JP2002066327A - Exhaust gas cleaning catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas cleaning catalyst having high exhaust gas cleaning performance and also having effective cleaning characteristics even in a low temperature range, e.g. immediately after starting an engine. SOLUTION: The exhaust gas cleaning catalyst comprises a heat resistant catalyst carrier substrate and a catalyst coat layer formed on the surface of the catalyst carrier substrate and comprising a β-zeolite, cerium-zirconium- yttrium multiple oxide, a catalyst metal and a fire resistant inorganic oxide. The exhaust gas cleaning catalyst is excellent in exhaust gas cleaning capacity and is very effective to particularly remove HC because of the presence of the β-zeolite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying catalyst for purifying exhaust gas.

[0002]

2. Description of the Related Art Exhaust gas emitted from an internal combustion engine such as an automobile engine includes hydrocarbons (HC) and carbon monoxide (C).
O) and harmful components such as nitrogen oxides (NOx). If the exhaust gas containing these components is discharged as it is, pollution will occur and the environment will deteriorate. For this reason, exhaust gas containing these components is exhausted to the atmosphere after being purified using an exhaust gas purifying catalyst or the like.

[0003] The exhaust gas purifying catalyst converts NOx, HC and CO contained in the exhaust gas into harmless nitrogen, carbon dioxide and water by a catalytic metal and discharges them. here,
In purifying exhaust gas with an exhaust gas purifying catalyst, purification of HC is strongly affected by exhaust gas temperature.
It is performed at a temperature of 00 ° C. or higher. For this reason, when the exhaust gas temperature is low immediately after starting the engine, the catalytic activity of the catalytic metal is low, and it has been difficult to purify HC in the exhaust gas. In addition, immediately after the engine was started, a large amount of HC was discharged, and the proportion of HC in the emission was large.

For this reason, suppressing the emission of HC at low temperatures has become an important problem in purifying exhaust gas.

As a catalyst for purifying exhaust gas which suppresses the emission of HC, a support layer made of alumina or the like is formed on the surface of a catalyst carrier substrate, and H on the support layer is used to purify HC.
An exhaust gas purifying catalyst in which a C purifying unit and a NOx purifying unit that purifies NOx and CO are separated in the axial direction of the catalyst carrier, and an HC purifying unit that purifies HC and a purifier for NOx and CO. There is an exhaust gas purifying catalyst formed in a structure in which a NOx purifying unit is disposed in a stacked structure.

[0006] Examples of these exhaust gas purifying catalysts include:
For example, Japanese Patent Application Laid-Open No. H11-253758 and
104462, JP-A-7-2113910, JP-A-6
No. 142525, JP-A-11-210451 and JP-A-11-221466.

[0007] Japanese Patent Application Laid-Open No. 6-142519 discloses Cu and P, which are formed on a monolithic carrier and are effective for adsorbing hydrocarbons.
ZSM ion-exchanged with at least one or more metals d
A first layer made of -5 zeolite, and a second layer formed on the first layer and containing at least one of Pt and Pd as a catalyst component in a powder mainly composed of activated ceria and / or alumina; Further, there is disclosed a hydrocarbon adsorption catalyst comprising a third layer provided on the second layer and containing Rh as a catalyst component.

[0008] Japanese Patent Application Laid-Open No. 7-2113910 discloses an adsorption catalyst in which zeolite is coated on a catalyst carrier, and a powder containing active ceria and / or alumina as a main component is coated on a zeolite layer with Pt, Pd and Rh as catalyst components.
An exhaust gas purifying catalyst comprising a catalyst layer containing at least one member selected from the group consisting of:

Japanese Patent Application Laid-Open No. 11-104462 discloses that a monolithic carrier is coated and supported with an adsorbing layer made of an adsorbing material having a hydrocarbon adsorbing ability, and has an ability to purify harmful components in exhaust gas on the adsorbing layer. An exhaust gas purifying catalyst-adsorbent, which is a catalyst-adsorbent for purifying exhaust gas obtained by coating and supporting a catalyst layer made of a catalyst material, wherein the catalyst layer has a thickness of 10 to 120 μm. It has been disclosed.

Japanese Patent Application Laid-Open No. H11-210451 discloses an HC adsorbing catalyst comprising a portion having a three-way catalyst layer as an upper layer of an HC adsorbent, and a three-way catalyst layer portion immediately downstream of an external part. Is provided in an exhaust passage, there is disclosed an exhaust purification catalyst device.

Japanese Patent Application Laid-Open No. H11-221466 discloses that a catalyst containing zeolite is provided with platinum (P
t), one or more components selected from the group consisting of palladium (Pd) and rhodium (Rh);
A first catalyst layer containing at least one component selected from the group consisting of an alkaline earth metal and a rare earth metal, a second catalyst layer containing alumina and / or silica, and a zeolite containing copper and cobalt components. A third catalyst layer including the third catalyst layer, the second catalyst layer being provided on the first catalyst layer, and a catalyst having the third catalyst layer provided on the second catalyst layer being disposed at a latter stage of the exhaust flow. An exhaust gas purifying catalyst characterized by the following is disclosed.

JP-A-11-253758 discloses that at least one component selected from a platinum component, a palladium component and a rhodium component and at least one component selected from an alkali component, an alkaline earth component and a rare earth component are disclosed. An exhaust gas purifying catalyst having a second catalyst layer containing a zeolite containing a copper and / or cobalt component as a main component, and further comprising silica (SiO ₂ ) in the second catalyst layer. There is disclosed an exhaust gas purifying catalyst characterized by containing.

In recent years, there has been a demand for improvements in the HC purification performance and exhaust gas purification performance of exhaust gas purifying catalysts, for example, as automobile exhaust gas regulation values have become more stringent.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has an effective purification characteristic even in a low temperature range immediately after the start of an engine and has a high exhaust gas purification performance. The task is to provide

[0015]

Means for Solving the Problems In order to solve the above problems, the present inventors have repeatedly studied HC purification and exhaust gas purification of an exhaust gas purifying catalyst. As a result, a β type zeolite having a high HC adsorption performance was obtained. It has been found that the above problem can be solved by using a cerium-zirconium-yttrium composite oxide having a high oxygen storage capacity.

That is, the exhaust gas purifying catalyst of the present invention comprises:
A catalyst formed on the surface of the catalyst carrier substrate, comprising a catalyst carrier substrate having heat resistance, β-type zeolite, a cerium-zirconium-yttrium composite oxide, a catalyst metal, and a refractory inorganic oxide. And a coat layer.

The exhaust gas purifying catalyst of the present invention is excellent in HC purifying ability because it absorbs HC up to a high temperature by β-type zeolite. Further, by having the composite oxide, the oxygen storage ability is high and the exhaust gas purification ability is excellent.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The exhaust gas purifying catalyst of the present invention comprises a catalyst carrier substrate and a catalyst coat layer.

The catalyst carrier substrate is a substrate having heat resistance. That is, it is only necessary to have heat resistance to the temperature of the exhaust gas to be purified.

Here, as the catalyst carrier substrate, a catalyst carrier substrate used for a normal exhaust gas purifying catalyst can be used. Examples of the catalyst carrier substrate include a monolithic honeycomb carrier formed of a heat-resistant material such as ceramics such as cordierite and a heat-resistant metal such as stainless steel.

The catalyst coat layer is a layer composed of a β-type zeolite, a cerium-zirconium-yttrium composite oxide, a catalyst metal, and a refractory inorganic oxide, and formed on the surface of the catalyst carrier substrate. .

Β-type zeolite has a high HC adsorption capacity and excellent heat resistance. That is, β-type zeolite is
The release temperature for releasing adsorbed HC is higher than other types of zeolites. When the adsorbed HC is released due to the high HC release temperature, the temperature reaches the temperature at which the catalytic metal exhibits catalytic activity. Therefore, H released from β-type zeolite
C is efficiently purified by the catalytic metal. As a result,
The HC purifying performance of the exhaust gas purifying catalyst of the present invention is improved.

The cerium-zirconium-yttrium composite oxide has an excellent oxygen storage capacity for releasing or taking in oxygen. More specifically, cerium oxide added to a normal catalyst for purifying exhaust gas undergoes grain growth at a high temperature, and the oxygen storage capacity is reduced.
However, by using a cerium-zirconium-yttrium composite oxide, the grain growth is suppressed, and the oxygen storage ability is exhibited even in a high temperature range. As a result, the exhaust gas purifying catalyst of the present invention has high exhaust gas purification efficiency.

Further, the cerium-zirconium-yttrium composite oxide may partially form a solid solution.

The cerium-zirconium-yttrium composite oxide preferably has a molar ratio of cerium, zirconium and yttrium in the range of 30 to 70:30 to 70: 1 to 10.

As a method for producing the cerium-zirconium-yttrium composite oxide, for example, the following method can be mentioned. First, a solution in which predetermined amounts of a cerium salt, a zirconium salt, and a yttrium salt are dissolved is prepared and mixed to precipitate a mixture of cerium, zirconium, and yttrium. Thereafter, the precipitate can be fired at a temperature of 500 ° C. or higher to produce the precipitate.

The catalytic metal purifies the exhaust gas. This catalyst metal is preferably made of at least one of Pt, Pd and Rh. That is, HC, CO, and NOx can be purified by using at least one of Pt, Pd, and Rh as the catalyst metal.

The refractory inorganic oxide forms the catalyst coat layer and holds the catalyst metal in the coat layer. Preferably, the refractory inorganic oxide is alumina. That is, alumina has high heat resistance and is chemically stable even at high temperatures. This alumina is preferably activated alumina (γ-alumina).

The catalyst coat layer is composed of β-type zeolite and formed on the surface of the catalyst support substrate, a cerium-zirconium-yttrium composite oxide, a refractory inorganic oxide, and a coat layer catalyst metal. And a catalyst-containing layer formed on the HC adsorption layer. The catalyst coat layer is preferably composed of an HC adsorption layer and a catalyst-containing layer. However, a β-type zeolite, a cerium-zirconium-yttrium composite oxide, a catalyst metal, and a refractory inorganic oxide are mixed. It does not exclude the formation of the catalyst coat layer in the state of being made.

That is, when the catalyst coat layer has a layered structure of the HC adsorption layer and the catalyst-containing layer, the purification performance of the exhaust gas purification catalyst is improved. That is, since the catalyst-containing layer is formed on the surface of the HC adsorption layer, when the HC adsorbed by the HC adsorption layer is released from the HC adsorption layer, the HC-contact layer can be completely contacted with the catalyst-containing layer. Therefore, HC is purified by the catalyst metal contained in the catalyst containing layer.

The catalyst metal is preferably supported on the surface of the refractory inorganic oxide and / or the cerium-zirconium-yttrium composite oxide. By supporting the catalyst metal on the surface of the refractory inorganic oxide and / or the cerium-zirconium-yttrium composite oxide,
A decrease in catalytic performance of the exhaust gas purifying catalyst can be suppressed. Here, when the catalyst metal is carried on the zeolite, HC adsorbed on the zeolite causes HC poisoning of the catalyst metal, and the catalytic performance of the catalyst metal is reduced.

The catalyst coat layer may have an additive which has been added to the catalyst support layer of a conventional exhaust gas purifying catalyst. Examples of such additives include additives such as BaO.

In the exhaust gas purifying catalyst of the present invention, the β-zeolite is preferably contained in the catalyst coat layer at 20 to 80 wt% when the catalyst coat layer is 100 wt%. When the β-type zeolite is contained at a ratio of 20 to 80, the catalyst coat layer can adsorb HC,
The HC purifying ability of the exhaust gas purifying catalyst is improved. If the amount of the β-type zeolite is less than 20 wt%, the amount of adsorbed HC decreases due to the small amount of zeolite, and the amount of H in the exhaust gas purifying catalyst decreases.
C Purification ability decreases. On the other hand, when the amount of the β-type zeolite exceeds 80% by weight, the catalytic activity is adversely affected. A more preferred range of the beta zeolite is 40
６０60 wt%.

The cerium-zirconium-yttrium composite oxide is preferably contained in the catalyst coat layer in an amount of 5 to 50 wt% when the catalyst coat layer is 100 wt%. By having the composite oxide, the oxygen concentration is stabilized at the time of purifying the exhaust gas. 5wt of compound oxide
%, The effect of addition is small, and CO, N
Components such as Ox cannot be sufficiently purified. On the other hand, when the compounding amount of the composite oxide exceeds 50 wt%, the proportion of the refractory inorganic oxide decreases, and the purification rate decreases. The preferred compounding amount of this composite oxide is 10 to 30% by weight.

As for the catalyst metal, 100 wt% of the catalyst coat layer is used.
Preferably, the content is 1 to 10 wt% in the catalyst coat layer. That is, when the catalyst coat layer contains the catalyst metal at 1 to 10 wt%, the exhaust gas is sufficiently purified. When the amount of the catalyst metal is less than 1 wt%, the purification of exhaust gas becomes insufficient because the amount of the catalyst metal is small. When the amount of the catalyst metal exceeds 10 wt%, the effect of improving the exhaust gas purification performance with respect to the increase in the amount of the catalyst metal becomes small. More preferably, the compounding amount of the catalyst metal is 3 to 8 wt.
% Range.

The exhaust gas purifying catalyst of the present invention can be produced by forming a catalyst coat layer on the surface of a catalyst carrier substrate. The formation of the catalyst coat layer can be performed by preparing a slurry having a substance constituting the catalyst coat layer, coating the slurry on the surface of the catalyst carrier substrate, drying and firing.

When the catalyst coat layer is composed of an HC adsorption layer and a catalyst-containing layer, it can be produced by forming an HC adsorption layer on a catalyst carrier substrate and then forming a catalyst-containing layer.

The exhaust gas purifying catalyst of the present invention is excellent in exhaust gas purifying performance because it has β-zeolite excellent in HC adsorption ability and cerium-zirconium-yttrium composite oxide excellent in oxygen storage ability.

[0039]

The present invention will be described below with reference to examples.

As an example of the present invention, an exhaust gas purifying catalyst was manufactured.

(Example 1) In Example 1, an HC made of β-type zeolite formed on the surface of a monolith honeycomb support was used.
An exhaust gas purifying catalyst comprising an adsorbent layer and a catalyst-containing layer formed on the HC adsorbent layer and comprising Pd, a cerium-zirconium-yttrium composite oxide, and alumina.

The exhaust gas purifying catalyst of Example 1 was produced by the following method.

First, an HC-adsorbed slurry comprising 100 g of β-zeolite having an average particle size of 5 to 50 μm and 150 g of water was prepared. Subsequently, the prepared HC adsorption slurry was coated on the surface of a monolith honeycomb carrier having a volume of 1.0 L, dried and fired to form an HC adsorption layer.
The coating amount of the HC adsorption slurry on the monolith honeycomb carrier was 100 g.

Subsequently, a Pd nitrate solution containing 5 g of Pd in terms of Pd, 100 g of alumina powder, and 100 g of water
Were mixed to carry Pd on the alumina powder surface.
After drying this mixture, it was baked at 500 ° C. for 1 hour and then pulverized to obtain an alumina powder carrying Pd. This Pd-supported alumina powder has an average particle size of 5
μm.

The cerium-zirconium-yttrium composite oxide powder was produced by mixing a cerium nitrate solution, a zirconium nitrate solution, and a yttrium nitrate solution, further adding aqueous ammonia, followed by drying and firing.

Thereafter, the alumina powder 1 carrying Pd was
A catalyst slurry was prepared which was composed of 05 g, 50 g of cerium-zirconium-yttrium composite oxide powder, and 200 g of water. Subsequently, this catalyst slurry is coated on the surface of a monolithic carrier on which zeolite is supported,
Drying and firing were performed to form a catalyst-containing layer on the surface of the HC adsorption layer. At this time, the coating amount of the catalyst slurry was 15
It was 5 g.

The exhaust gas purifying catalyst of Example 1 was manufactured by using the above manufacturing method.

(Example 2) In Example 2, a coating layer containing β-type zeolite, Pd, and a cerium-zirconium-yttrium composite oxide formed on the surface of a monolith honeycomb carrier, and containing alumina as a main component was prepared. It is a catalyst for purifying exhaust gas.

The exhaust gas purifying catalyst of Example 2 was produced by the following method.

First, an alumina powder carrying Pd and a cerium-zirconium-yttrium composite oxide powder were prepared in the same manner as in Example 1.

Subsequently, 105 g of alumina powder carrying Pd, 50 g of cerium-zirconium-yttrium composite oxide powder, 100 g of β-type zeolite, and 350 g of water
g was prepared.

The prepared slurry was coated on the surface of the same monolith honeycomb carrier as that used in Example 1, and dried and fired. At this time, the coating amount of the slurry was 255 g.

Example 3 Example 3 is an exhaust gas purifying catalyst manufactured by the same manufacturing method as in Example 1 except that Pd nitrate was changed to Pt nitrate.

Example 4 Example 4 is an exhaust gas purifying catalyst manufactured by the same manufacturing method as in Example 1 except that Pd nitrate was changed to Rh nitrate.

Example 5 Example 5 is an exhaust gas purifying catalyst manufactured by the same manufacturing method as in Example 1 except that Pd nitrate was changed to Pd nitrate and Rh nitrate.

The Pd nitrate and Rh nitrate had a weight ratio of Pd and Rh of 1: 1.

Example 6 Example 6 is an exhaust gas purifying catalyst manufactured by the same manufacturing method as in Example 1 except that Pd nitrate was changed to Pd nitrate and Pt nitrate.

The Pd nitrate and Pt nitrate had a weight ratio of Pd and Pt of 1: 1.

Example 7 Example 7 is an exhaust gas purifying catalyst manufactured by the same manufacturing method as in Example 1 except that Pd nitrate was changed to Pt nitrate and Rh nitrate.

The weight ratio of Pd and Rh to Pd nitrate and Rh nitrate was 1: 1.

Example 8 Example 8 is an exhaust gas purifying catalyst manufactured by the same manufacturing method as in Example 1 except that Pd nitrate was changed to Pd nitrate, Rh nitrate and Pt nitrate.

It should be noted that Pd nitrate and Rh nitrate are Pd, Rh
And the weight ratio of Pt was 1: 1: 1.

(Example 9) In Example 9, a monolithic honeycomb support formed of HC formed of β-type zeolite was formed.
An adsorbent layer and a catalyst-containing layer formed of Pd, a cerium-zirconium-yttrium composite oxide and alumina formed on the HC adsorbent layer, wherein Pd is composed of cerium.
An exhaust gas purifying catalyst supported on a zirconium / yttrium composite oxide.

The production of the exhaust gas purifying catalyst of Example 9 was carried out by the following method.

First, an HC adsorbing layer was formed on the surface of the monolith honeycomb carrier in the same manner as in Example 1.

Subsequently, a cerium-zirconium-yttrium composite oxide was produced in the same manner as in Example 1. Then, Pd nitrate having 5 g of Pd in terms of Pd
The solution, 50 g of the composite oxide powder and 50 g of water were mixed to carry Pd on the surface of the composite oxide. After drying this mixture, it was baked at 500 ° C. for 1 hour and then pulverized to obtain a composite oxide powder supporting Pd. The composite oxide powder carrying Pd had an average particle size of 5 μm.

Thereafter, the composite oxide powder 5 supporting Pd
A catalyst slurry comprising 5 g, alumina powder 100 g, and water 200 g was prepared. Subsequently, the catalyst slurry was coated on the surface of the monolithic carrier on which the HC adsorption layer was formed, and dried and fired to form a catalyst-containing layer on the surface of the HC adsorption layer. At this time, the coating amount of the catalyst slurry was 155 g.

The exhaust gas purifying catalyst of Example 9 was manufactured by using the above manufacturing method.

Comparative Example 1 Comparative Example 1 is an exhaust gas purifying catalyst similar to that of Example 1, except that the cerium-zirconium-yttrium composite oxide was changed to a cerium-zirconium composite oxide.

The cerium-zirconium composite oxide was produced by mixing a cerium nitrate solution and a zirconium nitrate solution, further adding aqueous ammonia, followed by drying and firing.

Comparative Example 2 Comparative Example 2 is an exhaust gas purifying catalyst similar to Example 1 except that the β-type zeolite was changed to ZSM-5-type zeolite.

Comparative Example 3 Comparative Example 3 is an exhaust gas purifying catalyst similar to that of Example 2 except that Pd is supported on β-type zeolite.

Comparative Example 4 Comparative Example 4 is an exhaust gas purifying catalyst similar to Example 2 except that β-type zeolite was not included.

(Evaluation) As the evaluation of the exhaust gas purifying catalysts of the examples and comparative examples, the evaluation was performed by operating the engine while actually mounted on the vehicle and purifying the exhaust gas discharged from the engine.

(Evaluation Test) The exhaust gas purifying catalyst was mounted 30 cm below the engine of an actual vehicle (displacement: 2.2 l). Thereafter, the engine of the actual vehicle is operated to purify the exhaust gas discharged from the engine, and the purification rates of the HC component, the CO component and the NOx component contained in the exhaust gas discharged from the exhaust gas purifying catalyst are measured. Was evaluated.

The purification rate of the HC component, CO component and NOx component contained in the exhaust gas is measured by sampling from a tail pipe using a chassis dynamo and measuring by an automobile exhaust gas analyzer. Was.
The test conditions of the actual vehicle were performed in the LA # 4 mode. Table 1 shows the measurement results.

[0077]

[Table 1]

As shown in Table 1, the exhaust gas purifying catalysts of Examples 1 to 9 show high values of the purifying rates of the HC component, the CO component and the NOx component.

From the examples, the catalyst metals were Pd, Pt, and Rh.
By using at least one of the above, high exhaust gas purification performance was exhibited. In addition, even when the catalyst metal was supported on either alumina or cerium-zirconium-yttrium composite oxide, high exhaust gas purification ability was exhibited.

In Comparative Example 1, the HC purification rate was as high as 97.8%, but both the CO purification rate and the NOx purification rate decreased. This is because the oxygen storage capacity of the composite oxide was reduced by changing the composite oxide from the cerium-zirconium-yttrium composite oxide to the cerium-zirconium composite oxide.

In Comparative Example 2, the CO purification rate and the NOx purification rate showed sufficient values, but the HC purification rate was 94.5%.
And has declined. This means that ZS
This is because the HC adsorbing ability was reduced by changing to the M-5 type zeolite.

In Comparative Example 3, the HC purification rate, the CO purification rate, and the NOx purification rate all decreased. This means
Since Pd was supported on zeolite, HC of zeolite was
The adsorption ability and the exhaust gas purification ability of Pd decreased.

In Comparative Example 4, the HC purification rate was reduced.
In this case, since there is no zeolite, it is not possible to adsorb HC, so that the purification rate of HC is lowered.

From Examples 1 to 9, it can be seen that the catalyst for purifying exhaust gas exhibits high purification performance because it has a cerium-zirconium-yttrium composite oxide and a β-type zeolite, and the catalyst metal is not supported on palladium. I understand.

[0085]

According to the exhaust gas purifying catalyst of the present invention, the catalyst coat layer contains β-type zeolite excellent in HC adsorption ability and cerium-zirconium-yttrium composite oxide excellent in oxygen storage ability. HC, CO, NOx
It has excellent purification ability. Further, β-type zeolite has good heat resistance and excellent HC adsorption performance, so that HC adsorption can be carried out up to a high temperature. As a result, the exhaust gas purifying catalyst of the present invention is particularly excellent in HC purifying ability.

Continued on the front page (72) Inventor Kenichi Taki 7800 Chihama, Oto-cho, Ogasa-gun, Shizuoka Prefecture F-term in Cataler Co., Ltd. BA11Y BA30Y BA31X BA31Y BA33Y BA41X BA41Y BA42X BA42Y EA04 4G069 AA01 AA03 AA08 BA01A BA01B BB06A BB06B BC40A BC40B BC43A BC43B BC51A BC51B BC71A BC72A BC72B BC75A CA03 CA09 FA03 FB23 Z

Claims (5)

[Claims] 1. A heat-resistant catalyst carrier substrate, β-zeolite, cerium-zirconium-yttrium composite oxide, catalyst metal, refractory inorganic oxide,
And a catalyst coat layer formed on the surface of the catalyst support substrate. 2. The catalyst coating layer, comprising: a HC adsorbing layer made of β-zeolite and formed on a surface of the catalyst carrier substrate; a cerium-zirconium-yttrium composite oxide;
The exhaust gas purifying catalyst according to claim 1, comprising a catalyst-containing layer formed of the refractory inorganic oxide and the catalyst metal and formed on the HC adsorption layer. 3. The exhaust gas purifying catalyst according to claim 1, wherein the catalyst metal is supported on a surface of the refractory inorganic oxide and / or the cerium-zirconium-yttrium composite oxide. 4. The exhaust gas purifying catalyst according to claim 1, wherein the catalytic metal is at least one of Pt, Pd, and Rh. 5. The exhaust gas purifying catalyst according to claim 1, wherein the refractory inorganic oxide is alumina.