JP2000051700A - Exhaust emission purifying catalyst and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission purifying catalyst enhanced in durability as compared with a conventional catalyst and having excellent low temp. activity and purifying capacity in a wide exhaust gas compsn. atmosphere even after long use. SOLUTION: This exhaust emission purifying catalyst is a monolithic structure type catalyst having a catalyst component supporting layer containing perovskite type composite oxide represented by the formula, AxNiyOz (wherein, A is at least one element selected from a group consisting of La, Ce and Ba; (x), (y) and (z) are atomic ratios of respective elements and, when (y) is 1.0, (x) is at least 0.01 and below 0.1 and (z) is the number of oxygen atoms necessary for satisfying the valencies of respective components), alumina and palladium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst and a method for producing the same, and more particularly to a hydrocarbon (hereinafter referred to as "HC") in exhaust gas discharged from an internal combustion engine such as an automobile.
), Carbon monoxide (hereinafter referred to as “CO”) and nitrogen oxides (hereinafter referred to as “NO _x ”) can be effectively purified even at a low temperature. The present invention relates to an exhaust gas purifying catalyst having excellent catalytic activity under an atmosphere of exhaust gas composition and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, during a low temperature period from the start of an internal combustion engine until the catalyst temperature reaches a reaction temperature for exhaust gas purification, the exhaust gas purification performance is not sufficient. The development of gas purification catalysts is expected.

As such an exhaust gas purifying catalyst, for example, Japanese Patent Laid-Open Publication No. 5-305236 discloses an exhaust gas purifying catalyst in which hexaaluminate containing no noble metal is mixed and dispersed in a noble metal-supported alumina such as platinum, rhodium and palladium. Specifically, a catalyst in which a hexaaluminate composition having a certain composition and alumina supporting at least one noble metal selected from the group consisting of platinum, rhodium and palladium are mixed at a certain weight ratio It is.

[0004] Japanese Patent Application Laid-Open No. 8-323205 proposes an exhaust gas purifying catalyst containing at least palladium and metal aluminate as catalyst components.

[0005]

However, the conventional catalyst described in the above publication uses a large amount of a noble metal in order to maintain high purification performance from the initial stage to after the endurance. For this reason, as a three-way catalyst for purifying exhaust gas, a catalyst that can obtain high purification performance even when the amount of noble metal used is small is desired. However, when the amount of the noble metal is reduced, there is a problem that the durability at high temperatures is insufficient, and after the durability, the catalytic activity and purification performance in a low temperature region are deteriorated.

This is based on a stoichiometric air-fuel ratio (hereinafter referred to as "stoichiometric"), and a reducing atmosphere (hereinafter, referred to as "stoichiometric") having an insufficient oxygen concentration.
Under the exhaust gas atmosphere of automobiles whose composition changes widely from an oxidizing atmosphere (hereinafter referred to as "lean") to an oxidizing atmosphere having an excessively high oxygen concentration (hereinafter referred to as "lean"), deterioration (sintering) of noble metal species is promoted As a result, it is considered that the purification performance is reduced. In particular, when reducing the amount of precious metals,
There has been a problem that the above-mentioned effects appear remarkably and the purification performance is further reduced.

Accordingly, an object of the present invention is to provide an exhaust gas purifying catalyst which has improved durability over conventional catalysts and has excellent low-temperature activity and purifying performance even after endurance under a wide range of exhaust gas composition atmospheres. It is to provide a manufacturing method.

[0008]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, the present inventors have found that a specific perovskite-type composite oxide, alumina, and palladium are contained, and a specific composition ratio is particularly high. Activation of a noble metal by using a material in which a perovskite-type composite oxide containing at least one selected from the group consisting of lanthanum, cerium and barium and nickel is highly dispersed on alumina as a noble metal-supporting substrate Is promoted, the low-temperature activity is improved from the initial stage to after the endurance, and HC, CO, and NO _x are obtained even in the rich region where the oxygen concentration is insufficient, mainly in the stoichiometric region.
The present inventors have found that the purification rate of methane is improved, and completed the present invention.

The alumina in which the perovskite-type composite oxide is dispersed is prepared by a specific production method.
By supporting the noble metal on alumina in which the perovskite-type composite oxide is dispersed, excellent structural stability at high temperatures,
In addition, they have found that the noble metal is also excellent in promoting the activation, and arrived at the present invention.

That is, the exhaust gas purifying catalyst according to claim 1 is an integrated catalyst having a catalyst component supporting layer,
A _x Ni _y O _z (where A is at least one element selected from the group consisting of La, Ce and Ba, and x, y and z are atomic ratios of each element as a catalyst component) Where y = 1.0, x = 0.01 or more and less than 0.1, and z is the number of oxygen atoms necessary to satisfy the valence of each component described above.) It is characterized by containing an oxide, alumina, and palladium.

According to a second aspect of the present invention, in the exhaust gas purifying catalyst according to the first aspect, the perovskite-type composite oxide is highly dispersed on alumina, and
The mixing ratio between the perovskite-type composite oxide and alumina is such that the molar ratio of Ni in the perovskite-type composite oxide to Al in alumina is Ni / Al = 0.15 to 1.0.

According to a third aspect of the present invention, there is provided an exhaust gas purifying catalyst according to the second aspect, wherein palladium is supported on alumina in which a perovskite-type composite oxide is highly dispersed. .

[0013] The exhaust gas purifying catalyst according to claim 4 is the same as the exhaust gas purifying catalyst according to any one of claims 1 to 3,
Further, one kind selected from the group consisting of an alkali metal and an alkaline earth metal is contained.

According to a fifth aspect of the present invention, there is provided a method for producing an exhaust gas purifying catalyst according to any one of the first to third aspects. After dispersing perovskite-type composite oxide and fine-particle alumina hydrate colloid in water, removing water, drying and calcining, the obtained alumina powder in which the perovskite-type composite oxide is dispersed, palladium Is carried.

According to a sixth aspect of the present invention, there is provided a method for producing an exhaust gas purifying catalyst according to any one of the first to third aspects. After dispersing perovskite-type composite oxide and fine-particle alumina hydrate colloid in water, ammonia water,
At least one aqueous solution selected from the group consisting of ammonium carbonate and ammonium bicarbonate is added, and the pH is adjusted to be in a range of 7.0 to 9.0. Then, moisture is removed, dried, and calcined. Palladium is supported on the alumina powder in which the obtained perovskite-type composite oxide is dispersed.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In order to increase the structural stability and surface area of an exhaust gas purifying catalyst of the present invention at high temperatures, the catalyst component supporting layer has the following general formula A _x Ni _y O _z (where A is Is at least one element selected from the group consisting of La, Ce and Ba, x, y and z indicate the atomic ratio of each element, and when y = 1.0, x = 0.01 or more. Is less than 1, and z is the number of oxygen atoms necessary to satisfy the valence of each of the above components).

In the above perovskite-type composite oxide, when y = 1.0 and x is less than 0.01, the effect of suppressing sintering of noble metals by lanthanum, cerium and barium elements is small, and a sufficient improvement effect can be obtained. Without
It is no different from a catalyst composed of powder obtained by impregnating and supporting nickel on alumina and palladium.

On the other hand, if x exceeds 0.1, physical properties such as BET specific surface area and thermal stability of a powder obtained by dispersing a perovskite-type composite oxide in alumina are deteriorated. , Sufficient performance can not be obtained in the early stage, or sintering of precious metal during durability,
Conversely, the performance after durability deteriorates.

As described above, by using a perovskite-type composite oxide having a specific composition ratio, sintering of a noble metal during durability is suppressed, performance after durability is improved, and
The lattice oxygen and the adsorbed oxygen in the oxide are easily transferred and released, and the catalytic performance such as low-temperature activity is improved.

Further, the above-mentioned perovskite-type composite oxide is highly dispersed on alumina, and the mixing ratio thereof is such that the molar ratio of Ni in the perovskite-type composite oxide to Al in alumina is Ni / Al = 0.15. It is preferably 1.0.

As described above, since the perovskite-type composite oxide is highly dispersed and coated on the alumina, the dispersibility of the perovskite-type composite oxide is improved, so that the contact between the palladium and the perovskite-type composite oxide is increased. . Therefore, the lattice enzyme and the adsorbed oxygen in the oxide are easily transferred and released, and the catalytic performance such as low-temperature activity is improved. In addition, since the perovskite-type composite oxide and the palladium catalyst are dense, the durability is also improved.

If Ni / Al is less than 0.15, the above-mentioned effect of the perovskite-type composite oxide cannot be obtained, which is the same as that obtained by supporting palladium on alumina. Also, Ni / A
When the l ratio exceeds 1.0, physical properties such as BET specific surface area and thermal stability of a powder obtained by dispersing a perovskite-type composite oxide in alumina are deteriorated. Performance cannot be obtained, or sintering of precious metals is promoted during durability, and conversely, performance after durability deteriorates.

Each of the constituent elements of the composite compound exerts the above-mentioned effects to the maximum when all of them contained in the catalyst are complexed, but when at least a part thereof can form a complex. However, the above effect can be sufficiently obtained.

Each constituent element of the composite compound can exist as a composite oxide instead of being separated as a separate oxide after heat endurance, which can be confirmed by, for example, X-ray diffraction measurement. .

Each of the constituent elements of the composite compound may contain a trace amount of impurities as long as it does not interfere with the above action. For example, strontium contained in barium and cerium, neodymium, samarium contained in lanthanum. And hafnium and sulfur contained in zirconium.

More preferably, palladium is carried on alumina in which the perovskite-type composite oxide is highly dispersed. In this way, palladium can come into close contact with the perovskite-type composite oxide, which facilitates the movement and release of lattice oxygen in the oxide and adsorbed oxygen on the surface, resulting in low-temperature activity and purification performance in an oxygen atmosphere. And the like.

The content of the palladium is 0.01 to 10 g / L in 1 L of the catalyst. If the amount is less than 0.01 g, the low-temperature activity and the purification performance are not sufficiently exhibited. Conversely, if the amount exceeds 10 g, the dispersibility of palladium deteriorates, the catalyst performance is not significantly improved, and it is not economically effective.

In order to ensure the dispersibility of the perovskite-type composite oxide and the palladium after endurance, the base material for supporting the perovskite-type composite oxide is
A heat-resistant inorganic material having a large specific surface area is suitable, and alumina, particularly activated alumina is desirable. Alumina to which a rare earth element, zirconia, or the like is added to increase the heat resistant specific surface area may be used.

The perovskite-type composite oxide used in the present invention is obtained by mixing nitrates, acetates, carbonates, citric acids, hydrochlorides, etc. of the respective constituent elements of the composite oxide in a desired composition ratio of the composite oxide. After calcination, pulverization, solid-phase reaction of heat treatment and calcination, nitrate, acetate,
Carbonates, citrates and the like are mixed in a desired composite oxide composition ratio and dissolved in water.If necessary, an alkaline solution such as NH ₄ OH or NH ₃ CO _{3 is} added dropwise to precipitate the solution. It can be adjusted by a coprecipitation method in which the precipitate is formed, filtered, dried and calcined, whereby a crystal structure having a uniform composition ratio can be obtained. However, the method is not limited to these methods, and any method other than the above may be used as long as the composite oxide is formed.

According to such a method, at least a part of each part constituting the composite oxide can be composited.

As described above, the raw material for preparing the catalyst of the composite oxide used in the present invention may contain a trace amount of impurities as long as the amount does not interfere with the above-mentioned effects. For example, strontium and lanthanum contained in barium may be contained. Cerium, neodymium, samarium and hafnium and sulfur contained in zirconium contained therein.

After the perovskite-type composite oxide thus obtained and fine-particle alumina hydrate Colorado (hereinafter referred to as “alumina sol”) are decomposed into water, the water is removed and the residue is dried. After firing, an alumina powder in which the perovskite-type composite oxide is dispersed can be obtained.

By using alumina sol as the aluminum raw material compound, the uniformity of the crystal structure and the heat resistance can be further improved as compared with those prepared using a water-soluble salt of aluminum, and the perovskite-type composite oxide is highly dispersed and supported. Specific surface area can be sufficiently secured. Therefore, the palladium and the active phase can be brought into more intimate contact with each other, so that the activation promoting action of the palladium is increased, and the low-temperature activity and purification performance of the exhaust gas purification catalyst are improved.

Another method for obtaining an alumina powder in which a perovskite-type composite oxide is dispersed is to disperse a perovskite-type composite oxide and an alumina sol in water, and then use ammonia water, ammonium carbonate and ammonium carbonate as precipitants. After gradually adding at least one aqueous solution selected from the group consisting of and adjusting the pH to be in the range of 7.0 to 9.0, the water is removed, the residue is dried, and then calcined. There is a way to get it.

By using the above-mentioned alumina sol as an aluminum raw material compound and producing it by the above-described precipitation method, a fine pore structure and a large specific surface of alumina can be obtained, and the active phase of perovskite-type composite oxide can be obtained. Is obtained, whereby the activation promoting action of palladium can be effectively exhibited.

The alumina sol has a colloid of 5 μm
Use of an alumina sol whose pH is adjusted to 2.0 to 7.0 in order to obtain a stable colloidal state having a size of about 200 μm improves the uniformity of the crystal structure and heat resistance, and activates palladium. It is preferable from the viewpoint of improving the action of promoting the action.

The method for preparing the alumina powder in which the perovskite-type composite oxide is dispersed is not limited to a special method, and may be any of known methods such as evaporation to dryness, precipitation, impregnation, and the like, unless the components are significantly unevenly distributed. It can be appropriately selected from various methods and used, but after dispersing the raw material of each of the above elements in water, in particular, ammonia water, at least one selected from the group consisting of ammonium carbonate and ammonium hydrogen carbonate The use of a precipitation method in which an aqueous solution of the compound of formula (1) is added as a precipitant makes it possible to obtain a sufficient BE of the alumina-based composite oxide.
It is preferable to ensure uniformity of the T specific surface area and the crystal structure, and to uniformly disperse the perovskite-type composite oxide and palladium.

If the above-mentioned aqueous ammonia or ammonium compound is used as a precipitant for the precipitation method, no metal element remains even if the precipitation cake is insufficiently cleaned, and an ammonium compound (mainly ammonium nitrate after dropping) is used.
Can be easily decomposed and removed in the subsequent firing. Furthermore, since alumina sol is used in place of ammonium nitrate, when drying and firing the precipitate, N
Exhaust gas or waste water treatment for the O _X or ammonium nitrate is significantly reduced.

In carrying out the above precipitation method, the p
By adjusting H in the range of 7.0 to 9.0, precipitates of various metal salts can be formed. pH is 7.0
If it is lower, a precipitate does not sufficiently form, and conversely, the pH is 9.0
If it is higher, some of the precipitated components may be redissolved.

The removal of water can be appropriately selected from known methods such as a filtration method, an evaporation to dryness method and a spray drying method. In the present invention, although not particularly limited, it is desirable to use a spray dryer in order to obtain a large specific surface area for improving the dispersibility of palladium. The first heat treatment for obtaining alumina in which the perovskite-type composite oxide is dispersed is not particularly limited, but is preferably performed, for example, in a temperature range of 700 to 1200 ° C. under air and / or air flow.

The starting palladium compounds used in the present invention include inorganic acid salts, carbonates, ammonium salts, organic acid salts,
Although halides, oxides, sodium salts, ammine complex compounds and the like can be used in combination, it is particularly preferable to use water-soluble salts from the viewpoint of improving the catalyst performance. The method for supporting palladium is not limited to a special method, and various methods such as a well-known evaporation and drying method, a precipitation method, an impregnation method, and an ion exchange method can be used as long as there is no significant uneven distribution of components. In particular, the impregnation method is preferable for supporting on alumina, from the viewpoint of increasing dispersibility.

In the case of the ion exchange method or the impregnation method, since the metal raw material is often used in a solution, the pH can be adjusted by adding an acid or a base to the solution. pH
By adjusting the value, it is possible that the particles can be further highly dispersed and supported.

The heat treatment of the alumina in which the perovskite-type composite oxide carrying palladium of the present invention is dispersed is not particularly limited, but after impregnation and drying, for example, at 400 ° C. to 7 ° C.
It is preferable to carry out at a temperature in the range of 00 ° C. in the air and / or under an air stream.

The catalyst of the present invention is preferably used by being supported on a monolithic carrier. The composite oxide and the noble metal-supported inorganic carrier are pulverized into a slurry, and the slurry is coated on the catalyst carrier.
By firing at a temperature of 400 to 900 ° C., the exhaust gas purifying catalyst of the present invention can be obtained.

The pulverization method for pulverizing the composite oxide and the noble metal-carrying inorganic carrier is not particularly limited. Preferably, an aqueous slurry containing these is wet-pulverized to adjust the average particle size to 4 μm or less. Can be used.

The apparatus that can be used for pulverization is not particularly limited, and a commercially available ball-type vibrating mill can be used. The ball diameter, the pulverizing time, the amplitude, and the vibration frequency are adjusted to obtain a desired particle size.

The catalyst carrier can be appropriately selected from known catalyst carriers, and includes, for example, a honeycomb carrier and a metal carrier having a monolith structure made of a refractory material.

Although the shape of the catalyst carrier is not particularly limited, it is usually preferable to use a honeycomb shape. As the honeycomb material, for example, cordierite materials such as ceramics are generally used. It is also possible to use a honeycomb made of a metal material such as stainless steel, and further, the catalyst powder itself may be formed into a honeycomb shape. By making the shape of the catalyst into a honeycomb shape, the area of the catalyst and the exhaust gas becomes large, and the pressure loss is suppressed, which is extremely advantageous when the catalyst is used for an automobile or the like.

More preferably, the obtained catalyst for purifying exhaust gas is impregnated and supported with an alkali metal and / or an alkaline earth metal. By supporting an alkali metal and / or an alkaline earth metal, effects of alleviating adsorption poisoning of hydrocarbons and suppressing sintering of palladium can be obtained. The usable alkali metal and alkaline earth metal are at least one element selected from the group consisting of sodium, potassium, cesium, magnesium, calcium, strontium and barium.

The alkali metal and alkaline earth metal compounds which can be used include oxides, acetates, hydroxides, nitrates,
It is water-soluble such as carbonate. This makes it possible to carry a basic element, an alkali metal and / or an alkaline earth metal, in the vicinity of palladium with good dispersibility. At this time, the starting compounds of the alkali metal and the alkaline earth metal may be contained simultaneously or separately.

That is, an aqueous solution of a powder comprising an alkali metal compound and / or an alkaline earth metal compound is contained in the above-mentioned catalyst supporting a washcoat component, dried, and then dried in air and / or under a stream of air. ° C to 600
It is baked at ℃. This is because if the alkali metal and alkaline earth metal raw materials are once heat-treated at a low temperature to be contained in the coat layer in the form of an oxide, it becomes difficult to form a composite compound even when exposed later at a high temperature. If the calcination temperature is less than 200 ° C., the alkali metal compound and the alkaline earth metal compound cannot be sufficiently formed into an oxide form. Conversely, if the calcination temperature exceeds 600 ° C., the raw materials are rapidly decomposed and the carrier is cracked. It is not preferable because it may be caused.

The shape of the catalyst carrier is not particularly limited, but usually it is preferable to use it in a honeycomb shape, and the catalyst carrier is used by applying a catalyst powder to various honeycomb-shaped substrates.
As the honeycomb material, cordierite materials such as ceramics are generally used in general, but it is also possible to use many honeycomb materials made of a metal material such as ferrite stainless steel, and further, the catalyst powder itself is formed into a honeycomb shape. May be. By making the shape of the catalyst into a honeycomb shape, the catalyst area of the catalyst and the exhaust gas is increased, and the pressure loss can be suppressed, so that it is extremely effective when used as an exhaust gas purifying catalyst for automobiles.

The amount of the catalyst component coat layer to be attached to the honeycomb material is determined as follows:
50-400 g is preferred. The larger the amount of the catalyst component, the better in terms of catalytic activity and catalyst life. However, if the coating layer is too thick, the reaction gas such as HC, CO, NO, etc. becomes poorly diffused. No longer, the effect of increasing the amount of activity is saturated, and the gas passage resistance is increased. Therefore, the amount of the coat layer is preferably 50 g to 400 g per liter of the catalyst.

[0054]

EXAMPLES The present invention will be described with reference to the following adjustment examples, examples and comparative examples. Preparation Example 1 21.7 g of lanthanum nitrate and 290.8 g of nickel nitrate were dissolved in 1000 g of pure water, and the pH was adjusted to 8.0 by adding 5% aqueous ammonia with stirring. Add this solution to 150
After boiling at ℃ for 4 hours, dry with a spray dryer,
400 ° C for 2 hours, 600 ° C for 2 hours, then 800 ° C
For 4 hours to obtain La _0.05 NiO _x (x is the number of oxygen atoms necessary for adding the valence of each component described above). The obtained La _0.05 NiO _x powder was converted to alumina (A1
₂ 0 ₃₎ was added to 10 wt% of alumina sol 2039g suspension dispersed in pure water 2500g in terms of stirring 5% ammonia water was added, the pH was adjusted to 8.0. The solution was boiled at 150 ° C. for 4 hours, dried with a spray dryer, and dried at 400 ° C. for 2 hours and at 600 ° C. for 2 hours.
And then calcined at 800 ° C. for 4 hours, La _0.05 NiO
_x / A1 ₂ O ₃ was obtained.

[0055] except that the Preparation Example 2 lanthanum nitrate was 4.3g, the same procedure as Preparation Example 1 to obtain a _{La 0.01 NiO x / A1 2 O} 3.

Preparation Example 3 La _0.09 NiO _x / A1 ₂ O ₃ was obtained in the same manner as in Preparation Example 1, except that the amount of lanthanum nitrate was changed to 39.0 g.

Preparation Example 4 In the same manner as in Preparation Example 1 except that 19.4 g of cerium nitrate was used instead of lanthanum nitrate, Ce _0.05 NiO _x /
Al ₂ O was obtained.

Preparation Example 5 In the same manner as in Preparation Example 1 except that 13.1 g of barium nitrate was used instead of lanthanum nitrate, Ba _0.05 NiO _x /
al ₂ O was obtained.

Preparation Example 6 21.7 g of lanthanum nitrate and 290.8 g of nickel nitrate were dissolved in 1000 g of pure water, and the pH was adjusted to 8.0 by adding 5% aqueous ammonia with stirring. Add this solution to 150
After boiling at ℃ for 4 hours, dry with a spray dryer,
400 ° C for 2 hours, 600 ° C for 2 hours, then 800 ° C
For 4 hours to obtain La _0.05 NiO _x (x is the number of oxygen atoms required to satisfy the valence of each of the above components). The obtained La _0.05 NiO _x powder was converted to alumina (A1
2039 g of alumina sol of 10% by weight in terms of ₂ O ₃ ) was dispersed in 2500 g of pure water and added to the suspension. After stirring for 60 minutes, the solution was boiled at 150 ° C. for 4 hours, and dried by a spray drier. 60 hours at 4000 ° C for 2 hours
Baking at 0 ° C. for 2 hours, then at 800 ° C. for 4 hours, La
Was obtained _{0.05 NiO x / A1 2 0 3} .

[0060] The addition of the Comparative Preparation Example 1 lanthanum nitrate was 2.2g in the same manner as in Preparation Example 1 to obtain a _{La 0.005 NiO x / A1 2 0} 3.

[0061] except that the Comparative Preparation Example 2 86.8 g of lanthanum nitrate in the same manner as in Preparation Example 1 to obtain a _{La 0.2 NiO x / A1 2 0} .

Comparative Adjustment Example 3 La _0.05 NiO _x / A1 ₂ was prepared in the same manner as in Adjustment Example 1, except that the alumina sol was 5098 g and the pure water to which the La _0.05 NiO _x powder and the alumina sol were added was 5000 g.
0 ₃ was obtained.

[0063] except that the 509.8g Comparative Preparation Example 4 Alumina sol in the same manner as in Preparation Example 1 to obtain a _{La 0.05 NiO x / A1 2 0} 3.

[0064] After the suspension is dispersed in Comparative Preparation Example 5 Alumina (A1 ₂ 0 ₃₎ Pure water 20 wt% alumina sol 1700g in terms of 2500 g, while stirring the 5% ammonia water was added, the pH 8 Was adjusted to 0.0. After boiling for 4 hours at a solution 0.99 ° C., dried in a spray drier, 2 hours at 4000 ° C., 2 hours at 600 ° C., and then calcined 4 hours at 800 ° C., to obtain a A1 ₂ 0 _3.

Comparative Preparation Example 6 21.7 g of lanthanum nitrate and 290.8 g of nickel nitrate were dissolved in 1000 g of pure water, and the pH was adjusted to 8.0 by adding 5% aqueous ammonia with stirring. Add this solution to 150
After boiling at ℃ for 4 hours, dry with a spray dryer,
400 ° C for 2 hours, 600 ° C for 2 hours, then 800 ° C
For 4 hours to obtain La _0.05 NiO _x (x is the number of oxygen atoms required to add the valence of each component described above).

[0066] _{La 0.05 NiO x / A1 2 0} 1.0 Palladium ₃ wt% on the powder obtained in Example 1 Preparation Example 1 (Powder A) 692 g
And cerium oxide powder containing 1 mol% of lanthanum ( ₂ % by weight in terms of La ₂ O ₃ ) and 32 mol% of zirconium (25% by weight in terms of ZrO ₂ ).
480 g of a powder (powder B) supporting 75 g by weight and 1200 g of a nitric acid aqueous solution were charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite-based monolithic carrier (1.3 L, 400 cells), baked at 400 ° C. for 1 hour, and a coat layer weight of 160 g /
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained. Then, after attaching the barium acetate solution to the catalyst component-carrying cordierite-based monolithic carrier,
It was calcined at 400 ° C. for 1 hour and contained 15 g / L of BaO.

[0067] Example 2 except for using _{La 0.01 NiO x / A1 2 O} 3 obtained in Preparation Example 2, coated layer weight in the same manner as in Example 1 160 g /
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained. Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour.
It contained 15 g / L of aO.

[0068] Example 3 except for using _{La 0.09 NiO x / Al 2 0} 3 obtained in Preparation Example 3, the coating layer weight in the same manner as in Example 1 160 g /
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained. Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour.
It contained 15 g / L of aO.

[0069] Example 4 except for using _{Ce 0.05 NiO x / A1 2 0} 3 obtained in Preparation Example 4, the same procedure as in Example 1 coated layer weight 160 g /
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained. Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour.
a015 g / L.

[0070] Example 5 except for using _{Ba 0.05 NiO x / A1 2 0} 3 obtained in Preparation Example 5, Example 1 coating layer weight in the same manner as 160 g /
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained. Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour.
a015 g / L.

[0071] Example 6 except for using _{La 0.05 NiO x / A1 2 0} 3 obtained in Preparation Example 6, Example 1 coating layer weight in the same manner as 160 g /
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained. Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour.
a015 g / L.

[0072] except for using _{La 0.005 NiO x / A1 2 0} 3 Comparative Example 1 Comparative Preparation Example 1, the same way coated layer weight 160g Example 1
/ L, palladium carrying amount 40 g / cf (1.42 g /
The catalyst of L) was obtained. Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour to contain Ba015 g / L.

[0073] Comparative Example 2 except for using _{La 0.2 NiO x / A1 2 0} 3 of Comparative Preparation Example 2, Example 1 coating layer weight in the same manner as 160 g /
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained. Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour.
a015 g / L.

[0074] except for using _{La 0.05 NiO x / A1 2 0} 3 Comparative Example 3 Comparative Example 3, the coating layer weight in the same manner as in Example 1 160 g / L,
A catalyst having a palladium loading of 40 g / cf (1.42 g / L) was obtained. Next, after a barium acetate solution was applied in the same manner as in Example 1, the barium acetate solution was baked at 400 ° C. for 1 hour to obtain Ba0.
It contained 15 g / L.

[0075] Comparative Example 4 except for using the comparative example of adjusting _{La 0.05 NiO x / A1 2 0} 3, coating layer weight in the same manner as in Example 1 160 g /
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained. Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour.
a015 g / L.

[0076] catalyst except for using the A1 ₂ 0 ₃ Comparative Example 5 Comparative Preparation Example 5, coating layer weight 160 g / L in the same manner as in Example 1, palladium weight 40g / cf (1.42g / L) I got Next, a barium acetate solution was applied in the same manner as in Example 1 and then calcined at 400 ° C. for 1 hour to contain Ba015 g / L.

Comparative Example 6 A catalyst having a coat layer weight of 160 g / L and a palladium carrying amount of 40 g / cf (1.42 g / L) was prepared in the same manner as in Example 1 except that La _0.05 NiO _x of Comparative Adjustment Example 6 was used. I got Next, a barium acetate solution was applied in the same manner as in Example 1 and calcined at 400 ° C. for 1 hour to obtain Ba015 g
/ L.

Table 1 shows the catalyst compositions of the exhaust gas purifying catalysts obtained in Examples 1 to 6 and Comparative Examples 1 to 6.

[0079]

[Table 1] Test Examples The exhaust gas purifying catalysts obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were subjected to durability under the following durability conditions, and then were evaluated for catalytic activity under the following evaluation conditions.

[0080]

Evaluation condition 1: Low-temperature active engine displacement 2000 cc fuel Unleaded gasoline Heating rate 10 ° C./min Measurement temperature range 150-500 ° C. The low-temperature activity of each exhaust gas purifying catalyst after endurance was determined by HC, C
The temperature at which the conversion of O and NOx reaches 50%
0 / ° C.), and the results are shown in Table 2.

[0082] The purifying performance of each exhaust gas purifying catalyst after the endurance was determined as the average conversion (%) of HC, CO and NOx in the stoichiometric atmosphere by the following equations (1 to 3), and the results are shown in Table 2.

[0083]

(Equation 1)

[0084]

(Equation 2)

[0085]

(Equation 3)

[0086]

[Table 2]

[0087]

The exhaust gas purifying catalyst of the present invention has excellent durability at high temperatures, suppresses sintering of noble metal species, has a uniform crystal structure, improves structural stability at high temperatures, and has an active phase. Of the noble metal can be enhanced to enhance the dispersion promoting state of the noble metal. Therefore, the durability is improved as compared with the conventional catalyst, and the catalyst has excellent low-temperature activity and purification performance even after durability under a wide range of exhaust gas composition atmospheres.

Further, according to the method for producing an exhaust gas purifying catalyst of the present invention, the exhaust gas purifying catalyst of the present invention has a large specific surface area, has a fine pore structure, and can carry a supporting material in a highly dispersed state. Can be manufactured efficiently.

Continued on front page F-term (reference) 3G091 AA17 AB01 AB03 BA02 BA03 BA11 BA14 BA15 BA19 BA38 BA39 FA02 FA04 FB02 FB03 FB10 FB11 FB12 FC07 FC08 GA06 GB01W GB01X GB02W GB03W GB04W GB05W GB07W GB10W GB13W GB15W AGB18A GBA BA03X BA03Y BA10Y BA15X BA15Y BA18X BA18Y BA19X BA19Y BA31X BA31Y BA38X BA38Y BB02 CC39 4G069 AA01 AA03 AA08 AA09 AA12 BA01A BA01B BA01C BA13B BA37 BB06A BB06B BB06BBC BCBC BCA BCBC BC BC BC BC BC FA02 FB06 FB30 FC02 FC08 FC09

Claims (6)

[Claims] An integrated catalyst having a catalyst component-supporting layer, wherein the catalyst component is represented by the following general formula: A _x Ni _y O _z (where A is selected from the group consisting of La, Ce and Ba) X, y and z indicate the atomic ratio of each element. When y = 1.0, x = 0.01 or more and less than 0.1, and z denotes the valence of each of the above components. An exhaust gas purifying catalyst comprising: a perovskite-type composite oxide represented by the following formula: (a number of oxygen atoms required to satisfy the above), alumina, and palladium. 2. The exhaust gas purifying catalyst according to claim 1, wherein the perovskite-type composite oxide is highly dispersed on alumina, and a mixing ratio between the perovskite-type composite oxide and alumina is perovskite-type composite oxide. N in things
i / Al in alumina is molar ratio of Ni / Al = 0.15
A catalyst for purifying exhaust gas, characterized by being in the range of 1.0 to 1.0. 3. The exhaust gas purifying catalyst according to claim 2, wherein palladium is carried on alumina in which a perovskite-type composite oxide is highly dispersed. 4. The exhaust gas purifying catalyst according to claim 1, further comprising one selected from the group consisting of an alkali metal and an alkaline earth metal. Purification catalyst. 5. In producing the catalyst according to any one of claims 1 to 3, the perovskite-type composite oxide according to any one of claims 1 to 3 and a fine particle alumina hydrate colloid are dissolved in water. After dispersing, remove water and dry,
A method for producing an exhaust gas purifying catalyst, characterized in that palladium is supported on alumina powder in which a perovskite-type composite oxide obtained by calcining is dispersed. 6. A perovskite-type composite oxide according to any one of claims 1 to 3, and a particulate alumina hydrate colloid for producing the exhaust gas purifying catalyst according to any one of claims 1 to 3. Is dispersed in water, and at least one aqueous solution selected from the group consisting of aqueous ammonia, ammonium carbonate and ammonium hydrogen carbonate is added, and p is added.
After adjusting H to be in the range of 7.0 to 9.0, removing water, drying and calcining, and supporting palladium on the obtained alumina powder in which the perovskite-type composite oxide is dispersed. A method for producing an exhaust gas purifying catalyst, comprising: