel ratio of the exhaust gas is also lean.
- the NOx exhausted from the combustion chamber 5 when the combustion is performed under the lean air-fuel ratio is purified by the exhaust gas purifying catalyst 20.
- the mechanism of NOx purification by the above is not always clear, the results of the analysis so far indicate that the NOx purification is probably performed by the mechanism described below.
- nitrogen oxides NO x in 2 such nitrogen monoxide NO and nitrogen dioxide NO in the exhaust gas
- excess oxygen ⁇ 2 when the burning fuel under a lean air-fuel ratio is performed.
- nitrogen oxides NO x contained in the exhaust gas are nitrogen monoxide NO. Therefore, the purification mechanism of the nitrogen monoxide NO will be described below as a typical example.
- the exhaust gas purifying catalyst 20 of the present invention has a super strong basic point. Nitrogen monoxide, which is acidic when such an ultra-basic point is present, is attracted to the ultra-basic point regardless of whether the temperature of the exhaust gas purification catalyst 20 is low or high, and as a result Nitrogen NO is captured at the ultra-basic point of the exhaust gas purifying catalyst 20 in the form shown in FIG. 4 (A) or (B). In this case, the exhaust gas The exhaust purification catalyst 20 adsorbs a very large amount of nitric oxide NO because the carrier of the exhaust purification catalyst 20 has innumerable ultra-basic points uniformly distributed throughout the catalyst. become.
- nitric oxide N 2 O When nitric oxide N 2 O is adsorbed at the super-basic point, the dissociation of nitric oxide N 2 and the oxidation reaction of nitric oxide N 2 occur. Therefore, the dissociation of nitric oxide N 2 O will be described first.
- nitric oxide NO in the exhaust gas is attracted to the ultra-basic basic point on the exhaust gas purifying catalyst 20 and is adsorbed and captured by the ultra-basic basic point.
- electrons e are donated to nitric oxide NO.
- NO dissociation of NO bond of NO occurs.
- the higher the temperature of the exhaust gas purifying catalyst 20, the higher the NO bond. are easily dissociated.
- the N--O bond dissociates shortly afterwards and dissociates into nitrogen N and oxygen O, at which time oxygen is shown in Fig. 4 (C).
- the oxygen ion is retained at the ultra-basic point in the form of O—, and nitrogen N moves on the exhaust gas purifying catalyst 20 away from the ultra-basic point.
- nitric oxide N ⁇ is adsorbed on the ultra-basic point
- nitric oxide NO is dissociated a while later, and oxygen O is captured on the ultra-basic point in the form of oxygen ion O—
- the ultra-basic points present in the exhaust gas purifying catalyst 20 are gradually filled with oxygen ions 0-.
- the ultra-basic basic points are filled with oxygen ions O-
- the nitric oxide NO combines with the nitrogen N of the nitric oxide NO adsorbed at the ultra-basic point, and as a result, N 20 is generated.
- nitrate ions NO 3 one can be cowpea to Rukoto be combined with oxygen ions 0 2 _ nitric oxide NO constitutes the crystals produced, also nitrate ions N 0 3 produced - is a crystal It may be held on the exhaust gas purifying catalyst 20 in a state of being adsorbed by the constituent zirconium Zr4 + .
- the exhaust gas purifying catalyst 2 nitrate ion N 0 at higher temperatures on the exhaust gas purifying catalyst 2 0 0 3 - is not almost exist.
- Most nitrate ions N0 3 on the good urchin exhaust gas purifying catalyst 2 0 - If the minimum temperature of the exhaust gas purifying catalyst 2 0 when there are no more called reference temperature, the reference temperature is the catalyst for purifying exhaust gases The reference temperature is approximately 600 ° C. in the exhaust gas purifying catalyst 20 of the present invention.
- the temperature of the exhaust gas purifying catalyst 2 0 When this reference temperature by Ri also low nitrate ion N 0 3 on the exhaust gas purifying catalyst 2 0 - is produced, the temperature of the exhaust gas purifying catalyst 2 0 This when even higher Ri by reference temperature becomes almost to the absence of nitrate ion N_ ⁇ 3 on the exhaust gas purifying catalyst 2 0.
- the metal supported on the exhaust gas purifying catalyst 20 by excess oxygen O 2 contained in the exhaust gas for example, cerium C e is oxidized (C e 2 0 3 + 1 /2 O 2 ⁇ 2 C e O 2), oxygen is stored on the I connexion exhaust gas purifying catalyst 2 0 it.
- the stored oxygen stably enters the crystal structure, and thus the stored oxygen is desorbed from the exhaust gas purification catalyst 20 even when the temperature of the exhaust gas purification catalyst 20 increases.
- the exhaust gas purifying catalyst 2 nitrate Ion N 0 is the temperature of the reference temperature by Ri also high Itoki 0 3 - is cause to decompose immediately even if they are generated if, thus to exhaust gas purifying catalyst 2 There is almost no ion nitrate N 0 3-on 0.
- the dissociation of the nitric oxide NO adsorbed at the ultra-basic point on the exhaust gas purifying catalyst 20 is actively performed, and therefore the oxygen ion trapped at the ultra-basic point is The amount of O-gradually increases.
- the ultra-basic point of the exhaust gas purification catalyst 20 is Holds the dissociated oxygen ion O—. Therefore, if the combustion continues at a lean air-fuel ratio, the ultra-basic point of the exhaust gas purifying catalyst 20 is gradually filled with oxygen ions O--, and thus, the super-strong basic point at which nitrogen monoxide NO can be adsorbed. The number of basic points gradually decreases. As a result, the NO x purification rate gradually decreases.
- the superbasic point is located between metal ions that are electrically positive, and thus the oxygen ion O—, which is electrically negative, is located between these metal ions. Almost retained. However, the bonding force between this oxygen ion 0-and the metal ion is weak. Therefore, the oxygen ion o— is in an extremely unstable state. Therefore, some of the oxygen ions held at the super strong basic point
- the exhaust gas purifying catalyst 20 is provided with the energy required to purge a part of the oxygen ions O— retained on the exhaust gas purifying catalyst 20 from the exhaust gas purifying catalyst 20.
- this purging action induces the exhaust gas purifying catalyst 2.
- the energy required for purging some of the oxygen ions O may be provided, so that there is a great advantage that the energy for purging the oxygen ions O can be reduced.
- Various energies can be considered as the energy to be applied.
- the oxygen ions O— held in the exhaust gas purifying catalyst 20 are more easily desorbed as the temperature of the exhaust gas purifying catalyst 20 increases. Therefore, as shown in FIG. 5, the amount of energy E required to purge a part of the oxygen ions O— retained on the exhaust gas purifying catalyst 20 from the exhaust gas purifying catalyst 20 is expressed by E Decreases as the temperature TC of the exhaust gas purifying catalyst 20 increases.
- energy can be applied at regular intervals, every time the integrated value of the engine speed exceeds a set value, or every time the traveling distance of the vehicle exceeds a constant distance. Further, in this case, the time interval between the time when the energy is applied to the exhaust gas purifying catalyst 20 and the time when the energy is next applied can be increased as the temperature of the exhaust gas purifying catalyst 20 increases.
- the oxygen ion O — held in 20 for exhaust gas purification It is also possible to estimate the total amount of NO and NO, and to apply energy when the estimated total amount exceeds the set amount. That is, the nitrogen monoxide NO contained in the exhaust gas is retained on the exhaust gas purifying catalyst 20 as it is or in the form of dissociated oxygen ion O—. Therefore, the total amount of oxygen ions 0— and nitric oxide NO held in the exhaust gas purifying catalyst 20 is the integrated amount of nitric oxide NO contained in the exhaust gas. The amount of nitric oxide NO contained in the exhaust gas is determined according to the operating conditions of the engine. Figure 6 shows the amount of nitric oxide discharged from the engine per unit time determined by experiments. Q (NO) is shown in the form of a map as a function of engine load L and engine speed N.
- the total amount of oxygen ions O and nitric oxide NO held in the exhaust gas purifying catalyst 20 is the amount of nitric oxide Q (NO) shown in FIG. It can be estimated from the integrated value of. Therefore, in the present invention, the integrated value of the amount of nitric oxide Q (NO) shown in FIG. 6 is calculated as the estimated total amount of the oxygen ion ⁇ ⁇ -and nitric oxide NO held in the exhaust gas purifying catalyst 20. Used.
- FIG. 7 shows the integrated value ⁇ Q of Q (NO) shown in FIG. 6 when the temperature of the exhaust gas purifying catalyst 20 is higher than the reference temperature, the temperature TC of the exhaust gas purifying catalyst 20 and This shows the relationship with the applied energy.
- the amount of energy applied to the exhaust gas purifying catalyst 20 decreases as the temperature TC of the exhaust gas purifying catalyst 20 increases.
- FIG. 8 shows an energy supply control routine
- step 100 the amount of nitric oxide Q (NO) is calculated from the map shown in FIG.
- step 101 the integrated amount ⁇ Q is calculated by adding Q (NO) to ⁇ Q.
- step 102 it is determined whether or not the integrated amount ⁇ Q has exceeded the set amount Q X.
- step 104 a process of applying energy is performed, and then in step 105, ⁇ Q is cleared.
- the air-fuel ratio in the combustion chamber 5 or the air-fuel ratio of the exhaust gas is periodically changed, for example, at regular intervals, or the engine is operated. Every time the integrated value of the number of revolutions of the vehicle exceeds a set value, or every time the traveling distance of the vehicle exceeds a certain distance, it can be set to the rich.
- the rich control of the air-fuel ratio can be performed based on the total integrated amount of the oxygen ion O— and the nitric oxide NO held on the exhaust gas purifying catalyst 20. it can.
- FIG. 9 shows a case where such a rich control is performed.
- a fuel containing a hydrocarbon or the like is used as the reducing agent.
- the fuel acting as the reducing agent is the amount of fuel that is excessive with respect to the stoichiometric air-fuel ratio. That is, in FIG. 9, the portion on the rich side of the stoichiometric air-fuel ratio indicated by the hatching indicates the amount Qr of the reducing agent.
- This reducing agent can be supplied into the combustion chamber 5 by increasing the injection amount from the fuel injection valve 6, or can be supplied into the exhaust gas discharged from the combustion chamber 5.
- combustion is performed under a lean air-fuel ratio, and the exhaust gas is purified.
- oxygen ions O— and nitric oxide NO are retained on the exhaust gas purifying catalyst 20, and furthermore, on the exhaust gas purifying catalyst 20.
- Stored oxygen is retained.
- the exhaust gas purifying catalyst 20 of the present invention when the air-fuel ratio A / F is switched from lean to rich, the oxygen ion O— held in the exhaust gas purifying catalyst 20 is desorbed. At this time, the oxygen concentration in the exhaust gas flowing out of the exhaust gas purifying catalyst 20 does not become zero due to the influence of the desorbed oxygen ions 0- as shown in FIG. That is, when the air-fuel ratio A / F is switched from lean to rich, some of the desorbed oxygen ions O— are reduced, but most of the desorbed oxygen ions O— are reduced by the reducing agent. Rukoto without exhaust gas purification in the form of oxygen molecules ⁇ 2 When the air-fuel ratio AZF is switched from lean to rich as shown in FIG.
- the oxygen concentration in the exhaust gas flowing out of the exhaust gas purifying catalyst 20 becomes a certain amount as shown in FIG. Become.
- the oxygen concentration gradually decreases to zero as shown in Fig. 10 because the amount of released oxygen ions O— decreases as time passes, and once the air concentration decreases to zero, the air-fuel ratio A / F increases. While being filled, the oxygen concentration is maintained at zero.
- the reducing agent By supplying the reducing agent in this way, a part of the oxygen ions O— can be purged from the exhaust gas purifying catalyst 20, and the purging action induces the oxygen ions O to be retained on the exhaust gas purifying catalyst 20. The remaining oxygen ions O can be purged from the exhaust gas purifying catalyst 20. Further, when the reducing agent is supplied, the nitrogen monoxide N 2 O adsorbed on the exhaust gas purifying catalyst 20 can be reduced. Therefore, it can be said that it is extremely preferable to generate energy to be provided by a reducing agent.
- Fig. 11 shows the amount of reducing agent, Qr, expressed as an equivalence ratio, which is required when the air-fuel ratio is switched to recover the purification performance of the exhaust gas purification catalyst 20, and the exhaust gas.
- the relationship between the temperature of the purification catalyst 20 and the temperature TC is shown.
- the reducing agent necessary to reduce the nitric oxide NO generated before the air-fuel ratio in the combustion chamber 5 or the air-fuel ratio of the exhaust gas is refilled again Is referred to as the reducing agent amount Qr when the equivalent ratio of the reducing agent ZNO is 1.
- nitric oxide NO in the exhaust gas are all nitrate ions N 0 3 - assuming that the occluded in the catalyst 2 0 purifier in the form of exhaust gas, the occluded nitrate Ion NO 3 - a
- the equivalent ratio of the amount of the reducing agent becomes smaller than 1.0.
- the combustion chamber 5 is purged to purge oxygen ions O— retained on the exhaust gas purifying catalyst 20.
- the reducing agent amount Qr when the air-fuel ratio in the internal combustion chamber or the exhaust gas air-fuel ratio is rich is determined from the time when the air-fuel ratio in the previous combustion chamber 5 or the air-fuel ratio of the exhaust gas was richened to this time.
- the amount of the reducing agent required to reduce the nitric oxide NO generated until the air-fuel ratio in the chamber 5 or the exhaust gas air-fuel ratio is reduced, that is, the equivalent ratio is 1.0. Less than the amount of reducing agent.
- the exhaust gas purifying catalyst of the present invention it is possible to purify NOx up to a temperature TC of the exhaust gas purifying catalyst 20 as high as about 1000 ° C.
- a reducing agent is supplied in an amount equal to or less than 1.0 when the air-fuel ratio is switched to a high temperature of about 100 ° C.
- the exhaust gas purification catalyst 20 Purification performance can be restored. That is, by supplying a reducing agent in an amount smaller than that required to reduce the nitrogen monoxide NO sent to the exhaust gas purifying catalyst 20, the NOx purification of the exhaust gas purifying catalyst 20 is performed. Performance can be restored, thus fuel consumption for NO x purification performance restoration The amount can be reduced.
- the amount Qr of the reducing agent to be supplied when the air-fuel ratio is increased depends on the exhaust gas when the temperature TC of the exhaust gas purifying catalyst 20 is about 800 ° C.
- the temperature TC of the exhaust gas purifying catalyst 20 is about 900 ° C, it is necessary to reduce the nitrogen monoxide NO contained in the exhaust gas flowing into the exhaust gas purifying catalyst 20.
- the amount Qr of the reducing agent supplied for purging the oxygen ion O— held on the exhaust gas purifying catalyst 20 is determined by the amount of the exhaust gas purifying catalyst 2. It can be seen that the higher the temperature TC of 0, the lower the temperature.
- the amount Qr of the reducing agent supplied when the air-fuel ratio is increased is equivalent to The ratio is set to an amount of reducing agent of 1.0 or more. That is, as described above, even when combustion is performed under a lean air-fuel ratio and the temperature TC of the exhaust gas purifying catalyst 20 is lower than the reference temperature T s, the temperature of the exhaust gas purifying catalyst 20 increases. At the point, oxygen ions 0— and nitric oxide NO are held at points, and stored oxygen is held on the exhaust gas purifying catalyst 20.
- the exhaust gas purifying catalyst 2 More reducing agent is required than the amount of reducing agent required to reduce nitrate ion NO 3 and nitric oxide NO stored in 0. Therefore, as described above, the amount of reducing agent 01: supplied when the air-fuel ratio is made rich is an amount of reducing agent having an equivalent ratio of 1.0 or more.
- FIG. 13 shows a reducing agent supply control routine.
- step 200 it is determined whether or not the temperature TC of the exhaust gas purifying catalyst 20 is higher than the reference temperature T s. If TC> T s, go to step 201 to exhaust gas The purging operation of the oxygen held in the purifying catalyst 20 is performed. That is, in step 201, the amount of nitric oxide Q (NO) is calculated from the map shown in FIG. Next, at step 203, the integrated amount ⁇ Q is calculated by adding Q (NO) to ⁇ Q. Next, at step 204, it is determined whether or not the integrated amount ⁇ Q has exceeded the set amount QX. When ⁇ Q> QX, the routine proceeds to step 205, at which the amount of reducing agent to be supplied is calculated. Next, in step 206, a process of making the air-fuel ratio rich by supplying a reducing agent is performed, and then, in step 207, ⁇ Q is cleared.
- step 200 determines whether or not the accumulated amount ⁇ Q (NO) has exceeded the allowable amount MAX.
- step 215 a process for enriching the air-fuel ratio by supplying a reducing agent is performed, and then in step 215, ⁇ 0 (NO) is cleared.
- the reducing agent for increasing the air-fuel ratio as the temperature TC of the exhaust gas purifying catalyst 20 increases.
- the quantity Qr can be reduced. This means that when the reducing agent amount Qr is almost constant, the time interval between the air-fuel ratio refill and the refill is defined as This means that the longer the temperature TC of the exhaust gas purifying catalyst 20 is, the longer it can be.
- the combustion chamber 5 is used to purge the oxygen ion O retained on the exhaust gas purifying catalyst 20.
- the time interval tX from when the air-fuel ratio of the exhaust gas or the air-fuel ratio of the exhaust gas is rich to the next time when the air-fuel ratio of the combustion chamber 5 or the air-fuel ratio of the exhaust gas is rich is determined as the exhaust gas purification.
- the temperature is made to increase as the temperature TC of the catalyst 20 increases.
- FIG. 16 shows a reducing agent supply control routine for carrying out the third embodiment.
- step 220 it is determined whether or not the temperature TC of the exhaust gas purifying catalyst 20 is higher than the reference temperature Ts.
- the routine proceeds to step 22 1, where the time ⁇ t from the previous processing cycle to the current processing cycle is added to ⁇ t, whereby the elapsed time ⁇ t is calculated.
- step 222 the elapsed time tX to be targeted is calculated from FIG.
- step 223 it is determined whether or not the elapsed time ⁇ t has exceeded the target elapsed time tX. If ⁇ t> tX, the process proceeds to step 224 to calculate the amount of reducing agent to be supplied. Is done.
- step 225 a process of making the air-fuel ratio rich by supplying a reducing agent is performed, and then in step 226, ⁇ t is cleared.
- step 220 when it is determined in step 220 that T C ⁇ T s, the process proceeds to step 208 and the NO reduction process shown in FIG. 14 is executed.
- FIG. 17 shows a fourth embodiment.
- N is set to detect the NOX concentration in the exhaust gas passing through the exhaust gas purifying catalyst 20.
- An Ox concentration sensor 44 is provided.
- the exhaust gas purifying catalyst 20 As long as the super-basic point of the exhaust gas purifying catalyst 20 is not filled with oxygen ions O—, N Ox contained in the exhaust gas is captured by the exhaust gas purifying catalyst 20 so that the exhaust gas purifying is performed.
- the exhaust gas flowing out of the catalyst 20 contains almost no NOX.
- the exhaust gas purifying catalyst 20 is not trapped by the exhaust gas purifying catalyst 20.
- the amount of N Ox passing through 20 gradually increases. Therefore, in the fourth embodiment, when the NOx concentration in the exhaust gas flowing out of the exhaust gas purifying catalyst 20 exceeds the allowable value, a considerable part of the ultra-basic basic point is filled with oxygen ions O-. Therefore, the air-fuel ratio of the exhaust gas flowing into the exhaust gas purifying catalyst 20 is made to increase from lean to spike-like.
- FIG. 18 shows a routine for controlling the supply of the reducing agent for implementing the fourth embodiment.
- step 230 the NOx concentration De in the exhaust gas flowing out of the exhaust gas purifying catalyst 20 is detected by the NOx concentration sensor 44.
- step 231 it is determined whether or not the NOx concentration De detected by the NOx concentration sensor 44 has become larger than the allowable value DX.
- D e the NOx concentration sensor 44 has become larger than the allowable value DX.
- the routine proceeds to step 23, where it is determined whether or not the temperature TC of the exhaust gas purifying catalyst 20 is higher than the reference temperature Ts. In the case of "c >>c3", the process proceeds to step 233 to calculate the amount of reducing agent to be supplied.
- step 234 a process is performed in which the air-fuel ratio is made rich by supplying a reducing agent.
- step 2 32 it was determined that TC ⁇ T s
- step 235 the amount of reducing agent to be supplied is calculated.
- step 236 a process is performed in which the air-fuel ratio is made rich by supplying a reducing agent.
- FIG. 19 shows still another embodiment.
- the exhaust gas purifying catalyst 50 is supported on the inner wall surface of the cylinder head 3 and the inner wall surface of the combustion chamber 5 such as the top surface of the biston 4 as shown by a broken line
- the gas purification catalyst 51 is carried on the inner wall surface of the exhaust passage such as the inner wall surface of the exhaust port 11 and the inner wall surface of the exhaust manifold 19.
- the exhaust gas purifying catalyst 50 is carried on the inner wall surface of the combustion chamber 5, the combustion gas or the burned gas in the combustion chamber 5 comes into contact with the exhaust gas purifying catalyst 50 and the combustion gas.
- the nitrogen oxides contained in the burnt gas mainly nitric oxide, NO are adsorbed on the exhaust gas purifying catalyst 50 and then dissociated into nitrogen N and oxygen O, and the exhaust gas purifying catalyst 51 exhausts.
- the exhaust gas is carried on the inner wall of the passage, the exhaust gas discharged from the combustion chamber 5 comes into contact with the exhaust gas purifying catalyst 51, and the NO contained in the exhaust gas is converted into NO. After being adsorbed on the catalyst 51, it is dissociated into nitrogen N and oxygen O.
- a reducing agent supply valve 52 is disposed in an exhaust manifold 19 upstream of the exhaust gas purifying catalyst 20.
- the reducing agent is supplied from the supply valve 52 into the exhaust gas.
- FIG. 21 shows a case where the present invention is applied to a compression ignition type internal combustion engine.
- the same components as those of the spark ignition type internal combustion engine shown in FIG. 3 are denoted by the same reference numerals.
- 1 is the engine body
- 5 is the combustion chamber of each cylinder
- 6 is the electrically controlled fuel injection valve for injecting fuel into each combustion chamber 5
- 13a is the intake manifold
- 1 9 is exhaust manifold Are shown.
- the intake manifold 13 a is connected to the outlet of the compressor 53 a of the exhaust turbocharger 53 via the intake duct 14, and the inlet of the compressor 53 a is connected to the air cleaner 15.
- a throttle valve 17 is arranged in the intake duct 14, and a cooling device 54 for cooling the intake air flowing in the intake duct 14 is arranged around the intake duct 14.
- the exhaust manifold 19 is connected to the inlet of the exhaust turbine 53 b of the exhaust turbocharger 53, and the outlet of the exhaust turbine 53 b is a catalytic converter 2 having a built-in exhaust gas purifying catalyst 20. Connected to 1.
- a reducing agent supply valve 55 for supplying a reducing agent composed of, for example, hydrocarbons is provided to make the air-fuel ratio of the exhaust gas rich.
- each fuel injection valve 6 is connected to a common rail 26 via a fuel supply pipe 25, and fuel is supplied into the common rail 26 from an electrically controlled variable discharge fuel pump 27. .
- combustion is continuously performed under a lean air-fuel ratio, and the air-fuel ratio of the exhaust gas is periodically changed in order to recover the purification performance of the exhaust gas purification catalyst 20.
- the reducing agent is supplied from the reducing agent supply valve 55 into the exhaust gas.
- the reducing agent supplied periodically when the temperature TC of the exhaust gas purifying catalyst 20 is higher than the reference temperature Ts determined by the exhaust gas purifying catalyst 20, the reducing agent supplied periodically.
- the amount is the amount of reducing agent required to reduce NOx that has flowed into the exhaust gas purifying catalyst 20 between the last time the reducing agent was supplied and the time this reducing agent was supplied.
- the temperature TC of the exhaust gas purifying catalyst 20 is lower than the reference temperature T s determined by the exhaust gas purifying catalyst 20, the amount of the reducing agent supplied periodically is reduced by the previous reduction.
- the amount of the reducing agent required to reduce the NO x flowing into the exhaust gas purifying catalyst 20 between the supply of the reducing agent and the supply of the reducing agent this time is increased.
- FIGS. 22 (A) and 22 (B) show the structure of this particulate filter.
- FIG. 22 (A) shows a front view of the particulate filter
- FIG. 22 (B) shows a side sectional view of the particulate filter.
- the particulate filter has a honeycomb structure and has a plurality of exhaust passages 60 and 61 extending in parallel with each other. These exhaust gas passages are constituted by an exhaust gas inflow passage 60 whose downstream end is closed by a plug 62 and an exhaust gas outflow passage 61 whose upstream end is closed by a plug 63.
- the hatched portions indicate plugs 63.
- the exhaust gas inflow passages 60 and the exhaust gas outflow passages 61 are arranged alternately via the thin partition walls 64.
- the exhaust gas inflow passage 60 and the exhaust gas outflow passage 61 are each surrounded by four exhaust gas inflow passages 60 by four exhaust gas outflow passages 61, and each exhaust gas outflow passage 61 has four exhaust gas inflow passages. It is arranged to be surrounded by the passage 60.
- the particulate filter is made of, for example, a porous material such as cordierite.
- the exhaust gas flowing into the exhaust gas inflow passage 60 is surrounded by an exhaust gas as shown by arrows in FIG. 22 (B). It flows through the partition wall 64 and into the adjacent exhaust gas outlet passage 61.
- the exhaust gas purifying catalyst is provided on the peripheral wall surface of each exhaust gas inflow passage 60 and each exhaust gas outflow passage 61, that is, on both side surfaces of each partition wall 64 and on the inner wall surface of the fine hole in the partition wall 64. A layer is formed.
- the air-fuel ratio of the exhaust gas is switched to the rich state.
- the particulates contained in the exhaust gas are captured in the particulate filter, and the captured particulates are sequentially burned by the heat of the exhaust gas. If a large amount of particulates accumulates on the particulate filter, a reducing agent is supplied to increase the temperature of the exhaust gas, and the accumulated particulates are ignited and burned.
- This low-temperature combustion has a feature that the generation amount of NOx can be reduced while suppressing the generation of smoke regardless of the air-fuel ratio. That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but since the combustion temperature is suppressed to a low temperature, the excess fuel does not grow into soot, and thus, smoke may be generated. Absent. At this time, only a very small amount of NOx is generated. On the other hand, when the average air-fuel ratio is lean or when the air-fuel ratio is the stoichiometric air-fuel ratio, a small amount of soot is generated when the combustion temperature increases, but the combustion temperature is suppressed to a low temperature under low-temperature combustion. No smoke and no NO x
- the solid line in FIG. 24 (A) shows the relationship between the average gas temperature T g in the combustion chamber 5 and the crank angle when low-temperature combustion is performed, and the dashed line in FIG.
- the graph shows the relationship between the average gas temperature T g in the combustion chamber 5 when the combustion is performed and the crank angle.
- the solid line in Fig. 24 (B) shows the relationship between the fuel and surrounding gas temperatures Tf and the crank angle when low-temperature combustion is performed, and the broken line in Fig. 24 (B)
- the graph shows the relationship between the fuel and ambient gas temperature Tf and crank angle when normal combustion is performed.
- the amount of EGR gas is larger than during normal combustion.
- Fig. 24 (A) before compression top dead center, that is, during the compression stroke,
- the average gas temperature Tg at the time of low temperature combustion shown by the solid line is higher than the average gas temperature Tg at the time of normal combustion shown by the broken line.
- FIG. 24 (B) the temperature Tf of the fuel and its surrounding gas is almost the same as the average gas temperature Tg.
- the inside of the combustion chamber 5 near the compression top dead center is shown.
- the average gas temperature T g is lower when low temperature combustion is performed. It is higher than when normal combustion is performed.
- the temperature of the burned gas in the combustion chamber 5 after the completion of the combustion is lower when the low-temperature combustion is performed than when the normal combustion is performed.
- the exhaust gas temperature increases.
- region I indicates the first combustion region in which the amount of inert gas in the combustion chamber 5 is larger than the amount of inert gas at which the amount of soot generation peaks, that is, the operation region in which low-temperature combustion can be performed.
- Region II is the second combustion where the amount of inert gas in the combustion chamber is smaller than the amount of inert gas where the amount of soot generation peaks, that is, the operation region where only normal combustion can be performed. Is shown.
- Fig. 26 shows the target air-fuel ratio A / ⁇ when performing low-temperature combustion in the rotation region I
- Fig. 27 shows the slot and throttle according to the required torque TQ when performing low-temperature combustion in the operation region I.
- the opening degree of the tor valve 17, the opening degree of the EGR control valve 23, the EGR rate, the air-fuel ratio, the injection start time ⁇ S, the injection completion time 0 E, and the injection amount are shown.
- FIG. 27 also shows the opening of the throttle valve 17 during normal combustion performed in the operating region II.
- the air-fuel ratio can be made rich without generation. Therefore, when the air-fuel ratio of the exhaust gas should be rich in order to restore the NOx purification action of the exhaust gas purifying catalyst, low-temperature combustion can be performed, and the air-fuel ratio can be rich under the low-temperature combustion. .
- a surfactant solution was prepared in a 3 L beaker, and an aqueous solution obtained by dissolving 0.03 mol of lanthanum nitrate in 140 parts of distilled water was added dropwise and stirred to prepare a microemulsion solution. did.
- a solution prepared by dissolving 0.12 mol of zirconium butoxide in 200 parts of cyclohexane was added dropwise to hydrolyze zirconium butoxide. Immediate white clouding occurred. Thereafter, the pH was adjusted to 8.5 with ammonia water to control the aggregation of the precipitate. Thereafter, stirring was continued for 1 hour to ripen the product.
- FIG. 28 also shows the corresponding data of similar lanthanum zirconia produced by the conventional coprecipitation method and alkoxide method.
- the solid line is ZrO 2 (La content ratio 0).
- L a Z r 0 3. 5 theoretical crystal lattice in the composition of (L a content of 50%) (1 1 1) is a straight line connecting between the values of the spacing, each composition (L a content ) Represents the calculated surface spacing in.
- co-precipitation and conventional alkoxy Sid method is short lattice constant below the ideal value, it indicates that the number of L a is not replaced by Z r 0 2 crystal lattice.
- the lanthanum zirconia of the present invention had perfectly the same spacing as the theoretical value, indicating that La 3 + ions were almost completely substituted by the ZrO 2 lattice.
- Example 2 the lanthanum zirconia produced in Example 1 was coated on a monolith substrate by a conventional method, lwt% of platinum was supported, and cesium was used as an alkali metal in the same molar amount as lanthanum. A number of the catalysts were carried to obtain an exhaust gas purifying catalyst of the present invention. For comparison, lanthanum zirconia obtained by the coprecipitation method and the alkoxide method was used to carry platinum and cesium in the same manner.
- the conventional catalyst rapidly lost its NOx retention ability at 700 ° C. or higher, whereas the catalyst of the present invention exhibited N at a high temperature of 1000 ° C. It became clear to retain Ox.
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Abstract
Description
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EP04792725A EP1681096B1 (en) | 2003-10-24 | 2004-10-14 | Catalyst for exhaust gas cleaning |
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2004
- 2004-10-14 CN CN200480034776A patent/CN100586559C/zh not_active Expired - Fee Related
- 2004-10-14 US US10/576,025 patent/US20070066479A1/en not_active Abandoned
- 2004-10-14 EP EP04792725A patent/EP1681096B1/en not_active Expired - Fee Related
- 2004-10-14 WO PCT/JP2004/015575 patent/WO2005039759A1/ja active Search and Examination
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007049778A1 (ja) * | 2005-10-24 | 2007-05-03 | Toyota Jidosha Kabushiki Kaisha | 触媒担体及び排ガス浄化用触媒 |
US7776783B2 (en) | 2005-10-24 | 2010-08-17 | Toyota Jidosha Kabushiki Kaisha | Catalyst carrier and exhaust gas purification catalyst |
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Also Published As
Publication number | Publication date |
---|---|
US20070066479A1 (en) | 2007-03-22 |
EP1681096B1 (en) | 2012-11-21 |
EP1681096A4 (en) | 2010-09-15 |
JP4120559B2 (ja) | 2008-07-16 |
EP1681096A1 (en) | 2006-07-19 |
CN100586559C (zh) | 2010-02-03 |
CN1886194A (zh) | 2006-12-27 |
JP2005125254A (ja) | 2005-05-19 |
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