JP2693980B2 - Method for producing exhaust gas purifying catalyst - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas purifying monolith catalyst used for purifying exhaust gas discharged from an internal combustion engine or the like of an automobile.

[Prior Art] An exhaust gas purifying monolith catalyst is generally made by supporting an expensive rare element such as Pd, Ce or Pt on an inorganic porous monolith carrier or the like. Some monolithic catalysts are used by being held in a catalytic converter container by fixing the peripheral edge of the catalyst end face with a retainer or the like. In such a catalytic converter, the amount of exhaust gas flowing into the cells in the outer peripheral portion of the catalyst close to the converter container and the cells in contact with the retainer for supporting the catalyst in the catalytic converter is very small, so that the exhaust gas purification is almost impossible near the retainer. Not done In response to this, attempts have been made to prevent unnecessary catalyst components from being carried in the catalyst carrier by plugging these cells with cordierite, alumina, etc. (See JP-A-62-284916, JP-A-62-294425, etc.) However, using a conventional method, for example, a catalyst support having a filling material may be preliminarily coated with, for example, alumina as a main component. If the catalyst is carried by immersing it in the catalyst component solution after the application, the catalyst component is also carried on the outer peripheral surface of the monolith carrier where the exhaust gas does not flow and the peripheral portion of the end face of the plugged portion, which is wasteful.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and it is possible to prevent unnecessary catalyst components from being carried on a portion into which exhaust gas hardly flows, and to reduce the cost of the catalyst. To aim.

[Means for Solving the Problems] In the method for producing a monolith catalyst for purifying exhaust gas of the present invention, the end face peripheral portion of the monolith carrier is clogged to close the cells of the carrier outer peripheral part, and the clogged end face peripheral part is formed. The catalyst component solution is supplied to the catalyst carrier from one end face side of the covered catalyst carrier, and the excess catalyst component solution is sucked from the other end face side to support the catalyst component on the carrier. It is characterized by being dried with warm air having a temperature of 40 ° C. or more and a wind speed of 5 m / sec or more after being dried.

It is preferable that the inner surface of the cell, which is not clogged, of the monolithic catalyst carrier provided with clogs is pre-coated with activated alumina as a main component, and then the catalyst component is supported. Further, it is preferable that the catalyst component solution is sprayed from the spray nozzle onto the monolith carrier, that is, is carried by spray. Suction is started by a blower from the end face side which is sucked immediately before the spray loading, and the excess catalyst component solution is recovered. The cover is arranged at a position to cover the clogging so that the catalyst component solution is not sprayed by this spray carrying. Also, the catalyst carrier is dried immediately after completion of the spray loading. This drying uses warm air of 40 ℃ or higher
Dry with ventilation at 5m / sec. If the temperature of the warm air is less than 40 ° C, the drying speed will slow down, the spray liquid will drip, and the wind speed will be 5 m.
If it is less than / sec, the spray liquid is likely to permeate the clogging part, and the amount of the clogging part supported increases. After that, the monolith catalyst of the present invention is obtained by performing usual activation treatment and heat treatment.

[Operation] When the method of the present invention is used, the catalyst component is hardly supported on the outer peripheral surface of the catalyst. Further, the catalyst component is hardly supported even on the plugs provided on the cells in the portions that come into contact with the retainer. That is, when the method of the present invention is used, the catalyst component is hardly supported in the portion where the exhaust gas hardly flows in the catalytic converter.

 Hereinafter, the present invention will be described specifically with reference to Examples.

EXAMPLES Example 1 Examples and comparative examples of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a state in which a catalyst is stored in a catalytic converter. Commercially available cordierite monolith carrier (40
0 cell / in ³ , major axis 146 mm, minor axis 76 mm, length 143 mm)
As shown in the figure, a cell at the peripheral portion of one end face, which corresponds to the retainer when stored in the converter container, is filled with alumina slurry to fill the cell, and a filling portion 10 is provided. This alumina slurry is 80 parts by weight of γ-alumina,
It was prepared by kneading 15 parts by weight of aluminum nitrate and 80 parts by weight of water. After plugging, it was dried at 80 ° C. for 1 hour. next,
In the same manner, apply 12 to the peripheral edge of the other end face,
After drying at ℃ for 1 hour, it was further baked at 500 ℃ for 1 hour. Thus, 100 g / piece of alumina coating was formed on the inner surface of each cell of the carrier in which both ends of the outer peripheral cell in which the exhaust gas did not flow were clogged by a usual method.

Next, the carrier was set in an apparatus as shown in FIG. This device is provided with a cover 21 arranged so as to cover the clogging portion 10 and the outer peripheral portion 13 on the end surface on the spray carrying side, and a cover 22 arranged so as to cover the clogging portion 10 on the end surface on the suction side. ing. The catalyst component sprayed from the spraying side through the spray nozzle 20 is sucked from the suction port 23 by a blower (not shown). Spray loading was performed using this device. First, a palladium nitrate solution containing 0.77% by weight of palladium was prepared as a catalyst component solution. While suctioning with a blower from the bottom of the carrier, the palladium nitrate solution was flown into the open cell of the monolith carrier at a flow rate of 5 l.
Sprayed for 8 seconds / minute. After the spraying was completed, suction was continued for another 3 seconds, and the excess palladium nitrate solution was blown off. Immediately after this, as shown in FIG. 3, set in a ventilation dryer having a warm air inlet 30 and a warm air outlet 31, adjust the temperature of the warm air to 60 ° C and the flow velocity in the cell to 25 m / sec, and ventilate for 5 minutes. Dried. Then, it dried at 250 degreeC in the commercially available dryer for 60 minutes. In this way, the open cell of the monolith carrier has a volume of 1
A catalyst A supporting 1 g of palladium was obtained.

Example 2 In the same manner as in Example 1, the cordierite-based monolithic carrier, which had been filled and had an alumina coating formed thereon, was spray-loaded.

Immediately after that, set in a ventilation dryer as shown in Fig. 3, adjust the temperature of warm air to 50 ° C, adjust the flow velocity in the cell to 10 m / sec, and perform ventilation drying for 5 minutes, and then in a commercially available dryer.
It was dried at 250 ° C for 60 minutes. Thus, a catalyst B carrying 1 g of palladium per cell volume of the monolith carrier was obtained.

Example 3 A cerium nitrate solution containing 18.0% by weight of cerium, instead of the palladium nitrate solution, was added to the carrier on which the cells at the peripheral edge of the end face were clogged and the alumina coating of 100 g / piece was formed in the same manner as in Example 1. (Cerium 1.2 mol / l) was used and spray-supported and dried under the same conditions as in Example 1 except that 35 g of cerium was supported per 1 volume of the catalyst cell. Then, the carrier was fired in an electric furnace at 600 ° C. for 1 hour.

Next, 0.77% by weight of platinum and rhodium were used as a catalyst component solution.
Platinum-rhodium mixed solution containing 0.077% by weight (platinum
7.7 g / l, rhodium 0.77 g / l) was prepared, and this solution was spray-loaded on this carrier in the same manner as in Example 1 and then dried.
35 g of cerium and 1 g of platinum per 1 volume of catalyst carrier cell,
A monolith catalyst C supporting 0.1 g of rhodium was obtained.

Comparative Example 1 A cordierite monolithic carrier similar to that of Example 1 was subjected to the same method as that of Example 1 to fill the peripheral cells with 100 g / piece of alumina coating.

This carrier was immersed in the same palladium nitrate solution as in Example 1 for 1 minute, and then the excess solution was blown off with an air gun. Then, it dried at 250 degreeC for 60 minute (s) in the commercially available dryer. Thus, a catalyst D carrying 1 g per 1 volume of the catalyst carrier cell was obtained.

Comparative Example 2 An alumina coating was formed on the same cordierite monolith carrier as in Example 1 by the same method as in Example 1, and a palladium nitrate solution was spray-supported.

Immediately thereafter, this catalyst was set in the warm air dryer shown in FIG. 3, the temperature of the warm air was adjusted to 35 ° C., the flow rate in the cell was adjusted to 4 m / sec, and air drying was performed for 5 minutes. Then, it dried at 250 degreeC in the commercially available dryer for 60 minutes. Thus, a catalyst E carrying 1 g of palladium per 1 volume of the catalyst cell was obtained.

Comparative Example 3 A cordierite monolithic carrier similar to that of Example 1 was subjected to the same method as that of Example 1 to fill the peripheral cells with 100 g / piece of alumina coating.

This was immersed in the same cerium nitrate solution as in Example 3 for 1 minute, the excess solution was blown off with an air gun, and dried at 250 ° C. for 60 minutes with a commercially available dryer. Next, this carrier was fired in an electric furnace at 600 ° C. for 1 hour.

Further, this carrier was immersed in the same platinum nitrate / rhodium chloride mixed solution as in Example 3 for 1 minute, the excess solution was blown off with an air gun, and the carrier was dried at 250 ° C. for 60 minutes. Thus, a catalyst F carrying 35 g of cerium, 1 g of platinum and 0.1 g of rhodium per 1 volume of the monolith carrier cell was obtained.

The following tests were conducted on the catalysts A to E obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

[Catalyst Component Carrying Amount Analysis Test] Of the cells on both end faces of Catalysts A to F, the plugged portion and the cells in the vicinity of the center were separately crushed, and then palladium, platinum, rhodium and cerium were analyzed. Palladium, platinum, and rhodium are Shimadzu atomic absorption spectrophotometers AA67.
Type 0 and cerium were quantitatively analyzed by an ICP emission spectroscopic analyzer (high frequency inductively coupled plasma emission spectroscopic analyzer) manufactured by Seiko Denshi. Table 1 shows the results.

[Catalyst Performance Test] Catalysts S to F were housed in a converter container as shown in FIG. 1, and this converter container was installed in a 2000cc 6-cylinder engine. Housing the engine was operated at air-fuel ratio (A / F) 14.5, hydrocarbons (HC) 2000 ppm as a gas component, carbon monoxide (CO) 0.6% and nitrogen oxides gas containing (NO _X) 2400 ppm to the converter vessel Connected catalysts A to F,
The purification rate of each gas component was measured. The catalyst inlet gas temperature was measured at 350 ° C. Table 2 shows the results.

In the table, HC indicates hydrocarbons, CO indicates carbon monoxide, and NO _X indicates nitric oxide.

As shown in Table 1, the catalyst component loading amount in the plugged portions of the catalysts of Examples 1 to 3 is much smaller than the catalyst component loading amount in the unopened cell openings, but When the catalyst carrier is immersed in the catalyst component solution as in the case of the catalyst of Example 1 or 3, or when the temperature and the air velocity of the warm air drying after the completion of the spray loading are low as in Comparative Example 2,
The amount of each catalyst component carried is almost unchanged. That is, as compared with Comparative Examples 1 to 3, in the catalysts of Examples 1 to 3, the amount of useless catalyst components carried in the portion that hardly participates in exhaust gas purification is very small.

On the other hand, as shown in Table 2, Examples 1 to 3
The catalyst performance of the catalyst of No. 1 is equivalent to that of the catalysts of Comparative Examples 1 to 3 having a larger amount of catalyst component supported than this. That is, the catalyst performance is not inferior even if the amount of the catalyst component carried in the plugged portion is small.

[Advantages of the Invention] By using the method of the present invention, in the outer peripheral portion of the exhaust gas purifying monolith catalyst attached to the catalytic converter container and used, a portion in contact with the converter container is
In a catalyst provided with a plugging formed by closing the catalyst cell,
It is possible to prevent wasteful catalyst components from being carried on a portion where almost no exhaust gas flows, and to reduce the catalyst streak without deteriorating the catalyst performance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which a catalyst according to an embodiment of the present invention is housed in a catalytic converter, FIG. 2 is a diagram showing an example of a catalyst component supporting device used in the present invention, and FIG. It is a figure which shows an example of the warm air drying device used for this invention.

Claims (1)

(57) [Claims] 1. A monolithic carrier having one end face of a catalyst carrier, which is provided with a cover at the periphery of the end face of the carrier to close a cell at the outer periphery of the carrier, and the peripheral end of the filled end face is covered. The catalyst component solution is supplied to the catalyst carrier from the side, and the catalyst component is supported on the carrier by sucking the excess catalyst component solution from the other end surface side, and the temperature is 40 ° C or higher, and the hot air velocity is 5 m / sec or more. A method for producing an exhaust gas purifying catalyst, characterized in that the exhaust gas purifying catalyst is dried.