WO2006008948A1

WO2006008948A1 - Catalyst for exhaust gas purification and process for producing the same

Info

Publication number: WO2006008948A1
Application number: PCT/JP2005/012325
Authority: WO
Inventors: Isamu Yashima; Yuichi Anno; Masatoshi Yamazaki; Hiromitsu Takagi; Yasuhisa Goto; Moei Chai; Yunosuke Nakahara
Original assignee: Mitsui Mining & Smelting Co., Ltd.
Priority date: 2004-07-16
Filing date: 2005-07-04
Publication date: 2006-01-26
Also published as: JP3786666B2; JP2006026554A

Abstract

A catalyst for exhaust gas purification which comprises a tetragonal-system composite oxide represented by the general formula A2BO4 (wherein A represents at least one member selected from the group consisting of Ca, Sr, and Ba and B represents at least one member selected from the group consisting of Mn, Fe, Ti, Sn, and V), a refractory inorganic oxide at least a surface layer of which is constituted of MgAl2O4, and a noble metal ingredient which forms a solid solution in the tetragonal-system composite oxide or has been deposited on the composite oxide or on the refractory inorganic oxide. The catalyst ingredient is inhibited from reacting/decomposing, and the catalyst for exhaust gas purification can exhibit its initial catalytic performance.

Description

Specification

Exhaust gas purification catalyst and method for producing the same

Technical field

TECHNICAL FIELD [0001] The present invention relates to an exhaust gas purifying catalyst and a method for producing the same, and more specifically, exhibits the desired catalytic performance by suppressing the reaction 'decomposition of a catalyst component comprising a specific tetragonal complex oxide. The present invention relates to an exhaust gas purifying catalyst that can be produced and a method for producing the same.

Background art

[0002] Exhaust gas discharged from internal combustion engines such as automobiles contains harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO). Therefore, three-way catalysts that purify and detoxify these harmful components have been used in the past.

[0003] As such a three-way catalyst, a first layer provided on a support substrate, containing at least alumina and having Zro added or supported on a surface layer, and a velovskite type provided on the first layer Structure

2

And an exhaust gas purifying catalyst in which a noble metal is supported on at least one of the first layer and the second layer (see, for example, Patent Document 1). See also.)

[0004] When such perovskite type complex oxides are used in a high temperature range of about 900 ° C or higher, there is a problem that the catalytic activity is remarkably lowered by reacting with other metal components. There is also a problem that the bottom busite structure is broken in a reducing atmosphere (rich atmosphere) with insufficient oxygen concentration based on the fuel ratio.

Patent Document 1: JP-A-7-80311

Disclosure of the invention

Problems to be solved by the invention

[0005] The present applicant has previously described a general formula A BO obtained by neutralization coprecipitation drying firing (wherein

twenty four

A represents at least one selected from the group consisting of Ca, Sr and Ba, and B represents at least one selected from the group consisting of Mn, Fe, Ti, Sn and V) An aqueous solution prepared by adding a complex oxide such as manganese (II) nitrate hexahydrate and calcium nitrate tetrahydrate to a molar ratio of 1: 2 is dropped into an aqueous ammonium carbonate solution. Precursor precipitation It is made of Ca MnO, which is obtained by filtering the precipitate, drying at about 120 ° C, and calcining at about 800 ° C. It has high low-temperature activity, excellent heat resistance, and stable exhaust gas. Purifying performance

twenty four

A patent application was filed for an invention relating to a catalyst for exhaust gas purification.

[0006] In the course of the invention, even if it is a tetragonal complex acid oxide represented by the same general formula A BO,

twenty four

However, there is a large difference in catalyst performance and stability performance depending on the production method, and tetragonal complex oxides obtained by mixing, drying, and firing, for example, MnCO powder and CaCO powder.

3 3

: When mixing Ca MnO obtained by stirring and mixing in pure water to a molar ratio of 2, dried at about 120 ° C and then calcined at about 1100 ° C on alumina, For example, car

twenty four

When used to purify harmful components contained in high-temperature exhaust gas discharged from internal combustion engines, etc., the reaction formula

Ca MnO + 2A1 0 → CaMnO + CaAl O

2 4 2 3 3 4 7

As a result, it was found that the catalyst performance gradually deteriorated by reacting with alumina gradually, and the desired catalyst performance could not be maintained for a long time.

[0007] The present invention has been made in view of the circumstances as described above, and even if the tetragonal complex oxide is obtained by the above-mentioned mixed drying firing, the tetragonal complex oxide is obtained. The purpose of the present invention is to provide an exhaust gas purifying catalyst capable of exhibiting the desired catalytic performance by suppressing the reaction and decomposition of the catalyst component comprising the product, and a method for producing the same.

Means for solving the problem

[0008] As a result of intensive studies to achieve the above object, the present inventors have found that a specific general formula A B

2

A tetragonal complex oxide represented by O, at least the surface layer being composed of MgAl 2 O

4 2 4

The present invention has been completed by finding that the above object can be achieved by coexisting with a refractory inorganic oxide.

That is, the exhaust gas purifying catalyst of the present invention has the general formula A BO (where A is Ca, Sr and Ba

twenty four

A tetragonal complex oxide represented by at least one selected from the group consisting of Mn, Fe, Ti, Sn and V), and at least one selected from the group consisting of And a refractory inorganic oxide whose surface layer is composed of MgAl 2 O and the tetragonal complex oxide.

twenty four

It is characterized by comprising a noble metal component which is supported or supported by the refractory inorganic oxide, which is a solid solution in the material. [0010] Further, the exhaust gas purifying catalyst of the present invention comprises

Even if it is composed of a carrier made of ceramics or a metal material and the above-mentioned catalyst layer for exhaust gas purification of the present invention supported on the carrier,

A carrier made of a ceramic or metal material, supported on the carrier, and the above-mentioned tetragonal complex oxide, and a refractory inorganic oxide comprising at least a surface layer made of MgAl 2 O.

twenty four

A first catalyst layer comprising a product, or a first catalyst layer serving as a catalyst for exhaust gas purification according to the present invention, and a noble metal component-supported refractory inorganic oxide supported on the first catalyst layer. A second catalyst layer consisting of

Even if it consists of

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A first catalyst layer composed of a product, or a first catalyst layer serving as a catalyst for exhaust gas purification of the present invention, and two or more noble metal component-supported refractories supported on the first catalyst layer. It is possible to use a catalyst layer made of a water-soluble inorganic oxide, and the types of noble metal components supported on each refractory inorganic acid oxide may be different.

[0011] In addition, the method for producing an exhaust gas purifying catalyst of the present invention includes alumina, basic magnesium carbonate, and a general formula A BO (where A is a group force consisting of Ca, Sr, and Ba, at least

twenty four

B represents a group force consisting of Mn, Fe, Ti, Sn, and V. At least one selected from the group consisting of tetragonal complex oxides) A tetragonal complex acid which is coated on a carrier, dried, and fired at 300 to 600 ° C. for 1 to 6 hours, and the noble metal component is in a solid solution and supports the noble metal component or the noble metal component. The calcination product is used, or the calcined product after calcination is immersed in an aqueous solution of a basic noble metal salt to carry a predetermined amount of noble metal, and then calcined at 300 to 600 ° C.

[0012] Furthermore, the method for producing an exhaust gas purifying catalyst of the present invention includes MgAl 2 O and a general formula A BO

2 4 2 4

(In the formula, A represents at least one selected from the group force consisting of Ca, Sr and Ba, and B represents at least one selected from the group consisting of Mn, Fe, Ti, Sn and V) The slurry containing a tetragonal complex oxide represented by the following formula is coated on a support made of ceramics or a metal material, dried, fired at 300 to 600 ° C. for 1 to 6 hours, and the noble metal component is solidified. Melting Be a body! / Use a tetragonal complex acid oxide that supports the metal or the precious metal component, or immerse the fired product after firing in an aqueous solution of a basic precious metal salt to support a predetermined amount of the precious metal. And then firing at 300 to 600 ° C.

The invention's effect

[0013] The exhaust gas purifying catalyst of the present invention is a catalyst comprising a tetragonal complex oxide even when used for purifying harmful components contained in high-temperature exhaust gas discharged from an internal combustion engine such as an automobile. The desired catalytic performance can be exhibited by suppressing the reaction 'decomposition of the components. Brief Description of Drawings

[0014] FIG. 1 is a chart showing XRD results of the products obtained in Test Examples 1 to 5.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] Embodiments of the present invention will be specifically described below.

The general formula A BO used as a catalyst component in the exhaust gas purification catalyst of the present invention (wherein

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A represents at least one selected from the group consisting of Ca, Sr and Ba, and B represents at least one selected from the group forces selected from Mn, Fe, Ti, Sn and V forces) Examples of the crystalline complex oxide include Ca MnO, Sr MnO, Sr FeO, Ba SnO, Sr VO and the like.

2 4 2 4 2 4 2 4 2 4 can be mentioned, and Ca MnO is particularly preferable in terms of catalytic activity.

twenty four

[0016] The tetragonal complex acid salt represented by the above general formula A BO is the above neutralization coprecipitation drying

twenty four

It may be a tetragonal complex oxide obtained by firing or a tetragonal complex oxide obtained by the above-mentioned mixed dry firing, but it can be obtained by the above described mixed dry firing. A remarkable effect is achieved in the case of a tetragonal complex oxide.

[0017] It should be noted that the tetragonal complex oxide has a K NiF type structure, that is, a tetragonal structure, whereas the perovskite complex oxide is cubic. In the lattice

twenty four

Since there are many spaces, oxygen can be taken in more than the stoichiometric composition, and the oxygen storage capacity is relatively free. For example, perovskite structures and OSC materials (CeO and ZrO and

2), which is significantly higher than 2).

[0018] In the exhaust gas purifying catalyst of the present invention, such a tetragonal complex oxide is used, so that the oxygen concentration is not high based on the change in the exhaust gas atmosphere, that is, the stoichiometric air-fuel ratio. Ten Oxygen entry and exit is relatively easy in response to changes in the oxygen concentration over a wide range from a rich reducing atmosphere (rich atmosphere) to an oxygen-excess oxidizing atmosphere (lean atmosphere).

[0019] Among the constituent elements of the general formula A BO, in particular, the valence change of the B site ion occurs.

twenty four

It is conceivable that there is a large space in the structure because it is easy. As described above, since oxygen can easily enter and exit, a window that becomes a reaction site with the purification target substance is widened to realize high activity, so that catalytic activity is enhanced and exhaust gas purification performance is improved. Performance is improved.

[0020] Further, since tetragonal complex oxides are excellent in heat resistance, even when an exhaust gas purifying catalyst is used in a high temperature range, it exhibits a very high oxygen storage capacity and catalytic activity. The exhaust gas purification performance can be improved.

In the exhaust gas purifying catalyst of the present invention, at least the surface layer is composed of MgAl 2 O.

twenty four

It is indispensable to make the refractory inorganic oxide present together with the above tetragonal complex oxide. As a state where at least the surface layer is composed of MgAl 2 O

twenty four

The inside of the refractory inorganic oxide is alumina and the surface layer is MgAl 2 O 3

Even if it is composed of 24, the entire refractory inorganic oxide is composed of MgAl 2 O.

twenty four

Also good. When CaAl O, BaAl O, etc. are used instead of MgAl O, the above

2 4 2 4 2 4

Reaction / decomposition of the catalyst component composed of the tetragonal complex oxide cannot be suppressed, and the desired catalyst performance cannot be exhibited. Therefore, the effect in the present invention is that the above-mentioned tetragonal complex oxide and the refractory inorganic acid at least the surface layer of which is composed of MgAl 2 O.

twenty four

It is considered to be a unique effect achieved in combination with a chemical compound.

[0022] In the exhaust gas purifying catalyst of the present invention, noble metal components such as rhodium, palladium and platinum are solid solution or supported in the tetragonal complex oxide. Or supported by the above-mentioned refractory inorganic oxide. The tetragonal complex oxide in which the noble metal component is in a solid solution in the tetragonal complex oxide has the general formula A B C O (

2 lx x 4 In the formula, A represents at least one selected from the group force consisting of Ca, Sr and Ba, and B represents at least one selected from the group force selected from Mn, Fe, Ti, Sn and V. C represents a noble metal, X is 0.01 to 0.5), and the tetragonal complex oxide in such a state is It can be obtained by immersing the tetragonal composite oxide in a basic noble metal salt aqueous solution and supporting a predetermined amount of noble metal, followed by firing at 300 to 600 ° C. Or MgAl O and

2 4 It can also be obtained by immersing the calcined product containing the above tetragonal complex oxide in an aqueous solution of a basic noble metal salt, supporting a predetermined amount of noble metal, and then calcining at 300 to 600 ° C. In this case, the noble metal component is solid solution or supported in the tetragonal complex oxide, and the noble metal component is supported on the refractory inorganic oxide. However, it does not matter whether the noble metal component is in a solid solution or is supported on the exhaust gas purification catalyst of the present invention. In any case, the mixed state is equally effective as an exhaust gas purifying catalyst.

[0023] The state in which the noble metal component is in solid solution in the tetragonal complex oxide is a noble metal component in which part of the element at the B site of the tetragonal complex oxide acts as a catalyst. For example, it is in a state where it is substituted with a palladium component, and as such a solid solution, for example, Ca Mn Pd O

2 1 4

, Sr Fe Pd O, Sr Mn Pd O, and the like. Thus tetragonal composite

2 1 4 2 1 4

By dissolving a noble metal component such as Pd in a uniformly dispersed state in the structure of the oxide, it is possible to widen the window that acts as a catalyst activity, and to ensure stable exhaust gas purification performance. Note that the value of X, which represents the amount of the precious metal component in the solid solution, is less than 0.01, the catalytic effect of the precious metal component is insufficient, and conversely, even if it exceeds 0.5, an effect commensurate with the cost is achieved. Not. Accordingly, x is preferably 0.01 to 0.5 in the tetragonal complex oxide of the general formula A B C O used for the exhaust gas purifying catalyst of the present invention.

2 1 4

That's right.

The exhaust gas purifying catalyst of the present invention comprises a tetragonal complex oxide as described above, a refractory inorganic oxide having at least a surface layer composed of MgAl 2 O, and a noble metal component. Also

twenty four

In general,

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A first catalyst layer made of a product or a catalyst for exhaust gas purification of the present invention. A second catalyst layer comprising a noble metal component-supported refractory inorganic oxide supported on the first catalyst layer;

Even if it consists of

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A first catalyst layer composed of a product, or a first catalyst layer serving as a catalyst for exhaust gas purification of the present invention, and two or more noble metal component-supported refractories supported on the first catalyst layer. The noble metal components may be different from each other in the kind of the noble metal component supported by each of the refractory inorganic acids.

[0025] In the exhaust gas purifying catalyst as described above, the shape of the carrier that also has ceramic or metal material power is not particularly limited, but in general, such as a hard cam, a plate, a pellet, etc. It is a shape, preferably a Hercam shape. Examples of the material of such a carrier include anolemina (Al 2 O 3), mullite (3A1 O—2SiO), cordierite (2M gO—2Al).

2 3 2 3 2

Examples thereof include ceramics such as O-5SiO2) and metal materials such as stainless steel. In addition,

2 3 2

Jiraito material are particularly effective because the thermal expansion coefficient is extremely low and 1.0 X 10- ⁶ Z ° C.

[0026] a layer comprising the above tetragonal complex oxide supported on a carrier having a ceramic or metal material strength and a refractory inorganic oxide having at least a surface layer composed of MgAl 2 O

twenty four

Refractory that the above tetragonal complex oxide and at least the surface layer is composed of MgAl 2 O

twenty four

The exhaust gas purifying catalyst layer comprising a porous inorganic oxide and a noble metal component includes a refractory inorganic oxide containing the above tetragonal complex oxide and at least a surface layer made of MgAl 2 O.

twenty four

It is formed by wash-coating on a support using a slurry containing a product or a slurry containing various components of the exhaust gas purifying catalyst, drying and firing. The exhaust gas purifying catalyst layer includes a calcined product containing the above tetragonal complex oxide and a refractory inorganic oxide whose surface layer is composed of MgAl 2 O on the support.

twenty four

After the layer is formed, it can also be formed by immersing in a basic noble metal salt aqueous solution and supporting a predetermined amount of noble metal, followed by firing at 300 to 600 ° C.

[0027] A refractory material in which the above tetragonal complex oxide and at least the surface layer are composed of MgAl 2 O

twenty four

Supported on a layer made of an inorganic oxide or a catalyst layer for exhaust gas purification A layer of a refractory inorganic oxide carrying a precious metal component, for example, a layer of porous alumina carrying a platinum component, immerses the refractory inorganic oxide in a basic precious metal salt aqueous solution and supports a predetermined amount of precious metal. After the noble metal component is supported on the refractory inorganic oxide by firing at ~ 600 ° C, the slurry containing the noble metal component-supported refractory inorganic oxide is used. The porcelain and at least the surface layer are composed of MgAl O

twenty four

It is formed by wash-coating, drying and calcining on a layer comprising a refractory inorganic oxide or the above-mentioned catalyst layer for exhaust gas purification. The noble metal component-supported refractory inorganic oxide layer is formed by forming a refractory inorganic oxide layer and then immersing it in a basic noble metal salt solution to support a predetermined amount of noble metal, and then 300 to 600 It can also be formed by baking at ° C. When two or more layers of the noble metal component-supported refractory inorganic oxide are used, the force that can be formed in the same manner as described above. In this case, the noble metal component of each noble metal component-supported refractory inorganic oxide layer is different. Shall.

[0028] In the exhaust gas purifying catalyst of the present invention, the tetragonal complex oxide is Ca MnO.

2 4 It is preferable that the precious metal component is rhodium, palladium or platinum, and that the refractory inorganic oxide is Al O, SiO, ZrO, CeO, CeO—ZrO composite oxide or

2 3 2 2 2 2 2

Is preferably a CeO 2 —ZrO—Al 2 O composite oxide.

2 2 2 3

[0029] The exhaust gas purifying catalyst of the present invention can obtain excellent heat resistance even when used in a wide range from a low temperature range immediately after starting an internal combustion engine such as an automobile to a high temperature range during continuous operation. In addition, stable exhaust gas purification performance with high low-temperature activity can be obtained.

[0030] The method for producing an exhaust gas purifying catalyst of the present invention comprises alumina, basic magnesium carbonate and a general formula A BO (wherein A is a group force consisting of Ca, Sr and Ba, at least one selected.

twenty four

A slurry containing a tetragonal complex oxide represented by the following formula: B or B represents a group force consisting of Mn, Fe, Ti, Sn, and V). It is applied onto a carrier in the form of a hard cam, plate, pellet, etc., dried and fired at 300 to 600 ° C. for 1 to 6 hours, and the precious metal component is used as a solid solution or a precious metal component. Use the tetragonal complex oxide that is supported, or immerse the calcined product after calcination in an aqueous solution of basic noble metal salt to carry a predetermined amount of noble metal, then at 300-600 ° C It consists of firing. [0031] Further, the method for producing an exhaust gas purifying catalyst of the present invention includes MgAl 2 O and general formula A BO (

2 4 2 4 In the formula, A represents at least one selected from the group force consisting of Ca, Sr and Ba, and B represents at least one selected from the group consisting of Mn, Fe, Ti, Sn and V. A slurry containing a tetragonal complex oxide represented by a seed) is applied onto a carrier in the form of a ceramic, a metal material, a hard cam, a plate, a pellet or the like, dried, and 300 to 600 Calcination for 1 to 6 hours at ° C, and the precious metal component forms a solid solution or supports the precious metal component, and uses a tetragonal complex acid silicate or a fired product after firing Is immersed in an aqueous solution of a basic noble metal salt, and after a predetermined amount of noble metal is supported, firing is performed at 300 to 600 ° C.

Hereinafter, the present invention will be described based on test examples, examples, and comparative examples.

Test examples 1 to 4

MnCO powder and CaCO powder are stirred and mixed in pure water so that the molar ratio is 1: 2.

3 3

And dried at about 120 ° C and calcined at about 1100 ° C to obtain Ca MnO powder. Ca

2 4 2

MnO production was confirmed by XRD measurement.

Four

[0033] Alumina powder and basic magnesium carbonate powder as magnesium compound powder (Test Example 1), acid magnesium powder (Test Example 2), magnesium acetate powder (Test Example 3), or magnesium hydroxide powder (Test) Example 4) and the above Ca MnO powder were mixed with Al: Mg: Ca = 4: 2

twenty four

: A slurry containing a quantity ratio of 1 was prepared. Each of the obtained slurries was dried at 120 ° C and calcined at 450 ° C for 2 hours to obtain a calcined product. Next, Ca MnO in these fired products

Reaction of 2 4 · In order to investigate the degradability, it was baked at 1000 ° C for 6 hours as an endurance test. The results of XRD of each product obtained are as shown in FIG.

[0034] Test Example 5

MgAl 2 O powder and Ca MnO powder obtained in Example 1 are in a quantity ratio of Al: Ca = 4: 1

2 4 2 4

A slurry containing was prepared. The obtained slurry was dried at 120 ° C. and calcined at 450 ° C. for 2 hours to obtain a calcined product. Next, the reaction 'decomposability of Ca MnO in this fired product is examined.

twenty four

Therefore, it was fired at 1000 ° C for 6 hours as a durability test. The XRD result of the obtained product is as shown in FIG. [0035] As is apparent from FIG. 1, in the case of Test Example 1 and Test Example 5, Ca MnO and MgAl

twenty four

The peak of O is high and the peak of CaMnO is low, but in the case of Test Examples 2 to 4, Ca MnO

The peaks of 2 4 3 2 and MgAl 2 O are low and the peaks of CaMnO are high. That is, each alumina powder

4 2 4 3

The surface of each particle has become MgAl 2 O by reaction with basic magnesium carbonate,

twenty four

When the entire particle of alumina powder is composed of MgAl 2 O, Ca Mn

2 4 2

The reaction decomposition of O is suppressed. The surface of each particle of alumina powder is MgA

Four

Ca is not coated with 1 O or incompletely coated with MgAl O.

2 4 2 4 2

MnO is reactively decomposed to produce CaMnO, and the expected catalytic performance cannot be expected.

4 3

Is clear.

[0036] Example 1

Stir and mix MnCO powder and CaCO powder in pure water so that the molar ratio is 1: 2.

3 3

In was添Ka卩the amount of palladium nitrate corresponding to 5 mol ^_0/0 manganese. Thereafter, it was dried at about 120 ° C. and calcined at about 1100 ° C. to obtain Ca MnO powder. In this case, palladium

twenty four

The components were supported on the surface of Ca MnO, and some of them were in solid solution in Ca MnO.

2 4 2 4

[0037] In addition, alumina powder and basic magnesium carbonate powder were mixed in an amount ratio of A1: Mg = 2: 1 and fired at about 1000 ° C. to obtain MgAl 2 O powder. Ca MnO and MgAl

2 4 2 4 2

O generation was confirmed by XRD measurement.

Four

[0038] Ca MnO powder in which at least a part of the palladium component obtained above is in a solid solution, and

A slurry containing 2 4 and MgAl 2 O powder was prepared and the slurry was transferred to a 600 cell / inch ² ha

twenty four

Wash coating was applied to the surface of the cam-shaped cordierite carrier. Thereafter, it was dried at about 120 ° C. and calcined at about 500 ° C. to form a first catalyst layer.

[0039] Next, on this first catalyst layer, a slurry containing platinum-supported alumina obtained by supporting a platinum component on porous alumina was wash-coated, dried, and calcined at about 500 ° C to be second. A catalyst layer was formed. Furthermore, on this second catalyst layer, a slurry containing rhodium-supported alumina obtained by supporting the rhodium component on porous alumina was wash-coated, dried, and calcined at about 500 ° C. to be third catalyst layer. The exhaust gas purifying catalyst of the present invention was obtained.

[0040] In this exhaust gas purification catalyst, 5% of manganese was replaced with palladium. In addition, the supported amount of radium is l.Og per liter volume of exhaust gas purification catalyst. Thus, the loading amount of platinum component and rhodium component was 0.2 g per 1 liter volume of the exhaust gas purification catalyst.

[0041] Examples 2-8

The exhaust gas purifying catalyst shown in Table 1 was prepared by adopting a method similar to the method described in Example 1.

[0042] [Table 1]

Table 1

Catalyst layer component Precious metal component Cg L) First catalyst layer Second catalyst layer Third catalyst layer P t P d Rh Example 2 C an G_t + Mg 1 Rh / Ά 1 ^ Os 0. 2 0.2 Example 3 C a ^ Mn, t-.. P d _K 0 ₄ + MA 1 _; ― 1. 0

Example 4 C a aMn i- „P d ^ O ^ + Mg A 1, c P t / A 1 sOs 0- 2] ·. 0

Example 5 S r F e C + Mg A l ^ O ^ P t / A 1 ₃ 0 ₃ Rb / A 1 _Ξ 0 ₃ 0- 2 0. 2 Example 6 S r ^ F e .... P d _x O ^ + Mg AI, c one 1. 0

Example 7 S re i- _¾ P d C + Mg A ί o ₄ P ί / Α 1 _Ξ 0 ₃ 0- 2 1. 0-Example 8 S re ix P dO ^ + Mg A 1: 〇 P t / AI sOa R h / AO ^ 0. 2 1 0 0. 2 Note) x of the composite oxide in the first catalyst layer is all 0.05.

[0043] Comparative Example 1

3 3

In was添Ka卩the amount of palladium nitrate corresponding to 5 mol ^_0/0 manganese. Thereafter, it was dried at about 120 ° C. and calcined at about 1100 ° C. to obtain Ca MnO powder. In this case, the palladium component was supported on the surface of Ca MnO, and a part of the palladium component was formed into a solid solution in Ca MnO. The production of Ca MnO was confirmed by XRD measurement.

[0044] A slurry containing Ca MnO powder and porous alumina powder in which at least a part of the palladium component obtained above is in a solid solution is prepared, and this slurry is formed into a Herkam shape of 600 cells / inch ² Wash cord on the surface of the cordierite carrier. Then about 120

It dried at ° C and calcined at about 500 ° C to form a first catalyst layer.

Next, a slurry containing platinum-supported alumina obtained by supporting a platinum component on porous alumina is wash-coated on this first catalyst layer, dried, fired at about 500 ° C., and then second-coated. Touch A medium layer was formed. Further, on this second catalyst layer, a slurry containing rhodium-supported alumina obtained by supporting the rhodium component on porous alumina was wash-coated, dried, and dried.

A catalyst for exhaust gas purification for comparison was obtained by calcining at 500 ° C. to form a third catalyst layer.

[0046] In this exhaust gas purifying catalyst, 5% of manganese was replaced with palladium. In addition, the supported amount of palladium is l.Og per liter of exhaust gas purification catalyst volume, and the supported amount of platinum component and rhodium component is 0.2 for each liter of exhaust gas purification catalyst volume. It became g.

[0047] Exhaust gas purification performance test

An evaluation test was conducted on the exhaust gas purification performance of the exhaust gas purification catalyst of Example 1 and Comparative Example 1.

[0048] The exhaust gas purifying catalysts of Example 1 and Comparative Example 1 were each mounted on a 2000 cc engine, and heat treatment was performed at 950 ° C for 100 hours under the condition that AZF was in the range of 13.6 to 15.6. did. Both catalysts thus heat-treated were installed in the exhaust passage of a vehicle equipped with a 660cc engine, and the exhaust gas amount (g / km) when running in the 10 · 15 mode was measured. The results are shown in Table 2.

[0049] [Table 2]

As is clear from the data shown in Table 1, the above tetragonal complex oxides undergo reaction 'decomposition when at least the surface layer coexists with refractory inorganic oxides composed of MgAl 2 O.

twenty four

The above-mentioned tetragonal complex oxide was able to maintain the desired catalytic performance. When coexisting with alumina, the reaction 'decomposition occurred and the catalytic activity decreased.

Claims

The scope of the claims

[1] General formula A BO (wherein A is at least one selected from the group force consisting of Ca, Sr and Ba)

twenty four

B represents a group force of Mn, Fe, Ti, Sn, and V force, and represents a tetragonal complex oxide represented by at least one surface layer composed of MgAlO.

twenty four

It consists of a refractory inorganic oxide and a noble metal component which is solidified or supported in the tetragonal composite oxide or is supported on the refractory inorganic oxide. Exhaust gas purification catalyst.

[2] The inside of the refractory inorganic oxide is alumina and the surface layer is composed of MgAl 2 O.

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The exhaust gas purifying catalyst according to claim 1, wherein V is an exhaust gas purifying catalyst.

[3] The exhaust gas according to claim 1, wherein the entire refractory inorganic oxide is composed of MgAl 2 O.

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Purification catalyst.

[4] The exhaust according to any one of claims 1 to 3, wherein the tetragonal complex oxide is Ca MnO.

twenty four

Gas purification catalyst.

[5] An exhaust gas purification catalyst comprising a carrier made of ceramics or a metal material and an exhaust gas purification catalyst layer according to any one of claims 1 to 4 supported on the carrier.

[6] a carrier made of a ceramic or metal material;

The first catalyst layer comprising the tetragonal complex oxide according to claim 1 supported on the support and a refractory inorganic oxide having at least a surface layer composed of MgAl 2

twenty four

A first catalyst layer comprising the exhaust gas purifying catalyst according to any one of claims 1 to 4;

A second catalyst layer comprising a noble metal component-supported refractory inorganic oxide supported on the first catalyst layer;

A catalyst for exhaust gas purification, characterized by

[7] a carrier made of a ceramic or metal material;

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A catalyst layer comprising two or more noble metal component-supported refractory inorganic oxides supported on the first catalyst layer; An exhaust gas purifying catalyst characterized in that the kind of noble metal component supported on each refractory inorganic oxide is different V.

8. The exhaust gas purifying catalyst according to any one of claims 1 to 7, wherein the noble metal component is rhodium, palladium or platinum.

[9] The refractory inorganic oxide is Al O, SiO, ZrO, CeO, CeO—ZrO composite oxide or

2 3 2 2 2 2 2

The exhaust gas purifier according to any one of claims 1 to 8, which is a CeO 2 -ZrO-Al 2 O composite oxide.

2 2 2 3

Catalyst.

[10] Alumina, basic magnesium carbonate and general formula A BO (where A is Ca, Sr and Ba

twenty four

A slurry containing a tetragonal complex oxide represented by (b) represents at least one selected from the group consisting of Mn, Fe, Ti, Sn and V) Is applied onto a ceramic or metal material carrier, dried and fired at 300 to 600 ° C. for 1 to 6 hours, and the noble metal component is supported by the solid solution or the noble metal component. Using a tetragonal complex oxide or calcination after immersion in an aqueous solution of a basic noble metal salt to support a predetermined amount of noble metal, followed by firing at 300 to 600 ° C A method for producing an exhaust gas purifying catalyst.

[11] MgAl O and general formula A BO where A is selected from the group consisting of Ca, Sr and Ba

2 4 2 4

A slurry containing a tetragonal complex oxide represented by at least one kind, and B represents a group force of Mn, Fe, Ti, Sn, and V force. It is coated on a carrier that also has a metallic material strength, dried, and baked at 300 to 600 ° C. for 1 to 6 hours. It is characterized by using a composite acid silicate or by immersing the calcined product after firing in an aqueous solution of a basic noble metal salt to carry a predetermined amount of noble metal and then firing at 300 to 600 ° C. A method for producing an exhaust gas purifying catalyst.