JP3506316B2 - Exhaust gas purification catalyst and exhaust gas purification 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 for purifying exhaust gas when starting an engine of an internal combustion engine. The present invention also relates to hydrocarbons (hereinafter referred to as “HC”), carbon monoxide (hereinafter referred to as “CO”), and nitrogen in exhaust gas discharged from an internal combustion engine of an automobile or the like at a low temperature immediately after the engine is started. Among oxides (hereinafter referred to as “NOx”), it particularly relates to an exhaust gas purifying catalyst capable of efficiently purifying HC and an exhaust gas purifying apparatus including the catalyst.

[0002]

2. Description of the Related Art In recent years, an HC adsorption catalyst using zeolite has been developed for the purpose of purifying a large amount of HC discharged in a low temperature range at the time of engine start of an internal combustion engine. The HC adsorbing catalyst temporarily adsorbs and retains a large amount of HC discharged in a low temperature range at the time of engine startup in which the three-way catalyst is not activated, and then the three-way catalyst is activated due to a rise in exhaust gas temperature. At times, HC is gradually desorbed and purified.

By the way, in the HC adsorption catalyst using zeolite, there is a correlation between the distribution of HC species in the exhaust gas and the pore size of the zeolite, so it is necessary to set the zeolite having the optimum pore size. Conventionally, MFI type (ZS
M5) was mainly blended with zeolites having other pore sizes (such as USY) to adjust the pore distribution, but after endurance, the pore size distortion and adsorption / desorption characteristics differ depending on the zeolite species. Therefore, there is a problem that the adsorption of the exhaust gas HC species is insufficient.

On the other hand, as a catalyst for a ternary noble metal, conventionally, a specification in which noble metal species such as Rh, Pt, and Pd coexist in the same layer, and a specification in which the Rh layer and the Pd layer are separately coated have been proposed. . For example, as shown in JP-A-2-56247, Pt, P is formed on the first layer containing zeolite as a main component.
An exhaust gas purifying catalyst provided with a second layer containing a noble metal such as d or Rh as a main component has been proposed.

Further, for the purpose of reducing HC in the exhaust gas discharged at a low temperature immediately after the engine is started, HC is temporarily stored using an adsorbent and is desorbed after the three-way catalyst is activated. A method of purifying with a three-way catalyst is being studied.

Examples of the invention using such an HC adsorbent (hydrocarbon adsorbent) include, for example, JP-A-6-74019, JP-A-7-144119, and JP-A-6-142.
457, JP-A-5-59942, JP-A-7
There is one disclosed in Japanese Patent Laid-Open No. 102957.

In Japanese Patent Laid-Open No. 6-74019, a bypass passage is provided in the exhaust passage so that HC discharged during cold immediately after the engine is started is once adsorbed by an HC adsorbent arranged in the bypass passage, and thereafter the passage is formed. It is proposed that after switching between the two, the downstream three-way catalyst is activated, part of the exhaust gas is passed to the HC adsorption catalyst, and the desorbed HC is gradually purified by the latter three-way catalyst.

Further, Japanese Patent Application Laid-Open No. 7-144119 discloses that
When cold, heat is absorbed by the three-way catalyst in the front stage to improve the adsorption efficiency of the HC adsorbent in the middle stage, and after activation of the three-way catalyst in the front stage,
We propose a system that facilitates the transfer of reaction heat to the rear-stage three-way catalyst through the tandem-arranged middle-stage HC adsorbent and promotes purification by the rear-stage three-way catalyst. In addition, JP-A-6-
Japanese Patent No. 142457 proposes a cold HC adsorption / removal system that promotes purification with a three-way catalyst by preheating exhaust gas containing desorbed HC in a heat exchanger when HC adsorbed in a low temperature range is desorbed. There is.

On the other hand, Japanese Laid-Open Patent Publication No. 5-59942 proposes a system for slowing the temperature rise of the HC adsorbent and improving the adsorption efficiency of cold HC by switching the catalyst arrangement and the flow path of the exhaust gas by the valve. ing. JP-A-7-1
JP-A-02957 discloses that in order to improve the purification performance of the latter-stage oxidation / three-way catalyst, air is supplied between the former-stage three-way catalyst and the middle-stage HC adsorbent to activate the latter-stage oxidation / three-way catalyst. We propose a system to promote.

[0010]

An exhaust gas purifying catalyst having a ternary layer on an HC adsorbent layer such as a zeolite layer as described above is adsorbed by zeolite in a low temperature range of exhaust gas immediately after the start of an internal combustion engine. When the generated HC is desorbed as the exhaust gas temperature rises, the exhaust gas becomes rich, so the three-way catalyst effective for purification in the stoichiometric air-fuel ratio region does not work sufficiently, and HC, CO, NOx There is a problem that it will not be possible to achieve a well-balanced purification. Further, conventionally, although the ratio of the coat layers of the zeolite layer and the ternary layer was not particularly shown, if the structure of the zeolite layer and the ternary layer is not optimum in the HC adsorption catalyst, HC adsorption / desorption / There is a problem that the purification cycle is not performed effectively.

On the other hand, in the system using the HC adsorbent described in the above-mentioned publication mentioned in the section [Prior Art], the durability of the HC adsorbent is insufficient, so that H
The C adsorption efficiency is lowered, and moreover, HC is desorbed before the subsequent three-way catalyst is activated, and the emission is deteriorated. Therefore, in order to improve the adsorption efficiency of HC adsorbent and delay desorption, a heat exchanger for hot gas bypass method and three-way catalyst warm-up is used, but the system configuration becomes complicated and sufficient. No effect is obtained, and the cost is significantly increased. Therefore, an HC adsorbent having high durability and high adsorption efficiency is desired.

Particularly, the three-way catalyst for purifying HC desorbed from the HC adsorbent uses a large amount of noble metal or maintains early purification in order to maintain high purification performance from the initial stage to the end of durability. Introducing air. Therefore, a catalyst that can obtain high performance even with a small amount of noble metal used is desired, but when the amount of noble metal is reduced, the durability is insufficient, and after endurance, the catalyst activity and purification performance in the low temperature range There was a problem that was worse.

[0013]

SUMMARY OF THE INVENTION The present invention is an integrated structure type exhaust gas purifying catalyst using a monolith carrier, in contrast to such a conventional exhaust gas purifying catalyst, which is provided on a predetermined monolith carrier. Is provided with an HC adsorbent layer containing an HC adsorbent containing zeolite as a main component, a catalyst component layer containing a predetermined noble metal as a catalyst component is further provided on the HC adsorbent layer, and further on the catalyst component layer. In order to solve the above problems, an exhaust gas purifying catalyst is provided in which a predetermined upper catalyst component layer is provided, and the weight ratio of the HC adsorbent layer to the catalyst component layer is within a predetermined range. Has an aim.

That is, the exhaust gas purifying catalyst of the present invention is G
SA (Geometrical Surface Ar)
ea: geometric surface area) 10 cm ² / cm ^{3 to} 35 c
A catalyst for purifying exhaust gas, comprising an HC adsorbent layer containing a hydrocarbon adsorbent, a catalyst component layer containing a catalyst component, and an upper catalyst component layer coated in this order on a monolithic carrier of m ² / cm ^3. , The hydrocarbon adsorbent of the HC adsorbent layer is mainly composed of zeolite, and the catalyst component layer is palladium (P
d), at least one noble metal selected from the group consisting of platinum (Pt) and rhodium (Rh) is used as a catalyst component, and at least Pd among them is contained, and the upper catalyst component layer has zirconium oxide and activated alumina. This zirconium oxide contains Pt, Rh, Ce, N
1 selected from the group consisting of d and La in terms of metal
To 30 mol% and Zr of 70 to 98 mol%, the above HC
The weight ratio of the adsorbent layer to the catalyst component layer is 9: 1 to 1: 4.
Is the total thickness of the HC adsorbent layer and the catalyst component layer in the flat portion in the cell of the monolith carrier,
The coat layer has a thickness of 30 μm to 400 μm.

In the exhaust gas purifying apparatus of the present invention, Pd, Pd and Pd are provided in front of the exhaust gas purifying catalyst as described above.
t or Pd-supporting powder containing Pd and Rh and having a Pd-supporting concentration of 4 to 20% by weight, and containing Pd per 1 L of catalyst.
Carrying amount is 100 g / cf (3.5 g / L) to 1000 g
/ Cf (35.4 g / L) of the Pd-containing catalyst is arranged, and the amount of hydrocarbons adsorbed by the exhaust gas purifying catalyst is
70% of the saturated hydrocarbon adsorption amount of this exhaust gas purification catalyst
It is characterized by the following settings.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION First, embodiments of the present invention will be described. The exhaust gas purifying catalyst coat layer structure of the present invention comprises a HC adsorbent layer containing a zeolite effective for adsorbing HC, preferably β-zeolite as a main component of the HC adsorbent, on a specific monolithic carrier. A catalyst component layer containing at least one noble metal selected from the group consisting of Pd, Pt, and Rh, in particular Pd as a catalyst component, is provided on the HC adsorbent layer. It is a type of the described "HC adsorption catalyst". Here, the amount of β-zeolite used is preferably 10 g to 400 g per 1 L of the catalyst. If the amount of β-zeolite used is less than 10 g, H
The C adsorption performance is not sufficiently expressed, and conversely, even if it exceeds 400 g, the HC adsorption performance and the desorption retarding effect are saturated, which is not economically effective. By providing an HC adsorbent layer on the monolith carrier and a catalyst component layer (three-way layer or three-way catalyst layer) having a so-called three-way purification capability on the HC adsorbent layer, the HC desorbed from the zeolite of the HC adsorbent layer can be reduced. Post-processing efficiency can be improved. As described above, since the catalyst is constituted as an integrated type catalyst having a multilayer structure, the heat loss is smaller than that of the 2-brick type catalyst, the activation of the catalyst component layer is quicker, and the HC desorbed from the HC adsorbent acts as the catalyst component layer. Since sufficient contact can be made, desorbed HC can be efficiently purified.

The weight ratio of the HC adsorbent layer to the catalyst component layer is 9: 1 to 1: 4. When the proportion of the catalyst component layer is higher than the specified value, gas diffusion to the HC adsorbent layer (zeolite layer) arranged in the lower layer becomes poor, and sufficient adsorption performance cannot be obtained. If the proportion of the catalyst component layer is less than the specified value, the oxidizing performance of desorbed HC and the exhaust gas purification performance cannot be sufficiently obtained. Furthermore, the monolithic carrier (specific monolithic carrier) provided with the HC adsorbent layer and the catalyst component layer has a GSA of 10 cm ² / cm ^{3 to} 3.
It is 5 cm ² / cm ³ . When GSA is larger than the specified value, desorption of HC in the HC adsorbent layer is accelerated, and desorbed HC discharged without being purified increases. On the other hand, if it is less than the specified value, the diffusion of HC into the HC adsorbent layer is slow and the adsorption performance is not sufficiently expressed, the contact between the exhaust gas and the catalyst component layer is deteriorated, and the exhaust gas component purification performance is sufficient. Will not be obtained.

Further, in the exhaust gas purifying catalyst of the present invention, in order to improve the purifying efficiency when the HC adsorbed by the HC adsorbent is desorbed, a catalyst component containing Pd is provided on the upper portion of the HC adsorbent layer. A layer (Pd-containing catalyst component layer) is arranged,
The Pd-containing catalyst component layer may contain cerium oxide containing 1 to 40 mol% and 60 to 98 mol% of cerium in terms of metal of one selected from the group consisting of Zr, Nd and La.

Particularly, in order to improve the purification performance and durability of Pd, Zr, Nd and La are contained in the Pd-containing catalyst component layer.
By containing a cerium oxide containing 1 to 40 mol% and 60 to 98 mol% of cerium in terms of metal of one selected from the group consisting of cerium oxide having a high oxygen storage capacity, a rich atmosphere and a vicinity of stoichiometry can be obtained. Since it becomes easy to release lattice oxygen and adsorbed oxygen, the oxidation state of Pd can be made suitable for purification of exhaust gas, and a decrease in catalytic ability of Pd can be suppressed. The amount of the cerium oxide used is 5 to 100 g per 1 L of the catalyst. If it is less than 5 g, sufficient dispersibility of noble metal cannot be obtained, and if it is used more than 100 g, the improving effect is saturated and it is not effective.

Further, in the exhaust gas purifying catalyst of the present invention,
In order to improve the poisoning resistance and purification performance of Pd, one kind selected from the group consisting of Pt, Rh, Ce, Nd, and La is added to the upper part of the Pd-containing catalyst component layer in an amount of 1 to 30 mol% in terms of metal, and Zr. Zirconium oxide containing 70 to 98 mol% of
Catalyst component layer containing activated alumina (upper catalyst component layer)
To place. As the base material on which Pt or Rh is supported, zirconium oxide is suitable in order to improve the durability of Pt and Rh. In particular, cerium-containing zirconium oxide having a high oxygen storage capacity easily releases lattice oxygen and adsorbed oxygen in a rich atmosphere and in the vicinity of stoichiometry.
The oxidation state of t and Rh can be made suitable for purification of exhaust gas, and the reduction of the catalytic ability of Pt and Rh can be suppressed.

The Ce content of the zirconium oxide is 0.01 mol% to 30 mol%. Ce content is 0.
If it is less than 01 mol% unchanged in the case of only ZrO _2, the improving effect by the oxygen storage capacity of ZrO ₂ of Ce of the elements described above does not appear. On the other hand, when the Ce content exceeds 30 mol%, this effect is saturated or, conversely, the BET specific surface area and thermal stability decrease. The amount of zirconium oxide used is 1
It is 5 to 100 g per L. If it is less than 5 g, sufficient dispersibility of noble metal cannot be obtained, and if it is used more than 100 g, the improving effect is saturated and it is not effective.

In order to improve the low temperature activity of Pd, K
And Ba can be contained. The content of such an element is 1 to 40 g in 1 L of the catalyst. If it is less than 1 g, the adsorption poisoning of HCs against noble metals cannot be alleviated and the sintering of Pd cannot be suppressed, and conversely, if it exceeds 40 g, a significant amount increasing effect cannot be obtained and the performance is deteriorated.

In another preferred embodiment of the catalyst of the present invention, β-zeolite is contained on the specific monolith carrier in order to effectively exhibit the HC adsorption / desorption ability characteristics and the purification performance of desorbed HC. An HC adsorbent layer containing at least one or more zeolite as a main component is provided, and a catalyst component layer containing Pd as a catalyst component (Pd-containing catalyst component layer) is provided on the HC adsorbent layer. A catalyst component layer containing Rh as a catalyst component (Rh-containing upper catalyst component layer) is provided on the component layer.

As described above, by providing the HC adsorbent layer on the monolith carrier and the catalyst component layer on the HC adsorbent layer, the efficiency of the post-treatment of HC desorbed from the zeolite of the HC adsorbent layer can be improved. Furthermore, by disposing Pd, which has excellent HC oxidation activity, as a catalyst component on the HC adsorbent layer, and providing the Rh-containing upper catalyst component layer thereon, the inside of the catalyst component layer having the three-way purification ability is removed. Even if it becomes a rich atmosphere due to separation HC,
It is possible to purify HC, CO, and NOx in good balance. Furthermore, by arranging Pd inside which is easily affected by poisoning due to phosphorus (P), lead (Pb), etc., the effect of poisoning can be reduced. Also, the HC adsorbent layer arranged in the lower layer has a slower warm-up time than the catalyst component layer in the upper layer, so that the adsorbed HC can be retained for as long as possible, and on the contrary, the catalyst component layer warms up quickly and is activated. Good balance of adsorption, desorption and purification of HC.

Furthermore, in the preferred embodiment of the catalyst of the present invention described above, the HC adsorbent layer, the catalyst component layer (Pd-containing catalyst component layer) and the upper catalyst component layer (Rh-containing upper catalyst component layer).
Total coat weight ratio of (if upper catalyst component layer is not present,
The total coating weight ratio of the HC adsorbent layer and the catalyst component layer) is 5: 1.
~ 1: 2. When the ratio of the catalyst component layer is higher than the specified value, gas diffusion to the HC adsorbent layer disposed in the lower layer is deteriorated and sufficient adsorption performance cannot be obtained. If the ratio of the catalyst component layer (and the Rh-containing upper catalyst component layer) is less than the specified value, the oxidizing performance of desorbed HC and the exhaust gas purification performance cannot be sufficiently obtained.

In the exhaust gas purifying catalyst of the present invention,
HC adsorbent layer, catalyst component layer having three-way purification ability, and R
GSA of the h-containing upper catalyst component layer is 10 cm ² / cm ³ to
It is provided on a monolithic carrier of 35 cm ² / cm ³ . When GSA becomes larger than the specified value, HC in the HC adsorbent layer
Desorption becomes faster, and desorption HC that is discharged without being purified increases. On the other hand, when the value is smaller than the specified value, the contact between the exhaust gas and the catalyst component layer is deteriorated, and the exhaust gas component purification performance cannot be sufficiently obtained.

Further, in the exhaust gas purifying catalyst according to the above preferred embodiment, at least one selected from the group consisting of alkali metals and alkaline earth metals is used in the HC adsorbent layer and / or the catalyst component layer, or the HC adsorbing layer. At least one of the material layer, the catalyst component layer and the Rh-containing upper catalyst component layer is impregnated and supported. Alkali metals and alkaline earth metals that can be used include lithium (Li), sodium (Na),
Potassium (K), Cesium (Cs), Magnesium (M
g), at least one element selected from the group consisting of calcium (Ca), strontium (Sr) and barium (Ba).

The alkali metal and alkaline earth metal compounds that can be used are water-soluble compounds such as oxides, acetates and hydroxides. This makes it possible to support the alkali metal and / or alkaline earth metal, which is a basic element, in the vicinity of the noble metal with good dispersibility.

That is, an aqueous solution of a powder of an alkali metal and / or alkaline earth metal compound is impregnated into the above monolith carrier carrying a washcoat component and dried,
Then in air and / or under air flow 200-600 ° C
Is fired at a relatively low temperature. If the baking temperature is less than 200 ° C., the alkali metal and alkaline earth metal compounds cannot be sufficiently converted into an oxide form.
Even if the temperature exceeds 0 ° C., the effect of the firing temperature is saturated, and no significant difference can be obtained.

Further, in the exhaust gas purifying catalyst of the present invention, the zeolite component of the HC adsorbent layer has two kinds of pore sizes, large and small, in order to effectively adsorb a large amount of HC discharged at the time of engine start. Si / 2Al ratio is 10
It is desirable to use 500 H-type β-zeolite as a main component. The β-zeolite has higher heat resistance than other zeolites and excellent structural stability. Also, while other zeolites have a narrow HC molecular size range effective for adsorption, β-
Since zeolite has two kinds of pore sizes, large and small, the pores are combined to complicate the pore structure, and various kinds of HC can be effectively adsorbed.

Further, the Si / 2Al ratio of the β-zeolite is preferably in the range of 10 to 500. Si / 2
When the Al ratio is less than 10, the adsorption of water molecules coexisting in the exhaust gas is largely inhibited and HC cannot be effectively adsorbed. Conversely, if the Si / 2Al ratio exceeds 500, HC
Adsorption amount of is reduced.

Further, in the exhaust gas purifying catalyst of the present invention, regarding the zeolite species of the HC adsorbent layer, MFI type, Y type, and
At least one of USY type, mordenite, ferrierite, A type zeolite, X type zeolite, AlPO4 and SAPO is used. These zeolites change the pore distribution of the zeolite species according to the composition ratio of the HC species in the exhaust gas and improve the adsorption capacity. By mixing these zeolite species with β-zeolite, the range of HC species that can be adsorbed is further widened. Conversely, to the HC species to be adsorbed, various zeolite species capable of adsorbing the HC species can be appropriately combined. It should be noted that at least one selected from the group consisting of mordenite, Y-type, USY-type, and MFI-type zeolite can be contained in an amount of 5 wt% to 45 wt% of the total amount of HC adsorbent. If it is less than 5% by weight, a sufficient pore size distribution effect cannot be obtained. On the contrary, if it is used in excess of 45% by weight, this effect saturates or the performance improving effect of β-zeolite is lowered.

In the exhaust gas purifying catalyst of the present invention, the zeolite of the HC adsorbent layer contains Pd (palladium), Mg (magnesium), Ca (calcium), S.
r (strontium), Ba (barium), Ag
(Silver), Y (yttrium), La (lanthanum), Ce
(Cerium), Nd (neodymium), P (phosphorus), B
It is preferable to contain at least one selected from (boron) and Zr (zirconium). Zeolite has sufficient adsorption capacity even in H type, but Pd, Mg,
Ca, Sr, Ba, Ag, Y, La, Ce, Nd, P,
By loading B, Zr and the like using a usual method such as an ion exchange method, an impregnation method, and a dipping method, it is possible to further improve the adsorption characteristics, the desorption suppressing ability and the durability of the zeolite.

Further, HC containing β-zeolite as a main component
Selected from the group consisting of Pt, Pd, P, B, Mg and Ca in order to improve the structural stability (heat resistance) of the adsorbent at high temperatures, the ability to adsorb cold HC and the ability to suppress HC desorption when the temperature rises. Can be included in the The content of such an element is 0.1% by weight to 10% with respect to the HC adsorbent.
% By weight. If it is less than 0.1% by weight, a sufficient improvement effect cannot be obtained. On the contrary, if it is used in excess of 10% by weight, the pores of the zeolite are blocked and the HC adsorbing ability is lowered.

Further, it is also preferable to further coexist Pt in at least one of the catalyst component layer and the Rh-containing upper catalyst component layer in the exhaust gas purifying catalyst of the present invention. Because Pt coexists with Pd or Rh,
This is because the poisoning resistance can be further improved.

Further, in the exhaust gas purifying catalyst of the present invention, C is contained in the HC adsorbent layer containing zeolite as a main component.
It is preferable to contain Rh and a zirconium oxide containing 1 to 40 mol% of at least one selected from the group consisting of e, Nd and La in terms of metal. Although the catalyst component layer and the Rh-containing upper catalyst component layer also have sufficient purification performance of desorbed HC, the HC adsorbent layer containing zeolite as a main component is composed of Rh, Ce, Nd, and La. The inclusion of zirconium oxide containing at least one selected from 1 to 40 mol% in terms of metal causes elimination of HC.
The purification performance of can be further improved.

Further, it is preferable that the catalyst component layer (noble metal layer) of the exhaust gas purifying catalyst of the present invention further contains alumina. In particular, in order to enhance the structural stability of alumina after high-temperature durability and suppress the phase transition to α-alumina and the decrease in BET specific surface area, the above-mentioned alumina contains Ce and Z.
At least one selected from the group consisting of r and La is contained in an amount of 1 to 10 mol% in terms of metal. If it is less than 1 mol%, a sufficient addition effect cannot be obtained, and if it exceeds 10 mol%, the addition effect is saturated. The amount of such alumina used is 10 to 200 g per 1 L of the catalyst. If it is less than 10 g, sufficient dispersibility of the noble metal cannot be obtained, and even if it is used more than 200 g, the catalytic performance is saturated, and a remarkable improvement effect cannot be obtained.

Further, the catalyst component layer of the exhaust gas purifying catalyst of the present invention may further contain cerium oxide in addition to the above catalyst component (noble metal). The cerium oxide contains at least one selected from the group consisting of Zr, Nd, and La in terms of metal of 1 to 40 mol%, and the balance of Ce in the range of 60 to 99 mol% of metal. By including cerium oxide, cerium oxide with high oxygen storage capacity releases lattice oxygen and adsorbed oxygen in rich atmosphere and in the vicinity of stoichiometry, making the oxidation state of precious metal suitable for purification of exhaust gas and improving catalyst performance. Can be suppressed. The content of 1 to 40 mol% means that at least one element selected from the group consisting of Zr, Nd and La is added to cerium oxide (CeO ₂ ), and the oxygen-releasing ability and BET specific surface area of CeO ₂ are This is to significantly improve the thermal stability. When it is less than 1 mol%, the effect of adding the above-mentioned elements does not appear as in the case of only CeO ₂ , and when it exceeds 40 mol%, this effect is saturated or, conversely, decreases.

Further, in the preferred embodiment of the exhaust gas purifying catalyst of the present invention, the Rh-containing upper catalyst component layer further contains C
It is also possible to contain a zirconium oxide containing at least one selected from the group consisting of e, Nd and La. The zirconium oxide contains 1 to 40 mol% of at least one element selected from the group consisting of Ce, Nd, and La in terms of metal, and the balance Zr is 6 in terms of metal.
It contains 0 to 99 mol%. 1 to 40 mol% means that one element selected from the group consisting of Ce, Nd and La is added to zirconium oxide (ZrO ₂ ),
This is because the oxygen releasing ability, the BET specific surface area, and the thermal stability of ZrO ₂ are remarkably improved. If less than 1 mol% Zr
As in the case of O ₂ only, the effect of adding the above-mentioned elements does not appear, and when it exceeds 40 mol%, this effect is saturated or deteriorated.

In the Rh-containing upper catalyst component layer, Ce, N
By incorporating a powder of zirconium oxide containing at least one selected from the group consisting of d and La,
Since the zirconium oxide releases lattice oxygen and adsorbed oxygen in a rich atmosphere and in the vicinity of stoichiometry and makes the oxidation state of the noble metal suitable for purifying exhaust gas, it is possible to suppress deterioration of the catalytic performance of the noble metal.

In the exhaust gas purifying catalyst of the present invention, the alkali metal and / or alkaline earth metal used include Li, Na, K, Cs, Mg, Ca, Sr and Ba. When these are contained in the catalyst component layer,
Since the HC adsorption poisoning effect in a rich atmosphere is mitigated and the sintering of precious metal is suppressed, the low temperature activity and the activity in a reducing atmosphere can be further improved. The content is 1 to 40 g in 1 L of the catalyst, and if it is less than 1 g, adsorption poisoning of HC and sintering of precious metals cannot be suppressed, and even if it exceeds 40 g, a significant amount increasing effect is not obtained and conversely the performance deteriorates. Let

In producing the exhaust gas purifying catalyst of the present invention, the HC adsorbent layer (zeolite layer) is disposed on the inner layer side in order to effectively develop the performance of the HC adsorbent layer and the catalyst component layer. The component layer (palladium layer) is on the intermediate layer side thereabove, and the Rh-containing upper catalyst component layer (rhodium layer) is further arranged on the surface layer side thereabove.

As the raw material compound of the noble metal (catalyst component) in the catalyst component layer and the upper catalyst component layer, any compound can be used as long as it is a water-soluble compound such as dinitrodiammine acid salt, chloride or nitrate. Water can be removed by appropriately selecting from known methods such as filtration and evaporation to dryness. The first heat treatment for obtaining the noble metal-supported powder used in the present invention is not particularly limited, but is 400 ° C. to 800 ° C. for supporting the added noble metal with good dispersibility.
It is preferable to carry out the calcination in the air and / or under the air flow at a relatively low temperature of ° C.

Further, P is added to the zeolite of the HC adsorbent layer.
d, Mg, Ca, Sr, Ba, Ag, Y, La, Ce,
At least one selected from Nd, P, B, and Zr can be impregnated and supported. These metal compounds are dispersed on zeolite by supporting water-soluble compounds such as oxides, acetates, nitrates and hydroxides by a usual method such as an ion exchange method, an impregnation method and an immersion method. It is possible to improve the property and carry it. As a method of removing water after supporting, drying is carried out, and then firing is carried out at a relatively low temperature of 200 to 600 ° C. in air and / or under air circulation.
If the firing temperature is lower than 200 ° C., the metal compound cannot be sufficiently converted into an oxide form, and conversely, if it exceeds 600 ° C., the effect of the firing temperature is saturated, and a significant difference cannot be obtained.

Further, Pt may be contained in the catalyst component layer and the upper catalyst component layer. As the raw material compound, any compound can be used as long as it is a water-soluble compound such as dinitrodiammine acid salt, chloride and nitrate.

Further, preferably, the catalyst component layer (noble metal layer), the alumina powder or the zirconium oxide powder, Z
By adding a cerium oxide containing at least one selected from the group consisting of r, Nd and La, the oxidation state of the noble metal is effectively maintained in a state suitable for exhaust gas purification in a reducing atmosphere. be able to.

Also, preferably, in the upper catalyst component layer,
It is also possible to add a zirconium oxide powder containing at least one selected from the group consisting of Ce, Nd and La. By adding a zirconium oxide powder containing at least one selected from the group consisting of Ce, Nd and La, the oxidation state of the noble metal can be more effectively maintained in a state suitable for exhaust gas purification in a reducing atmosphere. can do.

The thus obtained exhaust gas purifying catalyst according to the present invention can be effectively used even without a carrier, but it is crushed into a slurry and coated on a specific monolith carrier to obtain 400 to 900. It is used after firing at ℃. Specifically, as the HC adsorbent layer (inner layer side), silica sol is added to zeolite powder containing β-zeolite as a main component, and the mixture is wet pulverized to form a slurry, which is attached to a monolith carrier, and the temperature is 400 to 650 ° C. Firing is carried out in the air and / or under the air flow at a temperature within the range. Next, catalyst component layer (middle layer side)
As the Pd-supported powder, the alumina powder, and the cerium oxide powder, alumina sol is added, and the mixture is pulverized by a wet process to form a slurry, which is attached to a monolith carrier, and 400 to 6
Firing is performed in the air and / or under the air flow at a temperature in the range of 50 ° C. Next, as the upper catalyst component layer (surface layer side), R
h-supported powder, alumina powder, and zirconium oxide powder are added with alumina sol and pulverized by a wet process to form a slurry, which is attached to a monolith carrier and 400 to 650 ° C.
Calcination is carried out in the air and / or under the air flow at a temperature in the range. Pt is further added to the catalyst component layer and the upper catalyst component layer.
May be added.

The monolithic carrier which is a catalyst carrier can be appropriately selected and used from known catalyst carriers, and examples thereof include a honeycomb-shaped monolithic carrier made of a refractory material and a metal carrier. As the honeycomb material, generally, a cordierite material such as ceramic is often used, but it is also possible to use a honeycomb material made of a metal material such as ferritic stainless steel,
Further, the catalyst component powder itself may be formed into a honeycomb shape. The catalyst has a honeycomb shape, and in the present invention, the honeycomb-shaped carrier (monolith carrier) further has a GSA of 10c.
has the ^{m 2 / cm 3 ~35cm 2 /} cm 3, to limit the contact between the exhaust gas and the HC adsorbent layer, which is highly effective in delaying the desorption from the HC adsorbent layer of the adsorbent HC.

Further, by setting the number of cells of the monolith carrier to be 50 to 600 cells per square inch, the HC
Limit the contact between the adsorbent layer and the exhaust gas,
It is extremely effective in delaying desorption from the adsorbent layer.

Further, the hydraulic diameter of the monolith carrier is 0.7
By setting it to 5 mm to 5 mm, it is extremely effective in reducing the exhaust gas diffusion rate into the HC adsorbent layer and delaying the desorption of adsorbed HC from the HC adsorbent layer.

The amount of the catalyst component layer adhered to the monolithic carrier is 5 per 1 L of the catalyst in total of the entire catalyst component layer.
0g-600g is preferable. The more the catalyst component layer having the three-way purifying ability is, the more preferable it is in terms of the catalyst activity and the catalyst life. However, if the coat thickness of the catalyst component layer is too thick, the exhaust gas to the HC adsorbent layer inside the catalyst component layer is increased. Diffusion becomes poor, and conversely, the HC adsorption performance deteriorates. Further, the more the HC adsorbent layer is, the more preferable it is from the viewpoint of delaying the desorption of HC, but if the coat thickness of the HC adsorbent layer becomes too thick, the contact between the desorbed HC and the catalyst component layer becomes poor, On the contrary, desorption H
The purifying activity of C decreases. Therefore, it is preferable to set the coat weight ratio of the HC adsorbent layer and the catalyst component layer to 5: 1 to 1: 2. Further, the coat layer thickness in the flat portion in the monolith carrier cell, that is, the total thickness of the HC adsorbent layer and the catalyst component layer, is preferably 30 μm to 400 μm. By keeping the GSA, the number of cells, and the hydraulic diameter of the monolith carrier carrying the washcoat component within the specified values, it is possible to secure a sufficient HC adsorbent layer thickness to delay the desorption of HC, and desorb HC The purification performance of is improved.

Next, an embodiment of the exhaust gas purifying apparatus of the present invention will be described. This purification device has Pd, Pd and Pt, or Pd and R at the front stage of the above-described exhaust gas purification catalyst (HC adsorption catalyst) of the present invention, that is, at the upstream side of the exhaust passage.
The catalyst 1 contains Pd-supporting powder containing h and containing Pd so that the supported concentration of Pd is 4 to 20% by weight.
The amount of Pd supported per L is 100 g / cf (3.5 g /
L) to Pd of 1000 g / cf (35.4 g / L)
The present invention relates to an exhaust gas purification device in which a contained catalyst (three-way catalyst) is arranged (see FIG. 3 and the like). In this exhaust gas purification device, the amount of HC adsorbed by the exhaust gas purification catalyst (HC adsorption catalyst) is 70% or less, preferably 10% to 70%, of the amount of HC exhausted in the low temperature range immediately after the engine is started. Is set.

When the HC adsorbing catalyst of the present invention adsorbs all the amount of HC in the exhaust gas at a low temperature immediately after the engine is started, when desorption starts as the temperature of the catalyst component layer rises,
Since the catalyst component layer arranged above the HC adsorbent layer is exposed to the oxygen-deficient state for a long time, the purification performance for desorbed HC is significantly reduced. Therefore, before the above HC adsorption catalyst,
By disposing a Pd-containing catalyst excellent in HC purification performance in a low temperature range and setting the amount of HC adsorbed by the HC adsorption catalyst to 70% or less of the saturated adsorption amount of HC of the HC adsorption catalyst,
It is preferable in order to maintain and improve the purification performance for the desorbed HC of the catalyst component layer arranged above the adsorbent layer. But,
The amount of HC adsorbed by the HC adsorption catalyst depends on the H of the HC adsorption catalyst.
If it exceeds 70% of the C saturated adsorption amount, the cold HC adsorption efficiency of the HC adsorbent decreases, and the desorption becomes faster, so that the purification performance of desorbed HC deteriorates remarkably.

In a preferred embodiment of the exhaust gas purifying apparatus according to the present invention, the loading concentration of the Pd-supporting powder is 4% to 15% by weight, and the loading amount of palladium of the Pd-containing catalyst is 100 g / cf. (3.5 g / L) to 500
g / cf (17.7 g / L), and the ignition timing at engine start (first idle) is 40 seconds or less immediately after engine start, and 1 ° to 30 from top dead center.
Be retarded less than °. This accelerates the rise in exhaust temperature, accelerates the activation of the Pd-containing catalyst arranged in front of the HC adsorption catalyst, and reduces the amount of HC adsorbed by the HC adsorption catalyst to 70% or less of the saturated HC adsorption amount of the HC adsorption catalyst. Is set to.

In another preferred embodiment, the supported concentration of the Pd-supported powder is 4% by weight to 15% by weight,
Moreover, the amount of palladium supported on the Pd-containing catalyst is 100 g /
cf (3.5 g / L) to 500 g / cf (17.7 g /
L) or less, and air is supplied at an air flow rate of 10 L / min or more for 60 seconds immediately after the engine is started to dilute the cold air-fuel ratio immediately after the engine is started (A / F = 12 to 18). The activation of the Pd-containing catalyst is accelerated, and the H
The amount of HC adsorbed by the C adsorption catalyst is set to 70% or less of the saturated adsorption amount of HC of the HC adsorption catalyst.

Furthermore, in another preferred embodiment, the air-fuel ratio is set to 14.4 immediately before the desorption of HC from the HC adsorption catalyst is started.
Oxygen and / or air is added to the upstream side of the HC adsorbing catalyst or into the HC adsorbing catalyst using a means such as an air pump or the like. Before or at the same time as the start of desorption of the adsorbed HC from the HC adsorbent, oxygen and / or air is added to the upstream side of the HC adsorbent catalyst or into the HC adsorbent catalyst, and By supplying oxygen to the catalyst component layer, the purification performance of desorbed HC is improved.

Furthermore, in another preferred embodiment, in order to improve the purification efficiency of HC desorbed from the HC adsorption catalyst, H 2
When the detected value of the temperature detector installed in the front part (near the inlet) of the C adsorption catalyst exceeds a predetermined temperature, the A / F detector installed in the rear part (near the outlet) of the HC adsorption catalyst is 14.6. As described above, oxygen and / or air is added upstream of the HC adsorption catalyst or in the HC adsorption catalyst (see FIG. 3).

When the value detected by the temperature detector installed near the inlet of the HC adsorption catalyst is below a predetermined temperature, for example, 110 ° C., H
Since the activation of the catalyst component layer of the C adsorption catalyst is insufficient,
Conversely, the addition of oxygen and / or air lowers the purification performance of desorbed HC. Further, the oxygen and / or air added upstream of the HC adsorption catalyst is preferably added so that the A / F detector installed near the outlet of the HC adsorption catalyst has a value of 14.6 or more. When the A / F is less than 14.6, the effect of improving the purification performance of the catalyst component layer of the HC adsorption catalyst is not sufficient.

Further, in order to improve the purification efficiency of HC desorbed from the HC adsorption catalyst, when the detection value of the temperature detector inserted in the catalyst component layer of the HC adsorption catalyst exceeds a predetermined temperature, the HC Oxygen and / or air is added upstream of the HC adsorption catalyst or in the HC adsorption catalyst so that the A / F detector installed near the outlet of the adsorption catalyst is 14.6 or higher (see FIG. 4). . If the value detected by the temperature detector inserted in the catalyst component layer of the HC adsorption catalyst is lower than the predetermined temperature, the activation of the three-way catalyst layer of the HC adsorption catalyst is insufficient. Conversely, the purification performance of desorbed HC decreases. Further, the oxygen and / or air added upstream of the HC adsorption catalyst is preferably added so that the A / F detector installed near the outlet of the HC adsorption catalyst has a value of 14.6 or more. When the A / F is less than 14.6, the effect of improving the purification performance of the catalyst component layer of the HC adsorption catalyst is not sufficient.

Further, in order to improve the purification efficiency of HC desorbed from the HC adsorbing catalyst, when the desorption of HC is detected from the detection values of A / F detectors installed near the inlet and the outlet, Oxygen and / or air is added upstream of the HC adsorption catalyst or in the HC adsorption catalyst so that the A / F detector A / F = 14.6 or more arranged near the outlet of the adsorption catalyst (see FIG. 4).

In order to minimize the amount of oxygen and / or air added to the upstream side of the HC adsorbing catalyst and significantly accelerate the activation of the catalyst component layer of the HC adsorbing catalyst, the vicinity of the inlet and the outlet of the HC adsorbing catalyst should be set. When the desorption of HC is detected from the difference in the detection values of the installed A / F detectors, the A / F detectors installed near the outlet of the HC adsorption catalyst may be added so that the amount becomes 14.6 or more. preferable. When A / F is less than 14.6, H
The effect of improving the purification performance of the catalyst component layer of the C adsorption catalyst is not sufficient.

Further, in a preferred embodiment of the purifying apparatus of the present invention, in the exhaust gas purifying apparatus in which the Pd-containing catalyst is arranged before the HC adsorption catalyst, unpurified components (HC, CO, To efficiently purify NOx),
It is preferable that the Pd-containing catalyst contains Rh and the amount of Rh be smaller than the amount of rhodium contained in the HC adsorption catalyst arranged on the downstream side. Rh contained in the Pd-containing catalyst
Rh contained in the HC adsorption catalyst whose amount is arranged downstream thereof
By making the amount less than the amount, the unpurified components (HC, CO, NOx) in the hot region can be efficiently purified, and the Pd
The purification performance of low concentration exhaust gas components that could not be purified by the contained catalyst is improved.

The weight ratio of the Rh amount contained in the Pd-containing catalyst to the Rh amount contained in the HC adsorption catalyst arranged on the downstream side is preferably equal to or less than 1/1. The R
If the weight ratio of h is equal to or more than the equal value, the purification performance of low-concentration exhaust gas components is not sufficiently exhibited.

Further, another preferred embodiment of the purifying device of the present invention will be described. In this embodiment, in order to improve the purification efficiency of HC desorbed from the HC adsorption catalyst, a Pd-containing catalyst is arranged upstream of the exhaust gas, and two or more HC adsorption catalysts are arranged downstream thereof (HC adsorption catalyst according to the present invention). Catalyst and the HC
This is an exhaust gas purification device in which the same HC adsorption catalyst as the adsorption catalyst) is arranged. By arranging two or more HC adsorption catalysts, it is possible to disperse and adsorb HC in the low temperature range that is discharged immediately after the engine is started, and to shorten the time when the catalyst component layer placed on top of the HC adsorbent is exposed to oxygen deficiency. However, the purification performance for desorbed HC is significantly improved.

In still another preferred embodiment, a Pd-containing catalyst is arranged upstream of the exhaust gas, two or more HC adsorbing catalysts are arranged downstream thereof, and the plurality of HC adsorbing catalysts are arranged at a distance from the engine. Is an exhaust gas purifying apparatus that is provided at different positions and has a different temperature rising rate of each HC adsorption catalyst. Due to the different temperature rising rates of the HC adsorbing catalysts arranged in plurality, the unpurified desorbed HC of the HC adsorbing catalysts of the preceding stage can
It is re-adsorbed by the adsorption catalyst to remarkably improve the purification performance for desorbed HC.

FIG. 12 shows a flow sheet showing a procedure for setting a lean time in implementing the exhaust gas purifying apparatus of the present invention. Leaning time was defined according to this flow. In the sheet, S1 to S18 have the following meanings.

It should be noted that this flow is executed every predetermined time. S1 Determine if the engine is starting. For example, when the starter SW is ON when this flow was executed last time and is OFF this time, it is determined that the starter SW is being started, and the initial setting of S2 to S5 is performed. The temperature of the S2 HC adsorption catalyst (inlet temperature or catalyst component layer temperature) is detected. For simplicity, the engine cooling water temperature may be used instead. The adsorption capacity of the HC adsorption catalyst is estimated based on the catalyst temperature obtained in S3 and S2. Based on the adsorption capacity obtained in S4 and S2, the time when the desorption of HC from the HC adsorption catalyst is started (the elapsed time from the start) is estimated. Based on the adsorption capacity obtained in S5 and S2, the time required from the desorption of HC to the completion thereof is estimated. S6 Measure the elapsed time from the engine start. S7: Determine whether it is time to release HC from the HC adsorption catalyst. Here, the determination is made by comparing the HC desorption start estimated in S4 and the elapsed time from the start, but as another method, the catalyst temperature is continuously detected or estimated even after the engine is started, The determination may be made by comparing the catalyst temperature and the desorption temperature. S8 The elapsed time after the start is a predetermined time (for example, 60 seconds)
Determine if less than. If the determination in S9 and S8 is YES, the air-fuel ratio is set to lean. If the air-fuel ratio is made leaner by about 10% than the stoichiometric air-fuel ratio, the activation start temperature of the catalyst is lowered, and early activation of the catalyst can be achieved. If the determination in S10 and S8 is NO, the air-fuel ratio is set to stoichiometric. (Operating with a lean air-fuel ratio has the disadvantage of increasing the amount of NOx generated, so it is kept to a minimum.) S11 Elapsed time after starting for a predetermined time (for example, 40
Second)). If the determinations in S12 and S11 are YES, the ignition timing is set to a timing that is on the retard side with respect to the ignition timing during normal operation. By retarding the ignition timing, the exhaust gas temperature is raised and unburned HC is supplied to the catalyst, so that the catalyst can be activated early. If the determination in S13 and S11 is NO, the ignition timing is set to the normal ignition timing. (The ignition timing retardation has the disadvantage that it reduces the generated torque (= deteriorates fuel efficiency), so it should be kept to the minimum necessary.) S14 Measure the elapsed time from the start of desorption of HC. S15 It is determined whether or not HC desorption is in progress. S16 The output of the air-fuel ratio sensor arranged downstream of the catalyst is
It is determined whether it is less than a predetermined value, that is, whether it exceeds a predetermined lean air-fuel ratio. When it is determined in S15 that the HC is being desorbed, basically, the lean air-fuel ratio control is executed in the next S17, but the normal control is performed when the catalyst downstream air-fuel ratio sensor shows a predetermined lean air-fuel ratio or more. If YES in S17 and S15, the air-fuel ratio is set to lean. During desorption of HC, the catalyst becomes rich atmosphere and H
Since the efficiency of the C oxidation treatment decreases, the air-fuel ratio is made lean to prevent the efficiency from decreasing. According to the desorption characteristics of HC,
It is advisable to set the lean air-fuel ratio to the extent that oxygen corresponding to the amount of desorbed HC is supplied. If NO in S18 and S15 (= after completion of desorption of HC), normal control is performed.

[0069]

The present invention will be described with reference to the following examples and comparative examples. Example 1 β-zeolite powder (H type, Si / 2Al = 75) 51
1 g, 57 g of MFI (ZSM5) powder, 1215 g of silica sol (solid content 20%), and 1800 g of pure water were charged into a magnetic ball mill and mixed and ground to obtain a slurry liquid. This slurry liquid was attached to a cordierite monolith carrier (300 cells / 6 mil, GSA24.1 cm ² / cm ³ , hydraulic diameter 1.3 mm), excess slurry in the cells was removed by an air stream, and dried, It was baked at 400 ° C. for 1 hour. At this time, the coating operation was repeated until the coating amount became 100 g / L after firing to obtain catalyst-a.

Ce 3 mol% (converted to CeO ₂ , 9.
Alumina powder containing 5% by weight) was impregnated with an aqueous solution of dinitrodiaminepalladium or sprayed under high-speed stirring,
After drying at 0 ° C. for 24 hours, it was baked at 400 ° C. for 1 hour and then at 600 ° C. for 1 hour to obtain a Pd-supported alumina powder (powder a). The Pd concentration of this powder a was 6.23% by weight. The powder a includes lanthanum, zirconium,
Neodymium or the like may be included.

A cerium oxide powder containing 1 mol% La (1 wt% in terms of La ₂ O ₃ ) and 32 mol% Zr (25 wt% in terms of ZrO ₂ ) was impregnated with a dinitrodiamine palladium aqueous solution or stirred at high speed. Spray in, 150
After drying at ℃ for 24 hours, at 400 ℃ for 1 hour, then
It was baked at 600 ° C. for 1 hour to obtain a Pd-supporting cerium oxide powder (powder b). The Pd concentration of this powder b was 2.0% by weight.

The above Pd-supported alumina powder (powder a) 56
2 g, Pd-supporting cerium oxide powder (powder b) 288
g, 950 g of nitric acid-acidified alumina sol (sol obtained by adding 10 wt% nitric acid to 10 wt% of boehmite alumina) and 1000 g of pure water were put into a magnetic ball mill and mixed and ground to obtain a slurry liquid. This slurry liquid is attached to the above-mentioned coated catalyst-a, the excess slurry in the cell is removed by an air flow and dried, and the slurry is dried at 400 ° C. for 1 hour.
Baking for 60 hours / coating layer weight of 60g / L
b was obtained.

Alumina powder containing 3% by weight of Zr was impregnated with an aqueous solution of rhodium nitrate or sprayed under high-speed stirring.
After drying at 0 ° C. for 24 hours, it was calcined at 400 ° C. for 1 hour and then at 600 ° C. for 1 hour to obtain Rh-supported alumina powder (powder c). The Rh concentration of this powder c was 1.25% by weight.

The Rh-supported alumina powder (powder c) 36
6 g, La ₁ mol% (1.2 wt% in terms of La ₂ O ₃ ) and 300 mol% Ce (25.8 wt% in terms of CeO ₂ ) zirconium oxide powder 300 g, nitric acid-acidified alumina sol 1135 g The mixture was put into a ball mill and mixed and ground to obtain a slurry liquid. This slurry liquid was attached to the above coated catalyst-b, excess slurry in the cell was removed by an air flow, dried, and baked at 400 ° C. for 1 hour to apply a coating layer weight of 40 g / L to obtain a catalyst. It was The cerium oxide powder and the alumina powder may contain lanthanum, neodymium and the like. Next, a barium acetate solution was attached to the above-mentioned catalyst component-supporting cordierite monolithic carrier, followed by firing at 400 ° C. for 1 hour to obtain BaO of 10 g.
/ L was included. As a result, an exhaust gas purification catalyst (HC adsorption catalyst) of this example was obtained.

Example 2 As zeolite, β-zeolite powder (H type, Si /
2Al = 75) 313 g, MFI (ZSM5) powder 25
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that 5 g and 1215 g of silica sol (solid content 20%) were used.

Example 3 As zeolite, β-zeolite powder (H type, Si /
2Al = 75) 454 g, MFI (ZSM5) powder 57
g, USY powder 57 g, silica sol (solid content 20%) 1
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that 215 g was used.

Example 4 As zeolite, β-zeolite powder (H type, Si /
2Al = 75) 454 g, MFI (ZSM5) powder 57
g, AlPO4 powder 57 g, silica sol (solid content 20
%) 1215 g was used to obtain an exhaust gas purifying catalyst in the same manner as in Example 1.

Example 5 As zeolite, β-zeolite powder (H type, Si /
2Al = 75) 454 g, MFI (ZSM5) powder 57
g, SAPO4 powder 57 g, silica sol (solid content 20
%) 1215 g was used to obtain an exhaust gas purifying catalyst in the same manner as in Example 1.

Example 6 As zeolite, β-zeolite powder (H type, Si /
2Al = 75) 454 g, MFI (ZSM5) powder 57
g, mordenite powder 57 g, silica sol (solid content 20
%) 1215 g was used to obtain an exhaust gas purifying catalyst in the same manner as in Example 1.

Example 7 As zeolite, β-zeolite powder (H type, Si /
2Al = 75) 454 g, MFI (ZSM5) powder 57
g, ferrierite powder 23.5 g, A-type zeolite powder 23.5 g, silica sol (solid content 20%) 1215 g
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that was used.

Example 8 Pd was impregnated and supported on MFI (ZSM5) powder to give 150
After drying at ℃ for 24 hours, calcination at 450 ℃ for 1 hour, P
A d-supported MFI powder (Pd concentration: 2.0% by weight) was obtained. M
Instead of FI powder, Pd-supported MFI powder was used, and cordierite monolith carrier (200 cells / 10 mils, G
SA 19.0 cm ² / cm ³ , hydraulic diameter 1.53 mm)
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that was used.

Example 9 MFI (ZSM5) powder was impregnated with P and supported at 150 ° C.
After being dried for 24 hours at 450 ° C., it was baked at 450 ° C. for 1 hour to obtain P-supported MFI powder (Pd concentration 0.4% by weight). MFI
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that P-supporting MFI powder was used in place of the powder and the same monolith carrier as in Example 8 was used.

Example 10 Ca was impregnated and supported on MFI (ZSM5) powder to give 150
After drying at ℃ for 24 hours, calcination at 450 ℃ for 1 hour, C
An a-supported MFI powder (Ca concentration: 0.2% by weight) was obtained. M
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that Ca-supporting MFI powder was used instead of the FI powder and the same monolith carrier as in Example 8 was used.

Example 11 Mg was impregnated and supported on MFI (ZSM5) powder to obtain 150
After drying at ℃ for 24 hours, calcination at 450 ℃ for 1 hour, M
A g-supported MFI powder (Mg concentration 0.4% by weight) was obtained. M
An exhaust gas purification catalyst was obtained in the same manner as in Example 1 except that Mg supporting MFI powder was used in place of the FI powder and the same monolith carrier as in Example 8 was used.

Example 12 MFI (ZSM5) powder was impregnated with La to carry 150
After drying at ℃ for 24 hours, calcination at 450 ℃ for 1 hour, L
An a-supported MFI powder (La concentration: 0.4% by weight) was obtained. M
An exhaust gas purification catalyst was obtained in the same manner as in Example 1 except that the La-supported MFI powder was used instead of the FI powder and the same monolith carrier as in Example 8 was used.

Example 13 MFI (ZSM5) powder was impregnated and supported with B (boron), dried at 150 ° C. for 24 hours, and then calcined at 450 ° C. for 1 hour to obtain B-supported MFI powder (B concentration: 0.4% by weight). %) Was obtained. Instead of MFI powder, B-supported MFI powder was used,
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that the same monolith carrier as in Example 8 was used.

Example 14 P-Ca-Zr-L obtained by sequentially impregnating MFI (ZSM5) powder with P, Ca, Zr and La, drying and firing.
An a-supported MFI powder (each metal concentration 0.1% by weight, total metal concentration 0.4% by weight) was obtained. Instead of MFI powder, P-
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that the Ca-Zr-La-supported MFI powder was used and the same monolith carrier as in Example 8 was used.

Example 15 P-Mg-Zr-C supported by sequentially impregnating MFI (ZSM5) powder with P, Mg, Zr and Ce, drying and firing.
An e-supported MFI powder (each metal concentration: 0.1% by weight, total metal concentration: 0.4% by weight) was obtained. Instead of MFI powder, P-
An exhaust gas purification catalyst was obtained in the same manner as in Example 1, except that the Mg-Zr-Ce-supported MFI powder was used and the same monolith carrier as in Example 8 was used.

Example 16 B-Ca-La-N supported by sequentially impregnating MFI (ZSM5) powder with B, Ca, La and Nd, drying and firing.
A d-supported MFI powder (each metal concentration: 0.1% by weight, total metal concentration: 0.4% by weight) was obtained. Instead of MFI powder, B-
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that the Ca-La-Nd-supported MFI powder was used and the same monolith carrier as in Example 8 was used.

Example 17 Alumina powder containing 3% by weight of Zr was impregnated with an aqueous rhodium nitrate solution or sprayed under high-speed stirring and dried at 150 ° C. for 24 hours, then at 400 ° C. for 1 hour, and then at 600 ° C. for 1 hour. Firing was performed to obtain Rh-supported alumina powder (powder c). The Rh concentration of this powder c was 1.25% by weight.
La ₁ mol% (1.2 wt% converted to La ₂ O ₃ ) and Ce 20 mol% (25.8 wt% converted to CeO ₂ )
The zirconium oxide powder of No. 2 was impregnated with an aqueous solution of dinitrodiamine platinum or sprayed under high-speed stirring at 24 ° C at 150 ° C.
After drying for 1 hour, 400 ℃ for 1 hour, then 600 ℃
And was baked for 1 hour to obtain a Pt-supported zirconium oxide powder (powder d). The Pt concentration of this powder d is 1.53% by weight.
Met. Rh-supported alumina powder c366g, Pt
300 g of supported zirconium oxide powder (powder d) and 1135 g of nitric acid-acidified alumina sol were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. An exhaust gas purification catalyst was obtained in the same manner as in Example 1 except that this slurry liquid was applied to the above coated catalyst-b (however, the monolith carrier was the same as in Example 8).

Example 18 1 mol% La ( 1 wt% in terms of La ₂ O ₃ ) and Zr
Serum containing 32 mol% ( 25 wt% in terms of ZrO ₂ ).
Impregnated um oxide powder with dinitrodiamine platinum aqueous solution
Alternatively, spray under high speed stirring and dry at 150 ° C for 24 hours.
After baking at 400 ° C for 1 hour, then at 600 ° C for 1 hour
Then, a Pt-supported cerium oxide powder (powder e) was obtained.
The Pt concentration of this powder e was 2.0% by weight. Above P
d-supported alumina powder (powder a) 562 g, Pd-supported cerium oxide powder (powder b) 144 g, Pt-supported cerium oxide powder (powder e) 144 g, nitric acid acidic alumina sol 950 g (10% by weight of boehmite alumina 10% by weight)
The sol obtained by adding the nitric acid of 1.) and 1000 g of pure water were put into a magnetic ball mill and mixed and ground to obtain a slurry liquid. This slurry liquid was used as the above coated catalyst-a.
A catalyst-c was obtained in the same manner as in Example 1 except that the monolith carrier was the same as in Example 8. Rh above
Supported alumina powder c366 g, La ₁ mol% (La ₂ O
2% by weight in terms of ₃ ) and 20 mol% Ce (25.8% by weight in terms of CeO ₂ ) zirconium oxide powder 3
00g, nitric acid acidic alumina sol 1135g and pure water 10
00 g was put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. An exhaust gas purification catalyst was obtained in the same manner as in Example 1 except that this slurry liquid was applied to the above coated catalyst-c.

Example 19 A potassium acetate solution was used in place of the barium acetate solution,
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that 1 g / L was added as K ₂ O in the same procedure and the same monolith carrier as in Example 8 was used.

Example 20 Ag was impregnated and supported on MFI (ZSM5) powder to obtain 150
After drying at ℃ for 24 hours, calcination at 450 ℃ for 1 hour, A
A g-supported MFI powder (Ag concentration 0.4% by weight) was obtained. M
An exhaust gas purification catalyst was obtained in the same manner as in Example 1 except that Ag-supported MFI powder was used in place of the FI powder and the same monolith carrier as in Example 8 was used.

Comparative Example 1 Cordierite monolithic carrier (900 cells / 4 mils,
GSA41.1cm ² / cm ^3, the hydraulic diameter 0.74m
An exhaust gas purification catalyst was obtained in the same manner as in Example 1 except that m) was used.

Comparative Example 2 Example 1 except that the second layer (catalyst component layer = ternary layer) was the Rh layer and the third layer (upper catalyst component layer = ternary layer) was the Pd layer.
An exhaust gas purifying catalyst was obtained in the same manner as in.

Comparative Example 3 Example 1 was repeated except that the total coating layer weight ratio of the first layer (HC adsorbent layer = zeolite layer) and the second and third layers (ternary layer) was 10: 1. An exhaust gas purifying catalyst was obtained in the same manner as in.

Reference Example 1 Exhaust gas purifying was carried out in the same manner as in Example 1 except that the total coating layer weight ratio of the first layer (zeolite layer) to the second and third ternary layers was 1: 5. A catalyst was obtained.

Comparative Example 4 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that only the A-type zeolite was used as the zeolite species in the first layer and the same monolith carrier as in Comparative Example 1 was used. .

Comparative Example 5 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that only USY was used as the zeolite seed of the first layer and the same monolith carrier as in Comparative Example 1 was used.

Comparative Example 6 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that only MFI was used as the zeolite seed of the first layer and the same monolith carrier as in Comparative Example 1 was used.

The specifications of the exhaust gas purifying catalysts obtained in the above Examples, Reference Examples and Comparative Examples are shown in Tables 1 and 2.

[0102]

[Table 1]

[0103]

[Table 2]

FIG. 1 is a schematic view of the coat layer structure.

Regarding each example, reference example and comparative example, HC purification characteristic evaluation (EC mode, LA-4
A-bag) was performed using the evaluation system of FIG. The results are shown in Tables 3 and 4.

Endurance condition Engine displacement 3000 cc Fuel gasoline (Pb = 12 mg / u
sg, S = 300ppm) Catalyst inlet gas temperature 650 ° C Endurance time 100 hours Performance evaluation condition Catalyst capacity (one bank) Three-way catalyst 1.3L + HC adsorption catalyst 2.6L Evaluation vehicle Nissan Motor Co., Ltd. V type 6
Cylinder 3.3L engine Hydrocarbons (in gas at catalyst inlet) exhausted at engine startup

[0107]

[Table 3]

[0108]

[Table 4]

Compared with the comparative example, the example has a higher catalytic activity,
The effects of the present invention described below could be confirmed.

Precatalyst Example 1 3 mol% cerium (8.7 wt% in terms of CeO ₂ ) and 3 mol% zirconium (6% in terms of ZrO ₂ ).
Alumina powder (powder A) containing 3% by weight of lanthanum and 2% by mole of lanthanum (5.5% by weight in terms of La ₂ O ₃ ) was impregnated with an aqueous palladium nitrate solution and dried at 150 ° C. for 12 hours. The Pd-supported alumina powder (powder B) was obtained by firing at 400 ° C. for 1 hour. The Pd concentration of this powder B was 16% by weight. Cerium oxide powder (powder C) containing 1 mol% lanthanum (2 wt% in terms of La ₂ O ₃ ) and 32 mol% zirconium (25 wt% in terms of ZrO ₂ ).
Was impregnated with an aqueous palladium nitrate solution, dried at 150 ° C. for 12 hours, and then calcined at 400 ° C. for 1 hour to obtain a Pd-supporting cerium oxide (La _0.01 Zr _0.32 CeO _0.67).
x ) powder (powder D) was obtained. The Pd concentration of this powder D was 6.0% by weight.

565 g of Powder B, 377 g of Powder D, 58.5 g of activated alumina and 2000 g of nitric acid aqueous solution were put into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid was used as a cordierite monolith carrier (1.0
L, 600 cells / 4 mil, GSA34.5 cm ² / cm
⁽³ , hydraulic diameter 0.93 mm), the excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Do this work twice, and coat weight 100
A catalyst of g / L-support was obtained. Pd carrying amount is 320.0g
/ Cf (11.3 g / L) (Catalyst A).

Then, a barium acetate solution was attached to the above-mentioned catalyst component-supporting cordierite monolithic carrier, and then 4
It was calcined at 00 ° C. for 1 hour to contain 10 g / L as BaO (catalyst B).

First Stage Catalyst Example 2 Powder B565g, powder D377g and activated alumina 5
A magnetic ball mill was charged with 8.5 g and a nitric acid aqueous solution of 2000 g, and mixed and pulverized to obtain a slurry. This slurry liquid was attached to a cordierite monolithic carrier, excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Do this work twice, and coat weight 9
A catalyst of 1.7 g / L-support was obtained. The amount of palladium carried was 293.3 g / cf (10.36 g / L) (catalyst C).

An alumina powder containing 3% by weight of Zr (powder E) was impregnated with an aqueous rhodium nitrate solution, dried at 150 ° C. for 12 hours, and then baked at 400 ° C. for 1 hour to obtain an Rh-supported alumina powder (powder F). It was The Rh concentration of this powder F was 4.0% by weight. La1 mol% Ce20 mol% Z
A zirconium oxide powder (powder G) having an r of 79 mol% was impregnated with an aqueous platinum dinitrodiammnate solution, and the mixture was dried at 150 ° C. for 1 hour.
After drying for 2 hours, it was baked at 400 ° C. for 1 hour to obtain a Pt-supported zirconium oxide powder (powder H). The Pt concentration of this powder H was 4.0% by weight.

The powder F117.5 g and the powder H117.
A magnetic ball mill was charged with 5 g, 15 g of activated alumina, and 1000 g of a nitric acid aqueous solution, and mixed and pulverized to obtain a slurry. This slurry liquid was adhered to the cordierite monolithic carrier (catalyst C) supporting the Pd-containing catalyst component layer, the excess slurry in the cell was removed and dried by an air flow, and the mixture was calcined at 400 ° C. for 1 hour. Coat amount 25g / L
(Total coat weight 116.7 g / L) -A catalyst of a carrier was obtained. The loading amount of Rh is 13.3 g / cf (0.48 g /
L) and the amount of Pt carried are 13.3 g / cf (0.48 g /
L) (catalyst D). Then, a barium acetate solution was attached to the above-mentioned catalyst component-supporting cordierite monolithic carrier (catalyst D), followed by firing at 400 ° C. for 1 hour to obtain BaO.
Was added as 10 g / L (catalyst E).

Reference Example 2 H-type β-zeolite 800 g, silica sol 1000 g
(Solid content 20%) and 1000 g of pure water were put into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid was used as a cordierite monolith carrier (1.3 L, 200 L).
(Cell / 10 mil, GSA 19.0 cm ² / cm ³ , hydraulic diameter 1.53 mm), the excess slurry in the cell was removed and dried by air flow, and the mixture was calcined at 400 ° C. for 1 hour. A catalyst having a coat weight of 200 g / L-support was obtained (Catalyst F).

Zirconium oxide powder (powder G) containing 1 mol% of La, 20 mol% of Ce, and 79 mol% of Zr was impregnated with an aqueous rhodium nitrate solution, and dried at 150 ° C. for 12 hours.
00 was calcined 1 hour at ° C., to obtain a Rh-supporting di Rukoniumu oxide powder (powder I). The Rh concentration of this powder I is 8.0.
% By weight. Powder B 500 g, powder D 80 g,
Powder I353g, powder A47g and activated alumina 20g,
A magnetic ball mill was charged with 1000 g of a nitric acid aqueous solution, and the mixture was mixed and ground to obtain a slurry. This slurry liquid was attached to the catalyst F, the excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Do this work 2
The coat weight 100g / L (total weight 300g /
A catalyst G (L-support) was obtained. The amount of palladium loaded on the catalyst G was 240.0 g / cf (8.48 g / L), and the amount of rhodium loaded was 80.0 g / cf (2.83 g / L).
Then, a barium acetate solution was attached to the catalyst G, followed by firing at 400 ° C. for 1 hour to obtain BaO of 10 g / L.
Was included (catalyst H).

Reference Example 3 Instead of 800 g of H-type β-zeolite, 500 g of H-type β-zeolite, 100 g of ZSM5, 100 g of USY,
A catalyst I was obtained in the same manner as in Reference Example 2 except that 50 g of Y type and 50 g of mordenite were used.

Reference Example 4 A catalyst was prepared in the same manner as in Reference Example 2 except that 800 g of H-type β-zeolite containing 0.5% by weight of boron and 0.1% by weight of calcium was used instead of 800 g of H-type β-zeolite. I got J.

Reference Example 5 Instead of 800 g of H-type β-zeolite, 600 g of H-type β-zeolite containing 0.5% by weight of phosphorus and 0.1% by weight of magnesium, 0.5% by weight of boron and 0.1% of calcium.
A catalyst K was obtained in the same manner as in Reference Example 2 except that 100 g of ZSM5 containing 0.5 wt% of phosphorus and 100 g of USY containing 0.5 wt% of phosphorus and 0.1 wt% of calcium were used.

Example 21 To a solution of 20 g of ammonium dihydrogen phosphate dissolved in 1500 g of pure water was added 1000 g of H-type β-zeolite,
Further, 25% aqueous ammonia was added dropwise to adjust the pH to 9.0, and then the mixture was stirred and mixed for 24 hours. Β from this mixed solution
-Zeolite was collected by filtration, dried at 120 ° C for 24 hours, and then calcined in air at 650 ° C for 2 hours to obtain powder J. Further, this powder J was impregnated with a palladium nitrate solution to obtain a powder K containing 1% by weight of Pd and 0.5% by weight of Pd. This powder K8
00 g, 1000 g of silica sol (solid content 20%) and 1000 g of nitric acid aqueous solution were put into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid was used as a cordierite monolith carrier (1.3 L, 200 cells / 10 mil,
GSA19.0cm ² / cm ^3, the hydraulic diameter 1.53m
m), and the excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. A catalyst having a coat weight of 200 g / L-support was obtained (Catalyst L). The amount of Pd supported was 45.3 g / cf (1.6 g / L). The above-mentioned powder B (500 g), powder D (80 g), powder A (30 g), activated alumina (15 g) and nitric acid aqueous solution (1000 g) were put into a magnetic ball mill, and mixed and pulverized to obtain a slurry. This slurry liquid was adhered to the catalyst L, the excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. This operation was performed twice to obtain a catalyst M. Further, the above powder I3
A magnetic ball mill was charged with 53 g, 17 g of powder A, 5 g of activated alumina, and 1000 g of nitric acid aqueous solution, and mixed and pulverized to obtain a slurry. This slurry liquid was adhered to the catalyst M, the excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Do this work twice,
A catalyst N having a coat weight of 100 g / L (total weight of 300 g / L-support) was obtained. The amount of palladium supported on the catalyst M is 28
The amount of rhodium supported was 5.4 g / cf (10.08 g / L) and 80 g / cf (2.83 g / L). Then
After the barium acetate solution was attached to the above-mentioned catalyst component-supporting cordierite monolithic carrier (catalyst N), the temperature was adjusted to 1 at 400 ° C.
It was calcined for an hour to contain 10 g / L as BaO (catalyst O).

Example 22 Instead of 800 g of H-type β-zeolite, palladium 0.
28 wt%, phosphorus 0.2 wt%, boron 0.3 wt%,
500 g of H-type β-zeolite containing 0.1% by weight of magnesium and 0.1% by weight of calcium and 100 g of ZSM5 containing 0.33% by weight of Pt and 0.1% by weight of calcium.
200 g of USY containing 0.28% by weight of palladium and 0.2% by weight of phosphorus, 0.33% by weight of Pt, 0.1 of boron
Using 100 g of mordenite containing 20% by weight and 0.1% by weight of magnesium, a cordierite-based monolith carrier (20
A catalyst P was obtained in the same manner as in Example 1 except that 0 cell / 10 mil, GSA 19.0 cm ² / cm ³ , hydraulic diameter 1.53 mm) were used. The coating amount was 200 g / L, the Pd loading amount was 11.1 g / cf (0.39 g / L), and the Pt loading amount was 3.7 g / cf (0.13 g / L).

Powder A 30 g, powder B 500 g, powder D 80 g, activated alumina 20 g, nitric acid aqueous solution 1000 g
Was charged into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid is attached to the catalyst P, and the excess slurry in the cell is removed by an air flow and dried to 400 ° C.
It was calcined for 1 hour to obtain a catalyst Q. The above powder F176g,
Powder H117g, Powder I177g and activated alumina 30
g, and 1000 g of nitric acid aqueous solution are put into a magnetic ball mill,
A slurry was obtained by mixing and pulverizing. This slurry liquid was attached to the catalyst Q, the excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Then
After the barium acetate solution was attached to the above-mentioned catalyst component-supporting cordierite monolithic carrier, it was baked at 400 ° C. for 1 hour to contain 10 g / L as BaO (catalyst R).
Coat amount 50 g / L (total weight 250 g / L-carrier), P
The carried amount of d is 251.2 g / cf (8.87 g / L),
Pt carrying amount 16.9 g / cf (0.60 g / L), Rh
The supported amount was 40.0 g / cf (1.42 g / L) (catalyst R).

Pre-catalyst Example 3 1324 g of powder B, 106 g of powder F, 27 g of powder H, 43 g of activated alumina, and 2000 g of nitric acid aqueous solution were put into a magnetic ball mill, and mixed and pulverized to obtain a slurry. This slurry liquid was used as a cordierite monolith carrier (1.0 L,
900 cells / 2 mil, GSA 43.6 cm ² / cm ³ ,
It was attached to a hydraulic diameter of 0.78 mm), excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Do this work twice, coat weight 150g /
An L-supported catalyst was obtained. Then, after a barium acetate solution was attached to the above catalyst, it was calcined at 400 ° C. for 1 hour, and Ba was used.
As O, 10 g / L was contained. The amount of palladium carried is 600.0 g / cf (21.2 g / L), the amount of platinum carried is 3.0 g / cf (0.11 g / L), and the amount of rhodium carried is 12.0 g / cf (0.42 g / L). (Catalyst S).

Reference Example 6 H-type β-zeolite 800 g, powder I 88.3 g, powder E 161.5 g, silica sol 1000 g (solid content 20)
%) And 1000 g of pure water were charged into a magnetic ball mill and mixed and pulverized to obtain a slurry. This slurry liquid was used as a cordierite monolith carrier (1.3 L, 200 cells / 10 mil, GSA 19.0 cm ² / cm ³ , hydraulic diameter 1.53).
mm), excess slurry in the cell was removed by an air flow, dried, and fired at 400 ° C. for 1 hour. A catalyst having a coat weight of 250 g / L-support was obtained (catalyst T).

The above-mentioned powder B 500 g, powder D 80 g, powder I 176.5 g, powder E 203 g, powder A 40 g, activated alumina 20 g and nitric acid aqueous solution 1000 g were put into a magnetic ball mill and mixed and pulverized to obtain a slurry. This slurry liquid was attached to the catalyst T, the excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Do this work twice, coat weight 100g / L
(Total weight 300 g / L-carrier), palladium loading is 2
40.0 g / cf (8.48 g / L) and the rhodium carrying amount obtained the catalyst U of 80.0 g / cf (2.83 g / L). Next, a barium acetate solution was attached to the catalyst U, followed by firing at 400 ° C. for 1 hour to obtain BaO of 10 g /
L was included (Catalyst V).

Comparative Example 7 Catalyst W was used in the same manner as in Reference Example 2 except that a cordierite monolithic carrier (1.3 L, 600 cells / 2 mil, GSA36.2 cm ² / cm ³ , hydraulic diameter 0.97 mm) was used.
Got

Comparative Example 8 Catalyst X was used in the same manner as in Reference Example 2 except that a cordierite monolith carrier (1.3 L, 900 cells / 4 mil, GSA41.1 cm ² / cm ³ , hydraulic diameter 0.74 mm) was used.
Got

Comparative Example 9 H-type β-zeolite 800 g, silica sol 1000 g
(Solid content 20%) and 1000 g of pure water were put into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid was used as a cordierite monolith carrier (1.3 L, 200 L).
(Cell / 10 mil, GSA 19.0 cm ² / cm ³ , hydraulic diameter 1.53 mm), the excess slurry in the cell was removed and dried by air flow, and the mixture was calcined at 400 ° C. for 1 hour. A catalyst Y having a coat weight of 20 g / L-support was obtained. A catalyst Z was obtained in the same manner as in Reference Example 2 except that the catalyst Y was used instead of the catalyst F.

Comparative Example 10 H-type β-zeolite 800 g, silica sol 1000 g
(Solid content 20%) and 1000 g of pure water were put into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid was used as a cordierite monolith carrier (1.3 L, 200 L).
(Cell / 10 mil, GSA 19.0 cm ² / cm ³ , hydraulic diameter 1.53 mm), the excess slurry in the cell was removed and dried by air flow, and the mixture was calcined at 400 ° C. for 1 hour. A catalyst AA having a coat weight of 300 g / L-support was obtained. Powder J (Alumina powder in which Pd is supported on Powder A, P
d concentration 50% by weight) 160.0 g, powder K (powder C to P
Cerium oxide powder carrying the d, Pd concentration of 28 wt%) 17 g, flour powder L (zirconium oxide powder supporting Rh in the powder G, Rh concentration of 25 wt%) 113.0 g,
10 g of activated alumina and 500 g of nitric acid aqueous solution were put into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid was attached to the catalyst AA, excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Do this work twice, coat weight 30g / L
(Total weight 330 g / L-carrier), palladium loading is 2
40.0 g / cf (8.48 g / L) and a rhodium carrying amount of the catalyst BB of 80.0 g / cf (2.83 g / L) were obtained. Next, a barium acetate solution was attached to the catalyst U, followed by firing at 400 ° C. for 1 hour to obtain BaO of 10 g /
A catalyst CC containing L was obtained.

Comparative Example 11 Powder B 659 g, Powder D 80 g, Powder I35.3
g, 206 g of powder A, 20 g of activated alumina, and 1000 g of aqueous nitric acid solution were put into a magnetic ball mill, and mixed and pulverized to obtain a slurry. This slurry liquid was attached to the catalyst F, the excess slurry in the cell was removed by an air flow, dried, and calcined at 400 ° C. for 1 hour. Do this work twice,
A catalyst DD having a coat weight of 100 g / L (total weight of 300 g / L-support) was obtained. The amount of palladium carried on the catalyst DD was 312.0 g / cf (11.02 g / L), and the amount of rhodium carried was 8.0 g / cf (0.28 g / L). Next, a barium acetate solution was attached to the catalyst DD, followed by firing at 400 ° C. for 1 hour to obtain BaO of 10 g / L.
As a result, the catalyst EE containing

Comparative Example 12 Powder B 162 g, powder D 80 g, powder I 15 g, powder A 723 g and activated alumina 20 g, nitric acid aqueous solution 100
0 g was put into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid was used as a cordierite monolith carrier (1.0 L, 900 cells / 2 mil, GSA43.6).
cm ² / cm ³ , hydraulic diameter 0.78 mm),
Excessive slurry in the cell is removed by air flow and dried.
It was baked at 00 ° C. for 1 hour. This operation was performed twice to obtain a catalyst having a coat weight of 100 g / L. The amount of palladium carried on the catalyst DD was 73.3 g / cf (2.59 g / L), and the amount of rhodium carried was 6.7 g / cf (0.24 g / L). Then, a barium acetate solution was attached to the above catalyst and then calcined at 400 ° C. for 1 hour to obtain BaO of 10 g / L.
As a result, the catalyst FF containing

Tables 5 and 6 show the specifications of the exhaust gas purifying catalysts obtained in Examples 21 and 22, Reference Examples 2 to 6, Precatalyst Examples 1 to 3 and Comparative Examples 7 to 12.

[0134]

[Table 5]

[0135]

[Table 6]

Test Examples Examples 21 and 22, Reference Examples 2 to 6, Pre-stage Catalyst Examples 1 to 1
3 and Comparative Examples 7 to 12 obtained exhaust gas purification catalyst,
Durability was performed under the following durability conditions. Endurance conditions Engine displacement 3000 cc Fuel unleaded gasoline Catalyst inlet gas temperature 700 ° C Endurance time 100 hours Inlet gas composition CO 0.5 ± 0.1% O2 0.5 ± 0.1% HC Approx. 1100 ppm NO 1300 ppm CO2 15% A / F fluctuation 5500 times (cycle 65 seconds / cycle) cycle: A / F = 14.65 55 seconds Fuel cut 5 seconds Rich spike 5 seconds (CO = 2%)

Using the catalysts of Examples 21 and 22, Reference Examples 2 to 6, pre-catalyst Examples 1 to 3 and Comparative Examples 7 to 12 which were durable under the above conditions, Examples 23 to 29, Reference Examples 7 to 19 and Comparative Examples For Examples 13 to 24, HC purification characteristic evaluation (EC mode, LA-4 A-bag) was performed using the system (exhaust gas purification device) of FIGS. The results are shown in Tables 7 to 10.

Performance evaluation conditions Catalyst capacity (one-sided bank) Three-way catalyst 2.0 L (1.0 L +
1.0L) + HC adsorption catalyst 1.3L to 2.6L Evaluation vehicle Nissan Motor Co., Ltd. V type 6
Cylinder 3.3L engine Hydrocarbons (in gas at catalyst inlet) exhausted at engine startup

[0139]

[Table 7]

[0140]

[Table 8]

[0141]

[Table 9]

[0142]

[Table 10]

[0143]

[Effects of the Invention] First, the effects of the present invention will be generally described. (1) Optimization of zeolite type In the HC adsorption catalyst using zeolite, H in the exhaust gas is
Since there is a correlation between the C type distribution and the pore size of the zeolite, it is necessary to select the zeolite having the optimum pore size. Conventionally, MFI (ZSM5) was mainly blended with a zeolite having another pore size (for example, USY, etc.) to adjust the pore size distribution. -Since the desorption characteristics are different, there is a problem that the adsorption of exhaust gas HC species is insufficient. In the present invention, by adopting β-zeolite having two types of pore diameters and having excellent durability as a main component, there is little distortion due to durability, and since the pore distribution can be widely maintained from the initial stage to the end stage, Adsorption / desorption characteristics are improved compared to the conventional one. Further, by combining two or more kinds of zeolite, an effect of further widening the distribution of the zeolite pore size can be obtained. That is, in the present invention, ZSM5
Since mordenite is used as the seed crystal of
The depth inside the pores is wider than that of M5. When this ZSM5 is used as an HC adsorbing material, the HC diffusion rate inside the pores is slow (when HC with a large molecular diameter arrives at the entrance of the pores, the diffusion of other HCs is hindered and the cold is efficiently and quickly obtained. Since HC cannot be adsorbed), the adsorption performance is poor.
However, the HC once diffused into the pores is difficult to escape to the outside (desorption is slow). In the present invention, this ZSM5
By combining and β-zeolite, we have developed an HC adsorbent for automobiles that has excellent adsorption-desorption characteristics.

(2) Optimization of ternary noble metal species (catalyst component species) Conventionally, specifications in which noble metal species such as Rh, Pt, and Pd coexist in the same layer, or specifications in which the Rh layer and the Pd layer are separately coated Etc. were proposed. In the present invention, Pd is formed on the zeolite layer.
A layer and an Rh layer are provided on the layer, and Pt can be added to either or both layers. By providing a Pd layer with excellent low temperature HC activity on the zeolite, the HC desorbed from the zeolite can be preferentially purified, and by providing the Rh layer on it, the atmosphere slightly shifts from the stoichiometric air-fuel ratio. Even if the generated gas flows, HC, CO, NOx
Can be purified in a good balance. Furthermore, by adding Pt, the poisoning resistance can be improved.

(3) Optimization of coat layer structure of zeolite layer + ternary precious metal layer Conventionally, the coat layer ratio of the zeolite layer (HC adsorbent layer) and the ternary layer (catalyst component layer) and the coat layer are carried. Although no particular mention was made of GSA as a monolith carrier,
The C adsorption catalyst has a problem that the cycle of HC adsorption / desorption / purification cannot be effectively performed unless the structures of the zeolite layer and the ternary layer are optimal. In the present invention, the weight ratio of the coat layers of the zeolite layer and the ternary layer is 9: 1 to 1: 4.
Of the monolithic carrier with a coating layer
By defining the SA in the range of ^{10cm 2 / cm 3 ~35cm 2 /} cm 3, the balance of the HC adsorption and desorption and purification is a good design. That is, if the ratio of the ternary layer to the zeolite layer is too large, the gas diffusion to the zeolite layer arranged in the lower layer becomes poor, and sufficient adsorption performance corresponding to the amount of zeolite cannot be obtained. on the other hand,
When the proportion of the ternary layer is small, the oxidizing performance of desorbed HC and the exhaust gas purification performance cannot be sufficiently obtained. Also, if GSA becomes too large, HC in the zeolite layer
The holding power becomes small, and sufficient purification performance cannot be obtained with the ternary layer placed above. Further, if the GSA is small, the exhaust gas purification performance cannot be sufficiently obtained.

The exhaust gas purifying catalyst according to claim 1 is H
The C, CO, and NOx purification performance can be performed with good balance. Further, in addition to the above effects, the diffusivity (speed) of the exhaust gas passing through the monolith carrier cell and diffusing into the coat layer can be controlled to improve the HC purification performance. Furthermore, H
The desorption of C can be delayed and the purification performance of HC can be improved. In addition to the above effects, the purification performance can be further improved and the deterioration of the catalyst performance due to the poisoning of the catalyst component can be suppressed.

In addition to the above effects, the exhaust gas purifying catalyst according to claim 2 can further delay the desorption of HC and improve the hydrocarbon purifying performance.

In addition to the above effects, the exhaust gas purifying catalyst according to claim 3 can further delay the desorption of HC and improve the hydrocarbon purifying performance.

The exhaust gas purifying catalyst according to claim 4 is H
The C, CO, and NOx purification performance can be performed with good balance. Further, in addition to the above effects, the diffusivity (speed) of the exhaust gas passing through the monolith carrier cell and diffusing into the coat layer can be controlled to improve the HC purification performance.

In addition to the above effects, the exhaust gas purifying catalyst according to claim 5 can further improve the HC purifying performance.

In addition to the above effects, the exhaust gas purifying catalyst according to claim 6 can further improve the HC purifying performance. Furthermore, since an alkali metal or an alkaline earth metal is contained, sintering of the noble metal is suppressed, so that low temperature activity and purification performance are further improved.

In addition to the above effects, the exhaust gas purifying catalyst according to claim 7 can effectively adsorb various kinds of HC.

In addition to the above effects, the exhaust gas purifying catalyst according to claim 8 has a wide range of adsorbable HC species,
More types of HC can be effectively adsorbed.

In addition to the above effects, the exhaust gas purifying apparatus according to claim 9 adsorbs HC species exhausted at a low temperature immediately after engine start with high efficiency by combining various HC adsorbents having different pore sizes. In addition, the HC adsorption capacity can be improved.

The exhaust gas purifying catalyst according to claim 10 is:
In addition to the above effects, the adsorption characteristics and the desorption suppressing ability can be further improved.

The exhaust gas purifying catalyst according to claim 11 is
Since the HC species discharged at low temperature immediately after the engine is started are adsorbed with high efficiency, and the structural change and performance deterioration after endurance are small, the desorption rate can be delayed.

The exhaust gas purifying catalyst according to claim 12 is
In addition to the above effects, the poisoning resistance can be further improved.

The exhaust gas purifying catalyst according to claim 13 is
In addition to the above effects, the purification performance of HC can be further improved.

The exhaust gas purifying catalyst according to claim 14 is
In addition to the above effects, it is possible to suppress deterioration of the catalyst performance due to a change in the chemical state of rhodium after endurance.

The exhaust gas purifying catalyst according to claim 15 is
In addition to the above effects, it is possible to suppress the deterioration of the catalyst performance due to the reduction of the catalyst component.

The exhaust gas purifying catalyst according to claim 16 is
In addition to the above effects, it is possible to suppress structural stability after endurance and deterioration of catalytic performance due to change in chemical state of palladium.

The exhaust gas purifying apparatus according to claim 17 is a combination of a Pd-containing catalyst excellent in low-temperature activity and the HC adsorbing catalyst of the present invention, and the amount of HC adsorbed by the HC adsorbing catalyst is exhausted at a low temperature immediately after engine startup. By setting the amount of HC to 10% to 70%, the purification performance of desorbed HC can be improved.

The exhaust gas purifying apparatus according to claim 18 is a combination of a Pd-containing catalyst excellent in low temperature activity and an HC adsorption catalyst,
The amount of HC adsorbed by the HC adsorbing catalyst is set to 30% to 70% of the amount of HC discharged at low temperature immediately after engine start,
Furthermore, by combining the following means for promoting early activation of the exhaust gas purification catalyst, H
It is possible to further reduce the amount of C and improve the purification performance of desorbed HC.

The exhaust gas purifying apparatus according to claim 19 is the exhaust gas purifying apparatus according to claim 22, wherein the Pd-containing catalyst (three-way catalyst) arranged before the HC adsorption catalyst can be activated early. , The purification performance of HC desorbing the HC adsorption catalyst can be improved.

The exhaust gas purifying apparatus according to claim 20 is the exhaust gas purifying apparatus according to claim 22, which is capable of activating the Pd-containing catalyst (three-way catalyst) arranged upstream of the HC adsorption catalyst in an early stage. , The purification performance of HC desorbing the HC adsorption catalyst can be improved.

The exhaust gas purifying apparatus according to claim 21 is H
Pd-containing catalyst (three-way catalyst) arranged upstream of the C adsorption catalyst
It is possible to improve the purification performance of the desorbed HC by promoting early activation and purification performance of the above.

In addition to the above effects, the exhaust gas purifying apparatus according to the twenty-second aspect can suppress the temperature drop of the catalyst component layer and efficiently purify the desorbed HC.

In addition to the above effects, the exhaust gas purifying apparatus according to the twenty-third aspect can suppress the temperature decrease of the catalyst component layer and efficiently purify desorbed HC.

In addition to the above effects, the exhaust gas purifying apparatus according to the twenty-fourth aspect can further suppress the temperature decrease of the catalyst component layer and improve the purifying performance, and can efficiently purify the desorbed HC.

In addition to the above effects, the exhaust gas purifying apparatus according to claim 25 can efficiently purify low-concentration exhaust gas components (HC, CO, NOx) that have not been purified by the Pd-containing catalyst in the preceding stage.

In addition to the above effects, the exhaust gas purifying apparatus according to the twenty-sixth aspect can further improve the adsorption / desorption / purification performance of HC and can efficiently purify desorbed HC.

In addition to the above effects, the exhaust gas purifying apparatus according to claim 27 can purify desorbed HC efficiently.

[Brief description of drawings]

FIG. 1A is a perspective view showing a washcoat layer structure of a catalyst of the present invention. (B) is a partially enlarged portion of (a).

FIG. 2 is a system (evaluation system 1) diagram showing an exhaust system of an engine used for evaluating the catalyst of the present invention.

FIG. 3 is a system (evaluation system 2) diagram showing an exhaust system of an engine used for evaluating the catalyst of the present invention.

FIG. 4 is a system (evaluation system 3) diagram showing an exhaust system of an engine used for evaluating the catalyst of the present invention.

FIG. 5 is a system (evaluation system 4) diagram showing an exhaust system of an engine used for evaluating the catalyst of the present invention.

FIG. 6 is a system (evaluation system 5) diagram showing an exhaust system of an engine used for evaluating the catalyst of the present invention.

FIG. 7 is a system (evaluation system 6) diagram showing an exhaust system of an engine used for evaluating the catalyst of the present invention.

FIG. 8 is a system (evaluation system 7) diagram showing an exhaust system of an engine used for evaluating the catalyst of the present invention.

FIG. 9 is a graph (map) showing the relationship between the amount of precious metal (PM) and the engine out mission remaining rate for each engine type.
Is.

FIG. 10 is a flow sheet for creating a noble metal selection map for a three-way catalyst.

FIG. 11 is a graph showing the relationship between the engine out emission remaining rate and time.

FIG. 12 is a lean time calculation flow sheet.

[Explanation of symbols]

1 Hydrocarbon adsorption layer (HC adsorbent layer) 2 Three-way catalyst layer (catalyst component layer) 3 gas passage 4 three-way catalyst 5 HC adsorption catalyst

Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI F01N 3/24 F01N 3/28 301J 3/28 301 B01D 53/36 104A (56) Reference JP-A-7-174017 (JP, A) Kai 63-224740 (JP, A) JP 63-113112 (JP, A) JP 7-256114 (JP, A) JP 78755 (JP, A) JP 7-97918 ( JP, A) JP 10-263364 (JP, A) JP 11-104462 (JP, A) JP 6-327978 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01J 21/00-38/74 B01D 53/94

Claims (27)

(57) [Claims] 1. GSA is 10 cm ² / cm ^{3 to} 35 cm
^An exhaust gas purifying catalyst, comprising a hydrocarbon adsorbent layer containing a hydrocarbon adsorbent, a catalyst component layer containing a catalyst component, and an upper catalyst component layer, which are coated in this order on a monolithic carrier of ² / cm ³ . The hydrocarbon adsorbent of the HC adsorbent layer contains zeolite as a main component, and the catalyst component layer includes palladium (Pd) and platinum (Pt)
And at least one noble metal selected from the group consisting of rhodium (Rh) as a catalyst component and at least Pd among them, and the upper catalyst component layer contains zirconium oxide and activated alumina. Things are Pt, Rh,
1 to 30 mol% of metal selected from the group consisting of Ce, Nd and La and 70 to 98 mol% of Zr are included in terms of metal, and the weight ratio of the HC adsorbent layer to the catalyst component layer is 9: 1.
˜1: 4, and the coat layer thickness is 30 μm to 400 μm, which is the total thickness of the HC adsorbent layer and the catalyst component layer in the flat portion in the cell of the monolith carrier, Gas purification catalyst. 2. The exhaust gas purifying catalyst according to claim 1, wherein the number of cells per square inch of the monolith carrier is 50 to 600. 3. The monolith carrier has a hydraulic diameter of 0.75.
The exhaust gas purifying catalyst according to claim 1 or 2, wherein the catalyst has a diameter of 5 mm to 5 mm. 4. The exhaust gas purification catalyst according to claim 1, wherein the zeolite is β-zeolite. 5. The exhaust gas purifying catalyst according to claim 4, wherein the weight ratio of the HC adsorbent layer to the catalyst component layer is 5: 1 to 1: 2. 6. The upper catalyst component layer contains Rh,
The weight ratio of (HC adsorbent layer) to (catalyst component layer + upper catalyst component layer) is 5: 1 to 1: 2, and an alkali metal and / or an alkaline earth metal is further added to the HC adsorbent layer and the catalyst. The exhaust gas purifying catalyst according to claim 4 or 5, wherein the catalyst is contained in at least one of the component layer and the upper catalyst component layer. 7. The exhaust gas purifying apparatus according to claim 4, wherein the β-zeolite is an H-type β-zeolite having a Si / 2Al ratio of 10 to 500. catalyst. 8. The HC adsorbent layer further comprises at least one selected from the group consisting of MFI zeolite, Y-type zeolite, USY zeolite, A-type zeolite, X-type zeolite, mordenite, ferrierite, AlPO ₄ and SAPO. The exhaust gas purifying catalyst according to claim 7, wherein the exhaust gas purifying catalyst is contained. 9. The HC adsorbent layer contains 5 to 45% by weight of at least one selected from the group consisting of MFI zeolite, Y-type zeolite, USY zeolite, and mordenite. Exhaust gas purification catalyst. 10. The zeolite of the HC adsorbent layer comprises P
d, Mg, Ca, Sr, Ba, Ag, Y, La, Ce,
The exhaust gas purifying catalyst according to claim 1, wherein at least one selected from the group consisting of Nd, P, B and Zr is contained. 11. The hydrocarbon adsorbent comprises Pt, Pd,
The exhaust gas catalyst according to any one of claims 1 to 10, which contains at least one selected from the group consisting of P, B, Mg, and Ca. 12. The exhaust gas purifying catalyst according to claim 6, wherein Pt is further allowed to coexist in at least one of the catalyst component layer and the upper catalyst component layer. 13. The HC adsorbent layer contains Rh and zirconium oxide containing at least 1 to 40 mol% in terms of metal of at least one selected from the group consisting of Ce, Nd and La. Any one of claims 1 to 12
An exhaust gas purifying catalyst according to one of the items. 14. The upper catalyst component layer further comprises Ce and / or
Alternatively, the exhaust gas purifying catalyst according to any one of claims 1 to 13, further comprising a zirconium oxide containing 1 to 40 mol% of La in terms of metal. 15. The catalyst component layer comprises Zr, Nd and L.
The cerium oxide containing 1 to 40 mol% and 60 to 98 mol% of Ce in terms of metal of one selected from the group consisting of a is contained.
An exhaust gas purifying catalyst according to one of the items. 16. The catalyst component layer comprises Ce, Zr and L.
Alumina containing at least one selected from the group consisting of a in the range of 1 to 10 mol% in terms of metal, and cerium oxide containing 1 to 40 mol% in the range of metal selected from the group consisting of Zr, Nd and La. The exhaust gas purifying catalyst according to any one of 1 to 15 is further contained. 17. An exhaust gas purifying catalyst according to any one of claims 1 to 16, wherein Pd, Pd and P
t or Pd-supporting powder containing Pd and Rh and having a Pd-supporting concentration of 4 to 20% by weight, and containing Pd per 1 L of catalyst.
Carrying amount is 100 g / cf (3.5 g / L) to 1000 g
/ Cf (35.4 g / L) of the Pd-containing catalyst is arranged, and the amount of hydrocarbons adsorbed by the exhaust gas purification catalyst is set to 70% or less of the saturated hydrocarbon adsorption amount of the exhaust gas purification catalyst. An exhaust gas purification device characterized in that 18. The Pd-supporting concentration of the Pd-supporting powder is 4
˜15% by weight, the Pd supported amount of the Pd-containing catalyst is 100
g / cf (3.5 g / L) to 500 g / cf (17.7)
The exhaust gas purifying apparatus according to claim 17, wherein the exhaust gas purifying apparatus is g / L). 19. The ignition timing at the time of engine starting (first idle) mounted on an automobile engine is 40 seconds or less immediately after the engine is started, and 1 ° to the top dead center.
The exhaust gas purifying apparatus according to claim 17 or 18, wherein the retardation of 30 ° accelerates the rise in exhaust temperature and accelerates the activation of the Pd-containing catalyst. 20. An automobile engine is mounted, and air having an air flow rate of 10 L / min or more is supplied for 60 seconds immediately after starting the engine, and the cold air-fuel ratio immediately after starting the engine is A /
19. The exhaust gas purifying apparatus according to claim 17, wherein the activation of the Pd-containing catalyst is accelerated by diluting it to F = 12 to 18. 21. Oxygen and / or air is added immediately upstream of the exhaust gas purifying catalyst or into the exhaust gas purifying catalyst immediately before the desorption of hydrocarbons from the exhaust gas purifying catalyst is started. The exhaust gas purification device according to any one of claims 17 to 20, characterized in that. 22. A temperature detector is added near the inlet of the exhaust gas purifying catalyst, and an A / F detector is added near the outlet, and the A / F detector is used when the detected value of the temperature detector reaches 110 ° C. or higher.
22. Oxygen and / or air is added upstream of the exhaust gas purifying catalyst or in the exhaust gas purifying catalyst so that the F detector is 14.6 or more.
Exhaust gas purifier according to. 23. A temperature detector is added to the catalyst component layer of the exhaust gas purifying catalyst, and an A / F detector is added near the outlet, and when the detected value of the temperature detector reaches 110 ° C. or above, 22. Oxygen and / or air is added upstream of the exhaust gas purifying catalyst or in the exhaust gas purifying catalyst so that the A / F detector is 14.6 or more. Exhaust gas purification device described. 24. An A / F detector is added near the inlet and the outlet of the exhaust gas purifying catalyst, and hydrocarbons are desorbed from the detected values of the A / F detectors installed near the inlet and the outlet. Is detected, so that the A / F detector disposed near the outlet has A / F = 14.6 or more, upstream of the exhaust gas purifying catalyst or in the exhaust gas purifying catalyst,
The exhaust gas purification device according to claim 21, wherein oxygen and / or air is added. 25. The Pd-containing catalyst and the exhaust gas purifying catalyst contain Rh, and the Rh content of the Pd-containing catalyst is less than or equal to the Rh content of the exhaust gas purifying catalyst. The exhaust gas purifying apparatus according to any one of 17 to 24. 26. A contract is provided downstream of the exhaust gas purifying catalyst.
Exhaust gas purification according to any one of claims 1 to 16
The exhaust gas purifying apparatus according to any one of claims 17 to 25, characterized in that at least one catalyst for use is added. 27. The exhaust gas purifying catalyst, and the one or more other exhaust gas purifying catalysts are provided at positions different in distance from the engine in which they are mounted. Exhaust gas purification device described.