JP2004141864A - High thermal resistant catalyst carrier, catalyst for emission gas purification, and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress particulate growth of noble metal particles by suppressing movement of the supported noble metal particles. <P>SOLUTION: The noble metal is supported at least in spaces of a catalyst carrier composed of α-alumina having a multi-layered structure having spaces between the layers. Even at high temperature of 1,200°C, α-alumina is stable without causing sintering. The noble metal supported in the spaces between the layers of the catalyst carrier is in a sandwiched state between the layers, being restrained from moving even at a high temperature. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an exhaust gas purifying catalyst for purifying exhaust gas from an automobile engine and the like, a method for producing the same, and a highly heat-resistant catalyst carrier used for the exhaust gas purifying catalyst.

BACKGROUND ART Conventionally, a three-way catalyst that purifies exhaust gas by simultaneously oxidizing CO and HC and reducing NO _x has been used as a catalyst for purifying exhaust gas from automobiles. As such a three-way catalyst, a porous carrier layer made of γ-alumina is formed on a heat-resistant substrate made of cordierite or the like, and platinum (Pt), rhodium (Rh), or the like is formed on the porous carrier layer. Those supporting a noble metal are widely known.

By the way, in recent years, the installation place of the exhaust gas purifying catalyst tends to be located immediately below the manifold close to the engine, and the exhaust gas temperature becomes high during high-speed running. Therefore, the exhaust gas purifying catalyst is often exposed to high temperatures. . However, the conventional exhaust gas purifying catalyst has a problem in that sintering of γ-alumina is advanced by high-temperature exhaust gas, and the catalytic growth is reduced due to grain growth of the noble metal, thereby deteriorating the catalytic performance.

Therefore, for example, Japanese Patent Application Laid-Open No. 04-122441 discloses a method for producing an exhaust gas purifying catalyst in which a noble metal is supported using alumina that has been heat-treated in advance. According to this production method, since the alumina has already been heat-treated, the obtained exhaust gas purifying catalyst hardly progresses in sintering even when it is exposed to high-temperature exhaust gas, and can prevent grain growth of the noble metal. .

In recent years, lean-burn engines that supply an air-fuel mixture in excess of oxygen have become the mainstream in order to suppress carbon dioxide emissions. However, in the exhaust gas purifying catalyst manufactured by the manufacturing method disclosed in the above-mentioned publication, when a high temperature of 800 ° C. or more acts in a lean atmosphere containing excess oxygen, the noble metal grains grow remarkably, and the catalytic performance deteriorates. There was a problem.

For example, Pt carried on alumina surface becomes PtO2 in an atmosphere where oxygen coexists at high temperature, and diffusion and aggregation are promoted by gas phase movement. Therefore, in an oxygen-excess lean atmosphere or stoichiometric atmosphere, when exposed to a high temperature, Pt grains grow and the catalyst performance is greatly reduced due to a decrease in surface area.

Therefore, the applicant of the present application has proposed a production method in which a carrier supporting a noble metal is heat-treated at 800 ° C. or more in a non-oxidizing atmosphere, as disclosed in JP-A-08-338897. According to this manufacturing method, since the porous carrier is sintered and the pores shrink, the supported noble metal is tightly surrounded by the porous carrier. Therefore, even if a high temperature acts in a lean atmosphere, the movement of the noble metal is regulated by the porous carrier, so that the grain growth of the noble metal can be suppressed.

However, even with the exhaust gas purifying catalyst produced by the production method described in JP-A-8-338897, when a high temperature exceeding 800 ° C is applied for a long time in an oxygen-rich lean atmosphere, such as in the air, particles of the noble metal are formed. It was found that growth occurred. This is considered to be due to the fact that the noble metal particles supported outside the pores are not physically and chemically fixed to the carrier and can move freely.
JP-A-04-122441 JP 08-338897 A

The present invention has been made in view of such circumstances, and an exhaust gas purifying catalyst capable of suppressing grain growth by suppressing the movement of supported noble metal particles, and a high heat resistant catalyst used in the exhaust gas purifying catalyst. An object of the present invention is to provide a neutral catalyst carrier.

特 徴 A feature of the high heat-resistant catalyst carrier of the present invention that solves the above-mentioned problem is that it is formed of an oxide having a multilayer structure formed by firing a hydroxide and having a gap between layers. It is particularly preferable to use α-alumina having a multilayer structure having a gap between layers, but the method for producing α-alumina is not limited to this.

Further, the feature of the exhaust gas purifying catalyst of the present invention that solves the above-mentioned problem is that an oxide having a multilayer structure with a gap between layers formed by calcining a hydroxide or an α with a multilayer structure with a gap between layers is used. -A precious metal is supported at least in the gaps of a highly heat-resistant catalyst carrier made of alumina.

In the exhaust gas purifying catalyst of the present invention, it is preferable that oxide particles that do not react with the noble metal are further carried in the gap. The oxide particles are particularly preferably ceria.

The method for producing an exhaust gas purifying catalyst according to the present invention is characterized in that an oxide having a multilayer structure with a gap between layers formed by calcining a hydroxide or α-alumina having a multilayer structure with a gap between layers A method for supporting a noble metal by impregnating a noble metal compound solution into a highly heat-resistant catalyst carrier comprising and evaporating to dryness, and applying external stress until the solvent is completely evaporated during evaporation to dryness.

Further, another feature of the manufacturing method of the present invention is that the oxide is formed by firing a hydroxide and has a multilayer structure having a gap between layers, or an α-alumina having a multilayer structure having a gap between layers. The object of the present invention is to support a noble metal at least in the gaps of the high heat resistant catalyst carrier, and then to support oxide particles in at least the gaps.

It is particularly desirable that the oxide particles be ceria.

Still another feature of the production method of the present invention is that an oxide having a multilayer structure having a gap between layers formed by firing a hydroxide or α-alumina having a multilayer structure having a gap between layers is used. An object of the present invention is to support a noble metal in at least the gaps of a highly heat-resistant catalyst carrier, and then heat-treat the noble metal to grow grains of the noble metal.

熱処理 In this manufacturing method, the heat treatment is desirably performed by heating to 600 to 800 ° C. in an oxidizing atmosphere and to 900 to 1200 ° C. in a non-oxidizing atmosphere. Further, after the noble metal is supported, it is desirable to support oxide particles that do not react with the noble metal in the gap. It is desirable that the loading of the oxide particles be performed after the grain growth of the noble metal. It is particularly desirable that the oxide particles be ceria.

That is, according to the high heat resistant catalyst carrier of the present invention, it has a multilayer structure having a gap between layers. Therefore, according to the exhaust gas purifying catalyst of the present invention in which a noble metal is supported in the gap, grain growth of the noble metal is prevented, and the heat resistance is excellent.

Further, by further supporting oxide particles that do not react with the noble metal, the movement of the noble metal is further suppressed, so that the heat resistance and durability are further improved. If the noble metal supported in the gaps is grown to some extent, the catalyst activity can be greatly reduced even when used in a lean-rich fluctuating atmosphere.

高 The highly heat-resistant catalyst carrier of the present invention is composed of an oxide formed by calcining a hydroxide and having a multilayer structure having gaps between layers, or α-alumina having a multilayer structure having gaps between layers. Zirconia, titania, ceria, and the like can be used as long as they are stable at a high temperature of 1000 ° C. or higher, but α-alumina is a particularly preferred material. That is, α-alumina is extremely stable thermally and is stable even at a high temperature of 1200 ° C. without sintering.

In the exhaust gas purifying catalyst of the present invention in which a noble metal is supported in the gap between the layers of the high heat resistant catalyst carrier of the present invention, the supported noble metal is in a state of being sandwiched in the gap between the layers. Also, the movement of the noble metal particles is suppressed, and the noble metal particles are prevented from aggregating and growing more than the interval between the layers. Also, since the carrier itself has high heat resistance, grain growth of the noble metal due to sintering of the carrier itself is also suppressed. Due to these synergistic effects, even when a high temperature exceeding 800 ° C. is applied for a long time in a lean atmosphere containing excess oxygen, the noble metal maintains a highly dispersed state and has many active sites. High activity is expressed.

Αα-alumina having a multilayer structure having a gap between layers can be produced, for example, by drying crystal grains of aluminum hydroxide and then firing at a high temperature of about 1200 ° C. At the time of firing, it is considered that the aluminum hydroxide that has adhered in a layered manner in the crystal shrinks, thereby creating a gap between the layers. Aluminum hydroxide that is commercially available from Sumitomo Chemical Co., Ltd. or the like can be used. At a firing temperature of 1000 ° C. or less, it has been found that it is difficult to produce α-alumina having a multilayer structure.

間隔 The distance between the layers in the high heat resistant catalyst carrier of the present invention is desirably 2 nm to 50 nm. If the distance between the layers is larger than this, the noble metal particles are likely to move, and the particles may grow in a high-temperature atmosphere. If the distance between the layers is smaller than this, it becomes difficult to support a noble metal in the gap between the layers. The distance between the layers can be adjusted by adjusting the firing temperature of aluminum hydroxide and the like.

貴 As the noble metal supported in at least the gap of the highly heat-resistant catalyst carrier of the present invention, those used in conventional exhaust gas purifying catalysts such as Pt, Rh, Pd, Ir, and Ru can be used. In particular, it is effective in the case of Pt which has a high catalytic activity but tends to grow grains. The amount of the noble metal carried is 0.1% by weight or more, preferably 0.5 to 20% by weight, based on the carrier. If the supported amount is less than this range, the activity as an exhaust gas purifying catalyst is too low to be practical, and if the supported amount is more than this range, the activity is saturated and the cost rises.

貴 In order to support the noble metal in the gap between the layers of the highly heat-resistant catalyst carrier of the present invention, the noble metal compound can be supported by impregnating the gap using a capillary action using a noble metal compound chemical solution, and then evaporating to dryness. In this case, it is desirable to use a noble metal compound chemical that is not easily adsorbed on the carrier. When a chemical solution that is easily adsorbed is used, a large amount of noble metal is supported in a portion other than the gap, and there is a problem that the particles grow at a high temperature.

When evaporating to dryness, it is desirable to apply external stress such as stirring until the solvent is completely evaporated. In particular, it is desirable to continue applying external shear stress such as stirring until the solvent is completely evaporated. When stirring or the like is stopped in a state where the solvent remains, the noble metal compound chemical solution and the carrier are separated, and it becomes difficult to sufficiently support the noble metal in the gap. However, if external shear stress such as stirring is continuously applied until the solvent is completely evaporated, separation of the noble metal compound chemical solution and the carrier is avoided, and the noble metal can be uniformly and sufficiently supported in the gap.

排 ガ ス In the exhaust gas purifying catalyst of the present invention, it is desirable that oxide particles are further supported in the gap. The movement of the noble metal particles in the gap is further suppressed by the presence of the oxide particles, so that the grain growth of the noble metal can be further suppressed.

The oxide particles do not react with the noble metal supported in the gaps, and include alumina, zirconia, ceria, titania, and a plurality of composite oxides selected from these. Silica or the like is not preferable because it reacts with a noble metal to lower the activity. In particular, it has been clarified that when ceria is supported, the purification activity after high-temperature durability hardly decreases. Although the reason for this is not clear, it is thought to be due to the cooperation between the physical immobilization of noble metal particles by ceria and the chemical action due to ceria's ability to store and release oxygen.

担 持 The amount of oxide particles to be carried is not particularly limited, but is desirably 1% by weight or more based on the high heat resistant catalyst carrier. Below this, the carried effect is not exhibited. In addition, in order to support the oxide particles in the gap, a solution of a soluble salt that becomes an oxide upon firing can be used, and can be supported by being impregnated in the same manner as the noble metal and then firing.

(4) It is desirable to support the noble metal first, and then support the oxide particles. On the contrary, for example, when the amount of the oxide particles carried is large, it may be difficult to carry the noble metal in the gap.

However, it has been clarified that, even when the exhaust gas purifying catalyst of the present invention is used in a fluctuating atmosphere in which a lean atmosphere and a rich atmosphere are repeated, the catalytic activity may decrease. Although the cause is not clear, it is considered that the carried noble metal may come out of the gap between the layers while the particle size is small. The noble metal particles that have come out of the gap easily grow on the outer surface of the carrier, and the active sites rapidly decrease.

Therefore, it is desirable that a noble metal is supported at least in the gaps of the highly heat-resistant catalyst support and then heat-treated to grow the noble metal to some extent. As a result, the movement of the noble metal in the gap is further suppressed, it is possible to prevent the noble metal from going out of the gap, and it is possible to reliably suppress a decrease in the catalyst activity under a variable atmosphere.

The noble metal supported in the gap can be sufficiently prevented from going out if the grain is grown to a grain size of about 40 °. As a heat treatment condition for grain growth to such an extent, heating may be performed at 600 to 800 ° C. in an oxidizing atmosphere. In a non-oxidizing atmosphere, heating may be performed at 900 to 1200 ° C. At a temperature lower than this temperature range, noble metal grain growth hardly occurs. Further, if the firing is performed at a temperature higher than this temperature, it is considered that the noble metal does not grow more than the interval of the gap, but it is not preferable because the number of active sites is reduced by further progressing the grain growth. It is necessary to perform the treatment under either an oxidizing atmosphere or a non-oxidizing atmosphere, and when heated in a fluctuating atmosphere, the noble metal may come out of the gap.

In this case as well, it is desirable that oxide particles such as ceria are further supported in the gaps between the high heat resistant catalyst supports. As a result, a synergistic effect of the above-described action of the oxide particles and the action of the grain growth is exhibited, and the movement of the noble metal can be further suppressed, so that the durability of the catalytic activity is significantly improved.

It is possible to grow the noble metal by heat treatment after supporting the oxide particles, but the oxide particles cover the noble metal particles supported in a fine state, and it becomes difficult for the noble metal particles to grow. There are cases. Therefore, it is preferable to support the oxide particles after the noble metal is grown.

The exhaust gas purifying catalyst of the present invention, the remains in the oxidation catalyst, can be utilized as a three-way catalyst, be further utilized as a NO _x storage-and-reduction type catalyst if carrying _the NO _x storage material such as Ba and K it can.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

(Example 1)
Commercially available aluminum hydroxide crystal particles (manufactured by Sumitomo Chemical Co., Ltd.) are dried at 120 ° C. for 2 hours and dehydrated, and then fired in the air at 1200 ° C. for 5 hours to have a multilayer structure having gaps between layers. α-alumina was prepared. The α-alumina particles had an average primary particle size of 3 μm, a specific surface area of several m ² / g, and an interlayer spacing of 20 to 50 nm.

This α-alumina powder is impregnated with a predetermined amount of an aqueous solution of dinitrodiammine platinum having a predetermined concentration, evaporated to dryness with stirring until the solvent is completely evaporated, dried in the air at 120 ° C. for 2 hours, and dried at 400 ° C. By firing for 2 hours, Pt was supported. The supported amount of Pt is 1% by weight. The obtained catalyst powder was compacted to obtain a pellet catalyst of 0.5 mm to 1.7 mm.

(1) Scanning electron micrographs of the α-alumina particles prepared above are shown in FIGS. 1 (1000 times) and 2 (10,000 times). In addition, the transmission electron micrographs of the sections prepared by embedding the catalyst particles in a resin and thinly slicing with FIB are shown in FIGS. 3 (20,000 times), 4 (100,000 times), and 5 (200,000 times). Shown in It can be seen that the gray portions in FIGS. 4 and 5 are α-alumina, the white portions are the gaps between the layers, and the multilayer structure has a gap between the layers. The black dots are Pt particles, and it is recognized that Pt is carried in the gap between the layers.

(Example 2)
The catalyst powder prepared in Example 1 is impregnated with a predetermined amount of a cerium nitrate aqueous solution having a predetermined concentration, evaporated to dryness while stirring until the solvent is completely evaporated, and dried at 120 ° C. for 2 hours in the atmosphere. By baking at 500 ° C. for 2 hours, ceria (CeO ₂ ) was supported. The carried amount of ceria is 3% by weight. The obtained catalyst powder was compacted to obtain a pellet catalyst of 0.5 mm to 1.7 mm.

(Example 3)
The catalyst powder prepared in Example 1 is impregnated with a predetermined amount of an aqueous solution of zirconium oxynitrate having a predetermined concentration, evaporated to dryness with stirring until the solvent is completely evaporated, and dried at 120 ° C. for 2 hours in the atmosphere. Then, it was baked at 500 ° C. for 2 hours to carry zirconia (ZrO ₂ ). The loading of zirconia is 3% by weight. The obtained catalyst powder was compacted to obtain a pellet catalyst of 0.5 mm to 1.7 mm.

(Example 4)
The catalyst powder prepared in Example 1 is impregnated with a predetermined amount of a predetermined concentration of an aqueous solution of aluminum nitrate, evaporated to dryness with stirring until the solvent is completely evaporated, and dried at 120 ° C. for 2 hours in the atmosphere. It was calcined at 500 ° C. for 2 hours to carry alumina (Al ₂ O ₃ ). The amount of alumina carried is 3% by weight. The obtained catalyst powder was compacted to obtain a pellet catalyst of 0.5 mm to 1.7 mm.

(Example 5)
The catalyst powder prepared in Example 1 was impregnated with a predetermined amount of a mixed aqueous solution of cerium nitrate and zirconium oxynitrate at a predetermined concentration, and evaporated to dryness while stirring until the solvent was completely evaporated. carrying CeO ₂ -ZrO ₂ composite oxide was calcined for 2 hours at 2 h dried 500 ° C. at ° C.. The loading amount is 1.5% by weight of CeO _{2 and} 1.5% by weight of ZrO _2, for a total of 3% by weight. The obtained catalyst powder was compacted to obtain a pellet catalyst of 0.5 mm to 1.7 mm.

(Comparative Example 1)
A commercially available γ-alumina powder (“MI386” manufactured by Grace Co., Ltd.) was prepared, loaded with Pt in the same manner as in Example 1, and used as a pellet catalyst. This γ-alumina powder has an average primary particle diameter (in the lengthwise direction of a needle) of 10 nm, an average secondary particle diameter of 4 μm, and a specific surface area of 150 to 200 m ² / g. As a result of TEM observation, it was confirmed that Pt was uniformly and highly dispersed and supported throughout.

<Test Example 1 / Evaluation>
The pellet catalysts of Example 1 and Comparative Example 1 were subjected to an endurance test of heating at 700 ° C., 800 ° C., 900 ° C., and 1000 ° C. for 5 hours in the air. Then, each of the pellet catalysts after the durability test was placed in an evaluation device, and under a stoichiometric atmosphere model gas flow shown in Table 1, at a space velocity SV = 210,000 / h, and after pretreatment at 500 ° C. × 20 minutes and 20 ° C. / Min, and the HC purification rate was continuously measured during the heating. From this result, the 50% purification temperature of HC was calculated, and the result is shown in FIG. The pellet catalysts of Examples 2 to 5 were subjected to an endurance test in which each was heated at 800 ° C. for 5 hours in the atmosphere, and thereafter the HC 50% purification temperature was measured in the same manner. FIG. 6 shows the results.

よ り From FIG. 6, the catalyst of Comparative Example 1 has a low activity after the durability test, whereas the catalyst of each Example shows a high activity after the durability test despite the small specific surface area. That is, it is considered that the activity of the catalyst of Comparative Example 1 was reduced due to the growth of Pt particles, and that the activity of the catalyst of Example 1 was suppressed because the growth of Pt particles was suppressed. It is clear that this is an effect of supporting a noble metal in at least the gaps of the catalyst carrier made of α-alumina having a multilayer structure having gaps between layers.

In addition, since the catalysts of Examples 2 to 5 show high activity even after the durability test than Example 1, it is clear that it is preferable to further support oxide particles. The catalyst of Example 2 showed almost no deterioration even after the endurance test at 800 ° C., indicating that ceria is the most preferable oxide particle.

<Test Example 2 / Evaluation>
In the above test example, since the difference in the degree of deterioration of the catalysts of Examples 1 and 2 was small, the space velocity was 814,000 / h, and the amount of ceria carried was 5% by weight in the catalyst of Example 2. Except for the above, in the same manner as in Test Example 1, endurance tests were performed on the catalysts of Examples 1 and 2 at 800 ° C. for 5 hours in the atmosphere, and the subsequent 50% purification temperatures of HC and NO _x were measured. For the catalyst of Example 1, 50% purification temperature of the initial HC and NO _x before the durability test was also measured. FIG. 7 shows the results.

FIG. 7 shows that the catalyst of Example 1 had a low purification activity after the durability test, whereas the catalyst of Example 2 maintained a high purification activity after the durability test. It is clear that this is the effect of further supporting.

Therefore, a transmission electron micrograph (200,000 times) of a cross section obtained by burying the catalyst of Example 2 in a resin and slicing thinly by FIB after the endurance test, and an EDX chart of black particles and gray particles in the visual field are shown. As shown in FIG.

よ り From FIG. 8, black particles are recognized as Pt, and gray particles are recognized as ceria. Pt and ceria are both supported in the gap between the layers. Therefore, it is considered that the ceria particles intervene between the Pt particles, whereby the Pt became more difficult to move, and the grain growth of the Pt was further suppressed.

(Example 6)
A catalyst powder carrying 1% by weight of Pt was placed in a tubular furnace in the same manner as in Example 1 on α-alumina powder prepared in the same manner as in Example 1, and heated at 1100 ° C. under N ₂ gas flow. Heat treatment for heating for 5 hours was performed. As a result of measurement by the CO adsorption method, it was confirmed that the supported Pt had grown to a grain size of 40 to 60 °.

Next, the catalyst powder after the heat treatment is impregnated with a predetermined amount of an aqueous solution of cerium nitrate having a predetermined concentration, and evaporated to dryness while stirring until the solvent is completely evaporated, and dried at 120 ° C. for 2 hours in the air and 500 ° C. For 2 hours to carry ceria (CeO ₂ ). The loading of ceria is 30% by weight. The obtained catalyst powder was compacted to obtain a pellet catalyst of 0.5 mm to 1.7 mm.

(Example 7)
Except that the heat treatment was not performed, the same catalyst powder as in Example 6 was used, and ceria was similarly supported to prepare a similar pellet catalyst.

<Test Example 3 / Evaluation>

The pellet catalysts of Examples 6 and 7 are heated at 900 ° C., 1000 ° C., and 1100 ° C. for 5 hours in a fluctuating atmosphere in which a lean gas and a rich gas shown in Table 2 are alternately flown for 2 minutes. A durability test was performed. Each of the pellet catalysts before and after the durability test was placed in an evaluation device, and the HC 50% purification temperature was measured in the same manner as in Test Example 1. FIG. 9 shows the results.

From FIG. 9, it is clear that the pellet catalyst of Example 6 shows high activity even after high-temperature durability, which is an effect that Pt has grown to some extent by heat treatment in N ₂ gas.

<Test Example 4>
In the same manner as in Example 1, a catalyst powder in which 1 wt% of Pt was supported on α-alumina powder prepared in the same manner as in Example 1 was used as a pellet catalyst of 0.5 mm to 1.7 mm. This pellet catalyst was placed in a tubular furnace and subjected to a heat treatment of heating at 800 ° C., 900 ° C., 1000 ° C., and 1100 ° C. for 5 hours under N ₂ gas flow.

For each of the pellet catalysts after the heat treatment and the pellet catalysts not subjected to the heat treatment, a durability test was performed at 1100 ° C. for 5 hours under a fluctuating atmosphere in which a lean gas and a rich gas shown in Table 2 were alternately and repeatedly passed for 2 minutes. And each place each pellet catalysts after the durability test in the evaluation device, at different conditions as in Test Example 1, was measured 50% purification temperature for HC and NO _x. The results are shown in FIG.

It is clear from FIG. 10 that the higher the heat treatment temperature in N ₂ gas is, the higher the activity after the durability test is. The effect is small when the heat treatment temperature in N ₂ gas is 800 ° C. and 900 to 1200 ° C. Is considered appropriate.

3 is a scanning electron micrograph (× 1000) showing the particle structure of the catalyst of Example 1. 3 is a scanning electron micrograph (× 10,000) showing the particle structure of the catalyst of Example 1. 3 is a transmission electron micrograph (magnification: 20,000) showing a particle structure of a cross section of the catalyst of Example 1. 3 is a transmission electron micrograph (× 100,000) showing a particle structure of a cross section of the catalyst of Example 1. 3 is a transmission electron micrograph (magnification: 200,000) showing a particle structure of a cross section of the catalyst of Example 1. It is a graph which shows HC50% purification temperature after the endurance test of the catalyst of an example and a comparative example. Is a graph showing the HC50% purification temperature and the NO _x 50% purification temperature of the catalyst of Example 1 and Example 2. FIG. 5 shows a transmission electron micrograph (magnification: 200,000) showing a particle structure of a cross section of the catalyst of Example 2 after a durability test, and an EDX chart of a main part thereof. 9 is a graph showing HC50% purification temperatures of catalysts of Example 6 and Example 7 after a durability test. Is a graph showing the relationship between the 50% purification temperature of the HC and NO _x after heat treatment temperature and the durability test.

Claims (13)

(4) A highly heat-resistant catalyst carrier comprising an oxide formed by firing a hydroxide and having a multilayer structure having a gap between layers. (4) A highly heat-resistant catalyst carrier comprising α-alumina having a multilayer structure having a gap between layers. A catalyst for purifying exhaust gas, wherein a noble metal is carried in at least the gap of the highly heat-resistant catalyst carrier according to claim 1 or 2. The exhaust gas purifying catalyst according to claim 3, wherein oxide particles that do not react with the noble metal are further carried in the gap. The exhaust gas purifying catalyst according to claim 4, wherein the oxide particles are ceria. A method for supporting a noble metal compound by impregnating a highly heat-resistant catalyst carrier according to claim 1 or 2 with a noble metal compound solution and evaporating to dryness to support a noble metal, wherein the solvent is completely evaporated during evaporation to dryness. A method for producing an exhaust gas purifying catalyst, wherein a stress is applied from a pressure. 3. A catalyst for purifying exhaust gas, wherein a noble metal is supported in at least the gap of the highly heat-resistant catalyst carrier according to claim 1 or 2, and oxide particles which do not react with the noble metal are supported in at least the gap. Manufacturing method. 8. The exhaust gas purifying catalyst according to claim 7, wherein the oxide particles are ceria. A method for producing an exhaust gas purifying catalyst, comprising: supporting a noble metal in at least the gap of the highly heat-resistant catalyst support according to claim 1 or 2; 10. The method for producing an exhaust gas purifying catalyst according to claim 9, wherein the heat treatment is performed by heating to 600 to 800 ° C in an oxidizing atmosphere and to 900 to 1200 ° C in a non-oxidizing atmosphere. 11. The method for producing an exhaust gas purifying catalyst according to claim 9, wherein an oxide particle that does not react with the noble metal is supported in the gap after supporting the noble metal. 12. The method for producing an exhaust gas purifying catalyst according to claim 11, wherein the oxide particles are supported after the growth of the noble metal particles. 13. The method for producing an exhaust gas purifying catalyst according to claim 11, wherein the oxide particles are ceria.

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