JP2003170045A - Exhaust gas purification catalyst and exhaust gas purification system using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] NOx adsorption function, NOx desorption function and NOx
To provide an exhaust gas purifying catalyst in which a reduction purifying function is exhibited at low cost in a well-balanced manner, and an exhaust gas purifying method using the same. SOLUTION: An upstream catalyst portion and a downstream catalyst portion are provided, and the upstream catalyst portion and the downstream catalyst portion include a catalyst noble metal and a NOx adsorption catalyst, and the total moles of the catalyst noble metal in the upstream catalyst portion. The ratio of the total molar amount of the NOx adsorption catalyst in terms of oxide to the amount is an exhaust gas purification catalyst smaller than the ratio of the downstream catalyst portion. An exhaust gas purification system using the exhaust gas purification catalyst, wherein the inlet temperature of the upstream catalyst section is 350 ° C. or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst and an exhaust gas purifying system using the same, and more specifically to exhaust gas from an internal combustion engine such as an automobile (gasoline car, diesel car) and a boiler. Hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NO) in exhaust gas
The present invention relates to an exhaust gas purifying catalyst for purifying x) and an exhaust gas purifying system using the same, and particularly focuses on NOx purification in a lean 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 lean burn vehicles, the exhaust gas atmosphere becomes leaner than in the theoretical air-fuel state during lean burn running.However, when a normal three-way catalyst is applied in the lean region, the effect of excess oxygen causes a NOx purification effect to be impaired. Was enough. For this reason,
It has been desired to develop a catalyst that can purify NOx even if oxygen becomes excessive.

[0003]

[Problems to be Solved by the Invention]
Various catalysts for purifying Ox have been proposed. For example, as represented by "catalyst in which Pt and lanthanum are supported on a porous carrier" described in Japanese Patent Laid-Open No. 5-168860, NOx in a lean region is represented. A catalyst that adsorbs NOx and releases NOx in the stoichiometric-rich region to purify it has been proposed.

As an important function of such a catalyst, there is a function of adsorbing NOx in the lean region (hereinafter referred to as "NOx adsorbing function") and an N adsorbing in the rich to stoichiometric region.
There are three functions: a function of desorbing Ox (hereinafter referred to as "NOx desorption function") and a function of reducing and purifying NOx desorbed in the rich to stoichiometric region (hereinafter referred to as "NOx reduction purification function").

These three functions are deteriorated when poisoned by SOx derived from sulfur contained in fuel and lubricating oil. In this case, since the poisoning by SOx is the primary poisoning, the poisoning is released by heating the catalyst to remove SOx. However, SOx desorption temperature is 650 ° C
The temperature is very high at ˜750 ° C., and even if it is temporary, in order to raise the temperature of the catalyst, it is necessary to dispose the catalyst at a position close to the engine out. The catalyst inlet temperature is 350
There has been a problem that the NOx adsorption function is not sufficiently fulfilled due to the high temperature of ℃ to 500 ℃. As a solution to this problem, strong alkali is used, and NOx
A method of satisfying the adsorption function can be considered (Fig. 1).

However, NOx is generated by the strong alkali.
Adsorption function is satisfied, but at the same time the strong alkali is NO
x Reduces the activity of the noble metal for expressing the reduction purification function. Therefore, there is a problem that the NOx reduction purification function becomes insufficient.

The present invention has been made in view of the above prior art, and an object of the present invention is to achieve the NOx adsorbing function, the NOx desorbing function, and the NOx reducing and purifying function at a low cost in a well-balanced manner. An object is to provide an exhaust gas purification catalyst and an exhaust gas purification method using the same.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the catalyst precious metal and NO
x By adjusting and combining the content of the adsorption catalyst,
The inventors have found that the above problems can be solved and completed the present invention.

That is, the exhaust gas purifying catalyst of the present invention is an exhaust gas purifying catalyst in which an upstream catalyst portion is arranged on the upstream side of the exhaust gas passage and a downstream catalyst portion is arranged on the downstream side thereof. The upstream side catalyst part and the downstream side catalyst part are made of catalyst precious metal and NO.
The ratio of the total molar amount of oxide of the NOx adsorption catalyst to the total molar amount of the catalytic noble metal of the upstream side catalyst part is smaller than the ratio of the downstream side catalyst part. Is characterized by.

A preferred embodiment of the exhaust gas purifying catalyst of the present invention is the above-mentioned catalytic noble metal and NOx of the above-mentioned downstream catalyst portion.
The total coating amount of the adsorption catalyst is larger than the total coating amount of the upstream catalyst portion.

Further, in another preferred embodiment of the exhaust gas purifying catalyst of the present invention, the NOx adsorbing catalyst and the catalytic noble metal contained in the upstream side catalyst portion are the total number of moles of the NOx adsorbing catalyst in terms of oxide / Total number of moles of catalytic noble metal ≦ 10. 5 ... (1) is satisfied, and the NOx adsorption catalyst and the catalytic noble metal contained in the above-mentioned downstream side catalyst portion are represented by the following formula 2 NOx adsorption catalyst total number of moles converted to oxide / total number of catalytic noble metal > 10. 5 It is characterized by satisfying the relationship represented by (2).

Still another preferred embodiment of the exhaust gas purifying catalyst of the present invention is that the alkali metal and / or alkaline earth metal is at least one element selected from the group consisting of cesium, potassium and sodium. Is characterized in that.

Further, the exhaust gas purification system of the present invention is
An exhaust gas purification system using the above exhaust gas purification catalyst, characterized in that the inlet temperature of the upstream catalyst portion is 350 ° C or higher.

Further, a preferred embodiment of the exhaust gas purifying system of the present invention is characterized in that the upstream side catalyst section and the downstream side catalyst section are arranged in one converter.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The exhaust gas purifying catalyst of the present invention will be described in detail below. In addition, in this specification, "%" shows a mass percentage unless otherwise specified. As described above, the exhaust gas purifying catalyst of the present invention comprises an upstream catalyst section on the upstream side of the exhaust gas flow passage, and a downstream catalyst section on the downstream side thereof. The catalyst part comprises a catalytic noble metal and a NOx adsorption catalyst.

Now, the balance between the catalytic noble metal and the NOx adsorption catalyst will be described. For example, at a high temperature of 350 ° C. or higher, in order to satisfy the function of adsorbing NOx in the lean region (hereinafter referred to as “NOx adsorbing function”), it is required to use a strong alkali as a NOx adsorbing catalyst. The activity of the catalytic noble metal that expresses the function of reducing and purifying NOx desorbed in the rich to stoichiometric region (hereinafter referred to as "NOx reducing and purifying function") is reduced. However, if the amount of strong alkali used is reduced, the NOx adsorption function becomes insufficient. On the other hand, if the amount of the noble metal used is increased, the NOx adsorption function and the NOx reduction purification function can be satisfied, but resource problems and cost problems occur, so it is desirable to reduce the amount of the noble metal used as much as possible.

The present inventors have found that when the molar ratio of the noble metal which is the catalyst component and the strong alkali (NOx adsorption catalyst) is lower than a certain value, the NOx adsorption function is high and the NOx reduction and purification function is low. When the ratio is higher than a certain value,
By finding that the NOx adsorption function is low and the NOx reduction and purification function is high, and further by combining such catalysts having different molar ratios, they have found an exhaust gas purification catalyst that can efficiently purify NOx at low cost. The “oxide conversion” is, for example, when the strong alkali is Cs, the oxide is Cs ₂ O, and the molar ratio (the number of moles of Cs ₂ O / the number of moles of the catalytic noble metal) is calculated. Say that.

Therefore, in the exhaust gas purifying catalyst of the present invention, the ratio of the total molar amount of the NOx adsorbing catalyst in terms of oxide to the total molar amount of the catalytic noble metal in the upstream catalyst portion is
It is characterized in that it is smaller than the ratio of the downstream side catalyst portion. When such a molar ratio relationship is satisfied, the amounts of the catalytic noble metal and the NOx adsorption catalyst used are the minimum necessary, and the amounts of the catalytic noble metal and the NOx adsorption catalyst used are somewhat upstream and downstream. There is no particular limitation on the part and NOx
Three important functions for an adsorption catalyst (NOx adsorption function, NOx
The desorption function and the NOx reduction purification function) are efficiently exhibited at low cost. In other words, the upstream side catalyst part adsorbs and desorbs NOx (NOx adsorbing function and NOx desorbing function),
The desorbed NOx is purified by the downstream side catalyst unit (NOx
Reduction purification function). The reason why the NOx adsorbing catalyst is included in the downstream catalyst section is to improve the exhaust gas purification efficiency by rotating the NOx adsorption, desorption and purification cycle in the downstream catalyst section. Although the amount of the catalytic noble metal used varies depending on the type, about 0.353 g per 1 L of the catalyst is sufficient to exert the NOx adsorption function and NOx desorption function, and the NOx reduction purification function is exerted. Catalyst 1L
It may be about 1.4 g per unit.

Further, in FIG. 2, N for the catalyst noble metal is
The relationship between the oxide-based molar ratio of the Ox adsorption catalyst and the NOx adsorption function and NOx desorption function is shown. As described above, the exhaust gas purifying catalyst of the present invention can further enhance the NOx adsorbing function and the NOx reducing and purifying function by combining the catalyst parts whose molar ratios are set.

Specifically, the NOx adsorbing catalyst and the catalytic noble metal contained in the upstream side catalyst part are expressed by the following formula 1 as the total number of moles of oxide of NOx adsorbing catalyst / the total number of moles of the catalytic noble metal ≦ 10. 5 ... (1) is satisfied, and the NOx adsorption catalyst and the catalytic noble metal contained in the above-mentioned downstream side catalyst portion are represented by the following formula 2 NOx adsorption catalyst total number of moles converted to oxide / total number of catalytic noble metal > 10. When the relationship expressed by 5 (2) is satisfied, the NOx adsorption function can be further enhanced. On the other hand, the NOx adsorbing catalyst and the catalytic noble metal contained in the upstream catalyst section are represented by the following formula 3 NOx adsorbing catalyst total number of oxides / total number of catalytic noble metal moles ≦ 7.5 (3) The NOx adsorbing catalyst and the catalytic noble metal contained in the downstream side catalyst unit satisfy the following relation, and the total number of moles of the NOx adsorbing catalyst in terms of oxide / total number of catalytic noble metal> 7.5 (4) When the relationship expressed by is satisfied, the NOx reduction purification function can be further enhanced.

Further, it is preferable that the total coating amount of the catalytic noble metal and NOx adsorption catalyst in the downstream catalyst portion is larger than the total coating amount of the upstream catalyst portion. NO when the catalyst coat amount is small (for example, 200 g or less per 1 L of catalyst)
The x adsorption function and the NOx desorption function tend to increase, and the NOx reduction purification function tends to decrease. On the other hand, when the catalyst coating amount is large (for example, 300 g or more per 1 L of the catalyst), the NOx reduction purification function is likely to increase, and the NOx adsorption function and NOx desorption function are likely to decrease. From this, NOx adsorption function and NOx
By arranging the catalyst portion having the enhanced desorption function on the upstream side and the catalyst portion having the enhanced NOx reduction and purification function on the downstream side, excellent NOx purification performance as an exhaust gas purification catalyst can be exhibited.

Specifically, the ratio of the total coat amount of the upstream side catalyst portion to the total coat amount of the downstream side catalyst portion can be set to more than 1: 1 and 1: 1.5 or less. Desirably, the total coat amount of the downstream side catalyst portion is about 1.2 times the total coat amount of the upstream side catalyst portion.

As the NOx adsorption catalyst, a catalyst containing an alkali metal and / or an alkaline earth metal can be preferably used. Typical examples of the above-mentioned alkali metal and / or alkaline earth metal include cesium (C
s), potassium (K) or sodium (Na), and elements related to any combination thereof can be exemplified, and Cs is particularly desirable. These strong alkalis are preferable because they can sufficiently exert the NOx adsorption function even at a high temperature of 350 ° C. or higher.

Further, the NOx adsorption catalyst of the upstream side catalyst portion contains Cs, K or Na and an element related to any combination thereof, and the NOx adsorption catalyst of the downstream side catalyst portion is barium (Ba), magnesium ( Mg), calcium (C
It is preferable to include a) or strontium (Sr), and elements related to any combination thereof. Since strong alkalis such as Cs, K and Na reduce the activity of the noble metal, the NOx reduction purification function may be insufficient even if the NOx adsorption function is sufficiently expressed. However, as a NOx adsorption catalyst of the downstream side catalyst part, The use of an alkaline earth metal that is not so strong in basicity, such as Ba, Mg, Ca and Sr, is effective because the balance of each function can be adjusted.

Furthermore, the above NOx adsorption catalyst has the following general formula Ba _x Mg _y (CO ₃ ) ₂ (where x and y represent the atomic ratio of each element, and x = 0.
5 to 1.999, y = 0.001 to 1.5, and x + y
= 2.0), a complex carbonate represented by
It is effective from the viewpoint of stabilizing the alkali metal and / or the alkaline earth metal and suppressing deterioration. In particular, in the above general formula, x = 1 and y = 1, that is, BaMg
It is preferable to include (CO ₃ ) ₂ .

Although the reason for this is not clear at this point,
It can be inferred that this is because the complex carbonate and the remaining alkali metal and / or alkaline earth metal are more easily complexed. In addition, if this complex carbonate is used alone, XRD
However, the peak of the complex carbonate cannot be detected when it is contained in the catalyst. However, as shown in FIG. 3, a monoclinic system peak of BaCO ₃ can be newly detected instead, and it is considered that it is possible to determine whether the peak is complexed with this peak. Note that normally BaC
O ₃ has only orthorhombic peaks.

On the other hand, platinum (P
It is preferred to use t), palladium (Pd) or rhodium (Rh), and noble metals according to any combination thereof. In particular, it is desirable to use Pt and / or Rh, and at this time, the NOx adsorption function, the NOx desorption function, and the NOx reduction purification function are likely to be sufficiently exhibited.

When Pt is used as the catalyst noble metal, it is preferable that at least a part of this Pt be supported by the oxygen storage / release material. In this case, the present inventors have found that the effect of sulfur poisoning is mitigated.
That is, the following phenomenon occurs when Pt is loaded on the oxygen storage / release material. Normally, in the lean region, SO _{2 in} exhaust gas
Reacts with excess oxygen and is taken up as sulfate or sulfite (hereinafter referred to as “sulfate”) on Pt. In the rich region, most of SO _{2 in} exhaust gas is dissociated and adsorbed on Pt, It becomes a sulfide. However, when Pt is loaded on the oxygen storage / release material, SO ₂ in the exhaust gas is taken in in the form of sulfate or the like in the lean region, but oxygen is also released from the oxygen storage / release material in the rich region. The oxygen reacts with SO _{2 and} is taken in as a sulfate or the like on Pt supported on the oxygen storage / release material, and sulfuration of Pt is prevented. Pt sulfide and P
With the sulfate of t, etc., the latter is easier to desorb sulfur from Pt, and if retained as Pt's sulfate in the rich region, sulfur poisoning of Pt can be released in a short time. , I can work as an active point quickly.

Further, as the oxygen absorbing / releasing material, ceria (CeO ₂ ) or Pr ₆ O ₁₁ can be used, but CeO ₂ is particularly preferable. Furthermore,
When CeO ₂ is used, it is preferable to combine it with Zr and / or Pr to improve the durability.

B which can be contained in the NOx adsorption catalyst
A, Mg, Ca, Sr, Cs, K, Na and the like can be used in the form of carbonate, oxide or hydroxide. Also, the working air-fuel ratio when using this exhaust gas purification catalyst is
Air-fuel ratio (A / F) is between 15 and 50 and 10.0 to 14.
When it is between 6, NOx can be efficiently purified. Further, the exhaust gas purifying catalyst can be used in various shapes, for example, a honeycomb structure made of cordierite, stainless steel or the like can be used by supporting a catalyst component. Furthermore, the exhaust gas purifying catalyst is required to have high heat resistance in view of the situation of being exposed to high temperatures. Therefore, ceria, zirconia, lanthanum, barium, etc., which have been conventionally used in three-way catalysts,
The heat resistance may be improved by using a material such as noble metal or alumina. Further, these may have a multi-layer structure. Further, although a gasoline vehicle is used in the embodiment, it goes without saying that the same effect can be obtained even with a diesel engine vehicle. Furthermore, it is possible to prepare a plurality of exhaust gas purifying catalysts having different distinctive functions and make them continuous on the exhaust flow path to form a system.

Next, the exhaust gas purification system of the present invention will be described in detail. Such a system uses the above-mentioned exhaust gas purifying catalyst, and the inlet temperature of the upstream catalyst section is controlled to 350 ° C or higher. By adjusting the temperature of the exhaust gas flowing into the catalyst to the above temperature, the NOx adsorption function, the NOx desorption function, and the NOx
The reduction purification function is well balanced. The feature of this system is that it does not simply control the temperature to 350 ° C or higher, but removes HC at low temperatures (when the engine is started). However, it means that the exhaust temperature becomes 350 ° C or higher.

The upstream side catalyst section and the downstream side catalyst section are 1
It is preferably arranged in one converter. For example, each catalyst unit can be arranged as shown in FIG. If the two are too far apart, when purifying the NOx desorbed from the upstream side catalyst section by the downstream side catalyst section, the rich atmosphere in the downstream side catalyst section weakens, and the NOx reduction purification function tends to deteriorate. is there. Specifically, it is preferable that the distance between the catalyst parts is within 20 cm, although it depends on the size of the system and the like. It is not necessary to dispose two catalyst parts as long as they are arranged in one converter, and one catalyst part may be separately coated on the upstream side and the downstream side.

[0033]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 Powder A was obtained by impregnating activated alumina having a specific surface area of 180 m ^{2 with} a dinitrodiamine platinum solution, drying and calcining in air at 400 ° C. for 1 hour. The Pt concentration of this powder was 2.0%. Powder A 588
g, 60 g of activated alumina, 72 g of alumina sol, and 1080 g of water were put into a magnetic ball mill and mixed and ground to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolithic carrier (1.7 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 300g / L
The catalyst was obtained. The catalyst was immersed in an aqueous solution of cesium acetate to impregnate the catalyst with cesium. This catalyst contains P
t was 4.9 g / L (0.0251 mol), and Cs was 70 g / L (0.249 mol) in terms of oxide. The molar ratio is 9.9. In this way, a catalyst part I was obtained.

Activated alumina having a specific surface area of 180 m ² was impregnated with a dinitrodiamine platinum solution, dried and then 400
Firing was performed at 0 ° C. for 1 hour to obtain powder B. The Pt concentration of this powder was 0.22%. 654.2 g of powder B, 4.1 g of activated alumina, 61.7 g of alumina sol, 1 part of water
080 g was put into a magnetic ball mill, mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolithic carrier (1.7 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. A layer of 350 g / L of catalyst was obtained. The catalyst was immersed in an aqueous solution of cesium acetate to impregnate the catalyst with cesium. This catalyst contains Pt
Was 0.7 g / L (0.00359 mol), and Cs was 11 g / L (0.0391 mol) in terms of oxide. The molar ratio is 10.9. In this way, a catalyst part II was obtained.

The catalyst part I obtained as described above was arranged upstream of the exhaust flow, and the catalyst part II was arranged downstream thereof for evaluation. The coating amount ratio of the upstream catalyst portion I and the downstream catalyst portion II is 1.17.

(Example 2) 654.2 g of powder B, 4.1 g of activated alumina, 61.7 g of alumina sol, and 1 part of water
080 g was put into a magnetic ball mill, mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolithic carrier (1.7 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. A layer of 350 g / L of catalyst was obtained. The catalyst was immersed in an aqueous solution of cesium acetate to impregnate the catalyst with cesium. This catalyst contains Pt
Was 0.7 g / L (0.00359 mol), and Cs was 9.8 g / L (0.035 mol) in terms of oxide. The molar ratio is 9.7. In this way, a catalyst part I was obtained.

441.4 g of powder A and 2 of activated alumina
24.6 g, 54 g of alumina sol, and 1080 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 (1.7
L, 400 cells), remove excess slurry in the cells by air flow and dry at 130 ° C, then 400 ° C
And was baked for 1 hour to obtain a catalyst having a coat layer of 300 g / L.
The catalyst was immersed in an aqueous solution of cesium acetate to impregnate the catalyst with cesium. This catalyst contained Pt of 4.9 g /
L (0.0251 mol), Cs is 74.
5 g / L (0.265 mol) was supported. The molar ratio is 10.6. In this way, a catalyst part II was obtained.

Evaluation was carried out by arranging the catalyst portion I obtained as described above on the upstream side with respect to the exhaust flow and the catalyst portion II on the downstream side. The coating amount ratio of the upstream catalyst portion I and the downstream catalyst portion II is 1.14.

(Example 3) 588 g of powder A, 60 g of activated alumina, 72 g of alumina sol and 1080 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 (1.7 L, 400 cells), excess slurry in the cells was removed by an air stream, and the slurry was dried at 130 ° C.
Firing was performed at 400 ° C. for 1 hour to obtain a catalyst having a coat layer of 300 g / L. Immersing this catalyst in an aqueous solution of cesium acetate,
Cesium was impregnated in the catalyst. The catalyst supported Pt of 4.9 g / L (0.0251 mol) and Cs of 50 g / L (0.179 mol) in terms of oxide.
The molar ratio is 7.1. In this way, a catalyst part I was obtained.

654.2 g of powder B, 4.1 g of activated alumina, 61.7 g of alumina sol and 1080 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 (1.7 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 to obtain a catalyst having a coat layer of 350 g / L. Immersing this catalyst in an aqueous solution of cesium acetate,
Cesium was impregnated in the catalyst. On this catalyst, 0.7 g / L (0.00359 mol) of Pt and 8.1 g / L (0.0287 mol) of Cs as oxide were supported. The molar ratio is 8.0. In this way the catalyst part II
Got

Evaluation was carried out by arranging the catalyst portion I obtained as described above on the upstream side with respect to the exhaust flow and the catalyst portion II on the downstream side. The coating amount ratio of the upstream catalyst portion I and the downstream catalyst portion II is 1.17.

Example 4 The same operation as in Example 1 was repeated except that potassium acetate was used instead of cesium acetate,
The catalyst part I and the catalyst part II were manufactured, arranged, and evaluated.
The upstream catalyst portion I contains 4.9 g / L of Pt (0.0251
mol) and K are 23.5 g / L (0.24) in terms of oxides.
9 mol). The molar ratio is 9.9. The downstream catalyst portion II contains 0.7 g / L of Pt (0.00359
mol) and K are 3.7 g / L (0.039) in terms of oxides.
1 mol) was supported. The molar ratio is 10.9.

(Example 5) The same operation as in Example 1 was repeated except that cesium acetate was changed to sodium acetate, to manufacture and arrange the catalyst part I and the catalyst part II, and to evaluate them. The upstream catalyst portion I contains 4.9 g / L (0.02 Pt) of Pt.
51 mol), and Na is 15.4 g / L in terms of oxide.
(0.249 mol) was supported. Molar ratio is 9.9
Is. The downstream catalyst portion II contains 0.7 g / L of Pt (0.
(00359 mol), Na is 2.4 g / L in terms of oxide.
(0.0391 mol) was supported. Molar ratio is 1
It is 0.9.

Example 6 The same operation as in Example 1 was repeated, except that the cesium acetate of the downstream catalyst was changed to barium acetate, the catalyst part I and the catalyst part II were manufactured, placed, and evaluated. It was Pt is 0.7 g / L in the downstream catalyst section II.
(0.00359 mol), Ba is 6.0 in terms of oxide.
It was supported by g / L (0.0391 mol). The molar ratio is 10.9.

(Example 7) The same operation as in Example 1 was repeated except that the cesium acetate of the downstream catalyst was changed to magnesium acetate, the catalyst part I and the catalyst part II were manufactured, placed and evaluated. It was Pt is 0.7 g in the downstream catalyst part II.
/ L (0.00359 mol) and Mg were carried in an amount of 1.6 g / L (0.0391 mol) in terms of oxide.
The molar ratio is 10.9. In this way, a catalyst part II was obtained.

Example 8 A catalyst part I and a catalyst part II were manufactured and arranged by repeating the same operation as in Example 1 except that cesium acetate of the downstream side catalyst was changed to calcium acetate.
An evaluation was made. Pt is 0.7 g / L in the downstream catalyst section II.
(0.00359 mol), Ca is 2.2 in terms of oxide.
It was supported by g / L (0.0391 mol). The molar ratio is 10.9.

Example 9 The same operation as in Example 1 was repeated except that the cesium acetate of the downstream catalyst was changed to strontium acetate, the catalyst part I and the catalyst part II were manufactured, placed, and evaluated. It was Pt is 0.7 g in the downstream catalyst part II.
/ L (0.00359 mol) and Sr of 4.1 g / L (0.0391 mol) in terms of oxide were supported.
The molar ratio is 10.9.

Example 10 A catalyst part I and a catalyst part II were produced by repeating the same operation as in Example 1 except that the cesium acetate solution was changed to a mixed solution of cesium acetate, magnesium acetate and barium acetate. It was placed and evaluated. The upstream catalyst part I contains 4.9 g / L of Pt (0.0251 m
ol) and Cs are 19.1 g / L (0.06) in terms of oxide.
8 mol), Ba is 9.5 g / L (0.0
62 mol) and Mg is 4.8 g / L (0.
119 mol). The molar ratio is 9.9. The downstream catalyst portion II contains 0.7 g / L (0.00
359 mol), Cs is 3.0 g / L in terms of oxide.
(0.0106 mol), Ba is 1.5 g in terms of oxide
/ L (0.0098 mol), and Mg is 0.
It was carried on 75 g / L (0.0187 mol). The molar ratio is 10.9. In this way, a catalyst part II was obtained.

Example 11 Powder C was obtained by impregnating activated alumina having a specific surface area of 180 m ^{2 with} a rhodium nitrate solution, drying and firing at 400 ° C. for 1 hour in air. The Rh concentration of this powder was 2.0%. 490.1 g of powder A,
97.9 g of Powder C, 60 g of activated alumina, 72 g of alumina sol and 1080 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 monolithic carrier (1.7 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. A layer of 300 g / L of catalyst was obtained. This catalyst was immersed in a mixed aqueous solution of cesium acetate, barium acetate and magnesium acetate, and the catalyst was co-impregnated with cesium, barium and magnesium. This catalyst contains Pt of 4.08 g / L
(0.0209 mol), Rh is 0.82 g / L (0.
0080 mol), Cs is 19.1 g / L in terms of oxide
(0.068 mol), Ba is 9.5 g / in terms of oxide.
L (0.062 mol), Mg is 4.8 g in terms of oxide
/ L (0.119 mol) was carried. The molar ratio is 8.6. In this way, a catalyst part I was obtained.

Activated alumina having a specific surface area of 180 m ² was impregnated with a rhodium nitrate solution, dried and calcined in air at 400 ° C. for 1 hour to obtain a powder D. The Rh concentration of this powder was 0.
It was 22%. 545.6 g of powder B and 10 of powder D
9 g, activated alumina 3.7 g, and alumina sol 61.
7 g of water 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 attached to a cordierite monolith carrier (1.7 L, 400 cells),
Excessive slurry in the cell is removed by air flow and 130 ℃
And dried at 400 ° C. for 1 hour to form the coating layer 35.
0 g / L of catalyst was obtained. This catalyst was immersed in a mixed aqueous solution of cesium acetate, barium acetate and magnesium acetate,
Cesium, barium and magnesium were co-impregnated in the catalyst. This catalyst contained 0.583 g / L (0.00
299 mol), Rh 0.117 g / L (0.001
14 mol), and Cs is 3.4 g / L (0.
0122 mol), and Ba is 1.7 g / L in terms of oxide.
(0.0112 mol), Mg is 0.86 in terms of oxide
It was supported by g / L (0.0215 mol). The molar ratio is 10.9. In this way, a catalyst part II was obtained.

Evaluation was carried out by arranging the catalyst portion I obtained as described above on the upstream side and the catalyst portion II on the downstream side with respect to the exhaust flow. The coating amount ratio of the upstream catalyst portion I and the downstream catalyst portion II is 1.17.

(Example 12) Activated ceria having a specific surface area of 120 m ² was impregnated with a dinitrodiamine platinum solution, dried and then calcined in air at 400 ° C. for 1 hour to obtain a powder E. The Pt concentration of this powder was 2.0%. Powder A 392.
1 g, powder C 97.9 g, powder E 98.0 g, activated alumina 60 g, alumina sol 72 g, water 1080
g was 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 (1.7 L, 400 cells), excess slurry in the cells was removed by an air stream, and the slurry was dried at 130 ° C.
Firing was performed at 400 ° C. for 1 hour to obtain a catalyst having a coat layer of 300 g / L. This catalyst was immersed in a mixed aqueous solution of cesium acetate, barium acetate and magnesium acetate, and the catalyst was co-impregnated with cesium, barium and magnesium. This catalyst contained Pt 4.08 g / L (0.0209 mol) and R
h is 0.82 g / L (0.0080 mol), Cs is 19.1 g / L (0.068 mol) in terms of oxide, Ba
Is 9.5 g / L (0.062 mol) in terms of oxide, M
The amount of g was 4.8 g / L (0.119 mol) in terms of oxide. The molar ratio is 8.6. In this way, a catalyst part I was obtained.

Activated ceria having a specific surface area of 120 m ² was impregnated with a dinitrodiamine platinum solution, dried and then 400 ° C. in air.
After firing for 1 hour, powder F was obtained. The Pt concentration of this powder was 0.22%. 436.5 g of powder B and powder D
109 g, powder F 109.1 g, activated alumina 3.7 g, alumina sol 61.7 g, and water 1080 g were 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 (1.7 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 to obtain a catalyst having a coat layer of 350 g / L. This catalyst was immersed in a mixed aqueous solution of cesium acetate, barium acetate and magnesium acetate, and the catalyst was co-impregnated with cesium, barium and magnesium. In this catalyst, Pt is 0.583 g / L (0.00299 mo
l), Rh is 0.117 g / L (0.00114mo
l) and Cs are 3.4 g / L (0.0122) in terms of oxide.
mol) and Ba are 1.7 g / L (0.01
12 mol), Mg is 0.86 g / L in terms of oxide
(0.0215 mol) was supported. Molar ratio is 1
It is 0.9. In this way, a catalyst part II was obtained.

Evaluation was carried out by arranging the catalyst portion I obtained as described above on the upstream side and the catalyst portion II on the downstream side with respect to the exhaust flow. The coating amount ratio of the upstream catalyst portion I and the downstream catalyst portion II is 1.17.

Example 13 Ce-Zr in which 25% of ZrO ₂ was compounded with the active ceria of the powders E and F of Example 12
The same operation as in Example 12 was repeated, except that the composite oxide was used, to manufacture and arrange the catalyst part I and the catalyst part II, and to evaluate.

(Example 14) Activated alumina having a specific surface area of 180 m ² was impregnated with a dinitrodiamine platinum solution, dried and calcined in air at 400 ° C for 1 hour to obtain a powder G. The Pt concentration of this powder was 1.5%. Specific surface area is 18
0 m ² of activated alumina was impregnated with a dinitrodiamine platinum solution, dried, and calcined in air at 400 ° C. for 1 hour to obtain powder H.
Got The Pt concentration of this powder was 0.6%. A Ce-Zr composite oxide in which activated ceria having a specific surface area of 120 m ² and 25% of ZrO ₂ was composited was impregnated with a dinitrodiamine platinum solution, dried, and then calcined in air at 400 ° C. for 1 hour to obtain a powder I. It was The Pt concentration of this powder was 1.5%. Activated alumina having a specific surface area of 180 m ² was impregnated with a rhodium nitrate solution, dried and calcined in air at 400 ° C. for 1 hour to obtain a powder J. The Pt concentration of this powder was 1%. 579.6 g of powder H, 51.1 g of powder I, 57.6 g of activated alumina, 31.7 g of alumina sol, and 1080 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 monolithic carrier (1.7 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 200g / L
The catalyst was obtained. On this catalyst coat layer, powder G
8.9 g, powder I 67.7 g, powder J 226.8
g, activated alumina 92.9 g, and alumina sol 23.
7 g of water and 1080 g of water were put into a magnetic ball mill, and a slurry liquid obtained by mixing and pulverizing was attached to remove excess slurry in the cell with an air stream and dried at 130 ° C.
The catalyst was baked at 1 ° C. for 1 hour to obtain a catalyst having a coat layer of 150 g / L. This catalyst was immersed in a mixed aqueous solution of cesium acetate, barium acetate, and magnesium acetate, and cesium was added to the catalyst.
Barium and magnesium were co-impregnated. This catalyst has
Pt is 2.35 g / L (0.0121 mol), Rh is 0.47 g / L (0.0046 mol), Cs is 10 g / L (0.036 mol) in terms of oxide, and Ba is 5 g / L in terms of oxide. (0.033 mol) and Mg were carried in an amount of 2.5 g / L (0.63 mol) in terms of oxide.
The molar ratio is 7.8. In this way, a catalyst part I was obtained.

579.6 g of powder H and 51.1 of powder I
g, activated alumina 57.6 g, alumina sol 31.
7 g of water 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 attached to a cordierite monolith carrier (1.7 L, 400 cells),
Excessive slurry in the cell is removed by air flow and 130 ℃
And dried at 400 ° C. for 1 hour to dry the coat layer 20.
0 g / L of catalyst was obtained. On this catalyst coat layer, powder G
272.9 g, powder I 59.8 g, powder J 20
0.2 g, activated alumina 166.3 g, alumina sol 20.8 g, and water 1080 g were put into a magnetic ball mill, and the slurry liquid obtained by mixing and pulverizing was attached, and excess slurry in the cell was removed by air flow. And dried at 130 ° C., and then baked at 400 ° C. for 1 hour to obtain a catalyst having a coat layer of 170 g / L. This catalyst was added to cesium acetate, barium acetate,
It was immersed in a mixed aqueous solution of magnesium acetate, and the catalyst was co-impregnated with cesium, barium and magnesium. In this catalyst, Pt is 2.35 g / L (0.0121 mo
l), Rh is 0.47 g / L (0.0046 mol),
Cs is 20 g / L (0.071 mol) in terms of oxide,
Ba is 10 g / L (0.065 mol) in terms of oxide,
Mg was supported in an amount of 5 g / L (0.125 mol) in terms of oxide. The molar ratio is 15.6. In this way, a catalyst part II was obtained.

Evaluation was carried out by arranging the catalyst part I obtained as described above on the upstream side with respect to the exhaust flow and the catalyst part II on the downstream side. The coating amount ratio of the upstream catalyst portion I and the downstream catalyst portion II is 1.06.

Comparative Example 1 Powder K was obtained by impregnating activated alumina having a specific surface area of 180 m ^{2 with} a dinitrodiamine platinum solution, drying and firing it in air at 400 ° C. for 1 hour. The Pt concentration of this powder was 3.0%. Powder K to 586.
8g, activated alumina 61.2g, alumina sol 72
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 was attached to a cordierite monolithic carrier (1.7 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 200
g / L of catalyst was obtained. The catalyst was immersed in an aqueous solution of cesium acetate to impregnate the catalyst with cesium. This catalyst contained Pt of 4.9 g / L (0.0251 mol) and Cs.
Was 70 g / L (0.249 mol) in terms of oxide. The molar ratio is 9.9. In this way, a catalyst part I was obtained.

654.2 g of powder B, 4.1 g of activated alumina, 61.7 g of alumina sol and 1080 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 (1.7 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 to obtain a catalyst having a coat layer of 350 g / L. Immersing this catalyst in an aqueous solution of cesium acetate,
Cesium was impregnated in the catalyst. 0.7 g / L (0.00359 mol) of Pt and 11 g / L (0.0391 mol) of Cs in terms of oxide were loaded on this catalyst. The molar ratio is 10.9. In this way the catalyst part II
Got

Evaluation was carried out by arranging the catalyst portion I obtained as described above on the upstream side and the catalyst portion II on the downstream side with respect to the exhaust flow. The coating amount ratio of the upstream catalyst portion I and the downstream catalyst portion II is 1.75.

(Comparative Example 2) 588 g of powder A, 60 g of activated alumina, 72 g of alumina sol and 1080 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 (1.7 L, 400 cells), excess slurry in the cells was removed by an air stream, and the slurry was dried at 130 ° C.
Firing was performed at 400 ° C. for 1 hour to obtain a catalyst having a coat layer of 300 g / L. Immersing this catalyst in an aqueous solution of cesium acetate,
Cesium was impregnated in the catalyst. The catalyst supported Pt in an amount of 4.9 g / L (0.0251 mol) and Cs in an amount of 70 g / L (0.249 mol) in terms of oxide.
The molar ratio is 9.9. In this way, a catalyst part I was obtained.

Activated alumina having a specific surface area of 180 m ² was impregnated with a dinitrodiamine platinum solution, dried and then dried in air to 400
The powder L was obtained by firing at 1 ° C. for 1 hour. The Pt concentration of this powder was 0.35%. Powder L (576 g), activated alumina (72 g), alumina sol (72 g) and water (1080 g) were 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 (1.7 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 to obtain a catalyst having a coat layer of 250 g / L. Immersing this catalyst in an aqueous solution of cesium acetate,
Cesium was impregnated in the catalyst. 0.7 g / L (0.00359 mol) of Pt and 11 g / L (0.0391 mol) of Cs in terms of oxide were loaded on this catalyst. The molar ratio is 10.9. In this way the catalyst part II
Got

Evaluation was carried out by arranging the catalyst portion I obtained as described above on the upstream side with respect to the exhaust flow and the catalyst portion II on the downstream side. The coating amount ratio of the upstream catalyst portion I and the downstream catalyst portion II is 0.83.

(Comparative Example 3) The catalyst part I and the catalyst part II were manufactured, arranged and evaluated by repeating the same operation as in Example 1 except that the supported amount of cesium acetate was changed as follows. . The upstream catalyst portion I contains 4.9 g / L (0.02 Pt) of Pt.
51 mol), Cs is 77.6 g / L in terms of oxide.
(0.276 mol) was supported. The molar ratio is 11. In this way, a catalyst part I was obtained. Downstream catalyst section II
Is Pt 0.7 g / L (0.00359 mol), C
s is 10.1 g / L in terms of oxide (0.0359 mo
l) It was supported. The molar ratio is 10. In this way, a catalyst part II was obtained.

(Comparative Example 4) The catalyst part I and the catalyst part II were manufactured, arranged and evaluated by repeating the same operation as in Example 1 except that the supported amount of cesium acetate was changed as follows. . The upstream catalyst portion I contains 4.9 g / L (0.02 Pt) of Pt.
51 mol), Cs is 49.4 g / L in terms of oxide.
(0.176 mol) was supported. The molar ratio is 7. In this way, a catalyst part I was obtained. Downstream catalyst section II
Is Pt 0.7 g / L (0.00359 mol), C
s is 6.6 g / L (0.0233 mol) in terms of oxide
It was carried. The molar ratio is 6.5. In this way, a catalyst part II was obtained.

(Comparative Example 5) The same operation as in Example 1 was repeated except that platinum was changed to palladium, to manufacture and arrange the catalyst part I and the catalyst part II, and to evaluate them.

<Test Example> -Durability Method A catalyst was attached to the exhaust system of an engine with a displacement of 4400 cc, domestic regular gasoline was used, the catalyst inlet temperature was 700 ° C, and the engine was operated for 50 hours.

Evaluation Method A catalyst was attached to the exhaust system of an engine with a displacement of 2000 cc, and after running for 10 hours at 700 ° C., 10-15 mode was run and the conversion rate of the mode was determined. In the mode, lean (A / F = 25) during steady running, fuel cut during deceleration, rich (A / F = 11.0, 2 during acceleration).
Second) → Stoichi (A / F = 14.3). The catalyst inlet temperature was 400 ° C.

[0071]

[Table 1]

As shown in Table 1, it is understood that the exhaust gas purifying catalysts obtained in Examples 1 to 14 are the preferred embodiments of the present invention and exhibit an excellent NOx purification rate. On the other hand, in the exhaust gas purifying catalysts obtained in Comparative Examples 3 and 4, the NOx purification rate is low because the molar ratio of the upstream catalyst portion and the downstream catalyst portion does not satisfy the requirements of the present invention. Further, in the exhaust gas purifying catalysts obtained in Comparative Examples 1 and 2, the coating amount ratio of the downstream side catalyst part to the upstream side catalyst part exceeds 1.5 or 1
Since it is below, the NOx purification rate is low. Furthermore, Comparative Example 5
From the exhaust gas purifying catalyst obtained in step 1, it is understood that the catalyst used in the noble metal catalyst portion is preferably Pt and / or NOx rather than Pd.

[0073]

As described above, according to the present invention,
Since the contents of the catalytic noble metal and the NOx adsorption catalyst were adjusted and combined, the exhaust gas purification catalyst and the NOx adsorption function, the NOx desorption function, and the NOx reduction purification function that were exhibited in good balance at low cost were used. An exhaust gas purification method can be provided.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between NOx adsorption rate and temperature.

FIG. 2 is a graph showing the relationship between the molar ratio and the NOx adsorption rate or the desorbed NOx purification rate.

FIG. 3 is a diagram showing the detection results of XRD of barium carbonate.

FIG. 4 is a schematic view showing an arrangement example of an upstream side catalyst section and a downstream side catalyst section.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/10 F01N 3/28 301G 3/28 301 B01D 53/36 104A ZAB 102H F term (reference) 3G091 AA02 AA12 AA17 AA18 AA28 AB06 BA14 BA32 BA33 GA06 GA19 GB01W GB01X GB02W GB03W GB04W GB05W GB06W GB07W GB10X GB17X HA47 4D048 AA06 AA13 AA18 AB05 AB07 BA07 BA01 BA32 BA45XBA45XBA45XBA32X BA13A BA13B BB02A BB02B BB04A BB06A BB16A BB16B BC01A BC02A BC02B BC03A BC06A BC06B BC08A BC09A BC09B BC10A BC10B BC12A BC12B BC13A BC13B BC43A BC18A BC19A BC12A BC75ABC09A BC75A BC09A BC75A BC09A

Claims (16)

[Claims] 1. An upstream catalyst portion is provided on the upstream side of the exhaust gas flow path,
An exhaust gas purifying catalyst having a downstream catalyst section disposed downstream thereof, wherein the upstream catalyst section and the downstream catalyst section include a catalytic noble metal and a NOx adsorption catalyst, and the upstream catalyst section. The exhaust gas purifying catalyst, wherein the ratio of the total molar amount of oxides of the NOx adsorption catalyst to the total molar amount of the catalytic noble metal is smaller than the ratio of the downstream catalyst portion. 2. The exhaust gas according to claim 1, wherein the total coated amount of the catalytic noble metal and the NOx adsorption catalyst in the downstream catalytic portion is larger than the total coated amount of the upstream catalytic portion. Purification catalyst. 3. The ratio of the total coat amount of the upstream side catalyst part to the total coat amount of the downstream side catalyst part is more than 1: 1 and 1 :.
The exhaust gas purifying catalyst according to claim 1, wherein the exhaust gas purifying catalyst is 1.5 or less. 4. The NOx adsorbing catalyst and the catalytic noble metal contained in the upstream side catalyst portion are represented by the following formula 1 as the total number of moles of the NOx adsorbing catalyst in terms of oxide / the total number of moles of the catalytic noble metal ≦ 10. 5 ... (1) is satisfied, and the NOx adsorption catalyst and the catalytic noble metal contained in the above-mentioned downstream side catalyst portion are represented by the following formula 2 NOx adsorption catalyst total number of moles converted to oxide / total number of catalytic noble metal > 10. 5. The relation represented by (2) is satisfied.
The exhaust gas purifying catalyst according to any one of items 1. 5. The NOx adsorbing catalyst and the catalytic noble metal contained in the upstream side catalyst portion are represented by the following formula 3 NOx adsorbing catalyst total mole number as oxide / total catalytic noble metal mole number ≦ 7.5 (3) The NOx adsorbing catalyst and the catalytic noble metal contained in the downstream side catalyst portion satisfying the relationship represented by the following formula 4 are the total number of moles of NOx adsorbing catalyst in terms of oxide / the total number of moles of the catalytic noble metal> 7.5 ... The relation represented by (4) is satisfied.
The exhaust gas purifying catalyst according to any one of items 1. 6. The exhaust gas purifying catalyst according to any one of claims 1 to 5, wherein the NOx adsorption catalyst contains an alkali metal and / or an alkaline earth metal. 7. The exhaust gas purifying according to claim 6, wherein the alkali metal and / or alkaline earth metal is at least one element selected from the group consisting of cesium, potassium and sodium. catalyst. 8. An alkali metal and / or an alkaline earth metal contained in the upstream catalyst section is at least one element selected from the group consisting of cesium, potassium and sodium, and the downstream catalyst section contains The exhaust gas purifying catalyst according to claim 6, wherein the contained alkali metal and / or alkaline earth metal is at least one element selected from the group consisting of barium, magnesium, calcium and strontium. 9. The NOx adsorption catalyst has the following general formula Ba _x Mg _y (CO ₃ ) ₂ (where x and y represent the atomic ratio of each element, and x = 0.
5 to 1.999, y = 0.001 to 1.5, and x + y
= 2.0). The exhaust gas purifying catalyst according to any one of claims 1 to 5, further comprising a complex carbonate represented by the formula: 10. In the above general formula, x = 1 and y = 1.
The exhaust gas purifying catalyst according to claim 9, wherein 11. The exhaust gas purifying according to claim 1, wherein the catalytic noble metal is at least one noble metal selected from the group consisting of platinum, palladium and rhodium. catalyst. 12. The exhaust gas according to claim 1, wherein the catalytic noble metal contains platinum, and at least a part of the platinum is supported by an oxygen storage / release material. Purification catalyst. 13. The exhaust gas purifying catalyst according to claim 12, wherein the oxygen storage / release material is ceria. 14. The exhaust gas purifying catalyst according to claim 13, wherein the ceria is complexed with zirconium and / or praseodymium. 15. An exhaust gas purification system using the exhaust gas purification catalyst according to any one of claims 1 to 14, characterized in that the inlet temperature of the upstream side catalyst part is 350 ° C. or higher. Exhaust gas purification system. 16. The exhaust gas purification system according to claim 15, wherein the upstream side catalyst section and the downstream side catalyst section are arranged in one converter.