JP2014117680A - Catalyst attached particulate filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particulate filter that efficiently promotes the burning of PM deposited on the particulate filter.SOLUTION: The catalyst layer 22 provided on the exhaust gas passage wall 21 of the particulate filter comprises: Pd supporting ZrCe-based complex oxides that are ZrCe-based complex oxides 25 comprising zirconium (Zr) and cerium (Ce) and are supporting, as catalyst metal, palladium (Pd) 26; and Pt supporting active alumina particles that are active alumina particles 23 and are supporting, as catalyst metal, platinum (Pt) 24.

Description

  The present invention relates to a particulate filter with a catalyst provided with a catalyst used for collecting particulates discharged from an engine and burning and removing the collected particulates.

  A filter for collecting particulates (PM: Particulate matter) in exhaust gas is provided in an exhaust gas passage of an automobile equipped with a lean combustion engine such as a diesel engine. When the amount of PM deposited on the filter increases, the filter is clogged. Therefore, the PM accumulation amount is estimated based on the pressure difference of the pressure sensors provided before and after the filter, and when the accumulation amount reaches a predetermined value, engine fuel injection control (fuel increase, post-injection, etc.) Thus, the temperature of the exhaust gas reaching the filter is increased, and PM is burned and removed. In order to promote the combustion of PM, a catalyst is supported on the exhaust gas passage wall of the filter, and in particular, platinum (Pt) is supported as a catalyst metal.

  For example, Patent Document 1 contains zirconium (Zr), neodymium (Nd), and rare earth elements other than cerium (Ce) and Nd in the exhaust gas passage wall of the filter in order to improve the PM combustion rate. It is disclosed to provide a catalyst material in which Pt is supported or doped on the composite oxide particles. When such a catalyst material is used, active oxygen is released from the composite oxide particles via Pt, and this active oxygen reacts with PM, so that PM combustion can be promoted.

  Patent Document 2 discloses palladium (Pd) instead of Pt as a three-way catalyst, a selective catalytic reduction (SCR) catalyst, or a diesel oxidation catalyst disposed upstream or downstream of a filter. It is disclosed to use a catalyst material in which is supported on a Ce-containing composite oxide. Patent Document 2 does not disclose the relationship between such a complex oxide and PM combustion.

JP 2008-221204 A Special table 2012-518531 gazette

  By the way, in the conventional particulate filter with catalyst, when the amount of PM deposited on the surface of the catalyst layer is small, the PM is combusted and removed relatively efficiently. However, when the amount of PM deposited is large, it takes time for the PM to be removed by combustion. This tendency is seen. The reason is as follows according to findings based on experiments and research by the present inventors.

  That is, the graph of FIG. 1 schematically shows a change with time of the PM remaining ratio when PM deposited on the catalyst layer burns. Initially, the combustion of PM proceeds rapidly, but after passing through the rapid combustion region (for example, the first combustion period until the PM remaining ratio becomes 100% to 50%), the combustion of PM becomes slow (PM) It shifts to the combustion late stage until the remaining ratio becomes 50% to 0%. This point will be described in detail below.

  As shown in the photograph of FIG. 2, at the beginning of combustion, PM is in contact with the catalyst layer supported on the surface of the filter. For this reason, for example, when the catalyst layer contains Ce-containing oxide particles and Zr-containing oxide particles, as schematically shown in FIG. 3, active internal oxygen released from these oxide particles is generated in the catalyst layer. It is supplied in a highly active state to the contacting PM. As a result, the PM on the catalyst layer surface burns rapidly.

  However, as described above, the PM on the surface of the catalyst layer is burned and removed. As a result, a gap of about several tens of μm is partially formed between the catalyst layer and the PM deposit layer as shown in the photograph of FIG. Therefore, as schematically shown in FIG. 5, the active oxygen released from the inside of the oxide particles maintains the activity for a very short time, but the activity decreases before most of the active oxygen reaches the PM. For example, it becomes the same normal oxygen as oxygen in the gas phase. As a result, the combustion of PM becomes slow. Of course, as shown in the upper left and lower left of FIG. 5, the oxygen in the exhaust gas also contributes to the combustion of PM, but the combustion is slower than the combustion by the active oxygen described above.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is to increase the total PM combustion rate so that combustion proceeds efficiently in both the rapid combustion region and the slow combustion region of PM deposited on the filter. It is to be able to improve.

As a result of further experiments and researches to achieve the above object, the inventors of the present invention applied activated alumina particles and a particle material containing a ZrCe-based composite oxide containing Zr and Ce to Pt as a catalyst metal. It has been found that the catalyst material in which Pd is supported has a significantly higher NO oxidation performance for oxidizing NO and generating NO _{2 than} the catalyst material in which only Pt is supported on the particle material. Furthermore, among such catalyst materials, a catalyst material containing activated alumina particles carrying Pt and a ZrCe composite oxide carrying Pd is found to have a particularly high PM combustion performance. completed.

  That is, in the particulate filter with catalyst according to the present invention, a catalyst layer is provided on the exhaust gas passage wall of the filter that collects particulates in the exhaust gas, and the catalyst layer includes zirconium (Zr) and cerium (Ce). A Pd-supported ZrCe composite oxide in which palladium (Pd) is supported as a catalyst metal on a ZrCe-based composite oxide containing Pt, and Pt-supported active alumina particles in which platinum (Pt) is supported as a catalyst metal on active alumina particles; It is characterized by including.

As described above, a catalyst material in which Pd and Pt are supported as catalyst metals on a particle material containing activated alumina and a ZrCe-based composite oxide has high NO oxidation performance. For this reason, for example, NO in lean exhaust gas can be oxidized to promote the generation of NO ₂ , and as a result, the generated NO ₂ acts as an oxidant for the combustion of PM, thereby improving the PM combustion rate.

  In addition, the ZrCe-based composite oxide has an oxygen storage / release capability, and can release a large amount of active oxygen that works effectively for PM combustion by causing an oxygen exchange reaction. Furthermore, it is considered that when Pd is used instead of Pt as the catalyst metal, the active sites of the noble metal effective for promoting combustion in the rapid combustion region are increased. For this reason, Pd is supported by supporting Pd on the ZrCe-based composite oxide. A highly active oxidation state is maintained by the ZrCe-based composite oxide, and the combustion rate in the rapid combustion region can be improved. In the particulate filter with catalyst of the present invention, the Pd-supported ZrCe-based composite oxide may further support Pt.

  In addition, since the activated alumina particles have high dispersibility of the noble metal, when the activated alumina particles are used as a catalyst material, aggregation of the catalyst metal and the like can be prevented and reduction of the catalytic effect can be prevented.

  As a result, the particulate filter with catalyst according to the present invention can improve the total PM combustion speed, and the above-described engine injection control becomes a short time. In other words, the fuel consumption is reduced and the fuel consumption performance is improved. improves. Further, since a part of Pd is used instead of Pt as the catalyst metal, the amount of Pt to be used can be reduced and the cost can be reduced.

  In the particulate filter with catalyst according to the present invention, the catalyst layer preferably further includes an Rh-containing ZrCe-based composite oxide in which rhodium (Rh) is contained in the ZrCe-based composite oxide.

  As described above, it is considered that the ZrCe-based composite oxide has a high oxygen storage / release ability and can release oxygen having a high reaction activity by causing an oxygen exchange reaction. For this reason, even if oxygen of the combustion part is consumed locally with combustion of PM, oxygen is rapidly supplemented by ZrCe system complex oxide, and PM combustion is maintained. In addition, the inclusion of Rh can promote the oxygen storage / release and the oxygen exchange reaction, and the effect of supplying de-discrete elements with high activity persistence to PM that does not come into contact with the catalyst. Especially, the PM combustion rate in the slow combustion region after the gap is formed can be improved.

  According to the particulate filter according to the present invention, the PM combustion performance in the rapid combustion region and the slow combustion region can be improved, so that the PM combustion can be advanced efficiently and the fuel efficiency can be improved. Furthermore, since the amount of Pt used as the catalyst metal can be reduced, the cost can also be reduced.

It is a graph which shows typically a time-dependent change of PM residual ratio when PM deposited on the catalyst layer burns. It is an electron micrograph which shows the state (state in the rapid combustion area | region of FIG. 1) which PM deposit layer is contacting the catalyst layer. It is a schematic diagram which shows the combustion mechanism of PM in a rapid combustion area | region. It is an electron micrograph which shows the state (state in the slow combustion area | region of FIG. 1) with which the clearance gap was made between the catalyst layer and the deposit layer of PM. It is a schematic diagram which shows the combustion mechanism of PM in a slow combustion area | region. It is a figure which shows the state which has arrange | positioned the particulate filter in the exhaust gas path of an engine. It is a front view which shows the same filter typically. It is a longitudinal cross-sectional view which shows the same filter typically. It is an expanded sectional view showing typically the exhaust gas passage wall of the filter. A catalyst material in which Pd and Pt are supported on composite particles in which ZrCe-based composite oxide is supported on activated alumina particles, and a catalyst in which only Pt is supported on composite particles in which ZrCe-based composite oxide is supported on active alumina particles it is a graph comparing the NO ₂ generation ability with product. It is a figure which shows typically the catalyst layer of embodiment of this invention. It is a graph which shows the carbon burning rate of the particulate filter with a catalyst which concerns on the Example and comparative example of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its application.

<Particulate filter structure>
Hereinafter, the structure of the particulate filter for collecting PM will be described.

FIG. 6 shows a particulate filter (hereinafter simply referred to as “filter”) 10 arranged in the exhaust gas passage 11 of the diesel engine. In the exhaust gas passage 11 on the upstream side of the exhaust gas flow from the filter 10, an oxidation catalyst (not shown) in which a catalyst metal typified by Pt, Pd or the like is supported on an oxide or the like support material can be disposed. The exhaust gas component purification catalyst material according to the present embodiment can be used for the oxidation catalyst to be disposed. When such an oxidation catalyst is arranged on the upstream side of the filter 10, HC and CO in the exhaust gas are oxidized by the oxidation catalyst, and the temperature of the exhaust gas flowing into the filter 10 is increased by the oxidation combustion heat to heat the filter 10. This is advantageous for PM removal by combustion. Further, NO is oxidized to NO ₂ by the oxidation catalyst, and the NO ₂ is supplied to the filter 10 as an oxidant for burning PM.

  As schematically shown in FIGS. 7 and 8, the filter 10 has a honeycomb structure and includes a large number of exhaust gas passages 12 and 13 extending in parallel to each other. That is, in the filter 10, the exhaust gas inflow path 12 whose downstream end is blocked by the plug 14 and the exhaust gas outflow path 13 whose upstream end is blocked by the plug 14 are alternately provided, and the exhaust gas inflow path 12 and the exhaust gas outflow path 13 are provided. Is separated by a thin wall 15. In FIG. 7, hatched portions indicate the plugs 14 at the upstream end of the exhaust gas outflow passage 13.

In the filter 10, the filter main body including the partition wall 15 is formed of an inorganic porous material such as cordierite, SiC, Si ₃ N ₄ , sialon, or AlTiO ₃ . The exhaust gas flowing into the exhaust gas inflow passage 12 flows out into the adjacent exhaust gas outflow passage 13 through the surrounding partition 15 as shown by the arrows in FIG. That is, as shown in FIG. 9, the partition wall 15 has minute pores (exhaust gas passages) 16 that connect the exhaust gas inflow passage 12 and the exhaust gas outflow passage 13, and the exhaust gas passes through the pores 16. PM is trapped and accumulated mainly in the exhaust gas inlet 12 and the walls of the pores 16.

  A catalyst layer 17 is formed on the wall surface forming the exhaust gas passage (exhaust gas inflow passage 12, exhaust gas outflow passage 13 and pore 16) of the filter body. It is not always necessary to form a catalyst layer on the wall surface on the exhaust gas outflow passage 13 side.

<About catalyst material>
Next, the catalyst material used for the particulate filter according to the embodiment of the present invention will be described.

  As a result of conducting experiments and research on a catalyst material having good PM combustion performance, the present inventors have determined that Pd and Pt are added to composite particles in which a ZrCe-based composite oxide containing Zr and Ce is supported on activated alumina particles. It has been found that PdPt-supported composite particles on which is supported are used as a catalyst material. Here, the NO oxidation performance test was performed using the PdPt-supported composite particles and the Pt-supported composite particles in which only the Pt was supported on the composite particles (composite particles in which the ZrCe-based composite oxide was supported on the activated alumina particles). The results will be described below.

In the NO oxidation performance test, sample filters each carrying PdPt-supported composite particles or Pt-supported composite particles as catalyst materials were prepared, and each NO oxidation performance was evaluated using this sample filter. The sample filter was prepared by coating the above catalyst with 100 g / L (2.5 g) on a cordierite support (25 cc, 4.5 mil / 400 cpsi), and then calcining at 500 ° C. for 2 hours. The catalyst metal content was 0.3 g / L, and Pt: Pd was 2: 1 (mass ratio) in the PdPt-supported composite particles. Moreover, ZrCeLaYO _x containing lanthanum (La) and yttrium (Y) was used as the ZrCe-based composite oxide, and the ZrCeLaYO _x : Al ₂ O ₃ (active alumina) in the composite particles was set to 20:80 (mass ratio). .

The sample filter thus obtained was attached to a simulated gas flow reactor, and simulated exhaust gas (CO; 400 ppm, HC (C ₃ H ₆ ); 200 ppm, NO; 500 ppm, H ₂ O: 10%, remaining N ₂ ) Was passed through the filter. The flow rate of the simulated exhaust gas at this time was 35 L / min, and the space velocity was 84000 / h. As temperature conditions, the temperature at the filter inlet was increased from 100 ° C. to 600 ° C. at a temperature increase rate of 30 ° C./min. While increasing the temperature under these conditions, the NO concentration in the gas was measured in real time at the filter outlet. And the NO oxidation rate was computed using the following formula | equation.

NO oxidation rate (%)
= 100 x {[Initial (at 100 ° C) NO concentration (ppm)]-[NO concentration (ppm)]} / [Initial NO concentration (ppm)]
As a result, as shown in FIG. 10, it was confirmed that the PdPt-supported composite particles had significantly higher NO oxidation performance than the Pt-supported composite particles. That is, when PdPt-supported composite particles are used as the catalyst material, NO in the exhaust gas can be oxidized to NO ₂ with high efficiency, so that this NO ₂ acts as an oxidant and PM combustion performance can be improved.

  In order to increase the surface area of the particles of the catalyst material and improve the contact efficiency with the exhaust gas, the present inventors further added ZrCe to the activated alumina particles in the composite particles having high NO oxidation performance as described above. The catalyst metal was supported on each of them without supporting the composite oxide. Specifically, a catalyst material including a Pd-supported ZrCe-based composite oxide in which Pd is supported on a ZrCe-based composite oxide containing Zr and Ce, and Pt-supported active alumina particles in which Pt is supported on active alumina particles. A catalyst-attached particulate filter having a catalyst layer capable of improving PM combustion performance was used. Below, the structure of the catalyst layer in the particulate filter with a catalyst which concerns on this embodiment is demonstrated.

  As shown in FIG. 11, in the present embodiment, a catalyst layer 22 is formed on the wall surface (filter carrier 21) of the exhaust gas passage wall of the filter, and Pt 24 is supported on the activated alumina particles 23 in the catalyst layer 22. The Pt-supported activated alumina particles and the Pd-supported ZrCe-based composite oxide in which Pd26 is supported on the ZrCe-based composite oxide 25 containing Zr and Ce are included. As shown in FIG. 11, both Pd26 and Pt24 may be supported on the ZrCe-based composite oxide 25. The ZrCe-based composite oxide 25 may contain a rare earth element such as yttrium (Y) and lanthanum (La) other than Zr and Ce. Here, the constituent ratios of the activated alumina particles 23, Pt24, ZrCe-based composite oxide 25 and Pd26 contained in the catalyst layer 22 are not particularly limited, and can be appropriately prepared.

  In addition to the above particles, the catalyst layer 22 may further include an Rh-containing ZrCe composite oxide in which rhodium (Rh) 27 is contained in the ZrCe composite oxide 28. In this way, as described above, the Rh-containing ZrCe-based composite oxide can supply de-discrete elements having high activity persistence to PM that does not contact the catalyst, and therefore, there is a gap between the catalyst layer and the PM. In particular, the PM combustion rate in the slow combustion region after the formation of can be improved. The Rh27 is not limited to be supported on the surface as long as it is contained in the ZrCe-based composite oxide 28, and may be contained in the ZrCe-based composite oxide 28 after being dissolved, for example (dope type). Further, the composition of the ZrCe composite oxide 28 containing Rh27 may not be the same as the composition of the ZrCe composite oxide 25 supporting Pd26 as long as it contains Zr and Ce. Further, the particle diameters may not be the same.

  The catalyst layer 22 may contain an alkaline earth metal such as barium (Ba) and strontium (Sr). In this way, it is possible to prevent Pd from being poisoned by the sulfur (S) component in the exhaust gas.

<Method for preparing catalyst material>
Next, a method for preparing a catalyst material provided in the particulate filter according to the embodiment of the present invention will be described. Here, a ZrCeLaY composite oxide is prepared as a ZrCe-based composite oxide containing Zr and Ce.

First, a zirconyl oxynitrate solution, neodymium nitrate hexahydrate, lanthanum nitrate, and yttrium nitrate are dissolved in ion-exchanged water. A precursor (coprecipitate) containing a ZrCeLaY composite oxide is obtained by mixing and neutralizing an 8-fold diluted solution of 28% by mass ammonia water. This coprecipitate is centrifuged, and the dehydration operation for removing the supernatant and the water washing operation for adding ion-exchanged water and stirring are repeated alternately as many times as necessary. The co-precipitate after the final dehydration is dried in the atmosphere at 150 ° C. for one day, and then pulverized to a mean particle diameter of about 100 nm by a ball mill. Then, ZrCeLaY complex oxide (ZrCeLaYO _x ) can be obtained by firing at 500 ° C. for 2 hours in the air.

  Next, a method for supporting Pd and Pt on the obtained ZrCeLaY composite oxide will be described. Here, the evaporation to dryness method will be described as the carrying method.

  First, ion exchange water is added to the ZrCeLaY composite oxide to form a slurry, which is sufficiently stirred with a stirrer or the like. Subsequently, a predetermined amount of dinitrodiamine Pd nitric acid solution and dinitrodiamine Pt nitric acid solution are dropped into the slurry while stirring, and the mixture is sufficiently stirred. Thereafter, stirring is continued while heating to completely evaporate water. After evaporation, the PdPt-supported ZrCeLaY composite oxide is obtained as the PdPt-supported ZrCe-based composite oxide in which Pd and Pt are supported on the ZrCe-based composite oxide by firing at 500 ° C. for 2 hours in the air. When only Pd is supported, the above method may be performed using only a dinitrodiamine Pd nitric acid solution.

  Moreover, the method of carrying Pt on the activated alumina particles can be obtained by adopting a dinitrodiamine Pt nitric acid solution as the catalyst metal solution in the above-mentioned evaporation to dryness method.

Next, a method for preparing an Rh-doped CeZrNdO _x composite oxide as an Rh-containing ZrCe-based composite oxide containing Ce and Zr and further containing Rh will be described.

First, cerium nitrate hexahydrate, zirconyl oxynitrate solution, neodymium nitrate hexahydrate, and rhodium nitrate solution are dissolved in ion-exchanged water. A coprecipitate is obtained by mixing and neutralizing this nitrate solution with an 8-fold diluted solution of 28% by mass ammonia water. A dehydration operation in which the solution containing the coprecipitate is centrifuged to remove the supernatant and a water washing operation in which ion-exchanged water is added and stirred are repeated alternately as many times as necessary. The coprecipitate after the final dehydration is dried in the atmosphere at 150 ° C. for a whole day and night, and then pulverized to an average particle size of about 100 nm by a ball mill. Thereafter, the Rh-doped CeZrNdO _x composite oxide particle material can be obtained by firing at 500 ° C. for 2 hours in the air. In addition, in order to carry | support Pt here, what is necessary is just to use the evaporative drying method similarly to the above using only dinitrodiamine Pt nitric acid solution.

  Ion exchange water and a binder are added to each particle material obtained as described above and mixed to form a slurry. The slurry is coated on a filter, dried, and then calcined at 500 ° C. for 2 hours to obtain a particulate filter with catalyst.

  Below, the Example for demonstrating in detail the particulate filter with a catalyst which concerns on this invention is shown.

In this example, the above-mentioned Pt-supported Al ₂ O ₃ as catalyst material, Pd-supported ZrCeLaYO _x or PdPt-supported ZrCeLaYO _x , Rh-doped CeZrNdO _x composite oxide, or Pt / Rh-doped CeZrNdO _x composite supporting Pt on this. Each carbon combustion rate was examined by using an oxide and changing the ratio of Pd and Pt contained in the catalyst material. Further, as a comparative example was examined for the case where only Pt not Pd was used Pt-supported ZrCeLaYO _x carried on the ZrCeLaYO _x, Pd is a supported Pd supported _Al 2 _{O 3} particles to the active alumina particles. The composition of the catalyst material of each example and comparative example is shown in Table 1 below. In addition, each ratio shown in Table 1 has shown mass ratio.

Pt-supported Al ₂ O ₃ contained in the catalyst materials of Examples 1 to 16, Pd-supported ZrCeLaYO _x or PdPt-supported ZrCeLaYO _x , Rh-doped CeZrNdO _x contained in the catalyst material of Example 15, and catalyst of Example 16 The Pt / Rh-doped CeZrNdO _x contained in the material was prepared as described above. In each Example, the sample filter (particulate filter with catalyst) was obtained by coating them on the filter. The constituent ratio of ZrCeLaY and Al ₂ O ₃ contained in the catalyst material was 20:80 (mass ratio). Also t, component ratio ZrCeLaYO _x in Pd supported or PdPt carrying ZrCeLaYO _{x is, ZrO 2: CeO 2: La} 2 O 3: Y 2 O 3 = 39: 54: 5: and 2 (weight ratio). Further, in Rh-doped CeZrNdO _x and Pt / Rh-doped CeZrNdO _x , Rh is 0.1% by mass, and the composition ratio of other CeZrNdO _x is CeO ₂ : ZrO ₂ : Nd ₂ O ₃ = 28: 62: 10 (Mass ratio).

  In each example and comparative example, the coating amount of the composite particles on the filter was 20 g / L, and the total amount of noble metals of Pd, Pt, and Rh was 0.3 g / L. The composition ratios of these noble metals are as shown in Table 1. When Pt, Pd and Rh were included, Pt: Pd: Rh was set to 0.045: 0.045: 0.01 (mass ratio).

  Carbon (carbon black) was deposited on the sample filter obtained by coating the filter with the catalyst material of each Example and Comparative Example, and the carbon burning rate was measured.

  The carbon was deposited so that 5 g / L of carbon was deposited per liter of the carrier volume. After carbon equivalent to 5 g / L was stirred in ion-exchanged water using a stirrer, the inlet side of the sample filter was immersed and sucked from the outlet side using an aspirator. After excess water was removed by placing on a water-absorbent sheet, drying treatment was performed at 150 ° C. for 2 hours.

Each of the obtained sample filters was attached to a simulated gas flow reactor, and the gas temperature was raised while flowing N ₂ gas. After the filter inlet temperature was stabilized at 540 ° C., the simulated exhaust gas was switched from N ₂ gas to simulated exhaust gas (O ₂ ; 7.5%, NO; 300 ppm, remaining N ₂ ), and flowed at a space velocity of 40000 / h. Then, the CO and CO ₂ gas concentrations produced by the combustion of carbon are measured in real time at the filter outlet, and from these concentrations, the carbon combustion rate (unit time) is determined at predetermined intervals using the following formula. Per PM combustion amount) was calculated.

Carbon burning rate (g / h)
= {Gas flow rate (L / h) x [(CO + CO ₂ ) concentration (ppm) / (1 x 10 ⁶ )]} x 12 (g / mol) /22.4 (L / mol)
The time required for the carbon combustion rate to reach 0% to 50%, 50% to 90%, and 0% to 90% is obtained based on the carbon combustion rate for each predetermined time. The carbon combustion rate (PM combustion amount per minute (1 mg / min-L) in the filter 1 L) was obtained from the integrated value of the carbon combustion amount in the meantime. The result is shown in FIG.

As shown in FIG. 12, when Examples 1 to 16 are compared with Comparative Examples 1 and 2, Examples 1 to 16 including Pt-supported Al ₂ O ₃ and Pd-supported ZrCeLaYO _x or PdPt-supported ZrCeLaYO _x However, the carbon combustion performance is clearly superior to Comparative Examples 1 and 2 that do not contain them.

When Examples 1 to 7 including Pt-supported Al ₂ O ₃ and Pd-supported ZrCeLaYO _x and having different mass ratios of Pd and Pt were compared with each other, the greater the amount of Pd, the faster the combustion range (the carbon combustion rate was 0). % To 50%), and the combustion rate in the slow combustion region (carbon combustion rate is 50% to 90%) tends to decrease. As a result, the total carbon burning rate was almost the same in Examples 1-7.

When Examples 8 to 14 including Pt-supported Al ₂ O ₃ and PdPt-supported ZrCeLaYO _x and having different mass ratios of Pd and Pt are compared with each other, as in Examples 1 to 7, the amount of Pd increases. There was a tendency for the combustion rate in the rapid combustion region to improve and the combustion rate in the slow combustion region to decrease, and the total carbon combustion rate was almost the same in Examples 1-7. Further, when Examples 1 to 7 and Examples 8 to 14 having the same composition ratio of Pd and Pt are compared with each other, Examples 8 to 14 including PdPt-supported ZrCeLaYO _{x in} any case. However, the carbon burning rate was high. That is, it was suggested that carbon combustion performance can be improved by supporting not only Pd but also Pt on ZrCeLaYO _x .

Comparing Examples 1 to 14 with Example 15 containing Rh-doped CeZrNdO _x , in Example 15, since the combustion rate in the slow combustion region was improved by Rh-doped CeZrNdO _x , the total carbon burning rate was It was higher than 1-14. Furthermore, in Example 16 containing Pt / Rh-doped CeZrNdO _x , a further improvement in the total carbon burning rate was recognized as compared with Example 15.

On the other hand, in Comparative Examples 1 and 2 containing Pd-supported Al ₂ O ₃ supporting Pd instead of Pt and Pt-supporting ZrCeLaYO _x supporting Pt instead of Pd, the rapid combustion region In both the slow combustion region and the slow combustion region, results with a low combustion rate were obtained, and the total carbon combustion rate was lower than in Examples 1-16.

  As described above, it was suggested that the total PM combustion performance can be improved by using a particulate material containing Pd-supported or PdPt-supported ZrCe-based composite oxide and Pt-supported activated alumina particles as a catalyst material.

10 Filter 11 Exhaust gas passage 12 Exhaust gas inflow passage (exhaust gas passage)
13 Exhaust gas outflow passage (exhaust gas passage)
14 plug 15 partition 16 pore (exhaust gas passage)
17 catalyst layer 21 filter carrier 22 catalyst layer 23 activated alumina particles 24 platinum (Pt)
25 ZrCe complex oxide (supporting Pd)
26 Palladium (Pd)
27 Rhodium (Rh)
28 ZrCe complex oxide (containing Rh)

Claims (3)

A particulate filter with a catalyst in which a catalyst layer is provided on an exhaust gas passage wall of a filter that collects particulates in exhaust gas,
The catalyst layer includes a Pd-supported ZrCe composite oxide in which palladium (Pd) is supported as a catalyst metal on a ZrCe composite oxide containing zirconium (Zr) and cerium (Ce), and active alumina particles as a catalyst metal. A particulate filter with catalyst, comprising Pt-supported activated alumina particles on which platinum (Pt) is supported.   The particulate filter with catalyst according to claim 1, wherein Pt is further supported on the Pd-supported ZrCe-based composite oxide.   3. The particulate filter with catalyst according to claim 1, wherein the catalyst layer further includes an Rh-containing ZrCe composite oxide in which rhodium (Rh) is contained in the ZrCe composite oxide.