JP5954031B2 - Particulate matter combustion catalyst - Google Patents

Description

  The present invention relates to a particulate matter combustion catalyst for burning particulate matter contained in engine exhaust gas.

  In a diesel engine vehicle, a diesel particulate filter (DPF: Diesel Particulate Filter) may be provided with a catalyst for burning particulate matter (PM) contained in exhaust gas. Also, in gasoline engine vehicles, especially in direct injection type gasoline engines, fuel near the spark plug tends to be excessively concentrated during stratified lean combustion, and smoke is likely to be generated. Removal is desired.

  On the other hand, Patent Document 1 describes using a double oxide of Zr, at least one rare earth metal excluding Ce, and a noble metal as a catalyst material for burning the particulate matter. That is, it is known that the Zr-based oxide has oxygen ion conductivity that causes oxygen ions to move from a portion having a high oxygen concentration to a portion having a low oxygen concentration to release oxygen from the particle surface. Patent Document 1 discloses that the Zr-based oxide is a double oxide of Zr, at least one rare earth metal excluding Ce, and a noble metal, thereby improving the oxygen ion conductivity, thereby forming a particulate form. Disclosing improving the flammability of a substance is disclosed.

  Patent Document 2 discloses a Zr-based complex oxide containing Zr as a main component metal element and a rare earth metal excluding Ce and Y as a particulate material combustion catalyst material supported on a DPF, and Ce as a main component. It is described that a Ce-based double oxide containing a rare earth metal or an alkaline earth metal other than Ce as a component metal element and supporting a noble metal on the double oxide is described.

JP 2007-69076 A JP 2007-54713 A

  The Zr-based double oxides described in Patent Document 1 and Patent Document 2 also show excellent performance as a catalyst material for burning particulate matter, but the present invention further improves the combustibility of the particulate matter. It is an object to provide a catalyst.

  In order to solve the above problems, the present invention employs a configuration in which Zr-based double oxide is doped with Sr as an alkaline earth metal in addition to Y or La as a rare earth metal.

That is, in one embodiment of the particulate matter combustion catalyst presented here, a catalyst layer is provided on the support substrate, and Zr and Y for burning the particulate matter contained in the exhaust gas of the engine to the catalyst layer. , Sr, a noble metal, and oxygen are provided, and in the catalyst material, Zr, Y, and Sr form a double oxide, and the main component metal element of the double oxide is Zr. It is characterized by that.

In the double oxide, tetravalent Zr which is a main component metal element is doped with divalent alkaline earth metal Sr in addition to trivalent rare earth metal Y, so that oxygen vacancies (atomic vacancies) ) Increases and oxygen ion conductivity increases. For this reason, oxygen is actively released from the surface of the double oxide particles, and the burning rate of the particulate matter is increased. That is, it is advantageous for rapid combustion removal of the particulate matter by the noble metal. In addition, since the alkaline earth metal Sr forms a basic site in the double oxide, it has a strong ability to attract NO contained in the exhaust gas. As a result, oxidation of NO to NO ₂ by the noble metal is promoted, and particulate matter can be burned by the NO ₂ .

  If Sr is supported on the surface of the Zr-based double oxide, the Sr becomes a steric hindrance (because the noble metal is covered with Sr), so that the active site of the catalyst is reduced. On the other hand, in the present invention, since Sr is doped into the Zr-based double oxide, there is no problem of the steric hindrance.

  In addition, combustion of particulate matter due to movement of oxygen ions in the double oxide inevitably involves movement of electrons. In the case of the catalyst material, the noble metal contributes to the movement of electrons, thereby promoting the movement of oxygen or oxygen ions. As a result, the release of oxygen from the double oxide becomes active, which is advantageous for the combustion of particulate matter. In addition, the oxygen exchange reaction that takes in oxygen in the exhaust gas of the double oxide and releases the internal oxygen as active oxygen is promoted by the noble metal, which is advantageous for the combustion removal of particulate matter.

  The engine may be a diesel engine or a gasoline engine. Therefore, the carrier substrate is not limited to a DPF, and may be a honeycomb carrier. Moreover, as said noble metal, it is preferable to employ | adopt 1 type, or 2 or more types from Pt, Pd, Rh, etc.

  The catalyst material is composed of Zr, Y, Sr, Pr, a noble metal, and oxygen, the Zr, Y, Sr, and Pr form a double oxide, and the main component metal element of the double oxide is Zr. It can be. The dope of Pr to the double oxide increases the burning rate of the particulate matter.

  In a preferred form of the catalyst material, the noble metal is post-supported on the surface of the double oxide. Such a catalyst material can be obtained by bringing the noble metal solution into contact with the double oxide and calcining. For example, by adding a basic solution to an acidic solution containing Zr ions, Y ions, and Sr ions, firing the obtained coprecipitate, mixing this with the above-mentioned noble metal solution, and evaporating to dryness. A catalyst material can be obtained.

In such a form, the highly dispersed noble metal promotes dissociative adsorption of gas-phase oxygen and spillover to the double oxide on the surface of the double oxide whose oxygen ion conductivity is increased by doping with Sr as described above. As a result, the oxygen exchange reactivity of the double oxide becomes high, which is considered to lead to an improvement in the burning rate of the particulate matter. Further, it is considered that the oxidation of NO to NO ₂ by the noble metal highly dispersed on the surface of the double oxide is promoted, and the combustion of the particulate matter by the NO ₂ is further promoted. In addition, the above-mentioned double oxide increases the electronic conductivity of the portion where the noble metal is post-supported, thereby increasing the oxygen ion conductivity of the double oxide, which also leads to an improvement in the burning rate of the particulate matter. Conceivable.

Further, another aspect of the particulate matter combustion catalyst presented here is that a catalyst layer is provided on the carrier base, and Zr and La for burning the particulate matter contained in the exhaust gas of the engine to the catalyst layer. , Sr, noble metal, and oxygen are provided, and in the catalyst material, Zr, La, and Sr form a double oxide, and the main component metal element of the double oxide is Zr. It is characterized by that.

That is, this example is a case where the rare earth metal is La. Also in this case, as in the case of Y above, the above-described double oxide has oxygen vacancies (atomic vacancies) increased due to doping with divalent Sr, resulting in high oxygen ion conductivity. The burning rate of particulate matter is increased. In addition, Sr forms a basic site in the complex oxide, so that the force to attract NO contained in the exhaust gas is increased. As a result, the oxidation of NO to NO ₂ by the noble metal is promoted, and the particulate matter can be burned by the NO ₂ .

  Even in the case where the rare earth metal is La, similarly to the case of Y, there is no problem that Sr becomes a steric hindrance and the active site decreases. Further, since the noble metal contributes to the movement of electrons in the double oxide, the movement of oxygen or oxygen ions is promoted, and further, the oxygen exchange reaction is promoted, which is advantageous for the combustion removal of the particulate matter.

  The engine may be a diesel engine or a gasoline engine. Therefore, the carrier substrate is not limited to a DPF, and may be a honeycomb carrier. Moreover, as said noble metal, it is preferable to employ | adopt 1 type, or 2 or more types from Pt, Pd, Rh, etc.

  The catalyst material is composed of Zr, La, Sr, Pr, a noble metal, and oxygen, the Zr, La, Sr, and Pr form a double oxide, and the main component metal element of the double oxide is Zr. It can be. The dope of Pr to the double oxide increases the burning rate of the particulate matter.

  In a preferred form of the catalyst material, the noble metal is post-supported on the double oxide. Such a catalyst material can be obtained by bringing the noble metal solution into contact with the double oxide and calcining. For example, by adding a basic solution to an acidic solution containing Zr ions, La ions, and Sr ions, firing the obtained coprecipitate, mixing this with the above precious metal solution, and evaporating to dryness. Can be obtained.

In such a form, as in the case of Y above, the noble metal highly dispersed on the surface of the double oxide promotes dissociative adsorption of gas phase oxygen and spillover to the double oxide, resulting in oxygen exchange reactivity of the double oxide. It is thought that this leads to an improvement in the burning rate of the particulate matter. Further, it is considered that the oxidation of NO to NO ₂ by the noble metal highly dispersed on the surface of the double oxide is promoted, and the combustion of the particulate matter by the NO ₂ is further promoted. In addition, the above-mentioned double oxide increases the electronic conductivity of the portion where the noble metal is post-supported, thereby increasing the oxygen ion conductivity of the double oxide, which also leads to an improvement in the burning rate of the particulate matter. Conceivable.

According to the present invention, the catalyst material constituting the particulate matter combustion catalyst is composed of Zr, Y (or La), Sr, noble metal and oxygen, and Zr, Y (or La) and Sr are mixed oxides. forming a, because the main component metal elements of the mixed oxide is a Zr, or consists Zr and Y (or La) and Sr and Pr and noble metal and oxygen, Sr and its Zr and Y (or La) And Pr form a double oxide, and the main component metal element of the double oxide is Zr, which is advantageous for rapid combustion removal of particulate matter.

It is a figure which shows the state which has arrange | positioned the particulate filter in the exhaust-gas channel | 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 material which concerns on embodiment. It is a graph which shows the carbon combustion rate of the Example of the case which employ | adopted Y as a rare earth metal, and a comparative example. It is a graph which shows the relationship between the Sr dope amount of the same case, and a carbon combustion rate. It is a graph which shows the carbon combustion rate of the Example of the case which employ | adopted La as a rare earth metal, and a comparative example. It is a graph which shows the relationship between the Sr dope amount of the same case, and a carbon combustion rate.

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

  The particulate matter combustion catalyst according to the present embodiment is obtained by providing a catalyst material on a particulate filter that collects particulate matter in exhaust gas of a diesel engine. Of course, the present invention can be configured such that the honeycomb carrier is provided with a catalyst material so as to be used for the combustion removal of the particulate matter contained in the exhaust gas of the direct injection type gasoline engine.

<Particulate filter structure>
FIG. 1 shows a particulate filter (hereinafter simply referred to as “filter”) 1 disposed in an exhaust gas passage 11 of a diesel 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, the oxidation catalyst oxidizes HC and CO in the exhaust gas, and the temperature of the exhaust gas flowing into the filter 1 is increased by the oxidation combustion heat so that the filter 1 By heating, the particulates can be burned off. Further, NO is oxidized to NO ₂ by the oxidation catalyst, and the NO ₂ is supplied to the filter 1 as an oxidant for burning the particulate matter.

  As schematically shown in FIGS. 2 and 3, the filter 1 has a honeycomb structure and includes a number of exhaust gas passages 2 and 3 extending in parallel with each other. That is, the filter 1 is provided with an exhaust gas inflow path 2 whose downstream end is closed by the plug 4 and an exhaust gas outflow path 3 whose upstream end is closed by the plug 4, and the exhaust gas inflow path 2 and the exhaust gas are alternately provided. The gas outflow path 3 is separated by a thin partition wall 5. In FIG. 2, hatched portions indicate the plugs 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 shown in FIG. As shown by the arrow 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 minute 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. . Particulate matter is trapped and deposited mainly in the exhaust gas inflow passage 2 and the walls of the pores 6.

  A catalyst layer 7 is formed on the wall surface forming the exhaust gas passages (exhaust gas inflow passage 2, exhaust gas outflow passage 3 and pores 6) of the filter body as the carrier substrate. It is not always necessary to form a catalyst layer on the wall surface on the exhaust gas outflow path 3 side.

  The catalyst layer 7 contains a catalyst material for burning off particulate matter deposited on the filter 1. The catalyst material contains Zr, a double oxide of Y or La as a rare earth metal, and Sr, and a noble metal, and the main component metal element of the double oxide is Zr.

  In a preferable form of the catalyst material, as schematically shown in FIG. 5, primary particles 13 (black circles) of the noble metal are added to secondary particles 12 formed by agglomerating the primary particles 11 (white circles) of the double oxide. It is supported.

<Catalyst material adopting Y as rare earth metal>
-Example 1-1
Predetermined amounts of zirconyl nitrate, yttrium nitrate and strontium nitrate were dissolved in ion-exchanged water, and these aqueous solutions were mixed. By mixing the obtained mixed solution (acidic solution) with an 8-fold diluted solution of 28% by mass ammonia water as a basic solution and neutralizing it, a coprecipitate (Zr, Y and Sr double oxide) Precursor) was obtained. The coprecipitate is centrifuged to remove the supernatant (dehydration), and ion-exchanged water is further added and stirred (water washing). The solution was removed. The co-precipitate after the final dehydration was dried in the air at a temperature of 150 ° C. for a whole day and night, pulverized, and then fired in the air at a temperature of 500 ° C. for 2 hours. As a result, powder of Zr, Y, and Sr double oxide was obtained (generation of double oxide by coprecipitation method). A catalyst material was obtained by adding a dinitrodiamine platinum nitric acid solution to the ZrYSr double oxide powder, mixing and evaporating to dryness. In this catalyst material, primary particles of Pt are post-supported on secondary particles obtained by agglomerating primary particles of a ZrYSr double oxide.

The composition of the ZrYSr double oxide is SrO: ZrO ₂ : Y ₂ O ₃ = 1.9: 86.6: 11.5 (molar ratio) in terms of oxide. That is, in this double oxide, the main component metal element is Zr, and it can be said that the double oxide of Zr and Y is doped with Sr. The ratio between the double oxide and Pt is approximately double oxide: Pt = 40: 1 (mass ratio).

  The obtained catalyst material powder was mixed with a binder and ion-exchanged water to prepare a slurry. The filter body was immersed in the slurry from the inlet end, and suction was performed by an aspirator at the outlet end. Slurry that could not be removed by this suction was removed by air blowing from the inlet end face immersed in the mixed slurry. Thereby, the catalyst layer was formed in the filter main body. And after drying this at 150 degreeC in air | atmosphere, the sample for catalyst performance evaluation which concerns on Example 1-1 was obtained by carrying out heat baking (at the temperature of 500 degreeC for 2 hours) similarly in air | atmosphere.

The filter body is silicon carbide having a diameter of 17 mm, a length of 50 mm, a cell density of 178 per square inch (about 6.45 cm ² ), and a wall thickness separating the cells of 16 mils (about 0.4 mm). A product made of SiC) was used. The amount of catalyst material supported per 1 L of filter body is 20 g / L, and the amount of Pt supported is 0.5 g / L.

-Example 1-2
Example 1 except that the composition of the double oxide is converted to oxide to be SrO: ZrO ₂ : Y ₂ O ₃ = 4.8: 83.8: 11.4 (molar ratio) In the same manner as in Example 1, a catalyst material according to Example 1-2 and a sample for evaluating catalyst performance were obtained.

-Example 1-3
Example 1 except that the composition of the double oxide is converted to oxide to be SrO: ZrO ₂ : Y ₂ O ₃ = 9.5: 79.6: 10.9 (molar ratio) In the same manner as in Example 1, a catalyst material according to Example 1-3 and a sample for evaluating catalyst performance were obtained.

-Example 1-4
A mixed oxide powder of Zr, Y, Sr, and Pr was obtained from a mixed solution obtained by dissolving zirconyl nitrate, yttrium strontium nitrate, and praseodymium nitrate in ion-exchanged water by the above-described coprecipitation method. The composition is SrO: ZrO ₂ : Y ₂ O ₃ : Pr ₆ O ₁₁ = 1.9: 78.5: 13.7: 5.9 (molar ratio) in terms of oxide. That is, it can be said that the main component metal element of this ZrYPrSr double oxide is Zr, and the double oxide of Zr, Y, and Pr is doped with Sr.

  A catalyst material according to Example 1-4 was obtained by adding a dinitrodiamine platinum nitric acid solution to the ZrYPrSr double oxide powder, mixing, and evaporating to dryness. In this catalyst material, primary particles of Pt are post-supported on secondary particles obtained by agglomerating primary particles of a ZrYPrSr double oxide. The ratio between the double oxide and Pt is roughly double oxide: Pt = 40: 1 (mass ratio).

  The catalyst material was supported on the same filter body in the same manner as in Example 1-1 to form a catalyst layer, and a catalyst performance evaluation sample according to Example 1-4 was obtained. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Example 1-5
The composition of the double oxide is converted to oxide and becomes SrO: ZrO ₂ : Y ₂ O ₃ : Pr ₆ O ₁₁ = 4.8: 76.2: 13.3: 5.7 (molar ratio). A catalyst material and a sample for evaluating catalyst performance according to Example 1-5 were obtained in the same manner as Example 1-4 except for the above.

-Example 1-6
When the composition of the double oxide is converted to oxide, it becomes SrO: ZrO ₂ : Y ₂ O ₃ : Pr ₆ O ₁₁ = 9.5: 72.4: 12.7: 5.4 (molar ratio). A catalyst material and a sample for evaluating catalyst performance according to Example 1-6 were obtained in the same manner as Example 1-4 except that the above was performed.

-Comparative Example 1-1
A double oxide powder of Zr and Y was obtained from a mixed solution in which zirconyl nitrate and yttrium nitrate were dissolved in ion-exchanged water by the above-described coprecipitation method. A catalyst material according to Comparative Example 1-1 was obtained by adding a dinitrodiamine platinum nitric acid solution to the ZrY complex oxide powder, mixing, and evaporating to dryness. This catalyst material is one in which Pt is post-supported on a ZrY double oxide (not containing an alkaline earth metal). The composition of this catalyst material excluding Pt is ZrO ₂ : Y ₂ O ₃ = 88: 12 (molar ratio) in terms of oxide, and the ratio of the total amount of components excluding Pt and Pt is approximately 40: 1 (mass ratio).

  The catalyst material powder was supported on the same filter body in the same manner as in Example 1-1 to obtain a catalyst performance evaluation sample according to Comparative Example 1-1. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Comparative Example 1-2
ZrY double oxide powder was obtained in the same manner as Comparative Example 1-1. A catalyst material according to Comparative Example 1-2 was obtained by adding a dinitrodiamine platinum nitric acid solution and a strontium acetate solution to the ZrY complex oxide powder, mixing and evaporating to dryness. This catalyst material is obtained by post-supporting Pt and Sr on a ZrY double oxide. The composition of this catalyst material excluding Pt is SrO: ZrO ₂ : Y ₂ O ₃ = 1.9: 86.6: 11.5 (molar ratio) in terms of oxide, and the total amount of components excluding Pt The ratio of Pt and Pt is approximately 40: 1 (mass ratio).

  The catalyst material powder was supported on the same filter body in the same manner as in Example 1-1 to obtain a catalyst performance evaluation sample according to Comparative Example 1-2. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Comparative Example 1-3
A double oxide powder of Zr, Y, and Pr was obtained from a mixed solution in which zirconyl nitrate, yttrium nitrate, and praseodymium nitrate were dissolved in ion-exchanged water by the above-described coprecipitation method. A catalyst material according to Comparative Example 1-3 was obtained by adding and mixing a dinitrodiamine platinum nitric acid solution to the ZrYPr double oxide powder and evaporating to dryness. This catalyst material is obtained by post-supporting Pt on a ZrYPr double oxide. The composition of this catalyst material excluding Pt is ZrO ₂ : Y ₂ O ₃ : Pr ₆ O ₁₁ = 80: 14: 6 (molar ratio) in terms of oxide, and the total amount of components excluding Pt and Pt The ratio is approximately 40: 1 (mass ratio).

  The catalyst material powder was supported on the same filter body in the same manner as in Example 1-1 to obtain a catalyst performance evaluation sample according to Comparative Example 1-3. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Comparative Example 1-4
ZrYPr double oxide powder was obtained in the same manner as Comparative Example 1-3. A catalyst material according to Comparative Example 1-4 was obtained by adding a dinitrodiamine platinum nitric acid solution and a strontium acetate solution to the ZrYPr double oxide powder, mixing and evaporating to dryness. This catalyst material is obtained by post-supporting Pt and Sr on a ZrYPr double oxide. The composition of this catalyst material excluding Pt is SrO: ZrO ₂ : Y ₂ O ₃ : Pr ₆ O ₁₁ = 1.9: 78.5: 13.7: 5.9 (molar ratio) in terms of oxide. The ratio of the total amount of components excluding Pt and Pt is approximately 40: 1 (mass ratio).

  The catalyst material powder was supported on the same filter body in the same manner as in Example 1-1 to obtain a catalyst performance evaluation sample according to Comparative Example 1-4. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

[Particulate combustion performance of catalyst materials]
In order to evaluate the particulate combustion performance of each of the catalyst materials of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4, the carbon combustion rate was measured using the catalyst performance evaluation sample. Each sample was aged at a temperature of 800 ° C. for 24 hours in the air.

  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 portion of the sample subjected to the aging treatment was immersed in the obtained slurry, and suction by an aspirator was performed from the outlet end portion. Moisture that could not be removed by this suction was removed by air blowing from the end face on the side immersed in the sample slurry. And the sample was dried by hold | maintaining at the temperature of 150 degreeC for 2 hours.

Each of the obtained samples was attached to a fixed bed type model gas flow device, and the gas temperature at the sample inlet was raised from normal temperature to 580 ° C. while N ₂ gas was allowed to flow through the sample. After the temperature stabilizes at 580 ° C., the gas composition is switched to “7.5% O ₂ +300 ppm NO + N ₂ (balance gas)” while maintaining the temperature, and the space velocity of the model gas is set to 40000 / h for the sample. Washed away. Then, by measuring the concentration of a model gas of CO and CO ₂ generated by the combustion of carbon was measured the time course of carbon combustion amount in the sample. And the carbon burning rate was calculated | required from the time required for carbon to burn 50%.

[result]
The measurement results of the carbon burning rate are shown in Table 1, FIG. 6 and FIG.

  In each of the examples in which the Zr-based double oxide is doped with Sr, the carbon burning rate is higher than that of the comparative example without Sr support or without the alkaline earth metal (group 2A). From a comparison between Comparative Example 1-1 and Comparative Example 1-2, it can be seen that when Sr is post-supported on a Zr-based double oxide, the carbon combustion rate increases. However, the carbon burning speed of Example 1-1 is higher than that of Comparative Example 1-2. From this, it can be seen that doping Sr into a Zr-based double oxide is effective in increasing the carbon combustion rate. One possible reason is that the amount of lattice oxygen released from the Zr-based double oxide is increased by doping Sr. In addition, Example 1-4 has a higher carbon combustion rate than Example 1-1. From this, it can be seen that doping Pr with a Zr-based double oxide is further advantageous in increasing the carbon combustion rate.

  Looking at Comparative Example 1-1 and Examples 1-1 to 1-3 (without Pr), as shown in FIG. 7, the carbon combustion rate increases with an increase in the Sr doping amount. However, when the amount of Sr doping becomes excessive, the carbon combustion rate tends to decrease. Also in Comparative Example 1-3 and Examples 1-4 to 1-6 (with Pr), the relationship between the Sr doping amount and the carbon combustion rate shows the same tendency as the above “without Pr”. From the relationship between the Sr doping amount and the carbon burning rate, the Sr doping amount in the above-mentioned double oxide should be 1% or more and 10% or less in terms of mol%, and moreover 1.9% or more and 6.0% or less Can be said to be preferable.

<Catalyst material adopting La as rare earth metal>
-Example 2-1
In place of yttrium nitrate, lanthanum nitrate was employed, and the other materials were obtained in the same manner as in Example 1-1 to obtain a catalyst material and a sample for evaluating catalyst performance according to Example 2-1. The composition of the ZrLaSr double oxide constituting this catalyst material is SrO: ZrO ₂ : La ₂ O ₃ = 1.9: 86.6: 11.5 (molar ratio) in terms of oxide. That is, in this double oxide, the main component metal element is Zr, and it can be said that the double oxide of Zr and La is doped with Sr. The ratio between the double oxide and Pt is approximately double oxide: Pt = 40: 1 (mass ratio). The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Example 2-2
Example 2 except that the composition of the double oxide is converted to oxide to be SrO: ZrO ₂ : La ₂ O ₃ = 4.8: 83.8: 11.4 (molar ratio) In the same manner as in Example 1, a catalyst material according to Example 2-2 and a sample for evaluating catalyst performance were obtained.

-Example 2-3
A double oxide powder of Zr, La, Sr, and Pr was obtained from a mixed solution in which zirconyl nitrate, lanthanum nitrate, strontium nitrate, and praseodymium nitrate were dissolved in ion-exchanged water by the above-described coprecipitation method. The composition is SrO: ZrO ₂ : La ₂ O ₃ : Pr ₆ O ₁₁ = 1.9: 78.5: 13.7: 5.9 (molar ratio) in terms of oxide. That is, it can be said that this ZrLaPrSr double oxide has Zr as the main component metal element, and Sr is doped in the double oxide of Zr, La and Pr.

  A catalyst material according to Example 2-3 was obtained by adding a dinitrodiamine platinum nitric acid solution to the ZrLaPrSr double oxide powder, mixing, and evaporating to dryness. In this catalyst material, primary particles of Pt are post-supported on secondary particles obtained by agglomerating primary particles of a ZrLaPrSr double oxide. The ratio between the double oxide and Pt is roughly double oxide: Pt = 40: 1 (mass ratio).

  The catalyst material was supported on the same filter body in the same manner as in Example 2-1, to form a catalyst layer, and a catalyst performance evaluation sample according to Example 2-3 was obtained. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Example 2-4-
The composition of the double oxide is converted to oxide and becomes SrO: ZrO ₂ : La ₂ O ₃ : Pr ₆ O ₁₁ = 4.8: 76.2: 13.3: 5.7 (molar ratio). A catalyst material and a sample for evaluating catalyst performance according to Example 2-4 were obtained in the same manner as in Example 2-3 except for the above.

-Example 2-5
When the composition of the double oxide is converted to oxide, it becomes SrO: ZrO ₂ : La ₂ O ₃ : Pr ₆ O ₁₁ = 9.5: 72.4: 12.7: 5.4 (molar ratio). A catalyst material and a sample for evaluating catalyst performance according to Example 2-5 were obtained in the same manner as in Example 2-3, except for the above.

-Comparative Example 2-1
A double oxide powder of Zr and La was obtained from a mixed solution in which zirconyl nitrate and lanthanum nitrate were dissolved in ion-exchanged water by the above-described coprecipitation method. A catalyst material according to Comparative Example 2-1 was obtained by adding a dinitrodiamine platinum nitric acid solution to the ZrLa complex oxide powder, mixing and evaporating to dryness. This catalyst material is obtained by post-supporting Pt on a ZrLa double oxide (not containing an alkaline earth metal). The composition of this catalyst material excluding Pt is ZrO ₂ : La ₂ O ₃ = 88: 12 (molar ratio) in terms of oxide, and the ratio of the total amount of components excluding Pt and Pt is approximately 40: 1 (mass ratio).

  The catalyst material powder was supported on the same filter body in the same manner as in Example 2-1, to obtain a catalyst performance evaluation sample according to Comparative Example 2-1. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Comparative Example 2-2
ZrLa double oxide powder was obtained in the same manner as in Comparative Example 2-1. A catalyst material according to Comparative Example 2-2 was obtained by adding a dinitrodiamine platinum nitric acid solution and a strontium acetate solution to the ZrLa complex oxide powder, mixing and evaporating to dryness. This catalyst material is obtained by post-supporting Pt and Sr on a ZrLa double oxide. The composition of this catalyst material excluding Pt is SrO: ZrO ₂ : La ₂ O ₃ = 1.9: 86.6: 11.5 (molar ratio) in terms of oxide, and the total amount of components excluding Pt The ratio of Pt and Pt is approximately 40: 1 (mass ratio).

  The catalyst material powder was supported on the same filter body in the same manner as in Example 2-1, to obtain a catalyst performance evaluation sample according to Comparative Example 2-2. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Comparative Example 2-3
A double oxide powder of Zr, La, and Pr was obtained by a coprecipitation method from a mixed solution in which zirconyl nitrate, lanthanum nitrate, and praseodymium nitrate were dissolved in ion-exchanged water. A catalyst material according to Comparative Example 2-3 was obtained by adding a dinitrodiamine platinum nitric acid solution to the ZrLaPr double oxide powder, mixing, and evaporating to dryness. This catalyst material is obtained by post-supporting Pt on a ZrLaPr double oxide. The composition of this catalyst material excluding Pt is ZrO ₂ : La ₂ O ₃ : Pr ₆ O ₁₁ = 80: 14: 6 (molar ratio) in terms of oxide, and the total amount of components excluding Pt and Pt The ratio is approximately 40: 1 (mass ratio).

  The catalyst material powder was supported on the same filter body in the same manner as in Example 2-1, to obtain a catalyst performance evaluation sample according to Comparative Example 2-3. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

-Comparative Example 2-4-
ZrLaPr double oxide powder was obtained in the same manner as Comparative Example 2-3. A catalyst material according to Comparative Example 2-4 was obtained by adding a dinitrodiamine platinum nitric acid solution and a strontium acetate solution to the ZrLaPr double oxide powder, mixing and evaporating to dryness. This catalyst material is obtained by post-supporting Pt and Sr on a ZrLaPr double oxide. The composition of the catalyst material excluding Pt is SrO: ZrO ₂ : La ₂ O ₃ = 1.9: 78.5: 13.7: 5.9 (molar ratio) in terms of oxide, The ratio of the total amount of components except Pt to Pt is approximately 40: 1 (mass ratio).

  The catalyst material powder was supported on the same filter body in the same manner as in Example 2-1, to obtain a catalyst performance evaluation sample according to Comparative Example 2-4. The catalyst material loading per 1 L of filter body is 20 g / L (Pt loading is 0.5 g / L).

[Particulate combustion performance of catalyst materials]
In order to evaluate the particulate combustion performance of the catalyst materials of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-4, carbon was obtained by the method described above using the catalyst performance evaluation sample. The burning rate was measured. Each sample was aged at a temperature of 800 ° C. for 24 hours in the air. The measurement results of the carbon burning rate are shown in Table 2, FIG. 8 and FIG.

  In each of the examples in which the Zr-based double oxide is doped with Sr, the carbon burning rate is higher than that of the comparative example without Sr support or without the alkaline earth metal (group 2A). From comparison between Comparative Example 2-1 and Comparative Example 2-2, it can be seen that when Sr is post-supported on a Zr-based double oxide, the carbon combustion rate increases. However, Example 2-1 has a higher carbon combustion rate than Comparative Example 2-2. From this, it can be seen that doping Sr into a Zr-based double oxide is effective in increasing the carbon combustion rate. One possible reason is that the amount of lattice oxygen released from the Zr-based double oxide is increased by doping Sr. In addition, Example 2-3 has a higher carbon combustion rate than Example 2-1. From this, it can be seen that doping Pr with a Zr-based double oxide is further advantageous in increasing the carbon combustion rate.

  Looking at Comparative Example 2-1 and Examples 2-1 and 2-2 (without Pr), as shown in FIG. 9, the carbon combustion rate increases as the Sr doping amount increases. Also, in Comparative Example 2-3 and Examples 2-3 to 2-5 (with Pr), the carbon combustion rate increases with an increase in the Sr doping amount, but when the Sr doping amount becomes excessive, There is a tendency for the carbon burning rate to decrease. From the relationship between the Sr doping amount and the carbon burning rate, the Sr doping amount in the above-mentioned double oxide should be 1% or more and 10% or less in terms of mol%, and moreover 1.9% or more and 6.0% or less Can be said to be preferable.

  In the above embodiment, Pt as a noble metal is post-supported on the double oxide, but the noble metal may be doped into the double oxide. For example, in the above-described coprecipitation method, the coprecipitate (precursor of double oxide) is filtered by a centrifugal separation method, washed with water, and then dried and calcined before the dinitrodiamine platinum nitrate solution is added to the coprecipitate. Add and mix. This mixture is dried in the air at a temperature of 150 ° C. for a whole day and night, pulverized, and then baked in the air at a temperature of 500 ° C. for 2 hours. Thereby, the target catalyst material is obtained. In this case, since the coprecipitate (precursor of the double oxide) and the dinitrodiamine platinum nitric acid solution are mixed and dried and calcined, the obtained catalyst material is the primary particles of the double oxide and the primary particles of Pt. Are mixed and agglomerated. Even in such a catalyst material, excellent carbon combustion performance can be obtained as in the above embodiment.

1 Filter 2 Exhaust gas inflow passage (exhaust gas passage)
3 Exhaust gas outflow passage (exhaust gas passage)
5 Bulkhead (carrier substrate)
6 Fine pore (exhaust gas passage)
7 Catalyst layer 11 Primary particle of double oxide 12 Secondary particle of double oxide 13 Primary particle of noble metal

Claims (4)

Particles in which a carrier layer is provided with a catalyst layer, and the catalyst layer is provided with a catalyst material composed of Zr, Y, Sr, noble metal and oxygen for burning particulate matter contained in engine exhaust gas A material combustion catalyst,
In the catalyst material, a particulate matter combustion catalyst, wherein the Zr, Y, and Sr form a double oxide, and a main component metal element of the double oxide is Zr. The carrier base is provided with a catalyst layer, and the catalyst layer is provided with a catalyst material composed of Zr, Y, Sr, Pr, a noble metal, and oxygen for burning particulate matter contained in engine exhaust gas. A particulate matter combustion catalyst comprising:
  In the catalyst material, a particulate matter combustion catalyst, wherein the Zr, Y, Sr, and Pr form a double oxide, and a main component metal element of the double oxide is Zr. Particles in which a carrier layer is provided with a catalyst layer, and the catalyst layer is provided with a catalyst material composed of Zr, La, Sr, noble metal and oxygen for burning particulate matter contained in engine exhaust gas A material combustion catalyst,
In the catalyst material, a particulate matter combustion catalyst characterized in that Zr, La and Sr form a double oxide, and a main component metal element of the double oxide is Zr. The carrier substrate is provided with a catalyst layer, and the catalyst layer is provided with a catalyst material composed of Zr, La, Sr, Pr, noble metal and oxygen for burning particulate matter contained in engine exhaust gas. A particulate matter combustion catalyst comprising:
  In the catalyst material, a particulate matter combustion catalyst, wherein the Zr, La, Sr and Pr form a double oxide, and a main component metal element of the double oxide is Zr.

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