JPH05138042A - Metal carrier catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To obtain a catalytically active state by a reduced quantity of power in a metal carrier catalyst for purifying exhaust gas, by providing a device supplying a current to a metal carrier and providing a part where the resistance of the current supply route of the metal carrier becomes locally large on the inflow side of exhaust gas. CONSTITUTION:In a metal carrier catalyst for purifying exhaust gas consisting of a metal carrier composed of an outer cylinder 3 in which a honeycomb body 1 constituted of metal foil is inserted, the catalyst support layer formed to the surface of said carrier and the catalyst metal supported on the catalyst support layer, a device consisting of a power supply 4 supplying a current to the metal carrier and a lead is provided and a part where the resistance of the current supply route of the metal carrier becomes locally large is provided on the inflow side of exhaust gas. Since heat generation is concentrated and large heat value is obtained by increasing local resistance, a part reaching active temp. at an early state is generated. The exhaust gas passes through said and the heat exchange with the exhaust gas is generated to heat the whole of the catalyst.

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 metal carrier catalyst arranged in an exhaust system of an internal combustion engine such as an automobile engine to purify exhaust gas.

[0002]

2. Description of the Related Art An automobile is equipped with an exhaust gas purifying catalyst in its exhaust system in order to purify exhaust gas from an engine. This catalyst is used for unburned hydrocarbons (H
C), carbon monoxide (CO), nitrogen oxides (NOx) and other harmful components are purified by oxidation or reduction.
The purification efficiency of the catalyst is increased as the temperature of the catalyst rises, and particularly high purification efficiency is exhibited when the temperature exceeds the activation temperature. Generally, the catalyst obtains heat from the exhaust gas passing through the catalyst and is transferred to the entire catalyst by the heat transfer between the exhaust gas and the catalyst to be warmed up. There are two types of catalysts, ceramic-made catalysts and metal-supported catalysts.
Due to its high thermal conductivity, the temperature rises relatively quickly and the time to reach the activation temperature is short. However, when the exhaust gas temperature is low, such as when the engine is started, the catalyst does not reach the activation temperature and the purification efficiency is low. Therefore, conventionally, there is a metal-supported catalyst that efficiently purifies the exhaust gas by heating the catalyst without waiting for the temperature of the exhaust gas to rise so that the catalyst reaches the activation temperature quickly when the engine is started. For example, in Japanese Utility Model Laid-Open No. 63-67609, a metal-supported catalyst is arranged upstream of a ceramic catalyst, and one electrode is provided at the center of the metal-supported catalyst for energization, and an outer cylinder of the metal-supported catalyst is provided. Is used as the other electrode, and a metal carrier catalyst that generates heat by applying a voltage to the electrode at the same time when the engine is started and energizing the electrode is disclosed.

[0003]

In the metal-supported catalyst as described above, a current flows radially from the center of the cross-section of the metal-supported catalyst to the outer periphery, and the resistance gradually increases from the center of the cross-section to the outer periphery. It is getting smaller. Since the calorific value generated in each part of the metal-supported catalyst is proportional to the resistance in each part, in the structure as described above, the calorific value obtained for the whole metal-supported catalyst gradually decreases from the central part of the cross section toward the outer periphery and becomes smaller. Therefore, it consumes a lot of power to obtain the activation temperature. By the way, the heat generated by the heat generation causes the reaction heat of the catalyst and is also transferred to the catalyst by the heat transfer between the catalyst and the exhaust gas to warm up the catalyst, so that the catalyst can obtain the heat generation amount until the local temperature reaches the activation temperature. For example, the calorific value of other parts may be small. The present invention has been made in view of such circumstances, and instead of dispersing the heat generated in the metal-supported catalyst, locally increasing the electric resistance in the energization path of the metal-supported catalyst to locally The purpose of the present invention is to concentrate heat generation on the catalyst to reach the activation temperature of the catalyst at an early stage and to obtain the catalyst activated state with a small amount of electric power.

[0004]

As a first means for solving the problems according to the present invention, a metal carrier having a honeycomb shape, a carrier layer formed on the surface of the metal carrier, and a carrier layer supported on the metal carrier are provided. In a metal carrier catalyst for exhaust gas purification consisting of a catalyst metal, a device for energizing the metal carrier is provided, and a portion in which a resistance of a current path of the metal carrier locally increases on an exhaust gas inflow side is characterized in that And Here, the exhaust gas inflow side refers to a portion other than the end surface of the metal carrier on the exhaust gas outflow side.

As a second means for solving the problems according to the present invention, a metal carrier having a honeycomb shape, a carrier layer formed on the surface of the metal carrier, and a catalyst metal supported on the metal carrier. In the exhaust gas purifying metal carrier catalyst, the device is provided with a device for energizing the metal carrier, and a hole or slit is provided on the exhaust gas inflow side so that the resistance of the energizing path of the metal carrier is locally increased. Is characterized by. Here, the exhaust gas inflow side refers to a portion other than the end surface of the metal carrier on the exhaust gas outflow side.

As a third means for solving the problems according to the present invention, a metal carrier having a honeycomb shape, a carrier layer formed on the surface of the metal carrier, and a catalyst metal supported on the metal carrier. In a metal carrier catalyst for exhaust gas purification, which comprises a device for energizing the metal carrier, a portion where the thickness of the metal foil is changed so that the resistance of the energizing path of the metal carrier locally increases on the exhaust gas inflow side. Is provided. Here, the exhaust gas inflow side refers to a portion other than the end surface of the metal carrier on the exhaust gas outflow side.

As a fourth means for solving the problems according to the present invention, a honeycomb shape constituted by stacking and winding a metal flat plate and a corrugated plate, and a flat plate or only a corrugated plate are wound. A metal carrier having a composed part,
A metal carrier for exhaust gas purification, comprising a carrier layer formed on the surface of the metal carrier and a catalyst metal supported on the carrier layer, comprising a device for energizing the metal carrier in the winding axis direction. The exhaust gas outflow side has a honeycomb shape, and at least a part of the exhaust gas inflow side is wound with only a flat plate or a corrugated plate.

In the invention according to claim 1 of the present invention, the current-carrying path on the metal-supported catalyst has a portion where the resistance locally increases. When the resistance is large, the amount of heat generated is large, and when the resistance is small, the amount of heat generated is small. That is, by increasing the local resistance, heat generation is concentrated and a large amount of heat generation is obtained, so that a portion that reaches the activation temperature early is generated. Then, since the exhaust gas passes through that portion, heat exchange between the exhaust gas and the catalyst occurs, and the entire catalyst is warmed up.

Further, in the invention according to claim 2 of the present invention, the area of the current-carrying path in this portion is reduced by the hole or slit provided in a part of the current-carrying path. Therefore, the resistance of the peripheral portion is locally increased, heat generation is concentrated, and a large amount of heat generation is obtained, so that a portion that reaches the activation temperature early is generated. Then, since the exhaust gas passes through that portion, heat exchange between the exhaust gas and the catalyst occurs, and the entire catalyst is warmed up.

In the invention according to claim 3 of the present invention, the area of the current-carrying path is reduced by changing the thickness of the foil constituting the metal carrier in a part of the current-carrying path on the metal-support catalyst. Occurs. Therefore, the resistance of the peripheral portion is locally increased, heat generation is concentrated, and a large amount of heat generation is obtained, so that a portion that reaches the activation temperature early is generated. Then, since the exhaust gas passes through that portion, heat exchange between the exhaust gas and the catalyst occurs, and the entire catalyst is warmed up.

In the invention according to claim 4 of the present invention, the metal carrier catalyst is energized in the winding axis direction,
A part of the path is a part in which only a flat plate or a corrugated plate is wound, that is, a part having a small surface area. Therefore, the resistance of the portion having a small surface area locally increases, heat generation is concentrated, and a large amount of heat generation is obtained, so that a portion that reaches the activation temperature early is generated. Then, since the exhaust gas passes through that portion, heat exchange between the exhaust gas and the catalyst occurs, and the entire catalyst is warmed up.

[0011]

Embodiments will be specifically described below with reference to embodiments. (Example 1) Fig. 1 shows a schematic view of a metal-supported catalyst of this example. Although not shown, this metal-supported catalyst is formed by winding a flat plate and a corrugated plate having holes partially formed therein, and a honeycomb body 1 having a plus electrode 2 penetrating in the axial direction at the winding center, and a honeycomb body. A metal carrier composed of an outer cylinder 3 into which the body 1 is inserted, a catalyst carrier layer (not shown) formed on the entire surface of the metal carrier and composed of activated alumina, and a catalyst metal supported on the catalyst carrier layer. It is formed into a cylindrical shape having a diameter of 90 mm and a length of 50 mm.
Further, the power source 4 is provided on the end surface of the positive electrode 2 and the end surface of the outer cylinder 3.
It has a conductor leading to. The manufacturing method will be described below.

20 wt% Cr-5 wt% Al-the balance The balance consists mainly of Fe. Two strip-shaped flat plates having a thickness of 50 μm and a width of 50 mm are prepared, and as shown in FIG.
At the position of 2, the diameter is 10 so that it is evenly spaced in the width direction of the foil.
Provide 4 μm holes. And one is a substantially corrugated plate 9
To form. Furthermore, this corrugated sheet 9 is heated at a high temperature of 900 ° C.
It is heated for a period of time to form an alumina film on the surface for insulation treatment. The processed flat plate 8 and corrugated plate 9 are used as the plus electrode 2
The honeycomb body 1 was formed by winding it around the axis. At this time, the holes formed in the flat plate 8 and the corrugated plate 9 are substantially overlapped with each other.

This honeycomb body 1 was formed into S having a thickness of 1.5 mm.
Inserted in an outer cylinder 3 formed of US430MT (JIS standard) and also serving as a negative electrode, as shown in FIG.
An aqueous solution obtained by mixing a nickel-based high melting point brazing powder and an organic binder is poured into the outermost peripheral portion 5 and the central portion 7 of the honeycomb body other than the vicinity of the circumference including the portion having the pores,
It was dried and heat-treated at 1200 ° C. for 2 hours at a vacuum degree of 10 ⁻⁴ for brazing to prepare a metal carrier. Then, this metal carrier was dipped in an activated alumina slurry, and the excess slurry was blown off and then fired to form a catalyst supporting layer. After that, each was immersed in an aqueous solution of dinitrodiammine platinum and an aqueous solution of rhodium nitrate, dried and calcined to support a catalyst metal composed of platinum and rhodium on the catalyst supporting layer. The supported amounts are 1.0 g of platinum and 0.2 g of rhodium per liter of catalyst.

This metal-supported catalyst was connected in 2000cc in series 4
Installed in the exhaust system of a cylinder engine, air-fuel ratio (A / F) = 1
At 4.6, the engine was started and simultaneously energized. In the present embodiment, since the central portion 7 is brazed, the electric current is integrally conducted from the electrode to the outer surface of the central portion 7 when energized. Since the corrugated plate is insulated in the honeycomb portion 6 having the holes, the current flows spirally on the flat plate from the outer surface of the central portion toward the outer periphery. Due to the hole provided in the middle of the energizing path, the area of the energizing path is reduced, so that the resistance around the hole is locally increased. Therefore, a large amount of heat is generated around the hole,
The exhaust gas passing through obtains its heat, and the catalyst is warmed up by heat exchange between the exhaust gas and the catalyst. And engine start 15
10 mm from the exhaust side of the exhaust gas of the metal-supported catalyst after 2 seconds
The temperature of the exhaust gas was measured at a remote location. The results are shown in Table 1. (Examples 2 to 8) The same procedure as in Example 1 was performed except that holes were formed in the flat plate and the corrugated plate or only the flat plate, and the hole diameter, the number of holes, and the position were changed as shown in Table 1, and the flat plate was subjected to insulation treatment. To form a metal-supported catalyst. When two or more holes are drilled, the positions are such that they are equally spaced on the same circumference when wound at the center of the energization path of the plate to be drilled. Then, in the same manner as in Example 1, 15 seconds after the engine was started, the temperature of the exhaust gas was measured at a position 10 mm away from the exhaust gas outflow side of the metal carrier catalyst. The results are shown in Table 1. (Comparative Example 1) A metal-supported catalyst was formed in the same manner as in Example 1 except that holes were not formed in both the flat plate and the corrugated plate, and the exhaust gas of the metal-supported catalyst flowed out 15 seconds after the engine was started. The temperature of the exhaust gas was measured at a position 10 mm away from the side. The results are shown in Table 1. (Evaluation) From Table 1, in the metal-supported catalysts of the present invention, the temperatures after 15 seconds from engine start exceeded 300 ° C., which is the activation temperature of the catalysts, whereas the metal-supported catalysts of Comparative Examples were 300 ° C. You can see that it has not reached. That is, rather than simply energizing the metal-supported catalyst, it is possible to warm the air more quickly by providing holes in the foil of the metal-supported catalyst and energizing the metal-supported catalyst, so that the exhaust gas purification rate at engine startup can be increased earlier.

Further, in the metal carrier catalyst as seen in Comparative Example 1, the exhaust gas flows only in the axial direction in the catalyst. However, as in the present embodiment, since the foil has holes, the exhaust gas flows not only in the axial direction but also in multiple directions to generate turbulent flow. The heat exchange between the generated heat and the exhaust gas passing through the metal-supported catalyst is more actively performed by the turbulent flow of the exhaust gas, and the generated heat of the catalytic reaction is easily transferred to the carrier side, so that the catalyst warm-up performance is improved. It will be improved.

In this embodiment, the holes are provided at equal intervals in the width direction of the foil so that the end surface of the metal-supported catalyst can be arranged on the exhaust gas inflow side or the outflow side, and is actually mounted on the exhaust system. This is intended to improve the work performance at the time. However, if the holes are provided only on the exhaust gas outflow side, the effect of the present invention can be obtained. In this case, the exhaust gas inflow side generates heat, and the exhaust gas discharged after the engine starts flows into the metal-supported catalyst to the catalyst. After the heat generated at the end face is obtained, it passes through the inside of the catalyst, so the warm-up performance is improved. Further, if the hole is provided on the exhaust gas outflow side of the metal-supported catalyst and in the vicinity of the plus electrode, a large amount of heat generation is obtained at the exhaust gas inflow-side and in the central part of the metal-supported catalyst with a large exhaust gas flow rate, so that the warm-up is achieved. The machine performance will be improved. The position of the electrode has a positive electrode on the central axis of the metal-supported catalyst, but is not limited to this position, and may be a position deviated from the center. Further, a positive electrode may be arranged on the exhaust gas inflow side end surface of the metal carrier catalyst, and a negative electrode may be arranged on the exhaust gas outflow side end surface. In that case, the foil forming the metal carrier may or may not be insulated. Further, although the insulating treatment is performed in the present embodiment, it may be considered that the insulating treatment is not performed. In any case, the effect of the present invention is provided by providing a hole or slit in which the resistance on the exhaust gas inflow side is locally increased in the energization path, and generating the minimum amount of heat necessary for the catalyst to be activated. Is obtained. It is also conceivable to provide an exhaust gas temperature detection unit and turn off the electric current by a signal when the exhaust gas temperature exceeds a predetermined temperature. (Example 9) This metal-supported catalyst was composed of a corrugated plate and a flat plate with a partly thin plate thickness, and a honeycomb body having an electrode penetrating in the axial direction in the central portion and a honeycomb body inserted. A metal carrier composed of an outer cylinder, a catalyst carrier layer formed on the entire surface of the metal carrier and composed of activated alumina, and a catalyst metal supported on the catalyst carrier layer, and having a diameter of 90 mm and a length of 50 mm. It is formed in a cylindrical shape.
The manufacturing method will be described below.

20 wt.% Cr-5 wt.% Al-the balance is composed mainly of Fe, and is a substantially corrugated corrugated plate formed from a band-shaped flat plate having a thickness of 50 μm and a width of 50 mm, and approximately 1 / of the foil length of the flat plate. A portion having a plate thickness of 30 μm is provided at a position 2 over the entire length of the carrier axial direction of 50 mm. Then, the corrugated plate is heated at a high temperature of 900 ° C. for 24 hours to form an alumina film on the corrugated plate to insulate the corrugated plate. These processed flat plate and corrugated plate are wound in a roll shape with the positive electrode as an axis,
A honeycomb body was formed.

This honeycomb body was replaced with a SU having a thickness of 1.5 mm.
Nickel-based high melting point brazing material inserted into an outer cylinder formed of S430MT (JIS standard) that also serves as a negative electrode, and at the outermost peripheral portion and central portion of the honeycomb body other than the vicinity of the circumference including the thinned portion An aqueous solution prepared by mixing the above powder and an organic binder was poured, dried and treated at 1200 ° C. for 2 hours at a vacuum degree of 10 ⁻⁴ for brazing to prepare a metal carrier. Then, this metal carrier was dipped in an activated alumina slurry, and the excess slurry was blown off and then fired to form a catalyst supporting layer. After that, each was immersed in an aqueous solution of dinitrodiammine platinum and an aqueous solution of rhodium nitrate, dried and calcined to support a catalyst metal composed of platinum and rhodium on the catalyst supporting layer. The supported amounts are 1.0 g of platinum and 0.2 g of rhodium per liter of catalyst. Exhaust gas temperature of this metal-supported catalyst was measured at a position 10 mm away from the exhaust side of the exhaust gas of the metal-supported catalyst 15 seconds after the engine was started as in Example 1. The results are shown in Table 1.

[0019]

[Table 1]

(Evaluation) From Table 1, it is shown that the temperature after 15 seconds from engine start exceeds 300 ° C., which is the activation temperature of the catalyst, even in the case of the metal-supported catalyst whose plate thickness is partially changed. It can be seen that the temperature rises early. (Embodiment 10) FIG. 3 shows a schematic sectional view of a metal-supported catalyst of this embodiment. This metal-supported catalyst has a first honeycomb part 10 and a second honeycomb part 11 formed at both ends in the axial direction.
And the first honeycomb part 10 and the second honeycomb part 11 in the axial direction.
A metal carrier composed of a portion (hereinafter referred to as a roll portion) 12 in which only the flat plate is wound between the metal body and an outer cylinder 3 into which the honeycomb body 1 is inserted; It is composed of a catalyst-supporting layer formed on the entire surface and made of activated alumina, and a catalyst metal supported on the catalyst-supporting layer, and is formed into a cylindrical shape having a diameter of 100 mm and a length of 100 mm. Further, the outer end surface of the first honeycomb portion 10 and the outer end surface of the second honeycomb portion 11 have conducting wires that communicate with the power source 4. The manufacturing method will be described below. 20w
t% Cr-5wt% Al-remaining mainly Fe and thickness 5
A strip-shaped flat plate 15 having a width of 0 μm and a width of 100 mm, and this flat plate 1
5 and a substantially corrugated corrugated plate 16 having a width of 10 mm are prepared, and as shown in FIG. 4, two corrugated plates 16 are overlapped on both side edges of the flat plate 15 and wound in a roll shape to form a honeycomb. Body 1
Formed. As a result, the first honeycomb portion 10 and the second honeycomb portion 11 having the honeycomb passages on both sides in the axial direction are formed in the honeycomb body 1 to have a length of 10 mm, respectively, and between the first honeycomb portion 10 and the second honeycomb portion 11. The roll portion 12 was formed by winding only the flat plate. The number of cells of each of the first honeycomb portion 10 and the second honeycomb portion 11 is 400 per square inch. This honeycomb body 1
It is inserted into the outer cylinder 3 formed of SUS430MT (JIS standard) having a thickness of 1.5 mm, and is inserted between the first honeycomb part 10 and the outer cylinder 3 13 and the first honeycomb part 10 and the second honeycomb part 1.
An aqueous solution of nickel-based high-melting-point brazing material powder and an organic binder is poured into 1 and dried at 1200 ° C.
For 2 hours at a vacuum degree of 10 ⁻⁴ and brazing.
In addition, the second honeycomb portion 11, the roll portion 12 and the outer cylinder 3
Insulator 14 is interposed between and. Then, the metal-supported catalyst was immersed in an activated alumina slurry, and the excess slurry was blown off and then fired to form a catalyst supporting layer. After that, each was immersed in an aqueous solution of dinitrodiammine platinum and an aqueous solution of rhodium nitrate, dried and calcined to support a catalyst metal composed of platinum and rhodium on the catalyst supporting layer. The supported amounts are 1.0 g of platinum and 0.2 g of rhodium per liter of catalyst.

This metal carrier catalyst was mounted on the exhaust system of a 3000cc inline 6-cylinder engine, and the air-fuel ratio (A / F) =
At 14.6, [catalyst-containing gas temperature 850 ° C. × 10 minutes-
Gas temperature with catalyst 450 ° C x 10 minutes]
A durability test was conducted by operating for 0 cycles (100 hours). As a result, it was confirmed that the metal-supported catalyst did not show any abnormality such as cracks and had durability. Then, after the metal-supported catalyst was sufficiently cooled to room temperature, under the condition of A / F = 14.6 in the same engine, both ends of the metal-supported catalyst were used as electrodes at the same time when the engine was started, and electric current was applied in the axial direction.
In the case of the present embodiment, the roll portion 12 formed of only a flat plate is provided in the middle of the energizing path, and the area of the energizing path is reduced in this part, so the resistance locally increases and heat is generated. That is, the metal-supported catalyst will generate heat shortly after the engine is started. Immediately after starting the engine, H
Table 2 shows the purification rates when the purification rate of C, CO, and NOx by the catalyst is measured and the exhaust gas purification rate is 400 ° C., which is a temperature at which the purification rate is generally stable. At the same time, the time when the average purification rate reached 50% was measured. The results are shown in Table 2. It is considered that the shorter the time for which the average purification rate reaches 50%, the better the catalyst performance. It should be noted that the same measurement was carried out when the power was not applied, and the results are shown in Table 2. (Examples 11 to 13) Same as Example 10 except that the roll portion 12 was formed only from the corrugated plate and the number of cells of the first honeycomb portion 10 and the second honeycomb portion 11 was changed as shown in Table 3. To form the respective metal-supported catalysts. Then, a durability test was conducted in the same manner as in Example 10, but no abnormality such as cracks was observed in any of the metal carrier catalysts, and durability was observed. Further, the purification rate when the exhaust gas was 400 ° C. and the time until the average purification rate reached 50% were measured in the same manner as in Example 10, and the results are shown in Table 2. (Examples 14 to 17) FIG. 5 shows a schematic sectional view of the metal-supported catalysts of Examples 14 to 17. This metal-supported catalyst is provided in the first honeycomb unit 1 at an axially intermediate position of the roll unit 12.
0 and the third honeycomb portion 17 having a diameter smaller than that of the second honeycomb portion 11 is formed, and the conductor 1 is formed on the third honeycomb portion 17.
8 is connected. Then, the first honeycomb part 10
The second honeycomb part 11 and the third honeycomb part 17 are brazed to each other, and the insulator 14 is interposed between the second honeycomb part 11, the roll part 12 and the outer cylinder 3.
Further, the first honeycomb portion 10 and the outer cylinder 3 are connected to each other by the brazing portion 13
Are joined by. With the above configuration, 19 is provided between the third honeycomb part 17 and the second honeycomb part 11.
The portion indicated by (5) is preferentially energized, and since the foil forming the metal-supported catalyst is only the corrugated sheet in this portion, the resistance increases and heat is generated preferentially. The details of the configuration are shown in Table 3.
Shown in. And the exhaust gas temperature is 40
The purification rate at 0 ° C. and the time required for the average purification rate to reach 50% were measured, and the results are shown in Table 2. (Comparative Example 2) A metal-supported catalyst of Comparative Example was formed in the same configuration as in Example 10 except that the whole part was formed of a honeycomb portion and did not have a roll portion.
The purification rate at that time and the time required for reaching the average purification rate of 50% were measured, and the results are shown in Table 2.

[0022]

[Table 2]

[0023]

[Table 3]

(Evaluation) From Table 2, the metal-supported catalyst of the present invention exhibits a high purification rate, and the time for the purification rate to reach 50% is extremely shortened. As compared with the comparative example, the difference between when energized and when not energized is large, and it can be seen that the effect of energization is extremely large. It is clear that this is due to the presence of the roll section. In addition, Example 1
In Examples 4 to 17, the time required for the purification rate to reach 50% is shorter than that in Examples 10 to 13, but this is because the presence of the third honeycomb portion 17 gives priority to the axial center portion where the exhaust gas inflow amount is large. This is due to being heated. Although the third honeycomb portion 16 has been shown as an example in which it independently exists in the roll portion 12, the present invention is not limited to this. For example, the third honeycomb portion 16 may have a shape that extends in the axial direction from the first honeycomb portion 10 as well. Produce an effect. In the present invention, the effect can be obtained if the exhaust gas inflow side of the metal-supported catalyst is a roll portion and the outflow side is a honeycomb shape. However, Examples 10-1
In the case of a metal-supported catalyst having a roll portion between honeycomb shapes such as 7, when the engine is stopped, the honeycomb portion having a large surface area is likely to be cooled due to its large heat dissipation.
The roll portion has a small heat radiation property due to the heat insulating effect of air, and therefore is hard to be cooled. Therefore, at the time of restarting after a short stop, the temperature of the roll portion is sufficiently high, and the purification performance immediately after restarting is excellent. Also, even if the temperature of the roll part drops when restarting after being stopped for a long time, the roll part has a low heat radiation property toward the shaft center and the temperature is high. Rise to. As a result, high purification performance can be obtained. It is also conceivable to provide a detector for the exhaust gas temperature and turn off the current by a signal when the exhaust gas reaches a predetermined temperature.

[0025]

According to the present invention, when the metal-supported catalyst is energized, the electrical resistance of a part of the energization path locally increases, the amount of heat generation in that part increases, and the catalyst reaches the activation temperature early. Reach As a result, the reaction heat of the catalyst is transferred to the peripheral portion in a chain manner, and the catalyst is warmed up in combination with the heat diffusion action by the heat transfer with the exhaust gas. Therefore, the catalytically active state can be obtained with a small amount of electric power.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a metal-supported catalyst shown in Example 1 of the present invention.

[Fig. 2] Fig. 2 is a perspective view illustrating a method for manufacturing the honeycomb body of the metal-supported catalyst of Fig. 1.

FIG. 3 is a schematic cross-sectional view of a metal carrier catalyst shown in Example 10 of the present invention.

[Fig. 4] Fig. 4 is a perspective view illustrating a method for manufacturing the honeycomb body of the metal-supported catalyst of Fig. 4.

FIG. 5 is a schematic cross-sectional view of metal-supported catalysts shown in Examples 14 to 17 of the present invention.

[Explanation of symbols]

 1 ... Honeycomb body 2 ... Positive electrode 3 ... Outer cylinder (minus electrode) 4 ... Power supply

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area F01N 3/24 L 9150-3G

Claims (4)

[Claims] 1. A metal carrier catalyst for exhaust gas purification comprising a metal carrier having a honeycomb shape composed of a metal foil, a carrier layer formed on the surface of the metal carrier, and a catalyst metal supported on the carrier layer. An exhaust gas purifying metal carrier catalyst comprising a device for energizing the metal carrier, and having a portion on the exhaust gas inflow side where the resistance of the current passage of the metal carrier locally increases. 2. An exhaust gas purifying metal carrier catalyst comprising a honeycomb-shaped metal carrier composed of a metal foil, a carrier layer formed on the surface of the metal carrier, and a catalyst metal supported on the carrier layer. A device for energizing the metal carrier, wherein a hole or slit is provided on the exhaust gas inflow side so that the resistance of the current path of the metal carrier is locally increased. Metal-supported catalyst. 3. An exhaust gas-purifying metal carrier catalyst comprising a honeycomb-shaped metal carrier composed of a metal foil, a carrier layer formed on the surface of the metal carrier, and a catalyst metal supported on the carrier layer. , A device for energizing the metal carrier is provided, and a portion where the thickness of the metal foil forming the metal carrier is changed is locally provided on the exhaust gas inflow side so that the resistance of the current path of the metal carrier is locally increased. A metal carrier catalyst for purifying exhaust gas, which is characterized in that 4. A metal carrier having a honeycomb shape formed by stacking and winding a metal flat plate and a corrugated plate, and a metal carrier having a portion formed by winding only the flat plate or the corrugated plate, and a metal carrier of the metal carrier. An exhaust gas purifying metal carrier catalyst comprising a supporting layer formed on the surface and a catalytic metal supported on the supporting layer, comprising a device for energizing the metal carrier in the winding axis direction, and exhaust gas outflow of the metal carrier. The exhaust gas purifying metal carrier catalyst is characterized in that the side has a honeycomb shape, and at least a part of the exhaust gas inflow side is wound with a flat plate or a corrugated plate only.