JP3309711B2 - Exhaust gas purification catalyst and method for producing the same - Google Patents

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 of an automobile or the like.
), Carbon monoxide (hereinafter, referred to as “CO”) and nitrogen oxides (hereinafter, referred to as “NO _x ”) have excellent low-temperature activity that can be effectively purified even at a low temperature. The present invention relates to an exhaust gas purifying catalyst having excellent catalytic activity in all exhaust gas composition atmospheres such as an atmosphere and a stoichiometric air-fuel ratio, 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, JP-B-58-20307 and JP-A-5-305 are disclosed.
236 and JP-A-6-378. The exhaust gas purifying catalyst described in Japanese Patent Publication No. 58-20307 is a composition in which a composition comprising platinum, rhodium and cerium is supported on a refractory carrier, and specifically, alumina, cerium oxide, etc. platinum,
It has a structure in which a platinum group element such as palladium and rhodium is supported, and this is coated on a monolithic carrier.

Japanese Patent Application Laid-Open No. 5-305236 discloses that
An exhaust gas purification catalyst in which hexaaluminate containing no noble metal is mixed and dispersed in a noble metal-supported alumina such as platinum, rhodium, and palladium has been disclosed.Specifically, a hexaaluminate composition having a certain composition, platinum,
It is a mixture of alumina carrying at least one noble metal selected from the group consisting of rhodium and palladium at a constant weight ratio.

JP-A-6-378 discloses that activated alumina and cerium oxide are mixed with at least one of platinum and palladium as catalyst components, potassium as a basic element,
An exhaust gas purifying catalyst supporting an oxide of at least one metal selected from the group consisting of cesium, strontium and barium has been proposed. In other words, in addition to the catalysts such as platinum group elements, activated alumina and cerium oxide which have been conventionally used as catalyst components, the catalysts include potassium compounds, cesium compounds, strontium compounds and barium compounds which are basic elements. At least one type is combined.

[0006]

However, in order to obtain sufficient catalytic activity from a low temperature, the conventional catalysts described in the above publications require noble metals such as platinum and rhodium which are not abundant in resources and expensive. Is used in large quantities. Therefore, the use of relatively inexpensive palladium among the noble metals and the use of expensive noble metals at least with a catalyst having sufficient exhaust gas purification ability, or the use of rhodium as an exhaust gas purification with the least possible usage The development of catalysts for industrial use is expected. However, when palladium is used alone, there is a problem in that the purification ability is reduced when the exhaust gas is reduced, or the low-temperature activity and the purification performance itself are deteriorated when the amount of palladium is reduced.

Further, the catalyst for purifying exhaust gas purifies exhaust gas of automobiles whose composition fluctuates widely, such as an oxidizing atmosphere, a reducing atmosphere, and a stoichiometric air-fuel ratio, in a wide temperature range from a low temperature range to a high temperature range and at a high purification rate. Must be processed at a rate.

However, in purifying exhaust gas with palladium, at low temperatures immediately after starting the engine, or in a reducing atmosphere having a high hydrocarbon concentration and a low oxygen concentration, part of the hydrocarbons remain without being purified and the remaining hydrocarbons remain. Is strongly adsorbed on palladium and its activity is reduced or its active sites are reduced.As a result, purification performance is reduced.In an oxidizing atmosphere where oxygen concentration is high and hydrocarbon concentration is low, oxygen is adsorbed on palladium and nitrogen oxidation occurs. There is a drawback that substances are hardly adsorbed and purification performance of nitrogen oxides is greatly reduced. Further, when the amount of palladium in the exhaust gas catalyst is reduced, there is a problem that the above-described effect is remarkably exhibited and the purification performance is further reduced.

Accordingly, it is an object of the present invention to provide a low-temperature excellent low-temperature catalyst under all exhaust composition atmospheres such as an oxidizing atmosphere, a reducing atmosphere, and a stoichiometric air-fuel ratio even if the amount of a noble metal used is significantly reduced as compared with a conventional catalyst. An object of the present invention is to provide an exhaust gas purifying catalyst having high activity and excellent catalytic activity, and a method for producing the same.

[0010]

Means for Solving the Problems As a result of research for solving the above problems, the present inventors have found that an alumina-based composite oxide containing a transition metal element in a fixed composition ratio together with palladium in a catalyst component-supporting layer is obtained. The present inventors have found that by containing Pd, the catalytic performance of palladium can be improved, and the catalytic activity in a low temperature range and the purification performance under all exhaust gas composition atmospheres are remarkably improved.

The exhaust gas purifying catalyst according to claim 1 of the present invention is an integrated catalyst having a catalyst component-supporting layer, which comprises at least palladium as a catalyst component and a metal aluminate containing cerium and zirconium. The metal aluminate contains at least one selected from the group consisting of cobalt, nickel and zinc.

Further, in order to increase the structural stability and the BET specific surface area of the exhaust gas purifying catalyst at a high temperature, a first aspect of the present invention is provided.
In the exhaust gas purifying catalyst described above, the metal aluminate has the following general formula;

[Number 2] [X] _a Al _b O _c (wherein, X is cobalt, and at least one element selected from the group consisting of nickel and zinc, a, b and c are atomic ratios of respective elements When b = 2.0, a =
0.1 to 0.8, c is the number of oxygen atoms necessary to satisfy the valence of each component described above).

In the exhaust gas purifying catalyst according to the first aspect, the sintering (particle growth) of the palladium supported on the alumina-based composite oxide is suppressed. Is an alumina-based composite oxide containing at least one selected from the group consisting of cobalt, nickel and zinc, and further, at least one selected from the group consisting of cerium and zirconium in terms of metal with respect to aluminum. 0.1 to 5 mol%
It is characterized by containing.

Further, in order to further enhance the catalytic activity of the exhaust gas purifying catalyst of the first or second aspect in a reducing atmosphere, the exhaust gas purifying catalyst of the third aspect further comprises lanthanum, neodymium and zirconium. A cerium oxide containing 1 to 40 mol% of at least one selected from the group in terms of metal and 60 to 98 mol% in terms of metal in terms of metal is contained in the exhaust gas purifying catalyst.

Further, in order to further increase the low-temperature activity of the exhaust gas purifying catalyst according to any one of claims 1 to 3, the exhaust gas purifying catalyst according to claim 4 is contained in a catalyst component supporting layer. 30% by weight to 8 in metal conversion of the total amount of palladium
0% by weight of palladium is contained in the alumina-based composite oxide.

Furthermore, in order to further enhance the low-temperature activity and the catalytic activity in a reducing (lack of oxygen) atmosphere of the exhaust gas purifying catalyst according to any one of claims 1 to 4, the exhaust gas purifying catalyst according to claim 5 is further improved. Is characterized in that at least one selected from the group consisting of alkali metals and alkaline earth metals is contained in the exhaust gas catalyst.

Further, in order to further enhance the low-temperature activity of the exhaust gas purifying catalyst according to any one of claims 1 to 5, the exhaust gas purifying catalyst according to claim 6 further comprises rhodium and alumina powder. Preferably, it is contained in the gas purification catalyst.

Further, in order to further enhance the catalytic activity of the exhaust gas purifying catalyst according to claim 6 in a reducing (oxygen-deficient) atmosphere, the exhaust gas purifying catalyst according to claim 7 further comprises lanthanum, neodymium and cerium. Preferably, the exhaust gas catalyst contains a zirconium oxide containing at least one selected from the group consisting of 1 to 40 mol% in terms of metal and zirconium in an amount of 60 to 98 mol% in terms of metal.

Further, in order to further enhance the catalytic activity of palladium and rhodium, the catalyst for purifying exhaust gas according to claim 8 further comprises a rhodium-containing layer comprising palladium. Same layer and / or
Alternatively, the palladium-containing layer is disposed above the palladium-containing layer.

Further, the catalyst for purifying exhaust gas according to the ninth aspect is useful for producing the alumina-based composite oxide according to any one of the first to eighth aspects. ") And cobalt,
The method is characterized in that at least one water-soluble salt of nickel and zinc is dissolved or dispersed in water, then water is removed, and the resultant is calcined.

Further, in the exhaust gas purifying catalyst according to the eleventh aspect, in producing the alumina-based composite oxide according to any one of the first to eighth and tenth aspects, at least one of alumina sol, cobalt and nickel is used. And after dissolving or dispersing at least one water-soluble salt selected from the group consisting of zinc and water, adding aqueous ammonia, at least one aqueous solution selected from the group consisting of ammonium carbonate and ammonium bicarbonate, and adjusting the pH. After adjusting to be in the range of 7.0 to 9.0, water is removed, and then calcination is performed. The exhaust gas purifying catalyst according to any one of claims 1 to 8, further comprising an alkali metal and / or an alkaline earth metal impregnated thereon, wherein the alkali metal and / or the alkaline earth metal is in an oxide form. It is characterized in that it is contained in the coat layer.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Palladium is at least one of the noble metals contained in the catalyst component supporting layer of the exhaust gas purifying catalyst of the present invention. The content of the palladium is 0.1 to 20 g / L in 1 L of the catalyst. If the amount is less than 0.1 g, the low-temperature activity and purification performance are not sufficiently exhibited, and if the amount exceeds 20 g, the dispersibility of palladium deteriorates, the catalyst performance is not significantly improved, and it is not economically effective.

As a substrate on which the palladium is supported
Is used to improve the catalytic performance of palladium.
Luminates, especially alumina-based composite oxides, are suitable.
Low-temperature activity and purification performance of palladium (particularly in oxygen-deficient atmospheres)
NO in the vicinity of air and stoichiometric air-fuel ratio _xSteady conversion performance)
Therefore, cobalt and nickel
At least one selected from the group consisting of nickel and zinc
Is contained. Usage of such alumina-based composite oxide
Is 10 to 200 g per liter of the catalyst. 10g not yet
Alumina-based composite oxide activates palladium when full
The effect of improving the catalyst performance cannot be obtained.
Even if the amount exceeds 0 g, the effect of improving the catalyst performance is saturated or reversed.
A decrease in the catalyst performance is observed.

By supporting palladium on the alumina-based composite oxide powder, the alumina-based composite oxide powder containing at least one selected from the group consisting of cobalt, nickel and zinc comes into close contact with palladium, Lattice oxygen in the oxide and adsorbed oxygen on the surface are easily transferred and released through palladium, and the low-temperature activity of palladium is improved. Also, cobalt is dissolved in alumina composite oxide, at least one element selected from the group consisting of nickel and zinc, effectively function as adsorption active points such as NO _x, oxygen-deficient atmosphere, and the stoichiometric air This will improve the catalytic performance of palladium near the fuel ratio.

[0025] The exhaust gas purifying catalyst of claim 1 wherein the composition of the metal aluminate in the catalyst component, a = 0 when the [X] _a Al _b O _c wherein, b = 2.0 .1
~ 0.8. If a is less than 0.1, the effect of the transition metal element selected from the group consisting of Co, Ni and Zn added to the alumina-based composite oxide is small, and a sufficient improvement effect cannot be obtained. ₂ O ₃ ). On the other hand, if a exceeds 0.8, the BET specific surface area of the alumina-based composite oxide and the structural stability at high temperatures are reduced, so that the dispersibility of the noble metal is poor and sufficient performance cannot be obtained at the initial stage. In addition, the sintering of precious metals is promoted during durability, and the performance after durability deteriorates.

As described above, by using the alumina-based composite oxide having a specific composition ratio, the structural stability and the ratio at high temperatures can be improved as compared with the stoichiometric metal aluminate ([X] ₁ Al ₂ O ₄ ). The surface area is sufficient, and the added element forms a solid solution in the crystal structure of alumina and does not exist as an oxide on the surface, so that sufficient performance can be obtained.

In particular, the exhaust gas purifying catalyst according to claim 2 is characterized in that cerium and zirconium are further added to the alumina-based composite oxide in the exhaust gas purifying catalyst according to claim 1 in terms of metal relative to aluminum. 0.1 to 5 mol%. The content of 0.1 to 5 mol% is such that the effect of improving palladium sintering is added to the alumina-based composite oxide while maintaining the catalyst performance improving effect due to the interaction between palladium and the alumina-based composite oxide. To do that. When the content is less than 0.1 mol%, the effect of adding Ce and / or Zr does not appear as in the case of using only the alumina-based composite oxide. The surface is coated, and the function of the activation point of NOx adsorption, which acts as a cocatalyst for palladium, is deteriorated.

By adding at least one member selected from the group consisting of cerium and zirconium to the alumina-based composite oxide in advance, cerium and / or zirconium and palladium come into close contact with each other on the surface of the alumina-based composite oxide, Sintering is suppressed, and the durability and low-temperature activity of palladium are improved.

The catalyst for purifying exhaust gas according to claim 3 further contains cerium oxide in addition to the catalyst components in the catalyst for purifying exhaust gas according to claim 1 or 2. The cerium oxide contains at least one element selected from the group consisting of lanthanum, neodymium and zirconium in an amount of 1 to 40 mol% in terms of metal, and cerium in an amount of 60 to
It contains 98 mol%. The content of 1 to 40 mol% is determined by adding at least one element selected from the group consisting of lanthanum, neodymium, and zirconium to cerium oxide (CeO ₂ ), and the oxygen storage capacity and BET specific surface area of cerium oxide. , To significantly improve the thermal stability. If it is less than 1 mol%, the effect of adding the lanthanum and / or neodymium and / or zirconium elements does not appear as in the case of only cerium oxide, and if it exceeds 40 mol%, this effect is saturated or conversely decreases.

As described above, since the cerium oxide containing at least one selected from the group consisting of lanthanum, neodymium and zirconium is further contained in the catalyst component supporting layer, the cerium oxide having a high oxygen storage capacity is reduced. (Oxygen deficiency) Since lattice oxygen and adsorbed oxygen are released in the atmosphere and near the stoichiometric air-fuel ratio to make the oxidation state of palladium suitable for purifying exhaust gas, it is possible to suppress a decrease in catalytic ability due to reduction of palladium. . Further, by contact with the alumina-based composite oxide in the catalyst component supporting layer,
It is also possible to suppress a decrease in catalytic ability due to the reduction of the alumina-based composite oxide.

The exhaust gas purifying catalyst according to claim 4 is the catalyst component in the exhaust gas purifying catalyst according to claims 1 to 3, wherein the total palladium amount is 30 to 80 in terms of metal.
The weight-% palladium is supported on an alumina-based composite oxide powder containing at least one selected from the group consisting of cerium and zirconium. When the amount of palladium supported on the alumina-based composite oxide powder containing at least one selected from the group consisting of cerium and zirconium is less than 30% by weight, the effect of improving the low-temperature activity is not sufficiently exhibited, and conversely, 80% by weight. %, The effect of improving the steady-state NOx conversion performance saturates and is not effective.

The effect of improving the low-temperature activity of palladium by loading 30-80% by weight of palladium in terms of metal, based on the total amount of palladium contained in the catalyst component-supporting layer, in the alumina-based composite oxide. NO _x steady turning performance improving effect and can be obtained sufficiently.

In the exhaust gas purifying catalyst according to the fifth aspect, the alkali metal and / or alkaline earth metal used includes lithium, potassium, cerium, magnesium, calcium, strontium and barium. Its content is 1 to 40 g per liter of catalyst. 1
If it is less than g, adsorption poisoning of hydrocarbon species and sintering of palladium cannot be suppressed, and if it exceeds 40 g, a significant effect of increasing the amount cannot be obtained, and conversely, the performance is deteriorated.

When the palladium / alumina-based composite oxide powder and the cerium oxide and / or alkali metal and / or alkaline earth metal added as required are in close contact with each other, an effect of improving purification performance can be obtained. Alkali metals and alkaline earth metals have the ability to reduce the adsorption and poisoning of hydrocarbons.When they are contained in the catalyst component-supporting layer, they suppress palladium and sintering and reduce their activity in low-temperature regions and oxygen-deficient atmospheres. It can be further improved.

Further, the exhaust gas purifying catalyst according to claim 6 can further contain rhodium and alumina powder in the catalyst component supporting layer. The content of rhodium is 0.001 to 5 g per 1 L of the catalyst,
If the amount is less than 1 g, the effect of improving the low-temperature activity by rhodium is not sufficiently exhibited. Conversely, if the amount exceeds 5 g, the effect of improving the low-temperature activity by rhodium is saturated and is not effective.

As the substrate on which the rhodium is supported,
In order to increase the dispersibility of rhodium and improve catalyst performance,
Alumina containing zirconium is suitable. In particular,
In order to suppress rhodium from dissolving in alumina at high temperature and increase durability, the alumina powder contains zirconium in an amount of 0.1 to 10 mol% in terms of metal. If zirconium is less than 0.1 mol%, the effect of improving zirconium added to alumina cannot be obtained, which is the same as that of Al ₂ O ₃ alone, and if it exceeds 10 mol%, the specific surface area of alumina, etc. Since the physical properties are deteriorated, the dispersibility of the noble metal is deteriorated, and sufficient performance cannot be obtained. The amount of the alumina powder used is 1 to 100 g per liter of the catalyst. If the amount is less than 1 g, sufficient dispersibility of the noble metal cannot be obtained, and
No remarkable performance improvement is seen even with more than 00 g.

Rhodium supported on alumina powder containing zirconium is contained in the palladium, alumina-based composite oxide powder and, if necessary, a catalyst component-supporting layer containing cerium oxide, to achieve low-temperature activity. Purification performance in an oxygen-deficient atmosphere can be further improved.

Further, the exhaust gas purifying catalyst according to claim 7 further contains zirconium oxide in addition to the catalyst component in the exhaust gas purifying catalyst according to claim 6. The zirconium oxide contains at least one element selected from the group consisting of lanthanum, neodymium and cerium in an amount of 1 to 40 mol% in terms of metal, and zirconium as 60%.
９８98 mol%. The reason for setting the content to 1 to 40 mol% is that zirconium oxide (ZrO ₂ ) contains lanthanum,
This is because at least one element selected from the group consisting of neodymium and cerium is added to remarkably improve the oxygen storage capacity, BET specific surface area, and thermal stability of zirconium oxide. If it is less than 1 mol%, the effect of adding the lanthanum and / or neodymium and / or cerium elements does not appear as in the case of zirconium oxide alone, and if it exceeds 40 mol%, this effect is saturated or conversely decreases.

As described above, the zirconium-containing alumina powder supporting rhodium and, if necessary, the zirconium-containing alumina powder-containing catalyst component-supporting layer further include lanthanum, neodymium and cerium. By containing the zirconium oxide containing at least one selected element, the oxidation state of rhodium is made suitable for purifying exhaust gas, and therefore, a decrease in catalytic ability due to reduction of rhodium can be suppressed.

Further, in the exhaust gas purifying catalyst according to claim 8, the rhodium-containing catalyst component layer is the same layer as the palladium-containing layer and / or the palladium-containing catalyst component, in order to efficiently exhibit the synergistic action of palladium and rhodium. It is arranged above the catalyst component layer. Thereby, the catalytic performance of palladium and rhodium can be sufficiently ensured.

Further, the exhaust gas purifying catalyst according to the ninth aspect of the present invention provides an alumina-based composite oxide according to any one of the first to eighth aspects, wherein at least one of alumina sol, cobalt, nickel and zinc is used. After dissolving or dispersing a kind of water-soluble salt in water, removing water and drying,
Then, it is obtained by firing.

By using alumina sol as the aluminum source compound, the uniformity of the crystal structure and the heat resistance can be further improved as compared with an alumina-based composite oxide prepared with a water-soluble salt of aluminum.

Further, in the method for producing an exhaust gas purifying catalyst according to the eleventh aspect, in producing the alumina-based composite oxide according to any one of the first to eighth and tenth aspects, at least one of alumina sols; After dissolving or dispersing at least one water-soluble salt selected from the group consisting of cobalt, nickel and zinc in water, adding aqueous ammonia, at least one aqueous solution selected from the group consisting of ammonium carbonate and ammonium hydrogen carbonate. PH 7.0 to 7.0
After adjusting to a range of 9.0, moisture is removed, dried, and then fired.

By using the above-mentioned alumina sol as an aluminum raw material compound and producing it by a precipitation method, a BET specific surface area sufficient for carrying palladium in a highly dispersed state can be secured.

The alumina-based composite oxide containing at least one selected from the group consisting of cobalt, nickel and zinc and aluminum used in the production of the exhaust gas purifying catalyst of the present invention comprises nitrate and carbonate of each of the above elements. , Ammonium salts, acetates and the like and alumina sol can be produced in any combination, but it is particularly preferable to use a water-soluble salt and alumina sol from the viewpoint of improving the catalytic performance.

The method for preparing 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, etc., unless there is a significant uneven distribution of components. Can be selected and used as appropriate,
After dissolving or dispersing the raw materials of each of the above elements in water,
The use of a precipitation method in which an aqueous solution of at least one compound selected from the group consisting of aqueous ammonia, ammonium carbonate and ammonium hydrogen carbonate is used as a precipitant can provide a sufficient BET specific surface area and uniform crystal structure of the alumina-based composite oxide. This is preferable because it ensures the properties and uniformly disperses the noble metal.

In producing the alumina-based composite oxide for an exhaust gas purifying catalyst of the present invention, at least one kind selected from the group consisting of cobalt, nickel and zinc is added to a dispersion obtained by adding alumina sol to pure water. An aqueous solution in which a water-soluble salt of an element is dissolved in pure water is added and stirred. At this time, a liquid in which each raw material is dissolved simultaneously or separately may be added. Next, the water in the raw material mixed solution is removed, and the residue is heat-treated to obtain an alumina-based composite oxide.

When producing the alumina-based composite oxide for an exhaust gas purifying catalyst of the present invention, a dispersion of pure water and alumina sol is added to at least one selected from the group consisting of cobalt, nickel and zinc. An aqueous solution in which a water-soluble salt of one element is dissolved in pure water is added and stirred. At this time, a liquid in which each raw material is dissolved simultaneously or separately may be added. Next, an aqueous solution of at least one compound selected from the group consisting of aqueous ammonia, ammonium carbonate, and ammonium hydrogen carbonate is gradually added to the raw material mixed solution to adjust the pH of the solution to a range of 7.0 to 9.0. After the adjustment, moisture can be removed and the residue can be heat-treated to obtain an alumina-based composite oxide.

If the above-mentioned aqueous ammonia or ammonium compound is used as the precipitating agent in the precipitation method, no metal element remains even if the precipitation cake is insufficiently cleaned, and the ammonium compound (mainly ammonium nitrate after dropping) is used. Even if it remains, it can be easily decomposed and removed in the subsequent firing. Furthermore, in order to use instead alumina sol aluminum nitrate, when drying and firing the precipitate, gas and wastewater treatment for NO _x and ammonium nitrate-derived materials is greatly reduced.

In carrying out the above 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. pH 7
When the pH is lower than 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.

The removal of water 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 of the present invention is not particularly limited.
It is preferable that the reaction be carried out in the temperature range described above under air and / or air circulation.

The method of adding at least one selected from the group consisting of cerium and zirconium to the alumina-based composite oxide may be appropriately selected from known methods such as an impregnation method and a kneading method. Although it is possible, it is particularly preferable to use the impregnation method.

Preferably, the alumina-based composite oxide powder contains a specific amount of cerium and zirconium by impregnating with an aqueous solution of a water-soluble salt of cerium and zirconium, followed by drying and calcining. An oxide can be obtained. The heat treatment of the alumina-based composite oxide to which at least one selected from the group consisting of cerium and zirconium is added is not particularly limited, but is performed, for example, at a temperature in the range of 400 ° C to 700 ° C in the air and / or under a flow of air. Is preferred.

The method of supporting palladium on the alumina-based composite oxide to which at least one selected from the group consisting of cerium and zirconium is added is appropriately selected from known methods such as an impregnation method and a kneading method. However, it is particularly preferable to use an impregnation method.

The heat treatment of the alumina-based composite oxide containing at least one selected from the group consisting of cerium and zirconium supporting palladium of the present invention is not particularly limited, but after impregnation and drying, for example, 400 ° C. to 700 ° C.
And / or under air flow at a temperature in the range of

The method of preparing the zirconium-containing alumina 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, as long as the components are not unevenly distributed. Can be used as appropriate, but using an impregnation method using an aqueous solution in which zirconium acetate is dissolved in water ensures a sufficient BET specific surface area of the alumina powder and can uniformly disperse the supported noble metal. Therefore, it is preferable. The subsequent removal of water can be appropriately selected from known methods such as an evaporation to dryness method. Although the heat treatment of the zirconium-added alumina powder used in the present invention is not particularly limited, it is preferable to perform the heat treatment after impregnation and drying, for example, at a temperature in the range of 600 ° C to 1100 ° C in the air and / or under the flow of air.

The starting compounds of rhodium include nitrates,
Any water-soluble compounds such as halides and acetates can be used.

The method of supporting rhodium on the zirconium-added alumina can be selected, for example, from an impregnation method or a kneading method, but it is particularly preferable to use the impregnation method. The subsequent removal of water can be appropriately selected from known methods such as an evaporation to dryness method. The heat treatment of the rhodium-supported zirconium-added alumina powder used in the present invention is not particularly limited,
After the impregnation / drying, it is preferable to carry out, for example, at a temperature in the range of 400 ° C. to 700 ° C. in the air and / or under an air flow.

Preferably, an exhaust gas purifying catalyst according to claim 7 is obtained by adding zirconium oxide powder to said rhodium-supported zirconium-added alumina powder. The zirconium oxide powder contains at least one selected from the group consisting of lanthanum, neodymium and cerium. When cerium oxide powder is added to the exhaust gas purifying catalyst according to the sixth aspect, the cerium oxide strongly holds rhodium in an oxidized state, and consequently the purification performance is reduced. In contrast, by adding such zirconium oxide powder, rhodium can be more effectively maintained in an oxidation state suitable for exhaust gas purification.

The thus obtained exhaust gas purifying catalyst according to the present invention can be effectively used without a carrier. However, the catalyst is pulverized and slurry, coated on the catalyst carrier, and heated at 400 ° C. to 900 ° C. It is preferable to use it after firing. The catalyst carrier can be appropriately selected from known catalyst carriers and used, and examples thereof include a monolith carrier made of a refractory material and a metal carrier.

The shape of the catalyst carrier is not particularly limited, but usually it is preferably used in a honeycomb shape. The catalyst carrier is used by applying a catalyst powder to various honeycomb base materials.
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 contact area between the catalyst and the exhaust gas is increased and the pressure loss can be suppressed, which is extremely effective when used as an exhaust gas purifying catalyst for automobiles.

The amount of the catalyst component coat layer adhered to the honeycomb material depends on the total amount of the catalyst components per liter of the catalyst.
50-400 g is preferred. The more catalyst components is preferable from the viewpoint of catalytic activity and catalyst life, when the coating layer becomes too thick, HC, CO, since the reaction gas such as NO _x becomes poor diffusion, these gases sufficiently catalyst Contact cannot be achieved, and the effect of increasing the amount of activity is saturated, and further, the gas passage resistance increases. Therefore, the coat layer amount is
The amount is preferably 50 g to 400 g per liter of the catalyst.

More preferably, the obtained exhaust gas purifying catalyst can be impregnated with an alkali metal and / or an alkaline earth metal. Alkali metals and alkaline earth metals that can be used include lithium, sodium, potassium, cesium, magnesium, calcium,
At least one element selected from the group consisting of strontium and barium.

Compounds of alkali metals and alkaline earth metals which can be used include oxides, acetates, hydroxides, nitrates,
It is water-soluble such as carbonate. This makes it possible to carry the alkali metal and / or alkaline earth metal as a basic element 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 impregnated into the above-mentioned carrier carrying 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, once the alkali metal and alkaline earth metal raw material compounds are heat-treated at a low temperature and contained in the coat layer in the form of an oxide, it becomes difficult to form a composite oxide even when exposed to a high temperature later. If the calcination temperature is lower than 200 ° C., the alkali metal compound and the alkaline earth metal compound cannot be sufficiently converted into an oxide form. If the calcination temperature exceeds 600 ° C., the raw material salt is rapidly decomposed, and However, it is not preferable because it may crack.

[0066]

The present invention will be described with reference to the following examples and comparative examples. Unless otherwise specified, “parts” means “parts by weight”.

[0067]Example 1 485 parts of nickel nitrate dissolved in 1000 parts of pure water
The solution was converted to alumina (Al _TwoO_Three) 20% by weight of Al
Suspension of 1,700 parts of Minazol dispersed in 2500 parts of pure water
After adding to the solution, 5% aqueous ammonia was added with stirring,
The pH was adjusted to 8.0. 24 hours at 150 ° C
After drying for 2 hours at 400 ° C, 2 hours at 600 ° C,
Then, it is baked at 800 ° C. for 4 hours,_0.5Al_2.0O_x
(Powder A) was obtained. Next, 79 parts of cerium acetate, oxy
Water obtained by dissolving 26 parts of zirconium acetate in 1000 g of pure water
Ni solution_0.5Al_2.0O_x(Powder A) 1000 parts
In addition, the mixture was stirred and mixed for 2 hours. At 150 ° C
After drying for 24 hours, at 400 ° C. for 2 hours, then 600
At 2 ° C for 2 hours, and the metal
Ni containing 2 mol% of lithium and 1 mol% of zirconium
_0.5Al_2.0O_x(Powder B) was obtained. Add nitric acid to this powder B
After impregnated with an aqueous palladium solution and dried,
Calcium and cerium / zirconium added
Thus, a nickel aluminate powder (powder C) was obtained. This powder C
Was 1.0% by weight.

700 parts of the above powder C carrying 1.0% by weight of palladium, 1% by mole of lanthanum ( ₂ % by weight in terms of La ₂ O ₃ ) and 32% by mole of zirconium (ZrO 2
Powder carrying palladium 0.75 parts by weight of cerium oxide powder containing 25% by weight) in terms of ₂ (powder D) 4
80 parts, activated alumina 20 parts, nitric acid aqueous solution 1200
And the mixture 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),
For 1 hour to obtain a cordierite-based monolithic carrier carrying a catalyst component having a coat layer weight of 160 g / L and a palladium carrying amount of 40 g / cf (1.41 g / L). Next, a barium acetate solution was adhered to the catalyst component-carrying cordierite-based monolithic carrier, and then calcined at 400 ° C. for 1 hour to obtain Ba.
An exhaust gas purifying catalyst was obtained by containing 15 g / L of O.

Example 2 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that Co _0.3 Al _2.0 O _x obtained by using 291 parts of cobalt nitrate instead of nickel nitrate was used.

Example 3 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that Zn _0.3 Al _2.0 O _x obtained by using 299 parts of zinc nitrate instead of nickel nitrate was used.

Example 4 Co _0.1 Ni _0.3 Al _2.0 O obtained by using 291 parts of nickel nitrate and 97 parts of cobalt nitrate instead of nickel nitrate
Except for using _x , an exhaust gas purifying catalyst was obtained in the same manner as in Example 1.

Example 5 Zn _0.1 Ni _0.3 Al _2.0 O _x obtained by using 291 parts of nickel nitrate and 100 parts of zinc nitrate instead of nickel nitrate.
Except for using, an exhaust gas purifying catalyst was obtained in the same manner as in Example 1.

Example 6 Zn _0.1 obtained by using 291 parts of nickel nitrate, 100 parts of zinc nitrate and 97 parts of cobalt nitrate instead of nickel nitrate
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that Co _0.1 Ni _0.3 Al _2.0 O _x was used.

Example 7 Ni _0.7 Al _2.0 O obtained using 679 parts of nickel nitrate
Except for using _x , an exhaust gas purifying catalyst was obtained in the same manner as in Example 1.

Example 8 Ni _0.3 Al _2.0 O obtained by using 291 parts of nickel nitrate
Except for using _x , an exhaust gas purifying catalyst was obtained in the same manner as in Example 1.

Example 9 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that the amount of barium acetate deposited was changed and BaO was contained at 5 g / L.

Example 10 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that the amount of barium acetate deposited was changed and BaO was contained at 25 g / L.

[0078]Example 11 485 parts of nickel nitrate dissolved in 1000 parts of pure water
The solution was converted to alumina (Al _TwoO_Three) 20% by weight of Al
Suspension of 1,700 parts of Minazol dispersed in 2500 parts of pure water
The solution was added and stirred for 2 hours.
After drying for 4 hours, 400 ° C for 2 hours, 600 ° C for 2 hours
For 4 hours at 800 ° C._0.5Al_2.0
O_x(Powder E) was obtained. Next, 79 parts of cerium acetate,
Dissolve 26 parts of zirconium xyacetate in 1000 g of pure water
Ni solution_0.5Al_2.0O_xPowder (powder E) 10
00 parts were added and stirred and mixed for 2 hours. This suspension is
After drying at 50 ° C. for 24 hours, at 400 ° C. for 2 hours, then
At 600 ° C for 2 hours,
Contains 2 mol% of cerium and 1 mol% of zirconium
Mu Ni_0.5Al_2.0O_x(Powder F) was obtained. This powder F
Impregnated with an aqueous solution of palladium nitrate, dried,
Calcium for 2 hours at ℃, Pd-supported cerium-zirconium
An added nickel aluminate powder (powder G) was obtained. this
The Pd-supporting concentration of the powder G was 1.0% by weight.

700 parts of the above powder G carrying 1.0% by weight of palladium, 1% by mole of lanthanum ( ₂ % by weight in terms of La ₂ O ₃ ) and 32% by mole of zirconium (ZrO
Powder carrying palladium 0.75 parts by weight of cerium oxide powder containing 25% by weight) in terms of ₂ (powder D) 4
80 parts, activated alumina 20 parts, nitric acid aqueous solution 1200
And the mixture was charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was adhered to a cordierite-based monolithic carrier (1.3 L, 400 cells) and calcined at 400 ° C. for 1 hour to obtain a coat layer weight of 160 g / L and a palladium carrying amount of 40 g / cf (1.41 g / L). A cordierite monolithic carrier carrying a catalyst component was obtained. Next, a barium acetate solution was applied to the cordierite monolithic carrier supporting the catalyst component, and then calcined at 400 ° C. for 1 hour to obtain BaO 2.
An exhaust gas purifying catalyst was obtained by containing 15 g / L.

Example 12 Example 11 was repeated, except that Co _0.3 Al _2.0 O _x obtained using 291 parts of cobalt nitrate was used instead of nickel nitrate.
An exhaust gas purifying catalyst was obtained in the same manner as described above.

Example 13 An exhaust gas purifying catalyst was obtained in the same manner as in Example 11, except that Zn _0.3 Al _2.0 O _x obtained by using 299 parts of zinc nitrate instead of nickel nitrate was used.

Example 14 Co _0.1 Ni _0.3 Al _2.0 O obtained by using 291 parts of nickel nitrate and 97 parts of cobalt nitrate instead of nickel nitrate
Except for using _x , an exhaust gas purifying catalyst was obtained in the same manner as in Example 11.

Example 15 Zn _0.1 Ni _0.3 Al _2.0 O _x obtained by using 291 parts of nickel nitrate and 100 parts of zinc nitrate instead of nickel nitrate.
Except for using, an exhaust gas purifying catalyst was obtained in the same manner as in Example 11.

Example 16 Zn obtained by using 291 parts of nickel nitrate, 100 parts of zinc nitrate and 97 parts of cobalt nitrate instead of nickel nitrate
An exhaust gas purifying catalyst was obtained in the same manner as in Example 11, except that _0.1 Co _0.1 Ni _0.3 Al _2.0 O _x was used.

Example 17 Ni _0.7 Al _2.0 O obtained using 679 parts of nickel nitrate
Except for using _x , an exhaust gas purifying catalyst was obtained in the same manner as in Example 11.

Example 18 Ni _0.3 Al _2.0 O obtained by using 291 parts of nickel nitrate
Except for using _x , an exhaust gas purifying catalyst was obtained in the same manner as in Example 1.

Example 19 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that the amount of barium acetate deposited was changed and BaO was contained at 5 g / L.

Example 20 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that the amount of barium acetate deposited was changed and BaO was contained at 25 g / L.

Example 21 137 parts of zirconium oxyacetate was dissolved in 500 parts of pure water, and 1000 parts of activated alumina was impregnated. This is 150
After drying at 24 ° C. for 24 hours, at 400 ° C. for 2 hours, then 1 hour
Calcination was performed at 000 ° C. for 2 hours to obtain an alumina powder (powder H) containing 3 mol% of Zr. This alumina powder containing 3 mol% of Zr (powder H) is impregnated with an aqueous rhodium nitrate solution, dried and dried.
The mixture was calcined at 00 ° C. for 2 hours to obtain an alumina powder (powder I) containing 3 mol% of Rh-supported Zr. The Rh carrying concentration of the powder I was 1.6% by weight.

135 parts of the above powder I carrying 1.06% by weight of rhodium, 450 parts of the above powder H, and 1 part of lanthanum
400 parts of a zirconium oxide powder (powder J) containing 20% by mol ( ₂ % by weight in terms of La ₂ O ₃ ) and 20% by mol of cerium (13% by weight in terms of CeO ₂ ), and 15 parts of activated alumina And 1000 parts of a nitric acid aqueous solution were charged into a magnetic ball mill, and mixed and pulverized to obtain a slurry liquid. Example 1
175 g / L (palladium-containing coat layer 160 g / L, palladium carrying amount 40 g / cf)
(1.41 g / L), 15 g / L BaO) and a cordierite-based monolithic carrier (1.3)
L, 400 cells).
Baking at 0 ° C. for 1 hour, total coat layer weight 225 g / L (rhodium-containing catalyst component supporting layer 50 g / L), palladium carrying amount 40 g / cf (1.41 g / L), rhodium carrying amount 2 g / cf (0. (071 g / L) was obtained.

Example 22 The above-mentioned cordierite monolithic carrier carrying the catalyst component containing the coat layer weight of 160 g / L and the palladium carrying amount of 40 g / cf (1.41 g / L) obtained according to Example 1 (1. 3 L, 400 cells), the rhodium-containing slurry obtained in Example 21 was adhered, and baked at 400 ° C. for 1 hour, the total coat layer weight 210 g / L (rhodium-containing layer weight 50 g / L), and the palladium carrying amount 40 g /Cf(1.4
1 g / L), rhodium carrying amount 2 g / cf (0.07 g / L
A cordierite monolithic carrier carrying the catalyst component L) was obtained. Next, a barium acetate solution was adhered to the cordierite-based monolithic carrier supporting the catalyst component.
It was calcined for 15 hours and contained 15 g / L of BaO to obtain an exhaust gas purifying catalyst.

[0092]Example 23 Powder (powder C) 70 supporting 1.0% by weight of palladium
0 parts and 1 mol% of lanthanum (La_TwoO_ThreeConverted to 2
Wt.) And 32 mol% of zirconium (ZrO _TwoConvert to
Cerium oxide powder containing 25% by weight
480 parts of powder (powder D) supporting 0.75 parts by weight of
And 3 mol% of Zr carrying 1.06% by weight of rhodium
135 parts of added alumina powder (powder I) and Zr 3 mol%
450 parts of alumina powder (powder H) and lanthanum
% (La_TwoO_Three2% by weight) and cerium
0 mol% (CeO_Two13% by weight)
Conium oxide powder (powder J) 400 parts and activated aluminum
35 parts and 2200 parts of nitric acid solution
And mixed and pulverized to obtain a slurry liquid. This slurry
The solution was converted to a cordierite monolithic carrier (1.3 L, 40
0 cell), baked at 400 ° C for 1 hour, and coated
Layer weight 210 g / L, palladium carrying amount 40 g / cf
(1.41 g / L), rhodium carrying amount 2 g / cf (0.
071 g / L) cordierite monolith supporting catalyst component
A carrier was obtained. Next, the catalyst component-carrying cordieri
After attaching the barium acetate solution to the toy monolith carrier,
Baking at 400 ° C. for 1 hour to contain BaO 15 g / L
Thus, an exhaust gas purifying catalyst was obtained.

[0093]Example 24 Powder (powder C) 70 supporting 1.0% by weight of palladium
0 parts and 1 mol% of lanthanum (La_TwoO_ThreeConverted to 2
Wt.) And 32 mol% of zirconium (ZrO _TwoConvert to
Cerium oxide powder containing 25% by weight
480 parts of powder (powder D) supporting 0.75 parts by weight of
And 20 parts of activated alumina and 1200 parts of nitric acid aqueous solution
Put into a magnetic ball mill, mix and pulverize to obtain a slurry liquid
Was. This slurry liquid is used as a cordierite monolithic carrier.
(1.3L, 400 cells), 1 hour at 400 ° C
Baking, coat layer weight 160g / L, palladium supported
40 g / cf (1.41 g / L) palladium supported core
Thus, a jellyite monolithic carrier was obtained.

Zr3 carrying 1.06% by weight of rhodium
135 parts by mole of alumina powder (powder I) added with mol%
Includes 450 parts by mole of alumina powder (powder H) added with 1 mole% of lanthanum ( ₂ % by weight in terms of La ₂ O ₃ ) and 20% by mole of cerium (13% by weight in terms of CeO ₂ ). 400 parts of zirconium oxide powder (powder J), 15 parts of activated alumina, and 1000 parts of a nitric acid aqueous solution were charged into a magnetic ball mill, mixed and pulverized to obtain a slurry liquid. This slurry liquid was adhered to the palladium-supported cordierite-based monolithic carrier (1.3 L, 400 cells),
C. for 1 hour at a total coat layer weight of 210 g / L (palladium content weight 160 g / L, rhodium content weight 5
0 g / L), and the supported amount of palladium 40 g / cf (1.41)
g / L), rhodium carrying amount 2 g / cf (0.071 g /
A cordierite monolithic carrier carrying the catalyst component L) was obtained. Next, a barium acetate solution was adhered to the above-mentioned catalyst component-carrying cordierite monolithic carrier, and then calcined at 400 ° C. for 1 hour to contain 15 g / L of BaO to obtain an exhaust gas purifying catalyst.

Comparative Example 1 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that Ni _0.5 Al _2.0 O _x obtained by using 2500 parts of aluminum nitrate instead of alumina sol was used.

Comparative Example 2 Activated alumina (Al ₂ O ₃ ) 1 instead of alumina sol
Ni _0.5 obtained using 700 parts and 485 parts of nickel nitrate
Except for using Al _2.0 O _x , an exhaust gas purifying catalyst was obtained in the same manner as in Example 1.

Comparative Example 3 Instead of Ni _0.5 Al _2.0 O _x , activated alumina (Al ₂
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that O ₃ ) was used.

Comparative Example 4 1164 parts of nickel nitrate and 20% alumina sol 1700
Ni _1. the parts obtained with the except for using ₂ Al _2.0 O _x,
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1.

Comparative Example 5 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that cerium oxide (CeO ₂ ) powder was used instead of the zirconium-containing cerium oxide powder.

Comparative Example 6 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that BaO was not contained.

Comparative Example 7 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that 30 g / L of BaO and 30 g / L of K ₂ O were contained.

COMPARATIVE EXAMPLE 8 135 parts of Zr 3 mol% added alumina powder (powder I) carrying 1.06% by weight of rhodium, 450 parts of Zr 3 mol% added alumina powder (powder H) and 1 mol% of lanthanum
( ₂ parts by weight in terms of La ₂ O ₃ ) and 400 parts of zirconium oxide powder (powder J) containing 20 mol% of cerium (13 parts by weight in terms of CeO ₂ );
5 parts and 1,000 parts of a nitric acid aqueous solution were put into a magnetic ball mill, and mixed and pulverized to obtain a slurry liquid. This slurry liquid was applied to a cordierite monolithic carrier (1.3 L, 400 L).
Cell, and baked at 400 ° C. for 1 hour, a coat layer weight of 50 g / L and a rhodium carrying amount of 2 g / cf (0.07
1 g / L) of a rhodium-supported cordierite-based monolithic carrier was obtained.

Next, 700 parts of cerium / zirconium-added nickel aluminate powder (powder C) supporting 1.0% by weight of palladium and 1 mol% of lanthanum (La ₂ O
₃ % 2% by weight) and 32 mol% zirconium
A magnetic ball mill comprising 480 parts of powder (powder D) in which 0.75 parts by weight of palladium is supported on cerium oxide powder containing (25% by weight in terms of ZrO ₂ ), 20 parts of activated alumina, and 1200 parts of nitric acid aqueous solution And mixed and pulverized to obtain a slurry liquid. This slurry liquid was adhered to the above rhodium-supported cordierite-based monolith carrier (1.3 L, 400 cells), baked at 400 ° C. for 1 hour, and a coat layer weight of 210 g / L (rhodium-containing coat layer 50 g / L, palladium-containing coat) Layer 160 g / L), palladium loading 40 g / cf (1.41 g / L), rhodium loading 2
A g / cf (0.071 g / L) catalyst component-carrying cordierite-based monolith carrier was obtained. Further, a barium acetate solution was adhered to the above-mentioned catalyst component-carrying cordierite monolithic carrier, and then calcined at 400 ° C. for 1 hour to obtain BaO 15 g /
L was added to obtain an exhaust gas purifying catalyst.

Table 1 shows the compositions of the exhaust gas purifying catalysts of Examples 1 to 24 and Comparative Examples 1 to 8.

[0105]

[Table 1]

Test Examples The exhaust gas purifying catalysts of Examples 1 to 24 and Comparative Examples 1 to 8 were subjected to durability under the following durability conditions.
The catalyst activity was evaluated under the following evaluation conditions.

Endurance conditions Engine displacement 4400cc Fuel unleaded gasoline Catalyst inlet gas temperature 800 ° 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 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
O and NO _x temperature when the conversion reached 50% (T5
0 / ° C.), and the results are shown in Table 2.

[0109]

[Table 2]

Evaluation condition 2: Purification performance Engine displacement: 2000 cc Fuel Unleaded gasoline Catalyst exhaust gas temperature at the inlet of the catalyst 500 ° C. Stoic atmosphere Center A / F = 14.6 Amplitude ΔA / F = ± 1.0 Each exhaust gas purification catalyst after endurance purification performance of, HC, the average conversion of CO and NO _x (percent) was determined by the following equation in stoichiometric atmosphere, and the results are shown in Table 3.

[0111]

[Table 3]

(Equation 3)

(Equation 4)

(Equation 5)

[0112]

The exhaust gas purifying catalyst according to claim 1 is
It has excellent low-temperature activity and can improve the catalytic performance of palladium in an oxygen-deficient atmosphere and near a stoichiometric air-fuel ratio.

The exhaust gas purifying catalyst according to claim 2 can further improve the structural stability of the alumina-based composite oxide at high temperatures, in addition to the above effects.

The exhaust gas purifying catalyst according to claim 3 can suppress sintering of palladium carried on the alumina-based composite oxide and improve the durability and low-temperature activity of palladium in addition to the above effects. it can.

In the exhaust gas purifying catalyst according to the fourth aspect, in addition to the above effects, it is possible to suppress a decrease in catalytic performance due to reduction of the catalyst component.

The exhaust gas purifying catalyst according to claim 5, in addition to the above-mentioned effects, has the effect of improving the low-temperature activity of palladium and the NO.
_x constant conversion performance improving effect can be obtained sufficiently.

The exhaust gas purifying catalyst according to claim 6 can reduce the effect of poisoning by adsorption of hydrocarbons and suppress the sintering of palladium in addition to the above effects.

The exhaust gas purifying catalyst according to claim 7 can further improve the low-temperature activity and the purifying performance in an oxygen-deficient atmosphere by the aid of rhodium in addition to the above effects.

The exhaust gas purifying catalyst according to claim 8 is suitable for purifying exhaust gas with the oxidized state of rhodium in addition to the above-mentioned effects, and can suppress a decrease in catalytic performance due to reduction of rhodium.

The exhaust gas purifying catalyst according to the ninth aspect, in addition to the above effects, optimizes the arrangement of the palladium content and the rhodium content in the supported amount of the catalyst component to sufficiently enhance the catalytic performance of palladium and rhodium. Can be improved.

According to the method for producing an exhaust gas purifying catalyst according to the tenth aspect, it is possible to produce an exhaust gas purifying catalyst excellent in uniformity of crystal structure and heat resistance, and excellent in low-temperature activity and catalytic activity.

The method for producing an exhaust gas purifying catalyst according to the eleventh aspect of the present invention provides an exhaust gas purifying catalyst having a large BET specific surface area, a high dispersion of palladium, and excellent catalytic activity, in addition to the above effects. Can be manufactured.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-56-10334 (JP, A) JP-A-56-10333 (JP, A) JP-A-56-10338 (JP, A) 297147 (JP, A) JP-A-2-203938 (JP, A) JP-A-5-285391 (JP, A) JP-A 5-253495 (JP, A) JP-A 8-323205 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 53/94 B01J 21/00-38/74

Claims (11)

(57) [Claims] 1. A monolithic catalyst having a catalyst component-supporting layer, comprising at least palladium as a catalyst component and a metal aluminate containing cerium and zirconium, wherein the metal aluminate comprises cobalt, nickel and zinc. At least ## EQU1 ## (X) _a Al _b O _c (wherein, X is cobalt, selected from the group consisting of nickel and zinc; contains at least one selected from the group, and the following general formula A, b and c represent the atomic ratio of each element, and when b = 2.0, a = b
0.1 to 0.8, where c is the number of oxygen atoms necessary to satisfy the valence of each of the above components). . 2. The exhaust gas purifying catalyst according to claim 1, wherein cerium and zirconium are contained in the metal aluminate in an amount of 0.1 to 5 mol% in terms of metal with respect to aluminum. 3. The exhaust gas purifying catalyst according to claim 1, further comprising at least one selected from the group consisting of lanthanum, neodymium and zirconium in terms of metal.
An exhaust gas purifying catalyst comprising a cerium oxide containing 40 mol% and cerium at 60 to 98 mol%. 4. The exhaust gas purifying catalyst according to claim 1, wherein 30 to 80% by weight of the total palladium in terms of metal is contained in the alumina-based composite oxide. An exhaust gas purifying catalyst characterized by the above-mentioned. 5. The exhaust gas purifying catalyst according to claim 1, further comprising at least one selected from the group consisting of alkali metals and alkaline earth metals. Gas purification catalyst. 6. The exhaust gas purifying catalyst according to claim 1, further comprising rhodium and alumina powder. 7. The exhaust gas purifying catalyst according to claim 6, wherein
Further, at least one selected from the group consisting of lanthanum, neodymium and cerium is 1 to 40 mol% in terms of metal,
An exhaust gas purifying catalyst comprising zirconium oxide containing 60 to 98 mol% of zirconium. 8. The exhaust gas purifying catalyst according to claim 6, wherein the rhodium-containing layer is arranged on the same layer as palladium and / or above the palladium-containing layer. 9. In producing the exhaust gas purifying catalyst according to any one of claims 1 to 8, the alumina-based composite oxide is mixed with at least one of fine particle alumina hydrate colloid, cobalt, nickel and zinc. A method for producing an exhaust gas purifying catalyst, comprising dissolving or dispersing a kind of water-soluble salt in water, removing water, and calcining the water-soluble salt. 10. The exhaust gas purifying catalyst according to claim 1, further comprising an alkali metal and / or an alkaline earth metal impregnated thereon, and oxidizing the alkali metal and / or the alkaline earth metal. An exhaust gas purifying catalyst characterized by being contained in a coating layer in a physical form. 11. In producing the exhaust gas purifying catalyst according to any one of claims 1 to 8 and 10, the alumina-based composite oxide is mixed with fine-particle alumina hydrate colloid, cobalt, nickel and After dissolving or dispersing at least one water-soluble salt of zinc in water, 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.
A method for producing an exhaust gas purifying catalyst, wherein H is adjusted so as to be in a range of 7.0 to 9.0, water is removed, and then calcined.