JPH0333419A - Catalyst converter - Google Patents

Abstract

PURPOSE:To efficiently increase the temperature of a catalyst by continuously varying the loading density of chemical for catalyst over at least one of radial and axial directions of the catalyst. CONSTITUTION:A catalyst metal 9, being a chemical for catalyst, such as platinum of rhodium is distributed throughout about all of a catalyst 4. The region of the catalyst 4 along the center axis 8 thereof includes high density of the catalyst metal 9 to form a high density part 10 having a large loading density over the whole length in the axial direction. The loading density of the catalyst 4 is lower in the outer peripheral part thereof than that along the center axis 8, and gradually decreased from the center axis 8 to the outer part over the whole length in the axial direction. The temperature of the catalyst 4 is efficiently increased, so that the entire catalyst 4 is activated enough, for example at the time of starting under a cooled condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a catalytic converter for purifying exhaust gas installed in, for example, the exhaust system of an automobile engine.

(Prior Art) For example, some automobiles are equipped with a catalytic converter to purify harmful components in exhaust gas. That is, in this catalytic converter, a catalyst is arranged and housed inside a converter container.

Then, the catalytic converter causes the exhaust gas that has entered the converter container to flow into the front center portion of the catalyst.

Then, the exhaust gas is caused to flow from one axial end side of the catalyst to the other end side to pass through the catalyst, and the exhaust gas is caused to flow out from the converter container.

Further, in the catalytic converter, catalyst chemicals such as platinum and rhodium are loaded (supported) on the catalyst. Then, the temperature of the catalyst is raised using the thermal energy of the exhaust gas, etc.
Activate. The catalytic converter then reacts the chemicals with harmful components such as unburned hydrocarbons (HC), -carbon oxides (Co), and nitrogen oxides (NOx) in the exhaust gas, purifying the exhaust gas. .

(Problems to be Solved by the Invention) By the way, in the conventional products as described above, the catalyst chemicals were distributed over the entire catalyst at a substantially constant density. The distribution density of the catalyst chemicals, that is, the loading concentration, was approximately uniform throughout the catalyst. For this reason, the temperature distribution of the catalyst of the conventional catalytic converter during cold startup and the like is as shown in FIG.

In other words, the temperature of the catalyst during a cold start, etc. was highest in region A, which is located upstream of the exhaust gas and near the shaft center, as indicated by the arrow (■). Furthermore, the temperature of the catalyst became lower as it went from this area A toward the downstream side of the exhaust gas and the outer circumferential side of the catalyst.

In the above case, the temperature range A having different values from each other is
-F occurred in large numbers, and furthermore, the temperature gradient between each region was large. The temperature difference between the highest temperature region A and the lowest temperature region F was large. For these reasons, in the conventional catalytic converter, the heating temperature of the catalyst is slow during cold start, etc., and it takes a long time to activate the catalyst.

An object of the present invention is to provide a catalytic converter that can sufficiently activate the entire catalyst in a short period of time, such as during a cold start.

[Structure of the invention]

(Means and operations for solving the three problems) In order to achieve the above object, the present invention provides a catalytic converter that allows exhaust gas to pass from one axial end of a catalyst loaded with catalyst chemicals to the other axial end of the catalyst. , the loading concentration of the catalyst chemical is continuously changed in at least one of the direction from the outer circumferential side of the catalyst to the axial center side and the direction from the downstream side to the upstream side of the exhaust gas. It is in.

By doing so, the present invention is able to efficiently raise the temperature of the catalyst and fully activate the entire catalyst in a short period of time, such as during a cold start.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3.

FIG. 1 shows an embodiment of the present invention, where 1 indicates a catalytic converter and 2 indicates a converter container. The converter container 2 is formed into a cylindrical shape, and has an opening 2a and an outlet 2b at both ends along the axial direction. Furthermore, the converter container 2 is formed into a conical shape with both ends tapering toward the tip. The converter container 2 has an inlet side end connected to a front pipe 3 that communicates with an exhaust side of an engine (not shown).

Furthermore, the converter container 2 allows the exhaust gas supplied from the front vibrator 3 to flow in from the population side as shown by the arrow ■ in the figure. Then, the exhaust gas is made to flow in one direction from the population side to the outlet side, and is caused to flow out as shown by the arrow ■.

Further, numeral 4 in the figure indicates a catalyst. This catalyst 4 is
For example, it is a monolith type, and is formed almost entirely into a cylindrical shape. The catalyst 4 is disposed coaxially at the inner intermediate portion of the converter container 2 . Further, the catalyst 4 has a retaining layer 5 made of steel wool or the like interposed between its outer peripheral surface and the inner peripheral surface of the converter container 2 . The catalyst 4 is fixed to the converter container 2 by a retaining layer 5. Here, the holding layer 5 has functions such as holding the catalyst 5 and absorbing vibration energy of the catalyst 5.

Further, the center of the front surface 6 of the catalyst 4 faces the inlet 2a of the converter container 2. Further, the center of the rear surface 7 of the catalyst 4 faces the outlet 2b of the converter container 2. Then, the catalyst 4 allows exhaust gas to flow into the interior from its front surface 6 and pass through in the axial direction.

Further, the catalyst 4 is loaded with a catalyst metal 9 as a catalyst chemical such as platinum or rhodium over almost the entire surface (
carry). The catalyst 4 has catalytic metals 9... distributed at high density along its axis 8, as shown in FIG. The catalyst 4 forms a high concentration portion 10 with a high loading concentration over substantially the entire length in the axial direction.

Further, the loading concentration of the catalyst 4 at a portion remote from the outer circumferential side with respect to the portion along the axis 8 is smaller than the loading concentration at the high concentration portion 10 . And catalyst 4
is the loading concentration of each part over almost the entire length in the axial direction,
It gradually becomes smaller as it goes outward from the axis 8. The catalyst 4 has a minimum loading concentration near its outer peripheral surface.

That is, in the above-mentioned catalytic converter 1, at the time of cold start, etc., the catalyst 4 is heated from the center of its front surface 6 by the thermal energy of the exhaust gas passing therethrough, and its temperature increases. Further, the catalyst 4 starts activating the catalyst metal 9 by being heated, and the catalyst metal 9 and unburned hydrocarbons (HC) and carbon oxides (CO) in the exhaust gas are activated. , and harmful components such as nitrogen oxides (NOx).

Here, it is known that the reaction rate constant is expressed by the following formula.

kmAe exp (-E, / RAT) k: reaction rate constant A: frequency factor E,: activation energy R; gas constant T: temperature.・Using the heat of reaction between and the above harmful ingredients,
A vigorous reaction is caused in the high concentration portion 10. Further, the catalyst 4 rapidly causes the reaction to proceed along the axis 8 from the upstream side to the downstream side of the exhaust gas. As shown in FIG. 3, the catalyst 4 forms a temperature region A-D extending along the axis 8 from the rear surface 6 to the rear surface 7.

Therefore, the above-mentioned catalytic converter 1 can actively cause a reaction to occur in the part that is most likely to reach high temperature,
It is possible to efficiently raise the temperature of the catalyst 4 by effectively utilizing the thermal energy of the exhaust gas, the heat of reaction, and the like. And catalyst 4
can be fully activated in a short period of time, such as during a cold start.

In addition, in this example, the loading concentration of the catalyst metal was
Although the catalyst 4 is changed from the outer peripheral side to the axial center side, that is, in the radial direction, the present invention is not limited to this. For example, as shown in FIG. 4 and FIG. It may also be changed from the side to the upstream side, that is, in the axial direction of the catalyst 4. Here, A-D in FIG. 5 indicates the temperature range.

These temperature ranges become higher from the rear surface 7 side of the catalyst 4 to the front surface 6 side, that is, from D to A.

Further, the loading concentration of the catalyst metal may be changed in both the longitudinal direction and the axial direction of the catalyst 4.

Furthermore, although this embodiment has been described using a monolith type catalyst, other types of catalysts may be employed.

[Effects of the Invention] As explained above, the present invention provides a catalytic converter that allows exhaust gas to pass through a catalyst loaded with catalyst chemicals, in the direction from the outer circumferential side of the catalyst to the axial center side and from the downstream side to the upstream side of the exhaust gas. The loading concentration of the catalyst chemical is continuously changed in at least one of the lateral directions.

Therefore, the present invention has the advantage that it is possible to efficiently raise the temperature of the catalyst, and that the entire catalyst can be sufficiently activated in a short period of time, such as during a cold start.

[Brief explanation of drawings]

Figures 1 to 3 show one embodiment of the present invention.
The figure is a sectional view, Figure 2 is a perspective view of the catalyst, Figure 3 is a side view showing the temperature distribution of the catalyst, Figures 4 and 5 are modifications, and Figure 4 is a perspective view of the catalyst. , FIG. 5 is a side view showing the temperature distribution of the catalyst, and FIG. 6 is a side view showing the temperature distribution of the catalyst, showing a conventional example. 1...jl[converter, 2...converter container,
4... Catalyst, 9... Catalyst metal (chemical for catalyst).

Claims (1)

[Claims] In a catalytic converter in which a catalyst loaded with catalyst chemicals is disposed in a converter container, and the exhaust gas is purified by passing from one axial end side of the catalyst to the other axial end side of the catalyst, the outer periphery of the catalyst The loading concentration of the catalyst chemical is continuously changed in at least one of the direction from the side to the shaft center side and the direction from the downstream side to the upstream side of the exhaust gas. catalytic converter.