JP2001179098A - Exhaust gas cleaning catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas cleaning catalyst capable of being sharply reduced in the deterioration of exhaust gas cleaning capacity caused by the disappearance of an occluding agent. SOLUTION: In an exhaust gas cleaning catalyst obtained by adding at least one metal selected from the group consisting of alkali metal and alkaline earth metal on a catalyst layer 20 as an occluding agent, an acidic material 30 high in the affinity with the occluding agent is mixed with the same catalyst layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying catalyst, and more particularly, to an exhaust gas purifying catalyst capable of maintaining a high purification ability.

[0002]

[Related Background Art] Lean-burn engines such as lean-burn engines and in-cylinder injection engines use a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio in a predetermined operating range in order to improve fuel efficiency and exhaust gas characteristics. Be driven. NOx (nitrogen oxide) in exhaust gas during lean air-fuel ratio operation
Is not sufficiently purified by the three-way catalyst, a NOx catalyst for storing NOx in exhaust gas in an oxidizing atmosphere is provided, and the NOx stored in the catalyst is reduced to N ₂ (nitrogen) in a reducing atmosphere. Accordingly, it is known that the amount of NOx emission to the atmosphere is reduced. As this type of lean NOx storage catalyst, for example, Japanese Patent Application Laid-Open
As described in Japanese Patent No. 85093, potassium (K), which is one of alkali metals, is added as a NOx occluding agent to form N
Some improve Ox storage performance.

[0003]

However, if the potassium oxide-added NOx catalyst is kept at a high temperature for a long period of time, cracks may occur in the catalyst, which may cause a decrease in the durability of the NOx catalyst. ing. NOx
In order to investigate the cause of these durability reductions in the catalyst,
The present inventors manufactured a NOx catalyst in which potassium, which is one of the alkali metals, was added as a NOx storage agent to a catalyst layer supported on a honeycomb-type cordierite carrier (porous carrier). A bench test of an engine equipped with, and a running test of a vehicle equipped with this type of engine were performed. In the bench test and the actual vehicle running test, the engine and the vehicle were operated under the condition that the NOx catalyst was exposed to a high temperature of 650 ° C. or more for a considerable time. After the operation, the elemental analysis on the cut surface of the NOx catalyst is performed by EP.
The method was carried out by the MA method (electron probe micro-partial analysis method), and a compound of potassium, magnesium, aluminum, silicon and oxygen KMg ₄ Al ₉ Si ₉ was added to the cordierite (Mg ₂ Al ₄ Si ₅ O ₁₈ ) layer of the catalyst. It was confirmed that O ₃₆ and a compound KAlSiO _{4 of} potassium, aluminum, silicon and oxygen were present.

According to the above experiment, when the NOx catalyst is exposed to a high temperature, potassium added to the catalyst layer (wash coat) permeates into the cordierite carrier, and potassium reacts with the cordierite in a high temperature atmosphere. To form the above compound. Here, it is understood that the potassium compound easily penetrates into the cordierite carrier because of its high water solubility and low melting point. Then, when a compound having a different coefficient of thermal expansion from cordierite is formed in the cordierite carrier, cracks occur in the cordierite carrier due to a change in the catalyst temperature during and before and after use of the catalyst, and the strength is reduced. Will do.

As described above, a NOx catalyst containing potassium or the like as an occluding agent is used in an oxidizing atmosphere. In this oxidizing atmosphere, nitrates and sulfates of the occluding agent are formed by a chemical reaction between the occluding agent and nitrogen or sulfur components in the exhaust gas,
The NOx storage capacity decreases. In this case, the storage capacity can be restored by forming a reducing atmosphere around the NOx catalyst and decomposing nitrates and sulfates.However, even if such measures are taken, if the NOx catalyst is used at a high temperature for a long time, Purification capacity may decrease.

From the results of experiments conducted by the present inventor, one of the causes of the decrease in the purification performance is that the storage agent is NO at high temperatures.
It is considered that a considerable part of the occluding agent in the catalyst disappears due to the gradual evaporation and scattering from the catalyst. That is, the present inventor has produced a NOx catalyst in which a catalyst layer containing potassium as an occluding agent is supported on a cordierite carrier, and the potassium content in an unused NOx catalyst is determined by the XRF method (X-ray fluorescence spectroscopy). Then, after using this catalyst at a high temperature for a long period of time (for example, 850 ° C. for 32 hours), the potassium content of the catalyst is obtained. And the amount of potassium disappeared was determined. As a result, it was found that the disappearance of potassium ranges from several tens% to 50%.

The present invention has been made to solve such problems, and an object of the present invention is to provide an exhaust gas purifying catalyst capable of greatly reducing the degree of deterioration of exhaust gas purifying performance due to loss of an occluding agent. To provide.

[0008]

According to the first aspect of the present invention, at least one selected from the group consisting of an alkali metal and an alkaline earth metal is added to the catalyst layer as an occluding agent. The catalyst for purifying exhaust gas according to the present invention is characterized in that an acid material having a high affinity for the occluding agent is mixed in the same layer as the catalyst layer.

As a result, the movement of the occluding agent in the catalyst is suppressed, and the occluding agent is prevented from disappearing due to evaporation and scattering of the occluding agent from the catalyst, and furthermore, deterioration of the exhaust gas performance of the catalyst is prevented. According to the invention of claim 2, an acidic oxide containing at least one acidic substance selected from the group IV, group V, and group VI transition elements and the group IV, group V, and group VI element is included in the catalyst layer. A composite oxide containing the at least one acidic substance, a material that does not inhibit the reactivity between the nitrogen oxide and the occluding agent, and one or more materials selected from the group consisting of a material that adsorbs a reducing substance. .

For example, the catalyst layer contains at least one material selected from the group consisting of an acidic oxide containing at least one acidic substance and a composite oxide. At this time, each of the acidic oxide containing the acidic substance and the composite oxide is
Group IV, Group V and Group VI transition elements and Group IV, V
At least one acidic substance selected from the group consisting of Group IV and Group VI typical elements.

In this embodiment, the loss of the occluding agent is prevented by the acidic oxide or the complex oxide which is excellent in the occluding agent fixing ability and the thermal stability, so that the exhaust gas purification performance of the catalyst is prevented from deteriorating and the durability is improved. In this case, the composite oxide is preferably composed of a combination of oxides that express an acid point.
At this time, the at least one acidic substance is selected in consideration of the reactivity between the acidic substance and the occluding agent. For example, when the storage agent is potassium, it is preferable to use an acidic oxide or a composite oxide containing silica or tungsten as an acidic substance.

Further, for example, the catalyst layer contains an acid material which does not inhibit the reactivity between NOx and the occluding agent.
In this case, the action of suppressing the movement of the occluding agent on the catalyst is exhibited, and the NOx occluding action of the occluding agent is favorably exhibited. In addition, for example, an acidic material that adsorbs a reducing substance (for example, a reducing gas such as HC) is included. In this case, the sulfate and nitrate in the catalyst layer are decomposed by the reducing substance captured by the reducing substance adsorption ability, and the NOx storage performance is restored.

[0013] The invention according to claim 3 is characterized in that the occluding agent contains potassium and the carrier is made of a porous carrier. When potassium is added as the occluding agent in this manner, the movement of the occluding agent is favorably suppressed by the acidic material, and the loss of the occluding agent due to evaporation and scattering and, consequently, deterioration of the exhaust gas performance of the catalyst are suitably prevented. In addition, by using the porous carrier, the pressure loss of the exhaust gas is reduced, and the exhaust gas is brought into good contact with the catalyst layer, so that the exhaust gas is satisfactorily purified. On the other hand, in a catalyst having a porous carrier, the flow of exhaust gas containing high-temperature steam is improved, and the movement and evaporation of an occluding agent,
Scattering is more likely to occur, but in the present invention this is prevented by the acid material.

In fact, an exhaust gas purifying catalyst of the present invention, which is obtained by mixing a cordierite carrier as a porous carrier and a catalyst layer containing potassium as an occluding agent and an acid material, is mounted on an engine and subjected to bench tests. Elemental analysis of the cut surface by the EPMA method after conducting the actual vehicle running test showed that the amount of potassium in the cordierite carrier was a catalyst in which a simple catalyst layer was formed without mixing an acid material in the catalyst layer. It was recognized that the number was considerably smaller than in the case of.

The results of this experiment show that potassium was retained in the catalyst layer and that scattering of potassium and penetration of potassium into the cordierite carrier were suppressed. When the potassium content in the catalyst layer after using the exhaust gas purifying catalyst at a high temperature for a long time is measured by the XRF method, the potassium content in the catalyst layer is lower than that in the case where a simple catalyst layer containing no acid material is used. It has been confirmed that a large amount of Pd remained in the catalyst layer (see FIG. 3).

The reason why a large amount of potassium remains in the catalyst layer is that the acid material is mixed in the same layer as in the catalyst layer, so that potassium is converted into each acid material by the affinity of the acid material. This is probably because the particles are dispersed and attracted to the particles and held in the catalyst layer. In other words, in the present invention, the storage agent such as potassium is favorably retained in the catalyst layer without disappearing due to movement or scattering, so that generation of a compound due to penetration into the porous carrier is suppressed, and , Cracks are prevented, the durability of the exhaust gas purifying catalyst is improved, and the exhaust gas purifying performance is suitably maintained.

The invention according to claim 4 is characterized in that the catalyst layer contains zeolite. When zeolite is included in the catalyst layer in this way, zeolite has a cation exchange ability corresponding to affinity, and has the same advantages as those described above. That is, the storage agent moving in the catalyst may be in an ionized state in the presence of high-temperature steam. However, if the catalyst layer contains zeolite, the storage agent in this ionized state will be on the zeolite. It is considered that the acid site is fixed as an ion by the cation exchange ability of the acid site (see FIG. 6), and the migration to the carrier side is prevented.

Zeolite has a three-dimensional network structure and a high specific surface area, and thus has a molecular sieving effect. Therefore, the occlusion agent is highly dispersed on the zeolite having such a structure, It is difficult to penetrate into the carrier. Further, even when the internal combustion engine is in a lean operation state, slight H
Although C is contained, zeolite is excellent in the ability to fix the storage agent and the ability to adsorb HC, so that the HC adsorbed on the zeolite promotes the decomposition of the nitrate and sulfate of the storage agent. That is, even during lean operation, HC
The zeolite having an adsorbing ability continuously decomposes nitrate and sulfate of an occluding agent by utilizing a small amount of HC contained in exhaust gas, and contributes to recovery of NOx occluding performance of a catalyst.

When the NOx purifying efficiency of the exhaust gas purifying catalyst after actually using the exhaust gas purifying catalyst at a high temperature for a long time is examined, in the case of the present invention, a simple catalyst layer containing no acid material is mixed. It was confirmed that the NOx purification efficiency was maintained higher as a whole irrespective of the catalyst temperature than in the case where the catalyst was used (see FIG. 4). The acid material (including zeolite) may be in a highly dispersed state, or may be particles or blocks (mass) having a certain size, as long as they are mixed in the same layer as in the catalyst layer. In any case, the above-described effects are sufficiently exhibited.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an exhaust gas purifying catalyst according to the present invention will be described. The exhaust gas purifying catalyst is configured as a NOx catalyst having a honeycomb (monolith) type cordierite carrier composed of many cells. FIG.
Indicates a part of one cell of the cordierite carrier, and the cells of the cordierite carrier 10 are formed in, for example, a square shape. A catalyst layer 20 is supported on the surface of the cordierite carrier 10.

The cordierite carrier 10 is prepared by dispersing, for example, a mixture of alumina source powder, silica source powder and magnesia source powder such that the ratio of alumina, silica and magnesia becomes a cordierite composition. The solid content is formed into a honeycomb shape, and this honeycomb formed body is fired. The catalyst layer 20 is formed, for example, as follows. First, noble metals such as platinum, NOx
A slurry containing an alkali metal or alkaline earth metal such as potassium (K) or barium (Ba) as an occluding agent and an acid material 30 such as silicon (Si) is prepared. Next, the cordierite carrier 10 is immersed in the above slurry, dried and fired. Thereby, the acid property material 30 is mixed in the catalyst layer containing the noble metal and the alkali metal or the alkaline earth metal.

The NOx storage agent is typically potassium (K) or barium (Ba), but is not limited thereto, and may be any alkali metal or alkaline earth metal. The acid material 30 is typically silica (silicon oxide). However, as shown in FIG. 2, a transition element of a group IV, V, VI or a typical element of a group IV, V, VI (P, S , V, Cr, As, Nb, Mo, W
Etc.), and it is preferable that the affinity with an alkali metal or an alkaline earth metal is greater as shown in FIG. Is shown). In consideration of the reactivity with the NOx storage agent, when the NOx storage agent is, for example, potassium, the acid material 30 is preferably silicon (Si) or tungsten (W). Further, the acid material 30
Is preferably a material that does not inhibit the reactivity between NOx and the NOx storage agent.

Further, even a composite material (composite oxide) is included in the acid material 30 if it has an affinity for the NOx storage agent. Therefore, for example, zeolite having a cation exchange ability corresponding to affinity is also included in the acid material 30. As described above, a NOx catalyst obtained by coating the cordierite carrier 10 with the catalyst layer 20 is obtained. As is conventionally known, the NOx catalyst is housed in a case via, for example, a cushioning material, and arranged in an exhaust pipe of a lean burn internal combustion engine.

According to this NOx catalyst, NOx in exhaust gas is stored in the form of nitrate under the action of the catalyst species dispersed in the catalyst layer 20 during operation of the engine at a lean air-fuel ratio. Further, during operation of the engine at a rich air-fuel ratio, nitrate is decomposed, and the stored NOx is reduced to nitrogen and released from the NOx catalyst to the atmosphere. When an internal combustion engine equipped with such a NOx catalyst is operated for a long time, the NOx catalyst is exposed to a high temperature for a long time. In this case, in a conventional NOx catalyst obtained by coating a cordierite carrier with a catalyst layer to which only potassium or barium (hereinafter, referred to as potassium) as a NOx storage agent is added, potassium has already been described. It moves into the cordierite carrier and reacts with a silica component or the like in the carrier to generate a compound, which causes cracks in the cordierite carrier and impairs the durability of the NOx catalyst.

On the other hand, in the NOx catalyst of the present embodiment, according to the elemental analysis by the EPMA method, even when the NOx catalyst is used at a high temperature for a long time, the catalyst layer 2
It was found that the formation of a compound of potassium added to 0 and the silica component of the cordierite carrier 10 was suppressed. The reason for this is that, as described above, by mixing an acid property material 30 such as silicon in addition to potassium in the catalyst layer 20 in the same layer, potassium is dispersed in each acid property material particle by the affinity of the acid property material 30. This is considered to be due to the fact that it is attracted and is favorably held in the catalyst layer 20 without moving.

Actually, when the potassium content in the catalyst layer 20 after using the NOx catalyst at a high temperature for a long time is measured, as shown by a solid line in FIG. It was confirmed that potassium was considerably more left in the catalyst layer 20 than in the conventional case (shown by a broken line) in which Further, as a factor that a considerable amount of potassium remains in the catalyst layer 20, in the case of the conventional NOx catalyst, since the nitrate of potassium has a low melting point, it easily moves in the catalyst when exposed to a high temperature. In the NOx catalyst of the present embodiment, the evaporation and scattering of the potassium are suppressed by the affinity with the acid material 30, and the potassium is contained in the catalyst layer 20. It is conceivable that it is kept well.

In particular, the acid layer 30
When zeolite is contained as a material, zeolite has a cation exchange ability, so that a more preferable effect can be obtained. That is, the NOx storage agent such as potassium moving in the NOx catalyst may be in an ionized state in the presence of high-temperature steam. However, if zeolite is included, the NOx storage agent in this ionized state may be used. It is considered that as shown in FIG. 6, the acid is fixed as an ion by the cation exchange ability of the acid site on the zeolite, and the migration to the carrier side is prevented.

Zeolite has a three-dimensional network structure and a high specific surface area, and thus has a molecular sieving effect. A NOx storage agent such as potassium has a high sizing property on a zeolite having such a structure. This also has the effect of making it more difficult to penetrate into the carrier. Further, even when the internal combustion engine is in a lean operation state, the exhaust gas contains a small amount of HC, but zeolite is excellent in the ability to fix the NOx storage agent and the ability to adsorb HC, and the HC adsorbed on the zeolite This also promotes the decomposition of nitrates and sulfates of the NOx storage agent. In other words, even during the lean operation, the zeolite having the ability to adsorb HC continuously decomposes the nitrate and sulfate of the NOx storage agent by using a small amount of HC contained in the exhaust gas to recover the NOx storage performance of the catalyst. Contribute.

As the zeolite, MFI type, Y
Although various types of zeolites such as type, X type, mordenite, ferrierite and the like can be used, those suitable for the exhaust gas composition may be selected in consideration of the structural relationship with the adsorbed HC species. Further, the cation exchange ability and heat resistance of the zeolite depend on the composition of the zeolite. That is,
Cation exchange capacity is inversely proportional to the SiO ₂ / AlO ₂ ratio in zeolite, and heat resistance is proportional to this ratio. Therefore, for example, by increasing the above ratio as much as possible, the heat resistance of the catalyst can be improved. On the other hand, by decreasing the above ratio, the amount of the NOx occluding agent accompanying the long-time operation of the catalyst at a high temperature can be reduced. And the occlusion performance can be maintained.

As described above, in the exhaust gas purifying catalyst of the present invention, the NOx occluding agent such as potassium can be favorably held in the catalyst layer 20 without movement or scattering, and therefore, the thermal expansion of the cordierite carrier 10 can be prevented. By preventing the compounds having different rates from being generated in the cordierite carrier 10, it is possible to prevent the occurrence of cracks in the cordierite carrier 10 due to the generation of the compound, improve the durability of the exhaust gas purification catalyst, and improve the exhaust gas purification performance. It can be suitably maintained.

Actually, when the NOx purification efficiency of the NOx catalyst after using the NOx catalyst at a high temperature for a long time is examined,
As shown by the solid line in FIG. 4, in the case of the present invention, the NOx purification efficiency as a whole is independent of the conventional case (shown by a dashed line) using a simple catalyst layer without mixing an acid material, regardless of the catalyst temperature. It was confirmed that it was kept high. Also, N
As a substance that lowers the purification ability of the Ox catalyst, there is a sulfate by a sulfur component, but in the exhaust gas purification catalyst of the present invention,
Since the NOx storage agent such as potassium can be dispersed and held in the catalyst layer 20, such growth of sulfate can be suppressed.

In the above embodiment, the acid property material 30
If they are mixed in the same layer in the catalyst layer 20, they may be particles or blocks (mass) having a certain size as shown in FIG. 5. It is preferably applicable. In the above embodiment, the honeycomb cordierite carrier is used as the porous carrier. However, the present invention can be applied to an exhaust gas purifying catalyst including a carrier made of a material other than cordierite. When a metal carrier is used, the permeation of the NOx occluding agent into the carrier is not a problem, but the effect of preventing the occluding agent from scattering is obtained, and the exhaust gas purification performance of the catalyst is prevented from lowering.

When a honeycomb type cordierite carrier is used, the cells of the cordierite carrier are not limited to those having a square shape, and may be, for example, triangular or hexagonal.

[0034]

As described above in detail, according to the exhaust gas purifying catalyst of the first aspect of the present invention, an acid material having a high affinity for the occluding agent is mixed in the same layer as the catalyst layer. Therefore, the occluding agent can be dispersed and attracted to the respective acidic material particles by the affinity of the acidic material to be retained in the catalyst layer. Even if the catalyst is used at a high temperature for a long time, the occluding agent can be used. The loss of the occluding agent due to the movement of the occluding agent and the evaporation and scattering of the occluding agent can be prevented, and the exhaust gas performance of the catalyst can be prevented from lowering.

In the exhaust gas purifying catalyst according to the second aspect, at least one selected from the group IV, group V, and group VI transition elements and the group IV, group V, and group VI typical elements is contained in the catalyst layer. It is composed of an acidic oxide containing one acidic substance, a composite oxide containing the at least one acidic substance, a material that does not inhibit the reactivity between the nitrogen oxide and the occluding agent, and a material that adsorbs the reducing substance. Since it contains at least one material selected from the group, acidic oxides and composite oxides that have a high storage capacity for heat storage and heat stability prevent the loss of the storage medium and purify the exhaust gas of the catalyst. It is possible to prevent deterioration of performance and improve durability, and it is possible to prevent exhaustion of the occluding agent and prevent exhaust gas by NOx occluding action of the occluding agent by using an acid material which does not inhibit the reactivity between the nitrogen oxide and the occluding agent. Purification performance The reducing substance (for example, H
The reducing agent such as C) can be used to regenerate the occluding agent to recover the exhaust gas purifying ability.

According to the catalyst for purifying exhaust gas of the third aspect, the occluding agent contains potassium and the carrier is made of a porous carrier, so that the storage capacity of potassium is improved and the performance of purifying exhaust gas with the porous carrier is improved. While improving the acidity, the acid-based material favorably suppresses the movement of the occluding agent, which is likely to occur when a porous carrier is used, and favorably reduces the occluding agent due to evaporation and scattering and, consequently, reduces the exhaust gas performance of the catalyst. Can be prevented.

According to the exhaust gas purifying catalyst of the present invention, since the catalyst layer contains zeolite, the cation exchange ability of the zeolite allows the occlusion agent to move and the occlusion agent to evaporate and scatter. The disappearance of the agent can be effectively prevented, and a decrease in the exhaust gas performance of the catalyst can be suitably prevented.

[Brief description of the drawings]

FIG. 1 is a partially enlarged sectional view showing a quarter of one shell of an exhaust gas purifying catalyst according to the present invention.

FIG. 2 is a view showing the affinity of an acid material with potassium.

FIG. 3 is a diagram showing the potassium content in the catalyst layer after using the exhaust gas purifying catalyst at a high temperature for a long time.

FIG. 4 is a diagram showing the NOx purification efficiency of an exhaust gas purification catalyst after the exhaust gas purification catalyst has been used at a high temperature for a long time.

FIG. 5 is a partially enlarged cross-sectional view showing a quarter of one shell of the exhaust gas purifying catalyst according to the present invention, in a case where particles or blocks (lumps) are made of an acid-based material.

FIG. 6 is a schematic diagram showing a potassium fixing action by a cation exchange capacity of zeolite.

[Explanation of symbols]

 Reference Signs List 10 cordierite carrier (porous carrier) 20 catalyst layer 30 acid material

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B01J 27/057 B01J 27/185 A 27/185 27/186 A 27/186 29/068 A 29/068 29/076 A 29/076 F01N 3/08 A F01N 3/08 3/10 A 3/10 3/28 301C 3/28 301 B01D 53/36 102B 102H (72) Inventor Iwamido Uniform No. 33, Shiba 5-chome, Minato-ku, Tokyo No. 8 Inside Mitsubishi Motors Corporation (72) Inventor Keisuke Tashiro 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Industry Co., Ltd. (72) Osamu Nakayama 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation F-term (reference) BA41X BA42Y BB02 EA04 4G069 AA03 AA08 BA01A BA01B BA02A BA02B BA07A BA07B BA13A BA13B BA17 BB01A BB01B BB 02A BB02B BB04A BB04B BB06A BB10A BC01A BC03A BC03B BC08A BC13A BC13B BC20A BC24A BC27A BC27B BC49A BC53A BC55A BC55B BC57A BC58A BC58B BC59A BC59B BC60A BC60B BC69A BC75A BC75B BD02A BD02B BD07A BD07B BD08A BD08B CA03 CA08 CA09 EA18 EA19 EC28 ED05 FA03 FA06 FB15 ZA01A ZA01B ZA03B ZA04B ZA06B ZA11B ZA13B ZF05B

Claims (4)

[Claims] 1. An exhaust gas purifying catalyst comprising a carrier and a catalyst layer, wherein at least one selected from the group consisting of an alkali metal and an alkaline earth metal is added to the catalyst layer as an occluding agent. An exhaust gas purifying catalyst, wherein an acid material having high affinity is mixed in the same layer as the catalyst layer. 2. Group IV, Group V and VI
An acidic oxide containing at least one acidic substance selected from group IV transition elements and group IV, V, and VI typical elements; a composite oxide containing the at least one acidic substance; a nitrogen oxide; The exhaust gas purifying apparatus according to claim 1, comprising one or more materials selected from the group consisting of a material that does not inhibit the reactivity with an occluding agent and a material that adsorbs a reducing substance. catalyst. 3. The exhaust gas purifying catalyst according to claim 1, wherein the storage agent contains potassium, and the carrier is made of a porous carrier. 4. The exhaust gas purifying catalyst according to claim 1, wherein the catalyst layer contains zeolite.