JPH0557148A - Catalyst device for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To obtain a catalyst device for purifying exhaust gas which has sufficient purification capacity of hydrocarbon to purify the exhaust gas of an internal combustion engine. CONSTITUTION:A catalyst device for purifying exhaust gas is equipped with both an adsorbent layer 1 formed of zeolite used as the adsorbing and modifying agent of hydrocarbon in the upstream side of exhaust gas flow and a catalytic layer 2 formed of inorganic substance containing a catalytically active component in the downstream side. The said catalyst device is constituted by arranging at least two pieces of catalysts respectively equipped with the same honeycomb carrier as the adsorbent layer 1 and the catalyst layer 2 in a straight row state to the upstream side and the downstream side of exhaust gas flow. Or the honeycomb carrier equipped with the adsorbent layer 1 is provided to the upstream side of the exhaust gas flow and the other honeycomb carrier equipped with the catalyst layer 2 is provided to the downstream side. Furthermore the adsorbent layer 1 is constituted of both a zeolite layer 5 in the upstream side of the exhaust gas flow and a zeolite layer 6 different therefrom in the downstream side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst device for purifying exhaust gas of an internal combustion engine.

[0002]

2. Description of the Related Art Exhaust gas purifying catalysts are currently used for purifying exhaust gas from internal combustion engines, and many catalysts have been proposed. These catalysts are arranged and used in an exhaust gas purifying catalyst device. Under such circumstances, improvement in exhaust gas purification performance of hydrocarbons, which are harmful components of exhaust gas, is required from the viewpoint of environmental problems.

[0003]

The purification ability of hydrocarbons is strongly influenced by the temperature of gas and the species of hydrocarbons. With conventional exhaust gas purification catalyst devices that use only precious metal catalysts, sufficient purification performance of hydrocarbons can be obtained due to the effects of exhaust gas temperature and hydrocarbon species due to differences in engine combustion conditions. There was a problem of not having.

[0004]

The present invention has been made in view of the above-mentioned conventional problems, and is a hydrocarbon adsorbing and reforming material at the front portion of the honeycomb carrier, that is, at the upstream side of the exhaust gas flow. As a catalyst, the rear part, that is, the downstream side of the exhaust gas flow is coated with an inorganic substance containing a catalytically active component to form a catalyst, and two or more of the catalysts are arranged in series to form a catalyst device for exhaust gas purification. Alternatively, the front part of the honeycomb carrier, that is, the upstream side of the exhaust gas flow is coated with zeolite for adsorbing and reforming hydrocarbons, and the rear part, that is, the downstream side of the exhaust gas flow, is different in hydrocarbon adsorption and reforming properties from the front part. Sufficient hydrocarbon purification capacity is obtained by coating another zeolite carrier having a catalyst layer with a catalyst layer on the downstream side of the exhaust gas flow to form an exhaust gas purification catalyst device. One exhaust gas purifying catalyst device can be found that the resulting leading to achieve the present invention.

[0005]

In order to purify the exhaust gas of an internal combustion engine, an exhaust gas purifying catalyst is currently used. However, as mentioned above, the purifying ability of hydrocarbons in the exhaust gas depends on the temperature of the gas and the type of hydrocarbon species. Strongly affected. With conventional exhaust gas purification catalyst devices that use only precious metal catalysts, sufficient purification performance of hydrocarbons can be obtained due to the effects of exhaust gas temperature and hydrocarbon species due to differences in engine combustion conditions. There was a problem of not having.

In the exhaust gas purifying catalytic device according to the first aspect of the present invention, the adsorption of hydrocarbons on the upstream side of the exhaust gas flow, the adsorbent layer region made of zeolite as a modifier, and the catalyst on the downstream side. In an exhaust gas purifying catalyst device having a catalyst layer region made of an inorganic material containing an active component, a catalyst having an adsorbent layer and a catalyst layer respectively on the upstream side and the downstream side of the exhaust gas flow of the same honeycomb carrier, The exhaust gas purifying catalyst device includes two or more arranged in series.

FIG. 1 is a view showing an exhaust gas purifying catalyst device according to an example of the first invention. The illustrated device is one in which two catalysts are arranged in series, and 1 is an adsorbent layer of the first catalyst, 2 is the first
Catalyst layer of the above catalyst, 3 is the adsorbent layer of the second catalyst, and 4 is the second
3 shows a catalyst layer of the above catalyst.

In the second invention, a honeycomb carrier having an adsorbent layer is provided on the upstream side of the exhaust gas flow, another honeycomb carrier having a catalyst layer is provided on the downstream side, and the adsorbent layer is further provided. The catalyst device for purifying exhaust gas comprises a zeolite layer on the upstream side of the exhaust gas flow and a zeolite layer on the downstream side different from the zeolite layer. FIG. 2 is a view showing a honeycomb carrier provided with an adsorbent layer of an exhaust gas purifying catalyst device of an example of the second invention. 5 is a zeolite layer on the exhaust gas upstream side, and 6 is a zeolite layer on the exhaust gas downstream side. ..

Zeolite has the ability to adsorb hydrocarbons, and its adsorption characteristics differ depending on the type of zeolite and the type of element that performs ion exchange. Further, zeolite has not only the ability to adsorb hydrocarbons but also the property of reforming hydrocarbons, and this also varies depending on the type of zeolite and the type of element for ion exchange.

In the apparatus of the present invention, the reforming and adsorbent using zeolite is arranged in front of the noble metal catalyst, that is, upstream of the exhaust gas flow, so that hydrocarbons in the exhaust gas discharged from the engine are modified. When the gas temperature is low in the quality and adsorbent portions, it is removed by adsorption, and when the gas temperature rises, it is reformed into hydrocarbon species that are easily reacted by the noble metal catalyst to improve hydrocarbon purification ability. Also, since it is used in combination of two or more using different zeolites, it can handle a wide range of hydrocarbon species in exhaust gas,
It contributes to the improvement of hydrocarbon purification ability in a wide range.

[0011]

EXAMPLES The present invention will be described below with reference to examples and comparative examples. Example 1 A dinitrodiamine platinum nitric acid solution was sprayed with stirring while stirring activated alumina powder (BET specific surface area 120 m ² / g) carrying 3% by weight of Ce and thermally stabilized, and then dried in air.
It was calcined at 0 ° C. for 2 hours to obtain platinum-supported alumina having a platinum-supported amount of 1.0% by weight. Further, using a rhodium nitrate solution and activated alumina powder (BET specific surface area 120 m ² / g), a rhodium-supported alumina powder having a rhodium-supported amount of 1.0% by weight was obtained in the same manner.

1,266 g of the above platinum-supported alumina powder, 126 g of rhodium-supported alumina powder, 384 g of CeO ₂ powder, and nitric acid-acidified alumina sol (sol obtained by adding 10% by weight nitric acid aqueous solution to a 10% by weight suspension of boehmite alumina) 2,22
2 g was put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. Using this slurry, in the same manner for two cordierite monolithic carriers, a step of immersing only the rear part, air-blowing to remove excess slurry and drying, and then firing in air at 400 ° C for 2 hours. Repeated three times, a catalyst coat layer having a coat amount of about 270 g / L was obtained.

Further, the front part of one of the above-mentioned coated carriers was 1800 g of mordenite powder and silica sol.
(170% of solid content) 1.170 g of water and 1,170 g of water were put into a magnetic ball mill, immersed in a mixed and pulverized slurry liquid, and then the excess slurry was removed by air blow and dried,
The catalyst No. 1A was prepared by repeating the process of baking in air at 400 ° C. for 2 hours three times so that the coating amount was about 270 g / L.

With respect to the monolith carrier coated only with the above-mentioned precious metal slurry, the front part was 1,800 g of ZSM-5 zeolite powder, 1,170 g of silica sol (solid content 20%),
And 1.170 g of water are put in a magnetic ball mill, immersed in a slurry liquid which has been mixed and pulverized, the excess slurry is removed by air blow and dried, and then the process of firing in air at 400 ° C. for 2 hours is repeated 3 times. Catalyst No. 1 B was prepared by coating so that the amount was about 270 g / L.

A catalyst device 1 was obtained by arranging the prepared catalyst 1A in front with the prepared catalyst 1A in front.

Example 2 As one zeolite powder, Y was used instead of mordenite.
No. 1 of the catalyst device of Example 1 except that the zeolite of the type is used
A catalyst device 2 was prepared in the same manner as in. In the same manner as in Example 1, with respect to one carrier coated with a noble metal catalyst, 1,800 g of Y-type zeolite powder, 1,170 g of silica sol (solid content 20%), and 1,170 g of water were charged into a magnetic ball mill and mixed in the front part. After immersing in the crushed slurry liquid and removing excess slurry by air blow and drying,
Catalyst No. 2A was prepared by repeating the process of baking in air at 400 ° C. for 2 hours three times so that the coating amount was about 270 g / L.

Another coated carrier was coated with ZSM-5 zeolite in the same manner as in Example 1 to prepare catalyst No. 2.
B was prepared. The prepared catalyst No. 2A was arranged in series so that the catalyst device 2 was obtained.

Example 3 Catalyst device No. 3 was prepared in the same manner as catalyst device No. 1 of Example 1 except that X-type zeolite was used instead of mordenite as one zeolite powder. In the same manner as in Example 1, with respect to one carrier coated with a noble metal catalyst, 1.800 g of X-type zeolite powder, 1,170 g of silica sol (solid content 20%), and 1,170 g of water were charged into a magnetic ball mill and mixed in the front part. After immersing in the crushed slurry liquid and removing excess slurry by air blow and drying,
Catalyst No. 3A was prepared by repeating the process of firing in air at 400 ° C. for 2 hours three times so that the coating amount was about 270 g / L.

Another coated carrier was coated with ZSM-5 zeolite in the same manner as in Example 1 to prepare catalyst No. 3
B was prepared. The prepared catalyst No. 3A was placed in front with the catalyst No. 3A arranged in series to obtain a catalyst device 3.

Example 4 In the same manner as in Example 1, a slurry containing mordenite and ZSM-5 was prepared, and mordenite was coated on the front part of the monolith carrier and ZSM-5 on the rear part thereof to prepare catalyst No. 4A.
A slurry containing a noble metal similar to that in Example 1 was prepared and the entire monolith carrier was coated to prepare catalyst No. 4B.

The prepared catalyst No. 4A was placed in front with the catalyst No. 4A in front so as to obtain a catalyst device 4.

Example 5 In the same manner as in Example 2, a slurry containing Y-type zeolite and ZSM-5 was prepared and Y-zeolite was coated on the front part of the monolith carrier and ZSM-5 on the rear part to prepare catalyst No. 5A. did. A slurry containing a noble metal similar to that in Example 1 was prepared and the entire monolith carrier was coated to prepare catalyst No. 5B.

The prepared catalyst No. 5A was placed in front with the catalyst No. 5A in front to obtain a catalyst device 5.

Example 6 A slurry containing X-type zeolite and ZSM-5 was prepared in the same manner as in Example 3, and the front of the monolith carrier was coated with X-type zeolite and the rear was coated with ZSM-5 to prepare catalyst No. 6A. Prepared. A slurry containing a precious metal similar to that in Example 1 was prepared, and the entire monolith carrier was coated to prepare catalyst No. 6B.
Was prepared.

The prepared catalyst 6A was placed in front with the prepared catalyst 6A in front to obtain a catalyst device 6.

Example 7 A dinitrodiamine-palladium solution was sprayed while stirring activated alumina powder (BET specific surface area 120 m ² / g) thermally stabilized with 3% by weight of Ce as a carrier, dried and then in air.
It was calcined at 400 ° C. for 2 hours to obtain a palladium-supported alumina powder having a palladium-supporting amount of 1.0% by weight. Also, rhodium nitrate solution, activated alumina powder (BET ratio surface 120 m ² / g)
In the same manner as above, a rhodium-supported alumina powder having a rhodium-supported amount of 1.0 wt% was obtained.

The above-mentioned palladium-supported alumina powder 1266
g, rhodium-supported alumina powder 126 g, CeO ₂ powder 38
4 g and nitric acid acidic alumina sol (boehmite alumina
2,222 g of a sol obtained by adding a 10 wt% nitric acid aqueous solution to a 10 wt% suspension was put into a magnetic ball mill, and mixed and ground to obtain a slurry liquid. Using this slurry, in the same manner for two cordierite monolithic carriers, a step of immersing only the rear part, air-blowing to remove excess slurry and drying, and then firing in air at 400 ° C for 2 hours. Repeated three times, a catalyst coat layer having a coat amount of about 270 g / L was obtained.

Further, the front part of one of the above coated carriers was charged with 1,800 g of mordenite powder, 1,170 g of silica sol (solid content of 20%), and 1,170 g of water in a magnetic ball mill and immersed in a slurry mixed and ground. After removing excess slurry with air blow and drying, 400
The process of baking in air at ℃ for 2 hours was repeated 3 times to coat the catalyst so that the coating amount would be about 270 g / L.
No. 7A was prepared.

With respect to the monolith carrier coated only with the above-mentioned precious metal slurry, the front part was 1,800 g of ZSM-5 zeolite powder and 1,170 of silica sol (solid content 20%).
g and 1,170 g of water are put into a magnetic ball mill, immersed in a slurry liquid that has been mixed and pulverized, the excess slurry is removed by air blow, the product is dried, and then the product is baked in air at 400 ° C. for 2 hours three times. Repeat coat amount is about 270g / L
Was coated to prepare Catalyst No. 7B.

The catalyst No. 7A thus prepared was placed in front with the catalyst No. 7A in front to obtain a catalyst device 7.

Example 8 Catalyst device No. 7 of Example 7 except that Y-type zeolite was used instead of mordenite as one of the zeolite powders.
A catalyst device 8 was prepared in the same manner as in. In the same manner as in Example 7, with respect to one of the carriers coated with a noble metal catalyst, 1,800 g of Y-type zeolite powder, 1,170 g of silica sol (solid content 20%), and 1,170 g of water were introduced into a magnetic ball mill and mixed in the front part. After immersing in the crushed slurry liquid and removing excess slurry by air blow and drying,
Catalyst No. 8A was prepared by repeating the process of baking in air at 400 ° C. for 2 hours three times so that the coating amount was about 270 g / L.

The other coated carrier was coated with ZSM-5 zeolite in the same manner as in Example 1 to prepare catalyst No.
8B was prepared. The prepared catalyst No. 8A was arranged in series so that the catalyst No. 8A was placed in front and the catalyst device 8 was obtained.

In the above-mentioned examples, examples were shown in which mordenite, Y-type zeolite and X-type zeolite were used as zeolites, but as other zeolites 2-10Å
Any zeolite having a pore size of can be used in the same manner. As zeolite, metals such as copper, iron, zinc, manganese, cobalt and nickel, or Pd, Pt, Rh.
Similar effects can be obtained by using zeolite that has been subjected to ion exchange using a noble metal solution such as.

Comparative Examples 1 to 4 As comparative examples, the catalyst apparatus No. 101 of Comparative Example 1 using only the catalyst 1A of the catalyst apparatus 1 and the catalyst apparatus No. of Comparative Example 2 using only the catalyst 4B of the catalyst apparatus 4 were used. 401 and the catalyst 4 of the catalyst device 4
Comparative Example 3 in which only model night was coated as A
A catalyst device No. 701 of Comparative Example 4 using only the catalyst device No. 402 and the catalyst device No. 7A of the catalyst device 7 was prepared.

Regarding the catalysts of the above Examples and Comparative Examples, HC purification by LA-4 mode emission showing the HC emission characteristics of FIG. 3 and Table 1 using a vehicle (Cedric displacement 2000 cc manufactured by Nissan Motor Co., Ltd.) The results of evaluation of the rate are shown in Table 2.

[0036]

[0037]

[0038]

As described above, according to the present invention, the adsorption of hydrocarbons on the upstream side of the exhaust gas flow, the adsorbent layer region made of zeolite as a modifier, and the catalytically active component on the downstream side. In an exhaust gas purifying catalyst device having a catalyst layer region composed of an inorganic substance containing, a catalyst having an adsorbent layer and a catalyst layer on the upstream side and the downstream side of the exhaust gas flow of the same honeycomb carrier, respectively, in series Or two or more of them are used as exhaust gas purifying catalyst devices, or a honeycomb carrier having an adsorbent layer is provided on the upstream side of the exhaust gas flow, and another honeycomb carrier having a catalyst layer is provided on the downstream side. In addition, the adsorbent layer is a catalyst device for purifying exhaust gas, which comprises a zeolite layer on the upstream side of the exhaust gas flow and a zeolite layer on the downstream side, which is different from this, so that exhaust gas with sufficient hydrocarbon purification capacity Touch for gas purification It is possible to provide a device.

[Brief description of drawings]

FIG. 1 is a layout view of an exhaust gas purifying catalyst device according to an example of a first invention.

FIG. 2 is a layout view of a honeycomb carrier provided with an adsorbent layer of an exhaust gas purifying catalyst device according to an example of a second invention.

FIG. 3 is a diagram showing an HC emission state of LA-4 mode operation in an HC purification rate measurement test of catalysts of Examples and Comparative Examples.

[Explanation of symbols]

 1 Adsorbent layer of 1st catalyst 2 Catalyst layer of 1st catalyst 3 Adsorbent layer of 2nd catalyst 4 Catalyst layer of 2nd catalyst 5 Zeolite layer on exhaust gas upstream side 6 Zeolite layer on exhaust gas downstream side

Claims (2)

[Claims] 1. Adsorption of hydrocarbons upstream of the exhaust gas stream,
In an exhaust gas purifying catalyst device having an adsorbent layer region made of zeolite as a modifier and a catalyst layer region made of an inorganic substance containing a catalytically active component on the downstream side, the adsorbent layer and the catalyst layer are the same honeycomb. An exhaust gas purifying catalyst device, characterized in that two or more catalysts provided on the upstream side and the downstream side of an exhaust gas flow of a carrier are arranged in series. 2. The exhaust gas purifying catalyst device according to claim 1, wherein a honeycomb carrier having an adsorbent layer is provided on the upstream side of the exhaust gas flow, and another honeycomb carrier having a catalyst layer is provided on the downstream side. An exhaust gas purifying catalyst device further characterized in that the adsorbent layer comprises a zeolite layer on the upstream side of the exhaust gas flow and a zeolite layer on the downstream side different from this.