JP5334637B2 - Metal carrier for exhaust gas purification catalyst - Google Patents

Description

  The present invention relates to a metal carrier used as a catalyst for purifying exhaust gas discharged from an internal combustion engine, and an exhaust gas purification catalyst using the carrier.

  Since the exhaust gas purifying catalyst of the internal combustion engine is exposed to high temperature exhaust gas, heat-resistant ceramics or the like is used as the material of the catalyst carrier. However, such a ceramic carrier is vulnerable to mechanical shock, and there is a problem that pressure loss increases with use. From such a viewpoint, a metal carrier made of heat-resistant stainless steel or the like is generally used in a motorcycle that requires a catalyst having high strength and low pressure loss.

  Generally, a metal honeycomb carrier is formed by alternately winding flat foil and corrugated foil using a heat-resistant alloy into a cylindrical honeycomb body, and after inserting the honeycomb body into a cylindrical metal outer cylinder It is manufactured by joining them by means such as brazing. However, such a conventional metal honeycomb carrier cannot withstand the misfire generated from the engine because the metal foil constituting the honeycomb body is thin, and a part of the metal honeycomb carrier may melt and fall off from the outer cylinder.

  A material having higher durability than a standard metal honeycomb carrier has been developed. However, it cannot meet strict cooling and heat durability requirements, and may fall off like a normal metal honeycomb carrier.

  Japanese Patent Application Laid-Open No. 2008-190505 discloses a metal pipe-type catalyst. The catalyst can be arranged in an exhaust pipe (exhaust pipe) or silencer instead of the metal honeycomb carrier or together with the metal honeycomb carrier.

  In order for such a pipe-type catalyst to achieve a predetermined purification performance, a certain length of pipe is required. This is because when the gas flow rate is high, unreacted exhaust gas is discharged, and as a result, the catalyst performance decreases. However, if the pipe is made longer, there is a problem in terms of mountability. On the other hand, although the flow velocity can be lowered by widening the catalyst cross section, the space velocity (SV: space velocity) increases due to the relationship between the exhaust gas treatment amount and the catalyst capacity, and as a result, the unreacted gas increases.

  Further, a catalyst of a type in which a plurality of small diameter pipes are incorporated in the outer cylinder pipe as disclosed in JP-A-9-317452 has a problem in assembling the small diameter pipe in the outer cylinder. In particular, when the two are joined by brazing, a gap is not allowed, so that a very high dimensional accuracy is required for the manufacture of the pipe. Although it is conceivable to use general ERW pipes as such pipes, ERW pipes with a low degree of freedom in outer diameter size require secondary processing such as diameter reduction and pipe expansion, which increases costs. Can't escape.

Japanese Patent Laid-Open No. 9-317452 JP 2008-190505 A

  An object of the present invention is to provide a metal carrier for exhaust gas purification that is superior in terms of durability, exhaust gas purification performance, and mountability compared to conventional exhaust gas purification catalyst carriers, and a metal carrier catalyst using the carrier. It is in.

  As a result of intensive studies on the problem by the inventor, a large number of metal plates thicker than the metal foil used in the conventional metal honeycomb carrier are arranged in the outer cylinder like blades used in a turbine. As a result, it was found that an exhaust gas purification catalyst having greatly improved melting resistance, exhaust gas purification performance and mountability can be obtained, and the present invention has been completed.

That is, the present invention includes the following inventions.
[1] An exhaust gas purifying metal carrier in which one or a plurality of units composed of a plurality of metal curved plates and / or metal flat plates are arranged inside a metal pipe, the plate being the pipe of the pipe A metal carrier for an exhaust gas purifying catalyst, wherein the metal carrier is arranged radially at substantially equal angular intervals from a central portion of a transverse section to an inner wall surface of the pipe.
[2] The plate according to [1], wherein each of the plates has a substantially U-shape or V-shape, and is arranged so as to be divided into two hands from a central portion of a cross section of the pipe. The metal carrier for exhaust gas purification catalysts as described.
[3] The metal carrier for an exhaust gas purification catalyst according to [1] or [2], wherein the plate is provided with a punching hole.
[4] The exhaust gas purification according to any one of [1] to [3], wherein the metal pipe is an exhaust pipe, and the plurality of units are arranged in the exhaust pipe at predetermined intervals. Metal carrier for catalyst.
[5] A metal carrier catalyst for purifying exhaust gas, characterized in that the metal carrier according to any one of [1] to [4] is used as a base material.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the exhaust gas purification catalyst using the metal support | carrier for exhaust gas purification catalysts and the said carrier which were excellent in melt | dissolution resistance, exhaust gas purification performance, and mountability conventionally. Specifically, unlike the conventional metal honeycomb carrier using a thin metal foil, the metal carrier of the present invention can use a thick metal plate, so that the durability is greatly improved. And since the contact area with an exhaust gas flow is large compared with the conventional pipe type catalyst, high performance is also realized.

  A conventional tube-type catalyst in which a plurality of tubes are arranged in an outer cylinder has no degree of freedom in the radial direction, is difficult to assemble, and has insufficient strength. On the other hand, a unit composed of a curved plate like the metal carrier of the present invention is not only easy to assemble in the pipe because it is inserted while being inserted into the pipe, but the metal plate is also elastic due to its elasticity. There is a merit that sufficient rigidity can be secured because it tries to return to the shape (spring back). Furthermore, the metal carrier of the present invention that can utilize the springback phenomenon has an advantage that it can be applied to various pipes having different outer cylinder diameters by changing the curvature of the curved plate.

FIG. 1 is a cross-sectional view (a) and a perspective view (b) of a metal carrier in which one unit composed of a plurality of curved plates is arranged in a pipe. FIG. 2 is a diagram for explaining a unit (c) formed by bending (b) a rectangular cut plate (a) and collecting these six pieces, and a unit (d) using a curved plate as the plate. . FIG. 3 is a diagram for explaining a unit (c) formed by putting a groove (b) in a rectangular cut plate (a) and assembling these six pieces, and a unit (d) using a curved plate as the plate. It is. FIG. 4 is a diagram for explaining a unit (c) formed by cutting and twisting (b) a single disk (a) and bending them one by one. FIG. 5 illustrates a unit (c) formed by bending a rectangular cut plate (a) into a U-shape (b) and assembling six of them, and a unit (d) using a curved plate as the plate. It is a figure to do. FIG. 6 is a perspective view of a metal carrier in which two units composed of curved plates are arranged on the inlet gas side and the outlet gas side of the pipe. FIG. 7 is a perspective view of a metal carrier in which four units are inserted into a bent pipe. FIG. 8 is a cross-sectional view (a) and a perspective view of a metal carrier in which two units composed of curved plates are arranged on the inlet gas side and the outlet gas side of the pipe so that the phases of the curved plates are reversed. (B). FIG. 9 is a cross-sectional view of a metal carrier in which two units composed of curved plates with punched holes are arranged on the inlet gas side and the outlet gas side of the pipe so that the phases of the curved plates are reversed. It is (a) and a perspective view (b).

  The present invention is an exhaust gas purifying metal carrier in which one or a plurality of units comprising a plurality of metal curved plates and / or metal flat plates are arranged inside a metal pipe, wherein the plate is the pipe. An exhaust gas purifying catalyst metal carrier, characterized in that it is arranged radially at substantially equal angular intervals from the center of the cross section to the inner wall surface of the pipe.

  As the pipe constituting the metal carrier of the present invention, a metal outer cylinder usually used in a metal honeycomb carrier, for example, a stainless steel cylindrical outer cylinder such as SUS436 can be used. In addition, an exhaust pipe or a muffler may be used as the pipe.

  The unit inserted into the pipe is formed by arranging a plurality of metal curved plates and / or metal plane plates radially at substantially equal angular intervals from the center of the cross section of the pipe to the inner wall surface of the pipe. Become. For example, when twelve metal plates are radially arranged from the center of the pipe at equal intervals, the angular interval of each metal plate is about every 30 degrees. The number of metal plates and the angular interval at which they are arranged are appropriately adjusted from the viewpoints of manufacturing cost, desired strength, exhaust gas purification performance, and the like. This is because if there are many plate materials, it is complicated to determine the position when the plate materials are gathered and joined at the central portion, and the area of the gas circulation portion at the central portion becomes narrow. Accordingly, the number of plate members is not limited, but 3 to 20 sheets are preferable.

  The material of the metal plate to be used is not limited, but a metal used in a general metal honeycomb carrier, for example, stainless steel or heat resistant steel having a low heat capacity and excellent heat resistance and pressure resistance is preferable. Furthermore, since the lower the coefficient of thermal expansion, the less likely it is to distort, it is preferable as the metal plate used in the present invention. Examples of such stainless steel include steel materials such as ferritic stainless steel and austenitic stainless steel. Among these stainless steels, ferrite type (for example, SUS430 type, 436 type etc.) is preferable.

  In addition to the above stainless steel, a material having high antioxidant property, for example, a steel material such as 20Cr-5Al, or a stainless steel such as SUS340 may be used.

  As shown in FIGS. 2A to 2C, the unit can be configured by bending a metal cut plate having a predetermined size and joining a number of these cut plates together at the end. The number of times of bending is not particularly limited. As shown in FIG. 2D, the unit may be configured using a curved plate. The curvature of the curved plate can be determined as appropriate in consideration of the springback after being placed in the pipe. In addition, although the length until it reaches the inner wall surface from the center part of the cross section of a pipe is needed, the surface area increases in connection with it, so that a catalyst performance improves as a curvature is large. On the other hand, when the curvature is reduced, the degree of freedom of the exhaust gas flow in the pipe is increased, and the engine performance (back pressure) is improved. These cut plates are arranged radially at substantially equal angular intervals from the center of the cross section of the pipe to the inner wall surface of the pipe. As shown in FIG. 3, it is possible to make a unit as shown in FIG. 1 by cutting a part of the cut plate and folding them. Instead of a cut plate, a single disc can be used as a starting material (FIG. 4). In this case, it is possible to make a unit having a desired shape by making cuts so as not to be separated from the central portion of the disk at certain angles and twisting or bending them one by one.

  In another aspect, one cut plate may be bent and formed into a substantially U shape or V shape, and a plurality of the cut plates may be arranged in the pipe so as to be separated from the center of the cross section of the pipe. Good (FIG. 5).

  The metal carriers described in FIGS. 2 (c) and 2 (d) and FIGS. 3 (c) and 3 (d) are excellent in terms of ease of production. However, when the number of cutting plates to be used increases, the intersections of the blades concentrate near the center of the carrier, and as a result, there is a possibility that the room for exhaust gas to flow near the center is reduced. Moreover, if this center part is fixed with a brazing material, the exhaust gas flow in the vicinity of the center part is further hindered. Therefore, it is also preferable to employ the metal carrier described in FIGS. 4B and 4C from the viewpoint of preventing deterioration of the exhaust gas flow near the center. On the other hand, the metal carrier described in FIGS. 4B and 4C has few points for fixing each plate. Therefore, in consideration of durability and the like, it is also preferable to employ the metal carrier described in FIGS. 5C and 5D, which has many points for fixing in the pipe. Furthermore, as described later, it is also preferable to provide punching holes in the carrier to improve the exhaust gas purification performance.

  A plurality of units may be arranged in multiple stages at predetermined intervals in the pipe (FIG. 6). When a plurality of units are arranged in multiple stages in this way, the space created between the units causes disturbance in the exhaust gas flow, increasing the contact between the exhaust gas and the catalyst component supported on the unit surface, and as a result, exhaust gas purification. This is preferable because the performance is improved. Furthermore, when using a pipe bent in an arc shape, a unit having a short depth may be arranged in a plurality of pipes (FIG. 7).

  By arranging units of the same shape in a plurality of pipes or changing the bending direction of the metal plate in each unit, the phase of the arrangement of the metal plate can be shifted for each unit (FIG. 8). By shifting the phase, the exhaust gas can be prevented from being blown out, and as a result, the exhaust gas purification performance is improved.

  In order to reduce the heat capacity and activate the catalyst early, it is preferable to provide punching holes in the metal plate constituting the unit. Such punching holes can improve the diffusibility of the exhaust gas flowing into the catalyst, thereby increasing the contact between the exhaust gas component and the catalytically active component. The individual size of the punching hole is not particularly limited. Note that punch holes having a diameter smaller than the thickness of the metal plate are usually not suitable for mass production. FIG. 9 shows an example of a metal-supported catalyst provided with punching holes. The punching holes may be staggered.

  The unit is inserted into the pipe while being rotated and assembled. After the assembly, a brazing material such as nickel brazing is applied. Alternatively, a nickel brazing material may be applied around the unit and then inserted into the pipe. The metal carrier of the present invention can be prepared by treating the unit assembled in the pipe at a high temperature to join the inner wall of the pipe and the unit to each other.

Exhaust gas purification metal carrier catalyst The metal carrier catalyst of the present invention is produced using the above-mentioned metal carrier. Since the present invention is characterized by the metal carrier itself, the catalyst coat layer formed on the metal carrier may contain arbitrary components. The catalyst coat layer in the metal carrier catalyst of the present invention can be formed in the cell passage by supporting a catalyst noble metal on the metal carrier by a conventionally used method such as an impregnation method or a wash coat method. Depending on the application, the catalyst coat layer may include other catalyst metals or NOx occlusion materials such as alkali metals or alkaline earth metals. The catalyst coat layer is not limited to a single layer, and may be composed of a plurality of layers. Moreover, the thickness is not specifically limited.

  The present invention will be described more specifically with reference to the following examples. The present invention is not limited to these examples.

Example 1
Twelve stainless steel plates having a width of 23 mm and a total length of 90 mm were prepared, and each was curved in an arc shape so that the radius of curvature was approximately R13. The ends of 12 curved plates were gathered at intervals of about 30 degrees and joined by nickel brazing to form a unit for a metal carrier. The unit was inserted into a stainless steel outer cylinder having a diameter of 42.7 mm and a total length of 90 mm, and joined by nickel brazing. Catalyst material (Al ₂ O ₃ : 57.6%, Ce-Zr oxide: 32.4% (CeO ₂ : 27.5%), binder: 5.8%, Pt: 3.6% , Rh: 0.7%) was applied at 36 g / m ₂ and baked and baked to prepare the metal carrier catalyst of the present invention.

(Example 2)
Twelve stainless steel plates having a width of 23 mm and a total length of 30 mm were prepared and curved in an arc shape so that the radius of curvature was approximately R13, and two units for metal carriers were formed in the same manner as in Example 1. Insert one side of the unit into the stainless steel outer cylinder with a diameter of 42.7 mm and a total length of 90 mm, and insert it into the gas side while turning the other unit. They were inserted and joined by nickel brazing (FIG. 6). The metal carrier catalyst of the present invention was prepared by applying the catalyst material to the metal carrier thus prepared under the same conditions as in Example 1 and performing baking and baking.

(Example 3)
A metal-supported catalyst was prepared in the same manner as in Example 2 except that punching holes were provided (FIG. 9).

(Comparative Example 1)
Pipe catalyst A catalyst material was applied to the inner surface of a pipe having a diameter of 42.7 mm and a total length of 90 mm under the same conditions as in Example 1 and baked.

(Comparative Example 2)
Multi-tube catalyst A catalyst material was applied to the inner surface of a pipe having a diameter of 42.7 mm and a total length of 90 mm and the inner surface of a total of three punching pipes having a diameter of 18 mm and a total length of 90 mm under the same conditions as in Example 1, followed by firing and baking.

(Comparative Example 3)
Honeycomb Catalyst A catalyst material was applied to the inner surface of a metal honeycomb carrier having a diameter of 42.7 mm, a diameter of 90 mm, and a cell density of 100 cpsi under the same conditions as in Example 1 and baked.

1 Metal carrier 2 Pipe 3 Curved plate 4 Punching hole

Claims (5)

Inside the metal pipe, a one or a plurality placed the metal carrier for exhaust gas purification unit consisting of three or more metallic curved plate, diameter the plate, from the center of the cross section of each of the pipe It has a shape that is divided into two arcs in the direction of the direction, and is arranged radially at substantially equal angular intervals from the center of the cross section of the pipe to the inner wall surface of the pipe. Metal carrier for exhaust gas purification catalyst. The metal carrier for an exhaust gas purification catalyst according to claim 1, wherein the shape of the plate divided into two hands is substantially U-shaped or V-shaped , respectively .   The metal carrier for an exhaust gas purification catalyst according to claim 1 or 2, wherein the plate is provided with punching holes.   The metal for exhaust gas purification catalyst according to any one of claims 1 to 3, wherein the metal pipe is an exhaust pipe, and the plurality of units are arranged at predetermined intervals in the exhaust pipe. Carrier.   A metal carrier catalyst for exhaust gas purification, wherein the metal carrier according to any one of claims 1 to 4 is used as a base material.

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