JPH0352976Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention is used to purify automobile exhaust gas to remove harmful substances such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in automobile exhaust gas. related to monolithic catalysts. [Prior art] Monolith catalysts are made by coating a monolithic carrier with activated alumina on a monolithic carrier with a large number of cells (pores) provided along the flow direction of exhaust gas, and then applying an active component (usually is a precious metal). This monolithic catalyst has the advantage of having a smaller heat capacity than a granular catalyst, excellent warm-up performance, and low back pressure, and is therefore widely used as a catalyst for purifying automobile exhaust gas. By the way, in a conventional monolithic catalytic converter, in order to house and hold the monolithic catalyst within the catalytic converter, retainers are placed on the outer periphery of both end surfaces of the monolithic catalyst and fixed. For this reason,
Exhaust gas does not flow through the cells on the outer periphery that are in contact with the retainer because their entrances and exits are blocked. In a conventional monolithic catalyst, all parts are catalyzed, so the catalyst supported in cells through which exhaust gas does not flow does not contribute to exhaust gas purification and is wasted. [Problem to be solved by the invention] The present invention has been made to solve the problems of the prior art described above. The goal is to improve the purification performance of monolithic catalysts by making effective use of cells that are otherwise blocked. [Means for Solving the Problems] According to the present invention, this object is achieved by the following monolithic catalyst for purifying automobile exhaust gas. That is, the monolithic catalyst for purifying automobile exhaust gas of the present invention has catalyst components supported on a monolithic carrier that is columnar and has a large number of cells from the exhaust gas inlet side to the outlet side. A monolithic catalyst for automobile exhaust gas purification is mounted on a converter and supported in the axial direction by a retainer, and the exhaust gas inlet side and exhaust gas outlet side of this monolithic catalyst are oriented from the inlet side to the outlet side in the axial direction. From the outlet side to the inlet side, each cell is provided on the cell wall at the outer periphery where the inlet and outlet are annularly blocked by a retainer when the catalytic converter is installed, within a range of 1/4 or less of the length of the monolith catalyst. It is characterized in that it is communicated with the cell through the vent hole, the entrance of which is not blocked by the retainer. In the monolithic catalyst of the present invention, each cell on the outer periphery whose inlet/outlet is annularly blocked by the retainer when the catalytic converter is installed is communicated with the cells whose inlet/outlet is not blocked via the vent hole. In the axial direction of the monolithic catalyst, the vent holes should be provided in an area of 1/4 or less of the axial length of the monolithic catalyst from the exhaust gas inlet end face toward the outlet side, and from the exhaust gas outlet end face to the inlet side. It is desirable that the direction is within a quarter of the axial length of the monolithic catalyst. Also,
In the radial direction of the monolithic catalyst, this vent hole needs to communicate with the cells whose entrances and exits are not blocked by the retainer, and is usually provided at a portion less than 1/2 the radius of the monolithic catalyst from the outer peripheral end. The size of this ventilation hole is preferably 50 μm or more, more preferably 100 μm or more. Also, the number of monolithic catalysts in this vent hole in the axial direction is
An appropriate number can be provided in consideration of the size of the monolith catalyst, etc. [Function] According to the monolithic catalyst for purifying automobile exhaust gas of the present invention, when the catalytic converter is installed, a part of the exhaust gas that reaches the inlet side passes through the vent hole provided in the cell wall, and the inlet/outlet is blocked by the retainer. It is introduced into the separated cell, enters the cell whose end face is not closed by the retainer through a vent provided on the exit side, and is discharged to the outside of the catalytic converter. Therefore, the exhaust gas can pass through all the cells of the monolithic catalyst, and all the catalyst supported in the cells can be utilized. [Effects of the Invention] As described above, according to the monolithic catalyst for purifying automobile exhaust gas of the present invention, all the catalysts can be used, so that the purification performance of the catalyst is improved. [Example] Next, an example of the present invention will be described with reference to the drawings. Here, FIG. 1 is a schematic configuration diagram showing the outline of a monolithic catalyst for purifying automobile exhaust gas according to an embodiment of the present invention, and FIG. 2 is a diagram showing the arrangement of vent holes on the exhaust gas inlet side of the monolithic carrier used in the present invention. FIG. 3 is an explanatory diagram showing the range in which ventilation holes are provided in the axial direction of the monolith carrier used in the present invention. FIG. 4 is an explanatory diagram showing the range in which vent holes are provided in the axial direction of the monolith carrier used in the present invention. FIG. 3 is a cross-sectional view showing a state in which a catalyst is installed in a catalytic converter. A monolithic carrier 1 shown in FIGS. 1 to 4 was manufactured. This monolith carrier 1 has a diameter of 107 mm, a length of 90 mm,
The number of cells per square inch is 300, and as shown by hatching in Figures 2 and 3, in the exhaust gas inlet side 2, the distance from the inlet end face to the axial center is 20 mm, and the radius is 20 mm. 15mm from the outer circumferential edge toward the center, and 20mm from the outlet end face toward the axial center on the outlet side 3.
A large number of ventilation holes 5 having an average diameter of 100 μm are provided in the wall of the cell 4 at a distance of 15 mm from the outer peripheral edge toward the center. Next, add 700 g of alumina sol with an alumina content of 10% by weight (hereinafter, all percentages indicate weight%),
150 g of 40% aluminum nitrate aqueous solution was added, and further 450 ml of distilled water was added and stirred to obtain a mixed suspension.
1000 g of alumina powder was added to this and stirred to prepare a slurry. The monolithic carrier 1 was immersed in this slurry for 1 minute, lifted up by hand, and the slurry inside the cell was blown away with an air current. Thereafter, it was dried at 200°C for 1 hour, and then fired at 700°C for 2 hours.
As a result, an activated alumina layer was formed on the surface of the monolithic carrier 1. Next, this monolithic carrier 1 was immersed in distilled water to absorb enough water, then pulled out and the excess water was blown off, and dinitrodiammine platinum aqueous solution 1.0 g/
Soaked in for 1 hour. It was pulled out, excess moisture was blown off, dried at 120°C for 2 hours, and then fired at 700°C for 2 hours. Subsequently, it was immersed in an aqueous rhodium nitrate solution of 0.1 g for 1 hour, taken out, dried and fired in the same manner as above. As a result, a monolithic catalyst 6 on which platinum and rhodium were supported was obtained. (Comparative example) A monolith carrier having the same diameter of 107 mm, length of 90 mm, and 300 cells per square inch as in the example was used, and the other exceptions were that the vent hole 5 was not provided in the wall of the cell 4 in a predetermined portion. Platinum and rhodium were supported substantially in the same manner as in the examples. (Test Example) As shown in FIG. 4, the monolithic catalysts obtained in the above Examples and Comparative Examples were installed in a catalytic converter container 10 via a sealing material 7, a cushioning material 8, and a retainer 9 to form a catalytic converter. Afterwards, a durability test was conducted using the following method to evaluate the purification performance. This durability test used a 2.8 engine, air fuel ratio (A/F): 16.0, space velocity (SV): 60000hr,
It was operated at a catalyst bed temperature of 700°C, and the purification rate was measured after a time equivalent to driving 50,000 km. The purification rate was measured for each case where the exhaust gas temperature was 350℃.
A/F: I went at 14.6. The results are shown in Table 1.

[Table] However, all purification rates are shown in %. As is clear from Table 1, it can be seen that the monolithic catalyst according to the example of the present invention has higher activity than the conventional monolithic catalyst. Although a specific embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and includes various embodiments within the scope of the claims for utility model registration. It is.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an outline of a monolithic catalyst for purifying automobile exhaust gas according to an embodiment of the present invention, and Fig. 2 shows the range where vent holes are provided on the exhaust gas inlet side of the monolithic carrier used in the present invention. FIG. 3 is an explanatory diagram showing the range in which ventilation holes are provided in the axial direction of the monolithic carrier used in the present invention,
FIG. 4 is a sectional view showing a state in which a monolithic catalyst for purifying automobile exhaust gas according to an embodiment of the present invention is mounted on a catalytic converter. DESCRIPTION OF SYMBOLS 1... Monolith carrier, 2... Inlet side, 3... Outlet side, 4... Cell, 5... Vent hole, 6... Monolith catalyst, 7... Seal material, 8... Cushion material,
9...retainer, 10...catalytic converter container.

Claims (1)

[Claim for Utility Model Registration] A catalyst component is supported on a monolithic carrier that is columnar and has a large number of cells from the exhaust gas inlet side to the exhaust gas outlet side, and is attached to a catalytic converter and attached to a retainer. Therefore, the monolithic catalyst for automobile exhaust gas purification is supported in the axial direction, and the exhaust gas inlet side and the exhaust gas outlet side of this monolithic catalyst are axially supported from the inlet side to the outlet side and from the outlet side to the inlet side. Towards the side, within a range of 1/4 or less of the length of the monolith catalyst, each cell on the outer periphery whose inlet/outlet is annularly blocked by a retainer when the catalytic converter is installed is connected through the vent hole provided in the cell wall. A monolithic catalyst for purifying automobile exhaust gas, characterized in that the inlet/outlet of the monolithic catalyst is communicated with a cell whose inlet/outlet is not blocked by a retainer.