JP2009106856A - Catalyst material for cleaning exhaust gas component and particulate filter with the same catalyst material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst material for cleaning exhaust gas component which can improve cleaning performance for exhaust gas components (including HC, CO and particulates) and has improved heat resistance. <P>SOLUTION: The catalyst material for cleaning exhaust gas component comprises activated alumina and a CeZr-based conjugated oxide, wherein primary particles of the CeZr-based conjugated oxide are dispersively carried on the surface of secondary particles of activated alumina and the primary particles of the CeZr-based conjugated oxide contain CeO<SB>2</SB>at a proportion of 15 to 60 mol%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

    The present invention relates to an exhaust gas component purification catalyst material and a particulate filter with the catalyst material.

    In diesel engines that use light oil-based fuels and gasoline engines that burn leanly using gasoline-based fuels, in addition to HC (hydrocarbon), CO, and NOx (nitrogen oxides) Are known to contain particulates (particulate matter PM; suspended particulate matter containing carbon particles). Therefore, in order to suppress discharge of the particulates into the atmosphere, a filter for collecting the particulates is disposed in the exhaust gas passage of the engine. However, if the particulate accumulation amount of this filter increases, engine output and fuel consumption are reduced. Therefore, it is necessary to combust the accumulated particulate matter and remove it from the filter.

    In order to efficiently perform the combustion of the particulates (the particulates ignite at a relatively low temperature and complete the combustion in a short time), an alumina carrying a catalyst metal is disposed on the wall of the exhaust gas passage of the filter body. Formation of the catalyst layer containing is performed. This Pt-supported alumina is not only effective for purifying HC and CO, but also effective for burning particulates. In recent years, filter catalyst materials for burning particulates more efficiently have been developed.

    For example, Patent Document 1 describes that a catalyst material in which a catalytic metal such as Pt is supported on a composite oxide of a rare earth metal R selected from Pr, Nd, and La, Ce, and Zr is used for a filter. The content of R in the composite oxide is preferably 2 mol% or more and 11 mol% or less. Since such a complex oxide contains Ce, it has an oxygen storage / release capability, and oxygen released from the complex oxide promotes ignition and combustion of particulates.

    Patent Document 2 discloses a composite oxide ZrRO particle of R and Zr selected from Yb, Nd and Sc (R content is 18 mol% at the maximum), and a rare earth metal M and Ce selected from Sm and Gd. It is described that a catalyst material containing composite oxide CeMO particles and having a catalyst metal supported on the composite oxide particles is used for a filter. The ZrRO particles have oxygen ion conductivity and release active oxygen, but the oxygen release mechanism is different from that of CeZr-based composite oxide as disclosed in Patent Document 1.

    That is, the CeZr-based composite oxide has a high oxygen storage capacity and releases active oxygen due to a change in the valence of Ce ions. On the other hand, ZrRO particles have oxygen ion conductivity, so-called oxygen pumping function, and when there are a high oxygen concentration portion and a low oxygen concentration portion on the particle surface, the low oxygen oxygen concentration portion to the low oxygen concentration portion. Oxygen ions are transported to and released as active oxygen.

    Therefore, in the case of the above ZrRO particles, a small fire type that burns particulates can be formed on the surface, and when the fire type part is in an oxygen-deficient state, oxygen is transported from another part having a high oxygen concentration, and thus combustion continues. As a result, the combustion region easily spreads from the fire type.

    Patent Document 3 describes that a catalyst material containing ZrRO and alumina having oxygen ion conductivity as described above and having a catalyst noble metal supported thereon is used for the filter.

Patent Document 4 describes a method for producing an exhaust gas component purification catalyst material. That is, by adding ammonia water excessively to a mixed solution of an aqueous solution of Al nitrate and an aqueous solution of La nitrate, the first hydroxide containing Al and La is precipitated, and then mixing of an aqueous solution of Ce nitrate and an aqueous solution of Zr nitrate By adding a liquid, a second hydroxide containing Ce and Zr is deposited on the precipitate of the first hydroxide, and the resulting precipitate is filtered, dried and fired. . According to this production method, a catalyst material in which activated alumina particles containing La serve as a core and the entire surface is covered with a CeZr composite oxide as a shell material can be obtained.
JP 2006-326573 A JP 2007-54713 A JP 2007-83224 A JP 2007-98200 A

    The CeZr-based composite oxide particles having the above-described oxygen storage capacity and the Zr-based composite oxide particles having oxygen ion conductivity promote the oxidative purification of HC and CO, and also ignite particulates deposited on the filter. Although it promotes combustion, it has the following problems.

    That is, these composite oxide particles can be obtained by a coprecipitation method in which a basic solution is added to and mixed with an acidic solution containing metal ions such as Ce and Zr, and the resulting precipitate is dried and fired. In this case, primary particles of the composite oxide are formed by firing the precipitate, and the primary particles are further aggregated and grown into secondary particles. When such composite oxide secondary particles are exposed to high-temperature exhaust gas, they are further agglomerated and grain-grown and their surface area is reduced. As a result, the diffusion of the exhaust gas into the particles does not proceed smoothly, and the catalytic metal is buried or agglomerated inside the particles, thereby reducing the HC and CO purification performance and the particulate combustion performance.

    In addition, in the case of CeZr-based composite oxide particles having oxygen storage capacity, oxygen is stored / released mainly on the surface of the particle, and the inside of the particle hardly participates in storage / release of oxygen. When it becomes larger, the internal volume that is not used for oxygen storage / release increases, and the oxygen storage / release efficiency decreases accordingly.

    Also, in the case of Zr-based composite oxide particles having oxygen ion conductivity, when the particle size becomes large, the distance that oxygen ions conduct inside the particle from the particle surface portion having a high oxygen concentration to the particle surface portion having a low oxygen concentration. And the oxygen concentration gradient inside the particle is also reduced, so that the oxygen ion conductivity is lowered and the oxygen supplied from the inside of the particle is reduced.

    On the other hand, in the case of the catalyst material described in Patent Document 4, the particle size of the CeZr composite oxide particles serving as the shell material is relatively small, but the particle size of the activated alumina particles serving as the core material is also small (largely). Even about 0.1 μm). This is because when the precipitated particles of hydroxide containing Al and La become the precursor of activated alumina primary particles, the hydroxide containing Ce and Zr (CeZr composite) on the precipitated particles which are the primary particle precursors. This is because the aggregation of primary particles of activated alumina is hindered by the CeZr composite oxide because the oxide precursor) is deposited and covers the precipitated particles.

    As a result, the surface of the activated alumina particles is entirely covered with the CeZr composite oxide particles, and the catalyst metal is supported on the core of the activated alumina particles even if supported by the CeZr composite oxide. Is hardly carried. For this reason, the activated alumina particles are not effectively used as a support material for supporting the catalyst metal in a highly dispersed state, and high catalytic activity cannot be expected.

    Therefore, the present invention relates to a catalyst material comprising a combination of activated alumina and a composite oxide having an oxygen storage capacity, and aims to improve the purification performance of exhaust gas components (HC, CO, particulates, etc.) and to improve its heat resistance. The task is to improve.

    In order to solve the above problems, the present invention provides an exhaust gas component purification catalyst material in which primary particles of CeZr-based composite oxide are dispersed and supported on the surface of secondary particles containing activated alumina.

That is, the present invention contains Ce, Zr, and at least one rare earth metal R of Nd and Pr on the surface of secondary particles containing activated alumina particles as primary particles and aggregated with the primary particles. The primary particles of CeZr-based composite oxide are dispersed and supported.
The primary particles of the CeZr-based composite oxide is that exhaust gas component purifying catalyst material, characterized in that CeO ₂ is contained in an amount of less 15 mol% or more 60 mol%.

    The primary particles of the CeZr-based composite oxide have an oxygen storage capacity, and are dispersed and supported on the surface of secondary particles containing activated alumina particles. Therefore, even when exposed to high-temperature exhaust gas, Unlike the case where the object is a secondary particle, it is less likely to agglomerate and grow, so that the oxygen storage capacity is largely prevented from decreasing.

    Moreover, since the CeZr-based composite oxide particles are supported on the secondary particles in the form of small primary particles, the specific surface area is larger than when the composite oxide is large secondary particles. , Oxygen storage / release efficiency is high. When this CeZr-based composite oxide particle is used for a three-way catalyst that repeats an oxygen-excess state (lean state) and an oxygen-deficient state (rich state), it stores oxygen in the lean state and releases oxygen in the rich state. However, it has an “oxygen exchange reaction (oxygen substitution reaction)” that releases active oxygen from the inside of the particle while incorporating oxygen into the particle even in a lean state (Japanese Patent Application Laid-Open No. 2007-190460 by the present applicant). No. publication). Therefore, even in an oxygen-excess gas atmosphere, the composite oxide particles release active oxygen due to a change in the valence of Ce ions, which is advantageous for promoting the oxidation of HC and CO and promoting the combustion of particulates.

In addition, when a catalyst metal is supported on the catalyst material according to the present invention, the catalyst metal is not only supported on the CeZr-based composite oxide particles, but also can be viewed between adjacent CeZr-based composite oxide particles. Also supported on alumina particles. Therefore, the activated alumina particles having a large specific surface area effectively function as a support material for supporting the catalyst metal in a highly dispersed state. The catalyst metal supported on the activated alumina particles is used to oxidize HC and CO in the exhaust gas, and NO. Can be oxidized to NO ₂ . Moreover, the heat generated by the oxidation reaction of the exhaust gas component promotes the combustion of the particulates, and the NO ₂ becomes an oxidizing agent that efficiently burns the particulates. In addition, the catalytic metal effectively works to promote oxygen absorption / release in the composite oxide particles, and the active oxygen released from the composite oxide particles is used for the oxidation of HC and CO by the catalyst metal and the combustion of particulates. It will be used efficiently.

The primary particles of the CeZr-based composite oxide preferably contain CeO _{2 at} a ratio of 15 mol% to 60 mol%. Thereby, high flammability of particulates can be obtained while improving HC purifying properties and CO purifying properties at low temperatures. A more preferable CeO ₂ ratio is 20 mol% or more and 55 mol% or less, and further preferably 20 mol% or more and 45 mol% or less.

    The ratio of the primary particles of the CeZr composite oxide to the total amount of the primary particles of the activated alumina and the primary particles of the CeZr composite oxide is preferably 30% by mass or more and 90% by mass or less. Thereby, high flammability of particulates can be obtained while improving HC purifying properties and CO purifying properties at low temperatures. A more preferable ratio of the composite oxide particles is 35% by mass or more and 75% by mass or less, and further preferably 35% by mass or more and 50% by mass or less.

The secondary particles may be formed by agglomeration of only the primary particles of activated alumina, but the primary particles of a Zr-based composite oxide having oxygen ion conductivity containing Zr and rare earth metal M other than Ce. And primary particles of the activated alumina may be mixed with each other and agglomerated. In this case, ZrO ₂ the primary particles of the Zr-based composite oxide is contained in an amount of less 55 mol% or more 75 mol%, the primary particles of the CeZr-based mixed oxide is CeO ₂ is 45 mol% or less than 20 mol% It is preferable that it is contained in a proportion. Moreover, activated alumina may contain about ₃ to 6% by mass of La ₂ O _{3 in} order to increase its heat resistance.

    As the rare earth metal M contained in the Zr-based composite oxide particles, Nd, La, Pr, Sm, Gd, Y and the like can be adopted. Among them, at least one selected from La and Pr and Nd and Adopting a combination of these is preferable in terms of enhancing exhaust gas purification and particulate combustibility.

    When the exhaust gas component purification catalyst material is used in a particulate filter, a catalyst layer is formed on the exhaust gas passage wall surface of the filter body that collects particulates discharged from the engine, and the exhaust gas component purification catalyst is formed on the catalyst layer. The material may be included. Thereby, the particulates deposited on the filter body can be efficiently burned and removed while purifying HC and CO in the exhaust gas.

In that case, it is preferable to employ Pt as the catalyst metal. That is, when the supported Pt on activated alumina particles, be advantageous to the oxidation of NO to NO ₂ in the exhaust gas, the NO ₂ can be efficiently burn the particulates as an oxidizing agent.

As described above, according to the present invention, primary particles of CeZr-based composite oxide are dispersed and supported on the surfaces of secondary particles containing activated alumina particles as primary particles and aggregated with the primary particles. since the primary particles of the CeZr-based mixed oxide CeO ₂ is contained in an amount of less 15 mol% or more 60 mol%, with oxygen storage performance of the composite oxide particles is increased to improve the heat resistance, Patti This is advantageous for promoting the combustion of curates and for promoting the oxidative purification of HC and CO.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

In FIG. 1, reference numeral 1 denotes a particulate filter (hereinafter simply referred to as “filter”) disposed in an exhaust gas passage 11 of an engine. In the exhaust gas passage 11 on the upstream side of the exhaust gas flow from the filter 1, an oxidation catalyst (not shown) in which a catalytic metal typified by Pt, Pd or the like is supported on a support material such as activated alumina can be disposed. When such an oxidation catalyst is arranged on the upstream side of the filter 1, HC and CO in the exhaust gas are oxidized by the oxidation catalyst, and the temperature of the exhaust gas flowing into the filter 1 is increased by the oxidation combustion heat. Further, NO is oxidized to NO _2, the NO ₂ is to be supplied as an oxidizing agent for burning particulates to the filter 1.

    As schematically shown in FIGS. 2 and 3, the filter 1 has a honeycomb structure and includes a large number of exhaust gas passages 2 and 3 extending in parallel with each other. That is, in the filter 1, the exhaust gas inflow passage 2 whose downstream end is closed by the plug 4 and the exhaust gas outflow passage 3 whose upstream end is closed by the plug 4 are alternately provided. Is separated by a thin partition wall 5. In FIG. 2, the hatched portion indicates the plug 4 at the upstream end of the exhaust gas outflow passage 3.

In the filter 1, the filter body including the partition wall 5 is formed of an inorganic porous material such as cordierite, SiC, Si ₃ N ₄ , sialon, and the exhaust gas flowing into the exhaust gas inflow passage 2 is indicated by an arrow in FIG. As shown in Fig. 5, the gas flows out through the surrounding partition wall 5 into the adjacent exhaust gas outflow passage 3. That is, as shown in FIG. 4, the partition wall 5 has fine pores (exhaust gas passages) 6 that connect the exhaust gas inflow passage 2 and the exhaust gas outflow passage 3, and the exhaust gas passes through the pores 6. The particulates are trapped and deposited mainly on the wall surfaces of the exhaust gas inflow passage 2 and the pores 6.

    A catalyst layer 7 is formed on the wall surface of the exhaust gas passage (exhaust gas inflow path 2, exhaust gas outflow path 3 and pore 6) of the filter body of the filter 1. It is not always necessary to form a catalyst layer on the wall surface of the exhaust gas outflow passage 3.

[Embodiment 1]
A feature of this embodiment is that the catalyst layer 7 contains catalyst particles (catalyst material) schematically shown in FIG. That is, the catalyst particles are formed on the surface of secondary particles formed by agglomeration of primary particles of active alumina (white circle particles; Al ₂ O ₃ ), and at least one rare earth of Ce, Zr, Nd, and Pr. Primary particles of CeZr-based composite oxide containing particles R (particles with parallel oblique lines; CeZrRO) are dispersed and supported, and primary particles of activated alumina (Al ₂ O ₃ ) and CeZr-based composite oxide Each primary particle (CeZrRO) carries Pt (represented by a black circle) as a catalyst metal. The average particle size of primary particles of activated alumina is 1 nm to 100 nm (1 nm to 100 nm), the average particle size of secondary particles is 200 nm to 500 nm, and the average particle size of primary particles of CeZr-based composite oxide is 5 nm to 100 nm.

<Preparation method of catalyst material>
The exhaust gas component purification catalyst material can be prepared by the following method.

-Production of activated alumina particle precursor-
A raw material solution containing Al ions and La ions is prepared. Aluminum nitrate nonahydrate can be used as the Al source, and lanthanum nitrate hexahydrate can be used as the La source. A predetermined amount of each of the Al source and La source and water are mixed to obtain a raw material solution (acidic).

    A basic solution is added to and mixed with the raw material solution to produce precipitated particles of composite hydroxides of Al and La, which are precursors of activated alumina primary particles. In this case, after stirring the raw material solution at room temperature for about 1 hour, an aqueous ammonia having a concentration of, for example, about 7% may be added thereto as a basic solution. Other basic solutions such as aqueous caustic soda can also be employed.

-Washing and dehydration-
The solution containing the precipitate of the activated alumina particle precursor is centrifuged to remove the supernatant. The water washing and dehydration operation of adding ion-exchanged water to the precipitated dehydrated product from which the supernatant has been removed, stirring, and re-centrifuged (dehydrated) is repeated as many times as necessary. The excess basic solution is removed by the washing / dehydrating operation.

-Drying and firing-
The precipitate dehydrated product is dried, fired and pulverized. Drying can be performed, for example, by holding at a temperature of about 100 ° C. to 250 ° C. for a predetermined time in an air atmosphere. Firing can be performed, for example, by holding at a temperature of about 400 ° C. to 600 ° C. for several hours in an air atmosphere. Thereby, a powder of secondary particles formed by agglomerating primary particles of activated alumina containing La ₂ O ₃ is obtained.

-Generation of CeZr-based composite oxide particle precursors-
A solution is prepared by dispersing the powder of the secondary particles in an acidic solution containing Ce ions, Zr ions, and ions of at least one rare earth metal R of Nd and Pr. Cerium (III) nitrate hexahydrate can be used as the Ce source, and zirconium oxynitrate dihydrate can be used as the Zr source. As the R source, that is, the Nd source, neodymium nitrate can be used, and as the Pr source, praseodymium nitrate can be used. A predetermined amount of each of the Ce source, the Zr source, and the R source is mixed with the secondary particle powder and water.

    By adding and mixing a basic solution to the solution, a precipitate of Ce, Zr and R composite hydroxides, which are precursors of CeZr-based composite oxide primary particles, is deposited on the surface of the secondary particles. In this case, after stirring the said solution at room temperature for about 1 hour, ammonia water with a density | concentration of about 7% should just be added to this as a basic solution. Other basic solutions such as aqueous caustic soda can also be employed.

-Washing and dehydration-
The solution obtained by precipitating the CeZr-based composite oxide particle precursor on the surface of the secondary particles is centrifuged to remove the supernatant. After removing the supernatant, the water washing / dehydration operation of adding ion-exchanged water, stirring, and re-centrifuged (dehydrated) is repeated as many times as necessary. The excess basic solution is removed by the washing / dehydrating operation.

-Drying and firing-
The secondary particles on which the precipitation of the CeZr-based composite oxide particle precursor is deposited on the surface are dried, fired and pulverized. Drying can be performed, for example, by holding at a temperature of about 100 ° C. to 250 ° C. for a predetermined time in an air atmosphere. Firing can be performed, for example, by holding at a temperature of about 400 ° C. to 600 ° C. for several hours in an air atmosphere. As described above, the support material powder in which the primary particles of the CeZr-based composite oxide are dispersed and supported on the surface of the secondary particles can be obtained.

-Catalytic metal support-
A catalyst metal solution containing catalyst metal ions is added to and mixed with the obtained support material powder, evaporated to dryness, and then pulverized. Thereby, the catalyst material which consists of a catalyst particle shown in FIG. 5 is obtained. As the catalytic metal solution, a noble metal solution such as a dinitrodiamine platinum nitric acid solution or a palladium nitrate aqueous solution can be employed. The support material powder may be impregnated with the catalyst metal solution, dried and fired.

    Hereinafter, preferred compositions of the CeZr-based composite oxide particles and catalyst particles will be described based on a carbon combustion performance test and an exhaust gas (HC, CO) purification performance test using carbon as a particulate.

<About CeZr-based composite oxide particles>
-Preparation of test material-
Various composite oxide powders were prepared by changing the kind and blending ratio of the rare earth metal R in the CeZr composite oxide (CeZrRO). The molar ratio of CeO ₂ and ZrO ₂ was 1: 3. Each composite oxide powder is mixed with dinitrodiamineplatinum nitrate solution and ion-exchanged water, evaporated to dryness, dried sufficiently, and then fired at 500 ° C for 2 hours (in air) to support Pt. Each catalyst material was prepared. However, these catalyst materials do not contain activated alumina.

Each obtained catalyst material was mixed with a binder and ion-exchanged water to form a slurry, and a SiC filter carrier (filter body, capacity: 25 mL, cell wall thickness: 12 mil (304.8 × 10 ⁻³ mm), 300 cpsi ( After coating to 300 cells) per square inch (635.16 mm ² ), drying and firing for 2 hours at 500 ° C. in an air atmosphere, each test material (with catalyst) A particulate filter) was obtained. The amount of CeZr-based composite oxide powder supported per liter of filter was 50 g / L, and the amount of Pt supported was 0.5 g / L. Then, each sample material was subjected to a thermal aging treatment in which it was kept at a temperature of 800 ° C. for 24 hours in an air atmosphere.

    Next, 10 mL of ion-exchanged water was added to an amount of carbon (carbon black) equivalent to 10 g per liter of filter, and the carbon was sufficiently dispersed in water by stirring for 5 minutes using a stirrer. At the same time as immersing one end face of each specimen in this carbon dispersion, suction was performed from the other end face by an aspirator. Moisture that could not be removed by this suction was removed by air blowing from the one end face, and then the specimen was placed in a dryer and kept at a temperature of 150 ° C. for 2 hours for drying. Thereby, carbon was deposited on the exhaust gas passage wall surface of the test material filter.

-Carbon combustion performance test-
The test material was attached to the fixed bed simulated gas flow reactor, and the simulated exhaust gas (O ₂ ; 10%, NO; 300 ppm, H ₂ O; 10%, remaining N ₂ ) was passed through the test material at a space velocity of 80000 / h. The sample gas inlet gas temperature was increased at a rate of 15 ° C./min, and the carbon combustion rate when the temperature reached 590 ° C. was measured. In this case, the carbon burning rate was calculated by the following equation based on the amount of CO and CO ₂ generated by burning carbon.
Carbon burning rate (g / hr)
= {Gas flow rate (L / hr) x [(CO + CO ₂ ) concentration (ppm) / (1 x 10 ⁶ )]} x 12 (g / mol) /22.4 (L / mol)

    The results are shown in FIG. 6 represents the ratio (mol%) of the oxide RO of the rare earth metal R in the CeZr-based composite oxide.

According to the figure, in the case of Pr, a relatively large carbon burning rate is obtained when the ratio of the oxide is a small amount of 0.3 mol% or more and 2 mol% or less, and other rare earth metals Nd, La and Y In this case, it can be seen that a relatively large carbon burning rate can be obtained when the ratio as an oxide is 1 mol% or more and 7 mol% or less or 6 mol% or less. Of the four types of rare earth metals, Nd or Pr is most advantageous for improving the carbon combustibility. The Nd ₂ O ₃ ratio is 4 mol%, and the Pr ₂ O ₃ ratio is 1 It can be said that it is preferable to make it 4 mol%.

<Preferred composition of catalyst particles>
-Preparation of test material-
According to the catalyst material preparation method described above, the CeO ₂ ratio in the CeZr-based composite oxide particles (mol% of CeO ₂ / CeZrRO), and the activated alumina secondary particles (La ₂ O ₃ ratio; 5 mass%) and the CeZr system Each catalyst material of the Example from which the ratio (henceforth "CeZrRO ratio") of this CeZr type complex oxide particle which occupies for the total amount with complex oxide particle differs was prepared. Nd was adopted as the rare earth metal R of the CeZrR composite oxide particles, and the Nd ₂ O ₃ ratio was fixed at 4 mol%. Further, the evaporation to dryness method was adopted for supporting the catalyst metal Pt.

Further, as a comparative example catalyst material, CeZr-based composite oxide secondary particles (Nd ₂ O ₃ ratio; 4 mol%) having different CeO ₂ ratios were prepared by a coprecipitation method, which was also prepared by the coprecipitation method. It was physically mixed with the contained activated alumina secondary particles (La ₂ O ₃ ratio; 5 mol%) at an appropriate ratio to obtain various support material powders, and these were supported with Pt by evaporation to dryness. The secondary particles of the CeZr-based composite oxide were obtained by obtaining primary particle precursors by coprecipitation and then dispersing and supporting the primary particles of the CeZr-based composite oxide on the surface of the active alumina secondary particles. It is prepared by washing with water, drying and firing under the same conditions as in the case, and then pulverizing.

    By coating the catalyst materials of Examples and Comparative Examples on SiC filter carriers (capacity: 25 mL, cell wall thickness: 12 mil, cell number: 300 cpsi) according to the preparation method of the test material described above, each sample was prepared. A sample (particulate filter with catalyst) was obtained. The amount of catalyst material supported per liter of filter was 50 g / L, and the amount of Pt supported was 1.0 g / L. Subsequently, each sample material was subjected to a heat aging treatment in which it was kept at a temperature of 800 ° C. for 24 hours in an air atmosphere.

-Evaluation of carbon combustion performance-
About each test material of the said Example and a comparative example, after depositing 10 g of carbon (carbon black) per 1 L of filter on the wall surface of the exhaust gas passage, the carbon combustion rate at a temperature of 590 ° C. was determined by the above-mentioned carbon combustion performance test. It was measured. Table 1 shows the results of the examples and Table 2 shows the results of the comparative examples.

Below, each Example and each comparative example of Table 1 and Table 2 are specified by the combination of the number (number) given to each CeO ₂ ratio and the symbol (alphabet) given to CeZrRO ratio (for example, CeO _{An example in which the 2} ratio is 20 mol% (number 2) and the CeZrRO ratio is 50 mass% (symbol c) is referred to as “Example 2c”). This also applies to Tables 4 to 9 described later.

When Examples (Table 1) and Comparative Examples (Table 2) are compared, when the CeO ₂ ratio is 20 mol%, 45 mol%, and 60 mol%, respectively, there is an exception (CeO ₂ ratio is 45 mol% and CeZrRO ratio). The carbon burning rate is higher in the example than in the comparative example. Particularly in Example 3b (CeO ₂ ratio = 45 mol%, CeZrRO ratio = 35% by mass), the carbon burning rate is increased.

    This result shows that in the case of the example, the CeZr-based composite oxide is dispersed and supported on the surface of the activated alumina secondary particles in the form of primary particles having a small particle size. This is considered to be due to the increase in the release amount and the CeZr-based composite oxide that is difficult to aggregate due to heat, that is, the heat resistance of the catalyst material is increased.

Therefore, the carbon combustion rates of Examples 1b, 2b, 3b, 4b, and 5b and Comparative Examples 1b, 2b, 3b, 4b, and 5b in which the CeO ₂ ratio was changed while fixing the CeZrRO ratio to 35% by mass were graphed. (FIG. 7). In addition, the carbon combustion rates of Examples 3a to 3e and Comparative Examples 3a to 3e in which the CeZrRO ratio was changed while fixing the CeO ₂ ratio to 45 mol% were graphed (FIG. 8).

According to FIG. 7, the carbon burning rate when the CeO ₂ ratio is 15 mol% or more and 60 mol% or less is higher in the example than in the comparative example, and even when the CeO ₂ ratio is 15 mol%, Is larger than the comparative example. Therefore, it can be said that the CeO ₂ ratio is preferably 15 mol% or more and 60 mol% or less. A more preferable CeO ₂ ratio is 20 mol% or more and 55 mol% or less, and further preferably 20 mol% or more and 45 mol% or less.

    According to FIG. 8, the carbon burning rate when the CeZrRO ratio is 35% by mass or more and 90% by mass or less is higher in the example than in the comparative example, and also when the CeZrRO ratio is 30% by mass. Is expected to be larger than the comparative example. Therefore, it can be said that the CeZrRO ratio is preferably 30% by mass or more and 90% by mass or less. A more preferable CeZrRO ratio is 35 to 75% by mass, and further preferably 35 to 50% by mass.

-Evaluation of light-off characteristics of exhaust gas purification-
Unlike the case of the above-described carbon combustion performance test, the light-off characteristics regarding the purification of HC and CO in the exhaust gas were examined for each of the test materials of the above Examples and Comparative Examples without depositing carbon black. That is, each test material was set in a simulated gas flow reactor, and simulated exhaust gas (O ₂ ; 10%, H ₂ O; 10%, NO; 100 ppm, C ₃ H ₆ ; 200 ppm C, CO; 400 ppm, remaining N ₂ ) Was passed through the specimen at a space velocity of 50000 / h, and the specimen inlet gas temperature was increased at a rate of 15 ° C./min. Then, when the concentration of each component (HC, CO) of the gas detected downstream of the sample material becomes half of the concentration of each component (HC, CO) of the gas flowing into the sample material (that is, the purification rate is 50). The gas inlet gas temperature T50 (° C.) at the time when the sample gas was% was obtained. Table 3 shows the results of the examples and Table 4 shows the results of the comparative examples.

According to Tables 3 and 4, when the CeO ₂ ratio is 45 mol%, the light-off temperature of the example is lower than that of the comparative example at any CeZrRO ratio. When the CeZrRO ratio is 35% by mass, there are exceptions (when the CeO ₂ ratio is small and large), but the light-off temperature of the example is generally lower than that of the comparative example. This result is also considered to be due to the increased amount of oxygen occlusion / release and the higher heat resistance in the example than in the comparative example.

FIG. 9 is a graph of light-off temperatures of Examples 1b, 2b, 3b, 4b, and 5b and Comparative Examples 1b, 2b, 3b, 4b, and 5b in which the CeO ₂ ratio was changed while fixing the CeZrRO ratio to 35% by mass. FIG. 10 shows graphs of light-off temperatures of Examples 3a to 3e and Comparative Examples 3a to 3e, in which the CeO ₂ ratio was fixed at 45 mol% and the CeZrRO ratio was changed.

According to FIG. 9, it can be seen that for any light-off temperature of HC and CO, when the CeO ₂ ratio is 15 mol% or more and 60 mol% or less, the example is the same as or lower than the comparative example. In particular, it can be seen that the light-off temperature is low at 20 mol% or more and 45 mol% or less.

    According to FIG. 10, the light-off temperature when the CeZrRO ratio is 25% by mass or more and 90% by mass or less is lower in the example than in the comparative example, and even when the CeZrRO ratio is 20% by mass. The example is expected to be lower than the comparative example. In particular, in the range of 25% by mass to 75% by mass, it can be seen that the examples have a low light-off temperature and a high low-temperature activity of the catalyst.

[Embodiment 2]
This embodiment is characterized in that secondary particles supporting CeZr-based composite oxide particles are formed of primary particles of activated alumina and primary particles of Zr-based composite oxide, and other structures of catalyst particles. The characteristic features are the same as those of the first embodiment. In this case, primary particles of activated alumina and primary particles of Zr-based composite oxide having oxygen ion conductivity are mixed and aggregated to form secondary particles. The catalyst metal is supported not only on the primary particles of CeZr-based composite oxide and primary particles of activated alumina but also on the primary particles of Zr-based composite oxide. The average particle size of the primary particles of the Zr-based composite oxide is 5 nm to 50 nm.

    Zr-based composite oxide particles contain Zr and rare earth metal M other than Ce. As this rare earth metal M, Nd, La, Pr, Sm, Gd, Y and the like can be adopted, and among them, it is a particulate to employ at least one selected from La and Pr in combination with Nd. It is preferable for improving the flammability of. Hereinafter, a case (ZrNdMO) in which the Zr-based composite oxide particles contain Zr and Nd and further contain a rare earth metal M other than Ce and Nd will be described.

<Preparation method of catalyst material>
The exhaust gas component purification catalyst material of the present embodiment can be prepared by the following method.

-Preparation of activated alumina particle precursor-
By the method described in <Method for preparing catalyst material> in Embodiment 1, a solution in which a precipitate of active alumina particle precursor is generated is obtained.

-Preparation of Zr-based composite oxide particle precursor-
A raw material solution containing Zr ions, Nd ions, and ions of rare earth metal M other than Ce and Nd is prepared. As the Zr source, zirconium oxynitrate dihydrate can be used, and as the Nd source, neodymium nitrate can be used. As the rare earth metal M source, nitrates such as La, Pr, and Y can be employed. A predetermined amount of each of these Zr source, Nd source, and M source and water are mixed to form a raw material solution (acidic).

    A basic solution is added to and mixed with the raw material solution to produce precipitated particles of Zr, Nd, and M composite hydroxides, which are precursors of Zr-based composite oxide primary particles. In this case, after stirring the raw material solution at room temperature for about 1 hour, an aqueous ammonia having a concentration of, for example, about 7% may be added thereto as a basic solution. Other basic solutions such as aqueous caustic soda can also be employed.

-Mixing of activated alumina particle precursor and Zr-based composite oxide particle precursor-
The activated alumina particle precursor obtained in each of the above steps and the Zr-based composite oxide particle precursor are mixed. That is, a solution containing the activated alumina particle precursor precipitate and a solution containing the Zr-based composite oxide particle precursor precipitate are mixed. At that time, the pH of each solution is adjusted to be the same.

-Washing and dehydration-
The mixed solution containing the precipitate of the active alumina particle precursor and the Zr-based composite oxide particle precursor is centrifuged to remove the supernatant. The water washing and dehydration operation of adding ion-exchanged water to the precipitated dehydrated product from which the supernatant has been removed, stirring, and re-centrifuged (dehydrated) is repeated as many times as necessary. The excess basic solution is removed by the washing / dehydrating operation.

-Drying and firing-
The precipitate dehydrated product is dried, fired and pulverized. Drying can be performed, for example, by holding at a temperature of about 100 ° C. to 250 ° C. for a predetermined time in an air atmosphere. Moreover, baking can be performed by hold | maintaining at the temperature of about 400 to 600 degreeC for several hours, for example in an atmospheric condition. As a result, a powder of secondary particles in which the primary particles of activated alumina and the primary particles of the Zr-based composite oxide are mixed and aggregated is obtained.

-Supporting CeZr-based composite oxide particles-
As in the first embodiment, a raw material solution is prepared by dispersing the secondary particle powder in an acidic solution containing Ce ions, Zr ions, and ions of at least one rare earth metal R of Nd and Pr. Then, a basic solution is added to and mixed with this to precipitate the CeZr-based composite oxide particle precursor on the surface of the secondary particles. Thus, a support material powder in which the primary particles of CeZr-based composite oxide are dispersed and supported on the surface of the secondary particles is obtained by sequentially performing the steps of washing and dehydration and the steps of drying and firing.

-Catalytic metal support-
A catalyst metal solution containing catalyst metal ions is added to and mixed with the obtained support material powder, evaporated to dryness, and then pulverized. Thereby, the catalyst material which concerns on this embodiment is obtained. As the catalytic metal solution, a noble metal solution such as a dinitrodiamine platinum nitric acid solution or a palladium nitrate aqueous solution can be employed. The support material powder may be impregnated with the catalyst metal solution, dried and fired.

    Hereinafter, preferred compositions of the Zr-based composite oxide particles and catalyst particles will be described based on a carbon combustion performance test and an exhaust gas purification performance test.

<About Zr-based complex oxide particles>
-Preparation of test material-
In order to formulate a preferred composition of the Zr-based composite oxide, La, Pr and Y are used as the other rare earth metal M, and the compounding ratio of the oxides of Nd ₂ O ₃ and M is Various different complex oxide powders were prepared. Each composite oxide powder is mixed with dinitrodiamineplatinum nitrate solution and ion-exchanged water, evaporated to dryness, dried sufficiently, and then fired at 500 ° C for 2 hours (in air) to support Pt. Each catalyst material was prepared. However, these catalyst materials do not contain activated alumina.

    Each obtained catalyst material was mixed with a binder and ion-exchanged water to form a slurry, which was coated on a SiC filter carrier (capacity: 25 mL, cell wall thickness: 16 mil, number of cells: 178 cpsi), dried, and then in the atmosphere Each sample material (particulate filter with a catalyst) was obtained by carrying out baking for 2 hours at a temperature of 500 ° C. The supported amount of Zr-based composite oxide powder per liter of filter was 50 g / L, and the supported amount of Pt was 0.5 g / L. Then, each sample material was subjected to a thermal aging treatment in which it was kept at a temperature of 800 ° C. for 24 hours in an air atmosphere.

    Next, 10 g of carbon (carbon black) per liter of filter was deposited on the wall surface of the exhaust gas passage, and then the carbon combustion rate at a temperature of 590 ° C. was measured and the amount of CO generated was determined by the above-described carbon combustion performance test. The results are shown in Table 5.

    Specimens 5, 12, and 21 combining La, Pr, or Y and Nd have a higher carbon burning rate than specimens 3 and 4 that do not contain Nd, so Nd is essential. Can be said to be preferable. However, in the case where only Nd is used as the rare earth metal as in the test materials 1 and 2, the carbon combustion rate does not increase even if the amount of Nd increases, so La, Pr or Y and Nd can be combined. It can be said that it is preferable.

    In cases where the ratio of rare earth metal M is small (samples 7, 14, 22 or specimens 8, 15, 23), when La, Pr or Y is compared, it is better to use La as the rare earth metal M for carbon combustion. It can be said that it is advantageous in increasing the speed. On the other hand, in the case where the ratio of the rare earth metal M is large (the specimens 6 and 13, or the specimens 11, 20, and 25), when La, Pr, or Y is compared, it is better to use Pr as the rare earth metal M. It can be said that it is advantageous in increasing the burning rate.

Although there are exceptions, basically, increasing the ratio of the total amount of both Nd and M oxides increases the carbon burning rate. However, as can be seen from the test materials 16 to 20, when the total amount is increased to increase the carbon combustion rate, the amount of CO generated due to incomplete combustion of carbon tends to increase. Therefore, in order to increase the combustibility of the particulates, it is preferable to increase the ratio of the total amount. However, in order to suppress an increase in the amount of CO generated, the ratio of the total amount is set to less than 45 mol% (the ZrNd The ZrO ₂ ratio of the system composite oxide particles is preferably 55 mol% or more), and more preferably less than 40 mol% (the ZrO ₂ ratio is 60 mol% or more). Further, when looking at the test materials 16 to 20, when the ratio of the oxide M ₂ O ₃ of the rare earth metal M increases, the amount of CO generated tends to increase, so the M ₂ O ₃ ratio is 20 mol% or less. Is preferred.

    On the other hand, the ratio of the total amount can be 10 mol% or more. However, when the ratio exceeds 20 mol%, a large carbon combustion rate is generally obtained. Therefore, the ratio of the total amount is set to 20 mol in order to improve the combustibility of the particulates. % Can be said to be preferable. In particular, it is preferable to increase the ratio of Nd or Pr so that the ratio of the total amount is 20 mol% or more.

FIG. 11 shows a test in which a SiC filter carrier having a cell wall thickness and a cell number different from those of the previous case is coated with a Zr-based composite oxide (containing Nd) using Pr or La as the rare earth metal M. The result of having measured the carbon burning rate in 590 degreeC on the same conditions as the previous about a material is shown. However, it can be seen from Table 1 that the Nd ₂ O ₃ ratio is 6 mol% or more and 18 mol% or less, and good results are shown. Therefore, the Nd ₂ O ₃ ratio was fixed to 12 mol%. The filter body has a capacity of 25 mL, a cell wall thickness of 12 mil, and a cell count of 300 cpsi. Further, as in the previous case, the loading amount of the ZrNd-based composite oxide powder per 1 L of the filter was 50 g / L, the Pt loading amount was 0.5 g / L, and each test material was 800 ° C. in the air atmosphere. A thermal aging treatment was carried out at a temperature for 24 hours.

According to the figure, it is preferable to employ Pr as the rare earth metal M and to make the Pr ₂ O ₃ ratio 6 mol% or more in order to increase the carbon combustion rate. In addition, when La is used as the rare earth metal M, the carbon combustion rate reaches a peak when the La ₂ O ₃ ratio is 6 mol%, and when the La ₂ O ₃ ratio approaches 20 mol%, there is no significant difference from the addition of no La. The La ₂ O ₃ ratio is preferably 20 mol% or less.

<CeO ₂ ratio of CeZr-based composite oxide and ZrO ₂ ratio of Zr-based composite oxide>
-Preparation of test material-
The ratio of the Zr-based composite oxide containing CeAr and the active alumina and Nd to CeZr-based composite oxide is fixed to Al ₂ O ₃ : ZrNdMO: CeZrRO = 66: 22: 12 (mass ratio) by the above-described catalyst material preparation method. A plurality of examples of catalyst materials were prepared in which the CeO ₂ ratio of the CeZr-based composite oxide and the ZrO ₂ ratio of the Zr-based composite oxide were different. In this example catalyst material, Pt is supported on the support material powder, and the support material is a material in which the primary particles of CeZr-based composite oxide are dispersed and supported on the surface of the secondary particles. Is formed by mixing activated alumina particles and Zr-based composite oxide particles.

On the other hand, as a comparative example, similarly, Al ₂ O ₃ : ZrNdMO: CeZrRO = 66: 22: 12 was fixed, and the CeOr composite oxide was different in CeO ₂ ratio and Zr composite oxide ZrO ₂ ratio. A comparative catalyst material was prepared. This catalyst material is obtained by supporting Pt on a support material powder obtained by physically mixing activated alumina secondary particles, CeZr-based composite oxide secondary particles, and Zr-based composite oxide secondary particles.

Each sample material of Examples and Comparative Examples is supported by supporting each of the catalyst materials of the above Examples and Comparative Examples with a filter carrier made of SiC (filter body, capacity: 25 mL, cell wall thickness: 12 mil, number of cells: 300 cpsi). (Catalyzed particulate filter) was obtained. In both Examples and Comparative Examples, the amount of catalyst material supported per liter of filter was 50 g / L, the amount of Pt supported was 1.0 g / L, and the activated alumina had a La ₂ O ₃ ratio of 5 mol%. The CeZr-based composite oxide employs Nd as the rare earth metal R, the Nd ₂ O ₃ ratio thereof is 4 mol%, and the Zr-based composite oxide containing Nd employs Pr as the rare earth metal M, and the Pr _{The 2} O ₃ ratio was set to 12 mol%.

-Evaluation of carbon combustion performance-
After performing the above-mentioned thermal aging treatment and carbon deposition treatment on each sample material of the example and the comparative example, the carbon combustion rate at a temperature of 590 ° C. was measured by the above-described carbon combustion performance test. The results of Examples are shown in Table 6, and the results of Comparative Examples are shown in Table 7.

In this embodiment of the second embodiment, the weight ratio because it is _{"Al 2 O 3: ZrNdMO: CeZrRO} = 66:: 22 12 ", the mass ratio of _{CeZrRO / (Al 2 O 3 +} CeZrRO) is 15 wt% . On the other hand, among the examples of Embodiment 1 shown in Table 1, the smallest CeZrRO ratio is 25% by mass. Therefore, although simple comparison is not possible, in the case of Embodiment 1, when the CeZrRO ratio is 35% by mass and the ratio is small, the carbon combustion rate tends to decrease. Even at 35% by mass of the peak, the carbon combustion rate The maximum value is 0.815 g / hr of Example 3b. On the other hand, in the case of the example of Embodiment 2 (Table 6), except for the case where the ZrO ₂ ratio is 90 mol%, the carbon burning rate in each of the other examples is larger than that in the case of Embodiment 1. It has become. This is the effect of the Zr-based composite oxide primary particles having oxygen ion conductivity contained in the secondary particles of the second embodiment.

Thus, when Examples (Table 6) and Comparative Examples (Table 7) are compared, the CeO ₂ ratio of the CeZr-based composite oxide is 20 mol% or more and 45 mol% or less, and the ZrO ₂ ratio of the ZrNd-based composite oxide. Is 55 mol% or more and 75 mol% or less, the example shows better results than the comparative example. In the range of the CeO ₂ ratio and the ZrO ₂ ratio, a combination of secondary particles in which activated alumina particles and ZrNd-based composite oxide particles are mixed with primary particles of CeZr-based composite oxide increases the carbon burning rate. It can be said that the effective point is a specific phenomenon.

-Evaluation of light-off characteristics of exhaust gas purification-
Measure the light-off temperature for HC and CO purification by the above-mentioned light-off performance evaluation test without performing the carbon deposition treatment after performing the above-mentioned thermal aging treatment on each sample material of the above-mentioned examples and comparative examples. did. The results of Examples are shown in Table 8, and the results of Comparative Examples are shown in Table 9.

When comparing the example of the second embodiment (Table 8) and the example of the first embodiment (Table 3), there is no significant difference in the light-off performance of exhaust gas purification, but the example of the second embodiment (Table 8). ) And the comparative example (Table 9), the CeO ₂ ratio of the CeZr-based composite oxide is 20 mol% to 45 mol% and the ZrO ₂ ratio of the ZrNd-based composite oxide is 55 mol% to 75 mol in this case as well. When it is less than or equal to%, the example shows better results than the comparative example. In the range of the CeO ₂ ratio and the ZrO ₂ ratio, the combination of the secondary particles in which the activated alumina particles and the ZrNd composite oxide particles are mixed with the primary particles of the CeZr composite oxide improves the light-off property. It can be said that the effective point is a specific phenomenon.

From the above, when the secondary particles are formed of activated alumina primary particles and Zr-based composite oxide primary particles, the CeO ₂ ratio of the CeZr-based composite oxide is set to 20 mol% or more and 45 mol% or less, and the ZrNd-based composite oxide ZrO. It can be said that the ratio of ₂ is preferably 55 mol% or more and 75 mol% or less.

<Ratio of activated alumina: CeZr composite oxide: ZrNd composite oxide>
-Preparation of test material-
According to the method for preparing the catalyst material, four examples of catalyst materials having different ratios of active alumina, ZrNd-based composite oxide, and CeZr-based composite oxide (mass ratio of Al ₂ O ₃ : ZrNdMO: CeZrRO) were prepared. . In this example catalyst material, Pt is supported on the support material powder, and the support material is a material in which the primary particles of CeZr-based composite oxide are dispersed and supported on the surface of the secondary particles. Is formed by mixing activated alumina particles and Zr-based composite oxide particles.

    On the other hand, as a comparative example, four types of catalyst materials having different ratios of activated alumina, ZrNd composite oxide, and CeZr composite oxide were prepared. This catalyst material is obtained by supporting Pt on a support material powder obtained by physically mixing activated alumina secondary particles, CeZr-based composite oxide secondary particles, and ZrNd-based composite oxide secondary particles.

    The component ratios of the four types of catalyst materials in each of the examples and comparative examples are as shown in the triangular chart of FIG. The numerical value “33” of the center point (33:33:33) in the triangular chart of FIG. 12 is strictly “33 + 1/3”, but is expressed as “33” for convenience.

Each sample material of Examples and Comparative Examples is supported by supporting each of the catalyst materials of the above Examples and Comparative Examples with a filter carrier made of SiC (filter body, capacity: 25 mL, cell wall thickness: 12 mil, number of cells: 300 cpsi). (Catalyzed particulate filter) was obtained. In both Examples and Comparative Examples, the amount of catalyst material supported per liter of filter was 50 g / L, the amount of Pt supported was 1.0 g / L, and the activated alumina had a La ₂ O ₃ ratio of 5 mol%. The CeZr-based composite oxide is CeO ₂ : ZrO ₂ : Nd ₂ O ₃ = 20: 76: 4 (molar ratio), and the ZrNd-based composite oxide is ZrO ₂ : Nd ₂ O ₃ : Pr ₂ O. ₃ = 55: 33: 12 (molar ratio).

-Evaluation of carbon combustion performance-
After performing the above-mentioned thermal aging treatment and carbon deposition treatment on each sample material of the example and the comparative example, the carbon combustion rate at a temperature of 590 ° C. was measured by the above-described carbon combustion performance test. The results are shown in Table 10 and FIG.

According to Table 10 and FIG. 13, the carbon burning speed of the example is larger than that of the comparative example at any mixing ratio. Further, the carbon burning rate of the example is the highest when the ratio of Al ₂ O ₃ : ZrNdMO: CeZrRO is (66:22:12).

-Evaluation of light-off characteristics of exhaust gas purification-
Measure the light-off temperature for HC and CO purification by the above-mentioned light-off performance evaluation test without performing the carbon deposition treatment after performing the above-mentioned thermal aging treatment on each sample material of the above-mentioned examples and comparative examples. did. The light off temperature for HC purification is shown in Table 11 and FIG. 14, and the light off temperature for CO purification is shown in Table 11 and FIG.

According to Table 11 and FIGS. 14 and 15, the light-off temperature of the example is lower than that of the comparative example at any mixing ratio. In addition, the light-off temperature of the example is the lowest when the ratio of Al ₂ O ₃ : ZrNdMO: CeZrRO is (66:22:12).

    In the above embodiment, the catalyst material according to the present invention is employed in the particulate filter. However, the catalyst material is intended to purify HC, CO and NOx, and does not aim to collect particulates. Can also be used.

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 a particulate filter typically. It is a longitudinal section showing a particulate filter typically. It is an expanded sectional view showing typically the wall which separates the exhaust-gas inflow path and exhaust-gas outflow path of a particulate filter. It is a figure which shows typically the catalyst particle which concerns on this invention. It is a graph which shows the relationship between the ratio of the rare earth metal R oxide in CeZr type complex oxide, and a carbon combustion rate. It is a graph showing the relationship between the examples and CeO ₂ ratio and carbon burning rates of CeZr-based composite oxide of Comparative Example. It is a graph which shows the relationship between the CeZrRO ratio of an Example and a comparative example, and a carbon combustion rate. Is a graph showing the relationship between the CeO ₂ ratio and the light-off temperature of the CeZr-based mixed oxide of the examples and comparative examples. It is a graph which shows the relationship between the CeZrRO ratio of an Example and a comparative example, and light-off temperature. It is a graph which shows the relationship between the ratio of the rare earth metal M oxide in Zr system complex oxide, and a carbon combustion rate. Activated alumina _{(Al 2} O 3), a triangular diagram showing the mass ratio of Zr-based composite oxide (ZrNdMO) and Ce-based composite oxide (CeZrRO). It is a graph which shows the relationship between the mass ratio of the activated alumina of a Example and a comparative example, Zr type complex oxide, and Ce type complex oxide, and a carbon combustion rate. It is a graph which shows the relationship between the mass ratio of the activated alumina of a Example and a comparative example, Zr type complex oxide, and Ce type complex oxide, and the light-off temperature of HC purification | cleaning. It is a graph which shows the relationship between the mass ratio of the activated alumina of an Example and a comparative example, Zr type complex oxide, and Ce type complex oxide, and the light-off temperature of CO purification | cleaning.

Explanation of symbols

1 Particulate filter 2 Exhaust gas inflow passage (exhaust gas passage)
3 Exhaust gas outflow passage (exhaust gas passage)
4 Plug 5 Bulkhead 6 Pore passage (exhaust gas passage)
7 Catalyst layer

Claims (5)

A CeZr-based composite oxide containing activated alumina particles as primary particles and containing Ce, Zr, and at least one rare earth metal R of Nd and Pr on the surface of secondary particles formed by aggregation of the primary particles. Primary particles are dispersed and supported,
A catalyst material for exhaust gas component purification, wherein the primary particles of the CeZr-based composite oxide contain CeO _{2 at} a ratio of 15 mol% to 60 mol%. In claim 1,
Exhaust gas, wherein the proportion of primary particles of the CeZr-based composite oxide in the total amount of primary particles of the activated alumina and the primary particles of the CeZr-based composite oxide is 30% by mass to 90% by mass Catalyst material for component purification. On the surface of secondary particles formed by agglomerating primary particles of activated alumina and primary particles of a Zr-based composite oxide containing rare earth metal M other than Zr and Ce, agglomerated with each other, Ce, Zr, and Nd And primary particles of CeZr-based composite oxide containing at least one rare earth metal R of Pr are dispersed and supported.
The primary particles of the Zr-based composite oxide contain ZrO _{2 at} a ratio of 55 mol% to 75 mol%,
A catalyst material for exhaust gas component purification, wherein the primary particles of the CeZr-based composite oxide contain CeO _{2 in} a proportion of 20 mol% to 45 mol%. A particulate filter in which a catalyst layer is formed on an exhaust gas passage wall surface of a filter body that collects particulates discharged from an engine,
A particulate filter comprising the catalyst layer containing the exhaust gas component purifying catalyst material according to any one of claims 1 to 3. In claim 4,
The particulate filter, wherein the exhaust gas component purification catalyst material carries Pt as a catalyst metal.

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