JPH08257403A - Catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE: To obtain a catalyst characteristic having high NOx cleaning performance and thermal endurance by constituting of a multiple oxide containing one kind of transition metal and one kind of element between Al and Si and forming so that a part of a surface is formed with the transition metal. CONSTITUTION: The catalyst is composed of the multiple oxide containing at least one kind of transition metal and at least one kind of element between Al and Si, and a part of the surface is formed with the transition metal. Especially, heat resistance is improved dramatically since an active metal is fixed strongly in a catalyst structure, for example, even if the active metal is the metal which is unstable thermally and movable such as Cu differ basically from a catalyst in which an active metallic ion is deposited merely on the surface or the catalyst in which the active metallic ion is combined weak at an ion site in the catalyst having such a structure. Moreover, the catalyst is imparted with both high cleaning performance and thermal endurance which have heretofore been unobtainable, since a high dispersion in an atomic level near to the active metallic ion exchanged zeolite is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a high heat resistance and NO.
_X (Nitrogen Oxide) The present invention relates to an exhaust gas purification catalyst composed of a composite oxide having excellent purification ability.

[0002]

BACKGROUND OF THE INVENTION Diesel, zeolite catalysts as NO _X purification catalyst in an oxygen excess atmosphere such as lean-burn engine exhaust, but an active metal supported catalysts is known,
None have reached the level of practical use yet.

The conventionally synthesized oxide catalyst is usually prepared by a method of supporting an active metal on a carrier such as alumina.

[0004]

The active metal-supported catalyst conventionally synthesized is generally carried by impregnating a carrier such as alumina with an aqueous solution of a metal salt as described above. The supported active metal has a certain particle size (about 50-100Å
It is generally known that the smaller the particle size, the higher the catalytic activity. However, it is almost impossible to reduce the particle size because the supported metal particles grow or agglomerate during drying after impregnation. Further, since the active metal particles are only supported on alumina, there is a problem that the active metal particles are sintered by heat and the catalytic performance is irreversibly deteriorated.

On the other hand, the ion-exchanged zeolite prepared by ion-exchange of the active metal has a very high NO because the active metal exists in the ion-exchange site of the zeolite in an ionic state.
_Although it shows the _X purification rate, the binding force between the ion exchange site and the ion is very weak, and the ions move due to slight heat, so that the NO _X purification ability is irreversibly reduced. Also,
The ion-exchanged zeolite has low heat resistance and has a drawback that the pore structure of the zeolite collapses at high temperature.

The present invention is different from active metal particles simply supported on the surface or active metal ions weakly bound to the ion exchange site, and the active metal is highly dispersed in the catalyst structure at the single atom level. In addition, it has a structure in which the active metal is firmly incorporated in the structure, and the active metal forms a part of the surface, and has both high NO _x purification ability and high thermal durability. An object of the present invention is to provide an exhaust gas purifying catalyst having the above.

Further, according to the present invention, in the catalyst having such a structure, even if the active metal is a thermally unstable and easily movable metal such as Cu, the active metal is firmly fixed in the catalyst structure. As a result, the heat resistance is dramatically improved, and since the active metal forms a high dispersion at the atomic level close to that of ion-exchanged zeolite, it has a high NO _x purification capacity and high heat that have not been obtained in the past. The purpose is to obtain a durable catalytic property.

[0008]

That is, the present invention provides:
An exhaust gas purifying catalyst comprising a composite oxide containing at least one kind of transition metal atom and at least one kind of element selected from Al and Si, wherein the transition metal atom forms a part of the surface. Further, the transition metal atom of the composite oxide is related to the exhaust gas purifying catalyst, wherein the same atom does not exist within the second adjacent atom around the atom. In this case, if the above structure is included, even if there is a structure in which the same atom exists within the second neighboring atom around the transition metal atom, similar catalytic performance is obtained, so The provision of such an exhaust gas purifying catalyst is also included.

Further, the present invention relates to an exhaust gas purifying catalyst characterized in that the purifying activity is remarkably improved by subjecting the exhaust gas purifying catalyst to an autoclave treatment. Further, the autoclave treatment is performed at a temperature below a critical temperature at which a crystal phase of a composite oxide is separated. The present invention relates to an exhaust gas purifying catalyst, which is carried out in a temperature range, preferably with water or alcohol.

[0010]

The exhaust gas purifying catalyst according to the present invention contains at least one kind of transition metal atom which is an active metal and Al, S.
A composite oxide catalyst containing at least one element of i, which has a structure in which an active metal is highly dispersed in a catalyst structure at the level of a single atom, and the active metal is firmly incorporated in the structure, and Since the active metal forms a part of the surface, it is a catalyst having both extremely high NO _x purification capacity and high thermal durability, and the active metal particles are simply supported on the surface or ion exchange. Basically, it is different from the one in which the active metal ion is weakly bound to the site, and the catalyst having the above-mentioned structure is formed, for example, even if the active metal is a thermally unstable and mobile metal such as Cu. Since the active metal is firmly fixed in the catalyst structure, the heat resistance is dramatically improved, and the active metal forms a high dispersion at the atomic level close to that of ion-exchanged zeolite. There was no high NO _x purification It is possible to obtain catalytic properties having both chemical ability and high thermal durability.

When the autoclave treatment is further carried out using water or alcohol, due to the special environment inside the autoclave, the crystallinity is appropriately improved and stabilized, and further activation of the catalytically active sites is promoted. , NO _x purification capacity becomes extremely high.

However, if the temperature of the autoclave treatment is raised more than necessary, the crystallization is remarkably improved, the crystal phase is separated, and the transition metal atoms are precipitated as metal oxide particles, so that the special structure of the present invention is used. Therefore, it is necessary to keep the autoclave treatment temperature within the range of the critical temperature or lower since it is destroyed and high catalytic activity cannot be obtained.

[0013]

【Example】

Example (1) -1 [Synthesis of Cu-Al composite oxide by unclaved autoclave and autoclave using water] First, aluminum nitrate and copper nitrate were added so that CuO was 5% by weight (wt) in terms of oxide. To prepare an aqueous solution.

While stirring this aqueous solution, ammonia water diluted to 0.5 to 3% is slowly added dropwise to neutralize it to obtain a coprecipitate of Cu and Al. At this time, if the solution concentration is too high or the ammonia water dropping rate is too fast, a uniform mixture at the atomic level cannot be obtained. Solution concentration is 0.4 mol /
1 or less, and the ammonia water dropping rate must be 10 cc / min or less. This coprecipitate is filtered and washed with pure water to obtain a Cu-Al gel.

This was hydrothermally treated in an autoclave under various temperature conditions of 200 ° C. or lower. The hydrothermally treated product was air-dried, then dried at 110 ° C. overnight and crushed in a mortar. This powder was calcined at 700 ° C. for 1 hour to synthesize a hydrothermally treated desired composite oxide catalyst, that is, an exhaust gas purifying catalyst.

A Cu-Al gel prepared by the above method was also dried and calcined without hydrothermal treatment in an autoclave to synthesize it.

The Cu-Al gel prepared by the above method was directly dried and calcined without hydrothermal treatment, and a Cu-free Al oxide as a comparative example was prepared in the same manner as in the above method. ₂ O ₃ was produced and its γAl ₂
An aqueous solution was prepared by mixing copper nitrate such that CuO was 5% by weight in terms of oxide with respect to O ₃ , and γAl was added to the aqueous solution.
₂ O ₃ was added, and the aqueous solution containing γAl ₂ O ₃ was slowly added dropwise with stirring to a 0.5 to 3% diluted ammonia water to be neutralized to support Cu on γAl ₂ O ₃ . A catalyst was also prepared.

Specifically, as shown in Table 1, CuO is a Cu-Al composite oxide containing CuO in a weight percentage of 5% as shown in Table 1, which is heated by an autoclave at hydrothermal temperatures of 100 ° C, 120 ° C, and 150 ° C. ℃, 190 ℃ and 20
The samples treated at 0 ° C. and those not subjected to autoclave were treated with No. 1 to No. 6 was synthesized.

In addition, an oxide catalyst which retains CuO by a conventional method is also synthesized as CuO-supporting alumina having 5% by weight of CuO and autoclaved at a hydrothermal temperature of 150 ° C. and an autoclave. Those that are not processed in No. of the comparative example. 1b and No. It was synthesized as 1a.

The NO _x purification activity of the above synthesized catalyst was measured by a fixed bed atmospheric pressure flow reactor which is an existing measuring instrument.

The composition of the reaction gas is NO: 1000 ppm,
_{C 3 H 6: 1000ppm, CO} : 1200ppm, H
₂ : 400 ppm, O ₂ : 6%, CO ₂ : 10%, H _{2
O: 10%, N 2:} Bal. The GHSV (space velocity) was 200,000 h ⁻¹ . The results are shown in Table 1.

The product No. according to the present invention. 1 to No. 5
Indicates all purification rate satisfactory in cleaning items, improved up to 30% of the NO _X purification performance was observed. Further, at this time, generation of N ₂ O was not seen. However, hydrothermal treatment 20
0 ° C. product No. In No. 6, the NO _x purification rate was 10% or less, and it was found that the catalytic function was slightly deteriorated.

Further, a heat deterioration test at 800 ° C. in a reaction gas was conducted. The results are shown in Table 2.

According to Table 2, No. 1, No. It can be seen that the product of the present invention shown in FIG. 4 shows almost no thermal deterioration with respect to NO _x even in the 10-hour test, but the conventional comparative example No. It can be seen that the heat deterioration of the item 1a is extremely large.

Thus, it can be seen that the catalyst of the present invention has excellent heat resistance.

Furthermore, among the synthesized catalysts, N of the present embodiment is used.
o. 1, No. 2, No. 3, No. 4, No. 5 and No. When XRD (powder X-ray diffraction) was performed on No. 6, No. 3, No. 4 and No. As shown in FIG. 1 showing only No. 6, the catalyst after the autoclave treatment has a crystal structure of pseudo-boehmite which is close to amorphous, but the crystallinity of the pseudo-boehmite is improved as the autoclave treatment temperature rises. I understand. However, when the autoclave treatment temperature was set to a high temperature such as 200 ° C., the example No. As in No. 6, the crystallinity of boehmite was extremely improved, and Example No. 3, No. In Example 4, the active metal (Cu) incorporated in the structure was the same as in Example No. 4. In No. 6, it is clearly seen that the crystal phase of CuO is separated and present in addition to boehmite. Therefore, in Example No. It was found that when the autoclave treatment temperature was raised too high as in 6, the temperature was above the critical temperature at which the separation of the crystalline phase occurred.

This example No. 1, No. 2, No.
3, No. 4 and No. When 5 was autoclaved, it was calcined at 700 ° C in the air, and γA
Although it had undergone a phase transition to l ₂ O ₃ , the active metal was still incorporated in the structure and no precipitation of CuO was observed. However, in Example No. 6 has a phase transition to γ-Al ₂ O ₃ ,
CuO that had been precipitated during the autoclave treatment was still present, and No. 3, No. 4 and No. It can be seen that the structure of the present invention cannot be taken, as shown in FIG.

Thus, it is understood that it is necessary to carry out the autoclave treatment in a temperature range below the critical temperature at which the crystal phase does not separate.

Therefore, the local structure analysis in the vicinity of the active metal atom of the complex oxide in the autoclave treatment temperature range where the catalytic activity was good was analyzed by the wide area X-ray absorption fine structure analysis (hereinafter, EXAF).
S analysis was abbreviated), and the results shown in FIGS. 3 to 5 were obtained.

The graphs shown in FIGS. 3 to 5 show the Cu EX.
The radial distribution function which Fourier-transformed the AFS signal is shown. The graph shows the real and imaginary parts of the Fourier transform. The dots in the graph represent the actual measurement data, and the line represents the analysis result. The parameter was McKale, and the analysis was performed in the R space. As a result, it is found from FIG. 5 and FIG. 6 that the first adjacent atom is oxygen and the second adjacent atom is aluminum, and that Cu, which is an active metal, does not exist in the second adjacent atom. Table 3 shows the analysis results.

From this, it can be seen that when the autoclave treatment is carried out at 190 ° C. or lower, which is lower than the critical temperature, the active metal is highly dispersed at the level of a single atom in the catalyst structure and is firmly incorporated in the structure. .

By the way, the CuO-supported alumina catalyst prepared by the conventional method is
Exists on the surface of activated alumina, and is about 50 to 10
It is said that clusters of about 0Å are formed, and hundreds to thousands of atoms are gathered in one active metal particle. However, the catalyst of the present invention has a structure in which the active metal is highly dispersed in the catalyst structure at the level of a single atom, and further, the active metal is firmly incorporated in this structure, and the active metal has a surface structure. It has a partly formed structure. It is generally known that when atoms are present at the monatomic level, they exhibit different properties than when they are present in the bulk of clusters or larger. How useful is the NO _x purification when Cu is present in the state of a single atom is C
It is also clear by looking at the NO _x purification capacity of the Cu ion-exchanged zeolite in which the u ions have been ion-exchanged. The catalyst of the present invention is thermally stable because the highly dispersed active metal is firmly incorporated in the catalyst structure, and has both high NO _x purification capacity and high thermal durability. It is found that the catalyst is suitable as a NO _x purification catalyst for exhaust gas and the like.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

Example (1) -2 [Synthesis of Cu-Al complex oxide by unclaved autoclave and autoclave using water] Aluminum nitrate and nitric acid were added so that CuO was 15% by weight (wt) in terms of oxide. An aqueous solution containing copper was prepared.

Ammonia water diluted to 0.5 to 3% was slowly added dropwise to this aqueous solution with stirring to neutralize it to obtain a coprecipitate of Cu and Al. At this time, if the solution concentration is too high or the ammonia water dropping rate is too fast, a uniform mixture at the atomic level cannot be obtained. Solution concentration is 0.4 mol /
1 or less, and the ammonia water dropping rate must be 10 cc / min or less. This coprecipitate is filtered and washed with pure water to obtain a Cu-Al gel.

This was hydrothermally treated in an autoclave under the temperature condition of 200 ° C. or lower. The hydrothermally treated product was air-dried, then dried at 110 ° C. overnight and crushed in a mortar. This powder was calcined at 700 ° C. for 1 hour and hydrothermally treated to obtain the desired complex oxide catalyst No. 8 and No. 9 was synthesized.

The Cu-Al gel prepared by the above method was dried and calcined as it is without hydrothermal treatment (No. 7) and the Cu-free Al oxide as a comparative example was the same as the above method. To prepare γAl ₂ O ₃ ,
An aqueous solution was prepared by mixing copper nitrate so that CuO was 15% by weight in terms of oxide with respect to γAl ₂ O ₃ .
Put γAl ₂ O ₃ therein, the γAl ₂ O ₃ aqueous solution was dropwise slowly ammonia water diluted to 0.5% to 3% agitation were placed, GanmaAl a Cu by neutralizing ₂
A catalyst (No. 2a) supported on O ₃ was also prepared.

The NO _X purification activity was carried out in a fixed bed atmospheric pressure flow reactor. The composition of the reaction gas is NO: 1000 ppm,
_{C 3 H 6: 1000ppm, CO} : 1200ppm, H
₂ : 400 ppm, O ₂ : 6%, CO ₂ : 10%, H _{2
O: 10%, N 3:} Bal. And GHSV is 200,00
It was performed at ⁰ h ^-1 .

The results are shown in Table 4. The maximum increase of 31% of the NO _X purification performance as was seen. Further, at this time, generation of N ₂ O was not seen. However, in No. 1 where the autoclave treatment was performed at 200 ° C. No. 9 is above the critical temperature for separating the crystals of the composite oxide, and therefore it can be seen that the NO _x purification ability is lowered.

[0042]

[Table 4]

Example (2) [Cu-untreated autoclave and autoclaved with alcohol]
Synthesis of Al complex oxide] Aluminum nitrate and copper nitrate were mixed in a solution in which ethanol and pure water were mixed at a ratio of 1: 5 so that CuO was 5% by weight in terms of oxide. While stirring this mixed aqueous solution,
Ammonia water diluted to 5 to 3% is slowly added dropwise,
It is neutralized to obtain a coprecipitate of Cu and Al. The coprecipitate was filtered and washed with a solution of ethanol and pure water mixed at a ratio of 1: 1,
The filter is washed again with only ethanol to obtain a Cu-Al gel.

This was put in an autoclave for 100 to 2
Treated at a temperature of 00 ° C. The autoclaved product was air-dried, dried overnight at 110 ° C., and crushed in a mortar. This powder was calcined at 700 ° C. for 1 hour to synthesize an autoclave-processed composite oxide catalyst.

The Cu-Al gel prepared by the above method was dried and calcined as it was without autoclaving. 10 and a catalyst in which CuO was supported on an Al oxide γAl ₂ O ₃ containing no Cu in a pure water-ethanol mixed solution were also synthesized.

Specifically, as shown in Table 5,
CuO is a Cu-Al composite oxide containing 5% by weight of CuO, which was treated in an autoclave at 100 ° C, 120 ° C, 150 ° C and 200 ° C. 11-No. 14
What is not processed No. 10 was synthesized.

At the same time, an Al oxide containing no Cu was prepared in the same manner as in the above method to prepare γAl ₂ O ₃ , and its γA
A mixed solution of pure water and alcohol was prepared by mixing copper nitrate such that CuO was 5% by weight in terms of oxide with respect to l ₂ O ₃ , and γAl ₂ O ₃ was put in the mixed solution.
While stirring the aqueous solution containing ₂ O ₃ , 0.5 to 3% of ammonia water diluted slowly was added dropwise to neutralize C
A CuO-supported alumina catalyst was also prepared by supporting u on γAl ₂ O ₃ and performing filtration, washing, drying, firing and the like in the same manner as above. And what was processed with the autoclave of 150 degreeC No. No. 3b and one not processed. 3a was synthesized.

The NO _x purification activity of the above-synthesized catalyst was measured by a fixed bed atmospheric pressure type reactor which is an existing measuring instrument.

The composition of the reaction gas is NO: 1000 ppm,
_{C 3 H 6: 1000ppm, CO} : 1200ppm, H
₂ : 400 ppm, O ₂ : 6%, CO ₂ : 10%, H _{2
O: 10%, N 2:} Bal. And GHSV is 200,00
It was performed at ⁰ h ^-1 .

The amount containing Cu As can be seen from Table 5 that when the 5% maximum increase of 29% of the NO _X purification performance was observed.
Further, at this time, generation of N ₂ O was not seen.

Incidentally, among the examples, No. 1 whose autoclave treatment was 200 ° C. No. 14 resulted in a reduced NO _x purification rate.

Therefore, particularly in the case of autoclave treatment, No. 11-No. In No. 13, satisfactory results are recognized in all purification items.

[0053]

[Table 5]

Example (3) [Co, Ni, Fe, -Al
Composite Oxide Synthesis] A solution is prepared by mixing cobalt nitrate, nickel nitrate, and iron nitrate with aluminum nitrate so as to each be 5% by weight in terms of oxide. Hereinafter, the autoclave untreated and the autoclave hydrothermally treated composite oxide catalyst No. 1 were processed in the same manner as in Example (1). 15, 16, 17 were synthesized.

These composite oxides have satisfactory purifying ability not only when the autoclave is untreated as in the above-mentioned examples but also when the autoclave is treated at less than 190 ° C. which corresponds to a temperature range below the critical temperature. Was obtained.

Then, in the same manner as in Example (1), N
Table 6 shows the results of measuring the O _X purification activity. It can be seen that in each case, the NO _x purification effect was extremely stable.

[0057]

[Table 6]

Example (4) [Cu-Al-S untreated with autoclave and autoclaved with water]
Synthesis of i complex oxide] In the same manner as in Example (1), CuO was 5 in terms of oxide.
An aqueous solution was prepared by mixing aluminum nitrate, copper nitrate, and water glass so that the weight% and the SiO ₂ were 10% by weight.

Ammonia water diluted to 0.5 to 3% was slowly added dropwise to this aqueous solution with stirring to neutralize it to obtain a coprecipitate of Cu, Al and Si. At this time, if the solution concentration is too high or the ammonia water dropping rate is too fast, a uniform mixture at the atomic level cannot be obtained. Solution concentration is 0.4m
ol / l or less, ammonia water dropping rate is 10 cc / mi
must be n or less. This coprecipitate is filtered and washed with pure water to obtain a Cu-Al gel.

This was hydrothermally treated at a temperature of 200 ° C. or lower using an autoclave. The hydrothermally treated product was air-dried, then dried at 110 ° C. overnight and crushed in a mortar. This powder was calcined at 700 ° C. for 1 hour to synthesize a hydrothermally treated composite oxide catalyst (No. 19 to No. 23).

In addition, Cu-Al prepared by the above method
-Si gel was dried and calcined as it was without hydrothermal treatment (No. 18), and for comparison, a catalyst in which CuO was supported on an Al-Si oxide containing no Cu was also synthesized (No. 4a, No. 4b).

The NO _X purification activity measurement was carried out in a fixed bed atmospheric pressure flow reactor. The composition of the reaction gas is NO: 1000 pp
m, C ₃ H ₆ : 1000 ppm, CO: 1200 pp
m, H ₂ : 400 ppm, O ₂ : 6%, CO ₂ : 10
%, H ₂ O: 10%, N ₂ : Bal. And GHSV is 20
It was carried out at 10,000 h ^-1 . The results are shown in Table 7. Thus improvement of up to 30% of the NO _X purification performance was observed. Further, at this time, generation of N ₂ O was not seen.

As can be seen from this table, the hydrothermal treatment is 200
Since the critical temperature is exceeded at a temperature of ° C, the NO _x purification rate is lowered as in the other examples, which is not preferable.

In the above-mentioned examples, the synthesis of the complex oxide by the coprecipitation method was mainly described, but the other alkoxide method can also be carried out in the same manner. It is possible to obtain a state in which the same transition metal atom does not exist within the second adjacent atom of, and this has the advantage that the catalytic function can be remarkably improved and the heat resistance can be improved.

Liquids other than water and alcohol may be used for the autoclave treatment.

It is to be noted that although the case where the oxide conversion of the catalyst to be the carrier is mainly 5% by weight and 15% by weight of CuO has been described, it goes without saying that different amounts can be similarly used.

[0067]

[Table 7]

[0068]

The exhaust gas purifying catalyst obtained by the present invention is
A composite oxide catalyst containing at least one kind of transition metal atom which is an active metal and at least one kind of element of Al and Si, wherein the active metal is highly dispersed in the catalyst structure at the single atom level, and Has a structure in which the active metal is firmly incorporated, and the active metal forms a part of the surface, and is a catalyst having both high NO _x purification capacity and high thermal durability. Basically different from those in which the active metal particles are simply supported on the surface in a cluster state or those in which the active metal ions are weakly bound to the ion exchange sites, the catalyst having the structure as described above is, for example, Even if the active metal is a thermally unstable and mobile metal such as Cu, the active metal is firmly fixed in the catalyst structure, so the heat resistance is dramatically improved, and the active metal is ion-exchanged zeolite. Close atom Since forming the high dispersion of Le, a high NO _X purification performance which can not be obtained by the conventional, it becomes possible to obtain a catalytic properties with both surfaces of the high thermal durability.

When the autoclave treatment is further carried out, due to the special environment inside the autoclave, the crystallinity is appropriately improved and stabilized, the further activation of the catalytic active sites is promoted, and the NO _x purification capacity is extremely high. Get higher

[0070] Incidentally, although autoclaving can improve the NO _X purification performance, preferably the treatment temperature below a critical temperature at which the crystal phase of the composite oxide is separated can be formed as a catalyst having the best of the NO _X purification performance.

[Brief description of drawings]

FIG. 1 is a graph showing an XRD analysis after hydrothermal treatment of an exhaust gas purifying catalyst according to the present invention.

FIG. 2 is an XRD analysis graph of the same catalyst as above, after calcining at 700 ° C.

[Fig. 3] Similarly, an analysis graph of an exhaust gas purifying catalyst after hydrothermal treatment of the same catalyst at 150 ° C.

FIG. 4 is an analysis graph of an exhaust gas purifying catalyst after hydrothermal treatment of the same catalyst at 150 ° C.

FIG. 5 is an analysis graph of an exhaust gas purifying catalyst after hydrothermal treatment of the same catalyst as above at 150 ° C.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B01J 23/08 ZAB B01J 23/20 ZABA 23/10 ZAB 23/22 ZABA 23/20 ZAB 23/26 ZABA 23/22 ZAB 23/28 ZABA 23/26 ZAB 23/30 ZABA 23/28 ZAB 23/32 ZABA 23/30 ZAB 23/34 ZABA 23/32 ZAB 23/36 ZABA 23/34 ZAB 23/42 ZABA 23 / 36 ZAB 23/44 ZAB A 23/42 ZAB 23/46 ZAB 23/44 ZAB ZABA 23/46 ZAB 301A 23/52 ZABA 301 23/74 ZAB 23/52 ZAB 37/10 ZAB 23/74 ZAB B01D 53/36 ZAB 23/745 102Z 23/75 B01J 23/74 301A 23/755 311A 37/10 ZAB 321A

Claims (5)

[Claims] 1. At least one transition metal atom and A
An exhaust gas purification catalyst comprising a complex oxide containing at least one element of l and Si, and the transition metal atom forming a part of the surface. 2. The exhaust gas purifying catalyst according to claim 1, wherein the transition metal atom of the composite oxide is preferably a different atom within the second adjacent atom around the atom. 3. An exhaust gas purification catalyst obtained by subjecting the exhaust gas purification catalyst according to claim 1 to an autoclave treatment. 4. The exhaust gas purifying catalyst according to claim 3, wherein the autoclave treatment is carried out in a temperature range below a critical temperature at which the crystal phase of the composite oxide separates. 5. The exhaust gas purifying catalyst according to claim 4, wherein the autoclave treatment is performed with water or alcohol.