JPH09290159A - Exhaust gas purification catalyst and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas purification catalyst having excellent NOX treating function even in a low temperature range and improved durability to high temperature and provide a production method of the catalyst. SOLUTION: This catalyst is an integrated structure type catalyst having a catalyst component layer and contains a mixed oxide containing nickel, gallium, and aluminum as a catalyst component. This mixed oxide has a chemical formula; Nia Gab Al(2.0-b) Oc wherein (a), (b), (c) stand for atomic ratio of each element and (a)=0.2-1.0, (b)=0.2-1.1, and (c) stands for the number of oxygens necessary to satisfy the atomic valences of respective components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to hydrocarbons (H) in exhaust gas discharged from an internal combustion engine such as an automobile engine.
The present invention relates to an exhaust gas purifying catalyst for purifying carbon monoxide (CO) and nitrogen oxides (NOx) and a method for producing the same.

[0002]

2. Description of the Related Art As a conventional exhaust gas purifying catalyst, one having a structure in which platinum, palladium, rhodium, etc. are supported on alumina, cerium oxide, etc. and coated on a monolith carrier is used. However, since these catalysts mainly focus on improving the exhaust gas purifying ability at the stoichiometric air-fuel ratio (hereinafter, referred to as “stoichiometric atmosphere”), the catalyst is used in an oxygen excess atmosphere (hereinafter referred to as “lean atmosphere”). When used as a NOx purification catalyst, sufficient performance cannot be obtained. Therefore, the development of an exhaust gas purifying catalyst that is excellent in NOx purification performance even in a lean atmosphere is expected.

A number of proposals have been made regarding catalysts having improved NOx purification performance in such a lean atmosphere. Among these, as an exhaust gas purification catalyst using alumina, Japanese Patent Laid-Open No. 4-284843 and Japanese Patent Application Laid-Open No. Kaihei 4-35
There is one described in Japanese Patent No. 8525. In these exhaust gas purifying catalysts, by using alumina carrying metal as a catalyst or metal aluminate (complex oxide of spinel structure) which is a composite oxide of metal element and alumina, exhaust gas in a lean atmosphere N
Ox is reduced and removed, and NOx efficiently even in a lean atmosphere.
The catalytic performance is improved by purifying CO and HC.

Further, as an exhaust gas purifying catalyst using gallium, Japanese Patent Application Laid-Open Nos. 7-24317 and 7-
There are those described in JP-A-265703, JP-A-7-80300, JP-A-7-96191 and JP-A-7-284663. In these exhaust gas purification catalysts, by using a composite oxide of a metal element and gallium (a composite oxide having a spinel structure),
The catalyst performance is improved by reducing and removing NOx in exhaust gas in a lean atmosphere and efficiently purifying NOx, CO, and HC even in a lean atmosphere.

[0005]

However, in the exhaust gas purifying catalyst as described above, the catalyst containing alumina as the main component does not contain harmful components (HC, CO, etc.) in the exhaust gas.
Of the NOx) purifying ability, especially the NOx catalytic purifying ability is strongly influenced by the exhaust gas composition (HC species) and temperature and the water content in the exhaust gas, and sufficient NOx unless the temperature is higher than 500 ° C. Since no purification performance is exhibited, there has been a problem that a catalyst excellent in NOx purification performance has not been obtained in a low temperature range.

Further, in the catalyst containing gallium as a main component,
Compared with the above-mentioned catalyst containing alumina as a main component, the effect of water contained in the exhaust gas is alleviated and the NOx purification performance can be expected, but the low temperature activity and the purification performance deteriorate after the endurance. No catalyst has been obtained that is compatible with purification performance. Further, the catalyst containing gallium as a main component has a problem that the catalyst raw material is expensive and thus the catalyst cost is high and not practical.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide an exhaust gas having excellent NOx purification performance from a low temperature range and improved high temperature durability. It is intended to provide a purification catalyst and a method for producing the same.

[0008]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, a composite oxide containing nickel, gallium and aluminum in a fixed composition ratio (complex oxide of spinel structure type). ) Has a high NOx purification performance in a low temperature range even in a lean atmosphere and is excellent in high temperature durability, and has arrived at the present invention. That is, the exhaust gas purifying catalyst according to claim 1 is a monolithic structure type catalyst having a catalyst component layer, which contains a composite oxide containing at least nickel, gallium and aluminum as a catalyst component, and the composition of the composite oxide is , The following general formula Ni _a Ga _b Al _(2.0-b) O _c (where a, b and c represent the atomic ratio of each element, and
= 0.2 to 1.0, b = 0.2 to 1.1, and c is the number of oxygen atoms required to satisfy the valences of the above components). To do.

Further, the exhaust gas purifying catalyst according to claim 2 further enhances the catalytic activity of the exhaust gas purifying catalyst according to claim 1 in a low temperature range, and contains the above nickel, gallium and aluminum. The composite oxide contains at least one selected from the group consisting of chromium, manganese, iron, cobalt, copper and zinc, and has a composition represented by the following general formula: Ni _a Ga _b Al _(2.0-b) X _d O _c (X in the formula is at least one element selected from the group consisting of chromium, manganese, iron, cobalt, copper and zinc,
a, b, and d represent the atomic ratio of each element, and a = 0.2
˜1.0, b = 0.2 to 1.1, d = 0.01 to 0.5
And c is the number of oxygen atoms required to satisfy the valences of the above components).

Further, the exhaust gas purifying catalyst according to claim 3 is a catalyst in which the catalytic activity of the exhaust gas purifying catalyst according to claim 1 or 2 is further enhanced in an oxygen-deficient (reducing) atmosphere. It further contains cerium oxide as a component, and the cerium oxide contains at least one selected from the group consisting of lanthanum, neodymium, and zirconium in an amount of 1 to 40 mol% in terms of metal, and 60 to 98 mol% of cerium.
It is characterized by including.

The method for producing an exhaust gas purifying catalyst according to a fourth aspect is the method for producing the exhaust gas purifying catalyst according to any one of the first to third aspects.
A water-soluble salt of gallium and aluminum is dissolved or dispersed in water, and the resulting solution is an aqueous solution of at least one compound selected from the group consisting of ammonia water, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and ammonium hydrogen sulfate. Is added to adjust the pH of the solution to 7.0 to 9.0, water is removed, and the residue is heat-treated to obtain the above composite oxide.

Furthermore, the method for producing the exhaust gas purifying catalyst according to claim 5 is the method for producing the exhaust gas purifying catalyst according to any one of claims 1 to 3, in which fine particle alumina hydrate is used. (Fine particle alumina sol), a water-soluble salt of nickel and gallium is dissolved or dispersed in water, and the resulting solution has at least one selected from the group consisting of aqueous ammonia, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and ammonium hydrogen sulfate. An aqueous solution of a seed compound is added to adjust the pH of the solution to 7.0 to 9.0, water is then removed, and the residue is heat-treated to obtain the above composite oxide. And

[0013]

In the exhaust gas purifying catalyst according to the first aspect, the complex oxide containing at least nickel, gallium and aluminum is contained as the catalyst component. Therefore, even in a lean atmosphere, excellent NOx purification performance can be obtained from a low temperature range. In a lean atmosphere, nickel is NOx.
The gallium acts as an active point of selective adsorption and activation, and gallium acts as an active point of HC to mitigate the poisoning effect of water in the exhaust gas, so that the NOx purification performance can be improved. Further, in the exhaust gas purifying catalyst according to claim 1, the composite oxide is a metal aluminate (alumina-based composite oxide) having a specific composition ratio and having a spinel structure.
Therefore, Ni ₁ Al ₂ O ₄ and Ni ₁ G satisfying the stoichiometric ratio are
Compared with a ₂ O ₄ , the structural stability at high temperatures is improved, and sufficient catalyst performance can be obtained even after durability.

Further, in the exhaust gas purifying catalyst according to claim 2, the composite oxide contains at least one selected from the group consisting of chromium, manganese, iron, cobalt, copper and zinc.
Included seeds. Therefore, the catalyst activity and the NOx purification efficiency in the low temperature range can be further improved.

Furthermore, in the exhaust gas purifying catalyst according to claim 3, the catalyst component layer contains cerium oxide powder containing at least one selected from the group consisting of lanthanum, neodymium and zirconium. Therefore, the catalytic activity in an oxygen-deficient (reducing) atmosphere can be further enhanced, and reduction deterioration of the composite oxide can be suppressed.

Further, in the method for producing the exhaust gas purifying catalyst according to the fourth aspect, the effect of improving the NOx purifying performance is sufficiently obtained as compared with the single oxide of the metal element or the complex oxide prepared by the impregnation method.

Particularly, in the method for producing the exhaust gas purifying catalyst according to the fifth aspect, more sufficient durability can be obtained as compared with the complex oxide prepared by the precipitation method using the water-soluble raw material compound.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the exhaust gas purifying catalyst of the present invention will be described in detail. The exhaust gas purifying catalyst of the present invention is an integral structure type catalyst having a catalyst component layer,
The catalyst component supported on the catalyst component layer contains a complex oxide having a specific composition containing nickel, gallium and aluminum. Here, the composite oxide has the following general formula _{(I) Ni a Ga b Al} (2.0-b) O c ··· (I) (a in the formula, b and c are atomic ratios of respective elements Represents a
= 0.2 to 1.0, b = 0.2 to 1.1, and c is the number of oxygen atoms required to satisfy the valences of the above components).

In the above formula (I), when a is less than 0.2, nickel NOx is selectively adsorbed and activated.
Since the effect of improving the purification performance was not sufficiently obtained, alumina (Al
_{It is} not preferable because it becomes equivalent to the purification performance of ₂ O ₃ ). On the other hand, when a exceeds 1.0, the BET specific surface area decreases, and sufficient performance cannot be obtained in the initial stage. Also, b
= Less than 0.2, the effect of improving the NOx purification performance of gallium with respect to the effect of water on the NOx purification performance is not sufficiently obtained, and there is no great difference from the case of nickel aluminate (Ni ₁ Al ₂ O ₄ ), which is preferable. Absent. When b = 1.1 is exceeded, the thermal stability of the spinel type crystal structure is deteriorated and sufficient performance cannot be obtained after endurance.

The use amount (support amount) of the above-mentioned composite oxide can be appropriately changed according to the type of internal combustion engine used, the intended catalyst performance, etc., but is usually 3 per 1 liter of catalyst.
It is 0 to 300 g. If it is less than 30 g, sufficient catalytic activity cannot be obtained, and even if it is used in excess of 300 g, diffusion of the exhaust gas component in the catalyst component layer is deteriorated and the catalyst performance may not be improved, which is not preferable.

Further, chromium, manganese, iron, cobalt, copper or zinc and any mixture thereof can be added to the above-mentioned composite oxide, whereby the catalyst activity and the NOx purification efficiency in a lower temperature range can be added. Can be improved. In this case, the above formula (I) is expressed by the following general formula (I
I) Ni _a Ga _b Al _(2.0-b) X _d O _c ... (II) (X in the formula is at least one selected from the group consisting of chromium, manganese, iron, cobalt, copper and zinc. Elements of
a, b, and d represent the atomic ratio of each element, and a = 0.2
˜1.0, b = 0.2 to 1.1, d = 0.01 to 0.5
And c is the number of oxygen atoms required to satisfy the valences of the above components). Here, d = 0.
If it is less than 01, the effect of improving the purification performance of the additive element cannot be sufficiently obtained, and if it exceeds d = 0.5, the effect of addition is saturated, or conversely, sufficient post-durability performance cannot be obtained. It is not preferable because it exists.

Further, in the exhaust gas purifying catalyst of the present invention, cerium oxide can be supported as a catalyst component other than the above-mentioned composite oxide, whereby the catalytic activity in an oxygen-deficient (reducing) atmosphere is improved. It can be further increased, and reduction deterioration of the composite oxide can be suppressed. As the cerium oxide, those containing 1 to 40 mol% of lanthanum, neodymium or zirconium and any mixture thereof in terms of metal and 60 to 98 mol% of cerium can be preferably used. 1-40 was a mole percent, cerium oxide (CeO _2), lanthanum, adding at least one selected from the group consisting of neodymium and zirconium, the oxygen storage capacity and BET specific surface area of CeO _2, heat This is to improve stability. If it is less than 1 mol%, there is no great difference from the case of CeO ₂ alone, and the above-mentioned effect of improving the additional element does not appear. If it exceeds 40 mol%, this effect is saturated or, conversely, it is not preferable.

The amount of the cerium oxide used can be appropriately changed in the same manner as in the case of the composite oxide, but it is usually 10 to 150 g per liter of the catalyst. If it is less than 10 g, a sufficient catalytic activity improving effect cannot be obtained in an oxygen-deficient atmosphere, and even if it is used in an amount of more than 150 g, diffusion of exhaust gas components to the composite oxide that is an active component in the catalyst component layer becomes poor, and the catalyst becomes poor. It is not preferable because the performance may not be improved.

Next, a method of manufacturing the exhaust gas purifying catalyst of the present invention will be described. First, as a raw material compound for catalyst preparation, nitrates of various elements such as nickel and gallium,
Carbonates, ammonium salts, acetates, oxides and the like can be used in combination, but good results are obtained when a water-soluble salt is used.

The method for preparing the above-mentioned composite oxide catalyst is
The method is not limited to a special method as long as the components are not significantly unevenly distributed, and can be appropriately selected and used from various methods such as a conventionally known evaporation-drying method, precipitation method and impregnation method. . However, among these methods, after dissolving or dispersing a water-soluble salt of each of the above elements in water, at least one selected from the group consisting of aqueous ammonia, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate, and ammonium sulfate. Preference is given to using the precipitation method in which an aqueous solution of the compound is added. In the complex oxide catalyst prepared by such a precipitation method, the specific surface area effective for the reaction can be sufficiently secured, so that the catalytic activity is excellent in the low temperature region, and the metal element that is the active phase can be uniformly dispersed on the surface. It also excels in catalytic activity and catalytic performance after endurance.

From the above, the method for preparing the above complex oxide will be specifically described. First, pure water is added to a catalyst raw material containing nickel, gallium and aluminum components and sufficiently stirred. At this time, a liquid in which each catalyst raw material is dissolved simultaneously or separately may be added. Then, 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 sulfate is gradually added to the mixed solution containing the catalyst raw material to adjust the pH of the solution to 7. 0 to 9.0
Adjust so that it is in between. After that, water is removed and the residue is heat-treated to complete the preparation of the composite oxide and obtain the target composite oxide catalyst.

In the above-mentioned method for preparing a complex oxide, the use of the above-mentioned aqueous ammonia or ammonium compound as the precipitating agent does not cause the metal element to remain even if the washing is insufficient, or the ammonium compound remains. This is because (mainly ammonium nitrate) can be easily decomposed and removed by subsequent firing. On the other hand, when a metal salt such as sodium hydroxide or sodium carbonate is used, metal elements such as sodium remain in the obtained precipitate, and these residual elements adversely affect the catalytic performance. This is because it is not preferable because a washing step is required.

In the above preparation method, the pH of the solution
Is adjusted in the range of 7.0 to 9.0 to form precipitates of various metal salts. When the pH is lower than 7.0, various elements do not sufficiently form a precipitate, and conversely, the pH is 9.0.
If it is higher, some of the precipitated components may be redissolved, which is not preferable. Furthermore, various methods such as filtration and evaporation to dryness can be used to remove water.
The heat treatment is preferably performed in air or under air circulation at a temperature of 500 to 1000 ° C., for example.

The exhaust gas purifying catalyst of the present invention obtained as described above can be effectively used even without a carrier, but it is pulverized and slurried and coated on a honeycomb carrier having a monolith structure, for example, 400 to 900 ° C. It is preferable to use it after firing at the temperature. In this case, as the catalyst carrier,
The carrier can be appropriately selected and used from conventionally known carriers, and for example, a monolith carrier or a metal carrier made of a refractory material can be used.

The shape of the catalyst carrier is not particularly limited, but it is usually preferable to use a honeycomb shape, and by applying a catalyst powder to various honeycomb-shaped base materials, it is possible to form an integrated structure. Structural type catalysts can be obtained. As the honeycomb-shaped base material, generally, a cordierite-based material such as ceramic is often used, but it is also possible to use a metal material such as ferritic stainless steel, and further, the catalyst powder itself is formed into a honeycomb shape. Good. By making the catalyst into a honeycomb shape, the contact area between the catalyst and the exhaust gas becomes large and the pressure loss can be suppressed, so that it is extremely effective when used as a catalyst for purifying exhaust gas for automobiles.

The amount of the catalyst component coating layer adhered to the honeycomb-shaped substrate is the total amount of the catalyst components and the catalyst 1
It is preferably 50 to 400 g per liter. It can be said that the more the catalyst component is, the more preferable it is in terms of the catalyst activity and the catalyst life. However, if the coat layer becomes too thick, HC, C
Reaction gases such as O and NOx become poorly diffused, and these gases and the catalyst cannot be sufficiently brought into contact with each other. Therefore, the effect of increasing the amount of activity is saturated, and further, the gas passage resistance increases, so that the amount of the coat layer is preferably 50 to 400 g per liter of the catalyst as described above.

[0032]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following, "parts" and "%" represent "parts by weight" and "% by weight", respectively, unless otherwise specified. (Example 1) 290.8 parts of nickel nitrate, 400 parts of gallium nitrate and 375.3 parts of aluminum nitrate were added to pure water 10
It was added to 00 parts and stirred and dissolved. Then, while continuing stirring, 5% ammonia water was gradually added dropwise to the solution to p
H was adjusted to a range of 7.0 to 9.0. The precipitate formed was filtered off and dried at 150 ° C. for 12 hours,
It was calcined in air at 800 ° C. for 4 hours. The composition of the components other than oxygen of the obtained catalyst (hereinafter the same) was Ni _1.0 Ga _1.0 Al.
_1.0 .

Cerium oxide containing 700 parts of the powder thus obtained, lanthanum (1 mol%: 1% as La ₂ O ₃ ) and zirconium (32 mol%: 25% as ZrO ₂ ) (67 mol of cerium) %: 74 as CeO ₂
%) 300 parts and 2000 parts of pure water are mixed with a ball mill.
The resulting slurry was pulverized, adhered to a monolith carrier substrate, and calcined at 400 ° C. for 1 hour to prepare a catalyst of this example. In addition, the adhesion amount at this time was set to 300 g / l.

(Example 2) Ni _1.0 Ga _{1.0 was} prepared by using a 5% ammonium carbonate aqueous solution instead of 5% ammonia water.
The same operation as in Example 1 was repeated except that Al _1.0 was prepared to obtain the catalyst of this example.

Example 3 A Ni _1.0 G solution was prepared by using a 5% aqueous solution of ammonium hydrogencarbonate instead of 5% aqueous ammonia.
a _{1.0 A} procedure similar to that of Example 1 was repeated except that Al _1.0 was prepared to obtain a catalyst of this example.

(Example 4) A 5% aqueous solution of ammonium sulfate was used in place of 5% ammonia water to obtain Ni _1.0 Ga _1.0.
The same operation as in Example 1 was repeated except that Al _1.0 was prepared to obtain the catalyst of this example.

(Example 5) Ni _1.0 G was prepared by using a 5% ammonium hydrogensulfate aqueous solution instead of 5% ammonia water.
a _{1.0 A} procedure similar to that of Example 1 was repeated except that Al _1.0 was prepared to obtain a catalyst of this example.

(Example 6) The compounding amount of nickel nitrate was adjusted to 14
The same operation as in Example 1 was repeated except that Ni _0.5 Ga _1.0 Al _1.0 was prepared in place of 5.4 parts to obtain a catalyst of this example.

Example 7 Nickel nitrate, gallium nitrate and aluminum nitrate were mixed in amounts of 290.8 and 290.8, respectively.
_1.0 Ga _0.5 Al as parts, 200 parts and 563 parts
The same operation as in Example 1 was repeated except that _1.5 was prepared to obtain the catalyst of this Example.

Example 8 The same operation as in Example 1 was repeated using 24.2 parts of copper nitrate, 261.7 parts of nickel nitrate, 400 parts of gallium nitrate and 375.3 parts of aluminum nitrate, and Cu _0.1 Ni _0.9 Ga _1.0 Al _1.0 was prepared, and the same operation was repeated to obtain the catalyst of this example.

Example 9 The same operation as in Example 1 was repeated using 29.1 parts of cobalt nitrate, 261.7 parts of nickel nitrate, 400 parts of gallium nitrate and 375.3 parts of aluminum nitrate, and Co _0.1 Ni _0.9 Ga _1.0 Al _1.0 was prepared, and the same operation was repeated to obtain the catalyst of this example.

Example 10 The same operation as in Example 1 was repeated using 20 parts of chromium nitrate, 12.8 parts of manganese nitrate, 261.7 parts of nickel nitrate, 400 parts of gallium nitrate and 375.3 parts of aluminum nitrate. , Cr _0.05 Mn _0.05
Ni _0.9 Ga _1.0 Al _1.0 was prepared, and the same operation was repeated to obtain the catalyst of this example.

(Example 11) The same operation as in Example 1 was carried out using 20.2 parts of iron nitrate, 59.4 parts of zinc nitrate, 203.6 parts of nickel nitrate, 400 parts of gallium nitrate and 375.3 parts of aluminum nitrate. Repeatedly, Fe _0.05 Zn _0.2 Ni
_0.7 Ga _1.0 Al _1.0 was prepared, and the same operation was repeated to obtain the catalyst of this example.

(Example 12) Using 24.2 parts of copper nitrate, 29.1 parts of cobalt nitrate, 29.7 parts of zinc nitrate, 203.6 parts of nickel nitrate, 400 parts of gallium nitrate, and 375.3 parts of aluminum nitrate. The same operation as in Example 1 was repeated to prepare Cu _0.1 Co _0.1 Zn _0.1 Ni _0.7 Ga _1.0 Al _1.0, and the same operation was repeated to obtain the catalyst of this example.

(Example 13) An example using 24.2 parts of copper nitrate, 29.1 parts of cobalt nitrate, 29.7 parts of zinc nitrate, 203.6 parts of nickel nitrate, 200 parts of gallium nitrate, and 563 parts of aluminum nitrate. Repeat the same operation as 1.
Cu _0.1 Co _0.1 Zn _0.1 Ni _0.7 Ga _0.5 Al _1.5 was prepared, and the same operation was repeated to obtain the catalyst of this example.

(Example 14) 900 parts of Ni _1.0 Ga _1.0
Except that Al _1.0 and 100 parts of cerium oxide were used.
The same operation as in Example 1 was repeated to obtain the catalyst of this example.

(Comparative Example 1) Aluminum nitrate 375.3
Parts were added to 1000 parts of pure water, and stirred and dissolved. Then
While continuing stirring, 5% ammonia water was gradually added dropwise to adjust the pH of the solution to be in the range of 7.0 to 9.0. The precipitate formed is filtered off and dried at 150 ° C.
After being dried for 12 hours, it was baked in air at 800 ° C. for 4 hours. Composition of components other than oxygen of the obtained catalyst (hereinafter the same)
Was Al _2.0 . Powder 5 thus obtained
00 parts and 1000 parts of pure water are mixed and crushed by a ball mill,
The obtained slurry is attached to a monolith carrier substrate,
The catalyst of this example was obtained by firing at 0 ° C. for 1 hour. In addition, the adhesion amount at this time was set to 300 g / l.

(Comparative Example 2) Except that Ni _1.0 Ga _1.0 Al _1.0 prepared without using 5% aqueous ammonia was used.
The same operation as in Example 1 was repeated to prepare the catalyst of this example.

Comparative Example 3 The same operation as in Example 1 was repeated using 241.6 parts of copper nitrate, 290.8 parts of nickel nitrate, 400 parts of gallium nitrate and 375.3 parts of aluminum nitrate, and Cu _1.0 Ni _1.0 Ga _1.0 Al _1.0 was prepared, and the same operation was repeated to obtain the catalyst of this example.

Comparative Example 4 290.8 parts of nickel nitrate,
The same operation as in Example 1 was repeated using 800 parts of gallium nitrate to prepare Ni _1.0 Ga _2.0, and the same operation was repeated to obtain the catalyst of this example.

Comparative Example 5 290.8 parts of nickel nitrate,
The same operation as in Example 1 was repeated using 750.6 parts of aluminum nitrate to prepare Ni _1.0 Al _2.0, and the same operation was repeated to obtain the catalyst of this example.

(Performance Evaluation) Regarding the catalysts of Examples 1 to 15 and Comparative Examples 1 to 5 obtained as described above, the catalysts were modeled under the following evaluation conditions using a model gas simulating automobile exhaust gas. The activity was evaluated. Further, the NOx addition rate was calculated based on the following mathematical formula 1. [Evaluation conditions] Catalyst Monolith-type multi-component catalyst Total gas flow rate 40 l / min Catalyst inlet gas temperature 100 to 600 ° C. Temperature rising rate 30 ° C./min Space velocity About 20000 Hl Inlet gas composition Model corresponding to average air-fuel ratio 18.0 Gas composition CO 0.2% C ₃ H ₆ 5000ppm C NO 500ppm O ₂ 4.50% CO ₂ 10.0% H ₂ O 10.0% N ₂ balance A / F No amplitude

Table 1 summarizes the composition and outline of the use of the composite oxide catalysts in each of the examples and comparative examples. Also,
The results of the above performance evaluation are shown in Table 2. As is clear from Table 2, it was found that the catalysts of Examples belonging to the scope of the present invention had higher catalytic activity than the catalysts of Comparative Examples, which confirmed the effect of the present invention.

[0054]

[Equation 1]

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

As described above, according to the present invention, since the composite oxide containing nickel, gallium and aluminum in a constant composition ratio is used, the NOx purification performance from the low temperature range is excellent and It is possible to provide an exhaust gas purifying catalyst having improved high temperature durability and a method for producing the same. That is, the exhaust gas purifying catalyst of the present invention has a nitrogen content in an oxygen excess atmosphere which is not active in the conventional catalyst.
It excels in Ox purification performance and exerts and maintains high performance in the low temperature range with respect to NOx in exhaust gas.

Claims (5)

[Claims] 1. A monolithic structure type catalyst having a catalyst component layer, which contains a composite oxide containing at least nickel, gallium and aluminum as a catalyst component, and the composition of the composite oxide is represented by the following general formula: Ni _a Ga _b Al _(2.0-b) O _c (where a, b and c represent the atomic ratio of each element, and
= 0.2 to 1.0, b = 0.2 to 1.1, and c is the number of oxygen atoms required to satisfy the valences of the above components). Exhaust gas purification catalyst. 2. The above complex oxide has the following general formula: Ni _a Ga _b Al _(2.0-b) X _d O _c (wherein X is a group consisting of chromium, manganese, iron, cobalt, copper and zinc). At least one element selected from
a, b, and d represent the atomic ratio of each element, and a = 0.2
˜1.0, b = 0.2 to 1.1, d = 0.01 to 0.5
And c is the number of oxygen atoms required to satisfy the valences of the above components.) The exhaust gas purifying catalyst according to claim 1. 3. At least one selected from the group consisting of lanthanum, neodymium and zirconium as a catalyst component.
Seed metal 1 to 40 mol%, cerium 60 to 98
The exhaust gas purifying catalyst according to claim 1 or 2, further comprising cerium oxide, which is contained in an amount of mol%. 4. In producing the exhaust gas purifying catalyst according to claim 1, a water-soluble salt of nickel, gallium and aluminum is dissolved or dispersed in water to obtain a solution. To this, 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 added to adjust the pH of the solution to 7.0.
Adjusting to 9.0, then removing water and heat treating the residue,
A method for producing an exhaust gas purifying catalyst, characterized in that the above composite oxide is obtained. 5. In producing the exhaust gas purifying catalyst according to any one of claims 1 to 3, fine particle alumina hydrate, a water-soluble salt of nickel and gallium are dissolved or dispersed in water, 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 added to the resulting solution to adjust the pH of the solution to 7.0.
Adjusting to 9.0, then removing water and heat treating the residue,
A method for producing an exhaust gas purifying catalyst, characterized in that the above composite oxide is obtained.