JP2016061153A - Particulate filter with catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively arrange an alkali earth metal, to reduce a use amount of a noble metal catalyst, to raise a particulate combustion speed of a filter as a whole while correcting a disparity of regeneration degrees of the filter which is generated due to a temperature distribution in a radial direction, to shorten a regeneration time, and to improve combustion performance, in the particulate filter with the catalyst carrying the alkali earth metal.SOLUTION: An alkali earth metal which is high in a particulate combustion promotion effect at a higher temperature out of two kinds or more of alkali earth metals 26 is arranged at an inside zone 10a with a larger amount, and an alkali earth metal which is high in the particulate combustion effect at a lower temperature is arranged at an outside zone 10b with a larger amount.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a particulate filter with a catalyst that is provided in an exhaust gas passage of an engine and collects and burns away particulates in the exhaust gas.

  The exhaust gas of diesel engines and lean-burn gasoline engines contains particulates (particulate particulate matter) mainly composed of carbon. Therefore, a filter is arranged in the exhaust gas passage to collect particulates, and when the collected amount increases, the particulates are burned and removed from the filter to regenerate the filters. It is. A precious metal catalyst such as Pt is supported on the filter body in order to promote the combustion of particulates.

  Such a particulate filter with catalyst generally has a temperature distribution in the radial direction during its regeneration. That is, the outer zone close to the outer periphery of the filter loses temperature because heat escapes to the casing through the surrounding insulation, and the inner zone close to the center of the filter has a higher gas flow rate than the outer zone, and the particulates burn. Because it is easy, the temperature tends to rise. As a result, due to the temperature difference between the two zones, a difference occurs in the particulate combustion speed, so that the regeneration time of the entire filter becomes longer, leading to a reduction in fuel consumption performance.

  Therefore, for example, Patent Document 1 discloses that an alkali metal or an alkaline earth metal having an action of lowering the combustion start temperature is supported on the outer peripheral side portion of the filter so that the timing of the combustion start is advanced even at a low temperature outer peripheral portion. It describes that the variation in the regeneration degree in the filter is corrected.

JP 2003-97251 A

By the way, it is known that alkali metals and alkaline earth metals trap NOx in exhaust gas to become nitrates. When these are supported on the filter, active oxygen and NO ₂ released by the decomposition of nitrate during particulate combustion act as an oxidant, and have an effect of promoting particulate combustion.

  Therefore, supporting an alkali metal or alkaline earth metal on a filter is useful for reducing the amount of a noble metal catalyst such as Pt and reducing the cost of the catalyst.

  However, although the thing of patent document 1 has an effect which accelerates | stimulates the combustion start in the outer peripheral side site | part of a filter, since it is the structure which carry | supports an alkali metal or alkaline-earth metal only in this outer peripheral side site | part, the precious metal as a whole filter It is not possible to reduce the amount of catalyst used and effectively utilize these particulate combustion promotion performances.

  In addition, although both alkali metals and alkaline earth metals have the above-mentioned advantages, there is a problem that the alkali metal erodes the grain boundary of the filter carrier ceramic and causes a decrease in strength. It is more desirable to use a metal as a catalyst.

  In this respect, Patent Document 1 describes only an example in which an alkali metal is supported as an embodiment, and therefore it is unclear as to the effect of correcting the variation in the degree of regeneration in the filter when an alkaline earth metal is supported. It is.

  Therefore, in the present invention, in a particulate filter with a catalyst carrying an alkaline earth metal, the alkaline earth metal is effectively arranged to reduce the amount of noble metal catalyst used, and the filter is generated by a temperature distribution in the radial direction. The problem is to improve the fuel efficiency by reducing the regeneration rate of the entire filter while increasing the particulate combustion speed of the entire filter while shortening the regeneration time.

  In order to solve the above-mentioned problem, in the present invention, among two or more alkaline earth metal compounds, those having a high particulate combustion promotion effect at a higher temperature are used as the inner zone, and a particulate combustion promotion effect is higher at a lower temperature. More things were placed in the outer zone.

  That is, the particulate filter with catalyst presented here is a filter combustion catalyst provided on the exhaust gas passage wall of the filter body for collecting particulates in the exhaust gas. It contains inorganic oxide particles containing at least activated alumina, a catalytic metal, and two or more alkaline earth metal compounds, and the catalytic metal and alkaline earth metal compound are supported on the inorganic oxide particles. Of the alkaline earth metal compounds, a high particulate combustion promoting effect at the first temperature is supported in the inner zone of the filter body, and the particulate combustion promoting effect at the second temperature lower than the first temperature. Higher ones are carried by the outer zone of the filter body.

  As described above, a temperature distribution is generated in the radial direction of the filter during filter regeneration. Specifically, for example, assuming that the area occupying 1/3 of the entire filter as the area from the center of the filter is the inner zone and the outer side is the outer zone, the inner zone is 450 to 650 ° C. and the outer zone is 350 to 550 ° C. To reach.

  Therefore, for example, 550 ° C., which is a typical temperature reached by the inner zone of the filter during regeneration, is set as the first temperature, and 450 ° C., which is a typical temperature reached by the outer zone, is set as the second temperature, 550 ° C. or 450 ° C. , The alkaline earth metal having a high particulate combustion promoting effect can be supported on the inner or outer zone, respectively.

  According to the present invention, even if a temperature distribution occurs in the radial direction of the filter, the particulate combustion rate can be kept substantially uniform as a whole, and the difference in the degree of regeneration of the filter is corrected between the two zones while correcting the entire filter. The particulate combustion rate can be increased to shorten the regeneration time and improve fuel efficiency. In addition, by disposing the alkaline earth metal throughout the filter, the amount of noble metal catalyst such as Pt used can be reduced and the cost can be reduced.

  In addition, as said 1st temperature, the temperature of 450-650 degreeC, More preferably, 480-620 degreeC, Most preferably, 500-600 degreeC can be set. Moreover, as 2nd temperature, the temperature of 350-550 degreeC, More preferably, 380-520 degreeC, Most preferably, 400-500 degreeC can be set.

  Further, the inner zone of the filter is preferably a portion that occupies 1/4 to 2/3 of the entire filter as an area from the center of the filter.

  Furthermore, it is preferable to use carbonates such as Mg, Sr, Ca and Ba as the alkaline earth metal compound.

  As the inorganic oxide particles, activated alumina, Ce-based oxide, Ce-free Zr-based oxide, or the like can be preferably used.

  In a more preferred embodiment of the particulate filter with catalyst, the alkaline earth metal compound is supported on the activated alumina.

  In addition, as the activated alumina particles, pure alumina containing no additive, metal-containing alumina containing an additive such as a metal, or a mixture thereof can be preferably used. A particularly preferred embodiment is a configuration using a mixture of pure alumina and La-containing alumina.

  Moreover, as said catalyst metal, Pt, Pd, Rh, etc. can be contained, and these can be set as the structure carry | supported by the said inorganic oxide particle. In a particularly preferred embodiment, the catalyst metal contains Pt, and the Pt is supported on the activated alumina.

  As described above, according to the present invention, in the particulate filter with a catalyst supporting an alkaline earth metal, the amount of the noble metal catalyst is reduced by effectively arranging the alkaline earth metal, and the diameter is reduced. While correcting the difference in the degree of regeneration of the filter caused by the temperature distribution in the direction, the particulate combustion speed of the entire filter can be increased to shorten the regeneration time and improve the fuel efficiency.

The figure which has arranged the filter with a catalyst concerning a 1st embodiment in the exhaust gas passage of an engine. (A) is a front view schematically showing the filter, and (b) is a diagram for explaining an inner zone and an outer zone of the filter. The longitudinal cross-sectional view which shows the same filter typically. The expanded sectional view which shows typically the exhaust-gas channel | path wall of the same filter. Sectional drawing which shows the structure of the catalyst of the filter typically. The graph which shows the carbon combustion rate in filter temperature 550 degreeC. The graph which shows the carbon combustion rate in filter temperature 450 degreeC. The graph which shows the soot combustion speed of an Example and a comparative example. (A) is a front view which shows typically the filter with a catalyst which concerns on 2nd Embodiment, (b) is an enlarged front view of the segment which comprises the filter.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

[First embodiment]
As shown in FIG. 1, a particulate filter with catalyst (hereinafter simply referred to as “filter with catalyst”) 10 is disposed in an exhaust gas passage 11 of a diesel engine or the like, and particulates (hereinafter referred to as “PM”) in the exhaust gas. To collect. An oxidation catalyst (not shown) in which a catalyst metal such as Pt is supported on a support material made of an oxide or the like can be disposed in the exhaust gas passage 11 upstream of the filter 10 in the exhaust gas flow.

<Filter structure>
As schematically shown in FIGS. 2A and 3, the filter with catalyst 10 has a honeycomb structure and includes a large number of exhaust gas passages 12 and 13 extending in parallel with each other. Exhaust gas inflow passages 12 whose downstream ends are closed by plugs 14 and exhaust gas outflow passages 13 whose upstream ends are closed by plugs 14 are alternately provided. The exhaust gas inflow passages 12 and 13 They are separated by a thin partition wall 15. In FIG. 2, the hatched portion indicates the plug 14 at the upstream end of the exhaust gas outflow passage 13. In this embodiment, the cross section of the filter with catalyst 10 is circular as shown in FIG. 2A, but is not limited to this shape, and other shapes such as an elliptical shape and a rectangular shape are used. I can take it.

In the filter with catalyst 10, the filter 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 wall 15 as shown by an arrow in FIG. As shown in FIG. 4, the partition wall 15 has minute pores (exhaust gas passages) 16 communicating 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 deposited mainly in the exhaust gas inflow passage 12 and the walls of the pores 16.

  The wall surface forming the exhaust gas passage (exhaust gas inflow passage 12, exhaust gas outflow passage 13 and pore 16) of the filter 10 body is coated with a catalyst 20. It is not always necessary to provide a catalyst on the wall surface on the exhaust gas outflow path 13 side.

<About catalyst>
Next, the configuration of the catalyst 20 will be described.

  As schematically shown in FIG. 5, the catalyst 20 contains a plurality of types of activated aluminas 21 and 22, a catalyst metal 25 and an alkaline earth metal 26 supported thereon. This will be specifically described below.

  This embodiment has two types of activated aluminas 21 and 22, both of which are mainly γ-alumina, and one of them is pure alumina (first alumina) 21 containing no additive, The other is La-containing alumina (second alumina) 22 containing about 4 mass% of La as an additive in terms of oxide.

The pure alumina 21 has a smaller pore diameter than the La-containing alumina 22, so that the catalytic metal 25 supported on the surface thereof is increased. As a result, the exhaust gas easily comes into contact with the catalyst metal 25 and a large amount of NO ₂ is generated, which is advantageous for promoting the combustion of PM. Further, unlike the La-containing alumina 22 (basic), the pure alumina 21 is amphoteric and has an acid point, and therefore has a strong force for binding the catalyst metal 25. Therefore, even if the catalytic metal 25 is exposed to the high temperature exhaust gas, it is difficult to aggregate, and good PM combustibility is maintained for a long time.

  On the other hand, since the La-containing alumina 22 has high heat resistance, the durability of the filter with catalyst 10 can be improved. Moreover, since the bulk specific gravity is smaller than that of the pure alumina 21, that is, it is bulky, the gas diffusibility is good and the contact with the exhaust gas is good.

  Therefore, by mixing the pure alumina 21 and the La-containing alumina 22, the PM combustibility can be enhanced by the pure alumina 21 while ensuring the heat resistance and gas diffusibility of the catalyst by the La-containing alumina 22. The use of pure alumina 21 can suppress the bulkiness of the activated alumina as a whole, which is advantageous for preventing clogging of the exhaust gas passage 16. As a result, an increase in the engine back pressure due to the filter with catalyst 10 is suppressed, and the frequency of the regeneration process of the filter 10 is reduced, so that deterioration of fuel consumption can be avoided.

  The total supported amount of the activated aluminas 21 and 22 is preferably 5 g / L or more and 35 g / L or less. The mass ratio between the pure alumina 21 and the La-containing alumina 22 is preferably pure alumina / La-containing alumina = 1/8 or more and 4/1 or less.

As the catalyst metal 25 supported on the activated aluminas 21 and 22, metals such as Pt, Pd, and Rh, or a mixture thereof can be used. In this embodiment, Pt is used as the catalyst metal 25. Therefore, since the catalyst 20 contains the activated aluminas 21 and 22 carrying Pt, NO can be oxidized to NO ₂ with high efficiency, which is advantageous for promoting combustion of PM.

  The total amount of Pt supported on the activated aluminas 21 and 22 is preferably 1 to 6 wt%, more preferably 2 to 5 wt%.

The alkaline earth metal 26 supported on the activated aluminas 21 and 22 is Mg, Ca, Sr or Ba. These alkaline earth metals 26 are carbonates when NOx is not occluded, and occlude NOx in the exhaust gas in the form of nitrate (for example, in the case of Sr, SrCO3 ← → Sr (NO ₃ ) ₂ ). Then, the nitrate is decomposed, and active oxygen released by the decomposition of the nitrate becomes an oxidizing agent, so that PM combustion is promoted.

  The total supported amount of the alkaline earth metal 26 with respect to the activated aluminas 21 and 22 is 3 to 14 wt%, more preferably 5 to 12 wt%.

<Support of Pt and alkaline earth metal on activated alumina>
Pure alumina and La-containing alumina are mixed, and ion exchange water is added to form a slurry, which is sufficiently stirred by a stirrer or the like. Subsequently, a predetermined amount of ethanolamine Pt is dropped into the slurry while stirring, and a predetermined amount of alkaline earth metal salt solution (for example, alkaline earth metal acetate is added to the ion-exchanged water while stirring. The solution dissolved in is added dropwise and stirred sufficiently. Thereafter, stirring is continued while heating to completely evaporate water. After evaporation, the obtained dried product is pulverized and baked at 500 ° C. for 2 hours in the air. Thereby, the catalyst powder by which alkaline-earth metal and Pt were carry | supported by each activated alumina is obtained. In the present embodiment, the alkaline earth metal and Pt are supported at 10 wt% and 4.5 wt%, respectively, with respect to the activated alumina material.

Here, ethanolamine Pt is a complex of ethanolamine and Pt, and compared with a Pt raw material (Pt-P salt) having a planar tetragonal molecular structure in which a nitro group and an amine group are coordinated around Pt. It has an octahedral molecular structure in which a hydroxyl group is coordinated around Pt. In addition, since ethanolamine (NH ₃ C ₂ H ₅ OH) is present around the Pt-hydroxyl group complex, the complex is large. Therefore, when ethanolamine Pt is used, most of the complex is supported on the surface of the active alumina or active oxygen release material without entering the pores. That is, many Pt can be arrange | positioned on the surface of those support materials. As a result, the contact rate between Pt and the exhaust gas can be increased, the oxidation efficiency of NO in the exhaust gas by Pt can be improved, and the amount of NO ₂ generated can be increased. As a result, PM combustion efficiency can be improved.

<Evaluation of PM combustion performance of filters carrying different alkaline earth metals>
-Coating of catalyst powder on filter body-
The filter powder is coated on the filter body by the following procedure.

  That is, after adding a zirconia binder solution and ion-exchanged water to an activated alumina material powder supporting alkaline earth metal carbonate and ethanolamine Pt, mixing is performed while pulverizing with a ball mill to prepare a slurry.

  Then, the slurry is coated on the filter body. The washcoat amount is coated so that the support material is 20 g / L. After coating the slurry, drying at 150 ° C. and firing at 500 ° C. for 2 hours were performed.

-Evaluation of PM combustion performance of filter-
For the four types of alkaline earth metals Mg, Ca, Sr, or Ba, the filter with catalyst was adjusted by the above adjustment method. Each filter was aged at a temperature of 800 ° C. for 24 hours in the atmosphere, and then the PM combustion performance of each filter was examined.

  First, ion exchange water was added to carbon black corresponding to 5 g / L, and the carbon black was sufficiently dispersed by stirring using a stirrer. The inlet end of the aged filter was immersed in the obtained slurry, and suction was performed with an aspirator from the outlet end. Moisture that could not be removed by this suction was removed by air blow from the end face of the filter immersed in the slurry. And the filter was dried by hold | maintaining at the temperature of 150 degreeC for 2 hours.

Each of the obtained filters was attached to a fixed-bed model gas flow device, and the gas temperature at the filter inlet was raised from room temperature to the filter temperature T while N ₂ gas was allowed to flow through the filter. After the filter temperature stabilizes at T, with the temperature maintained, the gas composition is switched to “7.5% O ₂ +300 ppm NO + N ₂ (balance gas)”, and the space velocity of the model gas is set to 40000 / h. Washed away. Then, by measuring the concentration of CO and CO ₂ produced by the combustion of carbon in the model gas, the change over time in the amount of carbon combustion in the filter is measured, and the time required until 90% of the carbon burns (hereinafter referred to as “carbon”). , “90% combustion time (min)”). Further, the carbon burning rate (mg / L · min) was calculated from the 90% burning time.

  At the time of filter regeneration, the filter temperature T is set to 550 ° C., which is a typical temperature reached by the inner zone of the filter, and 450 ° C., which is the typical temperature reached to the outer zone of the filter. The combustion performance was evaluated.

  Table 1 shows the 90% burning time and carbon burning rate of each filter coated with a catalyst material containing activated alumina carrying various alkaline earth metals and Pt.

  6 and 7 show the carbon burning rates at the filter temperatures of 550 ° C. and 450 ° C. shown in Table 1, respectively.

  As shown in FIG. 6, when the filter temperature T is 550 ° C., when comparing the carbon burning rate for each supported alkaline earth metal, the carbon burning rate of the Mg or Ca supported activated alumina is Sr or Ba supported activated alumina. It can be seen that it is about 10 mg / L · min faster than.

  Moreover, as shown in FIG. 7, when filter temperature T is 450 degreeC, it turns out that Mg carrying | support alumina becomes slow compared with Ca, Sr, or Ba carrying | support alumina. This is presumably because, under the condition of 450 ° C., Mg is more stable with carbonate and the NOx occlusion rate becomes rate-determining.

On the other hand, at a sufficiently high temperature, Mg carbonate takes the form of nitrate by reacting with NO ₂ contained in the flow gas. For this reason, since the NOx occlusion speed is improved, it is considered that Mg exhibits a high carbon combustion promoting effect at 550 ° C. as shown in FIG.

  Therefore, it is preferable to use Mg or Ca, which has a higher carbon combustion promoting effect, as the alkaline earth metal when the filter temperature is 550 ° C., whereas the carbon combustion promoting effect is better when the filter temperature is 450 ° C. It can be seen that it is preferable to use high Ba, Sr, and Ca.

<Evaluation of PM Combustion Performance of Filter with Catalyst Supporting Two or More Alkaline Earth Metals>
-About the inner and outer zones of the filter-
With reference to FIG.2 (b), the inner zone and outer zone of the filter 10 with a catalyst shown to Fig.2 (a) are demonstrated.

  As shown in FIG. 2B, assuming that the entire cross section of the filter 10 has a circular shape with a radius R from the center O, a portion surrounded by a circle with a radius r from the center O is an inner zone 10a of the filter, and the outer side thereof. Can be the outer zone 10b.

  When the filter 10 is regenerated, the inner zone 10a reaches 450 to 650 ° C, more preferably 480 to 520 ° C, and particularly preferably 500 to 600 ° C. At this time, the outer zone 10b reaches 350 to 550 ° C., more preferably 380 ° C. to 520 ° C., and particularly preferably 400 to 500 ° C. due to the weaker gas flow than the inner zone and the influence of heat shrinkage.

  In addition, the inner zone 10a can be made into the part which occupies 1 / 4-2 / 3 of the whole filter as an area.

-Coating of catalyst powder on the inner and outer zones of the filter-
The inner and outer zones of the filter body are coated by the following procedure.

  After adding a zirconia binder solution and ion-exchanged water to powders of activated alumina material supporting various alkaline earth metal carbonates and ethanolamine Pt, mixing is performed while pulverizing with a ball mill to prepare a slurry. The slurry that coats the inner zone of the filter is called slurry A, and the slurry that coats the outer zone is called slurry B.

  Mask the gas inlet / outlet part of the inner zone of the filter body and coat slurry B. After the coating of the slurry B on the outer zone, the masking is removed and drying at 150 ° C. is performed, and then the gas inflow / outflow part of the outer zone of the filter body is masked to coat the slurry A. The amount of the washcoat is coated so that the sum of the inner and outer zones of the filter body is 28.5 g / L (of which Pt is 0.5 g / L). After coating slurry A, the masking is removed, drying at 150 ° C., and baking at 500 ° C. for 2 hours.

-Actual machine test-
About the filter with a catalyst adjusted by the said method, the aging which hold | maintains at the temperature of 800 degreeC in air | atmosphere for 24 hours was performed.

  The filter was attached downstream of the 2 L diesel engine exhaust with an oxidation catalyst in the front stage. Then, about 5 g / L of soot was deposited on the filter under predetermined engine operating conditions of 300 ° C. or lower on the filter inlet side.

  Next, a post-injection was performed on the engine side, and unburnt fuel was oxidized in the preceding oxidation catalyst to perform a regeneration test of the filter with catalyst. The filter inlet temperature was 580 ° C., and the filter outlet temperature and the filter inner zone temperature were the same 580 ° C., and the filter outer zone temperature was 480 ° C.

  The timing at which the soot burned 90% was estimated from the differential pressure before and after the filter with catalyst, and the regeneration test with the actual machine was completed. Then, the soot burning rate (mg / L · min) was calculated from the weight change before and after the test of the filter with catalyst and the regeneration time.

-Evaluation of PM combustion performance of filter-
Examples 1 and 2 in which Mg, Sr, Ca or Ba is used as the alkaline earth metal, and different alkaline earth metals are supported on the inner zone 10a and the outer zone 10b of the filter by the above-described method for producing a filter with catalyst. Each filter was adjusted and its PM combustion performance was evaluated by an actual machine test. In addition, the PM combustion performance of each filter shown in Table 1 was also evaluated by an actual machine test as Comparative Example 1-4. The results are shown in Table 2 and FIG. The inner zone 10a is a portion that occupies an area (r = R / 2 in FIG. 2 (b)) of the cross-sectional area with respect to the entire filter.

Example 1
According to Table 1, since the carbon combustion rate of the Mg or Ca-carrying filter is high at a filter temperature of 550 ° C. and the carbon combustion rate of the Sr or Ba-carrying filter is fast at a filter temperature of 450 ° C. A zone 10a with Mg and Ca and an outer zone 10b carrying Sr and Ba was prepared.

  That is, as the alkaline earth metal, slurry A is used using activated alumina in which Mg and Ca are supported in a ratio of 1: 1, and activated alumina in which Sr and Ba are supported in a ratio of 1: 1. Slurry B was created. And as above-mentioned, the filter with a catalyst was adjusted by coating the slurry A to the inner zone 10a of a filter, and the slurry B to the outer zone 10b of a filter, respectively.

(Example 2)
In Example 2, for the same reason as Example 1, slurry A is used using activated alumina supporting Mg as an alkaline earth metal, and slurry B is used using activated alumina supporting Ba. Created. And the filter with a catalyst was adjusted by coating the slurry A and the slurry B on the inner zone 10a and the outer zone 10b of the filter in the same manner as in Example 1.

(Comparative Example 1-4)
Comparative Examples 1, 2, 3, and 4 are filters with catalysts in which Mg, Sr, Ba, and Ca are supported as alkaline earth metals, respectively, as shown in Table 1.

(Evaluation of soot burning rate)
As shown in Table 2 and FIG. 8, it can be seen that the soot-burning rate of the filters with catalysts of Examples 1 and 2 is higher than that of the filter with catalysts of Comparative Example 1-4.

  In particular, in the Mg-carrying filter of Comparative Example 1, since the carbon combustion speed greatly varies depending on the filter temperature as shown in Table 1, the result is obtained when Mg is supported on the entire filter and a temperature distribution is generated in the radial direction of the filter. It is considered that the soot burning rate in the outer zone decreases, and the overall soot burning rate decreases.

  Therefore, as shown in Examples 1 and 2, the inner zone 10a of the filter carries only Mg and Ca having a high carbon combustion rate at a filter temperature of 550 ° C. in Table 1, or Mg, and the outer zone 10b of the filter. In Table 1, when Sr and Ba, which have a high carbon combustion rate at a filter temperature of 450 ° C., or only Ba are supported, it is considered that the soot combustion rate of the entire filter is higher than that of Comparative Example 1-4.

  As described above, in the filter with catalyst 10 according to the present embodiment, the alkaline earth metal having a high carbon combustion promoting effect at a typical temperature reached by the inner zone of the filter during filter regeneration is the inner side of the filter body. A large amount of carbon is carried in the outer zone of the filter body, and the carbon combustion promoting effect at a typical temperature reached by the outer zone of the filter is high.

  According to the present invention, even if a temperature distribution occurs in the radial direction of the filter, the PM combustion rate can be kept substantially uniform as a whole, and the PM of the entire filter can be corrected while correcting the difference in the regeneration degree between the two zones. The combustion speed can be increased to shorten the regeneration time and improve the fuel efficiency. In addition, by disposing the alkaline earth metal throughout the filter, the amount of noble metal catalyst such as Pt used can be reduced and the cost can be reduced.

  Hereinafter, other embodiments according to the present invention will be described in detail. In the description of these embodiments, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[Second Embodiment]
As shown to Fig.9 (a), the filter with a catalyst which has an elliptical cross section is employable.

  The filter with catalyst 10 is configured by combining a number of segments 41 each having an exhaust gas inflow passage 12 and an exhaust gas outflow passage 13.

  As shown in FIG. 9 (b), in the segment 41, the exhaust gas inflow passages 12 and the exhaust gas outflow passages 13 are alternately arranged in the same manner as in the filter with catalyst of the first embodiment shown in FIG. 2 (a). It has a structure.

  In the filter with catalyst 10 of the present embodiment, the inner zone 10a is an inner portion partitioned by a thick solid line, and the outer zone 10b is outside the inner zone 10a.

  Therefore, different types of alkaline earth metals can be used for the inner zone 10a and the outer zone 10b by changing the types of alkaline earth metals carried by the segment 41 located in the inner zone 10a and the segment 41 located in the outer zone 10b. Can be supported.

  Specifically, the segment 41 located in the inner zone 10a is coated with the slurry A, and the segment 41 located in the outer zone 10b is coated with the slurry B, and then dried at 150 ° C. and 500 ° C. for 2 hours. By performing firing and combining the segments 41, the filter with catalyst 10 shown in FIG. 9A can be formed.

[Other embodiments]
Moreover, in the said 1st or 2nd embodiment, although the catalyst 20 is the structure containing activated alumina 21 and 22 as a support material, Ce non-containing Zr system complex oxide, Ce system complex oxide, etc. or these It is good also as a structure containing a mixture.

  Here, the Ce-free Zr-based composite oxide takes in oxygen from the inside by an oxygen exchange reaction and releases active oxygen. Therefore, the catalytic metal such as Pt supported on the Zr-based composite oxide is kept in a highly active oxidation state and has excellent PM combustion performance. On the other hand, the Ce-based composite oxide has a high oxygen storage / release capability, and even if oxygen at the combustion site is locally consumed with the combustion of PM, the Ce-based composite oxide quickly compensates for oxygen. PM combustion is maintained.

  The present invention relates to a particulate filter with a catalyst carrying an alkaline earth metal, in which the alkaline earth metal is effectively arranged to reduce the amount of noble metal catalyst used and to regenerate between the inner and outer zones of the filter. This is extremely useful because it can improve the fuel efficiency by reducing the regeneration time by correcting the particulate burning speed of the entire filter while correcting the difference in degree.

10 Filter with catalyst (Particulate filter with catalyst)
10a Inner zone 10b Outer zone 11 Exhaust gas passage 12 Exhaust gas inflow passage (exhaust gas passage of filter body)
13 Exhaust gas outflow passage (exhaust gas passage of filter body)
14 Plug 15 Bulkhead (Exhaust gas passage wall)
16 pores (exhaust gas passage in the filter body)
20 Catalyst 25 Catalytic metal 26 Alkaline earth metal (alkaline earth metal compound)

Claims (3)

A particulate filter with a catalyst in which a catalyst for particulate combustion is provided on an exhaust gas passage wall of a filter body that collects particulates in exhaust gas,
The catalyst contains inorganic oxide particles containing at least activated alumina, a catalyst metal, and two or more alkaline earth metal compounds,
The catalyst metal and alkaline earth metal compound are supported on the inorganic oxide particles,
Among the alkaline earth metal compounds, those having a high particulate combustion acceleration effect at the first temperature are supported in the inner zone of the filter body, and the particulate combustion acceleration effect at the second temperature lower than the first temperature is exhibited. A particulate filter with a catalyst, characterized in that a high amount is supported by the outer zone of the filter body. In claim 1,
A particulate filter with catalyst, wherein the alkaline earth metal compound is supported on the activated alumina. In claim 1 or claim 2,
A particulate filter with catalyst, wherein the catalyst metal contains Pt, and the Pt is supported on the activated alumina.