JPH0889814A - Metal carrier - Google Patents

Abstract

PURPOSE: To provide an inexpensive metal carrier wherein the temp. can be elevated up to the activation temp. for a carried catalyst in a short time and high purification rate of an exhaust gas can be kept for a long time. CONSTITUTION: A metal carrier 1 consists of flat sheets and corrugated sheets 3 and is constituted in a shape wherein the flat sheets and the corrugated sheets 3 are alternately laminated and wound into a spiral shape. In the flat sheets and the corrugated sheets 3, slit parts 4 wherein rectangular slits are formed on a plurality of places, are formed approximately from the central part in the axial direction to the one end direction. These slits are formed at an equal intervals and continuously in the orthogonal direction to the axial direction of the metal carrier 1 and are formed at equal interval and continuously in the axial direction, too. In addition, the slits adjoining to each other in the axial direction are positioned alternately. On the other hand, a high density carrying layer wherein a catalyst substance is carried highly densely from the end part of the upstream side of an exhaust gas in a specified range 52a is formed on the surfaces of the flat sheets and the corrugated sheets 3 and a low density carrying layer wherein the catalyst substance is carried with a low density is formed in a range 52b wherein the range 52a is excluded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal carrier, for example, a metal carrier which is disposed in an exhaust path of an internal combustion engine and carries a catalyst capable of purifying exhaust gas of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a means for converting harmful components such as CO, HC and NOx contained in exhaust gas of an automobile engine into harmless gas and water, a metal carrier is interposed in the exhaust path of the engine. A method for purifying exhaust gas is known. An example of this type of metal carrier is an exhaust gas purifying catalyst metal carrier disclosed in Japanese Utility Model Publication No. 4-62316. This metal carrier for exhaust gas purification catalyst is a spirally wound or laminated metal flat plate and corrugated plate, and the activity of the carried catalytic substance is low in the low exhaust gas temperature such as at the beginning of engine start. Since it takes a long time to raise the temperature of the metal carrier to the activation temperature, there is a problem that the catalyst substance is not activated in a short time and exhaust gas is difficult to be purified.

Therefore, an exhaust gas purifying apparatus using a honeycomb heater disclosed in Japanese Patent Laid-Open No. 2-223622 causes heat to be generated in the metal carrier by energizing the honeycomb-shaped metal carrier itself made of stainless steel.
It is intended to activate the catalyst substance. However, since a large amount of electric power exceeding 1 kW is required to generate heat from this type of self-heating type metal carrier, there is a problem that a large amount of energy is consumed. Further, in the exhaust gas purifying apparatus using this honeycomb heater, the catalyst temperature and the exhaust gas concentration are uniform because the catalytic noble metal is uniformly supported on the entire metal carrier even though the catalyst temperature and the exhaust gas flow velocity vary depending on the site of the metal carrier. There is a problem that it is difficult to improve the exhaust gas purification rate of the catalytic precious metal that depends on and.

In view of this, according to Japanese Patent Laid-Open No. 61-46252, a monolith is provided with a catalyst component in a portion slightly inside from the exhaust gas inlet side and in a portion downstream of this portion and in the vicinity of the axial center portion more than other portions. An exhaust gas purifying monolith catalyst has been proposed, which is supported on a catalyst and purifies the exhaust gas optimally according to the flow velocity distribution and temperature distribution of the exhaust gas.

[0005]

However, according to the exhaust gas purifying monolith catalyst disclosed in Japanese Patent Laid-Open No. 61-46252, since the distribution concentration of the catalytic noble metal is partially changed, the density becomes high. The sintering phenomenon remarkably appears in the region where the distance between the particles of the supported catalytic precious metal is small, and the exhaust gas purification rate may gradually decrease. Here, the sintering phenomenon is a phenomenon in which the catalytic noble metal particles move to the surface due to thermal vibration and the catalyst surface area decreases due to the particle size growth of the catalytic noble metal particles. Further, in order to secure a high exhaust gas purification rate for a long period of time, it is necessary to increase the supported amount of the catalytic precious metal, which makes it difficult to increase the supported amount to satisfy the performance after endurance. Further, the catalyst precious metal to be supported is expensive platinum, rhodium, palladium, etc., because the amount thereof is rare, so that there is a problem that the cost increases as the amount of the supported precious metal increases.

The present invention has been made to solve such a problem, and can raise the temperature of activation of a supported catalyst in a short time and can maintain a high exhaust gas purification rate for a long time at a low cost. It is an object to provide a metal carrier.

[0007]

A metal carrier according to claim 1 for solving the above-mentioned problems is arranged in an exhaust path of an internal combustion engine, and metal flat plates and corrugated plates are alternately arranged. A metal carrier, which comprises a catalyst substance supported on a honeycomb body, which is formed by being wound or laminated on top of each other,
A plurality of slits extending in the direction orthogonal to the exhaust gas flow direction is formed on the exhaust path upstream side of at least one of the flat plate or the corrugated plate, and the honeycomb in the range including the slit near the end on the exhaust path upstream side. It is characterized by having a high-density support layer in which a catalyst substance is distributed at a higher density than on the downstream side of the exhaust path of the body.

The metal carrier according to a second aspect of the present invention is the metal carrier according to the first aspect, wherein the slit portion composed of the plurality of slits has an exhaust gas flow from the upstream side of the exhaust path of the flat plate or the corrugated plate. Is formed in the range of 5% to 60% of the axial length of the honeycomb body. Further, the metal carrier according to claim 3 of the present invention is the metal carrier according to claim 1 or 2, wherein the high-density supporting layer is formed in a range of 5 mm or more in the exhaust gas flow direction including the slit portion. Is characterized by.

According to a fourth aspect of the present invention, there is provided the metal carrier according to the first, second or third aspect, wherein the exhaust passage upstream end of the flat plate or the corrugated plate on which the slit portion is formed. Is 3 mm in the exhaust gas flow direction
A non-slit portion is formed within a range of up to 5 mm, and a low-density supporting layer having a low density distribution of the catalyst substance is formed in the non-slit portion.

The metal carrier according to claim 5 of the present invention is the metal carrier according to claim 1, 2, 3 or 4, wherein the catalyst substance is platinum, a rhodium catalyst or a palladium catalyst. Characterize. A metal carrier according to claim 6 according to the present invention is the metal carrier according to claim 1,
In the metal carrier described in 2, 3, 4 or 5, the loading density of the high density loading layer is 9 times or less the loading density of the non-high density loading layer.

The metal carrier according to claim 7 according to the present invention is the metal carrier according to claim 1, 2, 3, 4, 5 or 6, wherein the catalyst substance is platinum or rhodium-based catalyst, Total supported amount of substance is 1.5g / l
The carrier is 4.0 g / liter, and the weight ratio of platinum to rhodium is rhodium 0.2 or less relative to platinum 1 and the density of the high density carrier layer is 3.6 g / m ² or less. It is characterized by being done.

The metal carrier according to claim 8 of the present invention is the metal carrier according to claim 1, 2, 3, 4, 5 or 6, wherein when the catalyst substance is a palladium-based catalyst, The total supported amount is 4.0 g / liter to 6.0.
In addition to being g / liter, the high-density supporting layer is characterized in that it is carried so that the carrying density of the high-density carrying layer is 8.0 g / m ² or less.

The metal carrier according to claim 9 of the present invention is the metal carrier according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the catalyst substance is platinum or rhodium-based catalyst, The minimum supporting density of the supporting layer formed by supporting the catalyst substance on the honeycomb body is 0.45 g / m ² . The metal carrier according to claim 10 according to the present invention is the metal carrier according to any one of claims 1, 2, 3, 4, 5, 6 or 8, wherein when the catalyst substance is a palladium-based catalyst, The minimum supporting density of the supporting layer formed by supporting the catalyst substance is 1.0 g / m ² .

According to the eleventh aspect of the present invention, there is provided a metal carrier according to the first, second, third, fourth, fifth, sixth, seventh, eighth and ninth aspect.
Alternatively, in the metal carrier according to 10, the catalyst material may be γ-coated on the flat plate or the corrugated plate.
It is characterized in that it is supported on the Al ₂ O ₃ layer. Also,
A metal carrier according to claim 12 according to the present invention is the metal carrier according to any one of claims 1, 2, 3, 4, 5, 6, 7, 9 or 11, wherein when the catalyst substance is platinum or a rhodium-based catalyst, platinum is used. And rhodium total supported density 0.45 g / m
^2, the coating density of the γ-Al ₂ O ₃ layer is 3
It is characterized in that it is 1 g / m ² .

The metal carrier according to claim 13 of the present invention is the metal carrier according to claim 1, 2, 3, 4, 5, 6, 8, 10 or 11, wherein the catalyst substance is a palladium-based catalyst. In this case, the supported density of palladium is 1 g / m
^2, the coating density of the γ-Al ₂ O ₃ layer is 3
It is characterized in that it is 1 g / m ² . The metal carrier according to claim 14 of the present invention is the metal carrier according to claim 1, 2, 3,
4, 5, 6, 7, 8, 9, 10, 11, 12 or 13
In the metal carrier described above, the carrier density distribution of the catalyst substance is obtained by the number of times the flat plate or the corrugated plate is immersed in a solution containing the components of the catalyst substance.

[0016]

According to the metal carrier of the present invention, the slit portion formed of a plurality of slits extending in the direction orthogonal to the exhaust gas flow direction is formed on the upstream side of the exhaust path of at least one of the flat plate and the corrugated plate made of metal. Therefore, the heat capacity of the flat plate or the corrugated plate on the upstream side of the exhaust path becomes small. Moreover, since the flow of the exhaust gas is disturbed by the plurality of slits, the heat transfer efficiency is increased in the slit portion.
Further, for example, by arranging the slits adjacent to each other in the axial direction in an alternating manner, the heat dissipation path becomes longer, so that the amount of heat conduction becomes smaller. This has the effect of accumulating the heat that has risen on the upstream side of the exhaust path.

Further, according to the metal carrier of the present invention, since the high density supporting layer in which the catalyst substance is distributed in a high density is formed in the range including the slit portion, when the activation temperature of the catalyst substance is reached, There is an effect of accelerating the temperature rise on the upstream side of the exhaust path of the flat plate or the corrugated plate by the reaction heat associated with the activation of the catalyst material of the high-density support layer. Due to the effect of accelerating the temperature rise and the effect of accumulating the above-mentioned heat that has been raised, the temperature of the metal carrier can be easily raised by the heat from the exhaust gas, and the temperature rise dependency due to the reaction heat of the catalyst substance is suppressed. Therefore, it is possible to reduce the supported amount of the catalyst substance, and it is possible to reduce the required supported amount of catalyst for maintaining a higher purification rate for a long period of time. In addition, since it is possible to reduce the supported amount of the catalyst substance, it is possible to sufficiently secure the interparticle distance of the catalyst substance, suppress the sintering phenomenon, and maintain a high exhaust gas purification rate for a long time. is there.
Further, there is an effect that the amount of the catalyst used can be reduced and the cost can be reduced by reducing the required amount of the catalyst supported.

Further, according to the metal carrier of the present invention, the slit portion formed on at least one of the flat plate and the corrugated plate on the upstream side of the exhaust path is composed of the flat plate and the corrugated plate and has a length of 5 in the axial direction. Since it is in the range of 60% to 60%, there is an effect that the heat raised on the upstream side of the exhaust path can be efficiently stored and raised in a short time. Furthermore, according to the metal carrier of the present invention, 3 m in the exhaust gas flow direction is provided at the exhaust path upstream end of the flat plate or corrugated plate on which the slit portion is formed.
A non-slit portion is formed in a range of m to 5 mm, and a low density support layer having a low density distribution of the catalyst substance is formed on the non slit portion. As a result, even when a lead compound adheres to the upstream end of the exhaust gas due to lead halide contained in the exhaust gas, the performance of the catalyst substance is not significantly impaired, and the cost reduction is achieved by reducing the required catalyst loading amount. it can.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) A metal carrier according to a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG.
Eight exhaust manifolds derived from a V8, 4000cc engine 5 are assembled in groups of four,
The two exhaust manifolds 6a assembled together,
6b is configured as an exhaust path of the engine 5. A metal carrier 1 is arranged in the middle of each of the exhaust manifolds 6a and 6b, and a start caster list 7 having a large capacity of 1300 cc is arranged immediately below the metal carrier 1. The exhaust pipes 22 connected to the downstream side of the two start caster lists 7 are further assembled into one, and then connected to a 1000 cc main caster list (not shown).

The start caster list 7 is a monolith catalyst made of ceramics and is held in the start caster list outer cylinder 17 through a wire net or a ceramic fiber mat 18. A downstream flange 19 is formed on the downstream side of the start caster outer cylinder 17, and an exhaust pipe flange 20 formed on the exhaust pipe 22 and the downstream flange 19 are connected and fixed to each other by a bolt 21.

As shown in FIGS. 3 and 4, the metal carrier 1 is composed of a flat plate 2 and a corrugated plate 3, and is formed in a spiral shape by alternately superimposing the flat plate 2 and the corrugated plate 3. ing. In both the flat plate 2 and the corrugated plate 3, for example, Cr is 18 to 24 wt%, Al is 4.5 to 5.5 wt%, rare earth element (REM) is 0.1 to 0.2 wt%, and the balance Fe is Fe−. A heat-resistant stainless steel foil having a Cr-Al composition. In addition, the flat plate 2 and the corrugated plate 3 before winding are, for example, a plate width 5
0a is 60 mm, and the plate thickness is 0.03 to 0.20 mm.

As shown in FIG. 6, a slit portion 4 is formed in the flat plate 2 and the corrugated plate 3 from the substantially central portion in the axial direction toward the one end portion. Here, since the developed corrugated plate 3 and the flat plate 2 have the same shape, the developed shape of the flat plate 2 is shown in FIG. 6 as a representative. A space 50b, which is a welding margin for joining the flat plate 2 and the corrugated plate 3 to each other, is provided at one end of the flat plate 2, and the slit portion 4 is provided in a range of a width 50c from a position separated by the space 50b. Are formed. In the first embodiment, the interval 50b is, for example, 3 mm, and the width 50c is, for example, 31.2 mm.

As shown in FIG. 7, the rectangular slit formed in the slit portion 4 is formed, for example, by the following dimensions. Slit width w = 3 mm Slit height h = 1.2 mm Axial method Slit interval D = 1 mm Orthogonal slit interval H = 0.8 mm This rectangular slit is an interval H orthogonal to the axial direction of the metal carrier 1. Are continuously formed at a distance D in the axial direction. Further, the slits adjacent to each other in the axial direction are positioned so as to be offset from each other by (w + D) / 2.

The corrugated plate 3 has a repeating pitch of 4.9 m, for example.
m, and the height is 1.7 mm, which corresponds to the amplitude of the wave. After the flat plate 2 and the corrugated plate 3 are wound, the flat plate 2 and the corrugated plate 3 are wound such that the slit portions 4 are located on the upstream side of the exhaust gas. Simultaneously with this winding, the flat plate 2 on which the slit portion 4 is not formed
And the vicinity of both ends of the corrugated plate 3 is joined. This bond is
It is applied to the portion where the peaks or troughs of the corrugated plate 3 come into contact with the flat plate 2, and is performed by laser beam welding, resistance welding, brazing, or the like.

As shown in FIGS. 3 to 5, the metal carrier 1 composed of the wound flat plate 2 and corrugated plate 3 is covered with a cylindrical outer cylinder 8 made of, for example, heat resistant stainless steel SUS430. There is. The outer cylinder 8 is formed so that a space 9 can be secured around the metal carrier 1 in which the slit 4 is formed. The void 51a of the void 9 is, for example, 1.5
The height of the corrugated sheet 3 is equal to the height of the corrugated sheet 3. A notch 10 extending along the axial direction of the metal carrier 1 is formed in a part of the outer cylinder 8 that covers the exhaust gas downstream side of the metal carrier 1. The cutouts 10 are formed at eighteen points at 45 ° intervals in the circumferential direction of the outer cylinder 8.

The metal carrier 1 and the outer cylinder 8 are formed by the cutout 1
The corrugated plate 3 of the metal carrier 1 and the inner peripheral wall of the outer cylinder 8 are welded and fixed to each other by irradiating a laser beam from the outside of the outer cylinder 8 to the circumferential portion of the outer cylinder 8 except 0. The joining of the metal carrier 1 and the outer cylinder 8 is not limited to laser beam welding,
It may be applied by brazing. In FIGS. 3 and 4, a welding mark 11 by laser beam welding is shown. When the metal carrier 1 and the outer cylinder 8 are joined, welding cracks may occur on the corrugated plate 3 side due to a difference in heat capacity between the corrugated plate 3 located on the outermost periphery of the metal carrier 1 and the outer cylinder 8. for that reason,
When welding is performed by laser beam welding, welding cracks on the side of the corrugated sheet 3 can be prevented by placing two corrugated sheets 3 on the outermost periphery of the metal carrier 1 so as to overlap each other. When brazing, it is preferable to position the flat plate 2 on the outermost periphery of the metal carrier 1 in order to secure a sufficient brazing area.

An outer cylinder 8 for covering the exhaust gas upstream side of the metal carrier 1.
A flange 12 made of, for example, heat resistant stainless steel SUS430 is welded and fixed to the outer peripheral wall of the welded mark 13
Are formed. For the flange 12, the same material as that of the outer cylinder 8 is selected in consideration of weldability, and in order to secure higher weldability, the outer cylinder 8 and the flange 12 are welded by a γ-Al ₂ O ₃ coat described later. And a step before the catalyst supporting step.

As described above, the flat plate 2 and the corrugated plate 3 are wound and the slit portion 4 is formed on one end side, and the peaks or valleys of the corrugated plate 3 and the flat plate 2 are laser-welded. A metal carrier can be obtained. Next, a catalyst supporting step for supporting the catalyst on the metal carrier 1 described above will be described with reference to FIG.
And it demonstrates based on FIG.

By heating the metal carrier 1 at 800 to 1200 ° C. for 1 to 10 hours, an oxide of aluminum is deposited on the surfaces of the flat plate 2 and the corrugated plate 3 constituting the metal carrier 1. This heat treatment is performed for the purpose of peeling off the γ-Al ₂ O ₃ coat, and is to increase the surface area by forming alumina whiskers on the surfaces of the flat plate 2 and the corrugated plate 3. As a result, high reliability can be obtained,
It is preferable to perform this heat treatment.

After this heat treatment, the metal carrier 1 is impregnated in a slurry containing γ-Al ₂ O ₃ and baked. Thereby, the surfaces of the flat plate 2 and the corrugated plate 3 are γ-Al ₂ O.
₃ coats. The metal carrier 1 formed to have the above-described dimensions has a diameter of 66 mm, a length of 60 mm, and a volume of 205 c.
c, number of cells 150 / inch ² , total metal supporting surface area 40
Since it is 09 cm ² , the total weight of 12.38 g of γ-
An Al ₂ O ₃ layer will be formed. This γ-Al ₂ O
₃ layers are per 1 m ² surface area of the honeycomb metal foil (hereinafter,
It is 31 g / m ² in terms of “supported density” and 60.3 g / liter in terms of volume per liter (hereinafter referred to as “volume ratio”).

After the formation of the γ-Al ₂ O ₃ layer, the metal carrier 1 is dissolved in an aqueous solution in which, for example, platinum, rhodium, palladium, etc. are dissolved by the two catalyst loading steps shown in FIGS. 8 and 9.
Is impregnated and fired again. Thereby, as shown in FIG. 1, the exhaust gas upstream side and the exhaust gas downstream side of the metal carrier 1 can have different loading density distributions. As shown in FIG. 8, after forming the γ-Al ₂ O ₃ layer, for example, platinum was added to 0.
The step of immersing the entire metal carrier 1 in the supporting treatment tank 30 filled with 15 g of the platinum aqueous solution 31 and pulling it up is repeated several times. After this step, the metal carrier 1 is pulled up from the carrying treatment tank 30 and temporarily dried. After the tentative drying, as in the case of immersing in the platinum aqueous solution 31, the step of immersing the whole metal carrier 1 in the rhodium aqueous solution containing 0.0030 g of rhodium, which is filled in a supporting treatment tank not shown, and pulling up Repeat several times. After this step, the metal carrier 1 is pulled out from the supporting treatment tank and dried. By the first catalyst loading step, the loading density on the metal carrier 1 is 0.37.
g / m ² of platinum and rhodium having a loading density of 0.075 g / m ² are loaded, respectively. The total supported density of platinum and rhodium is 0.45 g / m ² .

Further, as shown in FIG. 9, after supporting platinum and rhodium on the entire metal carrier 1, a carrying treatment tank 30 filled with a platinum aqueous solution 32 containing, for example, 0.16 g of platinum is provided on the upstream side of the exhaust gas. The metal carrier 1 is dipped from the end to a predetermined range 52a. At this time, the platinum aqueous solution 3
The liquid surface 32a of No. 2 is the liquid surface 31 of the platinum aqueous solution 31 in the above process.
A platinum aqueous solution 31 which is lower than a and is immersed to the range 52a from the end of the metal carrier 1 on the upstream side of the exhaust gas is placed in the loading treatment tank 30. In the first embodiment, the range 52
a is set to 12 mm, for example. Therefore, the range 52a of the metal carrier 1 is supported by the catalyst by repeating the steps of dipping the metal carrier 1 and pulling it up several times. After this step, the metal carrier 1 is pulled up from the carrying treatment tank 30 and temporarily dried. Further, after tentative drying, the range 52a of the metal carrier 1 is immersed in a rhodium aqueous solution containing, for example, 0.032 g of rhodium, which is filled in a supporting treatment tank (not shown), as in the case of immersing in the platinum aqueous solution 32.
The pulling process is repeated several times. After this step, the metal carrier 1 is pulled out from the supporting treatment tank and dried. As a result, the catalyst supporting step of the metal carrier 1 is completed, and the metal carrier for the catalyst converter carrying the catalyst can be obtained.

By the above-described first and second catalyst loading steps, the range 52 of the exhaust gas upstream end portion of the metal carrier 1 is obtained.
The a, rhodium loading density 2.69 g / m ² of platinum and carrier density 0.54 g / m ² are supported respectively, the total loading density of platinum and rhodium is 3.23 g / m ^2. On the other hand, the range 52 of the exhaust gas upstream end of the metal carrier 1
In the range 52b excluding a, the supported density is 0.37 g / m ²
Of platinum and rhodium having a loading density of 0.075 g / m ² are loaded, respectively, and the total loading density of platinum and rhodium is 0.
It becomes 372 g / m ² . This represents 0.31 g of platinum, 0.062 g of rhodium, and 0.372 g of platinum and rhodium in total when expressed in terms of the total supported amount. Further, when converted into the total supported amount of the volume ratio, platinum is 1.5 g / liter, rhodium is 0.3 g / liter, and the total of platinum and rhodium is 1.8 g / liter. Further, comparing the respective carrying densities of the range 52a and the range 52b, it can be seen that the range 52a is set to a carrying density 9 times or less that of the range 52b. This is because the loading density in the range 52a, which is a high loading density layer, becomes high,
This is to prevent the above-mentioned sintering phenomenon from occurring due to the decrease in the distance between the catalyst particles.

Next, the process of attaching the metal carrier 1 to the exhaust path of the engine 5 will be described with reference to FIGS. 2 and 10. As shown in FIGS. 1, 2 and 10, the flange 12 of the metal carrier 1 is mounted by the bolt 16 between the exhaust manifold mounting flange 14a and the start caster list mounting flange 14b via the gasket 15. As a result, the metal carrier 1 is connected and fixed between the exhaust manifold 6a and the start caster list 7.

Next, the operation of the metal carrier 1 will be described with reference to FIGS. 1 and 2. After the engine 2 is started, the exhaust gas exhausted in the exhaust stroke of each cylinder reaches the metal carrier 1 via the exhaust manifolds 6a and 6b. The exhaust gas reaching the metal carrier 1 collides with the slit portion 4 located on the upstream side of the metal carrier 1, and the slit portion 4 listed next
In addition to the above effect, the temperature of the slit portion 4 rises fastest because the slit portion 4 and the outer cylinder 8 are thermally insulated by the air layer in the void portion 9.

The formation of the slits reduces the heat capacity of the slit portion 4. Since the cross-sectional area of the metal carrier 1 in the axial direction of the metal carrier 1 is reduced by forming the slit, the metal carrier 1
Suppresses heat conduction to the downstream side of. By staggering the formation positions of the slits, the heat transfer path becomes longer, so that heat conduction to the downstream side of the metal carrier 1 is suppressed.

Since the contact area between the flat plate 2 and the corrugated plate 3 is reduced by forming the slits, heat conduction to the outside of the metal carrier 1 in the radial direction is suppressed. Since the slit has a function of disturbing the flow of exhaust gas, heat transfer efficiency is improved. Further, the metal carrier 1 and the outer cylinder 8 are joined by a welding mark 11 on the downstream side of the metal carrier 1, and the outer cylinder 8 and the exhaust manifolds 6a and 6b are fixed by a flange 12 on the upstream side of the metal carrier 1. Therefore, a long heat transfer path for the heat of the metal carrier 1 to reach the exhaust manifolds 6a and 6b via the outer cylinder 8 can be secured. As a result, the heat radiation of the metal carrier 1 is suppressed and the heat radiation amount is extremely reduced.

Further, the exhaust gas downstream side of the metal carrier 1 in which the slit portion 4 is not formed has a large thermal conductivity in the radial direction and the axial direction as compared with the exhaust gas upstream side in which the slit portion 4 is formed. The heat conduction speed is extremely high, and the entire area of the metal carrier 1 on the downstream side of the exhaust gas is heated to the activation temperature of the catalyst in a short time. Furthermore, since the carrier layer in which the catalyst substance is distributed at a high density is formed in the predetermined range 52a of the metal carrier 1 on the upstream side of the exhaust gas, the activation temperature of the catalyst substance is set to 250 to 350 ° C. Range 52a reached,
When the catalytic substance in the range 52a is activated, the heat of reaction thereof further increases the temperature rise on the exhaust gas upstream side of the metal carrier 1.

Here, the catalyst material is not limited to platinum and rhodium type catalysts, but may be palladium type catalysts. Further, by using this palladium-based catalyst, the cost can be further reduced, and the sintering phenomenon is less likely to occur due to the palladium-based catalyst having excellent heat resistance, and high purification performance can be maintained for a long time. The slit portion 4 described above
Immediately after the start of the engine 2 due to the effects such as
The entire area of the metal carrier 1 is activated in a second, and the metal carrier 1 can be provided with a catalytically reactive area capable of sufficiently purifying exhaust gas. Further, in the start caster list 7 provided immediately below the metal carrier 1, the catalyst is sequentially activated from the upstream side of the start caster list 7 by the high temperature exhaust gas passing through the metal carrier 1. Even when a large amount of exhaust gas is discharged from the exhaust manifolds 6a and 6b when the engine 2 is under high load, about 90% or more of H in the exhaust gas is exhausted from the metal carrier 1 and the start caster list 7.
Purification of C and CO can be performed.

Next, the results of examining the temperature rise characteristics of the metal carrier 1 of the first embodiment and the metal carrier of the comparative example due to the exhaust gas will be described with reference to FIGS. 11 to 13. Table 1 shows the specifications of the metal carrier 1 and the metal carriers of Comparative Examples 1 and 2 in the comparative experiment.

[0041]

[Table 1]

As shown in FIG. 12, as the metal carrier 110 of Comparative Example 1, the metal carrier 1 of Comparative Example 2 in which a high-density supporting layer is not formed on the upstream side of the exhaust gas is used.
As the metal carrier 1, a metal carrier having no slit portion and a high-density supporting layer formed on the upstream side of the exhaust gas was used. As shown in FIG. 11, the metal carrier 1 is provided 2 immediately after the engine 5 is started.
It is attached in the middle of an exhaust pipe that reaches about 300 ° C in 3 seconds. Metal carriers 110 and 12 of Comparative Example 1 and Comparative Example 2
0 is also attached at the same position during the comparative experiment.

As shown in FIG. 12, the metal carriers 1, 11
In examining the temperature rise of 0 and 120, the distance 101 (19 m
m) The temperature condition of the central portion of the metal carrier shown at points B, C and D on the downstream side was measured. In addition, at the same time, the temperature state of the exhaust gas shown at a point A upstream of the exhaust gas upstream side end of each metal carrier by a distance 102 (20 mm) in the axial direction was measured.

As shown in FIG. 13, the metal carrier 1 reaches a temperature of about 300 ° C. for 4 to 5 seconds after the engine is started. On the other hand, the metal carrier 110 of Comparative Example 1
For 5 to 6 seconds, and for the metal carrier 120, 7
A temperature of about 300 ° C. is reached in about 9 seconds. In this way, the slit portion is formed on the exhaust gas upstream side of the metal carrier,
Furthermore, it was confirmed that a rapid temperature rise in the metal carrier can be obtained by supporting the catalyst substance at a high density.

It has been confirmed by experiments that the space 50b, which is the welding margin between the flat plate 2 and the corrugated plate 3 described above, is about 3 to 5 mm so as not to hinder the temperature raising performance of the metal carrier 1. Further, the slit portion 4 is preferably formed on the metal carrier in the range of 5 to 60% of the plate width 50a which is the axial length of the metal carrier from the exhaust gas upstream side in the exhaust gas flow direction. When the carrier layer in which the catalyst substance is densely distributed at least in the range of 5 mm or more in the exhaust gas flow direction on the upstream side of the exhaust gas including the slit portion 4 is formed, the catalytic substance is activated in the entire metal carrier in about 20 seconds immediately after the engine is started. It has been confirmed by experiments that it can be converted.

When the catalyst substance is platinum or rhodium-based catalyst, the total supported amount is 1.5 to 4.0 g / liter, and the weight ratio of platinum to rhodium is 0.2 to rhodium to platinum 1. If it is carried below, sufficient purification performance can be obtained immediately after the engine is started, as described above. When the catalyst substance is a palladium-based catalyst, if the total supported amount is supported at 4.0 to 6.0 g / liter, sufficient purification performance can be obtained immediately after the engine is started, as in the case where the catalyst substance is a platinum- or rhodium-based catalyst. it can.

Further, when the catalyst substance is a platinum or rhodium type catalyst, if the loading density of the loading layer in the region of the smallest loading density is loaded at a minimum of 0.45 g / m ² , sufficient purification performance can be obtained at high load. You can When the catalyst substance is a palladium-based catalyst, the catalyst substance is platinum when the carrier density of the carrier layer in the region having the smallest carrier density is supported at a minimum of 1.0 g / m ² .
Similar to the case of the rhodium-based catalyst, sufficient purification performance can be obtained under high load.

Next, the results of examining the durability of the metal carrier 1 using the metal carrier 1 and the metal carriers 110 and 120 of the comparative example will be described with reference to FIG. Durability test conditions are A / F = 14.6, inflow gas temperature 900 ° C., 200
It is time driving. Fig. 14 shows the purification characteristics before and after this durability test.
Shown in As shown in FIG. 14, the purification rate of the metal carrier 1 shows the highest value before and after the durability test as compared with Comparative Example 1 and Comparative Example 2 in which the catalyst supporting density distribution is not provided. Further, when the metal carrier 110 of Comparative Example 1 and the metal carrier 120 of Comparative Example 2 are compared, it is shown that the effect of the slit portion 4 provided on the upstream side of the inflow gas is great.

Thus, by forming the high density support layer and the slit portion on the upstream side of the inflow gas of the metal carrier,
It was confirmed by experiments that a metal carrier having high durability can be realized at low cost. In other words, by providing the slit portion, the loading density of the high-density loading layer on the upstream side of the inflow gas can be suppressed to be lower than that of the conventional one, and thus the interparticle distance of the catalyst substance loaded on the metal carrier can be sufficiently increased. Can be secured. Therefore, in the catalyst supporting step, the atomized catalyst substance can be supported without causing an increase in the particle size of the catalyst substance, and a high purification rate can be obtained.

Further, as a result of a durability test conducted by changing the amount of catalyst supported on the metal carrier to various values, it was confirmed that the purification rate deteriorates when the supported density is excessively high. This is because when the distance between the particles of the supported catalyst substance becomes small, the sintering phenomenon in which the catalyst substance particles move to the surface due to thermal vibration and the particle size grows easily occurs, and the surface area of the catalyst substance decreases.
According to the experiment, when the catalyst density of the high-density support layer was 3.6 g / m ² or less when the catalyst material was platinum or rhodium-based catalyst, good durability was exhibited. It was also found that when the catalyst substance is a palladium type catalyst, if the catalyst substance is 8.0 g / m ² or less, good durability is exhibited as in the case where the catalyst substance is a platinum or rhodium type catalyst.

Further, as a result of repeated experiments, it was confirmed that the durability performance affects the amount of γ-Al ₂ O ₃ forming the supporting layer. That is, when the catalyst substance is platinum or a rhodium-based catalyst, the total supported density of platinum and rhodium is 0.45 g /
To weight ratio distribution of m ² to γ-Al ₂ O ₃ in the applicable weight ratio distribution of the loading density of the catalytic substance supported density such that the rate of _{^{31g / m 2 γ-Al 2}} O 3 coating amount This showed the highest durability. When the catalyst substance is a palladium-based catalyst, the weight ratio distribution of the supported density of the catalyst substance is set so that the supported density of γ-Al ₂ O ₃ is 31 g / m ² with respect to the palladium supported density of 1.0 g / m ^2. The highest durability was exhibited by setting the weight ratio distribution of the amount of γ-Al ₂ O ₃ according to the above. This is 130-350
This is because the supporting density is such that the distance between the catalyst substance particles can be sufficiently secured with respect to the specific surface area of γ-Al ₂ O ₃ which is g / m ² . In addition, since palladium has excellent heat resistance, it has been confirmed by experiments that the sintering phenomenon hardly occurs and high purification performance is maintained for a long period of time.

According to the first embodiment, since the slit portion 4 is formed on the exhaust gas upstream side of the carrier 1, heat conduction to the downstream side of the metal carrier 1 is suppressed. This has the effect of lowering the heat capacity of the carrier 1 on the upstream side of the exhaust gas. In addition, according to the first embodiment, the slit portion 4 of the carrier 1 disturbs the flow of exhaust gas to improve heat transfer efficiency and reduce the contact area between the flat plate 2 and the corrugated plate 3.
The amount of heat conduction to the outside of the metal carrier 1 in the radial direction is suppressed. This has the effect of accumulating the heat that has been raised on the exhaust gas upstream side of the carrier 1.

Further, according to the first embodiment, since the carrier layer in which the catalyst substance is distributed at a high density is formed in the predetermined area 52a of the metal carrier 1 on the upstream side of the exhaust gas,
When the activation temperature of the catalytic substance in the range 52a is reached, the reaction heat associated with the activation of the catalytic substance causes the temperature of the exhaust gas upstream side of the metal carrier 1 to rise further. As a result, the temperature of the metal carrier 1 can be easily raised by the heat from the exhaust gas, and the temperature rise dependency due to the reaction heat of the catalyst substance can be suppressed. Therefore, compared to the conventional catalytic converter in which the exothermic reaction of the catalytic substance is used to raise the temperature of the metal carrier, the carried amount of the catalytic substance can be reduced, and a higher purification rate can be obtained for a long period of time. This has the effect of reducing the amount of catalyst supported necessary for maintaining. As a result, a sufficient distance between the particles of the catalyst substance supported on the metal carrier can be secured, and there is an effect that the atomized catalyst substance can be supported without increasing the particle size of the catalyst substance in the catalyst supporting step. is there. Furthermore, since the required amount of supported catalyst is reduced, there is an effect that the amount of expensive platinum, rhodium, palladium or the like used can be reduced to achieve cost reduction.

(Second Embodiment) A metal carrier according to a second embodiment of the present invention will be described with reference to FIGS. 15 and 16.
The same components as those in the first embodiment are designated by the same reference numerals. As shown in FIG. 15, in the second embodiment, in the range 41b on the exhaust gas upstream side of the flat plate 2 and the corrugated plate 3 which form the metal carrier 40, the loading density of a portion where a lead compound such as lead oxide is likely to be generated in advance is set. It is different from the first embodiment in that it is lowered.

As shown in FIG. 16, after the γ-Al ₂ O ₃ layer is formed, a range 41 on the exhaust gas upstream side of the metal carrier 40 is placed in the loading treatment tank 42 filled with the platinum aqueous solution 43 having a predetermined concentration.
The step of immersing the metal carrier 40 leaving only b and pulling it up is repeated several times. In the second embodiment, the range 41b is, for example, 3 to 5 mm. After this step, the metal carrier 4
0 is pulled up from the carrying treatment tank 42 and temporarily dried. After the temporary drying, similarly to the immersion in the platinum aqueous solution 43, the metal carrier is immersed in the rhodium aqueous solution containing a predetermined concentration of rhodium, which is filled in a supporting treatment tank (not shown), leaving only the range 41b, and then pulled up. Repeat the process several times. After this step, the metal carrier 40 is pulled out from the carrying treatment tank and dried. By these first catalyst supporting steps, the metal carrier 40 is loaded with platinum and rhodium having a predetermined loading density in portions other than the range 41b.

Next, as shown in FIG. 17, the metal carrier 40 is dipped from the end of the exhaust gas upstream side to a predetermined range 41d in the loading treatment tank 42 filled with the platinum aqueous solution 44 having a predetermined concentration. At this time, the liquid level 44a of the platinum aqueous solution 44 is lower than the liquid level 43a of the platinum aqueous solution 43 in the above step, and the platinum aqueous solution 44 is immersed in the range 41d from the end of the metal carrier 40 on the upstream side of the exhaust gas in the carrying treatment tank. It is put in 42. In the second embodiment, the range 41d is, for example, 15
It is set to mm and is equal to the sum of the range 41a and the range 41b. Therefore, by immersing the metal carrier 40 and pulling it up several times, only the area 41d of the metal carrier 40 is supported by the catalyst. After this step, the metal carrier 40 is pulled up from the carrying treatment tank 42 and temporarily dried. Further, after tentative drying, similarly to the immersion in the platinum aqueous solution 44, the range 41d of the metal carrier 40 is immersed in a rhodium aqueous solution containing a predetermined concentration of rhodium filled in a supporting treatment tank (not shown), and then pulled. Repeat the raising process several times. After this step, the metal carrier 40 is pulled out from the carrying treatment tank and dried. Thereby, the metal carrier 40
After the step of supporting the catalyst is completed, it is possible to obtain the metal carrier for the catalytic converter on which the catalyst is supported.

In the above-described first and second catalyst loading steps, the range 41 on the exhaust gas upstream side of the metal carrier 40 is shown.
Similarly to the range 41c, in the range b, since the catalyst is carried in the second catalyst carrying step and the catalyst is not carried in the first catalyst carrying step, the carrying density of the range 41b can be lowered. Due to this, the range 4 located upstream of the exhaust gas where the lead halide etc. contained in the exhaust gas is most likely to come into contact
In 1b, since the amount of catalyst carried is small in the initial use state of the metal carrier 40, when used for a long time,
It has the effect of not significantly impairing the purification performance. Further, there is an effect that the cost can be reduced by reducing the required amount of catalyst to be supported.

In the second embodiment, platinum and rhodium are used as the catalyst substance in the first and second catalyst supporting steps, but a rhodium catalyst may be used in the present invention. Further, in the present embodiment, the slit portion 4 is formed on both the flat plate 2 and the corrugated plate 3, but the present invention is not limited to this, and the slit portion 4 is formed on at least one of the flat plate 2 and the corrugated plate 3. The slit portion 4 is formed on the flat plate 2 and the slit portion 4 is not formed on the corrugated plate 3, or the slit portion 4 is formed on the corrugated plate 3 and the slit portion 4 is not formed on the flat plate 2. Even if good.

Further, in this embodiment, the metal carrier is formed by alternately winding the flat plate 2 and the corrugated plate 3, but
The present invention is not limited to this, and for example, the flat plate 2
The metal carrier may be formed by alternately stacking and corrugating plate 3.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a metal catalytic converter using a metal carrier according to a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram in which a metal carrier according to a first embodiment of the present invention is mounted in an exhaust path of an engine.

FIG. 3 is a perspective view showing a state in which the metal carrier according to the first embodiment of the present invention is attached to an outer cylinder.

FIG. 4 is a half cross-sectional view showing a state in which the metal carrier according to the first embodiment of the present invention is attached to the outer cylinder.

5 is a view from the direction of the arrow V in FIG.

FIG. 6 is a development view of a flat plate used for the metal carrier according to the first embodiment of the present invention.

FIG. 7 is a schematic explanatory view of a slit portion of the metal carrier according to the first embodiment of the present invention.

FIG. 8 is a schematic explanatory view of a first catalyst supporting step of the metal carrier according to the first embodiment of the present invention.

FIG. 9 is a schematic explanatory view of a second catalyst supporting step of the metal carrier according to the first embodiment of the present invention.

10 is a view taken in the direction of the arrow X in FIG.

FIG. 11 is an overall configuration diagram in which a metal carrier for performing a comparative experiment is mounted in an exhaust system passage of an engine.

12 (a) is a schematic side view of a metal carrier according to a first embodiment of the present invention, (b) is a schematic side view of a metal carrier of Comparative Example 1, and (c) is a metal carrier of Comparative Example 2. It is a schematic side view of.

FIG. 13 is a temperature state characteristic diagram showing an experimental result of a comparative experiment of the metal carrier according to the first embodiment of the present invention.

FIG. 14 is a purification performance characteristic diagram showing experimental results of a comparative experiment of the metal carrier according to the first embodiment of the present invention.

FIG. 15 is a schematic configuration diagram of a metal catalytic converter using a metal carrier according to a second embodiment of the present invention.

FIG. 16 shows a first metal carrier according to a second embodiment of the present invention.
It is a schematic explanatory view of a catalyst supporting step.

FIG. 17 is a second metal carrier according to the second embodiment of the present invention.
It is a schematic explanatory view of a catalyst supporting step.

[Explanation of symbols]

 1, 40 Metal carrier 2 Flat plate 3 Corrugated plate 4 Slit part 5 Engine (internal combustion engine) 6a, b Exhaust manifold (exhaust path) 7 Start casterist 8 Outer cylinder 9 Void part 10 Notch part 11, 13 Welding mark 12 Flange 22 Exhaust Tubes 31, 32, 43, 44 Platinum aqueous solution (solution) 41b Range (low density carrier layer) 41a, 52a Range (high density carrier layer) 41c, 52b Range (non-high density carrier layer)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B01J 35/04 321 A B01D 53/86 ZAB 53/94 B01J 23/40 ZAB A F01N 3/28 ZAB 301 P

Claims (14)

[Claims] 1. A metal, which is disposed in an exhaust path of an internal combustion engine, and which carries a catalytic substance on a honeycomb body formed by alternately laminating and winding metal flat plates and corrugated plates. In the carrier, a plurality of slits extending in the direction orthogonal to the exhaust gas flow direction are formed on the exhaust path upstream side of at least one of the flat plate or the corrugated plate, and the slits near the end on the exhaust path upstream side are formed. A metal carrier, characterized in that it has a high-density support layer in which a catalyst substance is distributed in a higher density than in the exhaust passage downstream side of the honeycomb body in a range including the same. 2. The slit portion composed of the plurality of slits is 5% to 60% of the axial length of the honeycomb body in the exhaust gas flow direction from the exhaust path upstream side of the flat plate or the corrugated plate.
The metal carrier according to claim 1, wherein the metal carrier is formed in the range of%. 3. The metal carrier according to claim 1, wherein the high-density support layer is formed in a range of 5 mm or more in the exhaust gas flow direction including the slit portion. 4. A non-slit portion is formed in a range of 3 mm to 5 mm in an exhaust gas flow direction at an exhaust path upstream end portion of the flat plate or the corrugated plate on which the slit portion is formed,
The metal carrier according to claim 1, 2 or 3, wherein a low-density supporting layer having a low-density distribution of the catalyst substance is formed on the non-slit portion. 5. The metal carrier according to claim 1, 2, 3 or 4, wherein the catalyst substance is composed of platinum, a rhodium catalyst or a palladium catalyst. 6. The metal carrier according to claim 1, wherein the loading density of the high-density loading layer is 9 times or less the loading density of the non-high-density loading layer. 7. When the catalyst substance is a platinum or rhodium-based catalyst, the total supported amount of the catalyst substance is 1.5 g / liter to 4.
0 g / liter, and the weight ratio of platinum and rhodium is platinum 1
Rhodium is 0.2 or less, and the high density loading layer is loaded so that the loading density is 3.6 g / m ² or less. 5
Alternatively, the metal carrier according to item 6. 8. When the catalyst substance is a palladium-based catalyst, the total supported amount of the catalyst substance is 4.0 g / liter to 6.0.
7. The carrier according to claim 1, 2, 3, 4, 5 or 6, wherein the carrier density is g / liter and the carrier density of the high density carrier layer is 8.0 g / m ² or less. Metal carrier. 9. When the catalyst substance is a platinum or rhodium-based catalyst, the minimum support density of the support layer formed by supporting the catalyst substance on the honeycomb body is 0.45 g / m ^2. The metal carrier according to claim 1, 2, 3, 4, 5, 6 or 7. 10. The minimum supporting density of a supporting layer formed by supporting the catalyst substance on the honeycomb body is 1.0 g / m ² when the catalyst substance is a palladium-based catalyst. The metal carrier according to 1, 2, 3, 4, 5, 6 or 8. 11. The catalyst material is supported on a γ-Al ₂ O ₃ layer coated on the flat plate or the corrugated plate. ,
The metal carrier according to 7, 8, 9 or 10. 12. When the catalyst substance is a platinum-rhodium-based catalyst, the total supported density of platinum and rhodium is 0.45 g / m 2.
^2, the coating density of the γ-Al ₂ O ₃ layer is 3
Claim 1, 2, 3, characterized in that a 1 g / m ^2,
The metal carrier according to 4, 5, 6, 7, 9 or 11. 13. When the catalytic substance is a palladium-based catalyst
, Palladium loading density 1g / m²Against the above γ-A
l₂O₃Layer coating density is 31g / m ²It is
And claim 1, 2, 3, 4, 5, 6, 8, 1
The metal carrier according to 0 or 11. 14. The support density distribution of the catalyst material is obtained by the number of times the flat plate or the corrugated plate is immersed in a solution containing the components of the catalyst material. 4, 5, 6, 7, 8, 9, 10, 1
The metal carrier according to 1, 12, or 13.