JP2002364339A - Exhaust emission control device and exhaust emission control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the clean-up efficiency of soot included in exhaust gas without causing clogging of a catalyst. SOLUTION: Soot included in exhaust gas of an internal combustion engine is cleaned up by using a clean-up catalyst carrying an active oxygen discharge agent. An upstream clean-up catalyst and a downstream clean-up catalyst are provided on an exhaust pipe. The upstream clean-up catalyst selectively collects the soot in the exhaust gas, lets the remaining soot pass through, and cleans up only the collected soot. The downstream catalyst non-selectively collects the soot passing through the upstream clean-up catalyst, and cleans up the collected soot. Therefore, the work of cleaning up soot can be shared by the upstream clean-up catalyst and the downstream clean-up catalyst, so that the soot is efficiently cleaned up, and clogging of the catalysts is hard to occur. The upstream clean-up catalyst may collect large soot only, and positively let small soot pass through, or may let the small soot pass through by providing a bypass passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for purifying suspended particulates contained in exhaust gas of an internal combustion engine.

[0002]

2. Description of the Related Art The exhaust gas of an internal combustion engine, especially a diesel engine, contains airborne particulates such as black smoke (soot), and in order to prevent air pollution, carbon-containing airborne particulates released into the atmosphere. There is a strong demand to reduce the total amount of. In addition, a so-called in-cylinder injection gasoline engine that directly injects gasoline into a combustion chamber may emit carbon-containing suspended particulates together with exhaust gas depending on operating conditions.

[0003] Techniques for reducing suspended carbon-containing particulates emitted from an internal combustion engine, particularly a diesel engine, into the atmosphere include:
A technique for purifying suspended particulates in exhaust gas using a heat-resistant filter supporting an oxidation catalyst has been proposed (Japanese Patent Publication No. 7-106290). In this technique, suspended particulates in the exhaust gas are collected by a filter, and the collected particulates are burned in an exhaust gas at a relatively low temperature (typically 350 to 400 ° C.) by the action of an oxidation catalyst. In this way, by trapping and burning the carbon-containing suspended particulates in the exhaust gas, the suspended particulates released to the atmosphere can be significantly reduced.

[0004]

However, such a technique cannot burn all of the trapped carbon-containing suspended particulates, and the filter eventually becomes clogged as the filter continues to be used. There was a problem that there is. That is, it is not uncommon for the temperature of the exhaust gas to be lower than the combustible temperature (350 ° C. to 400 ° C.) of the collected fine particles. In such a case, the carbon-containing suspended fine particles in the exhaust gas are Accumulate on the filter.
When the temperature of the exhaust gas rises, the accumulated fine particles start burning by the action of the oxidation catalyst. However, if a large amount of fine particles are deposited on the filter, it takes a long time to burn, so that unburned particles may remain. In addition, carbon-containing suspended fine particles,
It is known that it becomes difficult to burn gradually while being deposited on the filter.If such flame-retardant fine particles cover the oxidation catalyst, it becomes difficult to burn the carbon-containing suspended fine particles, and eventually The filter may be clogged.

In view of such problems, the inventors of the present application have developed a technique for purifying carbon-containing suspended particulates in exhaust gas using a heat-resistant filter (purification catalyst) carrying an active oxygen releasing agent. Has already been applied for a patent (Japanese Patent Application No.
001-45442). In this technique, while trapping carbon-containing suspended particulates in exhaust gas with a purifying catalyst, oxygen in the exhaust gas is captured to generate active oxygen, and the collected floating particulates are burned by the action of active oxygen. . Since active oxygen is a highly reactive substance, it is possible to burn the trapped carbon-containing suspended fine particles even in lower-temperature exhaust gas. Even if flame-retardant fine particles are generated, they can be easily burned by using active oxygen having high reactivity.

[0006] However, even in the technique of burning carbon-containing suspended particulates using active oxygen, the purifying catalyst is likely to be clogged in order to further reduce the amount of suspended particulates. That is, since the carbon-containing suspended particulates contained in the exhaust gas are distributed in a wide range in size, if the pore size of the purification catalyst is reduced to collect small particulates and reduce the emission amount of the particulates, it becomes large. The fine particles make the purification catalyst easily clogged.

The present invention has been achieved by solving the above-mentioned problems in the prior art and further improving the above-mentioned patent-pending technology. The present invention provides carbon-containing suspended particulates discharged from an internal combustion engine to the atmosphere. The aim is to provide technology that can significantly reduce

[0008]

Means for Solving the Problems and Their Functions and Effects In order to solve at least part of the above-mentioned problems, the exhaust gas purifying apparatus of the present invention has the following configuration. That is, an exhaust gas purifying apparatus for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, which captures and retains excess oxygen in the exhaust gas and retains the excess oxygen when the surrounding oxygen concentration decreases. A first purification catalyst that carries an active oxygen releasing agent that releases oxygen as active oxygen, the first purification catalyst selectively traps carbon-containing suspended particulates in the exhaust gas; And a purification catalyst for burning the collected carbon-containing suspended particulates using the active oxygen, wherein the second purification catalyst non-selectively removes the carbon-containing suspended particulates that have passed through the first purification catalyst. The present invention is characterized in that the catalyst is a purification catalyst that collects the carbon-containing suspended fine particles using the active oxygen.

Further, an exhaust gas purifying method of the present invention corresponding to the above exhaust gas purifying apparatus is a method for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, wherein the method comprises the steps of: When the first purification catalyst loaded with an active oxygen releasing agent that takes in oxygen and holds it and releases the held oxygen as active oxygen when the surrounding oxygen concentration decreases, the carbon-containing gas in the exhaust gas is used. Selectively purifying suspended particulates, and non-selectively purifying the carbon-containing suspended particulates having passed through the first purification catalyst using a second purification catalyst loaded with the active oxygen releasing agent. Make a summary.

In the exhaust gas purifying apparatus and the exhaust gas purifying method, the carbon-containing suspended fine particles contained in the exhaust gas are selectively collected by using the first purification catalyst, and the collected carbon-containing suspended particles are collected. The fine particles are purified using active oxygen. Next, the carbon-containing suspended fine particles that have passed through the first purification catalyst are non-selectively collected by the second purification catalyst, and the collected fine particles are purified using active oxygen. By purifying the carbon-containing suspended particulates while sharing the first purification catalyst and the second purification catalyst in this manner, the purification can be performed more efficiently, and the purified catalyst is released to the atmosphere without clogging. The carbon-containing suspended fine particles can be significantly reduced.

In such an exhaust gas purifying apparatus, the first
As a purification catalyst and a second purification catalyst, a catalyst including a plurality of pores through which exhaust gas passes is used, and the catalyst having a large average diameter of pores contained in the purification catalyst is used as the first catalyst.
The catalyst having a small average pore diameter may be used as the second purification catalyst.

In this case, the first purification catalyst selectively purifies relatively large carbon-containing suspended particulates, and the second purification catalyst purifies relatively small carbon-containing suspended particulates. Become. If the carbon-containing suspended particulates are shared and purified in this way, the purification can be performed more efficiently, and as a result, the carbon-containing suspended particulates released to the atmosphere can be significantly reduced without clogging the purification catalyst. Becomes possible.

[0013] In such an exhaust gas purifying apparatus, a purifying catalyst having an average value of the pore diameter in a range of 2 to 5 times the second purifying catalyst may be used as the first purifying catalyst.

The average value of the pore diameter of the first purification catalyst is as follows:
If the average value of the second purification catalyst is less than twice, the ratio of the carbon-containing suspended fine particles purified by the first purification catalyst becomes too large. On the other hand, if it is more than five times, the rate of purification by the second purification catalyst becomes too large. Therefore, it is preferable to set the range of 2 to 5 times, because the first purification catalyst and the second purification catalyst can purify the carbon-containing suspended fine particles while sharing at an appropriate ratio.

Alternatively, a purifying catalyst having an average pore diameter in the range of 20 μm to 50 μm may be used as the first purifying catalyst.

Since the carbon-containing suspended fine particles contained in the exhaust gas have a particle size distribution ranging from several μm to several tens μm, the average value of the pore diameter is from 20 μm to 50 μm.
Is used as the first purification catalyst, the first purification catalyst and the second purification catalyst can perform purification by sharing the carbon-containing suspended particulates at an appropriate ratio. This is preferable.

Furthermore, in the exhaust gas purifying apparatus of the present invention, purifying catalysts having the following relationship may be used as the first purifying catalyst and the second purifying catalyst, respectively. In other words, a purifying catalyst having a smaller particulate collection rate indicating the ratio of the trapped carbon-containing suspended particles with respect to the total amount of the flowing carbon-containing suspended particles is smaller than the second purification catalyst as the first purification catalyst. It may be used.

The purification catalyst having a small particle collection rate is
If used as a purification catalyst, the carbon-containing suspended particulates that have passed through the first purification catalyst can be purified using the second purification catalyst. In this way, if the carbon-containing suspended particulates are shared and purified by the first purification catalyst and the second purification catalyst, it becomes possible to purify more efficiently.
The carbon-containing suspended particulates released into the atmosphere can be significantly reduced without clogging the purification catalyst.

In the exhaust gas purifying apparatus, at least one bypass passage may be formed in the first purifying catalyst so that the inflowing exhaust gas passes without collecting the carbon-containing suspended particulates.

With this configuration, it is possible to purify a part of the carbon-containing suspended particulates using the first purification catalyst and purify the carbon-containing suspended particulates that have passed through the bypass passage with the second purification catalyst. it can. As a result, the carbon-containing suspended particulates are shared and purified by these purification catalysts,
It becomes possible to improve the purification efficiency of the carbon-containing suspended particulates.

Alternatively, in the exhaust gas purifying apparatus, a catalyst having the bypass passage formed in an outer peripheral portion of the first purifying catalyst may be used as the first purifying catalyst.

Generally, exhaust gas is less likely to flow in the outer peripheral portion of the purification catalyst than in the central portion, and accordingly, the catalyst temperature tends to be lower in the outer peripheral portion than in the central portion. On the other hand, if a bypass passage having a small passage resistance and allowing easy passage of exhaust gas is provided on the outer peripheral portion of the first purification catalyst, the temperature of the outer peripheral portion becomes higher and the catalyst temperature can be made uniform.
A purification catalyst loaded with an active oxygen releasing agent tends to exert purification efficiency depending on the catalyst temperature. Therefore, if the catalyst temperature is made uniform in this way, the entire purification catalyst can function efficiently, and as a result, Is preferable since the purification efficiency of the carbon-containing suspended particulates can be improved.

In the exhaust gas purifying apparatus, the ratio of the bypass passage portion in a cross section perpendicular to the exhaust gas inflow direction as the first purification catalyst is as follows:
It is also possible to use a purification catalyst set to be less than half.

Since the bypass passage has a low passage resistance, the exhaust gas tends to flow more easily than the other parts. However, if the proportion of the bypass passage in the cross section of the first purification catalyst is set to half or less, It is preferable because the ratio of the carbon-containing suspended fine particles passing through the first purification catalyst can be set to an appropriate ratio.

The proportion occupied by the bypass passage portion is as follows:
More preferably, it is set in the range of 10% to 40% of the cross section of the purification catalyst. The proportion occupied by the bypass passage is
If the ratio is less than 10%, the ratio of the carbon-containing suspended particulates purified by the first purification catalyst becomes too large.
If the ratio is excessive, the rate of purification by the second purification catalyst becomes too large. Therefore, if the ratio occupied by the bypass passage portion is in the range of 10% to 40%, the carbon-containing suspended particulates can be purified at an appropriate ratio by the first purification catalyst and the second purification catalyst. It is preferable because it is possible.

In such an exhaust gas purifying apparatus,
A detour passage may be provided from an upstream side to a downstream side of the first purification catalyst to detour part of the exhaust gas.

When the bypass passage is provided in this way, a part of the carbon-containing suspended particulates flows into the second purification catalyst through the bypass passage. As a result, the carbon-containing suspended fine particles are purified by being shared by the first purification catalyst and the second purification catalyst, and the purification efficiency of the carbon-containing suspended fine particles can be improved accordingly, which is preferable.

In the exhaust gas purifying apparatus of the present invention, the purifying catalyst carrying at least one element selected from the group consisting of alkali metals, alkaline earth metals, rare earths, and transition metals is used as the active oxygen releasing agent. , And may be used as the first purification catalyst and the second purification catalyst.

Since it has been confirmed that these elements can function effectively as an active oxygen releasing agent, if at least one element selected from these elements is supported,
This is preferable because it becomes possible to purify the carbon-containing suspended fine particles using active oxygen.

In the exhaust gas purifying apparatus of the present invention, in addition to the active oxygen releasing agent, a purifying catalyst carrying a noble metal catalyst belonging to the platinum group is used as the first purifying catalyst and the second purifying catalyst. It may be used as

It has been confirmed that the noble metal catalyst belonging to the platinum group promotes the function of the active oxygen releasing agent to release active oxygen. Therefore, if these noble metal catalysts are supported, the purification efficiency of the carbon-containing suspended fine particles can be improved. Is preferred because it is possible to further improve

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more clearly explain the operation and effect of the present invention, embodiments of the present invention will be described in the following order. A. Embodiment: B. Apparatus configuration: B-1. Configuration of Engine: B-2. Configuration of exhaust gas purification catalyst: B-3. Purification mechanism of carbon-containing suspended particulates using active oxygen: First embodiment: C-1. Exhaust gas purification catalyst of first embodiment: C-2. Purification action of carbon-containing suspended particulates in the first embodiment: Second embodiment: D-1. Exhaust gas purification catalyst of second embodiment: D-2. Purification action of carbon-containing suspended particulates in the second embodiment: Modifications: E-1. First modified example: E-2. Second modification:

A. Embodiment of the present invention: FIG. 1 is an explanatory diagram showing an embodiment in which an exhaust gas purifying apparatus of the present invention is applied to a diesel engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For convenience of understanding of the present invention, an outline of an embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 1, in an internal combustion engine such as a diesel engine or a gasoline engine, an exhaust gas generated by the operation of the engine is discharged to the atmosphere via exhaust passages such as an exhaust manifold 16 and an exhaust pipe 17. To be discharged. Since the exhaust gas contains so-called soot and other carbon-containing suspended particulates, the particulates are collected by a plurality of particulate purification catalysts provided in the exhaust passage so that these particulates are not released to the atmosphere. I do. Further, an active oxygen releasing agent is supported on the fine particle purification catalyst. Here, the active oxygen releasing agent is a substance having a function of taking in and holding excess oxygen in exhaust gas and releasing the held oxygen as active oxygen when the surrounding oxygen concentration decreases.
When the exhaust gas contains excess oxygen, the particulate purification catalyst collects the carbon-containing suspended particulates in the exhaust gas, and the oxygen concentration in the exhaust gas decreases, or the carbon-containing suspended particulates accumulate on the catalyst. When the surrounding oxygen concentration decreases, active oxygen is released to burn the carbon-containing suspended fine particles on the catalyst. By utilizing active oxygen having high reactivity in this way, the collected carbon-containing suspended fine particles can be reliably purified.

However, when a plurality of fine particle purifying catalysts are arranged in series, the purifying catalyst on the upstream side is mainly used, and therefore, for example, the carbon-containing suspended fine particles flow in beyond the purifying ability of the catalyst. The catalyst may be deteriorated or clogged. In the exhaust gas purifying device of the present invention, the carbon-containing suspended particulates in the exhaust gas are selectively collected and purified by the upstream particulate purification catalyst, and the suspended particulates that have passed through the upstream purification catalyst are converted to the downstream particulates. Collect and purify with a purification catalyst. By doing so, it becomes possible to make the upstream-side purification catalyst and the downstream-side purification catalyst work efficiently, and as a result, it is possible to further reduce the emission amount of the carbon-containing suspended particulates.

The exhaust gas purifying apparatus of the present invention has the following features.
Various embodiments are possible, and these embodiments will be described in detail below based on various embodiments.

B. Apparatus configuration: B-1. Engine Configuration: FIG. 1 is an explanatory diagram showing a schematic configuration of a diesel engine 10 equipped with the exhaust gas purifying apparatus of the first embodiment. Of course, the present invention is not limited to a diesel engine, and can be applied to other internal combustion engines such as a gasoline engine in which fuel is directly injected into a cylinder. Further, the present invention can be applied to all internal combustion engines such as those mounted on a vehicle or a ship, or those for stationary use.

The diesel engine 10 is a so-called four-cylinder engine, and has four combustion chambers # 1 to # 4. Air is supplied to each combustion chamber via an intake pipe 12, and when fuel is injected from a fuel injection valve 14 provided in each combustion chamber, the air and the fuel burn in the combustion chamber. Exhaust gas generated by the combustion is discharged from the exhaust pipe 17 to the atmosphere via the exhaust collecting pipe 16.

In the middle of the exhaust pipe 17, a supercharger 20 is provided. The supercharger 20 includes a turbine 21 provided in the exhaust pipe 17, a compressor 22 provided in the intake pipe 12, and a shaft 23 connecting the turbine 21 and the compressor 22. When the exhaust gas discharged from the combustion chamber rotates the turbine 21 of the supercharger 20, the compressor 22 rotates via the shaft 23, compresses the air, and supplies the air to each combustion chamber. An air cleaner 26 is provided upstream of the compressor 22, and the compressor 22 compresses air taken from the air cleaner 26 and supplies the compressed air to the combustion chamber. Since the temperature of the air rises when compressed by the compressor 22, an intercooler 24 for cooling the air is provided downstream of the compressor 22. After the compressed air is cooled by the intercooler 24, the compressed air enters the combustion chamber. Supplied.

An electric throttle valve 28 is provided in the intake pipe 12.
Is provided. Although the electric throttle valve 28 is open under normal operating conditions, it is possible to limit the amount of air flowing into the combustion chamber by closing the electric throttle valve 28 as necessary. The case where the amount of air flowing into the combustion chamber needs to be limited includes, for example, a case where it is necessary to reduce the oxygen concentration in the exhaust gas and a case where the exhaust gas temperature needs to be raised.

The intake pipe 12 and the exhaust manifold 16 are
They are connected by an EGR passage 60. Here, EGR is an Exhaust Gas Recirculatory.
Abbreviation of on (exhaust gas recirculation device), which means that a part of exhaust gas is intentionally returned into the intake pipe. E
An EGR valve 62 is provided in the GR passage 60.
By adjusting the opening of the GR valve 62, the amount of exhaust gas introduced into the intake pipe 12 can be controlled.

The engine control ECU 30 detects the operating conditions of the engine, such as the engine speed Ne and the accelerator opening θac, and according to the operating conditions, the fuel supply pump 18.
Also, the fuel injection valve 14, the electric throttle valve 28, the EGR valve 62, and the like are appropriately controlled. The fuel supply pump 18 and the fuel injection valve 14 inject an appropriate amount of fuel into the combustion chamber at an appropriate timing under the control of the engine control ECU 30 to start combustion in the combustion chamber,
Diesel engine 10 generates output.

Exhaust gas generated by combustion of fuel in the combustion chamber contains so-called carbon-containing suspended particulates such as soot. Therefore, in order to purify the carbon-containing suspended particulates in the exhaust gas, the exhaust pipe 1 on the downstream side of the turbine 21 is removed.
Inside 7, exhaust gas purifying catalysts 100 and 200 described later are provided in series. Here, the exhaust gas purifying catalysts 100 and 200 are described as being provided on the downstream side of the turbine 21, but may be provided on the upstream side of the turbine 21.

B-2. Configuration of exhaust gas purification catalyst: Fig. 2
FIG. 2 is an explanatory view showing the structure of an exhaust gas purification catalyst 100 on the upstream side. FIG. 2A is a front view of the exhaust gas purifying catalyst 100 viewed from the side where the exhaust gas flows, and FIG.
Is a side sectional view. Downstream exhaust gas purification catalyst 200
The basic structure is the same as that of the exhaust gas purifying catalyst 100.

As shown in the figure, the upstream side exhaust gas purifying catalyst 100 has a structure in which a catalyst component described later is carried on a cordierite ceramics filter having a so-called honeycomb structure. Of course, the material of the ceramic filter is not limited to cordierite, and a known ceramic material such as silicon carbide or silicon nitride can be used.
A large number of passages 102 through which the exhaust gas passes are formed inside the exhaust gas purification catalyst 100 having a honeycomb structure.
As shown, the seals 104 are provided alternately. In FIG. 2, the seals 104 are indicated by hatching.

When the exhaust gas containing the carbon-containing suspended particulates flows from the left side of FIG. 2B, the exhaust gas flows through the exhaust gas purifying catalyst 100 through the passage 102 where the seal 104 is not provided on the upstream side. Flows into. However, since the downstream side of the passage is closed by the stopper 104, FIG.
(B), as indicated by the arrow, the passage 10 through which the seal 104 is not provided on the downstream side through the partition 106 of the passage 102.
Go to 2. The cordierite has a porous structure formed therein during firing, and can capture carbon-containing suspended fine particles and the like in the exhaust gas when the exhaust gas passes through the porous structure in the partition wall 106.

A base layer mainly composed of alumina is formed on the surface of cordierite constituting the partition 106, and a noble metal catalyst and an active oxygen releasing agent are supported on the base layer. ing. The noble metal catalyst is in the form of fine particles having a particle diameter of 1 μm or less, and is uniformly dispersed and supported on the active oxygen releasing agent. Precious metals include platinum Pt and palladium Pd
Although platinum-based noble metals such as are mainly used, other metals having oxidizing activity can also be applied. As the active oxygen releasing agent, potassium K, sodium Na, lithium L
i, alkali metal such as cesium Cs, rubidium Rb, barium Ba, calcium Ca, strontium S
Elements selected from alkaline earth metals such as r, rare earths such as lanthanum La, yttrium Y and cerium Ce, and transition metals are mainly used. As the active oxygen releasing agent, an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, and strontium Sr is preferably used. it can.

B-3. Purification mechanism of carbon-containing suspended particulates using active oxygen: The exhaust gas purifying catalysts 100 and 200 having such a structure generate active oxygen by the following mechanism and use the active oxygen to form a catalyst on the catalyst. The carbon-containing suspended particulates collected in the furnace are burned.

FIG. 3 shows the exhaust gas purifying catalysts 100 and 200.
It is the conceptual diagram which expanded and showed the surface of FIG. On the surface of the exhaust gas purification catalyst 100, an active oxygen releasing agent 103 such as potassium K or barium Ba and a noble metal catalyst 104 such as platinum Pt or palladium Pd are supported.

FIG. 3A shows a case where excess oxygen is present in the exhaust gas. The exhaust gas of a diesel engine contains nitrogen oxides NOx generated by combustion in addition to carbon-containing suspended particulates. Since most of NOx is contained in the state of nitric oxide NO, FIG.
In (a), NOx is displayed as nitric oxide NO. Since nitric oxide NO is a polar molecule, NO in exhaust gas is quickly adsorbed on a noble metal catalyst such as platinum Pt. Since the platinum-based noble metal catalyst has a strong oxidation activity, nitric NO nitrate ions NO3 via nitrogen dioxide NO2 ^- it is oxidized to. Nitrate ions NO3 thus generated over a noble metal catalyst ^- so-called "spillover"
Move to the active oxygen releasing agent 103 by a phenomenon referred to as The "spillover phenomenon" is a phenomenon in which adsorbed molecules actively move around on a metal catalyst. On the catalyst, noble metal particles such as Pt are dispersed as uniformly as possible. To obtain, it is believed that the entire surface functions as a catalyst. As described above, under the condition that the oxygen is excessively present in the exhaust gas, the nitric oxide NO is oxidized on the noble metal catalyst, carried to the active oxygen releasing agent 103 by the spillover phenomenon, and stored in the form of nitrate. It should be noted that all of the nitrogen monoxide NO adsorbed on the noble metal catalyst is necessarily nitrate ions NO3 ^- not necessarily be oxidized to, some of nitrite ion NO2 ^- also be stored in the active oxygen release agent 103 in the state It is possible.

Thus, when the nitrogen monoxide NO in the exhaust gas is taken in as a nitrate, the active oxygen releasing agent 10
3 generates active oxygen. Since active oxygen has a very high reactivity, it can oxidize the carbon-containing suspended fine particles collected on the exhaust gas purification catalyst 100 and convert them into carbon dioxide and water.

The mechanism by which active oxygen is released from the active oxygen releasing agent 103 when nitric oxide NO is taken in the form of nitrate is considered to be as follows.
Since the active oxygen releasing agent 103 is heated to a high temperature by the exhaust gas, it is considered that the active oxygen releasing agent 103 is usually combined with carbon dioxide to be in a carbonate state. When nitrogen monoxide NO is stored in the active oxygen release agent 103, carbonate ion CO3 ^- nitrate ions NO3 ^- replaced by, evicted carbonate ions CO3 ^- is decomposed into carbon dioxide and active oxygen, the As a result, it is considered that active oxygen is released.

FIG. 3 (b) shows a case where the oxygen concentration in the exhaust gas has decreased and oxygen has been deficient. When the engine is operated under an operating condition in which oxygen in the exhaust gas is deficient, the exhaust gas contains a reducing compound such as a hydrocarbon compound or carbon monoxide CO.
Carbon-containing suspended particulates such as soot also act as reducing substances. In FIG. 3B, the hydrocarbon-based compound is represented as HC, and the carbon-containing suspended fine particles such as soot are schematically represented by C representing carbon. As described above, the platinum-based noble metal catalyst has a strong oxidizing activity. Therefore, if oxygen is present in the exhaust gas, these reducing substances are oxidized to form carbon dioxide C.
It can be converted to O2 or water.

However, when there is not enough oxygen in the exhaust gas to match the reducing substance, the noble metal catalyst 104 removes the nitric acid stored in the active oxygen releasing agent 103 as shown in FIG. The ion NO3 ^- is decomposed, and the reducing substance is oxidized using the generated active oxygen. This phenomenon also occurs when oxygen is present in the exhaust gas, but a large amount of carbon-containing suspended particulates are trapped on the catalyst and the surroundings of the catalyst are quasi oxygen-deficient. It can happen as well. FIG.
This phenomenon will be described with reference to FIG.
Nitrate ion NO stored in active oxygen release agent 103
3 ^- moves over a noble metal catalyst 104 by the spillover phenomenon. On noble metal catalyst 104, nitrate ions NO3 ^-
Electron cloud of the results of uneven distribution is attracted by the precious metal catalyst side, nitrate ions NO3 ^- have become state easy broken chemical bonds are between the nitrogen atom and an oxygen atom. In FIG. 3B, the nitrate ion is indicated as “N + 3 · O”
FIG. 3 schematically shows a state in which a bond between a nitrogen atom and an oxygen atom is easily broken. When a reducing substance acts on such a state, the bond between the nitrogen atom and the oxygen atom is broken, and active oxygen is generated. Active oxygen is an extremely reactive substance that reacts quickly with carbon-containing suspended particulates in addition to hydrocarbon compounds and carbon monoxide in exhaust gas, converting them to carbon dioxide, CO2, water, etc. I do. Moreover, nitrate ions NO3 ^- active oxygen release agent 103 releases a result of exposure to a high temperature by the exhaust gases to return to the state of the carbonate bonded to the carbon dioxide in the exhaust gas.

As described above, the exhaust gas purifying catalyst 100 of the present embodiment can be used under the condition that the excess oxygen exists in the exhaust gas.
Excess oxygen and NOx are taken in as nitrate, and when the surrounding oxygen concentration decreases, the nitrate is decomposed into nitrogen. In this way, it is possible to purify NOx and generate active oxygen while repeating uptake and release of excess oxygen and NOx, and also to purify carbon-containing suspended particulates using the generated active oxygen. .

The size of the suspended carbon-containing particles in the exhaust gas varies over a wide range. In order to purify more suspended carbon-containing particles, the pore diameter of the porous structure formed in cordierite must be reduced. It needs to be finer and trap small suspended particles. However, when the pore size is reduced,
Clogging by large fine particles is likely to occur. Also, the amount of fine particles that can be purified at once on the catalyst is naturally limited, so if the amount of fine particles to be collected by purifying even small suspended particles increases, fine particles that cannot be purified and accumulate on the catalyst are generated. Clogging of the catalyst is likely to occur. In order to avoid the occurrence of such a problem, in the exhaust gas purifying apparatus of the present embodiment, as described below, the exhaust gas purifying catalyst on the upstream side selectively collects carbon-containing suspended particulates, and The method employs a method of non-selectively collecting the fine particles passing through the catalyst on the downstream side by the exhaust gas purification catalyst on the downstream side.

C. First embodiment: C-1. Exhaust gas purification catalyst of the first embodiment: FIG.
FIG. 1 is an explanatory diagram conceptually showing a configuration of an exhaust gas purification device to which an exhaust gas purification catalyst of an embodiment is applied. As shown, in the exhaust gas purifying apparatus of the first embodiment, two exhaust gas purifying catalysts 100 and 200 are mounted on an exhaust pipe 17 of the diesel engine 10. Here, in the first embodiment, a combination of porous catalysts having different pore diameters formed in cordierite is used. That is, as the exhaust gas purifying catalyst 100 provided on the upstream side, a porous catalyst having a large pore diameter formed in cordierite is used, and as the exhaust gas purifying catalyst 200 on the downstream side, the pore diameter of cordierite is used. Of small catalysts are used. As described above, in the exhaust gas purifying apparatus of the first embodiment, by combining the catalysts having different pore diameters, it becomes possible to purify the carbon-containing suspended fine particles with high efficiency as a whole, and the catalyst is easily clogged. Such problems are avoided. Hereinafter, the action of these catalysts for purifying carbon-containing suspended particulates will be described.

C-2. Purification action of fine particles in the first embodiment: The size of the carbon-containing suspended fine particles contained in the exhaust gas has a wide particle size distribution. FIG. 5 is an explanatory view conceptually showing the particle size distribution of the carbon-containing suspended fine particles contained in the exhaust gas. In the figure, "Raw" indicates that the exhaust gas from the engine is used to remove the purification catalyst. The particle size distribution before passing through, and what is indicated as “SeL” is the particle size distribution after the carbon-containing suspended fine particles are selectively collected by the exhaust gas purification catalyst 100 on the upstream side. Further, what is indicated as “Tp” is a particle size distribution in a state where the particle size passes through the exhaust gas purification catalyst 200 on the downstream side and is discharged to the atmosphere. As shown in the figure, it is considered that almost all of the carbon-containing suspended particulates have been trapped, although small particles that cannot be trapped even by the downstream purification catalyst slightly pass through. Can be.

FIG. 6 is an explanatory view conceptually showing how carbon-containing suspended particulates in exhaust gas are collected on an exhaust gas purifying catalyst. FIG. 6A shows a catalyst having a large pore diameter.
That is, FIG. 6B shows the case of the exhaust gas purifying catalyst 100 provided on the upstream side, and FIG. 6B shows a catalyst having a small pore diameter, that is, the exhaust gas purifying catalyst 2 provided on the downstream side.
00 is shown. Honeycomb structure partition 106,
The cordierite portion constituting 206 is shown with a hatched line in the figure, and intricate pores are formed between cordierite. The carbon-containing suspended particulates are indicated by black circles. Further, the exhaust gas is supplied to the partition walls 106 and 20.
6 passes from top to bottom on the drawing. Arrows shown by solid lines in the figure schematically represent the flow of exhaust gas passing through the fine holes.

As shown in FIG. 6A, in the exhaust gas purifying catalyst 100 on the upstream side having a large pore diameter, the carbon-containing suspended fine particles having a large particle diameter in the exhaust gas are mainly collected.
The suspended fine particles having a small particle size pass without being collected. As described above, in the upstream side exhaust gas purifying catalyst 100, the fine particles having a large particle diameter are selectively collected. As a result, the carbon-containing suspended fine particles in the region indicated by hatching in FIG. Collected. FIG. 4 schematically shows that large carbon-containing fine particles in the exhaust gas are mainly collected by the upstream catalyst by hatching the exhaust gas purifying catalyst 100 downward and to the right.

The small carbon-containing fine particles that have passed through the upstream exhaust gas purifying catalyst 100 are converted into the downstream exhaust gas purifying catalyst 2.
Flow into 00. As shown in FIG. 6B, a catalyst having a small pore diameter is used as the exhaust gas purification catalyst 200 on the downstream side, and it is possible to collect suspended fine particles having a small particle diameter. Therefore, a clean exhaust gas containing no carbon-containing suspended particulates is discharged from the exhaust gas purification catalyst 200 on the downstream side. In FIG. 5, a region indicated by hatching that rises to the right indicates a particle size distribution of the carbon-containing suspended fine particles collected by the exhaust gas purification catalyst 200 on the downstream side. In addition, FIG. 4 schematically illustrates that small floating carbon-containing particles in the exhaust gas are collected by the downstream catalyst by hatching the exhaust gas purification catalyst 200 to the right.

As described above, in the exhaust gas purifying apparatus of the first embodiment, the exhaust gas purifying catalyst 100 provided on the upstream side is provided.
In this method, the carbon-containing suspended fine particles having a relatively large particle diameter are selectively collected, and the carbon-containing suspended fine particles having a small particle diameter that have passed through the upstream catalyst are collected by the exhaust gas purification catalyst 200 on the downstream side. For this reason, even if a catalyst having a small pore diameter is used as the exhaust gas purification catalyst 200 on the downstream side, there is no possibility that the pores are clogged with the suspended particles having a large particle diameter. In addition, since a catalyst having a smaller pore size can be applied to that extent, smaller suspended carbon-containing particles can be collected, and the purification efficiency of the particles can be improved as a whole.

FIG. 7 is an explanatory diagram conceptually showing a case where selective collection is not performed by the exhaust gas purification catalyst on the upstream side for reference. In the reference example shown in FIG. 7, a catalyst having a small pore diameter is also used on the upstream side in order to improve the purification efficiency by collecting small suspended carbon-containing particles. FIG. 8 is an explanatory diagram schematically showing a state in which the exhaust gas purifying catalyst of the reference example collects carbon-containing suspended particulates in exhaust gas. As shown in the figure, if a catalyst having a small pore diameter is used, suspended particulates having a small particle diameter can be collected, and the purification efficiency of the carbon-containing suspended particulates can be improved accordingly. However, the carbon-containing suspended particles in the exhaust gas have a wide particle size distribution, and when the pore diameter of the catalyst is reduced, the pores are likely to be clogged by the large suspended particles as shown in FIG.

In FIG. 7, the exhaust gas purifying catalyst 20 on the upstream side
By superimposing the right-downward hatching and the right-upward hatching on 0, the carbon-containing suspended fine particles having a large particle size (the fine particles in the hatched portion in FIG. 5) and the floating fine particles having a small particle size are provided. (Particles in the hatched portion in FIG. 5 that are upwardly hatched) indicate that the particles are collected by the upstream catalyst. As described above, even the suspended particles having a small particle diameter are collected by the exhaust gas purification catalyst 200 on the upstream side, so that the exhaust gas flowing into the downstream catalyst does not contain the suspended particles containing carbon, and The catalyst on the side cannot be used efficiently. In other words, almost all of the carbon-containing suspended particulates discharged from the diesel engine 10 are collected by the exhaust gas purification catalyst 200 on the upstream side. Since the amount of fine particles that can be purified by the exhaust gas purifying catalyst at one time is naturally limited, if such a large amount of fine particles are collected, the fine particles that cannot be purified easily cause clogging of pores.

On the other hand, in the exhaust gas purifying apparatus of the first embodiment, as schematically shown in FIG. 4, the carbon-containing suspended fine particles having a relatively large particle diameter are removed from the exhaust gas purifying apparatus provided on the upstream side. The catalyst is selectively purified by the catalyst 100, and the suspended fine particles having a small particle size are purified by the exhaust gas purification catalyst 200 on the downstream side.
As described above, since the suspended particulates are purified while utilizing the upstream catalyst and the downstream catalyst, there is no possibility that the upstream purification catalyst is clogged, and high purification efficiency can be achieved as a whole. it can.

The carbon-containing suspended particles having a large particle diameter are collected by the exhaust gas purification catalyst 100 on the upstream side, and the small suspended particles are collected by the exhaust gas purification catalyst 200 on the downstream side. If the two exhaust gas purifying catalysts are used to purify the fine particles, the whole system can be relatively easily formed even if one of the purifying catalysts (especially, the purifying catalyst on the upstream side) is small. Can be done. Normally, even if the purifying catalyst is brought closer to the engine so that higher-temperature exhaust gas flows into the engine, it cannot be made much closer due to mounting restrictions, and in many cases, exhaust gas with a sufficient temperature cannot be used. . On the other hand, in the present embodiment, the size of the exhaust gas purification catalyst on the upstream side can be reduced, so that the purification catalyst can be made closer to the engine without being restricted by mounting.

In particular, the exhaust gas purifying catalyst 10 of this embodiment
In the case of 0,200, excess oxygen and NOx in the exhaust gas are taken in as nitrate, and it is preferable that a certain temperature of the exhaust gas is always maintained in order to oxidize NOx to generate nitrate. Therefore, if the exhaust gas purifying catalyst 100 on the upstream side is mounted close to the engine side, there is an advantage that the temperature of exhaust gas flowing into the catalyst can always be kept at a certain level or more.

In addition, the exhaust gas purifying catalyst 1 of the first embodiment
If the pore diameter of the catalyst is increased as in 00, the passage resistance is reduced by just that much, and the exhaust resistance of the entire exhaust passage can also be reduced. If the exhaust resistance decreases,
There is also an advantage that the engine output is improved.

D. Second Embodiment: In the exhaust gas purifying apparatus of the first embodiment described above, the upstream side exhaust gas purifying catalyst 100 selectively collects carbon-containing suspended fine particles having a large particle diameter. The catalyst on the upstream side may be selectively purified based on the ease other than the particle diameter of the suspended fine particles. Hereinafter, such an exhaust gas purifying apparatus of the second embodiment will be described.

D-1. Exhaust gas purification catalyst of the second embodiment:
FIG. 9 is an explanatory diagram showing the structure of the upstream side exhaust gas purification catalyst 300 used in the second embodiment. FIG. 9 (a)
FIG. 9B is a front view of the exhaust gas purifying catalyst 300 viewed from the side where the exhaust gas flows, and FIG. 9B is a side sectional view. As the exhaust gas purifying catalyst on the downstream side, the same exhaust gas purifying catalyst as that of the first embodiment can be used.

As shown in the figure, the upstream exhaust gas purifying catalyst 300 used in the second embodiment is different from the exhaust gas purifying catalysts 100 and 200 used in the first embodiment in the upstream passage of the honeycomb passage. The difference is that the stop 104 has been removed. Seal 304 on the downstream side of the honeycomb passage
Are provided alternately similarly to the catalyst used in the first embodiment.

From the left side of FIG. 9B, when the exhaust gas containing the carbon-containing suspended particulates flows into the passage provided with the filler 304, the exhaust gas becomes the catalyst as indicated by the broken arrow in the figure. Pass through the partition wall 306 and pass through the passage 303 where no seal is provided. At this time, suspended carbon-containing particles in the exhaust gas are collected in the pores of the partition 306. For the pores of the partition wall 306, a catalyst having a small pore diameter is used so that small suspended fine particles can be collected. On the other hand, the exhaust gas that has flowed into the passage 303 where no seal is provided on the downstream side, as shown by the solid arrow in the drawing, does not trap the carbon-containing suspended particulates in the exhaust gas, and Pass as it is. As a result, in the exhaust gas purifying catalyst 300 used in the second embodiment, the carbon-containing suspended particulates of the exhaust gas flowing into the passage 302 provided with the seal 304 are selectively collected and provided with the seal. No passage 30
The carbon-containing suspended particulates of the exhaust gas flowing into the exhaust gas 3 flow into the downstream exhaust gas purification catalyst without being collected. In the exhaust gas purifying apparatus of the second embodiment as well, since the carbon-containing suspended particulates are selectively purified by the purification catalyst on the upstream side as described above, it is possible to avoid the possibility of clogging of the catalyst as a whole, The purification efficiency of carbon-containing suspended particulates can be improved. Hereinafter, the reason will be described.

D-2. Purification Action of Fine Particles in Second Embodiment: FIG. 10 is an explanatory view conceptually showing the configuration of an exhaust gas purification apparatus to which the exhaust gas purification catalyst of the second embodiment is applied. As shown, in the exhaust gas purifying apparatus of the second embodiment, the above-described exhaust gas purifying catalyst 3 is provided on the upstream side.
00, and the same exhaust gas purification catalyst 200 as in the first embodiment is mounted on the downstream side.

FIG. 11 is an explanatory diagram showing a state in which carbon-containing suspended particulates in exhaust gas are collected by the upstream catalyst and the downstream catalyst in the exhaust gas purifying apparatus of the second embodiment. is there. In the figure, “Raw” is the particle size distribution of the carbon-containing suspended particulates discharged from the diesel engine 10. As the upstream side exhaust gas purifying catalyst 300, a catalyst having a small pore diameter is used, and small suspended particulates can be collected. However, as described with reference to FIG. The suspended fine particles that have flowed into 303 pass without being collected. In FIG. 11, “SeL” is the particle size distribution of the carbon-containing suspended fine particles flowing downstream. That is, FIG.
In FIG. 1, a portion surrounded by “Raw” and “SeL” is a portion corresponding to the carbon-containing suspended particulates collected by the exhaust gas purification catalyst 300 on the upstream side.

Thus, the upstream exhaust gas purifying catalyst 300
Almost all of the carbon-containing suspended particulates that have passed through are collected by the exhaust gas purification catalyst 200 on the downstream side. As a result, as shown in "Tp", although extremely small particles are slightly contained in the atmosphere, the exhaust gas from which the carbon-containing suspended particles are substantially removed is discharged.

As described above, in the exhaust gas purifying apparatus of the second embodiment, the upstream exhaust gas purifying catalyst 3
At 00, the carbon-containing suspended particulates flowing into the passage 302 provided with the seal 304 are selectively collected, and the remaining suspended particulates are collected by the purification catalyst 200 on the downstream side. That is, the carbon-containing suspended particulates discharged from the engine are separated and collected by the upstream catalyst and the downstream catalyst. As a result, each purification catalyst does not collect a large amount of carbon-containing suspended particulates at a time, so that even if small suspended particulates are collected to improve purification efficiency, clogging is unlikely to occur. .

Further, the exhaust gas purifying catalyst 30 of the second embodiment
If a part of the exhaust gas passes as it is, like 0,
The exhaust resistance of the entire exhaust passage can be greatly reduced. To that extent, there is an advantage that the engine output can be improved.

Of course, if the carbon-containing suspended particulates in the exhaust gas are separated and purified by the two exhaust gas purification catalysts, the size of one of the purification catalysts (particularly, the purification catalyst on the upstream side) is reduced. Even if it is small, the whole system can be established relatively easily. Normally, even if the purifying catalyst is brought closer to the engine so that higher-temperature exhaust gas flows into the engine, it cannot be made much closer due to mounting restrictions, and in many cases, exhaust gas with a sufficient temperature cannot be used. . On the other hand, in the present embodiment, the size of the exhaust gas purification catalyst on the upstream side can be reduced, so that the purification catalyst can be brought closer to the engine without being restricted by mounting.

In the above description, the exhaust gas purification catalyst 300 is provided with the passage 302 provided with the stopper 304.
And the passages 303 not provided with the seals are present at substantially the same ratio, but the ratio of the passages 302 provided with the seals may be increased as necessary. In this way, since the exhaust gas does not flow only into the unobstructed passage 303, the carbon-containing suspended particulates can be appropriately collected on the exhaust gas purification catalyst 300 on the upstream side.

D-3. Modifications of Second Embodiment: There are various modifications of the exhaust gas purifying apparatus of the second embodiment described above. Hereinafter, these modifications will be briefly described.

(1) First Modified Example: FIG. 12 is an explanatory diagram conceptually showing the external shape of an exhaust gas purifying catalyst 400 as a first modified example. In the exhaust gas purifying catalyst 300 of the second embodiment described above, all the seals on the upstream side of the honeycomb passage are removed, or are removed evenly regardless of the position on the catalyst. On the other hand, in the exhaust gas purifying catalyst 400 of the first modified example, only the seal at the outer peripheral portion (the hatched portion in the figure) 402 is removed, and the seal at the central portion 404 of the exhaust passage is removed. Has not been removed.

Generally, the temperature of the catalyst tends to be lower at the outer periphery than at the center. This is for the following reason. First, since the outer peripheral portion of the catalyst is close to the pipe wall of the exhaust pipe, exhaust gas is less likely to flow than the central portion,
Accordingly, the temperature at the center of the catalyst tends to increase. In addition, since the outer peripheral portion of the catalyst is easily deprived of heat from the outside, the catalyst temperature tends to be lower than that of the central portion. Since the performance of the catalyst is affected by the catalyst temperature,
If such temperature non-uniformity occurs, it becomes difficult to exhibit sufficient performance as the whole catalyst, which is not preferable. In particular, in the exhaust gas purifying catalyst supporting the active oxygen releasing agent used in the present embodiment, when the catalyst temperature is low, the reaction of oxidizing NOx to generate nitrate is slowed, and the catalytic performance is lowered.

On the other hand, in the first modified example, since the seal of the outer peripheral portion 402 where the catalyst temperature is easily lowered is removed, the exhaust gas easily passes through the outer peripheral portion 402 and the temperature of the catalyst becomes lower. The distribution is made uniform. As a result, not only the central portion 404 of the exhaust gas purification catalyst but also the outer peripheral portion 40
2 can also be used effectively, and the purification efficiency of carbon-containing suspended particulates can be improved.

(2) Second Modification: FIG. 13 is an explanatory view conceptually showing the structure of an exhaust gas purifying apparatus as a second modification. In the exhaust gas purifying catalyst 300 of the second embodiment described above, by removing the seal on the upstream side of the honeycomb passage, the carbon-containing suspended fine particles passing through the unsealed passage 303 pass through the catalyst as it is. On the other hand, as shown in FIG. 13, a bypass passage 50 may be provided in the upstream side purification catalyst 100 to bypass a part of the exhaust gas.

In this way, a part of the exhaust gas can be flowed to the downstream exhaust gas purification catalyst without impairing the function of the upstream exhaust gas purification catalyst, so that the transmission of the exhaust gas purification device can be performed. Purification efficiency can be improved. Also, if the on-off valve 52 is provided in the bypass passage 50,
It is possible to control the bypass amount of the exhaust gas purification catalyst on the upstream side in accordance with the operating conditions of the engine, whereby an appropriate ratio of the carbon-containing suspended particulates between the upstream purification catalyst and the downstream purification catalyst can be controlled. It is preferable because it can be purified by

Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the gist of the invention.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a diesel engine to which an exhaust gas purification device of a first embodiment is applied.

FIG. 2 is an explanatory diagram showing a structure of an exhaust gas purifying catalyst of the present embodiment.

FIG. 3 is an explanatory view conceptually showing a function of the exhaust gas purifying catalyst of the present embodiment for releasing active oxygen to purify carbon-containing floating portion particles, nitrogen oxides and the like.

FIG. 4 is an explanatory view conceptually showing the configuration of the exhaust gas purifying apparatus of the first embodiment.

FIG. 5 is an explanatory diagram showing a particle size distribution of suspended carbon-containing fine particles collected by an upstream purification catalyst and a downstream purification catalyst in the exhaust gas purifying apparatus of the first embodiment.

FIG. 6 is an explanatory view conceptually showing a state in which carbon-containing suspended particulates are shared and collected by an upstream purification catalyst and a downstream purification catalyst in the exhaust gas purifying apparatus of the first embodiment. .

FIG. 7 is an explanatory view conceptually showing a configuration of an exhaust gas purifying apparatus of a reference example.

FIG. 8 is an explanatory diagram conceptually showing a state of trapping carbon-containing floating portion particles in exhaust gas in the exhaust gas purifying apparatus of the reference example.

FIG. 9 is an explanatory view showing the structure of an exhaust gas purifying catalyst on the upstream side in the second embodiment.

FIG. 10 is an explanatory view conceptually showing a configuration of an exhaust gas purifying apparatus according to a second embodiment.

FIG. 11 is an explanatory diagram showing a particle size distribution of carbon-containing suspended fine particles collected by an upstream purification catalyst and a downstream purification catalyst in the exhaust gas purifying apparatus of the second embodiment.

FIG. 12 is an explanatory view showing the structure of an exhaust gas purifying catalyst according to a first modification of the second embodiment.

FIG. 13 is an explanatory view conceptually showing a configuration of an exhaust gas purifying apparatus according to a second modification of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Diesel engine 12 ... Intake pipe 14 ... Fuel injection valve 16 ... Exhaust collecting pipe 17 ... Exhaust pipe 18 ... Fuel supply pump 20 ... Supercharger 21 ... Turbine 22 ... Compressor 23 ... Shaft 24 ... Intercooler 26 ... Air cleaner 28 ... Electric throttle valve 30 Engine control ECU 50 Bypass passage 52 Open / close valve 60 EGR passage 62 EGR valve 100 Exhaust gas purification catalyst 102 Passage 103 Active oxygen release agent 104 Precious metal catalyst 106 Partition wall 200 Exhaust Gas purifying catalyst 206 ... Partition wall 300 ... Exhaust gas purifying catalyst 302 ... Passage 303 ... Passage 306 ... Partition wall 400 ... Exhaust gas purifying catalyst 402 ... Outer peripheral part 404 ... Central part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/86 ZAB B01J 23/58 A 4G069 53/94 35/10 301F B01J 23/58 F01N 3/08 A 35/10 301 B01D 53/36 103C F01N 3/08 ZAB (72) Inventor Kazuhiro Ito 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G090 AA03 AA04 BA01 CB22 3G091 AA10 AA11 AA18 AB02 AB13 BA13 GB06W GB07W GB17X HA08 HA14 4D019 AA01 BA02 BA05 BA06 BC07 BC20 BD01 CA01 CB04 4D048 AA14 AB01 BA01Y BA02Y BA10X BA14X BA15X BA18Y BA19Y BA30X BA31X BA32Y BA33Y BB02 BB14 BB17 CC32 CC32 CC03 CC32 CC32 CC32 CC32 CC32 CC32 CC26 BB02A BB04A BC01A BC02A BC03A BC03B BC04A BC05A BC06A BC08A BC09A BC12A BC13A BC13B BC 29A BC38A BC42A BC43A BC69A BC72A BC72B BC75A BC75B CA02 CA03 CA07 CA18 EA19 EA27 EC10X EC17X EC17Y EE08

Claims (12)

[Claims] 1. An exhaust gas purifying apparatus for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, wherein the exhaust gas purifying apparatus captures and retains excess oxygen in the exhaust gas and reduces the ambient oxygen concentration. And a first and second purification catalyst loaded with an active oxygen releasing agent that releases the retained oxygen as active oxygen, wherein the first purification catalyst selectively removes the carbon-containing suspended particulates in the exhaust gas. A purifying catalyst for collecting and burning the trapped carbon-containing suspended particulates using the active oxygen, wherein the second purification catalyst removes the carbon-containing suspended particulates that have passed through the first purification catalyst. An exhaust gas purifying device, which is a purifying catalyst that non-selectively collects and burns the collected carbon-containing suspended fine particles using the active oxygen. 2. The exhaust gas purifying apparatus according to claim 1, wherein the first and second purifying catalysts include a plurality of pores through which the exhaust gas passes, and the first purifying catalyst. Is an exhaust gas purifying device which is a purifying catalyst having a larger average pore diameter than the second purifying catalyst. 3. The exhaust gas purifying apparatus according to claim 2, wherein the first purification catalyst has an average pore diameter, which is an average of the pore diameters, two to five times that of the second purification catalyst. An exhaust gas purifying device that is a purifying catalyst set in a range. 4. The exhaust gas purifying apparatus according to claim 2, wherein the first purifying catalyst has a value of the average pore diameter of 20 μm.
An exhaust gas purifying device, which is a purifying catalyst in the range from 1 to 50 μm. 5. The exhaust gas purifying apparatus according to claim 1, wherein the first purification catalyst determines a ratio of the trapped carbon-containing suspended particulates to a total amount of the carbon-containing suspended particulates flowing together with the exhaust gas. An exhaust gas purifying apparatus, wherein the particulate collection rate shown is a purifying catalyst smaller than the second purifying catalyst. 6. The exhaust gas purifying apparatus according to claim 5, wherein the first purifying catalyst has at least one bypass passage through which the exhaust gas passes without collecting the carbon-containing suspended particulates. Exhaust gas purification device being formed. 7. The exhaust gas purifying apparatus according to claim 6, wherein the first purifying catalyst has the bypass passage formed in an outer peripheral portion of the first purifying catalyst. 8. The exhaust gas purifying apparatus according to claim 6, wherein the first purifying catalyst has a ratio of the bypass passage portion in a cross section perpendicular to an inflow direction of the exhaust gas.
An exhaust gas purification device that is a purification catalyst set to less than half. 9. The exhaust gas purifying apparatus according to claim 1, further comprising: a detour passage for detouring a part of the exhaust gas from an upstream side to a downstream side of the first purification catalyst. apparatus. 10. The exhaust gas purifying apparatus according to claim 1, wherein the first and second purifying catalysts include, as the active oxygen releasing agent, an alkali metal, an alkaline earth metal, a rare earth,
An exhaust gas purification device carrying at least one element selected from transition metals. 11. The exhaust gas purifying apparatus according to claim 1, wherein the first and second purifying catalysts carry a noble metal catalyst belonging to a platinum group in addition to the active oxygen releasing agent. Exhaust gas purification device. 12. A method for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, wherein the method captures and retains excess oxygen in the exhaust gas and retains the excess oxygen when the surrounding oxygen concentration decreases. A first active oxygen-releasing agent that releases the released oxygen as active oxygen
The carbon-containing suspended particulates in the exhaust gas are selectively purified by using the purification catalyst of (1), and the carbon-containing suspended particulates that have passed through the first purification catalyst are converted to a second particulate containing the active oxygen releasing agent. A method for purifying exhaust gas which non-selectively purifies using a purification catalyst of the present invention.