JP3493879B2 - Exhaust gas purification catalyst and exhaust gas purification method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to hydrocarbons (HC) and carbon monoxide (C) in exhaust gas discharged from internal combustion engines such as automobiles (gasoline, diesel) and boilers.
The present invention relates to an exhaust gas purifying catalyst system for purifying O) and nitrogen oxides (NOx), and particularly to a NOx purifying method in an oxygen excess region.

[0002]

2. Description of the Related Art In recent years, the demand for fuel-efficient vehicles has been increasing due to the problem of exhaustion of petroleum resources and the problem of global warming, and the development of lean-burn vehicles has attracted attention for gasoline vehicles. In a conventional lean-burn vehicle, the exhaust gas atmosphere becomes leaner than the stoichiometric air-fuel state when running lean-burn, but when a normal three-way catalyst is applied in the lean range, the excess oxygen Due to the influence, there is a problem that the NOx purification action becomes insufficient. Therefore, it has been desired to develop a catalyst that purifies NOx even when oxygen becomes excessive.

Various catalysts for purifying NOx in the lean range have been proposed in the past, for example, Japanese Unexamined Patent Publication No. 5-168860.
As shown in the publication, there is proposed a catalyst that absorbs NOx in a lean region and releases NOx at the time of stoichiometry, as represented by a catalyst in which Pt carries lanthanum or the like. Further, for the purpose of further improving the NOx absorption capacity, for example, JP-A-5-261287 and JP-A-5-317652.
JP-A-6-31139, JP-A-6-28
As disclosed in Japanese Patent No. 5371, etc., a technique using an alkali metal or an alkaline earth metal, or JP-A-6-142.
As disclosed in Japanese Patent Application Laid-Open No. 458 and Japanese Patent Application Laid-Open No. 6-262040, a technique using a rare earth metal or an iron group metal in addition to an alkali metal and an alkaline earth metal is disclosed.

[0004]

However, these conventional techniques still have a problem that the NOx absorption capacity is insufficient or the performance after endurance is insufficient.

Further, since lean-burn engine vehicles run at the stoichiometric air-fuel ratio at the time of acceleration with a high load, the ternary function is also required in lean-burn vehicles. In the case of using the compounds, there is a problem that the basicity of the compounds affects the oxidizing ability of the noble metal, and in some cases, the conversion performance of HC and CO among the ternary functions becomes insufficient.

Further, in the above-mentioned prior art, if lean steady running is continued for a long time, the amount of NOx absorbed saturates, and eventually there is a problem that the absorbing action disappears.

An object of the present invention is to solve the problems of the prior art and to provide an exhaust gas purifying catalyst having a high NOx absorbing action even when oxygen is excessive.

[0008]

As a result of intensive studies in view of the above problems, the inventors have invented the following novel catalyst and exhaust gas purification method.

That is, according to the present invention, a) at least one selected from platinum, palladium, and rhodium on a monolithic structure type carrier, and b) (La _1-x A _x ) _1- α B O _3- δ 0 < x <1, 0 <α <0.2, 0 ≦ δ ≦ 1 A = Ba, at least one selected from K, B = complex represented by at least one selected from iron, cobalt, nickel, and manganese (composite Body-I), and c) a complex represented by Ce _y Zr _1-y O ₂ 0 <y <1 (complex-II),
Further, 20 to 80% of the noble metal is a catalyst supported on the composite-II, and purifies nitrogen oxides in an oxygen excess atmosphere.

At least one selected from iron, cobalt, nickel, and manganese is 5 to 50 g per 1 L of catalyst in terms of oxide, and lanthanum is 5 to 5 per 1 L of catalyst in terms of oxide.
50g, 5-10 barium per liter of catalyst in terms of oxide
0 to 20 g of potassium per liter of catalyst in terms of oxide
g, cerium is 5 to 100 per 1 L of catalyst in terms of oxide
g and zirconium are 5 to 10 per 1 L of catalyst in terms of oxide.
A catalyst containing 0 g of nitrogen oxide is used to purify nitrogen oxides in an oxygen excess atmosphere.

Nitrogen oxides in an oxygen-excess atmosphere are purified by a catalyst having a composite-I layer as a lower layer and a layer not containing the complex-I as an upper layer.

At least two catalysts are provided in the exhaust system of the engine, a catalyst containing zeolite supporting Cu is disposed in the front stage, and any one of the above-mentioned catalysts is disposed in the rear stage, and nitrogen is provided in an oxygen excess atmosphere. Purifies oxides.

Exhaust gas of a lean-burn engine vehicle in which the air-fuel ratio repeatedly changes between stoichiometry and 15 or higher is purified by any one of the above catalysts.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the catalyst used in the present invention will be described in detail below.

The monolithic carrier made of a heat resistant material is preferable as the monolithic carrier used in the embodiment of the present invention.
For example, a ceramic material such as cordierite or a metal material such as ferritic stainless steel is used.

The noble metal used in the embodiment of the present invention is preferably used by being supported on a heat resistant inorganic carrier. For the carrier, a material having a high specific surface area and excellent heat resistance is suitable for ensuring the dispersibility of the catalytically active component, and among them, activated alumina is preferable. Further, rare earth elements, zirconium or the like may be added for the purpose of increasing the heat resistant specific surface area.
The amount of activated alumina used is preferably 50 to 300 g per liter of catalyst.

The amount of the noble metal used in the embodiment of the present invention may be any amount as long as the NOx absorbing function and the three-way function are sufficiently obtained, but as used in a general three-way catalyst, it is per 1 L of the catalyst. It is preferably 0.1 to 10 g.

At least one selected from iron, cobalt, nickel, and manganese, and lanthanum, potassium, and barium exhibit their effects to the maximum when all of them contained in the catalyst are combined. Even if a part of the complex forms a desired effect. Similarly, cerium and zirconium can have the same effect if at least a part thereof forms a composite.

The constituent elements of the composites-I and II exist as a composite oxide without being separated as separate oxides even after thermal endurance. This can be confirmed by, for example, X-ray diffraction measurement.

In the catalyst used in the embodiment of the present invention,
Even if impurities contained in those raw materials are included, it does not matter if the amount does not hinder the action. For example, a small amount of strontium contained in barium, lanthanum contained in cerium, neodymium, samarium, or hafnium contained in zirconium may be contained.

As a method for producing a complex containing at least one selected from iron, cobalt, nickel and manganese, lanthanum, potassium and barium used in the present embodiment, for example, metal salts of each component (nitrate, carbonate) , Acetate,
An aqueous solution of citrate, hydrochloride, etc.) is prepared, and if necessary, a precipitant (ammonia, ammonium carbonate, etc.) is added to form a precipitate, and the solution or precipitate is dried and calcined to form a composite. There is a method of obtaining oxide powder. By such a method, at least a part of each component is composited, and it is suitable for the purpose. However, the method for producing the composite is not necessarily limited to the above method,
Any method other than the above may be used as long as the complex is formed. Further, the composite containing cerium and zirconium used in the embodiment of the present invention can be obtained by the same method.

The amount of Cu-supporting zeolite in the Cu-supporting zeolite catalyst used in the embodiment of the present invention is not particularly limited as long as it exhibits a NOx purification action, but catalyst carrier 1L
It is preferably 100 to 300 g per unit. Cu is preferably supported on zeolite by ion exchange. Additives for improving activity and durability, such as C
You may add o, Ca, P, Ce, Nd, etc. Zeolites having high activity after Cu ion exchange and excellent heat resistance are preferable, for example, pentasil-type zeolite,
Y-type zeolite, mordenite, ferrierite, etc. are used.

As a method of installing two catalysts, a Cu-supported zeolite catalyst and a NOx absorption catalyst, in the exhaust system, for example, 1
There are a method of mounting and arranging two catalysts in one catalytic converter, and a method of putting two kinds of catalysts in different converters and installing them. The installation position of the catalyst is not particularly limited, and examples thereof include a position directly under the manifold and a position under the floor. If the purification performance is not sufficient with one catalyst in each of the front stage and the rear stage, a plurality of one or both of the front stage and the rear stage may be provided, or another type of catalyst may be added.

[0024]

EXAMPLES The present invention will be described below with reference to Examples, Comparative Examples and Test Examples.

Example 1 Activated alumina powder was impregnated with an aqueous rhodium nitrate solution, dried and then calcined at 400 ° C. for 1 hour to obtain Rh-supported activated alumina powder (powder A). The Rh concentration of this powder was 2.0% by weight.

The activated alumina powder was impregnated with a Pd nitrate aqueous solution, dried, and calcined at 400 ° C. for 1 hour to obtain a Pd-supported activated alumina powder (powder B). The Pd concentration of this powder was 2.0% by weight.

Ammonia was added to a mixed aqueous solution of cerium nitrate and zirconium nitrate, and the resulting precipitate was dried.
Firing was performed at 0 ° C. to obtain cerium-zirconium oxide powder (powder C). This powder had a metal atom ratio of cerium / zirconium = 8/2. The powder C was impregnated with an aqueous Pd nitrate solution, dried and then baked at 400 ° C. for 1 hour to obtain a Pd-supporting cerium-zirconium powder (powder D). The Pd concentration of this powder was 2.0% by weight.

Citric acid was added to a mixture of lanthanum carbonate, barium carbonate and cobalt carbonate, dried and calcined at 700 ° C. to obtain (powder E). This powder had a metal atomic ratio of lanthanum / barium / cobalt = 2/2/5.

106 g of powder A, 305 g of powder B, 225 g of powder D, 225 g of powder E, 39 g of activated alumina powder, and 900 g of water were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolith carrier (1.0 L, 400 cells), and excess slurry in the cells was removed by an air flow to remove the slurry.
After drying at 0 ° C, it was baked at 400 ° C for 1 hour. This operation was performed twice to obtain (Catalyst-1) having a coat layer weight of 200 g / L-carrier.

Example 2 (Catalyst-2) was prepared in the same manner as in Example 1 except that potassium carbonate was used instead of barium carbonate in the production of powder E.

Example 3 Citric acid was added to a mixture of lanthanum carbonate, barium carbonate, potassium carbonate and cobalt carbonate, dried and calcined at 700 ° C., and the metal atomic ratio was lanthanum / barium / potassium / cobalt = 1/2/1. A powder of / 5 was obtained.

(Catalyst-3) was prepared in the same manner as in Example 1 except that this powder was used instead of the powder E.

Comparative Example 1 (Catalyst-4) was prepared in the same manner as in Example 1 except that the lanthanum of the powder E was removed.

Comparative Example 2 (Catalyst-5) was prepared in the same manner as in Example 1 except that powder E except for barium was removed.

Comparative Example 3 (Catalyst-6) was prepared in the same manner as in Example 1 except that the powder E except cobalt was removed.

Comparative Example 4 (Catalyst-7) was prepared in the same manner as in Example 1 except that powder C except for cerium was removed.

Comparative Example 5 (Catalyst-8) was prepared in the same manner as in Example 1 except that the powder C except for zirconium was removed.

Comparative Example 6 Activated alumina powder was impregnated with an aqueous solution of Pd nitrate and dried 4
The Pd-supported activated alumina powder (powder F) was obtained by firing at 00 ° C. for 1 hour. The Pd concentration of this powder is 4.0% by weight.
Met.

106 g of powder A, 265 g of powder F, 36 g of zirconium oxide, 189 g of cerium oxide, 71 g of lanthanum oxide, 71 g of barium oxide, 83 g of cobalt oxide, 79 g of activated alumina powder and 900 g of water.
Was charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolith carrier (1.0 L, 400 cells), excess slurry in the cells was removed by an air stream, and the slurry was dried at 130 ° C.
It was baked at 400 ° C. for 1 hour. This operation was performed twice to obtain (Catalyst-9) having a coat layer weight of 200 g / L-carrier.

Comparative Example 7 106 g of powder A, 265 g of powder F and 225 of powder C
g, 225 g of powder E, 79 g of activated alumina powder and 900 g of water were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry solution was adhered to a cordierite monolith carrier (1.0 L, 400 cells), excess slurry in the cells was removed by an air stream, dried at 130 ° C, and then calcined at 400 ° C for 1 hour. Do this work twice,
(Catalyst-10) having a coat layer weight of 200 g / L-support was obtained.

Example 4 Activated alumina powder was impregnated with an aqueous solution of dinitrodiammine Pt, dried and calcined at 400 ° C. for 1 hour to obtain Pt-supported activated alumina powder (powder G). The Pt concentration of this powder was 2.0% by weight.

Powder C was impregnated with an aqueous solution of dinitrodiammine Pt, dried and calcined at 400 ° C. for 1 hour to obtain Pt-supported activated alumina powder (powder H). The Pt concentration of this powder was 2.0% by weight.

106 g of powder A, 305 g of powder G, 225 g of powder H, 225 g of powder E, 39 g of activated alumina powder and 900 g of water were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolith carrier (1.0 L, 400 cells), and excess slurry in the cells was removed by an air flow to remove the slurry.
After drying at 0 ° C, it was baked at 400 ° C for 1 hour. This operation was performed twice to obtain (Catalyst-11) having a coat layer weight of 200 g / L-carrier.

Example 5 Example 1 was repeated except that powder E was replaced with powder having a metal atomic ratio of lanthanum / barium / cobalt = 1/3/5.
Was prepared in the same manner as in (Catalyst-12).

Example 6 Example 1 was repeated except that powder E was replaced with powder having a metal atomic ratio of lanthanum / barium / cobalt = 3/1/5.
Was prepared in the same manner as in (Catalyst-13).

Example 7 (Catalyst-14) was prepared in the same manner as in Example 1 except that the powder C was replaced by a powder having a metal atomic ratio of cerium / zirconium = 2/8.

Example 8 (Catalyst-15) was prepared in the same manner as in Example 1 except that the powder E was cobalt instead of iron.

Example 9 (Catalyst-16) was prepared in the same manner as in Example 1 except that the powder E was replaced by nickel.

Example 10 (Catalyst-17) was prepared in the same manner as in Example 1 except that manganese was used instead of cobalt in powder E.

Example 11 85 g of powder A, 244 g of powder B and 180 of powder D
g, 360 g of powder E, 31 g of activated alumina powder, and 900 g of water were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolith carrier (1.0 L, 400 cells), excess slurry in the cells was removed by an air stream, dried at 130 ° C, and then baked at 400 ° C for 1 hour to coat. Layer weight 125g /
An L-carrier was obtained.

142 g of powder A, 407 g of powder B, 300 g of powder D, 51 g of activated alumina powder, and 900 of water.
g was put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid is adhered to the above-mentioned 125 g / L carrier, and the excess slurry in the cell is removed by an air flow to remove 13
After being dried at 0 ° C., it was baked at 400 ° C. for 1 hour to obtain (Catalyst-18) having a coat layer weight of 200 g / L-carrier.

Example 12 Citric acid was added to a mixture of lanthanum carbonate, barium carbonate, potassium carbonate and cobalt carbonate, dried and calcined at 700 ° C., and the metal atomic ratio was lanthanum / barium / potassium / cobalt = 1/2/1. A powder of / 5 was obtained.

(Catalyst-19) was prepared in the same manner as in Example 11 except that this powder was used instead of the powder E.

Example 13 365 g of powder F, 225 g of powder D and 225 of powder E
g, 85 g of activated alumina powder and 900 g of water were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was used as a cordierite monolith carrier (1.0 L, 4 L
No. 00 cell), the excess slurry in the cell was removed by an air flow, the resultant was dried at 130 ° C., and then baked at 400 ° C. for 1 hour. This operation is performed twice, and the coat layer weight is 200
A g / L-support (Catalyst-20) was obtained.

Example 14 A 0.2 mol / L copper nitrate aqueous solution (5.2 Kg) and zeolite powder (2 Kg) were mixed, stirred and filtered three times, and then dried and fired to prepare a Cu-supporting zeolite powder (Powder J). ) Got. The Cu concentration of this powder was 5%.

810 g of Powder J, silica sol (solid content 2
0%) 450 g and water 540 g were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolith carrier (1.0 L, 400 cells), excess slurry in the cells was removed by an air stream, dried at 130 ° C, and then baked at 400 ° C for 1 hour to coat. (Catalyst-21) having a layer weight of 300 g / L-support was obtained.

The catalyst-21 was placed in the front stage and the catalyst-1 was placed in the rear stage.

Example 15 The catalyst-21 was placed in the front stage, and the catalyst-2 was placed in the rear stage.

Example 16 The catalyst-21 was placed in the front stage, and the catalyst-3 was placed in the rear stage.

Example 17 Catalyst-21 was placed in the front stage and catalyst-4 was placed in the rear stage.

Example 18 The catalyst-21 was placed in the front stage and the catalyst-11 was placed in the rear stage.

Example 19 Catalyst-21 was placed in the front stage and catalyst-19 was placed in the rear stage.

Example 20 Catalyst-21 was placed in the front stage and catalyst-20 was placed in the rear stage.

Test Example Durability Method A catalyst was attached to the exhaust system of an engine having a displacement of 4400 cc and operated at a catalyst inlet temperature of 600 ° C. for 50 hours.

Evaluation method A catalyst was attached to the exhaust system of an engine with a displacement of 2000 cc, and A / F = 14.6 was set for 30 seconds and A / F = 22 was set at 30.
The operation was repeated for 2 seconds. The catalyst inlet temperature was 400 ° C. The total conversion rate for one cycle of this switching operation was determined.

Table 1 shows the evaluation results of the conversion rates of Examples 1 to 19 and Comparative Examples 1 to 7. Table 2 shows the catalyst compositions obtained in the respective examples and comparative examples.

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

As described above, according to the present invention, the following effects can be obtained.

In the catalyst of the present invention, a high NOx absorption action can be obtained by the interaction of the two-type complex. Of these, the complex-II carrying a noble metal is used to convert NO into NO ₂ and N.
It has an action of oxidizing to O ₃ , and the complex-I has a action of rapidly absorbing it as a nitrate. Noble metal is originally NO
Has the ability to be converted to NO ₂ or NO ₃ , and its conversion ability will be further improved by loading it on the complex-II. Since each of the composites-I and II is composited, a high action and effect which cannot be obtained only by mixing oxides of each element alone are exhibited.

The amount of the noble metal supported on the composite-II is 20 to 80% of the noble metal contained in the catalyst, and the remaining noble metal is preferably supported on the high specific surface area carrier such as alumina. Since the noble metal supported on the high specific surface area carrier has high dispersibility, it is effective in low temperature activation and widening of the window width among the ternary functions. By loading the noble metal on both the composite-II and the high specific surface area carrier, it becomes possible to purify exhaust gas in a wide range from stoichiometric to lean regions.

Further, the present catalyst has high NO even after thermal endurance.
One of the characteristics is that it has an x-absorbing effect. This is because the effect of improving the thermal durability was exhibited by combining the respective components. Since the complex-I has a perovskite structure with a small proportion of A sites, solid-state reaction with other components (for example, alumina) is less likely to occur,
As a result, changes in physical properties after endurance can be suppressed. Since the composite-II has a small decrease in the specific surface even after the thermal endurance, the NO oxidation ability by the noble metal is maintained.

Thus, by incorporating two different kinds of composites in the catalyst, a high NOx absorption function, which is the object of the present invention, can be obtained.

In the present invention, at least one selected from iron, cobalt, nickel, and manganese is 5 to 50 g per 1 L of the catalyst in terms of oxide, lanthanum is 5 to 50 g per 1 L of the catalyst in terms of oxide, and barium is oxide. 5 to 100 g of catalyst per liter of catalyst, potassium 1 in terms of oxide
1 to 20 g per L, cerium 5 to 100 g per 1 L catalyst in terms of oxide, zirconium 1 L in terms of oxide
One of the features is that each of them is contained in an amount of 5 to 100 g.

When at least one selected from iron, cobalt, nickel and manganese is within the above range, sufficient NOx absorption capacity and durability cannot be obtained, and even when it is above the above range, a significant amount increasing effect is obtained. I can't. When the lanthanum is within the above range, sufficient NOx absorption capacity and durability cannot be obtained, and even when the lanthanum is above the above range, a significant amount increasing effect cannot be obtained. Sufficient NOx when barium is below the above range
Absorptive capacity cannot be obtained, and a significant amount increasing effect cannot be obtained even if the above range is exceeded. When potassium is below the above range, sufficient NOx absorption capacity cannot be obtained, and above the above range, no significant effect of increasing the amount can be obtained, and HC and CO oxidation reactions among the three functions are reduced. It will be. When the amount of cerium is less than the above range, the effect of improving the NOx absorption capacity and the effect of improving the ternary function cannot be obtained sufficiently. When the amount of zirconium is less than the above range, sufficient NOx absorption capacity improving effect and ternary function improving effect cannot be obtained, and even when it is more than the above range, a significant amount increasing effect cannot be obtained.

Further, one feature of the present invention is that the complex-I is provided as the lower layer and the layer not containing the complex-I is provided as the upper layer. With such a structure, NOx released during stoichiometry can be efficiently purified. This is because NOx released during stoichiometry once passes through the upper layer by sharing the absorption function with the lower layer, and as a result, NOx can be efficiently purified. With such a layered structure, high NOx can be obtained.
It is possible to secure three-way catalyst performance while obtaining absorption capacity.

Further, according to the present invention, at least two catalysts are provided in the exhaust system of the engine, the catalyst containing the zeolite supporting Cu is arranged in the front stage, and the catalysts in the rear stage are arranged in the first to third stages.
One of the features is to dispose the catalyst described in 1.
With this arrangement, NOx can be used under a wide range of operating conditions.
It is possible to purify.

The Cu-supported zeolite catalyst is used as a catalyst for purifying NOx in the oxygen excess region, for example, JP-A-63-1.
Although already disclosed as in No. 00919, this catalyst has a problem that the NOx purification performance becomes insufficient when the HC / NOx ratio is low. Further, although the action of the catalyst that absorbs and purifies NOx does not decrease even if the HC / NOx ratio is low, there is a problem that the NOx absorption amount becomes saturated when the lean steady running is continued for a long time, and eventually the absorption action disappears. In the present invention, the above problem is solved by disposing the Cu-supported zeolite catalyst in the front stage and the NOx absorption catalyst in the rear stage. That is, when the HC / CO ratio is low, the catalyst in the latter stage works, and the catalyst in the former stage works during lean steady running, enabling a wide range of operating conditions.

Further, it has been found that by adopting the arrangement as in the present invention, the action of the NOx absorption catalyst in the latter stage can be greatly enhanced. The cause is not yet clear, but for example, the Cu zeolite catalyst is rapidly oxidizing NOx necessary for NOx absorption, and the Cu zeolite catalyst is converted into HCD, NOx, and O ₂ concentrations that are convenient for NOx absorption. It is possible that

Furthermore, the present invention is characterized in that the exhaust gas of a lean-burn engine vehicle in which the air-fuel ratio repeatedly changes between stoichiometry and 15 or more is purified by the above-mentioned catalysts. By changing the atmosphere in this way, a cycle of NOx absorption and release is established, and NOx can be efficiently purified.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI B01J 23/64 104A (72) Inventor Hidetoshi Ito 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-5-31367 (JP, A) JP-A-4-367713 (JP, A) JP-A-5-86849 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01J 21/00-38/74 B01D 53 / 86,53 / 94

Claims (9)

(57) [Claims] 1. On a monolithic structure type carrier, a) at least one selected from platinum, palladium and rhodium, and b) (La _1-x A _x ) _1- α B O _3- δ 0 <x <1. , 0 <α <0.2, 0 ≦ δ ≦ 1 A = Ba, at least one selected from K, B = complex represented by at least one selected from iron, cobalt, nickel, and manganese (complex-I ), And c) the complex represented by Ce _y Zr _1-y O ₂ 0 <y <1 (complex-II), and 20 to 80% of the noble metal contained in the catalyst is contained in the complex- An exhaust gas purifying catalyst for purifying nitrogen oxides in an oxygen excess atmosphere, which is supported on II. 2. At least one selected from iron, cobalt, nickel and manganese is 5 per liter of catalyst in terms of oxide.
~ 50g, 5 to 5 per liter of catalyst in terms of oxide of lanthanum
0 g, barium is 5 to 100 per 1 L of catalyst in terms of oxide.
g, potassium is 1 to 20 g per 1 L of the catalyst in terms of oxide,
Cerium is contained in an amount of 5 to 100 g per 1 L of the catalyst in terms of oxide, and zirconium is contained in the amount of 5 to 100 g per 1 L of in terms of the oxide, purifying nitrogen oxides in an excess oxygen atmosphere according to claim 1. Exhaust gas purification catalyst. 3. Exhaust gas purification for purifying nitrogen oxides in an oxygen excess atmosphere according to claim 1 or 2, wherein Complex-I is provided as a lower layer, and a layer not containing Complex-I is provided as an upper layer. Catalyst. 4. An engine exhaust system comprising at least two catalysts.
Nitrogen in an oxygen-excess atmosphere, characterized in that a single catalyst is provided at the front stage, and a catalyst containing zeolite supporting Cu is disposed at the front stage, and the catalyst according to any one of claims 1 to 3 is disposed at the rear stage. Exhaust gas purification catalyst system that purifies oxides. 5. The exhaust gas purifying catalyst according to claim 1, which purifies exhaust gas of a lean-burn engine vehicle in which an air-fuel ratio repeats stoichiometry and 15 or more. 6. The exhaust gas from the lean burn engine,
Contacting with a catalyst containing zeolite supporting Cu,
Then, a) at least one selected from platinum, palladium, and rhodium, and b) (La _1-x A _x ) _1- α B O _3- δ 0 <x <1, 0 <α <0.2, 0 ≤ δ ≤ 1 A = at least one selected from Ba and K B = a composite (complex-I) represented by at least one selected from iron, cobalt, nickel, and manganese; and c) Ce _y Zr _{1- y} O ₂ 0 <y <1 and a complex (complex-II), and 20 to 80% of the noble metal contained in the catalyst is brought into contact with the catalyst supported on the complex-II. A characteristic exhaust gas purification method. 7. At least one selected from iron, cobalt, nickel and manganese is 5 per liter of catalyst in terms of oxide.
~ 50g, 5 to 5 per liter of catalyst in terms of oxide of lanthanum
0 g, barium is 5 to 100 per 1 L of catalyst in terms of oxide.
g, potassium is 1 to 20 g per 1 L of the catalyst in terms of oxide,
The exhaust gas purifying method according to claim 6, wherein cerium is contained in an amount of 5 to 100 g per 1 L of the catalyst in terms of oxide, and zirconium is included in the amount of 5 to 100 g per 1 L of in terms of the oxide. 8. The exhaust gas purification method according to claim 6, wherein the complex-I is provided as a lower layer, and a layer not containing the complex-I is provided as an upper layer. 9. The exhaust gas purifying method according to claim 6, wherein the exhaust gas of a lean-burn engine vehicle in which the air-fuel ratio repeats stoichiometry and 15 or more is purified.