JPH1190228A - Catalytic material for purifying exhaust gas, its production and catalyst for purifying exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for purifying exhaust gas in which low- temperature activity is enhanced during the period from the early stage to full operation after durableness and the purification rate of HC, CO, NOx is enhanced even in such the reduction atmosphere that the concentration of oxygen is insufficient while keeping a theoretical air-fuel ratio as a center. SOLUTION: The catalytic material for purifying exhaust gas contains alumina-based compound oxide incorporating nickel and cerium. Alumina-based compound oxide is shown in the following general formula. [X]a [Y]b Alc Od (in formula, X is cerium element, Y is nickel element and (a), (b), (c) and (d) show atomic ratio of each element. At time when (c) is 2.0, (a) is 0.01-0.10, (b) is 0.1-0.7, (d) is number of oxygen atoms necessary for satisfying valency of the above-mentioned each component.) The catalyst for purifying exhaust gas is constituted by carrying noble metal on the catalytic material for purifying exhaust gas.

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 material, a method for producing the same, and an exhaust gas purifying catalyst, and more particularly to an exhaust gas purifying catalyst containing an alumina-based composite oxide containing nickel and cerium at a fixed composition ratio. The present invention relates to a catalyst material, a method for producing the same, and an exhaust gas purifying catalyst.

[0002]

2. Description of the Related Art Conventionally, activated alumina, cerium oxide and the like have been used as a base material for supporting a noble metal which is a catalyst for purifying exhaust gas. As a method for producing an alumina-based composite oxide containing cerium and nickel, an impregnation method in which an aqueous solution of cerium is contained in nickel aluminate, and a kneading method in which a water-soluble salt of cerium and nickel aluminate are mixed are used. ing.

As this type of exhaust gas purifying catalyst, for example, Japanese Patent Application Laid-Open No. 5-305236 discloses that a noble metal-free hexaaluminate composition represented by a predetermined formula is supported on a noble metal such as platinum, rhodium or palladium. Discloses an exhaust gas purifying catalyst mixed and dispersed in alumina. More specifically, it is a mixture of a hexaaluminate composition having a fixed composition and alumina supporting at least one noble metal selected from the group consisting of platinum, rhodium and palladium at a fixed weight ratio.

JP-A-6-378 discloses a group consisting of activated alumina and cerium oxide, at least one of platinum and palladium as catalyst components, and potassium, cesium, strontium and barium as basic elements. There has been proposed an exhaust gas purifying catalyst supporting at least one metal oxide selected from the group consisting of:

The exhaust gas purifying catalysts include those conventionally used as catalyst components such as platinum group elements, activated alumina and cerium oxide, as well as basic compounds such as potassium compounds, cesium compounds, strontium compounds and barium compounds. At least one of them.

[0006]

However, when cerium is added to the alumina-based composite oxide by the impregnation method or the kneading method, the distribution of cerium becomes uneven, and the surface of the alumina-based composite oxide is coated. There has been a problem that the function of the NOx adsorption activation point, which plays a cocatalyst effect on noble metals, particularly palladium, is deteriorated.

[0007]

The object of the present invention is to improve the low-temperature activity from the initial stage to the end of durability when used as a support substrate for a noble metal, and to reduce the oxygen concentration around the stoichiometric air-fuel ratio (hereinafter referred to as "stoichiometric"). It is an object of the present invention to provide an exhaust gas purifying catalyst capable of improving the purification rate of HC, CO, and NOx even in an insufficient reducing atmosphere (hereinafter, referred to as "rich").

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that an alumina-based composite oxide containing nickel and cerium at a fixed composition ratio is used as a base material for supporting a noble metal. When used, the activation of precious metals is promoted, and the low-temperature activity is improved from the initial stage to after endurance,
Further, it has been found that the purification rate of HC, CO, and NOx is improved even in a rich region where the oxygen concentration is insufficient, mainly in the stoichiometric region.

Further, in producing this alumina-based composite oxide, a fine particle alumina hydrate colloid (alumina sol) and a water-soluble salt of nickel and cerium are dissolved or dispersed in water, and then ammonia water, ammonium carbonate, carbonate At least one aqueous solution selected from the group consisting of ammonium hydrogen, ammonium sulfate, and ammonium hydrogen sulfate was added, and after drying after removing water, calcined, nickel and cerium had very high dispersion. The present invention has been found to be in a state of being excellent in structural stability at high temperatures and also excellent in promoting the activation of the above-mentioned noble metal.

That is, the exhaust gas purifying catalyst material according to the present invention contains an alumina-based composite oxide containing nickel and cerium, as described in claim 1.
The alumina-based composite oxide is represented by the following general formula: [X] _a [Y] _b Al _c O _d (where X is a cerium element, Y is a nickel element, and a, b, c and d Represents the atomic ratio of each element, and when c = 2.0, a = 0.01 or more and less than 0.10;
b = 0.1 or more and 0.7 or less, and d is the number of oxygen atoms required to satisfy the valence of each of the above components. ) Is an alumina-based composite oxide.

[0011] Further, according to a second aspect of the present invention, there is provided a method for producing an exhaust gas purifying catalyst material, which comprises producing an alumina-based composite oxide according to the first aspect.
After dissolving or dispersing a water-soluble salt of at least one element selected from the group consisting of cobalt, nickel, zinc and cerium in fine-particle alumina hydrate colloid (hereinafter referred to as “alumina sol”) At least one aqueous solution selected from the group consisting of ammonia water, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate, and ammonium hydrogen sulfate is added, the water is removed, dried, and fired.

[0012] In an embodiment of the method for producing a catalyst material for purifying exhaust gas according to the present invention, as described in claim 3, the fine particle alumina hydrate colloid comprises cobalt, nickel, zinc and cerium. After dissolving or dispersing a water-soluble salt of at least one element selected from the group consisting of ammonia water, ammonium carbonate,
At least one aqueous solution selected from the group consisting of ammonium bicarbonate, ammonium sulfate and ammonium hydrogen sulfate is added, the pH is adjusted to be in the range of 7.0 to 9.0, and the mixed solution is further mixed with 100 to 300. Heat treatment (boiling) at 0 ° C., drying after removing water, and baking.

According to a fourth aspect of the present invention, there is provided an exhaust gas purifying catalyst comprising an alumina-based composite oxide according to the first aspect and palladium supported thereon. .

Further, in the embodiment of the exhaust gas purifying catalyst according to the present invention, as described in claim 5, 30 to 80% by weight of the total palladium amount in terms of metal.
Can be contained in the alumina-based composite oxide according to the first aspect.

Similarly, in an embodiment of the exhaust gas purifying catalyst according to the present invention, the exhaust gas purifying catalyst is further selected from the group consisting of alkali metals and alkaline earth metals. At least one kind may be contained.

[0016]

As described above, the catalyst material for purifying exhaust gas according to the present invention contains an alumina-based composite oxide containing nickel and cerium, and the structural stability of the alumina-based composite oxide at high temperatures is high. In order to increase the properties and the specific surface area, the following general formula: [X] _a [Y] _b Al _C O _d (where X is a cerium element, Y is a nickel element, a, b, c and d represents an atomic ratio of each element, and when c = 2.0, a = 0.01 or more and less than 0.10;
b = 0.1 or more and 0.7 or less, and d is the number of oxygen atoms required to satisfy the valence of each of the above components. ) Is an alumina-based composite oxide.

Thus, in the above general formula, when c = 2.0, a = 0.01 to less than 0.10 and b = 0.1 to 0.7 in the above general formula. Preferably, in this case, a = 0.01
If it is less than 1, the effect of the cerium element added to the alumina-based composite oxide is small, and a sufficient improvement effect cannot be obtained, which tends to be the same as that of nickel aluminate. Further, when a = 0.10 or more, physical properties of the alumina-based composite oxide such as BET specific surface area and thermal stability are reduced, so that noble metal dispersibility is poor and sufficient performance cannot be obtained in the initial stage. However, it is not preferable because sintering of the noble metal is promoted during the running, and the performance after the running tends to deteriorate.

On the other hand, when b is less than 0.1, the effect of the nickel element added to the alumina-based composite oxide is small, and the NOx adsorption activation point which acts as a co-catalyst for noble metals, particularly, palladium is used. Is not preferred because it cannot be obtained.
Further, when b exceeds 0.7, the BET specific surface area is reduced, so that the dispersibility of the noble metal is poor, and sufficient performance cannot be obtained at the initial stage, or sintering of the noble metal is promoted during the running, and after the running, Is not preferred because the performance of the device deteriorates.

When producing such an alumina-based composite oxide, fine-grain alumina water is used in order to further improve the thermal stability of the crystal structure at a high temperature and the effect of promoting the activation of the noble metal in the stoichiometric and rich regions. After dissolving or dispersing a water-soluble salt of at least one element selected from the group consisting of cobalt, nickel, zinc and cerium in water colloid (alumina sol), aqueous ammonia, ammonium carbonate, ammonium hydrogen carbonate At least one aqueous solution selected from the group consisting of ammonium sulfate, ammonium sulfate and ammonium hydrogen sulfate is added, water is removed, dried, and then calcined.

If necessary, when producing the above alumina-based composite oxide, more preferably 5 to 2
Alumina sol whose pH is adjusted to 2.0 to 7.0 in order to keep the alumina hydrate having a colloidal size of 00 μm in a stable colloidal state, and nitrates, carbonates and ammoniums of cobalt, nickel, zinc and cerium Salts, acetates and other salts can be produced in any combination,
In particular, use of a water-soluble salt is preferable from the viewpoint of improving the uniformity of the crystal structure and the heat resistance, and further improving the activation promoting action of the noble metal.

The method for producing the alumina-based composite oxide is not limited to a special method, and may be any of various known methods such as evaporation to dryness, precipitation, impregnation and the like, unless there is a significant uneven distribution of components. It can be appropriately selected from the following, but after dissolving or dispersing the raw materials of the above elements in water,
In particular, a precipitation method in which an aqueous solution of at least one compound selected from the group consisting of aqueous ammonia, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate, and ammonium hydrogen sulfate is used as a precipitant is sufficient for the alumina-based composite oxide. This is preferable in that the BET specific surface area and the uniformity of the crystal structure are ensured and the noble metal is uniformly dispersed.

In producing the exhaust gas purifying catalyst material according to the present invention, a dispersion of pure water and alumina sol is added to a dispersion of at least one element selected from the group consisting of cobalt, nickel, zinc and cerium. An aqueous solution in which a neutral salt is dissolved or dispersed in pure water is added and stirred. At this time, a liquid in which each raw material is dissolved simultaneously or individually may be added.

Next, an aqueous solution of at least one compound selected from the group consisting of aqueous ammonia, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and ammonium hydrogen sulfate is gradually added to the raw material mixed solution to adjust the pH of the solution. The mixture is adjusted to be in a range of 7.0 to 9.0, and the mixed solution is heated (boiled) at 100 to 300 ° C., dried after removing water, and then heat-treated (calcined) to obtain a residue. An alumina-based composite oxide can be obtained.

In the exhaust gas purifying catalyst material according to the present invention,
Fine pore structure and large specific surface area of the alumina-based composite oxide obtained by the precipitation method of agglomerating nickel and cerium hydroxides using the alumina sol of fine particles as the nucleus of the precipitation, and the activity of the alumina-based composite oxide The uniform dispersion state of the phase and the crystal structure having a uniform composition ratio play an important role in exhibiting the activation promoting action of the noble metal.

As a precipitant used in such a precipitation method,
If ammonia water or an ammonium compound is used, the metal element does not remain even if the precipitation cake is insufficiently washed,
Further, even if an ammonium compound (mainly ammonium nitrate after dropping) remains, it can be easily decomposed and removed in the subsequent baking. Furthermore, since alumina sol is used in place of ammonium nitrate, exhaust gas and wastewater treatment for NOx and ammonium nitrate derived from raw materials when drying and firing the precipitate are significantly reduced.

In carrying out the precipitation method, precipitates of various metal salts can be formed by adjusting the pH of the solution to a range of 7.0 to 9.0. in this case,
When the pH of the solution is lower than 7.0, various elements do not sufficiently form a precipitate, and when the pH is higher than 9.0, some of the precipitated components may be redissolved.

Further, when removing water, for example,
The method can be appropriately selected from known methods such as a filtration method and an evaporation to dryness method. The first heat treatment for obtaining the alumina-based composite oxide according to the present invention is not particularly limited, but is preferably performed, for example, in a temperature range of 700 to 1200 ° C. in the air and / or under an air flow.

In the exhaust gas purifying catalyst according to the present invention, the noble metal can be carried on the alumina-based composite inclusion obtained as described above, and particularly, the palladium is carried as the noble metal. Things. In this case, it is desirable that 30 to 80% by weight of palladium in terms of metal in the total amount of palladium be contained in the alumina-based composite inclusion, and the amount of palladium contained in the alumina-based composite inclusion is preferably When the amount is less than 30% by weight, the low-temperature activity and purification performance are not sufficiently exhibited, and when the amount is more than 80% by weight, the dispersibility of noble metals, particularly palladium, deteriorates, and the low-temperature activity and purification performance become remarkable. It is not preferable because it does not improve and is not economically effective.

In some cases, the exhaust gas purifying catalyst according to the present invention preferably contains at least one selected from the group consisting of alkali metals and alkaline earth metals. By containing at least one selected from the group consisting of alkali metals and alkaline earth metals, adsorption poisoning of hydrocarbon species and sintering of precious metals, particularly palladium, can be suppressed.

[0030]

The catalyst material for purifying exhaust gas according to the present invention comprises:
As described in claim 1, the composition includes an alumina-based composite oxide containing nickel and cerium, and the alumina-based composite oxide has the following general formula: [X] _a [Y] _b Al _C O _d ( In the formula, X is a cerium element, Y is a nickel element, a, b, c, and d represent the atomic ratio of each element. When c = 2.0, a = 0.01 to 0. Less than 10,
b = 0.1 or more and 0.7 or less, and d is the number of oxygen atoms required to satisfy the valence of each of the above components. ), It is possible to further enhance the structural stability and specific surface area of the alumina-based composite inclusion at a high temperature, and to improve the alumina-based alumina containing nickel and cerium. When the composite oxide comes into close contact with the noble metal species, the lattice oxygen in the alumina-based inclusions and the adsorbed oxygen on the surface are easily transferred and released, and the low-temperature activity and purification performance in an oxygen-deficient atmosphere (rich region) are improved. Not only is it possible to improve the catalyst performance, but also it is possible to suppress sintering of palladium and the like by the oxygen storage capacity of cerium, and it is possible to suppress deterioration of the catalyst performance due to durability. The effect is brought.

According to a second aspect of the present invention, there is provided a method for producing an exhaust gas purifying catalyst material, which comprises preparing a fine alumina hydrate colloid in producing the alumina-based composite oxide according to the first aspect. A water-soluble salt of at least one element selected from the group consisting of cobalt, nickel, zinc and cerium is dissolved or dispersed in water, and then dissolved in aqueous ammonia, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and ammonium hydrogen sulfate. At least one aqueous solution selected from the group consisting of the following was added, and after removing water, drying and calcining, compared with an alumina-based composite oxide using a water-soluble salt of aluminum,
It is possible to further improve the uniformity of the crystal structure and the durability performance (thermal stability, etc.), and it is possible to sufficiently secure a specific surface area for highly dispersing and supporting the noble metal. Since the noble metal and the active phase can be brought into close contact with each other, the activation promoting action of the noble metal can be increased, and the catalyst performance such as low-temperature activity and purification performance of the exhaust gas purifying catalyst can be further improved. A remarkably excellent effect is achieved.

And, as described in claim 3,
A water-soluble salt of at least one element selected from the group consisting of cobalt, nickel, zinc, and cerium is dissolved or dispersed in water in fine-particle alumina hydrate colloid, and then ammonia water, ammonium carbonate, and ammonium hydrogen carbonate are dissolved. , Ammonium sulfate and ammonium hydrogen sulfate are added, and the pH is adjusted to be in a range of 7.0 to 9.0 by adding at least one aqueous solution selected from the group consisting of
Further, the mixed solution is heated (boiled) at 100 to 300 ° C., dried to remove water, and then calcined, so that precipitates of metal salts of various elements can be sufficiently formed. A remarkably excellent effect is obtained that the thermal stability of the crystal structure at a high temperature and the effect of promoting the activation of the noble metal in the stoichiometric region and the rich region can be further improved.

The exhaust gas purifying catalyst according to the present invention comprises palladium supported on the alumina-based composite oxide according to the first aspect of the present invention. It has excellent durability, suppresses sintering of precious metal species, can promote activation of precious metal species, furthermore, homogenizes the crystal structure, improves structural stability at high temperatures, A remarkably excellent effect is obtained in that it is possible to provide an exhaust gas purifying catalyst capable of enhancing the activity of accelerating the noble metal by increasing the dispersed state of the phase.

And, as described in claim 5,
The low-temperature activity and steady-state NOx conversion performance of palladium are further improved by including 30 to 80% by weight of palladium in terms of metal in the total palladium amount in the alumina-based composite oxide according to claim 1. Significantly better effect.

According to a sixth aspect of the present invention, the exhaust gas purifying catalyst further contains at least one selected from the group consisting of alkali metals and alkaline earth metals. A remarkably excellent effect is obtained in that the sintering of palladium can be suppressed, and the activity at low temperatures and the activity in an oxygen-deficient atmosphere can be further improved.

[0036]

EXAMPLES Next, examples of the present invention will be described in detail together with comparative examples, but it goes without saying that the present invention is not limited to only the following examples.

Example 1 An aqueous solution obtained by dissolving 39.5 g of cerium acetate and 485 g of nickel nitrate in 1000 g of pure water was dispersed in 2500 g of pure water with 1700 g of 20 wt% alumina sol in terms of alumina (Al ₂ O ₃ ). After adding to the suspension, 5% aqueous ammonia was added with stirring, and p
H was adjusted to 8.0. This solution was boiled at 150 ° C. for 4 hours, dried with a spray dryer, and then dried at 400 ° C. for 2 hours.
For 2 hours at 600 ° C. and then for 4 hours at 800 ° C. to obtain the alumina-based composite oxide Ce _0.03 N of Example 1.
i _{0 . 5} Al _{2.0 Od} was obtained. Here, d is the number of oxygen atoms necessary to satisfy the valence of each component.

(Example 2) An aqueous solution in which 13.2 g of cerium acetate and 485 g of nickel nitrate were dissolved in 1000 g of pure water was dispersed in 2500 g of pure water in an amount of 1700 g of 20% by weight alumina (Al ₂ O ₃ ). After adding to the suspension, 5% aqueous ammonia was added with stirring, and p
H was adjusted to 8.0. This solution was boiled at 150 ° C. for 4 hours, dried with a spray dryer, and then dried at 400 ° C. for 2 hours.
And then calcined at 600 ° C. for 2 hours and then at 800 ° C. for 4 hours to obtain the alumina-based composite oxide Ce _0.01 N of Example 2.
i _{0 . 5} Al _{2.0 Od} was obtained.

(Example 3) 118.5 g of cerium acetate,
An aqueous solution obtained by dissolving 485 g of nickel nitrate in 1000 g of pure water was added to a suspension in which 1700 g of 20 wt% alumina sol in terms of alumina (Al ₂ O ₃ ) was dispersed in 2500 g of pure water. Add water,
The pH was adjusted to 8.0. This solution was boiled at 150 ° C. for 4 hours, dried with a spray drier, calcined at 400 ° C. for 2 hours, 600 ° C. for 2 hours, and then at 800 ° C. for 4 hours to obtain the alumina-based composite oxide Ce of Example 3. _0.09
Ni _0.5 Al _{2.0 Od} was obtained.

Comparative Example 1 An aqueous solution in which 6.6 g of cerium acetate and 485 g of nickel nitrate were dissolved in 1000 g of pure water was dispersed in 2500 g of pure water with 1700 g of 20 wt% alumina sol in terms of alumina (Al ₂ O ₃ ). After adding to the suspension, 5% aqueous ammonia was added with stirring, and p
H was adjusted to 8.0. This solution was boiled at 150 ° C. for 4 hours, dried with a spray dryer, and then dried at 400 ° C. for 2 hours.
For 2 hours at 600 ° C. and then for 4 hours at 800 ° C. to obtain the alumina-based composite oxide Ce _{0.005 of} Comparative Example 1.
Ni _{0 . 5} Al _{2.0 Od} was obtained.

Comparative Example 2 263.3 g of cerium acetate,
An aqueous solution obtained by dissolving 485 g of nickel nitrate in 1000 g of pure water was added to a suspension in which 1700 g of 20 wt% alumina sol in terms of alumina (Al ₂ O ₃ ) was dispersed in 2500 g of pure water. Add water,
The pH was adjusted to 8.0. This solution was boiled at 150 ° C. for 4 hours, dried with a spray drier, calcined at 400 ° C. for 2 hours, 600 ° C. for 2 hours, and then at 800 ° C. for 4 hours to obtain an alumina-based composite oxide Ce of Comparative Example 2. _0.2 N
i _{0 . 5} Al _{2.0 Od} was obtained.

Comparative Example 3 An aqueous solution obtained by dissolving 485 g of nickel nitrate in 1000 g of pure water was mixed with alumina (Al)
After adding 1700 g of alumina sol of 20% by weight in terms of ₂ O ₃ ) to a suspension in which 2500 g of pure water was dispersed, 5% aqueous ammonia was added with stirring to adjust the pH to 8.0. After drying this solution at 150 ° C. for 24 hours, 400
2 hours at 600 ° C., then 4 hours at 800 ° C. to obtain an alumina-based composite oxide Ni _{0 . 5} Al
_{2.0 Od} was obtained.

Next, 39.5 g of cerium acetate was added to 10 parts of pure water.
In aqueous solution prepared by dissolving 00g, _{Ni 0. 5} Al _2.0 O _d
100 g of powder was added, and the mixture was stirred and mixed for 2 hours. After drying this suspension at 150 ° C. for 24 hours, it is baked at 400 ° C. for 2 hours and then at 600 ° C. for 2 hours to obtain Ce supported Ni _0.5 containing 0.03 Co element to 2.0 Al element. Al
An alumina-based composite oxide of Comparative Example 3 consisting of _{2.0 Od} was obtained.

Comparative Example 4 An aqueous solution in which 485 g of nickel nitrate was dissolved in 1000 g of pure water was mixed with alumina (Al)
_The suspension was prepared by adding 1700 g of an alumina sol of 20% by weight in terms of ₂ O ₃ ) to 2500 g of pure water and adding 5% aqueous ammonia with stirring to adjust the pH to 8.0.
After drying this solution at 150 ° C. for 24 hours, it was baked at 400 ° C. for 2 hours, 600 ° C. for 2 hours, and then at 800 ° C. for 4 hours, to obtain an alumina-based composite oxide Ni _0.5 A of Comparative Example 4.
It was obtained l _2.0 O _d.

Example 4 692 g of powder (powder A) in which 1.0% by weight of palladium was supported on the alumina-based composite oxide Ce _0.03 Ni _0.5 Al _{2.0 Od} obtained in Example 1
Cerium oxide powder containing 1 mol% of lanthanum and 1 mol% (2 wt% in terms of La ₂ O ₃ ) and 32 mol% of zirconium (25 wt% in terms of ZrO ₂ O) and 0.75 wt% of palladium % Of the powder (powder B) carrying 480 g of
A nitric acid aqueous solution (1200 g) was 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 the coat layer weight was 160 g.
/ L, palladium carrying amount 40 g / cf (1.42 g /
The catalyst of L) was obtained.

Next, a barium acetate solution was adhered to the cordierite monolithic carrier carrying the catalyst component.
It was calcined at 00 ° C. for 1 hour to obtain an exhaust gas purifying catalyst of Example 4 containing 15 g / L of BaO.

Example 5 A coat layer weight of 160 g was prepared in the same manner as in Example 4 except that the alumina-based composite oxide Ce _0.01 Ni _0.5 Al _{2.0 Od} obtained in Example 2 was used.
/ 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 4 and calcined at 400 ° C. for 1 hour to obtain Ba.
An exhaust gas purifying catalyst of Example 5 containing 15 g / L of O was obtained.

Example 6 A coat layer weight of 160 g was prepared in the same manner as in Example 4 except that the alumina-based composite oxide Ce _0.09 Ni _0.5 Al _{2.0 Od} obtained in Example 3 was used.
/ L, palladium carrying amount 40 g / cf (1.42 g /
The catalyst of L) was obtained.

Then, after a barium acetate solution was applied in the same manner as in Example 4, the resultant was baked at 400 ° C. for 1 hour to obtain Ba.
The exhaust gas-purifying catalyst of Example 6 containing 15 g / L of O was obtained.

(Comparative Example 5) A coat layer weight of 160 g / g was obtained in the same manner as in Example 4 except that the alumina-based composite oxide Ce _0.005 Ni _0.5 Al _{2.0 Od} of Comparative Example 1 was used.
L, palladium carrying amount 40 g / cf (1.42 g / L)
Was obtained.

Then, a barium acetate solution was applied in the same manner as in Example 4, and calcined at 400 ° C. for 1 hour to obtain Ba.
An exhaust gas purifying catalyst of Comparative Example 5 containing 15 g / L of O was obtained.

(Comparative Example 6) The coat layer weight was 160 g / L in the same manner as in Example 4 except that the alumina-based composite oxide Ce _0.2 Ni _0.5 Al _{2.0 Od} of Comparative Example 2 was used. ,
A catalyst having a palladium loading of 40 g / cf (1.42 g / L) was obtained.

Then, a barium acetate solution was applied in the same manner as in Example 4 and calcined at 400 ° C. for 1 hour to obtain Ba.
An exhaust gas purifying catalyst of Comparative Example 6 containing 15 g / L of O was obtained.

Comparative Example 7 Ce-supported Ni of Comparative Example 3
_{The same} procedure as in Example 4 was carried out except that an alumina-based composite oxide composed of _0.5 Al _{2.0 Od} was used.
0 g / L, palladium carrying amount 40 g / cf (1.42 g
/ L).

Then, a barium acetate solution was applied in the same manner as in Example 4 and calcined at 400 ° C. for 1 hour to obtain Ba.
An exhaust gas purifying catalyst of Comparative Example 7 containing 15 g / L of O was obtained.

Comparative Example 8 A coat layer weight of 160 g / L and a palladium carrying amount were carried out in the same manner as in Example 4 except that the alumina-based composite oxide Ni _0.5 Al _{2.0 Od} of Comparative Example 4 was used. 40 g / cf (1.42 g / L) of the catalyst were obtained.

Then, after a barium acetate solution was applied in the same manner as in Example 4, the resultant was baked at 400 ° C. for 1 hour to obtain Ba.
An exhaust gas purifying catalyst of Comparative Example 8 containing 15 g / L of O was obtained.

(Test Examples) The exhaust gas purifying catalysts obtained in Examples 4 to 6 and Comparative Examples 5 to 8 were subjected to durability under the following durability conditions, and then evaluated for catalytic activity under the following evaluation conditions.

Endurance conditions Engine displacement 4400cc Fuel unleaded gasoline Catalyst inlet gas temperature 750 ° C Endurance time 100 hours Inlet gas composition CO 0.5 ± 0.1% O ₂ 0.5 ± 0.1% HC About 1100ppm NO 1300ppm CO ₂ 15% Evaluation condition 1: Low-temperature activity Engine displacement 2000cc 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 is determined by HC and CO.
And the temperature at which the conversion of NOx reaches 50% (T5
0 / ° C). Table 1 shows the results.

Evaluation Condition 2: Purification Performance Engine Displacement 2000cc Fuel Unleaded Gasoline Catalyst Inlet Exhaust Gas Temperature 500 ° C. Steak Atmosphere Center A / F = 14.6 Amplitude ΔA / F = ± 1.0 Average Conversion Rate Each exhaust gas purification after endurance The purification activity of the catalyst for use was determined by determining the average conversion (%) of HC, CO and NOx in the stoichiometric atmosphere by the following formula. The results are also shown in Table 1.

[0062]

(Equation 1)

[0063]

(Equation 2)

[0064]

(Equation 3)

[0065]

[Table 1]

As is clear from the results shown in Table 1, the exhaust gas purifying catalysts according to the present invention all have excellent low-temperature activity and further improved exhaust gas purifying performance. Admitted.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 23/75 B01D 53/36 104A 23/755 B01J 23/74 311A 23/89 321A

Claims (6)

[Claims] 1. An alumina-based composite oxide containing nickel and cerium, wherein the alumina-based composite oxide has the following general formula: [X] _a [Y] _b Al _c O _d (where X is cerium Y is a nickel element, a, b, c and d represent the atomic ratio of each element, and when c = 2.0, a = 0.01 or more and less than 0.10;
b = 0.1 or more and 0.7 or less, and d is the number of oxygen atoms required to satisfy the valence of each of the above components. A catalyst material for purifying exhaust gas, which is an alumina-based composite oxide represented by the following formula: 2. In producing the alumina-based composite oxide according to claim 1, the fine particle alumina hydrate colloid is
After dissolving or dispersing a water-soluble salt of at least one element selected from the group consisting of cobalt, nickel, zinc and cerium in water, it is composed of aqueous ammonia, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and ammonium hydrogen sulfate A method for producing an exhaust gas purifying catalyst material, comprising adding at least one aqueous solution selected from the group, removing water, drying, and firing. 3. A water-soluble salt of at least one element selected from the group consisting of cobalt, nickel, zinc and cerium is dissolved or dispersed in water in a fine-particle colloidal alumina hydrate. At least one aqueous solution selected from the group consisting of ammonium, ammonium bicarbonate, ammonium sulfate and ammonium hydrogen sulfate was added, the pH was adjusted to be in the range of 7.0 to 9.0, and the mixed solution was further added to 100 parts. 3. A heat treatment at a temperature of up to 300 [deg.] C., drying after removing water and firing.
4. The method for producing an exhaust gas purifying catalyst material according to item 1. 4. An exhaust gas purifying catalyst comprising the alumina-based composite oxide according to claim 1 carrying palladium. 5. The metal of the total palladium content is 30 to 30%.
The exhaust gas purifying catalyst according to claim 4, wherein 80% by weight of palladium is contained in the alumina-based composite oxide according to claim 1. 6. The exhaust gas purifying catalyst according to claim 4, wherein the exhaust gas purifying catalyst further contains at least one selected from the group consisting of an alkali metal and an alkaline earth metal.