JP2006299966A - Catalyst converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst converter preventing leakage of exhaust gas or the fall-away of a catalyst support during heating while preventing the breakage of the catalyst support. <P>SOLUTION: The exhaust gas purifying catalyst converter comprises the catalyst support 2 for supporting an exhaust gas purifying catalyst on a carrier, a metal shell 3 covering its outside, and a retaining seal material 3 held therebetween. At a temperature of 15-1,100°C, the liner thermal expansion coefficient of the catalyst support 2 is 2-15×10<SP>-6</SP>/°C and the linear thermal expansion coefficient of the metal shell 3 is 10-25×10<SP>-6</SP>/°C. The retaining seal material 3 has inorganic fibers arranged in a mat shape and a heat conductivity of 0.03-0.3 W/mK at the temperature of 15-1,100°C. In the catalyst converter 1, a thermal elongation amount difference between the outward thermal elongation amount (mm) of the metal shell 3 of the catalyst converter 1 and the thermal elongation amount (mm) of the catalyst support 2 at the temperature of 15-1,100°C is within a range of -0.5 to 0.5 mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purifying catalytic converter that purifies exhaust gas discharged from an engine or the like.

Conventionally, automobiles are equipped with a catalytic converter for purifying exhaust gas discharged from an engine.
As shown in FIG. 7, the catalytic converter 90 includes a catalyst carrier 93 in which an exhaust gas purifying catalyst is supported on a carrier made of ceramics, a metal shell 95 covering the outside thereof, and a holding member disposed between the two. And a sealing material 91. Further, an inlet connection portion 97 and an outlet connection portion 98 are coupled to both ends of the shell 95 by welding, respectively, and the catalytic converter 90 is disposed in the middle of a pipe 99 for exhaust gas discharged from the engine 92.

  In the catalytic converter 90, the holding sealing material 91 prevents the exhaust gas from leaking from between the catalyst carrier 93 and the shell 95, and prevents the catalyst carrier 93 from coming into contact with the shell 95 and being damaged. Can play a role. The holding sealing material 91 is disposed between the catalyst carrier 93 and the shell 95 with a constant surface pressure. Therefore, the catalyst carrier 93 and the shell 95 can be held together.

  Further, the exhaust gas purifying catalyst such as platinum or palladium supported on the catalyst support 93 can generally exhibit its activity at a high temperature of, for example, 300 ° C. or higher. Therefore, in order for the exhaust gas purification action of the catalytic converter 90 to function, it is necessary to heat the catalytic converter 90. For the heating, heat such as high-temperature exhaust gas discharged from the engine 90 is generally used.

  On the other hand, in recent years, environmental problems have been attracting worldwide attention, and in order to save energy, there is a tendency to obtain an output by increasing the rotational speed while reducing the displacement of the engine 90. When the rotational speed of the engine 90 is increased, the temperature of exhaust gas discharged from the engine generally increases. In fact, the exhaust gas temperature discharged from the recent high-performance engine 90 reaches a high temperature of about 950 to 1100 ° C.

Therefore, the catalytic converter 9 is heated at a higher temperature than before by the high-temperature exhaust gas of about 950 to 1100 ° C. Furthermore, in order to shorten the time required for the catalyst carrier 9 to reach the activation temperature, the catalytic converter 9 tends to be disposed closer to the engine 90 side. Therefore, the catalytic converter 9 is heated at a higher temperature and more rapidly than before, and the heat load on the catalytic converter 9 is increasing more and more.
As a result, when the catalytic converter 9 is heated, there is a possibility that the catalyst carrier 93 held inside the metal shell 95 by the holding sealing material 91 falls off from the metal shell 95. Further, exhaust gas may leak from between the catalyst carrier 93 and the metal shell 95, or the catalyst carrier 93 may be damaged.

So far, in order to prevent the catalyst carrier from falling, a catalytic converter having an auxiliary part made of a heat-resistant metal has been developed (Patent Document 1). In such a catalytic converter, since the catalyst carrier is held by the metal shell by the auxiliary parts, it is possible to prevent problems such as dropping during heating.
However, even in the catalytic converter provided with the auxiliary parts, the above problem of exhaust gas leakage and the problem of damage to the catalyst carrier cannot be avoided.

JP 7-317537 A

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a catalytic converter that can prevent exhaust gas leakage and catalyst carrier dropping during heating, and also prevent damage to the catalyst carrier. Is.

The present invention provides a catalyst carrier formed by supporting an exhaust gas purification catalyst for purifying exhaust gas on a carrier, a metal shell covering the outside of the catalyst carrier, and between the metal shell and the catalyst carrier. In a catalytic converter for exhaust gas purification comprising a sandwiched holding sealing material,
The catalyst carrier has a linear thermal expansion coefficient of 2 to 15 × 10 ⁻⁶ / ° C. at a temperature of 15 to 1100 ° C., and the metal shell has a linear thermal expansion coefficient of 10 to 25 × 10 at a temperature of 15 to 1100 ° C. ^-6 / ℃,
The holding sealing material is formed by arranging inorganic fibers in a mat shape, and has a thermal conductivity of 0.03 to 0.3 W / mK at a temperature of 15 to 1100 ° C.
In the catalytic converter, a thermal elongation amount which is a difference between a thermal elongation amount (mm) of the metal shell to the outside of the catalytic converter at a temperature of 15 to 1100 ° C. and a thermal elongation amount (mm) of the catalyst carrier. In the catalytic converter, the difference is in the range of −0.5 to 0.5 mm.

The catalytic converter of the present invention comprises the catalyst carrier having the specific linear thermal expansion coefficient and the metal shell, and the holding sealing material having the specific thermal conductivity. In the catalytic converter, the difference in thermal elongation between the metal shell and the catalyst carrier at a temperature of 15 to 1100 ° C. is set to −0.5 to 0.5 mm. That is, in the catalytic converter, the difference in dimensional change between the metal shell that expands and contracts in the temperature range of 15 to 1100 ° C. and the catalyst carrier is set within a specific range of −0.5 to 0.5 mm. .
Therefore, in the catalytic converter, the change in the surface pressure at the contact surface between the holding sealing material and the metal shell and the change in the surface pressure at the contact surface between the holding sealing material and the catalyst carrier can be reduced. it can. Therefore, in the catalytic converter, it is possible to prevent exhaust gas from leaking from between the catalyst carrier and the metal shell, or to prevent the catalyst carrier from dropping from the metal shell. In addition, the catalyst carrier can be prevented from being destroyed.

Hereinafter, the function and effect of the present invention will be described in more detail together with the conventional problems.
In the conventional catalytic converter, the cause of the problems such as dropping of the catalyst carrier, leakage of exhaust gas, and destruction of the catalyst carrier as described above is the cause of the heat between the catalyst carrier and the metal shell. It was made paying attention to the difference in expansion.

  That is, generally, when high-temperature exhaust gas is supplied to the catalytic converter, the catalyst carrier and the metal shell expand due to heat. In most cases, the catalyst carrier and the metal shell have different coefficients of thermal expansion, and since a holding seal material is disposed between the catalyst carrier and the metal shell, high-temperature exhaust gas is passed to the catalytic converter. A difference is likely to occur between the elongation of the catalyst carrier and the elongation of the metal shell when supplied.

  Specifically, when exhaust gas is supplied to the catalyst carrier, for example, when the engine is started, heat transfer does not sufficiently occur to the metal shell, so that the thermal expansion of the catalyst carrier is larger than that of the metal shell. Easy to be. As a result, the surface pressure of the holding sealing material increases, and the catalyst carrier may be damaged. Further, for example, when the entire catalytic converter is sufficiently heated after the engine is started, the thermal expansion of the metal shell tends to be larger than that of the catalyst carrier. As a result, the surface pressure of the holding sealing material is reduced, and the exhaust gas may leak from between the catalyst carrier and the metal shell. When the surface pressure further decreases, the catalyst carrier is detached from the metal shell.

  In the catalytic converter of the present invention, as described above, at a temperature of 15 to 1100 ° C., the difference in thermal elongation between the metal shell and the catalyst carrier is set to a specific range of −0.5 to 0.5 mm. Yes. Therefore, the change in the surface pressure can be reduced as described above, and problems such as dropping of the catalyst carrier, leakage of exhaust gas, and destruction of the catalyst carrier can be avoided.

  Thus, according to the present invention, it is possible to provide a catalytic converter that can prevent the exhaust gas from leaking and the catalyst carrier from falling off during heating, and can also prevent the catalyst carrier from being damaged.

Next, an embodiment of the present invention will be described.
The catalytic converter of the present invention comprises the catalyst carrier, the metal shell, and the holding sealing material. And in the said catalytic converter, the heat | fever which is the difference of the thermal elongation amount (mm) of the said metal shell to the outward of the said catalytic converter in the temperature of 15-1100 degreeC, and the thermal elongation amount (mm) of the said catalyst carrier. The difference in elongation is in the range of -0.5 to 0.5 mm.
Here, as described later, the difference in thermal elongation is a value obtained by subtracting the thermal elongation of the catalyst carrier from the thermal elongation of the metal shell.

At a temperature of 15 to 1100 ° C., which is a general operating temperature range of the catalytic converter, the thermal expansion coefficient of the catalyst carrier is 2 to 15 × 10 ⁻⁶ / ° C. Further, at a temperature of 15 to 1100 ° C., the thermal expansion coefficient of the metal shell is 10 to 25 × 10 ⁻⁶ / ° C.
When the thermal expansion coefficient of the catalyst carrier is less than 2 × 10 ⁻⁶ / ° C. or when the thermal expansion coefficient of the metal shell exceeds 25 × 10 ⁻⁶ / ° C., the metal shell is heated when the catalytic converter is heated. The difference in thermal elongation between the catalyst carrier and the catalyst carrier tends to be large, and it may be difficult to make the thermal elongation difference at a temperature of 15 to 1100 ° C. 0.5 mm or less. As a result, there is a risk that exhaust gas leaks or the catalyst carrier will easily fall off.
On the other hand, when the thermal expansion coefficient of the catalyst carrier exceeds 2 × 10 ⁻⁶ / ° C. or when the thermal expansion coefficient of the metal shell is less than 10 × 10 ⁻⁶ / ° C., the catalyst converter is heated when the catalytic converter is heated. The difference in thermal elongation between the metal shell and the catalyst carrier tends to be small, and it may be difficult to make the difference in thermal elongation at a temperature of 15 to 1100 ° C. to be −0.5 mm or more. As a result, the catalyst carrier may be easily damaged.

Moreover, in the temperature of 15-1100 degreeC, the heat conductivity of the said holding sealing material is 0.03-0.3 W / mK. When the thermal conductivity is less than 0.03 W / mK, when the exhaust gas is supplied to the catalyst carrier of the catalytic converter and the catalytic converter is heated, heat transfer to the metal shell is difficult to occur. . Therefore, when the catalytic converter is heated, the difference in thermal elongation between the metal shell and the catalyst carrier tends to be small, and it is difficult to make the difference in thermal elongation at a temperature of 15 to 1100 ° C. −0.5 mm or more. There is a risk of becoming. As a result, the catalyst carrier may be easily damaged.
On the other hand, when the thermal conductivity exceeds 0.3 W / mK, when the exhaust gas is supplied to the catalyst carrier of the catalytic converter and the catalytic converter is heated, the heat transfer to the metal shell is not performed. It tends to happen. Therefore, when the catalytic converter is heated, the difference in thermal elongation between the metal shell and the catalyst carrier tends to increase, making it difficult to reduce the difference in thermal elongation at a temperature of 15 to 1100 ° C. to 0.5 mm or less. There is a risk. As a result, there is a risk that exhaust gas leaks or the catalyst carrier will easily fall off.

  In the catalytic converter, the difference in thermal elongation is in the range of -0.5 to 0.5 mm. The difference in thermal elongation is the difference between the thermal elongation amount (mm) of the metal shell to the outside of the catalytic converter and the thermal elongation amount (mm) of the catalyst carrier in the temperature range of 15 to 1100 ° C. .

This difference in thermal elongation will be described, for example, when the catalytic converter is substantially cylindrical (see FIGS. 1 and 2).
The diameter of the catalyst carrier before heating of the catalytic converter is L ₀ , and the diameter (inner diameter or outer diameter) of the metal shell before heating is M _0, and the catalyst carrier when heated within the temperature range of 15 to 1100 ° C. Assuming that the diameter is L and the diameter of the metal shell is M, the thermal elongation amount of the catalyst carrier can be expressed as LL ₀ , and the thermal elongation amount of the metal shell can be expressed as MM ₀ . And when the said thermal elongation amount difference is set to (DELTA), a thermal elongation amount difference can be represented by following formula (1).
Δ = (M−M ₀ ) − (L−L ₀ ) (1)

  In the catalytic converter, when the difference in thermal elongation is less than −0.5 mm, the surface pressure of the holding sealing material increases, and the catalyst carrier may be damaged. On the other hand, when the thickness exceeds 0.5 mm, the surface pressure of the holding sealing material becomes small. As a result, exhaust gas leaks between the catalyst carrier and the metal shell, or the catalyst carrier becomes the metal shell. There is a risk of falling off.

More preferably, the difference in thermal elongation is preferably in the range of −0.2 to 0.2 mm.
In this case, the change in the surface pressure of the holding sealing material can be further reduced. As a result, the above-described problems of destruction of the catalyst carrier, leakage of exhaust gas, and dropping of the catalyst carrier can be avoided with higher reliability.

The holding sealing material is sandwiched between the metal shell and the catalyst carrier.
Preferably, the holding sealing material has a thickness of 4 to 18 mm and a bulk density of 0.15 to 1.0 g / cm ³ and is disposed between the metal shell and the catalyst carrier. ).
In this case, in the catalytic converter, the difference in thermal elongation can be reduced. Therefore, it becomes easy to make the said thermal elongation amount difference into the range of -0.5-0.5 mm.

  When the thickness is less than 4 mm, the holding sealing material made of the inorganic fibers cannot exhibit sufficient heat insulation, and the metal shell is easily heated when the catalytic converter is heated. As a result, the amount of thermal expansion of the metal shell tends to increase, and there is a risk that exhaust gas leaks and the catalyst carrier will easily fall off. On the other hand, when it exceeds 18 mm, the heat insulating property of the holding sealing material becomes too high, and the amount of thermal expansion of the catalyst carrier tends to increase. As a result, the catalyst carrier may be easily destroyed.

When the bulk density is less than 0.15 g / cm ³ , when the holding sealing material made of inorganic fibers is placed between the metal shell and the catalyst carrier, the holding sealing material is the catalyst. It may be difficult to ensure a sufficient surface pressure to hold the carrier, and the catalyst carrier may easily fall off. On the other hand, if it exceeds 1.0 g / cm ³ , it is necessary to dispose the holding sealing material made of inorganic fibers between the metal shell and the catalyst carrier at a high surface pressure. The catalyst carrier may be damaged. Further, in this case, the heat insulating property of the holding sealing material is reduced, the amount of thermal expansion of the metal shell is likely to be increased when the catalytic converter is heated, and there is a risk that exhaust gas leaks or the catalyst carrier is likely to fall off. There is.

More preferably, the holding sealing material is disposed between the metal shell and the catalyst carrier with a thickness of 6 to 10 mm and a bulk density of 0.15 to 1.0 g / cm ^3. ).
In this case, the difference in thermal elongation can be further reduced. Therefore, it becomes easy to make the difference in thermal elongation within the range of, for example, −0.2 to 0.2 mm as described above.

The catalyst carrier comprises the exhaust gas purification catalyst supported on a carrier.
The carrier is preferably composed of one or more selected from forsterite, mullite, alumina, silicon carbide, silicon nitride, titania, and zirconia (Claim 5).
In this case, the thermal expansion coefficient of the catalyst carrier can be lowered, and the holding sealing material can be prevented from being damaged by the expansion of the catalyst carrier. In addition, the carrier may be made of a heat-resistant metal material or the like.
Examples of the shape of the catalyst carrier include a substantially cylindrical shape, an elliptical column shape, and a polygonal column shape.

Further, as the exhaust gas purification catalyst, for example, a catalyst mainly containing a noble metal such as platinum or palladium can be used.
Moreover, as said metal shell, what consists of heat-resistant alloy steels, such as stainless alloy steel, for example can be used. Further, as the metal shell, for example, a cylindrical one having an inner diameter of 80 to 400 mm can be used.

The holding sealing material is formed by arranging inorganic fibers in a mat shape.
The inorganic fibers are preferably at least one selected from crystalline alumina fibers, alumina-silica fibers, silica fibers, and the like.
In this case, the holding seal material can maintain a stable generated surface pressure from a temperature of 15 ° C. to 1100 ° C.

The holding sealing material can be produced, for example, by producing a mat-like material made of inorganic fibers as follows and attaching an organic binder to the mat-like material.
That is, first, a spinning solution containing an inorganic fiber precursor that produces inorganic fibers such as alumina fibers after firing, an organic polymer such as polyvinyl alcohol, and water is prepared. Next, the spinning solution is spun by a blowing method, and the resulting aggregate of inorganic fiber precursors is fired. In this way, a mat-like material made of inorganic fibers can be obtained.
Further, the aggregate of the precursors obtained after the spinning can be folded and stacked to form a laminated state, and then subjected to needle punching treatment and firing to produce a mat-like material. By performing the needle punching treatment, the bulkiness of the precursor laminate can be eliminated to make it easy to handle, and the gap between the laminates can be strengthened.

The mat-like material may contain a spherical material called a so-called shot in the inorganic fiber. The content of the spherical substance having a diameter (maximum diameter) of 45 μm or more contained in the mat-like material is preferably 7 wt% or less. When the content of the spherical substance exceeds 7 wt%, when the protective sealing material is assembled to the catalyst carrier and the shell at a bulk density (GBD) of 0.15 to 1.0 g / cm ³ , There is a possibility that the fiber is damaged, the inorganic fiber is easily scattered, and the working environment is deteriorated.

Moreover, it is preferable that the average fiber length of the said inorganic fiber is 250 micrometers or more.
When the average fiber length is less than 250 μm, the inorganic fibers are not sufficiently entangled, and when the holding sealing material is used in the catalytic converter, the holding sealing material may be easily eroded by exhaust gas. More preferably, the average fiber length is 500 μm or more.

Next, the holding sealing material can be produced by attaching an organic binder to the inorganic fibers of the mat-like material.
As said organic binder, various rubber | gum, a thermoplastic resin, a thermosetting resin etc. can be used, for example.

As various rubbers, for example, natural rubber, acrylic rubber, nitrile rubber, butadiene rubber and the like can be used. Examples of the acrylic rubber include a copolymer of ethyl acrylate and chloroethyl vinyl ether, a copolymer of n-butyl acrylate and acrylonitrile, and a copolymer of ethyl acrylate and acrylonitrile. Examples of the nitrile rubber include a copolymer of butadiene and acrylonitrile.
As the thermoplastic resin, acrylic resin, acrylonitrile / styrene copolymer, acrylonitrile / butadiene / styrene copolymer, and the like can be used. Specifically, there are, for example, one kind of homopolymer selected from acrylic acid, acrylic acid ester, acrylamide, acrylonitrile, methacrylic acid, methacrylic acid ester, and / or two or more kinds of copolymers.
As the thermosetting resin, a bisphenol type epoxy resin, a novolac type epoxy resin, or the like can be used.

Preferably, the organic binder is an acrylic or acrylic resin.
In this case, the organic binder can be more uniformly attached to the surface of the inorganic fiber of the mat-like material. Further, the elongation of the organic binder after the drying step is improved, and it is possible to prevent the fibers from being restrained forcibly. Therefore, it is possible to prevent the inorganic fibers from being broken during the assembling work to the catalyst carrier and the shell, and to suppress the scattering of the inorganic fibers into the air.

The attachment of the organic binder to the inorganic fiber includes an impregnation step of preparing an aqueous dispersion obtained by dispersing the organic binder in water and impregnating the mat-like material with the aqueous dispersion, and an aqueous dispersion. It can implement by performing the drying process which dries a mat-like thing.
In the drying step, it is preferable to perform heating and compression.
In this case, excess water can be easily removed from the mat-like material. Moreover, the said holding sealing material of a compression state can be obtained using the adhesive force of the said organic binder. By making the compressed state in this way, the operation of assembling the holding sealing material to the catalyst carrier and the metal shell can be easily performed.
Furthermore, when exhaust gas is supplied to the catalytic converter using the holding sealing material in a compressed state, the organic binder contained in the holding sealing material can be burned out by heat. As a result, since the compressed holding sealing material is restored, the holding sealing material can be held more firmly between the catalyst carrier and the shell.

The said drying process can be performed at the temperature of 95-155 degreeC, for example.
When the drying temperature is less than 95 ° C., the drying time becomes long and the production efficiency may be deteriorated. On the other hand, when it exceeds 155 ° C., decomposition of the organic binder starts, and the adhesive ability of the organic binder may be impaired. The drying time is preferably 100 seconds or longer. If it is less than 100 seconds, there is a possibility that it cannot be sufficiently dried.
Further, as described above, the compression is performed by holding the holding sealing material between the metal shell and the catalyst carrier, so that the holding sealing material has a thickness of 4 to 18 mm and a bulk density of 0.15 to 0.15. It is preferable to carry out so that it may become 1.0 g / cm < ³ >.

Moreover, it is preferable that the attachment rate of the said organic binder in the said holding sealing material is 0.5 wt%-1.5 wt%.
When the adhesion rate is less than 0.5 wt%, the inorganic fibers may be scattered from the surface of the holding sealing material. On the other hand, when it exceeds 1.5 wt%, the amount of the organic binder increases, and harmful gases such as non-methane hydrocarbons and nitrogen oxides may be generated from the holding sealing material.

  Moreover, the solid content removal process which removes the excess solid content of the said organic binder adhering to the said mat-like thing can be performed between the said impregnation process and the said drying process. Thereby, the excess solid content of the organic binder adhering to the mat-like material more than necessary in the impregnation step can be removed. The solid content removing step can be performed, for example, by suction or the like.

The catalyst converter can be produced by covering the catalyst carrier with the thus obtained holding sealing material and placing the catalyst carrier covered with the holding sealing material in a metal shell. At this time, the metal shell arrangement structure may be a press-fitting structure, a clam shell structure, a curl structure, a contracted tube structure, or the like.
The press-fitting structure is a structure in which the catalyst carrier covered with the sealing material is pressed into a cylindrical metal shell. According to such a structure, the metal shell can be easily attached. The clamshell structure is a structure in which a catalyst carrier covered with a holding sealing material is mounted in a metal shell divided into two parts, and the mating portions of the metal shell are welded. According to such a structure, it is possible to mount a catalyst carrier having various shapes such as a polygonal column shape as well as a cylindrical shape. The winding structure is a structure in which a metal plate is wound around a catalyst carrier covered with a holding sealing material. According to such a structure, mounting without loosening is possible. The contracted tube structure is a structure in which a catalyst carrier covered with a holding sealing material is disposed in, for example, a cylindrical metal shell, and the metal shell is contracted by a contracted tube to be in close contact therewith. With this structure, the holding pressure can be adjusted optimally.

Example 1
Next, a catalytic converter according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 to 3, the catalytic converter 1 of this example includes a catalyst carrier 2, a metal shell 3, and a holding sealing material 4.
The catalyst carrier 2 carries an exhaust gas purification catalyst for purifying exhaust gas on a substantially cylindrical carrier. The metal shell 3 has a substantially cylindrical shape and is arranged so as to cover the outside of the catalyst carrier. The holding sealing material 4 is held between the catalyst carrier 2 and the metal shell 3.

In this example, the catalyst carrier 2 has a linear thermal expansion coefficient in the temperature range of 15 ° C. to 1100 ° C. within 2 to 15 × 10 ⁻⁶ / ° C. Moreover, the metal shell 3 has a linear thermal expansion coefficient in a temperature range of 15 ° C. to 1100 ° C. of 10 to 25 × 10 ⁻⁶ / ° C.
The holding sealing material 4 is formed by arranging inorganic fibers in a mat shape, and has a thermal conductivity of 0.03 to 0.3 W / mK in a temperature range of 15 ° C to 1100 ° C.
Further, in the catalytic converter 1, the difference between the thermal elongation amount (mm) of the metal shell 3 to the outside of the catalytic converter 1 and the thermal elongation amount (mm) of the catalyst carrier 2 in the temperature range of 15 ° C. to 1100 ° C. The difference in thermal elongation is in the range of -0.5 to 0.5 mm.

Hereinafter, the catalytic converter of this example will be described in more detail.
As shown in FIGS. 1 to 3, in the catalytic converter 1, the carrier of the catalyst carrier 2 has a substantially cylindrical shape (outer diameter (diameter) L ₀ about 250 mm, length 300 mm at room temperature (temperature 15 ° C.)). A silicon carbide carrier whose cross section was formed into a honeycomb shape was used. The carrier is provided with a number of square holes (cells) 22 along the axial direction thereof. A large number of honeycomb walls 21 serving as partition walls are formed between the cells 22 (see FIG. 1). The cell size of the carrier is 12 mil and the number of cells is 200. The carrier carries an exhaust gas purification catalyst mainly composed of platinum or palladium (not shown).
The catalyst carrier 2 has a linear thermal expansion coefficient at a temperature of 15 to 1100 ° C. within a range of 2 to 15 × 10 ⁻⁶ / ° C.

The metal shell 3 is cylindrical (outer diameter M _{0 at} room temperature (temperature 15 ° C.): about 269 mm, thickness: about 1.5 mm) and is made of heat-resistant alloy steel (stainless alloy steel, SUS409). The metal shell 3 has a linear thermal expansion coefficient of 10 to 25 × 10 ⁻⁶ / ° C. at a temperature of 15 to 1100 ° C.

The holding sealing material 4 is composed of a mat-like material made of crystalline alumina fibers and an acrylic resin attached to the mat-like material. The holding sealing material has a thickness of 8 mm and a bulk density of 0.35 g / cm ³ and is provided between the metal shell 3 and the catalyst carrier 2. The catalyst carrier 2 is held in the metal shell 3 by the holding sealing material 4.

  In the catalytic converter 1, the difference in thermal elongation, which is the difference between the thermal elongation (mm) of the metal shell to the outside and the thermal elongation (mm) of the catalyst carrier, is in the temperature range of 15 to 1100 ° C. As described above, the thickness and bulk density of the holding sealing material 4 are adjusted so as to be −0.5 to 0.5 mm.

Next, a method for manufacturing the catalytic converter of this example will be described.
First, the holding sealing material is prepared.
Specifically, first, a basic aluminum chloride aqueous solution having an aluminum content of 70 g / l and Al / Cl = 1.8 (atomic ratio) was prepared. Silica sol was blended into this aluminum chloride aqueous solution to form an alumina fiber precursor. The silica sol was blended so that the composition of the alumina fiber was Al ₂ O ₃ : SiO ₂ = 72 ± 2: 28 ± 2.

Then, an organic polymer such as polyvinyl alcohol was added to the alumina fiber precursor. Then, it concentrated and adjusted the spinning solution, and it spun by the blowing method using this spinning solution.
Thereafter, the alumina fiber precursor was folded and the folded ones were stacked to produce a laminated sheet of alumina fiber precursor.

  Next, as shown in FIG. 4, the laminated sheet 40 was subjected to needle punching (needling). This needle punching process is performed by a needle punch device 5 having a needle board 51 that can reciprocate in the piercing direction and a pair of support plates 52 that support both front and back surfaces of the laminated sheet 40 that is to perform this process.

A large number of needles 53 for piercing the laminated sheet 40 are fixed to the needle board 51. Needles 53 are fixed at a density of about 500 pieces in a needle board 100 cm ² . The support plate 52 is provided with a needle passage hole 520.
Then, when the laminated sheet 40 is passed between the pair of support plates 52 and the needle board 51 is reciprocated, the needle 53 is pierced into the laminated sheet 40, and the fibers in the laminated sheet 210 are entangled with each other.

Next, the laminated sheet after the needle punching treatment was fired to obtain a mat-like material of alumina fibers having a basis weight of about 1500 ± 150 g / cm ² . The firing was performed by raising the temperature from room temperature and continuously firing at a maximum temperature of 1250 ± 50 ° C.

  Next, the mat-like product was cut into dimensions of 500 to 1400 mm in length, 51000 to 52500 mm in width, and 16.8 mm in thickness. Moreover, about the mat-like thing, when the shot content rate of (phi) 45 mm or more was measured using the sieve and the weighing machine, it was less than 7 wt%.

Next, the mat-like material after cutting is impregnated with an aqueous dispersion of an organic binder.
Specifically, as an aqueous dispersion of an organic binder, an acrylic resin aqueous dispersion (“Lx811” manufactured by Nippon Zeon Co., Ltd., solid content concentration 50 ± 10%, 5.5 to 7.0 pH) is used. What was adjusted so that it might become 0.5-30 wt% was used. The aqueous dispersion was impregnated by the pouring method on the mat-like material disposed on the conveyor.

  Next, in order to remove the solid content of the excess organic binder adhering to the mat-like material, suction was performed for 1 second or longer. After the suction, when the impregnation rate of the organic binder was measured with a weighing meter, the impregnation rate was 55 wt%.

Thereafter, the mat-like product was heat-compressed and dried. The heat compression drying was performed under the conditions of a temperature of 95 to 155 ° C., a drying time of 100 seconds or more, and a pressurization narrow interval of 6.5 mm during drying.
Thus, a holding sealing material having a resin adhesion rate of 1.5 wt% and a thickness of 14.4 mm was obtained.
In addition, the holding sealing material produced in this example can be adjusted to a desired size and shape by performing subsequent punching or the like.

Next, an outer diameter (diameter) L _{0 of} approximately 250 mm and a length of 300 mm in a substantially cylindrical shape, a honeycomb-shaped silicon carbide support (cell size is 12 mil, number of cells is 200), platinum or palladium is mainly used. A catalyst carrier carrying an exhaust gas purification catalyst as a component was prepared. Further, a metal shell made of SUS409 and having an outer diameter M _{0 of} about 269 mm and a thickness of about 1.5 mm at normal temperature (temperature 15 ° C.) was prepared.

Then, the holding sealing material 4 produced as described above is wound around the catalyst carrier 2 (see FIGS. 5A and 5B), and the integrated product 10 on which the winding has been performed is press-fitted into the metal shell 3. (See FIG. 6). The press-fitting conditions are a press-fitting load of 10000 N and a press-fitting speed of 6000 mm / sec. At this time, the thickness of the holding sealing material 4 held between the catalyst carrier 2 and the metal shell 3 was 8 mm, and the bulk density was 0.35 g / cm ³ .
In this way, as shown in FIGS. 1 to 3, a catalytic converter 1 for purifying exhaust gas comprising the metal shell 3, the catalyst carrier 2, and the holding sealing material 4 sandwiched between them was produced. This is designated as Sample E1.

  In this example, a holding sealing material having a thickness of 14.4 mm is produced, and the holding sealing material is sandwiched between the catalyst carrier and the metal shell (gap 8 mm). For example, the thickness is 7.2 mm. It is also possible to prepare two holding sealing materials and sandwich them in a stacked state.

(Example 2)
Next, in this example, a plurality of catalytic converters (samples) in which the thickness of the holding sealing material provided between the catalyst carrier and the metal shell, the material of the catalyst carrier, etc. are different from the sample E1 of the first embodiment. E2-Sample E8 and Sample C1-Sample C6) are prepared.

Sample E2 is a catalytic converter manufactured by narrowing the holding sealing material between the metal shell and the catalyst carrier with a thickness of 10 mm and a bulk density of 0.35 g / cm ³ .
First, a holding sealing material having a thickness different from that of Example 1 was prepared. That is, first, a mat-like product made of crystalline alumina fibers was prepared in the same manner as in Example 1, and the mat-like product was cut into dimensions of 500 to 1400 mm long × 51000 to 52500 mm wide and 20.4 mm thick. Next, in the same manner as in Example 1, the mat-like material was impregnated with an aqueous dispersion of an organic binder, and after suction, heated and compressed and dried to obtain a holding sealing material having a resin impregnation ratio of 1.5 wt% and a thickness of 19.4 mm. Produced.

Next, in the same manner as in Example 1, a catalyst carrier in which an exhaust gas purification catalyst mainly composed of platinum or palladium was supported on a silicon carbide carrier whose cross section was formed in a honeycomb shape was prepared. In this example, the catalyst carrier has a cylindrical shape with an outer diameter of about 250 mm and a length of 300 mm at room temperature (temperature of 15 ° C.).
Further, similarly to Example 1, a metal shell made of SUS409 was prepared. In this example, the metal shell has a cylindrical shape with an outer diameter of about 273 mm and a thickness of about 1.5 mm at room temperature (temperature of 15 ° C.).

Next, in the same manner as in Example 1, an integrated product in which the holding sealing material was wound around the catalyst carrier was assembled into the metal shell by press-fitting to produce a catalytic converter (sample E2). In sample E2, the thickness of the holding sealing material sandwiched between the catalyst carrier and the metal shell was 10 mm, and the bulk density was 0.35 g / cm ³ .

  Similarly to the sample E2, the sample E3 to the sample E8, the sample C1, and the sample C2 have a holding sealing material sandwiched between the sample E1 of Example 1 and a thickness different from that of the sample E1 of Example 1. It was produced. In producing the same, the outer diameter and inner diameter of the metal shell, the outer diameter of the catalyst carrier, the thickness of the holding sealing material before assembly, and the like are changed in a thickness different from that of the sample E1, similarly to the sample E2. It was produced by holding the holding sealing material. The thickness of the holding sealing material in each sample is shown in Table 1 described later.

  Further, the catalytic converters of Sample C3 to Sample C6 are manufactured using a carrier made of cordierite as the carrier for the catalyst carrier. Further, Sample C3 to Sample C6 are similar to Sample E2 in that the outer diameter and inner diameter of the metal shell, the outer diameter of the catalyst carrier, the thickness of the holding sealing material before assembly, and the like are changed. It is produced by holding a holding sealing material with a thickness different from that of the sample E1. The thickness of the holding sealing material in each sample is shown in Table 1 described later.

  In this example, one holding sealing material is used as the holding sealing material sandwiched between the catalyst carrier and the metal shell, but the two or more holding sealing materials are stacked in a narrow state. It can also be held.

(Experimental example)
Next, in this example, a hot load test is performed on the catalytic converter of each sample (sample E1 to sample E8 and sample C1 to sample C6) produced in Example 1 and Example 2, and the catalyst carrier in each sample Evaluation of deviation and breakage was performed.
In other words, each sample is mounted on a hot punching load testing machine, each sample is heated by a heating wire built in the testing machine, and a certain load (pressure) is applied. At this time, the catalyst carrier is displaced or damaged. Was examined visually.

More specifically, each sample is mounted on a load tester, heated with a heating wire at a temperature of 850 ° C., the amount of thermal elongation between the metal shell and the catalyst carrier is measured in a straight scale, and the difference in the amount of thermal elongation is examined. It was. The difference in thermal elongation was calculated by subtracting the amount of change in the diameter of the catalyst carrier before and after heating from the amount of change in the inner diameter of the metal shell before and after heating. The results are shown in Table 1. The heating temperature of 850 ° C. corresponds to a temperature that is applied when the engine is started and the rotation of the engine is maintained at about 8000 rpm.
Further, each sample was pressurized with heating at a pressure of 50 kPa, and the deviation of the catalyst carrier from the metal shell and the presence or absence of damage to the catalyst carrier were visually observed. The results are shown in Table 1. The pressure of 50 kPa corresponds to the magnitude of exhaust pressure due to exhaust gas when the engine is rotated at a rotational speed of about 8000 rpm.

As is known from Table 1, the catalytic converters of Sample E1 to Sample E8 in which the difference in thermal elongation between the metal shell and the catalyst carrier is in the range of -0.5 to 0.5 mm are obtained from the metal shell of the catalyst carrier. No defects such as misalignment or damage to the catalyst carrier were observed. On the other hand, in Sample C1 to Sample C6 where the difference in thermal elongation was outside the range of −0.5 to 0.5 mm, the catalyst carrier was observed to be displaced or damaged.
Therefore, in the catalytic converter, by making the difference in thermal elongation between the metal shell and the catalyst carrier within the range of -0.5 to 0.5 mm, the catalyst carrier is displaced from the metal shell, and the exhaust gas leaks. It can be seen that the catalyst carrier can be prevented from falling off the metal shell, and the catalyst carrier can be prevented from being damaged.

In Samples E1 to E8, the thickness of the holding sealing material when the bulk density is 0.35 g / cm ³ is in the range of 4 to 18 mm. And by adjusting the thickness of the holding sealing material to a specific range of 4 to 18 mm, the difference in thermal elongation between the metal shell and the catalyst carrier can be easily controlled within the range of -0.5 to 0.5 mm. I understand.
Although not clearly shown in Table 1, the thickness of the holding sealing material sandwiched between the metal shell and the catalyst carrier is 4 to 18 mm, and the bulk density is 0.15 to 1.0 g / cm ^3. By adjusting to such a range, it has been confirmed that the difference in thermal elongation between the metal shell and the catalyst carrier can be easily controlled within the range of -0.5 to 0.5 mm.

  Further, as described above, when the difference in thermal elongation between the metal shell and the catalyst carrier exceeds the range of -0.5 to 0.5 mm, the catalyst carrier is displaced or damaged to the extent that it can be visually confirmed. (Sample C1 to Sample C6). Therefore, it is considered that the deviation or breakage of the catalyst carrier can be more reliably prevented by setting the difference in the amount of thermal elongation within the range of, for example, -0.2 to 0.2 mm.

As is known from Table 1, in samples E1 to E3 where the difference in thermal elongation between the metal shell and the catalyst carrier is in the range of −0.2 to 2.0 mm, the bulk density is 0.35 g / cm ³ . The thickness of the holding sealing material when mounted is in the range of 6 to 10 mm. Therefore, by adjusting the thickness of the holding sealing material to a specific range of 6 to 10 mm, the difference in thermal elongation between the metal shell and the catalyst carrier can be easily controlled within the range of -0.2 to 0.2 mm. I understand.
Although not clearly shown in Table 1, the thickness of the holding sealing material sandwiched between the metal shell and the catalyst carrier is 6 to 10 mm, and the bulk density is 0.15 to 1.0 g / It has been confirmed that the difference in thermal elongation between the metal shell and the catalyst carrier can be easily controlled within the range of −0.2 to 0.2 mm by adjusting the range to cm ³ .

1 is a perspective view showing an entire catalytic converter according to Embodiment 1. FIG. 1 is a front view of a catalytic converter according to Embodiment 1. FIG. The side view of the catalytic converter concerning Example 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the needle punching apparatus concerning Example 1. FIG. (A) State before winding a holding sealing material around a catalyst carrier according to Example 1, (B) An explanatory view showing a state where the holding sealing material is wound around a catalyst carrier. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the state which arrange | positions the integral product formed by winding the holding | maintenance sealing material around a catalyst carrier concerning Example 1 to a metal shell. Explanatory drawing which shows the state which has arrange | positioned the catalyst converter for the conventional exhaust gas purification in the middle of the exhaust pipe of the engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Catalytic converter 2 Catalyst support body 21 Partition 22 Cell 3 Metal shell 4 Holding sealing material

Claims (6)

A catalyst carrier formed by supporting an exhaust gas purification catalyst for purifying exhaust gas on a carrier, a metal shell covering the outside of the catalyst carrier, and the metal shell and the catalyst carrier sandwiched between the metal shell and the catalyst carrier. In a catalytic converter for exhaust gas purification consisting of a holding sealing material,
The catalyst carrier has a linear thermal expansion coefficient of 2 to 15 × 10 ⁻⁶ / ° C. at a temperature of 15 ° C. to 1100 ° C., and the metal shell has a linear thermal expansion coefficient of 10 to 25 at a temperature of 15 ° C. to 1100 ° C. × 10 ^-6 / ° C,
The holding sealing material is formed by arranging inorganic fibers in a mat shape, and has a thermal conductivity of 0.03 to 0.3 W / mK at a temperature of 15 ° C to 1100 ° C,
In the catalytic converter, the thermal elongation which is the difference between the thermal elongation amount (mm) of the metal shell and the thermal elongation amount (mm) of the catalyst carrier to the outside of the catalytic converter at a temperature of 15 ° C. to 1100 ° C. The catalytic converter, wherein the amount difference is in the range of -0.5 to 0.5 mm.   The catalytic converter according to claim 1, wherein the difference in thermal elongation is in a range of -0.2 to 0.2 mm. 3. The holding sealing material according to claim 1, wherein the holding sealing material has a thickness of 4 to 18 mm and a bulk density of 0.15 to 1.0 g / cm ³ and is disposed between the metal shell and the catalyst carrier. Catalytic converter. 4. The holding sealing material according to claim 1, wherein the holding sealing material has a thickness of 6 to 10 mm and a bulk density of 0.15 to 1.0 g / cm ³ and is disposed between the metal shell and the catalyst carrier. The catalytic converter characterized by the above-mentioned.   5. The catalytic converter according to claim 1, wherein the carrier is made of at least one selected from forsterite, mullite, alumina, silicon carbide, silicon nitride, titania, and zirconia.   6. The catalytic converter according to claim 1, wherein the inorganic fiber of the holding sealing material is at least one selected from crystalline alumina fiber, alumina-silica fiber, silica fiber and the like.

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