JP2010099638A - Catalyst, catalyst for purifying exhaust gas, and method for manufacturing the catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst which increases a specific surface area by maintaining an interval of perovskite type composite oxides constituting the catalyst and improves catalyst performance at a relatively low temperature of 600°C or lower, also to provide a catalyst for purifying exhaust gas, and further to provide a method for manufacturing the catalyst. <P>SOLUTION: The catalyst 1 is composed of the perovskite type composite oxide 2 represented by a formula A<SB>1-x</SB>A'<SB>x</SB>B<SB>1-y</SB>B'<SB>y</SB>O<SB>3-δ</SB>(wherein in the general formula A is at least one element selected from a group consisting of alkali earth metals, A' is at least one element selected from a group consisting of rare earth elements, B is at least one element selected from a group consisting of transition elements, and B' is at least one element selected from a group consisting of metallic elements, and 0≤x≤1, 0≤y≤1, and 0≤δ≤1.5), composite oxide spacers 3(3a-3e), and noble metals 4. The specific surface area calculated by a BET method is 20-50 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention suppresses catalyst agglomeration and pore clogging associated with the agglomeration, maintains the distance between the catalysts to increase the specific surface area, and improves the catalyst performance at a relatively low temperature of 600 ° C. or lower. The present invention relates to an exhaust gas purifying catalyst and a method for producing the catalyst.

Conventionally, a catalyst using a perovskite complex oxide has been studied for removing nitrogen oxides and the like discharged from power plants and automobiles.
For example, a nitrogen oxide decomposition catalyst is proposed in which a perovskite complex oxide, in which the Ti site of a perovskite complex oxide is partially substituted with a noble metal such as Pt, is supported on a basic metal oxide (MgO, etc.) support. (Patent Document 1)
JP 2000-197822 A

Also, NOx in exhaust gas discharged from a combustion engine decomposed directly without using a reducing agent, as a catalyst for removing, general formula _{AB 1-x M x O 3} + z ( where A is selected from alkaline earth elements One metal, B is one metal selected from titanium group elements, M is one metal selected from iron group, platinum group or copper group elements, 0 <x <1, z is room temperature atmospheric pressure A perovskite type complex oxide expressed by the number of oxygen defects or oxygen excess number of metal oxide at the time has been proposed (Patent Document 2).
Japanese Patent Laid-Open No. 11-151440

However, in the perovskite complex oxide, the raw material powder is agglomerated by the heat during firing (about 600 to 1000 ° C.), and this aggregation clogs the pores, reducing the specific surface area of the catalyst, and adsorbing and decomposing. Performance decreases.
In addition, the catalyst containing the perovskite complex oxide has a high temperature for activating the catalyst and exhibits a relatively high catalyst performance at a temperature of 800 ° C. or higher, but exhibits a catalytic performance at a temperature of 650 ° C. or lower. There may not be. The catalyst performance refers to, for example, nitrogen oxide adsorption performance.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to increase the specific surface area while maintaining the distance between the perovskite complex oxides constituting the catalyst. Another object of the present invention is to provide a catalyst capable of improving the catalyst performance (for example, the adsorption rate of NOx or the like) at a relatively low temperature of 600 ° C. or lower, an exhaust gas purifying catalyst, and a method for producing the catalyst.

  As a result of intensive studies to achieve the above object, the present inventors have provided a composite oxide spacer that can suppress the aggregation of the perovskite complex oxides and maintain the spacing, The present inventors have found that the above object can be achieved by supporting the present invention and completed the present invention.

That is, the catalyst of the present invention have the general formula _{A 1-x A 'x B} 1-y B' y O 3-δ (A in the formula is at least one selected from the group consisting of alkaline earth metals A ′ is at least one element selected from the group consisting of rare earth elements, B is at least one element selected from the group consisting of transition elements, and B ′ is A perovskite-type complex oxide represented by at least one element selected from the group consisting of metal elements, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ δ ≦ 1.5), The specific surface area which consists of a complex oxide spacer and a noble metal and is calculated by the BET method is 20 to 50 m ² / g.

  The method for producing a catalyst of the present invention comprises a step of forming a sol containing a metal alkoxide, a step of forming a slurry containing a perovskite complex oxide and a noble metal salt using water as a solvent, and mixing the sol and the slurry. And drying and firing.

  The method for producing a catalyst of the present invention includes a step of forming a sol containing a metal alkoxide, a step of forming a first slurry containing a perovskite complex oxide using water as a solvent, the sol and the first sol The slurry is mixed, dried, and fired to form a powder containing the perovskite complex oxide and the complex oxide spacer, and the second slurry containing the powder and the noble metal salt is formed using water as a solvent. And a step of mixing, drying and baking the second slurry.

The present invention is, in general formula _{A 1-x A 'x B} 1-y B' perovskite complex oxide represented by _{y O 3-δ,} by a composite oxide spacers provided, and further contain a noble metal A catalyst, an exhaust gas purifying catalyst, and a method for producing the catalyst, in which aggregation and pore clogging are suppressed, the specific surface area of the catalyst is increased, and the catalyst performance such as the NOx adsorption rate is improved at a relatively low temperature. Can be provided.

  Hereinafter, the catalyst of this invention is demonstrated in detail based on drawing. In the present specification, “%” for concentration, content, blending amount, etc. represents mass percentage unless otherwise specified.

FIG.2 (d) is a schematic diagram which shows notionally an example of a structure of the catalyst of this invention. FIG. 2C is a schematic diagram conceptually showing an example of a perovskite complex oxide in which aggregation occurs.
As shown in FIG. 2 (d), catalyst 1 of the present embodiment includes a general formula _{A 1-x A 'x B} 1-y B' y O 3-δ perovskite-type composite oxide 2 represented by, the The composite oxide spacer 3 is formed so as to protrude from the perovskite complex oxide 2 and has various shapes, and a noble metal 4.

Since the catalyst 1 of this example contains the composite oxide spacer 3, the aggregation of the perovskite composite oxides 2 and the clogging of pores due to the aggregation are suppressed, and the specific surface area calculated by the BET method is reduced. It can be increased to 20-50 m ² / g. In general, the perovskite complex oxide used for the catalyst has a specific surface area calculated by the BET method of 10 m ² / g or less.

Since the catalyst 1 of this example further contains a noble metal in the perovskite complex oxide and the complex oxide spacer, a reaction in which NO is oxidized to NO ₂ is promoted by the noble metal. NOx in the exhaust gas is easily adsorbed to the perovskite complex oxide by being oxidized to NO ₂ . Thus, the reaction of oxidizing NO to NO ₂ is the rate-determining step for the adsorption and purification reaction of NOx on the catalyst. Generation of NO ₂ by the noble metal can improve the catalyst performance such as the adsorption rate of nitrogen oxide (NO) at a relatively low temperature of 650 ° C. or less.
Thus, since the catalyst of this example shows high catalyst performance at a relatively low temperature of 650 ° C. or less, thermal shock to the support on which the catalyst is supported is reduced, and the catalyst can be supported on a relatively thin support. Therefore, it is possible to reduce the size of the purification device using the catalyst.

  As shown in FIG. 2D, the composite oxide spacer 3 includes a columnar spacer 3a, a plate-like spacer 3b, a cylindrical spacer 3c obtained by rolling a sheet, a sheet-like spacer 3d, and a needle-like spacer with a sharp tip. It has various forms such as 3e. Further, the composite oxide spacer 3 is in a state of extending straight from the perovskite-type composite oxide 2 like the columnar spacer 3a or the needle-like spacer 3e, or having a curve like the sheet-like 3d. It also includes those that are in a state.

Perovskite complex oxide 2 constituting the catalyst 1 of the present embodiment has the general formula _{A 1-x A 'x B} 1-y B' y O 3-δ A in the general formula, the group consisting of alkaline earth metals And at least one element selected from the group consisting of rare earth elements, and B is at least one element selected from the group consisting of transition elements. B ′ is at least one element selected from the group consisting of metal elements, and is represented by 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ δ ≦ 1.5. .

Here, the alkaline earth metal of the element A is preferably Ba (barium), Ca (calcium) or Sr (strontium), and more preferably Ba.
The rare earth element of the element A ′ is preferably La (lanthanum), Nd (neodymium), Sm (samarium), Eu (europium), Gd (gadolinium) or Y (yttrium), more preferably La. is there.

The transition element of element B is preferably Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), or Cu (copper), and more preferably Mn.
Examples of the metal element of element B ′ include metal elements belonging to Group 1 to 14 of the periodic table of elements, preferably Mg (magnesium) or transition elements, more preferably Mg, Fe, Zr (zirconium), Ni, Sn (tin), Ta (tantalum), Co (cobalt), Cr (chromium), Cu, Ga (gallium), In (indium) or Ce (cerium) can be mentioned, and Mg is particularly preferable.

Among the general formula _{A 1-x A 'x B} 1-y B' y O 3-δ, x is 0 ≦ x ≦ 1, is preferably 0 <x ≦ 0.5, more preferably 0 .Ltoreq.x.ltoreq.0.3.
In the above general formula, y is 0 ≦ y ≦ 1, preferably 0 <y ≦ 0.5, and 0.2 ≦ y ≦ 0.3.
In the above general formula, δ is 0 ≦ δ ≦ 1.5.
If the numerical values of x, y, and δ in the above general formula are within the above ranges, it is suitable as the composition ratio of the perovskite complex oxide that forms the catalyst of this example.

The average particle diameter of the secondary particles of the perovskite complex oxide is preferably 10 nm to 3 μm. The minimum particle size of the secondary particles of the perovskite complex oxide is preferably about 10 nm, and the maximum particle size is preferably about 3 μm.
Here, the secondary particles are a collection of primary particles, and the primary particles generally mean the smallest particles constituting the powder. Secondary particles refer to particles formed by aggregating primary particles.
When the average particle size of the secondary particles of the perovskite complex oxide is less than 10 nm, the perovskite complex oxide escapes from the interval between the complex spacers (for example, the column spacer 3a and the needle spacer 3e), thereby suppressing aggregation. It may not be possible. On the other hand, when the average particle diameter of the secondary particles exceeds 3 μm, the specific surface area cannot be increased even when a composite oxide spacer is provided.

The composite oxide spacer constituting the catalyst 1 of this example preferably has an aspect ratio of 1-50.
The aspect ratio of the composite oxide spacer refers to the ratio of the long side to the short side of the portion occupying the largest area of the composite oxide spacer having a three-dimensional structure.
For example, in the case of the plate-like spacer 3b shown in FIG. 2D, the ratio (bx / by) between the long side bx and the short side by of the portion showing the largest area of the plate-like spacer 3b is set to the aspect ratio of the composite oxide spacer. Ratio.
When the aspect ratio of the composite oxide spacer exceeds 50, the composite oxide spacer becomes weak in strength, and the composite oxide spacer may be easily broken by heat.

Moreover, it is preferable that the element which comprises a complex oxide spacer contains at least 1 sort (s) of elements among the elements which comprise the perovskite type complex oxide which comprises the catalyst of this example.
The mechanism by which the complex oxide spacer is formed is not yet elucidated, but a part of the perovskite complex oxide is deformed and / or a part of the elements constituting the perovskite complex oxide escapes and is complex. It is presumed that an oxide spacer is formed.

  The composite oxide spacer varies depending on the kind of element constituting the perovskite composite oxide and the content of the element, but the composite oxide spacer preferably contains a Ba—Mn—Mg composite oxide.

  The noble metal is preferably at least one selected from the group consisting of Pt, Pd and Rh, more preferably Pt.

The particle diameter of the noble metal is preferably smaller than the particle diameter of the secondary particles of the perovskite complex oxide.
Since the minimum particle size of the secondary particles of the perovskite complex oxide is about 10 nm, the particle size of the noble metal is preferably 10 nm or less.

By noble metal in the catalyst to act, NO in the exhaust gas is oxidized to NO _2. NOx in the exhaust gas is easily adsorbed to the perovskite complex oxide by being oxidized to NO ₂ . Then, NO ₂ adsorbed on the perovskite complex oxide is reduced, and exhaust gas purification is promoted. Thus, the catalyst performance of the catalyst of this example is enhanced by the interaction between the perovskite complex oxide and the noble metal.
If the particle size of the noble metal is the same as or larger than the particle size of the secondary particles of the perovskite complex oxide, the noble metal may be combined with the surface of the perovskite complex oxide or with the perovskite complex oxide. It becomes difficult to be supported between the object spacers. As a result, the noble metal acts alone and the interaction with the perovskite complex oxide is less likely to occur, so the catalyst performance may not be improved.

The catalyst composed of the perovskite complex oxide, complex oxide spacer, and noble metal of this example can be used as it is in powder form, or can be used after being molded into a granular form or pellet form.
Further, the catalyst of this example may be supported on a refractory inorganic carrier made of ceramics, metal oxide or the like and used as an exhaust gas purification catalyst. The catalyst of this example may be used as an electrode catalyst.
As the refractory inorganic carrier, for example, a cordierite, a honeycomb carrier made of ferrite stainless steel, alumina, or the like can be used.
As a method of supporting the catalyst of this example on such a refractory inorganic carrier, for example, the catalyst of this example and water are mixed to form a slurry, and this slurry is coated on the refractory inorganic carrier, The method of carrying | supporting etc. is mentioned.

Next, a preferred first embodiment of the method for producing a catalyst of the present invention will be described.
The method for producing a catalyst of this example includes a step of forming a sol containing a metal alkoxide, a step of forming a slurry containing a perovskite complex oxide using water as a solvent, and a noble metal salt and the sol in the slurry. Adding, mixing, drying and firing.

  The sol containing a metal alkoxide preferably contains a metal alkoxide, alcohols, water, and nitric acid.

  As the metal alkoxide, metal isopropoxide is preferably used. For example, titanium tetraisopropoxide, aluminum isopropoxide, zirconium tetraisopropoxide, and the like can be used, but are not limited to these examples. .

Examples of alcohols include alcohols having one hydroxyl group, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and / or diols having two hydroxyl groups, such as ethylene glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, 2,4-pentanediol and the like can be used.
Among these, 1,3-butanediol is preferably used.

As a ratio of each component which forms sol, alcohol; 80-90%, water; 0.5-1.5%. Nitric acid: 1.0-2.0%, metal alkoxide 8.0-20.0% are preferable.
The mixture obtained by mixing the above components can be stirred at room temperature for about 1 to 5 hours to obtain a sol.

  The mixing ratio of the perovskite complex oxide and water in the slurry is not particularly limited, but is preferably 1:10 to 1: 100.

As the perovskite complex oxide, it is preferable to use a secondary particle having an average particle diameter of 10 nm to 3 μm.
When the perovskite complex oxide added to water has an average particle diameter within the above range, the aggregation suppressing effect is exerted and the high specific surface area of the catalyst can be maintained.

As the noble metal salt, chloroplatinic acid (H ₂ PtCl ₆ ), hexaammine platinum chloride ([Pt [NH ₃ ] ₆ Cl ₄ ]), dinitrodiammine platinum (Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ), Palladium chloride (PdCl ₂ , H ₂ PdCl ₄ ), tetraammine palladium chloride (Pd (NH ₃ ) ₄ Cl ₂ ), rhodium chloride (RhCl ₃ ) and the like can be used.

Noble metal powder or the like may be added to the slurry, but the noble metal salt is more stable and easy to handle.
When a noble metal powder or the like is added to the slurry, the carrying state may be biased or the interaction between the base material and the noble metal may be less likely to occur. That is, since the powder of the noble metal simple substance is only physically on the base material, the noble metal is hardly fixed on the base material during use.
On the other hand, when this noble metal salt is added to the slurry (or solution) using a noble metal salt, it is present as noble metal ions in the slurry (or solution), so that the noble metal loading state is not biased and is supported with good dispersibility. Is done. Moreover, since it becomes easy to obtain interaction with a base material, it becomes a strong bond and a noble metal is stably fixed on the base material. For these reasons, it is preferable to use a noble metal salt.

The addition amount of the noble metal is preferably 5% or less with respect to 100% of the total amount of the catalyst containing the noble metal.
When the addition amount of the noble metal exceeds 5% with respect to 100% of the total amount of the catalyst containing the noble metal, the amount of the noble metal is excessively increased, so that aggregation of the noble metal tends to be promoted. If the noble metal grain growth is promoted, the catalytic activity may be lowered. For this reason, even if an excessive amount of the noble metal is added, the catalytic activity corresponding to the addition of the noble metal may not be obtained.

The temperature and time for mixing the sol and slurry are about 1 to 2 hours at room temperature.
As a calcination temperature of the mixture which mixed the said sol and slurry, Preferably it is 400-600 degreeC, More preferably, it is 500-600 degreeC. The firing time is preferably about 1.0 to 3.0 hours, more preferably about 1.5 to 2.0 hours.

Next, a second preferred embodiment of the method for producing a catalyst of the present invention will be described.
The method for producing the catalyst of this example includes a step of forming a sol containing a metal alkoxide,
A step of forming a first slurry containing a perovskite complex oxide using water as a solvent, and a mixture of the sol and the first slurry, dried, and fired to produce a perovskite complex oxide and a complex oxide spacer. Forming a second slurry containing the powder and the noble metal salt using water as a solvent, and mixing, drying, and firing the second slurry. .

As in the catalyst production method of this example, a powder containing a composite oxide spacer and a perovskite composite oxide is formed, and then the surface of the perovskite composite oxide and the perovskite composite oxide and composite oxide spacer are formed. In the meantime, a catalyst supporting a noble metal may be formed (see FIG. 2D).
In the second embodiment of the catalyst production method, the same method as in the first embodiment is used for the temperature and time for mixing the sol and slurry raw materials, the slurry, etc., the firing time, and the like.

According to the catalyst of the present invention, the exhaust gas purifying catalyst, and the method for producing the catalyst, since the composite oxide spacer is provided in the perovskite composite oxide, the composite oxide spacer allows aggregation of the perovskite composite oxide, The blockage of the pores accompanying this aggregation can be suppressed, and the specific surface area of the catalyst can be increased. In the catalyst of the present invention, the interval between the perovskite complex oxides is maintained by the complex oxide spacer even at high temperatures.
Since the catalyst 1 of the present invention further contains a noble metal in the perovskite complex oxide and the complex oxide spacer, a reaction in which NO is oxidized to NO ₂ by this noble metal is promoted, and a relatively low temperature of 650 ° C. or less. Catalyst performance can be enhanced at low temperatures.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

Example 1
In this example, a catalyst was produced by the production method of the second embodiment.
[Sol formation process]
1,3-butanediol: 70 g (85.5%), water: 0.8 g (0.97%), and nitric acid (concentration: 60%): 1.0 g (1.2%) were mixed. , Stirred. To this mixture, titanium tetraisopropoxide: 10 g (12.2%) was added over 1 hour, and then the mixture to which each component was added was stirred at room temperature for 4 hours to form a sol.
[First slurry forming step]
A sample (perovskite complex oxide: Ba0 _0.8 La _0.2 Mn _0.8 Mg _0.2 O ₃ , average particle size of secondary particles 600 nm) prepared by the citric acid method manufactured by Seimi Chemical Co., Ltd., and water Were mixed at a ratio of 1:30 to obtain a first slurry.

[Powder formation process]
The sol and the first slurry were mixed and stirred at room temperature for 1 hour, and then dried at 150 ° C. for 2 hours to form a powder. This powder was fired in air at 550 ° C. for 2 hours to obtain a powder containing a perovskite complex oxide and a complex oxide spacer.

[Second slurry forming step]
Hexammine platinum chloride: 4.98 g was added to water and stirred for 1 hour, then the above powder: 5.0 g was added, and the mixture was further stirred for 30 minutes to obtain a second slurry. This second slurry was dried at 50 ° C. to obtain a powder.
In addition, hexaammine platinum chloride was added so that it might become about 1.0% with respect to 100% of the total amount of the catalyst containing a noble metal.

[Baking process]
The powdery material obtained by drying the second slurry was calcined in air at 400 ° C. for 2 hours to produce a powdered catalyst.

In the catalyst of Example 1, a sheet-like or columnar complex oxide spacer is formed between perovskite complex oxides, and the surface of the perovskite complex oxide and between the perovskite complex oxide and the complex oxide spacer are formed. , Noble metal was supported.
FIGS. 1A and 1B show SEM (Scanning Electron Microscope) photographs (a: 20000 times, b: 50000 times) of the catalyst of this example.
In addition, when the component of the complex oxide spacer of the catalyst of this example was measured by EDX (Energy dispersion X-ray spectrometer), titanium (Ti) was contained in the complex oxide spacer. The composite oxide spacer was a Ba—Mn—Mg composite oxide. Further, the specific surface area of the catalyst of this example was calculated by the BET method. The results are shown in Table 2.

(Example 2)
In this example, a catalyst was manufactured by the manufacturing method of the first embodiment.
[Sol formation process]
A sol was obtained in the same manner as in Example 1.
[Slurry forming step]
In the same manner as in the first slurry forming step of Example 1, when water and the perovskite complex oxide are mixed, 4.98 g of hexaammine platinum chloride is added, and the slurry is stirred for 1 hour. Obtained.
In addition, hexaammine platinum chloride was added so that it might become about 1.0% with respect to 100% of the total amount of the catalyst containing a noble metal.
[Baking process]
20 g of the sol was mixed with 160 g of the slurry, and dried at 150 ° C. for 2 hours to obtain a powdery product. This powder was calcined in air at 550 ° C. for 2 hours to produce a powdered catalyst.

In the catalyst of Example 2, a sheet-like or columnar complex oxide spacer is formed between the perovskite complex oxide, and the surface of the perovskite complex oxide is interposed between the perovskite complex oxide and the complex oxide spacer. A noble metal was supported (not shown).
When the component of the composite oxide spacer of the catalyst of this example was measured by EDX, titanium (Ti) was not contained in the composite oxide spacer, and the composite oxide spacer was Ba-Mn-Mg composite oxide. there were. Further, the specific surface area of the catalyst of this example was calculated by the BET method. The results are shown in Table 2.

(Comparative Example 1)
A powdered catalyst was produced in the same manner as in Example 2 except that hexaammine platinum chloride (noble metal) was not added.

As shown in FIG. 2D, in the catalyst of this example (Examples 1 and 2), a sheet-like or columnar complex oxide spacer was formed between the perovskite complex oxides.
Moreover, when the component of the composite oxide spacer of the catalyst of Examples 1 and 2 was measured by EDX, the composite oxide spacer did not contain titanium (Ti), and the composite oxide spacer was Ba-Mn- It was Mg composite oxide. The specific surface areas of the catalysts of Examples 1 and 2 and Comparative Example 1 were calculated by the BET method. The results are shown in Table 2.

  For the catalysts of Examples 1 and 2 and Comparative Example 1, the temperature rise was evaluated under the conditions shown in Table 1, and the temperature (T50) at which the NOx conversion in the gas reached 50% was measured. The results are shown in Table 2.

As shown in Table 2, in the catalysts of Examples 1 and 2, the temperature (T50) at which the NOx conversion was 50% was lower by about 50 ° C. than that of the catalyst of Comparative Example 1.
From these results, it is confirmed that the catalysts of Examples 1 and 2 have an increased specific surface area of the catalyst and improved catalyst performance such as NOx adsorption rate at a relatively low temperature of 600 ° C. or lower. did it.

2 is a SEM photograph (a; 20000 times, b; 50000 times) of the catalyst of Example 1. (C) It is explanatory drawing which shows typically the state which the conventional perovskite type complex oxide aggregated, (d) It is explanatory drawing which shows notionally the catalyst of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Catalyst 2 Perovskite type complex oxide 3 Complex oxide spacer 3a Columnar spacer 3b Plate spacer 3c Cylindrical spacer 3d Sheet spacer 3e Needle spacer 4 Precious metal

Claims (18)

Formula _{A 1-x A 'x B} 1-y B' y O 3-δ (A in the formula is at least one element selected from the group consisting of alkaline earth metal, A 'is , At least one element selected from the group consisting of rare earth elements, B is at least one element selected from the group consisting of transition elements, and B ′ is selected from the group consisting of metal elements A perovskite complex oxide represented by 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ δ ≦ 1.5, a complex oxide spacer, and a noble metal And a specific surface area calculated by the BET method is 20 to 50 m ² / g.   2. The catalyst according to claim 1, wherein B ′ in the general formula is at least one element selected from the group consisting of Mg and a transition element.   B ′ in the above general formula is at least one element selected from the group consisting of Mg, Fe, Zr, Ni, Sn, Ta, Co, Cr, Cu, Ga, In, and Ce. The catalyst according to claim 1 or 2.   The average particle diameter of the secondary particle of the said perovskite type complex oxide is 10 nm-3 micrometers, The catalyst as described in any one of Claims 1-3 characterized by the above-mentioned.   The catalyst according to any one of claims 1 to 4, wherein the complex oxide spacer has an aspect ratio of 1 to 50.   The catalyst according to any one of claims 1 to 5, wherein the element constituting the complex oxide spacer contains at least one element of the elements constituting the perovskite complex oxide.   The catalyst according to any one of claims 1 to 6, wherein a particle diameter of the noble metal is smaller than a particle diameter of secondary particles of the perovskite complex oxide.   The catalyst according to any one of claims 1 to 7, wherein A in the general formula is Ba, A 'is La, B is Mn, and B' is Mg. .   The catalyst according to any one of claims 1 to 8, wherein x in the general formula is 0 <x ≦ 0.5 and y is 0 <y ≦ 0.5.   The x in the general formula is 0.1 ≦ x ≦ 0.3, and y is 0.2 ≦ y ≦ 0.3, according to any one of claims 1 to 9, Catalyst.   The catalyst according to any one of claims 1 to 10, wherein the composite oxide spacer is a Ba-Mn-Mg composite oxide.   The catalyst according to any one of claims 1 to 11, wherein the noble metal is at least one selected from the group consisting of Pt, Pd, and Rh.   The catalyst according to any one of claims 1 to 11, wherein the noble metal is Pt.   An exhaust gas purification catalyst comprising the catalyst according to any one of claims 1 to 13 supported on a refractory inorganic carrier. Forming a sol containing a metal alkoxide;
Forming a slurry containing a perovskite complex oxide and a noble metal salt using water as a solvent;
A method for producing a catalyst, comprising a step of mixing, drying, and calcining the sol and slurry. Forming a sol containing a metal alkoxide;
Forming a first slurry containing a perovskite complex oxide using water as a solvent;
Mixing the sol and the first slurry, drying and firing to form a powder containing a perovskite complex oxide and a complex oxide spacer; and
Forming a second slurry containing the powder and the noble metal salt using water as a solvent;
And a step of mixing, drying and calcining the second slurry.   The method for producing a catalyst according to claim 15 or 16, wherein the secondary particles of the perovskite complex oxide have an average particle diameter of 10 nm to 3 µm.   The baking temperature in the step of mixing and drying and baking the sol and slurry, or the step of mixing and drying and baking the second slurry is 400 to 600 ° C. The manufacturing method of the catalyst of description.

Images