JP2003305372A - Catalyst manufacturing method and humidification quantity adjusting apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance a catalytic capacity by positively controlling the coating amount distribution of a catalyst slurry in the radial direction of a catalyst carrier. <P>SOLUTION: In a method for applying humidification treatment to a monolithic type catalyst carrier 1 prior to coating the monolithic type catalyst carrier with a catalyst slurry, the carrier 1 is supported on a carrier support tray 2, and a shield plate 9, which covers the peripheral part of the lower end opening surface of the carrier 1, is arranged to the underside of the carrier 1. After water is allowed to flow down on the carrier 1 from above to apply humidification treatment to the carrier 1, a negative pressure suction force is allowed to act on the portion corresponding to an opening part of the shield plate 9 as the adjustment treatment of a humidification quantity distribution to suck and remove excess moisture. The humidification quantity distribution is adjusted so that the humidification quantity becomes relatively little in the center part of the cross section of the carrier 1 than in the peripheral part thereof and the catalyst slurry is subsequently applied to the carrier 1. Hence, the coating amount of the catalyst slurry becomes larger in the portion with a smaller humidification quantity contrarily. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a catalyst and a humidification amount adjusting device used for the method, and more particularly to a monolithic type ceramic or metal foil catalyst carrier used in an exhaust gas purification system of an automobile or the like and a catalyst slurry. The present invention relates to a method of humidifying (wetting) prior to coating a coating, and a humidification amount adjusting device used therefor.

[0002]

2. Description of the Related Art As described in JP-A-1-307455 and Japanese Patent No. 2616157,
Before coating a catalyst carrier made of honeycomb-shaped ceramic or metal foil (for example, stainless steel foil) with a catalyst slurry, the cell should not be clogged even if it is coated with a highly viscous slurry. Humidification treatment (wetting treatment) is performed as a pretreatment. When the catalyst carrier is made of ceramic, the ceramic itself has a hygroscopic property, so that it can be suddenly humidified, but in the case of a catalyst carrier made of metal foil, the catalyst carrier itself is Since it does not have hygroscopicity, the humidification treatment is performed each time before the second and subsequent coating treatments on the assumption that the coating and firing of the catalyst slurry are repeated several times.

[0003]

The conventional humidifying method is a method of removing excess water by allowing a predetermined negative suction pressure to act on the opening end surface of the catalyst carrier after absorbing pure water or the like. , The degree of humidification is not uniform in the cross section of the catalyst carrier, and, for example, a deviation in the amount of humidification occurs between the central portion and the peripheral portion of the catalyst carrier. There was a problem of being biased. That is, the larger the amount of humidification during the humidification process, the slower the moisture absorption of the catalyst slurry, and as a result, the coating amount of the catalyst slurry becomes insufficient.

Further, when coating the catalyst slurry subsequent to the humidifying process, a predetermined suction negative pressure is applied to the opening end face to suck and remove the excess catalyst slurry, so that the flow velocity is relatively large. The catalyst slurry in the central portion of the carrier tends to be sucked and removed in a larger amount, and as a result, the coating amount of the catalyst slurry in the central portion having the largest exhaust gas purification performance becomes smaller, which is not preferable in practice. Then, in order to compensate for such non-uniformity of the coating amount of the catalyst slurry, it is necessary to positively variably control the suction and removal amount of the catalyst slurry at a required place, which makes the control remarkably complicated. .

The present invention has been made by paying attention to such a problem, and in spite of a simple method, the amount of humidification is actively controlled in the peripheral portion and the central portion of the cross section of the catalyst carrier. The method for producing a catalyst and the humidification used therefor, which prevents the cell from being clogged during the subsequent catalyst coating and enables the coating amount to be actively controlled in the peripheral portion and the central portion in the cross section of the catalyst carrier. It is intended to provide a quantity adjusting device.

[0006]

The invention according to claim 1 is a method for producing a catalyst, wherein a monolithic catalyst carrier is humidified prior to coating the catalyst slurry with the catalyst slurry. It is characterized in that the catalyst slurry is coated after adjusting the humidification amount distribution so that the humidification amount in the radial direction is different in the cross section.

According to the second aspect of the present invention, on the premise of the first aspect, the humidification amount distribution is set so that the central part of the cross section of the catalyst carrier is relatively less humidified than the peripheral part. It is characterized in that it is adjusted and then coated with a catalyst slurry.

More specifically, as described in claim 3, the adjustment of the humidification amount distribution is performed when the excess moisture is removed from the one end opening surface side of the catalyst carrier after the humidification treatment by negative pressure suction force. In addition, the peripheral portion of the opening surface at one end is covered with a shielding member to limit the area on which the negative pressure suction force acts.

The shape of the shielding member may be any shape as long as it corresponds to the required humidification amount distribution. For example, if the catalyst carrier has a circular cross section, the shielding plate has a round hole. A disc-shaped product obtained by punching is used.

The moisturizing treatment may be carried out by a dipping method in which the catalyst carrier is directly immersed in a liquid tank containing pure water or the like, but in the case of mass production, it is substantially moistened as described in claim 4. It is desirable to perform the processing and the processing of adjusting the humidification amount distribution at the same time.

That is, the invention according to claim 4 is based on the description of claim 2 or 3, and the catalyst carrier is supported by a support so that the one end opening surface of the catalyst carrier is on the lower side, and the catalyst is also supported. A shield member that covers the periphery of the opening surface at one end of the carrier is placed under the carrier, and after the water is flowed down from above the catalyst carrier to perform the humidification process, the opening of the shield member is adjusted as the adjustment process of the humidification amount distribution. It is characterized in that a negative pressure suction force is applied to the corresponding portion to remove excess water adhering to the catalyst carrier.

In the invention according to any one of claims 1 to 4, as described in claim 5, it is necessary to secure a gap between the one end opening surface of the catalyst carrier and the shielding member in advance. It is preferable for gradually increasing or decreasing the distribution in a specific direction.

Further, as described above, when the catalyst carrier is made of ceramic, the ceramic itself has hygroscopicity, so that it is possible to suddenly perform humidification treatment, but the catalyst made of metal foil is used. In the case of a carrier, since the catalyst carrier itself does not have hygroscopicity, the humidification treatment is performed before the second and subsequent coating treatments on the assumption that the catalyst slurry coating and firing are repeated several times. I shall.

Therefore, in the invention according to any one of claims 1 to 5, the central portion is relatively more relative to the peripheral portion than the peripheral portion in the cross section of the catalyst carrier so that the humidification amount in the radial direction is different in the cross section of the catalyst carrier. If the catalyst slurry is coated after adjusting the humidification amount distribution so that the amount of humidification will be reduced, the coating amount of the catalyst slurry after that becomes smaller as the amount of water retained by the humidification process increases, and conversely The smaller the water content, the greater the coating amount of the catalyst slurry thereafter. As a result, as the catalyst carrier after the catalyst slurry coating treatment,
The central portion of the cross section of the carrier has a larger amount of attached catalyst slurry, and conversely, the amount of attached catalyst slurry gradually decreases toward the peripheral portion. This means that the catalyst holding amount is larger in the central portion that is the most important or effective in the exhaust gas purification performance, and is extremely preferable in improving the exhaust gas purification performance.

In particular, when a gap is secured in advance between the one end opening surface of the catalyst carrier and the shielding member as in the fifth aspect, the portion where the negative pressure suction force acts and the portion where it does not exist. The boundaries are less likely to appear, and the distribution of the amount of humidification in the cross section of the catalyst carrier gradually decreases from the periphery of the carrier to the center. The distribution is such that it gradually increases from the periphery of the carrier toward the center.

According to a sixth aspect of the present invention, as a humidification amount adjusting device used in the method for producing a catalyst according to the third aspect, the catalyst support after the humidification treatment is performed such that one end opening surface of the catalyst support is on the lower side. A shield member is placed below the catalyst support to cover the periphery of the opening surface of the catalyst support, and the negative pressure suction force is applied to the portion corresponding to the opening of the shield member as the adjustment processing of the humidification amount distribution. To remove excess water adhering to the catalyst carrier.

Therefore, in the invention described in claim 6, since the amount of water removed by the negative pressure suction force is relatively small in the portion covered with the shielding member, the humidification amount distribution in the cross section of the catalyst carrier is shown. As a result, the distribution gradually decreases from the periphery of the carrier toward the center. Then, after coating the catalyst slurry, the distribution of the amount of catalyst adhering on the cross section of the catalyst carrier has a distribution that gradually increases from the periphery of the carrier to the center thereof.

[0018]

According to the first aspect of the present invention, the distribution of the amount of humidification is positively controlled so that the amount of humidification in the cross section of the catalyst carrier is different in the radial direction. It is possible to positively control the distribution of the amount of deposited slurry in the radial direction without performing any special treatment during coating, and it is possible to make the amount of deposited catalyst have a gradient in the cross section of the catalyst carrier.

According to the second and third aspects of the present invention, in the cross section of the medium carrier, the humidification amount distribution is positively controlled so that the humidification amount is relatively smaller in the central portion than in the peripheral portion. As a result, the coating amount of the catalyst slurry after that becomes larger in the central portion where the moisture retention amount due to the humidification treatment is smaller, and conversely the coating amount of the catalyst slurry becomes smaller as the peripheral portion where the moisture retention amount due to the humidification treatment is greater. Since the catalyst holding amount can be increased in the central portion that is most important in terms of exhaust purification performance, it can greatly contribute to the improvement of exhaust purification performance.

According to the invention as set forth in claim 4, since the humidifying process by the flow of water or the like and the adjusting process of the distribution of the humidifying amount by the negative pressure suction force are carried out substantially in one step, Alternatively, in addition to the same effect as the invention described in 3, there is an advantage that the number of steps and the number of work steps can be reduced and the productivity can be improved.

According to the invention described in claim 5, a gap is secured in advance between the one end opening surface of the catalyst carrier and the shielding member, which is the same as the invention described in claim 3 or 4. In addition to the effect, the boundary between the portion on which the negative pressure suction force is applied and the portion on which the negative pressure suction force is not applied is less likely to appear, and there is an advantage that the humidification amount distribution can be a smooth distribution that gradually increases or decreases in a specific direction. is there.

According to the invention of claim 6, claim 3
Since the invention described in (1) is substantially regarded as a device configuration, the humidification is performed so that the central portion of the cross section of the catalyst carrier has a relatively smaller amount of humidification than the peripheral portion thereof even though it has a simple structure. There is an advantage that the quantity distribution can be controlled very easily.

[0023]

1 and 2 show a preferred embodiment of the present invention. In particular, FIG. 1 shows a humidification treatment and an amount of humidification on a catalyst carrier (monolith carrier) having a ceramic honeycomb structure having a cylindrical outer shape. FIG. 2 shows a schematic configuration of a distribution adjustment process, and FIG. 2 shows a schematic configuration of a catalyst slurry coating process on a catalyst carrier (hereinafter, simply referred to as a carrier) after humidification treatment and humidification amount distribution adjustment.

As shown in FIG. 1, a ring-shaped carrier support tray 2 which is slightly larger than the carrier 1 to be treated as a support is positioned and mounted on the support frame 3 (the diameter of the carrier 1 is, for example, about 110 mm). ), And the carrier 1 is placed thereon with one opening end surface of the carrier 1 as a seating surface. As shown in FIG. 3, the carrier support tray 2 has ventilation holes 4 formed to match the diameter of the carrier 1 and, for example, four claw pieces 5 on the inner peripheral side thereof.
And the lower opening end surface of the carrier 1 is supported only by the claw piece 5. A humidifying hopper 7 is mounted on the upper part of the carrier 1 via a seal member 6 to prevent splashing of splashes generated when the humidifying water such as pure water flows in a shower shape as described later.

On the other hand, a ring-shaped shield plate 9 which is a support is disposed above the suction tank 8 which is located directly below the carrier support tray 2 with a predetermined gap G, and faces the carrier support tray 2. Let The size of the gap G is, for example, 10
The thickness is set to about mm, and the atmosphere is released as it is. Further, a partition wall 10 is provided in the suction tank 8 and a suction fan 11 or a suction blower is connected to the suction tank 8.
It is configured so that a predetermined negative pressure suction force can be generated therein. The shielding plate 9 is formed by forming a ventilation hole 9a having an inner diameter R which is about half the outer diameter of the plate material having an outer diameter substantially the same as that of the carrier 1 (for example, the outer diameter of the shielding plate 9 is 110).
mm, the inner diameter R of the vent hole 9a is about 55 mm), and as shown in FIG. 1, the carrier 1 is provided so as to substantially shield the outer peripheral portion of the lower opening end face of the carrier 1 to function as a resistance plate. 1 has a function of limiting the effective opening area of the lower opening end face to about 1/4.

In the state shown in FIG. 1, for example, pure water as a humidifying water is made to flow from above the carrier 1 in a shower shape for a predetermined time to subject the carrier 1 itself to a humidifying process (wetting process). The water flowing down from the carrier 1 is collected in the suction tank 8.

After the supply of pure water is stopped, the suction fan 11 attached to the suction tank 8 is activated, and the negative pressure suction force generated in the suction tank 8 is applied to the carrier 1 as a process for adjusting the distribution of humidification amount. Forced suction and removal of excess water. In this case, a portion of the lower opening end surface of the carrier 1 other than the central portion is shielded by the shielding plate 9, and the effective opening area for the suction tank 8 is substantially limited to about 1/4 of the total area. Therefore, the central portion of the carrier 1, that is, the portion of the carrier 1 corresponding to the ventilation hole 9a of the shield plate 9 is positively sucked and removed, and is relatively hidden by the shield plate 9. Suction and removal of water from the water will be slow. On the other hand, even if a part of the lower opening end face of the carrier 1 is shielded by the shield plate 9 as described above, a gap G open to the atmosphere is secured between the two, so that gap A suction force is also generated in G, so that moisture is slightly sucked and removed even in the portion corresponding to the shield plate 9.

As a result, as shown in FIG. 4A, the carrier 1 which has been subjected to the humidifying process and the adjusting process of the humidifying amount distribution.
Has a humidification amount distribution in which the amount of humidification is smaller toward the central portion in the cross section and gradually increases toward the peripheral portion. That is, in (A) of FIG. 4, it is shown that the white portion has a smaller amount of humidification and the black portion has a larger amount of humidification.

The carrier 1 thus subjected to the humidification treatment and the adjustment treatment of the humidification amount distribution is coated with the catalyst slurry in the next step.

In this catalyst slurry coating treatment, as shown in FIG. 2, a carrier 1 which has been subjected to a humidification treatment and a humidification amount distribution adjustment treatment is placed on a carrier support tray 2 similar to that used in FIG. At the same time, the coating hopper 12 is placed on the upper surface of the carrier 1, the catalyst slurry S is charged into the coating hopper 12, and the catalyst slurry S is made to flow downward through the cells of the carrier 1 to form the wall surface of each cell. The catalyst slurry S is adhered to or carried by.

A suction tank similar to that shown in FIG. 1 is provided below the carrier supporting tray 2 to collect the catalyst slurry S flowing down from the carrier 1 by its own weight, and the inside of the suction tank. With the negative pressure suction force generated in
Excessive catalyst slurry S adhering to the carrier 1 is forcibly sucked and removed. Further, the catalyst slurry S is a well-known catalyst slurry S containing alumina, selenium or the like as a main component, and a noble metal such as platinum, rhodium or palladium, and a co-catalyst, which are crushed and mixed.

In such a coating process of the catalyst slurry S, since the humidifying treatment is performed in advance as the pretreatment, the coating amount (adhering amount) of the catalyst slurry S is smaller in the portion of the carrier 1 where the humidifying amount is smaller. On the contrary, the larger the humidification amount is, the smaller the coating amount of the catalyst slurry S is. More specifically, as shown in FIG. 4B, the carrier 1 coated with the catalyst slurry S is treated.
In the cross section, the catalyst slurry S has a larger coating amount in the central portion of the cross section, and the coating amount of the catalyst slurry S gradually decreases toward the peripheral portion. That is, FIG. 4 (B) shows that the black portion has a larger amount of the catalyst slurry S loaded, and the white portion has a smaller amount of the catalyst slurry S loaded, which means that (A) and (B) in FIG. It can also be understood from the fact that the black part and the white part are reversed when compared with).

In other words, the larger amount of catalyst slurry S is loaded in the central portion of the carrier 1 which is the most important and effective for the exhaust purification performance by the catalyst, and contributes greatly to the improvement of the performance of the carrier 1. It is possible to obtain the same catalytic performance even if the total amount of attached catalyst is reduced. The carrier 1 coated with the catalyst slurry S is dried and calcined in a post process as is well known. In addition, if necessary, the above humidification treatment, humidification amount distribution adjustment treatment, catalyst slurry coating treatment, and drying and firing treatments may be repeated one or more times as one cycle.

The present inventor has clarified what difference the film thickness of the catalyst slurry S coated on the carrier 1 shows when the shielding plate 9 is used and when it is not used in the step of adjusting the humidification amount distribution. In order to achieve this, we measured the coating amount of the catalyst. As shown in FIG. 5, the central portion of the carrier 1 after the catalyst slurry coating is defined as “center”, and the peripheral portions thereof are respectively “right”, “left”, “cup”,
The amount of coating was measured at five points, which was defined as "front".

When the humidification amount distribution is adjusted using the shielding plate 9 of the present embodiment, as is clear from FIG. 6 and Table 1, the coating amount in the "center" is the coating in the other parts. It can be seen that it is extremely large compared to the amount.

On the other hand, the shield plate 9 is used when adjusting the amount of humidification.
7 is not used, it can be seen that the coating amount in the "center" is slightly smaller than the coating amounts in the other regions, as is clear from FIG. 7 and Table 2.

[0037]

[Table 1]

[0038]

[Table 2]

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an outline of a step of humidifying a catalyst carrier and a step of adjusting a humidification amount distribution as a preferred embodiment of the present invention.

FIG. 2 is a structural explanatory view schematically showing a coating process of the catalyst slurry.

FIG. 3 is a perspective view showing details of the carrier support tray of FIG.

FIG. 4A is an explanatory diagram of a catalyst carrier showing a distribution of a humidification amount, and FIG. 4B is an explanatory diagram of a catalyst carrier showing a distribution of a coated catalyst slurry.

FIG. 5 is an explanatory plan view of a catalyst carrier.

FIG. 6 is a graph showing the distribution of catalyst slurry when the humidification amount distribution adjustment process is performed using the shielding plate of the present embodiment.

FIG. 7 is a graph showing a distribution of catalyst slurry when a humidification amount adjustment process is performed without using a shielding plate.

[Explanation of symbols]

1 ... Catalyst carrier 2 ... Carrier support tray (support) 8 ... Suction tank 9 ... Shielding plate (shielding member) 11 ... Suction fan S ... Catalyst slurry

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keisuke Honen             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F-term (reference) 3G091 AA02 AB01 BA39 GA06                 4D048 BA10X BA39X BB02                 4G069 AA01 AA08 BA13B BA17                       CA03 EA19 FA03 FB14 FB15

Claims (6)

[Claims] 1. A method for producing a catalyst, wherein a monolith type catalyst carrier is subjected to a humidifying treatment prior to coating the catalyst slurry, wherein the amount of humidification in the radial direction is different in the cross section of the catalyst carrier. A method for producing a catalyst, which comprises coating the catalyst slurry after adjusting the humidification amount distribution. 2. The catalyst slurry is coated after adjusting the humidification amount distribution so that the central portion of the catalyst carrier has a relatively smaller amount of humidification than the peripheral portion in the cross section. 1. The method for producing the catalyst according to 1. 3. The adjustment of the humidification amount distribution is such that, when excess water is removed from one end opening surface side of the catalyst carrier after humidification by negative pressure suction force, a peripheral portion of the one end opening surface is shielded. 3. The method for producing a catalyst according to claim 2, wherein the area covered with is limited to an area on which the negative pressure suction force acts. 4. The catalyst carrier is supported by a support so that one end opening surface of the catalyst carrier is on the lower side, and a shielding member is provided below the catalyst carrier to cover the peripheral portion of the one end opening surface, After performing a humidification process by flowing water from above the catalyst carrier, a negative pressure suction force is applied to the portion corresponding to the opening of the shielding member to adjust the distribution of the amount of humidification. The water of the above is removed.
Alternatively, the method for producing the catalyst according to Item 3. 5. The method for producing a catalyst according to claim 3, wherein a gap is secured in advance between the one end opening surface of the catalyst carrier and the shielding member. 6. A humidification amount adjusting device used in the method for producing a catalyst according to claim 3, wherein the catalyst carrier after the humidification treatment is supported by a support so that one end opening surface of the catalyst carrier is on the lower side. At the same time, a shielding member that covers the peripheral portion of the opening surface at one end is arranged below the catalyst carrier, and a negative pressure suction force is applied to the portion corresponding to the opening portion of this shielding member as the adjustment processing of the humidification amount distribution. A humidification amount adjusting device, characterized in that excess water adhering to a catalyst carrier is removed.