JP4647406B2 - Exhaust gas purification catalyst - Google Patents

Description

The present invention relates to an exhaust gas purifying catalyst used as a gas phase or liquid phase reaction catalyst.

To date, Pt (platinum), Rh (rhodium), and Pd (palladium) are used as three-way catalysts capable of simultaneously purifying carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) contained in exhaust gas. Noble metals such as are widely used as catalytic active components.
Further, it is known that an exhaust gas purifying catalyst in which these noble metals are coordinated with a perovskite complex oxide having a crystal structure of the general formula ABO ₃ exhibits high catalytic activity.

For example, a perovskite complex oxide of La _1.00 Fe _0.57 Co _0.38 Pd _0.05 O ₃ reversibly moves Pd into and out of a perovskite crystal structure in response to the oxidation-reduction fluctuation of exhaust gas. It has been reported that such self-regeneration suppresses grain growth and maintains high catalytic activity over a long period of time (see Non-Patent Document 1).
Examples of the perovskite complex oxide coordinated with such noble metals include La _0.90 Sr _0.10 Fe _0.54 Mn _0.36 Pt _0.10 O ₃ , La _0.95 Ag _0.05 Al _0.80 Mn _0.10 Pt _0.08 Ru _0.02 O ₃ , La _0.9 Ce _0.1 Co _0.9 Pt _0.05 Ru _0.05 O ₃ , Nd _0.80 Ba _0.10 Mg _0.10 Al _0.85 Pt _0.10 Rh _0.05 O ₃ , La _0.90 Ca _0.10 Fe _0.90 Pt _0.10 O ₃ , Y _0.50 Sr _0.50 Fe _0.50 Pt _0.50 O ₃ , La _0.90 Sr _0.10 Mn _0.90 Pt _0.10 O ₃ (for example, see Patent Document 1), La _1.00 Fe _0.95 Rh _0.05 O ₃ , La _0.70 Pr _0.30 Fe _0.95 Rh _0.05 O ₃ , La _0.80 Nd _0.15 Ce _0.05 Fe _0.60 Mn _0.35 Rh _0.05 O _{3, La 0.90 Y 0.10 Fe 0.70} Al 0.20 Rh 0.10 O 3, Pt -supported _{/ La 1.00 Al 0.95 Rh 0.05 O} 3, La 0.80 Ce 0.20 Fe 0.65 Rh 0.35 O 3, La 1.00 F _{0.90 Rh 0.105 O 3, La 1.00} Fe 0.60 Mn 0.30 Rh 0.10 O 3 ( for example, see Patent Document _{2.), La 1.00 Fe 0.95} Pd 0.05 O 3, La 1.00 Fe 0.90 Pd 0.10 O 3, La 1.00 Fe 0.57 Mn 0.38 Pd _0.05 O ₃ , La _0.80 Nd _0.20 Fe _0.90 Pd _0.10 O ₃ (see, for example, Patent Document 3) and the like have been proposed.
Y. Nishihata et al. , Nature, Vol. 418, no. 6894, pp. 164-167, 11 July 2002 (Nishihata et al., “Nature”, 418, 6894, 164-167, July 11, 2002) Japanese Patent Laid-Open No. 2004-041868 JP 2004-041867 A JP 2004-041866 A

  However, in the above perovskite complex oxide, it is necessary to coordinate the noble metal so that it can reversibly enter and exit in the crystal structure, so it is necessary to form a crystal structure by combining specific elements. Therefore, in order to produce the perovskite complex oxide, the raw materials to be used are limited, and it may be difficult to stably produce industrially due to fluctuations in raw material prices. Therefore, a proposal of a new crystal structure capable of reversibly entering and exiting a noble metal is desired.

An object of the present invention is to provide an exhaust gas purifying catalyst containing a novel perovskite complex oxide capable of reversibly entering and leaving a noble metal.

In order to achieve the above object, the exhaust gas-purifying catalyst of the present invention has a general formula (1)
A _x B _y B ′ _(1−yz) N _z O _{3 + σ} (1)
(In the formula, A represents at least one element selected from alkaline earth metals , B represents Mn, B ′ represents at least one element selected from Ti, Zr, and Hf , and N indicates the Pt, x is 1 <represents an atomic ratio of the numerical range of x ≦ 1.3, y represents an atomic ratio of 0 <y <1.0, z is 0 <z ≦ 0. 5 represents an atomic ratio, sigma represents an oxygen excess.)
It contains the perovskite type complex oxide represented by these.

In the present invention, in the general formula (1), z preferably represents an atomic ratio in a numerical range of 0 <z ≦ 0.05 .
In the present invention, in the general formula (1), (1-yz) preferably represents 0 .

In the exhaust gas purifying catalyst containing the perovskite type complex oxide of the present invention, the noble metal efficiently dissolves in a perovskite type complex oxide in an oxidizing atmosphere and precipitates in a reducing atmosphere ( Since the self-regeneration is repeated, they can be kept in a dispersed state, and the activity can be prevented from being lowered due to grain growth over a long period of time, and high catalytic activity can be maintained .

BEST MODE FOR CARRYING OUT THE INVENTION

The exhaust gas purifying catalyst of the present invention has the general formula (1)
A _x B _y B ′ _(1−yz) N _z O _{3 + σ} (1)
(In the formula, A represents at least one element selected from alkaline earth metals , B represents Mn, B ′ represents at least one element selected from Ti, Zr, and Hf , and N Represents Pt , x represents an atomic ratio in a numerical range of 1 <x ≦ 1.3 , y represents an atomic ratio of 0 <y <1.0, and z represents 0 <z ≦ 0. represents an atomic ratio of 5, sigma contains an oxygen excess indicates a.) perovskite-type composite oxide represented by.

That is, this composite oxide has a perovskite structure, and at the A site, at least one element selected from alkaline earth metals is coordinated as A, and A ′ is selected from rare earth elements. At least one element is coordinated. Further, at the B site, Mn is coordinated as B, and at least one element selected from Ti, Zr, and Hf is coordinated as B ′ as necessary. Further, as N, Pt Is coordinated.

In the general formula ( 1 ), examples of the alkaline earth metal represented by A include Be (beryllium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium), Ra (radium), and the like. Preferably, Ca, Sr, Ba, etc. are mentioned. These may be used alone or in combination of two or more.
In the general formula ( 1 ), examples of the rare earth element represented by A ′ include Sc (scandium), Y (yttrium), La (lanthanum), Nd (neodymium), Pm (promethium), and Gd (gadolinium). , Dy (dysprosium), Ho (holmium), Er (erbium), Lu (lutetium) and other rare earth elements that do not vary in valence, such as Ce (cerium), Pr (praseodymium), Tb (terbium), etc. Rare earth elements whose valence changes to trivalent or tetravalent, for example, rare earth elements such as Sm (samarium), Eu (europium), Tm (thulium), Yb (ytterbium), etc. Is mentioned. These may be used alone or in combination of two or more.

In the general formula (1), in the A site, x is from represents an atomic ratio of the numerical range of 1 <x ≦ 1.3, i.e., atomic percentage of elemental being coordinated on the A site exceeds 1, 1.3 or less. when x exceeds 1, the P t, a higher rate of solid solution can be stably dissolved. When x exceeds 1.3, by-products other than the above complex oxide may be generated.

In the B site, the elemental that indicated by B ', T i (titanium), Zr (zirconium), and the like Hf (hafnium).

These elemental may be used alone or may be used in combination of two or more.
In the B site, the element represented by N includes Pt (platinum) .
In the general formula (1), at the B site, y represents an atomic ratio in a numerical range of 0 <y <1.0, preferably 0.3 <y <1.0, and z is 0 <numerical range of z ≦ 0.5, preferably, represents an atomic ratio of the numerical range of 0 <z ≦ 0.05. That is, at the B site, Mn represented by B is always coordinated at an atomic ratio of less than 1, and Pt represented by N is always coordinated at an atomic ratio of 0.5 or less. In addition, at least one element selected from Ti, Zr, and Hf represented by B ′ is represented by the atomic ratio of (1-yz), that is, Mn and N represented by B described above at the B site. are optionally coordinated with the atomic ratio of the remaining at least one element selected from is Ru P t. Note that in the B site, if the total of Pt Ru indicated by Mn and N represented by B is 1, Ti represented by B ', Zr, at least one element selected from Hf, coordination Not.

In the general formula (1), sigma represents an oxygen excess, more specifically, the theoretical composition ratio of the perovskite-type composite oxide, A: B: O = 1 : 1: with respect to 3, A in sites occurs when obtained by coordinating element over over -, showing over atom percentage of oxygen atoms. Alternatively, a slight excess of the oxide, hydroxide, and carbonate of the A site component may coexist with ABO ₃ .

Such a perovskite structure composite oxide of the present invention is not particularly limited, and is prepared by an appropriate method for preparing the composite oxide, for example, a coprecipitation method, a citric acid complex method, an alkoxide method, or the like. Can be prepared.
In the coprecipitation method, for example, a mixed salt aqueous solution containing the salt of each element described above at the above stoichiometric ratio is prepared, and a neutralizing agent is added to the mixed salt aqueous solution to perform coprecipitation. The precipitate is dried and then heat-treated.

Examples of the salt of each element include inorganic salts such as sulfate, nitrate, chloride, and phosphate, and organic acid salts such as acetate and oxalate. Further, the mixed salt aqueous solution can be prepared, for example, by adding the salt of each element to water at a ratio such as the above stoichiometric ratio and stirring and mixing.
Thereafter, a neutralizing agent is added to the mixed salt aqueous solution to coprecipitate. Although it does not restrict | limit especially as a neutralizing agent, For example, organic bases, such as ammonia, for example, amines, such as a triethylamine and a pyridine, For example, inorganic bases, such as caustic soda, caustic potash, potassium carbonate, and ammonium carbonate, are used. Moreover, a neutralizing agent is dripped so that pH of the solution after adding the neutralizing agent may become about 6-10. If dripped in this way, the salt of each element can be efficiently coprecipitated.

The obtained coprecipitate is washed with water if necessary, and dried by, for example, vacuum drying or ventilation drying, and then heat-treated at, for example, about 500 to 1200 ° C., preferably about 600 to 1000 ° C. A perovskite complex oxide can be produced.
In the citric acid complex method, for example, an aqueous citric acid solution is added to an aqueous mixed salt solution so that the citric acid is slightly in excess of the stoichiometric ratio with respect to each of the above elements. An aqueous solution is prepared, and this citric acid mixed salt aqueous solution is dried to form a citric acid complex of each element described above, and then the obtained citric acid complex is calcined and then heat-treated.

Thereafter, the citric acid mixed salt aqueous solution is dried to form a citric acid complex of each element described above. Drying removes moisture at a temperature at which the formed citric acid complex does not decompose, for example, from room temperature to 150 ° C. Thereby, a citric acid complex of each element described above can be formed.
The formed citric acid complex is subjected to heat treatment after calcination. Temporary baking should just heat at 250-350 degreeC in a vacuum or an inert atmosphere, for example. Thereafter, the perovskite complex oxide can be produced by heat treatment at about 500 to 1200 ° C., preferably about 600 to 1000 ° C., for example.

Further, in the alkoxide method, for example , after preparing a mixed alkoxide solution containing the alkoxide of each of the above elements except for Pt in the above stoichiometric ratio, the mixed alkoxide solution is hydrolyzed to generate a precipitate. A slurry is prepared, an aqueous solution containing a salt of Pt is added to the slurry , and the resulting precipitate is dried and then heat-treated.
Examples of the alkoxide of each element include an alcoholate formed from each element and an alkoxy such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, and an alkoxy alcoholate of each element represented by the following general formula (2). Can be mentioned.

^{E [OCH (R 1) -} (CH 2) i -OR 2] j (2)
(In the formula, E represents each element, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ² represents an alkyl group having 1 to 4 carbon atoms, and i represents 1 to 1) (An integer of 3 and j represents an integer of 2 to 4.)
More specifically, the alkoxy alcoholate includes, for example, methoxyethylate, methoxypropylate, methoxybutyrate, ethoxyethylate, ethoxypropylate, propoxyethylate, butoxyethylate and the like.

  And a mixed alkoxide solution can be prepared by, for example, adding the alkoxide of each element to an organic solvent so that it may become said stoichiometric ratio, and stirring and mixing. The organic solvent is not particularly limited as long as the alkoxide of each element can be dissolved, and examples thereof include aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, ketones, and esters. Preferably, aromatic hydrocarbons such as benzene, toluene and xylene are used.

Thereafter, water is added to the mixed alkoxide solution for hydrolysis to produce a precipitate. Then, by distilling off the organic solvent from the mixed alkoxide solution, slurry was prepared, in the slurry, in a predetermined stoichiometric ratio, adding an aqueous solution containing a salt of P t.
Examples of the aqueous solution containing salts of P t, for example, aqueous nitrate solution, aqueous chloride solution, hexaammine chloride solution, dinitrodiammine nitric acid solution, hexachloro acid hydrate, such as potassium cyanide salt.

Then, after the obtained precipitate is dried by evaporating water by, for example, vacuum drying or ventilation drying, for example, heat treatment (firing) at about 500 to 1200 ° C., preferably about 600 to 1000 ° C. By doing so, a perovskite complex oxide can be produced.
Also, precipitation in such alkoxide method, for example, a mixed alkoxide solution described above, by mixing a solution containing organometallic salts of P t, to prepare a homogeneous mixed solution, adding water by hydrolysis to Then, the obtained precipitate can be dried and then heat-treated.

As an organic metal salts of P t, for example, acetates, carboxylates of the noble metal formed from such propionate, for example, beta-diketone compound represented by the following general formula (3) or beta-keto ester compound, And / or a metal chelate complex of the noble metal formed from a β-dicarboxylic acid ester compound represented by the following general formula (4).

R ³ COCHR ⁵ COR ⁴ (3)
(In the formula, R ³ is an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms or an aryl group, R ⁴ is an alkyl group having 1 to 6 carbon atoms, and a fluoro having 1 to 6 carbon atoms. An alkyl group, an aryl group, or an alkyloxy group having 1 to 4 carbon atoms, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)
R ⁷ CH (COOR ⁶ ) ₂ (4)
(In the formula, R ⁶ represents an alkyl group having 1 to 6 carbon atoms, and R ⁷ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)
In the general formula (3) and the general formula (4), examples of the alkyl group having 1 to ⁶ carbon atoms of R ³ , R ⁴ and R ⁶ include methyl, ethyl, propyl, isopropyl, n-butyl, s -Butyl, t-butyl, t-amyl, t-hexyl and the like. The alkyl group having 1 to 4 carbon atoms of R ⁵ and R ^7, for example, methyl, ethyl, propyl, isopropyl, n- butyl, s- butyl, t- butyl. Moreover, as a C1-C6 fluoroalkyl group of R < ³ > and R < ⁴ >, trifluoromethyl etc. are mentioned, for example. The aryl group of R ³ and R ^4, for example, phenyl. Examples of the alkyloxy group having 1 to ⁴ carbon atoms of R ⁴ include methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, s-butoxy, t-butoxy and the like.

  More specifically, β-diketone compounds are, for example, 2,4-pentanedione, 2,4-hexanedione, 2,2-dimethyl-3,5-hexanedione, 1-phenyl-1,3-butanedione. 1-trifluoromethyl-1,3-butanedione, hexafluoroacetylacetone, 1,3-diphenyl-1,3-propanedione, dipivaloylmethane and the like.

More specific examples of the β-keto ester compound include methyl acetoacetate, ethyl acetoacetate, t-butyl acetoacetate, and the like.
Specific examples of the β-dicarboxylic acid ester compound include dimethyl malonate and diethyl malonate.
Moreover , the solution containing the organometallic salt of Pt can be prepared, for example , by adding the organometallic salt of Pt to the organic solvent so as to have the above stoichiometric ratio, and stirring and mixing. The organic solvent described above is used as the organic solvent.

Then, a solution containing organic metal salts of the thus P t which is prepared, by mixing the mixed alkoxide solution described above, after preparing a homogeneous mixture solution, by adding water hydrolysis to the homogenous mixed solution Precipitate. The resulting precipitate is dried by, for example, vacuum drying or ventilation drying, and then heat-treated at, for example, about 400 to 1000 ° C., preferably about 500 to 850 ° C., thereby obtaining a perovskite complex oxide. Can be manufactured.

Further, the perovskite-type composite oxide of the present invention, described above, co-precipitation, citrate complex method, the alkoxide method, the above elements other than P t, a stoichiometric ratio of the, first, perovskite-type composite the oxide was prepared and then, the resulting perovskite-type complex oxide, in a stoichiometric ratio of the may also be obtained by solid solution of P t.

The perovskite-type composite oxide, in order to solid solution of P t, not particularly limited, and may be a known method. For example, to prepare a solution of a salt containing P t, after impregnating the chlorine solution perovskite-type composite oxide is calcined.
As the salt-containing solution, the above-described salt solutions may be used, and practically, an aqueous nitrate solution, a dinitrodiammine nitric acid solution, an aqueous chloride solution, and the like may be used.

  More specifically, as a palladium salt solution, for example, palladium nitrate aqueous solution, dinitrodiammine palladium nitrate solution, tetravalent palladium ammine nitric acid solution, etc., rhodium salt solution, for example, platinum salt solution such as rhodium nitrate solution, rhodium chloride solution, etc. Examples thereof include dinitrodiammine platinum nitric acid solution, chloroplatinic acid solution, and tetravalent platinum ammine solution. Moreover, after impregnating a perovskite type complex oxide with a noble metal, for example, it is dried at 50 to 200 ° C. for 1 to 48 hours, and further fired at 350 to 1000 ° C. for 1 to 12 hours.

The perovskite complex oxide of the present invention thus obtained can be used as it is as an exhaust gas purification catalyst , but is usually prepared as an exhaust gas purification catalyst by a known method such as being supported on a catalyst carrier. Is done.
The catalyst carrier is not particularly limited, and for example, a known catalyst carrier such as a honeycomb monolith carrier made of cordierite or the like is used.

In order to support the catalyst on the catalyst carrier, for example, first, water is added to the obtained perovskite complex oxide to form a slurry, which is then coated on the catalyst carrier and dried, and then about 300 to 800 ° C., Preferably, it heat-processes at about 300-600 degreeC.
Then, the exhaust gas purifying catalyst comprising a perovskite-type composite oxide of the present invention thus obtained, the crystal structure of the perovskite-type composite oxide, a solid solution with P t high rate of solid solution, the solid solution the P t is, under a reducing atmosphere, and precipitated from the crystal structure, under an oxidizing atmosphere, a solid solution in the crystal structure. Incidentally, the solid solution rate of the crystal structure of the perovskite-type composite oxide of the P t can be adjusted by the final sintering temperature and sintering time. Furthermore, rate of solid solution into the crystal structure of the perovskite-type composite oxide of P t (an oxidizing atmosphere), for each content of P t of the perovskite-type composite oxide, for example, 50 wt% or more, Preferably, it is 80 to 100% by weight.

As a result, the exhaust gas purifying catalyst of the present invention can effectively grow Pt grains even in long-term use by such a self-regenerative function that repeats solid solution in an oxidizing atmosphere and precipitation in a reducing atmosphere. It is suppressed and these dispersed states are maintained. As a result , even if the amount of Pt used is significantly reduced, high catalytic activity can be realized over a long period of time.

Further, in the exhaust gas purifying catalyst of the present invention, since the atomic ratio of element coordinated on the A site exceeds 1, it is possible to further increase the rate of solid solution P t, it can be provided with stable quality it can.
Therefore, the exhaust gas purifying catalyst containing the perovskite complex oxide of the present invention can be widely used as a gas phase or liquid phase reaction catalyst. In particular, there use since, for example, gasoline engines, and internal combustion engines such as diesel engines, such as the exhaust gas purifying catalyst for purifying exhaust gas discharged from the boiler can achieve long-term excellent exhaust gas purification performance be able to.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples and comparative examples.
Example 1
(Production of Ba _1.01 Mn _0.95 Pt _0.05 O ₃₊ σ)
Barium methoxypropylate (Ba content: 0.101 mol)
Manganese methoxypropylate (Mn content: 0.095 mol)
A mixed alkoxide solution was prepared by adding the above components to a round bottom flask and adding toluene to dissolve with stirring. Then, platinum acetylacetonate (Pt content: 0.005 mol) is dissolved in toluene to prepare an organometallic salt solution. This organometallic salt solution is further added to the mixed alkoxide solution in the round bottom flask, and BaMnPt is added. A homogeneous mixed solution containing was prepared.

Next, deionized water was added dropwise to the round bottom flask over about 15 minutes for hydrolysis. As a result, a brown viscous precipitate was formed by hydrolysis.
Then, after stirring for 2 hours at room temperature, toluene and water were evaporated to dryness under reduced pressure to obtain a BaMnPt composite oxide precursor. This was air-dried at 60 ° C. for 24 hours, and then heat-treated (fired) at 650 ° C. for 2 hours in the atmosphere in an electric furnace to obtain a Pt-containing perovskite composite composed of Ba _1.01 Mn _0.95 Pt _0.05 O ₃₊ σ. An oxide (Pt content: 3.92 wt%) powder was obtained.

As a result of powder X-ray diffraction, this powder was confirmed to have a single crystal phase of a Pt-containing perovskite complex oxide composed of Ba _1.01 Mn _0.95 Pt _0.05 O ₃₊ σ.
Example 2
(Production of Ba _1.01 Mn _0.475 Ti _0.475 Pt _0.05 O ₃₊ σ)
Barium methoxypropylate (Ba content: 0.101 mol)
Manganese methoxypropylate (Mn content: 0.0475 mol)
Titanium ethoxyethylate (Ti content: 0.0475 mol)
A mixed alkoxide solution was prepared by adding the above components to a round bottom flask and adding toluene to dissolve with stirring. Then, platinum acetylacetonate (Pt content: 0.005 mol) is dissolved in toluene to prepare an organometallic salt solution. This organometallic salt solution is further added to the mixed alkoxide solution in the round bottom flask, and BaMnTiPt is added. A homogeneous mixed solution containing was prepared.

Thereafter, a powder of Pt-containing perovskite complex oxide (Pt content: 3.67% by weight) composed of Ba _1.01 Mn _0.475 Ti _0.475 Pt _0.05 O ₃₊ σ was obtained by the same operation as in Example 1.
As a result of powder X-ray diffraction, this powder was confirmed to have a single crystal phase of a Pt-containing perovskite complex oxide composed of Ba _1.01 Mn _0.475 Ti _0.475 Pt _0.05 O ₃₊ σ.

Example 3
(Production of Ca _1.01 Mn _0.97 Pt _0.03 O ₃₊ σ)
Calcium isopropoxide (Ca content: 0.101 mol)
Manganese isopropoxide (Mn content: 0.097 mol)
A mixed alkoxide solution was prepared by adding the above components to a round bottom flask and adding toluene to dissolve with stirring. Deionized water was added dropwise to the mixed alkoxide solution for hydrolysis. As a result, a white viscous precipitate was formed by hydrolysis. Toluene was distilled off from the mixed alkoxide solution to form a slurry, and a dinitrodiammine platinum nitric acid aqueous solution (Pt content: 0.003 mol) was added to the slurry, followed by stirring at room temperature for 1 hour.

Subsequently, water was distilled off to dryness under reduced pressure to obtain a CaMnPt composite oxide precursor. This, in air, in an electric furnace, 800 ° C., subjected to 2 hours _{(baking), Ca 1.01 Mn 0.97 Pt 0.03} O 3+ consisting sigma Pt-containing perovskite-type composite oxide (Pt content: 3.96 % By weight) of powder was obtained.
As a result of powder X-ray diffraction, this powder was confirmed to have a single crystal phase of a Pt-containing perovskite complex oxide composed of Ca _1.01 Mn _0.97 Pt _0.03 O ₃₊ σ.

Example 4
( _{Production of} Ca _1.01 Mn _0.485 Zr _0.485 Pt _0.03 O ₃₊ σ)
Calcium isopropoxide (Ca content: 0.101 mol)
Manganese isopropoxide (Mn content: 0.0485 mol)
Zirconium isopropoxide (Zr content: 0.0485 mol)
After adding said component to a round bottom flask and processing like Example 3, dinitrodiammine platinum nitric acid aqueous solution (Pt content: 0.003 mol) was added, and it stirred at room temperature for 1 hour.

Next, water was distilled off to dryness under reduced pressure to obtain a CaMnZrPt composite oxide precursor. This was subjected to heat treatment (baking) at 800 ° C. for 2 hours in an electric furnace in the atmosphere, and a Pt-containing perovskite complex oxide (Pt content: 3) _{composed of} Ca _1.01 Mn _0.485 Zr _0.485 Pt _0.03 O ₃₊ σ. .54% by weight) of powder was obtained.
As a result of powder X-ray diffraction, this powder was confirmed to have a single crystal phase of a Pt-containing perovskite complex oxide composed of Ca _1.01 Mn _0.485 Zr _0.485 Pt _0.03 O ₃₊ σ.

Example 5
(Production of Sr _1.01 Mn _0.96 Pt _0.04 O ₃₊ σ)
Strontium isopropoxide (Sr content: 0.101 mol)
Manganese isopropoxide (Mn content: 0.096 mol)
After adding said component to a round bottom flask and processing like Example 3, dinitro diamine amine nitric acid aqueous solution (Pt content: 0.004 mol) was added, and it stirred at room temperature for 1 hour.

Next, water was distilled off to dryness under reduced pressure to obtain a precursor of SrMnPt composite oxide. This was heat-treated (baked) at 800 ° C. for 2 hours in an electric furnace in the atmosphere, and a Pt-containing perovskite complex oxide (Pt content: 3.96) composed of Sr _1.01 Mn _0.96 Pt _0.04 O ₃₊ σ. % By weight) of powder was obtained.
As a result of powder X-ray diffraction, this powder was confirmed to have a single crystal phase of a Pt-containing perovskite complex oxide composed of Sr _1.01 Mn _0.96 Pt _0.04 O ₃₊ σ.

Example 6
(Production of Sr _1.01 Mn _0.48 Zr _0.48 Pt _0.04 O ₃₊ σ)
Strontium isopropoxide (Sr content: 0.101 mol)
Manganese isopropoxide (Mn content: 0.048 mol)
Zirconium isopropoxide (Zr content: 0.048 mol)
After adding said component to a round bottom flask and processing like Example 3, dinitro diamine amine nitric acid aqueous solution (Pt content: 0.004 mol) was added, and it stirred at room temperature for 1 hour.

Next, water was distilled off to dryness under reduced pressure to obtain a precursor of SrMnZrPt composite oxide. This was subjected to heat treatment (baking) at 800 ° C. for 2 hours in an electric furnace in the atmosphere, and a Pt-containing perovskite complex oxide (Pt content: 3) composed of Sr _1.01 Mn _0.48 Zr _0.48 Pt _0.04 O ₃₊ σ. 0.63% by weight) of powder was obtained.
As a result of powder X-ray diffraction, this powder was confirmed to have a single crystal phase of a Pt-containing perovskite complex oxide composed of Sr _1.01 Mn _0.48 Zr _0.48 Pt _0.04 O ₃₊ σ.

Comparative Example 1
(Production of La _0.95 Sr _0.05 Al _0.90 Co _0.05 Pt _0.05 O ₃ )
Lanthanum ethoxyethylate (La content: 0.095 mol)
Strontium ethoxyethylate (Sr content: 0.005 mol)
Aluminum ethoxyethylate (Al content: 0.090 mol)
Cobalt ethoxyethylate (Co content: 0.005 mol)
After adding said component to a round bottom flask and processing like Example 2, dinitro diamine amine nitric acid aqueous solution (Pt content: 0.005 mol) was added, and it stirred at room temperature for 1 hour.

Next, water was distilled off to dryness under reduced pressure to obtain a precursor of LaSrAlCoPt composite oxide. This was subjected to heat treatment (baking) at 800 ° C. for 2 hours in an electric furnace in the atmosphere, and a Pt-containing perovskite complex oxide (Pt content: 4) made of La _0.95 Sr _0.05 Al _0.90 Co _0.05 Pt _0.05 O _3. .41% by weight) of powder was obtained.
As a result of powder X-ray diffraction, this powder was confirmed to have a single crystal phase of a Pt-containing perovskite complex oxide composed of La _0.95 Sr _0.05 Al _0.90 Co _0.05 Pt _0.05 O ₃ .

Comparative Example 2
(Production of Pt / α-Al ₂ O ₃ )
Commercially available α-Al ₂ O ₃ (specific surface area 13m ² / g), using a solution of diammine dinitro platinum nitric acid, was impregnated with Pt, 24 hours air drying at 60 ° C., in air, an electric furnace using And heat-treated at 500 ° C. for 1 hour. The amount of Pt supported by α-Al ₂ O ₃ was 2.00% by weight.

Test Example 1 (Physical property test)
1) Measurement of specific surface area The specific surface areas of the powders of Examples and Comparative Examples obtained above were measured according to the BET method. The results are shown in Table 1.
2) Measurement of solid solution ratio of noble metal The powder obtained in each Example and each Comparative Example was subjected to oxidation treatment (heat treatment at 800 ° C. for 1 hour in air) and reduction treatment (N ₂ containing 10% H ₂ ). In each gas, after heat treatment at 800 ° C. for 1 hour, each was dissolved in a 7 wt% hydrofluoric acid aqueous solution and allowed to stand at room temperature for 20 hours, and then each solution was filtered through a 0.1 μmφ filter. The amount of noble metal dissolved in the filtrate was quantitatively analyzed by ICP (radio frequency inductively coupled plasma) emission spectrometry, and the noble metal in the residue was qualitatively analyzed by XRD (X-ray diffraction) analysis. From these results, the precious metal solid solution rate after the oxidation treatment and after the reduction treatment was calculated. Moreover, the precipitation rate of the noble metal was calculated from the difference between the noble metal solid solution rate after the oxidation treatment and the noble metal solid solution rate after the reduction treatment. These results are shown in Table 1.

In the above method, when each powder was dissolved in a 7% by weight hydrofluoric acid aqueous solution, a fluoride residue was formed. However, the noble metal dissolved in the perovskite crystal structure was dissolved. By measuring the concentration of the noble metal in the solution, the ratio of the noble metal dissolved in the perovskite crystal structure could be determined.
Test example 2 (endurance test)
1) Oxidation reduction endurance test 5 minutes of inert atmosphere, 10 minutes of oxidizing atmosphere, 5 minutes of inert atmosphere, and 10 minutes of reducing atmosphere are defined as one cycle, and this cycle is repeated for 20 cycles for a total of 10 hours. The powders obtained in the examples and the comparative examples were alternately exposed to an oxidizing atmosphere and a reducing atmosphere, and then cooled to room temperature in the reducing atmosphere.

The inert atmosphere, the oxidizing atmosphere, and the reducing atmosphere respectively correspond to exhaust gas atmospheres that are discharged when the stoichiometric, lean, and rich air-fuel mixture is burned.
Each atmosphere was prepared by supplying a gas having a composition shown in Table 2 containing high-temperature steam at a flow rate of 300 × 10 ⁻³ m ³ / hr. The ambient temperature was maintained at about 1000 ° C.

２）活性評価
４％ＮＯおよび６％Ｈ₂を含むガス（Ｈｅバランス）を、合計５０ｍＬ／分流通させながら、上記の酸化還元耐久試験に供した各粉末４０ｍｇを、室温から４００℃まで、３℃／分にて昇温した。この間に、質量分析計にて、ＮＯ（質量３０）の信号を観測し、そのカウント数が室温に比べて３０％減少した温度を、ＮＯ３０％浄化温度とした。これらの結果を表１に示す。

2) Activity evaluation While supplying a gas containing 4% NO and 6% H ₂ (He balance) at a total flow rate of 50 mL / min, 40 mg of each powder subjected to the above oxidation-reduction durability test was transferred from room temperature to 400 ° C. The temperature was raised at ° C / min. During this time, a NO (mass 30) signal was observed with a mass spectrometer, and the temperature at which the count decreased by 30% compared to room temperature was defined as the NO 30% purification temperature. These results are shown in Table 1.

Claims (3)

General formula (1)
A _x B _y B ′ _(1−yz) N _z O _{3 + σ} (1)
(In the formula, A represents at least one element selected from alkaline earth metals , B represents Mn, B ′ represents at least one element selected from Ti, Zr, and Hf , and N Represents Pt , x represents an atomic ratio in a numerical range of 1 <x ≦ 1.3 , y represents an atomic ratio of 0 <y <1.0, and z represents 0 <z ≦ 0. 5 represents an atomic ratio, sigma represents an oxygen excess.)
A catalyst for purifying exhaust gas , comprising a perovskite complex oxide represented by the formula: In the general formula (1), z is 0 <characterized in that represents an atomic ratio of the numerical range of z ≦ 0.05, the catalyst for purification of exhaust gas according to claim 1. The exhaust gas-purifying catalyst according to claim 1 or 2 , wherein (1-yz) is 0 in the general formula (1) .