JPH01135543A - Preparation of monolith-type catalyst - Google Patents

Abstract

PURPOSE:To set a catalyst-carrying region highly precisely and uniformly, by moving the surface of a liquid carrier by shifting the bottom of a carrier bath upward and downward to a monolithic carrier which is, except an up stream part, held on the upper part of the carrier bath. CONSTITUTION:When the bottom surface 16a of a carrier bath 12 being at the highest level, the surface of a liquid carrier 24 comes to the upper side of a carrier 22 leaving a not-carried part 22a. Also, when the bottom surface of the carrier bath 12 being at the lowest level, the surface of the liquid carrier 24 comes near to the lower side of the carrier 22. As the bottom surface 16a moves upward and downward between the levels to elevate and lower the liquid carrier surface, contact degree between the liquid carrier 24 and the carrier 22 is increased and unevenness of the liquid carrier concn. is decreased and uniform catalyst-carrying is achieved. Further, it becomes easy to stop synchronously elevating the bottom surface 16a and liquid carrier surface.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a monolith type catalyst using a honeycomb carrier or a three-dimensional foam carrier, in which an unsupported portion of the catalyst is formed in a predetermined range on the upstream side. The present invention relates to a method for producing a monolithic catalyst.

This manufacturing method is used, for example, to manufacture a monolithic catalyst installed in an exhaust system of an internal combustion engine for an automobile.

[Conventional technology]

In order to purify exhaust gas from internal combustion engines of automobiles, monolithic catalysts such as oxidation catalysts and redox catalysts (three-way catalysts) are provided in exhaust systems. This monolith-type catalyst has superior performance, such as higher purification performance per unit volume, less pressure loss of exhaust gas, and higher durability, than conventional pellet-type catalysts. Although catalyst components are uniformly supported throughout the monolithic catalyst, poisonous substances such as lead and phosphorus present in the exhaust gas concentrate and adhere to the upstream portion of the monolithic catalyst. Then, the catalyst deteriorates in the portion to which the poisonous substance has adhered, resulting in a decrease in catalyst performance and a problem in that the catalyst components (precious metals such as Pt, Pd, Rh, etc.) carried on the upstream side are wasted. On the other hand, there is a technique that eliminates wastage of catalyst components by providing a non-supporting portion of catalyst components in the upstream portion where poisonous substances adhere (for example, Japanese Patent Publication No. 59
-25855).

Various methods can be considered to produce a monolithic catalyst with a non-supported portion of the catalyst component, but the simplest method is to leave the non-supported portion with the upstream side of the monolithic carrier facing upward. It is conceivable that the particles be supported by immersing them in a supporting solution and leaving them for a predetermined period of time.

[Problem that the invention seeks to solve]

However, in the above-mentioned supporting method, the monolithic carrier is supported in a vertical direction, and therefore, due to the influence of gravity, more catalyst components are supported toward the bottom of the monolithic carrier. As described above, when the distribution of the catalyst is non-uniform, there is a problem that the purification efficiency of the catalyst becomes lower than when the catalyst is uniformly supported.

On the other hand, as a method for uniformly supporting the carrier, a plurality of monolithic carriers are arranged in a multi-layered manner in the middle of the circulation path of the supporting liquid, and the supporting liquid is circulated through the honeycomb cell path to uniformly support the carrier. There is (Special Publication No. 60-15383).

However, with this method, it is not possible to provide an unsupported portion of the catalyst on the upstream side. In addition, 1 carrier housed in the carrier tank is
It is also conceivable to move the carrier liquid by moving only the layer, by bringing out only the upstream side from the carrier liquid level and rotating the pump in forward and reverse directions. However, since the supporting liquid is supplied by pump circulation, it is difficult to accurately control the flow rate, and the upstream non-supporting region cannot be set within a predetermined range.

If the non-supported area is small, the expensive precious metal used as a catalyst will be wasted accordingly. On the other hand, if there are many non-supported regions, that is, if there are few supported regions, a problem arises in that the desired catalytic performance cannot be obtained.

Therefore, an object of the present invention is to produce a monolithic catalyst in which a catalyst is supported except for the upstream portion.
It is an object of the present invention to provide a method for manufacturing a monolithic catalyst, which is characterized in that it is possible to set a catalyst-supporting area with high precision and to form a uniform catalyst-supporting portion.

[Means for solving problems]

Therefore, in the method for producing a monolithic catalyst of the present invention, for the carrier held at the upper part of the carrier tank leaving the upstream part
It is characterized by moving the supporting liquid level by raising and lowering the bottom of the supporting tank.

Specifically, the configuration of the present invention is as follows.

Note that the reference numerals in FIG. 1 are used for reference.

The present invention is a method for producing a monolithic catalyst in which a catalyst is supported on an integral carrier (22) having pores (22c) inside thereof, except for the upstream portion (22a).

First, a carrier (22) is prepared. Then, the bottom surface (16a) of the support tank (12) is moved up and down while the carrier is held at the top of the support tank (12) with its upstream side facing upward. Thereby, the upstream portion (22a) of the carrier (22)
) The catalyst is supported by raising and lowering the supporting liquid level until the position where the catalyst remains.

[Effect]

According to the above-described method for producing a monolithic catalyst of the present invention, the bottom surface (16a) of the support tank (12) is located at the top, and the liquid level of the support liquid (24) is on the upstream side of the support (22). It is located where the unsupported portion (22a) remains. Further, in a state where the bottom surface (16a) of the support tank (12) is located at the lower part, the liquid level of the support liquid (24) is located near the lower part of the carrier (22). The bottom surface (16a) moves up and down between these two positions to raise and lower the level of the carrier liquid, thereby increasing the degree of contact between the carrier liquid (24) and the carrier (22) and increasing the concentration of the carrier liquid (24). There is less bias in the results, and uniform loading becomes possible. Further, it is easy to synchronize the stop timing of the bottom surface (16a) at the rising end and the supporting liquid level, and the catalyst supporting area can be set with high precision.

〔Example〕

(First Example) Next, a first example of the method for manufacturing a monolithic catalyst according to the present invention will be described based on FIG.

In this embodiment, an air bag is used to move the carrier liquid.

FIG. 1 is a longitudinal sectional view of the carrier device.

The supporting device 10 includes a cylindrical container 12 as a supporting tank. A support frame 14 is provided slightly below the vertical center of the container 12 along the inner peripheral surface. An air bag 16 is provided at the bottom 12a of the container 12 below the support frame 14.
is accommodated.

The air bag 16 is made of rubber (for example, neoprene rubber) and is connected to a switching valve 18 outside the container 12 via an opening 12c.

Note that the bottom surface 16a of the airbag 16 is made of thick rubber material, and both sides are made of thin rubber material. Thereby, the airbag 16 can be moved up and down with the bottom surface 16a kept flat.

The upper surface 16a of the airbag 16 constitutes the bottom surface of the container 12.

The switching valve 18 includes an air supply pipe 18a from an air supply means such as an air pump (not shown) and an air discharge pipe 1.
8b is connected.

An opening 12C is formed above the support frame 14 of the container 12. The carrier liquid tank (
A carrier liquid 24 is supplied to the opening 12c via a valve 20 (not shown).

A monolithic carrier 22 is placed on a support frame 14 within the container 12 . As the monolith carrier 22, a cordierite honeycomb structure coated with alumina slurry was used.

The honeycomb structure used had a diameter of 107 mm, a length of 78 mm, and a square cell density of 400 cells/1 nch. The alumina slurry was prepared by mixing and stirring activated alumina powder, alumina sol, and water. After coating by dipping, drying and baking were performed.

The weight proportions of each component were 45 wt% alumina powder, 5 wt% alumina sol, and 50-t% water.

Next, a method of supporting a catalyst with a non-supported portion of the catalyst provided on the upstream side using the above-mentioned supporting device 10 will be described.

First, the monolith carrier 22 is placed on the support frame 14 and the container 1 is
2, open the valve 20 and supply the carrier liquid 24 from the carrier liquid tank into the container 12d. At this time, the switching valve 18 is connected to the air discharge pipe 18b side, and the air bag 16 is in the position shown by the broken line in the figure. A predetermined amount (400 cc) of the supporting liquid 24 is contained in the container 12a.
) is supplied and valve 20 is closed. Next, the switching valve 18 is switched to the air supply pipe 18a side, and 2 kg=/cd of air is supplied from the air supply source to the air bag 16.
supplied within. When air is supplied, air bag 1
The upper surface 16a of 6 pushes the supporting liquid 24 upward. Air was supplied until the level of the supporting liquid reached the position shown by the solid line. This upstream portion 22a was 25% of the length of the carrier 22. As the supporting liquid 24 is supplied, the downstream portion 22b
The supporting liquid 24 enters through the channel 22c of the cell, and the catalyst component is supported on the alumina material coated on the surface of the cordierite material. This support liquid 24 is a dinitrodiammine platinum aqueous solution (P t (NH3) z (N
.

, )2] was supplied into the container 12 in an amount of 400 cc.

After one minute, the switching valve 18 is switched to the air discharge pipe 18b side, the carrier liquid 24 is transferred to the container 12d, and the cell 22
The supporting liquid 24 in c is removed.

This operation was repeated 2 minutes, 5 minutes, and 10 minutes after the initial immersion of the supporting liquid, for a total of 30 minutes of immersion.

After the immersion was completed, the monolithic carrier 22 was taken out from the container 12 and dried (60 minutes). Thereafter, immersion and drying were performed in the same manner using 4 oocc of rhodium chloride aqueous solution (RhCj2.) as a supporting liquid.

As a result, a monolithic catalyst was obtained in which 1.0 g of platinum and 0.1 g of rhodium were supported per liter of carrier volume.

(Second Example) Next, a second example of the method for manufacturing a monolithic catalyst according to the present invention will be described based on FIG.

This embodiment uses a piston instead of an air bag.

FIG. 2 is a longitudinal sectional view of the carrier device.

It should be noted that members common to the supporting device of the first embodiment are numbered in the 100s with the corresponding reference numbers in FIG.

In the supporting device 100, a supporting tank is constituted by a cylindrical container 112. A carrier liquid 124 is supplied to the opening 112C via the valve 120, as in the first embodiment. Support frame 11
A piston 200 is provided in the container 112 below the container 4 . The piston 200 has a rod 202 connected to the container 11.
2 through the hole 204 in the bottom 112a of the hole 204.
It is sealed by a seal 206 that is fitted into the housing. The upper surface 2QOa of the piston constitutes the bottom surface of the container 112. This piston 200 is reciprocated between predetermined positions in the vertical direction by an air cylinder (not shown).

Next, a method of supporting a catalyst with a non-supported portion of the catalyst provided on the upstream side using the above-mentioned supporting device 100 will be described.

The monolith carrier 122 is placed on the support frame 114 and the container 11
2, the valve 120 is opened to supply the carrier liquid 124 from the carrier liquid into the container 112. At this time,
The air cylinder is at the retreating end, and the piston 200 is at the position shown by the broken line in the figure. The carrier liquid 124 is contained in the container 112.
d, and valve 120 is closed.

Thereafter, the air cylinder is moved to the forward end, and the piston 200 is raised to the position shown by the solid line in the figure. As a result, the carrier liquid 124 is pushed upward to the position where the bottom surface 200a of the piston 200 is shown by the solid line in the figure, and the carrier 12
2 is immersed in the support liquid 124.

These operations were repeated in the same cycle as in the first example. Note that the same monolith carrier 122 as in the first example was used.

As a result, a monolithic catalyst was obtained in which 1.0 g of platinum and 0.1 g of rhodium were supported per 11 carrier volumes.

(Experimental Example) The supported state of the catalyst produced in the above-mentioned example was confirmed, and the purification performance was measured using an experimental cap. In addition, as a comparative example, a catalyst was prepared in which 1 g/l of platinum and 0.1 g/l of rhodium were supported by holding the immersion state in a supporting liquid of the same composition for 30 minutes without moving the supporting liquid up and down. We also conducted an evaluation.

Regarding the supported state of the catalyst, as shown in FIGS. 3 and 4, for both platinum and rhodium, the catalyst of Example 1.2 has a supported portion and a non-supported portion separated by approximately 20 mm from the upstream side. On the downstream side, it is evenly supported. On the other hand, in the comparative example, although there is a relatively sudden change in the loading rate from 10 m to 20 m from the upstream side, there is a gradual change in the loading rate further downstream. It can be seen that the loading is non-uniform in the axial direction.

Next 1. Regarding the purification performance of these catalyst samples,
Evaluation was performed as follows.

Each catalyst sample was filled into a metal container with the upstream unsupported portion of the catalyst as the exhaust gas inflow side, and the container was installed in the exhaust system of an engine. The engine used was a 2.811 gasoline engine, and the H
The purification rate of C, Co5NOx was measured.

The results are shown in FIGS. 5 to 7.

As is clear from the figure, the catalysts of the first and second examples have higher HC than the comparative example even when the inlet gas temperature is lower.
Purification rate, CO purification rate and N.

It can be seen that it shows a purification rate of X. That is, the catalysts produced by the methods of the first and second embodiments have high low-temperature activity.

Although specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and includes various embodiments within the scope of the claims. .

〔Effect of the invention〕

From the above, according to the method for producing a monolithic catalyst of the present invention, the bottom surface of the support tank is moved up and down to move the support liquid level with respect to the support held at the top of the support tank, leaving the upstream part. , it is possible to set the catalyst supporting area with high precision and uniformity.

Further, since the bottom surface of the support tank is moved, the number of piping equipment for supplying the support liquid around the support tank including the support liquid circulation pump can be reduced, and the apparatus can be made smaller.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drawing for explaining a first embodiment of the method for producing a monolithic catalyst according to the present invention, and is a longitudinal sectional view of a supporting device. FIG. 2 is a diagram for explaining a second embodiment of the method for manufacturing a monolithic catalyst according to the present invention, and is a longitudinal cross-sectional view of a supporting device. 3 to 7 are drawings for explaining experimental examples of the first example, the second example, and the comparative example of the method for manufacturing a monolithic catalyst according to the present invention, and FIG. Figure 4 is a graph showing the relationship between the supported weight ratio of platinum and the axial direction of the catalyst, Figure 5 is a graph showing the relationship between the supported weight ratio of rhodium and the axial direction of the catalyst, and Figure 5 is the temperature at which exhaust gas flows into the upstream side of the catalyst. H for
FIG. 6 is a graph showing the relationship between the CO purification rate and the temperature at which the exhaust gas flows into the upstream side of the catalyst, and FIG. 7 is a graph showing the relationship between the temperature at which the exhaust gas flows into the upstream side of the catalyst. It is a graph showing the relationship between NOx purification rates. 10--Carrying device 12--Carrying tank 16 a--Bottom surface 22--Carrier 22a--One upstream portion 22c -・-・Pore (flow path) Applicant Toyota Motor Corporation Figure 1 a ” 3?-, 2pm 2

Claims (1)

[Scope of Claims] A method for producing a monolithic catalyst in which a catalyst is supported on an integral carrier having pores in the interior except for the upstream portion thereof, the method comprising: preparing the carrier, and supporting the catalyst on the upstream side thereof; With the carrier held at the top of the carrier tank with the carrier facing upward, the bottom of the carrier tank is moved up and down to raise and lower the carrier liquid level until the upstream portion of the carrier remains. A method for producing a monolithic catalyst characterized by supporting a catalyst.