JP2002336700A - NOx purification catalyst and NOx purification system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To release sulfur poisoning of a catalytic metal even during operation in a stoichiometric to rich range and to efficiently purify NOx.
To provide a purification catalyst and a NOx purification system. SOLUTION: It is used for an exhaust gas purification process in a lean region or a stoichiometric to rich region, and contains a catalytic metal and an oxygen absorbing / releasing material, and the catalytic metal carried on the oxygen absorbing / releasing material reduces SOx in the exhaust gas. NO adsorbed as sulfate or sulfite
x purification catalyst. The catalytic noble metal contains platinum. 5 platinum
This is a NOx purification catalyst that is supported on the ceria at a rate of about 50% and adsorbs SOx as sulfate or sulfite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a NOx purification catalyst, and more particularly, to an automobile (gasoline, diesel).
The present invention relates to a NOx purification catalyst for purifying hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxide (NOx) in exhaust gas discharged from an internal combustion engine such as a boiler. The NOx purification catalyst of the present invention is particularly suitable for lean NOx
x purification method and stoichiometric-rich catalyst component is SOx
It is made by paying attention to the method of taking in.

[0002]

2. Description of the Related Art In recent years, the demand for fuel-efficient vehicles has been increasing due to the problem of depletion of petroleum resources and the problem of global warming, and development of lean-burn vehicles has attracted attention for gasoline vehicles. In lean-burn vehicles, during lean-burn operation, the exhaust gas atmosphere is leaner than in the stoichiometric air-fuel state, but when a normal three-way catalyst is applied in the lean region, the NOx purification effect is reduced due to the influence of excess oxygen. There was a problem that it became insufficient. Therefore, development of a catalyst capable of purifying NOx even when oxygen becomes excessive has been desired.

[0003]

From such a background,
Various catalysts for purifying NOx in the lean region have been proposed. For example, as typified by a catalyst in which platinum (Pt) and lanthanum (La) are supported on a porous carrier (JP-A-5-168860), lean catalysts have been proposed. A catalyst that adsorbs NOx in a region and releases and purifies NOx in a stoichiometric to rich region has been proposed.

[0004] However, fuel and lubricating oil contain sulfur, which is emitted as oxides into exhaust gas, so that the catalyst is poisoned by sulfur and the NOx conversion performance is reduced. (This is called "sulfur poisoning"). This sulfur poisoning cannot be avoided as long as the exhaust gas contains sulfur in some form, and it has been an important issue how to remove sulfur attached to the catalyst. Up to now, attention has been paid mainly to NOx adsorbents in catalysts for sulfur poisoning, and a plurality of NOx adsorbents are combined so that the poisoning of the adsorbents can be easily released (Japanese Patent Laid-Open No. 7-5154).
No. 4) or high dispersion (JP-A-9-173).
No. 839).

Further, as a result of studying the above problems, the present inventors have found that it is more effective to remove sulfur poisoning of catalytic noble metal, which is an active site, than to improve a NOx adsorbent. That is, it has been found that the reaction for desorbing sulfur from the NOx adsorbent does not sufficiently occur unless the sulfur poisoning of the catalytic noble metal, which is the active point, is not released.

The present invention has been made in view of such problems and knowledge of the prior art, and an object of the present invention is to provide a NOx purification catalyst and a NOx purification system that can easily release sulfur poisoning. It is in.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems. As a result, when oxygen is insufficient, the oxygen absorbing / releasing material releases oxygen to prevent sulfuration of SO ₂ or the like. As a result, the above-mentioned problems have been solved, and the present invention has been completed.

That is, the NOx purifying catalyst of the present invention is a NOx purifying catalyst used for purifying exhaust gas from an internal combustion engine or a combustor that is operated in a lean region or a stoichiometric to rich region. An oxygen absorbing / releasing material that carries at least a part of the catalytic noble metal, wherein the catalytic noble metal carried by the oxygen absorbing / releasing material contains SOx in the exhaust gas.
Is adsorbed as sulfate or sulfite.

A preferred embodiment of the NOx purifying catalyst according to the present invention is characterized in that the catalytic noble metal contains platinum.

In another preferred embodiment of the NOx purifying catalyst of the present invention, the catalyst contains at least one metal selected from the group consisting of alkali metals, alkaline earth metals and rare earth metals, and has a lean air-fuel ratio. NOx is adsorbed in the stoichiometric range and the adsorbed NOx is reduced to nitrogen in the stoichiometric to rich range.

Still another preferred embodiment of the NOx purifying catalyst according to the present invention is characterized in that the catalytic noble metal contains rhodium.

In another preferred embodiment of the NOx purifying catalyst of the present invention, the catalyst comprises a layer having a large amount of oxygen absorbing / releasing material and a layer having a small amount of oxygen absorbing / releasing material, and the layer having a small amount of oxygen absorbing / releasing material has an oxygen absorbing / releasing material. It is characterized by being laminated on a layer with a large amount of release material.

Further, in still another preferred embodiment of the NOx purification catalyst of the present invention, the catalyst comprises barium and / or magnesium, ceria, and platinum and / or rhodium, and at least a part of the platinum is contained. It is supported on the ceria.

Still another preferred embodiment of the NOx purification catalyst of the present invention is characterized in that the refractory inorganic carrier further supports sodium and / or cesium and / or potassium.

In still another preferred embodiment of the NOx purification catalyst of the present invention, at least a part of the above barium and / or magnesium is compounded, and the following general formula: Ba _x Mg _y (CO ₃ ) ₂ (wherein X and y are atomic ratios of each element, x = 0.5 to
1.999, y = 0.001-1.5 and x + y = 2.
0) is formed.

Further, the NOx purifying catalyst of the present invention is a NOx purifying catalyst used for purifying exhaust gas from an internal combustion engine or a combustor operated in a lean region or a stoichiometric to rich region, and comprises platinum and ceria. The platinum is supported on the ceria at a ratio of 5 to 50% based on the total amount of platinum,
This platinum is characterized in that SOx in the exhaust gas is adsorbed as sulfate or sulfite.

Further, the NOx purifying system of the present invention is a NOx purifying system using the NOx purifying catalyst, wherein the air-fuel ratio (A / F) in the lean region is 15%.
It is characterized by the above.

The NOx purifying system of the present invention is a NOx purifying system using the NOx purifying catalyst, wherein secondary air flows from the upstream side of the NOx purifying catalyst when the engine is in a stoichiometric to rich region. And

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the NOx purifying catalyst of the present invention will be described in detail. In this specification, "%"
Indicates mass percentage unless otherwise specified. As mentioned above,
The NOx purification catalyst of the present invention comprises a catalytic noble metal and an oxygen storage / release material that carries at least a part of the catalytic noble metal. The catalytic noble metal supported on the oxygen storage / release material adsorbs SOx in the exhaust gas as sulfate or sulfite.

Here, usually, SO ₂ or the like (sulfur oxide) in the exhaust gas reacts with excess oxygen at the time of lean, and is taken in as a sulfate or sulfite on the catalytic noble metal. Most of the SO _{2 in} the catalyst dissociates and adsorbs on the catalytic noble metal (mainly Pt) to form sulfide.
In the present invention, at least a part of the catalytic noble metal is supported on an oxygen absorbing / releasing material (typically CeO ₂ ), so that SO ₂ can be incorporated into the catalytic noble metal as a sulfate or a sulfite during lean operation as described above. As shown in FIG. 1, at the time of stoichiometric to rich, oxygen is released from the oxygen storage / release material, and this oxygen reacts with SO ₂ or the like to form a sulfate or sulfite on the catalytic noble metal supported on the oxygen storage / release material. And the sulfurization of the catalytic noble metal is prevented. In this specification, “lean” means that reducing gas such as hydrocarbon (HC), carbon monoxide (CO), and hydrogen (H ₂ ) in an exhaust gas component is oxygen (O ₂ ), nitrogen oxide, or the like. (NOx)
"Rich" means that the exhaust gas atmosphere contains O ₂ , NOx as reducing gas such as HC, CO and H ₂ in the components.
And more states than oxidizing gases such as SOx,
“Stoichi” refers to a stoichiometric air-fuel condition.

Further, platinum (Pt) is used as the catalyst noble metal.
Can be used. Of the sulfurized Pt and the sulfate or sulfite of Pt, the latter is easier to desorb sulfur from Pt. As a result, sulfur poisoning of Pt can be released, and it can work as an active point quickly. The above operation is a phenomenon that occurs only when the catalytic noble metal (such as Pt) is supported on the oxygen absorbing / releasing material. In addition, palladium (Pd) and the like may be mentioned as the catalyst noble metal,
Pd sinters when it is poisoned with sulfur.
t is preferred.

Further, when Pt is carried on the oxygen storage / release material, it is possible to adsorb a part of NOx in the exhaust gas. However, in order to satisfy the current strict exhaust gas regulations, it is preferable to further increase the NOx adsorption capacity. For this reason, the catalyst can contain an alkali metal, an alkaline earth metal or a rare earth metal, and a metal according to any combination thereof. Thus, NOx is adsorbed in the lean region and NOx adsorbed in the stoichiometric to rich region is converted to nitrogen (N ₂ ).
And the purification ability can be improved. Normal,
Although strongly basic compounds such as alkali metals are strongly poisoned by sulfur, the NOx purification catalyst of the present invention, even if it is poisoned by sulfur, first uses Pt supported on the oxygen storage / release material.
Since sulfur is desorbed from the Pt and then the recovered Pt restores the adsorption performance of the NOx adsorbent, the sulfur poisoning can be released very easily. As the metal having the NOx adsorption ability, for example, barium (Ba) and / or magnesium (Mg), sodium (Na), cesium (Cs), and potassium (K) can be used. These metals can be selectively used in the operating temperature range of the catalyst. For example, the combination of barium and magnesium is 2
00 ° C to 400 ° C is preferable, and 250 ° C to 450 ° C when sodium is added thereto, and 250 ° C to 5 ° C when cesium is added to the combination of barium and magnesium.
When calcium is added to the combination of 00 ° C, barium and magnesium, 300 ° C to 550 ° C is suitable.

Further, rhodium (Rh) can be contained as the catalytic noble metal, and in this case, NOx purification performance when purifying NOx adsorbed in the lean region in the stoichiometric to rich region can be improved. Further, the oxygen absorbing / releasing material is very effective in releasing sulfur poisoning as described above, but if the amount is too large, it is originally used to reduce NOx when reducing the adsorbed NOx at the time of stoichiometric to rich. The reducing material reacts with the oxygen released from the oxygen absorbing / releasing material, resulting in N
There is a possibility that the reduction purification ability of Ox may be reduced. Therefore, it is necessary to divide the catalyst into two layers and to suppress the consumption of the reducing agent by setting the layer having a large amount of the oxygen absorbing and releasing material inside the exhaust gas flow and the layer having a small amount of the oxygen absorbing and releasing material outside. By doing so, the oxygen required to capture SO ₂ in the exhaust gas onto a noble metal as the sulphate or sulphite rich at the time of the inner catalytic layer, purification of NOx can be performed in the outer layer.
At this time, Rh for purifying NOx only needs to be on the outside, and even if it is on the inside, the effect is not sufficiently exhibited, and it is wasted. The ratio of the inside and outside of the catalyst layer of the oxygen storage / release material is 0.01:
The ratio is desirably 0.99 to 1: 1. If the inside is further reduced, the durability is reduced. (Fig. 2)

The metal having the NOx adsorbing ability (the NOx adsorbing material such as Ba) absorbs SOx similarly. Therefore, it is preferable that the NOx adsorbent and Pt and / or Rh coexist. For example, Pt formed by supporting at least a part of Pt on ceria (CeO ₂ )
t / CeO ₂ or the like can be used. In this case, the sulfur poisoning of Pt is first released, and then the recovered Pt / CeO ₂
Is a water gas shift reaction (CO + H ₂ O → CO ₂ + H ₂ )
The sulfur poisoning of the NOx adsorbent is released using the hydrogen generated by the above. Here, in particular, Pt is 5
To 50% NOx purifying catalyst supported CeO ₂ at a rate of, it is effective because the platinum adsorbs SOx in the exhaust gas as the sulphate or sulphite salt. At this time, if the content is less than 5%, the amount of Pt that can be released from sulfur poisoning is small, and the water gas shift reaction does not sufficiently occur. If it exceeds 50%, the amount of Pt that can release sulfur poisoning increases, but the reducing agent (CO or HC) that should reduce the adsorbed NOx reacts with the oxygen released from CeO ₂ before the NOx reduction, so that NOx → N ₂ reaction can no longer proceed. The NOx adsorbent varies depending on the temperature conditions used, and can be selectively used. For example, when the temperature at the catalyst inlet is 200 ° C. to 300 ° C., Mg, 2
Ba at 50 ° C to 400 ° C, N at 300 ° C to 450 ° C
a, Cs is effective at 300 ° C. to 500 ° C. Also,
The plurality of NOx adsorbents can be supported on one refractory inorganic carrier (such as CeO2). In this case, the NOx adsorbing function can be maintained over a wide temperature range, which is effective.

Further, it is preferable that CeO ₂ is contained at a rate of 3 to 100 g / L per 1 L of the catalyst capacity.
If it is less than 3 g / L, the sulfur poisoning cannot be sufficiently released, and if it exceeds 100 g / L, the reducing agent (CO, HC, etc.) which should reduce the adsorbed NOx has a C value before reducing NOx.
NO reacts with oxygen released from eO _2, resulting in NO
The x → N ₂ reaction may not proceed.

Further, it is preferable that the above-mentioned Pt / Rh is contained at a ratio of 1.4 to 4.3 g / L per 1 L of the catalyst volume. When the amount is less than 1.4 g / L, the catalyst performance is not satisfied. When the amount is more than 4.3 g / L, the catalyst performance is saturated, and the cost per catalyst may increase.

The above CeO₂As CeO₂When
Uses a composite oxide composed of zirconium (Zr)
Can be. Constant temperature to remove sulfur poisoning
Temperature or more can be used (specifically, the catalyst inlet is 5
50 ° C. or higher), for example, a NOx purification catalyst
If it is installed more upstream, it is possible to always use high exhaust temperature.
Can be. At this time, the active CeO ₂Specific surface area (representative
Typically 50m²/ G or more) to purify NOx
It is preferable to impart heat durability to the catalyst. for that reason
The above CeO₂It is effective to compound
You.

Further, as the NOx adsorbent, a composite carbonate of Ba and Mg can be used, and in this case, sulfur poisoning is more easily released. However, it is not necessary that all of Ba and Mg are compounded, and it is considered that the effect is obtained if at least a part of the compound is compounded. Specifically, Ba and Mg used as the NOx adsorbent are represented by the following general formula: Ba _x Mg _y (CO ₃ ) ₂ (where x and y are the atomic ratio of each element, x = 0.5 to
1.999, y = 0.001-1.5 and x + y = 2.
It is preferable to form a carbonate represented by the formula: By compounding, NOx can be efficiently removed in a temperature range where Ba and Mg are active, and the sulfur poisoning release performance can be improved. Although BaMg (CO ₃ ) ₂ can be detected by XRD alone, if it is contained in the catalyst, the peak disappears, and instead, a monoclinic peak of BaCO ₃ appears (FIG. 3). Normally, BaCO ₃ appears only in the orthorhombic system, and it can be considered from this that it is possible to determine whether BaMg (CO ₃ ) ₂ is complexed.

Further, as the above-mentioned Ba, barium oxide (BaO) can be contained at a ratio of 5 to 30 g / L per liter of the catalyst capacity. As the Mg, magnesium oxide (MgO) is used in an amount of 1 to 10 per liter of catalyst capacity.
g / L. Further, the above Na
The catalyst volume is 1 L with sodium oxide (Na ₂ O).
0.5 to 20.0 g / L. Further, as the Cs, cesium oxide (Cs
₂ O) a it can be contained in a proportion of catalyst volume per 1L 5 to 30 g / L. Further, as the K, potassium oxide (K ₂ O) is 0.5 to 30 g / L per 1 L of the catalyst capacity.
At a ratio of If the content of these NOx adsorbent components is less than the above range, the NOx adsorption capacity tends to be insufficient. If the content is more than the above range, the NOx adsorption capacity is saturated, and the excess alkali metal or alkaline earth metal becomes sulfur-poisoned. Not only promotes the heat resistance but also lowers the thermal durability of the noble metal (Pt or Rh).

In the NOx purifying catalyst of the present invention, when the internal combustion engine or the combustor is operated in a lean region, it is desirable that the air-fuel ratio be 15.0 or more. In this case, it becomes easy to adsorb oxygen to the oxygen absorbing / releasing material (mainly CeO ₂ ).
When the internal combustion engine or the like is operated in the stoichiometric to rich range, it is desirable to increase the oxygen ratio in the exhaust gas flowing to the NOx purification catalyst by means of secondary air. At this time, in addition to the oxygen released from the oxygen storage / release material, the oxygen concentration can be further increased, so that sulfur poisoning can be easily released.
Further, the working air-fuel ratio is 15 to 50 (lean range) and 10.
When it is 0 to 14.6 (rich range), NOx can be efficiently purified. The above B which can be contained as a NOx adsorbent
a, Mg, Na, Cs and K are not limited to the above-mentioned forms, and can be used in the form of carbonates, oxides and hydroxides.
Further, the NOx purification catalyst of the present invention can be used in various shapes,
For example, it can be used by supporting a catalyst component on a honeycomb structure made of cordierite, stainless steel, or the like. At this time, the catalyst component can be supported on the multilayer structure.

[0031]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Note that all the experiments in the examples and comparative examples were performed on gasoline-powered vehicles, but it goes without saying that similar effects can be obtained on diesel vehicles.

Example 1 Activated alumina having a specific surface area of 180 m ² was impregnated with a dinitrodiamine platinum solution, dried and calcined at 400 ° C. for 1 hour in the air to obtain a powder A. The Pt concentration of this powder was 1.5%. Specific surface area is 60m
The ^second active ceria was impregnated with dinitroamine platinum solution,
After drying, the powder was calcined at 400 ° C. for 1 hour in the air to obtain a powder B. The Pt concentration of this powder was 1.5%. 463.7 g of powder A, 100.8 g of powder B, 127.4 g of activated alumina, 28.8 g of alumina sol and 108 of water
0 g was charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry solution was adhered to a cordierite-based monolithic carrier (1.7 L, 400 cells), excess slurry in the cells was removed by an air stream, and dried at 130 ° C.
It was baked at 400 ° C. for 1 hour to obtain a catalyst having a coat layer of 200 g / L. This catalyst was immersed in a mixed aqueous solution of barium acetate and magnesium acetate, and the catalyst was impregnated with barium and magnesium to obtain a NOx purification catalyst of this example. As shown in Table 1, this NOx purification catalyst had Pt = 2.35 g /
L and Ba = 20 g / L in terms of oxide and Mg = 5 g / L in terms of oxide. Also, CeO ₂ was 28 g / L in the catalyst, and Pt on CeO ₂ was 18% of the total Pt amount.
Met.

Example 2 Specific surface area is 180 m²Activity
Alumina is impregnated with Rh nitrate solution, dried and
Calcination was carried out at 1 ° C. for 1 hour to obtain powder C. Rh concentration of this powder
The degree was 1%. 370.7 g of powder A and 8 of powder B
0.6 g, 135.9 g of powder C and 10 activated alumina
9.7 g, 23 g of alumina sol and 1080 g of water
The mixture was charged into a ball mill and mixed and pulverized to obtain a slurry liquid.
This slurry solution was added to a cordierite monolithic carrier (1.7).
L, 400 cells) and surplus in the cells by air flow
After removing the slurry and drying at 130 ° C, 400 ° C
For 1 hour to obtain a catalyst having a coat layer of 250 g / L.
This catalyst is mixed with barium acetate and magnesium acetate
Immerse in liquid and impregnate barium and magnesium in catalyst
Then, the NOx purification catalyst of this example was obtained. As shown in Table 1,
This NOx purification catalyst has Pt = 2.35 g / L, Rh
= 0.47 g / L, Ba = 20 g / L in terms of oxide, M
g = 5 g / L in terms of oxide was carried. Also, P
t / Rh = 5/1 (total 2.82 g / L), CeO ₂Is
28 g / L in catalyst, CeO₂The upper Pt is 1 of the total Pt amount
8%.

Example 3 Specific surface area is 180 m²Activity
After impregnating alumina with dinitrodiamine platinum solution and drying
The powder was fired at 400 ° C. for 1 hour in the air to obtain a powder D. this
The Pt concentration of the powder was 0.6%. 579.
6 g, powder B 51.1 g, activated alumina 57.6
g, 32.4 g alumina sol and 1080 g water
The mixture was put into a ball mill and mixed and pulverized to obtain a slurry liquid. This
Of the slurry solution of cordierite monolithic carrier (1.7
L, 400 cells) and surplus in the cells by air flow
After removing the slurry and drying at 130 ° C, 400 ° C
For 1 hour to obtain a catalyst layer 1 having a coat layer of 200 g / L.
Was. 308.9 g of powder A, 67.7 g of powder B, powder
226.8 g of C, 92.9 g of activated alumina, aluminum
23.8 g of Nasol and 1080 g of water in a magnetic ball mill
It was charged and mixed and pulverized to obtain a slurry liquid. This slurry liquid
The excess slurry in the cell is attached to the catalyst layer 1 by air flow.
After drying at 130 ° C, remove at 400 ° C for 1 hour
Then, the catalyst layer 2 having a coat layer of 150 g / L was obtained. This
The two-layer catalyst of barium acetate and magnesium acetate
Immerse in a mixed aqueous solution and add barium and magnesium to the catalyst.
The NOx purification catalyst of this example was obtained. See Table 1
Thus, this NOx purification catalyst has Pt = 2.35 g /
L, Rh = 0.47 g / L, Ba = 20 g in terms of oxide
/ L, Mg = 5 g / L in terms of oxide.
Further, Pt / Rh = 5/1 (total 2.82 g / L), C
eO ₂Is 28.2 g / L in the catalyst, CeO₂The above Pt is
It was 18% of the total Pt amount. Also, contained in the catalyst layer 1
CeO₂And CeO contained in the catalyst layer 2₂Is 1: 1
Met.

(Example 4) 579.6 g of powder D, 97.9 g of powder B, 10.1 g of activated alumina, 32.4 g of alumina sol and 1080 g of water were charged into a magnetic ball mill, mixed and pulverized to obtain a slurry liquid. I got This slurry solution was adhered to a cordierite-based monolithic carrier (1.7 L, 400 cells), excess slurry in the cells was removed by an air stream, dried at 130 ° C., and baked at 400 ° C. for 1 hour. 200 g / L of catalyst layer 1 was obtained. 308.9 g of powder A, 7.2 g of powder B and 226.8 of powder C
g, activated alumina 153.3 g, alumina sol 2
3.8 g and 1080 g of water were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid is adhered on the catalyst layer 1, the excess slurry in the cell is removed by an air flow, dried at 130 ° C., and baked at 400 ° C. for 1 hour,
A catalyst layer 2 having a coat layer of 150 g / L was obtained. The two-layer catalyst was immersed in a mixed aqueous solution of barium acetate and magnesium acetate, and the catalyst was impregnated with barium and magnesium to obtain a NOx purification catalyst of this example. As shown in Table 1,
This NOx purification catalyst has Pt = 2.35 g / L, Rh
= 0.47 g / L, Ba = 20 g / L in terms of oxide, M
g = 5 g / L in terms of oxide was carried. Also, P
t / Rh = 5/1 (total 2.82g / L), CeO2 is 28.2 g / L, Pt on CeO ₂ was 18% of the total amount of Pt in the catalyst. Also, CeO ₂ contained in the catalyst layer 1
And the amount ratio of CeO ₂ contained in the catalyst layer 2 is 0.97: 0.
03.

Example 5 The catalyst coat layer 1 of Example 3
After attaching 2, the catalyst was immersed in a mixed aqueous solution of barium acetate, magnesium acetate and sodium acetate, and impregnated with barium, magnesium and sodium in the catalyst,
The NOx purification catalyst of this example was obtained. As shown in Table 1, this NOx purification catalyst has Pt = 2.35 g / L and Rh =
0.47 g / L, Ba = 20 g / L in terms of oxide, Mg
= 5 g / L in terms of oxide, Na = 10 g / L in terms of oxide
L was carried. Pt / Rh = 5/1 (total 2.82 g / L), and CeO ₂ was 28.2 g / L in the catalyst.
Pt on L, CeO ₂ was 18% of the total Pt amount. The amount ratio of CeO ₂ contained in the CeO2 and a catalyst layer 2 contained in the catalyst layer 1 was 1: 1.

Example 6 The catalyst coat layer 1 of Example 3
After adhering No. 2, the catalyst was immersed in a mixed aqueous solution of barium acetate, magnesium acetate and cesium acetate, and impregnated with barium, magnesium and cesium to obtain a NOx purification catalyst of this example. As shown in Table 1, this NO
x Purification catalyst: Pt = 2.35 g / L, Rh = 0.4
7 g / L, Ba = 10 g / L in terms of oxide, Mg = 5 g / L in terms of oxide, and Cs = 20 g / L in terms of oxide. Pt / Rh = 5/1 (total 2.8)
2g / L), CeO ₂ is 28.2 g / L in the catalyst, CeO
Pt on O ₂ was 18% of the total amount of Pt. Also, CeO ₂ contained in the catalyst layer 1 and CeO ₂ contained in the catalyst layer ₂
Was 1: 1.

Example 7 The catalyst coat layer 1 of Example 3
After adhering No. 2, this catalyst was immersed in a mixed aqueous solution of barium acetate, magnesium acetate and potassium acetate, and impregnated with barium, magnesium and potassium to obtain a NOx purification catalyst of this example. As shown in Table 1, this NO
x Purification catalyst: Pt = 2.35 g / L, Rh = 0.4
7 g / L, Ba = 20 g / L in terms of oxide, Mg = 5 g / L in terms of oxide, and Cs = 20 g / L in terms of oxide. Pt / Rh = 5/1 (total 2.8)
2g / L), CeO2 is 28.2g / L in the catalyst, CeO2
Pt on O ₂ was 18% of the total amount of Pt. Also, CeO ₂ contained in the catalyst layer 1 and CeO ₂ contained in the catalyst layer ₂
Was 1: 1.

Example 8 The catalyst coat layer 1 of Example 3
Then, the catalyst was immersed in a mixed aqueous solution of barium acetate, magnesium acetate, sodium acetate and cesium acetate, and impregnated with barium, magnesium, sodium and cesium in the catalyst. Obtained. As shown in Table 1, this NOx purification catalyst has Pt
= 2.35 g / L, Rh = 0.47 g / L, Ba = 10 g / L in terms of oxide, Mg = 5 g / L in terms of oxide, N
a = 5 g / L in terms of oxide, Cs = 20 g in terms of oxide
/ L was carried. Pt / Rh = 5/1 (total 2.82 g / L), and CeO ₂ was 28.2 g / L in the catalyst.
Pt on L, CeO ₂ was 18% of the total Pt amount. Further, the quantitative ratio of CeO ₂ contained in the catalyst layer 1 to CeO ₂ contained in the catalyst layer 2 was 1: 1.

Example 9 The catalyst coat layer 1 of Example 3
After adhering No. 2, this catalyst was immersed in a mixed aqueous solution of barium acetate, magnesium acetate, sodium acetate, and potassium acetate, and impregnated with barium, magnesium, sodium, and potassium in the catalyst. Obtained. As shown in Table 1, this NOx purification catalyst has Pt
= 2.35 g / L, Rh = 0.47 g / L, Ba = 20 g / L in terms of oxide, Mg = 5 g / L in terms of oxide, N
a = 5 g / L in terms of oxide, K = 20 g / L in terms of oxide
L was carried. Pt / Rh = 5/1 (total 2.82 g / L), and CeO ₂ was 28.2 g / L in the catalyst.
Pt on L, CeO ₂ was 18% of the total Pt amount. Further, the quantitative ratio of CeO ₂ contained in the catalyst layer 1 to CeO ₂ contained in the catalyst layer 2 was 1: 1.

Example 10 After the catalyst coating layers 1 and 2 of Example 3 were applied, this catalyst was immersed in a mixed aqueous solution of barium acetate, magnesium acetate, cesium acetate, and potassium acetate, and barium was added to the catalyst. , Magnesium, cesium, and potassium were impregnated to obtain a NOx purification catalyst of this example. As shown in Table 1, this NOx purification catalyst has Pt
= 2.35 g / L, Rh = 0.47 g / L, Ba = 10 g / L in terms of oxide, Mg = 5 g / L in terms of oxide, C
s = 10 g / L in terms of oxide, K = 10 g in terms of oxide
/ L was carried. Pt / Rh = 5/1 (total 2.82 g / L), and CeO ₂ was 28.2 g / L in the catalyst.
Pt on L, CeO ₂ was 18% of the total Pt amount. Further, the quantitative ratio of CeO ₂ contained in the catalyst layer 1 to CeO ₂ contained in the catalyst layer 2 was 1: 1.

(Example 11) Catalyst coating layer of Example 3
After depositing 1, 2 the catalyst was replaced with barium acetate and acetic acid.
Magnesium, sodium acetate, cesium acetate and potassium acetate
Immersed in a mixed aqueous solution of barium and barium and magnesium in the catalyst.
Impregnated with gnesium, sodium, cesium and potassium
Then, the NOx purification catalyst of this example was obtained. As shown in Table 1,
This NOx purification catalyst has Pt = 2.35 g / L, Rh
= 0.47 g / L, Ba = 10 g / L in terms of oxide, M
g = 5 g / L in terms of oxide, Na = 5 g / L in terms of oxide
L, Cs = 10 g / L in terms of oxide, K = in terms of oxide
10 g / L was carried. Also, Pt / Rh = 5 /
1 (total 2.82 g / L), CeO₂In the catalyst.
2g / L, CeO₂The upper Pt is 18% of the total Pt amount.
Was. In addition, CeO contained in the catalyst layer 1₂And catalyst layer 2
CeO ₂Was 1: 1.

Example 12 The same operation as in Example 3 was repeated except that the activated ceria of the powder B in Example 3 was a Ce-Zr composite oxide in which ZrO ₂ was compounded by 25%. Example NOx purification catalysts were obtained.

Example 13 Example 4 was repeated except that the activated ceria of the powder B of Example 4 was a Ce—Zr composite oxide in which 25% of the total composite oxide was occupied by ZrO ₂ (composite). By repeating the same operation, the NOx purification catalyst of this example was obtained.

Example 14 The same operation as in Example 5 was repeated, except that the activated ceria of the powder B in Example 5 was a Ce-Zr composite oxide in which ZrO ₂ was compounded by 25%, to thereby obtain a powder. Example NOx purification catalysts were obtained. Table 1 shows the structure of the present catalyst.

Example 15 The same operation as in Example 6 was repeated, except that the activated ceria of the powder B in Example 6 was a Ce-Zr composite oxide in which ZrO ₂ was compounded by 25%. Example NOx purification catalysts were obtained. Table 1 shows the structure of the present catalyst.

Example 16 The same operation as in Example 7 was repeated, except that the activated ceria of the powder B in Example 7 was a Ce-Zr composite oxide in which ZrO ₂ was compounded by 25%. Example NOx purification catalysts were obtained. Table 1 shows the structure of the present catalyst.

Example 17 The same operation as in Example 8 was repeated, except that the activated ceria of the powder B in Example 8 was a Ce-Zr composite oxide in which ZrO ₂ was compounded by 25%. Example NOx purification catalysts were obtained. Table 1 shows the structure of the present catalyst.

Example 18 The same operation as in Example 9 was repeated except that the activated ceria of the powder B in Example 9 was a Ce-Zr composite oxide in which 25% of ZrO ₂ was composited, and Example NOx purification catalysts were obtained. Table 1 shows the structure of the present catalyst.

Example 19 The same operation as in Example 10 was repeated, except that the activated ceria of the powder B of Example 10 was a Ce-Zr composite oxide in which ZrO ₂ was compounded by 25%. Example NOx purification catalysts were obtained. Table 1 shows the structure of the present catalyst.

Example 20 The same operation as in Example 11 was repeated, except that the activated ceria of the powder B of Example 11 was a Ce-Zr composite oxide in which 25% of ZrO ₂ was composited. Example NOx purification catalysts were obtained. Table 1 shows the structure of the present catalyst.

[0052]

[Table 1]

(Comparative Example 1) The specific surface area is 180 m²Activity
After impregnating the alumina with the palladium nitrate solution, dry it in air
The powder was fired at 400 ° C. for 1 hour to obtain a powder E. Of this powder
The Pd concentration was 1.5%. Specific surface area is 180m²of
Activated alumina is impregnated with a palladium nitrate solution, dried and emptied.
The powder was fired at 400 ° C. for 1 hour in the air to obtain a powder F. This powder
The final Pd concentration was 0.6%. Specific surface area is 60m²
Activated ceria is impregnated with a palladium nitrate solution, dried and emptied.
The powder was fired at 400 ° C. for 1 hour in the air to obtain a powder G. This powder
The powdery Pd concentration was 1.5%. 579.6 powder F
g, 51.1 g of powder G, 57.6 g of activated alumina,
Add 32.4 g of alumina sol and 1080 g of water to a magnetic bowl.
And mixed and pulverized to obtain a slurry liquid. This
The lary liquor was transferred to a cordierite monolithic carrier (1.7 L, 4 L).
00 cell) and the excess slurry in the cell
After drying at 130 ° C, remove at 400 ° C for 1 hour
During the firing, a catalyst layer 1 having a coat layer of 200 g / L was obtained. powder
Powder E: 308.9 g, Powder G: 67.7 g, Powder C: 2
26.8 g, activated alumina 92.9 g, alumina sol
23.8 g and 1080 g of water into a magnetic ball mill
Then, they were mixed and pulverized to obtain a slurry liquid. This slurry solution is used as a catalyst
The excess slurry in the cell is deposited on the layer 1 by air flow.
After removing and drying at 130 ° C, baking at 400 ° C for 1 hour
Thus, a catalyst layer 2 having a coat layer of 150 g / L was obtained. This 2
Mixing layered catalyst with barium acetate and magnesium acetate
Barium and magnesium in the catalyst
Impregnation was performed to obtain a NOx purification catalyst of this example. As shown in Table 2
In this NOx purification catalyst, Pd = 2.35 g / L,
Rh = 0.47 g / L, Ba = 20 g / oxide equivalent
L, Mg = 5 g / L in oxide conversion was carried. Ma
Pd / Rh = 5/1 (total 2.82 g / L), Ce
O ₂Is 28.2 g / L in the catalyst, CeO₂Pd above is all
It was 18% of the Pd amount.

(Comparative Example 2) The specific surface area is 180 m²Activity
After impregnating alumina with dinitrodiamine platinum solution and drying
The powder was fired at 400 ° C. for 1 hour in the air to obtain a powder H. this
The Pt concentration of the powder was 1.75%. Specific surface area is 18
0m²Of activated alumina containing dinitrodiamine platinum solution
After immersion, drying and baking in air at 400 ° C. for 1 hour, powder I
I got The Pt concentration of this powder was 0.7%. Ratio table
Area is 60m²Of dinitrodiamine platinum in activated ceria
Impregnated with the liquid, dried and fired in air at 400 ° C. for 1 hour,
Powder J was obtained. The Pt concentration of this powder was 0.33%.
Was. 579.6 g of powder I, 51.1 g of powder J, activity
57.6 g of alumina, 32.4 g of alumina sol and
Charge 1080g of water into a magnetic ball mill, mix and pulverize
A slurry was obtained. This slurry solution is used for cordierite
Attached to a squirrel carrier (1.7 L, 400 cells), air flow
Remove excess slurry in the cell at and dry at 130 ° C
Then, it is baked at 400 ° C. for 1 hour, and the coating layer 200 g /
Thus, L catalyst layer 1 was obtained. 308.9 g of powder H and powder J
67.7 g, powder C: 226.8 g, activated alumina: 9
2.9 g, 23.8 g of alumina sol and 1080 g of water
Into a magnetic ball mill, mixed and pulverized to obtain a slurry liquid.
Was. This slurry liquid is adhered on the catalyst layer 1 and is air-flowed.
Excess slurry in the cell was removed and dried at 130 ° C
After that, it is baked at 400 ° C. for 1 hour to obtain a coat layer of 150 g / L.
Catalyst layer 2 was obtained. This two-layer catalyst is called barium acetate.
Immerse in a mixed aqueous solution of magnesium acetate, and
NOx purification catalyst of this example impregnated with lithium and magnesium
I got As shown in Table 2, this NOx purification catalyst includes:
Pt = 2.35 g / L, Rh = 0.47 g / L, Ba =
20 g / L in terms of oxide, Mg = 5 g / L in terms of oxide
Was carried. Also, Pt / Rh = 5/1 (total
2.82 g / L), CeO ₂Is 28.2 g /
L, CeO₂The upper Pt was 4% of the total Pt amount.

(Comparative Example 3) The specific surface area is 180 m²Activity
After impregnating alumina with dinitrodiamine platinum solution and drying
The powder was fired at 400 ° C. for 1 hour in the air to obtain a powder K. this
The Pt concentration of the powder was 0.89%. Specific surface area is 18
0m²Of activated alumina containing dinitrodiamine platinum solution
After immersion, drying and firing in air at 400 ° C. for 1 hour, powder L
I got The Pt concentration of this powder was 0.36%. ratio
Surface area is 60m²Activated ceria on dinitrodiamine platinum
Impregnated with the solution, dried and fired in air at 400 ° C for 1 hour
Thus, powder M was obtained. The Pt concentration of this powder was 4.3%.
Was. 579.6 g of powder L, 51.1 g of powder M,
57.6 g of reactive alumina and 32.4 g of alumina sol
And 1080 g of water into a magnetic ball mill,
To obtain a slurry. This slurry solution is
Attached to Norris carrier (1.7L, 400 cells), air
Remove excess slurry in the cell by flow and dry at 130 ° C.
After drying, baking at 400 ° C for 1 hour, 200 g of coating layer
/ L of catalyst layer 1 was obtained. 308.9 g of powder K, powder M
67.7 g, powder C 226.8 g, activated alumina
92.9 g, 23.8 g of alumina sol and 1080 of water
g into a magnetic ball mill, mix and pulverize
Obtained. This slurry liquid is deposited on the catalyst layer 1 and is converted into an air stream.
To remove excess slurry from the cell and dry at 130 ° C.
After that, it is baked at 400 ° C. for 1 hour, and the coating layer is 150 g / L.
Was obtained. This two-layer catalyst is barium acetate
Immersed in a mixed aqueous solution of
Impregnated with barium and magnesium, NOx purification catalyst of this example
A medium was obtained. As shown in Table 2, this NOx purification catalyst
Is Pt = 2.35 g / L, Rh = 0.47 g / L, B
a = 20 g / L in terms of oxide, Mg = 5 g in terms of oxide
/ L was carried. Also, Pt / Rh = 5/1 (total
2.82 g / L), CeO ₂Is 28.2 g /
L, CeO₂The upper Pt was 51% of the total Pt amount.

(Comparative Example 4) The specific surface area is 60 m²Activated
After impregnating the rear with a dinitrodiamine platinum solution and drying, air
The powder was calcined at 400 ° C. for 1 hour to obtain powder N. This powder
Was 11.8%. 634.7 powder D
g, powder N: 3.6 g, activated alumina: 49.7 g,
32.4 g of luminazol and 1080 g of water in magnetic balls
It was put into a mill and mixed and pulverized to obtain a slurry liquid. This sla
The solution was converted to a cordierite monolithic carrier (1.7 L, 40
0 cell) and the excess slurry in the cell by air flow.
Removed and dried at 130 ° C, then at 400 ° C for 1 hour
By calcining, a catalyst layer 1 having a coat layer of 200 g / L was obtained. Powder
338.4 g of A, 4.8 g of powder N, and 22 of powder C
6.8 g, activated alumina 150.2 g, alumina sol
23.8 g and 1080 g of water into a magnetic ball mill
Then, they were mixed and pulverized to obtain a slurry liquid. This slurry solution is used as a catalyst
The excess slurry in the cell is deposited on the layer 1 by air flow.
After removing and drying at 130 ° C, baking at 400 ° C for 1 hour
Thus, a catalyst layer 2 having a coat layer of 150 g / L was obtained. This 2
Mixing layered catalyst with barium acetate and magnesium acetate
Barium and magnesium in the catalyst
Impregnation was performed to obtain a NOx purification catalyst of this example. As shown in Table 2
In this NOx purification catalyst, Pt = 2.35 g / L,
Rh = 0.47 g / L, Ba = 20 g / oxide equivalent
L, Mg = 5 g / L in oxide conversion was carried. Ma
Pt / Rh = 5/1 (total 2.82 g / L), Ce
O ₂Is 2 g / L in the catalyst, CeO₂The upper Pt is the total Pt amount
Was 10%.

(Comparative Example 5) The specific surface area is 180 m²Activity
After impregnating alumina with dinitrodiamine platinum solution and drying
The powder was fired at 400 ° C. for 1 hour in the air to obtain powder O. this
The Pt concentration of the powder was 2.0%. Specific surface area is 60m
²The active ceria is impregnated with a dinitrodiamine platinum solution,
After drying, the powder is fired in air at 400 ° C. for 1 hour to obtain a powder P.
Was. The Pt concentration of this powder was 0.47%. Powder I
483.5 g, powder P 181.8 g, activated alumina
22.7 g, alumina sol 32.4 g and water 108
0g into a magnetic ball mill, mix and pulverize,
I got This slurry solution is transferred to a cordierite monolithic carrier.
(1.7L, 400 cells)
After removing excess slurry inside and drying at 130 ° C,
Baking at 400 ° C for 1 hour, 200 g / L of coating layer catalyst
Layer 1 was obtained. 225.6 g of powder O and 242.
4g, 226.8g of powder C, and 1.4 of activated alumina
g, 23.8 g of alumina sol and 1080 g of water magnetically
The mixture was put into a ball mill and mixed and pulverized to obtain a slurry liquid. This
Of the slurry liquid is deposited on the catalyst layer 1, and the inside of the cell is
After removing excess slurry and drying at 130 ° C, 4
Bake at 00 ° C for 1 hour, coat layer 150g / L catalyst layer
2 was obtained. This two-layer catalyst is formed by using barium acetate and
Immerse in a mixed aqueous solution of gnesium and add barium to the catalyst.
And magnesium to obtain a NOx purification catalyst of this example
Was. As shown in Table 2, this NOx purification catalyst has Pt
= 2.35 g / L, Rh = 0.47 g / L, Ba = oxidized
20g / L in material conversion, 5g / L in Mg = oxide conversion
Was held. Pt / Rh = 5/1 (total 2.8)
2g / L), CeO ₂Is 101 g / L in the catalyst, CeO
₂The upper Pt was 20% of the total Pt amount.

Comparative Example 6 A powder of dinitrodiamine platinum was impregnated into activated alumina having a specific surface area of 180 m ² , dried and calcined at 400 ° C. for 1 hour in the air to obtain a powder Q. The Pt concentration of this powder was 0.69%. Specific surface area is 18
0 m ² of activated alumina was impregnated with a dinitrodiamine platinum solution, dried and calcined at 400 ° C. for 1 hour in air to obtain a powder R.
I got The Pt concentration of this powder was 0.27%. Activated ceria having a specific surface area of 60 m ² was impregnated with a dinitrodiamine platinum solution, dried and calcined at 400 ° C. for 1 hour in the air to obtain a powder S. The Pt concentration of this powder was 0.69%. Activated alumina with a specific surface area of 180 m ²
h, impregnated with the solution, dried and calcined at 400 ° C. for 1 hour in the air to obtain a powder T. The Rh concentration of this powder was 0.47%. 579.6 g of powder R, 51.1 g of powder S,
57.6 g of activated alumina and 32.4 g of alumina sol
And 1080 g of water were charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry solution was adhered to a cordierite-based monolithic carrier (1.7 L, 400 cells), excess slurry in the cells was removed by an air stream, dried at 130 ° C., and baked at 400 ° C. for 1 hour. Layer 200
g / L of the catalyst layer 1 was obtained. 308.9 g of powder Q, 67.7 g of powder S, 226.8 g of powder T, 92.9 g of activated alumina, 23.8 g of alumina sol and water 108
0 g was charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid was adhered on the catalyst layer 1, the excess slurry in the cell was removed by an air flow, dried at 130 ° C., baked at 400 ° C. for 1 hour, and baked at 150 g / coat layer.
Thus, L catalyst layer 2 was obtained. The two-layer catalyst was immersed in a mixed aqueous solution of barium acetate and magnesium acetate, and the catalyst was impregnated with barium and magnesium to obtain a NOx purification catalyst of this example. As shown in Table 2, this NOx purification catalyst has Pt = 1.08 g / L, Rh = 0.22 g / L, B
a = 20 g / L in terms of oxide, Mg = 5 g in terms of oxide
/ L was carried. Pt / Rh = 5/1 (total 1.3 g / L), CeO ₂ was 28.2 g / L in the catalyst.
Pt on L, CeO ₂ was 18% of the total Pt amount.

Comparative Example 7 579.6 g of powder D, powder
B: 43.9 g, activated alumina: 64.1 g, alumina
32.4 g of sol and 1080 g of water in a magnetic ball mill
It was charged and mixed and pulverized to obtain a slurry liquid. This slurry liquid
Cordierite monolithic carrier (1.7 L, 400 cells)
To remove excess slurry in the cell by airflow.
After drying at 130 ° C, baking at 400 ° C for 1 hour
Thus, a catalyst layer 1 having a coat layer of 200 g / L was obtained. Powder A
308.9 g, powder B 76.8 g, powder C 83.7
g, activated alumina 153.3 g, alumina sol 2
3.8 g and 1080 g of water are put into a magnetic ball mill and mixed.
The mixture was ground to obtain a slurry. This slurry solution is applied on the catalyst layer 1
To remove excess slurry in the cell by air flow
And dried at 130 ° C., baked at 400 ° C. for 1 hour,
A catalyst layer 2 having a coat layer of 150 g / L was obtained. This two-layer structure
Mixed aqueous solution of barium acetate and magnesium acetate
Barium and magnesium in the catalyst
Then, the NOx purification catalyst of this example was obtained. As shown in Table 1,
This NOx purification catalyst has Pt = 2.35 g / L, Rh
= 0.47 g / L, Ba = 20 g / L in terms of oxide, M
g = 5 g / L in terms of oxide was carried. Also, P
t / Rh = 5/1 (total 2.82 g / L), CeO ₂Is
28.2 g / L in catalyst, CeO₂The upper Pt is the total Pt amount
18%. In addition, CeO contained in the catalyst layer 1₂
And CeO contained in the catalyst layer 2₂Is 1: 1.3.
Was.

Comparative Example 8 The same operation as in Example 3 was repeated except that the amount of Ba to be impregnated was changed to 4 g / L in terms of oxide and the amount of Mg was changed to 0.9 g / L in terms of oxide. NO
x purification catalyst was obtained. Table 2 shows the structure of the catalyst.

Comparative Example 9 The same operation as in Example 3 was repeated except that the amount of Ba to be impregnated was 31 g / L in terms of oxide and the amount of Mg was 11 g / L in terms of oxide.
x purification catalyst was obtained. Table 2 shows the structure of the catalyst.

Comparative Example 10 The amount of Ba to be impregnated was 4 g / L in terms of oxide, the amount of Mg was 0.9 g / L in terms of oxide, and N
Example 5 except that the amount of a was 0.4 g / L in terms of oxide.
By repeating the same operation as described above, the NOx purification catalyst of this example was obtained. Table 2 shows the structure of the catalyst.

(Comparative Example 11) The amount of Ba to be impregnated was 31 g / L in terms of oxide, the amount of Mg was 11 g / L in terms of oxide, and N
Example 5 except that the amount of a was 21 g / L in terms of oxide.
By repeating the same operation as described above, the NOx purification catalyst of this example was obtained. Table 2 shows the structure of the catalyst.

Comparative Example 12 The amount of Ba to be impregnated was 4 g / L in terms of oxide, the amount of Mg was 0.9 g / L in terms of oxide, and
The same operation as in Example 6 was repeated, except that the amount of s was 4 g / L in terms of oxide, to obtain a NOx purification catalyst of this example.
Table 2 shows the structure of the catalyst.

Comparative Example 13 The amount of Ba to be impregnated was 31 g / L in terms of oxide, the amount of Mg was 11 g / L in terms of oxide, and C
The same operation as in Example 6 was repeated, except that the amount of s was changed to 31 g / L in terms of oxide, to obtain a NOx purification catalyst of this example. Table 2 shows the structure of the catalyst.

Comparative Example 14 The amount of Ba to be impregnated was 4 g / L in terms of oxide, the amount of Mg was 0.9 g / L in terms of oxide, and K
The same operation as in Example 7 was repeated, except that the amount was 0.4 g / L in terms of oxide, to obtain a NOx purification catalyst of this example. Table 2 shows the structure of the catalyst.

(Comparative Example 15) The amount of Ba to be impregnated was 31 g / L in terms of oxide, the amount of Mg was 11 g / L in terms of oxide, and K
The same operation as in Example 7 was repeated, except that the amount was 31 g / L in terms of oxide, to obtain a NOx purification catalyst of this example.
Table 2 shows the structure of the catalyst.

Comparative Example 16 The amount of Ba to be impregnated was 4 g / L in terms of oxide, the amount of Mg was 0.9 g / L in terms of oxide, and N
The same operation as in Example 8 was repeated, except that the amount a was changed to 0.4 g / L in terms of oxide and the amount of Cs was changed to 4 g / L in terms of oxide, to obtain a NOx purification catalyst of this example. Table 2 shows the structure of the catalyst.

Comparative Example 17 The amount of Ba to be impregnated was 31 g / L in terms of oxide, the amount of Mg was 11 g / L in terms of oxide, and N
The same operation as in Example 8 was repeated, except that the amount of a was 21 g / L in terms of oxide and the amount of Cs was 31 g / L in terms of oxide, to obtain a NOx purification catalyst of this example. Table 2 shows the structure of the catalyst.

Comparative Example 18 The amount of Ba to be impregnated was 4 g / L in terms of oxide, the amount of Mg was 0.9 g / L in terms of oxide, and N
The same operation as in Example 9 was repeated, except that the amount a was 0.4 g / L in terms of oxide and the amount of K was 0.4 g / L in terms of oxide, to obtain a NOx purification catalyst of this example. Table 2 shows the structure of the catalyst.

(Comparative Example 19) The amount of Ba to be impregnated was 31 g / L in terms of oxide, and the amount of Mg was 11 g / L in terms of oxide.
The same operation as in Example 9 was repeated, except that the Na amount was 21 g / L in terms of oxide and the K amount was 31 g / L in terms of oxide, to obtain a NOx purification catalyst of this example. Table 2 shows the structure of the catalyst.

Comparative Example 20 The amount of Ba to be impregnated was 4 g / L in terms of oxide, the amount of Mg was 0.9 g / L in terms of oxide, and
The amount of s is 4 g / L in terms of oxide, and the amount of K is in the range of 0.
The same operation as in Example 10 was repeated except that the amount was set to 4 g / L, to obtain a NOx purification catalyst of this example. Table 2 shows the structure of the catalyst.

(Comparative Example 21) The amount of Ba to be impregnated was 31 g / L in terms of oxide, the amount of Mg was 11 g / L in terms of oxide, and C
The amount of s was 31 g / L in terms of oxide, and the amount of K was 3 in terms of oxide.
The same operation as in Example 10 was repeated except that the amount was 1 g / L, to obtain a NOx purification catalyst of this example. Table 2 shows the structure of the catalyst.

Comparative Example 22 The amount of Ba impregnated was 4 g / L in terms of oxide, the amount of Mg was 0.9 g / L in terms of oxide, and N
The same operation as in Example 11 was repeated except that the amount of a was 0.4 g / L in terms of oxide, the amount of Cs was 4 g / L in terms of oxide, and the amount of K was 0.4 g / L in terms of oxide. , NO in this example
x purification catalyst was obtained. Table 2 shows the structure of the catalyst.

(Comparative Example 23) The amount of Ba to be impregnated was 31 g / L in terms of oxide, the amount of Mg was 11 g / L in terms of oxide, and N
The same operation as in Example 11 was repeated except that the amount of a was 21 g / L in terms of oxide, the amount of Cs was 31 g / L in terms of oxide, and the amount of K was 31 g / L in terms of oxide. NOx
A purification catalyst was obtained. Table 2 shows the structure of the catalyst.

[0076]

[Table 2]

[Evaluation Test] Endurance Method A catalyst was attached to the exhaust system of a 4400 cc displacement engine, regular domestic gasoline was used, the catalyst inlet temperature was set to 700 ° C., and operation was performed for 50 hours. After that, the displacement 20
After installing a catalyst in the exhaust system of a 00cc engine and performing S poisoning (using 300 ppm gasoline with S concentration, setting the catalyst inlet temperature to 350 ° C and operating for 10 hours), desorbing S (using regular domestic gasoline) Used, the catalyst inlet temperature was set to 650 ° C., and the operation was performed for 5 minutes, A / F = 14.2).・ Evaluation method A catalyst was mounted on the exhaust system of an engine with a displacement of 2000 cc. After endurance for 50 hours at 700 ° C., after S poisoning, and after S desorption, the vehicle traveled in the 10-15 mode. The mode conversion was determined. The recovery rates shown in Tables 3 and 4 were determined by the following formula: recovery rate (%) = (NOx conversion rate after S desorption treatment / NOx conversion rate after endurance) × 100. In the mode, when the vehicle is running steadily, lean (A
/ F = 25), fuel cut during deceleration, rich during acceleration (A / F = 11.0) → stoichiometric (A / F = 14.7)
Driving. Here, "10-15 mode"
New vehicle test method specified by the Ministry of Land, Infrastructure, Transport and Tourism (TRIAS:
Traffic satellite andnuisanc
e Research Institute's au
mobile type Approval te
st Standard). The catalyst inlet temperature was 300 ° C.

[0078]

[Table 3]

[0079]

[Table 4]

As shown in Tables 1 to 4, the results of Example 3 and Comparative Example 1 show that it is preferable to include Pt as a catalytic noble metal. Since Pd is sintered by sulfur poisoning, it is difficult to release the poisoning, and the recovery rate becomes extremely poor. Also, from the results of Example 3, Comparative Example 2 and Comparative Example 3, the recovery rate is poor when the proportion of Pt on CeO ₂ in the total Pt amount in the catalyst is too small, and the recovery rate is good when the proportion is too large, but the durability is high. Later performance will deteriorate. The same can be seen from the results of Example 3, Comparative Example 4, and Comparative Example 5. If the content of CeO ₂ is too small, the recovery rate is poor, and if the content is too large, the recovery rate is good, but the performance after durability deteriorates. Also, from the results of Example 3, Example 4, and Comparative Example 7, it can be seen that the conversion ratio of NOx is better when the amount of CeO ₂ is larger inside the catalyst layer and smaller outside the catalyst layer. From the results of Example 3 and Comparative Example 6, it can be seen that if the amount of Pt and / or Pd carried is small, the performance deteriorates in all cases. From the results of Example 3 and Comparative Examples 8 to 23, it can be seen that if the amount of NOx adsorbent is too large, the performance after durability is good but the recovery rate is poor. If the amount is too small, the recovery rate is good but the performance after durability is poor.

[0081]

As described above, according to the present invention, when oxygen is insufficient, the oxygen absorbing / releasing material releases oxygen to release SO2.
_Since the sulfurization such as ₂ is prevented, it is possible to provide a NOx purification catalyst and a NOx purification system that can easily release sulfur poisoning.

[Brief description of the drawings]

FIG. 1 is a graph showing a peak of an infrared absorption spectrum of a sulfate.

FIG. 2 Oxygen absorbing / releasing material (CeO ₂ ) inside and outside the catalyst layer
4 is a graph showing the relationship between the amount ratio of NO and the NOx conversion rate.

FIG. 3 is a graph showing an XRD peak of barium carbonate.

FIG. 4 is a schematic view showing an example of a NOx purification catalyst.

FIG. 5 is a schematic view showing another example of the NOx purification catalyst.

FIG. 6 is a schematic diagram illustrating an example of a NOx purification system.

FIG. 7 is a schematic view showing another example of the NOx purification system.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F01N 3/28 301 B01D 53/36 104A ZAB 102H F term (reference) 3G091 AB02 AB05 AB06 BA11 BA14 BA39 FB10 FB11 FB12 GB02W GB03W GB04W GB05W GB16X GB17X HA02 4D048 AA06 AA13 AA18 AB05 AB07 AC06 BA01X BA02Y BA08X BA14X BA15X BA18Y BA19X BA30X BA33X BA41X BA42Y BA45X BB02 BB16 BC01 DA03 DA20 EA04 4G069 AA03 BA01A BA01B BA05A BA05B BA13B BB02A BB02B BB04A BB04B BB06A BB06B BB16A BB16B BC01A BC02A BC02B BC03A BC03B BC06A BC08A BC10A BC10B BC13A BC13B BC38A BC43A BC43B BC51A BC51B BC69A BC71A BC71B BC75A BC75B CA02 CA03 CA09 EA19 EB12Y EC19 FC08

Claims (20)

[Claims] 1. A NOx purifying catalyst used for purifying exhaust gas from an internal combustion engine or a combustor operated in a lean region or a stoichiometric to rich region, comprising: a catalytic noble metal; and at least a part of the catalytic noble metal. A NOx purification catalyst, comprising a supported oxygen storage / release material, wherein the catalytic noble metal supported by the oxygen storage / release material adsorbs SOx in exhaust gas as sulfate or sulfite. 2. The NOx purifying catalyst according to claim 1, wherein said catalytic noble metal comprises platinum. 3. The catalyst contains at least one metal selected from the group consisting of an alkali metal, an alkaline earth metal and a rare earth metal, adsorbs NOx when the air-fuel ratio is in a lean range, and absorbs NOx in a stoichiometric to rich range. 3. The N according to claim 1, wherein the NOx that has been adsorbed is reduced to nitrogen.
Ox purification catalyst. 4. The NOx purifying catalyst according to claim 1, wherein said catalytic noble metal comprises rhodium. 5. The catalyst according to claim 1, wherein the catalyst comprises a layer having a large amount of oxygen absorbing / releasing material and a layer having a small amount of oxygen absorbing / releasing material, and the layer having a small amount of oxygen absorbing / releasing material is laminated on the layer having a large amount of oxygen absorbing / releasing material. The NOx purification catalyst according to any one of claims 1 to 4, characterized in that: 6. The catalyst according to claim 1, wherein the ratio of the layer having a small amount of oxygen absorbing / releasing material to the layer having a large amount of oxygen absorbing / releasing material is 0.01: 0.99 to 1: 1.
The NOx purification catalyst according to any one of claims 1 to 5, wherein 7. The catalyst according to claim 1, wherein only a layer of the catalyst having a small amount of oxygen absorbing / releasing material contains rhodium.
NOx purification catalyst according to any one of the above. 8. The catalyst according to claim 1, wherein the catalyst comprises barium and / or magnesium, ceria, and platinum and / or rhodium, and at least a part of the platinum is supported on the ceria. The NOx purification catalyst according to any one of Items 1 to 7. 9. The refractory inorganic carrier further comprises sodium,
9. A carrier carrying at least one member selected from the group consisting of cesium and potassium.
The NOx purification catalyst according to the above. 10. The method according to claim 1, wherein the ceria is used in an amount of 3 to 1 per liter of the catalyst.
9. The composition according to claim 8, wherein the content is 00 g / L.
Or a NOx purification catalyst according to 9. 11. The NOx according to claim 8, wherein the platinum and / or rhodium is contained at a ratio of 1.4 to 4.3 g / L per 1 L of the catalyst volume. Purification catalyst. 12. The method according to claim 8, wherein said ceria is compounded with zirconium.
NOx purification catalyst according to any one of the first to third aspects. 13. At least a part of the barium and / or magnesium is complexed, and the following general formula: Ba _x Mg _y (CO ₃ ) ₂ (where x and y are atomic ratios of each element, x = 0 .5-
1.999, y = 0.001-1.5 and x + y = 2.
NO is represented by the following formula (1):
x purification catalyst. 14. A method according to claim 1, wherein said barium contains barium oxide at a rate of 5 to 30 g / L per 1 L of catalyst capacity, and said magnesium contains magnesium oxide at a rate of 1 to 10 g / L per 1 L of catalyst capacity. The NOx purification catalyst according to any one of claims 8 to 13. 15. The NOx purifying apparatus according to claim 9, wherein sodium oxide is contained as the sodium at a rate of 0.5 to 20.0 g / L per 1 L of a catalyst capacity. catalyst. 16. The NOx purification catalyst according to claim 9, wherein cesium oxide is contained as the cesium at a rate of 5 to 30 g / L per 1 L of a catalyst capacity. 17. The NOx purifying catalyst according to claim 9, wherein potassium oxide is contained as the potassium at a rate of 0.5 to 30 g / L per 1 L of a catalyst capacity. 18. A NOx purifying catalyst used for purifying exhaust gas from an internal combustion engine or a combustor operated in a lean region or a stoichiometric to rich region, wherein the NOx purifying catalyst contains platinum and ceria. The platinum is supported on the ceria at a rate of 5 to 50% based on the amount of SOx in the exhaust gas.
NOx purification catalyst characterized by adsorbing NO as sulfate or sulfite. 19. A NOx purification system using the NOx purification catalyst according to any one of claims 1 to 18, wherein an air-fuel ratio (A / F) in a lean region is 15 or more. A NOx purification system characterized by the above-mentioned. 20. A NOx purification system using the NOx purification catalyst according to any one of claims 1 to 18, wherein the secondary air is supplied from the upstream side of the NOx purification catalyst when the engine is in a stoichiometric to rich region. A NOx purification system characterized by flowing air.