JP2011056393A - Exhaust gas cleaning apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently clean an exhaust gas while suppressing a manufacturing cost with a simple configuration. <P>SOLUTION: The exhaust gas cleaning apparatus that cleans the exhaust gas discharged from a vehicle engine 11 includes a filter carrier 14 that filters the exhaust gas, a first catalyst layer 15a containing a noble metal, and a second catalyst layer 15b containing particulate matter (PM) combustion oxide, and is configured to include supporting the first catalyst layer 15a and the second catalyst layer 15b by the common filter carrier 14, supporting the first catalyst layer 15a upstream of the filter carrier 14, and supporting the second catalyst layer 15b on the filter carrier 14 downstream of the first catalyst layer 15a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus that efficiently burns and removes particulate matter (PM), which is a harmful component in exhaust gas discharged from an engine.

  In recent years, where protection of the global environment is strongly demanded, in engines such as gasoline engines and diesel engines that are generally used as driving sources for vehicles, nitrogen oxides (NOx) and hydrocarbons (HC) contained in exhaust gas, among others. , Technology of removing harmful exhaust gas components such as carbon monoxide (CO) or particulate matter (hereinafter referred to as PM) is increasing.

Among these, PM is mainly contained in the exhaust gas of diesel engines, and specifically consists of carbon fine particles (hereinafter referred to as soot), soluble organic substances (hereinafter referred to as SOF), sulfur oxide, and the like. Is.
An example of a technique for reducing the amount of PM released into the atmosphere is a technique in which a diesel particulate filter (hereinafter referred to as DPF) is provided in the middle of the exhaust gas passage, and the PM is collected with this DPF.

  However, since the amount of PM deposited on the DPF increases with time, the exhaust pressure loss increases. Therefore, the amount of PM accumulated in the DPF is estimated from the exhaust pressure loss and the vehicle travel distance, and the PM is forcibly removed by combustion (forced regeneration of the DPF) or while the engine is operated in a normal state. In general, PM is generally removed by combustion (continuous regeneration of DPF).

  By the way, in these DPF, paying attention to the difference in flammability between soot and SOF contained in PM, the efficiency of continuous regeneration of DPF is improved by separating and collecting both substances, and PM is discharged into the atmosphere. A technique for reducing the amount is known. For example, the following Patent Document 1 can be cited.

JP 2002-153733 A

  In the above-mentioned Patent Document 1, a flow-through type monolith catalyst having a function of adsorbing and burning SOF in exhaust gas and a function of passing soot is disposed on the upstream side of the exhaust gas passage, and downstream of the catalyst. In addition, a configuration is disclosed in which a filter catalyst having a function of collecting and burning the soot that has passed through the catalyst is disclosed. In other words, the flow-through type monolith catalyst disposed on the upstream side selectively separates and burns and removes the flammable SOF. On the other hand, the flame retardant soot passes through the flow-through monolith catalyst without being adsorbed, flows through the filter catalyst disposed on the downstream side, is collected, and is removed by combustion.

  However, the flow-through type monolith catalyst and the filter catalyst are separate from each other, and both the catalysts are arranged separately on the upstream side and the downstream side on the exhaust gas flow path, and the flow-through type monolith arranged on the upstream side. The reaction heat generated when burning the highly flammable SOF with the catalyst is difficult to conduct to the filter catalyst disposed on the downstream side. Therefore, when the flame retardant soot is burned by the filter catalyst, the reaction heat cannot be effectively utilized.

Further, the technique of Patent Document 1 has a problem in that it is unavoidable to use a relatively large configuration, and it is difficult to effectively use a limited vehicle space.
The present invention has been devised in view of such problems, and is capable of purifying exhaust gas by efficiently detoxifying PM, which is a harmful component in exhaust gas, while suppressing manufacturing costs with a simple configuration. An object is to provide an apparatus.

  Therefore, in order to achieve the above object, the present invention is an exhaust gas purification device for purifying exhaust gas discharged from a vehicle engine, a filter carrier for filtering the exhaust gas, a first catalyst layer containing a noble metal, PM A second catalyst layer containing an oxide for combustion, and the first catalyst layer and the second catalyst layer are supported on the common filter carrier, and the first catalyst layer is on the filter carrier. It is supported on the upstream side, and the second catalyst layer is supported on the filter carrier on the downstream side of the first catalyst layer.

  As a result, the PM combustion oxide and the noble metal are separately supported on the upstream side and the downstream side of the common carrier, so that the exhaust gas purification performance of the PM combustion oxide and the noble metal can be sufficiently exhibited. The PM, which is a harmful component in the exhaust gas, can be efficiently detoxified and the exhaust gas can be purified while suppressing the manufacturing cost with a simple configuration.

The PM combustion oxide is a perovskite complex oxide represented by the following formula (1).
_{La 1-x Ba x Mn y} Fe 1-y O 3 ··· (1)
(In the above formula (1), 0 <x <0.7 and 0 ≦ y ≦ 1.)
Thereby, even if the exhaust gas temperature is relatively low, soot can be burned efficiently.

Further, the noble metal is one or more selected from the group consisting of Pt, Rh, Pd, Ru and Ir.
Thereby, exhaust gas can be purified while suppressing manufacturing costs by using a noble metal that is relatively easily available.
In the exhaust gas purifying apparatus, the second catalyst layer may be formed on the filter carrier, and the first catalyst layer may be formed on the second catalyst layer.
Thereby, it is easy to manufacture the exhaust gas purification device, and it is easy to maintain the individual exhaust gas purification performance of the PM combustion oxide and the noble metal.

  As described above, according to the exhaust gas purification apparatus of the present invention, the PM combustion oxide and the noble metal are separately supported on the upstream side and the downstream side of the common carrier. Individual exhaust gas purification performance can be sufficiently exhibited, and PM, which is a harmful component in the exhaust gas, can be made harmless efficiently and the exhaust gas can be purified while suppressing the manufacturing cost with a simple configuration.

It is a lineblock diagram showing typically the vehicles which have the exhaust gas purification device concerning one embodiment of the present invention. It is a typical enlarged view showing an exhaust gas purification device concerning one embodiment of the present invention. It is a typical expanded sectional view which shows the principal part (code | symbol A in FIG. 2) of the exhaust gas purification apparatus which concerns on one Embodiment of this invention. It is a typical expanded sectional view which shows the principal part (code | symbol B in FIG. 2) of the exhaust gas purification apparatus which concerns on one Embodiment of this invention. It is a typical time chart which mainly shows the effect | action regarding PM integrated combustion amount of the exhaust gas purification apparatus which concerns on one Embodiment of this invention. It is a typical time chart which mainly shows the effect | action regarding the carbon monoxide discharge | emission amount which concerns on one Embodiment of this invention. It is a typical expanded sectional view which shows the support | carrier and catalyst layer of the exhaust gas purification apparatus which concern on the modification of one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a vehicle 10 is equipped with a diesel engine 11 as a drive source for the vehicle.
A diesel particulate filter (Diesel Particulate Filter, hereinafter referred to as DPF) 13 is connected to the downstream side of the diesel engine 11 via an exhaust gas passage 12.

This DPF 13 collects particulate matter (hereinafter referred to as “Diesel Particulate Matter”, hereinafter referred to as PM) contained in the exhaust gas, thereby preventing PM from being discharged into the atmosphere.
The PM in the exhaust gas of the diesel engine 11 is specifically composed of carbon fine particles (hereinafter referred to as soot), a soluble organic substance (hereinafter referred to as SOF), sulfur oxide, and the like.

The DPF 13 can be rendered harmless by heating and burning the collected PM.
More specifically, the DPF 13 in the present embodiment has a filter carrier 14, and this filter carrier 14 is mainly composed of SiC, and has a large number of honeycomb-shaped cell holes as shown in FIG. The part and the rear end part are alternately sealed. A filter having such a structure is generally called a wall flow type. Moreover, the porosity of SiC contained in the filter carrier 14 is, for example, about 52%, and the pore diameter is, for example, about 23 μm.

That is, the filter carrier 14 not only carries the catalyst layer 15 (described later) having the first catalyst layer 15a and the second catalyst layer 15b, but can also collect PM, which is a harmful exhaust gas component. It has become.
As shown in FIG. 2, the first catalyst layer 15a is carried on the surface of the filter carrier 14 on the upstream side with respect to the flow of the exhaust gas, and the second catalyst layer 15b is located on the downstream side of the first catalyst layer 15a. Is carried. That is, the first catalyst layer 15a and the second catalyst layer 15b are not mixed, and are supported on the common filter carrier 14 instead of being separated.

  The first catalyst layer 15a contains platinum (hereinafter referred to as Pt) as a noble metal. As shown in FIG. 3, the first catalyst layer 15a purifies the exhaust gas by combusting mainly good-flammability SOF (mainly containing HC) in the PM collected by the filter carrier 14. It functions as an oxidation catalyst. The reaction mainly performed in the first catalyst layer 15a is as shown in the following formula (1).

4HC + 5O ₂ → 4CO ₂ + 2H ₂ O (1)
Further, the Pt content in the first catalyst layer 15a is, for example, 0.1 g / L or more with respect to the volume of the first catalyst layer 15a.
On the other hand, the second catalyst layer 15b contains a perovskite complex oxide represented by the following chemical formula (2) as an oxide for PM combustion. As shown in FIG. 4, among the remaining components of PM that have passed through the first catalyst layer 15a, as an oxidation catalyst that mainly burns flame retardant soot (mainly containing C) and purifies exhaust gas. It is supposed to function. Further, the perovskite complex oxide used in this embodiment is excellent in lowering the combustion start temperature of PM. The reaction mainly performed in the second catalyst layer 15b is as shown in the following formulas (3) and (4).

La _0.8 Ba _0.2 FeO ₃ (2)
C + O ₂ → CO ₂ (3)
C + 2NO ₂ → CO ₂ + 2NO (4)
Further, the content of the PM combustion oxide in the second catalyst layer 15b is usually 10 g / L or more and 100 g / L or less with respect to the volume of the second catalyst layer 15b, for example.

  Thus, the DPF 13 in the present embodiment is a so-called continuous regeneration type DPF. Originally, PM is collected in a general DPF, and the accumulated amount of PM in the DPF 13 increases with the passage of time, so that the exhaust pressure loss increases. However, in the DPF 13 of the present embodiment, PM is continuously burned while the engine is operated in a normal state, and an increase in the exhaust pressure loss is suppressed.

Since the exhaust gas purification apparatus according to one embodiment of the present invention is configured as described above, the following operations and effects are achieved.
First, in the DPF 13, since the filter carrier 14 forms a wall flow type filter, PM can be collected. However, the collected PM is removed by combustion in order to prevent the amount of PM accumulated on the DPF 13 from increasing with time and increasing the exhaust pressure loss.

  Further, in the DPF 13, the first catalyst layer 15a containing Pt and the second catalyst layer 15b containing the perovskite complex oxide are separately supported on the upstream side and the downstream side in the common filter carrier 14, respectively. Moreover, Pt and the perovskite complex oxide are arranged in the vicinity without being mixed. For this reason, first, particularly good-flammable SOF in PM contained in the exhaust gas is selectively burned by Pt carried on the upstream side, and the exhaust gas is purified.

  At this time, the reaction heat generated by the combustion is from the first catalyst layer 15a upstream of the filter carrier 14 and containing Pt to the second downstream of the filter carrier 14 and containing the perovskite complex oxide. It is efficiently transmitted to the catalyst layer 15b. Therefore, on the downstream side of the filter carrier 14, the perovskite complex oxide is efficiently activated by the transmitted reaction heat, and PM can be burned and removed on the upstream side and the downstream side of the DPF 13.

The perovskite complex oxide represented by the above chemical formula (2) used in the present embodiment is excellent in soot combustion at a relatively low temperature. However, if the exhaust gas contains a large amount of SOF, soot combustion deteriorates. There is a characteristic to do. This is because SOF becomes a factor inhibiting soot combustion.
However, in the present embodiment, since Pt contained in the first catalyst layer 15a on the upstream side first combusts the highly flammable SOF in the PM, the second catalyst layer 15b containing the perovskite complex oxide is firstly burned. PM containing mainly soot flows on the downstream side of the filter carrier 14 on which is supported. For this reason, soot combustion is not deteriorated by SOF, and exhaust gas can be purified.

  That is, in the present embodiment, the second catalyst layer 15b carried on the downstream side burns in the first catalyst layer 15a while utilizing the reaction heat generated by the combustion of PM in the upstream first catalyst layer 15a. Soot contained in a large amount of PM that has not been burned is efficiently burned even in the low temperature range by the perovskite type complex oxide that excels in soot combustion at low temperatures, detoxifying PM in the exhaust gas upstream and downstream of the DPF 13 Can be discharged.

  Also, in order to prevent an increase in exhaust pressure loss due to an increase in the amount of PM accumulated over time, generally, the amount of PM accumulated in the DPF is estimated from the exhaust pressure loss and the vehicle travel distance, PM is forcibly removed by combustion (forced regeneration of DPF) or PM is continuously removed by combustion (continuous regeneration of DPF) while the engine is operated in a normal state. However, in the present embodiment, as described above, the second catalyst layer 15b containing the perovskite type complex oxide excellent in soot combustion at a relatively low temperature is used, and further, the second catalyst layer 15b is generated on the upstream side of the filter carrier 14. The heat of reaction can be used for the activity of the second catalyst layer 15b. Therefore, when the DPF 13 is regenerated, it is not necessary to increase the temperature in the DPF 13 by performing extra fuel injection for the activation of the oxidation catalyst for PM combustion. Can be purified.

Also, in order to replace part of the Pt purification performance generally used as an oxidation catalyst for PM, the amount of expensive Pt used can be reduced by using a perovskite complex oxide in addition to Pt. Manufacturing costs can be reduced.
Here, the present inventors paid attention to the point that when Pt and a perovskite complex oxide are mixed and then applied to the filter carrier 14, Pt is inactivated and the function as a catalyst is lowered. This inactivation of Pt is considered to occur because Pt is dissolved in the structure of the perovskite complex oxide. Further, when Pt is inactivated and the function as a catalyst is lowered, SOF that should be mainly burned on the upstream side of the filter carrier 14 remains in the exhaust gas and reaches the downstream side of the filter carrier 14. . Then, the purification performance of the exhaust gas for burning the soot of the perovskite complex oxide is lowered by the SOF, and there is a concern about the discharge of the soot into the atmosphere. This reduction in the exhaust gas purification performance of the perovskite complex oxide is due to the fact that the perovskite complex oxide has poor oxidation performance of SOF. It is thought to occur because it is inhibited.

  On the other hand, in this embodiment, Pt and the perovskite complex oxide are not mixed and are separately supported on the common filter carrier 14. Therefore, SOF in PM is mainly combusted by the first catalyst layer 15a containing Pt on the upstream side of the filter carrier 14 without causing inactivation of Pt, and the perovskite type composite on the downstream side of the filter carrier 14 The individual exhaust gas purification performances of Pt and perovskite type complex oxides such that the soot contained in the PM in the exhaust gas flowing into the second catalyst layer 15b is mainly burned by the second catalyst layer 15b containing oxide. The exhaust gas can be purified more reliably and efficiently.

Furthermore, since the filter carrier 14 is not a flow-through type structure but a wall flow type structure and has a filter function, a certain amount of soot can be captured and burned even on the upstream side, so that exhaust gas can be purified more reliably. it can.
Furthermore, by using Pt, which is relatively easily available, as the noble metal contained in the first catalyst layer 15a, it is possible to purify the exhaust gas while suppressing the manufacturing cost.

Here, referring to FIG. 5 and FIG. 6, Pt and perovskite complex oxide are mixed as compared with DPF in which a catalyst layer containing a mixture of Pt and perovskite complex oxide is supported on a filter carrier. A description will be given of what point the DPF 13 of the present embodiment carried on the common carrier 14 exhibits excellent exhaust gas purification performance.
5 and 6 show a DPF in which a catalyst layer containing a mixture of Pt and perovskite complex oxide is supported on a filter carrier (solid line in the figure, hereinafter referred to as DPF of Reference Example 1), and perovskite complex oxidation. DPF in which a catalyst layer containing an object but not containing Pt is supported on a filter carrier (the chain line in the figure, hereinafter referred to as DPF in Reference Example 2), and a catalyst layer containing Pt but not containing a perovskite complex oxide Shows the relationship with the DPF (broken line in the figure, hereinafter referred to as DPF of Reference Example 3) carried on the filter carrier. These DPFs have the same configuration except for the points described here. Moreover, temperature has shown the inlet temperature of each DPF which concerns on the reference examples 1-3. As experimental conditions, the temperature of the catalyst layer was increased by 20 ° C. per minute in a simulated exhaust gas atmosphere.

First, FIG. 5, which is a schematic time chart mainly showing an operation related to the PM accumulated combustion amount of each DPF according to Reference Examples 1 to 3, will be described, and the DPF 13 of the present embodiment is excellent in PM combustion. explain.
The graph shown in FIG. 5 is obtained by measuring the cumulative combustion amount of PM based on the amount of carbon monoxide (hereinafter referred to as CO) and the amount of carbon dioxide (hereinafter referred to as CO ₂ ) discharged from each DPF.

  Immediately after the engine is cold-started, at the time t1 when the DPF inlet temperature is about 25 ° C. (T1 in the figure), the PM accumulated combustion amount of each of the DPFs according to Reference Examples 1 to 3 is very small. That is, since the inlet temperature of each DPF is extremely low, the activity of the oxidation catalyst for PM combustion is low, and it can be seen that PM is hardly burned in any of the DPFs according to Reference Examples 1 to 3.

In addition, although the DPF inlet temperature has increased from time t1 to time t2 when the DPF inlet temperature is about 200 ° C. (T2 in the figure), it remains in any of the DPFs according to Reference Examples 1 to 3. Also, it can be seen that the PM accumulated combustion amount is small and PM is not combusted so much.
On the other hand, after time t2, an increase in the PM integrated combustion amount starts to be seen, and it can be seen that PM combustion is performed in each DPF.

However, at the time point t3 when the DPF inlet temperature is sufficiently increased (about T3 in the figure) (T3 in the figure), the DPF of the reference example 3 has a significantly larger PM integrated combustion amount than the DPFs of the reference examples 1 and 2, and actively It can be seen that PM is burning.
Thus, the reason why the PM accumulated combustion amount of the DPF of Reference Example 3 is very large is considered to be due to the strong oxidizing power of Pt contained in the DPF of Reference Example 3.

However, although the DPF of Reference Example 1 includes Pt, the PM integrated combustion amount is greatly different from the DPF of Reference Example 3 including Pt, and almost no difference is seen from the DPF of Reference Example 2 that does not include Pt. .
Thus, although the DPF of Reference Example 1 contains Pt having a strong oxidizing power, the reason why there is not much difference between the DPF of Reference Example 2 that does not contain Pt and the PM accumulated combustion amount is as follows. It seems like.

  Originally, Pt has a strong oxidizing power, and combustion of PM starts when Pt is activated as the DPF inlet temperature rises. Thereafter, the catalyst internal temperature rises due to the oxidation heat generated by the exhaust gas purification of Pt, thereby promoting PM combustion. However, in the DPF of Reference Example 1, by mixing Pt and the perovskite type complex oxide, Pt becomes a solid solution in the perovskite type complex oxide, and activation of Pt that should occur due to an increase in the DPF inlet temperature. This is thought to be because of the suppression.

  However, unlike the DPF of Reference Example 1, the DPF 13 of the present embodiment includes Pt and a perovskite complex oxide, but unlike the DPF of Reference Example 1, the DPF 13 includes the first catalyst layer 15a containing Pt. The second catalyst layer 15b containing the perovskite complex oxide is individually supported on the upstream side and the downstream side of the filter carrier 14 as shown in FIG. That is, in the DPF 13 of the present embodiment, unlike the DPF of Reference Example 1, Pt and the perovskite complex oxide are not mixed, so that the strong oxidizing power of Pt is maintained as in the DPF of Reference Example 3, Furthermore, since PM can be burned while exhibiting the exhaust gas purification performance of burning the soot of the perovskite complex oxide, it is excellent in burning PM.

Next, FIG. 6 which is a schematic time chart mainly showing an operation related to the CO emission amount of the DPF will be described, and the point that the DPF 13 of the present embodiment is excellent in PM combustion will be described.
SOF and soot contained in PM become harmless CO ₂ by complete combustion. However, in the combustion of PM, CO is generated when incomplete combustion occurs in part, and generally, as the amount of combustion of PM increases, the amount of CO emission increases.

The graph shown in FIG. 6 is obtained by measuring the ratio of CO generated by incomplete combustion of PM and discharged into exhaust gas in each DPF according to Reference Examples 1 to 3.
At the time t2 when the inlet temperature of each DPF according to Reference Examples 1 to 3 is relatively low and is about 200 ° C. (T2 in the figure), none of the DPFs according to Reference Examples 1 to 3 almost emits CO. . Considering in consideration of the graph shown in FIG. 5, it is considered that the reason why the amount of CO emission is small in any DPF is that PM is not burned much at the time point t2.

  In addition, at the time t3 when the inlet temperature of each DPF according to Reference Examples 1 to 3 is sufficiently increased and is about 600 ° C. (T3 in the figure), the DPF of Reference Example 3 still hardly emits CO. In consideration of the graph shown in FIG. 5, in the DPF of Reference Example 3, PM is actively burned at time t3. At this time, the strong burning power of Pt contained in the catalyst layer is PM burning. Therefore, it is considered that almost no CO is exhausted.

On the other hand, in the DPFs of Reference Examples 1 and 2, the CO emission rate is increased at time t3 compared to time t2, and it can be seen that incomplete combustion occurs when PM is burned.
Here, when comparing the DPFs of Reference Examples 1 and 2, the CO emission rate shown in FIG. 6 is greatly different at the time t3, although there is not much difference regarding the PM integrated combustion amount shown in FIG. Yes. The reason why the CO emission rate is different is considered as follows.

The DPF of Reference Example 2 does not contain Pt, which has a strong oxidizing power, as in the DPF of Reference Example 3, but contains a perovskite type complex oxide. Therefore, compared with the DPF of Reference Example 3, PM combustion However, a part of the combustion of PM is incompletely combusted and CO is discharged, but complete combustion is also performed relatively well by the oxidizing power of the perovskite complex oxide.
On the other hand, in the DPF of Reference Example 1, Pt and the perovskite complex oxide were mixed, so that Pt was dissolved in the perovskite complex oxide, and Pt and perovskite that should be generated by the rise in the DPF inlet temperature. Both oxidizing powers of the type complex oxide are reduced, and when PM is burned, the rate of incomplete combustion increases compared to the DPF of Reference Example 2, and the CO emission rate is higher than that of the DPF of Reference Example 2. It is thought that.

However, like the DPF of Reference Example 1, the DPF 13 of the present embodiment contains Pt and a perovskite complex oxide, but contains the first catalyst layer 15a containing Pt and the perovskite complex oxide. The second catalyst layer 15b is individually supported on the upstream side and the downstream side of the filter carrier 14 as shown in FIG. That is, in the DPF 13 of the present embodiment, Pt and the perovskite complex oxide are not mixed, and therefore, unlike the DPF of Reference Example 1, both the oxidizing power of Pt and the oxidizing power of the perovskite complex oxide are exhibited. be able to. Therefore, the DPF 13 of this embodiment suppresses incomplete combustion when PM is combusted, complete combustion is mainly performed, and CO emission can be suppressed.
(Other)
Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and can be appropriately changed without departing from the spirit of the present invention.

  In the above embodiment, as shown in FIG. 2, the first catalyst layer 15 a and the second catalyst layer 15 b are supported on the filter carrier 14 without overlapping from the upstream side toward the downstream side and without being interrupted. However, the first catalyst layer 15a and the second catalyst layer 15b may slightly overlap. Further, the first catalyst layer 15a and the second catalyst layer 15b may be supported on the filter carrier 14 with a slight gap between the first catalyst layer 15a and the second catalyst layer 15b.

Moreover, in the above-mentioned embodiment, although the case where the diesel engine 11 was mounted in the vehicle 10 was described, it is not limited to this. For example, a gasoline engine or an alcohol-mixed fuel engine may be used instead of the diesel engine 11.
In the above embodiment, the case where SiC is the main component has been described as the filter carrier 14 of the DPF 13. However, the present invention is not limited to this, and a filter called a wall flow type having many cell holes is not limited thereto. There is no limitation as long as it is formed. Therefore, what is used for the filter carrier of the conventional DPF which can collect PM in exhaust gas can be used suitably as a filter carrier. For example, a porous material such as zeolite, cordierite, alumina, or aluminum titanate can be used.

  In the above embodiment, the first catalyst layer 15a is carried on the upstream side of the filter carrier 14, and the second catalyst layer 15b is carried on the downstream side of the filter carrier 14 from the first catalyst layer 15a. As described above, as shown in FIG. 7, the second catalyst layer 15b may be formed on the filter carrier 14, and the first catalyst layer 15a may be formed on the second catalyst layer 15b.

  Thereby, since the noble metal and the PM combustion oxide are supported in a state of being stacked on the carrier without being mixed, it is easy to exert individual oxidizing power of the noble metal and the PM combustion oxide. Further, since the noble metal and the PM combustion oxide are arranged in the vicinity, the reaction heat due to the combustion of PM in the first catalyst layer 15a is easily transmitted to the second catalyst layer 15b, and the second heat is utilized by using this reaction heat. The PM combustion oxide contained in the catalyst layer 15b can be activated to efficiently purify the exhaust gas. Furthermore, since the first catalyst layer 15a containing the noble metal and the second catalyst layer 15b containing the PM combustion oxide are laminated in order, the production is easy.

Moreover, although said embodiment demonstrated the case where Pt was used as a noble metal contained in the 1st catalyst layer 15a of DPF13, it is not limited to this. For example, rhodium (hereinafter referred to as Rh), palladium (hereinafter referred to as Pd), ruthenium (hereinafter referred to as Ru), and iridium (hereinafter referred to as Ir) may be used alone as the noble metal. Alternatively, a precious metal that is appropriately selected from Pt, Rh, Pd, Ru, and Ir and mixed may be used. Any precious metal has the function of purifying exhaust gas by burning PM.
Further, the content of these noble metals in the first catalyst layer 15a is usually 0.1 g / L or more with respect to the volume of the first catalyst layer 15a, for example, as in the case of using Pt.

In the above embodiment, the case where the perovskite complex oxide is used as the PM combustion oxide contained in the second catalyst layer 15b of the DPF 13 has been described. However, the present invention is not limited to this. For example, as the PM combustion oxide, a material containing two or more of alkali metals, alkaline earth metals, or transition metals, or a material containing Ag may be used alone. Alternatively, as a PM combustion oxide, a perovskite complex oxide; a material containing two or more of alkali metals, alkaline earth metals, or transition metals; a material containing Ag; Also good. Any of the PM combustion oxides has a function of burning PM well and purifying exhaust gas even at a relatively low temperature.
Further, the content of the PM combustion oxide in the second catalyst layer 15b is usually 10 g / L or more, 100 g, for example, with respect to the volume of the second catalyst layer 15b, as in the case of using the perovskite complex oxide. / L or less.

  In the above embodiment, the DPF 13 has been described as a continuous regeneration type DPF, but can also be applied to a forced regeneration type DPF. That is, the exhaust gas purification apparatus of the present application can also be used in a configuration that performs fuel injection for increasing the DPF temperature for catalyst activity.

  Further, in the above embodiment, the noble metal having a function as an oxidation catalyst and the perovskite complex oxide which is an oxide for PM combustion are provided on the DPF 13, but further upstream or downstream of the DPF 13. Alternatively, an oxidation catalyst may be installed on both sides separately from the DPF 13.

10 Vehicle 11 Diesel engine (engine)
12 Exhaust gas passage 13 Diesel particulate filter (DPF)
14 filter carrier 15 catalyst layer 15a first catalyst layer 15b second catalyst layer A main part of exhaust gas purification device B main part of exhaust gas purification device

Claims (3)

An exhaust gas purification device for purifying exhaust gas discharged from a vehicle engine,
A filter carrier for filtering the exhaust gas;
A first catalyst layer containing a noble metal;
A second catalyst layer containing a PM combustion oxide,
The first catalyst layer and the second catalyst layer are supported on the common filter carrier,
The first catalyst layer is supported on the upstream side of the filter carrier,
The exhaust gas purification apparatus, wherein the second catalyst layer is supported on the filter carrier on the downstream side of the first catalyst layer. The exhaust gas purifying apparatus according to claim 1, wherein the PM combustion oxide is a perovskite complex oxide represented by the following formula (1).
_{La 1-x Ba x Mn y} Fe 1-y O 3 (1)
(In the above formula (1), 0 <x <0.7 and 0 ≦ y ≦ 1.) The exhaust gas purifying apparatus according to claim 1 or 2, wherein the noble metal is at least one selected from the group consisting of Pt, Rh, Pd, Ru, and Ir.

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