JP2006175380A - Catalyst, production method of catalyst and production apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst excellent in adhesion of a substrate and a catalyst film and having a stable catalytic activity even in severe use environment of high pressure and also high flow rate such as a catalyst combustor of a gas turbine, and provide its production method and its production apparatus. <P>SOLUTION: An undercoat layer, to be formed from a lower undercoat layer and an upper undercoat layer, is formed on the substrate 2 by spraying fine powder on the substrate 2 made of metal with a carrier gas from the tip of a fine-hole nozzle 4, the catalyst film containing a catalytic active component is formed on the undercoat layer by the wash-coat method, and then a calcination treatment is carried out, wherein the lower undercoat layer is composed of a constituent component having an affinity to the constituent component of the substrate 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a catalyst used in a catalytic combustor of a gas turbine or a steam reformer of a polymer electrolyte fuel cell (PEFC), a method for manufacturing the catalyst, and a manufacturing apparatus.

As a method for forming a catalyst film carrying a catalytically active component on a substrate, for example, in the patent document, a slurry of a heterogeneous water-soluble catalyst containing a specific water-soluble mixed liquid is prepared, and the slurry is a ceramic monolithic support. A so-called wash coat method is described.
When a catalyst film is formed on a substrate by a conventional wash coat method, the adhesion between the catalyst film and the substrate is poor. For this reason, when a catalyst film is used in a severe use environment with a high pressure and a high flow rate like a catalyst combustor of a gas turbine, there is a problem that the catalyst film peels off from the substrate. For this reason, there has been a problem that the catalyst component is lost with the passage of time of use, and the catalytic activity gradually decreases.
JP-A-6-205992

  The present invention has been made in view of the above circumstances, and provides a catalyst, a catalyst production method, and a production apparatus that have high adhesion to a substrate and do not peel even in severe use environments and maintain excellent catalytic activity. The purpose is to provide.

  In order to achieve the above object, the catalyst according to the present invention sprays a fine powder together with a carrier gas from the tip of a fine hole nozzle onto a metal substrate, and has an affinity for the components of the substrate on the substrate. An undercoat layer formed from a lower undercoat layer composed of constituent components and an upper undercoat layer is formed, and a catalyst film containing a catalytically active component is formed on the undercoat layer by a wash coat method. After that, it is characterized by being subjected to a baking treatment.

  Another aspect of the present invention is a method for producing a catalyst, in which fine powder is sprayed together with a carrier gas from the tip of a fine hole nozzle onto a metal substrate and has an affinity for the components of the substrate on the substrate. An undercoat layer formed from a lower undercoat layer composed of constituent components and an upper undercoat layer is formed, and a catalyst film containing a catalytically active component is formed on the undercoat layer by a wash coat method. Thereafter, a baking treatment is performed.

The component constituting the lower undercoat layer preferably has affinity with the component constituting the upper undercoat layer. The upper undercoat layer is preferably composed of Al ₂ O ₃ and / or ZrO ₂ . Still further, the lower undercoat layer is preferably made of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ .

Further, the catalyst or the production method according to the present invention is a preferred embodiment, wherein the lower undercoat layer is composed of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ , Al ₂ O ₃ and / or ZrO ₂ . Consisting of a mixture of In another preferred embodiment, the lower undercoat layer is made of a mixture of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ and Al ₂ O ₃ and / or ZrO ₂ , and the composition is It has a composition distribution in which Al ₂ O ₃ and / or ZrO ₂ increase from the metal substrate toward the upper undercoat layer.
The particle velocity of the particles ejected together with the carrier gas from the tip of the microhole nozzle is preferably 700 m / s or more.

Furthermore, the catalyst carrier for supporting the catalytically active component is preferably composed mainly of Al ₂ O ₃ and / or ZrO ₂ . The catalytically active component is preferably at least one catalytically active component selected from Pd, Ru, and Pt.

In addition, the present invention, in yet another aspect, is a manufacturing apparatus for manufacturing the lower undercoat layer of the catalyst, and the fine powder together with the carrier gas from the tip of the microhole nozzle onto the metal substrate. A manufacturing apparatus for spraying and forming a lower undercoat layer composed of a component having affinity for a component of the substrate on the substrate, wherein the carrier gas is branched into two systems The iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ is sprayed onto the metal substrate from the tip of one of the micro-hole nozzles, and from the tip of the other micro-hole nozzle, Al ₂ O ₃ and / or ZrO ₂ sprayed onto a substrate made of the metal, the lower a composition distribution Al ₂ O ₃ and / or ZrO ₂ toward from the metal substrate to the upper undercoat layer increases Characterized in that so as to form the Dakoto layer.

  According to the present invention, a catalyst having a stable catalytic activity, a catalyst production method, and a catalyst having stable catalytic activity even in a severe use environment of high pressure and high flow rate such as a catalytic combustor of a gas turbine, having excellent adhesion between a substrate and a catalyst film A manufacturing apparatus is provided.

  Hereinafter, the catalyst, the production method, and the production apparatus according to the present invention will be described in more detail with reference to embodiments thereof.

  First, a method for forming an undercoat layer on a metal substrate in order to produce the catalyst according to the present invention will be described. In the present invention, an undercoat layer formed of a lower undercoat layer and an upper undercoat layer is formed on a metal substrate. Each of the lower undercoat layer and the upper undercoat layer is formed by spraying fine powder together with a carrier gas from the tip of the microhole nozzle onto a metal substrate.

Here, the procedure for forming the upper undercoat layer made of Al ₂ O ₃ will be mainly described with reference to the outline of the apparatus shown in FIG. FIG. 2 shows the structure of the catalyst according to the present invention to be manufactured. As shown in the figure, the catalyst comprises a metal substrate 2, a lower undercoat layer 14, an upper undercoat layer 15, and a catalyst layer 16 by a wash coat method.

  As shown in FIG. 1, a substrate holder 3 that supports a metal substrate 2 is installed in a chamber 1 made of stainless steel. Further, a nozzle 4 for injecting the raw material powder conveyed by the carrier gas together with the carrier gas is installed in the chamber 1. The temperature of the substrate 2 may be room temperature, and it is not necessary to heat the substrate 2 specially. However, it can of course be heated.

  The substrate holder 3 is configured to be driven at a predetermined speed in the XY (plane) direction with respect to the nozzle 4 by a driving mechanism (not shown). Further, the distance between the nozzle 4 and the substrate holder 3 can be fixed at an arbitrary distance by a mechanism (not shown).

Further, the apparatus of FIG. 1 includes a powder feeder 5. The powder feeder 5 has a function of supplying raw material powder adjusted in advance by a predetermined method at a constant speed.
In the present embodiment, a rotary scraper feeder is used as the powder feeder 5. This type of powder feeder 5 has a function of supplying a certain amount of powder in a certain time by scraping the raw material powder supplied from the hopper to the rotary table with a metal fin. By controlling the number of rotations of the rotary table, the powder supply speed can be changed. The powder feeder 5 is not limited to the rotary scraping method as long as it has a function of supplying a certain amount of powder for a certain time.

  A carrier gas cylinder 6 is connected to the powder feeder 5 via a pressure regulator 7 and a mass flow controller 8. The atmosphere in the chamber 1 is exhausted by a rotary pump 10 and a mechanical booster pump 11 through a filter 9 for collecting dust.

  In the figure, the element indicated by 12 is an automatic valve or a manual valve. Moreover, the component shown by 13 in the figure is a pressure gauge. In the embodiment shown in FIG. 1, each valve 12 adjusts the flow rate of the fluid flowing through each line according to the operation status of the entire apparatus, and the pressure gauge 13 monitors the operation status of the apparatus using the pressure as a parameter. Means. For these operations, methods known to those skilled in the art can be employed.

Next, a procedure for forming the upper undercoat layer 15 (FIG. 2) made of Al ₂ O _{3 according} to the present invention using the apparatus of FIG. 1 will be described. Note that the lower undercoat layer 14 (FIG. 2) can also be formed by the same procedure.

  First, a metal substrate 2 having a predetermined shape is set on the substrate holder 3. As the substrate 2, for example, NAS442A5 steel having excellent heat resistance and containing 19 to 21 wt% Cr and 5 to 6 wt% Al can be used. In addition, the raw material of the board | substrate which can be used by this invention is not limited to this, For example, NAS444 steel, SUS409, SUS430, SUS304 etc. can be mentioned to others.

The powder feeder 5 is filled with α-Al ₂ O ₃ powder whose particle size is adjusted in advance. As α-Al ₂ O ₃ powder used as a raw material fine powder, primary particles having a particle size of 0.2 to 0.3 μm (center particle size) are aggregated to form secondary particles of several μm (center particle size). Powder is desirable. Examples of the powder having such properties include AKP-30 manufactured by Sumitomo Chemical.

In the present invention, as a compound constituting the upper undercoat layer 15, ZrO ₂ , HfO ₂ , Y ₂ O ₃ , Gd ₂ O _3, etc., and at least of these, in addition to Al ₂ O ₃ , are preferable. A mixture of two or more can be mentioned.

Among these, Al ₂ O ₃ and ZrO ₂ are preferable, and a mixture thereof may be used.
The reason why Al ₂ O ₃ and ZrO ₂ are preferable is that Al ₂ O ₃ and ZrO ₂ are the main components of the catalyst carrier of the catalyst layer 16 formed on the upper undercoat layer 15 by the wash coat method. This is because these materials have a certain affinity and are thermally and chemically stable and do not adversely affect the catalyst layer formed thereon. When using a mixture, in addition to making each mixture in advance, it may be sprayed simultaneously using multiple nozzles.

The constituent component of the lower undercoat layer is preferably a constituent component having an affinity for the constituent component of the substrate. Furthermore, it is preferable to have an affinity with the constituent components of the upper undercoat layer. Therefore, the lower undercoat layer is preferably made of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ . This is because the main constituent element of the substrate 2 is Fe and the upper undercoat layer 15 is made of an oxide of Al ₂ O ₃ and / or ZrO ₂ , so that the iron Fe ₂ O ₃ has a close thermal expansion coefficient. And / or Fe ₃ O ₄ is preferred.
That's why. Incidentally, if it has such characteristics, it may be employed other than iron oxide Fe ₂ O ₃ and / or Fe ₃ O _4.
The lower undercoat layer is also formed by adjusting and spraying the raw material as a fine powder. When using a mixture, in addition to making each mixture in advance, it may be sprayed simultaneously using multiple nozzles.

The lower undercoat layer is composed of a mixture of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ and Al ₂ O ₃ and / or ZrO ₂ , and the composition is changed from a metal substrate to the upper undercoat layer. It is more preferable to have a composition distribution in which Al ₂ O ₃ and / or ZrO ₂ increases as it goes. As a mode of increasing, it is most preferable that the increasing component increases linearly or almost linearly.

  The particle diameter of the raw material fine powder forming the above undercoat layer is preferably in the range of 0.1 to 2.0 μm, for example, as the center particle diameter of primary particles measured by a laser measurement method. This is because, in the process of spraying aerosol from a nozzle at a high speed by a method described later and colliding the particles with the substrate 2, when the particles collide with the substrate 2, the primary particles are crushed and the active new surface is exposed. This is because sufficient kinetic energy can be given to the. The range of 0.2 to 1.0 μm is particularly suitable.

  Prior to spraying the raw material fine powder, the inside of the chamber 1 is evacuated through the filter 9 by the rotary pump 10 and the mechanical booster pump 11. When the ultimate vacuum of 10 Pa or less is reached in the chamber 1, the carrier gas whose pressure and flow rate are set to predetermined values is sent from the carrier gas cylinder 6 to the powder feeder 5 via the pressure regulator 7 and the mass flow controller 8. .

Here, an inert gas such as helium He, argon Ar, or nitrogen N ₂ can be used as the carrier gas. Helium He is preferred for the purpose of increasing the particle velocity.

  When the carrier gas flow rate reaches a steady value and the pressure in the chamber 1 is stabilized, the fine powder supply mechanism of the powder feeder 5 is operated to form an aerosol in which the raw material powder is uniformly dispersed in the carrier gas. The aerosol generated in this way is introduced into the aerosol introduction part of the nozzle 4. The introduced aerosol is accelerated when sequentially passing through the throttle portion and the particle accelerating portion of the nozzle 4 and is ejected from the tip of the nozzle 4 toward the substrate 2 at a high speed.

The raw material powder in the aerosol colliding with the surface of the substrate 2 at high speed is crushed, and an active new surface is exposed to form a dense Al ₂ O ₃ film having high adhesion on the substrate 2. In order to form the upper undercoat layer 15 in the present invention, as described above, the raw material powder in the aerosol colliding with the surface of the substrate 2 at a high speed must be crushed to expose the active new surface. For this reason, the particles incident on the substrate need to have a certain level of kinetic energy. In the case of Al ₂ O ₃ or ZrO ₂ , this condition is satisfied at a particle speed of at least 700 m / s when the fine powder having the primary particle diameter described above is used. The speed of the incident particles can be controlled by the particle diameter of the raw material particles, the shape of the nozzle 4 and the carrier gas flow rate.

Then, the upper undercoat layer 15 made of Al ₂ O ₃ can be formed in a certain area on the substrate 2 by moving the substrate holder 3 in the XY (plane of the substrate 2) direction by a drive mechanism (not shown). .
A lower undercoat layer such as the lower undercoat layer 14 made of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ can be formed by the same procedure.

Next, a method for forming a catalyst carrier and a catalyst film by a wash coat method on the upper undercoat layer 15 made of Al ₂ O ₃ (a method for forming a catalyst film containing a catalytic active component) will be described. From the viewpoint of thermal stability and chemical stability, the main component of the catalyst support used in the present invention is preferably composed of either Al ₂ O ₃ or ZrO ₂ or a mixture of both. However, HfO ₂ , Y ₂ O _3, etc. can be used as long as they do not contradict the object of the present invention.

Here, a method for adjusting the ZrO ₂ · Al ₂ O ₃ catalyst carrier by the coprecipitation method will be described. In addition, if it is a method which can adjust the catalyst support | carrier which can be used for the washcoat method, it is not necessary to limit to a coprecipitation method.

Al ₂ O having a specific surface area as a starting material of ₃ large gamma-Al ₂ O ₃ are preferred. For example, Sumitomo Chemical's A-11 can be used.
As a starting material for ZrO ₂ , for example, zirconium oxychloride ZrOCl ₂ .8H ₂ O (manufactured by Mitsuwa Chemical) can be used.

The case of using the above raw materials will be described as an example. First, ZrOCl ₂ .8H ₂ O weighed to a predetermined amount is put into a plastic tank, a predetermined amount of distilled water is added, and ZrOCl ₂ .8H ₂ O is dissolved while stirring. . Next, γ-Al ₂ O ₃ weighed to a predetermined amount is gradually added while stirring. In this state, after stirring for several tens of minutes to about 1 hour, NH ₄ OH water is gradually added dropwise with stirring until pH becomes 9.2 to 9.3 to form a precipitate. When NH ₄ OH water is added dropwise until the pH reaches 9.2 to 9.3, the mixture is aged with stirring for about 1 hour. Next, after the precipitate is filtered using an aspirator, the precipitate is heated in the atmosphere at 100 to 120 ° C. for 10 to 12 hours to evaporate water. Next, it is calcined in the atmosphere at 500 to 600 ° C. for 5 to 10 hours and subsequently at 1100 to 1150 ° C. for 5 to 10 hours to obtain catalyst carrier powder.

  Next, a procedure for supporting palladium Pd as a catalytic active component on the above catalyst carrier will be described. Rh and Pt can also be supported in the same manner.

A predetermined amount of the catalyst carrier powder prepared as described above is put in an evaporating dish. Next, distilled water is poured so that the entire catalyst support powder is wet. To this is added palladium nitrate Pd (NO ₃ ) ₂ weighed to a predetermined amount. The evaporating dish is gradually heated on a hot plate, and the water is evaporated and evaporated to dryness while stirring. The evaporated and dried powder is calcined in the atmosphere at 500 to 600 ° C. for 5 to 10 hours and subsequently at 1100 to 1150 ° C. for 5 to 10 hours to prepare a catalyst carrier powder carrying the catalyst.

  Next, a procedure for forming a catalyst carrier film carrying a catalytically active component by the wash coat method in the present invention will be described. The catalyst carrier powder carrying the catalyst prepared as described above, a predetermined amount of distilled water, and a predetermined amount of binder are uniformly mixed by a ball mill method to produce a slurry.

Next, the metal substrate 2 on which the lower undercoat layer 14 (FIG. 2) and the upper undercoat layer 15 (FIG. 2), which have been weighed in advance, are immersed in the slurry prepared as described above, and then pulled up. Blow with an air gun to blow off any excess slurry. After drying the substrate 2 on which the slurry is formed, the weight is weighed to determine the coating amount. The above operation is repeated until a predetermined coat amount is reached. The substrate 2 coated with a predetermined amount of the catalyst layer is fired at 900 to 1000 ° C. in the atmosphere for 15 to 20 hours. In this way, a catalyst carrier film containing Pd as a catalytically active component can be formed on the undercoat layer. In this way, the catalyst according to the present invention can be obtained.
Note that the above-described procedure relating to film formation is merely an example, and the present invention is not limited to the above description.
The catalytically active component is Pd in the above description, but Ru, Pt, Rh, Ir, Co, Mn, Fe, Ni, Cr, etc. can also be used.

Hereinafter, the present invention will be further described by examples. Note that the reference numbers are the reference numbers given in FIG. 1, FIG. 2, or FIG. 4, and the components to be designated are according to the preceding description.
Example 1 and Comparative Example 1
As the substrate 2, a corrugated NAS442A5 having a thickness of 0.1 mm, a width of 50 mm, and a length of 200 mm was used. Next, as a raw material powder for the lower undercoat layer 14, the powder feeder 5 was filled with Fe ₂ O ₃ powder (JFE Chemical's center particle size 0.5 μm).

The film formation conditions of the lower undercoat layer 14 were set such that the distance between the nozzle 4 and the substrate 2 was 50 mm, the raw material powder supply rate was 1.5 g / min, the substrate 2 movement rate was 0.5 mm / sec, and the helium flow rate was 20 liters / min. Under these conditions, iron oxide Fe ₂ O ₃ having a thickness of 2.1 μm was formed as the lower undercoat layer 14 on the substrate 2.

Next, the powder feeder 5 was filled with α-Al ₂ O ₃ powder (AKP-30, center particle size 0.3 μm, manufactured by Sumitomo Chemical Co., Ltd.) as a raw material powder for the upper undercoat layer 15. Helium He was supplied from the carrier gas cylinder 6 to the powder feeder 5 as a carrier gas at a flow rate of 20 liters per minute. Next, the powder supply mechanism of the powder feeder 5 is operated to supply 1.3 g / min of α-Al ₂ O ₃ raw material powder together with a carrier gas to the nozzle 4 to form an upper undercoat layer made of Al ₂ O ₃ on the substrate 2. 15 was formed.

The substrate 2 was moved with respect to the nozzle 4 at a speed of 0.2 mm / sec. The film thickness of the upper undercoat layer 15 made of Al ₂ O ₃ was about 10 μm.
Thus, the lower undercoat layer 14 made of Fe ₂ O ₃ and the upper undercoat layer 15 made of Al ₂ O ₃ were formed on both surfaces of the NAS442A5 substrate 2.

  The NAS442A5 substrate 2 on which the undercoat layer was formed was wound so as to have a core diameter of about 25 mm, and was fixed with an outer cylinder made of NAS442A5, thereby producing a metal honeycomb having a core diameter of 25 mm and a length of 50 mm. Further, as Comparative Example 1, a NAS442A5 substrate on which the lower undercoat layer 14 and the upper undercoat layer 15 are not formed is wound in the same manner as in Example 1, and is fixed with an outer cylindrical material made of NAS442A5, with a core diameter of 25 mm and a length of 50 mm. A metal honeycomb was produced.

  The two types of metal honeycombs thus prepared (Example 1 and Comparative Example 1) were immersed eight times in the catalyst carrier slurry prepared as described above to form a predetermined amount of catalyst layer, Firing was performed at 950 ° C. for 20 hours.

Next, 150 Nl / min of air was circulated at atmospheric pressure through two types of metal honeycombs (Example 1 and Comparative Example 1) on which the catalyst layer was formed, and the weight reduction amount of the catalyst layer was measured.
FIG. 3 shows a change in the weight reduction amount of the catalyst layer with respect to the air circulation time. In Example 1 in which a 2.1 μm lower undercoat layer made of Fe ₂ O ₃ and a 10 μm upper undercoat layer 15 made of Al ₂ O ₃ were formed, the weight loss after 68 hours of air circulation was 0.052 g. In Comparative Example 1 in which the undercoat layer was not formed, the weight reduction amount increased with the air circulation time, and the weight reduction amount after 68 hours of the air circulation time reached 0.110 g. In Example 1 in which the undercoat layer is formed, the adhesion between the substrate 2 and the catalyst layer is strong through the undercoat layer, and the weight loss of the catalyst layer is small even when a large amount of air is circulated. On the other hand, in Comparative Example 1 in which no undercoat layer was formed, the adhesion between the substrate 2 and the catalyst layer was weak, so it is considered that the catalyst layer was peeled off and lost with the passage of the air circulation time.

Example 2 and Comparative Example 2
As the substrate 2, a corrugated NAS442A5 having a thickness of 0.1 mm, a width of 50 mm, and a length of 200 mm was used. Next, as a raw material powder for the lower undercoat layer 14, the powder feeder 5 was filled with Fe ₂ O ₃ powder (JFE Chemical's center particle size 0.5 μm). The film formation conditions of the lower undercoat layer 14 were set such that the distance between the nozzle 4 and the substrate 2 was 50 mm, the raw material powder supply rate was 1.5 g / min, the substrate 2 movement rate was 0.5 mm / sec, and the helium flow rate was 20 liters / min. Under these conditions, iron oxide Fe ₂ O ₃ having a thickness of 2.1 μm was formed on the substrate 2 as a lower undercoat layer.

Next, the powder feeder 5 was filled with zirconia ZrO ₂ powder (TZ-PX-136 center particle size 0.7 μm, manufactured by Tosoh) as a raw material powder for the upper undercoat layer 15. Helium He was supplied from the carrier gas cylinder 6 to the powder feeder 5 as a carrier gas at a flow rate of 20 liters per minute. Next, the powder supply mechanism of the powder feeder 5 was operated to supply 1.9 g / min of zirconia ZrO ₂ powder together with the carrier gas to the nozzle 4 to form the ZrO ₂ upper undercoat layer 15 on the substrate 2. The substrate 2 was moved with respect to the nozzle 4 at a speed of 0.3 mm / sec.
The film thickness of the upper undercoat layer 15 made of ZrO 2 was about 7 μm.

In this way, the lower undercoat layer 14 made of Fe2O3 and the upper undercoat layer 15 made of ZrO2 were formed on both surfaces of the NAS442A5 substrate 2.
The NAS442A5 substrate 2 on which the undercoat layer was formed was wound so as to have a core diameter of about 25 mm, and fixed with an outer cylindrical material made of NAS442A5, thereby producing a metal honeycomb having a core diameter of 25 mm and a length of 50 mm. Further, as Comparative Example 2, a NAS442A5 substrate on which the lower undercoat layer 14 and the upper undercoat layer 15 are not formed is wound in the same manner as in Example 2, and is fixed with an outer cylindrical material made of NAS442A5, with a core diameter of 25 mm and a length of 50 mm. A metal honeycomb was produced.

  The two types of metal honeycombs thus produced (Example 2 and Comparative Example 2) were immersed eight times in the catalyst carrier slurry prepared as described above to form a predetermined amount of catalyst layer, Firing was performed at 950 ° C. for 20 hours.

Next, 150 N liters / minute of air was circulated at atmospheric pressure through two types of metal honeycombs (Example 2 and Comparative Example 2) on which the catalyst layer was formed, and the weight reduction amount of the catalyst layer was measured.
In Example 2 in which a 2.1 μm lower undercoat layer made of Fe ₂ O ₃ and a 7 μm upper undercoat layer 15 made of ZrO ₂ were formed, the weight loss after an air circulation time of 75 hours remained at 0.055 g. However, in Comparative Example 1 in which no undercoat layer was formed, the weight loss increased with the air circulation time, and the weight loss after 68 hours of the air circulation time reached 0.115 g. In Example 2 in which the undercoat layer is formed, the adhesion between the substrate 2 and the catalyst layer is strong through the undercoat layer, and the weight loss of the catalyst layer is small even when a large amount of air is circulated. On the other hand, in Comparative Example 2 in which no undercoat layer was formed, the adhesion between the substrate 2 and the catalyst layer was weak, which is considered to be because the catalyst layer was peeled off and lost with the passage of the air circulation time.

Example 3 and Comparative Example 3
FIG. 4 shows a schematic view of an apparatus for forming the lower undercoat layer 14. The basic apparatus configuration is the same as that in FIG. 1 except that the carrier gas pressure gauge 12 and subsequent branches are branched into two systems, and the mass flow controller 8, the powder feeder 5 and the nozzle 4 are provided in two systems. This is because the lower undercoat layer 14 is composed of a mixture of iron oxide Fe ₂ O ₃ and Al ₂ O ₃ and the composition increases in Al ₂ O ₃ as it goes from the metal substrate to the upper undercoat layer. It was to have a distribution.

As the substrate 2, a corrugated NAS442A5 having a thickness of 0.1 mm, a width of 50 mm, and a length of 200 mm was used. Next, as raw material powders for the lower undercoat layer 14, Fe ₂ O ₃ powder (JFE Chemical's central particle size 0.5 μm) and α-Al ₂ O ₃ powder (Sumitomo Chemical's AKP-30 central particle size 0. 3 [mu] m) were filled in separate powder feeders 5 respectively.

The film formation conditions of the lower undercoat layer 14 were set such that the distance between the nozzle 4 and the substrate 2 was 50 mm, the substrate 2 moving speed was 0.4 mm / sec, and the helium flow rate was 20 liters / min. In addition, the raw material powder supply rate continuously decreased the Fe ₂ O ₃ powder from 1.5 g / min to 0.5 g / min, while the α-Al ₂ O ₃ powder decreased from 0.3 g / min to 1 Increased continuously to 8 g / min.

Under this condition, a lower undercoat layer 14 made of a mixture of Fe ₂ O ₃ and Al ₂ O ₃ having a thickness of 2.0 μm was formed on the substrate 2. FIG. 5 shows the result of analyzing the composition of the deposited lower undercoat layer 14 using an electron beam microanalyzer. The composition distribution was such that the Al ₂ O ₃ component increased from the substrate 2 side toward the upper undercoat layer 15.

Next, the powder feeder 5 was filled with α-Al ₂ O ₃ powder (AKP-30, center particle size 0.3 μm, manufactured by Sumitomo Chemical Co., Ltd.) as a raw material powder for the upper undercoat layer 15.
Helium He was supplied from the carrier gas cylinder 6 to the powder feeder 5 as a carrier gas at a flow rate of 20 liters per minute. Next, the powder supply mechanism of the powder feeder 5 is operated to supply 1.3 g / min of α-Al ₂ O ₃ raw material powder together with a carrier gas to the nozzle 4 to form an upper undercoat layer made of Al ₂ O ₃ on the substrate 2. Formed.
The substrate 2 was moved with respect to the nozzle 4 at a speed of 0.2 mm / sec. The film thickness of the upper undercoat layer 15 made of Al ₂ O ₃ was about 10 μm.

In this way, the lower undercoat layer 14 made of a mixture of Fe ₂ O ₃ and Al ₂ O ₃ and the upper undercoat layer 15 made of Al ₂ O ₃ were formed on both surfaces of the NAS 442A5 substrate 2.
The NAS442A5 substrate 2 on which the undercoat layer was formed was wound so as to have a core diameter of about 25 mm, and fixed with an outer cylindrical material made of NAS442A5, thereby producing a metal honeycomb having a core diameter of 25 mm and a length of 50 mm. Further, as Comparative Example 3, a NAS442A5 substrate on which the lower undercoat layer 14 and the upper undercoat layer 15 are not formed is wound in the same manner as in Example 3, and is fixed with an outer cylindrical material made of NAS442A5, with a core diameter of 25 mm and a length of 50 mm. A metal honeycomb was produced.

The two types of metal honeycombs thus prepared (Example 3 and Comparative Example 3) were immersed eight times in the catalyst carrier slurry prepared as described above to form a predetermined amount of catalyst layer, Firing was performed at 950 ° C. for 20 hours.
Next, 150 N liters / minute of air was circulated at atmospheric pressure through two types of metal honeycombs (Example 3 and Comparative Example 3) on which the catalyst layer was formed, and the weight reduction amount of the catalyst layer was measured.

In Example 3 in which a 2.0 μm lower undercoat layer made of a mixture of Fe ₂ O ₃ and Al ₂ O ₃ and a 10 μm upper undercoat layer 15 made of Al ₂ O ₃ were formed, the air flow time was 70 hours later. In Comparative Example 3 in which no undercoat layer was formed, the weight reduction amount increased with the air circulation time, and the weight reduction amount after 70 hours of the air circulation time was 0%. .111 g was reached. In Example 3 in which the undercoat layer was formed, the adhesion between the substrate 2 and the catalyst layer was strong through the undercoat layer, and the weight loss of the catalyst layer was small even when a large amount of air was circulated. On the other hand, in Comparative Example 3 in which no undercoat layer was formed, the adhesion between the substrate 2 and the catalyst layer was weak, so it is considered that the catalyst layer was peeled off and lost with the passage of the air circulation time.

It is the schematic explaining one Embodiment about the apparatus for forming the lower undercoat layer and upper part which concern on this invention. It is a conceptual diagram which shows the structure of the catalyst which concerns on this invention. It is a graph which shows the relationship between the air circulation time which concerns on Example 1 and Comparative Example 1, and the weight decreasing amount of a catalyst membrane. It is the schematic explaining one Embodiment about the apparatus for forming the lower undercoat layer concerning Example 3 into a film. 6 is a graph showing a composition distribution of a lower undercoat layer according to Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 2 Substrate 3 Substrate holder 4 Nozzle 5 Powder feeder 6 Carrier gas cylinder 7 Pressure regulator 8 Mass flow controller 9 Filter 10 Rotary pump 11 Mechanical booster pump 12 Valve 13 Pressure gauge 14 Lower undercoat layer 15 Upper undercoat layer 16 Wash coat method Catalyst layer

Claims (19)

A lower undercoat layer formed by spraying a fine powder together with a carrier gas from the tip of a microhole nozzle onto a metal substrate and having a component having an affinity for the component of the substrate on the substrate, and an upper undercoat layer And forming a catalyst film containing a catalytically active component by a washcoat method on the undercoat layer, and then performing a baking treatment. catalyst. 2. The catalyst according to claim 1, wherein the constituent component of the lower undercoat layer has an affinity with the constituent component of the upper undercoat layer. The catalyst according to claim 1, wherein the upper undercoat layer is composed of Al ₂ O ₃ and / or ZrO ₂ . The catalyst according to any one of claims 1 to 3, wherein the lower undercoat layer is made of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ . According to any one of claims 1 to 3, characterized in that the lower undercoat layer comprises a mixture of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ and Al ₂ O ₃ and / or ZrO ₂ catalyst. The lower undercoat layer is made of a mixture of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ and Al ₂ O ₃ and / or ZrO ₂ , and the composition is directed from the metal substrate to the upper undercoat layer. The catalyst according to claim 1, wherein the catalyst has a composition distribution in which Al ₂ O ₃ and / or ZrO ₂ increases. The catalyst according to any one of claims 1 to 6, wherein a particle velocity of particles ejected together with a carrier gas from the tip of the microhole nozzle is 700 m / s or more. Catalyst carrier for carrying the catalyst active component, the catalyst according to any one of claims 1 to 7, characterized in that a main component Al ₂ O ₃ and / or ZrO _2. The catalyst according to any one of claims 1 to 8, wherein the catalytically active component is at least one catalytically active component selected from Pd, Ru, and Pt. A lower undercoat layer formed by spraying a fine powder together with a carrier gas from the tip of a microhole nozzle onto a metal substrate and having a component having an affinity for the component of the substrate on the substrate, and an upper undercoat layer And forming a catalyst film containing a catalytically active component by a washcoat method on the undercoat layer, and then performing a firing treatment. To produce a catalyst. 11. The method for producing a catalyst according to claim 10, wherein the constituent component of the lower undercoat layer has an affinity with the constituent component of the upper undercoat layer. The method for producing a catalyst according to claim 10 or 11, wherein the upper undercoat layer is composed of Al ₂ O ₃ and / or ZrO ₂ . Process for preparing a catalyst according to any one of claims 10 to 12 in which the lower undercoat layer is characterized in that it consists of iron oxide Fe ₂ O ₃ and / or Fe ₃ O _4. According to any one of claims 10 to 12, characterized in that the lower undercoat layer comprises a mixture of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ and Al ₂ O ₃ and / or ZrO ₂ A method for producing a catalyst. The lower undercoat layer is made of a mixture of iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ and Al ₂ O ₃ and / or ZrO ₂ , and the composition is directed from the metal substrate to the upper undercoat layer. 13. The method for producing a catalyst according to claim 10, wherein Al ₂ O ₃ and / or ZrO ₂ has a composition distribution that increases with time. The method for producing a catalyst according to any one of claims 10 to 15, wherein a particle velocity of particles ejected together with a carrier gas from the tip of the microhole nozzle is 700 m / s or more. Catalyst carrier for carrying the catalyst active component, process for preparing a catalyst according to any one of claims 10 to 16, characterized in that a main component Al ₂ O ₃ and / or ZrO _2. The method for producing a catalyst according to any one of claims 10 to 17, wherein the catalytically active component is at least one catalytically active component selected from Pd, Ru and Pt. Manufacturing for forming a lower undercoat layer composed of a component having an affinity for a component of the substrate on the substrate by spraying the fine powder together with the carrier gas from the tip of the minute hole nozzle onto the metal substrate. An apparatus, wherein the carrier gas is branched into two systems, two microhole nozzles are provided, and iron oxide Fe ₂ O ₃ and / or Fe ₃ O ₄ is supplied from the tip of one microhole nozzle. Sprayed onto a metal substrate, Al ₂ O ₃ and / or ZrO ₂ was sprayed onto the metal substrate from the tip of the other micro-hole nozzle, and Al was moved from the metal substrate toward the upper undercoat layer. _2. A manufacturing apparatus characterized in that a composition distribution in which ₂ O ₃ and / or ZrO ₂ increases is formed in the lower undercoat layer.

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