JP3496252B2 - Exhaust gas purification catalyst and exhaust gas purification catalyst device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst.

[0002]

2. Description of the Related Art As a catalyst for purifying engine exhaust gas,
Oxidation of CO (carbon monoxide) and HC (hydrocarbons), N
A three-way catalyst that simultaneously performs reduction of Ox (nitrogen oxide) is known. A three-way catalyst is known in which Pt (platinum), Pd (palladium), and Rh (rhodium) are supported on γ-alumina, and the air-fuel ratio (A /
A high purification efficiency can be obtained when F) is near the stoichiometric air-fuel ratio of 14.7.

Of the exhaust gas of the engine, NOx must be prevented from being discharged into the atmosphere as much as possible. There are several methods for preventing the emission, but in the case of a mobile engine, it is realistic to purify by a catalyst provided in the exhaust pipe of the engine.

On the other hand, in the field of automobiles, a lean burn engine, a so-called lean burn engine, has been put into practical use in order to comply with fuel regulations concerning the engine. But,
Since the lean-burn engine has a high air-fuel ratio and the exhaust gas has a high oxygen concentration atmosphere, CO and HC can be oxidized and purified by the three-way catalyst as described above, but NOx can be reduced and purified. Can not.

Therefore, even in an atmosphere where the exhaust gas has a high oxygen concentration, NOx can be directly supplied or a reducing agent (for example, C
As a catalyst that can be catalytically decomposed into N ₂ and O _{2 in} the presence of (O, HC, etc.), a catalyst composed of a zeolite having a transition metal supported by, for example, ion exchange is considered promising. Further, various proposals have been made for this transition metal-supported zeolite catalyst in order to increase the NOx purification rate and improve the activity of the catalyst.

[0006] For example, the technique disclosed in Japanese Patent Laid-Open No. 3-202157 is an example, and according to the technique disclosed in the above-mentioned publication, Cu and one or more alkaline earth metals and a rare earth metal are contained in zeolite. By supporting one or more of these, the NOx purification capacity and durability of the catalyst are improved.

[0007]

However, the Cu ion exchange zeolite catalyst described in the above publication, which is said to be a catalyst capable of effectively removing NOx, generally purifies NOx in excess of 90% at the laboratory level. Despite showing the rate, when it is installed in an actual vehicle equipped with a lean burn engine, it is unavoidable that the NOx purification rate greatly decreases.

This is due to various condition differences between the model gas in the laboratory and the exhaust gas in the actual vehicle, but NOx is lower than 200 ° C. in an oxygen-rich atmosphere.
Despite the large tendency to exist as NO ₂ , the catalyst does not have a function as a catalyst for purifying NOx at a temperature of 200 ° C. or lower.

That is, in the Cu ion-exchanged zeolite catalyst as described above, the temperature at which the NOx purification function appears is 350 to 4
Since it is as high as 50 ° C, NOx under high oxygen concentration atmosphere
When the purification rate is evaluated, the total NOx purification rate becomes low. In particular, when the engine is operated under a low load, the catalyst inlet gas temperature of the exhaust gas becomes low. Therefore, it is highly necessary to expand the active temperature range of the catalyst to the low temperature side.

In view of the above, according to the present invention, the NOx purification activity is smoothly exhibited and the activation temperature is rich in heat resistance even in a high oxygen concentration atmosphere of exhaust gas and when the catalyst inlet gas temperature is low. The challenge is to obtain a catalyst with a wide range.

[0011]

Means for Solving the Problems and Actions The present invention addresses the above problems by using a noble metal having an excellent purification activity in a low temperature range in an active species-supporting base material such as zeolite, and the noble metal. By carrying it in combination with other metal species that interact with each other, the exhaust gas purification activity can be smoothly operated from the low temperature range to expand the activation temperature range and N
It improves the Ox purification rate and further improves the heat resistance.

<First Means> That is, the first means for solving the above problems (the invention according to claim 1) is to provide a metal-containing silicate with an active species-supporting base material.
In the supporting base material, Pt, Ir, and Rh are added as active species.
Is supported, and In, Ce, and Sb are added as active species.
One or more selected from the above are 5 by weight ratio to the above Rh.
It is characterized in that it is carried as follows .

More specifically, platinum group elements (Ru,
Among Rh, Pd, Os, Ir and Pt), Pt improves the low temperature activity of the catalyst as an active species. Pt, P
As shown in Table 1, the oxidation capacities of d, Rh, Ir, and Ru alone as the catalytic activity per the same weight are approximately Pt.
The order is ≧ Pd> Rh, Ir ≧ Ru (Rh and Ir are substantially the same), and the temperature characteristic relating to the oxidation ability is R.
About h and Ir, there is a tendency to appear on a slightly high temperature side as compared with Pt and Pd.

[0014]

[Table 1]

It is recognized that the effectiveness of Pt for the low temperature activity of the catalyst is related to the oxidizing ability.
Focusing on this point, the present inventor studied supporting other metals such as Ir as an active species on the base material in addition to the above Pt from the viewpoint of interaction between the Pt and other metals,
The specific behavior of each active species in the exhaust gas purification reaction and the synergistic effect produced by these active species were intensively studied.

As a result, P which forms the center of the active site
In the case of forming a catalyst by supporting Ir as an active species together with t on the base material, although the NOx purification ability of Ir itself is lower than that of Pt, the high oxygen concentration due to the interaction between Pt and Ir is caused. It was found that the NOx purification activity appears in the low temperature range in the atmosphere. Then, the Pt is used as the base material.
It was confirmed that the initial purification rate of the NOx purification catalyst (the NOx purification rate in the fresh state) can be further improved by supporting and adsorbing Ir and Ir in close proximity, and further the heat resistance of the catalyst can be improved. It was done.

-Regarding Interaction between Pt and Ir- Explaining the interaction between Pt and Ir described above, Pt
Is rich in oxidizing ability, and Ir is rich in NOx adsorbing power. Therefore,
The HC oxidized by Pt and given the activity attacks NOx captured by Ir to decompose the NOx into N ₂ and O ₂ . That is, it is considered that Pt and Ir have different roles in the NOx purification, and the NOx is efficiently decomposed.

Further, HC and CO in the exhaust gas act as a reducing agent for NOx by being oxidized on Pt, but HC and C that are not involved in the NOx purification reaction.
O is oxidized by the Ir because the Ir near the Pt has an oxidizing ability (Ir itself has a low NOx purification ability). Due to this oxidation, O ₂ generated in the NOx purification reaction and adsorbed on Pt is removed, and as a result, the activity of Pt is maintained, and the smooth activation of the activity in the low temperature range as described above. It is considered that high activity is obtained.

Further, as another interaction, the coexistence of Pt and Ir having an oxidation ability lower than Pt causes
By suppressing the strong oxidizing ability of Pt itself, in other words, by diluting it, H that is active during NOx purification is obtained.
It has a suitable oxidation ability that easily produces C combustion intermediates (HC partially oxidized). As a result, it is presumed that all of these reasons are combined to obtain smooth activation and high activity in the low temperature range as described above.

Further, Ir has a function of suppressing sintering (crystal growth) of Pt at a high temperature, and therefore the catalyst has a high NOx even after being used at a high temperature of about 800 ° C., for example. Maintain the purification rate.

According to experiments, the ratio (weight ratio) of Pt / Ir at which the maximum purification rate of 34% or more effective for NOx purification is obtained is Pt / Ir ≧ 1/3, which exceeds 50%. The same ratio at which such a purification rate is obtained is 6/1 ≧ Pt / Ir ≧
It was 1/1. Therefore, the Pt / Ir ratio may be set based on the above range .

As described above, Pt and Ir can improve the initial purification rate by the interaction between them, but Rh contributes to the improvement in heat resistance of the NOx purification catalyst.

That is, the sintering of Pt is Ir
However, when the catalyst is exposed to high heat, the selective reactivity with NOx is significantly lower than that for HC and CO, but the combustion mode of HC is also different. come. Therefore, in the catalyst supporting the Pt-Ir active species, the obtained HC combustion intermediate is different between the fresh state and the high-temperature exposed state, and NOx purification does not proceed efficiently. On the other hand, Rh prevents thermal deterioration of the catalyst and maintains its catalytic activity even at high temperatures.

Further, Rh has a function of suppressing or diluting the oxidizing ability of the active site with respect to the active site which is formed by closely supporting Pt and Ir and in which a catalytic reaction is carried out. It is considered that a large amount of HC combustion intermediate suitable for purification of NOx is produced from HC in the exhaust gas.

Further, in the catalyst formed by combining Pt, Ir and Rh as described above, NO and C in the exhaust gas are
The adsorption characteristics for O and HC are remarkably improved as compared with the catalyst formed by combining Pt and Rh, which is advantageous for purification of exhaust gas .

Further , in the present invention, as the active species,
Another feature is that one or more selected from In, Ce, and Sb are contained in a weight ratio of 5 or less with respect to Rh.

Generally, it is recognized that the NOx purification rate has a temperature dependence, and HC at an appropriate temperature in the process of reaching a high temperature range of 450 ° C. or higher, for example, around 250 ° C.
NOx when the combustion of HC starts and HC combustion intermediates are produced
Purification reaction is taking place. However, when the combustion of HC becomes vigorous as the temperature approaches the high temperature range, the HC reacts with O ₂ rather than reacts with NOx, so that the NOx purification rate tends to decrease in the high temperature range.

Therefore, N of the exhaust gas purifying catalyst in which the ternary active species of Pt, Ir and Rh are supported on the base material.
As a result of repeated experiments to further improve the Ox purification rate, I
By using one or more selected from the group IIB element In, the rare earth element Ce and the group VB element Sb in combination with the above ternary active species, it is possible to prevent the reduction of the NOx purification rate in the high temperature range of the exhaust gas. We have obtained the knowledge that.

In this case, the In, Ce or Sb suppresses HC in the exhaust gas from easily reacting with oxygen other than NOx in the high temperature range. That is, complete combustion of HC alone is suppressed, HC combustion intermediates are easily generated, and NOx decomposition proceeds efficiently. In addition, In, Ce or Sb also contributes to the improvement of heat resistance by preventing sintering of the noble metal active species.

As a result, as will be described later in detail in the examples, a significant decrease in the NOx purification rate in the high temperature range is avoided, and the NOx is increased by about 10% compared with the case where In, Ce, Sb, etc. are not added. The purification rate can be obtained. That is, although it is difficult for In, Ce and Sb to become active sites by themselves, Pt and Ir are diluted by diluting the oxidizing ability of Pt.
Since it contributes to the enhancement of the activity of, the active temperature range is expanded to the high temperature side.

It should be noted that In, Ce and Sb do not contribute to the improvement of the maximum NOx purification rate in the fresh state of the catalyst and a slight decrease may be rarely seen, but the range of such decrease is also small. It can be minimized by setting the optimum addition amounts of In, Ce, and Sb. Further, even when such a slight decrease in the maximum purification rate is observed, there is no problem with the excellent maximum purification rate obtained by the Pt-Ir active species, but rather the above I
The effect of preventing the reduction of the NOx purification rate in the high temperature range by adding n, Ce, and Sb is highly evaluated.

It is preferable that one or more selected from the above In, Ce, and Sb be contained in a weight ratio of 1.5 or less with respect to Rh (claim).
(Invention according to Item 2).

In this case, it is advantageous in increasing the maximum NOx purification rate in the fresh state of the catalyst and after being exposed to high heat .

As the metal-containing silicate, an aluminosilicate (zeolite) using Al as a metal forming a crystal skeleton is suitable, and if necessary, the above A
A metal-containing silicate in which a metal such as Ga, Ce, Mn, or Tb is used as a skeleton-forming material instead of 1 or together with Al can also be applied. As the metal-containing silicate, A-type, X-type, Y-type, mordenite, ZSM-5 and the like are suitable.

Further, as the metal-containing silicate, Na-type ZSM-5 whose cation species is Na or H-type ZSM-5 whose cation species is H ⁺ can be preferably used.

Further , about 20 as a binder is added to the catalyst.
Inorganic binder such as wt% hydrated alumina or silica sol
Is added to a suitable carrier such as cordierite honeycomb.
The washcoat makes it feel like a monolith
A media device can also be prepared.

In order to support each active species on the above base material,
Is the ion exchange method, impregnation method, coprecipitation method, evaporation to dryness method, sp
Although it is possible to use any method such as a ray dry method,
Ion exchange with a limited amount of supported base material per unit amount
Method, impregnation method, coprecipitation method, evaporation to dryness method, spray drier
Method a is advantageous in that it can support a large amount of active species.
is there. Also, using metal-containing silicate particles as the base material
If the particle size is
The average particle size is 0.5 to 1.5 μm when observed with a mirror).
Therefore, the particle size distribution is preferably 0.1 to 5 μm, more preferably
The average particle size is 0.5-1.0 μm, and the particle size distribution is
It is 0.1 to 2.5 μm. With such a particle size,
Exhaust when the engine is operated at λ = 1 (theoretical air-fuel ratio)
Gas (HC, CO, NOx) purification activation temperature on the low temperature side
This is because it can be shifted.

Preferred are the above-mentioned active species Pt, Ir and R.
The ratio of h is Pt with respect to the total amount of these three components.
45-92 wt%, Ir 50 wt% or less, Rh 15
It is to be below the weight%.

According to such a setting, the initial purification rate is high.
After the catalyst has been exposed to high heat (in the atmosphere
Even at 800 ° C x 8 hours) NO above the specified value
x Purification rate (20% or more) is obtained.

Preference is given to Pt, Ir and Rh.
The ratio of Pt to the total amount of these three components is 70
~ 90 wt%, Ir 6-25 wt%, Rh 8 wt%
It is to be as follows.

With this setting, the initial purification rate is high.
And NOx even after the catalyst is exposed to high heat.
This is advantageous in maintaining a high purification rate.

The above Pt, Ir and Rh are base materials carrying active species.
When Pt and Ir are supported on the substrate by evaporation to dryness
The proportions of Rh and Rh are based on the total amount of these three components, respectively.
80 to 90 wt% Pt, 7 to 15 wt% Ir, Rh
Is preferably 8% by weight or less.

With this setting, the initial purification rate is high.
The catalyst is exposed to high heat while being squeezed (eg above 55%)
After being exposed (800 ° C x 8 hours in air)
It is possible to obtain a high NOx purification rate (for example, 25% or more).
Wear.

The above Pt, Ir and Rh are base materials carrying active species.
P when it is carried by the spray dry method on
The ratio of t, Ir, and Rh is based on the total amount of these three components.
70 to 90% by weight of Pt and 6 to 25% by weight of Ir, respectively
%, Rh is preferably 8% by weight or less
Yes.

With such a setting, the initial purification rate is high.
The catalyst is exposed to high heat while being squeezed (eg above 55%)
After being exposed (800 ° C x 8 hours in air)
It is possible to obtain a high NOx purification rate (for example, 25% or more).
Wear.

< Second Means> A second means (an invention according to claim 3) for solving the above-mentioned problems is the first means ( claim 1 or 2).
The invention is characterized in that the exhaust gas purifying catalyst is supported on a catalyst carrier by a binder and that the binder contains Pt and Ir as active species.

In this means, since Pt and Ir are contained in the binder, it is possible to improve the dispersibility of active species while maintaining the total amount of active species in the exhaust gas purifying catalyst device at a predetermined value. As a result, the contact effect between the active species and the exhaust gas, that is, the SV
The dependence on (space velocity of exhaust gas) can be improved.

That is, the amount of the binder used when the exhaust gas purifying catalyst is carried on the catalyst carrier is often about 20% by weight of the base material of the catalyst, for example, the metal-containing silicate. Therefore, by dispersing and supporting a part of the preset amount of the active species in such an amount of the binder, the dispersion area for a fixed amount of the active species is expanded, and thus the above-mentioned activity is increased. It is easy to improve the dispersibility of the seed.

On the other hand, N in the exhaust gas purifying catalyst device
It is known that the Ox purification rate is also controlled by the magnitude of the SV value, and the contact property between exhaust gas and active species decreases as the SV increases, leading to a reduction in the NOx purification rate. That is, the NOx purification rate has SV dependency.

On the other hand, in this means, the dispersibility of the active species is improved as described above, so that the contact with the active species during the circulation of the exhaust gas is improved. As a result, the NOx purification rate of exhaust gas particularly in the high SV range is improved, and NOx is improved.
The SV dependence of the purification rate is improved.

However, if the distribution amount of the active species into the binder is too large, the binder has a lower porosity than that of the metal-containing silicate, so that the initial purification rate of the catalyst decreases. In addition, when the active species are supported on an oxide such as a binder, the activity developability is lower than when they are supported on a metal-containing silicate.

Therefore, the above-mentioned metal-containing silicate has an acid site, and in the metal-containing silicate, Pt-
In consideration of characteristics such as formation of active sites, the active species such as Ir have a set amount of 2 of the active species to be supported on the catalyst.
It may be distributed in the binder in the range of ˜20% by weight, the preferred distribution being 5-10% by weight.

A third means for solving the above problems (claim 4)
The invention described in 1) is a mother containing an active species containing a metal-containing silicate.
As a material, Pt and Ir as active species are added to the supported base material.
Exhaust which is supported or carries Pt, Ir and Rh
It is equipped with a catalyst for purifying air and gas, and the catalyst for purifying exhaust gas is
It is supported on the catalyst carrier by a binder and
Characterized in that the inder contains Pt and Ir
To do.

Therefore, according to the means, the low temperature activity of the catalyst is
Property and the NOx purification rate are improved, and Pt
And since Ir is contained in the binder,
Keep the total amount of active species in the catalytic converter for gas purification at a specified value.
However, it is possible to improve the dispersibility of the active species.
This results in a contact effect between the active species and the exhaust gas.
The result, that is, the dependence on SV (space velocity of exhaust gas)
The sex can be improved.

[0055]

According to the first means (the inventions of claims 1 and 2) , P is added to the metal-containing silicate as the active species supporting base material.
Since t, Ir and Rh are carried, the low temperature activity of the catalyst is improved and the NOx purification rate is improved , and
The heat resistance of the catalyst is improved. Furthermore, Pt as an active species
In addition to the -Ir-Rh component system, one or more selected from In, Ce, and Sb are supported on the base material, so that the active temperature range of the catalyst can be expanded to the high temperature side. The heat resistance can also be increased.

According to the second and third means (the inventions of claims 3 and 4 ), Pt in the active species having a preset loading amount is used.
And Ir are partly distributed in the binder constituting the exhaust gas purifying catalyst device, the dispersibility of the active species in the exhaust gas purifying catalyst device is improved, and thus SV
Even if the value is high, it becomes easy to obtain the initial NOx purification rate, and the practicality of the exhaust gas purification catalyst device is enhanced.

[0057]

EXAMPLES Reference examples and examples of the present invention will be described below.

Reference Example 1 In Reference Example 1 , Pt-containing Rh added to Pt and Ir.
This is an example in which Ir-Rh is carried as an active species on the carrying base material by the evaporation-drying method.

The supported weight ratio of Pt-Ir-Rh is 1
Pt-Ir-Rh-based catalyst having a ratio of 0/1 / 0.33 is a preferable Pt-I in the exhaust gas purification catalyst.
The r-Rh ratio was formulated.

-Preparation of catalyst-First, a catalyst having a Pt-Ir-Rh ratio of 10/1 / 0.33 was prepared as follows. Na-type ZSM-5 (Si which is a metal-containing silicate as a base material for supporting active species)
O ₂ / Al ₂ O ₃ = 30, the same below unless otherwise specified
15 g ) was weighed. As a Pt material, 0.5511 g of divalent platinum ammine crystal (Pt concentration 57.7%), Ir
0.04941 g of IrCl ₃ as a material and 0.2107 mL of a rhodium nitrate aqueous solution as a Rh material were weighed, and the divalent platinum ammine crystal and the rhodium nitrate aqueous solution were dissolved in water (ion-exchanged water), and IrCl _{3 was} added.
For, was dispersed in ethanol. These are the above N
In addition to 15 g of a-type ZSM-5, the mixture was stirred while being heated to about 60 ° C. After drying to dryness, it was dried in air at 150 ° C. for 2 hours to prepare a Pt-Ir-Rh-supported Na-type ZSM-5 catalyst.

The Pt-Ir-Rh-supported Na-type ZSM-5 catalyst was wash-coated on a cordierite catalyst carrier by a known method using hydrated alumina as a binder, and then dried at 150 ° C. for 2 hours. And 500
The catalyst of Reference Example A was prepared through calcination at 2 ° C. for 2 hours.

In this case, the active species in the catalyst of Reference Example A was carried in a total amount of Pt, Ir and Rh of 3 g in 1 liter of the catalyst. The ratio of Pt-Ir-Rh is 1
It is 0/1 / 0.33.

Next, regarding Pt, Ir, and Rh as active species, the Pt-Ir-Rh ratio is set to Pt of Reference Example A above.
The various Pt-Ir-Rh ratios as shown in Table 2 together with the -Ir-Rh ratio were prepared and the reference examples B, C, D, and
E, F, G, H, I, and J catalysts were prepared. Also, the catalysts of Comparative Examples 1 to 9 having various Pt-Ir-Rh ratios as shown in Table 2 were prepared.

Reference examples B, C, D, E, F, G, H,
The preparation method of each of the catalysts I and J was different only in the amounts of Pt material, Ir material and Rh material used as shown in Table 2 , and the other treatment operations were performed in the same manner as in Reference Example A above. . In addition, the preparation method of each catalyst of Comparative Examples 1 to 9 above,
The same treatment operation as in Reference Example A was performed except that the amounts of Pt material, Ir material and Rh material used were changed as shown in Table 2 and Ir material and / or Rh material were not used.

Then, in preparing each of the catalysts of these Reference Example and Comparative Example, Na-type ZSM-5 as a supporting base material was prepared.
Table 2 also shows the amounts of each of the Pt material (g), Ir material (g), and Rh material ( mL ) used for 15 g of the above.

[0066]

[Table 2]

The total supported amount of Pt, Ir and Rh as active species in each of the reference examples and the comparative examples shown in Table 2 above was 3 g per liter of the catalyst.

-Purification test-The above in Reference Example 1
Using the catalysts of Reference Examples A, B, C, D, E, F, G, H, I, and J and the catalysts of Comparative Examples 1 to 9 as samples, the maximum NOx purification rate in the fresh state and its expression were obtained. The maximum NOx purification rate after so-called heat resistance aged at 800 ° C. for 8 hours in the air and the expression temperature thereof were measured, and the results are shown in Table 3 . In addition, Table 3 also shows the deterioration rate, which is the difference in the purification rate between the NOx maximum purification rates measured above, expressed as a percentage of the NOx maximum purification rate in the fresh state. The above NOx maximum purification rate was measured by using a model gas in an oxygen-rich atmosphere corresponding to A / F = 22 and passing it through each of the above catalyst samples at SV = 55000 h ⁻¹ , while the catalyst inlet gas temperature was 450
This is based on the method of measuring the NOx purification rate while raising the temperature of the model gas at a rate of 30 ° C./minute until the temperature reaches 0 ° C.

-Test results-

[0070]

[Table 3]

According to the results shown in Table 3 , the above reference example
The catalysts A, B, C, D, E, F, G, H, I and J are
N excellent in initial activity compared with other catalysts of other comparative examples
There is a remarkable tendency that the practical NOx purification rate is maintained in the activity after endurance as well as the Ox purification rate.
As a result, it is clear that the NOx purification activity of the catalyst operates smoothly from the low temperature range and the active temperature range is expanded.

The above reference examples A, B, C, D, E, F,
The Na-type ZSM-5, which is the active species-supporting base material in each of the G, H, I, and J catalysts and each of the catalysts of Comparative Examples 1 to 9 , all had a Cavan ratio (= SiO ₂ / Al ₂ O ₃ ) = 30. The Cayvan ratio = 22.8 is used instead of this.
No change was observed in the maximum activity as shown in Table 3 above even when Na-type ZSM-5 was used.

Next, preferable conditions for the Pt-Ir-Rh component ratio (NOx maximum purification rate and deterioration rate in the fresh state and after heat resistance as shown in Table 3 above are values suitable for improving catalyst activity. in order to examine the result obtained condition), as shown in FIGS. 1, 5 and 6, reference example a,
The catalysts of B, C, D, E, F, G, H, I, and J and the catalysts of Comparative Examples 1 to 9 were plotted on the triangular coordinates of the Pt-Ir-Rh composition, and NOx in each fresh state. The highest purification rate, the highest NOx purification rate after heat resistance, and the deterioration rate were entered.

First, according to the NOx maximum purification rate distribution in the fresh state shown in FIG. 1 , the component ratio region in which the sample having the component ratio with the NOx maximum purification rate of less than 40% is distributed, and the NOx maximum purification rate are A ratio of 40% or more and less than 50%, in which a sample having a component ratio is distributed,
There is a component ratio region in which a sample having a component ratio having an Ox maximum purification rate of 50% or more and less than 55% is distributed, and a sample having a component ratio having the NOx maximum purification rate of 55% or more is distributed. There is a region of active ingredient ratio. In the research conducted by the present inventor, Pt, which is a catalyst in which Pt as an active species, Ir, and Rh are supported, has been remarkably recognized as having a function of improving the initial purification rate and the heat resistance.
Starting with the catalyst sample of Reference Example A having the component ratio of the active species such that the -Ir-Rh ratio is 10/1 / 0.33, the catalyst sample of Reference Example B having the component ratio of the active species approximate to this is It is contained in the high activity component ratio region.

Further, in the distribution of the component ratio region of the NOx maximum purification rate in the fresh state of the Pt-Ir-Rh component system shown in FIG. 1 , Pt / Ir is on the AA line where the ratio is 10/1. NOx purification rate, Pt / Ir is 5/1
The NOx purification rate on the B-B line and the NOx purification rate on the C-C line having a Pt / Ir ratio of 3/1 are R, respectively.
In order to study the state that changes depending on the amount of h, the state of change of the NOx purification rate on the line AA depending on the content of Rh is shown in FIG.
FIG. 3 shows the change state of the NOx purification rate on the BB line depending on the Rh content, and FIG. 4 shows the change state of the NOx purification rate on the CC line depending on the Rh content.

According to FIG . 2, FIG. 3 and FIG. 4 , in the component ratio region in which the above high activity is obtained, the NOx purification rate in the fresh state is very high depending on the content of Rh in the Pt-Ir-Rh component system. It is clear that it is sensitive. Therefore, it is understood that the excellent initial purification rate is obtained in the region where the Pt-Ir-Rh ratio is the thin component ratio region along the Pt-Ir side in FIG .

Further, according to the evaluation result of the NOx maximum purification rate distribution after heat resistance by aging shown in FIG. 5 , the component ratio region in which the sample of the component ratio having the NOx maximum purification rate of less than 10% is distributed, The component ratio region in which the sample having the component ratio of the NOx maximum purification rate of 10% or more and less than 20% is distributed, and the NOx maximum purification rate of 20% or more and 2
A component ratio region in which a sample having a component ratio of less than 5% is distributed,
There is a component ratio region in which a sample having a component ratio having the maximum NOx purification rate of 25% or more is distributed. Pt-I described above
The catalyst sample of Reference Example A having an active species component ratio of r / Rh ratio of 10/1 / 0.33 is NOx even after heat resistance.
The maximum NOx purification rate is higher than 25%, and the catalyst sample of Reference Example E having a similar active species component ratio has a maximum NOx purification rate after endurance.

Therefore, in order to maintain the maximum NOx purification rate after heat resistance of 20% or more, which is useful for NOx purification,
In the component ratio of the active species composed of the Pt-Ir-Rh component system, Pt is 45 to 92% by weight, Ir is 50% by weight or less, R
It is understood that it is preferable that h is in the range of 15% by weight or less. Further, a more preferable component ratio in the active species composed of the Pt-Ir-Rh component system such that the maximum purification rate of NOx after heat resistance is 25% or more is 80 to 90% by weight of Pt and 7 to 15% by weight of Ir. , Rh is in the range of 3 to 8% by weight.

Further, N by aging shown in FIG.
According to the deterioration rate distribution of the maximum Ox purification rate, the deterioration rate is 6
A component ratio region in which a sample having a component ratio of 0% or more and less than 70% is distributed and a component ratio region in which a sample having a component ratio of the deterioration rate of less than 60% is distributed are formed. There is. The maximum NOx purification rate after the heat resistance is NO
The component ratio of each catalyst sample that holds 20% or more, which is useful for x purification, is summarized in the above both component ratio regions.

Therefore, observing FIG . 5 showing the NOx maximum purification rate distribution after heat resistance and FIG. 6 showing the deterioration rate distribution, the heat resistance of the exhaust gas purification catalyst shows that Pt-I as an active species.
It can be seen that the amount of Rh in the r-Rh component system is more sensitive.

That is, Pt / I in FIGS. 5 and 6
Pt / Ir is 3/1 for each AA line with r of 10/1 ratio and each of BB line with Pt / Ir ratio of 5/1.
The NOx maximum purification rate and deterioration rate after heat resistance in each of the C-C lines having the ratio of P are P in FIG. 5 and FIG.
It shows that high heat resistance is obtained in a very thin layered component ratio region along the t-Ir side. As a result, the heat resistance of the catalyst supporting the active species of the Pt-Ir-Rh component system is very sensitively controlled by the content of Rh, and the addition of an appropriate amount of Rh improves the heat resistance of the catalyst. You can see that it has made a great contribution to.

-Comparison of heat resistance between Pt-Ir-Rh system and Pt-Rh system-Catalyst samples α and β shown in Table 4 were prepared by evaporation to dryness. As base material, SiO ₂ / Al ₂ O ₃ = 30 Na
Type ZSM-5 (MFI type) was used. Next, regarding the samples α and β, each NOx purification rate after freshening, after aging A, and after aging A → aging B was calculated as A /
SV = 90000h using model gas equivalent to F = 18
^It was measured under the condition of ^-1 . Aging A is heat treatment at 600 ° C. × 5 hours, and aging B is heat treatment at 800 ° C. × 8 hours. The results are shown in the table.

[0083]

[Table 4]

As a base material, H-type ZSM-5 (MFI
Type catalyst, SiO ₂ / Al ₂ O ₃ = 30) was used to prepare catalyst samples γ to ε with the active species composition shown in Table 5 , and H ₂ O
After aging treatment at 600 ° C. for 5 hours in the coexistence, using a model gas corresponding to A / F = 18, SV = 90
The NOx purification rate was measured under the condition of 000 h ^-1 . The results are shown in the table.

[0085]

[Table 5]

From Tables 4 and 5 above, Pt-Ir-Rh
It can be seen that the system catalyst is superior in heat resistance to the Pt-Rh system catalyst. For sample β in Table 4, the NOx purification rate after aging B was at a fresh or aging A
It is considered that the reason why the temperature is higher than that after that is that the activity expression temperature of the catalyst is shifted to a high temperature side by the aging B and that the catalyst is activated by the aging B.

-Pt type, Pt-Ir type, Pt-Ir-R
Regarding Noble Metal State in h-Based and Pt-Rh-Based Catalysts-Catalyst samples 1 to 4 having active species compositions shown in Table 6 were prepared by the evaporation-drying method. As the base material, SiO ₂ / Al ₂ O ₃
= 70 H-type ZSM-5 (MFI type) was used. Then, for each sample, the noble metal state of the sample that had been subjected to heat treatment for 2 hours in the atmosphere at a predetermined temperature condition was XRD.
(X-ray diffraction) and TEM (transmission electron microscope). The XRD results are shown in Figures 7-10 . T
EM is of after heat-treated at 500 ° C. × 2 hours and the results are shown in Figure 11-13.

[0088]

[Table 6]

First, FIG. 7 showing the XRD result of the Pt-based catalyst .
A peak due to Pt metal particles appears from around 250 ° C. From this, it is understood that the compound salt on the base material decomposes to produce Pt metal at around 250 ° C.

On the other hand, the XRD of the Pt-Rh type catalyst
Looking at FIG. 8 showing the results , P from around 400 to 500 ° C.
A peak due to t metal particles appears. Therefore, the Pt-based catalyst has a lower expression temperature of Pt metal particles. However, this expression temperature changes depending on the composition of the active species supported on the base material, and it is immediately understood that the expression temperature is low. It does not mean that the Pt metal particles become coarse (sintering). The change in the full width at half maximum of the peak with an increase in the treatment temperature was larger in the Pt-Rh-based catalyst, and coarsening of the Pt metal particles was observed. And Pt-R
Looking at the TEM photograph ( FIG. 11 ) of the h-based catalyst, it is possible to observe a cubic-shaped coarse crystal of Pt metal.
The coarsening of the t metal particles can be confirmed.

Next, referring to FIG. 9 showing the XRD result of the Pt-Ir type catalyst, the expression temperature of the Pt metal particles is around 250 ° C. as in the case of the Pt type catalyst, and the half width of the peak is also found. It does not seem to be much different from Pt-based catalysts, but P
A TEM photograph ( FIG. 12 ) of the t-Ir-based catalyst shows that no cubic shape or other coarse crystals are found, and that the metal particles of the catalyst are small, that is, coarsening does not occur much. From this, Pt for Ir
It can be said that it has a function of suppressing the grain growth of noble metal crystals containing as a main component.

Next, the XRD binding of the Pt-Ir-Rh type catalyst was conducted.
Results Looking at (10) and TEM image (FIG. 13), Pt
The results are similar to those of the -Ir catalyst. This Pt-I
In the r-Rh-based catalyst as well, about the same amount of Rh as the Pt-Rh-based catalyst was added, in spite of this, the fact that cubic-shaped crystal particles did not appear was
It means that the inhibitory effect of Ir on grain growth is not inhibited by Rh.

The above results show that the addition of Rh is harmful to the catalyst in terms of grain growth.
The addition of a small amount of h is still effective in preventing the thermal deterioration of the catalyst.

-Pt-Ir-Rh catalyst and Pt-Rh
Regarding Gas Adsorption / Desorption Characteristics of System Catalysts-The adsorption and desorption characteristics of NO, CO and C ₃ H ₆ gases were examined by the TPD device for the above-mentioned sample α and sample β. That is, each sample was heated to 600 ° C. in a He air flow to desorb the adsorbed material (cleaning the sample surface), and then NO, CO and C at room temperature.
Each gas of ₃ H ₆ was introduced into the sample at a concentration of 1% to be saturated and adsorbed, and then only He was introduced into the sample, and then the sample was heated from room temperature to 600 ° C. at a rate of 20 ° C./min. The temperature was raised and the temperature distribution of the desorbed gas was measured. As a result, the adsorbed amount of each gas in each of the samples α and β is shown in Table 7 .

[0095]

[Table 7]

According to Table 7 above, by adding Ir,
In the case of NO, the adsorption amount increases four times, and in the case of CO, it increases to 3.7.
It doubled, and in the case of C ₃ H ₆ , it increased 1.8 times. From this, in the case of the Pt-Ir-Rh-based catalyst, Pt-R
It can be seen that the active species are finer than the h-based catalyst, and that it is advantageous for purification of exhaust gas.

-Relationship between Noble Metal Content and Grain Growth- In the Pt-Ir-Rh catalyst, Pt: Ir: Rh =
Each catalyst having a composition ratio of 30: 6: 1 and a different total supported amount of noble metal was prepared by a spray drying method, and the firing conditions at that time were 500 ° C. × 2 hours, and the aging conditions were 800 ° C. × 8 hours ( In air), the grain growth rate was calculated by the following formula.

Grain growth rate = (particle size after aging−particle size after firing) ÷ particle size after firing × 100 The results are shown in Table 8 .

[0099]

[Table 8]

From Table 8 , it can be seen that the grain growth rate decreases as the total amount of precious metal supported increases.

Reference Example 2 This example is an example in which Pt, Ir and Rh are supported on the base material by the spray dry method.

-Spray Drying Device- FIG . 14 shows the overall structure of a co-current type spray drying device. In the figure, 1 is a slurry tank, 2 is a tube pump, 3 is a drying chamber, 4 is an electric heater, 5 is a primary cyclone, 6 is a secondary cyclone, and 7 is an exhaust fan.

The slurry tank 1 is a tank for storing a slurry consisting of an active species solution and a powder carrier, and the slurry is sent to the atomizer 8 at the top of the drying chamber 3 by the tube pump 2. A hot air chamber 9 is formed on the ceiling of the drying chamber 3, and heated air is supplied from the electric heater 4 to the hot air chamber 9. The blower holes for supplying the above-mentioned heated air, that is, hot air, from the hot air chamber 9 to the drying chamber 3 are opened around the atomizer 8. The electric heater 4 takes in outside air from its lower part through a filter 11 and supplies hot air from its upper part.

The drying chamber 3 is provided with an exhaust device 12 at the center of the inside thereof, and a first catalyst powder receiver 13 is provided below the exhaust device 12. The exhaust device 12 is the first exhaust pipe 14
The exhaust hole opened above is covered with an umbrella member. The first exhaust pipe 14 is connected to the upper side surface of the primary cyclone 5, and the top of the primary cyclone 5 and the side surface of the secondary cyclone 6 are connected to each other by a second exhaust pipe 16 having an air volume adjusting damper 15. . A second catalyst powder receiver 17 is provided at the lower end of the primary cyclone 5, and a third catalyst powder receiver 18 is provided at the lower end of the secondary cyclone 6. The exhaust fan 7 is provided in a third exhaust pipe 19 extending from the upper part of the secondary cyclone 6.

-Preparation of catalyst-Pt, Ir and Rh in a weight ratio of 30: 3: 1 (10:
The divalent platinum ammine crystal, iridium trichloride, and rhodium nitrate were weighed so that the ratio was 1: 0.33). The divalent platinum ammine crystal and rhodium nitrate are dissolved in water (ion-exchanged water), iridium trichloride is dispersed in ethanol, and then both are mixed, and further, H-type ZSM- with a Keiban ratio of 70 is added therein. 5 powders were added, and the mixture was stirred at room temperature for 2 hours.

The heating air from the electric heater 4 is fed to the drying chamber 3
To the atomizer 8 by the tube pump 2 from the tank 1 and sprayed into the drying chamber 3. Nozzle rotation speed of atomizer 8 is 8000rp
m.

The minute droplets of the slurry are rapidly dried by contact with hot air (for about 5 seconds), and a part of them is collected on the first catalyst powder receiver 13 along the wall surface of the drying chamber 3. The floating catalyst powder in the drying chamber 3 is guided to the primary cyclone 5 through the first exhaust pipe 14 together with hot air, and a part of the floating catalyst powder is received in the second catalyst powder receiver 1
Collected in 7. Further, the floating catalyst powder of the primary cyclone 5 is guided to the secondary cyclone 6 through the second exhaust pipe 16 and collected in the third catalyst powder receiver 18.

The obtained catalyst powder was heated to 200 ° C. × 14 in air.
After heat treatment for a long time (activation treatment), this is applied to a cordierite honeycomb carrier as a binder (hydrated alumina)
At the same time, wash coating was performed so that the total amount of Pt, Ir, and Rh was 4.5 g per 1 liter of the catalyst, followed by drying and calcination to obtain the catalyst of Reference Example a.

[0109] Moreover, the Pt, the weight ratio of Ir and Rh in place of the various as shown in Table 9, were prepared each catalyst of Example b~o and Comparative Example p in Reference Example a similar means .

-Regarding the ratio of Pt, Ir and Rh-A model gas corresponding to A / F = 22 was used for each of the catalysts a to p described above, and this gas was provided on the upstream side of each of the catalysts so as to have an SV of 55000 hr ^-1. Was passed to the downstream side, and the NOx maximum purification rate in a fresh state was measured. The results are also shown in Table 9 .

[0111]

[Table 9]

From Table 9 above, it is understood that when the spray dry method is adopted, the ratio of Pt, Ir and Rh may have an optimum range which is slightly different from that in the evaporation dry solidification method. Therefore, as shown in FIG. 15, the reference example a
.About.c, g to j, and m to o catalysts were plotted on triangular coordinates of the Pt-Ir-Rh composition, and the NOx maximum purification rate in each fresh state was entered.

According to FIG . 15 , it can be seen that a high NOx purification rate can be obtained in the shaded region. This area is
Pt is 70 to 70 with respect to the total amount of Pt, Ir and Rh.
This is a portion corresponding to a component ratio of 90% by weight, Ir of 6 to 25% by weight, and Rh of 0 to 8% by weight.

Next, for each of the above a to o catalysts, 800 ° C.
× 8 hours aging treatment, same as above
The maximum NOx purification rate was measured. The result is aboveTable 9To
It is shown together with the one at the time of rush. Also,Reference examplea
~ C, g ~ j, m ~ o for each catalystFIG.Also shown
Has been done.Reference exampleIn the case of, Rh is 0% by weightReference example
Relatively high NOx purification even after aging except i and o
Shows the rate. From this, in addition to Pt and Ir
Use of a small amount of Rh is effective in improving heat resistance
I understand.

Also, the Rh amount was set to 0.33% by weight for reference.
Examples a, g, and m are all subjected to activation treatment, but Reference Examples a ′ and g prepared under the same conditions as those of Reference Examples , except that the activation treatment was not performed. ´ 、
Also for m ′, the NOx maximum purification rate in the fresh state and the NOx maximum purification rate after the aging treatment were measured. The results are shown in Figure 17.

In the case of Reference Examples a, g, and m, the NOx purification rate of about 40% was obtained even after heat resistance (after aging), and also in Reference Examples a ′, g ′, and m ′, the data after heat resistance was obtained. Shows better results than the previous one.

From the above, the spray dry method can obtain a high NOx purification rate both in the fresh state and after the heat resistance, and further, the catalyst powder is subjected to the activation treatment to obtain further favorable results. I understand.
It is recognized that this is a result of the active species being uniformly supported on the metal-containing silicate by the spray drying method, and in the case of the activated treatment, the adsorbed water of the catalyst powder and the like is desorbed by it. Is considered to have been effective in improving NOx purification activity and heat resistance, and it is considered that desorption of active species during washcoating is also prevented.

-Regarding the total amount of Pt, Ir and Rh- In addition, the best result was shown among the above reference examples a to f.
For reference example c (Pt: Ir: Rh = 30: 6: 1),
Optimum amount of catalyst supported per liter of catalyst volume (total amount)
I checked. That is, the ratios of Pt, Ir and Rh were kept at the above values, and the total amount was changed to prepare catalysts, and the NOx maximum purification rate in the fresh state and after heat resistance was measured under the same conditions as above. In addition, for the reference example c ′ that had not been subjected to the activation treatment, the total amount was similarly changed and the NOx maximum purification rate was measured. These results are
It is shown in Figure 18.

According to FIG . 18 , good results are obtained when the total amount of Pt, Ir and Rh is 2 to 6 g / liter.

However, when the relationship between the ratio of Pt, Ir and Rh and the total amount of the NOx maximum purification rate in the fresh state was examined, the results shown in FIG. 19 were obtained. N
The measurement conditions for the maximum Ox purification rate are the same as in the previous case. According to the figure, the shaded area is the area where the NOx purification characteristics are good, but it is clear that the suitable range of the total amount differs depending on the ratio of Pt, Ir, and Rh. Pt: Ir: Rh =
In the range of 70-90: 6-25: 2-8, the total amount is 2-6.
It can be seen that good results are obtained at g / liter. Also,
When the NOx maximum purification rate after heat treatment at 800 ° C. for 8 hours was obtained under the same measurement conditions, the results shown in FIG. 20 were obtained.

Example I In this Example I , an example in which one or more selected from In, Ce and Sb is further added to the Pt-Ir-Rh component system as the active species, and is carried on the base material. Is.

In the Pt-Ir-Rh component system, the total supported amount of Pt, Ir and Rh is 3 g per liter of the catalyst, and the Pt-Ir-Rh ratio is 1.
Based on the case where the base material is supported so as to have a ratio of 0: 1: 0.33, the Pt-Ir-Rh component system serving as the reference has an I content.
n, Ce, and Sb were appropriately added, and the NOx purification rate by the addition was evaluated.

First, an H-type metal-containing silicate (Cayvan ratio = 70) was used as the active-species-supporting base material, and 15 g of the H-type metal-containing silicate was used for each of the same Pt, Ir, and Rh as in Reference Example 1 above. by carrying out the same processing operations with using the same amount of material, respectively, the reference
A catalyst of Example 1 was prepared in which an H-type metal-containing silicate was used as a base material instead of the supported base material Na-type ZSM-5 in the catalyst of Example A. The catalyst of Example 1 has the above-mentioned standard Pt / Ir / Rh ratio = 10/1 /.
0.33.

Further, by using In, Ce and Sb as the respective source materials, the Pt-Ir-Rh component system as the active species in the catalyst of Example 1 was added with In, Ce and Sb as shown in Table 10. Respectively added in Examples 2 and 3,
Each of 4 , 5 , 6 and 7 catalysts was prepared. The above
Since the catalyst of Example 1 is a standard, it is also shown in Table 10 .

In the catalysts of the respective examples shown in Table 10 , In, Ce and the Pt-Ir-Rh component system of Example 1 were added.
Sb has been added, and thus Examples 2, 3,
The total amount of the active species supported by each of the catalysts 4 , 5 , 6 , and 7 exceeds the weight of 3 g by the amount equivalent to the above-mentioned addition amount when converted into the supported amount in 1 liter of the catalyst.

[0126]

[Table 10]

Then, in the above-mentioned Examples 1, 2, 3, 4, 5,
For each of the catalysts 6 and 7, the maximum purification rate of NOx in the fresh state and the maximum purification rate of NOx after heat resistance aged in the air at 800 ° C. for 8 hours were measured, and the results are shown in Table 11 . Furthermore, Table 11 also shows the deterioration rates between the above two NOx maximum purification rates. The measurement of each NOx maximum purification rate was performed by the same method as in Reference Example 1 above.

[0128]

[Table 11]

In, Ce, S are added to the Pt-Ir-Rh component system.
When at least one selected from b is used together, Table 11
It is clear from the following.

(1) In, Ce and Sb are N after endurance
It has almost the same effect in terms of improving the Ox purification rate.

(2) Regarding In, Ce, and Sb, almost the same effect can be exhibited even if a plurality of kinds of In, Ce, and Sb are used together.

(3) The above In, Ce, and Sb have a limit of an appropriate addition amount, and addition of an excessive amount adversely affects the NOx purification rate.

I for the Pt-Ir-Rh component system
In order to clarify the appropriate addition amount of n, Ce, and Sb, I with respect to Rh in the standard Pt-Ir-Rh component system
The weight ratio of n was changed, and the maximum NOx purification rates under the fresh state and after heat resistance were measured under the respective ratios, and the results are shown in FIG .

According to the results shown in FIG . 21 , Pt-I
In the r-Rh component system, the range in which In contributes to preventing the reduction of the NOx maximum purification rate after heat resistance is within the above Pt-Ir-Rh
The weight ratio to Rh in the component system is 0 <In / Rh ≦ 2
Is the range.

In addition, In, Ce, and Sb have almost the same effect as the addition of a single kind, even if they are used in combination.
Considering that the maximum NOx purification rate in the fresh state may decrease due to the use of Ce and Sb, I
The weight ratio of n, Ce, Sb (alone or in combination) to the above Rh is preferably 0 to 5, and more preferably 0.5 to 1.5.

< Example II > In this Example II , by improving the dispersibility of the active species in the catalyst, the influence of the space velocity of the exhaust gas at the time of exhaust gas purification, in other words, the SV dependence of the exhaust gas purification The present invention relates to an improved exhaust gas purifying catalyst device.

The amount of divalent platinum ammine crystal added for supporting Pt was 0.1617 with respect to 5 g of Na-type ZSM-5.
In the present example, when the amount of IrCl ₃ added for supporting Ir is 0.0466 g, the divalent platinum ammine crystal of 0.14553 g is added to 5 g of Na-type ZSM-5. IrCl ₃ 0.04194
In addition to 0.01 g of divalent platinum ammine crystal and IrCl 2 with respect to hydrated alumina as a binder (1 g of hydrated alumina which is the amount of the binder used for 5 g of Na-type ZSM-5). 0.0 of ₃
0466g and P are added as the active species.
About 10% by weight of each of t and Ir is distributed in the binder.

As described above, the Pt—Ir component system as the active species is distributed in the Na-type ZSM-5 and the binder and carried on the exhaust gas purifying catalyst device for NOx purification.
V dependence was evaluated.

In the evaluation method, a model gas corresponding to A / F = 22 was circulated in the exhaust gas purifying catalyst device so that the catalyst inlet gas temperature was 250 ° C., and the space velocity of the model gas was SV value = 25,000 h. ^-1 , 55,000
h ^-1, 89000h ^-1, the NOx purification rate were measured for each SV is varied in four stages of 144000h ^-1. In addition, the active species carried on the exhaust gas purifying catalyst are all distributed over the Na-type ZSM without being distributed to the binder.
The NOx purification rate in four stages of SV was also measured for the comparative example of No. -5 carried out in the same manner as above. The results are shown in Fig. 22 .

According to FIG . 22 , the same exhaust gas S
When flowing through the catalyst device at V, the catalyst device of Example II has a NOx purification rate of 10 to 20 as compared with the catalyst device of the comparative example.
% Has improved. Further, the catalyst device of Example II can obtain the same level of NOx purification rate even when the SV is increased by about 50 to 60% as compared with the catalyst device of the comparative example.

Therefore, it can be seen that the catalytic converter of Example II has a significantly improved SV dependency during exhaust gas purification, as compared with the comparative example. Then, it can be seen that the effect of this improvement becomes more remarkable in the higher SV region.

The active species when a part of the active species is distributed and carried in the binder as in this example, is a Pt-Ir component system containing at least Pt and Ir. Is advantageous in the above effects. of course,
It goes without saying that the same effect can be obtained when part of the active species of the Pt-Ir-Rh component system is distributed and carried in the binder.

[Brief description of drawings]

FIG. 1 is a triangular coordinate diagram showing the relationship between the Pt-Ir-Rh component ratio in the dry evaporation method and the NOx maximum purification rate in the fresh state.

Figure 2 is a graph showing the NOx maximum purification rate distribution in the A-A line in FIG. 1

Figure 3 is a graph showing the NOx maximum purification rate distribution in the line B-B of FIG. 1

FIG. 4 is a graph showing the NOx maximum purification rate distribution along the line C-C in FIG . 1 .

FIG. 5 is a triangular coordinate diagram showing the relationship between the component ratio of Pt-Ir-Rh in the evaporation dryness method and the NOx maximum purification rate after heat resistance.

FIG. 6 shows the Pt-Ir-Rh component ratio and N in the evaporation dryness method.
Triangle coordinate diagram showing the relationship between the maximum Ox purification rate and the deterioration rate

FIG. 7: XRD (X-ray diffraction) characteristic diagram of Pt-based catalyst

FIG. 8 is an XRD characteristic diagram of Pt-Rh catalyst.

FIG. 9 is an XRD characteristic diagram of a Pt-Ir catalyst.

FIG. 10 is an XRD characteristic diagram of a Pt-Ir-Rh-based catalyst.

FIG. 11 is a TEM (transmission electron microscope) photograph showing the particle structure of the active species of the Pt-Rh-based catalyst (magnification increases stepwise from (a) to (d)).

FIG. 12: TE showing the metal particle structure of a Pt-Ir-based catalyst
M photo (magnification increases step by step from (a) to (d))

FIG. 13 is a TEM photograph showing the metal particle structure of a Pt-Ir-Rh-based catalyst (magnification increases stepwise from (a) to (d)).

FIG. 14 is a configuration diagram of a spray drying device.

FIG. 15 is a triangular coordinate diagram showing the relationship between the Pt-Ir-Rh component ratio in the spray dry method and the NOx maximum purification rate in the fresh state.

FIG. 16 is a triangular coordinate diagram showing the relationship between the component ratio of Pt—Ir—Rh in the spray dry method and the NOx maximum purification rate after heat treatment.

FIG. 17 is an Ir amount and N in a Pt-Ir-Rh component system.
The graph figure which shows the relationship with Ox purification rate

FIG. 18 is a graph showing the relationship between the total amount of active species carried and the NOx purification rate.

FIG. 19 is a graph showing the relationship between the total amount of active species supported and the Ir amount in the Pt-Ir-Rh component system regarding the NOx purification rate in the fresh state.

FIG. 20 is a graph showing the relationship between the total amount of active species carried and the Ir amount in the Pt-Ir-Rh component system regarding the NOx purification rate after heat treatment.

FIG. 21 shows In in a Pt-Ir-Rh-In component system.
Graph showing the relationship between the / Rh ratio and the NOx maximum purification rate

22] SV value and NOx for Example II and Comparative Example
Graph showing the relationship with the purification rate

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Iwakuni No. 3 Shinchi Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Makoto Kyogoku No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Incorporated (72) Inventor Kazuya Komatsu 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Ltd. (56) Reference JP-A-53-7591 (JP, A) JP-A-62-106843 ( JP, A 51-105993 (JP, A) JP 63-185453 (JP, A) JP 3-98644 (JP, A) JP 6-99068 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) B01J 21/00-38/74 B01D 53/00-53/96

Claims (4)

(57) [Claims] 1. A metal-containing silicate as a base material carrying active species.
Then, Pt, Ir and Rh as active species are added to the supporting base material.
Of In, Ce, and Sb supported as active species,
One or more selected from Rh is 5 or more by weight ratio to the above Rh.
An exhaust gas purifying catalyst, which is carried so as to be below . 2. A metal-containing silicate as a base material carrying active species.
Then, Pt, Ir and Rh as active species are added to the supporting base material.
Of In, Ce, and Sb supported as active species,
At least one selected from Rh is 1.
A catalyst for purifying exhaust gas, wherein the catalyst is supported so as to be 5 or less . 3. An exhaust gas, wherein the exhaust gas purifying catalyst according to claim 1 or 2 is supported on a catalyst carrier by a binder, and Pt and Ir are contained in the binder. Purification catalyst device. 4. A metal-containing silicate as a base material carrying active species.
Then, Pt and Ir are supported on the supporting base material as active species.
Or an exhaust gas carrying Pt, Ir and Rh
A catalyst for purifying exhaust gas, and the catalyst for purifying exhaust gas is a binder.
Supported on a catalyst carrier by the
Characterized in that it contains Pt and Ir
Exhaust gas purification catalyst device.