Exhaust gas purification catalyst

Abstract

To provide an exhaust purifying catalyst that has excellent exhaust purifying performance after being subjected to an endurance test.SOLUTION: An exhaust purifying catalyst has an integrally structured carrier, and a catalyst layer disposed on the integrally structured carrier. The catalyst layer includes a first catalyst that contains an iron-containing compound and an oxygen adsorbing / releasing material, with the oxygen adsorbing / releasing material having the iron-containing compound supported thereon, and a second catalyst containing a noble metal. The oxygen adsorbing / releasing material in the first catalyst contains at least yttrium.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification catalyst, and more particularly to a catalyst for purifying hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx).

Background Art

[0002] Conventionally, an exhaust gas purification catalyst that exhibits excellent NOx purification performance in a high temperature range and excellent low temperature activity has been proposed (see Patent Document 1). This exhaust gas purification catalyst includes a first catalyst in which an oxide having oxygen storage and release ability supports oxides such as La 0.8 Sr 0.2 FeO 3 and a second catalyst containing a noble metal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the exhaust gas purification catalyst of Patent Document 1, when the durability conditions are made more severe, (1) iron (Fe) reacts with the oxygen storage and release material, the oxygen storage and release material itself shrinks, and iron (Fe) aggregates with each other, (2) iron (Fe) as an oxygen intake port decreases from the surface, and the oxygen storage and release performance deteriorates. Thus, in the exhaust gas purification catalyst of Patent Document 1, there is a problem that the exhaust gas purification performance after durability is not sufficient for further performance improvement requirements.

[0005] The present invention has been made in view of such problems of the prior art, and an object thereof is to provide an exhaust gas purification catalyst having excellent exhaust gas purification performance after durability.

Means for Solving the Problems

[0006] As a result of intensive studies to achieve the above object, the present inventors have found that the object can be achieved by coexisting in a catalyst layer a first catalyst in which an iron-containing compound is supported on an oxygen absorption and release material containing at least yttrium, and a second catalyst containing a noble metal, and thus have completed the present invention. predetermined on an oxygen absorption and release material predetermined That is, the exhaust gas purification catalyst of the present invention includes a monolithic carrier and a catalyst layer disposed on the monolithic carrier. The catalyst layer includes a first catalyst containing an iron-containing compound and an oxygen absorption and release material in which the oxygen absorption and release material supports the iron-containing compound, and a second catalyst containing a noble metal. The iron-containing compound has a perovskite structure

[0007] (where x satisfies 0 ≦ x < 1), the oxygen absorption and release material contains ZrCe(Nd,La)YOx, and the noble metal contains any one of rhodium (Rh), platinum (Pt), and palladium (Pd). La x Sr 1-x FeO 3 (where x satisfies 0 ≦ x < 1), the oxygen absorption and release material contains ZrCe(Nd,La)YOx, and the noble metal contains any one of rhodium (Rh), platinum (Pt), and palladium (Pd). [Advantages of the Invention]

[0008] According to the present invention, since a first catalyst in which an iron-containing compound is supported on an oxygen absorption and release material containing at least yttrium and a second catalyst containing a noble metal coexist in a catalyst layer, an exhaust gas purification catalyst having excellent exhaust gas purification performance after durability can be provided. predetermined on an oxygen absorption and release material predetermined According to the present invention, since a first catalyst in which an iron-containing compound is supported on an oxygen absorption and release material containing at least yttrium and a second catalyst containing a noble metal coexist in a catalyst layer, an exhaust gas purification catalyst having excellent exhaust gas purification performance after durability can be provided. [Brief Description of the Drawings]

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the exhaust gas purification catalyst according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0011] FIG. 1 is an explanatory view schematically showing an exhaust gas purification catalyst according to an embodiment of the present invention. As shown in FIG. 1, the exhaust gas purification catalyst 1 of the present embodiment includes an integral structured carrier 10 and a catalyst layer 20 disposed on the integral structured carrier.

[0012] FIG. 2 is an explanatory view showing the structure of a catalyst layer 20a which is an example of the catalyst layer 20. As shown in FIG. 2, the catalyst layer 20a includes a first catalyst 21 and a second catalyst 23. The first catalyst 21 contains an iron-containing compound 211 and an oxygen storage and release material 213, and the oxygen storage and release material 213 supports the iron-containing compound 211. The second catalyst 23 contains a noble metal 231 and a carrier 233, and the carrier 233 supports the noble metal 231. Although not shown, the oxygen storage and release material 213 of the first catalyst 21 contains at least yttrium.

[0013] Furthermore, the catalyst layer 20a of this example further includes an oxygen storage and release material separately from the oxygen storage and release material contained in the first catalyst 21. When the catalyst layer 20a contains such an oxygen storage and release material, the oxygen storage and release material contained in the first catalyst 21 and supporting the iron-containing compound 211 is referred to as the first oxygen storage and release material 213, and the oxygen storage and release material contained separately from the first catalyst 21 and not supporting the iron-containing compound 211 is referred to as the second oxygen storage and release material 27.

[0014] FIG. 3 is an explanatory diagram showing the structure of a catalyst layer 20b, which is another example of the catalyst layer 20. As shown in FIG. 3, the catalyst layer 20b includes a first catalyst 21 and a second catalyst 23. The first catalyst 21 contains an iron-containing compound 211 and an oxygen absorption / emission material 213, and the oxygen absorption / emission material 213 supports the iron-containing compound 211. The second catalyst 23 contains a noble metal 231 and a carrier 233, and the carrier 233 supports the noble metal 231. Although not shown, the oxygen absorption / emission material 213 of the first catalyst 21 contains at least yttrium.

[0015] Furthermore, the catalyst layer 20b of this example further includes a partition material 25. The partition material 25 separates the first catalyst 21 and the second catalyst 23.

[0016] FIG. 4 is an explanatory diagram showing the structure of a catalyst layer 20c, which is still another example of the catalyst layer 20. As shown in FIG. 4, the catalyst layer 20c includes a first catalyst 21 and a second catalyst 23. The first catalyst 21 contains an iron-containing compound 211 and an oxygen absorption / emission material 213, and the oxygen absorption / emission material 213 supports the iron-containing compound 211. The second catalyst 23 contains a noble metal 231 and a carrier 233, and the carrier 233 supports the noble metal 231. Although not shown, the oxygen absorption / emission material 213 contains at least yttrium.

[0017] Furthermore, the catalyst layer 20c of this example further includes an oxygen absorption / emission material separately from the oxygen absorption / emission material contained in the first catalyst 21. Specifically, the catalyst layer 20c of this example includes a first oxygen absorption / emission material 213 that is contained in the first catalyst 21 and supports the iron-containing compound 211, and a second oxygen absorption / emission material 27 that is contained separately from the first catalyst 21 and does not support the iron-containing compound 211.

[0018] Furthermore, the catalyst layer 20c of this example further includes a partition material 25. The partition material 25 separates the first catalyst 21 and the second catalyst 23.

[0019] As described above, the exhaust gas purification catalyst of the present embodiment has a first catalyst in which an iron-containing compound is supported on an oxygen absorption and release material containing at least yttrium and a second catalyst containing a noble metal coexisting in the catalyst layer. Thereby, it is considered that the exhaust gas purification catalyst of the present embodiment has excellent exhaust gas purification performance after durability. Hereinafter, the exhaust gas purification performance will be specifically described.

[0020] FIG. 5 is a graph showing the results of hydrogen-temperature programmed reduction method (H 2 -TPR) after durability in the first catalyst of Comparative Example 1. FIG. 6 is a graph showing the results of hydrogen-temperature programmed reduction method (H 2 -TPR) after durability in the first catalyst of Example 1. FIG. 7 is a graph showing the results of hydrogen-temperature programmed reduction method (H 2 -TPR) after durability in the first catalyst of Example 3. FIG. 8 is a graph showing the results of hydrogen-temperature programmed reduction method (H 2 -TPR) after durability in the first catalyst of Example 4. In each of FIGS. 5 to 8, durability is carried out at 1100 ° C. for 3 hours. Also, in FIGS. 5 to 8, the horizontal axis represents temperature (° C.) and the vertical axis represents hydrogen (H 2 ) concentration (a.u.).

[0021] As shown in FIG. 5, in the first catalyst of Comparative Example 1 in which the oxygen absorption and release material does not contain yttrium, hydrogen (H 2 ) consumption is observed around 510 ° C.

[0022] On the other hand, as shown in FIGS. 6 to 8, in the first catalysts of Example 1, Example 3, and Example 4 in which the oxygen absorption and release material contains yttrium, as the content of yttrium oxide (Y 2 O 3 ) increases, the shoulder disappears. As shown in FIG. 7, in the first catalyst of Example 3 in which the content of yttrium oxide (Y 2 O 3 ) is 29.5% by mass, hydrogen (H 2 ) consumption is observed around 390 ° C. As shown in FIG. 8, in the case of yttrium oxide (Y 2 O 3In the first catalyst of Example 4 in which the content of 2 ) is 39% by mass, it is observed that the consumption of hydrogen (H

[0023] Figure 9 is a graph showing the relationship between the content of yttrium oxide (Y 2 O 3 ) after durability and the T50 of hydrocarbons (HC). Figure 10 is a graph showing the relationship between the content of yttrium oxide (Y 2 O 3 ) after durability and the T50 of carbon monoxide (CO). Figure 11 is a graph showing the relationship between the content of yttrium oxide (Y 2 O 3 ) after durability and the T50 of nitrogen oxides (NOx). In addition, each plot in Figures 9 to 11 is the data value of Comparative Example 1, Example 1, Example 2, Example 3, and Example 4 in order from the left. Also, in each example of Figures 9 to 11, the actual machine is used for durability at 920 °C for 300 hours as in the examples described later.

[0024] As shown in Figures 9 to 11, as the content of yttrium oxide (Y 2 O 3 ) in the oxygen storage and release material increases, the 50% conversion temperature (T50) of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) becomes lower, and it can be seen that excellent low-temperature activity is exhibited after durability.

[0025] Figure 12 is a graph showing the relationship between the content of yttrium oxide (Y 2 O 3 ) after durability and the BET specific surface area of the first catalyst. In addition, each plot in Figure 12 is the data value of Comparative Example 1, Example 1, Example 2, Example 3, and Example 4 from the left. Also, in each example of Figure 12, durability is carried out at 1100 °C for 3 hours.

[0026] As shown in Figure 12, as the yttrium oxide (Y 2 O 3The higher the content of

[0027] Figure 13 is a graph showing the relationship between the content of yttrium oxide (Y 2 O 3 ) after durability and the conversion rate of hydrocarbon (HC). Figure 14 is a graph showing the relationship between the content of yttrium oxide (Y 2 O 3 ) after durability and the conversion rate of carbon monoxide (CO). Figure 15 is a graph showing the relationship between the content of yttrium oxide (Y 2 O 3 ) after durability and the conversion rate of nitrogen oxides (NOx). In addition, each plot in Figures 13 to 15 is the data value of Comparative Example 1, Example 1, Example 2, Example 3, and Example 4 in order from the left. Also, in each example of Figures 13 to 15, like the examples described later, a real machine is used and durability is carried out at 920 °C for 300 hours.

[0028] As shown in Figures 13 to 15, it can be seen that the higher the content of yttrium oxide (Y 2 O 3 ) in the oxygen storage and release material, the higher the conversion rates of hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxides (NOx) after durability. This is considered to be because the dispersibility of the iron-containing compound supported by the oxygen storage and release material is maintained. Furthermore, as shown in Figures 13 and 14, it can be seen that the content of yttrium oxide (Y 2 O 3 ) in the oxygen storage and release material is preferably 19% by mass or more.

[0029] Here, each component will be described in more detail.

[0030] For the above-mentioned integrated carrier 10, it is preferable to use a monolith carrier or a honeycomb carrier made of a heat-resistant material such as ceramics such as cordierite or a metal such as ferritic stainless steel.

[0031] The above catalyst layer 20 is not particularly limited as long as it contains a predetermined first catalyst 21 and a second catalyst 23. It is preferable that the first catalyst 21 and the second catalyst 23 are contained in a single layer, but they may be contained separately in a plurality of layers. Other catalyst layers, underlayers, etc. may be disposed on the integral structured carrier 10 in addition to this catalyst layer 20.

[0032] The above iron-containing compound 211 is not particularly limited as long as it is a compound containing iron such as iron oxide (Fe 2 O 3 ). From the viewpoint that the reaction between iron (Fe) and the oxygen absorption and release material is suppressed in a high-temperature environment, the structure is more stabilized, and the durability is further improved, at least a part of the iron-containing compound 211 is, for example, an oxide having a perovskite structure represented by the general formula ABO 3 , or a mixture thereof.

[0033] As the iron (Fe)-containing compound having a perovskite structure represented by the general formula ABO 3 , for example, La x M 1-x FeO 3-δ (wherein La is lanthanum, M is at least one selected from the group consisting of barium (Ba), strontium (Sr), and calcium (Ca), Fe is iron, x satisfies 0 < x ≦ 1, and δ satisfies 0 ≦ δ ≦ 1) is preferably used. Among them, it is preferable that M is strontium.

[0034] The above (first) oxygen absorption and release material 213 has oxygen absorption and release ability and is not particularly limited as long as it contains at least yttrium, and is preferably a composite oxide containing zirconium and yttrium and having oxygen absorption and release ability. From the viewpoint that the (first) oxygen absorption and release material 213 can achieve both excellent catalytic activity and durability, for example, zirconium cerium yttrium oxide (ZrCeYOx), zirconium cerium neodymium yttrium oxide (ZrCeNdYOx), zirconium cerium lanthanum yttrium oxide (ZrCeLaYOx) are preferably used.

[0035] From the viewpoint that the conversion rates of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) at 480 °C are further improved, the content of yttrium in the above-mentioned (first) oxygen storage and release material 213 is preferably 19% by mass or more in terms of yttrium oxide (Y 2 O 3 ). From the viewpoint that both excellent catalytic activity and durability can be achieved, the content of yttrium in the (first) oxygen storage and release material is preferably 50% by mass or less.

[0036] The above-mentioned noble metal 231 is not particularly limited as long as it is, for example, platinum (Pt), rhodium (Rh), or palladium (Pd). From the viewpoint that the conversion rates of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) at 480 °C are improved compared to the cases using platinum (Pt) and palladium (Pd), it is preferable to use rhodium (Rh).

[0037] The above-mentioned carrier 233 is not particularly limited as long as it can disperse and support the noble metal. From the viewpoint that the durability is further improved in a high-temperature environment, for example, oxides containing zirconium and lanthanum such as zirconium lanthanum oxide (ZrLaOx), zirconium lanthanum yttrium oxide (ZrLaYOx), and zirconium lanthanum neodymium oxide (ZrLaNdOx) are preferably used. Aluminum oxide (Al 2 O 3 ), zirconium oxide (ZrO 2 ) are not preferable from the viewpoint of high-temperature durability. Oxygen storage and release materials containing cerium (Ce) such as cerium oxide (CeO 2 ) and zirconium cerium oxide (ZrCeOx) are not preferable from the viewpoint that the specific surface area of the carrier changes and the dispersibility of the noble metal decreases with oxygen storage and release.

[0038] The above-mentioned partition material 25 is not particularly limited as long as it can suppress the contact between the first catalyst and the second catalyst. The partition material 25 is, for example, alumina (Al 2 O3 ) is preferably used. Thereby, for example, it is possible to suppress the loss of reaction activity that may occur when a noble metal such as rhodium (Rh) comes into contact with an iron (Fe) - containing compound. This is said to be due to the catalyst poison of iron (Fe).

[0039] The above - mentioned second oxygen absorption - release material 27 is not particularly limited as long as it has oxygen absorption - release ability. The first oxygen absorption - release material 213 and the second oxygen absorption - release material 27 may be the same, but it is preferably different. The oxygen absorption - release ability of the second oxygen absorption - release material 27 is preferably higher than that of the first oxygen absorption - release material. The second oxygen absorption - release material 27 is preferably cerium oxide (CeO 2 ), zirconium cerium oxide (ZrCeOx), zirconium cerium neodymium oxide (ZrCeNdOx). Among them, from the viewpoint of achieving both excellent catalytic activity and durability, it is preferable to use zirconium cerium neodymium oxide (ZrCeNdOx). In addition, the second oxygen absorption - release material 27 is preferably separated from the first catalyst and the second catalyst by the partition material 25.

[0040] From the viewpoint of achieving both more excellent catalytic activity and durability, it is preferable that the total content of the first catalyst and the second catalyst is more than the content of the second oxygen absorption - release material.

[0041] The average particle diameter (D50) of the first catalyst and the second catalyst is preferably 50 - 300 nm, more preferably 100 - 200 nm, for example, from the viewpoint of further improving durability.

[0042] The exhaust gas purification catalyst described above is not particularly limited and can be produced by a conventionally known production method.

[0043] For example, an aqueous carboxylic acid solution of an iron-containing compound is impregnated into an oxygen absorption and release material and fired to obtain a powder in which the iron-containing compound is supported on the oxygen absorption and release material. Further, an aqueous noble metal salt solution is impregnated into a carrier and fired to obtain a powder in which the noble metal is supported on the carrier. The average particle diameters of these powders are adjusted, a binder and a solvent are added to obtain a slurry, which is spray-dried and fired to obtain a powder. A binder and a solvent are added to this powder to form a slurry, and the obtained slurry is suction-coated onto an integral structure type carrier, dried and fired to form a catalyst layer on the integral structure type carrier, whereby the exhaust gas purification catalyst of the present embodiment can be obtained.

[0044] The above-described exhaust gas purification catalyst is preferably disposed and used, for example, in an exhaust gas passage of an internal combustion engine such as a gasoline engine mounted on a vehicle, and more preferably disposed and used downstream of a plasma treatment device disposed in the exhaust gas passage.

Example

[0045] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0046] (Example 1) <Production of the carrier for the first catalyst> Zirconium cerium neodymium yttrium oxide (61% by mass zirconium oxide (ZrO 2 ) - 19.1% by mass cerium oxide (CeO 2 ) - 10% by mass neodymium oxide (Nd 2 O 3 ) - 9.9% by mass yttrium oxide (Y 2 O 3A hydroxide gel, which is a precursor of

[0047] <Preparation of the First Catalyst> La 0.8 Sr 0.2 FeO 3 Lanthanum carbonate, strontium carbonate and iron carbonate were added to a mixed aqueous solution of citric acid and malic acid (citric acid: 25% by mass, malic acid: 25% by mass) so as to form a 10% by mass solution, and stirred and dissolved to obtain a 10% by mass La 0.8 Sr 0.2 FeO 3 dissolution solution. Next, the obtained 10% by mass La 0.8 Sr 0.2 FeO 3 dissolution solution was impregnated into Powder 1-1 so as to contain 6% by mass La 0.8 Sr 0.2 FeO 3 , and this was calcined at 200°C for 1 hour, 400°C for 1 hour, 580°C for 1 hour, and 700°C for 1 hour to obtain the first catalyst powder used in this example. This is designated as Powder 1-2.

[0048] <Preparation of the Second Catalyst Support>

[0047] <Preparation of the First Catalyst> La 0.8 Sr 0.2 FeO 3 was prepared. Specifically, zirconium compounds (zirconium oxynitrate), cerium compounds (cerium nitrate), neodymium compounds (neodymium nitrate) and yttrium compounds (yttrium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, cerium compound aqueous solution, neodymium compound aqueous solution and yttrium compound aqueous solution were mixed so as to have a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while sufficiently stirring the obtained mixed aqueous solution, an aqueous sodium hydroxide solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of zirconium hydroxide gel, cerium hydroxide gel, neodymium hydroxide gel and yttrium hydroxide gel. Next, the dispersion of the obtained mixed hydroxide gel was filtered and washed with ion-exchanged water. Further, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100°C for 16 hours and further heat-treated at 600°C for 5 hours to obtain the carrier powder for the first catalyst used in this example. This is designated as Powder 1-1. 0.8 Sr 0.2 FeO 3 dissolution solution. Next, the obtained 10% by mass La 0.8 Sr 0.2 FeO 3 dissolution solution was impregnated into Powder 1-1 so as to contain 6% by mass La 0.8 Sr 0.2 FeO 3 , and this was calcined at 200°C for 1 hour, 400°C for 1 hour, 580°C for 1 hour, and 700°C for 1 hour to obtain the first catalyst powder used in this example. This is designated as Powder 1-2.

[0048] <Preparation of the Second Catalyst Support> ​​​​​​​​​​​​​​Zirconium lanthanum neodymium yttrium oxide (80% by mass zirconium oxide (ZrO 2 ) - 3% by mass lanthanum oxide (La 2 O 3 ) - 5% by mass neodymium oxide (Nd 2 O 3 ) - 12% by mass yttrium oxide (Y 2 O 3 )) hydroxide gel, which is a precursor, was prepared. Specifically, a zirconium compound (zirconium oxynitrate), a lanthanum compound (lanthanum nitrate), a neodymium compound (neodymium nitrate), and a yttrium compound (yttrium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, lanthanum compound aqueous solution, neodymium compound aqueous solution, and yttrium compound aqueous solution were mixed so that they had a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while sufficiently stirring the obtained mixed aqueous solution, a sodium hydroxide aqueous solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of zirconium hydroxide gel, lanthanum hydroxide gel, neodymium hydroxide gel, and yttrium hydroxide gel. Next, the obtained dispersion of the mixed hydroxide gel was filtered and washed with ion-exchanged water. Further, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100 °C for 16 hours and further heat-treated at 600 °C for 5 hours to obtain the carrier powder for the second catalyst used in this example. This is designated as Powder 1-3.

[0049] <Preparation of the Second Catalyst> Using an incipient wetness method with an aqueous rhodium nitrate solution (manufactured by Tanaka Kikinzoku Kogyo K.K.), rhodium was supported on Powder 1-3 to obtain the second catalyst powder used in this example. This is designated as Powder 1-4. Drying was performed at 150 °C overnight, and calcination was performed at 400 °C for 1 hour in a muffle furnace.

[0050] <Preparation of Powder A> The first catalyst powder 1-2 was ground in a bead mill until the average particle diameter (D50) reached about 150 nm. Separately, the second catalyst powder 1-4 was ground in a bead mill until the average particle diameter (D50) reached about 150 nm. For the measurement of the average particle diameter (D50), a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.) was used. Next, boehmite alumina and water were mixed, and the ground liquid of the first catalyst powder 1-2 and the ground liquid of the second catalyst powder 1-4 were added thereto and mixed to obtain a mixed liquid. The ratio of the first catalyst powder 1-2, the second catalyst powder 1-4, and boehmite was, by mass ratio, first catalyst powder:second catalyst powder:boehmite alumina = 50:30:20. Next, the obtained mixed liquid was filled into a spray dryer and dried, and the dried product was calcined in a muffle furnace at 550 °C for 3 hours to obtain powder A used in this example.

[0051] <Production of Powder B> A hydroxide gel, which is a precursor of zirconium cerium neodymium oxide (70 mass% zirconium oxide (ZrO 2 )) - 20 mass% cerium oxide (CeO 2 )) - 10 mass% neodymium oxide (Nd 2 O 3 )) was prepared. Specifically, a zirconium compound (zirconium oxynitrate), a cerium compound (cerium nitrate), and a neodymium compound (neodymium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, cerium compound aqueous solution, and neodymium compound aqueous solution were mixed so that they had a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while the obtained mixed aqueous solution was sufficiently stirred, a sodium hydroxide aqueous solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of a zirconium hydroxide gel, a cerium hydroxide gel, and a neodymium hydroxide gel. Next, the dispersion of the obtained mixed hydroxide gel was filtered and washed with ion-exchanged water. Further, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100 °C for 16 hours and further heat-treated at 600 °C for 5 hours to obtain powder B used in this example.

[0052] <Coating on the monolithic carrier> The obtained powder A, powder B, γ-alumina, and boehmite alumina as a binder were put into a magnetic pot at a mass ratio of 53:17:15:15. Further, nitric acid, pure water, and alumina balls were added together, and the mixture was shaken and pulverized to obtain a slurry. Furthermore, the obtained slurry was transferred to another container, and this slurry was suction-coated onto a ceramic honeycomb carrier (capacity: 0.119 L), and the excess slurry was removed by an air stream. Thereafter, the honeycomb carrier coated with the slurry was dried at 120 °C and calcined at 400 °C for 30 minutes under an air flow to obtain the exhaust gas purification catalyst of this example.

[0053] (Example 2) <Preparation of the First Catalyst Carrier> A hydroxide gel, which is a precursor of zirconium cerium neodymium yttrium oxide (52 mass% zirconium oxide (ZrO 2 ) - 19 mass% cerium oxide (CeO 2 ) - 10 mass% neodymium oxide (Nd 2 O 3 ) - 19 mass% yttrium oxide (Y 2 O 3 )) was prepared. Specifically, a zirconium compound (zirconium oxynitrate), a cerium compound (cerium nitrate), a neodymium compound (neodymium nitrate), and a yttrium compound (yttrium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, cerium compound aqueous solution, neodymium compound aqueous solution, and yttrium compound aqueous solution were mixed so that they had a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while the obtained mixed aqueous solution was sufficiently stirred, a sodium hydroxide aqueous solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of a zirconium hydroxide gel, a cerium hydroxide gel, a neodymium hydroxide gel, and a yttrium hydroxide gel. Next, the dispersion of the obtained mixed hydroxide gel was filtered and washed with ion-exchanged water. Furthermore, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100 °C for 16 hours and further heat-treated at 600 °C for 5 hours to obtain the first catalyst carrier powder used in this example. This is designated as powder 2-1.

[0054] <Preparation of the first catalyst, preparation of the support for the second catalyst, preparation of the second catalyst, preparation of powder A, preparation of powder B, coating on the integral structured support> In the preparation of the first catalyst, the same operations as in Example 1 were repeated except that powder 2-1 was used instead of powder 1-1, and the first catalyst powder used in this example was obtained. This was designated as powder 2-2. The powder 1-3 obtained in Example 1 was used as the support powder for the second catalyst used in this example. This was designated as powder 2-3. The powder 1-4 obtained in Example 1 was used as the second catalyst powder used in this example. This was designated as powder 2-4. In the preparation of powder A, the same operations as in Example 1 were repeated except that powder 2-2 was used instead of powder 1-2 and powder 2-4 was used instead of powder 1-4, and the powder A used in this example was obtained. The powder B obtained in Example 1 was used as the powder B used in this example. The same operations as in Example 1 were repeated except that the obtained powder A was used, and the exhaust gas purification catalyst of this example was obtained.

[0055] (Example 3) <Preparation of the support for the first catalyst> Zirconium cerium neodymium yttrium oxide (41.5 mass% zirconium oxide (ZrO 2 ) - 19 mass% cerium oxide (CeO 2 ) - 10 mass% neodymium oxide (Nd 2 O 3 ) - 29.5 mass% yttrium oxide (Y 2 O 3A hydroxide gel, which is a precursor of [[ID=]], was prepared. Specifically, a zirconium compound (zirconium oxynitrate), a cerium compound (cerium nitrate), a neodymium compound (neodymium nitrate), and a yttrium compound (yttrium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, cerium compound aqueous solution, neodymium compound aqueous solution, and yttrium compound aqueous solution were mixed so that they had a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while sufficiently stirring the obtained mixed aqueous solution, a sodium hydroxide aqueous solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of a zirconium hydroxide gel, a cerium hydroxide gel, a neodymium hydroxide gel, and a yttrium hydroxide gel. Next, the dispersion of the obtained mixed hydroxide gel was filtered and washed with ion-exchanged water. Further, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100 °C for 16 hours and further heat-treated at 600 °C for 5 hours to obtain a carrier powder for the first catalyst used in this example. This is designated as powder 3-1.

[0056] <Preparation of the first catalyst, preparation of the carrier for the second catalyst, preparation of the second catalyst, preparation of powder A, preparation of powder B, coating on the integral structured carrier> In the preparation of the first catalyst, the same operations as in Example 1 were repeated except that powder 3-1 was used instead of powder 1-1 to obtain the first catalyst powder used in this example. This is designated as powder 3-2. The powder 1-3 obtained in Example 1 was used as the carrier powder for the second catalyst used in this example. This is designated as powder 3-3. The powder 1-4 obtained in Example 1 was used as the second catalyst powder used in this example. This is designated as powder 3-4. In the preparation of powder A, the same operations as in Example 1 were repeated except that powder 3-2 was used instead of powder 1-2 and powder 3-4 was used instead of powder 1-4 to obtain powder A used in this example. The powder B obtained in Example 1 was used as powder B used in this example. The same operations as in Example 1 were repeated except that the obtained powder A was used to obtain the exhaust gas purification catalyst of this example.

[0057] (Example 4) <Preparation of the carrier for the first catalyst> A hydroxide gel, which is a precursor of zirconium cerium neodymium yttrium oxide (32% by mass zirconium oxide (ZrO 2 ), 19% by mass cerium oxide (CeO 2 ), 10% by mass neodymium oxide (Nd 2 O 3 ), 39% by mass yttrium oxide (Y 2 O 3 )) was prepared. Specifically, a zirconium compound (zirconium oxynitrate), a cerium compound (cerium nitrate), a neodymium compound (neodymium nitrate), and a yttrium compound (yttrium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, cerium compound aqueous solution, neodymium compound aqueous solution, and yttrium compound aqueous solution were mixed so that they would be in a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while sufficiently stirring the obtained mixed aqueous solution, an aqueous sodium hydroxide solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of zirconium hydroxide gel, cerium hydroxide gel, neodymium hydroxide gel, and yttrium hydroxide gel. Next, the obtained dispersion of the mixed hydroxide gel was filtered and washed with ion-exchanged water. Further, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100 °C for 16 hours and further heat-treated at 600 °C for 5 hours to obtain the carrier powder for the first catalyst used in this example. This is designated as powder 4-1.

[0058] <Preparation of the first catalyst, preparation of the carrier for the second catalyst, preparation of the second catalyst, preparation of powder A, preparation of powder B, coating on the monolithic carrier> In the preparation of the first catalyst, the same operations as in Example 1 were repeated except that powder 4-1 was used instead of powder 1-1, to obtain the first catalyst powder used in this example. This was designated as powder 4-2. The powder 1-3 obtained in Example 1 was used as the support powder for the second catalyst used in this example. This was designated as powder 4-3. The powder 1-4 obtained in Example 1 was used as the second catalyst powder used in this example. This was designated as powder 4-4. In the preparation of powder A, the same operations as in Example 1 were repeated except that powder 4-2 was used instead of powder 1-2 and powder 4-4 was used instead of powder 1-4, to obtain the powder A used in this example. The powder B obtained in Example 1 was used as the powder B used in this example. The same operations as in Example 1 were repeated except that the obtained powder A was used, to obtain the exhaust gas purification catalyst of this example.

[0059] (Example 5) <Preparation of the Support for the First Catalyst> Zirconium cerium lanthanum yttrium oxide (56 mass% zirconium oxide (ZrO 2 ) - 20 mass% cerium oxide (CeO 2 ) - 4 mass% lanthanum oxide (La 2 O 3 ) - 20 mass% yttrium oxide (Y 2 O 3A hydroxide gel, which is a precursor of [[ID=]], was prepared. Specifically, a zirconium compound (zirconium oxynitrate), a cerium compound (cerium nitrate), a lanthanum compound (lanthanum nitrate), and a yttrium compound (yttrium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, cerium compound aqueous solution, lanthanum compound aqueous solution, and yttrium compound aqueous solution were mixed so that they had a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while sufficiently stirring the obtained mixed aqueous solution, a sodium hydroxide aqueous solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of a zirconium hydroxide gel, a cerium hydroxide gel, a lanthanum hydroxide gel, and a yttrium hydroxide gel. Next, the dispersion of the obtained mixed hydroxide gel was filtered and washed with ion-exchanged water. Further, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100 °C for 16 hours and further heat-treated at 600 °C for 5 hours to obtain the carrier powder for the first catalyst used in this example. This is designated as powder 5-1.

[0060] <Preparation of the first catalyst, preparation of the carrier for the second catalyst, preparation of the second catalyst, preparation of powder A, preparation of powder B, coating on the integral structure type carrier> In the preparation of the first catalyst, the same operations as in Example 1 were repeated except that powder 5-1 was used instead of powder 1-1 to obtain the first catalyst powder used in this example. This is designated as powder 5-2. The powder 1-3 obtained in Example 1 was used as the carrier powder for the second catalyst used in this example. This is designated as powder 5-3. The powder 1-4 obtained in Example 1 was used as the second catalyst powder used in this example. This is designated as powder 5-4. In the preparation of powder A, the same operations as in Example 1 were repeated except that powder 5-2 was used instead of powder 1-2 and powder 5-4 was used instead of powder 1-4 to obtain powder A used in this example. The powder B obtained in Example 1 was used as powder B used in this example. The same operations as in Example 1 were repeated except that the obtained powder A was used to obtain the exhaust gas purification catalyst of this example.

[0061] (Comparative Example 1) <Preparation of the carrier for the first catalyst> A hydroxide gel, which is a precursor of zirconium cerium neodymium oxide (70 mass% zirconium oxide (ZrO 2 ), 20 mass% cerium oxide (CeO 2 ), 10 mass% neodymium oxide (Nd 2 O 3 )) was prepared. Specifically, a zirconium compound (zirconium oxynitrate), a cerium compound (cerium nitrate), and a neodymium compound (neodymium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, cerium compound aqueous solution, and neodymium compound aqueous solution were mixed so that they had a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while sufficiently stirring the obtained mixed aqueous solution, an aqueous sodium hydroxide solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of a zirconium hydroxide gel, a cerium hydroxide gel, and a neodymium hydroxide gel. Next, the dispersion of the obtained mixed hydroxide gel was filtered and washed with ion-exchanged water. Further, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100 °C for 16 hours and further heat-treated at 600 °C for 5 hours to obtain the carrier powder for the first catalyst used in this example. This was designated as Comparative Powder 1-1.

[0062] <Preparation of the First Catalyst, Preparation of the Carrier for the Second Catalyst, Preparation of the Second Catalyst, Preparation of Powder A, Preparation of Powder B, Coating on the Integrated Structure Type Carrier> In the preparation of the first catalyst, the same operations as in Example 1 were repeated except that Comparative Powder 1-1 was used instead of Powder 1-1 to obtain the first catalyst powder used in this example. This was designated as Comparative Powder 1-2. The powder 1-3 obtained in Example 1 was used as the carrier powder for the second catalyst used in this example. This was designated as Comparative Powder 1-3. The powder 1-4 obtained in Example 1 was used as the second catalyst powder used in this example. This was designated as Comparative Powder 1-4. In the preparation of Powder A, the same operations as in Example 1 were repeated except that Comparative Powder 1-2 was used instead of Powder 1-2 and Comparative Powder 1-4 was used instead of Powder 1-4 to obtain Powder A used in this example. The powder B obtained in Example 1 was used as the powder B used in this example. The same operations as in Example 1 were repeated except that the obtained Powder A was used to obtain the exhaust gas purification catalyst of this example.

[0063] (Example 6) <Preparation of the Support for the First Catalyst> The powder 4-1 obtained in Example 4 was used as the support powder for the first catalyst used in this example. This was designated as powder 6-1.

[0064] <Preparation of the First Catalyst> The powder 4-2 obtained in Example 4 was used as the first catalyst powder used in this example. This was designated as powder 6-2.

[0065] <Preparation of the Support for the Second Catalyst> A hydroxide gel, which is a precursor of zirconium lanthanum neodymium oxide (92% by mass zirconium oxide (ZrO 2 ) - 3% by mass lanthanum oxide (La 2 O 3 ) - 5% by mass neodymium oxide (Nd 2 O 3 )) was prepared. Specifically, a zirconium compound (zirconium oxynitrate), a lanthanum compound (lanthanum nitrate), and a neodymium compound (neodymium nitrate) were weighed to obtain each aqueous solution. Next, the obtained zirconium compound aqueous solution, lanthanum compound aqueous solution, and neodymium compound aqueous solution were mixed so that they had a predetermined ratio in terms of oxide conversion to obtain a mixed aqueous solution. Thereafter, while sufficiently stirring the obtained mixed aqueous solution, an aqueous sodium hydroxide solution as an alkaline aqueous solution was added to obtain a dispersion of a mixed hydroxide gel composed of a zirconium hydroxide gel, a lanthanum hydroxide gel, and a neodymium hydroxide gel. Next, the dispersion of the obtained mixed hydroxide gel was filtered and washed with ion-exchanged water. Further, decantation was performed until sodium was no longer detected. Thereafter, it was dried at 100 °C for 16 hours and further heat-treated at 600 °C for 5 hours to obtain the support powder for the second catalyst used in this example. This was designated as powder 6-3.

[0066] <Preparation of the Second Catalyst> Platinum was supported on powder 6-3 by the incipient wetness method using a diammine dinitroplatinum(II) nitrate solution (manufactured by Tanaka Kikinzoku Kogyo K.K.) to obtain the second catalyst powder used in this example. This was designated as powder 6-4. Drying was carried out at 150°C overnight, and calcination was carried out at 400°C for 1 hour in a muffle furnace.

[0067] <Preparation of Powder A> In the preparation of Powder A, the same operations as in Example 1 were repeated except that powder 6-2 was used instead of powder 1-2 and powder 6-4 was used instead of powder 1-4 to obtain the Powder A used in this example.

[0068] <Preparation of Powder B> The powder B obtained in Example 1 was used as the powder B used in this example.

[0069] <Coating on the monolithic carrier> The same operations as in Example 1 were repeated except that the obtained powder A was used to obtain the exhaust gas purification catalyst of this example.

[0070] (Comparative Example 2) <Preparation of the carrier for the first catalyst> The comparative powder 1-1 obtained in Comparative Example 1 was used as the carrier powder for the first catalyst used in this example. This was designated as comparative powder 2-1.

[0071] <Preparation of the first catalyst> In the preparation of the first catalyst, the same operations as in Example 1 were repeated except that comparative powder 2-1 was used instead of powder 1-1 to obtain the first catalyst powder used in this example. This was designated as comparative powder 2-2.

[0072] <Preparation of the carrier for the second catalyst> The powder 6-3 obtained in Example 6 was used as the carrier powder for the second catalyst used in this example. This was designated as comparative powder 2-3.

[0073] <Preparation of the second catalyst> Platinum was supported on Comparative Powder 2-3 by the incipient wetness method using a diammine dinitroplatinum(II) nitrate solution (manufactured by Tanaka Kikinzoku Kogyo K.K.) to obtain the second catalyst powder used in this example. This was designated as Comparative Powder 2-4. Drying was carried out at 150°C overnight, and calcination was carried out at 400°C for 1 hour in a muffle furnace.

[0074] <Preparation of Powder A> In the preparation of Powder A, the same operations as in Example 1 were repeated except that Comparative Powder 2-2 was used instead of Powder 1-2 and Comparative Powder 2-4 was used instead of Powder 1-4 to obtain Powder A used in this example.

[0075] <Preparation of Powder B> The powder B obtained in Example 1 was used as the powder B used in this example.

[0076] <Coating on the monolithic carrier> The same operations as in Example 1 were repeated except that the obtained Powder A was used to obtain the exhaust gas purification catalyst of this example.

[0077] (Example 7) <Preparation of the carrier for the first catalyst> The powder 4-1 obtained in Example 4 was used as the carrier powder for the first catalyst used in this example. This was designated as Powder 7-1.

[0078] <Preparation of the first catalyst> The powder 4-2 obtained in Example 4 was used as the first catalyst powder used in this example. This was designated as Powder 7-2.

[0079] <Preparation of the carrier for the second catalyst> The powder 6-3 obtained in Example 6 was used as the carrier powder for the second catalyst used in this example. This was designated as Powder 7-3.

[0080] <Preparation of the second catalyst> Palladium was supported on Powder 7-3 by the incipient wetness method using a palladium nitrate solution (manufactured by Tanaka Kikinzoku Kogyo K.K.) to obtain the second catalyst powder used in this example. This was designated as Powder 7-4. Drying was performed at 150°C overnight, and calcination was performed at 400°C for 1 hour in a muffle furnace.

[0081] <Preparation of Powder A> In the preparation of Powder A, the same operations as in Example 1 were repeated except that Powder 7-2 was used instead of Powder 1-2 and Powder 7-4 was used instead of Powder 1-4 to obtain the Powder A used in this example.

[0082] <Preparation of Powder B> The Powder B obtained in Example 1 was used as the Powder B used in this example.

[0083] <Coating on the monolithic carrier> The same operations as in Example 1 were repeated except that the obtained Powder A was used to obtain the exhaust gas purification catalyst of this example.

[0084] (Comparative Example 3) <Preparation of the carrier for the first catalyst> The comparative powder 1-1 obtained in Comparative Example 1 was used as the carrier powder for the first catalyst used in this example. This was designated as comparative powder 3-1.

[0085] <Preparation of the carrier for the second catalyst> The comparative powder 1-3 obtained in Comparative Example 1 was used as the carrier powder for the first catalyst used in this example. This was designated as comparative powder 3-3.

[0086] <Preparation of the second catalyst> The Powder 7-4 obtained in Example 7 was used as the carrier powder for the second catalyst used in this example. This was designated as comparative powder 3-4.

[0087] <Preparation of Powder A> In the preparation of Powder A, the same operations as in Example 1 were repeated except that comparative powder 3-2 was used instead of Powder 1-2 and comparative powder 3-4 was used instead of Powder 1-4 to obtain the Powder A used in this example.

[0088] <Production of Powder B> The powder B obtained in Example 1 was used as the powder B in this example.

[0089] <Coating on the Integrated Structure Carrier> The same operations as in Example 1 were repeated except that the obtained powder A was used, and the exhaust gas purification catalyst of this example was obtained. Table 1 and Table 2 show a part of the specifications of the exhaust gas purification catalysts of each example.

[0090]

Table 1

[0091]

Table 2

[0092] [Performance Evaluation] After subjecting the exhaust gas purification catalysts of each example to durability under the following durability conditions, the concentrations of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) were measured for the exhaust gas purification catalysts of each example using an exhaust gas analyzer (manufactured by Horiba, Ltd., MEXA - 7500D) under the following evaluation conditions.

[0093] <Durability Conditions> The exhaust gas purification catalysts of each example were installed in the exhaust gas flow path of a V - type 6 - cylinder 3.5L engine manufactured by Nissan Motor Co., Ltd., and the test was carried out for 300 hours at an inlet temperature of 920°C.

[0094] <Evaluation Conditions> · An engine manufactured by Nissan Motor Co., Ltd. was used. · Catalyst capacity: 119 cm 3 · Gas flow rate: 60 m 3 / h · Gas composition (stoichiometric): HC; approximately 2000 volume ppm C1, CO; approximately 0.54 volume %, NO; approximately 1500 volume ppm, O 2 ; approximately 0.56 volume %, CO 2 ; 14.6 volume % · Catalyst inlet temperature: 480 °C

[0095] Note that the above “ppmC1” means carbon conversion. For example, 1 ppm of benzene = 6 ppmC1.

[0096] The HC purification performance, CO purification performance, and NOx purification performance were determined by the conversion rate. Note that, for example, the NOx conversion rate is calculated as follows. The obtained results are shown in Tables 1 and 2 together.

[0097] NOx conversion rate (%) = (NOx in - NOx out ) / NOx in × 100

[0098] From Tables 1 and 2, when rhodium (Rh) is used as the noble metal, Examples 1 to 4 belonging to the scope of the present invention showed excellent HC conversion rate, CO conversion rate, and NOx conversion rate after durability as compared with Comparative Example 1 outside the present invention.

[0099] Furthermore, from Tables 1 and 2, when platinum (Pt) is used as the noble metal, Example 6 belonging to the scope of the present invention showed excellent HC conversion rate, CO conversion rate, and NOx conversion rate after durability as compared with Comparative Example 2 outside the present invention.

[0100] Furthermore, from Tables 1 and 2, when palladium (Pd) is used as the noble metal, Example 7 belonging to the scope of the present invention showed excellent HC conversion rate, CO conversion rate, and NOx conversion rate after durability as compared with Comparative Example 3 outside the present invention.

[0101] In the exhaust gas purification catalyst of each example, the crystal structure of the iron-containing compound in the first catalyst was identified. FIG. 16 is an electron diffraction pattern of the iron-containing compound in the first catalyst of Example 2. From FIG. 16, it was found that La 0.8 Sr 0.2 FeO 3 of Example 2 belonging to the scope of the present invention has a perovskite structure represented by the general formula ABO 3 .

[0102] Regarding the durability of the exhaust gas purification catalyst in each example, in order to have more margin, the dispersion state of the elements of the exhaust gas purification catalyst that was made more durable than the above durability conditions was observed. FIG. 17 is an element mapping obtained by using a scanning transmission electron microscope (STEM) and an energy dispersive X-ray detector (EDS) for the exhaust gas purification catalyst of Example 2 after durability. FIG. 18 is an element mapping obtained by using a scanning transmission electron microscope (STEM) and an energy dispersive X-ray detector (EDS) for the exhaust gas purification catalyst of Comparative Example 1 after durability. From FIGS. 17 and 18, it was found that in Example 2 belonging to the scope of the present invention, aggregation of iron (Fe) indicated in red does not occur. On the other hand, in Comparative Example 1 of the present invention, as indicated by arrow Z, it was found that aggregation (exceeding 300 nm) of iron (Fe) indicated in red occurs.

[0103] At present, from the viewpoint of the conversion rates of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) after durability, it is considered that Example 4 gives the best results.

Explanation of symbols

[0104] 1 Exhaust gas purification catalyst 10 Monolithic carrier 20, 20a, 20b, 20c Catalyst layer 21 First catalyst 211 Iron-containing compound 213 Oxygen absorption and release material (first oxygen absorption and release material) 23 Second catalyst 231 Noble metal 233 Carrier 25 Partition material 27 Second oxygen absorption and release material

Claims

1. An integrally formed carrier and a catalyst layer disposed on the integrally formed carrier, The catalyst layer includes a first catalyst containing an iron-containing compound and an oxygen absorption and release material, the oxygen absorption and release material supporting the iron-containing compound, and a second catalyst containing a noble metal, The iron-containing compound contains La x Sr 1−x FeO 3 (where x satisfies 0 ≦ x < 1) having a perovskite structure, The oxygen absorption and release material contains ZrCe(Nd,La)YOx, The noble metal contains any one of rhodium (Rh), platinum (Pt), and palladium (Pd), An exhaust gas purification catalyst characterized by this.

2. The exhaust gas purification catalyst according to Claim 1, wherein the noble metal is rhodium.

3. The content of yttrium in the oxygen absorption and release material is 19% by mass or more in terms of yttrium oxide (Y ２ O ３ ), and the exhaust gas purification catalyst according to claim 1 or 2, characterized in that.

4. The catalyst layer further includes a partition material, The partition material separates the first catalyst and the second catalyst, The exhaust gas purification catalyst according to any one of Claims 1 to 3, characterized by this.

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