CN101284233B - Catalyst for purifying exhaust gas and manufacturing method thereof - Google Patents

Abstract

Disclosed is an exhaust gas purifying catalyst exhibiting excellent purification performance for a long period of time by suppressing coagulation of a noble metal. A catalyst powder comprises a noble metal and first and second compounds. In the catalyst powder, the first compound carries the noble metal and is separated from another first compound carrying a noble metal by the second compound. At least one catalyst layer comprising the catalyst powder is formed on an inner surface of a substrate. The catalyst layer has fine pores. A fine pore volume of fine pores having a fine pore diameter of greater than 0.1 mum to less than or equal to 1 mum is 10% to 60% of the fine pore volume of fine pores having a fine pore diameter of 0.1 mum or less.

Description

Catalyst for purifying exhaust gas and manufacturing method thereof

technical field

The present invention relates to a catalyst for purifying exhaust gas and a manufacturing method thereof. The catalyst for purifying exhaust gas is suitable for purifying exhaust gas discharged from an internal combustion engine.

Background technique

Catalysts for exhaust gas purification are generally formed by supporting noble metal particles on the surface of particles composed of metal oxides. The noble metal particles oxidize harmful components in exhaust gas such as unburned hydrocarbons (HC) and carbon monoxide (CO) and convert them into The harmless components are water and _CO2 gas.

In recent years, the regulations on automobile exhaust gas have become stricter, and at the same time, catalysts for exhaust gas purification are required to purify the above-mentioned unburned hydrocarbons (HC) and carbon monoxide (CO) more efficiently. In order to meet this requirement, various improvements have been made. For example, using the phenomenon that the purification ability of catalysts generally increases with the increase of the surface area of noble metal particles, the surface area of the noble metal particles is increased by reducing the particle diameter of the noble metal particles in the exhaust gas purification catalyst to increase the surface energy, Improve the performance of catalysts for exhaust gas purification.

At this time, the noble metal particles of the exhaust gas-purifying catalyst are in the state of ultrafine particles of several nm or less in the initial stage. However, there is a problem that in actual use of the catalyst for exhaust gas purification, as it is exposed to a high-temperature oxidizing atmosphere, the surface of the noble metal particles is oxidized, and the adjacent noble metal particles aggregate and merge with each other, and become coarser to tens of nm, the surface area of the noble metal particles decreases, and the purification rate of harmful substances decreases with time.

In order to prevent the agglomeration of noble metals, in some exhaust gas purification catalysts, noble metal particles are uniformly dispersed throughout the catalyst layer formed on the inner surface of a support with many fine pores penetrating in a honeycomb shape. Regarding such As a catalyst for exhaust gas purification, there is a method of producing catalyst powder by mixing noble metal colloid and metal alkoxide, and hydrolyzing the metal alkoxide to produce catalyst powder (Patent Document 1).

In addition, in order to prevent the reduction of the surface area of the noble metal particles due to coarsening and achieve higher activation, the reverse micelle method is being developed as a production method capable of producing noble metal particles with a large surface area. In the production step of the reverse micelle method, an emulsion solution of reverse micelles in which an aqueous solution containing noble metal particle raw materials is formed is prepared, and the reverse micelles are destroyed after precipitation of the micronized precious metals in the reverse micelles, and after treatment The obtained precipitate is filtered, dried, pulverized and sintered to make a catalyst.

Regarding the reverse micelle method, there is a method for producing a heat-resistant catalyst in which a reverse micelle solution containing an aqueous solution of a noble metal colloid inside a micelle, a reverse micelle solution containing an aqueous metal hydroxide solution inside a micelle, and a metal alkoxide The resulting mixture was mixed and sintered (Patent Document 2). In addition, there is a method for producing a highly heat-resistant catalyst including the step of preparing a reverse micelle solution in which a noble metal salt solution and at least one metal salt solution as a cocatalyst component coexist (Patent Document 2 ).

Patent Document 1: JP-A-2000-15097

Patent Document 2: JP-A-2005-111336

Patent Document 3: JP-A-2005-185969

Contents of the invention

The problem to be solved by the invention

However, the catalyst for exhaust gas purification obtained by the method of producing a catalyst from a mixture of noble metal colloid and metal alkoxide has improved coarsening of the noble metal, but the micropore volume of the catalyst powder is small. In addition, the catalyst powder is coated on the carrier. However, the formed catalyst layer is very dense, and it is difficult for the exhaust gas to diffuse in the catalyst layer.

In addition, the catalyst for exhaust gas purification obtained by the method using the reverse micelle method has a problem in terms of yield because of cumbersome manufacturing steps and increased manufacturing cost.

Solution to the problem

The gist of the catalyst for exhaust gas purification of the present invention is that its structure includes a carrier and at least one catalyst layer formed on the inner surface of the carrier, the catalyst layer contains catalyst powder, and the catalyst powder includes a noble metal, a first compound and a second catalyst layer. compound, and the noble metal of the catalyst powder is loaded by the first compound, and the first compound loaded with the noble metal is separated from each other by the second compound; the catalyst layer has micropores, and in the micropores whose micropore diameter is 1 μm or less , the micropore volume of micropores with a micropore diameter of 0.1 μm to 1 μm is 10% to 60%.

In addition, the gist of the method for producing a catalyst for exhaust gas purification of the present invention is that it is used to produce the above-mentioned catalyst for exhaust gas purification of the present invention, the method includes the steps of preparing catalyst powder, and the step of forming the catalyst powder on the inner surface of the carrier, wherein , the step of preparing catalyst powder includes: the step of loading noble metal on the first compound, and the step of dispersing the second compound or the precursor of the second compound in water for slurrying, and then adding the second compound loaded with noble metal A step in which a compound is dispersed in the slurry of the second compound, dried and then sintered to obtain a catalyst powder; the step of forming the catalyst powder on the inner surface of the carrier includes: adding a compound that will disappear when sintered to the obtained catalyst powder The compound is slurried, coated on the carrier, then dried and sintered to form a catalyst layer with micropores in the region of 0.1 μm to 1 μm in the micropores of the catalyst layer.

Invention effect

According to the exhaust gas-purifying catalyst of the present invention, the diffusivity of exhaust gas can be ensured, and the catalytic activity can be maintained at a high level.

According to the method for producing a catalyst for exhaust gas purification of the present invention, the catalyst for exhaust gas purification of the present invention can be produced as designed.

Description of drawings

1( a ) and ( b ) are explanatory diagrams in which the catalyst carrier for exhaust gas purification of the present invention is formed.

2(a) and (b) are schematic views of the catalyst for exhaust gas purification of the present invention.

Fig. 3 is a schematic graph showing the pore distribution curve of the catalyst layer of the catalyst for purifying exhaust gas according to the present invention.

FIG. 4 is a graph showing T50 results of HC for samples in Examples.

Fig. 5 is a graph showing T50 results of HC for samples in Examples.

Fig. 6 is a graph showing T50 results of HC for samples in Examples.

Fig. 7 is a graph showing T50 results of HC for samples in Examples.

Fig. 8 is a graph showing T50 results of HC for samples in Examples.

Fig. 9 is a graph showing T50 results of HC for samples in Examples.

Fig. 10 is a graph showing T50 results of HC for samples in Examples.

Fig. 11 is a graph showing T50 results of HC for samples in Examples.

Symbol Description

1 carrier

10 catalyst layers

11 catalyst powder

12 precious metals

13 first compound

14 Second compound

Detailed ways

Hereinafter, embodiments of the exhaust gas-purifying catalyst of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating a state in which the exhaust gas-purifying catalyst of the present invention is supported on a carrier. As an example, in Fig. 1 (a), the carrier 1 is shown in a schematic perspective view, which is basically cylindrical in shape, made of heat-resistant materials such as ceramics, and has a plurality of honeycomb-shaped holes penetrating from one side to the other side. tiny holes. An enlarged cross-sectional view of a hole of the carrier 1 represented by area B in FIG. 1( a ) is shown in FIG. 1( b ). As shown in FIG. 1( b ), a catalyst layer 10 is formed on the inner surface 1 a surrounding one hole of the carrier 1 . And, the outer shape of the carrier 1 shown in Fig. 1 (a), the size of the micropores and the thickness of the catalyst layer 10 shown in Fig. 1 (b) are different from the actual carrier 1 and the catalyst layer 10, and this is for ease of understanding. this invention. Therefore, the exhaust gas-purifying catalyst of the present invention is not limited to the shape of the carrier 1 shown in FIG. 1( a ), the size of the micropores, and the thickness of the catalyst layer 10 shown in FIG. 1( b ).

The exhaust gas-purifying catalyst of the present embodiment includes at least one catalyst layer 10 . The catalyst layer 10 contains catalyst powder. The structure of the catalyst powder of the present invention will be described using FIG. 2 . Fig. 2(a) and Fig. 2(b) are schematic views of catalyst powder of the exhaust gas-purifying catalyst of the present invention. As shown in Fig. 2 (a), Fig. 2 (b), catalyst powder 11 comprises noble metal 12, first compound 13 and second compound 14, and its structure is: first compound 13 loads this noble metal 12, loads this noble metal Individuals or aggregates of first compounds 13 of 12 are separated from each other by second compounds 14 . In the catalyst for exhaust gas purification of the present invention, the catalyst layer 10 having such a structure of catalyst powder has micropores P1 containing the catalyst powder and micropores P2 as gaps between the catalyst powders, and the micropores with a micropore diameter of 1 μm or less Among them, the micropore volume of micropores with a micropore diameter of 0.1 μm to 1 μm is 10% to 60%.

In the exhaust gas-purifying catalyst according to the present embodiment shown in FIGS. 1 and 2 , as for the catalyst powder 11 contained in the catalyst layer 10 , the noble metal 12 is supported by the first compound 13 as shown in FIG. 2 . Thus, the first compound 13 functions as an anchor (anka material) chemically bonded to the noble metal 12 . Therefore, the first compound 13 suppresses the movement of the noble metal 12 . In addition, the surrounding of the first compound 13 supporting the noble metal 12 is covered with a second compound 14 such as alumina. Thus, the second compound 14 physically inhibits the noble metal 12 from detaching from the first compound 13 and moving. Furthermore, the second compound 14 physically separates the first compounds 13 to prevent the first compounds 13 from moving and contacting each other to cause aggregation, and as a result, the precious metal 12 carried on the first compound 13 is prevented from agglomerating. .

For the catalyst powder 11 with the above structure, the exhaust gas must diffuse to reach the noble metal 12. The inventors found that the second compound 14 covering the noble metal 12 and the first compound 13 in the catalyst powder 11 must have a certain range of voids. Specifically, the initial pore volume of the catalyst is about 0.24 cm ³ /g to ^{0.8 cm 3} /g. If the initial pore volume of the catalyst is less than about 0.24 cm ³ /g, the gas diffusibility of the exhaust gas will be insufficient; if it exceeds about 0.8 cm ³ /g, the gas diffusibility will not change.

In addition, with respect to the catalyst layer 10 containing the catalyst powder 11 having such a structure as described above, the requirement of the exhaust gas purification catalyst of the present embodiment is that the catalyst layer has micropores, and in the micropores with a pore diameter of 1 μm or less, The micropore volume of micropores with a micropore diameter of 0.1 μm to 1 μm is 10% to 60%.

Fig. 3 is a schematic diagram of the pore distribution curve of the catalyst layer of the exhaust gas purification catalyst of the present invention. In the pore distribution curve shown in FIG. 3 , the pore volume in the range where the pore diameter exceeds 1 μm is caused by surface flaws, cracks, etc., and does not represent the pores of the catalyst layer. Therefore, the pores of the catalyst layer are represented by the volume of pores having a pore diameter of 1 μm or less. The exhaust gas-purifying catalyst according to the present embodiment has a pore volume peak in the range of the pore diameter of 0.1 μm or less and in the range of the pore diameter of 0.1 μm to 1 μm, respectively. The peak of the pore volume with the pore diameter in the range of 0.1 μm or less is considered to be the micropore P1 of the catalyst powder shown in FIG. 2( b ). In addition, the peak of the pore volume having a pore diameter in the range of 0.1 μm to 1 μm is considered to be the pores P2 which are voids between the catalyst powders shown in FIG. 2( b ). In the present invention, the micropore volume of micropores having a pore diameter of 0.1 μm to 1 μm is 10% to 60%, so that the micropores P2 serving as voids between catalyst powders can be sufficiently ensured. Thereby, a path (passage) for the gas to diffuse in the catalyst layer is sufficiently ensured, so that the gas diffusion performance can be improved. Furthermore, in the prior art shown by the dotted line in FIG. 3 , there is a single peak of the pore volume only in the range where the pore diameter is 0.1 μm or less. In short, in the prior art, there is no peak of the micropore volume in the range of the micropore diameter of 0.1 μm to 1 μm. In such prior art, the pore volume of pores having a pore diameter of 0.1 μm to 1 μm is less than 10%, and the catalyst layer is dense, so that exhaust gas hardly diffuses in the catalyst layer.

In the exhaust gas-purifying catalyst of this embodiment, when the catalyst powder 11 is coated on the carrier 1 to form the catalyst layer 10, in order to diffuse the exhaust gas from the surface of the catalyst layer 10 to the depth of the coated catalyst layer 10, Here, the following range is defined: among the micropores of the catalyst layer 10 having a micropore diameter of 1 μm or less, micropores with a micropore diameter of 0.1 μm to 1 μm must account for 10% to 60%. When the micropore volume of the micropores with a micropore diameter of 0.1 μm to 1 μm is in the range of 10% to 60%, excellent catalyst performance can be obtained. If the micropore volume of the micropores with a micropore diameter in the range of 0.1 m to 1 μm is less than 10% of the micropore volume of the micropores with a micropore diameter of 1 μm or less, the gas will not diffuse sufficiently, and there will be the following hidden dangers: the gas produced by the present invention cannot be obtained. A sufficient catalyst performance improvement effect can be obtained with a catalyst particle structure. In addition, in the micropores with a micropore diameter of 1 μm or less, if the micropore volume of the micropores with a micropore diameter of 0.1 μm to 1 μm exceeds 60% of the micropore volume of the micropores with a micropore diameter of 1 μm or less, although in terms of gas diffusion There is no problem, but there is a danger that the strength of the diffusion layer decreases because the amount of voids in the diffusion layer is too large.

In the catalyst layer, assuming that the micropore volume of micropores with a micropore diameter of 0.1 μm or less is A, and the micropore volume of micropores with a micropore diameter of 0.1 μm to 1 μm is B, then preferably B is a micropore with a micropore diameter of 1 μm or less. 10% to 60% of the micropore volume, and B/A≥0.1. When B/A is 0.1 or more, the exhaust gas in the catalyst layer can easily circulate, and the effect of improving the gas diffusion performance desired by the present invention can be obtained.

More preferably, the pore volume (B) of the pores with a pore diameter of 0.1 μm to 1 μm is 20% to 60% of the volume of pores with a pore diameter of 1 μm or less. In the range of 20% to 60%, the gas diffusion performance can be further improved and the catalyst performance can be improved.

More preferably, the pore volume (B) of the pores with a pore diameter of 0.1 μm to 1 μm is 30% to 50% of the volume of pores with a pore diameter of 1 μm or less. In the range of 30% to 50%, particularly good gas diffusion performance can be obtained, and good catalyst layer strength can be obtained in a well-balanced manner, and particularly good catalyst performance can be realized as a catalyst for exhaust gas purification.

Furthermore, by measuring the pore distribution of the catalyst layer by a known method such as mercury intrusion porosimetry, the ratio of the pore volume of the pores in such a catalyst layer with a pore diameter within a certain range can be examined.

The first compound 13 in the catalyst powder 11 may contain 70wt%-85wt% of CeO ₂ and 15wt%-30wt% of ZrO ₂ . When the first compound 13 mainly contains _CeO2 , in the first compound 13, the compound consisting of 70wt%-85wt% _CeO2 and 15wt%-30wt% _ZrO2 (the total amount is 100%) is suitable for the purification of exhaust gas . In particular, when supporting Pt as the noble metal 12, performance can be improved by supporting with a composite compound containing CeO ₂ and ZrO ₂ compared to when supporting only CeO ₂ . This is because the oxygen storage performance is increased by containing _ZrO2 . In addition, by using the complex compound, the adsorption force between Pt and the first compound 13 is enhanced, and the aggregation of Pt due to the thermal history can be suppressed. Containing more than 15wt% of _ZrO2 can significantly exhibit the effect of using the composite compound, but the oxygen storage performance of _CeO2 becomes weaker when the _ZrO2 content exceeds 30wt%.

In addition, the first compound 13 may be a composite compound containing La ₂ O ₃ in addition to CeO ₂ and ZrO ₂ .

The first compound 13 in the catalyst powder 11 may include 90wt%˜99wt% of _ZrO2 and 1wt%˜10wt% _{of La2O3} . When the first compound 13 mainly contains ZrO ₂ , in the first compound 13, the compound composed of 90wt%-99wt% _ZrO2 and 1wt% _-10wt % _La2O3 (100% in total) is suitable for exhaust gas purification. In particular, when supporting Rh as the noble metal 12, it is more suitable to support with a composite compound containing ZrO ₂ and La2O ₃ than when the first compound ₁₃ is only ZrO 2 . This is because the first compound 13 contains La ₂ O ₃ in addition to ZrO ₂ , which suppresses the aggregation of ZrO ₂ and suppresses Rh from being buried between ZrO ₂ particles. La ₂ O ₃ containing more than 1wt% can remarkably exhibit the effect of using the composite compound, but if La ₂ O ₃ contains more than 10wt%, there is the following hidden danger: La ₂ O ₃ dissolves and covers Rh.

The second compound 14 in the catalyst powder 11 preferably contains aluminum oxide. In order to purify the exhaust gas, the exhaust gas must diffuse to the noble metal through the second compound 14, and alumina, especially γ-alumina, is a porous substance with good gas diffusion performance and excellent heat resistance, so it is suitable for the second compound. Compound 14.

The second compound 14 in the catalyst powder 11 may be alumina containing 5wt%-15wt% CeO ₂ and 3wt%-10wt% ZrO ₂ . Alumina contains CeO ₂ and ZrO ₂ , which can suppress the performance degradation of the catalyst over a long period of time. This is because adding CeO ₂ and ZrO ₂ to alumina suppresses the transformation of γ-alumina into α-alumina, thereby suppressing deterioration of alumina due to thermal history (sintering phenomenon). Containing one of CeO ₂ and ZrO ₂ in alumina can suppress the performance degradation of the catalyst over a long period of time, but containing both CeO ₂ and ZrO ₂ can more effectively suppress the performance degradation of the catalyst over a long period of time. The content of CeO ₂ and ZrO ₂ in alumina is preferably in the range of 5wt% to 15wt% for CeO2 and _3wt % to 10wt% for ZrO2. If the lower limit of _the range is not reached, the addition of _CeO2 and _ZrO2 is insufficient. In addition, if the upper limit of the range is exceeded, there is a hidden danger that the performance degradation of the catalyst over a long period of time will be more serious.

The second compound 14 in _the catalyst powder 11 may be alumina containing 3wt%-10wt% _La2O3 . Alumina contains La ₂ O ₃ , which can suppress the performance degradation of the catalyst over a long period of time. This is because adding La ₂ O ₃ to alumina suppresses deterioration of alumina due to heat history (sintering phenomenon). If the La ₂ O ₃ content in alumina is less than 3 wt %, the effect of adding La ₂ O ₃ will be lacking, and if it exceeds 10 wt %, there is a risk that the performance of the catalyst will degrade even more after a long period of time. Therefore, the content of La ₂ O ₃ in alumina is preferably in the range of 3 wt % to 10 wt %.

The noble metal 12 in the catalyst powder 11 is preferably at least one selected from Pt, Pd, and Rh. Pt, Pd, and Rh are all metals having catalytic activity for exhaust gas, and are suitable as the noble metal 12 supported on the compound Ce—Zr—Ox, Zr—LaOx suitable as the first compound 13 .

One catalyst layer 10 containing the above-mentioned catalyst powder 11 may be formed on the inner surface 1a of the carrier 1, but it is preferable to form a plurality of layers of different types of noble metals on the inner surface 1a of the carrier 1. In a particularly preferred embodiment, an underlayer described later is formed on the inner surface 1 a of the carrier 1 , and two catalyst layers having different types of noble metals are formed on the underlayer. By forming a plurality of layers with different types of noble metals, the noble metals contained in the respective catalyst layers exhibit excellent exhaust gas purification performance, and the catalyst as a whole formed on the carrier 1 can effectively purify exhaust gas.

When forming the multilayer catalyst layer 10 on the inner surface 1 a of the carrier 1 , it is preferable to have a noble metal-free substrate layer between the inner surface 1 a of the carrier 1 and the catalyst layer 10 . By having a base layer that does not contain a noble metal on the side closer to the inner surface 1a of the carrier 1 than the catalyst layer 10, the base layer fills the four corners ( four corners). Therefore, in the multi-layer catalyst, the thickness of the catalyst layer in contact with the substrate layer is uniform, and the exhaust gas purification function of these catalyst layers can be effectively exerted.

The base layer preferably includes at least one of alumina and a hydrocarbon-adsorbing compound. Alumina is a general material for supporting noble metals in the catalyst layer, and can be suitably used as a noble metal-free substrate layer. In addition, by using the hydrocarbon-adsorbing compound as the substrate layer, hydrocarbons contained in the exhaust gas can be adsorbed by the hydrocarbon-adsorbing compound of the substrate layer when the gasoline engine is started. Therefore, the exhaust gas purification performance at the time of so-called cold start can be improved. Examples of the hydrocarbon-adsorbing compound include zeolite and mesoporous silica.

When the multilayer catalyst layer 10 is formed on the inner surface 1a of the carrier 1, the suitable combination of the catalyst powder contained in the catalyst layer on the inner side of the carrier is: the noble metal is at least one of Pt and Pd, and the first compound contains 70 wt. %-85wt% CeO ₂ and 15wt%-30wt% ZrO ₂ , the second compound is alumina containing 5wt%-15wt% CeO ₂ and 3wt%-10wt% ZrO ₂ . When there is no substrate layer on the inner surface of the carrier and two catalyst layers are formed, the catalyst layer on the inner surface side of the carrier refers to the first catalyst layer on the inner surface side of the carrier; when the substrate layer is formed on the inner surface of the carrier, and the substrate layer When two catalyst layers are formed on top, that is, a total of three layers are formed on the inner surface of the carrier, the catalyst layer on the inner surface of the carrier refers to the middle layer among the three layers (the layer on the inner surface of the carrier among the two catalyst layers). It is preferable to use such a combination of the noble metal, the first compound, and the second compound as the catalyst powder of the catalyst layer on the inner surface side, since the catalyst performance of Pt and Pd can be sufficiently exerted.

When the multilayer catalyst layer 10 is formed on the inner surface 1a of the carrier 1, another suitable combination of the composition of the catalyst powder contained in the catalyst layer on the inner side of the carrier is: the noble metal is at least one of Pt and Pd, and the first compound includes 70wt%-85wt% CeO ₂ and 15wt%-30wt% ZrO ₂ , the second compound is alumina containing 3wt%-10wt% La ₂ O ₃ . Use alumina containing 3wt% to 10wt% of _La2O3 instead _of the above-mentioned alumina containing 5wt% to 15wt% of _CeO2 and 3wt% to 10wt% of _ZrO2 as the catalyst powder of the catalyst layer contained on the inner side The second compound, such a combination can also give full play to the catalyst performance of Pt and Pd, so it is preferred.

When the multi-layer catalyst layer 10 is formed on the inner surface 1a of the carrier 1, the suitable combination of the composition of the catalyst powder contained in the catalyst layer on the surface side of the carrier is: the noble metal is Rh, and the first compound is 90 wt% to 99 wt% ZrO ₂ and 1wt%-10wt% of La ₂ O ₃ , the second compound is alumina. When there is no substrate layer on the inner surface of the carrier and two catalyst layers are formed, the catalyst layer on the carrier surface side refers to the second catalyst layer on the side away from the inner surface of the carrier; when the base layer is formed on the inner surface of the carrier, and When two catalyst layers are formed on the base layer, that is, three layers are formed on the inner surface of the carrier in total, the catalyst layer on the surface side of the carrier refers to the outermost layer of the three layers (the one on the surface side of the two catalyst layers) layer). It is preferable to use such a combination of the noble metal, the first compound, and the second compound as the catalyst powder of the catalyst layer on the surface side, since the catalytic performance of Rh can be sufficiently exhibited.

In the catalyst powder of the catalyst layer on the surface side, the noble metal-supported first compound is preferably 40 wt % to 75 wt %, and the second compound is preferably 25 wt % to 60 wt %. When the content ratio of the first compound and the second compound is within the above range, the catalyst layer on the surface side can effectively purify exhaust gas.

Next, an example of a suitable method for producing the exhaust gas-purifying catalyst of the present invention will be described. An example of the production method includes a step of preparing a catalyst powder and a step of forming the catalyst powder on the inner face of the carrier.

Wherein, the step of preparing the catalyst powder includes: the step of loading noble metal on the first compound, and dispersing the second compound or the precursor of the second compound in water, dissolving the cerium compound, the zirconium compound and the lanthanum compound therein if necessary At least one compound in the catalyst is slurried, and then the first compound loaded with noble metal is dispersed in the slurry of the second compound, dried and then sintered to obtain catalyst powder.

In the step of supporting the noble metal on the first compound, the method for supporting the noble metal on the first compound can be a known method and is not particularly limited. For example, an impregnation method or the like can be applied.

Separately from the step of supporting the noble metal on the first compound, the following step is carried out: the second compound or the precursor of the second compound is dispersed in water, and at least one of the cerium compound, the zirconium compound and the lanthanum compound is dissolved therein if necessary. A compound for slurrying. There is no mutual sequence between this step and the step of supporting the noble metal on the first compound. What is dispersed in water may be the second compound or a precursor of the second compound. In addition, when the second compound in the catalyst to be produced is a compound containing cerium, zirconium, and lanthanum, at least one of the cerium compound, zirconium compound, and lanthanum compound is dissolved in water in which the second compound or the precursor of the second compound is dispersed. a compound.

The noble metal-loaded first compound is dispersed in a slurry of the second compound or its precursor, and the slurry optionally dissolves at least one of a cerium compound, a zirconium compound, and a lanthanum compound. Such dispersing treatment, that is, disintegrating the aggregate of the first compound carrying the precious metal and dispersing it in the second compound, can be a method using an organic compound dispersant. In addition, a homogenizer, a physical method of grinding force (zulika) obtained by high-speed stirring can also be used.

After the above dispersion treatment, drying is performed. The drying method may be, for example, a method using a spray dryer, a vacuum freeze-drying method, etc., but the first compound loaded with the noble metal should be kept covered with the second compound, and the necessary pore volume of 0.24 cm ³ /g should be ensured. ~0.8 cm ³ /g.

Thereafter, sintering is performed to obtain catalyst powder. The sintering conditions may be the sintering conditions of general exhaust gas purification catalysts.

After the above-mentioned catalyst powder preparation step, the catalyst powder is formed on the inner face of the carrier as a catalyst layer. The forming step includes the following steps: adding a compound that disappears during sintering to the obtained catalyst powder, making a slurry, coating it on a carrier, drying, and sintering to form a region of 0.1 μm to 1 μm in the micropores of the catalyst layer A step of a catalyst layer having micropores therein.

The catalyst layer formed through this step needs to be a catalyst layer in which the micropores in the region of 0.1 μm to 1 μm account for a certain proportion of the micropores of the catalyst layer. For this purpose, a slurry is prepared in which a compound that disappears during sintering after coating (hereinafter referred to as "disappearing compound") is added to the slurry when the catalyst powder is slurried and coated on a carrier. The added disappearing compound disappears when the prepared slurry is applied to the carrier and then fired. The disappearing part effectively participates in the formation of micropores with a micropore diameter of 0.1 μm to 1 μm in the catalyst layer. As the disappearing compound, any substance may be used as long as it disappears during sintering, for example, resin powder, starch, carbon black, activated carbon, and the like. As the disappearing compound, powder with a particle size of 1 μm or less can be used, and powder with a particle size of 1 μm or more can also be used because it is pulverized to a particle size of 1 μm or less during slurry preparation. In addition, a liquid such as methylcellulose can also be used.

Example

Examples 1 to 8 are examples in which the proportion of micropores of 0.1 μm to 1 μm in the catalyst layer formed on the carrier is different.

(Example 1)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

)，然后加入90g前面制备的铈锆复合氧化物粒子A，通过高速搅拌进行分散。其后，对该浆料进行干燥、烧结，制备了粉末a-1，其中用氧化铝包覆了铈锆复合氧化物粒子A。Add 118.42g acicular boehmite (10nmφ×100nm) (water content 24%) in the beaker, make it dispersed in water, degumming with acid (solution

), and then add 90 g of the previously prepared cerium-zirconium composite oxide particles A, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-1 in which cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-1, 7 g of boehmite alumina and 9.21 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-1 to prepare a slurry having an average particle diameter of 3 μm (slurry a-1).

Next, the zirconium-lanthanum composite oxide particles with an average particle diameter of 20 nm were impregnated with rhodium nitrate to prepare particles B carrying 0.814% rhodium. Add 118.42 g of acicular boehmite (water content 24%) to the beaker, disperse it in water, degumming with acid, then add 90 g of particle B prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and fired to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina, and 9.21 g of activated carbon powder were added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% aqueous solution of nitric acid were added to the ball mill, and pulverized to obtain an average particle diameter of 3 μm. The slurry (slurry b-1).

Slurry a-1 is coated on diameter 36φ (namely 36mm), 400 hole (cell) 6 mil (mil) (namely, the wall thickness of honeycomb is 6/1000 inches, 400 holes are arranged on 1 square inch) The honeycomb carrier (capacity 0.04L) was dried and sintered to form a catalyst layer coated with 140g/L (that is, the amount of powder in the slurry attached to 1L of the honeycomb carrier was 140g). Thereafter, the slurry b-1 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 1. The obtained sample of Example 1 is a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Example 2)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add acicular boehmite (10nmφ × 100nm) 118.42g (water content 24%) in beaker, make it disperse in water, carry out degumming with acid, then add the cerium-zirconium composite oxide particle A prepared in front of 90g, through high-speed Stir to disperse. Thereafter, the slurry was dried and sintered to prepare powder a-1 in which cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-1, 7 g of boehmite alumina and 19.44 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-1 to prepare a slurry (slurry a-2) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (water content 24%) to the beaker, disperse it in water, degumming with acid, then add 90 g of particle B prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina, and 19.44 g of activated carbon powder were added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% aqueous solution of nitric acid were added to the ball mill, and pulverized to obtain an average particle diameter of 3 μm. The slurry (slurry b-2).

Slurry a-2 was coated on a honeycomb carrier (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-2 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 2. The obtained sample of Example 2 is a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Example 3)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add acicular boehmite (10nmφ × 100nm) 118.42g (water content 24%) in beaker, make it disperse in water, carry out degumming with acid, then add the cerium-zirconium composite oxide particle A prepared in front of 90g, through high-speed Stir to disperse. Thereafter, the slurry was dried and sintered to prepare powder a-1 in which cerium-zirconium composite oxide particles A were coated with alumina.

168 g of powder a-1, 7 g of boehmite alumina and 33.33 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-1 to prepare a slurry (slurry a-3) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (water content 24%) to the beaker, disperse it in water, degumming with acid, then add 90 g of particle B prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 33.33 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-3).

The slurry a-3 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-3 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 3. The obtained sample of Example 3 is a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Example 4)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add acicular boehmite (10nmφ × 100nm) 118.42g (water content 24%) in beaker, make it disperse in water, carry out degumming with acid, then add the cerium-zirconium composite oxide particle A prepared in front of 90g, through high-speed Stir to disperse. Thereafter, the slurry was dried and sintered to prepare powder a-1 in which cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-1, 7 g of boehmite alumina and 46.51 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to the ball mill to pulverize the powder a-1 to prepare a slurry having an average particle diameter of 3 μm (slurry a-4).

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (water content 24%) to the beaker, disperse it in water, degumming with acid, then add 90 g of particle B prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 46.51 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-4).

The slurry a-4 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-4 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 4. The obtained sample of Example 4 is a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Example 5)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add acicular boehmite (10nmφ × 100nm) 118.42g (water content 24%) in beaker, make it disperse in water, carry out degumming with acid, then add the cerium-zirconium composite oxide particle A prepared in front of 90g, through high-speed Stir to disperse. Thereafter, the slurry was dried and sintered to prepare powder a-1 in which cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-1, 7 g of boehmite alumina, and 61.48 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to the ball mill, and the powder a-1 was pulverized to prepare a slurry having an average particle diameter of 3 μm (slurry a-5).

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (water content 24%) to the beaker, disperse it in water, degumming with acid, then add 90 g of particle B prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168g of the powder b-1, 7g of boehmite alumina and 61.48g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-5).

The slurry a-5 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-5 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 5. The obtained sample of Example 5 is a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Example 6)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add acicular boehmite (10nmφ × 100nm) 118.42g (water content 24%) in beaker, make it disperse in water, carry out degumming with acid, then add the cerium-zirconium composite oxide particle A prepared in front of 90g, through high-speed Stir to disperse. Thereafter, the slurry was dried and sintered to prepare powder a-1 in which cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-1, 7 g of boehmite alumina and 75 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to the ball mill, and the powder a-1 was pulverized to prepare a slurry having an average particle diameter of 3 μm (slurry a-6).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (water content 24%) to the beaker, disperse it in water, degumming with acid, then add 90 g of particle B prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 75 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-6).

The slurry a-6 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-6 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 6. The obtained sample of Example 6 is a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Example 7)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A2).

Add 118.42g of acicular boehmite (10nmφ×100nm) (24% water content) into a beaker, disperse with water, degelize with acid, then add 90g of the previously prepared cerium-zirconium composite oxide particles A2, and disperse by high-speed stirring . Thereafter, the slurry was dried and sintered to prepare powder a-2 in which cerium-zirconium composite oxide particles A2 were coated with alumina.

168 g of this powder a-2, 7 g of boehmite alumina and 33.3 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to the ball mill, and the powder a-2 was pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry a-7).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 33.3 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-7).

Slurry a-7 was coated on a honeycomb carrier (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-7 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 7. The obtained sample of Example 7 is a catalyst supporting Pd: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Embodiment 8)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-loaded cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A2).

Add 118.42g of acicular boehmite (10nmφ×100nm) (24% water content) into a beaker, disperse with water, degelize with acid, then add 90g of the previously prepared cerium-zirconium composite oxide particles A2, and disperse by high-speed stirring . Thereafter, the slurry was dried and sintered to prepare powder a-2 in which cerium-zirconium composite oxide particles A2 were coated with alumina.

168 g of this powder a-2, 7 g of boehmite alumina and 46.51 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-2 to prepare a slurry (slurry a-8) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 46.51 g of activated carbon powder were added to the ball mill. Then, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-8).

The slurry a-8 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-8 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 8. The obtained samples of Example 8 were catalysts in which Pd: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Examples 9 to 14 are examples in which the pore volumes of the catalyst powders are different.

(Example 9)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add 118.42g of acicular boehmite (10nmφ×100nm) (water content 24%) to the beaker, disperse with water, degelize with acid, then add 90g of the previously prepared cerium-zirconium composite oxide particles A, and disperse by high-speed stirring . Thereafter, the slurry was dried and sintered to prepare powder a-1 in which cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-1, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to the ball mill to pulverize the powder a-1 to prepare a slurry having an average particle diameter of 3 μm (slurry a-11).

Next, the zirconium-lanthanum composite oxide particles with an average particle diameter of 20 nm were impregnated with rhodium nitrate to prepare particles B carrying 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-11).

The slurry a-11 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-11 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 9. The obtained sample of Example 9 was a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L.

(Example 10)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add 113.92g of platy boehmite (20×20×10nm) (water content 21%) in the beaker, disperse it with water, degumming with acid, then add 90g of the cerium-zirconium composite oxide particle A prepared above, and stir it at a high speed to disperse. Thereafter, the slurry was dried and sintered to prepare a powder a-4 in which the cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-4, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and the powder a-4 was pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry a-12).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 113.92 g of platy boehmite (water content 21%) into a beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-3 in which particles B were coated with alumina.

168 g of this powder b-3, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-12).

The slurry a-12 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, the slurry b-12 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 10. The obtained sample of Example 10 is a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Example 11)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add 105.88g of cubic (20×20×20nm) boehmite (water content 15%) in the beaker, disperse with water, degelize with acid, then add 90g of cerium-zirconium composite oxide particles A prepared above, and stir at high speed to disperse. Thereafter, the slurry was dried and sintered to prepare a powder a-5 in which the cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-5, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to the ball mill, and the powder a-5 was pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry a-13).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 105.88 g of cubic boehmite (15% water content) into a beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-4 in which particles B were coated with alumina.

168 g of this powder b-4, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-13).

The slurry a-13 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-13 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 11. The obtained sample of Example 11 is a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L, respectively.

(Example 12)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add 102.27g of prismatic boehmite (20×20×60nm) (water content 12%) in a beaker, disperse with water, degelize with acid, then add 90g of the cerium-zirconium composite oxide particles A prepared above, and stir at a high speed to disperse. Thereafter, the slurry was dried and sintered to prepare a powder a-6 in which the cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-6, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-6 to obtain a slurry having an average particle diameter of 3 μm (slurry a-14).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 102.27 g of prismatic boehmite (12% water content) into a beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-5 in which particles B were coated with alumina.

168 g of this powder b-5, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-14).

The slurry a-14 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-14 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 12. The obtained samples of Example 12 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 13)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-loaded cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A2).

Add 113.92g of platy boehmite (20×20×10nm) (21% water content) into a beaker, disperse it with water to make it acidic, add 90g of the previously prepared cerium-zirconium composite oxide particles A2, and disperse by high-speed stirring . Thereafter, the slurry was dried and sintered to prepare powder a-7 in which cerium-zirconium composite oxide particles A2 were coated with alumina.

168 g of this powder a-7, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-7 to prepare a slurry (slurry a-15) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 113.92 g of platy boehmite (20×20×10 nm) (water content 21%) in a beaker, disperse with water to make it acidic, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-3 in which particles B were coated with alumina.

168 g of this powder b-3, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Then, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-12).

The slurry a-15 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, the slurry b-12 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 13. The obtained samples of Example 13 were catalysts in which Pd: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 14)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-loaded cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A2).

Add 105.88g of cubic (20×20×20nm) boehmite (15% water content) into a beaker, disperse with water, degelize with acid, then add 90g of cerium-zirconium composite oxide particles A2 prepared above, and stir at high speed to disperse. Thereafter, the slurry was dried and sintered to prepare powder a-8 in which cerium-zirconium composite oxide particles A2 were coated with alumina.

168 g of this powder a-8, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-8 to prepare a slurry (slurry a-16) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 105.88g of cubic (20×20×20nm) boehmite (15% water content) into a beaker, disperse with water, degumming with acid, then add 90g of particle B prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-4 in which particles B were coated with alumina.

168 g of this powder b-4, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-13).

The slurry a-16 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-13 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 14. The obtained samples of Example 14 were catalysts in which Pd: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

In Examples 15 to 17, the first compound contained CeO ₂ and ZrO ₂ , but the composite ratios of CeO ₂ and ZrO ₂ were different.

(Example 15)

As the first compound, cerium-zirconium composite oxide particles of 70% cerium and 30% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A3).

Add 105.88g of cubic (20×20×20nm) boehmite (15% water content) into a beaker, disperse with water, degumming with acid, then add 90g of the previously prepared particle A3, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-11 in which particles A3 were coated with alumina.

168 g of this powder a-11, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to the ball mill to pulverize the powder a-11 to prepare a slurry having an average particle diameter of 3 μm (slurry a-19).

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles of 90% zirconium and 10% lanthanum to prepare particles B2 carrying 0.814% rhodium. Add 105.88g of cubic (20×20×20nm) boehmite (15% water content) into a beaker, disperse with water, degumming with acid, then add 90g of the previously prepared particle B2, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-8 in which particles B2 were coated with alumina.

168 g of this powder b-8, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-17).

The slurry a-19 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-17 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 15. The obtained samples of Example 15 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 16)

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

Add 105.88g of cubic (20×20×20nm) boehmite (15% water content) into a beaker, disperse with water, degelize with acid, then add 90g of the previously prepared cerium-zirconium composite oxide particles A4, and stir at a high speed to disperse. Thereafter, the slurry was dried and sintered to prepare a powder a-12 in which particles A4 were coated with alumina.

168g of this powder a-12, 7g of boehmite alumina and 52.27g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-12 to prepare a slurry (slurry a-20) having an average particle diameter of 3 μm.

Next, the zirconium-lanthanum composite oxide particles of 95% zirconium and 5% lanthanum were impregnated with rhodium nitrate to prepare particles B3 carrying 0.814% rhodium. Add 105.88g of cubic (20×20×20nm) boehmite (15% water content) into the beaker, disperse with water, degumming with acid, then add 90g of the previously prepared particle B3, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-9 in which particles B3 were coated with alumina.

168 g of this powder b-9, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-18).

The slurry a-20 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-18 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 16. The obtained samples of Example 16 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 17)

As the first compound, cerium-zirconium composite oxide particles of 85% cerium and 15% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A5).

Add 105.88g of cubic (20×20×20nm) boehmite (water content 15%) in a beaker, disperse it with water, degelize it with acid, then add 90g of the previously prepared cerium-zirconium composite oxide particles A5, and stir it at a high speed to disperse. Thereafter, the slurry was dried and sintered to prepare powder a-13 in which particles A5 were coated with alumina.

168g of this powder a-13, 7g of boehmite alumina and 52.27g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-13 to prepare a slurry having an average particle diameter of 3 μm (slurry a-21).

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles of 99% zirconium and 1% lanthanum to prepare particles B4 carrying 0.814% rhodium. Add 105.88g of cubic (20×20×20nm) boehmite (15% water content) into a beaker, disperse with water, degumming with acid, then add 90g of previously prepared particle B4, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder b-10 in which particles B4 were coated with alumina.

168g of this powder b-10, 7g of boehmite alumina and 52.27g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-19).

The slurry a-21 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140g/L. Thereafter, slurry b-19 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 17. The obtained sample of Example 17 was a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L.

In Examples 18 to 20, the second compound was alumina containing CeO ₂ and ZrO ₂ , but the contents of CeO ₂ and ZrO ₂ were different.

(Example 18)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

101.46 g of acicular boehmite (10nmφ×100nm) (water content 24.6%) was added to a beaker filled with water, 4.5 g of cerium nitrate as cerium oxide was added thereto, and 9 g of zirconia was dispersed in water zirconium nitrate, and then add 90 g of the previously prepared cerium-zirconium composite oxide particles A, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-16 in which cerium-zirconium composite oxide particles A were coated with alumina.

168g of this powder a-16, 7g of boehmite alumina and 52.27g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% aqueous solution of nitric acid were added to the ball mill to pulverize the powder a-16 to prepare a slurry (slurry a-24) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-11).

The slurry a-24 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-11 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 18. The obtained samples of Example 18 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 19)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

101.46 g of acicular boehmite (10nmφ×100nm) (water content 24.6%) was added to a beaker filled with water, 9 g of cerium nitrate as cerium oxide was added thereto, and 4.5 g of zirconia was dispersed in water zirconium nitrate, and then add 90 g of the previously prepared cerium-zirconium composite oxide particles A, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-17 in which cerium-zirconium composite oxide particles A were coated with alumina.

168g of this powder a-17, 7g of boehmite alumina and 52.27g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-17 to prepare a slurry (slurry a-25) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-11).

The slurry a-25 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-11 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 19. The obtained samples of Example 19 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 20)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add 111.14 g of acicular boehmite (10nmφ×100nm) (water content 24.6%) to a beaker filled with water, add 13.5 g of cerium nitrate as cerium oxide to it, and disperse in water 2.7 g of zirconia. g of zirconium nitrate, and then add 90 g of the previously prepared cerium-zirconium composite oxide particles A, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-18 in which cerium-zirconium composite oxide particles A were coated with alumina.

168g of this powder a-18, 7g of boehmite alumina and 52.27g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-18 to prepare a slurry having an average particle diameter of 3 μm (slurry a-26).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-11).

The slurry a-26 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-11 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 20. The obtained sample of Example 20 was a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L.

In Examples 21 to 23, the second compound is alumina containing La ₂ O ₃ , but the content of La ₂ O ₃ is different.

(Example 21)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add acicular boehmite (10nmφ×100nm) 115.78g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 2.7g as lanthanum oxide, disperse with water, then add 90g previously prepared The cerium-zirconium composite oxide particles A are dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-21 in which cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-21, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-21 to prepare a slurry having an average particle diameter of 3 μm (slurry a-29).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-11).

The slurry a-29 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-11 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 21. The obtained samples of Example 21 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 22)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add acicular boehmite (10nmφ × 100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse with water, then add 90g previously prepared The cerium-zirconium composite oxide particles A are dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-22 in which the cerium-zirconium composite oxide particles A were coated with alumina.

168g of this powder a-22, 7g of boehmite alumina and 52.27g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-22 to prepare a slurry (slurry a-30) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 52.27 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-11).

The slurry a-30 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-11 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This is the sample of Example 22. The obtained samples of Example 22 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 23)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Add 107.43g of acicular boehmite (10nmφ×100nm) (24.6% water content) into a beaker filled with water, add 9g of lanthanum nitrate as lanthanum oxide to it, disperse with water, and then add 90g of the previously prepared cerium The zirconium composite oxide particles A were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-23 in which the cerium-zirconium composite oxide particles A were coated with alumina.

168g of this powder a-23, 7g of boehmite alumina and 52.27g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% aqueous solution of nitric acid were added to a ball mill to pulverize the powder a-23 to prepare a slurry having an average particle diameter of 3 μm (slurry a-31).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 52.27 g of activated carbon powder were charged into the ball mill. Then, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-11).

The slurry a-31 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Thereafter, slurry b-11 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 23. The obtained samples of Example 23 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Examples 24 to 27 include a substrate layer, wherein the second compound of the catalyst in the intermediate layer is alumina containing CeO ₂ and ZrO ₂ .

(Example 24)

180 g of γ-alumina powder and 20 g of boehmite alumina were added to a ball mill, and then 282.5 g of water and 17.5 g of 10% nitric acid were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry c-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

101.46 g of acicular boehmite (10nmφ×100nm) (water content 24.6%) was added to a beaker filled with water, 9 g of cerium nitrate as cerium oxide was added thereto, and 4.5 g of zirconia was dispersed in water zirconium nitrate, and then add 90 g of cerium-zirconium composite oxide particles A4 prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-26 in which cerium-zirconium composite oxide particles A4 were coated with alumina.

168g of this powder a-26, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to the ball mill, and the powder a-26 was pulverized to prepare a slurry (slurry a-34) having an average particle diameter of 3 μm.

Next, the zirconium-lanthanum composite oxide particles with an average particle diameter of 20 nm were impregnated with rhodium nitrate to prepare particles B carrying 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-31).

Slurry c-1 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L alumina layer. Next, slurry a-34 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-31 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 24. The obtained samples of Example 24 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 25)

180 g of zeolite beta, 288 g of silica sol (SiO ₂ : 15%), and 32 g of water were added to a ball mill and pulverized to prepare a slurry having an average particle diameter of 3 μm (slurry d-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

101.46 g of acicular boehmite (10nmφ×100nm) (water content 24.6%) was added to a beaker filled with water, 9 g of cerium nitrate as cerium oxide was added thereto, and 4.5 g of zirconia was dispersed in water zirconium nitrate, and then add 90 g of cerium-zirconium composite oxide particles A4 prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-26 in which cerium-zirconium composite oxide particles A4 were coated with alumina.

168g of this powder a-26, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-26 to prepare a slurry having an average particle diameter of 3 μm (slurry a-34).

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-31).

Slurry d-1 was coated on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L beta zeolite layer. Next, slurry a-34 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-31 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This is the sample of Example 25. The obtained samples of Example 25 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 26)

180 g of γ-alumina powder and 20 g of boehmite alumina were added to a ball mill, and then 282.5 g of water and 17.5 g of 10% nitric acid were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry c-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-supported cerium-zirconium composite oxide particles (this is particle A8).

101.46 g of acicular boehmite (10nmφ×100nm) (water content 24.6%) was added to a beaker filled with water, 9 g of cerium nitrate as cerium oxide was added thereto, and 4.5 g of zirconia was dispersed in water zirconium nitrate, and then add 90 g of cerium-zirconium composite oxide particles A8 prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-27 in which cerium-zirconium composite oxide particles A8 were coated with alumina.

168 g of this powder a-27, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and the powder a-27 was pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry a-35).

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (water content 24%) to the beaker, disperse with water, degumming with acid, then add 90 g of the particle B prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-31).

Slurry c-1 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L alumina layer. Next, slurry a-35 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-31 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 26. The obtained sample of Example 26 was a catalyst supporting Pd: 0.5712 g/L and Rh: 0.2344 g/L.

(Example 27)

180 g of zeolite beta, 288 g of silica sol (SiO ₂ : 15%), and 32 g of water were added to a ball mill, and then pulverized to prepare a slurry having an average particle diameter of 3 μm (slurry d-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-supported cerium-zirconium composite oxide particles (this is particle A8).

101.46 g of acicular boehmite (10nmφ×100nm) (water content 24.6%) was added to a beaker filled with water, 9 g of cerium nitrate as cerium oxide was added thereto, and 4.5 g of zirconia was dispersed in water zirconium nitrate, and then add 90 g of cerium-zirconium composite oxide particles A8 prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-27 in which cerium-zirconium composite oxide particles A8 were coated with alumina.

168 g of this powder a-27, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-27 to prepare a slurry (slurry a-35) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-31).

Slurry d-1 was coated on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L beta zeolite layer. Next, slurry a-35 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-31 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 27. The obtained sample of Example 27 was a catalyst supporting Pd: 0.5712 g/L and Rh: 0.2344 g/L.

Examples 28 to 31 include a substrate layer, wherein the second compound of the catalyst in the intermediate layer is alumina containing La ₂ O ₃ .

(Example 28)

180 g of γ-alumina powder and 20 g of boehmite alumina were added to a ball mill, and then 282.5 g of water and 17.5 g of 10% nitric acid were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry c-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A4 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-30 in which cerium-zirconium composite oxide particles A4 were coated with alumina.

168g of this powder a-30, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-30 to prepare a slurry (slurry a-38) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-31).

Slurry c-1 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L alumina layer. Next, slurry a-38 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-31 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This was used as a sample of Example 28. The obtained samples of Example 28 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 29)

180 g of zeolite beta, 288 g of silica sol (SiO ₂ : 15%), and 32 g of water were added to a ball mill, and then pulverized to prepare a slurry having an average particle diameter of 3 μm (slurry d-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A4 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-30 in which cerium-zirconium composite oxide particles A4 were coated with alumina.

168g of this powder a-30, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-30 to prepare a slurry having an average particle diameter of 3 μm (slurry a-38).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-31).

Slurry d-1 was coated on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L beta zeolite layer. Next, slurry a-38 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-31 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 29. The obtained sample of Example 29 was a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L.

(Example 30)

180 g of γ-alumina powder and 20 g of boehmite alumina were added to a ball mill, and then 282.5 g of water and 17.5 g of 10% nitric acid were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry c-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-supported cerium-zirconium composite oxide particles (this is particle A8).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A8 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-31 in which cerium-zirconium composite oxide particles A8 were coated with alumina.

168 g of this powder a-31, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-31 to prepare a slurry having an average particle diameter of 3 μm (slurry a-39).

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (water content 24%) to the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-31).

Slurry c-1 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L alumina layer. Next, slurry a-39 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-31 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 30. The obtained samples of Example 30 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 31)

180 g of zeolite beta, 288 g of silica sol (SiO ₂ : 15%), and 32 g of water were added to a ball mill, and then pulverized to prepare a slurry having an average particle diameter of 3 μm (slurry d-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-supported cerium-zirconium composite oxide particles (this is particle A8).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A8 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-31 in which cerium-zirconium composite oxide particles A8 were coated with alumina.

168 g of this powder a-31, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-31 to prepare a slurry (slurry a-39) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 118.42 g of acicular boehmite (24% water content) into the beaker, disperse with water, degumming with acid, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-1 in which particles B were coated with alumina.

168 g of this powder b-1, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Then, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-31).

Slurry d-1 was coated on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L beta zeolite layer. Next, slurry a-39 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-31 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 31. The obtained samples of Example 31 were catalysts in which Pd: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Examples 28 to 31 include a substrate layer, wherein the second compound of the catalyst in the intermediate layer is alumina containing La ₂ O ₃ .

Examples 32 to 37 have a substrate layer, but the ratios of the first compound and the second compound of the surface layer catalyst are different.

(Example 32)

180 g of γ-alumina powder and 20 g of boehmite alumina were added to a ball mill, and then 282.5 g of water and 17.5 g of 10% nitric acid were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry c-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A4 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-30 in which cerium-zirconium composite oxide particles A4 were coated with alumina.

168g of this powder a-30, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-30 to prepare a slurry having an average particle diameter of 3 μm (slurry a-38).

Next, rhodium nitrate was impregnated into zirconium-lanthanum (99:1) composite oxide particles having an average particle diameter of 20 nm to prepare particles B13 carrying 1.0175% rhodium. Add 142.1 g of acicular boehmite (water content 24%) to the beaker, disperse with water, degumming with acid, then add 72 g of the previously prepared particle B13, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-13 in which particles B were coated with alumina.

168 g of this powder b-13, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-41).

Slurry c-1 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L alumina layer. Next, slurry a-38 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-41 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This was used as a sample of Example 32. The obtained samples of Example 32 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 33)

180 g of gamma alumina powder and 20 g of boehmite alumina were added to a ball mill, and then 282.5 g of water and 17.5 g of 10% nitric acid were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry c-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A4 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-30 in which cerium-zirconium composite oxide particles A4 were coated with alumina.

168g of this powder a-30, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-30 to prepare a slurry (slurry a-38) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum (99:1) composite oxide particles having an average particle diameter of 20 nm to prepare particles B14 carrying 0.5814% rhodium. Add 71.1 g of acicular boehmite (water content 24%) to the beaker, disperse with water, degumming with acid, then add 126 g of the previously prepared particle B14, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-14 in which particles B14 were coated with alumina.

168 g of this powder b-14, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Then, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-42).

Slurry c-1 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L alumina layer. Next, slurry a-38 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-42 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 33. The obtained sample of Example 33 was a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L.

(Example 34)

180 g of gamma alumina powder and 20 g of boehmite alumina were added to a ball mill, and then 282.5 g of water and 17.5 g of 10% nitric acid were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry c-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A4 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-30 in which cerium-zirconium composite oxide particles A4 were coated with alumina.

168g of this powder a-30, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Then, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to pulverize the powder a-30 to prepare a slurry (slurry a-38) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum (99:1) composite oxide particles with an average particle diameter of 20 nm to prepare particles B15 carrying 0.5426% rhodium. Add 59.21 g of acicular boehmite (water content 24%) to the beaker, disperse with water, degumming with acid, then add 135 g of the previously prepared particle B15, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-15 in which particles B15 were coated with alumina.

168g of this powder b-15, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-43).

Slurry c-1 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L alumina layer. Next, slurry a-38 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-43 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This was used as a sample of Example 34. The obtained sample of Example 34 was a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L.

(Example 35)

180 g of γ-alumina powder and 20 g of boehmite alumina were added to a ball mill, and then 282.5 g of water and 17.5 g of 10% nitric acid were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry c-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-supported cerium-zirconium composite oxide particles (this is particle A8).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A8 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-31 in which cerium-zirconium composite oxide particles A8 were coated with alumina.

168 g of this powder a-31, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-31 to prepare a slurry (slurry a-39) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum (99:1) composite oxide particles having an average particle diameter of 20 nm to prepare particles B14 carrying 0.5814% rhodium. Add 71.1 g of acicular boehmite (water content 24%) to the beaker, disperse with water, degumming with acid, then add 126 g of the previously prepared particle B14, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-14 in which particles B14 were coated with alumina.

168 g of this powder b-14, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-42).

Slurry c-1 was coated on a honeycomb support (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L alumina layer. Next, slurry a-39 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-42 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 35. The obtained samples of Example 35 were catalysts in which Pd: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 36)

180 g of zeolite beta, 288 g of silica sol (SiO ₂ : 15%), and 32 g of water were added to a ball mill, and then pulverized to prepare a slurry having an average particle diameter of 3 μm (slurry d-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A4).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A4 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-30 in which cerium-zirconium composite oxide particles A4 were coated with alumina.

168g of this powder a-30, 7g of boehmite alumina and 38.41g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-30 to prepare a slurry (slurry a-38) having an average particle diameter of 3 μm.

Next, zirconium-lanthanum (99:1) composite oxide particles with an average particle size of 20 nm were impregnated with rhodium nitrate to prepare particles B14 carrying 0.5814% rhodium. Add 71.1 g of acicular boehmite (water content 24%) to the beaker, disperse with water, degumming with acid, then add 126 g of the previously prepared particle B14, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-14 in which particles B14 were coated with alumina.

168 g of this powder b-14, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-42).

Slurry d-1 was coated on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L beta zeolite layer. Next, slurry a-38 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-42 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Example 36. The obtained samples of Example 36 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Example 37)

180 g of zeolite beta, 288 g of silica sol (SiO ₂ : 15%), and 32 g of water were added to a ball mill and pulverized to prepare a slurry having an average particle diameter of 3 μm (slurry d-1).

As the first compound, cerium-zirconium composite oxide particles of 78% cerium and 22% zirconium were used. The particles were impregnated with dinitrodiammine palladium to prepare 0.85% Pd-supported cerium-zirconium composite oxide particles (this is particle A8).

Add acicular boehmite (10nmφ×100nm) 113.40g (water content 24.6%) in the beaker that water is housed, add therein the lanthanum nitrate that is 4.5g as lanthanum oxide, disperse in water, then add 90g prepared before The cerium-zirconium composite oxide particles A8 were dispersed by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder a-31 in which cerium-zirconium composite oxide particles A8 were coated with alumina.

168 g of this powder a-31, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-31 to prepare a slurry having an average particle diameter of 3 μm (slurry a-39).

Next, rhodium nitrate was impregnated into zirconium-lanthanum (99:1) composite oxide particles having an average particle diameter of 20 nm to prepare particles B14 carrying 0.5814% rhodium. Add 71.1 g of acicular boehmite (water content 24%) to the beaker, disperse with water, degumming with acid, then add 126 g of the previously prepared particle B14, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-14 in which particles B14 were coated with alumina.

168 g of this powder b-14, 7 g of boehmite alumina and 38.41 g of activated carbon powder were added to the ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill, and pulverized to obtain a slurry having an average particle diameter of 3 μm (slurry b-42).

Slurry d-1 was coated on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a 50g/L beta zeolite layer. Next, slurry a-39 was applied, dried, and fired to prepare a catalyst layer coated with 140 g/L. Thereafter, slurry b-42 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This was used as a sample of Example 37. The obtained samples of Example 37 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Comparative Examples 1 and 2 are examples for comparison with Examples 1-8.

(comparative example 1)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The cerium-zirconium composite oxide particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particles A).

90 g of aluminum isopropoxide in terms of Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 90 g of cerium-zirconium composite oxide particles A were added thereto, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-3 in which particles A were coated with alumina. The particle size of the alumina is 7 to 8 nm.

168 g of this powder a-3 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-3 to obtain a slurry having an average particle diameter of 3 μm (slurry a-9).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

Add 168g of this powder b-2 and 7g of boehmite alumina in a ball mill, then add 307.5g of water and 17.5g of 10% nitric acid aqueous solution, and pulverize to prepare a slurry with an average particle diameter of 3 μm (slurry b- 9).

Apply 140g/L slurry a-9 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, after drying, apply 60g/L slurry b-9, and sinter at 400°C after drying , as the sample of Comparative Example 1. The obtained samples of Comparative Example 1 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(comparative example 2)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The cerium-zirconium composite oxide particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particles A).

90 g of aluminum isopropoxide in terms of Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 90 g of cerium-zirconium composite oxide particles A were added thereto, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-3 in which particles A were coated with alumina. The particle size of the alumina is 7 to 8 nm.

168 g of this powder a-3, 7 g of boehmite alumina and 94.23 g of activated carbon powder were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-3 to obtain a slurry having an average particle diameter of 3 μm (slurry a-10).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

168g of this powder b-2, 7g of boehmite alumina and 94.23g of activated carbon powder were added to a ball mill, and then 307.5g of water and 17.5g of 10% nitric acid aqueous solution were added and pulverized to prepare a slurry with an average particle size of 3 μm. (Slurry b-10).

Slurry a-10 is coated on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, dried and sintered to form a catalyst layer coated with 140g/L, and then coated with slurry b -10, dried and sintered to make a catalyst layer coated with 60g/L. This was used as a sample of Comparative Example 2. The obtained samples of Comparative Example 2 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Comparative Examples 3 and 4 are examples for comparison with Examples 9-14.

(comparative example 3)

As the first compound, cerium-zirconium composite oxide particles having a pore volume of 0.15 cm ³ /g were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle Aa).

90 g of aluminum isopropoxide as Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 90 g of the particles Aa were added thereto, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-9 in which particles Aa were coated with alumina.

168 g of this powder a-9 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-9 to prepare a slurry (slurry a-17) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles with a pore volume of 0.16 cm ³ /g to prepare particles Bb carrying 0.814% rhodium. 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 90 g of the particles Bb were added thereto, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-6 in which particles were coated with alumina.

Add 168g of this powder b-6 and 7g of boehmite alumina in a ball mill, then add 307.5g of water and 17.5g of 10% nitric acid aqueous solution, and pulverize to prepare a slurry with an average particle diameter of 3 μm (slurry b- 15).

The slurry a-17 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Then, slurry b-15 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Comparative Example 3. The obtained samples of Comparative Example 3 were catalysts in which Pd: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(comparative example 4)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The cerium-zirconium composite oxide particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particles A).

Add 90.9 g of alumina nanoparticles (water content 1%) with an average particle diameter of 130 nm in a beaker, disperse with water, adjust to acidity, then add 90 g of cerium-zirconium composite oxide particles A prepared above, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare a powder a-10 in which the cerium-zirconium composite oxide particles A were coated with alumina.

168 g of this powder a-10 and 7 g of boehmite alumina were added to a ball mill. Then, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-10 to prepare a slurry having an average particle diameter of 3 μm (slurry a-18).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Add 90.9 g of alumina nanoparticles (1% water content) with an average particle diameter of 130 nm in a beaker, disperse with water, adjust to acidity, then add 90 g of the previously prepared particle B, and disperse by high-speed stirring. Thereafter, the slurry was dried and sintered to prepare powder b-7 in which particles B were coated with alumina.

Add 168g of this powder b-7 and 7g of boehmite alumina in a ball mill, then add 307.5g of water and 17.5g of 10% nitric acid aqueous solution, and pulverize to make a slurry with an average particle diameter of 3 μm (slurry b-16 ).

The slurry a-18 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Then, slurry b-16 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Comparative Example 4. The obtained samples of Comparative Example 4 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Comparative Examples 5 and 6 are examples for comparison with Examples 15-17.

(comparative example 5)

As the first compound, cerium-zirconium composite oxide particles of 60% cerium and 40% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (other particles A6).

90 g of aluminum isopropoxide in terms of Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 90 g of the particles A6 were added thereto, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-14 in which particles A6 were coated with alumina.

168 g of this powder a-14 and 7 g of boehmite alumina were added to a ball mill. Then, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-14 to prepare a slurry having an average particle diameter of 3 μm (slurry a-22).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having 80% zirconium and 20% lanthanum to prepare particles B5 carrying 0.814% rhodium. 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 90 g of the particles B5 were added thereto, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-11 in which particles B5 were coated with alumina.

Add 168g of this powder b-11 and 7g of boehmite alumina in the ball mill, then add water 307.5g and 10% nitric acid aqueous solution 17.5g, pulverize, make the slurry (slurry b-20 ).

The slurry a-22 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Then, slurry b-20 was applied, dried, and fired to prepare a catalyst layer coated with 60 g/L. This was used as a sample of Comparative Example 5. The obtained samples of Comparative Example 5 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(comparative example 6)

As the first compound, cerium-zirconium composite oxide particles of 90% cerium and 10% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (other particles A7).

90 g of aluminum isopropoxide in terms of Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 90 g of the particles A7 were added thereto, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-15 in which particles A7 were coated with alumina.

168 g of this powder a-15 and 7 g of boehmite alumina were added to a ball mill. Then, 307.5 g of water and 17.5 g of a 10% aqueous solution of nitric acid were added to a ball mill to pulverize the powder a-15 to obtain a slurry (slurry a-23) having an average particle diameter of 3 μm.

Next, the particles of 100% zirconium were impregnated with rhodium nitrate to prepare particles B6 supporting 0.814% of rhodium. 90 g of aluminum isopropoxide as Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 90 g of the particles B6 were added thereto, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-12 in which particles B6 were coated with alumina.

Add 168g of this powder b-12 and 7g of boehmite alumina in the ball mill, then add 307.5g of water and 17.5g of 10% nitric acid aqueous solution, pulverize, and make a slurry with an average particle diameter of 3 μm (slurry b-21 ).

The slurry a-23 was coated on a honeycomb support (capacity 0.04 L) with a diameter of 36φ and 400 holes of 6 mils, dried and sintered to form a catalyst layer coated with 140 g/L. Then, slurry b-21 was applied, dried, and fired to obtain a catalyst layer coated with 60 g/L. This was used as a sample of Comparative Example 6. The obtained samples of Comparative Example 6 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Comparative Examples 7 and 8 are examples for comparison with Examples 18-20.

(comparative example 7)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

87.3 g of aluminum isopropoxide as Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 1.8 g of cerium acetylacetonate as cerium oxide was added thereto, and in addition, The zirconium oxide was 0.9 g of zirconium acetylacetonate, to which 90 g of the particle A was added, and water was added to carry out hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-19 in which particles A were coated with alumina.

168 g of this powder a-19 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-19 to prepare a slurry (slurry a-27) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% of rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

Add 168g powder b-2 and 7g boehmite alumina in the ball mill, then add water 307.5g and 10% nitric acid aqueous solution 17.5g, pulverize, have made the slurry (slurry b-9 of average particle diameter 3 μ m) ).

Coat 140g/L slurry a-27 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, apply 60g/L slurry b-9 after drying, and sinter at 400°C after drying. A sample of Comparative Example 7 was produced. The obtained samples of Comparative Example 7 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(comparative example 8)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Dissolve 58.5 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 18 g of cerium acetylacetonate in terms of cerium oxide, and add Zirconium was 13.5 g of zirconium acetylacetonate, to which 90 g of the particle A was added, and water was added to carry out hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-20 in which particles A were coated with alumina.

168 g of this powder a-20 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-20 to obtain a slurry having an average particle diameter of 3 μm (slurry a-28).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

168 g of powder b-2 and 7 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry b-9) .

Apply 140g/L slurry a-28 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, and apply 60g/L slurry b-9 after drying, and sinter at 400°C after drying. A sample of Comparative Example 8 was prepared. The obtained sample of Comparative Example 8 was a catalyst supporting Pt: 0.5712 g/L and Rh: 0.2344 g/L.

Comparative Examples 9 and 10 are examples for comparison with Examples 21-23.

(comparative example 9)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Dissolve 89.1 g of aluminum isopropoxide as Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 0.9 g of lanthanum acetate as lanthanum oxide, and then add 90 g of the aluminum isopropoxide Said particle A is hydrolyzed by adding water. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-24 in which particles A were coated with alumina.

168 g of this powder a-24 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-24 to obtain a slurry having an average particle diameter of 3 μm (slurry a-32).

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% of rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

168 g of powder b-2 and 7 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry b-9) .

Coat 140g/L slurry a-32 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, apply 60g/L slurry b-9 after drying, and sinter at 400°C after drying. A sample of Comparative Example 9 was produced. The obtained samples of Comparative Example 9 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(comparative example 10)

As the first compound, cerium-zirconium composite oxide particles having an average particle diameter of 30 nm were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is cerium-zirconium composite oxide particle A).

Dissolve 76.5 g of aluminum isopropoxide as Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 13.5 g of lanthanum acetate as lanthanum oxide, and add 90 g of the Said particle A is hydrolyzed by adding water. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, and then sintered to prepare powder a-25, in which particles A were coated with alumina.

168 g of this powder a-25 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-25 to prepare a slurry (slurry a-33) having an average particle diameter of 3 μm.

Next, the zirconium-lanthanum composite oxide particles with an average particle size of 20 nm were impregnated with rhodium nitrate to prepare particles B supporting 0.814% of rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

168 g of powder b-2 and 7 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry b-9) .

Coat 140g/L slurry a-33 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, apply 60g/L slurry b-9 after drying, and sinter at 400°C after drying. A sample of Comparative Example 10 was produced. The obtained samples of Comparative Example 10 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Comparative Examples 11 and 12 are examples for comparison with Examples 24-27.

(comparative example 11)

As the first compound, cerium-zirconium composite oxide particles of 60% cerium and 40% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A6).

87.3 g of aluminum isopropoxide as Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 1.8 g of cerium acetylacetonate as cerium oxide was added thereto, and in addition, The zirconium oxide was 0.9 g of zirconium acetylacetonate, and 90 g of the particles A6 were added thereto, followed by hydrolysis by adding water. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-28 in which particles A6 were coated with alumina.

168 g of this powder a-28 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-28 to obtain a slurry having an average particle diameter of 3 μm (slurry a-36).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

168 g of powder b-2 and 7 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry b-9) .

Apply 140g/L slurry a-36 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, and after drying, apply 60g/L slurry b-9, and after drying, proceed at 400°C Sintered to prepare a sample of Comparative Example 11. The obtained samples of Comparative Example 11 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(comparative example 12)

As the first compound, cerium-zirconium composite oxide particles of 90% cerium and 10% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A7).

Dissolve 58.5 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 18 g of cerium acetylacetonate in terms of cerium oxide, and add Zirconium was 13.5 g of zirconium acetylacetonate, to which 90 g of the particles A7 were added, and water was added to carry out hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-29 in which particles A7 were coated with alumina.

168 g of this powder a-29 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-29 to prepare a slurry having an average particle diameter of 3 μm (slurry a-37).

Next, rhodium nitrate was impregnated into zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

168 g of powder b-2 and 7 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry b-9) .

Coat 140g/L slurry a-37 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, apply 60g/L slurry b-9 after drying, and sinter at 400°C after drying. A sample of Comparative Example 12 was produced. The obtained samples of Comparative Example 12 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Comparative Examples 13 and 14 are examples for comparison with Examples 28-31.

(comparative example 13)

As the first compound, cerium-zirconium composite oxide particles of 60% cerium and 40% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A6).

Dissolve 89.1 g of aluminum isopropoxide as Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 0.9 g of lanthanum acetate as lanthanum oxide, and then add 90 g of the aluminum isopropoxide The particles A6 are hydrolyzed by adding water. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-32 in which particles A6 were coated with alumina.

168 g of this powder a-32 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-32 to obtain a slurry (slurry a-40) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into the zirconium-lanthanum composite oxide particles having an average particle diameter of 20 nm to prepare particles B supporting 0.814% of rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

168 g of powder b-2 and 7 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution were added and pulverized to prepare a slurry with an average particle diameter of 3 μm (slurry b-9) .

Apply 140g/L slurry a-40 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, and apply 60g/L slurry b-9 after drying, and sinter at 400°C after drying. A sample of Comparative Example 9 was produced. The obtained samples of Comparative Example 9 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(comparative example 14)

As the first compound, cerium-zirconium composite oxide particles of 90% cerium and 10% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A7).

Dissolve 76.5 g of aluminum isopropoxide as Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 13.5 g of lanthanum acetate as lanthanum oxide, and add 90 g of the The particles A7 are hydrolyzed by adding water. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-33 in which particles A7 were coated with alumina.

168 g of this powder a-33 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-33 to prepare a slurry (slurry a-41) having an average particle diameter of 3 μm.

Next, the zirconium-lanthanum composite oxide particles with an average particle diameter of 20 nm were impregnated with rhodium nitrate to prepare particles B carrying 0.814% rhodium. Dissolve 90 g of aluminum isopropoxide in terms of Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 90 g of particle B, and add water to perform hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-2 in which particles B were coated with alumina.

Add 168g powder b-2 and 7g boehmite alumina in ball mill, then add water 307.5g and 10% nitric acid aqueous solution 17.5g, pulverize, made the slurry (slurry b-9 of average particle size 3 μ m) ).

Apply 140g/L slurry a-41 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, and apply 60g/L slurry b-9 after drying, and sinter at 400°C after drying. A sample of Comparative Example 14 was prepared. The obtained samples of Comparative Example 14 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

Comparative Examples 15 and 16 are examples for comparison with Examples 32-37.

(comparative example 15)

As the first compound, cerium-zirconium composite oxide particles of 60% cerium and 40% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A6).

Dissolve 89.1 g of aluminum isopropoxide as Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 0.9 g of lanthanum acetate as lanthanum oxide, and then add 90 g of the aluminum isopropoxide The particles A6 are hydrolyzed by adding water. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-32 in which particles A6 were coated with alumina.

168 g of this powder a-32 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-32 to obtain a slurry (slurry a-40) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum (99:1) composite oxide particles having an average particle diameter of 20 nm to prepare particles B16 carrying 0.50875% rhodium.

36 g of aluminum isopropoxide in terms of Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 144 g of particle B16 was added, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, and then sintered to prepare powder b-16, in which particles B16 were coated with alumina.

Add 168g powder b-16 and 7g boehmite alumina in the ball mill, then add water 307.5g and 10% nitric acid aqueous solution 17.5g, pulverize, made the slurry (slurry b-44 of average particle diameter 3 μ m) ).

Coat 140g/L slurry a-40 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, apply 60g/L slurry b-44 after drying, and sinter at 400°C after drying. A sample of Comparative Example 15 was produced. The obtained samples of Comparative Example 15 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

(Comparative Example 16)

As the first compound, cerium-zirconium composite oxide particles comprising 90% cerium and 10% zirconium were used. The particles were impregnated with dinitrodiammine platinum to prepare 0.85% Pt-supported cerium-zirconium composite oxide particles (this is particle A7).

Dissolve 76.5 g of aluminum isopropoxide as Al ₂ O ₃ in 2-methyl-2,4-pentanediol, add 13.5 g of lanthanum acetate as lanthanum oxide, and add 90 g of the The particles A7 are hydrolyzed by adding water. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder a-33 in which particles A7 were coated with alumina.

168 g of this powder a-33 and 7 g of boehmite alumina were added to a ball mill. Thereafter, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to a ball mill to pulverize the powder a-33 to prepare a slurry (slurry a-41) having an average particle diameter of 3 μm.

Next, rhodium nitrate was impregnated into zirconium-lanthanum (99:1) composite oxide particles having an average particle diameter of 20 nm to prepare particles B17 carrying 1.356% rhodium.

126 g of aluminum isopropoxide in terms of Al ₂ O ₃ was dissolved in 2-methyl-2,4-pentanediol, 54 g of particle B17 was added, and water was added for hydrolysis. Organic substances such as water and 2-methyl-2,4-pentanediol were evaporated to dryness, followed by sintering to prepare powder b-17 in which particles B17 were coated with alumina.

Add 168g powder b-17 and 7g boehmite alumina in the ball mill, then add water 307.5g and 10% nitric acid aqueous solution 17.5g, pulverize, have made the slurry (slurry b-45 of average particle diameter 3 μ m) ).

Apply 140g/L slurry a-41 on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 holes and 6 mils, and apply 60g/L slurry b-45 after drying, and sinter at 400°C after drying. A sample of Comparative Example 16 was produced. The obtained samples of Comparative Example 16 were catalysts in which Pt: 0.5712 g/L and Rh: 0.2344 g/L were respectively supported.

The catalysts prepared in Examples 1 to 37 and Comparative Examples 1 to 16 were installed in the exhaust system of a V-type engine with a displacement of 3500 cc, and 5 catalysts were installed in each bank. Using domestic standard gasoline in Japan, set the catalyst inlet temperature to 650°C, and operated for 30 hours to conduct thermal history through long-term use.

Further, each catalyst that has been used for a long time was assembled in a simulated exhaust gas circulation device, and the simulated exhaust gas with the composition shown in Table 1 was introduced into the simulated exhaust gas circulation device, and the catalytic temperature was raised at a rate of 30 °C/min. The temperature (T50) at which the purification rate of _x , CO, and HC (C ₃ H ₆ ) is 50%.

(Table 1)

Shown in table 2～9: adopt the microporous volume of the catalyst powder of each catalyzer of embodiment 1～embodiment 37 and comparative example 1～comparative example 16 that adopt gas adsorption method to measure, simultaneously, by on honeycomb carrier The sample obtained by coating the catalyst layer was cut into a test piece, and the micropore volume was measured by the mercury intrusion method. Tables 2 to 9 show that among the micropores with a micropore diameter of 1 μm or less, the micropores with a micropore diameter of 0.1 μm or less The ratio of the micropore volume (A) to the micropore volume (B) with a micropore diameter of 0.1 μm to 1 μm. The evaluation results are also shown together.

In addition, FIGS. 4 to 11 show the relationship between the temperature at which the HC (C ₃ H ₆ ) purification rate of each catalyst in Examples 1 to 37 and Comparative Examples 1 to 16 is 50%.

In the catalyst of Comparative Example 1 shown in Table 2 and Figure 4, the second compound of the first layer catalyst used aluminum oxide derived from aluminum isopropoxide, and the second compound of the second layer catalyst used isopropyl Aluminum alkoxide has the smallest micropore volume in the catalyst powder of the first layer and the second layer, and the proportion of micropores of 0.1 μm to 1 μm in the coated catalyst layer is very small, only 9.3%. The Pt particles after long-term use were observed by TEM, and the Pt particle diameter was about 10 nm, and there was little aggregation of the Pt particles. In addition, there is little aggregation of Rh. However, the catalyst activity is low. It can be considered that this is because: although the Pt particle size is small, the micropore volume is small, and it is difficult for the exhaust gas to pass through, and it is difficult for the exhaust gas to reach the Pt.

In Comparative Example 2 shown in Table 2 and Fig. 4, the same powder as Comparative Example 1 was used, and the proportion of micropores of 0.1 μm to 1 μm in the coating layer increased to 65%. layer, the coating disintegrated and could not be evaluated. It is considered that this is because the coating has too many voids and the strength of the coating decreases.

In contrast, the noble metal in the first layer is Pt in Examples 1 to 6, 9 to 12, 15 to 25, 28, 29, 32 to 34 , In each catalyst of Example 36, the Pt particle diameter after long-term use was about 10 nm, and there was little aggregation of Pt particles. In addition, Rh particles are about 6 nm in size, and there is little aggregation.

In addition, in Example 7, Example 8, Example 13, Example 14, Example 26, Example 27, Example 30, Example 31, Example 35, Example 37 where the noble metal of the first layer is Pd , The Pd particle size after long-term use is small, only about 7nm to 8nm, and the aggregation of Pd particles is small. In addition, Rh particles are about 6 nm in size, and there is little aggregation.

The catalyst activity of these examples was very good compared with the comparative example, and a high activity was obtained.

In the catalyst of Comparative Example 3 shown in Table 3 and Fig. 5, the first compound of the first layer of catalyst is cerium-zirconium composite oxide, and its micropore volume is 0.15cm ³ /g, and the first compound of the second layer of catalyst is The zirconium-lanthanum composite oxide has a micropore volume of 0.16 cm ³ /g, and the catalyst has low catalytic activity.

In the catalyst of Comparative Example 4 shown in Table 3 and FIG. 5 , large alumina particles of 130 nm were used as the second compound of the first-layer and second-layer catalysts. Therefore, the pore volume value also becomes large. When the Pt particles were observed by TEM after the catalyst had been used for a long time, the Pt particle diameter became larger, about 20 nm or more, and the aggregation of the Pt particles was observed. In addition, the aggregation of the cerium-zirconium composite oxide particles was also observed. It is considered that the alumina particles are large, and the gaps between the alumina particles are large, and the cerium-zirconium composite oxide particles with Pt attached move out of the gaps during long-term use, and the cerium-zirconium composite oxide particles aggregate. In addition, it is considered that Pt also aggregates along with the aggregation of the cerium-zirconium composite oxide particles, and the particle size of Pt becomes large. In addition, as for the Rh particles of the second layer, it can also be seen that the particle diameter increases to 15 nm. Therefore, it can be considered that although the micropore volume is large, the catalyst activity is low.

In Comparative Example 5 and Comparative Example 6 shown in Table 4 and FIG. 6 , the composite ratios of ceria, zirconia, and the like in the first compound of the first layer and the second layer are different. In Comparative Example 5, the composite ratios of cerium oxide and zirconium oxide in the first layer were 60% and 40%, and the composite ratios of zirconium oxide and lanthanum oxide in the second layer were 80% and 20%, but it was different from that of Example 15. , 16, 17, the catalyst activity is low. The Pt particle size of the first layer was observed by TEM and found to be about 10 nm. The Rh particles in the second layer are as small as about 6 nm, and were observed to be buried between the aggregated zirconium-lanthanum composite oxide particles.

In addition, in Comparative Example 6, the composite ratio of cerium oxide and zirconia in the first layer is 90% and 10%, and the second layer is 100% zirconia, but compared with Examples 15, 16, and 17, the catalyst activity is low . The Pt particle size of the first layer was observed by TEM and found to be about 10 nm. The Rh particles in the second layer were as small as about 6 nm, and it was observed that they were buried between the aggregated zirconia particles.

It is considered that, in addition to the small pore volume of the catalyst of Comparative Example 6, this is also attributable to the deterioration of the oxygen releasing ability of the composite oxide of ceria and zirconia. In addition, it is also considered that this is because: in such a relationship between the composite ratio of zirconia and lanthanum oxide, the zirconium-lanthanum composite oxide is easy to aggregate, and the Rh particles are buried in the zirconium-lanthanum composite oxide particles and zirconia particles. It is difficult to come into contact with exhaust gas.

In addition, it is also considered that the catalyst layer has small pores, so that the exhaust gas is difficult to reach, and the catalyst activity is low.

In Comparative Example 7 and Comparative Example 8 shown in Table 5 and FIG. 7 , compared with Examples 18, 19, and 20, the catalyst activity was lower. In Comparative Example 7 and Comparative Example 8, the Pt particles after long-term use were observed by TEM, and the Pt particle diameter was about 10 nm, and there was little aggregation of the Pt particles. In addition, there is little aggregation of Rh. However, the catalyst activity is low.

In Examples 18, 19, and 20, by adding a cerium compound and a zirconium compound to the alumina precursor, the heat resistance of the sintered alumina was improved, and a large pore volume was maintained even after long-term use. In addition, it is considered that since micropores of 0.1 μm to 1 μm in the catalyst layer were ensured, the diffusivity of exhaust gas was good and the catalyst activity was maintained.

In contrast, it can be considered that in Comparative Example 7 and Comparative Example 8, there is no effect of adding cerium compound and zirconium compound, the micropore volume after long-term use cannot be ensured, and the micropores of the catalyst layer are small, so it is difficult for exhaust gas to reach the catalyst layer. Low activity.

In Comparative Examples 9 and 10 shown in Table 6 and FIG. 8 , the catalyst activity was lower than that of Examples 21, 22 and 23. In Comparative Examples 9 and 10, the Pt particles after long-term use were observed by TEM, and the Pt particle diameter was about 10 nm, and there was little aggregation of the Pt particles. In addition, there is little aggregation of Rh. However, the catalyst activity is low.

In Examples 21, 22, and 23, by adding a lanthanum compound to the alumina precursor, the heat resistance of the sintered alumina was improved, and a large micropore volume was maintained after long-term use. In addition, it is considered that the catalytic activity was maintained because micropores of 0.1 μm to 1 μm in the catalyst layer were ensured and the diffusivity of exhaust gas was good.

In contrast, in Comparative Examples 9 and 10, there was no effect of adding the lanthanum compound, the pore volume was small, and the pore volume after long-term use could not be ensured. In addition, it is considered that the catalyst layer had small pores and it was difficult for exhaust gas to reach , low catalyst activity.

In Comparative Example 11 and Comparative Example 12 shown in Table 7 and FIG. 9 , the catalyst activity was lower than that of Examples 24, 25, 26, and 27. In Comparative Example 11 and Comparative Example 12, the Pt particles after long-term use were observed by TEM, and the Pt particle diameter was about 10 nm, and there was little aggregation of the Pt particles. In addition, there is little aggregation of Rh. However, the catalyst activity is low.

In Examples 24, 25, 26, and 27, there were three catalyst layers, and the bottom layer was coated with an undercoat, an intermediate layer, and a surface catalyst layer. Therefore, the coating thickness of the catalyst in the intermediate layer is uniform, and the catalyst works efficiently. The same goes for the surface. In addition, the heat resistance of sintered alumina is improved by the composite ratio of ceria and zirconia and the addition of cerium compound and zirconium compound to the alumina precursor, and the large micropores can be maintained even after long-term use. volume. In addition, it is considered that since micropores of 0.1 μm to 1 μm in the catalyst layer were ensured, the diffusivity of exhaust gas was good and the catalytic activity was maintained.

On the other hand, in Comparative Example 11 and Comparative Example 12, it is considered that the oxygen release ability of the composite oxide of cerium oxide and zirconia deteriorated, and also because there was no cerium compound or zirconium compound added to the alumina precursor. As a result, the micropore volume after long-term use cannot be ensured, and the micropores of the catalyst layer are small, and exhaust gas is difficult to reach, so the catalyst activity is low.

In Comparative Example 13 and Comparative Example 14 shown in Table 8 and FIG. 10 , the catalyst activity was lower than that of Examples 28, 29, 30, and 31. In Comparative Example 13 and Comparative Example 14, the Pt particles after long-term use were observed by TEM, and the Pt particle diameter was about 10 nm, and there was little aggregation of the Pt particles. In addition, there is little aggregation of Rh. However, the catalyst activity is low.

In Examples 28, 29, 30, and 31, the catalyst layer was three layers, and the bottom layer was coated with a primer, and then coated with a catalyst layer of an intermediate layer and a surface layer. Therefore, the coating thickness of the catalyst in the intermediate layer is uniform, and the catalyst works efficiently. The same goes for the surface. In addition, through the composite ratio of ceria and zirconia and the addition of lanthanum compound to the alumina precursor, the heat resistance of the sintered alumina is improved, and a large micropore volume can be maintained after long-term use. In addition, it is considered that micropores of 0.1 μm to 1 μm in the catalyst layer were ensured, the diffusivity of exhaust gas was good, and the catalyst activity was maintained.

On the other hand, it is considered that in Comparative Examples 13 and 14, since the oxygen release ability of the composite oxide of ceria and zirconia deteriorated, and also because there was no effect of adding a lanthanum compound to the alumina precursor, it was not possible to To ensure the micropore volume after long-term use, the micropores of the catalyst layer are small, and the exhaust gas is difficult to reach, so the catalyst activity is low.

In Comparative Example 15 and Comparative Example 16 shown in Table 9 and FIG. 11 , the catalyst activity was lower than that of Examples 32, 33, 34, 35, 36, and 37.

In Comparative Example 15 after long-term use, the Pt particles were observed by TEM. The Pt particle diameter was about 10 nm, and the Rh particles were as small as about 6 nm. They were observed to be buried between the aggregated zirconium-lanthanum composite oxide particles. However, the catalyst activity is low.

In Comparative Example 16 after long-term use, the Pt particles were observed by TEM, and the Pt particle diameter was about 10 nm, while the Rh particles were as small as about 6 nm. However, the catalyst activity is low.

In Examples 32, 33, 34, 35, 36, and 37, the catalyst layer is three layers, and the bottom layer is coated with a primer, and coated with a middle layer and a catalyst layer of the surface layer. Therefore, the coating thickness of the catalyst in the intermediate layer is uniform, and the catalyst works efficiently. The same goes for the surface. In addition, through the composite ratio of ceria and zirconia in the middle layer and the addition of lanthanum compound to the alumina precursor, the heat resistance of the sintered alumina is improved, and a large microstructure can be maintained even after long-term use. Pore volume. In addition, the mixing ratio of the zirconium composite oxide and alumina in the surface layer is also suitable. It is considered that since micropores of 0.1 μm to 1 μm in the catalyst layer were ensured, the diffusivity of exhaust gas was good and the catalyst activity was maintained.

In contrast, it is considered that in Comparative Example 15, the catalyst activity was low because: the oxygen release ability of the composite oxide of ceria and zirconia in the intermediate layer deteriorated; and there was no effect of adding the lanthanum compound to the alumina precursor. , the micropore volume after long-term use cannot be ensured; the micropore volume after long-term use cannot be ensured on the surface; the amount of alumina is small, and the aggregation of zirconium composite oxides cannot be inhibited. It cannot be reached; the micropores of the catalyst layer are also small, and the exhaust gas is difficult to reach.

In addition, it is considered that, in Comparative Example 16, the catalyst activity was low because: the oxygen release ability of the composite oxide of ceria and zirconia in the intermediate layer deteriorated; there was no effect of adding a lanthanum compound to the alumina precursor, and it was impossible Ensure the micropore volume after long-term use; the surface layer cannot ensure the micropore volume after long-term use; the amount of alumina is large, which inhibits the aggregation of zirconium composite oxides and Rh. , the exhaust gas is difficult to reach; the micropores of the catalyst layer are small, and the exhaust gas is difficult to reach.

That is, the present invention includes:

1. A catalyst for exhaust gas purification, comprising a carrier and at least one catalyst layer formed on the inner surface of the carrier, wherein,

The structure of the catalyst layer is: the catalyst layer contains catalyst powder, the catalyst powder includes a noble metal, a first compound and a second compound, and the noble metal of the catalyst powder is supported by the first compound, and the first compound of the noble metal is supported are separated from each other by a second compound;

The catalyst layer has micropores, and among the micropores with a pore diameter of 1 μm or less, the micropore volume of the micropores with a pore diameter of 0.1 μm to 1 μm is 10% to 60%.

2. The catalyst for exhaust gas purification according to item 1, wherein, in the catalyst layer, the micropore volume of micropores with a micropore diameter of 0.1 μm or less is A, and the micropore volume of micropores with a micropore diameter of 0.1 μm to 1 μm is B, in the micropore volume with a micropore diameter of 1 μm or less, B accounts for 10% to 60%, and B/A≥0.1.

3. The exhaust gas-purifying catalyst according to item 1, wherein, in the catalyst layer, the micropore volume of micropores with a micropore diameter of 0.1 μm or less is A, and the micropore volume of micropores with a micropore diameter of 0.1 μm to 1 μm is B is B, and B accounts for 20% to 60% of the volume of micropores with a micropore diameter of 1 μm or less.

4. The catalyst for exhaust gas purification according to item 1, wherein, in the catalyst layer, the micropore volume of micropores with a micropore diameter of 0.1 μm or less is A, and the micropore volume of micropores with a micropore diameter of 0.1 μm to 1 μm is B is B, and B accounts for 30% to 50% of the volume of micropores with a micropore diameter of 1 μm or less.

5. The exhaust gas-purifying catalyst according to item 1, wherein the catalyst powder has a pore volume of 0.24 cm ³ /g to 0.8 cm ³ /g.

6. The catalyst for exhaust gas purification according to item 1, wherein the first compound of the catalyst powder contains 70wt% to 85wt% of _CeO2 and 15wt% to 30wt% of _ZrO2 .

7. The catalyst for exhaust gas purification according to item 1, wherein the first compound of the catalyst powder contains 90wt% to 99wt% of _ZrO2 and 1wt% to 10wt% of _{La2O3 .}

8. The exhaust gas-purifying catalyst according to item 1, wherein the second compound of the catalyst powder contains alumina.

9. The exhaust gas-purifying catalyst according to item 1, wherein the second compound of the catalyst powder is alumina containing 5 wt % to 15 wt % of CeO ₂ and 3 wt % to 10 wt % of ZrO ₂ .

10. The exhaust gas-purifying catalyst according to item 1, wherein the second compound of the catalyst powder is alumina containing 3 wt% to 10 wt% of La ₂ O ₃ .

11. The exhaust gas-purifying catalyst according to any one of items 1 to 10, wherein the noble metal of the catalyst powder is at least one selected from the group consisting of Pt, Pd and Rh.

12. The exhaust gas-purifying catalyst according to item 1, wherein a plurality of said catalyst layers are formed on the inner surface of the carrier.

13. The exhaust gas-purifying catalyst according to item 12, wherein a base layer containing no noble metal is provided on the side closer to the inner surface of the carrier than the catalyst layer.

14. The catalyst for purification of exhaust gas according to item 13, wherein the substrate layer contains at least one of alumina and a hydrocarbon-adsorptive compound.

15. The catalyst for purifying exhaust gas according to item 12, wherein, in the catalyst powder of the catalyst layer located on the inner surface of the support in the multilayer catalyst layer, the noble metal is at least one of Pt and Pd, and the first compound is item 6 The first compound and the second compound are the second compound described in Item 9.

16. The catalyst for exhaust gas purification according to item 12, wherein, in the catalyst powder of the catalyst layer located on the inner side of the carrier among the multilayer catalyst layers, the noble metal is at least one of Pt and Pd, and the first compound is the catalyst powder according to item 6. The first compound described above, the second compound is the second compound described in item 10.

17. The catalyst for purifying exhaust gas according to item 12, wherein, in the catalyst powder of the catalyst layer located on the surface side among the multilayer catalyst layers, the noble metal is Rh, the first compound is the first compound described in item 7, and the second The compound is the second compound described in Item 8.

18. The catalyst for purifying exhaust gas according to item 17, wherein, in the catalyst powder of the catalyst layer located on the surface side among the multilayer catalyst layers, the first compound supporting the noble metal is 40 wt % to 75 wt %, and the second compound is 25 wt % %～60wt%.

19. The method for producing a catalyst for exhaust gas purification according to item 1, the method comprising: a step of preparing a catalyst powder, and a step of forming the catalyst powder on the inner surface of a carrier, wherein:

The step of described preparation catalyst powder comprises:

the step of supporting a noble metal on the first compound, and

the step of dispersing the second compound or a precursor of the second compound in water for slurrying, and

Then dispersing the first compound loaded with noble metal in the slurry of the second compound, drying and sintering to obtain catalyst powder;

The step of forming catalyst powder on the inner surface of the carrier comprises:

A step of adding a compound that disappears during sintering to the obtained catalyst powder, forming a slurry, coating on a carrier, drying and sintering to form a catalyst layer having micropores of 0.1 μm to 1 μm in the micropores of the catalyst layer.

Claims (19)

1. exhaust gas purification catalyst, it comprises carrier and is formed at the catalyst layer of one deck at least on the carrier inner face, wherein,

The structure of described catalyst layer is: described catalyst layer contains catalyst fines, this catalyst fines comprises noble metal, first compound and second compound, and by the noble metal of the first compound loaded catalyst fines, load separate each other by second compound between first compound of this noble metal;

Described catalyst layer has micropore, and in the micropore below micropore diameter is 1 μ m, micropore diameter is that the micropore volume of the micropore of 0.1 μ m～1 μ m is 10%～60%.

2. the exhaust gas purification catalyst of claim 1, wherein, in described catalyst layer, if micropore diameter is that the micropore volume of the following micropore of 0.1 μ m is A, micropore diameter is that the micropore volume of the micropore of 0.1 μ m～1 μ m is B, in the micropore volume below micropore diameter is 1 μ m, B accounts for 10%～60%, and B/A 〉=0.1.

3. the exhaust gas purification catalyst of claim 1, wherein, in described catalyst layer, if micropore diameter is that the micropore volume of the following micropore of 0.1 μ m is A, micropore diameter is that the micropore volume of the micropore of 0.1 μ m～1 μ m is B, and in the micropore volume below micropore diameter is 1 μ m, B accounts for 20%～60%.

4. the exhaust gas purification catalyst of claim 1, wherein, in described catalyst layer, if micropore diameter is that the micropore volume of the following micropore of 0.1 μ m is A, micropore diameter is that the micropore volume of the micropore of 0.1 μ m～1 μ m is B, and in the micropore volume below micropore diameter is 1 μ m, B accounts for 30%～50%.

5. the exhaust gas purification catalyst of claim 1, wherein, the micropore volume of described catalyst fines is 0.24cm ³/ g～0.8cm ³/ g.

6. the exhaust gas purification catalyst of claim 1, wherein, first compound of described catalyst fines comprises the CeO of 70wt%～85wt% ₂And the ZrO of 15wt%～30wt% ₂

7. the exhaust gas purification catalyst of claim 1, wherein, first compound of described catalyst fines comprises the ZrO of 90wt%～99wt% ₂And the La of 1wt%～10wt% ₂O ₃

8. the exhaust gas purification catalyst of claim 1, wherein, second compound of described catalyst fines comprises aluminium oxide.

9. the exhaust gas purification catalyst of claim 1, wherein, second compound of described catalyst fines is the CeO that contains 5wt%～15wt% ₂, 3wt%～10wt% ZrO ₂Aluminium oxide.

10. the exhaust gas purification catalyst of claim 1, wherein, second compound of described catalyst fines is the La that contains 3wt%～10wt% ₂O ₃Aluminium oxide.

11. each exhaust gas purification catalyst of claim 1 to 10, wherein, the noble metal of described catalyst fines is to be selected from least a among Pt, Pd and the Rh.

12. the exhaust gas purification catalyst of claim 1 wherein, forms the described catalyst layer of multilayer on the carrier inner face.

13. the exhaust gas purification catalyst of claim 12 wherein, possesses the substrate layer that does not contain noble metal in the side than the more close carrier inner face of described catalyst layer.

14. the exhaust gas purification catalyst of claim 13, wherein, described substrate layer comprises at least a in aluminium oxide and the hydro carbons adsorptivity compound.

15. the exhaust gas purification catalyst of claim 12, wherein, the catalyst fines of the catalyst layer that is arranged in the carrier inner face side in described multi-layer catalyst layer, noble metal is at least a among Pt and the Pd, first compound is described first compound of claim 6, and second compound is described second compound of claim 9.

16. the exhaust gas purification catalyst of claim 12, wherein, in described multi-layer catalyst layer, be arranged in the catalyst fines of the catalyst layer of carrier inner face side, noble metal is at least a among Pt and the Pd, first compound is described first compound of claim 6, and second compound is described second compound of claim 10.

17. the exhaust gas purification catalyst of claim 12, wherein, in described multi-layer catalyst layer, be arranged in the catalyst fines of the catalyst layer of face side, noble metal is Rh, first compound is described first compound of claim 7, and second compound is described second compound of claim 8.

18. the exhaust gas purification catalyst of claim 17, wherein, in described multi-layer catalyst layer, be arranged in the catalyst fines of the catalyst layer of face side, load first compound of noble metal be 40wt%～75wt%, second compound is 25wt%～60wt%.

19. the manufacture method of the exhaust gas purification catalyst of claim 1, this method comprises: the step of preparation catalyst fines and on the carrier inner face, form the step of this catalyst fines, wherein:

The step of described preparation catalyst fines comprises:

On first compound step of carried noble metal and

With the precursor of second compound or second compound be dispersed in the step of carrying out slurryization in the water and

Then with load first compound of noble metal be dispersed in the slurry of described second compound, after drying, carry out sintering and obtain the step of catalyst fines;

The described step that forms catalyst fines on the carrier inner face comprises:

The compound that can disappear when in the catalyst fines that obtains, adding sintering, slurryization is coated on carrier, and dry then, sintering form the step of the catalyst layer of the micropore that has 0.1 μ m～1 μ m in the micropore of catalyst layer.

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