JPS6012136A - Coating and supporting method of monolithic carrier - Google Patents

Abstract

PURPOSE:To obtain a monolithic catalyst wherein a noble metal is not supported by the peripheral part of a monolithic carrier closed by a retainer, but by a method wherein the peripheral part of one end of the monolithic carrier is covered in an arbitrary width while an alumina slurry is injected into the opened central part thereof and, after drying and baking, the baked carrier is immersed in an aqueous noble metal solution according to a specific method. CONSTITUTION:A monolithic carrier 1 made of cordierite is statically placed to the recessed part provided to the upper lid of a static tank 2 and a receiving t ray plate 3 having an opening formed to the bottom thereof is further placed on the carrier 1. The size of said opening is made equal to the diameter of the central part 1 supporting a noble metal of the carrier 1. That is, the width X of the peripheral part 1b in the drawing is equal to the width of a retainer. In the next step, a coating slurry 5 poured into the tray plate 3 from a pipe 4 while the tank 2 is evacuated from an exhaust port to be flowed down along the cell wall of the opened central part 1a and a prescribed amount of alumina is adhered to the cell wall. Subsequently, the carrier 1 after above mentioned treatment is dried in air and baked to obtain a carrier wherein only the central part 1a is coated with alumina so as to leave the peripheral part closed by the retainer. Finally, only the central part 1a of the carrier 1 is allowed to support platinum to obtain a monolithic catalyst.

Description

[Detailed description of the invention] [Industrial application field].

The present invention relates to a method for manufacturing a monolithic catalyst for purifying exhaust gas of an internal combustion engine.

[Secondary, advanced technology,]

Conventionally, Simo and Norris catalysts have been used to detoxify harmful substances contained in exhaust gas from internal combustion engines in automobiles and the like. The monolithic catalyst has many through holes inside (
An integrated ceramic structure (monolith carrier) with a nicum-like structure (monolith carrier) coated with alumina and supported with precious metals such as platinum, rhodium, and palladium, which are catalytically active components. , the exhaust gas is passed through this monolithic catalyst, and the harmful substances contained in the exhaust gas, such as hydrocarbons (HC), -carbon oxides (CO) and nitrogen oxides (NO), are removed.
x) can be efficiently purified by oxidation or reduction reaction. Additionally, compared to pellet catalysts, it has a higher porosity and produces less fine powder due to vibration friction, resulting in less pressure loss.

By the way, ring-shaped retainers, which are axial holding members, are arranged around both ends of the converter case that houses the monolithic catalyst in the direction in which the gas to be processed passes, so that the exhaust gas in the area where the retainers are located is disposed. passages are blocked and exhaust gas does not flow into the surrounding cells. Therefore, the effective volume of the monolith catalyst has been substantially reduced. On the other hand, eliminating the retainer will lead to a decrease in the holding force of the catalyst and its strength due to vibration, so if the monolith catalyst is made larger to compensate for the closed group part by the retainer, it will lead to the increase in the size of the Ikihoi converter. cause problems.

Therefore, emphasis has been placed on improving the performance of the monolithic catalyst itself, and methods have been proposed in which the amount of precious metal supported is gradually reduced from the center, where a large amount of gas passes, toward the periphery, but this requires complicated equipment to manufacture. For some reason, the problem has not been resolved.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a monolithic catalyst in which noble metal is supported on the periphery of a monolithic carrier that is closed with a retainer.

[Structure of the invention]

The present inventors discovered that the monolithic carrier is constructed as a combination of cells partitioned by partition walls, and that once gas or liquid enters the cells, it is blocked by the partition walls of the cells and does not permeate outward;
Focusing on the fact that precious metals are not supported in areas that are not coated with alumina, we masked the blocked areas in advance and then applied alumina coating, thereby ultimately increasing the density of precious metals supported per effective unit volume. We came up with the idea that catalyst performance could be improved by increasing
The invention has been completed.

That is, the method of coating and supporting the monolithic catalyst of the present invention involves coating the periphery of one end of the monolithic carrier with an arbitrary width, and then pouring the alumina slurry into the open center, or coating the periphery of both ends of the monolithic carrier with an alumina slurry. The alumina slurry is applied to the inner wall of the cell in the center by either settling and dipping in an alumina slurry while the center is coated, and then dried and fired to coat the center with alumina. A step of obtaining a monolithic carrier consisting of a "peripheral part" which is not covered with a periphery, and the monolithic carrier is sandwiched between upper and lower rings having the same diameter as the central part and immersed in a precious metal aqueous solution, or the monolithic carrier is immersed in a precious metal aqueous solution. While the surrounding area was coated, it was precipitated and immersed in an aqueous solution of precious metals, then turned and dried to remove iO in the above solution.
It is characterized by a process in which precious metals are supported only on the parts. '' □ [Function] The monolithic carrier is usually made by cutting out a cordierite honeycomb-shaped base material into the same shape, and there are approximately 500 square or hexagonal cells with a cross section of about A5-200 inside. They are arranged in the axial direction at a ratio of Either method can coat the alumina only in the center, which is not masked, by masking the periphery of both ends, standing it upright, and gently submerging it into the aluminium.After alumina coating Supporting of precious metals can be carried out by a normal method, and noble metals can be supported on the part coated with alumina.However, although it is difficult to support precious metals on parts that are not coated with alumina, when immersed in a precious metal aqueous solution, the cell The noble metal simply attached to the wall acts as a catalyst, leading to a loss of galvanic metal. Therefore, in order to prevent this, it is desirable to prevent the aqueous noble metal solution from adhering to the wall.

Embodiments of the present invention will be described below with reference to the drawings.

〔Example〕

Example 1 Monolithic carrier made of coreerite (diameter 100 mm x length 1
501q, ) 1 was placed in the recessed part of the upper lid of the static Ff tank 2 shown in FIG. The size of the above-mentioned pores is made equal to the diameter of the central portion 1a of the monolithic carrier 1 supporting the noble metal. That is, the width X of the peripheral portion 1b in the figure
: 10 am is equal to the width of the retainer. When the coating slurry 5 having the composition shown below is poured from the slurry pipe 4 onto the tray plate 6 while drawing air from the exhaust port 2a, the coating slurry 5 flows down along the wall of the cell in the open center 1a, and flows down the cell wall. A predetermined amount of alumina is attached to the wall, and the excess falls into the static tank 2. The alumina coating slurry 5 is a commercially available r-alumina powder with an average specific surface area of 100♂/l! 0 parts by weight of alumina silua with an alumina content of 10% by weight and 20 parts by weight of water.

After air drying the monolithic support 1 treated in this way,
By firing at 700° C. for 2 hours, a monolithic carrier 1 is obtained in which only the central portion 1a is coated with alumina, leaving the peripheral portion 1b closed with the retainer. Then, the width of the retainer (
By replacing the saucer plate 5 according to the illusion, the central part 1a
and the peripheral portion 1b can be arbitrarily determined by Kt.

The noble metal can be supported basically by following the conventional method, but in order to avoid wasteful +J deposition, the following method is used. That is, a lower ring 7 having the same diameter as the center portion 1a is placed at the center of the cylindrical support frame 6 shown in FIGS. , further overlap the lower ring 7 and the upper ring 8 of the same diameter.

Inside the support frame 6, a rubber rubber 9 having a width of about 101 m and having a shape that can wrap around the monolithic carrier 1 can push aside the lever body 1, the lower ring 7, and the upper ring 8, and fix the monolithic carrier 1 vertically. .

Therefore, in the upper ring 8, dinitrodiaminoplatinum aqueous solution (
Pour platinum (1.0 f/1) 11 to completely immerse the monolith carrier 1. After 68 minutes, the air is removed from the rubber rubber 9, the monolith carrier 1 is pulled up and dried at 200°C for 1 hour, and the amount of platinum supported is 1.56 f based on the volume of the center part 1a.
A monolithic catalyst A having a loading density of /l was obtained.

Example 2 A tape 12 with a width of 10 m, which is equal to the width of the retainer, is applied to the peripheral parts of both end openings of a monolithic carrier 1 similar to that in Example 1, and the cell is placed gently into a carrier frame 13 filled with coating slurry 5. The coating slurry 5 settles while excluding air and is immersed in the coating slurry 5. After a given time fifl,
It is taken out from the support frame 15 and dried and fired in the same manner as in Example 1 to obtain a monolithic carrier 1 consisting of an alumina-coated central portion 1a and an un-alumina-coated peripheral portion 1b having the same proportions as in Example 1.

The tape 12 has lost 13'A due to baking, so it is peeled off, a new tape 12 is pasted, and a dinitrodiaminoplatinum aqueous solution 11 with the same concentration as in Example 1 is placed in another support frame 13'.
Immerse yourself in i′, :t. After 60 minutes, monolith carrier 1
was pulled up and dried at 200°C for 1 hour, and platinum 4. Monolith touch with eye capacity -111,56f/l! ^I got a B.

Test Examples Examples 1 and 2 and monolithic catalysts A and B obtained by conventional methods
After conducting the following durability tests on and C, the purification performance was tested. Durability test is air fuel ratio (A/F)
14.6. After 300 hours of operation at a space velocity of 6 (LOOO1 hr) and a catalyst input gas temperature of 720°C,
The purification rate (ch) was measured for each case where the exhaust gas temperature was 500'C and 550C. The results are shown in the table below.

As is clear from the above table, monolithic catalysts A and B obtained by the method of the present invention have an increased amount of platinum supported per unit volume compared to monolithic catalyst C obtained by the conventional method, and have the same h
However, it can be seen that the catalytic performance is even more excellent than that.

As described above, the manufacturing method of the present invention requires a simple rfN device and operation, and it is possible to arbitrarily set the noble metal supporting part of the lithium catalyst. Since no noble metal is supported, the density of support per effective volume increases and the durability of the catalyst is improved. Furthermore, according to the conventional method, if the amount of alumina and precious metal that is adhered to or supported on the closed portion of the retainer is subtracted when preparing the alumina slurry and the noble metal aqueous solution, the effect of saving the amount of alumina and precious metal can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of the alumina coating process in Example 1, FIG. Figure 3-(A) represents a cross-sectional view of the alumina coating process of Example 2, Figure 5-(B) represents a plan view of the support frame, and Figure 4-(A) represents the Ei factor. A cross-sectional view of the n-metal supporting process of Example 2 is shown, and No. 41-(B) is a plan view of the supporting frame. In the figure, 1... Monolithic carrier 1a... Center part 1b... Peripheral part 2□... Standing tank ゛2a =-Exhaust port 5...
・The receiver is a plate plate 4...Slurry pipe 5...Coating slurry 6゛°゛carrying collar 7...Lower ring 8...Upper ring 9...Rubber rubber 10...Air inlet 11...・Dinitrodiamine platinum aqueous solution 12...Tape 13.13' °°°Support frame patent applicant Toyota Motor Corporation Figure 1 □ □, ・ ,' Figure 2.2 / /' Fang Figure 3 (A) ( b) Fang 4N (a) (b) 11 ・

Claims (1)

[Claims] After coating the periphery of one end of the monolithic carrier to a desired width, pour the minus slurry into the open center cell, or leave the periphery of both ends of the monolithic carrier coated.
The alumina slurry is adhered to the inner wall of the cell in the center by immersion in an alumina slurry, and then dried and fired to form an alumina-coated center, a non-alumina-coated periphery, and a roof. -/! A step of obtaining a JC carrier, and sandwiching the monolithic carrier between upper and lower rings having the same diameter as the center and immersing it in a noble metal aqueous solution,
Or coat the periphery of both i & of the monolithic carrier.
A method for coating and supporting a monolithic carrier, which comprises the steps of: immersing the core in a precious metal aqueous solution for precipitation, and then drying so that only the central portion supports KN metal.