JPH0416241A - Preparation of catalyst carrier - Google Patents

Abstract

PURPOSE:To obtain a catalyst carrier having a good function and a desired shape by applying a fine metal powder to the substrates arranged in a retaining mold by low temp. flame spraying to form a molded body and subsequently baking the molded body in a non-oxidative atmosphere. CONSTITUTION:Substrates 4 composed of urethane rubber or nylon are arranged in a retaining mold 8 and a fine metal powder 6 composed of Pt or Pd is applied to the substrates 4 by low temp. spray coating, using carrier gas 7 such as nitrogen or argon to form a molded body. Thereafter, this molded body is baked under a non-oxidative atmosphere such as N2 gas or H2 gas. Since the catalyst carrier thus obtained can be allowed to approach the close part of the engine in exhaust piping, catalystic reaction efficiency is enhanced and the efficiency and output of the engine are also enhanced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a metal supporting catalyst installed in the engine exhaust gas system of an automobile and used to treat NOx and SOx contained in the exhaust gas. The present invention relates to a method for producing a carrier.

(Prior Art) It has been more than 10 years since automobile exhaust gas regulations were implemented, and the current exhaust gas countermeasures are by improving engines and purifying exhaust gas using catalysts. The mainstream catalyst for exhaust gas purification is one in which a precious metal catalyst such as platinum is supported on a ceramic honeycomb such as cordiolite.

However, since these ceramic honeycombs have thick walls to ensure strength, it is necessary to increase the volume to ensure air permeability, resulting in a relatively large installation space.

In addition, this honeycomb is inserted and supported in the outer cylinder and installed in the engine exhaust gas system, or the honeycomb itself has thermal shock resistance, and the stress caused by vibration shock between the honeycomb and the outer cylinder that supports it and the difference in thermal expansion coefficient. Due to the heat resistance of the buffer stainless steel mesh inserted to absorb
It has the disadvantage that the operating temperature must be lowered.

In order to improve these drawbacks, metal catalyst carriers made of stainless steel foil have recently begun to be used. These metal carriers are naturally required to have heat and corrosion resistance to withstand high temperatures and high velocity exhaust gases during the reaction, and heat fatigue resistance to withstand intense heating and cooling cycles.

As shown in FIG. 2, this kind of metal carrier 1 generally has 5
〇- A stainless steel flat foil having a thickness of around 100 mm and a corrugated stainless steel corrugated foil are overlapped and rolled into a cylindrical or elliptical shape to form a honeycomb body 2, and this is inserted into an outer cylindrical tube 3 made of heat-resistant stainless steel. After that, the flat foil, corrugated foil, and outer tube are joined together by brazing, resistance welding, etc., and manufactured.

(Problems to be Solved by the Invention) In the conventional method, since the metal foil of the internal carrier portion is thin, only a carrier having a structure in which the void portion is straight in the axial direction can be manufactured. Furthermore, it is extremely difficult to bend the manufactured straight pipe carrier, and the metal foil inside the pipe carrier breaks, so that there is no technical prospect for practical use of bent pipe carriers.

In order to withstand bending, the internal metal foil must be made of a thicker metal plate, which poses the problem of lowering the porosity and specific surface area and significantly deteriorating its function as a catalyst carrier. be.

It is an object of the present invention to solve the problems of the prior art and to provide a catalyst carrier having good functionality and a desired shape that can be put to practical use.

(Means for Solving the Problems) The gist of the present invention for achieving the above objects is (1)
1. A method for producing a catalyst carrier, which comprises arranging substrates in a mold, forming a molded body by spraying fine metal powder onto the substrate at a low temperature, and then firing in a non-oxidizing atmosphere.

(2) A base material is fixed to a metal foil in advance with an adhesive, etc., a molded body is made by spraying a low 4A metal fine powder onto the base material, and the molded body is supported so as to be surrounded by a mold, and then, A method for producing a catalyst carrier, characterized by firing in a non-oxidizing atmosphere.

(3) A substrate is arranged in layers in a mold, the substrate is coated with fine metal powder by low-temperature spraying, and a molded body is formed by stacking the substrate layers coated with such metal powder by low-temperature spraying. A method for producing a catalyst carrier, comprising firing a molded body supported on a frame in a non-oxidizing atmosphere.

(4) The method for producing a catalyst carrier as described in (1), (2) or (3) above, characterized in that the catalyst is supported on the base material in advance.

The present invention will be explained in detail below.

Basically, the present invention involves low-temperature thermal spraying of metal onto a string-like base material, molding and solidification, creating a molded body, and firing the molded body in a non-oxidizing atmosphere to liquefy or vaporize the base material. A method for producing a catalyst carrier in which the sintering of the sprayed metal is further strengthened, the boundary is thin, the curved through holes of a long and narrow fixed shape are gathered, and the outer cylinder surrounding the whole is also a curved pipe. It is.

In the method of the present invention, a metal catalyst carrier having a more complicated shape can be manufactured by applying thermal spraying technology. Specifically, a resin such as urethane rubber or nylon is used as a base material, and the number, length, and shape of the molded product are adjusted to match the expected number. The base material is a material that maintains the shape of the sprayed metal molded object.
Any material can be used as long as it does not cause a large volume change during the sintering stage and does not destroy metal adhesion, and that evaporates before the sintering reaction is completed. In addition, the base material has flexibility,
It is preferable that it can be deformed to an arbitrary curvature so as to match the longitudinal shape of the formed body (honeycomb body).

The base material is coated with metal by low-temperature spraying.

Next, in the low-temperature spraying method used in the present invention, air is injected from a slit on the circumference of the arc, and within the cylindrical reduced pressure layer formed by this air, two melting seals (wires) are crossed, and the tip of the An arc is generated in the section to melt the seal. The molten metal is then vacuumed from within the jet cold air stream into the air stream,
The particles are pulverized into fine particles in a low-temperature pressure air stream, and the temperature of the particles is instantly lowered to make them collide with air and adhere to the base material.

During thermal spraying, if the surface of the base material is too smooth, the metal welding efficiency will decrease, and if the base material is easily deformed by heat, the dimensional accuracy of the welded product will deteriorate, so if necessary, an organic binder starch is used. It is a good idea to apply a substance that increases the roughness of the surface or improves the adhesion rate, or a substance that is resistant to heat. The coating agent can be any material that evaporates and disappears by the time the metal sintering is completed, similar to the base material.

In order to suppress oxidation of the metal to be sprayed at low temperature as much as possible, a non-oxidizing gas such as nitrogen or argon is used as the carrier gas. Furthermore, it is preferable to complete the low-temperature thermal spraying work in a dedicated room whose atmosphere is controlled with a neutral gas such as nitrogen or argon, preferably by remote control or by using automatic equipment.

In this process of welding metal to the surface of the base material, only one layer of film can be formed per cycle, so the process is repeated to assemble a long, thin tube with an ultra-thin wall thickness (approximately 40 to 100 w) to form the final product. Finish into a molded body stacked in layers. This molded body is fixedly supported by a mold made of metal such as heat-resistant steel such as stainless steel (constituting the outer cylinder of the catalyst carrier of the present invention),
It is convenient for manufacturing to use this formwork with a cylinder divided in half (hereinafter, the molded body fixedly supported by the half-split formwork will be referred to as a half-split structure), but the present invention is not limited to this. It's not something you can do.

Metal foils can be placed at the boundaries of the layers, thereby reducing variations in the strength of the structure. A half-split structure composed of the base material and the welded metal or the same and the metal foil is fired in a non-oxidizing atmosphere such as N2 gas, N2 gas, a mixed gas of N2 and N2, or vacuum. If the weld metal or metal foil is an alloy of iron and carbon, heat at 1400°C for 2 hours.
In the case of an alloy of iron and Ni, by ensuring a sintering time of 2 hours at 1200°C, it is possible to sinter a material for a catalyst carrier in which ultra-thin walled elongated grasses are assembled.

Thereafter, a catalyst carrier is manufactured by welding and integrating the pair of half-structures subjected to the above treatment.

Next, an example of the manufacturing flow of the catalyst carrier of the present invention will be explained with reference to FIG.

For example, a string-like base material 4 made of synthetic resin (Fig. 1(a)
) in the half-split formwork 8 with a minute gap (40 to 100-
Open the formwork and fix it in parallel with adhesive in parallel along the shape of the formwork, and then low-temperature spraying of stainless steel is applied (see Figure 1 (b)).
. The adhesive applied to the surface of the base material 4 is used for the purpose of fixing the base material and for improving the welding efficiency of the sprayed metal.

Therefore, bentonite, fine alumina powder, etc. may be mixed into the adhesive. If the catalyst has extremely high heat resistance, it is also possible to directly adhere the catalyst to the final product. For example, PL, Pd, Co.

Transition metals such as Rh and Ag30i or their oxides,
Or their composite oxide, PVA.

Adhere to the surface of the base material with an adhesive such as CMC, and attach it to the formwork before the adhesive hardens. After that, the metal that will become the catalyst carrier is sprayed by low-temperature spraying and shaped.

After the stainless steel 5 is low-temperature sprayed onto the base material 4 in this manner, fixing of the base material layer and low-temperature spraying of metal are repeated until the half-split formwork 8 is filled (see FIG. 1(C)). It is preferable to apply a metal brazing agent to the inside of the mold 8 in order to further strengthen the welding of the molded body.

Alternatively, the base material 4 may be fixed in advance on a stainless steel foil 9, and then stainless steel may be sprayed at a low temperature on top of the base material 4 (see FIG. 1(d)), and then stacked in the formwork (the first Figure (e
)reference). In that case, if necessary, a metal solder can be applied with an adhesive to improve the adhesive strength between the sprayed metal and the metal foil after phosphoric acid.

When the half-split structure formed in this manner is fired in the above atmosphere, the base material 4 is removed, and a catalyst carrier material 1O having a honeycomb structure in which ultra-thin walled elongated tubes are assembled can be fired. As shown in FIG. 1 ( ), the paired structures are welded together using the molds 8 to produce the catalyst carrier 11 .

Although FIG. 1 above shows a case in which the formwork is welded after firing the half-split structure, the present invention may be manufactured in another embodiment. In other words, a method may be used in which a pair of molds are welded to form an outer cylinder, and a carrier material having a metal-coated base layer supported within the outer cylinder is fired in the above-mentioned atmosphere, thereby removing the base and The coated metal layer is sintered, and a honeycomb body is integrally formed with the outer cylinder, with the removed base portion serving as the through hole.

In addition, when fixing a base material to metal foil with an adhesive or the like and spraying fine metal powder at a low temperature, a long metal foil is used and the base material is arranged so as to match the length and shape of the intended carrier. , low-temperature thermal spraying is performed, and then the metal foil is cut to the required dimensions to match the shape of the carrier and layered so that it can be stacked in a formwork, or the base material can be formed into a predetermined bent shape. Fine metal powder is sprayed at a low temperature on a long metal foil arranged and fixed, the long metal foil is wound in a spiral shape, and this spiral body is cut in half and inserted into a half-split formwork, or The spiral body may be inserted and supported within a cylindrical shape or a half-split formwork.

As explained above, the present invention is particularly advantageous for manufacturing a curved tube type catalyst carrier, and the formwork 8 may be formed into a curved tube.

Note that the cross-sectional shape of the base material can be of various shapes such as circular, square, etc.
It is not particularly limited.

(Example) Next, examples of the present invention will be described.

(Example 1) Using stainless steel with the components shown in Table 1, it was low-temperature sprayed onto a synthetic rubber string fixed with adhesive PVA in a stainless steel frame (half-shaped outer cylinder) (Fig. 1 (b) )reference). The fixing of synthetic rubber and low-temperature spraying were repeated until the mold was filled to create a molded body (see Figure 1 (c)), which was then baked at 1350°C for 3 hours in an H2 atmosphere to form an ultra-thin walled body. A pair of catalyst carrier materials with a half-split structure made up of long, thin tubes was made, and the pairs were welded together to create a monolithic carrier. Table 3 shows the dimensions of the completed product, and Table 4 shows the pressure loss measurement results.

(Example 2) A synthetic rubber string was fixed in advance to a stainless steel foil with a thickness of 50 μm using PVA adhesive, and stainless steel having the components shown in Table 2 was sprayed at a low temperature.
8244 bodies were molded (see Figure 1(d)). The plate-like structure whose final structure had been designed and manufactured in advance was set side by side on a half-split stainless steel tube that would serve as an outer frame, to produce a molded body (see FIG. 1(e)). It was heated to 900℃ under H2 atmosphere.
This was fired for 1 hour to produce a pair of half-structured catalyst carrier materials in which ultra-thin elongated tubes were assembled, and further fired at 1380°C for 2 hours in a vacuum furnace to increase the sintering strength. The pair was welded to create an integral structure. Table 3 shows the dimensions of the completed product, and Table 4 shows the pressure loss measurement results.

(Example 3) A synthetic rubber cord with an equilateral triangular cross section and a side length of 3
Immersed in VA 5% solution, P with an average particle size of lOμ is placed on the surface.
L powder was sprayed using a powder coating machine and fixed on the surface.

Thereafter, a 5% PVA solution was applied to a stainless steel foil having a thickness of 60 μm, and stainless steel having the components shown in Table 2 was sprayed at a low temperature. Synthetic rubber was pasted on stainless steel foil, the surface of the synthetic rubber was covered with Pt powder, and stainless steel was further sprayed on the surface to form a plate-like structure. The final structure was designed and manufactured in advance, and the plate-like structure was set side by side in a stainless steel tube cut in half to serve as the outer frame, to create a molded body. H that
2. Sintered at 900°C for 1 hour in a vacuum furnace to create a pair of catalyst carrier materials with a half-split structure made up of ultra-thin and long tubes, and then fired at 1380°C in a vacuum furnace for 2 hours to further increase the sintering strength.
Baked for an hour. The pair was welded to create an integral structure. The dimensions of the completed product and the pressure drop measurement results were almost the same as in Example 2, and the catalytic effect was almost the same as that of Example 2 manufactured by plating with P.

(Effects of the Present Invention) According to the present invention, the catalyst pusher can be brought close to the engine in the exhaust pipe to a distance that was technically impossible with conventional metal carriers. As a result, the catalyst can be operated while the temperature of the exhaust gas remains higher, thereby increasing the catalytic reaction efficiency and improving engine efficiency and output.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the manufacturing flow of the catalyst carrier of the present invention,
FIG. 2 is an explanatory diagram of a conventional metal carrier. 1... Metal carrier 2... Honeycomb body 3...
・Outer cylinder 4...Base material 5...Low temperature spraying machine 6...Low temperature spraying molten metal 7...Carrier gas
8...Outer tube 9...Metal foil 10...Catalyst carrier material 11 made up of elongated tubes...
・Catalyst carrier

Claims (4)

[Claims] (1) A method for producing a catalyst carrier, which comprises arranging substrates in a mold, forming a molded body by low-temperature thermal spraying of fine metal powder onto the substrate, and then firing in a non-oxidizing atmosphere. . (2) A base material is fixed in advance to metal foil, a molded body is made by low-temperature spraying of metal fine powder onto the base material, and the molded body is supported so as to be surrounded by a mold, and then placed in a non-oxidizing atmosphere. A method for producing a catalyst carrier, which comprises firing. (3) A substrate is arranged in layers in a mold, the substrate is coated with fine metal powder by low-temperature spraying, and a molded body is formed by stacking the substrate layers coated with such metal powder by low-temperature spraying. A method for producing a catalyst carrier, comprising firing a molded body supported on a frame in a non-oxidizing atmosphere. (4) The method for producing a catalyst carrier according to claim 1, 2 or 3, characterized in that the catalyst is supported on the base material in advance.